The Occurrence of Minor 

Elements in Ash of LowRank Coal From Texas 

Colorado, North Dakota 

and South Dakota

GEOLOGICAL SURVEY BULLETIN 1036-H

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

The Occurrence of Minor 

Elements in Ash of LowRank Coal From Texas 

Colorado, North Dakota 

and South Dakota

By MAURICE DEUL and C. S. ANNELL

A CONTRIBUTION TO GEOCHEMISTRY

GEOLOGICAL SURVEY BULLETIN 1036-H

This report concerns work done on behalf 

of the U. S. Atomic Energy Commission 

and is published with the permission of 

the Commission

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1956
UNITED STATES DEPARTMENT OF THE INTERIOR 

Fred A. Seaton, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D. C. - Price 25 cents (paper cover)
CONTENTS

	Page 

Abstract______._-_____________________. ___ 155

Introduction.--__-__________________________-___--__-_--____--- _ 155

Samples.______________________._____________-- 156

Preparation of samples for analysis___--__-_________-____---___-_- _ 157

Analytical procedures.______________________________________ 157

Spectrographic analysis________________________________ ____ 158

Analytical data_______________________________________________ _ 159

Uranium. ________________________________________________ 161

Molybdenum. _ ____________ ____________________________ __ 162

Cobalt and nickel______________________________ __ 162

Vanadium.________________________________________________ _ 162

Chromium______________________________________________ __ 162

Strontium and barium____________________________ ____ ___ 163

Titanium______________________________________ 163

Manganese. ________________________________ __________ ___ 163

Boron___________________________-______-____ 163

Zirconium.____________________________________________ 164

Scandium___________________ ___________________________ 164

Germanium_____________-_______-_-___-__-- _ ._ 164

Tm__._____________. ____________________________________.__ 165

Lead______________________________________ 166

Copper_____________________________________________________ 166

Gallium. ______________________________________ 167

Other elements__________________________________________ _ 167

Interpretation of analytical results_________--____-__-_____--__ _ 167

Coal from the Dakotas_______________________________________ 167

Coal from Jefferson County, Colo_____________________________ 168

Coal from Milam County, Tex____________________________ 169

Summary_______________________________________________________ 169

Literature cited--__--__-__-___--____-___________-_-___--__-_-----_ 171

ILLUSTRATIONS

PLATE 2. Comparison of concentration of 18 minor elements in ash of

coal from five localities.___________________________ Facing 172

FIGURE 17. Ashed lignite from Milam County, Tex__-________________ 170

TABLES

TABLE 1. Channel samples of lignite from Harding County, S. Dak_ _ 158

2. Spectrographic analysis of selected samples of ashed lignite from

Harding County____________________________________ 159

3. Chemical analysis of selected samples of ashed lignite from

Harding County______________________________________ 159

4. Standard sensitivities for the elements in samples of coal ash

determined by the semiquantitative Spectrographic method.. _ 160

5. Maximum concentration, in percent, of minor elements detected

in samples of coal ash examined_________________________ 161

m

A CONTRIBUTION TO GEOCHEMISTRY

THE OCCURRENCE OF MINOR ELEMENTS IN ASH OF 

LOW-RANK COAL FROM TEXAS, COLORADO, NORTH 

DAKOTA, AND SOUTH DAKOTA

By MATJBICE DETIL and C. S. ANNEEL

ABSTRACT

The distribution of 27 minor elements in the ash of 319 samples of low-rank 

coal from five localities was studied to determine whether any elements were 

correlated with uranium in the coal and also whether any elements occurred in 

amounts large enough to be of commercial importance.

The coal samples were ashed in a muffle furnace at 800 °C, and semiquantitative 

spectrographic analyses were made of six channel samples to establish analytical 

control on ash of this type. The uranium was determined chemically by a 

fluorimetric method.

None of the coal shows any general enrichment of minor elements over coal 

from any other area. Boron, barium, and strontium are enriched in all the ash 

samples analyzed. A correlation between uranium and molybdenum exists only 

for the coal from the Dakotas where enrichment from ground water has been 

postulated. No other correlation is apparent. Sufficient data for 18 minor elements permits a graphic comparison of the coal from the five localities. Histograms show high concentrations of tin, copper, zirconium, boron, barium, and 

strontium in the coal from Milam County, Tex.

INTRODUCTION

A study of uranium-bearing coal is being conducted by the U. S. 

Geological Survey on behalf of the Division of Eaw Materials of the 

U. S. Atomic Energy Commission. Suites of coal samples from many 

localities have been analyzed for uranium and ash content. From 

them, five suites of samples from five localities were selected for spectrographic analysis for minor elements. This was done to determine 

whether any elements were correlated with uranium in the coal and 

also whether any elements occurred in amounts large enough to be of 

commercial importance.

155
156 CONTRIBUTIONS TO GEOCHEMISTRY

This report is a compendium on the minor elements found in the 

ash of some low-rank coal. A complete coverage of the literature on 

minor elements in coal ash is not within the scope of this report. 

Reference is made to the encyclopedic work of Gibson and Selvig 

(1944), Goldschmidt (1935, 1937, and 1954), Headlee and Hunter 

(1953), and Butler (1953) ; their work, and that of many others, has 

been chiefly concerned with higher-rank coal. Salmi (1950) has 

reported on the content of 10 minor elements in the ash of 50 samples of 

peat; his data can not readily be compared to the data for the ash of 

low-rank coal because the changes in the minor-element content of the 

peat reflect the composition of the mineral soil and bedrock in the 

neighborhood of the bogs.

