The rock cycle document describes the three main types of rocks and how they are formed. Igneous rocks form from cooled magma, either deep underground forming coarse grains or near the surface forming fine grains. Sedimentary rocks form from compressed and cemented sediments at the surface. Metamorphic rocks form from intense heat and pressure transforming sedimentary and igneous rocks into denser forms with new minerals, without melting, deep within the earth's crust.