igneous
Pumice (likely)
Vesicular volcanic glass, typically rhyolitic or dacitic in composition
AI-generated identification · may be incorrectPinkish-tan, porous and lightweight, with a dull to slightly glassy surface; chiefly silica-rich volcanic glass with possible feldspar and quartz. Hardness is variable, roughly 5–6 Mohs for glassy material; crystal structure is mostly amorphous.…
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Physical properties
Pinkish-tan, porous and lightweight, with a dull to slightly glassy surface; chiefly silica-rich volcanic glass with possible feldspar and quartz. Hardness is variable, roughly 5–6 Mohs for glassy material; crystal structure is mostly amorphous. The specimen’s appearance suggests pumice, though a photo alone cannot confirm it.
Formation & geological history
Forms when gas-rich, silica-rich lava cools rapidly, trapping bubbles; it may be geologically young or much older depending on its volcanic source.
Uses & applications
Used as an abrasive, lightweight aggregate, and horticultural soil additive; selected pieces are also sold as curiosities.
Geological facts
Pumice can be light enough to float when its vesicles are open and interconnected.
Field identification & locations
Look for abundant rounded or elongated cavities and unusually low weight; common around volcanic regions worldwide. This thin, flat piece may be a cut or processed specimen.
