igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness 6 on Mohs scale, dark gray to black color, dull to sub-to-glassy luster, fine-grained aphanitic crystal structure, no prominent cleavage, specific gravity around 2.8-3.0.
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Physical properties
Hardness 6 on Mohs scale, dark gray to black color, dull to sub-to-glassy luster, fine-grained aphanitic crystal structure, no prominent cleavage, specific gravity around 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity basaltic lava exposed at or very near the surface of a planet or moon, typically originating from hotspot volcanism or seafloor spreading.
Uses & applications
Widely used in construction as crushed stone for road bases, concrete aggregate, railroad ballast, and in manufacturing stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins, and it is also abundantly found on the Moon and Mars.
Field identification & locations
Identified in the field by its dark, fine-grained matrix and heavy weight; common worldwide in volcanic regions, oceanic islands, and continental flood basalt provinces.
