Peridot (Olivine)

Peridot is the gem variety of forsteritic olivine, a magnesium iron silicate, and ranks among the few gemstones that occur in a single color: its characteristic lime to olive green arises from iron intrinsic to the crystal structure rather than from trace impurities. Unusually, it is one of the rare gems to crystallize in the Earth's mantle, carried to the surface within peridotite xenoliths by volcanic activity, and it has also been identified in pallasite meteorites. The finest historical material came from Zabargad, or St. John's Island, in the Red Sea, while major modern sources include the San Carlos Apache Reservation in Arizona, the Kohistan region of Pakistan, and Myanmar. With a Mohs hardness of 6.5 to 7, peridot is moderately durable and serves as the birthstone for August.