Coal
combustible sedimentary rock composed primarily of carbon
Coal is a combustible black or brownish-black sedimentary rock, formed as layers called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. It is a fossil fuel, formed when plants decay into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits formed from wetlands called coal forests that covered much of the tropics during the late Carboniferous and early Permian.
Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron and steel-making and other industrial processes burn coal.
The extraction and burning of coal damages the environment and human health, causing premature death and illness, and is the largest source of carbon dioxide contributing to climate change.
This brief starts where responsible research should: with the source description of “Coal” as combustible sedimentary rock composed primarily of carbon. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the general reference register because the source frames it as combustible sedimentary rock composed primarily of carbon. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 6, 2026. The linked authority identifier is Q24489. The Library of Congress control number is sh85027307. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 2020.
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This entry incorporates text from “Coal” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.