metamorphic
Banded gneiss
Quartz–feldspar–mica gneiss
AI-generated identification · may be incorrectTypically Mohs 6–7, gray to white with dark mineral bands, vitreous to dull luster, and granular interlocking crystals; foliation produces the prominent layered texture, with no strong cleavage as a whole rock.
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Physical properties
Typically Mohs 6–7, gray to white with dark mineral bands, vitreous to dull luster, and granular interlocking crystals; foliation produces the prominent layered texture, with no strong cleavage as a whole rock.
Formation & geological history
Forms when granite or other felsic rock undergoes high-grade regional metamorphism, causing minerals to recrystallize and segregate into bands during intense heat and pressure, commonly during Precambrian to Paleozoic mountain building.
Uses & applications
Used as dimension stone, decorative facing, landscaping rock, aggregate, and occasionally as a polished architectural stone; attractive specimens have modest collector value.
Geological facts
The specimen’s light-gray, strongly banded, foliated appearance is consistent with gneiss, though field identification cannot confirm the exact mineral proportions from the photograph alone.
Field identification & locations
Look for alternating light quartz/feldspar-rich layers and darker biotite- or amphibole-rich bands, with coarse interlocking grains and a hard, resistant surface; common worldwide in ancient continental shields and metamorphic mountain belts.
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