Bulletin No. 267 n . f A, Economic Geology, 60 

aeries | ^ Descriptive Geology, 70

DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

' CHAKLfiS D. WALCOTT, DIRECTOR

THE

COPPER DEPOSITS OF MISSOURI

BY

H. FOSTER BAIN AND E. O. ULRICH

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1905

CONTENTS.

Page.

Letter of transmittrJ.................. ..................................... 7

Introduction __..___.___________..-.. ..---_ ...-....--.-.....--..--........ 9

Scope of this report -.-----.-.---.-..:..-...-.....-........... 9

History...................................................... 9

General distribution of the copper............................ 10

Geology ..................................................................... 13

Former classifications of the rocks........................ ............ 13

Swallow's scheme............................................ 13'

Nason's work..................................._............. . 14

Winslow's table -....--......-..-.- .'..... 1................... 15

Keyes's report ......I----..-..--.---.--'----'---.--------.-.-. . 16

Nason's later discoveries ._.___.. _'___.:___.._..__._._____._. 17

The Ball and Smith report. -....-.....-..-'-....-.....'..... ..... 17

General remarks on the " Ozark series " of rocks. ..................... 19

 Description of formations .--------. ...I---------------.------------.. 20

La Motte sandstone ...-..---... '........................... ^...... 20

Bonneterre limestone ............................................. 21

Elvinsformationl.........--------------:-_--------------------.. 23

Potosi group...................................................... 26

Gasconade limestone..--...-------.-......-......--.-....-..- 28

Eoubidoux formation.......................................... 31

Jefferson City limestone....................................... 33

St. Peter (" Crystal City ") sandstone.............................. 35

Joachim limestone..-..-..-.----------....--......-.-...--........ 36

The ore deposits .......................................'........'....-....... 36

The Ste. Genevieve mines..........-.-...-..-...-.-.--...,---....-... 36

History....-...........-...-...--....--.--.-..--.--.-..-------.-- 36

Geology..-.-.------.---..---------.-...--------------:--------.-.. 37

Ore bodies-...---..----------------.-.-.---------.--------..-.-.. 37

Value of the deposits........--.....------.-.--.-----.---...-..--- ' 38

Mine La Motte................'. -....-.-.-...-----......--.......-.-.. 39

Shannon County mines.............. ................................... 40

Location............------.----.----.-..----...--..-.----..... 40

History...............--.----.---.-.------.----....--.-.-.--- 42

Bibliography ......... --.-...--...-.-..---..-.--..--.-.--... 42

Slater mine .................... .....^........................ 43

Jerktail mine....._......-.-...--..-------..---.-.---.-....-. 45

Sutton mine ...........-.-.-.. --.---..----.,.-..-----.-..... 45

Caseymine ............-..--....--....-.--.....--..--.-.-.-.... 46

Tyrell mine..:......'. ---.-.--..--..--.-----:.-...--.-....---. 46

- 3
4 CONTENTS.

The ore deposits Continued. PageShannon County mines Continued.

Bonanza prospect ...---.-........-..-.......----------..- ..... 46

Freeman prospect....---.-...-....--.-.-........:.--...-...-. 47

General conclusions.......................................... 47

The Sullivan mines ...........-----.-----------_._--------.-.-__-._.. 47

History _____.____._...._--._...__..__--_...._.__.,..-.________ 47

Geology ----.......-.-.-............--..-------..-----....-... 47

Ore bodies...........-----........-------.---..--..-....--.-. 48

Value of the deposits.-.-.--..-...--.--....--.-----........... 49

General summary and conclusions......................................... 50

Index -..___...----_----.-_-_-----------.------------_------------------- 51
ILLUSTRATIONS.

Page.

PLATE I. The workings of the Cornwall mine, Ste. Genevieve County....... 36

FIG. 1. Sketch map showing location of copper deposits................. 11

2. Sketch map showing occurrences of copper in Shannon County.. 41

LETTER OF TRANSMITTAL.

DEPARTMENT OF THE INTERIOR, 

UNITED STATES GEOLOGICAL SURVEY, 

Washington, D. C., February 77, 1905.

SIR: I submit herewith the manuscript of a report on the copper 

deposits of Missouri, by H. Foster Bain and E. O. Ulrich, and recommend its publication as a bulletin.

The report is the result of field work undertaken last season by. 

Messrs. Bain and Ulrich in response to numerous requests for information concerning the copper deposits .of Missouri. It contains a 

summary of all available information regarding the copper deposits 

and a preliminary statement of the stratigraphy of the region in as 

great detail as the facts at hand warrant and as is necessary to a 

proper understanding of the occurrence and geological relations of 

the copper.

Very respectfully,

C. W. HAYES,

Geologist in Charge of Geology. 

Hon. CHARLES D. WALCOTT,

Director United States Geological Survey.

COPPER DEPOSITS OF MISSOURI.

By H. FOSTER BAIN and E. O. ULRICH.

INTRODUCTION.

Scope of this report. Copper is now being mined and smelted near 

Sullivan, Mo., and at other points in the State copper deposits are 

attracting attention. The present paper is a brief account of those 

deposits which have so far been mined, with such suggestions as seem 

warranted regarding further prospecting. The occurrence of copper 

in quantities permitting actual exploitation in the midst of a great 

area of unaltered and little disturbed sedimentary ro^ks raises many 

interesting questions. of genesis. These, howeA^er, can not be adequately discussed until the general studies upon the lead, zinc, and 

other ores of the Mississippi Valley are somewhat further advanced.

The present paper is based upon work done in 1904 by the authors, 

assisted by E. E. Ellis. Mr. Bain is responsible for all statements 

relating to the ore deposits and mines, while Mr. Ulrich has made 

the determinations of the geologic horizons and lias written the 

description of the formations.

History. ,Attempts to mine copper have been made in Missouri 

since 1837, and at different times copper furnaces have been operated 

in Shannon, Ste. Genevieve, and Crawford counties, while a matte 

carrying in addition nickel and cobalt has been steadily produced at 

Mine La Motte. These localities are shown on the accompanying 

sketch map (fig. l,.p. 11). Copper has probably been shipped in small 

quantities from several other counties also. Shumard," writing in 

1860, enumerated 15 counties in which copper was known to occur. 

Even at that he missed Ste. Genevieve, the one from which the main 

output has come. Very little attempt had then been made to develop 

the deposits. After the work of Joseph Slater in Shannon County in 

1837 no serious effort to mine was made until 1876, when Charles T. 

Biser shipped a few carloads from the same locality. About the 

same time the Ste. Genevieve mines were developed, and they continued in operation until about six years ago. In 1904 the furnace of

" Shumarcl, B. F., Report of progress : Missouri Geol. Survey, 1861, pp. 7-9.

9
10 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

the Missouri Copper Mountain Mining Company, at Sullivan, was 

put in blast and metal began to be shipped to Chicago for refining.

There are no exact figures of the amount of copper so far produced. Ladd a estimated the total as haying been worth less than 

$20,000.. This is probably too low, since the Ste. Genevieve mines 

produced regularly for some years and in 1880 alone were credited 

by the Tenth Census with an output of $25,730. Local estimates of 

the production of the Slater mine, in Shannon County, indicated a 

production of approximately $50,000. In 1903 the State mine inspector, G. K. Williams, is quoted 6 as estimating the sales of copper 

ore for the year to amount to $30,210. In 1904 the furnace at Sullivan shipped two carloads of metal, and for some years a copper matte 

has been regularly shipped from Mine La Motte. From this it appears that copper in important amounts has been actually marketed 

from this State for some years.

 General distribution of the copper. Copper-bearing pyrites are 

widely distributed in Missouri, as in "many other States, and the brilliant colors of the alteration products lead to ready recognition. 

Occurrences have been noted in Benton, Clark, Crawford, Dade, 

Dallas, Dent, Franklin, Greene, Iron, Jasper, Jefferson, Lawrence, 

Madison, Maries, St. Francois, Ste. Genevieve, Shannon, Washington, 

and probably a number of other counties. For the most part these 

occurrences may be at once dismissed as of no economic importance. 

The four which have yielded ore have already been noted.

With the exception of one or two sporadic occurrences of merely 

mineralogic interest, copper is found only in the southern part of 

Missouri, within the region broadly known as the Ozark uplift. This 

is an elliptical, warped plateau having a major northeast-southwest 

axis of some 300 miles and reaching its topographic culmination at 

Cedar Gap, somewhat west of the copper-bearing territory.

Its geologic center is to the east, where, in Iron, Madison, St. 

Francois, and adjacent counties, there exists a series of semidetached 

elevations made up of crystalline rocks, known as the " St. Francis 

Mountains." These rocks, mainly granite and porphyry, but with 

subordinate amounts of basic intrusives and probably of metamorphosed sediments, are of pre-Cambrian age. Aroun'd them in concentric belts, each wider to the west than the east, are the Cambrian, 

Ordovician, and later rocks, more especially described below. The 

region is one of important and varied mineral wealth. Iron, lead, 

zinc, barite, and manganese, as well as copper, occur and are mined. 

Despite the fact that it includes some of 'the earliest American settlements, considerable areas within it are very sparsely settled, are 

undeveloped, and, in comparison with the surrounding territory, are

a Ladd, G. E., Mining: The State of Missouri, by Walter Williams, 1904, p, 179. 

"Eng. and Min. Jour., New York, vol. 76, 1903, p. 739.
UAIN AND") 

ULW1CH. J

INTRODUCTION. 11

inaccessible. It is not surprising, therefore, that promising mineral 

prospects have been, in some instances, inadequately investigated.

Copper occurs as far south and west as in the Joplin zinc district, 

where chalcopyrite is very common and many of the copper oxides, 

carbonates, etc., have been recognized. It is to be noted, however, 

that the areas in which it occurs so abundantly as to have induced 

efforts to mine it are all located near the core of crystalline rocks, a

FIG. 1. Sketch map showing location of copper deposits.

relation which becomes more striking as the individual occurrences 

are examined. The pre-Cambrian age of these rocks is well attested, 

and there is no evidence of any later igneous activity in the district. 

A possible exception is the occurrence of a dike of graphic granite 

in Camden County, which Professor Shepard has described. 0 Here 

an intrusion took place in post-Ordovician and probably post-Devonian time. It does not seem, however, to have been accompanied by 

important mineralization, and has no apparent connection"" with any 

copper deposit.

« Shepard, E. M., Spring system of the Decaturville dome, Camcleu County, Mo. : WaterSup, and 1 rr. Paper No. 110, U. S. Geol. Survey, 1904, pp. 113-lSo.
12 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

Classification and synonymy of'the formations of the "Magnesian" or " Ozark

series '' in Missouri.

System

1

O'C'o

 c i

1cS 0

Series.

Saratogan and Lower Ordovician.

d 

So

f i 

K|

o

 55

o "o

True Sar-atogan.

Acadian.

Formation.

Joachim limestone .

St. Peter ("Crystal City") sandstone.

Jefferson City limestone.

Roubidoux formation.

Gasconade limestone.

Elvins formation . '.

Bonneterre limestone.

La Motte sandstone

Thickness.

0-150

1 0-200

} 50-250

| 70-225+

UoO-650

0-120

}.........

0-300

Synonyms.

/First Magnesian limestone. 

\Folley limestone."

First or Saccharoidal sandCap-au-Gres sandstone. 

Pacific sandstone: 

" Key sandstone " in Yellville district of Arkansas .

Second Magnesian limestone. 

Winfield limestone. 

Finley limestone. b 

?Marshfield sandstone.

Second sandstone. 

Moreau sandstone. 

St. Elizabeth formation 

and Bolin Creek sandstone member. 

?Marshfield sandstone. 

?Bolivar sandstone.

Third and Fourth Magnesian limestones and 

Third sandstones. 

Includes Osage limestone. 

Cole Camp sandstone of 

Winslow; also Gasconade Hmestone, Gunter 

sandslone, and Proctor 

limestone of Ball and 

Smith. 

Lesueur limestone.

1 Basal part of the Potosi 

limestone and the "Potosi slates and conglomerates " of Nason.

f?Fourth Magnesian lime- 

< stone (in part) . 

[Decaturville limestone.

("Second sandstone of Shu- 

\ mard (in part) .

Archean granites and porphyries.

a The names "Polley limestone," "Cap-au-Gres sandstone," and "Winfield limestone," together 

with a number of other new names, were published by Keyes in a paper entitled Some geological formations of the Cap-au-Gres uplift: Proc. Iowa Acad. Sci., vol. 5,1898, pp. 58-63.

bThe names "Finley limestone," "Marshfleld sandstone," and "Decaturville limestone" appear in a provisional table of geologic formations in Missouri by Shepard, E. M., Bull. Brad. Geol. 

Field Sta., 1904, p. 42.
"ULKICH"] COPPEB DEPOSITS OF MISSOURI. 13

GEOLOGY. 

FORMER CLASSIFICATIONS OF THE ROCKS.

The geologic formations containing the copper deposits of Missouri, described in this paper, all belong to that difficult and muchdiscussed series of rocks commonly known as the " Magnesian series " 

and more recently called the " Ozark series."" Many and diverse 

attempts at subdividing and classifying these rocks have been made 

in the last fifty years. None has proved wholly satisfactory^ and 

some have merely increased the confusion.

It is obviously impracticable to discuss the numerous and important 

problems connected with the Ozark series of rocks except in thebriefest manner at this time. Besides, as it is proposed to continue 

the investigation of the stratigraphic problems during the coming 

field season, it would be unwise to hamper the final conclusions by a 

preliminary publication of views necessarily based on incomplete 

field observations and office studies. Still, these investigations have 

been sufficiently extended to induce the belief that the results here 

presented will not be materially modified.

In order that the following resume may be made as intelligible as 

possible, it has been thought well to precede it with a table giving 

(1) the successive thickness and provisional classification of the 

formations, (2) the names of the formations that after a careful 

study of the matter have seemed to accord best with the demands of 

the rules of nomenclature, especially the rule of priority, and (3) 

the principal synonyms of each name.

Swallow's sche'me, In 1855 Swallow and his assistants 6 published 

a scheme of classification of the rocks in which the subdivisions were 

based primarily upon the separation of the rock b}' beds of sandstone 

usually much thinner than the limestone. These sandstones were 

regarded as widespread and constant in position, and hence of high 

value in the correlation of the beds of more or less magnesian limestones between them. Fossils being rare, and generally in an unfavorable state of preservation when found, and the older geologists seeming 

to have had confidence in the persistence of the sandstone beds, the 

numbering of the beds from above downward promised to be a happy 

solution of the difficulties.

