A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Part 9

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 small _true topazes_ scratched 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_.

(From the same root that we have in "_citrus_" as applied to fruits.

For example the "California Citrus Fruit Growers' a.s.sociation," 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, little chance 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.

LESSON XX

THE NAMING OF PRECIOUS STONES (_Concluded_)

BERYL, EMERALD, AQUAMARINE. Coming now to _beryl_ we have first _emerald_, then _aquamarine_, 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 name _emerald_. 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 gla.s.s 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 gla.s.s to give the whole a proper color. All attempts to melt real emerald or beryl have yielded only a _beryl gla.s.s_, softer and lighter than true emerald, and not _crystalline_, but rather gla.s.sy in structure. Hence the names "reconstructed," "synthetic" and "scientific"

should never be applied to emerald.

The light green and blue green beryls are correctly called _aquamarines_, the pale sky-blue beryls should be named simply _blue beryl_. Yellow beryl may be called _golden 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 deserves to 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, and _zircon_ is 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 l.u.s.ter 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, with a 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 the _garnets_, as most of them are somewhat harder than quartz. As was said in Lesson XVIII. in our study of mineral species, there are several types of garnets, characterized by similarity of chemical composition, or at least by a.n.a.logy 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 in hand 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 species _almandite 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 "Arizona _rubies_" should _not_ be used. As was said under ruby, nothing but red corundum should receive that t.i.tle.

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 garnet_ furnishes yellowish-red and brownish-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 garnet_ furnishes 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 l.u.s.ter and dispersion. 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 course _amethyst_. 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 a _corundum_ gem. 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 for quartz 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 ma.s.s. 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 prominent among 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 flas.h.i.+ng 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 s.h.i.+eld, about 1-3/4 inches by 1-1/8 inches 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. "_Harlequin opal_"

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 ma.s.s is shaped and polished as a whole.

JADE. "_Jade_" should next receive attention. It is a much abused term.

Under it one may purchase _jadeite_, _nephrite_, _bowenite_, _amazonite_, or frequently simply _green gla.s.s_. 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 gla.s.s 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 p.r.o.nounced or so beautiful. The polished stones show merely a milky cloudiness without any 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. _Malachite_ and _azurite_ are 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 his _Gem-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.

LESSON XXI

WHERE PRECIOUS STONES ARE FOUND

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 princ.i.p.al 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 mining industry 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 Jagersfontein mine in South Africa resemble the Golcondas in 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.