As the time during which the oyster is allowed to work upon the cultured pearl is doubtless far less than is required for the growth of a large natural pearl, the number of layers of true pearly material is considerably smaller than the number of layers that take part in the multiple reflections explained in the previous lesson, and hence the "orient" of the cultured pearl is never equal to that of a fine true pearl. It is frequently very good however, and for uses that do not demand exposure of the whole surface of the pearl, the cultured pearl supplies a substitute for genuine pearls of moderate quality and price. The back parts of the cultured pearl, being only polished mother-of-pearl, have the appearance of the ordinary pearl button, rather than that of true pearl.

IMITATIONS OF PEARLS. Aside from these half artificial cultured pearls, the out and out imitations of pearls that have been most successfully sold are of two general types, first "Roman pearls," and, second, "Indestructible pearls." The Roman pearls are made hollow and afterward wax filled, the Indestructible pearls have solid enamel bases. In both types the pearly appearance is obtained by lining the interior, or coating the exterior, with more or less numerous layers of what is known as "nacre" or some times as "essence d'oriente." This is prepared from the scales of a small fish found in the North Sea and in Russia. The scales are removed and treated with certain solutions which remove the silvery powder from the scales. The "nacre" is then prepared from this powder. The fineness of the pearly effect becomes greater as the preparation ages, so very fine imitations are usually made from old "nacre." The effect is also better the larger the number of successive layers used. The artificial pearl thus resembles the true pearl in the physical causes for the beautiful effect.

In some cases the Roman pearl has a true iridescence which is produced by "burning" colors into the hollow enamel bead. Some of the indestructible pearls are made over beads of opalescent glass, thus imparting a finer effect to the finished product. While the cheaper grades of indestructible pearls have but three or four layers of nacre, some of the fine ones have as many as thirty or more. The earlier indestructible pearls were made with a coating material which was easily affected by heat, or by water, or by perspiration, as a gelatine-like sizing was included in it. The more recent product has a mineral binder which is not thus affected, so that the "pearls" are really about as durable as natural ones, and will at least last a lifetime if used with proper care.

Like fine natural pearls, the fine imitations should be wiped after use and carefully put away. They should also be restrung occasionally, as should real pearls both to prevent loss by the breaking of the string and because the string becomes soiled after a time, and this hurts the appearance of the jewel.

The "Roman" type of imitation will not stand much heat, as the wax core would melt and run out.

TESTING IMITATIONS OF PEARLS. As the making of imitations of pearls is mainly hand-work and as many treatments are required for the best imitations, fairly high prices are demanded for these better products, and the appearance and permanency warrant such prices. The best imitation pearls are really very difficult of detection except by close examination. They will not, of course, stand inspection under a high magnification.

Artificial pearls may also be detected by their incorrect specific gravity, by their incorrect degree of hardness, and in the case of the hollow pearls by making a tiny ink spot upon the surface of the "pearl" and looking at it through a lens. A reflection of the spot from the inside surface of the bead will appear beside the spot itself if the pearl is of the Roman type.

The artificial pearls so far described are high class products. Some of the very cheap and poor imitations are merely solid, or hollow, glass or enamel beads which have been made slightly pearly, either by adding various materials to the glass or enamel when it was made, or by crudely coating the beads without or within with wax containing cheap "nacre."



LESSON XXIX

THE USE OF BALANCES AND THE UNIT OF WEIGHT IN USE FOR PRECIOUS STONES

As precious stones are almost always sold by weight, and as the value at stake is frequently very great, it is almost as necessary for a gem merchant, as it is for the chemist, to have delicate balances and to keep them in good order and to use them skillfully.

A general understanding of the unit of weight in use for precious stones and how it is related to other standard weights is also necessary to the gem dealer. We will therefore consider in this lesson the use and care of balances and the nature and relative value of the unit of weight for precious stones.