From the beginning, however, of the later surveys of the State of 

Missouri, under Winslow, Keyes, and Bnckley, the inadequacy and

0 Broadhead, G. C., Am. Geol., vol. 8, 1891, p. 33. The term " Ozark series " is frequently 

employed in the following pages in a quoted sense. In the final nomenclature of the rocks 

of Missouri there can be no place for the term as defined by Broadhead. In the meantime, however, it is a convenient alternative for " Magnesian series."

b Swallow, G. C., First and Second Ann. Repts. Missouri Geol. Survey, 1855, pp. 114-131.
14 COPPEE DEPOSITS OF MISSOURI. [BULL.-267.

imperfections of Swallow's classification became more and more apparent. The impracticability of the prevailing mode of subdivision 

soon became obvious. They found not only more sandstones than 

were accounted for in Swallow's scheme, but also that most of these 

beds were mere lenses, appearing and disappearing Avith disconcerting frequency and irregularity.

Nasorfs work. Nason,0 in 1892, was the first to indicate these facts. 

However, in the course of his work on the rocks of the Ozark series 

he found that the general horizon that had been more constantly identified correctly than any of the other beds by Swallow and his assistants, and called the " Second sanc.otone," was really a persistent 

formation over a large part of the Ozark uplift. The name Roubidoux sandstone therefore was proposed by him as a geographic designation to take the place of Second sandstone. At the same time- he 

proposed to call the formation beneath the Roubidoux the Gasconade 

limestone. Perhaps it is unfortunate that Nason failed to fix the 

lower limit of his Gasconade formation. From another view it is 

rather fortunate that he did not, since with the fuller knowledge of 

the entire section now available the want may be supplied in a manner 

more in accord with the best interests of stratigraphy than might have 

been possible in 1892.

'Nason's supposition respecting the probable equivalence of the 

Roubidoux sandstone and Swallow's First or Saccharoidal sandstone 

as exhibited at Pacific and Crystal City (op. cit., p. 115) is unquestionably an error, and doubtless was occasioned by his justifiable loss 

of confidence in the ability of the geologists of the first survey to discriminate between the several beds of sandstone and limestone by 

lithologic characters only. It arose further, and perhaps especially, 

from the fact that neither he nor. any of the geologists before him 

recognized that the true First or Saccharoidal sandstone has been 

quite generally removed from the central areas of the Ozark Plateau. 

The sandstones identified by Shumard and other geologists in these 

central areas, and also along the western border of the outcrop of the 

Magnesian series, are not the same as the true." Saccharoidal sandstone " on the eastern flanks of Ozarkia, as this ancient land has 

recently been called, but are in nearly all cases, as believed or suspected by Nason, older and much thinner beds. Some of them may 

belong to the Roubidoux, most of them probably to the Jefferson City 

limestone, while a few particularly those at the contact with the 

overlying Devonian or Carboniferous rocks are the initial-deposits 

of much younger formations. As a rule, it may be stated that Avhere 

no later Ordovician rocks intervene between the ' ; Magnesian series " 

and. the Devonian or lower Carboniferous beds that generally rest

a Nason, F. L., Report on iron ores: Missouri Geol. Survey, vol. 2, 1892, pp. 85-115.
"ULUICH"] » EARLY CLASSIFICATIONS OF THE ROCKS. 15

on the eroded surface of the older magnesian limestones on the 

western and southern flanks of the Ozark uplift, the true " Saccharoidal sandstone " is missing entirely, it, together with more or less 

of the underlying limestone, having been removed by erosion prior to 

the Devonian and Carboniferous overlap. The long interval during 

which Ozarkia was elevated above sea level and subjected to erosion 

agencies was quite-sufficient to remove the sandstone, since it comprised the later half of Ordovician, the whole of Silurian, and the 

greater part of Devonian time.

Winslow's table. In 1894 Winslow published a table of formations 

in the lead districts of Missouri/1 A number of new names for divisions of the rocks under consideration are contained in this table, 

and in the matter following the table brief descriptions of most 

of the formations are given. The whole series in the southwestern 

district is included under one name White River limestone. This 

name had unfortunately been used and is in good standing ;for a Tertiary formation, and hence it is not available in this connection. 

Except for this fact it plight very well have been employed instead 

of the name Yellville limestone recently proposed by Adams 6 for 

rocks in northern Arkansas holding precisely the same position as 

the rocks of the Magnesian series along White River. Along this 

river, however, the top of the series is minus both the Joachim (First 

Magnesian) limestone and the St. Peter (First) sandstone, while the 

lowest rocks outcropping belong to the Gasconade formation.

In Winslow's table the Magnesian or Ozark series in central Missouri is as follows, beginning at the top: Roubidoux or Saccha: 

roidal sandstone, Jefferson City limestone, Moreau sandstone, Osage 

limestone, Cole Camp sandstone, and Proctor limestone. These formations presumably are equivalent to Swallow's divisions of the 

series in the same area, the only difference being that geographic 

names are used instead of lithologic. However, for reasons already 

pointed out, it was a mistake to employ Nason's name, Roubidoux, 

for the First or Saccharoidal sandstone instead of for the Second 

sandstone, which alone has a right to that name, and Roubidoux 

doubtless will displace the name Moreau, proposed by Winslow. 

As for the other names, Jefferson City limestone is proposed for 

Swallow's Second Magnesian limestone, Osage limestone for his Third 

Magnesian limestone, Cole Camp sandstone for the Third sandstone, 

and Proctor limestone for the Fourth Magnesian limestone. The 

last three divisions, as will be explained on a later page, all fall 

within the Gasconade limestone of Nason, according to the present 

writers' interpretation and definition of this formation.

"Winslow, Arthur, Lead and zinc deposits: Missouri Geol. Survey, vol. G, 1804, p. 381. 

6 Adams, George I., and others, Zinc and lead deposits of northern Arkansas: Prof. 

Paper U. S. Geol. Survey No. 24, 1904, pp. 18-20.
16 COPPER DEPOSITS OP MISSOURI.' [BULL. 267.

In the third column of his table Winslow presents an altogether 

different subdivision and nomenclature, which is proposed for the 

series in southeastern Missouri. Beginning at the top, the formations are as follows: (1) Joachim limestone, this being the name proposed for the First Magnesian limestone of Swallow; (2) Crystal 

City sandstone, the geographic name proposed for the " Saccharoidal 

sandstone; " (3) Potosi limestone, which is assigned by Winslow to 

the interval corresponding to the Jefferson City limestone and Moreau 

sandstone in central Missouri; (4) St. Joseph limestone, which is 

placed opposite the Osage limestone, Cole Camp sandstone, and Proctor limestone, in the central Missouri column of the table; and (5) 

La Motte sandstone, which is placed at the base of the Ozark series.

Concerning the Joachim limestone and the Crystal City sandstone, 

the present writers believe these to be well-marked formations and 

properly correlated by their, author. The Potosi limestone, however, 

corresponds to much more of the geologic column in central Missouri 

than is indicated by Winslow's table. As stated above, he made it 

correspond with only the Jefferson City limestone and the Ronbidoux 

(Moreau).sandstone, while we regard it as including also the Osage 

limestone, the Cole Camp sandstone, and the Proctor limestone of 

central Missouri.

The St. Joseph limestone includes two easily distinguishable lithologic units. According to the view of the Potosi formation just 

expressed, both the Bonneterre and Elvins formations the two beds 

comprised in the St. Joseph limestone are distinctly older than the 

Proctor limestone, or its equivalent, the " Fourth Magnesian limestone " of Swallow. The stratigraphic relations and fossil contents 

of the successive beds in the sections studied by the writers in southeastern and central Missouri, it is believed, establish the truth of 

these opinions. For a brief discussion of these features of the problem the reader is referred to the remarks following the succeeding 

descriptions of the formations in question. As to the La Motte sandstone, probably all agree that the name was well chosen and that the 

formation itself is an excellently defined lithologic unit lower than 

all the limestones now comprised in the Ozark series.

Keyes's report. In the year 1895, following Winslow's publication, Keyes published a report upon the section exposed in the La 

Motte quadrangle of Missouri.0 In this area only the lower part of 

the Ozark series occurs. This he divides into three formations, the 

La Motte sandstone at the base, the Fredericktown dolomite next 

above, and the Lesueur dolomite at the top. All the beds of the lastnamed formation occurring in the La Motte quadrangle belong in the

0 Keyes, Charles R., Missouri Geol. Survey Sheet Kept. No. 4, Mine La Motte, 124 pages. 

(Later hound in vol. 9.)
KULKicii.D ] EARLY CLASSIFICATIONS OF THE EOCKS. 17

Gasconade limestone of Nason. The new namej therefore, was superfluous. It would seem to have been better to employ Winslow's 

rather broad term Potosi limestone. The name Fredericktown covers 

°the same beds to which Winslow applied St. Joseph. The La Motte 

sandstone evidently is the same formation as that for which Winslow 

proposed the name.

N aeon's later discoveries. In 1901 Nason published a short paper 

on " The geological relations and age of the St. Joseph and Potosi 

limestones of St. Francois County, Missouri." a This paper contains 

at least three features of importance, viz: (1) The first description 

of a shale and conglomerate zone separating the St. Joseph and Potosi 

limestones, the discovery of which had been announced by the same 

writer earlier in the year; 6 (2) the announcement of the discovery 

by him. of sufficient fossils from the conglomerate bed, which he 

attaches to the base of the Potosi limestone, to enable Dr. C. E. 

Beecher to determine the age of the bed as " Middle or Upper Cambrian; " and (3) the first publication in a scientific journal of recognized standing of the name " Bonneterre limestone."

Nason did not overestimate the stratigraphic importance of this 

conglomerate bed. Its base marks an important break, no less than 

that between the Upper and Middle Cambrian. A very similar contact, with almost exactly the sanue kind of conglomerate and fauna 

above it, commonly defines the limits of these tAvo divisions of the 

Cambrian, not only in Missouri, but also in Indian Territory, central 

Texas, and at least locally in the upper Mississippi Valley. Classifying the " conglomeratic zone " with the Potosi is believed to have 

been a mistake, the writers preferring to make it the lower and 

greater part of a distinct formation, for which the name Elvins formation is proposed. Finally, the name Bonneterre limestone, used 

incorrectly and without comment as an alternative for Winslow's St. 

Joseph, is the most appropriate and probably the only strictly available designation for the limestone beneath the conglomerate of the 

 Elvins formation.

Ball and Smith report. An important contribution to the literature of the Ozark series appeared in 1903 in a volume by Ball and 

Smith on " The geology of Miller County." c In this report very 

full descriptions and numerous detailed sections are given of the 

forriiations corresponding, at least in a general way, to the Second, 

Third, and Fourth Magnesian limestones and the First, Second, 

and Third sandstones of Swallow's classification. The nomenclature

a Nason, F. L., Am. Jour. Sci., 4th ser., vol. 12, 1901, p. 358. 

6 Nason, F. L., Am. Jour. Sci., 4th ser., vol. 11, 1901, p. 396.

c Ball, Sidney H., and Smith, A. F., Missouri Bureau of Geology and Mines, 2d ser., vol. 1, 

5903, 197: pages.

'Bull. 267 05 M 2
18^ -COPPER DEPOSITS OF MISSOURI. [BULL. 2GT.

of the formations presented in this valuable work differs in several 

respects from that in the table on page 12 of this paper. For 

instance,' the name Gasconade limestone is applied by the authors 

mentioned to Swallow's Third Magnesian limestone. According to* 

our view, Nason, who is responsible for the ; name, 'included not 

only the Third, but the Fourth Magnesian as well, in his sections 

of the formation. The Gasconade limestone, therefore, if this name 

be used at all, should extend downward so as to include the Gunter 

sandstone and the Proctor limestone. This is not to say, however, 

that the Gasconade limestone in Miller County is not divisible into 

three members (or formations, perhaps), worthy of being mapped 

as separate lithologic units. Indeecl, such a division seems not only 

practicable, but even very desirable through a large part of the 

northwestern half of the Ozark uplift. In the southeastern half, 

however, the two limestone members and the intermediate Gunter 

sandstone, though in a general way recognizable, do not seem to be 

as readily separated. Indeed, the'Gunter sandstone, which is so 

definite a bed in Miller and adjoining counties, has entirely lost its 

identity or can not be distinguished from a number of similar sandstones occurring at about the same horizon. In Yell County, Ark., 

there seems to be no sandstone a!t all in the corresponding portion 

of the Gasconade. In Ste. Geneyieve County, Mo., On the other 

hand, the upper half of the formation contains a number of sandstones, but it is impossible to say that any one is equivalent to the 

Gunter.

The St. Elizabeth formation of the Miller County report seems to 

be essentially, if, indeed, not exactly, the same formation earlier 

named Roubidoux sandstone of Nason.

As regards the " Pacific sandstone " of the Miller County report, 

which Ball and Smith correlate with the, First or Saccharoidal sandstone of Swallow, it seems to the present writers highly improbable 

that it is the same as that outcropping at Pacific, Crystal City, and 

many localities on the eastern flank of the Ozark uplift. Some of the 

supposed occurrences of this befl may be thin lenses of sandstone in 

the Jefferson City limestone, but the majority probably are later than 

Ordovician possibly Devonian or Carboniferous. At the top of 

one section (op. cit., p. 80) pieces of " dolomite resembling cotton 

r#ck " occurred above the sandstone. These, it is said, " may be remnants of the First Magnesian limestone," but, for many reasons which 

can not be given at this time, the whole exposure described on the 

page mentioned is believed to belong to the Jefferson City limestone. 

Finally, the name " Pacific sandstone " seems entirely unnecessary. 

If a Missouri name for the true Saccharoidal sandstone is preferred 

to the adoption of St. Peter sandstone, with which the First sandstone doubtless is identical, then it should be Crystal City sandstone, 

a name proposed by Winslow several years before,
BULHICH D ] COPPER DEPOSITS OF MISSOURI. " . 19 

GENERAL REMARKS ON THE "OZARK SERIES '" OF ROCKS.

