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Coal Resource Classification System of the U.S. Geological Survey

By Gordon H. Wood, Jr., Thomas M. Kehn, M. Devereux Carter, and William C. Culbertson

GEOLOGICAL SURVEY CIRCULAR 891


Table 1. - Classification of coals by rank

Class Group Fixed Carbon (Dry, Mineral- Matter-Free Basis) Volatile Matter Limits, percent Limits, percent Dry, Mineral- Matter-Free Basis Calorific Value Limits BTU per pound (Moist,B Mineral-Matter-Free Basis)
    Equal or Greater Than Less Than
Greater
Than
Equal or Less Than Equal or Greater Than Less Agglomerating Character
I Anthracite* 1.Meta-anthracite 98     2     nonagglomerating
  2.Anthracite 92 98 2 8      
  3.SemianthraciteC 86 92 8 14      
II Bituminous 1.Low volatile bituminous coal 78 86 14 22      
  2.Medium volatilebituminous coal 69 78 22 31      
  3.High volatile A bituminous coal   69 31   14000D   commonly
  4.High volatile B bituminous coal         13000D 14000 agglomerating**E
  5.High volatile C bituminous coal         11500 13000  
            10500 11500 agglomerating
III Subbituminous
1.Subbituminous A coal         10500 11500  
  2.Subbituminous B coal         9500 10500  
  3.Subbituminous C coal         8300 9500 nonagglomerating
IV. Lignite 1.Lignite A         6300 8300  
  1.Lignite B           6300  

AThis classification does not include a few coals, principally nonbanded varieties, which have unusual physical and chemical properties and which come within the limits of fixed carbon or calorific value of the high-volatile bituminous and subbituminous ranks. All of these coals either contain less than 48 percent dry, mineral-matter-free fixed carbon or have more than 15 500 moist, mineral-matter-free British thermal units per pound.
B
Moist refers to coal containing its natural inherent moisture but not including visible water on the surface of the coal
CIf agglomerating, classify in low-volatile group of the bituminous class.
DCoals having 69 percent or more fixed carbon on the dry, mineral-matter-free basis shall be classified according to fixed carbon, regardless of calorific value.
EIt is recognized that there may be nonagglomerating varieties in these groups of the bituminous class, and there are notable exceptions in the high-volatile C bituminous group.
1ASTM, 1981, p. 215.
*Modified from ASTM, 1981.

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