Here's why:

* Coal is a sedimentary rock. It forms from the accumulation and compaction of plant matter over millions of years.

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

* Extrusive igneous rocks form when lava erupts onto the Earth's surface and cools.

So, while coal and igneous rocks are both types of rocks, they are formed through completely different processes.