GEOLOGICAL SURVEY CIRCULAR 622

U.S. Geological Survey 

Heavy Metals Program 

Progress Report 1968 

Topical Studies

U.S. Geological Survey 

Heavy Metals Program 

Progress Report 1968 

Topical Studies

GEOLOGICAL SURVEY CIRCULAR 622

Washington 1969
United States Department of the Interior

WALTER J. HICKEL, Secretary

Geological Survey

William T. Pecora, Director

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

Page

Introduction _________________________ 1

Stratigraphy of Roberts Mountains Formation _ _ _ 1 

Fluid-inclusion studies __________________ 1

Zoning in epithermal mineral deposits- _ ______ 2

Placer deposits, Western United States- _______ 2

Trace elements in gold __________________ 3

Solid-state solubility of gold in sulfide 

minerals __________________________ 4

Solubility of gold in ore-forming fluids _______ 4

Solution of gold by porphyry copper leach 

solutions __________________________ 4

Trace elements in supergene sulfate minerals- _ _ _ 4 

Studies on platinum-group minerals- _________ 4

Platinum-group minerals from Goodnews 

Bay, Alaska _______________________ 4

Miscellaneous studies __________________ 5

Platinum content of ultramafic rocks ________ 5

Abundance of gold in meteorites, rocks, and 

minerals __________________________ 5

Gold content of native sulfur from Cyprus _____ 5

Gold content of deer antlers _______________ 5

Fine-grained gold in sluice overflow _________ 5

Transport of gold particles along the Snake

River, Wyo. and Idaho _________________ 6

Fluvial transport of heavy minerals- _________ 6

Fluvial transport of gold and silver _ _________ 6

Subaqueous flow of slurries _ ______________ 7

Gold, other trace elements, and heavy

minerals in sedimentary rocks __________ 7

Heavy metals, Atlantic Coastal Plain and 

Triassic basins_ ____________________ 7

Trace elements in graphitic schist,

Alabama and Georgia ________________ 7

Gold in sedimentary rocks, Great Lakes 

region __________________________ 8

Cretaceous black sands, Rocky Mountain 

region __________________________ 8

Gold in Eocene and younger rocks, 

northwestern Colorado- _______________ 9

Silver content of Phosphoria Formation, 

Jackson Hole, Wyo __________________ 9

Heavy metals in rocks of the Colorado

Plateau- _ ________________________ 9

Gold content of Appalachian and 

midwestern coals___________________ 10

Page

Gold, other trace elements, and heavy minerals in 

sedimentary rocks Continued

Gold content of waste products from coal_ _ _ _ _ 10 

Covariation among elements in black shale __ _ _ 10 

Gold content of pyrite from Carlile Shale _____ 10 

Cretaceous and Tertiary conglomerates,

Utah and Idaho ____________________ 10

Gold content of marine phosphorites- _ ______ 11

Gold content of manganese nodule,

Blake Plateau-_ ________ ___________ 11

Heavy minerals in Van Horn Sandstone,

Texas_ __________________________ U

Research in geochemistry ________________ U

Mercury content of the atmosphere-________ H

Interpretation of geochemical anomalies- _ _ _ _ 12

Gold in humus-rich forest soil- ____________ 12

Heavy metals in organic environments- ______ 13

Role of soil microorganisms in solubilizing

minerals _________________________ 13

Sulfur isotopes, Bingham district, Utah_ _____ 13

Geochemical sampling _________________ 14

Sample preparation ___________________ 14

Statistical treatment of geochemical data_ _ _ _ _ 14

Data storage and retrieval ______________ 15

Research in geophysics __________________ 15

Use of very low frequency waves in

geophysical exploration _______________ 15

Detection of induced polarization effect

using natural telluric fields ____________ 15

Neutron activation as an exploration tool- _ _ _ _ 15

Direct-reading field detector for selected

elements- ________________________ 16

Research on analytical methods ____________ 16

Determination of the platinum metals ______ 16

Determination of platinum and palladium

by atomic absorption _________________ 16

Determination of rhodium by atomic

absorption- _______________________ 16

Chemical determination of rhodium in

rocks ___________________________ 17

Determination of platinum, palladium, and

rhodium by fire assay and emission

spectrography _____________________ 17

Determination of osmium and ruthenium _ _ _ _ _ 17

Analysis of platinum metals in chromite _____ 17

III
Page Page

Research on analytical methods Continued Research on analytical methods Continued

Gold analysis._______________________ 17 Chemical analysis with laser-fired

Gold content of quartz standard __________ 17 microprobe _______________________ 18

Intel-laboratory comparison of gold Analyses of tellurium in vegetation _ ________ 18

analyses ________________________ 18 Sensitive method for detection of mercury _ _ _ _ 18

Neutron activation methods of analysis ______ 18 Counter- current elutriator as a gold

Activation analysis for background concentrator ______________________ 18

amounts of gold_ __________________ 18 References cited-_ ____________________ 19

Activation analysis of uranium __________ 18

IV
U.S. Geological Survey Heavy Metals Program 

Progress Report 1968 Topical Studies

INTRODUCTION

Summaries of topical studies carried out in 

calendar year 1968 as part of the Heavy Metals 

program are presented in this circular. Background information on the program, summaries 

of field studies for 1968, and a list of resulting 

publications appear in U.S. Geological Survey 

Circular 621.

Abbreviations commonly used are: 

ppm= parts per million (1 ppm = 0.0001 percent, or about 0.03 oz per ton; for gold 

at $35.00 per oz, 1 ppm equals about 

$1.00 per ton)

ppb= parts per billion (1 ppb = 0.0000001 percent)

Analytical data for gold, platinum metals, and 

silver are usually given in parts per million or 

parts per billion. Results are frequently reported 

as "less than" a certain amount, this amount 

being the limit of detection of the analytical 

method employed. Such a result means that the 

element was not detected and, if present at all, 

occurs only in an amount below the detection 

limit.

STRATIGRAPHY OF THE ROBERTS MOUNTAINS 

FORMATION

The Roberts Mountains Formation (Silurian) 

or lithologically similar formations are the principal host rocks for a number of deposits of very 

fine grained gold in north-central Nevada, including Carlin, Cortez, Bootstrap, and Gold Acres 

(in part). Most gold particles are <1 micron 

across, many are <0.01 micron, and the largest 

are only about 5 microns in largest dimension. 

Detailed studies at Carlin and Cortez have suggested some sort of stratigraphic control finely 

laminated fine-grained black silty and carbonaceous limestone; thus, the regional extent,

stratigraphy, and geochemistry of the Roberts 

Mountains Formation are of the greatest interest 

in predicting areas most likely to contain undetected gold deposits.

During 1968 the formation was studied and 

sampled at about 25 localities over an area that 

is 200 miles north-south by 50 miles east-west 

and extends from the Bootstrap mine in Elko 

County south to Hot Creek in Nye County. These 

preliminary studies have revealed that limestone 

similar to that at the Carlin and Cortez mines is 

the principal rock type in the formation in Eureka, 

Lander, Nye, and Elko Counties. Each of the 

spectrographic analyses of about 100 samples for 

30 elements shows a nearly uniform trace-element 

content. (T. E. Mullens, Denver, Colo.)

FLUID-INCLUSION STUDIES

Fluid-inclusion studies are aimed at determining 

the range of temperature of ore-forming solutions 

and their salinity, as well as, if possible, their 

chemical and isotopic composition. Gangiie 

minerals associated with fine gold at the Cortez 

deposit, Eureka County, Nev., and the Gold Acres 

deposit, Lander County, Nev., generally contain 

fluid inclusions too small for studies with the 

heating and cooling stage, but some measurements and estimates made to date are in the 

range 150° to 230° C, with salinities equivalent 

to about 6 weight percent NaCl. Inclusions in 

vein quartz associated with the Cortez gold deposit homogenize at temperatures between 175° 

and 230° C, the large spread indicating either 

that some inclusions are secondary or that 

trapping from boiling solutions or leakage has 

occurred; most inclusions are <10 microns across, 

so filling temperatures cannot be measured 

directly but are estimated to be low, about 

200° C. Inclusions in 11 samples of vein quartz 

associated with gold ore in the Gold Acres pit 

homogenize in the range of 150° to 180° C.
Inclusions in quartz from quartz-pyrite-gold 

veins in quartz monzonite at Mill Creek near 

Cortez, Nev., indicate a formation temperature 

of about 250° C; for veins in the adjacent limestone, temperatures are lower, 200° to 225° C. 

Inclusions in quartz from base-metal veins in 

and near granitic intrusions at the Gray Eagle, 

Lander, and other small deposits in the Tenabo 

district, Nevada, homogenize from as high as 

325° C for main ore-stage quartz to 175° C for 

very late quartz.

Eleven samples of quartz, barite, sphalerite, 

and calcite from mine dumps in the Silver Cliff 

district, Custer County, south-central Colorado, 

have been studied. Some barite apparently was 

deposited at 250° to 270° C from highly saline 

solutions (as much as 25 wt percent NaCl). Inclusions in quartz have variable filling ratios and 

a wide range of salinity, suggesting that they 

were trapped from a boiling solution; on the 

assumption that inclusions with the smallest 

ratio of vapor to liquid were trapped from liquid 

only, their homogenization temperature of about 

200° C gives an estimate of boiling temperature 

and hence of depth of deposition, probably <500 

feet. The salinity of "normal" inclusions in 

quartz and sphalerite is about IM in NaCl, 

similar to that at Creede, Colo.

Five samples of late quartz probably postdating the ore from the Bodie district in Mono 

County, east-central California, have inclusions 

showing homogenization temperatures from 

225° to 255° C and very low salinities, 0.3 to 1.7 

wt percent NaCl. The low salinities indicate 

that boiling or mixing with meteoric water may 

have occurred. (J. T. Nash, Menlo Park, Calif.)

ZONING IN EPITHERMAL MINERAL DEPOSITS

The proposition that some epithermal mineral 

deposits containing manganese oxides, barite, 

and fluorite may pass downward into sulfide deposits of precious and base metals has been 

argued persuasively in recent years by D. F. 

Hewett of the U.S. Geological Survey; some data 

were presented in Geological Survey Circular 

553. A possible example may be the Magnet 

Cove mine near Walton, Nova Scotia, where a 

body of silver-bearing sulfide minerals was 

found recently beneath a large barite deposit.

