igneous
Vesicular basalt (scoria-like volcanic rock)
Basalt, composed mainly of plagioclase, pyroxene, and olivine; abundant vesicles formed by trapped gas
AI-generated identification · may be incorrectDark brown to black, fine-grained, porous, and dull to slightly vitreous; typically Mohs hardness 5–6, with no visible cleavage and a relatively high specific gravity despite its cavities.
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Physical properties
Dark brown to black, fine-grained, porous, and dull to slightly vitreous; typically Mohs hardness 5–6, with no visible cleavage and a relatively high specific gravity despite its cavities.
Formation & geological history
Extrusive mafic lava that cooled rapidly at or near Earth’s surface, with gas bubbles creating the vesicles; likely formed during a young volcanic eruption, though the specimen’s exact age cannot be determined from the image.
Uses & applications
Used as aggregate, road stone, landscaping rock, and occasionally as a decorative or lapidary material; vesicular pieces may be collected as volcanic specimens.
Geological facts
Its numerous rounded holes are vesicles, not fossil cavities. The brown coloration commonly reflects oxidation of iron-bearing minerals during weathering.
Field identification & locations
Identify it by its dark mafic color, fine texture, irregular vesicles, and heavy feel compared with pumice; common near volcanic fields, lava flows, and oceanic islands. The image could also represent weathered scoria, but a precise locality would require testing and context.