As has been already stated, none of the classifications and subdivisions of the Ozark series of rocks, briefly discussed in the foregoing 

pages, has proved wholly satisfactory. An arrangement that would 

be above criticism is perhaps impossible. Some of the beds vary so 

greatly from pladfcto place that it is difficult to follow them over any 

considerable area. The difficulties are greatly enhanced by the apparent scarcity and imperfect preservation of the fossils and by the general similarity in lithologic character exhibited by widely separated 

beds in the series. The occurrence of beds of sandstone at intervals 

in the mass of magnesian limestones was earl}' seized upon as affording a ready means for dividing the series into formations; but experience gradually taught that most of the sandstones wr ere mere lenses,. 

irregularly developed at unequal intervals and occurring locally as 

many successive beds or with only two or three. In the northern 

and central parts of the Ozark Plateau the sandstone beds seem to be 

more regularly developed than elsewhere, and here they are of considerable use in working out the stratigraphy. Along the southern 

border, however, only the First or St. Peter sandstone seems to have 

been so well developed as to mark a definite horizon. Along the 

eastern border, especially in Ste. Genevieve County, the upper half 

of the series is thicker than usual. It here contains so many beds of 

sandstone that it is very difficult to establish the boundary line 

between the Gasconade and Roubidoux formations and between the 

latter and the overlying Jefferson City limestone.

A careful study of the cherts has yielded perhaps the most reliable 

of the lithologic criteria employed in discriminating the three formations of the Potosi group. As this group covers by far the greatest 

part of the Ozark area, the opportunities for- studying and testing 

the value of certain varieties of chert as indices of particular horizons 

are. unusual. Having checked the results in many instances by evidence afforded by fossils, which really are much commoner in these 

rocks than is generally believed, we have gradually become convinced 

that the story as told by the cherts is rarely at fault. The mere 

presence of considerable quantities of chert is at once reliably indicative of the Potosi group, the underlying limestones being practically free from it, as is true also of the Joachim limestone at the 

top of the series. It is to be remembered, however, that the proportion of chert in a given bed may vary greatly in near-by exposures. 

This is shown often very strikingly in opposite faces'of a hill, the 

one side of which forms a bluff, the other a gentle, soil-covered slope. 

In- cases of bluff exposure where side erosion is active and takes 

place under conditions very different from those prevailing on gentle 

slopes the limestone b.eds may often seem to be almost entirely with-
20 " COPPER DEPOSITS OF MISSOURI. [BULL. 267.

out chert, but on the other side of the hill the surface may be thickly 

strewn with it.

The classification presented in tabular form on page 12 is based 

upon more or less extended investigations in all parts of the field. 

The formations are discriminated chiefly by lithologic differences, 

and limited in most cases by at least local stratigraphic discordances. 

As the formations are intended to express as much as possible lithologic units deemed worthy of being mapped separately, the evidence 

of the fossils found in them was. accorded secondary rank. However, in the .determination of the age of the deposits the faunas were 

depended upon almost exclusively.

It will be observed that the division between the Ordovician and 

Cambrian is drawn as a dotted line opposite the Koubidoux member 

of the Potosi. This seeming indecision concerning the point at which 

the line should be drawn is not due to the absence of a fauna, for we 

have succeeded in collecting a large one, but because of the conflicting elements contained in it. The trilobites from the Gasconade and 

the lower part of the Roubidoux are, so far as observed, nearly all 

of types that hitherto have been regarded as strictly indicative of the 

Upper Cambrian. On the other hand, the numerous gasteropods and 

fewer brachiopods found in the same beds are nearly all of Lower 

Ordovician types.

DESCRIPTION'OF FORMATIONS.

LA MOTTE SANDSTONE.

This formation generally consists of thick, massive beds of sandstone. Toward the top it is often thinly bedded or flaggy. The 

color of the sandstone is usually4 yellow or reddish brown, with occasional layers almost white. It is generally composed of large grains 

of quartz in a matrix of smaller grains. In the upper half of the 

formation the matrix is often calcareous, the proportion of limy 

material usually increasing upward until the rock grades into a 

sandy limestone. Near the top beds of limestone may alternate with 

layers of sandstone, and in such cases the transition to the overlying 

Bonneterre limestone may be gradual. Near the base there are frequently layers containing coarse grit and quartz pebbles and others 

with small pebbles of granite and porphyry. The upper beds are 

often chloritic, but so far as observed no part of the formation is ever 

micaceous.

The maximum thickness of the La Motte sandstone is not less than 

250 feet, and in the bottoms of the basins adjacent to granitic areas, 

which doubtless were the .main sources of supply, the thickness probably exceeds 300 or possibly 400 feet. From this it dwindles down to
I DESCRIPTION OF FORMATIONS. 2l

nothing along some of the old shore lines, where it is overlapped by 

the limestones of the next formation.

The principal areas of outcrop occur around the granite hills in 

the western half of Ste. Genevieve County and on the eastern flanks 

of the old Archean hills in Madison and St. Francois counties. How 

far from these areas this formation extends beneath the covering of 

higher rocks can not now be said. Possibly it is widely distributed, and 

it may even be continuous with what is believed to be nearly contemporaneous Middle Cambrian sandstones in Indian Territory and in 

the upper Mississippi Valley. However, considering the granitic 

rocks in southeastern Missouri as the principal if not the only source 

from which its quartz grains might be derived, it does not seem likely 

that the formation at any rate, as a sandstone could have attained 

any considerable thickness far from its present main outcrops. 

Masses of quartzite, etc., occurring apparently at the base of the 

Bonneterre limestone in the southern part of Camden County, where 

profound disturbances have brought this limestone to the surface, 

may be silicified blocks of a thin extension of the La Motte sandstone.

In the area of the St. Francis Mountains a conglomerate, consisting 

mainly, of pebbles of porphyry in a slaty or sandy matrix, often 

underlies the La Motte sandstone. In the Missouri Survey reports 

this bed is referred to under two names Pilot Knob conglomerate 

(Keyes) and Iron Mountain conglomerate (Winslow). The age of 

the bed is variously interpreted, some considering it, especially at 

Pilot Knob, as Algonkian; in other cases it seems not to be older than 

the lower part at least of the La Motte sandstone. The truth of the 

matter probably is that the conglomerate is primarily the initial 

deposit of the invading early Cambrian, and that during the subsequent deposition of the La Motte sandstone the conglomerate continued locally to be formed near the shore, perhaps more particularly 

where this was steep. The bed, therefore, it not to be regarded as a 

formation wholly beneath and older than the La Motte sandstone.

BONNETERRE LIMESTONE.

As a rule this formation consists of more or less heavily bedded, 

granular, and highly magnesian limestones. In texture these generally are compactly crystalline and often minutely vesicular, with 

dolomite crystals lining the cavities. A few beds are fine grained. 

The usual color is light or dark gray, especially when fresh, a yellowish tint being commonly acquired on weathering. Locally the 

mass may contain beds of a pink or of a more decidedly red color. 

Chert and drusy quartz seem to be entirely absent. Some of the 

beds, especially in the lower part of the formation, contain much 

chlorite, in places sufficient to give them a decidedly green color.
22 COPPER DEPOSITS OP MISSOURI. [BULL. 207.

Toward the base of the formation it contains some silica. This 

occurs as grain's of sand in the limestone. The contact Avith the 

underlying La Motte sandstone is rarely sharp, the two formations 

often appearing to grade into each other. The basal portion commonly also includes one or more thin beds of bluish shale. Where 

the top of the formation has suffered least from the widespread 

erosion that took place prior to the deposition of the Elvins formation 'it grades upward from the massive limestones into a thinly 

bedded zone, and this finally into a bed of blue shale. Locally 

the thinly bedded and shaly zones appear to be absent entirely.

Fossils are rare in this formation, except in the shaly bed near 

the base. This is crowded with a species of Lingulepis, related to 

L. lambornei Meek. Fragments of other fossils occur with this 

shell. A few specimens of trilobites and of orthoid shells related 

to Billingsella were observed also in the shales at the top of the 

formation. These fossiliferous horizons, however, have not been 

thoroughly exploited. The species so far found are comparable to 

those, characteristic of the Middle Cambrian.

Like the La Motte sandstone, this formation varies greatly in 

thickness, and seems even to wedge out on the old hillsides. In the 

vicinity of Mine La Motte and Fredericktown, where the basin is 

comparatively shallow, the maximum thickness probably does not 

exceed 200 feet, or possibly 250 feet. Farther north, in St. Francois 

County, deep drillings show it to be much thicker, the greatest thickness probably being nearly 500 feet. Winslow gives the maximum 

thickness in the vicinity of Flat River as " somewhere near 600 feet," 

but this estimate doubtless includes the whole, or at least a large part, 

of the overlying Elvins formation.

The Bonneterre limestone is the prevailing surface rock in the 

southeastern lead-mining district of Missouri. The formation 

probably underlies a large part of the Ozark uplift, but it does not 

again 'come to the surface within the borders of the State except 

in a small area near the southern boundary of Camden County. 

Here it occurs as a noncherty, massive, crystalline dolomite, standing 

nearly on edge about a dike of graphic granite. On account of the 

excessively disturbed character of the outcrop and the brevity of the 

time devoted to its study, the thickness of the formation was not 

determined exactly. It is safe to say, however, that it is not less 

than 200 feet.

That the base of the formation is exposed at this locality is indicated by the presence of a bed of limestone filled with rounded grains 

of quartz and of quartzite bowlders believed to be silicified masses of 

La Motte sandstone.. Closely associated with these, and apparently 

overlying the calcareous sandstone, is a bed of fine conglomerate 

that is believed to be the basal layer of the Bonneterre limestone.
BULUICXH°] DESCRIPTION OF FORMATIONS. 23

The pebbles in this conglomerate consist principally of greenish-blue 

shale and fragments of limy sandstone abundantly specked' with a 

green mineral supposed to be chlorite.

In southeastern Missouri, except in the few places where the formation overlaps the underlying sandstone and rests on the Archean, the 

base seems to be entirely conformable with the top of the La Motte 

sandstone. The upper boundary, however, as intimated above, is 

variable. Sometimes there is a considerable body of thin limestones 

interbedded with shale at the top that at other points is much 

thinner or perhaps may be wanting entirely. This irregularity of 

the top is due to an erosion interval, in which much of the shaly top 

of the formation was removed. There is, consequently, an unconformable contact between the Bonneterre and Elvins formations. In 

the outcrops, which occur chiefly in the marginal portions of the old 

basins, this unconformable contact is marked by one or more thin 

beds of lenticular pebbles. Where observed it generally occurs within 

what might otherwise appear as a continuous deposit of rapidly alternating thin limestones and shales. On this account it may be difficult, and in some cases impossible, to distinguish the upper part of 

the Bonneterre formation from the Elvins formation in records and 

cores of drill holes. In the outcrops, however, the boundary between 

the two may be drawn with little trouble. Considering that this 

line probably separates the Middle Cambrian from the Upper Cambrian, and that it may eventually mark the boundary between two 

systems, its stratigraphic importance becomes clear.

ELVINS FORMATION.

This name is proposed for the shales, shaly limestones, and more 

or less earthy dolomites that in St. Francois County intervene 

between the shaly top of the underlying Bonneterre limestone and 

the cherty limestones of the Potosi group above. In the vicinity of 

Elvins and Flat Rock the base of the formation is marked by a zone 

6 to 10 feet thick, consisting mainly of indurated platy shale. At 

the bottom of this zone is a layer, generally only a few inches in 

thickness, that is largely made up of lenticular pebbles usually 

arranged edgewise in a subcrystalline limy matrix. At the top of the 

zone there is usually a similar " edgewise layer," while between the 

two layers one or more smaller lenses of conglomerate may be 

observed. In the Elvins section given on pages 24-25 a bed of nearly 

white, compact, and apparently not highly magnesian limestone occurs 

about 8 feet above the base of the formation, which is well exposed 

in the railroad cut a half mile north of the Illinois Southern Railroad depot at Elvins. In the unfinished deep cut nearer the depot
COPPER DEPOSITS OF MISSOURI. [BULL. 267.

this layer is broken up into a series of large, bowlder-like masses that 

may be of concretionary origin.

The following detailed section of the typical exposures of the 

formation will give a better idea of the lithologic and other characters than could be acquired from a general description:

Section of the Elvins formation along the Illinois Southern Railroad between 

Elvins and 1 mile north.

Serial 

No. of 

beds.

Thickness. Description of beds. Thickness.

Ft. In. Ft. In.

Slope to top of hill covered abundantly with characteristic Potosi chert and masses of drusy 

quartz.

A bed of massive, pink, granular dolomite, without chert, regarded as the basal layer of the 

Gasconade limestone (about 4 feet).

9 60 Light-yellow to grayish-blue, apparently slightly 

arenaceous, magnesian limestone, in thin, even 

beds. Bedding planes with fucoids. small cavities lined with crystals of calcite and dolomite in 

rock ...--_._---._.___..__..___-.__-.___-....-.; 6 0

26 6 Very thinly bedded, earthy magnesian limestone. 

Near by this appears nearly solid. Two layers, 

one 6 feet, the other 11 feet beneath top, contain 

numerous but very poorly preserved fossils. 

.These consist chiefly of fragments of crinoids or 

cystids-....-------------_..-.._-------.---'-._-_. 17 0

Subcrystalline, brownish dolomite ....._:._.-.;.-. 0 6

Upper and lower thirds shale, middle third thinly 

bedded earthy magnesian limestone.---.----_--. 9 0

7 17 3 Yellowish, cellulose dolomite in thin, rough layers. 0 9 

Shale ............................................. 0 10

Yellowish, cellulose magnesian limestone _--.._--. 3 0

Shale ............................................. 1 0

Earthy magnesian limestone or dolomite ..........

Yellowish to light-blue soft shale. Upper Cambrian trilobites in limestone concretions......... 4 0

Earthy magnesian limestone with lenticular pebbles............................................ 1 3

Shale resembling and containing fossils like those 

in shale next above............................. 4 0

6 10 0 Dolomitic limestone, rather thinly bedded, locally

containing lenticular pebbles and a few fossils... 10 0

110 Blue shale with irregular lenses of dolomitic limestone near, middle.... ..........................^. 9 0 ^

Dolomitic limestone ............................... 2 0

4 22 0 Bluish shale with four or five layers of limestone

ranging from 3 to 12 inches in thickness......... 15 0

Interbedded dolomitic limestone and thinner layers 

of shale ......................................... 7 0
BAIN AND"! 