To test Hewett's ideas, a broad study of epithermal manganese-fluorite-barite deposits in 

the Western United States was started in 1968, 

and about 50 areas were visited in Arizona, 

Colorado, Idaho, Montana, Nevada, New Mexico, 

Utah, and Washington. Some sampling was 

done in most areas, and detailed sampling in 

eight. Some preliminary findings are that 

barite, fluorite, and manganese oxides form 

halos around deposits of base and precious 

metals, no zoning is evident among these three 

minerals or mineral groups, and all three generally are present in a given area if not in all 

deposits in that area. Detailed studies are 

planned in several districts in Colorado, Arizona, 

and New Mexico. (R. G. Worl, Denver, Colo.)

PLACER DEPOSITS, WESTERN UNITED STATES

A comprehensive study is being made of gold 

placer deposits in the following Western States: 

Arizona, New Mexico, Nevada, Utah, Colorado, 

Wyoming, Montana, Idaho, Washington, Oregon, 

and California. The purpose of the study is to 

locate the deposits accurately, to describe their 

geology and extent, and to compile all pertinent 

references.

Reports on placer deposits of New Mexico and 

Arizona are in preparation. Reports on placers 

of Nevada, Utah, and southern California are 

planned. These reports will describe most of the 

placer deposits of the arid to semiarid regions of 

the United States. The gold-bearing gravels in 

many areas of the Southwest are found in recent 

alluvium and on pediments flanking mountain 

ranges in the Basin and Range province. Difficulties in sampling and mining these "dry 

placers" have in many instances hampered their 

development. However, some placer deposits in 

the Southwest are in high mountains which 

receive sufficient rainfall to permit development 

by dredging. Minor placer deposits occur along 

the major rivers draining the Southwestern 

States.

The age of most of the placer deposits in the 

Southwestern United States generally ranges 

from Pliocene to Holocene, but a few deposits 

are older. Small amounts of gold were recovered 

from Paleozoic and Mesozoic conglomerates in 

the late 1800's, and Eocene gold-bearing gravels
at Goler Canyon in southern California were 

very productive between 1895 and 1900. Most 

commonly, the richest deposits are found in 

gravels which have been continuously deposited 

for many hundreds of thousands, or even millions, 

of years. The rich placer deposits at Manhattan 

in central Nevada are in Pleistocene gravels. 

The placer deposits in the Moreno River valley 

in northern New Mexico are in sediments which 

were continuously deposited from the Pliocene 

to the present. Many placers in the southwest 

are in caliche-cemented conglomerates which lie 

below recent accumulations of barren gravel 

deposits, but the age of most of these placers is 

unknown. (M. G. Johnson, Menlo Park, Calif.)

TRACE ELEMENTS IN GOLD

Isotopic composition of lead in placer gold is 

being studied as a clue to the source of the gold. 

Comparison of lead from gold in the Little Red 

Park placer deposit 2 miles northeast of Hahns 

Peak, Routt County, Colo., with lead from nearby 

ore deposits of Precambrian and Tertiary age 

strongly suggests that the placer gold was derived 

from a Tertiary source. Some uncertainty exists 

because the amount of uranium in the gold is 

unknown. (B. R. Doe, M. H. Delevaux, and J. C. 

Antweiler, Denver, Colo.)

Trace-element content of 23 samples of gold 

from eastern Alaska and the Kougarok River 

area of Seward Peninsula has been determined. 

Study of polished sections of all samples revealed

only one inclusion, suggesting that the trace elements are in solution in the gold rather than in 

grains of other minerals. Lead in placer gold 

from the Harold Tweet Camp on the Kougarok 

River is somewhat more radiogenic than lead in 

potassium feldspars of possible source rocks. (B. 

R. Doe, C. L. Sainbury, and A. L. Sutton, Denver, 

Colo.)

Isotopic analysis of lead in gold from the 

Pharmer placer deposit in Alder Gulch, Virginia 

City district, Montana, shows the lead to be much 

more radiogenic than lead in composite samples 

of ore from the Boulder batholith. Moreover, 

the lead in Alder Gulch gold is more radiogenic 

than any rock lead in Mesozoic or Cenozoic 

igneous rocks in the entire Rocky Mountain region; these rocks cannot be the sole source of 

lead in the gold. (B. R. Doe and K. L. Wier, Denver, Colo.)

The isotopic composition of lead in galena from 

gold ore at the Carlin mine, Eureka County, Nev., 

shows it to be the most radiogenic ore lead found 

to date in Nevada. The isotopic ratios are in the 

range of those known for lead from the Roberts 

Mountains Formation, the host rock for Carlin 

ore, and are higher than those for lead from Cenozoic igneous rocks in Nevada; thus it is likely 

that some or all of the lead was derived from the 

Roberts Mountains Formation. (B. R. Doe and 

M. H. Delevaux, Denver, Colo.)

Isotopic compositions of lead in gold analyzed 

in 1968 are summarized in the table below (B. R. 

Doe, Denver, Colo.).

Locality Collector Pb : Pb 204 Pb 207 : Pb 204 Pb 2«:Pb :

Harold Tweet camp, 

Kougarok River, 

Seward Peninsula, 

Alaska. ________

Fortymile area, 

east-central Alaska _

Thunder Creek, 

Talkeetna Mts.,

C. L. Sainsbury___________ ___19.587

S. H. B. Clark_ ______________ 19.005

C.C. Hawley__________,_____ 19.149

Little Red Park

placer, Hahns Peak,

Colo__ _________

Johnny Tamm placer,

Hahns Peak, Colo_ _ 

Pharmer placer,

Alder Gulch,

Virginia City,

Mont_ _________

Iron Canyon placer,

Battle Mtn., Nev__. 

Carlin mine, Nevada-

_ J. C. Antweiler __ ______

. J. C. Antweiler- _______

______ 18.131

______ 18.450

K. L. Wier. 20.685

T. G.Theodore, B.R. Doe_ ______ 19.386

R. J. Roberts__________-_--- 19.92

15.77

15.83

15.84

15.60

15.70

16.14

15.76

16.04

39.21

38.98

39.41

37.33

37.52

43.53

39.23

40.10
SOLID-STATE SOLUBILITY OF GOLD IN 

SULFIDE MINERALS

Quenching experiments and polished-section 

examination show that 600° and 690 °C the solidstate solubility of gold in pyrite, pyrrhotite, and 

arsenopyrite is <0.1 wt percent; the lower limit 

is indeterminate. At 690°C, chalcopyrite dissolves 

between 1.6 and 4.3 wt percent of gold at the 

sulfur pressure controlled by the pyrite+pyrrhotite buffer. Upon quenching, much of this gold 

exsolves as blebs about 1 micron across. At 

650 °C, galena dissolves between 0.1 and 0.5 wt 

percent of gold in equilibrium with liquid sulfur 

and a second liquid just on the sulfur-rich side 

of the galena-gold join. When bismuth is present in equal atomic proportion to gold, the solubility of gold increases to between 1 and 2 wt 

percent. This increase strongly suggests the 

substitution of AuBi for 2Pb analogous to the 

Ag-Bi-S system, and the assignment of the +1 

charge to at least some of the gold in solid solution in galena. (P. B. Barton, Jr., Washington, 

B.C.) 

SOLUBILITY OF GOLD IN ORE-FORMING FLUIDS

Measurements of the emf (electromotive force) 

of the Au-AuClI electrochemical couple are being 

made to supplement direct measurement of the 

solubility of gold in aqueous solutions, because 

of the very low measured solubilities at or below detection limits of the usual analytical 

methods of gold in synthetic ore-forming fluids. 

At 200 °C in a IN chloride and 0.1 JV sulfate+bisulfate solution in equilibrium with magnetite + 

hematite+pyrite, the concentration of dissolved 

gold is 16 ppb, and of dissolved iron, 4,000 ppm. 

If all dissolved iron and gold were deposited as 

auriferous pyrite, the pyrite concentrate would 

contain about $2.00 in gold per ton. (J. L. Haas, 

Washington, D. C.)

SOLUTION OF GOLD BY PORPHYRY COPPER 

LEACH SOLUTIONS

Tests of synthetic leach solution approximating 

the composition of solutions resulting from the 

commercial leaching of dumps of porphyry copper 

deposits have shown that the addition of sodium 

chloride to the solution results in solution of gold 

in the presence of manganese dioxide. The 

test solution of ferric sulfate and cupric sulfate 

(pH 1.5) contained 0.5 wt percent NaCl. Leaf 

gold was added to two 200-milliliter portions of 

solution, and 0.5 gram MnO£was added to one of

these portions. Air was bubbled through both 

solutions for 3 days, and the solutions were then 

filtered. The filtrate of the portion that had 

been in contact with Mn02 contained 400/^g (micrograms) of gold, the other portion only 4 jug. 

(H. W. Lakin, Denver, Colo.)

TRACE ELEMENTS IN SUPERGENE SULFATE 

MINERALS

Analyses of hand-sorted concentrates of supergene sulfates of copper and iron from underground workings of mines in the Empire district, 

Colorado, show as much as 11.7 ppm Au, 10 ppm 

Te, and 0.60 ppm Hg, all well above background 

amounts for the area. Higher-than-background 

amounts of manganese, bismuth, cobalt, nickel, 

and zinc also were detected. The analyses indicate that gold, tellurium, and mercury are 

mobile in the supergene environment. An 

attempt will be made to determine the chemical 

state of the gold in these sulfates and also the 

Eh-pH conditions in the mine environment. (H. 

W. Lakin, Denver, Colo.)

STUDIES ON PLATINUM-GROUP MINERALS

PLATINUM-GROUP MINERALS FROM GOODNEWS BAY,

ALASKA

A new palladium mineral has been found in 

concentrates from the platinum placer deposits 

at Goodnews Bay, Alaska. The concentrate was 

obtained from the Goodnews Bay Mining Co. 

and furnished by J. B. Mertie, Jr. The chemical 

formula is Pd7(Sb,As)2, and the mineral contains 

0 to 3 percent copper. It is the only mineral in 

the concentrates containing palladium as a major 

constituent. Mineralogical characteristics were 

determined by X-ray powder diffraction, quantitative ore microscopy, and electron microprobe 

analysis. The name mertieite has been proposed 

for the mineral, in honor of John B. Mertie, Jr.

Qualitative milliprobe X-ray fluorescence analyses of more than 200 grains of platinum-group 

minerals from Goodnews Bay have been completed. The nonmagnetic fraction of the precious 

metals consists chiefly of iridium-osmium alloys 

which contain ruthenium and traces of copper. 

In addition to a new palladium mineral, these 

concentrates also contain a few grains of sperrylite (PtAs2), a mineral not previously reported 

from this locality. (G. A. Desborough, Denver, 

Colo.)

