igneous
Basalt
Extrusive igneous rock
Hardness of 6 on the Mohs scale, typically dark gray to black in color, aphanitic (fine-grained) texture, dull to submetallic luster, and composed mostly of plagioclase feldspar and pyroxene.
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Physical properties
Hardness of 6 on the Mohs scale, typically dark gray to black in color, aphanitic (fine-grained) texture, dull to submetallic luster, and composed mostly of plagioclase feldspar and pyroxene.
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 rocky planet or moon.
Uses & applications
Used extensively in construction as crushed stone for road bases, concrete aggregate, and in the manufacturing of fiberglass and stone wool insulation.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the world's oceans and is also the most abundant volcanic rock on the Moon and Mars.
Field identification & locations
Can be identified in the field by its dark color, fine-grained or vesicular (gas-bubble pitted) texture, and high density; common worldwide in volcanic regions and oceanic crust.
