Quartz

Quartz is a hard mineral composed of silica (silicon dioxide). Its atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen atom being shared between two tetrahedra, giving an overall chemical formula of SiO2. Therefore, quartz is classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most common mineral or mineral group in Earth's lithosphere, comprising about 12% by mass.

thumb|Quartzite can have a grainy, glassy, sandpaper-like surface

anal for AG

human skull stone carvings made of clear quartz, claimed to be pre-Columbian Mesoamerican

glass consisting of pure silica

special kinds of glass used for making various components of optical devices and systems

economic upheavals caused by the advent of quartz watches in the 1970s and early 1980s

Data storage format