* Igneous rocks form from molten rock (magma or lava). The intense heat involved in the formation of igneous rocks would completely destroy any existing organic matter, making fossilization impossible.
* Fossils form in sedimentary rocks. Sedimentary rocks are formed from the accumulation and cementation of sediments like sand, mud, and organic matter. Fossils are preserved in these rocks because the slow process of sedimentation allows for the preservation of hard parts or even imprints of organisms.
Exceptions:
While rare, there are some exceptions:
* Volcanic ash layers: Volcanic ash can rapidly bury organisms, potentially preserving them before they decompose. This is more likely for small organisms or delicate structures.
* Fossil molds: In rare cases, the intense heat of an eruption could leave behind an imprint of an organism in solidified lava. This would be a mold rather than a true fossil.
In summary: Finding fossils in igneous rocks is extremely uncommon. You're much more likely to find them in sedimentary rocks.
