mineral

Blue Kyanite

Kyanite (Al2SiO5)

Hardness: 4.5-5.0 parallel to orientation and 6.5-7.0 perpendicular; Color: Light to deep blue; Luster: Vitreous to pearly; Crystal structure: Triclinic; Cleavage: Perfect; Specific gravity: 3.53-3.67.

Hardness: 4
Color: Light to deep blue
Luster: Vitreous to pearly

Identified May 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed during the regional metamorphism of clay-rich sedimentary rocks (pelites) at high pressures and relatively low temperatures. It is found in metamorphic rocks like schist and gneiss.

Uses & applications

Used industrially in the manufacture of refractory ceramics, spark plugs, and heat-resistant glass. It is also used as a gemstone in jewelry and as a popular collector specimen.

Geological facts

Kyanite is a polymorph with andalusite and sillimanite; they share the same chemistry but have different structures based on pressure and temperature. It is one of the few minerals that exhibits a significant variation in hardness depending on the direction of the cut.

Field identification & locations

Identify in the field by its distinct blue bladed crystal habit and its varying hardness (the 'knife test' will scratch it in one direction but not the other). Common locations include Brazil, USA (NC), Switzerland, and Nepal.