B. S. Butler and W. S. Burbank 

The Copper Deposits of Michigan

U S Geological Survey Professional Paper 144 (1929)

 

CONTENTS

Outline of report-------------------------------------------------------- XI
Geology------------------------------------------------------------ XI
General features------------------------------------------- XI
Lava tops or amygdaloids ----------------------------- XI
Oxidation of lavas ---------------------------------------- XI
Copper in trap---------------------------------------------- XI
Structure----------------------------------------------------- XI
Ore deposits------------------------------------------------------ XII
Conglomerate lodes ------------------------------------- XII
Amygdaloid lodes---------------------------------------- XII
Ore shoots-------------------------------------------------- XII
Mineralized fissures-------------------------------------- XII
Changes with depth ------------------------------------- XII
Genesis of the deposits --------------------------------- XII
Part 1. General features--------------------------------------------------- 1
Field work and authorship -------------------------------- 1
Scope of report----------------------------------------------- 1
Acknowledgments ------------------------------------------ 2
Previous investigation ------------------------------------- 2
Bibliography -------------------------------------------------- 3
Location------------------------------------------------------ 14
Topography------------------------------------------------- 14
Climate-------------------------------------------------------- 14
Industries---------------------------------------------------- 15
Transportation --------------------------------------------- 15
Power---------------------------------------------------------- 15
Physiography ----------------------------------------------------- 16
Bedrock geology-------------------------------------------------- 16
Broader relations ------------------------------------------- 16
Location and extent --------------------------------- 16
Character of the rocks ------------------------------ 16
Maps and sections ---------------------------------- 17
Age and relations ------------------------------------ 17
General character and distribution --------------- 17
Sediments ---------------------------------------------- 18
Distribution ------------------------------------- 18
General character ------------------------------ 18
Conglomerate ----------------------------------- 18
Felsite conglomerate -------------------- 18
Extent and thickness of beds--- 18
Vertical distribution--------------- 18
Character of material ------------- 18
Character of beds- ---------------- 19
Character of underlying bed---- 19
Source of material ----------------- 19
Manner of deposition------------- 20
Amygdaloidal conglomerate ---------- 20
Relation to felsite conglom-
erate ---------------------------------- 20
Origin -------------------------------- 20
Sandstone and shale--------------------------- 21
Ash and tuff-------------------------------------- 21
Part 1. General features-Continued.                                             Page
Bedrock geology-Continued.
Stratigraphy-Continued.
Igneous rocks -------------------------------------------- 21
Extrusive rocks ------------------------------------ 21
Distribution ---------------------------------- 21
Extent of beds ------------------------------- 21
Thickness ------------------------------------ 21
Composition of flows --------------------- 23
Textural types ------------------------------- 23
Ophite----------------------------------- 24
Porphyrites ---------------------------- 24
Glomeroporphyrites ----------------- 24
Melaphyre ----------------------------- 24
Dolerite --------------------------------- 24
Relation of texture to composition ----- 24
Distribution of the different
     rocks --------------------------------------- 24
Character of eruptive rocks -------------- 25
Location of volcanic vents--------------- 26
Amygdaloids -------------------------------------- 26
Trap -------------------------------------------- 26
Bottom amygdaloid layer------------------ 27
The lava tops -------------------------------- 27
Varieties ------------------------------- 27
Smooth tops-------------------------- 28
Fragmental or brecciated
      tops-------------------------------- 29
Character ---------------------- 29
Origin --------------------------- 31
Scoriaceous tops ------------------- 33
Alteration ------------------------------------------ 34
Alteration of traps ------------------------- 34
Alteration of the lava tops -------------- 34
Red color of amygdaloid tops----------- 34
Statement of the problem---------- 34
Red tops of unaltered western
    flows--------------------------------- 35
Oxidation in smooth-top flows of
     Keweenawan series-------------------- 35
Oxidation and concentration in
    brecciated-top flows ------------------- 36
Mineralogic features ---------------------- 37
Cause of iron oxidation and con-
    centration -------------------------------- 38
Modern weathering----------------- 38
Independent solutions------------- 38
Surface weathering immediately
after extrusion------------------------ 39
Hydrothermal alteration------------ 41
Atmospheric oxidation of hot
tops ------------------------------------- 42
Magmatic processes---------------- 42
Magmatic segregation------- 42
Fumarolic alteration----------- 42
Action of gases from the
flows------------------------------ 43