Low-rank coal has not generally been studied in as much detail as 

has bituminous coal, and consequently most compilations of coal and 

coal-ash analyses make little or no reference to the lower-rank varieties, 

especially lignite. Gibson and Selvig (1944, p. 5-6) reported only 

two complete analyses of lignite ash. Most of the ash samples analyzed for this report were obtained from cored coal. The lignite 

from North Dakota and South Dakota and the subbituminous coal 

from Colorado were sampled in divisions ranging from 4 to about 12 

inches in thickness. The thickness was controlled by coal petrographic factors. Each lignite sample from Texas was a split of an 

entire core; bed thicknesses ranged from 2.5 to 19 feet. For this report 

6 complete chemical analyses were made of lignite ash, and 284 samples 

of lignite and 35 samples of subbituminous coal ash were analyzed 

spectrographically.

Many analyses for one or more elements occurring in coal-ash 

samples are contained in the literature, and complete coal-ash analyses 

for commercial-grade coal are commonly made (Selvig and Gibson, 

1945), but complete spectrographic analyses for minor elements in lowrank coal are lacking.

SAMPLES

Lignite from Harding County, S. Dak., occurs in the Ludlow member of the Fort Union formation of Paleocene age. Of the 151 samples 

taken in Harding County, six were from channels and 145 were from 

eight cored holes. Lignite from Bowman County, N. Dak., occurs in 

the Tongue River member of the Fort Union formation. All 26 

samples from this county were taken from four cored holes. The 

lignite from Perkins County, S. Dak., also occurs in the Tongue River 

member of the Fort Union formation. All 59 samples from this 

county came from five cored holes. Subbituminous coal frpm Jef.-
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 157

fersori County, Colo,, occurs .in the Laramie formatipn; of Late 

Cretaceous age. All 35 samples from Jefferson County were from 

three cored holes. Lignite from Milam County, Tex., occurs in the 

Wilcox formation of early Eocene age. Each of the 48 samples from 

Milam County represents an entire coal core.

Four samples from McKenzie County, N. Dak., furnished by the 

Boukal-Noonan Coal Co., were analyzed as shown in table 5 to provide a comparison of nonuraniferous lignite with uraniferous lignite 

from the Dakotas.

PREPARATION OF SAMPLES FOR ANALYSIS

The coal samples were crushed in a Blake-type jaw crusher to 

minus one-fourth inch. A split of minus one-fourth-inch material 

was oven dried at 105 °C so that the sample could be pulverized to 

 80 mesh in a 6-inch disc grinder; undried material could not be 

pulverized in this type of grinder because the moist sample accumulates on the disc surfaces. Usually about 100 grams of 80-mesh 

material was prepared. A 1- to 2-gram sample of the pulverized 

coal was ashed in a muffle furnace at 800°C.

ANALYTICAL PROCEDURES

Six channel samples from Harding County, S. Dak. (p. 156 and 

table 1), were selected for chemical and spectrographic analysis of 

the ash. The samples were chosen from the 435 samples collected 

by N. M. Denson, G. O. Bachman, and H. D. Zeller of the U. S. 

Geological Survey in 1950. These samples were analyzed to determine the variability of the percentage of the major and minor constituents of the ash and also to determine whether the standard ashing 

methods used by the U. S. Bureau of Mines, as described by Fieldner 

and Selvig (1951, p. 7, 44), were suitable for preparation of the ash 

for uranium analysis. The uranium determinations, using the procedure developed by Guttag and Grimaldi (1954), were in no way 

hampered by the standard ashing method adopted. These six samples 

were selected for this purpose because: two from the same locality 

had the same percentage of ash but differing uranium percentages 

(samples SC-35 and SC-36), two from the same area had the same 

uranium content but differing ash percentages (samples F-95 and 

F-84), and one each from two areas was similar in uranium content 

of the ash to a sample from one of the pairs (S-29 and SC-35, and 

C-18b and SC-36).
158 CONTRIBUTIONS TO GEOCHEMISTRY

TABLE 1. Channel samples of lignite from Hardiny County, S. Dak.

[Analysts: W. Tucker, J. Warr, and J. J. McGee]

Sample no.

SC-35-. ... 

SC-36 _

F-95 ......

F-84 .... ..

C-18b. ......

S-29- _

Laboratory no.

47933

47934

42921

42922

44269

45367

Uin 

dry coal 

(percent)

0.028

.014

.012

on^

.018

.030

Ash in 

dry coal 

(percent)

25.1

25.2

32.1

if; 1

OA Q

25.5

Uin ash 

(percent)

0.116

.056

.035

.033

.053

.12

Thickness of 

bed sampled 

(feet)

3.5

3.5 

1.2-. 

2.8.. 

1

1.75- 

Location

South Cave Hills, NEJiSWM sec. 20, T. 20 N., R. 

5E. 

Do.

SEM sec. 5, T. 22 N., R. 4 E. 

Do.

North Cave Hills, N W^SWM

sec. 19, T. 22 N., R. 7 E. 

Slim Buttes area, NWMSEM

sec. 1, T. 17 N., R.7E.

The spectrographic analyses of these six samples (table 2) showed 

unexpectedly high percentages of barium, strontium, nickel, cobalt, 

zirconium, and molybdenum. These elements were determined 

chemically as a check on the spectrographic analyses, and the complete chemical analyses, along with ash and uranium determinations, 

are given in table 3.

SPECTROGRAPHIC ANALYSIS

The spectrographic analyses of the coal ash were made following a 

method described by Waring and Annell (1953). The equipment 

used was a 21-foot grating spectrograph with a d-c arc. A semiquantitative method of analysis was used by which the concentration of the 

elements was reported within limits differing by a factor of 10 (i. e., 

0.001-0.01 percent, 0.01-0.1 percent, etc.).

