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Bulletin No. 213 

Series A, Economic Geology, 24 






19 2 


Greologists in. Charge 



1 9 3 

e N T E NTS. 


Letter of transmittal 7 

Introduction, by C. W. Hayes 9 

Investigation of metalliferous ores, by S. F. Emmons 15 

Investigation of nonmetalliferous economic minerals, "by C. W. Hayes 29 

Gold and silver 31 

Progress report on Park City mining district, Utah, by J. M. Boutwell 31 

Placer gold mining in Alaska in 1902, by Alfred H. Brooks . , 41 

The Glenn Creek gold-mining district, Alaska, by Arthur J. Collier 49 
Gold and pyrite deposits of the Dahlonega district, Georgia, by Edwin 

C.Eckek _._ 57 

Neocene rivers of the Sierra Nevada, by Waldemar Lindgren (54 

Mineral deposits of the Bitterroot Range and the Clearwater Moun- 
tains, Montana, by Waldemar Lindgren 66 

The Chistochina gold field, Alaska, by Walter C. Mendenhall . 71 

Gold mining in central Washington, by George Otis Smith . . 76 
Ore deposits of Tonopah and neighboring districts, Nevada, by J. E. 

Spurr 81 

Gold mines of the Marysville district, Montana, by Walter Harvey 

Weed 88 

List of Survey publications on gold and silver 90 

Quicksilver, platinum, tin, tungsten, chromium, and nickel 92 

Stream tin in Alaska, by Alfred H. Brooks 92 

Platinum in copper ores in Wyoming, by S. F. Emm< >ns 94 

Tungsten mining at Trumbull, Conn., by W. H. Hobbs. 98 

Tin deposits at El Paso, Tex. , by Walter Harvey Weed . 99 

Tungsten ore in eastern Nevada, by F. B. Weeks 103 

List of Survey publications on quicksilver, platinum, tin, tungsten, 

chromium, and nickel . - 104 

Copper 1 05 

Ore deposits of Bingham , Utah, by J M. Boutwell 1 05 

Copper deposits of the Redding district, California, by J. S. Diller. 123 

Copper deposits at Clifton, Ariz. , by Waldemar Lindgren 1 33 

Copper deposits of the Mount Wrangell region, Alaska, by Walter C. 

Mendenhall and Frank C. Schrader 141 

Copper deposits of Bisbee, Ariz. , by F. L. Ransome 149 

Mineral resources of the Encampment copper region, Wyoming, by 

Arthur C. Spencer 158 

Reconnaissance examination of the copper deposits at Pearl, Colo., by 

Arthur C. Spencer 163 

Ore deposits at Butte, Mont. , by Walter Harvey Weed 170 

Copper deposits of the Appalachian States, by Walter Harvey Weed... 181 

List of publications on copper _ 186 



Lead and zinc •. - 1 87 

Zinc and lead deposits of northern Arkansas, by George I. Adams 187 

Lead and zinc deposits of the Joplin district, Missouri-Kansas, by W. S. 

Tangier Smith 1 97 

Lead, zinc, and fluorspar deposits of western Kentucky, by E. O. Ulrich 

and W. S. Tangier Smith 205 

Zinc and manganese deposits of Franklin Furnace, N. J. , by J. E. Wolff _ 214 

List of Survey publications on lead and zinc 218 

Iron and manganese 219 

Iron ores of the Redding quadrangle, California, by J. S. Diller 219 

Utilization of iron and steel slags, by Edwin C. Eckel 221 

Manganese ores of the Cartersville district, Georgia, by C. W. Hayes. 232 
Iron ores of the Cartersville district, Georgia, by C. W. Hayes and 

Edwin C. Eckel 233 

Iron-ore deposits of the Cranberry district. North Carolina-Tennessee, 

by Arthur Keith 243 

Geologic work in the Lake Superior iron district during 1902, by C. K. 

Leith 247 

Manganese deposits of Santiago, Cuba, by Arthur C. Spencer 251 

List of publications on iron and manganese 256 

Coal 257 

Coal fields of the United States, by C. W. Hayes 257 

Recent work in the bituminous coal field of Pennsylvania, by M. R. 

Campbell 270 

Coal resources of the Yukon Basin, Alaska, by Arthur J. Collier 276 

Recent work in the coal field of Indiana and Illinois, by Myron L. 

Fuller and George H. Ashley 284 

List of Survey publications on coal, lignite, and peat 294 

Oil, gas, and asphalt 296 

Origin and distribution of asphalt and bituminous rock deposits in the 

United States, by George H. Eldridge 296 

The petroleum fields of California by George H. Eldridge 306 

The Boulder, Colo. , oil field, by N. M. Fenneman 322 

Asphalt, oil, and gas in southwestern Indiana, by Myron L. Fuller 333 

Structural work during 1901 and 1902 in the eastern Ohio oil fields, by 

W. T. Griswold 336 

Oil fields of the Texas-Louisiana Gulf Coastal Plain, by C. W. Hayes, . 345 

Asphalt deposits of Pike County, Ark. , by C. W. Hayes 353 

List of publications on oil, gas, and asphalt 356 

Stone 357 

The stone industry in the vicinity of Chicago, 111. , by William C. Alden_ 357 
The slate industry at Slatington, Pa., and Martinsburg, W. Va., by 

T. Nelson Dale 361 

Limestone of the Redding district, California, by J. S. Diller 365 

Tennessee marbles, by Arthur Keith 366 

List of Survey publications on stone 371 

Cements _ 372 

Cement investigations in Arizona, by Edward Duryee 372 

List of xuiblications on cements 381 

Clays and fuller's earth 382 

Stoneware and brick clays of western Tennessee and northwestern 

Mississippi, by Edwin C. Eckel 382 

Fuller 's-earth deposits of Florida and Georgia, by T. Wayland Vaughan 
List of Survey publications on clays, fuller's earth, etc 




Gypsum, salt, borax, and soda 401 

Borax deposits of eastern California, by M. R. Campbell - 401 

Salt and gypsum deposits of southwestern Virginia, by Edwin C. 

Eckel _ . . 406 

List of Survey publications on gypsum, salt, borax, and soda 417 

Pli< >sphates and other mineral fertilizers 418 

Origin and extent of the Tennessee white phosphates, by C. W. Hayes- 418 

The white phosphates of Decatur County, Tenn., by Edwin C. Eckel _ . 424 

List of publications on phosphates and other mineral fertilizers 426 

Mineral paints 427 

Occurrence and development of ocher deposits in the Cartersville dis- 
trict, Georgia, by C. W. Hayes and Edwin C. Eckel. . 427 

Talc 433 

Talc deposits of North Carolina, by Arthur Keith 433 

Miscellaneous nonmetalliferous mineral products 439 

Index 441 

Digitized by the Internet Archive 
in 2013 


Department of the Interior, 
United States Geological Survey, 

Washington, D. C, March 9, 1903. 
Sir: I have the honor to transmit, for publication as a bulletin of 
the Survey, a manuscript entitled Contributions to Economic Geology, 

The report contains 61 contributions from X'} members of the Survey 
who have been engaged more or less continuously throughout the year 
in economic work, together with a brief statement bj~ the geologists in 
charge of the sect ion of metalliferous ores and the section of non- 
metalliferous economic minerals, of the extent and character of the 
economic work being carried on in the Survey. 
Very respectfully, 

C. W. Hayes, 
Geologist in Charge of Geology. 
Hon. Charles I). Walcott, 

Director United States Geological Surrey. 


S. F. Emmons, 

C. W. Hayes, 

Geologists in Charge. 


By C. W. Hayes, Geologist in Charge of Geology. 

This bulletin has been prepared primarily with a view to securing 
prompt publication of the economic results of investigations by the 
United States Geological Survey. It is designed to meet the wants of 
the busy man, and is so condensed that he will be able to obtain 
results and conclusions with a minimum expenditure of time and 
energy. It also affords a better idea of the work which the Survey as 
an organization is carrying on for the direct advancement of mining 
interests throughout the country than can readily be obtained from 
the more voluminous reports. Should this bulletin be favorably 
received by those interested in the development of the mineral indus- 
tries of the United States, it is proposed to publish early in each cal- 
endar year a similar bulletin containing the results of the last year's 
field work in economic geology. 

In the preparation of the present volume, promptness of publica- 
tion has been made secondary only to the economic utility of the 
material presented. The papers included are such only as have a 
direct economic bearing, all questions of purely scientific interest 
being excluded. 

The papers represent three classes: (1) Preliminary discussions of 
the results of extended economic investigations, which will later be 
published by the Survey in more detailed form; (2) comparatively 
detailed descriptions of occurrences of economic interest, noted by 
geologists of the Survey in the course of their field work, but not of 
sufficient importance to necessitate a later and more extended descrip- 
tion; (3) abstracts of certain economic papers which have appeared 
in Survey publications during the last year, chiefly such as give a 
general account of the distribution and mode of occurrence of 
particular mineral deposits throughout the United States. 

The papers have been grouped according to the subjects treated. 
At the end of each section is given a list of previous publications on 
that subject by this Survey. These lists will be found serviceable by 
those who wisli to ascertain what has been accomplished by the Sur- 



vey in the investigation of any particular group of mineral products. 
They are generally confined to Survey publications, though a few 
titles of important papers published elsewhere by members of the 
Survey are included. 

The results of the Survey work in economic geology have been 
published in a number of different forms, which are here briefly 
described : 

1. Papers and reports accompanying the Annual Report of the 
Director, United States Geological Survey. — Prior to the present year 
many economic reports were published in the ro}^al octavo cloth-bound 
volumes which accompanied the Annual Report of the Director. 
This form of publication for scientific papers has been discontinued 
and a new series, termed Professional Papers, substituted. 

2. Bulletins of the United Slides Geological Survey. — The bulletins 
of the Snrve} T comprise a series of paper-covered octavo volumes, 
each in general containing a single report or paper. These bulletins, 
formerly sold at nominal prices, are now distributed free of charge t 
those interested in the special subject discussed in an}^ particula 
bulletin. This form of publication facilitates promptness of issue for 
economic results, and most economic reports are therefore published 
as bulletins. Their small size, however, precludes the use of large 
maps or plates, and reports containing large illustrations are there- 
fore issued in the series of Professional Papers. 

3. Professional Papers of tin United States Geological Survey.— 
This series, paper covered, but quarto in size, is intended to include 
sueh papers as contain mapsor other illustrations requiring the use of 
a large page. The publication of the series was commenced in 1002, 
and the papers are distributed in the same manner as bulletins. 

4. Monographs ofthi United States Geological Survey. — This series 
consists of cloth-bound quarto volumes, and is designed to include 
exhaustive treat iseson economic or other geologic subjects. Volumes 
of this series are sold at cost of publication. 

5. Geologic folios of the United Stoics Geological Survey. — Under 
the plan adopted for the preparation of a geologic map of the United 
States the entire area is divided into small quadrangles, bounded by 
certain meridians and parallels, and these quadrangles, which num- 
ber several thousand, are separately surveyed and mapped. The | 
unit of survey is also the unit of publication, and the maps and 
descriptions of each quadrangle are issued in the form of a folio. 
When all the folios are completed thej T will constitute a C4eologic 
Atlas of the United States. 

A folio is designated by the name of the principal town or of a 
prominent natural feature within the quadrangle. It contains topo- 
graphic, geologic, economic, and structural maps of the quadrangle, and 
occasionally other illustrations, together with a general description. 

Under the law, copies of each folio are sent to certain public libra- 
ries and educational institutions. The remainder are sold at 25 cents 




each, except such as contain an unusual amount of matter, which are 
priced accordingly. 

Circulars containing lists of these folios, showing the locations of 
the quadrangular areas they describe, their prices, etc., are issued 
from time to time, and may be obtained on application to the 
Director of the United States Geological Survey. The tables on the 
following pages show the folios issued to date, with the economic 
products discussed in the text of each, the products of greatest 
importance being printed in italics. 

List of geologic folios showing mineral resources described. 


Name of folio. 



sq. in. 


Mineral products described 
as occurring in area of 


Mont ... 



Gold, copper, clays, lime, 
stone, coal. 

. 2 





Coal, iron, manganese, 
lime, clays, stone, road 


Placer ville 



Lindgren, W.; Tur- 
ner, H.W. 

(! iild, copper, quicksilver, 
chromite, stone. 






Coal, iron, lime, stone, 
road metal, clay. 





Lindgren, W 

Gold, copper, chromite, 
iron, coal, stone, lime, 





Hayes, C. W 

Coal, iron, lime, stone, 
road metal, clay. 

Pikes Peak-Crip- 
ple Creek. 



Cross, W 







Cool, iron, lime, stone, 
road metal, clay. 


Crested Butte. 




Coal, silver, stone, lime, 


Harpers Ferry 

Va.-W. Va.- 



Iron, ocher, copper, stone, 
road metal. lime, cement. 





Turner, H.W 

Gold, copper, chromite, 
iron, manganese, ocher, 
coal, stone, lime, clay. 





Campbell, M.E .... 



Preder icksbu r g 




Qreensand m.arZ,stone, ful- 
ler's earth, clays, sand, 
gravel, underground 



Va.-W. Va.:_ 



Iron, marble, lime, clay, 


Lassen Peak 



Diller,J.S .. 

Gold , in f usor ial earth, 
lime, stone, coal. 




Keith, A 

Marble, slate, stone, gold, 
lime, cement, (day, water 





Lindgren, W.; Tur- 
ner, H. W. 

Gold, coal, gas, clay, lime, 
stone, water supply. 






Gold, copper, quicksilver, 
iron, lime, clay, stone. 


Stevenson ... 



Hayes, C. W 

Coal, iron, lime, stone, 
road metal, clay. 


Cleveland . . 

Tenn _ . 













Coal, iron, stone, clay. 






earth, clay, stone, sand, 
gravel, un dergro u nd 


List of geologic folios showing mineral resources described — Continued. 


Narne of folio. 





Mineral products described 
as occurring in area of 


Three Forks 


3. S54 


Gold, silver, copper, iron, 
coal, lime, clay, pumice, 
mineral springs. 





Coal, marble, lime, stone, 
clay, iron, slate, water 





Campbell, M.R 

Coal, lime, stone, clay, 


Morristown .. 



Keith, A .. 

Marble, stone, lead, zinc, 
lime, cement, clay, water 





Darton,N. H.; Taff, 
J. A. 

Coal, iron, lime, stone, 
road metal, clay. 


Nevada City spe- 



Lindgren, W. 



Yellowstone Na- 
tional Park. 



Hague, A.; Weed, 
W. H.; Iddings, 
J. P. 

National Park; no mining 


Pyramid Peak 


( !al 


Lindgren, W._ 



Va.-W. V:i 



Iron, coal, manganese, 
lime, stone, road metal, 






Coal, iron, lead, marble, 
lime, stone, clay. 





Taff, J. A.; Brooks, 

Coal, lime, stone, clay. 





Hayes, C.W 

Coal, iron, lime, stone. 





Gilbert, G.K... 

Stone, gypsum, clay, iron, 
artesian water. 






Gold, iron, ehromite, lime, 


Butte special 



Emmons. S. F . ; 
Tower, G. W. 

( topper, silver, gold. 





Lindgren, W. 

Gold, silver, coal, stone, 
mineral springs. 


Wartl mrg 

Tenn . . . 



Coal, oil, iron, lime, clay. 




94 1 

Turner, H. W.; Ran- 
some,F. L. 

Gold, quicksilver, copper, 
ehromite, lime, stone. 



1. 035 


Stone, gravel, under- 
ground water. 






Gold, manganese, iron, 
ehromite, stone. 



Va.-W. Va . 

051 ) 

Campbell, M.R 

Coal, iron, barite. 




Lindgren. W 

Gold, silver, coal, diato- 
maceous earth, stone, 
clay, springs, artesian 




Campbell, M.R 

Coal, fluorite, phosphate, 
clay, stone, road metal. 


London __ 




Coal, stone. 


Tenmile district 


Emmons, S. F 





Diller, J S . 

Gold, copper, quicksilver, 
coal, clay, stone. 


Holy oke 

Mass.- Conn .. 


Emerson, B. K 

Granite, emery, ehromite, 
quartz, trap, sandstone, 


Big Trees 



Turner, H. W.; Ran- 
some, F. L. 

Gold, silver. 



Wyo ... 


Hague, A 






Campbell, M.R 

Coal, oil, lime, clay. 





Willis, B.; Smith, 

Coal, stone, clay. 


Fort Benton 

Mont . 


Weed, W. H . 

Gold, silver, lead, iron. 

gypsum, coal, stone, 
artesian water. 

hayes. 1 INTRODUCTION. 13 

List of geologic folios showing mineral resources described — Continued. 


Name of foli >. 



sq. m. 


Mineral products described 
as occurring in area of 


Little Belt Moun- 

Mont .. 


Weed,W. H 

Coal, silver, lead, copper, 

iron, sapphires, mineral 





Purington, C. W 

Gold, silver. 




Hills, R. C 




Va.-Tenn .... 


Campbell, M.R 

<'<»il, iron, zinc, barite, 
marble, clay. 


La Plata 



Purington, C. W 

(rolil, silver, coal. 



Va. W.Va. 


Darton, N.H 

Iron, stone, clay, road 


Menominee spe- 



Van Hise, C. R.; 
Bayley, W. S. 


68 , Mother Lode dis- 



Ransomo, F. L 

Gold, silver, manganese, 
quicksilver, stone. 





Vaughan, T. W 

Asphalt, gold, silver, iron, 
coal, water supply. 


Utah . 


To wer,G.W.; Smith, 
G. O.; Emmons, 
S. F. 

Gold, silver, lend, copper. 

66 | Colfax 



Lindgren, W 

Gold, stone, clay, water 





Campbell, M. R 

Coal, clay, gravel, under- 
ground water. 





Hills, R. C 

Coal, stone, clay, artesian 





Campbell, M. R 






Darton, N. H.; Keith, 

Gold, iron, clay, stone, 
road materials, green- 
sand marls, underground 


Spanish Peaks 



Hills, R. C 

Coal, stone, gold, silver, 
artesian water. 





Campbell, M.R 

Coal, salt, oil, gas, iron. 


Coos Bay ... 



Diller. J. S 

Coal, gold, stone. 





Tuff, J. A 

Coal, stone, clay. 





Keith, A . 

zinc, lime, road mate- 
rials, clay, water power. 





Hill, R.T.; Vaughan, 

Oil, stone, lime, clay, ce- 
ment, artesian water. 


Raleigh _ 



Campbell, M. R . . 






Hayes, C.W 

Bauxite, iron, slate, lime. 





Taff, J.A 

Coal, stone, clay. 





Darton, N.H 




111. Ind 



Stone, clay, molding sand, 
water power, water 





Campbell, M. R 

Coal, oil, clay, stone, glass 
sand, iron. 


New York City 



Merrill, F. J. H.; Hol- 
lick, A.; Darton, 

Trap, marble, granite, 
road material, clay, iron, 
water power, water 


Ditney __ 

Ind . 


Fuller, M. L.; Ash- 
ley, G.H. 

Coal, gas, clay, stone, iron. 



S. Dak.-Nebr 


Darton, N.H 

Stone, gypsum, lime, vol- 
canic ash, underground 





Smith, CO 

Budding stone, road metal, 
ground tenter, artesian 


Scotts Bluff 



Darton, N.H 

Volcanic ash. 


Camp Clarke 




Volcanic ash. 


6. Mineral Resources of the United States. — From 1883 to 1804, 
inclusive, an octavo cloth-bound volume bearing the above title was 
issued annually, with only two exceptions, the years L883-S4 and 
1889-90 being included by pairs in single volumes. The first of this 
scries was Mineral Resources of the United States, 1882; the last, 
Mineral Resources of the United States, 189o. In 1894 this form of 
publication was discontinued, in accordance with an act of Congress, 
and the material was included in certain parts of the sixteenth, seven- 
teenth, eighteenth, nineteenth, twentieth, and twenty-first annual 
reports. The separate publication of the series on mineral resources 
was resumed, however, in 1901, in accordance with an act of Con- 
gress, and two volumes of the new series, Mineral Resources of the 
United States for 1900 and for 1901, have been issued. 

This publication contains a systematic statement of the production 
and value of the mineral products of the United States, a summary 
of new mineral resources developed, and occasionally short papers 
on economic geology, when necessary in accounting for the new 


By S. F. Emmons, Geologist in Charge. 


In the years immediately following the organization of the United 
States Geological Survey its geological work was classed under two 
broad divisions, namely, general geology and mining geology. The 
primary object of the latter work was, by careful scientific studies of 
the most extensive mines and mining districts of the country, to 
gather together such an array of accurately determined facts with 
regard to the phenomena of ore deposition as would serve as a basis 
for generalizations, or laws governing the formation of metalliferous 
deposits. Incidentally it was expected that a demonstration of the 
correct geological structure and relations of the deposits in each indi- 
vidual district would prove of immediate practical value to those 
engaged in mining in that district, and serve as a guide to them in 
their explorations. This, however, was regarded as of secondary 
importance compared to the first object, since general laws are useful 
to mine owners the world over and are not confined in their applica- 
tion to the mines of a certain district. 

The commercial interest of mining industry was more directly sub- 
served by the collection of statistics of the mineral resources of the 
country, which was at first a branch of mining geology. As time has 
gone on and, with increasing pecuniary resources, the field of work 
of the Survey has widened, the above-mentioned classification of its 
work has been somewhat changed in title, as well as in the scope of 
the different divisions, but the main underlying principles have 
remained practically the same. 

The collection of mineral statistics is of direct commercial value to 
mining industry, which was readily recognized by the general public, 
and, direct and generous appropriations having been made for it, it 
lias become a special division. 


Whereas in the early days but little could be done toward preparing 
•i geological map of the whole country, which is theoretically the prime 
abject of a geological survey, because of the want of the indispensable 



topographic basis for such a map, so great progress lias now been 
made in the preparation of the topographic map that geological map- 
ping is in an advanced stage, and what was formerly called "general 
geology" is now mainly comprised under the term "areal geology." 

Under the folio form, in which the separate sheets of the Geological 
Atlas of the United States are published, there appears, together with 
the topographic and areal maps of the given fraction of a degree which 
it represents, a so-called economic map. The topographic map rep- 
resents the physical relief, or shape of the surface; the areal t map 
indicates by color conventions the area occupied on that surface by 
the different varieties of rocks which constitute the surface, while on 
the economic mail the different rock varieties arc so indicated that 
emphasis is given to those which carry minerals of economic value. 
Thus, the areal geologic work affords results of economic value, and 
is, moreover, an indispensable basis upon which all economic studies 
must be founded. 


What was formerly called "mining geology 11 is now designated 
"economic geology," and in late years the scope of this work has so 
greatly increased that it has been found advisable to have it con- 
ducted under two general heads, with a geologist in charge of each, 
namely, that of "metalliferous ore deposits," and that of "lionmetal- 
liferous deposits," those of iron being included in the latter class 
because of their close economic connection with coal deposits. 

The investigation of deposits of metalliferous minerals as at present 
conducted comprises several types of work varying with the condi- 
tions under which it is carried on. These are: First, the investiga- 
tion of important and extensive mining districts, such as Cripple- 
creek, Leadville, etc., which may be called "special district sur- 
veys." These are regions of unusually large concentrations of metal- 
liferous deposits, where within a small area the underground workings 
of a great many large mines have laid open to scientific observation 
relatively large portions of the interior of the earth, and whose indi- 
vidual outputs form a comparatively large fraction of the total 
product of the country. Even in cases where such districts have 
passed their prime from an industrial standpoint, their investigation 
is of the utmost value, since it affords a scientific record of critical 
phenomena which furnish material for the formulating of the general 
laws spoken of above. Hence, this work must be done with the 
highest degree of scientific accuracy and detail, and it generally occu- 
pies the work of at least two field seasons — one by the topographic 
corps in preparing the necessary maps, and one by the geologists in 
making the areal and underground surveys. 

To the general public, and especially to those who own mining 
property in a region, it often seems that the publication of such work 
is unduly delayed, since they are mainly anxious to learn the facts 


that directly aid in the development of their own property; but from 
the point of view of those engaged in the work, and who are respon- 
sible for a correct determination of the facts of nature, it is more 
essential that these facts, upon which future generalizations must be 
based, should be determined with the greatest possible accuracy than 
that the public demand for prompt publication should be yielded to. 

The second class of economic work may be called economic work 
incidental to areal work. In regions that are under areal survey it 
often happens that there are considerable mining developments, though 
the important mines are not gathered together into one small area or 
district, but occur at points so widely separated throughout the region 
that it would be inadvisable to survey the whole area with the amount 
of detail that is given to the work in special districts. In such cases, 
after the areal surveys have been completed and published, economic 
geologists are detailed to study the various mine developments of the 
area with a view to the determination of facts of structure and gene- 
sis of the ore deposits examined rather than of their immediate com- 
mercial value. Such are the reports on the Telluride quadrangle by 
Mr. Purington, and on the Silverton quadrangle by Mr. Ransome. 

A third class of economic work is the reconnaissance examina- 
tions, in which it is not intended to make a complete or exhaustive 
examination of a mine or district, but such a characterization as may, 
in a comparatively short time, bring out its most striking and evi- 
dent features, both structural and genetic. Here again the primary 
object, from the point of view of the Survey, is the gathering of facts 
bearing upon the broader questions of structure and origin. As to 
the practical bearing of such work in determining the probable value 
in depth of individual deposits in a region which is still in the pros- 
pect stage, mining men are apt to have somewhat exaggerated ideas. 
While a geologist who has had wide field experience in studying 
mining districts should be able to draw more valuable conclusions as 
to the future prospects of a region as a whole than the prospector or 
miner, as to an individual deposit, until it can be studied underground 
over a considerable extent, both vertically and longitudinal^, he can 
not, as a rule, obtain such scientific data as will enable him to give 
an authoritative estimate of its probable value. 

It has hitherto not been the policy of the Survey to publish this 
reconnaissance work in all cases. It has been considered that, inas- 
much as the very fact of publication of a report by the Survey gives 
to its statement a measure of official indorsement by the Government, 
and as courts of law have accorded to such publications an authority 
as evidence in mining cases equal to that of a text-book on geology 
or mining, incomplete material or opinions that are confessedly 
liable to be changed or modified by more complete studies should not 
be accorded the dignity of a Survey publication. Certain parts of 
this work, foi instance the rapid examinations of mining districts by 

Bull. 213—03 2 


heads of divisions for the purpose of determining whether or not they 
should be the subject of official examination in the immediate future, 
are primarily not intended for publication. Again, visits are often 
made to a number of different districts for the purpose of determining 
certain isolated and special facts that bear upon some important 
generalizations under consideration, and their immediate publication 
might defeat the end for which they were made. 

Facts of general interest, with regard either to special mines or to 
mining districts, or generalizations from facts gathered in studies of 
a great many mines or districts, but which are of a more or less tenta- 
tive nature, have been published from time to time by members of 
the Survey, under authorization of the Director, in some scientific 
publication, such as the Transactions of the American Institute of 
Mining Engineers, thus reaching directly and without delay the class 
of persons most immediately interested in them, namely, the mining 

The practical working of this system was well illustrated during 
the Washington meeting of the American Institute of Mining Engin- 
eers in 1900. At this meeting papers were read by different members 
of the Survey, as the result of their independent observations during, 
a series of years, on the following subject s : 

Some Principles Controlling Ore Deposition, by C. R. Van Hise. 
Secondary Enrichment of Ore Deposits, by S. F. Emmons. 
Enrichment of Gold and Silver Veins, by W. H. Weed. 
Motasomatic Processes in Fissure Veins, by W. Lindgren. 

These papers presented theoretical views upon the processes 
involved m the formation of ore deposits which the respective authorsi 
had been gradually arriving at during their Survey work. In most 
cases they represented rather preliminary statements, made for the 
purpose of stimulating discussion and investigation among mining 
engineers, than final and completed results, such as would be expected; 
from an official publication. Yet this prompt publication has been of 
the utmost practical importance to mining industry, for the first thr 
papers give a scientific means of answering a question of the most 
vital interest to the investor in mines, to which, in spite of all that has 
been written on it, only vague and contradictory answers had hitherto 
been presented — the question, namely, whether veins (or ore deposits) 
become richer or poorer with increasing depth. The answer was not 
categorical, for such answers are seldom possible in so complicated a 
science as geology, but it explained the manner of formation of the 
very rich bonanzas which have made certain mines famous and why 
they are succeeded by leaner ores in depth. 

The stimulation of discussion and investigation, which was the gen- 
eral purpose of such papers, has been so fully accomplished in thi&j 
case that they have been followed by a series of important contribu-i 
tions from the most eminent authorities on the study of ore deposits 


in Europe, as well as in this country, and all have been gathered 
together and published in a special volume by the Institute of 
Mining Engineers. Such publications are not intended to be final. 
Already, since the appearance of the above-mentioned volume, impor- 
tant modifications of the views therein presented have been suggested, 
and further important additions to our knowledge of the subject are 
to be expected from the constantly increasing amount of accurate 
work that is being done every year by the Survey. 

A brief review will now be given of the published results of this 
work, together with a statement of that which is in progress but has 
not yet reached the stage of publication. 

Economic Publications on Metalliferous Deposits. 

During the year 1901 there was published in the Bulletin series, by 
F. L. Ransome, a volume (Bulletin No. 182) on the Economic Geology 
of the Silverton Quadrangle, which belongs to the second class of 
economic publications mentioned above — that is, economic examina- 
tions incidental to areal work. The Silverton quadrangle had already 
been areally surveyed hy a party under the charge of Whitman Cross, 
who has been engaged for a number of j^ears past in making a geo- 
logical study of the whole region of the San Juan Mountains in south- 
western Colorado. Under the system adopted by the Survey, as each 
fraction of a degree — in this case one-sixteenth, or fifteen minutes — is 
surveyed topographicaltyand areally, the results are published in folio 
form, and when mining interests justify it an economic geologist is 
detailed to work either with the areal party or following it and to make 
a special study of the mines and ore deposits of the whole area. Such 
a study had already been made by C. W. Purington of the mines of the 

| Telluride quadrangle, and his results were published as a special 
paper in the Eighteenth Annual Report. 

The whole San Juan region is rich in ore deposits, occurring to an 
unusual degree in well-defined fissures and also in more irregular 
forms, called stocks or chimneys, which carry values in gold, silver, 

i' copper, lead, and zinc. The Silverton quadrangle, which lies next 
east of the Telluride, contains, like the latter, a large number of 
important mines within its area. In many of these the richer ores or 
bonanzas have been extracted and they are, for the time being, aban- 
doned; others, such as the Camp Bird, Silver Lake, and Tom Boy, are 
in active operation. The record obtained from the latter is naturally 
the most valuable, but the former also afford data of importance. 

IThis report contains not only a statement of the geological relations 
of each important deposit in the area which must prove of practical 
value to those engaged in mining there, but some very valuable gen- 
tliijeralizations which Mr. Ransome was able to make from the lode 
ilmi fissures and stocks or masses, also a statement of their contained min- 
erals and their paragenesis and origin, as well as important contri- 
butions to the new theory of enrichment of ores by descending waters. 


It is to be noted that under the new system of gratuitous distribu- 
tion of such papers, recently ordered by Congress, the edition of this 
report was exhausted within a few weeks of its appearance. 

In Bulletin No. 178, W. II. Weed has given the result of a recon- 
naissance examination of tin deposits in the Franklin Mountains, near 
El Paso, Tex. The openings upon these deposits were too shallow to 
afford very satisfactory data as to their probable value or continuity, 
and the paper is mainly useful as proving the actual occurrence of 
tin minerals at the locality named, since the existence of such miner- 
als has often been announced without any satisfactory basis of fact. 

Bulletin No. 18(5, on Pyrite and Marcasite, by H. N. Stokes, though 
more strictly classed as a chemical paper, deserves mention here 
because it represents the results of experimental observations on the 
chemical processes which take place during the secondaiy enrichment 
of ore deposits. 

These investigations were undertaken b} 7 the division of chemistry 
and physics at the request of the geologists who had read papers upon 
this subject at the Washington meeting of the American Institute of 
Mining Engineers, and who felt that the theory needed confirmation 
from the chemical side, since, while their field studies had shown that 
certain conditions produced certain results, they necessariby could not 
demonstrate the actual chemical processes by which those results had 
been brought about. 

Part II of the Twenty-Second Annual report, forming a volume of 
nearly 900 pages, published in 1902, was devoted exclusively to reports? 
upon ore deposits. These were: 

(1) The Old Tungsten Mine at Trumbull, Conn., by W. H. Hobbs. 

This is a geological description of an abandoned mine in a locality 
which had long been classic for the fine mineral ogical specimens 
obtained there. While not important from an economic point of view, 
the paper is valuable as furnishing data with regard to the manner of 
occurrence of the rare tungsten minerals — hiibnerite and scheelite. 

(2) Lead and Zinc Deposits of the Ozark Region, by H. F. Bain and C. R. Van 

This report was made in response to a demand for a prompt pre-« 
liminary statement concerning the lead and zinc ores of the Ozark 
region. It is both areal and economic in character, and in some respect? 
in the nature of a reconnaissance, since it was not possible under the 
circumstances to make the study exhaustive, and work is still being car- 
ried on in the region. Perhaps its most important result is the prac- 
tical demonstration and confirmation of Professor Van Ilise's theory 
with regard to the agency of surface waters in redistributing and!; 
enriching the lead and zinc deposits of the Mississippi Valley region.' 
and the indication of the practical deductions that may be drawr 
therefrom to guide the miner in his search for ore. 


(3) Ore Deposits of the Rico Mountains. Colorado, by F. L. Ransome. 

This urea is also situated in the San Juan Mountains, and the eco- 
nomic work followed an areal survey by Mr. Cross and his party, but 
the conditions there differ from those in the Silverton quadrangle, in 
that the ore deposits are concentrated within a limited area. It could 
thus be properly made the object of a special survey, especially as the 
peculiar nature of the ore deposits renders it unusually worthy of such 
detailed study. Unfortunately, by the time the Survey was in condi- 
tion to undertake this examination the principal mines had been prac- 
tically worked out and a large proportion of their underground work- 
ings had become inaccessible. This fact has given rise to some unfa- 
vorable criticism of the methods of the Survey on the part of those 
who consider that the most important result of its work is the imme- 
diate aid afforded by it to the miner in the development of the mines 
of the particular district under survey. In this case geological-con- 
ditions are such that it would have been impossible to make a satis- 
factory study of the ore deposits until the peculiarly complicated 
geology of the whole quadrangle had been worked out. Further- 
more, few mining districts present conditions so favorable for a definte 
determination of some of the undertying principles controlling ore 
deposition, conditions which the able mining engineers who had at 
different periods had charge of the principal mines of the district had 
of necessity been unable to completely understand, because the true 
geological relations of the deposits were not yet known. 

Mr. Ran some's report, in spite of the obstacles he had to contend 
with in making the examination, gives a remarkably able and satis- 
factory delineation of the conditions governing ore deposition along 
bedding planes of limestone under impervious shales, in part replacing 
a bed of gypsum, and associated with well-defined fissure systems and 
different ial movements along bedding planes, and of the genetic con- 
nection of its deposition with the intrusions of igneous rock in the 
immediate vicinity. It constitutes a most valuable contribution of 
well-determined facts bearing upon the general theoiy of ore deposits. 

(4) Geology and Ore Deposits of the Elkhorn Mining District, Montana, by 
W. H. Weed and Joseph Barrell. 

This is mainly the study of one great mine; a mine, moreover, that 
is practically worked out, and to which are applicable the same criti- 
cisms that were made of the Rico report. Here, also, the study has 
been extremely fruitful in presenting facts bearing upon the forma- 
tion of a rather unusual type of ore body. The deposit is considered 
Iby Mr. Weed to be in the nature of a saddle-reef deposit, formed in 
crushed limestone under a shaly roof within arches of pitching anti- 
clines, lie further considers the ore to have been deposited by hot 
solutions rising from a cooling batholith of eruptive rock. There is 
also evidence of secondary sulphide enrichment in the ore. 


(5) Gold Belt of the Blue Mountains of Oregon, by W. Lindgren. 

This report is the result of an elaborate reconnaissance examination 
made by' the author in the summer of 1900 of an area somewhat over 
50 by 100 miles in extent. It shows the ability and thoroughness that 
characterize all of Mr. Lindgren's work, and will no doubt prove a 
useful source of information to those engaged in mining in that 
region. In actual scientific results such work is generally less fruit- 
ful than would have been the same amount of time and labor devoted 
to a smaller area containing well-developed mines. 

(6) Ore Deposits of Monte Cristo, Washington, by J. E. Spurr. 

This, the final report of the volume, is also in the nature of a recon- 
naissance, since the region had not been previously mapped geolog- 
ically and the available topography was on so small a scale as to afford 
a very imperfect base for his geological observations. His time was 
also limited; nevertheless, as the area was small (3^ by 4 miles), he 
was able to make as fairly complete a study of the deposits and 
map the geology in as much detail as the economic importance of 
the region demands. His general conclusions are, first, that the ore 
occurs mainly as replacements of certain igneous rocks and to a less 
extent as the filling of open spaces; second, that they have been 
deposited by descending waters, and hence that the best deposits will 
be found relatively near the surface. 

The other economic publications that have appeared during the 
year 1902 are: 

Bulletin No. 193. — Geological Relations and Distribution of Platinum and 
Associated Metals, by J. F. Kemp. 

This is an account of few known occurrences of platinum and 
associated metals throughout the world, based upon the published 
literature on the subject and supplemented, in the case of a few 
occurrences in this country and Canada, by personal observations of 
the writer. It contains also a discussion on the mineralogical asso- 
ciation and probable origin of these metals. 

Professional Paper No. 1. — Ketchikan Mining District of Alaska, with an Intro- 
ductory Sketch of the Geology of Southeastern Alaska, by A. H. Brooks. 

This is the first paper of a new series of quarto publications by the 
United States Geological Survey, authorized by the law of Congress 
of May, 1902, which confines the report of the Director to a single 
volume, and directs that these papers, like the bulletins, shall be dis- 
tributed gratuitously. It is a reconnaissance report on the present 
mining development of this large district of southeastern Alaska, 
which includes Prince of Wales Island and the adjoining mainland. 
It is accompanied by a sketch of the geology of those parts of south- 
eastern Alaska that have been visited by members of the Survey. 


Economic Work on Metalliferous Deposits now in Progress. 

In enumerating the different pieces of work which have not yet 
readied the stage of completion, the order followed will be geo- 
graphic, taking each State and Territory, in which actual work has 
been done, in alphabetical order. 


Mining in the Appalachian region, except for iron and coal, has 
been conducted mainly in widely separated localities, and there are 
few concentrations of metallic deposits which form mining districts 
comparable to those in the West; hence hitherto no studies of special 
areas have been made. In the course of journeyings, however, obser- 
vations have been made in different parts of the region, especially by 
Mr. Weed, of the copper deposits, many of which have been reopened 
since the rise in the price of this metal. On later pages he gives an 
interesting summary of observations on various of these deposits, 
notably in New Jersey, along the contacts of the trap bodies which 
break through the Triassic rocks, in the interior of Maryland, and in 
the southern part of Virginia and North Carolina. Such observations 
will be continued from time to time as the conditions of Survey work 


The copper production of Arizona has in recent years assumed an 
economic importance rivaling that of the Lake Superior region and of 
Butte, Mont., which up to a comparatively recent date had together 
furnished more than two-thirds of the entire copper output of the 
country. Its principal mines had in consequence been developed to 
such an extent that their study promised to yield valuable data of vital 
importance in the theory of ore formation, especially in the line of 
secondary enrichment, a process which is particularly active in warm 
and arid climates. Since the commencement of the decade, therefore, 
considerable economic work has been done in this Territory, of whose 
geology up to this time but little was known. The following areas 
have been studied : 

Bradshaw quadrangle. — This area was geologically surveyed during 
the summer of 1901 and its economic resources studied, as far as their 
development permitted, by T. A. Jaggar, jr., and Charles Palache, 
instructors of geology at Harvard University. Under ordinary cir- 
cumstances it would have been more logical to have commenced work 
in this region on the Jerome quadrangle, which adjoins the Bradshaw 
on the northeast, but work in this area would have necessarily been 
incomplete because members of the Survey had been refused admis- 
sion to the most important copper mine of the region, the United 
Verde, by the owner of the mine, for reasons best known to himself. 


The Bradshaw quadrangle contains important deposits of both cop- 
per and gold in the same series of rocks in which those of the United 
Verde occur, but developments on most of them had, unfortunately, 
not been pushed to any great depth. The ores occur mainly as vein 
deposits in old Algonkian schists associated with eruptives. One 
important result of the work has been to detect a tendency in the ore 
deposits to arrange themselves peripherally around the bosses of the 
granite which outcrop in the area. The results of this work will be 
published in f^lio form. 

Glohe quadrangle. — This area was surveyed and its mines and ore 
deposits studied in the autumn of 1901 by F. L. Ransome, assisted 
during part of the time by J. D. Irving. It lies to the southeast of 
the Bradshaw quadrangle and in a similar relation to the great Plateau 
region of northeastern Arizona. It includes the important mines of 
the Old Dominion and United Globe companies, together with many 
other deposits, of both copper and silver, which are mostly replace- 
ments of limestone associated with eruptive rocks. The report on 
this district was completed during the summer of 1902 and will shortly 
appear as Professional Paper No. L2. 

Clifton-Mort nci quadrangle. — This area lies still farther southeast, 
near the borders of New Mexico and also not far from the southwest- 
ern edge of the great Plateau region. The three areas just mentioned 
thus give important data as to the remarkable change of structure 
from the horizontal attitude and comparatively undisturbed position 
of the strata in the plateau to 1 heir ex1 remely broken and complicated 
structure in the ranges of the Basin region. This area, which is of 
even greater economic importance than either of the other two, was 
studied by W. Lindgren, assisted by J. M. Boutwell. The field work 
was commenced in the autumn of 1901 and continued well on into the 
spring of 1902. The ore occurs mainly in limestone and associated 
eruptive rocks. Mr. Lindgren is now engaged in the preparation of 
his report, of which a brief summary is given on later pages. 

Bisbee mining district. — This district was studied in 1892 hy F. L. 
Ransome, assisted by J. Morgan Clements and A. B. Rock. The area 
lies in the extreme southern part of the Territory, near the Mexican 
boundary line. It has long been one of the most important copper 
producers of the Territory, and, as in the last-named district, mining 
has received a new impetus as the result of the recent impulse given 
to copper mining in general through the increased demand for the 
metal and its consequent rise in price. The ores occur in limestone 
near eruptive rocks, but without the contact phenomena that charac- 
terize the Clifton-Morenci deposits. They present remarkably clear 
evidence of secondary enrichment by descending solutions. Mr. Ran- 
some is at present engaged in preparing his report of the region, of 
which a brief statement is given in this bulletin. 



Shasta County. — The copper deposits around the head of the Sac- 
ramento Valley in California have been assuming considerable 
economic importance of late years, and as they present a somewhat 
different type from those hitherto studied it has been judged wise 
to make a special study of them. In preparation for this work 
J. S. Diller was engaged during the summer of 1902 in making an 
areal survey of the Redding quadrangle, which includes the most 
important copper deposits. He has prepared a brief summary of 
the results of his work, showing the general geological relations of 
the deposits. Detailed topographic maps are now being prepared 
of the smaller areas, in which the most important ore bodies occur, 
preparatory to special economic surveys, which will be made as early 
as practicable. 

Neocene river systems of the Sierra Nevada. — A very large pro- 
portion of the gold product of California is derived from gravels 
deposited in the beds of rivers belonging to an ancient system of 
drainage quite distinct and independent of the present river system 
of the Sierra Nevada. These gravels are now buried beneath more 
recent deposits and lava flows, and it is of great importance to miners 
to be able to trace their probable position in still undeveloped areas. 

In the course of his areal studies of the geology of the Sierra 
Nevada Mr. Lindgren had accumulated a great many facts concern- 
ing the location of these ancient river beds, parts of which had been 
studied and mapped by the able engineers in charge of various large 
hydraulic mining undertakings. During the summers of 1901 and 
1902 Mr. Lindgren was able to devote part of the time allotted to 
field work to a further examination of the Sierra Nevada region for 
the special purpose of supplementing his previous observations so as 
to give a comprehensive view of the whole river system and to 
enable him to map the probable course of the earlier or Neocene 
rivers. In this study, which is largely of a physiographic nature, he 
has been efficiently aided by J. M. Boutwell. It is a work which 
necessarily requires very careful platting and much deliberate con- 
sideration. It will be prepared for publication as rapidly as the 
press of work admits. Its condition is more fully described by Mr. 
Lindgren on later pages. 


In Colorado no new economic surveys have been commenced during 
the last three years. The writer, assisted by J. D. Irving, has con- 
tinued the gathering of data for a supplemental report on the geolog}^ 
of the Lead vi lie district during such time as could be spared from his 
regular duties of supervising the work in other fields. This work 
will be mainly of scientific interest, as at this late day it can hardly 


be of much value in directing the explorations of those engaged in 
mining. It will be chiefly valuable in furnishing a record of the 
immense ore bodies that have been mined in the district during the 
last twenty-five years, in showing the possibilities and limits of geo- 
logical induction by contrasting their actual geological relations with 
those predicated in the first report from such facts as were open to 
observation. It will also afford further data for testing and modify- 
ing the theories of ore formation propounded in that report. Circum- 
stances are such that it is impossible to determine when this report 
will be ready for publication. 


Mineral deposits of flu Bitterroot Range and Clearwater Moun- 
tains. — In the summer of L899 Mr. Lindgren was engaged in making 
a geological reconnaissance in those parts of Idaho and Montana lying 
north of the Salmon River and extending from the Bitterroot Vallej 7 
westward to the lava plains of the Columbia. In the course of this 
work he observed the scattered ore deposits that are developed in this 
region, without, however, having time to make an exhaustive study 
of them. The area is largely of granite, with some sedimentary quarts 
zites, slates, and limestones, principally upon the borders. It is 
notable thai in the central part of the granite area no important ore 
deposits have yet been discovered. In the subsequent pages Mi'. 
Lindgren gives an interesting summary of his observations and of the 
structural relations of the various deposits observed. 


Studies have been made during the summer of 1002 in the Missis- 
sippi Valley region, first, of the lead and zinc deposits of northern 
Arkansas by G. I. Adams, and, second, of the lead and zinc deposits 
of the Joplin district of Missouri and of the lead, zinc, and fluorspar 
deposits of western Kentucky by W. S. Tangier Smith. 

All these deposits belong to a general type geologically distinct from 
those found in the mountains of the West, and are of special interest 
on that account. Brief summaries of the results thus far obtained 
will be found on later pages of this volume. 


Copper mines of Butte. — The first study of the extremely important 
vein deposits in granite at Butte Mountain was made in the summer 
of 1896, and the results were published in folio form the following 
year. Not long after the completion of this report, as a consequence 
of litigation which sprung up between the most important mining 
companies of the region, a great deal of underground exploration was 
done for the express purpose of ascertaining more accurately the geo- 


logical structure and relations of the vein. So many new facts were 
thus learned, and so important was their bearing upon the theory of 
vein formation, that it was judged wise to make a second and more 
exhaustive study of the copper veins of the region. This has been 
carried on by Mr. Weed and his assistant since the spring of 1901 
almost continuously, though his work has been interrupted at times 
by the necessity of completing other pieces of work. It was not 
thought best to hurry this work to completion, for the reason that the 
geological questions at issue had most important bearing in the liti- 
gation that was going on, and it was desired to avoid, as far as possi- 
ble, influencing the results of this litigation, lest there might be a feel- 
ing that the opinions expressed, which must necessarily favor one 
side more than the other, indicated a partiality to the favored side. 
The work is now approaching completion, but, on account of its mag- 
nitude, will not be published for some time. A brief summary of the 
important results is given by Mr. Weed on later pages. 


A new mining district in southern Nevada has sprung into sudden 
prominence bj T its shipment of rich gold ores to the smelters, espe- 
cialty at Salt Lake. Nevada has hitherto been regarded as essen- 
tially a silver-producing State, and mining there has languished since 
the fall in the price of the white metal, hence the development of its gold 
resources is of the greatest importance. A brief account by the writer 
of the important gold mine at De Lamar, in southeastern Nevada, was 
published in the Transactions of the American Institute of Mining 
Engineers in 1901. 

During the autumn of 1902, J. E. Spurr, after assisting Mr. Spencer 
in the Grand Encampment work during October, was detailed to 
examine this new (Tonopah) district of Nevada. lie had been taken 
ill with typhoid fever just at the opening of the field season in July, 
hence was obliged to commence his field work at so late a date that 
he found it advisable during the winter to make microscopical and 
chemical studies of his rock specimens at Washington. He will com- 
plete his field work in the spring and early summer, and a reconnais- 
sance will then be made of neighboring mining districts in the Silver 
Peak quadrangle and elsewhere. 


Economic Resources of the Northern Black Hills, by J. D. Irving and S. F. 

This work was designed to be published in conjunction with the 
Sturgis-Spearfish folio, for which the field work was completed some 
years since. Its publication has been delayed by the calling off of the 
principal author, T. A. Jaggar, jr., to other duties, notably to the study 


of the volcanic eruptions in the West Indies in 1902. As soon as Ms 
introductory sketch of the geology of the region is received the manu- 
script will be sent to the printer. It comprises an account of the 
geological relations of the various ore deposits of the region, main]} 7 
gold bearing, and a partial sketch of the famous Ilomestake lode, 
which is, unfortunately, incomplete because permission to enter the 
mine was withdrawn by the management before the study had been 


During the summer of 1002 a geological party, under charge of 
A. C. Spencer, was engaged in an areal survey of the Grand Encamp- 
ment Mountains, of Wyoming, and in a study of the copper deposits 
occurring there. The writer spent some time with this party in the 
summer, and also examined the important deposits of the New Ram- 
bler mine, in the Medicine Bow Range, on the opposite side of the 
North Platte Valley. The mines in this region are as yet opened to 
only moderate depth and the study of their deposits can not yet be 
expected to yield important data bearing upon their genesis, but the 
extremely detailed and careful stud} 7 of the very complicated geological 
structure of the region made by Mr. Spencer and his associates will 
probably be of service in helping the development of its mines, and 
will certainly be an important contribution to our knowledge of the 
geology of the Rocky Mountain system. An abstract of this work is 
given on later pages. 



By C. W. Hayes, Geologist in Charge. 

The distinctly economic work being done by the Geological Survey 
has shown a steady growth in extent and importance since its organi- 
zation in 1879. As pointed out Iry Mr. Emmons, this was at first 
directed largely to the investigation of the ore deposits of the precious 
and semiprecious metals — gold, silver, mercury, copper, etc. With 
the extension of areal mapping in preparing the Geologic Atlas of 
the United States, investigation of the more widely distributed ores 
of iron, manganese, and aluminum and the nonmetalliferous minerals, 
as clay, stone, phosphate, coal, asphalt, oil, and gas, was taken 
up. The natural grouping of these two classes of mineral products 
and the importance of their investigation were recognized by organiz- 
ing, within the Geologic Branch of the Survey, in 1900, the two sec- 
tions of metalliferous ores and nonmetalliferous economic minerals. 
Since that time sj^stematic investigations of the nonmetalliferous 
minerals have been carried on, both in connection with areal geologic 
mapping and independently of areal work. It is impossible to 
describe in detail all of the work of this kind which has been done 
by the Survey, but its character and extent may be indicated by a 
brief mention of some of the more important investigations carried 
on in recent years. 

The nonmetamorphic iron ores have been studied chiefly in connec- 
tion with areal mapping, and their distribution is shown in the 
geologic folios for considerable areas in Virginia, West Virginia, Ten- 
nessee, Georgia, and Alabama. The same is true of manganese, ocher, 
stone, and slate. 

All known occurrences of bauxite, the ore of aluminum, have been 
visited and examined by Hayes. 

The slate quarries of Vermont and eastern Pennsylvania have been 
examined by Dale, and the more important slate localities in the 
Southern States by Keith and Hayes. 

Special studies of the marble belt of Vermont have been made by 
Dale, and Keith has mapped the marble of East Tennessee. 

The phosphate deposits of Florida have been investigated by 
Eldridge, and those of Tennessee by Ha.yes, Ulrich, and Eckel. 

Investigation of the coal fields of the United States has been of two 



kinds, detailed areal mapping and general summaries. Under the 
first class of work large areas have been covered in the Appalachian 
coal field, and the results have been published in numerous folios. The 
work in Pennsylvania and West Virginia has been carried on by 
Campbell and his assistants; in Tennessee by Campbell, Keith, and 
Hayes, and in Georgia and Alabama by Hayes. Work has also been 
done in southern Indiana by Campbell, Fuller, and Ashley; in the 
southwestern field in Indian Territory by Taff and Adams; in the 
Rocky Mountain fields in Montana and Colorado by Weed, and in 
the Pacific fields by Diller, AVillis, and George Otis Smith. 

The principal work of the second class has been the preparation of 
a series of papers, 12 in number, summarizing existing knowledge 
relating to coal fields of the United States. These are more fully 
described on later pages. 

The investigation of oil and gas fields has only recently been taken 
up. During the last year certain portions of the Appalachian field 
have been studied by Campbell, Griswold, and Fuller. The work of 
Griswold in the Cadiz field is especially noteworthy, since it is the 
most successful attempt thus far made to work out the structure of 
the oil-bearing sands by instrumental means and with a high degree 
of accuracy. A thorough reconnaissance of the oil fields of Califor- 
nia has been made by Eldridge, and of the Texas-Louisiana fields by 
Hayes and Kennedy. The Boulder oil field of Colorado has been 
studied by Fenneman. 

All known asphalt deposits of the United States have been exam- 
ined and reported upon by Eldridge, and those of Arkansas and 
Indian Territory have been examined in detail by Hayes, Adams, and 

A general reconnaissance of the clay resources of the United States 
east of the Mississippi River has been made by Ries, and his report 
is now in press. Detailed studies of particular deposits have been 
made by Vaughan in Georgia and Florida, and by various geologists 
in connection with their areal mapping. 

Important economic work has also been done under the section of pre- 
Cambrian geology, especially upon the iron ores of the Lake Superior 
region. All of the iron-bearing districts have been studied by Van 
Hise and his assistants, Clements, Bay ley, and Leith, and reports are 
either published or in press. Also under the supervision of Van Hise 
the lead and zinc mines of the Mississippi Valley have been examined 
in the Ozark region by Bain, Adams, and Tangier Smith, and in 
western Kentucky by Ulrich and Tangier Smith. 


In addition to the papers here included, which represent the results 
of recent work by the Survey in important precious metal mining 
districts, other reports bearing incidentally on the subject of gold and 
silver will be found Under the head of "Copper," on pages 105 to 186. 



By J. M. Boutwell. 


Field work. — During the field season of 1901 two detailed topo- 
graphic maps of portions of the Park City district were prepared by 
this Survey under the direction of E. M. Douglas, geographer in 
charge, by Pearson Chapman and J. F. McBeth. The general map, 
showing an area of approximately 32^ square miles on the scale of 3 
inches to 1 mile, embraces the general area in Park City through 
which mining operations have been conducted; and the other, on a 
scale of 1 inch to 1,000 feet, or 5.2 inches to a mile, includes only that 
portion of this area which lies in immediate proximity to the largest 
producing mines. 

Late in the field season of 1902 a detailed study of the areal and 
economic geology of the Park City mining district was undertaken by 
J. D. Irving and J. M. Boutwell, under the supervision of S. F. 
Emmons, geologist in charge of metalliferous deposits, and was con- 
tinued into December of that year. This was the first systematic 
geological work in this region since Emmons mapped the broad fea- 
tures of the range in 1869, while engaged in the " Geological Explora- 
tions of the Fortieth Parallel," under the late Clarence King, and was 
the first detailed geological examination of an extended area in the 
Wasatch Range. Before detailed work in the area under survey 
could be advantageously undertaken a general knowledge of the 
geological history of this portion of the range and the establish- 
ment of the geological succession were required. Accordingly, the 
general geology of the region surrounding the special field of work, 
including the main divide of the Wasatch Range to the west, its 

"This sketch is merely a preliminary statement indicative of progress. A complete report 
will be published after a detailed survey has been completed. 



eastern slope, and the adjacent portion of the Uintas to the east, was 
studied en reconnaissance, and detailed stratigraphical sections in the 
nearest undisturbed areas were examined and measured. The area 
included in the general map of the Park City district was then trav- 
ersed, a considerable part of this area and also of that shown on t lie 
map of the region immediately about the mines was mapped in final 
form, and a reconnaissance study of the chief mines was conducted. 

Dining the few weeks which have elapsed since the close of these 
field studies the nature of the writer's work has not enabled him to 
obtain any significant results from mineral and rock determinations 
and the correlation of geological data from this district beyond those 
which were gained in the field. It should be understood, therefore, 
that while broad geological conclusions have been reached, and in 
some cases detailed results secured, final conclusions regarding areal 
and economic problems have not been attained. In view of this fact 
it is a matter of some doubt as to how much value may lie in these 
general statements, based upon incomplete and unstudied data. The 
following brief statement is presented, however, in the hope that it 
may be of some service in the extensive development which is now in 
active progress. Only t he general geological facts thus far determined, 
and such broad economic features as seem least likely to be altered 
by detailed underground studies, are given, and the statements are 
to be regarded as field opinions and tentative conclusions, subject to 
partial or complete modification after further field work. 

After briefly touching on the geography, history, and production 
of the district these general preliminary results will be given under 
the following headings: Under "Areal geology" will be discussed the 
stratigraphy, igneous rocks, and structure; and under "Economic 
geology " will be treated the character and occurrence of ore and 
present mining activity. 

Geography. — Park City is pleasantly situated on the eastern slope 
of the Wasatch Range, in the north-central part of Utah. It lies 
about 25 miles southeast of and 3,000 feet above Salt Lake City, 
at an elevation of 7,200 feet above sea level. In its location on the 
southern edge of a high-lying mountain prairie, at the junction of 
three great canyons which there descend to the prairie from the main 
range, this thriving mining town (population, census 1900, 3,759) has 
a position of rare commercial value. A branch line of the Rio Grande 
Western unites it by way of Parleys Park with Salt Lake City (35 
miles), and a branch line of the Union Pacific (28 miles) extends from 
the main line at Echo. It thus forms a most convenient outlet point 
for the producing mines of the district, which are all located on the 
slopes of the canyons which rise from this point southward. 

The Wasatch Range in the portion south of Salt Lake City is a 
lofty mountain unit, trending generally north and south between the 
Great Basin on the west and mountainous plateau regions on the east 


Its western slope presents a wall-like front of striking steepness, 
which is deeply incised at regular intervals by narrow rock-walled 
canyons. The portions intervening between these canyons show a 
marked type of dissection, which is characterized by ravines that rise 
from the level of the desert with steep sides and bottoms, and fork 
repeatedly and symmetrically upstream. The eastern slope, in 
marked contrast, is a gradual descent to upland ranges, plateaus, and 
high-lying meadows, which extend in a north-south belt along the 
eastern base of the range. This unsymmetrical range may thus be 
compared to a mammoth step, about 3,000 feet in height, from the Great 
Basin on the west up to the highlands which extend from its upper 
portion eastward. That part of the upland which adjoins this range 
is drained by streams which flow westward through the great canyons 
into the basin. 

The Park City district embraces a tract which lies between the pre- 
cipitous walls of barren rock, inaccessible cliffs, and ledges that mark 
the crest of the main range to the west, and the grass}^, verdant, 
mountain meadows of Heber, Kamas, and Parleys, along its eastern 
foothills. This intermediate belt lies upon the northern portion of 
a prominent spur which stretches from Clayton Peak in the main range 
toward the east. This spur forms the head ward portion of East Can- 
yon, divides the Weber from the Provo, and is the connecting link 
between the Wasatch Range and the Uinta uplift. It comprises three 
topographical divisions — a steep slope southward, which overlooks an 
extensive, relatively level tract to the south, Bonanza Flat; a gradual 
descent northward, which is deeply cut by four narrow, steep-sided 
gulches, Thaynes, Woodside, Empire, and Ontario; and a long, steep, 
deeply incised slope eastward, which unites the Park City upland with 
the prairie belt. 

The climate is remarkably bracing, with short, cool summers, short 
autumns, and long rigorous winters marked by heavy snowfalls and 
low temperature. Being on the protected sunny side of the range, 
however, it escapes much of the harshness of such conditions which 
neighboring canyons suffer. Water, although hardly abundant, is 
not scarce. Springs and currents cut by underground workings sup- 
ply a constant flow of Avater the year round. Natural rock basins at 
the foot of the pinnacle of Clayton Peak are utilized as reservoirs, 
and a supply of water which is sufficient for domestic purposes is 
obtained from the Alliance tunnel. The outflow from the Ontario 
drain tunnel, which is generally believed to include the drainage 
from a large portion of the great mines, furnishes the power for the 
Park City electric-light plant. Although the slopes originally sup- 
ported a growth of pine timber 3 to 5 feet in diameter, this was early 
utilized for underground timber. Fuel is supplied from extensive 
veins of good coal at Coalville, 28 miles to the north, and from the 
forest growth on the distant portions of this and the Uinta ranges. 

Bull. 213—03 3 


History. — The earliest mining in this part of Utah was in the Miller 
mine, at the head of American Fork Canyon; in the Emma, Flagstaff, 
and other mines near Alta, at the head of Little Cottonwood Canyon ; 
and in the adjoining districts at the head of Big Cottonwood Canyon 
and Snake Creek. In those days the Miller and Emma were famous 
mines and the Park City region received slight attention. Although 
desultory mining had been carried on in this area on various properties, 
such as the Pioneer, Clara Davis, Badger, White Pine, McHenry, etc., 
for a few years previous, actual mining may be said to have begun 
with the discovery of the Ontario mine; and the early history of this 
mine is generally considered to constitute the early history of the 

The Ontario mine is generally believed to have been discovered by 
Rector Steen and his associates " about June 15, 1872." He describes 
the discoveiy as follows: 

When we discovered this mine we found a little knob sticking out of the 
ground about 2 inches. We scraped the dirt off the lead about 50 feet along the 
lead. It was about 18 inches wide, and when we got down 8 feet it narrowed in 
to 8 inches. We had the rock assayed and it went from 100 to 400 to the ton.« 

On August 21 of the same year the discoverers sold the property to 
Messrs. Hearst and Stanley for $30,000. During the succeeding years 
development work was energetically conducted through tunnels from 
the main ravine. In April, 1878, the first shaft was started. Since 
then two more shafts have been sunk (the deepest recently attained a 
depth of 2,000 feet), and extensive underground development work 
has been in constant progress. As a result of these operations since 
its final incorporation in 1883, this property has produced silver which 
has been sold for $33,255,950, and since 1901 dividends amounting to 
$13,752,500 are stated to have been paid. 

The success which attended these operations stimulated exploring 
and locating throughout the district, and the ground through which 
the Ontario lode was supposed to extend from the northeast to the 
southwest was quickly taken up and developed. This resulted in the 
extension of successful mining operations to the west, in the ground 
now owned and operated by the Daly, Daty-West, and Daly- Judge 
mining companies. In 1880, eight years after the discovery of the 
Ontario, there were 1,270 mining locations registered in this (the 
Uinta) mining district, although only 500 were active. Development 
progressed steadily until 1893, when the decline in the price of silver 
seriously crippled the camp. Improvement in the lead market, the 
high grade of ores, and important improvements in the treatment of 
ores made it possible to resume mining activity at an early date, 

"Mr. Steen, who is still enjoying good health after a succession of arduous hardships encoun- 
tered in prospecting in California, Montana, Wyoming, and Arizona, previous to his discovery 
of the Ontario, has kindly supplied valuable data concerning the early history of this camp, 
which will be included in a detailed historical sketch in the complete report. 




and this activity has continued and increased consistently to the 
present time. Since the middle nineties, when valuable ore bodies 
were discovered, outside of the previously productive area, in the 
Mayflower, Woodside, and Silver King properties, exploration has 
been carried on over a large tract, and the productive area has been 
widely extended. At present mining is extensively conducted in the 
Silver King, Daly- West, Ontario, and Daly- Judge properties; impor- 
tant work is being carried on in the Kearns-Keith, Keystone, Cali- 
fornia, Comstock, and other properties on the west; in the Little 
Bell, J. I. C, and Thompson groups on the south; and in the Nail- 
driver, Wabash, New York, etc., on the southeast. Work is con- 
templated for the coming season by owners of various properties on 
the eastern and northeastern borders of the district. 

Production. — The product of the Park City mines consists chiefly of 
silver, and, in minor quantities, of lead, copper, and gold. The pro- 
portionate value of these four metals (silver, lead, copper, and gold) 
in the present output may be roughly stated as 9.1 to 2.6 to 0.39 to 
0.28. The quantity and value of the output have increased strongly 
in recent years, and may be reasonably expected not only to have 
increased in 1902 but to continue that increase in the immediate 
future. The following table, taken from the report by B. H. Tatam 
in the Annual Report of the Director of the Mint for 1901, shows the 
kind, quantity, and value of ore produced in Salt Lake County, Utah 
(practically entirely from Park City), during the years 1900 and 1901. 

Kind, quantity, and value of ore produced in Salt Lake County, Utah, during 

1900 and 1901. 









Gold fine ounces. . 

Silver (coining value), 

..fine ounces.. 

Copper fine pounds. . 

Lead do 






















General geology of the region. — In its geological structure the Wasatch Range 
presents a type of extreme complication, contrasting strongly with the simplicity 
and regularity of its nearest neighbor, the Uinta Range. The simplest expres- 
sion of this structure would be that of a sharp north and south anticlinal fold 
over preexisting ridges of granite and unconformable Archean beds, whose axis 
has been so bent and contorted by longitudinal compression that it at times 
assumes a direction approximately east and west. In connection with the folding 
has been developed a widely-spread system of faulting and dislocation, in a direc- 
tion generally parallel with the main line of elevation, which has cut off and 
thrown down the western members of the longitudinal folds and the western ends 


of the transverse folds, which are now buried beneath the valley plains, while the 
detailed structure has been still further complicated by a system of transverse 
faulting. * * *a 

That portion of the range which is included between Utah Lake and Emigra- 
tion Canyon forms a geological whole, consisting of a series of sedimentary for- 
mations, flexed around a body of * * * granite. * * * Horizons from the 
Cambrian up to the Middle Coal Measures are at different points in contact with 
the granite body. * * * Of the immense arch which once covered this body 
the western half has been faulted down, while the top of the arch, with its thick- 
ness of 30.000 feet of rock masses, has been broken up and worn away by 
atmospheric agencies. b 

The composite crystalline mass comprising the granite of Lone 
Peak and Little Cottonwood Canyon, the granodiorite at the heads of 
Big and Little Cottonwood canyons, American Fork, and Snake Creek 
(Provo), and the diorite at the heads of Big Cottonwood, East Can- 
yon, and Snake Creek, with its extensions northeast through the 
Park City district, in the form of dikes, is the dominant factor in the 
greater geological structure of the middle Wasatch. The ages and 
the relationships of these great intrusive masses have not yet been 
completely established. In a broad structural sense the bodies may 
be regarded as forming an immense composite laccolith. In this light 
the striking obliteration of the normal anticlinal structure of the 
Wasatch, and the marked quaquaversal dip in this immediate section, 
become significant. The Algonkian on the west, the Cambrian to 
Mesozoic on the north, the Carboniferous on the east, and the Cam- 
brian to Carboniferous on the south, each dipping away from this 
intrusive center, are seen to be the flanks of a great laccolithic dome. 
This main structural feature, supported by the evidence afforded by 
the intrusive character of the contact between the crystallines and 
the elastics, by the marmorization and deformation of the adjacent 
country rock, and by the occurrence of an unusually complete series 
of typical contact-metamorphic minerals, is conclusive as to the part 
this intrusive mass has played in the history of the region. 

Stratigraphy of the district. — The stratigraphical series in the imme- 
diate vicinity of Park City has been so modified by faulting, intru- 
sion, and metamorphism that no reliable extended section could there 
be found. One on the north side of Big Cottonwood Canyon, between 
1 and 2 miles west of Park City, was studied in detail. As several 
requests have been received for information regarding this section, 
for the purpose of establishing the relative position of the ore-bearing 
members in this mining district, a general summary of that section 
is given. The sedimentary series includes three chief rock types — 
quartzite, limestone with calcareous sandstone, and shale. In gen- 
eral, the succession (from the older to the younger), the thickness, 

« Emmons, S. F., U. S. Geo!. Expl. 40tb Par., Vol. II, p. 341. 
&Ibid., pp. 353-355. 


and the probable age of the larger divisions are as follows: (1) lime- 
stones of improved thickness, probably of Lower Carboniferous age; 
(2) 1,500 feet of massive normal quartzite, unfossiliferous, probably 
of Upper Carboniferous age; (3) 590 feet of calcareous beds, mainly 
blue limestone, with some shale, of Carboniferous age; (4) 1,100 feet 
of red shale and sandstone, probably of Mesozoic age; (5). 450 feet of 
calcareous sandstone, interbedded limestone, shale, etc., Mesozoic; 
(6) 140 feet of red shale, Mesozoic; (7) 630 feet of limestone, calca- 
reous sandstone, and gray shale, Mesozoic; and (8) an unproved thick- 
ness of red shale, Mesozoic (?). 

The correlation of members of this series throws light upon their 
relation to the ore-bearing rocks in neighboring mining regions. The 
lowest limestones here may be tentatively correlated with those on the 
divide north of Alta and with those which underlie the main ore- 
bearing series at Bingham. Accordingly the main quartzite of Park 
City may be tentatively correlated with the great quartzite series in 
lower Weber Canyon in the vicinity of the railroad tunnels and with 
the main quartzite at Bingham. Valuable data upon the geological 
history of this region have been secured in the course of this strati- 
graphical study. They will not be considered in the present abstract, 
however, since the character of the country rock is of more direct 
economic interest. 

Igneous rocks. — Within this area igneous rocks of three types have 
been found — a fine, even-grained dioritic type, a coarser porphyritic 
type, and a poorly defined type which ranges from andesitic to basaltic 
facies. The first two are intrusive in origin; the last, so far as it may 
be judged from the present incomplete data, is extrusive or volcanic 
in origin. 

The origin of these rocks bears directly upon two in'actical matters 
of deep importance to mining men — the extent and the origin of ore. 
The extrusive or volcanic rocks (those which flowed out upon the 
surface) are often found to be in the form of a blanket overlying the 
country rock, and as such would not be expected to lead to ore forma- 
tion nor to truncate in depth previously formed ore bodies. The 
intrusive masses, however, having reached their present positions and 
forms through injection in the state of a semiliquid pasty magma into 
the sedimentary country rock, may reasonably be expected both to 
have generated ore and to have truncated any previously existing ore 
bodies which lay in their paths. That is to say, the intrusions of 
diorite and diorite-porphyry do not underlie the sediments as a foun- 
dation of older rocks, nor do thej^, like the extrusives, overlie the 
sediments, but they break irregularly across the sediments from bed 
to bed. When the molten magma came in contact with certain lime- 
stones, it led to the formation of various secondary minerals, and in 
those limestones which possessed suitable comrjosition it may have 
induced the formation of ore. 


Geological structure. — The sediments in the immediate vicinity of 
the Park City area have a general northeast-southwest strike, and an 
average dip of about 40° NW. In general, then, the highest, or young- 
est beds occur in the northwest portion of the area, and the lowest or 
oldest in the southern and southeastern portions. But they have suf- 
fered strong deformation from two potent factors — Assuring with fault- 
ing, and intrusion. Although intense fracturing occurred in both 
north east- south west and northwest-southeast directions, the prevailing 
trend of the principal fissures thus far studied is northeast- southwest. 
The more common dip is steeply to the northwest, although some impor- 
tant fissures of this series dip to the southeast. The intrusions occur 
as regular laccolithic masses and as dikes. They extend northeast- 
ward through the district, in a direction accordant with the zone of 
weakness indicated by t lie fissures, from the great dioritic body of 
Clayton Peak on the sout Invest to extensive extrusive masses on 
the northeast. They sometimes disturb the prevailing dip of the 
sediments and cause local doming, as on the divides to the southeast 
and southwest of "Bald Mountain. Distinct southerly dips noted in 
the latter locality emphasize the general laccolithic character of this 
great northeast-soul invest, belt of intrusives. 


General. — During the season of 1902 work was directed chiefly 
toward examining the areal geology with a view to establishing a firm 
foundation for later underground studies. Such information as was 
secured about economic questions was necessarily of a preliminary 
nature, so that only a few general characteristics will be given in this 
statement of progress. 

The Park City mining district stands very prominently among the 
great mining districts of this country as the home of large bodies of 
silver-lead ore carrying minor values of gold and copper. In 1901 
Park City mines supplied, roughly, seven -elevenths of the total out- 
put of silver from Utah and were the main factor in maintaining Utah's 
rank as third among the silver-producing States. 

Although relatively young, Park City is, in several ways, a great 
camp. Mining is conducted on an extensive scale, according to 
advanced methods, by able, experienced men. Ten shafts have 
reached a depth of at least 1,000 feet, 6 are down 1,300 feet or more, 
and 1 — that one, too, whose collar is lowest — has attained a depth of 
2,000 feet. There are four long drain or work tunnels, the longest of 
which extends out to the eastern slope, a distance of about 3 miles. 
Three large, highly efficient concentrating mills have been erected at 
individual properties for private work, and an enlarged sampler and 
a recently remodeled zinc plant are located below the town for custom 
work. An aerial tramway and a broad-gage railroad transport ores 


from the mines to the Rio Grande Western system for shipment to the 
custom smelters in the Jordan Valley. These perfected plants and 
extensive operations, by which mining expenses are reduced to a 
minimum, are rendered possible by a wise consolidation of interests. 
Thus large tracts are owned by single companies; the bulk of the 
output for the last year was supplied from two properties, and the 
reputation of the camp rests upon the record of five great properties. 

Character of the ores. — The values of the Park City ores (named in 
the order of their importance) lie in their silver, lead, copper, and 
gold contents. Silver has been reported in the form of several silver 
minerals, and doubtless lies principally in the galena and gray copper. 
Lead is present chiefly in the form of massive cleavable galena in the 
sulphide zone, and of crystalline cerussite, amorphous auglesite, and 
complex oxides in the zone of surface alteration. Copper occurs for 
the most part as gray copper (tetrahedrite) in the sulphide zone, and 
in the form of the blue and green carbonates (azurite and malachite) 
in the oxidized zone. The mineralogical character of the gold is not 
known, though it may occur as an impurity in pyrite. Zinc is a 
common associate in the fissure ores. 

Superficial alteration has descended to great depths. Some ore 
bodies in limestone have been almost entirely altered to oxides, car- 
bonates, and sulphates to the depth of 900 feet below the present 
surface, and the effects of oxidation may be observed upon the walls 
of sulphide ore bodies and adjacent to fissures cutting them, even to 
a depth of 1,300 feet. At present both the oxidized and the sulphide 
ores are mined. 

These include large amounts of both first-class smelting ore and 
milling ore. Several bodies of very high-grade ore — bonanzas — have 
been discovered. Ore from the upper levels, 100 to 400, on a great 
lode of this district is reported to have run from $40 to $700 a ton, 
with an average of $130, and in 188G "the best" Ontario "ore was 
sold to smelters and averaged $94.82 per ton. Ores of lower grade 
were milled averaging 54.32 ounces of silver."" The average value 
of crude ore shipped during the year 1902 from one of the principal 
properties of the camp was between $28 and $29 per ton. 

Occurrence of ores. — The Park City ores do not appear to be gener- 
ally distributed throughout the region in small amounts, but rather 
to be localized in certain well-defined occurrences in large bodies of 
pay grade. Three main types of occurrences have been recognized — 
fissure ores, replacement ores, and contact ores. In the first the ore 
carries either silver and lead, with or without zinc and gray copper, 
or gold with some silver, and occurs between well-defined fissure 
walls. In the second the ore holds silver and lead values chiefly and 
takes the form of elongated lenses within limestone, roughly parallel 

aAlmy, T. J., History of Ontario mine, Park City, Utah: Trans. Am. Inst. Min. Eng., vol. 16, 
p. 37. 


to the bedding. In the last the ore contains copper and gold, with 
or without lead and silver, and forms in irregular masses, pockets, 
lenses, and pencils in metamorphic limestones adjacent to intrusive 
bodies. Gold values appear to run highest in certain fractures in 
quartzite; zinc is reported to increase in the southwestern extension 
of the great fissure zone of the camp, and copper is said to reach its 
maximum in amount and value in the deeper portions of certain 
pseudo-fissures in quartzites. 

Present activity. — During the last year mining in this district has 
been remarkably active. Forty-eight new locations, the largest num- 
ber reported from any mining district in the State, have been recorded. 
A number of heavily capitalized companies have been incorporated, 
several deep shafts begun, and exploration work vigorously pros- 
ecuted in various quarters. Precisely what the results will be no 
one can foresee. Several pieces of virgin ground which are now 
being explored have been selected with considerable judgment. In 
a mining boom, however, some properties are inevitably overvalued, 
and it can not be expected that all will prove equally profitable. Nat- 
urally among the conservative men who have developed the present 
district by legitimate mining there is a strong feeling of opposition to 
anything in the nature of booming, which might be prejudicial to the 
permanent prosperity of the camp. In brief, it may be said that if 
no serious decline in the price of silver occurs the prospects for a con- 
tinued increase in the earnings of the camp through legitimate mining 
in the immediate future are most favorable. 


By Alfred H. Brooks. 


The great impetus given to prospecting for gold in Alaska, incident 
to the discovery of the rich Klondike fields, has resulted in the find- 
ing of a number of new and in the further development of several old 
placer districts. The gold output has shown a correspondent increase, 
rising from two and one-half millions in 1897 to about eight millions 
in 1902. While the development of quartz mining in the Pacific 
coast province of Alaska has steadily progressed during this time, 
more especially in the last two years, this development has not as yet 
affected the increase of output to any appreciable extent, for the pro- 
duction of the lode mines has remained practically the same. In 
southeastern Alaska plans have been formulated for extensive min- 

|| ing developments, and in many localities these plans are nearing com- 
pletion; but as yet, outside of the older mines, such as the Tread well, 

i there are few which are actually producing. The increase of 
$5,500,000 during the last five years has, therefore, been chiefly from 
the placer mines. It is to be expected, however, that the quartz 

| mines of southern Alaska, which are being opened up, will within 
the next two years add material^ to the mineral production of the 

Of the $6,000,000 or more a produced from the placer mines of 
Alaska in 1902, about $5,500,000 has come from the Seward Peninsula 
gold fields. The new diggings in the Copper River region have prob- 
ably produced $225,000, and the Cook Inlet region and Porcupine dis- 
trict have probably produced $100,000, while the remainder is from 
the Yukon Basin, chiefly from the new diggings on Glenn Creek. 


Placer gold has a wide distribution in Alaska. It has been found 
near the southern boundary of the Territory, and at various localities 
northward as far as the sixty-eighth parallel of latitude and west- 
ward as far as Bering Strait. Broadly speaking, the producing placer 

a The exact production is not yet known, but is not less than five aud one-half and possibly 
may be six and a half millions. 



mines of Alaska which have thus far been opened up fall within a 
zone having a maximum width of probably 200 to 300 miles, stretch- 
ing northwest from the southern Pacific coast, crossing the Arctic 
Circle, and bending westward to the shores of Bering Strait. It is 
not intended to imply that this zone in its entirety is a gold producer; 
such is far from being the case. This broad belt is simpty drawn 
attention to as having, up to the present time, been the locus of the 
placers of commercial importance. The factors which have deter- 
mined the formation of workable placers are frequently so local in 
their effect that the distribution of the placers is very irregular. 

The field studies lead to the conclusion that the source of the gold 
lies, for the most part, in small quartz veins and stringers which are 
disseminated in metamorphic rocks. Gold also occurs in these rocks 
in the mineralized zone, where there is little if any gangue mineral 
present. Iron pyrite is the commonest mineral found in association 
with the gold in the parent rock. The few observations made indi- 
cate that the gold occurs both free and combined with pyrite. Quartz 
is a common gangue mineral, associated with some calcite. Galena 
is frequently associated with the gold-bearing quartz veins, and chal- 
copyrite and arsenopyrite have also been found. This list of minerals 
will undoubtedly be much extended when closer studies have been 

The studies of the placer fields of Alaska lead to the conclusion that 
the gold in nearly every case lias not traveled far, and can usually be 
traced to a local source. In the gulch and creek placers it can usu- 
ally be traced to a source within basins which they drain. The excep- 
tion is where a change of drainage may have introduced material 
derived from regions outside the creek basin. In nearly all parts of 
Alaska the placer gold owes its present position entirely to the erosion 
of the bed rock in which it was formerly disseminated, and to the sort- 
ing action of water and gravity, which has brought about its pres- 
ent concentrated form. This elementary principle is here emphasized 
because it is not uncommon to find, even among well-informed men, a 
tendency to entirely ignore the very simple facts, and to regard placers 
as the result of glacial action, or as having had a still more cataclysmic 
origin. As a matter of fact, all of the placers of Alaska, except a few 
near the southern coast, are outside of the limit of former glacial 

As has been stated, the gold of the placers has its source in small 
veins and stringers in the bed rock or was disseminated in mineralized 
zones. The facts now obtainable indicate that the outlook for future 
quartz mining in the placer fields of the interior of Alaska is not hope- 
ful. While it is by no means impossible that larger gold-bearing 
veins carrying commercial values may be found, it seems probable 
that most of the placer gold has been freed from bed rock, where it 
was more or less widely disseminated, and subsequently concentrated 


by the sorting action of water. It is not uncommon to hear Alaskan 
prospectors speak of the "mother lode," as if the gold had all been 
derived from one lode or zone of mineralization. Of this there is no 
evidence whatever. In considering the question of quartz veins in 
the placer fields, it should be remembered that the dense coating of 
moss makes bed-rock prospecting difficult and uncertain. 

The auriferous deposits from which the placer gold is derived occur 
in metamorphic rocks of various kinds. They include schists of vari- 
ous types, phyllites, limestones, quartzites, and altered igneous rocks. 
Such metamorphic terranes find a wide development in Alaska, and 
probably occur in a number of different horizons. The study of the 
geology of Alaska has not progressed far enough to permit of correla- 
tions, or of definite statement in regard to the age of the metamorphic 
terranes or their structural relations. The mineralized metamorphic 
beds of southeastern Alaska are probably Mesozoic and older. Those 
of the Yukon are chiefly, if not entirely, pre-Carboniferous, and those 
of the Seward Peninsula are chiefly Paleozoic. Within the zone which 
\ has been designated as the one in which gold placers have been found, 
there are many large areas of these metamorphic rocks. These form 
belts which are not by any means continuous, as they are interrupted 
b ; areas of younger Mesozoic and Tertiary terranes. It has also been 
shown that they probably belong to widely different horizons. Broadly 
speaking, the mineral-bearing horizons of southeastern Alaska can be 
placed in one group, and those of the Yukon Basin and of the Nome 
\ region in another. It will remain for future studies to determine the 
relation between these two belts. 

The age of intrusion of the mineral-bearing solutions is largely an 
unsolved problem. In the coastal belt of southeastern Alaska the 
mineralization took place probably in Mesozoic time, while in the 
Yukon region it was probably considerably earlier. The studies thus 
far made indicate that the mineralization accompanied disturbances 
of the strata, either by deformation or by igneous intrusions, or both, 
which were rather local in their effect. They seem to be closeby 
affiliated to igneous rocks which are everywhere found in the regions 
of mineralization. 

The studies of the alluvial gold deposits of Alaska have shown that 
'mode of formation and concentration are the determining factors 
of the richness of the placer deposits. The writer has elsewhere a 
emphasized this fact in regard to Nome placers, and more recent 
observations convince him that it is also applicable to the gold deposits 
of the Yukon. In the simplest form of placers the gold is washed from 
the parent rock and concentrated in the beds of the streams, mingled 
with other detrital material Such placers have been exploited in 
many localities and have been found to be important gold producers. 

a Reconnaissance ot the Cape Nome and Norton Bay Regions, U. S. Geological Survey, 1901, pp. 


It is probable, however, that nearly all the very rich placers owe their 
origin to secondary concentration. This has been brought about by 
the erosion and dissection of an older placer and the reconcentration 
of the gold contained therein. This process of double sorting is 
probably the chief cause of the bonanzas which are not uncommon in 
the Alaskan placer mines, and will probably also account for those 
irregularities of distribution of the placer gold often within a single 
topographic basin, which are so puzzling to the miner. 

A common form of the enrichment is the dissection of an auriferous 
gravel bench of the slopes of a stream valley by a tributaiy stream. 
This tributary stream carries the gold derived from the bench to the 
main stream, where it is mingled with the gold of the main stream, 
and causes an enrichment of the placers located at and below the 
junction of the two streams. In some instances the gravels of an 
older drainage system, lying often at considerable altitudes above the 
present stream floors, are dissected by the present waterways, and 
the gold contained in the older gravels is thus resorted and recon- 
centrated. Instances of this kind are not uncommon in the Nome 
region, and have been observed by the writer in the Rampart region 
of the Yukon. 

Another form of concentration is that by wave action. In this 
mode of enrichment the waves concentrate the gold which lias been 
deposited in the gravels of the coastal plains. It is in such a manner 
that the marvelously rich beach placers of Nome were formed. 

It seems probable that the study of these questions of reconcentra- ! 
tion will \ct yield important commercial results, even in the better 
known mining districts of Alaska. A practical application of these 
principles would suggest, that the prospector seek to trace old drain- 
age channels and pay special attention to the junction of these with 
the present streams. 


During the last season the climatic conditions in the Seward Penin- 
sula were not, by any means, favorable to a large gold output. While 
there were heavy rains in the fall, the months of July and August 
were very dry, and hence but little sluicing was done. It should be 
noted, however, that the experience of the last three years indicates 
that such meteorological conditions are to be expected every third 
year, if not every other year. The output, therefore, is probably not 
nearly as large as it would have been had water been available early 
in the season. Moreover, much of the development was in the nature 
of dead work in p reparation for extensive operations during the pres- 
ent season. Ditches were dug, roads built, and pumping plants estab- 
lished, which will greatly accelerate the prosperity of the district and, 
undoubtedly, will materially increase its gold production. The prob- 
lem of transportation is still a serious one. Under the best conditions 
the landing of heavy machinery and supplies on the Nome beach is a 


difficult task, but during stormy weather it becomes well nigh impos- 
sible. After heavy machinery has been landed it is still a grave 
problem how to transport it from the coast to the mines. This involves 
the building of roads and, in some cases, the dredging of rivers. 

The region immediately tributary to Nome is better prepared to 
meet these conditions than the more isolated camps. The narrow- 
gage railroad, which runs from the beach to the head of Anvil Creek, 
makes the transportation problem at that particular locality a simple 
one. Roads, moreover, have been built to adjacent creeks from the 
railway, so it is now possible to handle heavy machinery. 

In Anvil Creek probably the most important development was in 
the auriferous gravels of the benches which are found on both sides 
of the valley. This gave a new impetus to mining, for the gravels in 
the creek bed itself were nearly all run through the sluices during 
the two previous years. The high-bench gravels, lying at altitudes 
of 500 to 800 feet above the sea, which were discovered in 1900, still 
continued to be developed. Some of these have great depth, and the 
extraction of the gold has been a difficult problem. 

The so-called "tundra placers," or more properly coastal plain 
placers, still continue to be worked, but their development has not 
been commensurate to their probable importance. It seems more 
than likely that the gravels which make up this coastal plain, in 
many places, car^ workable placers. These may be, in part, old sea 
beaches, or may be the channels of abandoned streams and rivers. 
The problem of handling large quantities of these gravels, which are 
a few feet above and below sea level, has not yet been solved. Most 
of the mining has been confined to shallow pits and trenches, and 
i the operations have been hampered by lack of means to handle the 
surface water. The extraction of the gold has been largely accom- 
plished by use of hand rockers. Winter mining has been carried on 
by means of petroleum and coal-burning steam thawers. With the 
aid of the thawer a pit is sunk to the pay streak, which is followed by 
drifting. The gold-bearing gravel is then hoisted to the surface and 
washed out during the open summer season. It is of interest to note 
that drills have been successfully employed in prospecting for the 
pay streak in the coastal plain gravels. The ground underneath the 
thick coating of vegetation is frozen throughout the year, but thaws 
to a depth of 2 or more feet where this coating is removed. If an 
economic method of mining these gravels in a large way and of 
extracting their gold contents could be devised, large profits would 
undoubtedly be made. 

During the four years which have elapsed since the discovery of 
the Nome placers, the gold seeker has gradually worked his way 
inland, so that now there has been some prospecting done over nearly 
the entire Seward Peninsula. 

During the last season gold mining was going on in the Nome region 
proper, in the Solomon and Eldorado River region, on the streams 


tributary from the south to the Kruzgamepa in the Kuzitrin basin, 
and on streams tributary to the Niukluk. All of these belong to the 
Bering Sea drainage. A number of the streams which are tributary 
to Port Clarence were also found to carry commercial values. Some 
developments of placers on streams flowing northward to the Arctic 
Ocean have been made. None of the northerly flowing streams have, 
as yet, been found to be as rich as those of the older and better known 
districts of the South. Many have, however, produced gold in com- 
mercial quantities, and with further developments will probably 
become important producers. 

What has been said of the Nome region proper applies in large meas- 
ure to the other creeks in the region. In nearly every case where dis- 
coveries have been made the first developments are along the present 
stream channels. When these are worked out, which does not take 
long where the streams are small, the prospectors turn their attention 
to the benches and terraces, and these often yield good returns. In 
some cases placers have been practically abandoned which it seems to 
the writer u\ay still carry gold in commercial quantities. Such may 
prove to be the case in districts like the Kugruk, where the miners have 
worked out the small creek beds and have neglected to thoroughly 
prospect the terraces and benches. Of special interest is the very 
large increase in the output of Ophir Creek, a northern tributary of 
the Niukluk. This stream was one of the first on which gold was 
discovered in the Seward Peninsula, and for several years was spas- 
modically worked, but it is only since the introduction of systematic 
methods of mining and extraction that Ophir Creek has become one 
of the largest producers of the region. It has been estimated that its 
production during the last year was upward of 11,000,000. These 
facts augur well for the future of the Seward Peninsula placer fields. 
It seems probable that there are other streams which may go through 
a history similar to that of Ophir Creek. 


Mining has been going on in the Upper Koyukuk Basin since the 
summer of 1899, and the basin has probably produced from $100,000 
to $200,000 annually. This money has been chiefly taken out of half 
a dozen creeks which are tributary to the Upper Koyukuk about (300 
miles from its mouth. About 500 miles of this distance can be made 
by river steamer. During the last season many miners returning 
from the Koyukuk seemed to be rather discouraged. There seems to be 
no question that there are workable placer fields in the district, but 
the high price of provisions and the short season have prevented many 
of these from being worked at a profit. With water transportation 
within a short distance of these placer mines there seems to be no 
reason why supplies should not be as cheap as on the Yukon. It is 
to be hoped that there will be a reduction in the cost of living, which 


will enable developments to continue in this region, which lies north 
of the Arctic Circle. 

Rampart is a small settlement on the Yukon about 1,000 miles from 
tide water. It has tributary to it a number of camps which have long 
produced some gold, and these are still producing, but not in great 
quantity. The important development of the season is that of Glenn 
Gulch, about 30 miles south of Rampart. Glenn Gulch is tributary to 
Baker Creek, which flows into the Tanana about 100 miles from the 
Yukon. The gulch itself has proved phenomenally rich, and a number 
of other streams in this region give promise of becoming producers. A 
description of this region by Mr. Collier will be found elsewhere in 
this volume. 

The region lying between the Yukon and the Tanana is one in which 
many gold-producing creeks have been found. The earliest discov- 
eries were all made on the Yukon side of the divide, but since 1898 
much prospecting has been done on strems tributaries to the Tanana 
from the north. In only a few cases have these yielded anything of 
value, and, as far as known to the writer, the gold-producing creeks 
are all tributary to the lower 200 miles of the Tanana. Little infor- 
mation is available in regard to this region, but it is stated that consid- 
erable gold has been taken out of streams which flow into the Chena 
River, which joins the Tanana about 300 miles from the Yukon. The 
daity press has recently contained references to phenomenally rich 
placers found somewhere in this region. Pedro Creek, whose loca- 
tion is not given, is said to have been found to be very rich, but these 
rumors have not received confirmation. 

The Birch Creek region embraces the headwaters of the stream of 
the same name, tributary to the Yukon near the Arctic Circle. It is 
one of the oldest placer districts of the Yukon, and still continues to 
produce some gold. With the cheapening of provisions on the Yukon 
the placer mining on some of the older creeks took a new lease of 
life, and such is the case on Birch Creek. Low-grade placers are now 
being developed in the Birch Creek Basin, which could not be eco- 
nomically developed under the old conditions. During the winter of 
1901-2 much mining machinery was taken into the district. It is 
reported that the district contains extensive deposits of low-grade 
placers, which it is proposed to mine with refined methods. 

Fortymile River enters the Yukon 20 miles above the international 
boundary. That its bars carry gold has been known for the last fif- 
teen years, and streams tributary to it have been important gold pro- 
ducers for the last eight years. Many of these streams are still being 
worked, and a few new ones have been discovered. In many instances 
bench claims are being developed. While the gold production of the 
district has not been large, the placers are by no means exhausted, 
and it is possible that important discoveries will still be made. 

During the last year placer mining has been done on a number of 
small creeks tributary to the Upper Yukon. On Boundary Creek, 12 


miles above Eagle, two or three claims were worked last summer. In 
the immediate vicinity, on American Creek and Colorado Creek, tribu- 
tary to Mission Creek, some mining was also done. Seventyinile 
River was also the scene of mining operations, about 15 miles from 
the Yukon, and one hydraulic plant was run. On Fourth of July 
Creek, 50 miles below Eagle, 12 men were at work on claims last 
summer. Three claims on Coal Creek and several on Woodchopper 
Creek, 140 miles below, also received some development of their 


Gold has been found in commercial quantities at two widely sepa- 
rated places in the Copper River Basin. The Chistochina gold field, 
which has produced nearly all the gold of the region, is in the drain- 
age basin of a river of the same name which joins the Copper about 
200 miles from the coast. This district contains several gold-producing 
creeks which can be reached by trail from Valdes. Gold placers have 
also been found at a number of widely scattered localities in the Cop- 
per River Basin. A description of this district by Mr. Mendenhall 
will be found elsewhere in this volume. 


The region lying adjacent to t he head of Cook Inlet and about 
Turnagain Arm has long been a small gold producer. No very rich 
placers have been found, but the accessibility of the district made 
it possible to develop deposits which could not have been worked at 
a profit if located in the interior. Hydraulic mining has been going 
on in a small way lor a number of years, and more elaborate plants are 
being installed. The open season of Cook Inlet comprises about five 
months, which gives the district two months' advantage, or more, over 
that of the interior, or of Nome. The developments of the last year 
have been rather in the way of introducing more refined methods of 
mining rather than of new discoveries. 


This is a small placer-gold district about 30 miles from Pyramid 
Harbor, an embayment of Lynn Canal, whence it is easily accessible 
bj r wagon road. It lies chiefly within the catchment basin of Porcu- 
pine Creek, a small stream which enters the Klehini about 20 miles 
above its junction with the Chilkat. The placers are so situated that 
they offer peculiarly difficult conditions for mining. They occur 
largely in small glacial benches and in the stream bed of Porcupine 
Creek, which has a very sharp rock-cut valley. To work these pla- 
cers it has been necessary to divert the water of the stream by means 
of sluices, to give access to the gravels in the creek bed. This involved 
a large expenditure of time and money. During the last season these 
developments were still going on, and the district has not yet reached 
a large productive stage. 


By Arthur J. Collier. 


Glenn Creek is a small tributary of Baker Creek, a large stream 
which enters the Tanana from the north, about 80 miles from the 
Yukon. The mining camp there located is the site of the most 
important discovery of placer gold made in the interior of Alaska dur- 
ing the seasons of 1901 and 1902. This camp is about 28 miles in a 
direct line nearly due south of the town of Rampart, on the Ynkon 
River. Rampart is the distributing point for Glenn Creek, as well as 
for several older mining camps, and has a population of about 300. 
It is approximately 1,000 miles from the mouth of the Yukon and 600 
miles from Dawson, and can be reached by river steamer from Daw- 
son in about three days, or from St. Michael in about a week. 

The Glenn Creek trail from Rampart follows up Big Minook Creek 
for a distance of 25 miles to its head, then crosses a divide having an 
elevation of about 1,700 feet above the river and drops down to the 
Glenn Creek Camp, which has an elevation of about 800 feet above the 
Yukon. The distance from Rampart to Glenn Creek by this trail is 
about 30 miles, and along it the footing is so soft that two days are 
usually required in summer to make the trip comfortably, either by 
walking or by riding. 

The camp is near Baker Creek, 18 miles from its junction witli the 
Tanana River, at which place a small trading post has been estab- 
lished, which can be reached by steamer coming up the Tanana from 
the Yukon. Baker Creek is navigable for canoes up to within a few 
miles of the Glenn Creek Camp, but the trail from Glenn Creek to 
the Tanana is reported to be very swampy. 

Since only five days could be spent by the writer in making the trip 
from Rampart to Glenn Creek and return, the information obtained 
is necessarily meager and the results are in many respects unsatis- 

"This paper is an abstract of a more extensive report, now in preparation. 

Bull. 213—03 4 49 


The Glenn Creek mining camp lies on the northern edge of an 
extensive lowland basin known as the Baker Flats. These flats, 
opposite Glenn Creek, have a width from north to south of from 7 to 
10 miles, but their greatest extension is in an east-west direction. 
This broad lowland is a depression which has been deeply filled b}^ 
fluvial deposits. Near the mouth of Eureka Creek a prospect hole 
penetrated 65 feet of gravel without reaching bed rock. Along its 
southern margin there is a range of low, flat- topped hills, which sep- 
arate it from the great lowland of the Lower Tanana, and through 
this range Baker Creek flows in a narrow gap. The creek forks just 
above this gap, and the eastern fork, which is the larger, is called the 
Hootlenana, while the western fork retains the name Baker Creek. 
Eureka Creek, which receives a large part of the drainage from the 
northern margin of the flats, enters Baker Creek near these forks. 
A broad bench was observed 100 to 200 feet above the valley level at 
the northern margin of Baker Flat. The gold placers thus far dis- 
covered are confined to a number of small creeks flowing into the 
Baker Flats from the north, and in the immediate vicinity of the Glenn 
Creek camp these streams are known lobe gold-bearing only Avhere 
they cnl across the above-mentioned bench. Several miles to the 
east Pioneer Creek and other tributaries of the Hootlenana are gold 
bearing and it is probable that the gold-bearing belt extends about 
20 miles along the north side of the Baker Flats, but it was notexam- 
ined by the writer except in the immediate vicinity of Glenn Creek. 

Active mining has been in progress on Minook Creek, near Ram- 
part, since 1 sin;, and the creek was probably prospected as early as 
1882. From Minook Creek as a center prospectors have extended 
their search across the divides in all directions. In the summer of 
1901 colors of gold were found on Eureka Creek and mining was 
attempted. Gold in paying quantities was discovered on Glenn Creek 
July 24, L901, by a miner who had a contract for supplying wood at 
the mine on Eureka Creek. Colors of gold, but not in paying quan- 
tities, had already been discovered on Rhode Island and Omega creeks 
in this region. 


In the vicinity of Rampart on the Yukon the bed rock consists of 
a series of volcanic rocks interbedded with siliceous slates and lime- 
stones, called by Spurr the Rampart series. a From fossils collected 
last season near Circle this terrane is believed to be of Devonian age. 

About 8 miles south of Rampart a series of siliceous slates, quartz- 
ites, and schists was found, which continues with more or less varia- 
tion across the divide to Glenn Creek. The relation of the Rampart 
series to this slate and schist series could not be determined with cer- 

o Spurr, J. E., Geology of the Yukon gold district, Alaska: Eighteenth Ann. Rept. U. S. Geol. 
Survey, Pt. II, pp. 155-169. 


tainty, but the evidence indicates that the Rampart series is younger. 
If this be true, the schist series of the upper part of Minook Creek 
and of Glenn Creek may be correlated with either the Fortymile or 
the Birch Creek series of Spurr. No evidence of faulting or intru- 
sions of granite in this series, as indicated by Spurr, a was seen along 
Minook Creek by the writer. The rocks contain small quartz veins 
and stringers in many places, and the debris from them includes peb- 
bles of igneous material other than granite, suggesting the presence 
of intrusions of various kinds. 

A few specimens of the sedimentary rocks have been examined micro- 
scopically. These vary in degree of alteration, in some cases being 
garnetiferous mica-schists, in others quartzites consisting of inter- 
locking quartz grains. All the specimens examined contained more 
or less muscovite. Microscopically these rocks resemble the Birch 
Creek series as described by Spurr. 6 A similar series of schists 
occurring at many places along the Tanana River c has been described 
by Brooks under the name Tanana schists. They outcrop for some 
distance along the Tanana below the mouth of Baker Creek, making 
it probable that the schist series forms a continuous area from Minook 
Creek, 8 miles above Rampart, to the Tanana below Baker Creek. 
These schists have been correlated by Brooks d with the Birch Creek- 
Fortymile series of Spurr. 


Glenn Creek is a small stream, in summer carrying less than a 
sluice-head of water, which rises in a bench on the north side of 
Baker Flats and flows southward to the flats. The creek occupies a 
broad, shallow depression less than 50 feet deep, which makes a hardly 
noticeable break in the topography. 

