igneous
Pumice
Pumice (Amorphous volcanic glass)
Hardness: 5.5-6 (Mohs scale), Color: light grey to cream, Luster: dull to pearly, Crystal structure: non-crystalline (amorphous), Specific gravity: 0.25 to 0.7 (floats in water)
- Hardness
- 5
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Physical properties
Hardness: 5.5-6 (Mohs scale), Color: light grey to cream, Luster: dull to pearly, Crystal structure: non-crystalline (amorphous), Specific gravity: 0.25 to 0.7 (floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected. The rapid cooling and depressurization create bubbles (vesicles).
Uses & applications
Used as an abrasive in cleaning products, skin exfoliants (pumice stones), lightweight concrete aggregate, and stone-washing denim.
Geological facts
Pumice is the only rock that can float on water until it becomes waterlogged. Sometimes giant floating islands of pumice called 'pumice rafts' are formed after undersea eruptions.
Field identification & locations
Identify by its extremely light weight, frothy texture filled with tiny holes, and ability to float. Commonly found near active or dormant volcanic regions like Italy, Greece, and the USA (West Coast).
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