CONTENTS. 7 



CHAPTER II. MINERAL VEINS Continued. Page. 



Veins of the Tonopah rhyolite-dacite period 96 



Characteristics of Tonopah rhyolite-dacite veins 97 



Age of Tonopah rhyolite-dacite veins 99 



General restriction of veins to rhyolite-dacite 99 



Effect of waters producing the Tonopah rhyolite-dacite veins on earlier-formed veins. 100 



The calcitic veins of Ararat Mountain 101 



The rhyolite of Ararat a volcanic plug 101 



Flow brecciation near contact 102 



Fissure- veins in the rhyolite plug 102 



Fissures due to movement after consolidation 104 



Paragenesis of vein materials 104 



Composition of vein-forming waters 104 



CHAPTER III. PRESENT SUBTERRANEAN WATER 105 



Water encountered in mining operations 105 



Outcropping water-zones 107 



Distribution and explanation- of water zones 107 



Usual absorption of precipitation by rocks 107 



CHAPTER IV. PHYSIOGRAPHY 109 



Origin of the range of hills 109 



Sketch of Tertiary and Pleistocene erosion 109 



General features 109 



Measures for the amount of material eroded 110 



Features of erosion in arid climates Ill 



Precipitation in region near Tonopah 112 



Dependence at Tonopah of topographic relief upon rock resistance 113 



Effects of faulting upon the topography 114 



CHAPTER V. DESCRIPTIVE GEOLOGY OP MINES AND PROSPECTS 115 



The known earlier andesite veins 115 



Mizpah vein system 115 



Mizpah vein 115 



Extent of vein ; 115 



Limitation of vein by Mizpah fault 115 



Limitation of vein by Burro fault 115 



Limitation of vein by Siebert fault 115 



Vein structure 117 



Effects of transverse premineral fractures 119 



Cross walls 119 



Branching veins 119 



Origin of ore shoots 119 



Post-mineral faults and fractures 122 



Vein composition 122 



Secondary nature of ore minerals 124 



Eearrangement of values during oxidation 124 



