LIST OF PLATES (AT END OF BOOK)

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Tourmaline crystals, growing amid feldspar crystals in a cavity in granite, from Paris, Me. 279

Plate 1.—Basal forms of the isometric system 311

Plate 2.—Basal forms of the tetragonal system. Basal forms of the orthorhombic system 312

Plate 3.—Basal forms of the monoclinic system. A cross section of the prism with its edges beveled so that a six-sided prism is formed (pseudo-hexagonal). Basal form of the triclinic system. 313

Plate 4.—Basal forms of the hexagonal system 314

Plate 5.—Gold in quartz from California (in color) 280

Plate 6.—Native silver in calcite. Argentite, the black masses throughout the white quartz (in color) 281

Plate 7.—Pyrargyrite as it appears after moderate exposure to the light; streak at left. Crystal form of pyrargyrite. Prousite as it appears after moderate exposure to the light; streak at left (in color) 282

Plate 8.—Native copper from Michigan. Chalcopyrite in tetrahedrons and an occasional octahedron; streak to the left (in color) 283

Plate 9.—Chalcocite crystals with the bluish tarnish. Tetrahedrite crystals; streak to left (in color) 284

Plate 10.—Tetrahedrons showing characteristic manner in which tetrahedrite occurs. A cube with the edges beveled and the corners cut in a form characteristic of cuprite 315

Plate 11.—Cuprite, the red crystals showing characteristic color, others showing the green tarnish of malachite. Malachite (green) and azurite (blue), the two minerals shown together as they very commonly occur (in color) 285

Plate 12.—Limonite. The crystal form in which goethite is found (in color) 286

Plate 13.—Hematite. Clinton iron ore, oolitic. Siderite crystals (in color) 287

Plate 14.—Crystal forms of hematite. A typical crystal of magnetite. The rhombohedron typical of siderite 317

Plate 15.—Pyrite crystals. Marcasite in concretionary form with radiate structure (in color) 288

Plate 16.—The pyritohedron. The pyritohedron with certain of its edges beveled by the cube faces, to show the relationship of these two forms 318

Plate 17.—Galena in crystals. Pyromorphite crystals (Green) (in color) 289

Plate 18.—Typical forms for cerrusite. Forms in which anglesite occurs 319

Plate 19.—Sphalerite, some the normal yellow and some crystals with the reddish tinge. (White is dolomite.) Zincite, streak to the left (in color) 290

Plate 20.—A characteristic form in which sphalerite may occur. Characteristic form for zincite crystals. Typical form of crystal of willemite 320

Plate 21.—Smithsonite in yellow crystals. Franklinite in octahedral crystals, streak to left (in color) 291

Plate 22.—Moss agates, showing the dendritic growth of manganitic minerals, like manganite or pyrolusite. Crystal form of manganite 321

Plate 23.—Crystals of green corundum in syenite, from Montana. Typical crystal forms of corundum 322

Plate 24.—Arsenopyrite, showing crystals massed so as to be incompletely developed. Realgar as it usually occurs in powdery incrustations (in color) 292

Plate 25.—Large crystals of stibnite; the light colored face is the one parallel to which cleavage occurs. Niccolite is a vein in slate (in color) 293

Plate 26.—Cobaltite, silver color, with pink tinge. Smaltite, pink is cobalt bloom (in color) 294

Plate 27.—Carnotite from Southwest Colorado. Cinnabar (in color) 295

Plate 28.—Cassiterite, twinned crystals. The crystal form in which both cassiterite and rutile occur when in simple crystals. Multiple twinning characteristic of rutile 323

Plate 29.—Crystal of spinel. Crystal forms in which dolomite occurs 324

Plate 30.—Two intergrowing or twinned quartz crystals. Diagram of the typical quartz crystal. A quartz crystal on which the left hand rhombohedron is represented by small faces, while the right hand rhombohedron has large faces 316

Plate 31.—Amethyst, not however deep enough colored for gems. Jasper, with botryoidal surface (in color) 296

Plate 32.—Banded agate from Brazil (in color) 297

Plate 33.—Common opal from Arizona. Siliceous sinter or geyserite from Yellowstone Park (in color) 298

Plate 34.—Orthoclase, a cleavage piece. Crystal forms of orthoclase. Diagram of a multiple twin of a plagioclase feldspar 325

Plate 35.—A group of microcline crystals from Pike’s Peak, Colo. Labradorite, showing multiple twinning (the striation) and the iridescent play of colors (in color) 299

