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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..404ed82 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #61096 (https://www.gutenberg.org/ebooks/61096) diff --git a/old/61096-0.txt b/old/61096-0.txt deleted file mode 100644 index 8edfc61..0000000 --- a/old/61096-0.txt +++ /dev/null @@ -1,3841 +0,0 @@ -The Project Gutenberg EBook of Diamonds, by William Crookes - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Diamonds - -Author: William Crookes - -Release Date: January 4, 2020 [EBook #61096] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK DIAMONDS *** - - - - -Produced by deaurider, John Campbell and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - - - - - TRANSCRIBER’S NOTE - - Italic text is denoted by _underscores_. - - Footnote anchors are denoted by [number], and the footnotes have been - placed at the end of the book. - - A subscript is denoted by _{x}, for example C_{2}. - - Basic fractions are displayed as ½ ⅓ ¼ etc; other fractions are - shown in the form a/b, for example 1/144 or 5/12. - - Some minor changes to the text are noted at the end of the book. - - - - -HARPER’S LIBRARY _of_ LIVING THOUGHT - -[Illustration: (publisher colophon)] - - - - -[Illustration: - - DIAMONDS - - BY - SIR WILLIAM - CROOKES - - HARPER & - BROTHERS - LONDON & NEW YORK] - - -[Illustration: THE CULLINAN DIAMOND. - -From a photograph by the Author. (See pages 76-79.) - - Frontispiece.] - - - - - ·DIAMONDS· - - - BY - - SIR WILLIAM CROOKES - LL.D., D.Sc., F.R.S. - - Foreign Sec. R.S., Hon. LL.D. (Birmingham), Hon. Sc.D. (Camb. - and Dubl.), Hon. D.Sc. (Oxon. and Cape of Good Hope); Past Pres. - Chem. Soc., Brit. Assoc., Inst. Elect. Eng., Soc. Psych. Res.; - Hon. Mem. Roy. Phil. Soc. Glasgow, Roy. Soc. N.S.W., Pharm. Soc., - Chem. Metall. and Mining Soc. of South Africa, Amer. Chem. Soc., - Amer. Philos. Soc., Roy. Soc. Sci. Upsala, Deutsch. Chem. Gesell. - Berlin, Psychol. Soc. Paris, “Antonio Alzate” Sci. Soc. Mexico. - Sci. Soc. Bucharest, Reg. Accad. Zelanti, Aci Reale; Corresp. - Inst. de France (Acad. Sci.), Corresp. Mem. Bataafsch Genoots. - Rotterdam, Soc. d’Encouragement pour l’Indust. Paris, For. Mem. - Accad. Lincei Rome. - - WITH 24 ILLUSTRATIONS - - - LONDON AND NEW YORK - HARPER & BROTHERS - 45 ALBEMARLE STREET, W. - 1909 - - - - - TO MY WIFE - - MY COMPANION AND FRIEND OF - FIFTY-FOUR YEARS. - - TO HER JUDGMENT AND ADVICE I OWE MORE - THAN I CAN EVER REPAY - AND TO HER I DEDICATE THIS BOOK. - - - - -PREFACE - - -The following pages are based on personal observations during two -visits to Kimberley, in 1896 and 1905, and on personal researches -on the formation and artificial production of diamonds. In 1896 I -spent nearly a month at Kimberley, when Mr. Gardner F. Williams, -the General Manager of the De Beers Consolidated Mines, and the -managers of neighbouring mines, did their utmost to aid in my -zealous quest for reliable information. They gave me free access -to all workings above and below ground, allowed me to examine at -leisure their stock and to take extracts from their books. I had -exceptional opportunities of studying the geology of the Diamond -and of noting the strange cataclysmal facts connected with the -birth, growth, and physics of the lustrous stones. - -In 1905 with my wife I returned to Kimberley. We were members of -the British Association which held its meeting that year in South -Africa. I was asked to give one of the Association lectures at -Kimberley and it was natural for me to discourse “On Diamonds.” -During our stay we were the guests of Mr. Gardner Williams. - -Returning to England after the visit of 1896, I gave two -lectures on Diamonds at the Imperial Institute and one at the -Royal Institution. These lectures, and the lecture delivered at -Kimberley, in 1905--hitherto only privately distributed--form -the basis of the present volume. On each visit I took abundant -photographs, many of which I now reproduce. A few are copied -from plans lent by Mr. Gardner Williams and one or two are from -photographs purchased at Kimberley. - -In obtaining statistical information of the Diamond industry, I owe -much to the Annual Reports of the De Beers Company. I have also -quoted freely from Reunart’s valuable book on _Diamonds and Gold in -South Africa_; and I render my acknowledgments to the authors of -the following papers and memoirs. - -_On a Visit to the Diamond Fields of South Africa, with Notices of -Geological Phenomena by the Wayside._ By John Paterson, Esq., M.A. - -_On the Mode of Occurrence of Diamonds in South Africa._ By E. J. -Dunn. - -_On the Origin and Present Position of the Diamonds of South -Africa._ By G. G. Cooper, Esq., of Graaf Reinet. - -_On the Character of the Diamantiferous Rock of South Africa._ -By Prof. N. Storey Maskelyne, F.R.S., Keeper, and Dr. W. Flight, -Assistant in the Mineral Department, British Museum. - -_Further Notes on the Diamond Fields of South Africa._ By E. J. -Dunn. - -_Notes on the Diamond Fields of South Africa, 1880._ By E. J. Dunn. - -_Analogies between the Diamond Deposits in South Africa and those -in Meteorites._ By M. Daubrée. - -_Notes on the Diamond-bearing Rock of Kimberley, South Africa._ By -Sir J. B. Stone, Prof. T. G. Bonney, and Miss Raisin. - -_Notes on the Diamond Rock of South Africa._ By W. H. Hudleston. - -_The Parent Rock of the Diamond in South Africa._ By the Reverend -Professor T. G. Bonney. - -The Presidential Address, by Grove Carl Gilbert, to the Geological -Society of Washington, on _The Origin of Hypotheses. Illustrated by -the Discussion of a Topographical Problem._ 1896. - -_Le Four Electrique._ By Henri Moissan. 1897. - -_The Diamond Mines of South Africa._ By Mr. Gardner F. Williams. -(In this publication the story of the rise and development of the -industry is exhaustively narrated.) - -_British Association, South African Meeting, 1896, Kimberley -Handbook._ - -_The Meteor Crater of Canyon Diablo, Arizona; its History, Origin, -and Associated Meteoric Irons._ By George P. Merrill. 1908. - -In the present volume I have tried to give some idea of the -underground wonders of the Kimberley mines. I have pictured the -strenuous toil of the men who bring to the surface the buried -treasures, and I have given some idea of the skill and ingenuity -with which their labours are controlled. I have done my best to -explain the fiery origin of the Diamond, and to describe the -glowing, molten, subterranean furnaces where they first begin -mysteriously to take shape. I have shown that a diamond is the -outcome of a series of Titanic earth convulsions, and that these -precious gems undergo cycles of fiery, strange, and potent -vicissitudes before they can blaze on a ring or a tiara. - -I am glad to have paid these two visits to South Africa. I always -recall with interest the dusky smiling natives at work and at -play. I am glad to have seen that Arabian Nights vision, the -strong-room of the De Beers Company. Above all, I have vividly -graven on my heart the friendly welcome, and the innumerable acts -of kindness shown us by our able, energetic, and enterprising -Colonial fellow-countrymen. - - W. C. - - - - -CONTENTS - - - CHAPTER PAGE - - I. PRELIMINARY 1 - - II. KIMBERLEY AND ITS DIAMOND MINES 14 - - III. KIMBERLEY MINES AT THE PRESENT DAY 34 - - IV. COLLECTING THE GEMS 55 - - V. THE DIAMOND OFFICE 73 - - VI. NOTEWORTHY DIAMONDS 76 - - VII. BOART, CARBONADO, AND GRAPHITE 81 - - VIII. PHYSICAL AND CHEMICAL PROPERTIES OF - THE DIAMOND 89 - - IX. GENESIS OF THE DIAMOND 115 - - X. THE NATURAL FORMATION OF THE DIAMOND 127 - - XI. METEORIC DIAMONDS 134 - - INDEX 141 - - - - -LIST OF PLATES - - - The Cullinan Diamond, from a photograph by the - Author (see pp. 76-79) _Frontispiece_ - - FIG. FACING PAGE - - 1. River Washings at Klipdam 10 - - 2. Plan of the Kimberley Diamond Mines 10 - - 3. Kimberley Mine. The “Pipe” 18 - - 4. Section of Kimberley Mine 18 - - 5. Wesselton Diamond Mine. Open Workings 34 - - 6. De Beers Compound 40 - - 7. De Beers Mine. Underground Workings 40 - - 8. De Beers Washing and Concentrating Machinery 48 - - 9. Sorting Concentrates for Diamonds. De Beers 54 - - 10. De Beers Diamond Office. 25,000 carats 72 - - 11. De Beers Diamond Office. The Valuators’ Table 72 - - 12. A group of large Diamond Crystals 76 - - 13. Some Historic Diamonds 80 - - 14. Crystalline forms of native Diamonds 86 - - 15. Triangular Markings on natural face of a Diamond - Crystal 88 - - 16. Triangular Markings artificially produced on a - Diamond Crystal 88 - - 17. Diamond-cut Glass and Shavings 98 - - 18. Diamonds in Röntgen Rays. A. Black Diamond - in gold frame. B. Pink Delhi Diamond. - C. Paste Imitation of B. 98 - - 19. Curve of Vapour Pressure of Carbon _page_ 113 - - 20. Moissan’s Electric Furnace 116 - - 21. Artificial Diamond made by the Author from - molten iron 120 - - 22. Moissan’s Artificial Diamonds 120 - - 23. Diamonds from Canyon Diablo Meteorite 138 - - - - -DIAMONDS - - - - -CHAPTER I - -PRELIMINARY - - -From the earliest times the diamond has fascinated mankind. It -has been a perennial puzzle--one of the “riddles of the painful -earth.” It is recorded in _Sprat’s History of the Royal Society_ -(1667) that among the questions sent by order of the Society to -Sir Philiberto Vernatti, Resident in Batavia, was one inquiring -“Whether Diamonds grow again after three or four years in the same -places where they have been digged out?” The answer sent back was, -“Never, or at least as the memory of man can attain to.” - -In a lecture “On Diamonds,” fifty years ago,[1] Professor Maskelyne -said, “The diamond is a substance which transcends all others in -certain properties to which it is indebted for its usefulness in -the arts and its beauty as an ornament. Thus, on the one hand, it -is the hardest substance found in nature or fashioned by art. Its -reflecting power and refractive energy, on the other hand, exceed -those of all other colourless bodies, while it yields to none in -the perfection of its pellucidity.” He was constrained to add, “The -formation of the diamond is an unsolved problem.” - -Diamonds are found in widely separated parts of the globe. In the -United States they have been found in Arkansas, where the work of -testing the deposits is now going on steadily and quietly. The -general geology and petrography of the area and the weathering of -the peridotite are described in a paper read before the American -Institute of Mining Engineers by Messrs. Kunz and Washington. In -tests made with a diamond drill the peridotite was proved to -depths of 200 feet. The green and yellow grounds underlying the -layer of black, sticky soil are found to extend down 40 feet in -places, and are estimated to average 20 feet in depth over the -area. The outcrop of the peridotite is estimated to cover about -40 acres, and may be larger. Some 540 diamonds have been found, -with an aggregate of 200 carats. The largest stone weighs about -6·5 carats, though the average size compares favourably with the -general run of most of the South African mines. There is a large -proportion of white stones, many of which are free from flaws and -are very brilliant. The genuineness of the occurrence of diamonds -in their matrix is again proved, one stone having been found -imbedded in the green ground at a depth of 15 feet. This peridotite -has the form of a volcanic pipe, and therefore its outcrop is -limited to one place. - -In California authentic finds of diamonds are recorded in Butte -County, especially at Cherokee, above Orville. These diamonds, -however, have come from alluvial deposits and have been found -generally in washing for gold. As yet no authenticated discovery of -diamond in its original matrix in California is recorded. - -In Brazil the diamond industry has been increasing of late years, -and the old mines in the Diamantina country are being worked by -American capital and by the American methods which have proved so -successful at De Beers. It is estimated that the annual value of -the diamonds exported from Brazil amounts to over £800,000, but -it is impossible to arrive at accurate figures owing to the large -quantities smuggled out of the country to avoid payment of the -export tax. - -British Guiana produces a small quantity of diamonds, mostly, -however, of small size. Between January and September, 1907, 1564 -carats were exported. - -Indian diamonds chiefly come from the states of Panna, Charkhari, -and Ajaigarh. In 1905 India exported 3059 carats, valued at £5160. - - -CAPE COLONY - -It is a standing surprise to the watchful outsider how little -attention is bestowed on some of our colonies. For instance, to -the Cape Colony, comprising vast, varied, and productive regions, -we have till recently manifested profound ignorance and consequent -indifference. When the Cape Colony was first incorporated with -the Empire, it was pronounced “a bauble, unworthy of thanks.” Yet -before the Suez Canal and the Waghorn overland route to India, the -Cape, as commanding our road to India, Australia, and China, had a -special importance. Even now it presents an alternative route which -under conceivable circumstances may be of capital moment. - -The high grounds above Cape Town are rich in medicinal -health-giving waters. The districts where these springs occur -are high-lying, free from malaria, and admirably adapted for the -restoration of invalids. It needs only some distinguished power to -set the fashion, some emperor, prince, or reigning beauty to take -the baths and drink the waters, and the tide of tourists would -carry prosperity to Aliwal North, Fraserburg, Cradock, and Fort -Beaufort. - -South Africa, as I shall endeavour to show in detail, is the most -important source of diamonds on the earth, and ranks with Australia -and California as one of the three great gold-yielding regions. But -the wealth of South Africa is not only in its gold and diamonds. -The province of Natal contains more coal than Britain ever owned -before a single bucket had been raised, and the beds extend over -the Orange River Colony, whilst valuable iron ores exist also in -large quantities. - -In the year 1896 I spent nearly a month at Kimberley. Mr. Gardner -F. Williams, General Manager of the De Beers Consolidated Mines, -and the Managers of neighbouring mines, did their utmost to assist -me in my inquiries and to ply me with valuable information. I had -full access to all the workings, above and below ground, and was -able to examine at leisure their stock and take extracts from their -books. - -Again, in the year 1905, I paid another visit to Kimberley as the -guest of Mr. Gardner Williams on the occasion of the meeting of the -British Association in South Africa. - - -RIVER WASHINGS - -Besides the matrix mines, where the stones are found in pipes -supposed to be of volcanic origin, the alluvial deposits on the -Vaal River are of considerable importance. The terraces and gravels -along the Vaal River for about 200 miles have been worked for -diamonds, the deposits sometimes extending several miles on each -side of the river, and varying from a few inches to 40 or 50 feet -in thickness. The diamonds are found almost everywhere through the -gravel deposit. - -Before describing the present mode of diamond extraction followed -in the important mines, I will commence with these “River -Washings,” where, in their primitive simplicity, can be seen the -modes of work and the simple machinery long since discarded in -the large centres of the industry. The drift or so-called “river -washings” present a very interesting phase of diamond industry. The -work is carried on in the primitive fashion adopted in the early -days of diamond discovery, every man working on his own little -claim, assisted by a few natives, and employing primitive machinery -(Fig. 1). The chief centre of the Vaal River washings is about 30 -miles to the north-west of Kimberley, at a place called Klipdam -No. 2. There was originally a Klipdam a few miles further, and -here the miners congregated, but the exhaustion of their claims -made them migrate to others not far off and reported to be richer. -Here, accordingly, they re-erected their iron houses and called it -Klipdam No. 2. - -It is a mistake to speak of “river washings.” The diamantiferous -deposits are not special to the old or recent river bed, but appear -to be alluvial deposits spread over a large tract of country by -the agency of water, which at some period of time subsequent to -the filling up of the volcanic pipes planed off projecting kopjes -from the surface of the country and scattered the debris broadcast -over the land to the north-west of Kimberley. The larger diamonds -and other heavy minerals would naturally seek the lowest places, -corresponding with the river bed, past and present. The fact that -no diamonds are found in the alluvial deposits near Kimberley -may perhaps be explained by supposing that the first rush was -sufficiently strong to carry the debris past without deposition, -and that deposition occurred when the stream slackened speed. At -Klipdam No. 2 the diamantiferous earth is remarkably like river -gravel, of a strong red colour--quite different from the Kimberley -blue ground--and forms a layer from 1 to 8 feet thick, lying over -a “hard pan” of amygdaloidal trap, the melaphyre of the Kimberley -mines. - -[Illustration: FIG. 1. RIVER WASHINGS AT KLIPDAM.] - -[Illustration: FIG. 2. PLAN OF THE KIMBERLEY DIAMOND MINES. - - To face p. 10.] - -When I was at Klipdam the miners had congregated at a spot -called “New Rush,” where some good finds of diamonds had been -reported. The gravel is dug and put into a machine resembling -the gold miner’s dolly, where it is rocked and stirred by rakes, -with a current of water flowing over it. Here all the fine stuff -is washed away and a rough kind of concentration effected. The -residual gravel is put on a table and sorted for diamonds--an -operation performed by the master. At one of the claims where -work was proceeding vigorously I asked the proprietor to let -me be present at the sorting out, as I should like to see river -diamonds. He willingly consented, but no diamonds were to be found. -On my expressing regret, he said he had not seen a diamond for a -fortnight! I remarked that the prospect was rather a poor one, -but he told me that a fortnight before he picked out one worth -£300, “and that,” he said, “will pay for several weeks’ wages of -my boys.” This is the kind of speculative gambling that goes on at -the river diggings. The miner may toil fruitlessly for months, and -then come across a pocket of stones, where they have been swept by -some eddy, by which he will net several thousands. Diamonds from -the “river washings” are of all kinds, as if contributed by every -mine in the neighbourhood. They are much rolled and etched, and -contain a good proportion of first-class stones; they are of very -good quality, as if only the better and larger stones had survived -the ordeal of knocking about. Diamonds from the drift fetch about -40 per cent more than those from Kimberley; taking the yield of the -Kimberley and De Beers mines as worth all round, large and small, -26s. 6d. a carat, those from the drift are worth 40s. - -As a rule the better class of natives--the Zulus, Matabeles, -Basutos, and Bechuanas--when well treated, are very honest and -loyal to their masters. An amusing instance of the devotion of a -Zulu came to my knowledge at Klipdam. He had been superintending -a gang of natives on a small claim at the river washings. It -yielded but few stones, and the owner--my informant--sold the -claim, handing over the plant and small staff, our friend the -Zulu remaining to look after the business till the new owner took -possession. In the course of a few months the purchaser became -dissatisfied with his bargain, not a single diamond having turned -up since the transfer. One night the Zulu came to his old master -in a mysterious manner, and laying a handful of diamonds on the -table, said, “There, Baas, are your diamonds; I was not going to -let the new man have any of them!” - - - - -CHAPTER II - -KIMBERLEY AND ITS DIAMOND MINES - - -The famous diamond mines in the neighbourhood are Kimberley, De -Beers, Dutoitspan, Bultfontein, and Wesselton (Fig. 2). They -are situated in latitude 28° 43´ South and longitude 24° 46´ -East. Kimberley is practically in the centre of the present -diamond-producing area. Besides these mines others of some -importance of the Orange River Colony are known as Jaggersfontein -and Koffyfontein, Lace, and Monastery, besides two new mines, the -Roberts-Victor and the Voorspoed. - -The areas of the mines are: - - Kimberley 33 acres - De Beers 22 acres - Dutoitspan 45 acres - Bultfontein 36 acres - -In 1907 the total number of carats raised from these mines was more -than two million and a half, the sales of which realised £6,452,597. - -The most important mine outside the Kimberley group is the new -Premier Mine, about 20 miles West-North-West of Pretoria, where the -famous Cullinan diamond was found. - -Other diamond mines are the Frank Smith, Wesselton, the Kamfersdam, -the Kimberley West, the Newlands, and the Leicester Mine. - -The surface of the country round Kimberley is covered with a -ferruginous red, adhesive, sandy soil, which makes horse traffic -very heavy. Below the red soil is a basalt, much decomposed and -highly ferruginous, from 20 to 90 feet thick, and lower still -from 200 to 250 feet of black slaty shale containing carbon and -iron pyrites. These are known as the Kimberley shales; they are -very combustible, and in a part of the De Beers Mine where they -were accidentally fired they smouldered for over eighteen months. -Then follows a bed of conglomerate about 10 feet thick, and below -the conglomerate about 400 feet of a hard, compact rock of an -olive colour, called “Melaphyre,” or olivine diabase. Below the -melaphyre is a hard quartzite about 400 feet thick. The strata -are almost horizontal, dipping slightly to the north; in places -they are distorted and broken through by protruding dykes of trap. -There is no water nearer than the Vaal River, about 14 miles away, -and formerly the miners were dependent on rain-water and a few -springs and pools. Now, however, a constant and abundant supply of -excellent water is served to the town, whilst good brick houses, -with gardens and orchards, spring up on all sides. To mark the -rate of progress, Kimberley has an excellent club and one of -the best public libraries in South Africa. Parts of the town, -affectionately called “the camp” by the older inhabitants, are not -beyond the galvanised iron stage, and the general appearance is -unlovely and depressing. Reunert reckons that over a million trees -have been cut down to supply timber for the mines, and the whole -country within a radius of 100 miles has been denuded of wood with -the most injurious effects on the climate. The extreme dryness of -the air, and the absence of trees to break the force of the wind -and temper the heat of the sun, probably account for the dust -storms so frequent in summer. The temperature in the day frequently -rises to 100° in the shade, but in so dry a climate this is not -unpleasant, and I felt less oppressed by this heat than I did in -London the previous September. Moreover, in Kimberley, owing to the -high altitude, the nights are always cool. - -The approach to Kimberley is deadly dull. The country is almost -treeless, and the bare veldt stretches its level length, relieved -only by distant hills on the horizon. - - -THE PIPES OR CRATERS - -The five diamond mines or craters are all contained in a circle 3½ -miles in diameter. They are irregularly shaped round or oval pipes, -extending vertically downwards to an unknown depth, retaining about -the same diameter throughout (Fig. 3). They are said to be volcanic -necks, filled from below with a heterogeneous mixture of fragments -of the surrounding rocks, and of older rocks such as granite, -mingled and cemented with a bluish-coloured, hard clayey mass, in -which famous blue clay the imbedded diamonds are hidden. - -[Illustration: FIG. 3. KIMBERLEY MINE. THE “PIPE.”] - -[Illustration: FIG. 4. SECTION OF KIMBERLEY MINE. - - To face p. 18.] - -The craters or mines are situate in depressions, which have no -outlets for the water which falls upon the neighbouring hills. The -watersheds of these hills drain into ponds, called pans or vleis. -The water, which accumulates in these ponds during the rainy -season, evaporates during the dry months, only one of them holding -water throughout the dry season. The rocks which surround the -craters are capped by red soil or calcareous tufa, and in places by -both, the red soil covering the tufa. - -The diamantiferous breccia filling the mines, usually called “blue -ground,” is a collection of fragments of shale, various eruptive -rocks, boulders, and crystals of many kinds of minerals. Indeed, -a more heterogeneous mixture can hardly be found anywhere else -on this globe. The ground mass is of a bluish green, soapy to -the touch and friable, especially after exposure to the weather. -Professor Maskelyne considers it to be a hydrated bronzite with a -little serpentine. - -The Kimberley mine is filled for the first 70 or 80 feet with what -is called “yellow ground,” and below that with “blue ground” (Fig. -4). This superposed yellow on blue is common to all the mines. -The blue is the unaltered ground, and owes its colour chiefly to -the presence of lower oxides of iron. When atmospheric influences -have access to the iron it is peroxidised and the ground assumes -a yellow colour. The thickness of yellow earth in the mines -is therefore a measure of the depth of penetration of air and -moisture. The colour does not affect the yield of diamonds. - -Besides diamonds, there have been detected more than eighty species -of minerals in the blue ground, the more common being magnetite, -ilmenite, garnet, bright green ferriferous enstatite (bronzite), -a hornblendic mineral closely resembling smaragdite, calc-spar, -vermiculite, diallage, jeffreysite, mica, kyanite, augite, peridot, -eclogite, iron pyrites, wollastonite, vaalite, zircon, chrome -iron, rutile, corundum, apatite, olivine, sahlite, chromite, -pseudobrookite, perofskite, biotite, and quartz. The blue ground -does not show any signs of passing through great heat, as the -fragments in the breccia are not fused at the edges. The eruptive -force was probably steam or water-gas, acting under great pressure, -but at no high temperature. According to Mr. Dunn, in the Kimberley -Mine, at a depth of 120 feet, several small fresh-water shells were -discovered in what appeared to be undisturbed material. - -A selection of thin sections of some of these rocks and minerals, -mounted as microscopic objects and viewed by polarised light, are -not only of interest to the geologist, but are objects of great -beauty. - -The appearance of shale and fragments of other rocks testify that -the _mélange_ has suffered no great heat in its present condition, -and that it has been erupted from great depths by the agency of -water vapour or some similar gas. - -The rock outside the pipes and encasing them is called “reef.” -Inside some of the mines occur large masses of “floating reef,” -covering an area of several thousand square feet. In the De Beers -Mine is what is called “the snake,” a dyke of igneous rock taking a -serpentine course across the mine, and standing like a vein nearly -vertical, varying in thickness from 2 to 7 feet. The main body of -the blue ground is entirely analogous to the snake rock, naturally -more decomposed, but in essential points the microscopic appearance -of the blue ground and of the “snake” is in an extraordinary degree -alike. Mr. Gardner Williams supposes that the “snake” is a younger -eruptive formation coming from the same volcanic source as the blue -ground. No diamonds have been found either in the “snake” or the -floating reef. The ground, however, is generally richer in diamonds -in the neighbourhood of the floating reef. - -Before the discovery of the mines there was nothing in the -superficial appearance of the ground to indicate the treasures -below. Since the volcanic ducts were filled with the -diamantiferous ground, denudation has planed the surface and the -upper parts of the craters, and other ordinary signs of volcanic -activity being smoothed away, the superficial and ubiquitous red -sand covered the whole surface. The Kimberley Mine seems to have -presented a slight elevation above the surrounding flat country, -while the sites of other mines were level or even slightly -depressed. The Wesselton Mine, within a mile of Dutoitspan, has -only been discovered a few years. It showed a slight depression -on the surface, which had been used as a shoot for dry rubbish. -There are other diamantiferous pipes in the neighbourhood, but they -are small and do not contain stones in payable quantities. More -recently another diamantiferous pipe has been discovered about -40 miles off, near Klipdam, and is now worked as the Leicester -Mine. Other hoards of diamonds may also be near; where there are -no surface signs, and the pipe itself is hidden under 10 or 20 -feet of recent deposits, it is impossible to prospect the entire -country. Accident has hitherto been the chief factor in the -discovery of diamond mines. - -How the great pipes were originally formed is hard to say. They -were certainly not burst through in the ordinary manner of volcanic -eruption, since the surrounding and enclosing walls show no signs -of igneous action, and are not shattered or broken up even when -touching the “blue ground.” It is pretty certain these pipes were -filled from below after they were pierced and the diamonds were -formed at some previous time and mixed with a mud volcano, together -with all kinds of debris eroded from the rocks through which it -erupted. The direction of flow is seen in the upturned edges of -some of the strata of shale in the walls, although I was unable to -see any upturning in most parts of the walls of the De Beers Mine -at great depths. - - -THE KIMBERLEY MINE IN OLD DAYS - -According to Mr. Paterson, who examined the diamond fields of -Kimberley soon after their discovery, “Wherever the diamond is -obtained perfect in form and smooth in finest smoothness of -surface, without depression, hump, or twist of any kind, such -diamonds were ever found in their own little moulds of finest -limey stuff,[2] and as if such mould of lime had been a necessity -to their perfect formation. And further, where the splinters of -diamonds, or boarty stuff, were chiefly met by the diggers, there -was much less presence of limey matter in the claim at the section -of it where such broken or fragmentary diamonds were found; and -that chiefly from among what the diggers termed ‘clay-ballast,’ or -‘burnt brick,’ were unearthed the bits or undeveloped crystals so -plentiful at New Rush.”[3] - -In the first days of diamond mining there was no idea that -diamantiferous earth extended to any particular depth, and miners -were allowed to dig holes at haphazard and prospect where they -liked. When the Kimberley Mine was discovered a new arrangement was -made, and in July, 1871, it was cut up into about 500 claims, each -31 feet square, with spaces reserved for about fifteen roadways -across the mine. No person at first could hold more than two -claims--a rule afterwards modified. - -The following quotation from a description of a visit to Kimberley -in 1872, by Mr. Paterson, taken from a paper read by him to the -Geologists’ Association, gives a graphic picture of the early days -of the Kimberley Mine: - -“The New Rush diggings (as the Kimberley Mine was at first called) -are all going forward in an oval space enclosed around by the trap -dyke, and of which the larger diameter is about 1000 feet, while -the shorter is not more than 700 feet in length. Here all the -claims of 31 feet square each are marked out with roadways of about -12 feet in width, occurring every 60 feet. Upon these roadways, by -the side of a short pole fixed into the roadway, sits the owner of -the claim with watchful eye upon the Kafir diggers below, who fill -and hoist, by means of a pulley fixed to the pole above, bucketful -after bucketful of the picked marl stuff in which the diamonds are -found. - -“Many of the claims are already sunk to a depth of 100 feet, -and still the diamonds continue to be found as plentifully as -ever. From the roadway above the marl is carted away to the -sorting-tables, outside the range of the diggings, among mounds of -marl stuff which seem like little hills. Here, amidst such whirls -of dust as are nowhere else seen, the marl stuff is pounded, sifted -from the finest powder of lime and clay, and from the residue put -on the sorting-tables, the diggers, with a piece of zinc 9 inches -long by 4 inches in breadth, search out in the successive layers -taken from the heap the precious gems. I need not tell you that -the search is by no means very perfect, or that perhaps as many -diamonds escape the digger’s eye as are discovered and taken out -by him, but you will perhaps confess with me that their aptness -in picking out the diamonds is by no means to be despised, when I -tell you that in one six months from the date of opening New Rush -diggings, little short of a million sterling in diamonds has been -extracted from them. At close of day the diggers take daily stock -of their finds, and between five and six o’clock in the afternoon -are to be seen hundreds and hundreds moving through the main street -of New Rush on visits to the tents of the buyers, seated behind -their little green baize tables, with scales all ready, and bags of -gold and silver and piles of banknotes, to buy the little gems.” - -It may help to realise the enormous value of the Kimberley Mine if -I say that two claims, measuring together 62 by 31 feet and worked -to a depth of 150 feet, yielded 28,000 carats of diamonds. - -The roadways across the mine soon, however, became unsafe. -Claims were sunk 100 or 200 feet each side of a roadway, and the -temptation to undermine roadways was not always resisted. Falls of -road frequently took place, followed by complete collapse, burying -mine and claims in ruin. At that time there were probably 12,000 or -15,000 men at work in the mine, and then came the difficulty how to -continue working the host of separate claims without interference -with each other. A system of rope haulage was adopted. - -The following description of the work at the Kimberley Mine at this -stage of its history is given by Mr. Reunert:[4] - -“A succession of tall, massive timber stagings was erected round -the margin of the mine. Each staging carried two or three platforms -one above the other, every platform serving as an independent level -from which to communicate with the claims below. Stationary ropes -were then stretched from the different levels of the stagings to -the claims, the ropes being anchored to the ground at both ends: -the upper platforms communicated with the claims in the centre of -the mine, the lower platforms with those nearer the margin. The -hauling ropes were attached to windlasses worked by Kafirs on the -several platforms, on which grooved guide wheels for the ropes were -also fixed, the buckets being swung from the stationary ropes by -little overhead runners and crooks. Arrived at the level of the -platform the bucket was tipped into a narrow shoot, down which the -ground ran into a bag held ready to receive it, in which it was -conveyed away to be sorted. The din and rattle of these thousands -of wheels and the twang of the buckets along the ropes were -something deafening, while the mine itself seemed almost darkened -by the thick cobweb of ropes, so numerous as to appear almost -touching. This mode of haulage continued in vogue during the whole -of 1873, and if the appearance of the mine was less picturesque -than when the roadways existed, it was, if anything, more unique. -By moonlight, particularly, it was a weird and beautiful sight.” - -The mine was now threatened in two other quarters. The removal of -the blue ground took away the support from the walls of the pipe, -and frequent falls of reef occurred, not only covering up valuable -claims with rubbish, but endangering the lives of workers below. -Moreover, as the workings deepened, water made its appearance, -necessitating pumping. In 1878 one quarter of the claims were -covered by reef, and in 1879 over £300,000 were spent on removing -reef and water. In 1881 over £200,000 were thus spent, and in 1882 -more than half a million sterling was needed to defray the cost of -reef removal. So matters went on until four million cubic yards -of reef had been removed, at a cost of two millions sterling, and -still little good was done, for out of 400 claims in the mine only -about fifty could be regularly worked. Ultimately, in November, -1883, the biggest fall of reef on record took place, estimated at -250,000 cubic yards, surging half across the mine, where the bulk -of it lies to this day. It became evident that open workings could -not be carried on at such depths, and after many experiments the -present system of underground working was devised. - -During this time of perplexity, individual miners who could easily -have worked one or two claims near the surface could not continue -work in the face of harassing difficulties and heavy expenses. -Thus the claims gradually changed hands until the mine became the -property first of a comparatively small number of capitalists, then -of a smaller number of limited liability companies, until finally -the whole of the mines have practically become the property of the -“De Beers Consolidated Mines, Limited.” - - - - -CHAPTER III - -KIMBERLEY MINES AT THE PRESENT DAY - - -The De Beers Consolidated Mines, Limited, was founded in 1888, -mainly through the genius of the late Cecil John Rhodes, for the -purpose of acquiring all-important diamond-mining interests in the -Kimberley area and thereby controlling the output. The two richest -mines, Kimberley and De Beers, have been actively worked ever -since, and have been the main contributors to an output which now -realises over five millions sterling annually. Dutoitspan Mine was -completely closed down, and practically the whole of Bultfontein -was kept idle for many years; but with a view to the requirements -of the future and the marked increase in the demand for diamonds, -notwithstanding the steady rise in prices that has taken place, -both these mines have now been equipped for underground working -on a grand scale. The youngest of the De Beers group of mines is -the Wesselton, which was discovered in 1890 by the late Mr. H. A. -Ward, and soon afterwards purchased by Mr. Rhodes on behalf of the -Company. The mine is now being worked opencast on a magnificent -scale and has largely exceeded original expectations (Fig. 5). The -success of the consolidation is proved by the fact that since it -was brought about £22,000,000 have been paid in dividends to the -shareholders, and it is roughly estimated that 40,000,000 carats of -diamonds have been produced of a total value of eighty millions. - -[Illustration: FIG. 5. WESSELTON DIAMOND MINE. OPEN WORKINGS. - - To face p. 34.] - -At the four mines about 8000 persons are daily employed, namely, -1500 whites and 6500 blacks. The wages are, whites, £5 or £6 a -week; blacks, underground, 4s. to 5s. a day, and aboveground, 21s. -a week. - - -THE COMPOUND SYSTEM - -With gems like diamonds, where so large an intrinsic value is -concentrated into so small a bulk, it is not surprising that -robbery has to be guarded against in the most elaborate manner. The -Illicit Diamond Buying (I.D.B.) laws are very stringent, and the -searching, rendered easy by the “compounding” of the natives--which -I shall describe presently--is of the most drastic character (Fig. -6). It is, in fact, very difficult for a native employee to steal -diamonds; even were he to succeed, it would be almost impossible to -dispose of them, as a potential buyer would prefer to secure the -safe reward for detecting a theft rather than run the serious risk -of doing convict work on the Cape Town Breakwater for a couple of -years. I heard of a native who, secreting a diamond worth several -hundreds of pounds, after trying unsuccessfully to sell it, handed -it back to the manager of his compound, glad to get the sixpence a -carat to which he was entitled. Before the passing of the “Diamond -Trade Act” the value of diamonds stolen reached nearly one million -sterling per annum. - -A “compound” is a large enclosure about 20 acres in extent, -surrounded by rows of one-story buildings of corrugated iron. -These are divided into rooms holding each about twenty natives. A -high iron fence is erected around the compound, 10 feet from the -buildings. Within the enclosure is a store where the necessaries -of life are supplied to the natives at a reduced price, wood and -water being provided free of charge. In the middle is a large -swimming-bath, with fresh water running through it. The rest of -the space is devoted to recreation, games, dances, concerts, and -any other amusement the native mind can desire. I have to thank -the superintendents of the respective compounds, who spoke all -the native dialects, for their kindness in showing us round, and -suggesting dances and concerts, got up at ten minutes’ notice, for -the benefit of my camera. The dancing was more of the character -of attitudinising and marching to a monotonous tum-tum, the -“orchestra” consisting of