Coal: Glossary

anthracite: a hard black coal that has a moisture content of less than 15 percent, carbon content between 86 and 98 percent, and a high energy output.

bituminous coal: a soft black coal that has a moisture content of less than 20 percent, carbon content between 35 and 86 percent, and a relatively high energy output.

coal: a combustible rock that had its origin in the deposition and burial of plant material.

coal-fueled power plant (coal-fired power plant): a power station that burns coal to produce electricity.

coal seam: a layer of coal occurring among other sedimentary rock layers.

electric generator: a device that converts mechanical energy to electrical energy, usually by rotating a conductor in a magnet field.

lignite: a brownish coal material that has a moisture content up to 45 percent, carbon content of around 25-35 percent, and low energy output.

nitric acid (HNO₃): a colorless to yellowish, highly corrosive liquid.

peat: a porous deposit of partly decomposed plant material at or not far below the Earth's surface.

surface mining: refers to mining techniques used to extract coal at or near the Earth's surface.

sulfuric acid (H₂SO₄): a colorless, odorless, highly corrosive oily liquid that is soluble in water.

turbine: a rotating machine or device that converts the mechanical energy of fluid flow into mechanical energy of rotation of a shaft.

underground mining: refers to mining techniques used to extract coal from below the Earth's surface.