metamorphic

Dark gray foliated metamorphic rock, likely slate or phyllite

Slate–phyllite; predominantly quartz, mica, and chlorite

AI-generated identification · may be incorrect

Fine-grained, dark gray, dull to slightly silky luster, with planar foliation and likely slaty cleavage; hardness approximately 3–5. The image does not resolve mineral grains or cleavage sufficiently for a precise identification.

Identified September 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone underwent low-grade regional metamorphism during mountain building; age depends on its source terrane and cannot be determined visually.

Uses & applications

Slate is used for roofing, paving, flooring, and landscaping; attractive slabs may be used decoratively, though this rough specimen has little commercial value.

Geological facts

Slate splits into thin, planar sheets, while phyllite has a more pronounced silky sheen and wavy foliation. Weathering commonly produces rusty brown iron-oxide patches.

Field identification & locations

Look for consistent splitting planes, fine grain, and mica sheen; a streak test, close-up inspection, and fresh fracture would distinguish slate from phyllite or schist. Common in metamorphic belts worldwide, including Wales, the Appalachians, and New England.