Anthracite Anthracite Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal 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%. The term is applied to those varieties of coal which do not give off tarry or other hydrocarbon vapours when heated below their point of ignition. Anthracite ignites with difficulty and
Coal forest Coal forest Coal forests were the vast swathes of wetlands that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times. As vegetable matter from these forests decayed, enormous deposits of peat accumulated, which later changed into coal. Much of the carbon in the peat deposits produced by coal forests came from photosynthetic splitting of existing carbon dioxide, which released the accompanying split-off oxygen into the atmosphere. This process may have greatly increased the oxygen level, possibly as high as about 35%, making the air more easily breathable by animals with inefficient respiratory systems,