igneous
Crushed dark aggregate, likely basalt
Basalt (fine-grained mafic volcanic rock; commonly plagioclase + pyroxene ± olivine)
AI-generated identification · may be incorrectDark gray to black, angular crushed fragments with a dull to slightly vitreous luster and fine-grained texture; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.8–3.0. The image appears to show quarry aggregate rather than a single diagnostic specimen.
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Physical properties
Dark gray to black, angular crushed fragments with a dull to slightly vitreous luster and fine-grained texture; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.8–3.0. The image appears to show quarry aggregate rather than a single diagnostic specimen.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface, commonly during Cenozoic volcanic activity; its exact age cannot be determined visually. Around 19.1°N, 72.9°E, basaltic Deccan volcanic rocks are a plausible regional source, though transported aggregate is also possible.
Uses & applications
Widely used as road base, railway ballast, concrete aggregate, riprap, and asphalt stone; attractive polished pieces can be used decoratively but are generally low-value.
Geological facts
The rough vesicle-free, dark appearance is consistent with basalt, but similar aggregate may be dolerite/diabase, amphibolite, or dark gneiss.
Field identification & locations
Check for a uniformly fine texture, black-gray color, and small white plagioclase grains; a steel file usually scratches it weakly or not at all. A hand lens, streak, magnetism test, and thin section would be needed for confident identification.
