igneous
Vesicular basalt (likely scoria or weathered pumice)
Vesicular basalt; chiefly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark gray-brown, porous, dull to slightly glassy surface with abundant gas vesicles; typically hardness 5–6, no obvious cleavage, fine-grained groundmass, and specific gravity roughly 2.4–3.0 (lower if pumice-rich).
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Physical properties
Dark gray-brown, porous, dull to slightly glassy surface with abundant gas vesicles; typically hardness 5–6, no obvious cleavage, fine-grained groundmass, and specific gravity roughly 2.4–3.0 (lower if pumice-rich).
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly, trapping bubbles; likely Cenozoic or younger, though exact age cannot be determined visually. Weathering may have enlarged or accentuated the vesicles.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and decorative rock; generally little jewelry value, though attractive pieces are collected.
Geological facts
The holes are vesicles, not fossils, and their abundance records gas release during eruption. The specimen appears unusually rounded, suggesting transport or deliberate tumbling/weathering.
Field identification & locations
Identify by its volcanic texture, low-to-moderate weight, irregular bubble cavities, and absence of sedimentary layering or crystal bands; common near basaltic volcanic fields and shorelines. A hand lens can reveal tiny dark pyroxene or olivine grains.
