The carbonates give usmalachiteandazurite, both carbonates of copper with combined water, the malachite having more water.
Owingto the confusion which may result from a lack of uniformity in the naming of precious stones, it is very desirable that jewelers and stone merchants inform themselves in regard to the correct use of the names of the gems, and that they use care in speaking and in writing such names.
As nearly all precious and semi-precious stones are derived from a relatively small number ofmineral species, as we saw inLesson XVIII., and as the science ofmineralogyhas a very orderly and systematic method of naming the minerals, the best results are had in the naming of gems when we use, as far as is possible, the language of mineralogy.
Ancient Usage.Long established customand usage, however, must be observed, for any system of naming must be generally understood in order to be useful. Thus the proper name for blood red, crystallized oxide of aluminum, of gem quality, according to the mineralogical system of naming, would be redcorundum, but that same material is referred to in the Old Testament thus (in speaking of wisdom), "She is more precious thanrubies." It is obviously necessary to keep and to use all such terms as have been for years established in usage, even though they do not agree with the scientific method of naming the particular mineral. It is, however, necessary that any name, thus retained, should be correctly used, and that it should not be applied to more than one material. Thus the termrubyshould be reserved exclusively for red corundum, and not applied to other red minerals such as garnet, spinel, etc., as is too often done.
It will be the purpose of this lesson to attempt to set forth as clearly and as briefly as possiblewhat constitutes good usage in the naming of the principal stones, and also to point out what incorrect usage is most in need of being avoided.
To cover the subject systematically we will adopt the order of hardness that we did in discussing mineral species inLesson XVIII.
Fancy Diamonds.Beginning with the hardest of all gems, thediamond, we have no difficulty as regards naming, as all specimens of this mineral, regardless of color, are called diamonds. When it is necessary to designate particular colors or tints, or differences in tint, additional names are used—for example, all diamonds of pronounced and pleasing color are called "fancy" diamonds in the trade. Certain of these "fancy" diamonds are still further defined by using a name specifying the color, as, for example, "canary" diamonds (when of a fine bright yellow), or "golden fancies," when of a fine golden brown, or "orange," or "pink," or"absinthe green," or "violet," as the case may be.
Names of Various Grades of White Diamonds.The great majority of the diamonds which come on the market as cut stones belong, however, to the group which would be spoken of as white diamonds, but many qualifying names are needed to express the degree of approach to pure white possessed by different grades of these diamonds. Thus the terms: 1,Jägers; 2,Rivers; 3,Blue Wesseltons; 4,Wesseltons; 5,Top Crystals; 6,Crystals; 7,very light brown; 8,Top Silver Capes; 9,Silver Capes; 10,Capes; 11,Yellows, and 12,Browns, describeincreasingdepth of color, and hencedecreasingvalue in diamonds.
Popular Names.Certain more popular names for diamonds of differing degrees of whiteness may next be set forth. The term "blue white" (a much abused expression, by the way) should be applied only to diamonds of such a close approach to pure whitenessof body substance, as seen on edge in the paper that, when faced up and undimmed, they give such a strong play ofprismaticblue that any slight trace of yellow in their substance is completely disguised, and the effect upon the eye is notably blue. This would be the case with stones of the grades from 1 through 4 in the list above. Grades 5 and 6 might properly be called "fine white," and grades 7, 8, and 9 simply "white." Grade 10 is frequently spoken of as "commercial white," and grade 11 sometimes as "off color." Grade 12 includes all degrees of brownness except the very light shades and the deep, pretty shades of the "fancy" browns.
Rubies.Leaving the naming of the different colors of diamonds we come to the gems furnished us by the mineral known ascorundum. As we have previously seen, this mineral occurs in many different colors and with wide differences of tint and shade in each of the principal colors. The best practice with regard to naming thecorundum gems is to call the red material, when of a good, full red of pleasing shade,ruby. The finest shades of blood red are usually called "Burmah rubies" because more rubies of this quality are found in Burmah than anywhere else. Any ruby of the required shade would, however, be called a Burmah ruby in the trade regardless of its geographical origin. The most desirable tint among Burmah rubies is that which is known as "pigeon blood" in color. This color is perhaps more accurately defined as like the color in the center of the red of the solar spectrum. Certain slightly deeper red rubies are said to be of "beef blood" color. The English are said to prefer these. Those of slightly lighter tint than pigeon blood are sometimes referred to as of "French color," from the fact that they are preferred by French connoisseurs.
Rubies of dark, garnet-like shade are known as "Siam rubies," many such being found in that country. Light pinkish rubies are called"Ceylon rubies." It should be clearly kept in mind that all these "rubies" are of red corundum, and that in all their distinctive properties except color they are essentially similar.
Sapphires.Corundum of fine blue color is known as "sapphire." The "cornflower blue" seems to be most in favor at present. Such sapphires are sometimes called "Kashmir sapphires" because many fine ones come from that State. "Ceylon sapphires" are usually paler than the cornflower blue. "Montana sapphires" are usually of greenish blue or pale electric blue. Such fine blue stones as are mined in Montana would be sold under another name according to the quality of their color, and not as "Montana sapphires." "Australian sapphires" are of a very deep, inky blue, and do not command a high price. Here again, as with rubies, the classification depends upon the color rather than upon the origin, although the geographical names thatare used, correctly state the usual source of stones of the particular color.
