igneous
Vesicular basalt (weathered lava rock)
Basalt, predominantly plagioclase, pyroxene, and minor olivine/iron oxides
AI-generated identification · may be incorrectDark gray to reddish-brown, fine-grained, dull to submetallic weathered surface with abundant rounded vesicles; hardness about 6, no obvious cleavage, and typical specific gravity 2.7–3.0. The cavities may contain secondary zeolites, calcite, or iron oxides.
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Physical properties
Dark gray to reddish-brown, fine-grained, dull to submetallic weathered surface with abundant rounded vesicles; hardness about 6, no obvious cleavage, and typical specific gravity 2.7–3.0. The cavities may contain secondary zeolites, calcite, or iron oxides.
Formation & geological history
An extrusive igneous rock formed when low-silica lava cooled rapidly at or near Earth’s surface, trapping gas bubbles; its exact age cannot be determined from the photograph. Weathering has enlarged or stained some vesicles.
Uses & applications
Used as aggregate, roadstone, riprap, landscaping stone, and lightweight construction material; attractive specimens may be collected, though this piece appears common rather than gem-quality.
Geological facts
Vesicular basalt is common in volcanic terrains and can resemble scoria, but basalt is generally denser and less glassy. The large cavities are gas vesicles, not necessarily fossil holes.
Field identification & locations
Identify it by its dark fine-grained matrix, vesicles, heavy weight, and lack of visible sedimentary layering; it commonly occurs in lava flows, volcanic islands, and flood-basalt provinces. Exact identification would benefit from a streak, magnetism, and thin-section or chemical test.
