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Ch. 5: Gem History Properties

Ch. 5: Gem History Properties Page of 515 Ch. 5: Gem History Properties Text size:minus plus Restore normal size   Mail page  Print this page
IMITATIONS OF GEMS.                                   17*3
fraction of light. He accomplished the task so for that in many instances, either all three, or one or the other of his objects, were attained. The strass is composed of silex (quartz, flint, or pure sand), potash, borax, red lead, and sometimes arsenic. To 300 parts of silex add 96 parts pot­ash, 27 parts borax (prepared from the boracic acid), and 514 parts of white lead, and 1 part arsenic; or according to another method, mix 7 ounces and 24 grains of quartz with 10 ounces and 7 1/2 drachms red lead, 3 ounces and 6 drachms pure pearlashes, 3 27/30 drachms borax, and 12 grains arsenic. The mixture is put into a covered Hessian cruci­ble, and kept at a great heat in a pottery furnace for twenty-four hours. The longer the mass is kept in a fluid state the harder and clearer it will be when turned out and cooled. This discolored strass is used by the lapidaries for imitating the" diamond, rock-crystal, and white topaz.
For imitating the colored gems various colored ingre­dients are employed. To obtain that intensity-of color ap­proaching nearest to the original gem, it is experience alone which can guide the manufacturer. In order to imi­tate the uniform and intense colors, the strass coloring in­gredients are to be of the finest powder, and very intimately mixed; the mass is then to be exposed to a very great heat, and in that state left for nearly thirty hours, so that the cooling may be gradual. Numerous establishments in Germany and France are now engaged in the manufacture of the strass and colored pastes, each of which possesses secrets, acquired by experience, for producing these articles iu the greatest perfection.
A.  Artificial Topaz. Take of perfectly white strass one ounce and six drachms, glass of antimony thirty-seven grains, and cassius purple one grain; or add to six ounces of strass half a drachm of crocus martis.
B. Artificial Ruby. This may be obtained, from the pre-
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Ch. 5: Gem History Properties Page of 515 Ch. 5: Gem History Properties
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