All corundums other than ruby and blue sapphire are usually called by the term "sapphire," with a qualifying adjective designating the color; thus we may have pink sapphire, golden sapphire, green sapphire, etc. When of very fine yellow color the yellow sapphire is sometimes called "Oriental topaz" by jewelers, the term "Oriental" as thus used indicating that the material is corundum. We also have "Oriental amethyst" and "Oriental emerald" for the purple, and the fine green, and "Oriental aquamarine" for the light blue-green corundum. The yellow corundum is also sometimes called "King topaz," especially in Ceylon. Inferior sapphires of almost every conceivable color are frequently assorted in lots and sold as "fancy sapphires." Such lots, however, almost always need reclassification as they often contain as many as a dozen mineral species besides corundum.
Sapphires and rubies of minute tubular internal structure frequently display a beautiful six-pointed star when cut to a round-topped cabochon shape and exposed to direct sunlight or to light from any other single source. Such stones are named "star sapphire" and "star ruby."
The artificial rubies and sapphires should all be calledscientific rubyorsapphire, and not "reconstructed" or "synthetic" as none are made to-day from small, real rubies, and as the process is in no sense a chemical synthesis.
Chrysoberyl.Leaving the corundum gems we come next to chrysoberyl. When the gems furnished by this mineral are of a fine green by daylight, and of a raspberry red by artificial light, as is sometimes the case, they should be called "Alexandrites" (after the Czar Alexander II., in whose dominions, and on whose birthday, the first specimens are said to have been discovered). When chrysoberyl is of fibrousor tubular internal structure it affords cat's-eyes (when cabochon cut), and these should be specifically named as "chrysoberyl cat's-eye" to distinguish them from the less beautiful and less valuable quartz cat's-eyes. Other varieties of chrysoberyl (most of those marketed are of a greenish-yellow color) are correctly named simply "chrysoberyls." Such stones are, however, sometimes incorrectly called "chrysolite" by the trade, and this practice should be corrected, as the term chrysolite applies correctly only to the mineralolivinewhich gives us theperidot.
Spinel.Next in the order that we have chosen comes "spinel." The more valuable spinels are of a red color that somewhat closely approaches the red of some rubies. Such red spinels should be called "Ruby spinel" (andnot spinel ruby). The stones themselves sometimes get mixed with corundum rubies (they are frequently found in the same gem gravels), and this makes it all the morenecessary that both stones and names should be clearly distinguished. Some dealers call reddish spinels "Balas ruby" (rose red), and orange red ones "rubicelle." Violet red spinel is sometimes called "almandine spinel." It is very desirable that the name of the mineral species,spinel, should be used, together with a qualifying color adjective, in naming gems of this species, rather than such terms as "rubicelle," "balas ruby," "spinel ruby," etc.
Topaz.We come now totopaz. True, orprecious topaz, as it is usually called, to distinguish it from the softer and less valuable yellow quartz, is seldom seen in the trade to-day. Jewelers almost always mean yellow quartz when they speak of "topaz." This is an unfortunate confusion of terms, and one which will be hard to eradicate. There is seldom any injustice done through this misnaming, as the price charged is usually a fair one for the material offered. Considerably higher prices would be necessary if true topaz was in question.
An instance from the writer's experience will serve to illustrate the confusion that exists in the trade as to what should be called topaz. A jeweler of more than ordinary acquaintance with gems exhibited some fine brooch stones as specimens of topaz. On remarking that they were of coursecitrine quartzrather thantrue topaz, the author was met with the statement that the brooch stones wererealtopaz. In order to make clear to the dealer the difference between the two species, the author asked him if he hadn't some smaller topazes in stock that had cost him considerably more than the brooch stones. The dealer replied that he had some small wine yellow topazes for which he had paid more, and he produced them. The latter stones were true Brazilian topazes. Most of them had tiny, crackly flaws in them, as is frequently the case, and, as the writer pointed out to the dealer, they had been bought by thecarat, whereas the large brooch stones had beenbought at a certain price perpennyweight. In fact the little stones had cost more per carat than the larger ones had per pennyweight.
The dealer was then asked if there must not be some difference in the real nature of the two lots to justify paying more per carat for small, imperfect stones than per pennyweight for large perfect ones. He of course acknowledged that it would appear reasonable that such was the case. He was next shown that his smalltrue topazesscratched his large stones easily, but the large ones could get no hold upon the surfaces of the small ones. (It will be remembered that topaz has a hardness of 8, while quartz has a hardness of 7.) The explanation then followed that the two lots were from two entirely distinct minerals, topaz and quartz, and that the former was harder, took a somewhat better polish, and was more rare (in fine colors) than quartz. Of course the yellow quartz should be sold under the proper name,citrine quartz. (Fromthe same root that we have in "citrus" as applied to fruits. For example the "California Citrus Fruit Growers' Association," which sells oranges, lemons, grape fruit, etc. The color implication is obvious.) If the jeweler still wishes to use the term "topaz" because of the familiarity of the public with that name, then he should at least qualify it in some way. One name that is current for that purpose is "Spanish topaz," another is "Quartz-topaz." Perhaps the latter is the least objectionable of the names that include the word topaz.
