phosphates, 104, 106
platinum, 238, 239
potash, 112
salt, 294
zinc, 214

Russia, commercial and political control of various minerals, 64
laws relating to ownership of mineral resources, 343

Russia, Asiatic, vanadium, 187
_See also_ Siberia.

Saar Basin, coal of, under Peace Treaty, 401

Salisbury, R. D., and Chamberlin, T. C., 415

Salt, 294-298, 397

Salt domes of Gulf Coast, 298

Sand, 15, 84, 267

Sand and gravel, 84-85

Sandstone, 15, 17, 23, 84, 90, 267, 269

Santa Rita, New Mexico, copper ores, 203

Sapphires, 289, 291, 293

Sargasso Sea theory, of deposition of lead and zinc sulphides, 217

Saxony, bismuth, 252
tin, 262

Scandinavia, molybdenum, 386
nitrogen-fixation plants, 102

Schistose structure, 26

Schlumberger, C., 319

Schuchert, Charles, 144

Schultz, Robert S., Jr., 417

Scotland, magnesite, 191
oil shales, 150

Searles Lake California, borax deposits, 276
potash deposits, 112, 113-114

Secondary enrichment, 7-8, 25, 46-50
_See also_ under Copper ores, Silver ores, etc.

Secondary ore deposits, use of term, 32

Sedigenetic deposits, use of term, 51

Sedimentary mineral deposits, unsolved problems, 9, 53, 56

Sedimentary rocks, formation of, 22-24, 96
mineral deposits associated with, 23, 51-57
principal minerals of, 15-16
proportions of principal types, 17
relative abundance of, 16
weathering of, 23

Sedimentation, relation to economic geology, 2

Segregation, magmatic, 34-35, 59

Sericitic alteration, 39

Serpentine, 83

Seward Peninsula, Alaska, tin ores, 261, 262

Shale, 15, 17, 23, 85, 90

Shasta County, California, copper ores, 204

Shipping Board, 356, 406

Siam, sapphires, 289, 293
tin, 260
tungsten, 183, 184

Siberia, emeralds, 293
gold, 222, 226
lead, 210
vanadium, 187
zinc, 214

Silesia, cadmium, 254
coal, under Peace Treaty, 401
lead and zinc ores, 54-55, 210, 211-212, 214-215, 216-218

Silica, 195-196, 267, 269
_See also_ Quartz, Quartzite, Sand, Sandstone, etc.

"Silt" (fine coal), use of, 370, 371

Silver ores, 36-50, 55, 231-237, 308, 313-314, 397

Silver Reef, Utah, deposits, 55

Slate, 85, 89

Slides, earth and rock, 78, 357, 415-417

Smelting capacity of world, 61

Smith, George Otis, 310, 367, 403

Smith, George Otis