igneous
Pumice
Pumice (Glassy Volcanic Rock)
Hardness: 6 on the Mohs scale, Color: Light gray, white, yellowish, or brownish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass), Cleavage: None, Specific Gravity: Less than 1.0 (floats on water due to high porosity).
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Physical properties
Hardness: 6 on the Mohs scale, Color: Light gray, white, yellowish, or brownish, Luster: Dull to earthy, Crystal structure: Amorphous (volcanic glass), Cleavage: None, Specific Gravity: Less than 1.0 (floats on water due to high porosity).
Formation & geological history
Formed from explosive volcanic eruptions where gas-rich, felsic (silica-rich) lava rapidly cools and depressurizes, trapping gas bubbles inside the solidifying glass.
Uses & applications
Used in lightweight concrete, landscaping, abrasive soaps, pumice stones for personal care, and horticulture.
Geological facts
Pumice is one of the few rocks that can float on water because of its extensive vesicular structure trapping air.
Field identification & locations
Easily identified by its extremely low weight, pale color, and abundant small holes (vesicles). Commonly found near regions of recent or historic explosive volcanic activity.