III

Part 1. General features-Continued.                                           Page
Bedrock geology-Continued.
Stratigraphy-Continued.
Igneous rocks-Continued.
Copper content of the basalts --------------- 45
Intrusive rocks----------------------------------- 46
General features -------------------------- 46
Quartz porphyry and felsite ----------- 47
Basic dikes --------------------------------- 47
Age of intrusive rocks------------------- 47
Folds------------------------------------------------------ 48
Faults----------------------------------------------------- 48
Age and cause of folding and faulting---------- 50
Rock-forming period --------------------------------- 53
Ore-forming period ----------------------------------- 53
Period of weathering --------------------------------- 55
Minerals of the Keweenawan copper
     bearing rocks --------------------------------------- 55
Native metals ------------------------------------ 55
Sulphides ----------------------------------------- 55
Arsenides ---------------------------------------- 56
Haloids -------------------------------------------- 58
Oxides---------------------------------------------- 58
Carbonates --------------------------------------- 59
Silicates-------------------------------------------- 59
Phosphates --------------------------------------- 62
Sulphates ----------------------------------------- 62
Molybdates and tungstates ------------------ 62
Hvdrocarbon ------------------------------------- 62
Part 2. Ore deposits-------------------------------------------------------- 63
Mining ---------------------------------------------------------- 98
Development ------------------------------------------- 98
Stoping -------------------------------------------------- 99
Open stope -------------------------------------- 99
Room and pillar --------------------------------- 99
Shrinkage stope --------------------------------- 99
Horizontal cut and fill -------------------------- 99
Transportation ---------------------------------------- 100
Underground conditions---------------------------- 100
Milling---------------------------------------------------------- 100
Smelting-------------------------------------------------------- 101
Principal types------------------------------------------------ 101
Distribution in the Keweenawan series ---------------- 101
Conglomerate lodes ----------------------------------------- 101
Physical character ------------------------------------ 101
Iron content-------------------------------------------- 102
Mineralization ----------------------------------------- 103
Mineralogy -------------------------------------- 103
Rock alteration---------------------------------- 103
Distribution of copper in the lode---------------- 103
General controls ------------------------------- 103
Richness in relation to depth--------------- 104
Sandstone and shale lodes ------------------------------- 105
General relations ------------------------------------- 105
Mineralization and rock alteration---------------- 105
Types of amygdaloid ------------------------------- 106
Brecciated amygdaloid lodes---------------------- 106
Physical character ----------------------------- 106
Iron content------------------------------------- 107
Mineralization ---------------------------------- 107
Mineralogy------------------------------- 107
Rock alteration-------------------------- 107
Part 2. Ore deposits-Continued.                                                 Page
Copper deposits-Continued.
Amygdaloid lodes-Continued.
Cellular amygdaloid lodes--------------------------- 108
Scoriaceous amygdaloid lodes -------------------- 109
Distribution of copper in amygdaloid
          lodes---------------------------------------------- 109
Distribution of shoots in the lodes-------- 109
Distribution of copper in the shoots------ 109
Richness in relation to depth----------------------------- 110
Fissure deposits--------------------------------------------- 110
General features -------------------------------------- 110
Distribution of copper in veins ------------------- 111
No evidence that the lodes are poor at the
       surface and richer below------------------------------ 112
Kearsarge lode ---------------------------------------- 112
Osceola lode ------------------------------------------- 112
Calumet & Hecla conglomerate ------------------- 112
Pewabic amygdaloid lodes ------------------------- 113
Atlantic lode ------------------------------------------- 113
Isle Royale lode --------------------------------------- 113
Baltic lode----------------------------------------------- 113
Evergreen and succeeding lodes ----------------- 113
Nonesuch lode----------------------------------------- 113
Veins------------------------------------------------------ 113
No evidence of leaching and removal of copper
       near the surface------------------------------------------ 113
No evidence of enrichment at the salt-water
       horizon----------------------------------------------------- 114
Summary and conclusions --------------------------------- 114
Persistence with depth-------------------------------------- 114
Conditions determining position of ore shoots ------------ 115
Permeability of rock------------------------------------------ 115
Barriers of relatively impermeable rock ----------------- 115
Fault barrier---------------------------------------------------- 116
Folds------------------------------------------------------------- 117
Strike fissures-------------------------------------------------- 117
Cross fissures------------------------------------------------- 117
Influence of thick flows ------------------------------------ 118
Chemical composition -------------------------------------- 118
Genesis of the deposits------------------------------------------- 118
Similar origin of all types ---------------------------------- 118
Features common to all types ---------------------------- 119
Single period of mineralization --------------------------- 119
Hypotheses of origin---------------------------------------- 120
Deposition by descending solutions ------------ 120
Source of copper-------------------------------- 120
Mode of transportation------------------------ 121
Cause of precipitation ------------------------- 122
Chloride water conception ------------ 122
Mine waters-------------------------------- 122
Deposition by ascending solutions -------------- 124
Source of the copper---------------------------------- 124
Direction of movement of the solutions---------- 125
Means of access of the solutions ----------------- 125
Ascent from contacts of the
        Duluth gabbro ----------------------------- 125
Ascent from the Keweenaw fault------------ 126
Gradual accumulation in permeable 
                  channelways ------------------------------------- 127
Causes and conditions of precipitation ---------- 127
Precipitation by reducing action
      of ferrous iron ------------------------------- 127
Precipitation in consequence of
       saturation------------------------------------ 129
Precipitation by oxidation -------------------- 129
Presence of sulphides------------------- 130

