CONTENTS. 
Fage. 
Location, climate, and population T 
Discovery and development 7 
Topography 9 
General geological history _ ; . 9 
Pre-Tertiary formations 9 
Early andesite eruption 9 
Later andesite eruption 10 
Rhyolite and dacite eruptions . 10 
Lake sediments 10 
Eruption of basalt and intrusion of later dacites and rhyolites 10 
Faulting of the region 11 
Recent erosion 12 
Sequence of formations and events 12 
Description of the rocks of the region 12 
Distribution and characteristics of the early andesite 12 
Distribution and characteristics of the later andesite 13 
Distribution and characteristics of the rhyolites 14 
Distribution and characteristics of the dacites 14 
Periods and nature of mineralization 15 
Mineralization subsequent to the early andesite intrusion 15 
Mineralization subsequent to the early rhyolite intrusion 16 
Mineralization subsequent to the later rhyolite intrusion 16 
Mineralization subsequent to the dacite intrusions 17 
Resume 17 
Vein groups of the early andesite mineralization 18 
Occurrence of ores in the veins 21 
Physical character : 21 
Primary ores 23 
Secondary sulphides 23 
Oxidized ores 23 
Ore shoots _ . . - 25 
Application of geological principles 25 
Index 29 
