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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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