Igneous is the hardest type of rock, because it was formed when volcanic material cooled and hardened.It is much harder then the other types.There are 2 other basic types of rock-sedimentary rock, which was formed from the compressed remains of plants and animals, and metamorphic rock, which is a rock which used to be either igneous or sedimentary, but changed due to great heat or pressure. Igneous is harder then both of these, especially sedimentary, which is usually quite soft.Examples of igneous rock include granite and basalt.