Economic geology, with special reference to the United States

Ries, Heinrich · 1910 · Historical

Economic geology, with special reference to the United States by Ries, Heinrich (1910). Full text and reference in the Mountain Man Mining Library.

Public-domain full text preserved in the Mountain Man Mining Library. Original source: archive.org.

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Economic Geology

With Special Reference To The United States

HEINRICH RIES, A.M., Ph.D.

Sew Amd Seyjsed Edition

The Macmillan Company

Ml right* ntanrni

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COPTUOBT, 1909, 1907, 1910, By the MACMILLAN COMPANY.

Sc< up ind dectiotyped. Publiihnl November, i;.

J.B.CasblngCa, — Berwlcfei Smith Co. HorwDod. Mu>., U.S.A.

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Preface

The f oUuniDg work on the Econotoic Geology of the United States coveis essentially the ground which is gone over in the eleraentaiy coarse in this subject in Cornell University, but it ia hoped that it vUl prove useful as a text-book in other colleges.

The mode of arrangement is markedly diSerent from that found in other books on the same subject, in that the non-metallic mate- rials are discussed first and the ore deposits laat. This, to the author, seems the most desirable method of treatment, for the reason that the non-metallics are not only the most important, the value of their production having exceeded the metallics by over one hun- dred and fifty million dollars in 1903, but also because it leads from a discussion of the simpler to the more complex forms of mineral deposits.

It has not been thought desirable to include a chapter on geologic and physiographic principles, since the space which could be allotted to it is altogether too small, and, moreover, the study of economic geology presupposes a knowledge of geology and mineralogy on the part of the student While the references given at the end of each chapter do not include every paper that has been written on the sub- ject to which they refer, still it is believed that they are sufficiently numerous to permit one to follow out the subject in considerable detail if he so desire.

[q the preparation of the manuscript all available sources of in- formation have been freely drawn upon, and the numbers in paren- theses in the text refer to the numbered references at the end of eah chapter.

All statistical figures, unless otherwise stated, are taken from the reports of the United States Geological Survey.

Descriptions of mineral occurrences in foreign countries are not included, except in a few cases where the deposits serve as an im- portant if not the only source of supply for the United States.

The writer wishes to express his thanks to Professor R. S. Tarr for examination and criticism of much of the manuscript, and to W. E. McCourt, Instructor in Geology, and H, Leighton, Assistant in Geology, for aid in the preparation of drawings and statistical

Vi PREFACE

tables. For the loan of photographs oi cuts acknowledgments are due to Messrs. H. F. Bain, J. R Spun, J. U. Boutwell, G. H. Eldridge, W. Lindgren, F. H. Oliphant, and J. H. Pratt of the United States Geological Survey ; Professor A. C. Lane, Michigan Geological Sur- vey ; Dr U. H. Newland, New York State Museiun ; Professor C. C. O'Harra, South Dakota School of Mines; Professor E. A. Smith, Alabama Geolccal Survey ; Professor G. H. Perkins, Vermont Geological Survey ; Dr. H. B. KUmmel, New Jersey Geological Survey; Dr. W. B. Phillips, Texas Geological Survey; Dr. G. P. Merrill, United States National Museum; also to Messrs. H. W. Turner, F. S. Witherbee, A. W. Sheafer, L. Martin, Wiley & Sons, Vermont Marble Co., and Bedford Quarries Co.

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Preface To The Second Edition

Thb publication of a second edition has become necessary in such & comparatirelj short time, that it has not been deemed advisable to materially alter the text. An attempt has, however, been made to correct all errors of which the author has knowledge. Recognizing the value of fresh statistics, those for 1905 (the most recent available), have been given in an appendix, and for the benefit of those who make ase of the bibliography, a second appendix has been included, cmtaiDing a list of the more important papers published since the appearance of the first edition.

COBIfBLC UhIVIBSITT,

Ithaca, H.Y., Nov. 10, 1908.

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Preface To The Third Edition

Although it is but little more than four years since the first edition of this work appeared, our knowledge of the subject of economic geology has expanded to such an extent, and so many [apera of importance have been published, that it was deemed advisable to make a somewhat complete revision of the book.

Id doing this the author has been guided partly by the dictates of hia own experience as a teacher of economic geology, and in part by the suggestions of other teachers who have found the work useful; to these persons the writer expresses his grateful acknowl- edgments.

While considerable matter of a general character dealing with tb principles of the subject has been added, a number of additional iescriptioua of individual occurrences have also been included, rithout abandoning the plan of giving the more important ones in (carser type.

As in earlier editions, the statistics given are in all cases taken from the Mineral Resources issued by the United States Geological Survey, except some for 190!*, which are from the Engineering and Mining Journal.

In the compilation of a mass of data from many scattered sources, such 83 has been involved in the preparation of this book, every reasonable attempt has been made to guard against errors, but it ia perhaps too much to hope that none have crept in.

The author takes pleasure in here acknowledging the efficient ind tireless aid which has been rendered him in the preparation of tliis edition by Mr. C. A. Stewart, Instructor in Economic Geology, Cornell University. Thanks are also due for the loan of photo- irraphs or cuts to: Mr, Donald Steel, Cornell University-, Mr. F. L. Uansome, United States Geological Survey ; Professor J. P. Kowe, Missoula, Mont ; Messrs. D. H. Newland and H. Leighton, New York Oeoiogical Survey ; Professor S. W. McCallie, Georgia Geological Survey; Dr. H. B. KUmmel, New Jersey Geological Survey; The liarber Asphalt Company, Philadelphia, Fa.; and the Pike Manu- tsi'tnring Company, Pike Station, N.H.

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Priface V

COHTBMTB Zi

List of iLLUBTBATiONa xxi

List or ABBBKViATtom xxxii

Part I

Nok-Metallw Minsbalb

Chapter I

Coal 1-49

Kind* of coal, 1; Peat, 1; Lignite, 2; SubJiilomiiious coal or black lignite, 2; Bituminous ooal, S; Cannel coal, 3; 8emi- bitaminons coal, 3; Semi-anthracite coal, 3; Anthracite coal, 8; Carbonite or natural coke, 4; Proximate analysis of coal, 4 j Ori- gin of coal, 7; Conditions of vegetable accumulation, 7; Char- acter of organisms forming coal, 6 ; Conditions of decomposition, 9; ClaeaiGcation of coals, 13; Structural features of coal beds, 16; OuteTops, 16; Associated rocks, IG; Variations in thickness, 16; Other irregularities, 17; Weathering of coals, IS; Coal fields of the United States, 18; Geologic distribution in the United States, 19; Estimated tonnage of the various fields, 19; Appalachian field, 20; FennsylTania anthracite field, 22; Appalachian bitumi- nous area, 24; Peonsjlvania, 24; Ohio, 25; Maryland, 25; West Tiinia, 25; Virginia, 3Q; Southern Appalachian field, 26; Eastern Interior field, 27; Northern Interior field, 29; Western Interior and Southwestern fields, 80; Western Interior field, 30; Southwestern field, 32 ; Rocky UounUin fields, 82 ; Gulf Province lignites, 34; Pacific Coast fields, 34; Alaska, 36; Production of coal, 37; Price per ton, 40; Exports and imports, 40 ; Peat, 43; Origin, 43; Uses of peat, 45; Distribution in the United States, 45 ; Production of peat, 40 ; Kefereuces on coal, 46 ; Befereocea on peat, 49.

CHAPTER n

Petboi-idm, Natural Gas, and Otber Htdrocarbons . 60-100

Introductory, 60; Properties of petroleum, 50; Properties of

natural gas, b2 ; Origin of oil and gas, 68 ; Inorganic theories, 69 ;

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Volcanic theory, 60; Organic theory, 60; Mode of Pressure of oil aud gas in wells, Oi; Mode of accumulation, 63; Life of a well, S7 ; Distributioii of petroleum in the United States, S8; Appalachian field, 68; Ohio-Indiana field, 71 ; Illinois field, 74; Mid-continental field, 75; California, 75; Texas-Louisiana oil fields, 77 ; Colorado, 7B ; Wyoming, 80 ; Alaska, 81 ; Summary, 81; Distribution of natural gas in the United States, 83; New York, 83; Penngylvania, 83 ; West Virginia, 83 ; Ohio, 83; Indi- ana, 64 ; Kansaa, 84 ; Uses of petroleum, 84 ; Uses of natural gas, 84; Solid and semi-solid bitumens, 85 ; Vein bitumens, 85; Alber- tite, 86; Anthraiolite, 86 ; Ozokerite, 86; Grnhamite, 86; Lake asphalt, 88; Manjak,88; Uintaite or Gilaonit, 83 ; Maltha, 89; Bituminous rocks, 00; Oil shales, 90; Origin of solid bitumens and bituminous rocks, 91 ; Uses of nnphalts, 92 ; Production of petroleum and natural gas, 92 ; Production of asphalt and bitu- minous rock, SO; Ibferencea on petroleum, 88; References on natural gas, 99 ; References on oil shales, 100; References on solid and semi-flolid bitumens, 100.

CHAPTER m

Building Stones 101-123

Properties of building stones, 101; Color, 101; Teiture, 102; Density, 102; Hardness, 103 ; Strength, 104; Porosity and ratio of absorption, 105; Resistance to frost, 106; Resistance to heat, 106; Chemical coniposition, 106; Life of a building stone, 106; Structural features affecting quarrying, 107; Granites, 107; Char- acteristics of granites, 107 ; Distribution of granites in the United States, 108; Eastern crystalline belt, lOH; Minnesota-Wisoonsin area, 109; Southwestern area, 109; Western states, 110; Uses of granite, 110; Miscellaneous igneous rocks. 110; Limestones and marbles. 111 ; Varieties of lime.stone. III: Distribution of lim&- stone in the United States, 112; Distribution of marbles in the United States, 113; Onyx marbles, 114; Uses of limestones and marbles, 115; Serpentine, 115; Sandstones, 110; General proper- ties, 116; Varieties of sandstone, 117; Distribution of sandstone in the United States, 117; Uses of sandstones, 118; Slates, 118; Distribution of slates in the United States, 119; Uses of slate, 120; Production of building stones, 120: References on building stoues, 122 ; References on onyx marble, 123.

Chapter Iv

Clat 124-138

Definition, 124; Residua] clays, 124: Tron-iported clays, 125; Marine clays, 125; Flood-plain clays, 125; Lake clays, 125; Gla-

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cil clays, 126 ; JEolian claya, 128 ; Properties of clay, 126 ; Physi- cal properties, 126; Plasticity, 126; Tensile strength, 126 Shrinkage, 126; Fusibility, 126; Specific gravity, 127; Chemical properties, 127; Chemical composition, 128; Classification of clay, 128; Kinds of clays, 130; Geological distribution, 180; Distribu- tioQof clays by kinds, 181; Kaolins, 131; Fire clays, 132 ; Pottery clays, 183; Brick and tile clays, 134 ; Miscellaneous clays of im- portance, 131; Uses of clay, 134; Production of clay and clay products, 135; References on clay, 136.

Chapter V

LuE AKi> Calcareous Cembnts 189-1B7

Composition of limestones, 139; Changesin burning, 140; Lime, 140; Hydraulic cements, 140; Pozzuolan cement, 140; Hydraulic limes, 141 ; Natural rock cements, 142; Portland cement, 143; Distribution of lime and cement materials ia the United States, 145; Limestone for lime, 145; Hydraulic limes, 146; N'atural rock cements, 14fi; New York, 148; Other states, 147; Portland cements, 148 ; Pennsylvania, 149 ; Other states, 152 ; Uses of lime, 153; Uses of cement, 153; Production of cement, 151 ; References on lime and cement materials, 158.

Chapter Vi

Salines and Associated Substances 158-17?

Salt, 158; Types of occurrence, 158 ; Occurreuces of salt in sea and lake waters, 158; Rock salt, 159; Origia of rock salt, 169; Evaporation theory, 159; Bar theory, 160; Dome theory, 181; Natural brines, 162 ; Salt marshes and soils, 1 82 ; Distribution of salt in the United States, 162; New York, 163; Michigan, 163; Ohio, 163; Virginia, 165; West Virginia, 165; Kansas, 166; Ijouisiana, 166; Other western states, 187; Analyses of salt, 188; Extraction, 168; Uses, 168; Production of salt, 169; References onHalM70; Bromine, 171; Sources,171; Uses, 171 ; Production of bromine, 171 ; References on bromine, 172; Sodium sulphate, 172 ; Occurrence and distribution, 172 ; References on sodium sulphate, 172; Sodium carbonate, 173 ; Referenceson sodium carbonate,178; Soda niter, 173; References on soda niter, 173; Borax, 174; Dis- tribution in the United States, 174 ; Uses, 176 ; Production of borax, 176; References on borax, 176; Iodine, 177; Sources, 177; Beferences on iodine, 177.

CHAPTER Vn

GvpsuM 178-186

Properties and occurrence, 178; Anhydrite, 178; Impurities in gypmm, 179 ; Origin of gypsum, 179 ; Gypsite, 179 ; Distribution

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ID the United States, ISO ; New Yoi, 18] ; Michigan, 181 ; Iowa, 181; KanaaB,181i Virginia, 183 ; Other occurrences, 183 ; AnaJjses ol gypeum, 183 ; UBeB,184; Calcining gypanm, 184 ; Production of gypsum, 186; Beferences on gypsom, 186.

CHAPTER Vm

Fkrtilizerb 187-200

Phoephate of lime, 187 ; Apatite, 187 ; AmorphouB phoephates.

188; Florida, 188; Origin, 188; South Carolina, 190; 190; Wyoming-Idaho-Utah.lOa; Arkansas, 195; Other phosphate occurrences, 195; Analyaeeof phoaphates, 196; GuAno,190; Gieen- saud,197; Uses, 197; Production of fertiliMrs, 197; Ezportaandim- pOTt 199 ; World's production, 109 ; Beferencea on fertilizers, 200.

Chapter Ix

Abrasives 201-210

lutroductory, 201; Millstones and buhratoaes, 202 ; Whetatones, oilstones, 202 ; Pumice and volcanic ash, 201; Diatomoceous earth, aO*; Tripoli, 205; CrystaUine quartz, 205; Feldspar, 206 ; Garnet, 20S; New York, 205; Uses, 205; Corundum and emery, 200; Corundum, 209; Distribution, 207; Emery, 208; Diamonds, 208; Artificial abrasives, 209; Production of abruives, 208 ; Referenoes on abrasives, 209.

Chapter X

UlKOR MiNKBALS — ASBBSTOS 211-240

Asbestos minerals, 211; Dietribntion in United States, 212; Vermont, 212; Georgia, 212; Viinia, 213; Western occurrences, 214; Quebec, Canada, 214; Uses of asbestos, 216; Production of asbestos, 218; Keferences on asbestos, 217; Barite, 217; Proper- ties and occurrence, 217; Minouri, 218; Virginia, 218; Georgia, 220; Other occurreuoes, 220; Origin of faarite, 220; Uses, 221; Production of barite, 221; Imports, 222; References on barite, 223; Diatomaceous earth, 222; Properties and occurrence, 222; Distribution in the United States, 223; California, 228; New Tork, 324 ; yigini 224 ; Maryland, 224 ; Other states, 224 ; UBes224; References on diatomaceous earth, 224 ; Feldspar, 225 ; Properties and occurrence, 235 ; Distribution of feldspar in the United States, 326; Analyses of feldspars, 228; Uses, 227; Pro- duction of feldspar, 227 ; References ou feldspar, 228; Fluorspar, 228; Distribution in the United States, 238; Kentucky, 228; Illinois; 229; Colorado, 230; Other states, 230; Imports, 230; Analyses of fliiornpar, 231; Uses, 331; Production of fluorspar, 231; References on fluorspar, 332; Foundry sauds, 232; Defini-

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tion, 232 ; Requisite propertieB, S38 ; Dietributioa in the United Stotes, 2a&; Referencea on foundry Bands, 295; Fuller's earth, 233; Properties, 285; Distribution in the United States, 286; Production of filler's earth, 2dS; Refeienoes on fuller's earth, 237 ; Glass sand, 237 ; Chemical conpouUon, 287 ; Physical prop- erties, 238 ; Distribution of glass sand, 289 i. Production of glaa sand, 240; Beferences on glass sand, 240.

CHAPTER XI MiNOB MuTEBALB — Graphite, MotiAZiTK - . . . 241-264

Graphite, 241 ; Properties and occurrence, 241 ; DistributioD of gtftpbite in the United States, 24S ; New Toric, 242 ; Rhode Islaud, 24S; FenusylTania, 248 ; Alabama, 243 ; New Mexico, 243; Otber itstes, 243; Origin of graphite, 243; Uses, 214; Production of graphite, 245; References on graphite, 246; Lithium, 240; Lithographic stone, 247 ; Properties, 247 ; Sources of supply, 247 ; References on lithographic stones, 218; Magnesite, 248; Propei ties and occurrence, 248; California, 248; Analyses of magnesite, 250; Uses, 250; Productiott of magnesite in United States, S51; References on magnesite, 251; Meerschaum, 251; Meer- schaum oi sepiolito, 251 ; Aualyses o£ meerschaum, 252 ; Refer- ences on meerschaum, 252 ; Mica, 252 ; Properties and occurrence 252; Distribution in the United States, 253; North Carolina, 253; Soutt) Dakota, 254; Other states, 254; Uses of mica, 256; Pro- duction of mica, 355; References on mica, 266; Mineral paints, 256 ; Hematite, 257 ; Debars, 257 ; Properties and occurrence, 267 ; Distribution of ocher, 258; Georgia, 258; Pennaylvania, 259; Siderite, 260; Slate and shale, 260; Gypsum, 261; Barite, 261; Asbestos, 261 ; Graphite, 261 ; Calcium carbonate, 231 ; Other paints, 261; Production of mineral paints, 261; References on mineral paints, 262; Monazite, 262; Properties and occurrence, 3S2; Uses, 264; Production of monazite, 264; References on monazite, 234.

CHAPTER Xn

PaecioiTs Stones — Wavellite 265-292

Precious stones, 265; Diamond, 265; Emerald, 267; Garnet, 267; Opal, 268; Peridot, 268; Ruby, 268; Sapphire, 269 ; Spodu- mene, Kunzite, 269; Topaz, 269; Tourmaline, 270; Turquoise, 270; Tariscite, 270; Production of precious atones in the United SUtes in 1906, 1007, and 1908, 272 ; Production of precious stones, 373; References on precious stones, 273 ; Quartz, 274 ; Vein quartz, 274; Quartiite, 274; Flint or chert, 274 ; Uses of quartz, 275; Pro- duction of quartz, 275 ; References on quartz, 275 ; Strontium, 275 ;

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Sources and occurrence, 275; Usea,276; References on Btrontium, 278; Sulphur and pyrite, 270; Sulphur, 276; Sol fataric type. 276; Miaeral Bprings deposits, 270; Gypsum type, 277; Metallic sulphide type, 277 ; DiatributioD of sulphur in tli United Stata, 277; Louisiiinft,277; Utah, 278; Wyoming. 278; Other states, 279; Uses of sulphur, 278; Production of sulphur, 2tiO; Referencee on sulphur, 21 ; Pyrite, 281 ; Properties aud occurrences, 281 ; Distribution in the United , 282; Virginia, 282; New York, 283; Massachusetts. 283; Other sUtes. 283 ; Uses of pyrite, 2S4; Production of pyrite. 284 ; Imports, 284 ; World's production, 2S4 ; References on pyrite, 2SJ ; Talc and soapstone, 280 ; Properties and occurreiice, 28*; Soapstone, 280; Distribution in the United State3,286; Virginia, 280 ; New York, 287; North Carolioa.2H7; VermonI, 238; New Jersey, 288; Uses, 288; Pyrophyllite, 280; Production of talc and soapstone. 289 ; References on talc and soapstone, 289; Tripoli, 290; Propertiea and occurrence, 200; Uses, 291 ; References on tripoli, 291 ; Wavellite, 291 ; References on wavellite, 292.

Chapter Xiii

UNDKRGROtSD Waters 293-TOI

Ground water, 293; Artesian water, 294; Stratified beds, 295; Crystalline rocks, 296 ; References on underground waters, 207 ; Mineral waters, 298 ; Distribution of mineral waters in the United States, 299; Analyses of American mineral waUra, 300; Production of mineral waters, 300; References on mineral waters,

Part Ii

Obe Deposits

Chapter Xiv

Ore Deposits . . 305-348

Definition, 305; Gangue minerals, 305; Origin of ore bodies, 306; Syngeuetic deposits, 306; Magmatic segregations, 300; Form , of magmatic bodies, 307; Syngenetic deposits of sediihentary origin, 307; Interstratified sedimentary deiosits, 308; Placer de- posits, 308; Epigenetic ore deposits, 309; Occurrence of metals in the rocks, 309; Mode of concentration, 311; Meteoric waters as collecting agents, 313 ; Magmatic waters as concentrating agenta, 310; DeposiLs from roagmafic emanatioua, 317; Tin and apatite veins, 319; Con tact-met amorphic deposits, 310; Gold and silver- bearing veins, 322; Ore deposits formed at shallow depths, 322 ;

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MiDcral deposits formed &t the sarfsoe by hot waters, 33S ; Forma- tion of cavities, 323 ; Deposition oi ore in open cavities, 321 ; Precipitation of metals from solution, 324 ; Other causes of pre- cipitation, 32S ; Replacement or metasomatism, 825; Forme of ore bodies, 828; Fissnre veins, 329 ; Linked veins, 331; Gash veins, 332 ; Bedded vein, 332 ; Filling of fissure veins, 332 ; Other forms of ore deposits, 332 ; Ore shoots, 333 ; Secondary changes in ore deposits, 334; Weathering or superficial alteration, 335; Second- ary depoffltion below gronnd-water level, 33B ; Reactions involved, 33S; Value of ores, 339 ; Allowable minimum of metal in an ore, 339; Classification of ore deposits, 340; Uetallogenetic epochs, 342; Fre<anibrian period, 342; Paleozoic, 343; Mesozoic, 348; Early Tertiary, 344 ; Lat Tertiary, 344 ; Post-Plioceoe, 345 ; Cre- taceous or later copper epochs, 346; Summary, 845; Beferences OS ore deposits, 345.

Chapter Xv

IttOK Okks 349-:

Iron-ore minerals, 849; Clascation, 850; Magnetite, 351; Distribution of magnetites in the United States, 352 ; Non-titan- iferouB mtnetites, 853 ; Adirondack region, New York, 352 ; Uineville, N.Y., 364; New Jersey, 355; Origin of magnetites, 358; Cornwall, Pa., 357; Other occurrences, 358 ; Iron Springe, Ctah, 359 ; Analyses of mnetite, 301 ; Titaniferous magnetites, 361; New York, 362; Wyoming, 363; Magnetite sands, 34; Hematite, 334 ; Distribution of hematite ores in the United Stetes, 384; Lake Superior region, 384; Character of formations, 385; Marquette range, 367 ; Menominee range, 368 ; Penokee-Gogebic range, 388; Mesabi range, 868; Vermilion range, 389; Cuyuna range, 369; Origin, 389; Wyoming, 371; Clinton ore, 372; Birmingham, Ala., 375 ; New York, 376; Analyses of Clinton ore, 377; Origin of Clinton ore, 378; Residual enrichment, 378 ; Sedi- mentary origin, 378; Replacement theory, 379; Limonite, 879; Residual limonites, 381 ; Gossan deposits, 381 ; Limouitea in re- sidual clays, 382; Origin of the Cambro-Siturian limonites, 383; Oriskany limonites, 384; Other limonite deposits, 384; Siderite, 385 ; Production of iron ores, 385 ; Iron-ore reserves, 390 ; Refer-

Chapter Xvi

Coprm 395-425

Ore minerals of copper, 895 ; Gangue minerals, 896 ; Superficial alteration of copper ores, 397 ; Distribution of copper ores in the United States, 397; Montana, 898; Michigan, 402 ; Arizona, 406 ;

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BisbM or Wamn district, 407 ; Clifton-Moranct district, 409 ; Globe district, 412 ; Jerome district, ilSi'Mineral Creek district, 413; Bingham Cofioo, Utah, 413; Elj, Sev., 415; Appalachian atatee, 417; California, 419; Other occurrences, 419; Alaska, 420; Ketchikan district, 420; Kotsinahitina region, 420; Prince William Sound district, 420 ; Uses of copper, 421 ; Production of copper, 422 ; Copper reserves, 423 ; Referen(s on copper, 424.

Chaptek Xvii

Lead akd Zimc 426-457

Ore minerals of zinc, 426 ; Ore minerab of lead, 427 ; Mode of

occurrence, 427 ; Superficial alteration of lead and ziec oreii, 428 ; Distribution of lead and zinc ores iu the United States, 428 ; Lead alone, 429; Appalachian belt, 429; Southeastern Missouri, 429; DesilTerized lead, 431 ; Zinc ores, 432 ; Eastern and southern stateg, 432 J Sussex Countj, N. 432; Virginia-Tennessee belt, 4S5 ; Pennsjlvania, 436 ; Mississippi Valley lead and zinc region, 436 ; Oiark region, 438 ; Joplin area, 437 ; Origin of the ores, 440 Centrnl Missouri district, 443; Northern Arkansas district, 443. Upper Mississippi Valley, 443; Rocky Mountain states, 446; Leadville district, Colo., 446; Other Western Uses of lead and zinc, 4S1 ; Uses of lead, 451 ; Uses of Production of lead and zinc, 453 ; References on lead and zinc, 456.

Chapter Xviii

Silvbb-Lead Oekb 458-467

Cteur d'Alene, Ido., 458 ; Origin of ores, 481 ; Aspen, Colo 461 ; Rico, Dolores County, Colo., 463 ; Other Colorado occurrences, 464 ; Park City, Utoh, 464 ; Tintic district, Utah. 466 ; Montana and Nevada, et., 467 ; Beferences on silver-lead ores, 467.

Chapter Xix

Gold and Silveb 468-615

Ore minerals of gold, 468 ; Ore minerals of silver, 468 ; Mode of occurrence, 469; Weathering and secondary enrichment, 470; Geological distribution, 470 ; Classification, 471 ; Extraction, 472 ; Distribution of gold and silver ores, 473; Cordilleran region, 474 ; Pacific const, Cretaceous gold-quarta ores, 474 ; Mother Lode belt, 476 J Nevada County, 477 ; Late Cretaceous or Eariy Tertiary deposits, 478; Mercur, Utah, 479; Other occurrences, 479; East- em belt of Tertiary gold-silver veins, 480 ; Cripple Creek, 481 ; San Juan region, Colo., 484; Telluride quadrangle, 485; Silverton quadrangle, 486; Ouray quadrangle, 487; Fissure veins, 488; Quartzite replacements, 488; Limestone replacements, 488 j

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Georgetown, Colo., 438; Goldfield, ., 190; Origin, 192; To- nopali, Nev., 4S3 ; Comstock Lode, NeT., 494 ; Other occunenom, 195; Aoriieroua gravels, 40G; Bl&ck Hills tegioQ, 406; Home- lUke belt, 498; Siliceous Cambriaa ores, 499; Michigan region, SOD; Eastern cryslsUine belt, 500; AhMka,601; Auriferous lodes, S02 ; Placer deporits, 503 ; Uses of gold, 505 ; Uses of BiWer, 506 ; Production of gold and silver, fiOS ; World's prodnotion, 509 ; Gold and silver reserves, 612 ; Beferenoes on gold and silver, 612.

CHAPTER XX llctOK MiTAX: ALnHiHCH, Manoakese, Mercdkt . 516-687

Aluminum, 516; Ores, 516; Distribution of bauxite in the United SUtes, 51B ; Georgia- Alabama, 510 ; Arkansas, 61S ; Wil- kinson County, Ga., 519 ; Tennessee field, G19 ; Other occurrences, 520; Usesof aluminam, 520; Uses of bauxite, 620; Production of bauxite, 521 ; World's production, 521 ; Referencea on aluminum and bauxite, 522; Manganese, 522; Ore minerals and ores, 62S; Origin, 524 ; Distribution of [nanganese-bearing oree in the United States, 624; Manganese ores, 524; Eastern area, 524; Virginia, 924; Georgia, 526 ; Other Eastern occurrences, 527 ; Lower MissiaBippi Valley and Gulf region, 627 ; Arkansas, 627 ; Other occurrences, 528; Western states, 628; Manganiferous iron ores, 52S; Man- ganiferons silver ores, 528; Usesof manganese, 629; Production of manganese, 529; World's production, 681; References on tnsnganea 532; Mercury, 682; Ores, 582; Mode of occurrence, 532; Distribution in the United States, 632; Origin, 532; Cali- fornia, 533; Texas, 584; Uses of meicuiy, 535; Frodnction of mercury, 636 ; References on mercury, 687.

CHAPTER XXI MiFOB MKTAi-e (continued) : AirxiMOifT to Vanadiuii . SSS-fiCS

Antimony, 538; Ore minerals, 588; Distribution of antimony in the United States, 588 ; Uses, 589 ; Production of antimony, 689 ; References on antimony, 640; Arsenic, 540; Ore minerals, 540; Distribution in the United States, 540 ; Uses of arsenic, 641 ; Pro- dnetioD of arsenic, 641 ; References on arsenic, 542 ; Bismuth, 542 ; Ore minerals, 642 ; Distribution, 542 ; Uses of bismuth, 642 ; Pro- duction, 643 ; References on bismuth, 643 ; Cadmium, 543 ; Uses cadmium, 548; Refereiicea on cadmium, 544; Chromic iron ore, 544; Ore minerals, 544; Origin of chromite, 544; Analyses, 645; Distribution in the United States, 645 ; Uses, 546 ; Production of chromite, 546; References on chromic iron ore, 647; Molybde- nnm, 547 ; Ores and occurrences, 647 ; Uses, 647 ; ftoductiou of molybdennm, 647; References on molybdenum, 547 ; Niokel and

cobalt, 546 ; Ore minerals, M6 ; Distribation, 548 ; Hissoari, 548 ; Eastern occnrrenoes oi niokel, 549 j Western occarrenoes, 549; Canadian occurrences, 549 ; Sudbury, Out., 650 ; Cobalt, Ont, 652; Uses of niokel, 654; Uses oE cobalt, 554; Production, 554; References on nickel and cobait, 655; Platinnm group of metals, 665 ; Flstmum, 665 ; Distribution in the United States, 555 ; Ubbb, 556; References on platinum, 55Q ; Palladitim, 65Ti Osmium, 557; Iridium, 567 ; Selenium, 557 ; Uses, 557 ; References on selenium, 558; Tantalum, 558; References on tantalum, 658; Tellarinm, 658 ; Tin, 656 ; Ore minerals, 656 ; Mode of occurrence, 559 ; Casuterite veins, 559; Ca3siterit dikes, 65S; Placer deposits, 569; Distribution of tin ores iu the United Stats, 560; North Carolina and South Carolina, 660; South Dakota and Wyoming, 660 ; Alaska, 661 ; Uses of tin, 501 ; Production of tin, 561 ; Ref- erences on tin, 662 ; Titanium, 563 ; Ores, 663 ; Occurrence, 663 ; Uses, 603; References on titanium, 663; Tungsten, 568; Ore minerals, 563 ; Distribution in the United States, 604 ; Colorado, 504; Arizona, 664; California, 504; Nevada, 604; South Dakota, 604; Uses of tungsten, 564 ; Production, 565; References on - sten,-505; Uranium, 566; Uses, 600; Vanadium, 660; Uses, 566; Referenoas on uranium and TUnadium, 567.

b,

List Of Illustrations

1. Diagnm showing changes oocamng in passage of vegetable tissue

to graphite 12

2. Section in Coal MetMores of western Pennyalvania, showing fire claj

under coal beds 16

3. SeetioD showing irregalarities in coal seam. a. split; b. parting

of shale ; e. pinch ; d. swell ; e. cut out 17

1. Section of faulted coal seam 17

5. Section across Coosa, Ala., coal field, showing folding and faulting

chancteristic of southern end of Appalachian coal field SI

1 Map of Pennsylvania anthracite field 22

7. Sections in Pennsylvania anthracite field 23

S. Coal breaker in Pennsylvania anthracite region 24 9. Structure section in Tazewell County, east of Richlands, southwest

Virginia coal field 26

10. General structure section of the Richmond basin in the vicini

of the James River 27

11. Section across Eastern Interior coal field 28

12. Shaft bouse and tipple, bituminous coal mine, Spring Valley, 111. 29

13. Generalized section of Northern Interior coal field ... 30

14. Composite section showing structure of Lower Cool Measures of

Iowa 80

15. Columnar section of coal-bearing rocks in Oklahoma coal field . 31

18. Generalized columnar section of the coal-bearing rocks of Ar-

kansas 32

17. Index map of Colorado coal fields 34

K Geologic seetionB (northwest-southeast) in southeastern part of

Anthracite, Colo sheet 36

19. Map of Alaska, showingdistrihution of coal and coal-bearing rocks,

so far as known 36

20. Yearly prodnction of anthracite and bituminous coal from 1856 to

1W8, in short tons .38

21. Digram showing bow plants fill depressions from the sides and

top, to form a peat deposit 43

il. Section of anticlinal fold, showing accumulation of gas, oil, and

water 62

23. Showing positions and vertical sections of wells southeast of

Humboldt, Kas., and differing thickness and number of sands

in neighboring wells 68

iv,Coog[c

Ust Of Illustrations

24. Sections of deep wella in the ClajriUe, Pa., quadmogle, BhowiDg

irregularity in tliickneas and number of the oil and gas sanda . 64

25. Map sbowing lines of sections in Plate Vll 69

Se. Diagrammatic section of sands in the central Appalachiaa region 70

27. Geological section of Ohio-Indiana oil and gas fields ... 71

28. Map showing approximate area of oil fields in southeastern

Illinois 74

2d. Index map of a portion of Southern California, showing location

of oil fields 76

80. North-south section, sbowing structure of western field of Los

Angeles district 77

3L Section of Spindle Top oil field near Beanmout, Tex. ... 77 82. Generalized section from Paleozoic outcrop in Arkansas tbrougb

Caddo oil field, and Sour Lake to Galveston, Tex. ... 78 ftS. Map of Wyoming, showing approximately the areas underlain by

oil and gaa 80

84. Section across portion of oil district of sonthwestern Wyoming 80

86. Map of Alaska, showing areas in which oil or gaa are known to

occur 81

88. Map of asphalt and bituminous rock deposits of the Uuited Slates 85

87. Map showing relation of grahamite fissure to anticlinal fold, in

Ritchie County, W. Ta. 87

88. Plan of Trinidad pitch lake 83

39. Section of gilsonite rein, Utah 88

40. Gilsonite mine at Dragon, Utah 89

41. Chart of oil production 93

42. Photo-micrograph of a section of granite 102

48. Photo -micrograph of a section of diabase 103

44. Photomicrograph of a aectioa of quartzitic sandstone . . . 105

45. Map showing distribution of crystalline rocks (mainly granites)

in United States 109

46. showing marble areas of eastern United States . 118

47. Section showing cleavage and bedding in 8tat . . . .118

48. Section in slate quarry with cleave parallel to bedding , 119

49. Map showing distribution of slate in the United States . . 120

50. Section showing formation of residual clay 124

51. Section of a sedimentary clay deposit 125

52. Geologic map through the VUghtberg at Roudout, N. Y. . 148

63. Geologic sections through the Vlightberg, showing position of

natural rock cement beds 149

64. Section in cement quarries at Utica, III. 148

55. Map of cement belt of eastern Pennsylvania 160

56. Diagrammatic section two miles long extending northwest from

Martin's Creek, N. J., showing overturned folds 161

57. Diagrammatic section five miles long, extending northwest from

Catasauqua 151

b,

LIST OP ILLUSTRATIONS xxiii

58. Map of Uoited States, showing locatton of mmeDt plants . . 103

59. Chart showing production of Portland and natural oeroento,

1800 to 1908 159

60. Figures representing the origin of dome structure by crystalline

growth 161

SI. Map showing distribotion of salt-producii areas in the United

SUtes 162

12. Section showing number and thtckuess of salt beds at different

localities in New York state 164

S3. Section across Ilolston and Saltrille valleys, midway between Salt-

Tille and Ptastrco, Va. 165

M. Geologic section from Arkansas City to Great Bend, Kos., showing

occurrence of rock salt 166

So. Map showing location of Petit Anse and other salt islands,

Louisiana . 166

66. Section illustrating dome salt occurrence, under Cedar Lick, La. 167

ST. Sketch map of California borax localities 171

68. Cross section of Furnace Caaon, Calif., borate deposits . 175

69. Map showing gypsum -producing localities of the United States 180

70. Map of New York, showing outcrop of gypsum-bearing formations 181

71. Section in gypsum deposit at Linden, N. Y 181

T2. Map of Florida phosphate deposits 188

73. Map showing distribution of phosphates in Tennessee . 190

74. Vertical section showing geologic position of Tennessee phos-

phates . . 191

75. Map of parts of Idaho, Wyoming, and Utah, showing localities of

Upper Carboniferous rocks containing phosphate beds 192

76. Section of Carboniferous strata on north Kde of Montpelier

Creek, Ido 193

77. Map of portion of LafFerty Creek, Ark., phoephat district, show-

ing position of phosphate outcrops 194

78. Section in La&er Creek, Ark., phosphate district 194

79. Map showing distribution of abrasives in United States 201 SO. Kortfa-eonth section through Missouri and Statehouse Mountains,

diowing folded character of novaculite and slata-bearing forma- tions of Arkansas 203

61. Volcanic ash from Madison Connty, Mont 204

82. Section showing occorcence of corundum aronnd border of dnnit

mass 207

8-3. Asbestos vein in serpentine 312

Si, Geologic map of Vermont asbestos area 213

So. Hap of Quebec asbestos area 214

86. Diagram showing asbestos and serpentine in peridotite . . 215

87. Barite veins in Fotoei dolomite, southeastern Missouri .. . 218

88. Barite deposit in residual clay near Mineral Point, Mo. . . 318 89- Hap of Viinia, showing location of worked areas of barita

Iv,

List Of Illustrations

DO. Ideal section in Bennett bant mine, ;tvani& Connty, Va. . 219

91. Sketch section shoning relations of l>arite and limonite to under-

lying fonnations near Cartersrille, Ga 220

92. DiatomaceouB earth from Loinpoc, CalU 222

98. Section of Memphis mine group, along line SA" of PI, xivii , , 229

94. Map of California, showing distribution of magnesite deposits . 249

95. Plan of magnesite veins and workings four miles nortbeaat of Por-

terville, Calif 248

96. Map showing areas in North Carolina in which mica has been

rained 253

97. Section across pegmatite at Thorn Mountain mine, Macon Co.,

N. C 254

98. Generalized cross section of No. 1 or New York Mine, near Cus-

ter, S. D 254

BS. Section showing relations of ocher, quartzite, and clay, near

CartersTille, Ga. 258

100. Map showing area of monazite deposits of known coniraetcial

value in southern Appalachian region 263

101. Map of Arkansas diamond area 266

102. Section showing stratigraphy and stmctnTe from crest of Owl

Creek Mountains to Owl Creek, and relations of sulphur de- posits near Thermopolis, Wyo 279

103. Plan of pyrite lenses at Sulphur Mines, Louisa County, Ya., show-

ing pyrite (a) and crystalline schists (£) 283

lOi. Plan of pyrite lens (a), showing stringers of pyrite, iiiterteaved

with schiste (6) on hanging wall 282

106. Ideal section across a river valley, showing the position of ground

water and the undulations of the water table with reference to

the surface of the ground and bed rock 203

106. Section showing effect of tide on level of water tabic . . . 294

107. Geologic section of Atlantic coastal plain, showing water-bearii

horizons 290

108. Section from Black Hills across South Dakota, showing artesian

well conditions 298

109. A. Ideal horizontal section, and B. Ideal vertical section, of the

flow of underground water through a homieneons medium from one well to another 314

110. Ideal vertical section of flow through a homogeneous medium.

A. Water entering at many points along a slope and issuing at a single point of lower elevation. B. Water entering at a number of points on a slope, and passing to a valley below, interrupted by two open vertical channels 315

111. Diagram illustrating the relations of the various types of ore

deposits directly derived from igneous rocks 320

112. Photo-micrograph of a section of quartz conglomerate, showing

replacement of quartz by pyrite 327

Iv,

U8T Op Illustrations Xxv

113. BeplacBment Tein in syenite rook. War Eagle mine, Roflslsnd, B. C. 327

114. Photo-microgrsphs of thin seetioiu of sulphide ore from Austia-

Tille, Va., mines '. . .828

115. Section of vein iii Enterprise mine, Rieo, Colo 329

. Section showing chaage in character of vein paaaing from gneies

(g) to quartz porphyry (p) 330

117. Tabulation of strikes of principal veins in Monte Cristo, Waah.,

district 831

U8l Linked Teins 882

m. Gash vein with associated " flats " (a) and "pitches" (A). Wis- consin zinc region 832

Section at Bonuetene, Ho., showing ore disseminated through

limestone 383

131. Sketch showing dimensions of an ore shoot 338

122. Section throngh Copper Queen Mine, Bisbee, Ariz., showiug vari-

able depth 6t weathering 835

123. Map showing distributiou of hematite and magnetite deposits in

the United States 351

121. Geol<ic map of Adirondack region, New York, showing location

of iron-ore depoeits 358

125, Map of MineviUe, N. Y., iron-ore district 354

12fl. Sections of the Old, 21-Bonanza-Joker, ore beds, Minevitle, N.Y. 356

127. Geologic column of the Iron Springs, Utah, district . . 358

123. Map of a portion of the Iron Springs, Utah, district, showing

occurrence of iron ore in limestone near andeeite contact and

also in the igneous rock 359

129. Cross section of Desert Monnd contact depoat, Iron Springs, Utah 360

130. Map of Iron Moantiun, Wyo., titaniferous magnetite deposit . 864

131. Map of Lake Superior iron regions (except Cuyuna), shipping

points, and transportation lines 367

132. Sections of iron-ore depowte in Marquette range 807

133. Generalized vertical section through Penokee-Gogebie ore deposit

and adjacent rocks 368

134. Generalized vertical section through Mesabi ore deposit and adja-

cent rocks 389

135. Map of eastern Dnitd States, showing areas of outcrop of Clinton

iron ore 378

130. Map showing outcrop of Clinton ore in Alabama 874

137. Outcrop of Clinton iron ore, Red Mountain, near Birmingham,

Ala. 875

138. Map showing outcrop of Clinton ore formation in New York state 377 ]-3fl. Typical profile of slope on Red Mountain 378

140. Map showing distribution of limonile and siderite in the United

States 880

141. Map showing location of iron-ore deposits in Virginia . . 880

142. Geologic section showing position of iron-ore deposito in Virginia 381

t,

Ust Op Illustrations

yl48. Vertical section Bbowing Btructure of the Tallay brown-ors de- posits at the Rich Hill mine, near Reed laUDd, Va. . . 8B2

141. Section illuitr&ting the formation of residual limonite in lime- stone 883

146. Section of Oriskaay limonite deposit 384

146. Diagram showing the production of iron ore, pig iron, and steel

in the United States, 1870 to 1909 387

147. Map showing distribution of copper orea in the United States 398

148. Section at Butt, Mont., showing mode of occurrence of ore . 809

149. Map of eastern part of Butte, Mont, district, showing distribn-

tion of veins and geology 400

100. Section across vsins of Pennlvania, Rarus, Mountun View, and

West Colusa mines, Butte, Mont. 401

161. Geologic map of western half of Butte district 403

162. Section across Keweenaw Point, Mich 403

168. Map of a portion of Michigan copper district, showing strike of

the lodes 403

154. Section shoving occurrence of amygdaloidal copper, Quincy Mine,

Mich 404

165. Map of Arizona, showing location of more important mining

districts 409

156. Geologic sections of Bisbee, Ariz., district 407

157. Geologic section at Bisbee, Ariz. 408

168. Geoloc map of vicinity of Morsnci, Arii 409

169. Section in Morenci, Ariz., district 410

150. Photo-miercn:apb showing replacement of Clifton -Morenci ores 410 161. Vertical section through Longfellow ore body, Clifton-Morenci

district 411

182. Vertical section showing ore body in schist. Mineral Creek dis- trict, Arizona 413

163. Geologic map of a portion of the Mineral Creek, Ariz., copper

district 413

184. Section showing replacement of limestone by pyrite and chalco-

cit, Bingham CaBon, Utah 413

165. Section of Ely, Nev., district 416

160. Map of Carroll County, Va., pyrrhotite area 418

167. Section of ore from Chestnut Yard, Va 419

168. Geologic map of Copper Mountain region. Prince of Wales Island,

Alas. 421

169. Chart showing production of copper in the United States from

1882 to 1909 422

170. Map showing distribution of lead and zinc ores in the United

States .429

171. Four and one half foot section, showing occurrence of ore in

Boiinetarre limestone. Doe Run, Mo 430

172. Model of Franklin zinc-ore body 483

b,

List Op Illu8Tbati0Ns

173. Plan of oatcrop and workings of Sterling Hill ore bod; . 433

174. Section of Berth* line mines, Wythe Co., V. . . 495

175. Section showing replacement of limestone bj sphalerite and

galena, Austinville, Va. 436

17e. Uap of Ozark ragion 436

177. General iresteast section through Jopliu and St. Francis Mouu-

ttuns, Miaioim 437

178. General sonth-north section through Springfield and Sedalia,

Uisaouri 487

179. Generalized geologic section of the Joplin district 438

180. Photo-micrograph of jasperoid 489

181- A typical small hoistingoatfit in Bouthwestei-a Missouri zinc legiou 440 '

182. Section showing occurrenoe of lead and zinc ore in Wisoonein . 444 L83. Hap of a portion of Wisconsin lead and zinc district, showing

strike of crerices, underground contours of Galena limestone,

and nndergronnd workings 445

184. Ideal section of Leadville, Colo., district 446

185. Vertical section along line AB of Fig. 186. Tucson shaft, Lead-

rille, Colo. 448

liiS. Geologic plan of fifth level and workings, Tucson shaft, Lead-

Tille, Colo 44

187. Cavities in Cambrian quartzite, Tucson shaft, Leadville, Colo. . 450

188. Chart showing production of refined lead and spelter in the

CD)td States from 1875 to 1009 452

189. Mop showing location of Cceur d'AIene, Ido., district . . 45S ISO. Geol<e map of Cceur d'AIene, Ido., district 469 IBI. Section of a lead-silver vein, CtBor d'AIene, Ido 460

192. Section of ore body at Aspen, Colo 462

193. Diagranimatic section acrom a northeasterly lode at Rico, Colo. . 468

194. Vdn filling a fault fissure, Enterprise mine, Rico, Colo. . 464 tOo. Map of Nevada, showii location of more important mining

districts 466

196. Geoli map of Tintic district, Utah 466

197. Hap showing distribution of gold and silver ores in the United

States 473

198. Hap of Califomia, showing location of more important mining

districts 475

19. Hap and section of poriiion of Mother Lode district, Calif. . . 476 200. Section illustrating relations of auriferous quartz veins at Nevada

City, Calif. 477

311. Mapof Utah, showing location of mora important mining districts 478

202. Section at Mercur, Utah 479

203. Uap of Colorado, showing location of mining regions . 480

204. Sections showii possible outline of the Cripple Creek volcanic

cone at the close of the volcanic epoch 481

205. Section of vein at Cripple Creek, Colo.

Iv,

List Of Illustrations

206. Vertical section tiirougb the Botdb ehaf t, Portland Mine, Cripple

Creek, Colorado 483

207. Geologic section acrosa the ntvthweat portion of the Telluride

quadrangle, Colorado 483

208. Geoliic map of the Telluride district, Colorado, showing out-

crop of more important veiuB 4S9

209. Map shoYring approximate distribution of prineipi silver, lead,

and gold regions of Colorado 489

210. Geologic section across the Goldfteld district, Nevada . . . 490

211. Generalized columnar section of geolical formations at Gold-

field, Nev 491

313. Map showing outcrope of siliceous ledges east of Uoldfleld, Nev. . 492

213. Ideal cross section of rocka at Tonopah, Nev 493

214. Section of the Comstock Lode 494

215. Generalized section of old placer, with technical terms . 490

216. Section of Homealake belt at Lead, S. Dak 499

217. Typical section of siliceous gold ores. Black HiUs, S. Dak. . . 500

218. Map showing mineral depiosita of Alaska 502

219. Sketch map of Douglas Island, Alaska 503

220. Cross section through Alaska Treadwell mine on northern Bide

of Douglas Island 508

221. Chart showing quantity and value of gold and silver produced in

the United States from 1830 to 1909 506

222. Chart showing production of gold in the United States, and of

the principal states and territories from 1885 to 1908 . . 508 323. Chart showing production of gold iu the principal countries of

the world from 1800 to 1906 508

224. Geologic map of Alabama-Georgia bauxite region . 517

225. Section of bauxite deposit 518

226. Sections of manganese deposit, Crtmora, Va 525

337. Map showing Georgia manganese areas 526

228. Section in Georgia manganese area, showing geologic relations of

manganese, limonite, and ocher 537

328. Section in Batesrille, Ark., manganese region, illustrating geo- lineal structure and relation of different formations to market- able and non-marketable ore 627

330- Map of California mercury localities 533

231. Map showing Texas mercury region 534

232. Vertical section of California Hill, Terlingua, Tex. ... 535

233. Section of cinnabar vein in limestone, Terlingua, Tex. . . 5,5 334. Geologic map of Sudbury, Ont., nickel district 650

235. Geologic section of Sudbury, Ont., nickel district , . . 551

236. Sketch map showing location of Carolina tin belt . .560 337. Map showing location aud relations of rutile deposite in Nelson

Connty, Va 562

bvCoog[c

Plates

I. Mp showing coal fields of the United StAtea . FrontitpUee

n. Map of PennHjlTaniK, showing distributioD of co&la by fael

ratios SI

m. F. I. Pit working (strippingB) near MilnsBviUs, Pa. The

mammoth seam is uncovered in bottom of pit . , 24

Fig. 2. View in Arkansas coal field. IV. Geologic section from Kansas City to Topeko, Kas. . 30

V. Fig. 1. View in sab-bituminoua coal area between Minera

and Canoel, Tex 83

Fig. 2. Lignite seam, Williston, N. D. VL Uap showing areas in United States in which oil and gaa are

known to occur 68

VII- Fig. 1. Generalized section in Appalachian oil field along line

J B of Fig. 25 69

g. 2. Northwest-southeast section in Pennsylvania oil field along CD in Fig. 35. TIIL Fig. 1. General view of Tnna Valley, in Pennsylrania oil field 75 Fig. 2. View in Los Angelea, Calif., oil field. IX. General view of Spindle Top oil field, Beaumont, Tex. . 78

X. Genera) view of Trinidad asphalt lake 88

XI. Fig. 1. View of portion of Trinidad asphalt lake, showing the

ding operations 90

Fig. 2. Quarry of bituminona sandstone, Santa Cruz, Calif.

XTI. F. L Grnite quarry, Hardwick, Vt 108

Fig. 2. Quarry in rolcanic , north of Phixnix, Ariz.

XHL Quarry in limestone, Bedford, Ind. 112

XIV. Marble quarry, Proctor, Vt 115

XV. Fig. 1. Marble quarry, Pickens County, Ga. . . . .116 Fig. 2. Slate quarry, Penrbyn, Pa.

XVI. View of green slate quarry, Pawlet, VL 120

XVTL Bank of sedimentary clay, Woodbridge, N. J. . . 130 XVIIL Fig. 1. Quarry of natural cement rock, Comberland, Md. . 146 Fig. 2. Natural cement rock quarry, Milwaukee, Wis. XIX Pig. 1. Limestone quarry in Lehigh cement district, Penn- sylvania 152

Fig. 2. Marl pit at Warners, N.T. XX Pig.l. InterioTTiewof8altmine.Livonia,N.Y. . . 163

Fig. 2. Borax mine, near Daggett, CaliL

iv,Coog[c

XXL Fig. 1. Viw in Nora Scotia gypcom qoAiry, showing

large maaa of anhydrite 179

Fig. 2. Gfpsani quarry. Linden, N. Y. XXIL Fig. 1. Gypsum quarry, Alabaster, Uich. 188

Fig. 2. View in scythestose quarry, Pike Station, N. H. XXIIL Fig. 1. Rock phospliate mine near Ocala, Fla. . . 189

Fig. Phosphate beds, Montpelier, Ido. XXrV. Fig. 1. Grindstooe quarry, Tippecanoe, O. . . . 202 Fig. 2. Corundum vein, between peridotito and gneiss, Corandum Hill, Ga. XXV. View in Arkansu novaculite quarry 206

XXVI. General view of Asbestos quarry, Thetford Mines, Quebec 212 XXVIL Map of portion of Kentucky fluorite district ... 230 XXVTIL Fig. 1. View in glass sand pit, on Bevera River, Md. . 250 Fig. 2. View showing sapphiro workings, Togo Gulch,

TCTTTT- Fig. 1. Section of an artesian basin 268

Fig. 2. Section illustrating conditions of flow Id jointed

crystalline rocks. Fig. 3. Section illustrating conditions of flow from solu- tion passages in limestone. Fig. 4. Sectiou illustrating conditions of flow from fis- sures in stratified rocks overlain by drift. XXX. Fig. 1. Section illustrating conditions of flow from folia- tion and schistosity plsnes 296

Fig. 2. Section illustiating conditions of flow &om

vesicular trap. Fig. 3. Section showing accumulation of water in strati- fied rocks with low intake. XXXI. Fig. 1. View of open cut in magnetite deposit. Mine.

Tille, N. Y 855

Fig. 2. General view of minetic separating plants and shaft bouses, MineviUe, N. Y. XXXIL General view of Mountain Iron mine, Mesabi Bange

Minn. 868

XXXm. Fig. 1. Iron mine, Soudan, Minn 871

Fig. 2. View of limonite pit near Ironten, Pa. XXXIV. Geologic map of western half of Birmingham, Ala., district S72 XXXV. Geologic map of eastern half of Birmingham, Ala., district 372 XXXVL Fig. 1. Pit of residual limonite, Shelby, Ala. . . .881 Fig. 2. Old limonite pit, Ivanhoe, Va., showing pinna- cled surface of limestone which underlies ore-bearing

XXXVIT. View of Anaconda group of mines, Butte, Mont. . . 401 i

XXXVIII. View from Houghton, Mich., looking towards Hancock . 404

XXXIX. Fig. 1. Smelterof Arizona Copper Company, Clifton, Aris. 413

Fig. 2. View of Bingham CaAon, Utah. ,

ooglc

XL Utah Copper Mine, Bingham, Utah 414

XLL Fig. 1. View looking northeast from Enieka ore pit of the NevadA Consolidated Copper Company, Ruth, Ely dis-

triot, Nerada 416

Fig. 2. South end of Eureka ore pit, Ruth, Nev. XLIL Go1ogic map of Franklin Furnace and vioinity, with sec- tions of the zintMtre bodies 482

XUn. Fig. 1. View from top of Carbonate Hill, Leadville, Colo.,

looking towaids Iron Hill 446

Fig. 2. View from south end of Carbonate Hill, LeadvUle, Colo., overlooking California Gulch in foreground, snd town of LeadviUe in the valley. XLIT. Fig. 1. View near Linden in Wisconsin lead and zino dis- trict 4G

Fig. 2. View looking north over the Coeur d'Alene Mann- tains, froin the Stemwinder tunnel above Wardner. XLT. Fig. 1. General view of Bico, Colo., and Enterprise group

of mines 467

Fig. 3. View of a portion of Marour, Utah, and the Merour Mine. XLTL Fig. 1. Kennedy Mine on the Mother Lode, near Jackson,

Calif 477

Fig. 2. Auriferons quartz veins in Maryland Mine, Ne- vada City, Calif. XLVIL General view in Cripple Creek district, Colo. . . .481 XLVHL Fig. 1. View of Independence Mine and Battle Uoonhun,

Cripple Creek, Colo 484

Fig. 2. Ueneral view of region around Tonopah, Nev. IHfty, General columnar section of A, Ouray quadrangle; B, Tel-

luride quadrangle 487

L Vertical and horizontal plan of Kelly tunnel and associated

mine workings, Georgetown, Colo., district . . 489

LL Hap showing veins and porphyry dikes in the Silver Flume,

Colo., region 490

lAL Flans of the principal leveb of the January Mine, with a diagrammatic section, showing relation of ore, ledge

matter, and country rock 492

LDL Fig. 1. General view of Goldfield, Nev., aud surrounding

country 491

Fig. 2. Ledge outcrop in dacite between the Bluebell and Commonwealth mines, Goldfield, Nev. LIV. Fig. 1. Hydraulic mining of auriferous gravel . . . 497

Fig. 2. An Alaskan placer deposit. LT. Uoraertake mills, hoisla, and open cuts at Lead, S. D. . 499 LTL F. 1. View of bauxite bank. Rock Run, Ala. ... 627 Fig. 2. Furnace for roasting mercury ore, Terlingoa, Tex.

iv,Coog[c

Abbreviations Used

In tbe referanoefl at end of each chapter, the volume nombera an pvea in Roman numerals. Numbers following a colon (:) indicate pagi nombera. The date of publicatioa follows these, and is separated iron them by a comma. Ala. hd. and Set. Soc, Proc. — Alabama Industrial and Scientific Society

Proceedings. Amer. Oeol. — American Geologist. A mer. Trut. Min. Engrt., Trans, or Bull. — American Institute Mining Eogi

neers, Transactions or Bulletin. Amer. Jour. Sci. — American Journal of Science. Can. Ming. Imt, — Canadian Mining Institute. Colo. Sci. Soc, Proe. — Colorado Scientific Society, Proceedings. Econ. Gtol. — Economic Geology.

Eng. and Min. Jour. — Enginenring and Mining JoumaL Geol. Soc. Amer., Bull. — Geological Society of America, Bulletin. Jow. Geol. — Journal of Geology, Min. and Met. — Mining and Metallnrgy. Afin. and Sci. Pr. — Mining and Scientific Press. Min. Indus. — Mineral Industry. Mil. Mag. — Mining Magazine. Min. Wld. — Mining World.

Mo. Bur. Geol. Min. — Missouri Bureau Geology and Mines. Mo. Geol. Sure. — Missouri Geological Survey.

N. Y. Acad. Sci., Tram. — New York Academy of Science, Transactions. N. Y. St. Mus., Bull. — New Tort State Museum, Bulletin. N, Ca. Geol. Surv. — North Carolina Geological Survey. Seh. of M. Quart. — School of Mines Quarterly. U. S. Geol. SuTv., Man., Prof. Pap., Bull., Ann. Kept, or W. S. Pap. — United

States Geological Survey, Monograph, Professional Paper, Bulletin,

Annual Report or Water Supply Paper. Zeifseh.f. Prak. Geol.— Zeitsohrift fur Praktische Geologie.

b,

Part I

Non-Metallic Minerals

t,,

b,

Coal

Kinds of Coal. — There ia such an intimate gradation between vegetable accumulation now in process of formation and mineral cottl that it is generally admitted that coal is of vegetable origin. By a series of slow changes (p. 11) the vegetable remains lose water and gases, the carbon becomes concentrated, and the ma- terials assume the appearance of coal. To the several stages of this process the following names are ven: peat, Ugnite, sub- Utuminous, bituminous, semi-bituminous, semi-anthracite, and anthracite.

Peat (119-130.) — This, which represents the first stage in coal fonmition, is formed by the growth and decay of grasses, sphagnum, Slid other plants in moist places. A section in a peat bog from the top downward may show: (1) A layer of living plants; (2) a layer of dead plant fibers, whose structure is clearly recognizable and which grades into (3) a layer of fully formed peat, a dense, brownish black mass, of more or less jellylike character, in which the vege- table structure is often indistinct.

The f oUowii analyses show the difference in compoation of the different layers.* They also show that while during this change the hydrogen and oxygen diminish, the carbon increases in propor- tion.

Akaltses of Ditfebent Liters op a Pkat Boo

Matxbiai.

Sphagnum

Porous, light brown sphagnum peat

Porous, id-brown peat

Heavy brown peat

Heavy black peat

OTTOEN NlTHOaEN

' Ths fact that Sphagnum occurs on the urfao is not neoeasaiily an indication it waa the oaiy peBt-formins plant present.

2 ECONOMIC GEOLOaY

Lignite. — This substance, also called brown coal, represent- ing the second stage in coal formation, is usually brown in color, woody in texture, and has a brown streak. It bums readily, but with a long smoky flame, and with lower heating power than the higher grades of coal. Because of the large amount of moisture it often dries out on exposure to the air, and rapidly didntegrates to a powdery mass.

The lisnites have been found in the more recent geologic&l periods. Because of the greater age and the greater compresaion of vegetable matter, due to the pressure of overlying strata, hgnite resembled true coal moi closely than peat. In fact, in favorable situations, the alteration of Ter' tlary and Cretaceous coals has proceeded as far as to transform tbem beyond the stage of lignite.

Jet is a coal-black variety of lignite, with rednous liuter and sufficient density to permit ita being carved into small ornaments. It is obtained on the Yorkshire coast of England, where a single seam produced 5180 pounds, valued at tl250. According to Phillips, jet is simply a coniferous wood, still showing the characteristic structure under the microscope. ("Geology of England and Wales," p. 278.)

Std>-bituminou8 Coal or Black Lignite. — A grade intermediate between lignite and bituminous, and sometimes difficultly dis- tinguishable from these. It is often black, and of brilliant luster. Campbell (13) has pointed out that it checks irregularly on drying and when weathered splits parallel with the bedding, while bitumi- nous coal shows a columnar cleavage.

BUuminoua Coal. — This represents the fourth stage in coal formation. It is denser than the ignites, deep black, compara- tively brittle, and breaks with cubical or sometimes conchoidal fracture. On superficial inspection it usually shows no trace of vegetable remains; but in thin sections examined under the microscope, traces of woody fiber, lycopod spores, etc., are eom- . monly seen. Bituminous coal burns readily, with a smoky flame of yellow color, but with greater heating power than lignite. It does not disintegrate on exposm-e to air as readily as lignite does. Most bituminous coal is of earlier age than lignite; but where the two occur in the same formation, as in parts of the West, the lignite is commonly in horizontal strata, while the bituminous coal occurs in areas of at least slight disturbance.

When freed of their volatile hydrocarbons and other gaseous constituents by heating to redness in a coke oven, many bituminous coals cake to a hard mass called coke. Since all bituminous coals do not possess this character- istic, it is customary to divide these coals into coking and non-coAtn; coals-

b,

Coal 3

The cause of coldne is not clearly understood, and the chemical analysis does not appear to throw much light on the matter. It haa been suggested ' ihat the quality of coiling may be due to the presence of gelosic algal, or sa- propelic aiattr, in the original ingredieiits of the fuel. A determination of tbe coking qualities of a coal has usually involved a practical teat, but it DOW appears that the coking qualities of a coal can be inferred with ftUr accuracy by its behavior when ground in an agate mortar. Coals of good making character stick to the mortar, while those of opposite quality aro easily brushed loose (28).

The coking value of a coal (20) seems to be indicated with fair accuracy hy the hydrogen-onygen ratio, calculated on a moisture-free basis. Practi- cally all coats with Pt cent seem to possess coking qualitiee, Most roals with down to 55 make coke of some kind, and a few with ratios as Ion as SO will coke, though the product is rarely good.

The hydrogeu-oxygen ratio may fail as a guide in those coals uoder- going antbracitisation.

The formation of coke by natural processes is referred to on p. 4.

Cannel Coal. — This is a compact variety of noa-cokii bitumi- nous coal, with a dull luster and conchoidal fracture. Owing to its unusually high percentage of volatile hydrocarbons, upon which its chief value depends, cannel coal ignites easily, burning with a yellow Same, and wheo heated tends to decrepitate.

Semirbitumirums Coal. — This term was proposed by Hj D. Rtliers ae early as 1858 ' to apply to those grades above bitumi- nous, whoee volatile matters were between 12 and 18 per cent; while Fraaer, in 1879,* used it to include those coals whose " fuel- ratios " (p. 13) ranged from 8 to 5.

Sena-ajiihracite Coal. — This term was employed by Rogers at the same time, and included those coals between bituminous and anthra- cite having less than 10 per cent volatile matter. Frazer later included under it those coala whose fuel-ratios ranged from 12 to 8.

Both terms persist, perhaps unfortunately, to the present day, and are sometimes no doubt rather loosely used. Possibly the disagreement among different people as to what shall be included under these terms may be partly responsible for the confusion.

An&iracUe CooZ. — This coal is black, hard, and brittle, with hi|h luster and conchoidal fracture. It represents the last stage in the formation of coal, and shows no traces of vegetable structure within its mass, although plant impressions are often abundant in the rocks immediately above and below it. Anthracite has a lower percentage of volatile hydrocarbons and higher percentage of fixed

iv,Coog[c

4 Economic Geologt

carbons than any of the other varieties. On this account, it ignites much less easily and burns with a short flame, but gives great heat.

The geological distribution of anthracite is more restricted than that of bituminous coal, and in fact its occurrence is often more or less intimately connected with dynamic disturbances.

Carbonite or Natural Cohe. — This term is applied to natural coke, which is formed by igneous rocks cutting across bituminous coal seams. As illustrative' may be mentioned an occurrence in central Utah,' where " dikes of igneous rocks ten feet in width have cut vertically across the coal bed, nine to wxteen feet thick, meta- morphong the coal into a coke-like substance to a distance of three feet on either side. The coal thus fused is distinctly colimmar, the columns standing perpendicular to the face of the dike; it has a graphitic luster, but is not vesicular like artificial coke." Natural coke is also found in New Mexico, Colorado, and Virginia.

The higher quantity of volatile matter in carbonite than arti- ficial coke may be due to its having formed at some depth below the surface, thus preventing the escape of the volatile matter, short beatii, or enrichment by gases from the neighboring coal.

Analtsbb

OF Natural Coke

20.S8

Volatile hydrocarbons

Ash

I. Rictunond, Va., coal basin. — Wataon, Min. Res. of Va., p. 343, 1907. II. Book CtiBa coat field, Utah. Taff, Science, N.S. XXIII : 696, 1906. III. Cemllos Hills district, N.M. — Johnson, Sch. of M. Quart., XXIV: 492, 1903.

Proximate Analysis of Coal. — An elementary analysis of coal (see p. 12) is of comparatively little practical value. Therefore proximate analyses are commonly employed, in which the probable method of combination of the elements is given. By the proa- mate method the elements in the coal are grouped as moisture, volatile hydrocarbons, fixed carbon, ash, and sulphur.'

' Taff, J. A.. Soienoe. N.a.. XXIII r 696. 1906.

' The proiimate analysis, though apporeuUy a simide operation, needs to carefully carried out to prevent variable reaulls. See in this oonnectiaii U. S. 0oL Burr., Prof. Pap. 48, I.

iv. ;

Coal

Tha moisture can be driven off at 100° C. and is usuall; highest in peat and [ignite; the volatile hydrocarbons are the easily oombustible elements, snd decrease toward the acthnioite end of the series; the fixed carbon bums with difficulty and is highest in the anthraoite ooals. The ash KpreseDt* nonoombustible mineral matter and bears no direct relation to the kind of ooal; and the same is true of sulphur, which is present as an ingredient of pyrite or gypaum.

The value of ooal for fuel or other purposes is determined mainly by the relative amounts of its fuel oonstituente, viz., the volatile hydrocarbons uid the nonvolatile or fixed carbons. The fuel value, or fvel raiio, is deiermined by dividing the fixed carbon percentage by that of the volatile hydrocarbons.

The fixed oarbon represents the beating element of the ooal, while the rolatile hydrocarbons bum easily, but have little heating power. The hEating power and fud ratio will, therefore, increase together. This increase in the heating power of the coal is only true, however, up to a certaJD point, after which the difBculty in making the coal bum offseta the otra amount of heat developed. Coals with a high percentage of fixed carbon develop great heating power, while those lower in fixed carbon Mid liigh in volatile hydrocarbons lack in heating power, but are free burning.

Moisture is a nonessential constituent of coal. It not only displaces so much oombustible matter, but requires heat for its evaporation. When present in large amounts it often causes the ooal to disintegrate while drying out. It ranges from perhaps 1 per cent in anthracite to 20 or 30 pra' cent in lignites.

Ash also displaces combustible matter, but otherwise it is in most cases an inert impurity. The olinkering ot coal is commonly due to a high per- tCDtage of fusible impurities in the ash, and for metallurgical work the composition of the ash often has to be considered.

The following analyses will also serve to illustrate the composition of the ash:—

Ash Analtbes

aio.

Al

Ferf),

C>0

MgO

MdO,

Bo.

P.0,

Pwt, average of Ignite . . .

,60

Sulphur is an objectionable impurity in Btaming coals on account of its iwrosive action on the boiler tubes. It is also undesirable in coals to be used for metallurgiccd purposes and gas manufacture.

The following table gives the proximate analysis of a number of coals from different parts of the United States and Canada, the analyses being arranged according to graces.'

'lie type names are in each can those given In the reports from which

b,

Economic Geology

Proxhiate Analtbbb g

F Coal

u.

Mom-

FiXID

Ash

Bnb-

IUtio

Peat

Dismal Swamp, Va. . . .

OrlaDdo. Ela

Salt-morsfa peat, Maiae . .

Salt-marsh peat, Maiae . .

Washington Co., Me. (mois- ture free)

LigniU Lehigh, Stark Co., N. Dak. . Crookett, HoustoD Co., Tex.

—

Rockdale, Tex

Pickens Landing, Ala. . . .

Pearl River, Scott Co., Miss.

(4.10)

Kootznaboo, Alas

Upper Yukon, Rampart prov-

ince, Alas

Red Lodge, Carbon Co.,

Mont

Weaver, N.Mex

Tesia, Alameda Co.. Calif. .

30.67 15.49

Cape Lisburne, Alas. . . .

BUuminow

Warrior, Jefferson Co., Ala. .

3,28

CokinffCoa], Raton field. Col.

Yampa field. Col

Canyon City, Col

Round Mountain, Ga. . . .

Lower Yukon, Alas. . . .

BeUevUle, 111

OannelCoal,Cannelburg,Ind.

Block coal. Brazil, Ind. . .

Bartshome, Okla

Cannel Coal, Cumberland Gap

field, Ky

Fort Dodge, la

Butler. Ky

Owosso, Mioh

Verne. Mich

Lexington, Mo

15.18 4.38

Hocking VaUey, Ohio . . . Pittsbuig eoal, ConnellsviUe,

5.13 1.09

Pa

Jellioo, Campbell Co., Tenn. Newcastle, Wash

29.031 53.806

Coking Coal, Sydney Mines,

N.8

InvemesH, N.8

Semi-bauminou*

Johnson Co., Ark

CoalHill,FranklinCo..Ark. .

2,36

Garrett Co., Md

Pocahontas, Tazewell Co., Va.

Cape Lisburne, Alas, . . .

iv,Coog[c

pROXWATB Amaltbkb Of CoAL — Continued

u.

Mob-

Voia-

rmm

Fubl

Ratio

Spdi coal. Ark

BBDkhead, Alberta, Con. . . AniiiracUe

Crested Butte. Col

CmiUos field. N. Mex. . , .

M

2.go

Mammoth eeain. N. Middle

Tsmpa field. Col

River, AUa

Origiii of Coal (1-12). — It has been shown that there are gradations between unquestioned plant beds and mineral coal, uid that coal, besides containing the same elements as plant tissue, often shows the presence of plant fibers, leaves, stems, seeds, etc., in addition to their occurrence in the associated rocks. Moreover, stumps or trunksof trees are sometimes found standing upright in the coal, with their roots penetrating the underlying bed of clay (6. 9), just as trunks of trees at present stand in bogs. White these facts point uamistakably to a vegetable origin of coal, it is less easy to UDderstand the exact manner in which the great accumulations of vegetable matter have been made, and the changes from plant tissue to mineral coal. The several points, requiring explanation therefore are: (a) conditions of accumulation, (ft) character of oianiems forming coal, (c) conditions and duration of initial pro- cess of organic decomposition, and (d) nature of forces bringing about subsequent alteration of organic residues.

Conditwnaoj Vegd(Ale Accumulation (5,9, 12). — At present there are several conditions under which plant remains accumulate to conaderable depth over areas in some cases of large size. All of these are closely associated with water, either fresh or salt, because plant remains faUing in water have their decay so retarded by the excluon of air that accumulation is possible. Of these the follow- ing are the most important: (1) accumulation due to aigse on the sea bottom lieneath a sargasso sea; (2) marine swamps, including salt marshes and mangrove swamps; (3) delta deposits; (4) peat bogs; (5) coastal-plain marshes.

While accumulations made in any one of these ways may form

I;.

8 Economic Geology

coal beds, and while individual beds may be formed which are due to any of these causes, to many of them there are Bucfa objections as to render them extremely improbable as general explanations for the great number of widely extended deposits of coal. The theory of accumulation from deposits of algte, for example, demands deep water of an open ocean for the circulation of ocean currents. But most coal beds are evidently formed either on the land or else in shallow water of lakes, lagoons, or seacoast swamps.

To the theory of various swamps there are two serious objections : (1) that in such deposits ae are now forming, the currents are biing- ing more fragmental sediments than are commonly present in coal beds; (2) that at present only one kind of tree, the mangrove, is adapted to growth in salt water. It is, of course, possible that in earlier ages the number of trees adapted to this mode of life was far grMiter.

The theory of the accumulation of vegetable matter in deltas is also open to serious objections. Streams are briing plant remains to lakes or oceans, and incorporating them in tbr deltas; but no- where are such extnve accumulations now forming as to make large coal fields in this manner. The perfect preservation of the plant remains in coal measures, upright trunks with roots extending into under clay, together with freedom from sediment, are against the theory that the coal is formed by accumulation of transported vegetable matter {aliochthonous origin) . And yet, as occasionally favoring this theory, we have coals without under clays, with abrupt clay partings, with marine shells, and even marine Hmestone im- mediately overlying the coal. In rare cases accumulationa may have formed in quiet bays.

A more reasonable and widely accepted theory regards the vege- table matter to have accumulated by growth in place {aviochikorunta origin). It is a well-known fact that thick deposits of vegetable matter, often covering areas of several square miles, are formed in the peat bogs that in so many places represent the last stage of lake or pond fillii. Each of these bogs would, under favorable circum- stances, change to a bed of coal, and some of them are extensive enough to form coal beds of large size. But such bogs are, com- pared to our lair coal fields, far too limited in area to admit of the acceptance of this explanation to account for great coal fields with- out assuming far more widespread bog-forming conditions than any at present known.

Perhaps the most pfect resemblance to coal-forming condition

COAL g

is that now found on such coastal plain areas as that of southern Florida and the Diemal Swamp of Virginia and North Carolina. Both of these areas are very level, though with slight depressions " ia which there is either standing water or swamp conditions. In both regions there is such general interference with free drnage that there are extensive areas of swamp, and in hoth there are beds of vegetable accumulations. In each of these areas there is a gen- eral absence of sediment and therefore a marked variety of vegetable deposit. If either of these areas were submerged beneath the sea, the vetsble remains would be buried and a further step made toward the formation of a coal bed. ReSlevation, making a coastal plain, would permit the acciunulation of another coal bed above the first, and this process might be continued again and again.

In support of the theory that coal was accumulated in some such situation as this, are a number of facts: (1) the coal beds occur over ride areas in sediments which were deposited near land borders and which may therefore have been agn and cfun raised above sea level to form exteoMve coastal pluns; (2) there are evidences of land conditions revealed in the workings of some mines ; (3) the enormous area of some coal fields calls for some such widespread conditions as coastal plains might provide; (4) slight admixture of sediment indi- cates the absence of conditions of sediment supply, e.g. rivers, waves, tidal currents, and wind-formed currents; (5) vegetable accu- mulations made in such situations would require but slight changes in land level to be buried beneath sedimentary strata as the coal beds have beeiL

Charader of Organiems forming Coal. — The view that coals are famed only of woody tissue or leaves is a popular one, but it is known that some cannel coals and splint coals are characterized by great numbers of spores and pollen grains, and a relatively small amount of woody matter. Boghead coals and oil shales have been found to be composed largely of remans of certain gelatinous algffi. It is often difficult to say, however, what proportion of some coals is woody matter and what is algal matter, but it is regarded by some that the latter may be the donunant factor in forming the properties of coal.

Conditions of Decomposition. — Two stages may be recognized in the coalification process, viz. (a) the putrefaction stage, which is a biochemic process, and (b) the alteration or metamorphic stage, iovolving dynamo-chemical action.

When dead vegetable matter accumulates under water, it does

z .IV,

10 Economic Qeologt

ot remuii unchanged, but undergoes a deoxygeoatioa and de- bydrogenation process, which is accomplished by fermentatioQ - or maceration in which minute plants (bacteria) and also animus take part. Ab a result of this the plant tissues break down into a somewhat jelly-like mass, the black peat, which jelly fonns the amor- phous ground-mass of coal and cements the plant tissues and sedi- ment together.

The decomposition of the orinal cellulose (CHuiOi) of the plant tissue liberates substances such as CH4, as well as COi, CO, HiO, etc. It seems probable that the jellification process leads no further than peat, and that for the development of the later stages dynamo- chemical changes are necessary.

While in peat beds the lower layers are under the gentle pressure of the upper layers, still peat is not changed even to lignite until buried under many feet of sediments. Indeed heat and pressure seem necessary for the chaise from lignite to bituminous coal, and iongperiods of time are apparently required for the slow changes that take place.

It has been commonly assumed that to produce the higher grades such as anthracite, strong folding was necessary, in order to develop sufficient heat and pressure for this dp-ee of metamorphism. M. R. Campbell (2, 10) has, however, argued with apparent reason that while the chemical changes involved are induced by heat (of ordi- nary temperature), still these changes are retarded or prevented unless the structural conditions (presence of joints, etc.) are favoralJe for the escape of the gaseous products of this change.

Thus, for example, the Pennsylvania anthracites are formed not so much because of heat and pressure, but because of the cracking of the rocks which allowed thorough oxidation. The same amount of folding in the Pocono rocks of Maryland has not produced any anthracite, as the structural conditions were not favorable for the free escape of the gases.

Cases are known, where the heat causing the changes is intense and local, as in the Cerrillos coal field of New Mexico (80), or the Greeted Butte district of Colorado (5B), where bituminous coal has been locally changed to anthracite by a near-by igneous intruon.

Some geologists, notably J. J. Stevenson, have argued that the anthracite coal has not been developed from bituminous coal by metamorphism, but that the volatile constituents were partly removed by longer exposure of the vegetable matter to oxidation ; before burial (11). Among paleobotanists there ia also a difference

c,q,z.<ib,Coogle

Coal 11

of opinion as to whether the succession, peat, lignite, etc., is a strictly lineal one.

The following theory of coal formation has recently been ad- vanced by Dowling (4). The death of a plant is marked by the loss of power to form oxidized hydrocarbon compounds, conse- quently chemical reactions are set up in the material of the dead plant. The formation of compounds of oxygen and carbon is the first evidence of decay. With the escape of these gases the hydro- Ririxins left behind become unstable, and loss of marsh gas follows. If fermentation accompanies decay, new hydrocarbon compoupds are formed by this parasitic form of life and the reduction of oxy- gen is accompUshed without great loss of hydrogen which is the element that ves character to the material, especially when in the coal stage. When sohdiSed by superposed load, the fermentation L' arrested and pressure and heat cause the subsequent alteration. Static pressure favors the combination of oxygen with carbon or hydrogen. Heat causes the combination of carbon with oxygen or tydrogen. Pressure effects the alteration without loss of carbon, bile heat wastes it.

Chemical Changes. The chemical changes referred to above maybe illustrated by the following chemical equations (19, p. 26):

TionABba TiMDB- Lou it DscoitfoaTnoH Cfuu

(1) 5C,oO, 6C0, + C0 + 3CH4-I-8H + CkHjiO,

CsUulaoB CuboD ddiIh Mfinh (u Livilta

(2) aCtHyjO, 8C0. + CO + 6CH( H

CtUuk Cuban dioxide Mmh

(3) 7C,Hk,0. 8C0, + 4CH4 + 19HiO +

Callulm Cubon diniidii MinhcM WkUr aami-blMialDaui

These equations are not intended to indicate that there is nece- ly a direct passage from cellulose to semi-bituminous coal, "ithout the development of intermediate stages; and to bring out this lineal succession as well as to show the changes by a graphical method we may use the following diagram (Fig. 1) prepared by the late Professor Newberry.

In this diagram the rectangle ABCD represents a pven volume of fresh vegetable matter, which contains a small percentage of mineral matter, the rest being organic substances consisting roughly of 50 per cent carbon (EFCD) and 50 per cent hydrogen, oxygen, and nitrcn (ABEF). In the change from fresh vegetable tissue to peat, part of these four elements pass off as gaseous compounds,

b,

ECONOMIC GEOLOaT

80 th&t the remaining volume of peat is leas {BOD H) than the ori- Dal volume of vegetable matter (ABCD). Since, however, H, O, and M have passed off in larger amounts than the carbon, tiie per- centage of the latter in the peat will be higher than it was in the fresh plant tissue. (Compare BPQI and FIDH with ABEF and EFCD.) The actual weight of mineral matter mil be the same.

but its percenter will be larger. This change, continued, will result finally in anthracite, the last of the coal series, in which the per cent of carbon (LKMN) is high and that of the other oianic elements low (J KL). The amount of compression that occurs in such changes as those illustrated in the diagram may be understood when it is stated that it is estimated that from 16 to 30 feet of peat are required to make one foot of true coal.

The following elementary analyses of peat, lignite, and various grades of coal clearly illustrate this gradual concentrataan of carbon by losses of volatile elements.

E1.EUENTART Analtsgs ot Coals

H

N

a

A-,

MoivriritB

Peat

.To.47

3t.51

Lignite

5H.41

5.r)fi

28,!W

M

4.7H

Bitumiaous

fl..fi

Semi-bituminoufl . . .

4..'W

4.ft5

Anthracito

—

—

Cluaiflcatloa of Coals. — At tbe preHent time a number of kinda of coal are reoognized in the United States &nd Canada, whose differentiation depends on their phjoal and chemical properties. But even these tvw type names am often used in a isther loose mj.

bvCoog[c

Coal 13

Perikapa the important attempt at olaaaiflcation wae that of P. ftuar, Jr., baaed on the fuel ntio (17). Thia was aa follows; — FuBL Ratio

Anthracite 100-12

Semi-anthisoito 12- 8

Bemi-bitmniiioua S- 6

Bituminous 5-0

Obieelaons which have been uied against this are that all ooals with a liul ntio of lew than 5 are grouped into one class and no provision made for lignite. It also groups good and poor bituminous coals ttether.

CoIUct (15) prapoaed that all ooajs having a moisture content of over 10 per sent should be classed as lignit and those with less as bituminous, kt this differentiation has been shown to be unreliable.

I. R. Campbell, while afpeing to tbe usefulness of the fuel ratio olassi- bstion for coab above the bituminous grade, oritioised its application to eals of this type or lower ones, and suggested a proviaional olassifloation Used on the carbon-hydrogen ratio (14).'

AfGnjihitc)

f. : Anthracite ?-30 (7)

D SemMuithracite 26 (?)-23 (?)

E Semi-bitnminoua 23 (?)-20

F : 20-17

I i 12.5-11.2

'Ugnile 11.2-9.3

Epu 9.3-?

LWood 7.2

This table is likewise faults, as it does not oompIetAly separate the VMit, lignites, sub-bituminous, and even some of the bituminous coals.

Pirr (19), in attempting to make a satisfactory classification, points out U>at the term volaUle atmimttibU is incorrect as it consiBts of combustible drocarbons and nonoombustible H, O, and N. Thus in a Pocahontas with 18.70 per cent volatile combustible, 14.5 per cent is hydrocarbons 4.2 per cent hydrogen, oxygen, and nitrogen. Again, a North Dakota Wte had 41.91 per ent volatile combustibles, made up of 20.28 per cent 'jliocarbonB and 21.63 per cent hydrogen, oxygen, and nitrogen. In a oUasiflcation, therefore, allowance should be made for this inert nktOe matter.

In Psir's olaaeification the terms used are: vc, or volafile carbon unssso- oiUd with hydrogen, obtained from C — fe (total carbon minus fluted carbon);

'Campbell found tliat subdividons baaed total carbon, total hydrosen, aod 'loiifie vahu were all unaatlsf aotoiy.

bCoogk'

Economic Qeologt

C, or total ovbon as determiiwd hj analysis; and mert voUUiie matter, ob- tained by Bubtraoting from 100 per oent the sum oF total oarbon, avail&ble hydrogen,' sulphur, aah. and water.

It will be Been that Parr's classification, which follows, requiresdata from both the elementary and the proximate analysis of the ooal.

Pabb'h Classification.

Anthracites Proper

Bemi-Anthtsoite Semi-Bituminous

Bitmninous Proper

Ratio below 4%.

Ratio between 4 % and S %.

Ratio from 10% to 15%.

Ratio from 20% to 32%. Inert volatile from 5% to 10 %.

Ratio from 20 % to 27 %. Inert v<tile from 10 % to 16 %.

Ratio from 32 % to 44 %. Inert volatile from 5 % to 10 %.

Ratio from 27 % to 44 %. Inert volatilerroinlO% to 16%.

Ratio from 27 % up.

Inert volatile from 16% to 20 %.

Ratio from 27 % up. Inert volatile from 20% to 30 % Orout's dasBifloation (18) is expressed by the formula; Fixed carbon 100 -Fixed carbon'

based on pure coal. He makes the following classes: —

Oraphite Fixed oarbon, over 99 percent.

Anthracite Fixed carbon, over 93 per oent.

b,

SemiHutthracite Semi-bitumiiMHU BitnmiiMHis

lignite . Brown lignite Peat&nd turf

Wood D. B. Dowling (16) notes that o:

Fixed carbon, 83 per oent te 93 per cent. Fixed o&rbon, 73 per oent to 83 per oent.

J Fixed carbon, 48 per cent to 73 per oent. ( Total oarbon, 82 per oent to 88 per cent. j Fixed carbon, 48 per eent to 73 per cent. t Total earbon, 76.2 per oent to 82 per oent.

IPMxed carbon, 35 per cent to 48 per cent. Total carbon, 76.2 per cent to 88 per oent. (Fixed carbon, 35 per cent to 60 per cent. Total carbon. 73.6 per cent to 76.2 per cent. I Fixed oarbon, 30 per oent to 55 per cent. ToieX oarbon, 65 per oent to 73.6 per oent. I Fixed oarbon, below 55 per oent. [ Total oarbon, belov 65 per odnt.

i objeotio

to Campbell's — classifioa-

tioQ ia the oeoesnty for Iiaving an elementary analysis, wliioh ii made, costly, and time requiring. As a substitute for Campbell'a cuioQ, he substitutes what he has provisionally termed the " split volatile Bitio " viz. Fixed carbon + j volatile combustible .

Moisture + i volatile combustible An arrangement of a series of coals by this method and also Campbell's ratio does not indicate great disagreement ; moreover, Dowling's classiflca-

lioD has the advantre ol being based on tbe proxim&to composition. He makes the following aubdivisions: —

Group

Splii Vol. Ratio

-Anthracite

15 up

High earbon bituminous

Ugnitioooal

Upiite

1.20-3.50

More reoently, Campbell has suggested the recognition of j.wo clasaea of bdow bituminous, calling the upper grade "sub-bituminous" and the lover grade " lignite." He suggests that the manner of weathering be used as a criton for separating the bituminous from the sub-bituminous, the former cleaving into prisms, while the latter checks irr:ularly on drying, Md when weathered on the outorop cleaves into plates parallel to the bedding. The sub-bituminous ooals with their black color he claims can bo distinguished from lignites, because the latter are brown.

iv,Coog[c

16 Economic Geology

WhUe'a ClasUfieatum. — White (20) has shown that if a series of coals of differeot ages, kinds, aad regions are pIotld aoxirdiiig to the C : (O + ash) ratios and calorific values aa components, they describe a curve, which shows a close illation between the increase of the above mentioned ratio and the colorific power. Weathered coals, those having over 78 per cent fixed carbon in pure coal, and the bnghead-cannel eroup (high in hydron) ore the greatest variants. Oxygen is ranked with ash in this ratio because the two are approximately equal in anti-calorific potency. This ratio can- not be uaed aa a baais for separation into kinds, such as peat, lignit, etc.

Structural Features of Coal Beds. — Outcrops (24, 25). — The

outcrop of a coal bed is usually easily recognizable on account of its

color and coftly character; but unless the exixjsure is a rather fresh

one, the material is disintegrated and mellowed, the wash from it

mingling with the soil, and if the outcroppii bed is on a hillside,

often extending eome feet down the slope. This weathered outcrop

has been termed the " smut " or " blossom " by coal miners. Iq

areas where the beds have been tilted and the

slopes are steep, the outcrops of coal can usually

be easily traced; but in regions where the dip is low

and the surface level, the search for coal is often

attended with difficulty, which is increased if the

country is covered with glacial drift. In such cases

boring or pitting is commonly resorted to.

The number of coal beds found in any given region varies, and may at times be large. Thus in the Pennsylvania section, as many as 20 beds are known; in Alabama, at least, 55 have been counted, but not all are workable; while in Indiana there are 25, of which 9 are minable over large areas. The beds are rarely parallel, and, moreover, thin out if followed any distance.

Assodaled Rocks. — Most coal beds are inter- bedded with shales, clays, or sandstones, though conglomerates or limestones are at times also found in close proximity. Coal beds are often underlain by a bed of clay, which in some repons is of refrac- - „ toi'y character (Fig. 2); but the widespread belief

coal mcMi these under clays are fire clays is un- ofwesteroPenn- Warranted.

sylvania. show- Variations in Thickness. — Coal beds or "seams" uirfer coal beds. rarely of uniform thickness over large areas; Ufier Hopkim.) indeed, a bed which is of sufficient thickness to

b,

Coal 17

work in one mine may be bo thin in a nghborii one as to be scarcely noticeable. This irregularity is in some cases due to variations in thickness of vegetable accumulations, in other cases to local squeezing of the coal bed subsequent to its formation.

Flo. B.- These thinnings and thickenings are commonly called "pinchinga" and "swellings" (Fig, 3). In regions of pronounced folding, the beds are usually found in separate aynclioal basins, the intervening anticlinal folds having been worn away.

Other IiTegulariiies. — Splitting (Big. 3) is a common feature of many coal seams. The Mammoth bed, so prominent in most of the anthracite basins of Pennsyl- vania, eplits into three sepa- rate beds in the Wilkesbarre basin. This splitting is caused by the appearance of beds of shale (called "slate" by coal miners), which often become so thick as to split up the coal seam into two or more beds. When narrow, such a bed of slate is called a parting. The Pittsburg seam of western Pennsylvania shows a fire-clay parting or " horseback " from ax to ten inches thick over many square miles.

An intereeting case of parting ia found in the 13-foot seam at Inverness, Xovs Sootia. At the outorop this showed three shale partings, of 1 foot, 9 inehea, and 11 inches respectively. At 2500 feet down the dip, these partr ingi had increased to 19, 3, and 22 feet respectively. A 7-foot seam, lying %1 feet below the 13-foot one, maintained its thickness, however, for this wne distance on the dip.

Id addition to these " slate " partings, which run parallel with the bedding, others are often encountered which cut across the beds

bvCooglc

18 Economic Qeologt

from top to bottom. These in some cases represent enmon channels formed in the coal during or subsequent to its formation, and later filled by the deposition of sand or clay. In other cases they are due to the filling of fissures formed during the folding of the strata.

Coal beds may pass into shale, the lattor representing possibly islands of mud or ridges which arose above the level of the marsh in which the coal plants accumulated.

Faulting (Fig. 4) is not an uncommon feature of coal beds, and the coal is sometimes badly crushed on either side of the line of fracture. The amount of throw and the ninnber and kinds of faults may vary, so that one might expect normal, reverse, overthrust, and even step faults.

WeBtheiinK of Coals. — Pair and Hamilton (27), aa a result of their investigatioas of the weathering of coal, ooncluded that submerged coal does not lose appreciably in beat value, but that outdoor e:q>osure results in a loss of heating value varying from 2 to 10 per cent. Dry etorage in only of advantage for high sulphur ooals, where the disintegrating effect of sulphur in prooees of oxidation facilitates escape of hydrocarbons by oxi- dation of the same. Storage loasea uaiudly appecur to be complete at end of five months.

Coal Fields of the United States.* (PI. I.) — Coal in commercial quantities occurs in thirty-three states and territories, as well as in Alaska. These occurrences can be grouped into the following fields: — AaiA,

(1) Appalachian, inoluding parts of Pennsylvania, Ohio,

Maryland, Titinia, West Virginia, EaBtm Eentuoky, Tennessee, Georgia, and Alabama 69,812

(2) Atlanlic Coatt Triaaaic, inoluding parts of Virginia and

North Carolina 210

(3) Eaelem Interior, inoluding parts of Indiana, Illinois,

and western Kentucky 48,500

(4) Norihem Interior, inoluding parts of Michigan . . . 11,000 (6) Wtitern Interior, including parts of Iowa, Missouri, Ne- braska, Kansas, Oklahoma, and Arkansas 71,664

(6) SoMhiiSesiem field, inoluding parts of Texaa 13,500

(7) Gulf Coast Lignite field, including portions of Alabama,

Mississippi, Louisiana, Arlcansas, and Texas . . . S4,3O0

(8) Roekj/ Mountain field, inoluding parts of Colorado, Ari-

zona, New Mexico, Utah, Wyoming, Idaho, Montana,

North Dakota, South Dakota 195,960

(9) Pacific Coatt Field, inoluding parts of Wsshiugton, Ore-

gon, and California 1.830

486,576

(10) Abuka

' The Rhode laland area o/ Knpbitic authiKcite, fonnecly included in thii list. Is referred to under Graphite.

Coal 19

Tha Mtim&toe of areas given above are tram oaloulations made by the Uoited States Oeologioal Survey, and ore to be regarded as fairly aocurate, but some of these fields may be extended in the future by the development of areas now classed as unproductive. This applies espeoially to those in which the ooal lies too deep to be profitably mined at present. It ia a noteworthy fact that the production of the fields is by no means pK>por- tional to their areas (compare above list with table, p. 30). Proximity to markets, value of the ooal for fuel, and relative quantity of ooal per square mile of productive area are factors of importance in determining the output of a field.

Geologic Distribntiot) of CoalB in the United States. — The coal- bearing formations of the United States range in age from Carbonif- erous to Tertiary. The Carboniferous coals occur east of the 100th meridian and on the whole include the the best coals of the country. The higher grades occur in the anthracite regions of Pennsylvania and Arkansas. Cretaceous coals lie between the 100th and 115th meridian, and Tertiary coals chiefly between the 120th meridian and the Pacific coast. Exceptions to this distribution are the occurrence of a SDoall area of Triassic coals in Yirgima and North Carolina, and a large area of Tertiary lignites in the Gulf states. Thia indi- cates that during the coal-forming periods there was in North America a slow westward shifting of the zone in which conditions favorable to coal formation occurred, the only exceptions being those mentioned above.

The Carboniferous coals are commonly grouped into several well- marked and clearly separated areas; but this isolation is probably the result of folding and erosion, all excepting the Michigan field having apparently been originally continuous.' To a certain ex- tent the same is true of the Rocky Mountains coal fields. These have often been seriously disturbed by post-Cretaceous upUfts which in many instances have improved the qualities of the coal. As a whole, the Tertiary coals are medium to low grade, though in some sections, notably in Washington, they are of excellent quality.

BatimaUd Tonnte of the Variou* Fieldi. — Much attention Iiaa been given in the last few years to the necessity of conserving the ooaJ supply, for this material has been mined in a waslful manner. The following table givM the estimate prepared by the United States Geological Survey, the quantity of coiJ contained in the several fields being given: ' —

ia this book and indeed

b,

ECONOMIC GEOLOGY ToiTNAOE (Short Tons) bt Pbotinceb amd Accrssibilitt

Aua

Otaaati, Coit

IWmc

Amouot Aaoewbla

withDiOdully

1. Eastern.

2. Interior .

3. Gulf . .

4. Northern

Sq. Mil-

144,664 84,300

555,634,000,000 406,667,000,000 13,045,000,000

8,000,000,000 91.000,000,000 10,045.000,000

563,634,000.000 497,667,000,000 23,090,000 Ooo

or Gre&t

Plaiaa .

5. Rooky Mountain

6. Pacific

103,564 92,396

©1,793.000.000 414,740,000,000

459.000.000,000 574,280,000,000

980,793,000.000 989,020,000,000

Coast .

1,830

11,100,000,000

10,900.000,000

22.000,000,000

Total .

496,776

1,922,979,000,0001,153,225,000,000

3,076,204,000,000

The distribution of this oripnal supply of coaJ, according to grades and accesability, is also shown below.

ToNNAQE (Short Tons) bt Gbadrb op Coal and Acckbsibilitt

Aau

Obioehai. Coal

Coal

Amount Euily

Amount AcMaiUg with DifflcuJty

EuUv Acoenfbia

Anthracite and bitu- minous .

Sub-bitu- minous .

Lignite. .

S(i.Mil

250,531

97,636 148,609

Tom

1,176,727,000,000

356,707,000,000 389,545,000,000

Tom

505,730,000,000

293,450,000,0001 354,046,000.000/

Tou

1,176,727,000.000 216,252,000,000

Total. .

496,776

1.922,979,000,000

1,153.225,000,000

132,979,000,000

It should be said that the limit of workable depth, based on foreign experience, is 3000 feet for coal and 1000 feet for lignite. Twenty iacbca ia reg&rded as the minimum minable thickness of bed for oool and 3 feet for lignite. If the rate of increase which has held for the last fifty years is maintained, the supply of easily avlable ooal wUI be exhausted before the middle of the next century.

