Stripping-Coal 

Resources of the 

United States

GEOLOGICAL SURVEY BULLETIN 1252-C

Stripping-Coal 

Resources of the 

United States

By PAUL AVERITT

CONTRIBUTIONS TO ECONOMIC GEOLOGY

GEOLOGICAL SURVEY BULLETIN I252-C

A review and analysis by States of 

data available on the stripping-coal 

potential of the United States

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1968
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 15 cents (paper cover)
CONTENTS

Page

Abstract _________________________________________________________ Cl

Introduction__ ____________________________________________________ 1

Acknowledgments __________________________________________________ 2

The strip-mining industry __________________________________________ 2

Stripping-coal sites described in published reports____________________ 6

Alabama _____________________________________________________ 6

Alaska _______________________________________________________ 6

Arkansas _____________________________________________________ 7

Illinois- __________________________________-_____--.______---- 7

Indiana ________________________________________________________ 7

Kansas.______________________________________________________ 8

Kentucky ____________________________________________________ 8

Missouri_ ___________________________________________________ 8

Montana-____________________________________________________ 8

North Dakota_--_______-______-___-__--____._--__-------_-_-- 9

Oklahoma,_____-____---_--___-_____-_______-_________-__--_-- 10

Pennsylvania.________-__-____-______-______-__-___-__-_--_-_- 10

South Dakota.______________________________________ 11

Texas___________________________________________ 11

Washington.. _________________________________________________ 11

Wyoming.. ___________________________________________________ 12

Other potential sites_______________________________________________ 12

Estimated total stripping-coal resources._____________________________ 13

Previous estimate of stripping-eoal resources __________________________ 14

Reclamation of strip-mined lands_______.____________________________ 15

Conclusions.______________________________________________________ 16

References.. ______________________________________________________ 17

TABLES

Page

TABLE 1. Average thickness of overburden removed and of bituminous 

coal and lignite recovered by strip-mining in the United 

States for selected years_________________________._______ C4

2. Estimated original resources of stripping coal in six States_ _____ 13

3. Estimated original resources of stripping coal in the United

States in beds generally less than 100 feet below the surface___ 14

HI

CONTRIBUTIONS TO ECONOMIC GEOLOGY

STRIPPING-COAL RESOURCES OF THE UNITED STATES

By PAUL AVEKITT

ABSTRACT

The amount of coal mined and potentially minable by strip-mining methods 

has increased steadily throughout the years, concomitantiy with an impressive 

increase in the size and efficiency of strip-mining machinery. An analysis by 

States of the geologic and technologic sources of information on stripping coal 

indicates that as of January 1, 1967, the remaining recoverable stripping-coal 

resources in the United States in the 0- to 100-foot-thick overburden range totaled 

about 108 billion tons. This figure is 28 times the cumulative strip-coal production 

from the beginning of mining to January 1, 1967, and it is 600 times the 1966 

strip-coal production of 179 million tons. These convenient comparisons are an 

aid in appreciating the magnitude of the stripping-coal resources, but they do 

not represent life expectancy because the rate of production and the estimated 

size of stripping-coal resources will surely change in the future.

The total estimated recoverable stripping-coal resources are widely distributed 

in 26 States as tabulated herein, but significantly large amounts are concentrated 

in North Dakota and eastern Montana, the Illinois basin, and the north half of 

the Appalachian basin.

INTRODUCTION

Since World War II, coal has been in intense competition with 

petroleum and natural gas and has lost many former markets to these 

more generally convenient fuels. Throughout this period of competition, coal has maintained a competitive advantage in areas where it 

can be mined on a large scale at very low cost by strip-mining methods. 

The electric utilities have fostered the development of strip mining 

because the demand for electricity has increased greatly over the years 

and because the huge generating plants are equipped to use the most 

economical fuel available; they are not deterred from using coal 

because of its bulk, its rank, or its moderate ash content provided 

the unit cost per Btu is satisfactorily low. In many areas, therefore, 

the utilities have demanded and have received large amounts of stripmined coal as the lowest cost fuel available, and this increased demand 

has been accompanied by a steady increase in strip-coal production.

Cl
C2 CONTRIBUTIONS TO ECONOMIC GEOLOGY

The anticipated future needs for low-cost strip-mined coal for use by 

the still-growing electric utility industry and possibly by an embryonic 

synthetic liquid fuels industry has brought about an increased demand 

for information about potential strip-mining localities.

Although strip-mining localities cannot be defined accurately, except 

in terms of the present technology, scale of mining, the time and place 

<of use of the coal, methods of transportation, and other purely 

economic factors, a certain amount of information about potential 

strip-mining sites and about the strip-mining potential of the United 

States is widely scattered in geologic and technologic reports published 

over the years. This short report is intended to provide a summary of 

this information.

ACKNOWLEDGMENTS

An earlier draft of this paper was reviewed by F. F. Barnes, H. M. 

Beikman, H. L. Berryhill, Jr., K. A. Brant, W. B. Cashion, W. C. 

Culbertson, K. J. Englund, B. K. Haley, A. L. Hornbaker, E. K. 

Landis, E. T. Luther, P. H. Price, W. V. Searight, J. A. Simon, A. A. 

Socolow, James Trumbull, and C. E. Wier, to whom the author is 

indebted for many suggestions and improvements.

THE STRIP-MINING INDUSTRY

111 strip mining, output per man-day is roughly 100 percent higher, 

overall recovery is 60 percent higher, and operating costs are 25-30 

percent lower than in underground mining. Because of these 

significant economic advantages the amount of coal produced by strip 

mining has increased steadily over the years. In 1917, strip mining 

accounted for only 1 percent of total United States production of 

bituminous coal and lignite as compared to 33.7 percent in 1966 (U.S. 

Bur. Mines, 1967, p. 9). By the end of 1966, strip and auger mining 

had accounted for about 10 percent of the total cumulative United 

States production. During 1966 almost the entire coal production of 

eight States Alaska, Kansas, Missouri, Oklahoma, Texas, Wyoming, 

North Dakota and South Dakota was obtained by stripping 

methods.

In 1966 Illinois was the leading State in strip-coal production with 

a total of 36.1 million tons. Kentucky was second with a total of 32.5 

million tons, derived mostly as a result of increased strip production in 

western Kentucky. Pennsylvania was third with 30 million tons, 

derived from operations in both the bituminous coal and anthracite 

regions. These leaders were followed in order by Ohio, Indiana, and 

West Virginia.

During the period 1941-64, Pennsylvania was the leading State in 

strip-coal production and in 1947-48 attained alltime record highs
STRIPPING-COAL RESOURCES OF THE UNITED STATES C3

of nearly 50 million tons annually. Following the 194:7-48 peak, stripcoal production in Pennsylvania declined markedly and during the 

period 1956-66 held almost constant at or near 30 million tons annually. In marked contrast, the strip-coal production of Illinois and 

western Kentucky increased significantly over the same period and in 

1965 both States surpassed Pennsylvania for the first time.