ULUICH. J DESCRIPTION OF FORMATIONS. 25

Section of the Elvins formation along the Illinois Southern Railroad between 

Elvins and 1 mile north Continued.

Serial 

No. of 

beds.

Thickness.

Ft. In. 

' 10 0

0-3 0

8 0

Description of beds.

Blue shale, increasing in hardness downward .._.,.

Soft clay shale. This rests on the white limestone 

beneath or. where that layer is broken up into 

bowlder-like masses, it fills the intervals between 

them.................----.-.....--.........--..

White, compact, apparently not highly magnesian 

limestone, occurring either as a continuous layer 

or as bowlder-like remnants embedded in shale. 

The. "remnants" are usually flat on the lower 

side and rounded above....-.......--.....--.--.

Indurated, platy shale,, with a layer of " edgewise 

conglomerate'' at the base and often another at 

top. (Base of the formation)...................

Total thickness of Elvins formation ...

Thickness.

Ft. In. 

6 0

4 0

0-3 0

8 0

118 9

Beneath these beds the upper part of the Bonneterre limestone 

shows as follows:

Section of Bonneterre limestone exposed along railroad 'between Elvins and

1 mile north.

Serial

No.

2 

1

Description of beds.

Bed here forming top of Bonneterre limestone. It is similar 

to the basal bed of the overlying Elvins formation, except 

that it contains more soft shale and thinner hard layers; 

also an occasional thin seam or lens of crystalline limestone with fossils of apparently Middle Cambrian types. ...

Impure magnesian limestone and shale, growing on the 

whole more calcareous downward in first 20 feet; then a 

shaly bed, and finally more limestone, passing gradually 

into the normal type of Bonneterre limestone; exposed in 

the bed of Flat River .....................................

Thickness 

in feet.

10 

30-40

The lower part of this formation was well described by Nason 

in 1901.a This writer also was the first to observe and note the 

importance of the beds of conglomerate marking the base and 

occurring also higher in the lower formation. Hanking the new 

horizon as a lower division of the Potosi limestone is believed to be 

an error, because (1) it constitutes a sharply defined lithologic 

unit; (2) its fauna is very different from that of the Potosi group, 

in wanting all the molluscan types which distinguish the Potosi from

a Nason, P. L., Am. Jour. Sci., 4th ser., vol. 12, 1901, pp. 358-361.
26 COPPER DEPOSITS 0$ MISSOURI. [BULL. 267.

all preceding rocks; and (3) it seems that the contact with the overlying Potosi is, at least locally, unconformable.

The bed of pink dolomite assigned to the base of the Potosi in the 

foregoing section contains no chert nor drusy quartz, and in that 

respect differs decidedly from the overlying beds of the formation. It 

may therefore be regarded as more properly referable to the Elvins 

formation. This is not here, for the reason that it or a similar 

bed inaugurates the Potosi sedimentation in areas where the Elvins 

formation is wanting. The similarity in lithologic character of the 

bed to the underlying rather than the overlying limestone is believed to result from a reworking of nonsiliceous matter derived 

from the dissolution of the underlying limestones. Beds above and 

beneath nearly conformable contacts are often very similar lithologically. The contact between the Bonneterre and Elvins formations affords a striking illustration of this.

Outcrops of the Elvins formation occur principally within St. 

Francois County. Here they are found in the slopes of perhaps all 

the hills that are capped by the residual cherts of the Potosi. The 

formation is frequently noticed also in drill holes in this county. 

Jn the northern part of the county these holes frequently pass through 

from 160 to as much as 250 feet of shales and chertless limestone, 

thus indicating a greater thickness for the formation than is found 

in the section measured at Elvins. However, it is at present not 

possible to say IIOAV much of these shaly beds underlie the conglomeratic layers and thus belong to the Bonneterre formation. 

On Kock Creek, east of Mine La Motte, no sign of the Elvins formation Avas observed, and the Potosi rested directly on the Bonneterre 

limestone.

POTOSI GROUP."

The group of rocks included between the Elvins formation beneath and the St. Peter (" Crystal City") sandstone above is 

characterized by large quantities of various kinds of chert and drusy 

quartz. The group includes mainly limestones, nearly all more or 

less highly magnesian, the proportion of magnesia in some cases 

approximating that contained in a theoretical dolomite. Intercalated 

with the limestones, especially in the upper half or two-thirds of the 

series, are more or less irregularly developed and usually thin lense? 

or beds of sandstone,

a Winslow is responsible "for the name Potosi as applied to a geologic formation. 

Unfortunately, in the original publication (Missouri Geol. Survey, vol. G, 1894) the formation is not clearly defined, and as a rule its beds are referred to under the broader term 

St. Francois limestone. There is, therefore, some chance .of conflict with the term 

T/esueur limestone proposed by Keyes the year following for essentially the same rocks. 

Most geologists and mining experts who have studied the Ozark rocks in southeastern 

Missouri have consistently used the name Potosi in the *ense here adopted. * This 

accords with Winslow's original intention as well as with his later definition of the 

term.
Bm«TPHD l DESCRIPTION OF FORMATIONS. 2iT

As the group forms the surface rock over quite nine-tenths of the 

large area of Ozark rocks in Missouri and northern Arkansas, it is 

highly desirable to subclivide.it into such formations and members 

as may be required to illustrate the stratigraphy and structure of- the 

"region. Where the sandstone beds are fairly persistent, as in nearly 

the whole of the northwestern half of the area, they afford convenient datum lines upon which to base the desired subdivision. 

Careful use of certain types and beds of chert likewise aids in accomplishing the purpose.

Building upon the combined results of the efforts of Nason, Winslow, and Ball and Smith, we have recognized three major divisions 

that we believe may be carried with more or less accuracy over much 

the greater part of the territory in which the group is at the surface. 

These are, (1) the Gasconade limestone, at the base; (2) the Roubidoux formation, in the middle; and (3) the Jefferson City limestone, 

at the top. In the central and northern parts of the area the Gasconade limestone is further divisible into an upper and a lower limestone formation or member by an intervening thin but widely distributed and easily identified sandstone member, called the "Cole 

Camp sandstone " by Winslow and the " Gunter sandstone " by Ball 

and Smith. Locally other subdivisions are possible, and in the final 

mapping will doubtless be made.

During practically the whole of Potosi time the waters of the sea 

in the region now exposing the rocks of this age were shallow and 

fluctuating in depth. Frequently the bottom was raised above 

sea level, or it may be that the waters subsided and thus caused the 

bottom to be exposed. These emergences were more or less local 

and, according to the evidence available, must have varied greatly 

in the length of time through which each endured. Evidences of 

this condition are abundant. Intraformational-'conglomerates, suncracked beds, oolites, unconformities, due to exposure and erosion, 

and cases of abrupt change in deposition from limestone to sandstone all occur frequently. The conglomerates in many cases indicate a considerable lapse of time. This is more particularly indicated for those containing pebbles of chert. Chert was only rarely 

present in this group of rocks when they were originally deposited., 

As it now occurs it is largely the result of segregation of siliceous 

matter under conditions of slow subaerial decomposition of the limestone. Hence the presence of rounded chert pebbles is strongly indicative of subaerial erosion and, for obvious reasons, of a longer time 

interval than is usually ascribed to an intraformational conglomerate. In these features the deposition of this part of the Ozark 

series differs from that of the corresponding parts in the Arbuckle 

limestone of Indian Territory and the Knox dolomite of the Appalachian Valley. The latter rocks Avere laid down in comparatively
28 COPPER DEPOSITS OP MTSSOUBI. [BULL. 267.

deep basins, while those of the Potosi group were spread unevenly 

over the summit of a low, broad dome. This explains also the occurrence in Missouri of a considerable fauna, whereas the corresponding 

deposits made in deeper waters are almost or entirely devoid of fossils. Tlie Cambric n and early Ordovician faunas flourished only in 

shallow waters and ilong shore lines.

The shallows of the Ozark area afforded the necessary conditions 

for life, and here the main types of the Upper Cambrian fauna 

especially the trilobites continued in existence longer, while the 

Lower Ordovician fauna began earlier than is'indicated elsewhere 

by faunas hitherto discovered.

As the copper deposits which constitute the principal subject of 

this contribution are contained, with one exception, in the rocks of 

this group, the major subdivisions will be described in some detail.

GASCONADE LIMESTONE.

In the report on Miller County, discussed earlier in this paper, the 

name Gasconade is restricted to the Third Magnesian limestone -of 

Swallow. This makes it the same as the Osage limestone, proposed 

in 1894 by Winslow as a subdivision of the Gasconade limestone. 

The term Osage, however, had been used by Williams and Branner 

some years before for a group of Mississippian rocks, a'nd, for this 

reason no doubt, Winslow's use of the name was objectionable to the 

authors of the Miller County report. Nason is responsible for the 

term Gasconade limestone. As adopted by Winslow, it became too 

broad, being placed opposite all the limestones beneath the Crystal 

City sandstone. This expansion of the meaning of the term was 

caused by the erroneous assumption that the Boubidoux and St. Peter 

sandstones were equivalent deposits. As employed here the Gasconade limestone embraces the chert-bearing limestones and included 

sandstones underlying the true Eoubidoux, as determined by studies 

of some of Nason's typical localities, and overlying the strictly noncherty limestones of the Elvins and Bonneterre formations. This 

conception of the Gasconade, it is believed, is in accord with Nason's 

intention. As his deepest sections, along the Current River, in 

Shannon County, undoubtedly contain at least the upper part of the 

Proctor limestone, Avhich is the basal member of the formation, we 

have, as is usual in such cases, drawn the lower limits of the formation 

at the first well-marked stratigraphic and lithologic change beneath 

the rocks included in the formations by Nason.

The Gasconade limestone consists chiefly of dolomitic limestone, 

varying greatly in color and composition and somewhat less in texture. The color of the majority of the beds is gray, in lighter and 

darker shades. Sometimes a bluish tinge is observable, but lightpink tints are more common. Other beds may be brown, green, or
DESCKIPTION OF FORMATIONS. 29

nearly white. As a rule, it may be said that bluish tints are more 

common in the lower parts than in the upper. The prevailing texture of the limestone rode is medium to coarse grained, crystalline, 

or granular, but comparatively fine-grained layers occur, and perhaps 

as commonly in one part of the formation as in another.

Several beds of sandstone occur, 'most of them small .sporadic 

lenses in the upper half of the formation. One bed, the Cole Camp 

sandstone of Winslow and the Gunter sandstone of Ball and Smith, 

is more than usually persistent in the centra,] and western .parts of 

the area. In these,districts its thickness ranges from 2 or_3 .feet to 

25 feet, and, as it is nearly always exposed, it constitutes an efficient 

boundary line between the Proctor limestone and the upper (Osage) 

limestone of the formation. The other divisions are more likely to 

confuse than help the geologist in working out the stratigraphy. In 

the southern part of the 0/ark area the Gunter sandstone, in common 

with the other sandstones interbeddod Avith the limestones of the 

Potosi group, is either absent entirely or so irregularly developed 

that it has i lost its stratigraphic value. On the east side of the St. 

Francis Mountains, in Ste. Genevieve County, this sandstone bed is 

probably represented, but there are so many sandstones in the 

Potosi of this region that it can not be certainly distinguished.

Under usual conditions of subaerial decomposition the silica of the 

rocks is segregated in the form of amorphous and lamellar or vesicular chert, or as drusy quartz, in'nearly all parts of this formation. 

However, under the present physiographic conditions, chert is on the 

whole more abundant in the upper part of the formation than in the 

lower, but this diiference seems not to be due to any marked variation 

in the composition of the limestones composing the two parts, but 

results rather from differences in the circumstances attending the 

decomposition and erosion of the upper member and those prevailing 

in the case of the lower. As is briefly suggested on page 27, rapid 

erosion is not conducive to the abundant segregation of chert. Therefore the lower, or Proctor, limestone, being rarely seen in the central 

area except in bluffs, appears to be characterized here by having 

much less chert than the upper division, which more commonly occupies upland ridges. In areas where the valleys are occupied by the 

Bonneterre limestone and the hills by rocks equivalent in age to the 

Proctor limestone, as in St. Francois and Madison counties, chert is 

extremely abundant in the lower as in the higher parts of the formation. It appears, therefore, that local superficial conditions are responsible for much of the unequal distribution of the chert.

Lamellar chert with drusy cavities occurs very abundantly in the 

lower and middle parts of the formation, but is comparatively rare 

in the upper beds. A highly characteristic form of chert, consisting 

of irregular rough stems, one-half inch or so in diameter, bound
30 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

together by anastomosis into masses a foot or more in length, was 

observed at many localities. It occurs commonly enough beneath the 

horizon of the Gunter sandstone, but is especially abundant in the first 

50 feet above that bed.

The cherts of the upper division embrace two common varieties 

that are believed to characterize this horizon over a large part of the 

Ozark area. They are both laminar varieties, and possibly of organic 

origin. One is a "Cryptozoon" differing from the C. minnesotensis, 

which is characteristic of the Jefferson City limestone in its looser 

and more irregular structure. The other is a very coarsely vesicular 

form, occurrin-g in masses 2 or 3 feet thick and making up whole 

layers of that thickness. When followed into the bank these layers 

gradually pass into solid limestone, but even in these a similar horizontal lamination of the mass is observable. The laminae are divided 

at intervals of about 2 inches into convex, minutely cellular plates, 

arranged one above the other so as to leave open spaces about equal 

to the thickness of the plates between them. This type occurs principally toward the top of the formation and is a reliable guide to one 

of the most prolific fossil horizons of the whole series. Thin conglomeratic layers, containing small chert pebbles and fragments of 

silicified and often sandy oolite, both commonly fossiliferous, occur 

with and above this coarsely vesicular type of chert.

Fossils occur more or less sparingly through all parts of the formation, but are generally distributed and of larger size in the upper 

beds. They consist chiefly of low-spired arid ventricose species of 

Gasteropoda. Associated with these are many fragments of trilobites, 

having unmistakable affinities with well-known Upper Cambrian 

species. Toward the base of the formation the fossils are sometimes 

abundant, but the species seen are not numerous, and, being'small, 

are easily overlooked.

