mineral

Tanzanite (Blue Zoisite)

Ca2Al3(SiO4)(Si2O7)O(OH) + (V) - Vanadium-bearing Zoisite

Hardness: 6-7 on Mohs scale; Color: Blue, violet, brown (trichroic); Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35

Hardness: 6-7 on Mohs scale
Color: Blue, violet, brown (trichroic)
Luster: Vitreous

Identified March 19, 2026More mineral →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Blue, violet, brown (trichroic); Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35

Formation & geological history

Formed roughly 585 million years ago during the Ediacaran Period through intense regional metamorphism in the Merelani Hills of Tanzania. It is created by the tectonic movement of the Mozambique Belt.

Uses & applications

Primary use is in high-end jewelry (rings, earrings, necklaces) as a gemstone. It is also a highly prized investment-grade collector's specimen due to its extreme rarity and single-source location.

Geological facts

Tanzanite is 1,000 times rarer than a diamond. It was discoverd in 1967 and named by Tiffany & Co. It is unique for its strong pleochroism, appearing blue, violet, or burgundy depending on the viewing angle.

Field identification & locations

Can be identified in the field by its distinct trichroic properties (changing color when turned) and its unique occurrence alongside graphite and grossular garnet in the Merelani Hills, Tanzania—the only place on Earth it is found.

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