Answer;
-Peat, lignite, bituminous, anthracite.
Explanation;
-Peat is formed from decaying vegetation, and is considered to be the precursor of coal. It is an important industrial fuel in some regions, including Ireland and Finland.
-Lignite is formed from compressed peat, and is often referred to as brown coal. Lignite is a low ranking and highly volatile coal which is used mainly in power stations.
-Formed from compressed lignite, bituminous coals are a dense, sedimentary rock which is usually black in colour, but can sometimes be a dark brown.
-Steam coal is the stepping stone between bituminous coal and anthracite. It was once used to fuel steam trains, and as the use of them declined, so did the use of steam coal.
-Anthracite is the highest rank of ignitable coal. It is hard, black and glossy, and as a natural smokeless fuel, is used primarily for residential and commercial space heating.