DELICATE BALANCES NEEDED. As it is necessary, on account of their great value, to weigh some gems, such as diamonds, emeralds, rubies, etc., with accuracy to at least the one hundredth part of a carat (which is roughly in the neighborhood of 1/15,000 of an ounce avoirdupois), balances of very delicate and accurate construction are a necessary part of the equipment of every gem merchant. While portable balances of a fair degree of accuracy are to be had, the best and surest balances are substantially constructed and housed in glass cases, much as are those of the analytic chemist, which must do even finer weighing. The case protects the balance from dust and dirt and prevents the action of air currents during the weighing. The balance itself has very delicate knife edges, sometimes of agate, sometimes of hardened steel, and these knife edges rest, when in use, on a block of agate or steel, so that there is a minimum amount of friction. When not in use the balance beam and knife edges are lifted from the block and held firmly by a metal arm, or else, as is the case with some balances, the post supporting the block is lowered, leaving the beam and knife edges out of contact with it. The object of this separation is to prevent any rough contact between the knife edges and the block on which they rest. Advantage should always be taken of this device whenever any fairly heavy load is put on or taken off of either pan, as the sudden tipping of the beam might chip the knife edges if not supported. When the load is nearly balanced there may be no harm in carefully adding or removing small weights while the knife edges are resting on the block, but even then it is safer to lower the beam and pans. It should be needless to state that as level and rigid a support should be had for one's balance as circumstances permit.

METHOD OF USE OF BALANCES. Before using a balance one should see that the pans are clean, that the base of the balance is properly leveled (the better balances have a spirit level attached) and that the pans balance each other without load. When slightly out of balance the defect may be adjusted by unscrewing the little adjusting nut at the end of the beam that is too light, or by screwing in the nut at the opposite end. Having seen that the adjustment is perfect the pans should be lowered and the object to be weighed placed on the left-hand pan (because a right-handed person will find it handier to handle his weights on the right-hand pan). One should next guess as nearly as possible the weight of the stone and place well back on the right-hand pan the weight that he thinks comes nearest to that of the stone. If the weight is too heavy the next lighter weight should replace it. Smaller weights should be added until a perfect balance is had, the small weights being neatly arranged in the order of their size, in order to more rapidly count them when the stone is balanced. This is the case when the pointer swings approximately equal distances to the right and to the left and there is then no need to wait for it to come to rest in the center.

It is well to count the weights as they lie on the pan (which is easily done if they have been arranged in descending order of size as suggested above) then write down the total, and on removing the weights count aloud as they are replaced in the box and note if the total checks that which was written down. It may seem unnecessary to be so careful in this matter, but it is better to be over-careful than to make a mistake where every hundredth of a carat may mean from one to five or six dollars or more. No dealer can afford to have a stone that he has sold prove to be lighter than he has stated it to be. One should be at least within one one-hundredth of a carat of the correct weight.

It should be unnecessary to add that accurate weights should never be handled with the fingers. Ivory tipped forceps are best for handling the weights. The forceps commonly used for handling diamonds will, in time, wear away the weights by scratching them so that they will weigh materially less. Unless the weights are of platinum or plated with gold, the perspiration of the hands would cause them to oxidize and gain in weight. It would be well to discard the smaller weights, which are most in use, every few years and obtain new and accurate ones. In case this is not done one should at least have the weights checked against others known to be of standard weight. Any chemist will have balances and weights far more accurate than the best in use for precious stones and will gladly check the weights of a gem dealer for a moderate fee.

To check the accuracy of your balance, change the stone and weights to opposite pans, in which case they should still balance.

One should never overload a balance, both because the balance might be injured and because the relative accuracy decreases as the load increases. If the weight of a parcel of stones heavier than the total of the weights provided with the balance is desired, the parcel should be divided and weighed in parts.

While many dealers neglect some of the precautions above suggested and somehow get along, yet it is safer to use care and to have correct technique in the handling of one's balances.

Having indicated a few of the refinements of method in weighing we will next consider the unit of weight in use for precious stones and see how it is related to other units of weight and in what manner it is subdivided.

THE UNIT OF WEIGHT FOR PRECIOUS STONES. The present unit for precious stones in the United States is the metric carat. Most of the more progressive countries have in recent years agreed upon the use of this unit. Its use in the United States became general July 1, 1913. It is by definition exactly one fifth of a gram (the unit of weight of the Metric System of weights and measures). Its relation to the grain is that there are 3.08+ grains in the metric carat. The carat in use in this country up to a few years ago was about 2-1/2% heavier than the present metric carat. It was equal to .2053 grams instead of .2000 grams (1/5 gram). The carats of countries not using the metric carat vary considerably, but yet approximate the metric carat somewhat nearly.

