   Coal
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Sigma KEE - Coal
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coal
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Coal is a black or brownish black solid combustible substance formed by the partial decomposition of vegetable matter without free access of air and under the influence of moisture and often increased pressure and temperature. Coal is a sedimentary rock containing a high proportion of carbon.
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fossil fuel |
FossilFuel is the subclass of Fuel whose instances are derived from fossilized organic deposits, such as Coal and LiquefiedPetroleumGas.
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mineral |
Any of various naturally occurring homogeneous substances (such as stone, coal, salt, sulfur, sand, petroleum), or synthetic substances having the chemical composition and crystalline form and properties of a naturally occurring mineral.
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rock |
Rock is any naturally formed aggregate of one or more minerals, consolidated or not, with some degree of mineralogic and chemical constancy, in popular use the term is usually restricted to those aggregates that are hard, compact, and coherent.
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brown coal | BrownCoal is a soft Coal harder than peat and softer than bituminous coal. Also called lignite, it is brownish in color. |
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