* Formation: Graphite forms from the intense heat and pressure that transform existing rocks, particularly sedimentary rocks rich in organic matter like coal. This process is called metamorphism.

* Types of Metamorphic Rocks: Graphite can be found in various metamorphic rocks, including:

* Schist: A type of metamorphic rock with a distinct layering or foliation.

* Gneiss: A metamorphic rock with a banded appearance due to mineral segregation.

* Marble: Metamorphosed limestone, usually containing other minerals along with graphite.

Less Common Occurrences:

While graphite is primarily found in metamorphic rocks, it can also occur in:

* Igneous rocks: Though rare, graphite can be found in some igneous rocks, particularly those that have undergone significant alteration or contact metamorphism.

* Sedimentary rocks: Graphite can sometimes be found in sedimentary rocks, especially those formed in environments rich in organic matter, but it's less common than in metamorphic rocks.

In summary, while graphite can occur in other rock types, its most common occurrence is within metamorphic rocks, specifically schist, gneiss, and marble.