mineral

Tanzanite

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

AI-generated identification · may be incorrect

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 →

Explore Tanzanite in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

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.