Magnetite Deposits of the Sterling Lake, N. Y.- Ringwood, N. J. Area By PRESTON E. HOTZ CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1952 GEOLOGICAL SURVEY BULLETIN 982-F UNITED STATES GOVERNMENT PRINTING OFFICE', WASHINGTON : 1953 UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price $1.25 CONTENTS Page Abstract.._._____.____.__..______--.-----__________-__.__.____--__ 153 Introduction _________________________________________ _ ___ _ ______ 155 Location and accessibility. __-_-._ ______________________ _ _ _ _ 155 Field work_________________ _ ______________________________ _ _ 157 Previous work...______________________________________________ 157 Geography..______________________________________________________ 159 --.-..------- ------------------ -----_ -- --------- 160 General statement.,._______._-_________-____.______._._-.--____ 160 Metasedimentary rocks.__._____________________________________ 161 Metamorphosed calcareous rocks. __________ _ ___ __.. __ 161 Occurrence and distribution..___________________________ 161 Marble.------.----------------------.----------- 162 Skarn__ _ _ _ __ _____ 162 Pyroxene amphibolite and amphibolite.__-_._----_._- 167 Origin.....____...._____....--_._....-..___...___..... 170 Problem of the term "Pochuck" ._____-...___..-....._. 172 Metamorphosed quartzose rocks.. ____ _ ________________ _ ___ 173 Occurrence and distribution..........___________________ 173 Garnetiferous quartz-biotite gneiss._ _ __________ _ ___ 173 Quartzite.._______________________________________ 174 Origin.. -__-_____._-------__--_-_--_---__.__.----.__. 174 Granitic rocks_._____.______---_-___---_____-________._-_____ 174 Quartz-oligoclase gneiss.______-___-___-_ __ _____ __ __ 174 Occurrence and distribution..___________________________ 174 Petrography. __.__.____ ________________ _ __ _ ______ 175 Composition _ _ ___________________________ _, - __. 177 Hornblende granite and related facies._______________________ 178 Occurrence and distribution....-_ ________ ________ _ _ 179 Petrography _ _____ ________________________________ 179 Composition __________-_-_-__-^_---____..___...____.__ 181 Pegmatite. __ ____ _ ___ __________ __.-__ ___ 182 Occurrence and distribution.___-_-_--__-____:_____._____ 182 Petrography,_____________ _ ___________ ____..___ ___ 183 Composition _____________ _____________ __ _ _ 185 Relations between the granitic rocks and metasedimentary rocks. 185 Relations between quartz-oligoclase gneiss and hornblende granite. 186 ,0rigin of the granitic rocks._-_-_.-----_-___---_____--_____. 186 Younger dike rocks.___ _ ____-____ ___ ___ _ ___ ___ _____ 188 Occurrence ___________________________________________ 188 Age of the dikes.......-.:-......-..-___:___.__..______ 188 Glacial and stream deposits.^.___________________________________ 188 Structural features..___________________________________________ 189 Foliation.._______.._._.-_--__.__...____________________ 189 Lineation__ _ ______________________________________________ 189 Origin of the gneissic structure__.___________________________ 190 Folds.__________________________________________________ 191 Faults..... _-__._-._..---.___--__--_._________ 192 Joints. _. ___-__...____.____-.___ _ _ _____ _________________ 193 m IV CONTENTS Page Magnetite deposits _______________________________________.:__ ______ 193 History-___--_--____-_-_--_------____---_--_--_-_____-_______ 193 Distribution _______..______-__-_____________-_.____-_-_-_-_--__ 194 Sterling Lake deposits____________________________________ 194 Ringwood deposits________________________________________ 196 Other deposits._______-_-------___----__--________________ 196 Production.._-_-__--__-__-_----_--------_-_--__--_-__________ 198 General character________--_---_----_-__-_--_-__-___-____--__ 199 Mode of occurrence.____________________________________________ 200 Deposits in pyroxene amphibolite and amphibolite..___________ 200 Deposits in skarn____-____-_-__-_-__-______-_______-____-__ 200 Structure of the magnetite deposits____________.__________________ 201 General structure of the ore bodies-------_-._________-____^_. 201 Folds--.-------.----.--------------------:------------.-- 203 Faults.--...----------------------------------------------- 203 Relationship to pegmatite-_----_-_----__---_--_________._._____ 203 Mineralogy and paragenesis_------------------_--__-__-_________ 204 Magnetite-_-----__--_------------------------_---_-----_- 204 Hematite----.---------------------------------------.---- 206 Gangue minerals __________________________________________ 207 Pyroxcene.___________________________________________ 208 Apatite ___ ____-_------_------_---_-_-_-_-___________ 209 Quartz-.