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.
What are the types of coal?
There are four major types (or “ranks”) of coal. Rank refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon-rich, and harder material. The four ranks are:
- 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.
- Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. Bituminous coal usually has a high heating (Btu) value and is used in electricity generation and steel making in the United States. Bituminous coal is blocky and appears shiny and smooth when you first see it, but look closer and you might see it has thin, alternating, shiny and dull layers.
- Subbituminous: Subbituminous coal is black in color and is mainly dull (not shiny). Subbituminous coal has low-to-moderate heating values and is mainly used in electricity generation.
- Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon. Lignite has a low heating value and a high moisture content and is mainly used in electricity generation.
The precursor to coal is peat. Peat is a soft, organic material consisting of partly decayed plant and mineral matter. When peat is placed under high pressure and heat, it undergoes physical and chemical changes (coalification) to become coal.
| COAL RANKS |
| Plant material --> Peat --> Lignite --> Subbituminous --> Bituminous --> Anthracite |
| ----------------------> Increasing heat and pressure ----------------------> |
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Related Content
What is coal used for?
Coal is primarily used as fuel to generate electric power in the United States. In coal-fired power plants, bituminous coal, subbituminous coal, or lignite is burned. The heat produced by the combustion of the coal is used to convert water into high-pressure steam, which drives a turbine, which produces electricity. In 2019, about 23 percent of all electricity in the United States was generated by...
What is coal?
Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. Coal is 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...
What is the biggest coal deposit in the United States?
The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which the USGS estimated to have 1.07 trillion short tons of in-place coal resources, 162 billion short tons of recoverable coal resources, and 25 billion short tons of economic coal resources (also called reserves) in 2013. The coal in the Powder River Basin is subbituminous in rank. Large coal deposits can also...
Which country has the most coal?
As of January 2020, the United States has the largest recoverable coal reserves with an estimated 252 billion short tons of coal remaining, according to the U.S. Energy Information Administration . Learn more: U.S. Coal Resources and Assessment World Coal Quality Inventory
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.
Lignite Coal
A sample of lignite, the lowest rank of coal. It is primarily mined for burning in steam-generation power plants.
A sample of lignite, the lowest rank of coal. It is primarily mined for burning in steam-generation power plants.
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.
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.
Clinker Coal
Clinker coal is the result of a seam of coal catching fire and burning so hot that it baked surrounding rock layers into brick-like formations. Some of the most famous clinker formations in the United States can be seen at the Theodore Roosevel National Park in North Dakota.
Clinker coal is the result of a seam of coal catching fire and burning so hot that it baked surrounding rock layers into brick-like formations. Some of the most famous clinker formations in the United States can be seen at the Theodore Roosevel National Park in North Dakota.
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.
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.
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.
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.
Pliocene Lignite Coal from BEN Village
Closeup of Pliocene lignite coal from a Balkan endemic nephropathy (BEN) village in Serbia. Lignite is low rank, or relatively unaltered (soft, or "brown") coal, and is characterized by a brownish color and appearance that often resembles wood. This lignite releases copious amounts of dissolved organic substances into groundwater.
Closeup of Pliocene lignite coal from a Balkan endemic nephropathy (BEN) village in Serbia. Lignite is low rank, or relatively unaltered (soft, or "brown") coal, and is characterized by a brownish color and appearance that often resembles wood. This lignite releases copious amounts of dissolved organic substances into groundwater.
Related Content
What is coal used for?
Coal is primarily used as fuel to generate electric power in the United States. In coal-fired power plants, bituminous coal, subbituminous coal, or lignite is burned. The heat produced by the combustion of the coal is used to convert water into high-pressure steam, which drives a turbine, which produces electricity. In 2019, about 23 percent of all electricity in the United States was generated by...
What is coal?
Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. Coal is 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...
What is the biggest coal deposit in the United States?
The biggest coal deposit by volume is the Powder River Basin in Wyoming and Montana, which the USGS estimated to have 1.07 trillion short tons of in-place coal resources, 162 billion short tons of recoverable coal resources, and 25 billion short tons of economic coal resources (also called reserves) in 2013. The coal in the Powder River Basin is subbituminous in rank. Large coal deposits can also...
Which country has the most coal?
As of January 2020, the United States has the largest recoverable coal reserves with an estimated 252 billion short tons of coal remaining, according to the U.S. Energy Information Administration . Learn more: U.S. Coal Resources and Assessment World Coal Quality Inventory
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.
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.
Lignite Coal
A sample of lignite, the lowest rank of coal. It is primarily mined for burning in steam-generation power plants.
A sample of lignite, the lowest rank of coal. It is primarily mined for burning in steam-generation power plants.
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.
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.
Clinker Coal
Clinker coal is the result of a seam of coal catching fire and burning so hot that it baked surrounding rock layers into brick-like formations. Some of the most famous clinker formations in the United States can be seen at the Theodore Roosevel National Park in North Dakota.
Clinker coal is the result of a seam of coal catching fire and burning so hot that it baked surrounding rock layers into brick-like formations. Some of the most famous clinker formations in the United States can be seen at the Theodore Roosevel National Park in North Dakota.
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.
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.
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.
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.
Pliocene Lignite Coal from BEN Village
Closeup of Pliocene lignite coal from a Balkan endemic nephropathy (BEN) village in Serbia. Lignite is low rank, or relatively unaltered (soft, or "brown") coal, and is characterized by a brownish color and appearance that often resembles wood. This lignite releases copious amounts of dissolved organic substances into groundwater.
Closeup of Pliocene lignite coal from a Balkan endemic nephropathy (BEN) village in Serbia. Lignite is low rank, or relatively unaltered (soft, or "brown") coal, and is characterized by a brownish color and appearance that often resembles wood. This lignite releases copious amounts of dissolved organic substances into groundwater.