mineral

Tanzanite

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

Hardness: 6.5-7.0 (Mohs scale); Color: Sapphire blue, violet, or burgundy (pleochroic); Luster: Vitreous; Crystal structure: Orthorhombic; Cleavage: Perfect one-directional; Specific Gravity: 3.35

Hardness: 6
Color: Sapphire blue, violet, or burgundy (pleochroic)
Luster: Vitreous

Identified March 26, 2026More mineral →

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Physical properties

Hardness: 6.5-7.0 (Mohs scale); Color: Sapphire blue, violet, or burgundy (pleochroic); Luster: Vitreous; Crystal structure: Orthorhombic; Cleavage: Perfect one-directional; Specific Gravity: 3.35

Formation & geological history

Formed through regional metamorphism. High-pressure, high-temperature environment. The specific deposit in Tanzania is approximately 585 million years old (Neoproterozoic), created by tectonic plate activity associated with the Great Rift Valley.

Uses & applications

Primarily used as a rare gemstone in high-end jewelry (rings, pendants, earrings). It is also highly sought after by mineral collectors for its unique tri-colored pleochroism and its status as a single-source gemstone.

Geological facts

Tanzanite is found in only one place on Earth: a 4km square area at the Merelani Hills in Tanzania. It was discovered in 1967 and was named by Tiffany & Co. It is 1,000 times rarer than diamonds.

Field identification & locations

Identify in the field by its distinct violet-blue hue and pleochroism (it looks different colors from different angles). Collectors should look for 'dicroscope' effects and check for the characteristic brittleness. Found exclusively in the Manyara Region of Tanzania.