High Quality Content by WIKIPEDIA articles! Pocahontas Coalfield, which is also known as the Flat Top-Pocahontas Coalfield, is located in Mercer County/McDowell County, West Virginia and Tazewell County, Virginia. The coal seams—Pocahontas No. 3, No. 4, No. 6, and No. 11—are some of the best coal to be found in the world, and are rated at 15,000 Btu/lb (35 MJ/kg).