metamorphic

Blue-gray metamorphic rock fragment

Likely slate or phyllite; exact identification is uncertain from the photograph

AI-generated identification · may be incorrect

Fine-grained, blue-gray material with subtle planar layering and dull to weakly silky luster; likely Mohs hardness 2.5–4, with good cleavage or foliation. Composition may include mica, quartz, chlorite, and clay-derived minerals.

Identified September 11, 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. Such rocks can range from Paleozoic to much younger ages depending on locality.

Uses & applications

Slate is used for roofing, paving, flooring, and decorative stone; attractive pieces may be sold as specimens, though this fragment has low commercial value.

Geological facts

Phyllite commonly has a silky sheen from aligned fine mica, while slate breaks into flatter, sharper plates. The blue-gray color may reflect chlorite, graphite, or iron-poor mineral assemblages.

Field identification & locations

Look for strong planar foliation, splitting into thin sheets, and a streak that is usually pale gray. Common sources include slate belts in Wales, Vermont, Spain, Portugal, and the Appalachian region; a fresh surface and hardness test would improve identification.