Ruby vs Tourmaline
Ruby is harder (Mohs 9) than Tourmaline (Mohs 7–7.5), so it resists scratching better.
Ruby has the higher refractive index (1.762–1.770 vs 1.624–1.644), which a refractometer can use to separate them.
Ruby is denser (SG 4 vs 3.06); a ruby of the same size weighs about 31% more.
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| Property | Ruby | Tourmaline |
|---|---|---|
| Species / material | Corundum | Tourmaline |
| Mohs hardness | 9 | 7–7.5 |
| Refractive index | 1.762–1.770 | 1.624–1.644 |
| Specific gravity | 4 | 3.06 |
| Crystal system | Trigonal | Trigonal |
| Birefringence | 0.008–0.010 | 0.014–0.021 |
Values are typical ranges from standard gemmological references; individual stones can vary.