Investigations of laurites (Ru,Os,Ir)S 2 from 

Goodnews Bay have provided quantitative ore
microscopy and chemical composition data for 

five laurites. These data show variations in 

composition and reflectivity. The range in composition indicated is as follows, in weight percent: 

Rueil^Sss; Ru53.5(Ir,Os)i2.i 834.4; Rug^I^Os^gSai.^ 

Ru4o.5(Ir ,08)^4831.1. (G. A. Desborough and B. F. 

Leonard, Denver, Colo.)

MISCELLANEOUS STUDIES

Mineragraphic and electron microprobe studies 

of samples of chromite from the Antelope-Pony 

chromite district in northern Madison County, 

southwestern Montana, revealed several grains 

<10 microns across of a platinum-group alloy in 

which the relative proportion of platinum 

metals was Ir < Ru < Os < Pt. Analysis of whole 

rock samples by a fire assay-neutron activation 

method indicated <1 ppm of combined Ir, Os, 

and Ru. In addition to the presence of the platinum-group alloys, alloys of iron, nickel, and 

cobalt are present in trace amounts.

Microprobe analyses of stibiopalladinite (Pd3Sb) 

from the discovery locality in the Republic of 

South Africa indicate that copper is probably an 

essential constituent; copper content is 1.6 ±0.2 

percent.

Laurite (RuS2) and OsSa have been synthesized 

in a vacuum by heating the respective sponge 

metals with pyrite at about 800° C for 15 hours. 

Pyrrohitite is a reaction product.

Eight samples of drill core from the mafic 

Shepherd Mountain intrusion near Pilot Knob, 

Mo., were analyzed for platinum, palladium, and 

rhodium by fire assay and quantitative spectroscopy. Results for all samples were: platinum 

<0.010 ppm, palladium <0.004 ppm, and rhodium 

<0.005 ppm. (G. A. Desborough, Denver, Colo.)

An iron-bearing variety of laurite (RuS2) has 

been found in chromitite from the I3 -zone in the 

Mountain View area of the Stillwater Complex 

in southcentral Montana. A platinum-iron alloy 

containing a little nickel and palladium and 

traces of iridium and osmium has been identified 

in the H-zone in the same area, where it is associated with copper-nickel-iron sulfide and pentlandite in chromitite. (N. J. Page, Menlo Park, 

Calif.)

PLATINUM CONTENT OF ULTRAMAFIC ROCKS

Ultramafic rocks of the alpine type from 

several localities have been analyzed for platinum, palladium, and rhodium, and the results, 

in parts per billion, are as follows:

Locality Rock type Pt Pd Rh

Red Mountain, California- _____

Red Mountain, California- _____ 

Butler Estate chromite

Crypress Island, Washington

Josephine ultramafic, Oregon. _ _ .

Peridotite _ _ _ . < 10 

Dunite . <10

Chromite____ 32-40

Dunite------ <10

Laterite_--__ 36

Tr. 

<4

8-12 

<4

<4 

<4

13

<5 

<5

9-10 

<5

<5 

<5

5

These results suggest that (1) platinum-group 

metals are associated with chromite concentrations in alpine-type ultramafic rocks and (2) these 

metals are concentrated by weathering in laterites. (N. J. Page, Menlo Park, Calif.)

ABUNDANCE OF GOLD IN METEORITES, 

ROCKS, AND MINERALS

Data compiled on the abundance of gold in 

meteorites and in the earth's crust were reported 

in Geological Survey Circular 603. Meteorites 

contain from 0.0003 to 8.74 ppm Au, mainly in 

the iron-rich phases, and estimates of abundance 

in the earth's crust range from 0.001 to 0.006 ppm. 

Circular 610 on the gold content of rocks and 

Circular 612 on gold in minerals and the composition of native gold were published early in 

1969. (R. S. Jones, Washington, D.C.)

GOLD CONTENT OF NATIVE SULFUR FROM 

CYPRUS

A sample of native sulfur from acid sulfate 

gossan on cupriferous pyrite deposits on the island 

of Cyprus contains 8,200 ppm Au. The sample 

was collected by the late Prof. C. F. Davidson and 

labeled "Devil's Mud." The gold particles are 10 

to 100 microns across and the smaller ones show 

poorly formed crystal faces. The larger particles 

are rounded, resembling framboidal pyrite which 

which many geologists believe to be of bacterial 

origin. (H. A. Tourtelot, Denver, Col.)

GOLD CONTENT OF DEER ANTLERS

The gold content of nine samples of deer antlers 

has been determined by neutron activation analysis to range from 0.7 to 5.5 ppb.

FINE-GRAINED GOLD IN SLUICE OVERFLOW

Studies of overflow material from a placer sluicing operation near Livengood, 50 miles northwest 

of Fairbanks, Alaska, have shown that a substantial amount of fine-grained gold is not being 

recovered by normal sluicing techniques. The
size range of the gold particles in the sample 

studied was about as follows:

Millimeter Percent

>0.35 _______________ 10

.2-.35____ __________ 40

.061-.2 _____________ 40

<.061_____ __________ 10

Under conditions of operation at the time the 

sample was collected, the loss of gold is estimated 

to be around 0.5 oz per minute, and total loss between sluice cleanups may be 30 to 40 oz.

These findings may have considerable economic 

significance, because it is unlikely that all such 

losses could be detected even by careful panning 

methods; about 35 percent of the gold is <0.150 

mm in diameter, which was the smallest size 

recovered by panning done by the placer operator, and about 15 percent is <0.100 mm in 

diameter, which is about the limit for recovery 

even by very careful panning. (H. A. Tourtelot, 

Denver, Colo.

TRANSPORT OF GOLD PARTICLES ALONG 

SNAKE RIVER, WYO. AND IDAHO

The mass of gold particles within a given size 

range decreases progressively downstream along 

the Snake River for more than 400 miles below 

the outcrops of auriferous conglomerates in 

Jackson Hole. For instance, in northern Jackson Hole, particles approximately 0.125 mm in 

diameter average about 10 JA g in weight, whereas 

near Twin Falls, Idaho, particles of the same 

diameter weigh only half as much. The striking 

correlation between weight of particles of a 

certain range of diameter and distance from 

source is useful in suggesting transport direction 

from the source of gold in the conglomerates. 

The data indicate that discrete gold particles can 

and do travel great distances despite their high 

specific gravity. (J. C. Antweiler and D. A. 

Lindsey, Denver, Colo.

FLUVIAL TRANSPORT OF HEAVY MINERALS

Fluvial transport of heavy minerals is being 

studied experimentally at Colorado State University, Fort Collins, Colo., by scientists of the U.S. 

Geological Survey. The study deals with the hydraulic environments in which heavy minerals are 

transported and deposited and with the formation 

of placer deposits.

Fall velocity of gold flakes and other heavy 

minerals has been measured in newly constructed 

fall columns. The concept of hydraulic equivalence of minerals is being thoroughly investigated, and the transportation, deposition, and reentrainment of minerals under different conditions 

of waterflow are being studied in two flumes. 

Minerals used in the hydraulic experiments 

include quartz, garnet, monazite, magnetite, lead, 

and gold; some minerals are dyed to facilitae 

recognition. In addition to the experimental 

work, transport rates of various heavy minerals 

have been measured under natural conditions 

in some irrigation channels in New Mexico. 

Results of the work during 1968 are to be published in 1969 in a series of papers in "Geological 

Survey Research 1969" and in technical journals.

A literature search aimed at gaining quantitative data on gold placers including dimensions 

of gold particles, size distribution of the enclosing sediments, and discharge and slope of streamindicated that only limited data are available 

and that field studies, including observations at 

operating placer mines, will be necessary to obtain 

adequate information. (R. S. McQuivey, Fort 

Collins, Colo.)

FLUVIAL TRANSPORT OF GOLD AND SILVER

The fluvial transport of gold and silver is being 

investigated at the Denver Federal Center. The 

project is concerned with the mode of transport of 

these and other metals in streams in bedload, 

suspension, and solution and possible applications to geochemical exploration. To date most 

work has been done on analytical methods for 

measuring the very low concentrations of silver 

and gold in natural waters. Some of the problems 

involved in analyzing for these small amounts, on 

the order of a few micrograms per liter (lfj,g/\ is 

1 ppb), are described in two articles in "Geological 

Survey Research 1968," chapter D. In summary, 

it has been found that adsorption of silver on the 

walls of polyethylene containers can be reduced to 

about 1 percent of the silver present if the water 

sample is acidified to a pH of 1 with either hydrochloric or nitric acid. Desorption can also be effected in several days by similar acidification. 

Adsorption of gold may be greatly decreased by 

(1) acidification to pH 1 with hydrochloric acid and 

addition of 5 to 50 mg/1 (milligrams per liter) of 

bromine, (2) acidification with hydrochloric acid to
IN without bromine, and (3) acidification with 

nitric acid to 2N or 3JV. Adsorption is also much 

reduced by adding 50 mg/1 of bromine to water 

of pH 6. On the other hand, acidification to pH 2 

or 3 with hydrochloric or acetic acid, or to pH 1 

with nitric acid, increases gold adsorption.

Water samples from six gold-producing districts 

(Iron Springs Divide and Hahns Peak in northwest 

Colorado, Central City and Empire in central Colorado, Cripple Creek west of Colorado Springs, 

Colo., and Encampment in south-central Wyoming) have been analyzed; their gold content 

ranges from 13 to 58 /zg/1. (T. T. Chao, Denver, 

Colo.)

SUBAQUEOUS FLOW OF SLURRIES

The subaqueous flow of slurries is being studied 

to gain an understanding of the transport and 

deposition of heavy minerals by turbidity currents. Investigations are being done at Stanford 

University, Stanford, Calif., under a research contract.

Experiments are being carried out in a tank 

8x8x4 feet deep and in a 20-foot flume with 

glass sides and a tiltable bottom. A conveyorbelt machine with controllable speed and variable 

slope also is being used to study velocity and 

mechanical properties of slurry flow in a channel. 

The nature of transformation from submarine 

slump or debris flow into turbidity currents is 

being studied in the flume, and particle sorting 

is being studied in the conveyor belt. (P. D. 

Snavely, Menlo Park, Calif.)

