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diff --git a/old/62879-0.txt b/old/62879-0.txt deleted file mode 100644 index 4c341d9..0000000 --- a/old/62879-0.txt +++ /dev/null @@ -1,2765 +0,0 @@ -Project Gutenberg's Gems in the Smithsonian Institution, by Paul E. Desautels - -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: Gems in the Smithsonian Institution - -Author: Paul E. Desautels - -Release Date: August 8, 2020 [EBook #62879] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK GEMS IN THE SMITHSONIAN INSTITUTION *** - - - - -Produced by Stephen Hutcheson and the Online Distributed -Proofreading Team at https://www.pgdp.net - - - - - - - [Illustration: Faceted, egg-shaped, 7000-carat rock crystal from - Brazil. The gold stand is inset mostly with Montana sapphires. The - gem was cut and the stand was designed and constructed by Capt. John - Sinkankas of California. (7¼ inches high in all.)] - - - - - _Gems_ - _in the_ - SMITHSONIAN - INSTITUTION - - - by PAUL E. DESAUTELS - - _Associate Curator_ - Division of Mineralogy - - WASHINGTON, D. C. - 1965 - - [Illustration: FOR THE INCREASE AND DIFFVSION OF KNOWLEDGE AMONG - MEN • SMITHSONIAN INSTITVTION • WASHINGTON 1846] - - SMITHSONIAN - INSTITUTION - PUBLICATION - No. 4608 - - LIBRARY OF CONGRESS - Card No. 65-60068 - - - - - CONTENTS - - - The National Gem Collection 1 - The Study of Gems 3 - The Shaping of Gemstones 10 - Gem Substitutes 20 - Gem Lore 24 - The Principal Gem Species 27 - Some Notable Gems in the Collection 70 - - [Illustration: Prof. F. W. Clarke, former honorary curator of the - Division of Mineralogy who assembled the Smithsonian Institution’s - first gem collection in 1884.] - - [Illustration: Dr. Isaac Lea, Philadelphia gem collector whose - collection was the nucleus around which the Smithsonian - Institution’s gem collection has been built through the years.] - - [Illustration: Dr. Leander T. Chamberlain, son-in-law of Dr. Isaac - Lea, who became honorary curator of the Smithsonian Institution’s - gem collection in 1897. Income from his bequest is used to purchase - gems for the Isaac Lea gem collection.] - - - - - 1 - THE NATIONAL GEM COLLECTION - - -Man has been using certain mineral species for personal adornment since -prehistoric times. However, of the almost 2000 different mineral -species, relatively few, perhaps only 100, have been used traditionally -as gems. To be used as a gem, a mineral species must have durability as -well as beauty. Lack of durability eliminates most minerals as gems, -although some relatively fragile gem materials such as opal are prized -because of their exceptional beauty. Actually, some gem materials are -not minerals at all. Pearl, amber, jet, and coral are formed by living -organisms. - -In the National Gem Collection, the Smithsonian Institution has -assembled a large representation of all known gem materials. The display -portion of the collection consists of more than 1000 items selected to -illustrate the various kinds of gems and to show how their beauty is -enhanced by cutting and polishing. All of these gems are gifts of -public-spirited donors who, by giving the gems directly or by -establishing endowments for their purchase, have contributed to the -enjoyment of the many thousands of persons who visit the Smithsonian -Institution each week. - -The National Gem Collection had its beginning in 1884 when Prof. F. W. -Clarke, then honorary curator of the Division of Mineralogy, prepared an -exhibit of American precious stones as a part of the Smithsonian -Institution’s display at the New Orleans Exposition. The same collection -was displayed at the Cincinnati Exposition the following year. Between -1886 and 1890 the growth of the collection was slow, but in 1891 most of -the precious stones collected by Dr. Joseph Leidy of Philadelphia were -obtained, and these, combined with those already on hand, were exhibited -at the World’s Columbian Exposition at Chicago in 1893. - -Great stimulus was given the collection in 1894 when Mrs. Frances Lea -Chamberlain bequeathed the precious stones assembled by her father, Dr. -Isaac Lea. Her husband, Dr. Leander T. Chamberlain, who in 1897 became -honorary curator of the collection, contributed a large number of -specimens and, upon his death, left an endowment fund. The income from -that fund has been used to steadily increase the collection over the -years. Extremely rare and costly gems suitable for exhibition are beyond -the income derived from the Chamberlain endowment, but this gap has been -filled by many important donations, the most notable being the gift of -the Hope Diamond by Harry Winston, Inc., New York City. Thus, from -modest beginnings in 1884, there has been accumulated the magnificent -collection of gems belonging to the people of the United States. The -collection is displayed in the Smithsonian Institution’s great Museum of -Natural History. - - [Illustration: Left to right: 42-carat brazilianite, 8.4-carat - euclase, 7.6-carat benitoite, 12-carat willemite, 20-carat - amblygonite, and 16-carat orthoclase. (About two-thirds actual - size.)] - - - - - 2 - THE STUDY OF GEMS - - -To the average person it might seem that a jeweler’s showcase of gems -presents innumerable kinds of precious stones, when actually only a few -species of minerals are there. Perhaps only diamond, ruby, emerald, -aquamarine, sapphire, opal, tourmaline, and amethyst would comprise the -entire stock. Yet, since the mineral kingdom consists of about 2000 -distinct species, it would seem that a few more kinds of gemstones would -be available. Certainly, many more minerals than are seen displayed by -the jeweler have been used as gems over the centuries. The study of all -these species of gem minerals constitutes modern gemology—a specialized -branch of the science of mineralogy. - -With the few exceptions already noted, all gems are minerals found in -the earth’s crust. A mineral is a natural substance having a definite -chemical composition and definite physical characteristics by which it -can be recognized. However, for a mineral to qualify as a gem it must -have at least some of the accepted requirements—brilliance, beauty, -durability, rarity, and portability. Of course, if a gemstone happens to -be “fashionable” it will have additional importance. Rarely does a -single gem possess all of these qualities. A fine-quality diamond, -having a high degree of brilliance and fire, together with extreme -hardness and great rarity, comes closest to this ideal, and in the world -of fashion the diamond is unchallenged among gems. The opal, by -contrast, is relatively fragile, and it depends mainly on its rarity and -its beautiful play of colors to be considered gem material. - -When a gem material, as found in nature, has at least a minimum number -of the necessary qualities, it is then the task of the lapidary, or gem -cutter, to cut it and polish it in such a way as to take greatest -advantage of all its possibilities for beauty and adornment. - - - PHYSICAL CHARACTERISTICS OF GEMSTONES - -When a gemologist or a gem cutter examines an unworked mineral fragment -(called _rough_) he looks for certain distinguishing characteristics -that will aid him in identifying the mineral and in determining the -procedures he should use in cutting it. - - Scale of Hardness - - Soft 1. Talc - ^ 2. Gypsum - 3. Calcite - 4. Fluorite - 5. Apatite - 6. Feldspar - 7. Quartz - 8. Topaz - v 9. Corundum - Hard 10. Diamond - -It is difficult to list these characteristics in the order of -importance, but _hardness_ would rank high. Hardness of a gem is best -defined as its resistance to abrasion or scratching. Most commonly used -for comparison is the Mohs scale, which consists of selected common -minerals arranged in the order of increasing hardness. On this scale, -topaz is rated as 8 in hardness, ruby as 9, and diamond, the hardest -known substance, as 10. Any gem with a hardness less than that of -quartz, number 7 in the scale, is unlikely to be sufficiently -scratch-resistant for use as a gem. A less precise scale, using common -objects for comparison, might include the fingernail with a hardness up -to 2½, a copper coin up to 3, a knife blade to 5½, a piece of window -glass at about 5½, and a steel file between 6 and 7, depending on the -type of steel. By this scale, any stone that remains unmarred after -being scraped by a piece of window glass will have a hardness greater -than 5½. The more important gemstones—which include diamond, ruby, -sapphire, and emerald—all have a hardness much greater than 5½. - -The size of a gemstone usually is indicated by its _weight_ in carats. -The expression “a 10-carat stone” has meaning—if somewhat inexact—even -to the nonexpert. Specifically, a carat is one-fifth of a gram, which is -a unit of weight in the metric system small enough so that approximately -28 grams make an ounce. A 140-carat gemstone, then, weighs about an -ounce. - -Another distinguishing characteristic of a gemstone is its specific -gravity, which is an expression of the relationship between the stone’s -own weight and the weight of an equal volume of water. We are aware of a -difference in weight when we compare lead and wood, yet it would not -always be correct to say that lead weighs more than wood, for a large -piece of wood can weigh more than a small piece of lead. Only by -comparing equal volumes of these materials can the extent of the weight -difference be clear and unmistakable. Diamond is 3½ times heavier than -the same volume of water, so its specific gravity is 3.5. Since each -species of gem has its own specific gravity, which can be determined -without harming the stone, this standard of comparison is a valuable aid -in identifying gems. Several techniques have been devised for -determining specific gravity, and most of them make use of some kind of -weighing device or balance. - -Among the most striking and useful of the distinguishing characteristics -of gemstones are those that involve the effects on light. - -An important effect of a gem on light is the production of color, upon -which many gems depend for their beauty. Some gem materials, such as -lapis lazuli, have little to offer except color. Many gemstones vary -widely in color, owing to the presence of varying but extremely small -amounts of impurities. Thus, the gemstone beryl may occur as blue-green -(aquamarine), as pink (morganite), as rich green (emerald), as yellow -(golden beryl), or even colorless (goshenite). - - [Illustration: Sketch of a simple balance used to determine specific - gravity of a gemstone. The operator places the gemstone in the upper - pan (A), moves the weight (B) along the beam (C) until it balances - perfectly, and notes the number at the weight’s position. He then - transfers the gemstone to the lower pan (D), which is completely - immersed in water, and moves the weight along the beam to restore - balance. He notes the scale number at the new position and - determines the specific gravity simply by dividing the first number - by the difference between the two numbers. If the gemstone is large, - the operator can use heavier sliding weights. (E).] - -Gemstones such as beryl and sapphire that depend on impurities for their -color are said to be _allochromatic_; others, such as peridot and -garnet, which are highly colored even when pure, are said to be -_idiochromatic_. The color of a gem is further described according to -its _hue_, _tint_, and _intensity_. Hue refers to the kind of color, -such as red, yellow, green, etc.; tint refers to the lightness or -darkness of the hue; and intensity refers to vividness or dullness. -Throughout history, the most popular colored stones have been those with -hues of red, green, or blue of dark tint and high intensity. - - [Illustration: A 43-carat albite from Burma (at left), 76-carat - tourmaline from Brazil, and 30-carat wernerite from Burma exhibit a - strong cat’s-eye effect because of reflection from inclusions in - parallel arrangement within the stones. (Actual size.)] - - [Illustration: Asterism (star effect) is caused by parallel - inclusions arranged in several directions related to the crystal - structure of the gemstone. Two rays in the 175-carat, 6-rayed star - garnet from Idaho (at left in photo) are weaker than the other four - because of fewer inclusions in that direction. The 23-carat star - orthoclase from Ceylon shows brightly all of its four possible rays. - (Actual size.)] - -The effect of a gem on light may be more than the production of color. -Several of the so-called phenomenal stones are prized for other effects. -Holes, bubbles, and foreign particles, when properly aligned in parallel -groupings, can produce interesting light effects. The play of colors of -opal and labradorite, the _chatoyancy_ or silky sheen of tiger’s-eye and -cat’s-eye, the _opalescence_ or pearly reflections of opal and -moonstone, and the _asterism_ or star effect of rubies and sapphires are -caused by the reaction of light to minute _inclusions_ or imperfections -in the gemstone. - -When light passes into or through a gemstone with little or no -interruption, the stone is said to be transparent, as opposed to a stone -through which light passes with greater difficulty, and which is said to -be either translucent or opaque, depending on the degree of light -interruption. - - [Illustration: Rays of light passing into a gemstone are refracted - (bent) in varying amounts depending on the gem species and also on - the angle at which the light strikes the stone. The light rays are - reflected back toward the top of the stone by internal faces - (facets), and they are refracted again as they leave.] - - [Illustration: How a gem refractometer, a simple device to operate, - is used to measure quickly the refractive index of a cut gemstone. A - light beam passing through the opening (A) is reflected from the - table of a gemstone (G) through a lens system (L) and, by prism (P), - into the eye of the observer (E). The maximum angle of reflection - (N), which depends on the refractive index of the gemstone, controls - the angle at which the beam comes through the eyepiece (EP). The - refractive index is read directly from a scale in the eyepiece.] - -The action of a gemstone upon the light which strikes its surface and is -either reflected or passed through it sometimes results in highly -desirable effects that enhance its beauty and aid in its identification. -Light passing into a stone is bent from its path, and the amount of -bending (_refraction_) depends upon the species of the gemstone. When -the degree of bending can be measured, the gem species can be -identified, since very few species of gemstones bend light to exactly -the same degree. An instrument called a gem refractometer is used to -determine the degree to which cut stones refract, or bend, light. The -measurement obtained is the _refractive index_ of the gemstone. - -Many gemstones can split a beam of light and bend one part more than the -other, thus producing _double refraction_, or two different measurements -of refractive index. - - [Illustration: When a ray of ordinary white light enters some - gemstones it is dispersed (split up) into rays of the separate - colors of which it is composed. These rays are reflected inside the - gem and are further separated by additional refraction as they leave - the gemstone. This dispersion accounts for the colored flashes of - light, or fire, for which diamond is highly prized.] - -Gems have the ability to separate “white light” (the mixture of all -colors) into its various colors, producing flashes of red, yellow, -green, and other colors. Separation occurs because the various colors, -or wavelengths composing white light passing through the gem, are each -bent or refracted a different amount. Red is bent least, followed in -order by orange, yellow, green, blue, and violet, which is bent most. -This characteristic of being able to produce flashes of color, as seen -prominently in diamond, is known as _dispersion_ or _fire_. Quartz and -glass have low dispersion, and hence they make poor diamond substitutes. -Some of the newer synthetic gemstones, such as titania, have extremely -high dispersion, with resulting fire. Zircon, a natural gemstone of -suitable hardness, exhibits high dispersion and is a commonly used -substitute for diamond. - - - CHEMICAL CHARACTERISTICS OF GEMSTONES - -Since gems are embraced in the mineral kingdom, and minerals are -naturally occurring chemical substances, it follows that all the -accepted terms of chemical description can be applied to them. When a -chemist learns that ruby is an impure aluminum oxide, he understands a -great deal about the nature, origin, and behavior of ruby. He can assign -to it the chemical formula Al₂O₃, symbolizing its basic composition as -two atoms of aluminum united with three of oxygen. Similarly, other -popular gemstones can be described chemically as follows: - - Diamond Carbon C - Sapphire Aluminum oxide Al₂O₃ - Quartz Silicon dioxide SiO₂ - Emerald Beryllium aluminum silicate Be₃Al₂(SiO₃)₆ - Spinel Magnesium aluminate Mg(AlO₂)₂ - -Significantly, ruby and sapphire are chemically identical, both being of -the mineral species corundum. As already explained, the difference in -color is due entirely to very slight traces of chemical impurities. -Frequently, the impurities are present in irregular patches that give -spotty color effects. - -Some mineral species possess many of the desirable qualities of -gemstones yet cannot be used as gems because they are chemically active -and therefore are less durable. They undergo alteration and -decomposition when exposed to light or to one or another of such -substances as air, water, skin acids and oils. - - - - - 3 - THE SHAPING OF GEMSTONES - - -Gemstone crystals often have naturally brilliant, reflecting faces, but -rarely are they perfect and unblemished. Also, their natural shapes do -not provide the best expression of their luster, brilliance, dispersion, -color, and other inherent properties. In fashioning a gemstone, the -skilled artisan tries to develop these hidden assets and to otherwise -enhance the gemstone’s general beauty. - -From ancient times until the 1600’s little was attempted in the way of -shaping gemstones other than to smooth or polish the natural form. -Although similarly smoothed, or _tumbled_, gemstones recently have -returned to fashion, the finest pieces of gem rough are now converted -mainly into _faceted_, or shaped, stones. Standard types of facets—the -flat faces that are ground and polished on the rough gem material—have -been given individual and group names. A typical example is the -_brilliant_ cut, which is most commonly used to best bring out the -qualities of a diamond. - - [Illustration: The standard brilliant cut, with a pattern of many - facets, is commonly used for gemstones having a high refractive - index and, therefore, great brilliance.] - - [Illustration: Characteristic of the standard brilliant cut are the - 32 crown facets surrounding a relatively small, flat, table facet - and the 24 pavilion facets and culet at the bottom of the stone.] - - [Illustration: Ideal proportions for the standard brilliant cut have - been carefully determined so that the maximum amount of light will - be reflected back out the top of the stone. Incorrect proportions - cause the light to be lost at the bottom of the stone.] - - [Illustration: The step cut, often called the emerald cut, - frequently is used for colored stones because the large table - permits a good view of the color.] - - [Illustration: The emerald or step cut provides a large table and a - full bottom for the stone. Although the number of crown and pavilion - facets may vary, the general pattern is maintained.] - - [Illustration: The simplified English brilliant cut takes maximum - advantage of the strong dispersion of diamond, with its flashes of - fire, but the fewer facets provide less sparkle than the standard - brilliant cut.] - -The diagram shows a brilliant-cut diamond with angles and facets -arranged to give the stone maximum internal reflection as well as to -make use of its strong dispersive ability. Certain of the light beams -passing into a brilliant-cut diamond produce colorless brilliance by -being reflected back out of the stone through the _table_ by which they -entered. Other light beams, emerging through inclined facets, are split -up by dispersion into the rainbow, or fire, effect so prized in -diamonds. A stone that has been cut too wide for its depth, with -incorrect facet angles, will look large for its weight but its -brilliance and fire will have been drastically reduced. - - [Illustration: The English brilliant cut has 28 crown and pavilion - facets—28 fewer than the standard brilliant cut.] - - [Illustration: The Dutch rose cut is a very simple one that is used - mainly for small diamonds in jewelry that features a larger, colored - stone. It is based on a form that originated in India and was - introduced through Venice.] - -For other purposes and for other kinds of precious stones a number of -basic cuts have been developed. The _brilliant_ and _step_ cuts are by -far the commonest of these basic cuts, but modern jewelry design -frequently uses such fancy cuts as the baguette, cut-corner triangle, -epaulet, half moon, hexagon, keystone, kite, lozenge, marquise, -pentagon, square, trapeze, and triangle. Some of these are shown here. - - [Illustration: Just as the English brilliant cut, because of its 28 - fewer facets, has less sparkle than the standard brilliant cut, the - step brilliant, with its 20 additional facets, has greater sparkle.] - - [Illustration: The step brilliant cut is a complicated modification - of the standard brilliant. With an additional 12 facets in the crown - and 8 in the pavilion, the step brilliant has 78 facets, compared - with the 58 of the standard.] - - [Illustration: Various kinds of cuts have been devised for special - purposes in jewelry design. These include the pentagon (1), lozenge - (2), hexagon (3), cut-corner triangle (4), kite (5), keystone (6), - epaulet (7), baguette (8), trapeze (9) and square (10).] - - [Illustration: With this typical trim saw, water is used as a - coolant for the rapidly rotating metal disk, which has a - diamond-impregnated rim. Here, the blade is cutting its way through - a piece of gem tourmaline.] - -In general, there are three operations in preparing a gemstone from the -rough—sawing, grinding, and polishing. Sawing usually is accomplished by -using a thin, diamond-impregnated, rapidly rotating disk of soft iron or -bronze, with oil or water being used as a coolant. The very hard diamond -dust literally scratches its way through the stone. Once the stone is -sawed to shape, the facets are ground and polished on a rotating -horizontal disk by the use of various abrasives. For rough grinding, -silicon carbide—or sometimes diamond powder—is used. Scratches are -removed and a high polish is given by the use of tin oxide, pumice, -rouge, or other fine-grained abrasives. The thick disks, or laps, are -made of cast iron, copper, lead, pewter, wood, cloth, leather, and -certain other materials. Since each species of gemstone differs in its -characteristics, each must be treated somewhat differently as to sawing -and lapping speeds, kind of lap, and choice of abrasives. Because of the -greatly increased interest in gem cutting as a hobby and the large -number of amateur cutters, a substantial market has developed in the -United States for lapidary supplies and equipment. New kinds of -machinery, new abrasives, and new kinds of saws and laps are introduced -regularly. Fundamentally, however, the process still involves sawing, -grinding, and polishing. - - [Illustration: The final step in preparing a gemstone from rough is - the applying of a high polish by pressing the stone against a - rotating disk that has an extremely fine abrasive on its surface. - Here, the disk is of felt, and the abrasive is tin oxide.] - - [Illustration: The cabochon cut gets its name from the French word - “caboche,” meaning pate or knob, a reference to the rounded top of - the stone. Here, from top to bottom, beginning at left, are - cabochons of turquoise, agate, and petrified wood; jasper, - smithsonite, and williamsite; and amazonite, petoskey stone, and - carnelian. (Two-thirds actual size.)] - - [Illustration: These exquisite bowls, measuring 2 to 3 inches - across, are part of a set of 35 carved by George Ashley of Pala, - Calif., from gem materials found in the United States. Left to - right: paisley agate from California, petrified wood from Arizona, - black jade from Wyoming, chrysocolla from Arizona, and variscite - from Utah. (One-third actual size.)] - -Shaping of gemstones is not limited to geometric faceting. Many stones, -especially those which are opaque or which produce stars and cat’s-eyes, -are cut as _cabochons_. This ancient, and probably oldest, cutting style -consists merely of a raised and rounded form. When extended completely -around the stone, the cabochon form results in a bead that can be -drilled and strung. Many cabochons, especially those of less expensive -gem materials, are now cut in large quantities to standard sizes in -order to fit mass-produced gem mountings. - -Sculpting in gemstones is a much more intricate, nongeometric kind of -shaping. Although tools differ in detail, and the gem sculptor must -possess an artistic eye as well as lapidary skill, the basic processes -of sawing, grinding, and polishing are the same. - - [Illustration: This coral carving, 11 inches tall without the stand, - owes its thin, graceful, willowy shape to the skill of the artist in - following the contour of a natural coral branch.] - - [Illustration: The contemporary sculptor Oskar III J. W. Hansen - visualized and created the likeness of a spirited stallion in this - 4½-inch turquoise carving, a gift of George Gilmer.] - - [Illustration: This world-famed crystal ball, given to the - Collection as a memorial to W. R. Warner by his widow, represents - another phase of the lapidary art. Cut from a block of Burmese - quartz estimated to weigh 1000 pounds, this extremely valuable, - flawless, colorless sphere has a diameter of 12⅝ inches and weighs - 106¾ pounds.] - - - - - 4 - GEM SUBSTITUTES - - -Because of their rarity and relatively high cost, the number of real -gems used throughout recorded times must be insignificant compared to -the number of gem substitutes used. There are records of glass and -ceramic imitations of gems as early as 3000 B.C. Certainly, the world -gem markets today are flooded with man-made gems. There even has been -developed a laboratory process for growing a coating of synthetic -emerald on the surface of a faceted stone of natural colorless beryl. -The recut gem looks like a natural emerald, and it has natural -inclusions that totally synthetic emeralds lack. - -In general, gem substitutes can be classified as imitation stones, -assembled stones, reconstructed and altered stones, and synthetic -stones. - - - IMITATION STONES - -Any material will serve as an imitation of a natural gem as long as it -resembles the real thing under casual examination. Because of the great -variety in types and colors available, glass and plastics are the most -commonly used materials for making imitation gems. Almost every gem has -been simulated effectively. The substitutes offer no difficulty of -identification to the expert, but many are deceptive to the layman. - - - ASSEMBLED STONES - -It has been the practice for centuries to build up gemstones by fusing -or cementing a shaped piece of natural gemstone to another piece, or -other pieces, of inferior or artificial material. - -A colorless common beryl crown cemented to a pavilion of green glass -produces an emerald doublet—part natural, part artificial—of good color -and high durability. A thin piece of beautifully colored opal cemented -to a base of inferior opal provides an assembled stone that looks like a -thick piece of high-quality opal. Triplets, and even stones in which -there are pockets of colored liquids or metal foil between the shaped -pieces, are known. - -Usually, assembled stones are easily detected, since the joint will show -under magnification, but sometimes they are mounted