About one-half mile west of Glenn Creek, Gold Run, a still smaller 
stream, also flows southward to Baker Flats, and about one-half mile 
farther west Rhode Island Creek, a larger stream, has cut a deep 
trench nearly to the local base-level of Baker Flats. About a mile 
east of Glenn Creek, Eureka, a large creek, enters Baker Flats, also 
from the north, occupying a deep, well-marked trench. Each of the 
creeks named above carries placer gold in paying quantities for a dis- 
tance of about a mile, and the bench between Glenn Creek and Gold 
Run also has been found in places to be covered with gold-bearing 
gravel rich enough for exploitation. 

The productive placers of Glenn Creek are confined to four or five 
claims within a mile of the head of the creek. In this distance the 
creek bed has a fall of about 5 feet in 100. 

"Geology of the Yukon gold district: Eighteenth Ann. Rept. U. S. Geol. Survey, Pt III, 

^ Ibid., p. 144. 

cSee Reconnaissance in the Tanana and White River basins, Alaska, 1898: Twentieth Ann. 
Rept. U S. Geol. Survey, Pt. VII, map 24. 

"Ibid., pp. 468 and 469. 


On Discovery Claim, at the edge of Baker Flats and at the lower 
end of the productive part of the creek, a prospect hole 40 feet deep 
failed to reach bed rock. In all the claims above Discovery bed rock 
can be reached at a depth of from 5 to 20 feet. The bed rock is a 
schist, usually called slate by the miners. It ranges in color from 
dark blue to gray, and is often graphitic. It represents a rather 
argillaceous sediment which has been subjected to only a moderate 
degree of metamorphism, sufficient to produce many metamorphic 
minerals, but not to entirely destroy the original structure. This bed 
rock is often cut by stringers of quartz, which are reported to strike 
nearly east and west. These stringers are white and at the outcrop 
are decomposed along with the remainder of the bed rock, which is 
often so disintegrated that it can be shoveled out like fine gravel. 

The width of the pay streak varies from 20 to 60 feet. In one place 
a pay streak 7 feet thick is reported. On the lower claims the pay 
streak is near the surface, so that summer work "by stripping and 
shoveling" is possible. In the Tipper claims the pay streak is found 
below several feet of muck and barren gravel, and is mined with steam 
thawers in winter and washed in the spring. Early in August, when 
the creek was examined, only one claim, known as Claim No. 2, was 
working. The others were shut down because the dumps had already 
been sluiced. On Claim No. 2 miners were shoveling into the sluice 
boxes directly from the pay streak. It was impossible to see the bed 
rock in place, or to see a full section of the gravel from the surface 
down in the deeper workings. The pay gravel consists of angular 
fragments of schisl and a small amount of vein quartz, with occasional 
rounded bowlders of a basic, igneous rock. The gold is not evenly 
distributed in the pay streak. Sometimes the best pay is found on 
the surface of a layer of decomposed bed rock. " Stringers" of gold 
on this bed rock were found carrying $10 to $35 to the pan. These 
"stringers" are lines of gold parallel with the bed rock, which look 
when uncovered as if the rock had been sprinkled with gold. On 
some of the claims values are reported to have been found to a depth 
of 2^ feet in a hard, blocky bed rock. On some of the lower claims 
above the bed rock there is a waxy clay, called by the miners "gumbo," 
which is probably decomposed rock in situ. This clay ordinarily does 
not carry gold, but on one of the upper claims a gumbo ball is reported 
to have carried $1 in fine colors. 

In the summer of 1901, after the discovery, a small amount of gold 
was taken out before the end of the season. During the winter of 
1901-2 a large part of the pay streak was taken out by drifting, and 
the dumps were washed in the following spring. It was estimated by 
a representative of the Eagle Mining Company, which owns several of 
the claims, that the creek had produced approximately $150,000 prior 
to the 1st of August, 1902. 

Gold Run occupies a very slight depression parallel with Glenn 


Creek and about one-half mile to the westward. It is a tributary of 
Rhode Island Creek, into which it empties a short distance above the 
Baker Flats. Claim No. 1 of Gold Run joins with Claim No. 3, Rhode 
Island. The bed rock consists of schists similar to those on Glenn 
Creek. It is described by the prospectors as a "blocky schist." 

The pay gravel consists of angular fragments of this bed rock, which 
show very little if any rounding, such as would be expected in chan- 
nel-washed gravel. The prospecting shows a pay streak from 12 to 
40 feet wide. At the lower end of Claim No. 1 the pay streak, which 
varies greatly in thickness, is divided by a reef. Beyond the limits 
of the pay streak the gravels continue to show prospects of gold. 
The pay streak in one instance is reported to be 3 feet thick and to 
underlie 11 feet of muck and barren gravel. 

Very little gold has as yet been taken from this creek, though the 
prospecting shows a distribution of gold somewhat similar to that on 
Glenn Creek. Preparations were being made for mining on five claims 
on this creek during the winter of 1902-3. During the winter of 
1901-2 the pay streak from an area 15 by 20 feet was mined out. This 
dump has yielded $1,000, but has not all been washed. 

It was proposed to work the creek during the winter of 1902-3 with 
steam thawers according to the following plan: Shafts were to be 
sunk to bed rock, a depth of 10 to 15 feet. From the foot of each 
shaft the pay streak would be drifted on for a distance of about 40 
feet, with a cover of 10 or 11 feet. It was regarded as impracticable 
to drift farther than this on account of the difficulty of carrying steam 
pipes and moving the pay dirt to the foot of the shaft and keeping the 
gangway open. Steam thawers, if properly managed, are more eco- 
nomical in mining frozen ground than the old method of "burning" 
with wood, for the reason that the steam points can be driven directly 
into the ground where thawing is needed, and the pay dirt can be 
mined immediately as it is thawed, whereas by the old method work 
is interrupted while the fire is burning and, at best, a night's burning 
will not thaw more than 1 foot of gravel. 

Gold Run does not carry sufficient water for sluicing after the snows 
have melted in summer, and mining operations will necessarily be 
suspended during the summer months. 

Rhode Island Creek is larger than either Glenn or Gold Run and 
flows in a well-marked valley cut about 100 feet below the level of the 
bench on which the streams described are located. 

The bed rock consists of schists similar to those at Glenn Creek, 
except that it probably contains more graphitic schist than at Glenn 
Creek. The strike of the bed rock is reported to be northwest and 
southeast. Stringers of quartz have not been found in it. 

The gravel consists of more or less angular fragments of schist sim- 
ilar to that at Glenn Creek, except that graphitic schists are more 
common, as well as pebbles and bowlders of igneous rocks. Two types 


of igneous rocks were recognized, one of which is a green, compact 
rock, probably an altered intrusive from the schist series, while the 
other is an unaltered rock of very basic type. The creek has not been 
thoroughly prospected on account of inundation of the prospect holes. 
In the middle of the creek, bed rock has not been reached, but good 
prospects have been found on the rims. At Claim No. 5, about one- 
fourth of a mile above the mouth of Gold Run, a shaft was being sunk 
on the left limit of the pay streak, with a view to draining the bed 
rock with a steam pump. This shaft penetrated, to a depth of 12 feet, 
broken bed rock similar to that on Glenn Creek. The pa}^ streak 
here is believed to be from 50 to 60 feet wide. The average yield from 
a number of pans taken from the pay streak was reported to be 11 
cents. About one-half mile above this place mining was in progress 
on a claim on which the bed rock has been partially drained. The 
claim had not been fully crosscut, but it was believed to have a pay 
streak 60 feet wide. Where it has been prospected the pay streak is 2 
feet thick and underlies 6 feet of muck and barren gravel. Twenty- 
five and 50 cent pans have been obtained from this pay streak. The 
owners of this mine were attempting to work it in summer, stripping 
off the muck and barren gravel and shoveling the pay dirt into sluice 

On the bench between Glenn Creek and Gold Run have been found 
shallow gravels carrying placer gold in paying quantities. It is 
reported that generally on this bench the bed rock is covered by a 
layer of clay, probably derived from the decomposition of the bed 
rock. This clay carries a little gold, the coarsest being near the 
surface. The gold does not extend far up the hill to the northward, 
but can be traced down the hill for several thousand feet. Two 
claims have been located on which gold is found in paying quantities. 
At the upper end of the upper claim the excavation shows 6 inches 
of reddish clay soil overlying 1 foot of gravel consisting of clay mixed 
with small pieces of gray schist similar to the bed rock, but containing 
occasionally large, well-rounded pieces of a basic igneous rock. This 
gravel is the pay streak and rests on bed rock. At the lower end of 
this excavation, about 200 feet from the point described, 4 feet of 
nearly barren gravel wash overlie the pay streak, which consists of 1 
foot of gravel made up of broken fragments of schist bed rock. The 
pay streak has a width of 65 feet. Beyond the pay, however, on the 
south side, a prospect hole was sunk through 4£ feet of broken schist 
debris, showing little, if any, gravel wash. Colors of gold were found 
near the bottom of this hole. On this claim the attitude of the gravel 
indicates a current from the north. 

The lower claim has been prospected at a point one-fourth mile 
southeast of the upper claim. Here prospect holes show the gravel 
to be from 6 to 8 feet thick. The position of the pebbles indicates 
deposition by a current flowing nearly east. The gravel contains a 


few large, round bowlders of igneous rock. It is claimed that this 
gravel from the surface down will pay for washing, and that the pay 
goes into the bed rock to a depth of 1 foot. The pay streak is more 
than 100 feet wide. 

The gold on these claims is comparatively coarse, nuggets as large 
as one dollar being common, though the average pieces are smaller 
than one cent. On the lower claim the pieces of gold are probably 
finer than on the upper. The pay streak at the former place is 
reported to average 6 cents to the pan. The gold nuggets have a 
rough surface, showing that they have not traveled far. 

At the upper claim some sluicing has been done with water col- 
lected in a system of ditches on the surface of the bench. These 
ditches provide a limited amount of water when the snow is going off 
in the spring and after heavy rains in the fall. A ditch about 2 miles 
long has recently been dug to bring water from Rhode Island Creek, 
but except in a rainy season the water from this source will probably 
be insufficient for sluicing. 

Mining has been in progress on Eureka Creek, 1 or 2 miles east of 
Glenn Creek, for the last two years. These mines have not been 
great producers of gold, and the writer was unable to visit them. 
They are reported to be confined to a section of the creek bed 1 mile 
long, and situated nearly opposite the mines on Glenn Creek. 

Good prospects of gold are reported from Omega Creek and McKin- 
ley Creek in this region, and within a few miles of Glenn Creek. 
Their exact location is not known and they were not examined by 
the writer. 

During the last season gold prospects were found on Pioneer Creek 
and several other northern tributaries of the Hootlenana. These lie 
east of Glenn Creek and probably within 10 miles of it. 

One prospect hole was sunk to a depth of 65 feet in the gravels of 
Baker Flats. While no pay streak has been located, colors of gold 
are reported. It will require further prospecting to show whether 
these gravels are workable as gold placers. 

On Minook Creek and on its several tributaries, known as Hunter, 
Little Minook, Rubj^, and Slate creeks, placer mines were in opera- 
tion last summer. 


In the vicinity of Glenn Creek the known gold placers are confined 
to the creeks and benches within an area about 1 mile wide and 2 to 
3 miles long, lying parallel to the north side of the Baker Flats. This 
area coincides roughly with the limits of a broad bench cut on bed 
rock, 100 to 200 feet above the level of the lowland. Two of the 
creeks carrying placer gold rise within this bench, while two larger 
ones are gold bearing only where they cross it. 

The bench generally is covered by a soil derived from the bed rock 


in situ, but in some places bodies of shallow gravel occur. These grav- 
els consist principally of angular material derived from the immediate 
bed rock, but they contain some bowlders and pebbles which have 
undoubtedly been transported. The gravels of the creeks and gulches 
incised in the bench are essentially similar to those found on the 

From the evidence in hand, it seems at least possible that the low- 
land of the Baker Flats is the bed of an extinct lake and that the 
broad bench at Glenn Creek is in part a beach and in part a local 
peneplain produced at the base-level of this lake while it existed. 
The mixture of local and transported material is readily explained in 
this way, either by water action alone or by floating ice. 

The pieces of gold found here are apparently not greatly water- 
worn, and have probably not been carried far from their original posi- 
tion in the bed rock. The bed rock of the gold-bearing area consists 
of schist, belonging to a series which has an extensive distribution 
in this region. On Glenn Creek, however, a system of quartz string- 
ers striking parallel with the longer dimension of the gold-bearing 
area has been noted, making it seem probable that there is a zone of 
mineralization in the bed rock underlying the gold-bearing area. 

The information at present available regarding the geology and 
physiography of this region is too meager to Avarrant any definite con- 
clusions as to the origin of the placers, but the following explanation, 
which is believed to agree with the facts as far as known, is advanced 
tentatively : 

The gold at Glenn Creek has been derived from a zone of mineral- 
ization in the bed rock north of Baker Flats. This zone extends east- 
ward for 10 or 12 miles, to the northern tributaries of the Hootlenana, 
on which placers have recently been found, but is less than a mile in 
width. As the bed rock was eroded, the gold from this mineralized 
zone was concentrated by both wave and stream action along the mar- 
gin of the old Baker Lake. By the draining of this lake the old beach 
was left as a high bench, and the gold from it has been partly recon- 
centrated in the beds of recent streams, to make the creek placers, 
while a part of the original beach deposit remains in the form of 
bench placers. 



By Edwin C. Eckel. 

Field work in the Dahlonega gold district of Georgia was carried 
on by the writer during September, 1902, under the direction of 
Dr. C. W. Hayes. While this field work was merely of reconnais- 
sance character, preliminary to the commencement of folio mapping 
in the area, it developed certain features of considerable importance 
in connection with the gold deposits of the district. A preliminary 
report on this work, with maps, will be issued this } 7 ear as a survey 
bulletin, while a brief statement of the principal results as regards the 
gold deposits has been published in a recent issue of the Engineering 
and Mining Journal. That portion of the present paper which relates 
to the gold deposits is essentially a reprint of that last noted, though it 
contains certain minor changes which affect the wording rather than 
the conclusions. 


Though numerous references to the Dahlonega district are to be 
found in geological and mining literature, the following six papers 
will suffice to give the reader a good idea of the geology and mining 
industr}^ of the region. In 1895 Dr. George F. Becker published, in 
the Sixteenth Annual Report of the United States Geological Survey, 
Part III, pp. 251-331, a valuable account of a "Reconnaissance of the 
gold fields of the southern Appalachians. " In the same year Messrs. 
Nitze and Wilkens published, in the Transactions of the American 
Institute of Mining Engineers, Vol. XXV, a paper on ' ' The present con- 
dition of gold mining in the southern Appalachians." These papers 
are still the best summaries of the geological features of the Appala- 
chian gold fields, and of the relations of the ore deposits. Dr. W. S. 
Yeates published in 1896, as Bulletin 4A of the Georgia Geological 
Survey, a "Preliminary report on a part of the gold deposits of 
Georgia." This volume, by Yeates, McCallie, and King, contains 
much interesting detail concerning both the mines and the mining 
history of the region. The principal advances in Dahlonega mining 
practice since that date are well described in the three following 
papers which have appeared in the Engineering and Mining Journal: 



"The Dahlonega Consolidated Gold Mining Company's plant," by 
W. Colvin, August 17, 1901; "The Crown Mountain gold mine and 
mill," by H. V. Maxwell, September 21, 1901, and "Gold dredging in 
north Georgia," by the same author, November 2, 1901. 


All the rocks of the Dahlonega district of Lumpkin County, Ga., 
are highly crystalline, no series of indisputably sedimentary origin 
occurring in the immediate vicinity. The rocks dip usually at a 
high angle to the east. The strike is, in general, about N. 60° E., 
but at the northern end of Findley Ridge this changes abruptly to 
N. 5° W. In consequence of this change of strike the mines, as 
would be shown on a mine map of the district, occur along two lines 
meeting almost at a right angle. Four rock types occurring in the 
district are sufficiently well marked and areally important to be 
separately described. 

Mica-schists. — For convenience (ho normal rocks of the district 
(excluding the doubtful feldspathic gneisses next described, and the 
granites and diorite, which are undoubtedly of igneous origin) will 
be grouped as mica-schists. More fresh material than is at present 
available must be examined before finer distinctions can be profitably 

Though the decomposed outcrops seem, in general, to be highly 
micaceous, examination of fresh material from several mine tunnels 
seems to show that these "mica-schists" are prevailingly siliceous, 
the mica being highly developed only along joint and shearing planes. 
This highly siliceous character would seem to point toward a possible 
sedimentary origin of at least part of these schists by metamorphism 
from impure sandstones. This question, however, requires much 
further investigation. 

As to age, nothing occurs in the district which can be used as proof 
of the absolute age of these rocks. Lacking such proof, they have 
been generally regarded as pre-Cambrian, but possibly they are of 
Cambrian or Lower Silurian age. As to relative age, it is certain that 
they are the oldest rocks of the immediate district, with the possible 
exception of certain feldspathic gneisses, which are next described 

Feldspathic gneisses. — At several points in the area under consid- 
eration highly feldspathic gneisses occur, notably in one northeast- 
southwest trending ridge, parallel to and some miles east of the 
Chestatee River. These rocks are well banded, some bands consist- 
ing largely of mica and quartz, while others contain much feldspar. 
It is possible that these feldspathic gneisses constitute a true rock 
type, but at present the writer is inclined to believe that the more 
feldspathic bands simply represent granitic material injected into a 
preexisting mica-schist and subsequently sheared with it. In some oi 
the larger bands of feldspathic material this derivation from granite 



seems to be strongly indicated, but farther detailed study will be 
necessary to determine this point. 

Diorite. — Several large bodies of hornblende-schist occur in the area 
under consideration, as well as in adjoining regions to the west and 
south. In general, this rock is a fine-grained, highly sheared horn- 
blende-schist, its schistosity being conformable to that of the mica- 
schists by which it is inclosed. At several points a less metamorphosed 
phase of this hornblende-schist is shown, and it seems certain that it 
was derived from an intrusive diorite. In fresh specimens the diorite 
| is a hard, tine-grained, greenish-black rock, occasionally spotted with 
white feldspar. It weathers to a reddish yellow, and is locally termed 
r brickbat," because, on weathering, it separates into rectangular 
blocks, owing to the presence of three systems of joints. The diorite 
appears to decay more readily than the mica-schists of the region; 
and this ease of decomposition seems to have fixed the location and 
direction of many of the valle3 r s of the area. The hornblende-schist 
is well shown in the court-house square at Dahlonega, and is exposed 
in most of the mines in Findley Ridge. It is an igneous rock, cutting 
the mica-schists; but it was intruded at an early period, and has been 
made thoroughly schistose. In age it is therefore intermediate between 
the mica-schists and the granite next to be described. 

Granite. — A light-colored, coarse-grained granite is exposed at the 
Mary Henry and Bennings mines, and also at several points west of 
Dahlonega. It consists largely of quartz and white feldspar, with 
some biotite. Near the Hand mine it is shown cutting across the 
lamination of the hornblende-schist. It is evidently a comparatively 
late igneous intrusive, having suffered little from shearing or faulting, 
and it may be roughly correlated, in point of age, with the Villa Rica 
granite described by Dr. C. W. Hayes as occurring in the Cartersville 
and Marietta quadrangles. 


As is well known, the earliest gold mining done in the district was 
on the placer deposits occurring along the various rivers and creeks. 
Later the attention of miners was called to the fact that in many 
places the decomposed rocks of the region carried gold, and, accord- 
ingly, sluicing these decomposed rocks came into practice. It was 
soon found, on working through the upper decomposed portions of 
these rocks to the fresh hard rocks below, that the free-milling ore 
found in the upper decomposed rock changed to sulphides in depth. 
In handling these sulphides, stamp milling and amalgamation did not 
recover a sufficiently large proportion of the assay values to justify 
exploitation o f the deposits in hard rock. Chlorination of the sulphides 
was then tried, and has succeeded to a limited extent. 
The placer deposits of the district have undergone treatment many 
Itimes, and in consequence few can now be profitably worked by ordi- 


nary methods. Dredging the river bottoms is, however, still profitable, 
and is carried on as explained by Mr. H. V. Maxwell in the interesting 
paper cited above. In the present article the placer deposits will not 
be further discussed, attention being confined to the gold-quartz veins 
of the district. 

From the point of view of the miner, the gold-quartz veins can be 
separated into two distinct classes, requiring very different treatment, 
both in the mine and in the mill. As is well known, the rocks in this 
portion of the southern Appalachians are very deeply weathered, and 
in many places solid rock does not occur within 100 feet of the surface. a 

In this zone of decayed rock — which on the average includes the 
upper 50 to 100 feet — both the country rock and the vein material are 
disintegrated, and resemble sand or gravel in texture and consistency. 
The two important effects to the miner of this deep weathering are 
that (1) the ore itself is free milling, the pja-ite having altered to 
limonite and released its gold; and (2) the entire mass of material 
can be mined and treated exactly like a thick placer deposit, by 
hydraulic mining. At present hydraulic mining is being carried on 
extensively in the Crown Point, Singleton, and Tahloneka properties, 
the material being washed into sluices by the giants and carried in 
this manner direct to the mills. 

In a proposition of this character such a combination of soft 
material and free-milling ore renders the cost of mining and milling 
very low, and even low-grade ores can be profitably worked. The 
ease of working is, however, partly offset by the fact that a large 
amount of worthless material is washed out by the giants and sent to 
the mill along with the profitable matter. 

As soon as the zone of weathered rock is passed in depth the work- 
ings eneounter solid rock (mica-schists, etc.) containing fairly distinct 
veins of gold-bearing quartz. In this hard material it is possible to 
mine only the vein, thus reducing the handling of worthless material to 
a minimum. This advantage over workings in weathered rock is, how- 
ever, much overbalanced by the two considerations that in deep 
mining in solid rock (1) the cost of mining, per ton of material moved, 
is very much higher than in soft material, and (2) the ores no longer 
carry ai^ very large proportion of free gold, for the pyrite is not 
decomposed. Simple stamping and amalgamation is therefore insuffi- 
cient, and some more expensive process must be substituted. Numer- 
ous "secret processes" have been tried without success. Chlorination 
is now practiced at two plants, but the results are not entirely 

Relations of the gold-ore deposits. — Since the visit of Dr. Becker to 
this district, in 1894, the mine workings have been deepened, and in 

a Becker suggested the use of the term "saprolite" for material such as this, which is the 
product of rock decay in place. Unfortunately "saprohte " has, in the Dahlonega district, been 
adopted by the miners and used in a sense entirely different from that intended by Becker. For 
this reason the term will not be used in the present discussion. 


consequence the relations of the ore deposits to the country rock can 
be studied to better advantage than was possible at that date. The 
most interesting feature developed by the recent work has been in 
relation to the position of the ore deposits. The writer believes it can 
now be accepted as proved that in the large majority of mines in the 
Dahlonega district the more profitable and continuous veins occur 
along the contact between the mica-schists and an igneous rock, the 
igneous rock being either a granite or a sheared diorite. This occur- 
rence was first pointed out to the writer by Gen. A. J. Warner, as 
occurring in the mines on Findley Ridge, and was, on further exam- 
ination, found to be the common type of occurrence throughout the 
entire district. There are, it is true, exceptions to this rule, but they 
are not numerous. In a few cases (Betz mine, etc.) a body of schist, 
not in the immediate vicinity of an igneous rock, is so cut by minute 
gold-bearing quartz veins as to permit the entire mass to be profitably 
mined, while in other instances, as on the Walker property, a small 
but rich gold-quartz vein occurs entirely within the schists. 

The genetic relationships existing between the ore deposits and the 
igneous rock, in the two cases presented (granite and diorite), are of 
very different character. The diorite, as noted earlier in this paper, 
was injected into the schists at a much earlier period than that dur- 
ing which the ore deposits were formed. This is proved by the fact 
that this diorite has been crushed and sheared to such an extent that 
it now appears as a hornblende-schist, the schistosity of which con- 
forms to. that of the normal mica-schists of the region; Avhile the gold- 
bearing veins cut both diorites and mica-schists, and have suffered 
very little from either folding or faulting. The fact that many promi- 
nent gold-bearing veins occur along the contact between the diorite 
and the mica-schists is not due, therefore, to any direct action of the 
diorite considered as an igneous rock, but to the facts (a) that fissures 
are most likely to be formed along the contact between two forma- 
tions differing in hardness and rigidity, and (b) that such fissures, 
minute at first, may have been enlarged by the solution of the 
relatively unstable diorite. 

With regard to those deposits which occur along the contact be- 
tween granite and mica-schist the case is somewhat different. Here 
the intrusion of the granite may possibly have some direct genetic 
connection with the formation of the ore deposits. As noted above, 
the granite is younger than the diorite, cutting the latter at several 
points in the area; it shows little or no banding and has been rela- 
tively little folded. At several points the granite shows slight band- 
ing; at other points minor faults occur within it. Rock movements 
have evidently occurred in the region since the intrusion of the 
granite, but such movements have been slight compared to those 
which occurred in the interval between the intrusion of the diorite 
ind the intrusion of the granite, as is evidenced by the relative amount 
)f shearing shown by the two rocks. 


Age of the gold-ore deposits. — The statement has frequently been 
made that the gold-bearing quartz veins of eastern United States are 
of pre-Cambrian age. While this may be true of certain areas, there 
seems to be little evidence anywhere in its favor. Gold-quartz veins 
occur, on the other hand, in Ocoee (Cambro-Silurian) rocks in Georgia 
and Tennessee, while in New York the three authenticated occurrences 
of gold-quartz veins are all in rocks of Lower Silurian age. 

In the Dahlonega district, even if the country rocks be regarded as 
pre-Cambrian in age (which the writer would not be inclined to be 
lieve), the structural relations of the ore deposits are such as to make 
it certain that they are not pre-Cambrian. It is possible, indeed, that 
the gold-quartz veins were not formed until late in the Paleozoic. 


The most interesting development of the last year in the Dahlonega 
district has been the opening of a large high-grade body of pyrite in 
the vicinity of the town. The occurrence of this mineral in at least 
one bod}^ of workable size has been known for some time, but until 
1902 the deposit had not been opened up sufficiently to justify any 
statement as to its value. During the last year, however, exploitation 
has been carried far enough to permit some idea being formed as to 
the size, uniformity, and grade of the deposit. 

The writer visited the mine in September, 1902, in company with 
Mr. N. P. Pratt, and the present description is the first based on an 
actual examination of the workings, as access to the incline and tun 
nels had been denied to all previous visitors. 

The property of the Chestatee Pyrites Company is located aboul 
6 miles from Dahlonega, in a direction a little north of east. The 
openings are located on the south side of the Chestatee River, aboul 
2 miles west of its junction with the Tessantee. 

The outcrop of the pyrite body has a direction about N. 45° E. 
while it dips at an angle of about 45° to the northwest. On examin 
ing the stratigraphy it is found that in position, form, and associa 
tions this pyrite deposit closely resembles the typical gold deposits 01 
Dahlonega, as described on pages 59 to 61 of the present bulletin 
The pyrite forms a "bedded" vein at this point, being conformable 
to the quartzose mica-schists which overlie it on the west. The rod 
adjoining the pyrite on the east, however, is of the same type of horn 
blende-schist as that described above in connection with the Dah 
lonega gold veins. As with those deposits, the pyrite body occurs 
on the contact between a normal (and possibly sedimentary) mica 
schist and a hornblende-schist, which is a much metamorphosee 
igneous rock of early date. 

The deposit has been thoroughly opened at two points, in additio 
to the pits and trenches which have been dug in order to test the con f 
tinuity of the deposit. The northeastern opening is a tunnel, drivei 


completely through the vein. Two drifts diverge from the tunnel at 
right angles, both being run parallel to the trend of the vein. One 
of the drifts is run on the western or hanging wall of the vein ; the 
other on the foot wall. About 100 feet southwest of the tunnel open- 
ing an incline has been sunk on the dip of the vein, a depth of 60 
feet below the mouth level having been attained at the time of visit. 

These workings, taken in connection with somewhat extensive 
diamond-drill explorations and the examination of natural outcrops, 
would seem to give a fair basis for calculation of the size of the 
deposits. The outcrop extends for a distance of at least 2,000 feet 
along the surface of the ground. Where it has been effectively cross- 
cut by tunnels and incline, the pyrite body is shown to be about 30 
feet in thickness, and trenches and drill borings would appear to 
prove that its thickness at»no point along the 2,000 feet of exposure 
falls below 20 feet. It has been followed down on the dip for a dis- 
tance of almost 150 feet. 

The body of ore seems, therefore, amply large enough for profitable 
exploitation. The operating company has adopted a wise policy in 
this respect, the intentions being to push underground working and 
accumulate a large supply of stock ore before commencing to build a 
treatment plant. 

The ore highest in sulphur occurs in the middle 20 feet of the vein, 
the ores along each wall running lower in sulphur and higher in cop- 
per than the average. Eight carloads of ore were taken from the 
tunnel, thus securing a sample entirely across the vein. The average 
of the analyses is as follows: 

Analysis (average) of Chestatee pyrite. 

Per cent. 

Sulphur 43.52 

Iron '. 39.70 

Copper 3.09 

Zinc '. .72 

Alumina 2. 53 

Magnesia . .43 

Arsenic ■_ None. 

Silica, etc 9.26 

Moisture .36 

| Analyses from the middle 20 feet would show a higher sulphur and 

lower copper content than the average analysis quoted, while analyses 

of the portions of the pyrite body near the walls would give lower 

t sulphur and higher copper. It is probable that this difference in 

a (Composition, which can be noticed even in a hand specimen, will be 

)ti taken advantage of in planning the treatment of the ores. 

In conclusion it is necessaiy for the writer to acknowledge the aid 
received from Mr. N. P. Pratt in this investigation, as the results 
obtainable would have been very slight if Mr. Pratt's assistance had 
been less freely and courteously given. 


By Waldemar Lindgren. 

During the geological mapping of the gold belt of the Sierra Nevada 
much information was gathered relating to the gravel mines, and 
attempts were made to reconstruct the drainage systems of the Neo- 
cene rivers, now represented by detached masses of lava-covered 
detritus, generally at high elevations above the present drainage 
level. Many of these deposits were described in the texts of the 
folios of the gold belt by Mr. II. W. Turner or myself. A very brief 
review of the gravel mines and the channels of the central gold- 
bearing region was given in the bulletin of the Geological Society 
of America.^ None of these publications, however, does full justice to 
the important and interesting problem of the Neocene stream gravels 
of the Sierra Nevada, a subject fascinating alike from the economic 
and the scientific side. Whitney's monograph on this same subject, 
while containing an enormous amount of valuable observations, is 
out of date, because of the careful geological mapping by which the 
country has been covered since that volume was written. 

It seemed advisable, therefore, to collect in one publication the 
principal facts and conclusions regarding the Neocene gravels. Some 
supplementary work was found to be necessary, and four months of 
the season of 1901 — from the beginning of July to the end of October — 
were devoted to the study of the gravels in Butte, Placer, Calaveras, 
and Tuolumne counties. In this work I was assisted by Mr. J. M. 
Boutwell, who made a special reexamination of the Forest Hill divide 
in Placer County. About one month of the summer of 1902 was also 
given to a reexamination of certain deposits in the same county. 

The data which have been brought together are very voluminous, 
and their compilation has necessarily been delayed by the pressure 
of other work, but it is hoped will be finished during the present 
year. It is intended to review briefly the present state of this min 
ing industry, its probable future, its production, and the methods of 
mining peculiar to it. The structure of the Sierra Nevada will be 
described, and some attention will be devoted to the interesting 

a Lindgren, W., Bull. Geol. Soc. Am., Vol. IV, 1893, pp. 257- 


region of the eastern slope. The gravels and the covering volcanic 
material are to he discussed from a geological and petrographical 
standpoint; and much space will he given to the question of the con- 
nection of the isolated gravel areas with Neocene river systems, 
a question which also includes a physiographical description of the 
Sierra Nevada during the Neocene period. As a general result the 
Neocene Sierra Nevada will be shown to have existed at that time as 
a well-defined range, similar to though lower than the present moun- 
tains. The rivers headed near the present divide, and flowing in a 
general westerly direction, emptied into the bay or marshes of the 
Sacramento and San Joaquin valleys. Finally, the probable char- 
acter of the orographic disturbance to which the range owes its 
present elevation will be discussed. 

Bull. 2i:J— 03 5 


By Waldemar Lindgren. 


In L899 a geological reconnaissance was undertaken of the country 
between the Bitterroot Valley in Montana on the east and the Lewis- 
ton Plateau on the west. During the reconnaissance I was assisted 
by Mr. G. W. Stose, of the United States Geological Survey, and Mr. 
H. R. Johnson. 

The region visited is bordered on the south by the Salmon River 
and on the north by the North Fork of the Clearwater. The fertile 
Bitterroot Valley lies at the eastern foot of the imposing range of the 
Bitterroot. This range, which attains an elevation of 11,000 feet, 
westward merges into the great dissected plateau of the Clearwater! 
Mountains, which in turn at their western edge descend rather 
abruptl} 7 to the plateaus of Camas Prairie and Cold Spring Prairie, 
forming part of the great Columbia River lava plateau. This latter 
plateau has a general elevation of 2,500 to 3,000 feet, and is built up 
of horizontal lava flows. 

From great glacial cirques in the western slopes of the Bitterroot 
Range the Salmon River and the several forks of the Clearwater 
River find their way westward in canyons from 3,000 to 5,000 feet deep. 
The canyon of the Salmon especially is remarkable for its great length 
and depth. In the lower plateau country these rivers flow in more 
sharply incised but less deep canyons, which continue to their junc- 
tion with the master stream, the Snake River. 

The area indicated forms a wild and very sparsely populated moun- 
tain region, heavity timbered except on the highest ridges, which 
usually show clear evidence of glacial action. The geology is com- 
paratively simple. The main Bitterroot Range and the larger part of 
the Clearwater Mountains consist of a massive biotite-granite, or, 
defining it more correctly, a quartz-monzonite, which is the northward 
continuation of the great batholith of the same rock which occupies 
so large an area in south-central Idaho. In the latter region this 
intrusive mass is of post-Carboniferous and probably late Mesozoic 
age, and there is no reason to believe that the granite of the Clear- 
water and the Bitterroots is of different age. 


Along the whole eastern slope of the Bitterroot Mountains this 
granite is made schistose by pressure, and forms a zone a few miles 
in width and 60 miles long, following the front of the range. A great 
fault accomimnies this schistose zone, dipping, like the schistosity, 
about 18° E. Otherwise the granite is generally massive and but 
little altered. Several smaller areas of a much older gneiss (pre- 
Cambrian?) occur in the Clearwater Mountains, the largest appearing 
near Elk City. The granite is intrusive in this gneiss. Along Lolo 
Fork at the northern end of the Bitterroot Mountains and near the 
head of the Bitterroot River are areas of quartzites and slates (prob- 
ably of Cambrian or pre-Cambrian age) into which the granite is also 
intrusive. Finally, along the western foot of the Clearwater Moun- 
tains, near Harpster and Mount Idaho, occur slates, limestones, and 
greenstones, which continue, with a northeasterly strike, up from the 
vicinity of the Seven Devils and the Lower Salmon River, and which 
are believed to be of Mesozoic age. Into this series, also, the granite 
is intrusive. 

The main structural features consist of the great Bitterroot fault 
and the uplift of the Clearwater Plateau. There is some evidence of 
comparatively recent movement along the former, although faulting 
is believed to have begun along that line in pre-Miocene times. The 
latter uplift is of pre-Miocene age. 


Character of mineral deposits. — The valuable mineral deposits 
occurring in the area described in this report consist chiefly of Assure 
veins containing gold, together with associated placers derived from 
the disintegration of the veins. Deposits containing lead and copper, 
and usually silver, occur also in several isolated places. Coal of a 
fair quality has also been found in the upper Bitterroot Valley and 
in the lower Clearwater drainage. The lead-silver veins of the Coaur 
d'Alene Mountains are outside of the limits of this reconnaissance. 

Distribution of deposits. — The metalliferous deposits are grouped in 
two belts, the first along the western side of the Bitterroot Mountains, 
chiefly in Montana; the second along the western foot of the Clear- 
water Mountains in Idaho. The deposits of each of these two belts 
are again grouped principally in two regions forming the four corners 
of the mountain area involved, while the central part of the Clear- 
water Mountains appears to be practically barren. The four metal- 
liferous areas are distributed as follows: The first occupies the lower 
Lolo Fork and the northern end of the Bitterroot Mountains; the 
second is found on the headwaters of the South Fork of the Bitterroot 
River and reaches over into Idaho, connecting with the mineral belts 
at Shoup and Gibbonsville ; the third and most important area includes 
Elk City, Buffalo Hump, Dixie, and Florence, as well as numerous 
places along the South Fork of the Clearwater River; the fourth area 


centers in Pierce, but also extends to the headwaters of Lolo Fork 
on the south and to the North Fork of the Clearwater on the north. 

Character of ore, — The primary deposits are almost exclusively 
fissure veins, and with them are associated extensive placers of an 
age ranging from Neocene to Recent. In the northern Bitter root 
Mountains and on Lolo Fork veins occurring in pre-Cambrian (?) 
schists contain chiefly copper, lead, and silver, although some gold is 
also found on Lolo Fork. The Curlew mine, at the eastern foot of 
the Bitterroot Mountains, contains argentiferous galena, and is located 
on a fissure with limestone (pre-Cambrian?) as the foot wall and, 
according to accounts. Pleistocene valley gravels as a hanging wall. 
The mine is not worked at the present time. On the Upper Bitter- 
root River veins cutting porphyry likewise carry chiefly copper and 
silver, while argentiferous galena is also known from the Monitor 
mine, worked on a vein in gneiss on the divide between the Bitter- 
root and Salmon livers. Gold-bearing gravels have been mined for 
many years on Hughe Creek. Southward this belt connects with the 
gold-bearing deposits at Gibbonsville and Shoup. The rocks at Hughe 
Creek and Gibbonsville are pre-Cambrian (?) quartzites and slates. 

West of these districts extends a wide granite area which, as far as 
known, is barren of mineral deposits. There can be no doubt that 
the Clearwater drainage was very thoroughly prospected for placers 
during the early days of mining, but outside of the South Fork very 
little of value lias been found. In the upper part of the mountains 
the glaciation would naturally have swept away any placer deposits 
which may have existed, and in this denuded portion it is not impos- 
sible thai veins may be found. Nothing of much value lias yet been 
encountered. A large vein containing silver is reported to occur on 
Rhodes Peak north of the Lolo trail. Along t he Salmon River the 
conditions are probably more favorable, and prospecting in the iso- 
lated region between Dixie and Shoup might develop something of 

As stated before, the western belt contains chiefly gold; only a few 
scattered copper deposits are known. The placers of Elk City and 
Florence are well known in the history of Idaho and are still worked 
to some extent. Veins which furnish the material for these placers 
are known to occur in all these localities. The principal mining dis- 
tricts are those of Florence, Dixie, Elk City, and Newsome Creek. 
The veins, occurring chiefly in gneiss, are almost exclusively of quart! 
zose character and contain from 1 to 10 per cent of sulphurets, besides 
more or less native gold. The Buffalo Hump district, discovered in 
1898, is situated on the high divide between the Clearwater and the 
Salmon. It contains many strong quartz veins in granite and slate, 
with a varying percentage of free gold and auriferous sulphides. 
Active work is in progress there at the present time. The north- 
western mineral-bearing area contains placers along Lolo Fork, 


Musselshell Creek, and Oro Fino Creek. Many quartz veins similar 
in character to those of the southwestern belt are also worked in 
these districts. They are generally incased in schists, more rarely in 
granite. Veins of sulphide ores containing gold and copper occur 
in amphibolite close to Mount Idaho. 

History and production. — The deposits on the eastern slope of the 
mountains have not proved of great importance and have chiefly been 
discovered and worked at a comparatively recent time. The produc- 
tion of all the mines on this side of the mountains probably does not 
exceed $1,000,000, of which the larger part has been derived from the 
Curlew mine on the north and from the placers of Hughe Creek, 
near the head of the Bitterroot River. The important gold belt on 
the western slope was discovered about 1860 and was very actively 
worked during the following years. Oro Fino or Pierce is reported 
to be the earliest discovery in Idaho. It was found in 1860, and dur- 
ing that season 25 men wintered there. The gravel near Pierce was 
not remarkably rich, but jDaid fairly well in 1861 and 1862. ft In 1874 
Pierce produced $70,000. But soon after this the discoveries in Mon- 
tana drew most of the miners away from this place and in 1867 but 
little mining was going on. Since that time, however, the placers and 
quartz mines have been worked each year, although in a somewhat 
desultory manner. The total production it is impossible to ascertain, 
but probably it has not exceeded a few million dollars. 

During late years placer mining has been carried on both in the 
low-stream gravels and on the benches. There has also been consid- 
erable activity in quartz mining and several small mills have been 
built. The output of the placer mines in 1902 is estimated at $30,000, 
and that of the quartz veins at the same amount. 

Elk City and vicinity proved to be of greater richness. Few quartz 
mines have been worked there, practically the whole production being 
derived from the placers. In 1863 or 1864 the white miners began 
to leave this field, which they considered about worked out, and for 
nearly thirty years there were only two or three of them left in the 
district, which was almost entirely turned over to the Chinese. In 
1892 the white miners began to come back and the Chinese simulta- 
neously disappeared, very few of the latter being left now. A certain 
amount of placer work is still done in this vicinitj^ each year, chiefly 
on bench gravels. The bars of the Clearwater River, which were 
worked extensively during the early days, are still occasionally washed. 
Regarding the total output of Elk City no satisfactory figures are 
available, but not unlike ty the production amounts to about $5,000,000. 

After the first few years of abundant production the output fell 
rapidly. In 1874 Elk City (including Newsome Creek and Clearwater 
station) produced $120,000. From 1882 to 1887 the Elk City district 
produced from $35,000 to $73,000 per annum. During recent years 
the output has again increased, due to the introduction of dredging 

Browne, J. Ross, Report on the Mineral Resources, Washington, 1860. 


and hydraulic operation, and during the last } T ears it has probably 
been from $20,000 to $40,000. Very similar were the conditions 
during later years in Florence, which Camp has been described in a 
previous report." The total output of Florence was, however, consid- 
erably larger than that of Elk City. 

Florence, Warren, and' Elk City are situated in Idaho County. 
According to the Mint reports, this county has, since 1880, produced 
an average of $200,000 per annum, or a total of about $6,000,000. 
Something like one-half of this amount probably comes from Warren, 
leaving $3,000,000 as the production of Florence and Elk City for the 
last twenty years. Pierce is located in Shoshone County. 

It is a somewhat surprising fact that in spite of the recent activity 
in prospecting and working quartz veins the production of Idaho 
County should have decreased during the last few years. The Mint 
reports give for Idaho County the following amounts: 

Precious-metal production of I<l<i/i<> Oounty, Idaho, 1895-1901. 

1895 . . $243, 700 

1896 . . 155, 350 

L897 ---- 230,500 

1898 ... 203,500 

1899 .. 166,000 
1900. ... 152,000 
1901.. 161,500 


Nearly all the vein deposits occur in granite or gneiss, and the pre- 
vailing strike of the veins seems to be in an east- west direction. The 
granite, which is the prevailing rock, represents the northward con- 
tinuation of the greal area of central Idaho north of Snake River. 
Gold-bearing veins occur both within this area and along its contacts 
with the surrounding, older, sedimentary rocks. But for a long dis- 
tance north and south of Salmon River the central large granite areas 
seem comparatively barren, contain ng few deposits, with the excep- 
tion of the Warren camp. 

Within the region here discussed a peculiar relation obtains: The 
large central areas of granite, whether sheared, as along the eastern 
margin of the Bitterroot Mountains, or massive, as is usually the case, 
seem conspicuously barren of deposits. The vein systems appear in 
or close to the four smaller areas of sedimentary or metamorphic rocks 
which are found at the perip ery of the great central granite area. 
This is the case in the quartzitic series of Lolo Fork, in the quartzites, 
slates, and gneisses of the upper South Fork of the Bitterroot, and in 
the old gneiss areas of Elk City and Pierce. While the age of the 
quartz veins is not established beyond doubt, it is probable that they 
were formed during the later part of the Mesozoic. 

"Lindgren, W., The gold and silver veins of Silver City, De Lamar, and other mining dis- 
tricts in Idaho: Twentieth Ann. Rept. U. S. Geol. Survey, Pt. Ill, p. £*1 


By Walter C. Mendenhall. 


The Chistochina gold field is a small placer area in the northwest- 
ern part of the Copper River Basin, Alaska, near the intersection of 
the one hundred and forty-fifth meridian west longitude and the 
sixty -third parallel north latitude. The district is among the foot- 
hills just south of the Alaskan Range, which rises to heights of 8,000 
or 9,000 feet in the vicinity, and serves as a gathering ground for ice 
fields and glaciers, from which torrential rivers flow north to the 
Tanana and south to the Copper. All of the diggings at present are 
on two streams, both tributary to Chistochina River, which flows into 
the Copper. The larger, but not the more important of these, the 
Chesna, is about 12 miles long and empties into the Chistochina 
11 miles below its source, in the Chistochina Glacier; the smaller, 
Slate Creek, which, with its tributary, Miller Gulch, yields nine-tenths 
of the gold of the district, is only -1 or 5 miles long and joins the Chis- 
tochina just as the latter emerges from the glacier. 

The field is usually entered over the military trail from Valdes, the 
nearest seaport, 225 miles to the south, but is accessible from Eagle 
City on the Yukon, about 250 miles north. The lack of navigable 
streams along these routes means that supplies must be transported 
practically the entire distance by pack train or sled, and that there- 
fore the district is one of the most remote and difficult of access in 


Our present knowledge of the geology of the region ma} 7 be briefly 
summarized as follows: 

That part of the Alaskan Range lying immediately north of the 
gold area is made up principally of micaceous schists whose thickness 
and age are unknown. 

Immediately south of the schists and separated from them by a 
fault, whose throw probably exceeds 10,000 feet, is a belt of Permian 

a This paper is an abstract from a more complete discussion which is shortly to appear in a 
j paper entitled: The Mineral Resources of the Moiint Wrangell District, Alaska. 



beds consisting in the upper part of shales and limestones, but includ- 
ing, at lower horizons, tuffaceous sediments and flows, which have 
an aggregate thickness of 6,000 or 7,000 feet. Many basic igneous 
masses occur as dikes or intrusive sheets in these sediments. They 
are especially abundant near the fault. The shales are slightly meta- 
morphosed in the vicinity of Slate Creek and Miller Gulch, where 
some cleavage has developed and a few quartz stringers are found 
cutting them. Eocene lignite-bearing beds occur here and there in 
small patches infolded with the Permian. 

South of the Permian belt occurs a complex terrane of older rocks, 
consisting of conglomerates, quartzites, tufaceous beds and probably 
flows, which appear to be faulted against the Permian. This terrane 
is intruded and altered by dikes and greater masses of granite and 
quartz-porphyry. One effect of the intrusion and alteration is a gen- 
eral impregnation by pyrite, whose oxidation products color the rocks 
rust -red and render them especially conspicuous. 

In addition to these easily separable consolidated rock masses, 
unconsolidated cla}^s and gravels, either primarily or secondarily of 
glacial origin, occur in the vallej^s generally. Near the sources of 
the streams these deposits are confined to flood plains or narrow bor- 
dering terraces, but downstream the area covered by them widens, 
until it merges with the broad drift-filled valley of the upper Copper 
Basin, from whose borders isolated bed-rock areas rise as islands. 

Besides these Pleistocene deposits in the lowlands, a thin sheet of 
cobbles, called by the prospectors the " round wash," is conspicuous 
on the hilltops about the head of Slate Creek, Miller Gulch, and some 
of the tributaries of the upper Chesna. 


Practically all of the gold mined at present is taken from Miller 
Gulch, Slate Creek, and the Chesna River, whose combined yield for 
1 91 >2 is estimated at $225,000. Of this amount, Miller Gulch probably 
furnished $175,000, Slate Creek $30,000, and Chesna River $20,000. 

Miller Gulch, whose yield is thus seen to be much greater than that 
of any other stream in the district, is a steep ravine, less than a mile 
long, tributary to Slate Creek. Its bed, decreasing in width from 200 
or 300 feet near its mouth to but 4 or 5 feet near its source, is sheeted 
over with gravel to a depth of from 4 to 8 feet. This gravel is com- 
posed principally of fragments of the somewhat metamorphosed Per- 
mian shales in which the ravine is cut, but has an admixture of diabase 
and " bird's-eye porphyry " from the intrusives in the shale, and of 
cobbles from the "round wash" which occurs over the tops of the 
adjacent hills. The gold is rather uniformly distributed across the 
gulch, but vertically exhibits the usual concentration near bed rock. 
The richness and shallowness of the gravels, and the steep gradient 
of the stream, giving abundant fall, have made it easy to win the 


gold by simple sluicing methods, and have caused the early develop- 
ment of Miller Gulch to a maximum of production, while the poorer 
or deeper diggings in the other creeks, wherein some instances expen- 
sive plants are required, have been neglected. 

The waters of Miller Gulch, discharging into Slate Creek, carry with 
them some of the gold from the gulch. As a consequence, for a short 
distance below the junction, Slate Creek is rich; indeed, nearly all of 
the gold which it has j^ielded has been obtained here. Above Miller 
Gulch, on Slate Creek, bed rock is not always within easy reach, in 
part because of burial beneath alluvial fans from tributary creeks, in 
part because of irregularities attributable to glacial action; and where 
bed rock is accessible, the yield is not more than $10 or $15 a day to 
the man — about the wage of the district. 

The gravels of Slate Creek contain representatives of all the rock 
types found in Miller Gulch, and in addition a certain proportion of 
material derived from the older quartzites, pyroclastics, and granitic 
intrusives occuring on the south side of its lower valley. 

On Chesna River the diggings are confined to two localities about 8 
miles apart, one near the source, the other near the mouth of the 
stream. The greater part of the work on the upper Chesna has been 
confined to a small tributary called Ruby Gulch. In the upper part 
of this gulch the conditions of accessibility of bed rock and of geo- 
logic relations resemble those of Miller Gulch, but the gravels are not 
so rich, and the workable ground is not so extensive. The operators, 
however, have been able to make satisfactory profits in their work. 
Along the lower course of Ruby Gulch the operations have been rather 
in the nature of development. Bed rock is not reached, the gravel 
being removed by ground sluicing to a clay stratum on whose surface 
the gold is found. The yield here is reported to about pay expenses. 

The valley of the middle Chesna is clogged by glacial deposits, and 
for a number of miles the cursory attempts to find bed rock have not 
been successful, but along the lower Chesna, beginning at a point 
about H miles above the mouth and extending thence upstream nearly 
the same distance, bed rock is within easy reach for short distances 
on either side of the river. There is a shallow canyon a few hundred 
feet long near the lower end of this stretch, and present operations 
are confined to small areas above and below this canyon on the dis- 
covery claim of the district. 

The Chesna has been tapped a few thousand feet above the canyon 
and the water conducted by a ditch along the. south bank of the river 
to a point just below the canyon, where a hydraulic plant has been 
installed with a head of 1 25 feet. 

Although over considerable areas the gravel is but 4 to 8 feet deep, 
it was found impracticable to handle it effectively by ordinary sluic- 
ing methods, because of the presence of large bowlders and much 
water, but those who have installed the hydraulic plant anticipate 


that b} T its use and the construction of drainage ditches the gold can 
be easily and profitably secured. As pans are reported to run from 
1.7 to 5.5 cents each below the canyon, with a maximum yield of $1 
on bed rock, their anticipations seem to be justified. 


The gold from the various streams on which operations are con- 
ducted is rather uniform in form, color, and assay value. It gener- 
ally occurs in flattened scales or grains, and is but rarely rough and 
irregular. It is clean looking and bright yellow in color, and its assay 
values are reported to vary from $18 or $18.50 per ounce on Miller 
Gulch and the upper Chesna to $18.72 on the lower Chesna. 

One-ounce nuggets are not unusual on Miller Gulch, and one piece 
is reported which weighed 4 ounces. On Ruby Gulch the largest nug- 
get found is valued at $12.75, but nuggets are very rare on the lower 
Chesna, the gold being in the form of thin, flat scales. These varia- 
tions in coarseness and in assay value are of the kind which would be 
expected if the source of the gold were in the region near the head of 
Miller and Ruby gulches, where the gold is coarser and the values are 

Some of the operators of the district, admitting that the gold comes 
from the vicinity of upper Slate Creek and Chesna River, maintain, 
with much show of reason, that it is derived there from the "round 
wash," which is particularly heavy about the head of Miller Gulch 
and Slate Creek. It is also present on the divide between Ruby 
Gulch and the next stream east, so that the advocates of this theory 
are able to prove that each stream at present worked to a profit drains 
an area in which the "round wash" is found. They likewise regard 
the smooth surface of the gold as evidence that it is waterworn and 
has therefore been brought from some extraneous source, as is so 
evidently true of the "round wash." 

Some facts, however, are distinctly opposed to this hypothesis, and 
others admit of as ready explanation on another basis. 

A small stream, on which a group of claims known as the "Big 
Four " has been staked, heads opposite Miller Gulch and flows down 
to the Chistochina Glacier. The heaviest deposit of the "round 
wash" known in the region occurs on the slopes drained by this 
brook, which seems therefore to be more favorably situated than 
Miller Gulch, relative to this deposit as a source of the gold; but the 
Big Four claims yield fine gold in moderate amount and are not to be 
compared in richness to Miller Gulch. Furthermore, Ruby Gulch 
and the creek next east of it seem to be equally favorably situated in 
relation to the deposit of the "wash" which occupies the divide 
between them, yet one has yielded operators a handsome return and 
the other is not profitable. 


It is even more significant that the sources of the gold-bearing 
creeks are all within an area whose extent coincides with a region of 
local metamorphism in the Permian shales, and that no other meta- 
morphosed areas of these beds and no other gold districts within 
them are known. Where they have been metamorphosed an incipient 
cleavage is developed and the shales carry a few narrow quartz 
stringers. It is believed that the flat, smooth character of much of 
the gold is sufficiently accounted for by its origin in these shales and 
by its purity and consequent softness, which lead to rapid smoothing 
and polishing with but little transportation. 

It is therefore concluded that the gold originates in these Permian 
beds, and that in its genesis it is related to the local metamorphism 
which they have suffered. It is evidently post-Permian in age, and 
since Eocene beds deposited unconformably upon the Permian are 
but little folded and wholly unmetamorphosed, it is probably also 


By George Otis Smith. 


The three principal gold-mining districts of central Washington are 
included in the Mount Stuart quadrangle. This area has been sur- 
veyed geologically, and the descriptive folio is in preparation. The 
Peshastin placers were discovered in I860 and have been worked inter- 
mittently ever since. The Swank placers have been worked rather 
more steadily since their discovery in 1808. Gold-bearing veins were 
fust located in the Peshastin district in 1873, and in the Swank in 
1881. The mineral veins of the Negro Creek district constitute a con- 
tinual ion of Ihose in the Peshastin district. Swauk Creek is a tribu- 
tary of Yakima River, and Peshastin Creek of Wenache River, so 
that both disi riots are on the eastern slope of the Cascade Range. 

Mining in these districts has been conducted by small owners, and 
it is impossible to secure any definite data regarding production. 
The output of gold of Kittitas County for the years 1884 to 1895, as 
reported by the Director of the Mint, aggregates $764,163. About 
$5,000 of silver was reported from that county for the same period. 
The Peshastin district is now included in Chelan County, but during 
this period was a part of Kittitas County. The years 1892 and 1891 
were seasons of maximum production, and the area would have prob- 
ably steadily increased its output had it not been for the exodus of 
miners to Alaska. In view of the activity in these districts in the 
years preceding 1884, as well as the production of the last seven years, 
it seems that $2,000,000 would be a conservative estimate of the total 
gold production of the districts. In the last five years companies 
with larger capital have purchased the claims of the small operators, 
and mining operations will now be conducted more economically and 
with a probable marked increase in the gold production. 


Swauk district. — The Pleistocene gravels along Swauk Creek and 
many of its tributaries are gold bearing. These alluvial gravels form 
the terraces, which are especially- prominent and extensive at the junc- 
tions of Swauk and Williams creeks and of Boulder and Williams 


creeks. The gravel deposits are from a few feet to 70 or 80 feet in 
thickness, and while red or yellow in color at the surface, the gravel 
is blue below. The upper portions of the gravel are also less easily 
worked, since induration of the gravel has followed the oxidation of 
the cementing material. 

While fine gold is found throughout the gravel deposits at some 
localities, most of the gold occurs close to bed rock and in channels 
other than those occupied by the present streams. Its marked char- 
acteristic is coarseness. Pieces several ounces in weight are common, 
while a number of nuggets weighing 20 ounces or more have been 
found, and one or more nuggets of about 50 ounces have been reported, 
the largest nugget of the district having a value of $1,100. These 
larger nuggets are usually well rounded, but on the tributary streams 
wire and leaf gold is found. The gold is not pure, containing consid- 
erable silver, which materially decreases its value. 

The bed rock, which belongs to the Swauk formation, of Eocene age, 
is usually of a nature to favor the collection of the gold. The 
inclined beds of hard shale form natural "riffles," and from the 
narrow crevices in the shale the best nuggets are often taken. The 
sandstone beds wear smooth, in which case the bed rock is apt to be 
barren. The old channels, both of Swauk Creek and of its tributaries, 
vary somewhat in position from the present course of the stream, but 
only within definite limits. The old valleys and the present valleys 
are coincident, but, within the wide terraced valleys of the present, 
older channels may be found, now on one side and now on the other. 
Thus, on Williams Creek and the lower portion of Boulder Creek, the 
old water course has been found to the south of the present channel of 
the stream, and is in other cases below the bed of the creek. On 
Swauk Creek the deposits worked are above the level of the stream, 
being essentially bench workings. Here hydraulic plants have been 
employed, but elsewhere the practice has been to drift on bed rock. 
While the endeavor is to follow the old channels, it is found that the 
" pay streak " can not be traced continuously. Ground that will yield 

to the cubic yard of gravel handled may lie next to ground that 
does not contain more than 50 cents to the cubic yard. In the last 
few years the operations in the Swauk Basin have been on a larger 
scale. Williams Creek has been dammed and methods have been 
devised to handle the tailings and bowlders on the lower courses of 
Swauk Creek, where the gradient of the valley is low. 

The source of the alluvial gold is readily seen to be the quartz veins 
known to occur in the immediate vicinity. These will be discussed 
in a following paragraph. The noticeable lack of rounding of much 
of the gold shows that it has not be<m transported far, and indeed the 
limited area of the Swauk drainage basin precludes any very distant 
source for the gold. It is only along the Swauk within a few miles of 
Liberty and on Williams Creek and its tributaries that gold has been 


found iD paying quantities, and, as will be noted later, this is approxi- 
mately the area in which the gold-quartz veins have been discovered. 
From the outcrops of these ledges the gold and quartz have been 
detached and washed down into the beds of the streams, where the 
heavier metal soon became covered by the rounded bowlders and 
pebbles with which the channel became filled. The conditions under 
which the gold was washed into the streams probably differed little 
from those of to-day, except that the streams were then filling up 
their valleys. 

Peshastin district. — The gravel deposits in the valley of the Peshas- 
tin are less extensive than in the Swauk district. The alluvial filling 
of the canyon-like valley of the upper half of Peshastin Creek is not 
as deep and does not show the well-marked terraces so prominent in 
the Swauk Valley. The gravel appears to be gold bearing through- 
out, and the gold is quite uniform in distribution. The largest 
nuggets are found on the irregular surface of the pre-Eocene slate 
which forms the bed rock. While the largest nuggets found in the 
Peshastin placers are less than an ounce in weight, and therefore not 
comparable with some of the Swauk gold, the Peshastin gold is fairly 
coarse and easily saved. The gold is high grade, being worth about 
$18 an ounce. 

The principal claims on the creek, below Blewett, are owned by the 
Mohawk Mining Company, which is hydraulicking the gravels with 
water from the upper Peshastin and from Negro Creek. Work which 
has been done on Shaser Creek shows the gravels to be gold bearing, 
and here also the gold is high grade. This fact is interesting, since, 
while the Shaser Creek drainage basin is almost wholly in the same 
formation as that of the Swauk Basin, the gold found in the two 
creeks is quite different, the Swauk gold containing a considerable 
amount of silver. 


Peshastin (list rid. — A few T mines in the vicinity of Blewett have 
been producers for about twenty-five years. The many changes of 
management and methods of operating these properties, however, 
make it impossible at the present time to determine accurate^ the 
character of the ore that has been mined, or to estimate even approxi- 
mately the product during this period. Much of the ore has been 
low grade, and the gold has been extracted by means of arrastres, 
stamp mills, and a small cyanide plant, but not always with very suc- 
cessful results. The small stamp mill first built in this district was 
the first erected in the State of Washington. Another mill, with 20 
stamps, has lately been rebuilt under the Warrior General manage- 

The best-known property in the district is the Culver group, com- 
prising the Culver, Bobtail, and Humming Bird claims, and now known 


as the Warrior General mine. This mine in its geologic relations and 
vein conditions is typical of the mines of the district. The country 
rock is the altered peridotite or serpentine, probably of Mesozoic age, 
which exhibits the usual variations in color and structure. The War- 
rior General and the other mines are located in a zone of sheared 
serpentine, where the mineral-bearing solutions have found conditions 
favorable for ore deposition. This mineral zone has a general east- 
west course, and extends from east of Blewett across thePeshastin, up 
Culver Gulch, and across to the valley of Negro Creek. 

The Warrior General vein has a trend of N. 70° -80° E., and is very 
irregular in its width. In the walls the serpentine is often talc-like 
in appearance, while the compact white quartz of the vein is some- 
times banded with green talcose material. Sulphides are present in 
the ore, but are not all prominent. The values are mostly in free 
gold, which is fine, although in some of the richer quartz the flakes 
may be detected with the unaided eye. 

The workings in this mine consist of a number of tunnels driven at 
different levels into the north wall of Culver Gulch. These follow the 
vein for different distances, the vertical distance between the lowest 
tunnel, No. 0, and the highest opening of importance, No. 5, being 
about 650 feet, and connections have been made between most of the 
levels. The vein is approximately vertical, although it has minor 
irregularities. The quartz is 7 to 8 feet in width in some places, but 
shows pinches in others. In the upper tunnel, No. 5, the ore appears 
to be broken, quartz of the same character as that in the lower tunnels 
occurring here much more irregularly, although the richest ore has 
been taken from the upper workings. Some very rich ore bodies have 
been mined, but they are small and their connections have not been 
traced. The most extensive work has been done from the lowest 
tunnel, and the latest work here shows that the serpentine, which is 
so much broken in many parts of this mineralized belt, is here more 
solid, a remarkably well-defined and regular wall having been followed 
for over 300 feet. 

Other properties in the same zone as the Warrior General are the 
Polepick, Peshastin, Fraction, Tiptop, Olden, and Lucky Queen. 
These have all produced ore which has been worked in the Blewett 

Siuavk district. — The gold-quartz veins of the Swauk are quite dif- 
ferent from those in the vicinity of Blewett. They are in part narrow 
fissure veins of quartz with some calcite and talcose material, the wall 
x)ck being the sandstone or shale of the Swauk formation, of Eocene 
ige, or in some cases a diabase or basalt dike may form one wall. 
Quartz stringers running off from the vein are common, and at one 
ocality thin bands of quartz follow the bedding planes of the sand- 
stone. A peculiar type of vein material is locally termed " bird's-eye " 
luartz. This occurs in several mines, and may be described as a 


friction breccia in which the angular fragments of black shale are 
inclosed in a matrix of quartz and calcite. The quartz shows radial 
crystallization outward from the separated fragments, and often open 
spaces remain into whicli the small crystals of quartz project. The 
walls of such veins are sometimes sharply defined, but in other cases 
many small veins of quartz traverse the shattered wall rock in every 
direction, so as to render it difficult to draw the limits of the vein 
itself. This transition from the peculiar type of vein into the shat- 
tered rock shows the "bird's-eye" quartz to be due to brecciation 
along more or less well-defined zones, followed by mineralization. 

The "bird's-eye" quartz has its gold content very irregularly dis- 
tributed. The values are mostly in free gold, with a small amount of 
sulphurets present. The gold occurs in fine grains within the quartz or 
next to the included shale fragments, and the approximate value of 
the ore may be readily found by panning, while in many cases the gold 
may be seen on the surface of the quartz, in the form of incrustations 
of leaf or wire gold. In a specimen from the Gold Leaf mine per- 
fect octahedral crystals of gold lie upon the ends of the quartz crys- 
tals. The silicification sometimes extends into the county rock, and 
some values are found there. The gold of the quartz veins, like that 
of the gravels, is Light colored and contains a considerable percentage 
of silver. In the Little York this silver is reported as amounting to 
about 20 per cent. 

The quartz veins that have been opened np in the upper basin of 
Williams Creek have a general uortheast trend, being thus roughly 
parallel with the basalt dikes. In the Cougar the hanging wall of 
the vein appears to be a badly decomposed basalt dike, while in the 
Gold Leal' one vein is wholly in sandstone and shale and another in a 
large diabase dike. The relation of the veins to the dikes is there- 
fore not const ant, but it may be noted that the fractures which have 
been filled by the vein material are usually approximately parallel to 
the fractures in the vicinity which have been filled by the intrusion 
of basalt. That there has been more than one period of fracturing, 
and that the period of mineralization was not exactly contempora- 
neous with the time of igneous intrusion, is shown by the occurrence 
of veins cutting the dikes themselves. It is quite probable, however, 
that the two processes occurred within the same geologic period and 
that the ore-bearing solutions derived their heat, and possibly their 
mineral content, from the intrusive and eruptive basalt of the area] 

A number of quartz veins on Swauk, Williams, Boulder, and Baker 
creeks are being prospected at the present time, and in view of the 
richness of the alluvial gold which has been derived from the veins 
in this vicinity it would seem that the prospecting is well warranted. 



By J. E. Spurr. 


Tonopah is situated in central Nevada, in a range of low, scattered 
volcanic mountains which form the southern continuation of the San 
Antonio Range, and which themselves, on the south, pass into the 
Ralston Desert. It lies about 60 miles east of Sodaville, on the Car- 
son and Colorado Railway, whence it can be reached by stage, and 
also about the same distance from Candelaria, on the same railroad, 
from which point another stage line runs. It can be reached by a 
long carriage drive from Belmont, the county seat of Nye County, 
and roads radiate from it to the other important points in the State. 

This region has been known for a long time and has not been more 
inaccessible to prospectors than other similarly situated districts in 
the desert region. A few years ago ore was discovered in the Tona- 
pah range of hills, some miles south of the present camp. This 
locality was called the Southern Klondike and attracted a considera- 
ble number of prospectors. Among others, Mr. James Butler, a resi- 
dent of Belmont, on his way from that place to the Southern Klondike 
camp, passed over the site of the present Tonapah district. Perceiv- 
ing a great deal of white quartz scattered upon the ground, he picked 
up some pieces and took them to an assayer in the Southern Klon- 
dike; but as they did not look particularly promising they were 
thrown aside and not tested. On his return trip, however, Mr. But- 
ler picked up some more samples and carried them to Belmont, 
where he turned them over to Mr. Oddie, a young lawyer and miner, 
offering him a share of the claims if he would pay for the assay. Mr. 
J Oddie sent the samples to an assayer and promised him half of his 
[share if he would assay them. When the assays came back, as they 
[did after some delay, they were found to be astonishingly rich, and 
|Mr. Butler and his wife started out from Belmont and located their 
iblaims in due form. 

It is known from certain monuments composed of piled-up quartz 
[fragments that Mr. Butler was not the original discoverer, but who 
phis was remains a mystery. The monuments are evidently old. 

" A more detailed report on this area is in preparation. 

Bull. 213—03 6 81 


Present developments. — The development of the new camp has been 
astonishingly quick. The property was offered to and refused by 
Western capitalists for a very small sum when the exploration pits 
were only down a few feet, the reason for refusal being that the rich 
ores were probably only superficial Later on, when the developments 
had progressed a little further, the property was acquired at a larger 
figure by a Philadelphia company. They adopted the principle of 
leasing to develop their mine. The leasers set to work vigorously and 
in a short time a number of them had extracted sufficient rich ore to 
make fortunes of various sizes. Being satisfied with the prospects 
of the mine, the company gave out no more leases, but took the 
management into their own hands as soon as possible. From that 
time to the present the chief mine, the Mizpah, has been conducted 
with a view to developing the resources as a basis for future opera- 
tions rather than to extracting ore. A number of fine shafts have 
been sunk, and the country has been and is being thoroughly investi- 
gated, both by drifts along the principal vein and by crosscuts. 

Outside of Mr. Butler's original local ions, which became the property 
of the Mizpah Company, and those immediately adjoining, numerous 
other locations were soon made, until now it is doubtful if there is a 
bit of unclaimed ground within several miles. Soon a number of other 
shafts were sunk, although with few or no surface indications. The 
Fraction shaft, not far from the Mizpah, passed downward through a 
body of cap rock of volcanic nature and found mineral veins contain- 
ing large values in some places. Later on, the Mizpah Extension, on 
the other side of the Mizpah, encountered veins of the same system 
after passing through several hundred feet of cap rock. This has 
encouraged other companies to sink shafts through the capping, and 
many of them are down several hundred feet. Among these may be 
mentioned the Ohio Tonopah, the California Tonopah, the Montana 
Tonopah, the New York Tonopah, the Tonopah City, and the MacNa- 
mara. Work is being pushed vigorously, and before long much of the 
underground composition of the district will be shown up. 


The topography around Tonopah is not one of great relief. A series 
of low and small, detached, and irregular mountains surrounds the 
town. The mountains are of volcanic origin, but have been worn 
down by erosion so that they have rugged and characteristic erosion 
features. The town itself lies in a shallow valley or wash, and from 
here a long, gentle wash-slope comes down to a nearly level desert 
valley both on the east and on the west. 


A f ew miles north of Tonopah ancient limestones, probably Cam- 
brian or Silurian, outcrop, and similar limestones are found some 
miles to the south, in the southern Klondike district. In the imme- 


diate vicinity of Tonopah, however, only volcanic rocks are found. 
These consist of flows, breccias, and derived tuff and ash accumula- 
tions. These volcanics are probably of Tertiary age, and represent a 
number of successive flows, with intervening showers of ash and 
breccia, and erosion intervals. On account of the confusion of these 
volcanics the relative order of eruption has not yet been certainly 
made out, but at the present time the sequence is considered to be 
somewhat as follows : 

1. Earlier andesite (latite?). 

2. Earlier rhyolite and breccias. 

3. Later andesite. 

4. Erosion interval. 

5. Volcanic breccias and flows. 

6. Great water-laid tuff formation containing infusorial silica. 

7. Later rhyolite. 

8. Latest lava flow (tlacite?). 

The oldest volcanic rock is the earlier andesite, which is commonly 
called the lode porphyry. Although originally an andesite, it is now, 
so far as examined, everywhere almost entirely decomposed and trans- 
formed into secondary products, consisting of fibrous muscovite, 
secondary quartz, pyrite, chlorite, iron carbonate, etc. In its present 
decomposed form, therefore, it is not an andesite, although originally 
one. Some forms of the altered rock are what has been described by 
early writers in this region as propylite; but Dr. G. F. Becker showed 
that the propylite of the Comstock region was an altered andesite, 
just as it is at Tonopah. The Tonopah rock and the Comstock rock 
are, as a matter of fact, apparently similar in composition, and prob- 
ably are also in point of age. 

The important veins of the district occur only in this earlier andes- 
ite or lode porphyry, and not, so far as yet found, in the later rocks. 
So it seems that the mineralization must have followed the first 
andesitic eruption. Therefore it is that the overlying volcanics do 
mot show these veins, and constitute cap rocks which overlie them, 
and which must be pierced in order to reach the lode porphyry and 
its associated ores. 

The ores are in the form of quartz veins of the kind which have 
been described by some writers as the noble quartz formation — that 
lis to say, the quartz constitutes almost the whole of the ore, and the 
valuable metals are very finely distributed, so as to appear barely or 
jnot at all to the naked eye. There is also a very small quantity of 
the less valuable metallic minerals. Silver is found in the form of 
chloride, sulphide (argentite), and ruby silver. Gold has been seen 
fin a free state in the ore. 

The deposits are well-defined veins, maintaining a nearly regular 
strike and dip. The principal veins average a few feet in width. 
,rhe chief trend of the veins is east and west, but in the developed 
Region the different veins diverge regularly from one another, so that 


they lie like the spokes of a wheel. Where they come together near 
the center from which they radiate, they join and fork in the manner 
of linked veins. There is evidence to show that these veins, although 
having the characteristics of true fissure veins, have formed along 
zones of fracturing or sheeting in the lode porphyry, and have replaced 
the porphyry in these zones to a more or less perfect extent. There- 
fore, in passing along the veins, at some places they are found to 
consist of pure quartz, in other places chiefly of highly silicified 

Probably contemporaneous with the mineralization has been the 
extreme alteration of the original hornblende-andesite. This altera- 
tion, together with the subsequent weathering, has produced a great 
variety of appearance in the originally nearly uniform rock. Pyrite 
and iron carbonate have been derived from the decomposition of 
the dark minerals (mica, hornblende, and pyroxene) of the original 
andesite. The decomposition of the feldspars and other minerals has 
furnished an abundance of secondary quartz. In some of the most 
decomposed and altered phases, therefore, the appearance is that 
of a highly siliceous, nearly fresh rock, apparently a rhyolite. This 
is one of the common phases in the vicinity of the Mizpah. Other 
phases are soft and light colored; others comparatively firm and dark 
colored, with abundant pyrite. 

The mass of Oddie Mountain is made up of a true rhyolite, later in 
point of age than the lode porphyry and containing, so far as yet 
known, no veins belonging to this period. It is also somewhat decom- 
posed, but not nearly to so great an extent as the lode porphyry. 

The later andesite occurs on Mizpah Hill in the same localities as 
the earlier andesite, and between certain phases of the two rocks it is 
often difficult to distinguish. Originally they both had nearly the 
same composition, and they have often been altered in nearly the same 
way. The large feldspar crystals of the later andesite, however, are 
generalty of greater size and more thickly set together than in the 
earlier andesite or lode porphyry. The mica or biotite crystals of the 
later andesite are also frequently intact and can be recognized in the 
hand specimen, while the micas of the older andesite have generally 
completely disappeared. The later andesite is also apt to be more 
highly colored in its present state than the earlier rock. It has often 
assumed various shades of purple and green, which led the writer to 
give it the field name of "purple porphyry." This later andesite is 
found in dike form, cutting the earlier eruptives, and also occurs in 
the form of extensive flows. It was possibl} 7 accompanied by breccias. 

About this time, and perhaps succeeding the later andesite, came the 
formation of the great series of stratified white volcanic tuffs which I 
is exposed around Tonapah. At one point a thickness of several 
hundred feet is shown. The perfect stratification indicates that this I 
formation was laid down in a lake which must have been of consider- 


able depth. Part of the formation is made up entirely of myriads of 
the microscopic siliceous shells of infusoria. Since the lake epoch, 
however, erosion has been considerable, leaving the tuff forming some 
of the low mountains in the vicinity. 

There was apparently a later flow of rhyolite, in general compo- 
sition like the earlier flow, but distinct in point of age and now 
consequently fresher in appearance. Some mineralization followed 
this flow, producing veins and coatings of chalcedony, iron car- 
bonate, iron oxide, etc., along the contact and in crevices in the 
adjoining rocks. These veins also carry small amounts of gold and 
silver, but have no connection with the earlier, more important min- 

Latest of all was the eruption of lava which forms most of the 
mountains around Tonopah. The nature of this lava is dacitic. a 

The writer spent two months in the autumn of 1902 making a pre- 
liminary investigation of the Tonapah mining district. Mr. W. J. 
Peters, of the topographic branch of the Survey, has just finished 
making a careful map of that portion of the district which is of great- 
est economic importance. This map is on a scale of 800 feet to the 
inch. The writer will continue and finish his investigation in the 
spring of 1903; will map the different geologic formations, and will 
prepare a report showing the relation of the ore deposits to the 
different rocks. 

There are several perplexing problems which are to be worked out 
in the district. One of the most important is the location, as nearly 
as possible, of the underground course of the upper contact of the 
earlier andesite or lode porphyry, so that mining men may know 
approximately where to sink their shafts with the chances of reaching 
the porphyry soonest. Another difficult problem will be to ascertain, 
if possible, the probable course and extension of the vein systems of 
the district. A third problem, perhaps the most important of all, is 
the study of the distribution of the rich ores within these veins. 
These questions will be dealt with in the forthcoming report. 


The writer made a number of brief examinations of certain ore 
deposits in the vicinity of Tonopah. 

Silver Peak district. — A slight examination was made of the prin- 
cipal mine in the Silver Peak district. This mine is on quartz veins 
of great thickness and surface extent, which hold relatively small 
quantities of gold. The veins have been worked near the surface for 
many j^ears past, although lately activity has not been very great. It 
is claimed that three-quarters of a million dollars' worth of ore has 
already been extracted. There are two parallel veins lying close to 

« Dacite is quartz -hearing andesite. 


one another, both of unusual size. The work which has been done 
lately is purely in the nature of development, and consists in running 
a tunnel to tap the vein at a lower level than has been reached in the 
workings from the surface. This tunnel has reached and explored 
the vein for some distance, and it is claimed that careful assays show 
that the values are as good there as nearer the surface. Taken in con- 
nection with the vast quantity of ore, these values are sufficient to 
make the mine a great low-grade proposition, provided that power, 
water, etc., can be procured with sufficient cheapness to leave a 
margin of profit. There is, of course, a scarcity of water in the Sil- 
ver Peak region, but hot springs occur in the valley below Silver 
Peak, and electrical transmission of power from the streams of the 
neighboring White Mountain Range or from the Sierras is one of the 

The veins lie in close connection with a mass of granite which is 
apparently intrusive into the ancient limestones, and it is believed 
that the vein has a close genetic relation to this granite. This point 
will be investigated more thoroughly the coining summer, and is an 
important one, inasmuch as it bears strongly upon the question of the 
persistence of the vein and its values in depth. 

Southern Klondike district. — This district has alread} r been referred 
to as lying '.» or 10 miles south of Tonopah. Its geology in general 
and its ore deposits are of an entirely distinct class from those at the 
first-mentioned camp. Topographically the country is much the same 
as at Tonopah, there being a number of low irregular mountains 
which do not rise greatly above the level of the desert vallej^s on each 
side. The district is surrounded by volcanic rocks, chiefly rhyolites, 
and these rhyolites occupy a portion of the district itself. The rest 
of the district is occupied chiefly by Paleozoic limestones, probably 
Cambrian or Silurian. 

There are two divisions of the Klondike camp — Klondike proper and 
East Klondike. In the former, which is the older camp, there is a 
long dike-like intrusion, in the limestone, of a siliceous granitic rock, of 
which some specimens examined seem to consist chiefly of quartz and 
muscovite, and are evidently closely related to similar rock described 
some years ago from Belmont, Nev., by the writer, and shown to be 
the same as the beresite of the Ural Mountains in Russia. The Bel- 
mont district lies nearly due north of Tonopah and Klondike. Close 
to the contact of this granitic mass with the limestone, and following 
the contact closely for a mile or more, is a quartz vein which at the 
surface carried scattered high values of silver and gold. The values 
were chiefly in silver chloride. Some parts of the vein contain galena, 
which is segregated in bunches. At the very contact of the granite 
or beresite with the limestone there is in i>laees a deposit of hard, 
nearly black hematite, which is seen to have been derived from the 
oxidation of original pyrite, which accompanied the contact in the 


granite, and probably also in the limestone. Deeper exploration of 
these deposits has shown them to be almost entirely barren. In the 
main vein the quartz has continued in full strength downward, but 
the values have become insignificant. Similarly, a tunnel driven to 
the contact of granite and limestone, beneath the iron-ore deposits 
of the surface, shows nothing. These facts indicate that w r e have 
here an excellent example of the concentration of values near the 
surface, in the extreme upper part of the zone of oxidation, by the 
same surface waters that have operated to wear away the district and 
produce its topographic relief. 

At East Klondike the same limestone is cut into and surrounded 
by rhyolite, which has produced almost exactly the same contact phe- 
nomena as the granite at the Southern Klondike. Indeed, the two 
rocks are probably closely connected in point of composition and ori- 
gin. At East Klondike the contact of the rhyolite is marked by a 
broad belt of jasperoid, and similar belts are found farther away in 
the limestone, along lines of original easy circulation for waters. The 
chief vein near this contact consists largely of white quartz, but is 
evidently due to the same solutions which produced the dark-blue 
jasperoid. The vein and the metallic contents are exactly like the 
vein at Klondike. In some places high values have been taken out 
of the vein, but exploration has not been pushed far enough to show 
the character of the vein in depth. Along certain fracture systems, 
which are later than the vein and have broken and displaced it to 
some extent, there seems to be a segregation of higher values, accom- 
plished probably by more recent circulating surface waters. 

Gold Mountain district. — This lies nearty half way between Tonopah 
and Klondike and is in the stage of development. Gold Mountain is 
composed of rhyolite, both in solid flows and in consolidated tuffs and 
breccias. Through these rhyolites run strong and persistent veins of 
quartz and delicately colored chalcedony veins, sometimes containing 
pyrite. In some parts of some of these veins, especially in the oxi- 
dized portions, rich assays have been obtained. The mineralization is 
probably of a later date than that which has produced the ores at 
Tonopah, but may be of the same age as those at Klondike, although 
the ore deposits themselves are of a different character. 

Hennepah district. — The Hennepah district was at the time of the 
writer's visit very young and so little developed that not much could 
be seen. It lies nearly east of Tonopah, on the other side of a broad 
desert valley. The rocks of the district are volcanic, bearing a gen- 
eral resemblance to those at Tonopah. The veins also, of which two 
or three were observed, are of the same general character as the Tono- 
pah veins, although so far they have not been shown to have anything 
like the strength of the better class of veins in the older camp. 


By Walter Harvey Weed. 

The Marysville mining district is the most important producer of 
the precious metals in the State of Montana, one mine alone having 
yielded a total of nearly 115,000,000, while the aggregate production 
of the mines of the district has been roughly estimated at double that 
figure. The district is located 18 miles northwest of Helena, and is 
reached by a branch railroad running north from the main line of the 
Northern Pacific Railway. The Great Northern Railway runs a few 
miles east of the district. The district comprises a mountainous 
country traversed by the continental divide, a few of the mines being 
on the western or Pacific slope. The development of the region began 
in the early seventies, the rich placer diggings of Silver Creek leading 
to the discovery of the ledges which have made the region famous. 
Although within its area there have been many productive mines, as 
a rule the values have been in rich ore shoots, and after these were 
exhausted the property has been abandoned. The most famous prop- 
erty of the district is undoubtedly the Drumlummon mine, which has 
yielded a larger amount of gold than any other mine in the State. A 
later discovery, the Bald Butte mine, has been steadily worked for 
many years, one year's dividends approximating the total amount of 
capitalization. At the present time the Bald Butte is the only mine 
actively worked, and the district therefore may be said to be in 

Geologic features. — The Marysville district consists of a central 
mass of granitic rock surrounded hy slaty shales and thin-bedded 
argillaceous sandstones. The granitic rock is probably part of the 
great granite area which underlies so much of the western portion of. 
Montana. The rock is technically a quartz-diorite of even and coarse 
grain, showing little variation in appearance or mineralogic develop- 
ment. The shaly rocks into which this diorite has been intruded 
belong to the Belt terrane and consist of a thickness of many thou- 
sand feet of thin-bedded argillaceous rocks. Near the granite con- 
tact these rocks are altered to hard and dense hornstones, while 
farther away they show a slaty fracture, the laminae corresponding, 
however, to the bedding planes. Outside of the district proper, to 
the south and west, the Cambrian and later sedimentary rocks 
appear. There are a few dikes of acidic porphyry and of dark trap 
rocks which cut the granite near its borders and penetrate the sedi- 
mentary rocks. These are especially abundant near Bald Butte. 


The veins. — The geologic map which was rjrepared in the summer of 
1901 shows that the veins occur either in close proximity to the granite 
contact or adjacent to the intrusive dikes. The vein systems devel- 
oped near the town of Marysville show three distinct directions. The 
northeastr-system, exemplified in the North Star vein, cuts through the 
sedimentary rocks and into the granite. The northwest system is 
prominent in the granite area, but has not produced any large ore 
bodies. The north-south system is the one to which the Drumlum- 
mon lode belongs, and at the Drumlummon mine is parallel to the 
granite contact. The ores occur in fissure veins, showing a distinct 
quartz filling, either as a solid mass or enveloping angular fragments 
of the country rock. The Drumlummon vein is the best known and 
may be taken as a type. It is a fault plane with white opaque quartz 
inclosing angular fragments of black, green, and drab slates, which 
are sometimes distinct and unaltered and at others have been much 
decomposed. Where the ore bodies are found the replacement has 
been complete and the former presence of the fragments is only recog- 
nizable by the outlines of the banded quartz. The vein has distinct- 
walls, which are rather wavy and vary from 2 to 20 feet apart. South- 
ward the Drumlummon vein itself splits into several branches. It 
has been developed for a distance of about 3,000 feet horizontally and 
to a depth of 1,600 feet, but no ore was found below the 1,000-foot 
level. This vein, which is the largest and the most productive in 
the district, consists in its lower levels of a mass of angular rub- 
bish, derived from the walls of the fissure, and in places cemented by 
quartz, in other places still retaining its original character. Com- 
pared with the Empire and other veins, it is much more extensive, 
both laterally and vertically, and the values have gone deeper. In 
general it may be said that all the veins of the district carry rich 
ores in bonanzas and ore shoots within the first 200 feet from the 
surface, but that in depth the ores rapidly decrease in value until 
the vein is no longer workable. It may also be said that the ore 
shoots were well defined, and the intervening vein matter barren 
and unworkable. The pitch of the ore shoots conforms to the usual 
habit, dipping to the right when looking down the dip of the vein. 
The ores consist of sulphides and sulphantimonides of silver, with 
gold aggregating 60 per cent of the total value. In the upper levels 
the ore is somewhat oxidized, and in the ore shoots of the Drumlum- 
mon mine carried extremety high values. In the Bald Butte mine 
the larger veins are clear instances of filled fissures with but little 
evidence of replacement, and the new vein recently opened contains 
a streak a few inches wide of soft ore whose value is extremely high. 
Recent attempts have been made to open up some of the large prop- 
erties which have been idle for many years. The Empire mine, par- 
ticularly, has been opened and new development work begun. There 
seems reason to believe that with the low rates of treatment now 
available many of these properties may be reopened and worked. 


The following list includes the more important publications by the 
United States Geological Survey on precious metals and mining dis- 
tricts. Certain mining camps, while principally copper producers, 
also produce smaller amounts of gold and silver. Publications on 
such districts will be found in the bibliography for copper, on page 
186. For a list of the geologic folios in which gold and silver 
deposits are mapped and described, reference should be made to the 
table on pages 11 to 13 of the present bulletin: 

Becker, G. F. Geology of the Comstock lode and the Washoe district; with 
atlas. Monograph III. 422 pp. 1882. 

Gold fields of the southern Appalachians. In Sixteenth Ann. Rept., 
Pt. Ill, pp. 251-331. 189.-). 

- Witwatersrand banket, with notes on other gold-bearing pudding 
stones. In Eighteenth Ann. Rept., Pt. V, pp. 153-184. 1897. 

Reconnaissance of the gold fields of southern Alaska, with some notes 
on the general geology. In Eighteenth Ann. Rept., Pt. III. pp. 1-86. maps. 1897. 

Brief memorandum on the geology of the Philippine Islands. In Twen- 
tieth Ann. Rept., Pt. II, pp. 3-7. 1900. 

Brooks, A. H. Reconnaissance in the Tanana and White river basins, Alaska, 
in 1898. In Twentieth Ann. Rept., Pt. VII, pp. 429-494. 1900. 

Reconnaissance from Pyramid Harbor to Eagle City, Alaska. In 
Twenty-first Ann. Rept., Pt. II, pp. 331-391. 1901. 

Preliminary report on the Ketchikan mining district, Alaska. Profes- 
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Of the metals here grouped only two — quicksilver and chromium — 
are at present worked on a large scale in the United States. The 
papers on tin and tungsten presented below are reprints, in slightly 
condensed form, of reports which have recently appeared in Survey 
publications. A description of the Rambler copper mine, in Wyoming, 
is included, as platinum has recently been discovered in the ores of 
this mine. 


By Alfred H. Brooks. 

White studying the gold placers at York, on the Seward Peninsula. 
Alaska, the writer's attention was called to the occurrence of stream 
tin (cassiterite) in the placers. The stream tin was found at two 
localities in the region. The first is on Buhner Creek, a westerly 
tributary of the Anikovik River. The mouth of Buhner Creek is 
about 3 miles from Bering Sea. The occurrence is best located by 
stating that it lies about 10 miles east of Cape Prince of Wales, and 
very near the northwestern extremity of the continent. On Buhner 
Creek 2 to 3 feet of gravel overlies the bed rock, which consists of 
arenaceous schists, often graphitic, together with some graphitic 
slates. The bed rock is much jointed, the schists being broken up 
into pencil- shaped fragments. They strike nearly at right angles to 
the course of the stream and offer natural riffles for the concentration 
of heavier material. A hasty reconnaissance of the drainage basin 
of this stream, which includes not more than a square mile of area, 
showed the same series of rocks throughout its extent. At a few 
localities some deeply weathered, dark-green intrusives were found, 
probably of a diabasic character. The slates and schists are every- 
where penetrated by small veins, consisting usualty of quartz with 
some calcite, and frequently carrying pyrite and sometimes gold. 
These veins are very irregular, often widening out to form blebs, and 
again contracting so as not to be easily traceable. 


The stream tin is concentrated on the bed rock with other heavy 
minerals, and was found by the miners in the sluice boxes. A sample 
of the concentrate in one of the sluice boxes was examined by Mr. 
Arthur J. Collier, and yielded the following minerals: Cassiterite, 
magnetite, ilmenite, limonite, pyrite, fluorite, garnets, and gold. 
The determination of percentage by weight was as follows: 90 per 
cent tin-stone; 5 per cent magnetite; other minerals, 5 per cent. The 
cassiterite occurs in grains and pebbles, from those microscopic in 
size to those half an inch in diameter; they have subrounded and 
rounded forms. In some cases there is a suggestion of pyramidal and 
prismatic crystal forms. The cassiterite varies in color from a light 
brown to a lustrous black. 

A second locality of this mineral was found on the Anikovik 
River about half a mile below the mouth of Buhner Creek. Here the 
cassiterite was also found with the concentrates from the mining 
operations. One pebble of stream tin obtained from this locality was 
about 2 inches in diameter. 

It will be necessary to make a more detailed examination of this 
region to determine where this mineral occurs in the bed rock. The 
facts obtained by the writer point toward the conclusion that its 
source was in the quartz and calcite veins in which the gold was found. 
No cassiterite was, however, found in this vein material. 

No evidence was found that this cassiterite is in any way connected 
with granitic intrusions, which is its usual association in other regions. 
As far as known there are no intrusives of such rocks within the 
drainage basins of streams where the tin was found. The nearest 
known granitic rock is the biotite-granite stock which forms the 
promontory of Cape Prince of Wales and which is at least 10 miles 

This discovery of stream tin has, at present, scientific rather than 
commercial interest. No developments have been made which would 
warrant the conclusion that valuable tin deposits exist in the York 
district. It is worth while, however, for the prospectors who visit 
this region to familiarize themselves with the physical properties of 
the mineral, so as to be able to recognize it if found. By this means 
deposits carrying values may be discovered, and the cassiterite will 
probably be traced to its source in the bed rock. 


By S. F. Emmons. 


The occurrence of platinum in the form of sperrylite (arsenide of 
platinum), associated with copper ores in the Sudbury district of 
Canada, has been known since 1889. a It has since been discovered 
by Hidden 6 in North Carolina. In the past winter the occurrence of 
platinum in the ore of the New Rambler mine of Wyoming was 
announced by Prof . Wilbur C. Knight/ and upon examination of the 
ore by H. L. Wells and S. L. Penfield/* of Yale University, it was 
found to occur in well-defined crystals in association with covellite 
and pyrite. 

The known occurrences of platinum in definite mineral combination 
are so rare as to render this new locality of considerable importance; 
hence a brief visit to the mine was made by the writer during the past 
summer, after spending some time in camp with Mr. A. C. Spencer, 
who Avas engaged in a geological survey of the Encampment group of 
mountains, a northern extension of the Park Range of Colorado, lying 
on the west side of the North Platte River. The following is a brief 
but necessarily incomplete statement of the geological relations of the 
deposits as far as they were ascertained : 

The mine is situated a little east of south of Medicine Peak, the 
highest point of the Medicine Bow Mountains on Beaver Creek, a 
little stream tributary to the headwaters of Douglas Creek. It is con- 
nected with Laramie City on the Union Pacific Railroad by mail and 
stage line, the distance being about 32 miles in a straight line, though 
by the windings of the road it is about half as much again. A slightly 
shorter but more precipitous road runs westward across the North 
Platte Valley to the town of Encampment, where there is a smelter 
in which 2,000 to 3,000 tons of ore from the Rambler mine were 
smelted during the winter of 1901-2. The little settlement which has 
sprung up about the mine is designated by the postal authorities 
"Holmes, ,, from the name of the manager and principal owner of the 

"Am. Jour. Sci., 3d series, Vol. XXXVII, 1889, pp. 67-71. 

''Idem, 4th series, Vol. I, 1898, pp. 381, 467. 

cEng. and Min. Jour., Dec. 31, 1901, p. 845. 

'?Ain. Jour. Sci., Feb., 1902, 4th series, Vol. XIII, p. 95. 



mine. A railroad is now building from Laramie City westward, which 
it is expected will eventually connect with Holmes. 

The mine is at present opened by a vertical shaft 200 feet deep, but 
at the time of visit, owing to certain changes which were taking place 
in machinery and ownership, the lower 100 feet were not accessible; 
hence a study of the unaltered ore must be postponed to a later date. 
A small matting furnace has been erected near the shaft for treating 
second-class ore. The ore shipped away from the mine is said to 
aggregate nearly 4,000 tons and to have assaj^ed 25 to -30 per cent cop- 
per. According to Professor Knight, it all contained more or less 


The Medicine Bow Range is topographically a northwestern contin- 
uation of the Front Range of Colorado, which, as it enters Wyoming, 
spreads out into two forks that inclose the broad valley known as the 
Laramie Plains. The eastern boundary of these plains is formed by 
the Black Hills of Wyoming, sometimes known as the "Laramie" 
Hills — a north-south uplift of older rocks, mainly granite, which ends 
at the north bend of the North Platte River, where these rocks dis- 
appear under Mesozoic sediments. 

The Medicine Bow Range on the west likewise dips down under the 
Mesozoic sediments and is lost as a range, its almost isolated northern 
point being known as "Elk" Mountain. As seen from the Laramie 
Plains a striking feature is the plateau-like structure of the main mass 
of the uplift. On its eastern flanks it rises abruptly from the plains 
about 2,000 feet; then slopes back almost at a level with an average 
elevation of 9,000 to 10,000 feet to the central uplift around Medicine 
Peak, which is again about 2,000 feet above the plateau. 

This plateau-like portion of the range is, for the most part, covered 
with a comparatively abundant forest growth, and its streams run in 
shallow swale-like valleys which change rapidly to deep rocky gorges 
in their lower courses as they leave the plateau. At Holmes, which 
is on the higher part of the plateau, the forest covering is unusually 
dense and the rock surface is covered by to 16 feet of wash, so that 
rock outcrops are rare and iirospecting has to be done by trenching 
and shaft sinking, and the geological relations are correspondingly 
difficult to decipher. 


In its geological composition and structure the Medicine Bow Range 
appears to resemble more closely the Encampment Mountains on the 
opposite side of the Platte Valley than the Colorado ranges, and there 
is some reason for assuming that the two once formed part of one and 
the same mountain uplift, and that their separation by the cutting of 
the Platte Valley has been of comparatively recent geological date. 

The principal distinction from the other ranges that have a core 


that has generally been assumed to be Archean is the prevalence of 
distinctly sedimentary beds, largely quartzites of pre-Cambrian age, 
which form the crest of the ridges in either group of hills. Around 
the lower flanks of the ranges, on the other hand, and, so far as can 
be seen, in the intermediate Platte Valley, the basement rocks are 
granite and gneisses like those called Archean in Colorado, a^d the 
sedimentary rocks are seldom, if ever, seen. 

The sedimentary series in the Encampment Range are quartzites, 
with some limestones and conglomerates, penetrated by sheets and 
dikes of eruptive rock, mainly diorite, and closely compressed into 
folds with an east-west strike, the whole highly metamorphosed. 
That the same series of rocks occurs in the Medicine Bow Range is 
evident from observation, though the structure could not be made 
out with any definite ness in so short a visit, owing to the covering of 
forest and wash on the plateau. According to the Fortieth Parallel 
reports, Medicine Peak is a mass of white quartzite with a general 
synclinal structure. The same rock is said to occur on Douglas 
Creek a few miles below the Rambler mine, and quartzites were 
observed in considerable masses on the ridge between French and 
Mullan creeks a few miles west of that mine. At the Rambler mine 
itself and for a considerable distance on either side, as shown by the 
dumps of the different prospects, the rock is diorite. That at the 
Rambler mine is coarsely granular, with thoroughly granitic struc- 
ture and some development of pegmatitic phases, and is thought to 
be part of a considerable stock breaking through quartzites and 
underlying gneisses. 

Microscopical study of two specimens from the bottom of the shaft, 
by Mr. Waldemar Lindgren, shows the latter rock to be a hornblende- 
biotite-diorite of normal type, its feldspars being labradorite, with 
quartz occurring sparingly in grains between the feldspars, and mag- 
netite in small contact grains, mostly embedded in hornblende or 
biotite. As secondary minerals are found sericite and epidote in the 
feldspars, and a little chlorite in places in hornblende and biotite. 
Some red hematite occurs in seams, and p3 7 rite in grains and cubical 
crystals, generally in the hornblende, and always associated with a 
little chlorite. 


The mine was originally opened by an incline, but after the discov- 
ery of the large bodies of ore a vertical two-compartment shaft was 
sunk, through which access is now had to the workings. At time of 
visit the mine below the 100-foot level was inaccessible. Above this 
level and for some little distance below, both ore and country rock 
are much altered, and so much transmigration of the former has 
taken place that it was quite impossible to determine the original 
form and nature of the deposit. 


Thus far three large bodies, about 40 to 50 feet iu diameter aud 12 
to 30 feet high, have been opened. The upper one immediately below 
the wash was a gossan of iron oxide carrying about 9 ounces of silver 
per ton, with a trace of gold, from which the copper had been pretty 
completely leached out. Below this came silicates and carbonates 
of copper. The zone of enriched sulphide below the oxidized body, 
which alone was accessible, is apparently larger and certainly richer, 
and extends 30 feet or more above the level. It shows two large ore 
bodies of no definite outline inclosed in highly decomposed diorite. 
The latter, in its extreme form called " talc" by the miners, is a white 
kaolinized mass of the consistency of soft clay, but often retaining 
something of the original granular structure of the rock. Near the 
ore bodies covellite grains are so uniformly distributed through it as 
to give the appearance at a little distance of basic silicates in a white 
feldspathic rock. The remarkable feature of the ore is the abun- 
dance of the rather uncommon indigo-blue copper sulphide, covellite 
(CuS). The upper part of the body is slightly stained with iron oxide, 
while in the lower part some pyrite is visible, but not in relatively 
large proportion. Cuprite occurs here and there in brilliant ver- 
milion red crystals, and is sometimes reduced to native copper. The 
covellite is rather irregularly distributed through the kaolin-like 
mass, but sometimes occurs in massive lenses up to 2 feet thick. In 
so plastic a mass no definite structure could be observed in the mine, 
but some of the pyritous ore on the dump showed a certain vein-like 
structure. A specimen of this, which was examined microscopically 
by Mr. Lindgren, shows that the covellite replaces the pyrite directly, 
without the formation of intermediate minerals; that the ore has a 
cellular structure, apparently resulting from reduction in volume 
during its conversion, and that the roughly rounded cavities are 
often lined with soft white silica in mammillary crusts, the manner of 
occurrence indicating that it was formed by solution, either simulta- 
neously with or immediately after the formation of the covellite. 
In two places secondary pyrite of later formation than some of the 
! covellite was observed. 

Sperrylite could not be distinguished in the thin section. From 
the description given by Wells and Penfield of that which they were 
able to separate, it probably occurred in ore similar in character to 
this, and from its fresh appearance it seems probable that the sper- 
rylite was an original constituent of the sulphide ore. More definite 
knowledge as to its manner of occurrence will probably be obtained 
when the deposit has been opened at greater depths and beyond the 
reach of surface alteration. 

Bull. 213—03 7 


By W. H. Hobbs. 

A deposit of tungsten ore of considerable economic importance is 
found at Trumbull, Conn. The ore occurs along the planes of contact 
between crystalline limestone and two bodies of hornblende-schist, 
the latter being a metamorphosed igneous rock. The tungsten min- 
erals (wolframite and scheelite) seem to be concentrated just below 
the contact of the limestone with the lower body of hornblende-schist, 
while in lateral distribution they are very variable. In 1898 exploita- 
tion of this deposit for the tungsten ores was commenced and was car- 
ried on until 1901, when operations were temporarily abandoned. 
The companies which managed the property carried out somewhat 
extensive mining operations, and expended considerable sums for 
buildings and machinery. 

