igneous
Vesicular basalt (possibly scoriaceous basalt)
Basalt, chiefly plagioclase feldspar, clinopyroxene, and iron-titanium oxides; approximate composition Mg- and Fe-rich mafic silicate rock
AI-generated identification · may be incorrectDark gray to black, fine-grained, matte to slightly vitreous, with abundant rounded vesicles and pale weathering or mineral infill. Hardness is about 5–6 Mohs; no prominent cleavage; typical specific gravity is roughly 2.7–3.0.
Identified More igneous →
Explore Vesicular basalt (possibly scoriaceous basalt) 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, matte to slightly vitreous, with abundant rounded vesicles and pale weathering or mineral infill. Hardness is about 5–6 Mohs; no prominent cleavage; typical specific gravity is roughly 2.7–3.0.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near the surface, trapping gas bubbles; commonly associated with Cenozoic to modern lava flows, though basalt occurs throughout geologic time.
Uses & applications
Used as crushed aggregate, road base, riprap, railroad ballast, and occasionally building or decorative stone. Vesicular pieces are also collected as volcanic specimens.
Geological facts
The holes are vesicles produced by escaping volcanic gases, distinguishing it from most dense basalt. Pale patches may be weathered basalt or secondary zeolite, calcite, or silica minerals.
Field identification & locations
Identify it by its black fine-grained groundmass, abundant vesicles, and greater density than pumice; a steel nail generally will not scratch fresh basalt. Common localities include Hawaii, Iceland, the Deccan Traps, oceanic islands, and continental volcanic fields.
