* Coal: Formed from the accumulation and compression of plant matter, primarily in swampy environments.
* Limestone: Mostly composed of the calcium carbonate shells and skeletons of marine organisms like coral, foraminifera, and mollusks.
* Chalk: A type of limestone made almost entirely from the microscopic shells of planktonic algae called coccolithophores.
* Diatomite: Composed of the fossilized remains of diatoms, a type of single-celled algae with silica shells.
* Oil Shale: Contains organic matter from ancient algae and other organisms that has been transformed into kerogen.
These rocks are all examples of how the remains of living things can be transformed into rock over millions of years.
