Geochemical Studies in the 

Coeur d'Alene District 

Shoshone County, Idaho

GEOLOGICAL SURVEY BULLETIN 1098-A

Geochemical Studies in the 

Coeur d'Alene District 

Shoshone County, Idaho

By VANCE C. KENNEDY

With a section on

GEOLOGY

By S. WARREN HOBBS

CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING 

FOR MINERALS

GEOLOGICAL SURVEY BULLETIN 1098-A

The use of geochemical prospecting techniques near known lead, zinc, and copper 

deposits and a discussion of their values

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : I960
UNITED STATES DEPARTMENT OF THE INTERIOR 

FRED A. SEATON, Secretary

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director

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

Washington 25, D.C. Price $1.25 (paper cover)
CONTENTS

Page

Abstract. _ _________--_-___--________-___..__________--____--__-__. 1

Introduction.______________________________________________________ 1

Acknowledgments. ________________________________________________ 3

Geology, by S. Warren Hobbs___-__-__----___--___-__,_---__--______ 3

Geochemistry.____________________________________________________ 8

Soil and rock studies.___________________________________________ 8

Methods of sampling soils and rocks._------_-___-_-__--.-_-_ 9

Normal soils and rocks.____________________________________ 9

Soil sampling near mineralized areas.---.----.------.-----.-- 11

Veins containing mainly lead minerals near the surface_____ 12

Veins containing mainly zinc minerals._..________________ 31

Veins containing copper minerals._______________________ 33

Vein containing gold and tungsten.______________________ 37

Vein containing antimony.____________________________ 37

Plant studies___-______-_-_.-____________ _____________________ 39

Water studies.______-___-___.___________________________________ 40

Significance of analytical results.________________________________ 45

Soas__._ ___ __- ---____-_-________________________ 45

Plants-...--__________ _______________________________ 47

Water.. ____-_ ---_--_ -_--_.__-__.._____ .____._..- 47

Conclusions.-.-.---___--_-___-._._ ___-_ _________________________ 47

Soils-__________________ -__.-_-______ __________________ 48

Plants.____-___________ _______________ _________________ 49

Water _ _ ________________________________________ _ _____ 49

References cited-_______-______________.____-__.__-_-_--_--_-__-__- 49

Appendix_ ______________________________________________________ 51

Methods of analysis.__________ _^-_______________-_--__-_-_--___ 51

Soil _-- _----_----------_-_ ___-._.__-_._. _____.__- 51

Plants.. .. --------- _________ ___.___._._.._._____..____. 53

Water___-_____-______-______-_____-._.-__-_--____--___- 53

Index______________________________________________________________ 55

ILLUSTRATIONS

[All plates are in pocket] 

PLATE 1. Index map showing location of soil-sampling areas.

2. Map showing lead concentration in soil at the Vindicator mine.

3. Map showing zinc concentration in soil at the Vindicator mine.

4. Map showing concentration of total heavy metals in soil near the 

Little Pittsburg mine.

5. Map showing concentration of lead in soil near the Little Pittsburg 

mine.

6. Map showing concentration of zinc in soil near the Little Pittsburg 

mine.

7. Map showing locations where water samples were taken, pH, and 

heavy-metal concentration in the samples.

m
IV CONTENTS

Page 

FIGURE 1. Plan view of soil-sampling traverses near the Jack Waite vein. 12

2. Plan view of soil-sampling traverse, and graph showing concentration of lead and heavy metals in soil near the Hercules vein.______________________________________ 13

3. Plan view of soil-sampling traverse, and graphs showing concentration of lead and zinc in soil in the Ouster peak area__ 15

4. Plan view of soil-sampling traverse, and graphs showing concentration of lead and zinc in soil near the Standard-Mammouth vein________________________________________ 16

5. Plan view of soil-sampling traverse, and graph showing the

lead and zinc concentration in the soil near the Frisco mine_ 17

6. Plan view of soil-sampling traverse, and a graph showing the

lead and zinc concentrations in the soil near the Star vein__ 19

7. Plan view of soil-sampling traverse, and a graph showing

concentration of lead and zinc in the soil, Gold Hunter vein, 20

8. Plan view of three closely spaced soil-sampling traverses, and 

graphs showing comparison of results of lead concentration 

in the soil at 2- to 4-inch and 12- to 14-inch depths, Vindicator vein________________________________________ 23

9. Graphs showing lead concentration in the soil near the Sidney

vein_-________________-_--_-_-_-_--__-____-__-__-__- 25

10. Graph showing concentration of lead and zinc in soil south of

point A, Little Pittsburg area.____-__--_-_--___________ 27

11. Graph showing concentration of lead and zinc in soil south of

point B, Little Pittsburg area._-____--___-___-_____-___ 28

12. Graph showing concentration of lead and zinc in soil across a 

vein located 35 feet northwest of point E, Little Pittsburg 

area._______________________________________________ 29

13. Graph showing concentration of lead and zinc in soil near the

"carbonate" vein in Grouse Gulch near Mullan__________ 32

14. Plan view of soil-sampling traverses, and a graph showing the 

lead and zinc concentrations in the soil, Curlew vein near 

the Page mine____-__-_-_--_---_---------_-------__-_ 33

15. Plan view of soil-sampling traverses near the Missoula tunneL 34

16. Plan view of soil-sampling traverse near a malachite-stained 

zone, and a graph showing concentration of copper in the 

soil, Gentle Annie Gulch._____________________________ 35

17. Plan view of soil-sampling traverse near the outcrop of the

Snowstorm copper zone____-_--__--___-__-__-_-_______ 36

18. Plan view of soil-sampling traverse, and graph showing concentration of copper in soil at the Hansy copper mine_____ 36

19. Plan view of soil-sampling traverse, and graph showing concentration of tungsten in soil at the Golden Chest mine___ 37

20. Plan view of soil-sampling traverse near the Star Antimony

vein.._______________________________ 38
CONTENTS V

TABLES

Page

TABLE 1. Normal, or background, content of lead, zinc, and copper in 

soils, rocks, and stream sediments near the Coeur d'Alene 

mining area______________________.____________________ 10

2. Relationship of zinc, lead, and copper content to particle size in

soils, Little Pittsburg area______________________________. 31

3. Concentration of zinc in plants and soil in the area near the

Little Pittsburg vein___-______--______________-------_ 39

4. Lead, zinc, and copper analyses of plants and nearby soils,

Coeur d'Alene district, Idaho________________________ 41

5. Summary of lead and zinc soil anomalies found near veins.____ 45

6. Comparison of the various analytical methods used for soil

samples...____________________________________________ 52

7. Precision of quantitative plant analyses.-._________-__--_--_ 54

CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

GEOGHEMICAL STUDIES

IN THE 

COEUR D'ALENE DISTRICT, SHOSHONE COUNTY, IDAHO

By VANCE C. KENNEDY

ABSTRACT

The Coeur d'Alene district has long been known for its production of lead, 

zinc, silver, and copper. These metals, as mined, occur mostly in the minerals 

galena, sphalerite, and tetrahedrite. The ore is in tabular shoots and pods 

along generally steeply dipping veins or mineralized faults which cut Precambrian rocks of the Belt series. Some of the veins, including ore shoots and 

intervening barren gangue filling, can be traced for thousands of feet along 

the strike and have been developed to depths over a mile below the surface. 

The soil cover over much of the area ranges from one to several feet in thickness, and has added to the difficulties of prospecting for new deposits.

This study was made to test the feasibility of using geochemical prospecting 

techniques in the search for ore in the Coeur d'Alene district. Semiquantitative 

chemical analyses were made principally for copper, lead, and zinc in soils 

collected near veins and in soils collected at a distance from known veins. In 

addition, some information was obtained regarding the use of soil analysis in 

prospecting for antimony and tungsten veins. Samples of leaves, twigs, and 

fruits were analyzed both from plants growing in normal soils and from plants 

growing near ore deposits. A few water samples also were collected, and the 

pH and total heavy-metal concentrations were determined.

Evidence obtained from these studies indicates that analysis of soil for lead, 

or for lead and zinc, offers promise as a method of prospecting for new leadzinc ore bodies in this area. Prospecting for copper by soil anaylsis may be 

feasible, but present data are not especially encouraging. Plants growing in 

mineralized areas contain abnormal amounts of the ore metals, but these 

anomalies are not so pronounced as those in the soil. The use of water analysis 

in the search for ore within the mining district is limited because of the contamination of surface waters by mine drainage.

INTRODUCTION

A study was made of the distribution of some of the ore metals 

in the soils (pi. 1), waters, and plants of the Coeur d'Alene district 

of northern Idaho during the summer and fall of 1950, the summer 

of 1951, and for a short period in August of 1952. The purpose of 

this study was to evaluate the usefulness of some known geochemi-
2 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

cal prospecting techniques as a means of locating new ore bodies in 

the district.

In an area such as the Coeur d'Alene district, the technique of 

applied geochemical prospecting should be a particularly useful tool. 

The heavy vegetation and prevailing soil cover obscure most vein 

outcrops. The steep slopes and ramifying drainage lines foster the 

development of widespread heavy-metal dispersion halos downslope 

and downstream from weathered outcrops of mineral-bearing parts 

of the veins. The steep dip and generally linear structure of the 

mineral belts and of the veins within them are established facts that 

should help to direct a program of geochemical prospecting to the 

best advantage.

Experience with geochemical techniques elsewhere indicated that 

soil analyses should be of help in prospecting an area of this type, 

and Lyman C. Huff, of the U.S. Geological Survey, obtained encouraging results in a reconnaisance study of the area (Huff, 1951, 

p. 528). These results led to the more detailed study that is reported in this paper. A preliminary report on the present study 

has been published (Kennedy, 1952).

To determine the feasibility of prospecting by soil analysis, soil 

samples were collected near the outcrops of many known ore bodies 

in the district and were tested for lead, zinc, and, in some samples, 

copper. (For the purposes of this paper the term "heavy metals" 

will be used hereafter, instead of listing "copper, lead, and zinc.") 

In addition, a few soil samples collected near an antimony-bearing 

vein and near a vein containing both gold and tungsten were analyzed. Both plant and soil samples were collected to see what correlation, if any, existed between the concentrations of copper, lead, 

or zinc in soil and the concentrations of these metals in plants growing in the soil. Some water samples from springs and streams were 

analyzed, but not much time was devoted to this phase of the project.

Extensive prospecting and mining have been carried on since the 

early 1880's. As a result, the entire area of the Coeur d'Alene district and its environs is pockmarked with prospect pits, small and 

large prospect adits, and the workings of past and present producing mines. The application of the bulldozer to prospecting, whereby 

many hundreds of miles of roads, trenches, and deep cuts have been 

made, has resulted in the movement of large volumes of overburden. 

The effect of this mining and prospecting activity has been to rearrange radically the areal distribution of heavy metals that occurred in the veins, the gossans, and the soil, and any program of 

geochemical prospecting must recognize and evaluate such artificial 

disturbances of the natural distribution of these metals.

To give necessary background for the geochemical studies, a geologic description of the ore deposits has been prepared by S. Warren
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 3

Hobbs. The discussion of geology is followed by a description of 

the geochemical studies made by the author. Several analytical 

methods were tried during the work, and the results obtained varied 

in accuracy. The method of analysis used is stated for each group 

of samples, and a detailed description of each method, along with 

comments on its usefulness, is given in the appendix.

ACKNOWLEDGMENTS

The mining companies in the area were most helpful and cooperative in making information about their properties available. Special attention was given to the area over the workings of the Little 

Pittsburg mine and to the area near the Vindicator mine because of 

the very favorable circumstances in these areas for the establishment 

of basic control data. Acknowledgment is made to the officials of the 

Denver Development Co., Hecla Mining Co., Vindicator Silver-Lead 

Mining Co., and Day Mines, Inc., for their full cooperation. Members of the U.S. Geological Survey engaged in studying the geology 

and mineral deposits of the area contributed invaluable assistance 

during the work. Particular mention must be made of the contribution of S. Warren Hobbs not only for preparing the section on 

geology in this report but for the great amount of effort which he 

devoted to furthering the geochemical studies.

Most of the semiquantitative analyses were performed by H. E. 

Crowe, F. Frieske, V. J. Kling, A. P. Marranzino, J. H. McCarthy, 

Jr., A. P. Pierce, and J. P. Schuch, all of the U.S. Geological Survey; the quantitative determinations were made by H. E. Crowe 

and Harold Bloom, of the U.S. Geological Survey. Field assistants 

were F. D. Frieske, V. J. Kling, and A. P. Pierce.

GEOLOGY

By S. WARREN HOBBS

The Coeur d'Alene district is in the very rugged mountainous 

country of the Panhandle of northern Idaho. Narrow V-shaped 

valleys, sharp ridge crests, and hillsides that in some places have 

slopes as steep as 45° are evidence of a stage of full physiographic 

maturity. A complex geomorphic history has resulted in the formation of several terrace levels, but the remains of these are fragmentary and attested today only by the scattered occurrences of 

relatively small patches of high-level gravels and the moderately 

extensive lower terrace gravels in the vicinity of Mullan and Kellogg. Valley glaciation modified the uppermost reaches of numerous tributaries to the Coeur d'Alene River, but only in the upper 

part of Canyon Creek did these glaciers coalesce into a sizeable ice

550998 61 2
4 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

stream that extended down the main valley and deposited rather 

extensive morainal debris. Neither the terrace gravels nor the glacial detritus cover appreciable parts of the surface of the Coeur 

d'Alene district.

Abundant rainfall and snow have fostered the growth of dense 

vegetation, and, except where logging and forest fires have depleted 

the large trees, the area is covered by a coniferous forest and fairly 

heavy underbrush. Soil, ranging from a few inches to many feet in 

thickness, covers most of the area and is held in place on even the 

steepest slopes by plant growth. In spite of the extensive soil cover, 

bedrock exposures are numerous, especially on the high peaks, the 

sharp ridge crests, the cirque basins and walls, the stream bottoms, 

and as more resistant rocky ribs on the hill slopes themselves. In 

certain areas where vegetation has been destroyed by one cause or 

another, erosion has removed much soil cover leaving a loose rubble 

of rock nearly in place. This latter condition is especially characteristic of parts of the western end of the valley of the South Fork 

of the Coeur d'Alene Eiver and its tributaries.

The district lies within a part of a very extensive area that is 

underlain by slightly metamorphosed, structurally complex sedimentary rocks that are a part of the thick Belt series of Precambrian age. These rocks are predominantly fine-grained quartzite, 

impure quartzite, and siliceous argillites, which in certain zones 

contain greater or lesser amounts of calcium, magnesium, and iron 

carbonate. A group of alined small monzonite stocks intrude the 

sedimentary sequence and numerous lamprophyre and diabasic dikes 

have been localized along faults and fractures in the area. The bedded rocks have been displaced by extensive faulting and folding that 

has resulted in local overturning. The faults and associated fractures have been the principal loci for the development of the lead, 

zinc, silver, and copper veins for which the area is famous.

Six units totaling over 20,000 feet in thickness constitute the sedimentary sequence of the Belt series in the district. From base to 

top these are Prichard formation, Burke formation, Eevett quartzite, 

St. Kegis formation, Wallace formation, and Striped Peak formation. The base of the Prichard is nowhere exposed, and the upper 

part of the Striped Peak and the formations that presumably overlay it have been eroded.

