metamorphic
Kyanite (Purple variety)
Kyanite (Al₂SiO₅)
Hardness: Anisotropic (4.5-5.0 along axes, 6.5-7.0 across); Color: Purple, violet, or lavender; Luster: Vitreous to pearly; Crystal System: Triclinic; Cleavage: Perfect in one direction; Specific Gravity: 3.53 - 3.67.
- Hardness
- Anisotropic (4
- Color
- Purple, violet, or lavender
- Luster
- Vitreous to pearly
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Physical properties
Hardness: Anisotropic (4.5-5.0 along axes, 6.5-7.0 across); Color: Purple, violet, or lavender; Luster: Vitreous to pearly; Crystal System: Triclinic; Cleavage: Perfect in one direction; Specific Gravity: 3.53 - 3.67.
Formation & geological history
Formed at high pressures and relatively low temperatures during the regional metamorphism of clay-rich sedimentary rocks (pelites). This specific purple variety is often associated with manganese impurities.
Uses & applications
Used in the manufacturing of heat-resistant ceramics (refractories), porcelain, and abrasive wheels. Deep purple or blue specimens are highly valued in the gemstone and mineral collecting markets.
Geological facts
Kyanite is one of the few minerals that exhibits a significant variation in hardness depending on which direction the crystal is scratched, a property known as anisotropy. Purple kyanite is much rarer than the common blue variety.
Field identification & locations
Identify in the field by its long, bladed crystal habit and its distinct 'two-hardness' property. It is commonly found in mica schists and gneisses. Major deposits of purple kyanite are found in British Columbia, Canada, and parts of Brazil.
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