igneous
Pumice
Pumice (Silicic volcanic glass with vesicular structure)
Hardness 5-6 (Mohs scale), light grey to pale cream color, dull to earthy luster, amorphous volcanic glass texture, extremely porous with low specific gravity causing it to float on water.
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Physical properties
Hardness 5-6 (Mohs scale), light grey to pale cream color, dull to earthy luster, amorphous volcanic glass texture, extremely porous with low specific gravity causing it to float on water.
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-saturated felsic lava (rich in silica) cools very rapidly, trapping gas bubbles (vesicles) within the rock matrix.
Uses & applications
Used extensively as a personal care abrasive (pumice stone for skin exfoliation), lightweight concrete aggregate, stone-washing denim, and in commercial polishes and filtration media.
Geological facts
Pumice is the only rock that floats in water due to its cellular, gas-filled structure. Massive volcanic eruptions can produce vast rafts of pumice that drift across oceans for thousands of miles.
Field identification & locations
Identified by its pale color, exceptionally light weight, rough tactile feel, and porous honeycomb structure. Commonly found near active or historic explosive volcanic regions worldwide.