The Prichard formation, for most part, is a very fine grained darkgray laminated siliceous argillite. Parts of it, particularly near the 

middle and at the top, contain lighter colored layers interlaminated 

with argillite layers, which give the rock a sharply laminated or 

thin-bedded appearance. Some massive pure quartzite beds occur 

in these more quartzitic parts of the formation. Abundant pyrite
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 5

is disseminated through the formation, and., on exposure to weathering 

processes, it oxidizes to hydrous oxides that color joint and bedding 

surfaces of outcrops a deep reddish brown. The Prichard formation is at least 12,000 feet thick.

The Burke formation is an impure quartzite usually medium to 

light gray green, with a few beds that have a delicate pink cast. 

The rocks are generally well bedded in layers 2 to 6 inches thick 

and on weathering break into slabs along bedding planes. Lamination is sparse and the individual layers or groups of layers are generally more uniform in composition than in the Prichard. In general, the Burke becomes more quartzitic toward the top, but a few 

rather thick beds of nearly pure quartzite may be found here and 

there throughout the section. The Burke formation ranges in thickness from 1,800 to 2,400 feet or more. Its contact with the Prichard 

formation below is fairly sharp but is completely gradational upward into the Revett quartzite through an interval of several hundred feet.

The Revett quartzite is a thick- to massive-bedded fine- to mediumgrained almost pure quartzite. It is generally very light gray to 

white on fresh surfaces. Certain parts contain blebs of disseminated iron carbonate which, upon oxidizing on weathered surfaces, 

form rusty speckles that make the rock appear mottled. Cross lamination is developed in many places. The lamination in the rock is 

most often marked by a concentration of dark-colored heavy minerals. On some weathered outcrops it is marked by an alineinent of 

small rusty speckles resulting from the oxidation of crystals and 

clots of iron-bearing carbonate whose localization was controlled by 

the laminae. Some less pure quartzite layers occur within the 

Revett, but these are generally not seen except in mine workings. 

On the surface they are usually covered by soil. Measurements of 

the Revett quartzite show the thickness to range from 2,400 to 3,400 

feet. Toward the top of the formation, the Revett quartzite becomes pinkish or reddish purple and includes increasing amounts of 

purplish-gray argillite and impure quartzite. Within a relatively 

short distance a transition is made into the characteristic overlying 

St. Regis formation.

The St. Regis formation is a somewhat heterogenous formation 

comprising thin-bedded argillites mixed with thin- to mediumbedded impure quartzites. Some considerable thicknesses of rocks 

in which argillite is predominant are interspersed in the section. 

The rocks are generally medium to dark shades of gray, purplish 

gray, and reddish gray. Although faint purplish coloration pervades the whole formation, only the more argillaceous facies are 

colored in more vivid shades of reddish gray and purplish gray.
6 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

Some parts of the St. Regis formation, particularly toward the top, 

contain appreciable amounts of ferrodolomite or ankerite that color 

the oxidized outcrop brown. After prolonged weathering, beds in 

which the carbonate is abundant become soft and punky, as well as 

dark brown. Throughout most of the district the purple part of 

the St. Kegis formation is overlain by a sequence of predominantly 

light-greenish-gray porcelaneous laminated argillites that range up 

to several hundred feet in thickness. The total thickness of the 

purple and green rocks included in the St. Regis formation ranges 

from 1,400 feet to well over 2,000 feet.

The Wallace formation comprises a heterogeneous assemblage of 

rocks, characterized by more carbonate than any other formation in 

the area and by certain rather diagnostic lithologic and structural 

features. Shenon and McConnel (1939) divided the Wallace formation into four parts that total nearly 4,500 feet of rock. Only the 

lowermost division comprising nearly 3,000 feet of the sections crops 

out extensively within the area. These rocks are predominantly thinto medium-bedded alternating light-gray quartzites and dark-gray 

to black argillites in layers from 2 to 6 inches or more thick. Ironbearing carbonate minerals are abundant at certain horizons and 

color weathered exposures brown. Small-scale crumpling and folding characterize much of the formation, and many shallow-water 

features are well formed. The Wallace formation above the lowest 

division is divided into three units: in ascending order, a thinly 

laminated, nearly black noncalcareous argillite; banded, dark-gray 

to black arenaceous limestone that weathers brick red, and a thinly 

laminated argillite like unit 1.

The Striped Peak formation overlies the Wallace formation but 

has, for the most part, been eroded from the area. The largest exposure is on Striped Peak itself where about 1,500 feet of strata of 

the lower part of the formation occur. The Striped Peak formation 

is composed principally of alternating purplish- or pinkish-gray and 

greenish-gray quartzites. Some layers containing carbonate occur in 

the sequence. The upper several hundred feet of the observable section is more argillaceous, laminated, and more vividly purple than 

the lower layers.

Stocks and small irregular masses of igneous rock, predominantly 

monzonite, but ranging from diorite to syenite have been intruded 

into the sedimentary rocks. These igneous rocks are mostly localized 

along a line trending north-northeast across the center of the district. 

An age determination from zircon contained in these rocks places the 

intrusion during the Laramide orogeny and suggests their relationship to the Idaho batholith. Diabase and lamprophyre dikes are 

also present in the area and are more randomly distributed than the 

monzonite stocks.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 7

All sedimentary rocks in the area have been subjected to relatively 

low-grade regional metamorphism that has converted the original 

mudstones, limy shales, and sandstones to argillites and quartzites, 

and in many places sericitic phyllites and schists have been produced 

in a complex history of deformation. Much of the fine-grained 

argillaceous material has been converted to sericite which, together 

with fine-grained quartz, constitutes the bulk of the rocks. Secondary 

tourmaline is sparsely but widely scattered throughout the sedimentary rocks. Near the intrusives more intense contact metamorphism 

has been superimposed on the regional effects. Widespread hydrothermal alteration that has bleached the rock has been localized 

along zones of more intense structural disturbance.

The rocks in the Coeur d'Alene mining area have been folded and 

faulted into a very complex pattern. The structure is dominated by 

the great Osburn fault that trends N. 70° "W. across the center of the 

area. Horizontal displacement along this fault is measured in miles, 

vertical displacement in thousands of feet.

North of the Osburn fault, the rocks have been moderately folded 

along axes that trend, in general, nearly north and south, but which 

swing sharply to the east where they adjoin the Osburn fault. South 

of the fault, the fold axes trend more westerly and tend to parallel 

the fault. Local contortions and irregularities are abundant, especially near the igneous stocks. There are several extensive areas in 

which the beds have been subjected to extreme deformation; the 

beds are in an overturned position and dip 60° to 80°.

Numerous faults, subparallel to the main Osburn zone, occur in 

a zone on either side of it. At a distance from the Osburn fault 

most notably to the north the faults tend to trend more north-south. 

Apparent displacement on the faults is normal on some and reverse 

on others. At least one low-angle thrust fault and one low-angle 

normal fault are exceptions to the generally steep dip of most of 

the faults.

The economically important metals for which the district is famous 

are lead, zinc, silver, and copper. Antimony, cadmium, tungsten, and 

small amounts of several minor metals are produced as byproducts. 

By far the greatest proportion of these metallic elements occurs in 

the minerals galena, sphalerite, and tetrahedrite. Gangue minerals 

of the productive veins include siderite, ankerite, quartz, pyrrhotite, 

pyrite, barite, and locally, some silicate minerals.

The economically important concentrations of these minerals form 

tabular ore shoots in generally steep-dipping veins or mineralized 

faults that are usually much more extensive than the ore shoots 

themselves. More than one ore shoot may be developed within a 

vein or fault; in some places the fault connecting the shoots may be 

barren or filled with gangue minerals. Some of the veins, including
8 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

ore shoots and barren gangue filling, can be traced for thousands of 

feet along the strike and have been developed to depths of more than 

a mile. Some of the ore shoots crop out at the surface; others have 

their tops at depths of as much as several thousand feet even though, 

in some places, the barren vein can itself be traced to the surface. 

Ore shoots in the district range in size from the smallest pod of ore 

than can be mined to such fabulous examples as the Morning-Star 

ore shoot that was more than 2,000 feet in strike length and over 

6,000 feet from the surface to the lowest levels mined. In the larger 

shoots the ore may be 20 or more feet wide, but the average width 

of minable ore in all shoots is probably 5 to 6 feet. The shoots tend 

to be longer down the dip than along the strike of the veins, and 

many of them are many times as deep as they are long. Most are 

essentially vertical in the plane of the vein, or they rake steeply in 

either direction. A few shoots, which are exceptions to the rule, 

have a flat rake or are essentially equidimensional in length and 

depth.

Most of the productive veins can be grouped in eight mineralized 

belts or zones, each of which is several thousand or more feet wide 

and from 6 to 12 miles long. These belts in general trend westnorthwest. Within each belt the individual veins may strike in several directions, but most approximate the trend of the mineral belt 

itself. Barren veins or veins of slight productivity occur outside 

the mineral belts, but usually they comprise gangue minerals of what 

is known as the early barren stage of mineralization. Such barren 

veins may contain scattered pockets of ore minerals, but very few 

have yielded more than a very small tonnage of commercial ore.

GEOCHEMISTRY 

SOIL AND HOCK STUDIES

The soil study constituted by far the largest part of the geochemical work done in the Coeur d'Alene area. This was for two reasons: 

first, from the start of the project, work on the soils showed promise; and second, plant and water analyses have disadvantages for 

prospecting in this district that limit their usefulness. The advantages of residual soil samples for prospecting include the following: 

The sample can be collected easily almost anywhere that information 

is needed; the sample is easily prepared for analysis; and the concentration of the ore element in the sample usually is related in a 

relatively simple way to the amount of the ore element present in 

the parent rock.

Rock analyses were made so that some understanding could be 

gained of the changes in heavy-metal concentration as rocks were 

weathered to form soil.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 9 

METHODS OF SAMPLING SOILS AND ROCKS

Soil samples were collected from the depth desired and then 

passed through a 5-mesh stainless steel screen at the sample spot. 

About 150 grams of the minus 5-mesh fraction was stored in halfpint waxed paper containers for later analysis.

Most samples were of surface soil taken by removing most of the 

humus and collecting a sample representative of the first 4 inches 

below the surface. In places where a sample was wanted from a 

greater depth, the soil was collected over a range of 4 inches centered at the desired depth.

Rock samples were usually obtained by breaking rock from exposures in roadcuts. A few boulders were broken open, and relatively 

fresh rock was obtained from their centers.

NORMAL SOILS AND BOCKS

As part of the work on soils, a total of 109 samples were collected 

beyond the periphery of the known mineralized district to serve as 

a basis for comparison with soil near mineralized areas. These samples were analyzed for copper, lead, and zinc by semiquantitative 

tests. Care was taken to be sure that the samples collected were 

typical of the soils on all sides of the mining district. The area 

surrounding the mining district was divided into quadrants by arbitrary lines, one north-south and one east-west, passing through a 

point about 4 miles northeast of the town of Osburn, Idaho. Approximately one-quarter of the samples were collected in each quadrant.

To assure that no soil sample collected for background study contained anomalous quantities of heavy metals, the data from the field 

analyses were carefully examined, and three samples containing obviously abnormal quantities of copper, lead, or zinc were removed from 

the group of samples. The remaining 106 samples were divided into 

4 groups representing each of the 4 quadrants, and 4 composite 

samples were prepared by taking 3 grams of the minus 80-mesh 

fraction from all samples in each quadrant and mixing thoroughly. 

In this way an average background sample for each quadrant was 

obtained. These average samples were analyzed by quantitative 

methods for copper, lead, and zinc. Similarly, 87 rock samples were 

grouped by quadrant and analyzed by field method. The anomalous 

samples were discarded, and composited samples were analyzed by 

quantitative methods which included a digestion in hydrofluoric acid. 

A total of 22 stream-sediment samples were collected at the same time 

as the soil and rock samples, and portions of the minus 2-millimeter 

fraction were mixed together to produce 1 sample of stream sediment
10 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

representing the whole area immediately surrounding the limits of 

the known mining district.

The data from the analysis of the composite soil, rock, and sediment samples are presented in table 1. The average composition of 

background soil was found to be about 21 ppm (parts per million) 

lead, 100 ppm zinc, and 24 ppm copper. It is evident that the lead, 

zinc, and copper concentrations in rock are less than that in the soil. 

The principal cause of this apparent enrichment in soil is not known, 

but there are several probable reasons. First, the soil samples were 

all minus 80 mesh and hence contain a higher percentage of fine 

grains than the soil as a whole, therefore, the heavy-metal content 

would be higher because the fine-grained material usually contains 

more copper, lead, and zinc than do the coarser grained parts of the 

samples. The rocks sampled were those found in roadcuts and outcrops (an attempt was made to get rock as fresh as possible); and 

these, being in general the more resistant rocks, usually contained 

less fine-grained material than the average rock in the area. The net 

result would be to cause the average soil to appear to have more 

heavy metals than the average rock collected. Second, selective 

leaching from the rocks of elements other than the heavy metals 

could cause enrichment. Third, concentration of metal-organic compounds in the soil could help account for the increase in heavy 

metals.

TABLE 1. Normal, or background, content of lead, zinc, and copper in soils, rocks, 

and stream sediments near the Coeur d'Alene mining area

Quantitative methods of analysis were used; analysts, H. E. Growe and Harold Bloom, U.S. Geological

Survey]

Quadrant in which 

composite sample

was collected

Soil

24

20

22

20

Lead 

(ppm)

Rock

15

15

10

10

12

Stream 

sediment

40

Soil

120

90

95

100

100

Zinc 

(ppm)

Rock

56

50

28

42

44

Stream 

sediment

76

Soil

22

23

27

24

24

Ooppe 

(ppm)

Rock

9

17

13

14

13

r

Stream 

sediment

45

The table shows that lead and copper are present in stream sediments in amounts greater than in rocks and soil and also that zinc is 

held in the stream sediments in amounts that are less than that in 

soil, but more than in the rock. The reasons for this are not known, 

but it seems probable that difference in particle size is not the entire 

explanation, for the sediments in general were coarser grained than 

were the soils.

When soil samples are digested in chemical reagents that are less
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 11

vigorous than the nitric-perchloric mixture used to obtain the results 

in table 1, only an incomplete extraction of the heavy metals can be 

expected, and the concentrations obtained for normal soils may be 

less than those listed. Should such an incomplete extraction of a 

sample indicate a concentration of ore metals that is several times 

background, a source other than normal bedrock can be safely assumed for the sample. In general, when using the standard field 

tests, ore-metal concentrations from 2 to 4 times the normal or background concentrations of lead, zinc, and copper given in table 1 

probably represent an anomalous condition; and concentrations 

greater than 4 times background, with a few exceptions, represent 

definite anomalies.

SOIL, SAMPLING NEAR MINERALIZED AREAS

When the present geochemical work was begun in the Coeur 

d'Alene district, soil samples were collected in 20 mineralized areas 

to measure the heavy-metal concentrations in soil near veins known 

to contain at least a small quantity of an ore metal, either at depth 

or near the surface. At most places the lack of time made it impractical to study the extent of any anomaly beyond the mere proof of 

its existence or absence. However, from the 20 areas, 2 more or less 

representative ones were selected for detailed study and analysis. 

These areas were: (1) near the Little Pittsburg vein in the Pine 

Creek area close to the west edge of the district; and (2) near the 

Vindicator vein, in the vicinity of Mullan at the east end of the 

district (pi. 1). The Little Pittsburg vein, for at least part of its 

length, crops out as a conspicuous quartz vein containing limonite 

and secondary lead and zinc minerals. The Vindicator vein is also 

mainly quartz, but its outcrop is much narrower and not as highly 

mineralized as the outcrop of the Little Pittsburg vein.

