Lignite, or BROWN COAL, a mineral substance of vegetable origin, like common coal, but differing from it in its more distinctly fibrous or woody formation, which is sometimes so perfect that the original structure of the wood can be discerned with the microscope, whilst its external form is also not unfrequently preserved. In this state it is often called Wood Coal; and it sometimes occurs so little mineralised that it may be used for the purposes of wood, as at Vitry on the banks of the Seine, where the woodwork of a house has been made of it. From this to the most perfectly mineralised state it occurs in all different stages. It is often brown or brownish black, more rarely gray. It burns without swelling or running, with a weaker flame than coal; emits in burning a smell like that of peat, and leaves an ash more resembling that of wood than of coal. Wherever it occurs in sufficient abundance it is used for fuel, although as a rule very inferior to common coal. Lignite occurs sparingly in Britain—the chief locality being Bovey Tracey in Devonshire, where it has long been worked. The principal repository of lignite in Europe is the Oligocene System (q.v.) of Germany, in which some of the beds attain a great thickness. Over the eastern slopes of the Rocky Mountains lignite is widely distributed, but the beds are rarely thick enough to be of economic importance. Thin beds of lignite are associated with the oligocene basalt rocks of Iceland (where it is known as 'Surtur-brand') and the Færoe Islands, just as is the case with the similar formations in Antrim and Mull.
Unlike wood, it is soluble in nitric acid and in alkaline hypochlorites, and refractory to caustic potash solution; in the latter respect it resembles coal, which is, however, not soluble in hypochlorites.