igneous
Vesicular volcanic rock, likely pumice or vesicular basalt
Pumice: highly vesicular volcanic glass, chiefly silica-rich; vesicular basalt: Fe-Mg-rich plagioclase–pyroxene rock
AI-generated identification · may be incorrectLight gray, strongly porous, dull to slightly glassy, with abundant gas cavities; likely hardness ~5–6 for basalt or ~5–6.5 for pumice, with no obvious cleavage. The image is blurry, so exact identification is limited.
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Physical properties
Light gray, strongly porous, dull to slightly glassy, with abundant gas cavities; likely hardness ~5–6 for basalt or ~5–6.5 for pumice, with no obvious cleavage. The image is blurry, so exact identification is limited.
Formation & geological history
Formed when gas-rich lava erupted and rapidly cooled, trapping bubbles; commonly Quaternary to modern, though vesicular volcanic rocks occur throughout geologic time. Pumice usually forms in explosive felsic eruptions, while vesicular basalt forms from fluid lava flows.
Uses & applications
Pumice is used as an abrasive, lightweight aggregate, horticultural medium, and exfoliant; basalt is used for aggregate, roadstone, and construction. Small pieces have modest collecting value.
Geological facts
Very low density and abundant vesicles are diagnostic; pumice may float initially, whereas basalt generally sinks. A dark, dense groundmass favors vesicular basalt; a pale, frothy, glassy texture favors pumice.
Field identification & locations
Common near volcanic fields, lava flows, and ash deposits worldwide, including Iceland, Italy, Japan, the western United States, and the Pacific Ring of Fire. Check density, streak, and whether it floats; avoid confusing it with concrete or industrial slag.
