gemstone
Tanzanite
Blue Zoisite (Ca2Al3(SiO4)3(OH))
Hardness: 6-7 (Mohs); Color: Violet-blue to deep blue; Luster: Vitreous; Crystal System: Orthorhombic; Specific Gravity: 3.35
- Hardness
- 6-7 (Mohs)
- Color
- Violet-blue to deep blue
- Luster
- Vitreous
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Physical properties
Hardness: 6-7 (Mohs); Color: Violet-blue to deep blue; Luster: Vitreous; Crystal System: Orthorhombic; Specific Gravity: 3.35
Formation & geological history
Formed roughly 585 million years ago during regional metamorphism related to the Pan-African Orogenic event. Found only in the Merelani Hills of Tanzania.
Uses & applications
Primarily used as a rare gemstone for jewelry (rings, pendants) and as a high-value collector's mineral.
Geological facts
It is one of the world's rarest gemstones, often cited as being 1,000 times rarer than diamonds. It was named by Tiffany & Co. after its country of origin.
Field identification & locations
Identify by its unique trichroism (showing blue, violet, and burgundy from different angles). In the field, look for its association with graphite-rich schists in the Manyara Region.
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