brown coal
brown coal
A low-rank coal which is brown or brownish-black, but rarely black. It commonly retains the structures of the original wood. It is high in moisture, low in heat value, and checks badly upon drying.
A light-brown to seal-brown substance intermediate between peat and bituminous coal; usually regarded as a variety of lignite, other varieties being darker or black. It may be distinguished from peat by three rough criteria: (1) many tissues and fibers can be recognized in peat, but only a few fibers or none in brown coal; (2) water can be squeezed out of fresh peat by manual pressure, but not from brown coal; and (3) peat can be cut, but brown coal cannot. Actually, there is no sharp distinction between peat and coal. Some have attempted to assign it a higher rank by defining lignite as containing at least 20% water, brown coal between 10% and 20% water, and bituminous coal less than 10% water.
A type of low-rank coal intermediate between bituminous coal and peat, and comparatively high in water content. In English-speaking countries, the terms "brown coal" and "lignite" are synonymous; in Germany and other parts of Europe, brown coal is restricted to megascopically compact structural varieties, and lignite is restricted to individual pieces of wood enclosed in brown coal. It may be subdivided into low-grade brown coal, consisting of visible vegetable remains, and high-grade brown coal, a compact, homogeneous, and tough rock.
Coal of the lowest rank, soft and friable, and having a high inherent moisture content.