igneous
Pumice
Pumice (Highly vesicular volcanic glass)
Hardness: 5-6 Mohs. Color: Light grey, tan, or dark grey. Luster: Dull to pearly. Texture: Vesicular with open, interconnected gas cavities. Specific gravity: Very low (0.25 - 0.9), often floats on water.
- Hardness
- 5-6 Mohs
- Color
- Light grey, tan, or dark grey
- Luster
- Dull to pearly
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Physical properties
Hardness: 5-6 Mohs. Color: Light grey, tan, or dark grey. Luster: Dull to pearly. Texture: Vesicular with open, interconnected gas cavities. Specific gravity: Very low (0.25 - 0.9), often floats on water.
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-charged molten rock (felsic to intermediate lava) rapidly cools, trapping gas bubbles before solidification.
Uses & applications
Used widely as an abrasive in cosmetics (pumice stones for skin exfoliation), heavy-duty cleaning products, stone-washed denim manufacturing, lightweight concrete aggregate, and horticulture soil additives.
Geological facts
Pumice is the only rock that can float on water due to its cellular, sponge-like structure filled with trapped air pockets. Huge floating 'pumice rafts' can form after submarine volcanic eruptions.
Field identification & locations
Easily identified by its extremely light weight, rough texture, and presence of tiny gas holes (vesicles). Commonly found in volcanic regions near active or dormant subduction zones.
