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Coal is a type of fossil fuel, formed when dead plant matter decays into peat which is converted into coal by the heat and pressure of deep burial over millions of years. [2] Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous ( Pennsylvanian ...
It is the most abundant rank of coal, with deposits found around the world, often in rocks of Carboniferous age. Bituminous coal is formed from sub-bituminous coal that is buried deeply enough to be heated to 85 °C (185 °F) or higher. Bituminous coal is used primarily for electrical power generation [1] and in the steel industry.
Carbon added to sedimentary rocks can take the form of carbonates, or organic carbon compounds. In order of source quantity the organic carbon comes from phytoplankton, plants, bacteria and zooplankton. However terrestrial sediments may be mostly from higher plants, and some oxygen deficient sediments from water may be mostly bacteria.
A fossil fuel [a] is a carbon compound- or hydrocarbon-containing material [2] formed naturally in the Earth's crust from the buried remains of prehistoric organisms (animals, plants or planktons), a process that occurs within geological formations.
Coal forms when organic matter builds up in waterlogged, anoxic swamps, known as peat mires, and is then buried, compressing the peat into coal. The majority of Earth's coal deposits were formed during the late Carboniferous and early Permian. The plants from which they formed contributed to changes in the Carboniferous Earth's atmosphere. [25]
Lignite (derived from Latin lignum meaning 'wood'), often referred to as brown coal, [1] is a soft, brown, combustible sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35% [ 1 ] [ 2 ] and is considered the lowest rank of coal due to its relatively low heat content .
Anthracite, also known as hard coal and black coal, is a hard, compact variety of coal that has a submetallic lustre. 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 coals.
Cannel coal from the Pennsylvanian of NE Ohio. Cannel coal or candle coal is a type of bituminous coal, [1] also classified as terrestrial type oil shale. [2] [3] [4] Due to its physical morphology and low mineral content cannel coal is considered to be coal but by its texture and composition of the organic matter it is considered to be oil shale. [5]