mineral

Kyanite (Blue Kyanite)

Kyanite (Al2SiO5)

Hardness: 4.5 to 7 on Mohs scale (anisotropic); Color: Light blue to indigo, occasionally white or grey; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in one direction; Specific gravity: 3.53–3.67

Hardness: 4
Color: Light blue to indigo, occasionally white or grey
Luster: Vitreous to pearly

Identified March 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed during high-pressure regional metamorphism of clay-rich sedimentary rocks (pelites). It is common in metamorphic schists and gneisses and is often associated with staurolite and garnet.

Uses & applications

Used industrially for the production of refractory materials like high-heat porcelain, ceramics, and spark plugs. In jewelry, it is used as a gemstone, and in collecting, it is valued for its unique bladed crystal habit.

Geological facts

Kyanite is unusual because its hardness varies significantly depending on the direction of the scratch (4.5 parallel to the long axis and 6.5–7 perpendicular to it). It was historically called 'disthene,' meaning 'two strengths.'

Field identification & locations

Identify in the field by its distinct bladed crystal habit and blue color. Look for it in metamorphic belts like the Appalachian Mountains in the US or regions in Brazil, Switzerland, and Nepal. Testing the dual hardness is a key identification tip.