The increased production by strip mining has been accompanied by 

continued improvement in the size and efficiency of earth-moving 

machinery. In 1917" the largest steam shovel in operation had a capacity 

of only a few cubic yards. By 1957" the largest shovel in operation had 

a capacity of 70 cubic yards, or 105 tons. In succeeding years larger 

shovels were constructed, and in 1965 the largest shovel in operation 

had a capacity of 180 cubic yards, or 265 tons, and was capable of 

removing 16,000 tons of overburden an hour. In 1966, shovels of 200- 

cubic-yard capacity were in the planning and construction stages. A 

shovel of 300-cubic-yard capacity is regarded as being technically 

feasible (Coal Age, 1966a). A walking dragline with a bucket of 220- 

cubic-yard capacity and a 310-foot boom is also in the planning stage 

(Mining Engineering, 1966). An even larger dragline with a 500-foot 

boom is regarded as being technically feasible.

Wheel excavators of the type used for many years in the brown 

coal areas of Western Germany have been used on a limited scale in 

the United States since 1944 (Huey, 1964). These wheels are highly 

efficient for the removal of soft and unconsolidated overburden, and 

they are technologically appealing because the operation is continuous 

and the broken-down overburden can be delivered by conveyor belt to 

any point desired. The most successful use of wheels in the United 

States has been in the removal of glacial drift in Illinois and of 

unconsolidated overburden in North Dakota. The most recent wheel 

excavator in the United States was installed in North Dakota in 1965; 

it was manufactured in Germany and has a capacity of 2,800 cubic 

yards an hour.

The increase in size and efficiency of strip-mining machinery has 

permitted a steady increase in the average maximum thickness 

of overburden that can be removed and a parallel increase in the ratio 

of average overburden thickness to average coal thickness. This trend 

is shown in table 1.

The averages presented in table 1 include several noteworthy extremes. In Alaska, for example, the average thickness of overburden 

removed in 1965 was nearly 67 feet, and the average thickness of coal 

recovered was nearly 43 feet; these figures yield a very favorable 

Statewide ratio of 1.4:1. In marked contrast, the average thickness of 

overburden removed in Oklahoma in 1965 was 43 feet, and the aver-
C4 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 1. Average thickness (in feet) of overburden removed 

and of bituminous coal and lignite recovered by strip mining 

in the United States for selected years

[Modified from Young (1967, p. 18)]

1946 1950 1955 1960 1965

Average thickness of overburden reMaximum thickness of overburden removed

Average thickness of coal recovered- . . . 

Ratio of average overburden thick32

5.2 

6:1

39

5.1 

8:1

42

70+

4.9 

8.5:1

46

100

5.1 

9:1

50

125

5.2 

10:1

age thickness of coal recovered was 1.5 feet; these figures yield a 

Statewide ratio of 29:1 (Young, 1967, p. 18). In at least one operation 

in Kansas, 45 feet of overburden was removed to obtain 1.5 feet of 

high-quality coal; these figures yield a ratio of 30:1. In Illinois ratios 

larger than 30:1 have been handled and are being planned in parts 

of large-scale stripping projects where the coal is 28-36 inches thick.

These examples suggest that the 30:1 ratio is technically feasible as 

a maximum for present and near-future strip mining. However, in the 

present highly competitive energy market, the success of each stripmining operation depends on many economic factors other than thickness of the overburden. These factors include thickness and quality 

of the coal, density and hardness of the overburden, capacity of 

machinery, size of property, selling price of coal from competing 

sources, distance to transportation facilities and markets, and availability of electric power, labor and supporting facilities. Because of 

the continued availability of coal with more favorable overburden 

ratios, the average nationwide ratio will continue to be less than 30:1 

for many years, as may readily be seen by an examination of the 

average ratios for recent years as shown in table 1.

The very large shovels mentioned previously are designed with the 

increased lift and swing required to handle overburden as much as 125 

feet thick, a maximum met in 1965 in parts of large stripping projects. 

Anticipating the trend toward stripping to greater depths, the Illinois 

and Indiana Geological Surveys, in outlining areas suitable for strip 

mining, are including beds with overburden thicknesses of as much as 

150 feet. Investigators in other areas have presented data on overburden to maxima of 90 and 120 feet.

Some of the most spectacular coal-mining operations in the United 

States are those in which the coal is being recovered by stripping 

methods. The thickest bed mined by stripping is at Wyodak, Wyo., 

where the coal is 90 feet thick; the overburden is generally less. The 

deepest strip pits in the United States are in the Pennsylvania anthracite fields where two major types of strip mining, termed "outcrop
STRIPPING-COAL RESOURCES OF THE UNITED STATES C5

stripping" and "basin stripping," are in progress. In outcrop stripping, operations proceed linearly and downdip along a steeply dipping 

outcrop. These outcrops were first mined many years ago by underground methods, which recovered about one-third of the coal. Later, 

during the 1920's and 1930's, they were stripped out along a very 

narrow shallow belt with small shovels. In the current operations 

the partly mined coal just below the older stripped-out zone is being 

recovered with large draglines and shovels. These pits are as much as 

200 feet deep. In basin stripping, the entire canoe-shaped end of a 

syncline is mined out and backfilled on a massive scale. In one such 

operation where the 20-foot-thick Mammoth bed lies in the syncline, 

the block of ground being strip mined is 800 feet wide and 290 feet 

deep at the deepest place on the synclinal axis (Coal Age, 1965, p. 79).

Strip mining greatly increases the amount of ultimately recoverable 

coal in the United States, for the method yields an average recovery 

of about 80 percent as compared to 50 percent for underground mining. 

Strip mining also adds to total recoverable coal by making possible 

the mining of coal under shallow overburden, in thin beds, in multiple 

beds, in badly faulted areas, or in small isolated pockets where underground mining would not be practicable.

In many individual operations, where strip mining has been 

terminated for reasons of economy and practicality, additional coal 

is being recovered by use of horizontal, power-driven augers that 

bore into the coal bed at the base of the highwall. The diameter of 

an auger is generally a little less than the thickness of the coal bed. 

The largest single auger thus far constructed is 84 inches in diameter. 

To avoid engineering problems caused by the use of large augers, 

some manufacturers have recently constructed augers consisting of 

two paired bits and shafts that operate simultaneously. In a typical 

operation, auger holes are drilled about 200 feet under the highwall. 

The method permits a maximum recovery of about 75 percent in the 

block of ground being mined, but actual recovery is generally much 

less because the diameter of the augers is generally less than the full 

thickness of the bed being mined, and because the holes are usually 

spaced several inches apart. In 1966 about 15 million tons, or 2.8 

percent of the total bituminous coal and lignite produced, was mined 

by the auger method (U.S. Bur. Mines, 1967, p. 4).

