mineral

Blue kyanite crystal

Kyanite, Al₂SiO₅

AI-generated identification · may be incorrect

Typically blue, bladed crystals with vitreous to pearly luster and strong directional hardness: about 4.5 parallel to blades and 6.5–7 across them. It has perfect cleavage in two directions, triclinic crystal symmetry, and specific gravity around 3.6–3.7.

Hardness: about 4

Identified August 15, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly during regional metamorphism of aluminum-rich sediments, commonly in schist and gneiss, under moderate-to-high pressure. Individual crystals may be hundreds of millions of years old, depending on the host rock.

Uses & applications

Used as a refractory and ceramic raw material because it expands predictably when heated; attractive transparent pieces are cut as gemstones, while opaque specimens are popular with collectors.

Geological facts

Its unusual hardness variation is diagnostic and results from its crystal structure. The blue color generally comes from trace iron and titanium.

Field identification & locations

Common localities include Nepal, India, Brazil, Kenya, Switzerland, and the United States, especially Virginia and Georgia. Identify it by its deep blue, elongated blades, strong cleavage, and hardness changing across the crystal; the pictured specimen appears consistent with rough blue kyanite.