Here's why:

* Igneous rocks form from the cooling and solidification of molten rock (magma or lava).

* Granite forms deep underground from slowly cooling magma. The slow cooling allows large crystals to form, giving granite its characteristic coarse-grained texture.

* Heat is essential for the formation of igneous rocks. The intense heat within the Earth melts rock, creating magma.

Let me know if you have more questions about rocks!