Coal is black when you buy it red when in use and grey when it is to be discarded.
Coal is a sedimentary deposit composed predominantly of carbon that is effectively combustible. Coal is black or brownish-black, and has a composition that (including inherent moisture) consists of more than 50 percentage by using weight and more than 70 percent by means of volume of carbonaceous material.
Coal is categorised into four major types, or ranks: anthracite, bituminous, subbituminous, and lignite. The ranking relies upon on the kinds and quantities of carbon the coal consists of and on the amount of warmth strength the coal can produce.
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