igneous
Pumice
Pumice (Vesicular Rhyolite/Dacite)
Hardness: 5-6 Mohs. Color: White, cream, grey, or brownish. Luster: Dull to pearly. Structure: Highly vesicular/porous glass. Specific Gravity: 0.25 to 0.9 (floats on water).
- Hardness
- 5-6 Mohs
- Color
- White, cream, grey, or brownish
- Luster
- Dull to pearly
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Physical properties
Hardness: 5-6 Mohs. Color: White, cream, grey, or brownish. Luster: Dull to pearly. Structure: Highly vesicular/porous glass. Specific Gravity: 0.25 to 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 solidified froth of volcanic glass.
Uses & applications
Used as an abrasive in polishing, skin care (pumice stones), heavyweight/lightweight concrete production, horticulture for soil aeration, and 'stone-washing' denim.
Geological facts
Pumice is the only rock that can float on water due to its air-filled vesicles. Large eruptions can create 'pumice rafts' that drift across oceans for years.
Field identification & locations
Identify by its extremely light weight, rough/scratchy texture, and visible holes. Highly abundant in volcanic regions like Italy, Turkey, Greece, and the Western United States.
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