Regarding this, which is the best form of coal?
The ranks of coal (from most to least carbon content) are as follows: anthracite, bituminous coal, subbituminous coal, and lignite. The coal with the highest carbon content is the best and cleanest type of coal to use.
How coal is classified?
Coal classification. Coal classification, any of various ways in which coal is grouped. Most classifications are based on the results of chemical analyses and physical tests, but some are more empirical in nature. In general, the calorific (heat) value of coal increases with rank from lignite through bituminous coal.
What is the highest grade of coal?
It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal except for graphite and is the highest ranking of coal. Anthracite is the most metamorphosed type of coal (but still represents low-grade metamorphism), in which the carbon content is between 92% and 98%.