igneous
Vesicular basalt
Basalt, commonly composed of plagioclase feldspar, pyroxene, and often olivine
AI-generated identification · may be incorrectDark gray to brown, fine-grained and commonly vesicular, with numerous gas cavities; typically dull to slightly glassy, hardness about 5–6, with no prominent cleavage and specific gravity around 2.8–3.0.
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Physical properties
Dark gray to brown, fine-grained and commonly vesicular, with numerous gas cavities; typically dull to slightly glassy, hardness about 5–6, with no prominent cleavage and specific gravity around 2.8–3.0.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near Earth’s surface. Its exact age cannot be determined from the image; basalt forms from Precambrian to modern eruptions.
Uses & applications
Used as crushed aggregate, road base, riprap, railway ballast, and building stone; attractive polished pieces are occasionally used decoratively, but this specimen has modest collector value.
Geological facts
The holes are vesicles formed by trapped gas bubbles in lava; later minerals may partially fill them, producing amygdaloidal basalt.
Field identification & locations
Identify it by its dark fine-grained matrix, rounded vesicles, high density, and lack of visible large crystals; common worldwide in volcanic regions, oceanic crust, and flood-basalt provinces.