Mining of a coal bed at the outcrop or under the highwall is in 

process of being greatly extended through use of remote-controlled, 

continuous mining machines similar to those now in common use in 

underground mining. These "highwall miners" have revolving cutting 

heads, or drums, or oscillating arms that break down the coal at the 

face and move it continuously to the rear as the machines advance. A

2&5-191 68 2
C6 CONTRIBUTIONS TO ECONOMIC GEOLOGY

remote-controlled, continuous mining machine now in an advanced 

state of experimental use for outcrop mining is capable of penetrating 

as much as 1,100 feet into the coal outcrop.

STRIPPING-COAL, SITES DESCRIBED IN PUBLISHED

REPORTS

The delineation of a stripping-coal deposit requires detailed information in three dimensions. The basic, two-dimensional information on the thickness, continuity, and dip of coal beds at the outcrop 

is readily obtained through routine geologic surveys. Information 

on the third dimension the thickness of the overburden and the contour of the overlying land surface can be obtained in a preliminary 

way from topographic maps, which are available for considerable 

parts of most coal-bearing areas and have done much to facilitate 

study and use of coal in the United States. However, the precise information on overburden composition, thickness, and tonnage needed 

for strip-mine development requires closely spaced test drilling, which 

is time-consuming and expensive, and, in fact, is rarely carried out 

until mining of the coal is contemplated. A few selected strippingcoal sites have been mapped and described, and other potential sites 

noted during the course of geologic surveys have been mentioned in 

published reports. A summary of this and related information follows.

ALABAMA

In the Fabius-Flat Rock area, Jackson County, Shotts and Rlley 

(1966) described a strippable deposit containing 40 million tons of 

coal in a bed averaging about 28 inches in thickness with 60 feet or 

less of overburden.

ALASKA

In the Nenana coal field, Wahrhaftig and Birman (1954) mapped an 

area of about 25 square miles extending from the Nenana River 6 miles 

up the valley of Lignite Creek, which is underlain by 95 million tons 

of coal in six beds ranging in thickness from 5 to 60 feet and at depths 

generally less than 200 feet.

In the Beluga River coal field, Warfield (1963) described a drilling 

program that delineated 20 million tons of coal within reach by stripping methods. This coal is reasonably convenient to Anchorage.

In the Homer district of the Kenai coal field, Barnes and Cobb 

(1959, p. 243) described an area of 28 acres on lower Deep Creek that 

is underlain by 200,000 tons of coal in a 4-f oot-thick bed with less than 

25 feet of overburden.
STRIPPING-COAL RESOURCES OF THE UNITED STATES C7 

ARKANSAS

As part of a summary study of the coal resources of Arkansas determinable from existing mapping and exploration, Haley (1960, 

p. 814) concluded that the original resources of low-volatile bituminous 

coal and semianthracite within 60 feet of the surface totaled 231 million 

tons, or 10 percent of the total of such coal in Arkansas. His maps 

(pis. 59,60) show the 60-foot overburden line on the Lower and Upper 

Hartshorne coal beds. Haley (1960, p. 824, 825) also reported on 32 

million tons of strippable lignite in beds generally more than 2^ feet 

thick and generally less than 100 feet below the surface. The two figures 

combined yield a substantial total of 263 million tons as the strippable 

coal resources of Arkansas.

ILLINOIS

A considerable amount of information on stripping coal in Illinois 

has been published by the Illinois Geological Survey. In the period 

1925-37, many potential stripping-coal sites were described by Culver 

(1925), Cady (1927,1937), and Henbest (1929) based on the capacities 

of the small shovels then in use. Subsequently, Cady (1952, p. 43-48) 

provided important summary information on the economics of strip 

mining in Illinois and on certain coal beds and localities of potential 

interest to strip miners. In 1955 the Illinois Geological Survey began 

a new program of study of stripping coal that has yielded five reports 

to date (Smith, 1957,1958, 1961; Smith and Berggren, 1963; Eeinertsen, 1964). On the basis of work completed and in progress, J. A. Simon 

(written commun., Sept. 28, 1966) has concluded that the remaining 

stripping-coal resources of Illinois as of January 1, 1966, in beds 18 

inches or more thick and at a maximum depth of 150 feet, total 21,223 

million tons. Simon also concluded that the original resources within 

the same parameters totaled about 23,000 million tons.

A map of the Illinois coal field recently prepared by Simon (1966) 

shows major operating strip and underground mines and provides 

subsidiary data on 1965 production, beds being mined, railroad lines, 

and freight rate districts.

INDIANA

The Indiana coal field contains large resources of stripping coal 

because of its location on the east edge of the large Illinois coal basin. 

As part of a study of Indiana coal resources, Spencer (1953, p. 7) concluded that the original stripping-coal resources with a maximum 

overburden of 40 feet for coal 14-28 inches thick, 60 feet for coal 28- 

42 inches thick, and 90 feet for coal more than 42 inches thick totaled 

3,524 million tons. This figure is 9.4 percent of the total for the State 

as estimated by Spencer. In 1966 the Indiana Geological Survey was
C8 CONTRIBUTIONS TO ECONOMIC GEOLOGY

engaged in a detailed study of selected stripping-coal sites, which included deposits with overburden to a maximum of 150 feet thick.

KANSAS

In a report on the coal resources of Kansas, Abernathy, Jewett, and 

Schoewe (1947, p. 3,13) stated that the proved resources of stripping 

coal in the ground as of January 1, 1946, totaled 60 million tons. This 

estimate is based on an assumed weight of 1,500 tons per acre-foot and 

is restricted to coal with less than 60 feet of overburden, or with an 

overburden ratio of not more than 35 cubic yards per ton of coal. The 

distribution of this tonnage is given in cited reports of the State 

Geological Survey of Kansas. Additional information on stripping 

coal is given by Schoewe (1955,1959). The distribution and extent of 

areas mined out by stripping methods as of 1945 are shown on a map by 

Abernathy (1946). Mined areas of the important Weir-Pittsburg 

bed are shown on a similar map by Abernathy (1944).

KENTUCKY

Since the late 1950's the U.S. Geological Survey and the Kentucky 

Geological Survey have been engaged in a cooperative program of 

geologic mapping in Kentucky. As of January 1, 1967, this program 

had yielded about 90 geologic maps covering parts of the eastern and 

western Kentucky coal fields. These maps are printed on topographic 

base maps at the scale of 1 inch to 2,000 feet. The geologic maps show 

outcrops of main coal beds, the range in thickness of coal beds, structure contours, and locations of underground mine adits and strip 

mines and thus provide the basic data needed to delineate potential 

strip-mining sites. It is not feasible to cite all these maps in this short 

summary, but they are listed in various bibliographies of geologic 

reports.

