Kyanite is an aluminosilicate mineral (Al₂SiO₅) known for its distinctive bladed crystal form and strong directional hardness. Typically found in metamorphic rocks, kyanite forms under high-pressure conditions deep within the Earth’s crust. These tumbled specimens have been smoothed and polished while retaining the mineral’s characteristic shimmer and layered appearance.
Features:
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Composition: Aluminum silicate (Al₂SiO₅), part of the sillimanite group.
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Appearance: Blue to blue-gray with a pearly to vitreous luster and visible layering or fibrous structure.
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Formation: Grows in high-pressure, low-temperature metamorphic environments, often in schists and gneisses.
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Physical Properties: Mohs hardness varies by direction—about 4.5 parallel to the crystal axis and up to 7 across it—making it unique among minerals.
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Educational Value: Demonstrates anisotropic hardness, metamorphic mineral formation, and the crystal chemistry of aluminosilicates.
Tumbled kyanites offer both visual appeal and a tangible example of how pressure and structure influence mineral properties in Earth’s dynamic systems.
