metamorphic

Banded gneiss

Quartz–feldspar gneiss, possibly biotite-bearing; exact identification requires testing

AI-generated identification · may be incorrect

Gray-green, coarse-grained specimen with irregular light and dark mineral bands. Likely quartz, feldspar, and dark mica or amphibole; typical quartz and feldspar hardness is about 6, with a crystalline, nonmetallic luster and no consistent cleavage at the rock scale.

Identified September 23, 2026More metamorphic →

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Physical properties

Formation & geological history

Gneiss forms when existing igneous or sedimentary rocks undergo high-grade heat and pressure, segregating minerals into bands. Its age and specific formation setting cannot be determined from the image.

Uses & applications

Used as dimension stone, paving, landscaping, and decorative facing; attractive pieces may be collected or cut for display.

Geological facts

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

Field identification & locations

Look for coarse, interlocking crystals arranged in alternating pale and dark bands; common in ancient continental mountain belts and shield regions. The image alone cannot establish the exact variety or locality.