metamorphic

Dark mica-rich metamorphic rock, likely schist

Mica schist; commonly quartz–biotite ± muscovite schist

AI-generated identification · may be incorrect

Fine- to medium-grained, dark gray rock with abundant reflective mica flakes and visible foliation; quartz and feldspar may appear as lighter grains. Typical hardness is about 2–3 for mica surfaces and 6–7 for quartz; mica has perfect basal cleavage, with a silvery to bronze vitreous/pearly luster.

Identified September 22, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sediment was regionally metamorphosed under moderate temperature and pressure, producing aligned mica layers. Such rocks range from Precambrian to younger Paleozoic–Mesozoic metamorphic terranes.

Uses & applications

Used locally as decorative stone, landscaping material, fill, and occasionally thin facing stone; its strong foliation limits structural construction use. Attractive mica-rich pieces are collected but usually have modest value.

Geological facts

The sparkling appearance comes from light reflecting off aligned mica crystals, not necessarily from metallic minerals. Foliation commonly causes the rock to split into platy slabs.

Field identification & locations

Identify it by its planar layering, flaky reflective surfaces, and tendency to split along foliation; a hand lens should reveal mica, quartz, and feldspar. Common in mountain belts and exposed metamorphic complexes worldwide, including the Appalachians, Alps, and Himalaya.