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.
(Eisenhower was born in Denison, Texas.) * Vermont is the smallest state with the biggest presidential punch as the birthplace of both Chester Arthur and Calvin Coolidge. * California has produced only a single president -- and it was Republican Richard Nixon.