Chapter PQ

COAL QUALITY AND GEOCHEMISTRY, POWDER RIVER

BASIN, WYOMING AND MONTANA

By G.D. Stricker and M.S. Ellis

in U.S. Geological Survey Professional Paper 1625-A
PQ-ii

Contents

Coal Quality and Geochemistry, Powder River Basin, Wyoming and

Montana ..............................................................................................................PQ-1

References Cited .................................................................................................PQ-4

Figures

PQ-1. Index map showing the Powder River Basin.

PQ-2. Index map showing coal quality data distribution in the WyodakAnderson coal zone in the Powder River Basin.

PQ-3. Ash yield in the Wyodak-Anderson coal zone in the Powder River Basin.

PQ-4. Total sulfur content in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-5. Moist, mineral-matter-free Btu/lb in the Wyodak-Anderson coal zone in

the Powder River Basin.

PQ-6. Pounds of sulfur dioxide per million Btu (lbSO2 ) in the WyodakAnderson coal zone in the Powder River Basin.

PQ-7. Antimony concentration in the Wyodak-Anderson coal zone in the

Powder River Basin.

PQ-8. Arsenic concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-9. Beryllium concentration in the Wyodak-Anderson coal zone in the

Powder River Basin.

PQ-10. Cadmium concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.
PQ-iii

Figures-continued

PQ-11. Chromium concentration in the Wyodak-Anderson coal zone in the

Powder River Basin.

PQ-12. Cobalt concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-13. Lead concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-14. Manganese concentration in the Wyodak-Anderson coal zone in the

Powder River Basin.

PQ-15. Mercury concentration in the Wyodak-Anderson coal zone in the, Powder

River Basin.

PQ-16. Nickel concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-17. Selenium concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

PQ-18. Uranium concentration in the Wyodak-Anderson coal zone in the Powder

River Basin.

Table

PQ-1. Summary data for coal in the Wyodak-Anderson coal zone in the Powder

River Basin
PQ-1

COAL QUALITY AND GEOCHEMISTRY, POWDER RIVER

BASIN, WYOMING AND MONTANA

Actively mined coal from the Wyodak-Anderson coal zone in the Powder River

Basin in Wyoming and Montana (fig. PQ-1) is considered to be “clean coal.” For

the location and description of this coal zone, see Chapter PF-Framework Geology

of Fort Union coal in the Powder River Basin. This coal zone contains a lowcontaminant, subbituminous coal resource that has the following arithmetic mean

values (on an as-received basis) for coal that is not presently being mined or under

lease to be mined in the future: moisture–27.66 percent, ash–6.44 percent, total

sulfur–0.48 percent, calorific value–8,220 Btu/lb, lb SO2 per million Btu–1.24,

and moist, mineral-matter-free Btu–8,820. Arithmetic mean concentration (in

parts per million and on whole-coal and remnant-moisture basis) of elements of

environmental concern for coal in the Wyodak-Anderson coal zone (and

stratigraphically equivalent beds in Montana and Wyoming) are: antimony–0.50,

arsenic–2.6, beryllium–0.54, cadmium–0.21, chromium–6.1, cobalt–1.9,

lead–3.0, manganese–26, mercury-–0.13, nickel–4.6, selenium–1.1, and

uranium–1.3. Table PQ-1 is a summary of coal quality of the Wyodak-Anderson

coal zone in Wyoming and Montana. Coal from the Wyodak-Anderson coal zone

is produced from 23 mines in the Powder River Basin. This coal is utilized for

electric power generation at power plants in 26 states. The Wyodak-Anderson coal

is sometimes blended with higher sulfur coal to produce a compliant fuel.

Both proprietary and public data are used in the summary data tables, but is not

shown on location maps or on other graphic displays. A common problem in

statistical summaries of trace-element data arises when element values are below

the limits of detection. This results in a censored distribution. To compute
PQ-2

unbiased estimates of censored data for the elements in this table, we adopted the

protocol of reducing all “less than” values by 50 percent to generate a real value

for these data. Summary statistics of range (minimum, with an “L” indicating “less

than”, and maximum values) and arithmetic means were generated using the

modified data. Moisture values are reported on an as-received basis (American

Society for Testing and Materials, 1994b, designation D3180-89). Because no

equilibrium moisture values are available for this report, apparent ranks can not

reliably be determined.

Between 1974 and 1994, the U.S. Geological Survey analyzed samples of coal for

major-, minor-, and trace-element contents. Prior to performing the analyses, most

of the coal samples were dried at room temperature and humidity for as much as 80

hours. Some samples, however, may have only been dried enough to allow

grinding (to less than 100 mesh). Moisture content in the samples is unknown,

although moisture contents were probably similar to that which would remain after

air-dry loss determination (American Society for Testing and Materials, 1994c,

D3302-91). Since the actual moisture content of the samples analyzed between

1974 and 1994 is unknown and can not be determined, the major-, minor-, and

trace-element contents are reported on a remnant moisture basis. Also, the

elemental analysis of the samples cannot be converted to any other moisture basis.

