igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; chiefly plagioclase feldspar, pyroxene, and iron-rich minerals, with vesicles from trapped gas
AI-generated identification · may be incorrectDark brown to gray, fine-grained, dull to slightly earthy luster, porous surface, and rounded water-worn shape; hardness about 5–6 Mohs, with no obvious cleavage and typical specific gravity around 2.7–3.0.
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Physical properties
Dark brown to gray, fine-grained, dull to slightly earthy luster, porous surface, and rounded water-worn shape; hardness about 5–6 Mohs, with no obvious cleavage and typical specific gravity around 2.7–3.0.
Formation & geological history
An extrusive igneous rock formed when basaltic lava cooled rapidly at or near the surface, leaving gas bubbles; its exact geological age cannot be determined from the photograph. The smooth form indicates later erosion or stream/beach transport.
Uses & applications
Used as aggregate, road base, drainage material, landscaping stone, and occasionally lightweight scoria in construction; generally little jewelry value.
Geological facts
The abundant small cavities are vesicles, not fossil holes; if vesicles are exceptionally abundant and the specimen is lightweight, it may be classified as scoria rather than ordinary vesicular basalt.
Field identification & locations
Identify it by its dark fine-grained matrix, magnetic tendency, and irregular gas cavities; common in volcanic regions, lava flows, cinder cones, and river or beach gravels. A streak, density, and fresh broken surface would improve identification.
