igneous
Weathered vesicular volcanic rock, likely basaltic scoria
Vesicular basalt/scoria; chiefly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectBrown, rounded, and strongly vesicular, with dark crystalline patches and a dull to slightly earthy luster. Estimated hardness is about 5–6 Mohs; crystals are fine-grained and not visibly cleaved, while the cavities reflect trapped volcanic gas.
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Physical properties
Brown, rounded, and strongly vesicular, with dark crystalline patches and a dull to slightly earthy luster. Estimated hardness is about 5–6 Mohs; crystals are fine-grained and not visibly cleaved, while the cavities reflect trapped volcanic gas.
Formation & geological history
Forms when mafic lava cools rapidly at or near the surface, allowing gas bubbles to remain; likely Cenozoic or younger, though the specimen’s age cannot be determined from an image. Weathering and water abrasion have rounded the piece and lightened its surface.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, and abrasive; attractive pieces may be collected, but it is generally not a jewelry gemstone.
Geological facts
The porous texture distinguishes scoria or vesicular basalt from dense basalt; brown coloration commonly results from oxidation of iron-bearing minerals. Some cavities may contain secondary zeolite or carbonate minerals.
Field identification & locations
Look for abundant irregular holes, dark fine-grained volcanic matrix, low density, and no sedimentary layering; common in volcanic fields, lava flows, cinder cones, and beaches near volcanic terrain. Likely worth $2–$15 as a common specimen, or $20–$50 if unusually attractive or locality-labeled.
