igneous
Pebble with vesicles, likely basalt
Vesicular basalt; chiefly plagioclase, pyroxene, and iron-magnesium minerals
AI-generated identification · may be incorrectFine-grained, dark gray-green, matte rock with rounded vesicles and a smooth weathered surface. Hardness about 5–6 Mohs; generally massive with no visible cleavage and specific gravity around 2.8–3.0.
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Physical properties
Fine-grained, dark gray-green, matte rock with rounded vesicles and a smooth weathered surface. Hardness about 5–6 Mohs; generally massive with no visible cleavage and specific gravity around 2.8–3.0.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near Earth’s surface, trapping gas bubbles; commonly Cenozoic or younger, though basalt occurs through much of geologic time.
Uses & applications
Used as aggregate, road stone, riprap, and occasionally decorative stone; this small rounded specimen is primarily a natural-history or beach-rock collectible.
Geological facts
The cavities are vesicles, produced by escaping volcanic gases. The greenish tint may reflect alteration of ferromagnesian minerals to chlorite or other secondary minerals.
Field identification & locations
Likely found in volcanic terrains or transported in river and beach gravels; identify by its fine texture, dark color, high density, and vesicles, distinguishing it from porous scoria by its relatively compact surface.
