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a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechartelierite

a white or colorless vitreous insoluble solid (SiO2); various forms occur widely in the earth's crust as quartz or cristobalite or tridymite or lechartelierite

Transparent, tasteless crystals found in nature as agate, amethyst, chalcedony, cristobalite, flint, sand, QUARTZ, and tridymite. The compound is insoluble in water or acids except hydrofluoric acid.