Quartz is a crystalline form of silica. The greatest concentrations of quartz are found in silica-rich igneous and metamorphic rocks. Often transparent, Quartz can be found in almost any color. Macrocrystalline Quartz is composed of visible crystals, microcrystalline Quartz is densely compacted microscopic quartz crystals. Quartz has piezoelectric properties, meaning it generates an electric charge in response to pressure.
Chemical composition: SiO2; Hardness: 7