Precious Metals

The article Gold (Vol. 12, p. 192) is a thorough workshop treatise, as well as a detailed study of existing mines and of the influence their production exerts upon the “price,” if it can be so called, of a metal which is its own standard of value. Silver (Vol. 25, p. 112) and Platinum (Vol. 21, p. 805) are treated with similar comprehensiveness. The articles Alloys (Vol. 1, p. 704), Assaying (Vol. 2, p. 776), Metal (Vol. 18, p. 198), Metallography (Vol. 18, p. 202), and Metallurgy (Vol. 18, p. 203), all by noted authorities, are full of information useful to the jeweller. Metal-Work (Vol. 18, p. 205), fully illustrated, incidentally touches upon the art of the silver- and gold-smith; and this branch of the subject is also treated in such articles as Plate (Vol. 21, p. 789), with over 30 typical illustrations—a most interesting historical account, by several well-known experts, of works in gold and silver which belong to any class other than those of personal ornament and coins; and Drinking Vessels (Vol. 8, p. 580), illustrated, by Dr. Charles H. Read of the British Museum, which discusses gold and silver cups. Mention must also be made of the description of American work in precious metals before the time of Christopher Columbus, in the section Archaeology of the article America (Vol. 1, p. 812), by the late Dr. O. T. Mason, of the National Museum, Washington; also of Mexico, Ancient Civilization (Vol. 18, p. 335), by the famous ethnologists, Dr. E. B. Tylor of Oxford and Dr. Walter Lehmann, of the Royal Ethnographical Museum, Munich; Egypt, Ancient Art (Vol. 9, p. 73), by W. M. Flinders Petrie; Greek Art (Vol. 12, p. 470), illustrated, by Dr. Percy Gardner, of Oxford; Roman Art, Work in Precious Metals (Vol. 23, p. 483), illustrated, by H. Stuart Jones, director of the British School at Rome; Japan, Art, Sculpture and Carving (Vol. 15, p. 176), by Capt. Frank Brinkley, author of A History of the Japanese People; and China, Bronzes (Vol. 6, p. 215), by C. J. Holmes, formerly Slade professor of fine art at Oxford.

Filigree (Vol. 10, p. 343) describes the delicate jewel work of twisted gold and silver threads, and also the “granulated” work which consists of minute globules of gold soldered to form patterns on a metal surface. In India the filigree worker has retained the patterns used by the ancient Greeks and works in the same way they did. Wandering workmen are given so much gold, coined or rough. This is weighed, heated and beaten into wire, and worked in the courtyard or on the verandah of the customer’s house. The worker reweighs the complete work when finished and is paid at a specified rate for his labor. Repoussé (Vol. 23, p. 108), by M. H. Spielmann, editor Magazine of Art; Chasing (Vol. 5, p. 956) and Inlaying (Vol. 14, p. 574) are other articles dealing with certain processes in jewel work. The jeweller also must not overlook two superb articles, Medal (Vol. 18, p. 1), illustrated, by M. H. Spielmann, and Numismatics (Vol. 19, p. 869), which is by three specialists, and is most fully illustrated by designs inviting practical use. Enamel (Vol. 9, p. 362), illustrated, by Alexander Fisher, author of The Art of Enamelling on Metals, goes very fully and practically into this interesting subject, which is further discussed in Japan, Cloisonné Enamel (Vol. 15, p. 189). Mosaic (Vol. 18, p. 883), illustrated, by Professor Middleton and H. Stuart Jones, deals in part with the ornamentation of jewelry by this method. In Brazing and Soldering (Vol. 4, p. 463) the composition of silver solder used for jewelry is described, and in Cement there is an account of Jeweller’s or Armenian Cement (Vol. 5, p. 659).

Precious Stones

The article Gem treats the subject in two sections, of which the first (Vol. 11, p. 560), by F. W. Rudler, of the Museum of Practical Geology, London, deals with Mineralogy and General Properties. Here are discussed hardness, specific gravity, crystaline forms and cleavage, colour, refraction, chemical composition, etc., and there is an interesting section on superstitions in regard to gems, the medical and magical powers with which they were reputed to be endowed. These beliefs are very remarkable, and it has even been suggested by archaeologists that jewelry did not have its origin so much in a love for personal decoration, as in the belief that the objects used possessed magical virtue. The article Mineralogy (Vol. 18, p. 509), by L. J. Spencer, of the British Museum, and editor of the Mineralogical Magazine, will be found especially valuable for reference in the workshop. It gives, among other things, the scale of hardness, and nomenclature and classification of minerals. The crystal formation of gems as well as their optical properties—characteristics by which the genuineness of precious stones may be tested—are discussed and explained in the article Crystallography (Vol. 7, p. 569), with over 100 illustrations, also by L. J. Spencer. The cutting of gem stones is treated under Lapidary and Gem Cutting (Vol. 16, p. 195), by Dr. George F. Kunz, the famous gem expert to Tiffany & Co., New York,—an article of uncommon historical interest and practical value, in which diamond cutting is considered at much length.

The second section of the article Gem, Gems in Art (Vol. 11, p. 562), by Dr. A. S. Murray, the famous British archaeologist, and A. H. Smith, gives an account of precious stones engraved with designs. The illustrations show more than 90 examples, including Cretan and Mycenaean intaglios, Greek, Phœnician and Etruscan scarabs and scarabæoids, cameos, seals, Oriental, Christian, and modern gems. This subject is further discussed in separate articles, such as Scarab (Vol. 24, p. 301), by Dr. F. Ll. Griffith, the Egyptologist, an account of the designs which, originating in Egypt during the Fourth Dynasty, have exercised a lasting influence on the design and shape of gems; Cameo (Vol. 5, p. 104), Intaglio (Vol. 14, p. 680), Seals (Vol. 24, p. 539), illustrated, by Sir E. Maunde Thompson, formerly principal librarian, British Museum, as well as in the articles on ancient and Oriental civilizations, already mentioned.

