Coal

Coal is a fossil fuel extracted from the ground by deep mining, coal mining (open-pit mining or strip mining). It is a readily combustible black or brownish-black sedimentary rock. It is composed primarily of carbon and hydrocarbons, along with assorted other elements, including sulfur. Often associated with the Industrial Revolution, coal remains an enormously important fuel and is the most common source of electricity world-wide. In the United States, for example, the burning of coal generates over half the electricity consumed by the nation.

Types of coal

As geological processes apply pressure to peat over time, it is transformed successively into:

Related Topics:
Pressure - Peat

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• Lignite - also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for steam-electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Iron Age.
• Sub-bituminous coal - whose properties range from those of lignite to those of bituminous coal and are used primarily as fuel for steam-electric power generation.
• Bituminous coal - a dense coal, usually black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
• Anthracite - the highest rank, used primarily for residential and commercial space heating.