in settings that -obscure the joint, and detection is more difficult. - - [Illustration: Assembled imitation gemstones. If it were measured on - its natural ruby table, the assembled stone shown at top would have - all the characteristics of a large ruby, including refractive index. - The color of the quartz and glass combination (middle) depends on - the color of the liquid in the cavity. Since emerald is green beryl, - an inexpensive colorless beryl sandwich of green glass (bottom) - would appear to be an expensive emerald. The joints of assembled - stones often are hidden in the jewelry mountings.] - - - RECONSTRUCTED AND ALTERED STONES - -Ruby fragments may be heated at high temperature to partially melt them -into a large mass that can be cut into a more valuable stone. Ruby is -the only stone that can be successfully reconstituted in this way, but -there are many other ways of tampering with natural stones to make them -more desirable. - -Sometimes natural stones are backed with foil or a metallic coating to -enhance their color, to provide brilliance, or to produce a star effect. -It is said that in an inventory of the Russian crown jewels by the -Soviet Government, the ruby-colored Paul the First Diamond was -discovered to be a pale pink diamond backed by red foil. Today, some -diamonds are coated on the back with a blue film to improve their color. - -Aquamarine, when pale greenish blue, may be heated in order to deepen -the blue color, and poorly colored amethyst may be heated to produce a -beautiful yellow-brown quartz, called citrine, that often is -misrepresented as topaz. By strong heating, the brown and reddish brown -colors of zircon can be changed to blue or colorless, both of which -states are unknown in natural zircon. Dyes, plastics, and oils are used -to impregnate porous gems such as turquoise and variscite, and even -jade. Off-color diamonds, when exposed to strong atomic radiation, can -be changed to attractive green, brown, and yellow colors, causing them -to resemble higher-priced _fancies_. - -In the constant search for something new, gem suppliers sometimes -introduce into gemstones colors that are not always an improvement. For -example, the beautiful purple of some amethyst can be converted, by heat -treatment, to a peculiar green. Such an altered stone is marketed as -_greened amethyst_. - -All of this tampering with gemstones complicates the problem of -identification, so it is a matter of serious concern to the gem trade. - - - SYNTHETIC STONES - -For over 200 years mineralogists have been devising techniques for -producing synthetic minerals in the laboratory, and attempts have been -made, sometimes with considerable success, to apply these techniques to -the production of synthetic gemstones. To qualify as a synthetic -gemstone the man-made product must be identical chemically and -structurally with its natural counterpart. Sapphire, ruby, spinel, -emerald, and rutile in gem quality have been brought to commercial -production. - -Two of the basic techniques used in producing synthetic gems are the -_flame-fusion_ and the _hydrothermal_ processes. - - [Illustration: The Verneuil furnace, for making synthetic gem rough. - A mixture of hydrogen (H) and oxygen (O) burns almost explosively, - heating the fusion chamber (F) to high temperatures. For example, - powdered aluminum oxide and coloring agents are sifted down from - hopper (A) to the fusion chamber and form a cylindrical boule (B) on - an adjustable stand (C).] - -In the flame-fusion process—invented in 1904 by the French chemist -Verneuil—powdered aluminum oxide, containing coloring agents, is sieved -down through the flame of a vertical blowtorch furnace. As it passes -through the flame, the powder melts and accumulates as drops on an -adjustable stand just below the flame, where it forms a single crystal -_boule_ of the synthetic rough. In a few hours a boule of several -hundred carats can be formed. When such furnaces are operated in banks -of several hundred units, the commercial production of corundum alone -becomes possible at the rate of many tons a year. Through the years, of -course, refinements have been made on Verneuil’s original furnace. - -In the hydrothermal process, which differs greatly from Verneuil’s -flame-fusion process, crystals are grown from solutions of the raw -materials that have been subjected to varying conditions of very high -pressure and temperature. Some of the quartz used for electronics -purposes also is manufactured in this way. - -Since chemical composition and crystal structure are the basic -characteristics by which a gemstone is identified, and these -characteristics are identical in both the manufactured stone and its -natural counterpart, the synthetic gemstones offer a very serious -challenge to those concerned with gem identification. - - - - - 5 - GEM LORE - - -All sorts of magic and symbolic properties have been ascribed to -gemstones through the ages; for example, the cat’s-eye has been -prescribed as a cure for paleness, citrine has been worn as a protection -from danger, and the opal cherished as the symbol of hope. The result -has been the creation of an intricate, chaotic, and contradictory but -interesting mass of gem lore. - -Among the treasures in the Smithsonian’s Museum of Natural History is a -very old silver breastplate that once was in an ancient synagogue and -supposedly was modeled after the one worn by Aaron, the first high -priest of the Hebrews. In this plate are mounted twelve stones -representing the Twelve Tribes of Israel. Among Christians, the Twelve -Apostles also were represented symbolically by precious stones. - - THE TWELVE TRIBES - Levi, _Garnet_ - Zebulon, _Diamond_ - Gad, _Amethyst_ - Benjamin, _Jasper_ - Simeon, _Chrysolite_ - Issachar, _Sapphire_ - Naphtali, _Agate_ - Joseph, _Onyx_ - Reuben, _Sard_ - Judah, _Emerald_ - Dan, _Topaz_ - Asher, _Beryl_ - - THE TWELVE APOSTLES - Peter, _Jasper_ - Andrew, _Sapphire_ - James, _Chalcedony_ - John, _Emerald_ - Philip, _Sardonyx_ - Bartholomew, _Sard_ - Matthew, _Chrysolite_ - Thomas, _Beryl_ - James the Less, _Topaz_ - Jude, _Chrysoprase_ - Simon, _Hyacinth_ - Judas, _Amethyst_ - -The number “12” seems to follow a chain of gemstone superstitions. -Gemstones were considered to have mystical relationship not only with -the Twelve Tribes and the Twelve Apostles but also with the Twelve -Angels, the Twelve Ranks of the Devil, and the Twelve Parts of the human -body. - -Some stones were even endowed with astrological significance and were -believed to be in sympathy with the twelve zodiacal signs. On the basis -of an elaborate system of prognostications, an astrologer was considered -able to foretell future events by proper observance of changes in hue -and brilliance of the symbolic stones. - - Aries the Ram, _Bloodstone_ - Taurus the Bull, _Sapphire_ - Gemini the Twins, _Agate_ - Cancer the Crab, _Emerald_ - Leo the Lion, _Onyx_ - Virgo the Virgin, _Carnelian_ - Libra the Scales, _Chrysolite_ - Scorpio the Scorpion, _Aquamarine_ - Sagittarius the Archer, _Topaz_ - Capricornus the Goat, _Ruby_ - Aquarius the Water Bearer, _Garnet_ - Pisces the Fishes, _Amethyst_ - -Perhaps in our own space-oriented times the ancient superstitions -sympathetically relating certain gemstones with the planets will be -revived. In the distant past, moonstone, topaz, and other white stones -were believed to be in sympathy with the Moon, diamond and ruby with the -Sun, jasper and emerald with Mars, amethyst, topaz, and emerald with -Venus, carnelian, topaz, and amethyst with Jupiter, turquoise and -sapphire with Saturn, and rock crystal, agate, and emerald with Mercury. -Since Uranus, Neptune, and Pluto were unknown to the ancients, these -planets have not been represented by gemstones. - -Of special interest to the American public are birthstones. Many -birthstone lists have been proposed, and in order to use this idea to -popularize gemstones the American jewelry industry has agreed upon an -official list. This list has served to bring about some uniformity in -the selection of birthstones for the twelve months. - - January, _Garnet_ - February, _Amethyst_ - March, _Aquamarine_ or _Bloodstone_ - April, _Diamond_ - May, _Emerald_ - June, _Moonstone_ or _Pearl_ - July, _Ruby_ - August, _Peridot_ or _Sardonyx_ - September, _Sapphire_ - October, Opal or _Tourmaline_ - November, _Topaz_ or _Citrine_ - December, _Turquoise_ or _Lapis lazuli_ - -All these associations and strange beliefs have served to create in the -general public a mental image of gemstones that gives to them an -increased exoticism and mysterious appeal far exceeding their monetary -value. - - [Illustration: {zodiac symbols}] - - - - - 6 - PRINCIPAL GEM SPECIES - - -An excursion into the literature of gems would reveal that there is much -to be discovered about them other than the cold facts of gemology, -techniques of gem cutting, and tales of gem lore. When all the -information about an individual species is assembled, it provides a -sketch of a fascinating gemstone personality. Whole books have been -written about diamond—books filled with essays on its mining history, -natural occurrences, scientific significance, and best known cut stones. - -In the following sections of this book, some of the facts about several -of the better known gem species have been gathered. The treatment is not -meant to be complete, but enough information is given so that the Museum -visitor may better understand and remember what he has seen. - -For each species described there are color illustrations of certain -gemstones displayed in the collection. Several photographic and artistic -techniques have been used to emphasize the various aspects of the beauty -of these stones, many of which are the largest and finest of their kinds -known; however, not all of the finest gems are pictured here. - -At the end of this descriptive section is a list of the significant -faceted gemstones in the collection. Obviously, this list will change, -because new gemstones constantly are being acquired. - - - DIAMOND - -Diamond is the king of gems. It is a form of pure carbon, and it is the -hardest substance known; only diamond will cut diamond. It is -interesting that the humble graphite, its close relative, is also pure -carbon, but graphite is so soft that it is used as a lubricant and for -making the “lead” in pencils. - -The ancients believed diamond to be indestructible, and even today many -people believe that diamond cannot be broken. Despite its great -hardness, however, diamond is not exceptionally tough, and it can be -split along what diamond cutters call its _grain_. - -The diamond’s high brilliance results from its very high refraction, or -ability to bend light, and its fire is caused by its high dispersion, or -ability to divide light into its rainbow colors. However, only in -properly cut stones are diamond’s brilliance and fire developed to their -maximum. - -At great depths in the crust of the earth and under conditions of very -high pressure and temperature, diamonds form in pipe-like bodies of -kimberlite, a heavy dark rock consisting primarily of two minerals, -pyroxene and olivine. In South Africa diamonds are mined from the -kimberlite, but they also are recovered there and elsewhere from beds of -sand and gravel where they have accumulated after being released from -their mother rock by erosion. - -The world’s largest diamond deposits are in Africa, and names such as -Congo, Sierra Leone, and the Union of South Africa bring to mind -colorful legends of fabulous discoveries of diamond. Smaller deposits -are found in South America—in Brazil, British Guiana, and Venezuela—and -in Asia. Even in the United States some diamonds have been found. - -India was the most important source of diamond until 1728, when -discoveries were made in Brazil. Among the important large diamonds -found in India were the Koh-i-noor, the Great Mogul, and, very likely, -the Hope Diamond. Like India, Brazil in turn declined as a major source -of diamond with the discovery and efficient recovery of large quantities -in South Africa. - - [Illustration: The Hope Diamond, because of its long and dramatic - history and its rare deep-blue color, is probably the best known - diamond in the world. By speculation, the Hope is linked to the - famous “French Blue,” which was brought to France from India in 1668 - to become part of the crown jewels of Louis XIV. The French Blue was - stolen in 1792 and never recovered, but in 1830 an extraordinary - 44.5-carat blue diamond—presumably cut from the missing gem—came on - the market. It was purchased by Henry Thomas Hope of England and - became known by its present name. In 1949 the gem was acquired from - the estate of Mrs. Evalyn Walsh McLean by Harry Winston Inc., of New - York. Ten years later, Harry Winston, Inc., presented the gem (shown - here in actual size) to the Smithsonian Institution.] - -Diamonds are extremely rare even in diamond mines. For example, the -famous South African mines contain only one part of diamond in more than -14 million parts of worthless rock. In spite of this, more than three -tons of gem- and industrial-quality diamond were mined in 1963. - -Among the British crown jewels is a cut diamond weighing 530.20 carats -(more than 3¾ ounces), one of several stones that were cut from the -largest gem diamond ever discovered. The rough stone, known as the -Cullinan Diamond, weighed 3106 carats (almost 1¾ pounds) when it was -found at the Premier Mine in South Africa in 1905. - - [Illustration: The Portuguese Diamond, weighing 127 carats, is the - 13th largest cut diamond on record. More unusual, it is from Brazil, - and is thought to have been part of the Portuguese crown jewels. In - addition to its brilliant color flashes, it has a slight milky - fluorescence that causes it to “glow” even in artificial light. - (Actual size.)] - -Diamonds vary from colorless to black and from transparent to opaque. As -they come from the mines, they are graded into two groups, gem and -industrial. Those whose color, imperfection, or shape make them useless -as gems—more than 8 out of every 10 carats