IV

Part 2. Ore deposits-Continued.                                               Page
Genesis of the deposits-Continued.
Hypotheses of origin-Continued.
Deposition by ascending solutions-Con.
Causes and conditions of precipitation-Continued.
Precipitation by oxidation-Con.
Presence of an oxidizing
agent------------------------------ 131
Destruction of oxidizing
agent-bleaching --------------- 133
Presence of sulphates-------- 136
Chemistry of the deposition of native copper
from ascending solutions, by R. C. Wells---------- 137
Deposition by cooling --------------------------- 137
Deposition by relief of pressure- -------------- 138
Deposition by fractional oxidation of 
     copper sulphide--------------------------------- 138
Deposition by dilution --------------------------- 139
Deposition by reduction of acidity ----------- 139
Conclusions ---------------------------------------- 141
Source of copper----------------------------------- 141
Transportation ------------------------------------- 141
Cause of deposition------------------------------- 142
Other related deposits ---------------------------------- 142
Coro Coro, Bolivia--------------------------------- 142
Triassic of New Jersey --------------------------- 142
Triassic of Connecticut -------------------------- 143
Cape d'Or, Nova Scotia--------------------------- 143
Oberstein, Germany ------------------------------ 143
Commander Island, Russia --------------------- 143
Faroe Islands--------------------------------------- 143
Sao Paulo, Brazil----------------------------------- 143
Upper Serbia---------------------------------------- 143
White River, Alaska------------------------------- 143
Copper River district, Alaska- ------------------ 144
Nova Zembla, Russia----------------------------- 144
Zwickau, Saxony ---------------------------------- 144
Algodones, Chile---------------------------------- 144
Comobabi, Mountains, Arizona- -------------- 144
Permian "Red Beds" of the Southwest------- 144
Montana---------------------------------------------- 145
Arctic Canada -------------------------------------- 145
Likelihood of finding new ore bodies---------------- 146
Conditions of exploration ------------------------------ 146
Drift covering---------------------------------------- 146
Distribution of deposits- ------------------------- 146
Grade of ore------------------------------------------ 146
Size of deposit and grade of ore---------------- 147
Size and grade necessary for success-------- 147
Exploration of lodes-------------------------------------- 148
Character of amygdaloid lodes----------------- 148
Conglomerates ------------------------------------- 149
Mineralogy as a guide in exploration and
      development ----------------------------------- 149
Mineralogic guides in amygdaloids---- 149
Mineralogic guides in conglomerates-- 150
Mineralogic guides in fissures ---------- 150
Ore shoots-------------------------------------------------- 150
Extent of lodes -------------------------------------- 150
Barriers------------------------------------------------ 150
Barriers in the lode itself ------------------- 150
Folds--------------------------------------------- 150
Part 2. Ore deposits-Continued.                                                  Page
Application of geology to mining-Continued.
Ore shoots-Continued.
Barriers-Continued. 
Faults-------------------------------------------- 150
Fissure deposits------------------------------------- 151
Geologic distribution ------------------------------ 151
Geographic distribution- -------------------------- 151
Relation to present surface ----------------------- 151
Exploration -------------------------------------------------- 151
Stages-------------------------------------------------- 151
Geologic reconnaissance ------------------ 151
Location of favorable lodes----------------151
Search for ore shoots ----------------------- 151
Development of prospects- --------------- 151
Extension of ore shoots--------------------- 151
Methods of exploration --------------------------- 152
Examination of surface---------------------- 152
Trenches and pits---------------------------- 152
Diamond drilling ----------------------------- 152
Churn drilling --------------------------------- 153
Underground opening --------------------- 153
Other methods-------------------------------- 153
Application of methods -------------------------- 153
Surface examination-------------------------- 153
Trenching -------------------------------------- 153
Diamond drilling ------------------------------ 153
Underground exploration ------------------- 154
Depth ------------------------------------- 154
Horizontal versus vertical 
     exploration --------------------------- 154
Transverse versus longitudinal
exploration ------------------------------- 155
Prospecting fissures -------------------155
Equipment for prospecting ---------- 155
Suggestions for future geologic work in the Copper
         Range---------------------------------------------------------- 155
Geophysical methods applied to exploration and geo-
logic mapping, by T. M. Broderick and C. D. Hohl-------- 156
Introduction -------------------------------------------------- 156
Use of geophysical methods----------------------- 156
Principles of geophysical methods --------------- 156
The three fundamentally different applica-
      tions of geophysics ------------------------------ 156
Direct application of geophysics to copper 
     finding-------------------------------------------------------- 157
Existing conditions ------------------------------------ 157
Electrical methods-------------------------------------- 158
Direct conductivity and resistance
methods-------------------------------------------- 158
Spontaneous polarization --------------------- 158
Equipotential lines ------------------------------ 158
Inductive methods ------------------------------ 158
Conclusions -------------------------------------- 159
Indirect application of geophysics to copper
finding----------------------------------------------------------- 160
Application of geophysical methods to geologic
mapping---------------------------------------------------------- 161
Early geologic work------------------------------------ 161
Ideal conditions for magnetic work --------------- 161
Magnetic contrasts in rocks ----------------- 161
Simplicity of geologic structure ------------- 161
Numerous geologic checks available- ----- 161
Favorable geographic and topographic
conditions ---------------------------------------- 162

