Triassic Period 51 Jurassic Period 52 Cretaceous Period 56 Cenozoic Era 59 Tertiary Period 59 Quaternary Period 68 III Geology and Man in Colorado 74 Gold, Silver, and Other Metals 77 Boulder County 79 Central City and Idaho Springs 80 Georgetown, Empire, and Silver Plume 81 Leadville 82 Breckenridge 83 Fairplay 84 Silverton 85 Ouray 87 Aspen 88 Creede 89 Cripple Creek 90 Climax 91 Radium, Uranium, and Vanadium 93 Oil, Natural Gas, and Oil Shale 94 Coal 96 Construction Materials 97 Sand, Gravel, and Clay 97 Stone 99 Lime and Gypsum 101 Gems 102 Water 103 Surface Water 103 Groundwater 105 Caves 106 Springs 109 Environmental Geology 111 Glossary 114 Suggested Reading 119 Index 121 ILLUSTRATIONS