metamorphic
Blue-gray kyanite
Kyanite (Al₂SiO₅)
AI-generated identification · may be incorrectLikely kyanite: blue-gray, glassy to pearly, with elongated bladed crystals and prominent lengthwise striations. Mohs hardness is strongly directional (about 4.5–5 parallel to blades, 6.5–7 across); specific gravity is about 3.6.
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Physical properties
Likely kyanite: blue-gray, glassy to pearly, with elongated bladed crystals and prominent lengthwise striations. Mohs hardness is strongly directional (about 4.5–5 parallel to blades, 6.5–7 across); specific gravity is about 3.6.
Formation & geological history
Forms during regional metamorphism of aluminum-rich rocks, commonly at medium to high pressure. Kyanite occurs in rocks of many ages; the specimen’s age cannot be determined from the image.
Uses & applications
Used in refractory ceramics and high-temperature kiln products; attractive crystalline pieces are collected and occasionally cut as gemstones.
Geological facts
Kyanite, andalusite, and sillimanite share the formula Al₂SiO₅ but form under different pressure-temperature conditions.
Field identification & locations
The blue, flattened blades and directional hardness are useful field clues; common sources include metamorphic belts in Brazil, India, Nepal, Switzerland, and the United States. Image-based identification is provisional.
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