mined—are used in industry. -Diamonds of industrial quality also are produced synthetically, and -these are used primarily in the manufacture of grinding wheels. - -The best gem diamonds are flawless and are colorless or slightly blue. -Their value depends on their color, clarity, cut, and carat weight. Most -costly are those called fancies, which have a distinct color such as -blue, pink, green, or deep yellow. - - - PEARL - -Pearl is included among gemstones only because it is a beautiful object -used as jewelry. As has been noted, pearl is not mineral because it is -formed by the action of a living organism. However, the pearl has long -occupied an important position among jewels, and it is unique in -requiring no lapidary art to enhance its beauty. Nature has perfected -pearls. - - [Illustration: The strand of matched pearls was presented to - President Van Buren by the Imam of Muscat. The three baroque - (irregularly shaped) pearls are freshwater pearls from the Wabash - River in Indiana.] - -The ancient Chinese believed that pearls originated in the brain of a -dragon. We now know, of course, that pearl is created by a secretion of -a mollusk. Very few mollusks have the ability to produce the fine -mother-of-pearl used in the jewelry trade, and even among those that -can, very few produce pearls with iridescence, or _orient_, as it is -known in the trade. Only two genera, the pearl oyster (_Margaritifera_) -and the pearl mussel (_Unio_) are important sources of the gem. Edible -oysters rarely produce pearls, and when they do, the pearls are of poor -quality. - -The shells of pearl-producing mollusks are composed of layers of calcium -carbonate in the form of either calcite or aragonite. These layers, -cemented together with an organic substance known as conchiolin, are -known as nacre. The layer closest to the animal is deposited in tiny -overlapping patches, producing an iridescent effect caused by the -interference of light rays reflected from the plates making up the -nacre. The same material coats the surface of a gem pearl. - -Seldom does a mollusk live out its time without attack by creatures -boring through its shell, or without intrusion through the normal shell -opening of tiny parasitic worms, sand, or other irritants. Usually inert -particles are forced against the inside of the shell, where they are -covered with layers of pearl that fasten them to the shell. This is the -source of most _blister pearls_. When the irritant remains in its fleshy -part, the mollusk deposits a protective shell of pearl to cover it -completely, and a spherical pearl may result. Pearls of less-symmetrical -shape, called _baroques_, are more common. - -The value of a pearl depends on its shape, color, orient, and size. -Pearls of highest value are white with a faint tinge of pink or yellow, -possess fine orient, are round, and are free of surface blemishes. The -grading of pearls for color requires considerable experience to detect -delicate differences. Various classification names, such as “rosée” for -delicate pink shades, are used. Fancy colored pearls are those with a -strong yellow, bronze, pink, green, blue, or black color. Grading for -shapes, which differ markedly, is easier. Spherical pearls are usually -drilled for beads; pear-shaped or drop pearls are used in earrings and -pendants; and “boutons” or button-shaped pearls, with one flat side, are -used for ear ornaments, cuff links, and rings. Irregular, baroque pearls -and tiny seed pearls are used in jewelry designs with noble metals and -perhaps other gemstones. - -The world’s finest pearls, called _oriental pearls_, come from the -fisheries of the Persian Gulf. Fine pearls also are found off the coasts -of Burma, Tahiti, New Guinea, Borneo, Venezuela and western South -America, and in the Gulf of California. Fresh-water pearls of high -quality, formed in pearl mussels, are found in various rivers in Europe -and the United States, especially in rivers in the Mississippi Valley. - -A method of growing _cultured pearls_ has been well developed. A -mother-of-pearl bead is inserted in the oyster as an irritant, and the -animal is replaced in the sea in a cage. When oysters so treated are -recovered after a period of three to seven years, the beads in the -harvested crop usually are found to be coated with a layer of nacre up -to almost a sixteenth of an inch thick. - -The cultured pearl can be identified only by the observance—through a -drill-hole or by X-ray—of the mother-of-pearl core, which had been -inserted in the oyster. An instrument called an endoscope, devised for -rapid testing of drilled pearls, relies on a beam of strong light -carried by a hollow needle. The needle is inserted into the drill hole, -and as it passes through the center portion of a natural pearl a flash -of light, reflected through a mirror system in the needle, is observed. - - - CORUNDUM - (RUBY AND SAPPHIRE) - -Both _ruby_ and _sapphire_, which are second only to diamond in -hardness, are of the mineral species corundum, an oxide of aluminum. -They are identical in all characteristics except color. Most corundum is -opaque, and it is mined in large quantities for use as an abrasive. In a -few places, such as Moguk in Upper Burma and in Ceylon, clear corundum -is found that is suitable for use as a gem. - -Red corundum is known as ruby. Its color, caused by traces of chromium, -ranges from rose through carmine to a dark purplish red referred to as -pigeon’s blood red. Rubies of this very desirable latter color often are -called Burma rubies, and they are the most costly of all the corundum -gems. - -All gem corundum having a color other than red is sapphire. The name -sapphire means blue, and this is the color most frequently associated -with this gemstone. The finest sapphires are a velvety cornflower blue, -and they come from Kashmir. Blue, white, yellow, gold, pink, and all the -other colors of corundum are caused by the presence of slight traces of -iron, chromium, titanium, and other metals present as dissolved -impurities in the aluminum oxide. Frequently sapphires are found that -show patches of blue and yellow, or that have alternating zones of red -and blue. Pure corundum is colorless. - - [Illustration: A piece of uncut ruby, from Burma, and five small - rubies of about half a carat each, from Ceylon. All have the classic - “pigeon’s blood” color. (Actual size.)] - -Most gem corundum comes from the Orient, at localities such as Moguk in -Upper Burma, near Bangkok in Thailand, Kashmir in India, and Ceylon. -Because of this primarily Asian origin, the word _oriental_ often is -used with the names of other gems to denote a sapphire of a particular -color. For example, green sapphire sometimes is called oriental emerald, -and the yellow sapphire sometimes is called oriental topaz. - - [Illustration: The sapphires in this group vary in color from deep - blue to gold, and they come from widely separated localities. The - scatter of small multicolored stones came from Montana, and the - magnificent 93-carat golden sapphire, encircled by the gold - bracelet, came from Burma. (Slightly less than half actual size.)] - -There are some notable exceptions to the generally oriental occurrence -of corundum. Some good-quality ruby has been found in North Carolina, -and sapphire of many colors has come from Montana. - -During the formation of a corundum crystal, extremely small needle-like -inclusions of rutile sometimes occur in the hexagonal pattern of the -host crystal. When such inclusions are arranged in this way by nature, -they cause, in properly cut stones, internal reflections that produce -the optical phenomenon known as asterism. The effect is that of a -6-rayed star, and the gems in which asterism occurs are known as star -sapphires and star rubies. Asterism is rarer in ruby. - - [Illustration: The Star of Asia, weighing 330 carats, is one of the - finest star sapphires in the world. It is of a clear, deep blue - color and has a strong, sharply defined, 6-rayed star. (Actual - size.)] - - [Illustration: Cutting a star stone requires careful attention to - the directions in which the cuts are to be made. Failure to align - the stone properly with the axis of the crystal will produce a stone - with an off-center, crooked, or dim star, or may even eliminate the - star completely.] - - CRYSTAL AXIS - POSITION STONE MUST TAKE TO SHOW STAR - OTHER STAR STONES MAY BE CUT, BUT MUST BE IN THE SAME POSITION WITHIN - THE CRYSTAL - ROUGH SAPPHIRE CRYSTAL - CRYSTAL AXIS - -Since corundum is easily manufactured, synthetic ruby and sapphire are -used extensively in jewelry. The synthetic stones can be distinguished -from natural stones by microscopic examination of the kinds of -inclusions and internal defects. - - VARIETIES - Ruby: Red. - Sapphire: Blue, yellow, pink, green, colorless, and any color except - red. - Star sapphire: Colored as sapphire and showing asterism. - Star ruby: Red and showing asterism. - - - BERYL - (INCLUDES EMERALD AND AQUAMARINE) - -Beryl is probably the most widely used colored gemstone, and under its -several names in the gem world it is probably the best known. When it is -a rich green it is known as _emerald_, and when it is the blue-green of -sea water it is called _aquamarine_. Varieties such as the rose-pink -_morganite_, golden-yellow _heliodor_, and colorless _goshenite_ are -less well known than emerald and aquamarine but are equally attractive -and satisfactory gemstones. - -Beryl is beryllium aluminum silicate. It frequently occurs in -well-formed hexagonal crystals, and its many colors result from the -presence of very small percentages of several different elements. -Emerald owes its rich green color to traces of chromium, and the -detection of this element is one of the means of identifying true -emerald. Aquamarine, comprising the green and blue-green beryls, gets -its color mainly from traces of iron. Practically all of the deep blue -aquamarine available in jewelry stores results from the heat treating of -greenish beryl or certain yellow-brown beryls. The stones are heated -carefully to about 800° F., and the color change is permanent. The -element lithium accounts for the color of pink beryl. As with -aquamarine, the color of yellow beryl is now considered to be the result -of traces of iron rather than uranium, as previously thought. Pure beryl -is colorless. - -Beryl usually is found in pegmatites, which are very coarse-grained -granite rocks formed by the cooling of molten material far beneath the -earth’s surface. As the rock cools and beryl and other crystals are -formed, the stresses introduced are so great that the crystals -frequently shatter so badly they are useless as gem material. -Frequently, too, impurities are introduced during crystal formation, and -consequently the gem materials are found only where the crystals were -able to form without interference—such as in openings or cavities in the -rock. - -Tremendous beryl crystals weighing as much as several tons, but not of -gem quality, have been discovered in a few localities. Large crystals of -gem quality also occur in nature, and large cut stones of aquamarine and -other colors of beryl are relatively common. Among the fine examples of -beryl in the National Gem Collection is a remarkably large (2054-carat), -flawless cut stone of rich yellow-green. This gem and others in the -collection weighing 1363 carats, 1000 carats, 914 carats, and 578 carats -accentuate the occurrence of large gem crystals of beryl in Brazil. - - [Illustration: Four large cut stones, all from Brazil, illustrate - the color range of beryl. Top, a 578-carat green beryl; left, a - 235-carat morganite, gift of Mr. and Mrs. Frank Ix, Jr.; bottom, a - 133-carat gold beryl; and, right, a 187-carat aquamarine. (Half - actual size.)] - -The finest emeralds are not found in pegmatites. At Muzo in Colombia, -the most prolific source of the finest emeralds, they occur in veins -with calcite, quartz, dolomite, and pyrite. The veins cut through -dark-colored, carbonaceous limestone and shale. Mining at Muzo began 350 -years ago and still continues sporadically to meet market requirements. -Russian emeralds occur as good-sized crystals in mica schist, a -metamorphic rock. They occur there with chrysoberyl, phenakite, and -common beryl. Some of the smaller stones have good color and have been -cut into valuable gems. Brazil, which produces many extraordinary -aquamarines and other beryls, has not produced quality emeralds. -Periodically, over the centuries, there have been reports of new -discoveries of emerald, but so far none of these has begun to rival the -Muzo source in either quantity or quality of the gems produced. - - [Illustration: This tremendous golden beryl from Brazil, weighing - 2054 carats, is the largest cut beryl known of this color. Cut - stones of this size that contain no visible flaws or inclusions are - most unusual. (Three-fifths actual size.)] - -Although Brazil supplies the finest aquamarine and Colombia the finest -emerald, several localities in the United States are sources of -good-quality beryl of these colors. Foremost among these localities are -Maine, California, and Connecticut for aquamarine and North Carolina for -emerald. Morganite of pale pink to deep peach color, from California, is -also notable. Various New England mines in Maine, New Hampshire, and -Connecticut and the gem mines of the Pala and Mesa Grande districts of -California have produced other colors of gem beryl. However, most of the -beryl mined in the United States is used as an ore for beryllium, as -little of it is of gem quality. - -Because of its hardness (about 8), vitreous luster, beautiful color, and -rarity, emerald always has been highly prized as a gem. Fine-quality -emeralds may be more costly than fine diamonds. Other kinds of beryl -have the same physical properties as emerald, but since they are less -rare their relative value is lower. - -Synthetic emerald of high gem quality has been marketed successfully. A -synthetic substitute for aquamarine is also available; it is really a -synthetic blue spinel. - - VARIETIES - Emerald: Grass green - Aquamarine: