Coal is made up of complex mixtures of organic and inorganic compounds. The organic compounds, inherited from the plants that live and die in the swamps, number in the millions. The more than 120 inorganic compounds in coal either were introduced into the swamp from waterborne or windborne sediment, or were derived from elements in the original vegetation; for instance, inorganic compounds containing such elements as iron and zinc are needed by plants for healthy growth.
After the plants decompose, the inorganic compounds remain in the resulting peat. Some of those elements combine to form discrete minerals, such as pyrite. Other sources of inorganic compounds used by the plants may be either the mud that coats the bottom of the swamp, sediments introduced by drainage runoff, dissolved elements in the swamp water, windborne sand, ash, or dust.
Coal is abundant in South Africa, is relatively inexpensive, and is an excellent source of energy and by-product raw materials. Because of these factors, domestic coal is the primary source of fuel for electric power stations and will continue to be well into the 21st century. In addition, other industries continue to use coal for fuel and coke production and there is a large overseas market for high quality South African coal.
Because humans have used coal for centuries, much is known about it. The usefulness of coal as a heat source and the myriad of by products that can be produced from coal are well understood.