metamorphic

Foliated metamorphic rock, likely slate or phyllite

Slate–phyllite; primarily quartz, mica, and clay-derived minerals

AI-generated identification · may be incorrect

Fine-grained, gray-green, thinly layered and strongly foliated, with dull to silky luster; hardness about 3–5. It splits along planar cleavage and may contain weathering stains, moss, and iron-oxide patches.

Identified August 15, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone underwent low-grade regional metamorphism, realigning clay minerals into cleavage; commonly Paleozoic to Precambrian in age, depending on location.

Uses & applications

Used locally for roofing, paving, landscaping, wall stone, and aggregate; attractive phyllite may be collected but is generally low-value.

Geological facts

Slate has very flat, sharp cleavage surfaces, while phyllite has a satiny sheen and slightly wavy foliation. The photographed outcrop appears weathered and may represent a foliated slate/phyllite transition.

Field identification & locations

Common in metamorphic belts worldwide, including the Appalachian Mountains, Wales, and New England. Identify it by thin planar splitting, fine grain, and aligned mica sheen; distinguish it from shale by its more pronounced cleavage and recrystallized texture.