igneous
Pumice
Pumice (Volcanic Rock / Glass Froth)
Hardness: 6 on the Mohs scale, Color: Light gray to white or yellowish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass with vesicular texture), Cleavage: None, Specific gravity: Extremely low (often less than 1.0, allowing it to float on water).
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Physical properties
Hardness: 6 on the Mohs scale, Color: Light gray to white or yellowish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass with vesicular texture), Cleavage: None, Specific gravity: Extremely low (often less than 1.0, allowing it to float on water).
Formation & geological history
Formed from explosive volcanic eruptions where gas-rich felsic to intermediate lava rapidly cools and depressurizes, trapping gas bubbles within the solidifying glass matrix.
Uses & applications
Used widely in lightweight concrete, abrasive soaps, pumice stones for personal care, horticulture as a soil amendment, and stonewashing denim.
Geological facts
Pumice is one of the only known rocks that can float on water due to its high porosity and trapped gas vesicles. Famous deposits are associated with explosive eruptions like Mt. Vesuvius and Krakatoa.
Field identification & locations
Easily identified by its extremely light weight, vesicular (sponge-like) texture, pale color, and ability to float. Found globally in regions with young volcanic activity.