Plate 36.—Crystal form of a pyroxene. Cross sections of a pyroxene crystal showing the lines of intersection of two cleavage planes. Cross sections of pyroxenes, showing typical forms taken by crystals. Augite crystals, in crystalline limestone (in color) 300

Plate 37.—Diagrams of amphibole crystals. Tremolite in silky fibrous crystals, asbestos. Hornblende crystals in quartzite 326

Plate 38.—The dodecahedron and the 24-sided figure characteristic of garnets. The garnet, grossularite. The garnet, alamandite (in color) 301

Plate 39.—Beryl of gem quality. Zircon in syenite (in color) 302

Plate 40.—Cyanite crystals in schist. A crystal of mica, showing basal cleavage (in color) 303

Plate 41.—Crystal form typical of topaz. A topaz crystal from Brazil. Crystal form typical of staurolite when simple. A typical twin of staurolite (in color) 304

Plate 42.—Epidote crystals. Typical forms of epidote crystals. Typical forms of tourmaline 327

Plate 43.—Serpentine. Chlorite (in color) 305

Plate 44.—The typical form of analcite. A typical natrolite crystal. The typical crystal form of stilbite. A sheaf-like bundle of fibrous crystals, typical of stilbite 329

Plate 45.—A group of calcite crystals. Typical forms of calcite 330

Plate 46.—Typical forms of aragonite. Typical form of the anhydrite crystal 331

Plate 47.—A piece of gypsum looking on the surface of the perfect cleavage, and showing the two other cleavages as lines, intersecting at 66°. Twinning is also shown. A simple crystal of gypsum. Twin crystals of gypsum. 332

Plate 48.—A group of barite crystals. Outline of the typical tabular barite crystal. The six-sided double pyramid, composed of three interpenetrating crystals, typical of witherite and strontianite 328

Plate 49.—Apatite crystals in crystalline calcite. The ends of apatite crystals showing common modes of termination (in color) 306

Plate 50.—A group of fluorite crystals. A group of halite crystals (in color) 307

Plate 51.—Sulphur crystals. Ice crystals, the top one, the end of a hexagonal prism; the two lower figures multiple twins as in snow flakes 333

Plate 52.—The Devil’s Tower, Wyoming, an example of igneous rock with columnar structure, and resting on sedimentary rocks 334

Courtesy of the U. S. Geological Survey

Plate 53.—A coarse granite. Graphic granite 335

Plate 54.—Syenite. Gabbro 336

Plate 55.—Basalt-porphyry. The large white crystals are phenocrysts of plagioclase feldspar. Basalt-obsidian 337

Plate 56.—Amgydoloid 338

Plate 57.—The north face of Scott’s Bluff, Neb., showing sedimentary sandstones above and clays below. The type of erosion is characteristic of arid regions 339

Courtesy of the U. S. Geological Survey

Plate 58.—Breccia. Conglomerate 340

Plate 59.—Calcareous shale. Coquina 341

Plate 60.—Foramenifera from chalk; enlarged about 25 diameters. Encrinal limestone; fragments of the stems, arms and body of crinoids 342

Plate 61.—Amber. Two bottles of petroleum, the left hand one with a paraffin base, the right hand one with an asphalt base (in color) 308

Plate 62.—Diatomaceous earth magnified 50 times. Two diatoms from the above enlarged 250 times 343

After Gravelle, by the courtesy of Natural History

Plate 63.—A metamorphic rock, showing the contortion of layers due to expansion under heat 344

Plate 64.—A conglomerate partly metamorphosed to a gneiss. A typical gneiss 345

Plate 65.—Mica schist, with garnets. Chlorite schist (in color) 309

Plate 66.—Phyllite. A white marble, with black streaks due to graphite 346

Plate 67.—Serpentine composed of serpentite, hematite, and some calcite (in color) 310

Plate 68.—Claystones, simple and compound. A lime concretion, which on splitting disclosed a fern leaf of the age of the coal measures 347

Plate 69.—A septeria from Seneca Lake, N. Y. Pisolite from Nevada 348

Plate 70.—A geode filled with quartz crystals 349

Plate 71.—A quartz pebble from the bed of a New England brook. A pebble of schist and granite from the foot of Mt. Toby, Mass. 350

Plate 72.—An iron-nickel meteorite, of 23 lbs., which fell in Claiborne Co., Tenn. An etched slice of an iron meteorite which fell in Reed City, Osceola, Co., Mich. 351

Plate 73.—A stone meteor, about natural size, which fell in 1875 in Iowa Co., Iowa 352

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