6 CONTENTS. 



CHAPTER I. GENERAL GEOLOGY Continued. Page. 

 Principles of faulting Continued. 



Intrusions controlled by intersecting fractures 79 



Corroboration of conclusions 79 



Accuracy of fault mapping 80 



Faulting due to volcanic action . 80 



Application of principles beyond map 80 



Suggested explanation of Great Basin Tertiary deformations 81 



End of volcanic epoch 82 



CHAPTER II. MINERAL VEINS 83 



Veins of the earlier andesite 83 



Period of mineralization 83 



Nature of circulation channels 83 



Veins due chiefly to replacement 84 



Portions of veins due to cavity filling 85 



Cross walls and ore shoots 85 



Nature of mineralizing agents 85 



Primary ores 86 



Locality 86 



Composition 86 



Minerals 86 



Quartz 86 



Adularia 86 



Sericite 87 



Carbonates 88 



Silver sulphides 88 



Silver chloride 88 



Chalcopy rite 88 



Pyrite 88 



Galena 88 



Blende 88 



Gold 89 



Analyses of primary sulphide ores 89 



Summary of vein minerals 90 



Oxidation 90 



Depth of oxidation 90 



Cap-rocks as protection from oxidation 90 



Silver chloride in oxidized zone of veins 91 



Analysis of oxidized ore 92 



Comment on the ore analyses 92 



Formation of gypsum by oxidizing waters 94 



Secondary sulphides 94 



Pyrite, argentite, and native silver 94 



Argentite, polybasite, and chalcopyrite in druses 95 



Comparison of secondary sulphides at Neihart and Tonopah 95 



Evidence favoring secondary deix>sition of sulphides by descending waters 96 



