mineral

Kyanite blade

Kyanite, Al₂SiO₅

AI-generated identification · may be incorrect

Pale blue, bladed crystal with pearly to vitreous luster and strong lengthwise striations; Mohs hardness is 4.5 parallel to the blade and 6.5–7 across it, with perfect cleavage in two directions. Commonly forms thin, flattened crystals rather than a granular mass.

Identified September 1, 2026More mineral →

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Physical properties

Formation & geological history

A high-pressure, medium-temperature metamorphic mineral formed mainly in schist and gneiss during regional metamorphism, commonly from Paleozoic to Precambrian rocks. It is an aluminosilicate polymorph of andalusite and sillimanite.

Uses & applications

Used as a refractory material in furnaces, kilns, and ceramics because it expands predictably when heated; attractive blue crystals are also sold as collectible or cabochon jewelry material.

Geological facts

The pronounced hardness anisotropy is diagnostic: a specimen can be scratched easily along its length but not across it. Blue color is typical, though white, gray, orange, and green varieties occur.

Field identification & locations

Identify it by its blue bladed habit, fibrous/striated surface, and directional hardness; distinguish it from sillimanite’s fibrous needles and blue sapphire’s uniform hardness. Common localities include Nepal, Brazil, Switzerland, India, and Virginia, USA.