GEOLOGICAL SURVEY CIRCULAR 541 

Gold-bearing Sedimentary Rocks 

In Northwest WyomingA Preliminary Report 

Gold-bearing Sedimentary Rocks 

In Northwest WyomingA Preliminary Report 

By J. C. Antweiler and J. D. Love 

GEOLOGICAL SURVEY CIRCULAR 541 

Washington 1967 
United States Department of the Interior 

STEWART l. UDAll, Secretary 

Geological Survey 

William T. Pecora, Director 

First and second printing 1967 

Free on application to the U.S. Geological Survey, Washington, D.C. 20242 
CONTENTS 

Page 

Abstract----------------------------------

Resuhs-----------------------------------

Page 

1 

1 

1 

2 

2 

2 

6 

6 

Geologic distribution of gold-Continued 

Miocene(?) conglomerate --------------- 7 

Geologic distribution of gold ---------------- Quaternary deposits-------------------- 7 

Harebell Formation----------------------

Pinyon Conglomerate---------------------

Fort Union Formation--------------------

Conglomerate of earliest(?) Eocene age ----

Wind River Formation--------------------

Pass Peak Formation of Eardley and 

Geochemical problems and procedures ----- 8 

Analytical method---------------------- 8 

Sampling------------------------------ 9 

Panned concentrates-their problems 

and contributions--------------------- 10 

References cited------------------------- 12 

others-------------------------------- 7 

ILLUSTRATIONS 

Page 

Figure 1. Index map of northwest Wyoming showing localities sampled for gold---------------------- 4 

Table 

2. Map of Jackson Hole area showing localities sampled for gold and major outcrop areas 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

of Harebell Formation and Pinyon Conglomerate -------------------------------------- 5 

TABLES 

Gold content of Cretaceous and Tertiary rocks and Quaternary deposits -------------------

Data on samples from Harebell Formation and Pinyon Conglomerate----------------------

Gold content of sampled localities in Harebell Formation --------------------------------

Gold content of sampled localities in Pinyon Conglomerate-------------------------------

Gold content of sampled localities of quartzite conglomerate in formations other than 

Harebell and Pinyon, northwest Wyoming---------------------------------------------

Gold content of miscellaneous igneous and sedimentary rocks in northwest 

Wyoming--------------------------------------------------------------------------

Gold content of sampled localities in Quaternary deposits derived chiefly from the 

Harebell Formation, Pinyon Conglomerate, Wind River Formation, and Pass Peak 

Formation of Eardley and others (1944) ----------------------------------------------

Gold content of alluvium derived largely or entirely from pre-Harebell.rocks --------------

Comparison of gold content in panned concentrates with that in unconcentrated samples -----

III 

Page 

2 

3 

6 

6 

6 

7 

7 

8 

11 

Gold-bearing Sedimentary Rocks in Northwest Wyoming-

, 

A Preliminary Report 

By J. C. Antweiler and J. D. Love 

ABSTRACT 

Thick sequences of gold-bearing quartzite conglomerate occur 

in latest Cretaceous and Tertiary formations and in Quaternary 

gravels derived from them in northwest Wyoming. Analyses of 

about 1,200 samples (by a new cyanide-atomic absorption method) 

and 750 panned concentrates representing 53 localities show the 

following averages in parts per billion and cents per cubic yard: 

Harebell Formation (latest Cretaceous), 65 (11 cents); Pinyon 

Conglomerate (Paleocene), 86 (14 cents); Fort Union Formation 

(Paleocene), 35 (6 cents); conglomerate of earliest(?) Eoceneage, 

94 (14 cents);WindRiverFormation(early Eocene),222 (35 cents); 

Pass Peak Formation of Eardley and others (middle(?) Eocene), 

47 (8 cents); Miocene(?) conglomerate, 65 (11 cents); Quaternary 

deposits, 103 (16 cents). These values are for the bulk rock 

although the gold is largely confined to sandstone layers and the 

sandy matrix of the conglomerates, which contain various proportions of pebbles and cobbles. The conglomerates were derived 

chiefly from Precambrian and possibly Paleozoic quartzite in a 

now-buried uplift northwest of the Teton Range. Although the 

grade is low, the volume, 50 cubic miles or more, is so large as 

to constitute a resource of enormous proportions. The presence 

of above-average grades in some localities suggests that local 

concentrations may exist and makes the conglomerates and their 

derivatives attractive for additional prospecting. 

RESULTS 

This report presents a summary of analyses (tables 

1 to 9) of the first 1,200 of 6,000 samples collected 

from a sequence of gold-bearing sedimentary rocks 

in northwest Wyoming and adjacent areas. The following conclusions and procedures, potentially useful 

to modern prospectors, are based on a preliminary 

study of the field and laboratory data related to these 

samples: (1)Goldoccursinallareas of Cretaceous and 

Tertiary quartzite-bearing conglomerate that have 

been sampled in northwest Wyoming, (2) the volume 

of low grade gold-bearing strata is so vast (50 cu mi 

or more) that development of new mining and recovery 

methods designed for low-cost handling of huge quantities of relatively poorly consolidated material may 

eventually be justified, (3) most of the gold was not 

derived from adjacent mountains but came from Precambrian and possibly Paleozoic quartzite in a nowburied uplift northwest of the Teton Range, (4) to 

analyze for gold in such low concentrations, a method 

1

Prepared with the cooperation of the Geological Survey of 

Wyoming and the Department of Geology, University of Wyoming. 

combining cyanide extraction and atomic absorption 

was found most reliable, and (5) analyses of 754 

panned concentrates demonstrate some of the problems 

of recovering gold by mechanical and chemical methods 

and of evaluating various types of analytical data. 

We believe that there are genuine, even though 

small, variations in amounts of gold from one place 

to another and that these are not necessarily random 

but may be clues to the locations of large-tonnage 

deposits of possible economic significance. Because 

of the current interest in gold, evidence supporting 

our conclusions is given in this preliminary report in 

advance of completion of the final study. Sampling 

has not yet been done in sufficient detail to locate any 

areas of relatively high gold content, but we feel that 

the data shown in table 1 indicate the desirability of 

further intensive prospecting. 

The results reported herein are based mainly on 

determinations of the gold content of small samples. 

