igneous
Black-veined pebble, likely basalt in a weathered host rock
Probable basaltic dike or vein in altered volcanic rock; exact identification requires testing
AI-generated identification · may be incorrectDark gray-brown, rounded and weathered, with a black fine-grained vein or inclusion and thin fracture lines. Basalt is typically Mohs 6–6.5, dull to weakly lusterous, dense, and composed mainly of plagioclase and pyroxene; the host may be softer and altered.
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Physical properties
Dark gray-brown, rounded and weathered, with a black fine-grained vein or inclusion and thin fracture lines. Basalt is typically Mohs 6–6.5, dull to weakly lusterous, dense, and composed mainly of plagioclase and pyroxene; the host may be softer and altered.
Formation & geological history
Likely formed when basaltic magma intruded cracks in older volcanic rock, then cooled and was rounded by erosion or transport. The specimen’s geological age and precise setting cannot be determined from the image.
Uses & applications
Primarily a study or decorative specimen; basalt is widely used as aggregate, roadstone, building stone, and occasionally ornamental material.
Geological facts
The contrasting black feature may be a true basalt vein, dark mineral-rich seam, or infilled fracture; a fresh broken surface and magnetic response would help distinguish these possibilities.
Field identification & locations
Common in volcanic terrains and stream gravels. Look for fine texture, high density, possible magnetism, and a black streak or vein cutting the lighter host; acid testing and hardness comparison may help.
