igneous
Vesicular basalt (likely weathered basalt cobble)
Basalt; primarily plagioclase, pyroxene, and sometimes olivine
AI-generated identification · may be incorrectDark brown to reddish, fine-grained, dull luster, with abundant rounded vesicles (gas holes); hardness about 5–6, generally massive with no visible cleavage. The reddish color likely reflects iron-oxide weathering.
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Physical properties
Dark brown to reddish, fine-grained, dull luster, with abundant rounded vesicles (gas holes); hardness about 5–6, generally massive with no visible cleavage. The reddish color likely reflects iron-oxide weathering.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near Earth’s surface; vesicles formed from escaping gas. Its exact geological age cannot be determined from the photograph; such rocks range from recent lava flows to ancient volcanic terrains.
Uses & applications
Used as crushed aggregate, road base, riprap, landscaping stone, and occasionally building stone; vesicular pieces are mainly collected or used decoratively.
Geological facts
Basalt is the most widespread volcanic rock on oceanic crust and commonly forms lava flows, dikes, and volcanic islands.
Field identification & locations
Identify it by its fine texture, high density, dark mafic color, and gas cavities; unlike pumice, it is usually relatively heavy and does not float. Common around volcanic regions, including Hawaii, Iceland, the Pacific Northwest, and many continental basalt fields.
