RocksdaySapphire vs Tanzanite
How to tell them apart
Gem corundum of any color except red. Blue sapphire gets its color from iron and titanium.
Photo: James St. John, CC BY 2.0
Blue-violet zoisite found in only one small area of Tanzania. It shows different colors from different directions.
Photo: Didier Descouens, CC BY 3.0
Quick tests
- Hardness: Sapphire is clearly harder: Mohs 9 versus 6–7.
Key differences
- Tanzanite is softer and more violet.
- Sapphire is much harder (9).
Side by side
| Property | Sapphire | Tanzanite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 9 | 6–7 |
| Luster | Adamantine to vitreous | Vitreous |
| Streak | White | White |
| Colors | Blue, Yellow, Pink, Orange | Blue, Purple |
| Crystal system | Trigonal | Orthorhombic |
| Specific gravity | 3.95–4.03 | 3.35 |
| Formula | Al₂O₃ | Ca₂Al₃(SiO₄)(Si₂O₇)O(OH) |
| Found in | Sri Lanka; Madagascar | Merelani Hills, Tanzania |
Properties that are the same for both are grayed out.
How to identify sapphire
- Hardness 9 — only diamond scratches it.
- Barrel or tapered six-sided crystals.
- Heavy for its size.
Crystal system: Trigonal
Full Sapphire guide →How to identify tanzanite
- Blue to violet, shifting color as you rotate it.
- Hardness about 6.5 — softer than sapphire.
- Most rough is brownish until heated.
Crystal system: Orthorhombic
Full Tanzanite guide →More comparisons
Could you tell them apart from a blurry close-up?
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