
440 
Pistazite, 24 
Pitchstone, 44, 49, 85, 89 
Placers, 232 
Plagioclase, 10, 12 
Plain-track of rivers, 417 
Plains of accumulation, 411 ; of erosion, 
404, 407, 412 
Planes of bedding, etc., 109 
Plants, geological action of, 371 
Plasma, 5 
Plateaus of accumulation, 405, 412; of 
erosion, 404, 413 
Platinum, 229, 232, 233 
Platy lodes, 245 
Pleistocene period, climatic conditions 
during, 98 
Pleonaste, 8 
Plutonic metamorphism, 220 
Pneumatolytic action, 62, 126, 219, 265, 
266, 271, 272 
Pockets of ore, 259 
Pollar willow, 98 
Polygenetic mountains, 404, 406 
Porphyrite, 49, 86; soils derived from, 
380. See also Andesite 
Porphyritic structure, 36 
Potosi, lodes of, 251 
Potstone, 23, 78 
Precipitates, ores, 231 
Primary minerals, 37, 38 
Prismatic joints, 148, 151, 204 
Prospecting for ores, 335 
Protogine-gneiss, 77 
Pseudomorphs, 7, 38 
Psilomelane, 9, 232, 256 
Pumice, 35, 45 
Pyrenees, 397 
Pyrite, 27 ; nodules of, 122, 229 
Pyroclastic rocks, 53, 210 
Pyrolusite, 9, 232 
Pyrope, 24 
Pyroxene, 16, 17; -syenite, 46 
Pyrrhotite, 28, 231, 249 
QUAQUAVERSAL folds, 134 
Quartz, 2; varieties of, 5; weathering 
of, 5; in crystalline igneous rocks, 
39; in clay, 121; -diorite, 48; 
-porphyry, 43, 85, 87, 88, 89, 379; 
-schist, 76; -trachyte, 43 
INDEX 

Quartzite, 76, 84, 382 
Quasi-bedded ores, 255 
Quicksilver formations, 250, 266 
RADIOLARIAN chert, 67 
Rain, action of, 370; 
-wash, 57 
Rainless regions, basins in, 419, 422 
Raised beaches, 317 
Rand gold-field, 261 
Rapids, 417 
Rattle-stones, 122 
Recumbent folds, 139 
Reefs, 248, 255 
Regional metamorphism, 220, 303 
Relict mountains, 405, 415 
Re-opening of lodes, 247 
Reservoirs, 348 
Resorption of minerals, 35 
Reversed faults, 170, 173, 298, 304 
Rhenish Schiefergebirge, 407 
Rhine Valley, 176, 391, 402, 414 
Rhyolite, 43, 85, 87, 89, 126, 379; -tuff, 
54 
Ridge-faults, 167 
Riesengebirge, 236 
Rift or grain of rocks, 152 
Rill-marks, 117 
Ring-ores, 247 
Rio Tinto iron ore, 232 
Ripple-marks, 116 . 
Rivers, action of, 415; as sources of 
water-supply, 349; older than hill- 
ranges traversed by them, 176, 416 
Roches moutonnées, 313 
Rock-beds, formation of, 104 
Rock-crystal, 5 
Rock, definition of, 32 
Rock-fall basins, 421 
Rock-flour, 311 
Rock-forming minerals, 1 
Rock-guano, 72 
Rock-phosphate, 73 
Rock-rubble, 57, 63 
Rock-salt, 27, 66 
Rocks, 32; crystalline igneous, 33; 
fragmental igneous, 53; derivative, 
55; metamorphic, 74; determination 
of, 81 ; fossiliferous, 93; concretionary, 
123 
-prints, 118; 

