igneous
Vesicular basalt (lava rock)
Basalt, a fine-grained mafic volcanic rock; chiefly plagioclase, pyroxene, and possibly olivine
AI-generated identification · may be incorrectDark gray, rough, and highly vesicular, with holes left by escaping gas; typically Mohs 5–6, dull to slightly glassy, and without visible cleavage. The specimen’s precise mineral makeup cannot be determined from the photo alone.
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Physical properties
Dark gray, rough, and highly vesicular, with holes left by escaping gas; typically Mohs 5–6, dull to slightly glassy, and without visible cleavage. The specimen’s precise mineral makeup cannot be determined from the photo alone.
Formation & geological history
Forms when gas-rich basaltic lava cools rapidly at or near the surface. Basalt is common throughout geologic time; this specimen’s age and locality are unknown.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and construction material; porous lava rock is also used in landscaping and grilling. This large, ordinary specimen has limited collector value.
Geological facts
The cavities are vesicles, not fossils; their presence records gas bubbles trapped in cooling lava.
Field identification & locations
Look for a dark, dense volcanic matrix with abundant rounded or elongated holes. Common in volcanic regions and lava fields; a photo alone cannot establish its exact locality or distinguish every vesicular volcanic rock.
