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Short notes about huminite of coal from chemical sedimentology....

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HUMINITE         

The term “huminite” was introduced by Szadecky-Kardoss (1949) for a structural constituent of brown coals (now commonly termed as lignites). Huminite group is subdivided into 3 macerals subgroups and 6 macerals. The macerals subgroups are divided by structure (degree of preservation of the plant residues) and the macerals by gelification (gelohuminite excluded). Huminite consists a group of medium grey macerals having reflectances between those of the associated darker liptinites and the lighter inertinites. Colour and reflectance depend on rank, gelification degree, botanical origin, and the chemical composition of the huminite macerals. Fluorescence colour and intensity depend on the rank, degree of degradation, humification, and the bituminization of the huminite. Huminite is derived from the parenchymatous and woody tissues and the cellular contents of roots, stems, barks and leaves composed of cellulose, lignin and tannin. Huminite is the precursor of vitrinite. Huminite occurs in coal seams formed as a result of anaerobic preservation of lignocelluloses material in mires. Besides, it also occurs in peat, soils and sediments.

Differences  Huminite and its macerals are defined only for lignites (soft brown coals). For subbituminous coal, the coal of the highest rank within the low rank coal, the vitrinite nomenclature is used.  In the new Huminite system, huminite terminologies are bold while the corresponding vitrinites are in normal font.  Maceral varieties show differences in reflectance.  The upper reflectance limit has been taken as the reflectance value separating low rank coal and medium rank coal in the ECE classification (1988)  Huminite is soft and shows no relief in relation to the accompanying liptinite and inertinite macerals (except corpohuminite)  Huminite is characterized by relatively high oxygen (O2) and low carbon (C) contents compared with the macerals of the other two groups.  From NMR and Py-GC-MS data, it is proven that amongst the chemical structures in lignitic wood and huminite, the catechol-like rings are dominant whereas the major components in vitrinite may be phenol-like structures....