various-sized drums and what they call -a piano--an octave or so of tuned slabs of wood held in order on -stretched strings and struck with a wooden hammer. The native music -as a rule is only marking time, but I have heard musical melodies -accompanying some of their songs. In case of accident or illness -there is a well-appointed hospital where the sick are tended. -Medical supervision, nurses, and food are supplied free by the -Company. - -In the compound are to be seen representatives of nearly all the -picked types of African tribes. Each tribe keeps to itself, and -to go round the buildings skirting the compound is an admirable -object-lesson in ethnology. At one point is a group of Zulus; next -we come to Fingoes; then Basutos; beyond come Matabele, Bechuanas, -Pondos, Shangains, Swazis, and other less-known tribes, either -grouped or wandering around making friendly calls. - -The clothing in the compound is diverse and original. Some of the -men are evident dandies, whilst others think that in so hot a -climate a bright-coloured handkerchief or “a pair of spectacles -and a smile” is as great a compliance with the conventions of -civilisation as can be expected. - -The natives are not interfered with in their various amusements, -always provided they do not make themselves objectionable to their -neighbours. They soon learn that tribal animosities are to be left -outside the compound. One Sunday afternoon my wife and I walked -unattended about the compound, almost the only whites present among -1700 natives. The manners of the fold were so friendly, and their -smiles so cordial, that the idea of fear vanished. At one part a -Kafir was making a pair of trousers with a bright nickel-plated -sewing-machine, in which he had invested his savings; next to him -a “boy” was reading from the Testament in his own language to an -attentive audience; in a corner a party were engaged in cooking a -savoury mess in an iron pot; further on the orchestra was tuning -up and Zulus were putting the finishing touches to their toilet of -feathers and beads. One group was intently watching a mysterious -game. It is played by two sides, with stones and grooves and -hollows in the ground, and appears of most absorbing interest. It -seems to be universal throughout Africa; it is met with among the -ruins of Zimbabwe, and signs of it are recorded on old Egyptian -monuments. I wanted to learn it, and an intelligent Zulu player -offered to teach it to me in a few minutes. Captain Dallas, -however, with a more accurate opinion of my intelligence than my -friend the Zulu, assured me it would take months before I could -begin to know anything about it. He had tried for years and could -make nothing of it. - -[Illustration: FIG. 6. DE BEERS COMPOUND.] - -[Illustration: FIG. 7. DE BEERS MINE. UNDERGROUND WORKINGS. - - To face p. 40.] - -They get good wages, varying according to occupation. The work -is appreciated, and there are always more applicants than can be -accepted. On entering, the restrictions to which they must submit -are fully explained, and they are required to sign for three months -at least, during which time they must not leave the compound or -mine. A covered way and tunnel lead the workers underground to the -down shaft, while those working on the depositing floors go and -come under guard. It is seldom that a man does not return once he -has lived the life in the compound; some come again and again for -years, only leaving occasionally to spend accumulated savings. -The most careful men save money, and carry it at intervals to the -superintendent to keep for them. Occasionally they ask to look -at their savings, which may amount to £30 or £40, accumulated -by driblets. They are ignorant of savings banks or interest, and -are content if they see their own money in the original rags and -papers. The Kafir, on demand, must behold his coins just as he -handed them in, wrappings and all. Sometimes the superintendent -will have as much as £1000 of savings in his care. - -On leaving, the men generally draw all their savings, and it is not -uncommon for a grateful Kafir to press £2 or £3 on Captain Dallas -in recognition of his trouble. They are astonished when their -offerings are declined; still more so when it is explained that if -they would put their savings in a bank they would have a few extra -pounds given to them for the privilege of taking care of it. - -A shrewd young Pondo, who had been coming year after year, applied -for some of his savings, and gave as a reason that he wanted to buy -a wife. “But you said the same thing last year,” replied Captain -Dallas; “I hope nothing has happened.” “No,” said the man; “one -wife, she quarrel with me; two wives, they quarrel with each other; -me peace!” - - -UNDERGROUND WORKINGS - -In the face of constant developments I can only describe the system -in use at the time of my own visits in 1896 and 1905. Shafts are -sunk in the solid rock at a sufficient distance from the pipe to -be safe against reef movements in the open mine. In 1903 the rock -shafts in the De Beers and Kimberley Mines reached depths of 2076 -and 2599 feet respectively. Tunnels are driven from these shafts -at different levels, about 120 feet apart, to cross the mine from -west to east. These tunnels are connected by two other tunnels -running north and south, one near the west side of the mine and one -midway between it and the east margin of the mine. From the east -and west tunnels offsets are driven to the surrounding rock. When -near the rock the offsets widen into galleries, these in turn being -stoped on the sides until they meet, and upwards until they break -through the blue ground. The fallen reef with which the upper part -of the mine is filled sinks and partially fills the open space. The -workmen then stand on the fallen reef and drill the blue ground -overhead, and as the roof is blasted back the debris follows. When -stoping between two tunnels the blue is stoped up to the debris -about midway between the two tunnels. The upper levels are worked -back in advance of the lower levels, and the works assume the -shape of irregular terraces. The main levels are from 90 to 120 -feet apart, with intermediate levels every 30 feet. Hoisting is -done from only one level at a time through the same shaft. By this -ingenious method every portion of blue ground is excavated and -raised to the surface, the rubbish on the top gradually sinking and -taking its place. - -The scene below ground in the labyrinth of galleries is bewildering -in its complexity, and very unlike the popular notion of a diamond -mine (Fig. 7). All below is dirt, mud, grime; half-naked men, dark -as mahogany, lithe as athletes, dripping with perspiration, are -seen in every direction, hammering, picking, shovelling, wheeling -the trucks to and fro, keeping up a weird chant which rises in -force and rhythm when a greater task calls for excessive muscular -strain. The whole scene is more suggestive of a coal mine than a -diamond mine, and all this mighty organisation, this strenuous -expenditure of energy, this costly machinery, this ceaseless toil -of skilled and black labour, goes on day and night, just to win a -few stones wherewith to deck my lady’s finger! All to gratify the -vanity of woman! “And,” interposed a lady who heard this remark, -“the depravity of man!” - - -THE DEPOSITING FLOORS - -Owing to the refractory character of blue ground fresh from the -mines, it has to be exposed to atmospheric influences before it -will pulverise under the action of water and mechanical treatment. - -From the surface-boxes, into which the blue ground is tipped -when it reaches the top of the main shaft, it is transferred to -side-tipping trucks and sent to the depositing floors by means of -endless wire-rope haulage. The speed of the haulage varies from 2½ -to 4 miles per hour. The trucks are counted automatically as they -are sent to the floor by a reciprocating engine-counter placed on -a frame near the tramline. - -The depositing floors are prepared by removing the bush and -grass from a fairly level piece of ground; this ground is then -rolled smooth and hard. The floors extend over many square miles -of country and are surrounded by 7-foot barbed wire fences, -vigilantly guarded day and night. The De Beers floors, on -Kenilworth, are laid off in rectangular sections 600 yards long and -200 yards wide, each section holding about 50,000 loads. The ground -from the Kimberley Mine is the softest and only needs a few months’ -exposure on the floors; the ground from De Beers is much harder and -requires at least six months’ exposure, while some ground is so -hard that it will not disintegrate by exposure to the weather under -one or two years. The De Beers Mine contains a much larger quantity -of this hard blue ground than the other mines, and in order to save -the loss of time consequent on keeping an enormous stock of blue -constantly on the floors, it has recently been decided to pass -the harder and more refractory stuff direct from the mine through -crushing mills. - -For a time the blue ground remains on the floors without undergoing -much alteration. But soon the heat of the sun and moisture produce -a wonderful effect. Large pieces, hard as ordinary sandstone when -taken from the mine, commence to crumble. At this stage the winning -of the diamonds assumes more the nature of farming than mining. -The ground is frequently harrowed and occasionally watered, to -assist pulverisation by exposing the larger pieces to atmospheric -influences. The length of time necessary for the ground to weather -before it becomes sufficiently pulverised for washing depends on -the season of the year and the amount of rain. The longer the -ground remains exposed the better it is for washing. - -[Illustration: FIG. 8. DE BEERS WASHING AND CONCENTRATING MACHINERY. - - To face p. 48.] - -It is curious to note that there is a marked difference in the -rapidity of disintegration of the blue ground in each of the four -mines. The longer the exposure, the more complete the pulverisation -and the better for washing. Under normal conditions soft blue -ground becomes sufficiently pulverised in from four to six -months, but it is better to expose it for a longer period, even for -a whole year. - - -WASHING AND CONCENTRATING MACHINERY - -After the blue ground has been weathered for a sufficient time, it -is again loaded into trucks and hauled to the crushing machinery -(Fig. 8). The first or “comet” crushers reduce the ground so that -it will pass into hoppers and thence into revolving cylinders -covered with perforated steel plates, having holes 1¼ inches in -diameter which separate the finely crushed from the coarse pieces. - -Pieces larger than 1¼ inches pass out of the end of the cylinders -and fall upon a conveyor belt, which takes them to the end of the -machine--these pieces are mostly waste rock which is found in the -blue ground. - -The fine ground which passes through the holes in the cylinder, -together with a plentiful current of water, flows into the washing -pans. These pans are of iron, 14 feet in diameter, furnished with -ten arms each having six or seven teeth. The teeth are so set as -to form a spiral, so that when the arms revolve the teeth carry -the heavy deposit to the outer rim of the pan, while the lighter -material passes towards the centre and is carried from the pan -by the flow of water. The heavy deposit contains the diamonds. -It remains on the bottom of the pan and near its outer rim. This -deposit is drawn off every twelve hours by means of a broad slot -in the bottom of the pan. The average quantity of blue ground -passed through each pan is from 400 to 450 loads in ten hours. The -deposit left in each pan after putting the above number of loads -through amounts to three or four loads, which go to the pulsator -for further concentration. - -About 14 per cent of all the ground sent to the depositing floors -is too hard to weather, so of late years crushing and concentrating -plant has been erected to deal effectually with the hard lumps, -thus saving the great lock-up of capital consequent on letting them -lie on the floor a year or two. - -The hard lumps being hauled to the upper part of the machine, -are tipped into bins, whence they pass to crushing rollers which -so reduce them that they will pass through a ring two inches in -diameter. The coarse powder is screened through revolving cylinders -having ½-inch and 1¼-inch perforations. The stuff passing through -the finer holes goes to the finishing mill, while the coarser stuff -goes to smaller crushers. Before the coarse lumps are re-crushed -they pass over revolving picking tables, where any specially large -diamonds are rescued, thus preventing the risk of breakage. From -the picking tables the ground is scraped automatically into two -sets of rolls, and the pulverised product screened again and graded -into three sizes. The finest size, passing a ½-inch screen, goes -to the washing pans, and the two coarser sizes to jigs. Large -diamonds which have been separated from their envelope of blue are -retained in the jig. The ground still holding the smaller diamonds -passes out of the end of the jig and then through a series of -rolls, screens, and jigs until the diamantiferous gravel is drawn -from the bottom jigs into locked trucks running on tramways to the -pulsator for further concentration and sorting. - -The pulsator is an ingeniously designed but somewhat complicated -machine for dealing with the diamantiferous gravel already reduced -one hundred times from the blue ground, the pulsator still further -concentrating it till the gravel is rich enough to enable the -stones to be picked out by hand. The value of the diamonds in a -load of original blue ground being about 30s., the gravel sent -to the pulsator from the pans, reduced a hundredfold, is worth -£150 a load. Stuff of this value must not be exposed to risk of -peculation. - -The locked trucks are hoisted by a cage to a platform, where they -are unlocked and their contents fed into a shoot leading to a -cylinder covered with steel sieving with holes from 1/16 to ⅝ of an -inch in diameter. The five sizes which pass through the cylinder -flow upon a combination of jigs, termed at the mines the pulsators. -The bottoms of the jigs are covered with screens, or sieving, the -meshes of which are a little larger than the holes in the revolving -cylinder immediately at the back of them. - -Over each screen is spread a layer of bullets to prevent the -rich deposit from passing too rapidly through the screens. The -jigs themselves are stationary, but from below an intermittent -stream of water passes in rapid pulsations with an up and down -movement. This pulsation keeps the diamantiferous gravel constantly -moving--“alive” is the expressive word used--and tends to sort out -the constituents roughly according to their specific gravity, the -heavier particles working to the bottom and the lighter material -washing off by the flow of water and passing into trucks, whence -it is carried to the tailings heap. The heavier portions, by the -up and down wash of the water, gradually work their way under the -bullets and pass through the screens into pointed boxes, whence -the heavy concentrates are drawn off upon endless belts. These -convey their precious load to small elevators by means of which the -concentrates are lifted into hoppers from which they are fed upon -shaking tables. - -[Illustration: FIG. 9. SORTING CONCENTRATES FOR DIAMONDS. DE BEERS. - - To face p. 54.] - - - - -CHAPTER IV - -COLLECTING THE GEMS - - -The sorting room in the pulsator house is long, narrow, and -well lighted (Fig. 9). Here the rich gravel is brought in wet, -a sieveful at a time, and is dumped in a heap on tables covered -with iron plates. The tables at one end take the coarsest lumps, -next comes the gravel which passed the ⅜-inch holes, then the -next in order, and so on. The first sorting is done by thoroughly -trustworthy white men; for here the danger of robbery is greatest. -Sweeping the heap of gravel to the right, the sorter scrapes a -little of it to the centre of the table by means of a flat piece of -sheet zinc. With this tool he rapidly passes in review the grains, -seizes the diamonds and puts them into a little tin box in front -of him. The stuff is then swept off to the left and another lot -taken, and so on till the sieveful of gravel is exhausted, when -another is brought in. The stuff the sorter has passed to his left -as temporarily inspected is taken next to another part of the room, -where it is again scrutinised by native convicts again and again, -and whilst diamonds can be found in quantity sufficient to repay -the cost of convict labour, it is passed under examination. - -The diamond has a peculiar lustre, and on the sorter’s table it is -impossible to mistake it for any other stone that may be present. -It looks somewhat like clear pieces of gum arabic, with a sort of -intrinsic lustre which makes a conspicuous shine among the other -stones. - - -AUTOMATIC DIAMOND COLLECTOR - -A series of experiments was initiated by Mr. Gardner Williams with -the object of separating the diamonds from the heavy, valueless -concentrates with which they are associated. An ordinary shaking -or percussion table was constructed, and every known means of -separation was tried without success. One of the employees of De -Beers, Mr. Fred Kirsten, was in charge of the experimenting, under -the supervision of the late Mr. George Labram, the manager of the -large crushing plant, and afterwards mechanical engineer to the -Company. Notwithstanding the fact that the specific gravity of -the diamond (3·52) was less than that of several of the minerals -associated with it, so that its separation would seem a simple -matter, it was found in practice to be impossible owing to the -slippery nature of the diamond. The heavy concentrates carried -diamonds, and diamonds flowed away from the percussion table with -the tailings. When it seemed that every resource to do away with -hand-sorting had been exhausted, Kirsten asked to be allowed to -try to catch the diamonds by placing a coat of thick grease on the -surface of the percussion table with which the other experiments -had been made. Kirsten had noticed that oily substances, such as -axle grease and white or red lead, adhered to diamonds when they -chanced to come into contact, and, he argued to himself, if these -substances adhered to diamonds and not to the other minerals in -the concentrates, why should not diamonds adhere to grease on the -table and the other minerals flow away? In this way the remarkable -discovery was made that diamonds alone of all minerals contained -in the blue ground will adhere to grease, and that all others will -flow away as tailings over the end of the percussion table with -the water. After this was determined by thorough experiments, -more suitable shaking tables were constructed at the Company’s -workshops. These were from time to time improved upon, until now -all the sorting (except for the very coarse size) is done by these -machines, whose power of distinction is far superior to the -keenest eye of the native. - -Only about ⅓ of 1 per cent of diamonds is lost by the first table, -and these are recovered almost to a stone when the concentrates are -passed over the second table. The discrimination of this sorter -is truly marvellous. Native workers, although experienced in the -handling of diamonds, often pick out small crystals of zircon, or -Dutch boart, by mistake, but the senseless machine is practically -unerring. - -The grease containing the diamonds, together with a small -percentage of very heavy minerals, such as iron pyrites and -barytes, is scraped from the tables, placed in buckets made of -steel plates with fine perforations, and boiled or steamed. The -grease passes away to tanks of water, where it is cooled and is -again fit for use. The diamonds, together with small bits of iron -pyrites, brass nails from the miners’ boots, pieces of copper -from the detonator used in blasting, which remain on the tables -owing to their high specific gravity, and a very small admixture -of worthless deposit which has become mechanically mixed with the -grease, are then boiled in a solution containing caustic soda, -where they are freed from all grease. The quantity of deposit from -the size of ⅝ of an inch downwards, which now reaches the sorting -table, does not exceed 1 cubic foot for every 12,000 loads (192,000 -cubic feet) of blue ground washed. As already stated, 5/12 of 1 -per cent of the whole mass of blue formerly passed to the sorting -tables; or, from 12,000 loads, which is about the daily average of -the quantity washed at De Beers and Kimberley Mines, 800 cubic feet -had to be assorted by hand. - - -THE YIELD OF DIAMONDS - -Sometimes as many as 8000 carats of diamonds come from the pulsator -in one day, representing about £20,000 in value. - -When the bare statement is made that nearly 5,000,000 truck-loads, -or more than 4,000,000 tons of blue ground, have been washed in a -year, the mind only faintly conceives the prodigious size of the -mass that is annually drawn from the old craters and laboriously -washed and sorted for the sake of a few bucketfuls of diamonds. It -would form a cube of more than 430 feet, or a block larger than any -cathedral in the world, and overtopping the spire of St. Paul’s, -while a box with sides measuring 2 feet 9 inches would hold the -gems. From two to three million carats of diamonds are turned out -of the De Beers mines in a year, and as 5,000,000 carats go to the -ton, this represents half a ton of diamonds. To the end of 1892 10 -tons of diamonds had come from this mine, valued at £60,000,000 -sterling. This mass of blazing diamonds could be accommodated in a -box 5 feet square and 6 feet high. - -The diamond is a luxury, and there is only a limited demand -for it throughout the world. From four to four and a half -millions sterling is as much as is spent annually in diamonds; -if the production is not regulated by the demand, there will be -over-production, and the trade will suffer. By regulating the -output the directors have succeeded in maintaining prices since the -consolidation in 1888. - -The blue ground varies in its yield of diamonds in different mines, -but is pretty constant in the same mine. In 1890 the yield per load -of blue ground was: - - CARATS - From the Kimberley Mine from 1·25 to 1·5 - ” De Beers Mine ” 1·20 ” 1·3 - ” Dutoitspan Mine ” 0·17 ” 0·5 - ” Bultfontein Mine ” 0·5 ” 0·33 - - -VARIETIES OF DIAMONDS - -FANCY STONES - -Diamonds occur in all shades, from deep yellow to pure white and -jet black, from deep brown to light cinnamon, also green, blue, -pink, yellow, orange, and opaque. - -Both in Kimberley and De Beers the blue ground on the west side -is poorer in diamonds than the blue ground in other parts of the -mines. The diamonds from the west side also differ somewhat from -those in other parts of the same mine. - -The diamonds from each mine have a distinctive character, and so -uniform are the characteristics that an experienced buyer can -tell at once the locality of any particular parcel of stones. An -isolated stone may, of course, be found occasionally in any one -mine which is characteristic of some other source of production, -but this is the exception to the general rule. - -There is a great similarity between the produce of the De Beers and -Kimberley mines. A day’s wash from either of these mines could be -distinguished from each other, but not so easily the majority of -the individual stones. - -The Kimberley Mine produces a small percentage of white crystals, -octahedral in shape, is noted for its large macles, and, in common -with the De Beers Mine, it also yields a large percentage of -coloured and large yellow diamonds. - -The De Beers Mine produces a comparatively small percentage of -really white diamonds, but is noted for its fine silvery capes. - -The Dutoitspan Mine is noted for its fine white cleavages, silver -capes, large yellows, and an exceptional proportion of large stones -generally. It also produces a small proportion of fine white, -octahedral-shaped crystals and a comparatively small proportion of -diamonds below 0·2 of a carat in size. - -The Bultfontein Mine produces a very large percentage of white -diamonds, mostly octahedral in shape and generally small in size. -It produces very few coloured stones, but a larger percentage of -flawed and spotted stones than any other mine. Even the apparently -pure stones from this mine frequently develop flaws in cutting, -which in the rough were imperceptible to the naked eye. - -The Wesselton Mine diamonds are noted for an abnormally large -percentage of octahedral stones, a large proportion of which are -free from flaws. White and brown stones predominate in this mine; -there is almost an entire absence of the ordinary yellow, but very -fine golden-coloured fancy stones are unearthed occasionally, -invariably in the form of cleavage, and hardly ever exceeding 2 -carats each in weight. - -For “golden fancies” this mine is unrivalled. Wesselton diamonds -are easily distinguished from the produce of every other mine by a -decided gloss common to them. - -Wesselton produces more stones of 10 carats each and over than -Bultfontein, but comparatively few large stones of over 50 carats -each. It produces a very large percentage of small diamonds under -0·2 of a carat. With Bultfontein it shares the distinction of -yielding cubical stones occasionally. It also produces a small -percentage of blue-whites. - -The Frank Smith Mine produces very fine white diamonds, fairly -regular in shape, mostly octahedral, and hardly any coloured -stones. Many of the stones are grooved at the edges. - -The Kamfersdam Mine yields diamonds of very inferior quality, dark -brown being the predominating colour, and even the majority of the -better-class stones from this mine are faintly tinged with brown. - -The Kimberley West, formerly known as Theron’s Mine, situated about -30 miles due west of Kimberley, yields a very small percentage of -blue-whites, fine “silver capes,” and a large proportion of brown -diamonds, somewhat better in quality than Kamfersdam and more -regular in shape. The diamonds from this mine present a distinctly -“alluvial” appearance, but they are nevertheless distinctive in -character from river diamonds and much inferior in quality. - -The diamonds from the Leicester Mine are of a distinctive -character; they are very much grooved, extremely bad shapes for -cutting, and many of the stones are cross-grained. - -The Newlands Mine, West Griqualand, about 40 miles north-west -of Kimberley, is interesting on account of the occurrence of -diamond in what the Reverend Professor Bonney considers to be its -true matrix. The workmen occasionally come across well-rounded, -boulder-like masses of eclogite, a rather coarsely crystalline -rock, sometimes more than a foot in diameter. Some of these -boulders have diamonds imbedded in them. One piece examined by -Professor Bonney measured approximately 4 inches by 3 inches by -2 inches, and appeared to have been broken off a larger eclogite -boulder. In it were seen ten diamonds, mostly well-crystallised -octahedra, perfectly colourless, with brilliant lustre, four of -them being comprised within a space of a quarter of an inch square. -All these diamonds were on the surface. Probably others would have -been found inside, but it was not considered desirable to destroy -the specimen by breaking it up. It is now in the Natural History -Museum, having been presented by the Directors of the Newlands Mine. - -Eclogite has been found in other diamond mines, but I am not aware -that diamonds have been found imbedded in it except in the Newlands -Mine. - -Stones from Jagersfontein, in the Orange River Colony, display -great purity of colour and brilliancy, and they have the so-called -“steely” lustre characteristic of old Indian gems. - - -FALLING OFF OF YIELD WITH DEPTH - -According to tables furnished by the De Beers Company, the yield -of the De Beers and Kimberley mines has declined as the depth -increases. At the same time the value of the stones has risen, and -diamonds are more expensive to-day than at any previous time. - - NUMBER OF VALUE - YEAR CARATS[5] PER CARAT - PER LOAD _s._ _d._ - 1889 1·283 19 8·75 - 1890 1·15 32 6·75 - 1891 0·99 29 6 - 1892 0·92 25 6 - 1893 1·05 29 0·6 - 1894 0·89 24 5·2 - 1895 0·85 25 6 - 1896 0·91 26 9·4 - 1897 0·92 26 10·6 - 1898 0·80 26 6·2 - 1899 0·71 29 7·2 - 1900 0·67 35 10·2 - 1901 0·76 39 7 - 1902 0·76 46 5·7 - 1903 0·61 48 6·3 - 1904 0·54 48 11·8 - - -STONES OTHER THAN DIAMONDS - -Accompanying diamonds in the concentrates are a number of other -minerals of high specific gravity, and some of notable beauty. -Among these are the rich red pyrope (garnet), sp. gr. 3·7, -containing from 1·4 to 3 per cent of oxide of chromium; zircon, -in flesh-coloured grains and crystals, sp. gr. 4 to 4·7; kyanite, -sp. gr. 3·45 to 3·7, discernible by its blue colour and perfect -cleavage; chrome diopside, sp. gr. 3·23 to 3·5, of a bright green -colour; bronzite, sp. gr. 3·1 to 3·3; magnetite, sp. gr. 4·9 to -5·2; mixed chrome and titanium iron ore, sp. gr. 4·4 to 4·9, -containing from 13 to 61 per cent of oxide of chromium, and from -3 to 68 per cent of titanic acid, in, changeable quantities; -hornblende, sp. gr. 2·9 to 3·4; barytes, sp. gr. 4·3 to 4·7; and -mica. Some of the garnets are of fine quality, and one was recently -cut which resembled a pigeonblood ruby, and attracted an offer of -£25. - -In the pulsator and sorting house most of the native labourers -are long-sentence convicts, supplied with food, clothing, and -medical attendance by the Company. They are necessarily well -guarded. I myself saw about 1000 convicts at work. I was told that -insubordination is very rare; apart from the hopelessness of a -successful rising, there is little inducement to revolt; the lot -of these diamond workers is preferable to life in the Government -prisons, and they seem contented. - -[Illustration: FIG. 10. DE BEERS DIAMOND OFFICE. 25,000 CARATS.] - -[Illustration: FIG. 11. DE BEERS DIAMOND OFFICE. THE VALUATORS’ -TABLE. - - To face p. 72.] - - - - -CHAPTER V - -THE DIAMOND OFFICE - - -From the pulsator the diamonds are sent to the general office -in Kimberley to be cleansed in a boiling mixture of nitric and -sulphuric acids. A parcel of diamonds loses about half a part per -1000 by this treatment. On one of my visits to the diamond office -the door opened and in walked two young men, each carrying a large -enamelled saucepan containing something steaming hot. They went to -one of the zinc-covered tables and turned out from the saucepans a -lustrous heap of 25,000 carats of diamonds (Fig. 10). They had just -been boiled in acid and washed. - -After purification the diamonds are handed to the valuators (Fig. -11), who sort them into classes, according to size, colour, and -purity. In the diamond office they are sorted into ten classes. In -the year 1895, in 1141·8 carats of stones, the proportions of the -different classes were as follows: - - Close goods (best stones) 53·8 - Spotted stones 75·8 - Fine cleavage 79·1 - Flats 39·5 - Macles 36·5 - Ordinary and rejection cleavage 243·4 - Rejection stones 43·2 - Light and brown cleavage 56·9 - Rubbish 371·8 - ------ - 1000·0 - ------ - Fine sand 141·8 - ------ - 1141·8 - -It is a sight for Aladdin to see the valuators at work in the -strong-room of the De Beers Company at Kimberley. The tables are -literally heaped with stones won from the rough blue ground--stones -of all sizes, purified, flashing, and of inestimable price; stones -that will be coveted by men and women all the world over; and -last, but not least, stones that are probably destined to largely -influence the development and history of a whole huge continent. - - - - -CHAPTER VI - -NOTEWORTHY DIAMONDS - - -Prodigious diamonds are not so uncommon as is generally supposed. -Diamonds weighing over an ounce (151·5 carats) are not unfrequent -at Kimberley. Some years ago, in one parcel of stones, I saw eight -perfect ounce crystals, and one stone weighing 2 ounces (Fig. -12). The largest diamond from the Kimberley mines weighed 428½ -carats, or nearly 4 ounces troy. It measured 1⅞ inch through the -longest axis and was 1½ inch square. After cutting it weighed 228½ -carats, losing 200 carats in the process. The largest known diamond -was discovered in January, 1905, at the New Premier Mine, near -Pretoria. This mine is of the same type as the Kimberley mines, but -larger in size, and, in fact, is the largest known diamantiferous -pipe in the world--the pipe containing the “blue ground,” along -the longer diameter of its oval-shaped cross-section, measuring -over half a mile, and its area is estimated at 350,000 square -yards. This pipe breaks through felsitic rocks. The diamond, called -“Cullinan” from the name of one of the directors of the company -on whose farm it was discovered, was presented to King Edward on -his birthday by the people of the Transvaal. It weighed no less -than 3025¾ carats, or 9586·5 grains (1·37 lb. avoirdupois). It was -a fragment, probably less than half, of a distorted octahedral -crystal; the other portions still await discovery by some fortunate -miner. The frontispiece shows this diamond in its natural size, -from a photograph taken by myself. I had an opportunity of -examining and experimenting with this unequalled stone before it -was cut. A beam of polarised light passed in any direction through -the stone, and then through an analyser, revealed colours in all -cases, appearing brightest when the light passed along the greatest -diameter--about 4 inches. Here the colours were very fine, but -no regular figure was to be seen. Round a small black spot in -the interior of the stone the colours were very vivid, changing -and rotating round the spot as the analyser was turned. These -observations indicated internal strain. - -[Illustration: FIG. 12. A GROUP OF LARGE DIAMOND CRYSTALS. - - To face p. 76.] - -The clearness throughout was remarkable, the stone being absolutely -limpid like water, with the exception of a few flaws, dark -graphitic spots, and coloured patches close to the outside. At one -part near the surface there was an internal crack, showing well -the colours of thin plates. At another point there was a milky, -opaque mass, of a brown colour, with pieces of what looked like -iron oxide. There were four cleavage planes of great smoothness and -regularity. On other parts of the surface the crystalline structure -was very marked. The edges were rounded in parts, and triangular -markings (depressions) were to be seen. I also noticed square -depressions, nearly as sharp and perfect as the triangular ones. - -The cleaving and cutting and polishing of the Cullinan diamond -was entrusted to the firm of Asscher and Co., in Amsterdam. The -cleavage of the diamond was very successfully accomplished by Mr. -Joseph Asscher. An incision half an inch deep was made with a sharp -diamond point in the proper place, then a specially designed knife -blade was placed in the incision and it was struck a heavy blow -with a piece of steel. The diamond split through a defective spot, -part of which was left in each portion of the diamond. - -Gigantic as is the Cullinan diamond, it represents in weight less -than half the daily output of the De Beers mines, which averages -about 7000 carats per day. - -Next in size to the Cullinan comes the one which was found at the -Jagersfontein Mine. It weighed 970 carats--over half a pound. - -The following table gives the names and weights of some historic -diamonds (Fig. 13): - - 1. Koh-i-noor, after the second cutting, 106 carats. - - 2. Loterie d’Angleterre, 49 carats. - - 3. Nizam of Hyderabad, 279 carats. - - 4. Orloff, 194 carats. - - 5. Koh-i-noor, after first cutting, 279 carats. - - 6. Regent or Pitt, 137 carats. - - 7. Duke of Tuscany, 133 carats. - - 8. Star of the South, 124 carats. - - 9. Pole Star, 40 carats. - - 10. Tiffany, yellow, 125 carats. - - 11. Hope, blue diamond, 44 carats. - - 12. Sancy, 53 carats. - - 13. Empress Eugenie, 51 carats. - - 14. Shah, 86 carats. - - 15. Nassak, 79 carats. - - 16. Pasha of Egypt, 40 carats. - - 17. Cullinan, 3025 carats. - - 18. Excelsior, Jagersfontein, 969 carats. - -[Illustration: FIG. 13. SOME HISTORIC DIAMONDS. - - To face p. 80.] - - - - -CHAPTER VII - -BOART, CARBONADO, AND GRAPHITE - - -The black inclusions in some transparent diamonds consist of -graphite. On crushing a clear diamond showing such spots and -heating in oxygen to a temperature well below the point at which -diamond begins to burn, Moissan found that the grey tint of the -powder disappeared, no black spots being seen under the microscope. -There also occur what may be considered intermediate forms between -the well-crystallised diamond and graphite. These are “boart” and -“carbonado.” Boart is an imperfectly crystallised diamond, having -no clear portions, and therefore useless for gems. Shot boart is -frequently found in spherical globules, and may be of all colours. -Ordinary boart is so hard that it is used in rock-drilling, -and when crushed it is employed for cutting and polishing other -stones. Carbonado is the Brazilian term for a still less perfectly -crystallised form of carbon. It is equally hard, and occurs in -porous masses and in massive black pebbles, sometimes weighing two -or more ounces. - -The ash left after burning a diamond invariably contains iron as -its chief constituent; and the most common colours of diamonds, -when not perfectly pellucid, show various shades of brown and -yellow, from the palest “off colour” to almost black. These -variations give support to the theory advanced by Moissan that -the diamond has separated from molten iron--a theory of which I -shall say more presently--and also explain how it happens that -stones from different mines, and even from different parts of the -same mine, differ from each other. Further confirmation is given -by the fact that the country round Kimberley is remarkable for -its ferruginous character, and iron-saturated soil is popularly -regarded as one of the indications of the near presence of diamonds. - - -GRAPHITE - -Intermediate between soft carbon and diamond come the graphites. -The name graphite is given to a variety of carbon, generally -crystalline, which in an oxidising mixture of chlorate of potassium -and nitric acid forms graphitic oxide. This varies in colour -from green to brown or yellow, or it is almost without colour, -according to the completeness of the reaction. Graphites are of -varying densities, from 2·0 to 3·0, and generally of crystalline -aspect. Graphite and diamond pass insensibly into one another. Hard -graphite and soft diamond are near the same specific gravity. The -difference appears to be one of pressure at the time of formation. - -Some forms of graphite exhibit the remarkable property by which -it is possible to ascertain approximately the temperature at -which they were formed, or to which they have subsequently been -exposed. Sprouting graphite is a form, frequently met with in -nature, which on moderate heating swells up to a bulky, very -light mass of amorphous carbon. Moissan has found it in blue -ground from Kimberley; my own results verify his. When obtained by -simple elevation of temperature in the arc or the electric furnace -graphites do not sprout; but when they are formed by dissolving -carbon in a metal at a high temperature and then allowing the -graphite to separate out on cooling, the sprouting variety appears. -The phenomenon of sprouting is easily shown. If a few grains are -placed in a test-tube and heated to about 170° C., the grains -increase enormously in bulk and fill the tube with a light form of -amorphous carbon. - -The resistance of a graphite to oxidising agents is greater the -higher the temperature to which it has previously been exposed. -Graphites which are easily attacked by a mixture of fuming nitric -acid and potassium chlorate are rendered more resistant by strong -heat in the electric furnace. - -I have already signified that there are various degrees of -refractoriness to chemical reagents among the different forms of -graphite. Some dissolve in strong nitric acid; other forms of -graphite require a mixture of highly concentrated nitric acid and -potassium chlorate to attack them, and even with this intensely -powerful agent some graphites resist longer than others. M. Moissan -has shown that the power of resistance to nitric acid and potassium -chlorate is in proportion to the temperature at which the graphite -was formed, and with tolerable certainty we can estimate this -temperature by the resistance of the specimen of graphite to this -reagent. - - -CRYSTALLISATION - -The diamond belongs to the isometric system of crystallography; the -prevailing form is octahedral. It frequently occurs with curved -faces and edges. Twin crystals (macles) are not uncommon. Diamond -crystals are generally perfect on all sides. They seldom show -irregular sides or faces by which they were attached to a support, -as do artificial crystals of chemical salts; another proof that the -diamond must have crystallised from a dense liquid. - -The accompanying illustration (Fig. 14) shows some of the various -crystalline forms of native diamonds. - -[Illustration: FIG. 14. CRYSTALLINE FORMS OF NATIVE DIAMONDS. - - To face p. 86.] - -No. 1. Diamond in the form of a hexakis-octahedron (the forty-eight -scalenohedron), or a solid figure contained by forty-eight scalene -triangles. According to Professor Maskelyne, this occurs as a -self-existent form only in the diamond. - -No. 2. Diamond in the form of a hexakis-octahedron and -octahedron. From Sudafrika. - -No. 3. Diamond in the form of octahedron with intersections. - -No. 4. Diamond from Brazil. - -No. 5. Diamond from Kimberley. - -No. 6. Diamond from Brazil. - -No, 7. A macle or twin crystal, showing its formation from an -octahedron with curved edges. - - * * * * * - -Some crystals of diamonds have their surfaces beautifully marked -with equilateral triangles, interlaced and of varying sizes -(Fig. 15). Under the microscope these markings appear as hollow -depressions sharply cut out of the surrounding surface, and -these depressions were supposed by Gustav Rose to indicate the -probability that the diamonds had at some previous time been -exposed to incipient combustion. Rose pointed out that similar -triangular striations appeared on the surfaces of diamonds burnt -before the blowpipe. This experiment I have repeated on a clear -diamond, and I have satisfied myself that during combustion -before the blowpipe, in the field of a microscope, the surface is -etched with triangular markings different in character from those -naturally on crystals (Fig. 16). The artificial striæ are very -irregular, much smaller, and massed closer together, looking as -if the diamond during combustion flaked away in triangular chips, -while the markings natural to crystals appear as if produced by -the crystallising force as they were being built up. Many crystals -of chemical compounds appear striated from both these causes. -Geometrical markings can be produced by eroding the surface of a -crystal of alum with water, and they also occur naturally during -crystallisation. - -[Illustration: FIG. 15. TRIANGULAR MARKINGS ON NATURAL FACE OF A -DIAMOND CRYSTAL.] - -[Illustration: FIG. 16. TRIANGULAR MARKINGS ARTIFICIALLY PRODUCED -ON A DIAMOND CRYSTAL. - - To face page 88.] - - - - -CHAPTER VIII - -PHYSICAL AND CHEMICAL PROPERTIES OF THE DIAMOND - - -I need scarcely say the diamond is almost pure carbon, and it is -the hardest substance in nature. - -When heated in air or oxygen to a temperature varying from 760° -to 875° C., according to its hardness, the diamond burns with -production of carbonic acid. It leaves an extremely light ash, -sometimes retaining the shape of the crystal, consisting of iron, -lime, magnesia, silica, and titanium. In boart and carbonado -the amount of ash sometimes rises to 4 per cent, but in clear -crystallised diamonds it is seldom higher than 0·05 per cent. By -far the largest constituent of the ash is iron. - -The following table shows the temperatures of combustion in oxygen -of different kinds of carbon: - - °C. - Condensed vapour of carbon 650 - Carbon from sugar, heated in an electrical furnace 660 - Artificial graphites, generally 660 - Graphite from ordinary cast-iron 670 - Carbon from blue ground, of an ochre colour 690 - Carbon from blue ground, very hard and black 710 - Diamond, soft Brazilian 760 - Diamond, hard Kimberley 780 - Boart from Brazil 790 - Boart from Kimberley 790 - Boart, very hard, almost impossible to cut 900 - - -HARDNESS - -Diamonds vary considerably in hardness, and even different parts -of the same crystal differ in their resistance to cutting and -grinding. - -Beautifully white diamonds have been found at Inverel, New South -Wales, and from the rich yield of the mine and the white colour of -the stones great things were expected. In the first parcel which -came to England the stones were found to be so much harder than -South African diamonds that it was at first feared they would be -useless except for rock-boring purposes. The difficulty of cutting -them disappeared with improved appliances, and they now are highly -prized. - -The famous Koh-i-noor, when being cut into its present form, showed -a notable variation in hardness. In cutting one of the facets near -a yellow flaw, the crystal became harder and harder the further -it was cut, until, after working the mill for six hours at the -usual speed of 2400 revolutions a minute, little impression was -made. The speed was increased to more than 3000, when the work -slowly proceeded. Other portions of the stone were found to be -comparatively soft, and became harder as the outside was cut away. - -The intense hardness of the diamond can be illustrated by the -following experiment. On the flattened apex of a conical block -of steel place a diamond, and upon it bring down a second cone -of steel. On forcing together the two steel cones by hydraulic -pressure the stone is squeezed into the steel blocks without -injuring it in the slightest degree. - -In an experiment I made at Kimberley the pressure gauge showed 60 -atmospheres, and the piston being 3·2 inches diameter, the absolute -pressure was 3·16 tons, equivalent on a diamond of 12 square mm. -surface to 170 tons per square inch of diamond. - -The use of diamond in glass-cutting I need not dwell on. So hard is -diamond in comparison to glass, that a suitable splinter of diamond -will plane curls off a glass plate as a carpenter’s tool will plane -shavings off a deal board. The illustration (Fig. 17) shows a few -diamond-cut glass shavings. - - -DENSITY OR SPECIFIC GRAVITY - -The specific gravity of the diamond varies ordinarily from 3·514 -to 3·518. For comparison, I give in tabular form the specific -gravities of the different varieties of carbon and of the minerals -found on the sorting tables: - - SPECIFIC - GRAVITY. - Amorphous carbon 1·45-1·70 - Hard gas coke 2·356 - Hard graphite 2·5 - Quartzite and granite 2·6 - Beryl 2·7 - Mica 2·8 - Hornblende 3·0 - Boart 3·47-3·49 - Carbonado 3·50 - Diamond 3·514-3·518 - Garnet 3·7 - Corundum 3·8 - Zircon 4·4 - Barytes 4·5 - Chrome and titanic iron ore 4·7 - Magnetite 5·0 - -There is a substance, the double nitrate of silver and thallium, -which, while solid at ordinary temperatures, liquefies at 75° C. -and then has a specific gravity of 4·5. Admixture with water lowers -the density to any desired point. - -If a glass cell is taken containing this liquid diluted to a -density of about 3·6, and in it is thrown pieces of the above-named -minerals, all those whose density is lower than 3·6 will rise to -the surface, while the denser minerals will sink. If now a little -water is carefully added with constantly stirring until the density -of the liquid is reduced to that of the diamond, the heterogeneous -collection sorts itself into three parts. The graphite, quartz, -beryl, mica, and hornblende rise to the surface; the garnet, -corundum, zircons, etc., sink to the bottom, while the diamonds -float in the middle of the liquid. With a platinum landing-net I -can skim off the swimmers and put them into one dish; with the -same net I can fish out the diamonds and put them in a second -dish, while by raising a sieve at the bottom I can remove the heavy -minerals and put them into a third. The accurate separation of -diamonds from the heterogeneous mixture can be effected in less -time than is taken to describe the experiment. - -The table shows that diamonds vary somewhat in density among -themselves, between narrow limits. Occasionally, however, diamonds -overpass these figures. Here is an illustration. In a test-tube of -the same dense liquid are three selected diamonds. One rises to the -top, another floats uncertain where to settle, rising and falling -as the temperature of the sorting liquid is raised or lowered, -whilst the third sinks to the bottom. Allowing the liquid to cool -a degree or two slightly increases the density and sends all three -to the surface. - - -PHOSPHORESCENCE OF DIAMOND - -After exposure for some time to the sun many diamonds glow in -a dark room. Some diamonds are fluorescent, appearing milky in -sunlight. In a vacuum, exposed to a high-tension current of -electricity, diamonds phosphoresce of different colours, most South -African diamonds shining with a bluish light. Diamonds from other -localities emit bright blue, apricot, pale blue, red, yellowish -green, orange, and pale green light. The most phosphorescent -diamonds are those which are fluorescent in the sun. One beautiful -green diamond in the writer’s collection, when phosphorescing in a -good vacuum, gives almost as much light as a candle, and you can -easily read by its rays. But the time has hardly come when diamonds -can be used as domestic illuminants! The emitted light is pale -green, tending to white, and in its spectrum, when strong, can be -seen bright lines, one at about λ 5370 in the green, one at λ 5130 -in the greenish blue, and one at λ 5030 in the blue. A beautiful -collection of diamond crystals belonging to Professor Maskelyne -phosphoresces with nearly all the colours of the rainbow, the -different faces glowing with different shades of colour. Diamonds -which phosphoresce red generally show the yellow sodium line on -a continuous spectrum. In one Brazilian diamond phosphorescing a -reddish-yellow colour I detected in its spectrum the citron line -characteristic of yttrium. - -The rays which make the diamond phosphoresce are high in the -ultra-violet. To illustrate this phosphorescence under the -influence of the ultra-violet rays, arrange a powerful source -of these rays, and in front expose a design made up of certain -minerals, willemite, franklinite, calcite, etc.--phosphorescing -of different colours. Their brilliant glow ceases entirely when a -thin piece of glass is interposed between them and the ultra-violet -lamp. - -I now draw attention to a strange property of the diamond, which -at first sight might seem to discount the great permanence and -unalterability of this stone. It has been ascertained that the -cause of phosphorescence is in some way connected with the -hammering of the electrons, violently driven from the negative -pole on to the surface of the body under examination, and so great -is the energy of the bombardment, that impinging on a piece of -platinum or even iridium, the metal will actually melt. When the -diamond is thus bombarded in a radiant matter tube the result is -startling. It not only phosphoresces, but becomes discoloured, -and in course of time becomes black on the surface. Some diamonds -blacken in the course of a few minutes, while others require an -hour or more to discolour. This blackening is only superficial, -and although no ordinary means of cleaning will remove the -discolouration, it goes at once when the stone is polished with -diamond powder. Ordinary oxidising reagents have little or no -effect in restoring the colour. - -[Illustration: FIG. 17. DIAMOND-CUT GLASS AND SHAVINGS.] - -[Illustration: FIG. 18. DIAMONDS IN RÖNTGEN RAYS. - - A. BLACK DIAMOND IN GOLD FRAME. - B. PINK DELHI DIAMOND. - C. PASTE IMITATION OF B. - - To face p. 98.] - -The superficial dark coating on a diamond after exposure to -molecular bombardment I have proved to be graphite. M. Moissan has -shown that this graphite, on account of its great resistance to -oxidising reagents, cannot have been formed at a lower temperature -than 3600° C. - -It is thus manifest that the bombarding electrons, striking the -diamond with enormous velocity, raise the superficial layer to the -temperature of the electric arc and turn it into graphite, whilst -the mass of diamond and its conductivity to heat are sufficient to -keep down the general temperature to such a point that the tube -appears scarcely more than warm to the touch. - -A similar action occurs with silver, the superficial layers of -which can be raised to a red heat without the whole mass becoming -more than warm. - - -CONVERSION OF DIAMOND INTO GRAPHITE - -Although we cannot convert graphite into diamond, we can change -the diamond into graphite. A clear crystal of diamond is placed -between two carbon poles, and the poles with intervening diamond -are brought together and an arc formed between. The temperature of -the diamond rapidly rises, and when it approaches 3600° C., the -vaporising point of carbon, it breaks down, swells, and changes -into black and valueless graphite. - - -TRIBO-LUMINESCENCE - -A few minerals give out light when rubbed. In the year 1663 the -Hon. Robert Boyle read a paper before the Royal Society, in which -he described several experiments made with a diamond which markedly -showed tribo-luminescence. As specimens of tribo-luminescent bodies -I may instance sphalerite (sulphide of zinc), and an artificial -sphalerite, which is even more responsive to friction than the -native sulphide.[6] - -Mrs. Kunz, wife of the well-known New York mineralogist, possesses, -perhaps, the most remarkable of all phosphorescing diamonds. This -prodigy diamond will phosphoresce in the dark for some minutes -after being exposed to a small pocket electric light, and if rubbed -on a piece of cloth a long streak of phosphorescence appears. - - -ABSORPTION SPECTRUM OF DIAMOND - -On passing a ray of light through a diamond and examining it in a -spectroscope, Walter has found in all colourless brilliants of over -1 carat in weight an absorption band at wave-length 4155 (violet). -He ascribes this band to an impurity and suggests it may possibly -be due to samarium. Three other fainter lines were detected in the -ultra-violet by means of photography. - - -REFRACTIVITY - -But it is not the hardness of the diamond so much as its optical -qualities that make it so highly prized. It is one of the most -refracting substances in nature, and it also has the highest -reflecting properties. In the cutting of diamonds advantage is -taken of these qualities. When cut as a brilliant the facets on -the lower side are inclined so that light falls on them at an -angle of 24° 13´, at which angle all the incident light is totally -reflected. A well-cut brilliant should appear opaque by transmitted -light except at a small spot in the middle where the table and -culet are opposite. All the light falling on the front of the -stone is reflected from the facets, and the light passing into the -diamond is reflected from the interior surfaces and refracted -into colours when it passes out into the air, giving rise to the -lightnings, the effulgence, and coruscations for which the diamond -is supreme above all other gems. - -The following table gives the refractive indices of diamonds and -other bodies: - - -REFRACTIVE INDICES FOR THE D LINE - - Chromate of lead 2·50-2·97 - Diamond 2·47-2·75 - Phosphorus 2·22 - Sulphur 2·12 - Ruby 1·78 - Thallium glass 1·75 - Iceland spar 1·65 - Topaz 1·61 - Beryl 1·60 - Emerald 1·59 - Flint glass 1·58 - Quartz 1·55 - Canada balsam 1·53 - Crown glass 1·53 - Fluor-spar 1·44 - Ice 1·31 - -In vain I have searched for a liquid of the same refraction as -diamond. Such a liquid would be invaluable to the merchant, as -on immersing a stone the clear body would absolutely disappear, -leaving in all their ugliness the flaws and black specks so -frequently seen even in the best stones. - - -THE DIAMOND AND POLARISED LIGHT - -Having no double refraction, the diamond should not act on -polarised light. But as is well known, if a transparent body which -does not so act is submitted to strain of an irregular character -it becomes doubly refracting, and in the polariscope reveals the -existence of the strain by brilliant colours arranged in a more or -less defined pattern, according to the state of tension in which -the crystal exists. I have examined many hundred diamond crystals -under polarised light, and with few exceptions the colours show how -great is the strain to which some of them are exposed. On rotating -the polariser, the black cross most frequently seen revolves round -a particular point in the inside of the crystal; on examining -this point with a high power we sometimes see a slight flaw, more -rarely a minute cavity. The cavity is filled with gas at enormous -pressure, and the strain is set up in the stone by the effort of -the gas to escape. I have already said that the great Cullinan -diamond by this means revealed a state of considerable internal -stress and strain. - -So great is this strain of internal tension that it is not uncommon -for a diamond to explode soon after it reaches the surface, and -some have been known to burst in the pockets of the miners or when -held in the warm hand. Large crystals are more liable to burst than -smaller pieces. Valuable stones have been destroyed in this way, -and it is whispered that cunning dealers are not averse to allowing -responsible clients to handle or carry in their warm pockets large -crystals fresh from the mine. By way of safeguard against explosion -some dealers imbed large diamonds in raw potato to ensure safe -transit to England. - -The anomalous action which many diamonds exert on polarised light -is not such as can be induced by heat, but it can easily be -conferred on diamonds by pressure, showing that the strain has not -been produced by sudden cooling, but by sudden lowering of pressure. - -The illustration of this peculiarity is not only difficult, but -sometimes exceedingly costly--difficult because it is necessary to -arrange for projecting on the screen the image of a diamond crystal -between the jaws of a hydraulic press, the illuminating light -having to pass through delicate optical polarising apparatus--and -costly because only perfectly clear crystals can be used, and -crystals of this character sometimes fly to pieces as the pressure -rises. At first no colour is seen on the screen, the crystal not -being birefringent. A movement of the handle of the press, however, -gives the crystal a pinch, instantly responded to by the colours on -the screen, showing the production of double refraction. Another -movement of the handle brightens the colours, and a third may -strain the crystal beyond its power of resistance, when the crystal -flies to pieces. - - -THE DIAMOND AND RÖNTGEN RAYS - -The diamond is remarkable in another respect. It is extremely -transparent to the Röntgen rays, whereas highly refracting glass, -used in imitation diamonds, is almost perfectly opaque to the rays. -I exposed for a few seconds over a photographic plate to the X-rays -the large Delhi diamond of a rose-pink colour weighing 31½ carats, -a black diamond weighing 23 carats, and a glass imitation of the -pink diamond (Fig. 18). On development the impression where the -diamond obscured the rays was found to be strong, showing that -most rays passed through, while the glass was practically opaque. -By this means imitation diamonds can readily be distinguished from -true gems. - - -ACTION OF RADIUM ON DIAMOND - -The β-rays from radium having like properties to the stream of -negative electrons in a radiant matter tube, it was of interest to -ascertain if they would exert a like difference on diamond. The -diamond glows under the influence of the β-radiations, and crushed -diamond cemented to a piece of card or metal makes an excellent -screen in a spinthariscope--almost as good as zinc sulphide. Some -colourless crystals of diamond were imbedded in radium bromide and -kept undisturbed for more than twelve months. At the end of that -time they were examined. The radium had caused them to assume a -bluish-green colour, and their value as “fancy stones” had been -increased. - -This colour is persistent and penetrates below the surface. It -is unaffected by long-continued heating in strong nitric acid and -potassium chlorate, and is not discharged by heating to redness. - -To find out if this prolonged contact with radium had communicated -to the diamond any radio-active properties, six diamonds were put -on a photographic plate and kept in the dark for a few hours. All -showed radio-activity by darkening the sensitive plate, some being -more-active than others. Like the green tint, the radio-activity -persists after drastic treatment. To me this proves that -radio-activity does not merely consist in the adhesion of electrons -or emanations given off by radium to the surface of an adjacent -body, but the property is one involving layers below the surface, -and like the alteration of tint, is probably closely connected with -the intense molecular excitement the stone had experienced during -its twelve months’ burial in radium bromide. - -A diamond that had been coloured by radium, and had acquired -strong radio-active properties, was slowly heated to dull redness -in a dark room. Just before visibility a faint phosphorescence -spread over the stone. On cooling and examining the diamond it was -found that neither the colour nor the radio-activity had suffered -appreciably. - - -BOILING- AND MELTING-POINT OF CARBON - -On the average the critical point of a substance is 1·5 times its -absolute boiling-point. Therefore the critical point of carbon -should be about 5800° Ab. But the absolute critical temperature -divided by the critical pressure is for all the elements so far -examined never less than 2·5; this being about the value Sir James -Dewar finds for hydrogen. So that, accepting this, we get the -maximum critical pressure as follows, viz. 2320 atmospheres: - - (5800° Ab.)/CrP = 2.5, or CrP = (5800 Ab.)/2.5, - or 2320 atmospheres. - -Carbon and arsenic are the only two elements that have a -melting-point above the boiling-point; and among compounds carbonic -acid and fluoride of silicium are the only other bodies with -similar properties. Now the melting-point of arsenic is about -1·2 times its absolute boiling-point. With carbonic acid and -fluoride of silicium the melting-points are about 1·1 times their -boiling-points. Applying these ratios to carbon, we find that its -melting-point would be about 4400°. - -Therefore, assuming the following data: - - Boiling-point 3870° Ab. - Melting-point 4400° - Critical temperature 5800° - Critical pressure 2320 Ats. - -the Rankine or Van der Waals formula, calculated from the -boiling-point and critical data, would be as follows: - - log. P = 10·11 - 39120/T, - -and this gives for a temperature of 4400° Ab. a pressure of 16·6 -Ats. as the melting-point pressure. The results of the formula are -given in the form of a table: - - Temperature Pressure - Ab. Ats. - 3870° 1·00 Boiling-point. - 4000° 2·14 - 4200° 6·25 - 4400° 16·6 Melting-point. - 4600° 40·4 - 4800° 91·2 - 5000° 193 - 5200° 386 - 5400° 735 - 5600° 1330 - 5800° 2320 Critical point (15 tons per square inch). - -[Illustration: FIG. 19. CURVE OF VAPOUR PRESSURE OF CARBON] - -If, then, we may reason from these rough estimates, above a -temperature of 5800° Ab. no amount of pressure will cause carbon -vapour to assume liquid form, whilst at 4400° Ab. a pressure -of above 17 atmospheres would suffice to liquefy some of it. -Between these extremes the curve of vapour pressure is assumed to -be logarithmic, as represented in the accompanying diagram. The -constant 39120 which occurs in the logarithmic formula enables -us to calculate the latent heat of evaporation. If we assume the -vapour density to be normal, or the molecule in vapour as C_{2}, -then the heat of volatilisation of 12 grms. of carbon would -be 90,000 calories; or, if the vapour is a condensed molecule -like C_{6}, then the 12 grms. would need 30,000 calories. In the -latter case the evaporation of 1 grm. of carbon would require -2500 calories, whereas a substance like zinc needs only about 400 -calories. - - - - -CHAPTER IX - -GENESIS OF THE DIAMOND - - -Speculations as to the probable origin of the diamond have been -greatly forwarded by patient research, and particularly by improved -means of obtaining high temperatures, an advance we owe principally -to the researches of the late Professor Moissan. - -Until recent years carbon was considered absolutely non-volatile -and infusible; but the enormous temperatures placed at the disposal -of experimentalists by the introduction of electricity show -that, instead of breaking rules, carbon obeys the same laws that -govern other bodies. It volatilises at the ordinary pressure at a -temperature of about 3600° C., and passes from the solid to the -gaseous state without liquefying. It has been found that other -bodies, such as arsenic, which volatilise without liquefying at -the ordinary pressure, will easily liquefy if pressure is added to -temperature. It naturally follows that if along with the requisite -temperature sufficient pressure is applied, liquefaction of carbon -will take place, when on cooling it will crystallise. But carbon at -high temperatures is a most energetic chemical agent, and if it can -get hold of oxygen from the atmosphere or any compound containing -it, it will oxidise and fly off in the form of carbonic acid. Heat -and pressure therefore are of no avail unless the carbon can be -kept inert. - -It has long been known that iron, when melted, dissolves carbon, -and on cooling liberates it in the form of graphite. Moissan -discovered that several other metals, especially silver, have -similar properties; but iron is the best solvent for carbon. The -quantity of carbon entering into solution increases with the -temperature. - -[Illustration: FIG. 20. MOISSAN’S ELECTRIC FURNACE. - - To face p. 116.] - -For the artificial manufacture of diamond the first necessity is -to select pure iron--free from sulphur, silicon, phosphorus, -etc.--and to pack it in a carbon crucible with pure charcoal from -sugar. The crucible is then put into the body of the electric -furnace and a powerful arc formed close above it between carbon -poles, utilising a current of 700 ampères at 40 volts pressure -(Fig. 20). The iron rapidly melts and saturates itself with carbon. -After a few minutes’ heating to a temperature above 4000° C.--a -temperature at which the iron melts like wax and volatilises in -clouds--the current is stopped and the dazzling fiery crucible is -plunged beneath the surface of cold water, where it is held till -it sinks below a red heat. As is well known, iron increases in -volume at the moment of passing from the liquid to the solid state. -The sudden cooling solidifies the outer layer of iron and holds -the inner molten mass in a tight grip. The expansion of the inner -liquid on solidifying produces an enormous pressure, and under the -stress of this pressure the dissolved carbon separates out in -transparent forms--minutely microscopic, it is true--all the same -veritable diamonds, with crystalline form and appearance, colour, -hardness, and action on light, the same as the natural gem. - -Now commences the tedious part of the process. The metallic ingot -is attacked with hot nitro-hydrochloric acid until no more iron -is dissolved. The bulky residue consists chiefly of graphite, -together with translucent chestnut-coloured flakes of carbon, -black opaque carbon of a density of from 3·0 to 3·5 and hard as -diamonds--black diamonds or carbonado, in fact--and a small portion -of transparent, colourless diamonds showing crystalline structure. -Besides these there may be carbide of silicon and corundum, arising -from impurities in the materials employed. - -The residue is first heated for some hours with strong sulphuric -acid at the boiling-point, with the cautious addition of powdered -nitre. It is then well washed and for two days allowed to soak in -strong hydrofluoric acid in cold, then in boiling acid. After this -treatment the soft graphite disappears, and most, if not all, the -silicon compounds have been destroyed. Hot sulphuric acid is again -applied to destroy the fluorides, and the residue, well washed, is -attacked with a mixture of the strongest nitric acid and powdered -potassium chlorate, kept warm--but not above 60° C., to avoid -explosions. This treatment must be repeated six or eight times, -when all the hard graphite will gradually be dissolved and little -else left but graphitic oxide, diamond, and the harder carbonado -and boart. The residue is fused for an hour in fluorhydrate or -fluoride of potassium, then boiled out in water and again heated -in sulphuric acid. The well-washed grains which resist this -energetic treatment are dried, carefully deposited on a slide, and -examined under the microscope. Along with numerous pieces of black -diamond are seen transparent, colourless pieces, some amorphous, -others with a crystalline appearance. Fig. 21 B shows one of these -crystalline fragments. Although many fragments of crystals occur, -it is remarkable I have never seen a complete crystal. All appear -shattered, as if on being liberated from the intense pressure -under which they were formed they burst asunder. I have singular -evidence of this phenomenon. A fine piece of artificial diamond, -carefully mounted by me on a microscopic slide, exploded during -the night and covered the slide with fragments. Moissan’s crystals -of artificial diamond sometimes broke a few weeks after their -preparation, and some of the diamonds which cracked weeks or even -months after their preparation showed fissures covered with minute -cubes. I have explained that this bursting paroxysm is not unknown -at the Kimberley mines. So far, all such artificial diamonds are -microscopic. The largest artificial diamond is less than one -millimetre across. - -[Illustration: FIG. 21. ARTIFICIAL DIAMOND MADE BY THE AUTHOR FROM -MOLTEN IRON.] - -[Illustration: FIG. 22. MOISSAN’S ARTIFICIAL DIAMONDS. - - To face p. 120.] - -These laboratory diamonds burn in the air before the blowpipe to -carbonic acid. In lustre, crystalline form, optical properties, -density, and hardness they are identical with the natural stone. - -In several cases Moissan separated ten to fifteen microscopic -diamonds from a single ingot. The larger of these are about 0·75 -mm. long, the octahedra being 0·2 mm. - -The accompanying illustrations (Fig. 22) are copied from drawings -in Moissan’s book _Le Four Electrique_. - -Along with carbon, molten iron dissolves other bodies which possess -tinctorial powers. We know of blue, green, pink, yellow, and orange -diamonds. One batch of iron might contain an impurity colouring the -stones blue, another lot would tend towards the formation of pink -stones, another of green, and so on. Cobalt, nickel, chromium, and -manganese, all metals present in the blue ground, would produce -these colours. - - -A NEW FORMATION OF DIAMOND - -I have long speculated as to the possibility of obtaining -artificially such pressures and temperatures as would fulfil the -above conditions. In their researches on the gases from fired -gunpowder and cordite, Sir Frederick Abel and Sir Andrew Noble -obtained in closed steel cylinders pressures as great as 95 tons -to the square inch, and temperatures as high as 4000° C. According -to a paper recently communicated to the Royal Society, Sir Andrew -Noble, exploding cordite in closed vessels, has obtained a pressure -of 8000 atmospheres, or 50 tons per square inch, with a temperature -reaching in all probability 5400° Ab. - -Here, then, we have conditions favourable for the liquefaction of -carbon, and were the time of explosion sufficient to allow the -reactions to take place, we should certainly expect to get the -liquid carbon to solidify in the crystalline state.[7] - -By the kindness of Sir Andrew Noble I have been enabled to work -upon some of the residues obtained in closed vessels after -explosions, and I have submitted them to the same treatment that -the granulated iron had gone through. After weeks of patient toil -I removed the amorphous carbon, the graphite, the silica,[8] and -other constituents of the ash of cordite, and obtained a residue -among which, under the microscope, crystalline particles could be -distinguished. Some of these particles, from their crystalline -appearance and double refraction, were silicon carbide; others -were probably diamonds. The whole residue was dried and fused at a -good red heat in an excess of potassium bifluoride, to which was -added, during fusion, 5 per cent of nitre. (Previous experiments -had shown me that this mixture readily attacked and dissolved -silicon carbide; unfortunately it also attacks diamond to a slight -degree.) All the operations of washing and acid treatment were -performed in a large platinum crucible by decantation (except the -preliminary attack with nitric acid and potassium chlorate, when a -hard glass vessel was used); the final result was washed into a -shallow watch-glass and the selection made under the microscope. -The residue, after thorough washing and then heating in fuming -sulphuric acid, was washed, and the largest crystalline particles -picked out and mounted. - -From the treatment the residual crystals had undergone, chemists -will agree with me that diamonds only could stand such an ordeal; -on submitting them to skilled crystallographic authorities my -opinion is confirmed. Speaking of the largest crystal, one eminent -authority calls it “a diamond showing octahedral planes with -dark boundaries due to high refracting index.” After careful -examination, another authority writes of the same crystal diamond, -“I think one may safely say that the position and angles of its -faces, and of its cleavages, the absence of birefringence, and the -high refractive index are all compatible with the properties of the -diamond crystallising in the form of an octahedron. Others of the -remaining crystals, which show a similar high refractive index, -appeared to me to present the same features.” - -It would have been more conclusive had I been able to get further -evidence as to the density and hardness of the crystals; but from -what I have already said I think there is no doubt that in these -closed vessel explosions we have another method of producing the -diamond artificially. - - - - -CHAPTER X - -THE NATURAL FORMATION OF THE DIAMOND - - -An hypothesis is of little value if it only elucidates half a -problem. Let us see how far we can follow out the ferric hypothesis -to explain the volcanic pipes. In the first place we must remember -these so-called volcanic vents are admittedly not filled with the -eruptive rocks, scoriaceous fragments, etc., constituting the -ordinary contents of volcanic ducts. - -Certain artificial diamonds present the appearance of an elongated -drop. I have seen diamonds which have exactly the appearance of -drops of liquid separated in a pasty condition and crystallised -on cooling. Diamonds are sometimes found with little appearance -of crystallisation, but with rounded forms similar to those -which a liquid might assume if kept in the midst of another -liquid with which it would not mix. Other drops of liquid carbon -retained for sufficient time above their melting-point would -coalesce with adjacent drops, and on slow cooling would separate -in the form of large perfect crystals. Two drops, joining after -incipient crystallisation, might assume the not uncommon form of -interpenetrating twin crystals. - -Many circumstances point to the conclusion that the diamond of -the chemist and the diamond of the mine are strangely akin as to -origin. It is evident that the diamond has not been formed _in -situ_ in the blue ground. The genesis must have taken place at vast -depths under enormous pressure. The explosion of large diamonds -on coming to the surface shows extreme tension. More diamonds are -found in fragments and splinters than in perfect crystals; and it -is noteworthy that although these splinters and fragments must be -derived from the breaking up of a large crystal, yet in only one -instance have pieces been found which could be fitted together, and -these occurred at different levels. Does not this fact point to the -conclusion that the blue ground is not their true matrix? Nature -does not make fragments of crystals. As the edges of the crystals -are still sharp and unabraded, the _locus_ of formation cannot have -been very distant from the present sites. There were probably many -sites of crystallisation differing in place and time, or we should -not see such distinctive characters in the gems from different -mines, nor indeed in the diamonds from different parts of the same -mine. - -I start with the reasonable supposition that at a sufficient -depth[9] there were masses of molten iron at great pressure and -high temperature, holding carbon in solution, ready to crystallise -out on cooling. Far back in time the cooling from above caused -cracks in superjacent strata through which water[10] found its way. -On reaching the incandescent iron the water would be converted -into gas, and this gas would rapidly disintegrate and erode the -channels through which it passed, grooving a passage more and more -vertical in the necessity to find the quickest vent to the surface. -But steam in the presence of molten or even red-hot iron liberates -large volumes of hydrogen gas, together with less quantities of -hydrocarbons[11] of all kinds--liquid, gaseous, and solid. Erosion -commenced by steam would be continued by the other gases; it would -be easy for pipes, large as any found in South Africa, to be -scored out in this manner. - -Sir Andrew Noble has shown that when the screw stopper of his -steel cylinders in which gunpowder explodes under pressure is not -absolutely perfect, gas escapes with a rush so overpowering and a -temperature so high as to score a wide channel in the metal. To -illustrate my argument Sir Andrew Noble has been kind enough to try -a special experiment. Through a cylinder of granite he drilled a -hole 0·2 inch diameter, the size of a small vent. This was made the -stopper of an explosion chamber, in which a quantity of cordite was -fired, the gases escaping through the granite vent. The pressure -was about 1500 atmospheres and the whole time of escape was less -than half a second. The erosion produced by the escaping gases and -by the heat of friction scored out a channel more than half an -inch diameter and melted the granite along the course. If steel -and granite are thus vulnerable at comparatively moderate gaseous -pressure, it is easy to imagine the destructive upburst of hydrogen -and water-gas, grooving for itself a channel in the diabase and -quartzite, tearing fragments from resisting rocks, covering the -country with debris, and finally, at the subsidence of the great -rush, filling the self-made pipe with a water-borne magma in which -rocks, minerals, iron oxide, shale, petroleum, and diamonds are -violently churned in a veritable witch’s cauldron! As the heat -abated the water vapour would gradually give place to hot water, -which, forced through the magma, would change some of the mineral -fragments into the existing forms of to-day. - -Each outbreak would form a dome-shaped hill; the eroding agency of -water and ice would plane these eminences until all traces of the -original pipes were lost. - -Actions such as I have described need not have taken place -simultaneously. As there must have been many molten masses -of iron with variable contents of carbon, different kinds of -colouring matter, solidifying with varying degrees of rapidity, -and coming in contact with water at intervals throughout long -periods of geological time--so must there have been many outbursts -and upheavals, giving rise to pipes containing diamonds. And -these diamonds, by sparseness of distribution, crystalline -character, difference of tint, purity of colour, varying hardness, -brittleness, and state of tension, have the story of their origin -impressed upon them, engraved by natural forces--a story which -future generations of scientific men may be able to interpret with -greater precision than is possible to-day. - - - - -CHAPTER XI - -METEORIC DIAMONDS - - -Sensational as is the story of the diamond industry in South -Africa, quite another aspect fixes the attention of the chemist. -The diamonds come out of the mines, but how did they get in? How -were they formed? What is their origin? - -Gardner Williams, who knows more about diamonds than any man -living, is little inclined to indulge in speculation. In his -fascinating book he frankly says: - -“I have been frequently asked, ‘What is your theory of the original -crystallisation of the diamond?’ and the answer has always been, ‘I -have none; for after seventeen years of thoughtful study, coupled -with practical research, I find that it is easier to “drive a coach -and four” through most theories that have been propounded than to -suggest one which would be based on any non-assailable data.’ -All that can be said is that in some unknown manner carbon, which -existed deep down in the internal regions of the earth, was changed -from its black and uninviting appearance to the most beautiful gem -which ever saw the light of day.” - -Another diamond theory appeals to the imagination. It is said -the diamond is a gift from Heaven, conveyed to earth in meteoric -showers. The suggestion, I believe, was first broached by A. -Meydenbauer,[12] who says, “The diamond can only be of cosmic -origin, having fallen as a meteorite at later periods of the -earth’s formation. The available localities of the diamond contain -the residues of not very compact meteoric masses which may, -perhaps, have fallen in prehistoric ages, and which have penetrated -more or less deeply, according to the more or less resistant -character of the surface where they fell. Their remains are -crumbling away on exposure to the air and sun, and the rain has -long ago washed away all prominent masses. The enclosed diamonds -have remained scattered in the river beds, while the fine light -matrix has been swept away.” - -According to this hypothesis, the so-called volcanic pipes are -simply holes bored in the solid earth by the impact of monstrous -meteors--the larger masses boring the holes, while the smaller -masses, disintegrating in their fall, distributed diamonds -broadcast. Bizarre as such a theory appears, I am bound to say -there are many circumstances which show that the notion of the -heavens raining diamonds is not impossible. - -The most striking confirmation of the meteoric theory comes from -Arizona. Here, on a broad open plain, over an area about five -miles in diameter, have been scattered one or two thousand masses -of metallic iron, the fragments varying in weight from half a ton -to a fraction of an ounce. There is no doubt these masses formed -part of a meteoric shower, although no record exists as to when -the fall took place. Curiously enough, near the centre, where most -of the meteorites have been found, is a crater with raised edges -three-quarters of a mile in diameter and about 600 feet deep, -bearing exactly the appearance which would be produced had a mighty -mass of iron struck the ground and buried itself deep under the -surface. Altogether, ten tons of this iron have been collected, and -specimens of the Canyon Diablo meteorite are in most collectors’ -cabinets. - -An ardent mineralogist--the late Dr. Foote--cutting a section of -this meteorite, found the tools were injured by something vastly -harder than metallic iron. He examined the specimen chemically, -and soon after announced to the scientific world that the Canyon -Diablo meteorite contained black and transparent diamonds. This -startling discovery was afterwards verified by Professors Moissan -and Friedel, and Moissan, working on 183 kilogrammes of the Canyon -Diablo meteorite, has recently found smooth black diamonds and -transparent diamonds in the form of octahedra with rounded edges, -together with green, hexagonal crystals of carbon silicide. The -presence of carbon silicide in the meteorite shows that it must at -some time have experienced the temperature of the electric furnace. -Since this revelation the search for diamonds in meteorites has -occupied the attention of chemists all over the world. - -Fig. 23 A, C, and D, are reproductions of photographs of true -diamonds I myself have extracted from the Canyon Diablo meteorite. - -[Illustration: FIG. 23. DIAMONDS FROM CANYON DIABLO METEORITE. - - To face p. 138.] - -Under atmospheric influences the iron would rapidly oxidise and -rust away, colouring the adjacent soil with red oxide of iron. -The meteoric diamonds would be unaffected and left on the surface -of the soil, to be found haphazard when oxidation had removed the -last proof of their celestial origin. That there are still lumps of -iron left at Arizona is merely due to the extreme dryness of the -climate and the comparatively short time that the iron has been on -our planet. We are here witnesses to the course of an event which -may have happened in geologic times anywhere on the earth’s surface. - -Although in Arizona diamonds have fallen from the skies, -confounding our senses, this descent of precious stones is what may -be called a freak of nature rather than a normal occurrence. To -the modern student of science there is no great difference between -the composition of our earth and that of extra-terrestrial masses. -The mineral peridot is a constant extra-terrestrial visitor, -present in most meteorites. And yet no one doubts that peridot -is also a true constituent of rocks formed on this earth. The -spectroscope reveals that the elementary composition of the stars -and the earth are pretty much the same; and the spectroscope also -shows that meteorites have as much of earth as of heaven in their -composition. Indeed, not only are the selfsame elements present in -meteorites, but they are combined in the same way to form the same -minerals as in the crust of the earth. - -It is certain from observations I have made, corroborated -by experience gained in the laboratory, that iron at a high -temperature and under great pressure--conditions existent at great -depths below the surface of the earth--acts as the long-sought -solvent for carbon, and will allow it to crystallise out in the -form of diamond. But it is also certain, from the evidence afforded -by the Arizona and other meteorites, that similar conditions have -existed among bodies in space, and that on more than one occasion a -meteorite freighted with jewels has fallen as a star from the sky. - - - - -INDEX - - - Able, Sir F., closed vessel experiments, 122 - - Absorption spectrum of diamond, 101 - - Aliwal North, 6 - - Alluvial deposits of diamonds, 9 - - Amygdaloidal trap, 10 - - Arizona meteor, 136 - - Arkansas, diamonds in, 2 - - Ash of diamond, 82, 89 - - Augite, 20 - - Automatic diamond collector, 56 - - - Barytes, 71 - -- density of, 93 - - Basalt, 15 - - Basutos, 12, 39 - - Bechuanas, 12, 39 - - Beryl, density of, 93 - -- refractive index of, 103 - - Biotite, 20 - - Blackening of diamonds, 98 - - Blue ground, 10, 47 - -- -- diamantiferous, 18, 19 - - Boart, 81, - -- combustion temperature of, 90 - -- density of, 93 - - Boiling-point of carbon, 110 - - Bonney, Rev. Professor, 67 - - Boyle on the diamond, 100 - - Brazil, diamonds in, 4 - - Breakwater, Cape Town, 36 - - Breccia, diamantiferous, 19 - - Brilliant cut diamond, 102 - - British Association in South Africa, 7 - - British Guiana, diamonds in, 4 - - Bronzite, 20, 71 - -- hydrated, 19 - - Bultfontein Mine, 14 - -- -- characteristics of diamond from, 64 - - Bursting of diamonds, 105 - - - Calcite, 20, 97 - - California, diamonds in, 3 - - Canada balsam, refractive index of, 103 - - Canyon Diablo meteorite, 136 - - Cape Colony, 5 - - Cape Town, 5 - - Carat, equivalent in grains, 69 - - Carbon, boiling and melting point of, 110 - -- combustion temperature of, 90 - -- critical point of, 110 - -- density of, 93 - -- dissolved in iron, 116 - -- volatilisation of, 115 - - Carbonado, 81 - -- density of, 93 - - Characteristics of diamonds from the different mines, 64 - - Chemical properties of diamond, 89 - - Chromate of lead, refractive index of, 103 - - Chrome diopside, 71 - -- iron, 20 - -- -- ore, 71 - -- -- -- density of, 93 - - Chromite, 20 - - Classification of rough diamonds, 73 - - Cleavage of diamonds, 78 - - Coke, density of, 93 - - Colesberg Kopje, 26 - - Collecting the gems, 55 - - Coloured diamonds, 62, 82 - - Combustion of diamond, 89 - -- temperatures of diamond, boart, graphite, and carbon, 90 - - “Comet” crushers, 49 - - Compound system, 36, 37 - - Concentrating and washing machinery, 49 - - Convict labourers, 71 - - Cordite, diamond from explosion of, 123 - - Corundum, 20 - -- density of, 93 - - Cradock, 6 - - Craters or pipes, 18 - - Crown glass, refractive index of, 103 - - Crusher, “Comet,” 49 - - Crystallisation of diamond, 86 - - Crystals, octahedra, of diamond, 63, 86 - - Cullinan diamond, 15, 76, 80, 104 - - - Dallas, Captain, 40 - - De Beers Consolidated Mines, 7, 33 - -- -- floors at Kenilworth, 47 - -- -- Mine, 14, 24, 34 - -- -- -- characteristics of diamonds from, 64 - -- -- strong-room, 74 - - Delhi diamond, 107 - - Density of diamond, 57, 93 - -- of graphite, 83, 93 - -- of stones accompanying diamond, 70, 71, 93, 95 - - Depositing floors, 46 - - Dewar, Sir J., conversion of diamond into graphite, 123 - - Diabase, olivine, 16 - - Diallage, 20 - - Diamond, absorption spectrum of, 101 - -- and polarised light, 104 - -- a new formation of, 122 - -- ash of, 82, 89 - -- collector, automatic, 56 - -- combustion of, 89 - -- -- temperature of, 90 - -- converted into graphite, 100 - -- density of, 57, 93 - -- etched by burning, 88 - -- explosion of, 120 - -- genesis of the, 115 - -- in meteors, 134 - -- in Röntgen rays, 107 - -- matrix of, 67 - -- natural formation of, 127 - -- Office at Kimberley, 73 - -- physical and chemical properties of, 89 - -- pipes or craters, 18 - -- radio-activity of, 109 - -- refractive index of, 103 - -- Trade Act, 36 - -- triangular markings on, 87 - -- tribo-luminescence of, 100 - - Diamonds, coloured or fancy, 62, 82 - -- Maskelyne on, 1 - -- noteworthy, 76 - -- phosphorescence of, 96 - -- produced, weight, value of, 35 - -- yield of, from De Beers, 60 - - Drift, diamonds from the, 12 - - Duke of Tuscany diamond, 80 - - Dutch boart, or zircon, 59 - - Dutoitspan Mine, 14, 23 - -- -- characteristics of diamonds from, 64 - - - Eclogite, 20 - -- containing diamonds, 67 - - Electrons, bombardment by, 98 - - Emerald, refractive index of, 103 - - Empress Eugenie diamond, 80 - - Enstatite, 20 - - Explosion of diamonds, 120 - - Excelsior diamond, 80 - - - Fancy stones, 62 - - Fingoes, 39 - - Flint glass, refractive index of, 103 - - “Floating Reef,” 21 - - Floors, depositing, 46 - - Fluor-spar, refractive index of, 103 - - Formation, new, of diamond, 122 - - Fort Beaufort, 6 - - Franklinite, 97 - - Frank Smith Mine, 15 - -- -- -- characteristics of diamonds from, 66 - - Fraserburg, 6 - - - Garnet, 20, 70 - -- density of, 93 - - Genesis of the diamond, 115 - - “Golden fancies,” 65 - - Granite, 18 - -- density of, 93 - - Graphite, 81, 83 - -- combustion temperature of, 90 - -- conversion of diamond into, 100 - -- density of, 93 - -- diamonds coated with, 99 - - Graphitic oxide, 83, 93 - - Grease, collecting diamonds by aid of, 57 - - - Hard blue ground, 47 - - Hardness of diamond, 90 - - Haulage system, 46 - - Hexakis-octahedron crystal, 86 - - Hope blue diamond, the, 80 - - Hornblende, 71 - -- density of, 93 - - - Iceland spar, refractive index of, 103 - - Ice, refractive index of, 103 - - I.D.B. laws (Illicit Diamond Buying), 36 - - Ilmenite, 20 - - India, diamonds in, 4 - - Inverel diamonds, 91 - - Internal strain in diamonds, 104 - - Iron a solvent for carbon, 116 - -- ore, density of, 93 - -- pyrites, 20 - - - Jagersfontein diamond, 79 - -- Mine, 14 - -- -- characteristics of diamonds from, 68 - - Jeffreysite, 20 - - - Kafirs, 42 - - Kamfersdam Mine, 15 - -- -- characteristics of diamonds from, 66 - - Kenilworth depositing floors, 47 - - Kimberley, 6 - -- blue ground, 10 - -- mines, 14, 23, 34 - -- Mine in old days, 25 - -- -- at the present day, 34 - -- -- characteristics of diamonds from, 63 - -- shales, 15 - -- West Mine, 15 - -- -- -- characteristics of diamonds from, 66 - - Kirsten’s automatic diamond collector, 57 - - Klipdam, 8, 23 - - Koffyfontein Mine, 14 - - Koh-i-noor diamond, 80 - -- hardness of, 91 - - Kyanite, 20, 71 - - - Lamp, ultra-violet, 97 - - Leicester Mine, 15, 23 - -- -- characteristics of diamonds from, 67 - - Loterie d’Angleterre diamond, 80 - - Lustre of rough diamonds, 56 - - - Machinery for washing and concentrating, 49 - - Macles, 86 - - Magnetite, 20, 71 - -- density of, 93 - - Maskelyne on diamonds, 1 - - Matabele, 12, 39 - - Matrix of diamond, 67 - - Melaphyre, 10, 16 - - Melting-point of carbon, 110 - - Meteor, Canyon Diablo, 136 - - Meteoric diamonds, 134 - - Meydenbauer on meteoric diamonds, 135 - - Mica, 20, 71 - -- density of, 93 - - Moissan’s experiments on the genesis of diamond, 115 - - Mud volcano, 24 - - - Nassak diamond, 80 - - Natal, coal in, 6 - - Natural formation of diamond, 127 - - Newlands Mine, 15 - -- -- characteristics of diamonds from, 67 - - New Rush diggings, 26 - - Nizam of Hyderabad diamond, 80 - - Noble, Sir A., experiments, 122, 131 - - Noteworthy diamonds, 76 - - - Octahedral crystals of diamond, 63, 86 - - Olivine, 20 - -- diabase, 16 - - Orange River Colony, coal in, 6 - -- -- -- diamonds in, 14 - - Orloff diamond, 80 - - - Pasha of Egypt diamond, 80 - - Paterson, Mr., description of Kimberley in old days, 25 - - Peridot, 20, 139 - - Peridotite, 3 - - Perofskite, 20 - - Phosphorescence of diamonds, 96 - - Phosphorus, refractive index of, 103 - - Physical properties of diamond, 89 - - Picking tables, 51 - - Pipes or craters, 18 - - Pitt diamond, 80 - - Polarised light and diamond, 104 - - Pole Star diamond, 80 - - Pondos, 39, 42 - - Premier Mine, 15, 76 - - Prodigious diamonds, 76 - - Pseudobrookite, 20 - - Pulsator, 52 - - Pyrope, 70 - - - Quartzite, 16, 20 - -- density of, 93 - -- refractive index of, 103 - - - Radio-activity of diamond, 109 - - Radium, action on diamond, 108 - - “Reef,” 21 - - Refractive indices, 103 - - Refractivity of diamond, 102 - - Regent diamond, 80 - - Reunert, Mr., description of Kimberley Mine, 30 - - Rhodes, Cecil John, 34 - - River washings, 7 - - Rock shafts, 43 - - Röntgen rays, diamond in, 107 - - Ruby, refractive index of, 103 - - Rutile, 20 - - - Sahlite, 20 - - Sancy diamond, 80 - - Savings of the native workmen, 41 - - Scalenohedron diamond crystal, 86 - - Serpentine, 19 - - Shafts, rock, 43 - - Shah diamond, 80 - - Shales, Kimberley, 15 - - Shangains, 39 - - Shells in blue ground, 21 - - Shot boart, 81 - - Silver and thallium, nitrate of, 94 - - Smaragdite, 20 - - Soft blue ground, 47 - - Sorting the diamantiferous gravel, 55 - - Specific gravity, _see_ Density - - Spectrum, absorption of diamond, 101 - - Sphalerite, 100 - - Spinthariscope, 108 - - Sprat’s _History of the Royal Society_, 1 - - Sprouting graphite, 84 - - Star of the South diamond, 80 - - Stones other than diamonds, 70, 71, 93, 95 - - Strain, internal, in diamonds, 104 - - Sulphur, refractive index of, 103 - - Swazis, 39 - - - Ultra-violet lamp to show phosphorescence, 97 - - Underground workings, 43 - - United States, diamonds in, 2 - - - Vaalite, 20 - - Vaal River, 8, 16 - - Valuators, 73 - - Value of diamonds per carat, 12, 69 - - Value of diamonds, progressive increase in, 69 - - Vermiculite, 20 - - Volatilisation of carbon, 115 - - Volcanic necks, 18 - - Volcano, mud, 24 - - - Wages, scale of, 35 - - Washing and concentrating machinery, 49 - - Wesselton Mine, 14, 15, 23, 35 - -- -- characteristics of diamonds from, 65 - - Willemite, 97 - - Wollastonite, 20 - - Workings, underground, 43 - - - Yellow ground, diamantiferous, 19 - - Yield of diamonds, annual, 60 - -- -- -- total, 35 - -- falls off with depth, 68 - -- per load of blue ground, 62 - - - Zimbabwe ruins, 40 - - Zircon, 20, 59, 71 - -- density of, 93 - - Zulus, 12, 39, 40 - - -W. BRENDON AND SON, LTD., PRINTERS, PLYMOUTH - - - - -FOOTNOTES: - -[1] _Chemical News_, Vol. I, p. 208. - -[2] Mr. Paterson called “limey stuff” what is now termed “blue -ground.” It was also formerly called “marl stuff,” “blue stuff,” -and “blue clay.” - -[3] The original name for the Kimberley Mine. It was also sometimes -known as “Colesberg Kopje.” - -[4] _Diamonds and Gold in South Africa._ By T. Reunert. -Johannesburg, 1893. - -[5] According to Gardner Williams the South African carat is -equivalent to 3·174 grains. In Latimer Clark’s _Dictionary of -Metric and other Useful Measures_ the diamond carat is given as -equal to 3·1683 grains = 0·2053 gramme = 4 diamond grains; 1 -diamond grain = 0·792 troy grain; 151·5 diamond carats = 1 ounce -troy. - -Webster’s _International Dictionary_ gives the diamond carat as -equal to 3⅕ troy grains. - -_The Oxford English Dictionary_ says the carat was originally 1/144 -of an ounce, or 3⅓ grains, but now equal to about 3⅕ grains, though -varying slightly with time and place. - -The _Century Dictionary_ says the diamond carat is equal to about -3⅙ troy grains, and adds that in 1877 the weight of the carat was -fixed by a syndicate of London, Paris, and Amsterdam jewellers at -205 milligrammes. This would make the carat equal to 3·163 troy -grains. A law has been passed in France ordaining that in the -purchase or sale of diamonds and other precious stones the term -“metric carat” shall be employed to designate a weight of 200 -milligrammes (3·086 grains troy), and prohibiting the use of the -word carat to designate any other weight. - -[6] Artificial tribo-luminescent sphalerite:-- - - Zinc carbonate 100 parts - Flower of sulphur 30 ” - Manganese sulphate ½ per cent. - -Mix with distilled water and dry at a gentle heat. Put in luted -crucible and keep at a bright red heat for from two to three hours. - -[7] Sir James Dewar, in a Friday evening discourse at the Royal -Institution in 1880, showed an experiment proving that the -temperature of the interior of a carbon tube heated by an outside -electric arc was higher than that of the oxy-hydrogen flame. He -placed a few small crystals of diamond in the carbon tube, and, -maintaining a current of hydrogen to prevent oxidation, raised the -temperature of the tube in an electric furnace to that of the arc. -In a few minutes the diamond was transformed into graphite. At -first sight this would seem to show that diamond cannot be formed -at temperatures above that of the arc. It is probable, however, for -reasons given above, that at exceedingly high pressures the result -would be different. - -[8] The silica was in the form of spheres, perfectly shaped and -transparent, mostly colourless, but among them several of a ruby -colour. When 5 per cent of silica was added to cordite, the residue -of the closed vessel explosion contained a much larger quantity of -these spheres. - -[9] A pressure of fifteen tons on the square inch would exist not -many miles beneath the surface of the earth. - -[10] There are abundant signs that a considerable portion of this -part of Africa was once under water, and a fresh-water shell has -been found in apparently undisturbed blue ground at Kimberley. - -[11] The water sunk in wells close to the Kimberley mine is -sometimes impregnated with paraffin, and Sir H. Roscoe extracted a -solid hydrocarbon from the “blue ground.” - -[12] _Chemical News_, vol. lxi, p. 209, 1890. - - - - - TRANSCRIBER’S NOTE - - Obvious typographical errors and punctuation errors have been - corrected after careful comparison with other occurrences within - the text and consultation of external sources. - - All misspellings in the text, and inconsistent or archaic usage, - have been retained: for example, unfrequent; clayey; friable; - slaty; imbed; stoped; peculation; situate. - - In the Table of Contents, the Index page number ‘145’ has been - replaced by ‘141’. - - In the Index, ‘Colesberg Copje’ has been replaced by - ‘Colesberg Kopje’, and ‘DeBeers’ has been replaced by - ‘De Beers’. - - - - - -End of the Project Gutenberg EBook of Diamonds, by William Crookes - -*** END OF THIS PROJECT GUTENBERG EBOOK DIAMONDS *** - -***** This file should be named 61096-0.txt or 61096-0.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/6/1/0/9/61096/ - -Produced by deaurider, John Campbell and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. 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You may copy it, give it away or re-use it under the terms of -the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: Diamonds - -Author: William Crookes - -Release Date: January 4, 2020 [EBook #61096] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK DIAMONDS *** - - - - -Produced by deaurider, John Campbell and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - - - - - - -</pre> - - - -<div class="transnote"> -<p><strong>TRANSCRIBER’S NOTE</strong></p> - -<p>Footnote anchors are denoted by <span class="fnanchor">[number]</span>, and the footnotes have been -placed at the end of the book.</p> - -<p>Basic fractions are displayed as ½ ⅓ ¼ etc; other fractions are shown -in the form <sup>a</sup>/<sub>b</sub>, for example <sup>1</sup>/<sub>144</sub> or <sup>5</sup>/<sub>12</sub>.</p> - -<p>Some minor changes to the text are noted at the <a href="#TN">end of the book.</a></p> - -</div> - - -<hr class="chap pg-brk" /> -<p class="p6" /> - -<p class="pfs150"><span class="smcap">Harper’s Library</span> <em>of</em> <span class="smcap">Living Thought</span></p> - -<p class="p4" /> - -<div class="figcenter"> -<img src="images/i_f001.jpg" width="230" alt="" /> -</div> - -<p class="p4" /> - - -<hr class="chap pg-brk" /> - -<div class="figcenter"> -<img src="images/i_f003.jpg" width="525" alt="" /> -<div class="captionx"> -DIAMONDS<br /> -<br /> -BY SIR WILLIAM CROOKES<br /> -<br /> -<span class="lsp2">HARPER &<br /> -BROTHERS</span><br /> -<span class="fs90">LONDON & NEW YORK</span> -</div> -</div> - - -<hr class="chap pg-brk" /> -<p class="p4" /> - -<div class="figcenter"> -<a name="FP" id="FP"></a> -<img src="images/i_f006.jpg" width="650" alt="" /> -<div class="caption"> -THE CULLINAN DIAMOND.<br /> -From a photograph by the Author. (See <a href="#Page_76">pages 76–79</a>.)<br /> -<p class="right">Frontispiece.</p> -</div> -</div> -<p class="p4" /> - - -<hr class="chap pg-brk" /> -<p class="p2" /> - -<h1>·DIAMONDS·</h1> -<p class="p4" /> - -<p class="pfs80">BY</p> - -<p class="pfs120">SIR WILLIAM CROOKES</p> -<p class="pfs90">LL.D., D.Sc., F.R.S.</p> - -<div class="blockquotx"> - -<p>Foreign Sec. R.S., Hon. LL.D. (Birmingham), Hon. Sc.D. -(Camb. and Dubl.), Hon. D.Sc. (Oxon. and Cape of Good -Hope); Past Pres. Chem. Soc., Brit. Assoc., Inst. Elect. Eng., -Soc. Psych. Res.; Hon. Mem. Roy. Phil. Soc. Glasgow, Roy. -Soc. N.S.W., Pharm. Soc., Chem. Metall. and Mining Soc. -of South Africa, Amer. Chem. Soc., Amer. Philos. Soc., Roy. -Soc. Sci. Upsala, Deutsch. Chem. Gesell. Berlin, Psychol. -Soc. Paris, “Antonio Alzate” Sci. Soc. Mexico. Sci. Soc. -Bucharest, Reg. Accad. Zelanti, Aci Reale; Corresp. Inst. -de France (Acad. Sci.), Corresp. Mem. Bataafsch Genoots. -Rotterdam, Soc. d’Encouragement pour l’Indust. Paris, -For. Mem. Accad. Lincei Rome.</p></div> - -<p class="p4 pfs90">WITH 24 ILLUSTRATIONS</p> - -<p class="p4 pfs120">LONDON AND NEW YORK<br /> -<span class="fs110 wsp">HARPER & BROTHERS</span><br /> -<span class="fs80 lsp">45 ALBEMARLE STREET, W.<br /> -1909</span></p> - - -<hr class="chap pg-brk" /> -<p class="p6" /> - -<p class="pfs100">TO MY WIFE</p> - -<p class="p1 pfs80 lht">MY COMPANION AND FRIEND OF<br /> -FIFTY-FOUR YEARS.<br /> -TO HER JUDGMENT AND ADVICE I OWE MORE<br /> -THAN I CAN EVER REPAY<br /> -AND TO HER I DEDICATE THIS BOOK.</p> - -<p class="p6" /> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_vii" id="Page_vii">[Pg vii]</a></span></p> - -<h2 class="p4 no-brk fs135"><a name="PREFACE" id="PREFACE"></a><a href="#CONTENTS">PREFACE</a></h2> - - -<p class="drop-capy">The following pages are based on personal -observations during two visits -to Kimberley, in 1896 and 1905, and on -personal researches on the formation and -artificial production of diamonds. In 1896 -I spent nearly a month at Kimberley, -when Mr. Gardner F. Williams, the General -Manager of the De Beers Consolidated -Mines, and the managers of neighbouring -mines, did their utmost to aid in -my zealous quest for reliable information. -They gave me free access to all workings -above and below ground, allowed me to -examine at leisure their stock and to take -extracts from their books. I had exceptional -opportunities of studying the geology -of the Diamond and of noting the strange -cataclysmal facts connected with the birth, -growth, and physics of the lustrous stones.</p> - -<p><span class="pagenum"><a name="Page_viii" id="Page_viii">[viii]</a></span></p> - -<p>In 1905 with my wife I returned to Kimberley. -We were members of the British -Association which held its meeting that year -in South Africa. I was asked to give one of -the Association lectures at Kimberley and -it was natural for me to discourse “On -Diamonds.” During our stay we were the -guests of Mr. Gardner Williams.</p> - -<p>Returning to England after the visit of -1896, I gave two lectures on Diamonds at -the Imperial Institute and one at the Royal -Institution. These lectures, and the lecture -delivered at Kimberley, in 1905—hitherto -only privately distributed—form the basis -of the present volume. On each visit I -took abundant photographs, many of which -I now reproduce. A few are copied from -plans lent by Mr. Gardner Williams and -one or two are from photographs purchased -at Kimberley.</p> - -<p>In obtaining statistical information of the -Diamond industry, I owe much to the Annual -Reports of the De Beers Company. I have<span class="pagenum"><a name="Page_ix" id="Page_ix">[ix]</a></span> -also quoted freely from Reunart’s valuable -book on <cite>Diamonds and Gold in South Africa</cite>; -and I render my acknowledgments to the -authors of the following papers and memoirs.</p> - -<p><cite>On a Visit to the Diamond Fields of South -Africa, with Notices of Geological Phenomena -by the Wayside.</cite> By John Paterson, Esq., -<span class="fs70">M.A.</span></p> - -<p><cite>On the Mode of Occurrence of Diamonds in -South Africa.</cite> By E. J. Dunn.</p> - -<p><cite>On the Origin and Present Position of the -Diamonds of South Africa.</cite> By G. G. -Cooper, Esq., of Graaf Reinet.</p> - -<p><cite>On the Character of the Diamantiferous -Rock of South Africa.</cite> By Prof. N. Storey -Maskelyne, <span class="fs70">F.R.S.</span>, Keeper, and Dr. W. -Flight, Assistant in the Mineral Department, -British Museum.</p> - -<p><cite>Further Notes on the Diamond Fields of -South Africa.</cite> By E. J. Dunn.</p> - -<p><cite>Notes on the Diamond Fields of South -Africa, 1880.</cite> By E. J. Dunn.</p> - -<p><cite>Analogies between the Diamond Deposits in<span class="pagenum"><a name="Page_x" id="Page_x">[x]</a></span> -South Africa and those in Meteorites.</cite> By -M. Daubrée.</p> - -<p><cite>Notes on the Diamond-bearing Rock of -Kimberley, South Africa.</cite> By Sir J. B. Stone, -Prof. T. G. Bonney, and Miss Raisin.</p> - -<p><cite>Notes on the Diamond Rock of South -Africa.</cite> By W. H. Hudleston.</p> - -<p><cite>The Parent Rock of the Diamond in South -Africa.</cite> By the Reverend Professor T. G. -Bonney.</p> - -<p>The Presidential Address, by Grove Carl -Gilbert, to the Geological Society of Washington, -on <cite>The Origin of Hypotheses. Illustrated -by the Discussion of a Topographical -Problem.</cite> 1896.</p> - -<p><cite>Le Four Electrique.</cite> By Henri Moissan. -1897.</p> - -<p><cite>The Diamond Mines of South Africa.</cite> By -Mr. Gardner F. Williams. (In this publication -the story of the rise and development -of the industry is exhaustively narrated.)</p> - -<p><cite>British Association, South African Meeting, -1896, Kimberley Handbook.</cite></p> - -<p><span class="pagenum"><a name="Page_xi" id="Page_xi">[xi]</a></span></p> - -<p><cite>The Meteor Crater of Canyon Diablo, -Arizona; its History, Origin, and Associated -Meteoric Irons.</cite> By George P. Merrill. -1908.</p> - -<p>In the present volume I have tried to give -some idea of the underground wonders of -the Kimberley mines. I have pictured the -strenuous toil of the men who bring to the -surface the buried treasures, and I have -given some idea of the skill and ingenuity -with which their labours are controlled. -I have done my best to explain the fiery -origin of the Diamond, and to describe the -glowing, molten, subterranean furnaces -where they first begin mysteriously to take -shape. I have shown that a diamond is the -outcome of a series of Titanic earth convulsions, -and that these precious gems -undergo cycles of fiery, strange, and potent -vicissitudes before they can blaze on a ring -or a tiara.</p> - -<p>I am glad to have paid these two visits -to South Africa. I always recall with<span class="pagenum"><a name="Page_xii" id="Page_xii">[xii]</a></span> -interest the dusky smiling natives at work -and at play. I am glad to have seen that -Arabian Nights vision, the strong-room of -the De Beers Company. Above all, I have -vividly graven on my heart the friendly -welcome, and the innumerable acts of kindness -shown us by our able, energetic, and -enterprising Colonial fellow-countrymen.</p> - -<p class="right">W. C.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_xiii" id="Page_xiii">[xiii]</a></span></p> - -<h2 class="p4 no-brk fs135"><a name="CONTENTS" id="CONTENTS"></a>CONTENTS</h2> - -<div class="smcap"> -<table border="0" cellpadding="4" cellspacing="0" width="90%" summary=""> -<tr><td class="tdc fs70">CHAPTER</td><td class="tdl"></td><td class="tdc fs70">PAGE</td></tr> -<tr><td class="tdrt">I.</td><td class="tdl">Preliminary</td><td class="tdrb"><a href="#Page_1">1</a></td></tr> -<tr><td class="tdrt">II.</td><td class="tdl">Kimberley and its Diamond Mines</td><td class="tdrb"><a href="#Page_14">14</a></td></tr> -<tr><td class="tdrt">III.</td><td class="tdl">Kimberley Mines at the Present Day</td><td class="tdrb"><a href="#Page_34">34</a></td></tr> -<tr><td class="tdrt">IV.</td><td class="tdl">Collecting the Gems</td><td class="tdrb"><a href="#Page_55">55</a></td></tr> -<tr><td class="tdrt">V.</td><td class="tdl">The Diamond Office</td><td class="tdrb"><a href="#Page_73">73</a></td></tr> -<tr><td class="tdrt">VI.</td><td class="tdl">Noteworthy Diamonds</td><td class="tdrb"><a href="#Page_76">76</a></td></tr> -<tr><td class="tdrt">VII.</td><td class="tdl">Boart, Carbonado, and Graphite</td><td class="tdrb"><a href="#Page_81">81</a></td></tr> -<tr><td class="tdrt">VIII.</td><td class="tdl">Physical and Chemical Properties of the Diamond</td><td class="tdrb"><a href="#Page_89">89</a></td></tr> -<tr><td class="tdrt">IX.</td><td class="tdl">Genesis of the Diamond</td><td class="tdrb"><a href="#Page_115">115</a></td></tr> -<tr><td class="tdrt">X.</td><td class="tdl">The Natural Formation of the Diamond</td><td class="tdrb"><a href="#Page_127">127</a></td></tr> -<tr><td class="tdrt">XI.</td><td class="tdl">Meteoric Diamonds</td><td class="tdrb"><a href="#Page_134">134</a></td></tr> -<tr><td class="tdl pad2" colspan="2">Index</td><td class="tdrb"><a href="#Page_141">141</a></td></tr> -</table></div> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_xiv" id="Page_xiv">[xiv]</a></span><br /> - <span class="pagenum"><a name="Page_xv" id="Page_xv">[xv]</a></span></p> - -<h2 class="p4 no-brk fs135"><a name="LIST_OF_PLATES" id="LIST_OF_PLATES"></a>LIST OF PLATES</h2> - -<div class="fs90"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl" colspan="2">The Cullinan Diamond, from a photograph by the Author<br />(see <a href="#Page_76">pp. 76–79</a>)</td><td class="tdrb"><em>Frontispiece</em></td></tr> -<tr><td class="tdlx fs70">FIG.</td><td class="tdrb fs70" colspan="2">FACING PAGE</td></tr> -<tr><td class="tdlx"> 1. River Washings at Klipdam</td><td class="tdrb"></td><td class="tdrb"><a href="#P_010">10</a></td></tr> -<tr><td class="tdlx"> 2. Plan of the Kimberley Diamond Mines</td><td class="tdrb"></td><td class="tdrb"><a href="#P_010x">10</a></td></tr> -<tr><td class="tdlx"> 3. Kimberley Mine. The “Pipe”</td><td class="tdrb"></td><td class="tdrb"><a href="#P_018">18</a></td></tr> -<tr><td class="tdlx"> 4. Section of Kimberley Mine</td><td class="tdrb"></td><td class="tdrb"><a href="#P_018x">18</a></td></tr> -<tr><td class="tdlx"> 5. Wesselton Diamond Mine. Open Workings</td><td class="tdrb"></td><td class="tdrb"><a href="#P_034">34</a></td></tr> -<tr><td class="tdlx"> 6. De Beers Compound</td><td class="tdrb"></td><td class="tdrb"><a href="#P_040">40</a></td></tr> -<tr><td class="tdlx"> 7. De Beers Mine. Underground Workings</td><td class="tdrb"></td><td class="tdrb"><a href="#P_040x">40</a></td></tr> -<tr><td class="tdlx"> 8. De Beers Washing and Concentrating Machinery</td><td class="tdrb"></td><td class="tdrb"><a href="#P_048">48</a></td></tr> -<tr><td class="tdlx"> 9. Sorting Concentrates for Diamonds. De Beers</td><td class="tdrb"></td><td class="tdrb"><a href="#P_054">54</a></td></tr> -<tr><td class="tdlx">10. De Beers Diamond Office. 25,000 carats</td><td class="tdrb"></td><td class="tdrb"><a href="#P_072">72</a></td></tr> -<tr><td class="tdlx">11. De Beers Diamond Office. The Valuators’ Table</td><td class="tdrb"></td><td class="tdrb"><a href="#P_072x">72</a></td></tr> -<tr><td class="tdlx">12. A group of large Diamond Crystals</td><td class="tdrb"></td><td class="tdrb"><a href="#P_076">76</a></td></tr> -<tr><td class="tdlx">13. Some Historic Diamonds</td><td class="tdrb"></td><td class="tdrb"><a href="#P_080">80</a></td></tr> -<tr><td class="tdlx">14. Crystalline forms of native Diamonds</td><td class="tdrb"></td><td class="tdrb"><a href="#P_086">86</a></td></tr> -<tr><td class="tdlx">15. Triangular Markings on natural face of a Diamond Crystal</td><td class="tdrb"></td><td class="tdrb"><a href="#P_088">88</a></td></tr> -<tr><td class="tdlx">16. Triangular Markings artificially produced on a Diamond Crystal</td><td class="tdrb"></td><td class="tdrb"><a href="#P_088x">88</a></td></tr> -<tr><td class="tdlx">17. Diamond-cut Glass and Shavings</td><td class="tdrb"></td><td class="tdrb"><a href="#P_098">98</a></td></tr> -<tr><td class="tdlx">18. Diamonds in Röntgen Rays. A. Black Diamond in gold frame. B. Pink Delhi Diamond. C. Paste Imitation of B.</td><td class="tdrb"></td><td class="tdrb"><a href="#P_098x">98</a></td></tr> -<tr><td class="tdlx">19. Curve of Vapour Pressure of Carbon</td><td class="tdrb" colspan="2"><em>page</em> <a href="#P_113">113</a></td></tr> -<tr><td class="tdlx">20. Moissan’s Electric Furnace</td><td class="tdrb"></td><td class="tdrb"><a href="#P_116">116</a></td></tr> -<tr><td class="tdlx">21. Artificial Diamond made by the Author from molten iron</td><td class="tdrb"></td><td class="tdrb"><a href="#P_120">120</a></td></tr> -<tr><td class="tdlx">22. Moissan’s Artificial Diamonds</td><td class="tdrb"></td><td class="tdrb"><a href="#P_120x">120</a></td></tr> -<tr><td class="tdlx">23. Diamonds from Canyon Diablo Meteorite</td><td class="tdrb"></td><td class="tdrb"><a href="#P_138">138</a></td></tr> -</table></div> - - -<hr class="chap" /> -<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> - -<p class="p4 pfs135 lsp2 bold">DIAMONDS</p> - -<h2 class="no-brk"><a name="CHAPTER_I" id="CHAPTER_I"></a><a href="#CONTENTS">CHAPTER I</a><br /> -<br /> -<span class="fs80 bold">PRELIMINARY</span></h2> - - -<p class="drop-capy">From the earliest times the diamond -has fascinated mankind. It has -been a perennial puzzle—one of the “riddles -of the painful earth.” It is recorded -in <cite>Sprat’s History of the Royal Society</cite> (1667) -that among the questions sent by order -of the Society to Sir Philiberto Vernatti, -Resident in Batavia, was one inquiring -“Whether Diamonds grow again after -three or four years in the same places where -they have been digged out?” The answer -sent back was, “Never, or at least as the -memory of man can attain to.”</p> - -<p>In a lecture “On Diamonds,” fifty years -ago,<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a> Professor Maskelyne said, “The diamond<span class="pagenum"><a name="Page_2" id="Page_2">[2]</a></span> -is a substance which transcends all -others in certain properties to which it -is indebted for its usefulness in the arts -and its beauty as an ornament. Thus, on -the one hand, it is the hardest substance -found in nature or fashioned by art. Its -reflecting power and refractive energy, on -the other hand, exceed those of all other -colourless bodies, while it yields to none in -the perfection of its pellucidity.” He was -constrained to add, “The formation of the -diamond is an unsolved problem.”</p> - -<p>Diamonds are found in widely separated -parts of the globe. In the United States -they have been found in Arkansas, where -the work of testing the deposits is now -going on steadily and quietly. The general -geology and petrography of the area and -the weathering of the peridotite are described -in a paper read before the American -Institute of Mining Engineers by Messrs. -Kunz and Washington. In tests made with -a diamond drill the peridotite was proved<span class="pagenum"><a name="Page_3" id="Page_3">[3]</a></span> -to depths of 200 feet. The green and -yellow grounds underlying the layer of -black, sticky soil are found to extend down -40 feet in places, and are estimated to -average 20 feet in depth over the area. -The outcrop of the peridotite is estimated -to cover about 40 acres, and may be larger. -Some 540 diamonds have been found, with -an aggregate of 200 carats. The largest -stone weighs about 6·5 carats, though the -average size compares favourably with the -general run of most of the South African -mines. There is a large proportion of white -stones, many of which are free from flaws -and are very brilliant. The genuineness of -the occurrence of diamonds in their matrix -is again proved, one stone having been -found imbedded in the green ground at a -depth of 15 feet. This peridotite has the -form of a volcanic pipe, and therefore its -outcrop is limited to one place.</p> - -<p>In California authentic finds of diamonds -are recorded in Butte County, especially at<span class="pagenum"><a name="Page_4" id="Page_4">[4]</a></span> -Cherokee, above Orville. These diamonds, -however, have come from alluvial deposits -and have been found generally in washing -for gold. As yet no authenticated discovery -of diamond in its original matrix in California -is recorded.</p> - -<p>In Brazil the diamond industry has been -increasing of late years, and the old mines -in the Diamantina country are being -worked by American capital and by the -American methods which have proved so -successful at De Beers. It is estimated that -the annual value of the diamonds exported -from Brazil amounts to over £800,000, but -it is impossible to arrive at accurate figures -owing to the large quantities smuggled out -of the country to avoid payment of the -export tax.</p> - -<p>British Guiana produces a small quantity -of diamonds, mostly, however, of small size. -Between January and September, 1907, -1564 carats were exported.</p> - -<p>Indian diamonds chiefly come from the<span class="pagenum"><a name="Page_5" id="Page_5">[5]</a></span> -states of Panna, Charkhari, and Ajaigarh. -In 1905 India exported 3059 carats, valued -at £5160.</p> - - -<h3><span class="smcap">Cape Colony</span></h3> - -<p>It is a standing surprise to the watchful -outsider how little attention is bestowed -on some of our colonies. For instance, to -the Cape Colony, comprising vast, varied, -and productive regions, we have till recently -manifested profound ignorance and consequent -indifference. When the Cape Colony -was first incorporated with the Empire, it -was pronounced “a bauble, unworthy of -thanks.” Yet before the Suez Canal and -the Waghorn overland route to India, the -Cape, as commanding our road to India, -Australia, and China, had a special importance. -Even now it presents an alternative -route which under conceivable circumstances -may be of capital moment.</p> - -<p>The high grounds above Cape Town are -rich in medicinal health-giving waters. The<span class="pagenum"><a name="Page_6" id="Page_6">[6]</a></span> -districts where these springs occur are high-lying, -free from malaria, and admirably -adapted for the restoration of invalids. It -needs only some distinguished power to set -the fashion, some emperor, prince, or -reigning beauty to take the baths and -drink the waters, and the tide of tourists -would carry prosperity to Aliwal North, -Fraserburg, Cradock, and Fort Beaufort.</p> - -<p>South Africa, as I shall endeavour to show -in detail, is the most important source of -diamonds on the earth, and ranks with -Australia and California as one of the three -great gold-yielding regions. But the wealth -of South Africa is not only in its gold and -diamonds. The province of Natal contains -more coal than Britain ever owned before -a single bucket had been raised, and the -beds extend over the Orange River Colony, -whilst valuable iron ores exist also in large -quantities.</p> - -<p>In the year 1896 I spent nearly a month -at Kimberley. Mr. Gardner F. Williams,<span class="pagenum"><a name="Page_7" id="Page_7">[7]</a></span> -General Manager of the De Beers Consolidated -Mines, and the Managers of neighbouring -mines, did their utmost to assist -me in my inquiries and to ply me with -valuable information. I had full access to -all the workings, above and below ground, -and was able to examine at leisure their -stock and take extracts from their books.</p> - -<p>Again, in the year 1905, I paid another -visit to Kimberley as the guest of Mr. -Gardner Williams on the occasion of the -meeting of the British Association in South -Africa.</p> - - -<h3><span class="smcap">River Washings</span></h3> - -<p>Besides the matrix mines, where the -stones are found in pipes supposed to be of -volcanic origin, the alluvial deposits on the -Vaal River are of considerable importance. -The terraces and gravels along the Vaal -River for about 200 miles have been worked -for diamonds, the deposits sometimes extending -several miles on each side of the<span class="pagenum"><a name="Page_8" id="Page_8">[8]</a></span> -river, and varying from a few inches to 40 -or 50 feet in thickness. The diamonds are -found almost everywhere through the gravel -deposit.</p> - -<p>Before describing the present mode of -diamond extraction followed in the important -mines, I will commence with these -“River Washings,” where, in their primitive -simplicity, can be seen the modes of -work and the simple machinery long since -discarded in the large centres of the industry. -The drift or so-called “river washings” -present a very interesting phase of diamond -industry. The work is carried on in the -primitive fashion adopted in the early days -of diamond discovery, every man working -on his own little claim, assisted by a few -natives, and employing primitive machinery -(<a href="#P_010">Fig. 1</a>). The chief centre of the Vaal River -washings is about 30 miles to the north-west -of Kimberley, at a place called Klipdam -No. 2. There was originally a Klipdam a -few miles further, and here the miners congregated,<span class="pagenum"><a name="Page_9" id="Page_9">[9]</a></span> -but the exhaustion of their claims -made them migrate to others not far off and -reported to be richer. Here, accordingly, -they re-erected their iron houses and called -it Klipdam No. 2.