- one of the commonest minerals, silicon dioxide, SiO2, having many varieties that differ in color, luster, etc., and occurring either in masses (as agate, bloodstone, chalcedony, jasper, etc.) or in crystals (as rock crystal, amethyst, citrine, etc.): the chief constituent of sand and sandstone, and an important constituent of many other rocks. It is piezoelectric and used to control the frequencies of radio transmitters.
- a colourless mineral often tinted by impurities, found in igneous, sedimentary, and metamorphic rocks. It is used in the manufacture of glass, abrasives, and cement, and also as a gemstone; the violet-purple variety is amethyst, the brown variety is cairngorm, the yellow variety is citrine, and the pink variety is rose quartz. Composition: silicon dioxide. Formula: SiO 2 . Crystal structure: hexagonal
- short for quartz glass
