Ash range: 3%-9% in most commercial coal. Ash is the unburnable portion of coal, mostly sand and clay that was blown into bog/swamp millions of years ago, and now inherent in the coal seam. Not really factored into the raw coal/clean coal definition. It is factored into BTU calculation.
Raw coal is run-of-mine coal (ROM), comprised of: coal, in-seam dilutions, or partings, such as rock, mudseams, fireclay, etc., that, if not removed, lowers the BTU value of the end product. Once all, or at least most of, that other non-burning material is washed/cleaned from the ROM coal, it's value to the marketplace increases. Whatever they contractor can do to minimize the "trash" in the ROM coal, the less costly it will be to wash/clean the coal, thus further increasing the value. Typical cost for cleaning coal is $2 to $3/ton
Important thing to remember here is that the profit lies in selling BTUs, not tons of coal.