</p> - -<p>It is a mistake to speak of “river washings.” -The diamantiferous deposits are not -special to the old or recent river bed, -but appear to be alluvial deposits spread -over a large tract of country by the agency -of water, which at some period of time -subsequent to the filling up of the volcanic -pipes planed off projecting kopjes from -the surface of the country and scattered -the debris broadcast over the land to the -north-west of Kimberley. The larger diamonds -and other heavy minerals would -naturally seek the lowest places, corresponding -with the river bed, past and present. -The fact that no diamonds are found in -the alluvial deposits near Kimberley may -perhaps be explained by supposing that the -first rush was sufficiently strong to carry<span class="pagenum"><a name="Page_10" id="Page_10">[10]</a></span> -the debris past without deposition, and -that deposition occurred when the stream -slackened speed. At Klipdam No. 2 the -diamantiferous earth is remarkably like -river gravel, of a strong red colour—quite -different from the Kimberley blue ground—and -forms a layer from 1 to 8 feet thick, -lying over a “hard pan” of amygdaloidal -trap, the melaphyre of the Kimberley -mines.</p> - -<div class="figcenter"> -<a name="P_010" id="P_010"></a> -<img src="images/i_p010a1.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 1. RIVER WASHINGS AT KLIPDAM.</div> -</div> - -<div class="figcenter"> -<a name="P_010x" id="P_010x"></a> -<img src="images/i_p010a2.jpg" width="350" alt="" /> -<div class="caption"> -FIG. 2. PLAN OF THE KIMBERLEY DIAMOND MINES.<br /> -<p class="right">To face p. 10.</p> -</div> -</div> - -<p>When I was at Klipdam the miners had -congregated at a spot called “New Rush,” -where some good finds of diamonds had -been reported. The gravel is dug and put -into a machine resembling the gold miner’s -dolly, where it is rocked and stirred by rakes, -with a current of water flowing over it. -Here all the fine stuff is washed away and -a rough kind of concentration effected. -The residual gravel is put on a table and -sorted for diamonds—an operation performed -by the master. At one of the claims -where work was proceeding vigorously I<span class="pagenum"><a name="Page_11" id="Page_11">[11]</a></span> -asked the proprietor to let me be present -at the sorting out, as I should like to see -river diamonds. He willingly consented, -but no diamonds were to be found. On my -expressing regret, he said he had not seen a -diamond for a fortnight! I remarked that -the prospect was rather a poor one, but he -told me that a fortnight before he picked -out one worth £300, “and that,” he said, -“will pay for several weeks’ wages of my -boys.” This is the kind of speculative -gambling that goes on at the river diggings. -The miner may toil fruitlessly for months, -and then come across a pocket of stones, -where they have been swept by some eddy, -by which he will net several thousands. -Diamonds from the “river washings” are -of all kinds, as if contributed by every -mine in the neighbourhood. They are -much rolled and etched, and contain a good -proportion of first-class stones; they are -of very good quality, as if only the better -and larger stones had survived the ordeal of<span class="pagenum"><a name="Page_12" id="Page_12">[12]</a></span> -knocking about. Diamonds from the drift -fetch about 40 per cent more than those -from Kimberley; taking the yield of the -Kimberley and De Beers mines as worth -all round, large and small, 26s. 6d. a carat, -those from the drift are worth 40s.</p> - -<p>As a rule the better class of natives—the -Zulus, Matabeles, Basutos, and Bechuanas—when -well treated, are very honest -and loyal to their masters. An amusing -instance of the devotion of a Zulu came to -my knowledge at Klipdam. He had been -superintending a gang of natives on a small -claim at the river washings. It yielded but -few stones, and the owner—my informant—sold -the claim, handing over the plant and -small staff, our friend the Zulu remaining -to look after the business till the new owner -took possession. In the course of a few -months the purchaser became dissatisfied -with his bargain, not a single diamond -having turned up since the transfer. One -night the Zulu came to his old master in a<span class="pagenum"><a name="Page_13" id="Page_13">[13]</a></span> -mysterious manner, and laying a handful -of diamonds on the table, said, “There, -Baas, are your diamonds; I was not going -to let the new man have any of them!”</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_14" id="Page_14">[14]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_II" id="CHAPTER_II"></a><a href="#CONTENTS">CHAPTER II</a><br /> -<br /> -<span class="fs80 bold">KIMBERLEY AND ITS DIAMOND MINES</span></h2> - - -<p class="drop-capy">The famous diamond mines in the -neighbourhood are Kimberley, De -Beers, Dutoitspan, Bultfontein, and Wesselton -(<a href="#P_010x">Fig. 2</a>). They are situated in latitude -28° 43´ South and longitude 24° 46´ East. -Kimberley is practically in the centre of the -present diamond-producing area. Besides -these mines others of some importance of the -Orange River Colony are known as Jaggersfontein -and Koffyfontein, Lace, and Monastery, -besides two new mines, the Roberts-Victor -and the Voorspoed.</p> - -<p>The areas of the mines are:</p> - - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" width="70%" summary=""> -<tr><td class="tdl">Kimberley</td><td class="tdl">33 acres</td></tr> -<tr><td class="tdl">De Beers</td><td class="tdl">22 acres</td></tr> -<tr><td class="tdl">Dutoitspan</td><td class="tdl">45 acres</td></tr> -<tr><td class="tdl">Bultfontein</td><td class="tdl">36 acres</td></tr> -</table></div> - -<p><span class="pagenum"><a name="Page_15" id="Page_15">[15]</a></span></p> - -<p>In 1907 the total number of carats raised -from these mines was more than two -million and a half, the sales of which realised -£6,452,597.</p> - -<p>The most important mine outside the -Kimberley group is the new Premier Mine, -about 20 miles West-North-West of Pretoria, -where the famous Cullinan diamond -was found.</p> - -<p>Other diamond mines are the Frank -Smith, Wesselton, the Kamfersdam, the -Kimberley West, the Newlands, and the -Leicester Mine.</p> - -<p>The surface of the country round Kimberley -is covered with a ferruginous red, -adhesive, sandy soil, which makes horse -traffic very heavy. Below the red soil is a -basalt, much decomposed and highly ferruginous, -from 20 to 90 feet thick, and -lower still from 200 to 250 feet of black -slaty shale containing carbon and iron -pyrites. These are known as the Kimberley -shales; they are very combustible, and in a<span class="pagenum"><a name="Page_16" id="Page_16">[16]</a></span> -part of the De Beers Mine where they were -accidentally fired they smouldered for -over eighteen months. Then follows a bed -of conglomerate about 10 feet thick, and -below the conglomerate about 400 feet of a -hard, compact rock of an olive colour, called -“Melaphyre,” or olivine diabase. Below -the melaphyre is a hard quartzite about -400 feet thick. The strata are almost -horizontal, dipping slightly to the north; -in places they are distorted and broken -through by protruding dykes of trap. -There is no water nearer than the Vaal -River, about 14 miles away, and formerly -the miners were dependent on rain-water -and a few springs and pools. Now, however, -a constant and abundant supply of -excellent water is served to the town, -whilst good brick houses, with gardens and -orchards, spring up on all sides. To mark -the rate of progress, Kimberley has an -excellent club and one of the best public -libraries in South Africa. Parts of the<span class="pagenum"><a name="Page_17" id="Page_17">[17]</a></span> -town, affectionately called “the camp” -by the older inhabitants, are not beyond -the galvanised iron stage, and the general -appearance is unlovely and depressing. -Reunert reckons that over a million trees -have been cut down to supply timber for -the mines, and the whole country within a -radius of 100 miles has been denuded of -wood with the most injurious effects on the -climate. The extreme dryness of the air, -and the absence of trees to break the force -of the wind and temper the heat of the sun, -probably account for the dust storms so -frequent in summer. The temperature in -the day frequently rises to 100° in the -shade, but in so dry a climate this is not -unpleasant, and I felt less oppressed by this -heat than I did in London the previous -September. Moreover, in Kimberley, owing -to the high altitude, the nights are always -cool.</p> - -<p>The approach to Kimberley is deadly -dull. The country is almost treeless, and<span class="pagenum"><a name="Page_18" id="Page_18">[18]</a></span> -the bare veldt stretches its level length, -relieved only by distant hills on the horizon.</p> - - -<h3><span class="smcap">The Pipes or Craters</span></h3> - -<p>The five diamond mines or craters are all -contained in a circle 3½ miles in diameter. -They are irregularly shaped round or oval -pipes, extending vertically downwards to -an unknown depth, retaining about the -same diameter throughout (<a href="#P_018">Fig. 3</a>). They -are said to be volcanic necks, filled from -below with a heterogeneous mixture of fragments -of the surrounding rocks, and of older -rocks such as granite, mingled and cemented -with a bluish-coloured, hard clayey mass, -in which famous blue clay the imbedded -diamonds are hidden.</p> - -<div class="figcenter"> -<a name="P_018" id="P_018"></a> -<img src="images/i_p018a1.jpg" width="500" alt="" /> -<div class="caption"> -FIG. 3. KIMBERLEY MINE. THE “PIPE.”</div> -</div> - -<div class="figcenter"> -<a name="P_018x" id="P_018x"></a> -<img src="images/i_p018a2.jpg" width="500" alt="" /> -<div class="caption"> -FIG. 4. SECTION OF KIMBERLEY MINE.<br /> -<p class="right">To face p. 18.</p> -</div> -</div> - -<p>The craters or mines are situate in -depressions, which have no outlets for the -water which falls upon the neighbouring -hills. The watersheds of these hills drain -into ponds, called pans or vleis. The water, -which accumulates in these ponds during<span class="pagenum"><a name="Page_19" id="Page_19">[19]</a></span> -the rainy season, evaporates during the -dry months, only one of them holding -water throughout the dry season. The -rocks which surround the craters are capped -by red soil or calcareous tufa, and in places -by both, the red soil covering the tufa.</p> - -<p>The diamantiferous breccia filling the -mines, usually called “blue ground,” is a -collection of fragments of shale, various -eruptive rocks, boulders, and crystals of -many kinds of minerals. Indeed, a more -heterogeneous mixture can hardly be found -anywhere else on this globe. The ground -mass is of a bluish green, soapy to the touch -and friable, especially after exposure to the -weather. Professor Maskelyne considers it -to be a hydrated bronzite with a little -serpentine.</p> - -<p>The Kimberley mine is filled for the first -70 or 80 feet with what is called “yellow -ground,” and below that with “blue ground” -(<a href="#P_018x">Fig. 4</a>). This superposed yellow on blue is -common to all the mines. The blue is the<span class="pagenum"><a name="Page_20" id="Page_20">[20]</a></span> -unaltered ground, and owes its colour chiefly -to the presence of lower oxides of iron. -When atmospheric influences have access to -the iron it is peroxidised and the ground -assumes a yellow colour. The thickness of -yellow earth in the mines is therefore a -measure of the depth of penetration of air -and moisture. The colour does not affect -the yield of diamonds.</p> - -<p>Besides diamonds, there have been detected -more than eighty species of minerals -in the blue ground, the more common -being magnetite, ilmenite, garnet, bright -green ferriferous enstatite (bronzite), a -hornblendic mineral closely resembling -smaragdite, calc-spar, vermiculite, diallage, -jeffreysite, mica, kyanite, augite, peridot, -eclogite, iron pyrites, wollastonite, vaalite, -zircon, chrome iron, rutile, corundum, apatite, -olivine, sahlite, chromite, pseudobrookite, -perofskite, biotite, and quartz. The -blue ground does not show any signs of passing -through great heat, as the fragments in<span class="pagenum"><a name="Page_21" id="Page_21">[21]</a></span> -the breccia are not fused at the edges. The -eruptive force was probably steam or -water-gas, acting under great pressure, but -at no high temperature. According to -Mr. Dunn, in the Kimberley Mine, at a -depth of 120 feet, several small fresh-water -shells were discovered in what appeared -to be undisturbed material.</p> - -<p>A selection of thin sections of some of -these rocks and minerals, mounted as -microscopic objects and viewed by polarised -light, are not only of interest to the geologist, -but are objects of great beauty.</p> - -<p>The appearance of shale and fragments of -other rocks testify that the <i lang="fr" xml:lang="fr">mélange</i> has -suffered no great heat in its present condition, -and that it has been erupted from -great depths by the agency of water vapour -or some similar gas.</p> - -<p>The rock outside the pipes and encasing -them is called “reef.” Inside some of the -mines occur large masses of “floating -reef,” covering an area of several thousand<span class="pagenum"><a name="Page_22" id="Page_22">[22]</a></span> -square feet. In the De Beers Mine is what -is called “the snake,” a dyke of igneous -rock taking a serpentine course across the -mine, and standing like a vein nearly -vertical, varying in thickness from 2 to 7 -feet. The main body of the blue ground -is entirely analogous to the snake rock, -naturally more decomposed, but in essential -points the microscopic appearance of -the blue ground and of the “snake” is in an -extraordinary degree alike. Mr. Gardner -Williams supposes that the “snake” is a -younger eruptive formation coming from -the same volcanic source as the blue ground. -No diamonds have been found either in -the “snake” or the floating reef. The -ground, however, is generally richer in -diamonds in the neighbourhood of the -floating reef.</p> - -<p>Before the discovery of the mines there -was nothing in the superficial appearance of -the ground to indicate the treasures below. -Since the volcanic ducts were filled with<span class="pagenum"><a name="Page_23" id="Page_23">[23]</a></span> -the diamantiferous ground, denudation has -planed the surface and the upper parts of -the craters, and other ordinary signs of -volcanic activity being smoothed away, -the superficial and ubiquitous red sand -covered the whole surface. The Kimberley -Mine seems to have presented a slight -elevation above the surrounding flat country, -while the sites of other mines were level or -even slightly depressed. The Wesselton -Mine, within a mile of Dutoitspan, has only -been discovered a few years. It showed a -slight depression on the surface, which had -been used as a shoot for dry rubbish. -There are other diamantiferous pipes in -the neighbourhood, but they are small and -do not contain stones in payable quantities. -More recently another diamantiferous pipe -has been discovered about 40 miles off, -near Klipdam, and is now worked as the -Leicester Mine. Other hoards of diamonds -may also be near; where there are no surface -signs, and the pipe itself is hidden<span class="pagenum"><a name="Page_24" id="Page_24">[24]</a></span> -under 10 or 20 feet of recent deposits, it is -impossible to prospect the entire country. -Accident has hitherto been the chief factor -in the discovery of diamond mines.</p> - -<p>How the great pipes were originally -formed is hard to say. They were certainly -not burst through in the ordinary manner -of volcanic eruption, since the surrounding -and enclosing walls show no signs of igneous -action, and are not shattered or broken -up even when touching the “blue ground.” -It is pretty certain these pipes were filled -from below after they were pierced and -the diamonds were formed at some previous -time and mixed with a mud volcano, -together with all kinds of debris eroded -from the rocks through which it erupted. -The direction of flow is seen in the upturned -edges of some of the strata of shale -in the walls, although I was unable to see -any upturning in most parts of the walls -of the De Beers Mine at great depths.</p> - -<p><span class="pagenum"><a name="Page_25" id="Page_25">[25]</a></span></p> - - -<h3><span class="smcap">The Kimberley Mine in Old Days</span></h3> - -<p>According to Mr. Paterson, who examined -the diamond fields of Kimberley -soon after their discovery, “Wherever the -diamond is obtained perfect in form and -smooth in finest smoothness of surface, -without depression, hump, or twist of any -kind, such diamonds were ever found in -their own little moulds of finest limey -stuff,<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a> and as if such mould of lime had -been a necessity to their perfect formation. -And further, where the splinters of diamonds, -or boarty stuff, were chiefly met by -the diggers, there was much less presence -of limey matter in the claim at the section -of it where such broken or fragmentary -diamonds were found; and that chiefly -from among what the diggers termed -‘clay-ballast,’ or ‘burnt brick,’ were unearthed<span class="pagenum"><a name="Page_26" id="Page_26">[26]</a></span> -the bits or undeveloped crystals so -plentiful at New Rush.”<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a></p> - -<p>In the first days of diamond mining -there was no idea that diamantiferous -earth extended to any particular depth, -and miners were allowed to dig holes at -haphazard and prospect where they liked. -When the Kimberley Mine was discovered -a new arrangement was made, and in July, -1871, it was cut up into about 500 claims, -each 31 feet square, with spaces reserved -for about fifteen roadways across the mine. -No person at first could hold more than two -claims—a rule afterwards modified.</p> - -<p>The following quotation from a description -of a visit to Kimberley in 1872, by Mr. -Paterson, taken from a paper read by him -to the Geologists’ Association, gives a -graphic picture of the early days of the -Kimberley Mine:</p> - -<p>“The New Rush diggings (as the Kimberley<span class="pagenum"><a name="Page_27" id="Page_27">[27]</a></span> -Mine was at first called) are all going -forward in an oval space enclosed around -by the trap dyke, and of which the larger -diameter is about 1000 feet, while the -shorter is not more than 700 feet in length. -Here all the claims of 31 feet square each -are marked out with roadways of about -12 feet in width, occurring every 60 feet. -Upon these roadways, by the side of a -short pole fixed into the roadway, sits the -owner of the claim with watchful eye upon -the Kafir diggers below, who fill and hoist, -by means of a pulley fixed to the pole -above, bucketful after bucketful of the -picked marl stuff in which the diamonds -are found.</p> - -<p>“Many of the claims are already sunk -to a depth of 100 feet, and still the diamonds -continue to be found as plentifully -as ever. From the roadway above the -marl is carted away to the sorting-tables, -outside the range of the diggings, among -mounds of marl stuff which seem like little<span class="pagenum"><a name="Page_28" id="Page_28">[28]</a></span> -hills. Here, amidst such whirls of dust as -are nowhere else seen, the marl stuff is -pounded, sifted from the finest powder of -lime and clay, and from the residue put -on the sorting-tables, the diggers, with a -piece of zinc 9 inches long by 4 inches in -breadth, search out in the successive layers -taken from the heap the precious gems. -I need not tell you that the search is by no -means very perfect, or that perhaps as -many diamonds escape the digger’s eye as -are discovered and taken out by him, but -you will perhaps confess with me that their -aptness in picking out the diamonds is by -no means to be despised, when I tell you -that in one six months from the date -of opening New Rush diggings, little short -of a million sterling in diamonds has been -extracted from them. At close of day the -diggers take daily stock of their finds, and -between five and six o’clock in the afternoon -are to be seen hundreds and hundreds -moving through the main street of New<span class="pagenum"><a name="Page_29" id="Page_29">[29]</a></span> -Rush on visits to the tents of the buyers, -seated behind their little green baize tables, -with scales all ready, and bags of gold and -silver and piles of banknotes, to buy the -little gems.”</p> - -<p>It may help to realise the enormous -value of the Kimberley Mine if I say that -two claims, measuring together 62 by 31 -feet and worked to a depth of 150 feet, -yielded 28,000 carats of diamonds.</p> - -<p>The roadways across the mine soon, -however, became unsafe. Claims were sunk -100 or 200 feet each side of a roadway, -and the temptation to undermine roadways -was not always resisted. Falls of -road frequently took place, followed by -complete collapse, burying mine and claims -in ruin. At that time there were probably -12,000 or 15,000 men at work in the mine, -and then came the difficulty how to continue -working the host of separate claims -without interference with each other. A -system of rope haulage was adopted.</p> - -<p><span class="pagenum"><a name="Page_30" id="Page_30">[30]</a></span></p> - -<p>The following description of the work at -the Kimberley Mine at this stage of its -history is given by Mr. Reunert:<a name="FNanchor_4_4" id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">[4]</a></p> - -<p>“A succession of tall, massive timber -stagings was erected round the margin of -the mine. Each staging carried two or -three platforms one above the other, every -platform serving as an independent level -from which to communicate with the -claims below. Stationary ropes were then -stretched from the different levels of the -stagings to the claims, the ropes being -anchored to the ground at both ends: the -upper platforms communicated with the -claims in the centre of the mine, the lower -platforms with those nearer the margin. -The hauling ropes were attached to windlasses -worked by Kafirs on the several -platforms, on which grooved guide wheels -for the ropes were also fixed, the buckets -being swung from the stationary ropes<span class="pagenum"><a name="Page_31" id="Page_31">[31]</a></span> -by little overhead runners and crooks. -Arrived at the level of the platform the -bucket was tipped into a narrow shoot, -down which the ground ran into a bag held -ready to receive it, in which it was conveyed -away to be sorted. The din and -rattle of these thousands of wheels and the -twang of the buckets along the ropes were -something deafening, while the mine itself -seemed almost darkened by the thick -cobweb of ropes, so numerous as to appear -almost touching. This mode of haulage -continued in vogue during the whole of -1873, and if the appearance of the mine was -less picturesque than when the roadways -existed, it was, if anything, more unique. -By moonlight, particularly, it was a weird -and beautiful sight.”</p> - -<p>The mine was now threatened in two -other quarters. The removal of the blue -ground took away the support from the -walls of the pipe, and frequent falls of reef -occurred, not only covering up valuable<span class="pagenum"><a name="Page_32" id="Page_32">[32]</a></span> -claims with rubbish, but endangering the -lives of workers below. Moreover, as the -workings deepened, water made its appearance, -necessitating pumping. In 1878 one -quarter of the claims were covered by reef, -and in 1879 over £300,000 were spent on -removing reef and water. In 1881 over -£200,000 were thus spent, and in 1882 -more than half a million sterling was -needed to defray the cost of reef removal. -So matters went on until four million cubic -yards of reef had been removed, at a cost -of two millions sterling, and still little good -was done, for out of 400 claims in the mine -only about fifty could be regularly worked. -Ultimately, in November, 1883, the biggest -fall of reef on record took place, estimated -at 250,000 cubic yards, surging half across -the mine, where the bulk of it lies to this -day. It became evident that open workings -could not be carried on at such depths, -and after many experiments the present -system of underground working was devised.</p> - -<p><span class="pagenum"><a name="Page_33" id="Page_33">[33]</a></span></p> - -<p>During this time of perplexity, individual -miners who could easily have worked one -or two claims near the surface could not -continue work in the face of harassing -difficulties and heavy expenses. Thus the -claims gradually changed hands until the -mine became the property first of a comparatively -small number of capitalists, -then of a smaller number of limited liability -companies, until finally the whole of the -mines have practically become the property -of the “De Beers Consolidated Mines, -Limited.”</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_34" id="Page_34">[34]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_III" id="CHAPTER_III"></a><a href="#CONTENTS">CHAPTER III</a><br /> -<br /> -<span class="fs80 bold">KIMBERLEY MINES AT THE PRESENT DAY</span></h2> - - -<p class="drop-capy">The De Beers Consolidated Mines, -Limited, was founded in 1888, mainly -through the genius of the late Cecil John -Rhodes, for the purpose of acquiring all-important -diamond-mining interests in the -Kimberley area and thereby controlling -the output. The two richest mines, Kimberley -and De Beers, have been actively -worked ever since, and have been the main -contributors to an output which now -realises over five millions sterling annually. -Dutoitspan Mine was completely closed -down, and practically the whole of Bultfontein -was kept idle for many years; but -with a view to the requirements of the -future and the marked increase in the -demand for diamonds, notwithstanding the<span class="pagenum"><a name="Page_35" id="Page_35">[35]</a></span> -steady rise in prices that has taken place, -both these mines have now been equipped -for underground working on a grand scale. -The youngest of the De Beers group of mines -is the Wesselton, which was discovered in -1890 by the late Mr. H. A. Ward, and soon -afterwards purchased by Mr. Rhodes on -behalf of the Company. The mine is now -being worked opencast on a magnificent -scale and has largely exceeded original -expectations (<a href="#P_034">Fig. 5</a>). The success of the -consolidation is proved by the fact that -since it was brought about £22,000,000 have -been paid in dividends to the shareholders, -and it is roughly estimated that 40,000,000 -carats of diamonds have been produced of -a total value of eighty millions.</p> - -<div class="figcenter"> -<a name="P_034" id="P_034"></a> -<img src="images/i_p034a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 5. WESSELTON DIAMOND MINE. OPEN WORKINGS.<br /> -<p class="right">To face p. 34.</p> -</div> -</div> - -<p>At the four mines about 8000 persons are -daily employed, namely, 1500 whites and -6500 blacks. The wages are, whites, £5 or -£6 a week; blacks, underground, 4s. to 5s. -a day, and aboveground, 21s. a week.</p> - -<p><span class="pagenum"><a name="Page_36" id="Page_36">[36]</a></span></p> - - -<h3><span class="smcap">The Compound System</span></h3> - -<p>With gems like diamonds, where so large -an intrinsic value is concentrated into so -small a bulk, it is not surprising that -robbery has to be guarded against in the -most elaborate manner. The Illicit Diamond -Buying (I.D.B.) laws are very stringent, -and the searching, rendered easy by the -“compounding” of the natives—which I -shall describe presently—is of the most -drastic character (<a href="#P_040">Fig. 6</a>). It is, in fact, very -difficult for a native employee to steal -diamonds; even were he to succeed, it -would be almost impossible to dispose of -them, as a potential buyer would prefer to -secure the safe reward for detecting a theft -rather than run the serious risk of doing -convict work on the Cape Town Breakwater -for a couple of years. I heard of a native -who, secreting a diamond worth several -hundreds of pounds, after trying unsuccessfully -to sell it, handed it back to the manager<span class="pagenum"><a name="Page_37" id="Page_37">[37]</a></span> -of his compound, glad to get the sixpence a -carat to which he was entitled. Before the -passing of the “Diamond Trade Act” the -value of diamonds stolen reached nearly -one million sterling per annum.</p> - -<p>A “compound” is a large enclosure -about 20 acres in extent, surrounded by -rows of one-story buildings of corrugated -iron. These are divided into rooms holding -each about twenty natives. A high iron -fence is erected around the compound, 10 -feet from the buildings. Within the enclosure -is a store where the necessaries of life -are supplied to the natives at a reduced -price, wood and water being provided free -of charge. In the middle is a large swimming-bath, -with fresh water running through -it. The rest of the space is devoted to -recreation, games, dances, concerts, and -any other amusement the native mind can -desire. I have to thank the superintendents -of the respective compounds, who spoke -all the native dialects, for their kindness in<span class="pagenum"><a name="Page_38" id="Page_38">[38]</a></span> -showing us round, and suggesting dances -and concerts, got up at ten minutes’ notice, -for the benefit of my camera. The dancing -was more of the character of attitudinising -and marching to a monotonous tum-tum, -the “orchestra” consisting of various-sized -drums and what they call a piano—an -octave or so of tuned slabs of wood held -in order on stretched strings and struck -with a wooden hammer. The native music -as a rule is only marking time, but I have -heard musical melodies accompanying some -of their songs. In case of accident or illness -there is a well-appointed hospital where -the sick are tended. Medical supervision, -nurses, and food are supplied free by the -Company.</p> - -<p>In the compound are to be seen representatives -of nearly all the picked types of African -tribes. Each tribe keeps to itself, and to -go round the buildings skirting the compound -is an admirable object-lesson in -ethnology. At one point is a group of<span class="pagenum"><a name="Page_39" id="Page_39">[39]</a></span> -Zulus; next we come to Fingoes; then -Basutos; beyond come Matabele, Bechuanas, -Pondos, Shangains, Swazis, and other -less-known tribes, either grouped or wandering -around making friendly calls.</p> - -<p>The clothing in the compound is diverse -and original. Some of the men are evident -dandies, whilst others think that in so hot -a climate a bright-coloured handkerchief -or “a pair of spectacles and a smile” is as -great a compliance with the conventions of -civilisation as can be expected.</p> - -<p>The natives are not interfered with in -their various amusements, always provided -they do not make themselves objectionable -to their neighbours. They soon learn that -tribal animosities are to be left outside the -compound. One Sunday afternoon my -wife and I walked unattended about the -compound, almost the only whites present -among 1700 natives. The manners of the -fold were so friendly, and their smiles so -cordial, that the idea of fear vanished. At<span class="pagenum"><a name="Page_40" id="Page_40">[40]</a></span> -one part a Kafir was making a pair of -trousers with a bright nickel-plated sewing-machine, -in which he had invested his -savings; next to him a “boy” was reading -from the Testament in his own language -to an attentive audience; in a corner a -party were engaged in cooking a savoury -mess in an iron pot; further on the orchestra -was tuning up and Zulus were putting -the finishing touches to their toilet of -feathers and beads. One group was intently -watching a mysterious game. It is played -by two sides, with stones and grooves and -hollows in the ground, and appears of most -absorbing interest. It seems to be universal -throughout Africa; it is met with among -the ruins of Zimbabwe, and signs of it are -recorded on old Egyptian monuments. I -wanted to learn it, and an intelligent Zulu -player offered to teach it to me in a few -minutes. Captain Dallas, however, with a -more accurate opinion of my intelligence -than my friend the Zulu, assured me it<span class="pagenum"><a name="Page_41" id="Page_41">[41]</a></span> -would take months before I could begin to -know anything about it. He had tried for -years and could make nothing of it.</p> - -<div class="figcenter"> -<a name="P_040" id="P_040"></a> -<img src="images/i_p040a1.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 6. DE BEERS COMPOUND.</div> -</div> - -<div class="figcenter"> -<a name="P_040x" id="P_040x"></a> -<img src="images/i_p040a2.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 7. DE BEERS MINE. UNDERGROUND WORKINGS.<br /> -<p class="right">To face p. 40.</p> -</div> -</div> - -<p>They get good wages, varying according -to occupation. The work is appreciated, -and there are always more applicants than -can be accepted. On entering, the restrictions -to which they must submit are fully -explained, and they are required to sign for -three months at least, during which time -they must not leave the compound or mine. -A covered way and tunnel lead the workers -underground to the down shaft, while those -working on the depositing floors go and -come under guard. It is seldom that a man -does not return once he has lived the life -in the compound; some come again and -again for years, only leaving occasionally -to spend accumulated savings. The most -careful men save money, and carry it at -intervals to the superintendent to keep for -them. Occasionally they ask to look at -their savings, which may amount to £30 or<span class="pagenum"><a name="Page_42" id="Page_42">[42]</a></span> -£40, accumulated by driblets. They are -ignorant of savings banks or interest, and -are content if they see their own money -in the original rags and papers. The Kafir, -on demand, must behold his coins just as he -handed them in, wrappings and all. Sometimes -the superintendent will have as much -as £1000 of savings in his care.</p> - -<p>On leaving, the men generally draw all -their savings, and it is not uncommon for -a grateful Kafir to press £2 or £3 on Captain -Dallas in recognition of his trouble. They -are astonished when their offerings are -declined; still more so when it is explained -that if they would put their savings in a -bank they would have a few extra pounds -given to them for the privilege of taking -care of it.</p> - -<p>A shrewd young Pondo, who had been -coming year after year, applied for some -of his savings, and gave as a reason that he -wanted to buy a wife. “But you said the -same thing last year,” replied Captain<span class="pagenum"><a name="Page_43" id="Page_43">[43]</a></span> -Dallas; “I hope nothing has happened.” -“No,” said the man; “one wife, she -quarrel with me; two wives, they quarrel -with each other; me peace!”</p> - - -<h3><span class="smcap">Underground Workings</span></h3> - -<p>In the face of constant developments I -can only describe the system in use at the -time of my own visits in 1896 and 1905. -Shafts are sunk in the solid rock at a sufficient -distance from the pipe to be safe -against reef movements in the open mine. -In 1903 the rock shafts in the De Beers and -Kimberley Mines reached depths of 2076 -and 2599 feet respectively. Tunnels are -driven from these shafts at different levels, -about 120 feet apart, to cross the mine from -west to east. These tunnels are connected -by two other tunnels running north and -south, one near the west side of the mine -and one midway between it and the east -margin of the mine. From the east and -west tunnels offsets are driven to the surrounding<span class="pagenum"><a name="Page_44" id="Page_44">[44]</a></span> -rock. When near the rock the -offsets widen into galleries, these in turn -being stoped on the sides until they meet, -and upwards until they break through the -blue ground. The fallen reef with which -the upper part of the mine is filled sinks -and partially fills the open space. The -workmen then stand on the fallen reef -and drill the blue ground overhead, and as -the roof is blasted back the debris follows. -When stoping between two tunnels the blue is -stoped up to the debris about midway between -the two tunnels. The upper levels -are worked back in advance of the lower -levels, and the works assume the shape of -irregular terraces. The main levels are -from 90 to 120 feet apart, with intermediate -levels every 30 feet. Hoisting is done from -only one level at a time through the same -shaft. By this ingenious method every -portion of blue ground is excavated and -raised to the surface, the rubbish on the -top gradually sinking and taking its place.</p> - -<p><span class="pagenum"><a name="Page_45" id="Page_45">[45]</a></span></p> - -<p>The scene below ground in the labyrinth -of galleries is bewildering in its complexity, -and very unlike the popular notion of a -diamond mine (<a href="#P_040x">Fig. 7</a>). All below is dirt, mud, -grime; half-naked men, dark as mahogany, -lithe as athletes, dripping with perspiration, -are seen in every direction, hammering, -picking, shovelling, wheeling the trucks to -and fro, keeping up a weird chant which -rises in force and rhythm when a greater -task calls for excessive muscular strain. -The whole scene is more suggestive of a -coal mine than a diamond mine, and all this -mighty organisation, this strenuous expenditure -of energy, this costly machinery, -this ceaseless toil of skilled and black labour, -goes on day and night, just to win a few -stones wherewith to deck my lady’s finger! -All to gratify the vanity of woman! “And,” -interposed a lady who heard this remark, -“the depravity of man!”</p> - -<p><span class="pagenum"><a name="Page_46" id="Page_46">[46]</a></span></p> - - -<h3><span class="smcap">The Depositing Floors</span></h3> - -<p>Owing to the refractory character of blue -ground fresh from the mines, it has to be -exposed to atmospheric influences before it -will pulverise under the action of water and -mechanical treatment.</p> - -<p>From the surface-boxes, into which the -blue ground is tipped when it reaches the -top of the main shaft, it is transferred to -side-tipping trucks and sent to the depositing -floors by means of endless wire-rope -haulage. The speed of the haulage varies -from 2½ to 4 miles per hour. The trucks -are counted automatically as they are sent -to the floor by a reciprocating engine-counter -placed on a frame near the tramline.</p> - -<p>The depositing floors are prepared by -removing the bush and grass from a fairly -level piece of ground; this ground is then -rolled smooth and hard. The floors extend -over many square miles of country and<span class="pagenum"><a name="Page_47" id="Page_47">[47]</a></span> -are surrounded by 7-foot barbed wire -fences, vigilantly guarded day and night. -The De Beers floors, on Kenilworth, are laid -off in rectangular sections 600 yards long -and 200 yards wide, each section holding -about 50,000 loads. The ground from the -Kimberley Mine is the softest and only -needs a few months’ exposure on the floors; -the ground from De Beers is much harder -and requires at least six months’ exposure, -while some ground is so hard that it will not -disintegrate by exposure to the weather -under one or two years. The De Beers -Mine contains a much larger quantity of -this hard blue ground than the other mines, -and in order to save the loss of time consequent -on keeping an enormous stock of blue -constantly on the floors, it has recently been -decided to pass the harder and more refractory -stuff direct from the mine through -crushing mills.</p> - -<p>For a time the blue ground remains on -the floors without undergoing much alteration.<span class="pagenum"><a name="Page_48" id="Page_48">[48]</a></span> -But soon the heat of the sun and -moisture produce a wonderful effect. Large -pieces, hard as ordinary sandstone when -taken from the mine, commence to crumble. -At this stage the winning of the diamonds -assumes more the nature of farming than -mining. The ground is frequently harrowed -and occasionally watered, to assist -pulverisation by exposing the larger pieces -to atmospheric influences. The length of -time necessary for the ground to weather -before it becomes sufficiently pulverised -for washing depends on the season of the -year and the amount of rain. The longer -the ground remains exposed the better it is -for washing.</p> - -<div class="figcenter"> -<a name="P_048" id="P_048"></a> -<img src="images/i_p048a.jpg" width="475" alt="" /> -<div class="caption"> -FIG. 8. DE BEERS WASHING AND CONCENTRATING MACHINERY.<br /> -<p class="right">To face p. 48.</p> -</div> -</div> - -<p>It is curious to note that there is a -marked difference in the rapidity of disintegration -of the blue ground in each of -the four mines. The longer the exposure, -the more complete the pulverisation and the -better for washing. Under normal conditions -soft blue ground becomes sufficiently<span class="pagenum"><a name="Page_49" id="Page_49">[49]</a></span> -pulverised in from four to six months, but -it is better to expose it for a longer period, -even for a whole year.</p> - - -<h3><span class="smcap">Washing and Concentrating Machinery</span></h3> - -<p>After the blue ground has been weathered -for a sufficient time, it is again loaded into -trucks and hauled to the crushing machinery -(<a href="#P_048">Fig. 8</a>). The first or “comet” crushers -reduce the ground so that it will pass into -hoppers and thence into revolving cylinders -covered with perforated steel plates, having -holes 1¼ inches in diameter which separate -the finely crushed from the coarse pieces.