metamorphic

Banded gneiss

Foliated gneiss, likely quartz–feldspar–biotite or amphibole gneiss

AI-generated identification · may be incorrect

Gray and white with dark, elongated mineral bands and a coarse, foliated texture. Typical minerals are quartz and feldspar with biotite or hornblende; Mohs hardness is about 6–7, with no consistent cleavage in the whole rock. Exact mineral composition cannot be confirmed from the photo.

Identified September 25, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when pre-existing igneous or sedimentary rock was recrystallized and segregated into bands under high heat and pressure. Gneisses occur in ancient continental crust, though this specimen’s age and source cannot be determined visually.

Uses & applications

Used as dimension stone, landscaping material, and decorative stone; attractive pieces may be collected.

Geological facts

Gneissic banding reflects mineral segregation during metamorphism and is not sedimentary layering.

Field identification & locations

Look for coarse, alternating light and dark mineral bands; unlike slate, it does not usually split into thin sheets. Gneiss is common in mountain belts and exposed continental shields worldwide.