metamorphic

Biotite-rich schist (likely mica schist)

Mica schist; predominantly quartz, biotite mica, and feldspar

AI-generated identification · may be incorrect

Typically Mohs 2.5–7 depending on mineral; this specimen appears brown-black, silvery, and glittery with a foliated, flaky texture and vitreous-to-pearly luster. Micas show perfect basal cleavage; specific gravity is commonly about 2.7–3.0.

Identified September 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when clay-rich sedimentary or igneous protoliths underwent medium-grade regional metamorphism, causing mica growth and alignment; age depends on its geological setting. Common in metamorphic belts and mountain roots.

Uses & applications

Used locally as decorative stone, aggregate, and occasionally dimension stone, but strong foliation limits structural use. Attractive pieces are collected for their sparkle and texture.

Geological facts

The reflective flashes are likely aligned biotite and/or muscovite flakes rather than metallic ore. Schistosity allows the rock to split into irregular plates.

Field identification & locations

Identify it by visible aligned mica flakes, foliation, and easy splitting; a streak test may reveal pale mica powder. Common worldwide in regions such as the Appalachians, Alps, Himalaya, and Precambrian shields.