MISSOURI

In a study of the mineral commodities of Putnam County, Gentile 

(1965, p. 24-26) discussed the strip-mining potential of an area of 130 

square miles in eastern Putnam County, where the Lexington coal is 

30 inches thick on the average and the overburden is generally less 

than 150 feet.

MONTANA

In eastern Montana 59 potential strip-mining localities, underlain 

at shallow depth by 5 billion tons of coal, have been described in 10 

reports of the U.S. Geological Survey (Baker, 1929; Bass, 1932; 

Brown and others, 1954; Collier and Knechtel, 1939; Culbertson, 1954; 

Kepferle, 1954; May, 1954; Parker, 1936; Pierce, 1936; Warren, 1959).
STRIPPING-COAL RESOURCES OF THE UNITED STATES C9

The information on stripping coal in these reports was summarized 

by Averitt (1965, p. 18-20, table 4, fig. 5). The figure of 5 biUion tons 

is 2.4 percent of the total coal resources in eastern Montana as determined by mapping and exploration. It is obviously less than the total 

strippable coal present in Montana, because the 59 areas selected 

for mention or study were the best noted in each locality. Other potential stripping-coal sites should be present in all parts of the Montana 

coal fields, particularly in northeast Montana where the coal-bearing 

rocks are concealed by glacial deposits. The total potential stripping 

coal resources of Montana should be at least three times the total 

described in published reports, or 15,000 million tons. This estimated 

figure would be much larger, except for the fact that in southeastern 

Montana, where the total resources are very large, the topographic 

relief tends to reduce the size of strippable areas; also many of the 

higher and more accessible beds are burned out along the outcrops.

NORTH DAKOTA

The strippable lignite resources of North Dakota are very large as 

evidenced by the great number and thickness of lignite beds, the 

gentle dip of the enclosing rocks, and the general low topographic 

relief. Brant (1953) has supplied data from which an estimate of the 

potential strippable resources may be deduced. According to Brant 

(1953, p. 1, 4), the original resources of lignite in North Dakota as 

determined by mapping and exploration totaled 350, 910 million tons, 

of which 70 percent, or 250,000 million tons, is within 500 feet of the 

surface. For reasons previously suggested, this large tonnage should 

be evenly distributed by 100-foot overburden categories. If so, onefifth of the total, or 50,000 million tons, is 100 feet or less below the 

surface. Brant also (1953) presented planimetric maps of individual 

counties showing lignite outcrops and locations of many strip mines.

North Dakota's modest annual lignite production of less than 3 

million tons is obtained from a few large, readily accessible stripmining localties, most of which have developed resources adequate 

for many years of continuous operation. Ball (1966, p. 11) estimated 

that operating strip-mining companies in North Dakota control, or 

have developed, properties containing about 1,850 million tons of 

strippable lignite in thick beds generally less than 90 feet below the 

surface. Ball also estimated that the total strippable resources of 

such lignite in North Dakota probably ranges from 7,000 to 10,000 

million tons. This is admittedly a conservative figure based on present 

and near-future mining practices and commercial needs.

Because of the abundance of strippable lignite in all parts of western
CIO CONTRIBUTIONS TO ECONOMIC GEOLOGY

North Dakota, only a few of the larger and more conspicuous deposits 

have been mapped and described. They are summarized as follows:

In the Wibaux area, which extends into Montana, May (1954) 

mapped and described 10 possible strip-mining areas. The largest of 

these covers about 55 square miles and is underlain by lignite 10-40 

feet thick. A part of this large area selected for special study contains 

339 million tons of lignite in a bed 24 feet thick and generally less 

than 60 feet below the surface.

In Slope and Bowman Counties, Kepferle and Culbertson (1955) 

mapped and described two areas underlain by 1,370 million tons of 

lignite in a bed 20-30 feet thick. About half of the total is 60 feet or 

less below the surface.

On a detailed geologic map of the Square Buttes coal field in Oliver 

and Mercer Counties, Johnson and Kunkel (1959, p. 50, pi. 1) delineated seven potential strip-mining localities in which the lignite is 6 

feet thick or more, and the overburden is generally less than 60 feet.

Van Sant and Ellman (1959) provided mining costs and other data 

on six strip mines that in 1955 supplied 70 percent of North Dakota's 

production.

OKLAHOMA

The bulk of Oklahoma's annual coal production, which in 1966 

totaled 850,000 tons, is obtained by strip mining. The distribution and 

extent of strip-mined areas as of 1960 are shown on a map by Doerr 

(1961, p. 27). Many of these areas were mined with small shovels and 

could possibly be mined deeper with larger equipment. In the Henryetta district, Okmulgee County, Dunham and Trumbull (1955, p. 211) 

discussed four areas of potential value for strip mining.

PEiKTKrSYLVANTA

Pennsylvania has been a major producer of strip-mined coal for 

many years. As a consequence, the outcrops of all the thicker and better 

known beds have been extensively stripped. The outcrop of the Pittsburgh bed, in particular, is largely mined out. Deasy and Griess (1960, 

p. 14) prepared a map showing the few remaining unstripped areas 

along the outcrop of the Pittsburgh bed; earlier they (1958, p. 112) 

prepared maps showing original outcrops and remaining unmined 

outcrops of the Lower Freeport coal in Clearfield County and the 

Upper Freeport coal in Armstrong County. Deasy and Griess (1960, 

facing p. 68) also prepared a map showing the cumulative strip-mined 

bituminous coal lands of Pennsylvania and more detailed maps of 

selected smaller areas (1958, p. 120; 1959, p. 4, 8). These maps demonstrate the widespread extent of strip mining, and they will aid in finding unmined areas.
STRIPPING-COAL RESOURCES OF THE UNITED STATES Cll

In a summary study of the coal resources of Beaver County, Patterson (1963, p. A19, A20, A22, A23) estimated that the original resources 

with less than 60 feet of overburden totaled 147 million tons, or about 

7 percent of the total original resources estimated for the county.

In a summary study of the coal resources of Lawrence County, Van 

Lieu and Patterson (1964, p. B17-B19) estimated that the remaining 

resources as of January 1, 1957, with less than 60 feet of overburden 

totaled 67 million tons, or about 9 percent of the total remaining 

resources estimated for the county.

SOUTH DAKOTA

Although South Dakota contains adequate resources of lignite 

suitable for strip mining, at least for local use, annual production is 

very small because of competition from coal in the adjoining States of 

Wyoming and North Dakota where the beds are thicker and more 

economical to mine. Most of past and present production in South 

Dakota has come from strip mines in the Isabel-Firesteel district, in 

Dewey and Ziebach Counties, advantageously located on a branch line 

of the Milwaukee Railroad. Summaries of information available on 

the Isabel-Firesteel district have been provided by Denson (1950) 

and by Brown (1952, p. 16). Brown (1952) also provided a summary 

of information available on the remainder of the South Dakota lignite 

field and cited three additional areas potentially suitable for strip 

mining.

