rv 



CONTENTS 



Page 



Mines -- 



New Almaden mines 



New Almaden mine - 



Cora Blanca area 130 



Harry area 



Velasco area 135 



Central stope area 



Victoria area 139 



North Randol area 141 



South Randol area.. 144 



San Francisco area. 146 



Santa Mariana area 148 



San Pedro-Almaden area 149 



America mine 



Providencia mine 151 



Enriquita mine 



San Antonio mine. - - 155 



San Mateo mine - 156 



Mines -Continued 



New Almaden Mines Continued 



Senator mine. 



Guadalupe mine 



Santa Teresa mine. 



Bernal mine 



Placer cinnabar deposit 



Future production 



Submarginal ore 



High-grade ore 



Extensions of known ore bodies 



Satellite ore bodies 



Possible new ore bodies 



Other suggestions 



Summary 



History of the New Almaden mines 



Annotated bibliography of the New Almaden mine- 

 Literature cited. 



Index - 



Pae 



158 

 162 

 169 

 169 

 169 

 170 

 171 

 172 

 172 

 172 

 172 

 176 

 176 

 176 

 195 

 199 

 203 



ILLUSTRATIONS 



Pe 



[Plates are In separate volume] 



PLATE 1. Geologic map and sections of the New Almaden district. 



2. Diagrammatic sketches showing the process of formation of the primary and placer quicksilver ores of the district. 



3. Geologic map of the New Almaden mine area. 



4. Composite map of the underground workings of the New Almaden and America mines. 

 5-10. Geologic level maps of the New Almaden and America mines. 



1 1 Cross sections through the New Almaden mine area. 



12. Geologic section through the Harry area and block diagrams of the Cora Blanca and San Francisco areas o 



New Almaden mine. 



13. Geologic map and section of the America mine. 



14. Geologic map and sections of the Guadalupe-Senator mine area of the New Almaden district. 



15. Composite map of the underground workings of the Guadalupe and Senator mines. 

 16-18. Geologic composite level maps of the Guadalupe and Senator mines. 



FIGURE 1. Index map showing the location of the New Almaden district. . 



2. Shaded contour map showing the main topographic features of the district and places referred to in the 



report 



3. Massive graywacke of the Franciscan group. .. 



4. Deformed graywacke exposed in roadcut between Bald Mountain and the crest of the Sierra Azul . 



5. Photomicrograph of feldspathic graywacke of the Franciscan group. . 



6. Photomicrograph of lithic graywacke of the Franciscan group 



7. Photomicrograph of siltstone of the Franciscan group. . 



8. Alta lying above intrusive serpentine. _ 



9. Hand specimen of alta 



10. Photomicrograph of alta. _ 



11. Outcrop of Calera-type limestone occurring in the Franciscan group.. 



12. Thin beds of limestone of the Franciscan group interlayercd with tuffaceous shale.. 



is! Calera type of limestone of the Franciscan group at locality from which Upper Cretaceous Foraminifera 

 have been obtained 



14. Oolitic limestone of the Franciscan group. . 



15. Photomicrograph of oolitic limestone of the Franciscan group. . 



16. Fossils from the limestone of the Franciscan group.. 



17. Sharp folds in bedded chert of the Franciscan group... 



18. Vertical out through "cauliflower" of botryoidal chert, showing internal structure.. 



19. Photomicrograph of chert of the Franciscan group containing Radiolaria.. 

 20-23. Photomicrographs of greenstones of the Franciscan group. . 



24. Polished sections of drill cores showing two kinds of tuffaceous greenstone in the Franciscan group. 



25. Photomicrograph of calcareous tuff from the Franciscan group... 



26. Polished surface on breccia composed chiefly of fragments of altered tachylite.. 



13 

 14 

 15 

 15 

 18 

 19 

 19 

 19 

 22 

 22 



22 

 23 

 23 

 25 

 26 

 27 

 28 

 32 

 34 

 35 

 36 