The method of mining lias been to sink pits at the contact and fol- 
low down the tungsten-bearing zone. The larger blocks obtained by 
blasting are broken with sledges and the picked ore sent to the mill. 
The ore on reaching the mill is sent through a 15 by 21 inch Blake 
crusher, with a capacity of 10 tons per hour. This crusher discharges 
its product on the upper end of the picking table. An endless rubber 
belt acts as carrier and feeds to two small crushers on the floor below. 
These crushers deliver their product to two sets of Cornish rolls, 
running one-fourth inch apart and having a 22-inch diameter and 
16-inch lace From the rolls the material is elevated to the top of the 
mill and delivered \ o a pair of revolving wire screens 36 inches in diam- 
eter and 8 feet in length. These screens are one-eighth-inch mesh, 
and therefore refuse most of the material. A considerable portion of 
the dust is here drawn out by a current of air which passes under the 
screens. The material refused by the screens is carried by gravity to 
a pair of high-speed rolls, of 30-inch diameter and 18-inch face, run- 
ning one-eighth inch apart. From them it is returned to the elevator 
and again sent to the one-eighth-inch screens. All the material pass- 
ing the one-eighth-inch screens at either the first or second trial is 
sent to Wolf gyrating screens of three sizes, the mesh being 40, 60, 
and 90, respectively. 

Concentration is effected by a dry process, the Hooper pneumatic 
concentrator being used. This delivers a clean concentrate and leaves 
little ore in the tailings. Each machine is capable of treating 10 tons 
of material a day, and the yield of tungsten ore is said to be 5 per 
cent. The ore carries a little pyrite, which must be removed by 
roasting. No attempt is made at the mine to reduce the mineral to 
tungstic oxide. 


By W. H. Weed. 

The El Paso tin deposits lie on the east flank of the Franklin Moun- 
tains, the southern extension of the Oregon or San Andreas Range, 
about 10 miles north of El Paso. The ores were discovered in 1899 
and have been prospected by several open cuts and pits, the deepest 
of which is about 50 feet below the surface. The place is distant 
about 14 miles by wagon road from El Paso. The Rock Island Rail- 
road crosses the flat 3 or 4 miles east of the property, and the main 
line of the Southern Pacific lies 10 miles to the south. There is a 
good spring one-fourth of a mile from the ledges, but there is no large 
supply of water nearer than the Rio Grande. The mesa is under- 
lain by water, the city of El Paso being supplied from driven wells 
sunk in the mesa gravels. 


The geological structure is simple and easily made out. The moun- 
tain range consists of Cambrian and other Paleozoic limestones, 
upturned by and resting upon an intrusive mass of coarse-grained 
granite that forms the central core of the range. This granite is well 
exposed for a distance of 4 or 5 miles along the eastern side of the 
mountains, forming the lower half of the mountains proper, and in 
places extending out to the foothills. The crest of the range consists 
of steeply tilted, heavily bedded, dark-gray limestones dipping west- 
ward. The basal quartzites were observed in the drift seen in arroyos, 
so that the granite is probably intruded between the base of the Cam- 
brian rocks and the underlying Archean complex. 

The eastern foothills consist mainly of limestones, but near the tin 
deposits these bedded rocks have been cut through and granite now 
forms the surface, remnants of the limestone cover showing as isolated 
j masses capping the hillocks. North of the tin mines a transverse 
iridge of the range shows the granite to be sheeted by well-marked 
planes, dipping eastward at an angle of about 45° to 50°. The granite 
is very much altered by surface decomposition, and crumbles readily 
to a coarse sand. The granite is sheeted near the veins, the planes 
of sheeting being parallel to the veins themselves. The general 
sheeting, however, is in a different direction, the average strike being 
|N. 20° E., and the dip 70° SE. A thin section of this granite, exam- 



ined under the microscope, shows the rock to be a coarse-grained 
normal soda granite, with much anhedral quartz and anhedral feld- 
spar, largely microperthite, with some few grains of microcline. A 
few small flakes of brownish-green hornblende and some small grains 
of magnetite were also seen. 

White aplite-granite occurs in veinlets and irregular masses intru- 
sive in the granite, but none was observed close to the veins. 


The ores consist of cassiterite, or oxide of tin, with wolframite 
(tungstate of iron and manganese) in a gangue of quartz. Specimens 
of nearly pure cassiterite weighing several pounds have been found 
on the surface, and this mineral occurs in the quartz, either alone or 
associated with wolframite. The most abundant ore is a granular 
mixture of tin ore and quartz which resembles a coarse granite and 
corresponds to the greisen ore of European tin deposits. Pyrite 
occurs rarely in the eastern exposures of the vein, but appears to 
constitute the bulk of the metallic contents in exposures seen in the 
westernmost openings. These ores occur in well-defined veins, which 
run up the slopes nearly at right angles to the direction of the range, 
the strike being approximately east- west and the veins dipping steeply 
to the north. Three veins have been discovered, all of which have 
been exposed by open-cut work and by pits for several hundred feet 
in length. The most northerly vein is traceable along the surface for 
a distance of about 1,200 feet. The middle vein lies about 300 feet 
south of the east end of the northern one, but apparently converges 
westward toward the northern vein. The southern vein, which is the 
smallest of the three, lies about GOO feet farther south. 

The veins exhibit the usual characters of the European tin veins, 
notably those of Cornwall, England, their clearly defined fissures show- 
ing a central core or lead of coarse quartz, sometimes containing tin 
ore, and flanked on either side by altered rock in which the tin ore 
replaces the feldspar of the granite. Where this metasomatic replace- 
ment is complete the ore shows a mixture of cassiterite, with or with- 
out wolframite and quartz. Where the replacement is only partial the 
greisen ore fades off into the unaltered granite. A cross section of 
the veins shows, therefore, the same phenomena seen in Cornwall. 
The central mass of quartz corresponds to the " leader" of the Cornish 
veins. It is composed of massive, coarsely crystalline quartz, some- 
times showing comb structure, and it is clearly the result of the filling 
of the open fissure by quartz. The adjacent ore-bearing material is 
a replacement deposit in which the mineral solutions have substituted 
ore for the feldspar of the granite by metasomatic action; in other 
words, the main mass of the ore occurs alongside of a quartz vein, and 
is due to the alteration of the granite forming the walls of the fissure. 
In general, the ore passes into the granite by insensible transition and 
there are no distinct walls. 


From a thin section of the ore, examined under the microscope, the 
rock is seen to be quartz cassiterite. It is a coarsely granular rock 
consisting of anhedral quartz, with grains of slightly brownish cassit- 
erite intimately intergrown with quartz along the edges. The quartz 
is full of fluid inclusions and makes up about 75 per cent of the mass. 
One small grain of tourmaline and a few flakes of sericite were seen. 
Neither topaz nor mica occurs in the section, and no remains of feld- 
spar were observed. If this is a metasomatic form of the granite a 
silicification has taken place. The microscope affords no direct evi- 
dence, however, that this ore is metasomatic. 

The north vein has a course of N. 85|° W. magnetic, as determined 
from the openings at the east end. At the west end of the workings 
the course observed, looking back along the outcrop, appears to be 
N. 80° E. for the northern vein and N. 80° W. for the middle vein; 
so that if these observations are correct the veins must intersect toward 
the Avest. The surveys by the owners of the property show a course 
N. 85|° W. for the middle and 05° W. for the south vein. 


A shaft 35 feet deep has been sunk on the north vein at the eastern 
end of the vein outcrop. This shaft is about 5 by 10 feet across and 
shows a very well-defined vein about 5 feet wide, having a dip of 
about 70° to the north. The sides of the shaft show excellent ore, 
mostly of the greisen variety, extending down for 8 to 15 feet below 
the top. At this point a slip crosses the shaft and cuts out the ore. 
This slip, or fault, is a clay seam, but one-fourth to one-half inch in 
thickness, and seems to have thrown the upper part of the vein to the 
north. The lower half of the shaft reveals only rusty granite, shat- 
tered and showing films of quartz, but without recognizable ore. A 
crosscut south from the bottom of the shaft should reach the vein if 
the fault is a normal one. In the exposure seen in the upper part of 
the shaft the ore occurs in bunches in altered granite and lies on the 
north side of a 15-inch streak of sheeted and rusty quartz. A second 
shaft on the north vein has been sunk at a point about 300 feet west 
of the one just noted. This shaft is about 25 feet deep. The vein is 
well exposed at the top, and shows a dip northward, but the shaft 
passes out of the vein into the sheeted granite, forming the foot Avail. 
A crosscut about 8 feet in length, driven from the bottom of the shaft, 
cuts the vein, but does not pass through it. The sheeting of the 
granite seen in this shaft is very pronounced, the rock being divided 
into plates from one-fourth inch to 12 inches in thickness by planes 
dipping Gl° E. and crossing the vein at 90°. The outcrop of the vein 
is traceable westward up the slopes by its rusty quartz, and a nearly 
continuous ledge can be followed. This outcrop has been opened at 
intervals of a few yards by trenches, Avhich expose the A^ein and show 
it to haA r e a thickness of from 2 to 6 feet, Avith about half this thickness 


of ore. No samples were, however, taken, and it is uncertain whether 
the altered granite does not contain a percentage of tin oxide. The 
most westerly working that could be surely identified as being upon 
the north vein is a pit 6 feet deep, which shows a 6-foot vein in wh ich 
the quartz is bluish in color and the tin ore is associated with much 
pyrite. This point is about 600 or more feet west of the first shaft; 
West of this point the ledge can not be traced across the slopes, but 
tin ore is seen on the slope 100 feet higher, and still farther north a 
good vein shows, carrying much pyrite, but devoid of any recogniz- 
able tin ore. 

The middle vein is developed by a shaft 50 feet deep, which shows 
a vein having a central leader of quartz 2 feet wide at the top and 
tapering to 1 foot 4 inches wide at the bottom of the shaft. The dip, 
as shown by the walls of the shaft, is 70° N. The central quartz 
mass is spoiled with cassiterite, and the altered granite on either side 
(•out a ins recognizable grains of tin oxide. 

The south vein lies 500 to 600 feet south of the middle vein. This 
vein is much narrower than the veins on the north, having an aver-i 
age width of about 1 foot. The strike, as shown near the shaft, is 
N. 50° W., and the dip 50° N. The vein walls are sometimes defined 
by a clay selvage one-sixteenth inch wide, but more often show a 
gradual fading off into the granite. 

It will be noticed from what has been said that the veins are all 
well defined at the surface and carry good values in tin ore, but that 
the ore apparently dies out in depth. Further development is needed 
to establish the existence of the ore at a greater depth than 50 feet, 
but it is believed that the veins have been thrown by local slips or | 
faults and will be found by crosscutting from the bottom of the pres- 
ent workings. The character of the fissures and the nature of the 
ore both indicate that 1 he veins are the result of deep-seated agencies, 
and are not merely segregations due to descending surface waters, j 
For this reason it is believed that further exploration will develop 
well-defined tin veins. 


By F. B. Weeks. 

A hubnerite-bearing vein was discovered about 12 miles south of 
Osceola, Nev., in 1900. It occurs in the foothills on the west slope 
of the Snake Mountains, near the base of Wheeler Peak. The near- 
est railway point is Frisco, Utah, on the Oregon Short Line Railwaj 7- , 
about 100 miles distant. 

The country rock is a rather coarse porphyritic granite, composed 
of quartz, mica, and hornblende, and having a rudely bedded structure 
parallel to that of the overlying Cambrian quartzite, which dips 20° 
to 25° SSW. The vein cuts across this granite, striking N. 68° E. 
and dipping 05° NW. The main vein is normally about 3 feet wide, 
pinching in places to a few inches, but rapidly regaining its usual 
width. Several smaller veins, from a few inches to a foot in width, 
outcrop on the slopes and can be traced to the main vein, entering it 
at a sharply acute angle. The main vein was traced for a distance of 
2,100 feet by croppings and float from its outcrop near the base of the 
lowest foothill up the slope of the mountain. 

Sufficient development had not been made at the time of visit to 
determine the extent of ore deposition. The vein walls are well 
defined. Where the vein has its average thickness, it is formed of 
milky-white quartz, carrying a large amount of hubnerite. Where 
the vein pinches, the quartz is schistose, and the ore is in small 
stringers and small in amount. The ore occurs in solid masses, fre- 
quently attaining a thickness of G to 12 inches. It is also disseminated 
through the quartz in thick plate-like forms, and also occurs crys- 
tallized with the quartz crystals. Small shoots of ore penetrate the 
country rock for a few inches. The vein material is easily crushed, 
and the hubnerite, because of its weight, can be readily separated 
by jigging. 

At one locality on the vein there was a somewhat remarkable 
occurrence of the ore. It was found in large bunches or blocks aver- 
aging 75 per cent tungstic acid, and from a small space 4^ tons of ore 
were obtained. Scheelite has been found in small bunches and 
streaks with the hubnerite. 

More recent information regarding the development of this ore 
body may be found in a paper by Mr. Fred B. Smith in the Engineer- 
ing and Mining Journal, volume 7:>, pages 304-305, 1902. 



The principal publications, by the United States Geological Survey, 
on the metals here grouped are the following: 

Becker, G. F. Geology of the quicksilver deposits of the Pacific slope; with 
atlas. Monograph XIII. 486 pp. 1888. 

Quicksilver ore deposits. In Mineral Resources U. S. for 1892, pp. 
139-168. 1893. 

Blake. W. P. Nickel: its ores, distribution, and metallurgy. In Mineral 
Resources U. S. for 1882, pp. 399-420. 1883. 

Tin ores and deposits. In Mineral Resources U. S. for 1883-84, pp. 
592 640. 1885. 

Brooks. A. H. An occurrence of stream tin in the York region. Alaska. In - 
Mineral Resources U. S. for 1900, pp. 207-271. 1901. 

Christy, S. B. Quicksilver reduction at New Almaden [California]. In Min- 
eral Resources U. S. for 1883-84, pp. 508-5:36. 1885. 

Glenn, W. Chromic iron. In Seventeenth Ann. Rept., Pt. Ill, pp. 201-273. 

Hobbs. W. H. The old tungsten mine at Trumlmll, Conn. In Twenty-second 
Ann. Rept., Pt. II, pp. 7-22. L902. 

Kemp, J. F. Geological relations and distribution of platinum and associated 
metals. Bulletin No. 198. 05 pp. 1902. 

Packard, R. L. Genesis of nickel ores. In Mineral Resources U. S. for 1892, 
pp. 170-177. 1893. 

Rolker, C. M. The production of tin in various parts of the world. In Six- 
teenth Ann. Rept., Pt. Ill, pp. 458-538. 1895. 

Ulke, T. Occurrence of tin ore in North Carolina and Virginia. In Mineral 
Resources U. S. for 1893, pp. 178-182. 1894. 

Weed, W. H. The El Paso tin deposits [Texas] . Bulletin No. 1 78. pp. 1901 . 

Weeks. F. B. An occurrence of tungsten ore in eastern Nevada. In Twenty- 
first Ann. Rept,, Pt. VI, pp. 319-320. 1901. 


The papers here presented represent the results of the last year's 
field work by the Survey in various copper-mining districts. These 
papers give, practically, a summary of the copper-mining industry of 
the United States, with the exception of the important Lake Superior 
district. The Lake Superior copper deposits were examined by the 
Survey at an early date, and the resulting report will be found cata- 
logued in the "List of Survey publications on copper," on page 186. 
Other districts producing copper, but to a less value than the precious 
metals, will be found discussed under "Gold and silver, 1 ' pages 31 
to 90. 




Field work. — During the field season of 1000 a detailed geologic 
examination of the Bingham Canyon district in the West Mountain 
Mining District, Utah, was conducted under the immediate direction 
of S. F. Emmons, geologist in charge, by Arthur Keith and J. M. 
Boutwell. The areal mapping was taken up in the summer by Arthur . 
Keith and J. M. Boutwell and continued into the fall by the latter, 
and the ore deposits were studied in the winter by J. M. Boutwell. 
In the summer of 1900 G. II. Girty was engaged for one week in 
special paleontological studies in this field. During brief visits by 
the writer in 1901-2 additional data on special areal and economic 
problems were obtained. 

An area of 24 square miles, embracing the Bingham Canyon mining 
listrict, was mapped geologically on a scale of 1,666+ feet to the inch. 
Those portions of the Oquirrh Range which adjoin this area on the 
lorth, west, and south were studied en reconnaissance, and the ore 
leposits in all accessible underground workings were examined. 
)wing to the fact that the geologists engaged in this work were 
letailed to other fields during the field season of 1901 and 1902 for 
exceptionally long periods, insufficient time for the earlier prepara- 
|ion of this report has remained. The complete report on the results 

■The complete report, of which this paper is an abstract, will appear at an early date asa 

|roft'ssiomil paper. 



of these studies is now well advanced, however, and will appear 
shortly. In the present sketch, conclusions on several important 
economic problems must be reserved, awaiting results of special 
investigations now being conducted ; and those here given are tenta- 
tive and subject to revision in the complete report. 

A brief sketch of the geography, history, and production intro- 
duces general statements on such major features of areal geology as 
stratigraphy, intrusions, general structure of the Oquirrhs, and struc- 
ture of the district; and on such major features of economic geology 
as the character and occurrence of the ores, placer deposits, and com- 
mercial considerations. 


The Bingham district, which is the chief mining section in the 
West Mountain Mining District, lies in the north-central part of Utah] 
in latitude 112° 9' north, longitude 40° 32' west, and is situated on the 
east slope of the Oquirrh Range, 20 miles due southwest from Salt 
Lake City. It is connected with the main line of the Rio Grande 
Western Railway by a branch line which extends westward from 
Bingham Junction (11 miles due south of Salt Lake City) a distance 
of 14 miles to Ihe main settlement in Bingham Canyon. 

The Oquirrh Range, the most eastern of the desert ranges of the 
Great Basin, lies 25 miles west of the Wasatch Mountains, and 
extends in a general north-south direction southward from Great 
Salt Lake for a distance of 30 miles. In its general form it may be 
likened to that of a mason's trowel, with a handle-shaped portion at 
the north expanding at a point about 12 miles south of the lake from 
an average width of 6 or 7 miles to a width at the head of the blade 
of about 15 miles, and then gradually narrowing southward for a dis- 
tance of about 18 miles to a point. 

The main slorjes rise rapidly from elevations of about 5,000 feet 
on the surrounding desert — except at the junction with the Traverse) 
Mountains on the east and the Stockton bench on the west — to eleva 
tions on the main divide of over 9,000 feet at the northern and over 
10,000 feet at the southern portion of the range. These general slopes)^ 
to the east and west are deeply incised by many narrow, stecp-sidecH 
canyons, which extend from the deserts far in toward the main divide 
on comparatively gently rising, partially graded slopes, and then rise 
abruptly by exceedingly steep slopes. The slopes inclosing these i 
canyons are steepest at the lowest and highest portions, being often I 
precipitous immediately over the narrow, occasionally graded canyor 
bottoms, and similarly steep and ledgy along the major divides 
while a partially graded slope sometimes marks the intermedial 
stretches. These topographic characteristics are also true of th< 
branches and subbranches of the main canyon, with the qualitica 
tion that grading is much less advanced. 

Snow falls commonly in late October, accumulates to great depths 


and lasts until late in May. The range as a whole is not well watered. 
In the region embracing Bingham Canyon only the main canyons and 
their immediate tributaries carry water, and after the spring passage 
of the accumulated precipitation of the winter the flow gradually 
decreases until in mid and late summer water becomes scarce, occa- 
sionally disappears for considerable stretches from the stream beds 
during the day, and seeps through the discrete material constituting 
the stream beds in their lower courses. Several good springs are 
known in the range, such as that in Ophir Canyon, those at the head 
of Butterfield Canyon, and that in Tooele Canyon. In the vicinity of 
the mining regions, however, the main sources of water supply for 
domestic and commercial use are subterranean courses tapped by 
underground workings. 

The vegetation is relatively sparse. This fact is doubtless due to 
the steepness and ledgy character of the slopes, and consequent thin- 
ness of the soil, and to low precipitation. Although more favored 
than man}^ of the basin ranges, the Oquirrhs, particularly in the region 
about Bingham, support neither the variety nor the extent of vege- 
table growth which flourishes upon their more loft} 7 and better watered 
neighbor, the Wasatch Mountains. Sagebrush (Artemisia) is the chief 
growth on the lower slopes adjoining the deserts. Scrub oak with an 
occasional cactus plant (Puntia vulgaris), juniper, spruces, and some 
pine characterize the middle elevations; and mountain mahogany, 
certain grasses, and Alpine varieties of wild flowers alone inhabit the 
higher peaks. 


The Bingham district is unique in that it includes the oldest recorded 
mining claim in the State, is the only district in Utah in which placer 
mining has been successfully prosecuted, and to-d&y leads the camps 
of Utah in the production of copper. Only the more important stages 
in the extremely interesting and instructive history of this unique 
camp may be noted here. 

Early in the fall of 1863 ore was discovered by George B. Ogilvie, 
an apostate Mormon, near the head of the main Bingham Canyon. 
On September 17, 1863, each of the 25 members of the Jordan Silver 
Mining Company formally located there " for mining purposes " one 
claim "of 200 feet each and one additional claim of 200 feet for the 
original discoverer. " rt This is the earliest recorded mining claim in 
Utah. Active prospecting led to the discovery and location of prom- 
ising croppings, but lack of facilities for transportation rendered 
extensive mining operations at this time impracticable. "The first 
shipment of ores from Utah was a carload of copper ore from Bing- 
ham Canyon, hauled to Uintah on the Union Pacific, and forwarded 
by Walker Brothers to Baltimore in June, 1868. " 6 

a Records at office of surveyor-general of Utah, Salt Lake City. 
''Bancroft, H H , History of (Mali, p. 741. 


Iii 1870 the connection of the Union Pacific and Central Pacific 
railroads by the Utah Central with Salt Lake Citj^, the inauguration of 
the branch road to Bingham, the gradual removal of the early oppo- 
sition of Mormon authorities to the entrance of their followers into 
mining operations, the results of experiments in the reduction of 
local ores, and the successful exploitation of the Emma mine and 
adjoining properties in the Wasatch Mountains, all combined to 
stimulate mining activities in Bingham. Many bodies of lead ore, 
mainly carbonate, were exploited. The first efficient development of 
the mines of the district was conducted by Messrs. Bristol & Daggett 
in the Winamuck and Spanish, and the largest body of argentiferous 
lead ore was developed in the Jordan and Galena mines. In 1874 
the bulk of lead-carbonate ore was exhausted, and in the Wina- 
muck, Neptune, Kempton, Spanish, and Utah sulphides had been 

Special attention was directed toward saving the gold in the super- 
ficial oxidized portions of the ore shoots in the silicified limestones. 
Various experiments in milling and cyaniding were conducted, and 
large stamp mills were erected. Despite claims that in special cases 
cyaniding was successful, the general opinion prevails that the pres- 
ence of copper necessitated the use of so inuch cyanide that no profit 
could be made, and, further, that the siliceous gold ores of Bingham 
have never been worked successfully. In the early eighties there 
were developed in the outer western slopes of the range bodies of 
carbonate ore which continued to afford an increasing output for 
about a decade. In 1801 and 1 S02 the leading productive mines were 
the old Jordan and Galena, Brooklyn, Highland, Telegraph, York, 
Petro, and Yosemito mines, [n L893 the decline in silver brought 
this period of activity to a close. 

A few years later the discovery of pay shoots of sulphide-copper ore 
at a time of strong demand for copper and a rise in the market value 
of lead inaugurated a new era in the camp. Reduction of copper 
sulphides having been successfully conducted, and the value of the 
Bingham copper ores having been demonstrated in 1890 on a shipment 
of 5,000 tons from the Highland Boy, exploitation for copper was 
vigorously begun and has continued to the date of writing. This has 
resulted in the disclosure of strong and valuable shoots of low-grade 
copper-sulphide ore. 

These bodies are now worked on both a large and a small scale. 
The largest ones are controlled by consolidations, including the Utah 
Consolidated, the United States Mining, Bingham Consolidated, and 
the Boston Consolidated companies, which (with exception of the lat- 
ter, which has not yet begun to ship from its well-proven shoot) trans- 
port their output either by aerial tramways or narrow-gage railroad 
to the Bingham terminal of the Rio Grande road, and thence by rail 
to smelters built and operated by each company at Bingham Junction. 


During 1900 the total output from 32 properties aggregated 101,132 
tons of ore, of an estimated value of $1,700,000. For the year 1901 
the value of the output of gold, copper, and silver increased, and that 
of lead decreased, with a result of a net increase in the value of the 
output for 1901 over that of 1900 amounting to about $2,000,000. In 
this total the copper shipments constitute the chief factor, their value 
as compared with the combined values of gold, silver, and lead ship- 
ments being roughly at a ratio of 23 to 16. The output for the present 
rear promises to show a continued increase. The value of the approxi- 
mated total output of Bingham to 1899, inclusive, as calculated from 
the most complete data obtainable, is between $26,000,000 and 


Stratigraphy. — In a general sense the sediments in the Bingham 
district are siliceous. Exceptions to this general character — first 1 lie 
relatively thin intercalated limestone, and second the calcareous 
shales — are, however, of greatest economic importance. The entire 
section may be broadly divided on lithologic grounds into two parts — 
i a lower, which is characterized by a great thickness of massive normal 
quartzite with a few relatively thin interbedded limestones, and an 
upper, which is composed largely of quartzites with black calcareous 
shales, sandstones, and impure limestones. 

The lower part includes three series of beds of geological and 
economic interest. The first of these is a thin calcareous member 
associated in quartzite with other limestones which cross Butterfield 
Canyon near its head at an elevation of about 7,000 to 7,500 feet. It 
carries a fauna which has been correlated by Dr. G. II. Girty with 
those of Lower Carboniferous age in the Mississippi Valley. Over- 
lying this is a thickness of about 1,250 feet of massive quartzite. 
The second series is composed of at least two heavy limestones, which 
aggregate, with intercalated quartzite, about 5,000 to 8,000 feet in 
thickness. In these limestones have been found a large portion of 
the ore bodies of this camp, and near the top of the lower limestone 
of this series occurs a fauna characteristic of the Upper Carboniferous. 
Extensive deformation by Assuring, faulting, and intrusion gives rise 
to some uncertainty as to the normal succession from this point to 
the top of this lower great division. The structure of an extensive 
region to the south, west, and north of this immediate area, beyond 
that which the writer could find time to study, must be carefully 
determined before this and some other large structural problems 
involving this immediate area can be conclusively settled. But the 
field evidence gained by thorough study in this immediate area and 
he country immediately adjacent thereto indicates that overlying 
his second limestone series is a thickness of approximately 1,500 feet 
m )f quartzite with intercalated thin blue limestones and calcareous 


sandstones, and that over this and at the top of the lower great 
division is a series of at least three limestones of a semilenticnlar 
character. The lower of these limestones included the largest single 
body of copper ore yet discovered in Bingham. 

The upper great division of the Bingham section, several thousand 
feet in thickness, is made up. in the main of normal quartzite, and 
includes in addition relatively thin calcareous sandstones, calcareous 
carbonaceous shales which occasionally attain a thickness of a few 
hundred feet, and thin blue limestones. No particular horizon in 
this series is of special economic importance. The principal bodies 
known to occur in it, however, are associated with calcareous shales. 
Scanty faunas indicate I he series to be of Upper Carboniferous age. 

Igneous rocks. — Igneous rocks of at least two distinct types and 
ages are recognized. The area studied was too Limited to afford the 
data necessary to prove the origin, source, and direct ion of movement 
of their magmas. Accordingly all statements concerning these sum 
jects must be regarded for the present as in the nature of tentative 
suppositions. In brief, molten masses have been injected into the 
sediments in this area from the lowest nearly up to the highest] 
These broke upward across ami along the beds in an extremely 
irregular manner and cooled in the form of irregular dikes, sills, and 
laccolil hs. 

The petrographic character of this intrusive varies from the fine- ,( 
grained, rather basic porphyry of the laccolith at Upper Bingham tq 
a coarse, slightly more acid type in Keystone Gulch, and to the coarse 
acid type north of Can- Fork toward its headward portion, and finally 
to the altered acid type between Bingham Canyon and Carr Fork. 

For general purposes these maybe considered as several fades of a 
single magma characterized by the occurrence in the Bingham lacco 
lith. Under the microscope thin sections appeared to be augite 
biotite-diorite-porphyry, but chemical analyses show the content of 
potash to exceed considerably the average potash content of diorite 
porphyry and to agree with that of monzonite. Accordingly the rock 
maybe regarded as an intermediate type between diorite-porphy ry 
and monzonite. It occurs chiefly in the lower half of the section, and 
assumes considerable economic significance, first in connection with 
the main limestones, and second as the home of valuable mineral 

The second tj^pe of igneous rock within this area is restricted to the 
lower slopes of the outer extreme eastern part of the range. Petro 
graphically it differs from the intrusive just described in being moil 
acid and allied to the andesites. No positive proof regarding the age 
and origin of this volcanic body has been found. A small prospect, 
tunnel exposes the andesite breccia overlying an old surface debris of 
quartzite similar to that which characterizes the present slopes. 
Accordingly it may be regarded as an extrusive mass which over- 


flowed and submerged an ancient topography. Nothing bearing upon 
the source. of this rock has been found since the work of Mr. Emmons 
in connection with the early survey of this region, when he determined 

the Traverse Mountains, which form a partial connection between the Wasatch 
Range and the Oquirrh Mountains, * * * seem to he composed mainly of 
trachyte, the flows of which extend * * * along the foothills of the Oquirrhs 
so far as the mouth of Bingham Canyon. « 

The date of the porphyry intrusions is not definitely fixed, although 
it was probably earlier than the date of the extrusion of the volcanic 
flows, and abundant underground evidence proves that it was earlier 
bhan the late faulting on northeast-southwest fissures, earlier than the 
period of mineralization on those fissures, and probably earlier than 
jhe Assuring which preceded this period of mineralization. 

Correlated studies, which the writer is now undertaking in another 
leld, will, it is believed, throw much light upon the geological history 
)f the igneous rocks of Bingham. So far as known, these extrusives 
lave never been found to carry mineral values. An interesting eco- 
lomic problem associated with this andesitic flow involves the east- 
vard extension of ore bodies. For if the pre volcanic land forms sim- 
dated present forms, and the andesitic breccia simply blankets an 
earlier surface, then there is no structural reason why the ore bodies 
n Carboniferous sediments may not be followed eastward under the 
olcanic flow. On the other hand, if this volcanic mass broke up at 
>r in proximity to the present surface contact, then it is probable 
hat this contact descends in depth approximately vertically and 
runcates the ore bodies. 

Structure of the range. — The general structure of the Oquirrh 
tange, so far as it has been studied, is characterized by broad exten- 
ive folds and complex fracturing and faulting on a small scale. It 
s not improbable, however, that further field work, which shall 
xtend our knowledge beyond the limited areas that have thus far 
»een studied in detail, will reveal extensive faulting. 
The beds in the southern portion of the range have been folded 
long northwest-southeast axes into two great anticlines, whose con- 
ecting syncline is occupied by Pole Canyon. b Northward "the main 
rest of the range, between Tooele and Lewiston peaks, is the rem- 
ant of the flat arch of an anticlinal fold." ' The northern extension 
f this anticline may be identical with the anticline which crosses 
'ooele Canyon about two miles below its head. Thence the Car- 
A oniferous limestones, with the overlying siliceous series above 
escribed, strike eastward across Bingham Canyon until, at a point 
ear its mouth, they turn up steeply on edge and strike northward. 

i j 

"Emmons, S. F„ U. S. Geol. Expl. Fortieth Par., Vol. II, p. 440. 
blbid., p. 443. 
<*Ibid.,p. 443, 


Beyond here the structure is not as well known. In a general way it 
is believed that the beds dip northwardly and pass through several 
minor folds and considerable faulting until "beyond Connor Peak 
the beds of the Lower Coal Measure group are found to be pushed up 
and crumpled together in short sharp folds, giving no less than three 
small anticlines. " a At the extreme north end of the range, along 
the general northeast-southwest strike, the dip is much disturbed and 
varies from vertical and 40° N. on the mainland to 5°, 10°, and 30° S. 
in Sheep Rock and outlying outcrops along the shore to the north. 

Structure of the district. — The Bingham district itself thus lies in a 
broad, shallow, synclinal basin which pitches gently northward and 
is limited on the west by the Tooele anticline and on the east by the 
abrupt Bingham upturn. Minor folds occur with various irregulari- 
ties of strike, but they are relatively unimportant. Fracturing and 
Assuring lias taken place very extensively throughout the district. 
The amount of displacement in the instances studied is not, however, 
great, rarely amounting to 100 feet. 

The general distribution of these sediments and intrusives is sim- 
ple, but the detailed distribution is most complex and irregular. 
Briefly, the three great limestone series and the massive quartzites 
which separate them occupy the southern and southeastern portions 
of the area, and strike from the main divide on the west northeast- 
ward through the district. The great siliceous upper series of quartz- 
ites, calcareous shales, sandstones, and thin limestones overlie them 
and occupjr the north and northwest half of the area. The intrusives 
lie mainly in the southern portion of the area in two great divisions, 
the lower, lying south of the middle limestone series (Old Jordan- 
Telegraph- Yosemite and Commercial-Brooklyn limestones), and the 
upper, which overlies this lime series. The sediments and their asso- 
ciated intrusives disappear on the east along a generally north-south 
line under the later volcanics, which in turn are blanketed by Quat- 
ernary deposits. In brief, the geological map of this area may be 
pictured roughly as follows: Conceive an oblong area in which the 
four points of the compass lie at the four corners; draw a straight 
line from the north corner to the middle of the southeast side, a sec- 
ond line from the same corner to the middle of the southwest side, 
and a third across the south corner in an east-west direction; then 
the first line will delimit the contact between the late deposits (Quat- 
ernary and volcanic) on the east and the Carboniferous on the west, 
the second will delimit the great siliceous series on the north from tin 
main mineralized area comprising the limestone series with separat 
ing quartzites and intrusives on the south, and the third will delimit 
the Lower Carboniferous to the south from the Upper Carboniferous 
to the north. 

« Emmons, S. F., U. S. Geol. Expl. Fortieth Par., Vol. II, p. 444. 



General. — The principal mines of this district are located on the 
slopes of Bingham Canyon, of its tributaries, and of the head ward 
portions of the northeastern tributaries of Butte rfield Canyon. They 
have revealed valuable ore bodies of two great types, those which 
occur as lenses, roughly parallel to the bedding, and those which 
occur in fracture or fissure zones. Under each of these forms of 
occurrence ores of copper, lead, silver, and gold occur, though the 
copper lies mainly in the lenses in limestone, and the lead and silver 
in fissures. For the purpose of this abstract the economic geolog3 T 
may best be considered with regard to character and occurrence of 
ores, placers, and commercial considerations. 

Character of the ores. — The ores of Bingham include a valuable 
variety of the desirable metals. Thus mining activity has been devoted 
successively to oxidized gold ores, carbonate ores of lead and cop- 
per, sulphide of lead, and finally sulphides of copper. The oxidized 
^old ores carried good values, but were not commercially profitable. 
Although some of the gold was free, no satisfactory treatment of its 
ares was obtained, the commonly accepted explanation being that the 
presence of copper required too much cyanide to leave a profit. The 
carbonates of lead and silver carried high values and were treated 
with comparative success, but are to-day worked out. Lead-silver 
sulphides later assumed commercial importance, and under the influ- 
ence of good market values lead is still extensively mined. This ore 
is made up of galena, tetrahedrite, considerable zinc sulphide, pyrite, 
and chalcopyrite, with a gangue of quartz and calcite. The mainstay 
3f the district, however, is copper sulphide ore. This is composed of 
cupriferous pyrite, chalcopyrite, and the black sulphides of copper, 
which may prove to be chiefly tetrahedrite and chalcocite, with occa- 
sionally a little galena, zinc, and a siliceous gangue. 

Pyrite (sulphide of iron with copper as an impurity: iron pyrites), 
-he most common metallic mineral known in Bingham, forms the bulk 
)f immense replacement ore bodies in limestone, plays a secondary 
*61e in fissure ores, and is freely disseminated through the igneous 
*ocks. Although large masses of perfect crystals of exceptional purity 
tfere found, its more prevalent occurrence is in massive form inti- 
nately combined with chalcopyrite, small amounts of bornite, pyrrho- 
ite, and alteration products of primary sulphides. Chalcopyrite 
sulphide of copper and iron : copper pyrites) occurs scattered in small 
)atches throughout bodies of massive pyrite in limestone associated 
vith pyrite bands; in fissures of lead-silver ores, and in grains dis- 
eminated through the main porphyry bodies. It appeal's, from 
cached and unleached specimens, and from a study of thin sections, 
hat much of the copper of cupriferous pyrite occurs as chalcopyrite 
n the state of a i)hysical mixture with pyrite. Certain samples of 

Bull. 213—03 8 


rich black copper-sulphide ore associated with cupriferous pyrite from 
the large mines have been found by Dr. H. N. Stokes, chemist of the 
Survey, to consist mainly of tetrahedrite (copper-antimony sulphide 
with silver, zinc, and arsenic associated; gray copper). This is not 
like normal tetrahedrite of some camps, and is believed to be inti- 
mately associated with chalcocite (black sulphide of copper) and pos- 
sibly some melaconite (black oxide of copper). 

In this camp tetrahedrite occurs occasionally in crystalline form, 
but more commonly, and far more prevalently than has hitherto been 
recognized, under two facies of the massive form. In the copper ores 
in limestone it occurs in large masses as a dull-black powder and a 
crushed gray metallic substance associated with cupriferous pyrite. 
In the lead-silver fissure ores it occurs in regular bands and patches, 
is fine grained, compact, homogeneous, with metallic luster, steel-lead 
gray color, pale-bronze line, and gives a dark-red streak. This 
species, freibergite, contains silver, and is commonly mistaken for 
ruby silver. Exceptionally fine crystals of enargite (sulphide of 
copper and arsenic) were obtained from a single occurrence. An 
excellent specimen of pisanite (hydrous sulphate of copper and iron), 
an alteration product of copper ores, was supplied by Mr. A. F. 
Holden, who suggested that it might be this mineral. It is believed 
that this is I he first occurrence of the mineral reported in this 
country. Other copper-bearing minerals which occur in Bingham are 
bornite, covellite, cuprite, malachite, azurite, chalcanthite, native 
copper, and possibly cubanite, binnite, bournonite, and tennantite. 

(ialena (lead sulphide), which forms the bulk of all the present 
shipments of lead and silver, occurs in tabular bodies in or adjacent 
to fractures which intersect limestone^ shale, porphyry, or quartzite, 
or in two or more of these. Although it is sometimes scattered in 
small amounts through the limestone, it occurs more commonly in 
irregular bands roughly intercrustified witli similar bands of pyrite 
and chalcopyrite, calcite or quartz, and blende. Lead occurs here 
also in cerussite (carbonate of lead), anglesite (sulphate of lead), 
yellow oxide, and dufrenoysite. 

Silver values probably lie chiefly in galena. It is a matter of com- 
mon report among mining men that the granular variety of galena 
carries higher silver values than the cleavable variety. An assay by 
Dr. E. T. Allen, chemist of this Survey, of a composite sample of 
cleavable galena from four of the best-known silver-lead mines in 
Bingham, shows 18.9 ounces silver present, and of a sample of granu- 1 
lar galena only 10 ounces. Native silver has been reported, but was 
not found during the present survey, although it was suspected to 
occur. Ruby silver has not been found. Crystalline specimens 
reported to be ruby silver have been proved, on study of the crystal 
forms, to belong to a different crystal system, and on chemical deter- 1 
minations by Dr. Ilillebrand and Dr. Allen, of this Survey, have been 


found to be tetrahedrite. In a mixture of the crystal and massive 
tetrahedrite Dr. Allen found 325 ounces of silver, which indicates 
that the mineral usually called ruby silver is the silver-bearing spe- 
cies of tetrahedrite, freibergite. 

Gold has been mined in Bingham in two forms — in its primary 
occurrence in country rock and in its secondary occurrence in detri- 
tal deposits. In the former it has been found in pay values included 
in sulphides, both in fissure ores, in pyrite, and possibly in galena 
and in tetrahedrite, and in replacement bodies in limestone. In 
the secondary occurrence rich gravel has been worked, though no 
free gold was obtained during the study of the camp. Unlike the 
primary gold, which is said to have been rough and jagged, placer 
gold is said to occur in thin beaten scales and washed nuggets. Flour 
gold has been found to be evenly distributed through the gravel for 
a distance of 30 feet above bed rock. In the early days when gold 
ores were mined from the silicified superficial portions of the great 
mineralized limestones and treated in stamp mills, only a portion of 
the gold was found to be free and no successful process was secured 
for treating the remainder of the gold content. In the present low- 
grade copper ores gold is an important associate, for it is the gold 
contained in these ores, low as it is, which renders more than one 
Bingham property a commercial possibility. 

Zinc is present in the gangue of lode ores and is most abundant in 
those which lie within porphyry. It forms uneven layers roughly par- 
allel to those of its associates, and irregular bunches and stringers inter- 
mixed with them. A few minute crystals of the light honey-yellow 
variety and of the black variety occur in vugs in veins, but by far the 
greater portion of this mineral is of the blackjack type and occurs 
occasionally granular, but usually massive cleavable. The Bingham 
occurrences of zinc deserve the attention of owners (see p. 121). 

Some other minerals which under suitable commercial conditions 
are of economic value occur here sparingly. Molybdenum occurs in 
grains and bands in the porphyry of the Bingham laccolith, but in 
too small quantities to be of economic value. Gypsum is found 
in fibrous and selenitic form in small amounts in calcareous shale. 
Barite in radiating plates lies at the cores of some veins. Iron is 
found besides in copper sulphides, in magnetite, specularite, and 
limonite, but does not assume commercial importance. In brief, 
then, the valuable ores of Bingham are the copper-iron-gold-silver 
replacement ore, and the lead-silver-copper-gold lode ore. 

Values. — The values of the Bingham ores average very low. Pay 
ore is widely distributed; prospecting in country rock in any part of 
the camp rarely fails to disclose some metals, but bonanzas have 
rarely been found. With very few exceptions the ore which is being 
mined to-day carries such low values as to render its successful 
extraction and reduction either a close-smelting or a concentrating 


proposition. Thus in certain instances it is the accessory gold, lead, 
and silver contents which raise the total value of low-grade copper 
ores safely above the commercial limit. It has been reliably esti- 
mated that a profit can not be guaranteed on a mixed copper ore 
from Bingham whose aggregate value falls below $6. It is under- 
stood, however, that this minimum limit has been lowered and may 
reasonably be expected to be still further reduced. The combination 
of a few higher grade bodies, several of medium grade, and many 
of low grade, together with the variety of types of ore, including cop- 
per, lead-silver, and gold, has proved most essential. This fact, by 
providing the mining industry against early exhaustion, baseless 
speculation, and market fluctuations, has made possible practically 
continuous mining operations from the date of the earliest mining in 
Utah to the present. 

Little reliable information regarding the copper values is available. 
The aA^erage of the assays of three characteristic shipments from a 
typical fissure mine shows a copper content of G.5 per cent. In the 
limestone replacement ore bodies the copper values are understood to 
run somewhat lower. Thus the average of three averages of a great 
number of assays on ore from two of the great copper properties shows 
a copper content of between 3 and 4 per cent. An assay of an average 
shipment from ore in a fissure in quartzite and porphyry gave 44.25 per 
cent lead, and the average of shipments for three years from a mine 
on a fissure in limestone is reported to be 45 per cent. These facts] 
la ken in connection with assays from many mines, warrant, the con- 
clusion that the average of typical lead ore in Bingham is about. 45 
per cent lead. The silver content in two famous lead bonanzas ^aver- 
ages 25.18 ounces per ton. In sulphide-copper ore from the replace- 
ment bodies silver runs from 2 to 4 ounces, and in fissure ores it 
ranges from 18 to several hundred, while ore from a fissure in quartz! 
ite and porphyry affords an average, based upon assays of three nor- 
mal shipments, of 8U) ounces. Gold values from the crests of the] 
great replacement bodies average $10 to 1-12 a ton. Those in cuprif- 
erous pyritic ores average about $2, and those in the porphyry ore! 
average about 25 cents. The pay in detrital deposits is stated in the 
description of placers. 

Occurrence of the ores. — The productive area in the Bingham dis- 
trict is not restricted to any local ore deposit nor to a single zone of; 
deposits. The most important productive belt comprises those mas- 
sive limestones described under "Area! geology" as the middle and 
upper series of the lower great division. They have been found to 
be productive from the desert on the east to West Mountain on the 
west, a distance in a direct line of about 3| miles. The known pro-] 
ductive area of Bingham extends from the Richmond mine on the 
east to the Star mine on the west and from the Midland and Broad 


Gauge mines on the north to the Queen and Lucky Boy mines on the 
south, an area of approximately 15 square miles. The vertical range 
of known ore deposits is marked by those in the Zelnora (8375) and 
the lowest levels in the Brooklyn (5875) and Dalton and Lark (5810), 
a vertical extent of 2,565 feet. 

Ore bodies occur in each of the lithoiogic types of rocks of the dis- 
trict, including limestones, quartzite, shale, and ijorphyry. The lime- 
stones, which have afforded the largest ore bodies, compose the main 
belt and include the Brooklyn-Telegraph and the Commercial and 
Highland Boy members. No ore bodies are known in the massive 
dark-blue limestone underlying these series, but some have been 
found in the siliceous limestone above the Highland Boy horizon and 
in the thin mottled limestone of the Petro-York "bedded vein." 
Although ore occurs in the calcareous shales which characterize the 
great siliceous series over the main limestone belt, exploration shows 
that the rich lead-silver bodies formed under rather than within these 
shales. High-grade lead-silver ore carrying minor values of copper 
and gold occur in fissures which transect the quartzite, porphyry, or 

If we may judge from the occurrence of known ore bodies, two litho- 
iogic types appear to have exerted the strongest influence upon their 
formation, namely, limestone and porphyry; for it is in the main lime- 
stones in the neighborhood of intrusive masses that the large shoots 
of copper sulphides have been discovered. Thus the country rock 
inclosing the great Highland Boy shoots overlies a broad, irregular 
dike sill. The newly proven shoot in the Boston Consolidated over- 
lies the great Last Chance intrusive, and is cut and overlain by por- 
phyry. The bodies in the Jordan-Telegraph-Brooklyn and in the 
Commercial- Yosemite limestones are complexly associated with dikes 
and sills. 

In influencing the position, form, and extent of ore bodies, defor- 
mation of the country rock appears to have constituted a third impor- 
tant factor in the formation of ore bodies, for in Bingham those 
limestones which have been intruded by porphyry inclose the larger 
and more numerous shoots in regions in which strong fracturing and 
Assuring have occurred. The entire country rock is excessively frac- 
tured, crushed, and fissured. These fissures are distinct loci of move- 
ment, of considerable horizontal and vertical extent, bounded by 
highly slickensided and polished walls, and possess in a general way 
the form of planes, but in detail exhibit many inequalities. They 
are not restricted to a few distinct trends, but trend in about equal 
number toward practically all points of the compass. 

The ore-bearing fissures, however, in far the greater number trend 
toward the northeast and southwest, and dip steeply to the northwest. 
Underground evidence shows that Assuring took place in northeast- 


southwest directions, and that later, following a period of mineral- 
ization and Assuring and faulting in northwest-southeast directions, 
recurrent Assuring and faulting took place on northeast-southwest 
planes. It is in connection with the great limestones which have 
thus suffered intrusion and recurrent Assuring and faulting at several 
periods that the larger bodies of copper ore occur, and in the fissures 
that the smaller but valuable bodies of lead-silver ore formed. 

The copper-sulphide ores occur in the general form of flat, attenu- 
ated lenses, mainly Avithin the great" limestone beds, and lie roughly 
parallel with the stratification. In the vicinity of fissures these bed- 
ded ore bodies thicken into well-marked shoots which, following the 
trends of the fissures, often pitch slightly. When these shoots display 
distinct structure, that of the original stratification is seen to be per- 
fectly preserved. 

The fissure ores carrying lead and silver, with subordinate amounts 
of gold and considerable zinc, differ much from the copper ores in 
the character of their occurrence. They form tabular bodies which 
mayor may not be sharply limited by fissure walls, and extend sev- 
eral hundred foot horizontally and in depth. These lodes occur as a 
series of thin, sinuous, irregular pay streaks, which combined consti- 
tute bodies which are relatively thin when the fissures lie in a quart zite 
or porphyry country, but arc of much greater width where the fissures 
cut calcareous bods. This selective act ion, indicated by bulging or 
increased lateral extent, which is exhibited between calcareous and 
noncalcareous rocks, is manifested in precisely similar manner 
between different bods of the same calcareous mineral. In addition 
to this change in the size of fissure veins, lesser variations occur, 
within lenses lying in a noncalcareous country, which constitute rec- 
ognized shoots. The structure of the fissure ore consists of a rough 
banding of the several constituent minerals which form the vein, in 
roughly systematic arrangement 'from the center of the vein to either 
wall. In brief, there is a rough comb or crustified structure. 

The copper- gold ores inclosed in the porphyry of the Bingham lac- 
colith, however, present an interesting form of occurrence of an 
entirely different character. This ore, which consists of grains of 
cupriferous pyrite and chalcopyrite, is thoroughly disseminated 
throughout the intrusive mass, and seems to increase slightly in value 
in the areas which have suffered the maximum shattering and 

The facts which have been observed with regard to the occurrence 
of the ore deposits of Bingham afford evidence for a very reasonable 
explanation of their formation, and these conclusions lead to several 
suggestions which it is hoped may prove to possess much commercial 
value. As the present abstract does not admit of such theoretical 
discussions, however, they must be deferred until the publication of 
the complete report. 



History of placer raining. — Bingham Canyon stands alone among 
the numerous successful mining districts of Utah as the only locality 
in the State where placer mining has been successfully prosecuted. 

Free gold was first discovered in Bingham in 1864 by a party of veteran Cali- 
fornia miners who, returning from Montana to pass the winter in Salt Lake, pros- 
pected the canyon in the early part of that year. It was not, however, before 
the spring of 1805 that much work was done in prospecting for that metal/' 

It is also stated 6 that gold in the gravels was first discovered in the 
fall of 1860 and was mined then by Peter Clays and G. W. Crowley. 

The chief period of placer mining in Bingham extended from the 
date of discovery to 1871. Since then there has been a steady decline 
in the output of placer gold, except during the year 1881, until the 
present day. As late as 1898, however, the Arganaut was hydrau- 
licked at the mouth of Carr Fork, and at present desultory work is 
conducted by the veteran gravel miner Bartholomew Gardella upon 
gravels on the continuation of this channel known as Dixon Bar and 
at the head of Bear Gulch. Late in the nineties the West Mountain 
Placer Company conducted extensive explorations in the gravels 
at the bottom of main Bingham Canyon, immediately below Dry 
Fork, and reported that gold occurred there in pay quantities, but 
that they were unable to handle the water. Since then (his property 
has remained idle. 

Occurrence. — Detrital gold has been found at several points in 
Bingham in gravels of different ages. These lie at various elevations 
in the canyon, and range from the rock bottom of the present canyon 
up to points on its side slopes several hundred feet above. They indi- 
cate former positions of the canyon bed, and the pay inclosed by the 
gravels then deposited shows that the streams were then transporting 
gold shed into them from their inclosing walls, and depositing it with 
their other burdens. The deepening and widening of the canyon 
through the same agencies which are to-day continuing that work 
resulted in cutting down through and removing the gravels from the 
early stream beds. So the high gravels or bars seem to be remnants 
of stream gravels deposited during the earlier stages of canyon 
cutting, and, occurring at different levels, they mark successive 
stages in the work of cutting down to the present level. 

The bars consist of isolated deposits of waterworn gravel tying 
upon waterworn bed rock at the noses of spurs and at such points as 
have escaped removal by development of the present topography. In 
some cases these are patches on the sides of the canyon — in one 
instance there is a complete section of an earlier channel showing 
both walls, which are truncated upstream and downstream by later 
transverse valleys; and in another, extensive buried stretches of an 

"Murray, J. R., Mineral Resources, Territory of Utah, 1872, i>. 
''Personal communication, 1900, from Daniel Clays. 


earlier channel have been preserved. The only possibility for placer 
mining on a large scale is in the gravels which cover the bed rock of 
the main canyon in its lower extent to a great depth. 

Values. — Values, as a rule, have been good. While some of the 
high-lying patches panned rather low, rich bars were not uncommon. 
Gravel from the bottom of main Bingham Canyon in this same vicinity 
is reported to have brought 18 to 20 cents a yard. The pay levels of 
the West Mountain gravel are said to yield 8 to 10 cents a pan, and 
some of them 6 and 9 and 15 cents a yard. A recent sampling of the 
gravel in the Arganaut cut shows that the lower 30 feet of gravel 
averages 6 cents per cubic yard, and that the lowest G feet averages 
18 cents. 

In general the gold is coarse, varying from half an ounce downward. 
A nugget reported to be the largest ever found in Utah was discov- 
ered in the Clays bar near the mouth of Damphool Gulch by Daniel 
Clays. This is stated to have weighed 17 ounces 15 pennyweight, 
and to have been valued at $128. The fineness is generally considered 
to range from 850 to 875. In round numbers the total known output 
of placer gold from Bingham is about $1,500,000, while the entire 
output would undoubtedly aggregate about $2,000,000. 


Although in the economic work of the Geological Survey "the 
fundamental principle * * * has been that its primary object is 
to determine the general laws which govern the foundation of ore 
deposits," a matters come to notice on which suggestions have been 
given which have frequently proved of immediate commercial value. 
During the progress of the work in Bingham, several points have 
appeared in which it would seem that some improvement would be 
advantageous. It, is hoped to develop some of these suggestions in 
the complete report. At present they may be barely stated. 

The geology of Bingham presents many extremely discouraging 
difficulties. A great thickness of rocks of similar physical character 
and structure have been intruded, crushed, and faulted to a degree 
of complexity which might reasonably have been considered impos- 
sible. Instances are known in which good miners and able experts 
have been thoroughly baffled by this complexity, and so it is not 
strange that mining men familiar with the camp should believe that 
successful mining in Bingham requires, to an unusual degree, thor- 
ough practical geological experience. One familiar with these prob- 
lems appreciates the significance of the common saying among miners, 
that to direct underground work in Bingham successfully one must 
have ' ' grown up with the camp. " 

The irregular porphyry bodies have led to unwise exploration 
through failure to comprehend their origin, and thus their form and 

« Emmons, S.F., Eng. and Min. Jour., Vol. LXXIV, p. 48. 


extent. The Bingham porphyry is intrusive in origin. It was forced 
into the country rock from "below along the ways of least resistance 
when in a molten, semiliquid state, and on cooling assumed forms of 
irregular dome-like masses, laccoliths; roughly vertical wall-like bod- 
ies, dikes; and nearly flat bed-like bodies, sills. Thorough examina- 
tion of the form of the body on the surface should give the key to the 
type of the intrusive, and thus determine the most direct and economic 
method of attack. 

Again, faulting, that common and characteristic feature of Bingham 
structure, has caused loss through misdirected exploration. Exten- 
sive detailed underground work throughout the camp goes to show 
that the prevalent idea among Bingham miners, that faulting is 
systematically of one type, with the character of displacement uni- 
versally the same, is an error. Instances are at hand which x>rove 
that many types of faulting exist at Bingham, and that the character 
of the displacement is not restricted to one form, but includes many. 
In view of this fact each case must be worked out on its own evidence. 
Further, no little time and money have been lost by guessing on the 
direction of offset of ore bodies by faulting, and driving aimlessly in 
accordance with such guesses. When a lens of copper ore which lies 
along the strike of the beds and well within a thick limestone is found 
to be cut, displaced, and temporarily lost by faulting, it is usually 
advisable, in case the surface geolog} 7 does not afford a clue, to drive 
to the nearest wall, quartzite foot or hanging. There the member 
which lias been brought opposite to the contact may be found, the 
usual criteria indicative of the direction of movement observed, and 
the fault duly proved. The fact that a lens of copper sulphide 
pinches when followed down on its dip is not necessarily an indication 
that the ore has permanently disappeared. It is the habit of such 
lenticular bodies to thicken and thin irregularly. Accordingly con- 
tinued exploration in depth might reasonably be expected to be 
rewarded by the discovery of similar lenticular ore shoots. Although 
copper shoots of this type attain great size and value in the large 
limestones, they are erratic and should not be expected to prove as 
constant in extent, either perpendicularly or horizontally, as smaller 
but more faithful fissure ore bodies. 

The zinc contents of the Bingham ores have never received the 
attention they merit. Highly zinciferous ores have not onlj r been dis- 
dainfully rejected, but they have been regarded as losing proposi- 
tions, owing to extra smelting charges. 

In several cases Bingham ores are reported to have carried regularly 
15 pei' cent of zinc. In some instances values of 32 and 45 per cent 
zinc have been reported in Bingham. Although these ores may pre- 
sent some problems different from those encountered in camps where 
zinc ores are successfully worked, it would seem highly advisable to 
conduct more extensive experiments on them before abandoning ore 


containing so high a percentage of this valuable metal. A recent 
proposal of the American Smelting and Refining Company in the 
Jordan Valley to treat zinc ore from southern Utah, the present 
remodeling of the Anchor mill, and the recent thorough equipment of 
the custom zinc plant of Park City, afford Bingham owners a further 
opportunity to attempt to save their zinc values. 

Even without either this additional saving or the discovery of new 
ore bodies, the present condition of the camp is promising. Unless 
the price of copper falls sufficiently to necessitate the suspension of 
mining operations, the fact that the United States Mining C'ompan^ 
has begun regular heavy shipments from the ore shoots which have 
been developed in their properties during the last few years; that 
valuable additional shoots of pay ore have recently been discovered 
in the Utah Consolidated property; that a valuable shoot of sulphide 
copper ore of pa} 7 grade has been proved in the Boston Consolidated 
ground; that the work of opening and developing the consolidated 
mines on the cast slope of the range, acquired by the Bingham Gold 
and Copper Company, is well advanced; and that extensive bodies of 
high-grade lead-silver ore have recently been discovered in the Com- 
mercial and Ashland properties, assure a strong consistent increase 
in the output from Bingham in the immediate future. Furthermore, 
although the camp has been rather thoroughly prospected, it is rea- 
sonable to expect that future exploration will reveal (1) new shoots of 
valuable copper-sulphide ore in the few stretches of the great lime- 
stones which remain unexplored, (2) pay lodes of the Silver Sheald 
type in fissures in t lie quartzite and porphyry about the upper portion 
of Bingham Canyon, and (3) new lead-silver bodies of the Montezunia- 
Ben Butler-Erie type in fractured or fissured zones in or adjacent to 
the calcareous carbonaceous shales of the upper series lying north- 
west of Bingham Canyon and Carr Fork. 


By J. S. Diller. 


The copper deposits of the Redding region of California lie among 
the foothills and mountains about the northern end of the Sacramento 
Valley, within the Redding quadrangle. This quadrangle was sur- 
veyed geologically in 1901-2, with a view to discovering the general 
relations of the ore deposits, and only such results can be announced 
at the present time, as detailed surveys have not yet been made. 
Four copper districts occur, more or less completely isolated, in which 
there lias been extensive prospecting, but only the two largest, Bully 
Hill and Iron Mountain, have thus far yielded paying mines. 


Sedimentary rocks. — The copper region contains an extensive series 
of sedimentary rocks, ranging from the Devonian into the Miocene, 
associated with igneous masses of various ages, shaj^es, ami kinds, 
which have been intercalated or intruded into the sediments. The 
general abundance of fossils in the Cretaceous, Jurassic, Triassic, 
Carboniferous, and Devonian sediments, from all of which large col- 
lections have been made, has rendered it i>ossible to work out the 
structure in detail with a high degree of probability. 

Unconformities. — The great succession of sediments is wholly of 
marine origin; but their relation to one another, whether conformable 
or unconformable, is not easily determined, for in most cases igneous 
rocks lie between them. Thus the relation in succession between the 
Devonian, Carboniferous, Triassic, and Jurassic is much obscured by 
igneous rocks, but between the Jurassic and Cretaceous there is a 
conspicuous unconformity which represents not only a long interval 
of time, but a great epoch of mountain building followed Iry erosion. 
The mountain-building epoch at the close of the Jurassic was a time 
of rock folding, faulting, and crushing, as well as igneous intrusion, 
which greatly modified the rocks and prepared the way for the asso- 
ciated ore deposits. 

Relation of ores to sedimentary' rocks. — Disseminated ores occur at 
many points in all the sediments of the copper region older than the 



Cretaceous, but thus far no large bodies of ore commercially workable 
have been observed in the sedimentary rocks, although such rocks 
occur in the neighborhood of some of the mines. In the Afterthought 
and Bully Hill districts the nearest sedimentary rocks are chiefly shales 
and limestones of Triassic age; in the Black Diamond district, shales 
and limestones of Carboniferous age; and in the Iron Mountain dis- 
trict, shales and limestones of Devonian age. Neither the kind of 
sediment (except the limestone at Black Diamond, to be noted later) 
nor its age is of special importance in relation to the ore bodies. 

Igneous rocks. — The more important rocks of the copper region, so 
tar as the ore deposits are concerned, are of igneous origin, and of 
these there is a great variety occurring in various forms. They may 
be most conveniently treated in this connection as lavas or surface 
flows, granitic rocks, and dike rocks. 

Lavas. — The most important body of igneous rocks of this type is 
an extensive series of lavas which penetrate the older formations and 
lie to a large extent between the Triassic and Carboniferous strata. 
The volcanoes from which they flowed burst forth during the closing 
stages of the Carboniferous, for the tuffs resulting from the earliest 
eruptions contain carboniferous fossils. The thick mass of volcanic! 
made up of tuffs and sheets of lava extends into the Triassic, for fos- 
sils of that group are found in the later tuffs. Many of the inter- 
bedded tuffs contain minute fossils of marine organisms, suggesting 
that the eruptions were largely submarine. 

M uch of t lie lava contains porphyritic quartz, and in general may be 
designated metarhyolite, but a large part, being without- free quartz 
and less siliceous, has the appearance of metaandesite. A peculiarity 
of many of these rocks is that they are rich in soda. 

A great belt of these ancient volcanic rocks lies east of the Car- 
boniferous limestone, between Squaw Creek and the McCloud, and 
forms a succession of prominent peaks from Bollibokka Mountain, 
through Salt Creek Mountain, Minnesota Mountain, Town Mountain, 
and Horse Mountain to Pit River and beyond a lower ridge to the 
Sacramento Valley. A second belt west of this lies about the Sacra- 
mento River, embracing the Iron Mountain district and extending as 
far north as Backbone Creek. These two areas of ancient lavas, with 
associated dikes, include all the productive copper mines and the 
most active prospects of the region. 

Ancient lavas occur also about Bagley Mountain, west of the Great 
Bend of Pit River, but they are usually of more basic types than 
those mentioned above. 

Granitic rocks. — Two areas of granitic rocks occur, one about 
Shasta, between Keswick and Iron Mountain, and the other about, 
Bayha and Pit River ferry, but neither of these masses is yet known 
to contain important bodies of copper ores, although \fo.&y contain 
some auriferous quartz veins. Dikes from these granitic masses cut 


the lavas noted above, and are themselves intersected locally by 
dikes of diabase, so that in order of age the granitic rocks come 
between the great mass of older lavas and younger dike rocks. 

Dike rocks. — The dikes are of a large variety of rocks, and range 
in size from a few inches to a hundred feet or more in width. They 
intersect older igneous rocks as well as sedimentary rocks, and are 
widely distributed throughout the field. Some are decidedly porphy- 
ritic, but the majority are fine grained and compact, without promi- 
nent crystals. 

Of the porphyritic type some contain prominent crystals of both 
quartz and feldspar, and are closely related to the granitic rocks, 
with which they may be connected. They may hold an important 
relation to the ore bodies, but the relation can not be fully determined 
without detailed investigation. Dikes of this sort occur most abund- 
antly in the western portion of the field, where they may be seen in 
places directly connected with the granitic rocks. 

A decidedly porphyritic type, containing prominent crystals of 
feldspar only, occurs near the Uncle Sam mine of Squaw Creek and 
at a number of points about Bear Valley, but deposits of ore have 
not been noted in their vicinity. 

The most abundant dike rock is an altered variety of basalt or 
metabasalt in which the feldspars usually have that ophitic arrange- 
ment which characterizes diabase. It is generally not porphyritic 
like the other diabasic rocks, but compact and greenish in color, espe- 
cially on fresh fracture. Large areas of it occur about the Carbon- 
iferous limestone from Gray Rock northward, and dikes of it cut 
through the limestone, giving rise to interesting and important con- 
tact deposits of ore unlike any others in the region. South and east 
of Bass Mountain is a large mass of this ancient igneous rock, and 
along the Sacramento River there are numerous dikes of it cutting 
the older lavas. 

Folding and displacement of the rocks. — The rocks of the copper 
region are folded and faulted, but the extent in both cases is limited, 
and varies with the kind of rock and locality. The shales, sand- 
stones, and tuffs are usually soft rocks with little rigidity. They show 
many sharp folds and faults, but an attempt to trace them reveals 
their very local character and small extent. To determine whether 
large folds and faults are present the Triassic, Carboniferous, and 
Devonian limestones afford the best horizons for observation. Owing 
<> their light color these rocks may be seen from a long distance in 
tracing structure, and each, having its own characteristic fossils, 
nay be identified with certaint}^ The general course of these rocks 
o«||icross the region is nearly north and south, but in the Furnaceville 
listrict, as well as about the head of Squaw Creek, the Triassic lime- 
ullstone turns easterly, sending a synclinal point in the one case southwest 
4 ;o Bear Mountain and in the other northwest to the head of Claiborne 

12() CONTRIBUTIONS TO ECONOMIC GE3LOGY, 1902. [bull. 213. 

Creek. With these exceptions there are no irregularities in distribu- 
tion of the Triassic and Carboniferous limestone to indicate folding or 
faulting on a large scale, although small gentle folds and faults are 
common along the limestone front in each case. The Devonian 
limestone is so cut by igneous rock as to afford no decisive evidence. 
The geological date of the folding and faulting accompanied by 
much crushing of the rocks was at the close of the Jurassic, when the 
Sierra Nevada and the Klamath Mountains were formed and raised 
above the ocean to initiate an epoch of vigorous erosion represented 
by the unconformity between the Cretaceous and Jurassic. The 
epoch of rock crushing gave rise to the shear zones which later became 
the seat of circulating waters and finally the ore deposits of to-day. 


The Afterthought district is very small. It lies near Cow Creek, 
where the copper-bearing rocks run under the later lavas from the 
volcanic ridge north of Lassen Peak. 

The country rock is chiefly igneous metarhyolite, and cuts Triassic 
slates, with large limestones near by. The ore bodies, which are 
chalcopyrite with other sulphides, as far as may be judged from sur- 
face openings — the tunnels, long unused, have caved in — occur near 
the contact between the two rocks without additional evidence of 
contact metamorphism. The adjacent rocks show extensive iron and 
copper staining. The conditions here appear to be similar to those 
of Bully Hill and Iron Mountain districts, but the extensive prospect- 
ing of years ago failed at that time to develop a paying mine. 
Later improvements in smelting low-grade ores may have changed 
the status of this property. 


Lor"/ inn and extent. — The Bully Hill district lies about 15 miles 
directly north of the branch railroad at Bellevista. It has a length 
of several miles in a direction a little east of north, and embraces not 
only the openings in Bully Hill, but also those about Copper City. 
Some openings on the slope of Horse Mountain might here be included, 
but at present the prospects, although in the same volcanic masses, 
are not sufficiently extenswe to furnish good ground for judgment. 
It is especially interesting, however, to note that Horse Mountain is 
the only locality in the region where native copper was found in the 
comparatively fresh-looking igneous rock. 

Country rocks. — The common country rocks are wholly igneous, j 
generally metarhyolite, rich in porphyrinic quartz like that of Bully | 
Hill, of which an analysis by Dr. E. T. Allen is given below (1). Some 
of the rock is metabasalt without porphyritic quartz. This is espe- 
cially the case in the Bully Hill mine, where the rock most intimately 



associated with the largest ore bodies yet discovered is basaltic in 
character and particularly rich in soda, as indicated by the following 
chemical analysis (2) by Dr. Allen. 

Analyses of country rock of Bully Hill district. 







Na 2 

K 2 0. 

H 2 0- 

H 2 OH 

Ti0 2 . 

Zr0 2 

C0 2 . 



Cr 2 3 





































100. 24 






1. Bully Hill mine 400 feet west of ore body, west end of tunnel 2. 

2. Bully Hill mine east of ore body, in tunnel 3. 

g through 

This interesting rock (2) occurs in the form of a dike cuttii 
the older igneous rocks and the Triassic slates. Much of the rock in 
he mine, especially in the Copper City workings, looks like slate and is 
so called by the miners. The resemblance, however, is only superficial 
md results from the squeezing and shearing of the metarhyolite until 
t possesses a slaty structure. The ore deposits are found in the zones 
)f shearing. 

The shear zones are usually of limited extent ; none have been traced 
ipon the surface for over a mile. They vary in width from a few 
nches to nearly a score of feet, and are either vertical or dip steeply 
o the west, trending a few degrees east of north. In Bully Hill there 
ppear to be three shear zones, two of which are well mineralized and 
ontain valuable ore bodies. They are nearly parallel and only a few 


hundred feet apart. The western one is wholly in the metarhyolite of 
Bully Hill; the other, near the surface, is within the dike of meta- 
basalt, and farther down follows the contact between the metabasalt 
and the metarhyolite more or less regularly to a depth of about 500 

The walls are sometimes sharp, but at many places are indistinct, 
grading into the material of the shear zone. 

Ore bodies. — The ore bodies occur very irregularly distributed in 
shear zones and range in size from lenticular or sheet-like nodules less 
than an inch in diameter to hundreds of feet long and up to nearly 
a score of feet in thickness. The crushed rock in the shear zone is 
not always mineralized, but generally it is more or less richly impreg- 
nated with ores, sometimes to complete replacement. In the Copper 
City workings, where these features are well displayed, the small ore 
nodules are chiefly zinc blende, with small amounts of pyrite and 

One of the most important matters concerning ore bodies as they 
lie in the shear zone is that their longer axis usually pitches steeply 
to the north, so that when an ore body is struck the general position 
is a guide to its prospecting. 

Zones in large ore bodies. — Near the surface each large ore body is 
naturally divided into three zones. Beginning at or near the surface 
with the zone of oxidation, where the material is generally known as 
gossan, it passes downward into the zone of enrichment, Avhere the 
so-called black oxides of the miners occur, and finally at greater 
depths into the zone of the original sulphides. These zones are often 
extremely irregular, but are generally well defined. 

Zone of oxidation. — The gossan of the Bully Hill ore bodies is, in 
the main, porous limonite, occasionally with small caves containing 
beautiful stalactites of the same mineral. It results from the altera- 
tion of the pyritous ores, from which nearly everything but the iron 
has been carried away by percolating waters, leaving the iron in the j 
form of a hydrous oxide — limonite. The gossan usually contains also 
a larger portion of the gold of the original ores, but the copper is 
mostly carried down to form rich sulphides in the next zone. It may 
combine with carbon dioxide and give rise to the green and blue car- 
bonates of copper, or be reduced and native copper result. All of 
these ores and also native silver occur locally in the lower part of thel 
gossan or upon the borders of the Bully Hill ore bodies at greater! 
depths. The red oxide (cuprite) rarely occurs at Bully Hill, but, 
according to Mr. Oxam, the mine superintendent, a mass several feeti 
in diameter was found in clay 6 feet from the ore body at a depth of 
151 feet. The bottom of the gossan is very irregular, extending fan 
down into the ore bodies along fissures favoring oxidation. On gentle 
slopes it usually extends 70 or 80 feet below the surface, and some- 1 
times much deeper, but upon steep slopes the gossan may be nearly 


all washed away and the original sulphides be near the surface. The 
gold from the gossan washed away in past ages accumulated in Town 
Creek and afforded the rich placer mines of the early days. 

Zone of enrichment. — Next below the gossan occur the dark ores 
which the miners usually designate " black oxide," but in reality they 
appear to be chiefly dark sulphides, chalcocite, and sphalerite, gen- 
erally mixed with pyrite, chalcopyrite, and barite. In some places 
there is only a thin film of this material between the gossan and the 
yellow sulphides, but generally in the Bully Hill district it extends 
for 10 feet or more to the predominantly yellowish sulphides. Chal- 
cocite is most abundant near the borders of the pyritous ore mass, 
and small nodules of it are found in the adjacent fissile clays at much 
greater depths. Bornite occurs locally near the gossan with black 
sulphides; also at greater depths with chalcopyrite, pyrite, and sphale- 
rite. While its secondary origin in the enriched zone not far beneath 
the gossan is evident, that at greater depths is more doubtful. 

Fresh chalcopyrite was found in the zone of enrichment incrusting 
secondary chalcocite ; hence it is evident that some of the chalcopy- 
rite must be secondary. The lower limit of the zone of enrichment 
is not sharply defined, and it will be discovered only by detailed 

Zone of primary sulphides. — The workings in the Bully Hill mine 
in October, 1902, had attained a depth of about 512 feet, which is 
considerably below the lowest level where the writer saw any of the 
secondary ores. 

However, some of the miners report local "black oxides" at that 
depth. The ore in this zone is chiefly pyrite, with some chalcopyrite 
and a varying amount of sphalerite. 

Gang ue. — The gangue mineral of a large part of the Bully Hill ore 
is barite. It is rarely abundant, and often is so finely disseminated 
as to be invisible in the ore, yet greatly increases its weight. The 
source of the barite is most likely to be found in the metarhyolite, 
whose feldspar appears to contain a notable amount of barium. 

Selvage. — On the east wall there is generally a white selvage-like 

material which ranges from a mere film to 12 feet in thickness. A 

hemical examination by George Steiger shows it to contain Na 2 20, 

K 2 3.28, and H 2 11.87, from which it appears to be a mixture of 

I J (kaolin and sericite. It affords an excellent material for lining the 

converters. This white selvage is sometimes found on both sides of 

jhe ore, and, combining, cuts off the ore. The selvage may be wholly 

bsent, in which case the ore is directly attached to the wall rock. 

he wall rock of metarhyolite on the west side is usually much fresher 

han that opposite, and shows the hard, knotted, flinty character of 

nil |ihe surface. 

.ml Prospecting. — It is evident that gossan, and to some extent also the 
;ii.j peculiar knotted or brecciated metarhyolite, is to be the main guide 

Bull. 213—03 9 


in prospecting about Bully Hill and the great volcanic belt extending 
north to Bollibokka Mountain. Prominent limonite deposits from 
iron springs strongly suggesting gossan beneath were seen at several 
points a short distance northeast of Bully Hill, on the area of Triassic 
slates. The slates along the contact with the volcanics are in places 
richly impregnated with pyrite, but thus far no mines have been 
opened. This field is well worthy of careful prospecting and is now 
receiving attention, for recently much work has been done on some 
claims near Bollibokka Mountain. 


The Black Diamond mine, which was practically closed in 1002 
except for a small amount of prospecting, is about 20 miles northeast 
of Redding. It furnishes an excellent example of ore deposits on or 
near the contact between limestone and diabase. The relations of 
the deposits in this district differ widely from those of the other dis- 
tricts. The limestone and associated sediments are well characterized 
by fossils of Carboniferous age. 

Small masses of pyrrhotite a and chalcopyrite occur, also pyrite and 
magnetite with limonite and other secondaiy minerals. The ore is 
associated with coarsely crystalline green fibrous pyroxene and gar- 
net, whose relations are not so easily perceived in the mine workings 
underground, but upon the surface are illustrated at many points in 
the neighborhood along contacts of diabase dikes which cut the lime- 
stone. The best exposures are upon the crest of the limestone ridge, 
where it is crosscut by a number of diabase dikes running east and 
west and ranging from 5 to 100 feet in width. Along the edges of 
these dikes in contact with the limestone at many points pits have been 
dug into the iron-stained fibrous masses of pyroxene mixed occasionally 
with garnet, serpentine, and traces of ores. The fibers of pj 7 roxene 
several inches in length are perpendicular to the contact and are 
conspicuous. Numerous open cuts and tunnels have been made in 
connection with the Black Diamond and Roseman group of mines. 
All were not examined, but as far as seen the relations were all 
essentially the same as described above. 

The dike rock in question, here designated diabase, is composed 
largely of calcic feldspar, which generally has the ophitic arrange- 
ment characteristic of diabase, and incloses chlorite, epidote, magne- 
tite, and quartz resulting from the alteration of feldspar and pyrox- 
enes. The amount of quartz varies, and in some cases it seems a 
primary constituent. 

These contact deposits have been exploited chiefly about Grey 
Rock, and to a less extent north of Pit River, where work is now 
progressing in an open cut, iron ore being taken out for flux at the 
Bully Hill smelter. The mass of magnetite incrusted by limonite is 

"The pyrrhotite was examined for nickel, but there is none present. 


large, and what it may lead to below is an interesting question. 
Associated with the magnetite are streaks of yellowish- green garnet 
and possibly also some pyroxenes, indicating that this mass of mag- 
netite is a contact phenomenon. 


The largest and most important district of the copper region, as 
far as known at present, lies west of the Sacramento River and 
extends from Iron Mountain northeast for about 25 miles to the Sum- 
mit mine northwest of Kennett. Only one mine in the district, that 
of the Mountain Copper Company at Iron Mountain, is productive, 
although there are a number of others — for example, the Shasta King 
and the Mammoth — that are not only extensively developed, but 
rapidly approaching the productive stage. 

Iron Mountain mine. — The Iron Mountain ore bodies are marked 
upon the surface by the most prominent gossan of that region. It is 
chiefly limonite, which in the early days was mined for gold and 
silver. In places the porous gossan extends to a depth of over 100 
feet, changing abruptly from the oxides to the sulphides, but upon 
the steep slopes bordering the canyons the gossan has been denuded 
and the bodies of sulphides lie near the surface. 

In the Iron Mountain vicinity there are two principal bodies of ore; 
one, the Iron Mountain, which has been large^ mined, is said to have 
been about 800 feet long, 100 to 400 feet wide, and traced to a depth 
of r>00 feet. The other ore body, the Hornet, has a greater length, 
but less width, and has been thoroughly prospected. 

The wall rock on both sides is metarhyolite, which, according to 
Dr. W. F. Hillebrand's partial analysis, contains 5.16 per cent Na 2 
and only 0.40 per cent K 2 0, with 0.015 per cent BaO and 74.52 per 
cent Si0 2 . It is somewhat remarkable for containing so much more 
soda than potash, and appears to be related to the soda rhyolites 
described by Dr. Palache near Berkeley, Cal. 

The shear zones containing the ores strike nearly northeast and 
southwest, dipping vertically or steeply co the northwest. The ore 
bodies are elongated, flattened, lenticular in shape, and at least in 
some cases pitch in the shear zone to the northeast. 

The ores where seen in the Hornet were wholly sulphides, with the 
[Copper as chalcopyrite intimately mixed with pyrite. Chalcocite, so 
common in the dark ore at Bully Hill, was not seen in the Hornet 
| body. Sphalerite is present and occasionally forms streaks through 
the pyritous ores, giving the mass a decidedly schistose structure. 
j Whether this structure is derived from the schist which the ore is 
supposed to have replaced, or originated in the ore during or after its 
(deposition, could not be determined without more detailed investiga- 
tion. Wherever the schistose structure was observed it was generally 
[parallel to that of the adjacent schistose igneous rock, but some of 


the small nodules inclosed in well-defined schistose structure show no 
trace of it internally. Quartz is often present in the ore, but barite, 
so common at Bully Hill, is absent in the Iron Mountain district. 

The ore bodies usually separate easily from the wall rock, and at 
many points there are considerable masses of sericite selvage, but 
none so large as in the Bully Hill mine. The ore bodies are cut by 
small transverse faults, and, as pointed out by Mr. Lewis T. Wright, 
the general manager of the Mountain Copper Company, the sides of 
the ore bodies are occasionally polished by movement since the ore 
was deposited. 

Balaklola and Shasta King. — Northeast of Iron Mountain, in the 
same district, there are many claims more or less extensively pros- 
pected, among which may be mentioned the Sugar Loaf, King Copper, 
Spread Eagle, and Balaklala; but it is not until Shasta King, on Squaw 
Creek, is reached that extensive activity is found. The Trinity 
Copper Company, Mr. A. H. Brown, general manager, controls the 
Shasta King, Uncle Sam, and numerous other claims in the neighbor- 
hood, and is cautiously developing them. The ores at the northern 
end of the district are in general not so rich as those of Iron Moun- 
tain and need to be handled under the most favorable conditions. 

SI last a King is north of and below Balaklala, which is on the oppo- 
site side of Squaw Creek, and it seems probable that their ore bodies 
lie in the same shear zone. The country rocks in both places may be 
most appropriately designated metarhyolite. At Balaklala a large 
pyritous bod}* of ore lies a short distance beneath the slope. It has 
the general strike of the district and dips to the northwest nearly par- 
allel to the slope. Although much gossan occurs in the region, the 
slopes are usually so steep that it has been removed, and the dark 
sulphides form a very thin layer between the gossan and the pyritous 

In the Shasta King the ore body lies nearly flat and at its western 
end above is firmly united — "frozen" — to the country rock. This is 
exceptional in the copper region and even about the same ore body, 
for along its eastern border it has a well-defined selvage ranging from 
a mere film to a foot in thickness. 

Beyond Squaw Creek the Mammoth mine and the Summit, on Little 
Backbone Creek, are near the northern limit of the district. 

Detailed maps on a larger scale than that of the folio publication, 
which is only 2 miles to the inch, are now being made, preparatory to 
a special detailed study of these mining districts. 


By Waldemar Lindgren. 


The study of the copper deposits at Clifton was begun in October, 
1901, and finished five months later, in May, 1902. During the exam- 
ination I was assisted by Mr. J. M. Boutwell. The results of the 
investigation are expected to be published in the form of a profes- 
sional paper. As yet, however, the necessary office work, including 
the examination of the ores and minerals, is not finished, and the 
following resume is therefore to be considered only as a preliminary 
statement, which may be modified in some respects in the final report. 


The Clifton mines were discovered in LS72, but owing to adverse 
conditions, principally the absence of railroad communication, the 
district did not attain prominence for a number of years. During late 
years the production lias been increasing steadily and rapidly, due prin- 
cipally to the discovery of very large bodies of low-grade ore adapted 
to concentration. During the last eight or ten years the Clifton dis- 
trict has, in point of production, ranked third among the copper dis- 
tricts of Arizona, being preceded by the United Verde and by Bisbee. 
The gradually increasing production amounted to 38,000,000 pounds 
of copper in 1901. During that year the sequence became reversed, 
Bisbee leading with 39,800,000 pounds, followed by Clifton with 
38,000,000 and United Verde with 34,500,000 pounds. It is believed 
that a still further increase took place in 1902, but statistics are not 
yet available. It is probable, indeed, that during the year just closed 
the Clifton mines produced more copper than any of the other camps 
in Arizona. 

The production of Arizona is at present a little more than one-fifth 
of the total production of the United States. 

At the present time there are three large companies at Clifton smelt- 
ing copper on an extensive scale. These are : (1) The Arizona Copper 
Company, having mines at Metcalf and Morenci, a few miles north- 
west of Clifton, and a smelter located at Clifton. The production of 
this company in 1901 was 20,500,000 pounds. (2) The Detroit Copper 
Company, having mines and smelting works at Morenci. In 1901 the 



production of this company was 17,500,000 pounds. (3) The Shannon 
Copper Company, having mines at Metcalf and smelting works a 
short distance below the town of Clifton. This company began oper- 
ations on a large scale in 1002, and started its furnaces in the month 
of May of that year. 

There are a number of smaller mines and prospects, but their pro- 
duction cuts a comparatively small figure. 

Situated in the southeastern part of Arizona, on the north side of 
the Gila River and only a few miles from the New Mexico line, Clif- 
ton is connected with the Southern Pacific Railway by an independent 
road leaving the main railroad line at Lordsburg, N. Mex. From a 
point on the Gila River along this road a narrow-gauge railroad 
branches and continues to Morenci, direct communication between 
Clifton and Morenci being impracticable on account of the great dif- 
ference in elevation. 


On the north of the broad valley of Gila River lies, in this vicinity, 
an irregular mountain region with no well-defined ranges. The ele- 
vations in the Cila Valley are about 3,000 feet. The highest elevations 
in the mountain region adjoining the valley on the north are about 
8,000 feet. Rising gradually from the Gila River to the base of the 
mountains is a broad terrace of detrital material, attaining at that 
point elevations of about 4,500 feet. From this line, where the older 
rocks emerge from the old alluvium of the Gila Valley, a steeper slope 
begins, furrowed by sharply incised ravines and gulches. The Gila 
River in this vicinity receives two tributaries — Eagle Creek and the 
San Francisco River, both flowing southward and heading on the high 
volcanic plateaus near the boundary line between Arizona and New 
Mexico. These streams flow in moderately deep and sharply incised 
canyons, and are evenly graded throughout their whole course, which 
is generally bordered by a strip of bottom land, the width of which 
rarely exceeds a few hundred feet. In their upper courses these 
rivers flow through canyons cut in Tertiary lavas or older rocks, 
while the lower part of the San Francisco River, at least, is cut to a 
depth of about 600 feet in the old Pleistocene terraces mentioned 
above as adjoining the Gila River on the north. Clifton is situated 
on the San Francisco River, near the point where the older rocks 
emerge from the Pleistocene terraces, and has an elevation of 3,405 
feet. At Clifton the San Francisco River is joined from the west by 
Chase Creek, a water course 10 miles in length and flowing in a south- 
southeast direction, most of the way through a deeply cut canyon. 
An irregular and high complex of mountains rises between San Fran- 
cisco River and Chase Creek, the most prominent of which is Copper 
King Mountain, attaining 6,825 feet. On the west side of Chase Creek 
the high ridges attain elevations up to 7,400 feet, the highest point 


being the flat-topped mass of Coronado Mountain. The town of Met- 
calf is situated on Chase Creek, 6 miles north-northwest of Clifton, 
while Morenei is 4 miles distant in a northwesterly direction from 
the same place, but located high up in the hills, 1,000 feet above 
Chase Creek. 


The old Pleistocene gravel plateau extending northward from Gila 
River to near Clifton and Morenei has already been mentioned. The 
older rocks rising above this plateau are to a very large extent of vol- 
canic origin and of Tertiary age. The whole region north of the Gila 
River for a distance of at least 100 miles, and probably much more, 
is covered with very heavy flows of basalt and rhyolite. It is, in fact, 
the southern edge of the great volcanic plateau of eastern Arizona. 

Near Clifton original high elevation and extensive subsequent ero- 
sion have combined in forming an exposure of pre-Tertiary rocks con- 
sisting of granite, porphyry, quartzite, and limestone. The Clifton 
area of older rocks may be considered as a small isolated mass, per- 
haps 12 miles long from east to west and 8 miles broad from north to 
south, appearing like an island in the surrounding vast lava flows. 

The oldest rock and that which occupies the largest area is granite, 
evidently of pre-Cambrian age. It forms the great mass of Coronado 
Mountain and the larger part of the precipitous complex of mountains 
between Chase Creek and San Francisco River. 

On the somewhat irregular surface of this granite rests a sedimen- 
tary series of Paleozoic age, the lower part consisting of 200 feet of 
quartzite. Immediately overlying the granite is coarse quartzite con- 
glomerate, in places reaching a thickness of 50 feet. This quartzite, 
in which no fossils have been found, is probably of Cambrian age. 

The quartzite is covered by 800 feet of limestone, the lower part of 
which belongs to the Silurian system, the middle part to the Devonian, 
and the upper hundred feet to the Lower Carboniferous series. 
Beginning from the base, the limestones gradually become purer, and 
the top stratum, well exposed at Morenei, is almost entirely pure car- 
bonate of lime. Within the Devonian portion about 100 feet of clay 
shale is intercalated in the limestones. 

A large mass of porpl^ry, running out at various points into com- 
plicated dike systems, has been intruded into these rocks, granites as 
well as quartzites and limestones, and this porphyry seems most inti- 
mately connected with the origin of the ore. Its character varies 
somewhat. The prevailing rock near Morenei is intermediate between 
a granite-porphyry and a diorite-porphyry, but at some points diorite- 
porphyries of typical character also occur. The porphyry at Metcalf 
is more acidic and contains large quartz crystals. It may more closely 
approach a granite-porphyry, but is, geologically, probabty the same 
body as the Morenei porphyry. 


At the Coronado mine and other places in that vicinity small dikes 
of diabase occur. 

Southwest of Morenci a sedimentary series has been found which 
appears to unconformably cover the Paleozoic rocks. At one place 
fossils, indicating a Cretaceous age, were obtained. These rocks, 
however, are only of secondary importance as far as the ore deposits 
are concerned. 


The geological structure of the pre-Tertiary rocks is rendered very 
complicated by extensive faulting. In few places does this faulting 
affect the covering basalt and rhyolite, from which it is to be con- 
cluded that the main epoch of disturbance antedates the volcanic 
eruptions of the Tertiary period. The Paleozoic era in this region was 
evidently one of quiescence and deposition, and it is believed that 
undisturbed deposition continued through the larger part of the Cre- 
taceous period. The intrusion of porphyry took place during the 
late Cretaceous or the earliest Tertiary, for we find bodies of that 
rock intruded into Cretaceous sediments as well as into older rocks. 
In many places this intrusion was accompanied by very great dis- 
turbance, causing a fracturing and shattering of the sedimentary series 
into which it was intruded. The important ore deposits were formed 
during and a short time after this intrusion of porphyry. Alteration, 
gradually changing and often enriching these ore deposits, has, how- 
ever, continued from their deposition to the present time. 

The deposition of the ores was followed by very extensive fractur- 
ing and faulting, affecting, as already mentioned, all of the rocks in 
the district except the younger lavas. 

From the form of the remaining patches of quartzite it would seem 
as if the surface of the granite and the whole overlying series had 
been buckled, perhaps elevated in dome-like shape, and then frac- 
tured extensively. The geological map will show the complicated 
nature of this faulting. The main faults extend in an east-west or 
northeast-southwest direction. Faults having a throw of over 1,000 
feet are common, and in the Paleozoic series, where conditions are 
favorable for deciphering the structure, as for instance near Morenci, J 
the complication is particularly apparent. Among more important 
faults may be mentioned that at the Coronado mine, where the south 
side is dropped 1,000 feet, and that cutting across Chase Creek east 
of Morenci, where again the Paleozoic series has been dropped 1,500 
feet or more. 

An extensive erosion, resulting in very irregular surface forms, fol- 
lowed these disturbances. Then, probably in the latter part of the Ter- 
tiary period, the whole region was flooded by rhyolites and basalts. 
Following this, probably in the early part of the Pleistocene, the level 
of the Gila River became grnatly raised by accumulations of detrital 


material, and the foothills of the mountain complex were buried, up 
to an elevation of 4,500 feet. 

The last phase in the geological history is the present period of 
erosion, which has removed large masses of these early Pleistocene 
gravels and deepened the canyons and gulches to the level which they 
had attained before the volcanic eruptions. 


Contact-metamorphic deposits. — There is no evidence of ore deposits 
having been formed in this region before the intrusion of porphyry. 
This event appears to be in most intimate connection with the origin 
of all the copper deposits in the region. Wherever the porphyry 
came into contact with the granite or the quartzite, little alteration 
is observed; but wherever we find the porphyry adjoining the lime- 
stones or the shales of the Paleozoic series, very extensive contact 
metamorphism is noted, resulting in the formation of large masses of 
garnet and epidote. This alteration is particularly observable at 
Morenci. The whole Paleozoic series is affected, but more particularly 
the pure limestone of the Lower Carboniferous, which, for a distance 
of several hundred feet from the contact, has been converted into an 
almost solid mass of garnet. The shales have suffered less from this 
metamorphism, but near the porphyry are apt to contain epidote and 
other minerals. This metamorphism appears not only at the contact 
of the main mass of porphyry forming the southern slope of Copper 
Mountain, but also in the hills between Morenci and the Longfellow 
mine, in which dikes have produced contact-metamorphic minerals 
along their sides. Wherever alteration has not masked the phe- 
nomena, magnetite, pyrite, chalcopyrite, and zinc blende accompany 
in various proportions the contact-metamorphic minerals, and are 
intergrown witli them in such a way that the contact-metamorphic 
origin of these ores appears be} T ond doubt. In many places the ores 
have accumulated along certain horizons in the sedimentary series, 
evidently more suitable than others to the processes of alteration 
which produced the deposits. The origin of these contact-metamor- 
phic deposits is conceived to be in the water and metallic substances 
which were originally contained in the magma of the porphyry, and 
which were released by decreasing pressure at the time of the intru- 
sion of the rock into higher levels of the earth's crust. We may 
thus speak of these deposits as contemporaneous with the cooling and 
solidification of the prophyry. 

As to form, the ore deposits in limestone are often irregular, but 
more frequently, perhaps, assume a tabular shape, due to the accu- 
mulation of the minerals along certain planes of stratification. 

Oxidizing waters have very greatly altered the deposits in lime- 
stone. The sulphides have been converted into carbonates, and mala- 
chite and azurite are the most common ores. Cuprite also occurs 


extensively, and seems to form by preference in the shale forming 
part of the Devonian system. Chalcocite and other sulphides are 
almost entirely absent. The zinc blende has been carried away as 
sulphate of zinc, which is frequently found in efflorescence on the 
walls of the tunnels. The magnetite and the garnet which originally 
formed a part of these deposits have also undergone decomposition, 
the resulting minerals being silica and limonite. 

The celebrated Longfellow mine is worked on one of these deposits 
occurring as, roughly speaking, a funnel-shaped mass in the Lower 
Silurian limestone, between two large porphyry dikes. Going farther 
west along the main porphyry contact, the Montezuma is encountered, 
and farther on the Detroit and the Manganese Blue mines. Both of 
the latter mines were worked on several tabular ore bodies, three 
or more in number, occurring in horizons varying from Silurian to 
the Lower Carboniferous. All of these deposits arc now largely 
exhausted. They contained a large quantity of very rich carbonate 
and oxide ore. The extent of these ore bodies was, however, much 
smaller than the large masses of chalcocite ore which now forms the 
main support of the camp. 

At Metcalf the Shannon mine contains several ore bodies of similar 
origin. A fragment of the Paleozoic series outcrops on Shannon Hill, 
and is cut b} r an extensive system of porphyry dikes, which in the 
lower part of the mountain join the main part of a large intrusive 
body of porphyry. In several horizons the limestones are greatly 
altered, the final product general^ being copper carbonates and 
limonite, with some quartz. In some places the ore bodies are less 
affected by oxidation, and their original character of garnet, epidote, 
magnetite, and sulphides may be plainly seen. 

Oxidation by surface waters, as at Shannon mine, also diffused 
much copper as chalcocite in some of the porphyry dikes, and the 
Metcalf mine on a lower spur of the same hill consists chiefly of a 
body of extremely decomposed porphyry containing chalcocite and 
carbonates. Very probably this copper has migrated into the decom- 
posing porphyry from bodies of contact-metamorphic rock at higher 
elevation, parts of which are probably now eroded. 

Fissure reins. — At many places in the district the copper deposits 
consist of fissure veins, cutting alike porphyry, granite, and sedi- 
mentary rocks. From the available evidence it would seem as if 
these veins had been formed a short time after the consolidation of 
porphyry. In lower levels the veins consist of pyrite, chalcopyrite, j 
and zinc blende, magnetite being conspicuously absent. At the sur- 
face many of the veins have been completely leached, and now show 
nothing but limonite and silicified porphyry. This rule is, however, 
not a general one, as, especially in porphyiy, oxidized ores are some- 
times found in the outcrops of the deposits. Between the leached 
croppings and the deep ores of pyrite and chalcopyrite is a more or 


less extensive zone of chalcocite or copper glance, deposited by sec- 
ondary processes on the pyrite. 

The most important vein system is that which, under the general 
name of the Humboldt vein, extends from northeast to southwest 
through Copper Mountain at Morenci. The outcrops of this vein are 
practically barren, but at the depth of about 200 feet the deposit 
becomes productive and contains chalcocite associated with pyrite. 
There are usually one or more central seams of massive chalcocite, 
some of which are fairly persistent. These seams are ordinarily 
adjoined by decomposed porphyry, now chiefly consisting of sericite 
and quartz, together with pyrite and chalcocite. These extensive 
impregnations of the country rock are rarely confined by distinct 
walls, but gradually fade into the surrounding porphyry. That 
these deposits are genetically connected with fissure veins can, how- 
ever, not be doubted. In lower levels the ore is apt to change to 
pyrite and chalcopyrite. Both the Arizona Copper Company and the 
Detroit Copper Company are now working the low-grade bodies of 
chalcocite ore accompanying the veins. The reserves thus far opened 
assure a high production for many years to come. 

Parallel veins, somewhat narrower, but similar in character, are 
those opened by the Arizona Central mine, also at Morenci. These 
veins are partly in porphyry, partly in contact metamorphosed lime- 
stone. While malachite and azurite sometimes occur, they are by no 
means as prominent as in the limestone deposits, and frequently the 
leached surface zone is immediately adjoined by the chalcocite ore. 

The Coronado mine represents a different type of deposits. It is 
formed on a fault fissure between granite and quartzite, indicating a 
throw of at least 1,000 feet. The fissure is followed in places by 
a diabase dike, showing some effect of crushing and movement on 
the vein. The croppings contain copper carbonates and silicate, but 
these minerals change at slight depth to chalcocite, and still farther 
| down it is believed that the ore bodies consist chiefly of pyrite and 

Somewhat different again are the fissure veins on Markeen and 
Copper King mountains. The granite of this complex of hills is cut 
by a great number of porphyry dikes which generally have a north- 
easterly direction. Along many of these dikes movement and As- 
suring has taken place, and varying amounts of copper ores have 
been encountered. The veins contain comparatively little gangue, 
the copper minerals being chiefly distributed through the altered por- 
phyry or through the granite adjoining the dike. At the surface a 
small amount of carbonates may be found, but they change at slight 
depth, sometimes only a few feet from the surface, into an ore com- 
posed of chalcocite and pyrite, which still farther down appears to 
change into pyrite and chalcopyrite. The most prominent deposit on 
this system of veins is the Copper King mine, which is situated only 


a few hundred feet below the summit of the mountain of the same 
name. The main mass of porphyry between Morenci and Metcalf 
shows evidence of very strong mineralization throughout. A great 
number of fissure veins have been encountered in it, although most 
of them are neither persistent nor strong. Close to the surface the 
ores are apt to spread through a considerable mass of rock, and in 
some cases important bodies of chalcocite, due to secondary deposi- 
tion on pyrite from solutions containing copper, have resulted. 

The granite adjoining this porphyry is sometimes also thoroughly 
altered and impregnated with pyrite and chalcopyrite. This may 
be seen in the narrow canyons of Chase Creek for a mile above Long- 
fellow Incline. While a number of more or less well-defined veins 
have been opened here, the results have not been encouraging. 


The gravels lying in front of the older rocks at Morenci and Clifton 
are sometimes gold bearing, though ordinarily the metal occurs in 
very fine distribution. The bench gravels above Clifton, along the 
San Francisco River, contain gold, and attempts have been made to 
work them. The results, however, have not been encouraging. This 
gold is probably derived from a system of veins cropping on thj 
Dorsey and Colorado gulch, a few miles north of Clifton on the wesj 
side of the San Francisco River. The system of dikes mentioned 
above as cutting Copper King Mountain continues in places still fail 
ther in a northeasterly direction, but the ore here contains less copper 
and more gold and silver. Attempts to mine these gold-bearing veins 
have not thus far been attended with much success. 

Another gold-bearing district is that of Gold Gulch, 2 or 3 miles 
west of Morenci. The diorite-porphyry which occurs here contains 
many inclusions and fragments of limestone, and this complex 
geological formation is again cut by many faults. Native gold accom- 
panied by limonite and other products of decomposition has been 
found in many small veins in this district, but the tenor of the ore 
seems very capricious, and the deposits have not yet been proved to 
be of much value. 

The copper ores of Morenci and Metcalf, whether occurring as 
contact-metamorphic deposits or as fissure veins, contain a very small 
quantity of gold and silver, in most cases amounting to little more 
than a trace. At the Copper King mine, however, in the system of 
fiesure veins following dikes of porphyry and granite, a notable 
amount of gold is found, and from here on northeasterly, as noted 
above, this tenor in gold increases considerably. 


By Walter C. Mendenhall and Frank C. Schrader. 


Near the southeast corner of the mainland mass of Alaska, very 
near the intersection of parallel 62° north latitude -and meridian 144° 
west longitude, stands Mount Wrangell, 14,000 feet high, an active 
volcano, and in many respects the most impressive, although not the 
highest, peak of the group to which its name is given. This group, a 
complex pile of volcanic material, with half a dozen or more great 
summits over 12,000 feet in height, occupies the angle between two 
diverging branches of the St. Elias Range. 

The drainage of a part of its northern and of all its western and 
southern slopes is carried to the Pacific by the Copper River, while 
White River and the two main branches of the Tanana, called the 
Nabesna and the Chisana, rise on the north slope east of the Copper 
and flow by way of the Yukon into Bering Sea. 

In the drainage basins of the upper portions of these streams, on 
both sides of the range, it has been known for many years that native 
copper exists. Yukon and White River Indians used it in the interior 
in the earlier days for knives and bullets, and Copper River natives 
exhibited similar specimens at the coastal trading stations long ago. 
Lieutenant Allen in 1885 secured specimens of bornite from Chief 
Nicolai at Taral, but most of the knowledge possessed by white men 
concerning these occurrences has been secured since 1898, when they 
first entered the region in force. Since then prospectors have explored 
rather thoroughly the southern field, which includes the basins of the 
Chitina and the Kotsina, large eastern branches of Copper River. 
As a result of this exploration, they have located maii}^ claims in this 
region and have done a little development work. At the same time 
somewhat less thorough prospecting has been carried on in the more 
distant and less accessible region north of the Wrangell Mountains, 
but thus far the search for promising copper deposits has been less 
successful there. 