V

Part 2. Ore deposits-Continued.                                                   Page
Geophysical methods applied, etc.-Continued.
Application of geophysical methods, etc.-Con.
Theory and practice of magnetic surveying------ 162
Fundamental principles ------------------------- 162
Instruments ---------------------------------------- 162
Plotting of results -------------------------------- 162
History of work in the Lake Superior 
     Keweenawan rocks --------------------------------- 163
Early observations ------------------------------ 163
Recent work --------------------------------------- 163
Recent work within the copper district ----------- 163
Work prior to 1925------------------------------- 163
Work in 1925-------------------------------------- 163
Work in 1926-------------------------------------- 164
Results---------------------------------------------------- 164
Determination of strike------------------------- 164
Tracing beds at specific horizons----------- 164
Location of faults, folds, and fissures------165
Other relations of magnetic features
      to geologic features ------------------------ 165
Persistence of magnetic features ------------ 166
Magnetic correlations -------------------------- 167
Present attitude toward magnetic surveying------------ 167
Part 3. Detailed description of lodes and fissures.----------------- 169
Nonesuch lode------------------------------------------------------- 169
Stratigraphic occurrence ----------------------------------- 169
Structure-------------------------------------------------------- 169
Mineralization ------------------------------------------------- 170
Ore minerals--------------------------------------------- 170
Favorable conditions --------------------------------- 170
Influence of shale beds ----------------------- 170
Influence of fissures --------------------------- 170
Mineralogic and textural influences -------- 171
White Pine mine ---------------------------------------------- 172
Location and topography --------------------------- 172
Production----------------------------------------------- 172
Rocks -----------------------------------------------------172
Structure------------------------------------------------- 172
Mineralization ------------------------------------------ 173
Extensions of ore bodies ---------------------------- 174
White Pine Extension mine -------------------------------- 174
Nonesuch mine----------------------------------------------- 175
Onondaga exploration--------------------------------------- 175
Other properties ---------------------------------------------- 175
Production ---------------------------------------------------- 175
Character of rock--------------------------------------------- 176
Mineralization ------------------------------------------------ 176
Developments ----------------------------------------------- 176
Copper Falls mine ------------------------------------ 176
Arnold mine ------------------------------------------- 176
Phoenix mine ------------------------------------------ 176
Hancock mine ----------------------------------------- 177
Atlantic mine ------------------------------------------ 177
Location and production --------------------------- 178
Character of flows ------------------------------------ 178
Character of amygdaloids -------------------------- 178
Mineralization ----------------------------------------- 179
Rock alteration ---------------------------------------- 179
Mineralization in different lodes ------------------ 180
Main branch-------------------------------------------- 180
Pewabic Far West lodes ---------------------------- 180
Fissures or "crossings ------------------------------ 180
Faults---------------------------------------------------- 181
Franklin Jr. mine -------------------------------------- 181
Rhode Island mine ----------------------------------- 181
