metamorphic
Weathered metamorphic rock, likely gneiss or schist
Indeterminate foliated silicate rock; commonly quartz–feldspar–mica assemblage
AI-generated identification · may be incorrectGray-brown, fine- to medium-grained, dull earthy luster with subtle foliation and weathering stains; typical hardness about 6–7 Mohs, no obvious cleavage at specimen scale, and specific gravity roughly 2.6–2.8.
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Physical properties
Gray-brown, fine- to medium-grained, dull earthy luster with subtle foliation and weathering stains; typical hardness about 6–7 Mohs, no obvious cleavage at specimen scale, and specific gravity roughly 2.6–2.8.
Formation & geological history
Likely formed when pre-existing igneous or sedimentary rock underwent regional metamorphism at elevated temperature and pressure, then eroded into a rounded cobble; age cannot be determined from appearance alone.
Uses & applications
Unusual hand specimens may be collected or used decoratively; related gneiss and schist are also used as dimension stone, paving, aggregate, and building veneer.
Geological facts
The rounded shape and softened edges indicate transport or prolonged weathering, while faint banding suggests metamorphic foliation rather than a massive volcanic rock.
Field identification & locations
Look for aligned mica flakes or alternating light and dark mineral bands, a sparkly fresh surface, and hardness sufficient to scratch glass; a thin section or chemical test is needed for confident identification. Common in eroded stream gravels and exposed metamorphic terrains.
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