Appalachian Field (33. 36, 39, 91, 99, 100, 101, eto.). — This, the most important coal field in the United States, extends 850 miles, from northeastern Pennsylvania to Alabama. It shows

Iv,

b,

b,

Coal

a mazimum of 180 miles at the DOrthem end, narrows to less than

30 mi]es in Tennessee, and expands again to 85 miles in Alabama,

About 75 per cent of its area contuns .

workable coal. At the southern end the §

coal measures pass beneath the coastal plain

depoats, and they may connect with the -i "

Arkansas Coal Measures beneath the Missis-

aippi embayment. -Xn-Ji -

Being closely associated with the Appala- chian Mountain uplift, the coal measures of this reon partake of the structural features of the Appalachian belt. The eastern margin of the field borders on a belt of steeply folded strata, forming the Appalachian Valley, and hence the coal-bearing formations are much folded here (Fig. 5, 9), while at the southern end of the field they are faulted in addition (fig. 5). Extensive erosion following the folding of the coal measures has resulted in the development of a number of basins.

The coal measures of the Appalachian Geld conast of a great thickness of over- Uppii lenses of conglomerate, sandstone, limestone, shale, fire clay, and coal. The formations in general show a thinning from i

the eastern margin of the field, westward, as " ' -

well as showii a decrease in the number and thickness of the beds. Owing to the lenticu- lar character of the deposits, and the local thickenings, it is difficult to trace individual beds of coal over wide areas, or correlate sections at widely separated points.

The middle Carboniferous or Pennsyl- , - aa a vanian includes most of the coal beds of the ti I I Appalachian field, but there are some also in the upper Carboniferous and in the Poccmo ot the lower Carboniferous or Mississippian.

The classic section of the Coal Measures, first worked out in Penn- sylvania, was as follows: —

(1) Dunkard or Upper Barren Measures.

(2) Moooiahela or Upper Productive Measures.

22 Economic Geology

(3) Conemaugh or Lower Barren Measures.

(4) Alleghany or Lower Productive Measures.

(5) Pottsville conglomerate.

At the time it was made the second and fourth members were thought to be the only ones carrying coal, and hence the name " Pro- ductive " ; but since then the Pottsville has been found to be locally productive, and a few seams have been found even in the Barren Measures. By some the Dunkard series is now placed in the Per- mian.

The divisions named above are recinizable also in Ohio, West Viinia, and Maryland, but farther south the identification of all becomes difficult.

The Appalachian field is divisible Into two parts of very unequal size, viz. (1) the aathracitfi field of northeastern Pennsylvania; and (2) the bituminous area, which occupies the balance of the field.'

Pennsybmnia Antkradle Field (100). — This field (Fig. 6) lies in the central part of the state, coverii an area of about 3300 square miles, about one-seventh of which is underlain by work- able coal measures. The field has four main subdivisions, known respectively as the north- ern, eastern middle, southern, and western middle. Intense folding (Fig. 7) has placed some of the coal in synclinal troughs, where it has been preserved from erodon which has removed the coal from the intervemng anti- clines. Therefore the anthracite is found in a number of more or less separated narrow bans. It has been estimated that from 94 to 98 per cent of the coal Fio. 6. — Map of Pennsylvama anthra- oHnally deported has been cite fieid. lA/ier Stoek. U.S. CM. removed from this field by Swv.. 224 Ann. Sept.. III.) j j .-

denudation.

The Coal Measures of the anthracite district consist of beds of

sandstone, shale, and clay, with coal beds at intervals varying from

This includs some aoail areas of seml-aDthracite.

Iv,

i few feet to several hundred feet, though rarely exceeding 200 feet. The coal beds, which vary in thickness from a few inches to 50 or 60 feet, occur throughout the entire section of the

Fb. 7. — Seetioiia in Pennsylvania anthracite field, (4/(r , U.S. QeoL Sun., 22d Ann. RepL, III.)

Coal Measures, but are most important in the lower 300 to 500 feet. Arnoi these the Mammoth is of importance, but splits in some

The anthracite gection, though not yet ooourately ooirelated with the bituminous field of Western Pennsylvania, is nevertheless known to oon- Uia the Pooono, Mauch Chunk, Pottaville, and Allhany series, as well aa Nme of the higher ones of the Coal Measures (39). The Pottaville oonglom- ente fonoB an important stratiKraphio horizon, recognizable by its htho- loeiral oharaoters and 1x>ld outoropa.

Tlie poratioD of the ooal beds and phjsieal oharacteristios of the eoal have oMesaitated the use of special methods of mining and of treatment after mdag (100). Sharpness of folding and steep dips prevail, these intro- daeing many mining problems not found in bituminous regions. When brooght to the surfaoe, the anthracite consists of lumps varying in size and mixed with more or less shaly ooal oaUed bone, so that before shipment lo market it is necessary to break, size, and sort it. This is done in a coal (Fig. 8), in which the coal is orushed in rolls and sized by soreeos, vMe the slate is separated either by hand, automatic pickers, or jigs. These hreakeis are a prominent feature of the authracite region, and much money has been Bi>eDt in increasing their efficiency. As the result of years at mining, the refuse from the breakers, consisting of a fine ooal-dust and

b,

24 Economic Geology

boae, termed " adm," has aooumulated in enormous piles. Much of it is now being washed to save the finer particles of olean coal; and much is also washed into the miaea to support the roof, so that the pillars of ooal. origi- nally left for that purpose, can be extracted.

On aceouat of its cleanliness and high fuel ratio, anthracite coal is much prized for domestic purposes. Most of that mined is marketed in the eastern and middle states, although small quantities are shipped to the western states, especially those that can be reached by way of the Great

Fra. 8. — Coal breaker in PeiiDsylvaiiia anthracite reckon.

Appalachian Bituminous Area (36, 41).- Pennsyhania. — The Pennsylvania bituminous field includes an area of about 12,000 square miles lying mostly in the western part of the state (PI. II), and having an exceedingly irregular boundary. In the north- western part, where folding ia slight, the coal measures form outliers, capping the high hills and ridges; but to the eastward, the more marked synclinal structure has resulted in the formation of a strung out series of basins. The most northeastern areas are quite isolated, and include the Bernice (semi-anthracite), Barclay, and Blossburg badns, as well as an easterly one, the Broadtop (PI. 11).

The coals range in age from Pottsville to Dunkard, and in about four-fifths of the territory the thickness of the Upper Carboniferous rocks, including Dunkard, is less than 1000 feet, while in one-third it is under 500 feet (41). Faults are rarely found. On account of the variation in thickness of the sandstones and other rocks, splitting of coal seams, and other irregularities, correlation is difficult. But in a general way the beds above the Pittsburg seam appear to be more regular in their appearance and more constant in their dis-

field. (H. Rita, pholo.)

ooglc

Iv,

Coal 25

tance one another, than the beds in the lower part of the section. The number of coal seams recognized in the several series is as follows (99) : —

Dimkard seriee, 1100-1200 feet thick. 12 ooab

MonongahelA, 200- 300 feet thiak, 6 ooaia

Conemaugh, 500- 700 feet thiok, 6 ooals, mostly unimportant

AIIeKhAoy, 300 feet thick, 4 ooaia

Pottaville, several

The Alleghany yields about forty per oent of the bitununoas ooali niaed in Pennsylvania. While most of the coal beds are of limited extent, tbe edebrated Pittsburg seam at the base of the Monongahela has an aver- age thickness of 7 feet over about 2100 square miles of its area and an eati- nated toniutge of 9,641,792,907 short tons, thus making it one of the most ifflportaot bituminous oosi beds in the world. This same seam is also mngnizable and important in Ohio, West Viria, and Maryland.

Ohio. — In Ohio (40, 90-92) the five subdivisions of the middle and I'pper Carboniferoua are also reoognized, and there are at least 16 ooal beds, of which 6 are important. These inolude the Pomeroy,' Pittsburg;, Meigs Sevickley of Pennsylvania), Clarion, Lower Kittanninf;, Middle Kittan- nine. Upper Ii¥eeport, Wellston, and Block (Sharon). The Pittsbui Kai is of high importance and the Middle Eattouning includes the well- known Hocking Valley coal.

Maryland. — In Maryland the coals lie in three broad nortfaeastou th- reat synclinal folds, the coal measures of these being separated by Mis9i- tippian or Devonian Rooks, exposed by erosion of the intervening anti- dioes. The eastern or Potomac basin is the most important of the three. The geologic position wid number of coals is as follows: Monongahela, vith Pittsburg (Elk Garden), Tyson, and Eoontz coals; Conemaugh, 2 mis; Alleghany with Upper Freeport (Thomas or three foot). Middle Eittanning (Davis or six foot), Brookville (Parker), and Clarion (Blue- bvieh); Pottsville, with two seams. The coals are good steaming fuels ud win ooke.

Wul Virginia. — In this state the Coal Measures occupy an irregular reetaogle standing from the Alleghany Mountain region northwestward to tite Ohio River. The deepest part of the Appalachian basin takes unthwest course across the stat, the axis rising to tlie southward. From this the strata rise to tbe northwest, while to the southeast the basin shows 1 series of folds of increasing steepness and height towards the eastern bouDdary of the fields.

The ooal beds range from the Pooono to the Dunkard in age. The INtcono contains some unimportant beds of anthracite along the eastern border of the field, but westward the formation is noted for its petroleum and absence of ooal.

The Pottsville carries the coals of the New River and Pocahontas series,

Pornwily regarded as Pittaburs, but shown by Bownoclcer to be equivalent of Redstone of PenmvuiB and WcM VirdQiB. (Ohio Geol. Surv., 4Ui ser., Bull. 0, p.96, 1908.)

C,q,-Z.-dbvGOOglC

Economic Geology

these underlying an aren of about 2600 square miles in the southeastern and eastern part of the field. These coals are of high quality, being low in sulphur and aah. In northern West Virginia the Alleghany series carries . several coal beds, but with one exception these dis- appear to the south westward. The Conemaugh carries two coal beds of im- portance, while the Monongahela oairiea six distinct beds, including the famous Httsburg seam. No coals of much importance are found in the Dunkard. Virginia {111), — The coals of the

J Moimtatn Province are of either Missis- ll sippian or Pennsylvanian age.' The first or least important forms a belt of small g areas of either semi-bituminous or semi- m i§ anthracitio character extending from -3 ,K Wythe to Frederick counties, but the only one of much importance ia the I Montgomery-Pulaski county area. " The Pennsylvania coals lie in the ex-

treme southwestern part of the state in i the Cumberland Plateau region, and are the moat important producers. The two chief fields are the Pocahontas or J Flat Top and the Big Stone Gap coal 'S: fields.

The coal measures, which are prob- S ably mostly of Pottsville age, show " § comparatively little disturbance, aJ- l though they lie immediately west of the 3 highly folded rocks of the Great Valley I (Fig. 9), but the Pocahontas field is ) abruptly terminated on the east by a i fault. In the Pocahontas field there are at least six workable beds; the coal is of exeellent quality for steaming pur- poses, shows often a remarkably low ash content, and makes a good coke. The Big Stone Gap field, which extends inlo Kentucky, contains eight workable aeams and ia even a more important producer of ooal and coke.

Sovihern Appalachian Fidd. — In the southern Appalachian field the coal-bearing rocks are mnly of ;

Coal 27

Pottsville age, and in the Birmingham, Ala., district have a thick- ness of probably 5000 to 6000 feet. The Coal Measures, which show much disturbance on their eastern main, with but little toward the west, are divisible into a lower (Lee, Lookout, or Millstone Giit) group, carrying about three thin seams in the lower part, and an upper group, with many beds of coal.

Although the coals and associated rocks were originally deposited in a broad trough, this has been subsequently folded, and faulted, while the basins are separated partly by faulting and partly by erosion of intervening anticlinal crests.

There are three mtun districts, known as the Jellico, Chattanooga, uid Birmingham, the latter containing four fields, viz., the Warrior, Cooaa, Cababa, and Blount Mountun.

The Triassic Held (ill, 112). — This coal field, wliich is more important historiciJIy than economically, having been worked as early as 1700, inehides aevwal small steep-sided basins (Fig. 10), lying in the Piedmont

Fio. 10, — GeneraJ stmcture section of tbe Richmond Ban in the vicinity of Junes River. A, A, A, minor flexures, with beds downthrown to the west; /,/. /. faults. The heavy block band represents the supposed position of tbe coal beds. North lUid south of this section tbe beds appear to be deeply faulted dawn against the western margiii, and the apparent syDclioal structure dis- ippeaia. The superficial portion of this section is tiased on observation and reliable information; the deeper portion is hypothetical. (A/Ur Shoier and WoodaiTrat, V. 3. Oecl. Sun., 19IA Ann. Kept., Pi. II.)

ngion of Virginia and North Carolina. It is probable that the ooal- benrine beds of the several areas, originally horizontal, were formerly Hintinuous, having been separated by folding, faulting, and denudation. In addition to this, the coal is cut by dikes and sheets of igneous rook, liiich have locally altered it to natural coke or carboniU,

Eastern Interior Field (34, 57-59, 65-69). — This field la an oval, elongated baan (Rg. 11), extending northeast and southwest, with the mainal beds dipping gently toward the lowest portion, which hes in Illinois, where the beds are nearly horizontal. It covers most of Ilhnois, southwestern Indiana, and a small part of Western Kentucky, with some small outliers in Missouri, near St. Louis and St. Charles, and two in Ilhnois.

bCoogk'

Economic Geology

The coal-bearing rocks rest unconformsbly on lower Carbonifer- ous, Devonian, and Silurian strata, the basal J J member being a sandstone, probably the equiv-

alent of the Pottsville, The entire Bection of

coal-bearing rocks, attaining a thickness of 1200

J feet, belongs to the Coal Measures, although

the upper part may be of Permian age, and

1' the highest workable coal beds are classed as

J Freeport or Conemaugh. The coal seams occur 7! in the lower portion of the section, and hence outcrop around the main, the mining opera- tions being therefore confined to a narrow belt, because near the center of the basin the coal beds underlie too great a thickness of unproductive strata to permit of profitable workii under

. present conditiops,

. Great difficulty has been encountered in at- a tempts at correlation of the coal beds of different parts of the field, because of the varying section I. shown from place to place, and lack of continuity of the beds. In consequence, the custom has S arisen of giving the coal beds numbers instead of names.

g The coals of the eastern interior field, S although varying widely in quality, are all Ji bituminous. On account of their higher per- " centage of aah and sulphur, they are little used I for coking. Most of the coal used in and near this field is supplied from it; but even within

I the field the Appalachian coals enter into com-

g petition. The cannel coal found near Cannels- .1 burg, Kentucky, which is the only good gas g producer found in this field, finds a ready

I market.

In Ulinois the section involves (57): — M a. Upper or Barren Coal Measures.

b. Lower or Productive Coal Measures .-ooalbeaEJng.

e. Millstone Orit or M&nsfleld Sandstone.

5 The old survey recognized 16 beds, of which 1-7

are commonly worked, but later work throws doubt

Q this olasuflcation; the areas of important development of the different

b,

Coal 29

bedi an not ooinoident, bat as & eiieral rule the coala above No. 2 in

tbeTeslern part of tbe state are persistent in extent and thioknesa over

lu mas, while in tlie eastern portion all the seams are irregular in

hotJi ertent and thickness. As a rale, the lower seams are better than

Ibe upper ones, and the quality also increases fram north to south. The

niinoia seams vary from 3 to 8 feet in thickness, and all are bituminous. Ashley subdivides the Indiana section as follows: — Permian-Meroin group; Upper or Barren Measures, O'-40O', Col Measures j group; main coal-bearing measures, 10O'-60O'.

1 Mansfield group; basal sandatone member, 0'-200'. The eoal field is roughly divisible into two areas, viz. an eastern or

"block-coal" area, and a westm or bituminous area. The former ia

ilao bituminous, but shows a peculiar blook-like jointing. The Indiana section

>1mws at least 25 di-

tiai;! coal beds (59),

uvl}' all of them 2 feet

maoK thick in some

FJaoes,aDdnineof them

KDtinuiag of minable

ibicknesa over large

WM. The upper five

ol the nine numbered

lam are coloDg and

wur in broad sheets, Fio. 12. —

while the lower four

oMiir in basins aad are

not eitensively workable. No. 5 is the most important bed in tbe state

ud can be correlated the entire length of the field. In Eentuoky the ooals have been numbered from 1-12, beginning at the

Iwitom and lettred beginning at the top. Noa. 9, II, and 12 are the

chief ones worked. One of these is exoeedingly persistent, being found

under a part of the whole of two counties, with an average thickness of

feet, and at a depth oommonly of less than 200 feet.

northern Interior Field (72). — This field forms a large basin in 'hich the coal dips irregularly from tbe margin toward the center ifig. 13), but on account of the heavy mantle of glacial drift it has been difficult to determine its exact boundaries, and prospecting is "WKssarily done by means of drilling. The Coal Measures, which ire probably of Pottsville age, attain a total thickness of 600 to 700 fet in the center of the basin, and include 7 horizons of workable wal with an average thickness of 2 feet and rarely exceeding 4 feet. The Verne coals near the top may correspond with the Mercer coals of Ohio (Lane). Coal is found near the center of the basin at 'ieptha of 400 feet or more, though the beds that are mined are rooatly at depths of 100 to 250 feet. All the coals are bituminous

b,

30 ECONOMIC QEOhOQY

and used chiefly for fuel, but some are coking, and others will prob- ably prove of value for gas manufacture. Sagaw and Bay City are important mining towns.

Western Interior Field and Southwestern Fields (35). — These two fields form a practically continuous belt of coal-bearing forma"

tions, extending from northern Iowa southwestward for a distance of 880 miles into central Texas, Throughout most of this area the beds lie horizontal, or have a gentle westward dip averaging 10 to 20 feet per mile, but a notable exception is found in the beds of east- em Oklahoma and Arkansas, which are rather strongly folded, reminding one of the Pennsylvania anthracite area.

Western Interior Field. — The Coal Measures, composed of lime stones, shales, fire clays, and coal beds, rest unconformably on thi Mis.<3sippian and dip westwardly under beds of Permian, Creta ceous, and Pleistocene. Toward the south and west the beds increas in thickness, the maximum being 1000 feet in Iowa (62), 3000 h Kansas (63), and 200 in Missouri (74). In a general way there i a prevailing dip westward of 10-20 feet per mile; in detail the dii

L;,q,-z.= bvCoOg[c

b,

b,

Coal 31

is south'southwest in Iowa, westortbwest in Missouri, and usually ortbwest in Kansas.

The Coal Measures are divisible into two parts. The lower is tnown as the Des Moines in Iowa, and the Cherokee and Marmaton m Kansas. The upper is termed the Missourian in Iowa, but in Kao&as is made up of the Pottawatomie, Houglas, and Shawnee. In both states most of the coal mined comes from the Cherokee shales boriion. Those found in the upper measures are thin, even though persistent.

Most of the coal mined in this field comes from the lower part of the coal measures, where the beds are irregular in thickness and distribution, in conse- quence of deposition on ipESTS!" cLAfsmcvnpif arr

.\11 the coals of this

field are essentially bitu-

minous and used chiefly for steaming and heating

value for either coking or gas making. Some of the seams will coke, but there is no demand for the ckTuu (o>t*bio product, and the sulphur and ash are too high for gas making.

The Oklahoma and Ar- Itansas portions of the Western Interior field are (iirectly cormected, but liieeoalsdififersomewhat.

The rocks of the Okia- LoiwciiMni homa field (60), belong to

the Coal Measures (Fie Fla. is. — Columnar eection of eoBl-bcarini rocks Oklahom* coal field. {After Toff, V. S.

Oeol. Siin,.. 22nd Ann. Repl., Pi. III.)

'5), the lowest coal beds

heing probably in the

upper part of the Lower Coal Measures, and the highest coal in

the Upper Coal Measures.

The coal field is characterized by both folds and faults. The antieliQes are generally narrower and deeper than the synchnes, with a tendency to overturn to the north, but the folds die out to the

; C'.OOgIC

32 Economic Geology

westward and uorthwestward. There are seven important beds of workable character, as well as some that are workable locally. The coala are bituminous and coking.

In the Arkansas field (49) the rocks (sandstones and shales) are all of Pennsylvanian age, and involve a section several thousand feet thick, which can be correlated furly well with the Oklahoma area. They are bent into a trough in which there are a number of sub- ' ordinate folds and some normal and thrust faults. The coals of the Hartsbonie horizon (Fig. 16) are economi- cally the most impor- tant, while those below it are probably thin and not continuous. The coals raie from bitu- minous to semi-anthra- cite, and, although not of coking character, excel in quality any found west of West Virginia.

Sffulktoestem Field (40). — This area, lying in northern Texas, is separable into a north- em and southern por- tion by an arm of Cre- taceous strata, extend- Fio. 16. — Generaliicd columnar Bection of the ingaCrOSsit. The COals cosl-bearing rocka of Arluuiaaa. {A/ter Collier, „i.:„u „„ „ii l' U.S. Gtol. Sun,.. BuU. 326.) Pennsyl-

vanian.rest unconform- ably on the Mississippian and are overlfun by the Permian on the north. There are five divisions, which carry three workable coal beds, and while all are of bituminous character, none of them are; coking.

Rocky Mountain Fields (38), — These cover a broad area extend- ing from the Canadian boundary southward into New Mexico,!

z .IV, I

b,

a and Cannel, Texas.

- Lignite seam, Williston, N. Dak. (AJter F. Wiider, pholo.)

Iv,

Coal 33

a, distance of about 1000 miles, and including a large number of fields of varying ze and irregular shape. Most of these beds lie within the mountunous region, but at the northern end of the area, in Wyomii and the Dakotas, the coal fields extend eastward under the Great Plains for some distance. The age of the coal ranges from Lower Cretaceous to Eocene (Tertiary), though most of it belong to the former.

While portions of this enormous area of coal-bearii strata are only slightly disturbed, mountuQ-buildii forces and igneous in- tniaons have affected a large proportion of the region, often materi- ally changing the character of the coal. Thus, while in imdis- turbed portions of the field the beds may be lignitic (PI. V, Fig. 2), in the disturbed parts they have been altered to bituminous. Igneous intrusions may have changed the latter locally to anthracite, as in the Crested Butte (55) area of Colorado or the Cerrillos field of New Mexico (80). Some of the bituminous coals produce an excellent quality of coke.

Colorado (54, 55) is the moat important ooal-produoing Btato (Fig. 17) of (be Rooky Mountain region. This is due, not only to the quality of ita toils, but also to the preseuoe within the state of extensive metalluririoal mdustrim. The Raton field in the southeaatem part of the state, extend- mginto New Mexioo (82),i9at present the most important producer. Like muiy of the fields of this region the age of the ooals in this b Laramie, ICretMeous), and the beds are both folded and faulted. They ore, more- over, crossed by igneous intrusions, which have in some places produced utunl ooke, but in others destroyed the value of the ooal. The coals are bituminous and some are ooking. Those of the South Platte field are sub- bitnminouB and worked mainly north of Denver; so too are those of the North Park and Yampa fields, but the lattr contains some antbraoite tomed by igneous intnisionfl. In the San Juan River reon, where I'pper Cretaceous coals occur, the latter changes from sub-bituminous in the southern part to bituminous on the flanks of the San Juan mountains. The CanjroQ City field carries bituminous noncoldng coal and the Uinta basin bituminous grades.

Wyoming (110-118) haa a larger percentage of its area underi&in by MMd-bearing rocks than any other Rocky Mountain state, but most of this lies in the Great Plains region, and hence the coals, which are mostly Cre- iMeous, are on the whole of lower quality. The location of the Adds is shown in part on the accompanying map. The ooals are mainly of sub- bituminous character, but some are bituminous, as around Rock Springa ud in the Hama Fork Region, as well as in part of the Green River and Black Hills fields.

A great area of Eocene lignitic coal is found in the Fort Union Ron of Xorth Dakota, South Dakota, and Montana (75-77). Farther west in Montana, in the Great Falls and Lewistown fields of the Judith Basin,

t,

34 Economic Geology

bituminous ooal, some of it of ooloDg quality, is found. These last two are of Kootenai (Cretaceous) age. Sub-bituminous ooals of Upper Cretaceous age are found in the Aasiniboine Region of northern Montana.

Utah (loe) has two larre coal areas. One of these, forming a part of the Uintah region and lying southeast of Salt Lake City, carries Upper Cretaceous coals of bituminous character, which can be coked. The second, in the southwestern part of the state, also supplies bituminous coal.

Gulf Province Lignites (70, 73, 105-107). — These are of Eocene (Tertiary) age and are all low grade, with the exception of those along the Rio Grande, northwest of Laredo, which may be regarded as sub-bituminous. Those found near Eagle Pass are of still better quahty, but occur in the Cretaceous.

Pacific Coast Fields (37). — Tertiary coals, partly bitumiaous, though mainly lignitic, occur scattered over a wide area in the states

Coal 35

of California (50-53), Washington (114), i ami Oron (93, 94). The separate fields

are limited in extent, and widely sepa- J

rated. Their output is small as compared -g

with some other states, but still it is be- I

coming of growii importance. '1

Of the scattered fields in Washington, i J

the most important lie directly east of

Seattle and Tacoma. The total thick-

oess of coal-bearing strata is about

10,000 feet, but important coal beds are J found only in the lower 2000 feet. The . ij

quality of the coal varies with the extent £ of the dynamic disturbance, and hence there may be variation even in a single

field, and, in fact, in a single mine. Call- A

fornia is an important market, even "

though the coal has to compete with fuel M

oik. J i

Both California and Oregon are small J producers. In the former coals of sub- bituminous character have been mined near Tesla, Alameda County, and re- cently coal of good bituminous grade has been worked in Stone Canyon,

Monterey County. Indeed this is of , g

sufficiently high quality to compete with I ,S §

foreign coals brought into San Francisco.

In Oregon, the Coos Bay field has been a small but fairly steady producer.

The coal trade conditions of the Pacific - ,

coast have been unique. The local sup- 'J

ply is not equal to the demand, and the J g fl Rocky Mountn fields are too far off to

supply the Pacific coast with cheap fuel, -

Therefore, much coal is imported, bring- J

ing about a competition in San Francisco "§

from other countries, including England,

Wales, Scotland, Australia, Japan, and i

British Columbia. These foreign coals ad

are often of better grade than the Pacific j

c,q,z.<ib,

it

I

1!

ij

Economic Oeologt

coast coals, and they can be imported with low rate as ballast in wheat-carrying vessels that come to San Francisco for cargoes. These coal imports form three-quarters of the total im- port coal tonnage of the United States; but mnce 1896 there has been a steady decrease in the importation of coal and an i in the Pacific coast production.

Alaska (45,46). — Although Alaskan coal was first mined in 1852 at Port Graham, the resources of the region are still but little known to most people, and only slightly developed. The ex- plorations for gold during the last few years, tiether with the field work done by the United States Geolocal Survey, have proved that coal is widely distributed in the Alaskan territory (Elg, 19). The depoats range geologically from the Carboniferous to the Tertiary, those of the latter age being the most abimdant.

Lack of knowledge regarding the better coats and insufficient transportation facilities are among the causes that have retarded the development of the coal fields.

b,

Coal

Id the Pacific eoast reon fields of Meeozoio and Tertiary ooals, ranginff from lignite to anthrsoite, are known &t sevsnil points, and while many of ttie beds are of great thiokneas, the irregularity of the structure produces unfavorable '"ining conditions. However, these ooals are well located for shipment.

The interior region, including the Copper and Yukon River valleys and their tributaries,, carries Cretaceous bituminous coal on the lower Yukon and Tertiary lignite and sub-bituminous ooal on the upper Yukon as well u in the Tonana, Koyukuk, and Copper River basins. This coal can only become of local importance.

la the Bering Sea and Arotie slope region ooals of Carboniferous, Ju< tssaic, Cretaceous, and Tertiary age are present. None of these are likely to beoome of immediate value, except for local use, although the high-grade ooal of Cape Lisbume may prove an important souroe of supply for Nome; bat still the shipping problem is a serious one.

Production of Coal. — The first mention of coal in the United States is probably in the journal of Father Hennepin, who in 1679 recorded the ate of a " cole mine " on the Illinois River near the pres- ent city of Ottawa, Illinois, but the first actual mining appears to have occurred in the Richmond basin, Virginia, about seventy yeara later. The first records of production are in 1822. Ohio probably ranks second in priority of production, as coal was discovered there in 1756, but the records of mining date only to 1838. The roinii of Pennsylvania anthracite began in 1790, and in 1807, 55 Ions were shipped to Columbus, Ohio. The rular production dates from 1814.'

The phenomenal growth of the coal mining industry is well shown by the diagram (Fig. 20).

The production of the individual states since 1904 is given on page 39.

Grouping the output by repons, the overwhelming importance of the Appalachian region is well seen.

Production of Coal in Unttbd States bt Regions fbom 1904 to 1908, IN Short Tons

1904 I90S

leoe

73,228.773 77,734.873

]!34z!s4a l!4T3i21] 61,682,313 55,255,541

71,342.8*9

l!34e!33S 69,457.660

3!386!7*B

86.668,401

266,501.627 2,035,8.Vi

3.775.wi2

83,310.412

b,

Economic Gbolooy

b,

40 Economic Geology

Price per Ton. — The average price per short ton of coal fluctu- ates somewhat from year to year, and yet not as much as one might imafpne. The figures below show the prices for the last ten years.

Awrmi-

BmiKi-

Tmu

Aiamu-

Brnmi-

c:iB

Moot

om

Ims

t .41

to.so

9M . . . .

t .90

-W

1.2*

Exports and Imports. — The exports conast of anthratnte and bi- tuminous coal, the quantity of bituminous bng the greater in the last few years. They are made principally by rail over the interna- tional bridges and by lake and sea to the Canadian provinces. Ex- ports are also made by sea to the West Indies, to Central and South America, and elsewhere.

The imports are principally from Australia and British Columbia to San Francisco, from Great Britun to the Atlantic and Pacific coasts, and from Nova Scotia to Atlantic coast points.

The statistics since 1904 are given below: —

Coal o

DouEeric Pboddction bxpobtid pbou the United States, 1904-1908, IN LoNO Tons

Ybai

AHTnBAcm

Brnmifous &mi> bai.e

Qu.Dtity

QiuntiW

i!ia4!sM

0.Sm1.30D

e.BseiMS

'3s

$lT.ieO,53S 173e7.M4

Coal ihpokted

&rATB8, 1904r-1908, i

YE*a

AKTBHACrr.

BmrHiHODi

amdShau

Qiumtity

ViJuo

Qu-otitr

VlllK

(230,004

I.SMJSI 'l.Hl 1.002 l,70!,799

l!452:efl2

3.S05.4S9

3.>64,S13

b,

Worid'a Production. — The following figures are those ven by the U. S. Geol. Survey, and compiled from various sources : —

tnitad States riaOS) Iodc t

Gnu Biiuia {1906) da.

Gmur<lS06) owtrio U

CniwtdMM) do.

Kuii uumDland 09177) do.

BumUSOS) do.

lima (1907) do.

Iid (ItOS) long t

Ctudm (I90S) bort I

Srr South Wal (IMS) lona t

Min IIB07) mstiiii I

T™!tm!{1908) loDf t

SewZflmnAliaOfT) do.

SitilHBOT) do.

VBud mad Violoiu (I9DT) do.

Ani(IK) metric!

HoUud (leOB) do.

lulrllKiT) do.

Sndai (1907) do.

CipF CoWr (leOT) loost

TiouiidBdS) do,

Wberaiijntrie.1 do.

ToUl ,

PinuUfn of the Uoitad Stall*

l!83l!0O9 305.33S

Siloes

28,686.532

24,099.303 15,301.000

QDANTnr (Sbobt Tons) and Value of Coke produced in Untted States from 1906 to 1908

Bun

QaiKTrTT

v*Li™

qnAHTITT

ViLUB

QDlimTT

v.„

'i

3.7i:

eoi

Om

Ml

i;

IJiOf

9(H

1,013

am

3.021.794

74!b34 372,891

10,210,194 4,747,43S 1,737,464

840,253 819,262

-fflffi

0,717.130 10,837,173

2.362,866

982,291 39,422

274,505 1M,578

''sa.'ssf

2'288'oi'

17,169,001

' sloii

32,569,621 B,287;05;

If

'Include* China, Turkey. Servia, Partugal, United States of Colombia, Chile, Boneo. tnd Labuon, Peru, Greece, etc. Included under other itatea.

bvGoog[c

Economic Oeolooy

The quantity of coal consumed in manufacture of coke in 1907 was 172,784,851, while the value of the coke was ,539,126. The production of 1908 was less on account of the financial depres- sion.

There were, in 1908, 551 establishments, operating 101,218 ovens. Of these about 3600 were by-product ovens, from which the average yield of coke is higher (73.6 per cent in 1908). The by-products saved from these were as follows for 1907 and 1908: —

Ibob

Q.xrr,

Qh H cubio Fbm

BdloDi

12Sj72.360

K, 130,839 1,242.S30

3.1 7*702

1S.206.93G 42,720,609

43.320,426 16,445,030

2.557,481 1,007,613

1,2B6.22(

7i382:2e

Coke AontoM

blemAW

7.U8,07I ai ,686,157

4.201.236

14.46S.429

aajiia.aia

Many of these by-product ovens are located in states producing no coal.

b,

Peat

Oiigiii. — So much atteation has been attracted to this material in tbe last few years that it seems desirable to treat it as a separate topic, and partly so because it can be used for other purposes than fuel.

Peat (128) may be defined as " vegetable matter in a partly de- canposed and more or less diEontegrated condition," and represents much of the "dark-colored or nearly black soil found in bogs and swamps.'" The dry peat may be very fibrous and light colored, or compact, structureless, and dark brown or black. If wet, it tonUuQS as much as 80 to 91 per cent or even more water. As pievioualy mentioned (p. 3) it is produced by tbe slow decay, under water, of accumulated plant remuns.

Vta. 21. — Diagram Hhowing how plants GU depresmoDB from the side and top. to fonn a peat deposit. — 1. Zone of Chant and Soating aquatics. 2. Zone of PatamogjIiOot. 3. Zone of water lilies, i. Floating sedge mat. 6. Advance Iilwita of omiifers and ahniba. 6. Shrub and Sphagnum loae. 7, Zone of Tam- uadc and Spruce. 8. Margiaal Foeae. {A/to- Davit, Mich. Qtol. 8utv., Ann. StfL for 1908.)

The two essential conditions for peat formation are (1) restricted access of air to impede growth of decay-producing organisms, and (2) abundance of water to permit profuse plant growth.

This decay is accomplished nuunly through the agency of f ui and atr-requiring bacteria which break down the tissues, the decay involving decrease in bulk, darkening in color, and Uberation of paeous constituents. Both moisture and air are essentials to this process.

Since an abundance of water is essential to peat formation, and as it is formed by accumulation of plants in the spot where they grew, it requires plants of a water-Ionng nature. But peat may form in lakes or ponds, or in moist depresons or flat areas, and hence [dants adapted to these different sets of conditions being differ-

I bum freely, it is technically

bvCooglc

44 Economic Geology

ent, it follows that the product may come from more than one kind.

Peat may be formed in lakes or similar depresraons by aquatic plants, including minute alga, building up a deposit from the bottom and around the sides, in water shallower than 15 feet. The exteoMon of this deposit into deeper water and building up of the bottom permits growth of aquatic seed plants, resulting tn estab- lishment of characteristic zones. These are characterised (127) by (1) the pond weeds, PotaTitogeton, next to the deepest water; (2) shoreward of this the pond lilies; (3) the lake bulrush, Sdrpus; and (4) the amphibious sedges, especially the turf-forming slender sedge. In some localities some of the zones may be absent. The sedges may also extend outward from the shore, forming a floating mat, which may cover the entire surface of the pond, and become covered by a growth of shrubs and even large trees, although the mat may not be more than 4 or 5 feet thick.

Peat may also form on moist, flat, or slopii surfaces, in depres- sions from which standing water is naturally absent, provided the plant remains are kept saturated with water, which they hold there partly by capillarity. In such situation plants of the rush, grasa, sedge type, or epkagnum are important. This type of peat accumu- lation flourishes best in reons of heavy rainfall and moist atmos- phere, and the depoat shows an irregularly stratified structure, but more uniform character than the fiUed-basin type first described, whose structure is more uniform below the original water level, but whose upper 3-5 feet is nearly always of different structure and com- position from Uiat below. Some bogs may be of composite origin.

The present surface vegetation of the bog does not necessarily indicate the kind of plant from which the peat was formed.

An interesting type of peat is that found in salt marshes, of which there are thousands of acres along the Atlantic coast, these marshes being poorly-drained plains subject to frequent overflow by the sea- water. Studies by Davis of the Maine marshes (128) indicate that the peat is either of " fresh-water orin below a relatively thin stratum of salt-water peat, or else made up entirely of plants similai to those growing on the marshes to-day at about high tide level." The suggested explanation is that the fresh-water peat has been formed in fresh-water bogs situated on a slowly sinking coast, while the upper or salt-water peat formed when the land was low enough to permit an influx of salt water, thus permitting the growth of only such plants as could stand it.

L:,.i,-z__iv,CoOg[c

Coal 45

Tlie fresh-water peat may be of fuel value, but that formed wholly by the growth of salt-marsh plants is too full of fine silt and mud tidal dep<ts to be of marketable character. (See analyses, p. 6.)

Uses of Peat (119, 126, 127). — The mun use of peat is for fuel, but it has never been extenavely used in America for this purpose. A number of experimental plants have been built in Canada, but most of them have not been successful nor have any been so in the United States. The failure may have been due to lack of capital, improper machinery, or lack of experience. Since a detailed dis- cimon of peat-fuel technology is beyond the limits of this work, those wishing to follow it up are referred to Nos. 126, 127, 128, of the bibliography.

For fuel purposes the peat may be used in tur-dried form as it )ra€9 from the bog, pressed into blocks (machine peat) , in briquettes with or without binder, or in gas producers. Peat charcoal and peat coke are manufactured in considerable and increasing quantities in Germany and Rusda for use in metallurgical work, but the by- product gases are saved in connection with the coking process.

Of importance is the use of the more fibrous kinds of peat as a material for bedding for stock and for packii, as well as for deodor- izing and disinfectii. Those varieties of powdered peat which are rich in nitrogen are dried and sold for filler in certain kinds of artifi- cial fertilizer, and although a use of recent orin it seems to be gromng. " Mull " is the finer matter separated from moss litter acreeniog, and sold for deodorizing, filterii, disinfectii, and packing purposes. It is manufactured at Garrett, Indiana.

The manufacture of fertilizer filler is at present the largest industry based on peat in the United States.

Those peats having a strong fiber can be used in the manufacture of cloth and paper, but the American material is uosuited to this purpose. Peat can also be utilized for making ethyl alcohol, ind also for presMng into a structural material resembling wood. Distribution in the United States. — Those regions possessing peat beds of sufficient size and depth to be of commercial value, lie mostly outside of the coal-producing territory.

lavis states that workable beds are found in many states lying lorth of the Ohio and east of the Missouri rivers, in the coastal por- tions of the Middle and South Atlantic and Gulf states, and in the fsrrow strip along the Pacific coast from southern California north- ward to the Canadian boundary.

46 Economic Geology

Production of Peat. — Few statistics showing the production of peat in the United States are available. The United States Geo- logical Survey report gives the total production of peat fertiUzer filler in 190S as 23,000 tons, averaging S5.25 per ton at the plant. Five peat fuel plants were operated in a small way during the year. Peat moss litter was manufactured at Garrett, Indiana, the material being sold in bales of 225 pounds, valued at $1.25 per bale. The pro- duction was 8000 bales.

The imports of peat moss for the last three years were as follows:

Yub

CJoATrrr

LotbTmu 7.(M0 T.flSO M03

Referbrcbs Oh Coal

Origin. 1. Ashley, Econ. Oeol,, II: 34, 1907. (Maximum rate of deposi- tion.) 2. CampbeU, Eoon. Geol., I: 36, 1905. (Oriein.) 3. Clarke. U.,8. Geol. Surv., BuU. 330: 642, 1908. 4. Dowling, Can. Min. Inat. Jour., XII, 1909. (Chemioal ohanses in oobJ fommtion.) 5. Lquereux, 2d Geol. Surv. Pa., Ann. Rept.: 95, 1885. (Origin.) 6. Lyell, Amer. Jour. Sei., CLV: 353, 1843. (Upright trees in ooal.) 7. Mof- fat, Amer. Inst. Min. Eners., Trans. XV: 819, 1887. (Change of mine prop to ooal.) 8. PotoniO, Klassifikation und Terminolosie rezenten brennb&ren BJolithe und ihrer Lagerstfttten. lYussian Oeol. Surv., Berlin, 1906. fl. Potonie, Die Entsthung der Steinkohle, Berlin, 1907. 10. Smith, Econ. Geol., 1:581, 1905-1906. (Diseus- aion of Campbell's theory.) 11. Stvensott, Geol. Soo. Amer. Bull., ¥ :39, 1893. (Origin Pa. anthracite.) 12. Whit, Eoon. Geol., HI: 292, 1908. (Problems in coal formation.)

CLABsmcATioN. 13. Campbell, Eoou. Geo]., Ill: 134,1908. 14. Campbell, Amer. Inst. Min. Engrs. Trans. XXXVI: 324, 1906. IS. Collier, U- 8. Geol. Surv., Bull. 218, 1903. 16. Dowling, Can. Min. Inst., Quart. Bull, No. 1 : 61, 1908. 17. Frazer, Amer. Inst Min. Engra., Trans. VI:430. 18. Grout, Eeon. Geot., 11:225, 1907. 19. Parr. EI. OeoL Surv., Bull. 3, 1906. 20. White, 'U. S. Geol. Surv., BuU. 382, 1909.

CoupoamoN, , etc. 21. Bain, Jour. Geol., Ill : 646, 1895. (Struotupe of ooal basins.) 22. Campbell, Eeon. Geol., 11:285, 1907. (Improvements in utilization of coal.) 23. Campbell, Eoon. Geol., Ill : 48, 1907. (Value of ooal mine sampling.) 24. Catlett, Amer. Inst. Min. Bng., Trans. XXX : 559, 1901. (Coal outcrops.)

25. Lesley, Manual of Coal and its Toptraphy, Philadelphia, 1850.

26. Lord and others, U. 8. Geol. Surv., Prof. P&p. 4S and Bulls. 261

f.Cooglc

Coal 47

ud 290. (Analjrses, teats, etc.) Other buBetina on fuel testing have been published from time to time. 27. Parr and Hamilton, Econ. OeoL. II : 693, 1907. (Weathering of coal.) 28. Pishel, Econ. Oeol.. Ill : 265, 1908. (Teat for coking coal.) 29. Much general informa- tion in the specdal ooal reports of Iowa, Kansas, Indiana, and Ohio Geological Surveys. General Areal Bkportb. 30. Hayes, U. S. Qeol. ., 22d Ann. Rept,, III: 7, 1902. (U. S. ooal fields.) 31. MacFarlane, Coal Regions of America, 700 pp.. 3d ed., 1877, New York. 32. NichoUs, The Story of Amerioan Coals, 1897 (Phila.). 33. White. U. S. Geol. Surv., BuU. 65. (Bituminous field. Pa., Ohio, and W. Va.) 34. Series of papers on the sevenl ooal fields of the United States, in U. 8. Oeol. Surv., 22d Ann. Rept., Ill : 11-571, 1902, as follows: Ashley, p. 271. (East- ern Interior.) 35. Bain, p. 339. (Western Interior.) 36. Hayes, p. 233. (Southern Appalaohians.) 37. Smith, p. 479. (Paciflo coast.) 38. Storrs, p. 421. (Rooky Mountain field.) 39. Stoek, p. 61. (Pl anthracite.) 40. Taff, p. 373. (Southwestern.) 41. White, Camp- hell, and Hazeltine, p. 125. (Northern Appalachians.) — Alabama : 42. Butte, U. S. Oeol. Surv., Bull. 316 : 76, 1907. (Cahaba field.) 43. Gibson, Ala. Oeol. Surv., 1805. (Coosafield.) 44. McCalley, Ala. Oeol. Surv., 1900. (Warrior field.) Also brief accounts in U. 8. 0. S. BuUe< IJiis,260and285.— AIaska:45. Brooks, U.S. Oeol. Surv., 22d Ann. Rept., ni:515, 1902. 46. Martin, Ibid., Bulls. 314:40, 1907, and 284: 18, 1906. — AEiioiia:47. Blake, Amer. Oeol., XXI : 345, 1898. 48. CampbeU, U.S. Oecd.Surv.,BulI.225:240, 1904. (DeerCreek field.)— Ai1tansa8:4g. Col- lier, U. S. Oeol. Surv., BuU. 326, 1907.— Califonua: 60. Arnold, Ilrid., BuU. 285 :223, 1906. (Mt. Diablo range.) 51. CampbeU, U. 8. Qeol. 8urv.. BuU. 316 : 435, 1907. (Stone Canyon.) 52. Smith, U. S. Oeol. Surv., 22d Ann. Rept., 111:470. 53. Also oounty reports in 11th Ann. Rept. Calif. State Mining Bureau.— Colorado: 54. Storrs, U. S. Geol. Surv., 22d Ann. Rept.; HI: 421, also special reporU of U. 8. Qeol. Surv.. BuUa. 297 (Tampa field), 316 (Duranfro field), 341 (N. W. Colo.). 55. U. S. Oeol. Atlas, FoUo No. 9. (Anthracite — Crested Butte area.)

— Geor : 56. McCallie, Oa., Oeol. Surv., BuU. 12, 1904. (General.)

— Illinois : 57. Parr, Trout, and others, lU. Oeol. Surv., Bull. 4 : 187, 1906; also Ibid., BuU. 8 : 151, 1907. 58. Ashley, U. S. Oeol. 8urv., 22d Ann. Rept., Ill : 271. — Indiana : 59. Ashley. Ind. Dept. Oeol. and Nat. Res., 23d Ann. Rept., 1899, and 33d Ann. Rept., 1909.

— Indian Territory : 60. Taff, U. 8. Geol. Surv., 22d Ann. Rpt., Ill: 387, 1902; also /Wi., BuU. 260:382, 1905.— Iowa : 61. Bam, U. 8. Geol. Surv., 23d Ann. Rept., Ill : 339. 62. Hinds, la. Qeol. Surv., XIX : 1909. (General.) — Kansas : 63. Haworth and Crane, Kas. Oeol. Surv., Ill: 13, 1898. — Kentucky : 64. Norwood, Ann. Rept., Inspector of Mines, 1901-1902. (Much general information.) 65. Moore, Ky. Oeol. Surv., Ser. 2, IV, pt. XI : 423. (Ea8tm border and Western field.) 66. Ashley and Glenn, U. S. Geol. Surv.. Prof. Pap. 49, 1906. (Cumberland Gap field.) 67. CrandaU. Ky. Geol. Surv., BuU. 4, 1905. (Big Sandy Valley.) 68. Stone, U. 8. Oeol. Surv., BuU. 316 : 42, 1907. (EUkhom field.) 69. For analyses, see Ky. Oeol.

i ECONOMIC QEOLOGT

Surv., new series, Chem. Rept., etc., pta. I, II, and III. — Louisiana : 70. Hftrria, Prelun. Kept, on Geol. of La. for 1899 ; 134. (Lignite.)

— MaryUnd: 71. Clark, Md. Gool. Surv., V. 1905. — Midiiein : 72. Lane, Mich. Oeol. Surv., VIII, pt, 2. — HissiSBippi : 73. Brown, Miss. Geol. Surv., Bull. 3. 1909; also Eeon. Geol., Ill : 219, 1908. (lignite.) — Missouri : 74. Winatow, Mo. Geol. Surv., 1891 : 19-220.

— Uontana : 75. Bowe, Univ. of Mont., Bull. 4. (Oener.) 76. Weed, Bng. and Min. Jour., LIII : 520, 542, and LV : 197. (Great Falls and Rooky Fork fielda.) 77. Scattered papers, on individual fields in Bulls. 225, 285, 316, 341, 356, and 390 of U. S. Geol. Survey.

— MebraBka: 78. Barbour, Neb. Geol. Surv., 1 : 198. 1903. — Nevada :

79. Spurr, U. 8. Geol. Surv., BuU. 225:289, 1904.— New Merico:

80. Johnson, Soh. of M. Quart., XXIV : 456. (Cemlloa.) 81. Schro- der, U. 8. Geol. Surv., BuU. 285 : 241, 1906. (Durango-OaUup.) Other papers in Ibid., Bulls. 225 (White Mountain reon), 285 (Engle), 316 (Durango-Gallup, Sandoval County, Lincoln County). 341 (Du- rango-Gallup). 82. Stom, U. S. Geol. Surv., 22d Ann Kept., Ill: 415.

1902. — Worth CaroUna : 83. Woodworth, U. 8. Geol. Surv., 22d Ann. Rept., 111:31, 1902. — North Dakota: 84. Babcook, N. Dak. Geol. Surv., Ist Bien. Kept., 1901 : 56. 85. WUder. Boon. Geol., July- Aug., 1906. (Lignites.) 86. Storra, U. 8. Geol. Surv., 22d Ann. Rept., Ill : 415, 1902. 87. Leonard, U.S. Gaol. Surv. Bull, 285 : 316, 1906. (N. Dak. — Mont. Ugnit area.) 88. Smith, 11. S. Geol. Surv., BuU. 341 : 15, 1908. (Sentinel Butte.) 89. Burohard, Ibid., Bull. 225: 276,

1903. (Missouri VaUey.) — Ohio : 90. Orton, Ohio Geol. Surv., VII: 255. 91. Lord, Bownocker, Somermeier, Ohio Oeol. Surv., 4th aer., Bull. 9, 1908. 92. White, U. 8. Geol. Surv.. Bull. 65, 1891. (Stratigraphy.) — Oklahoma: See Indian Territory. Oregon: 93. Smith, U. S. Geol. Surv., 22d Ann. Rept., Ill : 473,1902. 94. Diller, Ibid., 19th Ann. Rept., Ill : 309, 1899. (Coos Bay.) — Pennsylvania : 95. d'Invilliers, 2d Pa. Geol. Surv. Rept.. 1885 and 1886. (Kttsburg non.) 96. McFarlane, Coal Regions of America, 3d ed.; New York, 1877. 97. Report MM of 2d Pa. Oeol. Surv. contains many anases ; see also county reports of same survey. OS. Lesley, Final Sum- mary Rept., Ill, pts. 1 and 2. (Stratigraphy.) 99. Hioe and others, Top. and Geol. Surv.. Pa., 1906-1908 : 218, 1908. 100. Stoek, U. S. Geol. Surv., 22d Ann. Rept. Ill : 61, 1902. (Anthracite.) 101. White, Campbell, Hazeltine, U. 8. Geol. Surv., 22d Ann. Rept., Ill : 125, 1902. (Bituminous.) Numerous refciTences to coal in U. S- Q. S. bulletins and geologic atlas folios, for list of which see bibliography in Min. Res. 1907. — Rhode Island: See under Graphite. — South DakoU: 102. Todd, 8. Dak. Geol. Surv., Bull. 1 : 159. — Tennessee : 103. Hayes, U. 8. Geol. Surv.. 22d Ann. Rept., III. 227, 1902. 104. Ashley and Glenn, U. S. Geol. Surv., Prof. Pap. 49, 1906. (Cumberland Gap.) Many brief references in U. 8. G. 8, Geologic Atlas folios. — Texas : 105- Durable, Bull, on Lignite, Tex. Geol, Surv. 106. Phillips, Univ. Tex. Min. Surv., Bull. 3, 1902. (Coal and lignite.) 107. Vaugh&n, U.S. Geol. Surv.. Bull. 164,1900. (Rio Grande fields.) lOS.Taff.U.S. Geol. 8urv., 22d Ann. Report., Ill : 367, 1902. — Utah : 109. Storra.

Iv,

Coal 4Q

U. S. Oeol. Sarv., 22d Ann. Rept., Ill : 415, 1902. See ajBo utiolea in U. S. G. S. Bulls. 285 (Sanpete County, Weber lUver, Book Cliffs), 316 (Pleaa&nt Valley and Iron County), 341 (n. e. Utah, s. w. Kion), 371 (Book Cliffs). — VennoBt : 110. Hitchcock, Amer. Jour. Sd., ii, xv:95, 1853. (Lignite at Brnndon.) — Virginia : 111. Watson, Mineral Rasourees Virginia : 336, 1907. (General.) 112. Shaler and Woodworth, U. 8. Geol. Surv., 19th Ann. Rept., II : 393, 1898. (Richmond baain.) 113. Campbell, U. 8. Geol. Surv., Bull. Ill, 1893. (Big Stone Gap.) — WaBhington: 114. Landea and Ruddy, Waah. Oeol. Surv., II. (General.) — West Virginia : 115. White, W. Va. Geol. Surv., II, 1903. (General.) — Wyoming : 116. Storrs, U. 8. Geol. Surv., 22d Ann. Rept., Ill : 415, 1902. (General.) 117. V. 8. Surv., Bulls. 225 (Bighorn Basin), 280 (Black Hills), 285 (Uinta County), 316 (Central Uinta County, Lander field. Carbon County, lAramie Basin), 341 (Bighom Basin, Sheridan district, Little Snake River, Great Divide Basin, Rook Springs, Casper Douglas district). 118. Veatch, U. S. Geol. Surv., Prof. Pap. 56, 1908. (s. v. Wyo.)

Repbrehces Oh Peat

119. Ries, N. Y. State Museum, Mth Ann. Rept., 1903. (N. Y., Origin mi uses in general, Bibliography.) 120. Carter, Ont. Bur. Mines, Rept. (or 1908. (General.) 121. Shaler, U. 8. Geol. Surv., 12th Ann. Rept., p-311. (Peat and swamp soite.) 122. Eoller, Die Torfindustrie, Vienna, im 123. Wnderand Savage, la. Geol. Surv., Bull. 2, 1905. (la.) 124. Taylor, Ind. Dept. Geol. Nat. Res., 31st Ann. Rept., 1906. 125. Par- melee and McCourt, N. J. Geol. Surv., Rept., 1905: 223, 1906. 128. Kystrom, Dept. Mines Can., Spec. Bull., 1908. (Manufacture and uses.) 137. Davis, Mich. Geol. Surv., Ann. Rept., 1906 : 105, 1907. (General ud Mich.) 128. Bastin and Davis, U. 8. Geol. Surv., Bull. 376, 1909. Elaine, many analyses.) 129. Parsons, N. Y. Geol. Surv., 23d Ann, Kept., 1904. (N.Y.) 130. Taylor, Ind. Dept. Geol. Nat. Res., 3l8t Ann. Rept., 73, 1906. (Ind.)

b,

Chapter Ii Petroleum, Natural Gas, And Other Htdrocarboits

Introductory. — Under this head are included four well-known substances, viz. natural gas, petroleum, mineral tar or maltha, and asphaltum, all essentially compounds of carbon and hydrogen — hydrocarbons — or mixtures of such compounds. In addition they may contain many impurities, such as sulphur compounds, oxidized and ni trcnoua substances, etc. , whose exact nature may be doubtful.

The hydrocarbons are divisible primarily into a number of 868, each of which has a generaUzed formula as indicated below.

1. CDHsn+t 6. Oatlbi-i

2. CHb 7. CHiM

3. dHk.) 8. CdHi._]i

5. CnHk-s IS. CaSiB~ti

Members of the first eight series have been discovered in petro- leum. Of the above formulas, the first represents the parafiSn hydrocarbons, benning with marsh gas or methane, CH, and ranging at least as high as the compound Methane is gaseous, the middle members of the series are liquids, while the higher members are solids, Hke ordinary paraffin. Members of the second series are also important in petroleums, especially the define eubseries. The third or acetylene series is represented in some petroleimiB by its higher members. The fifth or benzioe series occurs in nearly all petroleums, but not in large amounts.

PropertieB of Petroleum (4, 10, 12). — Crude petroleum is a liquid of [complex composition and variable color and density. It conmsts of a mixture of hydrocarbons, mainly hquid, with some gaseous and solid ones, the last being in solution. The American petroleum may have either a paraffin base (most Pennsylvania oils), an asphaltic base (Texas), or a mixed asphaltic and paraffin base (some Illinois petroleums). It is probably safe to say that the paraffin oils predominate east of the Mississippi, while the asphaltic oils are more abundant west of it.'

iv,Coog[c

Petroleum. Natural Gas, Other Hydrocarbons 51

Most petroleum contains some nitrogen, but it rarely exceeds 3 per cent, except in some California oils, where it may reach 10 or 20 per cent,'

Sulphur is rarely absent, but the quantity found is usually quite small. The Lima, Ohio, and Texas oils carry it in sufficient quantity to require its elimination in refining.

The following are analyses of several petroleums from American and foreign localities: —

Elehentart Analtbes c

Petrolbuu

PiaCiHT

:

H

o

,0=1

Heavy oil, W. Va. . .

Ught oil, W. Va.

HMvy oil. Pa. .

tight oU. Pa. . .

Puma, Italy . .

Hmovot, Germany

Galicia. Austria .

S70

Light oil. Baku, Rua.

HMvy oil, Baku, Bus.

Java

Btaumont, Texas

Petroleums commonly vary in specific gravity between about -8 and .98, thefollowingbeingsomeof the limitsshown by American oils: —

Spzcino Gravitt or Soue Auebican Pbtrolettub

Br.™

Specvic Obatitt

CBfitomia (Placenta Canon) . Peimlvaoia

Obio

.777 +

.801-.817

.816-.860

.835-1.000

.841-.873

.904.925

.912-.945

.920-.983

60 + 46.2.6

West Virginia

BaumoDt, Texas

Wyoming

Cslifomia

37.6-30.0 24.8-31.1 23.3-11.9 21.9-12.3

' Jour. Soc. Cbem. Ind.. XIX : SOfi. 1900.

' A ipedSc mvi of I, compared with water, is 10° on the Beaume scale. Con* vcrnon from one scale to the other may be made by fallowing formula : —

130 + Beaume

Economic Geology

The temperature at vbicb crude petroleum solidifies ranges horn 82° F. in some Burma oils to several dnees below sero in certain Italian oUs. The flashing point, or tlie lowest temperature at which inflamniable vapors are given off, may be as low as zero degrees in the Italian oils to as high as 370° F. in an. oil found on the Qold Coast of Africa, but these are extreme limits. There is also a great range in the boiling point, which is 180° F. in some Pennsylvania oils and 338° F. in oils found at Hanover, Germany.

The various hquid hydrocarbons making up crude petroleum vary in their speoiflo gravity and boiUng point. The more important oils which can be separated from crude petroleum by distillation are gasoline, benzine, heavy naphthas, and residuum. Those with a paraffin base are ge&er&Uy later and more valuable on account of the higher quantity and quality of the naphthas, illuminating oils, and lubricating oils which tfaey produce. Those with an asphalt base are of inferior quality and chiefly valuable for fuel. Their transportation by pipe lines is also more difficult.

The percentage of the different distillates varies. The following average percentages of distillates wer' the oils of several fields in 1902 (Oliphant) : —

yielded by

Afphuchiah

Lm*. Ind.,

Fuld

Naphthas

Lubricating and heavy oils . Residuum

ucts and water

Is

In the following table (p. 53) there are given a number of deter- minations of distillates, etc., published by Dr. David T. Day, of the United States Geological Survey, and in part made by him.

Propertis of natural Gas. — This consists chiefly of marsh gaa — fire damp — CH,- It is colorless, odorless, burns readily with a luminous flame, and when mixed with air it is highly explosive.

Ethane (CaH,), the next member of the marsh gas series, may exist in considerable quantities in natural gas. Ethylene, or ole- fiant gaa (CsHs), burns with a much more luminous ilame than the two preceding, but it rarely exists in American gas in amounts greater than a email fraction of one per cent. Carbon monoxide occurs only in very small quantities, and the same is true of carbon dioxide. Nitrogen is found in variable amounts, and oxygen is not uncommon, but when present in large quantity in an analysis, it may be due to contamination of the sample analyzed with air.

D,q,z.<ib,Coogle

Petkoleum, Natural Gas, Other Hydrocarbons 53

(Mt

BBd)

ss s s £3 sss ss? s; s

Auuosfpoilg

3 S S SSI? SS!:i :S i:; K

Aiiiuo og!owIs

m 1

U) TtXA 'O BUIQ

3e

oogit

Economic Geology

(I.N..

Su)

S 5 3 aa a

3 5 3 S! S

Mi

Ooao ta-Xi

"

M

-UHIQ Oiaoa) TTiOX

s s 1 0 i 1

i. 1 i Ii i

-nnao 'mo

& 3 3 3 3 3

illl i i i ii i

sroeo "iqio

|gli 1 1 § il s

Elll 1 11

d

-fVK> asino

3 3 3 3 S S 3 5 S :

°

CO .) Toa M Bwo-a

§5SS SsSSBS

ii

II II 1 1 nil 1

if

s

?nimrawajaa

i i i ii I

. og.dg

iisi 1 1 Mi i

h

ji nil ji

{Ja!U> Tiaji Buaa

8 i i i g S 1 i

o

ift!8 ills

h.Coojlc

Petroleum, Natural Gas, Other Hydrocarbons 66

!

S ? a 3 31 I is

S i ai I II

ili'i

i i ii

H

i i I i

i i 11

niiiii

i I 3 i

§ i ssli

g Mil

i i ii

sjii i I s i

s I lips

% I i I i

11

153 3 3 S 3 3S 3 3S|2

s a s J 2

III iiijii- iiiii I ijiij mil

iiis IIH § I i i Si liii

IliiilM i 1 i i ii I llii

ii i i-i i i i I

C.oogic

Economic Geology

s s

m

:(l(A8]r) sycndg

AjAUQ aginds

CoJ " "noa

(MM) TIIjH dO BU1Q

& S S3

PilfiorfJaliiJlaM

. f.Cooglc

Petroleum. Natural Gas, Other Hydrocarbons 57

The following aDslyses represent a number of Ameritvm occur- rences. It will be Been that marsh gas is the predominating con- stituent in nearly all of them.

li ill I I

"IS iJS 8 o S

H.2

:

S Ik 1

1

i.

1

r

1 ? 1

1 .

s

n

11

o

|2M

g.Sl

1"

i "

Ss88 3,

S8SS 8fS good

ggg

isHMffl

.§1S1

°ss

t,,

Ecokomic Qeologt

The gas from Dexter, Kansas, (No. 4 of the preceding table) is in- teresting because of its high content of nitrcen. Of 47 samples of gaa examined ' by Cady and McFarland, all except one showed helium, in amounts averang .10 per cent. One Kansas sample contained 1.84 per cent more than the others, and this same one carried the high nitrogen contents referred to above. The rare element neoa was also discovered.

The following table brings out the essential diflereaoee between natural gaa and other fuel or illuminating gasea.

Analyses of natural and manufactured gases.

Ku.

MiinhOu,CII .

Boss

other hydrocaiboM

M

Jj8

l.BO

360,000

Origin of Oil and Gas. — That the solid, liquid, and gaseous hydro- carbons are more or less cltfflely related is evident from the fact that the gases ven off by petroleum are similar to those predominating in natural gas, while the exposure of many petroleums to the fur results in a change to a viscous mass and finally to a solid asphalt or paraffin-like substance. It is a well-known fact that petroleum is rarely free from natural gas, althoih this gas may sometimes form alone, as in coal mines, or from decaying vegetation in stag- nant pools. The orin of the hydrocarbon compounds has been the subject of much speculation among both chemists and geolo- gists, the former for a time arguing for an inorganic or mineral origin, the latter for an organic derivation, the same evidence curiously enough being sometimes used by persons holding opposite views.

It cannot be said that the matter has yet been settled to the satis- faction of ail, although it is probable that the majority of observers admit the organic orin of petroleum. One cause of uncertnty is that oils, unhke coals, do not usually contain visible traces of their orinal constituents. Moreover, we had until recently few un-

Jour. Anier. Chem. Soc., XXIX : 1524.

iv,Coog[c

Petroleum, Natural Gas, Other Hydrocarbons 59

doubted known instices of the recent formation of petroleum under conditions similar to those found in the older rocks.

Isotganic Theories (1, 3a, 10). — Several theories have been advanced to account for an inorganic origin of oil. Berthelot was perhaps the first to advance a general theory,' but that of Mendel- jff ' is somewhat better known, and is in a way an elaboration of Eome of the earlier ones. According to this theory, the interior of the earth contains metallic iron, as well as carbide of iron like that found in meteorites. Water percolating downward through the earth's crust, on reaching the heated interior, becomes converted iDto steam, which, attacking the carbide of iron, forms hydrocarbons. These are forced to the surface by the expansive force of the Gteam.

From a purely chemical standpoint, this theory is reasonable, and the production of hydrocarbons by this method has been done experimentally, but it does not accord with geoloc facts. If petroleum were formed in this manner, we should expect to find it widely distributed through the oldest rocks of the earth's crust.

On the contrary, hydrocarbon compounds like oil, gas, and as- phalt are practically unknown in crystalline rocks. In Ontario, a hard compressed asphalt is found in them, but it is significant that tMs material (Anthraxolite) which was probably originally petro- leum, occurs in rocks which may be metamorphosed sediments. A second case is found in California (17), where oil occurs in a much-folded crystalline schist, but its associations are such that it may have been derived from neighboring sediments.

A poemble point in favor of the derivation of oil and gas, from carbides has been noted by Becker (1), who has called atten- tion to the fact that the irregularities of the curves of equal mag- netic declination are strongly marked in the principal oil regions. While the agreement is not a very close one, it is most marked in the Appalachian field. There are, however, some systematic irregu- larities, as in the New Jersey magnetite rejpons, which are not known to contain any oil. Becker believes that the coincidence between the petroleiun occurrences and local disturbances of the compass are too numerous to be attributable to mere accident, and that there must be a direct or indirect historical connection between i the two phenomena in the regions of coincidence, thus suesting the possibility of the oil being derived from iron carbides.

iv,Coog[c

60 Economic Geology

VoUanie Theory. — A second inoiEania theory advooatod b; Beveral, and in recent yean expounded with great vigor and detail by E. Coste (3a), is the theory of volcanic origin of the hydrocarboaa.

Mr. Coate believes that all hydrocarbons cannot be of l.niml or table origin, but must be of volcanic derivation for the following roasons;

1. Animal remains are new entombed in rock formations. 2. Vegetable remains in rocks decompose into carbonaceous matter. 3. Further distilla- tion of carbonaceous matter haa not taken plaoe in nature. 4. Gaseous, liquid, and solid hydrooarbona are products of volcanic emanations. 5. Oil and gas are under strong pressure, and hence must be of volcanic origin, for nothing else could produce this pressure. 6. In some oil fields heated gas and water are met with. 7. Oil and gas fields are located along faulted and fissured zones of the earth's crust, parallel to great orogenio (mountain- making) and volcanic dislocations. 8. Oil, gas, and bituminous matter are never indigenous to the strata in which they are found. 9. The density of the rocks precludes possibility of anything but voloanio pressure having forced them upward.

The arguments against some of these points may be mentioned under the same numbers: 1. Animal remains are entombed in rooks, otherwise we could not have fossils of those lacking hard porta. 2. Vegetable remains in rock have been proven to decompose into hydrocarbons, as evidenced by natural gas suppUes found in glacial drift; moreover, some coal seams have oil seepages. 3. While hydrocarbons are known to oocur in some volcanio emanations, they might be formed by the direct union of oarbon and hydro- gen of these gases, or have been distilled out of sedimentary rooks through which the lava passed. Moreover, they are frequently formed from decay- ing vegetable matter. 5. The pressure may be due to the natural expansive force of the gas. 7. Oil and gas fields are sometimes found in regions of but little disturbance, as Illinois, Medicine Hat, Alberta, etc. 8. This may be true, but they are often clearly shown to have come from adjoining beds. 9. It volcanic pressure forced this oil and gas up through many feet of dense rock, why were they not forced all the way to the surface ?

One may also add that the restriction of oil and gas to sedimentary rocks is not in accordance with a volcanic onn, neither is the decrease in pressure which all wells show with time.

Organic Theory. — This conders that petroleum has been derived from either animal or vegetable matter by a process of slow distillation, althoi the exact changes involved are somewhat uncertain.

Perhaps the majority of geologists and even others have uncon- sciously assumed that petroleum has been derived from land plants and while in some cases this may be bo, some rather weighty ob- jections can be urged against it. These are the following: —

1. There is a general lack of association of coal or lignite and oil

2. Where lignite or carbonized wood is found with oil it has lost nori* of its essential constituents. 3. There is a great chemical differenoa

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Petroleum, Natural Gab, Other Hydrocarbons 61

between lignite tar oils and natural petroleums. 4. It requires a high temperature (geolocally speaking) to convert wood into iiquid bitumen, aod leave no trace of its original structure.' 5. An Mjument of doubtful is that limestones, being of marine origin, the <nl in them could not be derived from land plants.

The following arguments may be mentioned in iavot of the deri- vation of petroleum from marine plants such as seaweeds: 1. Sahne mter associated with some oils carries iodine.* 2. Certdn sea- reeds found on the coast of Sardinia become covered with an oily coating while decomposing.* 3. The Boghead mineral, or Torbanite, and the kerosene shale of Scotland are derived from gelatinous alg£ whose remuns are embedded in what was once a brown humic jeDy.* 4. In some localities the diatom cases found in rocks are known to contn small globules of oil, which have in some reons been rarded as a source of petroleum (19).

Some have also conadered that the oil may have been derived, in part at least, from animal remains, the oil havit thus a dual origin.

Recent investigations of the optical activity of oil show it to be of undoubted organic orin (1), for the reason that many petroleum products have the power of rotating the plane of polarization of , as is done by sugar, lactic acid, and other organic compounds. These optical phenomena are not shown by inorganically synthe- siied petroleum, and hence it ia argued that the substances to which it is beUeved to be due are only of organic derivation. These sub- ttances are phytosterol, found in the fatty parts of animals, and choleaterol, found in plants.

If the oils are derived from animal and plant remains of marine character, it is posble that the nitrogenous portions were elimi- nated by bacterial action soon after the death of the organism, and Ijefore it became buried under sediments. Subsequently the oil was produced by decomposition of the fatty matter of the plants and animab. Some geoltsts, including Orton (4) and Newberry (Ohio f-tate Ac. Rept. 1859), have believed that the formation of petro- '"um has taken place at lower temperatures; but others, including Peckham (6), have considered heat necessary. In the case of

' Sucb a proccBB would only be liluily to occur where a bed of land plants waa atiprooched by an intruaive.

'Watta. CaUf. SUlc Mid. Bur., Bull. 19 : 202. 'RfdwDod, PelTOleum and its Products. 2d edition. I. 128, 142. Comp. Rend., CXVII: 693, 1893. and Compt. Rend., VIII, Cong. Geol. Intemat. 1900 :US.

c,q,z.<ib,Coogle

Economic Geology

AppalachiaD oilfl the folding of the strata is supposed to have sup- plied this heat.

Mode of Occurrence (6, 8, 9, 13). — Oil is rarely found without gas, aad saline water is likewise often present. If the containing strata are horizontal, the oil and gas are usually irregularly scattered, but if tilted or folded, and the beds porous throughout, they appear to collect at the highest point possible. It was the result of obser- vations along this line that led I. C. White to develop what ia known as the " Anticlinal Theory " (13). According to this theory, in folded areas the gas collects at the summit of the fold, with the oil immediately below, on either side, followed by the water (Rg. 22). It is of course necessary that the oU-'bearii stratum shall be capped by a practically impervious one.

Fio. 33. — Section of aaticliniil fold showing accumulatioD of gas. oil, iid water. (ASier Uayea. V. S. Oeol. Sun.. BiiU. 212.)

If the rocks are dry, then the chief points of accumulation of the oil will be at or near the bottom of the syncline, or lowest portion of the porous bed. If the rocks are partially saturated with water, then the oil accumulates at the upper level of saturation.

In a tilted bed, which is locally porous, and not so througjiout, the oil, gas, and water may arrange themselves according to their gravity in this porous part.

While the anticlinal theory has been found to apply in most oil regions, some doubt has been rused regarding its possible applica- tion in parts of southwestern Pennsylvania (6),

Lesley and Ashbumer sueated that the porous areas in which the oil and gas accumulated represented old shore line deposits.

In the first discovered fields, the oil and gas were found in porous, sandy strata, varying from fine-gruned sandstones to conglomei ates. These rocks were termed sands, and the area of porous oil sand was called the pool. Later discoveries in Ohio and Indiana

Petroleum. Natural Oas, Other Hydrocarbons 63

showed that the g&s and oil mit occur in limestone alao, while in a few fields (Florence, Colorado, and parts of California) the oil has accumulated in fiasurea in shale, produced by earth movement.

The number and thickness of the oil and gas sands may som times vary in different parts of the same field (Figs. 23 and 24), thereby making correlation difficult.

Fto. 23. — Bhowing podtioiw utd vertioal seotloiu of welb touthewt of Humboldt, Kia., Mid differing thickncas nd number of Banda in Deighborinc well*. (JTot. IhoL Sun.. IX.)

The thickness of the producing rock (" pay sand ") varies in the different fields. White, referring to West Vlrnia, regards 5 feet of s&nd as sufficient for good productive territory, but thicker ones are found in the Appalachian field. The Illinois sands rai from 2 to over 30 feet in thickness, while that estimated for Spindle Top in Texas averages 75 feet. The Kem River field oi California is sud to have pay sands as- much as 100 feet thick.'

The quantity of oil which a cubic foot of apparently dense rock can hold is often surprising. White estimated that fairly produc- tive sands may hold from six to twelve pints of oil per cubic foot, but that probably not more than three-fourths of the quantity Btored in the rock is obtainable. According to Day (53) it has been cuatomary to consider 10 per cent as near the average porosity of the pay sand, with a latitude of variation from practically nothing in damp shales to over 30 per cent in the most porous strata. The

DAr. U. 8. a. 3., BulL 3H : 34, 1909.

Economic Qeology

degree of openuesa of the pores will, however, govern the rate of flow of oil from the rock.

Pressure of Oil and Gas Weila. — Since both oil aad gaa usually occur in the earth under pressure, any break in the porous rock or reservoir which contains them allows them to escape, frequently rise to surface indications, and the force with which oil and gas oftentimes issue from a well indicates the pressure under which they are confined. It is sometimes sufficient to blow out the drill- ing tools and caang, as well as to cause the oil to spout many feet into the ak.

There are several remarkable coses of tbe amount spouted by these shiug wells. One of these is the famous Lucas well at Beaumont. Te:ttia, which in 1901 for niue days gushed a six-inch stream to a height of 160 feet, at the mte of 75,000 barrels per day. This, however, is small compared with the records of some Russian oil wells. Although many wells flow when first drilled, this does not usually continue long, and the oil then has to be brought to the surface by pumping. The depth of the wells drilled in the United States ranges from 250 to 4000 feet.

The maximum pressure which a well develops when closed has been called rock pressure. As a result of his stucUes in the Ohio-

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Petroleum, Natural Gas, Other Hydrocarbons 65

Iiidi&aa field, Orton (42) found that the rock pressure was the same as that of a column of water whose height was equal to the differ- ence in elevation between the level of Lake Erie and that of the oil or gas-bearing stratum. He therefore conMdered it to be hydro- static pressure. This theory, while apparently applicable in many localities, was found to be inadequate to explain the great pressure nhown in many shallow wells. In these, as also in deep ones, the pressure is thought by many to be due to the expansive force of the imprisoned gas.

Either the drilling of additional wells or a drun by excesmve use from wells already bored commonly causes a slow decrease in pres- sureinanoilorgasfield. Thus in the natural gas region of Findlay, Ohio, the rock pressure in 1885 was 450 pounds per square inch; 400 in 1886; 360-380 in 1887; 250 in 1889; 170-200 in 1890. Some West Viinia wells have shown a measured rock pressure of 1110 pounds per square inch and an estimated pressure of 2000 pounds.

It has been not infrequently noticed, however, that the opening up of one or more wells close to a good producer may have little or no effect on it.

The table on page 66 (53) gives the closed or rock pressure in rsrious fields, in different years. They are interesting, but lose their comparative value as they do not probably in all cases represent the same well.

Mode of Accumvlaiion. — While the oil and gas are not neces- sarily, and probably rarely, indigenous to the rock containing them, & difference of opinion exists as to whether they have been trans- ported long distances ; indeed their source is often indicated in some under- or over-lying bed of shale.

If this be true, then, in order to reach the sandstone, they must ID part at least pass through the small pores of the shales, but the nature and cause of this movement are not clearly understood. Capillary action and great rock pressure have been suested as posfflble operatii forces, while Munn beheves it is caused by hydraulic action. According to his hydraulic theory (6), the diffused oil and gas are concentrated into pools or pay streaks by the action of currents of underground water. These collect the (h1 and gas and push them along. Since these underground cur- rents circulating through the rocks vary in the direction of their flow, there may be places where the meeting of conflicting currents form eddies or places of no movement. It is at such points that the accumulated oil and gas are held. If the water is flowing

Economic Geology

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Petroleum, Natural Gab, Other Hydrocarbons 67

through the rocka under the influence of capillarity alone, and conflicting currents are absent, there will be a tendency to force the oil and gas into the more porous beds where the capillarity is too weak for the water to follow.

The pressure of the oil is ascribed to the expansive force of the gas, which cannot diffuse because of the saturation of the surround- ing rocks. The association of oil with anticlines is thought to be due to the influence which these structures exert on the water cur- rents. The difference in specific gravity of oil and water is con- sidered iosufficiect to account for the widespread movement of oil ajnst the friction developed by its i>aB8age through rock pores.

The oil and gas are, tiien, held in the rock, not because of an im- pervious cap rock, but by the overlying and surrotmdii water

fteU of Sandt. — A pwoaity of 10 per oent would mean, a theoretical yield ot about 1 Ballon per oubie foot, or about 6000 barrels per acre with

Moot thioknew.

AlthotiKh many Pennajlvaiua sands are thicker than 5 feet, the figuTM of prodnetion indicate an average yield in the paat of not much over 800 burela per acre, but the average for the entire Appalachian field may be taken aa sliftly greater. Bain estimateB 2000 barrels per acre for Illinois.

However, it is a diffloult and conjeotuntl matter to estimate olosely the iverage yield (rf <dl in any field.

Li}t of a WdL — This may vary with the amount of supply, oompaotness of pay Band, and gas preesure accompanying the petroleum. It varies from

Tew months to 20 years or more. Some wells may gush forth tremendous qiuntities of oil and gas for a short period and then die down to almost nothing. Others may yield moderate quantities, or perhaps only a few bvreb daily, for a period of years. The average life of Pennsylvania wells

In aH fields the production inoreases at first and then begins to drop off, ud the increasing production of the United Btats is due to the discovery ud development of new fields, whose production more than offsets the decNase of the older ones.

As examples, the daily average production per well per day of New York and Pennsylvania has f&Uen from a maximum of 207 barrels to 1.7 barrels. The Weet Virginia production has dropped to 56 per cent erf its maximum, sod Ohio and Indiana have shown a still greater decline.

Od the other baud, Illinoia, Oklahoma, and California will probably

Day (£3) estimates that oonsidering the minimum amount of petroleum ia the United States as 15,000,000,000 barrels, the supply \rill be exhausted ftbout 1935 with the present rate of increase in production. With stationary production, about 90 years would be required.

68 Economic Geology

DistributtDii of Petroleum in the United States. — The impor- tant fields of the United States (PI. VI) t<ther with their ap- proximate area in square miles is as follows (53) : —

Tenn. . W. Va. Ky. . .

Pa 2000 3465

Ind

lUinoia . .

Ohio

Mid-CoDtinental . .

. Kas

California Wyoming Colorado Michigan

These figures of course represent only the areas actually under- lain by known pools, and not the entire area of the field,

Appalachian Field. — Thia is the largest oil field in the United States, and includes portions of New York, Pennsylvania, Ohio, West Virginia, Kentucky, and Tennessee,

The rocks are chiefly sandstones, with a few limestones, embedded in and underlain by a great thickness of shales, while below these are probably limestone beds. The sandstones have a thickness of probably 2000 feet or more, and in the middle and northern end of the field range from the Alleghany series nearly to the base of the Devonian, and still lower in Tennessee and Kentucky. Their deposition represents a period of continuous sedimentation, with the exception of the period between the Mauch Chunk and the Pottsville, where an unconformity indicates an interval of uplift and erosion.

It may be said of the Appalachian field as a whole that the oil- bearing rocks occupy the bottom and west side of a large structural trough, whose rim passes through central Ohio, then eastward south of the Great Lakes and then south along the western base of the

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Petroleum, Natural Gas, Other Hydrocarbons 69

Appalachians. It therefore crosses western Pennsylvania where petroleum has been found in large quantity. While the total area outlined is probably over 50,000 square miles, the area actually un- derlain by known oil-bearii sands does not appear to exceed 3500 (53).

Within this great trou there are a number of subordinate folds whose trend is northeast southwest, while still minor ones are foulid with their axes at rit ates to these.

Fra. 25. — Map ahowuig lines or sectbos in Plate VIL

The sandstones are, moreover, found at increasing depths as one goes southward, so that those outcropping in Ohio and New York may be 2000 or 3000 feet below the surface in southwestern Pennsyl- vania or West Virginia.

In this region there are a mimber of sandstones, the important ones individually underlying many square miles. These sand- stones are most numerous and attain their greatest thickness in the center of the region.

The upper or younger sands are usually white, and may be conomeratJc locally, while the older beds are brown or reddish, and generally more uniform in texture.

At some locaUties two or more sands produce oil, and the lowest then may be the most prolific. The wells range in depth from 100 to 4000 feet.

D,q,z.<ib,Coogle

Economic Geology

The character of the oil found in this ron is said by Dr. Day to differ eeseDtially from any other petroleum thus far found in the world. It is practically free from sulphur and usually from asphalt, but ia rich in paraffia wax. Added to this is its easy conversion into lamp oil, of which product it yields the greatest percentage, being far ahead of all others except the Lima and Ohio petroleums, wUch, however, are more expenMve to refine.

The Kentucky and Tennessee product, while inferior to that foimd in Pennsylvania, is much better than the Kussan or any other of the foreign products with which it has tfO compete.

The Appalachian region, however, has passed the seuith of its production, that of Pennsylvania having been reached seven- teen years ago; and yet some of the wells show a remarkably persistent, though small, production.

In New York State petroleum is obtained from the fineuned sandstones of Chemimg age in parts of Cattaraugus, Allegany, and Steuben counties. The wells range from 600 to 1800 feet in depth, and while of small capacity, they yield a product of good quahty, which ranges from amber to black in color.

The petroleum-producing belt extends across Pennsylvania, in a southwesterly direction, leaving it in the southwestern comer. Within this area (whose general structure has been referred to above) there are a number of oil pools, occurring in rocks ranging from the Conemaugh series of the Carboniferous down to and including the

Petroleum, Natural Gas, Other Hydrocarbons 71

Chemung divimon of the DevoniaD. In the space permitted here, it b not possible to go into detail regarding all the poob. Suffice j(, therefore, to say, that the oil id obtfuned from a number of dif- ferent sands, some of which are of high importance, as the Berea, Hundred Foot, Fifth, etc.

In the table given on pages 72 and 73, an attempt has been made lo show the oil (and gas) sands known in the different formations, but they are correlated only so far as occurring in the same fonnatJon.'

Ohio'Indiana Field (24-26. 39-44). — The discovery of oil and gas in the Trenton rocks of western Ohio in 1884 caused consider- able excitement, since it showed the existence of petroleum in lime- stone, an exception to previously known conditions, and at a much lower geological horizon than any in which oil or gas had hitherto been found. This field extends from Findlay in northwestern 0)uo southwestward into Indiana.

I I . - i

Most of the Trenton oil has been found in the upper 50 feet of the fomiation, in one of two thin streaks; but at several localities in both Ohio and Indiana, a productive horizon lying from 100 to 200 feet deeper has been discovered. The oils of this field contfun sufficient sulphur to require s[>ecial treatment for its elimination, but the oil is of paraffin base Eke that of the Appalachian region.

Outade of the main field, oil has been foimd in the Clinton for- mation of Ohio, the most important occurrence being in Vinton County (39). In Indiana oil has been obtuned from the Comif- erous limestone (Devonian) and from the Huron sandstone (Lower

These t&blea tie thcwe given by the raepective oUte euiveys.

Economic Geology

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Carboniferous) in Gibson County. The latter occurrence is ex- ceedingly pockety, and the oil, which is darker and thicker than the Trenton oil, has a low percentage of illuminants. Ohio and Indiana show a much smaller production than formerly. Illinois Field (23). — Oil and gas have been known in Illinois for some years, but the important discoveries were not made until 1904, and the production dnce then has increased at such a rapid rate that in 1908 it was exceeded only by that of the Mid-Conti- nental and CaUfomia reons.

As indicated by the map (Fig. 28), the approximate limits of the main producing territory extend from Clark and Cumberland coun- ties southward through Craw- ford and into Lawrence, so that the productive strip has & proven length of approximately 80 miles, which, however, is not underlain throughout by oil. The' limits may be extended in the future.

There has been no regular production in this field outside of these general limits, although oil has been found at a number of other pointa (23) in the state.

The principal horisons at which oil and gas have thus far been discovered are in the Car- boniferous rocks, the sands occurrii in both the Upper and Lower Coal Measures, the Pottsville group, and the Cbes- Fio. 28. — MapBhowing approximiite area ter group (Lower Carboniferous f. f ™ fouthtern luinoi,. Mississippian). The exact Cii/ter Bain, I. Geo/. Sum., Buii. 8.) , , , , j

identification of the beds ana correlation of di£Ferent sections in adjoining areas is often attended with difficulty.

The oil is usually found in aandstone, but the Westfield pool forms an interesting exception, for there it occurs in a locally doii>- mitized coal-measure limestone. A doubtful relation exists be- tween the occurrence of the oil and anticlines.

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PETROLEUM, NATURiL GAS, OTHER HYDROCARBONS 75

In general the depth of the weUs increases from north to south as foUows: Oilfield pool, 300-350; SiKinH pool, 400 and 570; Johnson township, 470 and 610; Crawford County, 900 to 1000; Lawrence County, 950, 1300, 1500.

The Illinois field is no longer included in the Ohio-IncUatia region, because the oils are of different horizon. Moreover, the product carries less sulphur and much of it is refined without special treat- ment. Some of it contains asphalt as well as paraffin, and the oils vary within wide limits of gravity and distillation products.

Mid-Continental Field (28). — This reon underlies a portion of EOutheastem Kansas and northeastern Oklahoma, and extends roughly from Paola, Kansas, to Muskogee, Oklahoma. The Fena- sylvanian rocks which outcrop in this area dip westward from 20 to 30 feet per mile in Kansas and double that in Oklahoma. At the base are the Cherokee shales (400 to 500 feet thick) which are over- lain by the Fort Scott limestone and shale and rest unconform- ably on the Missppian limestone.

All the shaJes, espedally the Cherokee, carry sandstone beds, wbich yield oil and gas, but the most important ones are at the base of the Cherokee, while another one is near the top, and still another in the Fort Scott limestone. The Misssippian carries but little oil, except near Muskogee, where an important sand was struck at a lower geolocal horizon than oil or gas bad previously been found in this re|on. Another lai pool, the Glen, has been pierced near Tulsa, Oklahoma. Southwest of this point the Etructure is much complicated by folding and faulting.

The oil and gas are struck in different part of the reon at depths &om 350 (CoffeyvUIe, Kansas) to 1600 feet (Bartlesville, Oklahoma).

Most of the Kansas oils are aspbaltic, but in Oklahoma oils of both asphaltic and paraffin types are found, those found near Mu- lH)gee rearanbfing the Pennsylvania oils.

This ron has become a large producer, but the output is sup- plied munly by the Oklahoma field, while the Kansas one is on the decline.

Cdifomia (15-20). — The oil fields of California (Fig. 29) lie mnly south of the latitude of San Francisco and on ther side of the Central Valley of the State, either in the Coast Range or on the Pacific front. The productive fields include the Kem River, Coal- ings, Santa Maria, McKittrick, Midway, Sunset, Bakersfield, Los Angeles, Puente KUs, and Simimerland. The sections in the dif-

C,q,-Z.-dbvCOOgk'

76 Economic Geology

ferent fields include a great thickness of strata, ranng in some cases from Jurassic to Quaternary, the oil occurring mnly in the Tertiary, sandstones, conglomerates, and shales. Inonedistrict (Placenta CafioQ, Puente Hills), it is found in a crystalline schist, overlying granite (17).

The productive areas show a close association with anticlines; indeed, strong folding and even faulting are not uncommon, the latter having often caused interstitial spaces in which the oil could accumulate. Owing to the fracturing of the rocks incident to strong folding and fault- Fm. 29. — ladsz map of a portion jng oil seepages are common in

of southern Califoniia, showiag j- .

location of oU fidda. WUr distncts. Arnold, U.S. Geol Surv., BuU. Eldridge hassufsted thaf'since 357) the stratigraphic and structural con-

ditions under which oil occurs in the known fields are many times repeated elsewhere, in the Coast Range and territory contiguous thereto," there is hope for extending the oil reon. Reference to two fields will serve to indicate the mode of concurrence.

In the Kem River field, which is the most important, the well records indicate & great body of Miocene (Tertiary) sands and clays in which the general weaterly dip away from the Sierra granites has been locally inter- rupted by anticlines, on the flanks of which the oil has been found.

The oil occurs in Bauds interbedded with the clays which underlie one heavy clay bed and overlie another. The thickness of the oil-bearing sands may vary from 200 or 300 to 400 or 500 feet.

The Santa Maria field comprises the Santa Maria, Lompoc, and Arroyo Grande fields, iu nortbera Santa Barbara and southern San Luis Obispo County- The formations involved range from Jurassic to Quaternary, in- volving beds of shale, stone, sandstone, diatomaceous earth, volcanic ash, and in the Jurassic even schist, jasper, and serpentine.

There are two structural systems in the district, (1) in northeast part, trending northwest and southeast, and (2) in southern part trending east and west. Faults are rare, but the productive territory is gently folded. Most of the wells are located along or near anticlines, and range in depth from 1500 to over 4000 feet. In the Santa Maria and Lompoc fields the oil is obttuned from zones of fractured shale, or sandy layers in tiie lower portioD of Monterey (Middle Miocene), and has an average gravity of 25° B. In the Arroyo Grande area it comes from sandstones at base of the Fernando, and has a gravity of 14° B.

Petroleum. Natural Gas. Other Hydrocarbons 77

Although the Kem River field leads in pomt of produotioa, the Santa Mui& leada in the production per well, and supplies most of the oil exported, \is situation giving it oommaod of the coast trade from Alaska to Chile, u weU as foreign trade with Japan and Hawaii.

The Summerland field is of interest, for the reason that Arnold believes ihn oil to have been derived from diatoms (i9), and other organisma found in the Monterey shale. It has subsequently migrated upward into the overlying Fernando, and to some extent Pleistocene formations, urged along. probably by gas or hydrostatic pressure. A similar origin is also ascribed to ibe oil in the Coalinga district.

The California oils are generally characterized by much asphalt and little or no paraffin, although in recent years there has been a considerable yield of lighter grade oils from tbe Santa Maria and -\!ontrey districts. Since these are well adapted to reflning, they will prob- ably be in strong demand.

Texas-Louisiana Oil Fields (34, 35, 49-51). —This includes a series of small scattered fields Ijing mostly in the coastal pliun reon of eoto-in Texas and Louisiana (PI VI). Underlying the coastal pln there is a series of Quaternary, Tertiary, and Cretaceous clays, sands, and gravels, with occasional limestones, having in general a gentle southeastern dip, interrupted by low

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Economic Qeologt

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J near the surface. Thus at Avery

1 Island, Louisiana, the heavy deposit of rock salt comes within 15 feet of the surface, but at Spindle Top, " Texas, the hmestone is 800 or 900

2 2 feet deep.

0 The oil is most frequently found "3. in or near the limestones. J § The oil pools are of small size, and q ttiat discovered at Beaumont, Texas,

1 o may serve as a type of many. This J "3 poo'' rfiich covers an area of about

200 acres (PI. IX), was discovered in 1901, and within a year and a half 280 successful wells had been drilled. The oil rock, which lies from 900 to 1000 feet below the surface, is a very porous, crystalline, dolomitic lime- stone, and the cap rock is clay. The occurrence of gypsum and salt under- lying the oil rock in some of the wells is unique (Fig. 31). Many of the welb in this pool were gushers, but so great was the drain on this field that by the end of the first year after its discovery the pressure was con- fflderably reduced, and in 1903 many of the wells had practically ceased im>ducing, while others were yielding . h.C.oojlc

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Petroleum, Natural Gas, Other Hydrocarbons 79

a mixture of salt water and oil. The production, however, is still conaderable, although the supply is no doubt exhaustible. The coastal-plain oils have an asphaltic base, or are " heavy," and at times contwn conEdderable sulphur.

In 1903 many wells were being developed in the Sour Lake dis- trict about 20 miles northwest of Beaumont. The oil is heavy like that of Beaumont, but runs lower in sulphur. In Louiana active driUiog operations have been carried on in the region around Jennings, and one well yielded 20,000 barrek per day while it was gushing. The oil resembles that of Beaumont.

The belt of Cretaceous rocks of central Texas has yielded both oil and gas at several localities, but the only important one is at Cora- i:ana, where both a light and heavy oil have been found in sands interbedded with dense clay shales. The two kinds of oil occur at different horizons.

Id northwestern Louimano, both oil and gaa are found in the more or less oonsoUdated Cretaceous rooks, which underUe the Tei*tiai7 and Quater- nary. Here the CretaoeouB rooks which dip to the southward show a dome- like uplift of ooneideiable dimenaions, which brin them within 7(K) feet of the surface. This inoludes the Ctwldo field, and although the oil and ess occur sepaiately or together at four horizons, viz. the Naoatoch, Austin, Eagle Ford, and Woodbine, of the Upper Cretaceous, most of the gta is obtained from the first or upper, and the oil from the fourth or lower division. The mun oil sand is about 2200 feet deep. The oil from this Geld is tit, similar to that of the Appalachian Ton, and thus differs strony from the Beaumont and Jennings oils (Harris).

Moat of the oils of the Gulf region contain considerable quantities of sul- phur,largely in the form of hydrogen sulphide, and therefore easily removed b/ steam before refining, or for use aa fuel. They make a good fuel oil, which because of the location of the field can be easily exported, but they ilso yield a good grade of lubricating oil. Moreover, the gasolene derived from them is aoceptable as a substitute for turpentine.

The Corsioana and Caddo field oils are lighter and run lower in sulphur.

Colorado. — Florence (21) and Boulder (22) are the two important oil-producing localities. At the former the oil is found in beds of Cretaceous age, at depths of from 1000 to 2000 feet, and, unlike many occurrences, appears to have accumulated in fissures, although the rocks of the respon as a whole form a syncline.

At Boulder, the oil is found associated with broad low anticlines in sandstones and shales of the Pierre (Cretaceous) formation, and is now being obtained at depths ranging from 2100 to 2350 feet.' The oil does not vary much in quality.

R. D. George, private c(

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Economic Geology

Wyoming (58-63), — This state contains a number of oil and districts (Fig. 33) , most of which are but slightly developed,

IS utidcriain by oil and

and the geology of them imperfectly known. The oil-bearing for- mations range in age from Carboniferous or Permian to Tertiary (62), but the Cretaceous contuns the bulk of the oil thus far discov-

ered. Many of the occurrences appear to be associated with anti- clines (62), but, in one field (Spring Valley, Uinta County) at least (63), the oil occurs in a synclinal basin (Fig. 34), whose bounding

Petroleum, Natural Oas, Other Hydrocarbons 81

fault on the northwest seems to have permitted somewhat abun- dant seepage.

The oils vary in their gravity, but, according to published data, are mainly of medium gravity. Those obtained near Evanston are refined (63).

Uinta and Converse counties are said to be the most im- portant producers, but still the entire output of the state is

Alaska (14). — Oil has thus far been found in Alaska at only four localities, at wliich the indications were sufficient to warrant drilling. Wells have been driven at tiiree, and disclosed the presence of oil similar to that of Pennsylvania. All of the fields lie in the Pacific coast region, but none have been extensively developed, a& Ibe low price of imported oil and high cost of driUii in Alaska have discouraged attempts towards development.

e known to ocour.

In the Katalla field, located near the mouth of the Copper lUver, the oil is found in complexly folded and faulted Tertiary shales and sandstones. At Cook Inlet, folded and faulted Jurassic shales and sandstones form the petroliferous horizon. At Cold Bay, where seepages are found as in the other fields, the structural conditions and age of the oil-bearing strata are similar to those at Cook Inlet. Seepages are found in Tertiary rocks near Cape Yakataga, but no wells have been driUed.

Summary. — The following table summarizes very briefly the mode of occurrence in the several fields : —

Economic Geology

Summary op Oil Occurbbwcb in the Pwncipai, Fields

rOLD

EiHDorRocE

FdkM.

Folded and fwltwL

Ebldod mod lnultod.

OldoYidU to

tftly limo.

Sbido. ur>d- MonlyBEodirtoiu

Pwaffinbue.

Llnifc-Iiidiui*.

Mtehhu-

Bolb pmSnic PinffiDlo-ud u-

P,£SLt Miiiii;"{Sphiii6.

Pknffio.

OuUCoMt. AlMkk.

OieuoMus.

Juruno to Ta>

tiMy.

DiBtributioD of Natural Gas in tlie United States. — The distribu- tion of gas is practically coextensive with that of petroleum, and most oil wells yield some gas ; but the regions from which supplies are obtained and utihzed are fewer than those of petroleum.

Day (53) gives the followii estimate of the area in square miles of gas pools in the several fields.

. . Kentucky . . . New York . . .

Ohio

Pennsylvania . . West Virginia , .

. . . Indiana Ohio

. . 280 . . 550

. . no

. . 2730 . . 1000

. . 2460

Mid-Continental . .

