igneous
Pumice
Pumice (Vesicular Rhyolite/Andesite)
Hardness: 5-6 (Mohs), Color: Light gray to tan, Luster: Dull to pearly, Crystal structure: Amorphous/Glassy, Specific Gravity: 0.25-0.90 (highly porous)
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Physical properties
Hardness: 5-6 (Mohs), Color: Light gray to tan, Luster: Dull to pearly, Crystal structure: Amorphous/Glassy, Specific Gravity: 0.25-0.90 (highly porous)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich molten rock (magma) is ejected into the air, cools rapidly, and traps gas bubbles inside.
Uses & applications
Used in construction for lightweight concrete, abrasive cleaners, cosmetic exfoliating stones, and filtration systems.
Geological facts
Pumice is the only rock that can float on water due to its extreme porosity and low density. Giant rafts of pumice have been known to float in the ocean for years after eruptions.
Field identification & locations
Identify by its extremely lightweight feel and sponge-like texture with numerous visible pores (vesicles). It is commonly found in areas of recent volcanic activity.
