igneous
Basalt
Extrusive Igneous Rock
Hardness of 5-6 on the Mohs scale, typically dark gray to black in color, dull luster, aphanitic (fine-grained) crystal structure, and often vesicular with gas cavities.
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Physical properties
Hardness of 5-6 on the Mohs scale, typically dark gray to black in color, dull luster, aphanitic (fine-grained) crystal structure, and often vesicular with gas cavities.
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the Earth's surface, often from volcanic eruptions.
Uses & applications
Used extensively in construction as crushed stone for road bases, concrete aggregate, railroad ballast, and in the manufacturing of rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans, and it is also the primary volcanic rock found on the Moon and Mars.
Field identification & locations
Identified by its dark, fine-grained matrix and often vesicular texture. Commonly found in volcanic regions worldwide, oceanic crust, and large igneous provinces like the Columbia River Plateaus.
