INGENUITY AND LUXURY 



how soon diamonds of marketable size may be pro- 

 duced; but in the mean time the similar problem of 

 manufacturing relatively large gems of other kinds 

 rubies, sapphires, oriental emeralds, the oriental 

 amethyst, and the oriental topaz has yielded its 

 full secrets to science. Artificial gems of these various 

 sorts are already on the market, in actual competition 

 with the natural gems, the properties of which they 

 duplicate rather than imitate. 



Just as the brilliant diamond is only a particular 

 state of so familiar and inexpensive a substance as 

 carbon, so these sister gems some of them even ex- 

 ceeding the diamond in value weight for weight have 

 for their basis, as already noted, the metal aluminum, 

 which, as is well known, is a most familiar constituent 

 of the soil everywhere. They are, in short, merely 

 crystalline forms of the clayey earth, alumina a 

 compound of aluminum and oxygen. If no coloring 

 matter is present, this crystal is called a white sapphire. 

 Usually, however, a trace of some chromium or cobalt 

 salt is present, and then the gem becomes a true sapphire, 

 a ruby, an amethyst, an oriental emerald, or a topaz, 

 according to color. The presence of a small percent- 

 age of magnesium and of sodium may greatly mar the 

 hardness and hence the real value of the stone, without 

 greatly altering its appearance to casual inspection. 

 A large proportion of the alleged rubies on the market, 

 for example, have this defect, and would not be classed 

 by legitimate dealers as true rubies, but as "spinel" 

 or "balas" rubies. The ordinary amethyst of the mar- 

 ket bears even less resemblance to the true oriental 



