mineral

Kyanite (Green and Blue varieties)

Kyanite (Al2SiO5)

Hardness: 4.5-5.0 (along axes) and 6.5-7.0 (across axes); Color: Emerald green, teal, and deep blue; Luster: Vitreous to pearly; Structure: Triclinic; Cleavage: Perfect in one direction

Hardness: 4
Color: Emerald green, teal, and deep blue
Luster: Vitreous to pearly

Identified March 15, 2026More mineral →

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Physical properties

Hardness: 4.5-5.0 (along axes) and 6.5-7.0 (across axes); Color: Emerald green, teal, and deep blue; Luster: Vitreous to pearly; Structure: Triclinic; Cleavage: Perfect in one direction

Formation & geological history

Formed through high-pressure regional metamorphism of clay-rich sedimentary rocks (pelites). Commonly found in metamorphic schists and gneisses ranging from the Proterozoic to Phanerozoic eras.

Uses & applications

Industrial use in refractory and ceramic products (porcelain, spark plugs) due to its high heat resistance. Used in jewelry as cabochons or faceted stones, and highly prized as mineral specimens for collectors.

Geological facts

Kyanite is strongly anisotropic, meaning it has two different hardness ratings depending on the direction it is scratched. Green kyanite is rarer than blue kyanite and often contains trace amounts of chromium.

Field identification & locations

Identify by its bladed/fibrous crystal habit and the 'double hardness' test. Commonly found in Brazil, India, and the Appalachian Mountains. Collectors look for translucent crystals with intense color saturation.

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