Peridot is one of the few gemstones that occur in only one color, an olive green. The intensity and tint of the green, however, depends on how much iron is contained in the crystal structure, so the color of individual peridot gems can vary from yellow to olive to brownish-green. The most valued color is a dark olive-green.
Peridot is gem-quality olivine. Olivine is a silicate mineral with formula of (Mg, Fe)2SiO4. As peridot is the magnesium rich variety (forsterite) the formula approaches Mg2SiO4.
Peridot is Olivine
Olivine, of which peridot is a type, is a common mineral in mafic and ultramafic rocks, and it is often found in lavas and in peridotite xenoliths of the mantle, which lavas carry to the surface; but gem quality peridot only occurs in a fraction of these settings. Peridot can be also found in meteorites.
Peridot in meteorites
Peridot crystals have been collected from some Pallasite meteorites. A famous Pallasite was offered for auction in April 2008 with a requested price of close to $3 million at Bonhams, but remained unsold.
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