Colorado Geological Survey

CONTENTS
Page
Introduction 7
Geographic position 7
Field work and acknowledgments , , 3
History of mining , 9
Bibliography ,_. 11
Chapter I. Physiography 16
Topography 16
Influence of structure , 16
Glaciation , 16
Landslides , , , 18
Vegetation 18
Alluvium and soil--. 19
Chapter II. Pre-Cambrian metamorphic rocks 20
Granite gneiss , , 20
Quartz-diorite gneiss 21
Granitic gneiss 21
Mica gneiss , , 21
Pyroxene gneiss , , 21
Slllimanite gneiss , 21
Mica schist 22
Garnet-mica schist 22
Quartzite 22
Marble 22
Chapter III. Igneous rocks , 24
Granite , 24
Quartz monzonite 25
Quartz diorite 26
Quartz-hornblende diorite : 26
Quartz-mica diorite (without essential hornblende) 27
Gneissoid quartz-mica diorite 28
Syenite , , 28
Hornblendite ,- 28
Peridotite , 29
Porphyry and felsite 29
Quartz-monzonite porphyry , 31
Quartz-diorite porphyry 32
Chapter IV. Paleozoic sedimentary rocks 33
Cambrian and Ordovician or Devonian sediments 33
Sawatch quartzite 33
Description , 33
Age 35
Cambrian 35
Ordovician or Devonian 35
Devonian-Mississippian sediments.- 35
Leadvill© limestone 35
Description 35
Age
Chapter Pennsylvanian General Minerals Faulting Description Age Aluminum Sulphide V. VI. Structural character of Mineral the enrichment , sediments ore of deposits geology the deposits ores , ,
37
, 38 46 47
40 43
46
47 38