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Terminology

Resources, Reserves, and DRBa and other terms used by the Energy Information Administration.

Resources are naturally occurring concentrations or deposits of coal in the Earth's crust, in such forms and amounts that economic extraction is currently or potentially feasible.

Measured Resources refers to coal for which estimates of the rank and quantity have been computed to a high degree of geologic assurance, from sample analyses and measurements from closely spaced and geologically well known sample sites. Under the U.S. Geological Survey (USGS) criteria, the points of observation are no greater than 1/2-mile apart (see Figure A1). Measured coal is projected to extend as a 1/4-mile-wide belt from the outcrop or points of observation or measurement.

Indicated Resources refers to coal for which estimates of the rank, quality, and quantity have been computed to a moderate degree of geologic assurance, partly from sample analyses and measurements and partly from reasonable geologic projections. Under the USGS criteria, the points of observation are from ½ to 1½- miles apart (see Figure A1). Indicated coal is projected to extend as a ½-mile-wide belt that lies more than ¼mile from the outcrop or points of observation or measurement.

Demonstrated Resources are the sum of measured resources and indicated resources.

Demonstrated Reserve Base (DRB) (or just "reserve base" in USGS usage) is, in its broadest sense, defined as those parts of identified resources that meet specified minimum physical and chemical criteria related to current mining and production practices, including those for quality, depth, thickness, rank, and distance from points of measurement. The "reserve base" is the in-place demonstrated resource from which reserves are estimated. The reserve base may encompass those parts of a resource that have a reasonable potential for becoming economically recoverable within planning horizons that extend beyond those which assume proven technology and current economics.

Inferred Resources refers to coal of a low degree of geologic assurance in unexplored extensions of demonstrated resources for which estimates of the quality and size are based on geologic evidence and projection. Quantitative estimates are based on broad knowledge of the geologic character of the bed or region where few measurements or sampling points are available and on assumed continuation from demonstrated coal for which there is geologic evidence. The points of measurement are from 1½ to 6 miles apart (Figure A1). Inferred coal is projected to extend as a 2¼-mile-wide belt that lies more than ¾ mile from the outcrop or points of observation or measurement. Inferred resources are not part of the DRB.

Recoverable refers to coal that is, or can be, extracted from a coalbed during mining.

Reserves relates to that portion of demonstrated resources that can be recovered economically with the application of extraction technology available currently or in the foreseeable future. Reserves include only recoverable coal; thus, terms such as "minable reserves," "recoverable reserves," and "economic reserves" are redundant. Even though "recoverable reserves" is redundant, implying recoverability in both words, EIA prefers this term specifically to distinguish recoverable coal from in-ground resources, such as the demonstrated reserve base, that are only partially recoverable.

Minable refers to coal that can be mined using present-day mining technology under current restrictions, rules, and regulations.


   aFor a full discussion of coal resources and reserve terminology as used by EIA, USGS, and BOM, see U.S. Coal Reserves, 1996, Appendix A, Specialized Resource and Reserve Terminology.
   Sources: U.S. Department of the Interior, Coal Resource Classification System of the U.S. Bureau of Mines and the U.S. Geological Survey, Geological Survey Bulletin 1450-B (1976). U.S. Department of the Interior, Coal Resource Classification System of the U.S. Geological Survey, Geological Survey Circular 891 (1983) U.S. Department of the Interior, A Dictionary of Mining, Mineral, and Related Terms, Bureau of Mines (1968).

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  © 2004-2009 Fred H. Hutchison

Edited on: March 27, 2009