igneous
Pumice or vesicular volcanic rock
Pumice; predominantly volcanic glass (silica-rich, commonly rhyolitic to dacitic)
AI-generated identification · may be incorrectLight gray, highly porous, dull to slightly glassy, with abundant tiny vesicles; typically Mohs hardness 5–6, no cleavage, and very low specific gravity, often allowing it to float. The dark patch may be a lithic fragment or weathered inclusion.
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Physical properties
Light gray, highly porous, dull to slightly glassy, with abundant tiny vesicles; typically Mohs hardness 5–6, no cleavage, and very low specific gravity, often allowing it to float. The dark patch may be a lithic fragment or weathered inclusion.
Formation & geological history
Forms when gas-rich felsic magma erupts explosively and rapidly cools, trapping bubbles in volcanic glass; commonly Quaternary to recent, though pumice occurs in volcanic deposits of many ages.
Uses & applications
Used as an abrasive, exfoliating stone, lightweight aggregate, horticultural additive, and in concrete or construction products; usually has little jewelry value.
Geological facts
Pumice is not a mineral but a glassy volcanic rock. Its extreme vesicularity distinguishes it from denser gray volcanic rocks such as andesite.
Field identification & locations
Identify it by its unusually low density, frothy texture, sharp porous surface, and pale color; common around volcanic islands, beaches receiving volcanic drift, and explosive volcanic terrains. A streak, density test, and hand lens can help distinguish it from porous limestone or artificial foam.