Part 3. Detailed description of lodes and fissures-Con.               Page
Production-------------------------------------------------------- 181
Character of conglomerate ----------------------------------- 182
Franklin Jr. mine ------------------------------------------------ 182
Rhode Island mine --------------------------------------------- 182
Allouez mine----------------------------------------------------- 182
Delaware---------------------------------------------------------- 182
Location and extent ------------------------------------------- 182
Production------------------------------------------------------- 183
Composition ---------------------------------------------------- 183
Iron oxide of the felsites and quartz 
     porphyries of Keweenaw Point ------------------ 183
Iron oxides in the Calumet & Hecla
conglomerate -------------------------------------------- 184
Changes in the iron oxides during
     mineralization----------------------------------------- 185
Thickness-------------------------------------------------------- 185
Texture------------------------------------------------------------ 185
Hanging wall---------------------------------------------------- 186
Footwall --------------------------------------------------------- 186
Structure--------------------------------------------------------- 186
Faults------------------------------------------------------ 186
Fissures and joints ------------------------------------ 187
Alteration------------------------------------------------------- 187
Soft boulders-------------------------------------------- 187
Mineralization ------------------------------------------ 187
Character ------------------------------------------ 187
Minerals------------------------------------------- 188
Distribution of the copper -------------------- 188
Influence of faults and fissures ------------- 188
Mineralization of the walls ------------------- 189
Change in grade of ore ------------------------ 189
Map showing "copper per unit area
     of lode"----------------------------------------- 189
Cause of convergence of solutions
     and influence of barriers ------------------- 190
Copper boulders and skulls ------------------ 190
Silver------------------------------------------------ 190
History and production ------------------------------------- 190
Osceola flow---------------------------------------------------- 191
Character of the Osceola amygdaloid -------------------- 191
Thickness-------------------------------------------------------- 191
Ranging wall----------------------------------------------------- 191
Structure---------------------------------------------------------- 192
Alteration and mineralization of the lode ---------------- 192
Oxidation-------------------------------------------------- 192
Alteration and mineralization later than
     oxidation----------------------------------------------- 192
Distribution of copper in the lode ------------------------- 192
Distribution through thickness of the
     lode----------------------------------------------------- 192
Distribution in the plane of the lode --------------- 192
Variation in copper content with depth ------------------ 192
Changes in method of mining ------------------------------ 192
History and production -------------------------------------- 194
Kearsarge flow ------------------------------------------------- 194
Extent and criteria for recognition ------------------ 194
Thickness------------------------------------------------- 194
Character of Kearsarge amygdaloid ---------------------- 196
General features ----------------------------------------- 196
Local observations ------------------------------------- 197
Structure---------------------------------------------------------- 197
Allouez anticline ---------------------------------------- 197
Faults and fissures ------------------------------------- 198

