Question

How is coal formed?

Answer 1

First dead organic matter falls to the ground and is covered with sediment ( a low oxygen environment).
Then peat is formed. This can be burned but produces very little heat and a lot of smoke. During the potato famine in Ireland, peat blocks from the peat bogs were the main source of fuel for much of the population.
More heat and pressure are applied by more sediment and Lignite is formed.
Lignite will, with more heat and pressure, metamorphose into Bituminous coal.
Even more heat and pressure metamorphose the bituminous coal into a nice hard shiny Anthracite.
Coal is usually classified into three grades: Lignite, brown coal; Bituminous coal, soft coal; and Anthracite, hard coal. Anthracite is dense, nice and hard, and shiny. It produces the most heat with the least amount of smoke.