Quartz , which is the most abundant silica mineral and which occurs in most igneous and practically all metamorphic and sedimentary rocks, is nearly pure silicon dioxide (SiO 2 ). It was also been found in some lunar rocks and meteorites. The name of quartz is believed originated in the early 1500s from the Saxon word querklufterz (cross vein ore), which was corrupted to queretz and then to quartz. Quartz was well known to the ancient, who called it crystal or rock crystal. Quartz is colorless and transparent when pure. Its hardness is 7 on the Mohs scale, and its specific gravity is 2.651. Quartz has no cleavage and fails by brittle fracture, the fracture surfaces have vitreous luster. Quartz is diamagnetic but does not conduct electricity. Piezoelectricity makes quartz valuable in pressure gauges, electronic frequency control devices, and radio equipment. Crystallography Quartz occurs in a wide range of crystal sizes, from single crystal weighing many tons to cryptocrytalline va