metamorphic

Biotite–quartz–feldspar schist

Mica schist; chiefly quartz (SiO₂), feldspar, and biotite mica

AI-generated identification · may be incorrect

Typically medium- to coarse-grained, gray-brown, and strongly foliated with glittering mica flakes; quartz and feldspar are harder (Mohs 6–7), while biotite is Mohs 2.5–3. It has a vitreous to pearly luster, mica cleavage, and a granoblastic–lepidoblastic texture.

Identified September 11, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or a clay-rich sedimentary protolith underwent regional metamorphism during mountain building, commonly at greenschist to amphibolite facies. Such rocks range from Precambrian to Phanerozoic ages depending on the terrane.

Uses & applications

Used locally as building stone, landscaping material, decorative facing, and aggregate, though pronounced foliation limits structural use; attractive pieces are collected as educational or display specimens.

Geological facts

The silvery or bronze sparkle comes from aligned mica flakes, producing schistosity. Garnet, staurolite, or graphite may occur as accessory minerals, but none is clearly diagnostic in this image.

Field identification & locations

Identify it by visible mica sparkle, planar foliation, and layers that split along mica-rich surfaces; distinguish it from granite by its pronounced alignment and from gneiss by its finer, more strongly schistose texture. Common in metamorphic mountain belts worldwide.