</p> - -<p>Pieces larger than 1¼ inches pass out of -the end of the cylinders and fall upon a -conveyor belt, which takes them to the end -of the machine—these pieces are mostly -waste rock which is found in the blue ground.</p> - -<p>The fine ground which passes through the -holes in the cylinder, together with a -plentiful current of water, flows into the -washing pans. These pans are of iron,<span class="pagenum"><a name="Page_50" id="Page_50">[50]</a></span> -14 feet in diameter, furnished with ten -arms each having six or seven teeth. The -teeth are so set as to form a spiral, so that -when the arms revolve the teeth carry the -heavy deposit to the outer rim of the pan, -while the lighter material passes towards -the centre and is carried from the pan by -the flow of water. The heavy deposit -contains the diamonds. It remains on the -bottom of the pan and near its outer rim. -This deposit is drawn off every twelve -hours by means of a broad slot in the -bottom of the pan. The average quantity -of blue ground passed through each pan is -from 400 to 450 loads in ten hours. The -deposit left in each pan after putting the -above number of loads through amounts to -three or four loads, which go to the pulsator -for further concentration.</p> - -<p>About 14 per cent of all the ground sent -to the depositing floors is too hard to -weather, so of late years crushing and concentrating -plant has been erected to deal<span class="pagenum"><a name="Page_51" id="Page_51">[51]</a></span> -effectually with the hard lumps, thus saving -the great lock-up of capital consequent on -letting them lie on the floor a year or two.</p> - -<p>The hard lumps being hauled to the upper -part of the machine, are tipped into bins, -whence they pass to crushing rollers which so -reduce them that they will pass through a -ring two inches in diameter. The coarse -powder is screened through revolving cylinders -having ½-inch and 1¼-inch perforations. -The stuff passing through the finer -holes goes to the finishing mill, while the -coarser stuff goes to smaller crushers. -Before the coarse lumps are re-crushed they -pass over revolving picking tables, where -any specially large diamonds are rescued, -thus preventing the risk of breakage. -From the picking tables the ground is -scraped automatically into two sets of -rolls, and the pulverised product screened -again and graded into three sizes. The -finest size, passing a ½-inch screen, goes to -the washing pans, and the two coarser<span class="pagenum"><a name="Page_52" id="Page_52">[52]</a></span> -sizes to jigs. Large diamonds which have -been separated from their envelope of blue -are retained in the jig. The ground still -holding the smaller diamonds passes out of -the end of the jig and then through a series -of rolls, screens, and jigs until the diamantiferous -gravel is drawn from the -bottom jigs into locked trucks running on -tramways to the pulsator for further concentration -and sorting.</p> - -<p>The pulsator is an ingeniously designed -but somewhat complicated machine for -dealing with the diamantiferous gravel -already reduced one hundred times from -the blue ground, the pulsator still further -concentrating it till the gravel is rich enough -to enable the stones to be picked out by -hand. The value of the diamonds in a load -of original blue ground being about 30s., -the gravel sent to the pulsator from the -pans, reduced a hundredfold, is worth -£150 a load. Stuff of this value must not be -exposed to risk of peculation.</p> - -<p><span class="pagenum"><a name="Page_53" id="Page_53">[53]</a></span></p> - -<p>The locked trucks are hoisted by a cage -to a platform, where they are unlocked -and their contents fed into a shoot leading -to a cylinder covered with steel sieving with -holes from <sup>1</sup>/<sub>16</sub> to ⅝ of an inch in diameter. -The five sizes which pass through the -cylinder flow upon a combination of jigs, -termed at the mines the pulsators. The -bottoms of the jigs are covered with screens, -or sieving, the meshes of which are a little -larger than the holes in the revolving -cylinder immediately at the back of them.</p> - -<p>Over each screen is spread a layer of -bullets to prevent the rich deposit from -passing too rapidly through the screens. -The jigs themselves are stationary, but -from below an intermittent stream of water -passes in rapid pulsations with an up and -down movement. This pulsation keeps -the diamantiferous gravel constantly moving—“alive” -is the expressive word used—and -tends to sort out the constituents -roughly according to their specific gravity,<span class="pagenum"><a name="Page_54" id="Page_54">[54]</a></span> -the heavier particles working to the bottom -and the lighter material washing off by the -flow of water and passing into trucks, -whence it is carried to the tailings heap. -The heavier portions, by the up and down -wash of the water, gradually work their -way under the bullets and pass through the -screens into pointed boxes, whence the -heavy concentrates are drawn off upon -endless belts. These convey their precious -load to small elevators by means of which -the concentrates are lifted into hoppers -from which they are fed upon shaking -tables.</p> - -<div class="figcenter"> -<a name="P_054" id="P_054"></a> -<img src="images/i_p054a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 9. SORTING CONCENTRATES FOR DIAMONDS. DE BEERS.<br /> -<p class="right">To face p. 54.</p> -</div> -</div> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_55" id="Page_55">[55]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_IV" id="CHAPTER_IV"></a><a href="#CONTENTS">CHAPTER IV</a><br /> -<br /> -<span class="fs80 bold">COLLECTING THE GEMS</span></h2> - - -<p class="drop-capy">The sorting room in the pulsator house is -long, narrow, and well lighted (<a href="#P_054">Fig. 9</a>). -Here the rich gravel is brought in wet, a -sieveful at a time, and is dumped in a -heap on tables covered with iron plates. -The tables at one end take the coarsest -lumps, next comes the gravel which passed -the ⅜-inch holes, then the next in order, -and so on. The first sorting is done by -thoroughly trustworthy white men; for -here the danger of robbery is greatest. -Sweeping the heap of gravel to the right, -the sorter scrapes a little of it to the centre -of the table by means of a flat piece of -sheet zinc. With this tool he rapidly -passes in review the grains, seizes the diamonds -and puts them into a little tin box -in front of him. The stuff is then swept<span class="pagenum"><a name="Page_56" id="Page_56">[56]</a></span> -off to the left and another lot taken, and -so on till the sieveful of gravel is exhausted, -when another is brought in. The stuff the -sorter has passed to his left as temporarily -inspected is taken next to another part of -the room, where it is again scrutinised by -native convicts again and again, and whilst -diamonds can be found in quantity sufficient -to repay the cost of convict labour, it is -passed under examination.</p> - -<p>The diamond has a peculiar lustre, and -on the sorter’s table it is impossible to -mistake it for any other stone that may be -present. It looks somewhat like clear -pieces of gum arabic, with a sort of intrinsic -lustre which makes a conspicuous shine -among the other stones.</p> - - -<h3><span class="smcap">Automatic Diamond Collector</span></h3> - -<p>A series of experiments was initiated by -Mr. Gardner Williams with the object of -separating the diamonds from the heavy, -valueless concentrates with which they are<span class="pagenum"><a name="Page_57" id="Page_57">[57]</a></span> -associated. An ordinary shaking or percussion -table was constructed, and every -known means of separation was tried -without success. One of the employees of -De Beers, Mr. Fred Kirsten, was in charge -of the experimenting, under the supervision -of the late Mr. George Labram, the manager -of the large crushing plant, and afterwards -mechanical engineer to the Company. Notwithstanding -the fact that the specific -gravity of the diamond (3·52) was less than -that of several of the minerals associated -with it, so that its separation would seem a -simple matter, it was found in practice to -be impossible owing to the slippery nature -of the diamond. The heavy concentrates -carried diamonds, and diamonds flowed -away from the percussion table with the -tailings. When it seemed that every resource -to do away with hand-sorting had -been exhausted, Kirsten asked to be allowed -to try to catch the diamonds by placing a -coat of thick grease on the surface of the<span class="pagenum"><a name="Page_58" id="Page_58">[58]</a></span> -percussion table with which the other -experiments had been made. Kirsten had -noticed that oily substances, such as axle -grease and white or red lead, adhered to -diamonds when they chanced to come into -contact, and, he argued to himself, if these -substances adhered to diamonds and not -to the other minerals in the concentrates, -why should not diamonds adhere to grease -on the table and the other minerals flow -away? In this way the remarkable discovery -was made that diamonds alone of all -minerals contained in the blue ground will -adhere to grease, and that all others will -flow away as tailings over the end of the -percussion table with the water. After this -was determined by thorough experiments, -more suitable shaking tables were constructed -at the Company’s workshops. -These were from time to time improved -upon, until now all the sorting (except for -the very coarse size) is done by these -machines, whose power of distinction is<span class="pagenum"><a name="Page_59" id="Page_59">[59]</a></span> -far superior to the keenest eye of the -native.</p> - -<p>Only about ⅓ of 1 per cent of diamonds -is lost by the first table, and these are -recovered almost to a stone when the concentrates -are passed over the second table. -The discrimination of this sorter is truly -marvellous. Native workers, although experienced -in the handling of diamonds, -often pick out small crystals of zircon, or -Dutch boart, by mistake, but the senseless -machine is practically unerring.</p> - -<p>The grease containing the diamonds, -together with a small percentage of very -heavy minerals, such as iron pyrites and -barytes, is scraped from the tables, placed -in buckets made of steel plates with fine -perforations, and boiled or steamed. The -grease passes away to tanks of water, where -it is cooled and is again fit for use. The -diamonds, together with small bits of iron -pyrites, brass nails from the miners’ boots, -pieces of copper from the detonator used in<span class="pagenum"><a name="Page_60" id="Page_60">[60]</a></span> -blasting, which remain on the tables owing -to their high specific gravity, and a very -small admixture of worthless deposit which -has become mechanically mixed with the -grease, are then boiled in a solution containing -caustic soda, where they are freed from -all grease. The quantity of deposit from -the size of ⅝ of an inch downwards, which -now reaches the sorting table, does not -exceed 1 cubic foot for every 12,000 loads -(192,000 cubic feet) of blue ground washed. -As already stated, <sup>5</sup>/<sub>12</sub> of 1 per cent of the -whole mass of blue formerly passed to the -sorting tables; or, from 12,000 loads, which -is about the daily average of the quantity -washed at De Beers and Kimberley Mines, -800 cubic feet had to be assorted by hand.</p> - - -<h3><span class="smcap">The Yield of Diamonds</span></h3> - -<p>Sometimes as many as 8000 carats of -diamonds come from the pulsator in one -day, representing about £20,000 in value.</p> - -<p>When the bare statement is made that<span class="pagenum"><a name="Page_61" id="Page_61">[61]</a></span> -nearly 5,000,000 truck-loads, or more -than 4,000,000 tons of blue ground, have -been washed in a year, the mind only -faintly conceives the prodigious size of the -mass that is annually drawn from the old -craters and laboriously washed and sorted -for the sake of a few bucketfuls of diamonds. -It would form a cube of more than 430 feet, -or a block larger than any cathedral in the -world, and overtopping the spire of St. -Paul’s, while a box with sides measuring -2 feet 9 inches would hold the gems. From -two to three million carats of diamonds are -turned out of the De Beers mines in a year, -and as 5,000,000 carats go to the ton, -this represents half a ton of diamonds. To -the end of 1892 10 tons of diamonds had -come from this mine, valued at £60,000,000 -sterling. This mass of blazing diamonds -could be accommodated in a box 5 feet -square and 6 feet high.</p> - -<p>The diamond is a luxury, and there is only a -limited demand for it throughout the world.<span class="pagenum"><a name="Page_62" id="Page_62">[62]</a></span> -From four to four and a half millions sterling -is as much as is spent annually in diamonds; -if the production is not regulated by the -demand, there will be over-production, -and the trade will suffer. By regulating -the output the directors have succeeded in -maintaining prices since the consolidation -in 1888.</p> - -<p>The blue ground varies in its yield of -diamonds in different mines, but is pretty -constant in the same mine. In 1890 the -yield per load of blue ground was:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" width="80%" summary=""> -<tr><td class="tdl"></td><td class="tdl pad4 fs70">CARATS</td></tr> -<tr><td class="tdl">From the Kimberley Mine</td><td class="tdl">from 1·25 to 1·5</td></tr> -<tr><td class="tdl pad3">” <span class="pad2">De Beers Mine</span></td><td class="tdl pad2h">” 1·20 ” 1·3</td></tr> -<tr><td class="tdl pad3">” <span class="pad2">Dutoitspan Mine</span></td><td class="tdl pad2h">” 0·17 ” 0·5</td></tr> -<tr><td class="tdl pad3">” <span class="pad2">Bultfontein Mine</span></td><td class="tdl pad2h">” 0·5 ” 0·33</td></tr> -</table></div> - - -<h3><span class="smcap">Varieties of Diamonds</span><br /> - -<span class="smcap">Fancy Stones</span></h3> - -<p>Diamonds occur in all shades, from deep -yellow to pure white and jet black, from -deep brown to light cinnamon, also green, -blue, pink, yellow, orange, and opaque.</p> - -<p><span class="pagenum"><a name="Page_63" id="Page_63">[63]</a></span></p> - -<p>Both in Kimberley and De Beers the -blue ground on the west side is poorer in -diamonds than the blue ground in other -parts of the mines. The diamonds from the -west side also differ somewhat from those -in other parts of the same mine.</p> - -<p>The diamonds from each mine have a -distinctive character, and so uniform are -the characteristics that an experienced -buyer can tell at once the locality of any -particular parcel of stones. An isolated -stone may, of course, be found occasionally -in any one mine which is characteristic of -some other source of production, but this -is the exception to the general rule.</p> - -<p>There is a great similarity between the -produce of the De Beers and Kimberley -mines. A day’s wash from either of these -mines could be distinguished from each -other, but not so easily the majority of the -individual stones.</p> - -<p>The Kimberley Mine produces a small -percentage of white crystals, octahedral in<span class="pagenum"><a name="Page_64" id="Page_64">[64]</a></span> -shape, is noted for its large macles, and, -in common with the De Beers Mine, it also -yields a large percentage of coloured and -large yellow diamonds.</p> - -<p>The De Beers Mine produces a comparatively -small percentage of really white -diamonds, but is noted for its fine silvery -capes.</p> - -<p>The Dutoitspan Mine is noted for its fine -white cleavages, silver capes, large yellows, -and an exceptional proportion of large -stones generally. It also produces a small -proportion of fine white, octahedral-shaped -crystals and a comparatively small proportion -of diamonds below 0·2 of a carat in size.</p> - -<p>The Bultfontein Mine produces a very -large percentage of white diamonds, mostly -octahedral in shape and generally small in -size. It produces very few coloured stones, -but a larger percentage of flawed and spotted -stones than any other mine. Even the -apparently pure stones from this mine frequently -develop flaws in cutting, which in<span class="pagenum"><a name="Page_65" id="Page_65">[65]</a></span> -the rough were imperceptible to the naked -eye.</p> - -<p>The Wesselton Mine diamonds are noted -for an abnormally large percentage of -octahedral stones, a large proportion of -which are free from flaws. White and -brown stones predominate in this mine; -there is almost an entire absence of the -ordinary yellow, but very fine golden-coloured -fancy stones are unearthed occasionally, -invariably in the form of cleavage, -and hardly ever exceeding 2 carats each in -weight.</p> - -<p>For “golden fancies” this mine is unrivalled. -Wesselton diamonds are easily -distinguished from the produce of every -other mine by a decided gloss common to -them.</p> - -<p>Wesselton produces more stones of 10 -carats each and over than Bultfontein, but -comparatively few large stones of over -50 carats each. It produces a very large -percentage of small diamonds under 0·2 of<span class="pagenum"><a name="Page_66" id="Page_66">[66]</a></span> -a carat. With Bultfontein it shares the -distinction of yielding cubical stones occasionally. -It also produces a small percentage -of blue-whites.</p> - -<p>The Frank Smith Mine produces very -fine white diamonds, fairly regular in shape, -mostly octahedral, and hardly any coloured -stones. Many of the stones are grooved at -the edges.</p> - -<p>The Kamfersdam Mine yields diamonds -of very inferior quality, dark brown being -the predominating colour, and even the -majority of the better-class stones from this -mine are faintly tinged with brown.</p> - -<p>The Kimberley West, formerly known as -Theron’s Mine, situated about 30 miles due -west of Kimberley, yields a very small -percentage of blue-whites, fine “silver capes,” -and a large proportion of brown diamonds, -somewhat better in quality than Kamfersdam -and more regular in shape. The -diamonds from this mine present a distinctly -“alluvial” appearance, but they are nevertheless<span class="pagenum"><a name="Page_67" id="Page_67">[67]</a></span> -distinctive in character from river -diamonds and much inferior in quality.</p> - -<p>The diamonds from the Leicester Mine -are of a distinctive character; they are very -much grooved, extremely bad shapes for -cutting, and many of the stones are cross-grained.</p> - -<p>The Newlands Mine, West Griqualand, -about 40 miles north-west of Kimberley, is -interesting on account of the occurrence of -diamond in what the Reverend Professor -Bonney considers to be its true matrix. -The workmen occasionally come across well-rounded, -boulder-like masses of eclogite, a -rather coarsely crystalline rock, sometimes -more than a foot in diameter. Some of -these boulders have diamonds imbedded in -them. One piece examined by Professor -Bonney measured approximately 4 inches -by 3 inches by 2 inches, and appeared to -have been broken off a larger eclogite -boulder. In it were seen ten diamonds, -mostly well-crystallised octahedra, perfectly<span class="pagenum"><a name="Page_68" id="Page_68">[68]</a></span> -colourless, with brilliant lustre, four of them -being comprised within a space of a quarter -of an inch square. All these diamonds were -on the surface. Probably others would have -been found inside, but it was not considered -desirable to destroy the specimen by breaking -it up. It is now in the Natural History -Museum, having been presented by the -Directors of the Newlands Mine.</p> - -<p>Eclogite has been found in other diamond -mines, but I am not aware that -diamonds have been found imbedded in it -except in the Newlands Mine.</p> - -<p>Stones from Jagersfontein, in the Orange -River Colony, display great purity of colour -and brilliancy, and they have the so-called -“steely” lustre characteristic of old Indian -gems.</p> - - -<h3><span class="smcap">Falling off of Yield with Depth</span></h3> - -<p>According to tables furnished by the -De Beers Company, the yield of the De -Beers and Kimberley mines has declined as<span class="pagenum"><a name="Page_69" id="Page_69">[69]</a></span> -the depth increases. At the same time the -value of the stones has risen, and diamonds -are more expensive to-day than at any -previous time.</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" width="80%" summary=""> -<tr><td class="tdl"></td><td class="tdc fs70">NUMBER OF CARATS<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a></td> - <td class="tdl fs70 pad4" colspan="2">VALUE</td></tr> -<tr><td class="tdl fs70"> YEAR</td><td class="tdc fs70">PER LOAD</td><td class="tdl fs70 pad3" colspan="2">PER CARAT</td></tr> -<tr><td class="tdl"></td><td class="tdc"></td><td class="tdl fs60 pad3"><em>s.</em></td><td class="tdl fs60 pad3"><em>d.</em></td></tr> -<tr><td class="tdl">1889</td><td class="tdc"> 1·283</td><td class="tdl">19</td><td class="tdl pad2">8·75</td></tr> -<tr><td class="tdl">1890</td><td class="tdc">1·15</td><td class="tdl">32</td><td class="tdl pad2">6·75</td></tr> -<tr><td class="tdl">1891</td><td class="tdc">0·99</td><td class="tdl">29</td><td class="tdl pad2">6</td></tr> -<tr><td class="tdl">1892</td><td class="tdc">0·92</td><td class="tdl">25</td><td class="tdl pad2">6</td></tr> -<tr><td class="tdl">1893</td><td class="tdc">1·05</td><td class="tdl">29</td><td class="tdl pad2">0·6</td></tr> -<tr><td class="tdl">1894</td><td class="tdc">0·89</td><td class="tdl">24</td><td class="tdl pad2">5·2</td></tr> -<tr><td class="tdl">1895</td><td class="tdc">0·85</td><td class="tdl">25</td><td class="tdl pad2">6</td></tr> -<tr><td class="tdl">1896</td><td class="tdc">0·91</td><td class="tdl">26</td><td class="tdl pad2">9·4</td></tr> -<tr><td class="tdl">1897</td><td class="tdc">0·92</td><td class="tdl">26</td><td class="tdl">10·6</td></tr> -<tr><td class="tdl">1898</td><td class="tdc">0·80</td><td class="tdl">26</td><td class="tdl pad2">6·2</td></tr> -<tr><td class="tdl">1899</td><td class="tdc">0·71</td><td class="tdl">29</td><td class="tdl pad2">7·2</td></tr> -<tr><td class="tdl">1900</td><td class="tdc">0·67</td><td class="tdl">35</td><td class="tdl">10·2</td></tr> -<tr><td class="tdl">1901</td><td class="tdc">0·76</td><td class="tdl">39</td><td class="tdl pad2">7</td></tr> -<tr><td class="tdl">1902</td><td class="tdc">0·76</td><td class="tdl">46</td><td class="tdl pad2">5·7</td></tr> -<tr><td class="tdl">1903</td><td class="tdc">0·61</td><td class="tdl">48</td><td class="tdl pad2">6·3</td></tr> -<tr><td class="tdl">1904</td><td class="tdc">0·54</td><td class="tdl">48</td><td class="tdl">11·8</td></tr> -</table></div> - -<p><span class="pagenum"><a name="Page_70" id="Page_70">[70]</a></span></p> - - -<h3><span class="smcap">Stones other than Diamonds</span></h3> - -<p>Accompanying diamonds in the concentrates -are a number of other minerals of -high specific gravity, and some of notable -beauty. Among these are the rich red -pyrope (garnet), sp. gr. 3·7, containing from<span class="pagenum"><a name="Page_71" id="Page_71">[71]</a></span> -1·4 to 3 per cent of oxide of chromium; -zircon, in flesh-coloured grains and crystals, -sp. gr. 4 to 4·7; kyanite, sp. gr. 3·45 to 3·7, -discernible by its blue colour and perfect -cleavage; chrome diopside, sp. gr. 3·23 to -3·5, of a bright green colour; bronzite, sp. -gr. 3·1 to 3·3; magnetite, sp. gr. 4·9 to 5·2; -mixed chrome and titanium iron ore, sp. gr. -4·4 to 4·9, containing from 13 to 61 per cent -of oxide of chromium, and from 3 to 68 per -cent of titanic acid, in, changeable quantities; -hornblende, sp. gr. 2·9 to 3·4; -barytes, sp. gr. 4·3 to 4·7; and mica. Some -of the garnets are of fine quality, and one -was recently cut which resembled a pigeonblood -ruby, and attracted an offer of £25.</p> - -<p>In the pulsator and sorting house most -of the native labourers are long-sentence -convicts, supplied with food, clothing, and -medical attendance by the Company. They -are necessarily well guarded. I myself saw -about 1000 convicts at work. I was told -that insubordination is very rare; apart<span class="pagenum"><a name="Page_72" id="Page_72">[72]</a></span> -from the hopelessness of a successful rising, -there is little inducement to revolt; the lot -of these diamond workers is preferable to -life in the Government prisons, and they -seem contented.</p> - -<div class="figcenter"> -<a name="P_072" id="P_072"></a> -<img src="images/i_p072a1.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 10. DE BEERS DIAMOND OFFICE. 25,000 CARATS. -</div> -</div> - -<div class="figcenter"> -<a name="P_072x" id="P_072x"></a> -<img src="images/i_p072a2.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 11. DE BEERS DIAMOND OFFICE. THE VALUATORS’ TABLE.<br /> -<p class="right">To face p. 72.</p> -</div> -</div> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_73" id="Page_73">[73]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_V" id="CHAPTER_V"></a><a href="#CONTENTS">CHAPTER V</a><br /> -<br /> -<span class="fs80 bold">THE DIAMOND OFFICE</span></h2> - - -<p class="drop-capy">From the pulsator the diamonds are -sent to the general office in Kimberley -to be cleansed in a boiling mixture of nitric -and sulphuric acids. A parcel of diamonds -loses about half a part per 1000 by this treatment. -On one of my visits to the diamond -office the door opened and in walked two -young men, each carrying a large enamelled -saucepan containing something steaming -hot. They went to one of the zinc-covered -tables and turned out from the saucepans a -lustrous heap of 25,000 carats of diamonds -(<a href="#P_072">Fig. 10</a>). They had just been boiled in -acid and washed.</p> - -<p>After purification the diamonds are handed -to the valuators (<a href="#P_072x">Fig. 11</a>), who sort them -into classes, according to size, colour, and<span class="pagenum"><a name="Page_74" id="Page_74">[74]</a></span> -purity. In the diamond office they are -sorted into ten classes. In the year 1895, in -1141·8 carats of stones, the proportions of -the different classes were as follows:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl">Close goods (best stones)</td><td class="tdr">53·8</td></tr> -<tr><td class="tdl">Spotted stones</td><td class="tdr">75·8</td></tr> -<tr><td class="tdl">Fine cleavage</td><td class="tdr">79·1</td></tr> -<tr><td class="tdl">Flats</td><td class="tdr">39·5</td></tr> -<tr><td class="tdl">Macles</td><td class="tdr">36·5</td></tr> -<tr><td class="tdl">Ordinary and rejection cleavage</td><td class="tdr">243·4</td></tr> -<tr><td class="tdl">Rejection stones</td><td class="tdr">43·2</td></tr> -<tr><td class="tdl">Light and brown cleavage</td><td class="tdr">56·9</td></tr> -<tr><td class="tdl">Rubbish</td><td class="tdr">371·8</td></tr> -<tr><td class="tdl"></td><td class="tdr">———</td></tr> -<tr><td class="tdl"></td><td class="tdr">1000·0</td></tr> -<tr><td class="tdl"></td><td class="tdr">———</td></tr> -<tr><td class="tdl">Fine sand</td><td class="tdr">141·8</td></tr> -<tr><td class="tdl"></td><td class="tdr">———</td></tr> -<tr><td class="tdl"></td><td class="tdr">1141·8</td></tr> -</table></div> - -<p>It is a sight for Aladdin to see the valuators -at work in the strong-room of the -De Beers Company at Kimberley. The -tables are literally heaped with stones won -from the rough blue ground—stones of all<span class="pagenum"><a name="Page_75" id="Page_75">[75]</a></span> -sizes, purified, flashing, and of inestimable -price; stones that will be coveted by men -and women all the world over; and last, -but not least, stones that are probably -destined to largely influence the development -and history of a whole huge continent.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_76" id="Page_76">[76]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_VI" id="CHAPTER_VI"></a><a href="#CONTENTS">CHAPTER VI</a><br /> -<br /> -<span class="fs80 bold">NOTEWORTHY DIAMONDS</span></h2> - - -<p class="drop-capy">Prodigious diamonds are not so uncommon -as is generally supposed. -Diamonds weighing over an ounce (151·5 -carats) are not unfrequent at Kimberley. -Some years ago, in one parcel of stones, -I saw eight perfect ounce crystals, and one -stone weighing 2 ounces (<a href="#P_076">Fig. 12</a>). The largest -diamond from the Kimberley mines weighed -428½ carats, or nearly 4 ounces troy. It -measured 1⅞ inch through the longest axis -and was 1½ inch square. After cutting it -weighed 228½ carats, losing 200 carats in -the process. The largest known diamond -was discovered in January, 1905, at the -New Premier Mine, near Pretoria. This -mine is of the same type as the Kimberley -mines, but larger in size, and, in fact, is the -largest known diamantiferous pipe in the<span class="pagenum"><a name="Page_77" id="Page_77">[77]</a></span> -world—the pipe containing the “blue -ground,” along the longer diameter of its -oval-shaped cross-section, measuring over -half a mile, and its area is estimated at -350,000 square yards. This pipe breaks -through felsitic rocks. The diamond, called -“Cullinan” from the name of one of the -directors of the company on whose farm it -was discovered, was presented to King -Edward on his birthday by the people of -the Transvaal. It weighed no less than -3025¾ carats, or 9586·5 grains (1·37 lb. -avoirdupois). It was a fragment, probably -less than half, of a distorted octahedral -crystal; the other portions still await discovery -by some fortunate miner. The -frontispiece shows this diamond in its -natural size, from a photograph taken by -myself. I had an opportunity of examining -and experimenting with this unequalled -stone before it was cut. A beam of polarised -light passed in any direction through the -stone, and then through an analyser, revealed<span class="pagenum"><a name="Page_78" id="Page_78">[78]</a></span> -colours in all cases, appearing brightest -when the light passed along the greatest -diameter—about 4 inches. Here the colours -were very fine, but no regular figure was to -be seen. Round a small black spot in the -interior of the stone the colours were very -vivid, changing and rotating round the spot -as the analyser was turned. These observations -indicated internal strain.</p> - -<div class="figcenter"> -<a name="P_076" id="P_076"></a> -<img src="images/i_p076a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 12. A GROUP OF LARGE DIAMOND CRYSTALS.<br /> -<p class="right">To face p. 76.</p> -</div> -</div> - -<p>The clearness throughout was remarkable, -the stone being absolutely limpid like water, -with the exception of a few flaws, dark -graphitic spots, and coloured patches close -to the outside. At one part near the surface -there was an internal crack, showing well -the colours of thin plates. At another -point there was a milky, opaque mass, of a -brown colour, with pieces of what looked -like iron oxide. There were four cleavage -planes of great smoothness and regularity. -On other parts of the surface the crystalline -structure was very marked. The edges -were rounded in parts, and triangular<span class="pagenum"><a name="Page_79" id="Page_79">[79]</a></span> -markings (depressions) were to be seen. -I also noticed square depressions, nearly -as sharp and perfect as the triangular ones.</p> - -<p>The cleaving and cutting and polishing of -the Cullinan diamond was entrusted to the -firm of Asscher and Co., in Amsterdam. -The cleavage of the diamond was very -successfully accomplished by Mr. Joseph -Asscher. An incision half an inch deep was -made with a sharp diamond point in the -proper place, then a specially designed -knife blade was placed in the incision and -it was struck a heavy blow with a piece of -steel. The diamond split through a defective -spot, part of which was left in each -portion of the diamond.</p> - -<p>Gigantic as is the Cullinan diamond, it -represents in weight less than half the daily -output of the De Beers mines, which averages -about 7000 carats per day.</p> - -<p>Next in size to the Cullinan comes the one -which was found at the Jagersfontein Mine. -It weighed 970 carats—over half a pound.</p> - -<p><span class="pagenum"><a name="Page_80" id="Page_80">[80]</a></span></p> - -<p>The following table gives the names and -weights of some historic diamonds (<a href="#P_080">Fig. 13</a>):</p> - -<p class="noindent pad4"> - 1. Koh-i-noor, after the second cutting, 106 carats.<br /> - - 2. Loterie d’Angleterre, 49 carats.<br /> - - 3. Nizam of Hyderabad, 279 carats.<br /> - - 4. Orloff, 194 carats.<br /> - - 5. Koh-i-noor, after first cutting, 279 carats.<br /> - - 6. Regent or Pitt, 137 carats.<br /> - - 7. Duke of Tuscany, 133 carats.<br /> - - 8. Star of the South, 124 carats.<br /> - - 9. Pole Star, 40 carats.<br /> - -10. Tiffany, yellow, 125 carats.<br /> - -11. Hope, blue diamond, 44 carats.<br /> - -12. Sancy, 53 carats.<br /> - -13. Empress Eugenie, 51 carats.<br /> - -14. Shah, 86 carats.<br /> - -15. Nassak, 79 carats.<br /> - -16. Pasha of Egypt, 40 carats.<br /> - -17. Cullinan, 3025 carats.<br /> - -18. Excelsior, Jagersfontein, 969 carats.<br /> -</p> - -<div class="figcenter"> -<a name="P_080" id="P_080"></a> -<img src="images/i_p080a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 13. SOME HISTORIC DIAMONDS.<br /> -<p class="right">To face p. 80.</p> -</div> -</div> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_81" id="Page_81">[81]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_VII" id="CHAPTER_VII"></a><a href="#CONTENTS">CHAPTER VII</a><br /> -<br /> -<span class="fs80 bold">BOART, CARBONADO, AND GRAPHITE</span></h2> - - -<p class="drop-capy">The black inclusions in some transparent -diamonds consist of graphite. -On crushing a clear diamond showing such -spots and heating in oxygen to a temperature -well below the point at which diamond -begins to burn, Moissan found that the -grey tint of the powder disappeared, no -black spots being seen under the microscope. -There also occur what may be considered -intermediate forms between the well-crystallised -diamond and graphite. These are -“boart” and “carbonado.” Boart is an -imperfectly crystallised diamond, having -no clear portions, and therefore useless for -gems. Shot boart is frequently found in -spherical globules, and may be of all colours. -Ordinary boart is so hard that it is used<span class="pagenum"><a name="Page_82" id="Page_82">[82]</a></span> -in rock-drilling, and when crushed it is -employed for cutting and polishing other -stones. Carbonado is the Brazilian term -for a still less perfectly crystallised form of -carbon. It is equally hard, and occurs in -porous masses and in massive black pebbles, -sometimes weighing two or more ounces.</p> - -<p>The ash left after burning a diamond -invariably contains iron as its chief constituent; -and the most common colours of -diamonds, when not perfectly pellucid, show -various shades of brown and yellow, from -the palest “off colour” to almost black. -These variations give support to the theory -advanced by Moissan that the diamond has -separated from molten iron—a theory of -which I shall say more presently—and also -explain how it happens that stones from -different mines, and even from different -parts of the same mine, differ from each -other. Further confirmation is given by -the fact that the country round Kimberley -is remarkable for its ferruginous character,<span class="pagenum"><a name="Page_83" id="Page_83">[83]</a></span> -and iron-saturated soil is popularly regarded -as one of the indications of the near -presence of diamonds.</p> - - -<h3><span class="smcap">Graphite</span></h3> - -<p>Intermediate between soft carbon and -diamond come the graphites. The name -graphite is given to a variety of carbon, -generally crystalline, which in an oxidising -mixture of chlorate of potassium and -nitric acid forms graphitic oxide. This -varies in colour from green to brown or -yellow, or it is almost without colour, -according to the completeness of the reaction. -Graphites are of varying densities, -from 2·0 to 3·0, and generally of crystalline -aspect. Graphite and diamond pass insensibly -into one another. Hard graphite -and soft diamond are near the same specific -gravity. The difference appears to be one -of pressure at the time of formation.</p> - -<p>Some forms of graphite exhibit the remarkable -property by which it is possible<span class="pagenum"><a name="Page_84" id="Page_84">[84]</a></span> -to ascertain approximately the temperature -at which they were formed, or to which -they have subsequently been exposed. -Sprouting graphite is a form, frequently met -with in nature, which on moderate heating -swells up to a bulky, very light mass of -amorphous carbon. Moissan has found it -in blue ground from Kimberley; my own -results verify his. When obtained by -simple elevation of temperature in the arc -or the electric furnace graphites do not -sprout; but when they are formed by dissolving -carbon in a metal at a high temperature -and then allowing the graphite to -separate out on cooling, the sprouting -variety appears. The phenomenon of sprouting -is easily shown. If a few grains are -placed in a test-tube and heated to about -170° C., the grains increase enormously in -bulk and fill the tube with a light form of -amorphous carbon.</p> - -<p>The resistance of a graphite to oxidising -agents is greater the higher the temperature<span class="pagenum"><a name="Page_85" id="Page_85">[85]</a></span> -to which it has previously been exposed. -Graphites which are easily attacked by a -mixture of fuming nitric acid and potassium -chlorate are rendered more resistant by -strong heat in the electric furnace.</p> - -<p>I have already signified that there are -various degrees of refractoriness to chemical -reagents among the different forms of -graphite. Some dissolve in strong nitric acid; -other forms of graphite require a mixture -of highly concentrated nitric acid and -potassium chlorate to attack them, and -even with this intensely powerful agent -some graphites resist longer than others. -M. Moissan has shown that the power of -resistance to nitric acid and potassium -chlorate is in proportion to the temperature -at which the graphite was formed, and with -tolerable certainty we can estimate this -temperature by the resistance of the specimen -of graphite to this reagent.</p> - -<p><span class="pagenum"><a name="Page_86" id="Page_86">[86]</a></span></p> - - -<h3><span class="smcap">Crystallisation</span></h3> - -<p>The diamond belongs to the isometric -system of crystallography; the prevailing -form is octahedral. It frequently occurs -with curved faces and edges. Twin crystals -(macles) are not uncommon. Diamond -crystals are generally perfect on all sides. -They seldom show irregular sides or faces -by which they were attached to a support, -as do artificial crystals of chemical salts; -another proof that the diamond must have -crystallised from a dense liquid.</p> - -<p>The accompanying illustration (<a href="#P_086">Fig. 14</a>) -shows some of the various crystalline forms -of native diamonds.</p> - -<div class="figcenter"> -<a name="P_086" id="P_086"></a> -<img src="images/i_p086a.jpg" width="450" alt="" /> -<div class="caption"> -FIG. 14. CRYSTALLINE FORMS OF NATIVE DIAMONDS.<br /> -<p class="right">To face p. 86.</p> -</div> -</div> - -<p>No. 1. Diamond in the form of a hexakis-octahedron -(the forty-eight scalenohedron), -or a solid figure contained by forty-eight -scalene triangles. According to Professor -Maskelyne, this occurs as a self-existent -form only in the diamond.</p> - -<p>No. 2. Diamond in the form of a hexakis-octahedron<span class="pagenum"><a name="Page_87" id="Page_87">[87]</a></span> -and octahedron. From Sudafrika.</p> - -<p>No. 3. Diamond in the form of octahedron -with intersections.</p> - -<p>No. 4. Diamond from Brazil.</p> - -<p>No. 5. Diamond from Kimberley.</p> - -<p>No. 6. Diamond from Brazil.</p> - -<p>No, 7. A macle or twin crystal, showing -its formation from an octahedron with -curved edges.</p> - -<hr class="tb" /> - -<p>Some crystals of diamonds have their surfaces -beautifully marked with equilateral -triangles, interlaced and of varying sizes -(<a href="#P_088">Fig. 15</a>). Under the microscope these markings -appear as hollow depressions sharply -cut out of the surrounding surface, and -these depressions were supposed by Gustav -Rose to indicate the probability that the -diamonds had at some previous time been -exposed to incipient combustion. Rose -pointed out that similar triangular striations -appeared on the surfaces of diamonds<span class="pagenum"><a name="Page_88" id="Page_88">[88]</a></span> -burnt before the blowpipe. This experiment -I have repeated on a clear diamond, and I -have satisfied myself that during combustion -before the blowpipe, in the field of a -microscope, the surface is etched with -triangular markings different in character -from those naturally on crystals (<a href="#P_088x">Fig. 16</a>). -The artificial striæ are very irregular, much -smaller, and massed closer together, looking -as if the diamond during combustion flaked -away in triangular chips, while the markings -natural to crystals appear as if produced by -the crystallising force as they were being -built up. Many crystals of chemical compounds -appear striated from both these -causes. Geometrical markings can be produced -by eroding the surface of a crystal -of alum with water, and they also occur -naturally during crystallisation.</p> - -<div class="figcenter"> -<a name="P_088" id="P_088"></a> -<img src="images/i_p088a1.jpg" width="500" alt="" /> -<div class="caption"> -FIG. 15. TRIANGULAR MARKINGS ON NATURAL -FACE OF A DIAMOND CRYSTAL. -</div> -</div> - -<div class="figcenter"> -<a name="P_088x" id="P_088x"></a> -<img src="images/i_p088a2.jpg" width="500" alt="" /> -<div class="caption"> -FIG. 16. TRIANGULAR MARKINGS ARTIFICIALLY -PRODUCED ON A DIAMOND CRYSTAL.