igneous
Pumice
Pumice (a highly vesicular volcanic rock)
Hardness: 5-6 Mohs (though brittle); Color: cream, light gray, or light pink; Luster: earthy to dull; Structure: highly vesicular (full of tiny holes); Density: low (often floats in water).
- Hardness
- 5-6 Mohs (though brittle)
- Color
- cream, light gray, or light pink
- Luster
- earthy to dull
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Physical properties
Hardness: 5-6 Mohs (though brittle); Color: cream, light gray, or light pink; Luster: earthy to dull; Structure: highly vesicular (full of tiny holes); Density: low (often floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when pressurized lava is violently ejected and rapidly cools, trapping gas bubbles within the rock as it solidifies.
Uses & applications
Used as an abrasive in cosmetics (pumice stones), in heavy-duty hand soaps, in construction as lightweight aggregate for concrete, and for stone-washing denim.
Geological facts
Pumice is the only rock that can reliably float on water for long periods due to its air-filled pores. Large eruptions can create 'pumice rafts' that travel across oceans for miles.
Field identification & locations
Identify by its unusually light weight and sandpaper-like texture. Commonly found in volcanic regions such as the American West, Italy, Iceland, and New Zealand.