Blue green - Morganite: Pink - Heliodor: Yellow - Goshenite: Colorless - - - TOPAZ - - [Illustration: Three different cutting styles and colors of topaz. - From top, a 235-carat colorless stone from Colorado, a 171-carat - dark champagne-colored stone from Madagascar, and a 129-carat - sherry-colored stone from Brazil. (Slightly less than actual size.)] - -Because yellow is the most popular color of topaz it has become -customary to believe that all topaz is yellow. Also, there is a tendency -to believe that all yellow gemstones are topaz. Neither belief is -correct. Stones of yellow, sherry, blue, pink, and colorless topaz all -make beautiful gems, and their characteristics are identical except for -color. On the other hand, citrine (a yellow quartz), although entirely -unrelated to topaz, often is disguised in the trade under the names -Brazilian topaz, topaz quartz, or just topaz. Great numbers of stones -described and sold as yellow topaz really are the much commoner citrine, -which has few of the characteristics of fine topaz. - - [Illustration: A cushion-cut topaz from Brazil that weighs 1469 - carats. It is an odd shade of yellow-green.] - - [Illustration: A 3273-carat topaz of soft blue that came from - Brazil. The Smithsonian Institution had this unique gem cut by Capt. - John Sinkankas of California. For several years it was the largest - topaz in the collection. (Both gems are shown in actual size.)] - -Topaz, an aluminum fluosilicate, has a hardness of 8, a vitreous luster, -and a relatively high refractive index. It is found in near-perfect -crystals that range in size from very small to very large, with some -giants weighing as much as several hundred pounds. Most of these -crystals, especially the largest ones, are colorless, a characteristic -that indicates relatively high purity of composition. Although topaz -gems have little fire, they take a high polish and can be very -brilliant. Great care must be taken in cutting and polishing topaz -because of its ready cleavage. The desired cut and high polish can be -secured by avoiding excessive heat or pressure during the operation and -by planning facets so that none lies exactly parallel to the cleavage -direction. - -Although crystals of gem-quality topaz are found in many localities, -perhaps the splendid blue ones from Russia and the yellow, wine, blue, -and colorless ones from Brazil are best known. Some fine topaz has been -found in the United States in such widely separated areas as New -Hampshire, Texas, Colorado, and California. The light, golden brown -topaz from Colorado has an unfortunate tendency to fade in strong -sunlight. It remains to be seen whether similar topaz coming recently -from comparable occurrences in Mexico also will fade. By a system of -heating and cooling, certain of the red-brown topaz crystals from Ouro -Preto, Brazil, can be converted to colors ranging from salmon pink to -purple red. Quick heating to high temperatures can completely remove -color, and sudden or uneven cooling may cloud or crack the stone. - - - OPAL - -Opal has been admired for its great beauty since ancient times, but this -gemstone lacked commercial appeal until the discovery of the Australian -black opal late in the 19th century. - -Opal is somewhat brittle, is sensitive to heat, and, in some cases, -tends to deteriorate despite the best of care. Therefore, this stone -lacks many of the physical characteristics required for an ideal gem. -These deficiencies would eliminate other species from the list of -gemstones, but the great beauty of its flashing and shifting color -patterns has made opal increasingly popular. Even its name, coming from -the ancient Sanskrit “upala,” means precious stone. - -With a hardness between 5½ and 6½, opal is the softest of the more -popular gems. It is sufficiently hard, however, to be used in jewelry, -where its setting usually helps to protect it from shock and abrasion. - - [Illustration: Black opal, so called because the color flashes - appear against a dark background, is found in Australia. It is quite - rare, and large pieces such as the ones shown here have become - extremely valuable. (Almost actual size.)] - -Opal is unlike most gemstones in that its flashing color is not due to -the color of the stone itself, or even to the color of its included -impurities. Rather, it is due to the way in which tiny opal particles -are grouped during its formation. Detailed photographs taken through an -electron microscope show clearly how precious opal is deposited as -spheres that are so small they are indistinguishable under powerful -optical microscopes. These spheres are packed together in very orderly -networks, row upon row and layer upon layer, with tiny open spaces, also -in rows, between them. Masses of common opal lack this orderly internal -arrangement of spheres. White light striking the precious opal is -reflected independently by each row of spheres, much like the -reflections from a series of slats in a venetian blind. Since these rows -of spheres are spaced at distances approximately the same as the -wavelength of light, a phenomenon known as _diffraction_ occurs. The -separate reflections interfere with each other in an organized manner, -cancelling out some of the light wavelengths and reinforcing others, -producing color. The brilliant color flashes are of different hues -depending on the sizes of the spheres of opal and, therefore, the -distances between rows. To provide the best display of this optical -effect, opal is almost always cut in cabochon form rather than as -faceted stones. - - [Illustration: Fire opals have rich fire; some have background - colors that vary from bright yellow through orange and red; and some - are colorless. Stones such as the ones shown here, which weigh 7, - 11, and 22 carats, have made Querétaro, Mexico, famous as their - source. (Actual size.)] - - [Illustration: This rare 34-carat opal from Brazil resembles closely - the opals found in Australia. (Actual size.)] - -Common opal, which shows milky opalescence, does not exhibit color -flashes, and it is not used as a gemstone. Each of the common -varieties—such as hyalite, cacholong, and hydrophane—has its own -slightly different set of characteristics, but only precious opal, with -its dazzling color display, is important for gem purposes. To take full -advantage of the small amounts of gem material available, or to bring -out its color better, _precious_ opal is often cut as thin pieces and -mounted as doublets on some other backing. Also, the seams in rock -sometimes are cut so that the thin layer is exposed on a thicker backing -of the adjoining rock. Precious opal, or gem opal, is classified as -_white opal_ when the color flashes are in a whitish or light -background, _black opal_ when the background material is gray, -blue-gray, or black, and _fire opal_ when the background is more -translucent and red, reddish orange, or reddish yellow. - -Precious opal has been found in several areas of the world—in nodules, -in seams in rock, or as replacements of other minerals or even of wood -and shell. Hungarian deposits were well known in Roman times, but these -and other deposits became insignificant with the discovery of opal in -Australia in the late 19th century. Opal deposits were discovered in -1889 at White Cliffs in New South Wales, and other important discoveries -in Australia followed, including deposits at Lightning Ridge in New -South Wales that produce very dark stones and the rich fields of white -opal at Coober Pedy in South Australia. Mexico has remained for a long -time the principal source of richly colored fire opals, with the most -important deposits located in the state of Querétaro, where mines have -been worked intermittently since 1835. This has made the town of -Querétaro today the center for the trade and cutting of Mexican opal. - - VARIETIES - White opal: Color flashes in light-colored background material - Black opal: Color flashes in dark gray or bluish background material - Fire opal: Orange or reddish background material - - - SPINEL - -Two of the more famous stones in the British crown jewels are the Black -Prince’s Ruby and the Timur Ruby, but neither of these stones is really -ruby. Like the great red gem in the crown that belonged to the Russian -Empress Catherine II, these two British stones are spinel. Although -spinel occurs in many colors, such as yellow, green, violet, brown, and -black, it is the red spinel that usually is seen in the gem trade. There -are several varieties of red spinel, such as _ruby spinel_, _balas -ruby_, _rubicelle_, and _almandine spinel_—all of which refer to the -color resemblance to ruby. - - [Illustration: The hues and tints of spinel show subtle variations - that are matched only by those of tourmaline. Unlike tourmaline, - however, spinel may be bright ruby red. The cut stones curving - around two pieces of rough from Burma weigh (left to right) 30 - carats (Ceylon), 34 carats (Burma), 36 carats (Burma), 30 carats - (Ceylon), and 22 carats (Ceylon). (Three-fourths actual size.)] - -Spinel is an oxide of magnesium and aluminum, and it is not related to -ruby. However, because its hardness (8) is only slightly less than that -of ruby and its brilliance is about equal to that of ruby, spinel makes -an excellent substitute for that gem. Also, because it is more -plentiful, spinel costs much less. It is interesting that red spinel, -like ruby, gets its color from the presence of traces of chromium. - -Synthetic blue spinel is widely used as a substitute for aquamarine, and -synthetic spinels of other colors are used as substitutes for many gems. -However, the synthetic stones are not ordinarily made in the subtle -shades so characteristic of natural spinel. Completely colorless spinel -apparently exists only as a synthetic material. Actually, because of its -hardness, durability, and many attractive colors, spinel makes a fine -gemstone in its own right. - -Like ruby and several other gemstones, spinel is found chiefly in the -gem gravels of Ceylon, Burma, and Thailand. Appreciable amounts of -spinel occur in the Ceylon gem gravels as worn, rounded pebbles of many -colors. In the Burmese gravel deposits the spinel is often found as -well-formed octahedral crystals. Near Moguk, in Burma, spinel has been -found in its original position in the limestone rocks as well as in the -eroded stream deposits. - - VARIETIES - Almandine spinel: Purplish red - Rubicelle: Orange-red - Balas ruby: Rose red - Ruby spinel: Deep red - Chlorospinel: Translucent grass green - Ceylonite or pleonaste: Opaque dark green, brown, or black - Picotite or chrome spinel: Translucent dark yellow-brown or - green-brown - - - QUARTZ - (INCLUDES ROCK CRYSTAL, AMETHYST, AND CITRINE) - -Few gemstones can compete with quartz for variety of color. Having a -hardness of 7 and occurring in many beautiful varieties, only the -relative abundance of quartz prevents the species from attaining top -rank among gemstones. - -The two kinds of quartz, crystalline and cryptocrystalline -(fine-grained) quartz, occur in all kinds of mineral deposits throughout -the world. Much of this material is suitable for cutting gems. - -Colorless crystalline quartz, or _rock crystal_, makes attractive -faceted gems, and it is used as a suitable substitute for diamond and -zircon even though it lacks the fire and brilliance of those gemstones. -Some very large, flawless crystals of colorless crystalline quartz have -been found. The great Warner Crystal Ball, with a diameter of 12⅞ inches -and weighing 106¾ pounds, was cut from such a crystal. In addition to -the name rock crystal, colorless crystalline quartz appears in the -jewelry trade under such names as rhinestone (not to be confused with -the glass substitute), Herkimer diamond (from Herkimer County, N. Y.), -and Cape May diamond (from Cape May, N. J.). - -The most popular variety of quartz is _amethyst_, a transparent form -whose color ranges from pale violet to deep purple. In many cut stones -of amethyst the color intensity changes sharply from section to section. -This is due to irregular color zoning common to amethyst crystals. The -actual cause of the purple color in amethyst is not very well -understood. There are fewer cut stones of amethyst in very large sizes -because of the rarity of large, flawless, well-colored crystals. - - [Illustration: This 4500-carat pale smoky quartz egg from California - rests on a gold stand set with Montana sapphires. The unique gem was - cut and its stand was designed and made by Capt. John Sinkankas as a - difficult exercise in the lapidary art. The quartz egg is 4 inches - long and almost 3 inches in diameter.] - -The name _citrine_ (from the French word for lemon) attempts to describe -the yellow color of another variety of quartz. Actually, the normal -coloring of citrine varies from yellow to red-orange and red-brown, but -the yellow sometimes rivals the yellow of topaz. In addition to the -normal color range, the colors of citrine may grade through a grayish -yellow variety known as _cairngorm_ and a grayish variety called _smoky -quartz_ to a black variety called _morion_. Other varieties that add -color dimensions to the group of quartz gemstones are _rose quartz_ and -_milky quartz_. Like amethyst, the reason for the color in rose quartz -has not been definitely established. Milky quartz owes its color to -myriads of tiny cavities containing water or liquid carbon dioxide. - - [Illustration: A 783-carat step-cut citrine of deep, rich color - dwarfs a 278-carat brilliant-cut citrine (at left), a 90-carat smoky - quartz, and a 91-carat briolette of citrine. The smoky quartz, from - Switzerland, is so dark that it appears to be opaque. The other - three stones came from Brazil. The briolette and brilliant-cut - citrines were cut and donated to the Smithsonian Institution by - Albert R. Cutter. (Slightly less than half actual size.)] - -The range of color in quartz is somewhat surprising, considering that -the mineral is a simple silicon dioxide. Some of the colors, as with -corundum and some other gemstones, are due to traces of impurities. In -quartz, these