igneous
Weathered basaltic rock (probable basalt or scoria)
Basalt; chiefly plagioclase feldspar, pyroxene, and commonly olivine or volcanic glass
AI-generated identification · may be incorrectDark brown-gray, fine-grained and dull, with irregular weathering and a few possible vesicles; typical hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.7–3.2. The photograph alone cannot distinguish dense basalt from porous scoria confidently.
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Physical properties
Dark brown-gray, fine-grained and dull, with irregular weathering and a few possible vesicles; typical hardness about 5–6 Mohs, no obvious cleavage, and specific gravity roughly 2.7–3.2. The photograph alone cannot distinguish dense basalt from porous scoria confidently.
Formation & geological history
An extrusive igneous rock formed when mafic lava cooled rapidly at or near Earth’s surface, generally in volcanic settings; its exact age and locality cannot be determined visually. Brown coloration likely reflects surface oxidation and weathering.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, riprap, and building stone; attractive varieties are polished for décor, but this specimen appears mainly of educational or nominal collector value.
Geological facts
Basalt is the most abundant volcanic rock and forms much of oceanic crust. Vesicular basalt (scoria) contains gas-bubble cavities produced during lava eruption.
Field identification & locations
Look for a heavy, dark, fine-grained texture, weak magnetism, and a gray-black fresh interior beneath the weathered rind; a streak, density test, and close inspection of vesicles would improve identification. Common worldwide, especially volcanic regions.