GOLD, OTHER TRACE ELEMENTS, AND HEAVY 

MINERALS IN SEDIMENTARY ROCKS

HEAVY METALS, ATLANTIC COASTAL PLAIN AND 

TRIASSIC BASINS

Reconnaissance sampling of Atlantic Coastal 

Plain sedimentary rocks has been done along the 

inner edge of the Coastal Plain from Alabama 

north to New Jersey, and the Triassic basins have 

been very sparsely sampled from South Carolina 

to Massachusetts. Detailed sampling has been 

done in the inner Coastal Plain of northern South 

Carolina and southern North Carolina. The Triassic has been sampled in detail in the Farmington 

basin of northern North Carolina, in parts of 

southern North Carolina near Mt. Gilead, and in 

northern Virginia.

An upland area of 15 square miles on the inner 

Coastal Plain near Jefferson, S. C., has been investigated and sampled in detail. Several streams 

draining this small area yield appreciable gold in 

panned samples; several to as many as 50 particles 

of gold, ranging from silt to very coarse sand size, 

have been obtained in concentrate from a single 

pan. Samples obtained from sand and gravel 

layers in the Coastal Plain sediments, both in 

outcrop and from auger holes, also have yielded 

gold.

Triassic sandstone and conglomerate in the Mt. 

Gilead area, North Carolina, contain from 0.10 to 

more than 2.0 ppm Au. Streams in the area yield 

particles of gold in panned concentrates, although 

they are not as abundant as in concentrates from 

the Jefferson, S. C., area. Coastal Plain sediments 

have gold values as high as 2.0 ppm. Traces of 

gold have been found in conglomerate in a small 

Triassic basin at Farmington, N. C., but higher 

values come from samples of quartz and schist 

exposed in a small area in the center of the basin; 

these rocks have from 1.0 to 12 ppm Au.

The Triassic rocks of southern Pennsylvania 

have not been examined in any detail, but three 

of four samples of siltstone, sandstone, and diabase had gold contents of as much as 4.5 ppm. 

These rocks are to be further investigated.

Five of seven samples of Triassic diabase near 

Leesburg, Va., showed detectable amounts of platinum minerals, and several more samples are 

being analyzed. Several zinc anomalies, containing as much as 7,000 ppm(0.7 percent), have 

been found along the border fault zone of the Triassic basin north of Leesburg.

As much as 4,000 ppm Cu, 2,000 ppm Ni, 5,000 

ppm Cr, and 1,500 ppm Co have been found in 

samples of weathered diabase and schist beneath 

the Coastal Plain sediments in South Carolina. (J. 

P. Minard, Washington, D. C.)

TRACE ELEMENTS IN GRAPHITIC SCHIST, ALABAMA 

AND GEORGIA

From northeastern Alabama and northern 

Georgia, 24 out of 100 samples of graphitic schist 

of Precambrian and Paleozoic age contain detectable amounts of gold ranging from 0.02 to 3.8 ppm. 

The gold-bearing samples came from the 

Wedowee, Ashland, Canton, and Brevard Formations of Crickmay (1936, 1952), mostly from the 

Blue Hill-Gregory Hill mine in Tallapoosa County, 

Ala. Gold-bearing samples from eastern outcrop 

belt of the Wedowee Formation seem to contain a 

little less boron, barium, cobalt, chromium, copper,
iron, manganese, magnesium, nickel, lead, scandium, titanium, vanadium, and yttrium than 

barren samples from the same unit, and about 

the same amount of beryllium, lanthanum, molybdenum, niobium, strontium, zinc, and zirconium. 

The trace element content of graphitic schists is 

similar to the trace element content of eugeosynclinal black shales and about the same as an 

average shale. (F. G. Lesure, Washington, D. C.)

GOLD IN SEDIMENTARY ROCKS, GREAT LAKES REGION

Sedimentary rocks of the Great Lakes region 

have been studied to determine whether they 

contain fossil placers derived from the Canadian 

Shield gold province to the north. The rocks 

sampled range in age from Precambrian to Cretaceous. Analytical results ranged from 20 ppb 

Au, the lower limit of detection, to 300 ppb. Of 

the 618 samples analyzed, 25 or 4 percent had 

detectable gold. The mean gold content of these 

25 samples was 58.5 ppb. The mode was 20 ppb.

Sandstones and conglomerates of late Precambrian, Cambrian, Ordovician, Mississippian, 

Pennsylvanian, and Cretaceous age were sampled. 

None had more than trace amounts of gold. The 

highest value was 300 ppb from a Precambrian 

conglomerate near Brokaw, Wis. Glauconitic 

Franconia Sandstone (Upper Cambrian) and the 

Fond du Lac Sandstone of Winchell (1899) (Upper 

Precambrian) each had one sample in seven that 

contained more than 20 ppb Au. Only one of 

37 samples of the Olean Conglomerate Member 

of the Pottsville Formation had more than 20 

ppb Au.

Gold has been reported in the phosphatic, pyritic, and carbonaceous basal Maquoketa Shale 

(Upper Ordovician) in northwestern Illinois, and 

45 samples of this unit were collected in Iowa, 

Illinois, and Missouri. One sample contained 20 

ppb Au, the rest less than 20 ppb.

A kame terrace near Marquette, Mich., reported 

to contain appreciable gold,was sampled. The 

panned heavy-mineral concentrates from 32 

samples of sand all contained less than 20 ppb Au.

Several samples of carbonate, a sample of 

halite, and a sample of gypsum from the sedimentary rocks of the Great Lakes region have 

from 20 to 60 ppb Au, which suggests that syngenetic chemical processes may have resulted in 

the removal and concentration of the gold 

contained in sea water.

Paleocurrent studies were made of basal 

Cambrian sandstones and some Precambrian

sandstones to determine source directions in order 

to relate anomalous gold values in the sandstones 

to known or unknown source gold deposits in the 

Precambrian rocks of the Canadian Shield. A 

Cambrian divide between two marine current 

systems was found in northern New York. This 

divide was infrequently covered by the sea, and 

dunes are preserved which indicate a prevailing 

wind from the east. Parts of the Chapel Rock 

Member of Munising Formation of Hamblin 

(1958) (Upper Cambrian), heretofore called 

marine, were found to be of eolian origin. The 

large-scale crossbedding of this unit records winds 

from the southeast. (D. A. Seeland, Denver, Colo.)

CRETACEOUS BLACK SANDS, ROCKY MOUNTAIN REGION

Deposits of fossil black sandstone of Late Cretaceous age have been reported at 105 localities 

in the Rocky Mountain region of the conterminous 

United States. Minerals of possible economic 

interest include ilmenite, altered ilmenite, titaniferous magnetite, a variety of intergrown irontitanium oxides such as ulvospinel-magnetite, 

chromite, zircon, rutile, monazite, niobium-bearing 

opaque minerals, and gold. Gold is not abundant, 

but deposits of Wyoming and Colorado contain 

as much as 1.3 ppm. In Wyoming, the younger 

deposits contain the higher gold contents.

Iron-titanium oxides show regional variations, 

with titaniferous magnetite most abundant in 

Montana, and ilmenite most abundant in New 

Mexico, Arizona, and Utah. Wyoming deposits 

are composed of a variety of complexly intergrown iron-titanium oxides along with ilmenite, 

titaniferous magnetite, and chromite. Most of 

the deposits in the south (southern Colorado, 

Utah, Arizona, and New Mexico) show extreme 

alteration of iron-titanium oxides with formation 

of anatase, rutile, brookite, goethite, and hematite 

from original detrital iron-titanium oxides. 

Three samples from a sandstone near Escalante, 

Garfield County, Utah, contain an average of 2.1 

percent rutile, and one sample has 3.9 percent 

rutile. Black sandstones in this area contain 

more rutile than do those elsewhere in the Rocky 

Mountains, suggesting the existence of a rutile 

province that warrants further study.

In general, older deposits, probably derived 

largely from sedimentary rocks, are richer in 

ilmenite, zircon, monazite, and rutile, although 

there are some exceptions. Younger deposits, 

especially those of Montana and northern and
eastern Wyoming, are dominated by volcanic 

mineral suites; titaniferous magnetite, intergrown iron-titanium oxides, oxyhornblende, 

pyroxene, sphene, apatite, euhedral biotite, and 

euhedral zircon are common. Rock fragments 

of volcanic origin are also abundant in many of 

these deposits. Trace elements in the heavy 

minerals include cerium, niobium, tin, vanadium, 

hafnium, cobalt, lanthanum, nickel, ytterbium, 

neodymium, and yttrium. Most of these elements are in monazite and zircon, but very rich 

samples of black sandstone from Montana contain over 0.10 percent V, suggesting that a significant amount of vanadium could be recovered 

from a magnetite concentrate. Niobium is 

probably present in niobium-bearing opaque 

minerals and in ilmenite.

These black sandstone deposits vary greatly in 

size and grade, but the aggregate content of 

heavy minerals is large, probably well in excess 

of 50 million tons. Certain deposits contain 

substantial heavy-mineral reserves. For example, the Dugout Creek deposit in Wyoming 

is over 2.7 miles long with a maximum exposed 

width of 1,500 feet; the Sanostee deposit in New 

Mexico is over 8,000 feet long with a maximum 

width of 1,000 feet and contains in excess of 

2,000,000 tons of heavy-mineral-rich sandstone; 

and a group of overlapping deposits at Choteau 

in Montana covers an area more than 2 miles 

long and 1.5 miles wide. Many of the deposits, 

especially in Montana, Wyoming, and New 

Mexico, should be readily strippable because they 

cap buttes as a result of their resistance to 

erosion. They are, however, well indurated and 

could not be processed as easily as recent beach 

placers. (R. S. Houston, Laramie, Wyo.)

GOLD IN EOCENE AND YOUNGER ROCKS, NORTHWESTERN 

COLORADO

The shaly unit correlative with the Tipton 

Tongue of the Green River Formation has been 

mapped through most of the north and northwest part of the Craig 30-minute quadrangle as 

part of a study of gold-bearing Cenozoic rocks 

in northwestern Colorado. The distribution of 

gold in modern sediments derived from the 

Tertiary rocks appears to reflect two principal 

controls. Most of the richest samples are near 

the outcrop of the Tipton, apparently reflecting 

deposition of gold near the arm of the Green 

River lake in which the Tipton was deposited.

The most likely explanation at present is deposition in the deltaic fans bordering the lake. 

The richest samples also have a fairly linear 

trend suggestive of a principal gold-bearing 

stream system on a particular fan. Within that 

system the optimum site for gold accumulation 

appears to be near the apparent pinchout of the 

Tipton along the east limit of its outcrop.

