mineral
Tanzanite (Rough)
Blue Zoisite (Ca2Al3(SiO4)3(OH))
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs); Color: Violet-blue to deep blue; Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35
- Hardness
- 6
- Color
- Violet-blue to deep blue
- Luster
- Vitreous
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Violet-blue to deep blue; Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35
Formation & geological history
Formed through regional metamorphism. High-pressure, low-temperature metamorphism of basaltic rocks created these blue crystals roughly 585 million years ago during the Pan-African orogenic event.
Uses & applications
Primarily used in high-end jewelry and collected as a rare mineral specimen. It is the birthstone for December.
Geological facts
Tanzanite is one of the rarest gemstones on Earth, found only in a small four-kilometer strip of land near the Merelani Hills of Tanzania. It is approximately 1,000 times rarer than diamonds.
Field identification & locations
Identified by its signature trichroism (showing blue, violet, and burgundy from different angles). In the field, look for the unique intense blue-violet hue in the Merelani mining district. It can be distinguished from sapphire by its lower hardness and specific gravity.
