metamorphic

Biotite-bearing mica schist (probable)

Mica schist, chiefly quartz + muscovite/biotite; composition is uncertain from the photograph

AI-generated identification · may be incorrect

Coarse, strongly glittery flakes suggest mica, with granular quartz and possible feldspar. Likely Mohs hardness 2–3 for mica and 6–7 for quartz; silvery-brown color, pearly to vitreous luster, platy crystals, and excellent mica cleavage.

Identified September 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was subjected to regional metamorphism, commonly during mountain building. The specimen’s exact geological age cannot be determined visually; schists range from Precambrian to recent orogenic belts.

Uses & applications

Used locally as decorative stone, aggregate, fill, and occasionally dimension stone; attractive mica-rich pieces are collected but are generally not jewelry-grade.

Geological facts

Its glitter comes from aligned mica sheets reflecting light, and the foliation records directed pressure during metamorphism.

Field identification & locations

Look for planar foliation, flakes that separate into thin elastic sheets, and a mixed quartz-mica texture. Common in metamorphic mountain regions worldwide, including the Appalachians, New England, Scandinavia, and the Himalaya.