igneous
Vesicular basalt (likely weathered scoria)
Basalt; predominantly plagioclase, pyroxene, and commonly olivine, with abundant vesicles
AI-generated identification · may be incorrectDark gray to black, fine-grained and dull to weakly vitreous, with irregular gas cavities; hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.7–3.0 (lower if highly vesicular).
Identified More igneous →
Explore Vesicular basalt (likely weathered scoria) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark gray to black, fine-grained and dull to weakly vitreous, with irregular gas cavities; hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.7–3.0 (lower if highly vesicular).
Formation & geological history
An extrusive volcanic rock formed when basaltic lava cooled rapidly at or near the surface, trapping expanding gas bubbles; typically Cenozoic or younger, though basalt occurs throughout geological time.
Uses & applications
Used as aggregate, road base, riprap, landscaping stone, and occasionally decorative material; generally low collector value unless unusually vesicular or locality-specific.
Geological facts
Its holes are vesicles, not fossils; weathering can enlarge cavities and produce the rugged surface visible here.
Field identification & locations
Identify by its dark fine-grained matrix, low density relative to solid basalt, and abundant rounded-to-irregular voids; common in volcanic regions, including Hawaii, Iceland, the western United States, and oceanic islands.
