metamorphic
Kyanite
Kyanite (Al₂SiO₅)
AI-generated identification · may be incorrectLikely a bladed blue-gray kyanite specimen with elongated, parallel striations and a vitreous-to-pearly luster. Mohs hardness varies by direction: about 4.5–5.5 across blades and 6.5–7 along them; crystals are triclinic with distinct cleavage.
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Physical properties
Likely a bladed blue-gray kyanite specimen with elongated, parallel striations and a vitreous-to-pearly luster. Mohs hardness varies by direction: about 4.5–5.5 across blades and 6.5–7 along them; crystals are triclinic with distinct cleavage.
Formation & geological history
Forms during medium- to high-pressure metamorphism of aluminous rocks, commonly in schist and gneiss. Its age depends on the host rock and can range from ancient Precambrian to younger metamorphic events.
Uses & applications
Used in refractory ceramics and kiln products because it expands when heated; attractive crystals are collected and occasionally cut as gemstones.
Geological facts
Kyanite is a polymorph of andalusite and sillimanite: all share the formula Al₂SiO₅ but form under different pressure-temperature conditions.
Field identification & locations
The long, flat, striated blades and strongly directional hardness are useful field clues; common sources include Brazil, Nepal, India, and the United States. The image is consistent with kyanite, though a photo alone cannot confirm identification.
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