In thickness this formation varies considerably from place to place. 

The greater amount of this variabilit}^ seems to occur in the upper 

member, which was laid down under less uniform conditions than 

the lower. Locally, in St. Francois and Madison counties, the lower 

member also is thinner than usual, the variation in this case appearing to be due to overlap and consequent absence of the basal beds.. 

The .average thickness, doubtless, is at least 500 feet for the whole 

formation, while the maximum thickness probably exceeds 650 feet.

Concerning the relations of the Gasconade limestone to adjacent 

formations, it may be said that the basal contact is believed to be 

rather generally unconformable. It is certainly so locally, as is shown 

by the occurrence of certain fossiliferous bands, local evidence of overlap, and a comparison of the basal beds in different sections. However, on account of the abundant wash from overlying beds, exposures 

showing the contact in a satisfactory manner are very rare. In Cam-
BULRICHD ] DESCRIPTION OF FORMATIONS. 31

den County, where the base is shown in the vicinity of the pegmatite 

dike, a massive white sandstone, 20 to 30 feet thick, intervenes between 

the Bonneterre limestone and the cherty limestone of the Gasconade, 

This sandstone is probably to .be regarded as the initial deposit of the 

Gasconade or possibly as in part representing the Elvins formation. 

The top of the formation is less sharply defined; indeed, it is often 

difficult to draw the line between it and the Roubidoux. There is no 

important unconformity between the two, the shallowing of the seas, 

which continued throughout and attained its culmination in the 

'Roubidoux, .having also prevailed in a less but increasing degree 

during Gasconade time.

KOUBIDOUX FORMATION.

This interesting formation is extremelv variable in its lithologic O ^ O

characters. It is, as described by Ball and Srnith,ffi who called it the

St. Elizabeth formation, " a complex consisting of beds of sandstone, 

chert, quartzite, dolomite, and shale, all of very uncertain thickness 

.and areal extent." Locally, as south of the Osage .River in Miller 

and adjoining counties, one of the sandstones is sufficiently persistent 

and well developed to warrant mapping it as a distinct member. In 

.Miller County this member has been distinguished under the name 

Bolin Creek sandstone.

The dolomites of this formation are prevailingly thin bedded, fine 

grained, dense, and hard. In texture and conchoidal fracture they 

simulate chert. Beds of " cotton rock," an argillaceous, compact, finegrained and comparatively soft dolomite, are not uncommon. This 

variety of rock is nearly always thinly bedded, of a light-yellowish or 

buff color, and generally exhibits dendritic markings on the bedding 

planes. , Thin layers of shale are often associated or interbedded with 

it. Although beds of coarse- or medium-grained dolomite are occasionally found in this formation, it will be noted that, on the whole, 

the dolomites are conspicuously different from those constituting the 

bulk of the Gasconade formation.

Chert is found in greater abundance in the calcareous portions of 

this formation than in any other of this great series of dolomitic limestones. It occurs in various forms, the brecciated, conglomeratic, 

and cellulose or " honej^combed " varieties being the most common. 

Certain varieties found in the underlying and overlying formations, 

particularly those containing drusj^ cavities, are notably absent.

Perhaps the most marked and widely distributed type occurs at or 

near the base of the formation. Because of its position it aids materially in locating the boundary between the Roubidoux and the 

Gasconade. This chert is of dense structure and brittle and ranges

0 Geology of Miller County : Missouri Bureau of Geology and Mines, 2d ser., vol. 1, 190o, 

p. 50.
32 COPPER DEPOSITS OF MISSOURI. [BOLL. 267.

in color from nearly white to dark gray or even black. It is always 

brecciated and splintered, and the angular fragments, having been 

subsequently recemented by quartz or limonite, now form large 

rugged masses and often thick beds. This bed has been observed in 

Miller, Camden, Shannon, Franklin, and Ste. Genevieve counties.

Another variety that is locally of service in recognizing the upper 

part of the formation is distinguished by its cellular character. 

Similarly honeycombed chert, however, has been observed in the 

Gasconade formation in Shannon County, so that it is not strictly 

characteristic of the Roubidoux. The conglomeratic variety, which 

is largely made up of small, rounded, and often lenticular pebbles of 

chert, and commonly with admixtures of quartz and oolite grains, 

likewise-occurs in the upper part of the underlying formation. This 

Avas found to be the case more especially in Shannon County.

The beds of sandstone found in this formation are its most variable 

part. Sometimes, particularly in the region west of Ste. Genevieve, 

where there are many such, the individual beds range in thickness 

from a few inches to over 30 feet. They vary greatly also in size of 

grain, color, and other features, but in these respects afford no means 

for distinguishing them from the occasional beds occurring'in the 

Gasconade formation. Nevertheless, they very commonly exhibit 

certain features, such as thin and distinct bedding, ripple-marked and 

sun-cracked surfaces, and occasionally fucoidal markings, that together reliably indicate this horizon. Another peculiarity that was 

noted in many places is the presence, often in great number, of lightcolored, flattened, apparently argillaceous pebbles, or of lenticular 

spaces resulting from their disintegration and removal.

Fossil remains are not uncommon in most of the cherts and in some 

of the sandstones of this formation. They are, however, but rarely 

in a good state of preservation, the most of them having been macerated before being covered by deposits, while all have suffered from 

subsequent changes in the rocks. The species consist mainly of gasteropods. In most cases they are closely related to, if not the same as, 

those found in a more favorable condition in the upper part of the 

underlying formation. A neat undescribed form of Helicotonia, characterized by revolving rows of small nodes on the upper and lower 

sides of the volutions, appears for the first time in this formation and 

may be confined to it.

There is in some places evidence of unconformity, and hence of an 

erosion interval, at the contact between this and the underlying Gasconade formation, but the fact is of less importance than usual. As 

stated on page 31, the shallowing of the seas with its attending phenomena had already begun in the preceding age, and merely attained 

its full and almost continuous expression in the Roubidoux. As the 

bottom of the sea could not have been perfectly flat, it- is obvious that.
DESCRIPTION OF FORMATIONS. 33

phenomena indicating periodic shoaling and local elevation above 

sea level must be correspondingly local in their extent. The Roubidoux stands for a condition rather than a time period, and as this 

condition must have been fully established in some localities a little 

earlier than it was in others, the lower boundary can not be everywhere drawn at precisely the same point. The case is similar with 

respect to the upper limits of the formation, except that here the 

phenomena took place in reverse order. Despite these facts, it is 

believed that the whole area under discussion was so nearty level 

through the greater part of Potosi time, and especially during this 

portion of it, that the Roubidoux may be defined and mapped so that 

it will represent an interval bounded both above and beneath as 

accurately as it is practicable to measure geologic time.

Considering the conditions under which this formation was deposited, it is to be expected that it Avould vary considerably in thickness 

from place to place. The minimum thickness, as reported by Ball 

and Smith (op. cit., p. 52), occurs near Iberia, Avhere it is said to 

be only 70 feet thick. In Miller County the thickness ranges from 

TO to 160 feet. However, the average thickness for this county, as 

well as for nearly the whole of the central part of the Ozark area, is 

between 100 and 125 feet. In -local basins along, the border of the 

area, as in the region between Ste. Genevieve and the Jonca granite 

hills, the thickness of the beds referred to the formation probably 

exceeds 225 feet.

Concerning the name of the formation, there seems to us to be no 

chance for reasonable doubt that Nason's Roubidoux, as based on his 

sections along the Osage and Current rivers, is essentially, if not 

exactly, the same as the St. Elizabeth formation of Ball and Smith. 

The only reason for doubting their equivalence is Nason's erroneous 

suggestion, subsequently adopted by Winslow, that the Roubidoux 

is represented in the counties along the Mississippi by the St. Peter 

(" Crystal City ") sandstone. Other synonyms are indicated in the 

table on page 12.

JEFFEBSON CITY LIMESTONE.

This formation consists principally of various kinds of dolomitic 

limestone. Interbedded with these are a few thin beds of sandstone, 

occurring chiefly in the lower part, thin beds of shale, and even 

thinner layers of chert. Nodules of concentrically banded, dense 

chert, most of them conforming with the doubtful organism known 

as Cryptozoon minnesotense. occur usually in considerable abundance 

in the residual clays. These nodules, which often contain drusy cavities lined with small quartz crystals, are characteristic of the forma-

. 267 05 M 3
34 COPPER DEPOSITS Otf MISSOURI. [HULL. 267.

/

tion. The.topography of areas in which the Jefferson City limestone 

outcrops is always less rugged than that of areas in which the two 

formations next beneath are exposed. Not uncommonly the undulations of the'surface are gentle enough in these"areas to justify classing 

them as prairie lands.

The majority of the Jefferson City limestones belong to two varieties, ^namely, " cotton rock " and medium-grained, massive dolomite. 

The cotton rock is an argillaceous, siliceous rock, usually containing 

over 40 per cent of magnesia. It is relatively soft, with a finegrained, earthy or clayey texture and conchoidal fracture. In color 

it varies from white or yellow to buff and gray. It is nearly always 

thinly bedded, with the bedding planes even and often exhibiting 

dendritic markings. Thin shaly partings are common. This variety 

of stone occurs locally and in limited quantity also in the Houbidoux 

formation, but the much greater development of cotton rock in the 

Jefferson City limestone affords probably the readiest of the criteria 

employed in distinguishing the two formations. The beds of cotton 

rock range in thickness from less than a foot to over 30 feet, and 

they may occur at any horizon in the formation.

On weathering, the surface of the massive dolomite assumes a 

peculiarly pitted or hackly surface that is sufficiently characteristic 

to be distinguished from that of the " pitted " dolomites found in 

lower members of the group.

Chert occurs less abundantly in the Jefferson City limestone than 

in the preceding formations of the Potosi group. Occasionally beds 

of brecciated chert occur in association with silicified oolites and 

sandstone, but these seem to be confined to the lower 100 feet. The 

Ste. Genevieve copper deposits occur in such a bed. The commonest 

and at the same time the most characteristic form of chert found in 

the formation is the " Cryirtozoon tninnesotense " variety already 

mentioned.

A number of generally very thin and irregularly distributed beds 

of sandstone, occurring chiefly in the lower 100 feet, are included in 

this formation. The thickness of the heaviest of these beds rarely 

exceeds 5 feet, the others ranging down to 1 inch. Often they contain 

enough calcareous matter to be called arenaceous limestones. Most 

of them are medium grained and friable, but here and there one may 

be found that has been silicified into a har.d quartzite. The color is 

usually a reddish brown, but yellow and white beds are not uncommon. Locally some of the heavier beds contain pebbles of chert and. 

dolomite. . ' ' 

The Jefferson City limestone is the surface rock over a large portion of the two marginal ranges of counties embraced in whole or in 

part within the Ozark area. Along the western and southwestern 

borders of the area and in most of the outliers in these parts of the
DESCRIPTION OF FORMATIONS. 35

State, the Jefferson City limestone is the youngest of the formations of 

the Ozark series remaining, the others having been removed prior to 

the deposition of the Devonian and Carboniferous rocks, which usually 

rest unconforinably on the older series'. . The St. Peter or First sandstone, and the Joachim or First Magnesian limestone, so far as our 

observation extends, are wanting in every case where either the Chattanooga shale or one of the basal members of the Boone formation is 

in contact with the Ozark series. The First sandstone has been seen 

only in sections containing some later representative of the Ordovician, while the Joachim outcrops only along the eastern border of the 

area, where the Plattin limestone of the Stones River group is present. 

Both the First sandstone and the First limestone of the series have 

been heretofore widely identified in the central and western, parts of 

the Ozark area, but the beds so correlated belong in every case examined to the Jefferson City limestone.

The upper beds being absent in the areas where the Jefferson City 

limestone is at the top of the series, the total original thickness of 

the formation in such localities can not now be determined. Where 

it is overlain by the St. Peter sandstone, as it is along the eastern and 

northeastern portions of the-border of the Ozark area, the maximum 

thickness of the formation probably exceeds 250 feet.

As has been said in the remarks on the Roubidoux formation, the 

conditions of shallow waters and frequent fluctuations of sea level 

that prevailed so constantly during the deposition of that variable 

series of beds gradually gave way to the gentle subsidence that obtained in this age. Shallows still prevailed in the earlier portion 

of the age, and it is in strata then laid down that a considerable and 

mostly characteristic fauna is to be found. In the middle and 

upper parts of the formation, however, fossils are either very rare 

or wanting entirely. This fact is believed to indicate that subsidence 

had progressed to such an extent that the shallow-water organisms 

of the time became "locally extinct.

At the close of the epoch the area was again elevated and, in places 

at least, sufficiently emerged to be subjected to erosion. The contact with the St. Peter sandstone in such localities is distinctly 

unconformable.

ST. PETER (" CRYSTAL CITY ") SANDSTONE.

This is the well-known true " Saccharoidal "sandstone. It outcrops in fine typical exposures at CiystalCity and Pacific, at Avhich 

places it is being worked for glass sand, and at numerous localities 

in. Ste. Genevieve, Perry, and Cape Girardeau counties. The formation has been so often and so well described that it is unnecessary 

to give any further description here. It may be worth while, however, to say that in the opinion of the writers the Crystal City, Pacific,
36 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

and Cap-au-Gres sandstones are unquestionably the same formation 

as the St. Peter sandstone of the upper Mississippi Valley.

Remarks concerning the distribution of this sandstone in Missouri 

will be found on page 19.

JOACHIM LIMESTONE.

This formation rests conformably on the St. Peter sandstone. The 

contact between the sandstone and the limestone seems, as a rule, 

not to be sharp, a certain amount of gradation occurring in all 

cases observed. Above these basal beds the formation usually consists of yellow and buff to .light-gray, thinly bedded magnesian 

limestone, alternating with beds of compact, brittle limestone. 

Locally thin beds of sandstone? rarely quartzose, are interbedded 

with the limestones. Fossils have not been observed, except in a 

single bed occurring about 60 or 70 feet above the base. This is 

sometimes filled with a species of Isochilina about one-fourth of an 

inch in length. Surfaces underlain by this "formation are commonly 

marked by large and deep sink holes.