South of the Little Snake River, a series of 

cobble-gravel terraces of Quaternary and perhaps late Tertiary age are clearly derived from 

the Sierra Madre Range in Wyoming. The 

presence of basaltic cobbles shows these terraces 

to be younger than the Browns Park Formation 

(Miocene?). The terraces appear to have only 

traces of gold. (P. K. Theobald, Jr., Denver, 

Colo.)

SILVER CONTENT OF PHOSPHORIA FORMATION, 

JACKSON HOLE, WYO.

The silver content of phosphatic black shale 

and mudstone near the base of the Phosphoria 

Formation (Permian) has been determined on 

samples from four localities near Jackson, Wyo. 

The sampled zone lies 7 to 14 feet above the base 

of the Phosphoria, is 1 to 7 feet thick, and contains 40 to 70 ppm Ag. (J. D. Love, Laramie, 

Wyo.)

HEAVY METALS IN ROCKS OF THE COLORADO PLATEAU

In a systematic study of the heavy-metal content of Mesozoic rocks of the Colorado Plateau, 

6,028 samples have been prepared to date and 

submitted for quantitative analyses of gold, silver, 

copper, and mercury. Semiquantitative spectrographic analyses for 30 elements are also 

being made. Analytical data are complete for 

about 60 percent of the samples. Some results of 

the study are the following:

1. The Moenkopi Formation (Triassic) (323 samples) is significantly low in iron, magnesium, 

copper, lead, mercury, yttrium, beryllium, and 

nickel and high in chromium, cobalt, silver (0.26 

ppm), and gold (0.016 ppm), as compared with a 

standard recently published by Turekian and 

Wedepohl (1961). This finding supports the 

interpretation that sediments which make up 

the Moenkopi were eroded from weathered 

terranes and deposited in an arid oxidizing 

environment.

2. Among the rocks of different textures in ;the 

Moenkopi, claystones contain significantly

9
more trace metals than the sandstones and 

siltstones. Iron, copper, and nickel are more 

than four times as high; gold (0.04 ppm) is 

twice as high. Siltstones show significant 

differences from the formation average; they 

are low in silver and high in manganese and 

chromium. Relative to the average for the 

formation, the medium- and fine-grained and 

very fine grained sandstones are significantly 

higher in copper and the very coarse and coarse 

sandstones are significantly higher in barium 

and lower in mercury.

3. Among stratigraphic subdivisions of the Moenkopi, the Tenderfoot Member contains generally more of all the trace metals than the 

entire formation. The Shnabkaib Member, a 

gypsum-limestone evaporite facies, is low in 

most trace metals, but significantly high in 

magnesium, strontium, lead, and silver. The 

Holbrook and Wupatki Members are generally 

low in trace metals, particularly magnesium 

which is present in only one-fourth the average formation concentration. The Hoskinnini 

Member is generally slightly low in most of 

the trace metals, but individual metals show 

no significant differences. Limestones and 

dolomites (containing more than 74 percent 

carbonates) and certain calcareous siltstones 

(50 to 74 percent carbonates) show a low content of nearly all trace metals, including titanium, barium, zirconium, iron, and mercury.

4. Mudstones from the top of the Moenkopi in 

areas in which uranium has been mined show 

large variations in metal content. Strontium, 

copper, yttrium, nickel, cobalt, beryllium, and 

gold (0.09 ppm) are four times as abundant as 

in the whole formation, whereas calcium, manganese, and silver are only one-fourth as abundant as in the entire formation. It seems 

likely that the metal content of these mudstones 

has been affected by metal-rich solutions related to the uranium deposits in the basal 

strata of the overlying Chinle Formation. It 

is probable that systematic sampling of these 

mudstones in the Colorado Plateau region 

would yield both large- and small-scale geochemical anomalies of value to a program of 

exploration for uranium deposits. (R. A. 

Cadigan, Denver, Colo.)

GOLD CONTENT OF APPALACHIAN AND MIDWESTERN 

COALS

Analyses of 100 samples of ash from coal from 

Appalachian and interior coal fields all showed 

less than 0.05 ppm Au. These samples were selected from about 1,000 samples previously collected by Taisia Stadnichenko and Peter Zubovic 

and are believed to be representative of their 

respective coal provinces. (J. D. Vine, Denver, 

Colo.)

GOLD CONTENT OF WASTE PRODUCTS FROM COAL

Traces of gold were found in several samples 

among about 75 samples of materials such as 

coal ash and coal-washing waste products received from various industrial plants. These 

samples have been separated into light and 

heavy components and will be reanalyzed to 

check the presence and mode of gold occurrence. 

(J. D. Vine, Denver, Colo.)

COVARIATION AMONG ELEMENTS IN BLACK SHALE

Analyses of covariation among element concentrations have been made for 17 suites of samples of black shale accumulated in many types 

of geologic environments. Results indicate considerable diversity among the geochemical 

associations. Minor elements most commonly 

enriched in association with organic material are 

vanadium, molybdenum, zinc, lead, chromium, 

and silver, whereas nickel, copper, cobalt, lanthanum, selenium, uranium, and titanium are only 

occasionally enriched in the same association. 

(J. D. Vine, Denver, Colo.)

GOLD CONTENT OF PYRITE FROM CARLILE SHALE

Pyrite from 30 feet of beds in the upper part 

of the Carlile Shale (Upper Cretaceous) was reported 12 years ago to contain 100 to 500 ppm 

Au. The shale contains about 2 percent pyrite, 

and therefore might have contained 2 to 10 ppm 

Au. The rock was resampled and analyzed to 

check this long-overlooked information, but all 

samples contained <0.02 ppm. (D. R. Shawe, 

Denver, Colo.)

CRETACEOUS AND TERTIARY CONGLOMERATES, UTAH 

AND IDAHO

A regional study of Upper Cretaceous and 

lower Tertiary erogenic conglomerates in northern Utah and southern Idaho has shown that the 

gold content of the rocks sampled is negligible 

and that the heavy-mineral suites are not useful

10
for stratigraphic correlations. The Evanston 

Formation (Upper Cretaceous and Paleocene) of 

southwestern Wyoming is now known to extend 

into northeastern Utah. (T. E. Mullens, Denver, 

Colo.)

GOLD CONTENT OF MARINE PHOSPHORITES

The gold content of a composite sample of 

phosphate nodules from Blake Plateau has been 

reported as 7 ppb, suggesting that other phosphorites should be checked as possible sources of 

byproduct gold. Therefore, the gold content of 

seven concentrates of marine apatite from four 

regions (Florida, Montana, North Carolina, and 

Morocco) was determined by a combined neutron 

activation-fire assay method. Eleven determinations were made. The highest gold content 

\xas 3 ppb, indicating that phosphorite probably 

cannot be considered as a potential source of 

gold with present technology. (Z. S. Altschuler, 

Washington, D. C.)

GOLD CONTENT OF MANGANESE NODULE, BLAKE 

PLATEAU

The gold content of a manganese nodule from 

Blake Plateau off northern Florida is a few 

tenths of a part per billion.

HEAVY MINERALS IN VAN HORN SANDSTONE, TEXAS

A detailed study of heavy minerals and possible fossil placer deposits in the Van Horn Sandstone of western Texas was begun in 1968 under 

a research grant to the University of Texas. The 

Van Horn is a Precambrian fluvial arkosic sandstone and conglomerate exposed over an area of 

about 100 sq mi in Culberson and Hudspeth 

Counties, westernmost Texas. The formation 

has a thickness of 800 feet or less, is unmetamorphosed and structurally simple, and was derived 

from an igneous source to the north. Some gold 

has been reported in placer deposits derived from 

the Van Horn. The project will include mapping 

of primary sedimentary structures, grain-size 

analyses, and petrographic studies, the aim being 

to reconstruct the paleoenvironments in which 

the formation \xas deposited. (A. J. Scott, Austin, 

Tex.)

RESEARCH IN GEOCHEMISTRY

MERCURY CONTENT OF THE ATMOSPHERE

The use of mercury in the atmosphere as a potential exploration tool was discussed in Geological

Survey Circular 609, published in 1969. Tests 

carried out in several mining districts (Cortez 

and Ivanhoe, Nev.; Coeur d'Alene, Idaho) have 

shown that the mercury content of gas contained 

in soil overlying mineralized ground is higher in 

some places more than an order of magnitude 

higher than in soil on barren ground. Analyses of the soils indicate that the mercury is not 

in the soils themselves and therefore probably 

was derived from bedrock sources. Variable 

thicknesses of soil did not adversely affect usefulness of the method in outlining the gold deposit at Cortez, where maximum cover was 100 

feet; furthermore, high concentrations of mercury were found atop the Sheep Creek Range 

north of Battle Mountain, Nev., where the mercury source may be covered by as much as 1,000 

feet of basalt.

The presence of mercury vapor over some ore 

deposits at ground level suggested that some 

might also be present in the air at considerably 

higher altitude, and therefore the mercury content in air at 100 to 1,000 feet altitude was 

measured from a light aircraft in Arizona. Air 

over two mercury deposits contained 10 to 20 

times background amounts of mercury, and air 

over two porphyry copper deposits, 5 to 10 times 

background. The 200-foot altitude was found 

to be the highest at which appreciable amounts 

of mercury were found, but some was detected 

at as much as 1,000 feet above terrain.

Resolution of the truckborne and airborne 

equipment available to date is very poor. However, it is hoped that in 1969 a much more sensitive and convenient instrument will be developed that will provide the resolution needed to 

determine whether this method does indeed have 

as much promise as its early tests indicate. (J. H. 

McCarthy and W. W. Vaughn, Denver, Colo.)

Measurements made of the mercury concentrations in several polymetallic deposits of Tertiary 

age in east-central and north-central Nevada 

show that mercury is greatly enriched in the soil 

gases in the vicinity of these deposits. In contrast, a relatively small concentration of mercury 

is present in the older (Precambrian) deposits of 

the Coeur d'Alene district, Idaho. Soil gases in 

the vicinity of the Nevada deposits contain up 

to about 200 nanograms Hg per cubic meter,

11
whereas the soil gases in the Coeur d'Alene 

district contain only about 10 nanograms Hg per 

cubic meter. In the Coeur d'Alene district the 

mine gases below the zone of oxidation contain 

no mercury, although the sulfide minerals contain up to 65 ppm Hg, thus indicating that little 

mercury is being released to the atmosphere 

from the sulfide minerals. The great difference 

in the amout of mercury vapor emanating from 

deposits of Tertiary and Precambrian age, respectively, suggests that the readily available 

mercury has already evaporated from the Precambrian deposits and that mercury vapor is 

most useful as a prospecting guide in the search 

for relatively young deposits. (G. B. Gott, 

Denver, Colo.)

