mineral

Kyanite

Kyanite (Al2SiO5)

Hardness: Variable (4.5 parallel to axes, 7 perpendicular); Color: Blue, white, grey, green; Luster: Vitreous to pearly; Crystal structure: Triclinic; Specific Gravity: 3.53-3.67.

Hardness: Variable (4
Color: Blue, white, grey, green
Luster: Vitreous to pearly

Identified June 20, 2026More mineral →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: Variable (4.5 parallel to axes, 7 perpendicular); Color: Blue, white, grey, green; Luster: Vitreous to pearly; Crystal structure: Triclinic; Specific Gravity: 3.53-3.67.

Formation & geological history

Formed during the high-pressure regional metamorphism of clay-rich sedimentary rocks. It is a common index mineral for identifying metamorphic grade in schists and gneisses.

Uses & applications

Used in the manufacture of heat-resistant ceramics (refractories), porcelain, and abrasive wheels. Transparent specimens are used in jewelry as gemstones.

Geological facts

Kyanite is unique because its hardness varies significantly depending on the direction of the scratch, a property known as anisotropy. It is a polymorph with andalusite and sillimanite.

Field identification & locations

Identified in the field by its distinct bladed crystal habit and variable hardness. Commonly found in Brazil, USA (North Carolina), and Nepal. Look for long, flat, splintery looking crystals.