metamorphic
Likely banded gneiss
Foliated quartz–feldspar gneiss, with dark biotite or amphibole
AI-generated identification · may be incorrectCoarse, irregular light and dark mineral bands; grains appear crystalline with a dull to mildly glistening luster. Typical hardness is about 6–7 Mohs; exact mineral composition cannot be confirmed from the photo.
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Physical properties
Coarse, irregular light and dark mineral bands; grains appear crystalline with a dull to mildly glistening luster. Typical hardness is about 6–7 Mohs; exact mineral composition cannot be confirmed from the photo.
Formation & geological history
Forms when pre-existing rock is recrystallized and segregated into mineral bands under high heat and pressure. Gneisses span a wide range of geological ages and occur in ancient continental crust.
Uses & applications
Used as building or landscaping stone and collected as a representative metamorphic rock; this small fragment has little commercial value.
Geological facts
Gneiss is identified by its compositional banding, unlike the flatter, finer foliation typical of schist or slate.
Field identification & locations
The visible contrasting, streaky bands suggest gneiss, but a close inspection would be needed to distinguish it from other foliated rocks. Common in continental shields and mountain belts worldwide.
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