mineral
Blue kyanite
Kyanite, Al₂SiO₅
AI-generated identification · may be incorrectUsually blue, bladed crystals with vitreous to pearly luster and prominent striations; hardness is anisotropic—about 4.5 parallel to blades and 6.5–7 across them. Triclinic crystal system, commonly with excellent cleavage and elongated blade-like habit.
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Physical properties
Usually blue, bladed crystals with vitreous to pearly luster and prominent striations; hardness is anisotropic—about 4.5 parallel to blades and 6.5–7 across them. Triclinic crystal system, commonly with excellent cleavage and elongated blade-like habit.
Formation & geological history
Forms mainly in aluminum-rich metamorphic rocks, especially schist and gneiss, during medium- to high-pressure regional metamorphism. It occurs in rocks ranging from Paleozoic to Precambrian age, depending on locality.
Uses & applications
Used as a refractory and heat-resistant ceramic material; transparent, attractive crystals are collected and occasionally cut as gemstones, though cleavage makes faceting difficult.
Geological facts
Kyanite is a polymorph of andalusite and sillimanite; all share the formula Al₂SiO₅ but form under different pressure–temperature conditions. Blue color commonly results from trace iron or titanium.
Field identification & locations
Identify it by its blue, flattened, strongly striated blades and unusual directional hardness; distinguish it from blue calcite or fluorite by its blade habit and cleavage. Notable sources include Nepal, Brazil, Switzerland, the United States, and Tanzania.
