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, aphanitic (fine-grained) crystal structure, and high specific gravity.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, aphanitic (fine-grained) crystal structure, and high specific gravity.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava flows at the Earth's surface.
Uses & applications
Used extensively in construction as crushed aggregate, railroad ballast, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's oceanic crust and also forms major volcanic features on the Moon and Mars.
Field identification & locations
Identified by its fine-grained dark matrix and vesicular texture; found globally in volcanic provinces and oceanic ridges.
