metamorphic
Kyanite-bearing metamorphic rock
Blue kyanite (Al₂SiO₅), likely in mica- and garnet-rich schist
AI-generated identification · may be incorrectKyanite forms bladed, blue crystals with vitreous to pearly luster and prominent lengthwise striations; hardness is strongly directional, about 4.5–5 parallel to blades and 6.5–7 across them. The matrix appears to contain dark biotite/amphibole, pale quartz or feldspar, and possibly reddish garnet.
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Physical properties
Kyanite forms bladed, blue crystals with vitreous to pearly luster and prominent lengthwise striations; hardness is strongly directional, about 4.5–5 parallel to blades and 6.5–7 across them. The matrix appears to contain dark biotite/amphibole, pale quartz or feldspar, and possibly reddish garnet.
Formation & geological history
Formed during regional metamorphism of aluminum-rich sedimentary rocks at moderate-to-high pressure, commonly during mountain building; ages vary by locality from Precambrian to recent orogenic belts.
Uses & applications
Collected as a mineral specimen; transparent blue kyanite can be cut as a gemstone, while lower-grade material is used in refractory ceramics, kiln furniture, and heat-resistant products.
Geological facts
Kyanite is polymorphous with andalusite and sillimanite—the same Al₂SiO₅ chemistry but different pressure-temperature conditions.
Field identification & locations
Identify it by its blue, elongated, striated blades and unusual directional hardness, commonly embedded in schist or gneiss; major sources include Nepal, Switzerland, Brazil, India, Kenya, and the United States.
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