Tanzanite
Image: Didier Descouens (CC BY 3.0)
Mineral NameTanzanite
Chemical FormulaCa₂Al₃(SiO₄)₃(OH)
Mohs Hardness6
Crystal Systemorthorhombic
Lustervitreous
Streak Colorwhite
CleavagePerfect on {010}
Fractureuneven to conchoidal
Specific Gravity3.1
Colorsblue, violet, purple
Transparencytransparent to translucent
Type LocalityC-Block Mine, Merelani Hills (Mererani), Lelatema Mts, Arusha, Tanzania
Mineral GroupSilicates
Usesjewelry, collector's item
Associated Mineralsgraphite, diopside, tremolite, grossular garnet, quartz
Rarityrare
Description
The image displays a rough, translucent blue-violet tanzanite crystal fragment alongside a smaller, oval-cut, transparent blue-violet gemstone, both exhibiting a vibrant color.
Geological Context
Tanzanite forms in regionally metamorphosed rocks, specifically in graphitic gneisses and schists, often associated with pegmatites and hydrothermal veins, resulting from the metamorphism of calcium-rich sedimentary rocks.
