igneous
Vesicular basalt (likely weathered scoria)
Basaltic scoria; predominantly calcium-rich plagioclase, clinopyroxene, and iron-magnesium oxides
AI-generated identification · may be incorrectHardness about 5–6 Mohs; gray to brown, strongly vesicular, dull to earthy luster, and fine-grained volcanic texture. The cavities are gas bubbles; the pale coating may be weathering or mineral encrustation.
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Physical properties
Hardness about 5–6 Mohs; gray to brown, strongly vesicular, dull to earthy luster, and fine-grained volcanic texture. The cavities are gas bubbles; the pale coating may be weathering or mineral encrustation.
Formation & geological history
Formed when gas-rich basaltic lava erupted and cooled rapidly, trapping bubbles; likely Quaternary or younger, though age cannot be determined from the image. Common in volcanic cones, lava flows, and cinder deposits.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, abrasives, and occasionally decorative rock. Usually has little gem or collector value unless unusually shaped or mineral-coated.
Geological facts
Scoria is denser and darker than pumice, while pumice may float in water. Its vesicles and irregular frothy surface distinguish it from sedimentary porous rocks.
Field identification & locations
Common in volcanic regions such as Hawaii, Iceland, Italy, the western United States, and the Andes. Field checks include low density, abundant irregular vesicles, dark streak, and lack of obvious sedimentary layering; exact identification would benefit from a fresh broken surface.
