metamorphic
Banded gneiss pebble
Feldspar–quartz gneiss; exact mineral composition cannot be confirmed from the image
AI-generated identification · may be incorrectRounded, coarse-grained pebble with pale blue-green and tan-pink bands, likely from feldspar and quartz-rich layers. Gneiss minerals commonly have Mohs hardness around 6–7 and a vitreous to dull luster; individual grains are too small to identify crystal structure or cleavage reliably.
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Physical properties
Rounded, coarse-grained pebble with pale blue-green and tan-pink bands, likely from feldspar and quartz-rich layers. Gneiss minerals commonly have Mohs hardness around 6–7 and a vitreous to dull luster; individual grains are too small to identify crystal structure or cleavage reliably.
Formation & geological history
Formed when pre-existing rock was subjected to high heat and pressure, separating minerals into compositional bands. Gneiss can be Precambrian or younger; the pebble’s age and source cannot be determined visually.
Uses & applications
Gneiss is used as dimension stone, paving, aggregate, and landscaping stone; this small pebble is mainly decorative or collectible.
Geological facts
The alternating light and dark mineral bands are called gneissic banding and distinguish gneiss from many uniformly textured rocks.
Field identification & locations
Look for visible, roughly parallel mineral bands and interlocking grains; confirm with a fresh surface and mineral tests. Gneiss occurs widely in ancient continental crust and glacial or stream deposits.
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