TEXAS

In a summary study of lignite resources in Texas, Perkins and 

Lonsdale (1955, p. 28-36) reported strippable resources totaling 3,282 

million tons in beds 5 feet thick or more and 90 feet or less below the 

surface. This tonnage is classed as measured and indicated and is 

demoiistrably conservative.

WASHINGTON

The stripping-coal resources of Washington are very small, because 

in most areas the coal-bearing rocks are folded, faulted, and steeply 

dipping. Nevertheless, mapping and exploration to date have revealed 

three areas of relatively gentle dips and thin overburden.

In the Centralia-Chehalis district, Lewis and Thurston Counties, 

Snavely, Brown, Roberts, and Rau (1958, p. Ill) delineated areas in 

the Tono basin that are suitable for strip mining. A 1-million-kilowatt 

steam-powered generating plant designed to use this low-cost stripmined coal is under construction by the Pacific Power and Light 

Company and the Washington Water Power Company.

In the Toledo-Castle Rock district, Cowlitz and Lewis Counties,
C12 CONTRIBUTIONS TO ECONOMIC GEOLOGY

Eoberts (1958, p. 49, 50, 52, 53; pis. 15, 16) described a small stripmining area that contains 8 million tons of lignite in two beds ranging 

in thickness from 5 feet to more than 20 feet and generally less than 

60 feet below the surface. (See also Toenges and others, 1947.)

In the E/oslyn field, Kittitas County, Beikman, Gower, and Dana 

(1961, p. 21) mentioned three areas in T. 20 N., E. 15 E., where the dip 

of the Big Dirty bed and the slope of the topography are approximately the same and where the Big Dirty bed is probably generally 

less than 120 feet below the surface.

WYOMING

Wyoming contains substantial resources of stripping coal around 

the edges of the Powder Kiver Basin, in the Hanna basin, and in the 

Kemmerer area of Lincoln County. The bulk of annual coal production 

in Wyoming is obtained from a few large strip mines in these areas. 

As in North Dakota, the amount of strippable coal already known and 

potentially present in Wyoming is so much larger than annual production that incentive to delineate additional areas has been lacking. 

Several potential stripping-coal localities are described, however, in 

two reports of the U.S. Geological Survey. In the Buffalo-Lake DeSmet area, Johnson and Sheridan Counties, Mapel (1959, p. 93, 94) 

discussed eight potential strip-mining areas. Three of these areas are 

underlain by coal locally as much as 224 feet thick in the Healy( ?) 

bed. (See also Mapel and 'others, 1953.) In the Crazy Woman Creek 

area, Johnson County, Hose (1955, p. 84-87) presented resource data 

by individual beds and townships in an overburden category of 0-150 

feet. This information used in conjunction with his geologic map will 

be helpful in delineating potential strip-mining areas.

The modern strip-mining operation of the Kemmerer Coal Co. at 

Elkol, Lincoln County, is described in a recent article in Coal Age 

(1963).

OTHER POTENTIAL SITES

Many additional strip-mining sites are undoubtedly present in the 

States mentioned and in other coal-bearing States not mentioned. These 

sites can be located by study of the relation between coal outcrops, dip 

of beds, nature of overlying rock, and the terrane. This study will be 

facilitated by the availability of geologic reports of various agencies 

for substantial parts of most coal-bearing areas and by the increased 

availability of modern topographic maps. The topographic map coverage of the United States coal field areas has increased steadily through 

the years and is virtually complete for most coal areas in the Eastern 

United States. Since the mid 1950's most topographic maps of coal field 

areas have been prepared on the improved scale of 2,000 feet to the inch,
STRIPPING-COAL RESOURCES OF THE UNITED STATES C13

which is ideal for study and planning. For the United States as a 

whole, these maps are being published at the rate of about 1,500 per 

year.

ESTIMATED TOTAL STRIPPING-COAL RESOURCES

From data summarized in the preceding paragraphs it is obvious 

that the stripping-coal resources of the United States are very large. 

In six States alone, where State-wide estimates of stripping-coal resources based on factual data have been prepared, the total is 95,069 

million tons, as shown in table 2.

TABLE 2. Estimated original resources of stripping coal in six States

[Figures are for resources in the ground, of which about 80 percent may be considered

recoverable]

Millions of Range of overburden 

State short tons (feet)

Arkansas__________________________ 263 0- 60; 0-100

Illinois_______-____________________ 23,000 0-150

Indiana___________________________ 3,524 0-90

Montana_-_______-_-_-____________ 15, 000 Various

North Dakota_____________ ______ 50,000 0-100

Texas_____________________________ 3,282 0-90

Total_______________________ 95,069 _____________

Accepting the figures in table 2 as a frame of reference, one can 

derive comparable figures for adjoining and intervening States and 

a total for the United States by a crude process of extrapolation, using 

for each State the following critical factors: (1) Size of the total 

resource, (2) tonnage in the major 0- to 1,000-foot overburden category, (3) average topographic relief, and (4) average dip of the 

coal-bearing rocks.

As figures for five of the six States in table 2 are for resources in 

overburden categories generally less than 100 feet, the extrapolation 

based on these figures is intended to include coal in the 0- to 100-foot 

overburden category, which represents most coal of present interest 

for strip mining. It would, of course, be possible to modify the figures 

in table 2 so that they would apply more closely to the 0- to 100-foot 

overburden category, but this process would substitute extrapolated 

estimates for figures arrived at by more accurate methods of calculation and would not improve the extrapolation in surrounding States. 

Furthermore, the smaller figures in table 2 are compensated by the 

larger figure for Illinois, which represents coal in the 0- to 150-foot 

overburden category.

The figures for the States listed in table 2 and the extrapolated 

figures for adjoining and intervening States are presented in table 3. 

The total of these figures 139,969 million tons represents the estimated total original stripping-coal resources of the United States,
C14 CONTRIBUTIONS TO ECONOMIC GEOLOGY

TABLE 3. Estimated original resources of stripping coal in the United States in beds 

generally less than 100 feet below the surface

[Figures are for resources in the ground, of which about 80 percent may be considered recoverable]

Millions of Millions of 

State short tons State short tont

Alabama..__.-________ 800 North Dakota._________ 50,000

Alaska,....________..._ 2,000 Ohio.-________-__-__.___- 5,000

Arizona_______-____________ 100 Oklahoma____-__--_-------- 500

Arkansas___________________ 263 Pennsylvania______________ 8,000

Colorado.____________ 1, 200 South Dakota.____________ 400

Illinois_________________ ! 23, 000 Tennessee._______________ 200

Indiana...____________ 3,524 Texas_______________ 3,282

Iowa________________. 600 Utah__________________ 300

Kansas________-_________ 600 Virginia__________________ 1,000

Kentucky________________ 6,000 Washington_;_______________ 100

Maryland.....___________ 100 West Virginia______._______- 6,000

Missouri___________________ 1,000 Wyoming_______--__-___-_- 10,000

Montana_________________ 15,000 

New Mexico____________ 1,000 Total.-----...._...139, 969

i Overburden, 0-150 feet thick.

