Sapphire vs Tanzanite
Sapphire and Tanzanite are easy to confuse. Here’s how they stack up on the properties that actually separate them.
| Sapphire | Tanzanite | |
|---|---|---|
| Also known as | Corundum (Corundum family) | Zoisite (Zoisite family) |
| Colour | Blue | Blue, Purple |
| Mohs hardness | 9.0 | 6.5 |
| Lustre | Vitreous | Vitreous, pearly on cleavage surfaces |
| Streak | Colorless | White or colorless |
| Crystal system | Trigonal | Orthorhombic |
| Transparency | Transparent to nearly opaque | Transparent to translucent |
| Cleavage | Poor | Perfect {010}, imperfect {100} |
| Fracture | Conchoidal, splintery | Uneven to conchoidal |
| Chemical formula | Aluminium oxide, Al 2 O 3 | Ca 2 Al 3 (SiO 4 )(Si 2 O 7 )O(OH) |
| Specific gravity | 3.98–4.06 | 3.10–3.38 |
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Frequently asked questions
What's the easiest way to tell Sapphire from Tanzanite?
Hardness is the quickest test: Sapphire is Mohs 9.0 and Tanzanite is Mohs 6.5.