Brownish-black coal in which the alteration of vegetal material has proceeded further than in peat but not so far as subbituminous coal. Heat content is less than 7,000 Btu (moist, mineral-matter-free).
Brownish-black coal in which the alteration of vegetal material has proceeded further than in peat but not so far as subbituminous coal. Heat content is less than 7,000 Btu (moist, mineral-matter-free).
