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.
Three U.S. presidents have been elected while living in Illinois: Abraham Lincoln, Ulysses S. Grant, and Barack Obama. Additionally, Ronald Reagan, whose political career was based in California, was the only U.S. president born and raised in Illinois. Today, Illinois honors Lincoln with its official state slogan, Land of Lincoln, which has been displayed on its license plates since 1954.