igneous
Pumice
Pumice (Felsic volcanic rock)
Hardness: 5-6 (but brittle), Color: Light gray to tan, Luster: Dull to pearly, Structure: Highly vesicular/porous, Density: Low (can float in water)
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Physical properties
Hardness: 5-6 (but brittle), Color: Light gray to tan, Luster: Dull to pearly, Structure: Highly vesicular/porous, Density: Low (can float in water)
Formation & geological history
Formed during explosive volcanic eruptions where magma is rapidly depressurized and cooled, trapping gas bubbles within the solidifying rock.
Uses & applications
Used as an abrasive in cleaning (pumice stones), in horticulture for soil aeration, in lightweight concrete, and as an exfoliant in cosmetics.
Geological facts
Pumice is the only rock that can float on water due to its high porosity. Large eruptions can create 'pumice rafts' that float across oceans for miles.
Field identification & locations
Identified by its extremely light weight and 'sponge-like' appearance. Commonly found near active or dormant volcanic regions.