INTERPRETATION OF GEOCHEMICAL ANOMALIES

A detailed soil and vegetation sampling program at Catheart Mountain, Maine, where a 

recently discovered copper-molybdenum porphyry-type deposit in quartz monzonite 

occurs beneath a thin blanket of glacial till, 

showed that strong copper and molybdenum 

anomalies in both soil and vegetation (red spruce 

and balsam fir) are genetically related to the 

deposit and its weakly mineralized alteration 

halo. However, the high mobility of copper in 

this acid podzolic environment causes an appreciable migration of copper from the source, 

so the spatial relationship between the mineralized rock and the copper anomaly is not as 

strong as for molybdenum. Preliminary analysis 

of the data suggests, therefore, that the molybdenum content of B-zone soils provides the most 

useful and direct guide to such deposits in a 

similar environment. In the alkaline environment of the Basin and Range province, on the 

other hand, molybdenum is very mobile and 

copper relatively immobile. At Catheart Mountain, the molybdenum content of twigs and 

needles of balsam fir trees (and to a lesser degree, red spruce) appears to correlate reasonably 

well with the molybdenum content of the soils, 

but the copper content of such trees shows less 

contrast.

Remote-sensing studies at Catheart Mountain 

have provided the first concrete evidence that 

remote sensing of geochemical anomalies in soil 

and tree-covered areas may be possible. The 

reflectance of fir and spruce trees growing in 

metal-rich areas and in areas of only background

metal content has been measured by Prof. 

Edward Yost of Long Island University. The 

reflectance curves of specimens rooted in soil 

anomalously high in copper and molybdenum 

are significantly different, especially in the nearinfrared region, from those of specimens rooted 

in areas of background metal content. (F. C. 

Canney, Denver, Colo.)

GOLD IN HUMUS-RICH FOREST SOIL

The utilization of humus-rich forest soil, or 

mull, in geochemical exploration for gold, with 

particular emphasis on the Empire district, Clear 

Creek County, Colo., was discussed in Geological 

Survey Circular 562.

In the Empire and Breckenridge districts, 

Colorado, in which the ore minerals are auriferous pyrite with minor lead-zinc sulfides, and 

in the Cripple Creek and Gold Hills district, 

Colorado, in which gold tellurides and pyrite are 

principal ore minerals, the presence of gold in 

vegetation suggests that gold is mobilized in 

oxidizing pyritic ore deposits. On the other 

hand, in some areas of the La Plata and Chicago 

Creek districts, Colorado, in which gold is associated with lead-zinc sulfides and minor pyrite, the 

absence of gold in most vegetation samples suggests that gold is only very slightly mobile in 

oxidizing ore deposits that contain abundant 

lead-zinc sulfides and minor amounts of pyrite.

In the Mill Canyon area, Eureka County, Nev., 

gold was found in mull under cedar growing over 

an auriferous vein of pyrite and sulfosalts in 

limestone. Distilled wash water used to disperse 

a sample of this mull contained gold that must 

have been finely divided or in solution, as no 

gold was found on the millipore filters (0.45 

micron openings) through which the water was 

filtered.

On the basis of work in Colorado, it had been 

assumed that acid solutions produced from pyrite 

were necessary for gold mobilization. It was 

also assumed that in a limestone host rock no 

adequate acid solution would be available. The 

results on samples collected in Mill Canyon cast 

doubt on the original assumptions and suggest 

that gold can be mobilized in nature in ways 

other than the classical Mn02 plus HC1 process.

An area rich in gold, bismuth, and copper and 

a second area rich in silver, lead, zinc, and molybdenum were revealed in maps of the metal

12
content of mull ash collected in the Empire district. Statistical analysis of the data showed a 

high degree of mutual association within these 

two distinct groups of elements. S. M. Ball, in 

Geological Survey Professional Paper 63,1906, 

suggested long ago that two periods of mineralization may have occurred in this district. (H. 

W. Lakin, Denver, Colo.)

HEAVY METALS IN ORGANIC ENVIRONMENTS

Research on geochemical processes that may 

result in the concentration of heavy metals in 

organic environments is being done at Colorado 

School of Mines, Golden, Colo., under a research 

grant. Preliminary results of studies of effects 

of organic acids extracted from peat and humate on the solution and transportation of gold 

are as follows:

1. The amount of metallic gold dissolved by 

either organic acid at concentrations of 20 to 

80 ppm C was below the limit of detection 

«0.020ppm).

2. Gold colloids are stabilized by organic acids, 

the stability increasing with concentration of 

organic acid. Stabilization is effective in the 

presence of NaCl at concentrations near that 

of sea water; at sea-water concentration, the 

gold sol probably would be coagulated.

3. The amount of gold chloride remaining in 

solution over a period of 2 weeks (initial concentration, 13 ppm) is independent of pH in the 

range 5 to 9, but gold is reduced by organic 

acids to metallic colloidal gold. 

The solubility of mercury, mercuric sulfide, 

mercuric oxide, and mercurous chloride in the 

presence of humic acids also has been investigated. The humic acids were extracted from 

mountain soil and peat. In the presence of 

humic acid (carbon concentration 166 ppm), the 

solubility of mercury and its compounds was 

three to five times higher than in the absence of 

humic acid. The association of Hg+2 with humic 

acid was shown by the fact that in the presence 

of humic acid, Hg+2 ^as retained on Amberlite 

XAD-I resin, whereas no Hg+2 was retained in 

the absence of humic acid. This association may 

be of some consequence in the interpretation of 

mercury geochemical anomalies. (R. E. Bisque, 

Golden, Colo.)

ROLE OF SOIL MICROORGANISMS IN SOLUBILIZING 

MINERALS

The ability of soil microorganisms to solubilize 

minerals containing various trace elements is

being studied at Colorado State University, Fort 

Collins, Colo. under a research grant. The first 

year's work was directed mainly to testing the 

ability of various soil bacteria and fungi to grow 

in liquid media containing different concentrations of the metals gold, silver, mercury, copper, 

lead, manganese, cobalt, chromium, molybdenum, 

tin, cadmium, uranium, vanadium, tungsten, 

zinc, and palladium. It was found that one 

fungus could grow in a concentration of 25 ppm 

Au, and 12 species of bacteria and fungi could 

grow in cultures containing 10 ppm Au. On the 

other hand, cultures containing >5 ppm Ag or 

Hg were lethal to all organisms tested; some 

organisms could grow in saturated solutions of 

copper, manganese, molybdenum, lead, uranium, 

tungsten, and zinc. Two bacteria species previously reported to be capable of solubilizing native 

gold (up to 1.5 ppm in solution) were also tested 

for a period of 3 weeks, with negative results.

Soils and stream sediments from Cripple 

Creek, Colo., were tested to determine whether 

specific bacteria or fungi occurred in materials 

containing gold. No significant differences in 

numbers or kinds of microorganisms present 

were found between gold-bearing and barren 

samples. Work will continue on the solubilization of gold and other minerals by soil microorganisms and on the mechanisms by which gold 

is released from plant materials known to concentrate gold. (K. G. Doxtader, Fort Collins, 

Colo.)

SULFUR ISOTOPES, BINGHAM DISTRICT, UTAH

A study of sulfur isotope fractionation in ore 

deposits of the United States mine area, Bingham 

district, Utah, is being carried out under a research grant to Oregon State University, Corvallis, Oreg. The aim of the study is to determine the magnitude of sulfur isotope fractionation in mesothermal deposits of base and precious 

metals peripheral to a major porphyry copper 

deposit; to identify the possible mechanisms by 

which fractionation occurred; and to establish 

the nature and extent of sulfur isotope trends 

and zonations and their relation to host-rock 

lithology and structure, ore mineralogy and 

textures, and depositional processes. Monomineralic concentrates of pyrite, galena, sphalerite, chalcopyrite, and tetrahedrite are to be 

analyzed.

13
About 90 sulfide samples, including standards, 

have been prepared, and isotopic analyses made 

on about one-half of these. Nearly 50 pyrite 

concentrates representative of the Galena fissure and B-limestone replacement deposits have 

been submitted for Se:S and Co:Fe determinations. These analyses will be compared with 

similar analyses made on disseminated pyrite. 

Preliminary results based on 18 samples indicate 

that (1) sulfur in massive sulfide deposits is 

heavier than that from disseminated sulfides, 

and (2) the depositional sequence of sulfide minerals shows a trend from heavy sulfur to light 

sulfur. (C. W. Field, Corvallis, Oreg.)

GEOCHEMICAL SAMPLING

Results of stream-sediment sampling studies 

in three drainage basins of the northwestern San 

Juan Mountains were published in Geological 

Survey Circular 592. The areas sampled comprised one in which no gold deposits were known, 

a second which had a few known veins, prospects, 

and small mines, and a third containing numerous veins and several productive mines. Gold 

analyses on a few panned heavy-mineral concentrates from each drainage sufficed to distinguish between barren and mineralized areas 

and also provided a measure of the relative 

amounts of gold in mineralized areas. (R. P. 

Fischer and F. S. Fisher, Denver, Colo.)

SAMPLE PREPARATION

A sample of gold- and silver-bearing quartzsulfide ore from the dump of the Bartow mine 

in the San Juan Mountains, southwestern Colorado, was prepared for analysis using two different sequences of crushing, fine grinding, and 

splitting and two different methods of splitting. 

Fire assays of eight 15-g portions from each of 

the four groups of samples showed that for both 

gold and silver: (1) distinctly better reproducibility is given by samples that are ground to 100 

mesh after coarse crushing (one-eighth to onequarter in.) and prior to splitting (standard 

deviation for gold 0.36 to 0.57) than by samples 

that are split before grinding to 100 mesh (standard deviation for gold, 1.08 to 1.17), and (2) 

splitting of samples using the Jones sample 

splitter gives almost the same results as splitting 

by the cone-and-quartering method but is at 

least twice as fast. The sample contained about 

5 ppm Au and 275 ppm Ag. (F. S. Fisher, 

Denver, Colo.)

The gold content of 205 raw (unconcentrated) 

samples of Harebell Formation and Pinyon Conglomerate from Jackson Hole, Wyo., has been 

compared with that of panned concentrates of 

the same samples. The raw samples weighed 

10 to 15 g. Histograms of the distribution of 

analytical results suggest that the mean gold 

content of raw samples is 10 to 20 times that of 

the panned concentrates. Inasmuch as the 

panned concentrates represent a much larger 

sample than the raw samples, their analyses 

should give a more reliable estimate of gold content. Analyses of small unconcentrated samples 

therefore appear to give spurious results and a 

probably exaggerated estimate of gold abundance. (J. C. Antweiler and D. A. Lindsey, 

Denver, Colo.)