In addition, these analyses can only provide an approximation of load factors (such

as, pounds of mercury per trillion Btu).

For the following graphical displays, figures PQ-2 through PQ-17, show public

data locations and values for variables listed in table PQ-1, except for calorific

value and moisture, for the Wyodak-Anderson coal zone. The locations of public

data points used in this summary are shown on figure PQ-2. When more than one
PQ-3

analysis was available per location, the analytical values were weight averaged on

coal sample thickness. For ash and total sulfur (figs. PQ-3 and PQ-4), the values

are color coded low, medium, and high, following guidelines established in U.S.

Geological Survey Circular 891 (Wood and others, 1983). For moist, mineralmatter-free Btu, which is used in conjunction with other factors to determine

apparent rank (fig. PQ-5), we utilized the apparent rank designations established by

American Society for Testing and Materials, (1994a), designation D388-92a. For

pounds of SO2 per million Btu (lb SO2) (fig. PQ-6), values are color coded to the

U.S. Environmental Protection Agency’s Phase I, Phase II, and non-compliant

limits for sulfur emission from coal-fired power plants (U.S. Environmental

Protection Agency, 1996).

No guidelines have been established for the elements of environmental concern

(also referred to as “hazardous air pollutants” or “HAPs”). Analytical values for

these elements (figs. PQ-7 through PQ-18) are color keyed based on the following

parameters: (1) each element of environmental concern was ranked from the lowest

to highest value for all data in the Northern Rocky Mountains and Great Plains

region and (2) quartiles were established for each element such that low represents

those values that are less than the .25 quartile (also known as the lower quartile or

the 25th percentile), medium represents those values that are within the .25 to .75

quartiles (two quartiles representing 50 percent of the values or between the 25th to

75th percentile), and high represents those values that are in the upper .25 quartile

(or greater than the 75th percentile).
PQ-4

REFERENCES CITED

American Society for Testing and Materials, 1994a, Annual book of ASTM

Standards, Section 5, Petroleum products, lubricants and fossil fuels, vol.

05.05 Gaseous fuels; coal and coke; section D388-92a; Standard

Classification of Coal by Rank: American Society for Testing and Materials,

Philadelphia, Pennsylvania, p. 168-171.

 1994b, Annual book of ASTM Standards, Section 5, Petroleum products,

lubricants and fossil fuels, vol. 05.05 Gaseous fuels; coal and coke; section

D3180-89; Standard Practice for Calculating Coal and Coke Analysis from

As-Determined to Different Bases: American Society for Testing and

Materials, Philadelphia, Pennsylvania, p. 318-320.

 1994c, Annual book of ASTM Standards, Section 5, Petroleum products,

lubricants and fossil fuels, vol. 05.05 Gaseous fuels; coal and coke; section

D3302-91; Standard Test Method for Total Moisture in Coal: American

Society for Testing and Materials, Philadelphia, Pennsylvania, p. 330-336.

Bragg, L.J., Oman, J.K., Tewalt, S.J., Oman, C.L., Rega, N.H., Washington, P.M.,

and Finkleman, R.B, 1994, U.S. Geological Survey Coal Quality (Coalqual)

Database: Version 1.3: U.S. Geological Survey Open-File Report 94-205,

CD-ROM.

U.S. Environmental Protection Agency, 1996, Standards of Performance for New

Stationary Sources, 40CFR, Part 60.43, Standards for Sulfur Dioxide:

Environmental Protection Agency, 27 p.
PQ-5

Wood, G.H., Jr., Kehn, T.M., Carter, M.D., and Culbertson, W.C., 1983, Coal

resource classification system of the U.S. Geological Survey: U.S.

Geological Survey Circular 891, 65 p.

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Data point location

Powder

River

Basin

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-2. Index map showing coal quality data distribution in the 

Wyodak-Anderson coal zone, Powder River Basin, Wyoming and Montana.

N

43 00'

46 00'

108 00' 106 00' 
Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

( < 8 % )

( 8 - 15 % )

( > 15 % )

Low

Medium 

High

Powder

River

Basin

Figure PQ-3 Ash yield in the Wyodak-Anderson coal zone, Powder

River Basin, Wyoming and Montana.

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

N

43 00'

46 00'

108 00' 106 00' 
43 00'

46 00'

108 00' 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

( < 1 % )

( 1 - 3 % )

( > 3 % )

Low

Medium 

High

Powder

River

Basin

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-4. Sulfur content in the Wyodak-Anderson coal zone, Powder

River Basin, Wyoming and Montana.

N
43 00'

46 00'

108 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

( < 8,300 )

( 8,300 -10,500 )

( > 10,500 )

Lignite

Subbituminous 

Bituminous

Powder

River

Basin

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-5. Moist, mineral-matter-free Btu in the WyodakAnderson coal zone, Powder River Basin, Wyoming and Montana.

