igneous
Pumice
Felsic/intermediate vesicular extrusive rock
Hardness: 5-6 (Mohs scale), Color: light grey to dark grey/brown, Luster: dull to silky, Texture: vesicular (highly porous/pitted), Specific gravity: 0.25-0.9 (often floats on water).
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Physical properties
Hardness: 5-6 (Mohs scale), Color: light grey to dark grey/brown, Luster: dull to silky, Texture: vesicular (highly porous/pitted), Specific gravity: 0.25-0.9 (often floats on water).
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-charged, viscous magma cools very rapidly, trapping expanding gas bubbles as tiny cavities within the solidifying glass.
Uses & applications
Widely used as an abrasive in soaps, skin exfoliators (pumice stones), and polishing compounds, as lightweight aggregate in concrete, in denim stonewashing, and for landscaping substrate.
Geological facts
Pumice is often light enough to float on water due to its air-filled vesicular cavities. Massive floating rafts of pumice produced by submarine volcanic eruptions can drift across oceans for thousands of miles.
Field identification & locations
Identified by its characteristic sponge-like porous texture and exceptionally light weight for its size. Common in volcanic regions around the world including Iceland, Italy, Greece, Japan, and the Western United States.