Thus, that in use in Great Britain was .2053 g., in Amsterdam .2057 g., in Berlin .20544 g., in Lisbon .20575 g., and in Florence 0.1972 g. The latter was the only one that was under the metric carat. The change to the metric carat was desirable, as it unified the practice of weighing, which not only varied in different countries, but even in the same country. Thus there was no very exact agreement among the makers of diamond weights in the United States prior to the adoption of the metric carat. One man's carat was a bit heavier or lighter than another's. With a definite and simple relationship to the standard gram there is now no excuse for any variation in weights. The Bureau of Standards at Washington affords manufacturers every facility for standardizing their weights.

THE DECIMAL SYSTEM OF SUBDIVISION OF THE CARAT. With the adoption of the metric carat the custom of expressing parts of a carat in common fractions whose denominators were powers of the number 2 (1/2, 1/4, 1/8, 1/16, 1/32, 1/64) was discarded as awkward and slow for computation and the decimal system of subdivision was adopted. Thus the metric carat is divided into tenths and one hundredths. It is customary, however, to sum up the one hundredths and express them as the total number of one hundredths and not to express them as tenths. Thus, a stone of 2.57 carats is said to weigh "two and fifty-seven hundredths carats." The decimal system of subdivision of the carat makes the figuring of values simpler where no tables are handy. Of course, new tables were at once prepared when the new carat was adopted and they afford a rapid means of ascertaining the value of a stone of any weight when the price per carat is known. Should it become necessary to convert the weight of a stone from its expression in the old system to that of the new, one need only get 1.02-1/2% of the old weight. (The old carat was approximately .205 g., while the new one is .200 g. Hence one old carat

.205 .102-1/2 is —— = ———— = 102-1/2% of a new one.) .200 .100

METHOD OF CONVERTING WEIGHTS. If the old weight has fractions these should first be changed to decimals for convenience. For example, suppose it is wished to change 2-1/4 1/16 old carats to metric carats. 1/4 = .25 and 1/16 = .0625. Hence 2-1/4 1/16 = 2.3125. Now get 102-1/2% of this: (2.3125 x 1.025 = 2.37 metric carats).

If, for any reason one should need to change from metric carats to old U. S. carats one should multiply by .9756

( .200 g. ) ( ———- = .9756 ) ( .205 g. )

As was said in Lesson XXV., pearls are sold by the pearl grain, which is arbitrarily fixed at 1/4 of a carat. With the change to the metric carat the pearl grain was correspondingly changed and its weight is now 1/4 of .200 g. = .05 g., as expressed in the metric system.



LESSON XXX

TARIFF LAWS ON PRECIOUS AND IMITATION STONES

Since it is necessary for a nation, as well as for an individual, to have an income, and since articles of luxury are more easily taxed than are those of necessity, the traffic in gems and their imitations has frequently been made a source of revenue to our government. Usually the per cent. charged as tariff has been comparatively low, especially upon very valuable gems, such as diamonds and pearls, for the reason that too high a tariff would tend to tempt unscrupulous dealers to smuggle such goods into the country without declaring them. When the margin of difference between the values, with and without the tariff, is kept small the temptation is but slight, when the danger of detection and the drastic nature of the usual punishment are taken into account. Rough stones have frequently been allowed to enter the country duty free because they were regarded as desirable raw materials which would afford employment to home industry.

The tariff laws of October 3, 1913, made, however, some sweeping changes in the policy of our government toward precious stones and as those laws are still in force (April 4, 1917) this lesson will attempt to set forth clearly the exact conditions under the present law.

Perhaps the paragraph of first importance to the trade is No. 357 which reads as follows.

"357. Diamonds and other precious stones, rough or uncut, and not advanced in condition or value from their natural state by cleaving, splitting, cutting, or other process, whether in their natural form or broken, and bort; any of the foregoing not set, and diamond dust, 10 per centum ad valorem; pearls and parts thereof, drilled or undrilled, but not set or strung; diamonds, coral, rubies, cameos, and other precious stones and semi-precious stones, cut but not set, and suitable for use in the manufacture of jewelry, 20 per centum ad valorem; imitation precious stones, including pearls and parts thereof, for use in the manufacture of jewelry, doublets, artificial, or so-called synthetic or reconstructed, pearls and parts thereof, rubies, or other precious stones, 20 per centum ad valorem."

It will be noticed that the chief changes over the previous law are first that which imposes a 10% duty on rough precious stones, which were formerly free of duty, and second the advance in the duty on cut diamonds and other cut stones from the former 10% to the present 20%.

