ARTIFICIAL GEMS. In recent years the produc tion of gems by artificial means has been at tempted by chemists, and the literature of the manufacture of diamonds by heat is extensive; but as yet no large stones have been obtained. In 1880 Hanney, in some experiments made to produce diamonds artificially, obtained some hard particles which experts declared to be diamonds; but as the expense was five times the value of the natural stones, the process wa3 not a commercial success. Later, by means of the electric furnace, Moissan (q.v.) not only succeeded in prepar ing minute diamonds, but Os') accomplished the synthesis of other gems by means of the high temperatures obtained by him. Sainte-Claire Devine and Caron, in 1858, described various processes by which they obtained small crystals of white and green corundum, rubies, sapphires, etc. Fr6my and Feil, in 1877, were able to pro duce crystals that possessed the form of natural rubies and easily scratched topaz. By adding cobalt oxide before fusion, they obtained sap phires. In 1888 Fr6my and Verneuil announced their successful preparation of artificial rubies by heating to redness a mixture of barium fluoride and alumina containing a trace of potas sium bichromate. Ebelmen, from the mixtures of oxides of aluminum and glucinum, using boracic acid as a solvent, succeeded in obtain ing (at a very high temperature) artificial spinels and chrysoberyls. Hydrofluoric acid and silicon fluoride have also been used to induce combination between silica and other oxides. By this method topaz, which is a complex fluosili cate, has been made by the action of fluoride of silicon upon alumina. More recently the manu
facture of artificial rubies has been successfully accomplished in Paris on a large scale, and gems having a pure transparency, with the rich red color of the pigeon's-blood ruby, have been pro duced and placed on the market. Crystals of over 40 carats in weight, valued as high as $25, 000 each, are said to have been recovered.
The electric furnace has yielded another prod uct which, while strictly speaking it is not a syn thetic gem, is nevertheless essentially an artifi cial gem. Imperfect rubies, chips, and small stones are fused in the furnace, together with a small amount of coloring oxide, such as that of chromium. The fused product is then cut and polished, and the result is a gem of good color and fairly large size. Emeralds and other colored stones have been made by this method, and so important has the industry become that the courts have been called upon to decide what constitutes an artificial gem. A decision which has applied to the rubies was obtained, in which it was decided that that word applied only to the red-colored corundum or anhydrous alumi num oxide that also occurs already formed in nature.
Consult: De Fontenelle and Malepeyre, Glass, Artificial Stones, etc. (Paris, 1854) ; Streeter, Precious Stones and Gems (London, 1879) ; Tas sin, Descriptive Catalogue of the Collections of Gems in the United States National Museum (Washington, 1902).