CATALOGUK <>K GKMS. 555 



Sophistications iiu'ludo suhstitutos puiv and simple, such as substi- 

 tutino- (juartz. whitc^ topaz, zircon, or other colorless stones for the 

 diamond, and so on. Ov the stone may be treated with chemicals or 

 heat to heiuhten or change its color. Topaz, sapphire, and other 

 stones may have their color removed or their brilliancy increased by 

 heatino-. 'I'ho color of the wine-yellow Brazilian topaz is changed to 

 a rose pink by heat; an oil' colored or spotted diamond is made to 

 appear whiter and more brilliant by the same means. The color of 

 the cairngorm, citrine quartz, and other stones is" altered and improved 

 in a similar manner. The color of the turquoise is deepened and its 

 permanency increased bj^ treating it with solutions of certain chemicals. 

 The colors of agates, chalcedony, ch^3^soprase, etc.. may be changed 

 or improved with the aid of dyes and chemicals, and in a similar man- 

 ner imitation moss agates may be manufactured from colorless chalce- 

 dony. An off colored diamond may be given a wash of aniline blue, 

 and the result is apparently a stone of good water as long as the wash 

 remains. The interior of a setting may be backed, painted, or enam- 

 eled ; in fact, there are a hundred or more methods by means of which 

 a tint is improved or given a beauty and depth not inherent in the 

 specimen. 



A sharp distinction is to be drawn between the imitation of a gem 

 stone and its formation l)y artificial methods. The imitation gem only 

 simulates the natural su])stance; the artificial gem is identical with it in 

 all its chemical and physical properties. Until recently the laborator}'^ 

 gem was hardly more than a curiosit}", though its synthesis has 

 undoubtedly been of value from a theoretical standpoint. Examples 

 of this class are to be found in the diamond as produced by Moissan in 

 the electric furnace and the synthesis of spinel and chrysoberyl b\' 

 Ebelmen from mixtures of alumina and glucina, respectively, using 

 ])oric acid at very high temperatures as a solvent. H^^drotluoric acid 

 and silicon fluoride have also been used to induce combination between 

 silica and other oxides. In this manner topaz, a complex fluo-silicate, 

 has been made by the action of fluoride of silicon upon alumina. 



The minerals thus formed have usually been verv small and of no 

 commercial value. Quite recently, however, rubies have been pro- 

 duced by the fusion of alumina with traces of chromium oxide in the 

 electric furnace, and the art has progressed to such an extent that the 

 product is now on the market for sale as watch jewels. The electric 

 furnace has also produced another product which, while strictly speak- 

 ing, not a synthetic gem, yet is essentially an artificial one. Imperfect 

 rubies, chips, and small stones are fused in the furnace together with 

 the addition of a small amount of coloring oxide such as chromium. 

 The fused product is then cut and polished, and the result is a ruby of 

 good color and fairlv large size. Emeralds and other colored stones 

 have been made in the same way, and so promising has the industry 



