Mechanical Movements

1847 Scientific American  
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 brittle
more » ... ders them brittle and easy to pulverize: then every impurity is rejected, and they are ground separately in a quartz or feld spar mortar to an im palpable powder, after which they are mixed together in proportion of about five parts feld spar t6 one of quartz The coloring matter is then added and thoroughly ground, which may be so varied in quality as to give an endless varie ty of tints and shades.
doi:10.1038/scientificamerican09111847-408c fatcat:hhbripoodnfebkzbrioyakupzm