In addition to the studies of lead, zinc, and copper veins in the 

district, some soil samples were collected over the Golden Chest gold 

vein near Murray and over the Star Antimony vein in the Pine 

Creek area. The Golden Chest contains at least one shoot of tungsten ore, and soil samples were collected to determine whether 

anomalous amounts of tungsten could be detected in soil near this vein.

Details of the soil analyses from the vein localities that were studied are presented on the following pages together with geologic 

information which might be of value in the interpretation of the 

analytical results. The descriptions of the studies are grouped 

according to the major ore metal present in the vein near the surface. Plate 1 is an index map showing the locations of the soilsampling areas.

550998 61 3
12 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

VEINS CONTAINING MAINLY LEAD MINERALS NEAR THE SURFACE

Jack Waite vein. The Jack Waite mine is near the head of Tributary Creek, a branch of the East Fork of Eagle Creek, about 6 miles 

east-northeast of Murray (pi. 1). Umpleby and Jones (1923, p. 85) 

state that 

"It is enclosed in Prichard beds at horizons probably between 3,000 and 4,500 

feet below the base of the Burke quartzite. The vein strikes N. 55° W. and 

dips 52° SW., crossing the bedding of the enclosing slates and quartzites, which 

dip 20° 40° NE. The deposit is a quartz-filled fissure that ranges from a fraction of an inch to 10 feet in width and averages perhaps 4 feet."

The soil samples were collected near the crest of the high ridge 

marking the Idaho-Montana State line and lying southeast of the 

main mine entrance. Two short prospecting crosscuts have been 

driven on the vein in the sampling area, but these have not contaminated the soil beyond the immediate vicinity of the dumps. Vein 

quartz was found on the dumps in small quantities, but apparently 

the vein did not contain much ore where these tunnels intersected it.

The location of the soil-sampling sites in relation to the projected 

outcrop of the Jack Waite vein, is shown on figure 1. The soil 

samples were analyzed for lead, zinc, and, when the samples were

EXPLANATION

.80

Soil-sampling point and lead 

concentration in parts per million

Projected outcrop of the Jack Waite vein

/ 

Approximate direction of downslope

>tCaved adit

Semiquantitative method of analysis was used

FIGURE 1. Plan view of soil-sampling traverses near the Jack Waite vein.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 13

high in lead, for copper using the 1:7 HNOs method of extraction. 

(See appendix for detailed description of method.) No samples 

were found which contained anomalous quantities of zinc or copper; 

hence, only the lead concentrations are shown on the map.

There are no large clear-cut anomalies associated with the Jack 

Waite vein in the area sampled. In the vicinity of the vein, the lead 

content of the soil certainly exceeds the normal background value 

of 10 to 20 ppm; but, compared to the lead content of soil near other 

veins in the district, the anomaly is very small. About 150 feet 

north of the Jack Waite vein on the east side of the ridge crest, a 

group of soil samples was taken which contains more lead than 

samples taken near the main vein. These samples may indicate the 

outcrop of a branch structure in the f ootwall of the Jack Waite vein.

Hercules vein. The Hercules vein, according to Kansome and 

Calkins (1908, p. 115), strikes west-northwest and dips south at a 

high angle.

The Hercules mine, about 1% miles north of Burke (pi. 1), has 

produced large amounts of ore from one main ore shoot that extended 

to the surface where its strike length was between 400 and 500 feet. 

The principal metals mined were lead arid silver. The position of 

the ore shoot, now essentially mined out in the upper parts, is 

marked by a large elongate caved area over the old stopes. The 

soil sampling was done near the large caved area above the uppermost tunnel of the Hercules mine.

Figure 2 is a sketch map of the sampling area. Lead concentrations in every sample were at least 10 times the normal lead concen12 11 10 9 8 7 6 5 4 3 

SAMPLE NUMBERS

EXPLANATION

Approximate location of vein

.7 

Sample number and location

-K

Caved adit

Dump

FIGURE 2. Plan view of soil-sampling traverse, and graph showing concentration of lead 

and heavy metals in soil near the Hercules vein.
14 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

tration in soil; so the sampling traverse was entirely within, or 

downslope from, the mineralized area. Because the samples were 

collected so near the mine workings, contamination may have been 

a factor in the high-lead concentrations found. However, evidence 

against the likelihood of much contamination is the fact that very 

little rock was thrown out near the large caved area. Considering 

the direction of landslope and the vein location, the soil anomalies 

indicate that there is a mineralized zone in the area rather than one 

distinct vein. Analyses for zinc and copper showed no definite 

anomalous concentrations of these elements in the samples collected. 

Sample extraction was by 1:7 HNOs.

On figure 2 it should be noted that the lead concentrations are 

greater than those of the total heavy metals. This is because of the 

different sensitivity of dithizone in analyzing for copper, lead, and 

zinc. To produce a given color change in dithizone, about four times 

as much lead or twice as much copper is required compared to zinc.

Because the relative proportions of the metals being estimated in 

the heavy metals test are not known, the total heavy-metals content 

is arbitrarily expressed as zinc even though the dithizone color obtained during analysis could also be produced by considerably more 

lead. Thus a sample containing 400 ppm of lead and no zinc or 

copper would yield a dithizone color equal to that produced by a 

sample containing only 100 ppm of zinc. A total heavy-metals 

determination would result in an estimate of 100 ppm of total heavy 

metals for either sample.

Ouster Peak area. Ouster Peak is about 1 mile northwest of 

Burke (pi. 1). A mineralized zone connecting the Sherman and 

Tamarack mines is believed to cross high on the south slope of the 

mountain. Only a little surface prospecting has been done in this 

area; so the slope is essentially uncontaminated by dump material. 

However, this mineralized zone has been explored at depth by a drift 

that connects the Sherman and Tamarack mines and is considered 

barren insofar as commercial ore is concerned. Figure 3 is a sketch 

showing the sample points in relation to topography and estimated 

location of the vein. Also shown are graphs of the lead content of 

soil samples taken from 2 to 4 inches and 10 to 12 inches below the 

surface. Soil analyses were made using a 1:1 HNO3 digestion. 

Apparently there is a concentration of lead in the soil as high as 

100 times background, but neither copper nor zinc anomalies were 

found in the area. The lead anomalies here are several times as 

large as those over the Jack Waite vein, and yet there are no known 

ore bodies within 1,000 feet of the point where the sampling traverse 

crosses the vein.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 15

2400- 

JJsterPeak^ N Z 2000-

.^ 

* ' -»_

^Ti ? ---

&

|

0

.10

7 .9

O

' ^1600

5

£1200-

a. ,

g 800-

< Q- 400-

b

8 0-

/ \

Downslope / \

' \Lead /

' \

>----« ^,4 ----».-__ '

\ _,«'"

\''''*"

_ _^ _ _^^^ 7inr ^

 * -~---^^ _ 0^.----^"- *

1 2 3 4' 5 6 7 8 9 10 1

EXPLANATION 

Approximate location of vein 

Sample number and location

6 2800-

2400-

 5 z

22000-

* 5 1600-

cc

.3 ^1200-

t/3

SAMPLE NUMBERS 

SAMPLES AT 2- TO 4-INCH DEPTHS

Downslope

? 3 4 5 6 7 8 9

SAMPLE ISRJMBERS 

SAMPLES AT 10- TO 12-INCH DEPTHS

10 11

FIGURE 3. Plan view of soil-sampling traverse, and graphs showing concentration of 

lead and zinc in soil in the Custer Peak area.

The persistence of the anomalous concentration of lead in the soil 

downslope from the vein may be caused by several factors. There 

is very little vegetation on the steep slope below the vein and, as a 

result, rains cause very rapid downslope movement of soil. The 

presence of additional veins downslope could add more lead to the 

soil to produce the effect noted, and evidence for this can be seen in 

the way in which the lead concentration increases near samples 2 

and 7. It is possible that the vein being studied intersects the traverse upslope from sample 7 instead of upslope from sample 11, for 

the exact vein location is not known. If this is so, however, a source 

of lead upslope from sample 11 must be assumed.

It may be of interest to calculate the total quantity of lead lying 

on the slope in the soil. If the lead concentration is assumed to 

remain constant for 50 feet on both sides of the line of traverse and 

the soil is about 1 foot thick, the lead in this area would amount to 

at least 6 tons if the soil contains an average of 0.06 percent lead.

Standard-Mammoth vein. Two sample traverses were run just 

east of an area where stoping on the vein had reached the surface 

about a mile northwest of Mace (pi. 1). Figure 4 shows both the 

locations where the soil samples were taken and the results of this 

soil sampling. The Standard-Mammoth vein strikes N. 83° W., 

dips about 80° N., and is entirely within the Burke formation. The
16 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

1000-

z 800-

g

=j 600-1

^

gyr

L4J

0_ 400-

QC ( < 200-

n 

f ^ 

' ' Downslope

/ \

/ \

/ \ Lead 

/ \

^ / X

 ^^j \

^* \

\

\

\

\

)

234567 

SAMPLE NUMBERS

Stope on vein ~

Dump

9 10 11 12 

SAMPLE NUMBERS

8

EXPLANATION

 3 

Sample number and location

FIGURE 4. Plan view of soil-sampling traverse, and graphs showing concentration of 

lead and zinc in soil near the Standard-Mammoth vein.

ore body where mined ranged in width from 5 to 15 feet; the principal ore mineral was galena. Some sphalerite and chalcopyrite 

were associated with the galena (Eansome and Calkins, 1908, p. 177).

Anomalous quantities of lead were found, but zinc was present in 

concentrations only slightly in excess of background. All samples 

were taken within the area of anomalous lead concentration; so the 

maximum distance downslope at which the presence of the vein was 

indicated by anomalous quantities of lead in the soil is unknown.

The samples which are highest in lead content are not immediately 

downslope from the projected vein outcrop. The reasons for this are 

not known; however, it is possible that the strike of the vein between 

the stope and the first sample traverse (samples 1 to 7) is not the 

same as the general strike of the vein the strike used in projecting 

the outcrop location. The second traverse was apparently not extended downslope far enough to cross the vein extension. Nevertheless, the presence of anomalous quantities of lead definitely indicates 

that the area is mineralized.

A 1:1 HNOs extraction method was used in analyzing these soil 

samples.

Frisco mine. The Frisco mine is on the south side of Canyon 

Creek near Gem (pi. 1). The Frisco vein is in the Prichard and
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 17

Burke formations and consists of stringers of galena and sphalerite 

enclosing many fragments of quartzite. The ore shoot has been mined 

for a maximum strike length of 1,000 feet and for a width of 10 to 

20 feet (Umpleby and Jones, 1923, p. 101).

Part of the outcrop of the Frisco vein lies near a ridge crest with 

a comparatively undisturbed hillside downslope to the north. These 

conditions offered an excellent chance to determine the concentration 

of lead and zinc in the soil associated with the Frisco vein. Figure 5 

shows the results of soil sampling on a traverse crossing the outcrop 

of the Frisco vein. Lead shows a very large concentration above 

background although the zinc concentrations are only 3 to 4 times 

background.

The wide variations in lead and zinc concentrations from one sample to the next are probably due to at least two factors: first, the 

field tests used (1:7 HNOs, the solvent in this test) are accurate to 

30 to 50 percent of the amount of the element present; second, the 

probable inclusion of individual pieces of gossan material in the 

soil sample can cause erratic results when the sample taken for 

analysis is small. The change from a low concentration of lead at 

point 4 (fig. 5) to the high concentration at point 5 is an increase 

by a factor of 15, which, along with the other high samples downslope, indicates a true increase in concentration. Although zinc concentrations do not show the sharp contrast that lead does, the fact 

that the average zinc concentration from point 3 onward is higher 

than that from point 1 to point 3 indicates that there is also a true 

increase in zinc.

16 t

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

SAMPLE NUMBERS

_^ 3 EXPLANATION

*"~ Direction of downslope

* v. W5 

^ Sample number and location

- 1 a

Raise

100 0 100 200 FEET X 

' ' ' ' ' Pit thought to be on vein

Approximate location of outcrop of vein

r Mine portal

FIGURE 5. Plan view of soil-sampling traverse, and graph showing the lead and zinc 

concentration in the soil near the Frisco mine.
18 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

The source of lead and zinc between samples 4 and 5 is not near 

the estimated location of the Frisco vein and must be assumed to be 

a separate source whose nature is not known.

Star vein. The Star vein crops out in Grouse Gulch about 2 miles 

north-northwest of Mullan (pi. 1), where some gossan thrown out 

from an old prospect pit on the vein contains much cerussite. The 

ore mined near the surface was predominantly zinc; however, the 

vein is contributing much more lead than zinc to the soil in the area 

studied, and it is therefore assumed that the vein contains more lead 

than zinc at the grass roots. For this study, the vein has been 

grouped with those having a high concentration of lead.

A series of soil samples was collected beginning about 500 feet 

upslope from the vein location as projected from the cerussite pit and 

continuing at about 100-foot intervals to a point about 400 feet 

downslope from the vein. The traverse was stopped at the edge of 

an area greatly disturbed by prospecting and bulldozing. Figure 6 

shows the location of the sample points and a graph of the concentrations of lead and zinc in the soil.

Although the soil contained anomalous amounts of lead for 500 

feet upslope from the vein, the position of the vein was easily located 

by the sharp increase in lead concentration in the soil just downslope 

from the vein. Zinc concentrations appeared to increase slightly in 

the vicinity of, and downslope from, the projected vein outcrop. An 

additional source of lead and zinc must be present upslope from 

sample point 2 (fig. 6).

A 1:7 HNOs extraction was used in obtaining the lead and zinc 

concentrations shown.

Gold Hunter vein. The Gold Hunter mine is in Gold Hunter 

Gulch about a mile northeast of Mullan (pi. 1). The ore body, now 

mined out, consisted of a zone of veins and veinlets at least YO feet 

wide. The zone strikes N. Y5° W. and dips 80° or more to the south 

(Ransome and Calkins, 1908, p. 169, 170). The ore in the upper 

part of the vein was valuable mainly for its lead and silver, but some 

copper, antimony, and zinc were present.

The soil-sampling traverse intersected the vein at a high angle 

about 150 feet west of the west edge of the glory hole on the vein. 

No evidence of mining activity was seen beyond a few feet from 

the glory hole, and it seems probable that contamination of soil 

samples due to mining activity is negligible. Figure Y shows the 

locations of sample points and a graph of the concentrations of lead 

and zinc in the soil.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 19

EXPLANATION 

.3

Sample number and location

100 200 FEET .. 

 w

10

NW Si

3000-

Z

° 2000-

o:

LU

CL

K 1000-

o:

t 

i

n_

^

Lead^' ^*N

V '-^

^^

\

1 \

t

~--^ - ' Zinc

k^"^ ^ « - -" "^

34567 

SAMPLE NUMBERS

9 10

FIGURE 6. Plan view of soil-sampling traverse and a graph showing the lead and zinc 

concentrations in the soil near the Star vein.
20 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

N. S.

2500 -

25';

12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 

SAMPLE NUMBERS

EXPLANATION 

Projection of vein

Direction and degree 

of downslope

Sample number and location

200 FEET

FIGURE 7. Plan view of soil-sampling traverse and a graph showing concentration of 

lead and zinc in the soil, Gold Hunter vein.

The concentration of lead in soil near the vein shows great contrast with background, but the concentrations of zinc and copper 

do not increase. The sharp increase in lead concentration between 

samples 11 and 12 suggest that the northern boundary of the mineralized zone lies between these two sample points. The southern 

boundary cannot be detected because of the movement of vein material downslope. Anomalous concentrations of lead in soil extend 

downslope for a distance of at least 450 feet from the known mineralized zone, and probably extend farther, but bulldozing operations downslope from the location of sample 1 have so disturbed 

the natural soil distribution that sample data would be meaningless.

