igneous
Pumice
Pumice (Vesicular volcanic glass)
Hardness: 5-6 (Mohs); Color: Light gray to tan; Luster: Dull to pearly; Structure: Vesicular (highly porous/frothy); Specific Gravity: 0.2-0.9 (floats in water).
- Hardness
- 5-6 (Mohs)
- Color
- Light gray to tan
- Luster
- Dull to pearly
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Light gray to tan; Luster: Dull to pearly; Structure: Vesicular (highly porous/frothy); Specific Gravity: 0.2-0.9 (floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when gas-rich magma cools so rapidly that gas bubbles are trapped in a glassy matrix. Most deposits are Cenozoic in age.
Uses & applications
Used as an abrasive in polishing, skin care (pumice stones), lightweight concrete aggregate, and horticulture as a soil amendment.
Geological facts
Pumice is the only rock that can float on water due to its incredible porosity. Massive 'pumice rafts' can form after submarine eruptions and drift for thousands of miles.
Field identification & locations
Identify by its extreme lightness and pitted, holey surface. Common in volcanic regions like the Cascades, Italy, or Iceland. If it floats on water, it is almost certainly pumice.
