igneous
Pumice
Pumice (Vesicular volcanic glass)
Hardness: 5-6 (Mohs); Color: White, cream, or light grey; Luster: Dull to pearly; Crystal structure: Amorphous/Vitreous (glassy); Cleavage: None; Specific gravity: 0.3-0.9 (floats on water)
- Hardness
- 5-6 (Mohs)
- Color
- White, cream, or light grey
- Luster
- Dull to pearly
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Physical properties
Hardness: 5-6 (Mohs); Color: White, cream, or light grey; Luster: Dull to pearly; Crystal structure: Amorphous/Vitreous (glassy); Cleavage: None; Specific gravity: 0.3-0.9 (floats on water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected. The rapid cooling and depressurization trap gas bubbles, creating a vesicular texture.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants (pumice stones), lightweight concrete, and water filtration.
Geological facts
Pumice is the only rock that can float on water due to its low density. Large rafts of floating pumice can travel across oceans for years after an eruption.
Field identification & locations
Identify by its extremely lightweight feel, porous (bubbly) texture, and ability to float. Commonly found in volcanic regions like the Andes, Cascade Range, and Mediterranean.
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