In addition to analyzing soil samples for lead, zinc, and copper, 

analyses were also made for silver and antimony on samples 8 

through 10. The silver concentration in these three samples was 

about 1.0 ppm, and the antimony about 3 ppm. This represents a 

concentration factor over background of about 10 for silver and 6 

for antimony.

The lead, zinc, and copper analyses were made using a 1:7 

digestion.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 21

Vindicator vein. The Vindicator vein crops out on the steep hill 

slope that bounds the north side of the valley of the South Fork of 

the Coeur d'Alene River about 1.2 miles east-northeast of Mullan 

(pi. 1). The vein strikes almost due west and dips about 60° north. 

A series of shallow prospect pits marks the outcrop, and 2 crosscuts 

have been driven to the vein; 1 about 100 feet below the outcrop, and 

1 slightly above the level of the river at about 380 feet below the 

outcrop. The main ore mineral is galena which is in a quartz gangue 

with small amounts of chalcopyrite and sphalerite. Some silver also 

is present in the ore.

A detailed study was made not only of the soil in the vicinity of 

the vein but also of the soil in the area to the north and east of the 

vein. All soil samples were analyzed for both lead and zinc using 

a 1:1 HNO3 digestion, and a few samples near the Vindicator vein 

were analyzed for copper. Plates 2 and 3 show the area studied, the 

location of the sample points, and the concentrations of lead and 

zinc in the soil.

This area was one of two selected for special attention because 

they presented conditions favorable to a systematic detailed study 

of the behavior of ore metals in soil. At the Vindicator mine, the 

location of the outcrop is well defined, the character of the mineralization is known, the soil cover is relatively undisturbed, and the 

metal content of the vein is rather low. At the other area studied 

in detail, that near the Little Pittsburg vein, to be described later, 

the conditions are similar to those at the Vindicator except that 

the known metal content of the vein is relatively high. Originally, 

the soil sampling at the Vindicator was intended to cover only the 

area near the vein; however, in extending the sampling traverses to 

the north into supposedly nonmineralized country, a second area of 

soil anomalies was found. After the soil sampling was complete, it 

was apparent that the area northeast of the Vindicator vein for an 

unknown distance was covered with soil that contained aboveaverage quantities of lead and zinc. The task of thoroughly outlining the extent of this large anomalous area was beyond the scope 

of this study.

The concentration of lead in soils as plotted on plate 2 and that 

of zinc as plotted on plate 3 shows a marked alinement of anomalous 

soils in a nearly east-west direction along the Vindicator vein and a 

second less well defined alinement of anomalous soils along a N. 65° 

W. trend about 600 feet northeast from the east end of the main 

Vindicator vein. The trend of the N. 65° W. anomaly is in accordance with the strike of a few veinlets found in one of the bulldozed 

trenches cut into the northeastern part of the mapped area (Robert 

E. Wallace, oral communication, 1952). It also alines with some
22 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

fracture zones found in the lower Vindicator crosscut north of its 

intersection with the Vindicator vein.

The fact that small but widespread anomalies in lead and zinc 

are in the soil over the entire northeastern part of the mapped area 

suggests that the metals are probably contributed to the soil by 

many small veinlets scattered over a rather wide area instead of by 

a single large vein.

Samples were taken along several traverses extending downslope 

across the Vindicator vein to determine the maximum distance from 

the vein at which anomalous quantities of lead and zinc could be 

detected in the soil. Three traverses were extended downslope from 

the vein for a distance of 500 or more feet, but all cut disturbed 

and possibly contaminated areas before soils containing background 

concentrations of lead were found. Zinc concentrations, however, 

decreased rapidly below the vein, so that soils within 50 to 100 feet 

downslope from the vein outcrop apparently contained only background amounts of zinc. Lead anomalies could be detected much 

farther downslope than zinc anomalies probably because the soil 

over the vein contains lead in quantities 20 to 30 times background, 

whereas the zinc concentrations are only about 3 times background. 

After the main vein had been located by the cross traverses and by 

examination of the prospect pits, a second series of samples was 

collected along a line 10 to 20 feet downslope from and parallel to 

the vein outcrop to determine the variations in lead and zinc along 

the strike of the vein. As expected, the results showed higher concentrations of lead and zinc downslope from areas where the prospectors had found lead, zinc, and copper in the vein and comparatively low lead and zinc concentrations below where the vein material appeared barren.

The effects on analytical results of the depth of the sample and 

of slight changes in sample location were tested by making three 

closely spaced traverses downslope across the Vindicator vein. The 

traverses were spaced 2 feet apart, and samples were collected near 

the surface and at a depth of 10 to 14 inches at each sample point. 

Samples were taken at 5-foot intervals along the traverses from a 

point 50 feet upslope from the vein to a point 50 feet downslope 

from it and also at points 60, 70, 90, and 110 feet downslope from 

the vein. A plan view of the sample locations and graphs of 

the analytical results are presented in figure 8. All traverses, both 

near the surface and at the 12- to 14-inch depth, show the same 

general pattern, although the analytical results do not show a smooth 

curve. Some of this variation from a smooth curve may be due to 

the semiquantitative nature of the field tests; the rest of the deviation may be due to the presence of small veinlets in the wallrock 

of the main Vindicator vein. The samples taken at about 12-inch
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 23

EXPLANATION

First traverse 

Second traverse 

Third traverse

20 40 60 SO ' ' 'l6o' ' 'l2o' ' 'l4o' ' 'l60 

SLOPE DISTANCE, IN FEET 

LEAD CONCENTRATION AT 2- TO 4-INCH-DEPTHS

Location of 

vein

Sample 

/ points

S. 

4000-1

3500-

g

IJ3000- 

UJ 2500- 

^2000-

- 1500-

9LU-"1000- 

500-

Downslope

EXPLANATION

20

First traverse

Second traverse

Third traverse

40 60 80 100 ' '120 140

SLOPE DISTANCE, IN FEET 

LEAD CONCENTRATION AT 12-TO 14-INCH DEPTHS

PLAN VIEW OF TRAVERSES

0 30 60 FEET

£2 isooSl 500

Downslope

Average value of three soil 

samples at 12- to 14-inch 

depths

Average value of three soil 

samples at 2- to 4-inch 

depths

20 0 60 80 100 120 140

SLOPE DISTANCE, IN FEET

COMPARISON OF LEAD CONCENTRATION AT 2- TO 

4-INCH AND 12-TO 14-INCH DEPTHS

FIGURE 8. Plan view of three closely spaced soil-sampling traverses, and graphs showing 

comparison of lead concentration in the soil at 2- to 4-inch and 12- to 14-Inch depths, 

Vindicator vein.
24 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

depth show a much larger anomaly at the vein outcrop than do those 

taken at the surface. This is probably due to the greater dilution 

of vein material in the upper soil horizons as normal soils move 

downslope across the vein.

An analysis of the detailed sampling shows two facts that require 

explanation. The first is an unusual quantity of lead present in the 

soil upslope from the outcrop of the Vindicator vein; this fact may 

be explained by the presence of mineral-bearing veinlets in the wallrock adjacent to the vein. The second is the fact that downslope 

from the outcrop the lead content of a soil sample taken at a 12-inch 

depth is about the same as the lead content at the surface. Ideally, 

the soil creeping downslope from a single source of metal should 

have a higher concentration in its upper part because the lower soil 

horizons are diluted by material derived from the adjacent country 

rock containing only background values. Again the explanation 

may be the presence of metal-bearing veinlets in the wallrock to the 

side of the main vein; however, thorough vertical mixing would also 

produce the effect noted.

In summary, the soil sampling at the Vindicator shows that it is 

possible to find slightly mineralized veins particularly lead-bearing 

ones and to detect the cumulative effects of many small veinlets 

which are contributing heavy metals to the soil over a broad zone. 

In addition, the depth in the soil from which the sample is collected 

is apparently not critical in this area.

Sidney vein. The Sidney vein is about 4 miles south-southwest 

of Smelterville (pi. 1). The vein strikes about due west and crops 

out in a line running almost directly upslope eastward from the 

valley of Denver Creek. In the upper levels of the mine, the ores 

were mainly oxidized lead and silver minerals. Several levels were 

driven on the vein above the bottom of the valley, but near the ridge 

crest, between Denver Creek and Red Cloud Creek, the projected 

outcrop of the vein is comparatively undisturbed. In recent years 

bulldozer cuts have been made on both sides of the ridge within a 

few hundred feet of the crest and the Sidney vein outcrop in the 

two cuts has been approximately located.

A series of six soil samples, spaced 20 feet apart on traverse, were 

collected along the upper side of the bulldozer cuts on each side of 

the ridge crest. Because the bulldozer cuts were made along the 

contour line and the strike of the vein was almost directly downslope, the line of outcrop of the vein was very nearly at right angles 

to the line of samples.

The analytical results from the soils collected are shown on figure 9. No anomalous quantities of zinc were found in the soil, but 

the lead concentrations increased to about 45 times background.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 25

0 20 40 60 SiO 100 

DISTANCE ALONG TRAVERSE, IN FEET

"0 20 40 60 80 100 

DISTANCE ALONG TRAVERSE. IN FEET

FIGURE 9. Graphs showing lead concentration in the soil near the Sidney vein.

Apparently the traverses were not of sufficient length to extend beyond the area of high concentration of lead in the soils near the 

outcrop of the Sidney vein, for none of the samples collected contained less than 3 times the normal concentration of lead in soil.

A 1:7 HNOs method of digestion was used in making the analyses.

Little Pittsburg vein. The Little Pittsburg vein crops out on the 

west side of Denver Creek about 4 miles south-southwest of Smelterville (pi. 1). The strike of the vein changes gradually from slightly 

west of north to northwest as it is followed northward. The dip 

to the southwest changes from about 70° near the surface to 50° or 

less at depth.

A detailed study of the Little Pittsburg area was made to obtain 

a better understanding of the behavior of lead and zinc in soil around 

a vein which contains considerable lead and zinc. Although several 

prospect pits mark the course of the vein on the surface, large areas 

of the soil cover are undisturbed, and the samples collected are believed to be uncontaminated. The data resulting from a general 

heavy-metals test, a zinc test, and a lead test on each sample are 

shown on plates 4-6. These data are presented in a somewhat different manner from that used at the Vindicator property because the 

range of lead-zinc concentration is much greater.

Plate 4 shows the results of the general heavy-metals test at the 

Little Pittsburg mine and is essentially a summary of plates 5 and 6 

which show lead and zinc concentrations. Copper concentrations 

when measured, were very low; and other metals, which would react 

with dithizone, are believed to be present in negligible amounts. It 

should be remembered that because of different sensitivity of dithizone for different elements, the figure for total heavy metals in parts 

per million approximately represents the sum of all the zinc, onehalf the copper, and one-fourth the lead.

The outcrop of the Little Pittsburg vein, as projected from the 

underground workings, is shown on plates 4-6. Moderately good 

correlation of the projected position with anomalous values of lead
26 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

and zinc in the soil, as well as with two prospect pits containing 

iron-stained rock, was obtained. Apparently the intensity of mineralization varies along the vein at the surface, for the amount of heavy 

metals entering the soil from the vein shows pronounced changes. 

This is to be expected, for the vein at depth is barren at some points 

and carries ore several feet in width at other points. The vein contains only slight amounts of lead and zinc in the area between the 

two drifts on level 4. This fact is consistent with the small amounts 

of lead and zinc in the soil at the outcrop of this part of the vein. 

To the northwest of this barren area the major ore shoot extends 

toward the surface, but ends at least 300 feet from the surface downdip on the vein. Nevertheless, geochemical evidence of this shoot is 

present at the surface for some of its length.

Several anomalies found during the soil sampling are not explained by the position of the Little Pittsburg vein. The anomaly 

in lead, zinc, and heavy metals at point E (pis. 4-6) cannot be related to an upward extension of the Little Pittsburg vein, and there 

is a series of unexplained anomalies about 150 feet to the east of the 

projected outcrop of the Little Pittsburg vein (points A, Z?, and /). 

The anomalies are slight to the north of point /, but at points A and 

B they are very pronounced. The anomalous amounts of lead at 

point N may be part of this same parallel zone. If the mineralized 

zone diverges from the Little Pittsburg vein, then points 7, K, Z, 

and M may mark its extension. Some sampling at depths of 12 to 

18 inches was done on the east-west traverses lying just south of 

points A and B, and a trench about 100 feet long was dug along the 

traverse near A. The analytical results from soil, rock, and vein 

samples are presented in figures 10 and 11.

A junction of the projection of the mineralized zone lying east of 

the Little Pittsburg vein with the southeastern end of level 5 (pis. 

4-6) apparently was not detected during mining activity; but, if the 

zone does cross level 5, it would be difficult to find because level 5 

follows the slightly mineralized Crystallite fault for about 300 feet 

in this area. Several holes were drilled from the Little Pittsburg 

mine into the area underlying the anomalous soil samples to the east 

of the Little Pittsburg vein. These holes found no commercial 

mineralization.

As there appeared to be a mineralized zone to the east of, and 

approximately parallel to, the Little Pittsburg vein, an effort was 

made to determine whether the anomaly at point E (pis. 4-6) lay 

on a similar zone to the west of the Little Pittsburg vein. The series 

of east-west sample traverses extending east from the ridge crest 

between points C and E was made to intersect this zone, if present, 

and additional samples were taken to the north and west of point E
GEOCHEMICAL STUDIES, COETJR D'ALENE DISTRICT, IDAHO 27

10,000 -

Point where traverse crosses 

outcrop of vein, showing 

index number of vein

80 120 160 200 240 280 320 360 400 

DOWNSLOPE DISTANCE ALONG TRAVERSE NEAR POINT A (See pis. 4-6)

FIGURE 10. Graph showing concentration of lead and zinc in soil south of point A,

Little Pittsburg area.

for the same reason. At point G a slight anomaly in zinc and lead 

was detected, but no connection with the anomaly at point E was 

established. The high concentrations of lead and zinc immediately 

to the south and east of point E can be explained by soil movement 

downslope from point E, but the anomaly in the area lying about 

75 feet northwest of point E could not be explained on this basis. 

Therefore, a northwest strike was indicated for the mineralized zone. 

On the basis of this information a trench 15 feet long was dug to 

bedrock about 18 inches below the surface and a search was made 

for gossan material at the point where geochemical evidence suggested mineralization. As a result of the trenching, a gossan zone 

about 3 inches wide was found trending N". 65° W. An assay of the 

gossan material by D. L. Skinner, of the U.S. Geological Survey, 

showed 17.26 ounces of silver to the ton. An estimate of the lead 

content by assay was 45 percent. The gossan contained little or no 

quartz and crumbled easily. Hence, very little float material from

550998 60 5
28 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

the vein was seen at the ground surface. The slight anomaly at 

point G is in line with the anomalies near point E, but the mineralization has been so slight, if present between G and Et that it would 

be difficult to prove a connection between the two points.