This increase in the tariff was regarded as unwise by many conservative importers, as the temptation to defraud the government is made much greater than before. The change was even feared by honest dealers who were afraid that they could not successfully compete with dishonest importers who might smuggle gems into the country. In spite of a rather determined opposition the change was made and our most representative dealers have been making the best of the situation and have been doing all that they could to help prevent smuggling or at least reduce it to a minimum. Through their knowledge of the movements of diamond stocks and of prices they are able to detect any unduly large supply or any unwarranted lowness of price and thus to assist the government agents by directing investigation towards any dealer who seems to be enjoying immunity from the tariff.

The question of the status of Japanese cultured pearls has been settled as follows. Paragraph 357 (quoted above) is ruled to cover them and they are thus subject to a 20% ad valorem tax.

Carbonadoes—miners' diamonds—are free of duty, under paragraph 474. Crude minerals are also free of duty, paragraph 549. Paragraph 607 declares "Specimens of natural history and mineralogy" are free.

In case the owner is not prepared to pay the tax on imported merchandise the government holds the goods for a period of three years pending such payments.

In case an importer shows that imported merchandise was purchased at more than actual market value, he may deduct the difference at time of entry and pay duty only on the wholesale foreign market value, under Section III., paragraph 1.

On the other hand, if the examiner finds merchandise to be undervalued on the invoice, such merchandise is subject to additional penal duties, but in case of disagreement between the importer and the examiner as to the actual market value, appeal may be taken to the Customs Court.

Since the Philippine Islands are possessions of the United States, pearls from those islands may be admitted free of duty when the facts of their origin are certified to.

In the case of precious stones which had their origin in the United States, but which were exported and kept for a time abroad it has been ruled that such stones may be imported into the United States free of duty.

When precious or imitation precious stones are imported into the United States and subsequently mounted into jewelry which is then exported, the duty which was paid upon entry may be refunded less a deduction of 1%.

The author wishes to extend his thanks to Examiner W. B. Treadwell of New York, for his assistance in regard to the subject dealt with in this lesson.



BIBLIOGRAPHY

The student of gems will, of course, want to read many books on the subject and the following brief bibliography will enable the beginner to select his reading wisely from the start. Much more complete bibliographies will be found in some of the books listed here, one which is notably complete to date of publication is contained in Diamonds and Precious Stones, by Harry Emanuel, F.R.G.S., London, John Camden Hotten, 1867. This covers many languages.

The book which will probably be found most useful by those who have mastered this little text is the work by G. F. Herbert-Smith, to which frequent reference has been made at the close of many of our chapters. It is thoroughly scientific, yet understandable, and is very complete on the scientific side of the subject.

Gem-Stones, G. F. Herbert-Smith, Jas. Pott & Co., N. Y.

For another work and one which contains information of trade character as well as scientific information about gems see Precious Stones by W. R. Cattelle, J. B. Lippincott & Co., Phila., or see A Handbook of Precious Stones, by M. D. Rothschild, G. P. Putnam's Sons, N. Y.

Gems and Gem Minerals, by Oliver Cummings Farrington, A. W. Mumford, publisher, Chicago, 1903, is another good general work on gems. Its color plates of rough gem minerals are especially good.

Those who are especially interested in the diamond should see The Diamond by W. R. Cattelle, The John Lane Co., N. Y., which gives a good account of its subject and is rich in commercial information, or Diamonds: A Study of the Factors which Govern their Value, by the present author, G. P. Putnam's Sons, N. Y., 1914.

Sir Wm. Crook's, the Diamond, Harper & Bros., N. Y., is very interesting, especially in its account of the author's visits to the S. African mines.

Students of pearls will find The Book of the Pearl, by Dr. Geo. F. Kunz and Dr. Chas. Stevenson, Century Co., N. Y., very complete. A smaller work, yet a good one, on pearls is The Pearl by W. R. Cattelle, J. B. Lippincott & Co., Phila., 1907. This book is strong on the commercial side.

An older work is Pearls and Pearling by D. Edwin Streeter, Geo. Bell & Co., London.

A work on gems and gem-cutting by a practical cutter is The Gem Cutter's Craft, by Leopold Claremont, Geo. Bell & Sons, London, but it should be said that very few trade secrets will be found exposed in the book.

