metamorphic
Banded gneiss pebble
Gneiss, likely quartz–feldspar–biotite gneiss
AI-generated identification · may be incorrectDark gray and tan alternating mineral bands with a mostly matte, fine-to-medium-grained surface. Typical minerals have Mohs hardness around 6–7; gneiss has no single crystal structure or cleavage, and its density is commonly 2.6–2.9 g/cm³.
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Physical properties
Dark gray and tan alternating mineral bands with a mostly matte, fine-to-medium-grained surface. Typical minerals have Mohs hardness around 6–7; gneiss has no single crystal structure or cleavage, and its density is commonly 2.6–2.9 g/cm³.
Formation & geological history
Formed when pre-existing rock was recrystallized and segregated into mineral bands under high heat and pressure, often deep in the crust. Such rocks occur across a wide range of geological ages.
Uses & applications
Used as building and paving stone, decorative aggregate, and landscape material; small polished or naturally smoothed pieces are collected.
Geological facts
The characteristic gneissic banding reflects mineral segregation during metamorphism, not sedimentary layering.
Field identification & locations
The visible alternating light and dark bands and interlocking granular texture suggest gneiss; similar pebbles occur in glacial deposits, river gravels, and exposed metamorphic terrains worldwide.
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