Some of the wine yellow true topazes lose the yellow, but retain the pink component, on being gently heated. The resulting pink stone is rather pretty and usually commands a higher price than the yellow topazes. Such artificially altered topazes should be sold only for what they are, and probably the name "pinked topaz," implying, as it does, that something has been done to the stone, is as good a name as any. There is, however, littlechance of fraud in this connection, as natural pink topazes are not seen in the trade, being very rare.
Some bluish-green topaz is said to be sold as aquamarine, and this confusion of species and of names should, of course, be stopped by an actual determination of the material as to its properties. Lacking a refractometer, the widely differing specific gravities of the two minerals would easily serve to distinguish them.
Beryl, Emerald, Aquamarine.Coming now toberylwe have firstemerald, thenaquamarine, then beryls of other colors to consider. There is too often a tendency among dealers to confuse various green stones, and even doublets, under the nameemerald. While the price charged usually bears a fair relation to the value of the material furnished, it would be better to offer tourmaline, or peridot (the mineral name of which is olivine), or demantoid garnet (sometimes wrongly called "Olivine"), or "emerald doublets," or emerald or "imitation emerald," as the case might be, under their own names.
There are no true "synthetic" or "scientific" or "reconstructed" emeralds, and none of these terms should be used by the trade.There has been an effort made in some cases to do business upon the good reputation of the scientific rubies and sapphires, but the products offered, when not out and out glass imitations, have usually been doublets or triplets, consisting partly of some pale, inexpensive, natural mineral, such as quartz or beryl, and a layer of deep green glass to give the whole a proper color. All attempts to melt real emerald or beryl have yielded only aberyl glass, softer and lighter than true emerald, and notcrystalline, but rather glassy in structure. Hence the names "reconstructed," "synthetic" and "scientific" should never be applied to emerald.
The light green and blue green beryls are correctly calledaquamarines, the pale sky-blue beryls should be named simplyblue beryl. Yellow beryl may be calledgolden beryl, or it may be called "heliodor," a name that was devised for the fine yellow beryl of Madagascar. Beautiful pink beryl from Madagascar has been called "morganite," a name that deservesto live in order to commemorate the great interest taken by J. Pierpont Morgan in collecting and conserving for future generations many of the gems in the American Museum of Natural History in New York.
Zircon.We now come to a number of minerals slightly less hard than beryl, but harder than quartz, andzirconis perhaps as hard as any of these, so it will be considered next. Red zircon, which is rare, is properly called "hyacinth." Many Hessonite garnets (cinnamon stones) are incorrectly called hyacinths, however. The true hyacinth has more snap and fire owing to its adamantine surface luster and high dispersive power, as well as to its high refractive index. A true hyacinth is a beautiful stone. Golden yellow zircons are correctly called "jacinths." Artificially whitened zircons (the color of which has been removed by heating) are known as "jargoons" or sometimes as "Matura diamonds." All other colors in zircon should be named simply zircon, witha color adjective to indicate the particular color as, "brown zircon," etc.
Tourmaline.Tourmaline furnishes gems of many different colors. These are all usually called simply tourmaline, with a color adjective to specify the particular color, as, for example, the "pink tourmaline" of California. Red tourmaline is, however, sometimes called "rubellite," and white tourmaline has been called "achroite." The latter material is seldom cut, and hence the name is seldom seen or used.
Garnet.We may next consider thegarnets, as most of them are somewhat harder than quartz. As was said inLesson XVIII.in our study of mineral species, there are several types of garnets, characterized by similarity of chemical composition, or at least by analogy of composition, but, having specific differences of property. The names used by jewelers for the several types of garnets ought to be a fairly true indication as to the type inhand in a particular case. At present there is considerable confusion in the naming of garnets. The most common practice is to call all garnets of a purplish-red color "almandines." As many such garnets belong to the mineral speciesalmandite garnet, there is little objection to the continuance of this practice. The somewhat less dense, and less hard blood red garnets are properly called "pyrope garnets" (literally "fire" garnets). Many of the Arizona garnets belong in this division. The term "Arizonarubies" shouldnotbe used. As was said under ruby, nothing but red corundum should receive that title. Similarly the pyrope garnet of the diamond mines of South Africa is incorrectly called "Cape ruby." Pyrope and almandite garnet tend to merge in composition and in properties, and the beautiful "Rhodolite" garnets of Macon County, North Carolina, are between the two varieties in composition, in color, and in other properties.
Hessonite garnetfurnishes yellowish-red andbrownish-red stones, which are sometimes also called "cinnamon stones." They are also frequently and incorrectly called jacinth or hyacinth, terms which, as we have seen, should be reserved for yellow and red zircon, respectively.
