igneous
Pumice
Pumice (Volcanic glass / Felsic igneous rock)
Hardness: 5.5 to 6 on the Mohs scale, Color: White, grey, yellowish, or brownish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass with a frothy texture), Cleavage: None, Specific gravity: Extremely low (less than 1.0, meaning it floats in water).
- Hardness
- 5
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Physical properties
Hardness: 5.5 to 6 on the Mohs scale, Color: White, grey, yellowish, or brownish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass with a frothy texture), Cleavage: None, Specific gravity: Extremely low (less than 1.0, meaning it floats in water).
Formation & geological history
Formed during explosive volcanic eruptions where gas-rich felsic lava cools rapidly under low pressure, causing gases to exsolve and create a high-porosity vesicular structure.
Uses & applications
Used in lightweight concrete, abrasive products, landscaping, horticulture, and personal care products like pumice stones for exfoliating skin.
Geological facts
Pumice is one of the few rocks that can float on water due to its trapped gas bubbles forming a network of interconnected voids.
Field identification & locations
Easily identified in the field by its very light weight, pale color, and characteristic sponge-like or frothy porous texture. Found globally in regions with active or historic explosive volcanism.
