COPPER ORES 197 Economic features 197 Geologic features 199 Copper deposits associated with igneous flows 200 Copper veins in igneous rocks 201 "Porphyry coppers" 203 Copper in limestone near igneous contacts 204 Copper deposits in schists 204 Sedimentary copper deposits 205 General comments 206 LEAD ORES 209 Economic features 209 Geologic features 211 ZINC ORES 213 Economic features 213 Geologic features 216 CHAPTER XI. GOLD, SILVER, AND PLATINUM MINERALS 221 GOLD ORES 221 Economic features 221 Geologic features 226 SILVER ORES 231 Economic features 231 Geologic features 234 PLATINUM ORES 237 Economic features 237 Geologic features 239 CHAPTER XII. MISCELLANEOUS METALLIC MINERALS 241 ALUMINUM ORES 241 Economic features 241 Geologic features 243 ANTIMONY ORES 246 Economic features 246 Geologic features 248 ARSENIC ORES 249 Economic features 249 Geologic features 251 BISMUTH ORES 252 Economic features 252 Geologic features 252 CADMIUM ORES 253 Economic features 253 Geologic features 254