metamorphic

Biotite-rich schist

Mica schist; primarily quartz, feldspar, and biotite mica

AI-generated identification · may be incorrect

Typically medium-grained and foliated, with abundant reflective brown-black mica flakes; Mohs hardness about 2.5–7 depending on mineral, vitreous to pearly luster, and mica’s perfect basal cleavage. The specimen appears weathered and may contain minor iron oxides.

Identified September 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was subjected to regional metamorphism, producing aligned mica and schistosity; commonly associated with Paleozoic to Precambrian metamorphic belts, though age cannot be determined from the image.

Uses & applications

Used locally as decorative stone, landscaping material, wall facing, and aggregate; attractive mica-rich pieces are collected, but it is generally unsuitable for high-wear construction surfaces because it splits along foliation.

Geological facts

The glitter comes from reflected light on aligned biotite or muscovite flakes, not necessarily gold. Schistosity allows the rock to break into flaky or platy fragments.

Field identification & locations

Identify it by visible foliation and abundant sparkly mica flakes; unlike granite, its minerals are aligned rather than randomly interlocking. Common in mountain belts and exposed metamorphic terrains worldwide.