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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

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Table 4. - Areas of reliability from figure 13 listed by overburden and coal thickness categories, and by countries

[Tonnage estimated for each area could be determined (1) by planimetering each area for acreage, and (2) by multiplying acreage by proper weight of coal per acre-inch by the average thickness of coal in the area. Average thickness of coal would be obtained by isopaching coal thickness as shown on figure 13]

Geologic Assurance Category Coal thickness
14 to 28 inches 28 to 42 inches
0 to 500 feet overburden:
Measured A, B, C None
Indicated D, E, F Do.
Inferred G, H, I, J, K Do.
 
500 to 1,000 feet overburden:
Indicated L, M, N None
Inferred O, P Do.
 
1,000 to 2,000 feet overburden:
Inferred Q, R None
 
2,000 to 3,000 feet overburden
Inferred S, T None
Hypothetical U Do.
 
Political division
Holmes County   Dead Bull County
A, F, G, H, N   B, C, D, E, I, J,
O, R, S, U   K, L, M, P, Q, T
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