metamorphic
Weathered granitic gneiss (probable)
Quartz–feldspar–biotite gneiss; compositionally similar to granite
AI-generated identification · may be incorrectGray, coarse-grained, rounded cobble with visible light quartz/feldspar and darker mafic grains. Likely hardness ~6–7 Mohs, vitreous to dull luster, massive or weakly foliated texture, and no obvious cleavage; density commonly ~2.6–2.8 g/cm³.
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Physical properties
Gray, coarse-grained, rounded cobble with visible light quartz/feldspar and darker mafic grains. Likely hardness ~6–7 Mohs, vitreous to dull luster, massive or weakly foliated texture, and no obvious cleavage; density commonly ~2.6–2.8 g/cm³.
Formation & geological history
Probably an ice-transported or stream-rounded Precambrian crystalline cobble, later weathered smooth. The Smolensk-region location is compatible with glacially transported Baltic/Fennoscandian crystalline rocks, though the photograph cannot establish age or exact provenance.
Uses & applications
Mostly a landscaping or collecting stone; similar durable rock is used as aggregate, paving stone, riprap, and occasionally dimension stone. This specimen has little commercial gemstone value.
Geological facts
The orange-brown patches are iron-oxide weathering, while the pale speckled appearance is typical of quartz and feldspar. A fresh broken surface would reveal the grain size and whether true gneissic banding is present.
Field identification & locations
Commonly found as rounded erratic cobbles in soils and river or glacial deposits around western Russia. Confirm by inspecting a fresh surface: quartz scratches glass, feldspar is usually white/pink, and mica may split into dark flakes; strong alternating bands would support gneiss over granite.
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