metamorphic

Biotite-rich schist (probable mica schist)

Mica schist, chiefly quartz + biotite mica; approximate composition varies

AI-generated identification · may be incorrect

Dark gray, strongly sparkly, platy texture from aligned mica; Mohs hardness about 2.5–3 for biotite and 7 for quartz, with good mica cleavage and a foliated crystalline structure. The specimen appears coarse-grained and may contain minor feldspar.

Identified September 17, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when clay-rich sedimentary rock was subjected to elevated temperature and pressure during regional metamorphism, commonly in mountain-building belts. Its exact geological age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally wall or paving stone; attractive pieces are collected, but it is not generally a jewelry gemstone.

Geological facts

The glitter comes mainly from reflective biotite flakes rather than metallic ore. Schistosity allows it to split along mica-rich foliation planes.

Field identification & locations

Look for visible, aligned mica flakes, planar splitting, and alternating dark mica with lighter quartz/feldspar; a glassy quartz grain should scratch glass while mica flakes can be scratched easily. Common worldwide in metamorphic mountain belts.