metamorphic
Banded gneiss pebble
Gneiss, typically quartz–feldspar–mica; exact mineral composition requires testing
AI-generated identification · may be incorrectGray, white, and dark mineral bands with a coarse crystalline texture and dull to slightly vitreous luster; usually Mohs 6–7, with no prominent cleavage as a whole and relatively high density (~2.6–2.8 g/cm³).
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Physical properties
Gray, white, and dark mineral bands with a coarse crystalline texture and dull to slightly vitreous luster; usually Mohs 6–7, with no prominent cleavage as a whole and relatively high density (~2.6–2.8 g/cm³).
Formation & geological history
Formed when granite or other felsic rock underwent intense regional metamorphism, causing mineral recrystallization and compositional banding; commonly Precambrian to younger, depending on source terrain.
Uses & applications
Used as crushed stone, aggregate, dimension stone, landscaping material, and decorative polish; this small rounded specimen has mainly educational or modest collecting value.
Geological facts
The light bands are commonly quartz and feldspar, while dark bands commonly contain biotite, amphibole, or pyroxene. Water abrasion produced the rounded pebble shape.
Field identification & locations
Identify it by alternating light and dark mineral bands, interlocking grains, and a non-layered crystalline texture; common in glaciated river gravels and exposed metamorphic terrains worldwide.
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