igneous
Vesicular basalt (likely scoriaceous basalt)
Basalt; chiefly plagioclase, clinopyroxene, and Fe–Mg minerals, with possible olivine and iron oxides
AI-generated identification · may be incorrectDark gray-black, fine-grained, rough and locally vesicular, with a dull to slightly glassy luster; typically Mohs 5–6, no obvious cleavage, and specific gravity about 2.7–3.0. The orange-pink patches may be weathering products or embedded feldspar/oxidized material.
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Physical properties
Dark gray-black, fine-grained, rough and locally vesicular, with a dull to slightly glassy luster; typically Mohs 5–6, no obvious cleavage, and specific gravity about 2.7–3.0. The orange-pink patches may be weathering products or embedded feldspar/oxidized material.
Formation & geological history
An extrusive volcanic rock formed when mafic lava cooled rapidly at or near the surface; commonly Quaternary to older in age depending on locality. Gas-rich lava can produce its vesicular or scoriaceous texture.
Uses & applications
Crushed for road base, aggregate, concrete, and riprap; dense basalt is also used as building and paving stone. Usually low collector value unless it has unusual crystals, native copper, or exceptional vesicles.
Geological facts
Basalt is the most abundant volcanic rock on Earth and forms much of the oceanic crust. It is commonly associated with lava flows, cinder cones, and volcanic plateaus.
Field identification & locations
Identify it by its black fine-grained matrix, heavy weight, irregular fracture, and tiny gas cavities; it is not strongly layered or foliated. Common worldwide in volcanic regions, including Hawaii, Iceland, the Pacific Northwest, India, and East Africa.
