metamorphic
Banded gneiss
Quartz–feldspar–mica gneiss; exact mineral composition cannot be confirmed from the image
AI-generated identification · may be incorrectTan and brown, coarse-grained, with alternating light and dark mineral bands and a rough, foliated texture. Likely minerals include quartz, feldspar, and mica; Mohs hardness is commonly about 6–7, with no single crystal structure or consistent cleavage for the whole rock.
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Physical properties
Tan and brown, coarse-grained, with alternating light and dark mineral bands and a rough, foliated texture. Likely minerals include quartz, feldspar, and mica; Mohs hardness is commonly about 6–7, with no single crystal structure or consistent cleavage for the whole rock.
Formation & geological history
Formed when pre-existing rock was subjected to high heat and pressure, causing minerals to recrystallize and segregate into bands. Gneiss forms across many geological ages and settings.
Uses & applications
Used as dimension stone, paving and landscaping material, aggregate, and a common educational or collector specimen.
Geological facts
Its characteristic banding, called gneissic foliation, reflects mineral separation during metamorphism; the bands are not sedimentary layers.
Field identification & locations
Look for coarse, interlocking grains arranged in distinct light and dark bands; this small specimen’s exact identity would require closer examination. Gneiss occurs worldwide in ancient continental crust and mountain belts.
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