igneous
Pumice
Pumice (a highly vesicular volcanic rock)
Hardness: 5-6 (but fragile); Color: light gray to cream; Luster: dull to silky; Crystal structure: amorphous/glassy; Cleavage: none; Specific gravity: 0.25 to 0.9 (floats on water).
- Hardness
- 5-6 (but fragile)
- Color
- light gray to cream
- Luster
- dull to silky
Identified More igneous →
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Physical properties
Hardness: 5-6 (but fragile); Color: light gray to cream; Luster: dull to silky; Crystal structure: amorphous/glassy; Cleavage: none; Specific gravity: 0.25 to 0.9 (floats on water).
Formation & geological history
Formed through rapid cooling and depressurization of gas-rich silica-rich lava during explosive volcanic eruptions. Typical of Plinian eruption events.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants, concrete additives (pozzolan), and in stone-washing textiles like jeans.
Geological facts
Pumice is the only rock that can float on water due to its incredible number of gas-filled vesicles. This specimen shows a weathered, rounded exterior typical of water transport.
Field identification & locations
Identify by its light weight and 'frothy' porous texture. It is commonly found in volcanic coastal regions or near active/dormant stratovolcanoes.