In 1801 Dr. C. Willard Hayes, a while en route with Lieut. Frederick 
Schwatka from Fort Selkirk to the coast at the mouth of Copper River, 
visited the Kletsan Creek deposits on the upper White River. In 

o An expedition through the Yukon district: Nat. Geog. Mag., Vol. IV., pp. 117-162. 



1899 the same locality was visited and described in some detail by 
Mr. Alfred H. Brooks, a of the Geological Survey, while en route from 
Pyramid Harbor to Eagle City with Mr. W. J. Peters. In addition to 
the Kletsan Creek occurrences Mr. Brooks gives notes on the exten- 
sion of the copper belt toward the west. 

In 1900 Messrs. Schrader and Spencer b visited the southern field 
and issued a comprehensive report on its geology and mineral 
resources, particular attention being given to the copper occurrences. 

In 1902, while Mr. W. C. Mendenhall extended the earlier work of 
Messrs. Schrader and Spencer in the western portion of the southern 
field, Mr. F. C. Schrader visited the region about the head of the 
Copper, the Nabesna, and the Chisana rivers. The results of all these 
studies, with such information as can be gleaned from other sources 
concerning the localities which the geologists have not visited, will 
shortly be issued as a paper on the mineral resources of the Mount 
Wrangell district, and for a full account of what is at present known 
on the subject this report should be consulted. Only that portion of 
it which bears upon the copper occurrences is summarized here. 


This, the best known and probably the richest of the two copper 
belts of the region, occupies a strip nearly LOO miles long and of vary- 
ing width along the southern base of the Wrangell Mountains. 
Throughout this zone, in the drainage basins of the Chitina, the Kot- 
sina, ami the Cheshnina there are scattered deposits of copper ores, 
some of them very promising. 


The lowest si rat igraphically, and therefore the oldest, of the econom- 
ically important formations of this belt, is a great series of successive 
basalt flows, now somewhat altered, which has been called the Nicolai 
greenstone. A thickness of not less than 4,000 feet of this basalt is 
exposed near the western part of the area in which it is known, and 
its maximum may be very much greater, as the base of the formation 
is nowhere exposed. The thin sheets in which this fluid lava issued 
now lend themselves to the determination of structure in the forma- 
tion almost as well as does bedding in sedimentary rocks. 

After the close of the period of great volcanic activity of which the 
Nicolai greenstone is the record an era of sedimentation set in, appar- 
ently without any intervening erosion. The first of the sediments 
deposited was a massive white limestone, which is particularly promi- 
nent along the Chitistone River and has therefore been called the 

«A reconnaissance from Pyramid Harbor to Eagle City, Alaska: Twenty-First Ann. Rept. 
U. S. Geol. Survey, Pt. II, 1900, p. 377 et seq. 

b Geology and mineral resources of a portion of the Copper River district, Alaska. Special 
publication of tbe U. S. Geol. Survey, 1901. 

cThis account of the geology is summarized from the report of Schrader and Spencer. 

iNDENHALL,-, -, . 


nnRATlF.H J 




Chitistone limestone. A series of interbedded thin limestones and 
shales which carry Triassic fossils were next laid down, and these 
had accumulated to a thickness of several thousand feet before the 
era of sedimentation was brought to a close. Within the Chitina 
Basin the massive Chitistone limestone does not carry fossils, but it 
has been correlated with similar beds beyond the Scolai Range to the 
north, from which Permian shells have been taken. If we accept 
this evidence as determining the Permian age of the Chitistone, it 
becomes highly probable that the greenstone beneath it, with no 
srosional interval intervening, falls in the Carboniferous, and per- 
haps in the Upper Carboniferous. A more definite conclusion than 
Ibhis can not be reached with the evidence at present available. 

Following the outpouring of the Nicolai lavas and the deposition of 
]he succeeding calcareous terranes a period of stresses was inaugu- 
rated, during which these rocks were everywhere thrown into a suc- 
cession of open folds. Accompanying or following this folding the 
*ocks were brought within reach of subaerial erosional agencies, and 
phe folds were truncated; but the land was not, it is believed, reduced 
o a plain. On the contrary, a distinct relief remained, and when the 
jiext period of deposition began the sediments were laid down in local 
basins and unconformably upon the truncated edges of the folds in 
he older rocks. These deposits were gravels and muds, which have 
:>ince consolidated into the conglomerates and shales of the Kennicott 
formation. They were deposited during Jura-Cretaceous time. 
i After the deposition of these gravel beds the region was again ele- 
vated and folded slightly, and a period of erosion began which reduced 
|he land to a generally plane surface. This plain was elevated, dis- 
ected, and partly buried under the extra vasated igneous material 
|\ r hose accumulations have produced the peaks of the Wrangell 

This, in brief, is the history, as at present understood, of the events 
jrhich have resulted in the accumulation, burial, folding, erosion, and 
iter partial reburial of the rocks which are economically important 
11 the region. Of these the chief is the Nicolai greenstone. As is 
ften true of greenstones in other parts of the world, this rock seems 
lo have contained originally minute quantities of copper dissemi- 
ated throughout its mass. During the operation of the processes to 
khich the formation has since been subjected some of this dissemi- 
nated copper has been concentrated at various points within the mass 
Iff the greenstone or the overlying limestone, and some of these 
iccumulations are of sufficient magnitude to constitute workable cop- 
er deposits. 
[ A plane which has seemed to be a favorite locus for these accumu- 
lations is the contact between the greenstone and the overlying 
limestone. Nearly all of the prominent ore bodies are on or near 
iris plane, sometimes in the greenstone just below it, sometimes, 


but more rarely, in the limestone just above it, and occasionally in 
fissures which cross it. 

The ore bodies have assumed various forms, and for convenience 
of discussion these forms have been divided into two general classes, 
vein deposits and bunch deposits. 

The vein deposits are so defined as to include all tabular ore masses, 
whether in true fissures or along joint or fault planes or shear zones. 
The ores may be found only in shoots within the planes which have 
controlled their form, but are characteristically of indefinite extent 
in one or two directions. 

The "bunch" deposits, on the other hand, are irregularly bounded 
masses of ore, from a few inches to a few feet in diameter, which 
usually are not obviously related to fractures or fissures or joint 
planes, but in form are much like basic segregations in igneous 
rocks — i. e., they generally have indefinite limits, grading from 
masses of practically pure ore at the center through leaner and leaner 
phases, into the entirely unmineralized inclosing country rock. 
These "bunches" are so numerous in certain parts of the field within 
the upper part of the greenstone that prospectors who have opened a 
number of them, 400 or 500 feet below the base of the limestone, have 
been led to conclude that a ledge of ore parallels the contact at this 


In order to give an idea of the different types of deposits and the 
conditions of development, some of the best-known occurrences will 
now be described. 

Nicolai mine. — The Nicolai mine is located near the eastern part of 
the Chitina copper district, on Nicolai Creek, a few miles west of the 
Nizina River. The vein, a fissure with definite walls, is in the green- 
stone not more than 50 feet below the base of the limestone. It 
trends about N. 50° E. and dips 75° SE., and a displacement of not 
more than 50 feet has taken place along it. The main fissure, which 
may be traced for several thousand feet, although it shows no 
ore except near the place of discovery, is paralleled at distances of 
90 and 140 feet by two other fissures, which also contain copper min- 
erals. In the vicinity of a shaft which has been sunk in the process 
of development, the vein has a width of from 8 to 12 feet and is about 
equally divided by a horse of greenstone 3 or 4 feet across. The ore 
on either side of this horse is practically pure bornite with only a 
small amount of quartz associated in an irregular way. Locally there 
is a band of chalcopyrite lying next the hanging wall. 

In 1900, when the shaft had been sunk to a depth of 30 feet, ore 
from 2 to 4 feet in thickness was exposed throughout this depth. 

Bonanza claim. — This claim is located upon a high ridge between 
Kennicott Glacier and McCarthy Creek, and is about 8 miles west of 
the Nicolai mine. This vein also is a fissure, which cuts across the 
contact between the greenstone and the limestone, although for some 

DENHALL-, ^ , _, 


JHiDER -• 




distance below the contact the vein is barren. It is irregular in 
width, varying between 2 and 7 feet, and has a strike of about 
N. 40° E. There is no quartz or other vein material associated with 
the ore, although there is sometimes a considerable amount of crushed 
limestone between the walls. The ore is practically pure chalcocite, 
or copper glance, which is exposed in solid masses 2 to 4 feet across 
and 15 feet or more in length. Besides the ore within the fissure 
there are bedded ore bodies running off into the limestone along the 
planes of stratification. The ore is regarded as a replacement of the 
limestone. A selected sample gave over 70 per cent copper and 14 
ounces of silver per ton, with a trace of gold. 

Louise claim, Elliott Creek. — Elliott Creek is a tributary of the Kot- 
sina River and is near the western end of the copper area. The 
Louise claim is on a small branch of Elliot Creek called Rainbow 
Creek. Here, in a shallow open cut, a slickensided face of greenstone, 
forming a well-defined and, so far as exposed, regular foot wall, is 
revealed. This face strikes N. 10° E. ami dips 70° NW. The cut does 
not expose an equally definite hanging wall, but adjacent to the foot 
wall is a crushed zone, which has an extreme width of 15 or 16 feet. 
Within this zone the greenstone is generally irregularly fractured, 
but at the j)resent surface there exists, in the center of this crushed 
mass, a "horse" of solid greenstone 7 or 8 feet wide. It is probable 
that the slickensided foot wall is a fault plane, but since no displace- 
ment was observed in the limestone above, its throw can not be great. 
The mineralization within this belt consists of an impregnation of 
chalcopyrite and bornite, the latter mineral being superficially more 
abundant. The impregnation follows the fractures and partakes of 
their irregularity, the exposed surfaces of the greenstone fragments 
generally showing more or less ore. 

Goodyear claim, Elliott Creek. — Across Rainbow Creek from the 
Louise claim and a few feet below it, an open cut in greenstone reveals 
a well-defined fissure vein 4 to 5 feet wide, striking N. 12° E. and 
dipping 45° SW. The vein can be traced 50 or 75 feet up the slope 
toward the limestone contact before it is buried under the talus. 

The gangue minerals are quartz and calcite, entirely distinct from 
the perfectly definite walls of greenstone, and this gangue carries 
heavy bodies of bornite and a smaller quantity of chalcopyrite. 
While the heavy ore bodies are confined to the vein, the shattered 
hanging wall and the more massive foot wall are impregnated with 
copper sulphides for some distance above and below. 

In the upper part of the open cut a slight horizontal fault has dis- 
placed the vein laterally, so that the hanging wall above the displace- 
ment is continuous with the foot wall below it. 

Eleanor, Davy, and associated claims, Kotsina River. — Two thou- 
sand five hundred feet above the level of the Upper Kotsina River, 
near the crest of a sharp ridge separating two tributaries, Peacock 
Bull. 213—03 10 


Creek and Roaring Gulch, a number of claims have been staked in that 
belt in the greenstone, a few hundred feet below the limestone, which 
seems everywhere to carry ' ' bunches " of copper ore. No development 
work has been done here, but the exposures on the faces of the green- 
stone cliffs show small ore bodies from a few inches to 2 or 3 feet in 
diameter and irregular in outline. They usually have cores of nearly 
pure bornite or chalcocite, but marginally these copper minerals 
become mingled with the surrounding greenstone as though the 
replacement had been less complete on the borders of the mass. 

In one or two instances narrow fissures from one-half inch to 1-J 
inches wide were noted which extend downward from ore pockets 
and are themselves filled with copper sulphides, but in the majority 
of cases no such connection between pocket and veinlet is to be seen. 

The most of the copper in the district is in the form of the sulphides, 
bornite, chalcocite, and chalcopyrite, but native copper also is known. 
A bowlder of the latter weighing several tons has been found in the 
gravels of Nugget Gulch, a tributary of the Kuskulana River, near 
the western end of the area; and on the upper Kotsina River several 
claims in which native copper occurs associated with other ores have 
been staked in the greenstone 4,000 or 5,000 feet below the contact 
witli the limestone. Two of these, the Keystone and the Copper 
King claims, are described here. 

Keystone claim. — Two short forks, both glacial streams, unite to 
form Kotsina River. The southern one of these drains two glaciers, 
and in a little narrow post-Glacial gorge just below the foot of the 
northernmost of these glaciers is the Keystone claim. Here in the 
wall of the canj^on, in the greenstone, are some compact quartz 
stringers and lenses, varying in width from a mere line to 5 or 6 
inches. They strike east and west and are approximately vertical. 

Epidote is associated with the quartz, sometimes in equal amount, 
as a gangue mineral in the veins. Native copper occurs in the epidote 
and in the quartz, but is more abundant in later irregular crevices 
traversing both minerals of the gangue. A small amount of chalcocite 
is present also, and in one prominent example it fills a narrow fissure 
which intersects masses of both epidote and quartz and is evidently 
later than either. 

Copper King claim. — This prospect is situated on the north side of 
the Kotsina Valley about one-fourth mile west of the Keystone claim 
and 700 or 800 feet above the river level. It consists of an altered 
belt of greenstone, in part amygdaloidal, extending several feet east 
from a well-defined north-south vertical crevice, along which there 
has probably been some movement. The greenstone within this 
altered zone has been rendered quartzose, the quartz occurring as 
si ringers and as a filling of the amygdules. The septa between the 
latter are sometimes changed to granular epidote and chlorite. 

Native copper occurs here and there in the mass in grains and 





flakes, sometimes intimately associated with chaleocite. The latter 
mineral occurs with the native copper and in minute crevices which 
seem to be later than the general alteration and silicification. 


North of the volcanic pile of the Wrangell Mountains, in the valleys 
of the Copper, of the two forks of the Tanana River, called the 
Nabesna and the Chisana, and of the White River, native copper has 
been reported from time to time, and the reports have been substan- 
tiated by prospectors and others who have brought out nuggets of 
the metal. 


The geologic conditions under which the copper occurs in the 
northern district are different from those which prevail in the Chitina 
Basin. Although the Nicolai greenstone, which is the great copper 
reservoir for the southern field, is probabty present, it does not play 
the important part that it does south of the mountains. 

A great calcareous series, which is believed to be equivalent to the 
Chitistone limestone, is clearly recognized over a large area. It has 
been affected by complex structures in the northern as in the southern 
district, and after its deformation and erosion Mesozoic beds have 
been deposited unconformably upon its edges, and the still later lavas 
of Mount Wrangell have buried many of its outcrops. In these 
respects its history is similar to that of the equivalent beds to the 
south. The essential difference, however, is in its relation to the 
basic igneous rocks. Instead of being clearly deposited conformably 
upon the surfaces of earlier flows, it has been extensively cut by later 
intrusives, and the contacts with these diabases, which are altered in 
many cases to greenstones, seem to be the loci for the accumulation 
of native copper and other copper ores. One occurrence, of no 
economic importance, is known in an altered mass of diorite. 


The evidence at present available, although incomplete, is better 
than that upon which earlier judgments were based. It does not indi- 
cate that these northern occurrences have much commercial value. 
A brief description of some of them follows: 

Monte Cristo Creek and California Gulch are respectively western 
and eastern tributaries of the Nabesna River, which they join within 
3 or 4 miles of the foot of the glacier. A mass of altered diorite 
occurs in this region, and along the lines of fracture in this diorite 
there occur sporadically films and blotches of malachite, which is prob- 
ably derived from a little chalcopyrite contained in the altered rock. 

In the mountains just east of California Gulch fragments of low- 
w grade copper ore, consisting essentially of pyrrhotite and copper 


pyrite, are found in the gulches. These are of such size as to indicate 
that the ore bodies from which they came must be at least 6 inches 
wide. The ore is of so low grade, however, assaying but six-tenths 
of 1 per cent, that the deposit is without value. This ore is supposed 
to be related to an intrusive contact between the greenstone and the 
limestone about the heads of the gullies in which the ore is found. 

On Camp Creek, an eastern tributary of the Nabesna, about 15 
miles below the glacier and about 3 miles above the mouth of Cooper 
Creek, Mr. Alfred B. lies reports a vein of chalcocite from (5 inches to 
2 feet in thickness. Both the limestone and the greenstone are pres- 
ent in this region, and it is probable that the ore occurs in association 
with them. 

Natives living on the Chisana (Upper Tanana) in 1002 had in then- 
possession a number of small copper nuggets, and one mass which 
weighs 35 to 40 pounds. These, they say, came from a small creek 
which (lows into the Chisana from the west at a point about 5 or G 
miles above the foot of the glacier. Occasionally the nuggets have 
adhering to them fragments of amygdaloidal greenstone and of calcite 
gangue. It is likely that they occur in the usual way, in association 
with the contact of the diabase and the Permian limestone. 

Prospectors, among whom may be mentioned Mr. D. K. Van Cleef, 
report the finding of numerous copper nuggets along the north base 
of the Nutzotin Mountains between the Upper White and the Chisana. 
Mr. Van Cleef reports also the probable existence of a sulphide vein 
in a canyon of 1 he middle White. 

Kletsan Creek, which drains the north base of Mount Natazhat, 
is a southern tributary of Upper White River. Native copper in 
placer form has been known in this region since Dr. Hayes a visited 
it in 1891, and it was probably a source of supply for the Indians long- 
before that. Mr. Alfred II. Brooks b in 1899 reported one nugget 8 or 
10 pounds in weight, and numerous other smaller pieces from this 
locality. In a search for the origin of the nuggets, Mr. Brooks found 
stringers of the native metal occurring in calcite veins in dioritic 
greenstones near the intrusive contact of the greenstone with Per- 
mian limestone. No other minerals except a superficial staining by 
malachite were observed. The character of the bed-rock geology and 
the finding of native copper in stream gravels led Mr. Brooks to infer 
that conditions similar to those at Kletsan Creek are likely to be 
found in the region between the Upper White and the Chisana. 

From these meager descriptions it will be realized that the search 
for valuable deposits in the field north of the Wrangell and Skolai 
Mountains has not thus far revealed any large ore masses, but as the 
search has been by no means exhaustive it is entirely possible that 
deposits of practical importance may be found in the future. 

"An expedition through the Yukon district: Nat. Geog Mag., Vol IV, pp. 117-162. 
'-A reconnaissance from Pyramid Harbor to Eagle City, Alaska: Twenty-first Ann. Rept. U. S. 
Geol. Survey, Pt. II, 1900, p 377 et. seq.. 


By F. L. Ransome. 


During the autumn and winter of 1002 a detailed geological inves- 
tigation was made of the Bisbee quadrangle, embracing the greater 
part of the Mule Mountains, by F. L. Ransome, assisted by J. Morgan 
Clements and Alfred M. Rock. The geology of the quadrangle was 
mapped on a scale of approximately 1 mile to the inch, Avhile an area 
of 8 square miles in the immediate vicinity of the principal mines was 
mapped geologically on a scale of 1,000 feet to the inch. The material 
gathered during the progress of the field work will shortly be embodied 
in a full report upon the geology and ore deposits of the district. In 
the meantime the following brief sketch includes only such salient 
results of the unfinished investigation as seem least likely to be modi- 
fied by further study. 


The Warren mining district, in which occur the ore bodies that 
have given Bisbee its prominence, lies in the central part of the Mule 
Mountains, a generally northwest-southeast range, some 30 miles in 
length, extending from the old mining town of Tombstone down to 
the Mexican border. In the vicinity of Bisbee the range attains an 
elevation of 7,400 feet and has a width of about 12 miles; but in the 
neighborhood of Tombstone and near the international boundary line 
it is represented by clusters of comparatively low hills. On the south- 
west the Mule Mountains are separated by the broad valley of the San 
Pedro from the Huachuca Mountains, and on the northeast by the 
similar wide expanse of Sulphur Spring Valley from the Swisshelm 
and Chiricahua ranges. On the north a few low hills just southeast 
of Tombstone connect the Mule Mountains with the Dragoon Range. 
The town of Bisbee, with a population estimated at about t>,000, is 
crowded into a few narrow confluent ravines in the heart of the range. 
It is connected by the El Paso and Southwestern Railroad with El 
Paso, with Benson on the main line of the Southern Pacific Railway, 
and with Douglas and Naco on the international boundary. 


The oldest rocks in the Mule Mountains are fine-grained sericite- 
schists, derived from ancient sediments. These were probably origi- 



nail} 7 shales or arkose sandstones which were folded and metamor- 
phosed into their present crystalline condition before Cambrian time. 
After long erosion these schists were reduced to a surface of very 
slight relief, which in Cambrian time was submerged beneath the sea 
and covered with the sands that are now represented by quartzite, 
from 400 to 500 feet in thickness. The submergence of the area con- 
tinued, and about 750 feet of thin-bedded, cherty, fossiliferous Cam- 
brian limestones accumulated on top of the quartzite. No record of 
Silurian time has been discovered in the Bisbee quadrangle. Over- 
lying the Cambrian limestone, apparently in perfect conformity, are 
340 feet of dark-colored, compact, rather thin-bedded limestones, with 
some intercalated shales, all carrying an abundant and characteristic 
Devonian fauna, consisting chiefly of brachiopods and corals. 

The opening of Carboniferous time was, in this region, unmarked 
by any interruption of the continued subsidence. No unconformity 
has been detected between the Devonian and the Lower Carbonifer- 
ous (Mississippian) rocks. The latter consist of white or light-gray 
granular limestones, often made up almost entirely of crinoid stems 
and containing a fairly abundant brachiopod and coral fauna. The 
thickness of the Lower Carboniferous limestone may be provisionally 
given as 700 feet. The beds are often 6 feet or more in thickness and 
commonly form cliffs overlooking slopes carved from the less resistant 
Devonian and Cambrian limestones. 

There is in the Mule Mountains no discoverable stratigraphic break 
between the Lower and Upper Carboniferous beds. Subsidence appar- 
ently continued, and the generally thinner beds of Upper Carbonifer- 
ous (Pennsylvanian) limestone accumulated to a thickness of over 
3,000 feet above the Lower Carboniferous. The Upper Carboniferous 
limestones are usually more compact in texture than those of the 
Lower Carboniferous, and are more fossiliferous. They are also some- 
what more variable in color, pinkish and yellowish beds being of fre- 
quent occurrence. 

The local Paleozoic section from the pre-Cambrian schists very 
nearly to the top of the Lower Carboniferous is well exposed on the 
northeast face of the main ridge about 1J miles west of Bisbee. The 
Upper Carboniferous beds are best seen in the hills just north of Naco 
Junction (5 miles southwest of Bisbee), and the relation between the 
lower and upper divisions is well shown near the Whitetail mine, 
about 2 miles due south of Bisbee. 

At some time during the interval between the close of the Carbon- 
iferous and the opening of the Cretaceous the long-continued subsi- 
dence and sedimentation of the region were interrupted by extensive 
faulting, probably connected with uplift. Accompanying or immedi- 
ately following the faulting came intrusions of granitic magma which 
solidified as granite, granite-porphyry, and rhyolite-porphyry. These 
intrusions took the form of dikes following fault fissures, of sills 
injected between sedimentary beds, and of irregular stock-like masses. 


The dikes are well shown along the southwest face of the main ridge 
west of Bisbee. The larger intrusions are exemplified by the granitic 
mass of Juniper Flat, which is inclosed in schists, and of the smaller 
body of mineralized and altered porphyry forming Sacramento Hill, 
just southeast of Bisbee, and intrusive into schists and limestone. 
The latter mass is of particular significance from its connection with 
the principal copper deposits of the district. The intrusion of the 
porphyry was accompanied by little or no contact metamorphism even 
in the limestones. 

After the intrusion of the granite-porphyry the region was eroded 
until the opening of Cretaceous time. It is probable that the princi- 
pal mineralization of the district followed closely the eruption of the 
porphyry, and thus dates from early Mesozoic time. 

At the beginning of the Cretaceous the region again began to sub- 
side, and a conglomerate was deposited by the advancing sea over the 
eroded surface of the pre-Cambrian and Paleozoic rocks, with their 
intruded masses of porplryry. In places this conglomerate was laid 
down to a uniform thickness of about 75 feet over an even surface, 
but elsewhere it is found filling hollows in a pre-Cretaceous hilly 
topography, and attains a local thickness of 500 feet. The pebbles 
are composed chiefly of schists, although those of limestone and gran- 
ite-porphyry are not entirely absent. With the continued subsid- 
ence of the region about 1,800 feet of unfossiliferous sandstones and 
shales, with occasional lenses of sandy limestone, accumulated above 
the basal conglomerate. Conformably overlying these are about 650 
feet of limestone beds containing abundant fossils belonging in the 
Comanche division of the Cretaceous. Most of these limestones, par- 
ticular! }' the lower beds, are thin bedded and impure, but hard, gray, 
massive beds, aggregating some 40 feet in thickness, occur near the 
middle of the calcareous member of the local Cretaceous section, and 
form a cliff that is a conspicuous topographic feature of the hills 
north and east of Bisbee. The limestones are conformably over- 
lain by more than 2,000 feet of sandstones and shales, much like 
those occurring in the lower part of the section. These upper arena- 
ceous beds are the youngest stratified rocks exposed in the Bisbee 
quadrangle. As their upper surface is everywhere one of erosion, 
their original thickness is unknown. The foregoing Cretaceous strata 
were first described by Dumble, and by him called the " Bisbee 
beds." a 

The Cretaceous beds of the Bisbee quadrangle have been deformed 
by folding and faulting. The folds are generally open, dips of more 
than 20° being rather exceptional. The general strike is northwest 
and southeast, and the prevailing dip northeast. About 7 miles 
southeast of Bisbee, however, where Paleozoic beds have been thrust 
by faulting over the Cretaceous, the latter have been turned up 

a Trans. Am. Inst. Min. Eng., Vol. XXXI, 1902, pp. 703-706. 


steeply and are in places nearly vertical. East of Bisbee the faults 
are normal, but southeast of Mule Pass Gulch faults of the reversed 
or overthrust type predominate. As Tertiary sediments are absent in 
the Bisbee region, this period was probably marked by the deforma- 
tion of the Cretaceous and older rocks and by erosion. 

The Pleistocene is represented by unconsolidated gravelly deposits 
flooring the broad valleys that surround the Mule Mountains on the 
west, south, and east. These are in the main fluviatile wash, with 
possibly some finer lacustrine beds at a distance from the mountains. 

It is impossible without the aid of a geological map to do more than 
indicate very crudely the general distribution and structure of the 
rocks of the Bisbee quadrangle. A northwest-southeast diagonal 
drawn through the quadrangle will pass through the town of Bisbee 
and form a rough division between the Cretaceous beds on the north- 
east and the pre-Mesozoic rocks on the southwest. The former, 
although folded and faulted, exhibit simple structures and have a 
prevalent dip to the northeast, away from the older rocks. They 
undoubtedly once extended farther over the Paleozoic rocks to the 
southwest, but have been removed by Tertiary and Pleistocene erosion. 

In contrast with the Cretaceous beds, the Paleozoic and pre-Cambrian 
rocks exhibit a highly complex structure, which, if we disregard the 
undecipherable pre-Cambrian deformation of the crystalline schists, is 
due to faulting, to intrusions of granite-porphyry, and to folding. In 
the northwestern part of the quadrangle the Paleozoic beds dip gen- 
erally to the southwest, but they change near Bisbee to a southeast- 
erly dip, which in turn swings round to a northeasterly dip a few 
miles southeast of the town. The pre-Cambrian schists, which are 
extensively exposed in the northern part of the district, pass gradu- 
ally beneath the Paleozoic beds to the southwest, being less and less 
frequently exposed in the various fault blocks, and finally disappear- 
ing altogether toward Naco Junction. 


Prior to the year 1880 Bisbee was an unimportant lead camp, a 
single furnace being then in operation upon cerussite mined from the 
Hendricks claim, close to town. The copper ore of the Copper Queen 
mine was discovered early in this year, and was profitably exploited 
until 1881. This ore was free from sulphur and had an average tenor 
of 23 per cent of copper. It was treated in two 36-inch furnaces, 
which, in spite of their small size were able, with wood as fuel, to 
turn out about half a million pounds a month. In 1882 the men com- 
posing the present Copper Queen Company bought the Atlanta claim 
near the original discovery and began prospecting. 

In 1884 the Copper Queen ore body, which had been worked for 
300 feet down an incline, was exhausted. The outlook was gloomy 
and work was almost abandoned, when a second ore body was simul- 


taneously discovered from the original Copper Queen incline and 
from the Atlanta workings. In order to avoid legal complications 
the two companies combined as the Copper Queen Consolidated Min- 
ing Company, which gradually absorbed the neighboring properties 
by purchase. In 1886 the old smelting plant became inadequate and 
was rebuilt. Greater economy was necessary, as the average tenor of 
the ore had fallen to about 8 per cent and the price of copper had 
notably declined. 

Shortly after 1890 the completely oxidized ores showed signs of 
failing, but in 1893 the works were remodeled by the introduction of 
converters, and sulphide and oxide ores have since that time been 
successfully worked together by the matte process. The introduc- 
tion of these converters was due to Dr. James Douglas, and marked 
the beginning of a new epoch in the smelting of copper ores in 

Up to the end of 1902 practically all of the copper from Bisbee was 
the product of the connected group of mines ow^ned by the Copper 
Queen Company. Recently, however, extensive ore bodies have been 
opened up in the Calumet and Arizona mine, and in the latter part of 
December, 1902, this company was turning out from 30 to 40 tons of 
copper a day from its new smelter at Douglas. 

This town, situated in the middle of Sulphur Spring Valley, on the 
international boundary, has sprung up with remarkable rapidity dur- 
ing the last year. Its growth is due to the erection here of the new 
smelters for the Copper Queen and the Calumet and Arizona companies, 
and to the fact that it is the junction point of the newly completed 
El Paso and Southwestern Railroad with the Naeosari Railroad into 
Mexico. It will undoubtedly become an important smelting point, 
not only for the Bisbee ores but for those from Mexico. 

From August, 1880, to the end of 1902 the total output of the Cop- 
per Queen Company was over 378,000,000 pounds of copper. The 
production of all the other mines within this period was probably 
something less than 2,000,000 pounds, so that the total production of 
the district may be given, in round numbers, as 380,000,000 pounds 
of copper. The maximum output was in 1901, when the Copper 
Queen mines produced 39,781,333 pounds of copper. 


(jfeneral occurrence of the ores. — The principal bodies of copper ore 
lie south of the town of Bisbee, within a radius of a mile. They occur 
in Carboniferous limestone, on the southwest side of a great fault, 
and closely associated with an intrusive mass of granite-porphyry. 
In the absence of the geological map and sections the structural rela- 
tions may perhaps be most clearly presented by a homely illustration. 
If half of a broken saucer be placed on a table with the fractured 
edge lying about west-northwest, and if the back of a book be laid 


against this edge, we shall have a rough illustration of the geological 
structure near the town of Bisbee. The saucer represents the synclinal 
attitude of the Paleozoic beds from the Upper Carboniferous limestone 
down to and including the Cambrian quartzite. The broken edge of 
the saucer is the great fault, while the book is pre-Cambrian schist, 
against which Upper Carboniferous limestone has been dropped by 
this fault with a throw of more than 1,500 feet. 

The town of Bisbee lies on the fault line. The hills northeast of 
town are composed of pre-Cambrian schists; those just south of it 
are Upper Carboniferous limestone, with Lower Carboniferous, Devo- 
nian, and Cambrian beds coming successively to the surface along the 
fault to the northwest. 

A little less than half a mile southeast of the center of town the 
fault encounters a mass of altered granite-porphyry and as a simple 
fracture disappears. This porphyry, which forms Sacramento Hill, a 
well-known local landmark, is a very irregular mass about a mile in 
diameter. It has invaded the pre-Cambrian schists on the northeast 
and the Upper Carboniferous (probably also the deeper-lying, older 
Paleozoic beds) on the southwest. The available evidence indicates 
that the intrusion of this porphyry took place after the dislocation of 
the invaded rocks by the great fault. The latter probably continues 
to the southeast of the porphyry mass, but it is concealed in this 
direction by the younger Cretaceous beds. The Paleozoic beds form- 
ing the faulted syncline are not merely flexed, but are cut by many 
faults, some of them of considerable throw. These faults are, as far 
as seen, of the normal type. 

The ore occurs very irregularly as large masses within the lime- 
stone. The horizontal extent of these bodies is usually much greater 
than the vertical. The}^ are rudely tabular in form and lie generally 
parallel to the bedding planes of the limestone. As a rule the impor- 
tant ore bodies have been found within a distance of 1,000 feet of the 
main porphyry mass or of the great fault fissure just northwest of the 
porphyry. In the Czar workings of the Copper Queen mine, partly 
under the town of Bisbee, ore bodies have been worked from the sur- 
face down to a depth of about 400 feet, but toward the southeast the 
bulk of the ore occurs at increasing depths. In the Calumet and Ari- 
zona mine, about 3,500 feet south of the Czar, no large ore bodies were 
encountered until the shaft had penetrated about 800 feet below thej 
level at which the first ore bod}- was discovered on the Copper Queen 
claim. The ore thus occurs at increasing depths toward the center 
of the local synclinal basin. Detailed structure sections will probably; 
show, however, that the upper limit of the ore increases in depth:: 
somewhat less rapidly than would be the case did it correspond to a 
definite stratigraphic horizon. 

With the exception of the extreme western part of the Copper Queen 
mine, all of the productive and important workings in the vicinity of 


Bisbee are in the Carboniferous limestones. It is probable that the 
greater number of the ore bodies occur in the granular limestones of 
the Lower Carboniferous, but the distinction between Upper and Lower 
Carboniferous beds can rarely be satisfactorily made underground. 
Some important ore bodies certainly occur in the lower part of the 
Upper Carboniferous. On the other hand, no ore bodies of conse- 
quence have yet been found in the deeper-lying Devonian and Cam- 
brian limestones. In the Copper Queen mine local usage has distin- 
guished an "upper lime " and a "lower lime." As far as could be 
seen, however, this distinction is largely imaginary and is based on 
no constant lithological or structural features. The "lower lime" 
appears to be any limestone lying underneath the known ore bodies. 
It is in the main Lower Carboniferous, and the ore-bearing possibility 
of the underlying and Devonian and Cambrian beds is yet to be ascer- 
tained by deeper prospecting. 

Although the ore masses in general are what are generally termed 
"flat" ore bodies, dipping gently with the inclosing beds, they are 
related to other structures as well as bedding planes. , Ore is usually 
found in large masses along the contact of the limestones with the 
main porphyry mass. This contact, however, has not been thoroughly 
explored, and much of the ore along it consists largely of low-grade, 
partly oxidized pyrite. Dikes and sills of porphyry occur in the lime- 
stones at various distances from the main intrusive mass, and the se 
are almost invariably associated with ore in the adjacent limestone. 
In some cases large ore bodies, followed for a long distance in the gen- 
eral plane of the bedding, have been known to turn down almost ver- 
tically alongside a porphyry dike. Fissures in the limestones have 
also undoubtedly influenced the distribution of the ore. 

While the main porphyry mass of Sacramento Hill is often heavily 
impregnated with pyrite, it has not been shown to contain workable 
ore bodies. It is possible that one or more of the oxidized ore bodies 
in the Copper Queen mine were formed by the mineralization of the 
granite-porphyry, but this is a point which the present investigation 
has not yet determined. It is certain that many of the porphyry dikes 
encountered in the workings of the Copper Queen mines show no 
appreciable mineralization, even when in contact with ore. 

Miner alogical character of the ores. — The ores worked by the Cop- 
per Queen Company up to 1893 were oxidized ores, consisting chiefly 
of malachite, azurite, cuprite, and native copper. In the upper 
levels the malachite and azurite occurred in beautiful incrustations 
and stalactites, lining caves in the limestones. These "cave ores" 
have been exhausted, and although oxidized ore is still abundant it 
occurs generally as soft earthy masses, often containing cuprite and 
native copper, and usually associated with large amounts of limonite 
and kaolin. Native copper and crystalline cuprite are still abundant 
in the recently opened workings ot the Calumet and Arizona mine. 


The original sulphide ores from which the oxidized ores have been 
derived consist of pyrite containing variable amounts of chalcopyrite. 
These pyritic ores are sometimes directly in contact with oxidized 
ores, but it is not uncommon to find masses of chalcocite between the 
two. Bornite has been reported from some of the ore bodies, but 
arsenical or antimonial compounds are absent, so far as known. 

Origin of the ores. — That the original ore deposition was genetically 
connected with the intrusion of the granite-porphyry is reasonably 
certain. The present incompleted investigation, however, has not yet 
established the details of this connection. As a whole, the ore bodies 
may be classed as typical replacement deposits in limestone. 

The ore bodies that have thus far proved workable have resulted 
from the operation of later processes of concentration acting upon the 
original pyritic ores. The occurrence of the chalcocite is closely 
related to the general progress of oxidation, and this mineral has 
plainly been formed by the action of descending solutions upon lean 
pyritic ores. It is probable that at least a .part of the chalcopyrite is 
ascribable to the operation of the same agency. There is an observed 
connection between good ore and permeability to downward-moving 
solutions. Such pyritic ore as proves profitable is soft and crumbling 
and usually shows upon close examination interstitial sooty material 
that is probably amorphous chalcocite. 

The lower limit of oxidation of the ores is very irregular, and is 
apparently uncontrolled by any constant groundwater level. In the 
Calumet and Arizona mine oxidized ore occurs at a depth of a thou- 
sand feet, while residual masses of sulphide ore occur in the adjoining 
Copper Queen mines within 150 feet of the surface. Masses of lean 
pyrite are sometimes inclosed in an envelope of high-grade chalcocite 
and oxidized ores. 


Although more or less mineralization occurs at many points in the 
Mule Mountains, there is little to indicate that any deposits of copper 
ore will ever be found to approach in importance those already known 
and awaiting discovery in the faulted limestone syncline about Sacra- 
mento Hill. For over twenty years the Copper Queen mine has pro- 
duced an average of more than 16,000,000 pounds of copper annually. 
Recentty the Calumet and Arizona Company has begun energetic 
operations in ground almost surrounded by the property of the Coppei 
Queen. Not onl}< is there sufficient known ore in these mines to keep 
them in operation for many years to come, but there is no evidence! 
that the bottom of the ore-bearing ground has been reached in any oi 
these extensive workings. Moreover, the statement maybe venturer 
that the specter of the "lower lime" has hitherto had an undue infiu 
ence in restricting prospecting to horizontal planes. There is cer 
tainly a reasonable hope of finding ore bodies in the Devonian anc 


Cambrian limestones beneath the masses that have been so profitably 
worked in the overlying Carboniferous beds. 

But more than this, it may be pointed out that less than half of the 
semicircular mineralized zone about the porphyry mass of Sacramento 
Hill has been explored at all. Ore was first discovered at the surface 
on Queen Hill, at the northwest end of the zone. From this discover} 7 
'developments have been pushed by underground exploration, often 
with little or no surface showing, to the south. There still remains, 
however, an extensive area of unknown but promising ground, lying 
just south of Sacramento Hill and extending eastward toward the south- 
eastern continuation of the great fault, which is here concealed by the 
ibasal conglomerate of the Cretaceous series. This is the eastern half of 
jthe semicircular mineralized girdle about the intrusive mass of por- 
phyry. Its exploration calls for no greater outlay or boldness than is 
already displayed in other parts of the district with less assured hope 
3f reward. 

In conclusion, it ma} 7 be said that Bisbee is less likely to suffer from 
■a lack of ore than from too rapid exhaustion of the high-grade oxidized 
ores which are necessary for the economic smelting by present pro- 
issses of low-grade sulphides. 



By Arthur C. Spencer. 


The town of Encampment is situated 43 miles by wagon road south 
of Wolcott station on the Union Pacific Railroad, in Carbon County, 
Wyo., in the foothills of the Park Range, which constitutes the conti- 
nental divide and is localty known as the Sierra Madre. 

The Encampment Special quadrangle occupies the area between 
latitudes 41° and 41° 15' north and longitudes 106° 15' and 107° 15' 
west, and includes the town of Encampment in its northeast corner. 
The greater portion of the area, which has an extent of about 450 
square miles, lies within the State of Wyoming, but a narrow strip of 
Colorado is included upon the south. 

In a more extended report now in preparation a statement of the 
several classes of ore deposits observed will be given, together with a 
general discussion of the conditions of ore deposition in the region. 


The geology of the Encampment region, when studied in detail, is 
found to be very intricate, but the more general features can never- 
theless be readily outlined and as readily perceived upon the ground. 

Among the most prominent features presented by the region are 
certain bands of white quartzite, which the visitor first notes a few 
miles southwest of the town of Encampment on the road to Battle. 
The bands or reefs of quartzite, which cross the country in a nearly: 
east-west direction, are separated from one another sometimes by bands 
of conglomerate, slate, and limestone, and in other cases by dikes 
of dark diorite. All of these formations have a general dip toward 
the south, and frequently stand at steep angles. Taken together, the}' 
occupied a narrow wedge-shaped area, extending for a distance of 
about 20 miles westward from its point or apex below the mouth 
of Purgatory Gulch on the Encampment River, a few miles south oi 
Encampment town site. The widest part of the quartzite area id 
upon the west, where it becomes covered by surface formations ii 
the drainage of Big Sandstone Creek and of Savery River. With thd 


exception of the diorite, all the rocks mentioned are of sedimentary 
origin, having been originally deposited as horizontal beds or strata, 
and afterwards thrown into east-west folds by comprehensive forces 
acting in a north-south direction. 

The diorites are igneous rocks which were intruded into the sedi- 
mentary series in a molten state after the greater part of the folding 
and compression had taken place. They occur in dikes from a few 
feet up to half a mile in width, frequently extending along the strike 
for several miles. They are of almost universal occurrence through- 
out the quartzite belt, and are also found cutting the granites, gneisses, 
and schists which occur both to the north and to the south of the 
quartzite area. 

The schists of the region are mostly hornblende-schists, which may 
be seen in typical development upon the north slopes of the conti- 
nental divide in the heads of Jack Creek and North Spring Creek, 
and also in the region of Huston Park. The other rocks of the min- 
eral belt may be classed under the general names of granite and 
granite -gneiss, and all of these appear to have been formed since 
the hornblende-schists, though they are probably older than quartz- 
ites and associated formations. The formations represented in the 
Sierra Madre are of pre-Cambrian age and belong to the most ancient 
series known within the Rocky Mountain province. In general, the 
formations are well exposed and easily accessible for examination, 
though locally they are covered by overwash or by glacial debris. 

The topography of the region is more than ordinarily smooth for a 
mountainous country reaching elevations above 10,000 feet, a fact 
which allows the building of wagon roads to almost any desired locality 
at comparatively slight expense. 


The ore deposits of the Encampment region have not, as a rule, 
been developed to a sufficient depth to afford opportunity for an 
exhaustive study. Hence, while those of the few mines in the dis- 
trict which have been opened to a considerable depth have been care- 
fully studied, the information obtained with regard to the occurrence 
of economic deposits as a whole is largely based upon general geolog- 
ical relations ascertained from surface examinations. 

Ores. — Copper is the predominant metal of value in the ores of the 
district, though there are a few deposits carrying values in silver, 
and gold occurs alone in quartz veins, or in variable but always small 
amounts accompanying the copper ores. The ores of copper comprise 
the sulphides, chalcopyrite, chalcocite, bornite, and covellite and 
their usual alteration products, malachite, azurite, chrysocolla, and 
the oxides. The silver-bearing ores are argentiferous galena, occur- 
ring with sphalerite and pyrite in fissures with a gangne of quartz, 
together with calcite, or the carbonate of iron, siderite. 


The copper deposits. — Considered in the most general waj 7 , the 
deposits of copper in the region fall into two classes. The first class 
includes all where the mineral is chalcopyrite or copper- bearing pyrite 
unaccompanied by oxides, carbonates of copper, or rich sulphides, 
except very superficially where the former minerals have been oxi- 
dized by surface weathering. Deposits of this sort, which occur 
invariably inclosed in undecomposed or "live" rock, are regarded as 
original ores. Their distribution is almost universal, and they are 
found in all sorts of rocks, frequently without any recognizable vein 
material, but sometimes accompanying masses of quartz with a small 
amount of feldspar, calcite, or siderite (carbonate of iron). In those 
cases where little vein matter is present the ore occurs, as a rule, in 
pockets or lenticular masses following the schistose or platy structure 
of the country rock, and more or less mixed with the inclosing mate- 
rial. No instances were observed where bodies of this character gave 
promise of sufficient size or permanence to warrant the expectation 
that they will lead to important masses of ore. 

As an exception to deposits of the above type where there is no 
well-defined lead traceable for any considerable distance upon the 
surface, there are others, still without associated quartz, occurring in 
strong leads traceable for long distances upon the surface. A typical 
example of this variety of deposit is the Verde or Ilinton property. 
The Verde lead is a zone along which intense metamorphism has taken 
place, involving hornblende-schists, a band of limestone, and some 
thin strata of quartzite. The lead seems to follow the limestone, 
which in turn appears to lie parallel to the general schistosity of the 
region. There is every reason to anticipate that metamorphic zones 
of this kind will persist in depth, though the extent to which copper 
has been deposited in them must be proved by exploration. 

In a third type of original ores the copper pj'rites occur in a 
matrix of quartz accompanied by calcite and siderite or by feld 
spar. The sulphide here occurs in bunches throughout the mass of 
the gangue, and the value of such veins is dependent upon their per- 
sistence. Some veins of this nature are lenticular bodies lying with 
their longest surface dimensions parallel with the platy structure of 
the inclosing rock. Certain of such masses of quartz reach a width 
of 50 feet or more, showing in outcrop a length of from twice to sev- 
eral times this figure, but these seldom show any considerable amount 
of copper, though they are reported to cany a small amount of gold. J 
They can hardly prove to be permanent in depth. In other cases the!; 
quartz occurs in a disconnected series of thinner lenses, extending 
along the same general trend in the schistose rocks. Sometimes these 
interrupted veins carry chalcopyrite in promising amounts. Their 
probable downward extent and regularity may be closely ascertained' 
by a study of their persistence along their strike. If they are irregu 
lar and interrupted upon the surface, they are likely to be discon 


tinuous in depth, but where strong and persistent in outcrop they 
may be expected to continue in depth. This type includes such 
deposits as the Continental in Cow Creek, the Cascade, and the 
Kurtz-Chatterton, in each of which it is anticipated that active devel- 
opment in progress should settle the question of permanence and 
extent of mineralization. 

In the ores of the two properties last named there has been some 
secondary deposition of ore, but the sulphides are regarded as mainly 

The second class of copper deposits includes all those where the 
principal copper minerals are rich sulphides, such as chalcocite or 
copper glance, covellite, and bornite, with or without high-grade cop- 
per pyrites. In the surface portion of such deposits large amounts of 
oxide and carbonate ore are found, and they are commonly capped at 
the outcrop with strong gossan. Also the inclosing country rock is 
often to a greater or less extent decomposed. 

Ores of this character are regarded as due to secondary concentra- 
tion or enrichment of ore bodies originally of low grade, through 
processes similar to those which have produced bonanza deposits in 
many other copper camps. 

The secondary deposits of the Encampment district have been thus 
far the only ones supporting productive mines. The ores of the 
Charter Oak, Doaue-Rambler, and Ferris-Haggarty mines are of this 
nature. At the Charter Oak, where the country rock is granite and 
diorite, the deposit appears to have been extremely irregular, but in 
the other mines mentioned the deposits show considerable regularity 
in their occurrence. The ore bodies, inclosed in quartzite of sedi- 
mentary origin, occur in zones of shattered rock which follow the bed- 
ding of the quartzite. Course's of easy circulation for underground 
water have been afforded by local shattering of the rock, which 
doubtless determined the position of original deposition, and later 
allowed of concentration to the form in which the ores are now found. 

In both the Doane-Rambler and the Ferris-Haggarty the secondary 
ores have been opened to a depth of more than 300 feet, though in 
neither instance lias the lowest level of the workings penetrated 
Bore than a short distance below the beds of the gulches adjacent. 

The question of the permanence in depth of these rich secondary 
lores need not be discussed here, since it is a subject which will soon 
be settled in a practical way by the developments now in progress. 
Thus far there seems to be no sufficient reason for supposing that the 
[bottom of the zone of enrichment has been closely approached in 
I either mine. 

From the present study of the region it appears that the future of 
|bhe district must depend very largely upon the discovery of addi- 
tional deposits of the secondary class or type. That such deposits 

Bull. 213—0:3 11 


exist it seems fair to anticipate, but the best method for their diseov- 1 
ery must be based upon a recognition of their character as distinct 
from the primary ores. 

Secondary ores will not be found where the inclosing rocks are tight | 
and impervious to the circulation of atmospheric waters. They requ ire t 
loose formations due to brecciation or crushing of the country rock, as ; 
in the cases mentioned, and in some cases it is to be expected that 
the country rock will be greatly decomposed. Several locations were ! I 
noted by the writer where gossan was present in encouraging amount, ! { 
but where no adequate work had been done to prove the condition of, 
the inclosing country rock or the significance of the gossan. Other! 
properties show the presence of rich sulphides in crushed and decom-fl 
posed diorite, and it is believed that these are worthy of careful 



By Arthur C. Spencer. 


Pearl, Colo., lias been a post-office for several years, but only within 
the last three years has it become known as a mining camp. It is 
located in Larimer County, near the northern boundary of Colorado, 
about 20 miles southeast of Encampment, Wyo., and an equal dis- 
tance south of the New Rambler copper mine. 

The area contiguous to Pearl over which active prospecting has been 
carried on for the last three years is drained by a tributary of the 
North Platte River, now known as Big Creek, but represented on the 
maps of the Fortieth Parallel Survey as Grange Creek. The region 
is mountainous, lying as it does in the heart of the Sierra Madre, or 
northern end of the Park Range, which forms the westernmost of the 
three elevated zones which compose the Rocky Mountains in this lati- 
tude. The crest of the Sierra Madre, from 10 to 25 miles south and 
west of Pearl, forms the continental divide separating the waters of 
Big Creek from the head of Elk River, which flows to the Yampa 
and thus to the Green River. 

Eastward from Pearl there is an easy line of travel to North Park, 
and toward the west the old Government road leading from Laramie 
to Hahns Peak gives a route to the head of Encampment River. 

The town itself is picturesquely situated in a broad basin near the 
junction of several wide valleys, which give access to all parts of the 
adjacent mountains. The elevation of this basin is about 8,000 feet, 
but within a distance of 10 miles there are mountains which rise to an 
altitude of from 10,000 to 12,000 feet. 

The surrounding slopes are covered by a dense growth of pine and 
spruce, while the valley bottoms, which were originally covered by a 
luxuriant growth of wild grass, are now devoted to the cultivation of 
timothy and other grasses for hay. 


The geology of the region is similar to that of a portion of the 
Encampment district, though the pre-Cambrian quartzite, which is 



a noticeable and important feature of that district, is not found. ! 
The country rock over large areas is a generally coarse though varia- 
ble granite of a red or gray color, frequently cut by small dikes of 
pegmatite. Minor areas are covered by diorite of a variable charac- 
ter. Though usually massive, as observed in limited outcrops, both 
the granite and the diorite, when considered in a broad way, show 
banded structures, due to a more or less evident parallel arrangement 
of the constituent minerals, and to the separation of light and dark 
minerals into narrow plates. These variations are most noticeable in 
areas where the granite preponderates, and in this rock the variations 
range from light-colored siliceous phases to very dark-colored basic 
types containing a large amount of mica and hornblende. Certain of \ 
the dark bands intimately connected with the granite can be distin- j 
guished only with difficulty from the diorites which occur in larger 
independent masses. The structure of these massive diorites is ty pi- j 
cally gneissic, and outcrops which are not banded are rarely observed. I 


Nine prospects showing the presence of copper minerals in encour- j 
aging quantities were visited. These have been developed by from 
50 to 200 feet of workings. Two days were devoted to a rapid exam- 
illation of the phenomena presented, and these observations form a 
basis for the notes which follow. 

In every case where limonite or iron oxide was found at the surface 
this material has proved to be only a shallow capping; and the zone 
carrying oxides and carbonates of copper beneath it, when present! 
at all, has been unimportant. In no instance did any property vis- 
ited fail to show unaltered pyrite and chalcopyrite at a moderate 
depth from the surface, but there are as yet no thoroughly developed! 
deposits, though on every hand intelligent efforts were being made to 
prove the value of the various discoveries. 

Big Creek shaft. — The property of the Big Creek Mining Company I 
lies northwest of Pearl at a distance of about 2-J- miles. The general 
character of the country rock in the vicinity is granite-gneiss, but 
there are frequent bands of diorite which vary from gray to almost 
black, with changing proportions of hornblende and feldspar. The; 
granite normally contains mica, but locally this mineral disappears 
and certain fine granular streaks in the granite have the appearances 
of being quartzite, though in fact they are made up of quartz 
and feldspar. The country rock at the shaft is a granite-gnei 
which contains more than the usual amount of mica. The workings 
were filled with water and therefore not accessible, but from the 
direction of the shaft the course of the vein seems to be about 
N. 00° W. The vein is said to stand nearly vertical for a distance 
of 100 feet from the surface, and then to dip about 70° S. to the 
bottom of the shaft, which is 145 feet deep. From the material 


found on the dump the ore is seen to be chalcopyrite occurring 
with ferruginous zinc blende in a segregation vein composed mostly 
of hornblende, but carrying a small amount of calcite. The country 
rock is very platy or schistose, but the vein material seems to be 
massive. The relations of the sulphides to the hornblende and cal- 
cite show that they are contemporaneous minerals. Unfortunately 
the vein does not afford a visible outcrop, so that its relations to the 
country rock can not be studied in detail. 

Sierra Madre shaft. — This property is located near the State line 
and about 1-J miles north of Pearl. A mineralized zone about 7 feet 
in width, having a course N. G0° E., occurs in dark micaceous gneiss. 
This zone, which is parallel to the structure of the gneiss, may be 
divided into two portions, one of which is made up of entirely mas- 
sive hornblende, free from banding and carrying pyrite, chalcopyrite, 
and zinc blende, with a small amount of galena; the other portion is 
a light-colored banded rock resembling the sugary granite mentioned 
as occurring near the Big Creek shaft. This portion of the vein car- 
ries zinc blende and a small amount of pyrite, in bands parallel with 
the course of the mineralized zone. The hornblende vein presents no 
sharp walls against the inclosing gneiss or against the siliceous por- 
tion of the mineralized zone, and it seems to have been formed by seg- 
regation accompanying the general metamorphism wiiich produced 
the banding of the country rocks. 

The zinc blende occurring in the siliceous gneiss possibly replaces 
the dark-colored minerals which it originally contained, and was 
probabty introduced at the time the hornblende vein was formed. 

Lizzie and Tally claims. — These are contiguous properties tying less 
than half a mile north of Pearl. In this region there are rapid 
alternations of granite and diorite in many varieties. The mineral- 
ized zones seem to conform to the structure of the gneiss, which has a 
course about N. 50° E. The two shafts appear to be located upon 
different zones, and still other zones are present upon the claims. In 
both shafts bornite and chalcocite have been found, but these minerals 
are confined to the upper portions of the workings. 

Swede or Hawkey e group. — These claims lie about 2 miles south- 
east of the town. In general the occurrence of the ores seems to be 
similar to that in the Big Creek and Sierra Madre claims. Granite is 
the usual country rock, but bands of diorite are also present, and the 
immediate walls of the ore-bearing material are of an intermediate 
type of rock. At the Copper Crown shaft, which is the principal 
opening, the course of the vein is N. 10° W. The vein matter is con- 
siderably weathered, but consists of pyrite, chalcopyrite, and zinc 
blende, occurring in a gangue of calcite and serpentine. Occasional 
specimens show that the serpentine has been derived from the altera- 
tion of hornblende or pyroxene, which indicates that the deposit is of 
the same nature as the Sierra Madre. 


Wolverine claims. — This property, owned by the Cold Water Min- 
ing Company, is located about 2^ miles south of Pearl. The eountrJ 
rock is extremely variable, showing all gradations from black dioritet 
to pink granite, and the granites are in part hornblende-granites 
related to the diorites. The ore in the discovery shaft is chalcocitel 
containing disseminated specks of chalcopyrite and zinc blende. I 
This ore is of a very friable nature, and on exposure crumbles to a 1 
sand. An examination of the material thrown out and of the neigh-' 
boring outcrops shows that the ore has resulted from the replacement! 
of biotite in a rock originally composed of quartz, biotite, and garnets 
Of these three minerals the quartz alone remains in the form of a 
granular gangne surrounded by the sulphides of copper. The extent 
of this ore and the shape of the ore body have not been ascertained,, 
but surface outcrops are sufficient to show that the mass of the rock in 
which it occurs is rather limited, having the shape of a wedge which! 
disappears toward the southeast. 

The shaft where the work is now being done is situated a few feet< 
north of the point of the wedge of granite, and through its top there' 
passes a vein having a course N. 40° W. This shaft is in pink gran-' 
ite, but diorite is present on both sides. The general trend of thei 
banded structure is N. 80° E. The various rocks near the mouth of) 
the shaft are cut in an intricate manner by small dikes of pegmatite, 
and certain coarse phases of granite in the vicinity contain red oxide 1 
of iron, which has been derived probably from magnetite. Some good; 
specimens of chalcopyrite have been taken from the shaft, but no 
regular deposit of the mineral has been proved thus far. 

Mount Zirlcd shaft. — The shaft on the property of the Mount ZirJ 
kel Company is located about 2,500 feet northeast of the Wolverine] 
shaft, and while the general nature of the country rock is identical,! 
the ore here occurs in a different manner, nainelj 7 , in granite pegma- 
tite and in a broken or brecciated gneiss adjacent. 

The shaft has been sunk to a depth of 185 feet, and drifts started 
at 71 and 155 feet. The pegmatite is extremely coarse grained, and 
is composed of quartz and cream-colored feldspar, with occasional 
flakes of mica. This material has been fractured and chalcopyrite 
has been deposited in the openings thus formed, sometimes as a filling 
of brecciated bands, and at other times occurring along cracks which 
pass from the feldspar into the quartz. As shown in the workings,! 
the pegmatite has a course approximately N. 80° E. For the first 35 
feet there is a dip of 70° S., then for 90 feet the vein stands nearly 
vertical, and below 125 feet it dips perhaps 75° N. The pegmatite is 
inclosed in a much broken gneiss of variable composition. On the) 
north side of the vein diorite and granite seem to be intricately mixed, 
and here local pockets of chalcopyrite are found in the 155-foot level, 
and also in the discovery shaft at the surface, where there is a well- 
defined streak of iron oxide stained with green copper mineral, evi-\ 


Sentry due to surface weathering of sulphide ores. The ores in the 
pegmatite are not accompanied by any contemporaneous quartz, but 
this mineral is present in small amount in the ores which occur in the 
country rock. The occurrence of ore, both in the pegmatite and in 
the inclosing rock, is very irregular, and seems to depend upon the 
fracturing which the rocks have undergone. There are two systems 
of joints, which, taken together with the gneissic structure, and with 
frequent rifts of low inclination, result in the production of angular 
blocks, by which the size and form of ore masses are often limited. 
The ore occurs, in some instances, as a probable replacement of coun- 
try rock, and in other cases as a deposit between adjacent blocks. 
The relations observed tend to show that the ores have been intro- 
duced in a manner independent of the formation of the pegmatite and 
subsequent to it. 

Gold King claims. — The workings of this property are located 
between 3,000 and 4,000 feet east of the Mount Zirkel shaft. The 
shallow openings which were visited seemed to have been located on 
carbonate stains occuring along a sheared zone in red granite. The 
heaviest stains amount almost to impregnation, and these occur at 
the intersection of closely spaced joints. In the granite near by there 
are certain bands which are very coarsely crystallized, and which 
carry red oxide of iron, probably derived from magnetite. Besides 
the large amount of granite there are also outcrops of diorite near the 

Bound Top, Copper Queen, and Big Horn. — These claims are 
located in close proximity to one another, and distant about 3 miles 
from Pearl in a southerly direction. The surface openings which 
constitute the development of the Round Top property show the pres- 
ence of yellow sulphides and of zinc blende in a siliceous vein-like 
segregation following the banding of the gneiss, which forms the 
country rock. It seems probable that the sulphides have been intro- 
duced in the form of replacements of hornblende grains in the streaks 
in which they occur. 

On the Copper Queen claim, about 400 feet southeast of the last, the 
developments consist of a shaft about 30 feet in depth. The materials 
thrown out show the presence of a mass of hornblende rock in the 
form of a vein-like segregation in diorite-gneiss, which forms the 
country rock. Upon the immediate walls of the vein the diorite 
looks like hornblende-schist, but the microscope shows that its platy 
structure is due to recrystallization and not to crushing. It is there- 
fore concluded that the vein matter and wall rock are of the same age 
and origin. The vein matter is entirely granular and massive, in 
which respect it corresponds with other occurrences that have been 
mentioned. Along with the hornblende there is some quartz, and 
this mineral is largely confined to coarse portions of the vein, where 
calcite is also found. The metallic minerals are chalcopyrite, iron- 


bearing zinc blende or black jack, and pyrrhotite. The latter mineral 
was tested for nickel and cobalt, neither of which was found to be 

The Big Horn shaft is located about 600 feet from the Copper Queen 
opening, in a direction S. 20° E. The country rocks are a schistose 
diorite, which breaks up into pencils or rod-like pieces instead of 
platy fragments and ordinary schist. The pencil structure is pro- 
duced by cleavage in two directions — N. 80° E. and N. 10° W. — the 
former being somewhat the more prominent.' A nearly horizontal 
rifting is noticeable both in the surface outcrops and in the mine 
workings. At the Go-foot level a drift 25 feet in length, running 
toward the southeast, shows a vein of hornblende gangue, carrying 
chalcopyrite in varying amounts. 

The width of the vein varies from 18 to 36 inches, but it is not con- 
tinuous toward the northwest, and it appears to be a lenticular segre- 
gation conformable to the structure of the country rock, which strikes 
N. 80° W. at the end of the drift, with a nearly vertical dip. The 
vein matter sometimes incloses fragments of the country rock, and 
while the ore occurs largely intercrystallized with the hornblende, it 
also impregnates the country rock to a distance of 2 or 3 feet. At 
the bottom of the shaft a mass of quartz occurs, about 30 inches 
across, which appears to cross the trend of the country rock. The 
formation of this quartz is probably distinct from that of the horn- 
blende, since the latter contains little or no quartz. 

Grand Republic. — This property is located about 3 miles southeast 
of the Big Horn. Here the country rock is made up of alternating 
zones of granite and diorite, each of varying composition. The loca- 
tion seems to have been made on a 3-foot vein of vitreous quartz 
carrying some fresh chalcopyrite. This vein follows the direction of 
the bands in the gneiss, or about N. 30° E, and dips 20° SW. A short 
distance east of the vein there is a metamorphosed zone in the diorite, 
in which a great deal of massive epidote has been developed. Though 
in a very different rock, this zone recalls the metamorphosed volcanic 
rocks occurring at the Verde mine in the Encampment region. 

The variations in the country rock at this place are extreme. Cer- 
tain light-colored bands are so siliceous that upon first sight they have 
the appearance of quartzites, while other bands of diorite are nearly 
black and contain only a very small amount of light-colored minerals. 
Between these two extremes all intermediate types occur. 

The development shaft, which has been sunk to a depth of 80 feet, 
penetrates a band of black hornblende rock, but though the quartz 
vein which has been mentioned dips toward the shaft, it has not yet 
been encountered. A small amount of chalcopyrite was found in the 
shaft in a massive segregation of hornblende, and a specimen taken at 
the bottom shows a small lens of glassy quartz surrounded by dark- 
green hornblende, with chalcopyrite disseminated throughout the 


latter, together with a small amount of zinc blende, revealed by the 


Other prospects. — At the time the region was visited many other 
prospects, apparently similar in character to those mentioned, had 
been located, and upon some of them about the same amount of 
development had been done. The ores of copper encountered were in 
most cases chalcopyrite, as in the properties described, though in one 
case large masses of richer sulphides, said to have come from an open 
cut about 12 feet in depth, were seen. 


The rapid examination of a few properties in the vicinty of Pearl 
made by the writer can not with fairness be made the basis of any 
opinion, favorable or otherwise, concerning the probable future of the 
milling industry of the region. All the properties visited are in the 
development stage, but the work in progress should soon determine 
in a practical way the important questions whether any of the ore 
bodies are of sufficient size and permanence to afford commercially 
important deposits. 


By Walter Harvey Weed. 


The geology of the Butte district and its ore deposits formed the 
subject of a report published by the Geological Survey as a geologic 
folio in 1897. a Subsequent development in the copper mines of the 
district, partly as a result of the greatly increased output of the prop- 
erties, but mainly because of the very large amount of work done to 
prove structural conditions, ore connections, and other evidence for 
use in the many lawsuits begun since 1896, has afforded opportunity 
to greatly extend the earlier work and to modify conclusions based 
upon the earlier incomplete data. A reexamination of the district, 
with a special study of the copper deposits, was therefore begun in 1 901. 
Owing to the necessity of completing other work for publication, and 
to the intricate nature of the study, involving a close 1 and detailed 
examination of over a hundred miles of underground workings, the 
field work was not completed until the autumn of 1902. The later 
workings show that the structural conditions are far more complex 
than was formerly supposed. The original veins are displaced by 
great faults, and these later fractures are themselves mineralized and 
again displaced. The working out of this structure has been diffi- 
cult because the deposits occur in a body of very homogeneous gran- 
ite, the rock alone affording no clue to the amount or direction of 
displacement. Nevertheless, the correlation of displaced areas is 
fairly satisfactory, based as it is upon a study of the quartz-porphyry 
and aplite intrusions in the granite and of the structural and miner- 
alogic variations of individual veins. 


The Butte district is situated in southwestern Montana, in the cen-| 
trai part of the Rocky Mountain region. The city which is built 
about and over the mines is the largest settlement of the State, while 
the neighboring city of Anaconda, 20 miles distant, is a dependent, 

a Geologic Atlas U. S., folio lis, Butte Special, Mont., 1897. 


having been built for and supported by the reduction of the Butte 
ores. Smelting' the Butte ores is also the largest industry of the city 
of Great Falls. Three transcontinental railways run to Butte, and 
its traffic surpasses that of all the other cities of the State combined. 
Originally named Summit Valley district, a name which is still 
retained in official records, and which is significant of its situation 
almost upon the transcontinental divide, where the waters of the 
Pacific and Atlantic separate, it is now universally known as rftitte, 
a name derived from a sharply conical hill that rises abruptly above 
the barren hillside on the edge of the city and forms a prominent 
landmark. The area comprising the district is a now barren hillside 
on the northern side of a flat valley bottom. This level valley is 
inclosed by an abrupt mountain range forming the continental divide 
on the east and the snow-capped peaks of the Highland Mountains on 
the south. To the westward a low plateau, now cut through by Silver 
Bow Creek, separates this valley from the great lake-bed area of the 
Deer Lodge Valley. 


The Butte district of Montana is to-day the most important copper- 
producing area in the world, the product aggregating 2,841,791,572 
pounds to the close of 1901, with a total value of $381,209,050. The 
discovery of the copper veins of Butte was not made until after the 
district had acquired some prominence for its gold placers, and sub- 
sequently as a silver camp. The placer gold was first worked in 1803, 
the date of greatest activit}^ being in 1867, since which period the 
product ion of placer gold has become quite insignificant. 

In 1804 the first lode location was made, upon a vein now known 
as the Travona. This was the beginning of a period of very prosper- 
ous silver mining, and the district became the center of energetic 
operations, large mills being erected, with a considerable output of 
i silver as a result. This period of active silver mining continued until 
1892, when in common with other silver camps of the country the 
Butte district suffered a crushing blow. The climax of the produc- 
tion of silver ore was reached in 1887, when the different mills treated 
about 400 tons of ore per day and the smelters an aggregate of about 
100 tons per day, the average yield being about $25 per ton in gold 
iind silver. 

In the j^ear 1881 the Dexter mill was leased by Marcus Daly, for 
the newly organized Anaconda Silver Mining Company, and 8,000 
tons of oxidized silver ore, from the Anaconda ledge, Avas treated in 
this mill, yielding about 30 ounces of silver to the ton. The ore con- 
tained just enough copper to make it unnecessary to add bluestone 
Iin the raw amalgamation, but the resulting bullion was very base, 
sometimes running only 400 fine. In working the vein a drift running 


few inches wide. Mr. George Hearst, visiting the district about 1S82, 
selected the site of the present Anaconda shaft as the most suitable 
place for future development. At a depth of 300 feet a crosscut run 
from the shaft encountered 5 feet of copper glance, and the ore was 
extracted and shipped to Swansea. During these early years the cop- 
per ores showing on the surface of several of the claims were receiving 
attention, and in 1867 an effort was made to smelt some of the ore from 
the Uarrot lode. 

To Senator W. A. Clark is due the first successful development of 
the copper veins of the district. In 1872 and the succeeding two years 
he began development work on the original Colusa, Mining Chief, an 
Gambetta claims. The ore extracted was shipped 400 miles in wagon 
to Corrine, Utah, thence by rail to the East, some of it going to 
Swansea, Wales. 

One of the purchasers was the Boston and Colorado Smelting Com- 
pany, located at Black Hawk, Colo., and in 1879, at Mr. Clark's sug- 
gestion, this company formed the Colorado and Montana Smelting 
Company and erected reduction works on the present site of the 
Colorado Smelter, thus furnishing a local market for the copper as 
well as the silver ore of the district. This smelter gave a great 
impetus to copper mining in the district, as previously shipments con- 
taining 35 per cent of copper from the Green Mountain claim gave no 
profit to the shipper after the cost was paid, although the gross value 
of the ore was $130 per ton in copper, the average price of that ore 
being 18f cents per pound. In silver the ore carried not less than $50 
per ton, but the works charged a high price for treatment, owing to ' 
the presence of arsenic, which made the metal brittle. 

Soon after the erection of the Colorado Smelter the Parrot, Montana 
Copper, Clark's Colusa, and the Bell Company began smelting opera- 
tions. The matte produced by these works was shipped to Eastern 
markets for refining. In 1884 the Anaconda Smelter began operal 
tions, followed rapidtyby the formation of the Butte Reduction Works, 
Boston and Montana, Butte and Boston, and Montana Ore Purchasing 
companies. The completion of the Utah Northern Railway from 
Ogden to Butte in December, 1881, and the connection of this railroad 
with the Northern Pacific at Garrison in 1893, and the coming of the 
Montana Central, part of the Great Northern system, in 1888, and of 
the local branch of the Northern Pacific in 1889 — all added to the 
prosperity of the camp. 

In the history of Butte the metallurgical advance in the treatment 
of the ores has been very steady; the free-milling silver plants gave 
place to chlorination and roasting, and these in turn to other improve- 
ments, so that the ores which could be profitabl} 7 treated became lower 
and lower in grade. With the great decline in silver of 1892-93 the 
silver-mining industry of the district became less and less important, 
until in 1890 all the large plants were closed down, and since that time 


the mining of silver ores has been of relatively slight importance and 
has been carried on chiefly by leasers working in the old properties. 
The importance of Bntte as a producer of silver and gold at the pres- 
ent time is due to the fact that the copper produced contains 0.0375 
ounce of silver and $0.0025 in gold for each pound of copper produced, 
or approximately 2£ cents in the precious metals for each pound 
of copper. On this basis the Butte copper mines yielded in 1801 
8,550,000 ounces of silver, which, at 55 cents per ounce, amounted to 
$4,702,500, together with $570,000 in gold, or a total of $5,272,500 in 
precious metals. Thus we see that in the production of precious 
metals the Butte district ranks among the great producers of the 
world. The total of 2,841,791 ,572 pounds of copper has been produced 
from a tonnage which may be safely estimated as at least 100 pounds 
per ton of ore, and on this basis over 28,000,000 tons of copper ore 
have been mined in the Butte district down to the close of 1901. 


The* rocks of the ore-bearing area are all igneous, the district form- 
ing part of an extensive region of Tertiary igneous activity. The 
prevailing rock, and the one in which all the veins occur, is a dark 
basic-gi'anite, technically known as quartz-monzonite, which is a part 
of a great mass of granitic rock extending from the snow-capped 
Highland Peaks*, seen 20 miles south of Butte, northward to Helena. 
This great mass of intrusive igneous granite is surrounded by altered 
limestone and other sedimentary rocks, and is in part covered by 
dark-colored andesite (both massive and fragmeutal varieties) of ear- 
lier age. Neither sedimentaries nor andesite occur in the district. 
Throughout the Butte mining district the granite is remarkably uni- 
form in color, texture, and composition, and the name Butte granite 
has been applied to it. This rock -is cut by dikes and irregular intru- 
sions of the Bluebird granite, a white aplite a composed of quartz and 
feldspar, with a little mica. This rock, though intrusive in the gran- 
ite, is supposed to have separated from the same magmas as the Butte 
granite and to have penetrated fissures in the latter while it was still 
hot, as the aplite is found in all sorts of small veins and masses which 
do not show any chilling along the contact. The rock is found fre- 
quently, but in relatively small masses. In the copper-bearing area 
the_Modoc porphyry appears in lenticular dikes, traversing both vari- 
eties of granite in very irregular fissures. It is a light-colored rock, 
carrying large and distinct crystals of feldspar and quartz in a dense 
ground mass, and is technically designated rhyolite-porphyry or quartz- 
porphyry. After the intrusion of the Modoc porphyry extensive frac- 
turing occurred, with vein formation, the veins cutting the porphyry 
in many instances. After the formation of these earlier veins, renewed 

"Called "granulite 1 ' by . some writers— a name applied by German geologists to a variety of 
schist, but by French petrographers to aplite. 


and very violent volcanic activity began, resulting in the intrusion 
and eruption of rhyolite, forming dikes cutting across the veins, and 
also great sheets and masses of fragmental material. 

The Big Butte is formed of rhyolite, both fragmental and massive, 
and this rock occurs in dikes cutting both the granite and veins in the 
silver area, while the fragmental form covers a large extent of coun- 
try west of the mines. These rocks are the product of volcanic action, 
and the Butte is the eroded remnant of a small volcano. 

The granites are of Tertiary age, for at the borders of the batholith 
late Cretaceous strata are cut by the intrusion, and, moreover, included 
fragments of the early Tertiary andesites occur in the granite. The 
rock is cut by rhyolite dikes, and as rhyolite ash-showers form lake 
beds containing Miocene vertebrate remains, the granite and the 
veins are of earlier age, probably Eocene or early Tertiary. West of 
the district the lake beds appear, formed in a great Tertiary lake that 
filled a long and relatively narrow valley extending from south of Dillon 
in southern Montana to (4arrison, a valley which was warped by later 
earth movements that drained it and carried the continental divide 
across its floor. 


The Butte Mat, a level valley bottom south of the city, contains no 
lake beds; it was formerly a normal erosion valley formed by the con- 
vergence of streams from east, west, and south of Butte, and was 
subsequently depressed by faulting along the base of the mountains 
east of Butte, which reversed its principal tributary and resulted in 
the filling of the valley by torrential debris and wash from the 
adjacent slopes. This faulting altered the ground-water level of the 
ore-bearing area and played an important part in concentrating the 
ores. The district is thus shown to be one of deep-seated igneous 
rocks, subjected to fracturing at various periods, the resulting frac- 
tures being in part filled by dikes, in part by veins, and in part 
displacing the veins; it is a region of continued and continuing 
crustal adjustment. 

The veins occur in an area showing few outcrops, the rocks being 
altered by decomposition and disintegration and forming smooth 
slopes; only rarely do the granite bowlders characteristic of the 
western part of the district show in the copper area. A few of the 
copper veins outcrop, but most of them, even the largest., are recog- 
nizable at the surface only by inconspicuous debris or do not show 
at all, a fact which has led to many lawsuits to determine ownership 
of ore bodies. 

The district embraces a well-defined area of copper lodes surrounded 
by silver veins with transition ores at the borders. Though the veins 
of these two areas present a strong contrast in mineralization and 
charaeter, the vein systems appear to be similar, so that the area may 
be described as a whole. 


The rocks of the entire district are traversed by a multiplicity of 
joints and fractures. These belong to three well-defined systems, as 
may be seen in excavations in the city or, more clearly still, in the 
great bowlder outcrops to the northeast where the veins are seen to 
be merely mineralized fissures, the exceptional instances in which 
the fractures have been channels for mineralizing solution. In the 
copper area the rocks are intersected by a multitude of fissures* 
which near the surface are filled by quartz and iron oxide, with 
rotted or disintegrated granite between, soft enough to yield to the 
pick. In depth the lesser fractures are not filled and are therefore 
less conspicuous. 

The veins of the district, both copper and silver veins, belong to 
three distinct systems. The oldest lodes have a general east- west 
course, the Parrot, Anaconda, and Syndicate lodes being examples. 
Another set of fractures has a northwest-southeast course, and lias 
displaced the earlier veins. A still later set has a northeast course 
and has displaced both the earlier systems of veins. The first two 
systems are heavily mineralized; the last shows a little endogenous 
ore, but the material mined is mainly the ore broken off from earlier 
deposits and included in the fault debris. This discrimination of the 
I different vein systems and the recognition of the faulting of one set 
by the other and of the resulting mineralization is the result of the 
study of the district made since the Butte folio was published. It 
has been made possible by the enormous development work expressly 
made to develop the structure and continuity of veins for the various 
lawsuits between the mining companies. 

The silver veins surround the copper lodes on the north, west, and 
southwest. Their course and geologic relations are very similar to 
those of the copper veins, but their structure and mineralogic charac- 
ter are different. The silver veins contain sulphide of silver, blende, 
pyrite, and a little galena, and commonly contain no copper save near 
the border of the copper area, where, though occasional bunches of 
copper ore occur, it consists of chalcopyrite and more rarely still tetra- 
hedrite, minerals which occur rarely and very sparingly in the copper 
lodes. The gangue consists of quartz with rhodonite and rhodochro- 
site, and shows marked banding and crustilication, in strong contrast 
to the structure of the coj)per veins. These silver veins form very 
prominent outcrops, the quartz being stained black by manganese 
oxide. The veins are largely due to the filling of open fissures, and 
show but slight alteration of wall rock. They are displaced by and 
traversed by faults with friction breccias and alteration clays like 
those in the coi>per area. 


Several of the copper veins were, as is well known, at first worked 
as silver veins. The upper portion of the veins consisted of quartz 


somewhat stained by iron, but not like the great iron gossan raps of 
other regions. This extends to a variable distance below the surface, 
200 to 400 feet in some instances, where it is replaced by partly oxi- 
dized and decomposed copper ores that form the upper limit of the 
remarkable glance, enargite, and bornite ore bodies of the district. 
Carbonates and Oxides are rare. 

The copper minerals occur in quartz-pyrite veins of remarkable 
width and extent. The Anaconda ledge is frequently Id) feet wide 
and will average half that width, as will also the Syndicate lode. 

The copper minerals of the Butte ores consist chiefly of chalcocite 
(copper glance), bornite (peacock copper), enargite (sulpharsenide of 
copper), and cupriferous pyrite. Govellite (cupric sulphide) occurred 
in considerable amount in one or two mines, but forms an insignifi- 
cant percentage of the total output. Tetrahedrite (gray copper) and 
chalcopyrite (copper pyrite) arc even rarer than the last-named min- 
eral. Until 1900 copper glance constituted the most important ore 
mineral of the veins, but it is now nearly equaled in quantity by 
enargite. In the great ore bodies of the upper levels of the Anaconda 
veins glance occurred in masses of nearly pure lead-like mineral 2| 
feet or more wide. In depth the mineral shows a more crystalline 
structure, and ii is found in all tin 1 mines in greater or less abundance 
and purity, but in the great bulk of the ores it forms small grains 
scattered through the ores. 

Bornite is less common than glance, and is practically restricted in 
occurrence to the veins in the western part of the copper area, where, 
however, ii occurs in great abundance, forming t lie chief ore of the 
( Original and Parrot mines. 

The gangue of all the veins is largely quartz, though there is also a 
large amount of altered granite with veinlets and bunches of ore. The 
vein walls are often defined by (day selvage, but these prove almost 
invariably to be due to post-mineral fracturing. More frequently 
there is a fading of ore into country rock, a feature characteristic of 
replacement deposits. 


Cliaracter of tin ores. — The copper ores average 55 per cent silica 
and 16 per cent iron. About 15 per cent of the tonnage mined is 
first-class ore, averaging 12 percent copper; the remaining 85 per cent 
carries 4.8 per cent copper, and is treated in concentrating mills, the 
resulting product containing but 15 to 20 per cent of silica, while the 
copper is increased to 18 per cent. 

The ores contain gold to the extent of about -2\ cents to each pound 
of copper, with 0.0375 ounce of silver. Native gold has been found 
upon crystallized glance, but with this exception no gold or silver 
minerals are recognizable in the copper ores. It is estimated that the 
total production of copper ore has been about 31,000,000 tons, averag- 


ing 5 per cent copper. The amount of arsenic (and antimony) pres- 
ent is very large, it being estimated that over 32,000 pounds a year 
pass off in smelter fumes. Tellurium is present in very small 
quantity in the ores, amounting to 2^ ounces, or 0.008 per cent, in 
the crude copper upon the converters. It is recovered in electrolytic 

Ore deposit/ion. — Three distinct periods of ore deposition are recog- 
nizable in the deposits of Butte. As many of the ore bodies are of 
composite character and derive their contents in part from each one 
of these periods, a careful study is necessary to discriminate the 
1 evidence and results of each period. In general it is necessary to 
differentiate primary deposits, or those formed of material brought 
to and deposited in the veins from outside sources, and the so-called 
"secondary" deposits of transposed and redeposited material. The 
former constitute the normal vein filling, the latter both the bodies 
of rich ore that have made the district famous and masses of low- 

i grade, concentrating ores. As a general statement, it may be said 
that the deposits of copper glance are secondary. 

The original source of the metallic contents of the primary deposits 
is still an unsolved question. It has been inferred by Mr. Emmons 
that, in the lack of direct evidence, "It is probable that circulat- 

I ing waters have somewhere in the depths extracted the metals from 
parts of the granite mass." To the writer the mineralogic evidence 

1 and the intimate connection between periods of ore deposition and 
igneous activity indicate a possible derivation from magmatic ema- 
nations — so-called mineralizing agents in waters partly of magmatic 
origin, mingled perhaps with predominating meteoric waters 

In general it may be stated that the original mineral-bearing solu- 
tions were probably hot and ascended through fractures in the granite. 

I The copper deposits are almost entirely replacement deposits formed 

I by waters ascending through mere cracks and attacking and replac- 
ing, particle by particle, the adjacent rock. The silver veins, on the 
contrary, are in large part due to the filling of open fissures, though 
replacement deposits also occur. In the replacement deposits there 
is a general lack of definition between country rock and ore, a wide 
zone of altered decomposed granite alongside of the vein, and com- 
monly an impregnation of the rock between the individual veins of a 
lode with ore minerals. This is especially noticeable in the eastern 
part of the copper area, in Leonard, Rarus, and adjacent mines. In 
the former an ore body is stoped out for 135 feet in width, consisting 
of altered granite, sheeted and intersected by a multitude of small 
veins crushed by later movements and impregnated by primary 
minerals in part replaced by secondary glance. 

In the central part of the copper area fresh unaltered granite is 
uncommon. There has been local development of intense thermal 
activity. The rocks are closely fissured as a result of several periods 

Bull. 213—03 12 


of fracturing, and the mineralizing solutions have penetrated and 
altered the rock between the fissures, converting and changing the 
rock to what is conveniently called pyritized granite, since the horn 
blende and mica are altered to pyrite. 

The deep development work of many of the mines shows a decided 
change in the amount of mineralization of the fractures. There is 
an increasing number of small veins of quartz and pyrite separated 
by altered granite. Some of the large lodes whose entire width is 
workable pass downward into a cluster of small veins of quartz and 
pyrite separated by altered granite. In other words, the replacement 
of inter- vein material by ore decreases with depth. There is also a 
decided increase in the number of small fissures devoid of ore and 
filled by friction breccia, but showing trifling displacement. This is 
particularly noticeable in the levels 1,600 feet or more below the sur 
face. On the other hand, some of the newer fault veins that show 
little or no ore in the upper levels contain pay ore below, because the 
open nature of the fault material permitted a deeper seepage than 
usual of descending waters. 

Secondary enrichment. — The enormous bodies of copper glance 
which have made the Butte district famous are probably the largest 
and best examples of secondary enrichment known. The fracturing 
of the veins has permitted the access of meteoric waters, which, dis 
solving the copper from the lean ores of the oxidized zone, deposit it 
by reaction with pyrite, in the depths. These deposits were greatest 
in the upper level of the mines and have gradually lessened with 
depth. In some of the veins the lower limit of enrichment has been 
reached, in others the deepest workings still show these enrichments. 

In general there is a marked association of faulting of the veins 
with bodies of rich ore, and these faulted areas are wet, so that the 
miners say: "A dry and tight vein is barren: a wet and crushed one 
is rich." This is particularly marked where the veins contain much 
pyrite, though the glance is more conspicuous in white quartz. In 
the deeper levels newly deposited quartz occurs with the glance. In 
the deepest levels, 2,000 feet or more below the surface, rounded 
masses of glance 2 and 3 feet across occur in crushed quartz contain- 
ing relatively little pyrite. 

Change of character of mineralization i villi, depth. — The most nota- 
ble change in mineralization with increasing depth is the greater 
abundance of enargite. In the eastern part of the copper area, in the 
Rarus Hill and its vicinity, this ore extends upward to the oxidized 
zone, sometimes very nearly to the surface. West of here there is a 
notable increase of enargite in depth, the mineral occurring for the 
first time in the very deep level of some mines (i. e., 1,800 to 2,200 
feet), an association that also prevails in some of the later veins, such 
as the Blue, as well as in the older ones. 

Influence of country rook.— There is a distinct association of the 


copper deposits with the Modoc porphyry occurrence, since the most 
productive lodes occur in the area penetrated by this rock. The 
veins cross the porphyry, however, even the earliest ones, and hence 
the vein fractures are of later occurrence. 

There is also a distinct genetic relation between ore and country 
rock, as a result of the deposition of the ore by metasoinatic replace- 
ment. Thus the Anaconda ledge is low grade where it crosses either 
the Bluebird granite or the Modoc porphyry, a feature explainable by 
the lack of easily replaceable, dark-colored, ferromagnesian minerals 
in those rocks. 


As a result of extensive legal development work the evidence is now 
conclusive that the east-west veins have been faulted. The identity 
of the Original-Parrot and Anaconda lodes is conclusively established, 
the displacement being due to the Blue vein. Farther east the Ana- 
conda ledge is again thrown to the north by the Mountain View fault, 
the displaced segment forming the South ledge of the Mountain View 
mine, terminated eastward by the Rarus fault, throwing the lode 
southward, so that its eastward extension appears in the Rarus mine. 
The same faulting has displaced the other veins of this part of the 

Earlier veins, east-west system. — The great veins of the district, the 
Anaconda, Parrot, Mountain View, West Colusa, Syndicate — in fact, 
all the great producers — belong to this east-west system, in which 
the trend is remarkably uniform, considering the length of the veins. 
The Silver Bow vein is a marked exception. There is some evidence 
to show that certain southeast fractures were mineralized in the ear- 
liest vein-forming period, and some of them reopened when the later 
faulting occurred. 

These earlier east-west veins are distinguished as lodes or com- 
i pound veins. They differ in structural and mineral character from the 
later lodes, and, except where faulted and enriched, lack the high sil- 
ver contents of the veins formed later. Fortunately they have been 
extensively fractured by strike faults, as well as the two other vein 
systems noted. 

Northwest fault veins. — The northwest system of fractures faulted 
and displaced the east- west veins. The three largest veins of this 
system, the Blue vein, Mountain View vein, and Grey Rock vein, are 
mineralized, but not so generally as the older veins; the ore occurs in 
chutes and is quite high grade and shows enrichment. The Blue vein 
has been developed for over a mile, and to a depth of 1,000 feet, prov- 
ing a heavy producer in several mines. It is cut and displaced by a 
northeast fracture in the Parrot workings. 

Northeast fault veins. — The veins of both the east- west and the 
northwest systems are cut and displaced by those of the northeast 


system. The largest and best-known example of this is the Rarns 
fault, and the ownership of immensely valuable ore bodies has hinged 
upon the geological conditions in the Rams and adjoining claims. A 
careful and prolonged examination of all the accessible workings of 
these mines, including stopes, has resulted in the establishment of 
the following facts: 

The Rams faults have cut and displaced all the veins. The cut-off 
is as sharp as if made by a knife, and high-grade ore abuts against 
fault breccia. The veins displaced are so close together that on cer- 
tain levels the cut-off ends of different veins are opposite. The fault 
is compound, consisting of two fissures, the easterly with a dip of 
45°, the westerly with a dip of 30°, and these fissures differ somewhat 
in strike. The interfault block is crushed and the included vein seg- 
ments are broken and their orientation is disturbed by a tilting of the 
block. The actual fault fissures are marked by attrition clay con- 
taining rock and mineral fragments. When indurated by infiltrating 
solutions this resembles the quartz-porphyry. As the interfault 
material contains workable ore bodies, stoping is sometimes continu- 
ous from one vein across the fault to another. Whatever the legal 
construction may be, there is no geological continuity. There has 
been some ore deposited in the fault fissure, but not sufficient to form 
a new north-south vein along the fault, being confined to the prox- 
imity of older ore, upon and about which it was precipitated. 

The Rams fissure has now been developed to a depth of 1,600 feet 
and its existence established for a distance of 1\ miles. Other fissures 
belonging to the Rams system exist in many parts of the district, 
notably at the Original, Diamond, and Leonard mines, in which 
extensive mineralization has taken place. 


By Walter Harvey Weed. 


Copper deposits occur at intervals along the Appalachian Mountains 
and the Piedmont Plateau to the east, extending from Canada to 
Alabama. The earliest known copper mines of the continent are 
included in this region, and many interesting historical facts are 
associated with them. The geology of so extensive a region is neces- 
sarily varied. The rocks are in most cases metamorphosed and of 
the types known as chloritic schists and hornblende-schists ; but their 
true nature is disclosed when the methods of modern petrographic 
research are applied to them, and in most cases the original nature 
and origin of the rock can be made out. It would be surprising that 
these deposits have not been studied in the light of our newer knowl- 
edge, both of petrology and of ore deposits, were it not for the fact 
that for many years past they have been of but little or no economic 
importance, and their workings have been filled by water and inac- 

While engaged in the collection of data to support or disprove the 
theory of secondary deposition and enrichment, a number of these 
old and formerly well-known mines were examined, as well as several 
newer properties whose development was inspired by the remarkably 
high price of copper in 1900-1901. The result of these examinations, 
necessarily brief and made primarily for the object stated, has been 
in part already published, but, the subject appearing attractive and 
the investigation timely, it was decided to extend the work and, from 
time to time, as opportunity offers, to examine and study all the 
known copper deposits of the Eastern, Middle, and Southern States. 

Early in this work it was recognized that, while many deposits arc 
of similar character, others present marked differences in mineral 
contents, structural character, and association. This led to an attempt 
to group deposits of similar nature, so that a description of a type 
would answer for many. This was done in a paper entitled "Type 
Copper Deposits of the South. " a Since then several copper properties 
in Maryland and New Jersey have been examined and found to be 
still different in character from those described. 

-(Trans. Am. Tnst. Min. Eng., 1899. 




The New Jersey copper ores occur in the eastern part of the State. 
They were worked more or less continuously from colonial days until 
some thirty years ago. Several properties have recently been reopened, 
and in one instance extensive development work has been carried on. 
The ores all occur at or near the contact between the shales and sand- 
stones of the Newark group (the red sandstone series of Triassic age), 
and the trap rocks. These traps all occur tilted at gentle angles, 
commonly conformable with the shale beds. Orange Mountain, and 
the second and third mountains back of it, collectively known as the 
Watchung Mountains, are formed by these trap sheets, the sand- 
stones forming the intervening valleys and foot slopes. These traps 
are lava flows contemporaneous in age with the shales, while all the 
other trap sheets of the State have proved to be intruded bodies. 
The copper ores occur above and below these trap rocks. 

In Watchung or First Mountain, back of Plainfield, and the contin- 
uation of the mountain south and west to Boundbrook and beyond, 
the trap is underlain by a stratum of altered shale that is almost con- 
tinuously copper bearing. This constitutes the most important cop- 
per deposit of the State, one that has been worked at fully 30 dif- 
ferent places in former years. The most important development has 
been near Somerville, at the American copper mine. The workings 
at this place follow down the ore stratum for a distance of 1,350 feet 
from the surface, the bed being inclined at an angle of about 10°, 
dipping into the mountain. The ore occurs in a well-defined bed, 16 
inches to 3 feet thick, lying immediately beneath the trap rock, the 
latter rock being also occasionally ore bearing for a few inches next 
the contact. 

For a distance of nearly 15 miles along the mountain front this con- 
tact stratum has p roved copper bearing. The ores consist of the red 
oxide of copper with green carbonate and silicate, sheets of native 
copper, and rarely peacock copper and glance. In the American 
mine the workings pass through the upper oxidized part of the bed, 
characterized by the ores just mentioned, into a lower zone in which 
they are wanting and in which native copper occurs in small masses 
scattered through the ore bed, together with a very little finely dis- 
seminated glance, associated with calcite. The native copper occurs 
in grains and irregular nodules in bunches of white or grajash-colored 
ore irregularly scattered through the purple rock. As no average 
sampling was attempted, it may be stated that the systematic sam- 
pling of the company's representative is said to have yielded 2^ per 
cent copper, a figure which if sustained by mill work will permit of 
the profitable working of the property. 

At Arlington and many of the other localities of the State the ore 
consists of oxide, carbonate, and glance, filling cracks and crevices in 


the sandstones above the trap sheets. Reduction works have been 
erected at the Arlington property, bordering the Newark meadows, 
and at the American mine near Somerville. a 


The Maryland properties are chiefly of historic interest, as the 
shafts and workings of most of the mines are now filled and inacces- 
sible. The Liberty mine is a noteworthy exception, and is particu- 
larly interesting because it appears to be representative of many, if 
not all, of the abandoned properties, and of many undeveloped pros- 
pects of the region. 

The deposits all occur in an open, gently rolling region underlain 
by so-called chloritic schists, whose true nature remains to be deter- 
mined. Near the copper deposits thus far examined these rocks 
appear to be altered volcanic rocks, probabty rhyolites, and resem- 
ble those of South Mountain, Pennsylvania, where copper deposits 
also occur. The Maryland ores impregnate these rocks but slightly, 
the main ore bodies occurring in what appear to be isolated blocks of 
limestone, or rather marble. The ores consist of bornite or peacock 
copper, with some chalcopyrite and associated calcite and rhodochro- 
site, and it occurs filling crevices, fracture planes, and cementing 
together the fragments of a crush-breccia of marble. 


Native copper occurs exposed at many localities along the Blue 
Ridge region of this State, but no workable mines have been developed 
on such properties. Copper sulphides occur, usually with large 
quantities of pj^rite, in southwestern Virginia, in Carroll and Randolph 
counties; and also in connection with pyrite and native gold in the 
old gold mines of the State. Copper ores also occur in the now vigor- 
ous^ exploited Virgilina field in Halifax Countj^ though the greater 
part of this field lies across the line in North Carolina. 

The deposits of native copper and associated oxide and carbonate 
ores of the Blue Ridge region prove to be of limited extent, and to 
have been derived from the metamorphosed and schistose basaltic 
rocks of that region. They have been designated the Catoetin type. 
The native metal often occurs in masses of several ounces or even a 
pound in weight, and is associated with epidote, quartz, and calcite, 
filling small irregular crevices along shear zones in the metamorphosed 
igneous rock. Though often traceable for miles by outcrops and 
scattered ore masses, the deposits so far explored do not go down 
more than 20 to 30 feet from the surface. 

The sulphide ores of southwestern Virginia occur beneath iron 

"Weed, W. H.. Copper deposits of New Jersey: Ann. Rept. Stale Geologist of New Jersey for 
1!M>:J, Trenton, N. J., 1903. 


ore or croppings, constituting what has been called the great Gossan 
lode of Virginia, the deposits extending in the same general direction 
into North Carolina (Ashe County). These deposits have not yet 
been visited, but published descriptions indicate their close resem- 
blance to the well-known deposits at Ducktown, Tenn. 

The Virgilina deposits consist of native copper in quartz-filled fis- 
sure veins traversing andesitic porphyries altered to metamorphic 
schists. The ores consist principally of glance occurring in small 
bunches and thin lenses and rarely in large ore shoots. Some bornite 
also occurs, and this forms the chief ore mineral in the calcite gangue 
at the Blue Wing mine, North Carolina. These minerals in decom- 
posing have produced the usual green carbonate, silicate, etc., near 
the surface of the ground. The character of the quartz indicates that 
it is* the filling of an open fissure, but the veins show the lenticular 
thinning and thickening characteristic of veins in schistose rock. In 
some cases they cross the schistosity at a sharp angle and send short 
spurs off into the parting planes. Dikes of massive diabase occur 
that are later in age than the schists. These dikes narrow and impov- 
erish the veins, but do not interrupt them. The ores are extremely 
siliceous, owing to the quartz gangue, hence careful sorting and con- 
centrating is necessary before shipment. 


This State is rich in copper deposits, I hough lew have been com- 
mercially developed. The larger pail of the Virgilina field, whose 
veins have just been described, occurs in this State and includes the 
Holloway, Bluewing, Durgee, and Person mines, the first named 
being a successful producer for many years, the ores going to Norfolk, 
where they are smelted with ores brought from Capelton, Quebec. 

The most extensive development is, however, at Gold Hill, 12 miles 
from Salisbury, N. C. The chief output is from the mine of the 
Union Copper Company. The veins show ore shoots of dark gray 
and white quartz, carrying chalcopyrite and having a characteristic 
gneissoid structure. The veins generally consist of altered schists, 
and the inclosing rocks have been classed as Cambrian. These 
deposits are closely allied to the pyritic gold deposits of the Carolinas, 
which occur for many miles along the border of a large area of erup- 
tive granite. The Gold Hill district has been the largest gold- 
producing district of the South, the gold occuring in the gossan of 
the copper lodes. The veins are lenticular in character, and thicken 
and thin rapidly. Although a large amount of money has been spent 
on these properties in the last three years and the veins have been 
opened for several hundred feet in depth, no definite assurance of 
their probable future value can be gotten from the data at hand. 
An expensive 1 milling and reduction plant has been erected and is in 


operation, but the ore proves difficult to dress and very siliceous in 


The only copper deposits in Tennessee are the well-known Duck- 
town mines, situated in the extreme southeast corner of the State. 
These properties were famous for their rich secondary ores half a 
century ago, were worked at intervals for thirty years, and are now 
in successful operation. The deposits are very large lenticular bodies 
of pyrrhotite or pyrite in mica-schists, shown by Kemp to be meta- 
morphosed shales. No igneous rocks are known near by, and the rocks 
are probably Algonkian. The schists have been broken by disloca- 
tions, along which the ores have been deposited, the ore bodies usu- 
ally conforming very closely in course and dip to the inclosing schists. 
There are two main and parallel lines of fracture. The ore bodies 
are huge lenticular masses of sulphides, several of them 100 feet or 
more thick. The common ore is a mixture of pyrrhotite and chalco- 
pyrite, with calcite, quartz, zoisite, garnet, and in some cases much 
actinolite. In some ore bodies pyrite replaces the pyrrhotite wholly 
or in part. Much of the ore is shattered and sometimes brecciated, 
the chalcopyrite filling the cracks. A second period of shattering 
was followed by the formation of coarsely crystalline pyrrhotite, cop- 
per p3 r rite, and blende. These ore bodies are covered by a gossan 
of porous-textured iron ore, consisting of hematite and limonite, pro- 
duced by the oxidation of the sulphides, which is mined in large 
quantities for iron furnaces. Beneath this gossan occurred the rich 
"oxysulphuret " ore, a loosely textured mass of amorphous copper 
glance, to 10 feet thick, lying above the unaltered sulphide ore. 
This secondary ore is, however, now all extracted, and the copper 
contents of the ore bodies being worked averages about 3.5 per cent. 


Brooks, A. H. Reconnaissance from Pyramid Harbor to Eagle City, Alaska. 
In Twenty-first Ann. Rept. U. 8. Geol. Survey, Pt. II, pp. 331-391. 1902. 

Reconnaissance of a part of the Ketchikan mining district, Alaska. 

Professional Paper, U. S. Geol. Survey, No. 1, 116 pp. 1902. 

Douglas, J. The metallurgy of copper. In Mineral Resources U. S., 1882, 
pp. 257-280. 1883. 

The cupola smelting of copper in Arizona. In Mineral Resources U. S., 

1883-84, pp. 397-410. 1885. 

Gignoux, J. E. The manufacture of bluestone at the Lyon mill. Dayton, 
Nevada. In Mineral Resources U. S., 1882, pp. 297-305. 1883. 

Howe, H. M. Copper smelting. Bulletin U. S. Geol. Survey, No. 20-, 107 pp. 
1885. [Out of print.] 

Irving, R. D. The copper-hearing rocks of Lake Superior. Monograph V, 
U. S. Geol. Survey, 464 pp. 1883. 

Lindgren, W. The copper deposits of the ' : Seven Devils." Idaho. In Mining 
and Scientific Press, vol. 78, p. 125. 1899. 

Peters, E. D. The roasting of copper ores and furnace products. In Mineral 
Resources IT. S., 1882, pp. 280-297. 1883. 

The mines and reduction works of Butte City, Montana. In Mineral 
Resources IT. S., 1883-84, pp. 374 396. 1885. 

