Olivine

Olivine, group of minerals or chemical compounds made from silicon, oxygen, magnesium, and iron, found in igneous rocks (those formed from a molten state), schists, and gray, pink, or white marble. A hard substance, olivine can withstand temperatures of more than 2,700°F (l,500°C) before igniting. It is used in making bricks and glass. Colors vary from clear green to brown; the gemstone peridot is deep, yellowish-green olivine.

See also: Peridot.