igneous
Pumice
Highly vesicular volcanic rock, typically rhyolitic to dacitic; chiefly volcanic glass with feldspar, quartz, and minor mafic minerals
AI-generated identification · may be incorrectMohs hardness about 5–6, pale gray to beige, dull to silky, extremely porous with abundant vesicles; generally lacks visible cleavage and has low density, often able to float. The rounded surface suggests water-worn pumice.
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Physical properties
Mohs hardness about 5–6, pale gray to beige, dull to silky, extremely porous with abundant vesicles; generally lacks visible cleavage and has low density, often able to float. The rounded surface suggests water-worn pumice.
Formation & geological history
Forms when gas-rich felsic lava erupts explosively and rapidly cools, trapping bubbles in glass; individual specimens may range from recent volcanic material to millions of years old. Common around volcanic arcs and explosive calderas.
Uses & applications
Used as a lightweight abrasive, exfoliant, polishing medium, horticultural additive, concrete aggregate, and lightweight construction material. Attractive pieces are sold as natural curiosities or educational specimens.
Geological facts
Its vesicles are frozen gas bubbles, and pumice is one of the few rocks that can float temporarily. The specimen’s unusually smooth, rounded form likely reflects prolonged transport in water or surf.
Field identification & locations
Identify it by very low density, porous texture, pale color, and a scratchy abrasive surface; distinguish it from scoria, which is usually darker, denser, and basaltic. Common sources include Italy, Greece, Turkey, Iceland, Japan, New Zealand, and the western United States.
