CONTENTS. 
Part I. General Description and Discussion of the Ore Deposits. 
I'age 
Introduction and acknowledgments 13 
Geographical position _. . .. _ 14 
Literature ... 14 
Historical sketch _ . 19 
Production ... .. ... _.. 25 
Climate . 25 
Vegetation . 26 
Topography 26 
Outline of geology, by Whitman Cross _ 29 
San Juan volcanic area 29 
Geology of the Silverton quadrangle . . . .. 30 
Location with regard to the volcanic area 30 
San Juan formation . 31 
Silverton series 32 
Potosi series 32 
Stock eruptions. . . _ 33 
Other intrusive rocks 33 
Formations underlying the volcanics 31 
Prevolcanic surface and the Telluride conglomerate . _ 36 
Structure of the pre-Telluride formations ... 37 
Faulting 37 
Landslides. . ... 37 
Methods of mining and treatment of ores . . 39 
Classification of the ore deposits 43 
The lode fissures ... 43 
Definitions 43 
Distribution of the ore-bearing fissures . 44 
Coordination of the fissures . .... 45 
Relation of fissures to kind of country rock and to rock structure 53 
Displacement or faulting as an accompaniment of the Assuring 55 
Intersections and relative ages of fissures . . . 56 
Geological age of the fissures . .. ..... 60 
Probable depth at which the portions of the fissures now exposed were 
originally formed. ... .... 60 
Persistence of the fissures horizontally and in depth 61 
Origin of the fissures 63 
Structures of the lodes . 67 
The ores of the lodes - - . 70 
Mineralogy of the ores - - 70 
Gangue minerals 70 
Ore minerals - 77 
Products of superficial decomposition - 87 