Synthetic Stones

The artificial duplication of certain gems by chemical processes which yield products identical in composition and physical properties with the natural stones is a subject of growing importance to the jeweller, and the latest developments are described in Gem, Artificial (Vol. 11, p. 569), by Sir William Crookes. This famous chemist and authority on precious stones does not hesitate to declare that although the artificial diamonds so far produced have been microscopic in size, scientists have now found the right method and that “there is no reason to doubt that, working on a larger scale, larger diamonds will result.” The artificial production of rubies, sapphires, Oriental emeralds, amethysts, topazes and zircons is also discussed. Descriptions of the several gem stones are found under their respective headings, for example Diamond (Vol. 8, p. 158), illustrated, by H. A. Miers, principal of the University of London, and former editor of the Mineralogical Magazine. Here are given its scientific characters, its uses (especially for faceting softer precious stones), distribution, and mining, and the wonderful history of the most famous diamonds of the world. Ruby (Vol. 23, p. 812), the most valued of gem stones, is often called “Oriental ruby” to distinguish it from Spinel (Vol. 25, p. 684), an aluminate stone of inferior hardness, density and value. It is interesting to note that many historic stones described as monster rubies were really spinels. The great ruby set in the Maltese Cross in front of the Imperial State Crown of England is a spinel. Sapphire (Vol. 24, p. 201) was known to the Greeks as “hyacinthus,” and the present name was formerly applied to lapis lazuli. Asteria or Star Stone (Vol. 2, p. 792) tells how the luminous star comes to be seen in sapphires, rubies and topazes. The name Emerald (Vol. 9, p. 332) is used for a number of stones, of which the most valued is not a true emerald at all; see Corundum (Vol. 7, p. 207). The same is true of the Topaz (Vol. 27, p. 48), the more prized Oriental topaz being a yellow corundum, harder and denser than the stone from which it takes its name. “Scotch” or “Spanish” topazes are yellow or smoke-tinted quartz, or cairngorm. The Amethyst (Vol. 1, p. 852) is violet or purple quartz, and the sapphire of a purple colour is often called an Oriental amethyst. The many varieties of the beautiful Zircon (Vol. 28, p. 989), such as Hyacinth (Vol. 14, p. 25) and Jargoon (Vol. 15, p. 276) are carefully described and distinguished. These valuable articles on the precious stones have been contributed by F. W. Rudler, of the Museum of Practical Geology, London. Pearl (Vol. 21, p. 24) discusses the results of the latest researches on the cause of pearl formation, and gives a graphic account of pearl-fishing.

Semi-Precious Stones

The material in the Britannica on the semi-precious stones is as complete. There are many articles, specified in the list at the end of this chapter. Alexandrite (Vol. 1, p. 576) is remarkable for its property of appearing dark green by daylight, and red by candle-light, which makes it especially popular in Russia where green and red are the military colors; Chrysoberyl (Vol. 6, p. 320), of which alexandrite is a variety; Chrysolite (Vol. 6, p, 320), often mistaken for chrysoberyl; Peridot (Vol. 21, p. 147), like chrysolite, a variety of olivine; Beryl (Vol. 3, p. 817), much prized by the ancients as a gem stone, and of which the Emerald (see above) and the Aquamarine (Vol. 2, p. 237) are the chief “precious” varieties; Tourmaline (Vol. 27, p 103), the remarkable stone of as much interest to the physicist as to the jeweller, on account of its optical and electrical properties; and Rubellite (Vol. 23, p. 804), its much prized red variety Garnet (Vol. 11, p. 470), together with Almandine (Vol. 1, p. 712), which, when cut with a convex face is known as carbuncle; Cinnamon-Stone (Vol. 6, p. 376), the light red garnet, so easily mistaken for a variety of zircon (the article tells how to distinguish them); Demantoid (Vol. 7, p. 979), the green garnet from the Urals, and Pyrope (Vol. 22, p. 695), usually known as Bohemian garnet; Jade (Vol. 15, p. 122), which occupies in China the highest place as a jewel, and whose many varieties are here clearly distinguished; Jet (Vol. 15, p. 358); Haematite (Vol. 12, p. 804); Moonstone (Vol. 18, p. 807); Cat’s-Eye (Vol. 5, p. 537), a term applied to several distinct minerals of which Crocidolite (Vol. 7, p. 477) has recently become very popular; Opal (Vol. 20, p. 120), an article in which the brilliant flashes of colour in this stone are explained; Quartz (Vol. 22, p. 715), with its many ornamental varieties such as Agate (Vol. 1, p. 368), Amethyst (Vol. 1, p. 852), Aventurine (Vol. 3, p. 54), Bloodstone (Vol. 4, p. 85), Cairngorm (Vol. 4, p. 952), Carnelian (Vol. 5, p. 365), Chalcedony (Vol. 5, p. 803), Chrysoprase (Vol. 6, p. 320), Heliotrope (Vol. 13, p. 232), Mocha Stone (Vol. 18, p. 637), Onyx (Vol. 20, p. 118), Rock-Crystal (Vol. 23, p. 433), Sard (Vol. 24, p. 209), and Sardonyx (Vol. 24, p. 2.18).