. . . Oklahoma . . . Missouri Kansas

. . 1000 . . 550

Others

bvCoog[c

Pbtbolkum, Natural Gas. Other Hydrocarbons 83

The most importaat producii states at the present time are Pennsylvania (78), Ohio (77), West Vira (56), Kansas (70), New York (74), and Indiana (68).

fieu) York (74, 75). — Gas is found in eeveral formations, includ- . ing the Medina (Silurian) and Oswego sandstones (Silurian), Utica shale (Ordovician), and Fotsdam (Cambrian) sandstone, but the main supply is distributed through the Devonian sandstones of south- western New York. A large field in Erie County obtmns its supply from the Medina sandstone, some of the wells having yielded as high as 1,000,000 cubic feet daily. In Onondaga County gas is found in the Trenton limestone (Ordovician).

PertTiaybmnia. — Gas is obtained from the same formations that carry the oil. The Bradford district was the first developed, and formerly yielded gas of tugh pressure. Much has, even recently, been obtained from McKean, Elk, and Warren counties. Exten- sive deposits were also found about Pittsburg, and later to the south of it. Greene and Washington counties now produce important supplies from a pool whose length is about 25 miles and width 3 to 4 miles, with pressure ranng from 800 to 1000 pounds. Although in recent years several new gas-bearing sands have been discovered in southwestern Pennsylvania, the enormous demand for the gas threatens exhaustion of the available supply at no very distant date.

Werf Virginia (see Petroleum references). — This state is now the leading producer of natural gas in the United States, and is even now an important source of supply for both Ohio and Pennsylvania, whose gas supply is slowly falling off. The main supply is obtuned from the Gordon and Fifth sands of the Catskill (Devonian) formation, this being a higher horizon than that yielding the gas in the Bradford district of Pennsylvania. Immense quanti- ties are obtained from the fields of Wetzel and Tyler counties, the n'ells being from 2700 to 3200 feet deep. Pipe lines are now run from this district to Pittsburg, and a line has been laid from Tyler County to Cleveland, Ohio. Unfortunately, by allowing it to escape uith the petroleum, many thousand cubic feet of gas have been wasted in this state.

Ohio (76-77). — The Trenton (Ordovician) limestone, which formerly supplied large quantities of natural gas, is now so nearly exhausted tiiat little gas is obtained except by pumping. Some gas is obtained from the Clinton (Silurian) sandstone of central and eastern Ohio, and small amounts from the Comiferous (Devonian)

84 Economic Geology

limestone; but many towns in thia state are now supplied by the West Vunia fields.

Indiana (67, 68), — The gas fields of this state, covering about 2600 square miles, were formerly among the most important in the country, the gas being obtained from the Trenton limestone. The supply is, however, rapidly ving out, and its complete exbausUon ia probable at no very distant date.

KoTisas (70). — Southeastern Kansas and also northern Okla- homa are underlain by what is probably an extensive sandstone gas field. The supply comes from the Cherokee (Carboniferous) shale, and is now much used as a source of fuel in the local metallur- cal and manufactiudng industries.

Some gas is obtained from eastern Kentucky. Scattered pockets of high-pressure gas have also been found at several localities in j Texas, Louisiana (73), and also in California. j

Uses of Petroleum. — The three most important uses are for light, beat, and lubrication; but the various disUllates have special uses. Rhigolene is used as a local anaesthetic, gasoUne is used as fuel, and naphtha as a solvent for resins in making varnish and in oilcloth manufacture, while benzine is of value for cleaning and as a substitute for and an adulterant of turpentine. Astral oil and min- eral sperm oil are special grades of illuminating oil with high flashing points. Crude petroleum is now much used for fuel purposes in engines, as along the Pacific coast and in the southwest, where good coal is so scarce that many of the locomotives are run by the use of crude oil.

The paraffin residue is placed on the market for medicinal pui poses under the name of vaseline, petroleum ointment, and cosmo- line. It is also used as an adiilterant of candy and for electrical in- sulation.

Uses of Natural Gas. — Natural gas is widely employed as a fuel in factories, metallurgical establishments, glass works, cement plants, etc. For domestic pmposes, such as heating, cooking, and lighting, it is also widely used. Its cheapness, cleanliness, and high calorific power, and the ease with which it can be used, have been important factors in insuring its widespread selection for the above purposes. Some is used in the manufacture of lampblack.

b,

Petroleum, Natural Gas, Other Hydrocarbons 85

Solid And Semi-Solid Bitumens

Under this heEwUng are included (1) bitumens of a more or less solid character which are found filling fissures in the rocks, or some- times occupyii basin-shaped depressions on the surface, and (2) Ntumen of viscous character, or maUka, which is found oozing from fissures or pores of the rocks and sometimes collecting in pools on the surface.

Both of these are usually of rather high purity, and those belonging lothe first-named group may have a rather wide geologic and geo- graphic (Kg. 36) range.

FiQ. 36. — Map of asphalt and bituminous rock depoails of the Unilfd Stutes. lA/Ur Eldridot, U. S. Otol. Sum.. 2M Ann. Rept.. IX.)

Those of the first group were termed asphaUUea by Eldridge, but ance they are not all true a.sphalts, it secma beat perhaps to avoid this term. They are most commonly found filling fissures, usually in sedimentary rocks,' and might perhaps be termed vein bitumens.

Vein Bitumens. — There are several varieties of these, all black or dark brown in color, commonly with a pitchy odor, burning readily with a smoky Same, and insoluble in water, but soluble to a

' The anthiazolite of Ontario oc< porphyry has been deacribed from i XIII: H7. 1909.)

c,q,z.<ib,C00gle

86 Economic Oeology

varying degree in ether, oil of turpentine, and naphtha. Their spe- cific gravity ranges from 1 to 1.1. They are closely related chemi- cally and in their mode of occurrence, but differ somewhat in their behavior toward solvents, as well as in their fusibility, so that their identification is often somewhat uncertain. The most impwtant varieties are described below.

AUiertite (91). A black bitumen with a brilliant luster and conchoidal fracture, a hardness of 1 to 2, and specific gravity 1.097. It is barely soluble in aloohol, and dissolves to the extent of 4 per cent in ether and 30 per oant in oil of turpentine.

Some Amerioaii ooourrences of vein bitumens are thought to belong here, but the moat important occurrence is at Albert Mines, New Bnins- niok (91) where a vein of albertit is found in the Upper Devonian shales. The vein had a length of about half a mile and was followed down its steep dip to a depth of 1500 feet. Its thickness varied from 15 feet to sera, and branch veinlets ran oB into the wall rook. It was worked for thirty years and proved to be one of the most profltile mineral industries of New Brunswick.

Anthraxolile (93) is a ooaly, lustrous, blaok mineral, with a hardness of 3 to 4, and spedflc gravity of 1.965. It is found at Sudbury, Ontario, forming veios in a black fissile slate, but has also been desoribod from other localities.

OKkerite (98, 106), also termed mineral ipax or native paraffin, is a wax- like hydrocarbon, yellow brown to green, tranduoent when pure, and of greasy feel. Its specific gravity ranges from .845 to .97. It is easily soluble in petroleum, benzine, benzole, tiuntine, and carbon disulphide, but mare difficultly so in ether and ethyl alcohol.

It is known to occur in Utah (100) where the material is found flllifg fissures in zones of crushed Tertiary shales, sandstones, and limestones, ear Midway, Soldiers Summit, and Coulters station on the Rio Grande and Western Railway. The conditions are not regarded as very favorHhle tor working. The most important deposit of Ozokerite is in Qalioia. There it is found forming veins from a few millimeters up to several feet in thick- ness, in much-disturbed Miocene shales and sandstones.

GrahamiU (97, 106, 108). — This has a hardness of 2, and a specific gravity of 1.145. It is pitch4ilack, slightly soluble in alcohol, partly so in ether, petroleum, and benzole, but almost oompletel; in turpentine. Carbon di- sulphide and chloroform dissolve it completely.

Grahamite, was originally found in the Carboniferous sandstones (rf Ritchie County, W. Va.' There it occurred in a deep vertical fissure 1 to 5 feet wide at the surface, and nearly a mile in length, which was opened up at right angles to the direction of an anticlinal fold (Fig. 37). Through tiiis the oil escaped upwards from an oil pool, known to oocur below, and was oia- dized to gni&mito. The vnn has long since been worked out.

Deposits of grahamite are also known in southeastern Oklahoma, where the material occurs in steeply pitching veins, in sandstones, and shales. White, Bull. Geol. Soc. Amer., X : 277, 1890.

iv,Coog[c

Petroleum, Natural Gas, Other Hydrocarbons 87

The mil rocks wliioh are of Ordovioiaa to Carboniferous age, vEuy from flu to higUjr folded, and the Krahamite shows coireaponding fluotuations im aampoddon which an due no doubt to differences in the degree of meto-

Plo. 37. — Map ahotting relatian of gnhamite fimire to onticlitml fold, in Ritchie County, W. Va. {Afler While, BtiU. Oeol. Soc. Amer., X.)

morphiflm which the rocks have undergone. The veins are uncertain in extent, and with two exceptions have not warranted extensive development. Other deposits are located in western Arkansas but the material is badly crushed and more highly metamorpboaed (lOd).

Phoximatk Amaltbes op

Oklaboua an

n Arkansas Bitumin

Ntoirtare

Volatile bitumen

RxedCwboB

Snlphur

I. Impson Valley Erahamite. II. Black Fork Mountain vein bitumen. III. Pourche Mountain vein bitumen. Nos. II and III occur in the more Ughl; folded risks, and show effects of metamorphism.

Wnrtzilite (97) isabitumen related possibly to gilsonite, but distinfniished from it by its behavior towards solvents, and by its elastic and seottle

oogle

88 Economic Geology

IwopertieB. It h&s a hardness of 2-3, and speeifio gravity of 1.03; is black, with pitohy luster, and petroleum-Uke odor. Tahbyite is regarded by some as simil&r. Wurtzilite is found fiD- ing fissures in Tertiary e&lcareous shales and limestones in the western part ot the Uinta Baain, Utah. It has been but little mined.

Lake AtphaU (103) is not found in the United States, but ooours in the famous pitch l&he on the island of Trinidad, off the coast of Yene-

The deposit PI. X and H. XI, PHg. I, appears to occupy a basin- shaped depression of about 100 acres and nearly circulw outline (Fig. 38) lying 138 feet above the sea level. The material evidently arises from some source below, as excavations made in the pitch fill up aain in a short time. Two forms of the asphalt are recognized, viz. the lake pitch and the land pitch, the latter being asphalt which has overflowed from the lake at a low point on its rim, and run down to the sea. Up to the present time about 3 million short tons of asphalt have been exported from the island. Manjak (lOOa) is the name applied to a bitumen

resembling UintMte, found on the island of Barbados.

It is a hydrocarbon of high purity, black color, brilliant

luster, and conchoidal fracture.

The Manjak is found in veins cutting obliquely

across the upper strata of the oil series (Oligocene)

and disseminated through the clays. The largest

vein is over 27 feet thick and often shows unusually

rich pockets. The close association of this asphalt

with the petroleum has led most geol(sts to assume

its derivation from the lattr.

UirUaite, or Gihonile (97), is a black, brilliant

bitumen, with conchoidal fracture, hardness 2 to 2.5,

and specific gravity ot 1.065 to 1.07. It is partly Fio. 39.— Section o(

soluble in alcohol (45.4 per cent), more so in ether, and Gilsoolte vein, Uuh.

completely in chloroform and warm oil of turpentine. (After Eldridge, U. S.

It is found filling a series of fissures (Pigs, 39 and Oail. SuTv.,nth Ann.

40), termed veins, in the Bridger beds of the Tertiwy

of Uintah and Wasatch counties, northeastern Utah, and, to aless extent, in n Colorado. The veins strike usually northeast-southwest, and vary

. h.C.oojlc

Fto. 38.-

c,q,z.<ib,

b,

Petroleum, Natural Gas, Other Hydrocarbons 89

greatly in width, extremes of 18 feet beins reported. They are tisoeable for long dia- Unros, but their vertical depth appears to be unknown.

MaUha. — This ie usually found bsuiog from crevices or pores of the rooks, the latter imag sometimes of bitumiiiaus character. It can also be extroctad from bituminous iDck and asphaltic oils.

Maltha is not known to ooour in large deposits in the Unit States, although it is aimewhat widely distributed in some of the California oil fields, where the petroleum uudes from the rooks, and on exposure to the air becomes converted into maltha by the loss of its more volatile constituents. In tbe Santa Barbara (18) and Kern County oil Gelds it is found in fissures of limited utent. Its occurrence has also been noted ID Oklahoma.

Oil asphalt is obtained from the distillation of certain asphaltio oils of California and Texas, and some of these He said to oontain orer 35 per cent of it.'

Tio. 10. — Gilsonite mine at DragoD, Utah. The cut represcDta poaitioD of vein. (Aepf. of Coat Mine In- ipedoT. Vlah. 1905-1906.)

ELEMENTAar Analtses of Bitumens and Maltha

e

h

1

tl

n

h

,3!

0 . .

ft5.25

8fi.57

7fl.4.'>

,59.20

86.04185.53 88,30

H. .

1I,S?

7.2fi

7.8?

8.96|l3.2t

9.9H

H.m

12.2;

—

1.4*

tr

1.7t

0 . .

—

—

lS.4h

s . .

—

tr

tr

Ash .

—

—

i9.;w

—

—

—

—

MoU-

—

—

—

—

—

—

—

—

—

—

ture

1,9. 10, 11. RiebuiiBn, "N>tun u>d Oriiin ol Aigdidt." 1S98. Z. Munlc. Enc. Mac. JaDe-Aiat. 1897. 3. Amar. Jour. Sci.. Sept, ISW, p. 221. i. Wurti, aaalyn, Amer. Jour. Sn., iii. VI: 415. 1873. S. Kite, BnalyK, Geol. Son, Amer., Bull. X: 283, 1899, A proiimsto uuJiii muls on another sample (Bve 1.13 nilpbur. 6. Tcans. Amer. Phiioa. Soe., Phila.: 8S3, 1:. 7. RuhardHO. Modsn Aepholt Pavement: 209, 190,'i. S. Jour. Frankl. Inat., CXL. No, 837, Sept. ISflS.

'Taff, U. S. Geol, Surv., Mia. Res., 1908,

iv,Coog[c

Economic Geology

Bituminous Rocks

Under this heading are included consolidated and unconsolidated Tocka, whose pores are more or less completely filled with bituminous matter, often of asphaltic character (97).

They are commonly classified according to the character of the containing rock as bituminous sands or sandstones, bituminous hmestonea, shales, or schists.

Bituminous rocks vary not only in their richness, but also in their value for paving purposes, for while In some the bituminous matter is purely asphalt proper, in others it may conast wholly or In part of maltha or some liquid bitumen, which may interfere with its use for paving purposes.

Deposits of bituminous rock are more widely distributed than the vdn bitumens, being found in several geolofpcal horizons, and are worked in Kentucky (97), Oklahoma (97), and California (97).

In California depoats of asphaltic shale and sandstone are not of rare occurrence in the oil regions from Santa Cruz southward. The bituminous sandstone quarried near the above named place (PI. XI, Rg. 2) is of blackisb or brownish-black color, weathering to gray, and occurs beneath the Monterey shales; it sometimes rests directly on the granites. The bitumen impregnates the heavy-bedded sand- stone inmiediately under the shale, and also the sand that fills cracks which extend up into the shale. These cracks, which vary in width from very minute size up to 2S or 30 feet, are aometimes traceable for several hundred feet, beii at times of value as guides in finding the main bed.

Analtses op BmjMiNona Rocks

LoCALm

CtCOt

SAHDOa

Califomia

Kentuclw

SeyBMl, France . . . Lunmer, Germimy . .

5.7S

on. SHALES

Shale containing sufficient petroleiun to permit its extraction by a process of distillation is known as torbanite or kerosene shale (80-84) . Such shales are found in the Carboniferous of New South Wales,

b,

The

University

b,

Petroleum, Natural Gas, Other Hydrocarbons 91

Australia, New Zealand, aod Scotlaad, and in the Cretaceous of Brazil. Those in New South Wales are being worked, and in Scot- land the industry has thrived under careful management for a niun- ber of years.

In Albert and Westmoreland Counties of New Brunswick, Canada, there is a considerable area underlain by black, brown, and gray shales of Upper Devonian age, which contain a number of bands of oil shale. Tests of some of these have yielded 63 gallons of crude oil per ton, and in 1909 investigations were under way looking towards their development.

Oil shales are but little known in the United States, although they DO doubt exist.

The following analyras indicates the composition of an oil shale :

Rich shale, Joadja. N.8.V

The o3 cut be obtained by distillation in retorts ; but in view of the large aviilable supplies or petroleum, obtainable in mahy parts of the worid, the material at present has but little oommercial value.

The onide oil extracted by distillation from a toa of Sootoh shale (Steu- til) varies from 16 to 35 gallons and the ammonium sulphate from 30-70 pounds. The refined products of the crude oil are spirit of naphtha, 4 per Nut; banungoil,33peroent;gasoil,7peroent; lubrioatinc oil, 20 percent; nlid paraffin, 10-12 per cent.

Origin of Solid Bitumens and Bituminous Rocks. — A study of the dei>osit8 leads to the conclusion that these solid bituminous compounds have been derived from petroleum (87, 88, 89, 90) , for the loUowing reasons: In the vein deposits the solid bitumens are often lasociated with petroleum springs, or with fissures leading down to or toward petroleum-bearing strata. In some cases the material not only fills such a fiseur, but impreutes the wall rock to a distance of a foot or more on either side of the vein, indicating that the material came up through the fissure in a liquid condition, filling it, and even penetratii the wall rock.

The bitumen in bituminous rocks may either have originated from organic remuns within the rock itself or have seeped into it from some neighborii pool. In either case the material seems originally to have been liquid petroleum, some of which later solidified.

92 Economic Geology

Uses of Asphalts. — Trinidad asphalt mixed with powdered rock and tar is much in use for pavements, and the bituminous rocks are employed for similar purposes. Ozokerite, known as Ceren in its purified form, is used in the manufacture of candles, ointments, powders, as an adulterant of beeswax, and for bottles to hold hydro- fluoric add.

The most important use of Uintaite and Manjak is for making low grade and dipping varnishes, such as are used for iron work and bak- ing Japans. Other uses to which the Uintaite at least has been put are for preventing electrolytic action on iron plates of ship bottoms, coating masonry, acid-proof lining for chemical tanks, roofing pitch, insulati'og electric wires, as a substitute for rubber in common garden hose, and as a binder pitch in making coal briquettes.

Production of Petroleum and Natural Gas. — Petroleum has long been known in many parts of the world because of its presence in bituminous springs or as a floating scum on the surface of pools. It was used at an early date on the walla of Babylon and Nineveh, and was obtuned by the Romans from Sicily for use in their lamps.

In the United States petroleum was mentioned by French mis- sionaries even in 1635, and the early Pennsylvania settlers obtained small quantities by scoopii out the oil from dug wells. Its dis- covery at a greater depth on the western slope of the Alleghanies was made diuii the drilling of brine weUs; but its early use was chiefly a medicinal one until 1863, when attempts were made to purify it for use as a lubricant and illuminant. The beginning of the oil industry is usually considered to date from the sinking of a successful well by Colonel Drake on Oil Creek, Pennsylvania, in 1860. From this center prospectors spread out in all directions, making valuable discoveries, until now petroleum production and refining rank amot the leading industries of the country, the supply coming from many states.

Natural gas was discovered and first employed for economic pu poses at Fredonia, New York, in 1821. In 1841 it was used in the Great Kanawha Valley as a fuel in salt furnaces, but its first ex- tenfdve use began in 1872 at Fairview, Pennsylvania. It was used in 1885 for iron smeltii at Etna Borough near Pittsbui, and in 1886 was piped nineteen miles from Murraysville to Httsburg. Now natural gas is piped long distances to cities, being used as ft fuel in many industries, as well as for domestic heating and Ughtlng.

The following tables give the production of oil and gas from 190* to 1908 inclusive. The production of oil since 1880 is shown di&-

Petroleum. Natural Gas, Othkr Hydrocarbons

H

:rr:rl'4"Tn

Ak

y

r

H

A

y

—

Vj

A

/

J

/

i'

p

¥

Si

:

Fro, 41, — Produotion of oil fields.

gramatjcally in Rg. 41. Where the production has fallen below 200,000 barrels no attempt has been made to ahow it. This affects only the Gulf and Mid-Continental fielda.

looe

*Sff"

V*Lini

V*L,™

""iSI"

Valdb

Kmlgcky and

'SSi" -

i8:s7B;e3i

988.28

izso!77l

;si

117,080, wo

Slit ,222. 242 23,730,51 ;

98<.838

12,236,674

5,447,822

8,156,220

80,704

1,811337 101,175,455

10,437,195 18,340,0<K

1,217,337

1 0,064 !24: 12,013,495 28,135,181 8.910:4 It 134|717!68(

Si4,B53.278 17,054,871

M3.2I1 8,548,398

iffii

U',787;76;

7;67a!477 21,718,648

9.077:528

18,170,293 9.553,430

'Sg

9.615,198 ' 4:000

bvCooglc

Economic Geology

QuANTm AND ?ALDE OF Petroleck Phoducbd rn United Statbb, 1904-1908— CorUinued

WettVirtini Cmliforaia . . Keatucky utd

Colorado

IBdiiiiui .

OkUkoma

Tsui

WyomliUE

9,999.306 12,307.448

9,095.296 30,74S.37S

9.434.339

10308,797 9,633,170 443U.737

(10381.194 14.1 78.502 10,911.805 23.433,M2

340,403

22.048,881

3303,883

17,004343

0,700.708

Petrolbdm in the United Statbs, 1904-1908, bt Fields, in Barrels

im

31,408,507 24,089.184

34831 Isoe

29,366,900 22.294.171

12.S36i777

27,741.472

4!397i060 22,838,653 20,5Z7,SZO

25342,137

13,Iz1,14

46 !S4 61207 100.095,330

33.885,106 48323,810

44,854.737

Total

117380.900

134.717380

120,493,938

179,072,479

The average price per barrel of petroleum naturally varies somewhat from year to year. In 1885 it was 87J /; in 1890 86jy; in 1900, $1,194; in 1903, 94i in 1906, .731 and in 1908,

The total number of barrels of petroleum produced in the United States from 1859 to the end of 1908 was 1,986,180,942, with a value of SI ,784,583,943, while the total value of natural gas produced in the United States from 1S82 to the end of 1908 was $581,479,911.

The world's production of petroleum from 1904 to 1908 was as follows: —

1 Includes Utah.

b,

PETROLEUM, NATURAL GAS, OTHER HYDROCARBONS 95 World's Prodoction or Cbiidii FnrBOUKni, 1904-1908, bt

Couhtsies

(Burela of 42 gallona)

Commi

Isos 1S06

Pwjono-

117,O8O,Be0 T8,G3,(I&5

7,Ss2,014

S,M7383

si

6S2.S7G 637,431 34G334 '40,000

t34.7IT.GS0 126,493,936 M,ee0.270 68307311

8.666304 6.662.672 6,766317 6.467.96' 4,420,987 6378.184

iSlS l:?iS:S

as sss

44738C 634,920 44,027 63,677 SftOOO '30,000

166.096336 ei3S0,734

S377.009

!ii

69,871

'aolooo

BunI*

Vtotfiotou

8,762.822 12.612,29;

3!4Sl!4I( 627,9S;

'30;00(

1, 43.243

1;Ss

64,188 70,40

8,344 4)000

-

2l9:iSl,SB

216.646,178 213393.410

261.628.631

284,614.023

38,063.383

Appboxihatk VaiiUb o

Btatb

lOOB

PsuMhruu

19, 197336

AUtanu.

14,082

136,882

Td

38,406,760

141,862366

884.323,300

(64,640374

Exports op Mineral Oiu

7.731.226

18.080.622 1.071,306

6.333,716

191210363

Kifihdw

64,000.649 14.313383

2.127.696

ToUl

179,640.939

(86,738366

01,383.064

108318,456

iv,Coog[c

Economic Geology

lypOKTs or Natural Oas

4B.237

sa.soe

1907 S2.107

Production of Asphalt and Bltumiaoue Rock. — The production of these two substances by kinds and by states as well as the importe and exports are given below.

J90*

leoe

Valitb

V.™

Q..,nnr

la?"

UrlU)

!i

liooo

44.40S

I14S

4Sb.

Wo

13E

3,13B

so. leg

47:04O

1.S00

', 13.847 1.B63

Milioe

1S0,60 10,433

ToW

SSTa.S38

11G.267

STss.isa

t3S.058

Valdi

Wunjllll. (.UMfite)

46,536

sliee

13e.204

is.oea

7,743 2,148

1,881,640

Is

102,381

48,780

30',340 3,600

1.333,010

ToUl

13.830.488

1S6,S81

S13Ssab1

' Tbe curiously larse decreaae in value aa given, doei Dot, it is claimed, a decrease la value per too. but instead iodicatea a chaDge in oonditiooa of portation to trunk lines of tailroadt from the mioea.

iv,Coog[c

Petroleum, Natural Gas, Other Hydrocarbons 97

Pboductiom or Abphai/t m 1908, bt Varistihs and bt Btatbb, IN Sbobt Tons

Caut

"-

Okuboha

Quality

ValiKi

Qmdtity

Viliw

Vd

KtomlDOtH

iMk . . . .

Iis

I2.7W Ss.114

ia8.S20 972,178

Mo

38,600

Tail"

Wnruilita

InniM) . . . (eUUiite) Ukd

13S,34I

tl.347,2S7

10,033

(100.324

(23330

KtmocKT

Tkus

Qoutity

Qnutlty

y-„

tU333

12Ji17

OOmpImH

11Jm8

187,010

17,167

Since depocuts of the purer type, such aa lake asphalt, are very Bc&rce in the United States, the supply for domestic cooaumption is obtained from foreign countries. The imports for the last five years are pven below: —

AflPaALT IHPOBTED VOB CoNSTTHPnON INTO THB UNITED StATBB,

1904-1008, IN Sbort Toms

Yub

Cbotb

ADTiSc

LlKWTOHl

T0T*L

Qoutitr

VdoB

Qui.Uty

QuAnUW

Vtiat

Quutity

ViUlw

lt04. . . . ISOS. . . .

(400J0D 381,471

S02!sil 632 JW7

14,178

7lS42

(100,081

(20.230

40.44S

D0,M7

Ss

51,874

(115,120

479.2Bs

gS;

Importa for 1907 iaoludg (3,100 muiurKtun

Most of the asphalt imported from foreign countries comes from the island of Trinidad, but other important sources are Venezuela

98 Economic Geology

(Bennudez), Cuba, Germany, Italy, and Mexico. Small amounts are also brought from Switzerland, France, the United Kingdom, Turkey in Asia, Colombia, and Netherlands.

The ozokerite imported for consumption in 1907 amounted to 1,451,231 pounds, valued at S149,507; in 190S it amounted to 3,595,393 pounds, valued at $374,953.

During the fiscal year eading June 30, 1908, domestic asphalt and manufactured asphaltic material to the value of S4S1,968 were exported from the United States to other countries, as agcunst simi- lar exports valued at $374,476 during the fiscal year ending June 30,

Rbferehcbs Oh Petroleuh

Okioin, Occurence, and Tbchnoloot. 1. Booker, U. S. Geol. Surv.,BuII. 401, 1909. (Relation maetio diaturbanoes to petroleum wigin.) 2. Clapp.Eeon. Oeol.,IV: 565,1909.. (AntioUn theory.) 3. Dolton, Eoon. Geol., IT : 603, 1909. (Origia. Exoellent.) 3 a. Coste, Amer. Inst. Min. Engra., Trans. XXXV: 288, and Can. Min. Inst, Jour., XII. (Volcanic orisin.) 4. Hofer, Du Erdl,2ded., 1906. (Brunswick, Ger.) 5. Mineral Industry, II : 497, 1894. (Mining and Technology.) 6. Munn, Eoon. Geol., IV: 141 and 509, 1909. (Anticlinal and hydnulio theories.) 7. Newberry, Ohio State Agrin. Rept., 1859. 8. Orton. Geol. Soo. Amer., Bull. IX : 85, 1892. (Origia and aocumulatioD.) 9. Orion, Kentucky Oeol. 3urv., 1894. (Ori.) 10. Clarke, U. a Geol. Surv., BuU. 330, 1908. II. Peokham, Day, Mabery, etc., Proo. Amer. Phil. Soo., XXXVI : 93. (Origin and composition.) 12. Red- wood, B., Treatise on Petroleum. (Excellent.) London. 13. White, Geol. Soc. Amor., Bull. Ill : 187, 1892. (Anticlinal theory.)

Areal Reports. Alaska: 14. Martin, U. S. Geol. Surv., BulL 250, 1905. Also U. S. Geol. Surv., Bull. 394 : 190, 1909. — CalifomU: 15. El- dridge, U. 8. Geol. Surv., Bull. 213 ; 306, 1903. (General, good.) 16. Watts, BuUh. Calit. State Min. Bureau, No. 3. (Central Valley.) 17. Eldridge and Arnold. U. 3. Geol. Surv., BuU. 309, 1907. (Santa Claia Vdey, Puente Hills, and Los Angeles.) 18. Arnold and Andenon, U. 8. Geol. Surv., Bull. 322, 1907. (Santa Maria district.) 19. Ar- nold, Ibid., Bull. 321, 1907. (Summerland diatriot.) 20. Arnold and Anderson, /bid., Bull. 357, 1908. (Coalinga.)~C(doEtdo: 21. Fenn- man, U. S. Geol. Surv., Bull. 260 : 436, 1905 (Florence field), and Washbume, Ibid., BuU. 381 D : 45, 1909. (Florence field.) 22. Fenne- man, U. 8. Geol. Surv., Bull. 225 : 383, 1904. (Boulder field.) — Waoia: 23. Bain, 111. Oeol. Surv., BuU. 8 : 273, 1907, and Boon. Geol., II :4S1, 1908. (lUinoia field.) — Indiana: 24. Blathley, Ind. Dept. Geol., 22d Ann. Rept. : 155, 1898. (Trenton limestone field.) 25. Chapters on petroleum in other annual reports of this aeries. 26. Orton, U. S. Geol. Surv., 8th Ann. Rept.. II ; 475. 1889. (Trenton limestone.) — Kansas : 27. Adams, U. S. Geol. Surv., BuU. 184, 1901. 28. Haworth and others, Kansas Qeol. Surv., IX, 1908. (Genwal.)

b,

Petrolbxjm, Natural Gas, Other Hydrocarbons 99

20. Seo also Volumes on Minenl Resources, issued by Eiuisu Oeol. Surv. from 1897 to 1901. 30. Schroder and Haworth, U. S. Oeol. Surv., Bull. 260 : 442. 1905. (ladepeadenoe quadrangle.) 31. Adams, Ha- worth, and Crane, /(rid.. Bull. 238, 1904. (lola quad.) — Kentncky: 32. Orton, Ky. Geol. Surv., 1894. (General.) 33. Hoeing, Ky. Qeol. Surv., Bull. 1, 1904.— LonisUna : 34. Fenoeman, U. & Oeol. Surv., Bull. 282, 1906. (General.) 35. Huris, Perrine, and Hopper, Ia. Geol. Surv., Bull. 8, 1909. (Caddo field.) — Hichlgan : 36. Gordon, Mioh. Gecd. Surv., Ann. Rept., 1901 : 269, 1902. (Port Huron field.) — Hew York : 37. Orton, N. Y. State Mus., BuU. 30, 1S99. (General.) 38. Annual bulletins on mining Industry, by N. Y. State Museum. Ohio : 39. BowQooker, Ohio Geol. Surv., 4th Series, Bull. 1, 1903. 40. Oris- wold, U. S. Geol. Surv., BuU. 198. (Berea grit oil.) 41. Mabery, Amer. Chem. Jour.; Deo., 1895. (Composition.) 42. Orton, Ohio Geol. Surv., VI : 60. 43. Orton. U. S. Oeol. Surv., 8th Ann. Rept., II : 475, 1889. (Trenton limestone field.) 44. Griswold. U. S. Oeol. Surv., Boll. 198. 1902 (Cadiz quadrangle), and Bull. 346, 1908. (Flush- ing quadrangle.) — OkUhoma: 45. Gould. Min. Wld., XXIX : 807, 1908. (Oenernl.) Taft and Shaler, U. S. Geol. Surv.. Bull. 260 : 441, 1905. (Muskogee Held.) — Pennsf Ivanla : 46. Carll, Ann. Rept. Fa. Oeol. Surv., 1885 ; II. 1886. 47. Reports I to 1 5 of the same survey. 4S. Itoport Pa. Top. and Geol. Surv., 1906-1908; App. E : 266, 1908. (General and oontains further referenoee. ) — Texas : 49. Adams, U. S, Geol. Surv., Bull. 184, 1901. (General.) 50. Fenneman. U. S. Geol. Surv., BuU. 2S2, 1906. 51. PhiUips, Tex. Univ. Min. Surv., BuU. No. 1,1900. (General.)— United Sutea: S2. See Map of Oil Fields in U.S. Oeol. Surv., Min. Res., I90S, also analyses in this and 1907 Min. Res., as weU as Bull. 381-D. 53. Day, U. S. Geol. Surv., BuU. 394, 1909. (Conservation of oil supply.) — Utah: 54. Richardson, U. S. Geol. Surv., Bull. 340 : 343, 190a — Washington: 65. lAudes, Wash. GeoL 8urv.,I:207. (General.)- West VirglnlB: 56. White, W. Va. GeoL Surv., I a : 1, 1904. (General.) 57. White, Oeol. Soe. Amer., Bull. 111:187, 1892. (Mannington field.) — Wyoming: 58. Knight and Sloeson, Bull. .4, Wyo. School of Mines. (General.) 59. Bull. 3. (Crookaud Uinta Cos.) 60.BuU.5. (NewoasUe field.) 61. BuU. 1. (&lt Creek field.) 62. Knight, Bug. and Min. Jour., LXXII : 358, 628, 1901; and LXXIII : 563, 1902. (General.) 63. Veatoh, U. S. Getd. Surv., Prop. Pap. 56, 1907. (S. W. Wyo.)

RBFSRtllCBS OH HAIURAL OAS

61 Ashbunm'. Am-. Inst. Min. Engrs., Trana. XIV : 428. (Geology and Distribution in the United States.) 65. Orton, Geol. Soo. Amer., BulL 1 : 87. (Rook pressure.) — CaUfomla : 66. Watts. Calif. Min. Boieui, BttU. 3. (Central VaUey.) — Indiana: 67. Phinney, U.S. Oeol. Surv., 11th Ann. Rept., I : 589, 1891. 68. See also Ann. Rept. lad. GeoL and Nat. Hist. Survey. — Kansas: 69. Adorns, U. S. Geol. Surv.. BuU. 184, 1901. 70. Haworth, Kan. Geol. Surv., IX, 1908. (GeneraL) 71. Orton, Qeol. Soo. Amer., BuU. X : 90, 1899. (lola field.) 72. Volumes on Mineral Reaouroee, issued by

100 Economic Gboloot

Kan. Geol. Surv., 18d7-1901. — LotdsUoa: 73. Harria, Paniae, sod Hopper, La. Qool. Surv., BuU. 8, 1909. (Caddo field.) — Hw Tork : 74. Orton, N. Y. State Mus., BuU. 30, 1899. (Oenenl.) 75. New- land, N. Y. State Mu8., BuU. 93:943. (New York.) — Ohio: 70. Orton, Ohio Geol. Surv.. I. 3d ser. : 56. 77. Orton, U. S. Geol. Surv., 8th Ann. RepL, II : 475, 1889. — PeonirlTUiia : 78. CarU and Phillips, Ann. Rept. Pa. Geol. Surv., 188e, Pt. II. 1887. (QenereJ.) — Tens: 79. Adama, U. & Geol. Surv., Bull. 184, 1901.

Rbfbrsmces Os Oil Shales

80. Branner, Amer. Inst. Min. Eagn., XXX:637. (Bnwil.) 81. Came Memoirs, Dept. Mines and Agric, New South Wales, Geoloe; No. 3: (General treatise.) 82. Baskerville, Eof. and Min. Jour., LXXXVIII. 149, 1909. (General and New Brunswick.) 83. Steuart, Eoon. Oeol., 111:573, 1908. (Scotland.) 84. EUs, Can. Min. Inst., Jour., X: 204, 1908. (New Brunswick, Can.) ; also Jour. Ming. Soo. N. S., X\' and Dept. Mines Can., Mines Branch, Bulls. Nos. 55 atid 1107, 1910. (E. Can.)

Kbferbkces Oh Solid Uid Sexisoud Bitiiheiis

Qbnbiui.. 85. Dow, Min. Indus., X : 51, 1902. (History of Asphalt Indnstr;.) 86. Richardson, The Modem Asphalt pavement, 2d ed., N. Y. 1908. (Wiley and Sons.) (Uses.) — Orioin. 87. Adams, Amer. Inst. Min. Eagn., Trans. XXXIII: 340, 1903. (Origin.) 88. Day. Eng. Record, XL : 346. 89. Eldridge. Econ. Geol., 1 : 437. 1906. (Asphalt vein formation.) 90. Peckham. Amer. Phil. Soc., XXX VII : lOS. (Genesis of bitumens.) — Special Pai>eks, 91. Bai- ley and ElU. Geol. Surv., Canada, 1876-1877. 384. (Albertite.) 92. Blake, Amer. Inst. Min. Engrs., Trans. XVIII : 563. (Uintaite, Albertite, and Grahamite.) 93. Coleman, Ontario Bur. Mines, 6th Ann. Rept., 159, 1897. (Anthnizolite.) 94. Bell, Amer. Inst Min. Engrs., Trans. XXXVIII : 836, 1007. (Athabaaoa River. Can,, tar sands.) Arbal. 95. Cooper, Calif. State Min. Bureau, Bull. 16. (California.) 96. Crosby, Amer. NatnraliBt, XIII: 229. (Trinidad.) 97. Eldridj, U.S. GeoL Surv., 22d Ann. Rept., 1:1901. (Oeneral ocourrenoe in United States, exoellent.) 98.' Oosling, Soh. of M. Quart.. XVI : 41. (Ozokerite.) 99. Gould, Okla. Geol. Surv., Bull. 1, 1908. 100. Hayes. U. S. Oeol. Surv., BuU. 213:253. (Bituminous sandstones. Pike Co., Ark.) 100 a. Hovey, Min. Wld., XXIX : 237, 1908. (Manjak, Barbados.) 101. line, Bug. and Min. Jour., LXXIII :50. (Mioh.) 102. Meti- vole, Eng. and Min. Jour., LXVT : 790, 1898. (Barbados.) 103. Peckham, Pop. Soi. Mo., LVIII : 225. 1901. (Trinidad and Venezuela.)

104. Phillips, Univ. of Tex. Min. Surv.. BuU. 3. 1902. (Texas.)

105. Taff, U. S. Oeol. Surv., BuU. 380 : 286, 1909. (Grahamite, s. e. OUa.) 106. Taff and Smith, U. S. Geol. Surv., BuU. 285: 369. 1906. (Utah Ozokerite.) 107. Vaughan. Eng. and Min. Jour., LXXIII: 344. (Cuba.) 108. White, BuU. Geol. Soo. Amer., X : 277, 1899, (W. Va. GrahamiW.)

CHAPTER III BUILDinG STONES

Undeb this term are included all stones for ordinary masonry construction, as well as for ornamentation, roofing, and Sagging. The number of different Idnds used is very great, and includes prac- tically all varieties of igneous, sedimentary, and metamorphic rocks, but a few stand out prominently on account of their widesprend occurrence and durability.

The cost of a building stone naturally exerts decided influence on iU use. Since the ease of splitting and dressing a stone influences its cost, the texture is also of importance. Color is another factor in determining the value of a building stone, and this, together with other considerations, sometimes ge a fashion leading to the wide- spread use of certain stones. This has been well illustrated in the eastern cities of the United States, where, for many years, Connecti- cut brownstone was in such great demand for use in building private dwelling that much inferior stone was put on the market. More recently Indiana Bmestone and Ohio sandstone have met the popular fancy, and these two are now used in vaat quantities.

Properties of Building Stones* (1-6). — The following prop- erties have an important bearing on the value of a building stone: —

Color. — The color of rocks varies greatly, and those shown by common building stones include white, black, brown, red, yellow, and buff, while some are green, blue, or mottled. The color may vary in the same quarry.

In igaeous rooks the oolor may be that of tfaa prevailing mineral, u io pink gniiite, where there ie an exoess of pink feldspar; or it may be t eompoeite due to the blending of the colors of several minerals, as in iba case of ordinary gray granite, where the color results from the mix- ture of blaok mica and whitish quartz and feldspar. Sedimentary roeka commonly owe their oolor to ferruginoUB oementa. or to carbonaceous matter. The former give brown, yellow, red, or green colors dopeading on the oondition of oxidation and form of oombioation of the iron, while the latter produoee gray, block, and bluish tints depending on the amount present. Sandstone and limeetone free from either of these coloring agents are nearly if not quite white.

Only Uie more important ooea are here conaidered. Eicdleot detailed dicu- BDn win be found in Refa. 3. 30. 41, 43 a. 51.

"" u ,__.,Cooglc

Ks Economic Geology

Some stones change color on exposure to the air. For example, lime- Btonea or Bandstonea containing carbonaceous matter may bleach; some black marblea fade to a white or gray; and some red and green TOofiDg slates, as well as a few red Kranites, change color. Oxidation of evenl? distributed pyrite may change gray or bluiah-gray sandstones to buff color. If the minerals responsible for such change in color are not uniforaily distributed, the atone assumes a blotchy appearanoe, but such changes are not necessarily an indication of deterioration.

reclure. — BuildiDg stones vary in their texture from coaree- grained granites and conglomerates to fine-grained sandstones, lime- stones, and porphyries.

Texture is an important property, tor it influences both the duis- biiity and the cost of stone. Other things being equal, a fln-grained rock is not only more durable, but splits better and dresses more evenlji than a coarse-grained rock. Uneven texture, whether due to minenl grains or cement, is imdesirable, since it often causes uneven weatheriog.

Density. — On the whole, dense stones resist weather better than porous ones, but there is great difference in the density of building stones.

b,

Building Btonbb 103

In geaenlt though with some exceptions, igneous and metamorphio rocks have high density because of the close interloddng of the crystal- Ene gniins. Sediinentary rocks of clastic origin, on the other hand, have lesa closely fitting grains, and unless the latter are very small, or the pores well filled with cement, they are apt to be porous.

The speoifio gravity of a stone indicates its density; and from the fpeeifio gravity the weight per cubic foot may often be approximately estimated by multiplying it by 62.5, the weight of an equal volume of >ter. While sufficiently accurate for very dense stones, this method ta liable to lead to incorrect results when appUed to very porous rocks. Following are some average specific gravities of common building stones, ssgiven by Hermann (1): granite, 2.65; syenite, 2.80; diabase, 2.80; gabbro, 2.95; serpentine, 2.60; gneiss, 2.65; limestone, 2.60; dolomite, 2.80; nndatone, 2.10; state, 2.70.

Hardness. — The hardness of a building stone is not necessarily dependent on the hardness of its component minerals, but is largely influenced by their state of aggration, and to some extent their hardness.

For example, a sandstone composed of quartz grains, but with little cementing material, may be so soft as to crumble easily in the fingers; while a limestone, whose grains of soft carbonate of lime fit closely and

t,

104 ECONOMIC GEOLOaY

are ffrnily oemented, may be difficult to break with hunmer. The nature of the eement in sedimentary rookB, that is, whether it is lime, silioa, OT iron, will also aSeot the hardness of the stone. Crystalline rocks owe their great hardness to thp firm interiocldng of tiie mineral grains. The abranre reaiatanoe (10) of a stone will depend in part on the state of aggregatioa of the miueral particles, and in part on the hardnosa of the gnuns themaelvea. Some stones wear very unevenly because of their irreg:ularity of hardness, and such may be lees desirable than one which is uniformly soft.

No standard form of abrasion test exists, and yet one should be applied to thoee stones which are used for paving, steps, or flowing, as well as to those placed in situatiana where they may be subjected to the attacks of wind-blown sand, or the rubbing action of running water.

Strength. — Two kinds of strengith, compreaeive and transverse, are to be conadered in building stones.

The compressive or crushing strength, which is repressed in pounds per square inch, is the resistanoe which the rook offers to a crushing toree, and is dependent chiefly on the size of the grains, state of aggrega- tion, and mineral composition. Because of the dose inteiiooking of the grains of igneous rocks they are stronger than those of sedimentary origin, in which the strength is due chiefly to the cement which binds, the grains together. Sedimentary rooks show greatest strength when dry, or when pressure is applied at right angles to the bedding.

Few building stones when in use are subjected to pressures even approxi- mately equal to their crushing strength. No domestic building stone at present used in the eastern market has a crushing strength of less than 6000 pounds, yet the pressure even in the tallest buildings does not require a stone with a crushing strength exceeding 314.6 pounds, and this includes the factor of safety of twenty usually allowed by architects. Computa- tions show that a stone at the base of the Waahington monument snstaiiu a maximum pressure of 6202 pounds per square inch, which indudes the usual factor of safety of twenty; the crushing strength of the stone used in the base of the monument is however not less than 10,000 to 12,000 pounds per square inch.

The crushing strength of some soft limestones or sandstones may be but little above 3000 pounds per square inch, while that of diabase often exceeds 30,000 pounds per square inch. The aooompanying table gives the crushing strength of a number of stones. (Many others are given in the state reports.)

Chtjshino Strength of Buildinq Stonkb

Granite, Vinal Haven, Me 13,381

Oranite, East Saint Cloud, Minn 2S,O0O

Granite, Port Deposit, Md 18,750

Dolomite marble, Tuckahoe, N.T 18,076

Limestone, Caen, France 3,550

Sandstone, Portland, Conn 1310

Sandstone, E. Long Meadow, Mass 8,813

bvCoog[c

Building Stones 106

Wide wiationB aometimes exut in atooes from different parts of the suae quairy, or in stoneB from the same locality tested at different times. The published erushing tests of different stones oannot really be fairly compared beoaiue all have not been tested under exactly the same oondi-

TTantaent Slrentfik. — The transvene strength is the load which a bu at stone, supported at both ends, is able to withstand without breok- ing. It is measured In terms of the Tnoduivg of rupture, which represents the force necessary to break a bar of one square inch cross section, rest- ing on supports one inch apart, the load being applied in the middle.

AlthoDgh stonee in buildings are rarely, if ever, crushed, they are frequently broken transversely, and therefore a knowledge of the transverse strength is of more importance than the orushing strength. A high oruHhing strength does not neoesaarily mean a high transverse strength. Unfortunately few itones have been tested in this manner.

Porosity and Ratio of AbeorpUon. — The poroaty of building stones varies widely. Most igneous rocks have little pore space and hence absorb little water; but sedimentary rocks, especially sandstones, are often very porous.

Muiy rooks, especially those of the sedimentary class, contain water in their pcoes when first quarried. This ia known to quarrymen as ftuury

OOglf

106 Economic Geology

tsofer, and it is present in some pomus sandstones in soffldent quanlitiee to interfere with quarrying during freezing weather. Mineral mattr io solution in the quarry watw is deposited between the grains when the water evaporates, often in mifBcient quantities to perceptibly harden the stone- Water is also present in the joint planes, and by its passage along these planes causes oxidation and rusting of the iron of the rook-forming minerala. This disoolars the stone along and on either side of the joint planes, eiving rise to a yellow oolor known as tap.

Resiance to Frost. — Building stones show a varying degree of resistance to frost.

Dense rocks, like granites, quortdtes, and many limestones, and even some very porous rocks, are Uttle affect; but many porous and lami- nated rocks, like open sandstones and schists, disintegrate undv frost action. This is due to the fact that moisture absorbed in the warmer weathw, on freezing in the pores, expands, and either foroee off small pieces or disrupts the stones. Since clay readily absorbs water, elayey rooks are sometimes similarly affected.

Resistaiux to Heat. — All rocks expand when heated, and con- tract when cooled, but do not shrink down to their original dimen- sions. This permanent increase in size is termed permanenl swell- ing, and though small when figured for one linear foot, is ipreciabb in long pieces.

The following figures give the average of a number of tests of pemuuient swelling in stone bars 20 inches long, heated from 32* F. to 212° F., and then oooled to the original temperature: granite, .009 inch; marble, .009 inoh; limestone and dolomites, .007 inch; sandstone, .0047.

The most severe test of a stone's resistance to rapid changes of tempera- ture is to heat it to about 800° C. and then immerse it in cold wator. Quartzites and hard sandstones withstand Huoh treatment best; some gr&n- ites oraok and crumble, and the carbonate rocks change to lime.

Chemical Composition. — Many chemical analyses of building stones have been made, but most of them are of little value, laiely because they tell us nothii regarding the phycal properties of the stone. They are perhaps of most value in the case of sedimentary rocks. The chemical analysis of a limestone will indicate whether it is dolomitic or not, also whether it is clayey in its character. So too the analyms of a sandstone will indicate whether it is siHceous or clayey.

Life of a Building Stone. — This may be considered as the period of time a stone will stand exposure to the weather without showing mgna of decay. Even for the same stone, it may vary with location

b,

Building Stones 107

and climate. Julien makes the following deductions from obeerva- tions made on stones in use : —

CcttTBe Ixvwnstone 5-15 yeiu-a

Fioe-Uminated brownstone 20-50 yean

Coarse rDBsOiferotis limestona 20- yean

Coarse dolomitto marble 40 yean

noe-gniaod marble 50-100 yean

Granite 75-200 years

Quartzite 75-200 years

Stnictnral Features aSectiiig Qtiarrjlii(. — All rocks are traversed by planes of separation of one sort or another. In sedimentary rocks these eoDsiBt of bedding and joint planes; in igneous rooks, the latter alone tre present; and in metamorphic rooks, joint planes, a banding of minerals utd, very often, cleavage planes.

BtddijiD planes. — (PI. XIII, and H. XVIII, Fig. 1.) These may be either an advantage or a disadvantage to the quarryman. They are desir- able because they faoiUtate the eictraotion of the stone; but if numerous ud closely spaced, the layws may be too thin for any purpose except Sagging. They often serve as a means of entrance for the agents of weather- ing, and the stone may be disintegrated along the bedding planes while dwwhere fresh.

Incipient planes of weakness, due either to the arrangement of minerals H to microscopic frsotures in them, often ve rise to planes of easy splitting rhich are of great value in quarrying, notably of granite. The most promi- MDt plane ia called rift; and a less prominent vertical plane, approxi- mately at light angles to the rift, is called the grain. Granites often ibow a sheeted (PI. XII, Fig. I) structure, due to the presence of horizontal joints. These are slightly curved, and hence tend to separate the granite DUBS into a series of lensee.

The position of the beds exerts an important influence on the cost d quarrying. When horizontal and of different quality, it may often be necessary to strip off worthless rock in order to reach the beds of good quality. In such cases, there is often less stripping to do in quarries opened 00 gently sloping ground. In regions of steep dip, it is sometimes possible to work the quarry as a cut, extracting the desired beds and leaving useless ones standing.

Granites

ChancteriBticB of GraniteB (3, 43a). — As commonly used by quanymen, the term granite includes all igneous rocks and gneiss; Imt in this book it is used in the geological sense, which is more restricted. From the geological standpoint a granite is a holocrys- talline, plutonic igneous rock consisting of quartz, orthoclase feld- i<I>ar, and either mica or hornblende, or both. There are also varying 1'ut usually small quantities of other feldspars, and there may be

iv,Coog[c

108 Economic Geologt

Bubordinate accessory minerals, such as pyrite, garoet, tourmaline, and epidote.

Granites vary in texture from fine to coarse gnuned, and in some cases are porphyritic. They pass into gneiaees by such insensible gradations that no sharp line can be drawn between the two. Id color they vary, beii, most commonly, gray, mottled gray, red, pink, white, or green, according to the color or abundance of the component minerals. Most granites are permanent in color, but some of bright red color bleach on continuous expoBure to sun- light.

The avenge apeoiflc gravity granites ta 2.65, whioh oorreeponds to a weight of 165.6 pounds per mibio toot. They oommonly contain less than 1 per cent of water, and often absorb two or three tenths more. Their oruahing strength varies, but is apt to lie between 15,000'and 30,000 pounds per square ineh.

Granites are among the most durable of building stones, but there is some variation in the durability of the different kinds. Other things being equal, flne-grained granites are more durable than ooarsfrrained, being less easily affected by ohanges of temperature. One of the most beautiful granites known, the Rapikivi granite of Finland, lacks in durability on thia account. Pyrite and maroarite are injurious mineials, since they rust rap- idly and may discolor the stone in an unsightly manner. Very few granites now in use show signs of decay; but in ose that do, the darker silicates are rusted, the luster of the feldspar is dulled, and, in some cases, the stone has begun to disintegrate.

Distribution of Granites in the United States (3). — Granite usually occurs in batholytic masses sometimes forming the cores of mountain chains. Uemoval of the overlying strata by denudation has revealed the granite, which, owing to its greater durability, is often left standing as peaks or domes by the farther removal of the surrounding, weaker strata. Granites show a wide geologic range, but most known occurrences are associated with the older forma- tions.

Granite forms an important source of durable building stone widely distributed in the United States (Fig. 45) ; but nearly 70 per cent of that quarried comes from the Atlantic states. There are several areas which will be briefly considered.

Eastern CryalaUine Belt (3, II, 19, 26, 31, 44, 45). — From north- eastern Maine southwestward to eastern Alabama there is an im- portant belt of granites and gneisses, mostly of pre-Cambrian age. Those at the northeastern end of the belt, as far south as New York, are most extensively quarried, largely because of pecul-

b,

b,

- Granito quarry, Hardwick, Vt. (PAoto. bu O. H. Perkina.)

— Quony in volcanic tuff, north of Phcenii, Ariz.

D,q,z.<ib,Coogle

Building Stones 109

iarly favorabk location. In this belt those of Quincy, Maesacliu- aette (28), Barre, Vermont (44), and Westerly, Rhode Island (41), are of value for monumental work. Many laie quarries have also been opened up in Mune (25), but their output is employed mnly fcT structural work. A gneisdc granite quarried at Fort Deposit, Maryland (26), a white granite from Mt. Airy, North Carolina (30), as well as a pinkish granite worked at Stone Mountain, Georgia (20), are also of some importance. Another important granite area is located near Bichmond, Virginia. (46).

Fn. 45. — Map Bhowing dutribution of orystaltiDe locki (mainly fraoitea) in United States. {After Mtrrill, Slonea for Buiiding and Decoraiim.)

MiTinetota-Wwcormn Area (51). — There are several detached unasinthese two 8tates,'ine of which supply granites of value for ORtftmental work. That from Montello, Wisconsin, bears a high reputation, and those from Wausau, WiBconsln, and Ortonville, Minnesota, are favorably known.

Southweem Area. — This includes portions of Missouri, Arkan- sas, Oklahoma, and Texas.

These four states contain small areas, worked mainly to supply a local demand. Those of southeastern Missouri vary from gray to red in color and fine gruned to porphyritic in texture. Some of the roek ia rhyolite. The ron around Predericktown is important (30). Important granite deposits are known in the Arbuckle and ictdta Mountuns of Oklahoma (38), but their development thus

b,

110 ECONOMIC GBOLOaT

far has been slight. Arkansas contains quarries of syenite west of Little Rock (3), and for purposes of convenience it is mentioned under granite. In Texas quarries have been opened in Uaoo County, and yield both pink and gray granite (3).

Western States. — There are many areas of true granite, and closely aUied rocks such as grano-diorite and rhyolite in the western states. The central portion of the Black Hills of South Dakota is a great granite mass, but little of it is quarried. .Granites are known in Colorado (17), and quarried to some extent, and the rhyolites of I Castle Kock are of conderable importance. In California the ' grano-diorite mass fonnii the central portion of the ESerra Nevada Mountains yields an inexhaustible supply, which is quarried at several points. Montana, Washington (47), and Oregon also con- j tn granites which are quarried for local uae. On the whole, how- ever, the CordlUeran granite industry is somewhat restricted be- cause of lack of demand.

Uses of Granite. — On account of its massive character and durability, granite is much employed for masdve masonry cottstruc- tion, while some of the granites that take and preserve a high polish, and are susceptible of being carved, are in great demand for orna- mental and monumental work. Because of its greater durability, : granite has in recent years largely replaced marble for monumental purposes.

The refuse of the quarries is often dressed for paving blocks or crushed for roads and railroad ballast. The size of the blocks which can be extracted from a granite quarry depends in part on the spacing of the joint planes, in part on the perfection of development of the rift, some of the monoliths that have been quarried beir of immense size; for example, one from Stony Creek, Connecticut, measured 41 ft. X 6 ft. X 6 ft. ; one from Vinal Haven, Maine, GO ft. X ft.; one from Barre, Vermont, 60 ft. X 7 ft. X 6 ft.

Miscellaaeous Igneous Rocks (3). — But little space need be given to these, for they are of minor importance as compared with the granites. In the eastern states the diabase or trap rock is quarried at several points in Connecticut, New York, New Jersey, and Pennsylvania. Owing to its great hardness it ie only occasion- ally used for dimension blocks, its chief value being for paving . blocks and road metal. The basaltic rocks of the western states, especially those of Washington and California, are often employed for milar purposes. Anorthosites and gabbroe, some of the former being of highly ornamental character when polished, occur in the

D,q,-Z.-dbvCOOgk'

Buildinq Stones 111

Adiroodftck Mountains, New York ; they are, however, but little utilized. Gabbros have been quarried for local use in Maryland and Minnesota, and diorites have been quarried to a small extent at scattered localities. Some of the porphyries and rhyolites of the Atlantic states possess considerable beauty when polished. A bandsome porphyry is quarried in Wisconsin (51), and in the Cor- dilleraa ron both rhyolite and porphyry occur in numerous lo- calities. Andesite tuffs are quarried in Colorado, and consolidated volcanic tuffs have also been used to some extent for building in Aiizona.

Limbstonss And Masblbs

General CharactsiisticB (1, 3). — A great series of sedimentary md metamorphic rocks, composed chiefly of carbonate of lime, or, in the case of dolomite, of carbonate of lime and magnesia, is included under the term Umeetone aiid marble. These rocks also contain varying, but usually small, amounte of iron oxide, iron carbonate, siica, clay, and carbonaceous matter. When of metamorphic character various dlicates, such as mica, hornblende, and pyroxene, etc., may be present.

These calcareous rocks vary in texture from fine-grained, earthy, to coarse-textured, fossliferous rocks, and from finely crystalline to coarsely crystalline varieties. There is, also, great range in color, the most common being blue, gray, white, and black, but beautiful shades of yellow, red, pink, and green, usually due to iron oxides, are also found. Their crushing strength commonly ranges from 10,000 to 15,000 pounds per square inch, while their absorption is generally low.

The nuneral composition of limestone exerts a strong influence on its durability. Those limestones which are composed chiefly or wholly of carbonate of lime are liable to solution in waters contaia- iog carbon dioxide; but dolomite limestones, especially coarse- grained ones, disintegrate rather than decompose. Streaks of mineral impurities cause the stone to weather unevenly. Pyrite is an especially injurious constituent, not only on account of its rusting, but also because the sulphuric acid set free by its decompo- sition attacks the stone. Tremolite, which is found in some dolo- mitic marbles, is also liable to cause trouble by its decay. Black or gray limestones will sometimes bleach on exposure.

Vuietiu rf UmestoDM. — the geolocal sense fimestones are of Momentary origin, wfafle marbles are of metamorphio character, but in the

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112 Economic Qeoloqt

trade the tenn mar6Ie is applied to any caJoareous rook capable erf taldiig a polish. In. addition to the different varieties of marble and the ordiimry limestones, there are certain kinds of oaloareous rook to whicli special namos sfe given, aa follows : —

Chidk is a fine, whit, earthy limestone, composed chiefly of fonuniniferal

Coquina is a loosely cemented shell aggregate, like that found aeu St. Augustine, Florida.

Dolomite, or dolomilic limestone, oomposed of carbonate of lime and magnesia, and to the eye alone often is indistingniishable from limestone.

Fosailiferoua limettonea ia a general trm applied to those limestones which contain many fossil remains. Under this heading are included cri- noidal limestone and ooral-shell marble.

Hydraulic Mmatone, an argillaceous limestone containing over 10 per cent of clayey impurities. Used mainly for oement manufaoture {p. 139).

LUhoffraphic limestone is an exceedingly fine grained, crystaJline limestone, of gray or yellowish hue. It is used for Uthographic and not structural work.

Oelitic limestone, oomposed of small, rounded grains of oonoretiooary character.

Staiaetitie and tlalagmUie depoiils, formed on the roofs and floors of oaves, respectively, are often of crystalline texture and beautifully colored, and, when of sufBcient solidity, are known as onyx marble.

Tratterline, or calcareous tufa, a limestone deposited from springs. It is often sufficiently hard and durable for building, in mild climate, but rarely occurs iu deposits of large size.

Distribution of LimeBtones in the United States. — Umestones are found in many states, and in all geological formations from Cambrian to Tertiary, but those of the Paleozoic, which are much used in the eastern and centra] states, axe more extensive and more masave than those of later formations. Although many large quarries have been opened to supply a local demand, the product is shipped to a distance from only a few localities. At present the sub-Carboniferous Bedford (22) oolitic limestone of Indiana (Pl- XIII) is, perhaps, the most widely used limestone in the United States. It occurs in massive beds from 20 to 70 feet thick, and is said to underlie an area of more than 70 square miles. Althougb soft and ealy dressed, it has good strength, and has been used in many important cities of the United States. The same rock ia quarried at Bowling Green, Ky.

In the eastern and central states the Paleozoic limestones are worked at many points, mnly to supply a loca' demand (3).

Cretaceous limestones are worked in Kansas, Nebraska, and Iowa, although the most important sources are in the Paleoioic formations.

b,

:i

1

b,

Iv,

Building Stones 113

Distribution of Marbles in the United States (3). — While some variegated marbles are produced in the United States, still most of those quarried are white, the greater part of the variated stones

i SUtPa. (After MerriU,

'>ning imported. The main supply comes chiefly from regions of nietamorphic rock, the eastern crystalline belt being the principal producer (Fig. 46). Vermont (44,45) leads all other states in marble production, supplying a large per cent of all the marbles

1 oogic

114 Economic Oeoloot

uaed for onuuneotal work in the country. The most important and laxgest quarries are thoee at Proctor (PI. XIV) and West Rutland. At the latter locality the marble bed has a thicknesa of 150 feet at the top of the quarry, narrovring to 75 feet at the bottom, and U diviable into a series of well-marked layers of varying thickness, quality, and color {4S),

The Vermont marbles usually show a bluishay or whitish ground, the latter often showing a pinkish or creamy shade, and traversed by vans or markings of a green or brown color.

A beautifully colored series of variegated marblea' is quarried at Swanton, Vt. (45), and much used throiout the United States for flooring and wainscoting. Owing to their highly siliceous char- acter they show excellent wearing qualities. White marbles for structural work are quarried at Lee, Massachusetts (3), and at South Dover and Gouvemeur, New York (3, 35), but gray ones are also obtned from the last-named locaUty. In Maryland important quarries have been opened up at Cockeysville (26). Large quantities of "white and also gray marble are quarried in Hckens Ck)unty, Georgia (19> (PI. XV., Fig. 1).

The Trenton limestone in eastern Tennessee (3) supplies marble of pinkish chocolate color with white variegation ; and certain layers are rendered peculiarly beautiful by the replacement of the fosals by calcite. It is used chiefly for interior decoration.

Marble has been reported from various states west of the Missis- appi, but as yet little quarrying has been done. A large deposit of white marble is said to occur at Marble, Colorado, and that quarried in Inyo County, California, has attracted considerable attention in recent years (16).

Most of the variegated marble used tor interior decoration in this ooun- try is obtained from foreiTi oountriea, especially France, Belgium, Greooe, et. Many of these imported stonea are of rare beauty, but are usually unfitted Tor exterior use in severe olimates, a tact often ignored by architots. Although ornamental stones of this class occur in the United States, up to the present time few attempts have been made to place them on the market. This may be due te the fact that most quarrymen do not oare to assume the temporary expense which their introduction might involve.

Onyi Harbles (SS-58), — Under this term are included two types of calcareous rock, one a hot- deposit, or travertine, formed at the surfaoe, the other a oold-water deposit formed in limestone oaves in the same manner as stalagmites and stalactites. Cave onyx is more coarsely crystalline and less translucent than travertine onyx. The beautiful

' Thoe ahmild pertiaps ba more property clused as calcaroous sandstones.

c,q,z.<ib,Coogle

b,

Plate XIV. — Murhlc quarty. Proclor. Vt. The banding of the rock ia vepticnl. Thp horizontal lini nrr rnused by the stoue being quarried in beaches. iPhola., Vtnnont UarbU Co.)

bGooglt'

Building Stones 115

bftDding of onyx is due to tbe depositioD of Buooessive \a,jeie of oarboaate cl lime, while the colored oloudinga and veinioga &re caused by the presence of metalllQ oxides, especially iron.

Neither variety of onyx occurs in extensive beds, though both are widely distnbuted. Onyx is found in Arizona, California, and Colcmulo, but it hss not been developed in any of these states exoept on a small scale. Most of the onyx used in the United States is obtained from Mexico, though null quantitiea are obtained from Egypt and north Algeria.

The value of onyx varies oonsiderably, the poorer grades selUng for ulittle as fiO cents per cubic foot, while the higher grades bring S50 or more. The eariiest-worked deposits were probably, those of Egypt, which were used by tbe ancients for the manufacture of ornamental articles sjid religious raaaels; and the Romans obtained onyx from the quarries of northern Al- exia. Man; of the travertine onyx deposits occur in regions of recent vol- mnio activity, and all of the known occurrences are of recent geological age.

Uses of limeBtones and Marbles. — The limestones are used Duunly for ordinary dimenBioii blocks, though some, as the Bedford stone, lend themselves well for carved work. The refuse from the quarry may be of value for road material, lime, or Portland cement manufacture. (See reference under Cement.)

Marbles are used in increasing quantities for ordinary structural work, although many of the Ughter-colored ones soon become soiled by dust and amoke. The output of many quarries, especially the Vermont ones, is well adapted to monumental purposes, and these, together with those from Georgia, Tennessee, and California, are much used for wunscoting and panelii. That from Swanton is also well adapted to flooring. Electrical switchboards are now frequently made of marble. The demand for marble tops for taUes, washbasins, and similar uses is probably decreaang. The refuse from marble quarries is sometimes utilized for the same pur- poses as limestone.

SERPEIfTIIVE

Pure BerpenlJne b a hydrous silicate of magnesia; but beds of serpentine are tanly pure, usually oontaining varying quantities of such impurities ss iron oxidee, pyrite, hornblende, and carbonates of lime and magnesia. The purer varieties are green or greenish yellow, while the impure types are various shades of black, red, or brown. Spotted green and white varieties are called ofdiiotite or ophicalite.

Serpentine is sometimes found in suflBdently massive form for use in tniotnial or decorative work; but, owing to the frequent and irreKuIar joints Found in neariyall serpentine quarries, it is difficult to obtejtt other than snull-sized slabs. Its softnesg and beautiful color have led to its eirtenave use for interior decoration; but since it weathers irregularly and loses luster, it is not adapted to exterior work.

116 ECONOMIC QEOLOaT

Thoug'h found in a umber of states, most of the numerous attempts to quarry Amerioan serpentine have been unsuccessful. Considenible Berpentine tor ordinary structural work has been quarried in CheEler County, Pennsylvania, and a variety known as verdolite has been worked near Baston, I*ennsylvania (33). Quarrying operations have also been carried on in the state of Washington (17).

Sandstones

General PropertieB (l, 3). — While most sandstones are com- poaed chiefly of quartz , some varieties contain an abundance of other minerals, such as mica, or, more rarely, feldspar, which in rare cases may even form the predominating mineral. Pyrite is occasionally present, and varying amounts of clay frequently occur between the grains, at times in sufficient quantity to materially influence the hardness and dressing qualities of the stone. The hardness of sandstones, however, usually depends on the amount and character of the cement, varying from those having so small an amount of sifica or iron oxide cement that the stone crumbles in the Augers to those quartzites whose grains are so firmly bound by silica that the rock resembles solid quartz. With these difference the chemical composition varies from nearly pure silica to sandstone . with a large percentage of other compounds. (For analyses, sec Kemp's " Handbook of Rocks.")

There are many colors among sandstones, but light gray, white, brown, buff, bluish gray, red, and yellow are most common. In denaty sandstones range from the nearly impervious quartzites to the porous sandrocks of recent geolopc formations, and conse- i quently they show a variable absorption. Moat sandstones con- I tain some quarry water, and those with appreciable amounts are softer and more easy to dress when first quarried; but they cannot be quarried in freezing weather. The average specific gravity of sandstone is 2.7, and accordingly a cubic foot weighs about 160 to 170 pounds.

On the whole, sandstones rest heat well and are usually of ex- cellent durabiUty, since they contain few minerals that decompose easily. When they disintegrate, it is commonly by frost action. The injurious minerals are pyrit, mtca, and clay. Pyrite is likely to cause discoloration on weathering; the presence of much mica may cause the stone to scale off if set on edge; and clay may cause injury to the stone in freezing weathet on account of its capacity for absorbing moisture. A slight quantity of clay, however, makes

I, z:-:l,vC00glc

- Marble quarry, Pickens County, Oa. {Photo, loaned by S. W. McCaUie.)

Fio. 2. — Slate quarry at Penrhyn, Pa. (H. Rien, photo.)

Iv,

b,

Building Stones 117

the stOQe eaaer to drefis. The value of a staDdstone is often leiiseoed by careless quarrying, or by placing it on edge in the building, thus exposing the bedding planes to the entrance of water.

VarietieB of Saadstoae. — With an increase in the size of their grains, saodstoneB pass into conglomerates on the one hand and ftith an increase in clay into shales. By an increase in the percent- age of carbonate of lime they may also grade into limestones.

On aooount of these variations, as well as the diSerenoe in oolor and the character oF the cement, a number of varieties of sandstone are recofr-- nized, of whioh the following are of eoonomio value: arkote, a sandstone ramposed chiefly of feldspar grains; Uueglone, a 6agstoae much quarried in New York; brovmalone, a, term fonnerly applied to sandstones of brown wlor, obtained from the eastern Triassic belt, and since stones of other ralors are now found in the same formation, the term has come to have geographio meaning sod no longer refers to any specific phydcat character; gttone, a thinly bedded, argillaceous sandstone used chiefly for paving purposes; fruttone, a sandstone which splits freely and dresses easily.

Distribution of Sandstones in the United States. — Sandstones occur in all formations from pre-Cambrian to Tertiary, They are ao widely distributed that for local supply there are numerous small quarries in many states, but there are several areas which bave been operated on an extensive scale, some of them for many years. Of these, one of the best known is the Triassic Brownstone belt, which e?ctends from the Connecticut Valley, in Massachusetts, Kuthwestward into North Carolina.

This is a red, brown, or even bluish sandstone, of moderate hard- ness, and somewhat variable texture. That from the Connecticut VaUey district was formerly used in enormous quantities.

Among the Paleozoic strata there are many sandstones, often maaove, and usually dense and hard. Of these the Medina and Potsdam are specially impmrtant and much quarried in New York State (34, 35). The same formations extend southward along the Appalachians and are avcdtable at several points. Devonian flt- rtones are extensively quarried at several locahties in New York and Pennsylvania. At the present time the Lower Carboniferous Bcrea sandstone of Ohio (37) is in great demand because of its light color, even texture, and the ease with which it is worked. More- over, it has the peculiar property of changing to a uniform buff on exposure to the air. There are nimieroua other Paleozoic sand- ptonea in the central states, among them the Potsdam, which covers a wide area in Michigan and Wisconsin (51). Some of this stone is bright red in color.

c,q,z.<ib,Coogle

118 Economic Geology

The Mesosoic and Tertiary strata of the West contain an abun- dance of good saodatone, and quarries opened in many of them yield a durable quality of stone. Though usually less dense and hard than the Paleozoic sandstones, they serve admirably for buildii in the mild or dry climates of the West.

Uses of Sandstones. — The wide distribution of sandstones makes them an important source of local structural material. They are chiefly used for. ordinary building work, and but little for masdve masonry or monuments. The thin-bedded flagstones are much used for flang, and some of the harder sandstones are split up for paving blocks. For other uses, see Abrasives.

Slates

General Gharacteri sties (3, 43a). — Slates are metamorphic rocks derived from clay or shale or more rarely from igneous rocks (14). Their value depends upon the presence of a well-defined plane of splitting, called deavage (Fig. 47), developed by metamorphism through the reammgement and flattening of the original

mineral gruns and the de- velopment of micaceous minerals. The cleavage usu- ally develops at a variable angle to the bedding planes

bedding m alate. [Afttr Dale, V. S. f j

a>i.Surv..\mAnn.iUpi..iii.) obliterated by the meta-

morphism. When not com- pletely destroyed, the bedding planes are marked by parallel bands, called ribbons, cutting across the planes of cleavage, but so perfect is the cleavage in the best slates that the rock readily splits into thin sheets with a smooth surface.

Slates are commonly so fine grained that the mineral composition is not evident to the eye, but the microscope reveab the presence of many of the varied mineral grains found in shale, and in addition much chlorite, developed by metamorphism. Owing to the pres- ence of carbonaceous particles, most slates are black or bluish black, but green, purple, and red slates are also known. The specific grav- ity of slate is about 2.7, and a cubic foot weighs between 170 and 175 pounds.

Most slates are furly durable, though the presence of pyrite

Building Stones 119

along the ribbons may lead to their decay. Lime carbonate if

present ia any quantity is injurious, and if the slate is to be used

for switchboards, it should be as free

from magnetite grains as possible.

Some colored slates fade on exposure to

the weather, but this change, which is

due to the bleaching of certain mineral

grains, does not necessarily result in loss

of strength or didntegration.

In slate quarrying it is of importanoe to distinguiah between bedding and cleavage.

The following eriteria may be used (43a). Fio. 48. — Sectioa in slate Quartzite and limestone bands of some per- quany with elenvase parel-

Hstenoe indjoato bedding, but care must be 'el to bedding, a, purpio

taken not to mistake vein quartz for quartz- """TOApd; ">d d.

it. Poaail impresdons are always on the viegted;eand/.BrD: g

Terse to cleavage, may be used, if other patched. (After DaU.)

niass fail, to iodieato divergenoe between bedding and cleavage, although in some places the two may agree.'

Special testa are neceesary for detomuning the quality of slate. They include the detonnination of its sonorousness, cleavability, abrasive resist- uce, absorption, elasticity, and presence of injurious minerals. The chemi- cal analysis is of limited value, but Merriman concludes that the strongest sl&te runs highest in sihca and alumina but not necessarily lowest in lime ud magnesium carbonates.

Dale divides slates into the following groups:

I. Aqueous sedimentary.

A. Clay slates; cemented by clay, lime carbonate, or magnesium

carbonate. Fissility, strength, and elasticity low.

B. Miea slates; 1. fading; with sufficient iron carbonate to dis-

color on eitposure. 2. Unfading; without sufficient iron carbonate to produoe any but very slight discoloration on prolonged exposure. Under each group we may have the following types: Graphitic (gray-block); chloritio (greenish); hemati tic and chloritio (pur- plish). The second group may also include hematitic (reddish), n. Aqueous.

A. Ash slates.

B. Dike slates.

Distribution of Slates in the United States (Fig. 49). — Since slates are of metamorphic origin, they are Hmited to those regions in which the rocks are metamorphosed, and at present the greater part of our supply comes from the Cambrian and Silurian strata of tbe eastern crystalUne belt of the Atlantic states.

iv,Coog[c

120 Economic Geology

A series of quarries producing red, green, purple, and variegated slates are located in a belt of Cambrian and Hudaon River strata along the border of New York (33) (PI. XVI) and Vermont {33, 4-5).

Black slates are quarried in Maine (3), New Jersey (32), Pennsyl- vania (3), (PI. XV., Fig. 2), Maryland (26), Georpa (3), and \irginia (46). Other producii; states are Minnesota, California (14, 43a), and Arkansas (12).

Uies of SUt. — Slate is best known as a roofing material, but it is also used for mantels, billiard-table tops, floor tiles, steps, flag- ging, slate pencils, acid towers, washtubs, etc. The process of mar- bleizing slates for mantles and fireplaces is carried on at several localities.

In quarrying slate there is from 40 to 60 per cent waste, which is greater than in any other building stone; but the introduction of channeling machines in quarrying has done much to reduce this. The discovery of a use for this waste has been an important problem, which has thus far been only partially solved. It is sometimes ground for paint, and attempts have been made to utilize it in the m£inuf£icture of bricks and Portland cement.

Production of Building Stones. — The production of building stones by kinds for the last 5 years was as follows; —

I; C.OOg[c

w of grecD-slate quarry. Pawlet, Vl. {Photo. 6ji H. Hies.)

b,

b,

Building Stones

Kind

iwn

Lmeiuaa

ll7.iai,4TB

117.683,138

27.327,142

118.084,708 7;837:98S

1 1 8.420 .080 4,283,400 £.831,231

JfflS

tS8.7as.716

53,788,748

aB,37S,794

I71.10e.80i

186,712.499

It should be noted that the stone statistics compiled by the I'njted States Geological Survey include not only building stone, but stone used for monuments, furnace fiux, road material, etc. Some idea of the quantity used for each of these purposes can be gained from the following table: —

VAiOB OF Stone used tor Difterent Pubpobes iw 1908

Kdto

'Ss"

Wl (Rodqh

PAvma

a,761.Z58

40,H3

2,606,381

t4.6Gl.0ei

(70,744

1,087334

"mm

908:317 12,908,207

118,040.630

18,948,841

11,217.159

(2,205.660

(3,536,212

120,362,012

The value of the building stones produced by the several more important states, together with the kind of stone produced chiefly in 1908, is given below: — pRoDncnow of Buildino Stones in uore Important States in 1908

PiCntofTot.i.

State

U. S. Stone Pno-

Chmfli

V-nwol

1 ,88

as

iv,Coog[c

Economic Qeoloqt

The order of rank is but little different from that of 1907, although Fennsylvania dropped to second place, because of decreased demand for limestone used for fluxing purposes in the stel industry.

Exports and ImporU. — The following figures show the value of the exports and imports for the years 1907 and 1908: —

EXPORTO OP &rONK FBOU THH UntTBD TATEB IN

1907 Aud 1908

im

I90S

1S:Se1

1.08S,W1

Imports of Stonb into ths United States in 1007 and 1908

K„.

1B07

Ims

KlXD

190B

QrulU:

gSf. : : : :

Total

ssa"' . . .

Rouch

QnndtoUl . .

8.77S

w

mIsss

Total

1.399.532

STTMsra'

tuna

I67,7Bs

71.a79 fl.822

Ii;as:(fi6-

181,801

rbpbrbucbs chi buildiho stores

General on Pbopkhtibs. 1. Hennaim, Stanbruohindiutrie imd Stein- bruohgeoloKie, BerUn. 1899. BorDtrfiger Bros. 2. Merrill, Min- eral Census, 1902. (Mines and Quarries.) 3. Merrill, StoDes for BuildiDS and Deooration, 3d ed., New York, 1904. (Wiley & Sons.) For Keneral infonnation on properties and testing see also, 4. Buck- ley, Jour. Qeol., VIII : 160 and 333, 1900. 5. Julian, Jour. FranUL iDst.. CXLVII, 1899. 6. Merrill, Maryland Oeol. Surv., II : 47, 1898. 7, Watson, Ga. Qeol. Surv., Bull. 9-A, 1903. & McCourt, N. Y. State Mua., BuU. 100, 1906 (Fire tests, N. Y.), aud N.J. Geol. Surv., Aon.' Rep. 1906: 17, 1907 (Fire tests, N. J.). 9. Humphreys, U. S. GeoL Burv., Bull. 370, 1909. (Fire tests.) 10. Gary, Baumaterialien Kunde, X : 133, 1905; and II : 11, 1897-1898. (Abnudon testa.)

Ark AL Reports. Alabama: 11. Smith, Eng. and Min. Jour., LXVI : 398.

— Alasks: 11 a. Wright, U. S. Geol. Surv., Bull. 345:116, 1908. (General.) — Arkansas; 12. Purdue, Ark. Geol. Surv., 1909. (Slate). 13. Hopkins, Ark. Geol. Surv., Ann. Rept., 1890, IV, 1893. (Marfalea.)

— Csliforala: 14. Eckel, U.S. Geol. Surv., Bull. 225:417. 1904. (Slate.) 15. Jackson, Cslif. SUte Min. Bureau, 8th Ann. Rept, 885, 1838. (Oeneial.) 16. Aubury and othen, Calif. State Min. Bur., BuU. 38, 1906. (General.) — Colorado : 17. lAkee, Mines, sod Minwals, XXII : 20 and 62, 1901. (General.) — 18. Merrill, 8(od

iv,Coog[c

Building Stones 123

for Building and Deooratioa, Nw York, 1904. — Georgia ; 19. MoOOlie, Oa. Qeol. Surv., BuU. I, 2d ed., 1904. (Marbles.) 20. Wataon, Ibid., Bull. 9-A, 1903. (Granites and Gneiesea.) — Indiana: 21. Hopkins, lad. Geol. and Nat. Hist. Surv., 20th Ann. Kept. : 18S. 1896. 22. Siebenthal, U. S. OeoL Surv., 19th Ann. Rept., VT : 292, 1898. (Bedford limMtone.) 23. Thompson, Ind. GeoL and Nat. Hist Surv., 17th Rept. : 19, 1891. (General.) —Iowa: 23a. Bejfr and Willianu, la. Geol. Surv., XVII : 185, 1907. (General.) 23 b. Maiston. /bid. : 541, 1907. (Teats.) — Maine: 24. Merrill, Stones for Building and Decoration. Wiley and Sons, New York, 1904. 25. Date, U. S. OeoL Surv., Bull. 275, 1906. (Slate.) — HaiTUnd: 28. Matthews, Md. Geol. Surv., II : 125, 189a (QeneiKL) — Hassa- chnsetts : 27. Dale, U. B. Qeol. Surv., BuU. 313, 1907. (Granites.)

28. Dale, U. S. OeoL Surv., BuU. 354. 1908. (Granites.) — Uicbigan:

29. Benedict, Stone, XVII : 153, 1898. (Bayport district.) — His- soori : 30. Buckley and Buehler, Mo. Bur. Oeol. and Mines, Vol. 2, 1904.- New Hampshire: 31. Dale, U. S. Oeol. Surv., BuU. 354, 1908. (Granites.) — Hew Jersey : 32. Lewis, N. J. Oeol. Surv., Ann. Rept. 1908: 53, 1900. (General.) — New York: 33. Dale, V. 3. Oeol. Surv., lOth Ann. Kept,, III : 153, 1899. AlsoU. S. Geol. Surv., BuU. 275. (Slate belt.) 34. Dickinson, N. Y. State Museum, BuU. 61, 1903. (Bluestone and other Devonian sandstones.) 36. boock, N. Y. State Museum, BuU. 3, 1888. — North CaroUna: 36. Watson. lAney and MeiiiU, N. Ca. Geol. Surv., Bull. 2, 1906. (General.)- Ohio: 37. Orton, Ohio Qeol. Surv., V : 578, 1884. (Gen- eral.) — Oklalioma : 38. Gould, Okla. Oeol. Surv., BuU. 1 : 46, 1908. — Peiuuylvmnia : 39. Hopkins, Penn. State ColI;e, Ann. Rept., 1895; Appendix. 1897; also V. S. Geol. Surv., 18th Ann. Rept., V : 1025, 1897. (Brownstonee.) 40. Lesley, Tenth Census, U. S., X : 146, 1884. (Qen- waL) — Rhode Island: 41. Dale, tJ. S. Qeol. Surv., BuU. 354, 1908. (Granites.) — SonthDakoU: 42. Todd.S. Dak. Geol. Burv., BuU. 3:81. 1902. (General.) — Tennessee ; 43. Keith, U. S. Geol. Surv.. BuU. 213 : 366, 1903. (Marbles.) See also Ref. 3. — United States: 43 a. Dale, U. S. GeoL Surv., BuU. 275, 1906. (Slate.) —Vermont: 44. Perldna, Rept. of State Geoltst on Mineral Industries of Vt., 1899-1900, 1900, 1903-1904, 1907-1908; and 45. Report on Marble, Slate, and Granite Industries, 1898. — Virginia: 46. Watson, Mineral Reeourcee ot Va., Lynchburg, 1907. — Washington: 47. Shedd, Waah. OeoL Surv., II ; 3, 1902. (General.) — West rginia : 48. Qrimaley. W. Va. Oeol. Surv., Ill, 1905. (Limestones.) 49. Ibid., TV : 355, 1909. (Sandstones.) 50. Dale, U. S. Geol. Surv., BuU. 275, 1906. (Slate.) — Wisconsin : 51. Buckley, Wis. Geol. and Nat. Hist Surv., BuU. IV, 1898. (Q.eoeral.) — Wyoming : 52. Enight, Eng. and Min. Jour., LXVI : 546, 1898.

rbfbrbucbs on okyz uarBlb 13. DoKalb, " Onyx Marbles," Trans., Am. Inst. Min. Engr., XXV : 557, 1896. 54. Merrill. Stones for BuUding and Decoration (New York), 3d ed., 1904. 55. MerriU, Ann. Rept. U. S. Nat. Mus. (Wash- ington), 1895. 56. MerriU, Min. Indus., Vol. II, "Onyx," liyli;

Chapter Iv

Clay

Deflnitioii. — Clay, which is one of the most widely distribute materials and one of the most valuable commercially, may be de- fined as a fine-gained mixture of the mineral kaolinite (the hydrated aluminura silicate) with fragments of other minerals, such as sili- cates, oxides, and hydrates, and also often organic compounds, the mass possesng plasticity when wet and becoming rock hard when burned to at least a temperature of redness.

Two important classes of clays are the residual and the trans- ported ones.

Residual Clays (8). — Clays are derived primarily and principally from the decompomtion of crystalline rocks, more especially felds- — pathic varieties, and

deposits thus formed will be found over- lying the parent rock and often grading down on to it. From its method of origia and position it is termed a residual

Fia. 60. — Section Bhoving lonnatioa oT residual day. day (Fig. 50). (After RUa, U. S. Gml. Sun., Prof. Pap. 11.) ,„ „ ,

All residual clays

probably contMn a variable amount of kaolinite (8) or clay EubstaDr. This mineral, which is white in color, results from the decomposition of feldspar, either by weathering, or, less often, by the actios of volcanic -a- pors. The decay of a large mass of pure feldspar would therefore yield a, mass of white clay, but, in most instances, the feldspar is associated with other minerals, such as quartz, mica, and hornblende, all of which, except the quartz, decay with greater or less rapidity, and some of theee, such; OS the hornblende, may likewise yield a hydrous aluminum silicate. Any ferruginous minerals in the rock will, in decomposing, yield limonite, which,

La:e masses of pure feldspar are rare, but feldspathic rocks, such as granite or syenite, are more common, and these will also decompose to clay; but, since the parent rock contains other minerals, such asquarti or mica, these will either remain as sand grains in the clay, or, by decom-

Clay 125

poBition, will form soluble oompounds, or iron stains. The decay of many r<ieks, for example, limestone and shale, in addition to the crystaUine rooks, producM a residuum of clay. White-burning residual clays are termed kaulins, but they are rare.

The extent of a deposit of residual clay will depend on the extent of the parent rock and the topography of the land, which also influences its thiek- Dis. On step slopes much of the clay may be washed away ; and residual I'Uys are also rare in glsteiaXed regions, for the reason that they have been A't'pt away by the ice erosion. They are consequently wanting; in most u! ihe Northern states, but abundant in many parts of the Southern states, there the older formations appear at the surface.

Transported Clays (8). — With the erosion of the land Burface ihe particles of residual clay become swept away to lakes, seas, or the ocean, where they settle down in the

aluminous sediment,

funning a deposit of ndswuk.

iedimenlary day (Fig.

51). Such beds are

often of great thick- ness and vast extent. the accumula- tion of many feet of other sediments on top of them, they become consolidated either by pressure or by the deposit of a cement around the . Consolidated clay is termed shale, and this upon being ground and mixed with water oftn becomes as plastic as an UDconsolidated clay.

Residual materials may also have been transported by wind or glacial action, to form clayey deposits.

The following are important types of transported clays : —

Marine Claya. — Formed by the deposition on the ocean floor of the finer particles derived from the waste of the land. Such ancient sea- hottom clays have been elevated to form dry land in all the continents, in many cases forming consolidated clay strata, but elsewhere, especially in coastal plains, in unconsohdated condition. Extensive clay deposits are aUo formed in protected estuaries and lagoons along the seacoast.

Flaod-plain Clayt. — Formed by the deposition of clayey sediment on the lowluids bordering a, river during periods of flood. Layer upon layer, tbis depoait builds a flood plain often of great extent and depth. Such areas of flood-plain clays are most extensive along the greater rivers and in the deltas which they have built in the sea.

Lakt Clayt. — Clay is deposited on the bottom of many lakes and poods in the same manner as on the ocean bottom. Where the streams

b,

126 Economic Qeology

bring only fine partiolee the filling of & lake may be entirely of olAy. Muir lakes have been either drained or completely filled and their elajH thero- tore made av&ilable. This is especially true Bm&ll, shallow lakes formed during the Qlaoial Period.

Qlaeial Clays, oommoulj' known as till or bowlder day, a rook flour ground in the glacial mill in which rook fragments were worn down to clay by being rubbed together or against the bed rook over which the ice moved. When the iae melted, this deposit was left in a sheet of varyioK thicknwa and oharaoteristios over a large part of the area which the ire covered. It is not always, strictly speaking, a sedimentary depodt.

£oUan Clay*. — Wind drifts dry clay about, and in favorable posi- tions causes its accumulation in beds. This is true of the Chinese loess, a wind-biown deposit derived from residua] aoila and drifted about in the arid climate of interior China. Some at least of the loees olays of the Mississippi Valley seem to have a similar origin, the source of the clay being glacial deposits; in other cases loess seems to be a water deposit either in shallow lakes or else in broad, slowly moving streams.

PropertieB of Clay. — These are of two kinds, physical and chemi- cal, and since they exercise an important influence on the behavior of the clay, the most important ones may be described.

Physical Properties (8, 1). — TThese include plasticity, tenale strength, air and Sre shrinkage, fuedbility, and specific graty.

PUutidty may be defined as the property which clay posseasee of forming a plastic mass when mixed with water, thus permitting it to be molded into any desired shape, which it retains when dry. This ia an exceedingly im- portant character of clay. Clays vary from exceedingly plastic, or "fat" ones, to those of low plasticity which are "lean" and sandy. Plasticity is probably due in part to fineness of gmia, and in part to the presence of colloids (1,8).

TensiU strength is the resistanoe which a mass of air-dried clay iers to rupture, and is probably due to interlocking of the particles. Tests show that the tensile strength of clays varies from 15 to 20 poonda per square inch up to 400 pounds or more per square inch. Many oommon brick clays range from 100 to 200 pounds.

Shrinkage is of two kinds — air shrinkage and fire shrinkage. The for- mer takes place while the clay is drying after being molded, and is due to the evaporation of the water, and the drawing together of the clay particles. The latter occurs during firing, and is due to a compacting of the mass as the particles soften under heat. Both are variable. In the manufacture of most clay products an average total shrinkage of about S or 0 per ceot is commonly desired. Excessive air or fire shrinkage causee cracking or warping of the olay. To prevent this a mixture of clays is oftn used.

FutibUUy is one of the most important properties of olays. When subjected a rising temperature, clays, unlike metals, soften slowly, and hence fusion takes place gradually. In fusing, the clay passes throu three stages, termed, respectively, incipient fusion, vitrification, and viscosity.

b,

Clay 127

Id the lower gradeA of oittj, that ia, those having a high peroentaee of fliudng impurities, inoipient fusion may ocour at aboat 1000° C, while in refractory days, which are low in fliudng impuritiea, it may not ooonr until 1300" or 1400° C. ia reached. The temperature interval between inoipient (uiion and vitrifioation may be aa low as 30° C. in calcareous clays, or as uich as 200° C. in some others. The reoogTiitioa of this variation ia of nnsiderable practical importance, and vitrified producta, auch as paving bricks and stoneware, have to be made from a clay in which the three stages uf tason are separated by a distinct temperature interval. The importance of this rests on the fact that it ia impoaaible to control the temperature of a luge kiln within a few desreea, and there must be no danger of running bto a oondition of visoosity in case the clay b heated beyond ita point of titriflcation.

Specific gravUv varies oommonly from about 1.70 to 2.30.

Chemical Properiiea (8). — The number of common elemeata which have been found in clays is great, and even some of the rarer ones have been noted; but in a ven clay the nmnber of elements present is usually small, being commonly confined to those deter- mined in the ordinary chemical analyses, which show their existence ia the clay, but not always the state of the chemical combination. The common constituents of a clay are silica, alumina, ferric or ferrous oxide, lime, magncEda, Alkalies, titanic acid, and combined water. Organic matter, and sulphur trioxide, though often pres- ent, are usually in small amounts. Carbon dioxide is always found in calcareous clays. The effect of these may be noted briefly.

Saica ts most often present in the form of quartz grains; but it may also be contained in grains of undecomposed minerals. It aida in lowering the plasticity and shrinkage, and helps to increase the refraotoriness at low temperaturea. A clay high in sihca (70 to 80 per cent) is usually sandy. Alumina, which is most abundant in white claya, is a refractory ingredient. Iron oxide acts as a coloring agent in both the raw and burned clay, small quaatjties usually eoloring a burned clay buff, and larger amounts (4 to 7 per cent), if evenly distributed, turning it red. It also acta as a flux in biiming. Whatever the iron compound preaent in the raw clay it changea to the oxide in burning. Lime, magneiia, and alkalie* are alao fluxing in- icredients of the clay. The combined percentage of fluxing impurities is tmall in a refractory clay, and often high in a low-grade one. Lime, if present in ooosiderable excess over the iroa, will. In burning, exert a bleach- ing effect on the latter. For this reason, highly calcareous clays, auch aa those in the Great Lake region, bum cream or buff. When lime is present in large unounta, it alao oausea clay to softn more rapidly in firing than It otherwise would.

ChrmieaUy combiTted water arid organic matter both pass off at a temperor- ture of very dull redness (450° to 650° C). Their loss leaves the clay tem- porarily porous until fire shrinkage seta in. Titanic add, though raiely

oogic

128 Economic Gboloqt

exceeding 1 per cent, acts as a flux M high temperatures at least. Sulpha trioxide ie r&rely present in suffioientl? high amounts to interfere with th< euoceasful burning of the clay.

Cariwn oolors a raw claj gray or black, and several per cent may giv' much trouble ia burning, unless driven out of the olay bore it become dense.

Chemical Composition. — As might be expected from their diverai modes of origin, clays vary widely in their chemical compotioD There is every gradation from those which, in compomtion, closel] resemble the mineral kaolinite, to those, like ordinary brick clays in which there is a high percentage of impurities. This variatioi is shown in the opposite table.

The absence of ferrous oxide, titanic oxide, sulphur trioxide, organi' matter, and manganous oxide in many of the analyses (p. 129) doe not neoessarily indioate their non-existence in these clays. Probably al ooDtain &t least small peroeatagee of these substances, but they are rarely detrmined.

Classification of Clay. — It is possible to base a ol&ssificatioa of clay either on origin, ohemical and physical properties, or uses. But since thi subdiviaiona which e&a be made aro not suIBaiently distinct, each of thee gives rise to a more or leas unsatisfactory grouping. The following class fleation is based pully on mode of origin and partly on physical char aoters (8) : —

A. Residual olays. (By deoompoaition of rocks in situ.)

I. Kaolins or china clays (white-burning).

(a) VduB, derived from pegmatite, rhyolite, etc.

(6) Blanket deposits, derived from extensive areas of igneous o

metamorphic rocka. (c) Pockets in limestone, as indianaite (24). II. Bed-burning residuals, derived from different kinds of rocks.

B. Colluvial days, rapresenting deposits formed by wash from the foore

going, and of either refractory or non-refractory character.

C. Transported olays.

I. Deposited in water.

(a) Marine clays or shales. Deposits often of great extent.

White-burning days. Ball olays and plastic kaolins.

Fire clays or stupes. Bufl-buming.

T , L T I Calcareous.

Impure <!layB or shales. . , ,

[ Non-c&loareous.

(6) lacustrine clays (deposited in lakea or swamps).

Fire olaya or ahalea.

Impure clays or shales, red-burning.

Calcareous clays, usually of surface character, (e) Flood-plain clays. Usually impure and sandy. id) Estuarineclaya (deposited in estuaries). Mostly impure anc

finely laminated.

iv,Coog[c

Analtbrb bhowino Variation ik CoupoetnoN or Ci/Atb

n

Silica (SiO,)

AlumiDa, (AliO.)

Fffric oxide (FetOt)

—

FefTouB oxid (F0)

—

—

—

Lmie(CaO)

—

tr

.\[aesis (MgO)

—

tr

PolMh (Krf))

—

1 .r

1 .6

1 (!1

Sjda(NjO)

—

1 .2

Titanic oide (TiOi)

—

—

—

—

Water (H.O)

—

rirboa diorido (CO.) . . . .

—

—

—

—

—

Sulphur trioxid (SO.) . . .

—

—

—

—

Ontuuo matter

—

—

—

—

—

—

—

Tol*l

Al<imm (A1.0.)

Fmic ojdde (Perf),)

Ffrroua ojride (PoO)

—

—

—

—

—

Ume(C&0)

Magneai* CMgO)

PolMh(Krf})

Sodx (Narf))

\i.