Rohn, O. Reconnaissance of the Chitina River and the Skolai Mountains, 
Alaska. In Twenty-first Ann. Rept. U. S. Geol. Survey. Pt. II, pp. 398-440. 

Schrader, F. C. Reconnaissance of a part of Prince William Sound and the 
Copper River district, Alaska, in 1898. In Twentieth Ann. Rept. IT. S. Geol. 
Survey, Pt. VII, pp. 341-423. 1900. 

Schrader, F. C, and Spencer, A. C. The geology and mineral resources of a 
portion of the Copper River district, Alaska, IT. S. Geol. Survey. 1900. 

Vaughan, T. W. The copper mines of Santa Clara Province. Cuba. In Eng. 
and Min. Jour., vol. 72, pp. 814-81(5. 1901. 

Weed, W. H. Types of copper deposits in the southern United States. In 
Trans. Am. Inst. Min. Eng., vol. 30, pp. 449-504. 1901. 

Weed, W. H.. and Pirsson, L. V. Geology of the Castle Mountain mining 
district, Montana. Bulletin IT. S. Geol. Survey, No. 139, 164 pp. 1896. 


Extensive investigations in the principal lead- and zinc-mining dis- 
tricts of the country have been carried on recently by the United 
States Geological Survey. The papers here presented include pre- 
liminary reports covering several of these districts. Other references 
to lead will be found in several papers in the section on gold and sil- 
ver, as all reports on districts in which silver-lead ores were prominent 
were included under the precious metals. 


By George I. Adams. 


During the summer of 1002 a party consisting of George I. Adams, of 
the United States Geological Survey, assisted by A. II. Purdue, of the 
University of Arkansas, and Ernest F. Burchard, was engaged in 
the studj 7 of the zinc and lead deposits of northern Arkansas. An 
extensive report on this field is now in preparation. The following 
statement of results and conclusions is made in advance of the final 
publication, which will be accompanied by detailed geologic maps 
and other illustrations. 


The lead and zinc deposits of northern Arkansas are in Marion 
County and adjacent portions of Boone, Baxter, Newton, and 
Searcy counties. Outside of this area there are a few scattered mines, 
notably in Sharp and Lawrence counties, The mining development 
is north of the Boston Mountains, in what is known as the Ozark 
Plateau. The country has a broken surface, as a result of dissection 
by streams, and there are numerous exposures of the mineral-bearing 
horizons in the valley slopes. This has greatly facilitated prospecting 
for the ores. 


Lead ore was discovered in northern Arkansas by the early explor- 
ers and pioneers, and at first was utilized for rifle bullets. Later it 
attracted considerable attention, and in the fifties was smelted in the 



vicinity of Lead Hill. There was a revival of the industry during 
the seventies, but the cost of transportation was so great that it was 
practically abandoned. 

Zinc ores at first attracted little attention, probably because they 
were not so well understood. Before the civil war, however, some 
zinc was smelted. In the eighties prospecting for it was carried on 
generally throughout the field, andTesulted in finding it at so many 
places and so readily accessible that about 1899 there was what might 
be called a rush into the field. 


From the information contained in published reports and gathered 
by inquiry, it lias been estimate^ that the output of the northern 
Arkansas district up to and including the year 1900 was 1,500 tons of 
zinc ore and 500 tons of lead. In 1901 about 500 tons of zinc were 
marketed, and in 1902 about 1,000 tons, or double the amount of the 
previous year. The production of lead during L901 and 1902 was 
unimportant. There is considerable ore now stored in the bins await- 
ing transportation facilities, and the production of the district promises 
•to increase during the coming year. 


The condition of the mining industry in northern Arkansas has 
been largely governed by transportation facilities. Until recently no 
railroad entered the held. In L903 the St. Louis and North Arkansas 
Railroad was built to Harrison, and since that time has been extended 
to Buffalo River. It is proposed to extend it southeastward, by way 
of Marshall, in the direction of Little Rock. The Missouri Pacific is 
now building a line in White River Valley from Batesville to Buffalo 
City, and it is proposed to extend this line northwestward, by way of 
Yellville, into Missouri. The completion of the railroads will afford 
facilities for shipping, and mines which have suspended operations 
will resume, and others which have attempted no development beyond 
prospecting are already erecting mills or determining more definitely 
the character of the ground preparatory to doing so. 


What has been done thus far in the way of mining is not a sat is- 
factory test of the field. Some companies which have been organized 
have been promoted by men inexperienced in the production of zinc 
and lead. The expenditure of money in erecting mills and bringing 
in machinery and the failure to market ore at a profit because of the 
long wagon hauls have usually resulted in the suspension of operations. 
The ore deposits of northern Arkansas are not such as mining men 
generally are familiar with, and some have been misled by the results 
of the prospecting. The mixed character of the ores found in surface 


workings has made it difficult to produce clean concentrates. With 
the continuance of deeper workings and the following of the ore bodies 
into the hillsides the sulphides are found to predominate, and this 
difficulty largely disappears. While it is impossible to predict with 
certainty the future of the field, there are mines now opened which 
are capable of large output, and many of the prospects are promising 
and well warrant fuller exploitation. With the completion of the 
railroads the northern Arkansas district promises to assume its true 
commercial importance. 


The ores are found in two formations, the lower being the Ordo- 
vieian dolomites, and the upper the Mississippian limestones. The 
Ordovician rocks occur extensively in Baxter County and in the 
northeastern part of Marion county, and in the other portions of 
the field, along the valleys of the streams, where erosion has cut down 
to them. The Mississippian limestones lie to the south and south- 
west, forming an irregularly fringed and dissected belt, lying some- 
what higher and extending to the base of the Boston escarpment. 
The Mississippian limestones formerly extended farther to the north 
and northeast and overlaid the Ordovician, but they have been 
removed by the wearing away of the land surface through the action 
of atmospheric agencies. In addition to these formations, which are 
the principal ore-bearing rocks, there are some thin formations found 
between the two in certain parts of the field, but for the immediate 
discussion of the problems connected with the ore deposits they need 
not be described. The Saccharoidal sandstone, however, which lies 
above the Ordovician dolomites, and accordingly separates the lower 
from the upper ore-bearing rocks, should be mentioned, since it is a 
convenient datum in this field. It is known locally as the "sand 
ledge," and is referred to in determining the horizons of the mines 
and prospects which occur below it in the Ordovician. To the south, 
lying upon the Mississippian limestones, and accordingly higher in the 
geologic column, are the shales and sandstones, which are extensively 
developed in the Boston Mountains. 


An examination of the mines of the district shows that the ore 
bodies are related to two classes of structure, viz, simple fractures 
and breccias. The rocks, considered broadly, are found to be nearly 
horizontal. Locally, however, they are undulating, and occasionally 
have well-marked dips. There are well-defined normal faults, which 
are later than the fracturing and brecciation above mentioned, but, 
except in certain instances where fault breccias have been developed, 
there is only a minor amount of mineralization along the fault planes 
or in the material filling the normal fault fissures. 


The fracturing of the Ordovician rocks was produced by compress- 
ive forces, and in certain zones has a considerable vertical extent. A 
second and equally important result was brecciation, which was pro- 
duced by the differential movement of the strata. The variation in 
the structure of the dolomite series, which is in places massively 
bedded and in other places thin bedded, laminated, and even shaly, 
resulted in the lateral movement being taken up in varying degree 
by the individual beds, so that the motion was such as is produced 
by forces acting in couples. The brecciation is due to the tendency 
of the pieces resulting from the breaking of certain brittle strata to 
shear past each other, or to rotate with the horizontal movements of 
the adjacent beds, so that the fragments are relatively displaced. 

In the Mississippian limestone the compression produced princi- 
pally fracturing and Assuring. The walls of the fissures not infre- 
quently exhibit slickensiding, which has been produced by the rocks 
moving past; each other horizontally. The Mississippian limestones 
do not exhibit brecciation, excepting in fracture zones or where they 
have been crushed by the dragging of the beds along normal faults, 
which in most cases are due to a later adjustment of the rocks of the 

The fracturing and brecciation above mentioned are probably due 
to stresses induced at the time of the folding in the Ouachita Moun- 
tain and Arkansas Valley regions. Al the close of the Carboniferous 
period the thick sediments which had accumulated in what is nowcen- 
tral Arkansas and western Indian Territory were folded in a manner 
which, suggests that they were thrust to the north. In the Ouachita 
Mountains there are close folding and thrust faulting; in the Arkan- 
sas Valley region open folds. Tn the southern border of the Ozark 
region, and particularly in the area here under discussion, the gen- 
erally horizontal position of the rocks was retained, but there was 
considerable movement of individual beds. This movement was one 
of accommodation, and resulted in fracturing without marked dis- 
placement. It took place largely along the bedding planes and 
resulted in brecciation of the beds. The normal faulting in this area 
is of later date, and is probably due to the readjustment following 
the crushing, or to subsequent oscillations of level. 

Geologic conditions influencing circulation of ground water. — The 
rocks which constitute the Ordovician system and the Mississippian 
limestones of the northern Arkansas district may be considered as 
relatively quite permeable. There are local beds of shale in the 
Ordovician through which water would not readily pass, and the 
Devonian, which has a very limited extent in the southern part of 
the field, is of about the same character and importance in controlling 
the path of the ground water. The shales do not have a wide influence, 
since they do not form persistent horizons. Where they occur they 
probably diverted the solutions laterally, but no localization of ore 
deposits seems to be directly due to them. 


The shales lying above the Mississippian limestones, on the contrary, 
have sufficient thickness to make them an important factor in deter- 
mining the movement of ground water. Formerly they extended from 
their present boundary, near the base of the Boston Mountains, north- 
ward into Missouri, and covered a considerable part of the Ozark 
Plateau. Before they were removed they acted as a confining or limit- 
ing horizon. Water entering the Ordovician dolomites and Mississip- 
pian limestones where they outcropped, and moving southward in the 
direction of the dip, was under a hydrostatic pressure beneath these 
shales. There may have been a first concentration of the ores, due to 
this circulation, and, if so, it could have taken place at some point 
between the upper portion of the Mississippian limestones which were 
below these shales and the bottom of the Ordovician. This reasoning- 
may be appealed to in accounting for the ore bodies now found in the 
Mississippian limestones near the base of the Boston Mountains, where 
these rocks have recently been uncovered by erosion. It is possible, 
however, that the concentration could have occurred through the 
agency of lateral circulation adjacent to the fractures in which the ore 
bodies are found, without appealing to causes which are of such wide 

As erosion progressed the shales and other formations tying above 
the Mississippian limestones were speedily removed from the more 
central portion of the Ozark region, so that the conditions which at 
first existed, as above outlined, were not long maintained. The main 
streams of the region, such as White River and its tributaries, soon 
cut through these formations, so that water which may have formerly 
been under hydrostatic pressure found issuance in their valleys. At 
the present time there are no upper confining shales in the northern 
part of the field, and this condition has prevailed for a long period. 
The surface water has been free to descend into the Mississippian 
limestones and Ordovician rocks, or through the Mississippian lime- 
stones into the Ordovician, and the point of issuance of such portions 
as have reappeared in the surface flow has been in the valleys of the 
larger streams. There, no doubt, has been lateral movement along 
bedding planes and through the more permeable strata and open and 
brecciated beds and along the surfaces of local shale beds. The Sac- 
charoidal sandstone, which is a conspicuous formation and one which 
is relatively porous, has probably been a horizon of lateral movement, 
assisting in the transfer of the ground water to places where it could 
find its way into the adjacent beds. 

Relations of belt of weathering and belt of cementation. — Under the 
action of atmospheric agencies the rocks at and near the surface suf- 
fer loss of their materials and waste away. . This process may be 
described as weathering. Deeper in the earth the materials derived 
from the upper rocks are largely redeposited. This process is one of 
cementation. The belt of weathering and the belt of cementation are 
not separated by a sharp line, and, moreover, with the processes of 


erosion the lower limit of the activity of the atmospheric agencies has 
constantly migrated downward. These belts are related to the topog- 
raphy of the country, the plane separating them being higher in the 
hills than in the valleys. Consequently, during the long period which 
has been required for the removal of tin' stratified rocks to their pres- 
ent limits, there has been a shifting downward and southward, as the 
streams have cut their valleys deeper and the escarpments have 
retreated southward. In the northern part of the field the belt of 
weathering which was formerly in the Mississippian limestones has, 
since the removal of these beds, reached the Ordovician rocks. To 
the south, as a result of the rugged topography, it lies partly in the 
Ordovician and partly in the Mississippian. At the base of the Boston 
Mountains, where the the shales a in 1 sand si ones have been but recently 
removed, it has descended but a short distance into the upper port ion 
of the Mississippian Limestones. The rocks in the northern portion of 
the zinc and lead district of northern Arkansas may accordingly be con- 
sidered as exhibiting the more advanced stages of the process of 
weathering and erosion. 


Source of the <>n.s. — It is generally accepted that- the zinc and Lead 
deposits of this region have been accumulated by the action of circu- 
lating waters which have dissolved the ores which were first broadly 
disseminated in the limestones of the region. Water has dissolved 
and carried them in solution to certain places where the conditions 
were favorable for their redeposil ion. Stating it differently, they 
have been derived from the belt of weathering and the belt of cemen- 
tation, and largely deposited in the belt of cementation. A study of 
the nature of the ores and their gangue materials and of the geologic 
history of the region makes it apparent that at least the latest concen- 
tration of the ores in the Ordovician has been largely the result of 
downward and lateral movements. The metallic sulphides may have 
been mainly derived from the Mississippian Limestones, which for- 
merly had a wider distribution, from the Ordovician, or from both 
formations. An examination of the Mississippian rocks shows that 
they have been leached by surface waters. Where they are exposed 
in railway cuts they exhibit decay to considerable depths, and within 
the area of their outcrop there are numerous sink holes in which the 
water disappears into underground channels. The surface cherts 
which have been derived from the weatliering of these rocks are fre- 
quently porous and spongy, thus indicating the loss of silica. In the 
Ordovician secondary silica is not infrequently a gangue of the ores. 
The Mississippian limestones contain notable deposits of zinc and 
lead at many localities in the Ozark region, and where there is ore in 
the Ordovician the Mississippian limestones have formerly overlain 
the area. The mines of southwestern Missouri around Joplin are in 


1 he Mississippian limestones, and in northern Arkansas, as has already 
been stated, prospecting has shown that in the portion of the district 
where they have been but recently exposed to the action of surface 
waters, probably as a result of a first concentration, they carry consid- 
erable lead and zinc. 

Classification of ore deposits. — The most important deposits of the 
district are the sulphide ores of lead and zinc, or, as they are com- 
monly called, galena and blende. In the Ordovician dolomites there 
are two principal classes of these deposits, which are characterized by 
the gangue material. One class is distinguished by the presence of 
secondary chert, which occurs as a siliceous replacement of the dolo- 
mites, or filling fractures in these rocks; in the other there is asso- 
ciated with the ore a large amount of dolomite spar, which forms a 
cementing material in the breccias. In certain of the mines there is, 
in addition to these main ore bodies, accessory ore which replaces the 
country rock to some extent adjacent to the main ore body without 
the development of secondary chert or spar. 

In the Mississippian limestones the primary ore deposits are accom- 
panied by secondary chert and calcite. They are related to fractures, 
and in some instances to fault planes. In the latter case they usually 
occupy breccias. Accessory ore replacing the country rock is some- 
times present with these deposits. 

The northern Arkansas field contains important deposits of oxi- 
dized ores. These are the carbonates and silicates. They are derived 
from the primary sulphides, and are due to the alteration of the sul- 
phides by the action of surface waters. In discussing the genesis of 
the ores the important problem is the origin of the sulphide deposits, 
the relation of the oxidized deposits to the sulphide deposits being 

Processes of primary deposition of sulphide ores. — The action of 
ground waters in the belt of weathering, and to a considerable extent 
in the belt of cementation, resulted in the solution and transportation 
of the ores. As the water percolated downward and moved laterally, 
and perhaps later upward, it reached a place where deposition took 
place. In the early part of the journey of the waters, through the 
action of the carbon dioxide and the humic acids, silica was taken 
into solution, and the waters accordingly contained it in notable 
quantities, along with the ores in solution. In the later part of the 
journey these waters caused the solution of lime and magnesium 
carbonate and the deposition of silica and sulphides, the resulting 
ores supposedly having been transported as sulphates. The reduction 
of the metals to sulphides was probably accomplished through the 
agency of organic matter and pyrite in the rocks, directly or indi- 
rectly, and deposition of the sulphides occurred along with the 
formation of the secondary chert and spar. 

The superposition of the original cherts in the Mississippian lime- 
Bull. 213—03 13 


stones and the occurrence of the secondary cherts and spar in the 
dolomites are entirely in accordance with this theory. 

Processes of deposition of oxidized ores. — The oxidized ores of 
northern Arkansas are the carbonates and silicates, which have been 
derived from the sulphide ore bodies. They are, accordingly, rela- 
tively later, and have been produced since erosion has brought the 
sulphides into the zone of weathering. The descending waters carry- 
ing carbon dioxide have transformed the blende and galena. In some 
cases redeposition has taken place immediately, and not infrequently 
oxidized ores are found as incrustations on the sulphides. In other 
cases they are found along water channels or in the open spaces and 
on the surfaces of the country rock. In the exposed faces of ore- 
bearing beds and in the upper portions of workings secondary ores 
often predominate. When mining operations are carried into the 
rocks that are under cover or have been protected from the action of 
ground waters, the carbonates and silicates decrease, and galena and 
blende are found to be the predominating ores. 

Secondary deposition of sulphides. — The sulphide ores which were 
dissolved by descending waters have not all been redeposited within 
the belt of weathering. Such portions as were retained in solution 
upon reaching the belt of cementation were redeposited as sulphides, 
the processes in this case being the same as in the primary deposition 
and the ore bodies belonging to a second generation. In the lower 
horizons of the Ordovician dolomites considerable zinc ore is found 
which occurs as bright, clean crystals associated with drusy quartz 
or in openings formed by fracture. Such deposits are usually lean, 
and thus far no workable body of ore of this nature has been 

Observations have not shown that there is a criterion for clearly 
distinguishing the secondary sulphide ores, which may have origi- 
nated by migration from the primary deposits, since it is not improb- 
able that the solutions at the time of the first concentration may have 
deposited most of their ore in the upper horizons, in which case the 
deeper deposits would have the characteristics above described and 
assigned to the ores of the second generation. 

Sulphide deposits associated with secondary chert. — Where chert is 
the principal gangue of the blende and galena, deposition in the 
Ordovician has taken place by the replacement of the dolomites and 
the filling of fracture spaces and cementation of breccias. Secondary 
chert when freshly exposed usually has a bluish color. It may be 
distinguished from the other country rocks by means of its hardness, 
since it can not be scratched with a knife. It frequently has a banded 
or bedded appearance, which corresponds to the bedding of the orig- 
inal dolomite, and crystals of ore usually well formed and distinct 
occur within the mass. In case some of the sulphides have been 
leached out, molds of the blende are seen, which give the chert a 


honeycombed appearance. The richer deposits appear to be related 
to fracture zones, and occur along the fissures and replacing the 
adjacent rocks. The path of the ore-bearing solutions in descending 
has apparently been along fractures and laterally along the bedding 
planes, and the mineralization decreases away from the fracture zone. 

Sulphide deposits in bedded breccias. — In the brecciated beds of the 
Ordovician dolomites the open spaces between the fragments have 
afforded channels for the ore-bearing solutions, and the precipitation 
of the sulphides and dolomite or pink spar has usually taken place 
without the dissolving of the country rock to any appreciable extent. 
The pink spar is not always accompanied by ore. The sulphides have 
been deposited in a somewhat local way, many factors being con- 
cerned. Not infrequently, in prospecting, breccias containing pink 
spar and but little ore are found; and, where the breccias are ore bear- 
ing, when they are followed for a considerable distance they usually 
show a decrease in the amount of ore. 

Sulphide deposits in fissures. — In the Mississippian limestones most 
of the mines and prospects are related to fissures, the ore occurring 
in material filling the fissures or in the fissure and the openings adja- 
cent to it. These deposits differ from those in the fractured dolomites 
in being more clearly defined. The gangue is usually secondary chert 
and calcite. The walls of the fissures exhibit slickensiding, as a 
result of the movement of beds, and frequently indicate displacement 
in a horizontal direction. 

Sulphide deposits in fault breccias. — Where the Mississippian lime- 
stones have been displaced by normal faulting and the rocks have 
been dragged, they not infrequently exhibit brecciation. The angular 
fragments are largely primary chert, and the ore occurs associated 
with a calcareous and siliceous matrix which cements the breccia. 

Sulphide ore in country rock. — In many of the mines and prospects 
the country rock has not been mineralized. In other cases, for a 
short distance adjacent to fissures, fractures, and water channels, the 
ore-bearing solutions have formed what is here called accessory ore. 
The action in this case has been one of replacement. The country 
rock exhibits recrystallization and carries small crystals of ore. 
Where accessory ore is found the main ore body is usually rich, and 
there is a suggestion that deposition in the country rock resulted 
because of the large amount of ore in solution at these places. In the 
northern Arkansas district the scattered crystals of blende in the 
country rock are spoken of as disseminated ore. This term, unfortu- 
nately, is not quite appropriate, and, accordingly, the word accessory 
is suggested, since it does not imply the mode of deposition usually 
ascribed to disseminated ores. Accessory ore, inasmuch as it is usu- 
ally found associated with rich ore bodies, is looked upon by the pros- 
pectors as a favorable indication. The ore in secondary chert is not 
included under this head. 


Ore associated with quartz druses.— Not infrequently, in the Ordo- 
vician dolomites, the lower ore horizons exhibit quartz druses and 
surfaces covered with minute quartz crystals. The ore in these rocks 
occurs as clean, bright crystals deposited on the quartz. It seldom is 
found in large masses, but is generally distributed through the rocks. 
The probability is that it represents a migration from the higher 
horizons, but it is possible that it was deposited from the depleted 
solutions at the time of primary deposition. 

Opinions of previous writers. — In the previous reports on the 
northern Arkansas field certain ideas have been advanced which are 
not accepted by the writer. These largely pertain to theoretical con- 
siderations, although some of them deal with the geologic facts. 
There is no opportunity in this article for a discussion of the differ- 
ences of opinion which have arisen, but it is thought best to mention 
certain points which are obvious from a review of the literature. 

The writer has argued that the bedded breccias were produced by 
the movement of strata past one another, as a result of compressive 
forces. Mi'. Branner, in speaking of the breccias, states that the 
bedded breccias were not formed on fractures, but along ancient 
underground water courses. The breccia deposits which Mr. Bain 
described were considered by him to have been formed along zones of 
pressure. He speaks of limestone conglomerates, which, in the opinion 
of the present writer, are in reality breccias. The relation of these 
so-called conglomerates to the brecciated beds, and the extensive 
brecciation due to differential horizontal movement, do not seem to 
have been recognized by Mr. Bain. 

In regard to the faulting of the region, the writer presents an inter- 
pretation which is decidedly opposed to that of Mr. Branner. lie con- 
siders certain of the most important faults, some of which were 
described and figured by Mr. Branner as thrust faults, to be normal 

In regard to the theory of ore deposition, all the differences can not 
be here pointed out. However, Mr. Branner described bedded 
deposits contemporaneous with the rocks in which they occur. Such 
ore bodies are believed by the writer to be the result of secondary 
alteration and replacement. Mr. ]>ain has given considerable promi- 
nence to what he calls disseminated ores in compact limestone and 
unbroken conglomerate. This description does not seem to be a cor- 
rect characterization of any of the main ore bodies of the district, 

a Branner, J. C, Zinc and lead deposits of northern Arkansas: Ann. Rept. Arkansas Geol. Sur- 
vey for 1892 (published in 1900), Vol. V; also Trans. Am. Inst. Min. Engrs., Vol. XXXI, p. 572. 
Bain, H. F., Preliminary report on the lead and zinc deposits of the Ozark region: Twenty-second 
Ann. Rept. U. S. Geol. Survey, Pt. II, 1902, pp. 195-202. Van Hise, C. R., and Bain, H. F., Lead and 
zinc deposits of the Mississippi Valley, read before the Institution of Mining Engineers at the 
general meeting at London, May 29, 1902: Excerpt from Trans. Inst. Min. Engrs., pp. 34, 35. 



By W. S. Tangier Smith. 


The lead and zinc deposits of the Mississippi Valley have been 
divided into three groups, those of (1) the Ozark region, (2) the Upper 
Mississippi Valley, (3) outlying districts. Of these the most impor- 
tant is the Ozark region, which extends from the Arkansas River on 
the south to the Missouri River on the north and from eastern Kansas 
on the west to the Mississippi River on the east. It contains four 
districts, (1) the Southeastern Missouri district, (2) the Central .Mis- 
souri district, (3) the Missouri-Kansas or Southwestern Missouri dis- 
trict, (4) the Northern Arkansas district. 


The Joplin subdistrict, as considered in this paper, includes that part 
of the Missouri-Kansas district lying along its western margin and 
between 04° 15' and 94° 45' west longitude and 37° and 37° 15' north 
latitude. While thus embracing an area of only 47G square miles, it 
produces more zinc than all the other districts of the Mississippi Val- 
ley combined, and is in fact the most important zinc-producing dis- 
trict of the United States. Tu addition to the zinc, it produces a smaller 
though still considerable amount of lead. In the year 1002 the lead 
production of the district was about 12 per cent of its zinc production, 
the latter being 223,337 tons. 

About three-fourths of the Joplin district is in Missouri, and includes 
among its larger towns Joplin, Webb City, Carterville, and Carthage. 
The remaining one-fourth (except for a fraction of a square mile fall- 
ing in Indian Territory) is in Kansas, and its largest towns are Galena, 
Empire, and Baxter Springs. 

The Joplin district lies on the western margin of the Ozark uplift, 
and its upland surface is almost flat, with a low general slope to the 
northwest. These level uplands are cut by numerous stream valleys, 
for the most part open and rather shallow. The courses of many of 

"A more extended article, of which this i>aper is an abstract, is in course of preparation for 
Survey publication. 




the smaller streams are determined bylines of shale deposits, alon 

zones of faulting and consequently lines of weakness. As the shales 

are the softest rocks of the region, there is thus a double reason for 

the correspondence of the valleys with these lines, and probably the 

same facts explain the general limitation of mining to the valleys and 

their slopes. 


Stratigraphy. — The geology of the district is simple. The rocks 
are wholly sedimentary, and those exposed on the surface are all of 
Carboniferous age, both Upper and Lower Carboniferous being repre- 
sented. The Lower Carboniferous rocks consist of about 350 feet of 
cherts and limestones in varying proportions. This is the ore-bearing 
formation of the district, the ore occurring especially in the more 
cherty portions. The limestone is generally nonmagnesian, but a 
comparatively small amount of dolomite occurs, mainly as the result 
of alteration of the limestone at the time of the deposition of the ores. 
The limestone generally contains a considerable amount of organic 
matter, evidenced by I lie vaseline-like odor which is characteristic of 
the rock when broken; and occurrences of bitumen are common, 
especially in association with the mineral deposits. Not far from the 
top of the series is a thin but persistent bed of oolite, outcrops of 
which occur over the entire district. Some distance below is a heavj^ 
bed of chert, about 50 feet thick, known as the Grand Falls chert. 

The Lower Carboniferous rocks are exposed over the greater part 
of the Joplin district. Above them, when not eroded, lie the Upper 
Carboniferous Coal Measure shales and sandstones. The shales, 
which constitute the greater part of the Coal Measure expos ures of 
the quadrangle, are frequently associated with thin beds of coal. 
The sandstone occurring with these shales is sometimes changed to 
a quartzite through the infiltration of secondary silica. There is a 
considerable area of these shales and sandstones in the northwest 
corner of the quadrangle, in addition to small patches of shale over the 
entire district. These smaller occurrences in some cases represent 
outlying hills left on the removal of the Coal Measure rocks; in other 
cases their persistence is due to their occurrence in pre-Coal Measure 
erosion basins, or in later basins formed by the folding of the rocks, 
while in still others they are the result of faulting. 

Beneath the Lower Carboniferous limestones and cherts is the 
Devono-Carboniferous shale. The occurrence of. this formation in 
the Joplin district has not been proved, though it is believed to be 
present as a thin bed of shaly limestone having an average thickness 
of only a few feet. The Cambro-Silurian rocks beneath the Devono- 
Carboniferous shale consist of a series of magnesian limestones, 
dolomites, and sandstones. As none of the rocks below the Lower 
Carboniferous are exposed in this district, their occurrence can be 
determined only from deep borings. 


Structure. — The rocks of the district have a low general dip to the 
northwest at an angle somewhat greater than the general inclination 
of the surface. Open folding' is common, both on a large and small 
scale. Noticeable faulting is not common over the quadrangle as 'a 
whole, though small slips occur here and there. In those parts of the 
district, however, where ore deposits occur, faulting and folding are 
both of more importance, but even here the amount of faulting, as 
a role, is not great. Both normal and reversed faults are found, 
both being the result of readjustment due to compression stresses. 
Where cherts predominate, brecciation has developed as a result of 
the faulting and folding. The individual faults are not known to 
continue for any considerable distance, but they occur (as do the 
folds also) mainty in zones. The ore deposits follow these zones of 
faulting and folding, and frequently come in and die out with the 
faults with which they are associated. The occur rence of cross folding 
and faulting, at an angle with the main lines, tends to make the zones 
of brecciated rocks more complex. As a result the deposits are, on 
the whole, extremely irregular. In at least one part of the district 
there is well-defined evidence of two periods of movement accom- 
panied by fracturing and faulting -of the rocks, both periods having 
been followed by ore deposition. 

In connection witli the phenomena of folding and faulting, shear 
zones and joints of compression and tension have been extensively 
developed, mainly in the cherts. Adjustments of small amount, also, 
have taken place along the bedding planes. The effects of these dif- 
ferent movements vary with the rocks. The shales have yielded to 
stresses by folding or by faulting; the limestones by folding and fault- 
ing with occasional complex fracturing. Stresses in the cherts, which 
are generally extremely brittle, are nearly always relieved by fractur- 
ing, more or less complex, and by brecciation, though occasionally by 
flexure. Many of the cherts are so brittle that only a slight amount 
of movement is necessary to cause complete brecciation, simple fold- 
ing being frequently sufficient. The brecciated cherts are often more 
or less firmly recemented, sometimes by a black secondary chert fre- 
quently containing disseminated sphalerite; sometimes by free sphal- 
erite or calcite, or by both. In many cases the cherts are thoroughly 
crushed, while still showing their original bedding planes. Examples 
have been noted of heavy-bedded cherts which have been cut by joint 
planes in several directions, the loosening of the mass by slight fault- 
ing or other cause giving rise to "bowldery ground" such as is char- 
acteristic of many of the mines. It is probable also that, during fold- 
ing, arching of the cherts occurred in some places, and that later, in 
many instances after the spaces had been filled with the material 
which now appears as the black secondary chert, the arches were 
broken down. It is mainly in the brecciated cherts that the ore 
bodies occur. 



Minerals. — The principal minerals of the Joplin district are sphal- 
erite (locally called "jack"), galena ("lead"), calcite ("tiff"), dolomite 
("spar"), marcasite and pyrite, mainly the former (both called "mnn- 
dic"), chalcopyrite ("copper"), cerussite and anglesite (both known 
as "drjr-bone"), calamine ("silicate"), and smithsonite. Calamine 
and smithsonite have generally been confused in this district, and 
most of the smithsonite, which in reality occurs more frequently than 
has been heretofore supposed, has been mined as "silicate." 

Distribution of ores and minerals. — Of the lead and zinc ores the 
sulphides, sphalerite and galena, occur for the most part below the 
level of underground water; the sulphate and carbonate of lead and 
the carbonate and silicate of zinc, being all oxidation products of the 
sulphide ores, occur mainly above that level, together with the more 
or less oxidized gangue and country rock. The deposits below ground- 
water level represent the concentrated ores, both those of first con- 
centration and those of secondary enrichment. They are frequently 
associated with more or less marcasite or pyrite, though these are as a 
rule inconsiderable in amount. In these deposits the galena is usually 
found at the upper levels (except in sheet ground, described here- 
after) tilling fractures in broken or brecciated cherts, and usually 
associated with more or less sphalerite. Only sphalerite (frequently 
with some iron sulphide) is found at the lower levels. It occurs (1) 
as a cement in chert breccia; and (2) disseminated in a black, second- 
ary chert which cements the brecciated cherts and also occurs in 
lenticular bodies along the bedding planes in sheet ground. Sphaler- 
ite is also found in small quantities disseminated in shale, in selvage, 
in mud, in limestone, or in dolomite. 

To sum up, the vertical distribution of the ores shows: 

First. Above underground water level, galena and occasionally 
some sphalerite; also the oxidation products, the carbonate and sul- 
phate of le ; ad and the carbonate and silicate of zinc. 

Second. Below underground water level, the sulphide zone. Some- 
times, but not always, galena dominates in the upper part of this 
zone, with sphalerite dominant in the lower and greater part of the 
zone. This succession does not always hold, and some mines have 
yielded mainly galena throughout, while mines yielding sphalerite 
with little or no galena are common. In the typical sheet ground 
galena and sphalerite usually occur together and associated with 

Forms of ore deposits. — In considering the forms assumed by the ore 
deposits, the ore bodies in the mines of this district may be roughly 
divided into two classes, (1) horizontal or nearly horizontal deposits; 
and (2) vertical or inclined deposits. The first class includes the 
tabular bodies of ore known as blanket veins or sheet ground. Depos- 
its belonging to this class are mainly limited in occurrence to a belt 


extending from the town of Duenweg northwesterly between Webb 
City and Carterville to Oronogo. They reach their greatest develop- 
ment south and southeast of Carterville. The rocks in which the ore 
occurs are bedded cherts, horizontal or nearly so. The ore is found 
mainly along the bedding planes, though it also occurs in seams in 
the somewhat broken beds. Much of that occurring along the bedding 
planes is disseminated in a dark secondary chert which appears to 
fill cavities left by the removal through solution of limestone lenses. 
The ore is mainly sphalerite, with a minor proportion of galena, and 
a still smaller amount of marcasite. Deposits of this form are always 
near ore bodies belonging to the second class. 

The latter may be divided into (1) linear deposits (runs), (2) circu- 
lar or elliptical deposits, and (3) irregular deposits. The linear depos- 
its consist of comparatively narrow bodies of ore, either vertical or 
inclined, following a roughty uniform direction. The ore is as a rule 
mainly or wholly sphalerite; where it is associated with galena the 
latter occurs usually in the upper part of the deposit. The sphalerite 
is found both disseminated., for the most part in a dark secondary 
chert matrix or in selvage, and cementing chert breccia or lining 
interstices of the breccia or solution cavities in limestone or dolomite. 
It is often associated with calcite and pink dolomite. The rocks in 
which the ore occurs are generally brecciated cherts which have been 
recemented to a greater or less extent, either with black secondary 
chert or with calcite, sphalerite, dolomite, or galena, either separately 
or in combinations of two or more. In the vicinity of Joplin this brec- 
cia with its ore occurs almost without exception against a barren wall 
of chert and limestone, the latter altered to a coarse-grained gray 
dolomite, apparently closely connected with the deposition of the 
sphalerite. In these same deposits galena, where it occurs, is usually 
found tilling cracks in the fractured cherts, near the upper limits of 
the sphalerite and for the most part near its outer margin, i. e., away 
from the dolomite. 

The chert breccias in which the linear deposits occur are due largely, 
to faulting, though to a minor extent developed by folding. Breccias 
produced by folding may be associated with those resulting from 
faulting. The ores in the former occur, as a rule, along the flanks of 
the folds. Where two faults meeting at an angle have developed at 
the same time, the brecciation, with its accompanying deposit, formed 
along one fault, instead of crossing the other fault at the point of 
meeting, may take the direction of the intersecting fault, thus forming 
one continuous deposit; and the two faults, instead of meeting at an 
angle, may be joined by a curve. Such deposits are closely related 
in manner of formation to the deposits of the following type. 

Circular or elliptical deposits are a modification of the Linear deposit. 
A horizontal section of these ore bodies would have the form of a 
roughly circular or elliptical ring, inclosing a central barren "core." 


The deposit as a whole has roughly the form of either a truncated 
cone or a dome, both types being commonly associated with an irreg- 
ularly circular or elliptical area of shale at the surface, over this 
central portion. The ores of the circles arc 4 similar in character to 
those described under linear deposits. In all the important cases 
studied, the circle has been formed by the intersection of faults. 
Small circular deposits are sometimes developed on the flanks of a 
dome produced by folding. In all the circular deposits near the city 
of Joplin which were examined, the inner walls were of the dolomitized 
limestone with chert. 

The vertical extent of the ore body, in both linear and circular 
deposits, may be limited to a few feet or it may continue for a hundred 
feet or more. The occurrence of the ore is not confined to a particular 
horizon, but it may be met at any level where the conditions were 
favorable for Ms deposition, and it maybe found at several levels, 
one above another, with barren or nearly barren ground between. 

Under the head of irregular deposits may be included all such ore 
bodies as do not correspond to any of the foregoing types. They are 
formed in breccias due either to complex folding or faulting, or to 
folding combined with faulting, and have no definite form. They 
may in most cases be considered as combinations of types already 

Individual runs of ore, associated with one or more faults or folds, 
may have a horizontal extent ranging from a few feet to one-fourth 
mile or more. Although there are areas in which no systematic 
arrangement of the individual ore bodies can be discerned, in most 
cases they can be grouped along a zone of faulting or folding, within 
which they mayor ma\ not show a general Linear or parallel arrange- 
ment; or the main lines parallel to the general direction of the zone 
m;i\ be associated with minor lines a1 an angle with it. Such zones 
usually have the same general trend as the main system of faulting 
for the part of the district in which they occur. There are several 
important systems of faults and folds in the Joplin district which 
vary somewhat in direction from place to place, and of which the 
most prominent throughout the district has a general northerly or 
northwesterly trend. A second important system having a general 
easterly or northeasterly direction sometimes predominates, though it 
is usually associated with the other and subordinate to it. 

The principal structural disturbances of the Joplin district appear 
to have been concentrated along certain lines or belts having the 
same general trend as the more pronounced zones of ore deposits, 
which group themselves roughly along these belts. The three main 
belts of the district are (1) the Jojuin belt, including the zones imme- 
diately around Joplin and northward to Tuckahoe, with the outlying 
groups southward to Shoal Creek and northwesterly to Carl Junction; 
(2) the Galena belt, including the deposits around Galena and just 


north and south of it; (3) the Webb City belt, including the mining 
zones from south of Duenweg northwesterly between Webb City and 
Carterville to Oronogo and beyond. Of these the Joplin belt is char- 
acterized b}^ the common association of the sphalerite with dolomitized 
limestone (as already noted), while in the Galena and Webb City belts 
dolomite is of comparatively rare occurrence. The latter belt is char- 
acterized by extensive sheet deposits which are either entirely absent 
or unimportant in the other belts. Around Joplin itself the breccias 
on the east side of the town are cemented mainly with calcite, and 
black secondary chert is not common, while on the west side of the 
city black chert is common, and in places forms the far larger propor- 
tion of the cement of the brecciated cherts. 

Deposition of ores. — In this district as elsewhere, the conditions 
governing ore deposition are partly physical and partly chemical. 
The physical conditions are those governing the circulation of under- 
ground waters in general; the chemical conditions are more complex, 
and as yet are only partly understood. Lead and zinc sulphides are 
known to be widely distributed in minute quantities in both the Car- 
boniferous and Cambro-Silurian rocks. The underground circula- 
tion probably takes lead and zinc sulphide from all the rocks where 
conditions are favorable to oxidation and solution, tending to concen- 
trate the ores as sulphides wherever favorable conditions for this 
process are met. The lead- and zinc-bearing waters come from both 
the Carboniferous and Cambro-Silurian rocks, and entering at the 
surface east of the Joplin district, they have flowed and still flow 
down the dip of the rocks. Reaching the Joplin district they meet 
conditions favorable to primary concentration, and the ores are 
deposited. It is believed that such deposition is still taking place, as 
it has done in the past. 

As the waters which give rise to the primary concentration flow 
down the dip of the rocks their motion is partly descending until the 
Joplin district is reached. There the waters coming from the Car- 
boniferous rocks have, on the whole, a lateral motion, while those 
bringing lead and zinc from the Cambro-Silurian into the Carbonifer- 
ous rocks are, on the whole, ascending. The direction of flow of the 
underground waters is not in general a fixed factor in ore deposition, 
but solution and redeposition of ores may take place in waters having 
either an ascending, descending, or lateral motion, provided other 
conditions are favorable to oxidation and solution at one point and to 
reduction and precipitation at another. 

Although this i>rocess of primary concentration is still effective, it 
was far more important when the entire district was covered with the 
comparatively impervious Coal Measure shales, and the conditions were 
more favorable than now to an artesian circulation. When erosion had 
largely removed this covering from the district, and had brought many 
of the ore deposits near or quite to the surface, within the reach of the 


doAvmward-inoving waters containing oxygen, the ores became oxidized 
to sulphates. The sulphate of lead (anglesite) underwent further 
alteration to the carbonate (cerussite). The sulphate of zinc, react- 
ing with the limestone or with the secondary chert which contained 
the ores, replaced the former with smithsonite and the latter, in part 
at least, with calamine, which also filled small cavities in the rocks. 
As the galena is less easily oxidized than the sphalerite, and its oxida- 
tion products are less soluble, the oxidized lead products are gener- 
ally found nearer the surface than those of zinc. The oxidized zinc 
ores extend generally from the surface, or close to it, downward to a 
short distance below ground-water level. In all observed cases the 
oxidized products have been deposited close to the place of original 
sulphide concentration, and are associated with secondary chert 
leached of its formerly contained sphalerite — the honeycomb rock of 
the miners. 

During the process of oxidation, carbonation, or silicification of the 
ores some of the products of oxidation of the sulphides were carried 
in solution below the level of underground water, where the} 7 were 
redeposited as sulphides. Gradually, also, the oxidation products 
deposited above ground-water level were taken into solution by sur- 
face waters and carried downward and redeposited in the same way. 
These sulphides, together with those of primary concentration, form 
an enriched /one, which is greatest not far below the level of under- 
ground water, and decreases downward. In the Joplin district the 
enrichment of the sulphide ores has resulted not in a better grade of 
the ore already existing, bu1 in an increase in the quantity of the ore 
of 1 he enriched /one. The lead sulphide is deposited at the highest 
levels, together with more or less sphalerite, and decreases in amount 
downward, while the sphalerite increases, so that in depth the latter 
dominates. Pyrite and marcasite are relatively unimportant in the 
Joplin district, and il can not be stated definitely that, they are more 
abundant, on the whole, at one level than at another. 

Where ores of secondary enrichment have been brought near the 
surface by the wearing down of the land through erosion, they would 
be acted on in the same way as ores of primary concentration, and 
would be again concentrated below ground-water level. As the 
Joplin district, however, has been so little eroded since the removal 
of the Coal Measure shales, it is believed that this concentration of 
enriched ores is of little importance. 


By E. O. Ulrich and W. S. Tangier Smith. 


By E. O. Ulkich. 


During the summer and fall of 11)02 a party consisting of the writer 
and Dr. W. S. Tangier Smith, with two field assistants, Messrs. A. F. 
Crider and F. Julius Fohs, was engaged in an extended investigation 
of the zinc, lead, and other valuable mineral deposits of western 
Kentucky and, in less detail, of those occurring on the northern side 
of the Ohio River in Pope and Hardin counties, 111. The latter 
counties, together with the counties of Crittenden, Livingston, Cald- 
well, and adjacent portions of Christian, Trigg, and Lyon, in Ken- 
tucky, are embraced in a lead and zinc district differing in several 
respects from the other lead and zinc districts of the Mississippi 
Valley. This district differs from the others in the presence of basic 
igneous dikes, in the ores -occurring principally along fault lines in 
true fissure veins, and, finalty, in having the lead and zinc ores almost 
invariably associated with fluorite, the latter as a rule forming the 
most abundant gangue mineral. 

The recent work in western Kentucky consisted largely in the 
verification and correction of the mostly unpublished results of a 
study of the geology of the three counties of Caldwell, Crittenden, 
and Livingston carried on by the writer in 1889 and 1890, while a 
member of the geological survey of Kentucky. The developments of 
the past decade permitted us to add many new observations and to 
advance the geologic knowledge of the district to a point where it is 
possible to describe the ore deposits and the systems of fractures and 
faults in and along which they occur as well as the geologic forma- 
tions and their geographic distribution in considerable detail. The 
following brief statement, however, is to be viewed merely as an 
advance publication of results and conclusions that will be more fully 
described, and will be illustrated, in a report now in preparation. 




History. — The ore deposits of this district have been known to 
settlers since early in the last century. The first attempt to mine 
them was made by a company headed by President Andrew Jackson. 
The operations of this company were carried on in Crittenden County, 
Ky., their shaft being sunk on the Eureka vein within 100 yards of 
the present main shaft of the Columbia mine. Between that time and 
the beginning of the civil war other equally primitive attempts were 
made to mine the ore deposits, most of them in Livingston County, 
notably at the Royal mines near Smithland. 

With the general resumption of mining activities in the seventies, 
and especially in the later years of that decade, when some excite- 
ment was evoked by the successful operations at Rosiclaire, on the 
Illinois side of the Ohio River, work was resumed at several of the 
mines in western Kentucky. Considerable activity, indeed, was 
shown in the development of the Columbia mines, in Crittenden 
County. In 1878, however, nearly all mining operations in the dis- 
trict ceased, because the market value of lead, which up to that time 
was the only mineral sought here, dropped to so low a figure that 
with the lack of transportation facilities mining operations became 

The demand for American fluorspar which set in at about this time 
served to maintain a small degree of interest in mining in the south- 
ern portion of the district, but only for a few years, when the same 
lack of cheap transportation and a slight drop in the value of the 
product rendered the otherwise equally good Kentucky mines incap- 
able of compet ing with the more fori unately situated Rosiclaire mines. 

In the last live or six years interest in the district has again revived, 
and, for the first time in its history, the numerous veins and mines 
are being systematically prospected and developed. 

Production. — It is impossible now to make any satisfactory state- 
ment concerning the output of the mines of the district prior to 1899, 
but it doubtless amounted to a thousand or more tons of lead and 
many times that amount of fluorspar. Estimates of the production 
of the Illinois mines were not secured, but those in Kentucky pro- 
duced, according to statements of shippers, about as follows: Fluor- 
spar, 1899, about 5,000 tons; 1900, 10,500 tons; 1901, 1:3,700 tons, and 
the first seven months of 1902, 12,000 tons. Zinc carbonate, 1901, 
1,136 tons; first seven months of 1902, about 2,450 tons. The produc- 
tion of lead was insignificant, chiefly because the mines in which 
galena is an important or predominating ore have only recently 
resumed operations or are awaiting improved transportation. The 
present year, however, promises to see a notable increase in the pro- 
duction not only of lead but also of zinc, and a smaller increase. in the 
output of fluorspar. 

Prospective development.— The mining operations so far carried on 
in the district can not be considered as a satisfactory test of its possi- 


Abilities. It seems probable, however, that a field containing mines 
that at various times were operated with profit for the lead ore alone, 
the zinc ores and fluorspar being left on the dump, should under 
economic and competent modern management become a producer of 
some importance. Two obstacles stand in the way at present. The 
first is a lack of a cheap and thorough method of separating the fine- 
grained sphalerite from the fluorspar with which it is almost invaria- 
bly associated. Now that the need of such a process is emphasized, 
it is possible that a satisfactory method will be discovered before the 
second impediment — lack of transportation — can be overcome. Many 
men are working on the problem and already several promising if not 
wholly satisfactory processes have been patented. A plant to do this 
work has just been completed in Paducah and another is being erected 
in St. Louis, while a third process is being perfected at a plant near 
Salem, Ky. 

The second difficulty in the way of the development of the district 
is one common to all new fields, namely, a lack of transportation 
facilities. The roads throughout the district are almost without 
exception very bad, rendering successful mining where the wagon 
haul exceeds 5 miles impossible. Fully two-thirds of the entire dis- 
trict lies more than that distance from the lines of the Illinois Central 
Railroad which traverse it. However, two navigable rivers, the Ohio 
and the Cumberland, are being used in a small way, and this cheap 
mode of shipment will doubtless exert a considerable influence on the 
development of the field. 


Stratigraphy. — The geologic formations exposed at the surface or 
penetrated in mining in the area under consideration are all of Car- 
boniferous age, the lowest being the St. Louis limestone of the Missis- 
sippian series, while the highest contains the two lower coal beds of the 
Coal Measures and is confined to the eastern and northern edge of the 
district. These lower Coal Measures constitute the western border of 
the western Kentucky coal basin, which extends into the district from 
the east and north. As is proved by outliers, remaining chiefly 
because they crown blocks thrown down in the faulting of the region, 
this border once extended much beyond its present limits, the basal 
Coal Measures perhaps having originally covered the whole of the 
area. The base of the Coal Measures or Pennsylvanian series is here 
always formed by a coarse brown sandstone containing more or less 
abundant quartz pebbles. Immediately beneath this come the sand- 
stones, shales, and limestones of the Chester group, the rapidly alter- 
nating beds of which have a total thickness of about GOO feet. Next 
beneath and intervening between the base of the Chester and the top 
of the St. Louis limestone is the Princeton limestone, 200 to 250 feet 
thick, which is light-gray and compact and includes more or less shale 
in its upper third, and more massive, oolitic, and light-gray or nearly 
white in its lower two-thirds. Between these two divisions of the 


Princeton there is a very persistent layer of calcareous sandstone, 
varying- from 1 to 12 feet in thickness. 

The St. Louis limestone underlying the Princeton limestone has a 
thickness of about 500 feet. Its basal portion is also oolitic, but of a 
darker color than the Princeton oolites. The remainder consists of 
dark-gray, highly siliceous limestone, the silica of which, on the 
weathering and decomposition of the limestone, to which it is more 
readily subject than the other limestones, is concentrated into nodular 
masses of flinty chert varying from 2 to 8 inches in thickness. These 
rounded lumps often occur in great abundance and are highly charac- 
teristic of the formation. Decomposition of t^he St. Louis limestone 
is always deep, sometimes extending to a depth of 50 feet beneath the 
surface, so that the limestone itself is rarely seen except along rapidly 
eroding si reams. ( )wing to complex faulting the area! distribution of 
these formations is very irregular and patchy. 

Beneath the St. Louis limestone there is an even more' siliceous and 
earthy limestone, representing the Tullahoma formation and Port 
Payne chert of the south, the Keokuk and Burlington limestones of 
western Illinois, and the Boone chert of Missouri and Arkansas. This 
horizon holds mosl of the zinc and lead deposits of the Joplin district 
and some of the deposits found in northern Arkansas. Whether it is 
ore bearing in this district or not can only be determined by sinking 
on the veins to its horizon. 

Structure. — The most marked structural feature of the district is an 
extensive series of fractures, nearly all of which are accompanied by 
more or less faulting. All available evidence tends to the conclusion 
that vein deposits of some kind occur in all the fractures where either 
one oi' both walls are limestone, excepting where the fractures are 
occupied by peridotite dikes. These usually are accompanied by 
only a slight displacement of the strata, and, with a single known, 
but very notable, exception, are not associated with valuable minerals. 
It is a fact that nearly all the mines of the district whose value 
has been proved by development, and nearly all the promising pros- 
pects, have either the St. Louis or the Princeton limestone on one or 
both sides of the fracture. As to the few exceptions where a promis- 
ing prospect occurs in a Chester area, in every case known to me one 
of the limestone beds of that group of rocks forms either the hanging 
or the foot wall of the fissure. We have met with several cases in 
the district that might appear to be exceptions to this rule, notably 
the Clements mine on the Crittenden Springs property, and the east- 
ernmost shaft of the Tabb mines. Critically examined, however, the 
exceptions prove to be more apparent than real, since in the first of 
these cases one of the walls of the adjacent main fault is the Prince- 
ton limestone, and in the other the St. Louis limestone, the openings in 
question being driven in fissures running parallel with and sudsidiary 
to the main faults. These subsidiary fissures were probably formed 
by large slices of country rock breaking away from the hanging wall, 


wliich is usually jointed parallel with the fault plane. If this is true 
then the two fissures should unite at some distance beneath the 

There are at least 30 faults in the district, with maximum dis- 
placements of from 400 to 1,400 feet, and traceable for distances of 
from 2 to 20 miles or more. Since many of these are connected with a 
series of subsidiary fractures and faults, whose displacement rarely 
exceeds 200 feet, they may be distinguished as the main 'faults. Of 
the subsidiary fissures, there are probably hundreds, and it is the 
belief of the writer that many of them will prove more productive, 
for equal lengths, than the veins in the main faults. 

As a rule the fault lines are practically straight, apparent slight 
deflections in the course being generally due chiefly to the dip of fault 
planes, which is usually considerable, upon the line of outcrop over 
the undulating surface. Occasionally, however, and perhaps oftener 
than the obscured surface indications now lead us to suspect, the 
faults are broken up into series arranged en echelon. The Tabb fault 
is a good example of the latter type. 

When the displacement of the strata is sufficient to bring two litho- 
logically distinct formations into juxtaposition, as, for instance, when 
the sandstones of the Coal Measures or Chester are thrown down to 
the level of the Princeton or St. Louis limestones, there is no diffi- 
culty in tracing the fault; but where the displacement is insufficient 
to produce this result very close stratigraphic comparisons are required 
to establish its presence. Indeed, the difficulties proved almost insur- 
mountable in the cases where the faults traversed the deeply weathered 
areas occupied by the St. Louis limestone. In the cases where differ- 
ent members of the Chester formation are on the two opposite sides 
of the fault plane the difficulties are not so great, since the various 
members of the Chester formation are usually distinguishable with- 
out much trouble, and the line of the fault is very commonly marked 
by protruding masses of quartzose sandstone. 

Taken as a whole, the fractures fall into at least two (and probably 
four) well-defined systems, one trending northeast, the other north- 
west. The northeasterly system is the more prominent and its frac- 
tures perhaps more generally mineralized than those of the other 
systems. When platted on a map this system of faults, on the Ken- 
tucky side of the river, presents an obscure fan-shaped arrangement, 
radiating and diverging eastwardly from the region between Salem and 
Pinckney ville, in Livingston County. The ribs of the fan pass through 
Crittenden County, and its successive lines become more and more 
easterly as we approach the southern boundary of that county and 
enter Caldwell, where they strike from a little north of east to a few 
degrees south. It is to be understood that the fan-shaped arrange- 
ment of the main fractures of this system has no known genetic rela- 
tion to the dikes of the district. No igneous rocks are known to occur 

Bull. 213—0:3 14 


within 6 miles of the imaginary converging point, while the trend of 
all the dikes sufficiently known to permit a statement concerning their 
directions is essentially at right angles to these fractures, being north- 
west instead of northeast. 

A well-defined northwest system of fractures, to which probably all 
the known dikes of the district belong, finds its best expression in the 
western half of Crittenden County. Here the trend of tin' dikes and 
faults belonging to the system varies between N. 30° W. and N. 37° W. 
The fractures of this system usually caused only a very limited dis- 
placement, but they contain some of the largest mineral deposits of 
the district, notably at the Eureka, Old Jim, and Holly mines. 

The northeast faults found in the northern and eastern parts of 
Livingston seem to indicate a distinct third system, extending across 
the Ohio from Hardin and Pope counties, 111. Similarly, the north- 
west fractures occurring in the northern parts of Crittenden and Liv- 
ingston counties, having a direction varying but a few degrees either 
way from N. 20° W\, probably belong to a fourth system, which, Like 
the other, has its strongest development in the Illinois counties 

The fractures, whether mineralized or not, frequently furnish chan- 
nels for descending underground waters, as is evidenced by the cor- 
rosion of the walls, forming in the case of some of the apparently 
unmineralized fractures open fissures or crevices filled with nn] clay. 
Sink holes are common along some of the fractures, and caverns are 
known to follow them for short distances. 

The formation of the mica-peridot ite dikes, of which seven or eight 
are known in Crittenden County, and one in Pope County, 111., is 
believed to have taken place prior to the extensive faulting of the 
region. They were probably produced by an accumulation of molten 
matter within this portion of the crust of the earth, causing its eleva- 
tion and fracturing and subsequent intrusion of the igneous masses. 
The strain on the continuity of the strata produced by 1 heir elevation 
caused the relatively brittle limestone to part along certain lines and 
form fissures. The more i>liable shales and sandstones of the Chester, 
however, frequently accommodated themselves to the strain, so that 
the intruded mass failed to pass through them, but spread itself hori- 
zontally in sheets between the bedding planes. The fissures occupied 
by the dikes are generally very nearly vertical and (pi ite straight in 
their courses, and although narrow, varying from about 2 feet to 
nearly 25 feet in width, some of them have been traced for miles. 


By W. S. Tangier Smith. 

The well-defined veins of this district almost without exception fill 

fissures due to faulting. They are found in the Princeton, St. Louis, 

and Chester formations; mainly in the first two. Where two of the 

formations have been faulted into juxtaposition, veins frequently 


occur along the fault or in a fissure not far from and parallel to the 
fault. Veins have been occasionally noted in groups of two or more, 
either parallel or arranged en echelon. Their width is variable; the 
maximum thus far recorded — in the case of well-defined veins — is 
nearly 15 feet. Most of the important veins, however, do not exceed 
6 or 8 feet in width. The veins all dip at a high angle. 

Most of the veins show distinct evidence of movement either in the 
displacement of the beds on the opposite sides of the fissure or in 
shearing with or without well-defined slickensiding. The shearing 
occurs both in the vein itself — especially near the walls — and in the 
country rock, where it may extend as much as 50 feet from the veins. 

The walls of the veins are usually, though not always, well defined, 
and are frequently marked by pronounced slickensiding. One or 
both walls are often fractured where the vein is in limestone, and are 
frequently much seamed with minute veins of calcite or fluorite. 
This seaming also frequently accompanies ordinary fracturing of the 
limestone where no vein has been formed. The shear planes are some- 
times marked by thin, clayey partings, especially in the Chester sand- 
stone. Also, where the veins are adjacent to this formation, dragged-in 
shales along the walls are not uncommon. These sandstones, where 
intersected by fissures, whether the latter are filled with vein matter 
or not, or where they have been filled with igneous rock, have been 
as a rule silicified, to a greater or less extent, to a hard quartzite. 
This quartzite, being resistant to erosion, appears in dike-like forms 
above the surrounding rocks, the shearing giving the effect of verti- 
cal or highty inclined bedding. 

The principal minerals of the district are galena and its oxidation 
products; sphalerite ("blende") and its oxidation products, smithson- 
ite (" carbonate"), and hydrozincite; pyrite (or marcasite), greenock- 
ite, fluorite ("fluorspar"), barite, calcite ("calc spar"), quartz, and 
ankerite. Nearly all of these occur either in the veins or in connec- 
tion with them. In addition, bitumen is occasionally found in the 

Fluorite. — Fluorite is by far the most important of the vein min- 
erals, comixhsing, as a rule, the greater part of the vein, the remainder 
being made up of a varying proportion of other minerals, with 
dragged-in country rock. In some cases the vein is composed almost 
wholly of fluorite ; in others the proportion of other substances is so 
large as to make it unprofitable to work the deposit. The associated 
minerals and rock fragments may be found throughout the vein, but 
in general they are mo^t abundant toward the margins. The fluorite 
veins frequently show a pronounced banding, due either to shearing 
or to a variation in the grain of the fluorite in bands parallel to the 
walls of the fissure. 

In the Chester sandstone fracturing has frequentty resulted in 
brecciation rather than in a well-defined fissure, and the breccia may 
be more or less completely cemented with fluorite. Barite may occur 


under similar conditions, and both are found replacing sandstone to 
a greater or less extent. 

The usual mode of occurrence of fluorite is massive and granular. 
It is also found as cubic crystals in vugs or coating the walls of small 
fractures in the country rock; but well-crystallized occurrences are 
comparatively rare. It is generally translucent, though rarely trans- 
parent; its color is usually white, sometimes purple, and occasionally 

Calcite and barite, — Of the minerals associated with the fluorite 
calcite is the most abundant, It occurs as white crystals or coarsely 
granular masses scattered through the veins. Barite is next in 
amount, though it is not found in most of the veins. AVhere it occurs 
with the fluorite it is apparently intergrown with it. There are also 
in both the St. Louis and the Princeton limestones veins of fine-grained 
barite occurring either alone or with a minor proportion of fluorite; 
but so far, except in one instance, this mineral has not been found in 
sufficient quantity to pay for mining. 

Galena, — Galena occurs in many of the fluorite veins, sometimes in 
quantities large enough to make it profitable as a by-product, though 
in most cases it is insignificant in amount. It usually occurs in grains 
and crystals of varying size, though generally small, disseminated in 
the fluorite, for the most part near the Avails of the veins, and fre- 
quently concentrated in lines parallel to the walls. Occasionally 
it is met in elongated columnar forms, due to shearing in the veins. 

Sphalerite. — Fragments of the wall rock, whether quartzite or lime- 
stone, are common in most of the veins. They have in some cases 
been replaced by fluorite to a greater or less extent. Sphalerite, 
which is found in many of the veins, occurs mainly as minute grains 
disseminated in the included fragments of limestone, frequently con- 
centrated near the contact between the fragments and the inclosing 
fluorite. It is also found occasionally disseminated in the fluorite 
and in the wall rock where this is of limestone. This fine-grained 
sphalerite is more abundant, on the whole, than the galena, and will 
prove of economic importance if a satisfactory method of separating 
it from the associated fluorite is found. Sphalerite is also found here 
and there (especially in the region southwest of Crittenden Springs) 
in coarser form and in greater amount. 

There are a number of deposits in which sphalerite or its oxidation 
products have been found apparently unassociated witli fluorite, 
notably in the Old Jim mine, where the ore (smithsonite with some 
hydrozincite) occurs adjacent to a dike of peridotite. Here as in other 
similar instances, however, mining has not been carried deep enough 
to show the character of the unoxidized ores. 

Effects of oxidation. — Above ground-water level the oxidized and 
carbonated surface waters have removed from the veins much or 
most of the calcite which they contained, as well as the included 
fragments of limestone, and have altered the country rock to a greater 


or less extent, but they have had comparatively little effect as yet on 
the fluorite and barite. The galena has not been oxidized to any con- 
siderable extent, and is still found near the surface. The fine-grained 
sphalerite has been largely removed from the veins, having been in 
part altered to smithsonite (zinc carbonate), which in turn is being 
slowl} x dissolved and removed by the surface waters. At the Old Jim 
mine the zinc salts in solution, reacting with limestone, have replaced 
it here and there with zinc carbonate. The result of the leaching out 
of the calcite and limestone fragments has been to leave the fluorite in 
a more or less honeycombed condition. Where it was not originally 
associated with these substances it is usually found in lumps. Wher- 
ever the grains have been loosened or separated it is found in a sand} 7 
or gravelly form known as gravel spar. In all these cases it is usu- 
ally associated with red clay formed as a residual product on the solu- 
tion of the adjacent limestone. 

The depth of oxidation along the course of the veins is variable and 
may be as much as 100 feet or more. In a few cases fresh, unaltered 
vein matter and country rock come nearly or quite to the surface. 
Descending surface waters have occasionally formed channels along 
a fissure, thus carrying oxidation and oxidized products considerably 
below the normal level of underground water. 

Vertical distribution of vein minerals. — As far as the deposits have 
been developed it can not be proved that the fluorite, on the whole, 
actually decreases with depth, though it is said to do so in some cases. 
This assumed decrease may be merely comparative, since the associ- 
ated calcite in many instances appears to increase with depth, 
although it is quite probable that in general this is due merely to the 
fact that it has been removed by surface waters at the higher levels. 
Galena, in general, appears to be most abundant near the surface, 
and on the whole to decrease with depth, though in many instances 
it is not apparently more abundant at one level than at an another. 
Above the level of underground water fine-grained sphalerite lias 
been generally removed or changed to carbonate. Below this level it 
seems probable, from what has been observed, that it does not materi- 
ally increase in amount with depth. The coarser occurrences of the 
sphalerite may be due to secondary enrichment, the finer-grained 
mineral having been oxidized and carried downward in solution 
below ground-water level, where it was redeposited in the coarser 
form. Connected with these deposits there appears to have been 
also some secondary concentration of the galena. No positive state- 
ment can be made on this point, as none of the mines yielding coarse 
sphalerite were accessible below ground-water level at the time the 
region was visited by the writer; but if this is the true interpreta- 
tion of the facts, these deposits of coarser sphalerite will be found to 
be most abundant just below ground-water level, and will tend to 
decrease with depth till only the finer-grained ore is found, the latter 
representing the primary concentration. 


By J. E. Wolff. 

According to a tradition, this celebrated occurrence of zinc and 
manganese ore was noticed and prospected as early as 1640, but Lord 
Sterling, after whom Sterling Hill is named, did the first mining in 
1774. About this time several tons of the red zinc oxide were shipped 
to London, yet the first description and analysis of this mineral were 
given by Dr. Bruce in 1810, and of franklinite by Berthier in 1819. 
The Mine Hill deposits were worked for iron ore about the beginning 
of the last century, but there was not much mining for zinc until 
after 1840. Different parts of the deposits have been worked more or 
less continuously since then by different companies and there has 
been long litigation, which has been finally settled by the consolida- 
tion of all the interests. The ores are now treated at the mines by 
magnetic separators, which separate the franklinite (as well as the 
garnet and other impurities) from the willemite and zincite, while the 
calcite is removed by jigging. The principal uses of the zinc ores are 
for metallic zinc and zinc white, and of the manganese for Bessemer 

The ores occur at Mine Hill (Franklin Furnace) and Sterling Hill 
(Ogdensburg), localities 3 miles apart, and at no other place has 
exploration found more than traces of the ores. The deposit is in the 
white Franklin limestone, and at Mine Hill, where t lie surface and 
underground workings are best developed, lies about 30 feet from the 
gneiss boundary on the west, along the west limb. 

The ores consist of zincite, the red oxide of zinc (ZnO), containing 
94 per cent zinc oxide and 6 per cent manganese oxide; willemite, 
silicate of zinc (Zn 2 Si0 4 ), containing 67 to 69 per cent zinc oxide 
and 5 to 10 per cent manganese oxide; and franklinite (FeZnMn) O 
(FeMn) 2 3 , containing 56 to 67 per cent ferric oxide, 4 to 10 per cent 
manganese sesquioxide, 7 to 23 per cent zinc oxide, 10 to 16 per cent 
manganese oxide. The ores are usually accompanied by varying pro- 
portions of calcite. The contrast between the deep-red zincite, green 
willemite, lustrous black franklinite, and white calcite is very strik- 
ing. The proportions of these minerals vary constantly, so that 
sometimes zincite is abundant, sometimes only present in traces, and 

o From the descriptive text of the Franklin Furnace folio, Geologic Atlas of the United States- 
in preparation. 



so with the relative proportions of the other three. The size and shape 
of the" minerals also vary greatly. A common form is the "shot" 
ore in which irregular rounded franklinite, willemite, and calcite 
grains, with or without zincite, occur together without marked band- 
ing; at other times the ore is finely banded or foliated, and these 
minerals are then seen to be in small flattened lenses or elongated 
pod- like masses parallel to the foliation; or such forms may be due 
to an aggregate of several grains. At other times large round masses 
of zincite, 1 or 2 inches in diameter, are scattered through coarse cal- 
cite like a pudding stone, or franklinite occurs similarly in rough 
octahedral crystals. These four minerals have evidently been formed 
contemporaneously, for each is found inclosed in the others and 
neither in general has any distinct external crystal planes, although 
the franklinite has a tendency to occur in rounded octahedral grains. 
These structures in general simulate so closely that of the associated 
gneisses that they must be classed together. 


At Mine Hill the zinc deposit is much like a bedded deposit, and 
forms a band which outcrops on the surface as far north as the 
extreme point of the gneiss band lying west of the white limestone, 
and runs southwest for about 2,700 feet (Trotter and other mines), 
when it makes a sharp curve and runs northeast about 600 feet (Buck- 
wheat mine) as far as the trap dike, where it disapijears from the sur- 
face, and has been worked underground in a northeast direction for 
about 600 feet on a pitch of 27° to 32°. By diamond-drill exploration 
the further underground continuation of this deposit to the northeast 
was found at depths of 1,000 feet more or less from the surface, a 
shaft was sunk, and extensive mining operations are carried on 
(Parker shaft workings). 

The west limb of the deposit is known as the " front vein" and the 
east limb as the "back vein," while the connecting point is known as 
the "South chamber." 

Along the west outcrop the ore body has a width toward the north 
end of 15 to 25 feet. It is separated from the gneiss by 30 feet of 
limestone and dips east at from 55° to 60°. The distance from the 
gneiss is remarkably constant, for the same 30 feet of limestone 
between the foot wall of the ore deposit and the gneiss is found at the 
surface, and 900 feet vertical^ below and 1,200 feet along the dip. 
The foliations of ore and limestone are conformable. 

At the Trotter mine the ore body is divided by a large mass of 
granite, which was also found underground for a long distance. South 
of this mine the deposit widens considerably. It has been followed 
down about 500 feet along the dip from the outcrop of the west vein, 
widening and narrowing and with some variation in the angle of dip. 


At the Buckwheat mine the ore has been worked from the outcrop 
down nearly 300 feet with the dip, which is very steep to the east, and 
at the Parker shaft workings 1,000 feet from the surface 

The comparison of the structure and extent of the workings along 
the west vein and those of the Parker shaft shows an evident con- 
tinuity of the deposit, dipping steadily downward to the east from 
the outcrop for 1,300 feet, where it begins to rise again for 150 feet, 
when the ore terminates. In the basin thus formed, and also in the 
part forming the eastern edge, there is a great thickening of the ore. 
At the Buckwheat mine the same structure is found, a crosscut driven 
west to the west vein shows that the foot wall of the east vein curves 
around to form the hanging wall of the west vein, the width of the 
ore in the north slope of the Buckwheat mine is about double the nor- 
mal width of the two veins (70 feet in the first, 35 or less in the sec- 
ond), and the limestone forms an arch over the ore, the foliation of 
which, and the structure of the franklinite bands in the limestone 
roof, conforming to the arch of the ore, which pitches downward at 
an angle of 27° to 32°. Putting all these facts together, the inter- 
pretation on which all observers agree is that the east and west veins 
are one continuous plane body of ore folded in a synclinal trough, 
which narrows to the south and finally spoons out at the surface 
in the south chamber workings; less positive is the theory that there 
is a sharp subordinate anticline on the east side, with the two sides 
compressed together and the axis pitching 27° or more to the north- 
east. The fact is plain that there is a thickening of the ore and 
that this thickened shoot pitches northeast at about the same angle 
as the axis of the main synclinal trough or basin. The compass direc- 
tion of this axis gradually curves to take a more northerly direction 
in the Parker shaft workings so as to conform to the strike of the 
west vein. The pitcli also flattens in the north workings to as low as 
0°, and certain facts from the diamond-drill records show that the 
structure is more complicated there, but the data available are too 
fragmentary to permit a definite conclusion. It is noteworthy that 
the pitch of 27° in the Buckwheat mine is also to be seen in the 
gneisses lying just west, an argument for the contemporaneity in 
present form of the gneiss, white limestone and ore deposit. 

In several places in the underground workings at Mine Hill, granite 
or syenite masses cut the ore. In 1898 several of these were studied 
in the Parker shaft workings. They run, like the surface granite 
outcrops, nearly parallel to the general trend of the foliation of the 
vein and yet cut distinctly across it in places. The granite is line- 
grained for several inches from the contact, the ore is hardened for 
some distance, and between granite and ore there is a band of yellow 
(Mn) garnet (polyadelphite) mixed with rhodonite, calcite, willemite, 
franklinite, and a Mn. Zn. pyroxene ( jeffersonite?) ; the granite itself 
also contains stringers and isolated masses of these minerals. Some- 


times a coarse vein-like aggregation of these minerals separates gran- 
ite from ore A large number of the rare minerals come from these 
underground granite contacts, and there can be no doubt that the 
granite is later than the zinc bed and intrusive into it. 

At Sterling Hill there is an analogous structure of east-west 
limbs of the ore bod} 7 , outcropping on the surface in a hook and pitch- 
ing under northeast at both ends, the west vein outcropping about 
GOO feet from the turn, and the east vein about 1,500 feet. 

The west vein has only been worked down a short distance from 
the outcrop ; the east vein in places about 650 feet at an average angle 
of 50° to 65°. 

In the center of the canoe joining the two veins the axis pitches 
50° NE. In the mines the pitch of the ore shoots is said to have been 
generally 65°. At the apex of the trough the limestone is filled with 
various silicates (diopside, jeffersonite, etc.), and was probably 
impregnated with franklinite and zinc ores, now mined out. A little 
farther north a large deposit of calamine was mined, which lay in a 
bowl-shaped cavity on top of the limestone, and was undoubtedly 
hydrated ore derived from the decomposition of the higher lying 
portions of the zinc deposits. 


The descriptions of the structure and relations of these deposits 
speak for their contemporaneity in present form and structure with 
the inclosing white limestone and associated gneisses, and therefore 
for a period of formation earlier than that of the intrusive granites, 
although the difference in time may have been small. The ore 
deposits are often not sharply defined from the limestone foot and 
hanging walls, and the latter are shot through with franklinite, willem- 
ite, etc. Horses of limestone or coarse calcite also occur in the mid- 
dle of the ore deposit. It is believed that the zinc deposits acquired 
their present structure and mineralogical composition contempora- 
neously with the limestone, and that they represented originally a 
local segregation of the zinc manganese and iron minerals in some 
other form which may have been originally that of sulphides which 
were then oxidized to carbonates, and the latter by metamorphism, 
which caused the loss of carbonic acid with or without the substitu- 
tion of silica, assumed the present form. Sphalerite (zinc sulphide) 
has been found very rarely in the ore deposits and only in small 
isolated masses, and the carbonates are equally rare, so that there is 
little positive fact upon which to base a theory. 


Many papers relating to silver-lead deposits will be found included 
in the list on pages 90 and 01 of this bulletin. The principal other 
papers on lead and zinc, published by the United States Geological 
Survey, are the following: 

Bain, H. F., Van Hise, C. R., and Adams, G. I. Preliminary report on the 
lead and zinc deposits of the Ozark region [Mo., Ark. J. In Twenty-second Ann. 
Rep., Pt. II, pp. 28-22*. 1902. 

Clerc, F. L. The mining and metallurgy of lead and zinc in the United States. 
In Mineral Resources U. S. for 1882, pp. 358-386. 1888. 

Hofmann, H. O. Recent improvements in desilverizing lead in the United 
States. In Mineral Resources U. S. for 1883-84, pp. 402-47:5. 1885. 

Iles, M. W. Lead slags. In Mineral Resources U. S. for 1883-84, pp. 440- 
462. 1885. 

Winslow, A. The disseminated lead ores of southeastern Missouri. Bulletin 
No. 182. 81 pp. 1896. 

•J is 


Reports on a number of the iron-ore fields of the country have been 
issued by the United States Geological Survey within the last year, 
and work in several important iron districts was carried on during 
the field season of 1902. Summaries, both of the published reports 
and of the unpublished results of the season's field work are presented 
below. A paper on the utilization of slags, prepared for the last 
volume of the report on Mineral Resources, United States, and sepa- 
rately printed, but omitted by error from the bound volume, is here 
republished. In addition to the papers included in the present sec- 
tion, the ocher deposits of Cartersville, Ga., which are closely allied 
to the iron deposits of the same region, will be found described on 
pages 427 to 432 of this bulletin. On pages 214 to 217 will be found a 
paper on the zinc-manganese-iron deposits of Franklin Furnace, New 
Jersey, which may be of interest in the present connection. A list of 
the principal previous publications by the Survey on iron and manga- 
nese ores and mining districts will be found on page 256. 


Bv J. S. Diller. 

Iron ore (magnetite) occurs in the Redding quadrangle at a number 
of points on the contact between diabase and the Carboniferous lime- 
stone. Numerous prospects have been opened on the contact about 
Grey Rock, northeast of Bayha and on Pit River, as well as farther 
northward, opposite the United States fishery. The openings gener- 
ally show limonite, but it is derived from the decomposition of ore in 
which magnetite and pyrrhotite play an important role, associated with 
pyrite, chalcopyrite, light-green fibrous pyroxene, and garnet result- 
ing from contact metamorphism. The prospects are generally made 
in searching for copper ore, but at one place, about a mile south- 
east of the United States fishery, on McCloud River, a much more 
promising opening is operated, furnishing the iron flux at Bully Hill. 
The ore is chiefly porous magnetite, which is often coated with irrides- 



cent and stalactitic limonite, and opened to a width of 40 feet without 
reaching the 1 imits. Small bands of garnet mixed with pyroxene occur, 
and I races of copper ores have been reported. Lying essentially upon 
the contact between the Carboniferous limestone and an igneous rock, 
the ore is believed to owe its origin largely to this relation. Its 
extent, however, is a matter of doubt, and the progress of the work 
disclosing what is underneath is watched with much interest. 

Similar bodies occur along the same limestone contact farther north, 
upon the west side of the MeOloud, and should the mass referred to 
above prove a large deposit it may lead to the development of an 
important industry in that region. 


By Edwin C. Eckel. 


Iii recent years the attention of many technologists has been directed 
to the problem, of slag utilization. Certain slags may, of course, be 
considered as low-grade iron ores, and have been used as such for 
many years. By far the greater portion of the slag annually j)ro- 
duced by iron and steel works is not available for this use, however, 
and it is only in comparatively recent years that uses have been found 
for many of these slags. At present, slag is utilized extensively in 
cement and slag-brick manufacture, as a fertilizer, and in the form of 
mineral wool; to a less extent in the manufacture of alum, paint, and 
glass; and a considerable quantity is disposed of less profitably for 
use as road metal, railroad ballast, and in land reclamation. These 
uses will be discussed in order. 


Slag cement, properly so called, is the product obtained by pulver- 
izing, without calcination, a mixture of granulated basic blast-furnace 
slag and slaked lime. This product, though in reality a member of 
the class of pozzuolanic cements, is usually marketed as "Portland 
cement," in spite of the fact that it differs from a true Portland 
cement in method of manufacture, ultimate and rational composition, 
and properties. Eight plants are at present engaged in the manu- 
facture of this material in the United States, the production for 1901 
being about 400,000 barrels, while that for 1902 was in the neighbor- 
hood of 800,000 barrels. The writer has discussed the manufacture 
of slag cement in detail in a recent publication." A brief resume of 
the technology of the material in question is here given. 

As to composition, the material used in the manufacture of slag 
cement must be basic blast-furnace slag. Tetmajer stated that the 

ratio should never be less than unity, and that the best results 

2 Al O 

were obtained when the ratio -^~~ gave a value of 0.45 to 0.50. 

Si() 2 

Prost and Mahon later obtained good results from slags in which the 

"Mineral Industry, Vol. X, pp. 84-95. See also Mineral Resources IT. S. 1SXX), p. 747, where a 
description of two Alabama slag-cement plants is given. 




alumina was much higher than indicated by Tetmajer's ratio, and 
analyses of slags used in practice are shown in the following table, 

with the ratios 5^2 and * :j calculated for each slag: 
kSi0 2 Si<J 2 

Analyses of slags in actual use. 


Si0 2 . 
A1 2 3 
FeO . 
CaO _ 
CaS0 4 
S __.. 

so 3 _. 

Si0 2 



boro, Eng- 


18. 56 

12. 22 
3. IS 







32. 90 



47. 30 





46. 83 


. 93 




. 02 

46. 10 



32. 20 

15. 50 

48. 14 
2. 27 



Slags allowed to cool slowly are only feebly hydraulic, even if of 
proper chemical composition. When used in the manufacture of slag 
cement, therefore, the slag must be cooled as suddenly as possible. 
This is effected by bringing the slag, as it issues from the furnace, in 
contact with a jet or stream of cold water. This sudden cooling 
"granulates" the slag, i. e., breaks it up into porous particles, and 
has also two important chemical effects. One is that the slag, if of 
suitable chemical composition, is rendered strongly hydraulic; the 
other, that most of the sulphur is removed in the form of hydrogen 
disulphide. After granulation the slag is dried, usually in rotary 
driers, the Ruggles-Coles being a favorite American type. 

The lime used for mixture with the slag should be low in magnesia, 
well burned, and carefully slaked. At Chicago, where the Whiting 
process is used, a small percentage of caustic soda is added to the 
water used for slaking, the effect being to accelerate the set of the 
cement. After slaking and drying, the lime is ready for mixture with 
the granulated and dried slag, which usually has received a prelimi- 
nary reduction in a crusher, ball mill, Kent mill, or other compara- 
tively coarse reducer. The proportions used will vary from 20 to 40 
parts of lime to 100 parts of slag. The mixture and final reduction is 
usually accomplished, in the American plants, in tube mills. The 
composition of a number of American and European slag cements is 
shown in the following table of analyses collected from various sources: 


Analyses showing composition of slag cements. 





Si0 2 _ 

ALO, - 
FeO ..... 
CaO .... 




Loss on ignition 



Donjeux, Saulnes, rhic . ai , T11 
France. France. cnicago, m. 

24. 85 

22. 45 



28. 95 










7. 50 


The composition of good slag cements may vary within the follow- 
ing limits: Silica, 22 to 30 percent; alumina and iron, 11 to 16 per 
cent; lime, 49 to 52 per cent; magnesia less than L per cent; sulphur, 
less than H per cent. It will be noted that the lime content is lower 
and the alnmina-iron content higher than in a cement of the Portland 
type. Slag cements also differ from Portland cement in being lower 
in specific gravity and lighter in color. Normally, they are slower 
setting than Portland cement, though this defect can be overcome by 
treatment during manufacture. They are deficient in resistance to 
mechanical wear, and do not set satisfactorily in dry situations. For 
use underwater or in permanently damp ground, however, they would 
seem to be of service. 


True Portland cements, which must be sharply distinguished from 
the slag (pozzuolanic) cements discussed in the preceding section of 
this paper, can be made from mixtures of which one element is blast- 
furnace slag. In this case the slag is ground, intimately mixed with 
powdered limestone, and the mixture calcined and reground. Two 
plants are engaged in the manufacture of Portland cement from slag 
and limestone in the United States. An analysis of the "Universal" 
brand of the Illinois Steel Company, a Portland cement made from 
these materials, follows: 

Analysis of Universal brand, manufactured by the Illinois Steel Company. 


Per cent. 
_. 23.62 




so 3 _- 

s. ....__ 

Loss on ignition 



0. 52 



Cecil von Schwarz, in a paper read before the Iron and Steel Insti- 
tute of Great Britain, has recently described in detail German and 
Belgian practice in the manufacture of Portland cement from blast- 
furnace slag. The slag is granulated in order to remove sulphur and 
to reduce the cost of crushing. The granulated slag is dried and mixed 
with about an equal amount of limestone. To the mixture is added 
about 3-J per cent of powdered slaked lime, and their intimate mixing 
and reduction are accomplished in ball mills and tube mills. About 
8 per cent of water is added, and the slurry is then made into bricks, 
which are dried before charging into the kiln. A ring kiln is used, 
with coke as fuel. The clinker is moistened, stored for six weeks, 
and reduced in ball and tube mills. 

Analyses of limestone, slag, and finished cement at << typical plant. 








30 -35 

10 11 

23. 70 

A1 2 3 

6. 14 

Fe 2 3 


FeO . 

0.2- 1.2 
3. - 4 


CaC0 3 


CaO . . 

46 -49 
0.5- 3.5 
0.2- 0.6 

59. 08 




S0 3 _. 


Loss on ignition . . 



Slag, run into molds on issuing from the furnace, furnishes blocks 
which have been used for paving, notably in Philadelphia. These 
slag blocks are very durable, but objectionable because of their slip- 
periness. This difficulty has been overcome, in English practice, by 
casting the blocks in a double-sized mold, with a projection which 
results in a notch passing around the slag block. The two halves of 
the block are then split apart at this notch, and the rough fracture 
surface of each is laid uppermost in paving. 


The manufacture of slag brick can hardly be considered as being 
more than a specialized phase of the manufacture of slag cement. 
Slags, approximately of the same composition as those usee! in cement 
making, are granulated, dried, and pulverized. Sufficient slaked lime 
is added to bring the calcium oxide content of the mixture up to about 
55 per cent, the mixing being carefully and thoroughly done. Dur- 
ing or after mixing, a small amount of water is added, and the moist- 
ened material is then fed to the brick machine. On issuing from this 
the bricks are placed on racks to dry. The drying takes from six to 
ten days, at the end of which time the bricks are ready for use. 




Slag bricks are light in color, varying from light to dark gray; they 
weigh less than clay bricks of equal size, require less mortar in laying 
up, and are equal to clay bricks in crushing strength. The following 
analyses of slags used in slag-brick manufacture are fairly represent- 
ative : 

Analyses of slags used in slag-brick manufacture. 


Si0 2 . 
A1 2 3 
FeO . 
S ___ 





22. 5 

25. 8 






















2. 33 













The highly phosphatic slags produced by basic Bessemer converters 
are valuable fertilizers, and are of great economic importance. In 
Germany, especially, large quantities are annually sold under the 
name of Thomas slag. In slags produced by this process the content 
of phosphoric acid usually runs from 10 to about 25 per cent. 

Analyses of basic Bessemer slags. 


Si0 2 

A1 2 3 _ 
Fe 2 3 -.._ 
FeO ._.. 




K 2 0, Na 2 



S0 3 

PA-- - 

H 2 0,etc_-_ 












5. 8 

15. 42 
3. 5 





5. 76 


47. 34 




5. 56 






19. 19 



1. Redgrave, Jour. Soc. Arts, Vol. XXXVIII, p. 230. 

2. German. Phillips, Trans. Am. Inst. Min Eng., Vol. XVII, p. 86. 

3. English. Phillips, ibid., p. 86. 

4. Redgrave. Jour. Soc. Arts, Vol. XXXVIII, p. 230. 

5. Pottstown Iron Company , Pennsylvania. Morris, Trans. Am. Inst. Min. Eng. , Vol. XXI, p. 232. 

6. Bohemian. Phillips, Trans. Am. Inst. Min. Eng., Vol. XVII, p. 87. 

Bull. 213—03- 



The possible commercial value for agricultural uses of these high 
phosphorus slags produced by the Thomas- Gilchrist process was early 
recognized. At first, however, it was argued that in an untreated con- 
dition they would be useless as fertilizers; that the phosphoric acid 
they contained was not directly available for plants, and that the fer- 
rous oxide would probably prove positively injurious to vegetable life. 
Attempts were accordingly made to dissolve out the phosphates of the 
slag and reprecipitate them. Fortunately this treatment was soon 
shown to be unnecessary, for field experiments with finely ground but 
otherwise untreated slags proved that they were excellent fertilizers. 
From this date (1882) onward the use of Thomas slag as a fertilizer 
has increased steadily, and it is now an important article of commerce. 

Regarding the chemical composition of these slags, facts of great 
economic importance were brought out by the work of Ililgenstock 
and later investigators, and the efficiency of Thomas slags as fertiliz- 
ing agents is now explained. In rock phosphates the phosphoric acid 
exists combined with lime as the tribasic lime phosphate (3Ca() 3 P 2 5 ). 
In the slags above mentioned, however, the combination existing is 
the tetrabasic lime phosphate (4Ca0 3 P 2 5 ). These two compounds 
differ greatty in the degree of their solubility in saline solutions, the 
tetrabasic phosphate being much more soluble than the tribasic. For 
this reason the phosphate slags are more efficient as fertilizers than 
the mineral phosphate. Jerisch states that about U percent of the 
total phosphorus of slags is present in the form of phosphide of iron, 
which is changed into phosphate in lie soil. 

Many types of crushers and mills have been experimented with in 
the pulverizing of Thomas slag. The ball mill, however, seems to be 
the only one capable of economically crushing this product to the 
fineness required — 75 per cent through a 100-mesh sieve. 

The slight development of the basic Bessemer steel industry in the 
United States necessarily renders the use of these phosphatic slags of 
less commercial importance than in Europe. During the year 11)01 
about 1,000 tons of phosphate slag, produced in the United States, 
were sold as fertilizer. This American material has been tested b} r 
the Maryland Agricultural Experiment Station, the report a of the 
results being that slag phosphate gave a greater total yield than did 
any of the other insoluble phosphates. The yield of corn with slag- 
phosphate was not quite so much as with bone meal, but the yield of 
wheat and of grass was greater. All yields were produced at less cost 
with slag phosphates than with bone meal. The slag used in these 
experiments was a commercial sample and contained 16.32 per cent 
total phosphoric acid. Other commercial analyses of this fertilizer 
show phosphoric acid contents of 21.03 and 22.24 percent. A com- 
plete analysis of the slag from the Pottstown, Pa., converters is given 
in the preceding table of analyses. 

a Bull. Maryland Agric. Exp. Sta. No. 68, p. 28. 


The slags produced in steel plants using the open-hearth process are 
less valuable as fertilizers than those produced by basic converters, 
as the former contain less phosphoric acid and more silica and lime 
than do the basic Bessemer slags. A two-stage modification of the 
open-hearth process — the Bertrand-Thiel process — gives slags higher in 
phosphoric acid than ordinary open-hearth slags. It is even claimed 
by Thiel a that the Bertrand-Thiel process produces a greater value 
of slag, if both quantity and phosphoric content be considered, per 
ton of finished steel than does the Thomas-Gilchrist process. 

The slags resulting from processes other than those above noted are 
not sufficiently phosphatic for use as high-grade fertilizers. Elbers 
has, however, called attention 5 to the fact that highly calcareous 
blast-furnace slags might be profitably used as fertilizers in place of 
the other forms of lime (marl, shells, etc.) now used by farmers. 


Over half of the material marketed as "mineral wool" or "silicate 
cotton" is derived from slag, the remainder being manufactured from 
natural rocks of different types. 

Originally the process was carried out at the furnaces. At present, 
however, the slag is bought from the furnace companies and remelted 
in a small cupola. From this the molten slag issues in a small stream, 
into which is injected steam or air under pressure. The effect is to 
scatter the slag, small spherules of slag being blown out from the 
main stream, each spherule carrying behind it a thread of slag. 
The fluidity and composition of the slag and the pressure of air or 
steam are manipulated so as to give the greatest proportion of fiber to 
spherules, as the spherules are commercially unavailable and must be 
separated from the fiber if present in much quantity. 

No analyses of slags used in the manufacture of slag avooI are at 
present available. A mineral wool made from natural rock gave on 
analysis the following result: 

Analysis of mineral wool made from natural rock. 

Silica 37. 5 

Alumina and iron oxide 20 

Lime '.. 30.6 

Magnesia 11.8 

The presence of sulphur is a defect in most mineral wools made 
from slag, as they must be carefully protected against moisture to 
prevent the oxidation of the sulphur and the consequent destruction 
of the pipes or other metallic surfaces on which the wool has been 

The most important property of slag wool, from a commercial point 
of view,. is that it is a very poor conductor of heat. This property 

a Chem. Zeit., 1901, p. 371. &Eng. and Min. Jour., November 3, 1900. 


renders it available for all uses for which a nonconductor is desirable, 
as steam-pipe coverings, safe linings, etc. In 1884, Mr. J.J. Coleman 
carried out a series of experiments on the heat-conducting power of 
various covering materials. His results" were as follows, the con- 
ducting power of slag wool being taken as unity: 

Comparative heat-conducting power of materials. 

Slag wool . ---- 1.00 

Hairfelt , 1.17 ' 

Cottonwool . 1.22 

Sheep's wool 1.36 

Infusorial earth . ^ 1. 36 

Charcoal 1 . 40 

Sawdust 1 . 63 

Gas-works breeze 2. 30 

Subseqently more elaborate experiments were made by Professor 
Ordway, 32 materials being tested under conditions closely approxi- 
mating to those encountered in actual practice. The following 
results 6 have been selected by the writer from Ordway's list and 
rearranged and recalculated to permit the heat-conducting power of 
slag wool to be taken as unit}*: 

Comparative heat-conducting power of materials. 

Loose wool 0.62 

Loose lampblack .75 

Hair felt .70 

Compressed lampblack . . .82 

Loose calcined magnesia .95 

Slag wo< >1 1 . 00 

Light carbonate of magnesia 1 . 05 

Compressed carbonate of magnesia 1. 18 

Ground chalk 1 . 58 

Asbestos paper „ 1 . 07 

Compressed calcined magnesia • 3. 28 

Fine asbestos 3. 78 

Sand 4.77 

It will be noted that though Orel way's results are not so favorable 
to slag wool as were Coleman's, both experimenters established the 
fact that this material is the best of the noninfiammable coverings 


In 1891 Mr. A. Sahlin described 6 a plant then in operation at Boon- 
ton, N. J., at which slag was utilized in the manufacture of paint 
stock. The slags used were puddle slags and reheating cinder, 
which, of course, can not be utilized in the manufacture of cements, 

a Engineering, September 5, 1384, p. 237. 
b Trans. Am. Soc. Meeh. Eng., Vol. V, p. 73. 
o Trans. Am, Inst. Min. Eng., 1891. 




fertilizers, alum, etc. Analyses of samples of these materials showed 
the following 1 compositions: 

Analyses of puddle slag and reheating cinder. 






19. 62 



. 38 




Fe 2 O s .. 






Si0 2 _._ 

20. 06 





The slag was crushed in a Blake crusher to pass a three-fourths inch 
screen, and finally reduced in a Cyclone pulverizer to pass 225 mesh. 
The finest dust was used directly as paint stock. The coarser mate- 
rial, after treatment with sulphuric acid, was calcined and reground. 
This industry has been discontinued at Boonton, and it is believed 
that no slag is at present used for that purpose in the United States. 


The preparation of alum from highly aluminous slags is accom- 
plished by means of the Lurmann process. So far the manufacture 
of alum by this process has not been attempted in the United States, 
though it has been carried out on a commercial scale in Europe. At 
Donjeux, France, the process has been employed in connection with 
the manufacture of slag cement, the gelatinous silica resulting from 
the alum-extraction process being used to accelerate the set of the 

The Lurmann process, in brief, is as follows: Slags, as high in 
alumina as possible, are decomposed by means of hydrochloric acid. 
The resulting solution of aluminum chloride is treated with lime car- 
bonate, which serves to precipitate the alumina and any dissolved 
silica that may be present. In treatment with sulphuric acid the 
alumina is dissolved, leaving the silica. It is stated a that 100 kilo- 
grams of slag, containing 25 per cent of alumina, will yield 180 kilo- 
grams of alum and 31 kilograms of gelatinous silica. The silica is 
used in the manufacture of soluble glass and, as above noted, in the 
manufacture of slag cement. The process may even be profitably 
arrested after the first stage, as the aluminum chloride then obtained 
is marketable for use in certain sewage purification processes. 

« Wagner, Chemical Technology, p. 439. 



Small quantities of slag have been used in Europe in the manufac- 
ture of the inferior grades of glass, but this use has never attained 
much commercial importance. In America slag has never, to the 
knowledge of the writer, been so utilized. 


In addition to its use as a paving material in the form of slag bricks, 
discussed in preceding sections of this paper, slag has been somewhat 
extensively used in highway construction as macadam. 

Sections of roads constructed in New Jersey with slag macadam, 
under State supervision, have proved entirely satisfactory. Near 
Buffalo, N. Y., slag has been used to some extent in highway con- 
struction, and to a greater extent in Pennsylvania and Alabama. 
The most extensive use of slag for this purpose is, however, probably 
in Maryland, where it has been utilized in highway construction in 
the counties of Baltimore, Howard, and Prince George. 

Prof. W. B. Clark refers to the use of slag for this purpose in 
Maryland in the following words:'' 

Furnace slag has been found to be, under certain conditions, a highly satisfac- 
tory road metal. It is not as valuable as the trap rocks, although its cementing 
properties are excellent, except in the case of some of the materials from the old 
furnaces. These old slags break down quickly and are readily ground into fine 
dust, and for these reasons are of little value in road construction. 

The slag from the present iron furnaces, on account of the large amount of lime 
contained in it, is very valuable as a highway material. It compacts easily when 
rolled and forms an even, smooth surface, while the fine particles unite as a hard 
cement that grows firmer with time. The iron furnaces at Sparrow Point afford 
material of this character that has already been demonstrated to be a valuable 
road metal. 


In several States, notably in Alabama, slag is Largely used as rail- 
road ballast. At the third annual convention of the American Rail- 
way Engineering and Maintenance-of-Way Association, a committee 
reported on this as follows: 

Blast-furnace slag containing a small excess of lime and being of a glassy nature 
will, when broken up under the track, fulfill the requirements of ballast to a very 
large degree, If a large excess of free lime be present the slag soon becomes too 
soft to hold the load, becomes concreted under the ties, and churns in wet weather. 
Slag-ballasted track usually requires a lift of 2 or 3 inches, and to be surfaced out 
of face at intervals of from two to six years, depending on the hardness of the 
slag and the amount of traffic. Slag composed almost exclusively of hard, glassy 
pieces approaches closely to the quality of rock ballast; on the other hand, slag 
with a large amount of free lime is inferior to reasonably good gravel. 

It will be noted that the noncalcareous, glass} 7 slags, which are thus 
said to be preferable for railroad ballast, are precisely the kinds that 

"Maryland Geological Survey, Vol. Ill, 1899, p. 10."). 


are unsuitable for use as macadam for highway construction. It is 
therefore evident that almost any type of slag will be of service for 
one of these two uses. 


In the vicinity of furnaces slag is of considerable local importance 
as a cheap and readily transportable material for filling purposes. 
Large quantities are annually used for land reclamation, filling of 
abandoned mine workings, etc. The greater part of the slag so used 
is, however, given away by the furnaces, and such uses may, there- 
fore, be regarded rather as a means of inexpensively disposing of a 
troublesome waste product than as a utilization of slag. Such meth- 
ods of disposal are, of course, economical only when the slags are 
unfit for the more profitable utilizations discussed in the preceding 
seel ions of this paper. 


By C. W. Hayes. 

Closely associated with the Georgia deposits of iron ore (see pages 
233-242) are extensive deposits of manganese. These have been 
quite fully described b}' Dr. Penrose, 6 and require only brief mention 
here. All the iron ore contains traces of manganese, but the main 
deposits of the latter ore are quite distinct from the iron. The ore 
occurs, like the brown hematite, embedded in a heavy mantle of 
residual clay, associated with chert and angular fragments of quartz- 
ite. The proportion of clay to ore is usually larger than in the 
deposits of brown hematite. The ore occurs as small concretions 
scattered through the clay, and also in the form of veins, penetrating 
the clay in an irregular manner. It has the appearance of having 
been deposited by solutions percolating through the residual mantle. 
The original source of the manganese was probably the Beaver lime- 
stone, although some of it may have come from the Weisner quartz- 
ite. The deposits occur with about equal frequency in the residual 
material derived from the two formations. 

Dr. Penrose holds the view that some at least of these deposits 
existed in their present form in the rocks of the region before weather- 
ing, and are therefore strictly residual. While this may be true in a 
few cases, the writer has found no evidence of it in the field; and the 
manganese ores are regarded, like the iron ores with which the} 7 are 
associated, as purely secondary deposits, their distribution being 
determined chiefly by chemical and physical conditions, rather than 
by the outcrop of beds especially rich in manganese. 

Although, in the aggregate, a large amount of ore has been mined 
from this district, most of the work has been done in a primitive and 
inefficient manner. It is probable that with modern appliances a 
large amount of material would pay for working which does not con- 
tain a sufficiently large proportion of ore to be profitably worked by 
the present methods. 

"Abstracted from the descriptive text of the Gartersville folio of the Geologic Atlas of the 

United States, in preparation. 

b Penrose. R A. F., jr., Manganese, its uses, ores, and deposits: Ann. Rept. Geol. Survey 
Arkansas, Vol. I, 1890, pp. 418-426. 



By C. W. Hayes and E. C. Eckel. 

One of the most productive iron-ore districts in the Southern 
Appalachians lies in the vicinity of Cartersville, Bartow County, Ga. 
The ore deposits of this region are so directly related to the stratigra- 
phy and structure of the area that a brief description of the geologic 
features must be given before taking up the subject of the origin and 
position of the ore deposits. 


Stratigraphy. — The area in question occupies the southeastern half 
of Bartow County, Ga. Its surface is about equally divided between 
the older crystalline and metamorphic rocks which occupy the Pied- 
mont Plateau and Appalachian Mountains in the east, and the unal- 
tered Paleozoic formations which occupy the Appalachian Valley on 
the west. The line of separation between these two groups of forma- 
tions in the Cartersville district is located as follows: Beginning at the 
north, it lies about half a mile east of Fairmount post-office, and 
runs almost due south for about 7 miles, when it swings eastward to 
near Martins Mill. From this point it takes a southwest direction, 
passing half a mile west of Rowland Springs, and then turns south- 
east, crossing the Etowah near the old iron works and crossing the 
railroad about a mile southeast of Emerson. From the point at 
which it crosses the railroad the line pursues an almost southerly 
direction for a few miles; then turns northwest, almost reaching the 
Etowah at the Free Bridge, 4 miles from Cartersville, and finally 
turns southwest, passing about 2 miles south of Stilesboro and Tay- 
lors ville. 

As noted later, this line between the two groups of formations 
marks, throughout most of its extent, the position of the Cartersville 
fault, which is the most important structural feature of the region. 

