Tanzanite
Zoisite var. Tanzanite · Precious Gemstone
Crystal System
Orthorhombic, prismatic habit
Mineral Group
Silicates, Sorosilicates
Chemical Formula
Ca2Al3(SiO4)(Si2O7)O(OH) with trace Vanadium
Formation Process
Metamorphic formation in complex orogenic events under high pressure and moderate to high temperature
About This Crystal
The specimen displays a deep violet-blue color with strong trichroism, showing intense blue and purple tones depending on the viewing angle. It is a raw, unpolished crystal fragment resting on skin, exhibiting a sub-vitreous to resinous luster and translucent to semi-transparent transparency.
Physical Characteristics
Body color ranges from sapphire blue to violet-purple; streak is white; perfect cleavage in one direction; uneven to conchoidal fracture; specific gravity around 3.35; brittle tenacity; inert to ultraviolet light.
Optical Properties
Strongly trichroic displaying deep blue, violet, and brownish-yellow/greenish-yellow depending on orientation; biaxial positive optical character with refractive indices around 1.691-1.700 and birefringence of 0.009.
Hardness & Durability
Origin Region
Merelani Hills, Simanjiro District, Manyara Region, Tanzania
Hardness & Durability
Mohs hardness of 6 to 7; fair to good toughness but vulnerable to sharp blows due to perfect cleavage; sensitive to thermal shock and sudden temperature changes; moderate wearability requiring protective settings for rings.
Care & Maintenance
Clean with warm soapy water and a soft brush; avoid ultrasonic and steam cleaners, harsh chemicals, and extreme thermal shock; store away from harder gemstones to prevent scratching.
Rarity & Value
Rare; found exclusively in one single location worldwide in Tanzania; value is determined by color saturation, clarity, cut, and carat weight; heat treatment is routinely applied to enhance the blue color from brownish-yellow raw stones.
Special Characteristics
Remarkable strong trichroism and pleochroism, making orientation during cutting critical to maximize the desirable blue or violet face-up color.
Lore & History
Discovered commercially in 1967 and named by Tiffany & Co. after its country of origin. In metaphysical lore, it is associated with spiritual awakening, psychic perception, and the third eye and crown chakras, though these remain traditional beliefs rather than scientific properties.