Although a great deal of subjectivity is inherent in the figures 

determined by extrapolation, the total of 139,969 million tons reflects 

control by estimates for the six States mentioned previously where 

subjectivity was at a minimum. This figure can be further evaluated 

by a second line of reasoning. Continuing study of United States coal 

resources has shown that of the total resources known through mapping and exploration to date, about 1,450 billion tons is in the 0- to 

1,000-foot overburden category. The figure for stripping-coal resources 

is 9.6 percent of this larger total, which suggests that it is a reasonable 

maximum.

The estimated total of 139,969 million tons is, of course, for original 

resources in the ground. Subtracting 4,850 million tons, representing 

cumulative past strip production of bituminous coal and anthracite 

of 3,876 million tons to January 1, 1967, plus estimated past losses 

of 974 million tons, and assuming future recoverability of 80 percent, 

the total is reduced to 108,095 million tons. This figure is too large 

to be appreciated except by comparison with smaller and more meaningful numbers. It is, for example, 28 times the cumulative strip-coal 

production of 3,876 million tons, from the beginning of mining to 

January 1, 1967, and it is 600 times the 1966 strip-coal production of 

179 million tons. These comparisons do not represent the life expectancy of stripping-coal resources because the rate of production and 

the estimated size of the resources will surely change in the future.

PREVIOUS ESTIMATE OF STRIPPING-COAL. RESOURCES

An estimate of 230,670 million tons as the stripping-coal resources 

of the United States has been presented previously (Coal Age, 1966b). 

For a few States where data were obtained from common sources,
STRIPPING-COAL RESOURCES OF THE UNITED STATES C15

the figures are identical in the Coal Age estimate and in the present 

estimate. Where figures were obtained by extrapolation, those in Coal 

Age are, in general, higher than those in the present estimate. For 

some States this increase is explained by the inclusion of coal with 

overburden to maxima of 120 and 150 feet. For others, the difference 

is too great to be satisfactory to the writer. The Coal Age figures for 

Kansas (6,807 million tons), Missouri (18,085 million tons), and 

West Virginia (30.400 million tons) seem to be too high for the 

stated 150-foot overburden range. When the Coal Age estimate of 

230,670 million tons is compared to the total estimated United States 

resources as determined by mapping and exploration, it is about 16 

percent of such resources in the 0- to 1,000-foot overburden category. 

This total and percentage are both somewhat high for the stated 

parameters.

RECLAMATION OF STRIP-MINED LANDS

The thousands of stripped-over areas in the United States cover 

about 1,500 square miles. The present rate of increase in strip mining 

is adding ever-increasing annual increment to this total, and the 

increase in size of strip-mining machinery will result in ever higher 

and wider spoil banks. Eecognizing this threat to the beauty of the 

land and to the utility of other resources, many States have enacted 

legislation to require reclamation of future strip-mined lands.

Existing spoil banks present serious problems to conservationists. 

In mountainous areas where contour stripping is practiced, the spoil 

banks may initiate landslides, which devastate larger areas than the 

original piles, and contribute excessive amounts of silt to the loca] 

drainage; in these areas, conservation objectives are directed toward 

reducing the possibility of slides and improving the opportunities 

for reforestation.

In areas of low relief, spoil banks are more stable, and conservation 

objectives vary according to the composition, texture, height, and 

slope of the banks. Many spoil banks are high in snlfuric acid, derived 

from sulfur in the coal and associated rock. A few are low in sulfuric 

acid. All are low in organic material and in available trace elements 

needed to support plant life. Highly acidic spoil banks will support 

little plant life; moderately acidic banks will support trees and plants 

adapted to an acidic soil; other less acidic banks will support a wider 

variety of plant life. The degree of reclamation and future utility 

thus depends on physical and chemical factors that require a great 

deal of preliminary study and experimentation. Within limits imposed 

by chemical and physical characteristics, spoil banks have been used as 

tree farms, recreational areas, grazing lands, game and fish preserves,
C16 CONTRIBUTIONS TO ECONOMIC GEOLOGY

city dumps, and sewage disposal ponds. A few of high calcareous content support orchards and other suitable forms of agriculture. Deasy 

and Griess (1963) provided an excellent summary and bibliography 

on the status of thought and effort thus far devoted to reclamation.

CONCLUSIONS

The information summarized permits several broad and perhaps 

self-evident generalizations that are worthy of emphasis:

1. The largest concentration of strippable coal in the United States is 

in North Dakota and eastern Montana. Eelatively little mining is 

carried on in this area, however, because of the small population 

and lack of industrialization.

2. The second largest concentration of strippable coal is in the Illinois 

basin, which embraces the coal-bearing parts of Illinois, Indiana, 

and western Kentucky. In 1964 the Illinois basin became the leading area in strip-coal production in the United States with an 

output of 66 million tons. This lead was increased in 1965 with an 

output of 72 million tons and further increased in 1966 with an 

output of 79 million tons the maximum thus far recorded for the 

Illinois basin.

3. The third largest concentration of strippable coal is in the north 

half of the Appalachian basin, which embraces the coal-bearing 

parts of Pennsylvania, including the Pennsylvania anthracite 

fields, West Virginia, and Ohio. Because this area is near centers 

of population and industrial activity, it was the leading area in 

strip-coal production for many years. It attained a maximum 

of 89 million tons in 1947. Since that date, however, strip-coal 

production in the north half of the Appalachian basin has declined, and during 1956-65 it ranged from 57 to 68 million tons 

annually. The 1964 production of 63 million tons was for the first 

time in many years less than that of the Illinois basin. The increased 1965 production of 68 million tons was also less than that 

of the Illinois basin.

The fact that strip-coal production in Pennsylvania and West 

Virginia is falling behind the national trend suggests that much 

of the readily accessible, low-cost strip coal has been mined out. 

Because of the substantial resources of strip coal remaining in 

these States, a resurgence in strip and related production is in 

prospect through use of larger equipment, augers, and highwall 

miners.

4. If the cumulative past production of 3,876 million tons of strip coal 

has resulted in spoil banks covering 1,500 square miles, then the 

removal of the remaining recoverable resources of 108,095 million 

tons could result in spoil banks covering 42,000 square miles an
STRIPPING-COAL RESOURCES OF THE UNITED STATES C17

area larger than the entire State of Ohio. This prospect is repugnant to public opinion, and future strip mining is likely to be 

more closely controlled by State and Federal laws. Nine or ten 

States have enacted or have under legislative consideration fairly 

stringent reclamation laws, and the stripping-coal industry is 

actively supporting research on reclamation methods. The future 

of the strip-mining industry is obviously strongly dependent on 

an effective nation-wide program of reclamation of stripped-over 

lands.