On the subject of scientific precious stones The Production and Identification of Artificial Precious Stones, by Noel Heaton, B.Sc., F.C.S., read before the Royal Society of Arts, Apr. 26, 1911, is very fine. It may be had in the annual Report of the Smithsonian Institution for 1911, p. 217. It gives one of the best accounts to be had of the history of the artificial production of precious stones, especially of the corundum gems. It also contains a splendid account of how to distinguish scientific from natural gems.

Most students of gems will need to refer frequently to some good text-book of mineralogy. Although old, Dana's Mineralogy is still a standard work. A newer book and one of a more popular nature is L. P. Gratacap's The Popular Guide to Minerals, D. Van Nostrand & Co., N. Y.

Among larger and more expensive books on gems may be mentioned Precious Stones, by Dr. Max Bauer. This is an English translation of a German work which is a classic in its field. As it is now out of print in its English edition, a somewhat detailed account of its character may be of value to those who may be inclined to go to the effort to seek a copy at a public library or perhaps to purchase one through second-hand book stores.

A popular account of their characters, occurrence and applications, with an introduction to their determination, for mineralogists, lapidaries, jewelers, etc., with an appendix on pearls and coral, by Dr. Max Bauer, Privy Councillor, professor in the Union of Marburg. Translated from the German by L. J. Spencer, M.A. (Cantab.), F.G.S., assistant in the mineral department of the British Museum. With twenty plates and ninety-four figures in the text. London, Chas. Griffin & Co., Ltd.: Phila., J. B. Lippincott Co., 1904.

The book is a large one, xv + 627 pages, and is divided into three parts with an appendix on pearls and coral.

Part I. deals with the general characters of precious stones.

1. Natural characters and occurrence. 2. Applications of Precious Stones. 3. Classification of Precious Stones. 106 pages.

Part II. Systematic Description of Precious Stones, Diamond, Corundum Gems, Spinel, etc. 450 pages.

Part III. Determination and Distinguishing of Precious Stones. 20 pages.

Appendix, 26 pages. Pearls and Coral.

Bauer is exhaustive in his descriptions of the more important precious stones and he also describes briefly very many little known and little used gem minerals.

On forms of cutting he is old-fashioned.

First 68 pages given to explanation of characters used in identifying stones. Good.

On the Process of Cutting. Pages 79-87. Good account. More practical than most books give.

Careful accounts of occurrence of precious stones with maps.

Character of the occurrence of diamond in India, Brazil, and Africa, quite in detail.

The student who wishes to master the subject of gems cannot afford to neglect Bauer.

For those who read French, the latest, the most complete and thorough book on gems is Jean Escard's Les Pierres Precieuses, H. Dunod et E. Pinat, Paris, 1914.

It is a large and finely illustrated work.

The author has really outdone Bauer. The detail in regard to diamonds especially is very fine. Even the use of diamonds in mechanical ways is very completely gone into and also details in regard to cutting diamonds are very completely given. It is to be hoped that an English translation will soon become available.

Another large and thoroughgoing work is Gardner F. Williams' The Diamond Mines of South Africa, MacMillan, N. Y.

Dr. Geo. F. Kunz's Gems and Precious Stones of North America, The Sci. Pub. Co., N. Y., 1890, 336 pages, 8 colored plates (excellent ones too), many engravings, is a very complete account of all published finds of precious stones in the United States, Canada, and Mexico, giving a popular description of their value, history, archeology, and of the collections in which they exist, also a chapter on pearls and on remarkable foreign gems owned in the United States. Many rare and little known semi-precious stones are described here. Dr. Kunz is also the author of several more recent gem books notably The Magic of Jewels and Charms and The Curious Lore of Precious Stones, Lippincott, Phila.

Among books on engraved gems is the old Hand Book of Gem Engraving by C. W. King; Bell & Daldy, London, 1866, and one by Duffield Osborne; Henry Holt & Co., N. Y. Another book on this subject is Engraved Gems by Maxwell Somerville; Drexel Biddle, Phila.

For those who wish still further references the following older works will prove interesting.

Precious Stones, by W. R. Cattelle; Lippincott, Phila. Precious Stones, by W. Goodchild; D. Van Nostrand & Co., N. Y.

Julius Wodiska, of New York, has also written an interesting work on precious stones, A Book of Precious Stones, Putnam's, 1907.

Still older works are Precious Stones and Gems by Edwin W. Streeter; Chapman & Hall, London, 1877. This is a book of 264 pages with nine illustrations. It contains much of value and was unsurpassed in its day. Its first-hand accounts of numerous important, even celebrated diamonds and other precious stones will always make it valuable to the student of gems.

