Topaz vs Peridot
Topaz is harder (Mohs 8) than Peridot (Mohs 6.5–7), so it resists scratching better; Peridot is softer than quartz dust (7) and needs more care in everyday rings.
Peridot has the higher refractive index (1.654–1.690 vs 1.609–1.643), which a refractometer can use to separate them.
Topaz is denser (SG 3.53 vs 3.34); a topaz of the same size weighs about 6% more.
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| Property | Topaz | Peridot |
|---|---|---|
| Species / material | Topaz | Olivine (forsterite) |
| Mohs hardness | 8 | 6.5–7 |
| Refractive index | 1.609–1.643 | 1.654–1.690 |
| Specific gravity | 3.53 | 3.34 |
| Crystal system | Orthorhombic | Orthorhombic |
| Birefringence | 0.008–0.010 | 0.035–0.038 |
Values are typical ranges from standard gemmological references; individual stones can vary.