metamorphic

Micaceous schist (likely muscovite–biotite schist)

Mica schist; primarily quartz (SiO₂), feldspar, muscovite and/or biotite micas

AI-generated identification · may be incorrect

Gray, sparkly, strongly foliated rock with abundant platy mica; sheets split readily along schistosity. Quartz and feldspar are ~Mohs 6–7, while mica is ~2–3; luster is pearly to vitreous and texture is crystalline.

Identified September 16, 2026More metamorphic →

Explore Micaceous schist (likely muscovite–biotite schist) in the encyclopedia →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sediment was subjected to elevated heat and pressure during regional metamorphism, commonly during mountain building. Its exact age cannot be determined from the image and depends on its locality.

Uses & applications

Used locally as decorative stone, wall or garden rock, fill, and occasionally roofing or facing material; attractive mica-rich pieces are collected but are rarely high-value.

Geological facts

The glitter comes from reflective mica flakes, not necessarily metallic minerals. Foliation records directed tectonic pressure and may make the rock split into thin slabs.

Field identification & locations

Identify it by its glittery platy surface, pronounced layering, and ability to break along mica-rich planes; a hardness test, streak, and locality information would distinguish it from phyllite or gneiss. Common in metamorphic mountain belts worldwide, including New England, the Appalachians, the Alps, and the Himalaya.