REFERENCES

Abernathy, G. E., 1944, Mined areas of the Weir-Pitteburg coal bed [Kansas] : 

Kansas Geol. Survey Bull. 52, pt. 5, p. 213-228.

 1946, Strip-mined areas in the southeastern Kansas coal field: Kansas 

Geol. Survey Bull. 64, pt. 4, p. 130-144.

Abernathy, G. E., Jewett, J. M., and Schoewe, W. E., 1947, Coal reserves in 

Kansas: Kansas Geol. Survey Bull. 70, pt. 1, p. 1-20.

Averitt, Paul, 1965, Coal deposits of eastern Montana, in Mineral potential of 

eastern Montana A basis for future growth: U. S. 89th Gong., 1st sess., 

Senate Doc. 12, p. 9-25, 71-77 [repr. as Montana Bur. Mines and Geology 

Spec. Pub. 33, p. 9-25, 71-77; repr. in Montana Bur. Mines and Geology 

Spec. Pub. 36, p. 69-80].

Baker, A. A., 1929, The northward extension of the Sheridan coal field, Big Horn 

and Rosebud Counties, Montana: U.S. Geol. Survey Bull. 806-B, p. 15-67.

Ball, C. G., 1966, An economic appraisal of lignite reserves in North Dakota, 

in Technology and use of lignite, Proceedings, Bureau of Mines and University of North Dakota Symposium, Bismarck, North Dakota, April 29-30, 

1965: U.S. Bur. Mines Inf. Circ. 8304, 124 p.

Barnes, F. F., and Cobb, E. H., 1959, Geology and coal resources of the Homer 

district, Kenai coal field, Alaska: U.S. Geol. Survey Bull. 1058-F, p. 217-260.

Bass, N. W., 1932, The Ashland coal field, Rosebud, Powder River, and Custer 

Counties, Montana: U. S. Geol. Survey Bull. 831-B, p. 19-105.

Beiknian, H. M., Gower, H. D., and Dana, T. A. M., 1961, Coal reserves of Washington : Washington Div. Mines and Geol. Bull. 47, 115 p.

Brant, R. A., 1953, Lignite resources of North Dakota ; U.S. Geol. Survey Circ. 

226, 79 p.

Brown, Andrew, Culbertson, W. C., Dunhain, R. J., Kepferle, R. C., and May, P. R., 

1954, Strippable coal in Custer and Powder River Counties, Montana: U.S. 

Geol. Survey Bull. 995-E, p. 151-199.

Brown, D. M., 1952, Lignite resources of South Dakota: U.S. Geol. Survey Circ. 

159,18 p.

Cady, G. H., 1927, Coal stripping possibilities in southern and southwestern 

Illinois: Illinois Geol. Survey Coop. Mining Ser. Bull. 31, 59 p.

 1937, Summary list of areas in western, northern, and central Illinois 

recommended for special investigation as possibly suitable for strip-mining : 

Illinois Geol. Survey Circ. 19, 6 p.

 1952, Minable coal reserves of Illinois: Illinois Geol. Survey Bull.

78,138 p. 

Coal Age, 1963, Subbituminous for power The Sorensen story: Coal Age, v. 68,

no. 9, p. 74-81. 

 1965, Getting bigger and better for deeper stripping: Coal Age, v. 70, no. 5,

p. 78-80.
CIS CONTRIBUTIONS TO ECONOMIC GEOLOGY

Coal Age, 1966a, Facing coal's major problems, mining machinery developments: 

Coal Age, v. 71, no. 7, p. 113.

 1966b, How much strip coal: Coal Age, v. 71, no. 8, p. 120.

Collier, A. J., and Knechtel, M. M., 1989, Coal resources of McCone County, 

Montana: U.S. Geol. Survey Bull. 905, 80 p.

Culbertson, W. C., 1954, Three deposits of strippable lignite west of the Yellowstone River, Montana: U.S. Geol. Survey Bull. 995-H, p. 293-332.

Culver, H. E., 1925, Preliminary report on coal-stripping possibilities in Illinois: 

Illinois Geol. Survey Coop. Mining Ser. Bull. 28, 61 p.

Deasy, G. F., and Griess, P. E., 1958, Some geographic aspects of Pennsylvania's 

bituminous coal strip pits: Pennsylvania Acad. Sci. Proc., v. 32, p. 115-121 

[repr. as Pennsylvania State Univ. Coll. Mineral Industries Contr. 58-68].

 1959, Coal strip pits in the northern Appalachian landscape: Jour. Geography, v. 58, no. 2, p. 1-10 [repr. as Pennsylvania State Univ. Coll. Mineral 

Industries Contr. 58-59].

 1960, Bituminous coal, Pt. 1 of Atlas of Pennsylvania coal and coal 

mining: Pennsylvania State Univ. Coll. Mineral Industries Bull. 73, 68 p. 

1963, An approach to the problem of coal strip mine reclamation: Pennsylvania State Univ. Coll. Mineral Industries, Mineral Industries, v. 33,

no. 1, p. 1-7. 

Denson, N. M., 1950, The lignite deposits of the Cheyenne River and Standing

Rock Indian Reservations, Corson, Dewey, and Ziebach Counties, South

Dakota, and Sioux County, North Dakota: U.S. Geol. Survey Circ. 78, 22 p. 

Doerr, A. H., 1961, Coal mining and landscape modification in Oklahoma: Oklahoma Geol. Survey Circ. 54, 48 p. 

Dunham, R. J., and Trumbull, J. V. A., 1955, Geology and coal resources of the

Henryetta mining district, Okmulgee County, Oklahoma: U.S. Geol. Survey

Bull. 1015-F, p. 183-225.

Gentile, R. J., 1965, Mineral commodities of Putnam County [Missouri] : Missouri Div. Geol. Survey and Water Resources Rept. Inv. 29, 48 p. 

Griess, P. R., and Deasy, G. F., 1958, Past, present, and future foci of bituminous

coal strip mining in Pennsylvania: Pennsylvania Acad. Sci. Proc., v. 32,

p. 108-114 [repr. as Pennsylvania State Univ. Coll. Mineral Industries

Contr. 58-67]. 

Haley, B. R., 1960, Coal resources of Arkansas: U.S. Geol. Survey Bull. 1072-P,

p. 795-831. 

Henbest, L. G., 1929, Coal stripping possibilities in Saline and Gallatin Counties

near Equality: Illinois Geol. Survey Coop. Mining Ser. Bull. 32, 26 p. 

Hose, R. K., 1955, Geology of the Crazy Woman Creek area, Johnson County,

Wyoming: U.S. Geol. Survey Bull. 1027-B, p. 33-118 [1956]. 

Huey, J. J., 1964, Development and history of wheel excavators in the U.S.A.:

Illinois Mining Inst. Proc. 1964, p. 65-90. 