Andradite garnetfurnishes brilliant green stones, which have been incorrectly named "Olivines" by the trade. The name is unfortunate as it is identical with the true name of the mineral which gives us peridot. The name does not even suggest the color of these garnets correctly, as they are seldom olive green in shade. As the scarcity of fine specimens and their great beauty make a fairly high price necessary, the public would hardly pay it for anything that was called "garnet," as garnets are regarded as common and cheap. Perhaps the adoption of the name "Demantoid" might relieve the situation. The stones are frequently referred to as "demantoid garnets" on account of their diamond-like luster anddispersion. The use of "demantoid" alone, if a noun may be made from the adjective, would avoid both the confusion with the mineral olivine, and the cheapening effect of the word garnet, and would at the same time suggest some of the most striking properties of the material.
"Spodumene" furnishes pink to lilac "Kunzite," named after Dr. George F. Kunz, the gem expert, and for a time an emerald green variety was had from North Carolina which became known as "Hiddenite," after its discoverer, W. E. Hidden. No confusion of naming seems to have arisen in regard to this mineral.
The next mineral in the scale of hardness is quartz. (Hardness 7.) When pure and colorless it should be called "rock crystal." Purple quartz is of courseamethyst. Some dealers have adopted a bad practice of calling the fine deep purple amethyst "Oriental" amethyst, which should not be done, as the term "Oriental" has for a long time signified acorundumgem. As Siberia has produced some very fine amethysts, the term "Siberian amethyst" would be a good one to designate any especially fine gem.
Quartz Gems.We have already considered the naming of yellow quartz in connection with topaz. "Citrine quartz" is probably the best name for this material. If it is felt that the name "topaz" must be used, the prefix "quartz" should be used, or perhaps "Spanish topaz" will do, but some effort should be made to distinguish it from the true precious topaz. In addition to amethyst and citrine quartz we have the pinkish, milky quartz known as "rose quartz." This is usually correctly named.
"Cat's-eye" is a term that should be reserved for the Chrysoberyl variety, and the quartz variety should always be called "quartz cat's-eye." "Tiger's-eye" is a mineral in which a soft fibrous material has been dissolved away, and quartz has been deposited in its place. "Aventurine quartz" is the correct name forquartz containing spangles of mica. Clear, colorless pebbles of quartz are sometimes cut for tourists. Such pebbles are frequently misnamed "diamonds" with some prefix, as for example "Lake George diamonds," etc. Among the minutely crystalline varieties of quartz we have the clear red, which should be called "carnelian," the brownish-red "sard," the green "chrysoprase," the leek green "prase," and the brighter green "plasma." The last three are not so commonly seen as the first two, and frequently the best-colored specimens are artificially dyed.
"Jasper," a material more highly regarded by the ancients than at present, is mainly quartz, but contains enough earthy material to make it opaque. "Bloodstone" is a greenish chalcedony with spots of red jasper.
"Agates" are banded chalcedonies, the variety called "onyx" having very regular bands, and the "sardonyx" being an onyx agate in which some of the bands are of reddish sard.
Just as we considered opal with quartz (because of its chemical similarity) when discussing mineral species, so we may now consider the proper naming of opals here. "Precious opal" is distinguished from "common opal" by the beauty of its display rather than by any difference in composition. The effect is of course due to the existence of thin films (probably of material of slightly different density), filling what once were cracks in the mass. The rainbow colors are the result of interference of light (see a college text on physics for an explanation of interference). The varying thickness of these films gives varying colors, so different specimens of opal show very different effects. The differences of distribution of the films within the material also cause variations in the effects. Hence we have hardly any two specimens of opal that are alike.
There are, however, certain fairly definite types of opal and jewelers should learn to apply correct names to these types. Most prominentamong the opals of to-day are the so-called "Black opals" from New South Wales. These give vivid flashes of color out of seeming darkness. In some positions the stones, as the name implies, appear blue-black or blackish gray. By transmitted light, however, the bluish stones appear yellow. Owing to the sharp contrast between the dark background and the flashing spectrum colors, black opals are most attractive stones and fine specimens command high prices. One fine piece, which was on exhibition at the Panama-Pacific Exposition was in the shape of an elongated shield, about 13⁄4inches by 11⁄8inches in size and rather flat and thin for its spread. It gave in one position a solid surface of almost pure ruby red which changed to green on tipping the stone to the opposite direction; $2,000 was asked for the piece.
"White opal" is the name applied to the lighter shades of opal which do not show the bluish-black effect in any position. "Harlequinopal" has rather large areas of definite colors giving somewhat the effect of a map of the United States in which the different States are in different colors.
"Fire opal" is an orange-red variety. It has some "play" of colors in addition to its orange-red body color.
"Opal Matrix" has tiny specks and films of precious opal distributed through a dark volcanic rock and the mass is shaped and polished as a whole.
Jade."Jade" should next receive attention. It is a much abused term. Under it one may purchasejadeite,nephrite,bowenite,amazonite, or frequently simplygreen glass. The use of the word ought to be confined to the first two minerals mentioned, namely, jadeite and nephrite, for they only possess the extreme toughness together with considerable hardness that we expect of jade. Bowenite, while tough, is relatively soft and amazonite is brittle and also easily cleavable, while glass is both soft and brittle.
Peridot and Olivine.The mineral "olivine" gives us the "peridot" (this name should be kept for the deeper bottle green stones), and the olive green gems of this same mineral may correctly be called "olivine" or "chrysolite." As was explained under garnet, jewelers frequently use the term "olivine" to designate demantoid garnet. The term chrysolite is also sometimes incorrectly used for the greenish-yellow chrysoberyl.
