igneous
Vesicular basalt (scoria-like lava rock)
Mafic volcanic rock, typically plagioclase + pyroxene ± olivine; vesicles formed by trapped volcanic gas
AI-generated identification · may be incorrectDark gray, fine-grained, highly vesicular, with a dull to slightly glassy luster; hardness about 5–6 Mohs, no visible cleavage, and relatively low density because of abundant air cavities. The rounded shape appears naturally weathered or tumbled.
Identified More igneous →
Explore Vesicular basalt (scoria-like lava rock) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray, fine-grained, highly vesicular, with a dull to slightly glassy luster; hardness about 5–6 Mohs, no visible cleavage, and relatively low density because of abundant air cavities. The rounded shape appears naturally weathered or tumbled.
Formation & geological history
Forms when gas-rich basaltic lava cools rapidly at or near the surface, preserving bubbles as vesicles; commonly Quaternary to recent in age. It occurs in lava flows, cinder cones, volcanic fields, and shoreline deposits.
Uses & applications
Used as lightweight landscaping stone, drainage aggregate, abrasive, and horticultural substrate; attractive pieces may be sold as decorative specimens. It is generally not a jewelry gemstone.
Geological facts
The specimen resembles scoria, but its gray color and small vesicles are also consistent with vesicular basalt. A magnet may show weak attraction if iron-bearing minerals are abundant.
Field identification & locations
Identify by its lightweight, porous texture, fine dark matrix, and lack of sedimentary layering; distinguish it from pumice, which is usually much lighter-colored and can float. Common worldwide near basaltic volcanoes, including Hawaii, Iceland, Mexico, and the western United States.
