mineral

Tanzanite

Blue/Violet Zoisite (Ca2Al3(SiO4)(Si2O7)O(OH))

Hardness: 6.5 to 7 on Mohs scale; Color: Deep blue to violet (pleochroic); Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35

Hardness: 6
Color: Deep blue to violet (pleochroic)
Luster: Vitreous

Identified March 10, 2026More mineral →

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Physical properties

Hardness: 6.5 to 7 on Mohs scale; Color: Deep blue to violet (pleochroic); Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: One perfect direction; Specific Gravity: 3.35

Formation & geological history

Formed approx. 585 million years ago by regional metamorphism. Resulted from tectonic shifts and intense heat during the formation of the East African Rift valley in Tanzania.

Uses & applications

Primarily used as a gemstone in high-end jewelry (rings, bracelets, necklaces). It is highly valued by collectors due to its rarity and trichroic color properties.

Geological facts

Tanzanite is a single-source gemstone, found only in a 4km square area at the foothills of Mt. Kilimanjaro. It was famously promoted and named by Tiffany & Co. in 1968.

Field identification & locations

Identify in the field by its distinct pleochroism (appearing different colors from different angles). In jewelry, it is often heat-treated to enhance blue tones. Found exclusively in the Merelani Hills of Tanzania.

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Arenite (SiO2 based)

sedimentary

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Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)

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Epidote - Ca2(Al2,Fe3+)3(SiO4)3(OH)

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