igneous
Weathered, vesicular volcanic rock (likely scoria or altered basalt)
Vesicular basalt/scoria; predominantly plagioclase, pyroxene, olivine, and secondary iron oxides
AI-generated identification · may be incorrectDark brown to rusty orange, highly porous, with a dull to locally vitreous luster and fine crystalline groundmass; typical hardness is about 5–6 Mohs, with no obvious cleavage. The orange-brown coloration likely reflects oxidation and weathering of iron-bearing minerals.
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Physical properties
Dark brown to rusty orange, highly porous, with a dull to locally vitreous luster and fine crystalline groundmass; typical hardness is about 5–6 Mohs, with no obvious cleavage. The orange-brown coloration likely reflects oxidation and weathering of iron-bearing minerals.
Formation & geological history
Formed from gas-rich basaltic lava that cooled rapidly at or near the surface, trapping vesicles; subsequent oxidation and alteration produced the rusty coating. Exact age cannot be determined from the image; such rocks range from recent volcanic deposits to ancient basalt flows.
Uses & applications
Used decoratively, in landscaping, lightweight aggregate, drainage media, and sometimes abrasive applications; generally low jewelry value.
Geological facts
Vesicles are gas bubbles frozen into lava, and iron oxidation commonly turns basalt red, orange, or brown. The specimen could also be weathered volcanic cinder rather than solid scoria.
Field identification & locations
Look for lightweight porous texture, irregular cavities, and a basaltic dark interior; a streak test, density, and fresh fracture would distinguish it from slag or weathered pumice. Common in volcanic regions such as Hawaii, Iceland, the western United States, and Mediterranean volcanic fields.
