igneous
Pumice
Pumice (volcanic glass)
AI-generated identification · may be incorrectHardness: 5-6 (can be brittle); Color: light gray to cream; Luster: dull to silky; Structure: highly vesicular (full of gas bubbles); Specific Gravity: 0.25 to 0.9 (floats in water)
- Hardness
- 5-6 (can be brittle)
- Color
- light gray to cream
- Luster
- dull to silky
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Physical properties
Hardness: 5-6 (can be brittle); Color: light gray to cream; Luster: dull to silky; Structure: highly vesicular (full of gas bubbles); Specific Gravity: 0.25 to 0.9 (floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected and cools rapidly, trapping gas bubbles as a frothy glass structure. Common in Cenozoic volcanic arcs.
Uses & applications
Used as an abrasive in soaps (pumice stones), cosmetic exfoliants, concrete additives (pozzolan), and for stonewashed jeans or landscaping.
Geological facts
Pumice is the only rock that can float on water until it becomes waterlogged. Large eruptions can create 'pumice rafts' that drift for thousands of miles across oceans.
Field identification & locations
Identify in the field by its extremely light weight, frothy texture, and ability to float. Commonly found in volcanic regions like the Cascades or the Andes.