A joint investigation with the U.S. Bureau of Mines is 

planned to develop methods for me as u r in g the gold 

content of much larger samples and for technological 

appraisal of the deposits. 

GEOLOGIC DISTRIBUTION OF GOLD 

Placer gold has been known in northwest Wyoming 

for more than 100 years, but it is in such small 

flakes (max diam. about 0.3 mm, and thickness less 

than 0.01 mm) that conventional recovery methods 

have not been commercially successful. 

Table 1 summarizes data on the Cretaceous and 

younger sequences sampled for this study and shows 

their average gold content. More detailed descriptions of these gold-bearing strata-Harebell Formation and Pinyon Conglomerate (Love, 1956; 1956a), 

Fort Union Formation (Pierce, 1966; Hewett, 1914; 

1926), Wind River Formation (Rohrer, 1967), Pass 

Peak Formation of Eardley and others (Eardley and 

others, 1944; Dorr, 1956), and Quaternary deposits 

(Maguire, 1899; Love, 1956a; Love and Taylor, 1961) 

-are found in the literature cited. The Miocene(?) 

conglomerates have not been described in publication 
Table 1.-Gold content of Cretaceous and Tertiary rocks and Quaternary u~posit::> 

Au content in ppb; dollars per 

Age Formation Lithology No. of No. of cubic l_ardY in ~entheses samples localities Average of Maximum in 

all samples single s~le 

Quaternary------- ---------------------- Gravel, sand, silt, and clay-- 178 14 103 ($0.16) 2,000 ($3.20) 

Miocene (?) ------- 65 ( .11) ( .46) ---------------------- Quartzite conglomerate and 21 l 290 sandstone with tuff matrix. Middle(?) Eocene- Pass Peak Formation Quartzite conglomerate, 25 l 47 ( .o8) 250 ( .40) 

of Eardley and sandstone, and siltstone. 

others (1944). 

Early Eocene----- Wind River Formation-- Sandstone and quartzite 40 222 .35) 2,000 ( 3.20) 

conglomerate. 

Earliesd?) Eocene ---------------------- ----do------------------------ 26 l 94 .14) 400 ~ .64) Paleocene-------- Pinyon l:onglomerate--- Quartzite conglomerate, sand- 652 16 86 .14) 6,000 9.6o) stone, coal, and shale. 

Paleocene-------- Fort Union Formation-- Quartzite conglomerate, and 14 35 .o6) 300 ( .48) 

sandstone. Late Cretaceous-- Harebell Formation---- Quartzite conglomerate 1 sand- 145 65 .11) 1,000 ( 1.60) 

stone, and siltstone. 

!/The value of placer deposits is commonly expressed in dollars per cubic yard. To convert to dollars per ton 1 divide dollars by 1,6, 

equals 1,6 tons; 10 ppb equals l cent per ton; 1 cent per ton equals 1,6 cents per cu yd. 

l cu yd; 

but are similar to those in the Colter Formation 

(Love, 1956), 20 miles to the southeast. 

Sample localities are shown on figure 1, and many 

are shown also on figure 2, a generalized geologic 

map (Love, 1956) that shows distribution of the Harebell Formation and Pinyon Conglomerate, the thickest 

and most widespread gold-bearing conglomeratic sequences in northwest Wyoming. 

HAREBELL FORMATION 

The Harebell Formation was deposited during latest 

Cretaceous time by a river system that flowed southeastward across Jackson Hole and brought quartzite 

debris from a now-buried source uplift northwest of 

the Teton Range. The trough line of maximum conglomerate deposition was near localities 10, 11, and 

12, along the present courseoftheBuffaloFork River. 

Conglomerates decrease in thickness and abundance 

to the north and south of that area. 

The distribution of gold in various rock types in 

the Harebell Formation is summarized in table 2. 

Gold is more abundant in saudstone than in conglomerate. Among conglomerates, gold 1s most abundant in ferruginous v a r i e t i e s having some round 

stones larger than 3 inches and in con g 1om e r at e 

having a soft matrix. Ferruginous rocks containing 

organic debris appear to be particularly favorable 

hosts for gold. Table :) gives the maximum, minimum, 

and average gold content at each of five sample localities, and table 1 shows a combined average. Regional 

distribution of gold elsewhere in the areas of outcrop 

(fig. 2) is being investigated. 

PINYON CONGLOMERATE 

The Pinyon Conglomerate was deposited by rivers 

that flowed from the quartzite source area eastward 

and southeastward across Jackson Hole although in 

2 

courses different from those of the rivers that deposited the Harebell Formation. One river turned 

northeast and went past the present location of the 

town of Cody (fig. 1) in the Bighorn Basin. The area 

of maximum conglomerate deposition was in the vicinity 

of locality 5 and Gravel Mountain (fig. 2), where more 

than 5,000 feet of strata, largely conglomerate, was 

deposited. Farther east and southeast, the conglomerates thin and intertongue with sandstone. 

Table 2 shows that the pattern of gold distribution 

in the Pinyon Conglomerate is similar to that in the 

Harebell Formation. In both formations gold is most 

abundant in sandstone. In th~ Pinyon, however, gold 

is appreciably more abundant than in the Harebell. 

Carbonaceous sandstone in the Pinyon has the highest 

average gold content of any samp1es. 

Table 4 shows that both average and maximum gold 

Content vary considerably from one locality to another. 

A cluster of localities (32, 33, 34, 36) in the southeast 

part of Jackson Hole displays moderately high values. 

Whether these richer localities a:re parts of linear 

trends of gold concentration has not yet been determined, for analytical data from the large areas of 

Pinyon Conglomerate farther north are presently incomplete. 

