Peridot is an olive green gemstone that is often called olivine, as it relates to the gemstone colour. Whereas olivine is actually the name of a group of minerals, of which fosterite is a species and peridot is a variety of the fosterite species.
It is one of the few gemstones found in only one base colour, green, which varies from light yellowish green, to olive green, to dark green.
Peridots are typically bright with good saturation and often show attractive yellow flashes in faceted stones due to pleochroism. Inclusions that resemble 'lily pads' are characteristic of peridot, they are stress fractures surrounding a small crystal. When present they are an identifing feature of peridot.
Although chatoyancy or asterism is rare, cat's eye peridot and star stones are occasionally produced.
The first source of peridot is believed to be the Red Sea island of Zebirget (Zabargad, St. John’s island) where it was mined over 3,500 years ago. The gemstones from Zebirget are of superior quality and although it is still sourced from the island, mining is sporadic.
The origin of the word peridot is uncertain, as there is more than one claimant. it is believed to have come from either:
The Arabic word faradat meaning 'gem'. The French word peritot meaning 'unclear' probably in reference to cloudy peridot. The Greek word peridona meaning 'to give generously, or richly, or plenty'. The Hebrew word pitah from the bible, meaning 'yellow' maybe in association with yellowish stones.
So the origin can not be determined with any certainty.
Source locations for peridot also include: Australia (Queensland), Brazil (Minas Gerais), China, Czech Republic, Kenya, Mexico, Myanmar, Norway, Pakistan, South Africa, Sri Lanka, Tanzania, the USA (Arizona) and St. John's Island (Zebirget) in the Red Sea.
Peridot is not normally treated.