metamorphic

Banded gneiss

Gneiss, likely quartz–feldspar–mica gneiss

AI-generated identification · may be incorrect

Coarse, irregular bands of pale quartz and feldspar alternating with darker mica-rich layers; generally Mohs 6–7, vitreous to dull luster, and no prominent cleavage. The image shows a rounded, weathered boulder; exact mineral proportions cannot be confirmed visually.

Identified September 27, 2026More metamorphic →

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Physical properties

Formation & geological history

Forms when pre-existing igneous or sedimentary rock undergoes high-grade heat and pressure, causing minerals to segregate into bands. Gneisses occur in ancient continental crust, often billions of years old.

Uses & applications

Used as dimension stone, paving, landscaping rock, and decorative facing; attractive banded pieces may be collected.

Geological facts

Gneissic banding is produced by metamorphic segregation and deformation, not by sedimentary layering.

Field identification & locations

Look for coarse, alternating light and dark mineral bands and a hard, crystalline texture; common in old continental shields and mountain belts. A large landscape boulder like this is typically worth about $20–$200, depending on size, locality, and transport costs.