igneous
Vesicular basalt (lava rock)
Vesicular basalt, a mafic volcanic rock composed mainly of plagioclase and pyroxene, often with olivine
AI-generated identification · may be incorrectBrown, rounded, and full of small gas-bubble cavities (vesicles); typically dull to slightly vitreous, with a fine-grained groundmass. Hardness is about 5–6 on the Mohs scale; individual crystals are too small to see clearly. The brown color may result from iron oxidation or surface weathering.
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Physical properties
Brown, rounded, and full of small gas-bubble cavities (vesicles); typically dull to slightly vitreous, with a fine-grained groundmass. Hardness is about 5–6 on the Mohs scale; individual crystals are too small to see clearly. The brown color may result from iron oxidation or surface weathering.
Formation & geological history
Formed when gas-rich basaltic lava cooled quickly at or near the surface, trapping bubbles. It may be millions to billions of years old; the specimen’s age cannot be determined from the image.
Uses & applications
Used as decorative stone, landscaping rock, and sometimes in lightweight construction or abrasive products; this small piece is mainly suitable for collecting.
Geological facts
Its holes are vesicles left by escaping volcanic gases, not fossils. A water-worn or tumbled specimen can become smoothly rounded while retaining the cavities.
Field identification & locations
Common in volcanic regions and as beach or river cobbles sourced from basalt flows. A basalt identification is supported by the dark, fine-grained matrix and vesicles; the image alone cannot confirm the exact rock type.
