The term was introduced by M.C. Stopes in 1919 to designate the macroscopically recognizable dull bands in coals. Bands of durain are characterized by their gray to brownish-black color and rough surface with dull or faintly greasy luster; reflection is diffuse; they are markedly less fissured than bands of vitrain, and generally show granular fracture. In humic coals, durain occurs in bands up to many centimeters in thickness. Widely distributed, but with exceptions not abundant. Compare: fusain; vitrain.