metamorphic

Biotite schist with quartz veins

Quartz–mica schist; primarily quartz (SiO₂), biotite mica, and feldspar

AI-generated identification · may be incorrect

Dark gray, fine-to-medium grained, foliated metamorphic rock with sparkling mica and contrasting white quartz patches or veins. Quartz has Mohs hardness 7; biotite is 2.5–3, with vitreous quartz and pearly mica luster; cleavage is strong in mica.

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sedimentary rock underwent regional metamorphism, producing mica alignment and schistosity; quartz segregated or crystallized in fractures. Typically Paleozoic or older, though exact age cannot be determined from the photograph.

Uses & applications

Used mainly as landscape stone, decorative slabs, building accent material, and teaching or collecting specimens; attractive pieces may be sold as cabinet specimens but are not usually jewelry-grade.

Geological facts

The pale crystals are likely quartz, although feldspar or calcite is possible without testing. Its foliated texture and visible mica distinguish schist from massive basalt or granite.

Field identification & locations

Identify by gently reflective, aligned mica flakes, planar splitting, and hard white quartz. Common in regional metamorphic belts worldwide, including the Appalachians, New England, Scotland, Scandinavia, and the Himalaya; a fresh surface, streak, hardness, and acid test would improve identification.