mineral

Blue Kyanite

Kyanite (Al2SiO5)

Hardness: variable 4.5–5 parallel to the long axis and 6.5–7 perpendicular to it; Color: Pale to deep blue, sometimes white or gray; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect in one direction; Specific gravity: 3.53 - 3.67

Hardness: variable 4
Color: Pale to deep blue, sometimes white or gray
Luster: Vitreous to pearly

Identified March 26, 2026More mineral →

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Physical properties

Formation & geological history

Formed during regional metamorphism of clay-rich sedimentary rocks at high pressure. It is a polymorph with andalusite and sillimanite, typically found in aluminous schists and gneisses.

Uses & applications

Used in the manufacturing of heat-resistant ceramics (spark plugs, kiln linings), high-refractory porcelain, abrasives, and as a gemstone for jewelry or metaphysical collecting.

Geological facts

Kyanite is unusual for its highly anisotropic hardness: it is much softer along the length of the crystal than across its width. Its name comes from the Greek word 'kuanos', meaning deep blue.

Field identification & locations

Identify in the field by its distinct bladed crystal habit and its two different hardnesses (the scratch test). Common locations include Brazil, India, Switzerland, and the USA (North Carolina). Collectors should look for transparent, deep blue blades.