igneous
Basalt
Extrusive igneous rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to sub-withish luster, composed mostly of plagioclase feldspar and pyroxene.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull to sub-withish luster, composed mostly of plagioclase feldspar and pyroxene.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the surface of a planet or moon.
Uses & applications
Commonly used in construction as crushed stone for road bases, concrete aggregate, and railroad ballast, as well as 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 also makes up extensive volcanic landforms on the Moon and Mars.
Field identification & locations
Identify by its dark, dense, fine-grained appearance often with small visible crystal vesicles; widely found in volcanic regions worldwide.