A series of closely spaced soil samples was collected on a short 

traverse across the vein discovered near point E. The results are 

presented in figure 12. Apparently the vein material travels downslope about 4 feet before working its way up to the surface.

w,

45,000-

40,000-

35,000-

30,000-

 , 25,000-

20,000-

15,000-

10,000-

EXPLANAT1ON

Lead concentrations 

in surface soil

Lead concentrations 

at 12- to 18-inch depth

Zinc concentrations 

in surface soil

Zinc concentrations 

at 12- to 18-inch depth

Caved area at junction of 

Crystallite fault and vein 

in hanging wall

Downslope 20°-30° 

Eastward

r

- -V

0 40 80 120 160 200 240 280 320 345 

DOWNSLOPE DISTANCE ALONG TRAVERSE SOUTH OF POINT B (See pis. 4-6)

FIGURE 11. Graph showing concentration of lead and zinc in soil Bouth of point B,

Little Pittsbnrg area.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 29

s

80,000 -

70,000 '

60,000- 

50,000-

z

§ 40,000-

_i

m

(£ 

LU 

Q.

{2 30,000-

C£

£

20,000- 

10,000

/ \ T° 7\

/ \120.000 /\ EXPLANATION 

/ LPPm / \

' \ / \ Lead in surface soil

/ V \ 

~ Lead in 

___ soil near bedrock

\ Zinc in surface soil

. «_ Zinc in soil near bedrock 

\ / »

\ / \

V \ k \

\ 

\ 

\

Downslope 10° \

Southward I

\ 

\ 

\ 

\ 

\

K--» « NB

A \

\ ' \ \

\ ^- ' \ VA

V/ V-- ^. ^,^»^ \

^- Vein*' ^-^rrl

4 6 8 10 12 

DISTANCE ALONG TRAVERSE, IN FEET

14

FIGURE 12. Graph showing concentration of lead and zinc in soil across a vein located 

35 feet northwest of point E (pis. 4-6), Little Pittsburg area.

A vein in the hanging wall rises almost vertically from the level 4 

of the Little Pittsburg vein in the area to the southeast of point E. 

The approximate length and position of this ore shoot is indicated 

by the short section of level 4. Point D is just east of a stope which 

has broken through to the surface on this vein. If the vein in the 

hanging wall undergoes an abrupt change in strike, it may account 

for the anomaly at point E, but detailed work would be necessary to 

establish this. Two faults, paralleling the Crystallite fault and exposed on level 5, lie about 70 and 120 feet, respectively, northeast of
30 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

the Crystallite fault. The anomaly at point E may be the outcrop 

of one of these mineralized faults, but again there is no way of 

checking this other than by considerable surface or underground 

work. The overall aspect of lead-zinc distribution in the Little 

Pittsburg area suggests that there are just two main mineralized 

zones. One of these, with a north-northwest trend, included the 

Little Pittsburg vein and subparallel structures discovered by geochemical work. The other zone is approximately parallel to the 

Crystalline fault and trends northwest. The junction of these two 

trends is indicated by the large lead-zinc anomalies at, and just west 

of, points A and B. It is probable that the lead and zinc near 

points G, E) and £?, part of the lead and zinc near points A and Z?, 

and the zinc at point H are related to the northwest-trending zone 

associated with the Crystallite fault. The rest of the lead-zinc mineralization is probably related to the north-northwest-trending zone.

The most pronounced anomalies near the Little Pittsburg vein 

are in lead. Zinc shows the smallest percentage increase over background, and the results of a heavy-metals test occupies an intermediate position in percentage increase.

The ratio of lead to zinc in the soil near the outcrop of the Little 

Pittsburg vein is 1:1 or more, despite the fact that the lead to zinc 

ratio in the ore, as mined, is in the range of 1: 3 to 1: 2. Mr. Claude 

E. Nugent, of the Denver Development Co., has informed the writer 

that there is a tendency for the lead-zinc ratio to increase as the top 

of the ore is reached, and this may account for the change in ratio. 

Another possibility is that the zinc is more easily leached from the 

soil, and the ratio of lead to zinc is thereby increased.

The series of samples taken just to the west of the road, and 

paralleling it, show what the results would be if one were doing 

reconnaissance prospecting by sampling on the upslope side of roads. 

It is evident that the Little Pittsburg vein would have been located 

by this means.

A study of the movement of heavy metals from point E was attempted by sampling between points F and E and by sampling the 

material in the dry stream bed below point F. The anomaly can 

be detected by lead tests at a distance of 200 to 300 feet from the 

source, but the zinc and heavy-metals tests do not permit tracing the 

anomaly so far. This is undoubtedly because of the much higher 

quantity of lead present at the source.

The relation between size of soil particles and intensity of geochemical anomalies was investigated briefly. A beginning was made 

on the problem of which size fraction should be analyzed to give the 

greatest anomaly near lead, zinc, or copper deposits. One sample
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 31

representing "local background," 1 and two samples representing 

high lead and zinc content were chosen from the vicinity of the 

Little Pittsburg vein and sieved into seven size fractions. These 

fractions were analyzed for lead and zinc by using quantitative 

methods, and the results are shown in table 2. Similarly, three 

samples were sized and analyzed for copper. No great difference 

was found in the metal content of different size fractions from the 

same sample. In practice, the material passing an 80-mesh screen 

is recommended for general prospecting because the use of a fine-size 

fraction probably decreases sampling errors.

TABLE 2. Relationship of zinc, lead, and copper content to particle size in soils,

Little Pittsburg area

Analyses were made by quantitative methods, H. E. Crowe and Harold Bloom, U.S. Geological Survey,

analysts]

Sieve diameter of soil particles (mm)

Composition (ppm)

Local background 

sample

Anomalous metal 

content

Sample 

No. 1

Sample 

No. 2

Ratio

Sample 

No. 1 to 

local background

Sample 

No. 2 to 

local background

Zinc

<0.061

0.061-0.117 ___ __ - .... ._. ... __ 

0.117-0.234 _

0.234-0.447 

0.447-0.98 

0.98-1.90 _____ . ______ . ___ .... .. -

1.90-4.04 

210

200

200

200

190

160

190

800

770

780

750

720

600

1,230

1,230

1,230

1,160

1,060

880

750

3.8

3.8

3.9

3.7

3.8

3.7

2 7

5.9

6.2

6.2

5.8

5.6

5.5

3.9

Lead

<0.061 

0.061-0.117 

0.117-0.234 __ . _____ . _____ ... .....

0.234-0.447 ........ ...

0.447-0.98 

0.98-1.90 

1.90-4.04 _

40

40

60

70

40

30

30

1,200

1,850

2,150

1,260

970

680

750

750

690

470

420

46.0

36.0

26.0

31.0

32.0

23.0

17.0

19.0

13.0

9.9

14.0

16.0

14.0

Copper

<0.061 

0.061-0.117 

0.117-0.234 

0.234-0.447 ______ ... ... _ _ _ ....

0.447-0.98 

0.98-1.90 

1.90-4.04 _ . ___ . __ ... __ 

50

50

55

60

45

45

40

350

360

330

360

390

330

250

450

460

430

430

320

300

200

7.0

7.2

6.0

6.0

8.7

7.3

6.2

9.0

9 2

7.8

7.2

7.1

6.7

5.0

VEINS CONTAINING MAINLY ZINC MINERALS

"Carbonate" vem. During the bulldozing in Grouse Gulch, about 

2 miles north-northwest of Mullan (pi. 1), a zone in the soil was

i The term "local background" is used to mean the normal concentration of an element 

within a restricted area as compared to that for the Coeur d'Alene district as a whole. 

The concentrations of heavy metals in the local background samples in the Little Pittsburg area are higher than that for the rocks surrounding the Coeur d'Alene district.
32 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

uncovered which contained gossan material of a type characteristic 

of the siderite veins in the area. Some of the gossan material was 

sampled and contained approximately 30,000 ppm zinc by field test. 

This mineralized area is about 620 feet N. 58° E. of the portal to 

the Grouse tunnel. The vein is not named, but for the sake of convenience, it is referred to as the "carbonate" vein in this report.

The vein strikes approximately N. 75° W., and the outcrop extends directly upslope from the bulldozer cut. Soil samples were 

taken at 10-foot intervals on a traverse which intersects the vein at 

a high angle; analytical results are presented graphically in figure 13. 

Small amounts of lead are present near the vein, but zinc is the 

element showing the greatest contrast with background. No increase 

in copper was found. A 1: 7 HNO3 digestion was used.

Liberal King vein. The Liberal King vein crops out high on a 

southwest-facing slope about 2.5 miles south-southeast of Pinehurst 

(pi. 1). The vein material, where seen at the surface, consists of 

quartz, with vugs containing limonite. Underground, according to 

Umpleby and Jones (1923, p. 108), much of the vein contains small 

amounts of pyrite, sphalerite, chalcopyrite, and galena, named in 

order of their abundance. Some stoping has been done on the vein 

since Umpleby and Jones' work, but most of this has been 1,000 to 

1,500 feet below the outcrop.

Soil samples were taken on a traverse across the vein outcrop, but 

no anomalous concentrations of lead or zinc were found.

Curlew vein near the Page mine. The Page mine is about onethird of a mile south-southeast of the town of page (pi. 1). A series 

of soil samples was collected at 50-foot intervals along the east side 

of the ridge which lies just east of the Page mine buildings. This 

traverse was laid out across the projected position of the Curlew 

vein and was extended to the north in an effort to find the outcrop

N.

30 40 50 60 70

DISTANCE ALONG TRAVERSE, IN FEET

FIGURE 13. Graph showing concentration of lead and zinc in soil near the "cabonate" 

vein in Grouse Gulch near Mullan.
GEOCHEMICAL STUDIES, COEUK D'ALENE DISTRICT, IDAHO 33

12345 789 10 11 12 13 14 15 16 17 18 19 20 21 

SAMPLE NUMBERS

 8 

 7

EXPLANATION

Direction and approximate 

! of downslope

Sample number and location

 5

 *

3

 *

FIGTJEE 14. Plan view of soil-sampling traverses and a graph showing the lead and zinc 

concentration in the soil, Curlew vein near the Page mine.

of the mineralized zone believed to parallel the Curlew vein. The 

results of this traverse are presented graphically in figure 14. The 

exact location of the outcrop of the Curlew vein in the sampling 

area is not known, but it probably lies between sample points 5 and 7. 

All soil samples contained at least 2 to 3 times the normal concentration of zinc and lead. The dissemination of metals from fumes of 

the nearby Sullivan lead and zinc smelter probably accounts for the 

overall high background of lead and zinc; Frank C. Canney's work 

(written communication, 1956) indicates that lead and zinc contamination is widespread within several miles of the smelter. However, 

the anomalies of 200 to 500 ppm lead may reflect an increase in the 

amount of lead in the soil due to underlying rock conditions, if 

smelter contamination is rather evenly distributed over the area 

sampled. Correlation between lead and zinc anomalies near sample 

point 9 (fig. 14) is good, but the reason for the lack of correlation 

near sample points 1 and 14 is not known.

VEINS CONTAINING COPPER MINERALS

Missoula tunnel copper zone. The portal of the Missoula tunnel 

is about 2.5 miles northeast of the town of Mullan, near the head of 

the east branch of Deadman Gulch (pi. 1). According to Ben 

Bowyer (written communication, 1952) there are four shear zones 

in the tunnel which have been replaced by quartz containing some 

copper and lead minerals. These zones cross the tunnel 200 feet, 

680 feet, 1,320 feet, and 2,290 feet from the portal; the one at 1,320 

feet contains the most copper and lead. All the veins strike northwest and dip 70° to 80° SW.
34 CONTRIBUTIONS TO GEOCHEMICAL PKOSPECTING FOE MINEKALS

The quartz vein which is 680 feet from the portal can be located 

on the surface, and the soil samples collected were taken near the 

outcrop of this vein. Figure 15 shows a plan view of the soil sample 

points in relation to the known vein.

Soil samples were collected along two traverses. One traverse consisted of 6 samples spaced at 5-foot intervals downslope from the 

outcrop of a zone containing disseminated malachite (fig. 15, samples 1-6). This mineralized zone is not a quartz vein, but is very 

near the area where a projection of the quartz vein would crop out. 

The material thrown from a small prospect pit about 50 feet to the 

northwest of sample point 6 contains malachite-stained quartz, and 

this is interpreted to mean that the mineralized zone at sample point 

6 is associated with an upward extension of the quartz vein found 

in the tunnel 680 feet from the entrance.

All soil samples taken along this first traverse contained copper 

concentrations in the range 120 to 200 ppm by field test. The traverse 

was not continued downslope more than 25 feet because of the presence of a footpath and streambed.

Samples Y through 18 (fig. 15) were collected in an attempt to 

cross the quartz vein in an area where the movement of copper downslope could be better studied. The sample collected at point 18 contained 40 ppm copper by field test and all other samples had copper 

concentrations of 10 to 20 ppm copper. No further work was done 

in the area. All samples were analyzed using a 1: Y HNOa digestion.

Gentle Annie copper zone. During bulldozer operations by the 

Bunker Hill Co., a shear zone in bedrock containing small

Prospect pit

EXPLANATION

Sample number and location

Approximate location 

of quartz vein

100 100 200 FEET

Portal of Missoula tunnel

FIGURE 15. Plan view of soil sampling traverses near the Missoula tunnel.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 35

quantities of disseminated malachite was uncovered about 730 feet 

N. 82° E. of the portal of the Snowshoe mine. The area is near the 

head of Gentle Annie Gulch and lies about 2.5 miles northeast of 

the town of Mullan (pi. 1).

Ten soil samples were taken near the mineralized zone to determine the intensity of the copper anomaly in the soil. A sketch 

showing the sample points and the copper concentrations in soil is 

presented in figure 16. Although the copper anomaly present in the 

soil near this slightly mineralized zone is not large, the copper concentrations are great enough that they can be easily detected. A 

1: 7 HNOs digestion was used.

Snowstorm copper mine. The Snowstorm mine, the only copper 

property in the northeastern part of the district which has produced 

much ore, is about 3 miles east-northeast of the town of Mullan near 

the head of Daisy Gulch (pi. 1). The ore minerals, principally 

bornite, chalcocite, chalcopyrite, and tetrahedrite in the unoxidized 

ore, and malachite where the ore is oxidized, are disseminated 

through a bed about 40 feet thick in the Revett quartzite. The 

strike of the ore zone is N. 60° W. and dip 65° SW. (Umpleby and 

Jones, 1923, p. 116).

Soil samples were taken downslope across the projected outcrop 

of the copper zone at a point a few hundred feet north-northeast of 

the uppermost portal of the Snowstorm. A plan view of the sample 

locations showing their approximate relation to the outcrop of the 

Snowstorm zone is presented in figure 17. The copper concentrations in soil indicate that the mineralized zone probably crosses south 

of sample point 3. The maximum copper anomaly in soil associated 

with the Snowstorm copper zone is 180 ppm, but evidence of the zone 

is shown by slight concentrations of copper for more than 150 feet 

downslope.

Hamy copper mine. The Hansy copper mine is 1.5 miles southeast of the town of Adair (pi. 1), on Olentange Creek about a mile

SAMPLE NUMBERS

0 100 FEET * ' / R

by malachite

EXPLANATION

.5 

Sample number and location

FIGURE 16. Plan view of soil-sampling traverse near a malachite-stained zone, and a 

graph showing concentration of copper in the soil, Gentle Annie Gulch.
36 CONTKIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

EXPLANATION

*(30)

Sample number and location and 

copper concentration, in parts per 

million

Approximate location of outcrop 

of mineralized vein

100 FEET

FIGURE 17. Plan view of soil-sampling traverse near the outcrop of the Snowstorm

copper zone.

from its junction with Loop Creek in the extreme southeast part of 

the Coeur d'Alene district. The copper mineral, as seen underground, 

is chaleopyrite present as disseminated grains and in small shoots 

of massive ore.

