Aquamarine vs Alexandrite
Alexandrite is harder (Mohs 8.5) than Aquamarine (Mohs 7.5–8), so it resists scratching better.
Alexandrite has the higher refractive index (1.746–1.755 vs 1.577–1.583), which a refractometer can use to separate them.
Alexandrite is denser (SG 3.73 vs 2.72); a alexandrite of the same size weighs about 37% more.
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| Property | Aquamarine | Alexandrite |
|---|---|---|
| Species / material | Beryl | Chrysoberyl |
| Mohs hardness | 7.5–8 | 8.5 |
| Refractive index | 1.577–1.583 | 1.746–1.755 |
| Specific gravity | 2.72 | 3.73 |
| Crystal system | Hexagonal | Orthorhombic |
| Birefringence | 0.005–0.009 | 0.008–0.010 |
Values are typical ranges from standard gemmological references; individual stones can vary.
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