Another book by the same author is The Great Diamonds of the World; Geo. Bell & Sons, London, 1882; 321 pages. Not illustrated. Its title adequately describes its contents. It is an excellent work. The author even traveled in India tracing the history of some of the famous diamonds that he describes.

Diamonds and Precious Stones, by Louis Dieulafait published in its English translation by Scribner, Armstrong & Co., N. Y., 1874, is another old but interesting work. It has 292 pages and 126 engravings on wood. It gives a fine account of diamond cutting as practiced at that time. There is also an excellent history of the production of artificial precious stones to that date.

The Natural History of Precious Stones and of the Precious Metals by C. W. King, M.A., Bell & Daldy, London, 1870, is rich in references to classical literature.

One or two interesting monographs on precious stones have been written and The Tourmaline, by Augustus C. Hamlin is one of these. Mr. Hamlin became interested in gems because of his accidental discovery of some of the fine tourmalines of Maine. His Leisure Hours among the Gems is also very readable. Jas. R. Osgood & Co., Boston, 1884. It deals especially with diamond, emerald, opal, and sapphire. He gives a good account of American finds of diamond, and a long account of European regalia. The book is full of interesting comment and contains many references to older authors.

The Tears of the Heliades or Amber as a Gem, by W. Arnold Buffum, G. P. Putnam's Sons, N. Y., 1900, is as its name implies a monograph on amber.

A good work on the history of precious stones and on historical-jewels is Gems and Jewels by Madame de Barrera; Richard Bentley, London, 1860. It deals also with the geography of gem sources. An interesting chapter on "Great Jewel Robberies" is also included.

Of still greater age but of great interest is John Mawe's old work, on diamonds and precious stones. In it the author discusses in a conversational style that is very attractive much of the gem lore of his day and shows a profound knowledge of his subject, a knowledge that was evidently first hand and practical, A Treatise on Diamonds and Precious Stones, by John Mawe, London. 2nd edition. Printed for and sold by the author.

For readers of French, Jean Baptiste Tavernier's Voyages, in six volumes, will be vastly interesting. Tavernier made six journeys to India and the East between 1640 and 1680 as a gem merchant during which time he purchased and brought back to Europe many celebrated gems including the famous French blue diamond which he sold to Louis XIV. and which was stolen at the robbery of the Garde Meuble during the French Revolution. Tavernier describes these famous stones and many others that he was privileged to inspect in the treasuries of the Grand Mogul. He also describes interestingly and at great length the curious manners and customs of the people of the East. Les Six Voyages de Jean Baptiste Tavernier, etc., Nouvelle edition, Rouen, 1724.

Pliny's Natural History, to go much further back, is full of references to gems, and gem students should run through it (it is to be had in English translation) for such interesting bits as that in which he describes the belief that quartz crystal results from the effect of very great cold upon ice, a belief which Pliny himself is careful not to subscribe to. He contents himself with relating what others believe in this regard.

Both the Hebrew scriptures and the New Testament afford many references to gems with which the eager student of the subject should be familiar. "She is more precious than rubies" (referring to wisdom) is but one of these.

In conclusion the author hopes that this little text may lead a few to pursue further this most fascinating theme and that the pursuit may bring much of pleasure as well as of profit.



INDEX

Absorption, 15

Adamantine luster, 40, 41

Agate, 128, 138, 172, 197

Alexandrite, 140

Almandite (see Garnet)

