igneous
Vesicular basalt pebble
Basalt, commonly plagioclase + pyroxene ± olivine, with vesicles
AI-generated identification · may be incorrectDark gray-brown, fine-grained and dull to weakly vitreous, with small gas cavities and a pale weathering or mineral-filled patch; hardness about 5–6 Mohs, no visible cleavage, typically dense except for vesicles, specific gravity about 2.7–3.1.
Identified More igneous →
Explore Vesicular basalt pebble in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray-brown, fine-grained and dull to weakly vitreous, with small gas cavities and a pale weathering or mineral-filled patch; hardness about 5–6 Mohs, no visible cleavage, typically dense except for vesicles, specific gravity about 2.7–3.1.
Formation & geological history
An extrusive mafic igneous rock formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface; commonly Cenozoic to modern, though basalt occurs throughout geologic time. The rounded shape indicates water or wave transport.
Uses & applications
Used as crushed aggregate, road stone, riprap, ballast, and dimension stone; attractive polished pieces are collected but are generally not jewelry-grade.
Geological facts
Vesicles formed from gas bubbles trapped during lava cooling; the pale material may be weathered basalt or secondary zeolite, calcite, or silica. Basalt is the most widespread volcanic rock and forms much of oceanic crust.
Field identification & locations
Identify it by its dark fine-grained matrix, rounded pebble form, and vesicles; a magnet may show weak attraction if iron-rich. Common near volcanic fields, lava flows, river gravels, and beaches.
