igneous
Pumice or vesicular volcanic rock
Pumice; chiefly volcanic glass with variable feldspar, quartz, and other silicates
AI-generated identification · may be incorrectVery light-colored, porous, and rough-textured; typically hardness 5–6 Mohs, dull to silky luster, and no visible cleavage. The specimen’s pale, irregular surface is consistent with weathered pumice, though the image is not diagnostic.
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Physical properties
Very light-colored, porous, and rough-textured; typically hardness 5–6 Mohs, dull to silky luster, and no visible cleavage. The specimen’s pale, irregular surface is consistent with weathered pumice, though the image is not diagnostic.
Formation & geological history
Forms when gas-rich felsic to intermediate lava rapidly cools, trapping abundant bubbles; commonly Quaternary to modern in age. It occurs around explosive volcanic centers and ash-flow deposits.
Uses & applications
Used as an abrasive, exfoliating stone, lightweight aggregate, horticultural medium, and cement additive; attractive pieces may be collected but are usually low value.
Geological facts
Pumice can float temporarily because its interconnected vesicles reduce bulk density; it eventually becomes waterlogged and sinks.
Field identification & locations
Identify by testing low density, abundant pores, and a glassy, noncrystalline texture; common localities include Italy, Greece, Turkey, Iceland, Japan, and the western United States. A hardness or acid test is generally unnecessary.