FORT UNION FORMATION 

The Fort Union Formation in the Bighorn Basin 

is an approximate eastern equivalent of the Pinyon 

Conglomerate plus the overlying sandstone, siltstone, 

and claystone of Paleocene age. Quartzite conglomerates were sampled in many places and parts of the 

section but, as yet, analyses are available for only 

one locality (52, fig. 1; table 5) in the lower 200 feet 

of a 5,000-foot succession. Table 1 shows that the 

gold content at this locality is much less than in the 

Pinyon Conglomerate. Analyses of con g 1om era t e s 

from other areas, however. may alter this preliminary 
Table 2.-Data on samples from Harebell Formation and Pinyon Conglomerate 

Material 

Roundstones (most are qu~rtzite, but some ~re 

schist, gr~nite, etc.)-----------------------------

Conglomerate, some roundstones larger than 3 in------

Ferruginous conglomerate, some roundstones larger 

th~n 3 in------------------------------------------

Conglomerate, roundstones sm~ller th~n 3 in----------

Ferruginous conglomerate, roundstones sm~ller th~n 

3 in--------------~--------------------------------

Conglomerate with tough m~trix----------------------­

Conglomerate with soft m~trix-----------------------­

Conglomerate overlying sandstone---------------------

Ferruginous conglomerate overlying sandstone---------

Conglomerate under sandstone-------------------------

Ferruginous conglomerate under sandstone-------------

Sandstone overlying conglomerate---------------------

Ferruginous sandstone overlying conglomerate---------

Pebbly sandstone lens--------------------------------

Sandstone lens---------------------------------------

Ferruginous sandstone lens---------------------------

Sandstone lens under conglomerate--------------------

Ferruginous sandstone lens under conglomerate--------

Massive sandstone------------------------------------

Sandstone-shale--------------------------------------

Ferruginous sandstone-shale--------------------------

Sandstone with organic content or plant fossils------

Ferruginous sandstone with org~nic content or 

plant fossils--------------------------------------

Shale------------------------------------------------

Limestone--------------------------------------------

Co~l-------------------------------------------------

Soil on, or derived from, conglomerate---------------

Stream sediment in area of conglomer~te-------------­

Conglomerate with cl~yey matrix----------------------

Silicified wood--------------------------------------

Summary.!/ 

Nonferruginous s~mples------------------------------­

Ferruginous samples----------------------------------

Conglomerate-----------------------------------------

Sandstone--------------------------------------------

Shale------------------------------------------------

Material cont~ining carbonaceous debris--------------

Limestone--------------------------------------------

Soil-------------------------------------------------

Roundstones------------------------------------------

No. of 

samples 

analyzed 

Harebell Pinyon 

ll 

37 

12 

5 

2 

23 

24 

5 

1 

4 

0 

10 

1 

2 

12 

9 

5 

5 

6 

2 

3 

2 

3 

l 

2 

0 

15 

84 

35 

56 

55 

6 

5 

2 

15 

ll 

ll2 

175 

31 

16 

3 

77 

127 

6 

0 

8 

2 

30 

2 

4 

50 

22 

18 

14 

3 

2 

12 

13 

ll 

9 

49 

75 

7 

4 

346 

60 

225 

152 

18 

12 

ll 

49 

ll2 

No. with Au 

content 100 ppb 

or greater 

Harebell Pinyon 

0 

6 

4 

1 

0 

3 

7 

0 

0 

0 

0 

3 

0 

0 

2 

2 

1 

2 

1 

1 

0 

0 

3 

1 

0 

0 

16 

11 

11 

14 

2 

3 

0 

1 

0 

4 

35 

6 

5 

2 

12 

30 

1 

0 

4 

0 

9 

1 

2 

11 

4 

5 

3 

1 

0 

4 

2 

1 

0 

6 

18 

3 

0 

78 

13 

48 

39 

3 

4 

1 

6 

4 

1/some samples are included in more than one category in the preceding detailed list. 

3 

Avg Au content in 

ppb; cents per cu 

yd in parentheses 

Harebell Pinyon 

19 (3) 

52 (8) 

73 ( 12) 

45(7) 

30(5) 

48(8) 

70( 11) 

40(6) 

30(5) 

23 (4) 

120 ( 19) 

60(10) 

40(6) 

123(20) 

45(7) 

98 ( 16) 

114(18) 

47(8) 

80(13) 

57(9) 

35(6) 

127(20) 

100 (16) 

20(3) 

48(8) 

72(12) 

72(12) 

55(9) 

81 ( 13) 

72(12) 

90(14) 

20(3) 

48(8) 

19 (3) 

26(4) 

77( 12) 

60( 10) 

143 (23) 

103 ( 16) 

52(8) 

88( 14) 

103 ( 16) 

0 --

153 (24) 

40(6) 

106( 17) 

348(56) 

94( 14) 

118( 19) 

74(12) 

61(10) 

55(9) 

100 ( 16) 

50(8) 

430 ( 69) 

42(7) 

41(7) 

27(4) 

36(6) 

192 (31) 

344(55) 

19 (3) 

104(17) 

77(12) 

80(13) 

122(20) 

52(8) 

430( 69) 

41 (7) 

36(6) 

26(4) 
111° uoo 109° 

" -·-·-·-·-·-·-·-·-·-· M 0 N T A N A I p-,-------- -------~~:-----------·---l.-------r--

1 I 

45° 

YELLO I, 

\ 

N A T I 

p A 

SPRINGS 

T 

' 

E T T E \ 

10 20 30 40 MILES 

Figure !.-Northwest Wyoming, showing numbered localities sampled for gold. Heavy line marks boundaries 

of area included in figure 2. 

4 
11o•oo· 

PITCHSTONE 

"15' 

·oo· 

Modified from Love U956) 

10 15 MILES 

Figure 2.-Part of Jackson Hole area, showirig numbered localities sampled for gold and major outcrop areas 

of Harebell Formation (Kh) and Pinyop ,Conglomerate (Tp). Boundaries of Grand Teton National Park and 

Teton Wilderness Area are approximate!¥ located. Geology ad/ilpted from Love (1956). 

5 

•30' 
observation. The gold almost certainly came from 

the same source area as that in the Pinyon. CONGLOMERATE Of EARLEST(?) EOCENE AGE 

Table 3.-Gold content of sampled localities in Harebell Formation 

Several hundred feet of quartzite conglomerate 

similar to that in the Pinyon and Fort Union but 

overlying the Fort Union in the Bighorn Basin has 

been considered to be part of the Willwood Formation 

of early Eocene age (Hewett, 1926, called it Wasatch 

but the name was later changed). Recent work by the 

writers suggests that the Willwood may unconformably 

overlap this conglomerate, so the conglomerate is 

herein called earliest(?) Eocene and tentatively set 

apart from both the Willwood and Fort Union Formations. The quartzite debris may have been derived 

from the Harebell, Pinyon, and Fort Union Formations, or it might have come directly from the same 

source area as the older conglomerates. Tables 1 and 

5 show that the gold content of samples from one 

locality (53, fig. 1) is higher than the average for any 

of the older formations in either the Bighorn Basin 

or Jackson Hole. 