STATISTICAL TREATMENT OF GEOCHEMICAL DATA

A STATPAC tape was prepared containing all 

of the geochemical data collected from the Ely, 

Nev., district. Preliminary statistical summaries 

showed that ratios of the metals to silica had a 

much wider range than the metal analyses alone. 

The use of these ratios is based on the assumption that the metals traveled in a silica solution 

and that therefore the metal content of samples 

should be computed relative to the silica content, 

not to the weight of the sample.

All geochemical data from the Coeur d'Alene, 

Idaho, project have been entered into the Rock 

Analysis Storage System (RASS). Preliminary 

statistical summaries and tabulations have been 

obtained, and computer gridding routines for 

geochemical data and computer plots of geochemical values are being developed.

A program designed to convert the now outdated geochemical census punched cards to 

STATPAC was written, compiled, and executed 

on stream-sediment geochemical data from central Maine. This program can be used to convert similar data from other projects.

Samples for chemical analysis have been collected in the Midas, Nev., district. Preliminary 

results indicate that the district does not have 

disseminated gold deposits of economic value 

near the surface. However, the presence of a 

disseminated deposit at depth, or the continuation 

of near-surface gold-silver veins at depth, are not 

precluded.

A remote data teleprocessing system is being 

developed that will provide immediate entry of 

field geochemical data into RASS, and another

14
system is being prepared to process data created 

by the eventual automated mobile and stationary 

analytical equipment. (R. L. Erickson and J. 

M. Botbol, Denver, Colo.)

DATA STORAGE AND RETRIEVAL

Computer programs have now been completed 

for storage of Heavy Metals-Wilderness analytical data on magnetic tape, for correction or replacement of previously stored data, and for 

search and retrieval of selected data. A special 

computer program, GEOSUM, has been developed to provide uniform reporting and summaries of geochemical data. The program will 

produce a readable listing of data, frequency 

distributions for each element, and estimates of 

geometric mean and geometric deviation.

Revision of the Request for Analysis form now 

makes it possible to keypunch descriptive data 

directly from the form, thus eliminating preliminary transfer of data to a key punch form 

and facilitating the entering of data into RASS.

Analytical data from the following projects 

are now or will shortly be routinely entered into 

RASS:

Geochemical halos in Utah and Nevada

Mineral exploration

Geochemical of mercury

Aurora and Bodie districts, Nevada and California

Northwest San Juan Mountains, Colo.

Southern Appalachians

The data retrieval program was completed in 

December, and nine data retrievals were made 

during that month. (R. V. Mendes, Denver, 

Colo.)

RESEARCH IN GEOPHYSICS

USE OF VERY LOW FREQUENCY WAVES IN 

GEOPHYSICAL EXPLORATION

An investigation into the use of very low frequency radio waves for geophysical prospecting 

is being done at the University of Colorado, 

Boulder, Colo., under a research grant. A number of high-power radio stations transmitting at 

very low frequencies (3 to 30 kilo-Hertz) have 

been placed in service during recent years by 

the U.S. Government. These low-frequency 

waves are used for time and frequency information, for navigation systems, and for long-distance communication. Inasmuch as these waves 

propagate in the upper part of the earth, to

depths as great as several hundred feet depending on the earth's conductivity, measurement of 

local variations in the waves at the surface is a 

means of detecting conductive ore bodies or 

other geologic features that might cause variations in electrical conductivity.

A modeling study is being made to develop 

and improve techniques of interpretation, using 

a wooden tank 12 x 12 X 2 feet filled with brine 

to simulate an electrically homogeneous earth 

and wire grids above and below the tank to 

produce "pseudo" plane waves. Electrical inhomogeneities are to be placed in the tank and 

their effects on these "pseudo" plane waves will 

be measured. (W. L. Flock and F. C. Frischknecht, Boulder, Colo.)

DETECTION OF INDUCED POLARIZATION EFFECT USING 

NATURAL TELLURIC FIELDS

A feasibility study of the possibility of detecting induced polarization and resistivity effects of frequency-dependent conductors using 

the earth's natural magnetotelluric fields as 

primary fields is being carried out at the University of California at Berkeley under a research grant. A modeling study has been done 

using the Berkeley computer, and measurements 

of magnetotelluric currents made in the field 

will be reduced by computer. The study will be 

completed in 1969. (H. P. Morrison, Berkeley, 

Calif.)

NEUTRON ACTIVATION AS AN EXPLORATION TOOL

The Geological Survey has for some years been 

experimenting with neutron activation as an exploration tool the "silver snooper" of several 

years ago was a truck-mounted neutron generator used to activate small areas of ground and 

measure the gamma-ray activity induced in any 

silver present near the ground surface. Similar 

equipment is now being tested as a gold detector. 

In 1968, a 100- jug californium-252 neutron source 

was tested at Savannah River, S. C., in collaboration with the U.S. Atomic Energy Commission. Tests were carried out successfully in a 

water well and also on gold and silver ores buried 

at shallow depth. The potential importance of 

californium-252 is due to its small physical size 

and its spontaneous emission of a large number 

of neutrons each gram emits about 2xl012 

neutrons/second, close to the neutron flux of a 

power reactor. A borehole 40 feet deep has been 

drilled in the laboratory floor in Building 104, at

15
the old Bureau of Standards campus, for testing 

of borehole techniques for neutron activation of 

ores using the califorium-252 neutron source.

Gold is one of the more difficult elements to 

work with, primarily because the activation 

product, gold-198, has a long half-life of 2.6 days. 

To help solve this particular problem a research 

grant was awarded to the University of Maryland for a feasibility study on the use of prompt 

gamma rays for detection of gold .These prompt 

gamma rays are emitted instantly when a neutron is absorbed in an atomic nucleus. Some 

work has been done on pure elements, but little 

is known about possible interferences or other 

limitations of the method. Certainly, the prompt 

gamma spectra are known to be complex; but 

prompt gammas also have higher energies, 

hence deeper penetration and ability to "see" 

larger samples. Hopefully, this study will point 

the way to another possible neutron activation 

technique. (F. E. Senftle, Washington, D.C.)

DIRECT-READING FIELD DETECTOR FOR SELECTED 

ELEMENTS

Development of a direct-reading field instrument to convert the multiple energy output of 

natural radioactivity, neutron activation, or Xray fluorescence systems to a single output 

characteristic of various preselected elements is 

being undertaken under contract by Tracerlab, 

a Division of Laboratory for Electronics, Waltham, Mass. Such an instrument would make it 

possible to analyze a spectrum of multiple 

energies in the field without the need for a 

costly multichannel analyzer and the difficult 

interpretation of its complex output.

Research was divided into five phases: (1) 

mathematical evaluation of applicability of the 

method, (2) design and construction of a 16- 

channel breadboard model, (3) construction of a 

prototype field model, (4) field testing of prototype, and (5) a final report summarizing results 

of the project. Phases one to three have been 

completed and phases four and five were in 

progress at the end of 1968. (F. E. Senftle and 

A. B. Tanner, Washington, D.C.)

RESEARCH ON ANALYTICAL METHODS

DETERMINATION OP THE PLATINUM METALS

A major achievement of analytical research in 

1968 was the development of two methods for 

the rapid accurate measurement of trace amounts 

of platinum, palladium, and rhodium in rocks;

these methods employ atomic absorption and fire 

assay-spectrographic techniques, respectively.

DETERMINATION OF PLATINUM AND PALLADIUM BY 

ATOMIC ABSORPTION

The determination of platinum and palladium 

by atomic absorption is strongly affected by the 

depressive effect of other platinum metals, silver, 

and gold. Studies of this interference have shown 

that CuS04 , LaCl 3 , La2 (S04 )3 , ZnS04 , Pb(N03 )2 , 

and CdS04 in the aspirated solution all overcome 

the depressive effect to some extent. It has 

been found that when CuS04 alone is used, both 

copper and sulfate are necessary, as either by itself depresses the absorbance of platinum. This 

unique action of CuS04 is without precedent in 

atomic absorption spectrophotometry and the 

mechanism is so far unknown. The best results 

are obtained using a combination of CuS04 and 

CdS04 , each at a concentration of 12,500 ppm, 

about one-half the concentration needed if CuS04 

is used alone; as much as 200 ppm each of Rh, 

Ru, Os, Pd, and Ir, and 20 ppm Au can be tolerated in the determination of platinum, and 200 ppm 

each of Rh, Ru, Os, Pt, and Ir and at least 500 

ppm Au in the determination of palladium.

Development of a rapid and a routine method 

has been completed. Platinum and palladium are 

concentrated into a gold bead by fire assay, the 

bead is dissolved in aqua regia, and a buffer mixture of cadmium and copper sulfates is added, 

after which the solution is analyzed by atomic 

absorption. Addition of cadmium and copper sulfates eliminates interelement interference and 

permits determination of platinum and palladium 

in the presence of substantial amounts of silver, 

aluminum, gold, bismuth, cobalt, chromium, iron, 

mercury, iridium, potassium, lanthanum, magnesium, molybdenum, sodium, nickel, osmium, 

lead, rhodium, ruthenium, tellurium, titanium, 

vanadium, yttrium, and zinc. The lower limit of 

detection is about 0.1 ppm on a 20-g sample. 

(F. S. Grimaldi and M. M. Schnepfe, Washington, 

D.C.)

DETERMINATION OF RHODIUM BY ATOMIC ABSORPTION

The determination of rhodium by atomic absorption is made difficult by the positive interference of gold and the negative interference of 

other noble metals. It has now been discovered 

that when rhodium is determined in the presence 

of lanthanum sulfate, not only is interference 

from other noble metals eliminated but the sensitivity of rhodium measurement is increased. 

Some 30 other elements in addition to the noble

16
metals have now been tested and none interferes. 

It thus appears possible to determine rhodium 

fairly directly by atomic absorption, and the 

method is being tested on ores. The limit of detection by this method is 7 ppb, and for an error 

not greater than ±15 percent is 10 ppb on a 20-g 

sample in a final solution volume of 5 ml. (F. S. 

Grimaldi and M. M. Schnepfe, Washington, B.C.)