In thickness the Joachim limestone varies greatly. This results 

from erosion to which the formation was subjected prior to the deposition of the succeeding Ordovician limestones. Except in the counties bordering on the Mississippi River it is absent entirely. Where 

it was not wholly removed the formation ranges in thickness from a 

few feet to the maximum of 150 feet reported by Shumard.

The unconformity at the top is often very conspicuous. It is well 

shown in a long and deep cut on the Illinois Southern Railroad, 

about 6 miles southwest of Ste. Genevieve. Here an abruptly defined 

solution channel, having a depth of about 12 feet, is filled with brown

and green shales, constituting the basal deposit of the overlying 

Plattin limestone.

THE ORE DEPOSITS. 

THE STE. GENEVIEVE MINES. .

History. The Ste. Genevieve copper deposits have been described 

by Frank L. Nicholson.0 According to him they were first noted 

in 1863, though the presence of copper in small amounts seems to 

have been recognized earlier at the Crow lead mines. Exploration 

began as early as 1868, the original discovery being followed by the 

opening in 1876 of the Chicago and Swansea mines and in 1879 of the 

Herzog. At the time of Nicholson's description the two last named 

were idle, while the originally discovered mine and the Chicago 

were being operated under the name of Cornwall mines. At present 

none of the properties are working.

a Nicholson, F. L., Review of the Ste. Genevieve copper deposits: Trans. Am. Iiisc. 

Min. Eng., vol. 10, 1882, pp. 444-456.
U. S. GEOLOGICAL SURVEY 

WORKINGS OF THE CORNWALL MINE, STE. GENEVIE
BDLRICHD ] THE STE- GENEVIEVE MINES. 37

1 There are no data available for a complete estimate of the production, but in the Tenth Census 0 these mines are credited with an 

output for the census year of 230,717 pounds, valued at $25,730. As 

they were operated more or less actively for nearly a quarter of a 

century their aggregate production presumably has been considerable.

Geology. The copper mines are situated aboiit 8 miles southwest 

of the town of Ste. Genevieve, in sections 15, 16, 21, and 22 of T. 37 

N., R. 8 W., along a small stream tributary to the Aux Vases River. 

The ore occurs principally at two horizons 125 feet apart, in the lower 

part of the Jefferson City limestone. The workings along the main 

horizon are shown in the photograph forming PI. I. The country 

rock is a coarse magnesian limestone with numerous flint nodules. 

These are ordinarily from 2 to 4 inches in diameter, and are arranged 

in horizontal bands along bedding planes. They are the clear white 

to blue flints, such as are common in the Mississippi Valley, and do 

not show the druses which characterize the flints of the Gasconade 

formation. Certain thin and irregular sandstones are interbedded 

with the limestone. A very hard, quartzose bed, about 2 feet thick, 

occurs 15 to 20 feet beneath the main ore body at the Cornwall mines.

Faulting of some magnitude occurs in the region, and there is 

some evidence of faulting near, but not at the mines. The beds are 

practically horizontal, though there is a slight dip toward the northeast. In the general region there are outcrops of underlying preCambrian crystalline rocks, though none of these are known at the 

mines. No other igneous rocks are found in the area. Topographically the region is a dissected plateau of some roughness.

Ore bodies. At the Cornwall mines the ore occurs, as stated, at 

two horizons, of which the upper has been mainly worked. A third 

horizon still higher in the hill and, so far as known, not economically 

important, is reported by Dr. E. D. Peters. Both horizons worked 

are above local water level. Workings in the lower bed are mainly 

closed and the upper only was especially investigated. The workings 

extend along the edge of a horizontal bedded breccia completely 

around the head of the small valley in which the furnace is located. 

Drifts have been run into the hill at intervals, and room-arid-pillar 

workings opened much like those of a coal mine. No map of the 

workings is available for reproduction; but there are a good many 

. hundred feet of drifts now open, and a number of excellent faces of 

ore may be seen.

The ore bed is from 18 inches to 3 feet thick in most parts of the 

mine. It seems to be thickest at the intersection of the breccia and 

certain small vertical fractures, along which chimneys of ore are 

formed, extending upward as much as 16 feet above the usual base.

a Tenth Census, vol. 15, p. 798.
38 COPPER DEPOSIT-S OF MISSOURI. [BULL. 207.

The ore also goes down at such intersections, but seemingly not to any 

important extent. It consists now of a breccia of Avhite flint, cemented 

mainly by chalcopyrite, but with malachite, azurite, limonite, and calcite present.^ Galena is reported to occur occasionally in small druses, 

but was not seen. Cuprite, chalcocite, tenorite, etc., occur in subordinate amounts. ' The cap rock and the floor of the workings consist of ordinary magnesian limestone.

An examination of the freshest specimens of the ore brings out 

the following details: The chalcopyrite, now very finely brecciated 

and in part cemented by " brown copper," is itself the matrix for 

fragments of white chert. This chert exists now- in two forms, (1) a 

clear, fresh, almost glassy material, similar to the usual chert of the 

surrounding country, and (2) an earthy granular material known 

to the miners as "chalk." A microscopic examination of the latter 

by Mr. Lin'dgren shows that it is composed mainly of finely divided 

quartz, with some sericite. This confirms the impression, based on 

macroscopic examination, that it represents an .alteration form of 

ordinary chert in which a portion of the silica has been removed by 

solution. Pari passu with this change has occurred the substitution 

of copper carbonate, and even in a single hand specimen all stages of 

the process can be observed, from the introduction of malachite along 

the cracks and the clouding of the clear chert to the complete substitution of the bright-green mineral for the sharp-angled white fragments. At the same time the brassy yellow chalcopyrite has been 

finely broken up and altered to the somewhat indefinite mixture 

known as " brown copper." It would seem, therefore, that the formation of malachite and other oxidation products marks a recent 

change, characterized by a tendency toward replacement of the silica. 

The introduction of the sulphides Avas evidently earlier and apparently the work of waters having other sources, since they were of 

such composition as to leave the chert unattacked even in small sharpangled fragments. Presumably these sulphides replaced the dolomite in which the chert was originally bedded or were deposited in 

the interstices of the breccia, but as to this and the origin of the chert 

itself there are at present no certain data.

In the lower horizon the Revere tunnel, now partly closed, shows 

copper pyrites disseminated through a bed of coarse granular dolomite. There does not seem to be here any chert breccia, though the 

ore appears to be bedded. So small a portion of the work is open, 

hoAvever, that no very certain conclusions can be drawn. The bed is 

said to be rich, but of small extent.

Value of the deposits. No attempt Avas made to sample the mine. 

Considerable ore is said to have been shipped,, running 20 to 27 per 

cent in copper, and the old dump is estimated to contain 5 per cent of 

metal. A 16 per cent grade is said to have been commonly produced.
MAIN AND*! TV/FT-VT-1 T t iv/rrvnrpT? QO uuticn. J MT.jN.Iii LA MO HE. ov

These claims, in the liglit of the appearance of the ore in the mine, 

do not seem extravagant. Faces of workable ore are certainly now 

open.

Drilling by Mr. Doak, a former owner, is reported to have shown 

three additional copper horizons at lower depths, and also to have 

shown something as to the extent of the ore body into the hill. The 

records of this drilling are not at hand. Dr. E. D. Peters states 

that 8 to 10 churn-drill holes put down under his direction several 

hundred feet apart and covering an area extending 1,800 feet eastward from the present workings all showed copper at the horizon of 

the main chert breccia. In the case of flat-lying, bedded deposits 

near the surface drilling is a very effective and cheap method of. 

proving the extent of an ore body. The method is especially well 

suited to these deposits.

At the time the mine was working no railway was near enough 

to be of service, and all. freight had to be hauled by wagon approximately 10 miles from the steamboat landing above Ste. Genevieve. 

Recently the Illinois Southern Railway has been built within 2-J 

miles of the mine. This line affords a direct and short route to the 

Illinois coal fields and materially affects the working conditions. 

It is quite probable that well-considered effort would result.in a small, 

but profitable, copper industry.

MINE LA MOTTE.

This famous property includes some of the oldest mines in the 

United States, and up to 1893 Mr. Winslow estimates that it had 

produced approximately $10,000,000 worth of lead alone. In addition, copper, nickel, and cobalt occur and have been sold in quantity. 

At present the old copper mines are being reopened and other changes 

made in the operation of the property. In 1904 approximately 55 

tons of metallic copper were produced in matte and ore. It is expected that in the future this product will be larger. . No extensive study of these mines was made in the course of the 

present investigation and no general account of the property will be 

given. The mines were visited, however, and the following notes are 

given for the sake of their bearing on the general problem of copper 

in this area. The history of the mines has been so completely summarized by-Mr. Winslow " that it is not necessary to discuss it.

The mines are located in Madison Countj^, east of the main St. 

Francis Mountains, and among some outlying knobs of granite and 

porphyry. The ore bodies are typical disseminated deposits originating by metasomatic replacement of the dolomite. They occur near 

the base of the Bonneterre limestone and principally in or near certain

"" Winslow, Arthur, Lead and zinc deposits: Missouri Geol. Survey, vol. G, 1804, pp. 

2G7-302 ; vol. 7, 1894, pp. G4G-G59.
40 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

shaly beds in which Lingidella and other forms occur! Copper 

pyrites with sulphides of nickel and cobalt are found constantly in 

connection with the lead and are mainly separated at the dressing 

works.

In the southwestern part of the estate is a property long known 

as the " Copper mine " and now being reopened by the Mine La Motte 

Development Company, a corporation holding a lease from the main 

La Motte company. The copper mine is located on the flank of a 

small porphyry hill and the ore occurs in the Bonneterre limestone 

near its base. The dolomite is dark colored, shaly. and includes 

small porphyry pebbles. The mine was originally opened some 

seventy-five years ago by means of an open pit, from the back of 

which an adit was driven in along the bed. The old drifts had not 

yet been cleaned up when visited and were badly caved. In the rooms 

opened along this adit the sulphides were seen disseminated through 

approximately 10 feet of the dolomite. Galena, pyrite, and chalcopyrite occur together, thoroughly disseminated through the rock. 

In one part of the mine the copper pyrite, with some dark mineral, 

probably chalcocite, was seen segregated in a distinct bed, 3 to 10 

inches thick, toward the base of the deposit as a whole, and yet above 

the most important bed of galena. This copper bed seems to have 

been the one mainly taken out when the mine was formerly worked. 

The galena below is largely undisturbed.

The strata throughout the mine roll slightly and irregularly, these 

rolls being very similar to those common in coa] mines, whereby 

separate irregular basins are marked out. In this case the irregularities very probably reflect the irregularities of the sea bottom 

upon which the beds were laid down.

The occurrence of copper in this mine as a sulphide is interesting 

because of its intimate relations to the great disseminated lead deposits of the region. . Any explanation of the genesis of the one 

must take into account the presence of the other, and no attempt will 

be made at present to discuss this large subject.

South of Fredericktown and at several other points in the vicinity 

copper is found.0 None of these prospects are now open. So far as is 

known the occurrences are similar to that at Mine La Motte.

SHANNON COUNTY MINES.

D

Location. In Shannon County there are showings of copper, and 

attempts have been made to mine at eight localities, which are indicated on the accompanying map (fig. 2). The largest amount of 

development work has been done at the Slater and so-called Jerktail 

properties. None of the prospects are now being developed. They 

are all within a few miles of Eminence, the county seat. Eminence

0 Keyes, C. R., Mine La Motte sheet: Missouri Geol. Survey, vol. 9, 1895, p. 79.
SAIN AND

ULRICHD ] SHANNON COUNTY MINES. 41

is connected by daily stage with Winona, on the Current River division of the .Frisco system.

FIG. 2. Sketch map showing occurrences of copper ih Shannon County.
42 COPPER DEPOSITS OF MISSOURI. [BULL, 207.

History. -The first attempt to regularly mine copper in Missouri 

seems to have been made in Shannon County some sixty-five years 

ago, when the Slater mine attracted attention. The following historical notes were compiled by J. H. Hahn, of Winbna, Mo., and by 

him placed at our disposal. They represent the best obtainable 

information regarding this interesting property.

In 1837, when Shannon County was practically a wilderness, 150 miles from 

a railroad, the French settlers at Ste. Genevieve, Mo., among whom were the 

Valles and Henry Janis, sent Joseph Slater, an experienced miner, to develop 

the copper deposits of Shannon County, which locality at that time was composed largely of unsurvcyed Government lands. Slater bought the possessory 

right of one George Smith, a hunter, who had discovered the copper; and, after 

erecting a small blast furnace of stone, he mined and smelted about $50,000 

worth of copper. :

In 1840 the lands of that locality were surveyed by the Government; whereupon a speculator by the name of. John Epps Cowan preempted the land, completely ousting Slater, but hot without a legal contest which was carried to the 

tribunal of last resort. Cowan sold the mine to other speculators in the East, 

who, thinking the property too remote from market to be successfully worked, 

closed it down.

The mine remained idle until the year 1876, when one Charles T. Biser, of St. 

Louis, having purchased many thousand acres of other lands in Shannon County, 

hunted up the owners of the mine and acquired the title to that tract. After 

mining and shipping a few carloads of copper, Biser sold all his holdings to the 

Current River Land and Cattle Company, a corporation composed of Michigan 

capitalists who take no interest in mining. " . For twenty-five years the Slater again lay idle, when attention was called to 

same by F. M. Rogers, a mining prospector from'Colorado. Mr. Rogers obtained 

.'!. 9|)-year lease on the mine, which is now owned by the Slater Copper Mine Company, a corporation of Winona, Mo.

When a land survey of this area was made, the occurrence of copper 

.was noted at a number of points and indicated upon the usual township plats. On the sectional map of the State, first published in 1865

by John T. Fiala, and revised and republished in 1881 by Campbell, 

the various copper localities are marked by symbols. - About a half 

dozen are indicated in Tps. 28 and 29, Us. 3 and 4 W. This map was 

compiled from all available data, and includes everything given on 

the Land Office map of 1811.

Bibliography. The literature relating to the field is very limited. 

Below is an abstract of the important papers:

[Hodge, .Tas. T., Wisconsin and Missouri lead region: Am. .Tour. Sci., 1st ser., vol. 43,

1842, pp. 05-72.] ; ,

Deposits found along contact of a red porphyry with a limestone. No regular 

contact. Fissures between the two rocks filled with iron ore, copper ore, clay, and 

gossan. Little veins of copper ore in limestone. Ores are malachite, cuprite (?), 

arid chalcopyrite. The " rotten vein " between the two rocks is a breccia of both 

with particles of malachite scattered through it. Ore is mined at three localities. 

