Lignite, often referred to as brown coal,[1] is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%,[1][2] and is considered the lowest rank of coal due to its relatively low heat content. When removed from the ground, it contains a very high amount of moisture which partially explains its low carbon content. Lignite is mined all around the world and is used almost exclusively as a fuel for steam-electric power generation.