There are no determinations listed for elements, such as sulfur and 

chlorine, which have been reported in lignite ash (Gibson and Selvig, 

1944, p. 9). The spectral sensitivities for 68 elements, as shown by 

table 4, vary widely and if some of these elements were present in 

lignite ash they occurred in concentrations too low to be detected. 

The elements for which no determinations could be made using this 

one-exposure method are listed below:

Halogens: F, 01, Br, I, At

Gases : H, O, N, He, Ne, A, Kr, Xe, Rn

Others: S, Se, C, Tc, Pm, Po, Fr, Ra, Ac, Pa

Table 4 lists the standard sensitivities for the elements determined 

by the semiquantitative spectrographic method and also the crustal 

abundances of the elements as compiled by Mason (1952, p. 41). 

Comparison of the maximum concentration of the elements (table 5) 

and the histograms to the abundances in table 4 makes it possible to
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 159

TABLE 2. Spectr&graphic analysis of selected samples of ashed lignite from 

Harding County, S. Dak. (in percent)

Sample 

no.

SC-35- 

SC-36.- 

F-95- .

F 84 

O-18b ... 

S-29--- 

More than 

10

Fe 

AL ...

Fe,Si, Al--

Fe, Si, Al--

Fe -

10-1

Al, Ca, Na, 

K, Si.

Fe, Si, Ca, Na.

Ca, Na .... -

Na, Ca 

Na, Fe, Mg, 

Ca, Al, Si.

Al, Na, Si,

Ca, K.

1.0-0.1

Mg, Mo, Sr, 

Mn, Zr.

Mg, K, Sr,

Mo, Mn, 

Ba.

Mg, Mn, Ni,

Sr, K, Zr, 

Co, Ti.

Mo, Ni, Ti, 

Zr. 

K, Sr, Ba.... -

Mg, Mo, Sr 

0.1-0.01

B, Ti, Ba, Ni, 

Pb, Co, Sc, 

Ga, V. 

B, Ti, Zr, Ni,

Pb, Co, Sc. 

Ba, Mo, Pb, Sc,

Y, V, Qa, B.

Pb, Sc, Y, V, 

Qa. 

Mo, Zr, Ti, Mn, 

Ni, Pb, Sc, 

Qa, B. 

B, Mn, Ti, Ba,

Ni, Pb, Co, 

Sc, Qa.

0.01-0.001

Y, Cr, Cu~. 

V, Qa, Y,

Cr, Cu. 

Cr, Cu 

V, Cr, Y, 

Cu.

V, Zr, Y.

Cr, Cu.

0.001-0.0001

Yb.

Yb.

Yb.

Yb.

Yb. 

Yb.

TABLE 3. Chemical analysis of selected samples of ashed lignite from Harding

County, S. Dak.

[Analyst: A. M. Sherwood]

Sample no.

LOI (1,000°C) .__ . _

SiOi. 

AlaOs .... .

FeaOs........ .............................

TiOs 

CaO ...

MgO-- ...... .- _ - . .

K2 O .

NasO _ -

MnO . ..

80s «. ...... . . . . ..

BaOj 

8rO»-. .... . .. 

NiO» ..... ........... .....

CoO 2

ZrOa 2 -

MoOs 2 --.

Ashs. _ .............. ---.. .. .---..

SC-35

3.32

9.64

14.75

22.50

.10

20.15

.12

1.11

3.14

.26

29.00

100.67

25.07

SC-36

5.62

21.76

23.80

12.40

.10

14.35

.18

1.11

3.45

AQ

100. 45

25.17

F-95

2.10

32.18

21.85

31.20

.60

10.80

.21

.82

1.90

1.01

1.35

.05

102. 39

32.1

F-84

7.80

28.46

19.60

33.81

.60

4.00

.21

.82

3.55

.26

4.68

95.99

15.1

C-18b

2.30

11.58

12.90

14.40

.10

14.70

7.30

.92

24.88

.05

13.40

.30

.53

101.06

34.82

S-29

7.30

15.20

17.65

34.50

.10

12.00

.23

1.54

4.38

.14

9.23

.23

95.20

25.53

1 The sulfur is calculated as SCh although part of the sulfur is present as sulflde and possibly sulflte. 

Inasmuch as varying conditions of ashing would result in different losses of sulfur and in varying proportions 

of sulflde, sulflte, and sulfate residues, it was not considered necessary to determine the exact form of the 

sulfur. Under these circumstances summation to 100 percent is not possible.

2 These determinations were made as spot checks only as listed.

3 From table 1.

determine the maximum enrichment of any element reported in these 

samples of coal ash. The writers believe little is to be gained by 

computing maximum, minimum, and average enrichments from semiquantitative analytical data; without considering the geochemical 

factors, numerical enrichment factors may be quite misleading.

ANALYTICAL DATA

In this report, all elements present in the earth's crust in weight 

percentages greater than 1 percent are considered major elements and

387604 56 2
160 CONTRIBUTIONS TO GEOCHEMISTRY

will not be described in detail. Eight major elements oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium 

comprise more than 98 percent of the earth's crust and are present in 

coal ash in about the same aggregate percentage. Coal represents a 

geochemical concentration of carbon and hydrogen, and, although its 

ash differs little from rocks of the earth's crust in gross chemical 

composition, it is not surprising that some elements are concentrated 

in coal ash when the geochemical history of coal is considered.

TABLE 4. Standard sensitivities for the elements in samples of coal ash determined by the semiquantitative spectographic method of Waring and Annell 

(1953), with crustal abundances of the elements (Mason, 1952)

[The standard plates were prepared with elemental concentrations differing by a factor of 10; hence, some 

elements were detected below the sensitivities listed but not necessarily to the next lower value. All 

elements detected below standard sensitivities were reported. All data in weight percent.]

