metamorphic
Weathered banded gneiss (probable)
Foliated quartz–feldspar gneiss; exact minerals cannot be confirmed from the image
AI-generated identification · may be incorrectTan, cream, and pale green-gray bands with a rough, layered fracture and dull to slightly glassy grains. Typical gneiss is chiefly quartz and feldspar with mica or other dark minerals; hardness about 6–7 Mohs, with no single cleavage.
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Physical properties
Tan, cream, and pale green-gray bands with a rough, layered fracture and dull to slightly glassy grains. Typical gneiss is chiefly quartz and feldspar with mica or other dark minerals; hardness about 6–7 Mohs, with no single cleavage.
Formation & geological history
Likely formed when pre-existing rock was recrystallized and compositionally banded under high heat and pressure during regional metamorphism. Such rocks occur in ancient continental crust; the specimen’s age cannot be determined from appearance.
Uses & applications
Gneiss is used as dimension stone, paving, landscaping aggregate, and sometimes decorative stone; this small rough fragment is mainly a collectible.
Geological facts
The alternating light and darker mineral bands are called gneissic banding and result from mineral segregation during metamorphism.
Field identification & locations
Look for coarse grains and distinct, roughly parallel mineral bands; the yellow-brown color may be surface iron staining. Gneiss is common in exposed ancient mountain belts and shield regions.
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