Lignite - Sometimes called "brown coal," lignite is the youngest of the coal types, and has the lowest energy content, containing between 25 and 35 percent carbon. Lignite usually has not been subjected to the extreme temperatures and pressures typical of the higher energy content coal types. It is crumbly, has a high moisture content, and is typically burned in power plants for electrical production. About 20 lignite mines produce about 7 percent of total US produced coal, mostly in Texas and North Dakota.