Element

Sensitivity Abundance

Element

Sensitivity Abundance

Element

Sensitivity Abundance

Minor elements (0.82 percent of crust)

^g As

B

Ba

Be

Co

Cu

Or

Qa

0.0001

.1

.001

.0001

.0001

.01

.0001

.001

.01

0.00001

.0005

.0003

.025

.0006

.0023

.007

.020

.0015

Qe

La

Lii

Mo

Mn

Ni

P

Pb

Sc

0.001

.01

.0001(0.1)

.001

.001

.01 .1

.01

.001

0.0007

.0018

.0065

.0015

.10

.008

.118

.0016

.0005

Sn

Sr

Ti

U

V

Y

Yb

Zn

Zr

0.01

.01

.001

.1

.01

.001

.0001

.01

.001

0.004

.03

.44

.0004

.015

.0028

.00027

.0132

.022

Major elements (51.99 percent of crust; 98.59 percent including oxygen)

Al

Ca

0. 0001 

.001

8.13 

3.63

Fe 

KI

0.001 

.01(1.0)

5.00 

2.59

Nai 

Si

0.001(0.1) 

.0001

2.83 

27.72

Elements not detected

Au

Bi

Od

Ce Csi

gy

Eu

Er

F2

Qd

Hf

Hg

0.01

.001

.01

1

.1(1.0)

.01

.01

.01 .1

.01 .1.1

Ho

In

Ir

Lu

Nb

Nd

Os

Pd

Pr

Pt Rbt

Re

0.01

.001

.1

.01

.01

.01 .1

.01

.01

.01

.01(10.0)

.1

Rh

Ru

Sb

Sm

Ta

Tb

Te

Tb.

Tl

Tm

W

0.01

.01

.01

.1

.1

.01

.1

.1

.1

.01 .1

1 A second exposure is required for the high sensitivity listed. 

! A special exposure is required for the fluorine estimation.

Twenty-seven minor elements have been detected in the ash of the 

samples of low-rank coal discussed in this report. Sufficient data 

for 18 of these elements permit a graphic presentation as histograms 

(pi. 2) of the analyses for each of the five localities from which coal 

samples were taken.
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 161

TABLE 5. Maseimum concentration, in percent, of minor elements detected in 

samples of coal ash examined

Number of 

samples

151

59

26

4

35

48

Locality

Dak.

Dak.

Dak.

Dak.

Colo. 

. Milam County, Tex...

10-1

P

1.0-0.1

Ti, Mo, Co, 

Ni, Zn, As, 

Pb, Zr, Be, U. 

B, Ba, Sr, P, Ti,

Mo, Zr, U.

B, Ba, Sr, Mn,

Ti, As, Pb, V, 

Zr. 

B, Ba, Sr, Mn,

Pb.

B, Ba, Sr, Mn,

Ti, Mo, Y.

B, Ba, Sr, Mn, 

Ti, Ni, Sn.

0.1-0.01

Cu, Or, V, Li,

Y, La, Ga, Ge,

Sc.

Cu, Or, V, Ni,

Co, Pb, Mn, 

Qa, Ge, Zn, 

La.

Cu, Cr, Mo, Ni,

Co, Ga, Ge, U. 

Ti, V, Cu, Li,

Sn, La, Zr, Co. 

Cu, Cr, V, Ni,

Co, Zr, Pb.

Cu, Cr, V, Co, 

Pb,Zr,Zn,Y.

0.01-0.001

Sn......... ...

Y, Sc, Sn.....

Y, Sc, Sn.....

Y, Mo, Ga,

Qe, Ni, Cr.

Sn, Sc, Ga, U,

Ge, La, Yb, 

Be. 

Mo, Sc, Ga, 

Ge, Be,Yb.

0.001- 

0.0001

Yb, Ag.

Be, Yb,

Ag. 

Be, Yb.

Be, Yb.

TTBANIUM

The coal from the Dakotas is from suites that contain samples 

enriched in uranium. The uranium is believed to have been concentrated from percolating ground water carrying uranium in solution (Denson, Bachman, and Zeller, in preparation). All these coal 

samples occurred in the same geologic environment and had a similar 

geochemical history. The cored coal from Harding and Perkins 

Counties, S. Dak., is from thicker beds than the cored coal from the 

Medicine Pole Hills area in Bowman County, N. Dak. Where present in thick coal beds uranium is generally concentrated near the top 

with the uranium content dropping to less than 0.001 percent in the 

middle and lower parts of the seam. Most of these samples contain at 

least 0.001 percent uranium in the ash.

The samples of coal from Jefferson County, Colo., showed a relatively low uranium content; 22 percent of the samples contained less 

than 0.001 percent uranium in the ash and 78 percent of the samples 

contained no more than 0.01 percent uranium in the ash.

The lignite from Milam County, Tex., showed such a low radioactivity that uranium determinations were not made.

In general, these coal ash samples, with the exception of those from 

Milam County, Tex., show an enrichment of uranium greater than the 

average percentage in the earth's crust. Other coal deposits, especially eastern anthracite and bituminous, are low in uranium content 

and their ash contains uranium in about the same, or lower, percentages as that in the earth's crust.
162 CONTRIBUTIONS TO GEOCHEMISTRY

MOLYBDENUM

Molybdenum occurs in ash of these low-rank coal samples from 

the Dakotas in percentages somewhat higher than that in the earth's 

crust. The highest concentration of molybdenum which Goldschmidt 

(1954, p. 559) reported was 0.05 percent in the ash of coal from 

Northumberland. One sample of this low-rank coal ash, sample S-29 

in table 3, shows a concentration of molybdenum 100 times that in 

the earth's crust, using the abundance estimate of Mason (1952, 

p. 41). Using the estimate of 1±0.5 parts per million given by 

Kuroda and Sandell (1954, p. 46), these coal-ash samples contain 

concentrations of molybdenum as much as 1,500 times the average 

for crustal rocks.

