It is the gem variety of the mineral olivine. The origin of its name is either the Arabic word "faridat" meaning "gem" or the French word "peritot" meaning "unclear". Peridot is one of the few gemstones that come in only one colour. The depth of green depends on how much iron is contained in the crystal structure. It is found in the USA, Myanmar, Egypt, China, Sri Lanka and Pakistan. Source: Encyclopedia of gemstones and minerals.