A constituent intermediate between vitrinite and fusinite showing a well-defined structure of wood and sclerenchyma. The cell cavities, either round, oval, or elongated in cross section, vary in size but are generally smaller and sometimes less well defined than those of fusinite. Occurs as lenses and bands of variable thickness, and as small fragments; associated with fusinite, or included in vitrite, clarite, duroclarite, clarodurite, and durite. It often lies as a transition material between vitrinite and fusinite, and the properties lie between those of fusinite and vitrinite; behaves as a semi-inert diluent in carbonization.