'In one the ore is more sulphide than carbonate, and the latter is partly azuri'te.
'ruMCiTl SHANNON COUNTY MINES- 43 

I.Wliitney, .1. D., Metallic Wealth of the United States, 1854, |>. Jill. I

No mining worthy of name. Deposits on contact between Lower .Silurian 

limestone and Archean quartz-porphyry. Not likely to be profitable.

[Report of the Current River Mining Company, accompanying charter and by-laws of! the 

Current Iliver Mining Company, of Missouri, l>y Stephen Bavvden, mine agent, New 

York, 1854.] . . ...

The vein is of promising character, being composed of "gossan spar" and 

sulphuret of copper, green carbonates, and malachites. The lode is embedded 

in red granite or porphyry. The mine has a regular or true vein with a dip 

of 1* feet to the fathom, running northeast-southwest. There are probably other 

parallel veins.

[Broadhead, G. C., Rept. Missouri Geol. Survey, 1873-74, chap. 5, p. 48.-]

No copper mining now done. Mining formerly carried on in five counties. 

Copper ore noted in twelve others. Ores are a/uritc, malachite, .and clialcopyrite.

| Nason, F. L., Report on iron'ores: Missouri Geol. Survey, vol. 2, 1802, p. 05.]

Chalcopyrite mined to some extent near Eminence, in Shannon County. 

Exact locality not reported.

IWinslow, A., Geology and mineral products of Missouri: Missouri at the World's Fair

[at Chicago], 1808.]

i

The principal occurrences of such (copper) ore are in Ste. Genevieve, Shannon, and Franklin counties. Found in magnesian limestones of Cambrian age.

[Tiaworth, Erasmus, Crystalline rocks of Missouri: Missouri Geol. Survey, vol. 8, 1804,

p. 207.]

The porphyry in Shannon County is very similar to that northeast. Portions are the ordinary red kind. Other portions are filled with the light-gray, 

or light-green feldspar phenocrysts, which are common to the northeast.

Slater mine. The Slater mine is about 2 miles east of Eminence, 

at a point Avhere one of the common porphyry ridges of the district 

projects through the Gasconade or Cambro-Ordovician dolomites. 

The particular knoll, on the east versant of which the copper occurs, 

is one of a chain extending for several miles in a northwest-southeast 

course. The porphyry is the usual.red type so common in southeastern Missouri. It is of pre-Cambrian age. Separated from it by 

a marked unconformity are the gently dipping granular dolomites of 

the Gasconade formation. The cherty dolomites and sandstones of 

the Koubidoux formation occur in the higher hills surrounding the fj . C3

exposure.

The contact between the porphyry and the limestone is in an 

irregular plane, dipping at a low angle to the east. It is occupied 

by a well-developed conglomerate in which there are bowlders and 

pebbles of porphyry in a matrix of coarse crystalline dolomite. This 

conglomerate is not now exposed in its full thickness, but old workings are said to have shown a total of 12 feet. At the particular 

.point at which the copper is found the surface of the porphyry dips
44 COPPER DEPOSITS OF MISSOURI. [BULL. 267.

down, forming a shallow basin or cove, in which the conglomerate 

was laid down.

Copper in the form of chalcopyrite (CuFeS2 ) and the green carbonate, -malachite (CuOH2C03 ), occurs in the matrix of this conglomerate. The chalcopyrite forms small, irregular crystals and 

grains varying in diameter from 1 millimeter to a half inch. They 

occur with rhombohedral crystals of dolomite of nearly uniform 

size and grains of quartz in a paste of greenish clay. The carbonate 

is found in similar disseminated grains, apparently the altered remnants of chalcopyrite, and also in flecks and thin seams penetrating 

and replacing the porphyry fragments. At the surface, where the 

rock has been exposed, the cracks and crevices contain a black, sooty 

powder, apparently mainly manganese oxide, bearing copper probably 

in the form of the oxide or of chalcocite (Cu2S). An assay of this 

material in the Survey laboratory, by George Steiger, gave 6.44 per 

cent copper.

The largest amount of work done on the property has evidently 

Been in the stripping and mining of this conglomerate over some 3 

acres. To the east, where the rock dips under cover,' it has not been 

followed. Along the strike less prominent copper showings are said 

to occur at intervals for nearly 2 miles.

Copper also occurs in the porphyry, and several shafts have been 

sunk, following small veins into this rock. One of these shafts is 

reported to be 160 feet deep. This was filled with water at the time 

the property was examined. The rock on the dump showed thin 

seams in the porphyry, and in these small crystals of quartz, dolomite, and chalcopyrite occur. In no specimen seen was the amount 

of the latter sufficient to make the rock workable. In other pits not 

so deep similar crevices in the porphyry were seen filled with the

green carbonate. This occurred at one place as much as 4 inches 

thick and practically free from admixture with other minerals. All 

the crevices examined were small, an inch or two in width at most, 

and all have a general northwest-southeast course, parallel to the 

general trend of the porphyry hill. They are not larger, more numerous, or, except for their content of copper, more impressive than 

at many other points in the porphyry of the region. Several of the 

earlier observers,,have mentioned "true fissure veins" as occurring 

in the porphyry, but so far as observations of the present writers go 

these minor crevices are the only foundation for such statements.

The prospective value of the property is so intimately connected 

with the probable genesis of the ores that it is necessary to consider 

at least the possible character of the latter.

The chalcopyrite is not apparently present in quantities of economic importance; the question of the origin of the sulphides is 

therefore relatively unimportant. It is believed that they were
BULKICHD ] SHANNON COUNTY MINES. 45

derived from the porphyry by leaching either (1) of minutely disseminated quantities of copper, known to be present in the rock, or 

(2) of small veins locally present, of which the ores now exposed are 

representatives. This is believed to have occurred at the time the 

conglomerate was formed, though it is quite possible that the process 

continued in operation through later geologic ages.

The carbonates, oxides, and possible chalcocite present are alteration products from the sulphides, and the topographic and structural features of the deposits indicate clearly that this alteration has 

been accompanied by at least some concentration. The open, porous 

conglomerate affords abundant opportunity for the circulation of 

waters, while the decomposition of the lime-soda feldspars of the 

porphyry fragments would serve to precipitate as carbonate any 

copper sulphate present. It is notable that the decomposed porphyry pebbles and the carbonate are closely associated. In any such 

process the carbonates would be carried down, more or less,.and precipitated in the upper fissured part of the porphyry below, and this 

is believed to have been the origin of the carbonate found in that 

situation.

It follows from the above considerations that future prospecting 

should be directed toward finding extensions of the conglomerate and 

points of local enrichment rather than toward following the small 

veins into the underlying porphyry. The cove in which the deposits 

occur opens out to the east, in which direction also the rocks dip. A 

series of drill holes parallel to the outcropping edge of the conglomerate should determine the depth and extent of mineralization very 

cheaply.

Jerktail mine. This is one of the older and better-known prospects. 

It is said to have been worked about 1840 and again in 1870, and shipments have been made from the property. There has been some 

recent prospecting. There are several shallow shafts and one drift. 

The conditions are very similar to those at the Slater mine. The 

Gasconade limestone rests on the porphyry with gently sloping contact, and the usual conglomerate is present. In this conglomerate 

both chalcopyrite and malachite occur, and there has evidently been 

some reconcentration of material. There is the same pre-Cambrian 

erosion basin or cove, in this case fronting to the southwest rather 

than east, and the geologic and topographic features of the two localities are almost identical. One exception is that present exposures at 

least do not show small veins running down into the porphyry, as 

observed at the Slater mine. There are no sufficient data for estimating the probable size and value of the deposit.

Sutton mine. This property, 5 miles southeast of Eminence, resembles the Slater and Jerktail, in that copper carbonate is found in 

the base of the limestone at the contact with the underlying porphyry.
46 COPPER DEPOSITS OF MISSOURI. [HULL. 207.

There are no recent openings, and the details of the occurrence are 

not so well displayed as at the other mines mentioned, but the phenomena seem to be essentially the same.

Casey mine. About 2 miles north of Eminence, in a saddle between 

high flint-capped hills, copper has been found in the limestone and 

away from any immediate contact with porphyry. The horizon is 

in either the basal portion of the Roubidoux or near the top of the 

Gasconade limestone, and is thus considerably above that of the 

copper at the Slater mine. The country rock is a coarse, granular 

dolomite, in which is a bed of shale 4 to 12 inches in thickness. In 

this shale, and at points completely replacing it, is copper, mainly in 

the form of malachite, but also occurring as chalcocite. The bed has 

been followed into the hill by means of an adit some 50 feet. A few 

years ago the property came into the hands of certain Pittsburg people, who abandoned the drift and began sinking. It is said that they 

have discovered a second, but seemingly less extensive, copper horizon 

below the ore worked in the drift.

The rocks are horizontal, bedded limestones, with no signs of faulting or of vein phenomena. There are no outcrops of porphyry in the 

immediate vicinity. The origin of the copper is somewhat more 

difficult of explanation than at the Slater mine. It can only be said 

that copper-bearing solutions have evidently circulated somewhat 

extensively through the rocks of the region, and that the shale band 

has afforded a favorable horizon for its lodgment, either by direct 

reduction through the action of organic matter or by the mechanical process recently described as adsorption.

The extent of the deposits is unknown, owing to the way the prospecting has been carried on. They do not seem likely to be large.

Tyrell mine. At this property, which was visited by Mr. Ellis, the 

copper occurs in the form of chalcocite and malachite in a brecciated 

dolomite, resembling in hand specimens some of the material found at 

Ste. Genevieve. So far, however, flats have not been developed, all 

the ore mined having come from a small vertical seam running 

northAvest-southeast. This has been followed down 48 feet, and is 

said to have shown some copper the whole distance. The slope above 

the prospect is covered with chert and sandstone, probably betokening the presence of the Roubidoux, so that the horizon is probably 

about the same as at the Casey mine.

Bonanza prospect. Situated'about 6 miles east of Eminence, this 

is instanced as typical of a number of small prospects scattered 

throughout the county. Not far from a porphyry outcrop, but in 

the limestone hill above it, a few small pits have been sunk. Apparently they merely reached the solid rock. No copper minerals of any 

kind are now shown on the dumps. A green mineral in small flakes, 

probably chlorite, has apparently been mistaken for malachite.
J ULKICH."] THE OEE DEPOSITS. 47

In the porphyry at the foot of the hill are some thin streaks of 

white quartz, and at the contact of the porphyry and the limestone a 

black earthy material is found in small quantity. This not improbably contains some chalcocite, since it is said to show on assay 4 per 

cent of copper and 1 ounce of silver per ton.

Freeman prospect: This is very similar to the Bonanza. Copper 

carbonate and galena are said to have been found in small quantity 

in shallow pits in the limestone. At present nothing but ordinary 

limonite and residual clay are exposed.

General conclusions. From the descriptions already given of the 

individual prospects it will be evident that there is small probability 

of true vein deposits of value being found in the porphyry. The 

largest amounts of'copper are in the limestone, and of the two horizons recognized the lower is the more favorable. Along this, where 

the structural and topographic conditions have been favorable, copper occurs in the conglomerate. The -deposits are thus essentially 

blanket veins, and in view of their shallow dip they may be most 

easily prospected by drilling and test pitting. Such ore as occurs is 

of a nature to be easily reduced, and the samples seen are evidently of 

good grade. The size of the ore bodies can be determined only by 

additional prospecting.

THE SULLIVAN MINES.

History. On the northeast flank of the Ozark uplift, in Franklin, 

Crawford, Phelps, arid adjacent counties, copper minerals have been 

found at a number of points, and several attempts have been made 

to develop mines. Recently some prospecting has been carried on 

near St. James, Phelps County, and the Missouri Copper Mountain 

Mining Company has put in operation a 20-ton furnace near Sullivan, on the Frisco system. This corporation, composed largely of 

persons living at Sedalia, Mo., owns nearly 7,500 acres of land in 

Washington and Crawford counties. Pevelopment has been under 

way for nearly three years, an attempt having first been made to 

concentrate and ship the ores and later a furnace having been built 

and put in operation. The works are located in sec. 24, T. 40 N., 

R. 2 W., in Crawford County. They are at the old Sullivan and 

Bridell mine, where the Hamilton Iron Company, up to 1873, took 

out specular iron ore.

Geology. The area in which the copper has been found is that 

known in the older geologic reports as the region of the " Second 

sandstone." Nason used " Roubidoux sandstone" to designate the 

surface rock of the district, and applied Gasconade limestone a to 

the heavy limestone beds found in the lower portions of the valleys.,

0 Nason, P. L., Report on h-on ores: Missouri Geol. Survey, vol. 2, 1892, p. 114.
48 . COPPER DEPOSITS OF MISSOURI. [BULL. 267.

The ore is found in residual clays, filling pits in the Gasconade limestone and near the outcropping edge of the overlying Eoubidoux.

The copper occurs in connection with or near to the specular ironore deposits which characterize the district. These iron deposits 

have been described .by Nason,a who considered them to represent 

concentrations made by surface waters in sink holes. He noted 

the common association with the hematite of sulphides of iron, copper, lead, zinc, and arsenic, and the fact that these sulphides occur 

most abundantly at the bottom of the deposits. Indeed, he considered 

the iron to have been originally concentrated as a sulphide, and to 

have been later altered to hematite. This theory of the origin of the 

ores would make them strikingly analogous to the iron cappings, 

or gossan, over mixed sulphide ore bodies, such as occur in the Western 

States.

In 1904 a number of the old iron pits of this area Avere reexamined 

and Nason's observations were confirmed. It was found very commonly that sulphides and carbonates of copper, in particular, occur 

in intimate mixture with the hemati'te at the bottom of the now 

abandoned pits. How important in amount this ore may be was not 

determined, but its widespread occurrence was very evident and its 

position is believed to be significant.

Ore bodies. The copper mined at Sullivan is obtained from shallow workings on the side of a hill, near the top of which iron was 

formerly mined. The old iron pits are now partially filled by surface 

wash. The ore body was evidently of the usual.irregular form, and 

the ore now remaining in the bottom of the pit and in the short 

drifts running back into the hill is low grade and siliceous. The 

dump shows the usual red hematite and ocher. Copper is reported 

to have been found in the lowest part of the old workings, but none

is now exposed.

