gemstone
Tanzanite
Zoisite (Ca2Al3(SiO4)(Si2O7)O(OH))
Hardness: 6.5 to 7 Mohs; Color: Blue-violet to violet-blue; Luster: Vitreous; Crystal system: Orthorhombic; Specific Gravity: 3.35; Cleavage: Perfect in one direction
- Hardness
- 6
- Color
- Blue-violet to violet-blue
- Luster
- Vitreous
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Physical properties
Hardness: 6.5 to 7 Mohs; Color: Blue-violet to violet-blue; Luster: Vitreous; Crystal system: Orthorhombic; Specific Gravity: 3.35; Cleavage: Perfect in one direction
Formation & geological history
Formed during the Pan-African orogenic event approximately 585 million years ago. Found in metamorphic schists and gneisses resulting from regional metamorphism of calcium-rich sediments.
Uses & applications
Primarily used in high-end jewelry (rings, pendants, earrings) and as a highly sought-after investment gemstone for collectors.
Geological facts
Tanzanite is 1,000 times rarer than diamonds, found only in a 4-kilometer strip near Mount Kilimanjaro in Tanzania. It is famous for its trichroism, showing different colors when viewed from different angles.
Field identification & locations
Identify by its distinct blue-violet hue and strong pleochroism. In the field, look for prismatic crystals with striations. It is exclusively found in the Merelani Hills of Tanzania.
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