igneous
Basalt
Extrusive Igneous Rock
Hardness of 6 on the Mohs scale, dark gray to black color, dull luster, aphanitic (fine-grained) crystal structure, 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 luster, aphanitic (fine-grained) crystal structure, 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 extensively in construction (crushed stone for road base, concrete aggregate), and 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 is also found abundantly on the Moon and Mars.
Field identification & locations
Easily identified by its dark, fine-grained appearance and vesicular texture (gas bubbles), commonly found in volcanic regions worldwide.