<br /> -<p class="right">To face page 88.</p> -</div> -</div> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_89" id="Page_89">[89]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_VIII" id="CHAPTER_VIII"></a><a href="#CONTENTS">CHAPTER VIII</a><br /> -<br /> -<span class="fs80 bold">PHYSICAL AND CHEMICAL PROPERTIES -OF THE DIAMOND</span></h2> - - -<p class="drop-capy">I need scarcely say the diamond is -almost pure carbon, and it is the hardest -substance in nature.</p> - -<p>When heated in air or oxygen to a temperature -varying from 760° to 875° C., -according to its hardness, the diamond -burns with production of carbonic acid. -It leaves an extremely light ash, sometimes -retaining the shape of the crystal, consisting -of iron, lime, magnesia, silica, and titanium. -In boart and carbonado the amount of ash -sometimes rises to 4 per cent, but in clear -crystallised diamonds it is seldom higher -than 0·05 per cent. By far the largest -constituent of the ash is iron.</p> - -<p>The following table shows the temperatures<span class="pagenum"><a name="Page_90" id="Page_90">[90]</a></span> -of combustion in oxygen of different -kinds of carbon:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl"></td><td class="tdl fs80 pad2">°C.</td></tr> -<tr><td class="tdl">Condensed vapour of carbon</td><td class="tdl">650</td></tr> -<tr><td class="tdl">Carbon from sugar, heated in an electrical furnace</td><td class="tdl">660</td></tr> -<tr><td class="tdl">Artificial graphites, generally</td><td class="tdl">660</td></tr> -<tr><td class="tdl">Graphite from ordinary cast-iron</td><td class="tdl">670</td></tr> -<tr><td class="tdl">Carbon from blue ground, of an ochre colour</td><td class="tdl">690</td></tr> -<tr><td class="tdl">Carbon from blue ground, very hard and black</td><td class="tdl">710</td></tr> -<tr><td class="tdl">Diamond, soft Brazilian</td><td class="tdl">760</td></tr> -<tr><td class="tdl">Diamond, hard Kimberley</td><td class="tdl">780</td></tr> -<tr><td class="tdl">Boart from Brazil</td><td class="tdl">790</td></tr> -<tr><td class="tdl">Boart from Kimberley</td><td class="tdl">790</td></tr> -<tr><td class="tdl">Boart, very hard, almost impossible to cut</td><td class="tdl">900</td></tr> -</table></div> - -<h3><span class="smcap">Hardness</span></h3> - -<p>Diamonds vary considerably in hardness, -and even different parts of the same crystal -differ in their resistance to cutting and -grinding.</p> - -<p><span class="pagenum"><a name="Page_91" id="Page_91">[91]</a></span></p> - -<p>Beautifully white diamonds have been -found at Inverel, New South Wales, and -from the rich yield of the mine and the -white colour of the stones great things were -expected. In the first parcel which came to -England the stones were found to be so -much harder than South African diamonds -that it was at first feared they would be -useless except for rock-boring purposes. -The difficulty of cutting them disappeared -with improved appliances, and they now are -highly prized.</p> - -<p>The famous Koh-i-noor, when being cut -into its present form, showed a notable -variation in hardness. In cutting one of -the facets near a yellow flaw, the crystal -became harder and harder the further it -was cut, until, after working the mill for six -hours at the usual speed of 2400 revolutions -a minute, little impression was made. The -speed was increased to more than 3000, -when the work slowly proceeded. Other -portions of the stone were found to be comparatively<span class="pagenum"><a name="Page_92" id="Page_92">[92]</a></span> -soft, and became harder as the -outside was cut away.</p> - -<p>The intense hardness of the diamond can -be illustrated by the following experiment. -On the flattened apex of a conical block of -steel place a diamond, and upon it bring down -a second cone of steel. On forcing together -the two steel cones by hydraulic pressure -the stone is squeezed into the steel blocks -without injuring it in the slightest degree.</p> - -<p>In an experiment I made at Kimberley -the pressure gauge showed 60 atmospheres, -and the piston being 3·2 inches diameter, -the absolute pressure was 3·16 tons, equivalent -on a diamond of 12 square mm. surface -to 170 tons per square inch of diamond.</p> - -<p>The use of diamond in glass-cutting I -need not dwell on. So hard is diamond in -comparison to glass, that a suitable splinter -of diamond will plane curls off a glass plate -as a carpenter’s tool will plane shavings off -a deal board. The illustration (<a href="#P_098">Fig. 17</a>) -shows a few diamond-cut glass shavings.</p> - -<p><span class="pagenum"><a name="Page_93" id="Page_93">[93]</a></span></p> - - -<h3><span class="smcap">Density or Specific Gravity</span></h3> - -<p>The specific gravity of the diamond varies -ordinarily from 3·514 to 3·518. For comparison, -I give in tabular form the specific -gravities of the different varieties of carbon -and of the minerals found on the sorting -tables:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl"></td><td class="tdc fs70 pad2" colspan="2">SPECIFIC</td></tr> -<tr><td class="tdl"></td><td class="tdc fs70 pad2" colspan="2">GRAVITY.</td></tr> -<tr><td class="tdl">Amorphous carbon</td><td class="tdr">1·45 –</td><td class="tdl">1·70</td></tr> -<tr><td class="tdl">Hard gas coke</td><td class="tdr"></td><td class="tdl">2·356</td></tr> -<tr><td class="tdl">Hard graphite</td><td class="tdr"></td><td class="tdl">2·5</td></tr> -<tr><td class="tdl">Quartzite and granite</td><td class="tdr"></td><td class="tdl">2·6</td></tr> -<tr><td class="tdl">Beryl</td><td class="tdr"></td><td class="tdl">2·7</td></tr> -<tr><td class="tdl">Mica</td><td class="tdr"></td><td class="tdl">2·8</td></tr> -<tr><td class="tdl">Hornblende</td><td class="tdr"></td><td class="tdl">3·0</td></tr> -<tr><td class="tdl">Boart</td><td class="tdr">3·47 –</td><td class="tdl">3·49</td></tr> -<tr><td class="tdl">Carbonado</td><td class="tdr"></td><td class="tdl">3·50</td></tr> -<tr><td class="tdl">Diamond</td><td class="tdr">3·514 –</td><td class="tdl">3·518</td></tr> -<tr><td class="tdl">Garnet</td><td class="tdr"></td><td class="tdl">3·7</td></tr> -<tr><td class="tdl">Corundum</td><td class="tdr"></td><td class="tdl">3·8</td></tr> -<tr><td class="tdl">Zircon</td><td class="tdr"></td><td class="tdl">4·4</td></tr> -<tr><td class="tdl">Barytes</td><td class="tdr"></td><td class="tdl">4·5</td></tr> -<tr><td class="tdl">Chrome and titanic iron ore</td><td class="tdr"></td><td class="tdl">4·7</td></tr> -<tr><td class="tdl">Magnetite</td><td class="tdr"></td><td class="tdl">5·0</td></tr> -</table></div> - -<p><span class="pagenum"><a name="Page_94" id="Page_94">[94]</a></span></p> - -<p>There is a substance, the double nitrate -of silver and thallium, which, while solid -at ordinary temperatures, liquefies at 75° C. -and then has a specific gravity of 4·5. Admixture -with water lowers the density to -any desired point.</p> - -<p>If a glass cell is taken containing this -liquid diluted to a density of about 3·6, and -in it is thrown pieces of the above-named -minerals, all those whose density is lower -than 3·6 will rise to the surface, while the -denser minerals will sink. If now a little water -is carefully added with constantly stirring -until the density of the liquid is reduced -to that of the diamond, the heterogeneous -collection sorts itself into three parts. The -graphite, quartz, beryl, mica, and hornblende -rise to the surface; the garnet, -corundum, zircons, etc., sink to the bottom, -while the diamonds float in the middle of -the liquid. With a platinum landing-net I -can skim off the swimmers and put them into -one dish; with the same net I can fish out<span class="pagenum"><a name="Page_95" id="Page_95">[95]</a></span> -the diamonds and put them in a second dish, -while by raising a sieve at the bottom I can -remove the heavy minerals and put them -into a third. The accurate separation of -diamonds from the heterogeneous mixture -can be effected in less time than is taken to -describe the experiment.</p> - -<p>The table shows that diamonds vary somewhat -in density among themselves, between -narrow limits. Occasionally, however, diamonds -overpass these figures. Here is an -illustration. In a test-tube of the same -dense liquid are three selected diamonds. -One rises to the top, another floats uncertain -where to settle, rising and falling as the -temperature of the sorting liquid is raised -or lowered, whilst the third sinks to the -bottom. Allowing the liquid to cool a -degree or two slightly increases the density -and sends all three to the surface.</p> - -<p><span class="pagenum"><a name="Page_96" id="Page_96">[96]</a></span></p> - - -<h3><span class="smcap">Phosphorescence of Diamond</span></h3> - -<p>After exposure for some time to the sun -many diamonds glow in a dark room. -Some diamonds are fluorescent, appearing -milky in sunlight. In a vacuum, exposed -to a high-tension current of electricity, -diamonds phosphoresce of different colours, -most South African diamonds shining with a -bluish light. Diamonds from other localities -emit bright blue, apricot, pale blue, red, -yellowish green, orange, and pale green -light. The most phosphorescent diamonds -are those which are fluorescent in the sun. -One beautiful green diamond in the writer’s -collection, when phosphorescing in a good -vacuum, gives almost as much light as a -candle, and you can easily read by its rays. -But the time has hardly come when diamonds -can be used as domestic illuminants! -The emitted light is pale green, tending to -white, and in its spectrum, when strong, -can be seen bright lines, one at about<span class="pagenum"><a name="Page_97" id="Page_97">[97]</a></span> -λ 5370 in the green, one at λ 5130 in the -greenish blue, and one at λ 5030 in the blue. -A beautiful collection of diamond crystals -belonging to Professor Maskelyne phosphoresces -with nearly all the colours of the rainbow, -the different faces glowing with different -shades of colour. Diamonds which phosphoresce -red generally show the yellow -sodium line on a continuous spectrum. In -one Brazilian diamond phosphorescing a -reddish-yellow colour I detected in its spectrum -the citron line characteristic of yttrium.</p> - -<p>The rays which make the diamond phosphoresce -are high in the ultra-violet. To -illustrate this phosphorescence under the -influence of the ultra-violet rays, arrange a -powerful source of these rays, and in front -expose a design made up of certain minerals, -willemite, franklinite, calcite, etc.—phosphorescing -of different colours. Their brilliant -glow ceases entirely when a thin piece -of glass is interposed between them and the -ultra-violet lamp.</p> - -<p><span class="pagenum"><a name="Page_98" id="Page_98">[98]</a></span></p> - -<p>I now draw attention to a strange property -of the diamond, which at first sight -might seem to discount the great permanence -and unalterability of this stone. It has been -ascertained that the cause of phosphorescence -is in some way connected with the -hammering of the electrons, violently driven -from the negative pole on to the surface of -the body under examination, and so great is -the energy of the bombardment, that impinging -on a piece of platinum or even -iridium, the metal will actually melt. When -the diamond is thus bombarded in a radiant -matter tube the result is startling. It not -only phosphoresces, but becomes discoloured, -and in course of time becomes black on the -surface. Some diamonds blacken in the -course of a few minutes, while others require -an hour or more to discolour. This -blackening is only superficial, and although -no ordinary means of cleaning will remove -the discolouration, it goes at once when the -stone is polished with diamond powder.<span class="pagenum"><a name="Page_99" id="Page_99">[99]</a></span> -Ordinary oxidising reagents have little or -no effect in restoring the colour.</p> - -<div class="figcenter"> -<a name="P_098" id="P_098"></a> -<img src="images/i_p098a1.jpg" width="300" alt="" /> -<div class="caption"> -FIG. 17. DIAMOND-CUT GLASS AND SHAVINGS. -</div> -</div> - -<div class="figcenter"> -<a name="P_098x" id="P_098x"></a> -<img src="images/i_p098a2.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 18. DIAMONDS IN RÖNTGEN RAYS.<br /> -<p class="noindent pad10"> -A. BLACK DIAMOND IN GOLD FRAME.<br /> -B. PINK DELHI DIAMOND.<br /> -C. PASTE IMITATION OF B.</p> -<p class="right">To face p. 98.</p> -</div> -</div> - -<p>The superficial dark coating on a diamond -after exposure to molecular bombardment -I have proved to be graphite. M. Moissan -has shown that this graphite, on account of -its great resistance to oxidising reagents, -cannot have been formed at a lower temperature -than 3600° C.</p> - -<p>It is thus manifest that the bombarding -electrons, striking the diamond with enormous -velocity, raise the superficial layer to -the temperature of the electric arc and turn -it into graphite, whilst the mass of diamond -and its conductivity to heat are sufficient to -keep down the general temperature to such -a point that the tube appears scarcely more -than warm to the touch.</p> - -<p>A similar action occurs with silver, the -superficial layers of which can be raised to -a red heat without the whole mass becoming -more than warm.</p> - -<p><span class="pagenum"><a name="Page_100" id="Page_100">[100]</a></span></p> - - -<h3><span class="smcap">Conversion of Diamond into Graphite</span></h3> - -<p>Although we cannot convert graphite -into diamond, we can change the diamond -into graphite. A clear crystal of diamond -is placed between two carbon poles, and -the poles with intervening diamond are -brought together and an arc formed between. -The temperature of the diamond rapidly -rises, and when it approaches 3600° C., the -vaporising point of carbon, it breaks down, -swells, and changes into black and valueless -graphite.</p> - - -<h3><span class="smcap">Tribo-Luminescence</span></h3> - -<p>A few minerals give out light when rubbed. -In the year 1663 the Hon. Robert Boyle -read a paper before the Royal Society, -in which he described several experiments -made with a diamond which markedly -showed tribo-luminescence. As specimens -of tribo-luminescent bodies I may instance -sphalerite (sulphide of zinc), and an artificial<span class="pagenum"><a name="Page_101" id="Page_101">[101]</a></span> -sphalerite, which is even more responsive -to friction than the native sulphide.<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a></p> - -<p>Mrs. Kunz, wife of the well-known New -York mineralogist, possesses, perhaps, the -most remarkable of all phosphorescing -diamonds. This prodigy diamond will -phosphoresce in the dark for some minutes -after being exposed to a small pocket electric -light, and if rubbed on a piece of cloth a long -streak of phosphorescence appears.</p> - - -<h3><span class="smcap">Absorption Spectrum of Diamond</span></h3> - -<p>On passing a ray of light through a diamond -and examining it in a spectroscope, -Walter has found in all colourless brilliants -of over 1 carat in weight an absorption -band at wave-length 4155 (violet). He<span class="pagenum"><a name="Page_102" id="Page_102">[102]</a></span> -ascribes this band to an impurity and suggests -it may possibly be due to samarium. -Three other fainter lines were detected in -the ultra-violet by means of photography.</p> - - -<h3><span class="smcap">Refractivity</span></h3> - -<p>But it is not the hardness of the diamond -so much as its optical qualities that make -it so highly prized. It is one of the most -refracting substances in nature, and it also -has the highest reflecting properties. In -the cutting of diamonds advantage is -taken of these qualities. When cut as a -brilliant the facets on the lower side are -inclined so that light falls on them at an -angle of 24° 13´, at which angle all the -incident light is totally reflected. A well-cut -brilliant should appear opaque by -transmitted light except at a small spot in -the middle where the table and culet are -opposite. All the light falling on the front -of the stone is reflected from the facets, and -the light passing into the diamond is reflected<span class="pagenum"><a name="Page_103" id="Page_103">[103]</a></span> -from the interior surfaces and refracted -into colours when it passes out into -the air, giving rise to the lightnings, the -effulgence, and coruscations for which the -diamond is supreme above all other gems.</p> - -<p>The following table gives the refractive -indices of diamonds and other bodies:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdc smcap" colspan="2">Refractive Indices for the D Line</td></tr> -<tr><td class="tdl">Chromate of lead</td><td class="tdr">2·50–2·97</td></tr> -<tr><td class="tdl">Diamond</td><td class="tdr">2·47–2·75</td></tr> -<tr><td class="tdl">Phosphorus</td><td class="tdr">2·22</td></tr> -<tr><td class="tdl">Sulphur</td><td class="tdr">2·12</td></tr> -<tr><td class="tdl">Ruby</td><td class="tdr">1·78</td></tr> -<tr><td class="tdl">Thallium glass</td><td class="tdr">1·75</td></tr> -<tr><td class="tdl">Iceland spar</td><td class="tdr">1·65</td></tr> -<tr><td class="tdl">Topaz</td><td class="tdr">1·61</td></tr> -<tr><td class="tdl">Beryl</td><td class="tdr">1·60</td></tr> -<tr><td class="tdl">Emerald</td><td class="tdr">1·59</td></tr> -<tr><td class="tdl">Flint glass</td><td class="tdr">1·58</td></tr> -<tr><td class="tdl">Quartz</td><td class="tdr">1·55</td></tr> -<tr><td class="tdl">Canada balsam</td><td class="tdr">1·53</td></tr> -<tr><td class="tdl">Crown glass</td><td class="tdr">1·53</td></tr> -<tr><td class="tdl">Fluor-spar</td><td class="tdr">1·44</td></tr> -<tr><td class="tdl">Ice</td><td class="tdr">1·31</td></tr> -</table></div> - -<p><span class="pagenum"><a name="Page_104" id="Page_104">[104]</a></span></p> - -<p>In vain I have searched for a liquid of the -same refraction as diamond. Such a liquid -would be invaluable to the merchant, as on -immersing a stone the clear body would -absolutely disappear, leaving in all their -ugliness the flaws and black specks so frequently -seen even in the best stones.</p> - - -<h3><span class="smcap">The Diamond and Polarised Light</span></h3> - -<p>Having no double refraction, the diamond -should not act on polarised light. But as is -well known, if a transparent body which -does not so act is submitted to strain of an -irregular character it becomes doubly refracting, -and in the polariscope reveals the -existence of the strain by brilliant colours -arranged in a more or less defined pattern, -according to the state of tension in which -the crystal exists. I have examined many -hundred diamond crystals under polarised -light, and with few exceptions the colours -show how great is the strain to which some -of them are exposed. On rotating the<span class="pagenum"><a name="Page_105" id="Page_105">[105]</a></span> -polariser, the black cross most frequently -seen revolves round a particular point in -the inside of the crystal; on examining -this point with a high power we sometimes -see a slight flaw, more rarely a minute -cavity. The cavity is filled with gas at -enormous pressure, and the strain is set up -in the stone by the effort of the gas to -escape. I have already said that the great -Cullinan diamond by this means revealed a -state of considerable internal stress and -strain.</p> - -<p>So great is this strain of internal tension -that it is not uncommon for a diamond to -explode soon after it reaches the surface, -and some have been known to burst in the -pockets of the miners or when held in the -warm hand. Large crystals are more liable -to burst than smaller pieces. Valuable -stones have been destroyed in this way, and -it is whispered that cunning dealers are not -averse to allowing responsible clients to -handle or carry in their warm pockets<span class="pagenum"><a name="Page_106" id="Page_106">[106]</a></span> -large crystals fresh from the mine. By -way of safeguard against explosion some -dealers imbed large diamonds in raw potato -to ensure safe transit to England.</p> - -<p>The anomalous action which many diamonds -exert on polarised light is not such as -can be induced by heat, but it can easily be -conferred on diamonds by pressure, showing -that the strain has not been produced by -sudden cooling, but by sudden lowering of -pressure.</p> - -<p>The illustration of this peculiarity is not -only difficult, but sometimes exceedingly -costly—difficult because it is necessary to -arrange for projecting on the screen the -image of a diamond crystal between the -jaws of a hydraulic press, the illuminating -light having to pass through delicate optical -polarising apparatus—and costly because -only perfectly clear crystals can be used, and -crystals of this character sometimes fly -to pieces as the pressure rises. At first no -colour is seen on the screen, the crystal not<span class="pagenum"><a name="Page_107" id="Page_107">[107]</a></span> -being birefringent. A movement of the -handle of the press, however, gives the -crystal a pinch, instantly responded to by -the colours on the screen, showing the production -of double refraction. Another -movement of the handle brightens the -colours, and a third may strain the crystal -beyond its power of resistance, when the -crystal flies to pieces.</p> - - -<h3><span class="smcap">The Diamond and Röntgen Rays</span></h3> - -<p>The diamond is remarkable in another -respect. It is extremely transparent to the -Röntgen rays, whereas highly refracting -glass, used in imitation diamonds, is almost -perfectly opaque to the rays. I exposed -for a few seconds over a photographic plate -to the X-rays the large Delhi diamond of -a rose-pink colour weighing 31½ carats, a -black diamond weighing 23 carats, and a -glass imitation of the pink diamond (<a href="#P_098x">Fig. 18</a>). -On development the impression where the -diamond obscured the rays was found to be<span class="pagenum"><a name="Page_108" id="Page_108">[108]</a></span> -strong, showing that most rays passed -through, while the glass was practically -opaque. By this means imitation diamonds -can readily be distinguished from true gems.</p> - - -<h3><span class="smcap">Action of Radium on Diamond</span></h3> - -<p>The β-rays from radium having like -properties to the stream of negative electrons -in a radiant matter tube, it was of -interest to ascertain if they would exert a -like difference on diamond. The diamond -glows under the influence of the β-radiations, -and crushed diamond cemented to a piece -of card or metal makes an excellent screen -in a spinthariscope—almost as good as zinc -sulphide. Some colourless crystals of diamond -were imbedded in radium bromide -and kept undisturbed for more than twelve -months. At the end of that time they were -examined. The radium had caused them -to assume a bluish-green colour, and their -value as “fancy stones” had been increased.</p> - -<p>This colour is persistent and penetrates<span class="pagenum"><a name="Page_109" id="Page_109">[109]</a></span> -below the surface. It is unaffected by long-continued -heating in strong nitric acid and -potassium chlorate, and is not discharged -by heating to redness.</p> - -<p>To find out if this prolonged contact with -radium had communicated to the diamond -any radio-active properties, six diamonds -were put on a photographic plate and kept -in the dark for a few hours. All showed -radio-activity by darkening the sensitive -plate, some being more-active than others. -Like the green tint, the radio-activity persists -after drastic treatment. To me this proves -that radio-activity does not merely consist -in the adhesion of electrons or emanations -given off by radium to the surface of an -adjacent body, but the property is one -involving layers below the surface, and like -the alteration of tint, is probably closely -connected with the intense molecular excitement -the stone had experienced during its -twelve months’ burial in radium bromide.</p> - -<p>A diamond that had been coloured by<span class="pagenum"><a name="Page_110" id="Page_110">[110]</a></span> -radium, and had acquired strong radio-active -properties, was slowly heated to dull -redness in a dark room. Just before visibility -a faint phosphorescence spread over the -stone. On cooling and examining the diamond -it was found that neither the colour nor the -radio-activity had suffered appreciably.</p> - - -<h3><span class="smcap">Boiling- and Melting-point of Carbon</span></h3> - -<p>On the average the critical point of a -substance is 1·5 times its absolute boiling-point. -Therefore the critical point of carbon -should be about 5800° Ab. But the absolute -critical temperature divided by the critical -pressure is for all the elements so far examined -never less than 2·5; this being -about the value Sir James Dewar finds for -hydrogen. So that, accepting this, we get -the maximum critical pressure as follows, -viz. 2320 atmospheres:</p> - -<p class="pad3"> -<span class="blkb"> - <span class="blka u">5800° Ab.</span> - <span class="blka">CrP</span> -</span> = 2.5, or CrP = <span class="blkb"> - <span class="blka u">5800° Ab.</span> - <span class="blka">2.5</span> - </span>,</p> -<p class="center">or 2320 atmospheres.</p> - -<p><span class="pagenum"><a name="Page_111" id="Page_111">[111]</a></span></p> - -<p>Carbon and arsenic are the only two -elements that have a melting-point above -the boiling-point; and among compounds -carbonic acid and fluoride of silicium are the -only other bodies with similar properties. -Now the melting-point of arsenic is about -1·2 times its absolute boiling-point. With -carbonic acid and fluoride of silicium the -melting-points are about 1·1 times their -boiling-points. Applying these ratios to -carbon, we find that its melting-point would -be about 4400°.</p> - -<p>Therefore, assuming the following data:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl">Boiling-point</td><td class="tdl">3870° Ab.</td></tr> -<tr><td class="tdl">Melting-point</td><td class="tdl">4400°</td></tr> -<tr><td class="tdl">Critical temperature</td><td class="tdl">5800°</td></tr> -<tr><td class="tdl">Critical pressure</td><td class="tdl">2320 Ats.</td></tr> -</table></div> - -<p class="noindent">the Rankine or Van der Waals formula, -calculated from the boiling-point and critical -data, would be as follows:</p> - -<p class="center">log. P = 10·11 - 39120/T,</p> - -<p><span class="pagenum"><a name="Page_112" id="Page_112">[112]</a></span></p> - -<p class="noindent">and this gives for a temperature of 4400° Ab. -a pressure of 16·6 Ats. as the melting-point -pressure. The results of the formula are -given in the form of a table:</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdc fs80">Temperature</td><td class="tdc fs80 pad2h">Pressure</td></tr> -<tr><td class="tdc fs80">Ab.</td><td class="tdc fs80 pad2h">Ats.</td></tr> -<tr><td class="tdc">3870°</td><td class="tdl pad3">1·00</td><td class="tdl">Boiling-point.</td></tr> -<tr><td class="tdc">4000°</td><td class="tdl pad3">2·14</td></tr> -<tr><td class="tdc">4200°</td><td class="tdl pad3">6·25</td></tr> -<tr><td class="tdc">4400°</td><td class="tdl pad2h">16·6</td><td class="tdl">Melting-point.</td></tr> -<tr><td class="tdc">4600°</td><td class="tdl pad2h">40·4</td></tr> -<tr><td class="tdc">4800°</td><td class="tdl pad2h">91·2</td></tr> -<tr><td class="tdc">5000°</td><td class="tdl pad2">193</td></tr> -<tr><td class="tdc">5200°</td><td class="tdl pad2">386</td></tr> -<tr><td class="tdc">5400°</td><td class="tdl pad2">735</td></tr> -<tr><td class="tdc">5600°</td><td class="tdl">1330</td></tr> -<tr><td class="tdc">5800°</td><td class="tdl">2320</td><td class="tdl">Critical point (15 tons per square inch).</td></tr> -</table></div> - -<p><span class="pagenum"><a name="Page_113" id="Page_113">[113]</a></span></p> - -<div class="figcenter"> -<a name="P_113" id="P_113"></a> -<img src="images/i_p113.jpg" width="250" alt="" /> -<div class="caption smcap"> -Fig. 19. Curve of Vapour Pressure of Carbon -</div> -</div> - -<p>If, then, we may reason from these rough -estimates, above a temperature of 5800° Ab. -no amount of pressure will cause carbon -vapour to assume liquid form, whilst at -4400° Ab. a pressure of above 17 atmospheres -would suffice to liquefy some of it. -Between these extremes the curve of vapour -pressure is assumed to be logarithmic, as -represented in the accompanying diagram. -The constant 39120 which occurs in the -logarithmic formula enables us to calculate -the latent heat of evaporation. If we assume -the vapour density to be normal, or the -molecule in vapour as C<sub>2</sub>, then the heat of<span class="pagenum"><a name="Page_114" id="Page_114">[114]</a></span> -volatilisation of 12 grms. of carbon would be -90,000 calories; or, if the vapour is a condensed -molecule like C<sub>6</sub>, then the 12 grms. -would need 30,000 calories. In the latter -case the evaporation of 1 grm. of carbon -would require 2500 calories, whereas a substance -like zinc needs only about 400 -calories.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_115" id="Page_115">[115]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_IX" id="CHAPTER_IX"></a><a href="#CONTENTS">CHAPTER IX</a><br /> -<br /> -<span class="fs80 bold">GENESIS OF THE DIAMOND</span></h2> - - -<p class="drop-capy">Speculations as to the probable origin -of the diamond have been greatly forwarded -by patient research, and particularly -by improved means of obtaining high temperatures, -an advance we owe principally to -the researches of the late Professor Moissan.</p> - -<p>Until recent years carbon was considered -absolutely non-volatile and infusible; but -the enormous temperatures placed at the disposal -of experimentalists by the introduction -of electricity show that, instead of breaking -rules, carbon obeys the same laws that -govern other bodies. It volatilises at the -ordinary pressure at a temperature of about -3600° C., and passes from the solid to the -gaseous state without liquefying. It has -been found that other bodies, such as arsenic, -which volatilise without liquefying at the<span class="pagenum"><a name="Page_116" id="Page_116">[116]</a></span> -ordinary pressure, will easily liquefy if pressure -is added to temperature. It naturally -follows that if along with the requisite temperature -sufficient pressure is applied, liquefaction -of carbon will take place, when on -cooling it will crystallise. But carbon at -high temperatures is a most energetic -chemical agent, and if it can get hold of -oxygen from the atmosphere or any compound -containing it, it will oxidise and fly -off in the form of carbonic acid. Heat and -pressure therefore are of no avail unless the -carbon can be kept inert.</p> - -<p>It has long been known that iron, when -melted, dissolves carbon, and on cooling -liberates it in the form of graphite. Moissan -discovered that several other metals, especially -silver, have similar properties; but -iron is the best solvent for carbon. The -quantity of carbon entering into solution -increases with the temperature.</p> - -<div class="figcenter"> -<a name="P_116" id="P_116"></a> -<img src="images/i_p116a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 20. MOISSAN’S ELECTRIC FURNACE.<br /> -<p class="right">To face p. 116.</p> -</div> -</div> - -<p>For the artificial manufacture of diamond -the first necessity is to select pure iron—free<span class="pagenum"><a name="Page_117" id="Page_117">[117]</a></span> -from sulphur, silicon, phosphorus, etc.—and -to pack it in a carbon crucible with pure charcoal -from sugar. The crucible is then put -into the body of the electric furnace and a -powerful arc formed close above it between -carbon poles, utilising a current of 700 -ampères at 40 volts pressure (<a href="#P_116">Fig. 20</a>). The -iron rapidly melts and saturates itself with -carbon. After a few minutes’ heating to a -temperature above 4000° C.—a temperature -at which the iron melts like wax and volatilises -in clouds—the current is stopped and -the dazzling fiery crucible is plunged beneath -the surface of cold water, where it is -held till it sinks below a red heat. As is well -known, iron increases in volume at the -moment of passing from the liquid to the -solid state. The sudden cooling solidifies -the outer layer of iron and holds the inner -molten mass in a tight grip. The expansion -of the inner liquid on solidifying produces -an enormous pressure, and under the stress -of this pressure the dissolved carbon separates<span class="pagenum"><a name="Page_118" id="Page_118">[118]</a></span> -out in transparent forms—minutely -microscopic, it is true—all the same veritable -diamonds, with crystalline form and -appearance, colour, hardness, and action on -light, the same as the natural gem.</p> - -<p>Now commences the tedious part of the -process. The metallic ingot is attacked with -hot nitro-hydrochloric acid until no more -iron is dissolved. The bulky residue consists -chiefly of graphite, together with -translucent chestnut-coloured flakes of carbon, -black opaque carbon of a density of -from 3·0 to 3·5 and hard as diamonds—black -diamonds or carbonado, in fact—and -a small portion of transparent, colourless -diamonds showing crystalline structure. -Besides these there may be carbide of -silicon and corundum, arising from impurities -in the materials employed.</p> - -<p>The residue is first heated for some hours -with strong sulphuric acid at the boiling-point, -with the cautious addition of powdered -nitre. It is then well washed and for<span class="pagenum"><a name="Page_119" id="Page_119">[119]</a></span> -two days allowed to soak in strong hydrofluoric -acid in cold, then in boiling acid. -After this treatment the soft graphite disappears, -and most, if not all, the silicon -compounds have been destroyed. Hot -sulphuric acid is again applied to destroy -the fluorides, and the residue, well washed, -is attacked with a mixture of the strongest -nitric acid and powdered potassium chlorate, -kept warm—but not above 60° C., to avoid -explosions. This treatment must be repeated -six or eight times, when all the hard -graphite will gradually be dissolved and -little else left but graphitic oxide, diamond, -and the harder carbonado and boart. The -residue is fused for an hour in fluorhydrate -or fluoride of potassium, then boiled out in -water and again heated in sulphuric acid. -The well-washed grains which resist this -energetic treatment are dried, carefully -deposited on a slide, and examined under -the microscope. Along with numerous -pieces of black diamond are seen transparent,<span class="pagenum"><a name="Page_120" id="Page_120">[120]</a></span> -colourless pieces, some amorphous, others -with a crystalline appearance. <a href="#P_120">Fig. 21 B</a> -shows one of these crystalline fragments. -Although many fragments of crystals occur, -it is remarkable I have never seen a complete -crystal. All appear shattered, as if on being -liberated from the intense pressure under -which they were formed they burst asunder. -I have singular evidence of this phenomenon. -A fine piece of artificial diamond, carefully -mounted by me on a microscopic slide, -exploded during the night and covered the -slide with fragments. Moissan’s crystals of -artificial diamond sometimes broke a few -weeks after their preparation, and some of -the diamonds which cracked weeks or even -months after their preparation showed -fissures covered with minute cubes. I have -explained that this bursting paroxysm is not -unknown at the Kimberley mines. So far, -all such artificial diamonds are microscopic. -The largest artificial diamond is less than -one millimetre across.</p> - -<div class="figcenter"> -<a name="P_120" id="P_120"></a> -<img src="images/i_p120a1.jpg" width="250" alt="" /> -<div class="caption"> -FIG. 21. ARTIFICIAL DIAMOND -MADE BY THE AUTHOR -FROM MOLTEN IRON. -</div> -</div> - -<div class="figcenter"> -<a name="P_120x" id="P_120x"></a> -<img src="images/i_p120a2.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 22. MOISSAN’S ARTIFICIAL DIAMONDS.<br /> -<p class="right">To face p. 120.</p> -</div> -</div> - -<p><span class="pagenum"><a name="Page_121" id="Page_121">[121]</a></span></p> - -<p>These laboratory diamonds burn in the -air before the blowpipe to carbonic acid. -In lustre, crystalline form, optical properties, -density, and hardness they are identical -with the natural stone.</p> - -<p>In several cases Moissan separated ten -to fifteen microscopic diamonds from a -single ingot. The larger of these are about -0·75 mm. long, the octahedra being 0·2 mm.</p> - -<p>The accompanying illustrations (<a href="#P_120x">Fig. 22</a>) -are copied from drawings in Moissan’s book -<cite>Le Four Electrique</cite>.</p> - -<p>Along with carbon, molten iron dissolves -other bodies which possess tinctorial powers. -We know of blue, green, pink, yellow, and -orange diamonds. One batch of iron might -contain an impurity colouring the stones -blue, another lot would tend towards the -formation of pink stones, another of green, -and so on. Cobalt, nickel, chromium, and -manganese, all metals present in the blue -ground, would produce these colours.</p> - -<p><span class="pagenum"><a name="Page_122" id="Page_122">[122]</a></span></p> - - -<h3><span class="smcap">A New Formation of Diamond</span></h3> - -<p>I have long speculated as to the possibility -of obtaining artificially such pressures and -temperatures as would fulfil the above -conditions. In their researches on the -gases from fired gunpowder and cordite, -Sir Frederick Abel and Sir Andrew Noble -obtained in closed steel cylinders pressures -as great as 95 tons to the square inch, and -temperatures as high as 4000° C. According -to a paper recently communicated to the -Royal Society, Sir Andrew Noble, exploding -cordite in closed vessels, has obtained a -pressure of 8000 atmospheres, or 50 tons -per square inch, with a temperature reaching -in all probability 5400° Ab.</p> - -<p>Here, then, we have conditions favourable -for the liquefaction of carbon, and were the -time of explosion sufficient to allow the -reactions to take place, we should certainly<span class="pagenum"><a name="Page_123" id="Page_123">[123]</a></span> -expect to get the liquid carbon to solidify in -the crystalline state.<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a></p> - -<p>By the kindness of Sir Andrew Noble I -have been enabled to work upon some of -the residues obtained in closed vessels after -explosions, and I have submitted them to -the same treatment that the granulated iron -had gone through. After weeks of patient -toil I removed the amorphous carbon, the -graphite, the silica,<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">[8]</a> and other constituents<span class="pagenum"><a name="Page_124" id="Page_124">[124]</a></span> -of the ash of cordite, and obtained a residue -among which, under the microscope, crystalline -particles could be distinguished. -Some of these particles, from their crystalline -appearance and double refraction, -were silicon carbide; others were probably -diamonds. The whole residue was dried -and fused at a good red heat in an excess of -potassium bifluoride, to which was added, -during fusion, 5 per cent of nitre. (Previous -experiments had shown me that this mixture -readily attacked and dissolved silicon -carbide; unfortunately it also attacks -diamond to a slight degree.) All the -operations of washing and acid treatment -were performed in a large platinum crucible -by decantation (except the preliminary -attack with nitric acid and potassium -chlorate, when a hard glass vessel was -used); the final result was washed into a<span class="pagenum"><a name="Page_125" id="Page_125">[125]</a></span> -shallow watch-glass and the selection made -under the microscope. The residue, after -thorough washing and then heating in -fuming sulphuric acid, was washed, and -the largest crystalline particles picked out -and mounted.</p> - -<p>From the treatment the residual crystals -had undergone, chemists will agree with me -that diamonds only could stand such an -ordeal; on submitting them to skilled -crystallographic authorities my opinion is -confirmed. Speaking of the largest crystal, -one eminent authority calls it “a diamond -showing octahedral planes with dark boundaries -due to high refracting index.” After -careful examination, another authority -writes of the same crystal diamond, “I -think one may safely say that the position -and angles of its faces, and of its cleavages, -the absence of birefringence, and the high -refractive index are all compatible with the -properties of the diamond crystallising in -the form of an octahedron. Others of the<span class="pagenum"><a name="Page_126" id="Page_126">[126]</a></span> -remaining crystals, which show a similar -high refractive index, appeared to me to -present the same features.”</p> - -<p>It would have been more conclusive had -I been able to get further evidence as to the -density and hardness of the crystals; but -from what I have already said I think there -is no doubt that in these closed vessel -explosions we have another method of -producing the diamond artificially.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_127" id="Page_127">[127]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_X" id="CHAPTER_X"></a><a href="#CONTENTS">CHAPTER X</a><br /> -<br /> -<span class="fs80 bold">THE NATURAL FORMATION OF THE DIAMOND</span></h2> - - -<p class="drop-capy1">An hypothesis is of little value if it only -elucidates half a problem. Let us -see how far we can follow out the ferric -hypothesis to explain the volcanic pipes. -In the first place we must remember these -so-called volcanic vents are admittedly not -filled with the eruptive rocks, scoriaceous -fragments, etc., constituting the ordinary -contents of volcanic ducts.