Peridot: Birthstone of August

661px-Gem peridot
Cut, gem-quality Peridot

Peridot is a type of Olivine, a common mineral in mafic and ultramafic rocks.  While Olivine is a generally abundant mineral, gem quality peridot is rather rare, and therefore is considered precious.  Peridot crystals have been found in Pallasite meteorites.  Peridot occurs in only one color, olive green.