igneous
Vesicular basalt (likely scoriaceous basalt)
Basalt, primarily plagioclase + pyroxene ± olivine; iron-oxide staining
AI-generated identification · may be incorrectDark gray to reddish-brown, fine-grained, dull to slightly glassy, with abundant gas vesicles; hardness about 5–6 Mohs and no obvious cleavage. The elongated, irregular holes and lightweight texture indicate scoria or vesicular basalt.
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Physical properties
Dark gray to reddish-brown, fine-grained, dull to slightly glassy, with abundant gas vesicles; hardness about 5–6 Mohs and no obvious cleavage. The elongated, irregular holes and lightweight texture indicate scoria or vesicular basalt.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near the surface, trapping escaping gas bubbles. Most examples are Cenozoic or younger, though basalt occurs throughout Earth’s geologic history.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive material, and occasionally in decorative collections; generally not a jewelry gemstone.
Geological facts
Red coloration commonly results from oxidation of iron-bearing minerals during or after eruption. Its vesicles may later become filled with minerals such as calcite, zeolites, or quartz.
Field identification & locations
Identify it by its black-to-red mafic color, fine matrix, abundant cavities, and relatively low density; it is commonly found in lava flows, cinder cones, and volcanic fields. Common worldwide, including Hawaii, Iceland, the western United States, and Mediterranean volcanic regions.
