metamorphic
Vein-bearing metamorphic rock, likely gneiss or schist
Banded silicate rock; likely quartz–feldspar–mica gneiss with a quartz vein
AI-generated identification · may be incorrectGray, coarse-grained, weakly foliated rock with darker and lighter mineral bands and a contrasting cream-white vein. Likely hardness 6–7, vitreous to dull luster, with quartz showing no cleavage and feldspar showing two cleavages; exact identification requires a fresh surface and tests.
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Physical properties
Gray, coarse-grained, weakly foliated rock with darker and lighter mineral bands and a contrasting cream-white vein. Likely hardness 6–7, vitreous to dull luster, with quartz showing no cleavage and feldspar showing two cleavages; exact identification requires a fresh surface and tests.
Formation & geological history
Formed when preexisting rock underwent high-pressure, high-temperature metamorphism, producing foliation; the pale vein likely formed when silica-rich fluids filled a fracture and crystallized as quartz. Its age cannot be determined from the photograph.
Uses & applications
Common varieties are used as crushed stone, aggregate, building and landscape stone, and occasionally as decorative specimens. This piece has modest collector value unless the banding or provenance is exceptional.
Geological facts
The pale linear feature is probably a mineral vein rather than a fossil or scratch. Gneissic banding reflects segregation of light quartz-feldspar minerals from dark biotite- or amphibole-rich minerals during metamorphism.
Field identification & locations
Look for alternating light/dark mineral bands, granular texture, and a vein that is harder and often more resistant than the host rock; a steel file may scratch feldspar but not quartz. Common in ancient continental shields and metamorphic mountain belts worldwide.
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