Feldspar Gems.Among the minerals softer than quartz, which are used as gems, we have also "feldspar," which gives us "moonstone," "Labradorite," and "Amazonite."
An opalescent form of chalcedony is frequently gathered on California beaches and polished for tourists under the name of "California Moonstone." This name is unfortunately chosen as the material is not the same as that of true moonstone and the effect is not so pronounced or so beautiful. The polished stones show merely a milky cloudiness withoutany of that beautiful sheen of the true moonstone. "Labradorite" is usually correctly named. "Amazonite" was originally misnamed, as none is found along the river of that name. The term has come into such general use, however, that we shall probably have to continue to use it, especially as no other name has come into use for this bluish-green feldspar. As has already been said, amazonite is sometimes sold as "jade," which is incorrect.
Malachite, Azurite, and Lapis Lazuli.Malachiteandazuriteare usually correctly named, but "lapis lazuli" is a name that is frequently misused, being applied to crackled quartz that has been stained with Prussian blue, or some other dye, to an unconvincing resemblance to true lapis. Such artificially produced stones are sometimes sold as "Swiss lapis." They are harder than true lapis and probably wear much better in exposed ornaments, but they are not lapis and are never of equal color, and names should not be misused,and especially is this true in a trade where the public has had to rely so completely upon the knowledge and the integrity of the dealer.
With the increase of knowledge about precious stones that is slowly but steadily growing among the public, it becomes more than ever necessary for the jeweler and gem dealer to know and to use the correct names for all precious stones. The student who wishes to learn more about the matter will have to cull his information from many different works on gems. G. F. Herbert-Smith, in hisGem-Stones, gives a three and one half page chapter on "Nomenclature of Precious Stones" (Chap. XIII., pp. 109-112). The present lesson has attempted to bring together in one place material from many sources, together with some suggestions from the author.
Occurrence of Diamond.Every dealer in precious stones should know something of the sources of the gems that he sells. The manner of the occurrence of the rough material is also a matter of interest. It will therefore be the purpose of this lesson to give a brief account of the geographical sources of the principal gems and of their mode of occurrence in the earth.
For the sake of uniformity of treatment we will once more follow the descending order of hardness among the gems and we thus begin by describing the occurrence of diamond. It will be of interest to note first that the earliest source of the diamond was India, and that for many years India was almost the sole source. Tavernier tells us that the diamond miningindustry was in a thriving state during the years from 1640 to 1680, during which time he made six journeys to India to purchase gems. He speaks of Borneo as another source of diamonds, but most of the diamonds of that time were furnished by India.
"Golcondas."Indian diamonds were noteworthy for their magnificent steely blue-white quality and their great hardness, and occasionally one comes on the market to-day with an authentic pedigree, tracing its origin back to the old Indian mines, and such stones usually command very high prices. One of a little over seven and one half carats in weight, in the form of a perfect drop brilliant, has lately been offered for sale at a price not far from $1,000 per carat. Such diamonds are sometimes called "Golcondas" because one of the mining districts from which the fine large Indian stones came was near the place of that name. Some of the stones from the Jägersfontein mine in South Africa resemble the Golcondasin quality. Many of the large historical crown diamonds of Europe came from the Indian mines.
The stones were found in a sedimentary material, a sort of conglomerate, in which they, together with many other crystalline materials, had become imprisoned. Their original source has never been determined. They are therefore of the so-called "River" type of stone, having probably been transported from their original matrix, after the disintegration of the latter, to new places of deposit, by the carrying power of river waters.
The Indian mines now yield very few stones. The United States Consular reports occasionally mention the finding of a few scattered crystals but the rich deposits were apparently worked out during the seventeenth century and the early part of the eighteenth century.
In 1725 and in the few following years the Brazilian diamond fields began to supersede those of India. Like the latter, the Brazilian fields were alluvial, that is, the materialswere deposited by river action after having been carried to some distance from their original sources.
Brazilian Diamonds.The diamonds of Brazil also resembled those of India in quality, being on the average better than those of the present South African mines. It may be added that even the African diamonds that are found in "river diggings" average better in quality than those of the volcanic pipes which form the principal source of the world's supply to-day. There seems to be a superabundance of iron oxide in the rocks of the African mines and in the diamonds themselves, imparting yellow or brownish tints to the material. The "River" stones seem to have lost this color to a considerable extent, if they ever had it. Possibly long extraction with water has removed the very slightly soluble coloring material. Whatever the cause of their superiority "River" stones have always been more highly regarded than stones from the volcanic pipes.
Brazil furnished the world's principal supply of diamonds until the discovery of the African stones in 1867. At present relatively small numbers of Brazilian stones reach the world's markets. Most of these come from the great Bahia district (discovered in 1844) rather than from the older mines of Brazil. The present Brazilian stones average of small size. They are, however, of very good quality as a rule. A few green stones are found in Brazil and these may be of an absinthe-green or of a pistachio-green tint.
