Coal

Coal is the largest source of energy for generating electricity in the world, and the most abundant fossil fuel. Coal is very different from mineral rocks, which are made of inorganic material. Coal is made of fragile plant matter, and undergoes many changes before it becomes the familiar black and shiny substance burned as fuel.

Ranking is determined by the degree of transformation of the original plant material to carbon. The ranks of coals, from those with the least carbon to those with the most carbon, are lignite, subbituminous, bituminous, and anthracite.