igneous
Basalt
Mafic extrusive igneous rock
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull luster, specific gravity of 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale, dark gray to black color, fine-grained (aphanitic) texture, dull luster, specific gravity of 2.8-3.0.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in magnesium and iron exposed at or very near the surface of a planet or moon.
Uses & applications
Used in construction, aggregate for roads, making asphalt, and occasionally in manufacturing rock wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance and heavy weight. Common globally in volcanic regions and oceanic crusts.