VI
Part 3. Detailed description of lodes and fissures---Con,          page
Kearsarge lode-Continued.
Alteration and mineralization -------------------------------198
Oxidation ------------------------------------------------- 198
Alteration accompanying mineralization---------- 198
Yield-------------------------------------------------------- 198
Probable causes of rich and poor ground -------------- 199
Character of rock ----------------------------------------------------------- 199
Influence of structure and texture -------------------------------------- 200
Structure------------------------------------------- 200
Texture -------------------------------------------- 200
Influence of fissures on the lode ------------------ 201
Conditions favorable to mineralization in the
     known productive portion of the Kearsarge
     lode --------------------------------------------------- 201
Effect of depth on the copper content of the
     lode---------------------------------------------------- 202
Mayflower-Old Colony mine ------------------------------------ 202
Structure-------------------------------------------------------- 202
Developments------------------------------------------------- 203
History and production ------------------------------------ 203
Extent and correlation -------------------------------------- 203
Character of lode -------------------------------------------- 204
Fragmental zone -------------------------------------- 204
Banded amygdaloid --------------------------------- 204
Foot inclusion zone --------------------------------- 204
Vein trap------------------------------------------------ 205
Main trap----------------------------------------------- 205
Hanging-wall trap ------------------------------------ 205
Distribution of types -------------------------------- 205
Structure------------------------------------------------------- 206
Isle Royale syncline --------------------------------- 206
Faults---------------------------------------------------- 206
Fissures------------------------------------------------- 207
Rock alteration and ore deposition -------------------- 208
First period--------------------------------------------- 208
Second period ----------------------------------------- 208
Chemistry of ore deposition ----------------------- 210
Arcadian lode-------------------------------------------------------- 211
New Arcadian lode------------------------------------------------- 211
Winona lode --------------------------------------------------------- 211
Production and character ---------------------------------- 211
Wyandot mine------------------------------------------------ 212
Elm River mine ------------------------------------------------ 212
Cherokee mine------------------------------------------------- 212
Wyandot No. 8 lode------------------------------------------------ 212
Evergreen and succeeding lodes ------------------------------- 212
Occurrence----------------------------------------------------- 212
Production ----------------------------------------------------- 213
Character of flows ------------------------------------------- 213
Structure-------------------------------------------------------- 213
Character of amygdaloids --------------------------------- 213
Mineralization ------------------------------------------------ 213
Rock alteration ----------------------------------------------- 213
Relation of mineralization to character of lode-------- 213
Butler lode ----------------------------------------------------- 214
Mass mine----------------------------------------------- 214
Lithologic character ---------------------------- 214
Structure ------------------------------------------ 214
Mineralization ----------------------------------- 214
Yield------------------------------------------------ 214
Adventure mine --------------------------------------- 214
South Lake mine --------------------------------------- 214
Lake mine------------------------------------------------ 214
North Lake mine --------------------------------------- 214
Evergreen lode------------------------------------------------ 214
Mass mine----------------------------------------------- 214
Adventure mine --------------------------------------- 215

