Lignite.
—This is a type of fuel that in point of geological formation represents the condition between true coal and peat. Lignite occurs in immense deposits throughout the middle portion of the western half of the United States, where beds 20 feet in depth are not uncommon. It varies in color from black to brown and in many localities is known as brown coal.
When newly mined, lignite contains a large percentage of water, sometimes as high as 50 per cent. On account of this large moisture content it has a relatively low calorific value, but when dry the amount of heat evolved per pound compares very favorably with soft coal.