Tanzanite

Physical Properties

Hardness: 6.5-7.0 (Mohs); Color: Violet-blue to blue-violet; Luster: Vitreous; Crystal Structure: Orthorhombic; Cleavage: Perfect one direction; Specific Gravity: 3.35

Formation & Geological History

Formed in regional metamorphic environments approximately 585 million years ago by extreme heat and pressure in the Mererani Hills. It involves the interaction of calcium-rich pegmatites and schist.

Uses & Applications

Predominantly used as a gemstone for high-end jewelry (rings, necklaces, earrings). It is a popular birthstone for December.

Geological Facts

Tanzanite is 1,000 times rarer than diamonds because it is found in only one place on Earth: a 4km by 2km area in Tanzania. It is famous for its strong trichroism, showing blue, violet, and burgundy colors from different angles.

Field Identification & Locations

Identify by its unique pleochroism and heat sensitivity. In the field, look for graphite and garnet-rich schist formations near the Kilimanjaro region in Tanzania. It is the only gemstone on the market that is geographically restricted to a single mine location.

Identified on: 4/14/2026

Mode: Standard