Chrysolite, an olive-green mineral composed of magnesium, iron, silicon, and oxygen. It is a hard, transparent or translucent mineral that is cut and used as a gem. One of its varieties, olivine, has commercial use as a molding sand in foundries. Another variety, peridot, is an August birthstone. Olivine is generally found in volcanic rocks; peridot often is found in surface gravel.
Chrysolite is (Mg,Fe)2SiO4. Hardness: 6.5 to 7. Specific gravity: 3.26 to 3.44.