Peridot is the gem variety of the mineral olivine. Iron causes its yellowish green colors.
Properties
| Refractive index | 1.65 to 1.69 |
|---|---|
| Birefringence | 0.035 to 0.038 |
| Optic character | Doubly refractive (biaxial) |
| Dispersion | 0.02 |
| Specific gravity | 3.34 (GIA); greenish peridots 3.3 to 3.4 (IGS) |
| Hardness (Mohs) | 6.5 to 7 |
| Crystal system | Orthorhombic |
| Pleochroism | Weak: green, yellow-green |
| Absorption spectrum | Strong band, 493 nm (Fe); narrow band, 473 nm (Fe); broad band, 453 nm (Fe) |
Published values. They change a little from stone to stone. Our tools do not model peridot yet. Sources: GIA · International Gem Society · LibreTexts Gemology · Gemdat
In more detail
Its color range is narrow: brown-green, yellowish green or pure green. It often occurs in volcanic basalts, and rarely in meteorites. There are no known treatments to improve peridot's clarity or color. Rapid heat can fracture it and acids attack it, so do not use ultrasonic or steam cleaners.
Related terms
- Gem variety: A variety is a subdivision of a gem species, usually by color. Ruby and sapphire are varieties of corundum, and emerald is a variety of beryl.
- Stability: Stability is a gem's resistance to damage from heat, light and chemicals.
- Toughness: Toughness is a gem's resistance to chipping and breaking. It differs from hardness, which is resistance to scratching.
- Birefringence: Birefringence is the difference between the two refractive indices of a doubly refractive stone. It shows how strongly the stone splits light into two rays.