two common examples of the three types of rocks
Examples of this rock type include gneiss and marble. Igneous. Igneous rocks are formed when magma (molten rock deep within the earth) cools and hardens. Sometimes the magma cools inside the earth, and other times it erupts onto the surface from volcanoes (in this case, it is called lava).xamples of this rock type include conglomerate and limestone. Metamorphic. Metamorphic rocks are formed under the surface of the earth from the metamorphosis (change) that occurs due to intense heat and pressure (squeezing).