igneous
Pumice
Pumice (Silicic volcanic glass)
Hardness: 5.5 - 6 (Mohs scale), but feels soft due to high porosity; Color: White to light grey or cream with tiny dark speckles; Luster: Dull to vitreous; Texture: Vesicular, extremely porous and lightweight, often floats on water.
- Hardness
- 5
- Color
- White to light grey or cream with tiny dark speckles
- Luster
- Dull to vitreous
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Physical properties
Hardness: 5.5 - 6 (Mohs scale), but feels soft due to high porosity; Color: White to light grey or cream with tiny dark speckles; Luster: Dull to vitreous; Texture: Vesicular, extremely porous and lightweight, often floats on water.
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-charged felsic (silica-rich) magma cools rapidly, trapping gas bubbles before solidification.
Uses & applications
Used widely as an abrasive in cosmetics (foot scrubs), horticulture (soil aeration), lightweight concrete aggregate, denim washing, and stone washing.
Geological facts
Pumice is the only rock that regularly floats on water until it eventually becomes waterlogged and sinks. Large volcanic eruptions can create floating pumice rafts that travel thousands of miles across oceans.
Field identification & locations
Identified by its distinctive porous, sponge-like vesicular texture and exceptionally light weight. Commonly found near active or historical explosive volcanic regions globally.
