Safeopedia explains Coal Washing. Coal is a type of sedimentary rock that is formed by buried vegetation that is transformed by pressure and heat over long periods of time. Coal will eventually turn into diamond formations with enough time, pressure and heat. Impurities include slate and other non-organic rocks etc..
The number of presidents born per state are: 1  One: Arkansas, California, Connecticut, Georgia, Hawaii, Illinois, Iowa, Kentucky, Missouri, Nebraska, New Hampshire, New Jersey, Pennsylvania, and South Carolina. 2  Two: North Carolina, Texas, and Vermont.  Four: Massachusetts, and New York.
Other early pioneers came from the Mid-Atlantic states, especially Pennsylvania and Virginia, some settling on military grant lands in the Virginia Military District. From Virginia came members of the Harrison family of Virginia, who rose to prominence in the state, producing Ohio's first of eight U.S. Presidents.