No. of 

Locality samples 

9 

10 

11 

12 

31 

23 

39 

59 

10 

14 

Au content (ppb) 

Range Average 

<10- 200 

<10- 200 

<10-1,000 

15- 250 

15- 400 

31.3 

43.3 

99-7 

70.0 

65.2 

Table 4.-Gold content of sampled localities in Pinyon Conglomerate 

No. of Au content (ppb) 

Locality samples Range Average WIND RIVER FORMATION 

2 13 40- 700 145.4 

5 74 <10-2,000 75.4 

6 37 <J..o-6,ooo 203.0 

7 31 <10- 250 52.9 

17 33 <10- 80 33.7 

18 84 <10- 340 50.4 

31 31 <10- 500 73.2 

32 103 <10-4,350 112.7 

33 26 <10-1,000 116.3 

34 39 <10-3,250 151.0 

35 45 <10- 200 30.2 

!/355 30 <20- 66o 85.0 

36 20 35- 500 138.0 

37 24 <10- 280 50.8 

38 31 <1.0- 200 27.6 

39 31 <10- 450 87.1 

y Scarp. 

The Wind River Formation of early Eocene age is 

present along the Continental Divide (fig. 2) between 

the Wind River Basin and Jackson Hole and includes 

several quartzite conglomerates and brown sandstones 

similar to those in the Pinyon Conglomerate. The 

Wind River is between 500 and 1,000 feet thick and 

is especially interesting because the average gold 

content of samples analyzed to date is more than 

twice that of any other formation (tables 1 and 5). 

These rocks lap southward onto the Flathead Sandstone (Cambrian) and the Precambrian crystalline 

core of the Wind River Range. An a 1 y s e s of four 

samples of Flathead Sandstone at two localities (44 

and 45, fig. 1; table 6) show 100 to 150 parts per billion (ppb ), or 16 to 24 cents per cubic yard, gold. Elsewhere (locs. 14 and 19), the Flathead has only 15 to 

25 ppb, or 2M to 4 cents per cubic yard, gold. These 

Table 5.-Gold content of sampled localities of quartzite conglomerate in 

formations other than Harebell and Pinyon, northwestern Wyoming 

Locality Rock No. of Au content (ppb) 

samples Range Av~rage 

52 Fort Unicn Formation------------ 14 <1.0- 300 35.4 

53 Lowest(?) Eocene conglomerate 

Bighorn Basin----------------- 26 15,. 400 ,94.4 

40 Wind River Formation------------ 23 <1.0-2,000 220.0 

41 ----do-------------------------- 3 70- 500 2~7.0 

42 ----do-------------------------- 14 10-1,250 223.2 

Summary (40, 41, 42)------- 40 <10-2,000 221.8 

50 Pass Peak Formation of Eardley 

and others (1944)--------------- 25 <1.0- 250 46.6 

1 Quartzite boulder conglomerate 

in Miocene(?) pyroclastic 

sequence---------------------- 21 <1.0- 290 64.8 

6 
Table 6.-Gold content of miscellaneous igneous and sedimentary rocks in 

northwestern Wyoming 

Rock 

No. of 

s;:~mples 

Au content (ppb) 

Range Average 

19 Fl~the;:~d S;:~ndstone-------------- 4 

4 

3 

20-25 22.5 

100-150 132.5 

15-70 38.3 

44, 45 

51 

-----------do-------------------

-----------do-------------------

14 Flathead S~ndstone ~nd volc;:~nic 

conglomerate of Oligocene 

Wiggins Formation------------- 2 (100 (100 

13 Prec~mbrian gneiss ~nd schist; 

C~mbri~n Fl~the~d Sandstone; 

~nd sediment in stre~ms 

draining Terti~ry volcanic 

rocks------------------------- 22 

2 

1 

<10-100 25.0 

15 15.0 

50 

19 

51 

Precambrian granite-------------

-----------do-------------------

preliminary data suggest that the Flathead may locally 

contain significant amounts of gold, probably derived 

from the Precambrian crystalline rocks of the Wind 

River Range. Some of this gold may have been reworked into the Wind River Formation. The Flathead Sandstone and adjacent beds of the Wind River 

Formation on both flanks of this part of the Wind 

River Range warrant further investigation. 

PASS P!AK FORMATION Of EARDLEY AND OTHERS 

The Pass Peak Formation of Eardley and others 

(1944) contains more than 2,000 feet of quartzite conglomerate along the south margin of the Gros Ventre 

Mountains; the conglomerate facies thins abruptly 

southward into sandstone. The age is uncertain but is 

probably middle Eocene. This conglomerate was almost certainly reworked from conglomerates in the 

Pinyon and Harebell Formations of Jackson Hole 

before the Gros Ventre Mountains rose to their present 

height (Dorr. 1956; Love; 1956b, 1960, p. 208-

209). About 1,000 feet of section was sampled (loc. 

50, fig. 1); the gold content averages somewhat less 

than that of all the older formations except the Fort 

Union (tables 1 and 5). 

MIOCENE(?) CONGLOMERATE 

A greenish-brown very coarse boulder conglomerate 

about 100 feet thick is in a sequence of pyroclastic 

rocks that directly overlies the Pinyon Conglomerate 

on the northwest side of the Teton Range at locality 

1 (fig. 2). Many of the boulders are of quartzite, 

highly rounded, 2 to 3 feet in diameter, and are identical in size, appearance, and composition to those in 

the pin yon. The matrix of the younger conglomerate 

is andesite crystal tuff, and the petrography, nature 

of matrix igneous material, and general appearance 

are much like those of the Colter Formation of Miocene age in Jackson Hole 20 miles to the southeast 

(Love, 1956). The gold content is slightly less than 

that in the Pinyon Conglomerate (tables 1 and 5). 