consist mainly of oxides of iron, manganese, and titanium. -However, all the reasons for quartz coloration in its many varieties are -not known. - - [Illustration: Pastel rose quartz has a delicate beauty in any cut. - The 375-carat step cut (top), the 84-carat step cut, and the - 46-carat marquise came from Brazil. (Two-thirds actual size.)] - - [Illustration: Amethyst, a purplish quartz, is the birthstone for - February. Here it is represented by a 1362-carat stone from Brazil - (top), a 54-carat stone from Pennsylvania (left), and a 21-carat - stone from North Carolina. (Almost actual size.)] - -In addition to possessing wide variation of color, quartz, like sapphire -and certain other gemstones, can exhibit asterism or chatoyancy. The -well-known _tiger’s-eye_ from West Griqualand, South Africa, owes its -eye effect to the fact that its material is a replacement of fibrous -asbestos by cryptocrystalline quartz. The color of tiger’s-eye arises -from the partial alteration of the asbestos to yellow-brown iron oxides -before it is replaced by quartz. Inclusions of rutile, tourmaline, or -actinolite needles may produce attractive patterns in quartz, but they -do not always cause chatoyancy. The material containing such inclusions -is called sagenitic quartz, or it may be descriptively named, such as -rutilated quartz, tourmalinated quartz, and so forth. Sagenitic quartz -is usually cut as cabochons rather than as faceted stones since the -inclusions are of greater interest than the quartz itself. - -If the foreign inclusions consist of tiny flakes of hematite or mica, -the quartz assumes a spangled appearance and is called _aventurine_. - -Crystals of quartz varieties that are opaque or that contain visible -inclusions normally are cut as cabochons to take advantage of the body -color or to make the inclusions more visible. Crystals of the -transparent varieties are fashioned in any of several cutting styles, -depending on whether it is desired to take maximum advantage of color or -of brilliance. Because of its availability in fairly large, flawless -pieces in various colors, quartz has been used extensively in carving. -The Chinese have excelled in carving large, ornate objects of rock -crystal. - -Although quartz occurs in many varieties and its crystals are cut in -many styles, it is easily identified by its refractive index of 1.55, -specific gravity of 2.65, and hardness of 7. - - CRYSTALLINE VARIETIES - Amethyst: Purple to violet - Cairngorm: Smoky yellow - Citrine: Yellow to red-orange and red-brown - Milky quartz: White - Morion: Black - Rock crystal: Colorless - Rose quartz: Rose to pink - Smoky quartz: Gray to black - - CRYPTOCRYSTALLINE VARIETIES (CHALCEDONY) - Agate: Pronounced color banding - Aventurine: Inclusions of sparkling flakes - Bloodstone: Dark green dotted with red - Carnelian: Red to yellow-red - Cat’s-eye: Chatoyant - Chrysoprase: Green - Jasper: Opaque brown to red-brown, green, yellow, etc. - Onyx: Color banding in straight layers of contrasting color - Sard: Light to dark brown - Sardonyx: Sard or carnelian bands alternating with white bands - Tiger’s-eye: Bright brownish yellow, sometimes blue: chatoyant - - - CHRYSOBERYL - (INCLUDES ALEXANDRITE AND CAT’S-EYE) - -With color ranging from shades of yellow and brown through blue-green to -olive, and with a hardness of 8½, chrysoberyl has most of the -characteristics necessary for a fine gem. Rare stones of high-quality -chrysoberyl demand fairly high prices, and they are sought eagerly by -the connoisseur of gemstones. - -Chrysoberyl is beryllium aluminate, and thus is closely related to the -gemstone spinel, which is magnesium aluminate. When pure, chrysoberyl is -colorless and relatively uninteresting as a gemstone because of its lack -of color dispersion and its moderate refractive index of 1.75. However, -few pure samples are known, as chrysoberyl normally contains some iron -or chromium in place of aluminum and some iron in place of beryllium. As -a result of such impurities, the color of chrysoberyl my be yellowish, -greenish, or brownish. - -Chrysoberyl and beryl are the only important gemstones containing the -element beryllium. The minerals beryllonite, euclase, hambergite, and -phenakite also contain this element, but they are rare and seldom are -seen as cut gems. - - [Illustration: One of the finest chrysoberyl cat’s-eyes in existence - is the 58-carat Maharani from Ceylon. (Actual size.)] - -The _alexandrite_ variety of chrysoberyl has two colors in delicate -balance, and it changes from a columbine red to an emerald green when -viewed under different light. When viewed in daylight, which is richer -in green, the color balance shifts toward green, and that hue is seen by -the observer. Under artificial light, normally richer in red, the color -balance shifts toward red, and the stone seems to have changed to that -color. This extremely rare stone, named after Czar Alexander II of -Russia, is found only occasionally, in Russia and Ceylon. The Russian -stones, found with emerald in mica schist, tend to be smaller than the -Ceylon stones and have a color change going from emerald green to -violet-red. The Ceylon stones, found as pebbles in gem gravels, have a -color change going from a less-emerald green to a browner red. The -66-carat, record-size alexandrite in the National Collection shows the -color change typical of Ceylon stones. A synthetic stone is commonly -marketed as synthetic alexandrite, but this substitute not only is -man-made but is actually synthetic corundum instead of synthetic -chrysoberyl. - - [Illustration: In addition to its fine cat’s-eyes and its - color-changing alexandrite varieties, chrysoberyl occurs in handsome - stones that vary in depth of color. Shown here with an uncut twinned - crystal of gem quality from Brazil are a 46-carat stone from Brazil - (left) and a 121-carat stone from Ceylon. The uncut crystal is a - gift of Bernard T. Rocca, Sr. (Two-thirds actual size.)] - -_Cat’s-eye_ chrysoberyl contains myriads of tiny fiberlike channels -arranged in parallel position. When the stone is cut as a cabochon, a -band of light is reflected from the curved top of the stone, producing -an effect that resembles the slit pupil of a cat’s eye. - - VARIETIES - Alexandrite: Green in daylight, changing to red in artificial light - Cat’s-eye: Chatoyant - - - TOURMALINE - -Because of its great color range, which includes pink, green, blue, -yellow, brown, and black in many different shades and combinations of -shades, tourmaline is one of the most popular of the colored gemstones. -Tourmaline with a color near emerald green is particularly popular. - -Chemically, tourmaline is a very complex borosilicate, and its color is -determined by the various elements present in it. Tourmaline crystals -having sodium, lithium, or potassium are either colorless, red, or -green; those having iron are blue, blue-green, or black; and those -having magnesium are colorless, yellow-brown, or blackish brown. - -Some crystals of tourmaline are of two colors, and stones of mixed -colors, such as pink and green, can be cut from these. The color mixing -may show as zoning with the core color of the crystal overlaid by -another color and perhaps even additional layers of other colors. Zoned -crystals with a core of deep pink covered by a layer of green have been -called “watermelon tourmaline.” Because its refractive index of about -1.6 is too low to give it marked brilliance, and its color dispersion is -too low to give it fire, the tourmaline relies almost solely on the -beauty of its color for its rank in popularity. - -Although tourmaline has a low refractive index and low dispersion, it -exhibits remarkable dichroism. In other words, it can present different -tints to the viewer depending on the direction that the light is -traveling through the crystal. When viewed down the long, or vertical, -axis of the crystal, the color of tourmaline is much stronger than when -viewed from the side. This means that if the crystal is dark the cutter -will have to cut the stone with the flat part, or table, parallel to the -long axis of the crystal. The color of the gemstone then will be -lightened when viewed from its table, since this is the direction of -lighter color. Similarly, the table of a lighter colored crystal can be -cut perpendicular to the long axis in order to produce a deeper colored -gem. - - [Illustration: Green seems to be the best known commercial color of - tourmaline, but this extremely variable gem species exhibits many - subtle shades of color, as shown here. At upper left, a 104-carat - stone from Mozambique; at upper right, a 173-carat stone from - Mozambique; at lower left, a 111-carat stone from Manchuria; and a - 35-carat stone from Brazil. (Actual size.)] - -Some tourmaline crystals contain threadlike tubes or inclusions of -microscopic size running parallel to its length. When cut as cabochons, -such crystals give a good “cat’s-eye” effect. - -Tourmaline has no distinct cleavage and has a hardness somewhat above 7, -and these characteristics make the stone sufficiently resistant to -normal shock and wear so that it is highly satisfactory for use in -jewelry. - -Noted deposits of tourmaline are located in the Ural Mountains of -Russia, Ceylon, Burma, South-West Africa, Madagascar, Brazil, Maine, and -California. Crystals from each of these localities seem to have their -own color specialties. The deposits in San Diego County, Calif., are -unique in that all colors except brown are found there. In the early -1900’s pink and red tourmaline was shipped from there to China for -carving, but this thriving trade stopped with the end of Chinese -imperial reign. The tourmaline deposits at Paris, Auburn, and Hebron, -Maine, have furnished a number of excellent gems, especially of blue and -green colors. - - VARIETIES - Achroite: Colorless - Indicolite: Blue - Dravite: Brown - Schorl: Black - Rubellite: Pink - - - ZIRCON - -Zircon, because of its high refractive index and high dispersion, -approaches diamond in degree of brilliance and fire. On only casual -examination it is quite possible to mistake a well-cut, colorless zircon -for a diamond. However, a careful examination of the back facets of such -a stone, when viewed through the table, would show strong double -refraction, a characteristic of zircon but not of diamond. Zircon’s -double refraction makes the back facet edges appear doubled. Since -diamond is “singly refracting,” it cannot produce this double appearance -of the back facets. - -Zircon is brittle and has a hardness of just over 7, while diamond’s -hardness, as we have seen, is rated at 10. After being worn in jewelry -for a long period of time, zircon will show signs of chipping on the -facet edges. Under the same conditions, diamond would remain unchanged. -Because of this tendency for facet edges to chip, it is the practice in -the gem trade to pack cut zircons separately. If a number of zircons -were placed in the same paper packet there would be a risk of “paper -wear.” - -In the gem trade, the most important zircons are those that are -colorless, golden brown, or sky blue. Such stones originally were -reddish brown zircon pebbles from Indochina, but they have been -converted by being subjected to temperatures approaching 1800° F. for -periods of up to two hours. When the original zircons are heated in a -closed container, the stones become blue or colorless; when a flow of -air is allowed through the container, the stones become golden yellow, -red, or colorless. In most of these converted stones the color remains -quite stable, but in some it may revert to an unattractive greenish or -brownish blue after a period of time. - - [Illustration: The beautiful colors of these brilliant zircons are - the result of heat treatment given to natural, reddish brown stream - pebbles. The three stones at the left (from top) weigh 118, 103, and - 98 carats, and the ones on the right weigh 106 and 29 carats. The - 106-carat stone came from Thailand, the others from Indochina. - (Four-fifths actual size.)] - -In addition to being reddish brown, natural zircon may vary from almost -colorless to yellow, red, orange, and brown or from yellow-green to dark -green and, occasionally, blue. - -The most important producing areas of gem zircon are in a region of -Indochina that comprises parts of Thailand, Viet Nam, and Laos. -Additional gem zircon, like so many of the other gem species, is -recovered from near Moguk in Upper Burma and from the gem gravels of -Ceylon. - -There is no synthetic zircon on the market, but a bright blue synthetic -spinel is sometimes used to simulate zircon successfully. - - - PERIDOT - -The relative rarity of peridot and the ease with which it can be -simulated in glass, whose luster it approximates, probably account for -the low popular demand for this gemstone. Although peridot has little -brilliance and no fire, its unusual color and glassy luster produce a -unique effect that serves to make it attractive. - -The color of peridot is an unusual bottle green that shades, in some -stones, toward yellow-green and, more rarely, toward brown. In 1952 it -was discovered that almost all of the brown gems believed to have been -peridot in various gem collections were actually of an entirely -unrelated species, which since has been named sinhalite. Brown peridot -still remains rare and is somewhat of a collector’s item. - - [Illustration: To exhibit its unique color to best advantage, - peridot usually is cut so as to have a relatively large table, as - shown in these examples. The largest gem, weighing 310 carats, is - from the Egyptian island of Zebirget in the Red Sea and is the - largest cut peridot known. The other two, weighing 287 carats and - 109 carats, are from Burma. (Three-fifths actual size.)] - -The green of peridot, which is quite different from the green of other -gemstones, is due to some iron included in its composition. It is -suspected that a trace of nickel contributes to the liveliness of the -color. - - [Illustration: This photo shows the color of peridot projected onto - the background. The larger gem is the 310-carat