Altered stones, 247-249, 250-257

Amazonite, 176

Amethyst, 94, 170, 195, 196

Aquamarine, 143, 189

Azurite, 132, 148, 177, 199

Balances, Care and use of, 283-293

Beryl, 84, 143, 190

Bibliography, 301

Bloodstone, 172

Blue diamonds, 91

Blue-white diamonds, 91

Brazilian diamonds, 182

Brilliancy, 203

Brilliant cut stones, 233

Brilliant, Theory of the, 205

Brittleness of gems, 119

Brown stones, 95

Bubbles in gems, 103

Bubbles in glass, 81

Bubbles in scientific stones, 103

Burmah rubies, 154

Cabochons, 45, 216, 227

Carbon, 136

Carborundum, 54, 55, 56

Carnelian, 128, 138, 172

Cat's-eye, 44-46, 138, 171

Chalcedony, 138

Chrysoberyl, 45, 85, 122, 140, 157, 188

Chrysoberyl cat's-eye, 45, 46, 85, 188

Chrysolite, 176

"Cinnamon stone," 144

Citrine quartz, 161, 171, 195, 196

Cleaving of diamonds, 208

Cleaving of precious stones, 213

Color, cause of, in minerals, 15

Color of gems, 66-92

Colorless stones, 97

Corundum gems, 68-70, 73, 101, 121, 134, 137

Corundum gems, defects of, 101

Cultured pearls, 277-279

Cutting of diamonds, 209

Cutting of precious stones, 201-226

Demantoid garnet, 62, 64, 82, 130, 144, 169, 193

Density of minerals, 23

Diamonds, 61, 73, 91, 120, 134, 151-153, 179-186

Dichroism, 15-22, 113

Dichroscope, the, 17-20

Dispersion, 60-65

Double refraction, 5

Doublets, 41, 241-246

Emerald, 75-82, 143, 164, 189

Emerald, wearing qualities of, 109

Epidote, 9

Extraordinary ray, 16

Fancy diamonds, 91, 151

"Fire," cause of, 207

Forms of precious stones, 227-236

Garnet, 69, 82, 96, 130, 143, 144, 167-170, 192-194

Garnet, Almandite, 143, 168, 193

Garnet, Andradite, 82, 130, 144, 169, 193

Garnet, Demantoid, 62, 64, 82, 130, 144, 169, 193

Garnet, Pyrope, 144, 168, 192, 193

Glass, 62, 142

Glass imitations, 81, 237-249

"Golcondas," 180

"Grain base," price of pearls per, 271

Hardness, 47-54, 55-59, 113

Hardness and wearing qualities, 119-132

Hardness, Mohs's scale of, 48-51

Hardness, table of, 54

Hardness, test of, 51-54, 58

"Heliodor," 165

"Hope Blue" diamond, 91

Hyacinth, 166

Imitations of precious stones, 237-249

Imitations of pearls, 277-282

Imperfections, 111

Imperfections in corundum gems, 101

Imperfections in glass, 81

Imperfections in scientific stones, 104

Jacinth, 166

Jade, 128, 147, 175, 197

Jadeite, 128, 197

Jargoons, 166

Jasper, 128, 172

Kunzite, 195

Lapis lazuli, 132, 177, 199

Labradorite, 176

Luster, 38-42

"Make" of diamonds, 205-207

"Make" of precious stones, 220

Malachite, 132, 148, 177, 199

Metallic oxides, 137

Mineral species, 133-148

"Mixed cut" stones, 236

Mohs's scale of hardness, 48-51

Moonstone, 44, 45, 131, 146, 176, 198

Morganite, 165

"Nacre," 280

Naming precious stones, 149-163, 164-178

Nephrite, 129, 197

Occurrence of precious stones, 179-200

"Olivine" (see Demantoid Garnet)

