Chapter VII: The Origin and Descent of Rocks

+Composition of Igneous Rocks+ 395
Leading elements, 396. Union of elements, 397. Formation
of minerals, 397. Sources of complexity, 398. The leading
minerals of igneous rocks, 399. The feldspathic minerals,
400. The ferromagnesian minerals, 400. Summary of salient
facts, 401.

+The Nature of Molten Magmas+ 401
Time required in crystallization, 402. Successive stages of
crystallization, 403.

+The Fragmental Products of Sudden Cooling+ 404
Pyroclastic rocks, 404.

+The Glassy Rocks+ 406
The solid glasses. 406. The first stages of crystallization,
407. The obsidians, 407.

+Special Structures+ 410
Flow structure, 410. Amygdaloids, 411.

+The Porphyritic Rocks+ 411

+The Phanerocrystalline Rocks+ 412
The phanerites, 412. The granites, 413. The syenites,
415. The diorites, 416. The gabbros, 416. The peridotites,
416. The basalts, 417. The dolerites, 417. General
names, 418.

+Derivation of Secondary Rocks+ 420
Regolith, 422. Disrupted products: arkose and wacke, 422.
Disintegrated products, 422.
_Classes of Sedimentary Rocks_ 422
Shales, sandstones, and conglomerates, 422. Limestones and
dolomites, 424. Precipitates, 424. Iron-ore beds, 425.
Silicious deposits, 425. Organic rocks, 426.

+Internal Alterations of Rocks+ 426
Oxidation and deoxidation, 427. Solution and deposition,
427. Hydration and dehydration, 428. Carbonation and
decarbonation, 429. Molecular rearrangements, 431.
_The Salient Features of Rock Descent_ 431

+The Reascensional Process+ 432
Induration under ordinary pressures and temperatures, 432.
Cavity filling, 436. Fissure filling; veins, 437. Solution as
well as deposition, 437. Concretions, 438. Replacements and
pseudomorphs, 439. Incipient crystallization, 439.

+Reconstruction under Exceptional Conditions+ 440
Slaty structure, 441. Foliation, schistosity, 443.
Metamorphism by heat, 446. Metamorphism by heat and lateral
pressure, 448. Deep-seated metamorphism, 449. Completion of
the rock cycle, 449.

+Various Classifications and Nomenclatures+ 449
_New System of Classification and Nomenclature_ 451
_The Proposed Field System_ 451
The phanerites, 451. The aphanites, 452.

+The Proposed Quantitative System+ 454

+Reference List of the More Common Minerals+ 460

+Reference List of the More Common Rocks+ 467

+Ore Deposits+ 474
Concentration, 474. Exceptional and doubtful cases, 474.
Original distribution, 475. Magmatic segregation, 475. Marine
segregation and dispersion, 476. Origin of ore regions,
477. Surface residual concentration, 478. Purification
and concentration, 478. Concentration by solution and
reprecipitation, 479. Location of greatest solvent action,
480. Short-course action, 481. Long-course action, 481.
Summary, 483. The influence of contacts, 484. The effect of
igneous intrusions, 484. The influence of rock walls, 484.

CHAPTER VIII.

STRUCTURAL (GEOTECTONIC) GEOLOGY.

The structural phases which rocks assume, 486.

+Structural Features of Sedimentary Rocks+ 486
Stratification, 486. Lateral graduation, 488. Special
markings, 489. Concretionary structure, 490. Secretions, 497.

+Structural Features of Igneous Rocks+ 498

+Structural Features Arising From Disturbance+ 500

Inclination and folding of strata, 500. Joints, 510.
Sandstone dikes, 514. Faults, 514. The significance of
faults, 521. Effect of faulting on outcrops, 522.