What type of rock is basalt?

Basalt is an igneous rock, which means it was formed deep in the bowels of the earth, often from the lava flow of a volcano. This makes it largely an extrusive rock.

Basalt is mostly made of the minerals plagioclase and pyroxene. It has a fine grain and is usually black. Basalt is found on the Earth, on Mars and on the moon. Much of the rock that makes up the lunar maria is made of basalt. Basalt may also be found beneath the ocean floor on Earth. Mars' enormous volcano, Olympus Mons, is also believed to be made of basalt.