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.
As of October 2016, 21 states claim the distinction of being the birthplace of a president. One claim is in dispute. North and South Carolina (British colonies at the time) both lay claim to Andrew Jackson, who was born in 1767, in the Waxhaw region along their common border.