metamorphic

Blue-gray metamorphic rock, likely slate or phyllite

Fine-grained foliated metapelite; commonly mica- and chlorite-rich

AI-generated identification · may be incorrect

Appears blue-gray, opaque, and dull to slightly silky, with fine foliation and possible mica sparkle. Typical hardness is about 3–5 Mohs, with planar cleavage; exact identification is limited by the photograph.

Identified September 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when clay-rich sedimentary rock was subjected to low-grade regional metamorphism, generally during mountain building. Its age depends on locality and may range from Precambrian to Paleozoic or younger.

Uses & applications

Slate is used for roofing, flooring, tiles, and writing surfaces; phyllite is mainly decorative or collected. Small specimens generally have modest value.

Geological facts

The sheen in phyllite comes from aligned microscopic muscovite or sericite mica. Slate splits more cleanly into flat sheets, whereas phyllite commonly has a crinkled or silky foliation.

Field identification & locations

Look for strong planar splitting, aligned grains, and a fine texture; a glassy streak or obvious crystals could indicate another rock such as schist. Common worldwide in metamorphic belts, including Wales, the northeastern United States, and the Alps.