What are the different types of coal?

An example of anthracite coal, the purest grade of coal. Image Copyright © Dr. Richard Busch.
Information on this page was collected from the source acknowledged below:
"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 usually has a high heating (Btu) value and is the most common type of coal used in electricity generation in the United States. Bituminous coal appears shiny and smooth when you first see it, but look closer and you may see it has layers.
  • Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has a higher heating value than lignite.
  • Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon.
Also, there is peat. Peat is not actually coal, but rather the precursor to coal. Peat is a soft organic material consisting of partly decayed plant and, in some cases, deposited mineral matter. When peat is placed under high pressure and heat, it becomes coal."

Learn More:

  • Quarterly Coal Report (Webpage), Energy Information Administration
    Detailed quarterly data on U.S. coal production, trade, price, consumption, quality, and more
  • Coal (Pamphlet), Ohio Geological Survey 
    Basic overview of the geology and formation of coal, different grades of coal, coal mining in Ohio, and clean coal technology
     
  • Coal Ranks (Webpage and Map), National Energy Technology Laboratory 
    Descriptions of the four main types of coal with a map showing coal deposits in the U.S. by type