metamorphic

Likely slate or fine-grained metamorphic rock

Slate–phyllite spectrum; commonly quartz, mica, and chlorite

AI-generated identification · may be incorrect

Dark gray, fine-grained, dull to slightly silky luster, with irregular planar cleavage visible along broken surfaces. Typical hardness is about 3–5 Mohs; exact identification is limited by the single photograph.

Identified September 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or mudstone undergoes low-grade regional metamorphism, commonly during mountain building. Its age depends on the source formation and cannot be determined visually.

Uses & applications

Used for roofing, floor and wall tiles, paving, writing slates, and decorative stone; attractive pieces may be collected but are usually low value.

Geological facts

Slate splits into thin sheets, whereas phyllite has a more pronounced silky sheen and wavy foliation. The specimen appears rough and naturally fractured rather than polished.

Field identification & locations

Look for consistent foliation, easy splitting, very fine grains, and absence of visible large crystals; a streak test, hardness test, and inspection of cleavage would help distinguish slate from shale, schist, or basalt. Common worldwide in metamorphic belts.