CONTENTS. 11 



CHAPTER V. DESCRIPTIVE GEOLOGY OF MINES AND PROSPECTS Continued. page. 

 Explorations on veins at the contact of the Tonopah rhyolite-da'cite Continued. 



Mizpah Extension shaft Continued. 



Correlation of the rhyolitic rocks in the shaft 196 



Age of the veins 197 



King Tonopah shaft 19" 



. Geological situation 19" 



Vein materials 197 



Nature of rock inclosing vein materials 197 



Correlation of veins with other occurrences 198 



Belle of Tonopah shaft 198 



Geological conditions 198 



Veins 198 



Shafts at the unmineralized contact of the Tonopah rhyolite-dacite 199 



Butte Tonopah shaft 199 



Little Tonopah shaft 199 



Shafts at the contact of the Brougher dacite 200 



Big Tono shaft 200 



Molly shaft 200 



Shafts wholly or chiefly in dacitic tuffs 200 



New York Tonopah shaft 200 



Fraction Extension shaft 201 



Geological section 201 



Fault 202 



Tonopah City shaft 202 



Geological section 202 



Indicated displacement of fault blocks 202 



Ohio Tonopah shaft 202 



Dacite tuffs in shaft 202 



Later andesite in shaft 203 



Solid Tonopah rhyolite-dacite 203 



Characteristics of the rhyolite-dacite 204 



Mineralization ., 204 



Pittsburg shaft 204 



Red Kock shaft 204 



Shafts entirely or chiefly in later andesite 205 



Halifax shaft 205 



Golden Anchor shaft 205 



CHAPTER VI. ROCK ALTERATION CONNECTED WITH MINERALIZATION 207 



Alteration of the earlier andesite 207 



Alteration of earlier andesite, chiefly to quartz, sericite, and adularia 207 



Alteration of hornblende and biotite 207 



Relations of pyrite and siderite 208 



Alteration of soda-lime feldspar to quartz and sericite 208 



Alteration of soda-lime feldspar to adularia 208 



Alteration of the groundmass 209 