A possible explanation for the high molybdenum content of the 

coal samples from the Dakotas is that the molybdenum was transported in the same solutions which carried uranium into the coal. 

?fhe histograms for molybdenum for the coal from Harding and 

Perkins Counties, S. Dak., closely resemble the histograms for 

uranium, and this comparison is supported by individual coal-ash 

analyses which show that a high uranium content parallels a high 

molybdenum content. The erratic distribution patterns of uranium 

and molybdenum in the thin seams of coal from Bowman County, 

N. Dak., may be due to greater irregularities in the entry and migration of mineralized ground water in thin seams of coal.

COBALT AND NICKEL

The relative abundances of cobalt and nickel are reflected in the 

histograms which show that nickel is below the limit of detection 

(0.01) in only 6 samples, whereas cobalt is below the same limit of 

detection in 58 samples. No unusual concentrations of cobalt or 

nickel are apparent in the samples examined.

VANADIUM

Vanadium, one of the generally more abundant minor elements, 

is present in these coal samples in relatively low concentrations. Only 

in the ash of coal from Milam County, Tex., does the percentage 

of vanadium approach the abundance of vanadium in the earth's 

crust.

CHROMIUM

All the samples of coal ash contained chromium in detectable 

amounts, but none of the ash showed an appreciable enrichment of 

chromium over that in the earth's crust. Chromium may be enriched
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 163

in some of the individual components of the lignite from Milam 

County, Tex., but gross sampling of an entire coal core did not permit 

the careful study that proof of this would require. Similarly, the 

Milam County lignite may show greater enrichments for more than 

one element, and it is discussed separately in this report on page 169.

STRONTIUM AND BARIUM

Very few data are in the literature regarding the percentage of 

strontium in coal ash. This is in contrast to the abundant data for 

barium in coal ash and is not what would be expected considering the 

greater abundance of strontium. The coal ash analyzed for this study 

showed that strontium is about as abundant as barium and that both 

elements are enriched in coal ash as compared with the crustal rocks. 

Sample C-18b (table 3) which was chemically analyzed for both elements showed a SrO content of 0.53 percent and a BaO content of 

0.30 percent. Goldschmidt (1954, p. 249) quotes Noll's figure of 100 

to 200 ppm SrO in coal ash but this is not in agreement with the data 

of this report and of Headlee and Hunter (1953, p. 549), which coincidentally averages for 35 column analyses of coal ash 0.54 percent 

SrO, and 0.31 percent BaO.

TITANIUM

Twenty-seven minor elements have been detected in the ash of the 

coal samples examined and they comprise only 0.82 percent by weight 

of the earth's crust. More than half of this amount is titanium. The 

analyses of these coal samples show that titanium is present in the 

ash of low-rank coal in about the same abundance as in the earth's 

crust.

MANGANESE

The average concentration of manganese in these ash samples of 

coal is low, somewhat less than 0.1 percent which is the abundance of 

manganese in the crustal rocks. This is in agreement with the data of 

Headlee and Hunter (1953, p. 549) who, for 16 major coal seams in 

West Virginia, have determined the average manganese content to be 

0.037 percent in the ash. Goldschmidt (1954, p. 639) gives preferential leaching of manganese under reducing conditions as the reason for 

the relatively low proportion of manganese to iron in reduced sediments.

BORON

The boron content of ash of these low-rank coals is high, averaging 

more than 0.1 percent (more than 1,000 ppm). This enrichment of 

boron is considerably higher than that in the earth's crust. Boron is
164 CONTRIBUTIONS TO GEOCHEMISTRY

perhaps the only element in coal ash which is directly attributable to 

the living plants which were the progenitors of coal.

Much information regarding boron in the ash of coal from various 

places is in the literature. Coal from Svalbard with an unusually high 

percentage of boron, as much as 2 percent in the ash, has been reported 

by Butler (1953, p. 11). Headlee and Hunter in their study of 16 

major coal seams in West Virginia (1953, p. 549) report an average 

of 0.035 percent boron for coal ash.

ZIRCONIUM

The zirconium content of the ash of the low-rank coal studied is 

highly variable, ranging from less than 0.001 to more than 0.1 percent. 

Undoubtedly some of the zirconium occurs as detrital zircon, but not 

all of the zirconium can be accounted for in this way.

Goldschmidt (1935, p. 1101) reports as much as 0.5 percent zirconium in the ash of coal, and Headlee and Hunter (1953, p. 549^ 

report a maximum of 0.089 percent ZrO2 in ash from a cube of coal 

from West Virginia. Butler (1953) reports from 0.004 to 0.11 percent zirconium in ash of coal from Svalbard. Sample F-95 (table 

3) contains 0.27 percent ZrO2. The histograms show that the average 

zirconium content of these ash samples is in the hundredths of a 

percent.

SCANDIUM

The data for the occurrence of scandium in coal ash are scant except 

for Goldschmidt's estimate (1954, p. 305) ranging from 0.004 to 0.026 

percent scandium in coal ash. The scandium content of the ash of 

the samples of low-rank coal examined for this report ranges from 

less than 0.0001 percent to 0.01-0.1 percent, which is in general agreement with Goldschmidt's findings.