QUATERNARY DEPOSITS 

Maguire (1899) estimated that alluvial gravel along 

the Snake River downstream from the town of Jackson 

(fig. 1) contains at least $2 billion worth of gold (at 

$20.00 per oz). Table 7 presents the gold content of 

similar Quaternary depositF farther upstrE'~m th~t 

were derived chiefly from quartzite conglomerate m 

the Harebell, Pinyon, Pass Peak, and Wind River 

Formations. Table 1 shows that the averagegoldcontent in 178 alluvial samples is higher than that of any 

parent formation except the Wind River. All types. of 

alluvial debris, ranging from coarse boulder deposits 

to very fine grained clay, were sampled. The greatest 

gold concentration is in gravel and coarse sand, but 

some high values have been found in finer grained sand 

7 

Table 7.-Gold content of sampled localities 

in Quaternary deposits derived chiefly 

from the Harebell Formation, Pinyon 

Conglomerate, Wind River Formation, 

and Pass Peak Formation of Eardley 

and others (1944) 

No. of 

Locality samples 

3 5 

4 5 

8 20 

15 14 

16 16 

20 49 

!/20 .20 

21 4 

23 9 

24 12 

30 8 

45 8 

46 7 

49 1 

Au content (ppb) 

Range Average 

<l.0-1,000 228.0 

<20-2,000 739.0 

<1.0- 300 66.0 

<1.0- 300 1o4.6 

<1.0- 250 65.0 

<1.0- 6oo 44.0 

<1.0-1,200 107.0 

<l.0-2,000 579.0 

<1.0- 30 3.3 

<1.0- 6oo 88.8 

<1.0- 40 21.2 

<1.0- 500 188.7 

25- 100 57.1 

25 25 

y River bot.itom. 
and silt trapped in sod and at the roots of willow bushes 

along stream margins. 

Alluvial deposits derived largely or entirely from 

pre-Harebell rocks were sampled in order to determine whether any significant amount of gold came 

from sources other than conglomerate. Results are 

given in tables 8 and 9. These data indicate that the 

Harebell and younger conglomeratic strata are the 

chief sources of gold in Quaternary deposits. 

GEOCHEMICAL PROBLEMS AND PROCEDURES 

In order to evaluate the significance of variations 

in distribution of gold in deposits such as those in 

northwest Wyoming, an adequate analytical method is 

necessary for determining chemically the amount of 

gold, and a satisfactory procedure must be devised 

to produce mechanical concentrates containing the 

maximum amount of gold; concentrates are useful 

not only to cross check analyses of unconcentrated 

samples but also to provide data on distribution and 

recovery of very small gold particles. 

Related problems are: (1) the large volume of material (50 cu mi or more) to be sampled, (2) terrane 

so rough that it cannot quickly be explored, and (3) 

serious sampling difficulties because of the erratic 

distribution of discrete particles of gold, which is so 

malleable that it does not break up easily in grinding. 

ANALYTICAL METHOD 

The analytical method described here was developed 

as a part of this study in order to secure reliable 

data in the part-per-billion range on the gold content 

of the material that is actually analyzed. Details of 

·the procedure and equipment needed are included here 

because they may be of value to others engaged in 

similar work. Most of the unconcentrated samples 

were analyzed by W. L. C a m p be 11 and Elizabeth 

Martinez, using this new method. In Addition, all 

were analyzed by other, less sensitive methods. The 

values reported in the tables are based on averages 

of at least two determinations for almost all samples; 

some samples were analyzed as many as five times. 

The other methods used and the analysts (names in 

parentheses) are: sodium bromate-hydrobromic aci~­

colorimetric method of Lakin and Nakagawa (196,::,), 

using 1- and 5-gram samples (J. C: Antweile.r~; 

sodium bromate-hydrobromic acid-atomiC absorption 

procedure, using 2-g samples (Walter Ficklin and 

Sharon Noble); cyanide-atomic absorption procedure, 

using 15-g samples (Walter Ficklin, Sharon Noble, 

Luther Dickson, and J. C. Antweiler); cyanide-colorimetric procedure, using 15-g samples ( J. C. Antweiler); and fire assay-atomicabsorptionprocedures, 

using approximately 15-g (half assay ton) samples 

(0. L. Parker, C. H. Huffman, Jr., and John Mensik). 

J. C. Antweiler assumes the responsibility for the 

values reported. 

The new method gave the best results. Recovery 

of gold was tested by analyzing scfgnples to which a 

known amount of radioactive Au1 had been added 

and then measuring the radioactivity of the recovered 

gold; recovery averaged 90 percent. Accuracy was 

constantly checked by preparing procedural blanks 

and standards on material similar to that being 

analyzed and by referring each sample to these blanks 

and standards for comparison. The true mean at the 

90-percent confidence limit for a 20 ppb standard is 

between 22 and 17 ppb (F. S. Fisher, written commun.). Values at 10 ppb are almost as good, and 

those at 100 ppb are considerably better. 

Table a.-Gold content of alluvium derived largely or entirely from preHarebell rocks 

Locality 

22, 25 

26, 27, 

28, 29. 

47 

48 

Material 

Stream sediments, landslide 

and glacial debris from 

Paleozoic and Mesozoic 

rocks in Gros Ventre 

Mountains-----------------

Stream sediment. Drainage 

from Precambrian granitEY 

of Wind River Mountains 

and in part from Wind 

River Formation-----------

Glacial debris left by 

glacier that flowed 

southward from Gras Ventre 

Mountains along valley of 

Granite Creek-------------

River gravel in Hoback River 

at u.s. 189 southeast of 

Bondurant-----------------

8 

No. of 

samples 

24 

2 

2 

2 

Au content (ppb) 

Range Average 

<10-50 11.3 

<10-70 35 

20-80 50.0 

<10 <10 
Apparatus and reagents 

Atomic absorption spectrophotometer. The instrument 

used in this work was a Perkin-Elmer 303. 

Shaker capable of handling 25- by 200-mm screwcap 

test tubes. 

25- by 200-mm screwcap test tubes. 

Water bath. 

Centrifuge. 

Sodium peroxide. 

0.25-percent sodium cyanide solution: Dissolve 2.5 g 

sodium cyanide in 1 liter of water. 

1:1 HBr solution containing free Br2: Add 1 liter of 

hydrobromic acid and 10 g sodium bromate to 

1 liter of water. 

Methyl isobutyl ketone (MIBK). 