</p> - -<p>Certain artificial diamonds present the -appearance of an elongated drop. I have -seen diamonds which have exactly the -appearance of drops of liquid separated in a -pasty condition and crystallised on cooling. -Diamonds are sometimes found with little -appearance of crystallisation, but with -rounded forms similar to those which a<span class="pagenum"><a name="Page_128" id="Page_128">[128]</a></span> -liquid might assume if kept in the midst of -another liquid with which it would not mix. -Other drops of liquid carbon retained for -sufficient time above their melting-point -would coalesce with adjacent drops, and on -slow cooling would separate in the form of -large perfect crystals. Two drops, joining -after incipient crystallisation, might assume -the not uncommon form of interpenetrating -twin crystals.</p> - -<p>Many circumstances point to the conclusion -that the diamond of the chemist and -the diamond of the mine are strangely akin -as to origin. It is evident that the diamond -has not been formed <i lang="la" xml:lang="la">in situ</i> in the blue -ground. The genesis must have taken place -at vast depths under enormous pressure. -The explosion of large diamonds on coming -to the surface shows extreme tension. More -diamonds are found in fragments and -splinters than in perfect crystals; and it is -noteworthy that although these splinters -and fragments must be derived from the<span class="pagenum"><a name="Page_129" id="Page_129">[129]</a></span> -breaking up of a large crystal, yet in only -one instance have pieces been found which -could be fitted together, and these occurred -at different levels. Does not this fact point -to the conclusion that the blue ground is -not their true matrix? Nature does not -make fragments of crystals. As the edges -of the crystals are still sharp and unabraded, -the <em>locus</em> of formation cannot have been -very distant from the present sites. There -were probably many sites of crystallisation -differing in place and time, or we should not -see such distinctive characters in the gems -from different mines, nor indeed in the -diamonds from different parts of the same -mine.</p> - -<p>I start with the reasonable supposition -that at a sufficient depth<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">[9]</a> there were -masses of molten iron at great pressure and -high temperature, holding carbon in solution,<span class="pagenum"><a name="Page_130" id="Page_130">[130]</a></span> -ready to crystallise out on cooling. Far -back in time the cooling from above caused -cracks in superjacent strata through which -water<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">[10]</a> found its way. On reaching the -incandescent iron the water would be converted -into gas, and this gas would rapidly -disintegrate and erode the channels through -which it passed, grooving a passage more and -more vertical in the necessity to find the -quickest vent to the surface. But steam in -the presence of molten or even red-hot iron -liberates large volumes of hydrogen gas, -together with less quantities of hydrocarbons<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">[11]</a> -of all kinds—liquid, gaseous, and -solid. Erosion commenced by steam would -be continued by the other gases; it would -be easy for pipes, large as any found in<span class="pagenum"><a name="Page_131" id="Page_131">[131]</a></span> -South Africa, to be scored out in this -manner.</p> - -<p>Sir Andrew Noble has shown that when -the screw stopper of his steel cylinders in -which gunpowder explodes under pressure -is not absolutely perfect, gas escapes with a -rush so overpowering and a temperature so -high as to score a wide channel in the metal. -To illustrate my argument Sir Andrew -Noble has been kind enough to try a special -experiment. Through a cylinder of granite -he drilled a hole 0·2 inch diameter, the size -of a small vent. This was made the stopper of -an explosion chamber, in which a quantity of -cordite was fired, the gases escaping through -the granite vent. The pressure was about -1500 atmospheres and the whole time of -escape was less than half a second. The -erosion produced by the escaping gases and -by the heat of friction scored out a channel -more than half an inch diameter and melted -the granite along the course. If steel and -granite are thus vulnerable at comparatively<span class="pagenum"><a name="Page_132" id="Page_132">[132]</a></span> -moderate gaseous pressure, it is easy -to imagine the destructive upburst of hydrogen -and water-gas, grooving for itself a -channel in the diabase and quartzite, tearing -fragments from resisting rocks, covering the -country with debris, and finally, at the subsidence -of the great rush, filling the self-made -pipe with a water-borne magma in -which rocks, minerals, iron oxide, shale, -petroleum, and diamonds are violently -churned in a veritable witch’s cauldron! -As the heat abated the water vapour would -gradually give place to hot water, which, -forced through the magma, would change -some of the mineral fragments into the -existing forms of to-day.</p> - -<p>Each outbreak would form a dome-shaped -hill; the eroding agency of water -and ice would plane these eminences until -all traces of the original pipes were lost.</p> - -<p>Actions such as I have described need -not have taken place simultaneously. As -there must have been many molten masses<span class="pagenum"><a name="Page_133" id="Page_133">[133]</a></span> -of iron with variable contents of carbon, -different kinds of colouring matter, solidifying -with varying degrees of rapidity, -and coming in contact with water at intervals -throughout long periods of geological -time—so must there have been many outbursts -and upheavals, giving rise to pipes -containing diamonds. And these diamonds, -by sparseness of distribution, crystalline -character, difference of tint, purity of -colour, varying hardness, brittleness, and -state of tension, have the story of their -origin impressed upon them, engraved by -natural forces—a story which future generations -of scientific men may be able to interpret -with greater precision than is possible -to-day.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_134" id="Page_134">[134]</a></span></p> - -<h2 class="p4 no-brk"><a name="CHAPTER_XI" id="CHAPTER_XI"></a><a href="#CONTENTS">CHAPTER XI</a><br /> -<br /> -<span class="fs80 bold">METEORIC DIAMONDS</span></h2> - - -<p class="drop-capy">Sensational as is the story of the -diamond industry in South Africa, -quite another aspect fixes the attention of -the chemist. The diamonds come out of -the mines, but how did they get in? How -were they formed? What is their origin?</p> - -<p>Gardner Williams, who knows more about -diamonds than any man living, is little -inclined to indulge in speculation. In his -fascinating book he frankly says:</p> - -<p>“I have been frequently asked, ‘What is -your theory of the original crystallisation of -the diamond?’ and the answer has always -been, ‘I have none; for after seventeen -years of thoughtful study, coupled with -practical research, I find that it is easier to -“drive a coach and four” through most -theories that have been propounded than to -suggest one which would be based on any<span class="pagenum"><a name="Page_135" id="Page_135">[135]</a></span> -non-assailable data.’ All that can be said is -that in some unknown manner carbon, which -existed deep down in the internal regions of -the earth, was changed from its black and -uninviting appearance to the most beautiful -gem which ever saw the light of day.”</p> - -<p>Another diamond theory appeals to the -imagination. It is said the diamond is a -gift from Heaven, conveyed to earth in -meteoric showers. The suggestion, I believe, -was first broached by A. Meydenbauer,<a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">[12]</a> -who says, “The diamond can only be of -cosmic origin, having fallen as a meteorite -at later periods of the earth’s formation. -The available localities of the diamond -contain the residues of not very compact -meteoric masses which may, perhaps, have -fallen in prehistoric ages, and which have -penetrated more or less deeply, according -to the more or less resistant character of the -surface where they fell. Their remains are -crumbling away on exposure to the air and<span class="pagenum"><a name="Page_136" id="Page_136">[136]</a></span> -sun, and the rain has long ago washed -away all prominent masses. The enclosed -diamonds have remained scattered in the -river beds, while the fine light matrix has -been swept away.”</p> - -<p>According to this hypothesis, the so-called -volcanic pipes are simply holes bored in the -solid earth by the impact of monstrous -meteors—the larger masses boring the holes, -while the smaller masses, disintegrating in -their fall, distributed diamonds broadcast. -Bizarre as such a theory appears, I am -bound to say there are many circumstances -which show that the notion of the heavens -raining diamonds is not impossible.</p> - -<p>The most striking confirmation of the -meteoric theory comes from Arizona. Here, -on a broad open plain, over an area about -five miles in diameter, have been scattered -one or two thousand masses of metallic -iron, the fragments varying in weight from -half a ton to a fraction of an ounce. There -is no doubt these masses formed part of a<span class="pagenum"><a name="Page_137" id="Page_137">[137]</a></span> -meteoric shower, although no record exists -as to when the fall took place. Curiously -enough, near the centre, where most of the -meteorites have been found, is a crater with -raised edges three-quarters of a mile in -diameter and about 600 feet deep, bearing -exactly the appearance which would be -produced had a mighty mass of iron struck -the ground and buried itself deep under the -surface. Altogether, ten tons of this iron -have been collected, and specimens of the -Canyon Diablo meteorite are in most collectors’ -cabinets.</p> - -<p>An ardent mineralogist—the late Dr. -Foote—cutting a section of this meteorite, -found the tools were injured by something -vastly harder than metallic iron. He -examined the specimen chemically, and soon -after announced to the scientific world that -the Canyon Diablo meteorite contained -black and transparent diamonds. This -startling discovery was afterwards verified -by Professors Moissan and Friedel, and<span class="pagenum"><a name="Page_138" id="Page_138">[138]</a></span> -Moissan, working on 183 kilogrammes of -the Canyon Diablo meteorite, has recently -found smooth black diamonds and transparent -diamonds in the form of octahedra -with rounded edges, together with green, -hexagonal crystals of carbon silicide. The -presence of carbon silicide in the meteorite -shows that it must at some time have -experienced the temperature of the electric -furnace. Since this revelation the search -for diamonds in meteorites has occupied the -attention of chemists all over the world.</p> - -<p><a href="#P_138">Fig. 23 A, C, and D</a>, are reproductions of -photographs of true diamonds I myself have -extracted from the Canyon Diablo meteorite.</p> - -<div class="figcenter"> -<a name="P_138" id="P_138"></a> -<img src="images/i_p138a.jpg" width="600" alt="" /> -<div class="caption"> -FIG. 23. DIAMONDS FROM CANYON DIABLO METEORITE.<br /> -<p class="right">To face p. 138.</p> -</div> -</div> - -<p>Under atmospheric influences the iron -would rapidly oxidise and rust away, -colouring the adjacent soil with red oxide -of iron. The meteoric diamonds would be -unaffected and left on the surface of the -soil, to be found haphazard when oxidation -had removed the last proof of their celestial -origin. That there are still lumps of iron<span class="pagenum"><a name="Page_139" id="Page_139">[139]</a></span> -left at Arizona is merely due to the extreme -dryness of the climate and the comparatively -short time that the iron has been on our -planet. We are here witnesses to the course -of an event which may have happened in -geologic times anywhere on the earth’s -surface.</p> - -<p>Although in Arizona diamonds have -fallen from the skies, confounding our -senses, this descent of precious stones is -what may be called a freak of nature rather -than a normal occurrence. To the modern -student of science there is no great difference -between the composition of our earth and -that of extra-terrestrial masses. The mineral -peridot is a constant extra-terrestrial visitor, -present in most meteorites. And yet no one -doubts that peridot is also a true constituent -of rocks formed on this earth. The spectroscope -reveals that the elementary composition -of the stars and the earth are pretty -much the same; and the spectroscope also -shows that meteorites have as much of earth<span class="pagenum"><a name="Page_140" id="Page_140">[140]</a></span> -as of heaven in their composition. Indeed, -not only are the selfsame elements present -in meteorites, but they are combined in the -same way to form the same minerals as in -the crust of the earth.</p> - -<p>It is certain from observations I have -made, corroborated by experience gained -in the laboratory, that iron at a high temperature -and under great pressure—conditions -existent at great depths below the -surface of the earth—acts as the long-sought -solvent for carbon, and will allow it to -crystallise out in the form of diamond. But -it is also certain, from the evidence afforded -by the Arizona and other meteorites, that -similar conditions have existed among -bodies in space, and that on more than one -occasion a meteorite freighted with jewels -has fallen as a star from the sky.</p> - - -<hr class="chap pg-brk" /> -<p><span class="pagenum"><a name="Page_141" id="Page_141">[141]</a></span></p> - -<h2 class="p4 no-brk"><a name="INDEX" id="INDEX"></a><a href="#CONTENTS">INDEX</a></h2> - - -<div class="index"> -Able, Sir F., closed vessel experiments, <a href="#Page_122">122</a><br /> -<br /> -Absorption spectrum of diamond, <a href="#Page_101">101</a><br /> -<br /> -Aliwal North, <a href="#Page_6">6</a><br /> -<br /> -Alluvial deposits of diamonds, <a href="#Page_9">9</a><br /> -<br /> -Amygdaloidal trap, <a href="#Page_10">10</a><br /> -<br /> -Arizona meteor, <a href="#Page_136">136</a><br /> -<br /> -Arkansas, diamonds in, <a href="#Page_2">2</a><br /> -<br /> -Ash of diamond, <a href="#Page_82">82</a>, <a href="#Page_89">89</a><br /> -<br /> -Augite, <a href="#Page_20">20</a><br /> -<br /> -Automatic diamond collector, <a href="#Page_56">56</a><br /> -<br /> -<br /> -Barytes, <a href="#Page_71">71</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Basalt, <a href="#Page_15">15</a><br /> -<br /> -Basutos, <a href="#Page_12">12</a>, <a href="#Page_39">39</a><br /> -<br /> -Bechuanas, <a href="#Page_12">12</a>, <a href="#Page_39">39</a><br /> -<br /> -Beryl, density of, <a href="#Page_93">93</a><br /> -— refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Biotite, <a href="#Page_20">20</a><br /> -<br /> -Blackening of diamonds, <a href="#Page_98">98</a><br /> -<br /> -Blue ground, <a href="#Page_10">10</a>, <a href="#Page_47">47</a><br /> -— — diamantiferous, <a href="#Page_18">18</a>, <a href="#Page_19">19</a><br /> -<br /> -Boart, <a href="#Page_81">81</a>,<br /> -— combustion temperature of, <a href="#Page_90">90</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Boiling-point of carbon, <a href="#Page_110">110</a><br /> -<br /> -Bonney, Rev. Professor, <a href="#Page_67">67</a><br /> -<br /> -Boyle on the diamond, <a href="#Page_100">100</a><br /> -<br /> -Brazil, diamonds in, <a href="#Page_4">4</a><br /> -<br /> -Breakwater, Cape Town, <a href="#Page_36">36</a><br /> -<br /> -Breccia, diamantiferous, <a href="#Page_19">19</a><br /> -<br /> -Brilliant cut diamond, <a href="#Page_102">102</a><br /> -<br /> -British Association in South Africa, <a href="#Page_7">7</a><br /> -<br /> -British Guiana, diamonds in, <a href="#Page_4">4</a><br /> -<br /> -Bronzite, <a href="#Page_20">20</a>, <a href="#Page_71">71</a><br /> -— hydrated, <a href="#Page_19">19</a><br /> -<br /> -Bultfontein Mine, <a href="#Page_14">14</a><br /> -— — characteristics of diamond from, <a href="#Page_64">64</a><br /> -<br /> -Bursting of diamonds, <a href="#Page_105">105</a><br /> -<br /> -<br /> -Calcite, <a href="#Page_20">20</a>, <a href="#Page_97">97</a><br /> -<br /> -California, diamonds in, <a href="#Page_3">3</a><br /> -<br /> -Canada balsam, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Canyon Diablo meteorite, <a href="#Page_136">136</a><br /> -<br /> -Cape Colony, <a href="#Page_5">5</a><br /> -<br /> -Cape Town, <a href="#Page_5">5</a><br /> -<br /> -Carat, equivalent in grains, <a href="#Page_69">69</a><br /> -<br /> -Carbon, boiling and melting point of, <a href="#Page_110">110</a><br /> -— combustion temperature of, <a href="#Page_90">90</a><br /> -— critical point of, <a href="#Page_110">110</a><br /> -— density of, <a href="#Page_93">93</a><br /> -— dissolved in iron, <a href="#Page_116">116</a><br /> -— volatilisation of, <a href="#Page_115">115</a><br /> -<br /> -Carbonado, <a href="#Page_81">81</a><br /> -<span class="pagenum"><a name="Page_142" id="Page_142">[142]</a></span>— density of, <a href="#Page_93">93</a><br /> -<br /> -Characteristics of diamonds from the different mines, <a href="#Page_64">64</a><br /> -<br /> -Chemical properties of diamond, <a href="#Page_89">89</a><br /> -<br /> -Chromate of lead, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Chrome diopside, <a href="#Page_71">71</a><br /> -— iron, <a href="#Page_20">20</a><br /> -— — ore, <a href="#Page_71">71</a><br /> -— — — density of, <a href="#Page_93">93</a><br /> -<br /> -Chromite, <a href="#Page_20">20</a><br /> -<br /> -Classification of rough diamonds, <a href="#Page_73">73</a><br /> -<br /> -Cleavage of diamonds, <a href="#Page_78">78</a><br /> -<br /> -Coke, density of, <a href="#Page_93">93</a><br /> -<br /> -Colesberg Kopje, <a href="#Page_26">26</a><br /> -<br /> -Collecting the gems, <a href="#Page_55">55</a><br /> -<br /> -Coloured diamonds, <a href="#Page_62">62</a>, <a href="#Page_82">82</a><br /> -<br /> -Combustion of diamond, <a href="#Page_89">89</a><br /> -— temperatures of diamond, boart, graphite, and carbon, <a href="#Page_90">90</a><br /> -<br /> -“Comet” crushers, <a href="#Page_49">49</a><br /> -<br /> -Compound system, <a href="#Page_36">36</a>, <a href="#Page_37">37</a><br /> -<br /> -Concentrating and washing machinery, <a href="#Page_49">49</a><br /> -<br /> -Convict labourers, <a href="#Page_71">71</a><br /> -<br /> -Cordite, diamond from explosion of, <a href="#Page_123">123</a><br /> -<br /> -Corundum, <a href="#Page_20">20</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Cradock, <a href="#Page_6">6</a><br /> -<br /> -Craters or pipes, <a href="#Page_18">18</a><br /> -<br /> -Crown glass, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Crusher, “Comet,” <a href="#Page_49">49</a><br /> -<br /> -Crystallisation of diamond, <a href="#Page_86">86</a><br /> -<br /> -Crystals, octahedra, of diamond, <a href="#Page_63">63</a>, <a href="#Page_86">86</a><br /> -<br /> -Cullinan diamond, <a href="#Page_15">15</a>, <a href="#Page_76">76</a>, <a href="#Page_80">80</a>, <a href="#Page_104">104</a><br /> -<br /> -<br /> -Dallas, Captain, <a href="#Page_40">40</a><br /> -<br /> -De Beers Consolidated Mines, <a href="#Page_7">7</a>, <a href="#Page_33">33</a><br /> -— — floors at Kenilworth, <a href="#Page_47">47</a><br /> -— — Mine, <a href="#Page_14">14</a>, <a href="#Page_24">24</a>, <a href="#Page_34">34</a><br /> -— — — characteristics of diamonds from, <a href="#Page_64">64</a><br /> -— — strong-room, <a href="#Page_74">74</a><br /> -<br /> -Delhi diamond, <a href="#Page_107">107</a><br /> -<br /> -Density of diamond, <a href="#Page_57">57</a>, <a href="#Page_93">93</a><br /> -— of graphite, <a href="#Page_83">83</a>, <a href="#Page_93">93</a><br /> -— of stones accompanying diamond, <a href="#Page_70">70</a>, <a href="#Page_71">71</a>, <a href="#Page_93">93</a>, <a href="#Page_95">95</a><br /> -<br /> -Depositing floors, <a href="#Page_46">46</a><br /> -<br /> -Dewar, Sir J., conversion of diamond into graphite, <a href="#Page_123">123</a><br /> -<br /> -Diabase, olivine, <a href="#Page_16">16</a><br /> -<br /> -Diallage, <a href="#Page_20">20</a><br /> -<br /> -Diamond, absorption spectrum of, <a href="#Page_101">101</a><br /> -— and polarised light, <a href="#Page_104">104</a><br /> -— a new formation of, <a href="#Page_122">122</a><br /> -— ash of, <a href="#Page_82">82</a>, <a href="#Page_89">89</a><br /> -— collector, automatic, <a href="#Page_56">56</a><br /> -— combustion of, <a href="#Page_89">89</a><br /> -— — temperature of, <a href="#Page_90">90</a><br /> -— converted into graphite, <a href="#Page_100">100</a><br /> -— density of, <a href="#Page_57">57</a>, <a href="#Page_93">93</a><br /> -— etched by burning, <a href="#Page_88">88</a><br /> -— explosion of, <a href="#Page_120">120</a><br /> -— genesis of the, <a href="#Page_115">115</a><br /> -— in meteors, <a href="#Page_134">134</a><br /> -— in Röntgen rays, <a href="#Page_107">107</a><br /> -— matrix of, <a href="#Page_67">67</a><br /> -— natural formation of, <a href="#Page_127">127</a><br /> -<span class="pagenum"><a name="Page_143" id="Page_143">[143]</a></span>— Office at Kimberley, <a href="#Page_73">73</a><br /> -— physical and chemical properties of, <a href="#Page_89">89</a><br /> -— pipes or craters, <a href="#Page_18">18</a><br /> -— radio-activity of, <a href="#Page_109">109</a><br /> -— refractive index of, <a href="#Page_103">103</a><br /> -— Trade Act, <a href="#Page_36">36</a><br /> -— triangular markings on, <a href="#Page_87">87</a><br /> -— tribo-luminescence of, <a href="#Page_100">100</a><br /> -<br /> -Diamonds, coloured or fancy, <a href="#Page_62">62</a>, <a href="#Page_82">82</a><br /> -— Maskelyne on, <a href="#Page_1">1</a><br /> -— noteworthy, <a href="#Page_76">76</a><br /> -— phosphorescence of, <a href="#Page_96">96</a><br /> -— produced, weight, value of, <a href="#Page_35">35</a><br /> -— yield of, from De Beers, <a href="#Page_60">60</a><br /> -<br /> -Drift, diamonds from the, <a href="#Page_12">12</a><br /> -<br /> -Duke of Tuscany diamond, <a href="#Page_80">80</a><br /> -<br /> -Dutch boart, or zircon, <a href="#Page_59">59</a><br /> -<br /> -Dutoitspan Mine, <a href="#Page_14">14</a>, <a href="#Page_23">23</a><br /> -— — characteristics of diamonds from, <a href="#Page_64">64</a><br /> -<br /> -<br /> -Eclogite, <a href="#Page_20">20</a><br /> -— containing diamonds, <a href="#Page_67">67</a><br /> -<br /> -Electrons, bombardment by, <a href="#Page_98">98</a><br /> -<br /> -Emerald, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Empress Eugenie diamond, <a href="#Page_80">80</a><br /> -<br /> -Enstatite, <a href="#Page_20">20</a><br /> -<br /> -Explosion of diamonds, <a href="#Page_120">120</a><br /> -<br /> -Excelsior diamond, <a href="#Page_80">80</a><br /> -<br /> -<br /> -Fancy stones, <a href="#Page_62">62</a><br /> -<br /> -Fingoes, <a href="#Page_39">39</a><br /> -<br /> -Flint glass, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -“Floating Reef,” <a href="#Page_21">21</a><br /> -<br /> -Floors, depositing, <a href="#Page_46">46</a><br /> -<br /> -Fluor-spar, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Formation, new, of diamond, <a href="#Page_122">122</a><br /> -<br /> -Fort Beaufort, <a href="#Page_6">6</a><br /> -<br /> -Franklinite, <a href="#Page_97">97</a><br /> -<br /> -Frank Smith Mine, <a href="#Page_15">15</a><br /> -— — — characteristics of diamonds from, <a href="#Page_66">66</a><br /> -<br /> -Fraserburg, <a href="#Page_6">6</a><br /> -<br /> -<br /> -Garnet, <a href="#Page_20">20</a>, <a href="#Page_70">70</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Genesis of the diamond, <a href="#Page_115">115</a><br /> -<br /> -“Golden fancies,” <a href="#Page_65">65</a><br /> -<br /> -Granite, <a href="#Page_18">18</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Graphite, <a href="#Page_81">81</a>, <a href="#Page_83">83</a><br /> -— combustion temperature of, <a href="#Page_90">90</a><br /> -— conversion of diamond into, <a href="#Page_100">100</a><br /> -— density of, <a href="#Page_93">93</a><br /> -— diamonds coated with, <a href="#Page_99">99</a><br /> -<br /> -Graphitic oxide, <a href="#Page_83">83</a>, <a href="#Page_93">93</a><br /> -<br /> -Grease, collecting diamonds by aid of, <a href="#Page_57">57</a><br /> -<br /> -<br /> -Hard blue ground, <a href="#Page_47">47</a><br /> -<br /> -Hardness of diamond, <a href="#Page_90">90</a><br /> -<br /> -Haulage system, <a href="#Page_46">46</a><br /> -<br /> -Hexakis-octahedron crystal, <a href="#Page_86">86</a><br /> -<br /> -Hope blue diamond, the, <a href="#Page_80">80</a><br /> -<br /> -Hornblende, <a href="#Page_71">71</a><br /> -<span class="pagenum"><a name="Page_144" id="Page_144">[144]</a></span>— density of, <a href="#Page_93">93</a><br /> -<br /> -<br /> -Iceland spar, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Ice, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -I.D.B. laws (Illicit Diamond Buying), <a href="#Page_36">36</a><br /> -<br /> -Ilmenite, <a href="#Page_20">20</a><br /> -<br /> -India, diamonds in, <a href="#Page_4">4</a><br /> -<br /> -Inverel diamonds, <a href="#Page_91">91</a><br /> -<br /> -Internal strain in diamonds, <a href="#Page_104">104</a><br /> -<br /> -Iron a solvent for carbon, <a href="#Page_116">116</a><br /> -— ore, density of, <a href="#Page_93">93</a><br /> -— pyrites, <a href="#Page_20">20</a><br /> -<br /> -<br /> -Jagersfontein diamond, <a href="#Page_79">79</a><br /> -— Mine, <a href="#Page_14">14</a><br /> -— — characteristics of diamonds from, <a href="#Page_68">68</a><br /> -<br /> -Jeffreysite, <a href="#Page_20">20</a><br /> -<br /> -<br /> -Kafirs, <a href="#Page_42">42</a><br /> -<br /> -Kamfersdam Mine, <a href="#Page_15">15</a><br /> -— — characteristics of diamonds from, <a href="#Page_66">66</a><br /> -<br /> -Kenilworth depositing floors, <a href="#Page_47">47</a><br /> -<br /> -Kimberley, <a href="#Page_6">6</a><br /> -— blue ground, <a href="#Page_10">10</a><br /> -— mines, <a href="#Page_14">14</a>, <a href="#Page_23">23</a>, <a href="#Page_34">34</a><br /> -— Mine in old days, <a href="#Page_25">25</a><br /> -— — at the present day, <a href="#Page_34">34</a><br /> -— — characteristics of diamonds from, <a href="#Page_63">63</a><br /> -— shales, <a href="#Page_15">15</a><br /> -— West Mine, <a href="#Page_15">15</a><br /> -— — — characteristics of diamonds from, <a href="#Page_66">66</a><br /> -<br /> -Kirsten’s automatic diamond collector, <a href="#Page_57">57</a><br /> -<br /> -Klipdam, <a href="#Page_8">8</a>, <a href="#Page_23">23</a><br /> -<br /> -Koffyfontein Mine, <a href="#Page_14">14</a><br /> -<br /> -Koh-i-noor diamond, <a href="#Page_80">80</a><br /> -— hardness of, <a href="#Page_91">91</a><br /> -<br /> -Kyanite, <a href="#Page_20">20</a>, <a href="#Page_71">71</a><br /> -<br /> -<br /> -Lamp, ultra-violet, <a href="#Page_97">97</a><br /> -<br /> -Leicester Mine, <a href="#Page_15">15</a>, <a href="#Page_23">23</a><br /> -— — characteristics of diamonds from, <a href="#Page_67">67</a><br /> -<br /> -Loterie d’Angleterre diamond, <a href="#Page_80">80</a><br /> -<br /> -Lustre of rough diamonds, <a href="#Page_56">56</a><br /> -<br /> -<br /> -Machinery for washing and concentrating, <a href="#Page_49">49</a><br /> -<br /> -Macles, <a href="#Page_86">86</a><br /> -<br /> -Magnetite, <a href="#Page_20">20</a>, <a href="#Page_71">71</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Maskelyne on diamonds, <a href="#Page_1">1</a><br /> -<br /> -Matabele, <a href="#Page_12">12</a>, <a href="#Page_39">39</a><br /> -<br /> -Matrix of diamond, <a href="#Page_67">67</a><br /> -<br /> -Melaphyre, <a href="#Page_10">10</a>, <a href="#Page_16">16</a><br /> -<br /> -Melting-point of carbon, <a href="#Page_110">110</a><br /> -<br /> -Meteor, Canyon Diablo, <a href="#Page_136">136</a><br /> -<br /> -Meteoric diamonds, <a href="#Page_134">134</a><br /> -<br /> -Meydenbauer on meteoric diamonds, <a href="#Page_135">135</a><br /> -<br /> -Mica, <a href="#Page_20">20</a>, <a href="#Page_71">71</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Moissan’s experiments on the genesis of diamond, <a href="#Page_115">115</a><br /> -<br /> -Mud volcano, <a href="#Page_24">24</a><br /> -<br /> -<br /> -Nassak diamond, <a href="#Page_80">80</a><br /> -<br /> -Natal, coal in, <a href="#Page_6">6</a><br /> -<br /> -Natural formation of diamond, <a href="#Page_127">127</a><br /> -<br /> -Newlands Mine, <a href="#Page_15">15</a><br /> -<span class="pagenum"><a name="Page_145" id="Page_145">[145]</a></span>— — characteristics of diamonds from, <a href="#Page_67">67</a><br /> -<br /> -New Rush diggings, <a href="#Page_26">26</a><br /> -<br /> -Nizam of Hyderabad diamond, <a href="#Page_80">80</a><br /> -<br /> -Noble, Sir A., experiments, <a href="#Page_122">122</a>, <a href="#Page_131">131</a><br /> -<br /> -Noteworthy diamonds, <a href="#Page_76">76</a><br /> -<br /> -<br /> -Octahedral crystals of diamond, <a href="#Page_63">63</a>, <a href="#Page_86">86</a><br /> -<br /> -Olivine, <a href="#Page_20">20</a><br /> -— diabase, <a href="#Page_16">16</a><br /> -<br /> -Orange River Colony, coal in, <a href="#Page_6">6</a><br /> -— — — diamonds in, <a href="#Page_14">14</a><br /> -<br /> -Orloff diamond, <a href="#Page_80">80</a><br /> -<br /> -<br /> -Pasha of Egypt diamond, <a href="#Page_80">80</a><br /> -<br /> -Paterson, Mr., description of Kimberley in old days, <a href="#Page_25">25</a><br /> -<br /> -Peridot, <a href="#Page_20">20</a>, <a href="#Page_139">139</a><br /> -<br /> -Peridotite, <a href="#Page_3">3</a><br /> -<br /> -Perofskite, <a href="#Page_20">20</a><br /> -<br /> -Phosphorescence of diamonds, <a href="#Page_96">96</a><br /> -<br /> -Phosphorus, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Physical properties of diamond, <a href="#Page_89">89</a><br /> -<br /> -Picking tables, <a href="#Page_51">51</a><br /> -<br /> -Pipes or craters, <a href="#Page_18">18</a><br /> -<br /> -Pitt diamond, <a href="#Page_80">80</a><br /> -<br /> -Polarised light and diamond, <a href="#Page_104">104</a><br /> -<br /> -Pole Star diamond, <a href="#Page_80">80</a><br /> -<br /> -Pondos, <a href="#Page_39">39</a>, <a href="#Page_42">42</a><br /> -<br /> -Premier Mine, <a href="#Page_15">15</a>, <a href="#Page_76">76</a><br /> -<br /> -Prodigious diamonds, <a href="#Page_76">76</a><br /> -<br /> -Pseudobrookite, <a href="#Page_20">20</a><br /> -<br /> -Pulsator, <a href="#Page_52">52</a><br /> -<br /> -Pyrope, <a href="#Page_70">70</a><br /> -<br /> -<br /> -Quartzite, <a href="#Page_16">16</a>, <a href="#Page_20">20</a><br /> -— density of, <a href="#Page_93">93</a><br /> -— refractive index of, <a href="#Page_103">103</a><br /> -<br /> -<br /> -Radio-activity of diamond, <a href="#Page_109">109</a><br /> -<br /> -Radium, action on diamond, <a href="#Page_108">108</a><br /> -<br /> -“Reef,” <a href="#Page_21">21</a><br /> -<br /> -Refractive indices, <a href="#Page_103">103</a><br /> -<br /> -Refractivity of diamond, <a href="#Page_102">102</a><br /> -<br /> -Regent diamond, <a href="#Page_80">80</a><br /> -<br /> -Reunert, Mr., description of Kimberley Mine, <a href="#Page_30">30</a><br /> -<br /> -Rhodes, Cecil John, <a href="#Page_34">34</a><br /> -<br /> -River washings, <a href="#Page_7">7</a><br /> -<br /> -Rock shafts, <a href="#Page_43">43</a><br /> -<br /> -Röntgen rays, diamond in, <a href="#Page_107">107</a><br /> -<br /> -Ruby, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Rutile, <a href="#Page_20">20</a><br /> -<br /> -<br /> -Sahlite, <a href="#Page_20">20</a><br /> -<br /> -Sancy diamond, <a href="#Page_80">80</a><br /> -<br /> -Savings of the native workmen, <a href="#Page_41">41</a><br /> -<br /> -Scalenohedron diamond crystal, <a href="#Page_86">86</a><br /> -<br /> -Serpentine, <a href="#Page_19">19</a><br /> -<br /> -Shafts, rock, <a href="#Page_43">43</a><br /> -<br /> -Shah diamond, <a href="#Page_80">80</a><br /> -<br /> -Shales, Kimberley, <a href="#Page_15">15</a><br /> -<br /> -Shangains, <a href="#Page_39">39</a><br /> -<br /> -Shells in blue ground, <a href="#Page_21">21</a><br /> -<br /> -Shot boart, <a href="#Page_81">81</a><br /> -<br /> -Silver and thallium, nitrate of, <a href="#Page_94">94</a><br /> -<br /> -Smaragdite, <a href="#Page_20">20</a><br /> -<br /> -<span class="pagenum"><a name="Page_146" id="Page_146">[146]</a></span>Soft blue ground, <a href="#Page_47">47</a><br /> -<br /> -Sorting the diamantiferous gravel, <a href="#Page_55">55</a><br /> -<br /> -Specific gravity, <em>see</em> Density<br /> -<br /> -Spectrum, absorption of diamond, <a href="#Page_101">101</a><br /> -<br /> -Sphalerite, <a href="#Page_100">100</a><br /> -<br /> -Spinthariscope, <a href="#Page_108">108</a><br /> -<br /> -Sprat’s <em>History of the Royal Society</em>, <a href="#Page_1">1</a><br /> -<br /> -Sprouting graphite, <a href="#Page_84">84</a><br /> -<br /> -Star of the South diamond, <a href="#Page_80">80</a><br /> -<br /> -Stones other than diamonds, <a href="#Page_70">70</a>, <a href="#Page_71">71</a>, <a href="#Page_93">93</a>, <a href="#Page_95">95</a><br /> -<br /> -Strain, internal, in diamonds, <a href="#Page_104">104</a><br /> -<br /> -Sulphur, refractive index of, <a href="#Page_103">103</a><br /> -<br /> -Swazis, <a href="#Page_39">39</a><br /> -<br /> -<br /> -Ultra-violet lamp to show phosphorescence, <a href="#Page_97">97</a><br /> -<br /> -Underground workings, <a href="#Page_43">43</a><br /> -<br /> -United States, diamonds in, <a href="#Page_2">2</a><br /> -<br /> -<br /> -Vaalite, <a href="#Page_20">20</a><br /> -<br /> -Vaal River, <a href="#Page_8">8</a>, <a href="#Page_16">16</a><br /> -<br /> -Valuators, <a href="#Page_73">73</a><br /> -<br /> -Value of diamonds per carat, <a href="#Page_12">12</a>, <a href="#Page_69">69</a><br /> -<br /> -Value of diamonds, progressive increase in, <a href="#Page_69">69</a><br /> -<br /> -Vermiculite, <a href="#Page_20">20</a><br /> -<br /> -Volatilisation of carbon, <a href="#Page_115">115</a><br /> -<br /> -Volcanic necks, <a href="#Page_18">18</a><br /> -<br /> -Volcano, mud, <a href="#Page_24">24</a><br /> -<br /> -<br /> -Wages, scale of, <a href="#Page_35">35</a><br /> -<br /> -Washing and concentrating machinery, <a href="#Page_49">49</a><br /> -<br /> -Wesselton Mine, <a href="#Page_14">14</a>, <a href="#Page_15">15</a>, <a href="#Page_23">23</a>, <a href="#Page_35">35</a><br /> -— — characteristics of diamonds from, <a href="#Page_65">65</a><br /> -<br /> -Willemite, <a href="#Page_97">97</a><br /> -<br /> -Wollastonite, <a href="#Page_20">20</a><br /> -<br /> -Workings, underground, <a href="#Page_43">43</a><br /> -<br /> -<br /> -Yellow ground, diamantiferous, <a href="#Page_19">19</a><br /> -<br /> -Yield of diamonds, annual, <a href="#Page_60">60</a><br /> -— — — total, <a href="#Page_35">35</a><br /> -— falls off with depth, <a href="#Page_68">68</a><br /> -— per load of blue ground, <a href="#Page_62">62</a><br /> -<br /> -<br /> -Zimbabwe ruins, <a href="#Page_40">40</a><br /> -<br /> -Zircon, <a href="#Page_20">20</a>, <a href="#Page_59">59</a>, <a href="#Page_71">71</a><br /> -— density of, <a href="#Page_93">93</a><br /> -<br /> -Zulus, <a href="#Page_12">12</a>, <a href="#Page_39">39</a>, <a href="#Page_40">40</a><br /> -</div> - - -<p class="p4 pfs70">W. BRENDON AND SON, LTD., PRINTERS, PLYMOUTH</p> - - -<div class="footnotes pg-brk"> -<h3><a name="FOOTNOTES" id="FOOTNOTES">FOOTNOTES:</a></h3> - -<div class="footnote"> - -<p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> <cite>Chemical News</cite>, Vol. I, p. 208.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> Mr. Paterson called “limey stuff” what is now -termed “blue ground.” It was also formerly called -“marl stuff,” “blue stuff,” and “blue clay.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> The original name for the Kimberley Mine. It -was also sometimes known as “Colesberg Kopje.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">[4]</span></a> <cite>Diamonds and Gold in South Africa.</cite> By T. Reunert. -Johannesburg, 1893.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> According to Gardner Williams the South African -carat is equivalent to 3·174 grains. In Latimer Clark’s -<cite>Dictionary of Metric and other Useful Measures</cite> the -diamond carat is given as equal to 3·1683 grains = -0·2053 gramme = 4 diamond grains; 1 diamond grain = -0·792 troy grain; 151·5 diamond carats = 1 ounce troy. -</p> -<p> -Webster’s <cite>International Dictionary</cite> gives the diamond -carat as equal to 3⅕ troy grains. -</p> -<p> -<cite>The Oxford English Dictionary</cite> says the carat was -originally <sup>1</sup>/<sub>144</sub> of an ounce, or 3⅓ grains, but now equal -to about 3⅕ grains, though varying slightly with time -and place. -</p> -<p> -The <cite>Century Dictionary</cite> says the diamond carat is -equal to about 3⅙ troy grains, and adds that in 1877 -the weight of the carat was fixed by a syndicate of -London, Paris, and Amsterdam jewellers at 205 milligrammes. -This would make the carat equal to 3·163 troy -grains. A law has been passed in France ordaining -that in the purchase or sale of diamonds and other -precious stones the term “metric carat” shall be employed -to designate a weight of 200 milligrammes -(3·086 grains troy), and prohibiting the use of the word -carat to designate any other weight.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> Artificial tribo-luminescent sphalerite:—</p> - -<div class="center"> -<table border="0" cellpadding="4" cellspacing="0" summary=""> -<tr><td class="tdl">Zinc carbonate</td><td class="tdl">100 parts</td></tr> -<tr><td class="tdl">Flower of sulphur</td><td class="tdl"> 30 ”</td></tr> -<tr><td class="tdl">Manganese sulphate</td><td class="tdl pad2h">½ per cent.</td></tr> -</table></div> - -<p>Mix with distilled water and dry at a gentle heat. -Put in luted crucible and keep at a bright red heat -for from two to three hours.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">[7]</span></a> Sir James Dewar, in a Friday evening discourse -at the Royal Institution in 1880, showed an experiment -proving that the temperature of the interior of -a carbon tube heated by an outside electric arc was -higher than that of the oxy-hydrogen flame. He -placed a few small crystals of diamond in the carbon -tube, and, maintaining a current of hydrogen to prevent -oxidation, raised the temperature of the tube in -an electric furnace to that of the arc. In a few -minutes the diamond was transformed into graphite. -At first sight this would seem to show that diamond -cannot be formed at temperatures above that of the -arc. It is probable, however, for reasons given above, -that at exceedingly high pressures the result would be -different.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">[8]</span></a> The silica was in the form of spheres, perfectly -shaped and transparent, mostly colourless, but among -them several of a ruby colour. When 5 per cent of -silica was added to cordite, the residue of the closed -vessel explosion contained a much larger quantity of -these spheres.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">[9]</span></a> A pressure of fifteen tons on the square inch -would exist not many miles beneath the surface of -the earth.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">[10]</span></a> There are abundant signs that a considerable -portion of this part of Africa was once under water, -and a fresh-water shell has been found in apparently -undisturbed blue ground at Kimberley.</p></div> - -<div class="footnote"> - -<p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">[11]</span></a> The water sunk in wells close to the Kimberley -mine is sometimes impregnated with paraffin, and -Sir H. Roscoe extracted a solid hydrocarbon from the -“blue ground.”</p></div> - -<div class="footnote"> - -<p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">[12]</span></a> <cite>Chemical News</cite>, vol. lxi, p. 209, 1890.</p></div> -</div> - - -<div class="transnote pg-brk"> -<a name="TN" id="TN"></a> -<p><strong>TRANSCRIBER’S NOTE</strong></p> - -<p>Obvious typographical errors and punctuation errors have been -corrected after careful comparison with other occurrences within -the text and consultation of external sources.</p> - -<p>All misspellings in the text, and inconsistent or archaic usage, have -been retained: for example, unfrequent; clayey; friable; slaty; imbed; -stoped; peculation; situate.</p> - -<p>In the <a href="#CONTENTS">Table of Contents</a>, the Index page number ‘145’ has been replaced by ‘141’.</p> - -<p>In the <a href="#INDEX">Index</a>, ‘Colesberg Copje’ has been replaced by ‘Colesberg Kopje’, -and ‘DeBeers’ has been replaced by ‘De Beers’.</p> -</div> - - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of Diamonds, by William Crookes - -*** END OF THIS PROJECT GUTENBERG EBOOK DIAMONDS *** - -***** This file should be named 61096-h.htm or 61096-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/6/1/0/9/61096/ - -Produced by deaurider, John Campbell and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive) - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. 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