igneous
Weathered basaltic rock, possibly vesicular basalt
Basalt; chiefly plagioclase feldspar, pyroxene, and iron-titanium oxides
AI-generated identification · may be incorrectDark brown-black, fine-grained and locally porous, with dull to weakly submetallic luster from weathering. Hardness about 5–6 Mohs; massive texture, no obvious cleavage, and typically dense (specific gravity ~2.8–3.0).
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Physical properties
Dark brown-black, fine-grained and locally porous, with dull to weakly submetallic luster from weathering. Hardness about 5–6 Mohs; massive texture, no obvious cleavage, and typically dense (specific gravity ~2.8–3.0).
Formation & geological history
Basalt forms when low-viscosity mafic lava cools rapidly at or near Earth’s surface; its exact age cannot be determined from the image and may range from ancient to recent. The rounded shape and brown oxidation indicate prolonged weathering or abrasion.
Uses & applications
Common basalt is used as crushed aggregate, road base, riprap, concrete aggregate, and occasionally building stone. This small weathered specimen has mainly educational or collecting value.
Geological facts
Iron-bearing minerals commonly oxidize to reddish-brown limonite, producing the rusty surface. Any pits may represent vesicles—gas bubbles trapped during lava cooling—or weathering cavities.
Field identification & locations
Look for a dark, fine-grained matrix, scattered tiny crystals, high density, and possible vesicles; a streak, magnet test, and fresh broken surface would improve identification. Common worldwide in volcanic regions, including Hawaii, Iceland, India, and oceanic crust.
