metamorphic

Dark metamorphic rock, likely schist or phyllite

Micaceous schist/phyllite; commonly quartz, mica, and feldspar

AI-generated identification · may be incorrect

Dark gray, fine- to medium-grained rock with weakly visible foliation and silvery reflective mica surfaces. Typical hardness is about 2–7 depending on mineral grains; mica shows perfect cleavage, while quartz is glassy and hard.

Identified September 20, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was buried, heated, and compressed during regional metamorphism, commonly during mountain building. Exact age cannot be determined from the image; it may range from Precambrian to much younger.

Uses & applications

Used locally as dimension stone, landscaping stone, and aggregate; attractive foliated pieces may be collected, but this specimen has little commercial value.

Geological facts

The planar alignment of mica produces schistosity or phyllitic cleavage, allowing the rock to split along preferred surfaces. Weathering commonly creates rusty patches from iron-bearing minerals.

Field identification & locations

Look for foliation, sparkly mica flakes, and layers that split more readily in one direction; a glass scratch test can distinguish abundant quartz from softer mica. Common in metamorphic belts worldwide, including the Appalachians, New England, Scotland, and the Alps.