igneous
Iron-stained vesicular volcanic rock (probable basalt/scoria)
Altered basaltic scoria; chiefly plagioclase, pyroxene, olivine, and iron oxides
AI-generated identification · may be incorrectDark brown to black, rusty orange weathering, rough and locally vesicular, with dull to slightly glassy luster. Likely Mohs hardness 5–6, no obvious cleavage, fine-grained volcanic texture; exact identification is limited by the photograph.
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Physical properties
Dark brown to black, rusty orange weathering, rough and locally vesicular, with dull to slightly glassy luster. Likely Mohs hardness 5–6, no obvious cleavage, fine-grained volcanic texture; exact identification is limited by the photograph.
Formation & geological history
Formed when iron-rich basaltic lava cooled rapidly, trapping gas bubbles; the brown coloration reflects oxidation and weathering. It may be relatively young volcanic material, but age cannot be determined visually.
Uses & applications
Commonly used as lightweight aggregate, landscaping stone, drainage material, and occasionally in lapidary work; generally low commercial value.
Geological facts
The rusty surface is characteristic of oxidation of iron-bearing minerals, while cavities indicate escaping volcanic gases. It may also be an iron-rich altered basalt rather than true scoria.
Field identification & locations
Look for a low density, vesicles, magnetic response, and a dark fine-grained interior on a fresh break; basalt commonly occurs around volcanic fields and lava flows. A streak, magnet test, and thin-section or elemental analysis would improve identification.
