Gabbro is an igneous rock which is formed by the gradual cooling of molten magma below the surface of the earth. It is an intrusive rock which means that its cooling and solidification was done below the surface of the earth. Gabbro should not be confused for basalt which has similar chemical compositions as gabbro. The only difference being that basalt has a smaller grain size which is as a result of its quick cooling and solidification process above the earth's surface (extrusive rock).