Procedure 

1. Roast 15 g of sample 1 hr at 600°C. When cool, 

add 0.1 g Na2o2• 

2. Add 30 ml 0.25-percent NaCN solution to 25- by 

200-mm screwcap test tube. Heat tube and contents to 85° in a water bath. 

3. When the sodium cyanide solution is hot, add the 

roasted samples containing sodiumperoxide. Allow to digest a few minutes in the water bath. 

4. Cap the tube and shake for 15 minutes. After shaking, allow the sediment to settle. and siphon or 

decant the solution into another 25- by 200-mm 

screwcap test tube. 

5. Add 10 ml 1:1 HBr solution containing free bromine to sediment remaining in first test tube. Heat 

tube and contents to 85° on water bath. Cap and 

shake 5 minutes. Allow sediment to settle after 

shaking, and siphon or decant HBr into the same 

test tube containing the cyanide extract. (CAUTION: Use a hood. Hydrogen cyanide is liberated.) 

6. Digest the combined cyanide and bromide solutions 

on the water bath at 85° for M hr. Allow the tube 

to cool to room temperature. 

7. Add 10 ml MIBK and shake for 2 minutes. Centrifuge if necessary to get a sediment-free layer 

of MIBK. Determine gold content in the MIBK layer 

by atomizing MIBK in the atomic absorption spectrophotometer, referring to the blanks and standards as described below. 

Preparation of blanks and standards 

Standard gold cyanide solution: Prepare a stock solution containing 1 mg of gold per ml by dissolving 

100 mg of gold with aqua regia and diluting to 100 

ml. Prepare a stock cyanide solution containing 

100 micrograms of gold per ml by neutralizing 10 

9 

ml of the aqua regia solution with sodium hydroxide and diluting to 100 ml with 0.25-percent sodium cyanide solution. Dilute the stock cyanide 

solution with appropriate volumes of0.25-percent 

sodium cyanide solution to obtain daily working 

solutions containing 1 and 10 micrograms gold 

per mi. 

Barren sample material: Roast 1 hr at 600°C several 

hundred grams of material known to contain less 

than a measureable amount of gold but similar in 

general composition to the samples to be tested. 

Procedural blanks and standards: Add 15 g of barren 

sample material and 0.1 g Na2o2 to a series of 

screwcap test tubes. Prepare a series of blanks 

and standards containing 0, 10, 20, 50, 100, 500, 

and 1,000 ppb gold by pipetting 0, 0.1. 0.2, 0.5, 

and 1.0 ml of the standard containing 1 microgram 

gold per ml, and 0. 5 and 1.0 ml of the standard 

containing 10 micrograms of gold per ml into the 

tubes (all the gold added is recovered in 10 ml 

MIBK; therefore each ml MIBK contains 1/10 of 

the gold added). Run these blanks and standards 

through procedure steps 2 to 7 exactly like samples, setting the atomic absorption instrument to 

obtain a reliable curve that spans the range of 

gold content of the samples to be analyzed. Determination of gold for each sample by atomic absorption should be preceded and followed by readings 

of the blank in order to verify instrumental stability. Refer to the standard curve after each lOth 

sample, and make instrumental adjustments if 

necessary. 

SAMPLING 

We wish to emphasize that this report is not intended 

to present a resource appraisal but rather the preliminary results of geological and geochemical exploration. 

The objectives are to establish guides to prospecting, to 

locate areas that may warrant more detailed studies, 

and to obtain information on the source, areal distribution, and stratigraphic extent of gold. Consequently, 

the samples collected were small (1 to 2lb), and preference was commonly given to sampling conglomerate 

matrix and s~ndstone lensesbecausepreviousanalytical work showed that such samples are more likely to 

have concentrations of gold than are round stones. 

Round stones were included in samples of conglomerate 

but commonly were not in proportion to their abundance 

because of their size and the limitations on the weight 

of sample that could be collected. It is readily apparent that removal of pebbles and larger round stones 

from· conglomerates will increase the gold content of 

the matrix material significantly. 

A statistical analysis by A. T. Miesch (writtencommun., 1966) of grade and particle size shows that even 

with a definite sampling pattern, sampling problems 

are certain to occur. Experimental data obtained in the 

present study confirm the statistics and show that the 
sampling error is large. The average mass of gold 

particles recovered by washing in a gold pan is about 

8 micrograms; the average grade found so far at most 

localities is between 50 and 100 ppb. To obtain reliable evaluation data at this level of particle size and 

concentration, very large samples (several hundred 

pounds) should be taken because most 15-g samples 

will not contain even one gold particle. Although the 

particles are very small(morethan l,OOOarerequired 

to make 1 cent's worth of gold), they are not evenly 

distributed, and wide deviations in analytical results 

are therefore inevitable. 

It is important to note that one or a few samples with 

relatively high gold content can change significantly the 

average grade at a locality and that these high values 

cannot be excluded because such scatter in analyses is 

typical of economic deposits. For example, in a study 

of gold ore from the Witwatersrand in South Africa, the 

U.S. Bureau of Mines found that one-half of the gold 

was in fewer than 10 percent of 495 samples; and in 

ore from the Homestake mine in South Dakota, onehalf of the gold was in 3 percent of 219 samples 

(George S. Koch, Jr., written commun., 1966 ). 

A final word of caution concerns gold analyses in 

all tables. The figures presented do not necessarily 

provide a basis for quantitative comparisons of gold 

values between one area and another because different 

sampling patterns rather than sampling problems or 

actual differences in gold content rna y account for some 

of the variations. 

PANNED CONCENTRATES-THEIR PROBLEMS AND CONTRIBUTIONS 

In an attempt to solve the difficult problem of determining reliably the gold content of rocks containing 

very small amounts of gold, extensive experiments 

were made to preconcentrate large samples and then 

to analyze the concentrates. 

As a test of the effectiveness of a simple concentration method in obtaining representative 15-g samples 

for analysis, 754 field samples, for which bulk analyses 

were available, were concentrated by hand panning with 

a gold pan, and the concentrates were analyzed. This 

procedure should facilitate determination of the gold 

content of several hundred grams of sample but, like 

the bulk sample analyses, is subje~t to error that may 

be very large. The panned concentrates were analyzed 

for gold using a sodium bromate-hydrobromic acidatomic absorption procedure that is quite satisfactory 

for small samples with high gold content. Panning was 

done by J. G. Frisken, W. H. Raymond, F. S. Fisher, 

and J. C. Antweiler, and analyses were made under the 

direction of J. C. Negri by Elizabeth Martinez, S. MeDana!, H. King, B. Hansen, A. Toevs, A. Meier, T. A. 