N

 00'
43 00'

46 00'

108 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

( < 1.2 )

( 1.2 - 2.4 )

( > 2.4 )

Low

Medium 

High

Powder

River

Basin

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-6. Pounds of sulfur dioxide per million Btu in the WyodakAnderson coal zone, Powder River Basin, Wyoming and Montana.

N

 00'
43 00'

46 00'

108 00' 106 00' 

Wyoming

North Dakota

South Dakota

Nebraska

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

( < 0.2 ppm )

( 0.2 - 0.5 ppm )

( >0.5 ppm )

Low

Medium 

High

Powder

River

Basin

Wyodak-Anderson

Study Limit

Montana

Northern Cheyenne

and Crow Indian

Reservations

Montana

Wyoming

0 30 60 Miles

Figure PQ-7. Antimony concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 0.23 ppm )

( 0.23 - 0.73 ppm )

( > 0.73 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

N

0 30 60 Miles

Figure PQ-9. Beryllium concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

43 00'

46 00'

108 00' 106 00' 
43 00'

46 00'

108 00' 106 00'

Custer

Treasure 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 0.052 ppm )

( 0.052 - 0.13 ppm )

( > 0.13 ppm )

0 30 60 Miles

Figure PQ-10. Cadmium concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

N
43 00'

46 00'

108 00' 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 3.0 ppm )

( 3.0 - 8.2 ppm )

( > 8.2 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

N

Figure PQ-11. Chromium concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.
43 00'

46 00'

108 00'		 	 	 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 0.87 ppm )

( 0.87 - 1.9 ppm )

( > 1.9 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

N

Figure PQ-12. Cobalt concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.
43 00'

46 00'

108 00' 106 00' 

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 1.8 ppm )

( 1.8 - 4.2 ppm )

( > 4.2 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-13. Lead concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N
43 00'

46 00'

108 00' 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 12 ppm )

( 12 - 49 ppm )

( > 49 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-14. Manganese concentration in the Wyodak-Anderson 

coal zone, Powder River Basin, Wyoming and Montana.

N
43 00'

46 00'

108 00' 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 0.06 ppm )

( 0.06 - 0.13 ppm )

( > 0.13 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-15. Mercury concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N
43 00'

46 00'

108 00' 106 00'	 	 	 	 	 	 	

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low

Medium 

High

( < 1.9 ppm )

( 1.9 - 5.2 ppm )

( > 5.2 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-16. Nickel concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N
43

46 00'

108 00' 106 00'

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low ( <0.5 ppm ) 

Medium ( 0.5 - 1.1 ppm )

High ( >1.1 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-17. Selenium concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N

 00'
43

46

108 106

Custer

Treasure 

 

Rosebud 

Powder River

Big Horn

Sheridan

Johnson

Natrona Converse 

Niobrara

Weston

Crook

Campbell

Powder

River

Basin

Low ( < 0.61 ppm ) 

Medium ( 0.61 - 1.6 ppm )

High ( >1.6 ppm )

Wyoming

North Dakota

South Dakota

Nebraska

Montana

Northern Cheyenne

and Crow Indian

Reservations

Wyodak-Anderson

Study Limit

Montana

Wyoming

0 30 60 Miles

Figure PQ-18. Uranium concentration in the Wyodak-Anderson coal 

zone, Powder River Basin, Wyoming and Montana.

N

 00'

 00'

 00' 00'
Table PQ-1. Summary data for coal in the Wyodak-Anderson coal zone in the

Powder River Basin, Wyoming and Montana. Calculated from the unpublished

U.S. Geological Survey coal quality database (USCHEM), February, 1992; Bragg

and others (1994); and proprietary source(s)

Variable Number Range Mean

of samples Minimum Maximum

Moisture 1300 14.50 42.30 27.66

Ash 1279 2.86 25.06 6.44

Total sulfur 1279 0.06 2.40 0.48

Calorific value 2277 3,740 9,950 8,220

lb SO2

3

277 0.14 7.88 1.24

MMMFBtu 4277 4,580 10,560 8,820

Antimony 5144 0.01L 17 0.49

Arsenic 5158 0.20L 19 2.6

Beryllium 5151 0.078L 3.3 0.54

Cadmium 5151 0.007L 3.0 0.21

Chromium 5161 0.59L 50 6.1

Cobalt 5160 0.38L 27 1.9

Lead 5162 0.50L 17 3.0

Manganese 5161 0.18 210 26

Mercury 5162 0.006L 27 0.13

Nickel 5161 0.71L 35 4.6

Selenium 5151 0.08L 16 1.1

Uranium 5157 0.11L 12 1.3

1

 Values are in percent and on an as-received basis.

2 Value is in British thermal units (Btu).

3 Value is in pounds per million Btu and on an as-received basis.

4 Value is in British thermal units on a moist, mineral-matter-free basis.

5 Values are in parts per million (ppm) on a whole-coal and remnant moisture

 basis; “L” denotes less than value shown.