igneous
Vesicular basalt (likely weathered basalt scoria)
Basalt; predominantly plagioclase, clinopyroxene, and iron-rich minerals, with possible secondary zeolite/calcite coatings
AI-generated identification · may be incorrectDark gray-green, fine-grained volcanic rock with abundant rounded vesicles and pale mineral infillings; typically dull to slightly glassy, hardness about 5–6, with no obvious cleavage. The bubbly texture indicates trapped gas, though the specimen appears heavily weathered or mineralized.
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Physical properties
Dark gray-green, fine-grained volcanic rock with abundant rounded vesicles and pale mineral infillings; typically dull to slightly glassy, hardness about 5–6, with no obvious cleavage. The bubbly texture indicates trapped gas, though the specimen appears heavily weathered or mineralized.
Formation & geological history
Formed when fluid basaltic lava cooled rapidly at or near the surface, preserving gas bubbles; pale fillings likely formed later from groundwater. Basalt ranges from Archean to modern in age and commonly occurs in volcanic provinces and oceanic crust.
Uses & applications
Used as crushed aggregate, road stone, riprap, and landscaping material; attractive specimens are collected, especially when vesicles contain zeolites, calcite, or agate.
Geological facts
The specimen’s exact identity cannot be confirmed from one dim photograph; it could also be amygdaloidal basalt or vesicular andesite. A streak, fresh broken surface, and acid test on the pale material would help distinguish mineral fillings.
Field identification & locations
Look for a dense dark volcanic matrix, vesicles, and lack of visible large crystals; common worldwide in lava flows, including Hawaii, Iceland, India, and the western United States. Typical hand specimens are worth about $5–$30; attractive mineral-filled pieces may bring $30–$100+.
