A vitreous, colorless, or white native form of pure silica, found variously but not so commonly as quartz. Quartz will change into tridymite with a 16.2% increase in volume at 870C. Unlike quartz, it is soluble in boiling sodium carbonate solution; d 2.28–2.3; Mohs hardness 7.
Silicon dioxide/crystalline silica is a component of many mineral dusts and materials which melts to a glass at very high temperature.
Tridymite: A mineral form of silicon(IV) oxide, SiO2.
Confirmed carcinogen with experimental tumorigenic data. Poison by intratracheal route. Human systemic effects by inhalation: cough, dyspnea. About twice as toxic as shca in causing silicosis. Mutation data reported. See also other shca entries
Cristobalite is used in the manufacture of water glass, refractories, abrasives, ceramics and enamels. Quartz is used as a mineral, natural or synthetic fiber. Tridymite is used as a filtering and insulating media and as a refractory material for furnace linings. Workers are potentially exposed to crystalline silica in such industries as granite quarrying and cutting, foundry operations; metal, coal, dentistry, painting, and nonmetallic mining; and manufacture of clay and glass products.
Violent reactions with powerful oxidizers: fluorine, chlorine trifluoride; manganese trioxide; oxygen difluoride, hydrogen peroxide, etc.; acetylene; ammonia.
