igneous
Vesicular volcanic rock, likely scoria
Scoria (vesicular basalt/andesite; composition uncertain from image)
AI-generated identification · may be incorrectDark brown to reddish-brown, highly vesicular, dull to slightly earthy luster, irregular subangular pieces, and likely hardness about 5–6 Mohs. The holes are gas bubbles preserved in volcanic lava; density is low compared with ordinary basalt.
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Physical properties
Dark brown to reddish-brown, highly vesicular, dull to slightly earthy luster, irregular subangular pieces, and likely hardness about 5–6 Mohs. The holes are gas bubbles preserved in volcanic lava; density is low compared with ordinary basalt.
Formation & geological history
Formed when gas-rich basaltic or andesitic lava cooled rapidly, trapping bubbles; commonly Quaternary to modern volcanic material. Exact age and chemistry require a fresh surface, density, and laboratory testing.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and sometimes in decorative or lapidary work. These small rough pieces have little jewelry value.
Geological facts
Scoria differs from pumice because it is generally darker, denser, and has thicker bubble walls. The reddish color commonly reflects oxidation of iron-bearing minerals during or after eruption.
Field identification & locations
Identify it by abundant irregular vesicles, rusty coloration, and a rough volcanic texture; it is commonly found near cinder cones, lava flows, and volcanic fields. Similar-looking furnace slag can contain glassy surfaces, metal droplets, or unusually smooth flow textures, so provenance matters.
