The process you're describing is called coalification. It's not a specific type of rock, but rather a process that transforms dead plant matter into coal.

Here's a breakdown:

* Peat: The first stage, where dead plant material accumulates in waterlogged environments.

* Lignite: Peat is buried under more sediment, increasing pressure and heat, which transforms it into brown coal (lignite).

* Bituminous Coal: Further burial and transformation lead to bituminous coal, a harder and more carbon-rich type of coal.

* Anthracite: The final stage, where extreme heat and pressure transform coal into anthracite, the hardest and most carbon-rich coal.

So, while "coal" is the common term used to describe the resulting rock, the process itself is called coalification.