metamorphic
Banded metamorphic pebble (possibly gneiss)
Likely banded gneiss; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectRounded, smooth gray-and-cream bands with a fine-grained appearance. Gneiss commonly contains quartz and feldspar with mica or other dark minerals; hardness is typically about 6–7 Mohs, with no consistent cleavage and a granular texture.
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Physical properties
Rounded, smooth gray-and-cream bands with a fine-grained appearance. Gneiss commonly contains quartz and feldspar with mica or other dark minerals; hardness is typically about 6–7 Mohs, with no consistent cleavage and a granular texture.
Formation & geological history
Gneiss forms when existing rock is recrystallized and compositionally banded under high heat and pressure. Such rocks are commonly Precambrian, though the pebble’s age and source cannot be determined from the image.
Uses & applications
Small polished pebbles are mainly used for collecting or decoration; gneiss is also used as dimension stone and aggregate.
Geological facts
The light and dark stripes resemble gneissic banding, but similar patterns occur in several other rocks; a close examination of grains would improve identification.
Field identification & locations
Check for interlocking mineral grains and alternating light and dark bands; common sources include metamorphic terrains and river or beach gravels. The rounded shape suggests transport or deliberate polishing.
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