Vitrinite macerals, classification

The macerals in lower rank coals, eg, lignite and subbiturninous coal, are more complex and have been given a special classification. The term huminite has been appUed to the macerals derived from the humification of lignocellulosic tissues. Huminite is the precursor to the vitrinite observed in... 

As unifying, underlying concepts, type and rank certainly can be employed to envision why coals have the properties that they do. However, it is time for a reevaluation of coal classification concepts. How can we measure rank when we analyze coals of different types and when there is no simple rank progression even when vitrinite or vitrinite-rich coals are compared And how can we assess type when maceral identification criteria are highly subjective, except for reflectance measurements that routinely are not even applied to the liptinite and highly variable inerti-nite macerals And, finally, how can coals be classified scientifically when empirical and derived properties like calorific value and fixed carbon yield are employed as classifying parameters ... 

---