igneous
Basalt
Extrusive igneous rock
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, microcrystalline or aphanitic structure, lacks prominent visible crystals, 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 color, dull luster, microcrystalline or aphanitic structure, lacks prominent visible crystals, specific gravity around 2.8 to 3.0.
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
Used in construction, aggregate for road bases, production of rock wool insulation, and dimension stone.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans and is also commonly found on the Moon and Mars.
Field identification & locations
Identify by its dark, fine-grained appearance, heavy weight relative to size, and occasional vesicular texture. Common worldwide in volcanic provinces and oceanic crust.
