igneous
Likely gabbro or basaltic rock fragments
Mafic igneous rock, chiefly plagioclase feldspar and pyroxene; exact identification requires testing
AI-generated identification · may be incorrectDark gray to black, coarse-grained pieces with a granular texture and dull to slightly vitreous luster. Typical hardness is about 5–6, with dense, massive structure and no obvious cleavage at specimen scale.
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Physical properties
Dark gray to black, coarse-grained pieces with a granular texture and dull to slightly vitreous luster. Typical hardness is about 5–6, with dense, massive structure and no obvious cleavage at specimen scale.
Formation & geological history
Formed when mafic magma crystallized; gabbro cools slowly underground, while basalt forms rapidly at or near the surface. Such rocks are commonly Precambrian to Cenozoic in age depending on locality.
Uses & applications
Used as crushed stone, road aggregate, dimension stone, and occasionally decorative material; these small pieces have modest collecting value.
Geological facts
The lighter gray grains are likely calcium-rich plagioclase, while darker grains may be pyroxene or amphibole. The image alone cannot reliably distinguish gabbro from basalt or identify possible alteration.
Field identification & locations
Common in oceanic crust, volcanic regions, and mafic intrusive complexes worldwide. Check grain size, streak, density, magnetism, and thin-section mineralogy; avoid assuming a specific locality from appearance alone.