GERMANIUM

Germanium is an element that most persons associate with coal ash, 

and the many recently published papers on germanium in coal ash 

(Stadnichenko and others, 1953, p. 11-12) show the interest in this 

element. The study of the ash of these samples of low-rank coal 

proved none to be highly germaniferous, and indeed in most of the 

samples of coal ash that were analyzed germanium was either not 

present or was below the limit of detection. Germanium tends to be 

concentrated in the upper or lower parts of coal seams or along 

partings in a coal seam (Stadnichenko and others, 1953, p. 6} and 

this is the relationship indicated in this study of low-rank coal.
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 165

The abundance of germanium in crustal rocks is 0.0007 percent 

and the average germanium content in the ash of these samples of 

low-rank coal is probably no higher. Only 4 of the 319 samples 

analyzed contained more than 0.01 percent germanium in the ash. 

The 35 columns of coal from West Virginia analyzed by Headlee and 

Hunter (1953, p. 549) contained an average of about 0.01 percent 

germanium in the ash.

To insure that the percentages of germanium in the coal ash were 

not abnormally low because of loss of germanium during ashing, as 

reported by earlier writers, experiments were designed to investigate 

the loss of germanium during ashing at temperatures as high as 

1,000°C. Waring and Tucker (1954) demonstrated that there were 

no losses in germanium when coal ash was prepared at 800 °C by the 

standard method (Fieldner and Selvig, 1951, p. 44). Their findings 

are confirmed by the work of Hawley (1955, p. 519). Aubrey and 

Payne (1954) did not report on ashing losses of germanium throughout the temperature range used by Waring and Tucker, but they did 

test the samples at 900°C, with no preheating. These samples showed 

a loss of as much as 20 percent germanium.

The geochemical cycle of germanium is not well understood because 

of the low percentage of germanium found in most rocks analyzed 

(Fleischer, 1955, p. 148). A clue to the behavior of germanium is 

contained in tabl^ 3 of a report by Breger, Deul, and Rubinstein 

(1955, p. 213) wh.ere spectrographic analyses of the ash of lignite 

and of sink-and-float separates show germanium to be present only 

in the sink fraction, composed essentially of the secondary minerals 

gypsum and jarosite, and not detectable in the original coal or in the

organic separate. Goldschmidt, with his intuitive understanding of

these problems, predicted this in his treatise on geochemistry (1954, 

p. 388), in which he states,

It is therefore reasonable to expect that germanium dioxide during weathering 

enters into ionic aquepus solution more readily than silica.

Searching for an explanation as to why silica deposits, formed from 

nonvolcanic aqueous solutions connected with the processes of weathering and sedimentation, contain no detectable germanium, Goldschmidt 

concludes,

It would appear thaft there must be one or more powerful precipitants for 

germanium in the course of soil formation and sediment formation, which 

prevent germanium f^om being collected either in sedimentary silica precipitation or in sea water.

TIN

Tin shows an erratic distribution pattern in the samples of low-rank 

coal studied. It w|as detected in only 7 of 151 samples from Harding
166 CONTRIBUTIONS TO GEOCHEMISTRY

County, S. Dak., yet it was found in all 48 samples from Milam 

County, Tex., and 5 of these samples contained from 0.1 to 1.0 percent 

tin.

The occurrence of tin in such relatively high concentrations in the 

Milam County, Tex., coal is difficult to explain without additional 

investigation. Separating mineral matter from the coal might show 

where the tin is concentrated, but rather than work with a sample of 

a whole coal seam it would be more desirable to select a coal increment 

which has a concentration of tin. A high concentration of tin is to 

be expected in such an increment if a sample from a thickness of several feet of coal contains as much as 0.1 to 1.0 percent tin.

Goldschmidt (1937, p. 669) reports a maximum concentration of tin 

of about 0.05 percent in coal ash, and Headlee and Hunter (1953, p. 

549) report a maximum of 0.15 percent tin in the ash of a cube of coal 

from West Virginia.

LEAD

Lead shows an erratic distribution pattern for the ash of samples of 

low-rank coal, much like tin, but, unlike tin, it is present in detectable 

percentages in most samples. Weathering may have been a factor 

in the occurrence of lead in the coal of the Dakotas, where uranium 

and perhaps molybdenum, lead, and other migrating elements were 

leached from the overlying tuffaceous rocks. Lead in coal from 

HardingCounty, S. Dak., (Breger, Deul, and Rubinstein, 1935, p. 213) 

is shown to have been present mostly in the minerals separated from 

the coal by sink-and-float techniques, and this is in direct contrast to 

other coal in which Deul (1955) has found lead to be concentrated with 

the organic separates.

Goldschmidt (1935, p. 110) has found a maximum of 0.1 percent 

lead in coal ash, and Headlee and Hunter (1953, p. 549) have found in 

coals from West Virginia a maximum of 0.24 percent and an average 

of 0.045 percent lead. Gibson and Selvig (1944, p. 12) report occurrences of coal with much higher percentages of lead but the coal has 

obviously been mineralized by ore-bearing fluids.

COPPER

The concentrations of copper in the ash of samples of low-rank, 

unmineralized coal appear to be uniformly low. Goldschmidt (1954, 

p. 184) found a maximum copper content of only 0.05 percent in coal 

ash, and Headlee and Hunter (1953, p. 549) show this concentration to 

 be about average for coal from West Virginia. For coal from Svalbard, Butler (1953, p. 11) found a maximum of 0.02 percent copper 

in the ash and found most samples below 0.01 percent. The coal from
MINOR ELEMENTS IN ASH OF LOW-RANK COAL

Milam County, Tex

other coal and will

The enrichment

167

:., has a somewhat higher copper content than the 

be discussed on page 169.

