metamorphic

Gray slate or fine-grained metamorphic rock

Slate–phyllite spectrum; predominantly fine-grained quartz, mica, and chlorite

AI-generated identification · may be incorrect

Gray, dull to slightly silky luster, very fine grained, with planar foliation and likely slaty cleavage; typical hardness is about 3–5 Mohs, with no visible large crystals. Exact identification is limited by the single photograph and lack of tests.

Identified September 15, 2026More metamorphic →

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Physical properties

Formation & geological history

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

Uses & applications

Slate is used for roofing, paving, tiles, writing slabs, and landscaping; attractive pieces may be collected, but this fragment has little commercial value.

Geological facts

The apparent layered splitting is characteristic of slaty cleavage, produced by aligned microscopic clay minerals and mica rather than original sedimentary bedding.

Field identification & locations

Common in metamorphic belts worldwide, including Wales, Vermont, Spain, and Appalachia. Test for thin planar splitting, a fine even texture, and a streak that is usually gray; a hardness and acid test can help exclude softer shale or carbonate rock.