igneous
Pumice
Pumice (volcanic glass with vesicular texture)
Hardness: 5-6 (but very brittle), Color: Cream, white, or light grey, Luster: Dull to pearly, Structure: Highly vesicular/porous, Density: Often floats on water.
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Physical properties
Hardness: 5-6 (but very brittle), Color: Cream, white, or light grey, Luster: Dull to pearly, Structure: Highly vesicular/porous, Density: Often floats on water.
Formation & geological history
Formed during explosive volcanic eruptions when lava is ejected into the air while highly charged with gases. The rapid cooling and depressurization trap gas bubbles, creating a frothy glass texture.
Uses & applications
Used as an abrasive in polishing, skin exfoliation, pencil erasers, and stone-washed denim. Also used as a lightweight concrete additive and in horticulture.
Geological facts
Pumice is the only rock that can famously float on water until it becomes waterlogged. Large 'pumice rafts' can float for thousands of miles across oceans after massive eruptions.
Field identification & locations
Identify by its light weight (low density) and porous, sponge-like surface. It will feel much lighter than other rocks of the same size. Commonly found near active or dormant volcanic regions.
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