TilMJo oride (TiO,)

—

—

f 3.04

Moiature

.m\

1"

fvbon dioxide (COil . . .

—

S(ilphMtrioxide{80.) . . .

—

—

—

—

ftnwuo matter

—

—

—

MiDganous oxida (MnO) . .

—

—

Total

I. KaoKnite.

II. Washed kaolin, Webster, N. Ca. HI. Ptwtic fire olay, St. Louia. Mo. IV. Flint flre clay, Salineville, O.

y. Loom elay, Guthrie Center, la. '1- Preswd-briok olay. Rusk, Tex.

Vri. Brick shale. Mason City, la. VIII. Calcareous brick olay, Mil- waukee, Wis. IX. Sandy brick clay, Colmesneil,

Tex. X. Blue shale clay. Fertia, Tex.

iv,Coog[c

130 Economic Gbologt

II. Glacial days, found ia the drift, and oftn atony. May either be

red- or oream-bumiag. III. Wind-formed deposits (some loess). D. Chemical deposits (some Sint days?).

Siads of Clays. — Many kinds of clays are known by special names, which in some cases indicate their use, but in others refer partly to certun physical properties. The more important ones are the following : —

Adobe. A sandy, often calcareous, fliay used in the west and south- west for making sun-dried brick. Boti day. A white-burning, plastic, sedimentary olay, employed by potters to give plastioity to their mixture. Brick day. Any oommoo clay suitable for making ordinary brick. CAina claji. A term appUed to kaolin (;.e>.). Earthenteare day. Clay suitable for the manufaoture of oommon earthenware, such as flower pots. Fire day. A olay capable of resisting a high degree of heat, flint day. A peculiar Sint-like fire olay, which when ground up and wet develops no plasticity. Chemically, it differs but little, if at oil, from the plastic fire clays. Moreover, the two often occur in the same bed, either in separate layers or irregularly mixed. Gumbo. A very sticky, highly plastic clay, occurring in the central states, and used for making bumed-day ballast (2). Kaolin. A white-burning residual olay, employed chiefly in manufaoture of white earthenware and porcelain. The term is also applied by some to the white-burning sedimentary days of Georgia and South Carolina. Loess. A sandy, calcareous, fine-grained olay, covering thouBands of square miles in the central states, and of wide use in brick making. Paper day. Any fine-grained clay, of proper color, that can be employed in the manufacture of paper. Pip day. A loosely used term applied to any smooth plastic clay. Strictly speaking, it refers to a clay suited to the manufacture of sewer pipe. Pot day. A denBe-buming fire olay, used in the manufaoture of glass pots. The domestic supply comes mainly from St. Louis, Missouri, but much is imporiied. Pottery day. Any day suitable for the manufacture of pottery. Retort day. A plastic fire day, used in making gas retorts. The term is a local one used chiefly in New Jersey. Sagger day. A loose term applied to clays employed in making saggers; they are of value for other purposes as well. Seu)er--pipe day. A term applicable to any clay that can be used for manufacture of sewerpipe. It is usually vitrifiable and red- burning. Slip day. Under this trm are induded those days which are easily fusible, and form a natural glase, when appUed to ware (such as stoneware) and burned at the proper temperature. The best-known variety comes from Albany, N. Y. Stoneware day. A very plastic day, which bums to a vitrified or stoneware body. It may be refractory. Terra-coUtt day. Clay suitable for the manufacture of terra cotta. The term has no special significance, as a wide variety of clays are adapted to this purpose.

GeologiGal Distribution. — Clays have a wider distribution than most other economic minerals or rocks, found in all former

Pwte Xvii, -

b,

b,

Clay

tioDs from the oldest to the youiest. The pre-Cambrian crystal- lines yield both white and colored redual clays, usually the result of weathering, though more rarely of solfataric action. In the Paleozoic rockB, depodta of shale, and sometimes of clay, are found in many localities; and, Educe they are usually marine sediments, t. beds are often of great extent and thickness. The weathered outcrops of these may yield a residual clay. With the exception of certain Carb(Huferous depoats, the Paleozoic clays are mostly im- pure. The Mesozoic formations contain large supplies of clays and shale suitable for the manufacture of , terra cotta, stone- ware, fire brick, etc.

The Pleistocene claj are all surface deposits, usually impure, and individually of limited extent, although they are thickly scat- tered all over the United States. Their chief value is for brick and tile making. They have been accumulated by glacial action, on flood plains, in deltas, or in estuaries and lakes.

Distribution of Clays by Kinds. — Kaolins (67). — Since kaolins proper are derived only from crystalline or igneous rocks, their dis- tribution is limited; indeed, at present the only deposits worked are in the eastern states. Being commonly formed by the weathei ing of pegmatite veins, kaolin deports have great length as com- pared with their width, which may be anywhere from 5 to 300 feet. Their depth ranges from 20 to 120 feet, depending on the depth to which the feldspar has been weathered.

CavBB Kaolin

WabhedKaolik

SiO,

PetO,

FeO

—

CaO

MgO

AlfcaUes

MoiBtUH.

Quartz and white mica are often present in kaolin, and it is then fre- quentl J necessary to put the clay through a washing procesa to remove these minends. The difference between a washed and unwashed kaolin is well shown by the two preceding analyses, from which it is seen that the quartz

OOglf

132 Economic Geology

oontenta have been ooiuiderably lowered, and that tlie washed product approaohes more olosely to the oomposition of kaolinite.

North Carolina (52) and Pennsylvania (58, 56) are the most im- portant redual kaoUn-producing states, but deposits are also worked in Connecticut (17 a), Maryland (36), and Virginia (67). It is known to occur in Alabama (10). All of these deposits ex- cept that in Connecticut are found south of the limit of the glacial drift. Kaohns occur in southeastern Missouri, but they have never become of great importance (45).

The Cretaceous of Geora (20) and South Carolina contains im- portant deports of white-burning sedimentary clays, which might perhaps be termed plastic kaolins to distinguish them from the residual ones.

The output from the American deposits is insufficient to supply the domestic clay-working industry, and consequently many thou- sand tons are annually imported from England. Since this can be brought over as ballast, it is possible to put it on the American market at a low price. The best grades of kIin sell for $10 to 112 per ton at Trenton, New Jersey, and East Liverpool, Ohio, these beit the two most important pottery centers of this country.

Fire Clays. — Fire clays are found in the rocks of all systems, from the Carboniferous to the Tertiary, inclusive, with the excep- tion of the Triassic.

The most extensive, and among the most important, beds of 6re clay are those found in the Carboniferous strata of Pennsylvania (56, 60), Ohio (54, 65), Kentucky (29, 30, 33), West Virginia (72), Maryland (36), Indiana (24), Missouri (45), and lUinois (21, 22) Those of the first two named states are on the average the most refractory. Here the fire clays are usually found underlying coal seams and often at well-marked horizons, especially in the Upper Productive Measures.

The section gven ia F, 2 is fairly representative of thar mode of occurrence.

Those of Indiana and Illinois are so placed that one mine shaft may be used for extracting coal, fire clay, stoneware day, and shale.

The beds of refractory clay, found in the Carboniferous strata near St. Louis (45), are not only used in the manufacture of fire brick, but are, in some cases, found suitable, after washing, for mixture with imported German clays for the manufacture of glass pots.

c,q,z.<ib,Coogle

Clay 133

Iq the Lower Cretaceous of New Jersey (49) there are many beds of refractory clay, variable in thickness and closely associated with beds of less refractory character. They not only support a thriving local lire-brick industry, but serve also as a source of supply for fac- tories in other states. Similar, but less extensive and less refractory, beds occur in strata of Cretaceous Age in the coastal plain of Mary- land (36), Ceorgia (20), South Carolina (61), and Alabama (10).

The Tertiary fonnations of Texas (64) and Mississippi (44) hold abundant deposits of refractory material , but many are undeveloped. The Missouri Tertiary also supplies some fire clays {45).

Vin olays ore found in th Black Hills of South Dakota (62), in the Ununie beda of ColonMio (14-17), and in California. (13); but, excepting near Denver, where used for making fire brick and aaeayer'a apparatus, these deposits are as yet slightly derdoped.

Pottery Clays. — Under this heading are included several grades of clay, the kaolins, already described, being the purest and beat suited to the manufacture of high grades of pottery.

Another highrade pottery clay of more plastic character, the ball clay, is of limited distribution in the United States. A small quantity is found in the Cretaceous (PI. XVII) of New Jersey (49), and a much lair amount in the Tertiary of western Kentucky (29, 31) and Tennessee (63), and southeastern Missouri (45) and Florida (19, 67). As in the case of kaolin, the domestic supply is not sufficient to meet the demand, and large quantities of ball clay are imported from England.

Stoneware clays form a third grade of pottery clays. They are usually of at least seinirefractory character, but differ from fire claj's proper in burning dense at a much lower temperature. Their distribution is essentially coextensive with that of fire clays; in- deed, the two are often dug from the same pit or mine. Large quantities are obtained in the Carboniferous of western Feimsyl- vania (56, 57) and eastern Ohio (55) and smaller amounts in the Xew Jersey Cretaceous formations (49).

Stoneware clays, usually in the same area as the fire clays, are also ob- tained in Illinois (21), Indiana, (24), Kentucky (29. 3i). Tennessee (63), Alabama (10), and Texas (64); and they occur also in Missouri (45), Iowa (26), Colorado (16), and California (13).

Many of the Pleistocene surface clays in various states are suffi- ciently dense-burning to be used locally by small stoneware factories.

c,q,z.<ib,Coogle

134 Economic Geology

Brick and TUe Clays (67). — None of our states lack an abundant supply of good brick and tile clays, and in many areas there are extensive deposits near the large markets, and often near tide water. In such cases the clay beds are exploited to an enormous extent.

In the northeastern states the Pleistocene surface clays are found almost everywhere in great abundance, and are made use of in many places, especially near the large cities.

In the middle Atlantic states Columbian loams and clay marls are an important source of brick material.

In Ohio, Illinois, and Indiana Pleistocene clays, in part of glacial, and in part of fiood-plain origin, are much used for brick and tile. Impure Paleozoic shales are also used in places, especially in the manufacture of vitrified paving brick, thousands of which are made annually in Ohio. Northern Illinois, Michigan, and draw their main supply of brick clays from the calcareous lake deposits.

Although facial clays and fiood-plain deposits are much used in the states west of the Mississippi, the loess which occurs over a wide area is probably even more important as a source of brick, while in the southwestern states loess and adobe are important. Residual clays, river alts, glacial clays, and other forms of clay are employed in brick making along the Pacific coast.

MivxUaneow Clays o/ ImportatKe. — Paper claya of good quality are muoh Bought for bj paper manufaaturera. Much English kaolin is used for this purpose, but the domestio kaolius are] also drawn upon, especially those of Georgia, South Carolina, North Carolina, southeaatem Pennsyl- vania, and Connecticut. A small amount of gtaatpot clay (45) comes from western Pennsylvania, but muoh more from eastern Missouri, and our chief supply is unsorted. Terra-cotta days are obtued from the same areas tltat supply fire clays. New Jersey being the principal produoer.

Uses of Clay. — So few people have even an approximate idea of the uses to which clays are put that it seems derable to call at- tention to them briefly. In the following table an attempt has been made to do this: —

Domestic. — PaUery of variout grade*; Polishing brick, often known as

balh bricks; Fire kindUra; Majolica *topes. Structural. — Brick; Tiles and Terra coUa; Chimney pols; Ckimttey flues;

Door kruibt; Fireproofing; Copingg; Fertce posts.

TaUe comtuled by R. T. Hill and modified by the author. c,q,z.<ib,C00gle

Hjgjealc. — Clotel bcnnU; SinJet, et.; Seroer pipee; VenlHatiitff fiutM;

PoundaHon bloeki; Vitrified brieke. Deeontite. — Omanttntal pottery; Terra eoUa; Majolica; Garden /urnt-

Hinor nses. — Food aduUeranlg; Paint JUler; Paper fiUing; Electrical intulationa; Pumpa; FiUing doth; Scouring soap; Packing horsea' hooja; Cktmieal apparalua; Condeneing teorma; Jnit bottle*; VltrO' marine manufacture; Emery wkeela.

Kefractory WareB. — Crucible* and other assaying appartaut; Rractory bricks of Tuious pattema; Glass pots.

EiigiQering Work. — Pitddle; Portland cement; Railroad baUaat; Water conduit*; Turbine toAcel*.

Prodaction of CUj and CUy ProductB. — Owiog to the fact that clays axe usually manufactured by the producer, it is uecessary to ve the value of the product, no record being kept of value of the ranr material.

Statm

fetr. : :

(131,023,348

3.3M.122

ToUl

Iu9.Bb7.188

r Clay PRooncra, bt Kindb, in the United States, 1904-1908

161,300,690 7!895!323

8,543,2X9 S,'739!4tlO

Much clay is mined and sold, especially to manufacturers of high- pade clay products who do not own depoaita themselves. The value of production of such clays is given below,

Economic Gbologt

Value of Citb mined and Sold in the United States, 1004-1906

KlHD

Iks

i9oe

I,30,053

Si

3Se.4AS

t340.3ll

316,243

i.iseitsg

ToUl

Z320.16Z

taMojiM

t3.44S.&4S

Rsfbkxncbs Oh Cu.T

Technoloot and Peopertibs. 1. Aahlej, U. 8. Oeol. Surv., Bull. 388. 1909. (CoUoid mfttter.) 2. B&in, Mid. lodus., VI : 157, 1898. (Clay bal- last.) 3. Barber, The Pottery aad Porcelain of the United Stats, 2d ed., N. Y., 1901 (Q. P. Putnam's Sons), 5.00. 4. Bourry, Treatise on Cwamio Arts, N. Y. (Van Noatrand & Co.), London (Seott Greenwood & Co.), 1901. S. Bisohof, Die Feuerfesten Thone, 3d ed., Leipzig, 1904 (Quandt & Handel), 12 Mks. 6. Branner, Bibliography of Clays and the Ceramio Arts, Atoerioan Ceramio Society, 1900. 7. Davis, A Praotioal Treatise on the Manufacture of Brieka, TUm, and Terra Cotta, 2d d., Philadelphia, S5.00. 8. Ries, Clays, Oocnirence, Prop- erties and Uses, 2d ed„ N. Y., 1908 (Wiley and Sons). 8 a. Mer- rill, Rooks, Rock Weathering and Soils, 2d ed., N. Y. (MacniiUan Co.). 9. Wheeler, Vitrified Paving Brick, Indiaoapolis, 1895 (Clay- worker Pub. Cq.),S1.00. Many excellent papers in Transactions Amer- ican Ceramic Society, Vols. 1-12 of which have appeared. See also Nos. 26, 36, 49, 51 for general properties and technology.

Areal Reports. Alabama: 10. Smith and Ries, Ala. Qool. Surv., Bull. 6, 1900. (Gheneral.) — Arkansas : 11. Branner, U. 8. Oeol. Surv., BuU. 351, 1908. 12. Also Amer. Inst. Min. Engrs., Trans. XXVIl: 42, 1898. (S. W. Ark.) — California : 13. Johnston, Calif. St&te Miner&logiat, 0th Ann. Rpt. : 287, 1890. (General.) See also Boattored notices in other annual reports. — Colorado : 14. Eldridge, U. S. Geol. Surv., Mon. XXVII, 1896. (Denvw Basin.) 15. Oeij- beek. Clay Worker, XXXVI r 424, 1901. (General.) 16. Rios, Amer. Inst. Min. Engrs., XXVII : 336, 1898. (Clays and Clay indus- try.) 17. Shaler and Gardner, U. 8. Oeol. Surv., BuU. 315 : 296, 1906. — Connecticut : 17 a. Loughlin, Conn. Oeol. Surv., Bull. 4, 1905. — Delaware: 18. Booth, Geol. of Ddaware : 94 and 106, 1841.— Florida : 19. Ries. U. S. Geol. Surv., Prof. Pap. 11:81, 1903. 19 a. Matson, U. S. Geol. Surv., Bull. 380 : 346, 1909. — Georgia : 20. Veatch, Oft. Oeol. Surv., Bull. 18, 1909. — Illinois : 21. Many scattered references in volumes on Economic Geology of Illinois Geol. Survey, lUsumS aF these in U. S. Geol. Surv.. Prof. Pap. 11, 1903. 22. Purdy and De Wolf, 111. Oeol. Surv., BuU. 4 : 131, 1907. (Fireclays.) 23. Rolfs and others. Ibid., Bull. 9, 1908. (Paving-brick clays.) — Indiana : 24. Blatchley, Ind. Dept. Geol. and Nat. Hist., 20th Ann. Rapt.: 23,

b,

Clay 137

1806. (CarbonifeTDUB clays.) 25. Sune Kuthor, 22d Ann. Bept. : 105, 189S. (N. W. Ind.) Scattered rererances in other annu&l re- ports. — Iowa : 26. Beyer, WilliaioB, and Weems, la. Oeol. Survey, XIV : 29, 1904. — Kansas : 27. Ptobhot, U. 8. Geol. Surv., Mineral BMOURwa. 1S92 : 731, 1893. 28. See also Reports on Miner&l Re- sources of Kansas, Kas. Oeol. Survey, 1897-1901. Kentucky : 29. Hiea, U. S. Qeol. Surv., Prof. Pap. 11,1903. 30. Many analyses in Ey. Qeol. Surv., Chem. Rept. A, pts. 1, 2, and 3, 1885, 1886, 1888. 31. Gardner, Ky. Gool. Surv., BuU. 6, 1905. (Weatera ooal field and Jaokson Purchase Region.) 32. Foerste, Ilnd. (Silurian, Devonian, Waverly. Irvine fortnationfl.} 33. Phalen, U. S. Qeol. Surv., Bull. 285:411, 1906. (N. E. Ky.) — Louisiana : 34. Clendonin, Eng. and Min. Jour.. LXVI : 456, 1898. 35. Ries, Preliminary Report on Oeology of La., I : 264, 1899. — Maryland : 36. Ries, Md. Qeol. Survey, IV, Pt. Ill : 205, 1902. — MasMchnsetts : 37. Crosby, Technol. Quart., Ill : 228, 1890. (Kaolin at Biandford.) 38. Shaler, Woodworth, and Marbut, U. S. Qeol- Surv., 17th Ann. Kept., I : 957, 1896. (R. I. and S. E. Mass.) 39. Whittle, Eng. and Min. Jour., LXVI : 245, 1898. — Michigan : 40. Ries, Mich. Qeol. Surv., VIII: Pt. I, 1903. (Clays and shales.) — HinnesoU : 41. Berkey, Amer. Oeol., XXIX : 171, 1902. (Origin and distribution.) 42. Winchell, Minn. Oeol. Surv., Miso. publications, No. 8, 1881. (Brick claya.) — HlsBiBsippi : 43. Eokel, U. S. Oeol. Surv., Bull. 213 : 382. 1903. (N. W. Miss.) 44. Logan, Miss. Qeol. Surv., Bull. 2, 1907. — Missouri:

45. Wbeeler, Mo. Qeol. Surv., XI, 1896. (Oeneral.) — Nebraska:

46. Neb. Oeol. Surv., 1 : 202, 1903. — New Hampshire : 47. Hitch* cock and Upham, Report on Oeology of New Hampshire, V : 86, 1878. — New Jeraey : 48. Cook. N. J. Qeol. Surv., 1878. (Special Report on Clays.) 49. Kununel, Ries, Knapp, N. J. Oeol. Surv., Final Reports, VI, 1904. — New Mexico : 50. Shaler and Gardner, U. S. Qeol. Surv., Bull. 315 : 296, 1906. (Durango-Gallup field.) — New York : 51. Riea, N. Y. State Museum, Bull. 35, 1900. (General.) — North Carolina : 52. Ries, N. Ca. Oeol. Surv.. Bull. 13, 1897. (Oeneral.) Nordi Dakota : 53. Baboock and Clapp, N. D. Oeol. Surv., 4th Bieu. Rept.. 1906. (General.) — Ohio : 54. Orton. Ohio Qeol. Surv., VII ; 45, 1893. (Geology.) 55. Orton. Jr., /Wd., p. 69. (Clay industries.) Pennaylranla : 56. Hopkins, Pa. State College, Ann. Repts. as foUowB, 1897, Appendix. (W. Pa.) Ibid., Append, to Rept. for 1899- 1900. (Philadelphia and vicinity.) 57. /6id., 1898-1899. (S. E. Pa.) 58. Many analyses in 2d Pa. Oeol. Surv.. Rept. MM : 257, 1879, and scattered references in Repta. H 5, H 4, C 4, C 5, etc. 59. Resume in U. 8. Qeol. Surv., Prof. Pap. 11 : 208, 1903. 60. Scattered papers in U. S. Oeol. Surv., Bulls. 285, 279. 315, 256. 225. — South Carolina :

61. Sloane. BuU. I, S. Ca. Oeol. Surv. (S. Ca.). — South Dakota:

62. Todd, S. D. Qeol. Surv., Bull. 3 : 101. — Tennessee : 63. Eekel, U.S. Geol. Surv., BuU. 213:382. 1903. (W. Tenn.) —Texas : 64. Univ. of Tex., Bull. 102. 1908. — United States r 65. Hili, U. 8. Geol. Surv.. Min. Res. 1891 : 474, 1893. 66. Ries, U. S. Oeol. Surv., 17th Ann. Rept., HI : 845, 1896. (Pottery Clays.) 67. Ries, U. S. Qeol.

b,

18 Economic Geoloqt

Surv., Prof. Pap. 11, 1903. (CUts east of Misrissippi River.) — Ter mont : 68. Naviua, Eng. and Mia. Jour. LXIV : 189, 1S97. (EaoUn.) 69. Ries, U. 8. Qool. Surv., Prof. Pap. 11 : 133, 1903. — Virgiaia : 70. Biea, Va. Geol. Surv., BuU. 2. 1906. (Coaatal Plain.) — Washington: 71. lAndes, Wash. Oeol. Surv., 1 : 173, 1902. (General.) — West Einla: 72. GrimBleyand Grout, W. Va. GeaL Surv., Ill, 1906, — WisMouln: 73. Buokley, Wis. Geol. and Nat. Hiat. 8urv.,BulL7. Ft. I, Goo. Series 4, 1901. (General.) 74. Hies, Wis. Geol. Sun'., Bull. 15, 1906. — Wyoming : 75. Knight, Wyo. Experiment Stotion, Bull. 14, 1893. (General.) 76. Fisher, U. S. Geol. Surv., Bull. 260 559, 1905.

b,

Chapter V

Uhbs And Calcareous Cements

Composition of Limestones (2, 43). — Limes aod calcareous cements form an important class of ecoaomic products, obtfuned from limestones by beating them to a temperature ranging from that of decarbonation to cUnkering. The term limestone is applied to one of the main divisions of the stratified rocks so widely distrib- uted, both geolocally and geographically, and formed under such different conditions, that its composition varies greatly, this raie of variation becoming appreciable from an inspection of the follow- ing table, which contns a few selected types : —

n

ni

nr

Silica (SiOi) . . . Alumina (AliO.) . . Feme oxide (FdtOi) . Lime (CaO) . . . M>EDeai& (MgO) . Sulphur trioxide (80.) Cubon dioxide (CO.)

[.92

a.d.

u.d.

I. Ptm limeatoDe, IIaco, Mo. II. Chalk, Marinas, Cuba. III. Dolomite, E. Canaan. Conn. IV. Magneaian limeotone, Clinton, HuDlerdoD Co., N. J. V. Siliceous limestoae for bydraulio lime, Teil, France. VI. Argillaceous (cement nek) limMbiDe, Lehigh district. Fa. VII. ArgiUaceous magneman limestone, Milwaukee, Wis. VIU. CUyey chalk.

From this table it will be seen that limestones vary from rocks composed almost entirely of carbonate of lime, or of carbonate of lime and carbonate of magnesia, to others which are high in clayey or aliceous impurities. The presence of such impurities in lai quantity usually imparts an earthy appearance to the limestone, and sometimes even gives it a shaly structure.

Marked variations in composition may at times be found even

in a single quarry (50), while in other cases a hmestone formation

may show remarkable uniformity of composition over a wide area.

. ,„

140 Economic Geology

Changes in Burning (2). — When limestooes are calcined or " burned " to a temperature sufficiently high to drive off volatile cooBtituents, such as carbon dioxide, water, and sulphur (in part), or, in other words, to the point of decarbonation, the rock is left in a more or less porous condition. If heated to a still higher tern- perature, the rock clinkers or fuses incipiently, but the temperature of clinkerii depends on the amount of dliceous and clayey im- purities in the rock.

Lime (2, 43). — Limestone free from or containing but a small percentage of argillaceous impurities is, by decarbonation, changed to quicklime, a substance which has a high af&nity for water, and which, when mixed with water, " slakes," forming a hydrate of lime. This change is accompanied by the evolution of heat and by swell- ing, and this action becomes the more marked the higher the per- centage of lime carbonate in the rock, for the slaking activity is retarded by the presence of magnea and especially by arl- laceous impurities. Limes may, therefore, be divided into " fat " limes and " meager " limes, depending on the rapidity with which they slake and the amount of heat they develop in doing 80.

Hydraulic Cements. — With an increase in clayey and siliceoua impurities, the burned rock shows a decrease in slaking qualities, and develops hydraulic properties, or sets when mixed with water, and even under the same. Products of this type are termed ce- ments, and owe their hydraulic properties to the formation during burning of silicates and aluminatea of lime. On mixing the burned ground rock with water, these take up the latter and crystallize, thereby producing the set of the cement.

Hydraulic cements can be divided into the following classes: Pozzuolan cements, hydraulic limes, oatuial cements, and Portland cements.

Pozzuolan Cement (2, 53). — This is produced from an uncal- cined mixture of slaked lime and a siUco-aluminous niaterial, such as volcanic ash or blast-furnace slag.

This process was known to the ancients, and is named from its early use around Pozzuolano, Italy. The composition of an Italian Pozzuolano earth may vary between the following limits:' SiO;, 52-60; AI,, 9-21; FeiOj, 5-22; CaO, 2-10; MgO, up to 2; al- kalies, 3-16; HjO, up to 12.

' Srhoch, Die Moderae Aufl>ereitung u. Wertung der MSrtel MateHalien. Beriin.

issa.

c,q,z.<ib,C00gle

Limes And Calcareous Cements

No deposits of volcanic ash, for use in Pozzuolan cement, are worked in the United States, although extensive depodts of the oiaterial are known to occur in the Rocky Mountain and Pacific coast states. The reported importation of Japanese volcanic ash to the Pacific coast states ' may serve to draw attention to the do- mestic material. The following composition of the Japanese asb does not fall within the limits fpven above. It is SiOt, 42.10; Al/)g, 25.72; FesO,, 18.28; CaO, 1.15; MgO, .86; Na,0 and KA 2.20; loss on ignition, 9.70.

The manufacture of slf cement is now carried on at several localities in the United States, and is a growing industry (2).

Hydraulic limes (2) are formed by burning a siliceous limestone to a temperature not much above that of decarbonation. Owing to the high percentage of lime carbonate, eoDEdderable free lime appears in the finished product. Hydraulic limes generally have a yellow color, and a gravity of about 2.9. They slake and set slowly, uid have tittle strength unless mixed with sand. This class is of little importance in the United States, although small quantities have, in the last few years, been produced in Maryland, Georgia, and New York, They are, however, of great importance in Europe, and it may be of interest to ve a few analyses of the raw material used abroad (2) :

Analtbeb of Htdracuc Liue Rockb

a

Alumiim (Alrf>.)

Iron oxide (FeiO)

Lime (CaO)

Mignesia (MgO)

Cwbon dioxide (CO.) ff&ter

undet.

) ..

1 41.30

J

44.S0

1. Teil, France. 2. Hauabergen, Oermany. 3. Malain, Frnnoe. 4. S&- DODohea, Franoe.

In the best types of hydraulic Umestones, silica varies between 13 and 17 per cent, while alumina and iron oxide together rarely exceed 3 per cent.

1 Min. Rea.. U. 9. Geoi. Surv., 1907 : 491, 1908.

iv,Coog[c

Economic Qeoloot

Natural Roek Cements {2, 43). — These, known also as Roman cement, quick-setting cement, and Rosendale cement, are made by burning a silico-aluminous limestone (containing from 15 to 40 per cent clayey impurities) at a temperature between decarbonation and clinkering. The product shows little or no free lime. The following analyses will give some idea of the range in compoation of natural cement rocks quarried in the United States : —

Aturai.

Ceubnt Rocks

VpCA.

Lo™

Fort

Huipocx

UAmu-

MixW.

SiO,

Aw).

Fe.0,

CaO

MbO.

8.4fi

Alk.

a.d.

n.d.

11

—

—

n.d.

Co. 1

Hrf) 1

32.87)

31.74 j

Bbhcb-

L*w-

a?

Jamm-

Mnr Wm.

ao,

A1,0.

4.17]

r 4.46

FcO,

i 1.54

CaO

MbO

Alk

n.d.

ii.d.

—

—

So,

—

—

n-d.

Co,

H,0

n.d.

ii.d.

—

'

Natural cements differ from lime in possessing hydraulic prop- erties, and refusal to slake unless ground very fine. They diHer from Portland cements in lighter weight, lower temperature of burning, quicker set, lower ultimate strength, and greater latitude of composition. Magneda is not regarded as a detrimental ini' purity in natural cements aa it is in Portland cement.

c,q,z.<ib,Coogle

Ume8 And Calcareous Cements 143

The following are some analyses of the burned material: — ANALrsea of Some Natural Rock Cbmehts

Co,

MgO

fliO,

Al

Fefi,

Ntfi.Kfi

lOHRtOH

Akron. N. Y. . .

Xittunl rock cement,

2.2tt

deradorf , Qerm&ny

4.S4

—

—

Poriland Cement (2), — Portland cement is the product obtuned by burning a finely ground artificial mixture conaeting essentially of lime, silica, alumina, and some iron oxide, these substances being present in certain definite proportions. Portland cement wa first made by Joseph Apsdin, of Leeds, England, who desired to make an artificial cement that would replace natural hydraulic cements. It received its name because it haidened under water to a mass resem- bling the Portland stone of England.

The following combinations of raw materials are at present used in the manufacture of true Portland cement in the United States: marl and day; limestone and day, or akale; dialk arul day; pure limestone and arffiUaceous limestone.

In tbeee oombinations it is evident that the mibHtanoes first muned iuppl7 most of the lime and the second most of the eilioa, alumina, and iron. In the fourth the argillaoeoua limestone supplies some lime, as well as the ulica and altunina. The nature of the raw materials ohosea depends to a Ive degree on the location of the plant, whether in a limestone- or a marl- producing ngiou. Where both of these raw matrials are available, M in parte of New York, questions of manipulation in the process of manu- facture eovem the selection of one or the other.

Marls, for example, though easier to excavate and reduce than lime- nones, contain so much more organic matter and water than limestones that thej are moreexpensive to handteand prepare. Marl beds are likewise apt to be of limited extent and irregular, while limestone beds are, so far as the needs of a manofactnring plant are ooncemed, praotioally limitless.

Comparing clay and shale,* the former is often etisier to exoavat, 1)ut. on oooount of the water it contains, has to be dried before it can be ETDund and mixed. The fossils in shales are sometimes an important

' It is probable that the refuse of man)' slate quames could alio be uwd in place

b,

Economic Geology

source of oalcium oarboiite, and then careful grinding and mixing is Doces- aary to bring about a uniform distribution of the Ume through the mass. Shale la, however, used by only a few wocIch.

Argillaoeoua limestone, mixed with a much anuJler quantity of purer limestone, as in PennBylvania and New Jersey, is superior to a limestoQe and day mixture, because lesa thorough mixing and fine grinding are re- quired. In suoh oements, even when grinding and mixing ore inoompleUily done, the partioles of argillaoeouB limestone so closely resemble the proper mixture in ohemieal composition as to affeot the result but Uttle.

The following table ves the analyses of some of the raw materials used in manufacture of Portland cement: —

NALTBBS OP Raw Matbbialb itsed po

B POBTLAMD CbUBNT

LoCALin

Ko,

AlA

f'fi.

CiCO.

H.

Calo. shale

Lehigh

or

CaSO,

Vafley, Penn.

cement rock

mixture

5.07 1

CaO

MgO

Olcns

RJls. N. T.

Limestone

CaO

MgO

So,

Clay

2J25

WMners,

Marl

J26

N.T.

Clay

Insol.

CaSO.

Sandusky,

Marl

Ohio

CaO

MgO

Clay

11.9 Id.g

White

Cliffs,

CaO

MgO

Ark.

Clay

S3.3

23.29 9.52

In the seleotion of the raw materials the um of the maoufactorera is to produce a raw mixture which runs approximately 75 per cent carbonate and the balanoe olay. In the burning of this mixture, which must be done at a high temperature (of tea estimated at 3000° F.), a fused mass termed choker is formed. This connsts probably of silicates, aluminatea, and ferritea of lime. The finely ground clinker, which is the Portland cement, is blue le gray in color, and has a speciflo gravity of 3 to 3.25.

In some localities argillaceous limestones are found which approach so closely to the proper compdsition, that but little additional material hu to be added to make a mixture of the proper oompositioii.

b,

Limes And Calcareous Cements

The raw matarials must not only have the propvt oomporiti<H), but they also must show proper physical character, extent, and location, with raepeot to market and fuel supplies. As regards composition, 5 or 6 per rent tnagneaium oarbonate is about the permiBsible limit. Chert, flint, or sand are also undesirable impurities, and alkalies and sulphates should not exceed 3 per cent. For a clayey limestone the limiting values for silica.

SiO,

->2 and -

BiO.

AliOi + fW)j AtiOi + FeiOi

The foUowing are analyaes of Portland cement mixtures before burning: ' —

ANALTBK8 OF PoBTLAND CEnNT MlXTUBBS

MgCO.

—

B7.47

The following analyses will serve to illustrate the composition of some American Portland cements: —

ANAI.TBB8 or CKUHNTfl

SiO,

Mo.

C.O

MiO

So,

Empire

Bwidusky

Alpha

Ditribntion of Lima and Cament Material! In tha United States. Limestone for Lime. — IJmestonea of suitable composition for making lime are so widely distributed that no particular regions or states require special mention.' In the New England states, crys- talline limestones are the chief source of supply. In the AppsJa- chian states, from New York to Alabama, there are many Paleozoic limestones of high purity, notably the Trenton, Lower Helderberg, and Carboniferous limestones (see state references). The same

' U. S. Geol. Surv., Min Res., 1907.

' AoalyBEa and detailed descriptjops will be found in the &real reports, mentioned in the list o( Beferenoea.

b,

146 Economic Geology

series of rocks are also of importance in the Misrassippi Valley states from Tenuessee (52) to Michigan (35). Ume of excellent quality is obtained from the Subcarboniferous in Iowa (23, 24), Kansas (25), and Misaomd (53), and from the Cretaceous in Texas (S3). Limtones suitable for lime manufacture are also found in a localities in the Pacific coast states (53).

Hydravlie Limes (2). — Laily because of the great abundance of natural-rock cements, which are of superior value, these materials, though much used abroad, are of no importance in the United -States.

It is stated that in 1906 and 1907 ' several natural cement plants have been makii and marketing a true hydraulic lime, but no output is ven for 1908.

Ifaiiaal Rock CemerUe (2, 43, 53), — Calcareous rocks for making natural cement are found at a number of points, the more impor- tant ones being pven in summarized form in the following table: —

Geologic Aqs or Natubal Cement Rocks in the United States

Srm

QsoLoaic Aqb

SrxTB

QboumicAdi

Oeoreia

Cambro-Ordivieian

Ohio

Devonian

IllJaoiB

Ordovician

Pennivani*

Ordovician

Indiana-Kentucky Devonian

Teras

Cretaceous

Kansas

Carboniferous

Virginia

Cambrian

MarUnd

Silurian

West Viiyinia-

Minnesota

Ordovician

Maryland

Cambrian

New York

Silurian

WiaoonBin

Devonian 1

North DakoU

CretaoeouB

In many districts the cement rocks occurs in more than one bed, and may be interstratified with limestones or shales of no economic value for cement making (Fig. 54).

Some of the important occurrences may be briefly referred to.

Nod York (43). — This state contains four localities in which natural cement rock is found, these in the order of their impor- tance bng: 1. Rosendale District in Ulster County; 2, Akron- Buffalo District in Erie County; 3. Fayetteviile-Manliua District in Onondaga County (mostly) ; 4. Howe's Cave, Schoharie County. The following chart shows their occurrence at different horinons in the Silurian: —

U. S. Geol. Surv., Min. Res.. 1907 : 490. 1908.

C,q,-Z.-dbvCOOgk'

— Quarry of natural nrmeDt rock, Cumberland. Md. {ff. RU, pholo.)

Fio, 2. — Natural cement rock quarry, Milwaukee, Wis, (H. RicF,

, "Niversity

bvGoogle

Limes And Calcareous Ckmknts

Fokhatioh

Ut4TUt Co.

Scboharib

Onondaga

Ebib

MajiUua

Present, not

cement

Worked at Howe's cave

Worked for oemeut at ManUua,et

Absent

Rondout

Upper ce- ment bed of Rondout diatrict

Worked tor cement at Howe's Cave

Present, but not worked

Absent

Preoent

Not used for cement

' Bertie

Lower ce- ment bed of

district

Absent

Present in Onondaga Co., but rarely used

Worked around Akron and Bufralo

Wnber

Limestonea

No cement

In Rosendale district (Figs. 52 and 53), two distinct beds are

Torked usually, which differ in chemical composition and geolo|pc

age. The lower or dark bed, according to Darton, averages about

21 feet, while the upper or light bed is about 11 feet, the two being

I separated by 14-15 feet of worthless limestone.

I The lower bed rests directly on Clintoo quartzite.

The folding and faulting are intense in the Kosendale district (Fig. 53), but the beds show little disturbance in the others.

Other Statet, Southward from New York natural oement rock is quar- ried at a number of points along the Appalachians, but owinfr to the folded cbuacter of the beds the extraction is often difficult (PI. XVIII, Pig. I). The Lehigh district of Pennsylvania is an important producer of natural Mment, but still more bo of Portland oement (p. 149).

Several beds am worked in the Cumberland-Hancock area of Maryland [33, 33), while in Virginia {5£) limestones of suitable oomposition for natural Mmeat manufactiuv occur at several horiEons, but only the argillaceous nagoesian limestones found in the lower part of the Shenandoah (Cambro- Ordovioian) limestone will probably prove of economic value. Others ue worked in Oeorgia (14, 15, 63.)

Nfttnial cement has been made at Utica, 111. (63), from dolomitic limestone (Fig. 54), for nearly fifty years.

Near Milwaukee, Wisconsiii (53), the cement beds occur interstratifled with Devonian limestone (PI. XVIII, Fig. 2). Farther west near Fort

iv,Coog[c

148 Economic Geology

Soott, Eansaa (25), slightly magnenan CarboniferouB argillaceoui limeBtones

Cement rook is also obtained in Boutheaatera Ohio (44), and ftt Louia* ville, Kentucky (29), probably the aeoond most important oenter in the United States.

t RoDdout, N. Y. iAJltr ma

a. 69.)

Portland Cemenis. — Clay and limestOQe, in one form or another, are so widely distributed throughout the United States that it is possible to manufacture Portland cement at many localities,

c,q,-z.-dbvCooglc ' ;

LIMES AND CAIiCAREOUS CEMENTS 149

FiQ. S3. — Geologie leotioni tiiroui the Vlichtbos, ahowing position of n&turd rock cement bedis. {After wm Ingen, N. Y. Slaie Mu.. BuU. 09.)

uid the geoloc fe of the materials used ranges from Ordovi-

cian to Pleistocene (53), (Refs.

under different states). Twenty- c„„(j, T t-"-

five states were makiDg this

cent in 1908, the factories

bring spread over the country

from the Atlantic to the Pacific

(Fi8.58).

Penntyhavia. — By far the most important district b the Lehigh Valley in Pennsylvania, which supplies about 39 per cent of the domestic product.

The cement belt lies in North- ampton and Lehigh counties, Pennsylvania (Fig. 55), and the geol(c section involved is as follows (50); —

1 I .

ZlZC

J L

J L

b,.Coog[c

Economic Geology

' '

H

RSffir

s

all -1 ,

e "

"Wm

Umes And Calcareous Cements

Bndaon River slate.

Probably 500 feet thick. No limestone. Sharp bouidaiy.

(More or less arllaoeoua elaty limestone, the oemeat rook. Nearly pur limeBtonee with some dolomitio beds. {Kittatinny dolomites and dolomitio limestooee. 3000' ± . Some beds flinty, and lowest are nliceous. Basal oonfomerates or quartzite. Pre-Cambrism rooks. Mainly gneisses.

The lower member of the Trenton varies in its physical character, and furnishes material to rfuse the lime content of the cement rock ior Portland cement manufacture. Its lime carbonate content varies from 80 to 97 per cent, but occasionally drops to 70 per cent, while the magneaan carbonate runs from 1.5 to 3 per cent. In a few it reaches 20 per cent, and these highly magnesian layers cause trouble in quar- rying. The upper w al&ty member of the Trenton grades into the lower one. The rocks of this region have, by poet-Carboniferous folding, been bent into a complex series of folds (Figs. 56 and 57),

Fid. so. — DUsnunatia eotioD two milca Iouk extendinc northwert (torn Muiin's Ctek, N. X.bowingovertUTDedfolda. Ouid l C>mbruuidolomite; 2aDd3'= Lower Trenton, rocks hi in lime; 4 cement loek, Upper Trenton, averaging 70 to 80 per cent CaCOi; 6-Upper Trenton cement rock with lea than 70 per cent C>COt; e=HudBon Klver slate. (Aflvr , Boon. OmL, IU.)

whose axes trend northeast and southwest, and while the folds are in many cases overturned, there is comparatively little faulting.

The cement rock extends as a continuous zone or belt of varying width southwest across Northampton County from the Delaware to the Lehigh River (Fig. 55), crosses into Lehigh County, and ends abruptly at a point four and a half miles west of Coplay.

152 Economic Geology

The same beds are found in the adjacent territory of New Jersey (38).

Other States. — In the eastern half of New York (43) the Ordovi- cian and Silurian limestones form an inexhaustible supply of ma- . terial to mix with Pleistocene surface clays. In the south central part of New York the TuUy limestone and Hamilton shales are employed, while in the central and southwestern portion beds of ' marl (PI. XIX, Fig. 2), associated with surface clays, are utilized. ;

Fio. 68. — Map of United States, nbowiiiK location of cement plants. (,Afler Eck, I U. S. Oeol. Sun., BuU. 243.)

Ohio (46, 47), Indiana (18-21), and Michigan (3-36) are im- portant Portland cement producing states. The abundance of , marl and Pleistocene clays makes them the favorite materials, not- withstanding the fact that beds of Paleozoic limestones occur in each of the states. Marl, although especially abundant in Michi- gan, is found in many states lying east of the Mississippi and north of the terminal moraine. It is precipitated from the waters of ponds through the agency of minute plants, especially Chara (35).

In Kansas Carboniferous shales and limestones are used for making Portland cement {25, 26, 28), and in Texas and Arkansas the Cretaceous shales and chalky limestones are employed (13, U, S3); Alabama has a Cretaceous limestone of such composition that very little clay or shale has to be added to it (12), Portland cement is also manufactured in North Dakota (53), South Dakota (51),

FiQ. 2. — Marl pit at Wamera, N. Y. The dark streaks are peat, and the marl i underUin by clay. (H. Ries, Jiolo.)

b,

b,

Umes And Calcakeous Cements

Utah (53), Colorado (33), and California (15, 53).

tTses of Lime (,2). — ThemoBt important single use of lime is for mixing with sand to form mortar, and many tbouBands of toDs are iised an- nually for this pur- pose. In addition to this use lime is employed for a great variety of purposes, of which the following are . the meet impor- tant: as a purifier b bade steel man- ufacture; in the ; manufacture of re- fractory bricks, am- moDiiitn sulphate, soap, bone ash, gas, potassium dichro- mate, paper, pot- tery glazes, and calcium carbide; as a dinfectant; as a fertilizer; as a pol- ishing material; for dehydrating alco- hol, preserving es, udin fanning.

Uses of Cement (2.5).— The use of hydraulic cement is constantly increas- ing in the United

J

:

j

!

(

/

f

'

A

s

.'

Is

Economic Geolooy

States, this being specially true of Portland cement, which is super- seding natural cement to a great extent, and is finding an increas- ii use in building and enneering operations. For pavements, Portland cement is probably more extenavely used in America than in any other country; and as an ingredient of concrete it is widely employed. Blocks weighing as much as 65 to 70 tons have been made for harbor improvements at New York City (5).

Productum of Cement. — The followiim; tables gjve the produc- tion of natural-rock and Portland cement. Those given for the latter cover a greater period than those of the former, and are grouped with figures of import and consumption in order to show more clearly the tremendous growth of the American Portland cement industry.

The diagram (Fig. 59) shows most clearly the remarkable in- crease in the production of Portland cement, and the rapid decrease j in the natural cement production, the latter being now of small im- j portance in the cement industry.

r P0RTI.AND Cbuent bt Status, in 1906

STiTB

VALin

8Iatb

tss

Illiaoi* . . .

i:i

480,100 eS,S74 821,764

,209,291

Ik

874,457

2a8,19fl

.sosaio

Okt*ll(HD> ' '.

Ariu . .

Sri ':

M&BUhUHtU

Sis.-: :

a )

! '

1 J

e 17,877 B(W,306 G07,e03

B02S2i 310,244

B24flM I,OS7,433 805,235

Si 1,118 274 .Ms

61.072,612

43,547.679

This is perhaps hardly a fair year to take, as nearly all mineral industries showed a fallii off, owing to the business depression of 1907-1908. Portland cement, however, showed a slight ii the quantity of production.

Pboduction of Pozzitolan Cement i:

D UmTBD Statks, 1904-igoS

Yeu

Quaktitt

Valdb

r=.7

Val™

3O3.04S

(228.851

Ssi

"g:JS

Is

bvCoog[c

Limbs And Calcareous Cements

pliii I

\Uh

ps iifi

H

PBMSIijJ!

iliiii- - i

liil- ii-iill-

s

Sll- P-ilH-

!J

m n

ill!

U

!1

Mi

Economic Geology

RBmtSHCES OR UMB AHD CKHBHT MATBRIALS

Technoloqt. 1. Cumminga, Amerioaa Cements, BoBton, 1898. (Many Knalysea.) 2. Eokel, Cements, Limee andPlAstera, New York, 1907. (Wiley and Sons.) 3. Green, Portkuid Cement InduHtr; of the World, Journal of Assooition of Civil Engiaeerine, XX : 391, 1898. 4. Humphrey, U. 8. Qeol. Surv., Bulla. 331 and 344. (TeeU of cemeot mortus and concrete.) 5. Eno, Ohio Geol. Surv., 4th ser.. Bull. 2, 1904. (Uses of hydiaulio oemente.) 6. Bleininger, Ohio Geol. Surv., 4th ser.. Bull. 3, 1904. (Manufacture of hydraulic cements.)

LocALiTT Reports. Alabama: 7. Meissner, Ala. Ind. and Soi. Soo., Proc., IV : 12. (Birmingham district limestone.) 8. Smith, Ala. Geol. Surv., Bull. 8, 1004. (Many analyses.) — ArkanMS : 9. Branner, Amer. Inst. Min. ., Trans. XXVII : 42, 1898. (9. W. Ark.) 10. Taff, U. S. Geol. Surv., 22d Ann. Sept., Ill :687, 1902. (8. W. Ark.)- Cillfomla : 11. Grimsley. Bng. and Min. Jour., LXXII : 71, 1901. (Cement industry.) 12. Irelan, 8th Ann. Rept., State Miaenlogiet: 865 to 883, 1888; also 9th Ann. Kept. : 309-311, 1889; 13th Ann. Rept. Calif. State Mineralogist : 627, 1896; 12th Ann. Rept. : 391. 1894. (Cements.) Anon., Calif. State Min. Bureau, Bull. 38.— Colorado : 12 a. Eokel, U. S. Geol. Surv.. BuU. 243 : 122, 1905. — Florida : 13, Fla. Geol. Surv., 1st Ann. Rept. ; 40, 1908. — Geor: 14. Spenoer, Ga. Geol. Surv., Paleozoio Group Report, 1892. 15. Cummings, U. S. Geol. Surv., 21at Ann. Rept., VI : 410, 1901. — Dli- nols : 16. Eckel. U. S. Geol. Surv., Bull. 243 : 339, 1905. 17. Bur- chard, HI. Oeol. Surv., Bull. 8 : 346, 1907. (Concrete materials, Chicago diatrict.) — Indiana : 18. Blatohley, 25th Ann. Rept. Ind. Dept. Geol. and at. Res., 1900:323, 1901. (Bedford Umeatone.) 19. Siebenthal, 25th Ann. Rept. Ind. Dept. Geol. and Nat. Res., 1900 : 331, 1901. (Silver Creek hydraulic Umestone.) 20. Blatohley, Ibid., 28th Ann. Rapt.: 211, 1903. (Lime industry.) 21. BUtohley and Ashley, /(iid.,25th Ann. Rept. : 31, 1901. (Mtu-ldepodU.)— Iowa:22. Bain and Eokel, la. Geol. Surv., XV : 33. 23. Williams, la. Geol. Surv., XVII, 1007. (Tests of Iowa limes.) 24. Bayer and Williams, Ibid., XVII : 29, 1907. (General.) Kansas : 26. Haworth, Eas. Geol. Surv., Ill : 31, 1898. 26. Adams and others, U. S. Oeol. Surv., Bull. 238, 1004. (lola Quadrangle.) 27. Annual bulletins on Minenl Resources, issued by Eansaa Geological Survey. 28. Haworth and Schnuler, U. S. GeoL Surv., Bull. 260 : 506, 1905. (Independence Quadrangle.) — Kentucky : 29. Kentucky Geol. Surv., New Series, IV: 404. 30. Eckel, U. S. Geol. Surv., BuU. 243 : 171. — Maine : 31. Bastin, U. S. Geol. Surv., Bull. 285 : 393, 1906. (Enox Count;.) — Maryland : 32. Clark and others, Md. Geol. Surv., Rept. on Alle- gany Co. : 185, 1900. (Lime and cements.) 33. Martin, Md. Geol. Surv., Rept. on Garrett Co. : 220, 1902. — Michigan : 34. Hale and others, Mich.Geol. Surv., .Pt. 3, 1903. (Marlfor Portland cement) 35. lAne, Eng. and Min. Jour., LXXI : 662, 693, and 725, 1901. (Mich. UmsBtones.) 36. Ruaaell, U. S. Oeol. Surv., 22d Ann. Rept., 111:620, 1902. (Mich. Portland cement industry.) — MiaaiBsippi:

Limes And Calcareous Cements 157

37. Crider. U. 8. Oool. Surv., Bull. 260 : SlU, 190S. (N. E. Miss.)— Ifew Jersey : 38. KQmmel, Ann. Rpt. N. J. Sttite QeoloKist, 1900 : 9, (N. J. Portland oement industry.) 39. KQmmel, N. J. Oeol. Surv., Aon. Rept., 190S ; 173, 1906. (LimeBtooea, Sussex wad Warren oouct- tisB.) — New Tork: 40. Bishop, 15tli Ann. Rept. N. Y. State Geolo- gist : 338. 1897. (Erie Co.) 41. Naaon, Rept. of N. Y. State Geolo- gist, 1893 : 375. (Ulster Co.) 42. Pohlman, Amer. Inst. Min. Eagre., Tnuis. XVIII :250, 1889. (Cement rock at Buffalo.) 43. Riea and Eckel, Bull. N. Y. State Museum. 44, 1901. (N. Y. lime and cement industrjr.)— Ohio: 44. Lord, Ohio GeoLSurv.,VI : 671, 1888. (Natund and artificial cemeats.} 45. Eno, OhioQeol. Surv., 4th Series, Bull. 2, 1904. (Usee of oement.) 46. Bleininger, /Ud., Bulls. 3, 1904. (Maaa- boture of oement.) 47. Orton and Peppel, Ibid., Bulls. 4 and 5, 1906. (Limestones.) — PeiuuylTsnia : 48. Prime, Second Geol. Surv. of Pa., Rep. DD : 59, 187a 49. Clapp, U. S. Geol. Surv., Bull. 249, 1905. (Umestones, S. W. Pa.) fiO. Peck, Eoon. Qeol. III. : 37, 1908. (Lehigh district.) Clapp, F. O., U. S. Geol. Surv., Bull. 249, 1905. (S. W. Penn.) — South DakoU : 51. S. Dak. Sch. of Mines, Bull. S, 1908. (Black HOIb.) — Tennessee : 62. Eokel, U. S. Oeol. Surv., BuU. 285 : 374, 1906. (Tenn.-Va.) — United States : 53. Eckel, U. S. Oeol. Surv., BuU. 243, 1905. (Details on aU states.) — Virginia : 54. Cat- lett. U. S. Geol. Surv., BuU. 225 :457, 1904. (Cement resources, VaUey of Va.) 56. Bassler, Min. Res. of Va., Lynchburg, 1907, p. 86. — Waahington: 56. Landes, U. S. Oeol. Surv., Bull. 285 : 377, 1906. — West Virginia: 57. Grimsley, W. Va. Geol. Surv., Ill, 1905. — Wiscoasla: 58. Chamberlain, Oeol. of Wis., II. Pt. 2: 395, 1873. (Natural rock cement.) — Wyoming: 59. Ball, U. S. Geol. Burv.l BuU. 315 :232. 1907. (E. Wyo.)

b,

Chapter Vi Salines And Associated Substances

Undbb this heading are included Salt, Borax, Sodium Sulphate, Sodium Carbonate, and Sodium Nitrate. Bromine and calcium chloride, being regardable as by-products from salt brines, are re- ferred to under Salt. Iodine is described under Sodium Nitrate.

Salt

Types of Occurrence. — Common salt, the chloride of sodium (NaCl), is a widely distributed mineral, being found: (1) in aoluti(n in sea water or salt lakes; (2) aa solid masses termed rock salt; (3) as natural brine in cavities or pores of the rocks, from wliich it may exude as salt springs or be tapped by wells; and (4) in marshes and soils.

Although all four of these types of occurrence may serve as com- mercial sources of salt, it is only the second that is of great economic importance.

Occurrenc8 of Salt in Sea and Lake Waters. — Salt is present in all ocean water, and also in that of most inland lakes or seas having no outlet. As can be seen from the following analyses, the percent- age of salt is greater in some salt lakes than in the ocean: —

!

fc

LocAurr

z

g

s

Black Sea . . . MediterriuieaD Sea. Atlantic Ocean . .

98Jj3

Dead Sea. . . . Great Salt Lake .

Co,

b,

Saukes Akd Associated Substances 159

Salt is sometimes obtiuned by artificial evaporation from both the ocean and salt lakes; but in the United States this plan is prof- itable only under exceptional conditions, as around San Francisco Bay, California (8), or Great Salt Lake, Utah.

Rock Salt. — Rock salt, which is the most important source of commercial salt, occurs commonly in layers of variable thickness and purity embedded with sedimentary rocks, such as shales or sandstones. It is frequently associated with gypsum, and less commonly with limestone, or easily soluble compounds of magnesia, potash, and lime. Less often, the rock salt is foimd in domelike masses in stratified rocks, but not conformable with them. Hock salt deposits vary in thickness from a few inches up to as much as 3600 feet (Sperenberg, Germany); and while found in all geolocal formations from the Cambrian to the Pleistocene, except the Creta- ceous, the rock salt of the United States ia not found in formations older thah the Upper Silurian.

Origin of Rock Salt (1, 5). — One of the interesting problems of geology has been to find a correct theory to account for the origin of salt deposits. Such a problem is not aa simple aa it may appear at first aght, for it must explain (1) the formation of salt depoEdte of extraordinary thickness, (2) the association of gypsum, either above or below the salt, and (3) the presence of other minerals, which may or may not be saline ones.

Evaporation Theory. — it is generally believed that most rock salt, or rock salt and gypsum, deposits have been formed by the evaporation of oceans and lakes, this process having gone on during a number of periods from the Silurian to the present.

Now in the evaporation of a body of sea water having a compoa- tion similar to that of the present ocean, the order of precipitation would be (1) iron hydroxide, (2) lime carbonate, (3) calcium sul- phate, (4) sodium chloride, (5) easily soluble compounds, such aa sulphates and chlorides of potash and magnesia, etc., these being often of quite complex compotion.

In such a series, of course, the periods of depoation are not sharply separated, but overlap somewhat as shown by t'aiglio.

Simple as the phenomena of concentration of sea water appear, they yet may be complex, and it is possible as well as probable that the order of precipitation is not always according to order of solu- bility, this being governed to some extent at least by other salts present, degree of concentration, and temperature.

160 Economic Qbologt

There are hw pUoee where a complete section can be found, tuid the most nearly perfect one ia that at Stasaf urt in Fnissia, where more than thirty saline minerals are known to occur.

The section there, beginning at the top, is given below, and it will be seen there that in the upper part of the section (especially Nos. 2-5}, the order of precipitation is not exactly according to the orderof solubility of the differ- ent salts.

1. Permian (?) sandstones and shales.

2. Gypsum and anhydrite of variable thickness.

3. Younger rock salt, thickness variable. Sometimes absent.

4. Anhydrite.' From 30 to 80 meters thick. Rarely absent.

5. Salt clay. Averages 5 to 10 meters. OcoasioiiaUy absent.

6. Potash salts (Carnallite, KCl, MgCli,6 HiO), 15 to 40 meters thick. Always mixed with kieserite and rook salt.

7. Kieserite (MgSOt, H]0} zone. Same thickness as preceding, and oontaining layers of rock salt.

8. Polyhalitezone(KsSOi, MgS0<,2 Ca80s,2HiO). About 60meteTS thick, and consisting of alternating layers of rock salt and polyhaUt.

9. Older rock salt and anhydrite. The anhydrite forms layers in the salt averaging 7 centimeters in thickness, and thought by some to represent annual deposits, caused by seasonal temperature variations, or alternating dry and rainy periods.

10. Anhydrite and gypsum.

Where layers of clay or shale occur between the beds erf salt or gypsum, they may represent sediment washed in during the period of precipitation, the influx of fresh water carrying this sediment being sufBcient to dilute the brine, and temporarily arrest the deposition of the salines.

Depoaita of gypsum alone may be accounted for by assuming that the concentration did not proceed far enough to precipitate the less soluble substances, or if deposited they may have been subsequently removed by solution in underground waters. The theory that the oceans of other periods had a different compoatioa from the modern one might likewise account for beds of salt or gypsum alone. Some thin deports of salt may have been formed by simple evaporation, and it is well known that salt is depodted in the course of evaporation of inland seas, such as the Dead Sea.

The great thickness of many salt deposits is, however, not so satis- factorily explainable; as it can be easily seen that in order to pro- duce even a 15-foot bed of salt, would require the evaporation of an ocean of enormous depth, assuming its saUnity to be anything like the present one.

Bar Theory. — This theory, which seeks to explain the orin of salt deposits of great thickness, was first suggested by G. Bischof,'

b,

Salines And Associated Substances

and later elaborated by Ochsenius (1, 4) . It assumes a barrier partly shutting out the ocean water. Evaporation on the inclosed area of the sea exceeds the supply of water from inflowing rivers and from the open ocean. Therefore the water on the surface of the sea becomes more dense and settles to the bottom of the basin, being prevented from escape into the open ocean by the barriers at the entrance. As the surface of the bay is lowered by evaporation, ocean waters enter, furnishing a constant supply of salt. If the barrier is complete, forming a bar, sea water may enter only at times of high tide or storm. Eventually evaporation will ao con- centrate the solution in the bay as to cause the precipitation of sodium chloride and other salts. So long as these conditions lasted, salt would be precipitated, but beds of clayey material would be de- posited wherever fine-grained sediment was supplied from the land.

m

km

rm

Dome Theory (FSg. 60). — In Louisiana and Texas as well aa some other locahties, there are found great domelike masses of rock salt, accompanied at times by gypsum, limestone, and even Bulphur. G. D. Harris (6) believes they have been formed as fol lows: Heated waters coming up through underlying formations have become saturated with salt from deposits occurring in lem. These waters found a pathway in fissures related to the differential uplifting of the rocks in the Mississippi embayment, and marking the position of antichnes. Cooling of the uprising solutions caused them to deposit the salt in these fissures. It is thought that the force exerted by the crystallizing salt was sufficient to Uft up the overlying Tertiary and Quaternary beds, aa the accumulation went on. These cores -of salt have been pushed up through Cre- taceous, Eocene, and even Quaternary strata.

Economic Geology

Natural Brines. — Theae, sometime found in porous layers of the rocks, may result either from sea water imprisoned in the layers of sediment or from the solution of rock salt by percolating waters.

Salt Haishes and Soils. — When away from the ocean, these owe salinity to the infiltration of brine from neighborii saiiferous formations. They sometimes represent the site of former salt lakes.

Distribution of Salt in the United States. — Salt deposits are found in a number of states, as shown on the map, Fig. 61, but nearly

Fio. 61. — Mbp (howioK distributioD of salt-producing arena in United States, com- piled trom vuious geological survey reporto.

75 per cent of the production in 1908 came from two states, New York and Michigan. Most of the domestic production is obtained either in the form of artificial brine obtained by forcii water throih wells to the salt, which is then brought up in solution, or else as rock salt, rused through shafts from underground workings.

The range of geoltc age of the United States deposits is ;iiown in the following table: — Table bhowino Oeoloqic Distribution of Salt in thb Unitbd States

California

Present

Permian

Tertiary

Siluritui

MiBsiBsippian

Silurian

Silurian

MJBBiaaippian

Oklahoma

Permian (?)

Texas

Virnia

Mississippian

West Virginia

(PotteviUe)

Of THE

University

Of

b,

b,

Balimes And Associated Substances 163

NeiD York (15). — Salt was manufactured from brine springs at Onondaga Lake as early as in 1788; but the presence of rock salt beds was not suspected until 1878, when a bed seventy feet thick was struck in drilling for petroleum in Wyoming County. Since then the development of the salt industry has been so rapid that for some years New York has been one of the two leading salt- producing states.

The salt occurs in lenticular masses interbedded with soft shales of the Sahna series (Fig. 62), which also carry gypsum deposits. The outcrop of the formation coincides approximately with the line of the New York Central Railroad, but owing to its soluble character, no salt is found along the outcrops. The beds dip south- ward from 25 to 40 feet per mile, so that the depth of the salt be- neath the surface increases in this direction.

At Ithaea, salt ia struck at 2244 feet, and there are seven beds. The thiok- Dess of the individual beda variea, but the greatest known thickness Js m a veil near Tully, where 325 Feet of solid salt was bored through. Recently salt has been struck by a deep boring in the oil field of southwestern New York at a depth of about 8000 feet. Though most of the New York product is obtuned from artificial brines, a small quantity ia mined by shafts.

Michigan (13). — Salt in Michigan is obtained both from natural brines and from bnnes obtained by dissolvii rock salt, as in New York. The natural brines occur in the sandstones of the Misssip- pian, the most important locality being in the Saginaw Valley, where the brines are found in the Napoleon or Upper Marshall sandstone. Hey are remarkable for the large amount of bromine contained, more than half the bromine produced in the United States being obtained here. The vast beds of rock salt which occur in the Sahna (Monroe) are exploited along the Detroit and St. Clair rivers and at Mamstee and Ludington. The salt is dissolved by lake water pumped down and then re-evaporated, and soda ash (sodium car- bonate) is made from the salt to a very great extent, by forced reaction with calcium carbonate.'

Ohio (16). — Natural brines are obtained from the " Big Salt Sand " (Mississippian) at Poraeroy, Meigs County, but the profit in pumiring them lies in the bromine and calcium chloride which , they contain. In northeastern Ohio the wells pierce a bed of rock salt in the SaUna (Silurian), which is 148 feet thick and interbedded with limestones and shales. The wells are about 1900 feet deep at Cleveland and 2800 feet at Kenraore, Summit County, 1 Mate coDunuiiicatioDa from Dr. A. C. Lane.

iv,Coog[c

ECONOMIC GEOLOaT

Salines And Associated Substances

The two following analyses are of interest, partly on account of their completeness. The absence of sulphate in the first is noticeable.

Akaltbbs or Ohio Brikeb

Guns ra Lrram

'

SiOi

tr.

FeiOi, AliOi .

MgCl,

NaCI .

MgBr,

C4So,

UOa . . .

Sp-gr

I. Natural brine, Pomeroy, 0. II. Artificial brine, Cleveland, O.

Virginia (23). — Salt, associated with gypsum, is obtEuned by wells from the Misaissippiftn shaly limestones in the Holston Valley near Plagtereo, Washington County (Fig. 63). Fart of the product is marketed as salt, and the bal- aoce ia used in the manufaoture of al- kaU (22). The geol- ogy is referred to under Oypsum (p. 183).

WettVirginia (M). — Brine is ob- tained from the Car- boniferous (Potts-

Fig. 63. — Section acron Bolstn and Saltville vallesrB, midway between Saltville aad Plaaterco, Va. {After Eektl. V. S. Oeol. Sun., BvU. 223.)

of the stat adjoining the

TiUe) and Mississippian (Berea) in that portio Meigs County salt distriot of Ohio. Pennsylvania supplies similar brines.

Kantas (9). — Salt ia found in thia state under the following conditions: (1) in the northern and central parta of Kansaa as brine in salt marshes derived by leaching from the aaliferoua Dakota Bhalea; (2) a hmited amount in eastern Kansas from wells s

oogle

Economic Geology

the CarboniferouB; (3) in the Pennian of south central Kansas as beds of rock salt (Fig. 64). At the present time the rock salt is the most important commercial source, being obtmned in part as arti- ficial brines and in part as rock salt. The thickness of the salt varies, the greatest aggregate thickness recorded in any well being 324 feet. The deposits thin out to the eastward, and the north and

south limits are fairly well known, but the western boundary re- mains undefined. The absence of gypsum in close association with the salt is a significant fact, but farther south it ia found at a lower horizon, and the separation of the two is explained by a shifting sea bottom, during deposition.

Louisiana (10, 11, 12). — Brine occurs in springs and wells in the Cretaceous areaof northern Louisiana, but the most important source of salt is in the exten- Mve beds of rock salt found in the southern portion of the state. These underUe a series of low knolls, called the Five Islands (Fig. 65), and are covered by a series of clay, sand, and gravel beds. The salt occurs as great dome- like masses which Harris thinks have been pushed up into Creta- ceous, Tertiary, and Quaternary beds (p. 161). Salt is mined on Grande C6te or

Iv,

Salineb And Associated Substances 167

Weeks Island and also on Avery Island. The age of the salt beds is pre-Pleistocene. Although the amount of rock salt present is ev-idently great, borings in one case revealing a thickness of 1756 feet of solid salt, these deposits yield but a small percentage of the country's output.

Other Weslem Stattt. — In California the main supply of salt is obtained by evaporating sea iratr (8), an elaborate aystemof ponds, covering thou- oDds of acree, having been built on San Francisco Bay. These ore filled It high tide, and the brine evaporated by solar heat, although artificial heat i- usmI at some of the plants. A remarkable deposit of salt has been worked II Salton Lake. This is a depressioa 27 miles long, to 9 miles wide, and

tt its loweat point 280 feet below sea level. The deposit is formed by evapo- Wion of the lake waters, which are fed by saline springs from the surround- ing foothilla. The salt, which has accumulated to a depth of 6 inches, is thered by scrapers. Salt ia also found in marshes, springs, or wells in a number of other localities in California (8).

In Idaho brine salt ia obtained in Bear Lake and Bannock counties, near the Wyoming line; some also is produced in Churchill and Washoe muDtiee, Nvada, Torrance County, New Mexico, and from saline lakes ia several parts of Texas. Rock salt has been found at several localities in Texas, notably in Mitchell County, and under the oil beds at Beaumont, but none ia yet produced.

In Utah, some salt is obtained by evaporating the waters of Great Salt Lake (21), and brines from several other localities. An enormous deposit or pure salt is reported from the west side of the Utah desert, near the Nevada sta( line.'

Throughout the Red Beds area of western Oklahama, and in parts of cutem Oklahoma, there are numerous salt springs and seepages, but Fer- fuson is the only locality of importance where salt is made (18).

1 U. a Geol. Surv.. Min. Res., 1908.

c,q,z.<ib,Coogle

Economic Qeologt

AaalyseB of salt-

Analtbeb

p Rock Sai,t from

Vabious Localitom

M

J

Jl

Retsof, N. Y. . . . Pearl Creek, N.Y. . Petite Ansa, La. . . SaltviUe, Va. . . .

Tr. Tr.

Tr.

F. E. EnglehMdt F. G. Enelelurdt P.Collier C.B.Hyden

Analtsbb of Soud

d&TTER OF Brines

FKOU Varioos Locautim

Si

jj

!1

'1 is

AoTuaarrr

Warsaw, N. Y.

.Si

,20

1.6R

2(134

1 wt

Syracuse, N.Y.

Bf

m

2M

Ir.V

1 14?

G. H. Cook

Saginaw, Mich.

W

:2

H9

.Soi

An

Bay City, Mich.

9!>

—

Kanawha, W. Va.

7E

K!

4S

1,073

G. H. Cook

Pittsburg, Pa.

J3

4.81J

—

—

„

2.Hc

I.Ois

G. H.Cook

SaltviUe, Va.

7)12

Tr

9Am.

C. B. Hayden

Great Salt Lake

d22

.0001 .364

J. E. Talmadge

Eztractioo. — When salt forms underground deposits, it has to be extracted either by a process of solution or miniI;. Id the former case water is forced down to the salt bed through a well, for the purpose of dissolving the salt, the brine being brought to the surface and evaporated, sometimes by solar heat, but more com- monly by arti&cial means. In the latter case a shaft is sunk to the salt bed, and the material mined like coal and brought to the suf* face in lumps, known as rock salt. Natural brines are pumped to the surface for evaporation. In the evaporation of brine care has to be taken to separate the gypsum and other soluble impuiities present, which precipitate before the salt does.

Uses. — Salt is largely used in the meat-packing business and the manufacture of djury products, as well as for domestic purposes. Therefore a number of different grades are called for, known under various names, such as table, dairy, common, fine, packers, solar, rock, milling, etc. Large quantities of salt are also consumed in the manufacture of soda ash, sodium carbonate, caustic soda, and

b,

Salines And Associated Siibstance8 169

other sodium salts. The chlorinatioa of gold ores calls for an ad- ditional large amount.

Production of Salt. — The increase in the amount of salt pro- duced has been very marked, but it has been accompanied by a decrease in price, as shown in the statistics given beiow: —

Production or Salt in Unitbd States frou 1880 to 1900

Tua

Valub

Ymab

Valub

s.9si.aeo

7.038,063

4,S28,fiM

43Z5,34S 4,7Sa.2S6

ISftS

13,899.Ms

t4.423,04

PnoDOCTtON or Salt bt States tbou 1901 t

Ims

QuiimTT

TALin

QDAHTlTt

Vai-db

Quantht

Valo.

8,978.030

Oil-reui . .

W9,07B

0.21fl

2W

23,030.002

Sa,021.222

35,9Sa.l23

W.O05.S22

28,173,380

e,658,350

Qdakittt

Valdb

Quamtitt

Valub

SwYofk. . .

K.33S1S0

6.078.743

(2.136,738

Tout. . ,

29,704,138

7,e08,333

28.822,062

t7.S53,e32

' iBriwM in ottwT Stain.

ViniBUi. Pnmiylvuii, Oklihomi. Neriida, Nv

IndodM , PwuiMylviuils. New Meiioo. a iMhidea Psniuvlvulh Nsw Meiico, und Mswik

iHtadM Srw MwlMh Oklitumu. Pemuylvuii,

mohiuMU. Ukd Idaho.

iv,Coog[c

Economic Qbologt

The exports in 1908 were 53,253,739 ib., valued at $202,338, smaller than for several years. The imports for the sajne year amomited to 319,285,638 lb., valued at 9iiifi90, this being less than any year since 1902.

World's Pboduction of Salt toe Laot Teas Availablk

Co™™,

BacatTTom

United 8tBt (19071

4.ias7s

JSffl

2,160,587 l,SS8.Me

fi

UnlMd Klacdom <1MT)

teXWrA"". :::::::

lis

5,3 ig ,273

SSr;asr.°"" ::::::::

B,7M335

18,340,663

$41,188,910

Refbreiicb3 Oh Salt

Tbchnoloot and ORrom. 1. Clarke, U. 8, Gool. Surv., Bull, 330, 1908.

2. Englehardt, N. Y. State Museum, BuU- No. XI : 38. 1893. 3.

Hubbard, Midi. Oeol. Surv., V, Pt. II : 1, 1895. 4. Ochsenius, Chem.

Zeit., XI, 1887. (Bar theory.) 5. Wilder, Jour. Gol., XI : 725,

1903. 6. Harris, Econ.Geol., IV; 12, 1909. (Dome theory.) 7. Lane.

Jour. Qeol., XIV : 221. (Chemioal evolution of ooean.) Abeai. California: 8. Bailey, Calif. State Min. Bureau, Bull. XXIV;

105, 1902. — Kansas : 9. Kirk and Haworth, Min. Beeouroea of Kas.,

1898 : 67. — LouisianB : 10. Veatoh, La. Exp. Sta., Pt. V : 209. 1899.

(Rock salt.) 11. Veatch, Ibid., Pt. VI :47, 1902. (N. 1a. salines,}

12. Harris, La. Oeol. Surv., BuU. 7, 1908. — Michigan ; 13. Lane.

Mich. Oeol. Surv., Ann. Rept., 1901 : 241. 1902. Hew Mexico;

14. Darton. U. 8. Oeol. Surv., BuU. 260 : 565, 1905. (Zuni.) — Hew

York : 15. Merrill, N. Y. State Museum, BuU. 11, 1893. — Ohio : 16.

Bownocker, O. Oeol. Surv., 4th Ser.. Bull. 8, 1906. — Oklahoma;

17. Gould, Kas. Acad. Boc., Trans. XVII : 181, 1901. (Salt plains.)

18. Gould, Okla. Oeol. Surv., BuU. 1 : 35, 1908.— Texas: 19. Cum- mins, Tex. Oeol. Surv., 2d Ann. Rept. : 444, 1890. (Northwest- ern Texas.) 20. Richardson, U. S. Oeol. Surv., Bull. 260 : 572, 1905. (Trans-Pecos regions.) — Utah: 21. U. S. Oeol. Surv., Min. Res., 1888 : 605, 1890. 21 a. Eckel. U. S. Oeol. Surv., BuU. 226 : 488, 1904. — VirginiB: 22. Eckel, U. S. Geol. Surv., Bull. 213:407. 1903. (S. W. Va.) 23. Watson, Min. Rea. Va., Lynchburg, 1907. (S. W. Va.) — West Virnia ; 24, Grimsley, W. Va. GeoL Surv., IV:

b,

Saunbs And Associated Substances

Bromine

Sources. — Bromine occurs in nature combined with eome metals, as in the minerals Embollte, Ag (CI, Br), Bromyrite (Ag Br), and lodobromite (2 Ag CI, 2 Ag Br, Ag I), which theoretically con- lain 25, 42.6, and 17.8 per cent respectively of bromine. None of these are commercial sources. Sea water contns about .06 gram per liter, and at Staasfurt, Germany, the mother liquor obtuned from salt refining contains from 15 to 35 per cent bromine.

In the United States bromine is extracted from natural brines found at several geolocal horizons, but not all rock brines contain it, aome, as those of New York State, being very low in it.

At the present time Ohio, West Viinia, Pennsylvania, and Michigan brines are used, the first bromine having been manufac- tured in 1846 at Freeport, Pennsylvania.

At Pomeroy and Syracuse, Meigs County, Ohio, and at Hartford and MasoD, Mason County, West Virpnia, it is obtained as a by- product of the salt industry, the brine coming from the Pottsville horizon (Big Salt Sand).

A plant has been operated also at Pittsburg, Pennsylvania, ob- taining the bromine from brines in the Pocono sandstone. That manufactured in Michigan comes from the Marshall sandstone of the Lower Carboniferous, the brine contning from .1 to .3 per cent bromine.

Uses. — Bromine is used for making bromides of potash, soda, and ammonia, for medicinal piu*po8es and photographic reagents. A small amount ia employed in the preparation of coal-tar colors known as Eorane and Hoffman's Blue. As a chemical reagent, it is utjliied for precipitating manganese from acetic acid solutions, for the conversion of arsenlouB into arsenic acid, etc. It may also be used as a disinfectant when dissolved in water, and has been employed in gold extraction.

Production of Brohiite

PuwDCTtON

Poubm

343,000

8B.900

140,790 1M.S72

1908 : : : : : :

S98.fi00

1 65)204

IgSi

L'.oog[c

Economic Geology

asrsKBiiCBS ok bkoiovb

1. MerriU, U. S. GoL Surv., Min. Res. 1904 : 1029, 1905. 2. Lane, Min Indus., XVI : 123.

Sodium Sulphate

Occurrence And Diitributioa. — The hydrous sulphate, mir&bilitf or Glauber salt (NaiSOt + 10 H|0), ia a white sahne materia, which is collected on or near the surface of some alkaUne marshes ia desert reons. It may also be extensively depoated in some saline lakes, its precipitation preceding that of salt, and beii affected more or less by the season of the year; for since it is much more soluble in warm than in cold water, the difference in temperature between summer and winter may cause its separation and re-solu- tion (3). The phenomenon has been noticed in Great Salt Lake (4). Exposure to warm, dry fur causes the mirabilite to lose ita water and change to thenardlte.

No production of sodium sulphate is recorded by the United States Geological Survey. It is known to occur at several localities in Wyoming (3). Deposits of some extent have also been noted id the lowest portion of the Carriso Plain, along the northeast boundai; of San Luis Obispo County, California (6). In this lake, which remains practically dry, except in very wet seasons, there have been deposited a series of saline beds, whose chief constituent is sodium sulphate. The salt has been derived from the leaching of soft beds of conglomerate, sandstone, and shale in the surrounding hills. An analysis of the salt crust yielded: Insoluble, .40; Al,Oa, .04; MgO, 1.66; CaO, .45; Na,0, 40.50; K,, .28; H, 3.65; SO,, 46.12; CI, 9.27; Total, 102.37; less oxygen, 2.09; 100.28. The superficial deposit is said to be from I to 6 feet in depth, and is underlain by a supersaturated solution of the sulphate and water. Opera- tions looking to the utilization of the deposit have been begun.

ItBFERESCES OS SODHIII SULPHATE

1. Attfield, Jonr. Soo. Chem. Ind., Jan. 31, 1895. 2. Knight. Min. Indus., Ill : 651, 1895. 3. Knight, Wyo. Agrio. Exper. Sta., BuU. 14, 1893. 4. Gilbert, U. 8. Geol. Surv., Mon. I : 253, 1890. 5. Clarke, U. 8. Geol. Surv., BuU. 330 : 186, 1908. (General.) 6. Arnold and Johnson, U. 8. Geol. Surv., BuU. 380, 1909 (Calif.).

b,

Salinbb And Associated Substances

Sodium Carbonate

Sodium carbonate, or natural soda, is obtained by the evapora- tion of the waters of alkali lakes, or is found as a deposit on or near the surface of alkaline marshes in arid regions. It is usually a mixture of sodium carbonate and bicarbonate in varying propor- tions, as well as impurities such as sodium chloride, sodium sulphate, borax, and sodium nitrate.

Sodium carbonate has been obtained from Owens Lake in Cali- fornia. An analysis of the waters by Chatard yielded: SiO,, ,220; FeA, AW„ .038; CaCO,, .055; MgCOj, .479; KCl, 3.137; NaCl, 29.415; Na.S04, 11.080; Na,CO,, 26.963; NaHCOj, 5.725. The soda is purified by fractional distillation. Soda is also known to occur in Orou and Nevada.

Rbfekehces Oh Sondh Caxbokatb

I. BaOey, Calif. Stat Min. Bur., BuU. 24 : 95, 1902. 2. Chatard, U. S. OeoL Surv.. Bull. fiO : 27. 1888. (AnalyseB.) 3. Russell, U. S. Geol. Surv., Mon. XI : 73, 1885. 4. Clarke, U. S. OeoL Surv., BuU. 330 : 189, 1908.

Soda Kiter'

Soda niter, or Chile saltpeter (NaNO, with 63.5 per cent NasOi irhen pure), is found in San Bernardino and Inyo counties, Cali- fornia, along the shore lines marking the boundary of Death Valley in Eocene times (1). It occurs in peculiar rounded hills of Eocene clay, the niter being found as a layer near the surface or distributed throu the clay. Very little soda niter is obtained from this Murce, and the main supply of this country continues to come from Chile, where extensve deposits are found in the desert region west of Iquique. There the niter (caliche) forms a bed 6 to 12 feet thick, under a cap of conglomerate (costra) 1 to 18 feet thick. The orio of this deposit is interesting, and has caused considerable discus- sion. One theory quite generally accepted is that the niter was fomied primarily by the slow oxidation in air of guano or other nitrogenous organic matter in contact with alkah; a second theory refers its orin to the oxidation of oianic materials and ammonia, by microflcopic organisms known as nitrifying germs.

RBFBIIEHCBS OH SODA HTTBa

1. Bailey, Calif. State Miu. Bur.. BuU. 24 ; 139. 1902. 2. Clarke, U. S. Oeol. Surv., Bull. 330 : 205, 1908. (Chemistry, analyses, origin.) 3. Penrose, Jour. Geo!. XVIII : 1, 1910. (Chile.)

' The term ttiltr. when usad aloDe, refers to poUah niter.

ooglc

ECONOMIC QEOLoay

Borax

Borax Minerals (3, 4). — The chief minerals containing boron are borax, tincal, or sodium biborate, NatBfOr, 10 H; coleman- ite,CaiB,,5HsO; ulexite,CaNaBA,8H; boracite, 2 MgsBsOu, MgCli. These minerals are found usually as incrustations in al- kaUne marshes, or in lake waters of arid regions, or as bedded de- posits. In some localities boric acid is found in fumarolic vapors.

{After Keuea, Am

Distribution in th United States. — Depoats of borax bare up to the present time been discovered only in California (I, 2, 5), Nevada, and Oregon (3, 8), Borax was originally obtained by evap- oration from the waters of Clear Lake,' north of San Francisro, being produced in commercial quantities in 1864, and the solution was enriched by crystalline borax obtained from the marshes sur- rounding the lake. This and other lakes of California were worked until the discovery of large deposits of nearly pure borax in alkaline

' Aq aiuUysU of the solids of bat spring from aulphur bank on margiD of Ckar Lake yielded CI. 16.49; 1, ,03; COa. 21.90; B4O1. 35,61; Na, 24.99; NHi, 7.8S; AlsOa, .40; SiOs, 2.64. (U. 8. Geol. Burv., Bull. 330 : 154.)

b,

Salines And Associated Substances 175

marshes of eastern California and western Nevada in the early seventies. Several refining plants were located at these marshes, and the product was sometimes hauled a hundred miles to the rail- road. Increased production and importation from Italy, however, reduced the price and caused these plants to be abandoned.

The discovery, in 1890, that the marsh borax was a secondary deposit, derived from easily accesble and extensive bedded deposits Id the Tertiary lake beds of that region, revolutionized the industry.

The Tertiary clays (2, 5) in which the borax depote are found occur mainly in southern California, but partly in Nevada (Fig. 67). They are exposed at intervals from Death Valley and the Nevada boundary, as far as the Pacific Ocean near Santa Barbara, north of Los Angeles. Daggett in San Bernardino County (PI. XX, Fig. 2) was formerly the chief locality, but more important deposits have recently been discovered in Furnace Cafion and Santa Clara. In

this region (Fig. 68), the borax, which forms a regular layer or layers, is interbedded with sands and clays, supposed by Campbell to have been deposited in a series of Tertiary lakes (2), but the beds are in many instances tilted, due to violent crustal movements, which interrupted sedimentation at intervals. Keyes estimates the section at 4000 to 5000 feet thick, but is not sure that all the borax beds occur at the same geol<c horizon.

In Furnace CaGon, for example, the richer borate beds range from a few inches to 50 feet in thickness. The unweathered por- tions consist of bluish clays, thickly interspersed with milk-white layers, nodular bands, and nodules of crystallized colemanit or calcium borate, which is termed locally " high grade ore."

The " lowrade ore " consists of clays impregnated with fine particles of the borate mineral, and yielding, on leaching, from 10 to 25 per cent of anhydrous boric acid. Selenite not infrequently ac- companies the coarse colemanite and in some places may be in excess.

ECONOMIC OBOLOaT

In 1907 important deposits were discovered in Tick Cafion, Los Angeles County, which promise to be of great importance because of their jvoximity to the railroad.

tJss. — The borax-bearing minertds are utilized chiefly for the manufacture of borax and boracic add. Borax is used in indus- trial chemistry, in medicine, and aa a laboratory reagent. It is also employed in the assaying of gold and silver ores, in soldering brass, and welding metals.

Boric acid is used in the manufacture of borax, in colored glazes for decorating iron, steel, and metallic objects, in enamels and glazes for pottery, in making Sint glass, as an antiseptic, and as a preser- vative for food. Chromium borate makes a green pigment used in calico printing, and manganese borate is sometimes employed aa a drier in paints and oils. Borax is also extenmvely used in numer- ous cosmetics.

The chief refiners are the Pacific Coast Borax Company with works at Bayonne, New Jersey, and Alameda, CaUfomia, and the Sterling Borax Company of San Francisco, California.

Production of Borax. — The California colemanite deposts form the main aoiUTie of domestic supply, the output being derived from the counties of San Bernardino, Inyo, and Ventura. The marsh deposits of Nevada are no longer productive.

The production of borax in California from 1904 to 1908 was as follows, the values being based on the boric-acid content of the correspondii number of crude tons of colemanite or borate of lime.

s,?

YsjlM

&

ViLIU

t5M7 48,334 SS,173

1698,810

i'.i82:4io

1908 : ; : ; : :

Ss.ooa

'mijMB

Referbhces Oh Borax

1. Bailey, Calif. State MioiiiE Bureau. Bull. 24 : 33, 1902. <CRlif. and general.) 2. Campbell, U. S. Geol. Surv., Bull. 200, 1902. (Calif.) 3. Clarke, U. 8. Oeol. Surv.. BuU. 330 : 195. 1908. (Chemistry of origin, etc.) 4. Kemp. Min. Indus. 1 : 43. 1893. (General.) 5. Keyes, Amer. Inst. Min. Bngra.. Bi-mon. Bull. Oct. 1909, p. 867. (General.) 6. Merrill, Non-Metallic Minerals : 313, N. Y. 1904. 7. Spurr, U. 8. Geol. Surv., Prof. Pap. 55 : 158, 1906. 8. Stafford, Ore. Univ. Bull.. New Ser, I, No. 4:6, 1904. (Oregon.) 9. Strong. Amer. Inst. Min. Engrs., Bull. 38 : 167, 1910. (Discussion of Rf. S.)

Iv,

Salines And Associated Substances

lODIKB

SonrcAS. — This element is known to occur in sea water, in min- eral spring, and in a few rare minerals, such as the iodides of silver, copper, and lead. In the Chilean nitrate deposits it exlets as lautarite [Ca(IOi)i] and as a double salt of calcium iodate and chromate [Ca(IOi)i, CaCrOJ. Some Silesian zinc ores and some of the phosphate rocka of France show small percectages of the element. It has been found in the ashes of sea weeds, and in some oil-well waters, certain Pennsylvania ones carrying ,5687 gram of calcium iodide per liter.

At present the entire production of iodine comes from two sources, viz., the ashes of sea weeds and the niter deposits of Chile.

RBFBRBHCBe OB lOEOHB

1. Clarke, U. 8. Geol. Surv., BuU. 330. : 17, 9!, 142, 1908. (Many refer- enow.) 2. Min. Indus., XVI : 582, 1907..

b,

Chapter Vii

Gtpsum

PropertieB and Occurrence. — Gypsum (1, 4), the hydrous sul- phate of lime (CaSOt, 2 HjO), occurs most frequently in sedimen- tary rocks, interbedded with shales, sandstones, and limestones, and often more or less closely associated with rock salt. It is also foimd as surface depodts mixed with clay igypsUe) (11), or in the form of sand (5 Ariz.). The first two types are the most impor- tant commenaally. It also occurs as efflorescent deposits, periodic lake deposits, in lumps and plates scattered through clays or shales, in veins, and in limited quantities in volcanic repons, especially in lavas (4). When occurring in bedded depouts (PI. XXI, Fig, 2) it is often massive, of crystalline texture or earthy appearance, and of variable color, although most commonly white and gray.

Transparent, colorleBE forms, known as tdeniu, are found as veins or oryBtals in the maaeive gypaum, or as plata and oryetals in many cluv!, shaleB, and limeatoneB. This variety by itsdf never forma depoaita of com- mercial importance, althou-h selenite scales are sometimes plentifully oattered through the purer vaiieties. AlahasUr is a pure white, fine- gruned, massive variety, whioh is sometimes used for ornamental work.

Gypsum when pure contains 46.6 per cent sulphur trioxide, 32.5 per cent lime, and 20.9 per cent water. It has a specific gravity of 2.3, and a hardness of 1.5 to 2. It is therefore sufficiently soft to be easily scratched with a knife or even by the thumb nail.

Anhydrite differs from gypsum chemically in the absence of water, but changes to it on exposure the and moisture. In some cases it may have been derived from gypsum. When present, it may occur as veinlets, beds or masses in the gypsum deposit; indeed, its irregularity of occurrence is at times puzzling (PI. XXI, Fig, 1).

Anhydrite contains 41.2 per cent lime, 58.8 per cent sulphur tri- oxide. Its specific gravity is 2.8 to 2.9 and its hardness 3 to 3.5. As it is of no conmiercial value, it may cause trouble in quarrying, if present in large quantities.

So far as published accounts go, anhydrite does not appear to be very abundant in the gypsum deposits of the United States. It is not uncommon in the Viinia mines, and Lane notes its occur- 178 .. ,

University

b,

i. 1. — View in a Nova Scotia gypaum quaiiy, showing largo maaa of anhydrite. The anhydriW Soma the buttress on right of quany face, and is not removed.

Good eypaum occurs on either side of it. (H. Aua, pKoto.)

n quaiT>', Linden, N Y. {Photo, loaned bu D. H. Xewland.)

bvCooglc

Gypsum 179

reoce in the deeper-lying parts of the Michigan gypsum series. Some extenMve beds also occur in Oklahoma. Scattered irregular masses and beds are abundant in some of the New Brunswick and N'ova Scotia gypsum areas.

Jmpurituain Gypsum. — Clay is probably the commonest impurity, and occurs either imiformly distributed through the gypsum, or else in layers. Lime carbonate is often present, though rarely in large amounts. The same may be said of magnesia, siUca, and iron oxide.

Origin of Gypsum (1, 4). — Gypsum is widely distributed both geographically and geologically, being found in various borisons from the Silurian to the Recent. Most beds of this substance have no doubt been formed by the evaporation of salt water either in inland seas or else in arms of the ocean, the process of precipitar tion having been discussed in the chapter on Soli. As gypsum separates from sea water after 37 per cent of the water is evapo- rated, while salt precipitates only after 93 per cent has been removed, it is evident that gypsum beds may be deported without salt. This may also explain why gypsum is more widely distributed than salt; and the fact that the percentage of gypsum in salt water is much less than that of salt probably accounts for its usual occur- rence in the thinner deposits.

The conditions under which anhydrite forms do not appear to be thoroughly understood. According to Vant Hoff and Weigert, an- hydrite forms from gypsum in sodium chloride solutions at 30°C., while in sea water the transformation takes place at 25°C, (Quoted by Clarke 4). Lane (12) believes that aO calcium sulphate precipi- tated at a greater depth than 600 feet is really anhydrite rather than gypsum. Indeed, some believe that perhaps much of the g}-psum now found was originally anhydrite.

If the change was brought about by penetrating surface waters, it might account for the irregularity of occurrence of the anhydrite in the gypsum. That such a transformation may extend to a con- siderable depth is shown by the deposits at Bex, Switzerland (4), where the alteration has reached a thickness of 60 to 100 feet.

Gypsum may also be formed by the decomposition of sulphides, such as pyrite, and the action of the sulphuric acid thus hberated on lime carbonate. Small quantities are formed in volcanic reons through the action of sulphuric vapors on the hme of volcanic tuffs or other rocks (4).

Gypsite, or gypsum dirt, is an earthy or sandy variety of gypsum forming a surface deposit in Kansas (11) and other western states

Economic Geology

(20, 23), which, ID spite of its impure appearance, may rim high in calcium sulphate. It is believed to be a <le[M>dt dther in tiie soil or in shallow lakes supplied by springs whose water has dissolved the calcium sulphate from gypsum beds or other rocks. During its precipitation by the second method, its impure character is caused by its becoming mixed with clay or sand washed in from the land.

Distribution in the United States (Fig. 69). — Eighteen states and territories are producers of gypsum, although three of these — New York, Michigan, and Iowa — produce over 50 per cent of the total quantity mined.

The wide geoloc rate of gypsum depoats in the United States can be seen from the following table: —

Tehhitort

Aam

Aoi

Alaska

Nevada

TriaBBie

New Merioo

Permian

Arizona

Triassic and Tertiary (Pliocene)

New York

Silurian

Tertiary

Ohio

Silurian

Tertiary

Oklalioma

Pleistocene

Colorado

Permian

Permian

Iowa

Permian

Permian

Kansas

Texas

Michigan

Lower Carboniferoua

Viinia

Carboniferous

Montana

Lower Carboniferous

Wyoming

Triassic

New York (13, 14) — In this state, which is one of the three largest producers, the gypsum occurs as rock gypsum, iuterbedded with shales and shaly limestones of SaUna (Silurian) age. The beds, several of which may occur in the same section, are lenticular in shape, but of such horizontal extent that in any one quarry they appear of uniform thickness (PI. XXI, Fig. 2). In most quarries they range from 4 to 10 feet, and their general dip is southward, but there are local irregularities. The main gypsum depoats occur in the upper part of the Salina, while the salt beds he lower down in this formation. The Area of outcrop of the Salina is Bhown in Fig. 70. The gypsum de- poats, which occur mostly in the central part of the state, are usually impure, except in Genesee County. Rgure 71 shows a not uncommoi mode of occurrence.

Michigan (12).— All the Michigan

Fra. 71. — Section in gypmira deposit at Lioden, N,Y. (After Eckel, U. S. Geol. Sun., BuU. 223.)

182 ECONOMIC GEOLOaY

gypsum is rock gypsum and of high purity. There are two im- portant areas, one being in the vicinity of Grand Rapids, and the other at Alabaster on Saginaw Bay (PI. XXII, Fig. 1), both in beds of Lower Carboniferous age. These beds, known as the Grand Rapids formation, surround the Michigan coal basin,' and carry the gypsum in their lower part. At Grand Rapids, the gypsum beds, which are interstratified with shale and limestone, run from 6 to 12 feet in thickness, and are worked either by quarrying or underground chambers. At Alabaster, Iosco County, the gypsum, which immediately underlies the glacial drift, is 23 feet thick.

A third, possibly productive, area is near St. Ignace on the upper peninsula, but there the gypsum occurs in the Salina or Monroe group (Silurian).

Iowa (10). — Important deposits are found in this state in an area of about 25 square miles in Webster County, especially near Fort Dodge. The gypsum, which is presumably of Permian age, rests on the Coal Measures, or the St. Louis limestone (Lower Carboniferous), and is covered by glacial drift, but in places is overlain conformably by red shales. It varies from 3 to 30 feet ia thickness, with an average of 16 feet, and much of it is sufficiently white for stucco.

Kansas. — Gypsum (ll) is found occurring as rock gypsum, or as gypte, the deposits forming a belt extending across the central part of the state in a northeast-southwest direction, and includes three important areas, viz. Northern, or Blue Rapids, in Marshall County, Central, or Gypsum City, in Dickinson and Saline counties, and Southern, or Medicine Lodge, in Barber and Comanche coun- ties. The beds of rock gypsum are of Permian age, interbedded with red shales, those at the southern end of the belt being strati- graphically 1000 feet higher than those at the northern end.

The gypsite or gypemn dirt, which is of more reoent age, ia fonnd in the oeatral area, as well as at a number or other localities. The spring waters which have supplied it have leached the calcium Bulphat either from the gypsum beds or the red shales. The gypsite is found especially in the central area, and the deposits were the first of their kind worked in the United Stats.

The product is used for fertilizer and cement p1astr, and much is also used for making Keene's cement.' The rook, hich ia quarried eapecially in the northern and southern areas, is white in color, and may range from 8 to 16 feet in thickness.

' It U interesting to note that wpIIb sunk in the central portion of the basin aho' that tJie (typaum p&asea into anhydrilo, indicating that if the gypaum ia oT primary character it was deposited around the borders of the old interior sea.

' A cement made by burning gypsum at high temperatures, and then tnating it with alum or other chemicals. , i

University

Of

s£jl.iFORi!

b,

Putb Xxii

[a. 1. — Gypsum quarry. AlabBster, Mich. Shows gypaum overlaia by glsi"' drift. The dump in foreground is overburden removed from Kypaum. (PAola.. A. C. Lane.)

FiQ. 2. — View i

bvCooglc

Gtpsum

Virginia. — Gypsum is also found JD beds of Lower Carbonif- erous Jage in the Holston Valley of southwestern Virnia (22), the deposits occurring in shales, between Carboniferous {Green- brier limestone) and Siluro-Devonian sandstones (Fig. 63). The section is faulted up agnst the Cambro-Siturian limestones, on the southeast, and both the gypsum and salt deposits seem to be limited to a narrow belt bordering on this fault.