Roemer, C. Cole, and R. Miller. 

Averages of the gold content in concentrates from 

each locality are given in table 9. The field saJ11.ples 

10 

and the concentrates obtained from them were weighed, 

and the percentage of gold recovered in the concentrates, shown in the last column of table 9, was obtained 

by computation from the gold content of the bulk samples. A few analyses were made of the material that 

floats and remains in suspension when the sample is 

first wet with water, and some analyses were made of 

the material washed out of the pan during the panning 

process. 

The tests made so far on concentration of samples 

by panning lead to several conclusions. First, some 

samples have gold particles that cannot be recovered 

by panning because they float on the surface of the 

water; this is shown by the high gold content of some 

of the very fine size fractions. Second, some gold particles cannot be recovered because they are washed out 

during panning, either because they are very small or 

because they are attached to lighter grains that are 

washed out; analyses of a few of the "tails" fractions 

show about the same gold content as the bulk samples. 

Third, some panned concentrates yield more gold than 

is indicated by the bulk sample analysis. During some 

panning, this gold is visible, but commonly it is not; 

the invisible gold may be attached to or tied up in the 

structure of heavy minerals such as magnetite. 

The gold that is recovered but not seen is finely 

divided and uniformly distributed so that analyses of 

replicate splits are in reasonable agreement. Visible 

gold particles, however, are few in number and so 

erratic in distribution that replicate analyses may 

give widely varying results. 

Recovery of gold by panning is influenced not only 

by the uncertainties just discussed but also by the skill 

of the panner. In one test, a weighed amount of gold, 

in particles somewhat larger than the average flake 

observed in the natural samples, was added to 500 g 

of typical sample material, and the sample was then 

panned by two people. Recovery by one operator was 

about 40 percent and by the other about 24 percent. 

In view of the fact that problems of panning all result 

in loss of gold, it is not surprising that average recoveries from concentrates shown in table 9 are low. 

Despite the low recoveries obtained by panning, we 

believe the effort is justified; gold missed in analysis 

of bulk samples is discovered in concentrates of some 

samples, and a crude knowledge is obtained of the particle size at various localiti.es. For example, at localities 1 and 2, at the northwest end of the Teton Range, 

analyses of bulk samples indicated average gold contents of 64.8 and 145.4 ppb(ll and23 cents per cu yd), 

respectively, but only 2.3 percent of the gold was recovered by panning at locality 1 and only 2.0 percent 

at locality 2. Practically no accessory heavy minerals 

were recovered at either locality. The very small particle size of gold suggests the possibility that gold precipitated after deposition of the conglomerate. If the 

gold is indeed not detrital at this place, then it may not 

be in many other areas of conglomerate in northwestern 

Wyoming. 
Table 9.-Comparison of gold content in panned concentrates with that in unconcentrated samples 

Au (ppb) recovered in 

concentrate by panning Average in-place content of Au (ppb) Percent of Locality No. of indicated Au No. samples Range No. of Average Computed from Indicated by analytical recovered by panned <100 samples having Au Au recovered data (No. of samples panning 

to- >1,000 ppb by panning in p~ ren theses) 

Harebell Formation (Upper Cretaceous) 

9 24 14,400 2 690 2.8 31. 3 (23) 8.9 10 25 38,000 10 4,930 19.4 43. 3 (39) 44.8 11 36 17,900 9 1,200 5.0 99.7 (59) 5. 0 12 7 400 0 165 . 5 70.0 (10) • 7 31 6 1,000 1 225 1.0 83.2 (14) 1.2 

y y y ]) )} ]) Y. 11 98 38,000 22 1,890 7.6 65.2 (145) 11.5 

Pinyon Conglomerate (Paleocene) 

2 8 3,500 3 994 2.9 145.4 (13) 2.0 

5 75 30,900 15 2,160 10.8 75.4 (74) 14.3 6 17 40,000 7 3,620 15.9 203.0 (37) 7.8 

7 20 55,000 8 5,210 14.1 52.9 (31~ 26.7 17 7 250 0 65 .6 33.7 (33 .2 

18 46 16,700 13 1,730 9.8 50.4 (84) 19.4 

31 11 6,000 2 750 1.9 73.2 (31) 2.6 

32 44 50,800 10 2,660 11.5 112.7 (103) 10.2 

33 25 28,500 9 2,770 15.6 116.3 (26) 13.4 34 35 55,100 11 3,880 21.8 151.0 (39) 14.4 

...!:./35 16 38,500 8 4,610 23.9 30.2 (45) 79.1 

355 39 32,000 22 3,670 34.4 85.0 (30) 40.5 36 19 4,700 1 295 1.5 138.0 (20) l.1 

37 18 1,000 3 228 1.2 50.8 (24) 2.4 

38 12 11,000 2 1,680 12.1 27.6 (31) 43.8 

39 17 8,400 4 1,240 19.3 87.1 (31) 22.2 

Il409 y 55,100 Yll8 1.72,480 )} 14.1 ]) 86.0 Ilc65i> )} 16.4 

Fort Union Formation (Paleocene) 

52 14 4,000 710 3.8 35.4 (14) 10.7 

Lowest(1) Eocene conglomerate, Bighorn Basin 

53 26 24,000 9 2,500 10.4 94.4 (26) 11.0 

Wind River Formation (lower Eocene) 

40 16 3,000 3 3,000 3. 4 220.0 (23) 1.5 41 2 4,500 1 2,250 50.0 227.0 ( 3) 22.0 

42 ll 40,400 6 6,260 54.1 223.~ (14) 24.2 

r/29 Y4o,4oo ylO 372,720 ]/24.2 ]/221.8 rlc4o> 'J}10.9 

Pass Peak Formation (middle ( 1) Eocene) of Eardley and others (1944) 

