The changing from one type of rock to another is the rock cycle. There are 3 types of rocks as named in the vocabulary section, they are igneous, sedimentary, and metamorphic. Metamorphic rocks are formed by heat and pressure from the Earth. Igneous rocks are shiny and are formed when lava or magma cools. Sedimentary rocks are formed when sediments, small pieces of rock, are packed together. They can all turn into each kind.