igneous
Pumice
Pumice (Volcanic Glass Foam)
Hardness: 6 on the Mohs scale, Color: White, grey, yellowish, or brownish, Luster: Dull to earthy, Crystal Structure: Amorphous (volcanic glass), Specific Gravity: Less than 1 (often floats in water)
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Physical properties
Hardness: 6 on the Mohs scale, Color: White, grey, yellowish, or brownish, Luster: Dull to earthy, Crystal Structure: Amorphous (volcanic glass), Specific Gravity: Less than 1 (often floats in water)
Formation & geological history
Formed from explosive volcanic eruptions where gas-rich, felsic to intermediate lava rapidly cools and depressurizes, trapping gas bubbles as a foam that freezes into glass.
Uses & applications
Used in lightweight concrete, landscaping, abrasive soaps, personal care for exfoliating skin, and horticultural soil amendments.
Geological facts
Pumice is one of the very few rocks that can float on water due to its high porosity and trapped air bubbles.
Field identification & locations
Easily identified by its extremely lightweight feel and vesicular (sponge-like, hole-filled) texture. Commonly found near active or historical volcanic regions worldwide.