-.----------.-------------------------------- 209 Biotite_-----_------------------------------------ 210 Chlorite and actinolite_-__-_--'-l___-___________________ 210 Serpentine- _ ______-_-_-------______-_______l__________ 211 Albite_----_--------------_-------------------------- 211 Epidote_.__.__.-.---------------------------.-1.----L 212 Calcite---------.-------------,--------------------!-- 212 Suifides.------------------------I:.::--------------- 212 Composition ____._________,_-_____-_-_-_--_-_-__-_--____--__-. 213 Origin of the magnetite deposits.---..___________________________ 213 Mines and prospects_____---_-------------------------------------- 216 Ringwood group____------------------------------------------- 216 General geology___________________________________________ 216 Peters rnine-_____-------------_----_-----_----_-_--------- 217 Cannon mine.______________-__-__-__--________---.!_-____- 218 Hope mines----_----__--------_-------_--_-----------_--_- 220 Cooper mine,_________-_--_--___-___--_-__-_______________ 220 Keeler-Miller-St. George mines._____________________________ 221 Ward-Bush mines.-.-------------------------------------- 221 Snyder and Hewitt mines-_-_---_---------_----_'_-__________ 222 Prospects-.--.-.------------------------------------------ 222 Sterling Lake group__________________________________________ 222 General geology-_-______-------_-----_____________________ 223 Sterling and Lake mmeS-_--------------------------_--_-___ 224 Tip Top mine-_-------------------------------------: _--_- 226 Summit, Upper California,- Lower California, and Whitehead mines-----.-----------------.------------------ ------- 227 Scott-Cook mine----..------------------------------------ 227 Augusta mine.-_________--_--_-_---_-_---_---____----_-__- 229 Long mine____'_-_____________-_____-_-__-_----___--_-___ 230 Smithmine--.----- --'----.-----------_-------.--_.------ 231 Mountain mine-_-___-l_---------_-----------------__------ 232 iCrossway mine.__________-___-_--.____-__--_----__________ 233 CONTENTS Mines and prospects Continued Other mines and prospects.------------------------------------.. 233 Crawford and Steele mines.. _-____-__--__------------------.. 233 Brennan prospect____ _ _.______._______________----______-... 235 The Redback belt___. .._...........-.__..__._-...._..--._. 235 Morehead mine. ____________________-____----_-___-__-_-_. 236 Bering mine. ______________-______..-____--.---__..-_---___ 237 Middle and Hard mines. __-_-________-___-_--__-_-_____---_ 237 Shaft-near-railroad- _ ______--_______-______- _-__-___-----___ 237 Patterson mine. ______ _____________________________________ 238 Board (Schermerhorn) mine__-_-_-------_-__----_-_-__-_-_-_ 238 Suggestions for prospecting. ____________________________________ 238 References cited. _ ______________---_-___.-._ ________ ______^__.__._- 240 Index. ___.... ..-________-._-_------__-_-----------------__-.----. 243 ILLUSTRATIONS [All plates in pocket] PLATE 19. Geologic map and sections. 20. Map of the Scott group and sections through drill holes. 21. Geologic map, projection, section, and plan of Peters mine. 22. Geologic map and projection of Cannon mine. 23. Geologic map of part of Scott mine. FIGURE 32. Index map of Sterling Lake and Ringwood districts.--.-.... 156 33. Photomicrograph of marble containing garnet and augite____ 163 34. Photomicrograph showing serpentine and chondrodite in marble ______.___--_------_-__-_______--_-___________ 163 35. Photomicrograph of typical dark skarn____________________ 164 36. Photomicrograph of light skarn with interstitial calcite______ 165 37. Photomicrograph of rock intermediate between skarn and amphibolite. _ .__.__-_______-_--________--____._______ 166 38. Photomicrograph of pyroxene amphibolite_._______________ 167 39. Photomicrograph of pyroxene amphibolite-_-__________-._. 168 40. Photomicrograph of amphibolite-_________________________ 171 41. Photomicrograph of quartz-oligoclase gneiss__-_____________ 176 42. Photomicrograph of granite____________________.__.__._._ 180 43. Photomicrograph of granoblastic hornblende granite.____-___ 180 44. Index map of the Sterling Lake district___-----_---____-___ 195 45. Sketch map of the Lake and Sterling mines._______________ 197 46. Index map of the Ringwood district.._____________________ 198 47. Block diagram showing relations of country rock to ore.-_-_. 202 48. Field sketch of hanging wall at Augusta mine.__._.________ 204 49. Photomicrograph showing unreplaced silicate gangue in mag- netite.___-------_----_----------------_--_-_----____ 205 50. Photomicrograph showing magnetite replacing pyroxene along grain boundaries...___________________________________ 205