igneous
Pumice
Pumice (volcanic glass)
Hardness: 5-6 (Mohs scale), Color: light gray to white, Luster: dull to vitreous, Structure: vesicular/glassy, High porosity and very low specific gravity (often floats in water)
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Physical properties
Hardness: 5-6 (Mohs scale), Color: light gray to white, Luster: dull to vitreous, Structure: vesicular/glassy, High porosity and very low specific gravity (often floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when pressurized gas-rich silica-rich magma is expelled and cools rapidly, trapping bubbles in the cooling glass
Uses & applications
Used as an abrasive in polishing, exfoliating skin (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 air-filled vesicles. Large eruptions can create 'pumice rafts' that drift for thousands of miles across oceans
Field identification & locations
Identified by its distinctive sponge-like appearance and extremely light weight. Found in volcanic regions worldwide including Italy, Iceland, and the Western United States