The gypaum oocurs in bowlder masees in gray and red days, and is inMrestine because of the abundant but irregular oeourrenoe of anhydrite, vhicfa grades into the gypsum. The rock is mined parti; by underground workinKa, luid some of the beds are fully 30 feet thick. The product is used for land and wall plaster.

In Ohio grypBum has been obtained from the lower Helderberg beds of Ottawa County, 10 milee west of Sandusky. The material occurs at differ- eat horizons, the beds being bent into rolls, the main ones having a thickness ot about 12 feet (15, 20).

Other Occurrencet. — - Additional oecurrences are known in Wyoming la, M), Utah {21), Nevada (20), California (8), Montana (20), Idaho (20), Colorado (9, 20), South DakoU (17-19), Oklahoma (16), Texas (20). and Aiizooa (7, 24). In the last, as well ae in New Mexico, there are found important deposits. of gypsum sand, composed of gypsum grains broken iown by stream action and water from rock gypsum outcrops, and then gathered into hills or dunes by wind action. Some of theae dunes are more than 100 feet high. The utilization of these sands in Otero County, New Mexico, was begun in 1908.

Gypsum (6) of Permian or Triassia age ia known'to ooour on Chiohagof IsUad in aouthea8tm Alaska. The beds, which are folded and steeply tilled, have been extensively developed during the last few years and shipped to Taooma for preparation. It oomee into competition with similar ma- terial from the western states.

Aualyaes of Gjpstun. — The following analyses indicate the com- poution of gypsum from different localities in the United States. They cannot all be guaranteed as being of average character, and serve mainly to show variation'in composition : —

Girenk

Ala-

m""

Baut-

."vf

Otf- mIb-

Gtp-

CoSOt . . .

,n

tr. n.d. n.d.

72.06|59.46 21.30 16.59

1.68110.67 1.95 .60

AliftandFerf). CsCO, . . MgCO,. . .

99.96,99.71

97.64 196,99|98.63

Economic Geology

Ft. Dodoe. U.

f 73.44

H-O

PesO,

MgO

—

—

Uses (1 a). — Gypsum ia sold either in the ground, uncalcined condition, or after calcining and screening. In the former state its chief value is as a fertilizer, it being marketed under the name of land plaster, which is also used as a disinfectant.

In its calcined form, gypsum is known as plaster of parts and has the following uses, dependent on its property of hardening or setting when mixed with water : stucco, plastering for walls, whitewash, pot- tery molds, statuary, and dental purposes, as a deodorizer, for cray- ons, and asaretarderoffermentationajidabaorbentof water in wines.

An important use is as a retarder in Portland cemeat, large quantities being sold for this purposes. It is also employed as a bed for rolling hot glass.

Caldning Gypnim. — When heated to 250' F., gypsum loses a portion oT ita water ot hydration, but if finely ground has the property of reoombtniDg with it. I! heated to 300° F. to 400° F., it loses this power and is aaid to be dead-burned. In addition to dehydration, burning also breaks up the crystals into minute particles. The set is due to the formation of a ciystsl- , line network of the rehydrated grtuns.

Since calcined gypsum sets in from 6 to 10 minutes, some retarding ma- terial, such as organio matter from slaughter-house refuse, is often added . to it, and thus the setting process may be delayed from 2 to 6 hours. Those plasters which set slowly are termed cemnt platlers.

The following analyses show the composition of (!) uncalcined gypsum; (2) the calcined rock; and (3) the plaster after it has taken up watw and set. From these it will be seen that the plaster takes up the amount of water lost in calcination.

BuBNiNa

Cbudb

F.Hube

Sit

FesO. and A1,0.

Co!

HsO

Gypsum

1S5

Though the softness of gypsum prevents its general employment as a building material, the pure white, massive varieties, known as (ddbasier, have been used for statuary, basins, vases, and other objects for interior decoration. Gypsum is also used to weight fertilizers, and as an absorbent of orgc materials in them ; as a flux in the manufacture of glass and porcelfun; and, under the name of "terra alba," as an adulterant of foods and medicinal preparations.

pTodnctioa of Gypsum. — Michigan, New York, and Iowa are the leading producers, but other states contribute considerable amounts.'

rKE United States in 1907 a Uses, in Shobt Tons

.„„

SoldOdiw

Qiun-

Uty

VlJuB

St

Value

Quan- tity

Value

llriiro, South tori, uid Ulh CtlDmiA. Neva

80.87S 251,871

334:60)

i;

34B

*G3.961 24:83] I9a:42l

6,IflI

1.56:

15,50(

isjee

M384

4;27t

n:68;

90,34'

i4:56i

343,961

227,1Se

701,268 374 .33(

626:771

402308

6S1

UlihdnuuSTffia

22s B3

l.7Si.74S

M24.227

46,851

16.841

1.126.301

14,402,196

M,942,264

UAl. AriBM. C.

Kiwi'S:;/

129,440

B3.7M

31S,04I 178.B04

72.205

26:421 S3:a7:

1,573

i:o8.

3.16:

a:fl7(

i!i

33, Soi

64.77]

192:40:

16

34;

57H

65Z

So

''ibhotna tad Tt%i

396.715

(91.623

1,125.617

$3,650,192

4.138,560

t iDcluiifla a imall quantLty of etoud

oateriaJ from Teiaa.

' Owing to the complexity of tabulation adopted by the United States Geologi' cal Survey, the state figures ore ven for 1907 and 1908 only.

Economic Geology

BauD Cbddi. LujD pLiraiB

Sold u CiLcmD

i"

VduB

Pm

toni

V.™

Vii.™

Is8!::

iwa. .

Ib08.' :

M,I37 226:261

424,227 396,748

(1.09 2!4(

i:7s

70,197 37:672

Bi:e23

965,340

i:i25:617

|2,sao.sai

2,S48.906 3,220.138

3;aM:iB2

S3.sa

3:24

C7S442S

3,837.975 4,M2Jt64

The imports for 1908 were valued at $354,403. WoHLD'fl Pboddction of GrpanH

waSOT) . . .

9Uit (19071 . da (1007) . . .

Oenuui Emtn (1 904)

REFERElfCBS OS CTPSUH

Pbophbtieb and Tdchnoloot. 1. Eokel, Cements, Limes, and Iasto 2d. ed., N. Y., 1907. 2. Grimslejr &nd BaHey, Kas. Oeol. Surv., V, 1899. 3. WUdo-. Eng. and Min. Jour., LXXIV : 276, 1902. 4. Clarke. U. 8. Geol. Surv., BuU. 330, 1908. (Origin.)

AsEAi,. 5. Adams and others, U. 8. Geol. Surv., Bull. 223, 1904. (United States.) — Alaska : 6. Wright, C. W., U. 8. Geol. Surv., Bull. 345 : 124, 1908. (S. E. Alas.) —Arizona : 7. Blake, Amer. Geol., XVITI : 394, 1S96. — California : 8. Crawford, Calif. State Mining Bureau, XII : 323, 1894. — Colorado : 9. Lee, Stone, XXI ; 35. 1900. (Lari- mer Co.) — Iowa : 10. Wilder, la. Geol. Surv., XII : 99, 1902, and Jour. Geol., XI: 723, 1903. — Kansas : II. Grimsley and Bailey, Kaa. Univ. Geol. Surv., V, 1899. — Michigan : 12. Orimaley. Mich. Oeol. Surv., IX, Pt. 2, 1904. — Hew York : 13. Merrill, N; Y. State Museum, Bull. 11 : 70, 1893. 14. Parsons, N. Y. State Geologist, 20th Ann. Kept. : r 177, 1902. — Ohio : 15. Orton, Ohio Geol. Surv., VI : 696, 1888. — Dklahonia : 16. Gould, Okla. Oeol. Surv., BuU. 1 : 26, 1908. — South DakoU : 17. U. S. Geol. Surv., Geol. Atlaa Polios, 85 : 6. 18. Todd. S. D. Geol. Surv., Bull. 3 : 99, 1902. 19. O'Hare, S. Dak. So. of M., Bull. 8, 1903. — United SUtes : 20. Adams and others, U. S. Geol. Surv., BuU. 223, 1904. — Utah : 21. Boutwell, U. 8. Oeol. Surv., BuU. 225 : 483, 1904. — Virginia : 22. Eckel, U. S. GeoL Surv., Bull. 213 : 406, 1903. 23. Watson. Min. Rea. Va. : 327, 1907. (Lynchburg). — Wyoming : 24. Knight, Wyo. Exper. Station, BuL 14 : 189, 1893. 25. Slosson and Moody, Wyo. Coll. Agrio. and Mecb., 10th. Ann. Kept., 1902.

Chapter Viii Fertilizers

this term are iacluded a number of mineral substances, limestone (p. 139), marl (p. 143), gypsum (p. 178), phosphate of lime, greensand, guano, kunite (KO, MgSOi, MgClt, 6 H|0) (p. 160), and niter (p. 173), which are of value for adding to the soil to increase its supply of plant food and also in some cases correct its physical condition. Some of these have other uses as well, i have been discussed elsewhere on those pages indicated by the nuJ bers following them in the foregoing lines.

Phosphate of Lime. — This occurs both as crystalline phosphate of lime, or apatite, and amorphous phosphate of lime, or rock phos- phate.

Apfttite (6, 8). — This mineral when pure contains about 90 per tent tricalcic phosphate, and 10 per cent calcium fluoride, which may be replaced by calcium chloride. It is widely distributed in some igneous and metamorphic rocks, especially granites, gneisses, sod some crystalline limestones, but rarely in sufficient quantity or in sufficiently concentrated masses to render its extraction prof- itable, at least while the supply of amorphous phosphate lasts. So, competition with rock phosphate has restricted mining to a few localities where it is associated with other valuable minerals.

la the United States apatite has been produced for several years at Mineville, N. Y. (7) where it occurs disseminated in small grains through the magnetite, forming sometimes as much as 5 per cent of the ore. In the process of magnetic separation the apatite is re- moved as tilings, the first grade of these carrying about 60 per cent tricalcium phosphate, and the second about 30 per cent. They are used in fertihzer manufacture.

A unique well as extensive ooourrence of pfaoaphatlo material is fouod at two localitiea in Nelaon (floured under Titanium) and Roanoke wunties, ViisioJa. The rock which Watson has named NeUonile (8 a) condsts of a hard granular aggregate of white apatite and black ihnenite, and tonns a dike-like mass in gneissea and schists. The commercial value this material aa a source of phosphate remains to be proven.

Economic Geology

Amorphous Phosphates. — These, though composed chiefly ol phosphate of Hme, also cany variable quantities of other substances. (See. table, p. 196). They occur (1) as concretionary bodies in coih solidated rocks; (2) as beds; (3) as Insular rocklike masaesj and (4) as nodular masses of varying size, often scattered throu unconsolidated beds. As is shown in the following descriptions amotphous phosphates occur in various geological horiaons, from the Silurian to Tertiary, and in several states, though most of the domestic supply at present comes from Florida, Tennessee, and South Carolina.

Florida (13, 25). — This state is at present the most important phosphate producer, although the full extent and value of the de- posit were unsuspected until the discovery of large beds along tba River In 1887. The phcrephate deposits which are associated -rith Tertiary limestones of various horizons from the Eocene to the Pliocene form a curved belt, banning west of the Appalachi- cola River and extendii east and then south through Dunnel' Ion, and approximately as f ar aa Punta Gorda (Fig. 72). The topography varies from gently rolling to flat pine lands and swampy areas, the general ele- . vation under 75 feet. El- dridge recognizes four types (A phosphates in this area, viz., hard rock, soft rock, land pebble, and river pebble. Of these the terd rock phosphaU (PI. XXIII, Fig. 1) is the richest, and has had more inBuence in the rapid de- Map of Florida phcwpbato velopment of the district. It Ilea in pockets of irregular occurrence and extent, and rests usually on limestones of Lower Oligocene (Tertiary) e. The material ia of hard, massive, close-textured character, variable color, and often contns irregular cavities which show a secondary depo- sition of phosphate. Accompanying the hard rock in some places is a second type, the soft phosphate, which is evidently a didntegratiou product. Bowlders of hard phosphate are at

L,--z:-:l,vC00glc

w

H

™'"

Ist

k

Fl

OBm

M

u

'J

"

-'

Fio. 72.

. deposits. {AJltT Bldridgt Inil. Min. Eng., . XXI.)

b,

puTE xxin

J- Ocala, Fla. (PAoio.. A. W. Sheafer.)

Fro. 2. — phosphate hia. Moiitprlier, Ido. Shows the alternating layer limestone and phosphate, (W. F. Ferrier, plioto.)

Fertiuzers 189

embedded in a matrix of soft phosphate, and also in sands and ckya overlying the Eocene limestone. In the Miocene it is also found at many places as a bedded deposit. While the hard rock has an average of a little over 36.65 per cent of phosphoric acid, ihe soft phosphate rarely avertes over 22.90. The former is com- monly sold under a guarantee of 77 per cent bone phosphate.

The land ptiiUe or matrix roek ia made up of pebbles of varying ite, shape, and color, and composed either (1) of earthy material with fossils, quartz grains and pisolitic grains of phosphate, or (2) of pebbles closely resembling the hard-rock phosphate. To render it nmrketable, the pebbles, which average 32.06 per cent phosphoric acid, have to be freed from the matrix by washing and screening. The unit composition of sale for land pebble is 68 per cent of the bone phosphate and 3 per cent of the combined oxides of iron and alumina, with moisture not above 3 per cent.

The river pMe consists of phosphate pebbles, having a blue, black, or dark gray surface, and mixed with sand, bones, and teeth. It is found in the present as well as in ancient river chan- oets, in the latter case being covered by coastal sands. That found in the Peace River district averages 28.40 per cent phos- pboric acid.

All the above-mentioned types, with the exception of the soft phosphates, are found underlying more or less separate regions (Fig. 72).

Origin. — The orin of the Florida phosphates has been a puzzling problem to geologists. Eldridge (13) has proposed two theories: (1) that they have been derived by the leaching of guano and bone beds, wd the depotion of the phosphate in the underlying limestone, either by precipitation in its pores or replacement of the lime car- bonate; (2) that they are due to the solution of the limestone and ' consequent concentration of the less soluble phosphate of lime which was originally disseminated through the rock.

At a later date underground waters may have removed the lime- stone from around the phosphate def)Osits, leavii them as bowl- ders, which, at a still later period, were rounded by water currents ntuch idso deposited sand around them.

The land pebble and river pebble probably represent nodules of a lughly phosphatized marl, formed in limestone, pebbles, or shell ists, by sregation of the lime phosphate contained in the lime- stones. Subsequent solution of the lime carbonate set free these nodules, some of which became concentrated as stream gravels.

Economic Geoloqy

South Carolina. — Phonphttte is found both on the l&nd uid in the river bottoma in a belt about 60 miles long lying inland from Ch&rleston uid Beau- fort (S, 20, 22). The phosph&te, which rarely averagea much over one foot in thickness, ia commonly of nodul&r chtu&cter, &nd often coutains m&ny bones and teeth. The presence of these animal remains, including both land and marine forms, has given rise to the belief that the deposits were caused by the accumulation of bones and exoremeuts along a shore line, probably of Upper Miocene (Tertiary) age. Leaching of these remains may have permitted a later replacement of limestone or the formation of phoaphatic concretions in swamp bottoms.

Two forms are recognized, viz. land rock and river rook. The former ranges from 1 to 3 feet in thickness and is overtaja by greensand mad. The river rook is little more than water-wom fntgments of the first type, aid is mined from the river channels.

The South Carolina phosphate rook was worked as early as 1867, and the production increased up to 1893, but since then it has fallen off almost steadily.

Tennessee (14-16, 18. 23, 25). — Since the rec<tion, in 1893, of considerable quantities of high-grade phosphates in western middle Tennessee (Kg. 73), there have been important develop- ments of the deposits. The phosphate areas lie mainly in Maury,

Fio. 73. — Map ahoi

; C.OOg[c

Fertilizbr8

Hickman, Ferry, and Lewis counties, but others are known in Giles, WiUiamsoQ, Davidson, Sunmer, and Decatur counties (Fig. 73).

Three types of phosphate deposits arc recognized. The first is brown reddual phoaphabe, occuiring mainly along Duck River in Maury County. The material is of Ordovi- nan age, and has been Formed by the leaching of phoaphatic lime- stones, the phosphate remaining as a redual deport, whose thick- ness is from 2 to 8 feet.

A second type of Uack or blue color oc- curs either in beds or nodules. The bedded material, which is of Devonian age, varies from ooUtic through compact and conglom- eratic to shaly forms ud IB underlain either gray Devonian

mdstone or by blue Silurian limestone, and by black shale. This type occurs in seams varying from 1 to 50 inches in thick- ness, although the high-grade material tarely exceeds 20 inches. Its phosphate of lime content From 30 to S5 per cent. A nodular variety oc- curs in a greensand fonnatioa overlying the black shale, and while the nodules carry about 60 per cent lime phosphate, they are not workable except

192 Economic Geology

in connection with the bedded rock. Both types are believed b be chemical precipitates on the floor of the Devonian sea. The third group includes white phosphate of post-Tertiar

Cd

Fia. 75. — Map of parta of Idaho, Wyommg, and Utah, showing localities of Upp* Carboniferous rucks eontaining phosphate beds. f.A/ler Weekt and , V- S Gecl. .Sun., B<m. 315, 1906.)

iv,Coog[c

Fertiuzers 193

age, occurring in three conditions; namely, stony, brecciated, and lamellar.

In the stony phase the phosphate has been deported in a sili- ceous limestone, replacing the Ume. It alternates with beds of stony chert, and contains usually only about 50 per cent lime phos- phate, but is not worked. The brecciated fonn, which is the most abundant, consists of angular fragments of Carboniferous chert in aphospbate matrix. These chert fragments vary from 3 to 4 inches in diameter. The lamellar variety was depouted in caverns in the Silurian limestone, and is therefore of irregular shape and extent. Since its depotion the limestone has weathered to a residual clay, m which the phosphate masses occur.

White phosphate has thus far been found only in Perry and De- catur counties, and may run as high as 85 per cent lime phosphate.

Hayes has advanced the theory that the lime phosphate of the white phosphates was originally extracted from sea water by or-

TiG. 76. — Section of Carboniferous strat (A/Ict Weelu and Penrier, V. 1

ganisms, and accumulated on the bottom either as nodules or dis- wnunated through the sediments. Later, when these strata were lifted above sea level and subjected to erosion and the action of per- colating waters charged with acids from the soil, the phosphate was leached out and carried to lower levels where it was redeposited either in cavities or by replacing limestone.

At the present time the brown rock phosphate is the most im- portant commercially.

Wyoming-Idaho-Utak (25, 26). — Large areas of phosphate rock We been discovered in the western states (Elg. 75), within the

ECONOMIC QEOLOGr

last few years. The depodts, which are sd to be the most exten- sive thus far discovered in the world, wilt no doubt prove to be ol great importance in the future, although at present their develop- ment has been retarded, partly by lack of transportation facihties and limited demand.

'V

, '-

iS

K

yM$

(

'

Si

'

jb!

/-

M

V

Kj

/

Fto. 77. — Map of portioD of Lafferty Creek, Ark., phosphate district, showing poii- tiotx at pboepbate outcrops. (.AJter Branner and Naatom, Ark. Agrie. Exp. Sta.. BvU. 74.)

The phosphate is found in rocka of Upper Carboniferous age,

interstratified with shales and sandstones, the average section being

as shown in Jig. 76. The beds strike northwest and southeast, oi

parallel with the

trend of the ranges

in which they out-

ctoiriM. crop, and show a

' variable dip, be-

and faulting thai

sftffK ... lias disturbed

them. At the baa

sIm ' ' " of the section is t

limestone, which il

separated by I

p*tp*rfM H/rMMu thin shale from thi

/ main or overijinl

phosphate bedj

This latter is 5 t

6 feet thick, and

Coojlc

FiQ. 78. — Section in Lafferty Creek, Ark., Phoephate

district. (After Branner and NoBiom, Ark. Agrie. Exp. Sta., BuU. 74.)

Fertiuzebs 195

oolitic character, but the range of thickneas is a few inches to 10 feet. The lime phosphate content in the workable beds varies from 65 to 80 per cent, with an average of 72 per cent.

A knowledge of the Btratier&phy in this region is of importance, beoaiise a! the similarity of the stratified Cambrian, Ordovioian, and Bilurjan ndiments to some of the Carboniferous ones. Some phosphate has been shipped from Montpelier, Id&ho, and used in superphosphate manufaoture It Martinez, California.

Arkanta* (9, 10, 21). — Phosphate deposits have been developed on lafferty Creek, on the western edge of Independence County, but the beds erteod from about 10 miles northeast of BatesviUe, to St. Joe in Searoy Coonty, a distance of about 80 miles. The phosphate which forms a bed 3 to 6 feet thick in the Cason shale of the Ordovioian is light gray, bnaieneoUB and oonglomeratio with small pebbles. It carries from 25 to 73 per oent lime phosphate. The following section is shown on lAfterty Creek (Pig. 78).

Ihc™

The Arkanaas'phosphates were discovered in 1895, but were not developed until 1900. The field will be of doubtful importance until low and medium- erade rock is marketable.

The true nature of these phosphate deposits does not appear to have been recognized for some years.

Bnumer and Newsom consider them to be deep-sea (though not abysmal) deposits, formed from the droppings of fishes and other marine animals, and to accumulations of organia matter that settled to the bottom of the quiet

Purdue believed the beds to have been laid down near shore as the sea advanced landward, and the phosphatie nature as due mainly to fragments of organic matter, but may have been in part the droppings of marine uimala. The conglomerate character is thought by him to confirm the liallow-wter theory.

OUi*r PhotphaU Oeearrenea. — Phosphate, in the form of nodules, white vesicular rook, and in limestone fragments, occurs along the ooataot of Oriskany (Devonian) sandstone and Lower Helderberg (Silurian) tuoestone, in Juniata County, Pennsylvania (17). It contains 30 to 54 pn cent bone phosphate. Nodular phosphate, although not worked for fertilizer, is known to ooour in Cretaceous uid Tertiary strata in Alabama Georgia (19), North Cardina (ii), and Virginia (2Sa).

iv,Coog[c

Economic Qeologt

Analyses of Phosplifttes. — The following analyses will serve to sbow the compotioa of some native phosphates. Of the impuri- tiea present, lime carbonate is undesirable, since it neutralizes the acid used in phosphate manufacture. Iron oxide, alumina, and silica are inert impurities displacing just so much phosphate of lime.

The richness of a phosphate is usually expressed in terms of the tribasic-calcic phosphate, commonly termed bone phoeph&te. Of this about 45.80 per cent is phosphoric acid.

Analyses of

Phobphatei Bock

s

f

j[

S

Tennessee

Mt. Reasant

Sw&n Creek,

Hickman Co.

White phos-

phate, StoDe

Quarry Hol-

low, Perry

Co. . . .

Florida

MbO

Hard rock .

Washed Und

pebble . .

1,35

River pebble

South Cabo-

Average, S. C.

Aoalyeis .

3.6S

Guano (31, 32). — Under this name are iaoluded auifaoe deposits of excrement, chiefly of birds. Penrose (25) reoognizea two classes: (11 soluble guano, of recent origin, which still oontuns most of its soluble in- gredients; (2) leached guano, which h&s lost its soluble constituents by the action of rn or sea water. Most of the soluble guano of commerce wu formerly obtained from Peru, where, it is said, the Ineas, as well as tb early Spaniards, valued it so highly that a death penalty was imposed for killing the birds which produced it. These deposits, trom which maay thousand tons have been obtained, are now eidiauBted. No large depoaO

Fertilizers

of bird guano &re known in the United States. Leached guanos occur on islanda in the southern Facifio and in the West Indies.

Bat guano has been found in the caves of Kentucky, Texas (32), and many other states, but few of the deposits have proved large enough to work, and none are of great extent, although one oave in Texas was known In yield 1000 tons. The following analysis is representative: ammonia, 9.44 per cent; available pliosphoric acid, 3.17 per cent; potash, 1.32 per

Greensaad. — This term is applied to beds of nutrine origin, made up in bige part of the green sandy grains of glauconite, the hydrated silicate - of iron and potash. It also contains small amounts of phosphoric acid. Green sands (29) are found at many localities in the Cretaceous and Tertiary formations of the Atlantic Coastal Plain, but New Jersey (28) and Viisiiiia ire tbe two important producers. The New Jersey greensand is spread OQ the soil in its raw condition, but that from Virginia is dried and ground tot use in commercial fertilizers.

The following analyses show its variable composition, and the oom- puatively small amount of PiOi and KiO necessary to make it of value as a Fertilizer.

Akaltskb op Greensand

P.0,

80,

Co,

K,0

Ni40 C0

M(0

Al,Oj

Ptmbwton, N. J.

Uses. — Fertilizers are used either in their raw condition or after imdergoii preparation. Lime carbonate is commonly calcined before being spread on the soil, while gypsum is first pulverized before being sold as land plaster.

Phosphate rock is treated with sulphuric acid to produce superphos- phate or acid phosphate, and in this treatment ammoniates, or potash, or both, are sometimee added to the material. Concentrated phosphate is mode by treating the phosphate rock with enough sulphuric acid to en- tirely decompose it, converting all the time into sulphate, the phosphoric Bcid solntion being drawn off and further treated with additional quantities oF high-grade phosphate. Since this form of phosphate therefore requires nv materials of a high grade, and is much more e:itensively manufactured in Europe than in the United States, most of the high-grade Florida rock is exported.

Prodtiction of Fertilizers. — The production of phosphate in the United States (or several years was as follows: —

b,

m

s ii

a sss

E

1

lis

r

!

Ip

n 1 i.

Ip

1

omj-MUY

!? Ss

5 i

i 1

g Si

Ip

P i

ife"

Ip

Im

3 M

S SiiSS

a :

1 1

B

3 " 1

1 p

1 Ip

mnij mmAV

m

s 3S

s ?s=

2 'i

i

8=1 Ip

1 3.S.

Ip

h I

iss"

Ip

ir

Sis

fi 1

si"

i P

11

rEBTiuzERS igg

Exports and Imports. — The following table shows what a large percentage of the phosphate rock produced in the United States is exported.

PUODCCTION AND EXPOBTATION OF pBOftPHATB RoCK IN THB UNITKD

States, 1904 to 1908, in Long Tonb

yu>

Pboddo-

Iss :

I,S74,U8

1.188.4U

These exports are sent to all parts of Europe, Germany being the largest consumer. The imports since 1904 have been as follows: —

Feetilucbs wportisd and knterbd fob Conbumption in the United Statkb, 1904-1908, in Long Tons

Yua

Guuro

ATiTira, Bom Dobt, Ckddi pHDOFIUTaS.

Totu,

ViLD.

(Juutity

Vilua

Quuitity

VtiM

QuMlity

ViJue

Ims : 1808 ;

37,137 6.7S8

tl .050,082

ijgo.MB

3,S2fl.S84

73o:eM

1M.12 M.09

t3.4U.Bia 2.MS.4S1

.004.403 4.681.134

IForU'a prodtidwn. — The table given below is of interest nce it brings out clearly the leading position of the United States as a producer of phosphates.

WoBU>'s Pboductiok of Phospbatb Rock, 1905-1907, bt Countries, IN Metric Tons

10Os

Quuititjr

VlllB

QiuDlity

Value

Vilue

Alcnta

ChriMxiu Idud (Stnita Bettis-

334,734

I.fi7S.34S

837B

I.813;4M (1.703,403

ESt

489108

79fl|o00 2.1l4.2fi2

4s;

1.873.000

3.304,400

8,B7M37

373,763

431,237

2,301J188

3,142.389

"wis

10.653.

' ValuB not ported.

iv,Coog[c

Kconomic Geology

KSFERBSCES Olf FERTILIZERS

General. 1. Adama, Amer. Inst. Min. Eners., Trans. XVIII : 649, 1890. (List of Commercial Phosphates.) 2. Clarke, U. 8. Qeol. Surv., Bull. 330 : 442, 1908. (General on composition and origin.) 3. Davidson, Bog. and Min. Jour,, LI II : 499. 1892. (Deep Sea Formations.) 4. Davidson, Amer. Inst. Min. Engrs., Tmna. XXI : 139, 1893. (United States and Canada.) 5. Matthew, N. Y. Acad. Sci., . XII : 108, 1893. (Nodules of Cambrian.) — Apatite : 6. Ells, Cm. Reo. Sci., VI : 213, 1895. (Canada.) 7. Newland, N. Y. State Museum. BuU. 102 : 50. 1906. (New York.) 8. Penrose, U. S. Geol. Surv.. Bull. 46, 1888. (General.) 8 a. Watson. Min. Res. Va. r 300, 1907 (Va). Phosphates : 9. Branner. Amer. Inst. Min. .. Trans. XXVI : 580, 1897. (Arkansas.) 10. Branner, and Newsom, Ark. Exper. Sta.. Bull, 74, 1902. (Arkansas. Many anafy- ses.) 11. Carpenter, N. Ca. Agric, Exper. Sta., BuU. 110, 1894. (North Carolina marls and phosphates.) 12. Eckel, U. S. Geol. Surv.. Bull. 213 : 424. 1903. (DecaturCounty. Tenn.) 13. Eldridge, Amer. Inst. Min. Engrs,. Trans. XXI : 196, 1893. (Florida.) 14. Hayes. U. 8. Geol. Surv.. 21st Ann. Kept., Ill : 473, 1901. 15. Also 17th Ann. Kept.. II : 513, 1896. 16. Hayes, 16th Ann. Rept., IV : 610, 1895. (Tennessee white phosphates.) 17. Iblseng. U. S. Oeol. Surr., 17th Ann. Kept.. III. (etd.) ; 955, 1896. (Pennsylvania.) 18. Johnson, Eng. and Min. Jour., LXXX : 204, 1905. (Tennessee. Treatment methods.) 19. MoCallie, Oa, Geol. Surv., Bull. 5-A, 1896. (Geoiiria.) 20. Penrose, U. S. Oeol. Surv.. BuU. 46, 1888. 21. Purdue, U. a Geol. Surv., Bull. 315 : 463, 1907. (Arkansas.) 22. Reese, Amer. Jour. Sci. iii, XLIII : 402. 1892. (South Carolina.) 23. Ruhm, Eng. and Min. Jour., LXXXIII : 522, 1907. (Tennessee. History and mining ) 23 a. SeUards. Fla. Geol. Surv., 2d Ann. Rept. : 235. 1909. (Florida.) 24. Smith. Ala. Geol. Surv.. Bull. 2 :9, 1892. (Alabama.) 25. Van Horn, U, S- Qeol. Surv.. BuU. 394 : 157, 1909. (United States deposits. and quantity available.) 25 a. Watson. Min, Res,. Va. : 302. 1907. (Va.) 26. Weeks and Ferrier, U. S. Geol. Surv,, BuU. 315 : 449, 1907. And Weeks. Ibid., BuU. 340:441, 1908. (Idaho. Wyoming. Utah.) Greensand : 27. Clark and Martin, Md. Oeol. Surv., Rept. on Eocene. 1901. (Maryland.) 28. Cook. Geol, of N. J„ 1868:261, 1868.

29. Parsons. U. S. Surv., Min. Res.. 1901 : 823, 1902. (Oeneml.)

30. Prather, Jour. Geol., XIII :509. 1905. (N. J. glauconite.) 30o. Watson. Min. Res. Va, : 396, 1907. Guano : 31. Penrose, V. S. Geol. Surv., Bull. 46 : 117, 1898. 32. PhUlips. Mines and Minerals, XXI : 440, 1901. (Texas Bat Guano.)

b,

Chapter Ex

Abrasives

Introductory. — Under thia beading are included those natural products which are employed for abraaive purposes. Since the noaia use of some is not for work of abrasion, they are dmply re- ferred to briefly in this chapter, the detailed description of them btig iven on another page. Brief reference will also be made to some artificial compounds which come into serious competition with the natural ones.

While some abrasive substances occur as constituents of vans, or in disseminated form, the great majority form a part of rocks of either sedimentary, igneous, or metamorphic origin, and of various degrees of consolidation. That they are widely distributed both geologically and geographically is shown in the following description of the individual groups, and the map (Fig. 79):-

Fia. 79. — Map showiiig distribution of abraaivss in United 8tatB.

202 Economic Oeologt

Millstones and Bohrstones' (2) are stones of iargp diameter used for grinding cereals, paint ores, cement rock, barite, fertilisers, etc. The American stones are ther coarse sandstone or quartz conglomerate, and are quarried at several points along the eastern side of the Appalachian Mountuns from New York to North Caro- lina. The most important beds are in the Shawanguuk Grit, wbi( is quarried in the Shaw&ngunk Mountains of eastern New Ych (20, 21). Some are also quarried in Pemisylvaoia, North Carolina, and Viinia (22). The material adapted to millstones is very limited in eirtent. Some of the stone is also cut into chasers, used for grinding quartz and feldspar. Owing to the use of improved grinding machinery the demand for millstones has fallen off greatly in recent years.

Many buhrstones are imported from France, Belgium, and Get- many. Those from the first two localities are hard, cellular rocks, consisting of a mixture of fine quartz particles and calcareous mate' rial; but the German buhrstone is basaltic lava.

Grindstones (2, 13). — These are made from sandstones of homo- geneous texture and sufficient cementing material to hold the quarts grains together, but not enough to so fill the pores as to make the rock wear smooth under use. Most of the grindstones produced in the United States are obtained from the Berea grit of Ohio (PI. XXIV, Fig. 1) and Michigan, certun layers of which are highly prized for this piupoae. West Virgima, Montana, and Missouri also contribute to the output.

Pulpstones, which have a diameter of 48 to 56 inches, a thickness of 16 to 26 inches, and a weight of 2300 to 4800 pounds, are a thicker variety of grindstone. They are used for grinding wood pulp in paper manufacture, and hence have to withstand continual ex- posing to hot water. On account of their superior quality, pulp- stones from Newcastle-upon-Tyne, England, supply most of the American demand; but it is probable that certain beds of tbe Ohio sandstones will be found suited for this purpose (2).

Whetstones, OUstones (2, 13, 17), etc. — The term " whetstone '' includes those stones used for sharpening tools, the term " oilstone " being often applied when oil is placed on tbe stone to prevent heat- ing and cling of the pores by grains of steel. The stones used for making whetstones are either sedimentary or metamorphic in character, and include sandstone, quartzite, mica schist, and novac-

PiTt XXIV

— Grindstone quany. Tippecanoe. Ohio. (J. H. Pratt, photo.)

b,

' OF rue

"JNIVERSiry

b,

Abrasives 203

iilit. The stone selected will naturally vary somewhat with the exact ti£e to which it is to be put, but even texture and compara- tively fine grain are essentials. A small amount of clayey matter adds to the fineness of grinding, but an excess lowers the abrauve efficiency of the stone. In the schists used, abrasive action is due to the grains of quartz, or sometimes garnet, which are embedded among the fine-grained scales of mica.

Rocks suitable for whetstone manufacture are found in many states, especially east of the Mismsfflppi (2, 13), but, on account of keen competition and hmited demand, only the better grades from the best-located de{>orats are employed. Most of the supply is therefore obtained from a few states, -especially Arkansas, Indiana, Ohio, New York, Vermont, and New Hampshire.

Among the whetstones quarried in the United States, the Hindo- stan or Orange stone of Indiana and the Deerhck oilstone of Ohio are much used for oilstones. Scythestones are made from schistose rock in Grafton County, New Hampshire, and Orleans County, Vermont.

At Pike Station, N. H. (PI. XXII, Fig. 2), the raw material quarried for scythestones is a fine-gruned, thinly laminated, micap ceous sandstone, whose quarts grains occur in definite layers, separ- ated by thin layers of mica flakes. Those portions of the rock in which the quartz grains are coarse or irregularly disposed, as well as argillaceous portions, are unfit for abrasive purposes.*

The novaculite quarried in Garland and Saline counties, Arkan- sas (17), represts a unique type, much prized for high-grade oilstones for sharpening small tools, and in demand both at home and abroad. It is an extremely fine grained sandstone made up of

IVi. so. North-aoutli section through Missouri and Statehoiue MountniiiB sliow- iag folded chatneter o( oovKulite aod OtM-bBaiing formatioiu of Arkaosas. a. BisfoTlc chert; b, Polk Craek shale; c. Missouri Mountaia slate; d. Aikaasas novKuIite; Stanley shale. {After Purdue, Aril. Oeol. Surv., 1909.}

finely fragmental quartz gnuns, visible under the microscope. The rock is chertlike in superficial appearance and has a conchoidal fracture. While the deposits, which are stratified, have a total thickness of over 500 feet, the commercial novaculite is found only in thin beds varying from a few inches to 15 feet in thickness. The Min. Res., U. S. Geol. Surv., 1008.

iv,Coog[c

201 Economic Gbologt

beds have a steep dip (PI. XXV and Fig. 80), and are cut by sev- eral series of joints, which greatly interfere with the extraction of lai blocks, and sometimes even with small ones. There are also Btructural irrularities and almost invisible flaws, so that much waste is caused in Quarrying the rock. The rock has been variously regarded as a metamorphosed chert, a mliceous silt, or a Eohcified limestone.

Pumice and Volcanic Ash. — The term " pumice," as used in the geolccal sense, refers to the spongy pieces of lava, whose peculiar texture is due to the rapid and violent escape of steam from the molten lava. It is put on the market either in lump form, or ground to powder, or in com- pressed cakes of the ground-up material. In the commercial sense the term " pumice " in- cludes volcanic ash (Fig. 81) as well aa true pumice.

Most of the pumice used in the United States is obttuned from the island of Lipari, north of Sicily. The stone, after being freed from the volcanic asb with which it is mixed, is sorted ac- cording to color, weight, andsize, before it is shipped to market. Depodts of volcanic ash are abundant in many western states, for example, in Nebraska (10), Utah (13), Montana (14), Oregon (12), Wyomii; (11), Colorado (15), etc., but owing to their inacces- ability these materials cannot compete with Lipari pumice, which is imported as ballast, and sells in its prepared form for 2 to cents per pound. The pumice produced in the United States comes from Harlan and Lincoln counties in Nebraska. The deposits must be very abundant in this state, as Barbour remarks that nearly the whole of it is overlain by pumice beds aa far east as Omaha.

Diatomaceoas Earth.* — This material has been used to some extent for abrasive purposes, either in the form of polishing powder or in scouring soap. Since it has many other and more important possible apphcations, it is described separately on a later page.

BometiaieB applied to Diatomaomut

b,

b,

bv

Abrasives 205

Tri|K>li. (See p. 290.) — Some of the Missouri tripoli is ground and sold as tripoli flour, whose value f.o.b. is S6-$7 per ton. Thia flour is employed as an abrasive for general polishing, burnishing, and buffing, as well as an ingredient of scouring soaps.

The so-called " silica " obtEuaed in Union County, lUincus, is similar to tripoli, and may have had the same orio.

Cr3r8tlline Quartz (2, 13). — Some of the vein quartz quarried in the United States, and also quartzite, is pulverized and used for abrasive purposes. Considerable quartz sand is employed by stone cutters as an abrave in sawing stone, and a small quantity ia utilized in making sandpaper. (See further, p. 274.)

Feldspar (13). — This also is used to a small extent for abrasive purposes, but since it has other and more important uses it is dis- cussed separately on p. 225.

Garnet (13, 16). — The garnet group includes several mineral Epecies which are essentially mlicates of alumina with iron or lime, magnesia, manganese, and chromium. They crystallize itt the iso- metric system, have a hardness of 6.5 to 7.5 and a specific gravity of 3.55 to 4.30. Their color is variable, but commonly a shade of red or brown. The two commonest species are Almandite IFeAl,(SiO0J and Groasularite [CaAl,(SiO0J.

Garnet is a common mineral in many metamorphic rocks, and thoi ordinarily a subordinate constituent of these, it may in some cases become the chief one. Its hardness, tcether with its ready cleavage and splintery fracture, make it a most valuable abrafflve for certain lines of work.

Though widely distributed, deposits of economic value are com- paratively scarce.

.Vem York (16). — The garnet industry is an important one in the Adirondack reon of New York, a steady production coming from Essex and Warren counties. The garnet is commonly as- sociated with an amphibolite which forms bands and lenses in the more acid country gneiss, and crystals ranging from an inch or less up to several feet in diameter are found. The garnet rock may represent a metamorphosed limestone. Other deposits have been exploited near Keeseville, etc.

Garnet deposits are known to occur in North Carolina, and have been worked from time to time, especially in Madison County. A Bttle has also been produced in New Hampshire.

Uses. — Garnet is used in the manufacture of garnet paper, a valuable abrave for leather and wood. It has also been

D,q,z.<ib,Coogle

Economic Geology

employed in polishing and grindii: brass, Attempts have been made to use it as a substitute for corundum in the manufacture of emery wheels, for, although softer, it possesses the advantage of havii a splintery fractm%, which prevents it from wearing smooth.

Corundum and EmoTj (3-9). — Corundum (AljO)) is, next to diamond, the hardest of the natural abrasives known, having a hardness of 9, but varying slightly from this.

Its fracture is irregular to conchoidal, and gves a good cutting surface, but the presence of parting planes decreases \ia value. A specific gravity of i helps to distinguish it from other lightwlored minerals found in the corundum refpons. Corundum shows a variable behavior when heated, some forms crumbling when ex- posed to a high temperature. Such kinds are worthless ica the manufacture of emery wheels, all of which must be fired in order to fuse the clay bond used in manufacture.

Nearly all corundum analyses show SiOi, FeiOg, and HgO, and it must be remembered that in analyses of commercial corundum the alumina percentage does not indicate the quantity of corundum present, as some of it may belong to other aluminous licates.

The following analyses represent selected rather than commercial

Analyses of Corundum

A],Q,

SiO.

Total

Haatines Co., ODt

Carundum HiU, N. Ca. . . . Laurel Creek Mine, Ga. . . . Ruby from India

98,79

9S.5S

Corundum may occur in masses, crystals, or irregular grains. It is found in both igneous and metamorphic rocks, as well as in alluvial deposits derived from them, although the last supply but little abrasive corundum.

Corundum forms a primary constituent (sometimes an importaat one) of feldspathic igneous rocks, both high and low in silica. It is found in granite, syenite, nephelite-syenite, and coarse pegma- tites. It is also known to occur in crystalline schists and meta- morphosed limestones.

Abrasives 207

A number of otiier minerals ma,j be assoeiated with it u follows (5): Auociated mineraU,

In gneiss and granite : Besides essentials, garnet magnetite, pyrite droon. rarely monazite and sodalite.

In peridotitea and basics ; Olivine, magnesian ampbibole, pyroxenes, I nrely plagiodase, while chromite and spinel are aocesaory primaries.

In contact zones : corundum, btotite, musoovite, garnet, staurolite, lounnaUne, rutUe, etc.

In regionally metamorphosed rooks: biotite, musoovite, amphibole, silli- manite, cyanite.

DirdnUion. — With the exception of a few localities in Mon- tana, two in Colorado, one in Idaho, and one or two in California, all the known United States occurrences are confined to the Appalachian reon, the commercially valuable depoats for abrasive purposes being found in a belt of basic magneaan rocks, extending from Massachusetts to Al- abama. These rocks reach their greatest development in

Orth Carolina (5) Fta. 82. — Sectbn showing occurrence of corundum and Georizia (3) tuound border of dunite mAsa. {AJter Pratt, U.S.

Most of the coniQ-

dum is found there, in peridotite, especially near its contact with

the surrounding gneiss.

It is believed that the corundum which was one of the earliest minerals to crystalhze out from the cooling peridotite was concen- trated around the borders of the mass by convection currents. This zone of corundum sent off torques toward the interior of the mass, uid now that erosion has removed the main zone of corundum, these tongues remain as apparently separate veins within the peri- dotite (Fig. 82).

Id North Carolina (5) the greatest development of corundum is in a belt in Macon County. Borne is also found east of the Blue Ridge. Georgia (3) contains scattered deposits, the most important being at Pine Mountain, Rabun County. Some mining has been done in South Carolina uid Geor-

t,

208 Economic Geoloqt

gia, and deposits in gameliferotis mioa Bohists out by gnuiite ham been recorded from Putriok County, Viisinia (9).

Emery. — This is a mechanical mixture of corundum, magnetite or hematite, and Bometimes spinel. Peekakill, New York (6-8), and Chester, Massachusetts, are the most important sources of pro- duction.

At the former locality, the deposits whioh lie southeast of the town, and were first opened for iron ore, ooour along the oontact of baaie intnisioiu belonging to the gabbro series. The emery deposits, aooording to Q. H. Williams, are simply segregations of the baaia ondes in the norite, and Iht ore is made up of corundum, magnetite, and hercynite (an irou'-aluniinum- spinel). In some specimens the corundum forms over 50 per cent of th mass, while in others the hercynite may make up nearly 100 per oent of it The Peekskill material ia very serviceable when made into wheels with t bond. The following are analyses of it.

lea

7.M tr.

Mjb

~ii

I. Am. Chemist, 1874, 4: 321. II and III. A. J. a, March, 18S7, p. 197.

At Chester, Massachusetts (13) , the emery occurs in a local widen- ii of a belt of amphibolite schists, and forms a vein traceable for nearly five miles. The emery-bearing vein varies in width from a few feet up to 10 or 12 feet, while the emery streak in it averages about 6 feet, it being bordered on both sidea by chlorite seams. The emery is in pockets, but these are traceable by a small vein of chlorite.

After mining, both corundum and emery need to be cleaned ami concentrated by special mechanical processes. The chief use of this material is an abrasive, and for this purpose it is used in tbe form of wheels and blocks, emery paper, and jrawder.

Practically all the corundum and emery used in the United States is imported. The emery is imported crude as ballast from Turkey and Greece. Corundum ia imported monly from Canad* in pulverized form.

Diamonds. — Black diamonds, known as borta and carbonari which are of no value for gem purposes, are much sought after

b,

Abrasives

use in drilling, set in the end of the cylindrical drill tube. They are often of rounded form, translucent to opaque, and lack the cleavage possessed by the gem diamonds. Brazil, Africa, Borneo and India serve as sources of supply, but the first-named country is said to yield the best ones. The ordinary sizes for drills weigh from i to 1 carat, but in special cases pieces weighing 4 to 6 carats are used. The price ranges from t50 to $75 per carat.

Diamond powder is also used as an abrasive for cutting other diamonds, gems, glass, and hard materials which cannot be cut by softer and cheaper substances.

Artificial Abradvas. — Several artificial abraaves are now much manufactured. Prominent among these is carborundum, which is produced by fufdon in the electric furnace of a mixture of silica, coke, and sawdust; the reaction being SiOi 4- 3 C CSi + 2 CO. The sawdust is added to give porosity to the mixture.

Artificial corundum or alundum, whose introduction is of more recent date, is made by fusing bauxite in the electric furnace. It is put on the market in the form of wheels, while carborundum is dther made into wheels or sold in powdered form.

Production of AbrasiTes. — The value of the abrauves produced in the United States during the last five years, ttther with the imports and artifidal abrasives, was as follows: —

Valcb or All Abrasivi! Matbbialb Conbitmkd i

Tateb, 1904 To 1908

N THE UnTPBD

lOM

tiss.esA

Us

Is

148,096

Iz68.D70

72!l08

157:000

6m!023

tunas*

53fl.oes

AbllBir* IridtpM Mid quMta . .

8,745

1,4Z7.Ss0 701,400

au32i

11.473,383

11.680,737

tapon.

830,930 M7,804

g!

t2.73t.001

S3,ie0.43S

13.403,123

KBPBRBIICBS OH ABRASIVBa

Qbhbbai, : 1. EisK, Oa. 0ol. Surv., BuU. 2 : 119, 1894. 2. Pratt, U. B. Gol. Surv., Min. Res., 1900 : 787, 1901. — Conindam and EmeT? : 3. King, G. Gool. Surv., BuU. 2 : 73, 1894. (Georgia.) 4. Pratt, U. 8. 0ol. Surv., Bull. 269, 1906. (United States.) 5. Pratt and

0 ECONOMIC OBOLOaT

liBwifl, M. Ca. Surv., 1, 1905. (Conmdum, N. Ca.) 6. Maeniu, N. Y. 8tat Qeologiet, 23d Ann. Kept. : 163, 1904. (N. Y. emery.) 7. waiiama, G. H., Amer. Jour. Soi.. iii, XXXIII ; 194, 1887. (N. Y. emery.) 8. Nevius, N. Y. State Mub., 53d Kept., 1901. (New Yorii emery.) 9. Watson, Min. Ree. Va., 1907. (Va. oonmdum.) 9 a. Btoane, S. Co. 0ol. Surv., Bfse. IV, BuU. 2 : ISO, 1908. (8. Ca. eoruit- dum.) Diatomacaons earth : See ref erenoee on p. 224. — Pumice ul volcanic aah : 10. Barbour, Neb. Qeol. Surv., I : 214, 1903. 11. Dai- ton and Siebonthal, U. S. Gool. Surv., BuU. 364 : 65, 1907. (Wyoming.) 12. DQlOT, U. 8. Geol. Surv., Prof. Pap. 3 : 40, 1902. (Oreeon.) 13. Menill, O. P., Non-metallie Minerals, New York, 1904. 14. Rowe, BuU. Univ. MoDt., No. 17, Qeol. Ser. No. 1, 1894. (Montana.) 15. Woolaey, U. S. Qeol. Surv., Bull. 285 : 476, 1906. (Colorado.)— Gii- net : 16. Newland. N. Y. State Mub., Bull. 102 : 70, 1906. (New York.) Also Ref. 13. Whetstonee, OrindMraeB, and HUlstonee ; 17. Gri- wold. Ark. Geol. Surv., Ann. Rept., 1890, III, 1892. (Ark. opvaculite.)

18. Grimsley, W. Va. Geol. Surv., IV : 375, 1900. (Grindstones.)

19. Kindle, Ind. Dept. 0ol. and Nat. Ree., 20th Ann. Rept. : 329, 1896. (Indiana.) 20. Naaon, N. Y. State Geol., 13th Ann. Rept., 1 : 373, 1894. (N.Y.) 21. Newland, N. Y. State Museum, BuU. 102: 110, 1906. (N. Y.) 22. Watson, Min. Res. Va. : 401, 1907. (Grind- Btones.) — Tripoli: See referenoes, p, 291.

bv

Chapter X

Minor Minerals. Asbestos

Asbestos Hioerals (1, 13). — Two different mineralB axe mined and Bold under this name, one a variety of ampMbole, the other a fibrous variety of serpentine, known as chrysotile.

The amphibole asbestos forms pockets or masses (mass fiber) or veins in gneissic or schistose rocks, and is of a whit, gray, or greeniah-white color. The veins may carry either dip fber, whose threads he parallel to the vein walls, or cross fiber, which extends across the vein. The following is an analysis of that found in Elzevir township, Hastings County, Ontario, Canada (1); SiOt, 61.82; MgO, 23.98; FeO, 6.55; CaO, 1.63; AlA, 1.12; H,0, 5.45.

The chrysotile (HMgiiO*) usually occurs as cross fiber, more rarely slip fiber, in veins of varying width in serpentine iDck, its color being greenish white, green, or yellow, and its luster silky. Its hardness is 3 to 3.5 and its specific gravity 2.2 to 2.3. The following analyses are ven by Cirkel (1).

Ui

SiO,

Meo

Aw.

I. luUon flber. BroughtOD. Qubeo.

II. Chrysotile. Tbetford, Quebec. III. Chi7aotil,

The difference in compodtion between the amphibole Mid chryso- tile are quite noUceable.

In both forms of asbestos the fibers are easily separated, but the amphibole variety often contuns gritty impurities which are diflB- ciilt to remove. The fibers of chrysotile are shorter than those of the amphibole asbestos, rarely exceeding 2i inches in length, but they have greater strength and are less brittle. Since the amphi- bole asbestos can be mined more easily, it is cheaper than the chry 211 OOgIc

212 ECONOMIC GEOLOaT

sotile variety, which, nevertheless, is in greater demand becauae more coastaot in character and suited to more uses. The two varieties are equal in value as non-conductors of heat,

Distributioa in United States. — The ancient crystalline rocks in which the famous Quebec de- posits occur, extend Bout hwes tward through the eastern states, as far as Ala- bama, and while a number of small de- posits of asbestos are knonn, yet nowhere are there any large ones, moreover, most of the deports are of the amphibole type. Vermont (8, 9).— ' The only chrysotile deposit worked in the eastern belt is in Lamoille and Orleans counties, Vermont, where the material is found occupying a rather hmited area In a large serpentine area (9). Two types of chrysotile are found, one form- ing branching veins aimilar in character and quality to the Canadian fiber, the other, of inferior quality, occurring as short fibers on slickenmdcd surfaces. In 1908 a mill was erected near Lowell, Vermont, for separatii the fiber.

Georgia (2). — Sails Mountain, Geora, has been the main source of supply of asbestos in the United States for over a dozen years, the material being of the amphibole type. The asbestos occurs as masses of fibrous amphibofite (mass fiber) in gneiss, the largest discovered body being about 75 feet long, and about 50 feet wide near the middle. The amphibolJte may be an altered eruptive.

Th fibers, which range in length from 1 inches down to a fraction of ui inch, may form over 90 per cent of the original rock. Thej contain a little i talc and lime carbonate aa well as numeroUB grains of pyrite luid magnetite (2). Weathering softens the mass without deetroying its fibrous structure, but the Btrengtb is somewhat reduced. The material is milled at Soils Mountain.

(PAolo. bu ,

Iv,

b,

Minor Minerai

Virginia (15). — Amphibole asbestos occurs in a number of the Piedmont coimties of Vbma, but Bedford has been the main producer. The asbestos is found in more or less well defined veins in granitic or schistose rock, the veins varying from 8 to 50 inches in width.

Fio. 84. — Geologio imp of Vennont aabetoa ares. (AJler Manta-g, Qtol. Soe. Amtr., BuU. XVI, 1905.)

AxALTBxa OF ViHOiNiA, Oeoroia, and VERMOifr Asbestos

SiO,

AliOi

FeO

C0

MgO

lei

1. Albmarie Co., Va. {Ret. 15). I III. SkUfl Mountain, Georgia (Ref. 10}. mont. (Rrf. 9).

. Roanoke Co., V. (Rf. 15). IV. Cross fiber duTsotile, Ver-

b,

214 Economic Geology

Wealern Oecwrencei. Chiysotile in serpentine aesoaiated with gmato liaa been fouad in the Casper region, Wyoming (3), and some has been used in Denver for pipe covering, but a more remarkable oeGUirenoe is that discovered in the Grand CaSon of the Colorado, 20 milee east of the Grand Cafion station on the Santa Fe Railway (4). Here the asbestos forms veins in serpentine layers and nodules which occur in an Algonldan Umestone, which in turn is covered by a diabase. It is suggested that the chrysotile is derived from pyroxene in the limeetone. If this is true it forms a, unique type of deposit. The locality is at present veiy inacoeesible.

Quebec, Canada. — The mun source of the world's supply is ob- tained from southern Quebec, aod aa it is the best known occurrence it may be properly referred to here.

The geoloc relations (Elg. 85) of the serpentines and associated rocks are imperfectly known, but it appears certtun that they rep-

L,;-Z-lv.C00g[c

MINOR MINBRAIi

resent an inbniEdve series, the latest of which cut sedimentary beds of middle Ordovician age. The rocks of the asbestos belt are peridotite, generally much altered to serpentine; pyroxenite, frequently altered to talc; hornblende granite; diabase; and a breccia, in part of volcanic material.

The serpentine ia an alteration product of peridotite, it and the pyroxenite being of laccolithic character, while the granite, which forms dikes and isolated masses, may be a final and extremely add product of differentiation of the general magma of which the basic equivalent is the olivine-rich portion of the peridotite.

Fw.86.-

a peridotite, (Afttr Dmaer,

The asbestos is found forming veins in the serpentine, the width of these varying from a mere line to two or three inches. It devel- oped probably first in joint planes, and afterwards in other cracks, forming thus a network (Fig. 86). An interesting and suggestive feature is the band of pure serpentine on either side of the vein (f. 86), the ratio of the asbestos vein to the entire band of ser- pentine and asbestos 1 : 6.6. The veins are formed by the erowth of minute crystals of chrysotile, perpendicular to the walls, and there is in most cases a central parting marked by a film of chromite or magnetite. The principal mines are near Thetford

216 Economic Geology

Mines (PI. XXVI), Black Lake, East Broughton, and Danville. The first named locality is of great importance.

The asbestos milling rock forms from 30 to 60 per cent of the quantity quarried, and 6 to 10 per cent of this is fib.

There has been some difficulty in explaining satisfactorily the orin of the chrysotile veins in serpentine, for we have here two quite different forms of the same mineral. Pratt, in attempting to explain the origin of the vein fiUing, believes that the fissures represent contraction cracks formed around the of the peri- dotite mass while cooling, and which were then filled by aqueous solutions from which the chrysotile crystallized. Merrill, on the other hand, believes the fissures to have been caused by shrinkage incident to a partial dehydration of the rocks and subsequent filling by crystallization extending from the walls inward (11, S). As suggested by Kemp, a loss of siUca may also have produced some shrinkage.

Cirkel (1), believes the vein crevices to have been formed by partial dehydration, and in part by fracturing resulting from the intrusion of the granite.

All investigators agree on the wall rock being the source of the chrysotile. Dresser (5), while admitting the filling of the veins by infiltration, suggests that they have been enlarged by replacement of the walls. But the Berp>entinization of the latter precedes the formation of the asbestos.

Uses of Asbestos. — The usefulness of asbestos depends mainly on the flexibihty of its fibers, and fibrous structure, and to a less extent on its low conduction of heat and electricity, and on its moderate refractoriness. Asbestos is used in fire-proof paints, boiler covering, for packing in fire-proof safes, and for electric in- sulation where some heat resistance is necessary. Chrysotile is also used in making fire-proof rope, felt, tubes, cloth, boards, blocks, etc. AabesHc is a name given to short-fibred chrysotile mixed with serpentine. A8&eftn is a pigment of which asbestos is an important ingredient, and serves to hold up other heavier pig* ments. Asbestos is also used for filtering in chemical work, and for this purpose the amphibole asbestos is better adapted. Many patented mixtures of asbestos and other materials, such as Portland cement, etc., are now used for making such products as asbestos wood, asbestos slate, asbestolith, etc.

Production of Asbestos. — The United States is the largest pro- ' ducer of manufactured asbestos products, but less than one per cent

I z .IV, '

Minor Minerai 217

af the raw material is mined ia this country. Canada ia the main source of supply, and will no doubt continue so for a long time. The production and imports from 1904 to 1908 were as follows: —

ViLD. or iMMsn

(.horttcSi)

Vidua

S=T

"tA"

Total

im

s

Oss

28,565

ti.see

19,624

i27;h8

The range in price for the various grades of Canadian asbestos is M follows : —

Okadb Puce rat Sbobt Ton

So. 1 crude ftsboatoa $275-350

No. 2 orade asbestoa 150-250

Asbestos (aooording to gndiug) 25-150

Rnea (acoordiag to gradlDg) 10- 25

Asbestic (a b-produot) averagiiig ia 1907 . . . Less than SI

Rbexrsrcbs Oh Asbestos

1. Cirkel, Can. Dept. Inter., Mines Branch, 1905. (Canada ooourrense and usee.) 2. DiUer, U. S. Geol. Surv., Min. Rea., 1907 : 717, 1909. (Oeaiia.) 3. DiUer, Ibid. : 720, 1909. (Wyoming.) 4. Diller, Ibid. : 720, 1909. (Arizona.) 5. Dresser, Bcon. Oeol., IV : 130, 1909. (Qaebeo.) 6. Jones, Asbestos and Aabestic : Their PropertieB. Oc- ooireocea, and Use (London), 1897. 7. Kemp, U. 8. Geol. Surv., Min. Rea., 1900 : 862, 1901. (Vt.) 8. Maraters, Rept. State OeoloKiat Vermont, 1903-1904 : 86. 1004. (Vermont.) 9. MarstorB, Geol. Soo. Amer., Bull. XVI : 419, 1905. 10. Merrill, National Museum Guide to Study of Non-metallio Minerals, 296, 1901. (GenenJ.) U. Mt- riB. Gaol. SoQ. Amer., BuU. XVI r 416, 1905. (Origin.) 12. Pratt, Mineral Census, 1902, Report on Mines and Quarries : 073, 1904. 13. Merrill, Pro©. U. 8. Nat. Mus., XVIII : 281. (Asbestos and aibestifonn minerab.) 14. Pratt, Min. World, July 8, 1905. (Ariz.) 15. Watson, Min. Rea. Va. : 285, 1907.

Barite

PioperdeB and Occurrence. — Barite, the sulphate of barium, contains when pure, BaO 65.7 per cent, and SOa 34.3 per cent. Its specific gravity is 4.3 to 4.6 and its hardness 2.5 to 3.5. It is com-

; C'.OOgIC

218 Economic Geology

monly white, opaque to translucent, and crystalline, while the texture is granular, fibrouB, or more rarely earthy. The conunon impurities are silica, lime, magnesia, ferric oxide, and alumina, but commercial grades contain usually over 95 per cent BaSO. Barite occurs commonly as a gangue mineral in some metallif- erous veins, as veins, in schists, sandstones, and limestones or sometimes as replacements of the last. In many localities, however, the limestone has weathered down to residual clay, the barite forming nodular coa- centrations in the same. De- posits of commercial value are known in Missouri, Virginia,

Fio. 87. — Barite vdm b Potosi dolomite. Kentucky, Tennessee, and other

aoutbeaateni Mmouri. {After Buck- Irvi u j l c

Uv, Afo. Bur. Oeoi. and Mina, ix.) States. Ut these named the hist is the most important producer. Missouri (3). — Barite forms scattered deports in Washington and adjacent counties, though many of the occurrences are clus- tered around Mineral Point, Washington County. The material is obtned from the Potosi (Ordovician) hmestones, in which it occurs as replacement veins (Fig. 87) mixed with lead, or in residual

clay with chert and drusy quartz, the whole fomung a sheet-like deposit, at no great depth {Ilg. 88).

ViTginia (11). — Barite occurs in many parts of the state (Fig. 89), but the industry has been confined mmnly to a few locahties.

Minor Minera.1 219

The barite deports may be grouped into three areas, as foUon: 1. Deposits of the Triasdc red shale-Baadstone series, in which the barite is associated with red shales and impure limestones. It has been depoated from solution in fractures in the red shales, or

more rarely as thiu, tabular replacement masses in the Umeatone. 2. Deposits of the crystalline metamorphic area, probably for the most'part of pre-Cambrian age, and iu which the barite occurs either aa irregular lenses of 100-200 feet di- ameter in lime- stone, or as nodules in a, reddual lime- stone-schist clay (Fig. 90). In one locality the barite fills a vein in edU- ceoua schists, re- mote from calcare- ous rocks. 3. The mountain region of

BOUthwestem Vir- Fio. 90. — Weal secUon in Bennett Barite Mine, Ktt- fitia Here the sylvania County, Va. {Afler WaUon, Min. Ra.

b.rite, which is '""

associated with the Shenandoah limestone (Cambro-Ordovician),

is found either as lumps in the residual clay, or in the fresh rock.

220 Economic Geology

The frequeDt aasociation of the barite with limestone in all the areas is quite noticeable.

The second ron is the most important producer.

Wataon believes that the soiu-ce of the barite is the rocks in viiich the depoata are now found. Thus in the Valley reon it was no doubt derived from the Shenandoah limestone, while in the IMed- mont area it may have come either from the crystalline Bchiata or limestone mass. That of the Thaxton area was doubtless obtiuned trom the alicates of the granite. The liberation and removal of the barium in solution is considered to have been accomplished by shallow circulations. The barite is always crystalline in texture.

OeoTffia (a). — Baiit depoaita are known to occur new CarteraviDe, 0&., oaaooiated with tbe Beaver (Cambrian) limestone and Weianer (Cambritui} quartzite (Fig. 91). It is thought that the barits wag originally depodtd by the raplacement of certain beds of the shaly limestone overlying tlM quartdte, bat it now forma nodules and maaaoB scat- tered through a reddual day, and mixed with some quartzite fragments.

Fio. ei.-8ketchrtioDwiirdtion.ofb- aidd iu oonoentrating the rite and limooito to uoderlying formationii near workable Carteravaie, Gs. {After Haya and PhaUn, V . S. depowtB- Gi>i. Sun., Bull. 340.) Otker Oeewrtnett. —

The barite of Gaston County, North Carolina, occurs as lenticular fissure fllliogs in schist, associated with quartz, galena, sphalerite, and pyromorphite, while that of Sonth Carolina is in similar rocks; that in Tennessee is in residual clay overlying the Knox dolomite (Cambro-Ordovioian), and that found in Central Kentucky is in veins in the Trenton (Ordovician) and mbied with galena, fluorite, caloite, and sphalerite.

Origin of Barite. — Sulphate of barium is but slightly soluble, but is perceptibly decomposed by a dilute solution of carbonated alkali. If present in one of the silicates (feldspar) in granite it mit be decomposed by sulphates of the alkahes, lime sulphate, or ma nesium sulphate, resultii in precipitation of barium sulphate.

Buckley (3) believes that the Missoiu-i barite was posbly de- rived from solutions of the bicarbonate, precipitated with alkaline sulphates.

iv,Coog[c

Minor Minerals

Wataon (11) suggested that in the case of the Vtrnia barite it was probably taken into Bolution as the soluble bicarbonate, and precipitated under favorable conditions as the insoluble sulphate. Laboratory experiments by Dickson (4) with solutions of barium carbonate on selenite crystals and pure anhydrite in presence of C0(, and on pyrite crystals in presence of an oxidizing agent, water, caused precipitation of barium sulphate in each case.

UaeB. — Barite, which is pulverized and sometimes purified by washing, is used in the manufacture of paper, for coating canvas ham sacks, in pottery glases, and in the manufacture of barium hydroxide. Its main use perhaps is in white pigments to mix with white lead, zinc white, or a combination of both of these pigments. Although formerly regarded as an adulterant of white pigments, it is DOW considered to make the mixture more permanent, less likely to be attacked by acids, and freer from discoloration. Lithophone paint is a mixture of barium sulphate (68 per cent), zinc oxide (7,28 per cent), and sine sulphide (24.85 per cent).

Barite ia usually prepared for the market by band sortii, crush- ing, washing or jing, bleaching, and grindii. Minerals like galena, quartz, calcite, and limonite are common impurities and require separation.

Since the barite depodts are usually small and pockety, the mill mmt he located to permit its drawing on numerous and changing sources of supply.

Production of Barite. — The production of barite for several years is ven below. The decrease in 1908 was due to the bumness depreasion of 1907.

Pboduction of Cbuok Babitb in the TTnited Statbs, 1906-1908, BT States, in Short Tons

18M

leoT

Quan-

Ayer

Urn

ssr

per

loo

w

2sU

I03.Tb

8,7B2 4S.33e

w!24

i.a;

tiflz.4sg 18,86;

it;

5.23;

8.B18 U.M5

S31.S04

Tm

tieo,e37

89,821

Im1.777

*3.2a

34.B1S

, '"rindM, isoa. m. OHtcia, Nort

QHtcb, North Cunliaa. wid Virslnik.

forth CuDliu; 1907. OaonH* Mid Kuitiuky;

iv,Coog[c

Economic Geology

Imports. — The imports of barium compounds for 1906 to 1 were as follows: —

VaiiTtb of tbe Imports of Basiuh Compounds, 1908-1906

,..

t55,40£

Is

'is

Buium ehloride

Blue &u, or utifidal luuiiim lulpluto

T3.I31

319.114

Referbhces 0

Barttb

1. Anon.. Mtn. Indus., XIV : 44, 1906. (Tenn.) 2. Burch&nl, U. 8. Geol. Surv., Min. Res., 1906 : 1111, 1907. (Mo.) 3. Buckley, Mo. Bur. Oeol. and Mines., IX, Pt. I : 238. (Mo). 4. Dickson, Sch. of M. QuBJ-t., XXIII ;36fl. (Conc'n. in limeBtone.) 5. Fay, Eng. and Min. Jour., LXXXVII : 137, 1909. (Tenn.) 6. Hayes and Phaleo. U. 8. Geol. Surv- Bull. 340 : 458, 1908. (Ga.) 7. Higgins. Eng. and Min. Jour., LXXIX : 465, 1905. (Bleaching barite.) 8. MiUer, Ky. Geol. Surv., Bull. 2 : 24, 1905. (Ky.) 9. Pratt, N. Ca. Geol. Sun., Boon. Pap. 6:62, 1902. (N.Ca.) 9 a. Steel, Amer. Inst. Min. Engrs.. BuU. 38 : 85. 1910. (Mo.) 10. Sto8e,U.8.Geol.Surv.,BuU.225 :515. 1904. (Pa.) 11. Watson, Amer. Inst. Min. Engrs., Trans. XXXVIII: 710, 1907. (Va.)

Diatomaceous Earth

PropertieB and Occurrence (1,8). — This material when pure is made up of the siliceous tests of diatoms (Fig. 92). Chemically it is a variety of opal. It re- sembles chalk or clay in appear- ance, but is very much lighter than either of these, and can also be distinguished from the former substance by the fact that it does not effervesce with acid. A microscopic examina- tion serves to identify it at once. Diatomaceous earth is commonly white or light gray in color, but Fm.92.-DUtomac>usearthfromLompoo. '"y brownish, dark gray, or CaUi. {Calif. Slate Min. Bur., BuU. 3s.) evcn black, dufl to the presence . f,

Minor Minekals

of organic matter. It 19 exceedingly porous. If pure, it ahould show little else than dlica and water on analysis, but most earths show at least small amounts of other substances, and some eontun a large amount of clayey impurities (aee analyds VI below).

The following analyses represent the composition of a number of American earths : —

Analtsbs

DF DlATOUACEOCS EaRTH

BiO, . . .

Ai=0,

Pe,0.

—

MgO.

tr.

tr.

—

—

Alkaliea

—

3,14

—

TiO, .

—

—

—

—

—

Ign. loss

—

I. Poroeliun diatomaeeous sbale, Point Sal, Santa Barbara Co., CUf. II. Soft shale, Orcutt, Santa Barbara Co., Caiif. III. Monterey, Sinta Barbara Co., Calif. IV. Iike Uinbagc. N. H. V. Pope's Creek, Md. VI. Wilmot, Virginia; very clayey. VII. Richmond, Virginia. VIII. Herkimer, N. Y.

Distribution in the United States. — Diatomaeeous earth occurs as deposits of comparatively small extent in the bottoms of ponds, lakes, and swamps, sometimes mixed with oianic matter, or it may form bedded deposits of marine orin and showii at times great extent as well as thickness. A few localities may be mentioned.

C<Uifomia (1, 2, 4). — Important deposits of diatomaeeous earth are known to occur at a number of points in the Coast Raises of CalifOTnia, but the most important, perhaps, are those found in northern Santa Barbara County. There it occurs mainly in the Monterey (Middle Miocene) and in the lower part of the Fernando (Upper Miocene) formations.

The depodts range from those of high purity, through impure shaly beds, to flinty deposits. The earth is found interbedded with volcanic ash at some localities (south of Lompoc), and with limestones at others. The thickness of the diatom deposits is often remarkable, being 2400 feet south of Harris, and 4700 feet between the Santa Ynez and Los Alamos valleys.

224 ECONOMIC aEOLOQY

New York (3, 5, 6). — Although diatomaceouH earth is known to occur at several localities, the only one recently worked is near Hinckley, Herkimer County, where it forms a bed 2 to 30 feet in White Head Lake. It is purified by washing and pressed into cakes.

Virginia (8). — In the Atlantic Coastal Plain, deposits of diatomaceoiu ! earth are not unoonunon in the Miocene (Tertiar7) formations, and those around Richmond have long been known. Along the Rappahannock River, especially below Wilmot, there are lone exiiosureB, the bliUfs of the material standing out prominently in the sunlight.

Marylattd. — Beds of diatomaoeous earth occur at the base of the Calvert (Tertiary) formation, deposits being known in Anne Aiundel, Calvert, and Charles counties. Few of them are worked, although some attain a thickness of at least 25 or 30 feet.

Otker Stales. — Conneotiout, Massachusetts, are also prodnoers, but the deposits are of limited extent Other oocurreuoes are noted on the map. Fig. 79.

Uses. — Diatomaceous earth, on account of its porous character, was formerly used as an absorbent of nitroglycerine in dynamite, but little or none appears to be now employed for this purpose in the United States. It can be used for polishing powders, and as a nonconductor of heat it has been occaooally utilized for steam boiler backing, for wrapping steam pipes, and for fireproof cement. Mixed with clay, or even alone, it can be used for making porous partition brick or tile. Some of the California material can be cut into any desired shape, and used as a filter stone, or even for build- it piu-poses.

In Europe, especially in Germany, it has of late years found extended application. It has been used in the preparation of arti- ficial fertilizers, especially in the absorption of liquid manures, in the manufacture of water glass, of various cements, of glazing for tiles, of artificial stone, of ultramarine and various pigments, of aniline and alizarine colors, of paper, sealing wax, fireworks, gutta-percha objects, Swedish matches, solidified bromine, scouring powders, papier-macb, and a variety of other articles. There is said to be a large and steadily growing demand for it.

The production is given under Abraves, where it is included with Tripoli.

REPEREHCES OH DIATOHACBOUS EARTd

1. Arnold and Anderson, U. 8. Oeol. Surv., Bull. 315 : 438, 1907. (Csli- foniia.) 2. Aubury, CaJif. State, Min. Bur.. Bull. 38. 3. Cox, Tnto- N. Y. Acad. Sci., XIII : 98, 1893. (New York.)' 4. FtobKilo;

Minor Minkrals 225

U. 8. Geol. AtlM Folio, 101 : 14, 1904. {California.) 5. MerriU. N. State Mub., Bull. 15: 555. 6. Newland, N. Y. 8tat Mus., BuU. 102 : 67, 1906. (New York.) 7. Phalen, U. 8. Qeol. Surv., Min. Res., I90S. 8. Ries, Va. GeoL Surv., Bull. II : 143, 1906. (ViiKinia.)

Feldspar

Properties and Occurreace. — The feldspar group includes several species, all licates of alumina, with one or more of the bases — potash, soda, and lime. These species may be divided into two groups, viz. the potasb-aoda feldspars, and the lime-soda feld- spars, a division which is not without practical value, dnce the two groups differ somewhat in their fusibility and mineral associates.

Orthoclase and microclioe, whose compotion is expressed by tbe formula KAlSisOa, are the chief representatives of the first group. Expressed in percentages their compoation is SiOi, 64.7 per cent; 01tA, 18.4 per cent; K, 16.9 per cent. Soda may partly or wholly replace tbe potash. If the latter occurs, &northo> clase results. Potash-soda feldspars are usually pinkish to nearly wlute, but some, as that mined in Ontario, is a distinct reddish color. Nevertheless, even the strongly colored ones may calcine to a pure white color, and show a sufficiently low iron oxide content to permit their use in pottery manufacture.

The lime-soda feldspars, or ptaoclases, present a series of com- pounds ranng from the soda feldspar, albite, through soda-lime feldspars, to the pure lime spar, anorthite, at tbe other end.

Albite, whose formula is JJaAlSijOg, has SiO, 68.7 per cent; AlA, 19.5 per cent; Na,0, 11.8 percent. Anortbite, CaAli,0), has SiO,, 43.2 per cent; MjOt, 36.7 per cent; CaO, 20.1 per cent.

All feldspars in meltii pass gradually from a solid condition to that of a very stiff fluid (5), complete fusion occurring usually about Seger cone 9 (1310° C). A mixture of soda and potash spar seems to have a slightly lower point, while the lime spar, anorthite, does not melt until 1532° C. (6).

Most of the feldspar quarried in the United States is the potash- soda type, but in some localities the soda spar, albite, may be present. It ploclase is present in feldspar used for pottery, it is generally alWte.

Feldspars are widely distributed in many igneous and metamor- phic rocks, but in most cases they are so intimately mixed with other minerals, that their extraction is not commercially practi- cable, and it is only when found in pegmatites that they are worked

Economic Geology

Of these rocks, two types are recognizable, viz. the granite peg- matites, which are very coarse-grained and carry quartz, potash feldspar, muscovite, biotite, tourmaline, etc., and the soda pegma- tites, which consist mainly of albite with a little hornblende. Most of the deposits worked in the United States belong to the first tj'pe, only a few from southeastern Pennsylvania and northeastern Mar}'- land falUng in the second class.

It may be mentioned here that all pegmatite deposits are not worked for their feldspar contents, some serving as sources of other minerab, such as mica, quartz, or gems. Thrar value as spar de- posits depends on the quantity and purity of the material present.

The pottery trade demands that the spar be free from iron-bearing minerals. Muscovite is also undesirable on account of the diffi- culty encountered in grinding it, while the permissible limits for quartz rai from 5 to 20 per cent.

In quarrying or mining some sorting is often necessary, and in those states lying south of the glaciated area the depoat may be capped with residual clay.

Distribution of Feldspar in th United States. — In the United States feldspar quarries are operated in New York, Connecticut, Mune, Pennsylvania, and Maryland. The general form of deposit is similar in all the states, but those worked in Pennsylvania aud Maryland are albite spar, while the others are potash spar. The wall rock is gneiss or schist.

The foilowii table gives the composition of feldspar from a number of localities : —

Analtbbs op Feldspabs

SiO, . . . .

65.%

Al,Oa

18.0(1

PeiOj

—

tr.

CaO .

tr.

Doae

none

MgO.

—

none

none

none

tr.

Krf) .

NasO

—

Loss on igmtion

—

Total

icrocline (eldsptv, Sauth Qlutat

BBtcbelhrville. N. Y.

llMtonbuiy. Co . PiDk ortboclu

crocliue, 2. Norweciim fddipu'. u n Bedford. Ont. Muoh imd by An

_i„Coog[c

Minor Minerai

Analyse

B OF Fbldbpabb

la

Is

SiO. . . . .

AliO. .

FerfJ. .

tr.

tr.

none

none

K,0 . .

NmO. .

H,0 . .

.3(1

LoBsaaigmtioa

—

—

—

—

—

Total .

fl. Ufbt llow ortboolmae-DunriicliDa feldflwr, , .,. .,

Connty.PB. ID. WhilBleldwu.Embiwville. Pa, 11. Potuh feldapu. Wooduock. -

ulHodii Mdifwr. HsUTtoa, Md, 13. Lime-aods feldapv (bytoi>iatJ,_PcnDtCi>ruii(luD

U. B. d. B

illen, but not for pottery. (Ail uUw tram Min. IbS qiurry, Bxdlonf, N, Y., No. 3 cnd, ud bi cU,

Dses (1). — Feldspar is used chiefly as a flux in the manufacture of pottery, electrical porceln, and some enameled wares. For all these purposes it should be as free from iron as posable, but some of the ground commercial spar carries as much as 15 to 20 per cent free quartz.

Feldspar is also employed as a flux or binder in emery and car> bomndum wheels, and to some extent in the manufacture of opales- cent glass. For the last purpose it can carry more quartz and mus- covite than pottery spar; and does not have to be as finely ground, 50 to 60 mesh being sufficient.

As an ingredient of scouring soap, feldspar possesses advantages over quartz, because it is softer and less liable to scratch glass. Selected feldspar is used in the manufacture of artificial teeth.

The posbihty of using feldspar as a fertilizer, because of its potash contents, has been suggested; but no commercially practicable means of extracting the dedred element has as yet been found (2).

Production of Feldspar. -"— The production of feldspar from 1904 to 1908 is ©ven below. The crude refers to that sold in the un- ground state, but all spar is crushed before use.

Phodochon of Pbldspah, 1904 to 1908. in

Short Tons

Gboitnd

Total

Qumtity

Value

Quntity

VaJue

Quantity

Value

1B08

lfi.413

Is

iiS9.eiz

67:240

t2ns.32e Ma,i57

55gE

228 Economic Geology

The preceding figures do not Include feldspar used for abrasive purposes.

Dealers usually divide feldspar into the following three grades:

No. 1, which is free from iron-bearing minerals, mostly free from muscovite, and contns less than 5 per cent quartz.

No. 2, which is largely free from iron-bearing minerals, and in the potash spar usually carries 15 to 20 per cent quartz.

No. 3, which is less carefully selected and may carry enough iron- bearing minerals to render it unfit for pottery purposes.

The average price in 1908 of crude feldspar used for pottery and enamel ware was about S4 per short ton f.o.b., while the aver- age price of the ground was about S8.20 per short ton f.o.b. mills.

Repbk2Hcb9 Ok Pblispar

1. Baatin,U.8.Gol.8un'.,BuU. 420, 1910. (General and United States.) 2. Cuahman, U. 8. Dept. Agric, Bur. Int InduBtr;, Bull. 104, 1907. (Fertilizer usea.) 3. Day and Allen, Amer. Jour. Sci., XIX : 98, 1905. (Thermal properties.) 4. Hopkins, Ann. Rept. Pa. State College, 1898 to 1899, Appendix, Pt. II. S. Mathews, Md. Oeol. 8urv., RepL on Cecil Co. : 217, 1902. 6. Watwn. Min. Res. Va, 1907 : 275. (Va.)

Pluorspar

Fluorspar, or fluorite (CaFi), contains 48.9 per cent fluorine and 51.1 per cent calcium. Its hardness is 4, its specific gravity, 3.18, and it has a pronounced octahedral cleavage. Fluorite shows a variety of colors, including white, green, purple, etc. The mineral is commonly found in veins which may be fissure fillings or replace- ments, and is often associated with ore minerals, especially lead and tin. limestone is the most important wall rock of the American deposits, but in some districts granites, gneisses, or volcanic rocks may form the vein wall.

DistributioD in the United States. — In the United States fluorite is found at a number of points in the Piedmont and Appalachian areas from Mune to Virginia, and is likewise noted (usually in small amounts) in many metalliferous veins of the west; but the most important producing districts are in Kentucky and Illinois. Colo- rado, Arizona, and Tennessee are also to be included in the produc- ing states.

Kentucky (3, 4). — In the western Kentucky district, which is one of the largest producers of the world, the fluorite occurs as vein deposits in fault fissures cutting limestones (PI. XXVII, and Fig.

Minor Minerai 229

93), sandstones, and shales of Carboniferous age. The minerals have been deposited by (1) a filling of the fissure cavity, (2) replac- ing the wall rock of the fissure, or (3) cementing a breccia of the same. Associated with the fluorspar are barite, calcite, galena, and sphalerite, as well as other minerals in smaller amounts. The different minerals may occur in the veins, either intimately inter- grown or in separate bands; in some cases, however, only one min- eral may be present in the vein. The fault fissures strike northeast and northwest, but the former carry more fluorite.

J . . i

rr- ea*;-;""

It is supposed that the Buorite has been deposited by thermal ters, which were ven off during cooling by the dikes of mica peridotite which are found in the district. The fissures, fault planes, and dike contacts served as trunk channels along which the waters ascended, and from which they also spread out into the ad- jacent rocks. Weathering has produced a disintegration of the fluorite. The veins show a maximum width of 36 feet for gravel ore and 16 feet for lump ore.

The product of the veins is divided into lump, representing the coarse product; gravel, which is the naturally or artificially dian- tegrated spar, and ground fluorspar. Washing and jigging are Necessary to separate clay and associated minerals. Number 1 fluorite is usually white and carries 96 per cent or more of calcium fluoride; Number 2 grade has at least 90 per cent calcium fluoride and under 4 per cent dlica; while Number 3 carries from 60 to 90 pCT cent calcium fluoride.

lUitum. — Until 1898 the mines of Hardin and Pope counties, lUinois, were the only domestic source (1), and this area continues

z .IV,

230 ECONOMIC GEOLOaY

to be an important producer. There the depoeits fill fault fissures in Lower Carboniferoua limestones or sandstones. Dikes of mica peridotite also occur in the district, but not in contact with the veins. These latter in some places attua a widtii of 45 feet and a proven depth of 200 feet. This great width is due partly to enlargement of the fissure by solution, and partly to a replacement of the limeetooe walls. In the limestone footwall, the fluorspar sometimes forms a solid mass from 2 to 12 feet thick, but that on the hanging wall is less pure. The vein filling is chiefly fiuorite and calcite, while as- sociated with these are smaller amounts of galena, sphalerite, and occaaonally pyiite or chalcopyrite. It is agnificant that the galena is slightly argentiferous.

The origin of the fluorite is somewhat doubtful, but Bmu (1) be- lieves that it has probably been derived from heated waters of either meteoric or mtmatic origiii which leached the mineral from some large mass of low-lying igneous rocks of which the dikes are off- shoots. These heated ascending solutions are thought to have carried fluosilicates of zinc, lead, copper, iron, barium, and calcium. The dissolved compounds were probably broken up by cold de- scending waters, which possibly also furnished the sulphur to com- bine with the metals.

Cdorado (2) . — In eastern Colorado fluorspar occurs in conad- erable quantities in a belt extending from Boulder County to Custer County. The veins, in most cases, cut granites and gausses of pre-Cambrian age that have been intruded by later dikes, especially of quartz porphyry. Metalliferous minerals are associated with the fluorite, but in several instances the latter forms most of the vein filling. The deports have thus far not been extenvely de- veloped, and much of the material lies rather far' from the rdl- road. The three producing localities are Jamestown, Boulder County; Eveieen, Jefferson County; and near Rosita, Custer County.

Other States. — Tennessee (3, 5) fluorspar comes from Smith, Trousdale, and Wilson counties of that state; while that obtained in Arizona (5) is mnly from the Castle Dome district, Yuma County. '

Importa. — Considerable gravel spar is produced as tailings from the Ethsh lead mines and shipped as ballast to the United States, and has entered duty free, thus competing with the American product as far west as Pittsburg. It is high in silica and is almost i entirely consumed by open hearth steel makers. The estimated imports for 1908 were not over 22,000 short tons. j

z .1,, '

-"Jiversjty

b,

Minor Minerals

Analyses of Fluorspar. — The following analyses (3, 2) will i dicate the variation in compositioB of the American product: —

Analtsbs 0

F Fluobspar

CftF,

810,

SSs

Sgr

Memphis Mines. K?

Hodge Mines, Ky

N'uioy Hanks Mines, Ey. . . .

Gravel Fluorspar

Rosita, Colorado

Juuestown, Colorado

Marion, Ky

Firview, ID

tr.

tr.

tr.

n.d. 1.

Uses. — Fluorspar was formerly uaed chiefly for makii hydro- fluoric acid, but not more than 5 to 10 per Cent of the domestic prod- uct is now employed for this piupose, while increai quantities arc sold for the manufacture of opalescent glass. The greatest demand for it, however, is as a flux in iron manufacture, ance it saves from 3 to 5 per cent more iron than limestone flux, reduces the Eulphur and phosphorus contents, and increases the tensile strength of the metal. On account of its valuable reducing properties, it is so used in mulcing spiegeleisen, in foundry work, and in cupola furnaces.

It is also used in the manufacture of enamels, glazes, and fire- proof ware, for apochromatic lenses, for gems, cheap jewelry, paper weits, and for carbon electrodes for flaming arc lamps. Its use as a flux in cement manufacture has been discontinued.

Prodoction of Flaorspar. — The table on page 232 gives the quantity and value of fluorspar marketed from 1906 to 1908.

The fluorspu is prepared for market by hand sorting, crushing, j'ng, and sometimes fine grinding. The grades produced are;

1. American lump No, 1, with under 1 per cent silica, and sold ntaialy to glass, enameling, and chemical industries.

2. American lump No. 2, which includes colored spar, and may run as high as 4 per cent silica, though usually sold under a 3 per cent guaranty. It is used by blast furnaces in the production of

. f,

232 Economic Geology

ferrosilicon and ferromanganese, and in basic oi>en hearth steel furnaces.

3. Gravel spar, including all with over 4 per cent Bilica, and spar mixed with excite. It is used in iron and braes foundries.

FLUoaepAB Mabkktbd in

1906 to 1908, IN Shobt Tons

Outel

G Bound

5™

Ks

St*™

ValuB

QlUD-

Valua

s-

V.liig

Ibos

40iDS4>

28.268

816003 S3,4n'

Total . .

31.Mb

1S3.483

S.S50

90.542

4ft7M

S244,0Zs

Colondo . . lUinoia . . . KeDliioky . .

3,300

iffl

6.Ta2

ez,595

3J0O

ai!o58

tn.too

Total. . .

3S,186

llSfl.03S

3.03S

22.828

10,202

898,4 7B

49,486

387 J41

Ims

lUinoii . '. '. Kentucky . .

sH

"Taoa

is

31,727

48,641

Total. . .

(1Is.069

a,4B6

*3S,00S

7,382

t225,MS

[nsludH onidc ud (rsTsl apat.

loludss oiudc ud armvel intr from Colnnulo ukd TsnuaenB. idudH producliao imm Ccdondo SDd TeoneaseE. idude* uniU [xoduBtioD ol lump ipu- tram Ariioiu.

Rbfbrbhcbs Os Pluorspab

Bain, U. 8. Geol. Surv., Bull. 255, 1905. (lU.) 2. Burcharf, U. 8. Oeol. 8urv., Min. Bes. for 1908. (Colo.) 3. Foha, Ky. Gol. Surv., Bull. 9, 1907. (Ky. and Oeneral.) 4. Fobs, Amer. Inst. Min. ., Bi-MoQ. Bull., April, 1909. (Ky. apar and use in iron industries.)

5. Pratt, U. S. GeoL Surv., Min. Res., 1901 : 879, 1902. (Aril.)

6. Ulrich and Smith, U. 8. Geol. Surv., Prof. Pap. 36, 1905. (Ky.)

7. Watson, Va. Geol. Surv., Bull. 1 : 42, 1905. (Va.)

Foundry Sands

Definition. — Under the term foundry sand there are included (I) sands for making the mold proper into which the metal is cast, and (2) core sand, utilized for making the cores which occupy the hollow spaces of the cast piece.

The molding sands proper are usually of finer texture and more loamy character than the core sands, still the two grades overiap, and both show considerable range of texture. In selecting molding sands, the fine-grained ones are used for small castings, while the

Minor Minerau9

coarser grades are employed for heavy castings. The core sands have but little coheveneea, owing to their lack of clayey matter, and hence require the addition of an artificial binder.

Reqniaite Properties. — The requisite physical qualities of foun- dry sands are: 1. sufficient cohesiveness to make the cohere whea pressed together to form the parts of the mold, the defidency in this respect in cure sands beii supplied by artificial binders; 2. sufficient refractoriness to prevent extensive fusion in the sand when exposed to the beat of the molten metal; 3. texture adapted to the grade of castii to be poured in it; 4. sufficient porosity md penneability to permit the escape of the gases given off by the cooling metal; 5. durabifity, or sufficient length of life, to penmt as much of the sand as posable being used over again.

The laboratory examination of a molding sand might properly include the determination of (1) its texture (by mechanical analy- sis), (2) porosity, (3) permeability (by aspirator method), (4) average fioeness (by aspirator method),' (5) tenale strength, and (6) refrac- toriness.

Chemical analyses of foundry sands are in most cases of little value, mainly because they shed no light on the phyical properties. A few are, however, given below: —

CaisiacAL Analyses FooNDEr Sands

Sk),

Ai,o,

FoO.

co

MgO

K,0

Tk),

Uobt

1,42

5,32

tt.

y.

14.66'

Undet.

Undet.

12. ; 81.57

1. Pine sand for light oastinga, Richmond, Va. 2. Coarse, gravelly core "and, Richmond, Va. 3. Stove plate sand, Albany, N. Y. 4. Stove plate sand, Newport, Ky. 5. " Philadelphia" brass sand. 6. Lumberton, K- J., brass sand (mild). 7. Lumberton, N. J., hnaa sand (strong). 8. Upper sand bed, Rockton, 111. 9. Lower sand bed, Rockton, 111. 10. Sand for medium weight castings. 11. Coarse sand for heavy castings. 12. Stove plate aaud, Conneaut, O. AU quoted from Ref. 6.

% other ways, but these w

leasae-

ECONOMIC QBOLOar

The following table gives the mechanical analyas, specific gravity, and poroedty of a number of samples of foundry sand.

Phtsical Tests of Foundrt Sands

Cut

!

H

No,

3D

u

so

3S0

ti

"

h

u

—

—

—

—

U

—

—

—

—

—

—

—

—

—

—

—

—

—

2.S8

—

39

—

M

19J22

—

1. Fine oore sand, Jaokaon, Mich. 2. Sand for eeneral work, ZanesviUe, 0., district. 3. Riverside, Mich. 4. Core sand, Nilea, Mioh. 5- Stove plate Band, Conneaut, O. 6. Sand for general work, Vineland, Mich. 7. Leoni, Mioh. 8. Sand for heavy work, Battle Creek, Mioh. 9. No. 5 Band, Newport, Ky. 10. No. 3 sand, Akron, 0. Nos. I-IO quoted from Ref. 6. II. Sand for general work, Manchester, Va. 12. Coarse Band, Richmond, Va. 13. Peterabui.Va. Nos. 11-13 quoted from Ref. 6. 14. Sand for small castings, Berlin, Wis. 15. Core Band for heavy oastingv. Janesville, Wis. 16. Sand for heavy castiufrs, Eenoafaa County, Wis- 17. No. 4 sand, for malleable and gray iron, and brass, Waterford, lU. Nob. 14-17 quoted from Ref. 4. 18. Lumberton, N. J. 19. Stmag ssiid, Hainespoit, N. J. Nos. 18-19, Ref. 2.

Minor Min£Rai£ 235

Distributioii in the United States. — Many tbousaadB of tons of foundry sand axe used annually by foundries, scattered all over the United States. In meet cases these represent natural mixtures, but for some grades of work, especially steel casting, artificial mix- tures of quartz, clay, etc., are used.

Sands for cores and molds for general work are widely distributed and obtunable from many surface formations, luiually of recent age; but the finer-grained sands, such as are required for stove plate and brass casting, are of rarer occurreDce. The reons around Albany, Xew York, Conneaut, Ohio, Newport, Kentucky, Valparuso, In- diana, etc., are noted for their supplies of the finer grades of mold- ing sands. New Jersey is also an important producer, but there the sand is obtained largely from Cretaceous and Tertiary depodts. In the digging of molding sand, careful sorting is sometimes neces- sary, the depoat of good sand being often thin, or of irrular thickness, and interbedded with other sands of no value, although closely resembling the good material.

The Uterature on molding sands is not extenave.

The value of molding sand produced in the United States in 1908 is reported as $1,342,802, but these figures are probably only ap- proximate.

Rbfbkbhcbs Oh Fouhdrt Bauds

1. Eokel, N. Y. State Ooologist, 2lBt Ann. Rept., 1901. 2. EOniniel and Pftnoelee, K. J. Qeol. Surv., Ann. Rept. 1904: 189, 1905. (GeneraJ and N. J.) 3. Merrill, Non-Metallio Minerals ; New York, Wiley and Sons. (OeneraL) 4. Ries and OaUup, Wis. Oeol. and Nat. Hiat. Surv., BuU. XV : 197, 1906. (Wis. and Gener.) 5. Riee. Metal Indnatr;, Jnna and July, 1908. (Relative advantages of obemjoal andphymcalexamin&tion.) 6. RiesandRasen,Mioh.Qol.3urv., Ann. Rept. for 1907. (Qenersl and Mich.) 7. Watson, Min. Res. Va. LynohbuiK, 1907:394. (Va.)

Culler's earth

Properties. — Fuller's earth (7) may be regarded as a peculiar type of clay which has a high absorbent power for many substances, on which account it is of value for deccdorizing oil and other Uquids. Its color and chemical composition are variable, and its spedfic pavity ranges from 1.75 to 2.5. The quantitative analysis shows it to differ chiefly from oonmion clay in having a relatively higher percentage of combined water.

The following analyses represent the composition of fuller's earth

z .IV,

Economic Geology

from different localities, but it should be emphasised that they a of little value in judging the quality of the earth: —

Chemical Anai.tbeb c

r PVllek's Earth

u

vu

SiOi . . AM). . .

PetO, . . CaO . . MgO . . K,0 . . NaiO . . H.0 . . Moisture .

H.86

Total .

I. Wobum BEmda, Eng. (YeUow.) II. Gadsden County, Fla. III. Decatur County, G. IV. Fairbum, S. Dak. V. Sumter, 8. Ca. V!. B&kerafield, Calit. VII. Alexander, Ark. All quoted from Ref. 7.

The cauee of the bleaching power of fuller's earth still remains to be explfuned, but Parsons (3) has suggested that the phenomenon is one of simple absorption. Lime carbonate seems to injure the i bleaching power of the earth, and in some cases appears to be coun- . teracted somewhat by acid treatment. A practical test affords the only satisfactory method of determining the value of fuller's earth.

Distribution in the United States (1,3,7). — In former years nearly all of the fuller's earth used in the United States was imported from England, where large deposits of this material exist; but oc- ' currences are now known in a number of states, including Florida, Geora, Alabama, Arkansas, Colorado, South Carolina, etc.

At most localities the earth is found interbedded with sands or clays, which may sometimes difFer from it but little in appearance.

Fuller's earth is not confined to any particular formation, but the known depomts occur in sedimentary rocks raing from the be- ginning of the Mesozoic up to the Pleistocene. In Gadsden County, Florida (6,8) and in Decatur County, Georgia (8), for example, it is obtained from the upper Oligocene of the Tertiary, the former locality being the most important in the country. The earth from this region is used for bleaching mineral oils.

Production of Fuller's Earth. — The domestic output has never been large, and much is still imported from England.

