A black-colored compacted organic rock which is made up of more than 50% organic matter from plant debris, which have accumulated in situ as swamp peats. Metamorphic classifications range from peat through lignites and bituminous coals to anthracites. Visual classifications usually designate two major coal types: humic (including fusinite, micrinite, vitrinite, exinite, and resinite) formed from plant cell and wall material deposited under aerobic conditions and sapropelic, which are formed from spores, pollens, and algae deposited under anaerobic conditions (including cannel and boghead).