CHEMICAL DETERMINATION OF RHODIUM IN ROCKS

A method for determining rhodium in the 

presence of indium has been developed for analysis of portions of samples remaining after separation of rock-forming elements and platinum 

and palladium. Rhodium and iridium are converted to complex chlorides in order to prevent 

interference by iridium, and rhodium is determined colorimetrically in HC104 -HBr medium to 

which SnBr2 is added. The sensitivity is about 

10 ppb Rh in a 10-g sample. (F. S. Grimaldi and 

M. M. Schnepfe, Washington, B.C.)

DETERMINATION OF PLATINUM, PALLADIUM, AND

RHODIUM BY FIRE ASSAY AND EMISSION

SPECTROGRAPHY

A relatively simple, sensitive, and precise 

method for simultaneous determination of platinum, palladium, and rhodium in rocks has been 

developed. Samples weighing 15 to 30 g are preconcentrated into a gold bead by standard fireassay techniques and the bead is dissolved in aqua 

regia. After dilution to volume with IM HC1, 

100 microliters of solution is evaporated onto each 

of two flat-top graphite electrodes and the residue analyzed by emission spectrography. Limits 

of determination are 10 ppb Pt, 4 ppb Pd, and 5 

ppb Rh for a 15-g sample. (Joseph Haffty and 

L. B. Riley, Benver, Colo.)

DETERMINATION OF OSMIUM AND RUTHENIUM

Research continues on the determination of 

osmium based on catalysis of the reduction of 

Ce +4 by As+3 . Although some problems remain 

to be solved, it is now possible to determine as 

little as 0.0003 ng Os in 5 ml pure solution (or 

0.06 ppb) at the 99.7 confidence level. A plot of 

reaction rate versus concentration of osmium is 

straight in the interval 0 to 0.01 ng Os in a 5 ml 

solution (0 to 2 ppb); the determination in the 

range 0.06 to 2 ppb is more than a magnitude 

more sensitive than previously reported.

Trace amounts of osmium and ruthenium can 

now be recovered by extraction of Os04 and Ru04 

with CCU following leaching of the sample and 

oxidation of osmium and ruthenium by silver

peroxide. These elements are stripped into NaOH 

and osmium is separated from ruthenium by oxidation to Os04 using nitric acid (ruthenium is not 

oxidized to Ru04 by HN03), followed by extracting into CC14 . Use of tracers indicates that 

80 percent of the ruthenium and 60 percent of the 

osmium are recovered. Previous low recoveries 

of both osmium and ruthenium were found to be 

caused by adsorption on polyethylene and polypropylene containers. The successful isolation of 

these metals is a major step toward developing a 

reliable activation method for their analysis. (J. J. 

Rowe and J. I. Binnin, Washington, B.C.)

ANALYSIS OF PLATINUM METALS IN CHROMITE

Research continues on the mode of occurrence 

of the platinum metals in chromite and on the 

problem of developing a suitable flux for fireassay determinations of these metals in chromite. 

None of the common fluxes tested to date effects 

complete decomposition of chromite.

The following results have been obtained:

1. Rhodium is present in chromite entirely in 

solid solution. A possible but unlikely alternative explanation of experimental results is that rhodium occurs as uniformly 

distributed very minute inclusions.

2. Palladium occurs as a separate mineral phase 

entirely outside the chromite.

3. Platinum is present partly (about 28 percent) 

as separate phase outside the chromite and 

partly (about 72 percent) in solid solution 

or as inclusions in the chromite; further 

work is planned to more closely determine 

the mode of occurrence of this metal. (F. S. 

Grimaldi and M. M. Schnepfe, Washington, 

B.C.)

GOLD ANALYSIS 

Gold Content of Quartz Standard

Many determinations of gold on the gold quartz 

standard in the Washington, B.C., laboratories 

by various methods (neutron activation, isotope 

dilution, and several chemical procedures followed 

by atomic absorption) have resulted in a figure 

of 2.60 ppm, somewhat higher than the figures 

of 2.0 ppm (fire assay-atomic absorption) and 

2.2 ppm (cyanide leach-fluorimetric) previously 

reported. (H. T. Millard and F. 0. Simon)

Gold content of the standard was determined 

in the Benver, Colo., laboratories by fire assayatomic absorption as 2.65 ppm, and by cyanide 

leach-atomic absorption as 2.64 ppm. These 

results agree closely with the 2.60 ppm deter17
mined in Washington, B.C. (L. B. Riley, Denver, 

Colo.)

Intel-laboratory Comparison of Gold Analyses

Duplicate splits of eight samples of gold ore 

from Cripple Creek, Colo., have been analyzed by 

atomic absorption in the Denver, Colo., laboratory 

of the Geological Survey and by fire assay by the 

U.S. Bureau of Mines and two reputable commercial laboratories. For ore containing gold in 

the range of approximately 1 to 5 ppm, the results 

among the four laboratories are in general closely 

.similar; for ore containing <1 ppm, results varied 

by factors of as much as eight or more.

NEUTRON ACTIVATION METHODS OF ANALYSIS 

Activation Analysis for Background Amounts of Gold

A simplified procedure for activation analysis 

uses a strongly basic anion exchange disk to recover previously irradiated gold from solution. 

The gold retained on the disk is relatively free 

from radioactive contaminants, allowing the activity of gold-198 to be determined by gammaspectrometry. Analyses made by this method on 

eight Geological Survey standard rocks agree 

closely with those obtained by more lengthy and 

complex methods. (H. T. Millard and J. E. 

McLane, Washington, D.C.)

A simple and practical method for routine 

determination of background amounts of gold was 

reported in Geological Survey Circular 599. The 

method involves irradiation of a 1-g sample in the 

Naval Research Laboratory reactor for 10 to 16 

hours, cooling for 10 days to permit radioactivity 

to decrease sufficiently for safe handling, fire 

assay using gold metal as a carrier, and gamma 

counting of the gold bead. The limit of detection 

is 0.05 ppb. Although an analysis requires about 

3 weeks total elapsed time, less than 8 hours of an 

analyst's time is needed to process 40 samples. At 

present, analytical capacity, limited only by availability of reactor time, is 250 samples per month. 

(J. J. Rowe and F. 0. Simon, Washington, D.C.)

Activation Analysis of Uranium

Analysis of uranium by neutron activation 

using a californium-252 source and both a solidstate detector and a scintillation counter is being 

studied. Uranium-239, formed when a uranium 

atom absorbs a neutron, decays by beta emission 

and an 0.074 MeV gamma. A technique to minimize interference by X-rays from lead and bismuth is being investigated. (F. E. Senftle, 

Washington, D.C.)

CHEMICAL ANALYSIS WITH LASER-FIRED MICROPROBE

Chemical analysis by the laser-fired microprobe 

has proved useful for nondestructive in-situ determinations of silver, gold, bismuth, copper, lead, 

nickel, and vanadium in rocks and minerals as 

well as organic-rich materials such as vegetation, 

trees, tar sands, and petroleum. The instrument 

is especially useful for identifying such things as 

small inclusions and contaminants in sample 

storage containers.

The laser microprobe appears to be potentially 

useful in detecting trace amounts of metals such 

as copper and silver in vegetation by direct sampling without any preconcentration (such as 

ashing). Copper has recently been shown to 

cause the green stain of a tree trunk, and anomalous concentrations of silver have been identified 

around the new growth of aspen twigs. (F. N. 

Ward, Denver, Colo.)

ANALYSES OF TELLURIUM IN VEGETATION

An analytical method for determining tellurium 

in plant samples with a sensitivity of 0.06 ppm in 

the dry plant or humus has been devised. Using 

this method, humus samples from the Gold Hill 

district, Boulder County, Colo., were found to contain from 0.12 to 12.5 ppm Te in mineralized areas. 

The tellurium-gold ratio in these samples varies 

from 4 to 24 with a mean of 12.5. Thus tellurium 

in humus may be useful for delineating gold deposits in telluride districts. (H. W. Lakin, Denver, 

Colo.)

SENSITIVE METHOD FOR DETECTION OF MERCURY

A new and highly sensitive field test for mercury uses the change in potential of a specific 

iodide electrode caused by formation of a tightly 

bound mercury-iodide complex in alkaline solution. Concentrations of mercury as low as 0.1 ppb 

are easily measured. (F. N. Ward and M. Hinkle, 

Denver, Colo.)

COUNTER-CURRENT ELUTRIATOR AS GOLD 

CONCENTRATOR

A counter-current elutriator has been calibrated 

in terms of total discharge and distribution of velocities within the elutriator as compared to the 

fall velocities of different sized particles of gold, 

and the results indicate that the elutriator is probably a highly effective tool for rapid determination of the gold content of unconsolidated sediments or disaggregated sedimentary rocks. Since 

only water is used, the method is cheaper, faster, 

and more convenient than other methods of separ18
ation such as heavy liquids. If material coarser 

than 2 mm is removed from a sample, and the remainder divided into fractions of four sizes, that 

is, coarser than 0.5 mm, coarser than 0.15 mm, 

coarser than 0.061 mm, and finer than 0.061 mm, 

the gold in each fraction can be removed in a matter of minutes; if the elutriator is of an appropriate size for the mass of the fractions, the time 

depends chiefly on the handling of materials 

rather than the settling of the gold. Only gold 

coarser than 0.024 mm will be removed from the 

finest fractions. These size boundaries are suggested because the fall velocity of gold is about 

30 percent higher than quartz in the two coarse 

fractions and 50 percent higher in the two fine 

fractions. The greater difference in fall velocity 

for the fine fractions is desirable because gold in 

these sizes tends to be flaky. The size of elutriator that would be effective has no evident theoretical limit, and the process might even be 

adaptable to some commercial operations. Further experimental work is underway to explore

these indications. 

Colo.)

(H. A. Tourtelot, Denver,

REFERENCES CITED

Crickmay, G. W., 1936, Status of the Talladega 

series in southern Appalachian stratigraphy: 

Geol. Soc. America Bull., v. 47, no. 9, p. 1371- 

1392.

___1952, Geology of the crystalline rocks of 

Georgia: Georgia Geol. Survey Bull. 58, 54 p.

Hamblin, W. K., 1958, The Cambrian sandstones 

of northern Michigan: Michigan Geol. Survey 

Pub. 51, 146 p.

Turekian, Karl K., and Wedepohl, Karl Hans, 1961, 

Distribution of the elements in some major 

units of the earth's crust: Geol. Soc. America 

Bull., v. 72, no. 2, p. 175-191.

Winchell, N. H., 1899, The geology of the Pigeon 

Point, Vermillion Lake, Carlton, and Duluth 

plates: Minnesota Geol. Survey, Final rept. 4, 

p. 502-580.

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