Minor Miherals 237

PaoDucTnoN or 's Earth in United States ntou 1906 to

BaoBiTom

Valdi

aa,040

Rsfsrehcbs Oh Fuller'S Earth

1. Daj, Jour. Frank. Inst., CL, 1900. (Distribution.) 2. MerriU, Guide to Study of Nonmet&llic Minerals : 337. 1901. (Geufinl.) 3. ParaoDS, Jour. Amer. Cfaem. Soo., XXIX, No. 4, April, lfi07. (Proper- tjes.) 4. Porter, U. 8. Qeol. Surv., BuU. 315 :26S, 1907. (Properties and teste.) 5. Riee.U. 8. Oeol. Surv., 17th Aim. Rept,, Ft. Ill (ctd.): 877. (Oenenil.) 6. Riea. Amer. Inst. Min. Bnerrs., Trans. XXVII : 333, 1S9S. 7. Ries, Clars, Ooouirenoe, Propties and Usee, 2d ed. : 516, 1908. (General.) 8. Vaushan. U. S. Oeol. Surv., Min. Res., 1901 : 922, 1903. (Oft. and F1&.)

Glass Sand

Glass sand is obtaioed from quartzose sands, sandstones, or quartzites. When sand is employed, it is sometimes necessary to put it through a washing process in order to separate the impurities, while ia the case of sandstone or quartzite, at least a preliminary miahing and screening are usually necessary.

Chemical CompoEition.' — Since siUca is the major ingredient of the sand, it influences the character of the ware to a marked degree. Sand with impurities is therefore to be avoided, especially if it is to be used for the higher grades of glassware. Chemical analysis of almost any sand may show at least traces of iron oxide, alumina, titanium oxide, hme, magnesia, and organic matter, but most of these are included in mineral griuns other than quartz.

Iron oxide, even in small amounts, colors the glass green, and is avoided by a selection of the whitest sand, although whiteness does not necessarily indicate freedom from impurities. Washing may remove much of the iron, and the iron color may also be counter- acted to some extent by the addition of arsenic. Magnesia causes trouble by rendering the batch less fusible, but it is more apt to be

' Frink (Ref. 14) brieve* that maiiy of the view* bdd regarding allowable limit of MgO and AliOi are iDcoirect, and these substances are less hannful thaji is com- monly imaguied.

c,q,z.<ib,Coogle

ECONOMIC QBOLOaY

introduced through the limestone than the sand. Clay is u able, since it tends to cloud the glass.

Chemical Akaltbbb of QiaABB Sands

SiO,

A1,0,

F.

Co

UtO

Toru.

1. Ottftwa, lASalle Count j.

m

tr.

—

2. Utic*. HI.

—

3. Klondike, Mo

—

—

—

—

4. GmyB Summit, Mo. . .

—

—

—

Ho

5. Everton, Boone Co., Ark.

—

—

—

6. Flora, Grant Co., Wis. .

lea-

7. Co:mUe, Ind

tr.

Upd.

8. Tip Top. Ky. (.elected) .

9. MMsiUon, O

—

—

10. NUee, 0

tr.

—

11. Berkley, W. Va. (Orie-

kan; sandatone) . .

—

—

—

—

—

13. Columbia, Pa. (Oriakany)

etc.

14. Cheshire, Mass. (Cam-

briau)

15. Lewi9toa,Pa. {Oriakany)

ir.

tr.

Ifn.

16. Hanover, N.J. (Tertiary)

17. Clayton, la. (Ordovioian)

Lost etc.

18. W.Vienna, NY. (Pleis-

tocene)

tr.

Noa. 1-6, Ref. 3; Nob. 7-10, Rof. 4; Nos 11-12, Ref. 10.

Phrsical Propertiss (3). — Contrary to the belief of glass manu- facturers that rounded grains are best, much good glass la made from sands of angular or subangular grain. Uniformity of grain is highly desirable, and should range between 30 and 120 mesh. If larger than 30 mesh, the sand is more difficult to fuse; while if finer than 120 mesh, it is to " bum out " in the batch.

L;,q,-z.= bvCoOgk'

Minor Minerals 239

Few mechanical analyses of glass sands have been published, but the following will serve to show the texture of several from dif- ferent locahties (2,).

Mechakicai. Analtbbs of Olass Sands

SlMTLB

aOMHa

OOMmb

FineBtgTuned . .

Ottawa, m. . .

Coaneet grained

9Q

Ottaw.IlL . .

Crude, direct from pit.

99 +

Ctia, m. . . .

Crude from oar .

99 +

Etondike, Mo. .

Extra quality . .

Gras ,

finished product

Mo.

Gra; a Summit,

Crude, from

Mo.

quarry.

Crystal City, Mo.

Prepared . . .

99 +

CtyatalCity.Mo.

Average mine run

Berkeley Springs,

Crushed aandatone,

W. Va.

flniahed product

Everton, Art. .

Networked . .

99 +

no(a,WiB. . .

Not worked . .

99 +

Distribution of Glass Saad. — Sand for ass makii is obttuned from a number of different geological formations, ranging from Cambrian to Pleistocene. Those obtajned from the Pleistocene <tepoBit8, as in New York (12), are not as a rule of high purity, but those from the Tertiary and Cretaceous formations are of better quality. In New Jersey there are extensive pits in the Tertiary, around Bridgeton (11), the material being used in the glass works of gouthem New Jersey and southeastern Pennsylvania. Large pits have also been opened in the Raritan formation of the Creta- ceousalong the Severn River in Maryland. The Oriskany sandstone is found to be of high purity in West Virginia between Berkeley Springs and a point on the border near Hancock, Maryland, the locality having been worked for a number of years (10). Sand- stones of the same age are also worked in Pennsylvania (6, 8).

The glass-sand industry of Illinois (2), is developed mainly in La Sdle County, the rock used being the St. Peter (Ordovician) sand- stone. Much of it is very soft. Sandstone of similar age is worked in Missouri (1. 2), in a belt between Klondike on the Missouri River

z .IV,

Economic Geology

imd Crystal City on the MisaiBappi River. Indiana (4) eontuns sandstone suitable for glass manufacture in the Silurian, Devonian, Carboniferous, and Tertiary formations, but most of it cones from the Mansfield sandstone of the Carboniferous La the south- western part of the state. Beds of high-grade sandstone occur in- terbedded with Silurian limestones in northwestern Ohio (4), but the most important depoats are found in the Mississippian, Potts- viUe, and Lower Coal Measures in the eastern portion of the State. Production of Olass Sand. — About 19 states report a production of glass sand, but all of the material may not be used in glass manu- facture. The production of the 6 leading producers as well as the total for the United States is ven below.

QrAKTiTr AND Value of Olabs Sand in TJnitbd Btatbs 1906 to

law

8m™

ViLDB

T™

Valdb

Bbobt

Tokb

Vald.

WeUVirb . . .

iails62

1,089,430

In

?1

23B:716 171,338 138,483 9S.44B

48B,fl89

...Si

'is

1.093.653

si

REFBKEHCBS OH GLASS SAnS

I, Broadhead, Mo. Geol. Surv., 1872 : 289, 1873. (Mo.) 2. Burchwd, U. S. Geol. Surv., BuU. 285 : 459. 1906. (Middle Mississippi Basiii.)

3. Burohard. tbid., BuU. 285 : 452, 1906. (Glass sand requirements.)

4. Burehard,/W((.. Bull. 315 : 361, 1907. (Ind., Ky.. O.) 5. Calvin, la. Geol. Surv- I r24, 1893. (la.) 6. Campbell, U. S. Geol. Surv., Atl. Fol., No. 94 : 49, 1903. (Pa.) 7. De Groot, Calif. State Min. Bur., 9tb Ann, Rept. : 324, 1890, also Ibid., Bull. 38, 1906. (Calif.) 8. D'lavilliers, Sec. Pa. Geol. Surv., F, 1878. (Pa.) 9. Grimsley, First Bien. Uopt. Kas. Bur. Labor, 1901-1902 : 343, 1903. (Eaa.) 10. Qrimaley, W. Va. Gool. Surv., IV : 375, 1909. fW. Va.) 11. KfM- mel, N. J. Geol. Surv., Rept. for 1906 : 77, 1907. (N.X) 12. New- land, N. T. Stat Mus., BuU. 93 : 927, 1905. (N.Y.) 13. Raudolpb, Bug. and Min. Jour., Dec. 28, 1907. (Silioa sand industry.) 14. Frink, Amer. Ceramio Soo., Trans., XI : 296, 1909, (Propertiea of glass sands.)

b,

Chapter Xi

UmOR HraERALS— GBAFHITB HORAZITB

PropertieB and Occuirence. — Graphite, or black lead, as it is often termed popularly, is a form of carbon, of which two varieties are generally recognized, especially in the trade. The first of these, the crystalline, has a lamellar or flaky structure, and is of high purity, while the other form, which is classed as amorphous, lacks crystalline structure, and may be quite impure. However, even the purest graphite may contn at least a few tenths per cent ash and volatile matter, and commercial graphite often contuns an appreciable content of impurities. Those containing 90-95 per cent graphitic carbon meet the requirements of the general trade, but for many purposes, especially painl>-making, graphites with as low as 30 to per cent graphitic carbon can be employed.

The following analyses of graphite from a number of locaUties (6) show the variation in its composition, but probably do not in all cases represent commercial samples.

Analtses of Grapbtte

Sp. Out.

Au

Cumberland, first quality . .

2.2S52

I.Io

Ceylon, oommereial quality . . Gulf of Spencera, 8. Australia . GolTofSpencera, 8. Australia .

Pide. Dep. Hautes Alpes . .

Ticouderoga, N.Y., vein graphite

"

242 ECONOMIC QEOLOar

Graphite ia usually easily recognized by its peculiar phyacal properties, such as extreme softness, steel-gray to blue-black color, greasy feel and black streak. The specific gravity is 2.20 to 2.27. Molybdenite is the only mineral with which it might be con- fused, but this has a bluish or greenish tinge and a greenish streak.

Distribution of Graphite in the United States. — Crystalline graphite is widely distributed in the United States, occurring in contact zones between igneous and sedimentary rocks, in metsr morphic rocks, etc., but the known depoats of commercial value are few in number.

Most, of the domestic supply has been obtained from New York State.

Nets York (4, 10, 11, 12). — The producing mines are located on the southeastern side of the Adirondacks in Essex, Warren, Wash- ington, and Sarat< counties, and .the state leads all others in ita production of graphite, partly because of the steady production of one large mine.

The graphite occurs in the following ways: 1. In pegmatite veins, forming bunches, associated chiefly with quartz, but also feldspar, pyroxene, hornblende, mica, calcite, scapolite, apatite, sphene, etc. This type of deposit is of little commercial value. 2. Veinlets of graphite with quartz in gneiss. 3. Graphitic quartzites, represent- ing metamorphosed pre-Cambrian setments. These are the most important type. 4. Graphitic disseminations in Algookian lime- stones.

At the American Graphite Company's mine, which is represen- tative of 3, the material worked is a medium-grned, quartz- graphite schist, which averages 6.25 per cent graphitic carbon. The associated minerals are quartz, mica, and apatite. The graph- ite rock varies from 3-20 feet in thiclcness, and is overlfun by garnet .

Rhode Island (5) . — Amorphous graphite, graphitic antbradte, or graphitic shale, as it has been variously called, has been known for many years to occur in the metamorphosed Carboniferous rocks near Providence and Tiverton, Rhode Island, but the production has been irregular. At the Cranston Mines near Providence, which are the largest, the section shows a series of interbedded, sandy, carbonaceous, and graphitic shales, eomethii over 300 feet thick, all folded and perhaps faulted. The nuun graphitic bed is 30 feet tiiick.

D,q,z.<ib,Coogle

Minor Minerals

The following analyses represent the composition of an average (1) and a selected (2) specimen respectively.

Analtbbs of OoAPHinc Shali wrou Ckanstoit Mines

a

Vol&tUe

Qnphib

Total

The material is used chiefly for punt.

Penntyhania (6). — Crystalline graphite is also mined in Chester County, Pennsylvania, where it forma two layers from 4 to 6 feet thick in decomposed mica schist.

Alabama (14).— Crystalline graphite ia found ia Knuutes and sohists in Clay, Chilton, and Coosa counties. In Clay County, for eitample, the graph- ite 19 uniformly disseminated throughout a zone of mioa-free weathered Ennite, ten miles long and several hundred feet wide. Its depth has been proven to 75 feet, with an average of 4,5 per cent eiB.phite. A graphitio clay found in the slightly oryatalline sahists of the PaUeozoic area of Clay snd Tallapoosa counties is used as a lubricant.

£10 Mexico (3). — Amorphous graphite is known to occur in the oaflon o( the Canadian River, about 7 miles southwest of Raton. The bed, whieb is nearly horizontal, has been traced laterallyinto the principsl bituminous eoal Beam of the Raton field, and that portion which is graphitized owes its chuacter to diabase intrusions, the change being most complete where the bed was fractured and the diabase forced into it. The graphite is said to occur in pockets or irregular masses in the diabase, and is columnar normal to the faoes of the igneous rock. It has been mined somewhat and sold for the manufacture of mineral paint.

Other States. — Developments of graphite have been made in other statos, such as Michigan, Wisoonsia, Virginia (17), Montana (13], Wyoming (2), Maine (16), Georgia (9), etc., but the output is not steady.

Origin of Graphite. — There seems no doubt that graphite shows a aomewhat diverse mode of orin.

Where the material occurs in disseminated form in schists or quartates, as in the Adlrondacks, and the sedimentary origin of these rocks is clearly proven, there is little doubt that the graplute represents original carbonaceous material that has been changed to its present form by dynamic or contact metamor- phism.

Graphite has in some cases been formed by the heat of igne-

244 Economic Geology

OUB intrufflons acting od coal-beds, aa in New Mexico (q-v.)> or in Central Sonora, Mexico, where coal-beds up to 24 feet thick- ness, inclosed in sandstone, have been metamorphosed by granite.

In other localities, where the graphite occurs in pmatite veins as in some Hconderoga, New York, deposits, Ceylon, or in Maine, or where it is found in lenticular enrichments associated with lime- stone in a decomposed gneiss near granite contact, as at Passau, Bavaria, a different explanation is required.

Id these it seems probable that while the graphite must have been introduced in va[>orous form, it may have been derived from two possible sources. Thus it might have been ven off by igneous rocks during cooling, or else represent carbonaceous matter from neighboring sediments, which has been vaporized by heat, and migrated during metamorphism.

Graphite is known to occur in small quantities in some granites, and has been sparingly noted in other igneous rocks, but in some of these it may not be intUgenous.

Uses. — On account of its refractoriness and hi heat conduc- tivity, graphite is employed in the manufacture of crucibles for use in the steel, brass, and bronze industries. For making these it is mixed with clay and some sand. Ceylon graphite is spedally j suitable for this class of work, because of its peculiar Bbrous struc- ture. Amorphous graphite has not given success in crucible, work. In addition graphite is employed for making stove pohsh, foundry faci:, paint, lead pencils, lubricating powder, glazing, electro- i typing, steam piping, for adulterating fertilizers, colorii and I ing coffee beans or tea leaves, etc.

Both amorphous and crystalline graphite can be used for lubri- I eating purposes. The use of graphite for pencil manufacture, though an early one, and perhaps the best known, consumes but a i small percentf (under 10 probably) of the world's supply. For this purpose amorphous graphite is demanded, and while Bohemian

and Bavarian graphite were originally used, Sonora, Mexico, now supplies American manufacturers with all they need.

Graphite is also made artificially from anthracite coal, but its introduction has not seriously affected the market for the natural product.

Crystalline graphite is put through a concentrating process be- fore shipment to market. This is necessary in order to free it from the associated minerals. Both wet and dry methods of separation

Minor Minerai

are employed, while more recently air separation has been tried with some success.

Prodactioii of Graphite. — The domestic production of erya- tallioe graphite does not fonn more than a smalt proportion of the entire consumption. In the two following tables are given the pro- duction by states in 1908, and the total United States production from 1901 to 1908.

Production i

) Valitb of Natctbai. Qhapbite j States, 190S, by States

THE UnITBD

St*™

Amob

Peo™

CBTaTALUNI

Tot*I,

Quutitjr

Valua

Qumtity

V*hH

AUb*au> . . . .

New YoA

OtberMMM' . . .

"mo

Pound,

1,032.000

116,100

Sliort ton,

sea

s

iielioo

1!S

1,M3

2,238.000

132340

2.S87

t20S,000

' todudea Aloikft. Colorado, Midiicu, NavsdB. New Maiica. and Wuoi

Pboducttion of Natural Qrapbitb, 1904-1908

c™

QoMility

Value

Quutity

Valua

Qiuuitity

iws

1908 :

5,8S7,9§2 2;28s!oO0

I238.M7 23S!0M

lfl,927

ie!s53

2e.S03

182,025

76:250

Shartlmi

a.537

Isis

29e!e70

808,090

The imports of graphite and the production of artificial graphite for the same period as above are also given.

Ymu

lUPOns N*TU>AL Q KArBITD

Artificul GB™rr

Qiiantfty

Value

Valua

PricBper PouDd

aiLOrlbHU

Is

905,581

'is

Pound,

sli'i

e',6m!ooo

7.335,511

Is

ao2,em

e.so

iv,Coog[c

!46 Economic Geoloot

The world's production in 1907 ia ven below: — Wobld'b Pbodoction or Orapbite in 1907

Codhtbi

BaoKT

Co™

SHOItT

Tons

v.„

United 3uicg . . .

IndTr

29,377

slis

ISSi: : ;: :

ToUl

12,125

!;if

5,222

3.787,14!

Sefsrehcbs Ob Oraphitb

. Anon., Min. Indus., espec. XI : 343, 1903 and XII : 183, 1904. 2, BftU, U. 8. Geol. Surv., Bull. 315 : 426. (Wjo.) 3. Baatin, U. S . GoI. Surv., Min. Res., 1908, 1909. (N.Mex.) 4. Baatin, U. S. Qeol. Surv., Min. Res., 1908, 1909. (N.Y.) 5. Brown, U. 8. Oeol. Burv., Min. Res., 1908, 1909, (R.I.) 6. Cirkel, Rpt. on Graphite, Dept. Inter. Can., Mines Branch, 1907. (General.) 7. Downs, Iron Age, April 19 to June 14, 1900. (GenenJ on uses and technology.)

8. Frazer, Amer. Inst. Min. Engs., Trans. IX : 730, 1881. (Pa.)

9. Hayea and Phalen, U. 8. Geol. Surv,, Bull. 340 : 463. (Oa.)

10. Kemp. U. S. Geol. Surv., Bull. 225:512, 1904. (N.Y.) 11. Kemp and Newland, N. Y. SUte Mus., 51st Ann. Rept., II : 539. (N.Y.) li a. Kemp, Soienoe. n. s., XII :81, 1900. (Origin.) 12. (vie, N. Y. State Mub., Bull. 96, 1905, (N.Y.) 13. Rowe, Min. Wld., XXVIII : 839, 1908. (Mont.) 14. Smith, E. A., Mia. Indus., XVI : 567. (Ala.) 15, Smith, G. 0., U, S. Geol. Surv., Bull. 285 : 480, 1905 (Me.) 16. Smith, P. S., U. 8. Geol. Surv., Bull. 345 : 200, 1907. (Alaska.) 17. Watson, Min. Res. Va., 1907 : 188. (Va,) 18. Weinsohenk, Zur Kenntnisa der Graphitlagerst&tten, Munich. 1897. {Origin.) 19. Weinschenk, Zeitaohr.f. Kryst-u. Min., XXVII : 135, 1897. (Passftu diatriot.)

Lithtom

The two minerals most commonly used ae a source of lithium are LejndotHe (KU[AI(OH,F,)]AI(SiO,),) and Spodumene (LiO,, Al„ 4 SiOj). The largest deposits of lepidolite at present known in the United States are found near Pala, California, Spodumene occurs in some quantities in the Black Hills of South Dakota and in Con- necticut and Massachusetts, hut none of these occurrences have yet been worked to supply lithium.

In the last few years there has been a great demand for lithium minerals for use in the manufacture of lithium carbonate. Since

I z .IV,

Minor Minerals 247

most of this substance now in use is made in Germany, nearly all the American mineral has been shipped to that country. The American supply of carbonate is imported from Germany, selling in New York for $4.20 a pound. The chief use of lithium salts is in the preparation of mineral waters.

The production of Hthium minerals in the United States in 1908 amounted to 203 short tons, valued at $1550.

Uthographic Stone

Properties. — Lithographic stone (1, 3) is a very fine-grained, hom<aeous limestone, used for lithographic purposes. It may be either pure lime carbonate or magnesian limestone, but so far as known this difference in compoation exerts no important influence on its phyacal character. The two following analyses will serve to indicate this difference in composition, No. 1 being the standard Bavarian stone and No. 2 the Brandenburg, Kentucky, rock: —

ImOLUBLB IH HCI J SOLDBLm IH HCl

SiO, (AlFc), CbO Ufi, FoO MgO C0 Nn K,0 Moist. H,0 CO,

1. 1.15 .22 Traoe .23 .26 .56 53.80 .07 .23 .69 42.69 a. 3.15 .45 .09 .13 .31 6.75 44.76 .13 .41 .47 43.06

The phydcal character of the stone is of prime importance, for in order to yield the best results it should be fine-grained, homogene- ous, free from veins or cracks, of just sufficient porosity to absorb the grease holding the ink, and soft enoi to permit its beii carved vrith the engraver's tool. Owing to these strict requirements but few locahties have produced good stone.

Sources of Supply. — Lithographic stone is not confined to any one geologic formation, and deposits have been reported from many states both east and west. Some of these appear to be of inferior quality, while others are too far from railroads. The most prom- ising developed deposit is that found at Brandenburg, Kentucky (2, 6), at which locality a bed of blue-gray stone three feet thick is quarried and used by some establishments in the south and south- west. Another bed of good quality has also been described from Iowa (1).

The main sooroe of the worid's supply ia obtained from the Jur&eaia luneslone of the SoleDhoten district in Bavaria; (4), in which the quarries have been worked for a number of years, but the supply is said to bs becoming unsatisfaatorr and unreliable. The stones are trimmed at the qnaniee, and sizes of 22 or 28 by 40 inches are in the greatest demand.

248 ECONOMIC GBOLOaY

From these they range up to sizes 40 by 60 inches. The best quality stDei sell for 22 cents per pound.

The domestic demand is not large, and it is probable tiiat one or two well-developed and well-managed native quanies could do doubt satisfy it.

The successful substitution of zinc or aluminum plates for certain classes of litb(ppbic work is SMd to have had a noticeable in- Suence on the demand for lithographic stone. Onyx has also, in , some cases, been found to make a good substitute.

RBFERBHCBS OH UTHOGRAPmC STOITES

1. Hoen, lo. Qeol. Surv., XIII : 339, 1902. (la., also gnenJ.) 2. EQbd.

Eng. and Min. Jour., LXXII ; 668. 1901. (Ky.) 3. KObel, Min. .

Reaouroes, U. S. Oeol. Surv., 1900 : 869, 1901. (Excellent general i

article.) 4. Merrill, Nonmetallio Minerals : 146, 1904. 5. Mo. '

Geol. Surv., Bull. 3 : 3S, 1800. (Mo.) 6. UMch, Eng. and Min. I

Jour., LXXIII : 895, 1902. (Ky.) I

Magnesite

PropertieB and Occurrence. — This mineral, which is a carbonate of magnesium with 47.6 per cent magnesia (MgO), has a hardness of 3.5 to 4,5 and a specific gravity of 3 to 3.12.

It commonly occurs in veins or in masses replacing other rocks rich in magnesia, such as serpentines, talcose schists, etc' Its color is white or yellowish, and when massive it sometimes resembles unglazed porcelan, but is quite brittle.

Most of the magnedte used in the United States is imported from Styria and Greece, the only important domestic occurrence being Cahfornia, and although small ones are known in Pennsylvania and Maryland, they are not worked, as they cannot compete nitb the imported magnesit.

California (1). — Deposits of magnete (Fig. 94) are scattered along the Coast Raie from Mendocino County at least to a point south of Los Angeles, and along the western slope of the Sierra Ne- vada from Placer County to Kern County. The greatest produc- tion comes from near Porterville in Tulare County (Fig. 94). The deposits all occur as veins in serpentine, the larger number being in the Coast Range.

The much-fractured and faulted serpentines of the Coast Ranges,

a interestiiiB exoepUoQ, being probably of

Minor Minerai

which are probably of Lower Cretaceous age, appear to have been derived from olivine-pyroxene rocks, and the minesite may have

been formed from both the serpentine-making minerals and I serpentine itself.

and ntt Aaru *'5. — Plan of ni8nesite vdna and workings 4 auu oiten QCpOB- northeast of PortcrvUle. Calif. {After Hiu, U.S.

Sun., BuU. 355.)

iv,Coog[c

2S0

Economic Gbologt

quartz in other vans, or with the magnedte. In some cases the mognesite forms a network of veins in the serpentine, but since its origin is due to the action of surface waters, the deposits may be of limited depth. As the magnesite weathers leas readily than the serpentine, the vein outcrops often stand out in bold relief.

The following analyses show the compodtion of the magnedte from several locaUties: —

Analtbeb of Maonebite

a

a

BiO,

2M

AliO.

2S&

Ferf).

CaO

MgO

Co,

1. Siliceous MagnesiM, 8 m. Dortb of Cftzadero, Sonoma County. 2. Ala- meda olaim, Santa Clara County. 3. Four miles northeast of Porter- vjlle, Tulare County. Too high in lime for good oemeat. Used in wood-pulp whitening. 4. Calcined magnesite, Nyustya, Hungary- 5. Calcined magnesite, Greece. 1-5 from Ref. 1.

Uses. — The chief use of magnesite Sb for the manufacture of refractory bricks. These are produced at several works in Penn- sylvania, but only imported material is used, the low price of ax to seven dollars per ton making California magnerate profitable only for local markets. The main use of this western magneGdte is for making carbon dioxide,' while the residue is changed to sulphite and used in paper manufacture. Magnedteisused as a toilet prep- aration, or in medicine, and as a boiler covering when mixed with asbestos. A moistened mixture of magneda and mneum chlo- ride forms a strong cement known as oxyrJdoride cement. The metal magnesium is not obtained from magncEdte, but from magneEDum chloride obtned from the Stassfurt, Germany, and other

The domestic pnxluction and has been as follows: —

; obtned entirely from California

iv,Coog[c

PiTB

— View in glaw sand pit. on Severn River, Md. — The tunnel shows posi- 1 of bed of glaaa aand. The overlying beda carry too much iron oxide. Rie, pAoto.)

1 of Bapphire-bearinB diki!.OOg[e

(Phou bu Jt F

Of

b,

Minor Minerals 251

Production of MAONEarrz in United States, 1906-1908

Yub

QDAariTT

Vu.Vu

si

RBVEREITCSS (HI MAflHBSITB

1. Hem, U. S. Geol. Surr., Bull. 355, 1908. (Calif.)

2. Struthers, U. 8. GoI. Surv., Mid. Ree., 1902 : 983, 1903.

3. Tala, Eng. and Min. Jour., LXX7III : 2, 1904. (CaHf.)

Meerschaum

Meerschaum or Sepiolite, which is well kuown on account of its use for maJdng pipes, and other smoker's articles, has for many years been obtfuned mainly from Asia Minor, although other oc- currences are known. Recently, however, deposits of promisii character have been located in Grant County, New Mexico, and although not yet commercially developed, deserve mention.

Sepiolite has a probable compodtion of H'MgiiOio, and when pure is a white, porous mineral, with a specific gravity of about 2. It absorbs water readily, becoming somewhat plastic, but hardens again on drying. It has a hardness of 2 to 2.5, great toughness, and earthy or conchoidal fracture, the toughness being most pronounced in those forms having a leathery or fibrous texture. Its peculiar physical properties make it of great value for carving into pipes. .Jp New Mexico two localities are known, both of which lie in the upper Gila River valley, at poiots located respectively 23jQile8 east of north, and 12 miles northwest of Silver City.

At the Dorsey mine, northwest of Silver City, the meerschaum occurs as veins, lenses, seams, and balls in a limestone of probable Ordovidan age. The veins are filled with chert, quartz, calcite, clay, and meerschaum, and the chert which is the most important gangue mineral, occurs in the veins with meerschaum in bands, lenses, and nodules.

The meerschaum itself occurs either as irregular nodules, or in maaave form. Both kinds are tough, but the latter is finer grained, less leathery, and heavier.

The three following analyses represent, (1) the Dorsey mine product; (2) the theoretic compostion of meerschaum; and (3) a

z .IV,

Economic Geology

material from another deposit, which resembles the true meer- schaum, but iers from it id its high alumina coatent.

'.

AljOt

Feri).

tr.

CaO

Hrf)

Total

The deposit cannot as yet be regarded as a commercial proposi- tion, but may become so.

REPERBirCES OK HEERSCHAOH

1907. (N. Mot.) 2. Stairett, (General and N. Mex.)

Hica

Properties and Occurrence. — There are few minerals more widely distributed in crystalline rocks than mica, aud yet deposits of economic value are rare because the mica fiakes are either too small, or too intimately mixed with other minerals for profitable extraction. Only two of the several known varieties of mica, mufr cqyite (HJCAlgSiiOu) and pUojgte (H<KftMg,AI,(SiO,)r), are~of economic value, the former only being found in depodts of economic value, in the United States. The commercial depodte are usually found in pegmatites, cutting granites, gneisses, and schists. In these the mica is associated with quartz and feldspar (usually ortho- clase or microcline, more rarely plagioclase), being found in rou crystals called blocks or books, and which are either irrularly distributed through the vein or collected near its sides.

In addition to the quartz and feldspar, other minerals such as tourmaline, beryl, zircon, columbite, samarskite, uranium minerals, garnet, etc., are sometimes present. The pegmatite, which carries the mica, and may be of igneous or gas-aqueous origin, occurs as lenses, veins, irregular masses, etc., of varying thickness and length.

L,.i,-z:-:l,vC00glc

Minor Minerai 253

The value of the depodt depends more on the abundance and quaUty of the mica than the size of pegmatite body.

The best mica is obtned from the more coarsely crystalline rocks; but the widest veins do not necessarily contain the largest blocks. As a rule the mica does not form more than 10 per cent of the vein, and usually not more than 10 or 15 per cent of that mined can be cut into plates, the rest being classed as scrap mica.

There has been some discussion as to whether the pegmatites are true igneous dikes or veins, but the matter cannot be said to be definitely settled in all cases. It is probable that each type of origin is represented.

Distribution in the United States. — Deposits of mica have been worked in a number of states both east and west, and yet but few &re steady producers. The more important ones may be de- scribed.

North Carolina (4, 9), — The mica mined in this state, which is the leading producer, comes from three belts (Fig. 96); viz., the Cowee-Black Mountain, the Blue Ridge, and the Piedmont belts. That from the first is chiefly clear and of light color (" wine " or "rum"); that from the second is dark smoky brown and often more or less speckled, while that from the third is often of good

quality and similar to the Cowee- -sns- s*ik- -aiasr

Black Mountain product. Owing Fio. 96. — Map Bhowiog areas in North to a frequent capping of residual CHrolina in which mica haa been

„ J. r iL J mined. (Atler SlerTett. U. S. Oeoi.

soil, discovery of the deposits is gj, 35 , difficult.

The mica-bearii pegmatites occur in mica, garnet cyanite, hornblende, and granite gneisses and schists, all of Archaean age, the important formations being the Carolina and Roan gneisses. The rocks of these two are interbanded with, and cut by, streaks of granitic or pegmatitic material, the latter forming lenticular bodies or vein-like deposits, which may, or may not be conformable with the schistosity of the country rock.

While they vary in size, 1 to 2 feet seems to be the minimum workable limit for rich and regular " veins." The muscovite, which is the mtun mica present (biotite being the other), shows a variable mode of occurrence. At one time it is evenly distributed

OOglf

264 Economic Qeologt

through the pegmatite, at another large crystala are found in clusten scattered throvb the vein (Hg. 97).

The better grades of North CaroUna mica are used for the glazing

industry, while the less perfect sheet material is employed for elec-

— I tricalwork. The pegmatite veins

' also carry a number of rare min-

erab. I SmUh Dakota (8). — Mica is mined in the ron around Custer, South Dakota. The muscovite,

as is usual, occurs in pmatite,

f-'v-.V cutting sehista and gneisses, and

" "" granite. The material is of evenly

FiQ. 97. —SecUoQ acrora pegmatite at i i i,

Thon. Mountain nune. Mawu Co.. granular texture, or showa an ir- N. Co. (After Sierreu, u. s. Otol. regular segregation of the miner- Sun-., BuK. 315.) als, with but little banding. This latter is sometimes roughly produced by a segregation of the mica along the walls of the deposit. Very few of the pegmatites around Custer, however, carry enough mica to pay for working them.

In the New York mine (Fig. 98), for ex- ample, the rough mica obtained along the walls amounts to 6 or 7 per cent, while the interior portion of the

pegmatite carries Fia. OS. — GeQerBliied'croweectioaor No. l or New about 0.5 per cent, and Cuater. South Dakota. <-l/&r

i 1 J rr-v Sterrett, V. S. Oeol. Sun., BuU. 380.)

IS not worked. Ihe

shape of the pegmatite bodies around Custer is variable, but in gen- eral they resemble the dike type, and appear to represent an end phase of the granite intrusions of that region, for they not only cut the granite itself, but in places grade into it. Their is not definitely known.

Other Siatei. — Mica in pegmatite has been worked at Mica Hill, 4 miles northwest of ('sflon City, Colorado, and 6 miles north of Texas Creek. That obtained at the former locality ia peculiarly adapted to grinding pur- poses (10). The Viinia (12) occurreaoes, especially those in Amelia County, are of some importance. That found near Amelia Court Houn

t,

Minor Mineraib

ocenre in pegmatite dikee, whiah intorseot the biotite sneisa of the diatriet. The lugest dikea are more than 50 feet wide, and the mica oocurs in them as thiek, highly eleavable blocks, and masses of varying size. Deposits are also known to occur in aorthwest Georgia (7), and while they resemble the North Carolina deposits, they have not been worked much.

Uses of Mica. — The chief use of mica is for electrical purposes, it beii employed as an inaulatiog material in dynamos, motors, high voltage induction apparatus, Bwitchboards, lamp sockets, etc. The domestic product is found to be uniformly satisfactory for electrical work, except for insulation between the copper bars of conmiutator segments. This use seems to be best served by the amber or pblogopite mica obtained in Canada and Ceylon. The superiority of this variety is due to its easier wearing qualities, which cause it to wear down even with the copper segments. Mi- eaniie or mica board is sheet mica obtained by cementing small clear pieces of scrap mica together under pressure. Since it can be bent, rolled, and punched, it is utilized mostly for the same purposes as sheet mica. The use of mica for stove doors and chimneys is de- creaat, although the glazing industry still demands a considerable amount of the finest grades of sheet mica. Scrap mica is ground for use in the manufacture of wall papers, lubricants, fancy pfunts, and micaniie. That used tor electrical work must be free from metallic minerals, and that for wall paper and punts must have sufficient luster.

Production of Mica. — The quantity and value of mica produced in the United States from 1904 to 1908 by kinds is given below. The complete production by states is not given by the United States Geological Survey.

pKODUcnioM or Mica in tbh Unitiid States raou 1904 to 1908

SbutfHica

BatATlilCA

Total

Quimtity

Vilua

QumnHty

ees,358

2:417

Ii0,8M 17,856

Examination of the statistics since 1880 shows a strong fluctua- tion in the total value of production.

Economic Geology

The average price of sheet mica in the United States in 1908 wks 24.1 cente per pound, as compared with 33 cents in 1907 and 17.7 cents in 1906. The average prices for the individual states vary greatly from year to year, due in part to variation between popo tion of rough and trimmed mica, and aze of sheeta produced. The prices per pound of several aizes of selected mica in New York in 190S were as follotra:

2X2 in., tO.87; 2X3 in., $2.75; 3X4 in., $3.25; 4 X

$1.10; 2X5 in., $1.70; 3 X 3 in., i in., $4.75; 6 X 8 in., $6.75.

The imports of mica are given for the last five years, since to state those of one year would not clearly show the fluctuations. . The remarkable drop in 1908 is not expluned.

Mica imported and entebed for Consumption Statbb, 1903-1908. tw Poondb

IN THF United

Y.

Tmu.

QuMtlty

Qumtity

VlJuB

Quutily

Viln

1,147.329 1.504,570

as

A small quantity of mica is exported each year.

Rejbrshces Ok Mica

1. Ball, TJ. S. Geol. Surv., 315 : 423, 1907. (Wyo.) 2. Cirkd, Mioa, Ita Occurrence, Exploitatioa aod Usee. Dept. Intr.,MiiieflBraiiob,CAiL, 1900, (Cfw. tLDdgensral.) 3. CoUea.Micaandthe Micalndustry.New York, 1906. (General.) 4. Holmes, U. S. Geol. Surv., 20th Ann. Kept., VI:691,1899. (U. 8.) 5. Hoskina, Min. Indus., X : 458. 1902. (N.H.) 6. Pratt, Mineral Census, 1902, Mines and Quarries : 1031, 1901. (General.) 7. Sterrett, U. 8. Geol. Surv., Min. Res,, 1908. (Ga.) 8. Sterrett, U. S. Geol. Surv., Bull. 380 : 382, 1909. (8. Dak.) ft Sterrett, U. 8. Geol. Surv., BuU. 315 : 400, 1907. (N. Ca.) 10. Ster- rett, U. S. Geol. 8urv., Min. Rea., 1908. (Colo.) II. Sloan, S. Ca. Geol. Surv., Ser. IV. Bull. 2 : 142, 1908. (8. Ca.) 12. Watson, Min. R8. Va., 1907 : 278. (Va.)

Hineral Paints

Under this head are included a number of mineral substances which are used in the manufacture of paints. Some of these can be

D,q,-Z.-dbvCOOg[C

Minor Minbrals 257

sed directly after cleaning and grinding, while others are roasted to give the desred color.

The substances used and considered in this chapter include ocher, umber, sienna, hematite, siderite, ground slate, and shale. Other BubstoQces used in the paint trade, but mentioned elsewhere, are asbestos (p. 211), asphalt (p. 85), barite (p. 217), clay (p. 124), graphite (p. 241), gypsum (p. 178), mnesite (p. 248), pyrite (p. 281), silica (p. 274), talc (p. 286), and whiting.

Hematite. — Certain kinds of hematite, such as the Clinton ore (see Iron Ores), are ground and sold under the name of metallic paints, and much used for coating wooden surfaces and coloring mortar. The ores are sometimes roasted before grinding to improve their color and durability. Altboi hematite deports are wide- spread, and sometimes of large se, the quantity of material show- ing the necessary uniformity of color, freedom from grit, etc., re- quired for mineral paint is small. Much crude material is supplied by the Clinton ore mines at Clinton and Ontario, New York (8).

At some localities in northwest Geoia and southeast Tennes- see the Clinton oolitic hematite occurs in beds too thin to be now mined for iron ore, but its softness, high percentage of iron oxide and color make it avulable for red p(unt (3).

The following analyses show the compodtion of this material.

FeK),

ao,

P

Mn

I. Estelle, Oa. II. Ooltewah, Teim. III. Hiuch'a Switch, Tenn.

Ochen. — The term ocher, as commonly used, includes the earthy and pulverulent forma of the minerals hematite and limon- ite. More or less clayey matter ia usually present.

Properties and Occurrence. — The ochers show a variety of colors, dependii mainly on the chemical composition. Thus hematites 0ve a deep red color, while limonitea have some shades of yellow or brown, but whatever the color, uniformity of tint ia necessary. Ochers may contwn as much as 50 to 75 per cent iron oxide (10). Brown ocher or umber is colored by manganese, and sienna is a yellowish-brown variety.

" L,-z__lv,C00g[c

Economic Geology

Ochers may result from (5, 10) : the leaching actjoa of percoia1> ing waters and subsequent deposition; as redual products, formed by the removal or solution of the soluble parts of the orinal Txx;k, leaving the insoluble portions, clay and iron oxide, to form the different ocherous colored clays; from the decomposition of rocks rich in iron-bearii sihcates; by oxidation of beds of pyrite; by alteration or decompositioa of hematite beds; by alteration of more compact forms of limonite; by replacement; by sedimentation.

DiBtribntion of Ocher. — Georgia and Pennsylvania are the largest producers of ocher, but California, Vermont, and oth states help to swell the total.

Georgia (5, 6, 10). — In this state the ocher deposite occur in a north-south belt, S mile long, lying east and southeast of Carters- ville. The ocher is limited to the Weisner (Cambriaji) quartsite, in which it occupies an extensively shattered zone of dmilar poa-

tion to that of the residual clay derived from the rock decay (Fig. 99). The following analyses represent its composition.

Analtsbb of Georgia Ochbr

Fe,0.

FeO

MnO,

SiOi (free sand)

SiOiCoonb)

HiO above 105° C

I. Crude ocher, MftOBfield BroH, Lot. 462,4th dist., 3d eeo. BartovCo. II. Crude ocbernearEmenoD.Bartov Co. III. Refined oober, Blue Kdge Ocher Co.

bvCoog[c

Minor Minerals 259

The average percentage of limonite in a Dumber of analyses waa 74.15 per cent for both the crude and refined ocher. There is ad- mixed with it about 20 per cent of clay and finely divided quartz which cleansing will not eliminate. The ocher of this district ranges from a dark to a light yellow color dependent chiefly on the amount of admixed clay.

According to Watson (10), the Bartow County ocher deports have been formed by molecular replacement of the quartzite, and subsequent weathering has resulted in the other bodies being in- closed in many cases in residual clays derived from the decay of the orinal Tock. Hayes (S) states that the ocher forms a series of irregular branching veins, extending in all directiotu, but often ex- panding into bodies of conderable mze.

It is believed by Wataon (10) that the iron oxide of the ocher was derived largely irom the decay of surface rocks and carried down- ward by surface waters in the form of soluble ferrous salts, but that some was possibly contributed by pyrite in the quartzite. The deposition may have been due to the carbon-dioxide solution of ferrous carbonate meeting an oxidizii solution, resulting in a precipitation of the iron and a solution of the silica of the quart- rite.'

The main use of the Georgia yellow ocher is in the manufacture of linoleum and oilcloths, especially in England and Scotland. It is employed to a limited extent for paint manufacture.

Pentisjflvama. — The ocher deposits of eastern Pennsylvania include the residual deposits of the Reading-Allentown district and the bedded depodts of the Moosehead district. The first named includes the principal ocher belt of Pennsylvania and lies in Berks and Lehigh counties, where the ocher deposits occur as irregular masses in a residual clay derived from the Shenandoah (Cambro- Siliuian) limestone. Associated with the ochers are nodules and geodes of Lmonite, as well as smaller quantities of tuite, ilmenite, aderite, and pyrite. The product after washing, drying, and grind- ing contns from 12 to 30 per cent FetOs.

In the Moosehead area a bed of soft, buff-colored shale, found at

the base of the Mauch Chunk shale, and resting on the Pocono

sandstone (Lower Carboniferous), is mined for paint. It is of low

grade, and the product carries from 6 to 7 per cent ferric oxide.

Umber and sienna have been produced in small quantities in

1 Tan HlM, Treatin an Metamorphlsm, p. 417.

260 Economic Geology

niinois and Pennsytvaoia, and sienna in addition has been obtwned from New York.

Siderite (1). — In Southern Carbon County, Pa., there occurs a, somewhat extensive but not very thick bed of siderite lying between the Oriskany (Devonian) and Hamilton (Devonian) formations. The section shows

Cement rook 25 feet

Paint "ore" 2 feel

01 8 feet

35 feet

The brown paint " ore," which conoatfi chiefly of iron carbonate, varies in thickness, often between 1 and feet, and rardy reaching 4 feet. It is in places changed to limonite at the surface, and growa leaner with depth, leading to the belief that it represents a replace- ment of Umeatone by surface waters.

Below are given (I) an analysis of the crude ore (7), and (II) an analysis of the roasted product (4).

Analyses of Sidkeitb Paint "Orb" frou Pbnnbtlvania

n

Pe

Ferf),

Mn

MqO

SiO.

SiO

A1,0.

Alrf),

CaO

CaO

MgO

MgO

S

So,

P

PtO,

Lobs od roaatinK . .

H,0

Co, .

This paint is used munly for freight cars, and in lesser amounts for painting steel, tin, boats, and as a filling in oilcloth and linoleum.

Slate and Shale. — The refuse from slate quarries is sometimes gtwid and sold as a pigment, and in some looalities shales of the proper oolor anil texture are utilized for the same purpose. Their value depends on their oolor, fineness, and amount of oil required in mixing.

Pennsylvfuiia and New Jersey are the chief producers. The Hamiltoo (Devonian) shales have been worked for some years in Cattaraugus

Minor Minerals

County, N. T., uid a product known aa miTteral black ia made from the slatei <tf the Hudson River (Ordovioian) series.

OypBum,' known also as teira alba or miners white, is used to some ffitteut as a pigment for printing wall paper.

Baiite.i or barium sulphate, which ia used aa an adulterant of white lead, is purified after mining by grinding and washing.

Asbestos ' is used to some extent in paint manufacture for the so-called DOD-infianunable or fireproof paints, but the total quantity thus utilized

GraphitB,! either natural or artificial, supplies a black pigment of per- manent color which, on account of its reeistance to the atmosphere and ordinary chemicals, is of much value for ooating oxidizable metals, such as iron and steel.

Calcjam Carbonate, in the form of chalk, known oommeroially aa whiting or pans white, is used as a pigment to alter the shade of other pig- ments as a basis for whitewash.

Other PaxTtl*. — Paints sometimes classed as mineral paints are made from other crude minerals, as follows : zinc white from sine ore; white lead, red lead, and orange mineral from lead; Venetian red from iron sul- phate; vermilion or artificial cinnabar from quicksilver; chrome yellow from chromite; cobalt blue from cobaltite.

Production of Mineral Paints. — The productioa of mineral paints, aa well as the imports, are tven below.

Peoducttiom of Natdrai. Minebai. Piomentb, 1904-190S, in Short

Tons

RlHD

190S

Quihtitt

VALum

q™

Is

204,377 84,42.

as9

6,181

Ks

Mortu colon

Til

ToUl

is,eoo

Mfl8,074

4S,2S5

i4S4.eis

4e.e2i

Kb1.72B

Km*

190B

Qcabttit

QnABTlTt

V.Ld.

16,B7l

tlB4,T42

Iks

8S

MeuUiepdnt

as

ToUl

4S.Ms

IS30.48fl

49,86a

tiae.su

' For mode of occiureace and diitributiou, see aai on other pages.

'locludaa a amall quantity of unground materiaL

I tteatment of these minerals

iv,Coog[c

!62 Economic Geoloqt

The importB in 1907 and 1908 were as followB : -

1B08

Quwiitr

Kixm

msa

France is the laiest producer of ocher, the United States bng Becond.

Rbperekcbs Or Hhibral Padits

1. Agthe and Djman, U. S. 0ol. Surv., Min. Bes.. 1908. Chapter on Mineral Iints. (Siderite, Pa.) 2. Anon., Calif. State Min. Bur., Bull. 38 : 338, 1906. (CaW.) 3. Burohard, U. S. Oool. Surv., BuB. 815, Pt. I : 430, 1907. (Clinton ore, Tena., Oa.) 4. Eckel, Ibid., Pt. 1 : 435, 1907. (Siderite.) 5. Hayes, Amer. Inst. Min. Engn., TiMB. XXX : 415, 1901. (Oa. ooher.) 6. Hayea and Eckel, U. S. GooL Surv., BuU. 213 : 427, 1903. (Oa. ooher.) 7. HiU, Bee. Pa. GeoL Surv., Kept, for 1886, Pt. 4 : 1386, 1887. (Siderite, Pa.) 8. Newland. N. Y. State Museum, Bull. 102 : 111, 1906. (New York.) fl. Stoddard and CoUen, U. S. Geol. Surv., Min. Rea. 1908, Chap. Mineral Paints. (Ocher, Pa.) 10. Watson, Oa. Geol. Surv., Bull. 13, 1906. Also Amer. Inst. Min, Engrs., Trans., XXXIV : 643, 1904. (Oa. ocher.) 11. Watson, Min. Res. Va. : 225, 1907. 12. Scattered notes in the Mineral Industry (AnnuaJ published by Eng. and Min. Jour.) and in U. 8. Oeol. Surv., Mineral Resouroes.

Monazite

Properties and Occurrence. — This mineral is an anhydrous phosphate of the raj'e earth metals, cerium, lanthanum, praseodym- ium and neodymium; but its economic value is due chiefly to the ffinall amount of thoria which it contains. The percentage of thoria in monazite ranges from less than I to 20 or more, and in commercial monazite varies between 3 and 9 per cent. Although grains of monazite are found scattered through many granites and gneisses, still no occurrences of this type have thus far proven to be of commercial value. The economically valuable deposits are all found in stream gravels, derived from the diantratjon of mona* zite-bearing rocks. Monazite is usually light yellow to honey yellow, red, or brown in color, has a rednous luster, a specific gravity of 5.203 (Penfield and Sperry) and a hardness of 5 to 5.5. It is very brittle. Its gravity and color aid in its ready determination.

b,

Minor Minebaw

In the United States deports of monazite sand have beea found in the granite and gneiss areas of North Carolina (2, 4) and South Carolina (3), and these, together with deposits found in Brazil (1), supply nearly the entire world's demand. A small quantity is also obtained from southern Norway, aa a by-product in feldspar nuning. The following analyses indicate the compotion of monazite: — AmaiiTses op Nostb Carolina Monazitb

Ce,0.

l.

ThO,

8iO,

Bfi

Burke Co.. N. C. . . . Aleander Co., N. C. .

The depoats known in the Carolinaa have been found within an area of about 3500 square miles (Fig. 100), which lies wholly within the Piedmont Plateau re|pon. The chief rocks are gndsses of different kinds, schists, granite, pegmatite, peri- dotite, quartz- diorite, and dia- base, but the Btnietural condi- tions are complex. Fig. 100. — Map aboinDg ue& of inoiuulte depodte of and metamor- known commercial Talue in southern Appalachian re-

obscured the originfd character of the rocks. The latter are, more- over, often concealed by a heavy mantle of residual soil.

Where the monazite has been found in the bed rock, it has been chiefly in a porphyritic pegmatized gneiss. In the ordinary gneiss, and in the hiy pegmatized gneiss, the monazite is far less abun- dant. These occurrences in bed rock have not, however, proved to be of commercial value, and the only important deposits are the placers, and gravel beds in the streams and bottom lands, as well as some surface soils, adjoining the rich gravel deposits.

hi some areas the saprolite or rotted rock underlying gravel de- posits has been washed with favorable results.

The mouazite-bearing gravels range in thickness from (me to two

; C'.OOgIC

264 Economic Gbologt

feet, including overburden, up to 6 to 8 or more feet, and the mona- zite on account of its gravity has collected more abundantly in the lower portion. The depoeitfi are richest in those regions contn- ing an abundance of granitic rocks, pegmatized gneisses, and schists, while in the gravel itself, the presence of considerable quartz dbiis, and fragments of such rocks as pegmatite, granite, mica, -and cyanite gneiss, are favorable signs.

In some cases the supply of monasite in the stream gravels may be replenished by wash from the hillsides which are underlain by re- sidual soils containing monazite grains.

The monazite found in the pegmatized gneiss is believed to have been derived from aqueo-igoeoua solutions pasang through the rock, and depositing and recrystaUizing portions of it into the mia- erals of pegmatite.

0868. — Monazite is usually separated from the gravels by a washing process, and in addition magnetic separation has in some eases been employed to separate it from the associated gamet, magnetite, and quartz.

The value of monazite hea in the incandescent properties of the oxides of the rare earths, cerium, lanthanum, didymium, and tho- rium, which it contains, and which are utilized in the manufacture of mantles for incandescent lights.

Production ot Monazite. — The production of monazite for several years was as follows: —

Production or Monazitb in the Unttbd States fbom 1905 to 1908

T>u

v.„

Poimdi

'fi

The 1907 produotion includes a small quantity of zircon ; the 1905 pro- duction includes smt quwititiea of ziroon and oolumbite. The imports oF thorium nitrate in 190S were 65,289 pounds, valued at (173,239.

Repereiicbs Oh Hokazitb

I. Dennis, Min. Indus., VI : 487, 1898. (General.) 2. Nitzo, N. C. Geol. Surv., Bull. 9, 1895. 3. Pratt, U. 8. Geol. Surv., Min, Res., 190B : 1003, 1903; and 1903 : 1163, 1904. (N. Ca. and 8. Ca.) 4. Sterrett, U. 8. Geol. Surv., BuU. 340 : 272, 1908. (N. Ca. and S. Ca.)

Chapter Xii

MinOR HIHBRALS- PRECIOUS STOHBS— WAVELLITB

Precious Stohbs

The names gemg and precious stories (l, 2) are applied to certn mmerals, which on account of their rarity, as well as hardness, color, and luster, are much prized for ornamental use. The hardness is of importance as influencing their durability, while their color, luster, and even transparency affect their beauty. A distinction is some times made between the more valuable stones, or gems (such aa diamond, ruby, sapphire, and emerald), and the less valuable, or precious stones (such as amethyst, rock crystal, garnet, topaa, moonstone, opal, etc.).

Most gems are found in unconsolidated surface deposits represent- ing either residual material or alluvium derived from it, and in the latter their concentration and preservation is due to their weight and hardness. When found in solid rock, the metamorpbic and igneous types are more often the source than the sedimentary ones.

Many different minerals are used as gems (1, 2), but only a few of the important ones can be mentioned here, and the number of the more valuable kinds found in the United States is very Umited (4, 12). Every year, however, discoveries of one kind or another are reported, and reference is usually made to these in the Mineral Re- sources of the United States published annually by the United States Geological Survey.

Diamond. — This mineral, which is the hardest of all known natural substances, is pure carbon, crystallizes in the isometric system, and has a specific gravity of 3.525. It occurs in many different colors, of which white is the commonest, and is found either in baac igneous rocks or in alluvial gravels.

The masfflve forms, known as bort or carbonado, have little or no cleavage, and are of value only as an abrave.

The greatest number of diamonds come from South Africa, but other depodta of commercial value occur in India, Borneo, and Braal. '

265 L, -ziv.CoOglc

266 ECONOMIC GEOLOaT

In the United Statea a few scattered diamonda have been found in the drift or soil of the aouthem Allhaniea, CaUfomia, Wisconsin, and Indiana, but they are all small (10, 12, 13, 15).

The only and first locality in North America where diamwidB have been foimd in place, is in Rke County, Ark. (9, 13), where, at a locality 2i miles south-

east of Murfreesboro, there is a Hmall area of peridotite. This igaeous rock fonoa a small stock which has cut through indi&- tinctly bedded Car- bomferous sandstones and quartates, which are overlain uncon- formably by Creta- ceous sandstones, and the latter in turn by post-Tertiary con- omerates.

The readual clay derived from the peri- dotite is of two kinds, the one of yellowish- green color represent- ing more advanced decomposition, and

the other of bluish-green shade and usually underlying the

first. The bluish-green material is known to extend to a depth of

from 20 to 60 feet. The diamonds are found disseminated through

the decomposed peridotite. Up to July 1, 1909, over 700 tUamonds had been found. Of the

first 540 stones discovered (9), 505 weighed 217 carats. The largest

one found weighs 6i carats. Three have been cut and yielded gems

valued at from 160 to S175 per carat.

More recently a new peridotite area has been described, which is

located three miles south of east of Murfreesboro. This has also

yielded a few diamonds (2i).

The probable origin of the diamond haa provoked much disoussioa

among raentiats, and a number of sucoeaaful attemt>ta been made W

t,

Minor Minerals 267

produce it Artifloially. These indio&te ita formation by aryat&llizatiou from a fused magmft, which in moat eases has a oompoaitioii resembling peridotite. As oorroborative of this we have the ooourrenoe of South African diamonds in or near voloanio pipes of peridotitio oharaoter, and Lewis haa suggested that the stones were formed by the solvent action of the molten peridotite magma on oarbonaoeous shales. Some have disputed this idea, and believe that the diamond is an original oonstituent of the magma, from which it crystallized on cooling. Aa opposed to an igneous origin is the statement of Q. F. Williams, that he found an inclusion of apophyUite (a highly hydrous mineral) in a Kimberly diamond. All dia- mouds do not occur in peridotite, for in Brazil hydromioa schists and quartz- ite may contain them, while certain Indian ones appear to have been derived from pegmatite, and some Australian ones in homblendeliabaae. The moat that can perhaps be said is that, while much of the evidence indicates an igneoua origin, the diamond has not necessarily been obtained in all caaee from the same kind of magma.

Emerald. — "Hub gem is a variety of beryl, essentially a gluciaum- aluminum mlicate. Its hardness is 7.5 to 8, and its specific gravity 2.5 to 2,7. Its brilliant green color is attributed by some to chro- mium, by others to organic matter. Brazil, Hindustan, Ceylon, and Siberia are all important sources. In the United States a few have been found in western North Carolina (12, 15) in gravel de- poMta. Flawless emeralds are very rare, and equal in value to diamonds. , AqaamariTie and oriental cat's-eye are also varieties of beryl. Braian emerald is a green variety of tourmaline, and lithia emerald on emd-green spodumene.

Garnet. — Of the several varieties of garnet, three are well known as gem stones, vis, the precious garnet, or almandite, Bohemian garnet, or pyrope, and manganese garnet, or spessarite. The first two are of deep crimson, the last of orange-red or light red-brown color. India is the main source of supply. All three varietiea mentioned are found in the United States, but there is a regular production only of the pyrope from Arizona and New Mexico, and a purplivred garnet Imown as rhodolite from North Carolina {4. 12, 15).

Those found in the southwest (22) have for many years been collected by the Navajo Indians. Clear red gamete associated peridot gems, which have been weathered out of basic igneoua rocks, have been found at several places around and north of Fort I>efiance, Utah, but those obtained from these localities are small and not worth cutting. The supply of gem gamete comes from close to the Utah-Arizona line, at a point 12 miles southwest of the

Iv,

268 Economic Gbologt

junction of the Chin See Valley and San Juan Biver in Utah. In thia region, which is underlain by sandstone of probable Triassic age, pierced by numerous basic igneous rocks, the garnets are found chiefly in a coarse, unconsohdated drift or gravel layer, associated with feldspar, chopeide, quarts, and igneous rock fragments. The garnets range in size from small grains to others over 3 centimetera in diameter, but the gem stones are uot over 12 millimeters across.

Opal, which is hydrous ulica chemically, is amorphous, with conchoidal fracture, yellow, red, green, or blue color, and often showing considerable iridescence. The varieties recognized are the precious opal, fire opal, girasol, and common opal. The finest examples of precious opal are obtuned from Hungary. Others are also found at Queretaro, Mexico, and in Oregon and Washington. The United States production is small, although it is thought that that are many scattered occurrences in the igaeous rocks of Wash- ington, Idaho, Oregon, Cahfornia, Nevada, and Utah (4, 12).

Peridot. — This name is applied to a deep olivereen variety of chrysolite, a silicate of magnesium and iron. Peridot has a low hardness (6.75) as compared with other gems, while its specific gravity, 3.3 to 3.4, is relatively high.

Gem peridot is found in two cegious in Arizona (22) viz. north of Forth Defiance in the Navajo Indian Reservation, and near Bice in tiie White Mountains Apache Indian Reservation. In the former district the peridot is. plentiful, and is found associated with volcanic rocks. These are monzonite [rarphyry, orthoclase basalt, and peridotite agglomerate. The peridot, which appears to have been derived from the aomerate, is found in the soil, and asso- ciated with it are such minerals as garuet, diopside, quartz, calcite, titanic iron, etc. Gems of 1 to 2 carats' weight are fairly abundant, and some of 3 to 4 carats are found. Those of dark yellowish>green color are conunonest.

In the Rice district peridot is found not only in the original basalt rock matrix, but also loose in the soil.

Ruby. — A red, transparent variety of corundum (AliOj), having a hardness of 9 and a specific gravity of 4. The most valuable color in ruby is a deep, clear, carmine red. Rubies of large ze are scarce, so that a S-carat stone of good color and flawless is worth several times as much as a diamond of the same size. The best ones come from Burma. In the United States they have been found in the stream gravels of Macon Ckiunty, North Carolina, but the production is not a steady one. Those found in Arizona and

L;,q,-z.= bvCoOgk'

Minor Minerai3 269

other western states are not true rubies, but a variety of garnet {4, 12. 15).

Sapphire ia a blue, transparent variety of corundum (AliOi)' It is of slightly greater hardness and specific gravity than the ruby, though of similar composition. Sapphires of good color and size are more common than rubies and cheaper. "Rie best sapphires come from Siam. In the United States they have been found in the gravels of Cowee County, North Carolina, but Yogo Gulch, Montana, is now the main source of domestic supply. They range ia weight from under 1 up to 4 or 5 carats (4, 12, 18).

The Montana sapphires were first found in gravel bars on the Missoiui River, but subsequently they were discovered in dikes of baeac igneous rock cutting Carboniferous (?) limestone in south- western Fergus County. The rock is of somewhat basic character lielonng to a type known as monchiquite, and the sapphires are obtained from the somewhat decomposed portions of the dike.

There are two companies, both operating on the same dike, which has a width of 10 to 20 feet, and has been traced for a distance of 5 to 6 miles.

Spodnmene. — A remarkable transparent lilac-colored and pale pink to white spodumene, known as Kurudte (14) has been found in California not far from the nibellite locality, and occurring in a pegmatite dike, where it is closely associated with gem tourmalines.

Topaz. — This is a fluosilicate of alumina, crystallizing in the orthorhombic stem, with a hardness of 8, specific gravity of 3.5, litreous luster, and yellow, green, blue, red, or colorless. It occurs in gneiss or granite, as well as in other metamorphic or igneotis rocks, and is associated with beryl, mica, tourmaline, etc. It is also found in alluvial deposits. The best gem stones come from Ceylon, the Urals, and Brazil. In the United States they have been found in small quantities in Mne, Colorado, California (12), and Utah.

In Utah topaz (17) ia found in the Thomaa range of mountaina about 40 miles north of Sevier Ike, &t a. locaJity known as Topaz Mountain. The tranfiparent oratala occur in lithophysfe in rhyolite, and vary from color- less to wine oolor. Rough opaque crystals are scattered through the solid rhyolite. The oryHtala are believed to have been formed by vapors or solu- tions contemporaneous or nearly so with the floaJ consolidation of the rock. In the weathering of the rook the crystals fall out and become mixed with the soil, the colored ones fading on exposure to the light.

Topaz is obtained from pegmatite veins near Ramona, San Diego County, where it oocurs in pockets in albite and orthoolase. The topazes are white, yellow, sereen, uid sl-blue, some of them being of large size (14).

270 Economic Geology

TonmtaUns. — Tliis is a complex olicate, of aluminum and boron, with usually varyii amounts of iron, magneaum, alkalies, and water. It has a hardness of 7 to 7.5 and a ajwcific gravity of 2.98 to 3.20. The color is variable, and this variation may exist in the same crystal.

The opaque, black, or brown tourmaline is a somewhat c(Hnnion mineral in many metamorphic rocks, as well as in gratute and oter eruptive rocks, but this variety has no value as a gem.

Gem tourmalines are, however, rather rare, bng known in Brazil, Russia, and Ceylon, and in this country in the states of Maine, Connecticut, and California. Of the gem tourmalines the red onea are most Mly prized, especially the darker ones; the green ones are usually dark green.

A large number of green tourmalines have been obttuned from a pegmatite granite at Paris, Maine, and many are found in a belt ex- tending from Auburn to Newry (23) . The gems here are likewise found in pegmatite, and are associated with beryl.

An interesUng and important occurrence of red tourmaline (rubeUHe) has been worked at Pala, San Diego County, California. The crystals here form radiating groups in lepidolite and the earlin discovered ones were clear enough for cutting. Valuable crystals, many of gem character, have nnce been found in pmatite veins near Pala, and near Mesa Grande (14).

Turquoise is a masdve hydrated aluminum copper phosphate, of waxy luster, blue to green color, and opaque. Its hardness is 6, and specific gravity 2.75. It usually occurs in streaks and patches in volcanic rocks. The best varieties are obtuned from Persa, but it is also obtained from Asia Minor, Turkestan, and Siberia. In the United States turquoises are found in the Los Cerillos Mountains near Santa F4, New Mexico, and Turquoise Mountain, Arizona, as well as in Colorado.

It is interesting to note that turquoise was hardly known in the United States in 1890, but now the bulk of the world's supply comes from the southwestern states and territories (16 a, 22, 25).

In 1908 the production of turquoise in the United States came from New Mexico, Nevada, Arizona, California, and Colorado.

Turquoise mines have been operated in the Burro Mountains, 15 miles southwest of Silver City, New Mexico. The country rock of granite, which is cut by andesite-porphyry, andesite, and dadte,. is much altered, and the turqu<Hse is found in a vm or

L,-z__lv,C00g[c

Minor Minerals 271

fissured zone, which contuna kaollmzed feldspar and secondary quartz.

la this strip, which is 40 to 60 feet wide, the turquoise occurs as veins and ni:etB, the former fillii cracks in the granite to inches wide, and the latter in the kaolin. The veinlets often cross and indicate successive periods of deposition.

A diversity of opinion exists regarding the oria of the turquoise. Silliman (Amer. Jour. Sci., 1881, July, p. 67) believes it to have been formed by heated water and vapors, which destroyed the orig- inal character of the rock and produced new compounds. Clarke and Diller suggested that the turquoise represents a replacement of the apatite of the granite. Johnson (16 a) advanced the theory that gases played a rdle in the decomposition of the rock, and called attention to the association of fluorite with the turquoise. The alununa of the turquoise, he thinks, was derived from the feldspar, the phosphorus from the apatite, and the copper froOi cupriferous solutions which formed the ores in that region.

Zalinski (25) believes that hot solutions, coming from below, caused a kaolinization of the granite, the silica set free in this connec- tion being deposited in cracks and fractures with the tiu-quoise. Solutions carrying aluminum phosphate rose along fissures parallel with the walls, while the copper solutions came along an intersect- ing series. Intermingling of the two solutions formed the turquoise. In Mohave County, Arisiona (22), the turquoise is found in the younger intrusive jKjrphyries and granite, both of which have beea more or less altered, especially around the turquoise deposits. This alteration consts of kaoHnization, but there has also been some silicification, as shown by a depodtion of quartz in joints and between the grains. Some of the turquoise seems to have been derived from the kaohn by the addition of phosphoric add and copper, but much of it has been deposited from solution, as it occurs as seams and vdnlets, as well as in patches or streaks in quarts seams and veinlets. The nodular turquoise is less conunon.

The Colorado turquoise deposits are associated with trachyte, but they show relations similar to the Arizona material.

Variadte. — This mineral alone is not used as a gem stone, but it is cut with its associated matrix. This mixture, which is some- times called amatrice (26), is composed of variscite, wardite, and probably other associated minerals such as chalcedony and quartz. The first two are hydrous phosphates of aluminum, showing vary- ing shades of green, of compact, tough character, and having a

Economic Oeolooy

hardDess of 4 aad 5 respectively. The matrix consists of chalcedony and quartz with other minerala, among them yellowish gray and white phosphates. The decorative value of the material lies in the variety and arrangement of ita colors.

Apia, ehBlndoDV. >ta,

Isoo

toso

11,125

CiJilotiiia. Utah, ud MiehicuL

aso

Banitoite

Ijoo

3,038

1,018 out ilaiin. roucfa mumil.

.UllUMoW.

40,Kw

484*5"

1,110

2,850

2.iOSjpuad.; Colanda u>d NhH

e.4BD

CaliTamii. Utah, ud North Ci-

PlwoMito

Petrified rood

3Zs

Qiiiirti, rock aryst, nDoky

e8

O.SOD pDUsdi in tCenugh:

SiSar-: : : : :

No E!rli''ll" ported.

30,100

220,800'

1.055.402 cuBta; MuaUu vd

go pound! ; Cdifoniui.

,

3,300 pounda: CtlitoniA, Cocmni-

72,500'

S4,120>

Turqnotaa uid matrix . .

32.2K

23,840

147,050'

7,500

14,250

1208,000

1471,300

W15.0O3

iv,Coog[c

Minor Minerals 273

Prodaction of Precious Stonoa. — The ITnited States produces a number of different kinds of gems and precious stones, but the total output is by no means large. Moreover, those kinds most used are produced in but small amounts. The collection of ac- curate statistics of production is, for several reasons, quite difficult, and therefore the output has to be esUmated in some cases. The figures of production for 1906 to 1908, together with the producing states in 1908, are ven on the oppoeite page.

The imports of precious stones into the United States for 1904 to 1908 as reported by the Biueau of Statistics is given below.

ViLM

Turn

v„

RETEKBHCBS OH PRBaOUS BICRIBS

Qewebai. WoKKB. 1. Bauer, Edelateiokunde. (Leipzig, 1896. Transla- tion hy h. J. Spencer, London.) 2. Farrington, Qems and Qem Minerals. (Chicago, 1903.) 3. Goodohild, Precious Stones. (N.T., 1908.) 4. KuDZ, Oems and Precious Stones of North America. (N. Y., 1892.) 5. Streeter, Precious Stones and Qema. (London, 18.)

Spbciai. Papb. 6. BaskorviUe, Science, n. s., XVIII : 303, 1903. (Kunz- ite.) 7. Blatohley, Ind. Dept. Oeol. Nat. Res., XXVII: 11. (Dia- monds in drift, Ind.) 8. Clarke, U. S. Oeol. Surv., Bull. 330 : 262, 1908. (Diamond Kenesis.) 9. FuUer, Eng. and Min. Jour., LXXXVII : 152, 1909. (Ark. diamonds.) 10. Hobbs, Jour. Oeol., VII : 375, 1899. (Wis. diamonds.) 11. Kunz, V. 8. Oeol. Surv., Min. Res., 1905 : 1249, 1906. (Opal, Ore.) 12. Kunz, Mineral Census, 1902, Mines and Quarries. (QenenJ on U. S. Oems.) 13. Kunz and Washington, Amer. Inat. Min. Engrs., Trans. XXXIX : 169, 1908. (Ark. dia- monds.) 14. Kunz, Cat. State Min. Bur., BuU. 37, 1905. (Calif. gems and ornamental stones.) 15. Kunz, N. Ca. Oeol. Surv., Bull. 12, (History N. Ca. industry.) 16. Kunz, Amer. Jour.

Sd., IV ;417, 1897. (Mont, sapphire.) 16 o. Johnson, 8ch. of Mines Quart., XXIV : 493, 1903. (N. Mex., Turquoise.) 17. Patton, GeoL Soo. Amer., Bull. XIX : 177, 1908. (Topaz, Utah.) 18. Pirsson, Amer. Jour. Soi., IV : 421, 1897. (Petrography Montana sapphire took.) 19. Pratt, U. 8. Oeol. Surv., Bull. 269, 1906. (Sapphire.) 20. Pratt and Lewis, N. Co.. Oeol. Surv.. 1 : 180, 1905. (Ruby.) 21. Purdue, Boon. Geol., Ill : 525, 1908. (Ark. diamonds.) 22. Strrett. U. S. Oeol. Surv., 1908. Chapter on Precious Stones. (Moss agate, Wyo.; Peridot, Ariz.; Garnet, Ariz. ; Turquoise, Ariz, and Colo.; Variscite, Utah.) 23. Wade, Bng. and Min. Jour., June 5, 1909. (Tourmaline and Beryl, Me.) 24. Watson, Min, Ree. Va. 1907 : 386.

iv,Coog[c

274 Economic Gboloot

(Amethyst, Va.) 25. ZalinHki, Econ. Gol., II : 464, 10O7. (TorquoBe, M. Mex.) 26. Zalinski, Eng. and Min. Jour., May. 22, 1909. (VUli Amatrioe.)

Quartz

Although thifl material haa been briefly referred to under abre- dves and glass sands, it is sufficiently important to require treatment as a special topic.

Silicon is the second meet abundant constituent of the earth's crust, and quartz, of which it is an important iiredient, is the most abundant of all mioerals, but varies greatly in its mode of occurrence and uses. Thus some varieties, such as rose or amoky quartz, amethyst, etc., are used as gems. Quartz in the form of sand is employed for molding (p. 232), building, glass-makiiig (p. 237), and pottery manufacture, etc. In the form of sandstone and quartzite (p. 116) it is of value as a structural material.

The forms of quartz condered here are the massive crystalline quartz (often known as vein quartz), flint, and quartzite used for purposes other than building or paving.

Vein Qttartz (1-3). — This form of quartz, which is white, or leas often rose or smoky, occurs in veins or dike-like masses, usually in metamorphic rocks. It may be of high purity, or may be mixed with feldspar, mica, etc., as an ingredient of pegmatite, in which case it is obtained as a by-product in the mining of feldspar. Vein quartz is produced in Connecticut, New York, Pennsylvania, and Maryland. A crystalline quartz, not of vein character, obtained in southern Illinois is referred to under Tripoli (p. 290).

QuarizUe. — This rock ia quarried at a few locaUties for special purposes. Thus in Cherokee County, North Carolina, a vitreous Cambrian quartzite has been quarried for use as a flux in (pper smelting. Large quantities of a hard brittle quartzite have also been quarried near Wausau, Marathon County, Wisconsin, the ground product being used for sandpaper and other abraave pur- poses, filters, bird grit, wood filler, etc. It analyses 99.07 per cent dlica.

Flint or Chert. — This term is applied to lusterlees quartz of very compact texture and conchoidal fracture, which often forms nodules in limestone or chalk. In some cases these concretions may represent silicified fossils. Flint nodules are found in many formations in the United States, but little of the domestic mate- rial has been utilized except for road metal. The entire supply of true flint demanded by this country for special purposes is obttuned

L,--z:-:l,vC00glc

Minor Minerai

from France, England, Norway, and even Greenland, being brought over as ballast. The smaller nodules are used in tube mills, but much of the supply is calcined to whiteness and then ground for use in pottery manufacture.

Vses of Quartz. — Quartz is extensively used in pottery manu- factiire to diminish the shiinkage of the ware in burning, and for this purpose it should have under 1 per cent of iron oxide. In recent rears quartzite and sandstone have been more used than vein quartz. It is also employed in the manufacture of wood filler, punts, scouring soaps, sandpaper, filters, and tooth powders. Blocks of masEDve quartz and quartzite are employed as a filter for arid towers. Quartz is also used as a flux in copper smelting uid in the manufacture of silicon and ferrosilicon. Much chemical ware is now made of fused quartz.

Prodnction of Quartz

Pbodcchoii or Qdaktz (ExcLuaira or Abrasive Quabtz) in thk

United States, 1904 to 1908, in Shoet Tons

TbK

Ccdb

T„

QuMtity

VllM

QianUty

QtuuMitv

VlJUB

4l!3I4

38.S90

s!383 T,3Sg

t7l,700

loalaoa

S2.270

t00,S90

The imports of and flint abniM in 1908 were valued at $219,754 (un- Eraond). Pure ciTstalline quartz, for potterr, paint, and wood filler brings iboat S2 to $3.50 per long ton, crude, f.o.b. quarries, while the ground prod* uctaellsfor $6.50 to $10 per short ton f.o.b. mills. Quartzite for ssjidpapers sells for $1 to $2 per long ton f.o.b. mines, and $6 to $8 ground, f.o.b. nillg. The finest ground quartz for tooth powders sells for as high as $20 per ton. Imported French flints are quoted at $3.50 to $4 per long ton U.b. Philadelphia.

Rbfbrshcbs Or Quartz

1. Bftstin, U. 8. Oeol. Surv., Min. Roe. for 1907. (General and U. 8.) 2. Baatin, U. B. Qeol. Surv., Bull. 315 : 294, 1907. (N. Y.) 3. Rice and QregoT?, Conn. Oeol. Surv., Bull. 6 : 136, 1906. (Conn.)

Strontium

Sonrces and Occurrence. — The two minerals serving as sources of strontium salts are celestite (SrSOO and strontianlte (SrCOi).

OOglf

276 Economic Geologt

Of these two the former is the more impmtaiit, but the latter is the more valuable, as the strontium salts can be more eamly extracted from it.

Both celestite and strontianite have been found at a number of localities in the United States, but seldom in large quantities. One important depomt of celestite has been found in limestone caves near Put-in Bay, Strontian Island, in Lake Ee, and in opening up the cave 150 tons of the mineral were taken out. Similar occurrences have been found in limestones in other states, but none of them have any commercial value.

Nearly all the strontium salts now used in the United States are imported from Germany, the crude material being obtained in part from Westphalia, Germany, and also from Thuringia, Germany, and Sicily.

TTseB. — Strontium salts are used in sugar refining, in fireworks manufacture, and to a small extent in medicine.

RSFEREHCE OH STROHTnni

1. Pratt, U. 8. Oeol. Surv., Min. Rea., 1901: 956, 1902. SITLPHUR AND PTRITE

These two minerals are discussed in the same chapter because both serve as sources of sulphur or sulphuric acid.

Sulphur

Native sulphur may be formed in several diffraent ways as f olloira :

Solfaiaric Type. — Sulphur is often found in fissures of lava and tuff around many active and also extinct volcanic vents.* When thus formed as a volcanic sublimate it may be a product of reactions between sulphur dioxide and hydrogen sulphide. It may also be formed by incomplete combustion of hydrogen sulphide, probably as foUows; 2 + 0, 2 H/i + 2 S. This latter change prob- ably occurs at least a short distance below the surface, where oxygen is deficient, as at the surface the US may form H3O4.

Deposits of the solfataric type are rarely of commercial unfor- tance, but they are worked in Japan, and have also been worked in the crater of Popocatepetl in Mexico.

Mineral Spring Deposits. — Sulphur is not an uncommon de- posit aroimd mineral springs, its depomtion being due to imperfect

I, uid might, owing

iv,Coog[c

Minor Minerals 277

oxidation of hydnen sulphide. The latter may have origDated by action of add waters upon sulphides, through reduction of sulphates (gypsum, for example) by microorganisms, or in some cases it is possibly of magmatic origin. The hydrogen sulphide is brought up by spring waters, which are not necessarily of magmatic

Gypsum Type. — Sulphur is thotht to be sometimes formed by the reducing action of bituminous matter on gypsum, in which event it would be found in sedimentary rocks.

The change involved is a reduction of the calcium sulphate of the D'psum to calcium sulphide, with the production also of carbon dioxide and water. The sulphide, then, by reaction with the carbon Uoxide of the air and with water, yields calcium carbonate, native sulphur, and hydrogen sulphide.

This type of sulphur is often of great economic value, and de- podt3 are found in a number of countries. Both the Sicilian and Louisiana deposits are thoit by some to have orinated in this manoer, while others have aied for a different derivation. (See Ref. 3, and La. Ref. under Oil.)

It is of interest to note in this connection that gypsum and sulphur might be aBsooiated without one having been derived the other, by nactioiu between hydrogen sulphide and calcium carbonate (Ref. 3, p. 496).

Whatever the orin of sulphur, it can be sd that in sedimentary rocks, the association of limestone, gypsum, sulphur, and hydrogen sulphide is not uncommon.

Metallic Sulphide Type (4). Sulphur may result from alteration of pyrite, marcadte. or related sulphides, possibly through action of bitumi- Doiu matter. Gypsum is a oommon associate. No deposits of eoonomio value have been formed in this maoner.

Distrlbntioa of Sulphur in the United States. — LoulEdaua and Utah are the most important producers, smaller quantities coming ftom other western states, especially Wyoming.

Louisiana (4, 6, 10). — The deposits of sulphur found in this state ue the most important domestic source of this material. They occur in Calcadeu Parish, and were discovered as early as 1868 in boring for oil and gas at the head of Bayou Choupique, 15 miles west of Lake Charles.

The bed of sulphur, which is of Cretaceous age (Harris and Veatch), lies 300 to 400 feet below the surface, is over 100 feet thick, and is underlain by gypsum and salt. It is supposed by some to have been derived from gypsum, but Harris suggests the pOB-

278 Economic Gbologt

ability of its pretdpitatioa from ascending hot waters (see undet Salt, p. 161).

Owing to the quickBand-like character of the overlying beds, attnpts to sink a shaft to the deport were unsucoessful. It is now obtained by puminng superheated steam down through pipes, melt- ing the sulphur, and drawing it to the surface, where it is dischai into vate to cool and solidify.

Utah (6). — Sulphur haa been mined at Sulphiu*dale in central Utah more or less continuously for thirty years. In this district there are foimd a seiies of rhyolites and andeeites, overln in places by basalts, the whole resting probably on Paleozoic sedi- ments.

The sulphur, which occurs in a soft rhyolitic tuS (sometimes caUed gypsum), sometimes forms cyliadrical masses or cones 10 to 15 feet in diameter, and with a rudely radial stoicture, but most of it is found as a dark-colored imprnation or cementii substance of the tuff.

Occasionally there are seen branching veins of nearly pure yellow sulphur, with a banding parallel to the walls, and these may repre- sent fissure fillings from solution, since add water partly filled with yellow sulphur issues from the fissures.

The crude material varies greatly in richness, some showing as much as 80 per cent sulphur, but rock running as low as 15 per cent is marketable. An analysis of the sulphur from the retorts yielded: S, 99.71; nonvolatile matter (SiO,, Fe,0,, etc.), .23; free 8<X,tr.j mfflsture at 100° C, .06.

A volcanic origin is suested for the sulphur, because of its close association with volcanics, and the pomtioa of the beds along a fault line. Gas now escapes from the deposits in large volumes, and hydrogen sulphide bolls up through water standing in the workings. The sulphur may therefore have been precifutated by the oxidation of the hydrogen sulphide, which is presumably of volcanic origin. Oxidation of the sulphur may ve SOs and this by reaction with water, Hd. Analysis of water issuing from the beds showa sulphuric add.

Wyoming. — Native sulphur has been mined in Wyoming near Cody (12), and near Thermopolis (11), the mode of occurrence at the two localities being almost identical. At the latter locality the depodts are found in the altered Embar (middle Carboniferous) limestone which immediately underlies a travertine deposit (Fig. 102).

C,q,-Z.-dbvCOOg[C

Minor Minerai 279

The Bulphur occurs in small yellow crystals filling vns or cavi- ties in the rocks, and in massive form as a replacement of calcium carbonate by sulphur, the original structure of the limestone retained.

'The distribution of the sulphur appears to be very irregular, and confined to those portions of the limestone surrounding the chan- nels of the hot springs that depodted the travertine. The at- tempted ex[danation of the orin of the deposits is that surface waters worked way downward along the sandstones from the

Fio. 102. — Seotion showing Btratigrphy and Btnictun from creat of Oiri Creak MountoiDS to Owl Creek, and relations of sulphur deposits Deal Thermopolis. Wyo. (.After Woodruff, U. 3. Oeal. Sun.. Bull. 380.)

OvA Creek Mountains (Fig. 102), and came into contact with some uncoolcd body of igneoua rock, which not only heated them, but also supplied them with hydrogen sulphide. Following this they passed upward through the much-fractured beds of the anticline with which the deposits are associated. As these waters ap- proached the stuiace, the sulphur was precipitated by oxydation. Hot springs carrying both and CO] exist there at present.

The depth of the deposits at these two locahties is not beUeved to be great, but in the rich pockets the sulphur may form 30 to 50 per ceot of the rock.

Other Siatet. — 8]ilphTiT deposita have been worked in Colorado and Nevada, (i), while oocurrances of possible value exist in Texas (7, 9) and Calitomia (a).

Sicily is the most important source of supply for the United States. There the Bulphur is found in veinleta and cavities in a. cellular Miocene limestone, which underlies and overlies gypsum. The sulphur-bearine beds are generally from 3 to 10 feet thick and vary in their thickness as well as dip, the latter being from 25° up to 70°. The percentage of sulphur varies [ram 8 to 25 per eent, the first figure representing the lowest eoonomio limit- The mines contain more or less petroleiun and bitumen, and sometimes even explosive gases, while barite and celestite are associated minersU. Owing h) improper methods of mining, there is much waste.

Uses of Sulphur. — The most important use of sulphur is for the tnanufacture of sulphuric acid and in paper manufacture. Some

oogic

ECONOMIC aEOLOOY

is also used in tuakii matches, for medidnal purposes, and in making gunpowder, fireworks, iiisecti(3de8, for vulcanizing india rubber, etc.

In recent years pyrite has largely replaced sulphur for the manu- factiu-e of sulphuric add, and the increase in price of Sidhan sulphur has helped this.

The greater portion of the world's supply of sulphur is obtained from Sidly, the United States consuming the largest amount.

Productioii of Sulphur. — The sulphur industry of the United States has grown rapidly in the last few years, and in 1907, for the first time in its history, the value of the importations fell below the million dollar mark, due to the great decline in the imports of crude sulphur. Louisiana continues to be a great producer, and the com- petition of the product from this state with imported Sidlian mate- rial has reacted somewhat disastrously on the latter.

The production for 1904 to 1908 is ven below.

Production op Sulphcb in the ttNiTED States, 1904-1908

LoHoTtw*

ViLtH

if

mi 06 3ae,4M

Sri-PHUR iMPOBTED AND ENTEBBD FOB CoNsuuPTiON IN THK United States, 1904-1908, in Long Tons

Cbupi

pLOWMBBOr

Sulfecs

Jttrnna

TtniL

St-

V.™

T-

Vdue

Value

1008 ... .

Tii

'3fiS,94i 3I8.S77

'to

X9.5W

93

12,611,269 l,S67.i 1.333.5H0

lacludai milpbur 1m *a6 athr sradM not othcnriH ini>vldeil (or. but not pyrite.

The imports came mfunly from Italy and Japan. The exports in 1908 amounted to 27,894 long tons, valued at $561,534, this being nearly 7000 tons in excess of the total importation for consumption.

L, . f,

Minor Minerals 281

These figures indicate that the country is producing more than enough sulphur to supply its own needs.

RSFEREHCES OH SULPHnR

1. AdujuB, U. 8. Geol, Surv., Bull. 225 : 497, 1904. (Nev.) 2. Aubrey. Calif. State. Min. Bur., Bull. 38 : 354, 1906. (Calif.) 3. Clarke, U. 8. Geol Surv., BuU. 330 : 495, 1908. (Origin, many referenoea.) 4. Eemp, Min. Induat., II : 5S5, 1894. (General.) 5. Kerr, AMOo'n. Eng. 8oo. Jour., XXVIII : 90, 1902. (U.) 6. Lee, U. 8. GoL Surv., Bull. 315:485, 1907. (Utah.) 7. Richardson, U. 8. Geol. Surv., Bull. 260 : 589, 1905. (Tex.) 8. Spun-, U. S. Geol. Surv., Prof- Pap. 55 : 157, 1906. (Sulphur and alum, SUver Peak, Nev.) 9. Thomas, Miniug World, XXV : 213, 1906. (Texas.) 10. Willey Ene. and Min. Jour., LXXXIV : 1107, 1907. (Mioins, Ia.) U. Woodruff, U. 8. Geol. Surv., BuU. 380:373,1909. (Thermopolis, Wyo.) 12. Woodruff, U. 8. Geol. 8urv., BuU. 340:451, 1908. (Cody, Wyo.) 13. Min. and Soi. Preas, Aug. 10. IWT. (Colo.)

Pywte

Propertiss and Occurrences. — Pyrite, FeSt, when chemically pure, has 46.6 per cent iron and 53.4 per cent sulphur, and occurs in well-defined cubes or modifications of the same, in irregular grains or as granular masses, of a brassy yellow color.

It is widely distributed in nature, being found in many kinds of rocks and in all formations, and in these may occur as disseminated gnuns, in contact iones, as concretions in sedimentary rocks, in fissure veins, and as lenticular bodies of variable mze usually in metamorphic rocks.

Pyrite as mined is never chemically pure, but contfuns admix- tures of other sulphides, as well as non-metallic minerals.

If cluilcopyrite is present in sufficient quantity to bring the copper content of the ore above 3 or 4 per cent, the material may be sold for copper making instead of acid manufacture. Pyrrhotite is abundant in aome of the Viinia deposits. In some regions the pyrite carries enough gold to render ita extraction profitable, but such deposits are not worked for their sulphur contents.

Pyrite as offered to the trade rarely contains over 43 per cent sulphur, and if the content falls below 38 per cent, the acid makers object. Careful sorting and jibing of the pyrite is usually neces- sary.

When pyrite is roasted SO* ia e:iven off, which is changed to SOg by mixing with fumes given off from a mixture of NaNOo and HiSOi in properly conr ttnicted lead chambers. In thoroughly roasted pyrite there remains a resi-

282 Economic Geoloot

du of iron oxide, which is known aa "blue billy" or purple ore, and can be used in the blast furnace for iron maDufaoture. The roasted chaloopyriu is sometimes also used for copper maklug.

Distribution in the United States. — The most important domes- tic occurrences are found in a belt of pre-Cambrian metamorpbic rocks extending from New Hampshire to Alabama (8), in which the pyrite occurs in lenticular deposits. Virginia and New York are the most important eastern producers, California is the only western state producing appreciable quantities.

Virginia (7, 8).- — The counties of Louisa and Prince William contin workable deposits of pyrite, which have been most exten- fflvely developed, and yield a little more than half of the total domea- tic production.

Fio. 103. — Plan of pyrite lenses at Sulphur Mines, Louisa County. Vk, ahowinf pyrite (d) and crystalline schists (6). (A/ter WaUm, Mm. Ittt., Va., 19070

Fio. 104. — Flan o( pyrito lens (a), shawing tdnserH of pyrite. interleaved witb schists lb) on hunging wall. Arminius mine, Louisa County, Vo. (,Afla- Watton, Min. Rf., Va., 1907.)

In these counties the pyrite occurs as bodies of lenticular shape (Figs. 103, 104), in quartz-mica schists, which may contfun more or less hornblende and garnet locally developed. The schists, which are completely and thickly foliated, have a general strike of N. 10 to 20° E., and a variable dip.

MINOR MINERAia 283

The pyiite is massively granulaj', and the associated minerals in the order of importance are sphalerite, chalcopyrite, galena, pyrrhotite, and minetite. Calcite, quartz, green hornblende, and red garnet are present, but the last two rather favor the tnarn of the ore besides.

The lenses of pyrite follow each other along the strike, sometimes overlapping, and may also be connected by stringers of ore (Fig. 104). The main bodies may be several hundred feet long, indeed one in Lomsa County has & length of 700 feet and a thickness of 60 to 80 feet. Another in Prince William County is 1000 feet long. Pinches and swells are common, and while the pyrite bodies are usu- ally sharply defined, they may at times grade into the country rock.

An analyas of Louisa County pyrite gave: S, 49.27; Fe, 43.62; Cu, 1.50; Zb, .38; insol., 4.23; CaO and MgO, 1.32. Traces of arsenic may be present. The sulphur averages 43 to 45 per cent.

Watson considers that the inclodng schists are undoubtedly metamorphosed sedimentary limestones, aa shown by the presence of bands and stringers of impure limestones and the abundant de- velopment of lime-bearii silicates. The pyrite is believed to have been formed by replacement.

The ore ia worked by underKrouad methods, the schist picked out, ud the pyrit cmiahed and jifKed. The entire output ia used for aoid makiDg. The Roesan of the pyrite was originally worked for iron ore.

Sulphurio add ia also obtained from the pyirhotite-ohaloopyrite depos- its of Carroll County, etc. These are mentioned under Copper.

New York (2). — Pyrite deposits are worked near Canton and Gouver- neur, St. Lawrence County. The pyrite is low grade, carrying 20 to 35 per oent sulphur which can be raised to 45 to 50 per cent by concentration. The ore deposits, which are associated with crystalline Itmeatoaes and schists of the Orenrille series, appear to represent impregnation zones in the schist, whioh by local enrichment may give lens-tike aooumulations.

Maatachugetta (3, 5). — Pyrite is produced near Davis, Franklin County. The material forms a somewhat tabular deposit of irregular width in steeply dipping, northeasterly striking, crystalline schists. The deposits have been opened up along the strike for about dOO feet, and to a depth of 1400 Feet on the dip. Horses of country rook occur in the pyrite. Five feet is regarded as the minimum workable thickness. Qaraets and chalcopyrite tre preaent, the latt forming either masses or in the pyrite. An analysis of the pyrite concentrates yielded, B, 47 per cent; Fe, 44 per cent; SiOi, 3 per cent; Cu, 1,5 per cent; Zn, trace; As, none.

Other Statet. — Some pyrite ia produced from deposits in crystalline schist in Clay County, Alabsjna (8), near Aoworth and Villa Rica, Geoi, and in Ctiifomia (1). In Indiana, Ulinois, and Ohio some is obtained aa a by- product in the mining of coal (s).

iv,Coog[c

Economic Geology

Uses of Pyrite. — Pyrite is used chiefly and in increamag quan- tities for the manufacture of sulphuric add and sulphate of iron, while small amounts are consumed in the manufacture of mineral pfunt. It is not used as an ore of iron, except in the fonn of roasted residues. Recent experiments have demonstrated the posatdllty of savii the sulphuric acid gas from the roasting of zinc ores, and the utilization of pyirhotite for making sulphur and sulphuric add.

Prodactioa of Pyrite. —

pBODTKTrioM or Ptrith in the United States, 1904-1908, IN Long Tons

"

19M

ivoe

Sfa

Qc

VlLDB

s

s

Valdi

pS

K

VAiq.

CaliforDw .

1S,3S0

Zs.902 4,465

81,837

4,837

120.S71

1S,24Z M0.753

la

7I.S03 148. Ms

moa

.Si

as;

4313Ss

t3.I)l

Virgmi. . .

Is14,80S

(938.492

(3.7!

Ib31J0S

ST*ra

ssi?-

VitTTIl

pet Ton

Qt-*K-

,„„

tS

VirgialB

e.§ifl

(3.02

Is

119,340

tee,e3fi

14!l87

43s:62a

ta.ei

t3.21

232.50S

S£7,113

*3.U

' iDcludca the ptoductin

Imports. — The imports of pyrite have increased steadily up to 1908, in which year they amounted to 668,117 long tons, valued at $2,624,339. They came chiefly from Spn, Portugal, Canada, and Newfoundland,

World's Production. — This is given for 1906, that bang the latest year for which complete statistics are available.

Minor Minerai

World's

Production of Ieon Ptrite im 1906

Codiitbt

LoxaToxa

Loa Toira

2ei!os4

1M,770

180,033

"is

ToUl

Sulphur diivKKed (bued on

2S,I32

81B,38S

Consumption or Sulphur i

DoDMtio Hlphur and sulphur contan

ofpyril. . . -

H

1?-fJI

76fi.36B

709.M8

791.402 .

The following table is of intereat aa showing tha quantity of sulphurio Acid used in 1900 in difterent manufooturing industries.'

SHOBTTONa

SitricKid

M7.462

KSn,S-. ::::::

Chrome products

1S.Bs1

1.034,e59

RBFSRBHCES OH PYRITB 1. Anon., CaL State Min. Bur., Bull. 38 : 349, 1906; and Bull. 23 : 144. 2. Newland.N. 7. State Museum, BuU. 93 : 945,1905.; Bull. 102 : 122, 1906; Bull. 132 : 51, 1909. {N. Y.) 3. Phalen, U. 8. Gool. Surv., Min. Res., 1908. (Brief description, Maaa. and Va.) 4. Phillipa, Amor. Irt., XXVI : 10, 1907. 5. Rutledgo, Bng. and Min. Jour.. LXXXII ; 674, 724, and 772, 1906. (Mass.) 6. Struthers. Min. Indns., XI : 577, 1903. {General.) 7. Watson, Min. Res., Va., IjrnohbuTg, 1907 : 190. (Va.) 8. Wendt, Soh. of M. Quart., VII : 218, 1885. (AllaKhanies deposits.)

in. Indus., XrV ; 702.

iv,Coog[c

Economic Geolooy

Talc And Soapstone

Properties and Occurrence. — Talc, a hydrous nuneaiuin sili- cate [H]Mga(SiOg)ij, is a widely distributed mineral, but rarely occurs in lai quantities.

It is characterized by it extreme softness, soapy feel, and freedom from grit. The color is white, gray, or green; and though generally fohated, it may be fibrous.

Soapalone is a term ordinarily apphed to a dark, bluish gray or greenish rock, composed essentially of talc, but conttuning oth minerals as impurities, such as mica, chlorite, amphibole (tremo- lite), pyroxene (enstatite), and also quartz, magnetite, pyrrhotit, and pyrite. It too is soft enoih to be easily cut with a knife, and has a pronounced soapy or greasy feel.

Talc is an alteration product of other magneda minerals, such as tremolite, actinolite, pyroxene or enstatite, and is often associated with talcose or chlorite schists, serpentine, and such bade igneous .rocks as peridotite and pyroxenite. It is also fomid associated with dolomite.

Soapstone, which often forms large masses, is found chiefly in association with the older crystalline rocks. In some cases, it has no doubt been derived from an altered eruptive rock, but in others probably from magnedan sediments by metamorphism.

Distribution in the United States. — The production of talc and BOapstone is limited almost excluavely to the belt of old crj's* talhne rocks forming the axis of the Appalachian Mountain system, and although quarried in eight or ten states, but few are important producers, and these are mentioned below.

Depodts of talc and soapstone are known in some of the western states, but commercial conditions are not at present favorable to their development. Small quantities of talc have been produced in the past in both Cahfomia and Washington.

Virffinia (10). — This state is the most important produca* of soapstone, and while the material is foimd at a number of localities in the state, nearly the entire production comes from a narrow northeast belt at least thirty miles long, extending from Nelson into Albemarle counties.

The soapstone occurs in a number of sheet-like masses called " veins," 30 to 165 feet in thickness, and separated by intervals of 500 to 800 feet.

The deports dip southeast 60°, conformable with the inclong

MmOR MINERAI 287

crystalline schiets, which vary from a micarquartz schist to a mica- ceous sandstone. Occasionally the wall rock is a dark graphite echist, or an altered basic eruptive.

The aoapstoiie varies in oolor fram light bluiah gray to dark K'eeniah gny, the former or higher gmde ooatainiug the most talo, and being the eoaieat mad most Batisfactory to work.

