What is coal?
Coal is a sedimentary rock made predominantly of carbon that can be burned for fuel. Coal is readily combustible, black or brownish-black, and has a composition that, including inherent moisture, consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time.
Coal is found all over the world including our country, predominantly in places where forests and marshes existed prehistorically, before being buried and compressed over millions of years. Some of the largest deposits, though, are located in areas of the Appalachian basin in the eastern U.S., the Illinois basin in the mid-continent region, and throughout the Rocky Mountain basins in the western U.S.
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Assessing U.S. coal resources and reserves
The U.S. Coal Resources and Reserves Assessment Project, as part of the U.S. Geological Survey (USGS) Energy Resources Program, conducts systematic, geology-based, regional assessments of significant coal beds in major coal basins in the United States. These assessments detail the quantity, quality, location, and economic potential of the Nation’s...
Shaffer, Brian N.
Coal--a complex natural resource : an overview of factors affecting coal quality and use in the United States
Schweinfurth, Stanley P.; Finkelman, Robert B.
World coal exploration and development
Wood, Gordon H.
Assessments Evolved: USGS Coal Research in the 21st Century
Although often associated with helping fuel the Nation’s growth during the Industrial Revolution, coal is very much part of our space-age present. In 2016, coal-fired power plants provided 30.4 percent of the country’s electricity, and it is an important source of employment in many states.
Cannel Coal
Cannel coal is a type of bituminous coal, which is the second-highest rank of coal (just behind anthracite). This particular sample has a high carbon content with high pollen and spore content as well. Unlike most bituminous coal, Cannel coal can be carved into ornaments. This sample came from the Eastern Interior Coalfield in Kentucky.
Peacock Coal
This sample is of peacock coal. Peacock coal is not a specific class of coal, but rather the name for an effect in which oxidizing materials in the coal create a dazzling array of colors on the surface of the coal. Usually it is short-lived, as the material fully oxidizes away shortly after exposed to air. Read more about our coal research here:
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Cannel Coal
Cannel coal is a type of bituminous coal that is also sometimes referred to as a type of oil shale. It's name likely came from the word "candle." Cannel coal was once used as a source for kerosene. Read more about our coal research here:
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Anthracite Coal
This is anthracite, the highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter. Anthracite is not as commonly mined as other ranks of coal. It played a significant role in Pennsylvania coal during the Industrial Revolution in the United
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Lignite Coal
A sample of lignite, the lowest rank of coal. It is primarily mined for burning in steam-generation power plants. Read more about our coal research here: https://www.usgs.gov/centers/cersc/science/us-coal-resources-and-reserves-assessment