igneous
Pumice
Pumice (volcanic glass with vesicular texture)
Hardness: 5-6 Mohs (though brittle), Color: White to light grey, Luster: Pearly or dull, Structure: Vesicular (full of holes), Specific Gravity: Often less than 1.0 (floats in water)
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Physical properties
Hardness: 5-6 Mohs (though brittle), Color: White to light grey, Luster: Pearly or dull, Structure: Vesicular (full of holes), Specific Gravity: Often less than 1.0 (floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, silica-rich gas-charged magma is violently ejected and cools rapidly, trapping gas bubbles in a glass-like matrix.
Uses & applications
Used as an abrasive in polishing, skin exfoliation (pumice stones), lightweight aggregate in concrete, and in horticulture to improve soil aeration.
Geological facts
Pumice is the only rock that can float on water due to its extremely low density and gas-filled vesicles. Large pumice rafts can drift in the ocean for years after an eruption.
Field identification & locations
Identify by its light weight and porous 'sponge-like' appearance. Commonly found in volcanic regions like Italy, Turkey, Greece, and the Western United States. It will feel much lighter than it looks.