The formations of the valley belt, to the west or the Cartersville 
fault, are, in ascending order, the Weisner quartzite, the Beaver 
limestone, the Rome and Conasauga shales, and the Knox dolomite. 
All, except the latter, belong to the Middle and Lower Cambrian; and 
the lower portion of the Knox dolomite should probably also be classed 
with the Cambrian. The principal outcrop of the Weisner quartzite 



forms a nearly continuous band, 15 miles in length, and generally 
from 1 to 3 miles in width, which occupies the central portion of the 
area. The formation is in contact on the east with the Cartersville 
fault; its base is nowhere shown. It consists chiefly of fine-grained 
vitreous quartzite, although it also contains some beds of fine con- 
glomerate and, probably, considerable beds of siliceous shales. The 
latter, however, are usually concealed by the abundant debris from 
the quartzite beds, which tend to break up into angular fragments 
when exposed to atmospheric conditions. Two subordinate outcrops 
of the quartzite occur near the western margin of the area, being- 
brought to the surface by small faults. The thickness of the forma- 
tion is probably 2,000 or 3,000 feet, and ma}^ be considerably more; 
but it can not be accurately determined because of the intense fold- 
ing which its beds have undergone, and the absence of satisfactory 

West of the quartzite is a narrow belt of deep, red soil, usually 
forming a level valley. This is underlain by the Beaver limestone, 
a formation which rarely appears at the surface, its outcrops being 
almost every where covered with a deep mantle of red clay, in which 
occasional masses of vesicular chert are embedded, along with much 
angular quartzite derived from the adjacent quartzite ridges. The 
few natural exposures of this formation which have been observed, 
together with the results of drilling, indicate that it is a gray crystal- 
line dolomitic limestone, becoming shaly in places, and containing 
occasional masses of chert. It is much more readily soluble than the 
purer blue limestone; and its impurities form an abundant residual 
mantle. In addition to the main belt which it forms along the west- 
ern base of the quartzite ridges, it underlies a broad level valley near 
the western margin of the district extending southward from Grass- 
dale to the line of the Atlantic and Western Railroad. The thickness 
of the Beaver limestone has not been accurately determined; but it 
is probably between 800 and 1,200 feet. With these two formations, 
the Weisner quartzite and the Beaver limestone, a majority of the ore 
deposits in this region are associated. 

Overlying the Beaver limestone is a very great thickness of shales, 
constituting the Rome and Conasauga formations; and above the 
shales is the Knox dolomite. The latter is a massive formation from 
3,000 to 5,000 feet in thickness, composed of gray crystalline dolomite, 
with an abundance of chert. In adjacent regions it is intimately 
associated with extensive deposits of iron-ore; but it is unimportant 
in the present connection. 

The rocks on the opposite side of the Cartersville fault, occupying 
the eastern half of the district, present considerable variety in com- 
position and age. A large area, extending from Stamp Creek south- 
ward across the Etowah River, to the Atlantic and Western Railroad, 
is occupied by the Corbin granite, which is, for the most part, a mas- 


sive coarse-grained rock, containing large porphyritic crystals of feld- 
spar (microcline), in a groundmass of plagioclase feldspar, muscovite 
mica, and bine quartz. Some portions of the rock have undergone 
considerable alteration, by which it has been converted into an augen- 
gneiss. This area of Corbin granite at one time probably formed an 
island, since it is surrounded, in part at least, by rocks derived from 
its waste. These are feldspathic conglomerates in which the blue 
quartz and the porphyritic crystals of microcline, which characterize 
the granite, can be readily distinguished. In some places the transi- 
tion from granite to conglomerate is so gradual that it is difficult to 
determine the exact boundary between the two formations. The 
development of the gneissoid structure in the granite evidently took 
place after it was deeply buried by sediment, for the alteration of the 
latter is even more marked than that of the granite itself. Wher- 
ever the granite is not bordered by coarse conglomerate or quartzite 
it is in contact with black graphitic slates, which generally overlie the 
coarser sediments. 

These conglomerates and slates associated with the granite belong 
to the Ocoee series, which reaches its greatest development in eastern 
Tennessee and western North Carolina. No fossils have yet been 
found in the rocks of this series, although man} 7 of them are only 
slightly altered. They contain limestones and slates similar to por- 
tions of the adjacent valley formations, but the latter are always found 
to contain more or less abundant traces of life. In the absence of 
fossil evidence their age can not be definitely determined, but on 
structural evidence, obtained chiefly in Tennessee, they are believed 
to be Lower Cambrian with possibly some pre-Cambrian. 

The rocks of the Ocoee series generally show an increasing degree 
of metamorphism toward the southeast; and within a few miles of 
this region they pass into schists and gneisses, the original form of 
which, whether igneous or sedimentary, can not be readily deter- 
mined. This increased metamorphism toward the southeast is due in 
part to the greater compression which that region has suffered, and 
in part to the presence of considerable bodies of various igneous rocks 
which have been intruded into the sedimentary beds. These intrusive 
rocks present considerable variety in composition, varying from 
extremely basic diabase to acid granites. The most common variety 
is a diorite, which was among the earlier intrusions, and has been 
snbsequently converted for the most part into amphibolite-schist. 
Two belts of this basic schist pass across t lie southeastern corner of 
the district. Its southeastern corner is occupied by the Acworth 
gneiss, which, like the Corbin granite, is probably Archean in age, 
and formed the foundation on which the oldest sediments of the region 
were deposited. 

Structure. — In common with other portions of the southern Appa- 
lachian region, the Cartersville district has been subjected to intense 


compression in a northwest-southeast direction. From evidence 
obtained in adjoining regions, it appears probable that this compres- 
sion, and the subsequent folding, began in early Paleozoic time, and 
continued at intervals up to its culmination at the close of the Car- 
boniferous. It resulted in the formation of folds and faults in the 
valley rocks and in the development of a slaty cleavage or schistose 
structure in the older rocks to the east, while the latter were thrust 
upward and westward relatively to the former, producing the great 
Cartersville fault. The region west of the Cartersville district is 
occupied b} T a broad, gentle syncline of Knox dolomite. This mas- 
sive formation appears to have resisted folding, and to have trans- 
mitted the thrust in such a manner that while its own beds retained 
very nearly their original horizontal position, the beds coming to the 
surface in narrow belts on either side were intensely folded. Thus 
the shales which occupy the western portion of the district are highly 
contorted, and* are doubtless intersected by numerous small faults. 
Also, considerable slaty cleavage has been developed in them. The 
Weisner quartzite likewise resisted folding to some extent, although 
its beds were thrown into the form of an anticline with numerous 
irregular minor folds. The irregularity of the anticline is shown by 
the character of its contact with the overlying limestones to the west. 
In addition to the folding which the quartzite has undergone, it is 
doubtless intersected by numerous faults, the evidence of which is 
seen in its crushed and brecciated condition at many points. Owing 
to the character of the outcrops, however, these faults generally can 
not be located or traced. 

The folding referred to brought about certain mechanical and 
chemical conditions favorable for the deposition of mineral deposits, 
and hence has an important bearing on the economic geology of the 
district. It is frequently observed that the originally compact vitre- 
ous quartzite is converted into a rock somewhat resembling jasper. 
Chert from the overling limestone, under similar conditions, is 
altered in the same manner; and it is often impossible to distinguish 
between the final products of the alteration of rocks originally wholly 
unlike. Portions of the quartzite have been converted into a spongy 
rock, containing innumerable fine cavities lined with small quartz 
crystals and stained with yellow ocher. This form of alteration is 
probably due to the circulation through the rock of thermal waters, 
by which the quartz was taken into solution and in part redeposited, 
along with more or less iron oxide. 

The line marking the Cartersville fault departs in this region from 
its rather regular course across northwestern Georgia, making a dis- 
tinct embayment to the east in passing around the belt of Lower 
Cambrian quartzite and limestone. On either side of this region the 
fault brings the soft slates of the Ocoee series in contact with Cam- 
brian shales of a similar character. The actual plane of contact 


between the formations on opposite sides has been observed at many 
points. The older rocks above always have a well-developed slaty or 
schistose structure, and are but little more altered immediately at the 
fault than elsewhere. The underlying rocks, on the other hand,, are 
much more intensely folded and brecciated immediately at the fault 
than a few feet distant. The fault plane itself is usually marked 
by a bed of breccia, a few inches or feet in thickness, and made 
up of the comminuted fragments of the formations on either side. 
This fault inane dips to the east, usually at angles varying between 
5° and 20°, and is parallel, in a general way, with the cleavage and 
bedding of the rocks on either side. 

The Weisner quartzite varies greatly in thickness within a short 
distance. It has the appearance of a delta formation rather than an 
evenly distributed littoral or marine deposit. North and south of its 
present outcrops in this region it probably becomes very much thin- 
ner, and its local thickening has doubtless influenced the structure in 
this region. Another factor which has been important in producing 
this peculiar structure is the presence of the great mass of granite to 
the east of the fault. This is the only point at which massive rocks 
of this character approach so near the fault line. They are usually 
separated from the western margin of the metamorphic rocks by a 
belt, several miles in width, of readily yielding slates and schists. It 
is evident that the conditions for the formation of a thrust fault of 
great lateral extent are much more favorable in bedded sedimentary 
rocks than in the massive igneous rocks, such as the Corbin granite 
The latter appears to have acted like an immovable buttress against 
which the rocks from the west were thrust. It will readily be under- 
stood that, on account of these massive quartzites on the west and the 
still more massive igneous rocks on the east, this portion of the Car- 
tersville fault differs materially from that to the north and south; and 
further, the reasons will be seen for the very considerable alteration, 
both physical and chemical, in the valley rocks adjacent to the fault. 


The iron ores of the southern Appalachian region fall naturally into 
five distinct groups, as follows: (1) Magnetite, (2) specular hematite, 
(3) red hematite or fossil ore, (4) carbonate or black-band ore, and 
(5) brown hematite or limonite. Only two of these groups occur in 
the Cartersville district, namely, the specular nematite and the brown 
hematite or limonite, and of these, the latter is much the more 

Specular hematite. — This variety of ore occurs at two points in the 
district in sufficient abundance to be mined with profit. One is 
about 2 miles southeast of Warford and the other between Emerson 
and the Etowah River. The ore occurs at both localities as a band 
in the quartzite, and both the ore and the inclosing qua tzite have a 


strongly developed schistose structure. The ore passes into the 
quartzite by a gradual transition, and only the richest parts of the 
bed can be worked. The greater part of it is quite siliceous. Even 
the purer portions of the ore contain many inclusions of white sac- 
charoidal quartz, generally drawn out into long, slender filaments. In 
some cases the iron appears as flattened oolitic grains embedded in a, 
ground mass of white quartzite. It is evident that in these deposits 
the iron existed in the quartzite before the alteration of the latter. 
It may have been in the form of the carbonate or of the hydrous 
oxide, and possibly, in £>art at least, of the sulphide. Some portions 
of the ore contain what may possibly be greatly altered pseudomorphs 
after pyrite. The ore is not appreciably magnetic; is nearly black in 
color and has a bright metallic luster. It is called "gray ore" by the 
miners, to distinguish it from the brown hematites of the district. 

The specular hematite outcrops at short intervals, along a line 
lying a short distance east of the Western and Atlantic Railroad, from 
a point about 1 mile north of Emerson station to the north side of the 
Etowah River. It is possible that this belt extends still farther north, 
so as to include the workings noted near Warford, but outcrops 
have not been noted in the intervening space. South of the Etowah 
River the specular hematite has been worked to some extent, by 
means of pits, open cuts, and a short tunnel, on the properties of the 
Roan and Etowah Iron companies. The ore from these properties 
ranges from 55 to G5 per cent in metallic iron, and at several of the 
pits it falls within the Bessemer limit for phosphorus. The ore 
bodies, however, do not appear to be sufficient in size to justify 
exploitation on a large scale. In many of the pits the silica content 
is high, and no cheap and simple concentrating system is available 
for separating the purer ores from the more siliceous portions. 

Broivn hematiti or limonite. — Several varieties of this ore occur in 
the southern Appalachians, and are more or less distinct in their 
appearance, manner of occurrence, and mode of formation. The 
most important of these are (1) gossan ores, (2) Tertiary gravel ores, 
(3) concentration deposits, and (4-) fault deposits. Only the two 
latter varieties occur in the Cartersville district; but all four of 
the classes occur in the immediate vicinity, and may be briefly 

1. The best-known deposits of gossan ore occur in the Ducktown 
district. As is well known, copper occurs there associated with great 
quantities of pyrrhotite. The latter has been oxidized at the surface 
to limonite, and during the process of oxidation the copper has been 
concentrated at the bottom of the weathered zone, forming the rich 
deposit of "black copper" overlying the unaltered pyrrhotite. The 
gossan ore has a variable depth, down to 50 feet or more, and con- 
sists of soft, porous, ocher-yellow limonite. 

2. During Tertiary time the valley region was reduced very nearly 


to sea level, and in its lower portions, chiefly those underlain by the 
Chiokamauga limestone (the next formation above the Knox dolo- 
mite), swamps were formed which received drainage from the 
adjacent regions, and in which extensive deposits of bog ore were 
formed. When the region was elevated, the limestone areas were 
again reduced more rapidly than the adjacent areas underlain by 
dolomite, and doubtless much of the accumulated iron ore was 
removed by erosion. Around the margins, however, the ore remained 
embedded in the residual clay. Deposits of this character are 
especially abundant in the Rockmart and Cedartown districts, south- 
west of the Cartersville area. These districts comprise a number 
of areas of Chickamauga limestone, surrounded by zones which 
contain large quantities of iron ore. This is usually in the form 
of gravel ore, composed of concretions from the size of shot up 
to a foot or more in diameter, embedded in the residual red clay, 
and associated with more or less chert from the underlying Knox 

3. The brown hematites of the third class, here called concentration 
deposits, constitute the most important deposits of the Cartersville 
district. They may occur wherever a limestone is underlain by an 
insoluble and impervious stratum, such as sandstone or quartzite. 
Favorable conditions for this accumulation occur in northwest Geor- 
gia and Alabama, at the contact of the Lower Carboniferous lime- 
stone with the sandstones which sometimes underlie it, and at the 
contact of the Beaver limestone with the underlying Weisner quartz- 
ite. The Beaver limestone is more readily soluble than the forma- 
tions on either side, and hence, in the erosion of the region, it has 
always formed valleys. At various times these valleys have received 
the drainage, not only from the adjacent quartzite and limestone, but 
probably also from other of the valley formations, and the widely dis- 
seminated iron leached from these formations during the process of 
decay has been transported to the limestone valley and there concen- 
trated upon the underlying impervious quartzite. As the surface of 
the limestone was lowered, chiefly by solution, upon successive eleva- 
tions of the region, remnants of the ore deposits thus formed were left 
resting upon the underlying quartzite and marking elevations at which 
the surface of the limestone had remained for considerable periods. 
These deposits are composed in part of gravel ore and in part of 
masses of considerable size, in some cases reaching many feet in diam- 
eter. Where the large masses of ore preponderate, it is probable that 
they represent replacements of the limestone by iron-bearing solutions 
rather than ordinary bog-ore deposits. When the deposition was by 
direct replacement of limestone below the level of ground water, the 
iron was probably in the form of carbonate, changing to limonite as 
the ground-water level was gradually lowered with the progress of 
erosion. At a few points the limonite deposit has been traced down- 


ward directly into the unchanged carbonate. This is well shown in 
the Sugar Hill deposits, later discussed. From the distribution of the 
ore banks it will be seen that a large proportion of them are located 
near the contact of the Beaver limestone and the Weisner quartzite. 
These generally belong to this class of concentration ores ; and this 
contact is marked by a more or less continuous band of ore deposits. 
The red clay in which they are embedded is chiefly derived from the 
limestone; and the surface is generally covered with fragments of 
quartzite from the higher portions of the quartzite ridges. 

4. As already remarked, the quartzite has been considerably folded 
and is doubtless also intersected by numerous faults of small throw, the 
evidence of the faulting being chiefly the occurrence of breccias. The 
latter usually consist of fine angular fragments of quartzite cemented 
by limonite; and associated with these breccias are often found con- 
siderable deposits of iron ore. These are sometimes irregular deposits 
embedded in the residual material which covers the surface, and are 
not sharply differentiated from the concentration deposits above 
described. In other cases, the ore appears to form well-defined fis- 
sure veins, with distinct walls of the inclosing formation. This is 
notably the case at the Wheeler bank, about 4 miles southeast of Car- 
tersville. The vein is from 12 to 15 feet in width, with occasional off- 
shoots. The inclosing rock is a gray siliceous schist, with some blue 
curly talcose slate and quartz stringers; also occasional bands of 
schistose deldspathic conglomerate. The vein dips east about 80° and 
strikes neatly north and south, parallel with the schistosity of the 
inclosing rock, and with the adjacent Cartersville fault. The ore 
appears in part to have filled an open fissure and in part to have 
replaced the schist, numerous fragments of which remain in the ore 
body. It consists for the most part of geoidal shells, containing many 
cavities with stalactitic and botryoidal forms, which have glazed sur- 
faces showing brilliant iridescent colors. It generally has a fibrous 
structure, and further differs from the concentration deposits in the 
almost complete absence of residual clay associated with the ore. 
This ore body has evidently been deposited subsequent to the devel- 
opment of schistosity in the inclosing rocks, since it shows no evidence 
of movement in the way of brecciation or slickensides. 

At no point in this district has development gone below water level. 
The deposits are generally worked only to a depth permitting direct 
drainage. Hence, the bottoms of the ore bodies are seldom reached. 
Of the depth to which the our classes of deposits enumerated above 
extend, it may be stated (1) that the gossan ores are sharply limited 
by water level; (2) that the Tertiary gravel ores are generally super- 
ficial, the greater part of the deposits being near the surface, below 
which they rarely extend more than 30 feet; (3) that the concentra- 
tion deposits go considerably deeper, and, under favorable conditions, 
may extend to the depth of 100 feet or even more, and (4) that the 


deposits associated with faults and formed in fissures are undoubtedly 
the deepest of all. If, as appears probable, they were formed b} T solu- 
tions ascending from considerable depths, they may extend downward 
several hundred feet, although the character of the ore would doubt- 
less be found to undergo some change with depth, the oxide being 
accompanied by increasing proportions of sulphide and perhaps 

The general belief among the ore miners that certain of these brown 
hematite deposits are stratified, occupjang a definite geologic horizon, 
is, of course, entirely erroneous. Also, the view which has been 
held a that in this and adjoining districts the deposits of brown hema- 
tite follow the outcrops of particular beds rich in iron is almost equally 
erroneous. The present distribution of these deposits, as shown above, 
depends entirely upon the geologic structure which determined chem- 
ical and physical conditions requisite for their deposition. In all cases 
the iron has been transported to a greater or less distance from the 
beds in which it was originally disseminated. The specular hematite 
above described, and the red hematites which occur at various hori- 
zons in the Silurian rocks, belong to an entirely different class of 

The deposits of brown hematite which are at present best exposed, 
and which furnish excellent examples of the type of "concentration 
deposits" described above, are those now worked by the Hurt Iron 
Company at Sugar Hill. The mines are located about 12 miles north- 
east of Cartersville, and 3 miles southeast from Pine Log Village. 
Supplies are obtained and ore is shipped over a branch road which 
leaves the Western and Atlantic tracks at a point about 3 miles west 
of Cartersville. 

Occurrence of ores. — Mining is being carried on in a number of 
large open cuts, which, with natural exposures in the vicinit} 7 , permit 
a good idea of the structural relations of the deposits to be obtained. 
The ore deposits are associated at this point with the upper beds of 
the Weisner quartzite (Cambrian). In the vicinity of the mines, the 
quartzite beds are seen to lie in a series of low folds, cross folded so 
as to form a number of shallow pitching basins. The ore deposits 
occur as a mantle over the impervious quartzite strata, and are 
in turn often overlain by thin beds of talcose slates, which are com- 
monly much decomposed. Taking the Sugar Hill group of mines 
as a whole, their ore deposits seem to occupy a fairly regular strati- 
graphic position. They appear to have originated by a replacement 
of the strata which originally lay between the quartzite and the talcose 
slates, by the deposition of iron from surface or underground waters. 

a Spencer, J. W., Economic resources of the Paleozoic group of Georgia: Geol. Survey of 
Georgia, 1893. 

Bull. 213—03 16 


The strata which have been thus replaced may have been thin beds 
of impure limestone, or other relatively soluble materials. The con- 
centration of the iron-bearing waters at this horizon, and the conse- 
quent deposition of their iron, was favored by the solubility of this 
replaced bed, and the relative imperviousness of both the underlying 
quartzite and the overlying talcose slates. The iron-bearing waters 
were probably, in part, merely surface waters, coining to rest in drain- 
age basins and there depositing their iron, under favorable conditions 
at points where the decay or complete removal of the talcose schists 
gave easy access to the soluble bed. Part of the ore deposition, how- 
ever, may have taken place through the action of iron-bearing waters 
gaining access to the soluble and pervious replaced beds at some 
point where these were exposed, and following down these particular 
beds, which formed good channels of communication, even under the 
areas where the}' were covered by the impervious talcose slates. It 
will be evident that the resulting ore deposits, in the two cases, will 
differ somewhat in extent. If deposited entirely from surface waters, 
the ore deposits could not extend beyond the limits of the drainage 
basin in which they were laid down. If deposited from waters flowing 
underground, acting under the principles of artesian flow, the deposits 
might have a greater extent, reaching under oilier beds, and it the 
underground structure was favorable, extending beyond the surface 
limits of the minor drainage basin. 

The ore deposits in the Sugar Hill group of mines usually vary 
between 5 and 10 feet in thickness, occasionally passing these limits. 
The ore commonly carries 50 to 55 per cent metallic iron, and about 1 
per cent of phosphorus. 


By Arthur Keith. 


Deposits of magnetic iron oxide occur along a line passing through 
Cranberry in a northwest direction. The ore has long been worked 
at Cranberry and produces iron well known for its purity. Beginning 
near Old Fields on North Toe River, the magnetite has been traced 
with small intervals, south of Smoky Gap, through Cranberry, and 
on to Shell Creek in Tennessee. This line of outcrop lies in the 
Cranberry granite, which is in places mashed and metamorphosed so 
as to resemble gneiss, and it is nearly parallel to the boundary of the 
granite and Roan gneiss, a relation which is repeated in other districts 
toward the west. 

At the Cranberry mines open cuts have been made at intervals 
over an area 000 by 300 feet and through a vertical distance of 250 
feet. From these tunnels are run in for considerable distances. The 
ore occurs as a series of lenticular bodies of magnetite in a gangue of 
hornblende, pyroxene, epidote, with a little feldspar and quartz, and 
a few unimportant minerals. The ore and gangue occur as a series 
of great lenses dipping toward the southwest at angles of 45° to 50°, 
about parallel to the planes of schistosity in the gneiss. The ore is 
found in the gangue in the shape of smaller lenses, dipping southwest 
from 40° to 60°. These vary from 50 feet down to a few inches in 
thickness, and are from two to five times as long as they are thick. 
Sometimes the lenses have sharp limits, but usually the gangue and 
ore grade into each other at the contact. Considerable ore is sprinkled 
through the gangue, and more or less gangue is scattered through the 
ore bodies. The ore is very free from the objectionable elements, 
phosphorus and sulphur, though it is not high in iron. It yields an 
average of 42 to 4G per cent of iron with ordinary concentration. 
Considerable trouble is experienced in freeing the ore from the 
gangue before smelting, on account of the tough and refractory nature 
given to the mass by the epidote. 

Because of the occurrence of the ore as a series of lenses the quan- 

(i Abstracted from descriptive text of the Cranberry Geologic Folio, now in press. 



tity is rendered more or less uncertain. Each lens will be worked 
out in time and its place supplied by other lenses, and to what depth 
or distance the occurrences will go on it is quite impossible to state. 
The ore bodies may diminish, they may remain about the same, or 
they may increase. As judged by openings, tests by diamond drill, 
and surface outcrops, the deposit has a length of over a half mile, 
carrying bodies of ore throughout that distance. Large quantities of 
ore have been taken out, far greater quantities are now in sight, and 
there is every reason to expect a large output in the future. 

The minerals composing the ore and gangue were deposited at a 
time much later than the production of the inclosing rock. They are 
also younger than the period of deformation which produced the 
schistose arrangement in the granites. The minerals of the ore deposit 
are only slightly crushed or rearranged, although they arc the same 
varieties which, in adjacent formations, show the greatest metamor- 
phism. The ore deposit, therefore, was not due to original segrega- 
tion from the igneous granite, but is entirely of a secondary nature. 
It may have replaced a preexisting mass of rock by solution and sub- 
stitution of new minerals, or it may have been deposited from solu- 
tion in open spaces in the inclosing formation. This latter result is 
quite unlikely, on account of the great dimensions of the opening 
required by the size of the ore deposit. If the deposit represents a 
substitution of new minerals for old, the latter were either portions 
of the inclosing granite or a mass of a different original character. 
The shape of the ore deposits agrees with the general form taken by 
the smaller intrusive bodies in this region. The minerals composing 
the granite — quartz, mica, and feldspar — are among the least suscep- 
tible to chemical alterations. It is therefore probable that the rock 
replaced by the ore body had a less simple chemical composition. If 
the present minerals represent a recrystallization of those preexisting, 
the original rock might well have been a diabase similar to the Lin- 
ville metadiabase. This rock contains almost exactly the same min- 
erals as the ore deposit, but even the greater alteration through which 
it has passed has not produced anything in the nature of an ore. 
Accordingly, some additional or separate cause must be sought besides 
dynamic altera! ion. An agency fulfilling the conditions, and one thai 
is everywhere at work, is water charged with mineralizing agents. 
This dissolved and perhaps added to the rock minerals and redeposited 
them in favorable places, either in the old or in new chemical combi- 
nations. In this case the deposits have not the size or shape of veins, 
but are discontinuous and lenticular in shape, as above stated. They 
are plainly con trolled and directed by the schistosity of the granite in 
this and many other areas toward the west and southwest. 

There is no indication whether or not the channels through which 
the solution entered corresponded with the schistosity of the granite, 
although such correspondence is probable. In the red feldspathic 


granites near Cranberry small veins and stringers of magnetite are 
found at many places. These may represent deposition from the min- 
eralizing solutions, where there was no body of readily altered rock 
which could have been changed into an ore deposit. Also, northwest 
of Cranberry the gangue minerals and even magnetite are developed 
in the mass of the red granite along more or less mashed zones. 
These perhaps represent the places where alteration was most active; 
that is to to say, the actual channels through which the mineralizing 
solutions passed. 

As to the cause that put into action the mineralizing solution some 
suggestions can be made. In many areas the heated solutions and 
vapors arising from bodies of intrusive rock have produced mineral 
alterations and deposits. As stated above, the magnetite deposits are 
later than the folding movements. That is also true of the Bakers- 
ville gabbro. These intrusive masses are frequent in the area of 
Roan gneiss west and southwest of Cranberry, and the magnetite 
bodies swing around their circumference. It is thus suggested that 
the magnetites are due to alterations begun by the gabbro intrusions. 
Whether true or not in this locality, this explanation does not hold 
for the magnetite deposits in Ashe County, for there are no recent 
igneous rocks in that area. 

Of the source of the iron there is as little evidence. The adjacent 
formations, the Cranberry granite and the Roan gneiss, both carry 
iron chemically combined in the biotite and hornblende. Solution of 
either might furnish the iron. There is, however, no apparent altera- 
tion or diminution of the ferruginous minerals in the adjacent granite. 
From the Roan gneiss iron might more readily have been obtained on 
account of the extreme abundance of hornblende in that formation. 
That the mineralizing solutions passed through these formations at 
more than one epoch is clear from the existence of a band of titan- 
iferous magnetite deposits parallel to and southeast of this band. 
These are as regularly titaniferous as the ores of the Cranberry band 
are free from that mineral. Inasmuch as the two belts are in close 
proximity and each is extensive without overlapping the other, their 
depositing solutions were probably active at different times. Still 
another period of mineralization left its record in the pegmatite veins 
and lenses so common in this region. These, however, were crushed 
and distorted during the folding of the strata, and thus are so much 
older than the magnetite deposits that they can have no origin in 


This ore is found in one locality in this area, on the east side of 
Bull Ruffin Mountain. It occurs in the schistose metarhyolite next 
to a fault plane, and it is rather an impregnation of the schist with 
hematite than a distinct and pure deposit of ore. Little work has 
been done in development of the ore, and its value and amount are 



Iron ore of this nature is found at several points along the south 
slope of Beech Mountain. It is found in a small vein'in black schist, 
which occurs as a narrow band in the Cranberry granite about 2 miles 
long. The ore appears at several places along this line. It has not 
been developed beyond shallow prospecting, so that neither the depth 
nor the extent of the deposit is known. In association with similar 
black schist beds on Big Ridge, a northern spur of Beech Mountain, 
are a number of other veins of specular hematite. These have been 
examined only by test pits. In all of these localities the ores exposed 
are siliceous. The veins arc of small or only moderate thickness, and 
have a steep dip. The course of the veins is nearly east and west, 
and is marked by scattered outcrops and fragments of ore. In the 
same black schist beds at various points northwest of Beech Moun- 
tain these ores are found, indicating a considerable range for the 


Ores of this nature are abundant in the Tennessee district, and 
include limonite and various combinations of the oxide and hydrate 
of iron. They occur as Lumps ami masses in the residual clays of the 
Watauga shale and the Shady limestone, and are most plentiful in 
the northeastern pari of the district. Ores of the Watauga shale are 
siliceous and present all grades between pure limonite and pure chert. 
Masses in this formation at lain a diameter of 6 feet. As a rule they 
are not available on accounl of the silica, and only within 2 or 3 miles 
of Shoun Crossroads have t hey been found sufficiently pure to be used. 
Ores of the Shady limestone are usually very pure, and were worked 
in the old forges for many years. The deposits form two classes, 
masses scattered irregularly through the limestone clay and ores lying 
along the fault planes. The Latter usually contain considerable silica 
in the form of sand grains and fragments of Erwin quartzite, and they 
grade from good ore through ferruginous breccias into ordinary sili- 
ceous and calcareous fault breccias. The deposits in clay are very 
pure and have received the greatest development. Like all deposits 
of this nature, the amount of ore in the clay varies much. In this 
region, however, the ore lumps are distributed with unusual frequency 
and regularity. The lumps attain a size as greal as i> and 3 feet, and 
the deposits have been tested to a depth of 50 feet. The richest and 
most frequent deposits are found in the lower part of the limestone, 
near its junction with the Erwin quartzite. Considerable pyrite is 
found in the upper layers of the quartzite, and may be the source of 
much of the iron. The deposits of ore occupy the S3niclinal basins for 
the most part, and may be due to downward concentration toward the 
bottoms of the folds. This correspondence of structure and ore 
deposits is most striking in Shady Valley just north of the Cranberry 


DURING 1902. 

By C. K. Leith. 

In the early part of the year there was distributed a general paper 
by C. R. Van Ilise on the Iron Ores of the Lake Superior Region, con- 
taining a general account of the geology of the region and of the 
origin of the ores, and accompanied by small scale maps of some of 
the districts. 

There have also been sent to press during the year Monograph 
XLIII, on the Mesabi iron-bearing district of Minnesota, by C. K. 
Leith, and Monograph XLV, on the Vermilion iron-bearing district 
of Minnesota, by J. Morgan Clements. W. S. Bayley has spent the 
year in the preparation of another monograph, on the Menominee 
iron-bearing district of Michigan, which will be published in 1903. 
The work in all of these districts has been directed by C. R. Van 


The Mesabi monograph (XLIII), by C. K. Leith, is a volume of 301 
pages, accompanied by a general map of the range, covering the area 
between Birch Lake and Grand Rapids on a scale of 1 mile to the 
inch, and by 33 plates and 12 figures, including many detail maps 
and sketches. 

The Mesabi iron ores have developed from the secondary alteration 
of a rock composed largely of green ferrous silicate granules, resem- 
bling glauconite, and so called by Spurr, but here shown not to be 
glauconite and called " greenalite." The greenalite granules are sup- 
posed to develop in much the same way as iron carbonates of other 
parts of the Lake Superior region, described by Van Hise, and to owe 
their occurrence in the form of granules to organic agencies. The 
concentration of the ores has consisted essentially in the oxidation, 
under weathering conditions, of the ferrous iron in the greenalite 
granules and the segregation of the iron and silica. The alteration 
of the greenalite and concentration of the ore has occurred through 
the agency of moving underground waters and the ore deposits have 
been localized in places where the circulation has been vigorous. 
Broad, shallow synclines in the iron formation (Upper Huronian) have 
exerted a primary control of the circulation of the underground waters 



concentrating the ores, but other factors, the cross fracturing of the 
formation affording trunk channels for water circulation and the 
ponding of water by impervious slate layers within and above the 
iron formation, have had strong modifying effects on the circulation 
and have locally been dominant. So important are these modifying 
factors and so complex their effect that the ore deposits have most 
irregular shapes and erratic distribution, and it is scarcely possible 
to indicate from the structure of the iron formation an area which is 
more likely than any other to reveal ore on exploration. 

The ore deposits are shallow, seldom exceeding 350 feet in depth, 
but have great horizontal dimensions, sometimes a mile or more. 
The ore bodies come to the rock surface for most of their area, but 
are covered with glacial drift to a depth varying from a few feet to 
100 feet. The rich ore deposits thus far discovered are confined to 
the central part of the district. At the east end of the district the 
ores are hard and magnetic and associated with amphiboles, and have 
not been shown to occur in bodies large enough to warrant mining. 
In the west end of the district some good ore has been found, but 
here for the most part the ores are of low grade and contain abundant 
chert particles resulting from the disintegration of associated chert, 
making it necessary to wash the ores before using them. 

The iron formation is overlain to the south by a thick slate forma- 
tion. Exploration has not yet shown whether or not ore will be found 
beneath this slate, but certain geologic facts indicate small proba- 
bility. The boundary between the slate and iron formation as siiown 
on the geologic map is, because of the heavy covering of glacial drift, 
only approximately correct. Much more exploration will have to be 
done before the true limits of the iron formation on the south can be 
mapped. The iron formation itself contains interbedded slate hiyers 
which closely resemble the slate overlying the iron formation, making 
it difficult in individual areas to determine whether the area should 
be mapped as iron formation or as overlying slate. 

The total tonnage of high-grade ore thus far discovered in the 
Mesabi district has been estimated at from 500,000,000 to 700,000,000 
tons, a common estimate being 000,000,000 tons, of which nearly 70 per 
cent is of Bessemer grade. This tonnage is over twice that of all the 
other Lake Superior iron districts combined. The United States 
Steel Corporation in 1902 owned and controlled 85 per cent or more of 
the Mesabi ore. Shipments from the Mesabi district first began in 1801, 
and in 1902 the shipments were nearly half of the total for the Lake 
Superior region, namely, 13,329,953 tons, and more than one-third of 
the total of the United States. 

The ores are mined in open ruts by steam shovel, or underground 
by either ordinary or " milling "« methods. In 1 902 about 40 per cent 

a Chutes, known as mills, are run from the level of the bottom of the shaft up to the working 
levels. The ore is loosened and dumped into the chute, falling into ears at the bottom, being 
trammed to the shaft and hoisted. 


of the ores was mined by open-pit steam shovel, 46 per cent by ordi- 
nary underground methods, and 7 per cent by " milling." 

When lirst introduced Mesabi ores were considered too soft for 
extensive use in furnace charges, but now they constitute an average 
of 50 per cent of the ore burden, and individual ores may be used in 
percentages as high as 100 per cent. 

The iron and water content of the Mesabi ores is greater than in the 
other ores of the Lake Superior region. The phosphorus in the ores 
(determining their Bessemer or non-Bessemer character) is shown to 
have been introduced into the ores by percolating waters during the 
concentration of the ore and not to be a residual product of alteration. 
The precipitation of phosphorus from percolating waters is believed to 
be connected in some way with aluminous compounds in the ores. 


The Vermilion monograph (XLV), by J. Morgan Clements, is a vol- 
ume of 403 pages, accompanied by a general map of the Vermilion 
range covering the area from west of Tower to Gunflint Lake, an atlas 
of 24 detail maps, and 13 plates and 23 figures in text. 

The iron ores are shown to be confined to the Basement Complex 
or Archean, to be closely associated" with jasper and greenstone, and 
to have been concentrated by underground waters in steep pitching 
troughs formed by the folding of the greenstone. No direct evidence 
of the original source of the ore has been found, but it is believed 
that the iron has developed from an iron carbonate, in this feature 
resembling the old ranges of the Lake Superior region rather than 
the Mesabi range. 

The ores are hard, blue and red hematites, and up to the present 
time have been found in large quantities in only two areas in the 
district — near Soudan and near Ely. The detail maps show iron- 
formation belts at man}^ other places in the district in which explora- 
tion is warranted. 


At the completion of work in the Mesabi district in 1902, C. K. 
Leith, with the direction and assistance of C. R. Van Ilise, took up 
the revision of the published geologic maps of the Marquette, Gogebic, 
and Crystal Falls districts with the jmrpose of preparing for publica- 
tion corrected editions showing the results of the vast amount of 
recent exploration, and with the further purpose of combining the 
geology shown on these maps in a large geologic map of the Lake 
Superior region, including all of the iron districts, to accompany a 
final monograph of Lake Superior geology to be submitted in 11)04 by 
C. R. Van Ilise, with the assistance of C. K. Leith. Many changes 
in the boundaries of the iron formal ions in the differen! districts 


were noted. Facts were collected that seemed to indicate that the 
phosphorus in these districts, as in the Mesabi district, is the result 
of the concentration of the percolating waters rather than a residual 
product, and that the precipitation of the phosphorus from such 
waters may be in some way connected with aluminous compounds in 
the ore, notwithstanding the fact that some of the phosphorus is now 
present in the ores as apatite, as shown by Prof. A. E. Seaman, of 
the Michigan School of Mines. 


Late in the season a visit was made to the new iron-bearing dis- 
trict, the Moose Mountain district, northeast of Lake Superior. Mag- 
netite ore was observed in large quantities. This is the first district 
in which iron ores in large quantity have been discovered in Canada. 
The district in its geologic features resembles the Vermilion of Min- 
nesota more closety than any other district, and because of this 
resemblance the Moose Mountain iron-bearing rocks are supposed to 
be of Archean age, although no structural connection of the two dis- 
1 nets is possible. The ores are closely associated with quartzites and 
graywackes bearing iron pyrites, and alterations of iron pyrites to 
iron ore may be observed on a small scale, and these facts, together 
with the abundance of other sulphide ores in this area, lead us to sus- 
pect that further work may sho*v r llie origin of the iron ores to be in 
some way connected with the iron pyrites. 


By Arthur C. Spencer. 

The deposits of manganese which have thus far been worked in 
Cuba are all located in the vicinity of the city of Santiago, in the 
province of the same name, which is the easternmost on the island. 
The first ore, shipped in 1887, was a picked lot of 50 tons, and in spite 
of adverse conditions in regard to facilities for transportation, the 
output had increased by 1890 to 21,810 tons. From this time up to 
1898 the amount of ore annually mined was not so great, but various 
deposits were discovered and several mines were opened with varying 
success. As many as eight mines, which were worked previous to the 
revolution of 1895-1898, have been visited by the writer. 

The manganese ores of the Santiago region are mixtures in various 
proportions of the common oxides of manganese, probably including 
manganite, pyrolusite, braunite, and wad. The deposits occur in a 
region lying back of and parallel to the Sierra Maestra, between 
Guantanamo on the east and Manzanillo on the west, and in general 
coincident Avith the drainage basins of the Rios Cauto and Guan- 
tanamo. The geologic structure between the latitudes of the two 
cities named is that of a broad synclinal fold, with an east-Avest axis. 
From Cabo Cruz on the Avest to Guantanamo on the east the stratified 
rocks which compose the northern slopes of the Sierra Maestra dip at 
angles of from 10° to 20° toward the depressed area of the interior 
occupied by the Rios Cauto, Guaninicum, and Guantanamo, Avhile 
upon the north side of these drainage basins the strata rise as the 
mountains which occupy the country between them and the north 
coast are approached. The rocks exposed along the crest of the Sierra 
Maestra are coarse, well-stratified volcanic breccias, but upon the 
northern slope these soon jmss beneath strata showing an alternation 
of marine sediments and fine-grained volcanic tuffs, which are in turn 
covered by flows of basalt and still other f ragmental A r olcanic deposits. 

This essentially volcanic series grades into and finally gives place 
lo limestones and other purely marine sediments, as may be well 
observed along the neAv military road which crosses the high range of 
hills north of Santiago Bay, and at Cristo, Avhere the Moroto and 

"Report on a geological reeonnoissanee of Cuba, made under direction of Q-en. Leonard Wood, 
military governor; also Eng. and Min. Jour., August :.':», L903, pp. 62-69. 



Sabanilla Railway crosses the same range in a deep notch or pass. 
On both sides of the railroad south of this pass there are several old 
manganese mines in rocks belonging to the upper part of the mixed 
volcanic and marine series. The manganese was also formerly 
worked near the station of Dos Bocas, several miles west of the 
deposits located south of Cristo, and apparently in rocks occupying 
approximately the same stratigraphic position. The beds exposed in 
these mines are very much disintegrated, and the rock is frequently 
impregnated to a considerable extent by manganese ore. It is varie- 
gated in its coloring, being green with red splotches. It exhibits no 
gritty material, and it appears to have been made up of fragments 
which were originally angular in form. At the Boston mines, located 
between 2 and 3 miles to the east of Cristo, the country rocks are 
limestones and glauconitic greensands, cemented by lime, and both 
of these rocks are found replaced by ore. When decomposed they 
resemble the disintegrated beds south of Cristo. 

In the deposits south of the Cristo divide, between the drainage 
which flows directly to the sea by way of Rio San Juan and the basin 
of the Rio Cauto, which finds its outlet to the west of Cabo Cruz, the 
strata all dip at varying angles toward the north, excepting in such 
instances as they are overturned, when the reversed dips are very 
steep toward the south. Associated with the ore there are large 
amounts of siliceous rock in the form of dense amorphous jasper, or 
bayate, as it is locally called. Traced in a broad way, the bayate 
may be made out to follow the stratification of the bedded rocks, 
along which it occurs in interrupted masses. But studied locally, the 
irregularity of the bayate is such that, with the poor exposures of 
the strata which exist, it would be impossible to say that it did not 
have the form of cross-cutting veins, as sometimes appear. However, 
the interbedded character of the siliceous rock is established with a 
good degree of certainty. Across the stratification the thickness of 
the jasper masses is found to vary from a few inches to 15 or 20 feet, 
while along the bedding they may have a length reaching in some 
cases several hundred feet. 

The ore occurs principally in a very irregular way, filling spaces 
between the jasper and the country rock, but also in the form of veins 
in the masses of jasper, and disseminated through the decomj)osed 
country rock adjacent to the jasper. In the last case the ore frequently 
has the form of nodules arranged in the bedding planes of the parent 
rock, which it seems to have replaced in part. The relations of the 
ore and the jasper are very intimate, and specimens may be found 
in which veinlets of ore penetrate the jasper as though there had 
been molecular replacement of the latter by the former. On the other 
hand, cases may be observed in which the opposite condition seems 
to have obtained, so that the ore w r as replaced by siliceous material 
introduced after the first deposition of the metallic mineral. In gen- 


eral the mode of occurrence is such that both the ore and the associ- 
ated jasper appear to have been introduced in a secondary way after 
the deposition of the strata in which they are found and the original 
substance of which they now replace. The jasper and the oxides of 
manganese are of contemporaneous origin, and for their introduction 
into the strata where they now occur the action of the heated water 
in circulation is suggested. The constitution of the greensand beds 
was evidently favorable for a chemical reaction between their substance 
and the materials held in solution by ascending hot waters, which 
doubtless, originating at a considerable depth, found easy channels 
of outlet through the more porous of the disturbed and upturned 
strata occurring in the region. 

Oilier manganese mines, and in fact the only ones at present in 
operation, lie about 3 miles east of Cristo, and 12 miles to the north- 
east of the same town. The former comprise the Boston group of 
claims already mentioned and the Ysabellita near by, and the latter 
includes the Ponupo mines. Owing to the limited time at the writer's 
disposal it was impossible to sufficiently test the theory formed in the 
field that all of these deposits lie at approximately the same geo- 
logic horizon. There are, however, some facts which tend to sup- 
port this idea. Perhaps the most important of these is the occurrence 
of a band of limestone, composed almost entirely of foraminifera 
belonging to the type Oi'bitoides, just above the ore horizon at four 
distinct and widely separated localities, namely, near the mines cast 
of the railroad south of Cristo, at the Boston mines, at the Ponupo 
mines, and at San Nicolas, about 8 miles west of San Luis, where 
manganese ores also occur in green, disintegrated sandstones. Again, 
in almost all of the places where the strata in which the ores occur 
are exposed, they are exactly similar, being loose, disintegrated sand- 
stones, mostly of a dark green color. At the Boston mines the green, 
decomposed sandstones have been uncovered at a short distance from 
the ore body, and here, though resembling in general appearance the 
sand which occurs with much of the ore, they are found to be made 
up in large part of the shells of a large variety of foraminifera filled 
with glauconite and accompanied by grains of the same mineral to 
which the green color of the sandstone is due. It seemed evident that 
these rocks and the ore-bearing beds were originally of the same 
nature, but that the calcareous shells of the foraminifera had been 
removed from the near neighborhood of the ore deposits by the solu- 
tions which deposited the silica and manganese. A similar removal 
of the calcareous contents may be taken to explain their absence from 
the other localities, where the only strata observed were those in 
close proximity to the ore bodies and jasper. 

The rocks in the region south of Cristo were found to have been 
tilted toward the liQrth, as though they were lying upon the south side 
of a great structural syncline. This, in fact, they do, as more gen- 


eral observations in Santiago province show. The structure in the 
immediate vicinity of the Boston and Ponupo mines is quite dif- 
ferent. These lie well within the great syncline, where the strata 
have been thrown into minor folds, and it is observed that the ore 
deposits in both places occupy the central or axial portion of articlines 
or arches of the strata. The Ysabellita mine is less than a mile from 
the Boston, and appears to be located upon the same arch, but the 
structural relation between this fold and the one at the Ponupo mine 
is not known. Though the altitude of the strata is different, the 
relations of the ore, jasper, and country rock are exactly the same as at 
Cristo, and the deposits have been the result of metasomatic replace- 
ment of calcareous strata by manganiferous minerals and jasper. In 
the case of the Boston, Ysabellita, and Ponupo mines, and probably also 
at San Nicolas, it may be argued that the hot waters to which the 
-replacement is attributed ascended through rissures locally developed 
along the axis of the folds rather than through the strata, as has been 
suggested for the occurrences in the vicinity of Cristo, where the 
stratified formations are standing on end. This would account for the 
local character of the deposits along the folds, as well as the presence 
of undissolved shells and the absence of both jasper and ore in the 
beds of green sand as they rest on the flanks of the arch at the Boston 

In both the Boston and Ysabellita mines the amount of jasper is 
large, and it occurs in large masses, around which the richest ore is 
found, with deposits in which the ore is mixed with rock, dissemi- 
nated locally in the portions of the decomposed greensand or glau- 
conitic rock adjacent to the jasper. Sometimes the ore is found to 
entirely surround the masses of siliceous rock along its contact with 
the country rock. An illustration of this is seen in the Boston mine, 
where a large block of jasper has been worked about on all sides and 
a large amount of ore extracted. Another is seen in the workings of 
the Ysabellita mine. Next to the large mass of jasper a bed of 
loose, sandy material, containing oxide of manganese in the form of 
small nodules arranged along the planes of stratification, extends to a 
distance of not less than 25 feet from the jasper, and the thickness 
of the ore-bearing bed is not less than 20 feet as exposed. 

In this vicinity there are no less than six distinct outcrops of jasper 
in large masses within a radius of about 150 feet, but only one has 
been sufficiently developed to prove the presence of large quantities 
of ore. 

At the Ponupo mine the conditions are quite similar to those at the 
two mines just mentioned. The deposit occupies the center of an 
anticlinal fold, and there are large amounts of jasper, with high-grade 
ore occurring in contact with it, and ores of lower grade, because 
mixed with decomposed rock lying adjacent to it. Here the ore 
extends up to the horizon of the foraminiferal limestone, which it 


has replaced in part, as was well seen upon the north side of the mine. 
The ores in these three mines occur about the summits and slopes of 
knolls which owe their elevation to the durability of the jasper against 
the processes of erosion. This jasper occurs in very irregular masses, 
between which the ore is found in equally irregular pockets, either 
pure, or, as has been stated, mixed with decomposed country rock. 
Frequently the ores are intimately veined or impregnated with streaks 
of jasper, when they become valueless, but as a rule the jasper occurs 
in well-defined nodules, which may be easily separated from the rock, 
which must be mined with the ore. 

The mode of occurrence in all of the localities mentioned is such 
that very large deposits can not be expected. A yield of 100,000 tons 
of first-grade ore from any one mine is estimated as all that can be 
expected in most cases, though if the attempt now being made to con- 
centrate the ores at the Boston mine is successful the marketable out- 
put will be greatly increased. 

The Ponupo mine has been worked on a large scale since the winter 
of 1898. It has standard-gage tracks laid to the ore chutes. A track 
has also recently been completed to the Boston mine, and can readily 
be connected with the Ysabellita. It is from these mines that the 
supply of Cuban manganese will be drawn for some time, though with 
the completion of the Cuba Central Railway a few other mines of 
importance may be developed. The amount of ore which ma}^ be 
anticipated from any one of them will not, however, warrant the 
construction of special tracks of any great length to bring their 
product to the trunk line. 


A number of the principal papers on iron and manganese ores pub- 
lished by the United States Geological Survey, or by members of the 
Survey, are listed below: 

Barus, P. The present technical condition of the steel industry of the United 
States. U. S. Geol. Survey Bulletin No. 25, 85 pp. 1885. (Out of print.) 

Birkinbine, J. American blast-furnace progress. In Mineral Resources U. S. 
for 1883-84, pp. 290-311. 1885. 

The iron ores east of the Mississippi River. In Mineral Resources U. S. 

for 1886, pp. 39-98. 1887. 

The production of iron ores in various parts of the world. In Sixteenth 

Ann. Rept. U. S. Geol. Survey, Pt. Ill, pp. 21-218. 1894. 

Iron ores. In Nineteenth Ann. Rept. U. S. Geol. Survey, Pt. VI, pp. 

23-63. 1898. 

Manganese ores. In Nineteenth Ann. Rept. U. S. Geol. Survey, Pt. 

VI, pp. 91-125. 1898. 

Chisolm, F. F. Iron in the Rocky Mountain division. In Mineral Resources 
U. S. for 1883-84, pp. 281-286. 1885. 

Clements, J. M. The Vermilion iron-bearing district of Minnesota. Mono- 
graph U. S. Geol. Survey Vol. XLV. 463 pp. 1903. 

Clements. J. M., Smyth. H. L., Bayley, W. S.. and Van Hise, C. R. The 
Crystal Falls iron-bearing district of Michigan. Monograph U. S. Geol. Survey 
Vol. XXXVI, 512 pp. 1899. 

Hayes, C. W. Geological relations of the iron ores in the Cartersville district, 
Georgia. In Trans. Am. Inst. Min. Eng., Vol. XXX, pp. 403-419. 1901. 

Irving, R. D., and Van Hise, C. R. The Penokee iron-bearing series of Michi- 
gan and Wisconsin. Monograph U. S. Geol. Survey Vol. XIX, 534 pp. 1892. 

Kemp, J. F. The titaniferous iron ores of the Adirondacks [New York]. In 
Nineteenth Ann. Rept. U. S. Geol. Survey, Pt. III. pp. 377-422. 1899. 

Leith, C. K. The Mesabi iron-bearing district of Minnesota. Monograph 
U. S. Geol. Survey Vol. XLIII. 316 pp. 1903. 

Smith, E. A. The iron ores of Alabama in their geological relations. In Min- 
eral Resources U. S. for 1882, pp. 149-161. 1883. 

Smith, Geo. O. , and Willis, B. The Clealum iron ores, Washington. In Trans. 
Am. Inst. Min. Eng., Vol. XXX, pp. 356-366. 1901. 

Spencer, A. C. The iron ores of Santiago, Cuba. In Eng. and Min. Jour. , Vol. 
LXXII, pp. 633-634. 1901. 

Swank. J. M. The American iron industry from its beginning in 1619 to 1886. 
In Mineral Resources U. S. for 1886, pp. 23-38. 1887. 

Iron and steel and allied industries in all countries. In Sixteenth Ann. 
Rept. U..S. Geol. Survey, Pt. Ill, pp. 219-250. 1894. 

Van Hise, C. R. , Bayley, W. S. , and Smyth, H. L. The Marquette iron-bearing 
district of Michigan, with atlas. Monograph U. S. Geol. Survey Vol. XXVIII, 
608 pp. 1897. 

Weeks, J. D. Manganese. In Mineral Resources U. S. for 1885, pp. 303-356. 1886. 
Manganese. In Mineral Resources U. S. for 1887, pp. 144-167. 1888. 
Manganese. In Mineral Resources U. S. for 1892, pp. 169-226. 1893. 

Yale, C. G. Iron on the Pacific coast. In Mineral Resources U. S. for 1883-84, 
pp. 286-290. 1885. 

In addition to the papers listed above, iron deposits of more or less 
importance have been described in the following geologic folios (for 
location and further details see pp. 11-13) : Nos. 2, 4, 5, 6, 8, 10, 11, 12, 
14, 18, 10, 20, 21, 22, 24, 25, 28, 32, 33, 35, 36, 37, 40, 43, 44, 55, 56, 59, 

61, 62, 64, 70, 72, 78, 82, 83, 84. 


The first paper presented below is a reprint, in slightly condensed 
form, of the introduction to the series of special reports on the coal 
fields of the United States, published in 1902/* It is republished 
here to serve as a summary of the subject for this volume. Fol- 
lowing it will be found two reports, hitherto unpublished, on the 
results of field work b}^ the Survey during 1002 in the coal fields of 
Pennsylvania, Indiana, and Illinois, and of Alaska. Field work was 
also carried on by the Survey in other coal districts, but the results 
are not now in shape for publication. 

The series of reports on United States coal fields above mentioned 
covered the entire coal industry of the country. Owing to the length 
and importance of these reports, it is impossible to present satisfac- 
tory abstracts of them in this bulletin. For detailed information in 
regard to the various fields it will be necessary, therefore, for the 
reader to consult the reports themselves. 


By C. W. Hayes. 


Coal occurs in commercial quantities in 27 of the 47 States and Ter- 
ritories of the United States and in Alaska. The following table 
shows the areas of coal-bearing formations in the several States and 
the rank of the coal-producing States in area and production: 

Rank of coalfields and coal-producing States hi area and production. 

Area of 









in area. 


Coal field, and State or Territory. 




ton at 


cent of 



Anthracite field: 

Sq. miles. 










Atlantic coast Triassic: 






J 57,912 

North Carolina 






"Twenty-second Ann. Rept., Pt. III. For a list of Survey's publication on coal, see p. 294. 

Bull. 213—03 17 257 



Rank of coal fields and coal-producing States in area and production — Cont' d. 

Area of 









in area 


Coal field, and State or Territory. 




ton at 


cent ol 

• Rank 


Northern Appalachian: 

Sq. miles 
15, 8(H) 



4,024, CSS 


29. 58 










West Virginia 

Kentucky (eastern) 





Southern Appalachian: 





















Northern Interior: 










Eastern Interior: 











. 92 

9. 55 



Kentucky (western) 





Western Interior: 











1 . 9:5 


Missouri . 












Indian Territory . 

14, 848 

1 . 728 


















Rocky Mountain: 
South Dakota... 




1. 36 


















Colorado . . . 


New Mexico 







Pacific coast: 















1,050 . 


2,704,665 . 


Areas of lignite-bearing formations are not included in the above 
table. These areas are extensive and their beds of lignite contain a 
vast reserve of valuable fuel, but they are not strictly comparable 
with the higher-grade fuels of the anthracite and bituminous fields. 
There are approximately 56,500 square miles of lignite-bearing forma- 
tions, chiefly Cretaceous, in Montana, the Dakotas, and Wyoming. 
The Tertiary lignite-bearing formations of Alabama, Mississippi, 
Louisiana, Arkansas, and Texas constitute another area of about 
equal extent. The percentage of the areas of coal-bearing formations 
which is probably productive is fairly well known in a few of the 
thoroughly developed fields. In most of the fields, however, the figure 
given is merely an estimate based on incomplete data, while in a few 
the available data are of such a character that an estimate would 
have little if any value. The estimates given are believed to be con- 
servative in eveiy case. It should further be remembered that large 
areas which under present conditions are, for various reasons, classed 
as unproductive, may in the future, under changed conditions, become 
productive. This is the case with those fields in which the coal lies 
too deep to be mined with profit at the present time. 

The true rank of the several coal fields and States in value of the 
available fuel which they contain is not indicated by the table, since 
area of coal-bearing formations and percentage of productive area are 
only two of the factors which determine that value. Other factors 
are the number and thickness of the workable beds of coal, its quality 
as fuel, and the ease with which it can be mined. The data are not 
at present available for bringing these factors into the problem. 

It will be noted that the rank of the States in production is quite 
different from their rank in area of coal-bearing formations. Thus the 
Northern Appalachian field, which ranks third in area, ranks first in 
tonnage and value of product, while the Western Interior field, which 
ranks first in area, is fourth in production. This result is due to sev- 
eral causes, among the most important of which are (1) proximity to 
markets, (2) suitability of the coal to the fuel requirements, (3) rela- 
tive quantity of workable coal per square mile of productive area. 


The coal-bearing formations of the United States range in age from 
Carboniferous to Tertiary. The Carboniferous coals are confined to 
the region east of the one hundredth meridian and the Triassic coals 
to the Atlantic coast. Most of the Cretaceous coal fields lie in the 
Rock}^ Mountain region, between the one hundredth and one hundred 
and fifteenth meridians, and the Tertiary coal fields are between the 
one hundred and twentieth meridian and the Pacific coast. During 
the three great coal- forming periods, therefore, the Carboniferous, 
the Cretaceous, and the Tertiary, there has been a successive west- 
ward shifting of the zone within which conditions favorable for the 


accumulation of coal prevailed. Exceptions to this westward pro- 
gression of the coal-forming zone were the deposition of coal east of 
the Carboniferous fields in Triassic time and south of the Carbonifer- 
ous fields during Tertiary time. 

Carboniferous coal fields. — There are five main subdivisions of the 
Carboniferous coal fields. They may be briefly characterized as 
follows : 

The anthracite field is confined to eastern Pennsylvania and con- 
tains 484 square miles of productive area. It consists of several long, 
narrow, synclinal basins, whose axes are approximately parallel, 
extending in a northeast-southwest direction. They do not differ 
materially from the ordinary synclines of the sharply folded Appa- 
lachian belt, except that they are sufficiently deep to have preserved 
the Coal Measures, which have elsewhere throughout this folded belt 
been generally removed by erosion in the synclines as well as upon 
the anticlines. This field has been thoroughly developed, and a larger 
proportion of its coal has been mined than of any of the other fields. 

The Appalachian field, which has been subdivided into northern 
and southern fields, extends from the northern border of Pennsylvania 
southwestward 850 miles to central Alabama. It embraces portions 
of nine States, and contains, approximately, 70,800 square miles, of 
which about 75 per cent contains workable coal. The eastern margin 
of this field forms the western border of the sharply folded Appala- 
chian belt, and along this margin the strata have suffered some fold- 
ing, a few outlying synclines being nearly or quite separated from the 
main field by steep eroded anticlines. In general, however, the strata 
in this field are either gently undulating or essentially horizontal. 
The formations which make up the Coal Measures are generally 
thickest along the eastern margin of the field, thinning rapidly west- 
ward. In the same direction there is a corresponding decrease in 
number and thickness of the coal beds. These formations consist of 
overlapping lenses of conglomerate, sandstone, shale, coal, and occa- 
sionally limestone, none of which can be traced throughout the entire 
field. Some coal beds, as the Pittsburg and Sewanee, may be identi- 
fied over several thousand square miles, but more generally the work- 
able coal is in local thickenings of beds that are elsewhere worthless. 
For this reason correlations of individual beds in distant parts of the 
field are of doubtful value, although particular horizons may often be 
closely correlated by means of the fossil plants they contain. Some 
portions of the field have been carefully prospected, chiefly those hi 
which development has been most active, but large areas, particularly 
in West Virginia and Kentucky, remote from lines of transportation, 
remain practically unknown. 

The Northern Interior field lies wholly within the State of Michigan 
and has an area of approximately 11,000 square miles. It forms an 
oval area Avhose outlines are imperfectly known, since the region is 


deeply covered by glacial drift. Prospecting is done entirely by 
means of the drill, and on account of the expense involved the pro- 
portion of the field underlain by workable coal can not at present be 
estimated. The strata appear to dip from the margins of the field 
toward its center, the formations thickening in the same direction. 
It is probable that this field was formed in an isolated basin and that 
its strata have never been continuous with those of the fields to the 
southeast and southwest, in Ohio and Indiana. 

The Eastern Interior field embraces portions of Indiana, Illinois, 
and Kentucky, having an area of 58,000 square miles. It forms an 
oval basin whose longer axis extends northwest and southeast, nearly 
at right angles to the axis of the Appalachian field. The strata about 
the margins of the basin have gentle dips toward its center, while in 
the interior of the basin they are practically horizontal. The work- 
able coal beds are confined to the lower portion of the Coal Measures, 
and hence reach the surface in a broad belt about the margins of the 
basin. The development of the field has been confined to this belt, 
although the coal beds are supposed to extend beneath the unproduc- 
tive formations which occupy the surface in the central portion of the 
field. It is estimated that about 55 per cent of the area is productive 
under present conditions, and that a considerable proportion of the 
remainder will become productive when conditions render mining at 
greater depths profitable. The Eastern Interior field is separated 
from the fields on either side by broad, gentle anticlines, from which 
the Coal Measures, which may originally have been continuous, have 
been removed by erosion. 

The Western Interior and Southwestern fields form a practically 
continuous belt of Coal Measure rocks extending from northern Iowa 
southwestward 880 miles to central Texas, and embrace an area of 
94,000 square miles in Iowa, Missouri, Nebraska, Kansas, Indian 
Territory, Arkansas, and Texas. At the eastern margin of these 
fields the underlying older formations reach the surface, while along 
their western margin the Coal Measures pass beneath the Permian 
and other formations of the plains region. 

In the Western Interior field and the northern portion of the South- 
western in Indian Territory, as well as in the portion lying in Texas, 
the strata are nearly horizontal, having a uniform gentle dip to the 
west. In that portion of the field which lies in Arkansas and extends 
westward through the central part of Indian Territory the strata are 
somewhat sharply folded. This belt forms the northern border of the 
intensely folded and faulted Ouachita Mountain zone, whose structure 
corresponds closely with that of the Appalachians. 

Triassic coal fields. — Several small basins of Triassic rocks in the 
Piedmont region of Virginia and North Carolina are coal bearing. 
They contain an aggregate area of about 1,000 square miles. The 
most important of these, and the only ones at present productive, are 


the Richmond and Deep River areas. The strata of these basins rest 
directly upon the crystalline rocks of the Piedmont Plateau. They 
may originally have been continuous and nearly horizontal, but are 
now separated and considerably folded and faulted. They have also 
been invaded by dikes and sheets of igneous rocks, which have at some 
points converted the coal into natural coke or carbonite. While the 
coal is in some places of excellent quality, it shows great irregularity, 
as would be expected from the conditions under which it was depos- 
ited and the movements to which it has subsequently been subjected. 
These fields are chiefly of historic interest, since the first systematic 
coal mining in the United States was carried on within their borders. 

Cretaceous coalfields. — As conditions had been favorable for the 
accumulation of coal in the region east of the one hundreth meridian 
during Carboniferous time, so thej r were favorable for its accumula- 
tion during Cretaceous time in the region between the one hundredth 
and one hundred and fifteenth meridians. Since the deposition of the 
Cretaceoiis formations in this region it has been subjected to the 
action of mountain-building forces and to intense volcanic activity. 
Hence the coal-bearing formations, which may originally have been 
continuous over much of this region, occur in small, irregular basins 
separated by larger areas of elevation and erosion or by areas of igne- 
ous rocks. Although the folding of the strata and their invasion bj^ 
igneous rocks have greatly reduced the area of the coal-bearing forma- 
tions, the quality of the coal has been thereby greatly improved. In 
the extensive undisturbed Cretaceous areas which extend eastward 
from the Rocky Mountains beneath the plains region in Montana, 
Wyoming, and the Dakotas, there are numerous beds of lignite, while 
the same horizons on the flanks of the mountains yield high-grade 
bituminous coal. 

The Cretaceous coal fields are included within a belt that extends 
from the Canadian boundary southeastward for a distance of 1,200 
miles. Its axis coincides with the main range of the Rocky Moun- 
tains, but includes also numerous outlying ranges. Its greatest 
breadth is about 500 miles. It embraces portions of Montana, South 
Dakota, Wyoming, Colorado, Utah, and New Mexico. Mr. Storrs has 
described 45 separate areas within this belt, having an aggregate extent 
of 43,010 square miles/' All of these areas are known to contain work- 
able coal, but many of them are undeveloped and practically unex- 
plored, so that estimates of the productive area are not by any means 

Two small areas of Cretaceous coal-bearing formations in western 
Texas properly belong with the Rocky Mountain fields. The west- 
ernmost of these is the San Carlos coal field, in El Paso County. 
Considerable outlay has been made here in development, but all the 

a Twenty-second Ann. Eept. U. S. Geol. Survey, Pt, III, p. 422. 


coal thus far discovered is a low-grade fuel, and the field is not now 
producing. The Eagle Pass field is much the larger and more iinpor- 
1 taut of the two, and contains some coal of excellent quality. It 
extends from the northern border of Uvalde County about 75 miles 
southwestward to the Rio Grande, and beyond the international 
boundary expands to a broad area in Mexico. The strata have been 
considerably disturbed, and probably only a small proportion of the 
field will prove to be productive. 

Practically all the available information concerning these Texas 
Cretaceous coal fields is contained in a report by T. WaylandVaughan, 
entitled Reconnaissance in the Rio Grande coal fields of Texas: Bull. 
IT. S. Geol. Survey No. 164, 1900. 

Tertiary coalfields. — The Tertiaiy formations in various parts of 
the United States contain a large amount of vegetable organic matter 
which, in many places, forms beds of lignite. In a few places near 
the Pacific coast conditions have been favorable for the conversion of 
this lignite into true coal. The most important deposits of this Ter- 
tiary coal are in Washington. Here the folding of the inclosing 
strata and the intrusion of igneous rocks have converted the lignite 
into coal of fair quality. Similar conditions have prevailed at a few 
points in the extreme western portion of Oregon and in central and 
southern California. The productive fields are all small and have a 
total area of about 1,000 square miles. How much of this is produc- 
tive has not yet been determined, even approximately, except in a 
few of the most thoroughly developed basins. As in the Rocky Moun- 
tain Cretaceous fields, the coal beds show great variability in thick- 
ness and character, and mining is attended by considerable difficulty, 
owing to the disturbed condition of the strata. 

In addition to the coal-bearing Tertiary areas of the Pacific coast, 
large areas of Tertiary formations occur in the southern portion of 
the United States, which contain extensive beds of lignite. These 
Tertiary lignites contain a large amount of fuel which will doubtless 
some time be utilized. Beginning at the Georgia- Alabama line, a nar- 
row belt of lignite-bearing formations extends westward nearly to the 
Mississippi River. West of the Mississippi the same formations 
occupy a much broader belt, extending from Little Rock southwest- 
ward through Arkansas, Louisiana, and Texas. The boundaries of 
these areas are quite indefinite, owing to the presence of later deposits, 
and probably only a small proportion of the area contains lignite beds 
of sufficient thickness and purity to be utilized. 


The various fuel requirements call for coals of varying composition, 
and the adaptability of any coal to a particular purpose is determined 
largely by the relative abundance of the several fuel constituents. 


These consist of the volatile hydrocarbons and of the nonvolatile or 
fixed carbon. This relation is expressed by the fuel ratio, a quantity 
obtained by dividing the percentage of fixed carbon by the percentage 
of the volatile combustible constituents of the coal. In general the 
fuel value or heating power increases with the increase of the fuel 
ratio, since more heat is developed in the combustion of carbon than 
of the hydrocarbon compounds. This increase in fuel value, how- 
ever, continues only to a certain point, beyond which the difficulty of 
effecting combustion more than makes up for the greater amount of 
heat evolved. Thus the graphitic anthracite of the Rhode Island 
field can not properly be regarded as a fuel, since the percentage of 
volatile constituents is so small that these have to be supplied by. the 
addition of another coal before it will burn. 

In addition to its fuel constituents, a coal contains others which are 
nonessential. The most important of these are water and ash. The 
former not only replaces an equal weight of combustible matter but 
also absorbs heat in its volatilization. An excessive amount of water, 
therefore, detracts seriously from the fuel value of a coal. Its pres- 
ence is further detrimental in causing the coal to break up into fine 
particles as it dries out. The amount of water generally varies 
inversely as the fuel ratio, being less than 1 per cent in some anthra- 
cites and from 15 to 25 per cent in lignites. 

The ash simply occupies the place of combustible matter and is in 
general purely negative in its influence on the fuel. When very 
abundant it may seriously retard combustion, and Avhen it contains 
easily fusible constituents it may become a positive detriment by 
forming clinker on the grate bars. Sulphur is detrimental in a steam- 
ing fuel chiefly by reason of the corrosive effect that its products of 
combustion exert on iron surfaces with which they come in contact. 

For most metallurgical purposes it is essential that the coal should 
be relatively free from certain injurious constituents, such as sulphur 
and phosphorus. 

The amounts of water and ash which a coal contains are not shown 
by its fuel ratio, and hence this does not serve to indicate its fuel value 
so much as its adaptability for specific purposes. Thus it is evident 
that for gas-producing purposes a coal should be chosen having a 
large proportion of volatile constituents; in other words, a Ioav fuel 

The coking quality of a coal depends on conditions which are in 
a measure independent of its chemical composition, although coking 
coals do not have a very wide range in fuel ratios, which generally 
fall between 1. 20 and 2. 50. By no means all coals will coke, however, 
whose ratios fall between these limits. 

The coal of the Carboniferous fields considered as a whole show a 
decrease in their fuel ratios from east to west. In the Rhode Island 
field the coal has suffered so high a degree of metamorphism that it 


has passed the anthracite stage and has been partially converted into 
graphite, practically all the volatile compounds having been driven 
off. The Pennsylvania anthracite has fuel ratios varying within 
rather wide limits. In the analyses accompanying Mr. Stoek's paper a 
the maximum is 27 and the minimum 5.11, though most of the samples 
analyzed fall between 9 and 22, the average of 10 analyses being 14.11. 

Within a narrow belt along the eastern margin of the northern 
Appalachian field the coal is relatively hard and high in carbon, form- 
ing an intermediate variety between the true anthracite on the east 
and the true bituminous on the west. The fuel ratios within this belt 
are generally between 3 and 5. 

In the greater part of the Appalachian field the coals have fuel ratios 
ranging from 1 to 3, and as a rule the ratios are higher in the north- 
ern and eastern portions of the field as compared with the southern 
and western portions. There are, however, many exceptions to this 

The field presents certain well-marked types of coal which for par- 
ticular purposes are regarded as the standard fuels. Thus the coal of 
the Pittsburg bed, in the Connellsville district, is usually taken as 
the standard with which other coking coals are compared. In the 
same way the Pocahontas coal may be considered a standard steam- 
ing fuel. Small areas occur in this field containing special varieties 
of coal, such as splint, cannel, block, etc. , which are particularly well 
suited for certain purposes — as gas-making, domestic, and locomotive 

The Northern Interior field contains only bituminous coal, which 
forms a fair steaming fuel, though it is inferior to most of the Appa- 
lachian coals. It generally contains a high percentage of ash and 
sulphur. Its fuel ratios vary from about 1.13 to 1.63, the average 
of 8 representative analyses given in Dr. Lane's paper 6 being 1.40. 

Three varieties of coal occur in the Eastern Interior field. By far 
the largest part of the coal mined is soft bituminous, making a good 
steam fuel. In a belt along the eastern margins of the field in Indiana 
is a variety known as block coal, which differs from the ordinary 
bituminous in its physical characteristics rather than in chemical 
composition. It is especially well adapted for domestic fuel. In the 
Kentucky portion of the field are numerous small areas of cannel coal, 
particularly valuable for gas making and domestic purposes. The 
means of the fuel ratios obtained from a large number are as follows: 
For Indiana coals, 1.30; Kentucky, 1.57, and Illinois, 1.71. 

The coal of the Western Interior field is fairly uniform in compo- 
sition, having an average fuel ratio of about 1.30 and forming a fair 
steaming fuel. In the Southwestern field considerable more diversity 
is found, the coal varying from soft bituminous, with a fuel ratio of 

a Twenty-second Ann. Rept. U. S. Ueol. Survey, Pt. Ill, p. 73. &Ibid., p. 81)7. 



1.14 in northern Texas, to a semianthracite in Arkansas, with a fuel 
ratio of nearly 9. The range in character of the coals in this field is 
shown in the accompanying table : 

Table showing fuel ratio* of coals in flic Southwestern field. 



Indian Territory : 
Bituminous . 

North Texas: 


Number of 




fuel ratio. 

5. 04 
3. 51 

1 . 26 


Maximum ' Mean fuel 
fuel ratio. ratio. 


5. 22 

5. 79 

2. 68 


The Atlantic coasl Triassic <•< >al closely resembles the Carboniferous 
coals of the Appalachian field, but is generally higher in ash and 
sulphur. In the Richmond area the fuel ratios range from 1.8 to 3.4, 
the average of "analyses given by Mr. Woodworth being 2.4.° In the 
Deej) River area they range from 1.6 to 3, the average of 17 analyses 
being 2.11. 

In the Rocky Mountain and Pacific fields the coal presents very 
great diversity in character, the same basin sometimes containing all 
the intermediate varieties between Lignite, with a fuel ratio less than 
1, and anthracite with a ratio of 20 or more. These abrupt changes 
in chemical composition and physical properties are due to the vary- 
ing degrees of alteration which the coal lias undergone. The altera- 
tion is produced by the pressure due to the weight of overlying strata 
or to the folding of the strata by mountain-building forces and by the 
metamorphism of intrusive igneous rocks. The first of these agen- 
cies, vertical pressure, is least effective, but most widespread in its 
effects; the second, lateral pressure, is more effective and relatively 
local, while the third, intrusion, produces effects which are extremely 
localized and correspondingly intense. As a result of these condi- 
tions the coal of the plains region is largely lignite, although the 
lowest beds, those which have been most deeply buried, approach 
most nearly to true coal. Along the flanks of the mountains and in 
the interior basins, where the inclosing strata have been moderately 
folded, the coal is chiefly bituminous. In the same regions more 
intense folding and the intrusion of igneous rocks have converted the 
bituminous coal into seinibituminous or anthracite. 

"Twenty-second Ann. Rept. U. S. Geol. Survey, Pt. Ill, p. 37. 



The first development of the several coal fields of the United States 
las been in response to the fuel demands of adjoining regions, while 
m abundant fuel supply has determined the location of many indus- 
trial establishments, which have in turn greatly increased the demand. 
The tonnage of coal produced in the various coal fields, as shown in 
the table on p. 257, is not proportional to their area, but depends on 
other conditions, such as transportation facilities, extent of markets, 
and character of the fuel. The largest output in proportion to area 
|is in the Pennsylvania anthracite field, where 118,528 tons were pro- 
duced in 1800 for each square mile of productive area. This large 
output is due to the superiority of anthracite as a domestic and loco- 
motive fuel and the density of the population in regions adjacent to 
this field. The distribution of the anthracite product to the various 
States and the extent to which it competes with the product of other 
fields are shown in Mr. Stoek's paper. a 

Owing to its location and the excellent character of its coal, the 
Northern Appalachian field controls the market for bituminous coal 
in the Eastern States, coming in competition in the northeastern por- 
tion of this territory only with the Nova Scotian field. It is the near- 
est of the large bituminous fields to the seaboard, and will therefore 
supply a large proportion of the coal which must be mined to meet 
the growing demands of the export trade. Its coal reaches the sea- 
ports between New York and Norfolk by a number of direct railroad 
lines, the most important of which are the Pennsylvania, Baltimore 
and Ohio, Chesapeake and Ohio, and Norfolk and Western. 

The Southern Appalachian field supplies the South Atlantic and 
Gulf States as far west as the Mississippi. Its southern portion is 
almost as near the seaboard as the Northern Appalachian field, and it 
will in time support a large export trade, particularly to Central and 
South American ports, and on the completion of an isthmian canal to 
Pacific coast ports also. 

Appalachian coal has an outlet to the West by way of the Great 
Lakes, the Ohio River, and numerous trunk-line railroads. Lake 
transportation is interrupted in winter, but during the summer season 
the Northern Appalachian field supplies most of the markets on the 
Great Lakes, competing with the nearer Northern and Eastern Interior 
fields. By means of the Ohio River the Northern Appalachian field 
supplies adjacent portions of Ohio, Kentucky, and Indiana, as well 
as markets along the Lower Mississippi, where it competes with the 
Southern Appalachian field. 

The markets for the coal of the Northern Interior field are chiefly 
within the field itself and in the immediately adjoining region. A 

"Twenty-second Ann. Rept. U. S. Geol. Survey, Pt. Ill, p. L03. 


small amount finds a market in the northern peninsula of Michigan 
and in Wisconsin. The coal of this field is inferior to that of Penn- 
sylvania and Ohio, and can compete with the latter only when it has 
a decided advantage in the matter of freights. 

The markets of the Eastern Interior field are also chiefly within its 
own limits and in immediately adjacent regions. It supplies the 
Chicago market in part and also some territory to the northwest and 
southwest. It occupies a central position among the Carboniferous 
coal fields, and its product comes in competition with that from all 
the others. It supplies the markets westward to the margin of the 
Western Interior field, but goes eastward only a short distance into 
the region which separates it from the Appalachian field, where it 
competes not only with the better coal from the latter field, but also 
with the cheap fuel supplied by the natural gas fields of Ohio, Indiana, 
and Kentucky. 

The Western Interior field supplies the markets within its own 
borders and toward the north and west, where it comes in competi- 
tion with the Rocky Mountain fields. 

The Southwestern field supplies the markets in a large territory 
toward the south and west, in which it had little competition until the 
development of the California and Texas oil fields made liquid fuel 
available. Practically all the coal used by the Southern transconti- 
nental railroads, as well as the Texas roads, comes from the north 
Texas and Indian Territory fields. The hard coals of the Arkansas 
field supply an extensive region west of the Mississippi River with 
a high-grade domestic fuel, which bears a relation to the neighbor- 
ing soft coals somewhat similar to that borne by the Pennsylvania 
anthracite to the Appalachian bituminous coals. 

Considering the entire region between the Appalachian coal field 
and the Rocky Mountain fields, there is observed a general westward 
movement of the coal. Thus the product of the Western Interior 
field goes west almost exclusively, that of the Eastern Interior field 
goes west to and within the borders of the Western Interior field, 
while the Appalachian coal goes west across both the Eastern and 
Western Interior fields and beyond the territory of the latter, com- 
peting with the Rocky Mountain coals to some extent. This west- 
ward tendency is due chiefly to the higher grade of the Eastern coals, 
but in part also to the fact that railroad freight rates are generally 
lower westward than eastward; water transportation also favors the 
westward rather than the eastward movement of coal. 

The region west of the one hundredth meridian, which constitutes 
about half the area of the United States exclusive of Alaska and the 
other outlying possessions, contains less than 20 per cent of the coal 
fields. The largest area entirely without coal lies between the Rocky 
Mountains and the Pacific coast. This, however, is a region in which 


tin* population is scanty and the fuel requirements are consequently 
small. The Pacific coast markets are supplied chiefly by the Wash- 
ington fields, though considerable coal comes from the Nanaimo dis- 
trict in British Columbia, and some also from England as ballast in 
grain vessels, and from Australia as a return cargo. 

The development of the coal resources of Alaska is as yet in the 
experimental stage. A local fuel supply is of the greatest importance 
to this territory, and the present indications are that such a supply 
will be furnished by some of the fields now known or others not yet 
discovered. a 

a Practically all the information at present available concerning these Alaskan coal fields was 
summarized by Mr Brooks in the Twenty-second Ann. Rept. U. S. Geol. Survey, Pt. Ill, pp. 


By M. R. Campbell. 


During the past three years the United States Geological Survey, in 
cooperation with the State, has been engaged in a geologic survey of 
the bituminous coal field of Pennsvlvania. The region is one in 
which considerable geologic work has already been done, and con- 
sequently particular attention has been paid to those features which 
had received least attention in the previous work. 

In this region the feature of greatest economic importance is coal, 
but petroleum, natural gas, and clay have each come to be recog- 
nized as second in value only to the great coal beds which have made 
this part of the State famous. Inasmuch as the accumulations of 
oil and gas are directly influenced by the geologic structure of the 
region, and since the economical mining of coal and clay also depends 
upon the same element, it was decided to give most attention to the 
working out in detail of the form and dimensions of the folds which 
traverse the strata in the bituminous coal field. As is well known, 
the rocks of the northern end of this field are crumpled into long, nar- 
row folds which traverse t he basin along lines rudely parallel with the 
Allegheny front and gradually decrease in magnitude from east to 
west and also from the point of the basin tow 7 ard its center in the 
southwestern corner of the State. Although these facts have long been 
understood, the exact form and irregularities of these folds have never 
been accurately determined. 

Since the geologic structure is based upon very accurate contour 
maps, in which the vertical element is generally ascertained with a 
spirit level, the determination of the attitude of the beds is a com- 
paratively easy matter. Some particularly prominent bed was selected 
as the reference stratum, and its altitude was determined at a great 
many points. From these collected data contours of equal elevation 
were drawn upon the surface of the stratum so selected, and by this 
means the size and shape of the folds are made manifest. 

Aside from this structure work, the outcrops of the coal were care- 
fully studied and correlated, and they are represented on the geologic 
maps by means of heavy lines, which show the extent of their known 
outcrops and the position which they occupy in the hillsides. 



Up to the present time six 15-minute quadrangles have been sur- 
veyed in the southwestern part of the State, where the great Pittsburg 
coal bed outcrops. In this territory coal is by far the most important 
economic factor. The area so far snrvej^ed covers nearly the whole 
of the celebrated Connellsville coke field, a portion of the gas coal 
field of the Irwin or Port Royal basin, and much of the territory 
along Monongahela and Youghiogheny rivers, in which the coal is 
mined for fuel only. The determination of the geologic structure in 
this field is of the utmost importance to coal operators, for their mines 
must be developed in accordance with it, and for this purpose alone 
the representation of the structure by means of contour lines is worth 
many times the cost of the work. 

In this part of the field there are a number of coals higher in the 
series than the great Pittsburg bed, but they are not utilized at 
present, and presumably the} 7 will not be until the great coal bed 
beneath them is exhausted. Of these coals the more important are the 
Redstone, lying from 50 to 80 feet above the Pittsburg; the Sewickley, 
at about 120 feet, and the Waynesburg coal, at from 330 to 400 feet. 
The last-mentioned coal is the thickest bed above the Pittsburg hori- 
zon, but it is generally so full of impurities that its value is not so 
great as that of some of the smaller beds. 

Below the Pittsburg coal there are several beds of coal in the Alle- 
gheny measures, but they probably will not be utilized until the 
better coal is exhausted. The most important of these beds is the 
Upper Freerjort, which lies at the top of the Allegheny formation. 
Along the west foot of Chestnut Ridge this bed attains a great aggre- 
gate thickness, but it is so badly broken by shale partings that it is 
expensive to mine, and the fuel when mined is of inferior quality. 

Associated witli the coal beds of the Allegheny formation are some 
valuable deposits of fire clay, which are being worked to some extent 
along the Youghiogheny River and on Chestnut Ridge. These clays 
are highly refractory and of great importance in the coke regions, 
where the consumption of fire brick in the building of ovens is 

The territory surveyed in Monongahela Vallej 7 includes two or three 
prominent gas fields and a few very small pools of oil. The largest 
gas fields are located along the crest of the Bellevernon or Waynes- 
burg anticline. They have two points of development — one near 
Waynesburg, in Greene County, and the other where 1 he axis crosses 
the Monongahela River near Bellevernon. A small but very produc- 
tive field has lately been developed upon the Fayette anticline in 
Fayette County, just west of Uniontown. These gas fields a re usually 
found upon the crests of the anticlines, and it is possible that they 
may be extended along the axial lines. The highest point of the Fay- 
ette anticline, near Jacobs Creek, has never been tested by the drill, 


and it is possible that a new field may be developed at this point. 
From a structural standpoint it seems to be a verj^ promising field, 
and it is to be hoped that before long the drill will be put down in 
this region. 

The quadrangles surveyed in this part of the field are the Union- 
town, Masontown, Brownsville, Connellsville, Latrobe, and Waynes- 
burg. The work on the first two quadrangles has been completed, 
and the results are published in the Masontown-Uniontown folio. 
The Brownsville and Connellsville will likewise be published together, 
and will soon be ready for distribution. The reports on the Waynes- 
burg and Latrobe have not yet been submitted, and it will be some 
time before they are published. 


Regular areal surveys have also been carried on in the Allegheny 
Valley and in territory adjacent on the east. This includes the Kit- 
tanning, Rural Valley, Eldersridge, and Indiana quadrangles, and is 
located mainly in Armstrong and Indiana counties, but includes also 
a narrow strip of the eastern part of Butler County. 

So far as the stratigraphy is concerned the work is almost identical 
with that of previous surveys. No marked differences occur, except 
that in places extensive developments have taken place in late years, 
and some of the coal beds may be traced beneath the surface with 
much more certainty than was possible at the time of the other sur- 
veys of the region. From an economic standpoint the Upper Freeport 
and the Lower Kittanning coal beds are the most important strati- 
graphic features, and their underlying fire clays are also of great 
value. They have a wide distribution over this territory, and they 
are worked along the Allegheny River, Redbank and Cowanshannock 
creeks, and on the Kiskiminitas River. 

The key rocks in this part of the basin are not so good as they are 
in the Monongahela Valley, and consequently folds have not been so 
definitely located as in the Monongahela Valley. The principal work 
of the present survey is the determination of the structure, and the 
results are very different from those contained in the published 

The opinion is prevalent among oil men in this region that the pools 
of oil bear no definite relation to the geologic structure. As deter- 
mined by the second geological survey, the structures in the vicinity 
of Bradys Bend trend regularly about 35° E,, while the oil pools gen- 
erally extend either in an east- west direction, or nearly at right angles 
to this, in a north-south direction. It is manifest that it is impossible 
to harmonize these supposed facts, and consequently it was natural 
for the oil men to arrive at their conclusion that the accumulations of 
oil bear little or no relation to the geologic structure. 

Oil does not occur in the eastern part of the territory, but the prin- 


cipal anticlinal folds show some extensive fields of gas. The exten- 
sions of these fields are always along the crest of the anticlines, and 
the gas men soon found that the folds as previously mapped are incor- 
rect. Instead of coming to the conclusion that the gas fields bear no 
relation to the structure, they at once satisfied themselves that the 
previous determination of the structure was inaccurate. 

The areal mapping of the territory shows conclusively that the gas 
men are correct in their conclusions, and that when the structure of 
the oil field is correctly represented it is entirely in harmony with the 
location of the oil pools. 

One of the most pronounced changes in the interpretation of this 
region is in what was formerly called the Bradys Bend anticline. 
This was supposed to cross the river at the mouth of Redbank Creek 
and to extend in a straight line along a course about north 35° E. 
The present work shows that the location of this anticline near the 
Butler County line is correct, but instead of crossing the river at the 
mouth of Redbank Creek it swings sharply to the east and crosses 
the river just above the mouth of Mahoning Creek, corresponding at 
that point with the anticline formerly known as the Kellersburg, and 
extending across Redbank Creek on the line formerly supposed to 
represent Anthonys Bend anticline. In other words, the anticlines 
formerly designated Bradys Bend, Kellersburg, and Anthonys Bend 
are all on the same fold. The synclinal basin west of Bradys Bend 
anticline shows a corresponding swing to the east and agrees approx- 
imately with the Lawsonham syncline, as previously determined. 
The abrupt bend in this synclinal basin gives strikes nearly east and 
west in the vicinity of Bradys Bend and also nearly north and south 
on the Butler County line. This is in perfect agreement with the 
trend of the oil pools in this region, and is conclusive proof that when 
the structure is well understood it may be used as a guide in extend- 
ing oil operations. 

The Fairmount syncline was fairly well determined in previous sur- 
veys, except that in the vicinity of Mahoning Creek it bifurcates and 
the right branch swings to the east along the creek and replaces what 
was formerly called the Leechburg syncline. This change has no 
direct effect on any economic product, but it shows that the previous 
determination of straight axes is very misleading. 

The most important change in the eastern part of Armstrong County 
is in the anticline which lies next east to the Fairmount syncline. In 
previous work this had been broken up and received different names; 
along Crooked Creek and Kiskiminitas River it was known as the 
Bagdad anticline, while on Pine and Mahoning creeks it was called 
Greendale anticline. These two folds are now known to be continuous, 
and instead of extending in a straight line to the northeast after 
crossing Pine Creek, it swings sharply to the right in harmony with 

Bull. 213—03 18 


the right fork of the Fair mount syncline, and at the crossing of Mahon- 
ing Creek corresponds with what was formerly known as the Glade 
Run anticline. We have, then, instead of the Bagdad, Greendale, and 
Glade Run anticlines one continuous fold which will probably receive 
the name of the Greendale anticline. This eastward swing of the 
anticline between Pine and Mahoning creeks had been determined by 
the gas men previous to the present survey, but it had never been 
mapped, and consequently its position is not generally known. 

The data concerning the great synclinal basin east of the Greendale 
anticline have not yet been worked up, and consequently it is impos- 
sible to say what are the details of structure in this broad basin. 

In the southern part of Armstrong and Indiana counties, errors 
have been found in the former determination of the position of the 
axes. Heretofore the Roaring Run anticline was not supposed to 
extend to the north much beyond the crossing of Crooked Creek. In 
the course of the present work this fold was found to cross Crooked 
Creek and then swing sharply to the east and to enter Indiana County 
along the South Fork of Plum Creek. 

One of the most pronounced errors in the previous determinations 
of the structure of this region occurs in Indiana County, where numer- 
ous diamond-drill holes show that there is a pronounced syncline 
through the town of Indiana, where formerly an anticline was supposed 
to exist." The first anticline west of Chestnut Ridge is one of the 
most pronounced folds of the region. It has been traced continuously 
from the AVest Virginia line to Coneinaugh River, and in previous 
reports it was extended across Indiana County, and was given the 
name of the Indiana anticline. This name has been extensively used 
by several writers, and is in current use to-day to designate the long 
anticlinal fold previously described. The present work has demon- 
strated clearly that this anticlinal fold dies out near the Conemaugh 
River, and the two synclinal basins on either side coalesce and extend 
beyond the town of Indiana along a continuation of the same line 
that the anticline follows farther south. 

The direct results obtained during the course of this survey in the 
Allegheny Valley are regarded as the most important contribution to 
the economic geology of the coal field that has appeared during the 
present decade. When rightly understood they are of the greatest 
importance to oil and gas men and of nearly equal value to coal 

The amount of data required for such work is enormous, and con- 
sequently the work of office preparation is necessarily slow. The 
maps of the Indiana folio are now being engraved, and before many 
months they will be ready for distribution. The reports on the other 
quadrangles are not so far advanced, but will be published as soon as 
it is possible to assemble the data and engrave the maps and print 

"Richardson, G. B., The misnamed Indiana anticline: Jour. Geol., Vol. X, pp. 700-702. 



Only a small territory has been surveyed in Beaver Valley. This 
territory is included in the Beaver quadrangle, which lies mainly in 
Beaver County. The structure and stratigraphie results differ very 
little from those obtained in previous surveys. The principal point 
of improvement is in the excellent topographic map upon which the 
material will be shown and in the great detail with which the stratig- 
raphy was worked. The Upper Freeport and Lower Kittanning coal 
beds are the principal sources of fuel in this region, but the most 
valuable deposits are probably the fire clays which are associated 
with the Kittanning group of coals. These are widely developed 
geographically and have been worked for a great many years. They 
have given the region prominence in the manufacture of clay pro- 
ducts, but not all of the raw material has been derived from the local 
beds. Some oil and gas occurs in this region, but the fields are not 
large and the wells are generally small producers. 


By Arthur J. Collier. 


The coal beds of the Alaskan part of the Yukon Basin occur in soft 
sandstones and shales, with intercalated beds of conglomerate. These 
beds are in part in the Nulato series of the Upper Cretaceous and 
in part in the Kenai series of the Eocene. The two series are appar- 
ently conformable and have strikingly similar lithologic characters. 
They can be separated only after close stral [graphic and paleontologie 
study, and hence it is not now possible to state definitely what part 
of the coals are Cretaceous and what part are Eocene 

For the purpose of discussing its coal resources the Yukon Basin of 
Alaska may be divided into three provinces. The Upper Yukon 
includes that part of the valley lying between the international 
boundary and the great lowland known as the Yukon Flats. The 
Middle Yukon includes that part of the valley lying between the 
Yukon Flats and the mouth of the Tanana, and the Lower Yukon the 
portion of the valley from the mouth of the Tanana to the sea. In 
the Upper and Middle Yukon provinces the coal-bearing rocks occur 
in small basins surrounded by older rocks. The sandstones of these 
basins, as far as determined, belong to the Kenai series, and are cor- 
related with the coal-bearing beds of southern Alaska. With a single 
exception these coals are either high-grade lignites or lignitic bitumi- 
nous coals. h 

The coal-bearing beds of the Lower Yukon are exposed continu- 
ously for 200 miles along the river, and they probably extend west- 
ward to include the area which has been reported near Norton Sound. 
This terrane is made up of sandstones, shales, and conglomerates, 
which probably form an uninterrupted sedimentary series, ranging in 
age from the Middle Cretaceous to the Upper Eocene, and hence 
including both the Nulato and the Kenai series. Both these series 
carry coals of economic importance in this province, practically all of 
which are of a bituminous character. 

In the following pages the localities will be described according to 

"Abstract of paper in preparation. 

& A coal whose content of water is above 10 per cent and whose fuel ratio is less than 1 is 
regarded as a lignite. The fuel ratio is the quotient of the fixed carbon divided by the volatile 
combustible matter. Coals whose classification by this rule is in doubt have been called lignitic 
bituminous coals. 



their geographic position, beginning at the international boundary 
and going down the river. 


Mission Creek and Seventymile River. — A small basin of coal-bearing 
rocks, 7 or 8 miles in width, lies near Mission Creek, 12 miles below 
the international boundary. The beds are of Kenai age and the coals 
are probably lignites. Twenty-five miles below, on Seventymile 
River, is another small basin of Kenai rocks from which coal has been 
reported, but nothing of economic importance has as yet been devel- 
oped at either of these localities. 

Washington Creek. — On Washington Creek, which enters the Yukon 
from the south, about 82 miles below the international boundary, there 
is a large area of coal-bearing rocks which is probably a part of a long 
basin or series of basins lying south of the Yukon and including the 
coal-bearing formations on Seventymile River, Bonanza Creek, and 
Coal Creek. No fossils were obtained in the Washington Creek coal 
basin, but an Upper Eocene age is inferred from the lithologic character 
of the sandstone, the mode of occurrence of the coal beds, and the 
character of the coal. In all these respects this coal basin resembles 
that at Cliff Creek, in Canadian territory, from which Eocene fossils 
were obtained. The coal here occurs in a formation consisting of alter- 
nating beds of lignite, clay, and carbonaceous shale, resembling that 
at Cliff Creek. In this formation seams of clear coal above 5 feet in 
thickness occur. The coal is a high-grade lignite, having an average 
fuel ratio of about 1 and a water content of from 10 to 15 per cent. 
The ash in samples analyzed varies from 2 to 4 per cent, and the sul- 
phur is less than three-tenths of 1 per cent. Wherever they have 
been opened the coal beds of the Washington Creek Basin show no 
evidence of faulting, and the coal is not crushed, but can be obtained 
in large pieces which "check" but do not break up readily on expo- 
sure to the air. Coal beds have been opened in this basin at localities 
several miles apart, showing that they have considerable extent. 
Where these beds have been prospected the dips vary from 35° to 45°. 

The relief of the basin is low, and probably the greater part of the 
coal lies below drainage level, so that pumping will be necessary if 
the mines are worked. 

This coal has not been mined on a commercial scale. The develop- 
ment in evidence consists of a tunnel 65 feet long and a slope 106 feet 
long. Other workings were of a temporary nature and have caved 
in. A good winter trail has been opened from the coal beds to the 
Yukon River, and last winter 5 tons of coal were sledded to the Yukon 
for a steam test on a river steamer. This is reported to have given 
entire satisfaction. A railroad 10 to 12 miles in length will be required 
to bring this coal to the Yukon. 

Bonanza and Coal creeks. — A similar basin is reported on Bonanza 


Creek, a tributary of Charley River, about 10 miles northwest of the 
Washington Creek Basin. 

Coal Creek, about 11 miles below Charley River, has coal of a sim- 
ilar character. These deposits are about 6 miles from the Yukon, 
and they have not yet been successfully exploited. 

Nation River mine. — The localities thus far described all lie on the 
south side of the Yukon and seem to belong to a series of Kenai 
basins which extends from the Klondike River, in Canadian terri- 
tory, northwest to Coal Creek, in American territory, a distance of 
about 160 miles. 

On the north side of the Yukon, 52 miles below the international 
boundary, coal outcrops, and has been mined to some extent on Tah- 
kandit or Nation River, 1^ miles from the Yukon. The coal-bearing 
formation extends down the Yukon for several miles and is generally 
more intensely folded than the sandstones above described. From 
the evidence in hand it may be regarded either as Permian or a later 
formation, presumably Kenai, infolded with Permian rocks. 

The coal is distinctly bituminous, having a fuel ratio of 1.39 and a 
water content of 1.39 per cent. The ash percentage is 3.04, while the 
percentage of sulphur is very high as compared with other Yukon 
coal, being 2.98 per cent. This coal shows no vestige of woody struc- 
ture and in the laboratory makes a good coke. The coal has been 
intensely crushed and affected, probably by a shearing movement of 
the inclosing sandstone, so that the bed is not well defined, but the 
coal was found in lenses and kidneys often as large as 8 feet thick 
and 13 feet long. 

In 1897 the Alaska Commercial Company attempted to open a coal 
mine at this place. About 2,000 tons" of coal were mined and sledded 
to a landing on the Yukon River. Owing to the irregularity of the 
bed and the consequent uncertainty of the suppl} 7 and expense of 
mining it was abandoned several years ago. 


Between the Upper Yukon and Middle Yukon provinces, along the 
river, there is a break of about 300 miles in which there are no coal 
beds known. 

Dall River. — On Dall River, which enters the Yukon from the north 
side, at the lower end of the Yukon Flats and about 450 miles below 
the international boundary, a coal bed occurs, 70 miles from the Yukon, 
in shales which are supposed to belong to the Kenai series. This coal 
bed contains irregular streaks of clay, but the lower 4 or 5 feet of the 
seam are believed to be of good quality. No practical tests and no 
analyses of the coal have been made. b 

a For estimates of the amounts of coal produced the writer is indebted to Mr. W. E. Williams, 
a mining engineer who has had charge of coal mines on the Yukon since 1897. 

&Mendenhall, W. C, Reconnaissance from Fort Hamlin to Kotzebue Sound: Professional Paper 
U. S. Geol. Survey No. 10, 1902. 


Salt Creek. — Coal is also reported by prospectors to occur on Salt 
Creek, which enters the Yukon from the north, 2-5 miles below Dall 

Drew mine. — The Drew mine is the only point at which coal has 
actually been mined in this province. It is on the right bank of the 
Yukon opposite the mouth of Hess Creek, 25 miles above Rampart 
and about 500 miles below the international boundary. Its position 
is an important one, since there are no valuable coal deposits known 
along the Yukon, either above or below it, within 200 miles. The coal- 
bearing formation exposed here is confined to a great bend of the 
Yukon River, and its known extent does not exceed 4 square miles, 
though it may be continued beneath the silts of the Yukon and Hess 
Creek. The coal-bearing formation here consists of a great thick- 
ness — probably over 5,000 feet — of soft sandstones, shales, and con- 
glomerates of Kenai age, standing nearly vertical and striking at right 
angles with the course of the river. 

From croppings seen along the river bank, it is believed that there 
are seven seams of coal contained in about 1,000 feet of soft sand- 
stone and shale of the upper part of the series, but only one has been 
exploited. Within the mine this bed was found to consist of two 
seams of clean coal in about 19 feet of coaly shale. These seams 
measured 13 and 25 inches and were separated by 4 feet of bony coal 
and black shale. The analyses show that the coal from the two 
seams is lignitic and quite similar in quality, having fuel ratios 
between 0.93 and 1.08, and a water content above 9.5 per cent. Both 
samples show over 13 per cent ash. A sample taken from the crop- 
pings of one of the other veins which has been partially opened up 
had a fuel ratio of 0.72 and a water content of 14.44 per cent, but the 
percentage of ash is only 4.04. 

The development in this mine includes a shaft 75 feet deep, from 
the foot of which a crosscut tunnel about 30 feet long reaches the 
coal bed. The shaft is cribbed and housed and equipped with steam 
hoisting gear. A bunker of about 80 tons capacity is conveniently 
located on the river bank, from which the coal can be loaded on 
steamers. About 1,200 tons of coal have been mined here, the greater 
part of which was used for steaming purposes on river boats, but 
did not give entire satisfaction. This dissatisfaction was due in part, 
no doubt, to the inexperience of the firemen and the unsuitable 
grates used. The coal was carelessly mined so that, as supplied at 
the bunkers, it contained more or less unnecessary dirt, but in spite 
of this it sold readily for $15 per ton while the mine was in operation. 
For the past two years the mine has been shut down under an attach- 
ment suit instituted by the Northern Commercial Company. 