Under the miratiscope the better grade is Been to consist moatly of tale, vith snutU quantities of ohlorite, magnetite, as weU as traces of amphibole ud pyroxene. The dark green soapstone owes its color and greater hsrdness in put to ohlorito and other Bilioates, such as hornblende and pyroxene. The produot is used mainly for laundry tubs, while smaller amounts are converted into table tops, sinks, and switoh boards. Much of it is shipped to foreign markets.

New York (8). — All of the tale mined in the state is obtuned from a small area southeast of Gouvemeur. The most abundant country rocks of this area are pre-Cambrian gneisses, in which there occur irregular northeast-southwest belts of crystalline lime- stone, the greater portion of which is impure. The schistose layers of impurities carry tremolite and enstatite as their chief constitu- ents, and it is the alteration of these that has produced the talc, the cbaoge being indicated by the following equations: —

ENBTATrra Talc

4 MgSiO, + H,0 + CO, H.M&S!,0 + MgCO,

TREHOLTTa Talc

CaMgiOu + H,0 + COi H,M&Si40i, + CaCO,

Ttus change of the enstatite and tremolite to talc is supposed to tave been accomplished by the action of water charged with CO,, but whether it occurred at shallow or greater depths is uncertun. The talc layer, which varies in thickness from a few feet to over 50 feet, averaging about 20, shows either a fibrous or bladed structure. It is used mainly as a filler for writing papers, being even exported to Europe.

liorlk Carolina (fi). — The talc deposits of this state form an intoiesting contrast with those of Virginia, for here the material oocurs as a series of IsDticuIsr nuMsee and sheets in blue and white Cambrian marbles, thus indicating its probable derivation from a sedimentary roek. In other de- ports the talc is found in a Cambrian conglomerate, in Arohiean roolu *swnted with peridotite, showing an undoubted derivation from igneous twki.

The flist-mentioned group is associated with the Murphy Marble, in

c,q,z.<ib,Coogle

288 Economic Geology

Sw&in County, ajid fonns lenticular bodies, with a main mi im size of 50 feet thjoknesa and 200 feet length. It orumbles down under weathering action, and the deposits are detected by float material. Most of the North Carolina talo is ground to powder, but some is sawed into slabs, or made into pencils, oiayona, gas tips, eto.

VeTTnonl (7). — Talo occurs at a number of localities in Vermont, son of which are worked. That worked at East Granville is a talo schist, iu- olosed between other schists. That at Chester and Athens occurs in gneiss.

Neie Jersey (4). — Talc haa been found at a number of points in tba vicinity of PhiUipsburg, New Jersey, and also across the river near Easton, Pennsylvania. The talo occurs with serpentine in dolomite and near pegma- tite intrusions. The latter by contact metamorphism developed tremoUU, whitepyroxene, and phlogopite in the limestone. Later, during break-thrust faulting, accompanying minor folding, squeezing, and faulting in this area, the maenesian silicates were altered by water to talc and other products.

The following analyses from several localities show the kind and quantity of impurities which good talc may contain: —

Analtsbb of Couuebcial Talc

Lociutt

Kinsey Mine,

N. C. . .

tr.

St. Lawrence

MnO

Co., N. Y.

UBes. — Talc is marketed ae rough talc, sawed slabs, or ground talc. Its peculiar physical character, extreme Sneness, softness, and freedom from grit adapt it to a number of uses, of which the following are most important: fireproof paints, foundry facings, boiler and steam-pipe coverings, soap adulterants, toilet powders, dynamite, in wall plasters, for dressing skins and leather, as a base for lubricants, as a filling for paper, and for sizing cotton cloth. It has been used to a slight extent for adulterating food. It can, on account of its softness, be eaIy sawed or carved, and is extensively used for wasbtubs, sanitary appliances, laboratory tanks and tables, electrical switchboards, hearthstones, mantels, footwarmers, etc. Moat of the New York fibrous talc is used as a paper filler, being better suited for it than the North Carolina product. The com- pact varieties of pure talc are employed for pencils, and for coal- and acetylene-gas tips.

b,

Minor Minerals

PTTOphyllite differs from talc chemically, being a hydrous alumi- num silicate, instead of a magnesium silicate, hut when sufficiently free from grit, it is put to the same use as talc. It is sometimes in- correctly called agalmatolite, because of its resemblance to the true mineral of that name. Deposits, more extensive than those of tc, are found near Glendon, North Carolina (S). It varies from green and yeUowieh white to white, but in all cases becomes nearly white when dried.

ProdnctioD of Talc and Soapstone. — The production for the last four years has been as follows: —

Peoddction of Talc and Soapstonb, 1905-1908, bt States, Shobt Tons

leos

looe

inr

V*ii™

VitUB

s-

VitUB

V*u™

N=nh CDlin.

S38,241 446,000

J:S

33!Glt

2.Ss9

13,981 a 1,872

23.810 S2,9ei

loiios;

8,064

4,Dsg

tt 1.473 32,260

74',34- 82,Kx

70!739

a9;27e

TotJ . . .

120.6*4

139,810

117.3S4

11,401.223

Cililomia. MiMMliiuatta, and Rhod*

' Georcis, MiBKhOMtW. ud Rhodt Iilud, la 190( Itni. In 1907; Georfia. Moryluid, MiBmshuHtta. Gntfiii, Muylud, MuumhuMtU, ud WMhinsloa in 1905.

The total imports of talc in 1908 amounted to 7429 short tons, ' valued at $97,096, which was a decrease of over 26 per cent in quan- tity from 1907, but an increase of 4 per cent in the average price per ton.

KSFESXIICBS on TALC AKD SOAPSTOIVB

I. Anon., U. 8. Geol. Surv., Atlas Folio, 162, 1908. (Pb..) 2. Anon., Maryland Mineral Industries, 1896-1907, Md. Geol. Surv,, special publtc&tion, VIII, Pt. 2, p. 160. (Md.) 3. Keith, U. S. CFeol. Surv., Bun. 213 :443, 1903. (N. Ca.) 4. Peok, N. J. Geol. Surv., 1904 Kept. : 163, 1905. (N. J. and Pa.} 5. Perkina, Eng. and Min. Jour., LXXXVI : 753, 1908. (Vt.) 6. Pratt, N. Ca. Geol. Surv., Boon. Papere, No. 3 : 99, 1900. (N. Ca.) 7. Pratt, U. S. Geol. Surv., Min. Reg., 1905 : 1361, 1909. (Vt.) 8. Smyth, Soh. of M. Quart., XVII : 333, 1896. (N. Y. and bibliography.) 9. Waldo, Min. Indus., II : 603, 1894. 10. Wataon, Min. Res., Va., Lynchburg : 293, 1907. CVa.)

b,

ECONOMIC GEOLOaT

Tripoli

Proparttes and Occurrence. — The term Tripoli ia somewhat loosely used to include many siliceous substances used for abraave purposes, but in this place it is restricted to certun siliceous rocka . found in Missouii (2, 4) and Illinois (1, 3).

The Missouri tripoli is a light, porous, siliceous rock which has been extensively quarried near Seneca, Missouri, but it is known at other localities in the state, and even in Oklahoma.

The deposits occur in the Boone (Lower Carboniferous) forma- tion (4), consisting of alternating limestones and cherts having an aven thickness of 350 feet, and with only an odlitic limestone as an easily rectpiized bed. The tripoli beds, which occur mostly above the last, are 4 to 12 feet thick, and overlmn by chert, gravel, and red clay. Chert may also occur in the tripoli itself, and even form a large proportion of it.

The tripoli is an even-textured, finely porous rock, nose grains are mostly under .01 mm. in diameter, and are probably cbal- ' cedony. The following analyses represent the compomtion of the i stone from Seneca, Missouri : —

Anaitsss of Tbipou

FBOM SSNECA, Mo.

SiO.

9S.I0

AliO,

M

PoA

CaO

tr.

K.0

—

J23

iwi.

.So

Oqj

—

—

1. R. N. BraclMitt, Ark. Geol. Surv., V : 267, 1892. 2. W. H. Seanuu), Soi. Am. Supp., July 28, 1894 : 15487. 3. Mo. Oool. Surv., VII : 731, 1894.

A commonly accepted theory is that the tripoli results the decomposition of chert, but while chert is in the tripoli beds, it is not posMble to find a transition from tripoli laterally to unaltered rock. It is also difficult to see how the common chert of this regon could form the masave, non-fossiliferous tripoli.

b,

Minor Mineral 291

Siebenthal (4) believes the tripoli to have been derived by the leaching of lime carbonate from beds hke certmn gray, dull, massive limeatones now found in this region.

UseB. — The rough blocks are sawed up into filter stones, while the spalls and small pie<!es are ground up for tripoli flour, and there lias been a great increase in the production since 1885. The tripoli is vorth $6 to $7 ton f.o.b. Tripoli stone b used to some extent for blotter blocks and scouring bricks. Tripoli flour is used as an abrasive for general polishing, burnishing, and buffing, and also as an ingredient of scouring soaps.

In southern Illinois, in Union and Alexander counties, there are beds of fine-grained silica, which may be similar to the Missouri tripoli. Its orin and extent are, however, imperfectly known. An analysis yielded SiO, 98.00; MgO, .20; A1,0,, 1.21; Moist., .15; Und., .44. The silica consists of minute particles from .50 to .2 mm. diameter, of crystalline structure, transparent character, and irregu- lar shape, loosely cemented by a small amount of clay. It may be used for wood polishing and other piuposes.

Rbfbrbrcbs Oh Tsipou

1. Bain, HI. GoI. Surv., Bull. 4.185, 1007. (lUinois.) 2. Hovey, Sai. Amer. Suppl., July 28, 1894, p. 15487. (Misaouri.) 3. Parr, Ernest and Williiins, Jour. Indus, and Eng. Chem., 1 : 692, 1909. (Illiiiois.) A. Siebenthal and Mesler, U. S. Oeol. Surv., Bull. 340 : 429, 1908. (Miaaonri.)

Wavellite

Wavellite has been used to a small extent in the United States as a substitute for rock phosphate, in making phosphorus.

This mineral does not usually occur in minable quantities, but a eomewhat unique deposit has been found on South Mountain, near Mount Holly Springs, Pa. There the wavellite occurs in a white readual clay derived from talcose schists, and associa,td with man- ganese and iron ores. The iron and manganese have been concen- trated during the weathering of the rocks, and deposited in the residual materials, near the contact of the limestones of the valley and the mountun sandstones. The phosphate occurs as nodules, scattered through a white clay, lying between a manganese-bearing red clay and the mountain. The width of the deposit is 40 to 50 feet. The mining of this material was reported by the United States Geological Survey for 1906, but mnce then no production has l)een recorded.

b,

292 Economic Geology

Phosphorus is used mainly for making matches as well as for fuse compositions, rat and insect poison, phosphoric acid, and for other compounds used in medicine and the arts. It is also used in the preparation of precious metals, electrotyping, and in phosphor bronze.

Refbrehcb8 Oh Wavbluts

1. Stose, U. S. Qool. Surv., Bull. 315 : 325, 1907. 2. Hopkms, Ann. Rept. Pa. State Coll(e, 1889-1900, appendix III : 13.

b,

' UNIVERSlT'f

Iv,

Platk XXIX

FlO. 1. — Section of an artesian basin. A, poTOUa si beloiv and above .i4, acting 08 confinins strata: F, bed .4, or, in other words, height in reservoir oi wetU Bpriiigiiig from the porous water-filled bed

-stum; B, C, impervious beds height of water level in porous fountain head; D. E, Sowing

— Section illustrating artesian conditions in jointed cryatallinc rocks without surface covering. A. C. flowing wells fed by joints: B. intermediate well between A and C of greater depth, but with no water: D, deep well not encountering joints: E. pump well adjacent to D, obtaining water at shallow depths: S, dry hole adjacent to a spring, showing why wells near springs may fail to obtain

[o. 3. — Section illustrating conditions of flow from solution passages in limestoDe. A. brecciatcd lone (due to caving rooO serving as confining agent to waters reached by well 1 : B, silt deposit filling passage and acting as confining agent lo waters reached by weU 2; C. surface debris clogging channel and confining waters reached by well 3; D. pinching out of solution crevice resulting io confinement of watras reached by well 4.

iitions of flow from joints, cracks, and 9 Qvercd by impervious clays and fed from m

b,

Chapter Xiii Uhdergrouhd Waters

The investigation of underground waters has assumed such im- portance in the last few years, that it is hardly possible to do it justice in the limited space which can be devoted to it here. How- ever, some of the more salient points can perhaps be touched upon, and those who desire more detailed information are referred to the selected bibliography at the end of the topic.

Vllile much of the water uaed for supplying towns and cities, for irrigation purposes, etc., is obtained from below the surface, all of it originates in rainfall. The rain water falling on the surface is disposed of in part by evaporation and surface run-off, but a vari- able and sometimes large percentage seeps into the ground.

Ground Water (5, 6) — A small part of the water soaking into the ground is retiuned by cap- illarity in the' surface soil, to be returned again to the atmosphere,

either hv direct — section bctobb k river vnllcy, showing the

oy uircM; poutioD of ground water and the undulatioiu of the water

evaporation or table with reTereDcc to the surface of the srouad aod bed

through plants* {After SMiMer, U.S. Geol. Surr.,WaUrSuppti/

but most of it °""1"

finds its way into deeper layers of the soil, which it completely

saturates.

The water in this saturated zone, which is termed the ground Hifer {Fig. 105), forms a great reservoir of supply for lakes, springs, and wells; and its upper surface, known as the water table, agrees somewhat closely with that of the land surface, but is farther from it under hills (Fig. 105), and nearer to it under the valleys. Under some depressions it may even reach the surface and form springs or Swampy conditions (see Fig. 105). The depth of the water table is quite variable, being but a few feet below the surface in moist climates, while in arid regions it may be 100 feet or more. 293 OOglf

294 Economic Geoloot

In any area, however, the water table may show periodical fluctua- tioD8, due in part and mtdnly to variation in the supply. Near the coast line, the rise and fall of the tide may also affect it (Fig. 106). In all ground water there is a slow but constant movement from higher to lower levels, just as in the case of surface waters, so that the ground water flows toward the valleys. There it may dis- charge into the streams, but in some instances it follows the valley bottom below the river bed, separated from the river water by a more or less impervious layer (6). The composition of the ground water also shows a somewhat close relation to the rocks or soils in which it acciunulates.

Artesian Water. — Under this heading are included those waters confined in rocks of consoUdated or unconsolidated character, under sufficient pressure to cause the water to rise toward the surface, along an avenue of escape, but not necessarily- hi enough to produce an outflow.

The artan water found in rocks may collect there in cani- ties of diverse size, origin, and Fio. loe.— Section showing effect of tide shape, Buch as pores between the on level of water ubic. (After BUiK, arains, joint cracks, beddinir U.S.OeoLSun..W.a.Bua.232.) , ' ', .. .,.' ...

planes, solution cavities, cavities due to brecciation, gas cavities of lavas, etc. (PI. XXIX), The surface water finds its way down into these open spaces in the rocks, and if there is some confining agent, such as denser rock, or other more or less impermeable barrier, present, it may be held there. Under these conditions it may be under more or less pressure and if some avenue of escape, such as a drill hole, is opened up, the water rises towards the surface.

The requisite conditions of an arteMan flow might therefore be stated as follows (2); (1) adequate source of water supply; (2) a retaining agent offerii more reastance to the passage of water than the well or other opening; (3) an adequate source of pressure.

The retaining agent may be a stratum, vein, or dike wall, joint, fault, a water layer, etc., while the pressure is due primarily to variations in level in the different parts of the artesian system, although there may be numerous modifying factors. It will be understood, from what little has been stated above, that a supply of artesian water might be found under a variety of conditioas. Only

z .IV,

Underground Waters 295

two of these vill be conadered here, although several othere are shown in Pla. XXIX and XXX.

Stratified Beds. — The structure sometimes found in stratified rocks closely approaches the most favorable conditions for aQ ar- tedan circulation. That is, we have inclined layers of pervious rock, inclosed between beds of impermeable, or but slightly per- meable, character. Water Sowing down these permeable beds, either through the pores, or in the pores and joints together, may accumulate in sufficient quantity to yield a large and sometimes steady supply. While sandstones usually show the highest porosity of any of the sedimentary rocks, limestones may also yield a good flow, although in these the water must accumulate largely In the joint planes. Such a structural type, composed of water-bearing beds between denser ones, may be termed an artesian slope (PI. XXIX, Fig. 1), and it is of great importance. The wells tapping such a supply are sometimes many miles from the area of intake, and may be sunk to depths of as much as 2000 feet in order to reach the water-bearing bed. A more or less tight bed over the porous one is essential, but the underlying bed need not be impervious.

A not uncommon type of artesian reservoir is that found in ial drift where water-bearing lenses of sand or gravel are over- \aia or more or leas surrounded by clay. In this case the water seep- ing downward from the surface collects in the gravel pocket.

There are many areas in the United States in which the condi- tions are favorable to an artesian water supply in stratified rocks, as the various state and government reports will show. A few of the more important ones may be briefly referred to.

Aloi the Atlantic and Gulf coastal plain an abundant supply of artesian water is obtained from the Cretaceous and Tertiary beds at depths varjdng from 50 feet along the inland border, to 1000 feet and over along the coast (7, 10, 22, 41, 48) (Fig. 107).

A second area is that of the upper Mississippi Valley (50), in which an abundant supply of potable water is obtained from the St. Croix and St. Peters sandstone, whose outcrop in Minnesota and Wisconsin covers some 14,000 square miles.

In the Great Plains (8) reon water is obtuned from the Dakota sandstone, whose collecting area is around the border of the Black Hills (Fig. 108) and eastern edge of the Rocky Mountains. This source is available in South Dakota and eastern Nebraska and Kansas and Colorado. The chief use of the water in this region is for irrigation.

D,q,z.<ib,Coogle

296 Economic Geology

For the arid reons of the west this eource of supply haa been of inestimable value and has been the means of reclaming many an area of hitherto useless laud

CrystaUine Rocks. — Recent investigations have shown that a considerable amount of water may seep downward along the ver- tical joint planes of crystalline rocks (PI. XXIX, Fig. 2), such as granite, crystalline limestone, gneiss, and schist, and become stored in the horizontal joint fissures, but owing to the denaty of these rocks, very little water can accumulate in the pores. If now a well

Fig. 108. — SeotiOD (Tom Black HOli aarosa South Dakota, shoimg artcaiaii well conditiooa. {AJter Darion.)

is drilled so as to strike these water-bearii joints, a more or less steady supply may be obtained. In most cases the volume is not more than 10 gallons per minute, but occasionally as much as 90 gallons has been obtained by pumpii.

Wliile the finding of a supply of water in crystalline rooks is more

— Section illuBtratJug ci

iH of How from foliation tuid Bchiatoaity pluies.

A, Foliation plane feeding flowing well 1. (_After Fuller.)

b,

b,

Undekgkound Waters 297

or less a matter of chance, stiU the proportioD of successful wells is large, although the possibility of success decreases greatly below 200 feet, and is less even below 50 feet than above it.

A number of wells have been bored in the crystalline rocks of New England and even other eastern states (3, 21, 31).

KErSRSHCES OH UHDBBSROURD WATERS

Obiqin and Accumulation. 1. Chambeilin, U. S. Qeol. Surv., 5tti Ann. Kept. : 125, 18S5. (Artesiui wter supply.) 2. p\iller, U. S. Oeol. Surv., Bull. 319, 1908. (CoatroUins faotors of Arteuan flow.) 3. Clapp, Eog. Reo., LX : 525, 1900. (Water in oiyBtalline rooka.) 4. Johnson, U. S. Oeol. Surv., W. S. pap. 122, 1905. (Relation of l&w to undergrouml water.) 5. King, U. S. Oeol. Surv., 19th Ann. Rept., II ; 59, 1899. (UndeTKround water oirculation.) 6. Sohlichter, U. 8, Geol Surv., W, S. pap. 67, 1902. (Oeneral on underground waters.)

Ahiai. General: 7. Darton, U. S. Qeol. Surv., Bull. 138, 1896. (At- l&ntio Coastal Plain.) 8. Darton, U. 8. Oeol. Surv., Prof. Pap. 32, 1905. (Central Oreat Plainfl.) 9. Darton, U. S. Qeol. Surv., W. S. pap. 149, 19(3. (Deep well borings of U. S.) See also Fuller and others. No. 284, 1905. 10. Fuller and othera, U. S. Oeol. Surv., W. S. pap. 114,1905. (E.U.S.) 11. Fuller, /bid.. No. 100. 1905. (Hydrography U. S.) 12. Fuller and othera, U. 8. Qeol. Surv., W. S. paps. 120, 1905, and 163, 1906. (Biblitraphy.) — Alabama : 13. Smith, Ala. Qeol. Burv., Bull., 1907. — Arkansas : 14. Veatoh, La. Oeol. Surv.. BuU. I, 1905. (8. Ark.) — CaUfomla: 15. Leo, U. 8. Oeol. Surv., W. S. pap. 181, 1906. (Owens Valley, Calif.) 16. MendenhaU. Ibid.. No. 225, 1909. (Indio region.) 17. MendenbaU, Ibid., No. 222, 1908. (San Joaquin Valley.) 18. Mendenhall, /6id., No. 219.1908. (Calif.) — Colorado: 19. Eldridge, U. S. Qeol. Surv., Mon. 27. (Denver basin.) 20. GUbert, Ibid., 17th Ann. Rept., II : 557, 1896. {Ark. valley.)

— Connecticut: 21. Qregoir, U.S. Gool. Surv., W. 8. pap. 232, 1900. — Georgia : 22. MoCallie, Qa. Oeol. Surv., Bull. 7, 1899.

— Illinois: 23. Udden, lU. Oeol. Surv., BuU. 8 : 313. 1907. (Peoria district.) 24. Savage, Ibid., Bull. 4 : 235, 1907. (Springfield quad- rangle.) 25. Leverett, V. 8. Oeol. Surv., 17th Ann. Rept., II : 701, 1896. — Indiana ; 26. Leverett, U. 8. Qeol. Surv., W. S. pap. Nos. 21 and 26. — Iowa : 27. Norton, la. Oeol. Surv., VI : 115, 1897. — Ken- : 28. Matson, U. S. Oeol. Surv., W. 8. pap. 233, 1909. (Blue grass region.) — Louisiana: 29. Harris and Veatoh, Ia. Qeol. Surv., Bull. I, 1905. 30. Harris, U. 8. Oeol. Surv., W. S. pap. 101, 1904. (S. La.) — Maine: 31. Clapp and Bayley, U. 8. Oeol. Surv., W. 8. pap. 223, 1909. — Hichigan : 32. Lane, U. 8. Qeol. Surv., W. 8. papa. 30 and 31. 33. Leverett, Ibid., 183, 1907. — Mississippi: 34. Crider and Johnson, U. 8. Qeol. Surv., W. S. pap. 150, 1906.

— Hiaaoori: 35. Shephard, U. S. Oeol. Surv., W. S. pap. 105, 1907.

— Montana: 36. Fisher, U. S. Qeol. Surv., W. S. pap. 221, 1909. (Great Falls region.) — Nebraska : 37. Condra, U. S. Qeol. Surv., W. 8. pap. 215, 1908. {N. E. Neb.), See so Ref. 8. — New

iv,Coog[c

298 Economic Qeologt

Hampshire : 38. Smith, U. S. Oeol. Surv., W. S. pap. 145, 1005. (Portsmouth region.) — New Jersey : 39. Wocman, N. J. Geol. Surv., Ann. Rept. 1902 : 59, 1903. See also Ref. 7. — New Uexico : 40. Lee, U. S. 0ol. Surv., W. S. pap. 188. 1907. (Rio Grande valley.) — Hew York : 41. Veatoh and othora, U. 8. GeoL Surv., Prof. Pap. 45, 1905. (Long Island.) — OkUlmnu : 42. Gould U. S. Geol. Surv., W. S. pap. 148, 1905. — Oregon : 43. Waring, U. S. Geol. Surv.. W. 8. pap. 220, 1908. (8. Cent. Ore.) — Texaa : 44. Gould, U. S. Geol. Surv., W. S. pap. 191. 1907. (Panhandle region.) 45. Taylor, Ibid., No. 190, 1907. (Coastal plain.) — Utah : 46. Lee, U. S. Geol. Surv., W. 8. pap. 217. 1908. (Beaver Valley.) 47. Rich- ardson, Ibid., No. 157, 1906. (Utah Ike and Jordan River). — Tlrgiiua: 48. Watson, Min. Rea. Va. : 259, 1907. — Wuhinston: 49. Ruddr, Wash. Geol. Surv., I : 296. 1901. — Wisconain : SO. Kireh- offer. Bull. Univ. Wis.. No. 100, 1905. (OeneraL) SI. Weidman, Wis. Oeol. Surv, Bull. 16 : 666, 1907. (Crystallinea area, N. Cent. Wis.) — Wyoming : 52. Knight, Wyo. Univ. Exper. Sta., Bull. 45,

Mineral Waters

This term is cwnmonly applied to those spring waters containiog a variable amount of diasolved solid matter of such character as to make them of medicinal value. Their orin, although often regarded as curious, is dmple, the dissolved substances having been derived from the rocks through which the spring waters have rarcu- lated. Many mineral waters contain carbonic and even other acids, and alkalies, which further increase their powers of solution. There is apparently some connection between hot mineral springs and geological structure, as they are more abundant ia rons of fault- ing or recent volcanic activity. Waters flowing from shallow sources usually show the lowest mineralizataon, and those derived from sedimentary rocks often show a greater quantity of dissolved material than those occurring in igneous rocks.

Springs whose temperature is above 70° F. are termed thermal, those between 70° F. and 98° F. being classed as tepid, and those hotter than this as hot springs. The following will serve as ex- amples to show the temperature of different thermal springs: Sweet Springs, West \rginia, 74° F.; Warm Springs, French Broad River, Tennessee, 95°; Washita, Arkansas, 140° to 156°; San Bernardino Hot Springs, California, 108° to 172°; Las , New Mexico, 110° to 140°.

The volume of discharge shown by mineral springs is quite vari- able. The famous Orange Spring of Florida discharges 5,055,000 gallons per hour, while others are as follows: Champion Springs,

Iv,

Underground Waters 299

Saratta, New York, 2500 gallons; Roanoke Red Sulphur Springs, Virgima, 1278 gallons; Warm Sulphur Springs, Bath, Vu-pnia, 360,000 gallonfl; Glen Springs, Waukesha, Wisconsin, 45,000 gallons.

While a classification of mineral waters may be geographic, geo- loc, therapeutic, or chemical, that prepared by A. C. Psale is perhaps as satisfactory as any. He subdivides mineral waters into the following classes: —

AlkalinMaline I 8lphated [ Murifited

IMiiri&ted

f Bulphated J Muri&ted

Sodio Lithie PoMsaio

Magnedo

Chalybeate

Aluminoua

J Sulph&ted I Muriated

The springs falling in the above groups may be either thermal or nonthermal, and may be ather free from gas or contain COi, HiS, N, or CH4.

Other classifications will be found in references.

Moat mineral water olasaifications are unsatisfaetor;. partly for tlis nuon that, though they give the important salt present in each class, they do not give the amount, a matter of some importanoe. Thus it has been pointed out for example that two mineral waters might oontain, re- spectively, 250 and 2000 parts per million of mineral matter of the same relative composition, and would therefore fall in the same class. Both might be earboTuUed, todie, ealeic, tnurtofaj, alkidine-ialine. Now the former would be satisfactory, but the latter would not only be too hard for household uses, but would contain so much salt as to give it a decided taste.

Again, it is important in somecases to know the probable oombinationa present. To a phyaioian it is immaterial to know whether sulphates present >re those of sodium or magnesium, since they have similar medioinal effects. The engineer must know which, as the former is harmless, while the latter forms boiler scale.

Distrlbutioii of Mineral Wateis In the United States. — There fire, according to Feale, between eight and ten thousand mineral springs in the United States, and of this number 695 reported pro- ducUoa, 1908. The majority of the commercially valuable mineral springs are located in the eastern United States and Mississippi Valley. West of the lOlst meridian they are confined chiefly to

oogle

Economic Geology

the Pacific coast. No thermal springs are known in the New England states. Among the American springs, those at Saratoga, New York, have an international reputation, and compare well with many of the fordgn ones. Others of importance are the Hot Springs of Viria and the Hot Springs of Arkansas.

The following table contains the analyses of several types of mineral waters from the Unitd States: —

Analtsbs of American Mineral Waters

Sodium carbonate . . Sodium bicarbonate Sodium Bulohste . . Calcium carDouate . . Maeainin carbonate . Calcium bicarbonate . Magiiesium bicarbonate Litmum bicarbonate Iron bicarbonate . . Magnesium sulphate . Potassium sulphate Sodium chloride . - - Potassium chloride Potassium bromide Sodium bromide . Sodium iodide . Siliea Calcium sulphate

'ir

8S3

Prodaction of Mineral Waters. — The production of mineral waters in the United States for the last five years was as follows: —

EsTtUATED PnoDucnoN of Mineral Watebb, 1904 to 1908

Yeab

SruHoa

GlLLOHS Soul'

V.™

fifl, 108,830

Ss

i,vCoog[c

Underground Waters

Rank of States babxd on Sprihos RBPORTtNO, on Qdantiti OK Value of OnTPnT, 1909

"Ih'

Total Valci

,

iDdiuU

WiKOnidn

Wiwondn

Ktw York

Nir York

Ne York

Viremia

WbcopHD

Indiuu

CulTiomui

Ohio

Taiu

Gilifomi.

CtlUomte

ssa,

NairYork

MBiDe

MiMouri

NnHunp.

New Hamp-

Nnr Hmip-

tbin

Viitfnim

gSir

Tu

Michlsu

k™

Vinini.

VksioU

Sbtbrencbs Ob Witbral Waters

1. Bftiley, Kas. 061. Surv., VII : 1902. (Eas.) 2. Bartow, Udden, , and EWmer, 111. Oeol. Surv., BuU. 10, 1009. (General and lU.) 8. Branner. Ark. Geol. Surv., Rpt., 1, 1891. (Ark.) 4. Crook, Mineral Waters of United States and their Therapeutic Value. {N. Y., 1899.) 5. Haywood, U. S. Dept. Agrioult., Dept. Chem., Bull. 91. (Classi- fieation.) fl. I*ne, U. S. Geol. Surv., Water Supply Bull. XXXI, 1899. 7. Peale, U. S. Geol. Surv.. 14th Ann. Rept.. II ; 51. (U- S.) 8. Sohweitzer, Mo. Geol. Surv., Ill, 1892. (Mo., also general.)

b,

b,

Pabt Ii Ore Deposits

bvGoogle

Iv,

Chapter Xiv Orb Deposits

Definition. — The term ore deposits is appHed to concentrations of economically valuable metalUferoua minerals found in the earth's crust, while under the terra ore are included those portions of the ore deposit of wluch the metallic minerals form a sufficiently lai proportion and are in the proper combination to make their esrtrac- tion posable and profitable. The term ore mineral can be applied to those minerals carrying the desired metallic elements which occur within the depoat. These ore minerals may in some cases make up the entire mass of the ore.

A metalliferous mineral or rock might therefore not be an ore at the present day, but become so at a later date, because improved methods of treatment or other conditions rendered the extraction of its metallic contents profitable.

A few metallic minerals serving as ore minerals, such as gold, copper, platinum, or mercury, sometimes occur in a native condi- tion; but in most cases the metal is combined with other elements, forming sulphides, hydrous oxides, carbonates, sulphates, silicates, chlorides, phosphates, or rarer compounds, the first five of these being the most nimierous. A deposit may contn the ore minerals of one or several metals, and there may also be several compounds of the aame metal present.

Gangue Minerals. — Associated with the economically valuable metalhc minerals there are usually certn common ones, of metallic or non-metallic character, which carry no values worth extracting. These are termed the gangue minerals. They often form masses in the ore deposit which can be avoided or thrown out in mining, but at other times they are so intermixed with the valuable metal- liferous minerab that the ore is crushed and the two separated by special methods.

Quartz is the most abundant gangue mineral, but calcite, barite,

fluorite, and aderite are also conunon, while dolomite, hornblende,

pynaene, feldspar, rhodochrosite, etc., are found in some ore bodies.

r 305 OOgIc

306 Economic Gbologt

Ofigin of Ore Bodies. — The fact that ores form masses of greater or lesB concentration is explainable in two ways : cither they have been fonned at the same time as the inclosing rock (contemporor neow or syngen ', or else they have been fonned by a process of concentration at a later date isubseguenl or epigenetic). The first theory is found to be applicable to some ores in eous rocka, and probably a few in sedimentary ones, while the second applies to most ore deposits, regardless of the character of the inclosiDg rock.

It must not be inferred from this, however, that the origin of all known ore bodies has been definitely settled, for a strong difference of opinion ennetimes exists among geolosts regarding the same deposit, and some have been placed first in one class and then in another ; but with all this shiftily the number of occurrences f allii in the syngenetic class has increased considerably and now includes some large and important ore occurrences.

Syngenetic deposits. — These may be divided into two groups, viz. those of mmatic orin, and those of sedimentary origin.

Mogmatic legregationB (1, 7, 10, 13, SO, 89). — Under this head- ing are included a small class of deposits, whose intimate associa- tJon with igneous rocks seems to prove beyond doubt that they have been derived from the igneous magma by a process of segre- gation during crystallization from it.

These separations usually take place during the early stages of cooling, and they form the first of a series of minerals, usually crystaUizii out in definite order. The first to separate out from the cooling magma are certain oxides such as magnetite, speculsr hematite, and more rarely chromite and picotite, t(ther with a few alicates such as zircon and titanite.

Following these come some metallic sulphides, as pyrite and pyrrhotite, while after them the ferro-magnesaa sihcates separate, and lastly other Bihcates.

A separation of the heavy metals appears to be characteristic of igneous mmas defideut in acid-fonnii constituents, but this is not BUrpring, for a consideration of the composition of igneous rocks shows us that since the bascity of an eruptive rock depends partly on the percentile of the oxides of heavy metals, the base ones are more apt to yield mmatic separations than the add ones. In some cases, however, metallic concentrations may occur in rocks.

In these segregations it is seen that the metallic minerals which L,-z .iv.

Ore Deposits 307

have gathered together to fonn the ore depomts are amply common accessory, and not important, constituents of the igneous rocks. That is, the ore body and the country rock contfun the same min- erals, but the relative abundance of the silicates and metals are reversed. As an example : the average percentage of chromium in the rocks of the earth's crust is about .01 per cent. In a peri- dotite mfma it forms about .2 per cent, but in segregations within the magma we find 40 to 60 per cent Cr,.

Form of Moffmaiic Ore Bodies. — Ore depodts formed by ma- m&tic segration not only show a varying degree of concentration, but vary greatly in their size and form. Some exhibit vast dimen- sions, as the Scandinavian iron ore deposits of Kirunavara and Ijioasavara (Sjogren) ; indeed, these are much larger than any of tiiis type known in North America, the nearest approach to them bng the nickel depcits of Sudbury, Ontario.

Magmatically aegrated ore bodies may occur : (I) as irregu- larly distributed deposits, which show a transitJon into the sur- roundins igneous rock ; (2) as deports on the border of the igne- ous rock, but lying mainly within the former and sendit tongues out into either; or (3) as dikes in the igneous rock. In the latter case they might be regarded as very basic segregations, which have been forced up from below, subsequent to the intrusion of the baEdc rock itself. (See Iron ore, Wyoming.)

As stated above, the number of ore deports formed by magmatic segregation is small in number, but the following types can probably be referred to this class :

1. Titaniferous iron ores in basic and intermediate eruptives (Adirondacks, New York, Iron Mountain, Wyoming, etc.), and perhaps some iron ores in add eruptives (Mineville, New York).

2. Chromite in peridotites and the secondary serpentines.

3. Some sulphide ores (Sudbury, Ontario, and Lancaster, Penn-

sylvania (?).

4. Nickel-iron ores in eruptive rocks (no value).

5. Platinum in basic eruptives (no value).

6. lln ores in some pegmatites (South Carolina).

7. Some gold ores in quartz veins (Silver Peak, Nevada).

Syngenetic Deposits of Sedimentary Origin. — If ores in sedi- mentary rocks are of contemporaneous origin they must have been formed at the same time as the rock in which they occur, the process either a chemical or mechanical one, mmilar to that by which

D,q,z.<ib,Coogle

308 Economic Geology

the different kinds of stratified rocks have been formed. Two classes might be recognized, viz. (1) interstratiSed depoaite, and (2) surficial deposits or placers.

IrUerstratified sedimeniary depoaita. — These may have originated by processes analogous to those which have formed the inclosing rocks. Some may have accumulated by precipitation from sea water or fresh water, a process which is going on evenat the present day, as shown by the deposition of limonite in ponds, or the fonnar tJOQ of nodules of limonite, pyrite, or manganese on the ocean bot- tom.

Others may be of mechanical origin, the grains of metallic minerals having been Bet free by disintration of rocks on the land, and the particles later becomii segreted, as in the caseofmie- tite sands, formed along the beaches by wave action. Both types may be subsequently covered up by other sediments, or in rarer cases by igneous flows.

Sedimentary deposits of the two types just mentioned are of tabular form, and thin out horizontally in all directions, but many of them are of great extent (Clinton ores) and even of curiously uniform character. They are sometimes sharply separated :rom the inclosing rocks, or at others grade into thn. Further charac* teristics to be noted are the absence of fragments of the overlying country rock in the ore, and of veinlets branching off from the bed. If folding of the rocks has occurred, the beds follow the folds. Sedimentary depodts are occaaonally enriched by water orcu- lating through the beds and causing a concentration of the contents.

Placer deposits. — Placer deposits now found on the surface are of recent geologic age, thus differing from meciianically formed interbedded ores, and have usually orinated by stream action.

When the products of rock decay are washed down the slopes and into the streams, the hghter material is carried off to sea, while the heavier particles such as pebbles and metallic mineral grains remn behind in the stream channels. The metallic fragments by reason of higher specific gravity settle to the bottom oi the channel, and sH become more or less rounded by the rublNDg action they are subj ected to while moved along by the stream 1 current.

Placer depodts may also be formed aloi beaches by wave action, . while a rare type are those which orinate in dry climates by tbe

C,q,-Z.-dbvCOQg[C I

Ore Deposits 309

diant!;ration of rock, little of the material being removed, except sandy particles which are blown away by the wind.

From what has been said above, one must not get the idea that placer depodts did not form in the past, for they did, and are known to exist in sedimentary fonnationB as far back as the Cam- brian. (See Gold, South Dakota.)

Epigenetic Ore Deposits. — These, aa previously stated, are of later than the incloEdi rock. In other words, they have been concentrated in the rocks by natural processes.

In order to demonstrate this it is necessary to show: (I) the source of the metala found in the rocks ; (2) the existence of a car- rier which could transport the metals, in solution probably ; and (3) the existence of conditions favorable to the precipitation of the

Occurrence of Metala in the Rocks. — It is well known that metallic minerals in small quantities are widely distributed, in both Igneous and sedimentary rocks. Sandberger (76), for example, has shown by analyses the presence of nickel, copper, lead, tin, and cobalt in such minerals as hornblende, ohvine, and mica ; and Curtis has found traces of silver, gold, and lead in the quartz-por- phyries at Eureka, Nevada,' and silver, arsenic, lead, copper, and gold in the granite at Steamboat Springs, Nevada.' Winslow has pointed out the presence of small quantities of lead and zinc in the limestones of Missouri and Wisconsin (see lead and Jiinc references), and Wagoner has made dmilar tests on California sediments (92 a). Since, however, the sediments were orinaUy derived from the igneous rocks, it follows that the latter must be the original source of the minerals. It is interesting to note Uiat even in the igneous rocks the metals are not impartially distributed, but that certn metals seem to favor certain rocks. Thus iron, manganese, nickel, cobalt, chromium, platinum, and titanium seem to favor basic rocks; while tin, tungsten, and some rarer metals favor the acid ones.

While the occurrence of metallic minerals in the rocks of the earth's crust is widely recognized, few, perhaps, reaUze the small percental existing outside of those concentrated portions, the ore deposits; and the following table, showing the average com-

' In many caaee cavities in the rocka offer a favorable point of precipitation, but it ii DOW rectxiiied that open Bpacea are not necess&ry for ore depoedtioa. ' U. S. Geol, Surv., Mon. VII : 80. ' Itrid. Mon. XIII : 350,

' De Launay, Ann. d, Min., Aug., 1807.

Economic Geology

poatioD of rocks of the earth's crust,* will serve to nphaaie this p<ant: —

Manganew 089

Sulphur 11

Barium .09

Chromium .034-

Niekel .023-

Lithium .01

Chlorine .06

Fluorine 02+

Zirooniiun .026-

Vanadium .014-

Stroatium .034

Oxygen 47.08

Saioon 28.30

Aluminum 7.99

Iron 4.47

Calcium 3.46

Magnesium 2.36

Potomium 2.46

Sodium 2.54

Titanium 44

Hydrogen 16

Carbon 13

Phosphorus II

An examination of the above figures shows that, of some twenty , metals that are of importance to us for daily use, only five, viz. aluminum, iron, manganese, chromium, and nickel, are included in the above list, and that the others must be present in amounts of less than .01 per cent.

Professor Yogb has endeavored to estimate the approximate average amount present of other important (economically) metes, not included in the above table. Accordii to him, the p>ercentage amount of tin, zinc, and lead is expressed by a difpt in the ,third or fourth dedmal place, copper in fourth or fifth, silver in axth or seventh, gold and platinum in seventh or eighth. Mercury would show a slightly larger percentage than silver, and arsenir, antimony, molybdenum, and tungsten, between copper and slver. Bismuth, selenium, and tellurium would be placed between alver and gold in the list.

As actual examples of the amounts present, we may quote the following determinations made on eruptive rocks from several localities.

Mbtil

Pen cBHT

LocAurr

Lead

Zinc

saver

Silver

Gold

Gold

Missouri Colorado

MiBBOuri

Missouri Leadvillo, Colo. Eureka, Nov. Eureka, Nev. Owyhee Co., Ido.

oogic

Ore Deposits

It is quite evident that the percentage of metal normally dis- tributed in the rocks of the earth's cniat, as indicated above, ia far too low to be regarded as workable ore, for, in order to be classed as such, the rock must contain at least a certain percentage of the metal, which varies not only with the metal, but even with the same metal under different conditions, such as location and nature of ore.

Iron ores, for example, especially low-grade ones, cannot be suc- cessfully worked, unless favorably located; whereas gold ores, being of higher unit value, are much less affected by this factor. Aun, the nature of the ore has to be conadered, some beii quite eaaly treated, but others less so, and here the manner of association comes into consideration. Thus the presence of copper or lead may fadlitate the extraction of gold and silver, while zinc hinders it. Lastly, with changed conditions, a rock which was formerly of no econooiic value may become a profitable ore to work, partly be- cause improved methods of treatment have lowered the cost of production. The quantity of metal necessary in an ore for profit- able working is referred to under " Value of Ores " in this chapter.

Mod ol CoDceotratioo. — It is now generally admitted that water, whatever its source, is an important agent in the concentra- tion of many ores. While cold water, free from impurities, has com- paratively little solvent power, the presence of acids or alkalies materially increases its solvent capacity, while heat and pressure have aiao a great influence. Analyses of mine, sprii, and surface waters have shown the presence of many dissolved alkalies and other - sts (24), and occafflonally small quantities of metals.

The following two analyses, which will serve as examples, give the calculated composition of (1) vadose, or shallow water, from the 500-foot level of the Geyser alver mine. Silver Cliff, Colorado, and (2) deep water from the 2000-foot level of the same mine. The ore occurs in rbyolite. The figures are grams per 1000 hters.

s

SiO,

Ai=0,

A!rf).,P,0

FoCO,

MnCO,

CaCO.

CiLJ,0

tr.

Cap,

tr.

Economic Gboloot

SrCO,

MgCO,

KiSO,

Kcl

KBr, KI

—

tr.

Na,CO,

NaNO,

—

N,B,0,

tr.

—

Co,

PbCO,

tr.

CuCO,

tr.

ZnCO.

The higher percentage of dissolved substaaces in the deep water is quite marked.

While the importance of hot water as an agent in the formation of ore depicts is clearly recognized by many, and traces of metals in solution are sometimes found, still examples of such depota now formii are rare.

Weed tui9 described a hot spring near Boulder, Montana (lOO), which is depositing auriferous quartz, and the deposit is pointed out by him to be identical with silver- and gold-be&riog quartz veins of the region between Butte and Helena, Montana. At Steamboat Springs, Nevada, it has been found that the alluvial gravels underlying the hot-spring sinters are ce- mented by stibnite and pyrite.' Of still more interest is the oollectioa.bT evaporation, of copper from certain Javan hot springs, in which the metal occurs as iodide of copper.'

Lindgren has also recently called attention to the occurrence of certain mineral springs near Ojo Oaliente, New Mexico (04), whose strongly alfea- line water contains much sodium carbonate as well aa fluorine, boron, and barium, the last being present in considerable amount.

The pre-Cambrian gneiss near by contains veinlets of colorless fluorile, probably deposited when the spring waters issued at a higher level. Higher up the dope is a narrow vein, carrying small amounts of gold and silver in ft gangue of colorless fluorite and some barite, and capped by a calcareous tufa. The latter is supposed to have been deposited at the surface while the fluorite was precipitated farther down in the vein fissure.

Water is known to be widely (11, 39), but not uniformly, dis- tributed in the rocks of the earth's crust, and much of it is in slow

Lindsren. Amer. Inst. Min. Eugn., , 1005 : 27S. ' atevens. Copper Handbook, IV : 166, 1904.

oog[c

Ore Deposits 313

but constant drculation. While it is admitted by moat geoltsts that this water has been an important ore carrier, there exists a difference of opinion regarding its source, one class mntaining that it is largely of meteoric orin, the other that it is derived chiefly from igneous intruaons.

Meteoric Waters as Collecting Agents. — That meteoric waters were the most important, if not the only, collecting agents of ores was advocated by many of the earlier geologists, includii J. Le Conte,* F. Posepny,* and L. De Launay,* while in recent years the theory of ore formation by meteoric waters has been Btrongly urged by C. R, Van Hise (12), He points out that the earth's crust may be divided into three zones : (1) an upper zone of frac- ture, beginning at the surface ; (2) a zone of combined fracture Sewage ; and (3) a zone of rock flowage, or of no fracture.

In zone 1, or that of rock fracture, the rocks, if rapidly deformed, respond by fracturing. If, however, the deformation is exceedingly slow, folding may result, but it is due to the rock slipping along numerous, small, parallel fractures. The conditions in this zone, then, are favorable for the development of numerous fissures or cavities in the rocks.

Most ore deposits occur within this zone, owing to the existence of favorable conditions for the free circulation of water.

In zone 2, that of combined fracture and flowage, the pressure is sufficient to cause some rocks to flow, while others of greater strength will only be fractured. Other factors, such as rapidity of deformation, temperature at which deformation occurs, and amount of moisture present may affect the result. In this zone, then, fractures may exist in certfun rocks but not in others.

In zone 3, that of rock flowfe, the pressure is so great that deformation of the rocks is accomplished by flowing rather than bredng, and practically no cavities can exist, as they will be closed up as soon as formed.

Van Hise estimates that at a depth of about ten thousand meters the strongest rocks will be deformed by flowing.

Into this zone of no fracture water from the surface cannot penetrate, but above it there may be active percolation by water. It is well known that rain water, falling on the earth's surface. Beeps through the soil into the underlying rocks, permeating them

Amer. Jour. Sci.. July, 1883. p. 1.

Traiu. Amcr. Inst. Min. EDgn., XXIIl. p. 213.

' La Recherche Captase, et Amenaecment dea Sourcea ThenDi>-mliiefaleB.

z .IV,

Economic Geology

to a variable depth, and fonning a more or lees saturated eone, whose upper limit, lying at a variable depth, is known as the ground- water level. A second belt of underground-water circulation lies above this, and extends to the surface. The ground-water level is found at a variable depth below the surface. (See Chapter XIII, Underground Waters.)

The water, filtering down from the surface into the rocks, flows through various openings, such as fissures due to jointing, faulting, stratification, or cleavage, through the pores between the , or through irregular openings.

FiQ. 109. — A, ideal horiioiital aection. tuid B, ideal vertical sectioii, of the floir of underKTound water tbrouBh a homogeneoua medium from OD well to an- other, {After Van HUe.)

It should be noted, in this connection, that the permeability does not necessarily increase with the porosity, because a highly porous rock might have such small pores as to be but slightly permeable.

While the movements of underground waters are complex, Van Hise points out that they resolve themselves into two components, viz. horizontal and vertical ones, with the horizontal movement being probably the more important. The entering waters then flow downward first by gravity, and then in general laterally, finally emerng again at the surface. The motion is in general from areas of high to low pressure, and the path traversed may be very irregular and circuitous.

Van Hise has indicated graphically the vertical and horizontal z .IV,

Ore Deposits 315

paths by which waters might pass from one opening to another (Fig. 109). This shows two wells, separated by a homogeneous porous medium. The well A is assumed to be empty, and the well B is filled. It will be seen that some of the water talces a very direct course, while other portions follow a very curved path.

figure 110 shows the circulation of undeiound waters from higher to lower levels. Of course to produce such uniform per- colation must require the presence of homogeneous rocks. There will be a strong tendency for the circulating waters flowing through the pores of the rocks to flow towards, and concentrate in, the

Flo. 110. — Ideal vertical section of flow through a homogeneoua mediuni. A, wnter eDlriiig at s number of points on a slope and passiag to a valley below, intemipted by two vertical open cbaonela, through which they may Bsceiid. B, water CDterine the ground at one point on a elope and emerging at a lower point. iA/la- Van Hiie.)

larger openings, such as fault planes, joint planes, etc., where several different waters may mingle, and the principal deposition of metals occur (Fig, 110). While gravity is the chief cause of the circulation of the groimd waters, other factors are not without influence. Thus, as the waters reach increasing depths, their temperature rises, and this is accompanied by a decrease in the viscodty of the water, accelerating its circulation at those depths. In considering the work performed by ground waters, it is neces- sary to regard the zone of fracture aa divided into two belts, viz. an upper belt of weathering, and a lower belt of cementation. The

316 Economic Qeoloqt

first, in which the ordinary weathering processes go on, fs* tends to ground-water level. The second lies below this, and is characterized by such changes as cementation, induration, hydration, deporation, and increasing volume of the rocks. They are chains involved in the transfer of mineral matter from one point to another. Now, according to Van Hise's theory the descending waters are dissolving more or less mineral matter from the rocks through which they are percolating, this solution going on munly in the belt of weathering; but in the belt of cementation depostion is the dominant process. Moreover, since there is a concentration of currents toward cavities or fissures, most of the precipitation wiU go on there. Furthennore, it is the ascending currents in the larger cavities which are likely to be depositing ones, because in them the temperature and pressure are decreaang, conditions tending to reduce the solvent power and saturation; point of the solution.

Solutions of different kinds meeting at the intersection of two fissures might deposit some of their dissolved mineral matter, because of reactions. While the main depotion is performed by ascending solutions, descending waters may become at times depositing ones.

Magmaiic Waters as Concenlraiing Agents (28, 47. 48, 49, 59, 61), — While some ores undoubtedly owe their primary concen- tration to meteoric waters, still the majority of geolosts probably believe that in most cases the work has been performed by mag- matic waters.

According to this theory the waters issuing from cooling magmas carry metals with them, which they deposit at varying distances from the intrusive as they rise towards the surface. (See further under Mtpnatic Emanations.) In addition, these magmatic solu- tions may also gather some additional metalliferous minerals from the rocks through which they pass. This theory, altliough it has grown greaUyin recent years, is not a new one, for it was suggested by Elie de Beaumont as early as 1850,' but its full dgnificance was not grasped until some years later, when the writings of ' (m 1894), Spurr,' Lindgren (59a), and esi>ecially Kemp (48) did much to emphasize its importance.

Many of the points brought out have been used as arguments against Van Hise's theory of meteoric circulations, and include the

;

Ore Deposits 317

following : Meteoric waters do not reach great depths, in fact prob- ably not more than 2000 feet or sometimes less from the surface, and when they do penetrate to a greater distance, it is because they have followed acme fissure. The lower levels of many deep mines are so dry as to be dusty. Ores have been concentrated at a much greater depth than that reached by surface waters. It is perfectly reasonable to regard igneous rocks as an important source of water, and the experiments of Daubree have shown that a mol- ten granite contains a large amount of vapor which it retains while at great depths, but pves off on approaching the surface and cool- ing. Moreover, vast quantities of steam are emitted by volcanoes during periods of eruption, and certain quickly cooled rocks, such as pitchstones, contain several per cent of water. The sigestJOD that this water has filtered in from the surface is scarcely con- ceivable, as the heat of the molten rock would tend to drive it away.

It is an undeniable fact that most metalliferous veins are found in areas of igneous rocks, and Lindgren (see Metallogenetic Epochs on a later page) has shown that in the case of the gold deports of North America the periods of vein formation agreed closely with those of igneous activity. It is also a noteworthy fact that, with the exception of some deports of commoner metals, such as iron, and some copper, lead, and zinc, ores are foumd in close association with igneous intruaons, which seems to postulate a close connection be- tween igneous rocks and ore deports, as advocated by such authori- ties as Weed, Kemp, IJnten, and Enmions. While the importance of magmatic waters as agents of primary deposition is quite gener- ally admitted, it is true that the metalliferous minerals as originally deposited have not always been sufficiently concentrated to serve as ores, but they have become concentrated at a later date by meteoric waters, as at Bisbee, Arizona. (See Bansome, under copper references.) Posepny (68), in his work on the Genesis of Ore Deposits, distinguishes between descending surface waters, or vadose circulations, and ascending waters from great depths. It is the former that have been active in the secondary concentra- tion of ores.

Depodts from Magmatic Emanations. — Under mmatic ema- nations are included gases, vapors, or liquids, given off by molten magmas during cooling.

In order to point out more clearly the several processes by which ores may be depodted from magmatic emanations it may be well

c,q,z.<ib,Coogle

318 Economic Obology

to turn for a momeat to the molten magma and conaideT certmn changes which take place during the period referred to.

A study of large intruave masses has shown us that the molten mass after coming to rest sometimes tends to separate into two parts, the one baac, the other acid, with a gradational zone between. Tlie add portion may be either the outer or central part of the mass.

A segregation of metallic minerals may occur, though, even if the magma as a whole does not split up. But whether or not such a differentiation occurs, the molten magma, after coming to rest, will cool first in its outer and upper portion, the contraction inci- dent to solidification causing numerous fractures. Into these there may be forced molten rock from the still uncooled lower portions of the mass, or water and gases forced out of the solidifying parts of the mma. This water, however, must be in a vaporous form, because the heat is undoubtedly sufficiently great to nuse its tem- perature above the critical point, and the pressure is likewise heavy. In many cases no doubt the fissure may become filled by a mixture of water and magma, the former in such excess that it may be difB- cult to say whether this should be called an igneous fusion, or a watery solution, for under pressure water can mix with a magma in all proportions, giving us a series of mixtures, with a fused mass at one end and a hot solution at the other.

Many magmas in cooling off mixtures of watery vapors and gases (such as fiuoriue, boron, etc.) ; and these before leaving the igneous mass no doubt extract metallic or other elaneats and carry them along, only to depodt them later, tber in the outer parts of the cracks in the border of the intrusion or in the siUTOUod- ing rocks.

As these emanations from the mma get farther away from it, where temperature and pressure are less, the watery vapors con- dense, and these hot solutions (magmatic or juvenile waters) grad- ually work their way towards the surface, sometimes reaching it, and flowii out as hot springs.

It is posble and indeed probable that as they reach shallower depths they may become more or less mixed with meteoric waters.

These magmatic emanations with their burden of mineral matter may not only deport this at a varying distance from the intruave, but they in many cases often attack the rocks through which they pass, altering them to a marked degree, and in addition dissolve materials from the rocks they permeate.

The kind of materials deposited and the character of the altera-

Ore Deposits 319

tion depend to a large dree upon physical conditions, primarily temperature and pressure.

If the depontJon and alteration occur while the magmatic emana- tiona are stiO in a vaporous form (due to high temperature and pressure), the process is termed jmeumatolysis (gaseous). If it occurs when the water is in hquid form, it is tenued kydalogenesis (aqueous). In some instances both gases and Uquids may be pres- ent, the work then being gaa-<iqueou9 or pneuTnato-kydato-genic.

It is naturally difficult to prove in many cases whether the phe- nomena observed were produced by pneumatolytic or hydatcenetic

Certain important types of depoats, formed under these varying physical conditions, may now be referred to.

Tin and ApatUe Veins (7. 10. 61, 92). — Around the borders of certun granitic masses there are found pegmatite carrying caesiterite, wolframite, etc., as well as fluorspar, topaz, and tour- maline.

The wall rocks of such veins have been strongly attacked, the feldspar and mica especially being replaced by quartz, tourmaline, topaz, lepidolite, etc., giving a rock type known as greisen.

It is pretty generally conceded that these , which are closely assodated with the magma, have been deposited from a mixture of magma, watery vapor, and gases, ven off during the cooling. If the first was in excess, the intergrowth of the quartz and feld- spar has the appearance of crystallization from fusion, although the coarse texture of these minerals points to the presence of a marked amount of watery vapor. In other caaes, however, where it is quite clear that the minerals have grown from the walls toward the center, sometimes incompletely filling the cavity, we are forced to the concluon that watery vapor was greatly in excess, and that the process is largely if not wholly a pneumatolytic, or at most a gas-aqueous one ; moreover, the peculiar kind of alteration of the wall rock indicates the presence of water and gases.

The apatite veins form an analogous group, which are related to basic rocks such as gabbro and contn chlorine as the prominent minerahzing agent in the place of fluorine. They may carry specu- larite and pyrrhotite as ore minerals, and scapolite, diopside, bomblende, and biotite as shcates.

CmUact-metamorphic deposiU (53, 54, 60, 97), — These include inasses of metallic minerab and silicates which are found in some sedimentary rocks, chiefly calcareous ones, near their contact with

z .IV,

Economic Geology

igneous intrusions, specially tliose of a more or less addic char- acter.

It has long been known that an igneous mass may often exert considerable effect on the rocks which it has penetrated, sandstone, for example, being altered to quartzite, clay or shale to homstone, and limestone to marble. Moreover, the contact-metamorphism is accompanied by the development of new minerals in the wall rock.

Thus in limestone there may be formed gamet, wollastonite, epidote, diopside, amphibole, wemerite, vesuviardte, etc.; while in aluminous rock such as shale and slate we find andaluate, silli- manite, biotite, etc.

Fia. 1 11. — DiaerBm illuatratiiiR the rclationa of the various types of ore deposilB directly derived from igneous rocks. (Afler Tkomat and MacAtiMter.)

This figure shows diagramatically the relative width of the sodm characteriied by differeot processes (pneumSitolytic, etc.), and their coatractioD as tbe eruptive

Even until recently it was thought by many that these silicates, as in the Umestones, must be segregated and recrystallised impuri- ties, and hence could form only in impure rocks, the pure Umestones yielding simply a marble.

Investigation of these contact zones has shown us, however, that , they contained many elements which were not found in the lime- stone outade of this belt of metamorphism, and we are therefore driven to the conclusion that they represent substances which have been given off by the magma and lodged in the lime rock.

iv,Coog[c

Ore Deposits' 321

The theory usually advanced to explain the orin of these con- tactnetamorpbic deposits is that, during cooling, the magma gave off watery vapor, heated above its critical temperature (365* C.) and under high pressure. With this there were also mineralizing vapors, such as fiuoiiiLe and boron, and metals as well as silica. The metals are believed by some to have combined with the fluorine or boron to form volatile compoundB,' These were forced out into the fissures and pores of the hmestone, and replaced the latter wholly or in part. The silica, alumina, and iron combined with the lime to form garnets and other licates, and after these came the metals, which were also deported by replacement.

In no case did the substances entering the limestone to form the sihcates wander very far from the eruptive, because they be- came locked up in the limestone, where we find the metaUic minerals intergrown with the contact silicates.

Contact-metamorphic deposits were probably formed at a con- siderable distance below the surface, from a depth of not less than one thousand feet to unhmitable ones, provided the heat was Dot high enough to fuse the sedimentaries. That this has not occurred is shown by the sharp line of contact between the erup- tive and the limestone, which is believed by some to warrant the assumption that no melting of the country rock has occurred.

Contactr-metamorphic deposits are usually of irregular shape and somewhat bunchy in character, but very little can be said regardii the depth to which they may extend.

The common ore minerals found are magnetite and speculante, mixed with sulphides such as bomite, chalcopjTite, pyrite, pyr- rhotlte, and more rarely galena and zinc blende. Some gold and silver may also be present, but tellurides are probably very rare. A characteristic feature is the occurrence of both sulphides and oxides, thus differentiating them from fissure vns.

The gangue minerals are in general lime-alumina sihcates, and include garnet,' wollastonite, epidote, amphibole, pyroxene, nnmte, vesuvianite, quartz, and calcite, but rarely barite, fluorite, apatite, and tourmaHne. The first of these is especially abundant and may form nearly the entire mass of the rock.

Contact-metamorphic deports, though sometimes rich enough

The rarity of fluorine and boron minerala in most contact-metamorphio de- poaita may reasonably cause some to doubt this.

' Mainly andradite, the iioD-litDe gamet, and lew often grouulsrite, the lime- alumioa samet.

b,

322 ECONOMIC GBOLOaY

to mioe where not secondarily enriched, need this process in many cases to make the ore workable. This is well illustrated in the case of the Morenci, Arizona, copper ores.

Although this class of deposits was recognized by Van Groddeck, as early as 1879, he failed to appreciate the true importance of the aasodated intruave. In more recent years the writings of Vogt, Kemp, Weed, Lindgren, and Barrell have greatly increased our knowledge of the true nature of these interesting deposits, and we DOW know, moreover, that they form a very important and somewhat common type, which in the United States is restricted mainly, however, to the Pacific Cordilleras.

Gold- and SUt)er-bearing Veins (61, 13), — These as described by Lindgren form a most important class which carry gold and Eolver, as well as varyii amounts of other metals, and have probably beea formed at considerable depths, where temperature and pressure were ' relatively high. They are usually associated with granite intruons in schists, and show a strong replacement of the country rock.

Ore Deposits formed at ShaUmo Depths (61, 13),— These m- clude a number of fissure-vein depodts, found in the CordUleraii reon, and carrying gold with much fdlver, as well as subordinatA amounts of lead, isinc, and copper. The fact that they are found in flows of volcanic origin indicates their formation at compara- tively shallow depths, that is, from a few hundred to four or five thousand feet. They include most of the vans of western Nevada, the San Juan reon of Colorado, CrippleCreek,Colorado,di3trict, etc.

Gold and silver are prominent, althou the former is more abundant and the native gold usually more finely divided.

Like the deeper veins they may carry pyrite, ena, and sphal- erite, but in addition chalcopyrite, arsenopyrite, argentite, and Btibnite are characteristic ore minerals. Quartz is a common gangue mineral, and calcite, dolomite, siderite, barite, and fluorite are also found.

Metasomatism varies somewhat with the different rocks. In moderately add rocks sericitazation and even pyritization seem to be common near the vein, and propylitization ' farther away. In basic igneous rocks, propylitization may extend dose to tie vein, but sericitization occasionally takes its place. Siticification of the wall rock is common even in calcareous rocks.

This class would also include cinnabar deposits.

1 This consists in the derelopment of chlorite and epidoto as wall u pyrite, from dark slicates, and the breakmg down at feldspar to quarti, chlorite, and epidots.

c,q,z.<ib,CpOgle

Ore Deposits 323

Mineral Deposila formed at the Surface by Hot WtUera (61). — At or near the surface mineral deposits may be formed by hot springs, but they are not usually of economic importance.

Such springs may depoat earthy carbonates as ednter, and silica as opal or chalcedony. Ore minerals developed under these con- ditions in crystallized form are stibnite, marcasite, and dnnabar, but other sulphides have been detected by chemical means. Cal- dte, fluorite, barite, and celestite may also develop.

According to what has been afud above there is a somewhat continuous series of depoats from the deepest to the higher and cooler zones, the mineral comlnaations gradually changing from those of magmatic and contact-metamorphic conditions, to those known to exist in surface hot springs.

Formation of Cavities. — The depoatJon of ores in the rocks is greatly facilitated by the presence of cavities along which the ore-bearing solutions freely pass, and consequently a great many ore depoats occur in such spaces. There are a number of different vays in which cavities may be formed in rocks. The percolation of surface water through certain ones, such as limestones, often results in the formation of solution cavities, these in many instances attaining the size of veritable caverns ; a soluble rock may contain more or less insoluble material, such as clay or chert, which col- lapses when the surrounding rock is dissolved, and partly fills the cave thus formed. At times the more reBistant parts are so bound together that they remain in their orinal position, forming a porous mass, in the cavities of which mineral matter is later de- posited.

Dynamic disturbances produce cavities of variable extent in many different rocks. These raie from microscopic cracks, like the rift planes of granite, to enormous faults of great depth and linear extent, and include the joint planes so common in the rocks of almost all repons. Fault fissures form one of the most important types of passageways for ore-bearing solutions. They are often irregular, branching, and partly filled by fault breccia, caused by the breaking of the rock during the movement aloi the fault plane. A third important group of cavities in the rocks are those resulting from shrinkage of the mass, which may be due to (1) shrinkage during cooling, as in igneous rocks; (2) shrinkage durii certain forms of replacement. For example, the change of carbonate of lime to dolomite is accompanied by a shrinkage of the maas, which renders the dolomite more porous than the original

324 Economic Geology

tock ; and in the alteration of siderite to limonite there ia a shrink- age of fully 20 per cent (25). A fourth type of channelway for the passage of underground water is the contact plane between two quite different kinds of rock, one of them fairly dense and impervious.

Deposition of Ore in Open Cavities. — Open cavities may, ac- cording to general belief, exist to a depth of many thousands of feet below the surface. If rock pressure alone were active, they could not theoretically exist below the zone of fracture, but it seems probable that hydrostatic pressure due to gravity may to some extent counteract rock pressure.

There is evidence to show that some large cavities must have existed at great depths, and here it is supposed that the force of crystallization has been sufficient to force the walls apart. Becker and Day have demonstrated the actual existence of such a force,' but Undgren points out that it seems scarcely possible to attribute such power to it as would be necessary to force deep-seated crevices apart to form room for the crystals, and moreover that it would " seem imposble that under these conditions comb structure and coarsely, even-gained quartz could be produced." Graton'si- gests that the crevices formed below the zone of fracture have been opened by the pressure of solutions forced out of the cooling magma.

PredpHation of Metals from Solution. — In some cases the metalliferous and other minerals found in ore deposits have no doubt been taken into solution by surface waters, and precipitated at no great depths; but in the majority of instances the metals were taken into solution at some point considerably bdow the piont of precipitation, where heat and pressure were evidently high. The depotion of the metals may then have been due to several causes, such as the mingling of waters, resulting in chemical re actions, contact of the solution with reducing agents such as car- bon or ferrous sulphate, decrease in temperature and pressure, or where the precipitation occurs near the surface, by oxidation.

As has been pointed out by Lindgrea (61) the physical conditions during deposition, especially temperature and pressure, are of great importance in determining the mineral association in ores formed by deposition from solution.

CertMn minerals, for example, are very stable under hi pres- sure and temperature, and could not therefore exist under condi-

iv,Coog[c

Ore Deposits 325

tioDs prevUng near the surface. That is to say, that the different minerals have their " critical level," above or below which they cannot form or exist. Other minerals are termed " persistent minerals," because they have a large interval of existence,'

The conditions under which different ore minerals, as well as some others, may exist are pven in the following table (p. 326) compiled by Lindgren (61).

OUter Causes of Precipitation. — Other conditions may, how- ever, operate to cause precipitation, for, as shown by Sullivan (86), the n&tural dlicates have the power of precipitating metals from solutions of salts, "while at the same time the bases of the alicates are dissolved in quantities nearly equivalent to the pre- cipitated metals." The bases which most commonly replace metals in such a process are potaium, sodium, magnesium, and calcium, and the metals are precipitated as hydroxides or basic salts. Cu- pric sulphide, for eTcample, is precipitated as a baac cupric sulphate amilar to brochanUte or laite.

The same investigator (87) has also found that when a solution of ferric sulphate is passed through a Pasteur filter, 18 per cent of the iron is held in the tube. Repeated passage of the same solu- tion caused the retention of additional quantities of the same metal. The explanation advanced is that hydrolyas has pro- duced a colloid form of the iron oxide, which is caught in the pores of the porcelain. The experiment is highly suestive and indicates that metalliferous solutions in passing through porous rocks may be robbed of some of their metaUic contents by a similar process.

Some fifty years ago not a few geologists, prominent among them De la Beche, advocated the theory of ore precipitation by galvanic action (20, 35), and a number of experiments were made attempting to prove the existence of such action; now little wat is attached to this theory.

More recently Gillette (39) has expressed the view that osmotic pressure is an important factor in ore deposition, aiding to spread the dissolved metals through the water in the rocks, toward centers of crystailization.

Recement, or Hetasomatism (59 6) . — It is a well-known fact

that under favorable conditions mineral-bearing solutions may

attack the minerals of the rocks which they penetrate, dissolving

them wholly or in part, and depositing some of the orinal burden

' A. GnibennisDD. Die KriatallJncu Schiefcr, Berlin, 1904, p. 55.

26 Economic Geology

Minerals roRiiBD ih Obe Depositb undeb Vaktino CoNVinotra

Its

Oss

OgOWg

CuLoopyr BontiM Anmopyrite .

Zincblende Molybdeall Odd. .

AlUte

aiderlw . CiDnabKr Mmnuite . . TetishediiU .

Slepbanite . Polybuiu .

a.i" :

AdlilHril

CelMtito

Ops) sod Chalccduny

Ore Deposits 327

in place of the material removed. This replacement, termed " metasomatism," is an important factor in the formation of many ore deports, and may involve a total or partial loss of certtun con- stituents of the rock attacked and a gidn of others, even to the extent of introduction of entirely new compounds and elements. The change takes place molecule by molecule, a grain of vein material being deported for each grfun of rlaced rock dissolved. The ore- bearing solutions penetrate the rock first along the smallest cracks, and

. , , . , , , . section of quarta coagjoraerate,

viduaJ Duneral grains along their showing replacement of quart. cleavage planes, until they finally (white), by pyrite (black), x 25 . permeate the entire mass (Figs. STx/'/T""*"' 112, 113, and 114). ., . o

Metasomatic processes show great variety, and are not confined to one kind of rock or mineral. In its simplest form the result of metasomatism may often be seen in fossiUferous rocks, where organic remains have been re- placed by common mineral com- pounds, as in the replacement of the lime carbonate of corals by quartz, or the replacement of molluscan shells by pyrite. From such simple conditions there is every gradation to the complete replacement of extensive areas of rock by ore, or to the extenave operation of metasomatism along the walls of fissure veins. In most cases the changes are believed

''-Rephicement vein m yenito tO be due tO the action of Undcr- rock. War Eajjle Mine, Rosaland. .

B. c. (0) granular orthodaw with ground Water ; but lu some in- little sericite ; (6) aeeondary bio- stances It Seems probable that tite;(,),™DdTy quart. M)chio. (he processcs of poeumatolysis

nte; bliKk. secondary pyrrhotite, , . . , , r, ,

iAfi Lindffren. Amer. Intl. uin. (9"-) were involved. Replace- Btigrt., rnwM. XXX.) ment is no doubt accomplished

I . f,

328 Economic Geology

in some cases by cold waters; but id many instances high taper- ature, pressure, and concentration seem to have been present, especially in the case of ore deposits in fissure veins. It is rarely possible, without examination of a thin section with the micro- scope, to decide whether minerals present are due to replacement or to simple interstitial filling;.

Some minerals are more easily replaceable than others, conse- quently the rocks in which such predominate might be more widely affected than others. (See Butte, Montana, and CUfton, Arizona, under Copper.)

The theory of metasomatism was first applied in America by Pumpelly, in 1871, in explanation of the copper depodts of Michi-

Fio. 114. — Photo-microErapfas of thin sections ol sulphide ore from AuatiDviHe, Vs., mioes. X 20 diam. croased nicolB. Shows crystalline sraDutar dolomitic limestone, and the filling of fine cracks accompanied by replacement o[ limestone grains along crystalloBrBphic directions by the sulphides. Very dark irrpgulir areB in center represent sulphides. HeSntrant angles along marina of the Bulphidee Bud the spider-like airsngement of the sulphide areas as a whole well shown. (A/ler Walton, Va. Geo/. Sum,, BvU. I.)

gan; but the ore bodies of LeadviUe, Colorado, and Eureka, Nevada, were the first large deposits whose origin was explnwl by it. Since then the great importance of metasomatism has been widely recognized, and it has become evident that pre&dsting cavities are not necessary to the formation of ore bodies.

Forms of Ore Bodies (31). — Ore bodies vary greatly in their form, and this character has at times been used as a basis of class' fication by some writers ; but the more modem tendency is to use genetic characters instead, making shape of secondary importance in the grouping. Certain forms of ore bodies are so numerous as to deserve special mention.

Ore Deposits 329

Fifsure Veins (30, 38, 45, 59o, 74, 99). A fissure veia maybe defined (596) as a tabular mineral mass occupying or cloeely asso- ciated with a fracture or set of fractures in the inclosing rock, and formed either by filling of the fissures as well as pores in the wall rock, or by replacement of the latter (metasomatism). When the vein is simply the result of fissure filling, the ore and gangue minerals are often deposited in succesve layers on the walls of the fissure {Rico, Colorado), the width of the vaa de- pending on the width of the fissure and the boundaries of the ore mass being sharp. In most cases, however, the ore-bearit solu- tions have entered the wall rock and either filled its pores or re- placed it to some ex- tent, thus ping the vein an indefinite boundary. Therefore the width of the fissures does not necessarily stand in any direct re- lation to the width of the vein (99) (Butte,

Montana). The term fw. lis. — Secon of vein in Enterprise mine. , ... , . Rico. Colo. The riaht aide shows Uter banding

Wn mai£nai is best due to reopenlne of the fissure. ((rfta-Mo™,

US?d to apply to the U. S. Geol. Sum., 22d Ann. Kept.. II.)

abrogate of materials

which make up the ore body. Vein stone, thoih sometimes used,

is leas dearable (Emmons).

Veins formed by the simple filling of a fissure often show a banded structure of varying regularity termed cmstification' by Posepny (Fig. 115), which may sometimes be brecciated by later movements along the fissure. Secondary bands may be formed after reopening of the fissures (Fig. 115), and such a movement may cause breccia- tion of the vein material. This later movement may sometimes

b,

330 Economic Qeology

form a layer of soft, clayey material, known as gimge or savage, between the vein and the country rock. Where the fissure has not been completely filled, thus leaving a central space into which the crystals of gangue project, a comb structure is formed. The baacU ia a filled fissure may consist of gangue and ore alternating, or of different ores. Amoi the conmionest ore minerals seen in these fissure vans are pyrite, chalcopyrite, galena, blende, and sulphides of silver. Some rons afford especially fine examples of banded veins, notably those of Grass Valley, California, and Rico, Colorado. Abroad the mines of Freiberg, Saxony, and Clausthal, Prussia, also often yield magnificent specimens. Even in a siie vein the ore may follow certun streaks which are termed shoots (q.v.) or agun it may be restricted to pockets of great richness, which are known as bonanzas.

In some veins the friction breccia or dragged in fragments of the country rock form a conMderable portion of the vein filling, and the ore has been deposited in layers around these f Foments.

Fissure veins in which metasomatic action has predominated show great irregularity of width and an absence of well-defined boundaries ; they also lack as a rule the symmetrical banding and the breccias cemented by vein material. There are all gradations between these two types of fissure veins ; and even in a single vdn ample fillii may occur in one part and replacement in another.

Veins often split or intersect, and at the point of intersection or splitting the ore is apt to be richer. There are other reasons for variations in richness, among the most important being the char- acter of the wall rocks, some " kinds being more ealy replace-

able or more porous than others. Their physical character wilt

moreover exercise conderahle influence on the shape and mee Fia. lie. — Section Hhowinn change in of the fissure. Toih rocka like character of vein paasjog from gneias gneiss, for example, give a clean- (0) to quart, porphy "1, cut fissuTe, but in brittle rock

Beck. von der EntagtraUUIxn: '

135.) the fissure is apt to sput fre-

quently, and therefore a vein may be workable in one kind of rock, but becomes worthless when passing to another, since the profuse branching interferes with eco- nomical mining (Fig. 116). A dike may also cause local irregu-

Ore Deposits

to. 117, — Tabulation of Btrlkea of principal veins in Monte Cridto. Wash., diBtrict. (A/ler SpuTT, V. S. Otol. Sum., 324 Ann. Rapt.. II.)

laritiefi, and in a ven ron the fiaaurea not imciunmonly show great variation in their direction. Thus at Butte, Montana (q.v.), east- west veins predominate, h while in the Silverton dis- trict of Colorado they cut the rocks in all directions, but the majority show a north of east trend. In the Monte Cristo, Washington, district the veins with i northeast trend are pre- dominant (Fig. 117).

Erasures veins vary con- siderably in width, Hwellii at some points and pinching or narrowing at others. They also at times show lateral enrichment (Ouray, Colorado) ; for in- stance, where the ore cuts through stratified beds, into which the ore-bearing solutions have spread out laterally aloi the planes of stratification or other planes. It has been noticed in some , especially those formed by replacement, that the fillii varies with the wall rock, at times chanfpng suddenly ; but where the vein is formed wholly by the filling of an open fissure, the rock exerts no influence on the character of the ore (99). If the vein is inclined, the lower wall is spoken of as the foot wall and the upper one as the having vxtU.

Parallel fissures are not uncommon, but the several veins do not necessarily show an equal degree of richness. Where the vdn ia of compOBte character, — that is, consisting of closely spaced parallel fissures accompanied sometimes by a mineralization of the interven- ing rock, — it ia termed a lode.

The term vein systems ia suggested for a larger assemblage of vein fissurea, which may include several lodes.

Subordinate fractures, such as little veins, that cross the material included within the vein walls, are called veirUets or striTigeTs.

The top of the vein is called the apex, and is occasionally traceable tor a long distance. It does not necessarily outcrop at the surface.

Linked veins represent a type in which the parallel fissures are con-

iv,Coog[c

Economic Geology

(After Ordona.)

nected by diagonal ones (lilg. 118), ving a series resembling the links of a chain. Gash veina are a special type of fiaaure vdn, formed by the en- laronent of planes and sometimes bedding planes. They are characteristic of the upper Misassippi Valley lead and zinc reon, but are usu- ally of limited extent and local importance. In the simplest form they are a vertical fissure, but develop into types shown in fig. 119. dvetn. — This term is sometimes appUedto a depoat con- forming with the bedding. It is also called bedded deposit. Among miners the term blavJcet vein is commonly applied to any nearly flat depodt.

Fining Fiatwre VHnt (46). — The manner in which fimure veins ha™ been filled, and the source of the metals which they oontaia, farmed a most fruitful subject of discussion among the earlier geoltsts. The Bererel theories advanced and the argrumenta for and against them are well set forth in Kemp's paper (45), and it may simply be said here that most geolots now believe that the primary deposition of ores in flsaure-vein deposits was accomplished by solutions ascending: along the fissures, which sometimes spread out into the wall rocks, to a variable distanoe.

Other Forma of Ore Deposits. — Chimney is a term applied to ore bodies which are rudely circular or elliptical in horizontal cross sec- tion, but may have great vertical extent. A stock is a somewhat milarly shaped ore body, but of greater irregularity of outline. Fahlband is a term orinally used by German miners to indicate certain bands of schistose rocks impregnated with finely divided sulphides, but not always rich enough to work. It is occasionally used in tins country. Impregnation ia a term indicating the occur'

Fio. 119. — Gash rein with aasodated "flats" (o) aad "pitches" (W- WisoaoBJo sine region. {After Oram, Wi*. Gecl. and Nal. BUL SuTV.. Baa. IX.)

bvCoog[c

Ore Deposits 333

rence of minerals in a finely dissemiiiated condiiion in rocks, either as a filling of open spaces or as a replacement of certwn minerals. DissemiTiaied deposUa (Fig. 120) is regarded as a better term by some. CofUact-meiamarphic depoeits, as now imderstood, represent ore bodies formed along the contact of a mass of igneous and sedimen- tary rock (usually calcareous), the ore having been derived wholly

Longitudinal Section

or in part from the intrumve mass (Clifton, Arizona, in part).' Ore chanriels include those ore bodies formed along some path which the mineral solutions could easily follow, as the boundary between two different kinds of rock (Mercur, Utah). Bedded de- jmnU, found parallel with the stratification of sedimentary rocks, and sometimes of contemporaneous origin (Clinton iron ore).

Ore shoots (43, 67, 65, 104). — Few ore deposits are of uniform character throughout, indeed the occurrence of pay ore is apt to be more or less irregular, the richer material being cross oftensomewhatrestricted section in its occurrence. These richer portions, if small, may be called Tiesta, or pockets, but if large, the term ore shoot is commonly appUed to them. Accord- ing to some authors the ore shoot includes only the richer portion of the workable ore. (Van Hise.)

Other writers, among them Emmons, Lindgren j sndRansome, employ the

(.Aflfr lAndgrm and Raruome.)

' IF Ihe term amiaeimtlamorphic dtpotit 'a used for this type, it would not "'csiarily conflict with the term coittact depotit, applied to soy ore body occurring tioag the bouudary between two formationi or two kiuda of rook.

iv,Coog[c

334 Economic Gbolooy

term ore shoot or pay shoot to signify the workable part of a lode or similar deport.

Ore shoots are commonly of irregular shape, and usually steep dip, although they may be nearly horizontal.

According to Emmons the ore shoot, as a rule, has a longer axis that forms a large ane with a horizontal plane. This longer axis may be called the pitch lengthy and the horizontal dimenaons aloi% the level the stope length. Ore shoots are evidently caused by vary- ing chemical and physical conditions in different parts of the deposit, at the time the ore was formed, thus cauang a more abundant pre- cipitation of the ore minerals in certn parts of the depomt. More abundant fissuring, or brecciation, in certain parts of the rock may operate to promote deposition in those parts of the mass ; clay walla may be influencing factors in guiding the ore solutions towu certain spots ; or intersecting fissures may permit the mingling of reacting solutions, thereby bringing about more abundant precipita- tion of ore at these crossing points. The existence of fissures in certain parts of the ore body might produce additional depoation in those parta, by serving as a guiding channel to either ascendii or descending enriching solutions.

The examples cited above apply espedally to epigenetic deposits; but if the term ore shoot is used in its broadest sense, one might reasonably include ore masses formed by magmatic segregation.

Several attempts have been made to classify ore shoots, all of them being on a genetic basis. Thus Van Hise divides them into three groups as follows: (A) thoseexplainedlargelybystructuralfeatures; (B) those formed by the influence of wall rocks; and (C) those formed by secondary concentration by descending waters.

Irvii (43) has classified them as (1) shoots of variation, or those which vary from the inclosing material only in relative richness of the ore; and (2) shoots of occurrence, or those which occur in iso- lated positions with no other ore of any kind about them.

Winchell ' makes a division into (1) paragenetic shoots, or those developed mostly at the time of the orinal formation of the ore deposit inclosing them; and (2) postgenetic shoots, or shoots devel- oped mostly after the original formation of the inclosing ore deposit.

Secondary Changes in Ore Deports (26, 65, 66, 70, 73, 7S, 94).— Ore deposits are often changed in their upper parta, and swnetames to a conaderable depth, by weathering agents, while the lower-

bvCooglc

Ore Deposits 335

lying portions, below the ground-water levd, are often enriched by secondary processes.

The two zones each show a somewhat characteristic set of com- pounds. Thus in the weathered zones we find sulphates, carbonates, silicates, oxides, chlorides, arsenates and native metals; while in the lower zone the compounds are sulphides, tellurides, arsenides, and andmonides.

Weatberii may disguise the true character of an ore body most effectually. For example, the ore found in the outcrop may be a gold ore, and mills are sometimes erected and operated for a period on such ore, without any suspicion that beneath there may be great bodies of copper or lead sulphides. Such a change has been found at Biiham, Utah; Ely, Nevada; or Mount Morgan, Australia. The last has been one of the world's greatest gold mines, but is now producing copper from its lowest levels. In other cases, the base metals may all have been leached out of the upper part of the ore body, and too little gold remains in the gossan to make it profitable. Butte, Montana, is a well-known example of this, for the nearly barren outcrops gave little clew to the great secondary ore bodies lying below, and which might never have been discovered but for the presence of another system of closely aBBoeiated veins carrying silver.

Weathering or Saperfidal Alteration (66). — Nearly all minerals are attacked by the weathering agents, but the metallic njinerala are more ealy and more profoundly affected than the non-metallio ones.

This weathering process involves both chemical and phycal chaises mmilar to the decay and dintegration of common rocks, but in ore bodies the great number of minereds involved, includ- ing many with a metallic base, gjve rise to a large number of in- tricate chemical reactions.

L;,q,-z.= bvCoOg[c

336 Economic Geology

As s result of weathering worthless minerals may be rnoved, ' leaving the weathered part more porous, and this may increase the richness, because we have a greater quantity of metala per ton of rock.

Since many of the metalliferous minerals are more eaaly de- composed than the common rock-forming minerals, the alteration in an ore body is more rapid and extends to a greater depth than in the country rock. There is, however, a marked variation in the rate at which the different ore minerals decay, and this variation : exists even in a ngle group like the sulphides, in which the order or rate of decompodtion is arsenopyiite, pyrite, chalcopyrite, blende, galena, chalcOcite, and tetrahediite.

The weathered part of the ore body, so often stroiy stained by limonite, is known as the gossan, or iron hat (French, diapeau- j de-fer; German, eisener hvt).

The first chemical changes in the weathering of an ore body are ; oxidation or hydration, or both; and these, together with other changes, produce many soluble compounds, which can be, and often are, leached out of the gossan by percolating waters. An example of oxidation is the alteration of pyrite to ferrous and ferric sulphate, and by hydration and further oxidation to limonite. Chalcopyrite oxidizes to copper sulphate and by hydration and further oxidation to copper carbonate, silicate, or oxide. We see therefore that the first change in each of the above cases is the same, sulphates formed from sulphides; but that the later changes are different, the iron sulphate chani to hydrous oxide, while the copper forms a different set of cwnpounds.

Many of the sulphates formed may be removed in solution, but not a few of the new compounds produced, such as sulphates, chlorides, carbonates, silicates, or even native metab, remain mixed with the limonite in the weathered zone.

The porosity of the gossan is sometimes due to leaching, some- times to shrinkfe, as when siderite or pyrite changes to Umonik. Hydration, on the contrary, causes expansion.

The depth of weathering depends on topographic conditions, chemical nature and porosity of the deports, climate, etc. ; but in any event it is liable to vary in the same depoat, owing lo variation in the permeabiUty of different parts of the mass (Fig- 122). In Arizona many copper deposits have been changed from sulphides to carbonates, to a depth ranging from 100 to 700 feet ; the oxidized ores of the Appalachian region average about 100 feet

L,;,-z__lv,C00g[c

Ore Deposits 337

in depth ; while those of the Rocky Mountain area range from 50 to 700 or more feet in depth.

The ferric sulphate produced by the weatherii of pyrite is a most important factor in the alteration of ore deposits. When formed it attacks pyrite and other sulphides, converting them into sulphates, at the same time being itself reduced to ferrous sulphate, which ia in part changed to limonite and sulphuric acid. That portion remaning unreduced bens anew the scale of change. Fenic sulphate is thus the mn agent by which the sulphides are dissolved. Moreover, it also acts as a solvent of free gold.

All the metaUic contents are not, however, leached from the gossan, for some minerals are either difficult to dissolve or remfdn unattacked. Thus in some cases the leaching produces an enrich- ment by the removal of worthless constituents and a consequent increase per ton of valuable minerals. The soluble compounds produced by weathering are often carried downward by percolat- ing water and deposited in an irregular zone between the gossan and the unweathered ore below, as in some copper deposits where there is found a rich zone of black copper between the gossan and unaltered sulphides.

Secondary Deposition Ground-tDoler Level. — In many ore bodies, rich masses of ore occur below the oxidized zone, which microscopic investigation has shown to be of secondary character. The secondary deposition is most often seen in gold, silver, copper, lead, and zinc ores, and is due to the downward migration of the products of weathering and their redeposition below the water level. If the body of unaltered sulphides below is broken by fissures, the solutions contning the various metallic sulphates and sul- phuric acid will enter them, penetrating at times to condderable depths. Reactions may then take place between the dissolved sulphates and the sulphides present, resulting in the precipitation of new sulphides on the walls of the fracture, and forming rich patches of ore known as bonanzas (73, 94). The association of these fractures formed after the primary sidphides is an important character of value to the mining engineer, and from what has been amd above, it can be seen what an important rdle sulphides play in the secondary enrichment process. It has been noticed, how-. ever, that pyrite is not the only reducing and precipitating agent b ore deports. Carbon is a strot reducer, and other minerals also exert a variable influence (42). (See deposition of lead and iDc in Wisconsin and Ozark reon. Chapter XVII.)

338 Economic Geology

With continued erosion of the surface, there is a continuous downward removaJ, and the lower-lying ores become more aod more enriched; but the secondary enrichment process is affected by a number of factors.

Thus if erofflon is more rapid than oxidation, the body of eui- phides may extend to tiie surface, for even if any gossan forma it is rapidly removed. On the other hand, if oxidation is more rapid than erosion, a gossan develops.

Both weathering and secondary enrichment are - therefore de- pendent on the physical structure and solubiUty of the rock, tem- perature (and indirectly topography), quantity of water, mi length of time.

BeacHoTu Involved. — One or two oases may be cited which will give in greater detail the ohanges referred to above.

If, for ewnple, we have an ore containing pyrite, galena, and aphalerit in limestone the following ohangea may take place : —

The ephalerite, galena, and pyrite may be changed to solphateB, thus : — Zn8-|-40 Zn80„or PbS+40 - PbSOi.

1. Thesulphatesroay react with the limeetone; —

ZnSO, + CaCO, + 2H,0 ZnCO, + CaSO,, 2H,0, PbSO* + CaCO, + 2H,0 - PbCO, + CaSOi. 2H,0.

2. The sulphates or some carbonates mfty be carried down below water level into the sone of unaltered sulphides, where the following reaoliotu

PbS04 + PeS, + O, PbS + FeSO, + SO,,

PbCO, + PeS, + O, PbS + FeCO, + SO,,tHr PbSO, + ZnS PbS + ZnSO*. PbCO, + ZnS - PbS + ZnCO,. These zinc compounds, being soluble, might be carried down still farther and there react with iron sulphides, as follows : —

ZnSO. + FeS, + 20 ZnS + FeSO, + SO,, alao ZnCO, + PeS, +20 ZnS + FeCO, + SO,. Second Cast. — In an ore consisting of a mixture of chalcopyrite (CuPeS,) and pyrite (FeSt), the following Changes might take place on weathering:— CuPeS, + 80 - CuSO. + PeSO., and FeS, + 70 + H,0 - FeSO* + H,SO*. This last equation involves intermediate stages in which S, H,S, and 30| may be formed.

The FeSO( gives Fe,(SOi}i which is easily deoomposed to a basic sul- phate, free hydrates, and free acid.

If the pyrite is cupriferous, the H,SO< will oxidize more of it. The Pe,(SO()i may attack pyrite and other sulphides, changing them to sulphates and being itself reduced to FeSOi; aa

5Pe,CS0i), + Cu,S + 4H,0 2Cu804 + 10 PeSO, + 4H,S0,.

b,

Ore Deposits 339

This cycle of reaotdons will prob&bly continue until all of the sulphides exposed to oxidation have been obaoged to oxysalta, and most of the iron chaagwi to Umonite. The CuSOi formed in the zone of weathering may by further reactions develop (1) minerals ohiuacteristia of the oxidized zone, or (2) it may be carried in solution down into the sulphide zone, and there be reduced to sulphides. As illustntive of the first class we have: — 2CuS0. + 2H,Ca(C0,), CuCO, (CuOH), + SCO, + 2CaS0* + H,0, 3Cu80. + 3 ir,Ca(C0,), 2CuC0, (CuOH), + 3Ca80, +4C0, + 2H,0. 2CuSO, + 2Fe80, + H,0 - Cu,0 + Fe,(SO.), + H,80, Cu,0 + H.80* - Cu + CuS0 + H.O, CuSO. + H,Ca(CO,), + H.SiO, - CuO, HiO. + CaSO + H.O + CO..

In the second olaas, where CuSOi is carried downward into the sulphide body, the reactions given below no doubt occur: — Ca30, + CuFeS, - 2CuS + FeSO.. or

2Cu804+CuFe8. +80, +2H,0 - Cu,S + Cu8 + FeSO. + 2 H,80h CuSO, + 2FeS, + 20 - CuFeS, + FeSO. + 80„ or CuJeS, + CuSO, + 0, - 2Cu,S + FeSO, + 80,. or CuSO, + 2CnFeS, + O, - Cu,PeS, + PeSO. + SO,.

Value of Ores. — The terms rich aad poor, as applied to ores, are used with great frequency, although most indefinite and often meaningless. Under very favorable conditions it is possible to profitably work an ore of given value at one locality, while if found under other less favorable conditions at another point it might' be almost worthless.

Those who have not ven speciEiI study to ore deposits often ful to realise that in the majority of ores the percentage of metal coatfuned in the ore falls considerably below the theoretic per- centfe of the metallic contents in the ore-bearii minerals, due of course to the presence of a greater or less quantity of gangue minerals which tend to dilute the metaUic values of the vdn, Many low-grade lead ores are profitably mined because their gold and Iver contents more than pay the cost of metallurgical treat- ment. In many cases the metEc contents of the ore is increased by mechanical concentration or by roasting (in the case of sul- phides), or both, before the ore is smelted.

Allowable Minimum of Metal in an Ore (52). — Iron ores are of little vikhie, wherever they may be located, unless they oontun at least 30 per cent of uxin when charged into the furnace.

Copper has an average minimum of about 2 per cent, but the Lake Superior oree, because of their peculiar oharaoteristics, can be operated on a lower percentage. In the case of these low-grade ores the metallic contents raised by mechanical concentration or roasting, or both, before entering the furnace.

Ltad. — In southeastern Missouri lead ores are profitably mined when

340 ECONOMIC QBOLOaT

Dairying as little as 5 to 10 per oeat metal, but the oonoentration taiaes the percentage up to 65 or 70 per cent.

Zinc ores ou entering furaaoe should have a minimum of 25 to 30 per cent zino, but the contents are sometimes raised to 60 or more per cent by concentration.

Quid and Siker. — The metallic contents of these ores are expressed, not in percentages, but in troy ounces per Um, a troy ounce in a ton being per cent. The market value of silver is, in round numbw, 50-60 cents per ounce, while gold in round numbers is figured at S20 per ounce.

Silver rarely oocurs alone, and the ore may be treated primarily for its associated lead and copper.

In the base ores there should "be enough silver to yield a minimum of S5 or 10 ounces in the resulting ton of copper, to make its extraction profitable. If now in a 5 per cent copper ore 20 tons of ore are concentrated to 1 ton of pig copper (or 21 tons, allowing for losses), it follows that we need 10 ounces of silver, in 21 tons of ore, or a minimum or i ounce silver per tan, or i4b per cent.

Under favorable conditions gold can be extracted down to ft ounce per ton or iiAnr pcr cent. It usually runs from 1 to 1 ounce.

In some copper or lead ores the saving of even iV ounce gold may be an object. In gravels, a gold content of as low as 7 to 10 cents per cubic yard dij to xio ounce) may be saved.

Tin. — For this metal the crude ore commonly ranges from 1.5 to 3 per cent, but by concentration it can be raised to 70 per cent.

ffiekd should reach 2 to 5 per cent in the crude ore.

Platinum. — Owing to the scarcity of this metal, few figures are aviul- able, but in Russia placers are worked which carry ounce per cubic yard, which is the equivalent of A ounce pw ton or 6.5 hundred-thou- sandths per cent.

Manganete ore must yield 50 per cent manganese to be marketabK although if iron is i8ent it may drop to 40 pw cent.

Chromium ore should carry 40 per cent of the metai.

Classification of Ore DepositB. — Many attempts have been made to develop a suitable elasaification of ore deposits, and noaay schemes have been suggested (46). These are usually based either on form, mineral contents, or mode of origin. The first is perhaps the most practical from the miner's standpoint, the second is un- desirable because several kinds of ore may often be found in the same ore body, while the third is the most scientific, and is of value to the iTiinjng geolost and engineer.

Those dering to look into this phase of the subject in more detail are referred to the bibliography at the end of this chapter, especially the papers by Kemp (46), Posepny (68), Van Hise (2), and Vogt (13).

Only one classification is given here, viz. that of W. H, Weed, not because it is condered entirely satisfactory or especially

D,q,-zMbyC00g[c

Ore Deposits 341

simple, but because it embodies the results of the more modem studies of ore deposits and thar genetic character.

CLABBincATioM OF Ore Dbposits (after Weed)

A. Igneous, magmatio segregation.

(a) Siliceous.

1. Masses, Aplitic masses. Ehrenberg, Shartash.

2. Dikes, Beresite or Aplite. Berezovsk.

3. Quartz veins. Alaska, Randsburg, Black Hills.

(b) Bao.

1. Peripheral masses. Copper, iron, niekel. (Sudbury, Ont.)

2. Dikes, titaniferous iron. Adirondaoks, Wyoming.

B. Igneous emanations. Deposits formed by gases above or near

the critical point, e.g. 365" C. and 200 atmospherea for H|0.

