igneous
Vesicular basalt (likely weathered scoria)
Basaltic volcanic rock; primarily plagioclase, pyroxene, and olivine, with iron oxides
AI-generated identification · may be incorrectDark reddish-brown, highly vesicular, rough and dull to weakly earthy luster; typically about Mohs 5–6, with no obvious cleavage and fine-grained crystalline groundmass. The reddish color commonly reflects oxidation of iron-bearing minerals.
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Physical properties
Dark reddish-brown, highly vesicular, rough and dull to weakly earthy luster; typically about Mohs 5–6, with no obvious cleavage and fine-grained crystalline groundmass. The reddish color commonly reflects oxidation of iron-bearing minerals.
Formation & geological history
Forms when basaltic lava cools rapidly at or near the surface, trapping gas bubbles; oxidation and weathering produce the brown-red exterior. Usually Quaternary to older volcanic age, depending on locality.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and sometimes abrasive or decorative rock; generally not a gemstone.
Geological facts
Its many cavities distinguish scoria from dense basalt; unusually light weight and abundant open vesicles suggest scoria. A fresh broken surface would better reveal the dark basaltic interior.
Field identification & locations
Common in volcanic regions such as Hawaii, Iceland, the western United States, Mexico, Italy, and East Africa. Test weight, inspect vesicles, and check that it does not fizz with dilute acid; a magnet may respond weakly because of iron oxides.
