metamorphic

Banded gneiss

Quartz–feldspar–mica gneiss; exact mineral composition cannot be confirmed from the image

AI-generated identification · may be incorrect

Coarse, irregular light and dark bands suggest quartz and feldspar with dark mica or amphibole; typically Mohs 6–7, vitreous to dull luster, and no prominent cleavage. The specimen’s pale cream, reddish-brown, and dark gray bands are visible, but its crystal structure and specific gravity cannot be determined from the…

Identified October 13, 2026More metamorphic →

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Physical properties

Formation & geological history

Likely formed when pre-existing rock underwent high-grade heat and pressure, separating minerals into bands. Gneisses occur in ancient continental crust and can be billions of years old; this specimen’s age and locality are unknown.

Uses & applications

Gneiss is used as dimension stone, paving and landscaping material, and aggregate; attractive pieces may be collected or displayed.

Geological facts

Gneissic banding records mineral segregation during metamorphism and can resemble sedimentary layering, though the bands are typically recrystallized.

Field identification & locations

Look for coarse, interlocking crystals arranged in distinct light and dark bands; common in exposed ancient mountain belts and continental shields. A close-up or hardness and mineral tests would help distinguish gneiss from other banded rocks.