Quartzite is a metamorphic rock formed when sandstone deposits are compressed through geologic forces, usually by forces within tectonic plates. Under heating and pressure, the individual grains of sand and cementing materials recrystallize to form a very hard mass. Quartzite is valued as a decorative stone as well as for its hardness and resistance to corrosion. Its color is normally whitish or gray, often pinkish, and sometimes yellowish or other colors because of impurities.

The recrystallized structure distinguishes quartzite from sandstone, whose separate sand grains remain cemented together.

Quartz is the mineral, while quartzite is the metamorphic rock. A pale or pink color alone does not identify either material.