Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. It is the most abundant fossil fuel produced in the United States. Over 90 percent of the coal used in the United States is used to generate electricity. It's also used as a basic energy source in many industries, including, steel, cement and paper.

For more facts and figure on coal, check out the
Energy Information Administration’s Coal 101.