Johnson, W. D., Jr., and Kunkel, R. P., 1959, The Square Buttes coal field, Oliver

and Mercer Counties, North Dakota: U.S. Geol. Survey Bull. 1076, 91 p. 

Kepferle, R. C., 1954, Selected deposits of strippable coal in central Rosebud

County, Montana: U.S. Geol. Survey Bull. 995-1. 

Kepferle, R. C., and Culbertson, W. C., 1955, Strippable lignite deposits, Slope

and Bowman Counties, North Dakota: U.S. Geol. Survey Bull. 1015-E,

p. 123-182. 

Koenig, R. P., 1950, Economics and technique of strip coal mining, in Coal and

metal mining: Colorado School Mines Quart., v. 45, no. 2 B, p. 27-39.
STRIPPING-COAL RESOURCES OF THE UNITED STATES C19

Mapel, W. J., 1959, Geology and coal resources of the Buffalo-Lake DeSruet area, 

Johnson and Sheridan Counties, Wyoming: U.S. Geol. Survey Bull. 1078, 

148 p. [1961].

Mapel, W. J., Schopf, J. M., and Gill, J. R., 1953, A thick coal bed near Lake 

DeSmet, Johnson County, Wyoming: U.S. Geol. Survey Circ. 228, 47 p.

May, P. R., 1954, Strippable lignite deposits in the Wibaux area, Montana 

and North Dakota: U.S. Geol. Survey Bull. 995-G, p. 255-292.

Mining Engineering, 1966, Ohio Power orders biggest dragline yet: Mining 

Engineering, v. 18, no. 9, p. 19.

Parker, F. S., 1936, The Richey-Lambert coal field, Richland and Dawson 

Counties, Montana : U.S. Geol. Survey Bull. 847-C, p. 121-174.

Patter son, E. D., 1963, Coal resources of Beaver County, Pennsylvania: U.S. 

Geol. Survey Bull. 1143-A, p. A1-A33 [1964].

Perkins, J. M., and Lonsdale, J. T., 1955, Mineral resources of the Texas Coastal 

Plain: Texas Univ. Bur. Econ. Geol. Mineral Resources Circ. 38, 65 p.

Pierce, W. G., 1936, The Rosebud coal field, Rosebud and Custer Counties, Montana : U.S. Geol. Survey Bull. 847-B, p. 43-120.

Reinertsen, D. L., 1964, Strippable coal reserves of Illinois, Pt. 4 Adams, Brown, 

Calhoun, Hancock, McDonough, Pike, Schuyler, and the southern parts of 

Henderson and Warren Counties: Illinois Geol. Survey Circ. 374, 32 p.

Roberts, A. E., 1958, Geology and coal resources of the Toledo-Castle Rock district, Cowlitz and Lewis Counties, Washington: U.S. Geol. Survey Bull. 

1062, 71 p.

Schoewe, W. H., 1955, Coal resources of the Marniaton group in eastern Kansas: 

Kansas Geol. Survey Bull. 114, pt. 2, p. 49-112.

 1959, Mulky coal, [Pt.] 1 of Coal resources of the Cherokee Group in

eastern Kansas: Kansas Geol. Survey Bull. 134, pt. 5, p. 184-222. 

Shotts, R. Q., and Riley, H. L., 1966, Coal resources of the Fabius-Flat Rock

area, Jackson County, Alabama: U.S. Bur. Mines Inf. Circ. 8295, 36 p. 

Simon, J. A., 1966, Shipping coal mines in Illinois: Illinois Geol. Survey, map,

scale 1: 500,000. 

Smith, W. H., 1957, Strippable coal reserves of Illinois, Pt. 1 Gallatin, Hardin,

Johnson, Pope, Saline, and Williamson Counties: Illinois Geol. Survey

Circ. 228,39 p.

 1958, Strippable coal reserves of Illinois, Pt. 2 Jackson, Monroe, Perry, 

Randolph, and St. Clair Counties: Illinois Geol. Survey Circ. 260, 33 p.

 1961, Strippable coal reserves of Illinois, Pt. 3 Madison, Macoupin,

Jersey, Greene, Scott, Morgan, and Cass Counties: Illinois Geol. Survey

Circ. 311, 40 p. 

Smith, W. H., and Berggren, D. J., 1963, Strippable coal reserves of Illinois,

Pt. 5A Fulton, Henry, Knox, Peoria, Stark, Tazewell, and parts of Bureau,

Marshall, Mercer, and Warren Counties: Illinois Geol. Survey Circ. 348,

59 p. 

Snavely, P. D., Jr., Brown, R. D., Jr., Roberts, A. E., and Rau, W. W., 1958,

Geology and coal resources of the Centralia-Chehalis district, Washington,

with a, section on Microscopical character of Centralia-Chehalis coal by

J. M. Schopf: U.S. Geol. Survey Bull. 1053, 159 p. 

Spencer, F. D., 1953, Coal resources of Indiana: U.S. Geol. Survey Circ. 266,

42 p. 

Toenges, A. L., Turnbull, L. A., and Cole, W. A., 1947, Exploration, reserves,

bed characteristics, and strip-mining possibilities of a lignite deposit near

Toledo, Lewis County, Washington: U.S. Bur. Mines Tech. Paper 699, 55 p.
C20 CONTRIBUTIONS TO ECONOMIC GEOLOGY

U.S. Bureau of Mines, 1924 31, Mineral resources of the United States [annual 

volumes for the year indicated].

 1932-65, Minerals yearbook [annual volumes for the years indicated].

 1967, Weekly coal report 2609, 21 p.

Van Lieu, J. A., and Patterson, E. D., 1964, Coal resources of Lawrence County,

Pennsylvania: U.S. Geol. Survey Bull. 1143-B, p. B1-B33. 

Van Sant, J. N., and Ellman, R. C., 1959, Methods and costs of mining lignite

in North Dakota: U.S. Bur. Mines Inf. Circ. 7891, 82 p. 

Wahrhaftig, Clyde, and Birman, J. H., 1954, Stripping-coal deposits on lower

Lignite Creek, Nenana coal field, Alaska: U.S. Geol. Survey Circ. 310, 11 p. 

Wax-field, R. S., 1963, Investigation of a subbituminous coal deposit suitable for

opencut mining, Beluga River coal field, Alaska: U.S. Bur. Mines Rept.

Inv. 6238,100 p. 

Warren, W. 0., 1959, Reconnaissance geology of the Birney-Broadus coal field,

Rosebud and Powder River Counties, Montana: U.S. Geol. Survey Bull.

1072-J, p. 561-585. 

Young, W. H., 1967, Thickness of bituminous-coal and lignite seams mined in

1965: U.S. Bur. Mines Inf. Circ. 8345, 18 p.

U.S. GOVERNMENT PRINTING OFFICE: 1968