igneous
Basalt
Mafic extrusive igneous rock
Hardness of 6 on the Mohs scale; dark gray to black color; dull to sub-aphanitic luster; microcrystalline or aphanitic crystal structure; no notable cleavage; specific gravity around 2.8-3.0.
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Physical properties
Hardness of 6 on the Mohs scale; dark gray to black color; dull to sub-aphanitic luster; microcrystalline or aphanitic crystal structure; no notable cleavage; specific gravity around 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, as crushed stone for road bases, concrete aggregate, and in the production of stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's ocean basins, and it is also extensively found on the Moon and Mars.
Field identification & locations
Identified by its dark color, fine-grained texture, and high density. Commonly found in volcanic regions worldwide.
