igneous
Pumice
Pumicite / Vesicular Rhyolite
Hardness: 5-6 (but brittle), Color: Cream, white, or light grey, Luster: Dull to pearly, Structure: Highly vesicular/glassy (frothy texture), Density: Often floats on water.
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Physical properties
Hardness: 5-6 (but brittle), Color: Cream, white, or light grey, Luster: Dull to pearly, Structure: Highly vesicular/glassy (frothy texture), Density: Often floats on water.
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich molten rock (magma) is violently ejected and cools rapidly, trapping gas bubbles.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants (pumice stones), lightweight concrete aggregate, and in stonewashed denim production.
Geological facts
Pumice is the only rock that can float on water until it becomes waterlogged. Massive 'pumice rafts' can form in the ocean after undersea volcanic eruptions.
Field identification & locations
Identify by its extreme lightweight feel and numerous tiny holes (vesicles). It is commonly found near volcanic arcs and subduction zones.
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