CHAPTER VII. THE FERTILIZER GROUP OF MINERALS 99
GENERAL COMMENTS 99
NITRATES 101 Economic features 101 Geologic features 102
PHOSPHATES 104 Economic features 104 Geologic features 105
PYRITE 107 Economic features 107 Geologic features 108
SULPHUR 109 Economic features 109 Geologic features 110
POTASH 111 Economic features 111 Geologic features 112
CHAPTER VIII. THE ENERGY RESOURCES--COAL, OIL, GAS (AND ASPHALT) 115
COAL 115
ECONOMIC FEATURES 115 World production and trade 115 Production in the United States 117 Coke 118 Classification of coals 119
GEOLOGIC FEATURES 123
PETROLEUM 127
ECONOMIC FEATURES 127 Production and reserves 128 Methods of estimating reserves 134 Classes of oils 136 Conservation of oil 137
GEOLOGIC FEATURES 140 Organic theory of origin 140 Effect of differential pressures and folding on oil genesis and migration 142 Inorganic theory of origin 143 Oil exploration 144
OIL SHALES 150
NATURAL GAS 151 Economic features 151 Geologic features 151
ASPHALT AND BITUMEN 151 Economic features 151 Geologic features 153
CHAPTER IX. MINERALS USED IN THE PRODUCTION OF IRON AND STEEL (THE FERRO-ALLOY GROUP) 154
GENERAL FEATURES 154
IRON ORES 158
ECONOMIC FEATURES 158 Technical and commercial factors determining use of iron ore materials 158 Geographic distribution of iron ore production 160 World reserves and future production of iron ore 162
GEOLOGIC FEATURES 166 Sedimentary iron ores 166 Iron ores associated with igneous rocks 171 Iron ores due to weathering of igneous rocks 171 Iron ores due to weathering of sulphide ores 173
MANGANESE ORES 173 Economic features 173 Geologic features 176
CHROME (OR CHROMITE) ORES 178 Economic features 178 Geologic features 179
NICKEL ORES 180 Economic features 180 Geologic features 181
TUNGSTEN (WOLFRAM) ORES 182 Economic features 182 Geologic features 184
MOLYBDENUM ORES 185 Economic features 185 Geologic features 186
VANADIUM ORES 187 Economic features 187 Geologic features 188
ZIRCONIUM ORES 189 Economic features 189 Geologic features 189
TITANIUM ORES 190 Economic features 190 Geologic features 190
MAGNESITE 191 Economic features 191 Geologic features 192
FLUORSPAR 193 Economic features 193 Geologic features 194
SILICA 195 Economic features 195 Geologic features 196