MONAZITE (THORIUM AND CERIUM ORES) 288 Economic features 288 Geologic features 289 PRECIOUS STONES 289 Economic features 289 Geologic features 291 SALT 294 Economic features 294 Geologic features 295 TALC AND SOAPSTONE 299 Economic features 299 Geologic features 299 CHAPTER XIV. EXPLORATION AND DEVELOPMENT 301 THE GENERAL RELATIONS OF THE GEOLOGIST TO EXPLORATION AND DEVELOPMENT 301 PARTLY EXPLORED VERSUS VIRGIN TERRITORIES 303 THE USE OF ALL AVAILABLE INFORMATION 304 COOPERATION IN EXPLORATION 305 ECONOMIC FACTORS IN EXPLORATION 306 GEOLOGIC FACTORS IN EXPLORATION 307 MINERAL PROVINCES AND EPOCHS 308 CLASSIFICATION OF MINERAL LANDS 309 OUTCROPS OF MINERAL DEPOSITS 311 Some illustrative cases 312 Topography and climate as aids in searching for mineral outcrops 314 Size and depth of ore bodies as determined from outcrops 315 The use of placers in tracing mineral outcrops 316 The use of magnetic surveys in tracing mineral ledges 317 THE USE OF ELECTRICAL CONDUCTIVITY AND OTHER QUALITIES OF ROCKS IN EXPLORATION 319 THE USE OF STRUCTURE AND METAMORPHISM IN EXPLORATION 319 DRILLING IN EXPLORATION 320 QUANTITATIVE ASPECTS OF GEOLOGIC EXPLORATION 321 ORIGIN OF MINERAL DEPOSITS AS A FACTOR IN EXPLORATION 322 LAKE SUPERIOR IRON ORE EXPLORATION AS AN ILLUSTRATION 323 DEVELOPMENT AND EXPLOITATION OF MINERAL DEPOSITS 326 CHAPTER XV. VALUATION AND TAXATION OF MINERAL RESOURCES 328 POPULAR CONCEPTION OF MINERAL VALUATION 328