Australian and American Sources.While a few diamonds now come on the market from New South Wales, and while an occasional stone is found in the United States (usually in glacial drift in the north central States, or in volcanic material somewhat resembling that of South Africa in Arkansas) yet the world's output now comes almost entirely from South Africa and mainly from the enormous volcanic pipes of the Kimberly district and those of the Premier Co. in the Transvaal.
South African Diamonds.The nature of the occurrence of diamond in the "pipes" of South Africa is so well known to all who deal in diamonds to-day that but little space need be devoted to it. The "blue ground," as the rock in which the diamonds are found is called, seems to have been forced up from below, perhaps as the material of a mud volcano, bringing with it the diamonds, garnets, zircons, and the fifty or more other minerals that have been found in the blue ground. The fragmentary character of some of these minerals would indicate that the blue ground was not their original matrix. How the diamonds originally crystallized and where, is still probably a matter for further speculation.
While at first the mines were worked, like quarries, from the surface, and while the great Premier mine is still so worked, most of the present mines are worked by sinking shafts in the native rock outside of the blue ground and then tunneling into the diamond-bearingrock laterally, removing it to the surface, allowing it to weather on the "floors" until it crumbles, then crushing and washing it and concentrating the heavy minerals by gravity methods. Large diamonds are then picked out of the concentrates by hand and small ones and fragments are removed by the "greasers," which are shaking tables heavily smeared with grease over which the concentrates are washed and to which diamond alone, of all the minerals in the concentrate, sticks. The grease is periodically removed and melted, and the diamonds secured. The grease can then be used again.
German South West Africa furnishes a considerable output of very small diamonds, which are found in dry sand far from any present rivers. These diamonds cut to splendid white melee and the output is large enough to make some difference in the relative price of small stones as compared to large ones. The South West African field seldom yields a stonethat will afford a finished quarter-carat diamond.
Rubies.Passing on to the occurrence of thecorundumgems we will consider first theruby. Most fine rubies come from Burmah. The district in which they are found is near Mogok. Practically all the fine pigeon-blood rubies come from this district. The fashion for red stones being for the time little in evidence rubies are not now in great demand. This cessation of demand can hardly be laid to the competition of the scientific ruby, for the sapphire is now very much in vogue, yet scientific sapphires resemble the natural ones even more closely than do the rubies.
Siam furnishes a considerable number of dark garnet-like rubies. These do not command high prices. They are, however, sometimes very beautiful, especially when well cut for brilliancy, and when in a strong light.
Ceylon furnishes a few rubies and a few red corundums have been found in North Carolina.
The Burmese rubies appear to have been formed in a limestone matrix, but most of those obtained are gotten from the stream beds, where they have been carried by water after weathering out from the mother rock.
The rubies of Ceylon, too, probably originated in a limestone matrix, but are sought in stream gravels.
Sapphires.Fine blue sapphires originate in Siam in larger numbers than in any other locality. Kashmir, in India, also supplies splendid specimens of large size. Ceylon, too, furnishes a good deal of sapphire, but mostly of a lighter color than the Kashmir sapphire. The Ceylon sapphires are found in the streams, but originate in rock of igneous origin.
Montana furnishes considerable quantities of sapphire, some of which is of very good color. It is, of course, as good as the Oriental if of equal color, being of the same material. The better colored sapphire from Montana is mined from the rock. Most of the sapphires found in theriver gravels near Helena, Mont., are greenish blue or of other colors, and not of fine blue.
Queensland and Victoria in Australia supply considerable quantities of sapphire. When blue the Australian sapphire is usually too dark to be very valuable. The golden and other "fancy" sapphires of the trade come largely from the Ceylon gravels. Siam yields silky brown stones and some fine green ones. Some of the Australian sapphires when cut in certain directions yield green stones.
Chrysoberyl.Chrysoberyl of the variety Alexandrite now comes mainly from Ceylon, although formerly from the Ural Mountains.
The cat's-eyes also come chiefly from Ceylon.
The yellowish-green chrysoberyls (which jewelers sometimes call chrysolite) come both from Ceylon and from Brazil. They are frequently found in papers of "fancy sapphires" or "fancy color stones," so called.
Spinel.Spinels are found along with ruby in Burmah and in Siam and they also occurin the gem gravels of Ceylon. Limestone is the usual matrix of spinel, although it is more often mined in gravels resulting from the weathering of the matrix.
Topaz.True topaz, of wine-yellow color, comes mostly from Brazil. Ceylon also furnishes yellow topaz. Asiatic Russia furnishes fine large blue or blue-green crystals resembling aquamarine in appearance. Most of the topaz found in other localities is pale or colorless. Several of our western States, notably Utah, Colorado, and California, furnish colorless topaz. Mexico and Japan also produce it. It is seldom cut, for, while producing a rather brilliant stone, it has little "fire" and is therefore not very attractive.
Emerald and Aquamarine.Beryl of the emerald variety is exceedingly scarce in the earth. Most of the best emerald comes from Colombia, South America. Large crystals of paler color come from the Urals.
Like ruby and spinel, emerald usually originatesin limestone. One is tempted to suspect that these stones are of aqueous origin and that sapphires, and beryl, other than emerald, are more likely of igneous origin.
