mineral

Blue Kyanite

Kyanite (Al2SiO5)

Hardness: Variable (4.5 parallel to the length of the crystal; 6.5–7.0 perpendicular). Color: Blue, frequently with white or gray streaks. Luster: Vitreous to Pearly. Crystal Structure: Triclinic with long bladed crystals. Cleavage: Perfect in one direction.

Hardness: Variable (4
Color: Blue, frequently with white or gray streaks
Luster: Vitreous to Pearly

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the regional metamorphism of clay-rich sedimentary rocks under high pressure and relatively low temperatures. It is commonly found in metamorphic rocks like schists and gneisses.

Uses & applications

Used industrially for the production of refractory materials (heat-resistant ceramics, spark plugs, and foundry molds) because it remains stable at high temperatures. It is also popular in jewelry as a gemstone and as a display specimen for mineral collectors.

Geological facts

Kyanite is one of only a few minerals that exhibit two different hardnesses on the same crystal surface, a property known as anisotropy. Its name is derived from the Greek word 'kyanos', meaning deep blue.

Field identification & locations

Identify in the field by its distinct bladed crystal habit, deep blue color, and the 'fingernail test' where it can be scratched with a knife along the long axis but not across the width. Commonly found in Brazil, Nepal, Switzerland, and the United States (North Carolina).