Part 3. Detailed description of lodes and fissures-Con.            Page

Evergreen and succeeding lodes-Continued.
Evergreen lode-Continued.
South Lake mine --------------------------------------- 215
Lake mine------------------------------------------------ 215
North Lake mine --------------------------------------- 215
Knowlton lode------------------------------------------------ 215
Mass mine---------------------------------------------- 215
Adventure mine -------------------------------------- 215
Lake mine ----------------------------------------------- 215
Michigan mine ----------------------------------------- 215
Ogima lode ---------------------------------------------------- 216
Other lodes---------------------------------------------------- 216
Forest ("Victoria") lode ------------------------------------------- 216
Production----------------------------------------------------- 216
Geologic horizon---------------------------------------------- 216
Character of amygdaloid ----------------------------------- 216
Mineralization ------------------------------------------------- 216
Extent of development -------------------------------------- 216
Lake lode-------------------------------------------------------------- 216
Production------------------------------------------------------ 216
Location -------------------------------------------------------- 216
Structure-------------------------------------------------------- 217
Correlation ----------------------------------------------------- 217
Character------------------------------------------------------- 217
Algomah lode-------------------------------------------------------- 217
Baltic lode------------------------------------------------------------- 217
History and production ------------------------------------- 217
Extent and correlation --------------------------------------- 218
Baltic flow------------------------------------------------------- 218
Structure--------------------------------------------------------- 218
Folds------------------------------------------------------- 218
Cross faults and slips --------------------------------- 218
Strike fissures-------------------------------------------- 219
Character of Baltic amygdaloid ---------------------------- 219
Oxidation--------------------------------------------------------- 219
Mineralization -------------------------------------------------- 219
Minerals--------------------------------------------------- 219
Rock alteration ------------------------------------------ 220
Relation of mineralization to character of
      lode----------------------------------------------------- 220
Results of operation ------------------------------------------ 220
Baltic West lode ----------------------------------------------- 221
Relation of fissure mineralization and lode 
     mineralization------------------------------------------------ 221
Occurrence------------------------------------------------------- 221
Production-------------------------------------------------------- 221
Character--------------------------------------------------------- 222
Mineralization -------------------------------------------------- 222
Ore shoots------------------------------------------------------- 222
Isle Royale ------------------------------------------------------------- 222
Felsite of Indiana mine ---------------------------------------------- 222
Development ---------------------------------------------------- 222
Mineralization --------------------------------------------------- 222
History------------------------------------------------------------- 223
Production-------------------------------------------------------- 223
Distribution ------------------------------------------------------ 223
Distribution of copper in the fissures --------------------- 223
State of division of copper ----------------------------------- 225
Exploration of fissures ---------------------------------------- 225
Incentive to exploration -------------------------------- 225
General features of exploration ----------------------- 225
Method of exploration ---------------------------------- 226
Suggested explorations -------------------------------- 226
Fissure mines and prospects of Keweenaw
     and Ontonagon Counties -------------------------------- 226
Star---------------------------------------------------------- 226

VII

Part 3. Detailed description of lodes and fissures-Con.              Page
Fissure deposits Continued.
Fissure mines and prospects of Keweenaw and Ontonagon
Counties-Continued.
Clark------------------------------------------------------- 226
Iron City-------------------------------------------------- 226
Medora --------------------------------------------------- 226
Native Copper------------------------------------------- 226
Conglomerate ------------------------------------------- 227
Connecticut --------------------------------------------- 227
Amygdaloid -------------------------------------------- 227
Eagle Harbor ------------------------------------------- 227
Madison------------------------------------------------- 227
Dana------------------------------------------------------ 227
Copper Falls ------------------------------------------- 227
Petherick ------------------------------------------------ 228
Old Copper Falls -------------------------------------- 228
Northwestern ------------------------------------------ 228
Central--------------------------------------------------- 228
Winthrop ----------------------------------------------- 229
Eagle River---------------------------------------------- 229
St. Clair -------------------------------------------------- 229
Part 3. Detailed description of lodes and fissures-Con.                 Page
Fissure deposits Continued.
Fissure mines and prospects of Keweenaw and Ontonagon Counties-Continued.
Bay State--------------------------------------------------- 229
Phoenix----------------------------------------------------- 229
Phoenix fissure ------------------------------------------ 229
Robbins or West ---------------------------------------- 229
Old Phoenix----------------------------------------------- 230
Vaughnsville --------------------------------------------- 230
Cliff --------------------------------------------------------- 230
North Cliff ------------------------------------------------- 231
North American------------------------------------------ 231
Albion-Manhattan ------------------------------------- 231
Mohawk -------------------------------------------------- 231
Fulton ----------------------------------------------------- 231
Mass ------------------------------------------------------ 231
Arsenide ------------------------------------------------- 231
Minesota and Branch fissures and Calico
      lode---------------------------------------------------- 232
Norwich--------------------------------------------------- 233
Index --------------------------------------------------------------------------- 235

VIII

Some portions of the professional paper have not been included in this website. These include the bibliography, theories of deposition, geophysical exploration, production history and index. Large plates that were in separate pockets have also not been reproduced. See the original work for these topics. See List of Illustrations for plates and figures available.

The pages reproduced are 1-3, 14-33, 46-63, 98-120, 141-156, 169-233

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