Beryls of the aquamarine type occur in many places, but usually of too pale a tint, or too imperfect, to be worthy of cutting. Fine gem beryl of blue and blue-green tints comes from Siberia and from several places in the Ural Mountains on their Asiatic slopes.
The Minas Geraes district of Brazil, famous for all kinds of gem stones, furnishes most of the aquamarine of commerce. The pegmatite dikes of Haddam Neck, Conn., of Stoneham, Me., and of San Diego County, Cal., have furnished splendid aquamarine and other beryl. These dikes, according to the geological evidence, are the result of the combined action of heat and water. Thus both melting and dissolving went on together and as a result many fine gem minerals of magnificent crystallization were formed during the subsequent cooling. Thelonger the cooling lasted and the more free space for growth the crystals had, the larger and more perfect they got. The author has himself obtained finely crystallized aquamarine and tourmaline from the Haddam, Conn., locality and the best specimens there occur in "pockets" or cavities in the coarse granite. Within, these pockets are lined with crystals of smoky quartz, tourmaline, beryl, and other minerals. Sometimes crystals occur in mud or clay masses inside the cavities and such crystals, having been free to grow uninterruptedly in every direction, were perfect in form, being doubly terminated, and not attached anywhere to the rock.
Madagascar has in recent years furnished the finest pink beryl, which has been named Morganite. Yellow beryl (Heliodor) and aquamarine also occur in Madagascar.
Zircon.Zircon comes on the market mainly from Ceylon. It deserves to be as much esteemed in this country as it is in Ceylon, forits optical properties are such that it is a very snappy stone. Some of the colors in which it occurs, such as the golden browns, lend themselves nicely to the matching of gems and garments, and, with the growth of education in such matters, jewelers would do well to get better acquainted with the possibilities of zircon and to introduce it to their customers. The supply from Ceylon is sufficient to justify popularizing the stone. Small zircons are found in almost every heavy concentrate, as, for example, in the concentrates of the diamond mines of South Africa, and in those of gold placers in many places. The rough stones resemble rough diamonds in luster and are sometimes mistaken for diamonds.
Garnets.Garnets of various types are found widely distributed in nature. Perhaps the Bohemian supply is best known, having furnished a host of small stones which have usually been rose cut for cluster work or made into beads. The Bohemian garnets are of the pyrope orfire-red type. Relatively few large stones of sufficient transparency for cutting are produced in the Bohemian mines. The so-called "Cape rubies" of the diamond mines of South Africa are pyrope garnets and some large and fine ones are found. The "Arizona rubies" are pyrope garnets, and while seldom of notable size, some are of very fine color, approaching deep rubies, and the color remains attractive by artificial light.
Almandite garnet, the "almandine" of the jeweler is less abundant than pyrope, when of gem quality. Ceylon furnishes some and India furnishes perhaps more. Brazil, from its prolific gem gravels at Minas Novas, supplies good almandite, and smaller quantities are found in many different localities.
Hessonite garnet, the cinnamon stone or "hyacinth" (incorrect) of the trade, comes mainly from Ceylon.
Andradite garnet, of the variety known as demantoid, from its diamond-like properties,and which is usually sold under the misleading name "olivine" in the trade, comes from the western slopes of the Ural Mountains.
Tourmaline.Gem tourmaline comes from Ceylon, from Madagascar, from the Ural Mountains, from Brazil, from Maine, from Connecticut, and from California.
The Ceylon tourmalines are mostly yellow or yellowish green, sometimes fine olive-green. Those from the Urals may be pink, blue or green. Brazilian tourmalines are usually green, but sometimes red. In fact in many localities several colors of tourmaline are usually found together and it may be that a single crystal will be green in most of its length but red or pink tipped. Some crystals have a pink core and a green exterior. The author has found both of the two latter types in the Haddam, Conn., tourmalines, and on one occasion was surprised to get back a wine-colored tourmaline from a cutter to whom he had sent a green crystal. There was buta thin shell of the green material on the outside of the crystal.
Some of the Madagascar tourmaline is of a fine brownish red, almost as deep as a light garnet, and much clearer than most garnet.
Would it not be fitting on account of its occurrence in several localities in the United States, for Americans to use more tourmaline in their jewels? The quality of some of the tourmalines of Maine, and of California especially, is not excelled by tourmaline from any other locality. Some of the Maine tourmaline is of a delightful, slightly bluish-green tint that almost approaches emerald.
Kunzite.Spodumene, of the variety kunzite, comes from San Diego County, California.
Quartz Gems.Coming now to the quartz gems we find amethyst and citrine, or golden quartz widely distributed so that only the localities that furnish the better grades of these stones need be mentioned. Siberia and Uruguayfurnish fine amethyst. Brazil also furnishes large quantities of very good quality.
Amethyst.The chief charm of the Siberian amethyst lies in its large red component, which enables it to change from a deep grape-purple by daylight to a fine red by artificial light that is rich in red rays, and poor in blue ones. The paler types of amethysts that were once esteemed, probably for lack of the rich deep variety, become gray in appearance and much less lovely under artificial light. India furnishes some amethysts, and papers of "fancy color stones" containing native cut gems from Ceylon, frequently contain amethysts, but Brazil, Uruguay, and Siberia furnish the great bulk of the stones that are regarded as choice to-day.
