igneous
Pumice
Pumicite
Hardness: 5-6 (but very brittle); Color: Light gray, cream, or tan; Luster: Dull to pearly; Texture: Highly vesicular (porous); Specific Gravity: 0.25-0.9 (floats in water).
- Hardness
- 5-6 (but very brittle)
- Color
- Light gray, cream, or tan
- Luster
- Dull to pearly
Identified More igneous →
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Physical properties
Hardness: 5-6 (but very brittle); Color: Light gray, cream, or tan; Luster: Dull to pearly; Texture: Highly vesicular (porous); Specific Gravity: 0.25-0.9 (floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected into the atmosphere. The rapid cooling and depressurization trap gas bubbles, creating a frothy glass structure.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants (pumice stones), lightweight concrete aggregate, and for stone-washing denim jeans.
Geological facts
Pumice is the only rock that can consistently float on water. Large eruptions can create 'pumice rafts' that drift for thousands of miles across oceans.
Field identification & locations
Identified by its extremely lightweight feel, light color, and sandpaper-like texture. Commonly found in volcanic regions such as the Cascade Range or the Mediterranean.