Minook Creek. — A series of sandstones, probably of Kenai age, out- 
crops along the Yukon in the vicinity of Minook Creek, and also 


extends up the valley of that stream. Attempts at coal mining havt 
been made on Minook Creek, near the mouth of Hunter Creek, but the 
workings have been abandoned and have since caved in, so that the 
thickness of the bed could not be determined. A sample taken from 
the dump of the old prospect shows the coal to be a glossy lignite, 
which tends to break up into small cubical grains on drying. The f 
analysis shows a fuel ratio of 0.87 and a water content of 11.21 per 
cent. Probably in freshly mined coal the water content would be 
much higher. 

Below Rampart. — A similar coal outcrops 2 miles below Rampart 
on the left bank of the Yukon. A sample from the dump of an old 
prospect showed upon analysis a fuel ratio of 0.86 and a water con- 
tent of 16.43 per cent. Between Rampart and the mouth of the Tan- 
ana two large areas of Kenai sandstone occur which have been 
reported to carry beds of coal, but so far as is known to the writer they 
have no commercial importance. 

Cantwell River. — On the Cantwell River, which is a southern tribu- 
tary of theTanana River, about 100 miles from its junction with the 
Yukon, Brooks reports a great thickness of lignite-bearing sandstones 
believed to be Eocene. At one locality about 50 to 60 feet of lignite is 
contained in fifteen different seams. The analyses of this fuel shows 
that it has a fuel ratio of 0.66 and a water content of 13.03 per cent. 


Palisades. — At the Palisades, a series of silt cliffs about 55 miles 
below Tanana, a number of beds of lignite are exposed in the face of 
1 he cliff. This lignite is of Pleistocene or late Tertiary age and occurs 
in beds often several feet in thickness. It is of inferior quality, being 
but little changed from wood or peat, and lias no economic value. 

Nohatatiltin. — The Nohatatiltin coal bed is situated on the right 
bank of the Yukon 55 miles above Nulato and about 760 miles below 
the international boundary. It is in sandstones containing fossils of 
Eocene age, which probably overlie conformably Upper Cretaceous 
rocks of the Nulato formation. Two beds of coal were examined and 
two others are reported to have been opened by prospectors. Owing 
to the disturbed condition of the sandstone it is not certain that these 
may not all be parts of one faulted bed. The largest bed seen has a 
thickness of 1 foot and is not. of commercial importance. The coal 
is a low-grade bituminous, having a fuel ratio 1.17 and a water con- 
tent 6.88 per cent. 

Pichart mine. — This mine is 10 miles above Nulato, on the right bank 
of the Yukon, and 425 miles from its mouth. The coal bed is con- 
tained in a typical exposure of the Nulato sandstone, from which 
Upper Cretaceous fossils have been obtained. One coal bed 30 inches 
thick and having a dip of 35° has been exploited. The coal is bitu- 




urinous, having a fuel ratio of 2.38 and a water content of 1.03 per 
li e cent. In the laboratory it makes a compact coke. 

Mining was begun at this place in 1898- by the Pickart Brothers. 
About two years ago the mine passed into the hands of the Alaska 
Commercial Company, and in the summer of 1902 it was abandoned on 
account of some " rolls" in the floor of the bed which cut off the coal. 
The development consists of a drift tunnel about 600 feet long, above 
which all the available coal has been mined. No bunkers were used. 
The coal was piled on the river beach at the mouth of the mine and 
loaded on steamers by means of wheelbarrows. 

Nulato coal bed. — About 1 mile above Nulato, a prospect hole shows 
2^ feet of bony coal, with several bands of clay, in the Nulato sand- 
stone. This seam contains 6 inches of clean coal, which is used to a 
limited extent for blacksmithing at Nulato. 

Bush mine. — This mine is located on the right bank of the 
Yukon, 4 miles below Nulato. The inclosing rock is Nulato sand- 
stone. The development is not far enough advanced to show the 
nature of the coal bed. In the tunnel, which extends about 40 feet, 
large bodies of crushed coal 4 or 5 feet in thickness are exposed. 
The coal is regarded as bituminous, having a fuel ratio of 1.76 and a 
water content of 11.17 per cent. The high percentage of water is 
probably due to decomposition of the coal in the croppings. No coal 
has been produced, but the owners have contracted to deliver 400 
tons before next summer. 

Blatchford a mine. — This mine is located 9 miles below Nulato. 
The coal bed occurs in sandstone, probably of Upper Cretaceous age, 
which has been correlated with the Nulato sandstone. One workable 
coal bed has been opened at this place. This bed has been crushed 
and sheared by the movements of the inclosing strata, making it very 
irregular. Large masses, 8 feet in diameter, have been found and 
mined out, showing that before it was disturbed the coal bed probably 
had considerable thickness. The coal has a tendency to break up 
into fine pieces, though it is a bituminous coal, having a fuel ratio of 
3.30, the highest of any coal on the Yukon, and a water content of 
1.36 per cent. The ash is only 2.22 per cent, making it by proximate 
analysis the best coal seen by the writer on the Yukon River. This 
mine has no visible development or permanent equipment. The 
workings lie below the level of the river, and the entrance is covered 
with water during the summer months, so that it can be worked only 
in winter after the freezing up of the river, when the ice filling the 
upper workings must be mined out before the coal can be reached. 
The mine has probably produced about 300 tons of coal. 

Williams mine. — This mine is located on the right bank of the 

"This name is also written Blatsford. The correct spelling is in <!<>ul>t . 



Yukon, about 90 miles below Nulato. The coal is in sandstones, from 
which fossils of Eocene age have been collected. 

One bed 39 inches in thickness, in two nearly equal benches, sepa- 
rated by a clay parting about 1 inch thick, has been opened. The 
bed, which has a dip of 45°, is very regular and shows no variation, 
either in strike or thickness, in a distance of 400 feet. The coal is | 
bituminous, having a fuel ratio between 1.20 and 1.50 and water con 
tent between 6 and 7 per cent. The ash in the lower bench is 3.53 per ] 
cent and in the upper bench 8.63 per cent. The coal does not coke. 
This mine produced some coal as early as 1900, and early in 1902 it 
passed into the hands of the present owners. The equipment consists 
of a drift 400 feet long, starting from the river bank above high water. 
The greater part of the coal above this drift has been mined. The 
coal cars bring the fuel to the mouth of the mine, where it is piled on 
the river beach and loaded on steamers by means of wheelbarrows. 
One thousand seven hundred tons 'of coal, which sold at the mine for 
from $10 to $15 per ton, have been produced. 

Coal mine No. 1. — This mine is on the right bank of the Yukon, 25 
miles below the Williams mine. The coal is contained in sandstones, 
which may be either Upper Cretaceous or Eocene in age. One coal bed, 
having a thickness of from 2^ to 3 feet, has been mined. A sample 
of the coal taken from the cropping shows on analysis that the coal is 
bituminous, with a fuel ratio of 1.61 and a water content 4.82 per cent. 
The Alaska Commercial Company attempted in the winter of 1898 to 
open a mine here, and 900 tons of coal were taken out, but the mine 
was abandoned the same year on account of the difficult}' encountered 
in keeping out the water. 

Hall Rapids. — Near Hall Rapids, about 30 miles above Anvik, a 
small bed of coal'has been found in a formation consisting of white 
and yellowish tuft's of undetermined age. This coal has a lignitic 
appearance, but on analysis shows a fuel ratio of 1.35 and a water 
content of 8.23 per cent. The coal bed is probabl} 7 of no value on 
account of its limited extent. Similar coals or lignites are of frequent 
occurrence in these tuffs. 

On the Upper Koyuhuk River. — A coal bed containing 9 feet of com- 
paratively pure coal occurs near Tramway Bar. a This coal is either 
Upper Cretaceous or Eocene, but the exact age is undetermined. The 
analysis shows that it is a bituminous coal, having a fuel ratio of 1.40 
and a percentage of moisture of 4.47 per cent. 

Anvik River. — On the Anvik River, about 50 miles up, coal is 
reported by Mr. J. W. Chapman, missionary at Anvik. The point is 
about 10 miles back from the Yukon and probably is in a general way 
opposite the Williams mines. The coal is exposed in the river bank 
and is used by the natives in making black paint. 

aScnrader, F. C, Reconnaissance on Chandlar and Koyukuk rivers: Twenty-first Ann. Rept. 
U. S. Geol. Survey, Part II, p. 485. 



The coal-bearing formations are distributed along the Yukon con- 
veniently for steaming purposes from the international boundary 
nearly to the mouth of the river. The coal beds are practically unde- 
veloped, though limited amounts of coal have been mined at eight 
different points scattered along 1,000 miles of the river. Probably 
about 9,000 tons have been produced in American territory, which 
have sold at from $10 to $20 per ton. The seams from which coal has 
been produced vary in thickness from 13 inches to 5 feet, and in some 
instances they have been crushed and broken by movements of the 
inclosing strata, so that the beds are very irregular. The coal varies 
in quality from lignite to semibituminous. It has been used chiefly 
for steaming purposes on river boats and has come into competition 
with wood cut along the river. During the summer of 1903 crude oil 
from California Avillbe burned on some of the steamers on the Yukon. 
Should its use on the Yukon prove practicable, the development of 
the coal beds will no doubt be retarded by it. 

The Yukon will probably never supply coal for exportation, but the 
coal beds at present known seem to be capable, with proper develop- 
ment, of furnishing all that will be required for local use. 


By Myron L. Fuller and George H. Ashley 


The coal investigations recently conducted by the United States 
Geological Survey in the States of Indiana and Illinois were limited to 
the southern portions of the two States, the areas covered being 
included in two adjacent thirty-minute quadrangles. The easterly 
one, known as the Ditney, embraces portions of Pike, Gibson, Van- 
derburg, Warrick, Spencer, and Dubois counties of Indiana, and the 
westerly quadrangle, known as the Patoka, includes the remaining 
parts of Gibson and Vanderburg counties, portions of Posey and Knox 
counties in Indiana, and of Wabash, Edwards, and White counties in 
Illinois. The combined area of the two quadrangles is 1,872 square 

The investigations in the Ditney quadrangle were prosecuted in 
1900 and 1901, and the results have already appeared in the form of 
a geologic folio, a in which are given, in addition to the descriptions, 
maps showing the outcrops of the geologic formations, contours show- 
ing the approximate depth of the principal coal, and a large number 
of sections showing the thickness, character, and structural relations 
of the coals. The investigations in the Patoka quadrangle were pros- 
ecuted in the latter part of 1902, and the results will be prepared and 
published in the same form as those relating to the Ditney quadrangle. 


Five or more beds of this quadrangle are of sufficient thickness to 
warrant development, at least for local' supplies, but only one of the 
beds, the Petersburg coal, is worked for purposes of shipment. The 
other veins, however, especially the Millersburg coal, are extensively 
mined in the fall and winter months to supply local demands. The 
coals vary greatly in thickness at different points, and all of them 
show marked and sudden changes, due to their accumulation, it is 
believed, in basins of variable depth, or in series of basins that were 
only partially connected or even completely separated. The coals 
above the Millersburg are few in number, are usually under a foot 
in thickness, and, except in rare instances, are not workable even for 
local purposes. 

« Geologic Atlas U. S., folio 84, Ditney, Ind. 




Because of the covering of glacial drift and of certain confusing 
associations there is not that certainty in the tracing of this bed that 
characterizes the tracing of the more prominent Petersburg coal, but 
what appears to be a single bed, or at least a bed of a closely equiva- 
lent horizon, has been traced in the area under discussion from near 
Chandler on the south to Petersburg on the north, the outcrop passing 
near Lynville, Oakland City, Ingleton, Dongola, Glezen, Rumble, and 
Clark. The outcrop is worked by stoppings at over a hundred points, 
the workings being especially numerous along Squaw Creek east of 
Millersburg, south of Lynville, north of Ingleton, on both sides of the 
Patoka River at Dongola, along Robinson Creek, southeast of Rumble, 
and between Rumble and Petersburg. The thickness is generally 
insufficient to warrant shafting, but the coal is worked from shallow 
shafts at Millersburg, east of Elberfeld, and at Union. A shaft is 
now (1902) being sunk to this coal near Buckskin, where the coal is 
reported to reach a thickness of over 6 feet. 

The thickness of the Millersburg coal varies from 2 to 6 feet or 
more, 3 feet probably being a fair average for the area as a whole. 
A number of the more characteristic local measurements are given in 
the table on page 288. 

The interval separating the Millersburg coal from the next lower or 
Petersburg bed is generally from 70 to 90 feet, but if the correlations 
are correct the interval increases to about 100 feet near Ingleton and 
to 120 feet near Oakland City. 


The outcrop of the Petersburg coal is largely hidden by glacial 
deposits in the northern portion of the quadrangle, but over an area 
beginning near Cato and continuing to the southern border, south of 
Boonville, it has been opened at many points and is worked at short 
intervals. The dip being very gentle, averaging only about 20 feet 
to the mile to the west, and the coal lying at or near drainage level 
over considerable areas, the outcrop partakes of all the sinuosities of 
the drainage lines, its length being several times that of the 

The coal is of variable thickness, but probably averages about 5 feet 
in this quadrangle. East and northeast of Boonville, however, its 
average thickness is somewhat greater, being not far from 6 feet, and 
thicknesses of 7 feet are common in many of the mines, while in 
pockets a thickness as high as 9£ feet is reported. In this region it is 
solid and uniform throughout, except that the upper 3 to 6 inches is 
dry, resembling cannel coal in places. Thicknesses of 8 feet occur in 
many of the mines about Petersburg. At other points thicknesses of 
4 to 6 feet are most common. Measurements at a large number of 
points are given in the table on page 289. 



It is believed locally that the coal worked at or near the surface at 
Ayrshire and between Winslow and Littles is a " floating vein," lying 
about GO feet above the Petersburg bed, and it is claimed that an 
8-foot bed has been found by drilling about 60 to 80 feet below the 
one now worked. A careful study of the available data, however, 
leads to the belief that the coal at Ayrshire, Winslow, Oakland City, 
and Littles all comes from the Petersburg bed, and that the 8-foot 
bed below is either a newly discovered bed or the continuation of one 
of the thin beds of the Brazil formation which outcrops farther east. 

The coal frequently carries partings of bony coal, shale, etc., which 
sometimes reach considerable thicknesses. Such a parting occurs at 
Scalesville and continues to thicken southeastward, until at a mine 
northwest of Folsomville it forms a parting 34- feet thick between the 
two benches, but south of Folsomville it soon runs out. At several 
points the coal is associated with a small overlying vein known as a 
"rider." In the region between Winslow and Selvin the rider is a 
6-inch vein, occurring from 5 to 15 feet above the main bed. At 
Cabel a rather thick rider occurred just above the main coal, and the 
two were worked together at one time, but the working did not prove 
profi table. 

The following analyses, made by the State geological and natural 
history survey, give some indication of the chemical character of the 
bed in this quadrangle. While they do not indicate a coal of very 
high grade, the ease and cheapness with which it may be worked 
makes it a valuable vein. The roof, as a rule, is excellent, being of 
the tough, black, sheety variety which maintains itself without props 
for years, even in large rooms. 

Analyses of Petersburg coal. 


De Forest 



Woolley, Petersburg 

Total Volatile 
corn- j com- 
bustible bustible 
matter, matter. 


39. 09 





10. 75 




5. 20 




3. 56 


a Pounds of water evaporated per pound of coal. 

Mines of small size are operated at a large number of points, and 
in the aggregate have a large output. The larger mines, however, are 
of necessity located near the railroads. There are perhaps 20 mines 
shipping coal, the most important locations being Petersburg, Ayr- 
shire, Littles, Oakland City, Massey, Cabel, Boonville, De Forest, 
and Chandler. The small mines, frequently only strippings, are 
especially numerous north and northeast of Winslow, south of 
Augusta, west of Stendal, north and northeast of Scalesville, between 
Scalesville and Folsomville, and between Folsomville and Boonville. 

fullkk and ashley.] COAL FIELDS OF INDIANA AND ILLINOIS. 287 


The coals below the Petersburg bed in this quadrangle are of rela- 
tively little importance. Several of them, however, reach a thickness 
of 3 feet in places, are usually of a semiblock character, and on the 
whole are of much better quality than the Petersburg bed. On 
account of the cheapness of the coal from the latter, however, little 
attempt has been made to develop the lower beds; and as natural 
outcrops are very rare, their tracing is attended with much difficulty 
and uncertainty, and it is only in exceptional cases that their thick- 
ness and quality can be determined. While some of the coals may 
locally thicken to workable beds, it does not seem probable that they 
will be developed for at least a considerable length of time. The 
more important of the lower beds are the Ilouchin Creek, Survant, 
Velpen, Rock Creek, and Holland, although some of the still smaller 
and less persistent beds have been opened occasionally. 

Houcliin Creek coal. — This coal is one of the minor beds and lies 
between the Petersburg and Survant coals. It is exposed in the 
vicinity of Ilouchin Creek, Selvin, and Hemenway, and at other places. 
Its thickness is somewhat variable. Near Hon chin Creek, south 
of Cabel, and in the district northwest of Hemenway it has a 
thickness of 12 inches, but at the Ileming opening north of Selvin 
and elsewhere it reaches a thickness of 18 inches. It is almost invari- 
ably overlain by black, sheety, bituminous shale like that overlying 
the Petersburg coal. 

Survant coal. — This is frequently a coal of some importance, reach- 
ing a thickness of 5 feet in the hills near Gentry ville, though its 
thickness is not usually over 3 feet. It lies, on an average, about 45 
feet below the Houchin Creek coal and outcrops in the hills from near 
Velpen, southward to near Tennyson, passing near Stendal, Selvin, 
and Heilman. It is a semicoking coal, and is characteristically over- 
lain by a massive sandstone or by a light-colored shale that breaks 
into rhombs. At one point near Survant the interval is only 6 feet 
between this coal and the coal above, but as a rule the space is at 
least 30 feet. The Survant coal is probably the same as the Garrison 
coal north of Tennj^son, the Taylor coal at Selvin, the Corn coal north 
of Stendal, the Miller coal west of Pikeville, the coal under the bridge 
at Survant, and the Hollenburg coal southwest of Velpen. The table 
on page 289 includes a number of the characteristic measurements of 
this coal. 

Velpen coal. — At a distance of from 30 to 60 feet below the Survant 
coal is the Velpen coal, one of the most persistent beds in the region. 
It is frequently spoken of as "the 18-inch vein," as it maintains that 
thickness with great persistency. It is characteristically covered 
with a black, bituminous, sheety ^shale, above which there is often 
a foot or two of limestone. The interval between it and the Survant 
coal is, as far as seen, all clay shale, with the exception of the 
black shale and the limestone over the lower coal and the clay under 



the coal above. The Velpen coal is abundantly exposed around 
Velpen, at Pikeville, northeast and south of Selvin, and southwest 
of Heilman, and is probably the coal occurring just east of Grass. 
Around Selvin it is reported in a number of places to be underlain at 
a distance of only a few feet by 3 feet of coal of poor quality. At no 
place was this underlying coal seen. One or two thin bands of impure 
coal are reported to come between the two in places. Among the 
measurements taken are the following : Lynch opening, northeast of 
Velpen, 18 inches; near Velpen, 30 inches; llagmyer opening, east of 
Stendal, 12 inches; Byers opening, north of Selvin, 18 inches, and 
Irwin opening, east of Grass, 20 inches. 

Rock Greek coal.— This coal underlies the Velpen bed at an inter- 
val of from 40 to 50 feet. It is usually of a better thickness than 
the latter, often running up to 3 feet. It frequently, however, splits 
into two benches, usually not more than a foot apart and often sepa- 
rated by a mere film, though it is supposed to be in places split into 
benches 5 or 6 feet apart. The thickness of the benches and of the 
intervening partings are given in the table on page 290. Its outcrop 
extends from near White Sulphur Springs, north of Velpen, to near 
Ohrisney, passing near Velpen, Pikeville, Zoar, and Holland. It 
shows as a double coal, with a parting of variable thickness at numer- 
ous points, notably near Velpen, Pikeville, Zoar, west of Holland, 
and throughout Warrick and Spencer continues generally. 

Holland coal. — This coal normally lies from 70 to 90 feet below the 
Rock Creek bed, and although it is often thin or wanting, it some- 
times acquires a workable thickness. The outcrop of the coal or the 
cherty limestone associated with it has been traced from a point some 
3 or 4 miles north of Duff southward to Gentryville and vicinity and 
eastward to Dale. The limestone outcrops abundantly southeast of 
Holland, but the coal, if there, frequently fails to show in outcrop. 
The thickness of the coal at various points is shown in the following 
table. Where there are partings the figures given are for the com- 
bined thickness of the benches. 

Coal thicknesses, Millersburg, Petersburg, Survant, and Holland coals. 


Whitlock mine, west of Petersburg... 
Alexander opening, south of Peters 


Carr opening, southwest of Rumble . . 

Dongola clay and coal bank 

Oakland City quarry 

Bird shaft, Francisco 

Tevault opening, south of Spurgeon . . 
Daubs opening, east of Lynnville 






McGladden opening, southeast of 

Orths opening, west of Eby 

Thompson mine, east of Elberfeld 

Grander opening, Millersburg 

Edward opening, northeast of Chan- 

Exposure near Ne wburg 






fuller and ashley.] COAL FIELDS OF INDIANA AND ILLINOIS. 289 

Coal thicknesses, Millersburg, Petersburg, Survant, and Holland coals — Cont'd. 












Sims opening, north of Dickey ville 

McCarty opening, northeast of Dickey - 


John Bradfield mine, north of Alfords. 
Willis opening, northeast of Cato 


Nelson opening, south of Whiteoak 

Johnson opening, southwest of Cato, . . 

Hodge opening, east of Dickey ville 

Zint opening, northwest of Folsom- 
ville.. _ 


Shaw opening, southeast of Winslow - . 

Kelly opening, northeast of Boon ville.. 

Caledonia mine, east of Boonville 

Reynolds opening, southeast of Boon- 


Harding opening, southeast of Wins- 


Hog Branch, southwest of Survant 

Day opening, west of Midway... 


Blackburn mine, northeast of Peters- 

Fettinger opening, south of Cabel 

Simmons opening, southwest of Cabel. 

McKinney opening, southeast of Spur- 



Smith mine, northeast of Petersburg . . 
Woolley mine, Petersburg 


Mine at Littles 


Win. Stevens opening, northeast of 

Carbon mine, Sophia . 


Massey mine, east of Dongola 


Budka opening, south of Stendal 

Wilmeyer opening, south of Stendal. .. 
Wildes opening, north of Scales ville... 
Spradley opening, northwest of Selvin 
Douglass opening, northeast of Scales- 

Ingleton opening, northeast of Oak- 


Johnson shaft, Oakland City 




Broadwell opening, northeast of Eby . . 


Cox opening, north of Scalesville 

Vicinity of Scalesville 



Taylor opening, south of Boonville 



Crow opening, north of Algiers 

Hollenburg opening, southwest of Vel- 



Miller opening, northwest of Pikeville 
Davis opening, southwest of Pikeville 
Sickman opening, southeast of Pike- 

Taylor opening, near Selvin 

Hemenway opening, southwest of Sel- 

Garrison opening, north of Tennyson . 
Fisher opening, southeast of Tennyson. 


Highway north of Duff 

Payne opening, east of Velpen 

Stoncamp opening, west of Duff 

Coto opening, south of Duff 

Cooper opening, southeast of Holland 

Tormohlen opening, southwest of Hol- 

Romines opening, east of Gentry ville. 

Woods opening, southwest of Dale 

Brant opening, southeast of Chrisney. 

Bull. 213— OS- 



Thicknesses of benches and partings of the Rock Creek coal. 


Gray opening, Bertr Creek, north of Otwell. 

Proman opening, northeast of Velpen 

Rock Creek, northeast of Pikeville — 

Ilert opening, southeast of Pikeville. 

District west of Duff 

Myers opening, east of Stendal 

Hildebrand opening, east of Stendal 

District east of Zoar 

District west of Holland 

Thickness Thi k 




of lower 



8 + 



of coal. 



Rather pronounced local dips are occasionally found, but a careful 
tracing- of the Petersburg and Millersburg coals by outcrops, wells, 
or shafts, shows that although there are many irregularities and even 
reversals, the general dip is nearly west, the amount varying from 15 
to 40 feet, with an average of about 20 feet to the mile. As a result 
of that dip the coals disappear one after another beneath the surface 
to the west, and at the western limits of the area are from about 50 
feet, in the case of the Millersburg, to nearly 500 feet, in the case of 
the Holland coal, beneath the level of the bottom of the deepest val- 
leys. The depth of the Petersburg coal below the valley bottoms in 
the western part of the quadrangle appears to vary from 150 to about 
200 feet. 


Coal. — With one or I wo exceptions none of the coals outcropping in 
that portion of Indiana included in the Patoka quadrangle are now 
worked, even for local supply, though temporary openings have fre- 
quently been made in the past. The one mine in the area — the Oswold, 
at Princeton — gets its supply from a bed supposed to be the Peters- 
burg, reached by a shaft at a depth of about 440 feet. The coal aver- 
ages about 6 feet 6 inches in thickness. The mines working the same 
bed at Evansville are just outside the quadrangle. 

A considerable number of deep borings have been made at Prince- 
ton and elsewhere, in which coals of some thicknesses were encoun- 
tered. Some of these are given on the following table : 


Depth and thickness of coals in deep wells. 








Kurtz place ______ _ _ _ 

( 146 

I 258 



r 199 



Southern Railway shops _ _ _ _ _ _ 

| 346 




f 365 





Hall place. _ . 






r 62 



Evans place 




I 514 


f 80 







Near preceding. _ 














Tompkins place _ 






I 723 


f 44 



Thorn place _ 





Top of bluffs 2 miles east of town 

( 116 

I 172 


r 56 


Fort Branch 

Peter Hoffman place _ - - - 



[ 250 



Grove mill _ _ 

( 301 
I 408 




Sec. 3, T. 3 S., R. 11 W , 

| 60 

I 80 to 100 



A coal sometimes reaching a thickness of 18 to 24 inches outcrops 
near the levels of the flats along the tributary of the Patoka River, 
northeast of Princeton, and near Townsend's quarry, north of the 
Patoka. It was formerly opened by strippings at several points. 
Two or more very thin coals show in the river bluff south of Patoka, 
one of which also outcrops near the base of the sandy bluffs H miles 
northwest of the town. A coal of variable thickness occurs along the 
bluffs bordering the White River, east of Hazelton, and is now being 
worked locally on a limited scale. This coal is not found at Hazelton, 
but about 2 miles northwest of the town it outcrops with a thickness 
of 3| feet in the banks of the White River, and is now worked by a 
stripping at the Wharf mine. Very thin coals occur in the Gorden 
Hills, near the dam at Grand Rapids, in the hills 2 miles southwest 
of Princeton, and at several points northeast of Owensville. A coal 
reaching a thickness ol* several feet is reported in the the Mumford 
Hills. With the exceptions noted above, none of the occurrences 
mentioned have been developed. 

In the southwestern portions of Vanderburg and in southeastern 
Posey County there is a rather persistenl coal, lying about 100 
feet above the main limestone (Somerville) of the region. Where 
pure it is but a few inches in thickness, but where shaly it sometimes 
increases to is inches or more. Il is associated with a thin limestone 
and appears t<> be persistenl for a considerable number of miles. 
West of Blairsville and Lippe this coal disappears below the sin-face 
and is succeeded by another small coal of similar character and asso- 
ciation about 70 feet higher up. r l nis can be traced to a point west, 
of the Mount Vernon division of the Evansville and Terre Haute 
Railroad, where the ouicrop disappears beneath a deep covering of 
glacial drift, loess, and marl. Both coals have been worked occasion- 
ally for fuel for thrashing machines, but are not worthy of systematic 

Lignite. — Coals from a few inches to a foot in thickness have been 
reported from a large number of the wells sunk in the glacial drift of 
the Patoka area. No samples were seen, but from the descriptions the 
material would seem to be a poor grade of lignite. The lignites appear 
to occur in a dark-grayish clay, usually reported as "blue mud," but 
they are also associated with water-bearing gravels in several 
instances. Though apparently sometimes overlaid by till, the beds 
associated with the lignites are probably water deposited. 


Friendsville coal, — Only one coal has been mined in the portion of 
Illinois included in the quadrangle, though several smaller coals with 
thicknesses varying from 6 to 18 inches have been opened. These, 
however, are not persistent. The Friendsville coal outcrops near 
Friendsville and possibly at a few other points, but has seldom, if 

puller and ashley.] COAL FIELDS OF INDIANA AND ILLINOIS. 293 

ever, been opened on itsouterop. It underlies the surface of Wabash 
County at a moderate depth from a point north of Friendsville south- 
ward to Bellmont and Keensburgaud westward to the bottom land of 
Bonpas Creek. No coal which could be correlated with the Friends- 
ville bed has been recorded in the wells near Bonpas Creek, with the 
possible exception of one point southwest of Cowling. It has not been 
found in Edwards County. Neither has it been recognized at Mount 
Carmel nor southward along the Wabash River above Rochester, 
and there is every evidence that it has pinched out and disappeared. 
A deep drilling at Grayville, made expressly for information regard- 
ing coals, failed to find any over a few inches in thickness, indicating 
that the Friendsville vein has disappeared to the southwest as well as 
to the west and east. 

The Friendsville coal maintains rather persistently an av T erage 
thickness of about 3 feet. It is mined by shafts 1 mile east of Friends- 
ville, 2 miles southeast of Friendsville, 1| miles south of Bellmont, and 
at McClearys Bluff, on the Wabash River. It has been mined in the 
past at Sugar Creek, Maud, and at several points northwest of Mount 
Carmel. The coal burns moderately freely, but has a large ash con- 
stituent and does not coke. 

The dips of the Friendsville coal are more irregular in character 
but less in amount than those exhibited by the coals in Indiana. The 
general dip, however, is still to the west. The highest altitudes at 
which the coal occurs is from 450 to 460 feet, these altitudes being 
reached at a number of points between Mount Carmel and Friends- 
ville. East of Friendsville the altitude of the coal declines to 400 feet 
or less near Crawfish Creek, while to the west, southwest, and south 
the gentler but more persistent dip carries it downward to an altitude 
of about 350 feet in the vicinity of Cards Point, 385 feet at Maud, 395 
feet at Bellmont, 360 feet at Keensburg, 370 feet at Rochester, and 
335 feet 1^ miles southwest of Cowling. 


A number of the more important United States Geological Survey 
publications on the subjects of coal, lignite, and peat are listed 

Ashley. G. H. The Eastern Interior coal field [Illinois and Indiana]. In 
Twenty-second Ann. Rept., Pt. Ill, pp. 265-300. 1902. 

Bain, H. F. The Western Interior coal field [Iowa, Missouri, Kansas]. In 
Twenty-second Ann. Rept., Pt. Ill, pp. 333-360. 1902. 

Brooks, A. H. The coal resources of Alaska. In Twenty-second Ann. Rept., 
Pt. Ill, pp. 517-571. 1902. 

Campbell, M. R. Geology of the Big Stone Gap coal field of Virginia and 
Kentucky. Bulletin No. 111. 106 pp. 1893. 

Campbell, M. R., and Mendenhall, W. C. Geologic section along the New 
and Kanawha rivers in West Virginia. In Seventeenth Ann. Rept., Pt. II, pp. 
473-511. 1896. 

Chance, H. M. Anthracite coal mining. In Mineral Resources U. S. for 
1883-84, pp. 104-143. 1885. 

Dall, W. H. Report on coal and lignite of Alaska. In Seventeenth Ann. 
Rept., Pt. I, pp. 763-808. 1896. 

DlLLER, J. S. The Coos Bay coal field. Oregon. In Nineteenth Ann. Rept., 
Pt. Ill, pp. 309-370. 1898. 

Haseltine, R. M. The bituminous coal field of Ohio. In Twenty-second Ann. 
Rept., Pt. Ill, pp. 215-226. 1902. 

Hayes, C. W. The coal fields of the United States. In Twenty-second Ann. 
Rept., Pt. III. pp. 7 21. 1902. 

The southern Appalachian coal field [Alabama, Georgia, Tennessee, 
Kentucky, Virginia]. In Twenty-second Ami. Rept., Pt. Ill, pp. 227-264. 1902. 

Lane, A. C. The Northern Interior coal field [Michigan]. In Twenty-second 
Ann. Rept.. Pt. Ill, pp. 307-332. 1902. 

Shaler, N. S. Origin, distribution, and commercial value of peat deposits. In 
Sixteenth Ann. Rept., Pt, IV, pp. 305-314. 1895. 

Smith, G. O. The Pacific coast coal fields [Oregon, Washington, California]. 
In Twenty-second Ann. Rept., Pt. Ill, pp. 473-514. 1902. 

Stoek, H. H. The Pennsylvania anthracite coal field. In Twenty-second Ann. 
Rept., Pt. Ill, pp. 55-118. 1902. 

Storrs. L. S. The Rocky Mountain coal fields [Montana, Wyoming, Colorado, 
Utah, New Mexico]. In Twenty-second Ann. Rept., Pt. Ill, p. 415-472. 1902. 

Taff, J. A. Geology of the McAlester-Lehigh coal field, Indian Territory. In 
Nineteenth Ann. Rept., Pt. Ill, pp. 423-600. 1898. 

Preliminary report on the Camden coal field of southwestern Arkansas. 
In Twenty-first Ann. Rept,. Pt. II, pp. 313-329. 1900. 

The Southwestern coal field [Indian Territory, Arkansas, Texas]. In 
Twenty-second Ann. Rept., Pt. Ill, pp. 367-414. 1902. 

Taff, J, A., and Adams, G. I. Geology of the eastern Choctaw coal field, 
Indian Territory. In Twenty-first Ann. Rept., Pt. II, pp. 257-311. 1900. 


Vaughan, T. W. Reconnaissance in the Rio Grande coal field of Texas. Bul- 
letin No. 164. 100 pp. 1900. 

Weeks, J. D. The manufacture of coke. In Mineral Resources U. S. for 
1883-84, pp. 144-213. 1885. 

White, D. The bituminous coal field of Maryland. In Twenty-second Ann. 
Rept.. Pt. Ill, pp. 201-214. 1902. 

White, D., and Campbell, M. R. The bituminous coal field of Pennsylvania. 
In Twenty-second Ann. Rept., Pt. Ill, pp. 127-200. 1902. 

White, I. C. Stratigraphy of the bituminous coal field of Pennsylvania, Ohio, 
and West Virginia. Bulletin No. 65. 212 pp. 1891. {Out of print.) 

Willis, B. The lignites of the Great Sioux Reservation [Dakota] . Bulletin 
No. 21. 16 pp. 1885. 

Some coal fields of Puget Sound [Oregon] . In Eighteenth Ann. Rept. , 

Pt. Ill, pp. 393-436. 1898. 

Woodworth, J. B. The Atlantic coast Triassic coal field [Virginia, North 
Carolina]. In Twenty-second Ann. Rept., Pt. Ill, pp. 25-54. 1902. 


A number of papers describing the results of recent field work by 
the Survey in various oil, gas, and asphalt fields are here presented. 
In addition to this new material, a chapter on the origin and distribu- 
tion of asphalt and bituminous rocks in the United States is here 
reprinted, in greatly condensed form, from a detailed publication on 
that subject issued by the Survey in 1902. This has been done, as 
the portion reprinted serves as an excellent summary of the subject, 
and as an introduction to the other papers on asphalt here included. 


By Gr. H. Eldridge. 


The classification of W. P. Blake, slightly modified, follows. 

Classification of natural hydrocarbons. 

, Gaseous /Marsh gas. 

\" Natural gas." 
Fluid /Naphtha. 

I Petroleum. 

Viscous ( malthite) 







I Coal 

Mineral tar. 

Elastic jElaterite (mineral caoutchouc) 

I Wurtzilite." 

Uintaite (gilsonite). 

Bituminous coal. 
Semibituminous coal. 
Anthracite coal. 

{Succinite (amber). 
Ambrite, etc. 
Cereous _ / Ozocerite . 

IHatchettite, etc. 

Crystalline . /Fichtelite. 

lHartite, etc. 



" Wurtzilite might, perhaps, better be classed with the asphaltites. 



Classification, or grouping, of natural and artificial bituminous compounds. 

Mixed with limestone (''asphal- rSeyssel, Val de Travers, Lobsan, Illinois, 

tic limestone "). I Utah, and other localities. 

Mixed with silica and sand ("as- r California, Kentucky, Utah, and other 


phaltic sand''). 
Mixed with earthy matter ("as- 

phaltic earth " ) . 
Bitnminons schists 

I localities. " Bituminous silica." 

•J Trinidad, Cuba, California, Utah. 
jCanada, California, Kentucky, Virginia, 
and other localities. 

pn • , J Thick oils from the distillation of petro- 

leum. ''Residuum." 


Gas tar. 


I Pitch. 

Refined Trinidad asphaltic earth. 
Mastic of asphaltite. 
Gritted asphaltic mastic. 
Paving compounds. 

A glance at the above tables will convince one of the impossibility 
of establishing hard and fast lines between the substances enumerated. 
The classification, however, seems to the writer to be the most satis- 
factory of the several attempts met with in the literature of the 

It will be observed that there has been omitted from the table one 
of the commonest terms in use, ' ' asphalt," or ' ' asphaltum. " By many 
disinterested authorities this word is restricted to the solid forms of 
the purer bitumens, forms including those grouped by Professor Blake 
under the general derivative, "asphaltite." This usage is reasonable, 
and by adhering to it confusion will be avoided in both science and 
trade. Industrially, however, the word "asphalt" is unfortunately 
made to include almost every compound of bitumen with a foreign 
material, chief among the latter being sandstone and limestone. 

Mr. Clifford Richardson, in his Nature and Origin of Asphalt, a 
contribution (October, 1898) from the laboratory of the Barber 
Asphalt Paving Company, gives the following definition of asphalt : 

The natural bitumen, which is known as asphalt, is composed, as far as we have 
been able to learn, of saturated and unsaturated dicyclic, or «polycyclic, alicyclic 
hydrocarbons and their sulphur derivatives, with a small amount of nitrogenous 
constituents. Asphalt may, therefore, be defined as any hard bitumen, composed 
of such hydrocarbons and their derivatives, which melts on the application of heat 
to a viscous liquid; while a maltha or soft asphalt may be defined as a soft bitu- 
men, consisting of alicyclic hydrocarbons, which, on heating, or by other natural 
causes, becomes converted into asphalt. The line between the two classes can 
not be sharply drawn. 

- "Bitumen," also, is a term that has been omitted from the table, 
although its adjective, "bituminous," is employed. The word 

a In the original report the word "or" was inadvertently placed after instead of before 
" poly cyclic. 1 ' 


"bitumen " has in the main been used to include the three varieties of 
hydrocarbon compounds known as petroleum, maltha or mineral tar, 
and the solid substances included under the asphaltites and often 
designated, one or another of them, ' ' asphalt. " The adjective ' ' bitu- 
minous," however, may be applied to a sandstone or other rock 
impregnated with bitumen, as thus understood; and if such bitumen 
has any of the characteristics of the so-called asphalts, the compound 
may receive the name "asphaltic sandstone," "asphaltic limestone," 


The relations, chemical or other, between the hydrocarbons of the 
table on pages 297-298, were they worked out, would doubtless show the 
utmost complexity, for complexity exists even in the substances them- 
selves, nearly all of which are separable by the action of solvents or 
by fractional distillation into two or more components that are in turn 
divisible into series of hydrocarbons, in many instances of great 

In Dana hatchet t ite and ozocerite are found among the simple hydro- 
carbons as members of the paraffin series C„Il2„+2, while fichtelite, 
hartite, and a number of others occur in this division of the hydro- 
carbons, but of series other than the paraffin, and in many instances 
altogether of doubtful reference. 

The resinous compounds belong to the class of oxygenated hydro- 
carbons, the membership in which is very extended and of great 
variety. Concerning this class, Dana remarks that it embraces 
"chiefly the numerous kinds of native fossil resins, many of which are 
included under the generic term 'amber;' also other more or less 
closely related substances. In general, in these compounds, weak 
acids (succinic acid, formic acid, butyric acid, cinnamic acid, etc.), or 
acid anhydrides, are prominent." 

Between the coals — especially the bituminous and cannel varieties — 
and the resinous and asphaltite divisions of this table relations are 
readily found ; indeed, for a number of years, only two or three decades 
ago, grahamite, on account of its composition, was regarded by men 
high in authority as a true coal, notwithstanding its wholly different 
mode of occurrence. 

Albertite, grahamite, uintaite, etc., are now accepted as closely 
related varieties of asphaltum. This relationship is evident both in 
their chemical composition and in their mode of occurrence, yet they 
are readily distinguished by their behavior toward solvents, by the 
action of heat upon them — their fusibility, so called — and by other 

Wurtzilite, in outward appearance, bears a striking resemblance to 
the asphaltites, but is distinguished from them by its behavior toward 
solvents and by its marked sectile and elastic properties. Yet, while 



of lintaite itself is exceedingly brittle, one of its leading features, devel- 
>ped in the manufacture of black japans and varnishes made from it, 
s this very property of elasticity, attainable in such perfection in no 
)ther hydrocarbon compound except elaterite and wurtzilite. 

Elaterite, though elastic, is quite distinct from wurtzilite. Dana, 
n remarking upon the results attained by the authorities which he 
consulted, states that this substance "appears to be partly a carbo- 
lydrogen near ozocerite and partly an oxygenated insoluble material." 
The viscous bitumens of the table vary markedly in consistency. 
Maltha has the greatest fluidity, brea and chapapote the least — these 
ire, in fact, solids. Each member of the group shades into the next 
m either side, even maltha into petroleum and chapapote into the 
isphaltites. From this it will be inferred that the application of the 
several terms is decidedly indefinite. In regard to brea and chapa- 
pote, usage seems to make them synonymous, unless it be that the 
solidity of chapapote is a degree greater than that of brea, by no 
means an assured distinction. 

The viscous compounds stand between the solid asphaltites on the 
one hand and petroleum on the other. "The fluid kinds," observes 
Dana, "change into the solid by the loss of volatile matter by a proc- 
ess of oxidation which is said to consist first in the loss of hydrogen 
and finally in the oxygenation of a portion of the mass." 
Richardson, in his Nature and Origin of Asphalt, observes: 

Asphalts are distinguished by the large amount of sulphur they contain, and it 
is to its presence that many of the important characteristics, and perhaps, in part, 
the origin of this form of bitumen, is due. The soft asphalts or malthas contain 
much less sulphur than the harder ones, or if the former are rich in sulphur, they 
are then in a transition stage and will eventually become hard. But a small por- 
tion of the constitutents of a hard asphalt are volatile even in vacuo, but they can 
| be separated by solvents into an oily portion, which is soft, or softens readily when 
heated, and a harder portion, which does not melt by itself without decomposition, 
and is a brittle solid, but soluble in the oily or softer portion. The harder and 
least soluble portion always contains the larger part of the sulphur. It seems, 
therefore, that sulphur is the effectual hardening agent of [many] natural asphalts, 
in the same way that it is of artificial asphalts which are produced by heating a 
soft natural bitumen with sulphur. 

But Mr. Richardson adds that "some natural bitumens occur which 
have become hardened in another way and perhaps by oxygen." This 
refers particularly to the asphaltites. 

Boussingault's investigation, in 1837, into the composition of asphalt 
also developed son 3 results of especial interest. He took for his 
experiments the viscid bitumen of Pechelbronn, France. At a temper- 
ature of 230° C, in an oil bath, he separated an oily liquid, to which 
he gave the name "petrolene," regarding it as the liquid constitu- 
ent of bitumen, which, mingled in varying quantities with a solid sub- 
stance, "asphaltene," forms the bitumens of different degrees of 
fluidity. He describes asphaltene as brilliant black in color and luster, 


with a conchoidal fracture, and heavier than water. Toward a tem- 
perature of 300° C. it becomes soft and elastic. It begins to decom- 
pose before it melts, and burns like the resins, leaving an abundance 
of coke. 

Dana, in his System of Mineralogy, quotes several analyses of 
petrolene by Boussingault, one of which gives C. 87.45, H. 12.30.. 


The distribution of asphalts and bituminous rocks in the United ; 
States is wide. The asphaltites are found in West Virginia, Indian 
Territory, Colorado, and Utah; bituminous limestones in Indian Ter- 
ritory, Texas, and Utah; bituminous sandstones in Kentucky, Mis- 
souri, Indian Territory, Texas, Utah, and California; a earthy bitu- 
men of greater or less purity, occurring as veins, in California; while 
brea may occur in all petroleum areas, but in the present investiga- 
tion was found only in Indian Territory, Wyoming, and California, 
although small bodies are reported in Montana. 

The stratigraphic range of the bitumens and their compounds is as 
wide as their geographic distribution. Their oldest association | 
observed is with the Ordovician shale of the Tenmile region in eastern 
Indian Territory, where impsonite, an asphaltite closely related to 
albertite, occurs in vein form. Other veins of like material, as well 
as a bituminous sandstone, occur in the series of Ordovician sand- 
stones overlying the shales along the Indian Territory- Arkansas line. 
In central Indian Territory, in the Buckhorn district, are other bitu- 
minous sandstones, also of Ordovician age, though perhaps not to be 
correlated with the foregoing. Above these, in direct succession, is 
the summit limestone of the Ordovician, at least for this locality — a 
massive bed of variable thickness, the maximum being approximately 
400 feet. The entire body of rock is varyingly impregnated with bitu- 
men, the more highly enriched portions to an average of 6 to 8 per 
cent. In this same locality the Lower Coal Measures also, at one or 
more horizons, are richly infiltrated with bitumen, one of their lime- 
stones carrying an average of 14 per cent. The Lower Coal Measures 
are unconformable with the underlying formations, and the occur- 
rence of bitumen at the several horizons suggests a common source and 
origin for it, and an inflow to its present reservoirs, perhaps subse- 
quent to the laying down of all the sediments involved, if not, indeed, 
subsequent to their folding. On the other hand, from the presence 
in the Coal Measure conglomerate of an occasional pebble, believed to 
be of Ordovician bituminous sandstone, particularly observed by Mr. 
Taff, there may have been two or more distinct flow periods. 

West and south of the Arbuckle Mountains the Coal Measures again 

a Since the writer's field investigation indefinite accounts of bituminous sandstones in Alabama 
and Illinois have appeared in certain newspapers. 


cany bitumen in some of their members — grits and limestones. These 
horizons, however, may be quite different from those in the Buckhorn 

Near Higginsville, Mo., the Warrensburg sandstone, which occu- 
pies what Mr. Arthur Winslow, the State geologist, considers a channel 
of erosion in the Coal Measures, and which is assigned to the Car- 
boniferous, is also infiltrated with bitumen to about 6 per cent. 

In West Virginia the grahamite vein, which has brought much 
renown to the region of its occurrence, occupies a vertical fissure in 
the Waynesburg sandstone and adjoining beds above and below, 
all of which are horizons in the Upper Productive and Upper Barren 
Coal Measures of the Carboniferous age. 

The bituminous sandstones of Kentucky are closely successive 
members of the Chester formation and the basal portion of the Coal 
Measures, and all, at one point or another, are impregnated to a 
degree sufficient to render them economically available for paving 
purposes, their contents ranging between 5 and 9 per cent. 

The Permian, or what is at j>resent accepted as the Permian, in 
central Indian Territory has been penetrated by fissures, through 
which petroleum has risen into its surficial sandy members and 
has also been converted to brea as surface deposits. This occurs at 
Wheeler, a settlement about 40 miles west of Ardmore. The locality 
is practically that of the enriched Coal Measure sandstones south of 
the Arbuckle Mountains, and there is little doubt that a common 
source supplied all the different horizons that now constitute the 
exposed storage reservoirs of the former fluid petroleum. 

The Trinity sand of the Lower Cretaceous is a bitumen-bearing for- 
mation at many points in its area of outcrop in southern Indian Ter- 
ritory and northern Texas. This is particularly the case where it 
rests upon the Carboniferous, an occurrence that is significant of the 
derivation of its bitumen from a source perhaps identical with that 
from which the several members of the Coal Measures have derived 

The Glenrose formation, also a member of the Trinity division of 
the Lower Cretaceous, in one of its limestones carries the bitumen 
of the deposits of Post Mountain, near the town of Burnet, Burnet 
County, Tex. The Anacacho formation of the Texas Upper Cretace- 
ous, corresponding to a horizon near the base of the Montana of the 
Rocky Mountain section, carries the rich bituminous limestones 
extensively quarried in the vicinity of Anacacho Mountain, 18 miles 
west of Uvalde, in southern Texas. In this connection the presence 
of important oil horizons in the Montana formation of the Florence 
oil field in Colorado is not unworthy of note. 

The Middle Park formation of Middle Park, Colorado, largely a 
terrane of eruptive material and a correlative of the Denver of the 
plains — a formation for the present termed post-Laramie, without 


assignment to Cretaceous or Tertiary — also carries bitumens. The 
deposit occurs in the northern portion of Middle Park, almost in the 
heart of the Rocky Mountains. It is here an asphalt resembling gil 
sonite and occupying an irregular fissure or series of fissures in the 
clays, sandstones, and conglomerates of the formation referred to. 
The occurrence is, so far as known, limited to the immediate region 
in which it is found, and is thus comparatively isolated, the nearest! 
asphalt being the gilsonite found along the Colorado-Utah line, 150ji 
miles distant. 

The bitumens of the Tertiary horizons are apparently confined to 
the West — to Colorado, Utah, and California. The various divisions 
of the Eocene in eastern Utah and just across the line in Colorado are 
noted both for the variety of their asphalts and for the size of their 
veins. It is in this region, of the White and Green rivers and the 
celebrated Book Cliffs, that the great veins of uintaite are found andj 
that the minor seams of wurtzilite, ozocerite, and nigrite occur. 
Bituminous limestones are also of wide distribution, though confined 
to the Green River shales. The asphaltites occur in fissures both in 
this formation and in those overlying, especially the Bridger and 
Uinta. Maltha springs also occur, and even petroleum is reported 
in one of the members of the Cretaceous, a few miles east of the 
Utah-Colorado line. The Green River shales are noted throughout 
the West for their bitumen contents, and it is surmised that they are 
the source of the asphalts, at least, of this vast area. The variation 
in the ultimate material as it to-day fills one fissure or another is per- 
haps due in part to a change somewhat allied to fractional distillation 
in petroleum technology and in part t<> the degree to which oxygen 
absorption lias been carried on. In any event, the variety of bitumen 
found can hardly excite wonder when considered as to the origin of 
the material and the differentiations that take place in artificial dis- j 
filiation. It is, indeed, to be expected. 

The occurrence of bitumens in the Neocene is confined to California. 
The rocks of this period here embrace a heavy series of shales with 
local sandstones, tuffs, etc. — the Monterey formation; a conspicuous 
body of massive sandstone with a minor proportion of shales, known 
as the San Pablo formation, but in doubt as to its position as a mem- 
ber of the Miocene or Pliocene, and hence in the region of its occur- 
rence regarded as Middle Neocene; and a succession of sandstones, 
conglomerates, and clays, probably Pliocene, but for the present 
termed Upper Neocene, with the specific name Paso Robles assigned 
to it. 

In addition to the foregoing, there are certain and important sand- 
stones and sand aggregates of somewhat doubtful age, but where 
encountered seeming to lie beneath the shales of the Monterey rather 
than in them, and often against and upon granite. Such is their 
occurrence in the vicinity of Santa Cruz, and again at one or two points 


in the range bordering the Salinas Valley on the east. These sand- 
stones are locally heavily impregnated with bitumen, and near Santa 
Cruz are extensively quarried for paving purposes in San Francisco 
and elsewhere. 

The Monterey formation is of particular importance, in that for 
almost the entire length of the State its terrane is more or less con- 
spicuously marked with petroleum or maltha seepages, while its sandy 
members may appear as minor storage reservoirs of oil, these now 
altered at the outcrop to a material of pasty consistency, which forms 
with the sand grains an asphaltic compound of considerable richness. 
| Such sandy beds occur at Point Arena, in the San Antonio Valley, 
and in the region of the Sisquoc. The shales of the Monterey are not 
only generally bituminous, but some of their more arenaceous and 
porous members are also especially rich, doubtless having received 
an inflow of petroleum from their adjoining and less open associates. 
It is in the shales of the Monterey, too, as well as in the Middle Neo- 
cene, that veins of the more solid bitumens, mixed with elastic mate- 
rial derived from the country rock, are found. Except for the clastic 
material, the bitumen would resemble in structure the asphaltites, 
though still differing from them in other features. Veins of this 
description are conspicuous in the vicinity of Santa Maria, Santa 
Barbara, and Asphalto. Near the latter place the asphaltic material 
is intimately related to, even associated with, petroleum. 

The San Pablo formation, at least that portion of it in the San Luis 
Range, has been converted into a vast storage reservoir. It is the 
surface terrane over an area of nearly 50 square miles a short dis- 
tance southwest of San Luis Obispo, and perhaps half its outcrop here 
shows impregnation with bitumen in greater or less degree, locally 
to a high degree. In the same region scattered bodies of the Paso 
Robles formation have also been infiltrated where resting on the San 
Pablo or the Monterey. 

The San Pablo is also, perhaps, represented in the region of the 
Sisquoc, 40 miles southeast of Santa Maria, where along the southern 
base of the San Rafael Range is a highly enriched body of sandstone, 
of doubtful correlation from its structural association with recognized 
Monterey sandstones, but possibty of the age suggested. It is locally 
one of the richest sandstones in California. 

In the region of La Graciosa Hills, to 10 miles south of Santa 
Maria, there rests upon the Monterey, unconformably, a heavy body 
of loosely coherent sands or sandstone commonly regarded as Plio- 
cene. Cracks have developed in the formation, and have been 
filled with bitumen carrying from 30 to 60 per cent of clastic matter. 
The material resembles in general appearance that already referred 
to as of vein form in the Middle Neocene near Asphalto. Here, 
again, it has been found in association with petroleum. 

Post-Pliocene sandstones are found with small gash veins and 



other irregular but more or less extensive bodies of the solid bitu- 
mens in the region of Mores Landing, 7 miles west of Santa Barbara. 
A material in many ways resembling gilsonite was found as a minute 
pocket in the sandstone, but the mass of the bitumen is of the solid 
variety, mixed with 20 to 40 per cent of clastic material. Twelve 
miles east of this occurrence is the important petroleum-producing 
region of Summerland. Pleistocene or Recent sands have been heav-1 
ily charged with bitumen at Carpinteria, 12 miles east of Santa Bar- i 
bara. They have been for the most part removed, but the continuous | ,' 
flow of maltha in the floor of the quarry would quickly impregnate an .. 
equal body were the excavation to be filled with fresh sand from the | 
adjoining ocean beach. 

Surficial deposits of brea are well distributed over the United 
States. Those observed by the writer were in Indian Territory, 
Wyoming, and California, the first no longer increasing from active 
springs, the others still forming. The source of their malthas is 
naturally extremely varied. In addition to the above, there are doubt- 
less many others of but little less importance scattered through the 
oil regions of the country. 


The origin of the hydrocarbons and bituminous compounds may be 
traced, the writer believes, to petroleum. This is a natural inference 
from chemical relations. The fact that there may be a wide variation 
in the composition and physical aspect of the bitumens, whether of 
asphaltites or of sandstones, matters not, for important differences 
are found in petroleums themselves ; the variation in the asphaltites, 
indeed, may be somewhat more marked, for in Die passage from 
petroleum to its derivatives the process may have stopped at any 
point, with a corresponding development of physical as well as chem- 
ical distinctions. But in the geologic investigation of the asphaltites, 
bituminous sandstones, and related materials the view of their origin 
suggested by chemistry has in many ways been reenforced. The 
asphaltic earths, and solid bitumens in part, are frequently associated 
with active petroleum springs, or are found in regions renowned as 
oil producing. The sandstones and limestones are found resting upon 
formations conspicuous for their yield at other points; indeed, in one 
instance they were found upon a formation actively yielding oil directly 
beneath them, and this at the present day. The sandstones, therefore, 
can hardly be regarded other than as storage reservoirs for the oil 
thus received; the limestones, it is sometimes thought, may have been 
the locus of origin as well as of storage. 

The asphaltites and closely associated hydrocarbons — ozocerite, for 
example— can hardly have been derived otherwise than by the draining 
of petroleum pools or strata richly saturated with oil. In the case of 
gilsonite, the absence of every trace of petroleum in the inclosing sand- 


tones and its evident prevalence in the underlying Green River shales 
ndicate the latter series as the one-time source of the oil which on 
sntering the fissures was converted into the asphaltites. Moreover, 
ocally, for a foot or two adjacent to the veins, the sandstone is filled 
vith interstitial gilsonite, which is evidence of infiltration from the 
ietrolenm-filled fissure into the sandstones rather than into the fissure 
:rom the rock on either side. The channels by which the shales were 
Irained are cracks that extend from the bottom of the main portion of 
;he fissures, in some instances several hundred feet, into the underlying 
)itumen-bearing beds, but even here the draining of the strata must 
have been marvelously rapid to have been so complete as the condi- 
tions indicate before being interfered with by the closing of the fis- 
sures from the settling or readjustment of the shale, always a rock of 
exceeding instability. The writer believes, however, that the filling 
of the fissure could have been derived from no other source. The 
origin of the cracks is, of course, well understood. They occur in all 
formations and in all localities and are a concomitant feature of fold- 
ing, though perhaps at times developed from shrinkage 

In the filling of all reservoirs, whether fissures or sandstones, the 
investigator is struck Avith the almost inevitable slowness of the proc- 
ess and the vastness of the area of fine-grained sediments that must 
have been drained to yield the supply absorbed. Then, too, in the 
case of the asphaltites the hardening must have been very gradual, the 
material passing through a viscous stage, during which fragments 
dropped from the walls into the bitumen and yet were supported, even 
as a rock is supported upon the surface of a thickening maltha pool at 
the present day. After solidification was complete the crushing strains 
from readjustment of the strata became manifest in the penicillate 
structure developed in the asphalt next to the walls of the vein. It is 
probable that during the filling of the crack this readjustment was 
continuously going on, but it could become evident only after the vein 
material had been hardened sufficiently to record it. 

Bull. 213—03 20 


By G. H. Eldridge. 


The petroleum fields of California, as at present known, lie on 
either side of the Central Valley of the State, in the Coast Range, and 
along the Pacific front. The greatest development has taken place 
south of the parallel of San Francisco, although northward from this 
are many prospects and one developed field of minor commercial 
importance — that in the vicinity of Eureka, Humboldt County. 

The Coast Range, considered as a topographic province, includes 
all the mountains lying between the great Central Valley of California 
and the Pacific Ocean. It has no well-defined axis, either topographic 
or geologic, but consists rather of a number of parallel ridges having 
a general elevation of between 3,000 and 4,000 feet, with occasional 
peaks extending to somewhat greater heights. 

Structurally the Coast Range consists of numerous parallel anti 
clines and their corresponding synclines. There is no dominant 
axial fold, the crust having been crumpled into a close succession of 
ridges of varying amplitude and height of arch. The topographic 
trend of the general range from San Louis Obispo north is about 
N. 30° W., veering westward south of this. The structural trend of' 
the folds composing it, however, is between N. 20° and 40° W. from 
the thirty-sixth parallel north, N. 50° or 60° W. in the region of San 
Luis Obispo, and from Point Conception east N. 80° to 90° W. 
Throughout the entire range it is distinctly diagonal to the coast line, 
except, perhaps, along the Santa Barbara Channel. Faults, of course, 

The large productive oil fields of southern California include the Oil 
City, adjacent to Coalinga; the McKittrick ; the Sunset and its exten- 
sion, the Midway; the Kern River; La Graciosa; the Suminerland; 
the Santa Clara Valley; the Los Angeles; and those of the Puente 



This district extends along the eastern base of the Mount Diablo 
Range for a distance of about 30 miles, Coalinga, the small town from 


which it is named, lying somewhat nearer the northern end. Three 
areas of oil development exist, which may be designated the Oil City 
field, the Kreyenhagen field, and the Avenal field, but the first only 
is of special productiveness. Coalinga is accessible by rail from the 
main lines of both the Southern Pacific and the Atchison, Topeka 
and Santa Fe railroads. 

The topographic features of the region are those of a high, rugged 
range, bordering a desert. The line of mountain and desert passes 
southeast from Coalinga in a direct course for 30 miles, but immedi- 
ately north of the town there is the reentrant angle of a valley and syn- 
cline which separates the main range from one of the diagonally 
transverse spurs and anticlines that are such conspicuous features of 
the structure of the Coast Range. It is at the southeast end of this 
anticline that the Oil City petroleum field has been developed. 

The formations involved in the anticline embrace at least 1,000 to 
2,000 feet of massive concretionary sandstones of Tejon (Eocene) age, 
overlain by 800 to 1,000 feet of purple and gray shales, clays, thin 
sandstones, and limestones, that have also been referred by some to 
this period; 100 or 200 feet of clays and sandstones that may prove to 
be Lower Miocene ; 200 feet of siliceous shales typical of the Monterey 
(Upper Miocene); and, unconformable with these, a great thickness 
of conglomerates, sandstones, and clays, recognized by their fossils to 
be San Pablo (Middle Neocene). The conglomerates of the San Pablo 
in this region contain pebbles of quartz, black chert, jasper, serpen- 
tine, siliceous shale, and sandstone, the matrix being of the same 
materials; the sandstones, which are coarse, are chiefly quartzose; 
the clays are generally gypsiferous. 

The Oil City field, as already suggested, is developed about the 
southeastern terminus of one of the diagonally tranverse anticlinal 
spurs that extend from the Coast Range into the valley of the San 
Joaquin. The axis here dips rapidly to the southeast, and within 10 
miles of the higher crest of the range evidence of the fold has com- 
pletely disappeared beneath the valley deposits. The line of junc- 
tion between mountain and desert on the northeast side of the fold 
extends for 20 to 30 miles without conspicuous break. With the excep- 
tion of severe crumpling in the immediate vicinity of the axis, accom- 
panied perhaps by some faulting, and a comparatively gentle flexure 
on the southern periphery of the uplift in the vicinity of Oil Creek, 
the anticline appears to be unaffected by minor folds. The measures 
exposed in the heart of the anticline are the massive Tejon sandstones. 
Encircling these are the overlying shales, and these in turn are fol- 
lowed by the heavy and resistant conglomerates and sands of the San 

The oil-bearing horizons of this field are two: one, a sandstone in 
the lower portion of the shales that are by some regarded as the upper 
member of the Tejon; the other, the lower sandstones and conglomer- 


ates of the San Pablo. It is estimated that approximately 1,500 feet 
of measures separate the two horizons. Owing- to this distribution 
there are two distinct areas of wells — an inner, in immediate prox- 
imity to the axis of the anticline; and an outer, of more extended 
area, encircling the point of the anticline in the San Pablo formation, 
and extending well along the southwest side of the general fold. The 
oil from the shales regarded as Tejon is of greenish color and varies 
in gravity from 33° to 38° B. ; that from horizons in the San Pablo is 
brownish black and of a gravity from 16° to 24° B., the higher in the 
eastern portion of the field. The production from both horizons is 
large. The depth of wells varies from 800 to 2,000 feet. 


This district lies on the edge of the desert at the eastern base of the 
Coast Range, about 50 miles west of Bakersfield. The railway station 
is McKittrick. The Coast Range in the vicinity embraces a number 
of parallel ridges, the highest constituting the eastern border of thJ 
Carriso Plains. From this each succeeding ridge attains a lower 
altitude, until the outermost line of hills is but a gentle elevation 
above the general valley. The developed oil field in the region of 
McKittrick lies along an interior ridge, separated from the outer ridge 
by a valley 1.1 miles wide. The Length of this district is about 25 

The formations involved in the occurrence of oil are the Monterey 
and the San Pablo, an unconformity existing between the two. The 
Monterey consists principally of siliceous shales, with their chalky, 
earthy, or more argillaceous modifications. Gypsiferous clays, lime- 
stones, and sandstones are but slightly developed, except in the north- 
western portion of the field, where certain beds have the general 
aspect of the Lower division of the Miocene. The siliceous shales 
within a zone 200 or 300 feet in width extending for S or 10 miles 
along the middle portion of the field, have, in a great degree, lost 
their stratified nature and become tissile by reason of the severe crush- 
ing to which they have been subjected in the sharp folding and fault- 
ing that has here taken place. Along this line of faulting the shales 
are of a chocolate brown, from the dried bitumen with which they 
have been infiltrated. 

The San Pablo, consisting of the conglomerates, sandstones, and 
clays typical of it, is well develoj^ed, and the terrane is marked, as else- 
where, by a deep deposit of dust wherever weathering has been car- 
ried to an extreme. The lowest stratum of the formation exposed in 
the field is a sandstone, conglomeratic in layers, the pebbles of which 
are of granite, siliceous shale, quartzite, and occasionally a pyritic 
rock that has been derived, perhaps, from some bed of much earlier 
age. This sandstone and conglomerate is generally exposed in close 


proximity to the fault referred to above, and is also stained with bitu- 

The structure of the McKittrick district is that of a sharp anticline, 
en echelon with adjacent anticlines of the range. Along its axis is 
developed the fault mentioned, which locally is of the nature of an 
overthrust, the siliceous shales of the Monterey west of the plane being 
pushed up well over the sands, conglomerates, and clays of the San 
Pablo. While this fracture and fold, along which most of the produ- 
cing wells of the district are located, are the most important of the 
region, other folds and faults exist in lines parallel with these, and at 
either end of the district one or another of them may become the chief 
fissure, j'et apparently, so far as is at present known, without especial 
accumulation of petroleum. Of the overthrust nature of the main 
fold interesting evidence exists in the material that is brought up by 
the bailer in drilling — not only sands more or less saturated with oil, 
but pebbles characteristic of the San Pablo. Conspicuous among the 
latter are those of siliceous shale of the Monterey type, bearing foram- 
iniferal remains, fish scales, and pholas borings. A noteworthy fea- 
ture of the line of disturbance for several miles, both northwest and 
southeast of McKittrick, also, are the dikes of sandstone richly impreg- 
nated with bitumen. These vary in length from a few feet to a half 
mile or more, and in width up to 10 or 15 feet; their depth, of course, 
is unknown. Gash veins of high-grade asphalt also occur. 

The productive oil wells of this district for its entire length lie 
within a zone less than a quarter of a mile wide, and in places less 
than 200 feet wide. Their depth varies from 200 to 1,500 feet, the 
shallower holes being in the center of the field, opposite McKittrick. 
The yield is from a few up to 700 barrels, the latter exceptional. 
In gravity the oil varies between 11° and 17° B. While the narrow, 
productive zone is persistent in the general directness of its trend — 
about N. 60° W. — it is, nevertheless, somewhat undulating, according 
as the axis of crumpling or faulting varies. 


This district lies in the southwest corner of the San Joaquin Valley, 
along the eastern base of the San Rafael Range, about 35 miles in a 
direct line southwest of Bakersfield, with which it is now connected 
by a branch of the Atchison, Topeka and Santa Fe Railway. It. is 
also distant from the McKittrick district about 25 miles, but recent 
developments in the Midway field, the northwestern extension of the 
Sunset, are gradually diminishing this gap. The Sunset field, like 
those to the northwest, is developed in the lower foothills of the 
Coast Range. The physical aspect of the region is that of moderately 
rugged mountains, 3,000 to 4,000 feet in altitude, bordered by a desert. 

The formations involved in the geology of the district include, in 
the higher portions of the adjacent range, a great series of massive, 


gray, concretionary sandstones and dark-colored shales, probably! 
Tejon; on the slopes, local developments of gritty sands, brown and 
yellow limestones, and gypsiferons clays, perhaps a lower division of 
the Miocene, the upper division consisting of siliceous shales, typical 
of the Monterey; in the low outer ridges, a successiou of conglomer 
ates, sandstones, and clays, many hundred feet thick, the equivalent 
of the San Pablo, of Middle Neocene age; and in the valley, Recent 
gravels. Between the San Pablo and older formations — the horizon 
of most importance from the petroleum point of view — there exists a 
marked unconformity, the line of union as exposed lying now at one 
horizon, now at another, in beds both above and below the break 
in continuity. Just within the border of the younger formation the 
development of the oil field has taken place, the wells drawing their 
petroleum from one or more of the conglomerates and sandstones 
adjacent to the plane of unconformity. 

Structurally, the strata of the Sunset district, while thrown into an 
anticline of great extent, present in detail a succession of folds, those 
of greatest amplitude lying farthest within the mountains, the gen- 
eral trend of all being about N. 50° W. Faults also exist, but none of 
large displacement was detected within or near the oil-producing area 
itself. The greatest crushing has been effected in the shales of the 
Monterey, but along the desert edge the San Pablo also shows a 
number of minor flexures, sonic developed en echelon, to which is 
due the frequent offsets to be observed in the trend of the oil belt. 
The general dip of the strata in the oil-yielding territory is northeast 
or toward the valley. Its direction is, however, modified by the 
flexures referred to, and by other and local variations in strike. 

The wells of the Sunset district attain a depth of from 500 to 1,500 
feet, and while there is a similarity in the oil sands, it is questionable 
whether the same horizon is everywhere the productive zone, for the 
San Pablo is deposited against a slope of the Miocene, from which it 
might have drawn the petroleum into several beds abutting it at the 
plane of unconformity. The wells in the Midway field are somewhat 
deeper than those in the Sunset area proper, having been drilled 
farther out on the slope of the anticline. The especial interest of 
these wells is their position along the exterior of the anticline at a 
very considerable distance from both axis and end, and in a locality 
where the strike and dip are apparently maintained with great regu- 
larity. The gravity of the oil in the Sunset district varies from 11° B. 
in very shallow wells in the southeastern part of the field, to 17° or 
18° B. in the deeper ones in the northwestern portion. 


The Kern River field, the most productive in California, lies about 
3 miles north of Bakersfield, in Kern County, near the southeastern 
extremity of the San Joaquin Valley. As at present developed it 


occupies an area north of the river of approximately 12 square miles, 
extending but a few hundred feet south of the stream. The general 
trend of the oil-yielding zone is N. 40° W. , coincident with the strike 
l ' of the rocks. The field has excellent railway facilities, and an 8-inch 
pipe line to Point Richmond, on San Francisco Bay, about 300 miles 
distant, is under construction. In addition, there is a tank storage 
capacity in the field of nearly 2,000,000 barrels. Refineries, also, are 
nearing completion. The production of the field at the time of the 
writer's visit was approximately 3,000 cars a month, actual shipments. 

In topographic position the field lies at the edge of the uplands of 
k the San Joaquin Valley, 12 miles from the base of the Sierras, and on 
the southwest slope of the low ridge which separates Kern River 
from its tributary, Poso Creek, about 7 miles to the north. Although 
immediately adjacent to the fertile farms of the valley, the surface 
aspect of the region itself is that of a desert hopelessly beyond recla- 
mation. The strata underlying are soft and yielding to atmospheric 
agents, and lie at but a shallow dip (SW.,), and as a result, erosion 
has transformed the area for many miles into typical "bad lands." 
South of the river a mesa country prevails. 

The surface geology of the Kern River field is comparatively sim- 
ple. The principal geologic formation of the region adjacent on the 
east is determined by its fossils to be of Lower Miocene age. This 
passes beneath the productive area, but whether upon more detailed 
examination some of the surficial beds of this area will not be found 
to be representative of the San Pablo is an open question. The strata 
of the Lower Miocene include conglomerates, sandstones, and clays, 
the several members of this series into which it may be differentiated 
upon physical or other grounds arranging themselves in broad or nar- 
row zones of outcrop according to the thickness to which they have 
been developed and the angle of their always gentle dip. But while 
the differentiation of horizons mentioned is comparatively distinct 
over broad areas, there are local gradations from one zone to another 
that frequently render it impossible to trace a maintenance of regu- 
larity in the succession of strata. The entire series of beds, in fact, 
has the appearance of a shore deposit along the granite range of the 
Sierra, in which currents and waves have played their part in the dis- 
tribution of materials, with the result that a sandstone at one point 
may thicken or thin, and, according to conditions, be replaced by clay 
or conglomerate, which, in their turn, again act in like manner. This 
relation of the sediments one to another, which is evident from the 
surface outcrops, is especially emphasized in the hundreds of wells 
bored in the 12 square miles of the Kern River field. Even in the 
wells of a single company, where the records have been uniformly 
kept, this variation of sediments is a conspicuous feature, and it is 
impossible for one to say from the record of one well what may be 
expected in a hole to be drilled at a distance of 200, 400, or 600 feet 


from it. A feature that is to be considered in this connection, how- 
ever, is the fact that because of the lenticular form assumed by the 
deposits of sands, gravel, and clays, a certain interlocking of sedi- 
ments has taken place that has permitted a free circulation of oil 
throughout the entire thickness of the oil-bearing zone, rendering it 
remarkably productive. 

The geologic structure of the entire region of which the Kern River 
field is a part has not yet been worked out. There is a general south- 
westerly dip of the Miocene beds from the Sierra granites outward, 
and there is abundant evidence also of subordinate folds, the axes of 
which lie more or less diagonal to that of the Sierra uplift. It is on 
the southwestern slope of one of the anticlines of this series that the 
oil field has been developed. The axial trend of this fold is approxi- 
mately N. 40° W., with Local variation to N. G0° or 70° W. With the 
rarest and most local exceptions, the dip is southwest, usually under 
5° and often but 2° or 3°; and in an examination of the Lower Mio- 
cene beds from the immediate vicinity of the granite outward there 
was found at no point a dip in excess of 10°. Along the line of the 
granite, however, the dip maybe considerably steeper, indicating the 
extent to which the Tertiaries have been involved in the general 
uplift of the main range. The axis of the Kern River anticline 
appeal's to lie in the valley of Poso Creek, but the minor undulations 
are so numerous that without detailed examination it is hazardous 
to say just where the center of the arch is situated. 

A study of the well records of this field points to the existence of a 
general body of sands and gravels from the surface to a varying 
depth up to 200 feet. Beneath this there is usually a stratum of blue 
clay, also varying in thickness from a few feet up to 100 feet. This 
clay is impermeable to the waters which nearly everywhere exist in 
the sands above. Below 1 lie clay in all wells is an alternation of sand 
and clay without regularity and varying in their relative thicknesses 
from point to point. These sands constitute the oil reservoir of the 
field, and as high as 400 or 500 feet, of them have been encountered 
in a single well. In a great many wells 200 or 300 feet of oil-bearing 
sand are found. Below the oil sands is another thin, blue clay, in 
which the casings are, as a rule, landed. Occasionally a well has 
perforated this, penetrating a water-bearing sand beneath, and in one 
or two instances holes have been carried to still greater depths, pene- 
trating a second clay underlying the oil sands, and finally passing 
into a mass of sand and gravel which yields an enormous amount of 
water. Many of the wells of this field at first flow, but sooner or 
later all require pumping. The production is from light up to 600 
barrels a day, according to the age of the well, its condition, and 
the amQunt of sand upon which the well has to draw. The gravity of 
the oil varies from 13° to 17° B., the lighter being found in the 
western portion of the territory. The color of the oil is black. 




This district lies in La Graciosa Hills, 10 miles south of Santa 
Maria, in the northwestern part of Santa Barbara Count}- . The hills 
attain an altitude of 500 or 600 feet above sea level, and 1heir trend 
is northwest-southeast, coincident with the structural development of 
the country. Their surface aspect is that of grassy pasture lands or 
of areas more or less densely covered with the live oaks peculiar to 
the Pacific coast. The region is rendered accessible by a line of rail- 
way to Santa Maria and San Luis Obispo. 

The geology of the region embraces an underlying series of folded 
Monterey shale, of both the soft and more organic material and that 
which is hard and siliceous, the former predominating. So far as 
observed by the writer, this series of beds is not exposed at any 
point in its entirety. Overlying the Monterey unconformably is a 
heavy and extensive deposit of Pliocene sands, grits, and conglom- 
erates. The composition of these is chiefly quartzose, although there 
is a mingling of other debris derived from the underlying shales and 
from the granite and eruptives of more or less distant localities. 
The full thickness of the Pliocene deposits is undetermined. 

The structure of La Graciosa Hills is that of an anticline, the axis 
of which has a general trend of N. 55° W. The Monterey shales, 
which occupy its heart and are exposed over considerable areas, are 
greatly contorted, but the younger sands of the Pliocene, where 
mantling the older formation, dip to the northeast and southwest 
from but 2° to 25°, according to their position on the flanks of the 
fold. A marked unconformity exists between the Pliocene and 
Miocene deposits, and it is impossible to suggest the surface con- 
figuration of the sea floor upon which the younger of the two forma- 
tions was laid down. 

The developments in the fall of 1902 were chiefly confined to the 
Carreaga ranch, on the southwestern slope of the anticline and hills, 
but drilling was being prosecuted at a number of points west of the 
producing area. On the Carreaga ranch the wells start in the Plio- 
cene conglomerates and sandstones, passing into shale below, and 
thence to the oil sands. Whether the shale was of the Monterey or 
not is a question for future determination.. Difficulty will attend its 
solution because of the uncertainty of measurements by reason of the 
uneven surface attendant upon the unconformity existing between 
the siliceous shales and the younger sands. Texture, however, 
may aid, 

The wells of this territory are large producers and the oil is of high 


This oil field extends along the Pacific shore for nearly a mile in 
front of the small village of Summerland, 5 miles east of Santa Bar- 



bara. The wells are located on the bluffs, the shore, and upon wharves * 
extending into the sea for nearly a quarter of a mile. The physical 
aspect of the country is that of an undulating but highly cultivated | 
terrace, 3 or 4 miles wide, lying between the sea and the lofty and" 
abrupt range of the Santa Ynez Mountains, which parallels the whole f 
coast of Santa Barbara County. 

The formations of the region are the equivalents of the great red 
sandstone series of the Sespe Canyon, 50 miles to the east; a series of 
rusty sandstones and shales, with their interbedded, concretionary 
limestones overlying the foregoing; siliceous and argillaceous shales 
of Monterey type; a succession of conglomerates, sandstones, and 
clays believed to be the equivalent of the San Pablo, and from 100 to 
200 feet of Quaternary sands and gravels. An unconformity is evi- 
dent between the Quaternary and the San Pablo and between this 
latter formation and the Monterey. 

The structure of the region has not been entirely worked out, but 
there exists an anticline with axis exposed in the red beds along a line 
midway between ocean and mountain base. North of the axis there 
is, for a distance, apparently the same succession of strata as in the 
Sespe region ; that is, the red beds are overlain by a series of rusty 
sandstones, shales, and limestones. Beyond these, however, along 
the higher mountain slopes, the present examination did not extendi. 
South of the anticlinal axis the red beds, with a dip southward of 
from 45° to 80°, are succeeded by shales of Monterey type, and these, 
in the immediate vicinity of the shore, by the probable equivalent of 
the San Pablo. The Quaternary is exposed in the ocean bluffs, and 
here and there overlaps the older formations far toward the moun- 
tains. From the difference in the succession of the formations south 
and north of the anticlinal axis it is possible that an important fault- 
extends along the bench lands of this portion of the ocean's front, the 
throw of which can not be less than 4,000 or 5,000 feet. An alterna- 
tive of this fault may be an unconformity between the siliceous shales 
of the Monterey and the red beds of the Sespe formation. 

The Summerland oil field is developed in strata having a southerly 
to southwesterly dip of from 30° to 90°. It lies at a distance of approx- 
imately 1 mile from the axis of the anticline. The source of the 
oil is in one or more sands of the formation believed to be the equiv- 
alent of the San Pablo, at a distance not far from its line of union 
with the underlying Monterey. The well records in the main point 
to a body of oil sand from 80 to 120 feet below the derrick floor, and 
to another 40 or 50 feet below this, but many of the wells extend to 
depths of 400 or 500 feet. The oil throughout the field is mixed with 
a considerable amount of water, which is probably due to careless 
methods in drilling, although it may be from the shallow depths of 
the wells that sea water has penetrated to the productive beds. The 
gravity of the oil in the upper and lower sands is said to be, approx- 


inately, 10° and 14° B., respectively. The yield of the Summerland 
veils averages a barrel and a half to two barrels a day, although 
>ccasionally a well is found that for a while has a yield of 10 or 15 
parrels, but such wells are the exceptions. The district has been 
productive for several years, and the comparatively large original 
field of the wells has now been reduced to a minimum. 


The valley of the Santa Clara is of structural development, modified 
by erosion. It heads in the San Gabriel Rauge and in the mountains 
bo the north connecting this with other portions of the Coast Range 
and with the Sierras, and, after a westerly course of 75 to 100 miles, 
enters the Pacific a little south of the town of Ventura. The valley 
is given over to agriculture, but the mountains on either side are the 
Loci of many important oil fields. 


The mass of rugged mountains north of the Santa Clara Valley, 
forming the watershed between it and the great Central Valley of 
California, represents the convergence of the several ranges which to 
the northwest maintain a conspicuous individuality. Pine Mountain, 
8,826 feet in altitude, is their culminating point. The area thus 
occupied is a part of that recently set aside by the United States 
Government to be known as the Pine Mountain and Zaca Lake 
Forest Reserve. It is accessible only by trail, and is almost wholty 
uninhabited. The southern edge of this great range is one of the 
important oil fields of the Pacific coast. 

The geologic structure of the region as a whole has never been 
determined, but, in the present investigation, that along the edge of 
the Santa Clara Valley was in part deciphered. It is probable that 
the converging ranges have each their own structural representative 
in this mountain mass, of which that studied is but a single member — 
the eastward continuation, perhaps, of the Santa Ynez Range. 

The formations involved in the composition of the oil fields and their 
contiguous territory embrace several thousand feet of dark-gray 
quartzites and interbedded shales, which are believed to be Eocene. 
Overlying these are from 1,000 to 2,000 feet of red sandstones, con- 
glomerates, and shales, the last in the minority. The age of these, 
also, may prove to be Eocene. From their remarkable development 
on the Lower Sespe River they are commonly designated by the name 
of this stream. Above the red beds is a succession of 200 or 300 feet 
of brown, rusty sandstones, followed by 1,000 or 2,000 feet of gray 
and purple shales, with thin, interbedded, fossiliferous limestones 
containing Lower Miocene forms. Succeeding the shales is a promi- 
nent, cliff-forming, yellowish-white, concretionary sandstone 200 or 


300 feet thick, followed by other shales which are hard, very siliceous, 
and light gray or white. Overlying these is a second sandstone, | 
somewhat similar to the first, but less concretionary, and this again 
is overlain by other shales siliceous in tendency, but generally more 
earthy and friable, and of a brownish color. The correlation of this 
series in its entirety is in doubt, but the lower, highly siliceous shales ! i 
are unquestionably of the Monterey type, while the sandstones and 
the associated shales may also prove to be of the same formation. 
Unconformable upon the foregoing rest several thousand feet of con- 
glomerates, sandstones, and clays, which carry fossils that identify 
the beds as of the San Pablo horizon in the Middle Neocene. Youngest 
of all are some late Pliocene or Pleistocene conglomerates along the 
slopes of the Santa Clara Valley. 

The structure of the region is that of an anticline of very consid- 
erable proportions, modified by subordinate folds and faults of the 
utmost intricacy. Its axis has a somewhat irregular trend, varying 
from N. 70° W. to N. 80° E., the principal curvature occurring in 
the hills opposite the town of Pirn. The heart of the anticline lies 
in Topa Topa Mountain and is occupied by the series of Eocene 
quartzites and shales. Around these circle successively the Sespe 
red beds, the Lower Miocene shales, the Monterey, and the equiva- 
lents of the San Pablo, the last occupying vast areas extending from 
15 to 30 miles or more east of the heart of the fold. On the north the 
anticline is limited by other folds of equal importance, On the south 
the flexure is modified by a succession of sharp folds of greater or 
less extent, and by faulting, an especially important line of fracture 
passing east and west in front of San Cayetano Mountain, extending 
westward into the Ojai Valley, and eastward, perhaps, crossing the 
Santa Clara Valley. Numerous branches are given off from this 
fracture, particularly toward the west. 

It is in such an assemblage of strata, with the intricate folding 
to which they have been subjected, that the oil wells of the region 
under discussion occur. In horizon the oil is drawn from the lower, 
middle, and upper portions of the Sespe red beds, from the rusty 
series at the base of the Lower Miocene, and from sandy measures in 
the overlying shales; from the great sandstones which succeed and 
are associated with the shales of Monterey type; and, finally, from 
the equivalents of the San Pablo beds themselves. In addition, oil 
is known to occur in the Eocene quartzites forming the heart of the 
anticline. Fifteen thousand feet of strata, therefore, yield petroleum 
at one point or another in this field. The distribution of the devel- 
oped oil areas is either in a broad sweep about the axis of the main 
anticline itself, in close proximity to the axes of some of the subor- 
dinate folds, or along one or more of the great fault lines of the terri- 
tory, such, for instance, as that south of the San Cayetano Mountain 
and extending westward through the Silverthread district into the 


Ojai Valley. The wells of this field vary in depth from 1,000 to 2,000 
feet. The oil is said to have a minimum gravity of about 12° B., 
and a maximum of about 25° B. The yield of old wells varies from 1 
i to 20 or 30 barrels a day, though that of new ones rises considerably 
above this. 


On the south of the Santa Clara Valley, separating it from that of 
the Simi, are the Santa Susana Mountains and their westward exten- 
sion, Oak Ridge. The former of these is in direct continuation also 
with the San Gabriel Range, farther to the east. This linear series 
of ridges in its entirety may be regarded as a unit both topographic- 
ally and structurally. The San Gabriel Range has an altitude of 
over 5,000 feet, the Santa Susana Mountains of nearly 4,000 feet, and 
Oak Ridge rises a little above 3,000 feet. The northern face of the 
uplift is particularly rugged. 

The formations entering into the composition of the Santa Susana 
Mountains and Oak Ridge are as follows: At the base, heavy-bedded 
yellow sandstones, here and there pebble-bearing; overlying these, in 
their most differentiated form, are from 300 to 500 feet of conspicu- 
ously banded red and gray arenaceous clays, clayey sandstones, and 
grits; above this, a yellow and gray sandstone, vaiyingly prominent; 
still higher, from 400 to (500 feet of alternating gray and chocolate- 
brown shales, sandstones, and thin fossiliferous limestones. These 
are followed by from 200 to 500 or more feet of chalky and siliceous 
shales of the Monterey type, and these, again,. unconformably, by a 
great mass of heavy, coarse, granitic sands and conglomerates. Of 
the foregoing beds the last may be the equivalent of the San Pablo, 
while the portion underlying the siliceous shale is, in part, perhaps 
wholly, of the Lower Miocene, fossils of this age occurring a short 
distance above the banded red and gray series. Correlation, how- 
ever, of this series of beds with those north of the Santa Clara Valley 
has only in part been possible. The San Gabriel Range is a crystal- 
line complex. 

While the Santa Susana Mountains and Oak Ridge may be regarded 
as a structural unit, there are, nevertheless, within the limits of the 
uplift many anticlinal flexures, at least four of which derive especial 
importance from being the loci of highly productive oil areas. Of 
these anticlines one extends from the western end of Oak Ridge for 
fully three-quarters of its length, the axis lying in the lower slopes 
bordering the Santa Clara Valley. The second, third, and fourth anti- 
clines, instead of paralleling the general ridge, lie diagonally trans- 
verse to it and en echelon with one another. The western of these 
extends along the easterly fourth of Oak Ridge and crosses the divide 
in the gap between it and the Santa Susana Mountains; the middle 
anticline follows diagonally the northern face of the Santa Susana 
Mountains, crossing the divide a mile or two west of the low point 


between them and the San Gabriel Range ; the eastern flexure conforms 
to the western extremity of this latter range, its axis, however, pass- 
in «• into the lower slopes of the Santa Susana Mountains about a mile 
north of the middle anticline. In addition to the foregoing are sev- 
eral intermediate flexures of minor importance. Faults, also, are 
present, the most prominent region of fracture and general dis- 
turbance being that of the Torrey wells, opposite the town of Piru. It 
is noteworthy that the line of this disturbance is in the direct trend of 
one to the north of the Santa Clara that may prove to be connected 
with the San Cayetano fault. 

The productive oil wells of the Santa Susana Mountains and Oak 
Ridge lie in proximity to the axes of the anticlines or to the zones of 
crushing described. The horizons from which the oil is derived 
include one several hundred feet below the lowermost sandstones 
exposed in Oak Ridge; another, perhaps these sandstones themselves; 
a third, some of the sands in the brown and gray banded shales; and 
a fourth, possibly the lower beds of the probable equivalent of the 
San Pablo formation. The depth of the wells varies from 1,000 to 
2,000 feet, according to location and the strata pierced. Their yield 
has been much greater than al present, except in instances where the 
territory is comparatively new. The gravity of the oil varies from 
14° to 40° B., the former in the eastern portion of the field, the latter 
in certain of the wells in front of the Santa Susana Range and Oak 



Los Angeles occupies an area about 8 miles square, the greater por- 
tion lying west of the Los Angeles River at its debouchement from 
the low hills which to the west pass gradually into the Santa Monica 
Range and to the east into the San Rafael Hills and the Verdugo 
Mountains. The Elysian Park Hills north of the city attain an alti- 
tude of about 750 feet above sea level, about 500 feet above the 
city itself. Their trend is northwest-southeast, their southwestern 
slope gentle and extending well within the city limits, their north- 
eastern slope abrupt and paralleling the Los Angeles River. The 
area of productive oil wells extends in a belt one-fourth of a mile wide 
from a point near the river at the northern edge of town to the west- 
ern limits of the city in the vicinity of Third street, a distance of 
about 3| miles. Still farther to the west, 8 or miles beyond the 
municipal boundary, are a half dozen more wells that may prove to 
be in an area structurally related to the Los Angeles field proper. 

The formations involved in the geology of the oil field embrace a 
series of heavy-bedded, quartzose, somewhat concretionary sandstones, 
with thin, interbedded shale and an occasional calcareous layer, con- 
stituting the main portion of the hills north of the city; overlying 
these, at least 300 or 400 feet of siliceous shale of Monterey type, 
and above this a succession of sandstones and sandy clays which 


have generally the appearance of the Pliocene strata of the Pacific 
coast, and some of which also carry fossils of this age. An uncon- 
formity doubtless exists between the last formation and that under- 
lying. Above all, here and there, are recent gravels. 

The structure of the Los Angeles field is anticlinical, the axis of 
the fold lying along the river valley above the city, its direction 
approximately northwest-southeast. The extent and precise nature 
of the anticline is undetermined, but the region of Los Angeles is 
apparently near the eastern end of the fold as it appears in the lower, 
concretionary sandstones, for the lines of stratification of these 
sandstones and of the overlying shales are traceable into the hills 
east of the river, where they turn northward, cross the Arroyo Seco 
into the San Rafael Hills, and thence veer to the west. The dip 
in the latter territory is northeast, the opposite of that in the same 
formation southwest of the river. Locally the anticline is modified 
by subordinate flexures, some of which are of important significance. 
Faults also are present. 

The Los Angeles oil field is developed in the strata believed to be 
Pliocene, on the southern leg of the general anticline. The trend of 
the productive belt, however, instead of conforming to the axis of 
the main fold, follows the strike of the formations on the south of a 
subordinate fold divergent from the main flexure, and hence has 
assumed a direction closely approximating east and west. Evidence 
of this subordinate flexure and of the syncline which separates it from 
the main fold is to be found in the northwestern portion of the city. 
The average dip of the strata adjacent to the oil belt is between 30° 
and 50°, but local disturbances of the beds, sometimes marked, are 
found here and there, and it may be that faulting, too, has played 
its part in the accumulation of oil in the field. 

The Los Angeles field was one of the earliest developed in Califor- 
nia, and the lapse of time since the inception of drilling renders 
almost futile present-day attempts to obtain reliable data concerning 
the conditions of occurrence of the oil. There exist, however, the 
reports of the California State mining bureau, in which the progress 
of development has been well recorded by Mr. Watts. It is sufficient 
here that the wells probably draw their oil from two, three, or more 
horizons in the sands and arenaceous clays that overlie the siliceous 
shales. The general depth of the wells is from 600 to 1,200 feet. 
Their individual production is small compared with many in the great 
fields of the State, and, moreover, they show a gradual decrease year 
by year. This, however, has been partially compensated by the prod- 
uct of new wells. The gravity of the Los Angeles oil varies between 
11° and 18° B. 


The Puente Hills are a low east-west anticlinal ridge about 25 miles 
long and of varying breadth, their western end lying i<> miles a lill Le 


south of east from Los Angeles. The altitude of their highest point 
is 1,655 feet above sea level. Their slopes are comparatively smooth 
and well grassed, and in certain localities there are limited areas of 
oaks. Tributaries of the San Gabriel drain them on the north, and 
of the Santa Ana on the south, but for most of the year the stream 
courses are dry. 

The formations embrace sandstones, shales, and conglomerates, 
which from present evidence are to be regarded as equivalents of the 
Lower Miocene, Monterey, and San Pablo formations. The Lower 
Miocene is represented by several hundred feet of yellow and gray 
concretionary sandstones, with thin, interbedded layers of siliceous 
shales of Monterey type. These sandstones have an enormous devel- 
opment in the eastern half of the Puente Hills, and according to 
report continue southeastward across the Santa Ana River into the 
Santa Ana Range, where fossils have been found in them which 
determined their horizon. 

The interbedded shales of this series, while of the Monterey type, 
arc hardly to be classed in this division of the Miocene, by reason of 
their occurrence in the midst of sandstones which are known to carry 
Lower Miocene fossils. On the other hand, in the western half of the 
hills there are strongly developed siliceous shales that carry Monterey 
fossils and are to be regarded of this age. 

The third and youngest series of rocks in the Puente Hills, forming 
a prominent terrane along their southern base, is referred, from its 
fossils and its lithologic features, to the horizon of the San Pablo. 
The formation here consists of several heavy conglomerates, sand- 
stones, and argillaceous shales and clays. The sandstones and clays 
break down and disintegrate to the same impalpable powder as do 
those of the formation in the region of Sunset, McKittrick, and Coal- 
inga. This formation rests unconformably upon those below. 

The structure of the Puente Hills is that of an anticline modified 
by numerous subordinate flexures, the axes having a general trend 
of N. 65° W. The western half is greatly contracted in its width, 
while the eastern half is correspondingly expanded. Faults, also, 
have entered to an important degree into the structure of the hills, 
especially along the southern slope. Of these, or of an excessively 
sharp crumple accompanied by minor anticlinal flexures, an especial 
instance is to be found in a line of disturbance that passes immedi- 
ately north of the Santa Fe wells, crosses to Brea Canyon, and is, in 
fact, traceable at intervals over the entire distance to the region of 
the Whittier wells. The Santa Fe and Brea Canyon wells are close 
to this line of disturbance ; perhaps, also, the wells east of Whittier. 
The Puente wells, lying between the latter and those of Brea Canyon, 
are situated at some distance from the fractured zone, yet are to be 
found in an area of considerable crumpling immediately adjacent to 
the axis of the main fold. The geology in the immediate vicinity of 


the Santa, Fe, Brea Canyon, and Whittier wells is rendered still more 
complex by the proximity of the line of unconformity between the 
San Pablo and underlying formations. 

The horizons believed to furnish petroleum in the Puente Hills are: 
For the Brea Canyon wells and most of those lying, east of Whittier, 
the sands of the San Pablo formation; for the Santa Fe, the strata of 
uncertain horizon in the disturbed area at the base of the hills in 
their vicinity, in part, at least, of the Miocene; for the Puente wells, 
probably the more sandy horizons in the great body of shales consti- 
tuting the heart of the main anticline in its more contracted part, the 
precise horizon of which in the Miocene is somewhat indefinite. 

The wells in the Puente Hills are of wonderful productiveness, the 
yield of many rising above 200 barrels a day, and in instances ap- 
proaching 1,000 barrels. As in the case of all fields, however, the 
production falls off: in greater or less degree according to the life and 
condition of the wells and the territory drained. The depth of the 
wells is between 900 and 3,000 feet. The gravity of the oil varies 
from about 15° to 33° B. In color, both the black and green varieties 

The region is connected by pipe line and rail with the main railways 
of the Santa Ana Valley. 


From the facts established in the preliminary examination of the 
oil fields of California it appears — 

That the productive areas have been in every instance developed 
in connection with anticlines, either in proximity to their axes, along 
their flanks, or about their terminals. 

That in several instances faults, or intense disturbances of the 
strata, have accompanied the folding, causing along their lines inter- 
stitial spaces in which petroleum could accumulate, and thus result- 
ing in an increased supply and yield. 

That there are at least ten or twelve horizons in the 20,000 feet or 
more of strata from Eocene to Pliocene that carry oil in quantities of 
economic value. 

That the reservoirs are either conglomerates, sandstones, or the 
arenaceous members of the great shale groups in the Miocene. 

That oil derived from shales is generally lighter than that of which 
sandstones and conglomerates are the source. 

That the stratigraphic and structural conditions under which oil 
occurs in the known fields are many times repeated elsewhere in the 
Coast Range and the territory contiguous thereto, from which it may 
be argued that additional fields will in turn be discovered; and that 
this view is strengthened by small wells already drilled and by the 
known distribution of petroleum as evidenced by its seepage. 

That the supply is exhaustible. 

Bull. 213—03 21 


By N. M. Fenneman. 


For many years the rocks near Boulder have been popularly sup- 
posed to contain petroleum. The basis of such rumors lay partly in 
the strong bituminous odor of certain rocks and partly in certain 
cases of seepage known as "oil springs." Reports based on the 
former can be traced back to 1867, at which time the black Benton 
shales were dug into in search of coal. Their evident bituminous 
character led Mr. Joseph Wolff and others about ten years later 
to attempt the formation of an oil company, with the intention of 
drilling near the center of the present developed field. The proposed 
location at that time was determined by going straight east from the 
excavations in the upturned Benton of the foothills to a point on the 
plains where it was supposed the same strata might be horizontal. 
The project failed for lack of funds. 

The oil springs which have been reported lie north of this area, the 
one best known being on the Culver ranch on the north bank of the 
Little Thompson, 17 miles north of Boulder and several miles east of 
the foothills. Here, at the base of the heavy sandstone stratum in 
the Pierre (mentioned below), a seepage of oil has been observed for 
forty j^ears. Several similar but less-known occurrences are reported 
from 5 to 10 miles north of Boulder. 

In 1892 a well was drilled on Gunbarrel hill, 1 mile north of Boulder 
Creek and 7 miles east of the foothills. Accounts of this well are 
very conflicting. Sufficient encouragement seems to have been 
obtained from this attempt to keep alive the idea that future efforts 
in the vicinity would develop a producing field. 

Upon the renewal of interest in 1001 the Boulder Oil Company was 
organized through the efforts of Mr. Isaac Canfield and Mr Charles 
Page. The McKenzie well was drilled by this company. This well 
struck oil in January, 1902, since which time many companies have 
been organized and the exploiting of the field has proceeded without 

The exact location of most wells has been determined by "bobbers." 
Rumors ascribe to Hayden various utterances on the subject of oil, 

fenneman] THE BOULDER, COLO., OIL FIELD. 323 

and it is even claimed that he set stakes to mark the proper location 
of wells. A part of Sheet XII of his published atlas has been freely 
used as "Hayden's oil map," and the area of outcrop of his Colo- 
rado formation (including the Pierre) has been largely advertised as 
"Hayden's oil belt." The belief even exists among some investors 
that his survey was made for the purpose of locating oil. 


The Boulder oil held, so far as developed, has its center about 3 
miles northeast of the city of Boulder, Colo. Most of the wells which 
have attracted attention as producers lie in a north-south line a little 
less than 3 miles east of the prominent Dakota hogback which marks 
the eastern limit of the foothill belt. 

Stratigraphy. — Practically the entire Mesozoic group is represented 
in this district, and most of it is of interest in the study of the oil. 
At the base are 2,000 feet of Red Beds of the foothills consisting largely 
of coarse, red, feldspathic sandstones or conglomerates, upturned at 
a high angle and forming a sharp and rugged ridge. The upper 400 
feet are more argillaceous and vary more in color, from light-colored 
shales to dark-colored, ocherous, red shales and sandstones. These 
Red Beds rest upon the uneven surface of the pre- Cambrian and are 
themselves practically free from fossils and carbonaceous matter. 
They therefore form a definite base in which and below which it is 
useless to look either for the accumulation of oil or for its sources. 
All higher formations are associated in some way with indications 
of petroleum at various places in the Rocky Mountains, and in this 
connection will be mentioned below under the occurrence of the oil. 

Overlying these Red Beds is the Morrison formation, consisting of 
about 250 feet of clays and limestones, with argillaceous and calcare- 
ous sandstones. These beds, like the upper ones of the Red Beds, are 
easily eroded, and the line of their outcrop is marked by a continuous 
valley. They are not notably fossiliferous in this immediate vicinity. 

The Dakota sandstone (Upper Cretaceous) overlies the Morrison. 
Its outcrop, forming the well-known Dakota hogback, is, next to the 
crags of the red rocks, the most prominent feature of the foothill topog- 
raphy. The Dakota is here a 350-foot stratum of gray sandstone, some- 
times at the base conglomeratic and often at higher horizons quartzitic. 
Its outcrop would, on the whole, indicate that the Dakota is here as 
elsewhere a porous stratum, though its high dip toward the plains 
soon carries it beyond the reach of the drill. Like the strata below 
this is also poor in fossils. 

In general conformable on the Dakota are the Benton shales, 
dark and bituminous, with a thickness of 500 feet. Locally, as at 
the north end of the field, these shales become dense black limestone. 
Certain horizons are crowded with fossils, especially species of Ostrea 
and Inoceramus. 