stone shown in the - prior illustration. The stone on the right weighs 109 carats and is - from Burma; the other peridot weighs 46 carats and is from Egypt. - (Almost actual size.)] - -Peridot has a hardness of only 6½ and a rather strong tendency to -cleave, and these characteristics reduce its value for use in jewelry -exposed to rough wear. It is better used in pins, earrings, and pendants -than in rings. - -Peridot is a gem name for the common mineral olivine, a magnesium -silicate. Olivine is fund in numerous places, and small gemmy pieces are -found in many localities. Many of the largest and best gems of peridot -have come from mines on the Egyptian island of Zebirget (Island of St. -John) in the Red Sea, but most gem peridot now comes from Burma. Great -numbers of small stones have been cut from olivine found in Arizona -gravels. - -Centuries ago, peridot was known by the name topaz, since the stones -came from Topazos, the island now known as Zebirget. The name topaz, as -we have seen, is used today for an entirely different mineral species. - - - SPODUMENE - -Spodumene, a lithium aluminum silicate, is one of the very few gemstones -containing lithium. It has had more importance as a gemstone in the -United States than elsewhere, a situation due to early discoveries of -unique occurrences of a lavender-pink variety at Branchville, Conn., in -1879 and in San Diego County, Calif, about 20 years later. At the time -of the discovery of the California material, the variety was named -_kunzite_ in honor of G. F. Kunz, a noted American gemologist of the -times. - - [Illustration: The 177-carat kunzite (at lower left) is a large - flawless stone cut from California material of this variety of - spodumene. It was given to the Smithsonian Institution by the - American Gem Society. The other stones, all from Brazil, represent - the more usual shades of spodumene. They weigh 327 carats (top - left), 256 carats (top right), and 69 carats. (About half actual - size.)] - -The finding of a bright green variety, _hiddenite_, in North Carolina -about 1880 greatly stimulated the interest of American gem collectors. -Some of the bright green spodumene coming from Brazil in recent years -compares very favorably in color with North Carolina hiddenite. Other -than in a scattered few of these unusual occurrences of kunzite and -hiddenite, spodumene usually is found in yellow and yellow-green shades, -with Brazil and Madagascar being the chief sources. - - [Illustration: This 880-carat kunzite from Brazil is one of the - largest stones of its kind. (About actual size.)] - -Spodumene has a hardness of about 7, but with a refractive index of -about 1.66 and a low dispersion there seems to be relatively little to -recommend it as a gemstone. The fact that it exhibits a very strong -tendency to cleave in two different directions would seem to rule it out -completely as being too difficult to cut. Nevertheless, the production -and purchase of cut stones of spodumene persist because of the beauty of -the gem. - -The kunzite and hiddenite varieties of spodumene show strong -_pleochroism_, or the ability to show three different colors when viewed -in the direction of different axes. Some of the large Brazilian kunzite -crystals mined in the early 1960’s have an intense rose-violet color -when viewed along the long axis of the crystal but have pale blue-violet -and pale tan colors when viewed from the other two directions. When heat -treated, or exposed to strong light, this Brazilian kunzite loses its -tan and bluish colors but retains the intense rose-violet. Because of -spodumene’s pleochroism, the direction of cutting in the stones becomes -extremely important, as it must be done in a manner that will take -advantage of the violet color in kunzite and the green color in -hiddenite. - - VARIETIES - Kunzite: Lavender violet to rose violet - Hiddenite: Deep green - - - GARNET - -The name garnet is applied to a group of six closely related silicate -minerals that are alike in crystal structure but that differ mainly in -the substitution of certain metallic elements in their composition. -These minerals are: - - _Pyrope_, magnesium aluminum garnet - _Almandine_, iron aluminum garnet - _Spessartine_, manganese aluminum garnet - _Uvarovite_, calcium chromium garnet - _Grossular_, calcium aluminum garnet - _Andradite_, calcium iron garnet - -Most natural garnets have compositions intermediate between members of -the basic group of six. For example, there are garnets having -compositions anywhere between pyrope and almandine, depending on the -amount of difference in the magnesium or iron content. These same -garnets may even have varying amounts of manganese, and thus be -partially spessartine. - -The six garnets in the basic group are found in considerable quantity in -many areas, but seldom are they of sufficiently high quality to be -considered gemstone material. Even when stones of gem quality are found, -their colors—particularly the reds—tend to be so intense that they seem -to be opaque. - - [Illustration: Garnets occur in several colors, although most people - think of them as red. Shown here are a 54-carat spessartine from - Brazil (top right), a 6-carat rhodolite from North Carolina (at - left), a magnificent 10-carat green demantoid from Russia, a 9-carat - grossular from Ceylon (bottom), and a 26-carat spessartine from - Virginia. (Seven-eighths actual size.)] - -Garnet has a hardness (about 7) suitable for gemstone material and a -fairly high refractive index (1.74 and above). - -Ruby red pyrope is the most popular variety of garnet. It is found in -Bohemia, in Czechoslovakia, where it occurs as small, poorly shaped -crystals. Red pyrope also is found in Africa, where it is called Cape -ruby, and in Arizona, where it is sold as Arizona ruby. Another kind of -pyrope called _rhodolite_ is noted for its soft, rosy purple color. -Actually, rhodolite is one of the intermixed garnets with a composition -somewhere between pyrope and almandine. Most of the fine rhodolite gems -have come from North Carolina. - -Almandine is popular in its deep red, transparent form, but since the -red is so dark and intense that it appears black, the stones usually are -cut as cabochons with the back hollowed out. This makes them thinner, -and thus lightens their color. Garnets cut in this manner are all known -as carbuncles. Brazil, India, Ceylon, Australia, and parts of the United -States are important sources of almandine. - -Although spessartine has a rich orange color, it is not often used as a -gemstone because of the relative rarity of gem-quality cutting material. -This mineral gets its name from the town of Spessart, Germany, where it -was first found. Excellent spessartine with colors ranging from orange -to brown has been found at Amelia Court House, Va., and quality gems -have been cut from such material. Ceylon, Burma, Madagascar, and Brazil -also have furnished some gem spessartine. - -The chromium garnet, uvarovite, generally is too poor in quality for -cutting. Uvarovite crystals, which are emerald green in color, occur in -only small sizes. They are found mostly in Russia, Finland, and -California. - -Grossular varies in color. It occurs chiefly in some shade of red, -green, yellow, or brown, depending on the impurities present. When pure, -grossular is colorless. A kind of grossular called _hessonite_ has an -attractive cinnamon color, and it is found mainly in Ceylon. Because of -its color it can easily be confused with spessartine, which it closely -resembles. - -Andradite, a very common garnet, usually is found in shades of red, -black, brown, yellow, or green. Some types of gem andradite have special -names for different colors: _topazolite_, yellow; _demantoid_, green; -and _melanite_, sparkling black. The very valuable demantoid is found in -Russia and Italy. - - VARIETIES: - Grossular: Colorless, green, amber, brownish yellow, rose - Hessonite: Cinnamon colored - Pyrope: Deep red - Rhodolite: Rose red and purple - Almandine: Deep red - Spessartine: Brownish red to orange - Andradite: Yellow, greenish yellow, emerald green, brownish red, - brownish yellow, brown, black - Topazolite: Yellow to greenish - Demantoid: Grass green to emerald green - Melanite: Black - Uvarovite: Green - - - JADE - -The name jade is applied to two unrelated minerals—_nephrite_ and -_jadeite_—that have somewhat similar characteristics. - -Jadeite, the rarer of the two, is a sodium aluminum silicate that -belongs to a group of rock-forming minerals known as pyroxenes. Its -color varies from white to emerald green and many other colors. Jadeite -is highly prized, and when it occurs as emerald green it is considered -one of the most valuable gemstones. This kind of jade is found in many -places, but the most important occurrence is in Upper Burma. Nephrite, a -more common species, is a calcium magnesium iron silicate belonging to a -group of rock-forming minerals known as amphiboles. The color varies -from white to a dark spinach green and black. Among the places where -nephrite occurs are New Zealand, Turkestan, Siberia, Alaska, China, -Silesia, and certain parts of the western United States, notably in -Wyoming and California. - - [Illustration: This emerald green jadeite carving, dating from the - Ch’ien-lung period (1736-1795), stands 6½ inches without the base. - It was given to the Smithsonian as part of the Maude Monell Vetlesen - collection.] - -Jade is not particularly hard (6½), but it is very tough, and this -characteristic makes it an excellent material for carving. Even when -subjected to punishing usage, jade resists chipping and wear. It was -used for making tools and weapons by primitive peoples who lived in what -is now Mexico, Switzerland, France, Greece, Egypt, Asia Minor, and in -other places. The jade implements fashioned by these peoples have -survived well the ravages of time. - -The Chinese and Japanese prize jade highly. In their countries, -tradition has assigned to jade medicinal and spiritual values, and has -associated with it the cardinal virtues of charity, modesty, courage, -justice, and wisdom. As a consequence, these peoples long ago developed -the carving of jade as a high art. Among the magnificent Chinese jade -carvings in the National Gem Collection are 130 pieces produced mostly -during the Ching Dynasty (1644-1912), when the art of jade carving was -at its peak. Many of these jades were carved in imitation of the revered -bronze ceremonial vessels of ancient times. This collection was -presented to the Smithsonian Institution in 1959 by Mr. Edmund C. Monell -in behalf of the estate of his mother, Mrs. Maude Monell Vetlesen of New -York. - - [Illustration: This pale green jade vase of the Ch’ien-lung period - is 14½ inches high without the base. It is one of a matched pair - presented as part of the Maude Monell Vetlesen collection of carved - jade.] - - - CHARACTERISTICS OF SOME COMMON GEMS - - Approximate average of - (1) hardness - (2) specific gravity (4) Dispersion - (3) refractive index (5) Durability - Species (1) (2) (3) (4) (5) Usual color range - - Beryl 7¾ 2.70 1.58 Low High Green (emerald), blue-green - (aquamarine), pink (morganite), - colorless (goshenite) - Chrysoberyl 8½ 3.71 1.75 Low High Yellow, green, brown - Corundum 9 4.00 1.77 Low High Red (ruby), various (sapphire) - Diamond 10 3.52 2.42 High High Colorless - Garnet group 7½ 3.70- 1.74- Medium High Yellow, red, green, brown - 4.16 1.89 to high - Jade 6½ 2.96 1.62 None High Green, white - (nephrite) - Jade 7 3.33 1.66 None High Green, white - (jadeite) - Opal 6 2.10 1.45 None Low Red, dark gray, orange, white, - with or without varicolored fire - Pearl 3½ 2.71 None None Low White - Peridot 6½ 3.34 1.68 Low Medium Yellow-green, brownish green - Quartz 7 2.65 1.55 Low High Purple (amethyst), yellow - (citrine), colorless (rock - crystal) - Spinel 8 3.60 1.72 Low High Shades of red, green, blue, - violet - Spodumene 7 3.18 1.66 Low Low Colorless, pink, yellow, green - Topaz 8 3.54 1.63 Low Medium Colorless, sherry, pink, blue - Tourmaline 7 3.06 1.63 Low High Wide range, except bright red - Zircon 7 4.02 1.81 High High Almost colorless, blue, brown, - green, yellow - - - GEMSTONES FOR THE COLLECTOR - -A number of mineral species have produced cut gemstones that fulfill -every necessary requirement of beauty, durability, and rarity, but their -popularity and commercial success have been sharply limited because of -insufficient supply. In some cases of even adequate supply such -gemstones do not compete with other, more plentiful kinds that exhibit -the same characteristics. The scarcity of these minerals does not -diminish their standing as potential gem material—it merely points up -the effect of accidental natural distribution of these species. - - [Illustration: A magnificent set of 16 matched sphenes from - Switzerland, gift of Nina Lea, almost encircles a 110-carat - sinhalite (a rare magnesium borate) and a 22-carat kornerupine, both - from Ceylon. The man’s gold ring indicates the sizes of these - unusual stones.] - -Among the rarer minerals that produce good gemstones are cordierite, -benitoite, euclase, phenakite, beryllonite, willemite, wernerite, -danburite, datolite, axinite, brazilianite, andalusite, sillimanite, -kyanite, kornerupine, enstatite, diopside, epidote, sphene, sinhalite, -and orthoclase. Willemite, a rare zinc silicate found in only a few -localities, is typical of these rarer minerals. The famous zinc mines at -Franklin, N. J., produced a few large gemmy crystals of willemite, and -some fine gemstones were cut from some of these. Willemite’s borderline -hardness of 5 to 5½ and its extreme rarity effectively eliminate it from -the gem market, but the collector who is able to obtain a good stone of -this material is indeed fortunate. - - [Illustration: Exotic gems that represent collectors’ items lie - beside a 3¼-inch-long box of Russian lapis lazuli. The stones are - (left row, from top) a 28-carat andalusite from Brazil, gift of Fred - C. Kennedy, a 10-carat cordierite from Ceylon, a 29-carat apatite - from Burma, and (right row) a 42-carat brazilianite from