Soil samples were collected at 25- to 60-foot intervals on a traverse intersecting the projected vein outcrop at an agle of about 60°. 

A sketch of the sample locations showing their relation to the vein 

outcrop is shown in figure 18. Only a very small anomaly in copper 

was found despite the fact that the vein contains copper minerals. 

Samples were collected at uneven intervals in order to avoid soil 

disturbed by small prospect pits. A nitric-hydrofluoric acid extraction was used in the analysis.

EXPLANATION

.5 

Sample number and location

Approximate location of vein

Portal of upper 

tunnel

6 54 

SAMPLE NUMBERS

FIGURE 18. Plan view of soil-sampling traverse and graph showing concentration of 

copper in soil at the Hansy copper mine.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 37

Richmond mine. The Richmond mine is at the head of Mineral 

Creek about 1.5 miles east-northeast of Adair (pi. 1). According to 

Umpleby and Jones (1923, p. Ill) the Richmond mine produced 

oxidized ore averaging 10 percent copper for a short time in 1916. 

The vein strikes N. T5° E., dips steeply north, and is from 5 to 10 

feet in width. It has been opened by several shafts and one tunnel.

At the Richmond mine a series of soil samples were collected at 

50-foot intervals crossing the projected vein outcrop about 100 feet 

west of the westernmost shaft on the vein. No abnormal concentration of copper was found in any of the soil samples.

VEIN CONTAINING GOLD AND TUNGSTEN

Golden Chest vein. The Golden Chest vein, in Reeder Gulch 

about 1.5 miles east of Murray (pi. 1), has been worked extensively 

underground for gold and tungsten. It is traced by surface pits and 

shallow workings for more than 1,000 feet along the strike. A sample traverse was run downslope across the vein. The results of 

analysis of the samples for tungsten are presented graphically in 

figure 19. Two areas were found where the soil had high concentrations of tungsten. One is related to the outcrop of the main vein ; 

the cause of the other, represented by a high value in sample one, 

is not known.

VEIN CONTAINING ANTIMONY

Star Antimony, The Star Antimony property is on the northeast 

side of the East Fork of Pine Creek and lies on a ridge between 

Highland and Blue Eagle Creeks about 5.5 miles south-southeast of

EXPLANATION

Jl

Downslope 

25°-30°

12

,13

Prospect pit

.4 

Sample number and location

Approximate location of vein

100 0 100 FEET

FIGURE 19.-

567 

SAMPLE NUMBERS

-Plan view of soil-sampling traverse, and graph showing concentration of 

tungsten in soil at the Golden Chest mine.
38 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

Pinehurst (pi. 1). The vein (Umpleby and Jones, 1923, p. 122) has 

been opened by three tunnels and consists of a fault zone 4 to 8 feet 

in width containing quartz, stibnite, a little pyrite, sphalerite, gold, 

and much gouge material. The richest stibnite ore occupied a zone 

ranging from 1 to 28 inches wide, but stibnite was also disseminated 

in the wallrock. Umpleby and Jones record the strike of the vein 

as east and the dip 25° to 60° S.; however, in the only adit now 

open, the largest vein strikes N. 34° E. and dips 65° SE. The enclosing rock is the Prichard formation.

A sketch map of the soil-sample locations, along with the concentration of antimony in soil near the upper tunnel, is shown on figure 26. The results of soil analyses, as well as an examination of 

the veins underground, indicate that the veins in the open adit 

probably have a different strike than those in the caved adits described by Umpleby and Jones (1923). Another vein, not observed 

in the open adit, may be present to the southwest of the portal, for 

concentrations of antimony in soil approximately 400 times background were found about 50 feet southwest of the upper portal. The 

westernmost traverse was extended downslope for a distance of several hundred feet in order to determine how far anomalous quantities of antimony could be detected downslope from the main mineralized zone. The results suggest that there may be small additional 

sources of antimony downslope from the main zone.

Adit with strike and dip of cross' 

cutting vein

Vein outcrop location based on underground veins and antimony content of soil

CONTOUR INTERVAL 50 FEET 

DATUM IS MEAN SEA LEVEL

FIGURE 20. Plan view of soil-sampling traverse near the Star Antimony vein.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 39

PLANT STUDIES

The plant types which were sampled are representative of most 

of the plants growing in the mining district and are the logical ones 

to use in prospecting, if widespread sampling is desired. The pines, 

larches, spruces, and firs make up the largest proportion of the plants 

in the forested areas; the spirea and tall whortleberry (huckleberry) 

grow abundantly in the areas where most of the trees have been cut 

or burned; and beargrass grows at the higher elevations where the 

conifers and low-growing shrubs are not present.

Plant samples were collected from various places in the mining 

district where data were available on the lead, zinc, or copper content of the soil. Twigs were cut from several kinds of coniferous 

trees, and the needles and cones removed for separate analyses. Some 

low-growing deciduous plants of various kinds were sampled by 

collecting parts of the plants which appeared to be uncontaminated 

by dust or soil.

In the fall of 1950, samples were collected from 19 trees near the 

Little Pittsburg vein and analyzed for zinc by the field test of 

Reichen and Lakin (1949). As the samples were all collected in 

the area where detailed soil sampling had been done, it was possible 

to compare the zinc content of the trees with that of the soil nearby. 

The locations of the trees sampled are shown on plate 6 and the comparison between concentration of zinc in soil and concentration of 

zinc in needles and twigs is made in table 3.

TABLE 3. Concentration of zinc in plants and soil in the area near the Little

Pittsburg vein

Plant field No.

P-1-.. ..........

P-2-- .-. .. ..

P-3 . . 

P-4 ...... ...........

P-5 .-- ............

P-6- ._ . 

P-7 -.- _.-_ 

P-8 ...... -_ __ _

P-9 ..... ..-..

P-10 _ . ___ --- ...

P-ll ..... -... --.--

P-12 __ ..... __ ...

P-13 -

P-14 .... ............

P-15 . 

P-16 .... . _ ..... ...

P-17 

P-18- ..... .... .....

P-19 ........ _ .....

Description of plant

Name 3

.... .do .. ... 

Approximate height 

(feet)

30

60

10

10

50

12

25

20

25

20

75

30

20

20

20

15

15

25

15

Needles

120

170

70

40

40

50

40

40

100

20

90

60

20

50

30

40

40

70

90

Zinc (ppm)i

Twigs

130

150

60

50

30

40

60

40

60

50

40

4n

50

80

40

4n

90

140

Soil within 

25 feet of 

plant

1, 800-3, 000

1,400-3,000

i Ann 3 nnn

350

250

150

100-250

1 Kfl

200-750

400

300

150-300

9on

100

150 ififi

(8)

(3)

1 Semiquantitative plant analyses made on an air-dried basis. 

8 Identification by G. M. Richmond and V. O. Kennedy. 

3 Growing in outcrop of Little Pittsburg vein.
40 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

Because the field tests for zinc in plants, like those for zinc in soil, 

are susceptible to variations in both the extraction and the estimation 

steps, the concentrations given are probably accurate only to within 

±30 percent of the zinc present. Despite the various sources of possible error, the twigs and needles of both the Western yellow pine 

and the Douglas-fir show a definite increase in zinc content where 

growing in soil containing 1,000 ppm or more zinc.

During August 1951, Helen L. Cannon, of the U.S. Geological 

Survey, visited the field project and, with the author, collected plant 

samples within the mining district in areas where information was 

available on the lead, zinc, and copper concentrations in the soil. 

The samples were identified by H. L. Cannon and analyzed by members of the U.S. Geological Survey using standard quantitative procedures. A few additional samples collected by the author during 

August 1952 were analyzed by quantitative methods. The copper, 

lead, and zinc content of the plant parts is compared in table 4 with 

that of the soil in which the plant was growing.

Despite the reconnaissance nature of the plant study, some tentative conclusions appear warranted from present data. In general, 

the plants that were sampled showed changes in lead and zinc concentration with changes in the concentration of these elements in the 

soil in which they were growing. However, lead and zinc anomalies 

were found to be much greater in the soil than in plants growing in 

that soil. No soils containing large concentrations of copper were 

found; so it is not possible to state how high copper concentrations 

in soil (25 to 500 times background) affect the copper content of the 

plants growing in such soil. Of the three kinds of plants sampled, 

both from normal soil and from soil containing 10 times the normal 

amount of copper, none growing in the high-copper soil showed more 

than 2.5 times the amount of copper present in the plants growing 

in normal soil.

WATER STUDIES

Samples of water were collected from springs, streams, and mine 

drainage in the eastern part of the mining district and analyzed for 

heavy-metal content. In addition, the pH of many of the samples 

was measured using a Hellige standard comparator, and a few sulfate analyses were made. When the water was to be analyzed for 

heavy metals only, it was collected in a 100-milliliter glass-stoppered 

pyrex graduated cylinder and analyzed at the sampling spot. If 

sulfate content was also to be measured, a separate sample of the 

water was placed in a plastic bottle and returned to the field laboratory for analysis. In plate 7 a sketch map of the drainage near 

Mullan and the results of water analyses are presented. The pH 

values given are probably accurate to ±0.2 of a pH unit, and the 

heavy-metal concentrations are believed to be within 50 percent of 

the true value.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 41

TABLE 4. Lead, zinc, and copper analyses of plants and nearby soils, Coeur

d'Alene district, Idaho

[Analytical data are reported on an air-dried basis. Soil samples were collected at a depth of 2 to 6 inches. 

Analyst: H. E. Crowe, U.S. Geological Survey]

Plant part 

or associated 

soil

Concentration of ore metals in plants 1 and nearby soil 

(parts per million)

Lead

(a) (b) (c) (d)

Zinc

(a) (b) <W (d)

Copper

(a) (b) (c) (d)

Western white pine, Pinus monticola Dougl.

'P W1CTO

Soil near

20

100

5

20,000

6

20

8

150

6

22

2

20

280

320

22

2,000

110

95

50

1,500

25

60

25

50

5

5

8

70

5

6

7

30

5

3

25

Western yellow pine, Pinus ponderosa Laws

Needles...-.

Soil near

24 

73

20,000

7 

14 

1

2,000

11 

12 

8

15

270 

200

2,000

55 

50 

34

400

3 32 (34) 

40 (29) 

37

100

5 

7

70

8 

6 

7

70

4 

8 

10

20

Common Douglas-fir Pseudotsuga. taxifolia Britt.

Needles. -

Soil near

31 

130

20,000

18 

73 

13

5,000

11 

47

150

7 

16

7

20

140 

130

2,000

100 

120 

50

1,000

200 

100

1, 500

50 (24) 

82 (40) 

30

100

8 

8

70

6 

8 

16

70

6 

6

30

5(3) 

8(6) 

10

20

Alpine fir, Abies, fasiocarpa Nutt.

Needles _ .. 

Twigs

Soil near 

plant _ 

7 

26 

1

100

10 

12

25

70 

50 

30

100

50 (30) 

40 (45)

50

4 

8 

12

300

10 (5) 

8 (6)

25

Engelmann spruce, Picea engelmanni Engelm.

Needles... 

Twipro

COHGS

Soil near 

plant.. 

5 

56 

4

100

6 

11

25

58 

120 

38

100

55 (40) 

65 (60)

100

3

16 

8

300

12 (4) 

11 (9)

50

Lodgepole pine, Pinus contorta var., latifolia, S. Wats

Needles. 

T'witTQ

Soil near 

plant _ 

21 

39 

9

1,500

12 

30 

26

25

55 

45 

16

150

75 (38) 

65 (36) 

15

200

3

5 

7

20

11 (5) 

3 (6) 

3

25

Western larch, Larix occidentalis Nutt.

Needles. 

Soil near 

plant-.. 

47 

100

1,000

30 

95

25

50 

44

100

35 

50

100

5 

25

20

8 

10

60

Creambush rockspirea, Holodiscus discolor (Pursh) Maxim

Leaves . 

Soil near 

plant. 

77 

20,000

19 

15

90 

2,000

57 

100

17

70

6 

20

See footnotes at end of table.
42 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

TABLE 4. Lead, sine, and copper analyses of plants and nearby soils, Coeur 

d'Alene district, Idaho Continued

Plant part 

or associated 

soil

Concentration of ore metals In plants ' and nearby soil 

(parts per million)

Lead

(a) (b) (c) (d)

Zinc

(a) (b) (c) (d) (a) C

Copper

b) (c) (d)

Brachen, Pteridium aquilinum (L.) Kuhn.

Stem and

Soil near

61 10

*>^

o>ai

2,000

27

100

16

70

8

20

Big whortleberry (locally huckleberry) Vaccinium membranaceum Dougl.

Soil near

23

9

1,500

5

8

150

6

6

100

4

25

Oft

19

100

559*;

1,500

21

11

100

36

100

6

6

25

6

14

30

6

5

300

5

25

American sweet vetch Hedysarum americannum (Miehx.) Britt.

Soil near

3

inn

3

20

23

100

115

100

14

300

6

30

Common beargrass Xerophyllum tenax (Pursh.) Nutt.

Soil near 

plant ___

00

1,500

7

150

6

100

4

25

Oft

150

Oft

1,500

20

100

18

100

7

40

5

30

8

300

6

40

1 Letters in parentheses indicate plant samples. Plant (a) under lead is the same plant as that listed a 

plant (a) under zinc and copper.

2 Field and laboratory serial numbers are given below: 

Western white pine:

Needles: a, H.C. 1-85, 513807; b, H.C. 1-123, 513845; c, 67N, 52-3632

Twigs: a, H.C. 1-86, 513808; b, H.C. 1-124, 513848; c, 67T, 52-3633

Cones: a, H.C. 1-87, 513809; b, H.C. 1-150, 513847; c, 67C, 52-3634 

Western yellow pine:

Needles: a, H.C. 1-88, 513810; b, H.0.1-98, 513820; e, H.C. 1-106, 513828

Twigs: a, H.C. 1-89, 513811; b, H.C. 1-99, 513821; c, H.C. 1-107, 513829

Cones: b, H.C. 1-100, 513822; c, H.C. 1-108, 513830 

Common Douglas-fir:

Needles: a, H.C. 1-92, 513814; b, H.C. 1-94, 513816; c, H.C. 1-129, 513851, d, H.C. 1-107, 513825

Twigs: a, H.C. 1-93, 513815; b, H.C. 1-95, 513817; c, H.C. 1-130, 513852, d, H.C. 1-104, 513826

Cones: b, H.C. 1-96, 513818; d, H.C. 1-105, 513827 

Alpine fir:

Needles: a, H.C. 1-112, 513834; b, 64N, 52-3626

Twigs: a, H.C. 1-113, 513835; b, 64T, 52-3627

Cones: a, H.C. 1-114, 513836 

Englemann spruce:

Needles: a, H.C. 1-115, 513837; b, 65N, 52-3628

Twigs: a, H.C. 1-116, 513838; b, 65T, 52-3629

Cones: a, H.C. 1-117, 513839 

Lodgepole pine:

Needles: a, H.0.1-132, 513854; b, 68N, 52-3635

Twigs: a, H.C. 1-133, 613855; b, 68T, 52-3636

Cones: a, H.C. 1-134, 513856; b, 68C, 52-3637 

Western larch:

Needles: a, H.C. 1-137, 513859; b, 66N, 52-3630

Twigs: a, H.C. 1-138, 513860; b, 66T, 52-3631 

Creambush rockspirea:

Leaves: a, H.C. 1-91, 513813; b, H.C. 1-101, 513823 

Brachen:

Stem and

fronds: a, H.C. 1-90, 512812; b, H.O. 1-102, 513824 

Big whortleberry:

Leaves: a, H.C. 1-135, 513857; b, H.C. 1-127, 512849; c, H.C. 1-110, 513832; d, H.C. 1-121, 513844

Berries: a, H.C. 1-139, 513861; b, H.O. 1-128, 51385.; c, H.C. 1-111, 513833 

American sweet vetch:

Leaves: a, H.C. 1-119, 513841; b. H.C. 1-120, 512842 

Common beargrass:

Leaves: a, H.C. 1-136, 513858; b, H.C. 1-131, 513853; c, H.O. 1-118, 513840; d, H.C. 1-122, 513844

s The numbers in parentheses are the concentrations suggested as being normal tor the same kind of plant 

in British Columbia (Warren and others, 1952). The plant part denoted as "twig" here is not strictly 

comparable to Warren's "stems," for the twigs constituted all of the first year's growth including the tip, 

whereas, the term "stem" apparently does not include the tip.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 43

Most of the water containing an abnormal concentration of heavy 

metals comes at least in part from mine workings. The highest 

concentration of heavy metals found was 5 ppm in mine drainage 

about 1,600 feet east-northeast of the Star mine in Grouse Gulch. 

