metamorphic

Likely biotite-rich schist with a quartz/feldspar inclusion

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

AI-generated identification · may be incorrect

Typically medium–coarse grained, dark gray to black, with strongly reflective platy mica and foliation; hardness about 2.5–3 for biotite and 6–7 for quartz, with mica cleavage and a micaceous luster. The image is low-resolution, so exact identification is tentative.

Identified September 6, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sedimentary rock underwent medium- to high-grade regional metamorphism, commonly during mountain building; age depends on locality and may range from Precambrian to Phanerozoic.

Uses & applications

Used as decorative stone, wall cladding, landscaping material, and occasionally aggregate; attractive pieces may be collected, though it is generally unsuitable for high-wear countertops because mica flakes weaken the rock.

Geological facts

The shiny surfaces are aligned mica flakes produced by directed pressure and recrystallization. A pale, rounded area may be quartz or feldspar, but the image alone cannot confirm its identity.

Field identification & locations

Look for pronounced foliation, glittering elastic mica flakes, and layers that split along schistosity; common in regional metamorphic belts worldwide, including the Appalachians, Alps, and Himalaya.