igneous
Pumice
Pumice (a highly vesicular extrusive igneous rock)
Hardness: 5-6 (but very brittle); Color: light gray, white, or cream; Luster: dull to pearly; Structure: highly vesicular (full of gas bubbles); Specific Gravity: 0.6-0.9 (floats in water).
- Hardness
- 5-6 (but very brittle)
- Color
- light gray, white, or cream
- Luster
- dull to pearly
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Physical properties
Hardness: 5-6 (but very brittle); Color: light gray, white, or cream; Luster: dull to pearly; Structure: highly vesicular (full of gas bubbles); Specific Gravity: 0.6-0.9 (floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected. The rapid cooling and depressurization trap gas bubbles inside as the lava solidifies into glass.
Uses & applications
Used as an abrasive in cleaning products, skin exfoliants (pumice stones), lightweight concrete, dental polishing compounds, and in stone-washed denim production.
Geological facts
Pumice is the only rock that consistently floats on water. Massive 'pumice rafts' created by underwater volcanoes can drift for thousands of miles across oceans.
Field identification & locations
Identify by its extremely light weight, frothy texture, and ability to float. It is commonly found in volcanic arc regions near the Ring of Fire or Mediterranean.
