igneous
Pumice
Pumice (Vesicular volcanic glass)
Vesicular (pitted with gas bubbles), highly porous, very low density (often floats on water), Mohs hardness of 5-6, light gray to cream color, dull luster, vitreous texture, no cleavage.
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Physical properties
Vesicular (pitted with gas bubbles), highly porous, very low density (often floats on water), Mohs hardness of 5-6, light gray to cream color, dull luster, vitreous texture, no cleavage.
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected. The rapid cooling and depressurization cause gas bubbles to be trapped as the rock solidifies quickly into glass.
Uses & applications
Used as an abrasive in cleaning and personal care (pumice stones), lightweight aggregate in concrete/cinder blocks, a soil conditioner in horticulture, and for stone-washing denim.
Geological facts
Pumice is the only rock that can float on water due to its air-filled vesicles. Large eruptions can create 'pumice rafts' that drift across oceans for years.
Field identification & locations
Identify by its unusually light weight and sponge-like appearance. It is commonly found in areas of recent volcanic activity such as Iceland, Italy, Greece, and the Western United States.
