igneous
Weathered basalt pebble (likely vesicular basalt)
Basalt, chiefly plagioclase feldspar and pyroxene, with possible olivine and iron oxides
AI-generated identification · may be incorrectFine-grained, brown to gray weathered surface with dark inclusions or vesicles; typically dull to weakly lustered, hardness about 5–6 Mohs, no visible cleavage, and specific gravity roughly 2.8–3.0.
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Physical properties
Fine-grained, brown to gray weathered surface with dark inclusions or vesicles; typically dull to weakly lustered, hardness about 5–6 Mohs, no visible cleavage, and specific gravity roughly 2.8–3.0.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface; its exact age cannot be determined from the photograph and may range from recent to billions of years.
Uses & applications
Used as aggregate, road stone, riprap, and building stone; attractive polished pieces may be collected, though this small weathered pebble has modest value.
Geological facts
The pale circular spots may be weathering halos, altered mineral patches, or infilled vesicles rather than true fossils. The dark central area could be a mafic mineral-rich inclusion or surface cavity.
Field identification & locations
Common in volcanic regions and stream or beach gravels worldwide; identify by its fine texture, heavy feel, dark mafic composition, and lack of obvious layering. A fresh broken surface and streak, magnetism, or acid testing would improve identification.
