igneous
Basalt
Mafic extrusive igneous rock
AI-generated identification · may be incorrectHardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to aphanitic structure, specific gravity around 2.9.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline to aphanitic structure, specific gravity around 2.9.
Formation & geological history
Formed from the rapid cooling of low-viscosity, iron and magnesium-rich lava flows at Earth's surface.
Uses & applications
Used widely in construction as crushed stone for road bases, concrete aggregate, and in the production of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crustal portions underlying the ocean basins and also forms massive volcanic features like the Columbia River Plateaus.
Field identification & locations
Identify in the field by its dark, fine-grained matrix, sometimes containing small olivine or pyroxene phenocrysts. Found globally in volcanic regions.
