xii LIST OF ILLUSTRATIONS. 



FIGS. PAGE 



20. Cross section of the Colby mine, Penokee-Gogebic district, Mich- 



igan, to illustrate occurrence and origin of the ore. After C. R. 

 Van Hise 109 



21. General cross section of ore body at Biwabik, Mesabi Range, Minn. 



After H. V. Winchell 112 



22. Cross section of Pilot Knob, Mo. From a drawing by W. B. Potter. 114 



23. View of open cut at Pilot Knob., Mo., showing the bedded char- 



acter of the iron ore. From a photograph by J. F. Kemp 115 



24. View of Iron Mountain, Mo. From a photograph by H. A. 



Wheeler 116 



25. Cross section of Iron Mountain, Mo., showing the knob of por- 



phyry, with the veins of ore, the conglomerate, etc. After 

 W. B. Potter 117 



26. View of open cut and underground work in Mine 21, Mineville, 



near Port Henry, N. Y. From a photograph by J. F. Kemp. . . 121 

 27a and 27b. Model of the Tilly Foster ore body. After F. S. Rutt- 



mann and the model itself 124 



28. Cross section of the magnetite ore body at Cornwall, Penn. After 



Bailey Willis 127 



29. Illustration of overlapping lenses of pyrite. After A. F. Wendt. . 132 



30. Cross section of the Bob-tail mine, Central City, Colo. After F. M. 



Endlich 138 



31. Geological sections of Keweenaw Point, Mich., near Portage Lake 



and through Calumet. After R. D. Irving 140 



32. Cross section of the St. Genevieve copper mine, illustrating the re- 



lations of the ore. After F. Nicholson 144 



33. Section at the St. Genevieve mine, illustrating the intimate rela- 



tions of ore and chert. After F. Nicholson 144 



34". Geological map of the Morenci or Clifton copper district of Ari- 

 zona. After A. F. Wendt 145 



35. Vertical section of Longfellow Hill, Clifton district, Arizona. Af- 



ter Wendt 146 



36. Horizontal sections of Longfellow ore body. After Wendt 146 



37. Geological section of the Metcalf mine, Clifton district, Arizona. 



After Wendt 147 



38. Section of Copper Queen ore body, Bisbee district, Arizona. Af- 



ter A. F. Wendt 148 



39. View of the Copper Queen mine, Bisbee district, Arizona. From 



a photograph by James Douglass 149 



40. Cross section of the Schuyler copper mine, N. J. After N. H. 



Barton 153 



41. Gash veins, fresh and disintegrated. After T. C. Chamberlain . . . 162 



42. Idealized section of " flats and pitches," forms of ore bodies in 



Wisconsin. After T. C. Chamberlain 163 



43. Vertical section of a typical zincblende ore body, near Webb City, 



Mo. After C. Henrich 168 



44. View of the Motley mine, Webb City, Mo. After a photograph by 



W. P. Jenney 169 