GALLIUM

of gallium in coal ash has been known since Goldschmidt's classic work. Almost every sample of low-rank-coal ash 

showed an enrichment of gallium greater than the percentage in 

 crustal rocks. All available comparative data show that gallium is 

more abundant in <poal ash than in rocks.

OTHER ELEMENTS

Beryllium, yttri urn, and ytterbium occur in almost every sample of 

the low-rank-coal ^ish examined. Beryllium is usually present in the 

lowest reported raiige, 0.001 to 0.0001 percent. Ytterbium is usually 

present in the same low range, and yttrium is usually in a somewhat 

higher range. As shown in table 5, these elements reach a maximum 

percentage range piat is unusual, but the variation in the data is 

insufficient to pernjiit an evaluation that is geochemically significant.

Some elements have such relatively poor spectral sensitivities by 

this single-exposure semiquantitative method that insufficient information was provided to permit a meaningful graphic presentation. 

In most of the coal ash, phosphorus, arsenic, lithium, lanthanum, and 

zinc were not present in percentages high enough to be detected.

Silver has an extremely high spectral sensitivity, but is detected in 

only a few of the coal ashes in the lowest percentage range, 0.001 to 

0.0001.

INTERPRETATION OF ANALYTICAL RESULTS

The results of tie geochemical study of the occurrence of minor 

elements in the as'i of low-rank coal are in general agreement with 

the results of detailed geologic investigations. The geology of the 

coal from the Dakotas and of the Jefferson County, Colo., coal has 

been recently studied; detailed regional studies of the coal from the 

Dakotas were being conducted by the Geological Survey in 1955. The 

Milam County, Tex., coal is, in minor element content, perhaps the 

most interesting coal, yet less detailed information on its occurrence 

is available and sampling has been less detailed than for any other 

coal discussed in tlnis report.

COAL FROM THE DAKOTAS

Lignite from Hording and Perkins Counties, S. Dak., and from 

Bowman Comity, ]$. Dak., is much weathered in outcrops; abundant 

gypsum and jarosite are formed from oxidation of pyrite. Rarely is"
168 CONTRIBUTIONS TO GEOCHEMISTRY

pyrite found in exposed lignite beds. Several samples of cored coal 

obtained from each of the counties were pulverulent and crumbly. 

Denson and his co workers (in preparation) postulated that the source 

of the uranium was in the overlying Oligocene and Miocene strata of 

the White River group and the Arikaree formation, respectively, and 

that the uranium was leached from these rocks and transported by 

circulating ground water. Mechanisms by which uranium could have 

been introduced into the coal by ground water have been discussed by, 

Breger, Deul, and Kubinstein (1955, p. 224-225) and by Breger, Deul, 

and Meyrowitz (1955, p. 620, 621) in reports on the geochemistry and 

mineralogy of a sample of uraniferous lignite and a sample of uraniferous subbituminous coal. These mechanisms and Denson's theory 

require the coal to be in contact with ground water and at least a 

limited circulation of water through the coal.

Some of the elements, both minor and major, must have been added 

to the coal from the Dakotas by circulating ground water. Uranium 

and molybdenum and their apparent parallel relationship have been 

discussed in the molybdenum section of this report. Uranium is correlated with no other minor element in the coal, but it is not unlikely 

that other elements were added or removed from the coal by circulating 

ground water. Although vanadium-bearing uranium minerals have 

been found in sandstone overlying the coal at Slim Buttes, Harding 

County, S. Dak., vanadium is not a controlling factor in the fixation 

of uranium by the coal and no vanadium and uranium correlation is 

apparent.

The histograms for cobalt and nickel for the ashed coals from the 

Dakotas are distinctly different from the histograms for the ashed 

coals from Texas and Colorado, which are similar to each other. The 

differences are certainly a reflection of the geochemical histories of 

the coal, but there is no evidence from these data that the distribution 

patterns of cobalt and nickel are not due to modification of their distribution before weathering of the coal. Barium and strontium provide 

an interesting contrast to cobalt and nickel and to each other in that 

the distribution pattern for strontium is similar in all five localities, 

but that the barium distribution shows no dependence on the source of 

the samples.

COAL FROM JEFFERSON COUNTY, COLO.

The coal in Jefferson County, Colo., which has been known since 

1875 to contain uranium, has been studied in detail by the Geological 

Survey. The coal bed is cut by a shear zone and the uranium is 

believed to have been derived from hydrothermal solutions.1 MinA. J., 3d, and McKeown, F. A., Results of exploration at the Old Leyden coal 

mine, Jefferson County, Colo. : U. S. Geol. Survey Trace Elements Memo. Rept. 292 (openfile rept.), 1953.
MINOR ELEMENTS IN, ASH OF LOW-RANK COAL 169

eralization of the coal, except for silicification, was weak; molybdenum is the only element that reaches a concentration high enough to 

indicate hydrothermal enrichment, except for uranium which occurs 

in concentrations below 0.01 percent in the ash. Vanadium, associated with the uranium in the rocks in which the coal occurs, is 

not enriched in this coal although it is present in higher percentages 

than uranium. A few samples of coal containing as much as 0.1 

percent uranium are reported by Gude and McKeown, but these are 

exceptional.

COAL FROM MILAM COUNTY, TEX.

The ashed lignite samples from Milam County, Tex., show uniformly high concentrations of copper, zirconium, boron, and tin. This 

lignite may provide samples of smaller bed thickness which have substantially higher concentrations of these and other elements. Figure 

17 shows the distribution of eight elements, each within a narrow percentage range. Such a uniformity of distribution is likely to be the 

reflection of an averaging effect of using as a sample a split of core 

from a full bed thickness of coal. Nevertheless the high concentration of tin is worthy of note.

