Gabbro is classified as an intrusive igneous rock.
Intrusive rocks, also known as plutonic rocks, are formed from the slow crystallization of magma beneath the Earth’s surface. In contrast, extrusive rocks, or volcanic rocks, are formed from lava that cools quickly on the Earth’s surface. Gabbro typically has a coarse-grained texture, which indicates that the minerals within it had ample time to grow large before the rock was solidified. This slow cooling occurs deep underground, distinguishing gabbro from its extrusive counterpart, basalt, which has a similar chemical composition but cools rapidly at the surface and has a much finer-grained texture.