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Stone artificial teeth, with the exception of the material with which they ar!! colored, are cOlll posetl entirely of silex, the generic name of wl;Jich is quartz, or feld spar. Quartz, a clear white stone, is found abundant in this State. Quartz and s l 'ar are both very firm and durable, �o hard as even to scratch glass and blunt the edge of the hardest tile. These two stones are fir.t calcined by being exposed to a red heat, then suddenly immer sed in cold water, which renders them brittledoi:10.1038/scientificamerican09111847-408c fatcat:hhbripoodnfebkzbrioyakupzm