Inertinite

Inertinite is fossilised charcoal. It is found as tiny flakes within sedimentary rocks. The presence of inertinite is significant in the geological record, as it signifies that wild fires occurred at the time that the host sediment was deposited. Inertinite is a common maceral in most types of coal.

The optical properties of inertinite are very similar to those of vitrinite. They differ in that inertinite is black, whereas vitrinite is brown, and inertinite also has a higher reflectance than vitrinite.