Basalt, Scoria, which is also a type of basalt and Pumice are extrusive rocks, while Granite is an intrusive rock. Instrusive rocks, as the name suggests, are formed within the Earth's crust and tend to solidify slowly. This causes them to be coarse-grained. Extrusive rocks are formed outside the Earth's crust and tend to cool and solidify faster than intrusive rocks. So, these rocks are smooth and fine-grained.