Tanzanite (with Matrix)
Zoisite var. Tanzanite · Precious Gemstone / Mineral Specimen
Crystal System
Orthorhombic; typically found as prismatic crystals with striations, though this specimen is a rough crystalline fragment with associated matrix.
Mineral Group
Silicates (Sorosilicates); Epidote group.
Chemical Formula
(Ca2Al3(SiO4)3(OH)) containing trace amounts of Vanadium (V3+)
Formation Process
Metamorphic; formed during the Pan-African orogenic event through the regional metamorphism of calcium-rich rocks in the presence of vanadium.
About This Crystal
A rough mineral fragment showing deep blue-to-violet crystalline faces embedded in a tan and dark greyish-brown host rock matrix. The tanzanite sections exhibit a vitreous luster and distinct pleochroism, while the matrix is dull to sub-metallic.
Physical Characteristics
Color ranges from ultramarine blue to sapphire blue and violet. Streak is white to colorless. Cleavage is perfect in one direction (pinacoidal). Specific gravity is 3.10–3.38. It is brittle and non-magnetic.
Optical Properties
Strongly pleochroic, showing blue, violet, and burgundy/red-brown depending on viewing angle. Biaxial (+) with a refractive index of 1.691–1.700. Birefringence is 0.006–0.013.
Hardness & Durability
Origin Region
Merelani Hills, Manyara Region, Tanzania (the only known commercial source in the world).
Hardness & Durability
Mohs hardness 6 to 7. It has fair to poor toughness due to perfect cleavage, making it susceptible to cleavage planes if struck. It is sensitive to thermal shock.
Care & Maintenance
Clean only with warm, soapy water. Avoid ultrasonic and steam cleaners. Store away from harder gems like sapphires or diamonds to prevent scratching. Keep away from high heat and sudden temperature changes.
Rarity & Value
Extremely rare (found in only one location on Earth). Value is primarily driven by the saturation of 'vivid' blue or violet color. Most stones are heat-treated to remove brown/yellow tones; raw specimens with deep blue are highly prized.
Special Characteristics
Strong trichroism (showing three different colors from three different axes). Most specimens are heated to 400-600 degrees Celsius to transform brown zoisite into the desired blue/violet tanzanite.
Lore & History
Discovered in 1967 by Manuel de Souza and named by Tiffany & Co. after its country of origin. It is the birthstone for December. Metaphysically, it is believed to bridge the heart and mind, stimulating the throat and third eye chakras.