metamorphic
Kyanite in Quartz
Al2SiO5 in SiO2
Hardness: 4.5-7 (Kyanite is anisotropic), 7 (Quartz); Color: Blue blades in white/tan matrix; Luster: Vitreous to pearly; Crystal structure: Triclinic (Kyanite), Hexagonal (Quartz); Specific Gravity: 3.5-3.7 (Kyanite).
- Hardness
- 4
- Color
- Blue blades in white/tan matrix
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 4.5-7 (Kyanite is anisotropic), 7 (Quartz); Color: Blue blades in white/tan matrix; Luster: Vitreous to pearly; Crystal structure: Triclinic (Kyanite), Hexagonal (Quartz); Specific Gravity: 3.5-3.7 (Kyanite).
Formation & geological history
Formed through high-pressure regional metamorphism of clay-rich sedimentary rocks (pelites). The blue kyanite crystals grew within a quartz vein or matrix during intense tectonic activity.
Uses & applications
Kyanite is used in high-heat industrial ceramics, insulators, and brake pads; as a specimen, it is popular for mineral collecting and metaphysical use.
Geological facts
Kyanite is unique because its hardness varies significantly depending on the direction of the crystal: it is soft (4.5) parallel to the long axis and hard (7.0) perpendicular to it.
Field identification & locations
Identify by the elongated blue bladed crystals and the 'scratch test' difference in hardness. Commonly found in metamorphic belts such as the Appalachian Mountains (USA), Brazil, and the Swiss Alps.
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