igneous
Vesicular basalt (possibly scoriaceous basalt)
Basalt; predominantly calcium-rich plagioclase, clinopyroxene, and often olivine, with volcanic glass
AI-generated identification · may be incorrectDark gray to black, fine-grained, dull to slightly vitreous, and porous with vesicles; hardness about 5–6 Mohs, no visible cleavage, and typically dense except where vesicular. The image is somewhat blurred, so exact identification is provisional.
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Physical properties
Dark gray to black, fine-grained, dull to slightly vitreous, and porous with vesicles; hardness about 5–6 Mohs, no visible cleavage, and typically dense except where vesicular. The image is somewhat blurred, so exact identification is provisional.
Formation & geological history
Extrusive mafic lava that cooled rapidly at or near Earth’s surface, commonly during Cenozoic volcanic activity or older oceanic volcanism; its precise age cannot be determined visually.
Uses & applications
Used as aggregate, road base, riprap, building stone, and landscaping material; attractive polished pieces may be used decoratively, but this specimen appears common rather than gem-quality.
Geological facts
Vesicles formed when dissolved volcanic gases escaped from cooling lava; abundant vesicles indicate scoria, while fewer or elongated cavities may indicate basaltic lava.
Field identification & locations
Identify by its black fine-grained matrix, volcanic texture, and gas bubbles; test hardness against glass and inspect a fresh surface for tiny crystals. Common worldwide in volcanic regions, including Hawaii, Iceland, the Deccan, and oceanic islands.