Lower on the slope are the shafts recently sunk in search of copper. 

The dumps around these shafts show red hematite, broken and 

brecciated, and with thin flakes and seams of copper carbonate running through it. The surface is mainly covered with red cla,y and 

chert fragments, though limestone and sandstone are also present. 

On the dumps are pieces of a dark-colored limestone which shows 

veins of calcite one-sixteenth to one-eighth inch thick, with similar 

but still thinner veins of pyrite, which also occurs in very fine-grained, 

irregular particles through the rock. Portions of the limestone have 

been altered to a brown, vitreous, porous rock, greatly resembling 

garnet-in appearance. Under the microscope it is seen to be now 

composed almost wholly of crystalline quartz with occasional small 

aggregates of malachite. Running through the quartz, without re-

? Nason, F. L., Report on iron ores: Missouri Geol. Survey, vol. 2, 1892, pp. 116-157.
BOLRICHD ] TIiE SULLIVAN MINES. 49

gard to the crystal boundaries, are irregular convoluted bands of 

brown iron oxide. Apparently these outline the grains of 'the original limestone, now wholly replaced by silica.

The main workings are below these shafts, the entrance being by 

adit connected with one of them. The adit is cut through a bar of 

limestone, beyond' which is a body of soft red clay, in which the 

copper occurs. Both chalcopyrite and the usual alteration products 

occur, irregularly distributed through the clay. Balls of the chaleopyrite a half foot or more in diameter and coated with malachite 

and chalcocite are found. Not enough work has yet been done to 

develop the form of the ore body, but it is known to be somewhat 

irregular. Both lead and zinc ores occur on the same land, though 

neither were seen in the copper workings.

It would seem that the copper occurs in a residual clay occupying 

an irregular pit in the limestone of the hillside. It is above water 

level and below the main body of iron ore. It was originally in 

the form of a sulphide, and the present ore has resulted in part from 

concentration in situ by residual action. Probably also copper has 

been leached out of the higher portion of the hill, the iron being left 

behind as a gossan. Accompanying this action there has been at 

least local silicification of the limestone. The original introduction 

of the sulphides was by waters Avhich were of different composition, 

since for a long time the waters of the region have been destroying 

rather than building up the sulphides. The nature and. source of 

these waters are for the present uncertain. So far as known, the 

original sulphides are not sufficiently rich to be worked alone for 

copper, and only the pockets found in the coves of residual recoiicentration warrant prospecting.

Value of the deposits. No general sampling of the mine was 

attempted. An average sample of the face of one drift, as nearly 

as it could be taken, was found, on assay in the Survey laboratory by 

George Steiger, to carry 12.55 per cent of copper. It is impossible to say what the average of the whole ore body would run. It 

is estimated by H. H. Graham, manager of the property, that the 

ore going to the furnace runs 5 to 8 per cent. From, a twenty-day run 

in 1904 30,000 pounds of pig copper and matte resulted. This is 

equivalent to 22,500 pounds of metallic copper. . According, to the 

records of W. H. H. Myers, secretary of the company, the ore used 

in the furnace during this run averaged .14 per cent. The ore is 

practically self-fluxing and easily and cheaply handled. So long 

as no greater difficulties than those now apparent arise, it should be 

possible to work this ore profitably. In view, however, of the very 

great irregularities in form and richness characteristic of residual 

ores, it is impossible to make any valid estimates for the future.

Bull. 267 05 M 1
50 COPPEE DEPOSITS OF MISSOURI. [BULL. 267.

GENERAL SUMMARY AND CONCLUSIONS.

Copper in the form of sulphides and carbonates has been found at 

many points in southern Missouri and has been mined in several 

localities, notably in'Ste. Genevieve, Madison, Shannon, and Crawford counties. Very large deposits, rivaling those of the West, have 

not been found and are not to be expected. The character of the ore 

and the low cost of flux, fuel, and labor make it possible to work some, 

at least, of the deposits with profit.

The ores show a preference for certain stratigraphic horizons, 

and, being bedded, may be prospected with ease and economy. The 

common association of sulphides with specular iron of the sandstone 

region points to the advisability of the investigation of the old iron 

pits. While any copper deposits found will probably not be large, 

they should be easily and cjieaply mined. In Shannon County the 

most favorable localities are along the contact of porphyry and dolomite at points'where the conglomerate beds at the base of the latter 

fill in shallow basins in the crystalline rocks. In the disseminated 

lead district of southeastern Missouri copper occurs in connection 

with the lead, and at a few points can be saved to advantage.

The ores were doubtless formed by concentration of material 

originally disseminated in the surrounding rocks. Winslow andRobertson ° some time since proved that both the crystalline rocks 

and the dolomites of this region contain copper in minute but sufficient amounts. The preference of the ore bodies for certain horizons 

is believed to be dependent mainly upon original unequal distribution 

of material resulting from land and sea conditions at the time the 

rocks were laid down. Excepting the Mine La Motte deposits, all 

the important copper deposits of Missouri are found in that part of 

the Potosi rocks which was laid down in shallow waters and when

frequent changes of shore line Avere evidently occurring. The Ste. 

Genevieve deposit occurs in brecciated horizontal chert in the lower 

part of the Jefferson City limestone; the Sullivan deposit has been 

segregated from beds near, probably just beneath, the Roubidoux 

sandstone; and in the Casey mine the ore is found in the Roubidoux. 

The Slater, Jerktail, and Sutton mines, in Shannon County, occur 

along the contact between old porphyry islands and the dolomites 

of the Gasconade formation. The Mine La Motte ores occur where 

the similar Bonneterre limestone laps upon similar porphyry hills. 

Everywhere the distribution of the copper seems related to original 

shallow-water conditions. At some later period in the course of the 

work of underground waters this originally disseminated copper was 

segregated in the bodies now found.

0 Winslow, Arthur, and Robertson, J. D., Lead and zinc deposits : Missouri Geol, Sur-. 

yey, vol. 7, 1894, pp. 479-480,
INDEX.

Page. 

Acadian rocks, occurrence .and character

of............................... 12

Adams, G. I., on Missouri geology.......... 15

Archean rocks, occurrence of............... 12

Bain, H. Foster, work of ................... 9

Ball, S. H., and Smith, A. F., on Missouri

rocks.......................... 12,17

on Koubidoux formation............... 31,33

Barite, occurrence of........................ 10

Billingsella sp., occurrence of.............. 22

Biser, C. T., copper shipped by............. 9,42

Bolin Creek sandstone member, correlation

of............................... 12,31

Bonanza prospect,description of.....'......46-47

Bonneterre.limestone, copper in ........ 39-40,50

occurrence and character of..... 12,17,21-23

section of............................... 25

Broadhead, G. C., on Ozark series.......... 13

Cambrian rocks, occurrence and character

.. of............................... 12

Camden.County, graphic granite in..:..... 11

Camp Cole sandstone. See Gasconade lime- -,

stone.

Cap-au-Gres sandstone. See St. Peter sandstone. 

Casey mine, .description of................. 46,50

Chicago mine, opening of.................. 36

Cobalt, occurrence of ........... . .. 9,39

Copper deposits, character of............... 50

descriptions of.....i............"........ 36-49

distribution of.......................... 10-11'

location of, maps showing.............. 11,41

mining of, history of ................... 9-10

origin of................................ 50

production of ore from ................. 10,39

value of.......................... 38-39,49-50

Cornwall mine, account of................. 36-39

workings of, plate showing ............ 36

Cowan, J.E.,sale by ......................i. 42

Crawford County, copper in................ 47,50

smelting in............................. 9

Cryptozoonminnesotensis.occurrenceof. 30,33-34 

Crystal City sandstone. See St. Peter sandstone. 

Decaturville limestone. See Bonneterre

limestone. 

Doak, , drilling by...................... 39

Ellis.E.E., work of......................... 9

El vins, sections near ....................... 24-25

Elvins formation, occurrence and character

of......................... 12,17,23-26

section of .............................. 24-25

Eminence, copper near............ 40-41,43,45-46

Fiala, J. T., map published by ............. 42

Finley limestone. See Jefferson City limestone. 

First Magnesian limestone. See Joachuim

 ' limestone.

First sandstone. See St. Peter standstone. 

Folley limestone. See Joachuim limestone. 

Fossils, evidence from ..................... 20

.occurrenceof.................. 22,28,30,32,36

Fourth Magnesian limestone. See Gasconade limestone; Bonneterre limestone. 

Franklin County, copper in................ 47

Fredericktown, copper near................ 40

Freeman prospect, description of.......... 47

Gasconade limestone, copper in............ 46,50

occurrence and character of........... 12,

14-18,28-31,43,47-48 

stratigraphic limits of.................. 28

Geology of Ozark uplift.................... 13-36

Graham, H. H., estimate by................ 49

Gunter sandstone. See Gasconade limestone.

Hahn, J. H., on Shannon County mines ... 42 

Hayes, C. W., letter of transmittal by...... 7

Helicotoma sp., occurrence of.............. 32

Herzogmine,.opening of..\ .............. 36

Iron, occurrence of......................... 10,48

Iron Mountain conglomerate. See Pilot

Knob conglomerate. 

Isochilina, occurrence of................... 36

Jefferson City limestone, copper in......... 37,50

occurrence and character of.. 12,14-16,33-35 

Jerktail mine, description of............... 45,50

Joachuim limestone, occurrence and character of...................... 12,16,36

Joplin district, copper in........"........... 11

Key sandstone. See St. Peter sandstone. 

Keyes, C. R., on Missouri rocks ......... 12,16-17

La Motte sandstone, occurrence and character of................ 12,16-17,20-21

Ladd, G. E., on copper production ......... 10

Lead, occurrence of........................ 10

production of .......................... 39

Lesueur limestone. . See Gasconade limestone. 

Lindgren, Waldemar, on Ste. Gene vie vc

ores............................. 38

Lingulella, occurrence of................... 40

Lingulepis lambornei, occurrence of....... 22

Madison County, minesof..................x39,50

Magnesian series, formations of, classification of, attempts at............. 13-2C

51
52 INDEX.

Page.

Magnesian series, formations of, classification of, table showing.......... 12

Manganese, occurrence of.................. 10

Map showing locations of copper deposits.

in Missouri..................... 11

Map showing locations of copper deposits

in Shannon County ............ 41

Marshfleld limestone. See Jefferson City 

limestone; Roubidoux formation. 

Mine La Motte, copper from ............. 9-10,50 

description of.......................... 39-40

production of .......................... 39

Mine La .Motte Development Co., work of.. 40 

Missouri Copper Mountain Mining Co.,

smelter of .................... 9-10,47

Moreau sandstone. See Roubidoux formation. 

Myers, W.' H. H., information from ........ 49

Nason, Frank L., Gasconade limestone

named by ...................... 28

on Magnesian series.............. 12,14-15,17

NicholsOn, F. L., on' Ste. Genevicvc mines.. 36 

Nickel, occurrence of...................... 9,39

Ordovician rocks, occurrence and character of......J:..........'.........' 12

Ore deposits, occurrence and character of. 36-50 

Osage limestone. See Gasconade limestone. 

Ozark series. See Magnesian series. 

Ozark uplift, copper in, occurrence of...... 10

geology of.............................. 10-36

location of..................'............ 10

Ozarkia, location of........................ 14

Pacific sandstone. See St. Peter sandstone. 

Peters, E. D., copper deposits reported by.. 37-38 

Phelps County, copper in................... 47

Pilot Knob conglomerate, occurrence and

character of.................... 21

Potosi group, copper in .................... 50

deposition of ........................... 27-28

divisions of.............................. 12,27

occurrence and character of............ 12,

16,19-20,25-35 

Potosi limestone, etc. See Elvins formation.

Proctor limestone. See Gasconade limestone.

Rogers, F. M., Slater mir e leased by....... 42

Roubidoux formation, copper in........:.. 46,50

occurrence and character of........... 12,

14,16,18,31-33,43,47-48

Saccharoidal sandstone. See St. Peter sandstone..

St. Elizabeth formation. See Roubidoux 

formation.

Page. 

St. Francis Mountains, location of.......... 10 .

rocks of.............................. 10-11,21

St. James, copper near ..................\.. 47

St. Peter sandstone, occurence and character of.................. 12,14-18,35-36

Ste. Genevieve, copper mines near......... 37

Ste. Genevieve County, copper in .......... 9,50

copper in, production of................ 10

Ste. Genevieve mines, description of..... 36-39,50

value of................................. 38-39

workings of, plate showing............. 36

Saratogan rocks, occurrence and character

of............................... 12

Second Magnesian limestone. See Jefferson

City limestone. 

Second sandstone. See Roubidoux forma- .

tion; La Motte sandstone. 

Shannon County, copper in, deposits of.... 40-43

copper in, deposits of, character of...... 42^13

deposits of, map showing........... 41

mines of, account of................. 40-47,50

smelting in.......................'...... 9

Shepard, E. M., on Missouri rocks.......... 11-12

Shumard, B. F., on copper.................. 9

Slater, Joseph, copper mining by........... 9,42

Slater mine, description of.............. 43-45,50

location of............................... 42

production of........................... 10,42

Smith, A'. F., and Ball, S. H., on Missouri

rocks ........................... 12,17

Smith, George, copper discovered by....... 42

Steiger, George, assay by................... 49

Sullivan, Mo., copper at.'................... 9-10

copper at, shipments of................. 10

smelter at.............................. 47

Sullivan mines, description of ............. 47-50

location of.............................. 47

Sutton mine, description of.............. 45-46,50

Swallow, G. C., on magnesian series........ 13-14

Swansea mine,opening of... 1.............. 36

Third Magnesian limestone. See Gasconade limestone.

Third sandstone. See Gasconade limestone. 

Tyrrell mine, description of................ 46

Williams, G. K., on copper production..... 10

Winfield limestone. See Jefferson City

' limestone.

Winslow, Arthur, on La Motte sandstone .. 22,39 

on Missouri rocks.................... 12,15-16

on Potosi group ........................ 26

Ulrich, E. 0., work of ...................... 9

Yellville group, occurrence and character

of......... ..................... 12

Zinc, occurrence of......................... 10

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