Olivine, 83, 176

Onyx, 172

Opal, 44, 131, 139, 173

Ordinary ray, 16

"Orient" of pearls, 261

"Oriental" stones, 84, 156

"Paste" gems, 142, 237-241

Pearls, 258-276

"Peeling" pearls, 265

Peridot, 8, 130, 176, 198

Pink stones, 93

"Pinked" topaz, 250

Plasma, 172

Polishing of diamonds, 210

Polishing of precious stones, 218

Prase, 138, 172

Properties, definition of, 1

Purple stones, 94

Quartz, aventurine, 171

Quartz, citrine, 161, 171, 195, 196

Quartz gems, 45, 127, 171, 195, 197

Reflection, total, 204

Refraction, 4

Refraction, double, 8-13

Refraction, double, test for, 10, 112

Refractometer, 5

Rhodolite garnet, 168

"Roman" pearls, 279

Rose cut stones, 231

Rose quartz, 171, 197

Rubellite, 93

Ruby, 12, 67, 69, 153, 154, 186

Ruby, scientific, 99-108

Sapphires, 63, 87, 88, 155, 187

Sard, 172

Sardonyx, 172

Scientific stones, 99-108

Scientific stones, defects in, 104

Scientific stones, tests for, 99-108

Siam rubies, 154

Silicates, 141

"Silk" in rubies, 117

Slitting of precious stones, 213

South African diamonds, 184

Specific gravity, 23-37, 114

Sphene, 9, 62, 64

Spinels, 71, 90, 123, 140, 158, 188

Spodumene, 95, 170, 195

Star stones, 44, 46, 157

"Step cut" stones, 235

Structure of pearls, 258

Table, of hardness, 54

Table of refraction, 12-13

Table of specific gravity, 29

Tariff laws, 294-299

Test for double refraction, 10

Testing hardness, 51-54, 58

Testing imitations of pearls, 281

Testing unknown gems, 109-118

Tiger's-eye, 45, 138, 171

Topaz, 67, 73, 91, 124, 145, 159, 189

Toughness in stones, 119

Tourmaline, 72, 77, 79-81, 96, 146, 167, 194

"Triplets," 79, 246

Turquoise, 130, 148, 198

Unit of weight, 289

Variscite, 148

Vitreous luster, 41

Wearing qualities of gems, 119

Zircon, 9, 62, 72, 92, 97, 125, 147, 166, 191



Diamonds

A Study of the Factors that Govern their Value

By

Frank B. Wade

"I shall speak a little more of the diamonds, that they who know them not may not be deceived by chapmen who go through the country selling them, for whoever will buy the diamond, it is needful that he know them, ..."—Chap. XIV., The Voyages and Travels of Sir John Maundeville.

Table of Contents

I.—Colour. II.—Flaws. III.—"Make." IV.—Repairing and Recutting. V.—Mounting. VI.—Buying the Engagement Ring.

* * * * *

G. P. Putnam's Sons

New York London



A Book of Precious Stones

The Identification of Gems and Gem Minerals and an Account of Their Scientific, Commercial, Artistic, and Historical Aspects

By Julius Wodiska

8vo. With 33 Full-page Illustrations and 4 Colored Plates

A description, in altogether a new fashion, of gems and gem minerals, their nature and history, comprehensible to every reader, and of prime value to students and to jewelers.

The general reader will enjoy the simple descriptions of the origin, development, and treatment of the diamond, sapphire, and other precious stones, as well as of the beautiful semi-precious stones. Just enough of the technical has been provided to make the new gem book a vade mecum for students of gem minerals and for the army of jewelers in the United States, as well as their fellow-craftsmen and merchants in all English-speaking places. The art and industry of mounting gems is somewhat elaborately covered, especially as exemplified in the work of students at technical schools and the many unattached workers in jewelry designing and making who form a part of the Arts and Crafts movement. Some of the quaint superstitions about gems in the chapter on folklore have a curious interest. The author takes cognizance of the public desire nowadays for the novel and uncommon in gems, and shows that prospectors, gem miners, mineralogists, and jewelers are co-operating to greatly lengthen the lists of popular semi-precious stones. A chapter is devoted to collections of gems in museums.

* * * * *

G. P. Putnam's Sons

New York London



* * * * *



Transcriber's Note:

Inconsistent hyphenation and spellings have been standardised, although consistent variants remain as printed. Minor typographical errors have been corrected without note, whilst significant changes are listed below.

p. 13, 'indentity' amended to identity: '... of unknown identity comes along ...';

p. 20, 'dischroism' amended to dichroism: '... but shows hardly any dichroism.';

p. 67, 'quart' amended to quartz: '... (quartz topaz) ...';

p. 118, 'Saphire d'eau' amended to Saphir d'eau;

pp. 140, 143, 'berylium' amended to beryllium;

pp. 148, 318, 'Varicite' amended to Variscite;

p. 157, 'Csar' amended to Czar: '... Czar Alexander II., in whose ...';

p. 167, 'rubelite' amended to rubellite: '... sometimes called "rubellite," and white ...';

p. 190, 'Minas Garaes' amended to Minas Geraes;

p. 199, 'Khorassan' amended to Khorasan: '... province of Khorasan in Persia ...';

p. 227, 'caboch' amended to caboche;

p. 258, 'uniomargarifer' amended to Unio margaritifera;

p. 298, 'mechandise' amended to merchandise: '... tax on imported merchandise ...';

p. 301, 'Emanual' amended to Emanuel: '... Diamonds and Precious Stones, by Harry Emanuel ...';

p. 301, 'Hatten' amended to Hotten: '... John Camden Hotten ...';

p. 308, 'Streetor' amended to Streeter: 'Precious Stones and Gems by Edwin W. Streeter ...';

p. 314, 'Epidot' amended to Epidote.

THE END