This water, along with the large volume of water draining from the 

Star, causes the heavy-metal concentration to remain near 1.0 ppm 

in Grouse Creek until it joins the South Fork of the Coeur d'Alene 

River. In Mill Creek, as in Grouse Creek, mine drainage causes 

anomalous concentrations of heavy metals in the water, although 

dilution from the east branch of the stream is responsible for decreasing the heavy-metal concentration to 0.04 ppm near Mullan. 

The heavy-metal concentration in Gold Hunter Gulch is slightly 

higher than the normal background of about 0.002 ppm, probably 

owing to the presence of the Gold Hunter mine. Similarly, mine 

drainage contaminates Daisy Creek. In Deadman Gulch, water from 

the Copper King mine and also from the National mine mingles with 

the normal stream waters, but the water leaving the mouth of the 

gulch has a normal concentration of heavy metals. Dilution of the 

mine water undoubtedly accounts for some of the decrease, and precipitation from solution may account for the rest. In Gentle Annie 

Gulch, mine drainage is believed responsible for the value of 0.01 ppm 

heavy metals found near the mouth of the stream. South of the 

Coeur d'Alene River, water samples were collected from several 

tributaries; but none, except Dry Creek, contained unusual quantities of heavy metals. The reason for the anomalous amounts of 

heavy metals in solution in Dry Creek is not known.

A study of copper concentrations in waters of a mine adit up 

Willow Creek in the southeastern part of the map area about 1,600 

feet northeast of the Reindeer Queen mine (pi. 7) indicated a nearly 

complete removal of copper from mine drainage by a slight change 

in chemical conditions. Small quantities of copper were known to be 

disseminated in the enclosing rock; yet the waters draining from the 

mine were low in copper. Investigation disclosed the presence of 

light-green stalactites, 1 to 2 inches in length, hanging from the roof 

of the drift at a distance of about 200 feet from the portal. Water 

was slowly seeping down from above and dropping from the stalactites. Analysis of the water dripping from the stalactites showed 

an average copper content of approximately 1 ppm. Splashes of 

light-green carbonate were deposited where some of this water struck 

the walls in falling. Analysis of water in small pools under these 

stalactites showed a copper content of about 0.02 ppm. This decrease 

in copper concentration probably results from the combined effects 

of precipitation and of dilution by water containing little copper. 

The small amount of water trickling along the floor of the drift in
44 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

the area of stalactite formation contained less than 0.01 ppm copper. 

Although dilution of the copper-bearing solutions undoubtedly 

helped decrease the copper concentration in the drainage from the 

drift, precipitation is believed to be the major factor. The pH of 

the water dripping from the stalactites ranged from 7.0 to 7.3, and 

the water draining from the drift had a pH of 7.3. Although a 

slight rise in pH may account for the copper precipitation where the 

water is exposed to air, the evidence for this is not conclusive.

Coprecipitation with hydrous ferric oxide may also cause a nearly 

complete removal of heavy metals from drainage. At the portal of 

the Midnight mine, water samples contained about 0.1 ppm heavy 

metals and had a pH of 7.2 in August 1951. A year later, the heavymetal concentration was 0.08 ppm and pH was 6.4. At a distance 

of about 175 feet outside the portal, water samples collected in 1951 

contained 0.003 ppm heavy metals and had a pH of 7.2, and samples 

collected in 1952 had a heavy-metal concentration of 0.007 ppm and 

a pH of 7.3. Between these two sample points, the mine water flowed 

in a broad shallow stream from which hydrous ferric oxide apparently was precipitating because a layer of red-brown flocculent material covers the streambed to a thickness of i/s to 1/2 inch. Very probably, ferrous iron in solution is oxidized on exposure to air, and 

the ferric iron thus formed then precipitates. No dilution of the 

mine water by other sources was noted; so the decrease in heavymetal concentration is believed to be due to coprecipitation.

The water draining from another mine tunnel, about 800 feet westnorthwest of the Midnight mine, was also studied. The data are 

presented as follows:

Concentration

Location pH of heavy metals (ppm) 

At portal ___________________ _ 7.2 0.1 

150 ft outside portal ________________ 7.4 .05 

220 ft outside portal ________________ 7.4 .04

Between the portal and the point 150 feet downstream, much hydrous 

ferric oxide covered the streambed, but from 150 to 200 feet very 

little ferric oxide was seen.

These data are also interpreted as an indication that precipitation 

of hydrous ferric oxide, associated with aeration of the water and 

rise in pH, may be responsible for the removal of heavy metals from 

solution.

In Daisy Gulch, water draining from a shear zone 100 feet or 

more wide was analyzed and found to contain about 0.004 ppm heavy 

metals. The pH was 8.6. A few quartz veinlets an inch or so in 

width were found throughout the shear zone, and enough zinc was 

present so that the soil overlying the sheared area contained 400 to 

600 ppm zinc. This is the only locality examined in which the water
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 45

analyzed was draining from mineralized ground undisturbed by 

mining activity.

The comparatively few sulfate determinations which were made 

suggest that mine water in the Coeur d'Alene district contains several hundred times as much sulfate as does normal surface water. 

However, many of the samples of surface water contained sulfate in 

quantities too low to be measured accurately by the equipment used, 

and the only conclusion to be drawn regarding sulfate analysis is 

that more work seems worthwhile.

SIGNIFICANCE OF ANALYTICAL RESULTS 

SOILS

The results of studying 13 lead- and zinc-bearing veins (table 5) 

show that, near 11 of the 13, lead has been concentrated over background to a greater extent than zinc. Because lead background is about 

20 ppm and zinc background about 100 ppm, the actual percentage of 

zinc may be greater than that of lead and yet not be shown in the 

table as having a greater ratio to background. The ratio of anomalous concentration to background concentration is shown in the table 

because it permits a better evaluation of the correct metal to use in 

prospecting than does the absolute concentration of the elements.

TABLE 5. Summary of lead and zinc soil anomalies found near veins

Name of area

Frisco ___ - _ __ - _ 

Star..... . ... .

Little Pittsburg 

Ratio of highest lead concentration 

found to 

background 

concentration i

20

45

125

KA

100

110

135

32

45

1500

12

1

25

Ratio of highest zinc concentration 

found to 

background 

concentration i

1

2.2

2.5

9 7

3.5

1.8

3.0

6.0

1

36

15

1

6

1 Background lead is taken as 20 ppm and background zinc as 100 ppm.

In general, the analytical data resulting from the study of these 

13 veins strongly suggest that successful prospecting for new leadzinc veins could be done using soil analysis for lead. Where low or 

questionable lead anomalies are detected, a specific test for zinc could 

be used to check the lead data.

At the Liberal King vein there are no lead or zinc minerals known 

to be in the vein for a depth of several hundred feet from the surface
46 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

where the samples were collected, and this probably accounts for the 

lack of anomalous amounts of lead or zinc in the soil.

Of the 5 copper-bearing veins studied, 4 contributed enough copper 

to the soil to be detected by the soil test for copper. The highest 

concentration of copper found was 450 ppm at the area in Gentle 

Annie Gulch. Despite the presence of considerable malachite staining in the bedrock near the Missoula tunnel, at the Snowstorm mine, 

and in Gentle Annie Gulch, relatively low copper anomalies were 

found in soil. One possible explanation for this is that copper ore 

minerals may be leached during soil formation. The very slight 

copper anomaly near the Hansy copper mine, where chalcopyrite ore 

is known to be a few tens of feet below the surface, is further evidence suggesting removal of copper during soil formation. In contrast to these data, studies of nonmineralized rock and overlying soil 

suggest that copper may be somewhat concentrated in soil during 

soil formation. The explanation for this apparent contradiction of 

data is not known.

Although the data available do not permit drawing definite conclusions regarding geochemical prospecting for copper by soil analysis, the work thus far does suggest that in the Coeur d'Alene district, 

copper anomalies are relatively small near known copper deposits. 

There is a possibility, which cannot be ignored that each of the 

sample traverses near copper veins crossed the veins in an area of 

rather low copper content. This would account for the low amounts 

of copper in the soil.

The analysis of soils for antimony and tungsten as a means to 

prospecting for veins containing these elements is probably worthwhile, but further work is necessary before recommendations can be 

made. The southern vein seen in the crosscut at the Star Antimony 

mine is about 2 feet wide and contains perhaps 1 to 3 percent 

crushed and broken stibnite in a gangue which is primarily quartz. 

If such a vein contained 1 to 3 percent galena instead of stibnite, 

the soil downslope from its outcrop would very probably contain 

several thousand parts per million lead. The relatively low concentrations of antimony found in the soil near the projected outcrop of 

the southern vein suggest that either the vein seen underground is 

greatly different in antimony content at the surface or else the antimony is removed in solution during weathering and soil formation. 

The concentration of tungsten in the Golden Chest vein is not known 

at the point where the soil-sampling traverse crossed it. Hence, the 

sensitivity of soil analysis as a prospecting tool for tungsten cannot 

be evaluated. However, the fact that anomalous amounts of tungsten 

were found in the soil indicates that soil analysis should be considered when prospecting for tungsten.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 47

PLANTS

The analysis of plants growing in normal and in high lead-zinc 

soils indicates a positive correlation between the concentration of lead 

and zinc in plants and the concentration of lead and zinc in soil in 

which the plants are growing. In general, a given percentage increase in lead or zinc in soil will result in a corresponding, but 

smaller, increase in plants growing in that soil. Thus, in prospecting, a larger anomaly should be detected by sampling residual soil 

than by sampling plants.

Plant sampling may be of value in the Coeur d'Alene district when 

prospecting in areas covered by alluvium or terrace gravels. However, such areas represent a very small percentage of the total area 

in the Coeur d'Alene mining district; so no effort was made to investigate the feasibility of prospecting through such deposits.

WATER

The normal concentration of heavy metals in stream water is approximately 0.002 ppm and the normal pH is about 7.1. Mine waters 

range in heavy-metal concentration from 0.002 ppm to 5.0 ppm and 

the pH ranges from 6.0 to 8.6. The pH variations do not correlate 

with variations in heavy-metal concentrations although oxidation of 

pyrite associated with most ores would be expected to depress the pH 

with an increase of heavy metals in solution.

Because of the difficulty of determining the localities from which 

spring water may have obtained anomalous quantities of heavy 

metals, the analysis of such waters is essentially a tool for reconnaissance prospecting in areas which have been little disturbed by 

mining activity. Where there are many known veins in an area, as 

in the Coeur d'Alene, the surface water and much of the ground 

water may be contaminated by solutions from the rapidly oxidizing 

ore which has been exposed by mining; this contamination complicates the interpretation of water analysis data. With such limitations in mind, however, analysis of surface water and springs or 

seepages might prove helpful. During the author's study, relatively 

few springs were found, and many of the streams were contaminated 

by mine drainage; hence the conclusion that the water-analysis 

method of prospecting was of limited usefulness in the mining 

district.

CONCLUSIONS

Three methods of prospecting by geochemical techniques were used 

in the study of the Coeur d'Alene district. These methods were, in 

order of decreasing time expended on them, analyses of soils for 

lead, zinc, copper, antimony, and tungsten; analyses of plants for
48 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

zinc, lead, and copper; and analyses of surface, mine, and spring 

water for total heavy metals. The conclusions regarding each method 

are presented in the following paragraphs.

SOILS

1. Soil analysis as a means of prospecting is feasible in the Coeur 

d'Alene.

2. The concentration of lead in soil should be measured when prospecting for ore bodies having a zinc to lead ratio of about 3:1 or less.

3. Analyses for zinc are valuable when looking for ore bodies in 

which the zinc to lead ratio is high.

4. Analysis of soil for copper has yielded relatively poor results. 

Therefore, if neither lead nor zinc in quantity is associated with the 

copper, soil samples should not be spaced more than 50 feet apart 

and concentrations of 50 to 100 ppm copper should be checked.

5. Present results for antimony and tungsten are encouraging, but 

neither has been studied in sufficient detail to permit definite recommendations.

6. Normal concentrations of lead, zinc, and copper in soil are 20 

ppm, 100 ppm, and 25 ppm, respectively. The normal concentration 

of antimony in soil is about 0.5 ppm, and that of tungsten is apparently less than 10 ppm.

7. In the process of formation of soil from unmineralized bedrock, 

lead, zinc, and copper seem to be concentrated, but this may be only 

an apparent concentration due to the method of sampling.

8. When using the field tests described, soil samples should be considered probably anomalous if the ore-metal concentration is 2 to 

4 times the normal concentration and almost certainly anomalous if 

the concentration is more than 4 times background.

9. In general, depth of soil sampling is not critical in detecting 

an anomaly in areas where the soil is a foot or less in thickness. 

Sharp changes in ore-metal concentrations between consecutive, 

closely spaced samples should not be found except in the immediate 

vicinity of a vein outcrop. However, sample-digestion methods resulting in partial extraction of heavy metals may cause a greater 

apparent variation in heavy-metal concentration than is actually 

present.

10. Sample spacing will vary with the type or strength of mineralization being sought and with the accuracy of the chemical test 

being used, but, in general, a spacing of 50 "feet should be suitable 

when searching for small veins and 200 feet when searching for 

large veins topography being taken into account.

11. In this mining district, when making analyses for lead, zinc, 

or copper, the soil which passes an 80-mesh sieve is satisfactory as 

a sample.
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 49

12. Soil analysis as used in this study is sufficiently quantitative 

so that two parallel veins, one above the other on a slope, can be 

distinguished with suitable sample spacing.

13. Because a wide zone of tiny veinlets can produce an anomaly 

as large as that produced by one large vein, soil analysis should be 

helpful in searching for ore bodies represented at the land surface 

by only a series of veinlets.

14. Soil analysis is preferable to plant or water analysis if only 

one method of prospecting is to be used. However, under favorable 

circumstances, plant and water sampling also might be of value.

PLANTS

1. Ill general, above-normal concentrations of copper, lead, and 

zinc in soil will be reflected in above-normal concentrations of these 

metals in plants growing in the abnormal soil. However, the percentage increase over background in the plants will not be so great 

as in the soil.

2. The work done thus far suggests that western white pine, western yellow pine, and Douglas-fir show lead anomalies best in the 

twigs and that zinc anomalies are best shown in the needles. Many 

more samples should be analyzed before drawing definite conclusions.

