* Igneous rocks: They can melt and solidify again, creating a new igneous rock. This is called re-crystallization.
* Sedimentary rocks: These are formed from sediments, which can be eroded from any type of rock (including igneous). These sediments can then be buried, subjected to heat and pressure, and eventually melt to form magma. This magma then cools and solidifies to form igneous rock.
* Metamorphic rocks: These are formed from existing rocks (igneous, sedimentary, or even other metamorphic rocks) that have been changed by heat and pressure. When metamorphic rocks are subjected to even more intense heat and pressure, they can melt and solidify, forming igneous rocks.
Essentially, the key to turning any rock into an igneous rock is through melting and then solidification.
