mineral

Kyanite with pyrite

Kyanite (Al₂SiO₅), with possible pyrite (FeS₂) inclusions

AI-generated identification · may be incorrect

The specimen shows a dark blue-gray, bladed crystal with metallic-brassy patches. Kyanite has Mohs hardness 4.5–5 parallel to its length and 6.5–7 across it, vitreous to pearly luster, and perfect cleavage; pyrite is harder (6–6.5) and metallic.

Identified October 11, 2026More mineral →

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Physical properties

Formation & geological history

Kyanite forms during regional metamorphism of aluminum-rich sediments, commonly in schist or gneiss; associated sulfides may crystallize during metamorphism. Such rocks are often hundreds of millions to billions of years old, but the specimen’s age cannot be determined from the image.

Uses & applications

Kyanite is used in high-temperature ceramics and refractory products; attractive blue crystals are collected and sometimes cut as gemstones. Pyrite is chiefly a collector mineral.

Geological facts

Kyanite’s hardness varies markedly with crystal direction, an unusual diagnostic feature. The brassy patches may be pyrite, though the image alone cannot confirm their identity.

Field identification & locations

Look for elongated, bladed blue crystals in metamorphic schist, with directional hardness and cleavage; common sources include Brazil, Nepal, India, and the United States. The visible blue blade and brassy inclusions support this identification.