metamorphic

Banded gneiss

Quartz–feldspar gneiss, with dark biotite or amphibole

AI-generated identification · may be incorrect

Coarse, irregular light and dark bands; likely quartz, feldspar, and dark mica/amphibole. Typical hardness is about 6–7 Mohs, vitreous to dull luster, with no consistent cleavage visible; exact minerals cannot be confirmed from the photo.

Identified October 4, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when pre-existing rock was altered by high heat and pressure, causing minerals to segregate into bands. Gneisses occur in ancient continental basement rocks, commonly billions of years old.

Uses & applications

Primarily a decorative or collecting specimen; sound gneiss is also used as building stone, paving, and crushed aggregate.

Geological facts

The distinctive banding is called gneissic foliation and reflects mineral alignment or separation during metamorphism.

Field identification & locations

Look for coarse, alternating pale quartz/feldspar and dark mineral bands; the pictured hand-sized, apparently naturally shaped specimen fits this appearance. Gneiss is widespread in ancient mountain belts and continental shields.