Here's why:

* Peat is a partially decayed plant matter, primarily mosses and other water-loving plants, that accumulates in waterlogged environments like bogs and swamps.

* Coal forms over millions of years through a process called coalification.

* This process involves increasing pressure and heat transforming peat through several stages:

* Peat -> Lignite -> Sub-bituminous coal -> Bituminous coal -> Anthracite coal

Anthracite, the highest grade of coal, is the result of intense heat and pressure on existing coal deposits. It is very hard, dense, and has the highest carbon content of all coal types.