WATER

1. Normal concentrations of heavy metals in stream and spring 

water is about 0.002 ppm, and the normal pH is about 7.1.

2. Water sampling within the mining district may be feasible under favorable conditions as a method of prospecting, but present data 

indicate that contamination of surface drainage is a major problem 

in any water analysis program. It is very probable, however, that 

reconnaissance prospecting by water analysis outside the mining district would be of value.

REFERENCES CITED

Almond, Hy, and Morris, H. T., 1951, Geochemical techniques as applied in 

recent investigations in the Tintic district, Utah: Econ. Geology, v, 46, 

p. 608-625.

Almond, Hy, Stevens, R. E., and Lakin, H. W., 1953, A confined-spot method for 

the determination of traces of silver in soils and rocks: U.S. Geol. Survey 

Bull. 992, p. 71-81.

Holmes, R. S., 1945, Determination of total copper, zinc, cobalt, and lead in soil 

and soil solutions: Soil Sci., v. 59, p. 77-84.

Huff, L. C., 1948, A sensitive field test for heavy metals in water: Econ. Geology, v. 43, p. 675-684.

 1951, A sensitive field test for detecting heavy metals in soil or sediment: 

Econ. Geology, v. 46, p. 524-540.
50 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

Kennedy, V. C., 1952, Geochemical studies in the Ooeur d'Alene mining district, 

Idaho: U.S. Geol. Survey Circ. 168.

Lakin, H. W., Stevens, R. E., and Almond, Hy, 1949, Field method for the determination of zinc in soils: Econ. Geology, v. 44, p. 296-306.

Piper, C. S., 1944, Soil and plant analysis: New York, Interscience Publishers.

Ransome, F. L., and Calkins, F. C., 1908, The geology and ore deposits of the 

Coeur d'Alene district, Idaho: U.S. Geol. Survey Prof. Paper 62.

Reichen, L. E., and Lakin, H. W., 1949, Field method for the determination of 

zinc in plants: U.S. Geol. Survey Circ. 41.

Shenon, P. J., and McConnel, R. H., 1939, The silver belt of the Coeur d'Alene 

district, Idaho: Idaho Bur. Mines and Geology, Pamph. 50.

Ward, F. N., 1951, A field method for the determination of tungsten in soils: 

U.S. Geol. Survey Circ. 119.

Ward, F. N., and Lakin, H. W., 1954, Determination of microgram quantities 

of antimony in soils and rocks: Anal. Chem., v. 26, p. 1168-1173.

Warren, H. V., Delavault, R. E., and Irish, R. I., 1952, Biogeochemical investigations in the Pacific Northwest: Geol. Soc. America Bull., v. 63, p. 435- 

484.

Umpleby, J. B., and Jones, E. L., Jr., 1923, Geology and ore deposits of Shoshone 

County, Idaho: U.S. Geol. Survey Bull. 732.
APPENDIX

METHODS OF ANALYSIS 

SOIL

The method of analysis to be used for soil samples from this area 

posed several problems. These problems fell into essentially two 

groups: first, those dealing with the completeness of extraction of 

the heavy metals from the sample and the accuracy of estimating 

heavy metals in solution; and second, those dealing with the choice 

of the element or elements for which analyses should be made. Some 

information regarding these problems was obtained, and this information should be of help in determining appropriate methods of 

prospecting in the Coeur d'Alene district.

A general heavy-metals test of the type described by Huff (1951) 

was used on some of the soil samples. This test is designed to indicate the presence of very small amounts of copper, lead, zinc, and 

any other element which reacts with the organic reagent dithizone 

(diphenylthiocarbazone) under the conditions of the test. Elements 

other than copper, lead, and zinc which react with dithizone are 

present in negligible quantities in most soils and usually may be disregarded as was done in the Coeur d'Alene area.

Briefly, the heavy-metals test is performed by shaking a buffered 

aqueous solution of pH about 5.5 (obtained by adding buffer solution to an aliquot of the acid extract from a soil sample) with a 

carbon tetrachloride solution of dithizone. Prior to shaking, the 

carbon tetrachloride layer is clear green, but, after shaking, the color 

will be some shade of green, blue, purple, or red, depending upon the 

quantity of heavy metals originally present in the aqueous phase. 

If essentially no heavy metals are present the color remains green 

upon shaking; as the amount of heavy metals is increased the carbon 

tetrachloride layer becomes blue, then purple, then red. When the 

carbon tetrachloride layer is a clear red, no further color change 

will take place regardless of the amount of heavy metals present. 

The metal content of the aliquot is determined from the color of the 

dithizone layer by comparison with standard series of dithizone solutions whose heavy-metal content is known. The amount of heavy 

metals in the aliquot and the size of the aliquot are used to calculate 

the heavy-metal content of the original sample.

The sensitivity of dithizone is different for each of the heavy 

metals. This fact is important and must be taken into account in 

interpreting the heavy-metals test. To match the color produced by 

any given weight of zinc, approximately twice as much copper or

51
52 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

4 times as much lead by weight is required. Therefore, anomalies 

in parts per million (ppm) of copper and lead must be greater than 

those in zinc in order to give comparable results.

Specific tests for lead, zinc, and copper were made using the soil 

solutions prepared for the heavy-metals test. The test for zinc described by Lakin and others (1949) and the tests for lead and copper 

devised by Almond and Morris (1951) were used in estimating the 

quantity of these elements in solution. It is possible to make specific 

tests using any of the three methods of digestion described below, 

but standard heavy-metals tests should not be made when using the 

1:1 HNOs digestion, for this digestion leaves an undesirably high 

concentration of acid in the final solution.

The methods of analysis for tungsten, antimony, and silver have 

been described, respectively by Ward (1951), Ward and Lakin 

(1954), and Almond and others (1953).

During the summer of 1950, the only method used for putting the 

sample into solution for a total heavy-metals test was Huff's (1951) 

method B. This method consists of an hour-long 1:7 nitric acid 

digestion. The extraction of zinc and lead was found to vary rather 

widely when this digestion was used on Coeur d'Alene soil samples; 

therefore, at the end of the 1950 field season, a more intense digestion using HF and HNOs, Huff's (1951) method D, was tried, resulting in more consistent extraction of zinc. As a consequence, the 

nitric-hydrofluoric acid digestion was used during the 1951 field season even though the lead extraction by this method was not all that 

was desired. In the spring of 1952, a third method of digestion 

(0.33 gram of soil digested for an hour in 2 milliliters of 1:1 HNOs) 

was tried. A comparison of the three methods was made under the 

direction of Harold Bloom, and the results are shown in table 6.

TABLE 6. Comparison of the various analytical methods used for soil samples 

[Analysts: H. E. Crowe, A. P. Marranzino, and J. H. McCarthy, U.S. Geological Survey]

Number of samples

Percent of semiquanti tative 

(field) analyses 

agreeing within 

±25 percent of 

quantitative

Percent of semiquantitative 

analyses agreeing 

within ±50 percent of the quantitative value __

Huff's method B (1951) 

1: 7 HNO3 digestion

Heavy 

metals

50

36

78

Lead

47

65 

91

Zinc

47

19 

70

Copper

10

40 

50

Huff's method D (1951) 

HF-HNOs digestion, 

nitric-hydrofluoric acid

Heavy 

metals

50

70 

94

Lead

52

38 

71

Zinc

47

60 

94

Copper

10

50 

80

1:1HN03 digestion

Heavy 

metals

Lead

31

77 

90

Zinc

31

65 

100

Copper

......
GEOCHEMICAL STUDIES, COEUR D'ALENE DISTRICT, IDAHO 53

Each of the three methods of sample extraction has its advantages 

when used on soil samples from the Coeur d'Alene area. Although 

the 1: 7 HNO3 method yields rather poor results for zinc, the reagents 

used are relatively mild (a desirable feature in a field test), and the 

lead extraction is good enough for general prospecting. If zinc were 

the main ore metal, the 1:7 HNOs method would be less desirable 

than one of the other two methods. The nitric-hydrofluoric acid 

method is suitable for use when general heavy metals, zinc, or copper 

tests are to be made. The disadvantages are the relatively poor lead 

extraction and the need for both platinum ware and standard laboratory facilities. The 1:1 HNOs method does not require platinum or 

the use of standard laboratory facilities and yields satisfactory extraction of lead and zinc. The disadvantage is that the general 

heavy-metals test cannot be made unless a large amount of buffer 

is used to counteract the higher acid concentration.

In describing the results of soil studies, reference is made to the 

methods of extraction as follows: 1:7 HNOs, nitric-hydrofluoric 

acid, and 1:1 HNO3.

PLANTS

Plant samples collected in 1950 from near the Little Pittsburg 

mine were analyzed for zinc only, using the seniiquantitative field 

method of Reich en and Lakin (1949). Plant samples collected in 

1951 from various parts of the mining district were analyzed by the 

quantitative method used by Reichen and Lakin (1949). The latter 

method consists of a wet oxidation of the dried plant parts by nitric 

and perchloric acids (Piper, 1944) followed by estimation of the 

lead, zinc, and copper in the manner described by Holmes (1945).

No data were obtained on the accuracy or precision of the results 

for zinc in plants using the field seniiquantitative method, but some 

information was obtained on the precision of the quantitative method 

used. The data are presented in table 7, shown on the following page. 

As the precision of the results from separate determinations was as 

good as that from repeat estimations of the lead, zinc, or copper in the 

same solution the percentage extraction must be very consistent and 

is probably near 100 percent.

WATER

Analyses of water were made for zinc alone and for total heavy 

metals using the technique described by Huff (1948). Determinations of pH were made by means of a Hellige standard comparator 

and sulfate analyses were done using a Hellige turbidimeter.
54 CONTRIBUTIONS TO GEOCHEMICAL PROSPECTING FOR MINERALS

TABLE 7. Precision of quantitative plant analyses. 

[Analyses were made by H. E. Crowe, U.S. Geological Survey]

Zinc (ppm)

First 

analysis

Repeat 

analysis

Lead (ppm)

First 

analysis

Repeat 

analysis

Copper (ppm)

First 

analysis

Repeat

analysis

Results of repeat analyses

320

35

30

110

320

30

25

110

103

1

1

6

98

2

1

6

6

7

12

5

6

8

13

6

Results of repeat estimations from same sample solution

65

50

40

60

45

35

13.0

34.0

6.0

20.0

8.5

10.0

15.0

1.5

14

35

6

20

7

4

14

1

6

5

6

8

6

7
INDEX

Page

Acknowledgments..________.____ 3 

Adair, Idaho.....__ __ ..._ __ 35 

Analysis, methods of.._______.____ 51-S4 

Antimony.________.. 2,7,18,20,37-38,46, 48, 52 

Appendix_.____.____________ 51-54 

Argillites, siliceous.. .- .... .. 4

Belt series, of Precambrian age.. ____ 4

Bornite .._.____._..___...__... 35

Bulldozer, application to prospecting.__.... 2

Burke formation.__.____________ 4,5

Cadmium___________________ 7 

Canyon Creek..._..___ ___... 3 

"Carbonate" vein.______________ 31-32 

Cerusslte____________________ 18 

Chalcocite___________________ 35 

Chalcopyrite ..._______.. . .. 21,32,35 

Conclusions-__________________ 47^9 

Copper.__.. 2,10,18,20,31,33-37,40-44,46-49, 51-54 

Coprecipitation, as cause of removal of heavy

metals from drainage__.________.. 44 

Crystallite fault.... .................... 26,29-30

Curlew vein, near the Page mine _____ 32-33 

Ouster Peak area__.___... _____ 14-15

Daisy Gulch...__._._._._.......... 35,44

Deadman Gulch...._________.___ 33,43

Denver Creek ..... __ 24

Dikes._______............_..__.... 4,6

Dlthizone (diphenylthiocarbazone)____ 14,25,51 

Dry Creek.....__ .___ __. 43

Enrichment . 10

Faults . _.__..._.___._____ 7,29 

Frisco mine.._________________ 16-18

Galena.._......._____...... 1,7,16,21,32,46

Gangue minerals ...____ ___ 7,8 

Gentle Annie copper zone...__._____ 34-35 

Gentle Annie Gulch._____________ 35 

Geology-___ . __ ____.. 3-8 

Glaciation.____________.___.__ 3-4 

Gold..........__..._.__...___._ 2,37

Golden Chest gold vein __. _.____ T __ 11,37 

Gold Hunter vein. _______________ 18-20 

Grouse Creek....__.__... ____ 43

Grouse Gulch______________.__ 18,31

Hansy copper mine______________ 35-36 

Heavy metals_______._______ 2,13-14, 

25-26, 30,40,43-44,47-49,51-53 

Hercules mine_________________ 13-14 

Hercules vein. _ ____ ___.... 13

Igneous rocks..________________ 6-7 

Introduction. __ _____ 1-3

Jack Waite vein_-.-.._.. ....___.. 12-13

Lead..._.__....... 2,10-33,40-42,45,47-49, 51-54

Liberal King vein... . 32,45-46

Little Plttsburg vein.. .-_.... 11,25-31

"Local background," term explained-____ 31 

Location of district________ _____ 3-4

Page

Mace, Idaho_____.____..____ 15 

Malachite....__.. ...............____ 34,35

Metamorphism, regional...-_________ 7 

Mill Creek._____._...__ __._ 43 

Missoula tunnel copper zone_________ 33-34 

Morning Star ore shoot_____________ 8 

Mullan, Idaho_... _____________ 18 

Murray, Idaho__..._____________ 12

Nitric-hydrofluoric acid method, for sample 

extraction..____,.___________ 53

Olentange Creek_______________ 35

Ore deposits.....___._______.____ 7-8

Osburn fault________________ 7

Page, Idaho.-... ... .. ... 32

Page mine____________________ 32 

Pinehurst, Idaho________________ 37 

Plants . . 39-42,45,47,49,53,54 

Prichard formation....___._________ 4

Pyrite . - - 7,32

Quartzite. . ......................... 4,5,7

Rainfall_ 4

Reeder Gulch.._________________ 37 

References, cited......____ _____ 49-50

Reindeer Queen mine.... . ___... 43

Revett quartzite_____ __________ 4, 5 

Richmond mine__..______._____ 37 

St. Regis formation....______._____ 4,5-6

Sample extraction, methods...._._____ 51-53

SampUng methods, soils and rocks.._____ 9-11 

Sedimentary rocks .. ... _____ 4-7 

Sericite. ------ . .. .... 7

Sidney vein..._. . _....... 24-25

Silver--..-.-.._-_..-.--._..._ 2,18,20,27,52 

Smelterville, Idaho______.._______ 24 

Snowstorm copper mine 35 

Soil . 4,18-11,45-46,48-49,51-53

Sphalerite-.. - 1,7,32

Stalactites.. - 43,44

Star Antimony property 37-38 

Star vein___________ _____ 18 

Standard-Mammoth vein...__...____-- 15-16 

Stibnite-. .- . 38,46 

Stocks. . --.. . - 4,6 

Striped Peak formation__.... . 4,6

Sulfate determinations______ _____ 45

Tetrahedrite . 1,7

Tungsten 2,37,46,48,52

Vegetation.._ . 4 

Veins ..___ _----- . .... 8

containing antimony. 37-38 

copper minerals__ ... . 33-37 

gold and tungsten. 37 

mainly lead minerals near the surface.. 12-31 

mainly zinc minerals. 31-33 

Vindicator vein.... 11,21-24

Wallace formation....__ 4,6

Water- -~/40,43-45,47,49,53

Zinc 2,10-33,39-42,45,47-49,51-54

Zircon, age determination from.- 6

55

o