metamorphic
Likely gneiss
Gneiss, composed chiefly of quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, strongly banded rock with pale quartz-feldspar layers and dark biotite- or amphibole-rich bands; typical hardness is about 6–7 Mohs, with vitreous to pearly luster and weak or absent cleavage as a whole rock.
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Physical properties
Coarse-grained, strongly banded rock with pale quartz-feldspar layers and dark biotite- or amphibole-rich bands; typical hardness is about 6–7 Mohs, with vitreous to pearly luster and weak or absent cleavage as a whole rock.
Formation & geological history
Forms when granite or other crustal rock undergoes high-grade metamorphism involving intense heat and pressure, commonly during mountain building; specimens may range from Precambrian to younger ages.
Uses & applications
Used as dimension stone, paving, landscaping aggregate, wall stone, and occasionally polished architectural stone; generally has low jewelry value.
Geological facts
The image is blurry and overexposed, so exact identification is uncertain; the dark–light compositional banding is most consistent with gneiss rather than ordinary granite.
Field identification & locations
Identify it by alternating light and dark mineral bands, coarse visible grains, and a hard, massive texture. Common worldwide in ancient continental shields and mountain belts, including Scandinavia, Canada, India, Brazil, and the Alps.
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