Tanzanite vs Opal
Tanzanite is harder (Mohs 6–7) than Opal (Mohs 5.5–6.5), so it resists scratching better; Opal is softer than quartz dust (7) and needs more care in everyday rings.
Tanzanite has the higher refractive index (1.691–1.700 vs 1.450), which a refractometer can use to separate them.
Tanzanite is denser (SG 3.35 vs 2.15); a tanzanite of the same size weighs about 56% more.
Advertisement
Ad space (in-content)
| Property | Tanzanite | Opal |
|---|---|---|
| Species / material | Zoisite | Opal (hydrated silica) |
| Mohs hardness | 6–7 | 5.5–6.5 |
| Refractive index | 1.691–1.700 | 1.450 |
| Specific gravity | 3.35 | 2.15 |
| Crystal system | Orthorhombic | Amorphous |
| Birefringence | 0.008–0.013 | None |
Values are typical ranges from standard gemmological references; individual stones can vary.