igneous
Likely basalt or weathered mafic rock
Basalt; predominantly plagioclase feldspar and pyroxene, possibly olivine
AI-generated identification · may be incorrectDark gray to black, fine- to medium-grained, dull to weakly vitreous luster, with rounded weathered surfaces. Hardness about 5–6 Mohs; typically massive with no obvious cleavage and specific gravity around 2.8–3.1.
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Physical properties
Dark gray to black, fine- to medium-grained, dull to weakly vitreous luster, with rounded weathered surfaces. Hardness about 5–6 Mohs; typically massive with no obvious cleavage and specific gravity around 2.8–3.1.
Formation & geological history
Formed when iron- and magnesium-rich lava cooled at or near Earth’s surface, commonly in volcanic flows; age cannot be determined from the photograph and may range from recent to billions of years.
Uses & applications
Used widely as crushed aggregate, road base, riprap, building stone, and occasionally ornamental material. Small ordinary specimens generally have little commercial value.
Geological facts
The lumpy surface may reflect vesicles or weathering, but the image is too blurred to confirm texture or mineral grains. It could also be another dark volcanic rock, such as andesite or gabbro.
Field identification & locations
Common in volcanic regions and oceanic crust, including Iceland, Hawaii, the Pacific Northwest, India, and ocean-floor environments. A fresh broken surface, streak, magnetism, and visible crystals would improve identification; avoid relying on color alone.
