igneous
Pumice
Pumice; vesicular volcanic glass, typically silica-rich rhyolitic composition
AI-generated identification · may be incorrectVery lightweight, pale gray-white, porous and dull to slightly glassy; hardness about 5–6 Mohs, with no distinct cleavage and a fine, mostly amorphous glass structure. The holes are gas-bubble cavities (vesicles).
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Physical properties
Very lightweight, pale gray-white, porous and dull to slightly glassy; hardness about 5–6 Mohs, with no distinct cleavage and a fine, mostly amorphous glass structure. The holes are gas-bubble cavities (vesicles).
Formation & geological history
Forms when gas-rich, silica-rich lava cools rapidly during explosive eruptions; specimens can range from recent to geologically ancient, depending on the eruption.
Uses & applications
Used as an abrasive and exfoliant, in polishing and cleaning products, and as a lightweight aggregate in concrete and horticultural mixes.
Geological facts
Pumice can be buoyant enough to float and travel long distances on water, though small pieces may sink once their pores fill.
Field identification & locations
Identify by its unusually low weight and abundant cavities; commonly found near explosive volcanoes and in deposits transported by rivers or oceans. The pictured piece is consistent with pumice.