50 20 11,200 6 1,770 25.8 46.6 (25) 55.4 

Quartzite boulder conglomerate in Miocene(1) pyroclastic sequeot:e 

1 18 10,000 84o 1.5 64.8 (21) 2.3 

Quaternary deposits derived chiefly from the Harebell Formation, Pinyon Conglomerate, 

Wind River Formation, and P~ss Pe~k Form;otion of Eardley Pnd others ( 1944) 

3 3 5,000 2 2,370 18.3 228.0 ( 5) 8.0 

4 5 21,000 3 7,700 101.0 615.8 ( 6) 16.4 

7 5 2,520 3 9,000 13.6 64.6 (15) 21.1 

8 14 23,500 8 4,360 58.7 n.o ( 5) 82.7 

15 14 2,800 1 200 1.9 lo4.6 (14) 1.8 

16 15 10,900 4 1,250 6. 5 65.0 (16) 10.0 

2/~g 35 12,000 7 1,000 5.2 44.0 (49) ll.8 

15 18,100 8 3,600 21.6 107.0. (20) 20.2 

24 7 6,8oo 3 <:,140 ll. 7 88.8 (12) 13.2 

45 (. 7,500 2 1,750 6.6 188.7 ( 8) 3. 5 46 ·r <J.OO 0 <J.OO <J.. 0 57.1 ( 7) 0 

49 1 4,900 1 4,900 25.0 25.0 ( 1) 100.0 

~7 £723,500 Y42 "'Jl2,050 1' l7. 5 "'Jl98. 3 r; (158) "'j} 17.8 

Pre...Harebell rocks (or alluvium derived therefrom) 

43 2 1,750 1 850 6.0 35.0 ( 2) 17.1 

44 3 1,700 1 Boo • 7 132.5 ( 4) • 5 

47 2 1,100 1 550 1.5 50.0 ( 2) 3.0 

48 2 300 0 150 • 5 <J.O ~ 2) 51 4 6,900 1 1,800 4.9 41.2 4) 11.9 

Y13 y 6,900 Y4 rJ 980 rJ 2.4 17 21.3 Y(l4) l1u.2 

YTota1. YHigheat value. lf Overall average. !!scarp. 2/River bottom. 

11 
The samples taken northwest of Upper Slide Lake 

(loc. 31), along the South Fork of Fish Creek (locs. 

36 and 37), and from near Leeds Creek (loc. 40) likewise show low gold recovery from panned concerntrates. A majority of these samples are sandstone, 

shale, limestone, and coal; the sandstone contains 

abundant muscovite and biotite. One possibility is that 

gold of very small particle size (the size lost during 

the panning process) was deposited wit;,h the sediment 

in special environments at the sample sites; a second 

possibility is that colloidal gold or gold in solution was 

later deposited in some of these rocks. 

Recovery of gold from samples at locality 35 (near 

North Fork of Fish Creek) is considerably higher than 

from samples at most localities, presumably because 

the gold is much coarser here than elsewhere in the 

region. The average gold content of the samples collected at stream level through a stratigraphic thickness of several hundred feet (samples from loc. 35, 

table 4) is only 30.2 ppb (5 cents per cu yd) compared 

with 85.0 ppb (14 cents per cu yd) for approximately 

the same stratigraphic interval on the adjacent face 

of the scarp (samples from loc. 35S, table4). The actual gold content of the two groups of samples is probably more nearly the same than the analytical data 

suggest·; the discrepancy is likely due to the difficulty 

in obtaining representative samples of material containing coarsely particulate gold. The reason for the 

much larger particle size of gold at this locality has 

not been determined. 

REFERENCES CITED 

Dorr, J. A., Jr., 1956, Post-Cretaceous geologic history of the Hoback Basin area, central western 

Wyoming, in Wyoming Geol. Assoc. Guidebook, 

11th Ann. Field Conf., 1956; p. 99-108. 

Eardley, A. J., and others, 1944, Hoback-Gros VentreTeton Field Conference: Geol. map, private 1 y 

printed. 

12 

Hewett, D. F., 1914, TheShoshoneRiversection, Wyoming: U.S. Geol. Survey Bull. 541, p. 89-113. 

1926, Geology and oil and coal resources of the 

----oregon Basin, Meeteetse, and Grass Creek Basin 

quadrangles, Wyoming: U.S. Geol. Survey Prof. 

Paper 145, 111 p. 

Lakin, H. W., and Nakagawa, H. M., 1965, A spectrophotometric method for the determination of traces 

of gold in geologic materials, in Short papers in 

the geologic and hydrologic sciences: U.S. Geol. 

Survey Prof. Paper 525-C, p. C168-C171. 

Love, J. D., 1956, New geologic formation names in 

Jackson Hole, Teton County, northwestern Wyoming: Am. Assoc. Petroleum Geologists Bull., 

v. 40, no. 8, p. 1899-1914. 

1956a, Cretaceous and Tertiary stratigraphy of 

----rile Jackson Hole area, northwestern Wyoming, in 

Wyoming Geol. Assoc. Guidebook, 11th Ann. Field 

Conf., 1956; p. 76-94. 

1956b, Summary of geologic history of Teton 

---c0unty, Wyoming, during Late Cretaceous, Tertiary, and Quaternary times, in Wyoming Geol. 

Assoc. Guidebook, 11th Ann. Field Conf., 1956: 

p. 140-150. 

1960, Cenozoic sedimentation and crustal move-

---rilent in Wyoming: Am. Jour. Sci., v. 258-A,p. 204-

214. 

Love, J.D., and Taylor, D. W., 1961, Faulted Pleistocene strata near Jackson, northwestern Wyoming, 

in Short papers in the geologic and hydrologic sciences: U.S. Geol. Survey Prof. Paper 450-D, 

p. 136-139. 

Maguire, Don, 1899, Snake River gold fields: Mines 

and Minerals, v. 20, p. 56-58. 

Pierce, William G., 1966, Geologic map of the Cody 

quadrangle, Park County, Wyoming: U.S. Geol. 

Survey Geol. Quad. Map GQ-542. 

Rohrer, W. L., 1967, Geologic map of the Fish Lake 

quadrangle, Fremont County, Wyoming: U.S. Geol. 

Survey Geol. Quad. Map (in press). 

-tr U. 5. GOVERNMENT PRINTING OFFICE : 19117 0-2114-4111