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Variety · Silicate · of Forsterite

Peridot

(Mg,Fe)₂SiO₄ gem

The gem olivine — one of few stones that exists in only one color.

Hardness6.5–7
Crystal systemOrthorhombic
LusterVitreous
Sp. gravity3.27–3.37
ClassSilicate
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Peridot specimen

Peridot — Photo: Daderot · CC0

What is Peridot?

Peridot is gem-quality olivine — one of the only gemstones that occurs in a single color, the olive-green its iron content guarantees. Ancient Egyptians mined it on the Red Sea island of Zabargad for 3,500 years, calling it the 'gem of the sun'.

Peridot is idiochromatic — its green comes from iron essential to its structure, not a trace impurity, so it can't be any other color. Some peridot isn't even terrestrial: pallasite meteorites are iron lattices studded with olivine gems.

In one sentence: The only-color gem — oily olive green from basalt and meteorites.

Physical Properties

The full data table is in the panel alongside. Here’s what those numbers actually mean.

One color. Fe²⁺ is structural — peridot can only be green.

Double refraction. High birefringence — doubling of back facets is visible in a loupe.

Sources. Basalt xenoliths (Arizona), island veins (Zabargad), and pallasite meteorites.

What It’s Used For

GemstoneAugust birthstone — always green, the color is intrinsic to the Fe it needs.
Space gemsPallasitic peridot is extraterrestrial — cut from meteorites.

How to Identify It

Oily green — only gem species in this single colorStrong double refraction visible through the tableH ~7, conchoidal fractureBasalt xenolith source
Looks like…But differs because…Quick test
EmeraldEmerald is hexagonal, brighter green, Cr-coloredCrystal form
DemantoidGarnet dispersion fire, isometricOptics

Where It’s Found

Notable localities for fine specimens:

Peridot Mesa, San Carlos, United States Zabargad (St. John's Island), Egypt Mogok, Myanmar Kohistan, PakistanOpen the locality map →