igneous
Pumice
Pumice; highly vesicular volcanic glass, primarily rhyolitic to dacitic composition
AI-generated identification · may be incorrectLight gray-brown, extremely porous, frothy texture, dull to slightly glassy luster, and no visible crystal structure; typically Mohs hardness 5–6 and unusually low density, often floating in water. The rounded shape suggests natural abrasion or tumbling.
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Physical properties
Light gray-brown, extremely porous, frothy texture, dull to slightly glassy luster, and no visible crystal structure; typically Mohs hardness 5–6 and unusually low density, often floating in water. The rounded shape suggests natural abrasion or tumbling.
Formation & geological history
Forms when gas-rich felsic magma violently erupts and rapidly quenches, trapping bubbles in volcanic glass. It can form at any volcanic age, commonly in Quaternary explosive eruptions.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, concrete additive, horticultural soil amendment, and decorative stone; generally little jewelry value.
Geological facts
Its abundant vesicles are gas bubbles preserved during rapid cooling; pumice rafts can travel across oceans. It is commonly confused with scoria, which is darker, denser, and usually basaltic.
Field identification & locations
Identify it by its abundant interconnected holes, low weight, rough surface, and pale color; common sources include volcanic regions of Italy, Iceland, Greece, Turkey, Japan, New Zealand, and the western United States.
