Peridot is gem-quality olivine, and it is one of the few gemstones that comes in only one colour: green, from yellowish spring green to rich olive, coloured by the iron built into its own chemistry. It forms deep in the Earth's mantle and hitches a ride to the surface in volcanic rock, and small amounts even arrive from space inside pallasite meteorites. The ancient Egyptians mined it on the Red Sea island of Zabargad over 3,000 years ago and called it the gem of the sun. Today it comes from Arizona, Pakistan, Myanmar and China, and it is the birthstone for August.
At 6.5 to 7 on the Mohs scale, peridot handles regular wear, though it dislikes sharp knocks, rapid temperature swings and acids, so take rings off for rough work. It is usually faceted, and its slightly oily-looking sparkle is part of its character. It is essentially never treated, which is always nice to know. Clean it in lukewarm, soapy water only, skipping ultrasonic and steam cleaners. Green glass is the usual imitation and lacks peridot's distinctive doubling of facets seen under a loupe.
Pallasite meteorites carry the same olivine crystals; chrome diopside and emerald are its green rivals.
