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Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. [1] 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]
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 .
Peat "hags" are a form of erosion that occur at the sides of gullies that cut into the peat; they sometimes also occur in isolation. [80] Hags may result when flowing water cuts downwards into the peat and when fire or overgrazing exposes the peat surface. Once the peat is exposed in these ways, it is prone to further erosion by wind, water and ...
A coal ball. Carbonate mineralization involves the formation of coal balls. Coal balls are the fossilizations of many different plants and their tissues. They often occur in the presence of seawater or acidic peat. Coal balls are calcareous permineralizations of peat by calcium and magnesium carbonates. Often spherical in shape and ranging from ...
Raw coke. Coke is a grey, hard, and porous coal-based fuel with a high carbon content. It is made by heating coal or petroleum in the absence of air. Coke is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges.
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]
Coal forest of tree ferns and lycopod trees, in a 1906 artist's rendering. The coal forests seem to have been areas of flat, low-lying swampy areas with rivers flowing through from higher, drier land. [4] When the rivers flooded, silt gradually built up into natural levees. Lakes formed as some areas subsided, while formerly wet areas became ...
Common charcoal is made from peat, coal, wood, coconut shell, or petroleum. Sugar charcoal is obtained from the carbonization of sugar and is particularly pure. It is purified by boiling with acids to remove any mineral matter and is then burned for a long time in a current of chlorine to remove the last traces of hydrogen. [2]