Peridot is a female name of French origin, meaning "Green Gemstone." The name is derived from the yellow-green transparent variety of olivine, sometimes called chrysolite. Peridot is one of the few gemstones that occurs in only one color, an olive-green, with the intensity depending on the percentage of iron in the crystal structure. It is also one of the birthstones for the month of August. The gemstone's chemical formula is (Mg,Fe)2SiO4 and it is primarily found in mafic and ultramafic rocks, occurring in lava, peridotite xenoliths of the mantle, and pallasitic meteorites. Gem-quality peridot is rare due to its susceptibility to alteration during movement from deep within the mantle and weathering at the surface. In ancient times, the mining of peridot was called topazios and it has been prized for its claimed protective powers, superstitions, and as a birthstone for August.