Ruby vs Emerald
Ruby is harder (Mohs 9) than Emerald (Mohs 7.5–8), so it resists scratching better.
Ruby has the higher refractive index (1.762–1.770 vs 1.577–1.583), which a refractometer can use to separate them.
Ruby is denser (SG 4 vs 2.72); a ruby of the same size weighs about 47% more.
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| Property | Ruby | Emerald |
|---|---|---|
| Species / material | Corundum | Beryl |
| Mohs hardness | 9 | 7.5–8 |
| Refractive index | 1.762–1.770 | 1.577–1.583 |
| Specific gravity | 4 | 2.72 |
| Crystal system | Trigonal | Hexagonal |
| Birefringence | 0.008–0.010 | 0.005–0.009 |
Values are typical ranges from standard gemmological references; individual stones can vary.