Above these shales the Niobrara formation has at its base 20 to 30 
feet of limestone, compact, brittle, and fossiliferous. The remaining 
300 feet vary from calcareous shales to shaly limestones; they are 
fossiliferous and bituminous, and certain beds, from a few inches to 
a few feet in thickness, are almost solid masses of Ostrea shells. 
The topmost beds are of a gritty, shaly limestone having a buff color. 

Overlying these and prominent from their contrast in color are the 
dark shales at the base of the Pierre. They are-spar ingly fossiliferous, 
but contain much finely disseminated carbonaceous matter. The 
Pierre has a total thickness in this vicinity of probably 7,000 feet. 
The dark color belongs more particularly to the lower part, the 
remainder being generally lighter and having, after weathering, a 
characteristically greenish-drab tint. 

While, as a whole, a remarkably uniform mass of shale, the Pierre 
has occasional beds which are more or less sandy, the constitution of 
these varying from clay shale to pure sand. Only One such sand- 
stone attracts attention by its outcrop. This is a gritty bed lying 
about 2,000 feet above the base. Three miles north of Boulder it is 
about 100 feet thick, but it thickens rapidly toward the north. From 
about 3 miles north of Boulder its outcrop is almost continuous for 
many miles to the north. There has been considerable speculation 
concerning the relation of this sandstone to the oil, but, as will be seen 
below, the stratum has no special significance. The texture of the 
Pierre will be mentioned more particularly in connection with the 
subjects of drilling and the occurrence of the oil. 

Structure. — All the strata are steeply upturned against the moun- 
tains. The Red Beds immediately west of the oil fields dip toward 
the plains at an angle of about 55°. Higher strata outcropping 
farther to the east have successively greater dips until the Niobrara 
is reached, which is about vertical. Eastward from this line there is 
a rapidly diminishing dip, and within a very few miles the position 
may be horizontal or even show local westward dips. 

Minor folds almost certainly exist. In the absence of ledge-making 
strata they can not be determined by outcrops and have no influence 
on the topography. Excavations have, however, revealed occasional 
dips which are plainly not a part of the general eastward inclination. 
Also the data from one small group of wells, but 2^ miles from the 
foothills, strongly indicate local folding with dips as high as 15° or 
20°. Here again the data are so limited that the direction of the 
folding is uncertain. If parallel to the mountains, it may be regarded 
as attendant upon mountain making; if the minor folds trend east 
and west, they are in harmony with the Boulder arch so far as that 
existed. a Other indications of a compressive force acting north and 
south are locally observable in the sinuous strike of the Niobrara 

"Eldridge, G. H., Mori. U. S. Geol. Survey Vol. XXVII, p. 110. 

penneman.] THE BOULDEE, COLO., OIL FIELD. 325 

Of faulting it can only be said that it is as yet undiscovered and 
probably undiscoverable unless it affects the strong sandstone ledge 
mentioned above. Faults abound, however, near by, as in the vicin- 
ity of Marshall, where the stronger Laramie preserves at the surface 
the records of displacements. The possibility of such dislocations 
within the oil field demands consideration both in the explanation of 
1 he occurrence of the oil and in the exploitation of the field. 


With few exceptions the wells thus far put down have been drilled 
in the Pierre. The exceptions are among the scattered wells to the 
east, which are on the very similar Fox Hills or even on the Laramie. 
These also traverse the Pierre for the greater part of their depths. 

Rate of drilling and expense. — Drilling in this formation is com- 
paratively easy and rapid. It is not uncommon to make 100 feet in a 
day at considerable depths, and this is sometimes done without change 
of bits. On the other hand, slow progress is made in certain beds. 
The average expense of drilling a wed] under contract with respon- 
sible parties is, at the present time, about 11.65 per foot for the first 
2,000 feet. Below that depth the cost is greater. Under such con- 
tracts the owner of the well furnishes casing. 

Water. — Surface water is usually encountered at about 15 feet and 
may be found in the first 100 or even the first 200 feet. Below the 
surface the wells are commonly "dry;" that is to say, the seepage 
into the well from the dense shales is so slow as to be of no signifi- 
cance in drilling. In isolated cases deep water-bearing strata are 
encountered, and such water is sometimes salt. At Lafayette, 11 
miles east of the foothills, water is reported as spouting from 4 to 5 
feet between the 10-inch drive pipe and the 8^-inch casing. This 
water was struck at depths of from 400 to 700 feet and is still flowing 
after a period of four months. Hot water was reported found at 
nearly 2,800 feet about 12 miles north of Boulder. In one well the 
water from this depth was distinctly briny. Other wells have yielded 
salt water from much smaller depths. In one well now pumping the 
oil is mixed with about 10 per cent of salt water, which was encoun- 
tered just below the oil. A slight admixture is found in at least one 
other well. 

Many wells are cased only to the depth of the surface water. 
Others require 1,000 or even 2,000 feet of casing. In general deep 
casing is not for the purpose of shutting off water so much as to avoid 
caving, which is common though not general. It has necessitated the 
abandoning of several wells. 

Reports of materials passed through. — By far the most common item 
in reports is shale or "slate," occasionally varied as "clay" or "soap- 
stone." Sand or sand rock is often reported. With a showing of oil 
it is often called "oil sand," with no particular reference to correla- 


tion with the sands of other wells. The composition of these "sands" 
is generally far from that which the name would suggest. They are 
not generally distinguished from the shales in color, but contain vary- 
ing proportions of siliceous grains. They are simply more arenaceous 
beds in the great mass of shale. Individual beds have all possible 
compositions between a good clay and a good silica sand, the latter 
being very rare. The thickness of these sandy beds may reach sev- 
eral hundred feet, but they are generally much thinner. In drilling, 
such beds are distinguished from the shales by their greater hardness, 
by the more rapid wear of the tools, and by the smaller amount of 
suspension in the water of the bailer. The washed-out samples com- 
monly appear under close examination as a collection of gritty shale 
granules whose edges have been rounded under the drill. The better 
grades show an admixture of quartz grains, and exceptional beds are 
almost pure sand. 

"Streaks" and "shells" are other terms used to indicate more than 
usual hardness at certain horizons. In the outcrops of these shales 
may frequently be detected hard beds a few inches or even several 
feet in thickness. They are either very calcareous or stained with 
iron oxide or both, and owe their superior hardness to concentration 
of these substances. Such induration may affect the entire bed 
equally, or may be concentrated into ellipsoidal concretions, which 
may be more or less separated, so that there are all gradations between 
the continuous hard plate and the isolated concretions. The word 
"shell" is suggestive of the latter, as the word "streak" is of the 
former, but in the reports the two words may be taken to be synony- 
mous and alike indefinite. The comminuted fragments of these hard 
masses are not easily suspended in the water of the bailer and (prob- 
ably for this reason, as well as their superior hardness) are not infre- 
quently reported as sand. On the other hand, many of the so-called 
hard streaks are no doubt siliceous. The reports of "lime rock" are 
probably to be traced to the same occurrences. Many concretions, 
also, have been cracked, and the cracks subsequently filled with 

The use of data obtained. — In such a mass of slightly differentiated 
shale the record of a well is somewhat monotonous and few have been 
carefully kept. Moreover, since the distinction between the shale 
and the so-called "sands" is merely one of degree, some drillers report 
large numbers of sand strata where others would report all shale. 
Under such circumstances a complete series of samples would seem 
to be the best possible log book. It has been difficult to obtain these, 
largely because of the same monotony which, to the superficial 
observer, has made the keeping of records unprofitable. Neverthe- 
less, records and samples taken under all possible circumstances have 
been reduced to as much system as possible. For all important cor- 
relations the data have been carefully sifted. Only such observations 

fenneman ] THE BOULDEK, COLO., OIL FIELD. 327 

have been employed as are least liable to error when made by the 
driller- Such, for example, are the "showings" of gas and oil, the 
occurrence of water-bearing strata, the character of such water, 
whether fresh or salt, and the hardness of the strata, as revealed by 
the frequency of the change of bits. 


TJie oil-bearing strata. — The beds from which the oil is obtained are 
the highly variable sands or sand rock described above as varying 
between clay shale and silica sand. Such beds may be met with at 
any depth and there is no depth at which such rock is certain to be 
found. Reports might indicate that it is slightly more abundant at 
a depth approaching 2,000 feet, but this may be due to the sharper 
lookout for sand as the well gets deeper. Not all of these strata con- 
tain oil or gas; some of the most porous sands give no indication of 

The thickness of such beds may be anything up to 100 or 200 feet, 
but a stratum ma}' yield oil or gas from a part of its thickness only. 
Such strata are plainly not so homogeneous as would appear from the 
bailings and are not porous sandstones. Except in an oil well they 
would probably not be called sands at all. It is not uncommon to drill 
many feet into such strata and then strike a showing of oil or gas 
with no attendant change in the texture of the rock that can be 
detected in the bailings. 

The lateral extent of these "sands" is generally small and always 
uncertain. Their outcrops are so few, so short, and so far apart as 
to afford little clue to the continuity of any one bed. As revealed by 
the drill, no one bed can thus far be definitely known to be more 
than half a mile in extent. Even that is a liberal assumption, based 
upon the encountering of sand at similar depths in all the wells 
within a radius of 80 rods. In even the best instance of this kind the 
texture of the sand varies from well to well, some having small quan- 
tities of oil, while others are dry. Moreover, a considerable local dip 
must be assumed in this case in order to correlate the sands of each 
well in a single continuous stratum. Hence it can not yet be affirmed 
with confidence that even in this case there is an uninterrupted sandy 
stratum one-half mile in extent. On the other hand it may well be 
that more discriminating reports would show continuity at many 
places where it does not appear from the reports received. 

The horizontal limitations of these sandy strata are in'obably best 
accounted for upon the supposition that their composition and tex- 
ture vary from place to place, and hence a sand stratum may grade 
into a shale at no great distance. The supposition that the deposits 
are in lenses of somewhat homogeneous character must also be 
admitted as possible, though direct evidence of such stratification 
is lacking. Such lenses should be readily recognized in a group of 


wells. Variations in thickness doubtless accompany the variations 
in material. 

The number of such strata passed in one well varies greatly. The 
drill may pierce several thousand feet of shale with little change in 
character, or a single boring may traverse half a dozen arenaceous 
strata, two or three of which may yield showings of oil or gas or both. 
These more porous strata are generally well separated, one from 
another, by the intervening compact shales. Oil may be found in 
any one of such strata or may be absent from all. It may appear in 
a lower while absent from a higher stratum, and seemingly the reverse 
may be equally true. Showings of oil or gas may occur in relatively 
dense beds while absent from porous sands near by. 

The isolation of the porous beds is well illustrated by the occur- 
rence of deep veins of water in some wells and their absence from 
neighboring wells at similar depths, or the deeper waters of one well 
may be salt and those of a near-b} 7 well fresh. 

The mutual independence of the several oil pockets is not empha- 
sized by any great diversity in the character of the oils from the differ- 
ent wells. With a few exceptions there is approximate uniformity, as 
shown by standard physical tests. Considering the striking uniform- 
ity of the great body of shales, this approximate uniformity is to be 
expected. It is too early to tell to what extent the yield of one well 
may be influenced by the pumping of adjacent wells. 

Relation to folds. — 11 will be seen from the above that the accumu- 
lation of oil is not yet seen to be related to folds in the strata. Anti- 
clinal arches of impervious stata are unnecessary to farm receptacles 
for oil and gas in so dense a rock as the Pierre shales. If such folds 
exist they do not appear al Hie surface, and they can not be recognized 
from well data until the same stratum can be identified in different 
wells. This would require a degree of precision in observation and 
reports not yet attained in this field. In the meantime the ever- 
increasing closeness of the wells is making the correlation of data 
more definite. 

While there is as yet no evidence thai deformation of strata has 
anything to do with forming receptacles for the oil, it is not yet cer- 
tain that the distribution of oil is independent of folds. According 
to the most plausible theories w r e may suppose that the substance of 
these oils was at a former time disseminated through lower rocks rich 
in organic matter. The concentration of this widely disseminated 
bituminous matter implies a movement through the rocks, perhaps 
for long distances. Such movement is conditioned by the texture of 
the rocks traversed. The permeability of rocks in the axial plane of 
an anticline may differ materially from that in the axial plane of a 
syncline. It is conceivable, therefore, that in a system of folds, how- 
ever gentle, the upward movement would be affected both in velocity 
and in direction by the position of the rocks to be traversed, whether 

i-knneman.] THE BOULDER, COLO., OIL FIELD. 329 

under an anticline, a syncline, or the limb of a fold. Oil might there- 
fore accumulate along certain lines, not because of being trapped in 
anticlinal arches, but because the products of the original decompo- 
sition or li distillation" (or whatever the process may be conceived to 
be) have been able to rise along certain lines and not along others. 

Whatever the explanation finally adopted, it is a noteworthy fact 
that the wells now pumping are, almost without exception, located on 
a nearly straight line, whose trend is north and south, parallel to the 
mountains. Should this line be found later to bear any relation to 
stratigraphic deformation, that relation will doubtless become an 
important element in future attempts to locate oil in this region. Such 
folds or faults, if determined at all, must be detected largely in accu- 
rately kept well records, because the rock disintegrates so readily as to 
make exposures of dips in surface outcrops of rare occurrence. There 
is no other way in which the same amount of work can yield results of 
such great financial importance as by the keeping of careful and 
minute daily records. 

The distribution of oil in belts parallel to the mountains can not be 
considered proved by the meager data thus far obtained ; and if proved, 
it might be due to causes not connected with structural deformation. A 
line parallel to the mountains was probably parallel to the shore line 
of the Cretaceous sea in which the sediments were laid down. The 
presence of oil might therefore be due to conditions of sedimentation 
at a nearly uniform distance from the shore, either the pl^sical char- 
acter of the sediments or the conditions favoring life. But these will 
not be discussed here. 

Shooting of wells. — All the wells pumped up to the close of the year 
1902 have been shot. The amount of nitroglycerin used in these 
shots has varied from 10 to 120 quarts. Dynamite charges have been 
as large as 500 pounds, 70 per cent nitroglycerin. The effects of these 
shots have not been uniformly favorable. The beneficial effects in a 
few of the best wells have doubtless been responsible for most of the 
later attempts. It is by no means certain as yet that this practice will 
be universal in this field. At least one well has recently begun pump- 
ing without being shot, and the owners have no immediate intention 
of shooting. The fact that the flow of some wells has decreased since 
the shooting will lead to greater caution, and it is to be hoped that 
it will lead to a more careful study of the conditions present in each 

The beneficial or harmful effects of a shot must depend largely upon 
the texture of the stratum yielding the oil, for it seems to be true that 
some shales are compacted rather than shattered by the explosion. 
For this reason, shooting is not practiced in the Florence field, which, 
of all the older oil districts, the Boulder field most resembles. Owing 
to the difference in texture of the various' beds yielding oil in the 
Boulder field, it is but reasonable to expect that the same shot which 


would prove beneficial to one well would be ruinous to another. On 
this account, if on no other, the texture and composition of the oil 
strata should b3 carefully studied by methods far more discriminat- 
ing than the superficial ones now used. 

A second reason for injurious effects from shooting lies in uncer- 
tainty about the exact depth of the sand which it is intended to shat- 
ter. Measurements of depths by steel tape are indeed becoming more 
common, but in a considerable number of wells the depths of all for- 
mations are known only by cable measurement. Even in wells but 
recently sunk, it is not uncommon that the stated depths of impor- 
tant sands are thus liable to errors of 25 to 50 feet. 

The possible injuries from a shot at the wrong place may be readily 
seen from the following considerations: Given a porous rock satu- 
rated with oil which is under a certain pressure. This rock is now 
pierced by the drill. The oil soon fills the hole and is pressed upward 
for the sole reason that it has no outlet in any other direction, being 
surrounded (as in this field) by impervious rocks. This well is now 
shot in such a way as to rupture the impervious rocks which have 
surrounded the oil sand. The oil may now leave the sand by other 
openings beside the well and may thus be dissipated in other porous 
beds and the well may be ruined. Such an effect may be produced 
even by shooting at the proper depth if the charge employed be too 
heavy. In one instance a well was shot at 740 feet with 500 pounds 
of dynamite, 00 per cent nitroglycerine. The formation above the 
sand was a uniform dense shale. A good quality of sandstone was 
blown from the hole in chunks reaching a maximum of 14 pounds* 
The shale was ruptured to the surface. Open cracks of an inch or 
more extended for some rods from the well. Presumably also, cracks 
reached a considerable depth below the sand which was to be shattered* 

It can not be too carefully borne in mind that the one object in 
shooting is to shatter the rock which carries the oil and that only. 
With this object in view, it is plain that intelligent and discriminat- 
ing shooting must depend upon information which the following 
questions may suggest: Is the texture of the oil stratum such as to 
give promise that it will be shattered rather than compacted? What 
is the exact depth of its top (and bottom if drilled through)? How 
much of a shot will the overlying rocks bear without giving other 
outlets to the oil? This last question is one of great importance in 
this field. It is needless to say that such questions can be answered 
only by a carefully kept log and close study of samples, not only of 
oil sands but of all strata in order to properly forecast their behavior 
under the influence of a shot. 

Sources of the oil. — The source of the oil is not yet determined 
within narrow limits. Much of the lower part of the Pierre is black 
with disseminated carbonaceous matter. The Niobrara below is simi- 
larly bituminous, yielding a strong odor from its more fossiliferous 

fenneman.J THE BOULDER, COLO., OIL FIELD. 331 

beds. The same is true of the Benton, whose shales are character- 
isticalty dark and whose bituminous odor is at least as well marked 
as that of the Niobrara. The Dakota bears oil in Wyoming, and 
asphalt oozes from its cracks at various places from Wyoming to 
southwestern Colorado. Even the Morrison beds contain some oil, as 
seen near the Florence field. 

The strata thus enumerated have a combined thickness of from 
5,000 to G,000 feet below the horizon of the lowest oil reached in the 
Boulder field. Not all parts of this great thickness are equally prob- 
able sources of the oil. The lower beds of the Pierre are usually 
darker in color and richer in organic matter than those horizons 
immediately below the Boulder oil. The best of the "oil springs" 
also point to a source not higher than the principal sandstone stratum, 
which is about 2,000 feet above the base of the Pierre. The Benton 
and Niobrara are probably richer in oil than any higher strata, and 
surely in this immediate locality far richer than anything below. 
The more probable sources, therefore, lie between the top of the 
Dakota and the middle of the Pierre, a thickness of strata probably 
limited to 4,000 feet. 

Of these 4,000 feet probably containing oil, from 400 to GOO feet of 
the most bituminous beds (the Benton shales) lie below the compact 
basal limestone of the Niobrara. This limestone, though less than 30 
feet thick wherever quarried for lime west of the oil territory, is very 
dense, and where unbroken must probably prohibit the accumulation 
of oil above from sources below this horizon. That it is unbroken 
beneath the oil field is by no means certain. Within 5 miles (the 
vicinity of Marshall) faults abound, many of them having displace- 
ments far greater than the thickness of the Niobrara basal limestone. 
Pronounced rupturing of the strata is shown within 2 miles, by the 
Valmont dike. Such faulting as that at Marshall could not be 
detected on the outcrop of the homogeneous and easily weathered 
Pierre shales. 

The folding which is almost certainly present would easily joint or 
brecciate the brittle Niobrara limestone to such an extent as to make 
it no barrier to the accumulation of oil above from the carbonaceous 
constituents of the beds below. For the present, therefore, the 
Benton shales should be taken into account, along with the higher 
strata, in the consideration of possible sources of oil in this locality. 


Since January 1, 1901, there have been built within 5 miles of the 
McKenzie well about 120 derricks. At 82 of these, wells have been 
drilled to depths varying from 200 or 300 to 3,400 feet. In addi- 
tion to these, 13 scattered wells have been drilled at various distances 
from the foothills, both north and south of Boulder from the Cache 
la Poudre River on the north to Coal Creek on flic south. Of these 


82 wells within 5 miles of the McKenzie, 57 lie within a rectangle hav- 
ing a length of 3 miles north and south and a width of 2 miles east 
and west, comprising sees. 8, 9, 16, 17, 20, and 21, T. 1N,R. 70 \V~. 
Outside of this rectangle but three pumps have yet been installed, 
none of which are at work at the present writing. Within this rec- 
tangle there have been installed in all 17 pumps, of which 13 arc at 
work regularly. The records of shipment from the entire field to 1 lie 
present represent substantially the products of these 13 pumped wells. 

Shipments prior to December 15, 1902, aggregated 9,000 barrels. 
At the present time the daily shipments are about 8,500 gallons, or 
about 200 barrels of crude oil. A small margin may be added to 
these figures representing the amount consumed at the wells for light 
and occasional fuel and sold at the wells for similar purposes. A 
small refinery has been erected, having a stated capacity of 70 barrels 
a day, but not much oil lias yet been handled here. 

The United Oil Company has laid its own pipe lines to all produc- 
ing wells and has bought practically the entire product, which has 
been shipped to its refineries at Florence, Colo. The price now paid 
on six months' contract is $1 a barrel at the mouth of the well. As 
may be inferred from the price, the oil is of high grade. It is a light 
illuminating oil with paraffin base. A valuable residuum now sold 
for fuel may in the future add materially to the price of the crude 


By Myron L. Fuller. 


During the field work in southwestern Indiana in 1902 two discov- 
eries, one of asphalt and one of oil, resulted from the sinking of deep 
wells. While up to the end of the year no important developments 
had taken place, it is not impossible that the discoveries may lead to 
such developments in the near future. In the following paragraphs 
brief notices of the recent discoveries and a short discussion of the 
geologic structure are given. 


During the drilling of a well by the Interstate Gas and Oil Company 
at Princeton, in 1902, a bed of asphalt several feet in thickness was 
found somewhat over a hundred feet below the Petersburg coal, or 
that which is mined three-fourths of a mile west of the well. 

In this connection it may be of interest to note that a similar bed is 
supposed to have been encountered in the old Hall well on the south- 
west outskirts of the town, about a mile south of the new well, and 
that in the mine to the west of the well a black substance, known as 
liquid asphalt, seeps into the bottom of the mine at 450 feet to such 
an extent that some of the rooms have been abandoned and closed. 
It is said to enter through a nearly vertical "break," filled with clay. 


Probably the best showing of oil found in this portion of the Slate 
was obtained near Birdseye, Dubois County, in the summer of 1902. 
The first well was drilled by the Southern Indiana Oil Company, of 
Evansville, Ind. Oil was found in what the drillers call the "Trenton 
rock," at a depth of about 1,000 feet. The well is stated to have 
afforded about 5 barrels a day, but no pumping for the market has yet 
been done. Up to the end of 1902 three wells had been drilled, two of 
which obtained oil. Early in March, 1903, a flowing well in sec. 3, 
T. 3 S., R. 3 W., was reported to have been brought in by the Stand- 
ard Oil Company, while another was about to be drilled in by the 
Southern Indiana Oil Company. The Ohio Oil Company is also 
operating in the field. 



The producing formation was penetrated to a depth of only 30 feet. 
The oil is described as a high-grade 42 per cent lubricating oil. Very 
little gas was encountered, and no determinations of pressure or vol- 
ume were made. 


Some years ago a considerable pool of natural gas was struck in the 
"Jumbo" gas well, near the Woolley coal mine, at Petersburg, but 
although considerable deep drilling was done at various times about 
Petersburg, Oakland City, Princeton, and other points in the region, 
no commercial pools were developed. The "Jumbo " well, after flow- 
ing for a time, ceased to produce, but has since been cleaned out and 
now supplies the illumination for the town and furnishes the fuel for 
several hundred gas stoves. It is said to show a rock pressure of 585 
pounds. A new well was being drilled at Petersburg during the sum- 
mer of 1002. 



While it is probable that similar if not greater pools may occur at 
other points in this region, their position can not be predicted in 
advance of drilling. The positions which are geologically the most 
favorable for drilling are the low anticlinal swells and the areas along 
the strike lines of the rocks just east of the points where their west- 
ward dip changes from flat to steep. Maps showing, by means of 
underground contours drawn on the Petersburg coal, the structure of 
the rocks in Pike, Warrick, and parts of Vanderburg, Spencer, and 
Dubois counties have been recently published by the United States 
Geological Survey." 


The general strike of the beds in southwestern Indiana is nearly 
north and south. Although there are many irregularities and even 
reversals of the dip, the general inclination of the rocks is commonly 
not far from due west. The amount of dip varies from 10 to 40 feet, 
with perhaps an average of about 20 feet to the mile. 

Among the more noticeable of the irregularities shown by the 
structural contours of the published maps of the Ditney folio are the 
shallow synclinal troughs near Littles, Ayrshire, Winslow, and near 
the county line north of Scalesville, and the low anticlinal swells 
northwest of Glezen, between Oakland City and the Patoka River, 
south of Winslow, near Arcadia, and southwest of Boonville. The 
crests of the swells afford, from a geologic standpoint, the most favor- 
able locations for gas wells, while their flanks afford the most promis- 
ing points for oil wells. 


a Geologic Atlas U. S., folio 84, Ditney. Descriptions by M. L. Fuller and G. H. Ashley. 


The anticlinal swell northwest of Glezen is a broad, low swell, the 
crest of which may be considered as starting near Clark and as pass- 
ing sonthwestward about midway between Glezen and Rumble and 
through the group of coal strippings at the head of Robinson Creek, 
finally subsiding at a point a little to the east of Oatsville. The second 
swell mentioned is first noticeable at a point about a mile south of 
Winslow. The crest passes a mile south of Ayrshire and through 
Sophia and Turkey Hill. It subsides before reaching Oakland City. 
The swell near Arcadia appears to be a somewhat irregular dome, the 
highest point of which is probably a little west of town. The axis of 
the last of the swells mentioned as occurring southeast of Boonville is 
apparently located a little over a mile south of the railroad at this 
place, from which point it extends southeastward toward Midway. It 
has, however, been traced only as far as the alluvial flats. 

The change from flat to steep dips and vice versa are usually grad- 
ual and do not admit of very exact location. In general the dips are 
steeper east of a north-south line drawn through Oakland City, and 
are flatter from this line westward to the vicinity of Francisco, where 
they again appear to steepen. The minor irregularities, sometimes 
characterized by dips as high as 5° or 10°, are likely to be of more 
importance as regards the occurrence of oil and gas than some of the 
broader features, but they do not usually extend for more than a few 
hundred feet at the outside and their location can seldom be predicted. 



By W. T. Griswold. 


In the latter part of the field season of 1901 the writer undertook 
the investigation of two important economie problems relating to the 
accumulation of oil, the field work being continued during 1902. The 
problems noted were, first, the determination of the degree of accu 
racy with which a stratum at considerable depth can be plotted under 
favorable conditions, viz, easily distinguished outcropping strata and 
high degree of accurac} 7 in topographic and geologic work, and, second, 
the effect of geologic structure on the accumulation of oil and gas. 


Structure. — The theory that the accumulation of oil and gas is con- 
trolled by the geologic structure of the porous strata in which it is 
contained has been advanced by Prof. I. C. White, and discussed by 
many leading geologists under the general designation of the anti- 
clinal theory. 

The anticlinal theory ascribes the accumulation of oil and gas in 
pools of economic value to the influence of geologic structure. The 
oil and gas are supposed originally to have been widely disseminated 
throughout the sedimentary deposits in which they were formed, and 
their segregation is thought to be due to the different specific gravi- 
ties of the various fluids occurring in the rocks. If a porous stratum 
contains gas, oil, and water, these fluids will arrange themselves 
according to their specific gravities, and if this stratum is not hori 
zontal the lighter fluids will be forced toward the higher part of the 
stratum until their progress is stopped by change in structure or other 
conditions. In this case an accumulation of gas and oil will be formed 
that may be of sufficient quantity to be of economic value. 

This theory is now generally accepted by leading geologists. Unfor- 
tunately, however, only a small percentage of the men actually 
engaged in the production of oil attach much value to any geologic 
theory. This is probably owing to the fact that the method of repre- 
senting geologic structure by contours has not been previously applied 


to the oil-bearing strata, so that each oil operator might himself study 
the structural conditions which have produced valuable oil pools in 
the past. The many failures of those hunting for oil on the anti- 
clinal theory have thrown discredit upon the ability of geologists to 
assist in the location of productive territory. Most of these failures 
have been due to lack of knowledge concerning the geologic structure 
or to the absence of other conditions necessary for the accumulation 
of oil. Although geologic structure is of primary importance, it is 
only one of three or more conditions that must be fulfilled in order to 
produce an oil pool of economic value. 

Porosity of the sand. — The condition of the sand as to degree of 
porosity and capability of holding a fluid is a factor of great impor- 
tance, and One that, with the geologic structure, governs the accu- 
mulation of oil. It is evident that when a sand is loose and composed 
of large grains fluids may pass easily between the particles, and that 
a much less slope or grade would cause salt water, oil, and gas to 
accumulate in separate bodies than if the sand were fine and close 
grained. The condition of the sand can in no way be determined 
except by the sinking of a test well. , In many instances, within a dis- 
tance of 600 feet from wells of large production from a good sand, 
other test wells have found the sand hard and closely cemented and 
incapable of holding fluids of any description. 

Degree of saturation of sand and position of water line. — The sat- 
urated condition of the porous stratum is another factor of primary 
importance in the formation of a pool of oil, and one that has not been 
given due prominence. The water-line theory, as advanced by the 
writer, assumes that the tops of the anticlines often contain no liquid 
upon which the oil may climb, so that, while the gas from its lesser 
gravity may pass on to the very highest point of the stratum in which 
it is contained, the oil will rise only so far as it has the water for a 
supporting medium. Tfre height of the water line thus gives a line of 
equal elevation along the strike of a stratum, which, when once deter- 
mined by the drill, should be followed to keep on the line of oil-pro- 
ducing territory. The belt of oil accumulation may be illustrated by 
a comparison of it to the sand beach along the shore of the ocean, 
where the sea represents the salt-water area, the upland the area of 
dry rock, and the sand the belt of saturated oil stratum. This belt, 
like the ocean beach, may be narrow or widen out over considerable 
space, so that the saturated portion of the oil stratum may be wider or 
narrower, forming what appears to be a line of separate pools. The 
amount of saturation is different in different sands and also in A T arious 
parts of the same sand. In a sand containing only small saturated 
areas the oil accumulation may be low down in the syncline, with an 
area reaching far above it that upon test would only produce dusters. 
Each independent structural basin must be considered separately as 
to the location of the water line. Great assistance would have been 

Bull. 2113—03 22 


given in the location of this line of complete saturation had the unsuc- 
cessful test wells of the past been divided into two classes, as salt- 
water wells and dusters, instead of calling them all dry holes, as has 
generally been done. 

The question of saturation does not assume the same prominence 
when searching for gas, though had it been noted and reasoned 
from, it would have saved many thousands of dollars expended in 
searching for oil near large gas wells. 

In territory where the anticlinal folds are entirely below the satu- 
rated area the water-line theory is of no value, as the accumulations 
of gas are in the anticlinal arches, with the oil immediately below. 
Under this condition the crest of the anticline should be followed to 
find productive territory and the extent of the gas accumulation 
determined by test wells. 


The area selected for investigation in 1901 was the Cadiz quadran- 
gle, an area containing about 240 square miles in Harrison and 
Jefferson counties, Ohio, and lying east and norch of the town of 
Cadiz. The surface forms a plateau, which has been dissected by the 
streams to a depth of nearly 300 feet, exposing in outcrops six or 
seven easily distinguished beds of limestone and coal. The geologic 
section extends upward from near the base of the Conemaugh (Lower 
Barren) Measures to about the middle of the Monongahela (Upper 
Productive) Measures. The Pittsburg coal outcrops in the lowest 
valleys in the southeast corner and tops the highest hills in the 
northwest corner of the quadrangle. 

Parallelism of strata. — As these beds are of sedimentary origin it is 
evident that there must be a certain degree of parallelism between 
the strata, hence a stratum lying 1,000 or 1,500 feet below the surface 
may be platted by data obtained from deep. wells and from the out- 
cropping strata with the same degree of accuracy as one but a couple 
of hundred feet below. The distance between two prominent strata, 
such as an outcropping coal at the surface and an oil sand below, 
maybe increasing or decreasing. In the Cadiz quadrangle the dis- 
tance from the top of the Pittsburg coal to the cap of the Berea grit 
sand is 1,481 feet at tin' Bricker oil pool, 1,490 feet at Hopedale, 1,527 
feet at Bloomfield, and 1,564 feet at Smithfield. 

The rate of variation of the interval between two strata can be 
determined only by actual boring tests. Over the Appalachian oil 
fields such tests have been made in great numbers by the "wild cat" 
wells searching for oil. There is hardly a portion of the country lying 
within the now producing oil fields where the record of such a well 
can not be obtained within a distance of 5 miles from a given point. 

In extending the platting of substrata into entirely new territory 
a rate of increase or decrease must be assumed, which introduces a 
degree of uncertainty into the results. 



Each outcrop was carefully located upon a topographic map previ- 
ously made by the Geological Survey, and from the bench marks 
established by the Survey a spirit-level line was run to each outcrop, 
establishing its exact position above sea level. Then by adding to 
or subtracting from the elevation of the outcrop an amount equal to 
the vertical distance at that point between the bed leveled to and the 
Pittsburg coal the elevation of the Pittsburg coal at that point was 
determined. In this way the true altitude of the key horizon (in this 
case the Pittsburg coal) was established at five or six hundred places 
over the quadrangle. By connecting the points of equal elevation a 
contour map of the key horizon was constructed. The position of 
each oil well which had been drilled in the quadrangle was care 
fully located upon the topographic sheet. Spirit-level lines were run 
to the mouth of each well, establishing its elevation above sea. In 
most cases the steel-tape measurement of the distance from mouth of 
well to the Berea grit sand was obtained from those interested in the 
wells. By comparing the elevation of the mouth of the well to the 
contour map of the key horizon the distance from this horizon to the 
cap of the Berea grit sand was determined in different portions of the 
quadrangle. The distance was found to vary, increasing gradually 
toward the southeast. At the position of each test well the vertical 
distance between the Pittsburg coal and the Berea grit was marked 
upon the map. 

The positions of the different test wells were connected by straight 
lines, and these lines were divided so that each subdivision repre- 
sented the horizontal distance in which the vertical distance from the 
Pittsburg coal to the Berea grit decreased 5 feet. The points of equi- 
distance from coal to sand were then connected, and a drawing was 
constructed, called the " convergence sheet." This shows by a series 
of lines the points of equal distance between the Pittsburg coal and 
the Berea grit. The convergence sheet was then placed over the plat 
showing elevations of the key horizon, and it showed at once the 
amount that should be subtracted from the elevation of the Pittsburg 
coal to determine the elevation of the Berea sand at any point. The 
elevation of the Berea sand at every point where it was determined 
was then marked upon the map and the points of equal elevat ion 
were again connected, resulting in a contour map of the oil-bearing 


The contour map of the Berea grit sand shows a system of parallel 
folds in a northeast-southwest direction, crossed at nearly right angles 
by a system of broader and less pronounced folds, which break up the 
major structures into a series of elongated domes and canoe-shaped 
basins very similar to those of western Pennsylvania, as delineated 
by Mr. M. R. Campbell. 


The most prominent feature is the main anticlinal arch, which 
extends from near Cadiz in a northeasterly direction, passing just 
cast of the town of Salem, where it attains its greatest height. 
Thence it swings to a more easterly direction and rapidly falls away 
before reaching Richmond. The corresponding syncline parallels 
this fold on the western side, but it is interrupted by two cross anti- 
clines, one near the line of the Pittsburg, Cincinnati, Chicago and 
St. Louis Railroad, the other very nearly agreeing with the location 
of the ridge road from East Springfield north toward Bergholz. It 
thus forms a canoe-shaped basin, whose lowest point is but a short 
distance east of the town of Jefferson. A part of another basin, 
which extends almost due east and west, appears in the northeast cor- 
ner of the quadrangle, its center line being very near the location of 
a topographic feature known as Middle Ridge. To the east of the 
main anticline the sand descends in terraces or steps to the eastern 
limit of the quadrangle, the crests of the terraces extending in lines 
parallel to the main anticlinal fold. Over this slope the intersection 
of the cross folds moves I lie terrace toward the east. This causes the 
steep slope below the terrace to have a southeast strike for a short 
distance before again taking up a direction parallel to the major 

No long and steep slopes exist in the quadrangle. The descent is 
steepest on the face of the terraces, where it seldom amounts to 100 
feet to the mile. This lack of decided slope for a considerable dis- 
tance is unfavorable to the accumulation of a large pool of oil, since 
no large area of oil-producing territory has been drained into a single 
continuous reservoir. 


All of the oil developments that existed at the time of survey are 
represented upon the map in Bulletin No. 198 of the United States 
Geological Survey — The Berea Grit Oil Sand in the Cadiz Quad- 
rangle, Ohio. The valuable oil pools then known consisted of the 
Bricker and Snyder on the eastern side of the main anticline, the 
Jewett pool on its western side, and the Amsterdam pool at the head 
of the canoe-shaped basin east of Jefferson. 


During the year 1902 a number of new wells were drilled within 
the area mapped, with the object of extending the known productive 
territory and in the hope of finding new pools. 

With a view of determining the degree of accuracy with which the 
contour map of the Berea grit sand had been made in the Cadiz quad- 
rangle, and to learn if the future development of valuable territory 
would follow the theoretical reasoning of the published bulletin, a 
careful watch of the new work was kept during the last summer and 


level lines carried to the mouth of each new well of which a record 
could be obtained. 

Piney Fork district. — In Bulletin No. 198 this locality is described 
as follows: 

To the west of Smithfield, on and near the Piney Fork of Short Creek, four test 
wells have heen drilled. Well No. 182, on the farm of Alexander S. Thompson, 
gave a fair show of oil. This well is shown on the map to be on a small terrace. 
The other wells, Nos. 181, 183, and 240, were simply dry holes. 

During- the last year the Sutherland Oil Company, of Chicago, 
drilled two test wells in the Piney Fork district. The first well is on 
the Finley farm in the middle of sec. 22, T. 8 N., R. 3 W., on the east 
side of a small stream flowing into Piney Fork and just south of the 
Updegraff-Smith field road. The map of the sand shows that the 
Berea grit is 505 feet below sea level and that the well is located at 
the foot of a rather steep slope. This latter condition would indicate 
the probability of a salt-water area. The elevation of the mouth of 
well is'984 feet above sea level, making, according to the map, a dis- 
tance of 1,489 feet from well mouth to the Berea grit. The Berea grit 
was actually found at a depth of 1,487 feet, and the well produced 
salt water which rose 1,000 feet in the casing. The second test in this 
locality by the same company was made on the Thompson farm, on 
the east side of the creek and very near the northeast corner of sec. 
29. The map shows the sand at this point to be 445 feet below sea 
level, and the well seems to be on the terrace previously referred to. 
The elevation of the mouth of the well is 1,012 feet above sea level; 
therefore theoretically the distance from surface to the sand should be 
1,457 feet. The sand was found at 1,469 feet, showing the map to be 
in error 12 feet at this point. A showing of oil is reported from the 
Berea grit, with a strong flow of gas and some oil from the Big Injun. 
No further tests have been made in this locality. 

In Bulletin No. 198 the following suggestions were made as to the 
northern extension of producing territory along the main anticline: 

North and northeast of the Snyder pool six wells have been sunk in the attempt 
to find other pools "by an extension of the alignment of the Bricker and Snyder 
pools, with uniformly unfavorable results. With the information shown on the 
contour map these results might have been anticipated. It is here that the cross 
anticline hreaks up the regular structure, and the terrace face is moved over to 
the east of the town of Hopedale, where it again takes up its northeasterly direc- 
tion and is, in fact, the extension of the Bricker and Snyder pool terrace. Two 
test wells have heen drilled in the southeast end of this terrace. The first well. 
No. 203, found a show of oil, and this led to the drilling of the second well, No. 
204, with the intention of striking the sand fully 10 feet higher than in the first 
well. This the drillers failed to do, finding the sand only 2 feet higher in the 
second well than in the first. This slightly increased elevation caused an increase 
in the amount of oil found. The well was put to pumping, resulting in from 1£ 
to 2 barrels a day. 

Spellacy pool. — During the last summer Mr. Spellacy and partners 
drilled a test well on the line between sees. 14 and 15, T. 10 N., R. 4 W., 


in about the middle of the sections and about 1,500 feet north of the 
Cadiz-Hoped ale road. The sand is here represented by the map to be 
270 feet below sea level, and the location of the well is in the direct exten- 
sion of the center of the Snyder pool. The elevation of the mouth of 
the well is 1,157 feet, making, according to the map, 1,427 feet from 
the mouth of the well to the Berea grit. The record by actual drilling 
gives 1,431 feet. This well produced 8 barrels a day for the first thirty 
days. Another well was drilled a short distance to the southwest, 
resulting in a producer, but smaller than No. 1. The next well drilled 
is to the east of No. 1 and about GOO feet distant. It came in a pro- 
ducer good for 20 barrels a day. 

This new development, known as the Spellacy pool, caused new 
testing to decide whether the producing territory would keep to the 
northeast or make a sharp turn to the southeast, as shown by the 
contours of the geologic structure map. Testing was done in both 
directions. Messrs. Scott, Ripley, and others located a well on the 
Grant Bowles farm in the eastern part of sec. 13, T. 10 N., R. 4 W., 
just south of the Hopedale-Falks station road. At this point the sand 
is represented by the map to be 256 feet below sea level. The elevation 
of the well mouth is 1,203 feet, making an estimated depth of well of 
1,459 feet. The elevation of the sand at the location of this well was 
shown by the map to be at the same elevation as the top limits of 
productive territories in the Snyder pool. This would indicate a 
small well or total absence of oil. The sand was found by drilling at 
1,465 feet, and the result is a perfectly dry hole. 

The Sutherland Oil Company, after careful study of the Berea grit 
map, decided to try a test well in the north part of sec. 8, three- 
quarters of a mile southeast from the Spellacy pool. The location 
selected is on the J. R. Skelley farm, one-quarter of a mile southwest 
of the limits of the town of Hopedale, south of the small stream and 
north of the 270-foot contour, as represented on the map of the sand. 
This contour passes through the most productive area of the Spellacy 
and Snyder pools. The elevation of the well mouth is 1,130 feet, and 
sand is represented by the map to be 2G8 feet below sea level, making 
an estimated depth of well of 1,398 feet. The sand was found at 
1,407 feet, and a small producing well was obtained. A second well 
was at once put down in a line with the first well and the Spellacy 
pool. The elevation and record of well were not obtained, but it has 
come in a producer. 

Hopedale development. — A new development entirely independent 
of the Spellacy pool, and due to the following suggestion quoted from 
page 23 of Bulletin No. 198, was undertaken to the east of Hopedale 
by the Welch Oil Company: 

From the structure and indications of test wells already drilled, a very favor- 
able line for finding oil seems to exist in a northeasterly direction from the south- 
east quarter of sec. 3, toward the town of Unionport. 


The first location of a test well was made on the Allison farm, 1,200 
feet south of the Hopedale-Bloorn field road and 1,000 feet east of 
the Lake Erie, Alliance and Wheeling Railroad. The sand is rep- 
resented by the map to be 270 feet below sea level. The elevation of 
well mouth is 1,229 feet, making an estimated depth of well of 1,499 
feet. The sand was found at 1,504 feet. The well is a small oil pro- 
ducer, with large amounts of salt water. In order to strike the sand 
above the limit of salt water, a well was drilled 500 feet north of the 
road just east of the town of Ilopedale, on the farm of Mr. William 
Stringer. The location, as shown by the map, is at the highest point 
of the anticlinal nose, which extends south at the town of Hopedale. 
The sand is represented to be 242 feet below sea level, and the eleva- 
tion of the mouth of the well is 1,228 feet, making an estimated dis- 
tance to the sand of 1,470 feet. The sand was found at 1,176 feet. 
The result was a gas well with a pressure of about 400 pounds to the 
square inch. It now seems very probable that there is oil-producing 
territory between the Stringer gas well and the Allison small oil well. 

Test welled Unionport. — The same company also drilled a "wild- 
cat" test well in sec. 35, T. 9 N., R. 3 W,, south of the railroad, and 
very near the eastern line of the section, on the farm of Mr. Lewis, 
west of the town of Unionport. The sand is here represented by the 
map to be 245 feet below sea level. The elevation of the well mouth 
is 972 feet above sea, making an estimated depth to the sand of 1,217 
feet. The sand was found by the drill at 1,220 feet. The well 
resulted in a perfectly dry hole, with a hard and close sand. 

Eastern Ohio Oil Company's test wells. — During the past year the 
Eastern Ohio Oil Company, of Chicago, drilled a number of test wells 
in the area southeast of Cadiz, with unfavorable results. No records 
of these wells have been obtained, and for that reason the expense of 
leveling to the mouths of the wells was not incurred. 

Amsterdam pool. — Little new development has been undertaken in 
the north half of the area covered by the Cadiz quadrangle. The 
following reference to the Amsterdam pool is taken from page 24 of 
Bulletin No. 198: 

The accumulation from the canoe-shaped basin on the west side of the main 
anticline has been discovered in part at Amsterdam. 

The sand at the Amsterdam well is of such a poor quality that it probably 
would have been reported as all lime had it not been oil producing. The wells 
are small, but will probably improve when areas of better sand are found. The 
limits of this field have been determined across the dip of the sand by a salt-water 
well. No. 205, and a gas well in sec. 19, not located on the map. The extensions 
along the strike are as yet not defined by test wells. The indications are that the 
extensions will be to the southwest in a diagonal line through sec. 80, and to the 
east in an almost due east line through the south half of sec. 7. 

The pool has during 1902 been slightly extended to the southwest 
by a well on the McGarey farm in sec. 30, which was located near the 


house of Mr. McGarey on the road from Yellow Creek to Kilgore. 
This well, although small, will produce a paying quantity of oil. 


The results of the developments during the last year seem to afford 
strong evidence in support of the theories advocated in Bulletin 
No. 198. 

Over the area tested the map has proved to be of such accuracy 
that it may be relied upon within a limit of the contour interval. 
This should make the map of great value to the oil producer as a 
guide to the location of new wells. 

It is believed that a map of the different oil sands can be made over 
the Appalachian oil field by careful geologic work and the united 
assistance of the oil operators in furnishing full and reliable well 
records that will be of immense value to the oil industry. 

The result of the extension of the Snyder pool in a line exactly 
agreeing with the contour line representing the Berea grit furnishes 
strong evidence in favor of the water-line theory. 


The use of a contour map of an oil sand to locate new pools in 
unprospected territory will materially aid the prospector, but can not 
be absolutely relied upon, as the other conditions necessary for an 
accumulation can only be learned by actual tests. 

In the north part of the Cadiz quadrangle is an east- west syncline 
with a decided rise on its north sid<\ Here is a favorable structure 
for an accumulation of oil and gas, though the exact point at which 
the oil would be found would be hard to select. 

In making a systematic search for productive territory in this 
neighborhood the first test well should be drilled in the southeast 
corner of sec. 25, T. 11 N., R. .'), with a view of determining the condi- 
tion of the sand, expecting if a favorable sand without oil is found to 
obtain salt water. If no good sand is found, the result is a complete 
failure and no information of value is gained. If, however, a good 
sand containing salt water is found, a move to the northwest equal to 
a distance that will cover two or three contours on the map of the 
sand would be advisable, and so on until oil or dry sand is found. 
If moves not longer than the distance bet ween two contours are taken, 
it is not probable that the oil belt will be jumped, for the indications 
near the oil are such as to be distinguished by any operator. If oil 
is found, it probably lies in a narrow belt along the slope, and the 
extensions of the pool should be sought along the same structure con- 
tours upon which it is procured. 


By C. W. Hayes. 


Shortly after the discovery of oil at Beaumont, in 1901, the system- 
atic study of the stratigraphy and structure of the Gulf Coastal Plain 
was undertaken. Mr. William Kennedy spent nine months in the 
field and the writer about two months collecting data for an economic 
report. A report has been prepared as a Survey bulletin, and is now 
in press, under the above title. The following is a brief summary of 
the conclusions there stated at length : 

Location of the field. — The Gulf Coastal Plain oil field includes a belt 
of country from 50 to 75 miles wide bordering the Gulf of Mexico and 
extending from the vicinity of the Mississippi River in Louisiana 
westward about two-thirds of the distance across Texas. 


While the whole of this belt is a nearly featureless plain, rising 
gradually from sea level at the Gulf coast toward the north and north- 
west, it may be divided into three subordinate belts, which are some- 
what distinct: (1) Along the margin of the Gulf is a fringe of marsh 
land only slightly above sea level and subject to occasional overflow. 
This fringe is widest in Louisiana and decreases westward to the 
vicinity of Galveston, beyond which it is inconspicuous or absent. 
(2) Inland from the coast marsh is a somewhat broader belt of prairie 
land, its surface rising inland at the rate of about a foot to the mile. 
It has a stiff clay soil and is generally treeless, except for occasional 
bunches of live oak and a fringe along the water courses. (3) The 
third belt has a generally sandy or gravelly soil and is well wooded. 
Its surface rises more rapidly and forms a less perfect plain than the 
other two belts. 

The only topographic features which relieve the monotony of the 
Coastal Plain are occasional low mounds or swells, which rise island- 
like above its even surface. These swells are of exceptional impor- 
tance in the present connection, since they appear to be the external 
indication of conditions which have favored the accumulation of oil 
in commercial quantities. They vary considerably in size and amount 
of relief. At the one extreme are the " salt islands" of Louisiana, and 



High Island, Big Hill, and Damon Mound in Texas, which rise from 
40 to 80 feet above the surrounding plain and contain several thou- 
sand acres. At the other end of the series are the low, barely percep- 
tible swells, such as Sulphur in Louisiana and Spindletop and Sour 
Lake in Texas. Experience has shown that the latter afford the more 
favorable conditions for oil accumulation. 


The formations which underlie the Coastal Plain belong to the 
latest geologic periods, the Tertiary and Quaternary, and consist 
largely of unconsolidated clay, sand, and gravel. Some of the sand 
beds have become cemented, forming sandstones, and there are occa- 
sional beds of limestone, but these are relatively inconspicuous. The 
region has been repeatedly elevated and depressed and the coast line 
has migrated back and forth across it many times. 

The formations of the Coastal Plain are briefly described below: 

Beaumont clays. — These are brown, blue, and yellow clays contain- 
ing nodules of limestone, also brown and bine sands and cypress logs; 
they have a thickness of 25 to 400 feet; they generally form clay soil 
and underlie the coastal marsh and prairie bell. 

Columbia sands. — These are white, yellow, gray, and mottled sands 
with beds of blue and yellow clay and a heavy bed of graved at base. 
They occupy a broad belt inland from the Beaumont clays and pass 
under the latter toward the Gulf. They have a thickness of 50 to 200 
feet and form sandy and gravelly soil. 

Lafayette sands. — These are blue and red thinly laminated clays 
and red and brown cross-bedded sands and gravels. They have a 
thickness of from 30 to 375 feet, form sandy soil, and are discrim- 
inated with difficulty from the Columbia. 

'Buried, beds. — These beds do not outcrop at the surface, being 
entirely concealed by overlapping later formations, and are revealed 
only by drilling. They consist of (a) 300 to 480 feet of blue, brown, 
and gray clays and sand with thin beds of limestone and containing 
small quantities of oil ; (b) 200 feet of blue clays and thin-bedded, 
irregularly deposited sandstones; and (c) 300 feet of blue, red, and 
gray clays and sands; thin-bedded limestones; limestones dolomitized 
and associated with sulphur, gas, and petroleum, and the Spindletop 
oil rock. 

Frio clays. — These consist of 2G0 feet of variously colored thinly 
laminated clays, containing gypsum crystals and calcareous con- 

Su mtnary. — The foregoing descriptions of the Coastal Plain forma- 
tions are necessarily very much generalized since the formations 
themselves vary greatly from place to place. The logs of closely 
adjacent wells present only a general resemblance, and it is impos- 
sible to identify with certainty any particular bed in wells separated 


by a greater distance than a few hundred feet. Even in the Beaumont 
district, where so much drilling lias been done, it is possible to make 
only general statements regarding the stratigraphy. A part of this 
uncertainty results from the difficulty of obtaining an accurate record 
by means of the universally employed rotary drill, but a part also is 
due to the extreme variabilitj 7 in the character of the beds. 


The beds making up the Coastal Plain formations were deposited 
near the margin of a sea which varied in depth from time to time, or 
upon a coastal belt as wave-built beaches on river flood-plain deposits. 
The surface on which they were laid down had a gentle slope toward 
the southeast, and this slope was increased during their deposition 
by a slight tilting. Hence the beds all have a gentle dip to the south- 
east, but the lower or older beds have a somewhat greater dip than 
the higher or newer ones. 

While this gentle southeast dip is the prevailing structure through- 
out the Coastal Plain, it is interrupted at numerous points by low 
oval domes in which the beds dip away from the center in all direc- 
tions. This structure has been found to characterize all hills or swells 
which interrupt the even surface of the Coastal Plain. These domes 
do not appear to have been formed by lateral compression, such as 
has given rise to the anticlines of the Appalachian field, but rather 
are due to some force acting vertically and lifting a small portion of 
the earth's crust. This force appears to have become active some time 
during the Tertiary and to have continued since the deposition of the 
recent Beaumont clays. 


The conditions which are essential for the accumulation of oil and 
gas in commercial quantities are everywhere the same. They are 
(1) a source for the oil, either organic or inorganic; (2) a porous 
stratum which may serve as a reservoir; and (3) an impervious cap 
rock which will prevent its escape. Conditions which favor its accu- 
mulation, but are not always essential are (4) gentle undulations of 
the strata forming anticlinal arches or domes; and (5) complete satu- 
ration of the rocks with water and its slow circulation. 

In the Gulf Coastal Plain there appears to be a very large amount 
of oil disseminated through the several thousand feet of undertying 
Tertiary and Cretaceous, and possibly also Carboniferous strata. 
Scarcely a well has been drilled in this region to any considerable 
depth which has not encountered traces of oil in some of the beds 
passed through. There is also an abundance of porous beds adapted 
to form reservoirs for the oil. These are unconsolidated sands and 
gravels, and in some cases, as at Spindletop, a very porous limestone 
or dolomite. The impervious cover required to retain the oil and pre- 


vent its escape from the reservoir roek to the surface is found in the 
beds of clay and compact limestone which make up the "buried beds " 
described in the above section on stratigraphy. 

The structure of the Coastal Plain is not generally favorable for oil 
accumulation. The gentle southeastward dip of the beds does not 
appear to be sufficient for the easy migration of the oil to points of 
accumulation, and it is only where this uniform dip is interrupted by 
the dome-like structures mentioned above that accumulation has 
taken place. Hence the prospector should search for these favorable 
structures and while, as experience has shown, not all of them contain 
oil in commercial quantities, they afford by far the most probable 
localities for drilling. The elevations above the surrounding level 
plain which are depended on to indicate the presence of these favor- 
able structures are due to the continued action of the elevating force, 
whatever it may have been, down to a very recent date. Where this 
force has been most active and the elevation has been greatest, as at 
High Island and Damon Mound, no oil is found. It is quite possible, 
therefore, that there may be within the Coastal Plain similar struc- 
tures not marked by surface elevations, even more favorable to oil 
accumulation than any thus Car discovered. These can be revealed 
only by the drill, but a careful study of the arrangement of the known 
domes may afford valuable suggestions as to their location. 

The fifth condition favorable for oil accumulation, complete satura- 
tion of the strata with water, is probably very general in the Coastal 
Plain, but how much circulation this ground water has and what its 
effect on the accumulation of oil may be are poinls concerning which 
there are few data available 


The actually productive oil territory, so far as at present known, 
forms but an extremely small fraction of the area of the Gulf Coastal 
Plain. Excepting the Spindletop pool the limits of the productive 
territory are in no case defined wit li any degree of accuracy. The 
separate areas or "pools," as they are generally called, will probably 
be found to vary in size from 200 to 2,000 acres. In this respect the 
field differs widely from the Corsicana field of central Texas and from 
the great Appalachian field, where the pools are much larger, but 
where the oil is in smaller quantity and generally under less pressure. 

In this field productive territory has been developed at Beaumont, 
Sour Lake, Saratoga, and Jennings, while encouraging indications are 
found at Sabine Pass, Dayton, Columbia, Velasco, Anse la Butte, 
Vinton, and a few minor localities. 

Of these the Spindletop pool at Beaumont is by far the best 
known. Oil was discovered in the Lucas well in January, 1901, and 
within a year and a half there were 280 producing wells, and a large 
number of dry wells had been drilled outside of the limits of the 


pool. It occupies an oval area about 3,000 feet in length and 2,700 
in width, containing approximately 200 acres. The depth to the sur- 
face of the oil rock varies between 000 and 1,000 feet, a few wells only 
being outside of these limits. The oil rock is a crystalline dolomitic 
limestone, having an extremely porous structure. The most compact 
portions of the rock, as shown by the microscope, contain a larger 
proportion of vacant space than most of the oil-bearing Trenton dolo- 
mite of Ohio and Indiana. In addition to these minute spaces 
between the crystals of the rock, such as characterize ordinary oil 
sands, it contains many large cavities, certainly as much as an inch 
across, and probably much more. While no accurate determination 
of the relative volume of the open cavities can be made, it can hardly 
be less than one-third, and may be somewhat more when account is 
taken of the minute spaces between the crystalline grains. The 
exceptional character of this oil rock explains in a measure the 
remarkable features of the Spindletop pool. Its extreme porosity 
favors the storage of a very large volume of oil, and also favors the 
yielding of this oil with great rapidity when the reservoir is tapped. 
It also favors the early exhaustion of the oil in the pool and its rapid 
replacement by the underlying brine. It should have suggested to 
those concerned in the development of the pool that a few wells prop- 
erly distributed would have drained the pool quite as effectively as 
the large number which have been drilled. 

Associated with the dolomite, which forms the oil rock, is consider- 
able selenite or crystalline gypsum. Another abundant accessory min- 
eral is native sulphur. Large crystals, an inch or more in diameter, 
have been obtained from many of the wells, and it is reported by sev- 
eral of the drillers that the oil rock is overlain by a bed of sulphur, in 
some cases reaching a thickness of 40 feet. The thickness of the oil 
rock throughout the greater part of the pool is not known, though it 
has been penetrated to a depth of 96 feet. Toward the western edge 
it is probably less than 50 feet thick and, as shown by the Robertson 
well and the Higgins No. 3, is underlain hy about 100 feet of white 
gypsum. Below the gypsum the Higgins No. 3 penetrated rock salt 
to a depth of 310 feet without passing through it. 

Associated with the oil is always found a large amount of gas, and 
at several localities this form of hydrocarbon is found unaccompanied 
with oil. The composition of the gas has not been carefully investi- 
gated, but it is known to contain in addition to the light hydrocar- 
bons a large proportion of sulphureted hydrogen. 

At nearly all points in this field where oil has been found in com- 
mercial quantities it occurs under great pressure, which gives rise to 
the familiar phenomenon of gushing. Just how high the pressure 
has been in the Spindletop pool is not known, but it appears to vary 
between wide limits. In some wells it has shown almost explosive 
violence, blowing out casing and breaking heavy cast-iron valves. 


This maximum pressure has never been even approximately measured. 
Some elosed pressures of 500 pounds and over per square inch have 
been reported, but these are not well vouched for, and the only reli- 
able measurements vary from 79 to 350 pounds. 

While the cause of this pressure is not certainly known, it appears 
highly probable that it is due largely, if not entirely, to the expansive 
force of the associated gas. When the oil rock is penetrated by the 
drill it is usually necessary to remove the water from the casing by 
bailing. When the pressure is thus relieved there is first a rush of 
gas, followed by a stream of oil, which is expelled with great violence. 
The oil, however, never flows in a steady stream, like water from an 
artesian well, but by a series of jets or pulsations. These may be 
relatively slow, each flow lasting for several minutes, followed by an 
equal or longer period of quiescence in which only gas escapes; or 
they may be rapid, several pulsations occurring in a single minute. 
The rapidity of the pulsations appears to depend, among other things, 
upon the depth to which the well is drilled into the oil rock. Their 
rapidity and consequently the yield of the well is generally increased 
by deeper boring. 

In addition to the expansive force of the gas there is also probably 
some hydrostatic pressure in this field, but its influence in producing 
the phenomena of a gusher must be relatively insignificant. The 
existence of a slight hydrostatic pressure in the Spindletop pool is 
shown in the invasion of some wells by salt water, which was first 
noticed after the pool had been producing about eighteen months. 
This invasion will continue as the oil is removed, though the head may 
not be sufficient to bring the salt water to the surface. 

If the pressure producing the gushing in an oil pool is due chiefly 
to the expansive force of gas, it follows that this force will expel only 
a part of the oil, and the remainder will necessarily be won by pump- 
ing or by supplying the place of the natural gas by compressed air. 
It is evident, therefore, that the gas should never be allowed to escape 
freely from an oil pool, for, aside from the waste of a valuable fuel, 
the force needed to expel the oil is at the same time being lost. 

The history of the Spindletop pool is very instruct ive in this con- 
nection. The Lucas gusher came in in January, 1901, and was wild 
for nine days, during which the flow is variously estimated from half 
a million to a million barrels. Drilling at once became very active, 
and within a year about 200 wells had been completed within the 
productive territory, which was then well defined. The pressure 
undoubtedly began to decline within three months or less after the 
field was opened, though it was still so high that the decline was not 
readily noticeable. At the end of the first year of production the 
pressure, although still manifesting itself occasional^ with almost 
explosive violence, was perceptibly lowered. New wells rarely gushed 
spontaneously, as at first, but required bailing to remove the entire 


column of water and oil in the casing. Wells which had been shut 
off did not generally flow when the valves Avere opened, but to induce 
a flow it was necessary to agitate the oil in the casing, either with a 
bailer or by conducting compressed air to the bottom of the well. 
This general decrease in pressure continued until in the latter half of 
the second year few wells had a natural flow, and in some the oil was 
cut off by the invasion of salt water. This fate awaits every well in 
the pool, and it is only a matter of time when even pumping will no 
longer be profitable. 

The development of this pool has been accompanied by enormous 
waste in the drilling of a large number of unnecessary wells and the 
loss of great quantities of oil, which has been allowed to flow over 
the surrounding country and invite further loss by fire. The even 
greater loss which has been inflicted upon the commercial world by 
the overcapitalization of oil companies and the sale of worthless stock 
is a matter which might be dwelt upon at length, but is not germane 
to the present discussion. 


The character of the oil found in various parts of the Texas-Louisi- 
ana Gulf Coastal Plain is practically the same, but it is very different 
from that found in other fields of the United States. It is dark 
reddish-brown, almost black, and has a disagreeably pungent sul- 
phurous odor. It has a high specific gravity, varying from 0.904 to 
0.963, Pennsylvania petroleum having a specific gravity from 0.800 to 
0.817. In this, as in other respects, it is more nearly related to the 
California oils. 

The flash point or the lowest temperature at which the oil gives off 
an inflammable vapor varies, according to different observers, from 
110° to 180°. The wide variation is probably due to the different 
lengths of time the several samples on which the tests were made had 
been -exposed to the air Since the flash point depends on the pro- 
portion of the lighter hydrocarbons in the oil, it is gradually raised 
by exposure to the air, which permits these lighter constituents to 

The oil contains a large amount of sulphur, both as hydrogen 
sulphide, which largely escapes on standing and is more thoroughly 
expelled b} T blowing air or steam through the oil, and also as other 
sulphur compounds. After freeing it from the hydrogen sulphide it 
has been found by various chemists to contain from -1.75 to 2.4 per 
cent of sulphur. At least a part of this appears to be sulphur as 
such simply dissolved in the oil and not in chemical combination. It 
is probable that this high sulphur would not form a serious obstacle 
to the utilization of the oil for the preparation of illuminants. The 
chemical constitution of the distillates, however, apjDears to be such 


that with any refining process now in use the yield of illuminants is 
small and the quality poor. 

It is as a fuel that the Coastal Plain oil has thus far been chiefly 
utilized, and this will probably continue to be its principal use in the 
future. Tested in various forms of calorimeter, this oil is shown to 
have practically the same heating value as Pennsylvania petroleum, 
which is regarded as the standard liquid fuel. Practical tests in 
steam raising have been made with the Texas oil, and it has been 
found to have an evaporative power of 15.29 to 15.55 pounds of water 
per pound of oil used. Of the steam generated 3.1 to 4.8 percent 
was used by the burner in sprajing the oil. There was thus left 
available for use the steam from 14.74 to 15.16 pounds of water per 
pound of oil used. In ordinary practice, without the use of special 
precautions to guard against waste, 13 pounds of water should be 
evaporated by 1 pound of Texas oil, as compared with 6 to 6.5 pounds 
by the bituminous coals of Indian Territory, 8.7 pounds by Pittsburg 
coal, and 9 by Pennsylvania anthracite. From these relative fuel 
values it appears that 3.1 barrels of Texas oil may be regarded as 
having the same fuel value as 1 ton (2,000 pounds) of Southwestern 
bituminous coal and 4.31 barrels of oil as 1 ton of Pittsburg coal. 

It should be noted, however, that the conditions under which coal 
and petroleum are used in ordinary practice favor the obtaining of a 
larger per cent of the theoretical fuel value in the petroleum than in 
the coal. Also a deduction of at least 10 per cent should ordinarily 
be made from the fuel cost of petroleum on account of the economy 
in handling the liquid fuel as compared with coal. 

As a locomotive fuel petroleum has many additional advantages 
over coal. Practical tests have shown that its use may add as much 
as 30 per cent to the efficiency of the boiler, while it weighs only 07 
per cent as much as coal having the same heating capacity. From 
these tests it appears that with coal at $3 per ton petroleum should 
be worth 97 cents per barrel as a locomotive fuel. 


By C. W. Hayes. 

The Trinity group, which is the lowest member of the Cretaceous 
in Arkansas, Indian Territory, and Texas, consists largely of coarse 
unconsolidated sands with some beds of clay, and is overlain by 
highly fossiliferous limestones. In Arkansas the Trinity beds rest in 
an almost horizontal position upon sandstones and shales of Paleozoic 
age. These older rocks have been intense \y folded, the dips being 
from 50° to 90°. After the folding, but prior to the deposition of the 
Trinity sands, much erosion took place, so that the Trinity beds were 
I deposited on an uneven surface composed of these folded Paleozoic 
rocks. Both Trinity and Paleozoic were, at a still later date, covered 
by a thin and irregular deposit of coarse sand and gravel called the 

At many points in the area under discussion the sands of the 
Trinity group contain notable quantities of bituminous matter, 
usually in the form of asphalt, though in Texas small quantities of 
petroleum are reported to occur at this horizon. 

The most extensive of these deposits occurs in Pike County, about 
2^ miles southeast of Pike City, on a branch of Wolf Creek. This 
has recently been developed by the Arkansas Asphalt Company, of 
Little Rock. Two hills south of Wolf Creek contain in their upper 
portions the fossiliferous limestones of the Lower Cretaceous, and 
around their bases and extending under them is the Trinity sand. 
The asphaltum deposit occurs in a depression between these hills, 
where only the lower portion of the Trinity formation remains, con- 
sisting chiefly of coarse sand, in some places quite calcareous, with 
beds of clay. The deposit is in the form of a sand stratum, which 
varies in thickness from to 12 feet, more or less thoroughly 
saturated with asphaltum. The deposit was discovered by the escape 
of small quantities of asphaltum to the surface in a spring, and this 
led to prospecting for its source. A pit was dug about 12 feet in 
depth, passing through the bed, and the thick, viscous asphalt has 
slowly oozed out into this pit for the last thirty years. 

The asphaltic rocks show considerable variation in character and 
in the amount of asphaltum which they contain. This variation is 
shown by the following analyses made for the Arkansas Asphalt Com- 
pany by G. W. Howard, of New York City. 

Bull. 213—03 23 353 


Specimen No. 1, known at the pit as brown cap sand, contains 5.0C 
per cent of bitumen, or 1.73 per cent of petrolene and 3.33 per cent of 
asphaltene. It is essentially a sandstone, since it contains 92.40 pei 
cent silica. 

Specimen No. 2 is a black sand rock containing 16.53 per cent bitu- 
men, of which 14.13 per cent is petrolene and 2.40 per cent asphaltene. 
The percentage of silica in this rock is 81.20. 

Specimen No. 3, a grayish rock exhibiting banding, contains 0.(38 
per cent of bitumen, 69.15 per cent of silica, and 20.35 per cent of 
carbonate of lime. 

Specimen No. 4 is a black, gummy rock carrying 8.86 per cent of 
bitumen, 7!). 50 per cent of silica, and 0.14 per cent of carbonate of 
lime. The bitumen determined as petrolene amounts to 6.61 per cent, 
and the asphaltene to 2.25 per cent. 

Specimen No. 5, which is a calcareous sandstone, contains 4.58 per 
cent bitumen, which equals 3.46 per cent petrolene and 1.12 per cent 
asphaltene. The carbonate of lime in this specimen amounts to 46 
per cent, and the silica to 49.42 per cent. At the pit this rock is known 
as limestone. 

No doubt specimens taken from these classes of rock would vary 
from place to place in the pit. The analyses, however, probably rep- 
resent fairly the materials obtainable. 

Like similar deposits in other regions, there can be little doubt that 
this asphalt um is merely the residuum from petroleum, the lighter 
and more volatile portions of which have escaped by evaporation. It 
lias also doubtless Undergone certain chemical changes, chiefly oxida- 
tion, during its long exposure to atmospheric conditions. 

By means of test borings the asphaltuni bed lias been proved to 
extend over a number of acres, under a cover sufficiently thin to per- 
mit profitable mining by stripping. At the time the deposit- was last 
visited, in November, L902, a pit about 100 feet in diameter had been 
opened and a tramway built to the railroad, about- half a mile distant. 

It is proposed to use the materials in such proportions as will pro- 
duce a good paving mixture. The occurrence of the limestone with 
the sandstone makes this possible without the addition of material 
from other sources. A practical test will be made at Little Rock, 
where a contract has been obtained for paving certain streets. 

The utilization of this deposit is a technical matter which can not 
be entered upon here. Its chief value will doubtless be as a paving 
material. As stated above, some portions of the bed form a natural 
paving mixture, which hardens on exposure to the sun, and, so far as 
could be judged, would be fully as durable as the ordinary artificial 
mixtures made from Trinidad asphalt. Other portions are too rich 
to be used in a natural state. Tests of these portions in the prepara- 
tion of a paving mixture have been made by the St. Louis Testing and 
Sampling Works, with excellent results. 


The extent to which the deposit can be used for paving purposes in 
competition with other asphalts will be determined entirely by the 
matter of freight rates. It should easily control the market in near-by 
cities, such as Little Rock, Texarkana, and Fort Smith, and the 
richer portions of the deposit should compete advantageously with 
other asphalts in cities as distant as Memphis and St. Louis. 

No experiments have yet been made in refining the asphaltic sand 
for the preparation of pure asphaltum, and this may be found to be 
more profitable than shipping the crude product. 

From the large amount of bituminous matter in these sands, it was 
inferred that petroleum in commercial quantities might be found by 
deep boring, and two wells were drilled for oil. The wells penetrated 
from 100 to 120 feet of the Trinity formation, consisting chiefly of 
sands and clays, with a few thin seams of limestone, and then entered 
the Paleozoic sandstones and shales. The latter are highly contorted, 
dipping at angles of 45° to 55°, and are intersected by numerous 
fractures. No oil in commercial quantities has ever been discovered 
in rocks of this character, and it will readity be understood that, even 
if they had originally contained oil, it would, before the deposition of 
the Trinity, have had abundant opportunity to escape to the surface 
through the fractures which resulted from the folding of the strata. 
The expectation of finding oil, therefore, in this region at greater 
depth than 100 or 200 feet, that is to say, in the underlying Paleozoic 
rocks, has no rational basis. Also, it need not be expected that oil 
in commercial quantities will be found at shallower depths, since the 
conditions are not favorable for its retention in these sands. 

In view of the foregoing considerations, deep drilling in this region 
is not justified by even a remote probability of finding oil in commer- 
cial quantities. On the other hand, the conditions for the accumu- 
lation of asphaltum are most favorable, and it \p quite probable that 
other valuable deposits will be found in this region, similar to that 
above described and at the same horizon. 


The following list contains the more important papers relative to 
oil, gas, and asphalt published by the United States Geological Sur- 
vey or by members of its staff : 

Adams, G. T. Oil and gas fields of the western interior and northern Texas 
coal measures, and of the Upper Cretaceous and Tertiary of the western Gulf coast. 
Bulletin U. S. Geol. Survey No. 184, 64 pp. 1901. 

Eldridge, G. H. The Florence oilfield, Colorado. In Trans. Amer. Inst. Min. 
Eng., Vol. XX, pp. 442-462. 1892. 

— The uintaite (gilsonite) deposits of Utah. In Seventeenth Ann. Rept. 
U. S. Geol. Survey, Pt. I, pp. 909-949. 1896. 

— The asphalt and bituminous rock deposits of the United States. In 
Twenty-second Ann. Rept. U. S. Geol. Survey, Pt. I, pp. 209-452. 1901. 

Fuller, M. L. The Gaines oil field of northern Pennsylvania. In Twenty- 
second Ann. Rept. U. S. Geol. Survey, Pt. Ill, pp. 573-628. 1902. 

Griswold, W. T. The Berea grit oil sand in the Cadiz quadrangle, Ohio. 
Bulletin U. S. Geol. Survey No. 198, 43 pp. 1902. 

Hilgard, E. W. The asphaltum deposits of California. In Mineral Resources 
U. S. for 1883-1884, pp. 938-948. 1885. 

McGee, W J. Origin, constitution, and distribution of rock gas and related 
bitumens. In Eleventh Ann. Rept. U. S. Geol. Survey, Pt. I, pp. 589-616. 1891. 

Phinney, A. J. The natural gas field of Indiana. In Eleventh Ann. Rept. 
U. S. Geol. Survey, Pt. I, pp. 617-742. 1891. 

Richardson, C. Asphaltum. In Mineral Resources U. S. for 1893, pp. 626-669. 

Vaughan, T. W. The asphalt deposits of western Texas. In Eighteenth Ann. 
Rept. U. S. Geol. Survey, Pt. V, pp. 930-935. 1897. 

Willis, B. Oil of the northern Rocky Mountains. In Eng. Min. Jour., Vol. 
LXXII, pp. 782-784. 1901. 


Several brief papers on building stone are here presented. During 
the last year other extensive investigations in various important 
quarry districts have been commenced by the Survey, the results of 
which are not yet in form for publication here. The slate industry 
has been given particular attention, reports being published or in 
preparation on the slates of Vermont, New York, Pennsylvania, 
West Virginia, and Georgia. 


Bv William C. Alden. 


The supply of limestone within the Chicago district, so exposed or 
so thinly covered as to be easity reached, seems to be quite adequate 
to the demand; at least, not all the exposures are utilized for the pro- 
duction of the commodity. The exposures are so distributed as to be 
convenient to Chicago and its nearest suburbs, but the country dis- 
tricts lying in the morainal track are not so well supplied. 


The strata considered by Dr. Bannister as the lower division of the 
Niagara group afford one of the best building stones in the State. 
These are exposed on the floor of Desplaines Valley northeast of 
Lemont. The location, being formerly known as Athens, gave the 
name "Athens marble" to the rock, by which name it is known wher- 
ever used. The same beds are seen in the western end of the Sag, at 
its junction with Desplaines Valley. The rock at the Western Stone 
Companj^'s quarries, Lemont, is a fine-grained, even-textured lime- 
stone, of an agreeable light-drab color when first taken from the 
quarry. On exposure to the air the color changes to a buff or yellow. 
The rock rubs well, though not capable of receiving a very fine polish. 

a Abstract from Geologic Atlas U. S., folio 81, Chicago. 



It is regularly bedded, the layers ranging from 6 inches to nearly 3 
feet in thickness, thus affording fine cut and sawed dimension stone 
and flagging. 

The quarries of the Illinois Stone Company in the same vicinity 
show the same even-bedded limestone and produce dimension and 
rubble stone and flagging. 

At Sag Bridge the quarries of the Phoenix Stone Company produce 
a fine grade of even-grained, solid limestone. The courses increase 
in thickness downward, becoming nearly 8 feet thick at the bottom, 
with little or no fracturing. The product is fine cut and sawed 
dimension stone, rubble, and five grades of crushed stone for 

The quarry of the Calumet Stone Company, 1-J miles east of Sag 
Bridge, shows stone of excellent quality. A small quarry on t he north 
side of the Sag has turned out a small amount of a dense, fine-grained 
rock of very good quality. 

These are the principal localities yielding good dimension stone, as 
here the strata have suffered little or no disturbance and hence show 
little fracturing. The facilities for transportation by railroad and by 
canal are excellent. 

The quarry 1 mile west of Elmhurst, on the Chicago and North- 
western Railway, puts out building stone, including some dimension 


As most of the quarries furnish crushed stone for macadam and 
rubble for foundations, and sonic furnish lime, they will be noted in 
oidcr, beginning with those in Chicago. The rock at all the quarries 
is well adapted for macadam, as it is a hard, gray dolomite, in places 
very siliceous, and the fractured condition of the strata makes it com- 
paratively easy to remove. At the intersection of Chicago and West- 
ern avenues, about three-fourths of a mile southeast of Humboldt 
Park, the quarries of the Artesian Stone and Lime Works Company 
produce crushed stone for macadam and lime. 

The quarries of the Chicago Union Lime Works Company at the 
intersection of Nineteenth and Lincoln streets, about a mile east of 
Douglas Park, have been excavated to a depth of 175 feet. The lime- 
stone is a dolomite containing about 54 per cent carbonate of lime and 
44 per cent carbonate of magnesium. 

The quarries of the Stearns Lime and Stone Company at Bridge- 
port, near Twenty-seventh and Halsted streets, produce lime and 
crushed stone for macadam. 

The quarries of Dolese & Shepard, at Hawthorne, on the Chicago, 
Burlington and Quincy Railway, produce building and dimension 
stone, crushed stone for macadam and concrete, and limestone for 

At Thornton, on the Chicago and Western Indiana Railroad, the 


faarries of the Brownell Improvement Company produce crushed stone 
or macadam containing about 36 per cent of silica, giving it a very 
iurable quality. Their quarries at Gary, 111., on Desplaines River, 
produce a dense, even-grained limestone in little-fractured strata. 
"I Some foundation stone is gotten out, but the rock is rather hard to 
dress. The product is largely crushed stone for paving. 

At the outcrop, 1 mile southwest of Blue Island, considerable rock 
has been removed for foundation stone. It is stated that a bed of 
bluish, impure limestone has been worked here for hydraulic cement. 
Mi'. .1. V. < t >. Blaney reports the following analysis of this limestone: 

Analysis of limestone 1 mile southeast of Blue Island. 

Clay and insoluble matter 4:5. 56 

Carbonate of lime 31. 60 

Carbonate of magnesium 22. 24 

Peroxide of iron 1 . 20 

Soluble silica ' .16 

Alkalies, loss, etc . 1. 30 

Total 100. 06 

At his place about 2 miles southwest of Blue Island, Mr. Henry 
Schwartz has quarried a limited amount of good foundation stone. 
There is abundant rock here, easily accessible. 

The quarry 1 mile west of Elmhurst, on the Chicago and North- 
western Railway, produces crushed stone. 

The quarry of Kogle & Smith, about 3 miles southeast of Elmhurst, 
yields crushed stone. Some building stone is also taken out. 

At the outcrop, 1 mile northwest of Lagrange, on the bank of Salt 
Creek, a quarry has been opened which is turning out crushed stone 
for macadam. 

Mr. Fred Schultz puts out crushed stone and lime from his quarry 
at Lyons. 

At McCook, on the Santa Fe Railway, near the canals, are the quar- 
ries of the Chicago Crushed Stone Company. Rubble for foundations 
is also produced. 

Not all of the rock exposures have been utilized for economic pur- 
poses. The following may be noted as affording productive sites 
should the demand require: One mile northwest of Humboldt Park; 
corner of North Central Park avenue and Humboldt avenue; two 
blocks west of Humboldt Park; in the vicinity of Robey and Twenty- 
third streets; on the lake shore in Windsor Park, at the foot of Chel- 
tenham place; on either side of Railroad avenue, between Ninety- 
fourth and Ninety-fifth streets, and six blocks west, between Ninety- 
fifth and Ninety- sixth streets. 

At " Stony Island " two quarries have produced considerable rock, 
but are now unused. There is abundant rock thinly covered north 
and west of Thornton. Two miles south of Grlenwood and three- 


fourths of a mile east of the Chicago and Western Indiana Railroad 
the rock is rather thinly covered in the hill slope. Three and one-half 
miles south of Elmhurst rock can be obtained in the west bank of Salt 
Creek. Abundant rock is thinly covered south and east of Lyons; 
also down Desplaines Valley from McCook, along the north side of 
the river. At Sag Bridge and at Leinont abundant rock is easily 
quarried. The southwestern part of the area is most poorly supplied, 
though the proximity of Joliet may counterbalance this deficiency. 
Only two exposures were noted in this part of the area, one 5 miles 
east of Orland, along the banks of a small creek; the other along the 
bed of Hickory Creek, near New Lenox. 

Where the bituminous limestone has been used for building pur- 
poses the staining gives a peculiarly venerable appearance to the 
structure. There is, however, the disadvantage that the melting and 
running out of the bitumen may give a disagreeable streaking to the 

The abundant drift bowlders of limestone, sandstone, igneous and 
metamorphic rocks have furnished material for many picturesque 
and beautiful buildings within the district and could supply a further 
demand. These are also of value in the construction of piers and 


The wide distribution of sand and gravel over the Chicago Plain 
has afforded abundant material for building sand, roofing and road 
gravels, and for filling. The extensive deposits of dune sand along 
the present lake shore, along the west side of the Blue Island ridge, 
southwest and south of Hammond, Ind., and east of Thornton, furnish 
abundant fine, clean sand. The deposits of glacial gravel furnish 
the coarser gravels, with some sand and fine gravel. Several large 
pits have been opened about a mile north of Willow Springs, in the 
north slope of Desplaines Valley. The deposits here are assorted into 
several grades of gravel for building, paving, and ballast purposes. 
The output at these pits is 20 to 25 carloads per day. Numerous pits 
have been opened at various points along Desplaines Valley, showing 
material grading from sand and gravel to very stony till, composed 
almost entirely of well-*worn limestone pebbles and bowlders. In 
places this limestone is partially cemented into a conglomerate, so as 
to come out in large masses. One-half mile southwest of Worth 
Messrs. Henke & Read have opened a large gravel pit. The gravels 
here are assorted into grades of two sizes. Ten to twelve thousand 
cubic yards have been taken out per annum. At Blue Island, just 
north of the Chicago, Rock Island and Pacific Railway station, there 
is an extensive deposit of the coarser beach gravel. The entire south 
end of the ridge seems to be composed of these gravels. 

BURG, W. VA." 

By T. Nelson Dale. 


The basis of the slate industry here is a belt of Lower Silurian 
(Hudson) slates, shales, and grits which stretches along the southern 
side of the Blue or Kittatinny Mountain from east-northeast to west- 
southwest. This formation is about half a mile thick, overlying the 
great magnesian limestone formation on the south and underlying the 
Upper Silurian conglomerate and sandstone on the north. The struc- 
ture of this formation is a succession of minor folds generalty over- 
turned to the north, and in places crossed by a southward-dipping 
slaty cleavage. 

Although the formation covers many square miles of Lehigh County, 
west of the Lehigh River, and prospects have been made at man}^ 
points, yet the Slatington industry is confined to an area of 3 to 4 
square miles along Trout Creek and its branches. Within that area 
about 100 openings have been made, of which only about 45 are now 
being worked. These range from 50 to 300 feet in depth. 

The slate is black and has a very fine cleavage. It is calcareous, as 
shown by its effervescing in cold dilute hydrochloric acid, and contains 
carbonate of iron, as shown by its discoloration after continued expo- 
sure. Under the microscope it is found to consist of a matrix of mus- 
covite (potash mica), with much carbonate, carbonaceous matter, and 
pyrite, some angular quartz and feldspar grains, chlorite scales, and 
the usual slate needles (rutile, Ti0 2 ). It is geologically between a 
phyllite and a clay slate. The roofing-slate industry here seems to 
owe its success largely to the fine cleavage, which enables the pro- 
ducers to undersell slates of more durable character, but of poorer 
fissility. Some beds unsuitable for roofing are made into school 
slates. A large establishment for the manufacture of school slates 
has just been erected. 

The slate beds vary in thickness and alternate with grit beds from 
a fraction of an inch to several feet in thickness. The gril consists 
mainly of quartz grains, carbonate, carbonaceous matter, and pyrite. 
It represents coarser marine sediments, brought in possibly by shift- 

'i Detailed reports on these areas are in preparation. 



ing currents, while the slate is the finer off-shore material powerfully 
compressed and largely altered to mica. 

The chief difficulty attending the Slatington slate industry is the 
complex structure of the slate beds. The frequency of the grit beds, 
"rock" or " ribbon " of the quarrymen, is one element in this. Then 
the folds vary greatly in width. One limb of a trough (syncline) may 
measure over 200 feet at the horizon or the arch (anticline) maybe so 
sharp as to measure scarcely 25 feet across. These folds are more or 
less overturned, so that the ribbon intersects the cleavage at different 
angles on the sides of the fold, thus differently determining the size 
of the slate blocks and to some extent the quality of the slate. The 
axes of these overturned folds pitch alternately east -southeast and 
west-northwest at from 5° to 10° or bend 10° laterally, i. e., north- 
south. The folds have all been truncated at the surface by erosion, 
so that it is difficult to trace any one bed across the strike. The 
rock surface may be but a few inches below the turf or may be 
buried beneath 30 to 40 feet of glacial deposits. There is frequently 
a flexure of the cleavage ("curl") for a few inches near the ribbon; 
more rarely there is a curvature of the cleavage across the entire bed. 
Slates cut from such beds are called "bents," and are used for cov- 
ering curved or conical roofs. At the old Hughes quarry this curva- 
ture in 25 feet along the dip of the cleavage amounts to a change of 
20° in the dip, the dip at the top being 45°, but 05° below. Exception- 
ally the joints, instead of crossing bedding and cleavage at a certain 
angle, undulate like bedding planes. Faulting seems to occur rarely. 

It would seem that nothing less than an exhaustive study of the 
stratigraphy of the region with the aid of a perfectly reliable large- 
scale topographic map would suffice to furnish a safe basis for 
such an industry, but in fact the industry has attained its present 
prosperity without such aid, and it is even doubtful whether a 
pocket compass could be found on the person of any foreman in the 
quarries. In view of the very small collective area of all the open- 
ings about Slatington compared to the extent of the slate beds as 
shown by the location of these openings, and in view also of the finan- 
cial risks growing out of the difficult st rat tgraphy, it is surprising that 
the diamond drill, used so effectively in marble and other regions, has 
not been brought into requisition here also. The core from such a 
drill would not only show the quality of the slate but its thickness, 
in many cases, as well as the dip of the cleavage and ribbon. A 
less costly drill, which secures a core by the rotation of a wrought-iron 
pipe upon steel shot, has been successfully used in the Vermont slate 

Attention ought to be called to certain outcrops of dark reddish 
shales a mile southeast and southwest of Werleys Corners in Weisen- 
berg, or about 1-0 miles southwest of Slatington. A microscopic exam- 
ination of a surface specimen from the first of these places shows it to 


be almost a slate. It is possible that a dark red clay slate, suitable 
,for roofing, oecurs below the top roek in that vicinity. 


This recently prospected slate district lies in Berkeley County, W. 
Va., within the geologic belt designated Martinsburg shale in the 
Harpers Ferry folio. This belt lies about 13 miles west of the Blue 
Ridge and mostly on the western side of Opequon Creek, a tributary 
of the Potomac. It measures at least 14 miles in length, from north- 
northeast to south-southwest, and from 2 to -1 in width. Martinsburg 
lies just beyond its western edge. 

This shale and slate formation, estimated to be from 700 to 1,000 feet 
in thickness, is of Lower Silurian age, and overlies the Siluro-Cambrian 
Shenandoah limestone in a series of folds represented in the folio 
as overturned to the west. The rock is generalty a dark grayish 
shale, weathering into a yellowish or white clay, known locally as 
"soapstone." The general character of this rock and its appearance 
when weathered would hardly be regarded as good indications of the 
presence of roofing slate. But at several points, usually near the 
Opequon or its tributary "runs" or creeks, where the mass has been 
denuded of its weathered portions, it has a well-marked easterly dip- 
ping' (in one case, westerly) slaty cleavage crossing the bedding at 
various angles; and pieces, when struck with the hammer, give the 
typical ring of a slate. A superficial examination of this slate shows 
that its cleavage is far from being as fine as that of the Slatington 
quarries and that the cleavage surface, although quite as black, yet 
lacks the smoothness and luster of the Slatington product, On the 
other hand, it effervesces far less readily or not at all with cold dilute 
hydrochloric acid. Its relative commercial value will be soon deter- 
mined scientifically by the usual physical and chemical tests and by 
comparing the results of these tests with those obtained from tests of 
"Peach Bottom" slates. Meanwhile preliminary microscopic exam- 
inations of specimens taken from several localities have been made 
with the following results. 

All the transverse sections show a rather coarse and poorly defined 
cleavage and a very faint polarization of the matrix, in some cases 
none at all, indicating incomplete sericitization. All the sections 
show carbonate, some in very small amount, others in large. Car- 
bonaceous matter is present in all the sections, but is less conspicu- 
ous than in the Slatington slates. The following minerals are also 
present: pyrite in spherules, angular quartz grains, plagioclase grains 
very rarely, rather large muscovite scales, chlorite usually interleaved 
with muscovite, and the usual slate needles (Ti0 2 ), but these are not 
as abundant as in other slates. 

The above suffices to show that these slates are neither true phyl- 
lites nor midway between phyllites and clay slates, like the Slatington 


and Vermont slates, but are closely related to clay slates. They 
resemble in structure, but not in composition or color, the Welsh 
Penrhyn dark purple ("red") slates/' 

Microscopic examination shows that the slates will cleave less read- 
ily than the Slatington or Vermont " sea-green " slates, and that they 
will be liable to lose some of their blackness on continued exposure, 
and that the amount of discoloration will vary in different beds and 
localities. Although a clay slate even with a small amount of car- 
bonate could hardly prove as durable as a phyllite without any, yet 
it may compare favorably with slates intermediate between phyllites 
and clay slates and containing much more carbonate. 

Slate has been found at the following points in the Martinsburg 
belt: Two miles north 10° west of Middleway, or about 9 miles south of 
Martinsburg, 5 miles northeast, 3£ miles northeast, 2'^ miles southeast, 
2^ and 5| miles south-southeast, 6| miles south-southwest of Martins- 
burg. Numerous other localities will probably be found. The cause 
for the development of slaty cleavage at one point in the shale belt 
and not at another is not yet clear. Thus the railroad and highway 
cuts east of Martinsburg along Tnscarora Creek, which bisects the belt, 
are in shale, but slate occurs north-northeast and south-southwest of 
this along the strike. 

What is needed to develop the industry is to thorough^ open one 
experimental quarry and introduce its product into the market. 
Should that experiment prove successful the growth of the industry 
will be assured. 

aSee Nineteenth Ann. Rept. l T . S. Geol. Survey, Pt. Ill, p. 2H2. 


By J. S. Diller. 

More limestone occurs in the copper region of Shasta County, Cal., 
than in an equal area of any other part of the State. A thick lime- 
stone of Triassic age occurs along the stage road east of Furnaceville, 
and subordinate masses crop out around the upper slope of Bear 
Mountain a few miles northwest of Sherman, but the principal mass 
of this belt forms Brock Mountain, on Squaw Creek, and may be 
traced for many miles to the north. This limestone is full of fossils 
and is especially noted for the large lizard-like animals it contains. 
It is generally pure, and at Brock Mountain is used for flux in the 
Bully Hill smelter. 

A belt of more prominent limestone ridges and peaks extends from 
near Lilienthals north b} r Grey Rock, the Fishery, and Hirz Moun- 
tain, along the McCloud for many miles. The limestone where best 
developed is over 1,000 feet thick, and until recently has been used 
for flux at Bully Hill. It is cut by numerous irregular dikes of igne- 
ous rock, which locally interfere with quarrying. If the projected 
branch railroad up Pit River is ever built, it would pass near this 
great limestone. 

A third belt of limestone occurs near Kennett, within a few miles of 
the railroad, and furnishes not only flux for the Mountain Copper 
Company at the Keswick smelter, but also lime, which is burned at 
Kennett and shipped to many points on the Southern Pacific Rail- 
road. This limestone is of Devonian age, and consequently much 
older than the others. Although the limestone is not nearly as large 
as the others, and isolated on ridge crests by igneous rocks, it is more 
valuable because more accessible. Smaller masses occur near Horse- 
town and at several points on the plain no: oheast of Buckeye where 
lime has been burned, but since the Kennett locality has been opened 

they are of little importance. 



By Arthur Keith. 


Beds of workable marble are found in a belt in the center of the 
valley of East Tennessee, extending nearly across the State. The 
general belt is composed of a number of nearly parallel bands or lines j 
of outcrop of the marble formation. They were brought into their 
present attitudes during the folding of the strata of that region, and 
bear their present relations to the surface in accordance with the 
progress of erosion of the rock materials. The exposures of the mar- 
ble are to be seen in the following counties, beginning at the north- 
east: Hawkins, Hancock, Hamblen, Grainger, Claiborne, Union, Knox, 
Sevier, Blount, Roane, Loudon, Monroe, and McMinn. 

All of the marble is found in the strata of Silurian age, much the 
greater part of it in the Chickamauga limestone. On account of the 
prominence and extent of the marble in that formation near Ilolston 
River, it has been called "Ilolston" marble in the folios of the United 
States Geological Survey. A considerable development of marble is 
also seen in the lower portion of the Sevier shale in Sevier, Knox, 
Blount, and Monroe counties. Practically all the quarrying has been 
done in the Chickamauga limestone, although in Knox and Blount 
counties some of the higher beds have also been used to a small extent. 

In the lower part of the Chickamauga formation are many beds of 
more or less coarsely crystalline marble. These do not appear, 
except in a most local way, northwest of the S3mclinal fold from 
which Clinch Mountain rises. In that syncline and southward, how- 
ever, marble is usually well developed in all the areas of the forma- 
mation. It is from 600 to 650 feet thick near Clinch Mountain and 
thins in all directions from that area. Its average thickness is 300 
to 400 feet, where well developed. The position of the marble beds 
in the limestone varies much from place to place. Usually there is a 
considerable thickness of blue and gray limestone below the marble; 
north of Clinch Mountain, however, this is not the case, as the marble 
beds are thicker and rest directly upon the Knox dolomite. The 
same condition was observed on the south side of Black Oak Ridge. 

a A resume of material presented in folios of the Geologic Atlas of the United States. 


The marble differs from most of the rocks of the formation in 

being coarsely crystalline. It may have been altered after its forma- 
tion by the passage of water through the rock, dissolving and recrys- 
tallizing the carbonate of lime, or it may have been deposited in its 
present form. The shaly parts containing less lime are not crystal- 
line. The forms of the fossils inclosed in marble are plainly visible, 
although wholly recrystallized. The marble varies considerably in 
color, most of the rock, however, being of two types, a dark bluish 
gra}^ and a variegated reddish brown or chocolate. Of these two 
varieties the latter or reddish marble is considerably more common. 
Both are extensively quarried for ornamental stone. 

Workable beds are rarely over 50 feet thick, and usually in that 
thickness there is a combination of several varieties. Quarries far 
separated from one another have quite distinct series of beds, and 
each quarry has its special variety of marble. All marbles of this 
region are free from any siliceous impurity, and all of reasonable 
purity take a good polish and are unaffected by weather. 

The total thickness of the marble beds is by no means available for 
commercial use. The rock must be of desirable color, must quarry in 
blocks of large size free from cracks or impure layers, and must be of 
fine, close texture. 

The variations in all of these characters are duo to differences in 
the sediment at the time of its deposition. Carbonate of lime, iron 
oxide, and clay were deposited together with shells of large and small 
mollusks. The firmness of the rock depends upon a large proportion 
of the lime, while the dark, rich colors are due to the oxide of iron; 
but if the latter be present with clay in large proportion the rock 
becomes a worthless shale. The colors vary from cream, yellow, 
brown, chocolate, red, and pink to blue, in endless variety. Absence 
of iron oxide results in gray, grayish white, and white. The colors 
are either scattered uniformly through the rock or are collected into 
separate crystals or patches of crystals; forms such as fossils are 
usually of pure, white calcite. The curious and fantastic arrange- 
ment of the colors is one of the chief beauties of these marbles. Like 
the shaly matter, the iron oxide is an impurity, and the two are apt 
to accompany each other. The most prized rock, therefore, is a bal- 
ance between the pure and impure, and slight changes in the form of 
sediment result in deterioration or better quality. Such changes are 
common in most sediments and must be expected in quarrying the 
marble. Not only may a good bed become poor, but a poor bed may 
develop into good marble. 

Tests for absorption of water show a high resistance in the better 
grades of marble, and the rock is very well fitted for withstanding 
weather. Its crushing strength is also very high in the purer layers. 
Tests of a number of samples gave an average strength of 10,000 
pounds per square inch. 


The nature and associations of this marble are subject to great 
variations. An instance of this is the disappearance of red marble 
northeast of Thorn Hill in the belt running north of Clinch Mountain, 
its place being taken by blue and gray marbles. These latter beds 
are of good body, but lack the most prized color. More marked! 
changes are seen in the disappearance of the massive marble and the 
increase of shale in the same belt after it passes southwest from Lut- 
trell. Similar changes are seen east and south of McMillan and 
Strawberry Plains. The position of the marble in the Chickamauga 
limestone also varies. Near the northeast end of Black Oak Ridge, 
and also northeast from Luttrell, the Chickamauga limestone appears 
only above the marble. Along Holston River, however, the limestone 
appears only below the marble, above the latter being the Tellico 
sandstone. In other places the marble occupies an intermediate posi- 
tion. In the next basin north of the Clinch syneline no marble 
appears except northeast of Maynardville, where some unimportant 
beds of gray marble occur. North and west of this no marble has 
been observed, nor does any of consequence occur along the southern 
border of the Maynardville quadrangle. 

The marble above the Tellico sandstone in the base of the Sevier 
shale is comparatively thin and shaly. Occasionally, however, a 
local thickening takes place and the beds resemble the Holston marble 
in all respects. This is notably the case in the area of Sevier shale 
extending southwest from Strawberry Plains past Knoxville. The 
Sevier marble beds are much more variable than those of the Chicka- 
mauga, and there is a smaller amount of workable material in them; ! 
consequently they have not been successfully quarried. 

Other variations in the marble are shown in the disappearance of 
good marble for a few miles in the belt running through the northern 
portion of Knoxville. The belt which is productive south of Knox- 
ville becomes of minor importance 8 miles northeast of Knoxville; and 
the bed at the bottom of the Sevier shale is the productive one in that 
locality. These latter marbles in the region of Knoxville are usually 
shaly and of less value, although they contain many beds of good body 
and color. Workable beds are rarely over 10 feet thick, and usually 
there are several varieties in close proximity. 

Southwest of Knoxville the Holston marble varies in similar fashion. 
It disappears in the belt northwest of Madisonville and shifts down- 
ward into the beds next to the Knox dolomite at Marble Bluff, west 
of Loudon. As a rule, however, the marble in this region remains 
very constantly in the upper part of the Chickamauga limestone. 
The different belts continue south westward to the vicinity of Sweet- 
water. They then disappear rather abruptly and are not found in 
areas farther southwest. 

The marbles of the Sevier shale are prominent at the bottom of that 
formation, but occasionally occur in the upper strata as well. They 


ire similar to the Chickamauga marbles, but usually have not such 
•ich colors, being oftenest of a gray color; and they contain more 
jhaly beds. The belts passing south of Loudon and Louisville have 
this marble more highly developed than the other belts. It has been 
quarried only in the southeastern belt, near Mountain ville, and farther 
southward at the Tellico River, and its beds are not now worked, for 
want of transportation facilities. These marbles extend a little farther 
southwest than the Holston marble. 


Owing to the soluble nature of the pure marble, it is either com- 
pletely unaltered and fresh or it is entirely reduced to red clay. The 
best marbles, therefore, are nearly as solid at the surface as at great 
depths. Marbles which are shaly at the surf ace become less weathered 
in going down, and appear solid; but when these are sawed and 
exposed to the weather their inferiority appears in splits along the 
argillaceous seams and in cracks through the thicker masses. Solu- 
tion of the pure beds has produced holes and eaves down to the adja- 
cent stream levels. Through these openings the quarry men attack 
the rock more easily, but much valuable stone has been lost by 

The available localities for quarrying are limited in part by the atti- 
tude of the marble beds. At the northeast end of the marble belt 
the best situations are those just north and northwest of Rogersville, 
where the strata dip at a high angle and there is little stripping to be 
done. Here the location of the marble, well above drainage, is an 
added advantage. In the areas north of Clinch Mountain the dip is 
such as to carry the marble beneath the surface with narrow out- 
crops, but is not steep enough to avoid considerable stripping. 

In the same belt southwest of Clinch Mountain the dip is usually 
steep, so that the amount or earth to be stripped is not great. Near 
Holston River, owing to the recent cutting of the streams, the marble 
is usually at some distance above the water level. In the more north- 
ern areas, where the streams have not cut their valleys deeply, the 
marble usually occupies the lowest portions of the valleys, being the 
most soluble of the formations, and the drainage of the quarry becomes 
an important problem. This is also the case even in areas well above 
drainage level, when springs and underground streams are encoun- 
tered, as frequently happens. 

The best situations are those in the belt im