Ruby vs Cubic zirconia
Ruby is harder (Mohs 9) than Cubic zirconia (Mohs 8–8.5), so it resists scratching better.
Cubic zirconia has the higher refractive index (2.15–2.18 vs 1.762–1.770), which a refractometer (over-the-limit reading) can use to separate them.
Cubic zirconia is denser (SG 5.8 vs 4); a cubic zirconia of the same size weighs about 45% more.
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| Property | Ruby | Cubic zirconia |
|---|---|---|
| Species / material | Corundum | Synthetic zirconium oxide |
| Mohs hardness | 9 | 8–8.5 |
| Refractive index | 1.762–1.770 | 2.15–2.18 |
| Specific gravity | 4 | 5.8 |
| Crystal system | Trigonal | Cubic |
| Birefringence | 0.008–0.010 | None (isotropic) |
Values are typical ranges from standard gemmological references; individual stones can vary.