igneous
Weathered dark rock fragment
Indeterminate; possibly basalt or iron-rich volcanic rock
AI-generated identification · may be incorrectDark brown-black, dull to weakly earthy luster, fine-grained and massive, with irregular fracture and no visible crystals; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.2.
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Physical properties
Dark brown-black, dull to weakly earthy luster, fine-grained and massive, with irregular fracture and no visible crystals; estimated Mohs hardness 5–6 and specific gravity about 2.7–3.2.
Formation & geological history
Likely a weathered volcanic fragment formed by cooling of mafic lava, generally ranging from Precambrian to recent age depending on locality; the image alone cannot establish its precise geology.
Uses & applications
Common basalt is used as crushed aggregate, road material, riprap, and building stone; this small weathered piece has negligible commercial value unless locality or unusual composition is established.
Geological facts
Brown coloration likely reflects oxidation of iron-bearing minerals such as pyroxene, olivine, or magnetite. Its granular appearance may also fit a weathered industrial slag fragment, which would require testing to distinguish.
Field identification & locations
Test for a uniform fine texture, hardness greater than a steel nail, and possible attraction to a strong magnet; a streak, density, fresh broken surface, and acid test would improve identification. Basalt is widespread in volcanic regions and on ocean floors.
