440 



INDEX 



Pistazite, 24 



Pitchstone, 44, 49, 85, 89 



Placers, 232 



Plagioclase, 10, 12 



Plain-track of rivers, 417 



Plains of accumulation, 41 1 ; 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, 2 [9, 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, 1 34 



Quartz, 2 ; varieties of, 5 ; weathering 



of, 5 ; in crystalline igneous rocks, 



39; in clay, 12 1 ; -diorite, 48; 



-porphyry, 43, 85, 87, 88, 89, 379 J 



-schist, 76 ; -trachyte, 43 



Quartzite, 76, 84, 382 

 Quasi-bedded ores, 255 

 Quicksilver formations, 250, 266 



Radiolarian chert, 67 



Rain, action of, 370; -prints, 118; 



-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 moutonnees, 313 



Rock-beds, formation of, 104 



Rock-crystal, 5 



Rock, definition of, 32 



Rock-fall basins, 421 



Rock-flour, 311 



Rock-forming minerals, I 



Rock-guano, 7 2 



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 