SUMMARY

These data show the occurrence of 27 minor elements in the ash of 

samples of low-rank coal. The 319 ash samples analyzed were 

enough to permit a graphic presentation of the data. The general 

agreement with data obtained by other workers for most of these 

elements shows that, for coal from any one of the areas studied, there 

has not been any general elemental enrichment over that for coal 

from other areas. Certain elemental concentrations are apparent and 

these concentrations, on the basis of geological evidence, can be related 

to certain stages in the geochemical history of the coal. Boron is 

an element that is concentrated from the soil by living plants and 

is not lost during degradation of plant tissues in the early stages of 

coalification, hence the high concentration of boron in all these samples 

of coal ash. The addition of uranium and molybdenum to the coal 

from the Dakotas during a cycle of weathering by ground water is 

reflected in their distribution in the ash of this coal as compared to 

the coal ash from the other two areas. The coal from the Dakotas 

shows a correlation of molybdenum with uranium; from these data 

there is no detectable correlation of uranium with any other element. 

The unusual concentrations of tin, zirconium, and copper found in the 

coal from Milam County, Tex., probably represent elements com-
170 CONTRIBUTIONS TO GEOCHEMISTRY

^ 1000'

TOO'

TO'

100'

10'

fl 100'

10'

n

TOO'

JI

TO'

TOO'

10'

II

TOO'

TO'

TOO'

in8

8 I

SBHdWVS JO lN30y3d
MINOR ELEMENTS IN ASH OF LOW-RANK COAL 171

bined with the organic matter during degradation of the organic 

matter and during compaction and burial.

It is our experience that the most useful geochemical minor-element 

data are to be obtained from the analysis of the ash of a whole coal 

and of the ash of the mineral and organic separates derived from the 

original coal.

LITERATURE CITED

Aubrey, K. V., and Payne, K. W., 1954, Volatilization of germanium during the

ashing of coal: Fuel, v. 33, p. 20-25. 

Breger, I. A., Deul, Maurice, and Meyrowitz, Robert, 1955, Geochemistry and

mineralogy of a uraniferous subbituminous coal: Econ. Geology, v. 50,

p. 610-624, 

Breger, I. A., Deul, Maurice, and Rubinstein, Samuel, 1955, Geochemistry and

mineralogy of a uraniferous lignite: Econ. Geology, v. 50, p. 206-226. 

Butler, J. R., 1953, Geochemical affinities of some coals from Svalbard: Norsk

Polarinstitut, Skr. 96, 26 p. 

Denson, N. M., Bachman, G. O., and Zeller, H. D., 1956(?) ; Uranium-bearing

lignite in northwestern South Dakota and adjacent states: U. S. Geol.

Survey Bull. 1055-B [in preparation]. 

Deul, Maurice, 1955, The origin of ash-forming ingredients in coal [abs.]: Econ.

Geology, v. 50, p. 103-104. 

Fieldner, A. C., and Selvig, W. A., 1951, Methods of analyzing coal and coke:

U. S. Bur. Mines Bull. 492.

Pleischer, Michael, 1955, Estimates of abundances of some chemical elements and 

 their reliability, in Poldervaart, Arie [ed.], Crust of the earth: Geol. Soc.

America, Special Paper 62, p. 145-154. 

<Jibson, F. H., and Selvig, W. A., 1944, Rare and uncommon chemical elements

in coal: U. S. Bur. Mines Tech. Paper 669. 

Goldschmidt, V. M., 1935, Rare elements in coal ashes: Indus, and Eng. Chemistry,

v. 27, p. 1100-1102.

 1937, The principles of distribution of chemical elements in minerals and 

rocks: Chem. Soc. London Jour. 1937, pt. 1, p. 655-673.

 1954, Geochemistry [edited by Alex Muir], London, Oxford Univ. Press.

Guttag, N. S., and Grimaldi, F. S., 1954, Fluorimetric determination of uranium 

in shales, lignites, and monazites after alkali carbonate separation, in 

Grimaldi, F. S., and others, Collected papers on methods of analysis for 

uranium and thorium: U. S. Geol. Survey Bull. 1006, p. 111-119.

Hawley, J. E., 1955, Germanium content of some Nova Scotia coals: Econ. 

Geology, v. 50, p. 517-532.

Headlee, A. J. W., and Hunter, R. G., 1953, Elements in coal ash and their industrial significance: Indus, and Eng. Chemistry, v. 45, p. 548-551.

Kuroda, P. K., and Sandell, E. B., 1954, Geochemistry of molybdenum: Geochimica et Cosmohimica Acta, v. 6, p. 35-63.

Mason, Brian, 1952, Principles of geochemistry, New York, John Wiley and Sons.

Salmi, Marti, 1950, Trace elements in peat: Geol. Tutkimuslaitos, Geotek. julkaisuja, v. 51, p. 1-20; see also Chem. Abs., v. 45, p. 6976 (1951).

Selvig, W. A., and Gibson, F. H., 1945, Analyses of ash from coals of the United 

States: U. S. Bur. Mines Tech. Paper 679.
172 CONTRIBUTIONS TO GEOCHEMISTRY

Stadnichenko, Taisia, Murata, K. J., Zubovic, Peter, and Hufschmidt, E. L., 1953,

Concentration of germanium in the ash of American coals: a progress report:

U. S. Geol. Survey Circ. 272. 

Waring, C. L., and Annell, C. S., 1953, A semiquantitative spectrographic method

for analysis of minerals, rocks, and ores: Anal. Chemistry, v. 25, p. 1174-1179. 

Waring, C. L., and Tucker, W. P., 1954, Effect of ashing temperature on the

volatility of germanium in low-rank coal samples: Anal. Chemistry, v. 26,

p. 1198-1199.

O