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Ch. 27: Imitation Gems

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Imitations and Reconstruction 217
magnifying glass, the gem stones thus produced —that are worthy of notice—contain the same component parts in their proportions that the natural stones do, and equal them in the prin­cipal characteristics of hardness, specific grav­ity, and refractiveness. To quote Wirt Tassin:
*A sharp distinction is to be drawn between the imitation of a gem stone and its formation by artificial methods. The imitation gem only sim­ulates the natural substance; the artificial gem is identical with it in all its chemical and physical properties. Until recently the laboratory gem was hardly more than a curiosity, although its synthesis has undoubtedly been of value from the 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 chryso-beryl by Ebelmen from mixtures of alumina and glucina, respectively, using boric acid at very high temperature as a solvent. Hydrofluoric 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 very small and of no commercial value. Quite recently, however, rubies have been produced by the fusion of alumina with a trace of chromium oxide in the electric furnace, and the art has progressed to such an extent that the product is now on the market
Ch. 27: Imitation Gems Page of 451 Ch. 27: Imitation Gems
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