Tourmaline vs Amethyst
Tourmaline and Amethyst have similar hardness (Mohs 7–7.5).
Tourmaline has the higher refractive index (1.624–1.644 vs 1.544–1.553), which a refractometer can use to separate them.
Tourmaline is denser (SG 3.06 vs 2.65); a tourmaline of the same size weighs about 15% more.
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| Property | Tourmaline | Amethyst |
|---|---|---|
| Species / material | Tourmaline | Quartz |
| Mohs hardness | 7–7.5 | 7 |
| Refractive index | 1.624–1.644 | 1.544–1.553 |
| Specific gravity | 3.06 | 2.65 |
| Crystal system | Trigonal | Trigonal |
| Birefringence | 0.014–0.021 | 0.009 |
Values are typical ranges from standard gemmological references; individual stones can vary.
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