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.
Two states are next in line, having given the U.S. four presidents each. Massachusetts was the home of John Adams, John Quincy Adams, Calvin Coolidge (technically born in Vermont), and John F. Kennedy. Texas also has bragging rights. (What else is new, considering itâs Texas?!) The former republic has been the birthplace or home to four U.S. presidents: Dwight Eisenhower, Lyndon B. Johnson, George H. W. Bush, and George W. Bush.