igneous
Pumice (likely)
Pumice; vesicular volcanic glass, typically rhyolitic to dacitic in composition
AI-generated identification · may be incorrectLight gray, highly porous and rough with abundant vesicles; glassy to dull luster, no visible cleavage, and hardness about 5–6 Mohs. Usually very low density and may float in water.
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Physical properties
Light gray, highly porous and rough with abundant vesicles; glassy to dull luster, no visible cleavage, and hardness about 5–6 Mohs. Usually very low density and may float in water.
Formation & geological history
Forms when gas-rich, silica-rich magma explosively erupts and rapidly quenches, trapping bubbles in volcanic glass. It commonly formed during Quaternary to recent explosive volcanism, though older deposits are widespread.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, horticultural additive, concrete component, and polishing stone; attractive pieces have modest collector value.
Geological facts
Its extreme vesicular texture results from decompression and rapid cooling during eruptions. The pictured specimen may also be a porous volcanic scoria, but its pale color favors pumice.
Field identification & locations
Identify by its frothy texture, very low weight, sharp porous surfaces, and lack of visible crystals; pumice is common around volcanic regions including Italy, Iceland, Japan, the Andes, and the western United States.
