metamorphic

Blue-andalusite (likely chiastolite-bearing metamorphic fragment)

Andalusite, Al₂SiO₅; possibly mixed with quartz/mica

AI-generated identification · may be incorrect

Hardness 6.5–7.5, blue-gray to black with white veining, vitreous to dull luster, typically orthorhombic crystals and poor cleavage. The image is insufficient for confident identification; kyanite or blue schist minerals are alternatives.

Identified September 8, 2026More metamorphic →

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Physical properties

Formation & geological history

Al₂SiO₅ minerals form during regional metamorphism of aluminous clay-rich rocks, generally at moderate temperature and pressure. Specimen age depends on its host terrane, commonly Paleozoic to Precambrian.

Uses & applications

Andalusite is used in refractory ceramics and furnace linings; attractive crystals are collected, though this small rough piece has limited gem value.

Geological facts

Color alone is unreliable because inclusions and weathering can produce blue-gray tones. A hardness test, streak, crystal habit, and host-rock examination would substantially improve identification.

Field identification & locations

Look for prismatic orthorhombic crystals, high hardness, and association with mica, quartz, and schist. Andalusite occurs in metamorphic belts worldwide, including Spain, France, Brazil, Australia, and the United States.