igneous
Vesicular basalt
Basalt, predominantly plagioclase + pyroxene ± olivine; vesicles formed by trapped volcanic gas
AI-generated identification · may be incorrectDark gray, fine-grained, dull to weakly submetallic surface with abundant rounded vesicles; typically Mohs 5–6, massive, with no obvious cleavage, and specific gravity about 2.7–3.0 (lower if highly vesicular).
Identified More igneous →
Explore Vesicular basalt in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray, fine-grained, dull to weakly submetallic surface with abundant rounded vesicles; typically Mohs 5–6, massive, with no obvious cleavage, and specific gravity about 2.7–3.0 (lower if highly vesicular).
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near Earth’s surface; likely Cenozoic or younger, though basalt occurs from Archean to recent ages. Vesicles developed as dissolved gases escaped during cooling.
Uses & applications
Used as aggregate, road base, riprap, building stone, and decorative landscaping rock; attractive polished pieces may be collected, though this specimen is not typically jewelry-grade.
Geological facts
The holes are gas bubbles, not fossil cavities. Dark weathering coatings or metallic-looking flecks may represent iron oxides or secondary minerals.
Field identification & locations
Identify by its dark color, fine texture, high density, and vesicles; distinguish it from pumice because basalt is much denser and less frothy. Common worldwide in lava flows, volcanic islands, and oceanic crust, including Hawaii, Iceland, and the Pacific Northwest.