Yellow Quartz.Citrine or golden quartz comes mainly from Brazil. The "Spanish topaz" is sometimes the result of heating smoky quartz from Cordova province in Spain. Our own western mountains furnish considerable yellow and smoky quartz fit for cutting.
Rose Quartz.Rose quartz of the finest quality comes from South Dakota. Bavaria, the Ural Mountains, and Paris, Maine, have also furnished it.
Agate.Agates of the finest types, such as carnelian and sard, come principally from Brazil and from India.
Opal.Opals now come most largely from Australia, the Hungarian mines yielding but few stones at present. The fine black opals of New South Wales are unsurpassed by any that have ever been found elsewhere. Mexico furnishes considerable opal, and is notable for its fine "fire opal" or "cherry opal."
Jade.Most of the jade of the variety nephrite that is obtained to-day comes from several of the provinces of China or from Siberia or from Turkestan. A dark-green nephrite comes from New Zealand.
Jade of the jadeite variety, which is harder than nephrite and more highly valued, is rare. The best specimens come from UpperBurmah. It is also found in China and in Tibet.
Peridot.Peridot, and the brighter olivine or chrysolite, while of the same mineral species, do not seem to occur together. The darker bottle-green specimens come from the Island of St. John in the Red Sea. It is said that many of the finer peridots now available have been recut from old stones mined many years ago.
Queensland supplies light-green chrysolite, and Arizona a yellowish-green variety. Light-green stones have been found near the ruby mines of Upper Burmah.
Moonstone.Moonstone comes mainly from Ceylon. The native cut specimens are sent here and recut, as, when native cut, the direction of the grain is seldom correct to produce the moonlight effect in symmetrical fashion. The native cutters apparently try to retain all the size and weight that is possible, regardless of the effect.
Turquoise.Turquoise of the finest blue andmost compact texture (and hence least subject to color change) comes from the province of Khorasan in Persia. Several of our western states supply turquoise of fair quality, notably New Mexico, Arizona, Nevada, and California.
Lapis Lazuli.Lapis Lazuli comes from Afghanistan, from Siberia, and from South America.
Malachite.Malachite is found in many copper mines, but principally in those of the Ural Mountains.
Azurite.Azurite is found in the Arizona mines and in Chessy, in France (hence the name chessylite, sometimes used instead of azurite).
References.Students who wish to get a fuller account of the occurrence of precious stones should run through G. F. Herbert-Smith'sGem-Stonesunder the different varieties. This work is the most recent authentic work of a strictly scientific character. Dr. George F. Kunz'sGems and Precious Stones of NorthAmericagives a detailed account of all the finds in North America up to the time of publication. Many of these are of course of little commercial importance. TheMineral Resources of the United Statescontains annually a long account of the occurrences of gem materials in this country. A separate pamphlet containing only the gem portion can be had gratis from the office of the United States Geological Survey, Washington, D. C.
Rough Precious Stones.John Ruskin, who had the means to acquire some very fine natural specimens of gem material was of the opinion that man ought not to tamper with the wonderful crystals of nature, but that rather they should be admired in the rough. While one can understand Ruskin's viewpoint, nevertheless the art of man can make use of the optical properties of transparent minerals, properties no less wonderful than those exhibited in crystallization, and indeed intimately associated with the latter, and, by shaping the rough material in accordance with these optical properties, greatly enhance the beauty of the gem.
No material illustrates the wonderful improvement that may be brought about by cuttingand polishing better than diamond. In the rough the diamond is less attractive in appearance than rock crystal. G. F. Herbert-Smith likens its appearance to that of soda crystals. Another author likens it to gum arabic. The surface of the rough diamond is usually ridged by the overlapping of minute layers or strata of the material so that one cannot look into the clear interior any more than one can look into a bank, through the prism-glass windows that are so much used to diffuse the light that enters by means of them. Being thus of a rough exterior the uncut diamond shows none of the snap and fire which are developed by proper cutting.
As the diamond perhaps shows more improvement on being cut than any other stone, and as the art of cutting the diamond is distinct from that of cutting other precious stones, both in the method of cutting and in the fact that the workers who cut diamonds cut no other precious stones, it will be well to consider diamond cutting separately.
Before discussing the methods by which the shaping and polishing are accomplished let us consider briefly the object that is in view in thus altering the shape and smoothing the surface of the rough material.
How Cutting Increases Brilliancy.Primarily the object of cutting a diamond is to make it more brilliant. So true is this that the usual form to which diamonds are cut has come to be called thebrilliant. The adjective has become a noun. The increased brilliancy is due mainly to two effects: First, greatly increased reflection of light, and second, dispersion of light. The reflection is partly external but principally internal.
Taking up first the internal reflection which is responsible for most of the white brilliancy of the cut stone we must note that it is a fact that light that is passing through any transparent material will, upon arriving at any polished surface, either penetrate and emerge or else it will be reflected within the material, depending uponthe angle at which the light strikes the surface. For each material there is a definite angle outside of which light that is passing as above described, istotally reflectedwithin the material.