igneous
Rounded vesicular volcanic rock, likely pumice or scoriaceous basalt
Vesicular basalt (probable); possibly pumice, composed mainly of plagioclase, pyroxene, and volcanic glass
AI-generated identification · may be incorrectGray-brown, highly porous, and dull to faintly glassy with rounded stream or beach abrasion; likely Mohs hardness 5–6, with low to moderate specific gravity. The specimen is too weathered and low-resolution for definite mineral identification.
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Physical properties
Gray-brown, highly porous, and dull to faintly glassy with rounded stream or beach abrasion; likely Mohs hardness 5–6, with low to moderate specific gravity. The specimen is too weathered and low-resolution for definite mineral identification.
Formation & geological history
Formed when gas-rich lava cooled rapidly, trapping bubbles; subsequent erosion rounded the stone. Likely Quaternary or younger, though its exact age and source cannot be determined from the image.
Uses & applications
Used mainly as a teaching or display specimen; vesicular basalt can serve as lightweight aggregate, while true pumice is used for abrasives, polishing, and horticultural soil amendment.
Geological facts
Pumice is often light enough to float, whereas vesicular basalt generally sinks; this specimen’s dense, fine pores suggest basalt more than classic pumice.
Field identification & locations
Look for abundant connected vesicles, a lightweight feel, and a streak-free gray to brown surface; test density by placing it in water and avoid acid testing, which is uninformative. Common in volcanic regions and eroded river or beach gravels.
