igneous
Likely pumice
Pumice, vesicular volcanic glass (typically rhyolitic to dacitic composition)
AI-generated identification · may be incorrectVery light gray, highly vesicular, dull to silky luster, and extremely low density; hardness about 5–6 Mohs, with no visible cleavage and irregular fracture. The pores and fine glassy matrix are characteristic, though the specimen appears cut or shaped.
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Physical properties
Very light gray, highly vesicular, dull to silky luster, and extremely low density; hardness about 5–6 Mohs, with no visible cleavage and irregular fracture. The pores and fine glassy matrix are characteristic, though the specimen appears cut or shaped.
Formation & geological history
Forms when gas-rich felsic lava explosively depressurizes and quenches into frothy volcanic glass, generally during young explosive eruptions. Commonly associated with volcanic ash and pyroclastic deposits, ranging from recent to geologically ancient.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, concrete additive, horticultural soil amendment, and decorative stone; rarely collectible unless unusually textured or colored.
Geological facts
Pumice can float temporarily because of abundant connected vesicles, although waterlogged pieces eventually sink. It differs from scoria by being generally lighter colored, more silica-rich, and often much less dense.
Field identification & locations
Identify it by its pale color, abundant holes, rough texture, and unusually low weight; common sources include Italy, Iceland, Greece, Turkey, Japan, New Zealand, and the western United States. The image alone cannot exclude porous tuff or weathered volcanic rock.
