igneous
Vesicular volcanic rock, likely pumice or scoria
Pumice/scoria; predominantly volcanic glass with plagioclase, pyroxene, and/or olivine
AI-generated identification · may be incorrectHardness about 5–6; gray-brown, highly porous, dull to weakly glassy luster, and irregular vesicles rather than cleavage. Pumice is usually very lightweight and may float; darker, denser scoria generally sinks.
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Physical properties
Hardness about 5–6; gray-brown, highly porous, dull to weakly glassy luster, and irregular vesicles rather than cleavage. Pumice is usually very lightweight and may float; darker, denser scoria generally sinks.
Formation & geological history
Forms when gas-rich basaltic to rhyolitic magma erupts and rapidly cools, trapping bubbles in volcanic glass; specimens may be geologically young, from Quaternary eruptions, or older volcanic deposits. The exact type cannot be confirmed from the image alone.
Uses & applications
Used as lightweight aggregate, abrasive, horticultural medium, concrete additive, and occasionally as a decorative or lapidary specimen; scoria is also used in landscaping and road construction.
Geological facts
The specimen’s rounded cavities and rough, frothy texture strongly indicate vesicular lava or volcanic ejecta, though weathering may obscure its original color and density.
Field identification & locations
Common in volcanic regions worldwide, including Iceland, Italy, Japan, the western United States, and Mexico. Test density and hardness: a very light specimen that floats is pumice; a darker, heavier specimen is more likely scoria.
