igneous
Pumice
Pumice (volcanic glass rock)
AI-generated identification · may be incorrectHardness: 5-6 (but fragile); Color: light gray, cream, or tan; Luster: dull to pearly; Texture: highly vesicular (porous); Specific Gravity: 0.2-0.9 (floats on water).
- Hardness
- 5-6 (but fragile)
- Color
- light gray, cream, or tan
- Luster
- dull to pearly
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Physical properties
Hardness: 5-6 (but fragile); Color: light gray, cream, or tan; Luster: dull to pearly; Texture: highly vesicular (porous); Specific Gravity: 0.2-0.9 (floats on water).
Formation & geological history
Formed during explosive volcanic eruptions when high-pressure gas-rich magma is ejected. The rapid cooling and depressurization trap gas bubbles, creating a frothy glass foam.
Uses & applications
Used as an abrasive in soaps (lava soap), stone-washing denim, skin exfoliation (pumice stones), lightweight concrete aggregate, and horticulture (soil aeration).
Geological facts
Pumice is the only rock that can float on water. Huge 'pumice rafts' can sometimes be found floating in the ocean for years after a major underwater volcanic eruption.
Field identification & locations
Identify in the field by its extreme lightness (low density) and sandpaper-like feel. Commonly found in volcanic regions, near active or extinct stratovolcanoes.
