mineral

Kyanite

Kyanite (Al2SiO5)

Hardness: variable 4.5 to 7 on Mohs scale; Color: Blue-white; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect; Specific Gravity: 3.53 to 3.67

Hardness: variable 4
Color: Blue-white
Luster: Vitreous to pearly

Identified May 31, 2026More mineral →

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Physical properties

Hardness: variable 4.5 to 7 on Mohs scale; Color: Blue-white; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect; Specific Gravity: 3.53 to 3.67

Formation & geological history

Formed during regional metamorphism of clay-rich sedimentary rocks at high pressures. Commonly found in metamorphic rocks like schist and gneiss.

Uses & applications

Used in the manufacture of refractory products such as high-temperature bricks and mortars, ceramics like kiln furniture, as well as in jewelry as a gemstone.

Geological facts

Kyanite is highly anisotropic, meaning its hardness varies significantly depending on the crystallographic direction. It is a polymorph with andalusite and sillimanite.

Field identification & locations

Identify in the field by its bladed crystal habit, distinct blue color, and variable hardness (it is softer when scratched parallel to the length of the crystal). Found in Nepal, Brazil, and the USA.