metamorphic
Likely gneiss pebble
Gneiss, a foliated metamorphic rock composed mainly of quartz, feldspar, and mica
AI-generated identification · may be incorrectThe image shows a rounded gray pebble with pale, irregular mineral bands. Typical gneiss has Mohs hardness about 6–7, a granular texture, and alternating light and dark mineral layers; exact properties cannot be confirmed from the image.
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Physical properties
The image shows a rounded gray pebble with pale, irregular mineral bands. Typical gneiss has Mohs hardness about 6–7, a granular texture, and alternating light and dark mineral layers; exact properties cannot be confirmed from the image.
Formation & geological history
Gneiss forms when existing rocks undergo intense heat and pressure, commonly deep in continental crust. Its age varies widely, from ancient Precambrian rocks to younger metamorphic belts.
Uses & applications
Gneiss is used as dimension stone, paving, and aggregate; small pebbles are mainly collected or used decoratively.
Geological facts
Its distinctive banding reflects mineral segregation during metamorphism and may be folded or contorted.
Field identification & locations
Look for coarse grains and visible alternating light and dark bands; the pictured pebble’s pattern is suggestive but not diagnostic. Gneiss occurs in exposed metamorphic terrains worldwide.
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