igneous
Vesicular scoria (oxidized basaltic scoria)
Scoria; vesicular mafic volcanic rock, typically composed mainly of plagioclase, pyroxene, and iron-rich glass/oxides
AI-generated identification · may be incorrectDark gray to reddish-brown, highly vesicular, with rough matte luster and irregular fracture; hardness about 5–6, no prominent cleavage, and relatively low density due to abundant gas cavities. The rusty color indicates oxidation of iron-bearing minerals.
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Physical properties
Dark gray to reddish-brown, highly vesicular, with rough matte luster and irregular fracture; hardness about 5–6, no prominent cleavage, and relatively low density due to abundant gas cavities. The rusty color indicates oxidation of iron-bearing minerals.
Formation & geological history
Forms when gas-rich basaltic magma erupts and rapidly cools, trapping bubbles; commonly Quaternary to Recent in volcanic cones, lava flows, and cinder deposits. The specimen may have weathered or oxidized after formation.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, abrasive material, and occasionally in cement products; generally not used as a gemstone.
Geological facts
Its vesicles are frozen gas bubbles, distinguishing scoria from dense basalt; abundant reddish oxidation commonly reflects exposure to air and weathering.
Field identification & locations
Identify by its very porous, lightweight texture, dark mafic composition, and reddish-brown iron staining; common near basaltic volcanoes such as Hawaii, Iceland, the Cascades, and Mediterranean volcanic fields. Test density and avoid confusing it with porous slag or pumice—the darker, heavier appearance favors scoria.
