Coal mining industry
“A hard black or blackish substance, mainly carbonized plant matter,…used as a fuel.” Canadian Oxford Dictionary.
Coal has been used for a very long time as a fuel and energy source. Its use has changed remarkably in recent decades. It used to be sorted by hand, but now the sorting process is much simpler thanks to modern equipment. DMS cyclones, samplers and spirals do a very efficient job of separating, sorting and washing coal.