Coal formed when prehistoric forests and marshes were buried and compressed over hundreds of millions of years.
Mineable coal is usually found as beds (also called “seams”) in other rock layers, both close to the surface as well as deep underground.
Coal reserves are a subset of coal resources. To be classified as reserves, the coal must be considered economically producible at the time of classification, but facilities for extraction need not be installed and operative.
In-place coal resources include in-place tonnage estimates of total coal volumes. In-place resources are those quantities that are estimated, as of a given date, to be contained in known deposits prior to production.
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:
Coal is primarily used as fuel to generate electric power in the United States. The coal is burned and the heat given off is used to convert water into steam, which drives a turbine.
Coal is a sedimentary rock made predominantly of carbon that can be burned for fuel.
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 o
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.
The United States has the largest proven coal reserves, with an estimated 260.5 billion short tons of coal in 2008, according to the U.S. Energy Information Administration.