Peridot
Varietyof Forsterite
Peridot is gem-quality forsterite (olivine). As a variety of Forsterite, it shares that species' composition (Mg2(SiO4)), crystal structure, and hardness; the distinction is the appearance defined above.
Photos
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About Forsterite
Full reference data — crystallography, X-ray diffraction, and cited physical properties — is on the Forsterite species page.
| Formula | Mg2(SiO4) |
|---|---|
| Hardness (Mohs) | 6-7 |
| Specific gravity | 3.21-3.33 |
| Density (calculated) | 3.217 |
| Crystal system | orthorhombic |
| Color range | gray, red, white, yellow |
| Luster | vitreous |
| Streak | white |