igneous
Basalt
Mafic extrusive igneous rock
Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity around 2.8 to 3.0
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black in color, fine-grained aphanitic texture, dull luster, specific gravity around 2.8 to 3.0
Formation & geological history
Formed from the rapid cooling of low-viscosity, magnesium- and iron-rich lava exposed at or very near the surface of a planet or moon
Uses & applications
Used 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 crustal portions of ocean basins and makes up most of the oceanic crust as well as volcanic islands like Hawaii and Iceland
Field identification & locations
Identified by its dark color, heavy feel for its size, and fine-grained texture; commonly found in volcanic regions worldwide and ancient lava flows
