Ruby vs Sapphire
Ruby and Sapphire have similar hardness (Mohs 9).
Both are varieties of Corundum; they differ mainly in colour, so standard tests (RI, SG) overlap.
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| Property | Ruby | Sapphire |
|---|---|---|
| Species / material | Corundum | Corundum |
| Mohs hardness | 9 | 9 |
| Refractive index | 1.762–1.770 | 1.762–1.770 |
| Specific gravity | 4 | 4 |
| Crystal system | Trigonal | Trigonal |
| Birefringence | 0.008–0.010 | 0.008–0.010 |
Values are typical ranges from standard gemmological references; individual stones can vary.