Brazil, a - 13-carat euclase from Brazil, a 29-carat wernerite from Brazil, and - a 61-carat orthoclase from Madagascar.] - -Some mineral species, although beautiful when cut, and prized by -collectors, are entirely too soft, are too easily cleaved, or have some -other physical weakness that renders them useless as commercial -gemstones. Sphalerite, apatite, fluorite, calcite, cerussite, zincite, -and hematite are included in this group. Sphalerite is typical; it -produces brilliant and colorful gemstones that hold their own among -other stones of great beauty. Unfortunately, this zinc sulfide, with a -hardness of 3½ to 4, is so soft and cleaves so readily that it is very -difficult to cut properly, and it cannot be used in jewelry. - - - - - 7 - SOME NOTABLE GEMS IN THE COLLECTION - - -The Smithsonian’s collection of gems continues to grow and improve -rapidly, and it changes character constantly as important new gemstones -are added and less important ones are retired. Approximately one-third -of the gems in the collection in 1965 are itemized in the following -list. Included are some of the largest gems of each kind, some of the -more interesting stones, and some small gems notable for the places from -which they came. Though listed by species and size, some of the larger -stones are not included, and neither are most cabochons, rough opal, -beads, carvings, and spheres. The descriptions listed include, in order, -weight in carats; color; popular name or other description, if any; -place of origin; and U. S. National Museum catalog number and name of -donor. Gems in the Lea and Roebling collections usually are indicated by -the letters “L” and “R.” - - DIAMOND - 127, colorless (_The Portuguese_), Brazil (3398) - 44.5, blue (_The Hope_), India (3551, Winston) - 18.3, yellow (_The Shephard_), South Africa (3406) - 2.9, pink, Tanzania (3772, De Young) - CORUNDUM: Ruby - 50, red-violet (a star), Ceylon (173, L) - 34, red (a star), Ceylon (1922, L) - CORUNDUM: Sapphire - 330, blue (_Star of Asia_), Burma (3688) - 316, blue (_Star of Artaban_), Ceylon (2231, Ingram) - 93, yellow, Burma (3549) - 52, yellow, Burma (3419) - 40, blue (a star), Ceylon (174, L) - 35, yellow-brown, Ceylon (2147, L) - 26, gray (a star), Ceylon (3902) - 26, colorless, Ceylon (2016, L) - 25, blue (4-starred), Ceylon (3923, Krandall) - 22, yellow-orange, Ceylon (3875, L) - 16, colorless, Ceylon (3581, L) - BERYL: Emerald - 157, green, India (3601) - 117, green, Colombia (4158, Erickson) - 27, green, Colombia (3922) - 17, green (3920, MacVeagh) - 7, green, North Carolina (3075, L) - 4.6, green (a cat’s-eye), Colombia (2256, R) - BERYL: Aquamarine - 1000, green, Brazil (3889, Evyan) - 264, blue, Russia (3606, Neal) - 187, blue, Brazil (3683) - 126, blue, Brazil (4159, Erickson) - 71, pale blue, Ceylon (3172, L) - 66, pale blue-green, Maine (2148, L) - 15, blue-green, Idaho (2249, Montgomery) - 14, blue, Connecticut (779) - 10, blue, North Carolina (776, L) - BERYL: Morganite - 236, pink, Brazil (3780, Ix) - 122, pale pink, California (1988, R) - 80, pale pink, Brazil (4190, R) - 64, pink, Brazil (3721, R) - 56, pink, Madagascar (2223, R) - 51, pink, Brazil (3623) - BERYL: Beryl - 2054, green-gold, Brazil (3725, R) - 1363, green, Brazil (3916) - 914, green, Brazil (3919) - 578, green, Brazil (3227, R) - 133, yellow, Madagascar (1977, L) - 114, yellow-green, Brazil (2245, R) - 98, pale green, Brazil (3949, Cutter) - 62, colorless (goshenite), Brazil (3366) - 46, gold, Madagascar (2121, L) - 44, gold (a cat’s-eye), Madagascar (3248) - 40, pale green, Connecticut (1037, L) - 40, yellow-green, North Carolina (2260, Roebling) - 20, brown (a star), Brazil (3355, L) - TOPAZ - 7725, yellow, Brazil (3976) - 3273, blue, Brazil (3633) - 1469, yellow-green, Brazil (3891) - 685, pale blue, Brazil (3003) - 398, pale blue, Russia (3400, R) - 235, colorless, Colorado (3309, L) - 187, colorless, Brazil (3612, Cutter) - 171, champagne, Madagascar (3890) - 155, blue, Russia (262, L) - 146, pale blue, Texas (3625, L) - 129, sherry, Brazil (3550) - 94, orange, Brazil (3401, R) - 54, blue, Brazil (2219, L) - 51, colorless, Japan (268) - 44, blue, Maine (2047, L) - 41, orange, Brazil (2174, L) - 34, gold, Brazil (2046, L) - 34, deep pink, Brazil (2232, L) - 24, pale blue, New Hampshire (3307, L) - 18, rose pink, Brazil (3402, R) - 17, blue, California (3679, Ware) - 15, sherry, Colorado (318, L) - TOURMALINE: Rubellite - 111, pink, Manchuria (3173, R) - 62, pink, Brazil (3411, R) - 51, magenta, Brazil (4160, Erickson) - 35, pink, Brazil (2254, R) - 34, pink, Brazil (3148, R) - 30, pink, Madagascar (3409, R) - 18, pink (a cat’s-eye), California (3786, Lea) - 18, pink, Maine (1109, L) - 15, pink, California (3412, R) - TOURMALINE: Tourmaline - 173, champagne, Mozambique (3590, R) - 125, champagne, Mozambique (3576, R) - 123, green, Mozambique (3575, R) - 110, green, Brazil (4197) - 104, rose, Mozambique (3256, L) - 76, dark green (a cat’s-eye), Brazil (3599, L) - 60, blue-green, Brazil (3410, R) - 58, green, Maine, (1108, L) - 53, green (a cat’s-eye), Brazil (3119, L) - 48, red and green, California (3363) - 42, yellow, Brazil (2251, R) - 42, brown, Ceylon (3245, L) - 40, red-brown, Brazil (2097, R) - 40, green, Madagascar (4081, R) - 34, red-brown, Brazil (2253, L) - 31, rose-brown, Brazil (3416, R) - 26, blue (indicolite), Brazil (3298, R) - 20, blue-green, Madagascar (2032, L) - 18, yellow-green, Elba (3368, R) - 18, green, South Africa (2095, L) - 15, yellow, Brazil (3415, R) - SPINEL - 46, pale purple, Ceylon (2180, L) - 36, indigo, Burma (3685) - 34, red, Burma (3354, L) - 30, pink-violet, Ceylon (2165, L) - 30, violet, Burma (3344, L) - 26, blue-gray, Burma (3593, L) - 22, blue-violet, Ceylon (2247, R) - 22, rose-brown, Ceylon (2166, L) - ZIRCON - 118, brown, Ceylon (2236, R) - 106, brown, Thailand (3568) - 103, blue, Indochina (2222, R) - 98, yellow-brown, Ceylon (2237, R) - 76, red-brown, Burma (3068, L) - 64, brown, Indochina (3397, R) - 48, colorless, Ceylon (3554, L) - 29, blue, Indochina (3394, R) - 23, green, Ceylon (2233, R) - 21, tan, Australia (1887, L) - SPODUMENE: Kunzite - 830, deep violet, Brazil (3940) - 336, deep violet, Brazil (3942, Nelson) - 297, deep violet, Brazil (3941, Nelson) - 177, violet, California (3797, American Gem Society) - 25, pale violet, Madagascar (1979, L) - SPODUMENE: Spodumene - 327, yellow, Brazil (3396, R) - 256, yellow, Brazil (3429, R) - 71, yellow, Madagascar (3698, L) - 69, yellow-green, Brazil (3885, R) - PERIDOT - 310, olive green, Egypt (3398, R) - 287, olive green, Burma (3705) - 46, olive green, Egypt (1978, L) - 23, olive green, Arizona (3620, L) - GARNET: Almandine - 175, red (a star), Idaho (3670) - 67, red-brown (a star), Idaho (3560, L) - 41, red-brown, Madagascar (2137, L) - 26, red-brown, Idaho (3423, L) - GARNET: Demantoid - 10.4 green, Russia (2175) - GARNET: Grossular - 64, orange-brown, Ceylon (493, L) - GARNET: Rhodolite - 25, rose-violet, Tanzania (4080, L) - 6.4, violet, North Carolina (460, L) - GARNET: Spessartine - 109, red, Brazil (4203) - 40, orange, Virginia (147, L) - 26, orange, Virginia (3597, L) - QUARTZ: Amethyst - 1362, purple, Brazil (3879) - 183, purple, Brazil (1272, L) - 62, purple, Brazil (3162, Capps) - 61, purple, Brazil (3914, Cutter) - 56, purple, Brazil (3165, Capps) - 54, purple, Pennsylvania (1299, L) - 45, pale purple, North Carolina (1298, Lea) - 36, purple, Pennsylvania (1283, L) - 33, pale purple, North Carolina (1288, Lea) - 27, purple, Arizona (3291, R) - 23, purple, Maine (1271, L) - 19, purple, Virginia (1301, L) - QUARTZ: Citrine - 1180, golden brown, Brazil (1870, L) - 783, light golden brown, Brazil (3640) - 278, golden brown, Brazil (3732, Cutter) - 265, light golden brown, Brazil (2041, Roebling) - 218, golden brown, Brazil (4199, Cutter) - 169, golden brown, Australia (1373, L) - 143, yellow, Colorado (456, L) - 120, golden brown, Brazil (2116, L) - 115, golden brown, Brazil (3932) - 91, yellow, Brazil (3615, Cutter) - 55, light golden brown, Maine (2178, L) - 48, yellow, Brazil (3915, Cutter) - 43, yellow, Brazil (3719, Cutter) - QUARTZ: Rock Crystal - 7000, colorless, Brazil (3957, R) - 625, colorless (a star), New Hampshire (3125, Burroughs) - 350, colorless, North Carolina (1398, L) - QUARTZ: Rose Quartz - 375, pink, Brazil (3592, L) - 84, pink, Brazil (3421) - 49, pink, Brazil (3420, R) - QUARTZ: Smoky Quartz - 4500, pale smoky, California (3738, L) - 1695 smoky, Brazil (3697, L) - 785, pale smoky, Colorado (1335, L) - 284, pale smoky, North Carolina (1340, Lea) - 163, pale smoky, Colorado (1336, L) - 145, smoky, Scotland (3079, R) - CHRYSOBERYL: Alexandrite - 66, green to red, Ceylon (2042, L) - 17, green to red, Ceylon (3407, R) - 11, green to red, Ceylon (2200, Walcott) - CHRYSOBERYL: Chrysoberyl - 172, gray-green (a cat’s-eye), Ceylon (3924) - 121, green (_The Maharani_, a cat’s-eye), Ceylon (3642) - 46, green-yellow, Brazil (1923, L) - 32, brown, Ceylon (2151, L) - OPAL - 155, white with fire, Australia (3285, Roebling) - 83, white with fire, Australia (3300, R) - 58, black with fire, Australia (3960, R) - 56, colorless with fire, Mexico (2240, R) - 54, black with fire, Australia (3962) - 44, black with fire, Australia (3284, R) - 39, pale yellow-orange with fire, Brazil (3637) - 38, black with fire, Australia (3961) - 30, black with fire, Australia (3405, R) - 24, black with fire, Australia (1897, L) - 22, orange with fire, Mexico (2106, L) - 22, orange with fire, Mexico (2028, L) - 21, yellow with fire, Mexico (2111, L) - 15, orange with fire, Mexico (2096, L) - 11, orange with fire, Mexico (3886, Lewis) - OTHER, LESS-KNOWN SPECIES - Albite: 43, white (a cat’s-eye), Burma (3311, L) - Amblygonite: 63, yellow, Brazil (4079, Lea) - 20, yellow, Burma (3562, R) - Andalusite: 28, brown, Brazil (3619, Kennedy) - 14, green-brown, Brazil (3364, L) - Apatite: 29, yellow-green, Burma (3247, Lea) - 29, yellow, Mexico (3594, L) - 15, colorless, Burma (3720, R) - 9, yellow-green, Canada (3122, R) - 8.8, pale blue, Ceylon (3639) - 5.4, green, Madagascar (3676, Durand) - Axinite: 9.4, brown, Mexico (3787, R) - 9, brown, Mexico (3773, L) - Barite: 61, colorless, England (3349) - Benitoite: 7.6, blue, California (3387, R) - Beryllonite: 5, colorless, Maine (423) - Brazilianite: 42, yellow, Brazil (3083, L) - Calcite: 46, gold-brown, Mexico (3305) - Cassiterite: 10, yellow-brown, Bolivia (3250) - Cobaltocalcite: 3.3, 3.9, pink, Spain (3724, L) - Cordierite: 16, blue, Ceylon (3882) - 10, indigo, Ceylon (3580, L) - 9.4, blue, Ceylon (3881) - Danburite: 18, yellow, Burma (3345, L) - 7.9, colorless, Japan (3801, L) - Datolite: 5.4, colorless, Massachusetts (3876, Boucot) - 5, colorless, Massachusetts (3283, Sinkankas) - Diopside: 133, black (a star), India (3977) - 24, black (a cat’s-eye), India (3956, Lea) - 14, black (a cat’s-eye), India (3880) - 11, green, Madagascar (2264, R) - 6.8, yellow, Italy (3634) - 4.6, yellow, Burma (3346, L) - 2.2, pale green, New York (572, L) - 1.6, green (chrome diopside), Finland (3693) - Enstatite: 11, brown, Ceylon (3638) - 8.1, brown, Ceylon (2294, R) - Epidote: 3.9, brown, Austria (579) - Euclase: 13, green, Brazil (3214, R) - 9, yellow, Brazil (3215, R) - 8.9, yellow, Brazil (2181, L) - 3.7, blue-green, Brazil (3388, R) - Fluorite: 354, pale yellow, Illinois (3877) - 125, green, New Hampshire (3294) - 117, green, Africa (2153) - 63, yellow, Illinois (3595, L) - 33, colorless, Illinois (3626) - 8.5, pink, Switzerland (3730, R) - Friedelite: 12, red-brown, New Jersey (3013, D’Ascenzo) - Gadolinite: 8.6, black, Texas (587, L) - Idocrase: 3.5, brown, Italy (4179, R) - Kyanite: 11, blue, Brazil (3557, L) - 9.1, green, Brazil (3558, L) - 3.7, blue, North Carolina (364, Bowman) - Kornerupine: 22, brown, Ceylon (3706, Lea) - 11, brown, Madagascar (3567, L) - 7.6, green, Madagascar (3782) - Labradorite: 11, pale yellow, Utah (3121) - Microlite: 3.7, brown, Virginia (3588, Lea) - Oligoclase: 6, colorless, North Carolina (404, L) - Orthoclase: 250, yellow, Madagascar (3878) - 105, pale green (a cat’s-eye), Ceylon (3883) - 61, yellow, Madagascar (1838, L) - 26, gray (a cat’s-eye), Ceylon (3579, Lea) - 23, white (a star), Ceylon (3578, L) - Petalite: 11, colorless, South-West Africa (3096) - Phenakite: 22, colorless, Russia (3739) - 10, colorless, Brazil (2263, R) - Phosphophyllite: 5, green, Bolivia (3950, Roebling) - Pollucite: 9, colorless, Maine (2056, L) - 7, colorless, Connecticut (3802, R) - Proustite: 9.9, red, Germany (4082, L) - Rhodizite: 0.5, colorless, Madagascar (3219, Canfield) - Rhodochrosite: 9.5, pink, South Africa (4189, L) - Samarskite: 6.6, black, North Carolina (588, L) - Scheelite: 37, colorless, California (3701, L) - 12, gold, Mexico (3803, R) - Scorodite: 2.6, purple, South-West Africa (3793) - Sillimanite: 5.9, black (a cat’s-eye), South Carolina (3600, L) - Sinhalite: 110, brown, Ceylon (3587) - 44, brown, Ceylon (3548, L) - Sphalerite: 73, yellow-brown, Utah (3556) - 69, yellow-brown, Utah (3362) - 60, yellow-green, New Jersey (3874, Roebling) - 48, yellow, Mexico (2167, L) - 46, yellow, Spain (3707, L) - Sphene: 0.8-9.3, sixteen stones, gold, Switzerland (2043, Nina Lea) - 8.5, brown, New York (550) - 5.6, yellow-brown, Mexico (3290) - 5.2, yellow-brown, Mexico (3292) - Staurolite: 3, dark red-brown, Brazil (3795) - Tektite: 23, brown, Czechoslovakia (681, L) - Wernerite: 288, colorless, Burma (3783) - 30, colorless (a cat’s-eye), Burma (3301, L) - 29, pale yellow, Brazil (2098, L) - 17, pink (a cat’s-eye), Ceylon (3238, Roebling) - 12, pink, Burma (3674, L) - Willemite: 12, orange-yellow, New Jersey (1898, L) - 11, orange-yellow, New Jersey (4187, Lea) - Zincite: 20, red, New Jersey (3386, R) - - [Illustration: Seal of the Smithsonian Institution] - - - - - Transcriber’s Notes - - -—Silently corrected a few typos. - -—Retained publication information from the printed edition: this eBook - is public-domain in the country of publication. - -—In the text versions only, text in italics is delimited by - _underscores_. - - - - - - - -End of the Project Gutenberg EBook of Gems in the Smithsonian Institution, by -Paul E. 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