(a) Contact-metamorphic deposits.

1. Deposits confined to contact. Magnetite deposits (Hanover,

N. Mex.), chalaopyrit deposits, Kristiania type, gold ores, Bannock, Ido., type.

2. Deposita impnnating and replacing beds of oontaot zone.

Chalcopjnte deposits, pyrrhotite ores, magnetite ores, Can- anea type, gold tellurium ores, Elkhom type, uaenopyrite ores, Similkameen type.

(b) Veins dosely allied to magmatic veins and to Division D.

1. Ca8Biterit. Cornwall.

2. Tourmaline copper. Sonora.

3. Tourmaline gold. Helena, Mont., Minas Oeraee, eto.

4. Augite copper, eto. Tuscany.

C. Pumarolic deposits.

(a) Metallic oxides, etc., in clefts in lava. Ko oommeroial impor- tance. Copper, iron, etc.

D. Gas-aqueous or' pneumato-hydato-genetic depodta, igneous emana-

tions, or primitive water mingled with ground watr.

(a) Filling deposits.

1. Fissure veins.

2. Impregnation of porous rock.

3. Cementation deposits of breccia.

[b) Replacement deposits.

1. Ipylitic. Comstock.

2. Seridtio kaolinic, oalcitio. Copper silver, Silver Isad. Claus-

thai. De lAinar, Ido.

3. Silicic dolomitic, silver lead. Aspen.

4. Silicic calcitic. Cinnabar, California.

6. Sideritic silver lead. Cceur d'Alene, Slocan, Wood River.

6. Biotitic gold copper. Rossland, Brit. Col.

7. Fluoric gold tellurium. Cripple Creek, Colo.

8. Zeolitie. Michigan copper ores.

b,

342 Economic Qeolooy

SlrtuUuTe Typet of Above

Fissure veins. (Son Juan, Colo.) Volcanic etooks, Nagyag. Cripple Creek. Contact chimneys. Judith. Dike replacements and impregnations. Bedding or contact plaaea. Mercur.

Axes of folds, synclinal tMsins, anticlinal saddles. Bendigo. Elkhorn. E. Meteoric waters. (Surface derived.) (a) Undeiground.

1. Veins. (Wisoonsia lead and zinc.)

2. Replacements. Iron ores, Michigan ; lead, line.

3. Residual. Gossan iron ores, manganese deposits. (Virginia.) (6) Surflcial.

1. Chemical. Bog iron ores, sinters. Some bedded iron ores, eir.

(Clinton ore.)

2. Mechanical. Gold and tia placers. I P. Metamorphio deposits. Ores eonceatrated from older rocks by

metamorphism, dynamo or ronal.

MetoUogenetic epochs. — The term metallogeDeUc epoch refers to a period of time daring which a depoation of metals was taking place, and usually accompanied or immediately followed periods of igneous activity. This process has been active, during a number of periods in the past, as shown by the geoloc records, and the available data for North America have recently been well sum- marized by Lindgren (62),

Pre-Cambrian Period. — The pre-Cambri&n rocks, which under- lie a number of extenve areas in the Umted States, include not only metamorphosed scliists and gndsses, but also various types of intrusives, the characteristic metals being iron, copper, nickel, . gold, and silver. Lead and zinc are less abundant than they are in the later periods, while quicksilver and antimony are rare.

The ilmenites and magnetites of the eastern states are chiefly of igneous origin, while the hematites of Lake Superior are partly igneous and partly sedimentary, but subsequently oxidized and concentrated by surface waters, a process which is believed to have gone on in pre-Cambrian times. The copper and nickel ores are associated with basic igneous rocks, some of these, as in Michigan, being of effusive nature. This copper concentration lindgrea suggests must have gone on in pre-Cambrian times, following the close of Keeweenawan (Algonkian) volcanic activity. Of ffltnilM Ee are the cobalt-silver veins of Ontario. The auriferous-quarti vns of the southern states, whose deposition followed that of

. h.C.oojlc

Orb Deposits 343

granitic mtruaotui in schists, are also to be placed here, although some writers would date them later.

In the Cordilleran region the pre-Cambrian was productive of gold and copper deposits, which are found at many points from South Dakota and Wyoming to Arizona. These gold ores are usually lenticular quartz veins in schists, associated with such gangue minerals as tourmaline, garnet, etc. The copper ores often contain chalcopyrite, and form veins or irregular masses, which are probably of magmatic origin, and have been modified by dynamo-metamorphism. Sphalerite may accompany the cbal- copyrite, but lead is almost entirely wantii.

Paleozoic. — Duti: this time a number of granitic iatnmons occurred from New York and New England northward to Quebec and Nova Scotia, and these were accompanied by the formation of some gold-quartz veins; but little metaUization occurred in the West during this period.

Two periods of iron-ore formation occurred during Paleozoic time in the East. One of these was in the Silurian, when the per- fdatent beds of low-grade Chnton hematite were formed; the other was during the Carboniferous, when the layers of carbonate black- band ores were deposited.

Mesozmc. — During the Triaadc, small deposits of copper and iron ores were formed in the eastern states, aloi the contact of the trap sheets and sedimentary rocks. The deposits were in part veins and in part of contact-metamorpbic character.

In the West important accumulations of ores were beginning, for during the Triaseic there began a series of eruptions which continued through the Jurassic, the products of these being baae lavas which were extruded from California to Alaska. The metal- lization accompanying or following these yielded copper deports, which include some of those found in California, British Columbia, and those of the Copper Biver ron in Alaska.

Another important metallization epoch followed the intruon of the great early Cretaceous quartz-monzonite or grano-diorite bathoUtbs of the Pacific coast.

These injections were of vast extent, one batholith extending through California, and another from Washington up throifh British Columbia to Alaska, while other smaller masses occur in several of the western states. These intrusions were followed by intense metaUization, mineral deposits being formed in abundance around the margin of the batholiths, as in the gold belt of Cali-

z .IV,

344 Economic Geology

fornia. Gold was tbe chief metal formed, with copper next. Along the Padfic coast, where there is little limestone in the intruded sediments, lead is rarely found, but in the interior (Nevada and Idaho) where limestones were present, lead and ainc both occur. Silver is everywhere present, but is rarely important unless asao- dated with lead ; arsenic and antimony ore rare; and mercury is wanting in commercial quantities.

Early Tertiary. — About this time, perhaps a little earlier, or a little later, important concentrations of lead and aac took place in the MisaBoppi Valley, but they appear to have been independ- ent of igneous intruaionB, and are thought by most geol<sts to represent tbe work of surface waters, the ultimate soiuw of the metals being the pre-Cambrian rocks. This is questioned by IJndgren, who points out the scardty of the lead and zinc in tbe rocks of that age, and also that there are transitional types between the normal ore depodts and certain lead-zinc depoats in Arkansas and Kentucky which resemble western vein types formed by hot waters.

At the close of the Cretaceous violent outbursts began along the eastern margin of the Cordilleran reon, the magmas of intermediate character and laccolithic form. They occur British Columbia through Montana, Colorado, New Mexico, and eastern Arizona down into Mexico.

There ensued then another or third epoch of Cordilleran metal- lization, during which many contact-metamorphic deposits and were formed around the marns of the laccoliths. Gold and diver are the characteristic metals, with abundant lead and zinc, especially where the intrusions cut hmestones. The latter may also show copper and iron along the contact. Arsenic and antimony are more common than they were in the earlier epochs, but mercury is still rare.

LcUe Tertiary. — After a period of mountain-making disturbances, uphft, warping, and dislocations, there were extruded a series of lava flows which spread over a large area in the far West, and an prominent in California, Washington, Oregon, Idaho, Colorado, Utah, Nevada, New Mexico, and Arizona. Andesites and rhyo- lites predominate. This was accompanied by a fifth metallization, whose characteristic metals are gold and diver, forming depodta often of great richness; lead and zinc are not abundant, except in limestone, and neither is copper. Tellurium and antimony are; not that they are absent in older metallizations, but the tellurium

C,q,-Z.-dbvCOOg[C

Ore Deposits

Eeema to be especially chfiracteriatic of this epoch. The metallic deposits seem to be somewhat restricted, occurring mainly near the foci of igneous activity.

Post-Pliocene. — There came finally an epoch of metallization at a late date, restricted, however, to the Pacific coast line, and characterized by the mercury deports of the Pacific coast belt.

Cretaceous or Later Copper Epochs. — Tliese, being of wide time range, cannot be included in the previous classes. They represent disseminations of copper in sandstone shales or conglomerates, and carry in moat eases primary chalcocite with a little silver.

Summary. — The following table of lindgren's summarizes the conditions for the western states : —

Dsposm

I. Deposits of the pre-Cam- brian period

Gold and copper . .

f Granites

I Dioritea, gbro

2. Deposits of the early Mesozoio epoch . . .

Copper

1 Basalt, diabase 1 Gabbro

3. Deposits of the late Meso- loio epoch

1 Oranodiorite

4. Deposits of the early Ter- tiary epoch

aold,sUver . . . Copper, lead, zino .

f Granodiorite

5. Deposits of the late Ter- tiary epoch

Gold, silver . . .

fAnderite 1 Rhyolite

6. Depofflts of the Poatr Pliooeae epoch . . .

Quioksilver . . .

Basalt

7. Cretacous or later oon- centrationa in sedimen- tary rocks

Copper

I Conglomerate

REFBRXHCES Olf 0R£ DBPOSnS

Oehxral Wobks. 1. Beck, Lehre tod den Erzlaeerst&tten. Berlin, 3d ed., 1909. 2. Bergeat, Die Erzlagerstatten. Leipzig, 1904. 3. Clarke, U. S. Geol. Surv., Bull. 330: 551, 1908. 4. Kemp, Ore De- posits of United States and Canada, New York, 1906. 5. Krusoh, Die Unteriuohung und Bewertung von Erzlageratatteii. Stuttgart, 1907. 6. Pucha et De Launay, Traits des Gites Minfiraux et Metalli- fSrea. Paris, 1S93. 7. Parka, A Text-book of Mining Geology.

oogic

346 Economic Geology

Philadelphia, 1906. 8. Phillipa, Treatise on Ore Deposita. LondoiL I 1884. 9. Rickard, Ore Deposits. New York, 1906. 10. Thonws ' and MacAlieter, The Oeology of Ore Deposits. London, 190!). - 11. SpuTT, Geology applied to Mining. New York, 1904. 12. Van j Hiae, Treatise on Metamorphism, U. 8. Geol. Surv., Mon. XLVII.

1905. 13. Vogt, Enisoh and BeTsohlag, Die Lagerstatten der Nuti- ; baron Minerien und Gesteine. Stuttgart, 1909. 14. Wallace, Stud; : of Ore Deposits for the Practical Miner. New York. 15. Weed- fieck. The Nature of Ore Deposits. (Translation.) New York, 1909. 16. Whitnej, Metallic Wealth of United States. Philadelphia. 1S54.

Papers, uobtlt or Special Cbaracter. 17. Bain, Econ. Oeol., I: 331,

1906. (Classification.) 18. Bancroft, Aiaw. Inst. Min. Engrs., Ball, July, 1909. (Formation and enrichaient of reins.) 19. BwrtH. Amet. Jour. Sci., XIII: 279, 1902. (Contact metamorphism.) 20. BaruB, Amer. Inst, Min. ., Trans. XIII: 417, 1885. (Eleiv tricol activity in ore bodies.) 21. Beck, Trana. Geol. Soo. S. Afr.. VIII I 147. (Ore veins and pmatites.) 22. Buehler and Oolt- sohalk, Eoon. Geol., IV : 28, 1910. (Oxidationof sulphides.) 23. Camp- bell, Econ. Geol., 1:751, 1906. (Metallography.) 23 a. v. Gotta, Die Lehre von den Erzlagerst&tteo. Freiberg, 1859. 24. Don, Amer. Inst. Min. Engrs., Trans. XXVII : 564, 1898. (Genesis ot gold.) 25. Delkeskamp, Zeitsoh. f. prak. Oeol., XVI: 401, 1908. (Mineral springs.) 28. Emmons, Amer. Inst. Min. Engrs., Trans. XXX: 177, 1901. {Seo'y- enrioh't.) 27. Etomons, Ibid., XXII:53, 1S94. (Geol. dtstrib'n, useful metals.) 28. Enunons, Oeol. Soc Amer., Bull. XV: 1, 1904. (Theories of ore deposition.) 29. E mons, Amer, Inst. Min. Engrs., Trans. XVI : 804, 1888. (Stnictunl relations of ore deposits.) 30. Emmons, Colo. Soi. Boc., Proc. II : 1S9, 1885-1887. (Origin of fissure veins.) 31. Enunons, Min, and Sri. Pr., Sept. 22, 1906. (Forms of ore bodies defined.) 32. Emmoni. W. H., Min. and Sci. Pr., Deo. 4 and 11. 1909. (Outcrops.) 33. Em- mons, W. H., Econ. Geol., IV : 755, 1909. (Segregated veins.) Emmons, W. H., Econ. Geol., 111:611, 1908. {Mineral classifira- tion.) 35. Fox, Amer. Jour. Sci., i, XXXVII : 199, 1839. (Vein formation by galvanic agenoy.) 36. Fineh, Colo. Sci. 3oc., Proe. VIT : 193, 1904. (Underground waters and ore deposition.) 37. Gautier, Ann. d. Mines, 6 ser., IX : 316, 1906. Translation in Eoon. Geol., 1 : 688, 1906. (Thermal waters, their eonnection with vulcao- iam.) 38. Glenn, Amer. Inst. Min. Engrs., Trans. XXV : 499, 1896. (Fissure walls.) 39. Gillette, Amer. Inst. Min. Engrs., Tnoa. XXXIV: 710. (Osmosis theory.) 40. Hastings, Amer. Inst. Min. Engrs., Bull. Feb., 1908. {Volcanic waters.) 41. Hastings, Ibid.. (Origin of pegmatites.) 42. Jenney, Amer. Inst. Min. Engrs., Trans. . XXXin:44S, 1904. {Chemistry of ore deposition.) 43. Irving. ; Econ. Geol.. Ill : 143, 908. (Class'n of ore shoots.) For discussion on this see Ibid., Ill: 224, 326, 425, 534, 637, 1908. 44. Kemp. , 8. of M. Quart., X : 54, 166, 326, 1889; XI : 3.i9, 1890; xri:2I8.

1891. (Literature on ore deposits.) 45. Kemp, Ibid., XIII: 20.

1892. (Pilling of veins.) 46. Kemp, Ibid., XIV: 8, 1893. (Ore

Iv,

Ore Deposits 347

depomts, claasiilcation.) 47. Kemp, Mio Indus., IV: 755, 1896. (Theories of origin of ores. See also articles on ore deposits appearing ftimaaUy in this publication.) 48. Kemp, Amer. Inst. Min. . Ti&ns. XXXIII : 699, 1903. (Relation of ieneous rooks to ore depo- sition.) 49. Kemp, Ibid., XXXI : 169. 1901. (Igneous rook and vein formation.) 50. Kemp, Can. Min. Inst., XII, 1909 ; also Min. and Sci. Pr., Mar. 20, 1909. (What is an ore?) 51. Kemp, Min. and Sci. Pr., May 23, 1908. {Meteoric and matrmatic waters.) 52. Kemp. Boon. Oeol., 1:207, 1006. (Problem of metalliferous veins.) 53. Kemp, Eoon. Oeol., II : I, 1907. (Limestone contacts.) 54. Kemp, Min. and Sci. Pr., Mar. 31, 1906. (OMnet zones.) 55. Kemp, Econ. Geol.,1: 11, 1906. (Seo'y. enrieh'tinooppcrores.) 56. Keyes, Eeon. Oeol., IV : 365, 1909. (Depth of oontaet-metamorphio ores.) 57. Ine, Can. Ming. Inst., Jour. IX, 1906. (Magmatio segra- tion.) 58. Lane, Can. Ming. Inst., Jour. XII, 1909. (Mine ters.) 59. Lincoln, Eoon. Oeol., II : 258, 1907. (Magmatio emanatioms.) 59a. Liadgren, Oeol. Boo. Amer., Rull. VI: 240, 1895. (California gold quartz veins.) 59b. Lindgren, Amer. Inst. Min. Engrs., Trans. XXX: 578, 1901. (Metasomatio processes in fissure veins.) 59c. Lindgren, Araer. Jour. Sci., iv, V:418, 1898. (Orthoclaae gangue.) 59rf. Lindgren, Eeon. Oeol., 1:34, 1906. (Ore deposition and deep mining.) 60. Lindgren, Amer. Inst. Min. Engrs., Trans. XXXI : 226,

1902. (Contact deposits.) 61. Lindgren, Econ. Geol., II : 105, 1907. (Physical conditions of ore deposition.) 62. Liudgren, Econ. Oeol., IV:409, 1909. (MetaUogenetic epochs.) Also Can. Min. Inst., XII. 63. Lindgren, Amer. Inst. Min. Engrs., Trans. XXXIII : 790, 1903. (N. Amer. gold and silver.) 64. Lindgren, Econ. Oeol., V: 22, 1910. (Ojo Caliente hot spring deposits.) 65. Pearoe, Austr. Inst. Min. Engra., Ptoo., July. 1909. (Nomenclature of shoots.) 66. Penrose, Jour. Oeol., 11:288, 1894. (Weathering of ore deposits.) 67. Pen- rose, Eoon. GeoL, V : 97, 1910. (Causes of ore shoots.) 68. Posepny, Amer. Inst. Min. Engrs., Trans. XX!lII: 197, 1894. (Genesis of ore deposits.) 69. Ransoms. Eoon. Oeol., Ill : 331, 1907. (Rel'n between certain ore veins and g&ngue-filled fissures.) 70. Read, T. T., Amer. last. Min. Engrs., Trans. XXXVII ; 297, 1907. (Seo'y. enrioh't.) 71. Read, T. T., Eeon. Oeol., I; HI, 1906. (Phase rule and igneous magmas.) 72. Rickard, Eng. and Min. Jour., LXXIII: 106, 1902. (Recent advances in study of ore deposits.) 73. Rickard, Amer. Inst. Min. Engrs., Trans. XXXI : 198, 1902. (Bonanzas in gold .) 74. Rickard, Amer. Inst. Min. Engrs., Trans. XXVI : 193,

1897. (Vein walls.) 75. Rickard, Eng. and Min. Jour., LXV:494,

1898. (Minerals accompanying gold.) 76. Sandbeiger, Untersuch- ungen fiber Erzgilnge, Wiesbaden, 1882. 77. Smyth, Amer. Jour. Sci.. XIX : 277, 1905. (Pyrite replacing quartz.) 78. Stokes, EcOn. Qeol., 1:644, 1906. (See'y. enrioh't.) 79. Spurr, Eng. and Min. Jour., LXXVI : 54, 1903. (Relation of rock segregation to ore deposi- tion.) 80. Spurr, Amer. Inst. Min. Engrs., Trans. XXXIII : 288,

1903. (Magmatic segregation of rocks and ores.) 81. Spurr, Econ. Qeol., II : ITS, 1907. (Theory of ore deposition.) S2. Steidtman,

iv,Coog[c

S ECONOMIC GBOLpor

Econ. Qeot., Ill : 381, 1908. (Oraphio comparison of altentioiu by weathering aiid hot solutiona.) 83. Stevena, Amer. Inst. Min. Engrs., Bull.. Aug., 1909. (Laws of flsaures.) 84. Stokes, En. OeoL, U: 14, 1907. (Aotion of BolutionH on tnorcasite and pyriM.) 85. Suest, Eng. and Min. Jour., LXXVI : 52, 1003. (Hot springs.) 86. BuUi- van, Boon. Geol., 1 : 67. 1906. Also U. S. Geol. Surv., Bull. 312. {On deposition.) 87. SuUtvan, Ibid.. Ill : 760, 1908. (Precip'n by filtra- tion.) 88. Van Hiae, Amer. Inst. Min. Engts.. Trans. XXX: 27, 1901. (Deposition of ores.) 89. Vogt, Zeitsoh. t. Prak. Qeol. I: 4, 125, 257, 1893. (Magmatic segregation.) 90. Vogt, Min. Indus.. IV: 743, 1896. (Formation of eruptive ore deposite.) 91. Vogt. Zeitsch. f. Prak. Geol, VI : 225, 314. 377, 413, 1898 ; VII : 10, 1S99. . (Distribution of elements and concentration of metals in ore bodies.] 92. Vogt, Amer. Inst. Min. Engra., Trans. XXXI : 125. 1902. (Prob- lems in geology of ore depomta.) 92 a. Wagoner, Amer. Inst. Min. Engra., Trena. XXXI : 798, 1902. (Gold and silver in sedimenttij- rooks.} 93. Washington, Amer. Inst. Min. Engrs., Trans. XXXIX: 735, 1909. (Distribution of elements in igneous rooks.) 94. Weed, Amer. Inat. Min. Engrs., Trans. XXX: 424, 1901. (Enrich't gold and silver veins.) 95. Weed, Eng. and Min. Jour., LXXVI : 193, 1903. (Cross-vein ore shooU.) 96. Weed, Ibid., LXXIV : 545, 1903. (Vein enrichment by ascending alkaline waters.) 97. Weed, Ibid., LXXIV : 513. 1902. (Contaot-metamorphio depoaita.) 98. Weed. Amer. Inst. Min. Engrs., Trans. XXXIII : 747, 1903. (Vein enrich't by ascending hot waters.) 99. Weed, Ibid., XXXI : 634, 1902. (InSu- enoe of wall rook on mineral veins.) 100. Weed, U. B. Geol. Surr.. Bull. 260, 1905. (Hot spring deposits.) 101. Weed, U. 8. GeoL Surv., 21st Ann. Rept., II : 227, 1900. (Hot springs depoaiting gold.) 102. Weed, Amer. Inst. Min. Engrs., Trans. XXXIII : 731. 1903. (Contact-metamorphio deposits.) 103. Weed, Eng. and Min. Jour., LXXXIII:1145, 1907. (Diaplaoement by intersecting veins.) 104. Weed, Ibid., LXXXII : 196," 1906. (Ore shoots.) 105. Weed, Ibid., LXXIX : 365, 1905. (Adsorption.) 106. WeUs, Eoon. Geol., V : 1, 1910. (Fractional preoip'notBulpfaides.) 107. Winoliell, Econ. Geol., II : 290, 1907. (Ox'n of pyriite. )

b,

Chapter Xv Iron Ores

Iron ia an abundant constituent of the earth's crust, and yet few minerals are capable of serving as ores of this metal, because they do not contain it in the right combination or in sufficient quantity to make its extraction posble or profitable.

The iron ores having the greatest commercial value at the present day are usually those which are favorably located, of high quality, in considerable quantity, and possessing s structure such as to reader their extraction easy. These four requirements have been met to Buch tat eminent degree by the deposits located in the Lake Superior district that they now form the mn source of supply for furnaces in the eastern and central stats, and many of the iron mines in the eastern part of the United States have found it difficult to com> pete with them, although it ia true that a number of deposits are worked to supply local demand, owing to their proximity to furnace, flux, and coal, or because they possess certain desirable character- istics.

Iron-ore Minerals. — The ore minerals of iron, leather with their composition and theoretic percentage of metallic iron, are : —

Magnbtite. Maeoetio iron ore, FejOt 72.4%

UtUATTTB. Speoular iroa ore, red hematite, fosail ore, Clinton

ore, Fe,0, 70%

LmoNiTE.' Brown hematite, bog iron ore, ochre, brown ore

2Fe,0 3H,0 59.89%

SiDEsiTE. Spathio ore, blaekband, day-iron stone, kidney

ore,FeCO. 48.27%

W lubordinate value: —

BiTE. FeS, 46.6%

PiwuNiTE. (Fe, Zn, Mn)0. (Pe, Mn),0, ±44.1%

PraBHOTPra. Chiefly Fen Si. ±61.6%

hUgnetite btaok, oben granular, and may run high in titanium, specially in those oconrrenoes found in baeio igneous rooks. Hematite

'The croup name " i>re" Lb ometimee lued to include Bererol hrdroui '"Ues, nich as limomte, tursite. and gOthite.

349 L, -ziv.CoOgL-

350 Economic Geology

is red to browuBh red, steel-gray, or even bltMsk. It is commonly fine- grained, but the apeoulor varieties may be quit coarse. It ranges troni massive to powdery, and b&9 a speoifio Gravity of 5.2. Limonite is Dever cryBtalline, and varies widely in appearance ; some forma are powdfry. others massive, these may be porous, vesicular, stalaotitic, or even, though rarely, solid. The specifio gravity is 3.8. The color is brow to brownish yellow on the fracture, but may be black and shining on lfa . natural surface. Giitbite (FeiOi, HiO) and other hydrous oxides with less water than limonite are sometimes associated with it. Siderite, when occurring in commercial quantities, is rarely in oleavable form, but occurs as a flne-grained rock, with impurities. Hematite is by far the most valuable of the iron-ore minerals, chiefly on aooount of its easier reduction, but also because of the greater richness of the known important depoails.

The deficiency in iron contents shown by many ores is due to the presence of common rock-forming minerals in the gangue, the im- purities which they supply being alumina, lime, magnea, silica, titanium, arsenic, copper, phosphorus, and sulphur. The effect of the last six is in general to weaken the iron.

Silica is objectionable because it displaces iron, and because just so muefa lime is required to flux it, but some furnaces turn out iron for foundry pur- poses oontaining 10 or more per cent. Ores carrying as high as 40 per cent 8iOi are used in small quantities. Lime in small amounts does no harm, but in large quantities needs to be fluxed off. It is not present in any quantity in limonite, but may run high in the Clinton ores. Alumina may run somewhat high in limonites, because of admixed clay. Irrite ia the oonunon source of the sulphur, but in some limonites it may come from gypsum or barite. Titanium, a common but injurious ingredieiLt, is found in many magnetite deposits (see Titaniferous magnetites, tiso refs. 28, 30) and up to the present time has rendered them practically useless, not because it interferes with the quality of the iron, but because it makes the ore highly refractory, and drives much of the iron into the s]a£. Experiments have been taken looking towards the utilization of ibtse titaniferous magnetites for the manufacture of ferro titanium. Manganese, when present, is found mostly in the limonite ores, and for certain purpose is desirable. It is also prominent in some of the lAke Superior ores. Apatite yields the phosphorus. As this cannot be eliminated in either the blast furnace or the acid converter used in Tnalring Bessem steel, and as the allowable limit of phosphorus in pig iron used for this purpose is fis per cent, a distinction is usually made between Bessemer and non- Bessemer ores, the nuutimum amount of phosphorus permissible in iron ore to be used for this purpose being j- of the percentage of metallic iron contents of the ore. The phosphorus contents of many high-grade ores falls considerably below the allowable limit.

Classijicalion. — The iron-ore deposits found in the United States have originated in a number of different ways, but the chief tj-pes may be grouped as follows : I. Magmatc sregation deposits

bvCoog[c

Iron Ores

(LakeSanford, New York, etc.)- 2. Contactmetamorphic deports {Iron Springs, Utah; Hanover, New Mexico), 3. Sedimentary ores (Clinton hematite, bog ores, etc.). 4. Ores concentrated by meteoric waters, and deposited as replacements (some Lake Superior hematites, Oriskany limonites), or in residual materials (Virginia Cambro-Silurian limonites). 5. Lenticular masses in metamorphic rocks, of variable origin (some maetite and pyrite deposuts). 6. Gossan ores (limonite capping of many sulphide ore bodies).

Iron-ore bodies may show a variety of form, but many of the important deposits known in this country are lens- or bamn-Bh{Q>ed in outline. Irregular masses and beds are not uncommon.

The iron ores found in the United States are widely distributed and their age ranges from pre-Cambrian to Recent. The occurrencea of the different kinds of ore are best discussed separately, and for practical as well as other purposes a mineralogic and geographic grouping seema better than a genetic tme.

Magnetite occurs in the United States (_¥\g. 123) (1) as lenticular masses commonly in metamorphic rocks ; (2) as more or less lens- shaped and tabular bodies in igneous rocks ; (3) as sands on the shores of lakes and seas (4) as contact-metamorphic deposits;

'10. 123. — Map BhowiDg dUtributioa ol hemi

and msKnetite deposits ii

United SUtea. iAfter Harder. U. S. Oeol. Sun.. Min. Bel., 1907.)

352 Economic Geology

(5) as replacements in limestoae, not of contact-metamorphic char- acter ; (6) as veins, and (7) in residual clays.

The first class includes the most important deposits now worked in this country. The second and third groups run too high in tita- nium to have any commercial value at the present time, but the second may become of importance in the future, and moreover some of its representatives are of laie size. Examples of the fourth class are known at a number of points in the West, and while few of them are worked, they may some day become of great importance. They carry hematite in addition to magnetit. The fifth, sixth, and seventh groups are unimportant.

Distribution of Magnetites in the United States (Fig. 123). Nm- Titanifermis Magnetiles. — These are usually found in the form of lenticular deposits in metamorphic rocks. The most important series of occurrences lies in the crystalline belt of rocks extending from New York into Alabama, deposits being known in New York, New Jersey, Pennsylvania, Virginia, and North Carolina.

The lenses, which are interbedded with gneisses of cither add or basic character and often conform with the latter in dip and strike, are of variable size, and may occur either siily or in series, the ore body commonly showing pinching and swelhng, or even faulting. Well-defined boundaries are sometimes wanting. Feldspar, hom- tilende, and quartz are common gangue minerals, while apatite B prominent in some. Although the ore as mined is frequently of sufficient purity to be shipped direct to the blast furnace, in some instances it is so lean as to require concentration by magnetic methods. A description of one or two occurrences will serve as types :

Adirondack Regirni, New York (27, 30) — The rocts of the Adiron- . dack region (Fig. 124) are almat exclusively of preambrian age, with occasional inhers of the bordering Paleozoic strata, whose basal member, the Potsdam sandstone, rests unconformably on the older crystallines. The latter have in most cases been subjected to power- ful compression, and sometimes greatly changed by metamorphism, in fact so much so that their original character is determinable with difficulty.

The following members are rcccnized, beginning with theoldest:

I. Meiarrwrpkic rocks. — SedimerUary or OrentdUe Series. These consist of limestones and dolomites, often imprnated with pjTite, graphite, and silicates, and by an increase in the latter may pass into schists. Both rock types occur in long narrow belts, bounded by sedimentary gnoiascs. 2. Gneisses of add to basic charader, often

Iron Ores 353-

showing garnet, sillimamte, graphite, cyanite, pyrite, etc. 3. Am- phibolUes, composed mainly of hornblende or feldspar, and which may be metamorphosed dikes or magnesian shale. 4. Quartziiea of infrequent occurrence. 5. Gneisses of doubtful relationships. iy

II. IgneousTOcks. — These include : (1) anorthosite (theearUest), gabbro, syenite, and granite, all connected by intermediate rock tj-pea and probably representing derivations from the same magma. (2) Dikes, mostly diabases.

Fic. i:

Ores. — The non-titaniferoua magnetites are the most widespread of the Adirondack ores, and occur on both the eastern and western side of the mountains.

The ores vary from impure lean varieties, consisting of magnetite mixed with the country-rock minerals (i.e. quartz, feldspar, pyrox- ene, hornblende, etc.), to pure magnetite. The richest ore averages 60 to 70 per cent iron, and comes chiefly from Minevitle, while those 2 a ; L'.OOgIc

. 354 Economic Geology

ores carrying under 50 per cent have to be concentrated. The phos- phorus content is variable, but aeema to be lower in the leaner ones, while in the non-Bessemer ores it may reach 2 per cent. The amount of sulphur is also changeable, but is bluest in those ore bodies foimd in the Grenville gneiss. ' r-j y

While the ore bodies are variable iji shape they show in general a somewhat lenticular cross section, with the tabulation extending par- allel with the strike ; but regulanty is more common on the north

{AJUt OranbeTTf, Eng. and

and west sides of the province, for in the eastern districts there is the greatest irregularity due to a complexity of pinches, swells, and compressed folds. The wall rocks include gneisses of granitic, syen- itic, and dioritic composition, as well as schists and occasionally limestones.

MineviUe, New York. — The ore bodies at this locality are the largest and most productive in New York State at the present time.

They are of lenticular character, but in some cases the' lenses are so

b,

Flaw XXXI

i'la. 2. — Ucucr&l vipw of mOKntii' separating plants and shaft houses, Mineville, N. Y. (.AJler WiOerbee. Iron Age, 1903.)

b,

Iron Ob£S 355

fiat sad of such extent aa to be commonly spoken of aa beds ; more- over, some of them have been bent over into a southwesterly pitch- ing fold, whose crest has been stretched and pinched, while faulting at the northern end of this has complicated the structure.

The ores occur aa intral members of the syenite series, and are in the form of layers conformable to the banding or foliation of the inclosing rocks.

There are at least three large ore bodies (Fig. 126), viz. : —

1. The Barton Hill ore body, forming a practically continous bed, whose outcrop is approximately 3500 feet long in a direction a little east of north.

2. The Hannony bed, lyii to the southwestward of Barton Hill, and striking northwest, with a rather flat southwest dip. It is 10 to 20 feet thick and cut by several narrow trap dikes which occupy fault planes of 10 to 50 feet displacement.

3. A large we body which appears to be made up of three principal Bad separated parts, known as the Miller, the Old Bed or Mine 23, and the " 2I"-BonanzanJoker. This is the chief source of the ore. There is some doubt whether there is any connection between the Joker and the Harmony. This Old Bed group extends in a prac- tically unbroken stretch for about a. half mile, exhibiting at the same time a most complex fold, referred to above.

The ores axe granular masses of magnetite which in the Barton Hill group were prevailingly of Bessemer grade, but which in the Old Bed series are high in phosphorus.

The lean ores are mixed with the minerals of the wall rocks, and among these the basic syenite is the chief one.

At Ion Mountain (30) the ore is a lean magnetite traceable for 6 miles and from 20 to 200 feet wide, and occurs in a rock intermediate between gnuite and syenite. Most of the ore is low in phosphorus, the oonoen- tratce a&rr3'ing about .008 per cent and 65 per cent Fe.

Neie Jeraey. — In northern New Jersey, the maetite deposits form layers or bands in the Franklin (pre-Cambrian) limestone, or as flat lenses in the assoeiated gneisses.

The ore according to Bajley (24a) consists mainly of magnetite, horn- blende, pyroxene, and apatite, sometimes intimately mixed. Pyrite and quartz are not uncommon, imd all the aasociatad minerals occur in the country gneiss.

The ore bodies, which are lens-shaped, lie with their longer axes conform- ing to the foliation of the gneisses, and the ore usually grades into the eneits, although sharp boundaries are in some cases known. Several lenses nuy overlie eaoh other, and then the intervening rook may be either gatam, pegmatite full ot magnetite, or coarsegrained homblendic rook.

Economic Geology

with ore veinlets panlleUng the foliation of the gomet. This soies of magnetites exteoda northeastward into the F'g'''*" region of Kew York.

-

- I.J

- i;-J-

V'.

rT-r-j-

-, 1 . J-

Origin of Magnetites. — The origin of the magnetites found in the gneisses has formed a most puzzling problem to geologists, whose

Iron Ores 357

correct solution depends in part at least on the correct interpretation of the origin of the inclosing rocks.

If the gneisses are of sedimentary origin, then it is possible that the ores may represent metamorphosed deposits of magnetite sands, limonites, or siderite, and the parallelism of the ore bodies with the foliation of the gneisses might be regarded by some as evidence in favor of such a view.

But even if the gneisses were of sedimentary origin, it might still be possible that the ores were of later introduction, as has been suggested by some. Thus Keith held the view that the North Caro- lina magnetites were replacement deposits (26), while Kemp for- merly advanced the theory that the ore bodies at Mineville (27) have been formed by iron-bearing magmatic waters, which were given off from the neighboring gabbroa and penetrated the gneisses while the latter were probably still at great depths, and before their metamorphism was complete. The presence of apatite and fiuorite was thought to show that mineralizing vapors also played a part, A similar origin was suested by Spencer for the New Jersey mf- netites (34).

Recent studies by Kemp and Newland in the Adirondacks (30) seem, however, to indicate that the acid gneisses are probably of igneous origin, and that the magnetites themaelvea are products of magmatic differentiation. That there is no obstacle to this theory is shown by Newland, who points out that the acid igneous rocks of that region contain a laige excess of iron over the amounts combined with the lime and magnesia to form silicates. The pe- culiar form of some of the ore bodies is likewise perhaps only explainile by this theory. A fact not to be overlooked, however, is the occurrence of fluorite, apatite, hornblende, etc., intercrystal- lized with magnetite, or the frequent association of the latter with pegmatite or vein quartz, a group of conditions which are sues- tive of mineralizing agents, and their deposition by pneumatolytic OT aqueous action.

CornmiU, Pennsylvania (35). — A Bomewhat unique deposit occurs at CHTiwidI, Lebanon County, Pennsylvania, and at several other localities in aoutbern Pennsylvania. The ores are found along the contact of Triasaic diftbase, with Cambro-OrdoviciaD limestones or more rarely Triassio shales, nnd consists mainly of magnetite, but carries sufficient pyrite require roasting, and occasionally a little specular hematite. The ore forms Urge and small masses of irregular shape, lying either within the "sdimenlB or along the contact, and while it appears to be a true contact deposit, the contact silicates are not prominent. The ore averages about

I;

Economic Geology

45 per cent iron, is low in phoBphoras, but high in sulphur, Bilio&, lime, tnd magnesia. It &lso carries some copper.

ISr

* dtcHi (J001

EtilytnehyM lO*- eoC

Srin"s?r'<.ss3;r

{Afl€r irirt

OOier OeourrenetB f 12). — Small depoaitB of magnetite are found in Ihe limestones of the Shenandoah Group and their residual olays in south- western Virginia (12, 22 a). The magnetite, which is assfieiated wit hematite and siderite, is of high grade and low in phosphorus (22 a). Mag-

iv,Coog[c

Iron Ores 350

netit occurs sparingly in the Marquette Range of Michigan, where it is toiind in the scliiatB. Contact-metamorpliio deposits are found at a number of localities in the West, but the cliief occuirenoea are in Colorado, New Mexico, Ut&fa, and California. Few of these have been described in detail.

Iron SpriTigs, Utah (29), — Iron depoats are widely scattered over the western states, but few have been worked, owing to the limited demand in that region. They can be regarded, however, i& reserves which may become of importance in the future. Among the best known of these are those of the Iron Springs district of southwestern Utah.

Fhi. 128. — Map of a portaon of the Iron Spring, Utah distljct, showiDg

of iroa ore in limeBtone near andeaite coatact. and also in the igneous rock. {Aftr Lath and Harder, U. S. Oeol. Sun.., BuO. 338.)

At this locality the series of sedimentary rocks ranges from Car- boniferous to Pleistocene {Fig. 127), and is intruded by three lacco- liths of biotite andesite, which have especially affected the Home- stake (Carboniferous) limestone, and to a lesser extent the Claron (Tertiary) limestone.

The ore bodies are of three types, viz.: (I) fissure veins in andesite; (2) fissure and replacement deposits on the contact of the andesite and Carboniferous limestone; and (3) as breccia cement in Cretaceous quartzite.

D,q,-Z.-dbvCOOg[C

360 Economic Geology

The Becond of these is the most important, and while the ore bodies are roughly lens-shaped, with their longer diameters parallel to the contact, still there are numerous irregularities, due to faulting and other causes. The vertical dimensions are unknown, as the deepest test shaft is down only 130 feet, and has not reached w&ter level.

The ore consists of magnetite and hematite with a small amount of limonit, the first two, of course, beii characteristic of contad- metamorphic deposits. The ore shows a hard, crystalline texture at the surface, but, as is sometimes found in arid regions, becomes softer with depth. The gaiue is chiefly quartz or chalcedony near the surface, but calcite increases with depth. The contact minerals, garnet, diopside, apatite, mica, hornblende, and other silicates, are minor constituents.

Fio. 129. — Cro8s section of Desert Mound contact deposit. Iron Springa. I'nh dutrict. a. iroD ore ; b. loccoUthic andeaite ; c. Homest&ke limestone : d, sltered Homestake liineelanc ; t, Piato sandatone. (A/ltr LtUhand Hardtr, V. S. Gtol. 3urt.. BuU. 338.)

While much of the ore runs above 60 per cent in iron, the average is about 56. Phosphorus is uniformly high, but sulphur, copper, and titanium are not in prohibitive amounts.

Leith and Harder believe that the ores are closely related in origin i to the andesite laccolite intrusions, and suggest the following:

The contact metamorphism first produced a zone of about 60 ' feet width, containing varying amounts of albite, kaolinite, actin- olite, diopside, quartz, orthoclase, serpentine, phlogopite, andrs- i dite, iron ores, osteolite (earthy apatite), andalusite, woUastonite, j calcite, etc. There is also glassy material which appears to repre- sent fused wall rock. Solutions given off by the andeate dis- solved out the lime and magnesia carbonates, while the residue recrj'stallized to form silicates. Later the iron was brought in from the eruptive, probably as ferrous chloride, which reacted with water (above 500° C), yielding mnetite and hydrochloric acid, thus:— 3 FeCI, + 4 H,0 Fe,0, 4- 6 HCI + H, + 77 calories.

c,q,z.<ib,Coogle

Iron Ores

The HCl attacked the limestone, which was replaced by the mag- netite.

This view that the eruptive contributed but little material to the contact zone is diEuted by Kemp, who, by taking the author's analyses and recasting them, shows that the reverse may be true. Moreover, if Leith's conclusions are true, then a contact zone 60 feet thick must represent a shrunken residue of a limestone belt 300 feet thick which, as pointed out by Kemp, seems hardly posble.

Analyses of Magnetites. — The following table ves the com- position of non-titaniferous magnetites from a number of localities. It ia not possible in all cases to obtain analyses of recent date.

Analtbbs op

Ft, .

m, .

Ti ;

llgO .

'If

*.49 1.54fl

f

18.W 1.30'

'.ae

'i

ss.as

lit

2.*

low

I. Sunple eo culowb. 11. Sunple 35 csrloadi. 21 pit. both MinevULe, N. Y., N. Y. Stmte MianiiD. Bull. 116:82. III. Wunn County. N. J.. N. J.Geol. Rurv.. Ann. Rt. 1BT3 : SO. tv. Philpol, Patrick CountT, Vs.. U. S. GboI. Surv., Bull. 3S0 : 210. V. Limntime munetita. AbnudoD. Vs.. Ibid. VI. Conmll. Pb., Anwr, Iiut. Min. EoEn.. Tniu, XIV : S92. Vl[. Inn SpriDEs, Utah. U. H. Geol. fturv., Bull. 338. VIII. Huaver. N. Meiioo, U. S. OmI. Bm., BuiL3a):313. IX. KuisU Couoty Calif., Eoon. Owl., lU :72.

TiUniferous Magnetites (24, 28, 30). — These form a peculiar class by themselves, and with only one or two exceptions are found always associated with rocks of the gabbro family. The ore bodies occur in the midst of igneous intrusions, and according to Kemp Beem to have been formed by the segregation of fairly pure titanifer- 0113 iron oxide, either before or during the process of coolii and con- solidation.

Mineralogically they may conttun both ilmenite, FeO, IHOi (FeO, 46.75 ; TiOi, 53.25), and titaniferous mnetite, which is of variable eompoaition. The gangue minerals may be pyroxene, brown horn- blende, hyperethene, enstatite, olivine, spinel, garnet, and plagio- clase. The ores are usually low in phosphorus and sulphur, but Va, Cr, Ni, and Co are almost always present. In the United States tliey are fotmd in New York, New Jersey, Colorado, Minnesota, Wyoming, Virginia, and several other states, but are not worked.

' FdiO,. 'FerfJt "MaO,. ' MnO. 'Pfi

t62 ECONOMIC GEOLOGY

The following analyses illustrate their compodtioD : — Analyses of Titaniferoub MAaincnTBa

S

S

T

PeO .

127.95)

51.44'

j 15.85 1

(48.97

Tio, .

12.0S

SiO, .

—

A1,0, .

—

—

Cr,0, .

—

—

Tr.

—

V,0, .

Tr.

—

MnO .

—

—

Tr.

—

—

—

—

MgO .

.

—

—

—

P,0. .

—

.022'

.97'

—

—

—

.028"

—

N.,0.

—

—

—

—

—

—

—

K,0 . Zn

—

—

—

—

—

—

—

Co,Nl.

—

—

—

—

—

—

" —

Pb .

—

— Tr.

1. Grape Creek, Col. 2. Majhew Range, Minn. 3. SpUt Rook.N.T. 4. Greeosboro, N. Ca. ; Nos. 1-4. U. 8. Geol. Surv., 19th Aon. Rept., Ill : 377, 1899. 5. Lake SanTord, N. Y.. N. Y. State Mas., Bull. 119 : 163. 6. Cumberland Hill, R. I., Amer. Jour. Sci., Jan., 1908. 7. Iron Mountain, Wyo.. U. 8. Gool. Surv., BulL 316 : 309. 8. Marksville, Va., Min. Res. Va., 1907 : 419.

Descriptions of two localities will serve to illustrate the mode of occurrence of these titaniferous ores.

New York (28, 30). — -Titaniferous magnetite deposits of large size occur in the Adirondack region, and while they carry TiO, as an essential ingredieat, the percentage of this element may vary con- siderably. Thus in the Adirondack ores it is at least S to 9 per cent (TiOi), and averages 15 per cent.

The ores are closely associated with gabbro-anorthosite intrusons, and are found chiefly in Essex and southern Franklin counties. At Lake Sanford, where the most important ore bodies occur, the small deposits are found in gabbro dikes cutting the anorthosite and having a tabular form conformable with the strike of the dikes, but

iv,Coog[c

Iron Ores

large ones occur in the anorthosite and may be segregations during cooling, or actual intrusions forced into the anorthosite after partial consolidation.

The ores are essentially magnetite and ilmeoite, the richest show- ing little else and running about 60 per cent Fe. The magnetite grains are recognizable by parting planes parallel to the octahedron and smooth breaks, while the ilmenite grains show a rough fracture, brighter luster, and but slight magnetism.

Other minerals present are plagioclase, pyroxene, hornblende, biotite, olivine, garnet, pyrite, apatite, spinel, and quartz. The usual order of crystallization is reversed, beii ralicatee, pyrite, ilmenite, magnetite. Analyses of the Sanford deposits show 70.73-87.60 Fe,04, .87-2.46 SiO,; 9.45-20.03 TiO,; .53-4.00 AlA; ,007-.022P; .027-.028 S.

The following results were obtained by magnetio Reparation after onisli- ing to 40 mesh. Finer orushiiig would probably improve the produot.

a

UunriTi

CoHtmnun

iLuunr- AHi>

PeO

TiO,

. 30.93

Wyoming (24). — An oocurrenoe of titaniferona magnetite of some importance is found at Iron Mountain in southeastern Wyoming. Iron Mountain is a ridge 300 to 600 feet wide, and U miles long, which rises huplf from the anorthosite hills to the east and pre-Cambrian uplands lo the west. The pre-Cambrian oompleic near the iron ore dike consiatH of three granular igneous rocks, viz. anorthosite, iron ore, and granite, the anorthosite, or oldest, being cut by dikes and leutioular masses of iron ore and granite.

The ore, which forms a dike miles long, 40 to 300 feet wide, and has 1 northerly strike, is sharply bounded on both sides by anorthosite, and mmlleled by several smaller dikes. It is a black, granular, holocrystal- line rock, which carries as impurities biotite, olivine, and feldspar. The Von contnt averages about 50 per cent.

It is suggested (Ball) that the ore and anorthosite are differentiation products from a common magma, the iron having been intruded ter tbe comidete solidification of tJie anorthosite; but the relationship of the two is shown by the presence in each of nmilar minerals, although their IHoportions are different.

bvCoog[c

Economic Oeolooy

S3 Ea

The granite is probably the youngest of the pr0&mbri&n rocks, and gradea into, as well as being cut by, a biatit-peemalite which canie!' some magnetite.

MagneUU Satu, — These found in those regions where tlte beach atmds are compoeed of weathering products at metamorpfaii; and igneous rocks. The sorting action of the waves serves to can: the heavy mineral grains high up o: the beaches, where they form black streaks, composed mostly of mag- netite (usually titanifarous), mixtl with monazite, apatite, and other heavy minerals.

Deposits are known in oountry on the shores of Isk ChamplaJn, Long Island, ete., bu they are of small extent as well a lacking in quaUty.

New Zealand and Brazil are said

Fro. 130. — Map of Iron MouDtain, Wyo., titsniferous magnetite deposit, a, post- Devoniaa; b, anortbodte: c granite: to possess magnetite sands of rf,giieiBs:e,ore. (A/ler Kemp. ZtiUehr. mercdal Vtdue. prak. Oeol., 1905.)

Hei/Latttb

This is by far the most important ore of iron in the United Stat*?, having in 1908 formed about 88 per cent of the total production, and about 85 per cent of the hematite mined came from the Lake Superior region. The varieties rained in the United States include the earthy, specular, oolitic, and fossiUferoua.

The deposits are mostly of basin-ahaped character, having been fonned largely by replacement, but contact deposite, bedded deports, and other types are known.

Distribution of Hematite Ores in the United States (Fig. 1Z3). — j At the present day there are but two very important hematite- ! producing regions, in the United States, viz. the Lake Superior ; region and the Birmingham, Alabama, area. Other areas which are ' worked will also be referred to, but they are less important.

Lake Superior Region (45, 47). — Under this head are included a great series of deposits lying in the region surrounding the south and west sides of Lake Superior (13). The rocks are of remote

Iron Ores

geolofpc age, as can be seen from the following generalized

section; —

EeweenawBH

Middle Hurooian

(iron-bearing) Lower Huronian

Meaabi

Penokee

Vermilion '

Marquette

Crystal Falls

Menominee

Cujmna

I Termilion

Each of the above series is separated from its neighbor by a great unconfonnity due to intervals of elevation above the sea level and periods of erosion.

The ore-bearing districts themselves have been studied in con- siderable detail, but the intervening parts are less well known, and it is therefore difficult to correlate the major geological units of the eeveral districts.

Character offarmaiiona. — The Archaean includes a complex series of acid and baac igneous rocks, and two or more sedimentary for- mations, including the iron formations and slate of the Keewatin. The Algonkian includes four unconformable sedimentary series, all associated with igneous rocks, the entire succession being separated by an unconformity from the Archiean below and the Potsdam aliove.

The iron ores occur as concentrations in the so-called irbn forma- tions, which range in thickaese from a few hundred to a thousand (cet.

In their present form these iron formations represent alterations of chemically deposited sediments, such as cherty iron carbonates, which are usually interbedded with normal clastic sediments such as slate and quartzite.

In general terms the iron formations may be described aa consisting mainly of chert or quartz and ferric oxides, usually segregated into bands, but sometimes irregularly mixed. Jasper is a banded rock of highly stalline charaoter with the quartz layers colored red. Ferruginous chart differs from it in being leas crystalline, and with the quartz either banded or irregularly mingled. This latter type is known as laconite in

' Not productive.

iv,Coog[c

Economic Geology

the Mesabi district. Other phasea of the iroa ronnation are olay sUtn, paint rocks (alterations of preoeding), ampbibole-magnetite whists, cherry iron caFbonate, hydraua ferrous silieate (Kreeoalite), and iroa cms.

The orinal iron rocks were cherty iron carbonate, ferrous silicate, and pyritic iron carbonate, and unaltered reoinants of these are still found.

Since their formation the rocks have been folded, faulted, ani sometimes brecciated, and much of the ore is found in these struc- tural troughs; but in some instances, as in the Mesabi Range, the ore bodies are somewhat flat as compared with th&x length and breadth.

The ores of the Lake Superior region vary from bard blue oth to soft earthy ones. They are mostly hematite with small quanii- ties of limonite, but some maietite is known in the Marquetie district.

The following table, taken from Birkenbine's report ves a number of typical analyses. Many additional ones can be found in the reports on Mineral Resources issued annually by the United States Geological Survey.

Typical Analtsbs or Lakb Sopbriob Iron Obbs

CoNTMirr

R&Hub

lUNoa

lUMaa

Rahoi

lUsm

Iron

fi6.308

PhosphoniB . .

BilJoa

Sulphur

—

—

—

—

Moisture . . .

12.315S

Analtbeb or Siuceoob Obis

Co

M*ito™r™

Ruiam

lUirai

Iron

Phosphorus

Silica

Sulphur

—

—

Moisture

Seven districts, or ranges, are recognizable in the Lake Superior region, viz. Marquette (48) and Crystal Palls (41) in Michigan;

Iron Ores 367

Menominee (89) in Wisconfiin; Penokee-G(ebic (42) on the Michi- gan-Wisconsin boundary ; Mesabi (44), Vermilion (40), and Cuyuna (46) in Minnesota.

FiQ. 131. — Map of lAke Superior ii

The general mode of occurrence of the ore in several of these ia shown in Figs. 132 to 134, and they are referred to individually below.

Marquette Range (48). — This occupies a rather large area west and southwest of Marquette, Miohigan, and carries iron formations in both the Upper and Middle HuroniaD, the latter being the more important. That of the Upper Huronian is underlain bj quartzite and covered by Blate, while the Middle Huron- ian iron formation is underlun by Btat which in turn rests on quartzites. Igneous intru- BJons of Keweenawan age are common. The structure of the range is that of a great Mit-west synclinal basin oon' taioing number of minor

I; Coojic

368 Economic Geology

folde, aod while the ores occur on both lunba of the basm, they are most abundftDt od the northern one.

The ores may be divided into tliree claaBes, namely, (1) ores at the base of the iron-bearing Negaunee (Middle Huronian) formation. (2) the ores within the Naunee formation, (3) detrital ores at the base of the Goodrich (Upper Huronian) quartzite. Ores of the first and second chiBs are mostly soft faydrated hematite, while those of the third class are bard specular ores with some magnetite from metamorphism due to greater movements along the contact of the Middle and Upper Huronian during the faulting within these rocks themselves.

Henomiaee Range (39). — -While this carries iron formations in both the Middle and Upper Huronian, only the former are commercially im- portant and are confined to the southern part of the district. The iron ores are mainly gray, finely banded hematite with leeaer amounts of a flinty hematite which shows local banding.

Penokee-Gogebic Range (42). — The ores occur in Upper Huronian, the iron formation being overlain by slate and underlain by quartzite and black slate. The latter is covered by a gabbro of Eeweenawan age, which is found in contact with the iron formation in places and has altered it to jasper and amphi bole-magnetite rock. Most of the iron formation. however, is ferruginous chert. The steeply dipping sedimentary rocks are cut by dikes of basic igneous rocks, thus forming troughs in which the ores are concentrated. Most of the deposits reached depths of 1000 feet and upwards, but the horizontal extent is small. While soft hydisted hematite is the normal type of ore. still the hard slaty ore is not uncom- mon. Manganese is found in a few deposits.

Mesabi Range (44).— The rocks of this region are less folded and metamorphosed, and dip slightly to the southeast. The iron formation, which is mainly ferruginous chert, is overlain by a thick slate and under-

iv,Coog[c

c,q,z.<ib,

b,

Iron Ores 369

Iain b; & tliin quartzito, which in turn reets on graoile, or KraywEtcke cutd sUte of lower Middle Huronian. At the eastern end of the range the iron fonnation has been metamorphoBed to amphibole-magnetite rock by a gabbro intrusion. The iron-ore deposits are very irregular in shape, but ibeir horizontal extent is great as compared with their depth (Fig. 134), moat of them being less than 200 feet. The mining is done mainly by open pits (PI. XXXIl), and the ore is a rather soft hematite of high grade. It preserves the Htratifloation of the original iron formation and in places is found grading into the latter.

e deposit and adjacent

VennOion Range (40). — The chief ore deposits occur in the highly folded and metamorphosed Keewatin rooks, and the iron formation is largely altered to jasper. The country rock is mostly greenstones in which the jasper occurs in basins or troughs. The ores associated with lie jasper in these troughs usually have a greenstone foot wall and con- sist of dense hard red or blue hematite, which is sometimes brecciated but rarely specular.

Coyuna Range (4B). — This range lies to the southwest of the Mesabi range and shows a series of small northeast-southwest anticlines in a broad synclinal baatn on whose northern limb the Mesabi range is situ- ated, while on the southern limb we find the Penokee. Owing to the Limited number of outcrops and lack of development at the present time, the geology is not yet perfectly known, but the formations seem to include quartzite and its altered equivalents, iron formations, slate, and intrusive granite and diorite. The ores form the altered and concentrated upper parts of the steeply dipping iron-formation strata, which are exposed by the erosion of the anticlines. The hanging wall is commonly chloritie elate and iron carbonate in varying proportions and degrees of alterations, while the foot wall is either a quartz schist or amphibole-magnetite schist. The ore bodies thus far found seem to be in the form of lenses 100 to 250 feet thick, with their longer dimensions parallel to the highly tilted bed- ding of the series.

Origin. — The orin of these ores has for years been a puzzling problem to geologists. Foster and Whitney considered them erup- tive, while Brooks and Pumpelly looked upon them as altered limo- nitebeds.

c,,,z.-.b,Coogle

370 Economic Oeoloot

The work of Van Hise and has shown ua that the Lake Superior ores were concentrated in certain sedimentary iron forma- tions, and it was at first believed that these sediments were derived from the weathering of land areas containing much igneous rock.

Further study has led them to conclude, however, that the iron formations have not only been derived in this way, but that the iron has actually been contributed by greenatone magmas directly to the water in magmatic solutions and that there are all intermediate stages between the two processes.'

The iron ore as GiBt deposited conasted essentially of chemically precipitated iron carbonate or ferrous ulicate (greenalite) with some ferric oxide, all finely interlayered with chert.

Later on, when these sediments were uplifted to form the land surface and exposed to weatherii, the ferrous compounds, the siderite and greenalite, were oxidized to hematite and limonite. While this occurred mEunly in place, some of the iron was carried off and redepoted elsewhere. This resulted in a femnous chert carrying leee than 30 per cent of \roa.

Further concentration of the iron to 50 per cent or over was accom- complisbed mainly by the silica being leached from the bands of ferruginous chert.

Whe the concentration of the ore has occurred in trough the chemistry of the process is thought to be as follows : —

Part of th ferrio oxide was deponted ae an original sediment ooatun- ing Bilioa aod other Impuritiea, or in some oases as sulphides or earboiMtos. This was later enriched by the addition of iron carbonate. These were orinally contained in the rooks near the surface, and beoame oxidised by peroolating waters, whioh took up the carbon dioxide liberated, and were thus able to dissolve iron carbon&ta or silicates, which they came in contact with in their downward course toward the troughs in which the ore is found.

The preoipitation of the ore was then caused by these solutions meet- ing with others which had filtered in by a more open and direct path from the surface, and hence contained some heo oxygen, which converted the dissolved iron compounds into oxides.

The same solutions, carrying carbon dioxide, dissolved the alkalies out of the basic igneous rocks, and these waters were then able to dissolve silica. In some caeea the solution of silica proceeded faster than the deposition of the iron ore, and made the rook quite porous. The general result was therefore a oonoontration of the iron and removal of silica.

The weathering processes have yielded mainly soft ores and femi-

gous cherts, while metamorphism has formed hard red and Uue

Can. blin. Inst., XI: SI, 1908.

b,

r Of THE

University

bv

PlTB XXXIIl

FiQ. 1. — Iron mine, SoudaQ. Minn. Shows old open pit with jasper horse id middle

Fio. 2. — View of limonite pit nenr Irooton, Pa. (H. Hio, photo.i D,q,z.<ib,C00gle

specular ores and brilliant jaspers, as well as changed the ir<Hi fat' mation ialo amphibole-magnetite schists.

Moat of the rich ores are found above the lOOOoot level, axcept in the Mesabi distriot, whwe the deposits are shallow, ae compared with their horizontal extent, some, however, being over 400 feet deep.

In the earl; period of mining many of the Lake Superior bodies we worked as open outs, but with depth underground working has been re- sorted to- There are many deposits in the Mesabi distriot whioh ore worked as open pits from which the anular ore is dug with a steam Bhov and loaded direetly on to the ore oars, whioh are run along the working face (PI. XXXII).

The market value of the wes is based on the iron contents, percentage of water, and amount of phosphorus, and at times the manganese oontents is taken into consideration. Some objeotion was at first raised to the fine aharaotr of the Mesabi ore and its tendenoy to clog the blast furnace, therefore requiring the admixture of lump ore from the other ranges; but this objection has disappeared, and some furnaces now use over 75 per cent of Mesabi ore in their charge.

The Lake Superior iron ore region is not only the most important in the world, but the production of some of the individual mines is startling. (See production of individual mines at end of thia chapter.) The M.ta- quette range was developed as early as 1849, the Mesabi as late aa 1892, and the Cuyuna some yeaxs after this. The total yield of the Lake Buperior region from 1850 to the end of 190S has been about 434,000,000 long tns. While the output has been phenomenal, and the supply huge, high-.grade ore is no longer abundant, and much ore running hi in silica is now shipped.

Wyoming (60). — Important depodts of hematite are found in the pre-Cambrian schiste at several localities in Wyoming, viz, in the Hart- ville District, Laramie County, and near Rawlins, in Carbon County.

The Hartville depodta form a portion of the Hartville uplift, which 13 a broad, low dome milar to that formed by the Black Hills, and while the iron range extends from Guernsey to Frederick, a distance of 8 miles, the productive area extends only from a point 2 miles northeast and 1 mile southeast of Sunrise.

The pre-Cambrian sediments have been folded into a complex syncltnorium, and faulting has been a common phenomenon, while the brecciation which accompanied both the folding and faulting was an important structural factor in the ore formation.

The most important ore bodies are lenses occurring in the schist along a limestone footwall, the ore either replacing the schist or to a lesser extent filling the joint, fault, and breccia cavities. These lenses range up to 1000 feet in length, and conform to the foliation of the schists. Detrital ores derived from the foregoing are also fotmd.

372 Economic Geology

The followiDg geolocal section ia involved : —

HeiBtocene

TertiaiT (Arikaree)

Sandstone.

Jura-Trias and Cretaceous

HartviUe 650' thick. White or gnj lime- stone. Red sandstone.

Guernwy ISff thick. Conglomeretio qosrU- it or sandy limestone.

Pre-Cambrian rocks, the stratified onea with steep dip.

Quartzose beds, partly conglomerate and smo-

oiated jaspers. Unconfo4.it

vite and biotite schists with beds and lenses of quartz aud jasper rock.

phyrites, derivative hornblende and ddoril* schisU.

The ores axe high-grade hematites (chiefly hydrated), CLvera over 60 per cent iron. Sulphur is absent, silica may be high, and I much of the ore is nonBessemer. Two grades of ore are recogdwd, viz. a hard gray hematite, and a soft greasy one of brown color.

Siderite and limonite are of subordinate importance, while the associated minerals are caicite, quartz, gypsum, chalcedony, barite, chrysocolla, etc. The copper minerab occur in the fractures in tbe hematite. Both types of hematite grade into the schist, but much I of the soft ore has been derived from the hard by percolating waters.

Ball asfflgns an epigenetic orin to the ore, believing that it viaa deposited by descending water, because (1) the ore ia along zones of maximum downward circulation, (2) lenses and vinsare found along joints at a distance from the main body, and (3) the associated min- erals, quartz, caicite, and limonite, are all water-formed ones. The magnetite and iron pyriteof the schist lying above the limestone foot- wall are regarded as the source of the iron. During pr&-Cambriiin times there was extensive erodon of this schist, and a downward transferal of this iron by carbonated surface waters flowing along the impervious limestone footwall, where it was precipitated by oxygen-bearing waters coming by a more direct path.

Clinton Ore (51-59). — This ore, which is also called foaail, JW. ->r dyeetone ore, was ven the name on account of the ore bed

University

bv

andJussr

Via

[Z]

Piia XXXIV. — Gcologir map of s

CAftCT Barduird, Amcr. Inal. Min. Engn.. BtdL 24, llBS'?

]

P"T XXXV. — CeoloRic mnp of eastern halt of Birmiifgham, p,,i(tv4tt. (AJter Burchard, Amer. Intl. Mia. Engrs., BuU. 24. 190S.)

b,

Iron Ores

having been orignaUy discovered at Clinton, N. Y. It is one of the most perastent iron-ore deposits that is known (Fig. 135), for it occurs at moat points where rocks belonging to the Clinton stage of the Silurian are found.

The following districts may be enumerated as sbowit the loca- tion of the more im- portant deposits: (1) west central New York; (2) several nar- row belts in central Pennlvania; (3) Al- lhany County, Va.; (4) a belt through Lee and Wise counties, Va., extending southwest- ward into the La Fol- lette district of Ten- nessee; (5) narrowbelts in the region of Chat- tanooga, Tennessee; (6) Birmingham, Ala- bama; (7) Bath County, Kentucky; and (8) DodgeCounty, Wisconsin. Other known occurrences of minor importance are indicated on the map, lig. 135, and in addi- tion the ore haa been recently discovered by — eaateni Umtl States, showiDg J -„. . . areaB ot outcrop of Clinton iron ore. (After

dnlling m Miseoun. McC<ulic. Oa. aot. Surv.. BuU. 17.)

Of these districts, the Birmingham, Alabama, one is the most important, with Chat- tanooga, Tennessee, and central New York ranking respectively second and third.

The Clinton ore deposits occur as beds, or lenses, interstratified with shales and sandstones at different horizons in the Clinton, and as many as three or four beds may be present at any one locality. They show extremes of thickness, ranging from a few inches to 40 feet, but rarely exceeding ten feet. The thicker beds often contain

. f,

s

hf

f

t&

$&

Economic Oeoloot

BEDdstoDe and shale partings, and any bed is sometimes traceable for miles along the outcrop.

Fio. 136. — sliawiiig outcrop of CliDtoD ore in AlabluiM. {Afltr BunAanJ, Amtr. Intt. Min. Engrt., BuU. 24, 1908.)

The dip of the beda depends on the intensity of foldii that has occurred in any given area, Thus the ore beds in New York State

iv,Coog[c

Iron Ores 375

are nearly horizontal, and can at times be mined for some distance from the outcrop by stripping; while those found in the Appa- lachian region Ehow a variable and sometimes steep dip, and hence require to be worked by underground methods.

Two textural varieties of Clinton ore are recognized, viz, (1) fossil ore, and (2) oolitic ore.

The former is made up abnost entirely of a mass of fossil fragments, while the latter conaste of small, rounded gnuns of concretionary character. These two varieties may occur in the same or separate beds.

A second classification, based on grade, includes (1) soft ore, and (2) hard ore. The former is found in the outcropping portion of the seam and may extend to variable depths, sometimes as much as 400 feet, while the latter, which is usually sharply separated from the former, occurs lower down. The soft ore runs high in iron and dlica, but low in lime, because this has been removed by weath- erii. The hard ore runs high in lime, but low in alica and iron. Both varieties are high in phosphorus and hence of non-Bessemer grade.

Birmingham, Alabama (51). — The great development of the Bir- mingham district is due to peculiar local conditions, for we find the

z .IV,

Economic Geology

iron ores, flux, and fuel all in close pronmity to each other (Pis. XXXIV, XXXV).

The Clinton ore beds are found in Red Mountain (Figs. 136, 137) on the east side of the valley in which the city of Binoingham lies. There the Clinton fonnation, which is 200 to 500 feet thick and dips westward from 20° to 50°, is composed of beds of shale and , sandstone and includes four well-marked iron-ore horisons, gener- ally in the middle third of the formation.

These beds are known as the Hickory, Ida, Big, and Irondale setims, but there ia difficulty in correlating them in different parts of the field. ,

Of these four beds the Big and Irondale are the most important. The , thickness of the former ia estimated at from 16 to 30 feet, but the good ore is rarely more than 10-12 feet thiek, and at most places only 7 to 10 feet are mined. In the middle of the district, the bed is separated into . two benches by a porting along the bedding plane, or by a shale bd. ' Either bench, though producing in one part of the district, may gnuie into ahaly low-grade ore in another part.

The following analyses are given by Harder (Miu. Rea. 1908), to show the gradation from hard ore to soft ore.

Analtses or Clinton Ibon Oaa vbou Alabaua

t

Fe.

fiiO,

AliOi

CaO

Mn

P

The unweathered ore is aaid by Burchard to range fi am a richly ferru- ginous sandstone to a ferruginous- siliceous limestone.

New York (55), — In this state the outcrop of the ore extends across the central and western part of the state (Fig. 138). The whole formation dips gently southward, with a gentle north-south synclinal trough in Cayuga and Wayne counties. Both oolitic and fossiliferous ore are found, and at least two beds, and stHnetimes four, may be present at any given locality. The ore varies in its richness, and while the deposits are very extenave, they have been but little developed.

b,

Iron Ores

-u

jW,

m

m

'i

Tia. 13S. — Mkp showins outcrop of Clinton on tornuitioD in New Yotk Stftte. {AJltr Neutand.)

Atudysea of Clinton Ore. — The followii are analyses of the Clinton ore from eevenil localitiea, which serve more to show its variation in character, than as types. Others are given above under Alabama.

nr

Fe

P

8iO,

TiO,

-Ma

MnO

CaO

MgO

So,

Co,

H,0

Tr.

Undet.

None

1.202' 1.143'

.15*

1, 11, N. T. State Mus., BuU. 123 : 33, 1908. III. On. Geol. Surv., Bun. 17: 130. IV. U. 8. Geol: Surv., Bull. 385. V. U. 8. Geol. Surv., Bull 285 : 188, Alleehany Co.,* Va.

iv,Coog[c

Economic Obologt

Origin of Clinlon Ore. — The origin of this ore has created con- siderable discusaion, and whatever theory is advanced, it must explain the following features: (1) the fossiliferous character of some beds, (2) the oolitic characters of others, (3) the bedded structure, (i) the soft non-Kcareous ore at the surface, and the hard or more calcareous ore at lower levels.

The three theories which have been advanced are the followiDg : (1) original depoation, (2) residual enrichment, (3) replacement. As can be easily seen, the correct solution of the problem is of practi- cal value, since it indicates the posable extent of the ore body.

Residual BnrichmCiit. — This theory mppoaes th&t the ore beds rep- resent the weathered outcrops of fermginotu limestones. Th&t is to ssj, the lime oarbonate was leached out by surface waters down to the water level, leaving the insoluble portion carrying the iron, in a more conceii* trated form. If this theory is correct, then the ore should pass into lime- stone below the water levd.

Russell (67), who was an earnest advocate of this theory, noted that at AttsUa, Alabama, the Clinton limestone at a depth of 250 feet from the surface oarriee only 7.75 per oent of iron, while at the outcrop it has 57 per oent of iron. Thew I figures would seem lo bear out tlus theory, but Eckel (51) has recently claimed that they must be incorrect, as the hard I at the depth men- tioned above carries 38 to 42 per cent of iron. Moreover, in none of the many fairly deep mines in Clinton ore has any change to limestone been noted,

Sdimentaiy Origin. — This supposes that the ores are of eontin- poraneous origin with the inclosing roolis, having been deposited on the sea bottom as chemical precipitates.

This view was advocated at an early date by James Hall, who believed that the iron came from the old crystalline rooks, which leached of their iron contnts, the ofilitie ore being a chemical precipitate on the ocean floor. '

Smyth (59) in amplifying this theory agrees with Hall as to the source of the ore. He points out that during Clinton times the drainage from the crys- talline area was carried into a shallow sea T>r basin. When the iron was carried into these inclosed basins, it was slowly oiddized and precipitated, gathering layer upon layer about the sand grains, thus forming oiUitic ore.

. f,

la. 139. — Typical profile or dope oa Red Mountain, tBTtios on the iron-ore out--crop. Shows bedded chsnictr of ore. (A/Ur Bvnhard, Amtr. ItuL Min. Engri.. BuW. 24. 1008.)

Iron Ores 379

Where the ferruginous waters came in contact with shell fragments the iron was preaipitated around thew, either due to a reaction with the earbonate of lime in the shells, or more often by oxidation. Later both types of deposit became oovered by ordinary sediments such as ihalea, BSQtlstoiies, or even limestones.

Additional evidence' favoring a sedimentary origin is the continuation of the ore with depth, some mines in Alabama being 2000 feet from the outcrop. Moreover some borings in Alabama have struck the ore to 1 mQe from the outcrop and 400 to 800 feet below the surface. The occur- rence of fragments of ore in the overlying limestone also pointfl to the ore being laid down before the lime rock.

McCallie (54), after studying the Georgia ores, while admitting their sedimentary origin, believes that the original iron mineral was greenalite or glauconite.

Replacement Theorr. — This theory assumes that the ores were of much later origin than the inclosing rock, and were formed by the replace- ment of the lime carbonate by iron, brought in by percolating waters, which had leaohed the ferruginous oonstituents from the overlying strata.

The structure of the formations, the comparative absence of iron in the limestone overlying the ore, and restricted vertical range of the ores have been advanced as arguments against this theoryJ

Rutledge (6S), however, as a result of his studies of the Clinton ores of Stone Valley, Pennsylvania, eopcludes that they represent replacement de- posits, and that the only part of the iron content which is of sedimentary efasracteris that contained in tbesiliceousconeretioDH, most of the iron hav- ing come from the shale overlying the ore beds ; the hematite depositB have thus t)een formed by replacement of limestone and concentration of the oie. The evidence presented in favor of this view is: (1) the invariable issMiatioD of the soft, rich ore with the leaohed decolmiced shales, aiid of the hard, lean ores with unweathered bright shales ; (2) the relations of the ores to the shattered sandstones and to the topographic situation of the ores ; (3) the fact that analogous replacements are now taking place ID the Medina ; (4) the observed progressive steps in the transformation of the limestone to an ore, which may be followed in the field, in thin sections, and in chemical analyses, and (£) the absence of conditions, nich Bs a local crumpling, including a shrinking of the strata, pointing to s relative rather than an absolute enrichment of the ores.

In view of the fact that the advocates of the several theories often bring apparently good evidence to support their case, one may perhaps question whether several different methods of eoncentration have not been operative. To the author, it seems that the sedimentary mode of sccumulation baa probably been the dominant one in most cases.

LIMONITE Limonite (13. 22, a, 62-72), or brown hematite, la, like magnetite, of little importance in the United States as compared with hematite, liaving yielded but 7.2 per cent of the total domestic iron-ore pro- duction in 1908.

c,q,z.<ib,Coogle

ECONOMIC GBOLOaT

the United Slatta

Although deposits of limonite are widely scattered over the United States (Fig. 140), about nine tenths of the quantity produced comes from five states, viz., Alabama, Virginia, Tennessee, Georgia, and Pennsylvania; indeed, the first two supply over 50 per cent of the total output.

Limonites are rarely of hi purity, munly because of the fact they are frequently associated with clayey or dliceous matter. This can sometimes be separated to a large extent by washing.

iv,Coog[c

b,

Pl*tb XXXVI

FiQ 2. — Old limonite pit. Ivanhoe. Va., showinK pinnacled surfaro of limestone whinh underlies the ore-bearinR clay. The level of Burfaoe before mioing bejiBti U Been on cither side of excavation, (ff. BU, pKoto.)

b,

Ibon Qres 381

Limonite ores may occur under a variety of conditions and asso- ciated with different kinds of rocks, but two important types are those included under the residual class and occurring as irregular lumps and masses in residual clays, or as gossan ores. Other types are replacement de- posits, bog ores, bedded deposits of sedimentary character, etc.

Residual Limonites. — The residual limon- ites supply a large per- centage of the domestic production, and have been formed (1) by the weathering of pyritifer-

ous sulphide bodies (see „

gossan), or (2) more often by the weatherii of ferruginous rocks.

Gossan deposits (13, 22a). -—Limonite gos- san ores derived from tbe oxidation of pyrite, chalcopyrite, and pyr-

rbotjte deposits are

found at a number of localities in the crystal- line belt of New Eng- land and the southern

Ihey are of limited im- Fw. H2. — Geologic eection ehowine position o( iron- portance at the present "" depomta in Virpnia. {After Walton, Min.

time. One belt of his- '

toric and former commercial importance is the " Great Gossan t*ad " found mainly in southwestern Virginia (22 a), and traceable for over 20 miles, its contents averaging 40 to 41 per cent metallic iron. (See also Ducktown, Teimessee, and Copper in Virginia.)

Limonite gossan ores are not uncommon in many of the western sulphide deposits, and many of them carry' more or less manganese oride, some, as those at Leadville, having sufBcient to be used in the Mnufacture of spiegeleisen. Their main use, however, is as a flux

logic

382 Economic Geology

in copper and silver smelting in the western states. The most im- portant ones are in the Black Hills, South Dakota; Leadville, Col- orado ; Neihftrt, Monarch, and EUdiorn, Montana ; the Tintic dis- trict, Utah ; Tombstone, Arizona ; and Pioche and Eureka, Nevada. LimoniteeinResidiud Clays. — The other class of residual limonites has many scattered representatives, but the most important oixa form a belt extending from Vermont to Alabama (71, 51), and divisible into two groups, viz., the mountain and the valley ores. In these the iron occurs as grains, lumps, or masses scattered through residual clays, associated with Cambro-Silurian limestones, shales, and quartzites.

SuU. 380.)

The mountmn ores are located in the eastern part of the Appala- ' cbian limonite belt, generally in the Blue IU( or Appalachian Mountains, or at least near their western edge.

The valley ores are closely associated with them on the west, and there is no sharp Kne of separation between the two. The two types, however, present certain important differences.

Thus the mountain ores usually form relatively small, discon- nected pockets in the residual material over the Lower Cambrian i quartzite, at or near its contact with the overlying formation, usually a limestone, while other types of less common occurrence ! are known. The valley ores, on the other hand, form more extensiw though shallower deposits in residual clay overiyii; limestonei (Fig. 143) above the quartzite.

In either case, however, the ore is not uniformly distributed

Iron Ores 383

throib the clay, so that individual pockets soon become worked out, necesdtating the finding of a new one.

Mountn ores may extend to a depth of several hundred feet, but the valley ores rarely exceed fifty feet in depth, and in neither case do the deposits as a rule exceed 500,000 tons, the average being 100,000 to 200,000. The ore may form from 5 to 20 per cent of the clay and sand in different deposits or different parts of the same deposit. Limonite and gothite are the two iron-ore minerals, the higher grades carryii as much as 55 per cent metallic iron, but the average shipments run about 45 per cent. The mountain ores are usually poorer than the valley ones, and phosphorus is generally high enough to make the ore non-Bessemer.

The following t&blea show the penwatage range of the chief oonstitueots (Harder) of I, moiintun ore, and II, vaJlej' ore: —

PbCut

Fe

SiO,

35.00-50.00

10.00-30.00

.10-22.00

.50-10.00

40.00-56.00 5.00-20.00

Mn

.30- 2.00

While Viinia is the mn producer of residual limonites, aUll Alabama's output is of importance, and some is also obtained from Georgia (67, 72) and Pennsylvania (69).

Origin of the CambroSilurian Limonites. — Both the valley and mountain ores are believed to have been formed by the action of weatherii.

a limestone. {After

As the shale and limestones overlying the Cambrian quartzite weathered, the iron oxide was set free, either by the decomposition of ferruginous silicates, or of pyiite or siderite in the limestones. This was then carried downward and concentrated first in the resid-

ooglc

3S4 Economic Geology

ual clays of the limestone, fomuDg the valley ores. If weathering continued still deeper, the downward percolating iron solutions reached the impervious quartzite, the ores (mountain type) becom- ing concentrated in the clay overlying this, although some was deposited in crevices in the quartzite.

Oriskany lAmonUes (22 a). — These are so called because of their association with the Oriskany sandstone. To be more exact, they are found in the Lewisbown (Silurian) limestone, under the Monterey (Oriskany) sandstone, or the Romney (Devonian) shale. The maia pro- ducii districts are in Alleghany County, Virginia, and central Pennsylvania, but local deposits are found at the same horizon in West Virnia, Ken- tucky, and Ohio.

The deposits (Fig.

145) form replacements

in the upper portion

of the Lewiatown Ime-

stone, and may extend

along the strike for a

distance of several

miles. The thickness

and depth are variable,

but in some cases may

reach 75 feet and 600 feet respectively. The formations in which

the ore occurs have been folded and the Oriskany removed from

the crests of the folds by erosion, so that the ore is found along

the outcrops on the flanks of the ridges.

The Oriskany ore resembles the mountain ore in texture, grade, and impurities, but differs from it in forming larger and more eoD- tinous deposits. It shades into limestone with depth.

Other Limonite Deposits. — In northwestern Alabama, western Ken- tucky, and Tennessee, limooite occurs in residual and sedimentary cisj's overlying the Mississippian limestone.' Brown ore also ooours in the Claiborne (Tertiary) forma,tion of Dortheastern Texas (65, 70), and adjoin-

iv,Coog[c

Iron Orbs 385

ing' paita ot Louisiana and Arkanau. The ore forms horizontal beds, of ight thickneea but some extent. It is of little value.

In the Ozark ron of Missouri and Arkansas (73), limonitea are found in readu clays over Cambrian limestane, but are of little eeonomio value.

Small deposits are known in Iowa (63), WieooDsin (62), Minnesota, . and Orecon (12).

The analyses on page 386 give the compodtJOD of limonitea from a number of different localities.

The brown ores of the Appalachian belt ar9 much used by pig iron manufaoturers beoauae, owing to their siliceous oharaoter, they can be mixed with high-gTade LAke Superior ores which are deficient in silica. They are also cheaper, and their mixture with other ores seems to faoUir tate the reduction of the iron in the furnace.

Sideritb

Siderite (74-78) ia the least important of all the ores of iron mined in the United States, both on account of the small extent of the deposits (Fig. 140) and it low iron contents. When of concretionary structure with clayey impurities, it is termed day iromtone, and these concretions are common in many shales and olays. In some districts siderite forms beds, often sev- eral feet in thickness, but containing much carbonaceous and argillaceous matter, and is known as bloat band ore. This is found in many Car- boniferous Bhales.

Iron carbonate in bedded deposits is found in the Carboniferous rocks of western Pennsylvania, northern West Virginia, eastern Ohio, and north- eastern Kentucky. These ores were formerly the baus of an important iron-mining industry, but little is obtained now except in soutbeastii Ohio (12).

Concretions and layers of iron carbonate occur in the Cretaoeo'iu clays of Maryland (10) and were formerly mined somewhat extensively in the vicinity of Baltimore and Washington. Small depouts are also known in the ChickanuHiga (Ordovieian) limestone of southwestern Virginia (22 a). In the western stals iron carbonate nodules are found associated with the Laramie (Cretaceous) formation in Colorado and northern New Mex- ico, but they possess no commercial value (12).

Production of Iron Ores. — The iron-ore mining industry in the United States has progressed with phenomenal strides, and this country now leads the world in the production of iron ore. Indeed 80 great has the production become that in 1903 it was equal to the combined output of Germany and Luxemburg and the British Empire for 1902. Moreover, the average iron content of the ore mined in the United States is higher than that mined in foreign countries, thereby resulting in the production of a greater amount of pig inm from a ven quantity of ore.

iv.Cook'

Economic Geology

.So

tr.

S

tj

K

B

g

S

a

B

tr.

MiiL.M. §

-I Iii 11

-Ill's

fe . g -g . fi ca g

"Rilfiii

s" 11 to £ a 2 g.-sl sAm.

s a II u- i 5

.Iv,

Iron Ores

IBTO 1B7B 1880 IBS* 1890 laSB 1900 190E

y

r

'I i

/

'

y

"V

y

.-'

r#

r:

146. — Diagram showiiig the production of iron ore, pig iroD. and Bteel in tb United States. 1870 to 1909. (Afttr Harder.)

The phenomenal growth of the iron>iiiining industry is shown in the followii tsble:

Duasb

QuumiT

PlBCBNT:iaB or

1870-1879 18S0-188B 1890-1899 1900-1909'

LonaOmt

43.770.527

91.043,854

163.989.193

392,000,000

iv,Coog[c

Economic Geology

The Lake Superior ron ia now producing at least three quarters of the iron ore used in the United States, and it has large reaaves of ore, although the high-grade ones are beeoming rapidly ex- hausted. The low-grade ores of this region and others will, bow- ever, be avlable for a much longer time.

While there is not danger of the present supply of ore soon becom- ing exhausted, still, with the present consumption, it is well to con- sider possible sources of the future.

In the United States the Utah and some other western depoats will no doubt be drawn upon, and many ores now looked upon as too low grade to work will also be conadered. Aside from domestic sources of supply there are foreign ones which may perhaps be even- tually turned to, such as those from Canada, Newfoundland, and Brazil on this de of the Atlantic, or even those of Scandinavia on the European side. In the last-mentioned country especially, attention has been drawn in the last few years to magnetite deposits located well within the Polar circle and of stupendous size.

pKODDcnoN or

Ihon Oebb

IN THE United States Long Tons

Frou 1904

to 1908-

190S

190A

Isos

Hematite . . Brown ore . . Manietite . .

23339,477 2,146,795

1,638,846 19,212

37,567,a')5 2.646.662 2,390.417

42,481,375

2,781,063

2,469,294

17,996

46,060,486

2.957,477

2.679,067

31.788.561 2.620.39)

1,547.797 26.5S5

Total . . .

27.644.330

42,526,133

47,749,728

51,720,619

35.983,336

Production

p Ibon Ore in the More Iupobtant States

FKOM 1904 to 1906

fe

i9oe

V.™

Loko

Toss

ViLOT

te: 1 v..™

12,728.835

ttS.141.903

21.73S.182

B2,820

am

iS8.ice

Iron Orbs

I2.313.0T4

tS. 150361 4,3SS.903

r Ranodb, 1898-1908, ex

Yuh

Miaut

653 205 1

13.7711.308

Tl

070.014 4

1M8

3J09.Bi7 1 2

on 3

.aw

"

Twelve Ikon Mines op the United States which produced the Largest Tonnage in 1908

LocALin

Vamtt or Oni

LONQ Tom

HuURust . . . .

Hibbing, Minn.

Hematite

2,926,614

Burt

do.

do.

1,461,068

Pftyml

Bveleth, Minn.

do.

1.450,829

Red Mountain Group

do.

1.329,079

Adams

Bveleth. Minn.

do.

781,374

Newport

Ironwood, Mich.

do.

716,365

Morrie

do.

do.

698,345

Virginia

Virpnia, Minn.

do.

673,683

Mahoning

Hibbing, Minn.

do.

611,592

Morris

do.

do.

528,169

Pioneer

Ely. Minn.

do.

525,045

Stevenson

Hibbing, Minn.

do.

496,785

b,

Economic Oeclogy

rROM THE Unitbd States,

Imports

Exports

LONaToxa

V*I,Ub

LoBoTom

v™

1,229.168

3,937,483 2,224.248

278,608

J763.422 1,012.924

Wobld'b Pboddction of Ibon Ore i

Ton.

To™

rnited States . . .

51,720,619'

Cuba

658.331

Genn&ny luid Liuc-

Algeria

973,445

27.697.128

Oreeoe

Oreat Britain .

15,731.614

Italy .

Spun . . .

9.896.178

Belgium

316,250

RuBHia . . .

5,700,000

India .

Sweden . . .

4.480.070

Japan .

Atutria-Hu ngary

4.356.804

Norway AuBtraUa

Canada-Newfound-

land

887,321

' Look tons; other figurea represent metric toot.

Iron-ore Reserves (3). — As a result of the recent agitation over the conservation of our mineral resouroee, attempts have been made by the Unitd St&teB Geologioal Survey to estimate the quantity of both at presenl available and non-available ore still remajning in the ground.' That such estimates can only be very approximate is self-evident, partly because the irregularity of most iron-ore deposits makes it difficult to eBtimat their contents. Bedded ores like those of the Clinton can be most closely figured on, while in the case of the Adirondack ores there may be mi error of 15 to 20 per cent.

The estimate of availability ia infiuenoed by the cost of ore delivered tl furnace, cost of reduction, and aooessibility; and any of these factors might change at no distant future.

The metallic iron content of ores now used ranges from about 30 to 65 per cent, this wide variation being due in part to character of other ele- ments in the ore, and in part to favorable location. Thus the Clinton ores, running as low as 30 per cent iron, can be used, because th high lime content makes them practically self -fluxing, but they must be used near the point o( production.

Siliceous ores running under 40 per cent iron are not at present avail- able unless located near fuel supplies, because they will not bear coat of transportation and are expensive to reduce.

b,

Ibon Ores 391

EsTiMATiiB or Iron-obe Supplies or the United States

Magnetic Ores

COMUUCIIL DinsiCTi

—

Trr.,.o..

AvuUbb

NotAnilabls

Avmilabki

NotAyniUble

.V Rocky MounUin C. PiciSc Slapc

LonToiu

1 lalsooiooo 1 oslesolooo

Loiic Tou

111,500,000

23.000.000

,600,000,000

lilsoolooo

Long Ton.

Lon,Too.

25';ooo,ooo

1.500.000

202.936,000

4.761.740,000

90,000,000

128.500.000

Hematite Oees

CStatm)

Cuhtok

Avulkble

Not AvmiLBbla

Avulnbto

Not AviiUbEe

a. p.dS Slops

Lone Tom a.000.000

Long Toni

.000,000

67.47 'Oooiooo

;

Long Ton.

35.000,000 483,640,000

10,000,000

Long Ton. 820.000,000 070,600.000

3.029,275,000

87,662,100.000

608.540,000

1.82O.50O.0O0

BaowH Omb

CumoviTE Omn

ToTAi. gnrruB

AY>UablB

AvaiUbk

aAU

Lone Too.

11.000,000

2,000,000

13.600,00r

560.000,000

i,8a.voot

Long Tona 248,000.00(

Lone Ton. 288,000.000 638.440.00

'aiBlooo.'oo

67,780,00

Long Ton.

1.095.000.000

120',665:000

367,400,000.743,230,000

—

310.000,000 4,478,150.000

75,118,070,000

t, MtiHHiliuntt.. Coaneotwut. New York, Nw Jsraey. Peiiiuvl*">i>, Maryland, „ Wnn Virginia, HMam ScDtocky, Nraih Carolina. South CaroliD., Osorgla, Ala-

Y, Iowa. MuHHiri. ArkauBU, Teiu.

3. Michigan, MauuKiCs.

5. Montana, Idaho. Wyoming. Colorado. t, WutungUn, OngOB. Califoni*.

b,

393 Economic Geology

So, too, tlie &mouat of other constituents present, such as phosphonis. sulphur, copper, chromium, numganeBe, and alumina, exert a detrmimng iufluenoe on the cost of production and quality of the iron.

Two tendencies are noticeable in the iron industry of the preaent daj. viz., the use of ores with a lower average iron content, and the deoentrizs- tion of the iron industry.

This involves a corresponding increase in the cost of transportation unit of iron, and aJi increase in the proportion of fuel which goes la the ote- producing region. An acoompaniment of this will be the general adoption of by-product coking, and Hayes points out that in certain furnaces now operating in the Ike Superior district the profit corresponds approxi- mately to the value of the by-products from the coke ovens.

The table on page 391 gives a summary of Hayes' estimates of domestic iron ore reserves by commercial districts and varieties of ores.

RBPBRBRCES OH ntOR ORES

Qekbbau 1. Birkenbine, Mining Census, 1902, Mines and Quarries. 2. Birkenbine, Amer. Inst. Min. ., Trans. XXVII : 519, Iffitr. (Iron ore supply.) 3. Hayes, U. 8. Geol. Surv., BuU. 394 : 70. 191)9. (Iron ore supply.) 4. Jeans, Iron and Coal Trade Review, Novem- ber 27, 1908. (World's iron and steel export trade.) 5. Kimball. Amer. Geol., XXI : 155, 1898. (Concentration by weathering, i 6. Leith, Econ. Geol., I : 360, 1906. (Iron ore reserves.) 7. rose. Jour. Geol., I : 356, 1893. (Chemical relations of iron and manganese.) 8. Winchell, Amer. Geol., X : 277, 1892. (Theories of origin.)

State Repobtb of General Cbabactbb. 0. Chauvenet, Amer. Inst. lin. Engrs., Trans. XVIII : 266, 1890. (Colo.) 10. Clark and Matbev°. Md. Geol. Surv., VIII, Pt. II : 152, 1908. (Md.) 11. Grimsley, W. Va. Geol. Surv., IV ; 1, 1909. (W. Va.) !2. Harder, U. S. Geol. Surv., Min. Res. 1903, I : 61, 1909. (Brief risum U. S. and bibliography.) 13. Harder, U. 8. Geol. Surv., BuU. 380, 1909. (\".l

14. Leith, U. 8. Geol. Surv., BuU. 285 : 194, 1906. (U. S. and Can.i

15. McCreath, Sec. Pa. Geol. Surv., MM : 229, 1879. (Many analyses.) 16. Nason, Mo. Geol. Surv.. II, 1892. (Mo.) 17. Nil/*. N. Ca. Geol. Surv., BuU. 1, 1893. (N. Ca.) 18. Orion. 0. GpoL Surv., V : 371, 1884. (Ohio.) 19. Putnam, lOth Census, XV : 4G9. (U. S.) 20. Shaler, Ky. Geol. Surv., New Ser., Ill : 163, 1877. 21. Shannon, Ind. Dept. Geol. Nat. Res., 31st Ann. Rept. : 299, 1907. (Ind.) 22. Smock, N. Y. State Mus., BuU. 7, 1889. (N. Y.i 22 a. Watson and Holden, Min. Res. Va., 1907 : 402. (Vai 23. WincheU, Minn. Geol. Surv., BuU. 6, 1891. (Minn.)

Magnetite. 24. BaU, U. 8. Geol. Surv., Bull. 315 : 206, 1907. (Iron Mtn., Wyo.) 24 o. Bayley, U. S. Geol. Atl. Folio, 157. (N. J.) 25. D'lnviUiers, Sec. Pa. Geol. Surv., D 3, II, Pi. I : 237. I8R3. (Berks Co.) 26. Keith. U. S. Geol. Surv., BuU. 213 : 243, 1903. (N. Ca.) 27. Kemp, Amer. Inst. Min. Engrs., Trans. XXVIII : 146, 1898. (MinevUle, N. Y.) 28. Kemp, U. 8. Geol. Surv., 19th Ann.

b,

Iron Ores 393

Rpt., 111:377, 1899.- (Adirondack titaniferous ores.) 29. Leith &nd Harder, U. S. QeoL Surv.. Bull. 338, 1908. (Iron Springs, Utah.) 30. Newland uid Kemp, N. Y. State Mua., BuU. 119, 1908. (Adirondacks.) 31. Paige, U. 8. Oeol. Surv., Bull. 380, 1909. (Uaao- ver, N. Mex.) 32. Presoott, Eoon. OeoL, 111:465, 1908. (Shaita Co., Calif.) 33. Prime, Sec. Pa. Geol. Surv., I r 190, 1883. (Lehigh Co.) 34. Spencer, Min. Mag., X : 377, 1904. (Origin Sussex Co., N. J., magnetite.) 35. Spencer, U. S. Oeol. Surv., Bull. 359, 1908. (Cornwall.) 36. Spencer, U. S. Oeol. Surv., Bull. 315 : 185, 1907. (Berks and Lebanon Cos., Pa.) 37. Stewart, Soh. of M. Quart., April, 1908. (Putnam Co., N. Y.) 38. Wolff, N. J. Oeol. Surv., Ann. Rept. 1893 : 359, 1894. (N. J.)

Lake Superior Dialntt. 39. Bayley, U. 8. Geol. Surv., Mon. XLII, 1904. (MenoQiinee.) 40. ClemenU, U. S. Oeol. Surv., Mon. XLV : 1903. (VermiliDn.) 41. Clements, Smyth, Bayley, and Van Rise, U. S. Oeol. Surv., 19th Ann. Rept., Ill : 1, 1898, and Ibid., Mod. XXXTI, 1899. (Crystal Falls.) 42. Irving and Van Hise, U. S. Geol, Surv., 10th Ann. Rept., I : 341, 1889. (Penokee.) 43. Lane, Can. Min. Inst., XII. (Mine waters.) 44. Leith, U. 8. Oeol. Surv., Mon. XLIII, 1903. (Mesabi.) 45. Leith. Amer. Inst. Min. Engrs., Trans. XXXV : 454, 1904. (Summary L, Superior Geology. See also torth- coming U. a. Geol. Surv. report.) 46. Leith, Econ. Geol., II : 145, 1907. (Cuyuna.) 47. Van Hise, U. S. Geol. Surv., 2l8t Ann. Rept., Ill : 305, 1901. (Oenerai.) 48. Van Hise, Bayley and Smyth, U. 8. Geol. Surv., Mon. XXVIII. 1897. (Marquette.) 4S. Weid- man, Wis. Oeol. and Nat. Hist. Surv., Bull. 13, 1904. (Baraboo.) 50. Woodbridge, Series of articles on Mesabi Range in Bng. and Min. Jour., 1905.

Olinfam Ore. 51. Burchard, Butts, and Eokel, U. 8. Oeol. Surv., Bull. 400, 1909. (Bimiingbam, Ala.) 52. Chamberlin, Oeology of Wis- oonsiii, II: 327. (Wis.) 53. Kindle, U. S. Oeol. Surv,, Bull. 285 : 180, 1906. (Bath Co.. Ky.) 54. McCaUie. Oa. Geol. Surv., Bull. 17. 1908. (Oa.) 55. Newland and Hartnagel, N. Y. State Mus., BuU. 123, 1908. (N. Y.) 56. Phalen, Econ. Oeol., I : 660, 1906. (N. E. Ky.) 57. Russell, U, S. Oeol. Surv., Bull. 52 : 22, 1889. (Residual theory of origin.) 58. Rutledgo, Amer. Inst. Min. Engrs., Trans. XXXIX : 1057, 1908. (Stone Valley, Pa.) 59. Smyth, Amer. Jour. Sci.. XLIII : 487, 1892. (Origin.)

HemaiUes (other than Clinton and L. Superior). 60. Ball. U. S. Oeol. Surv., Bull. 315 : 190. 1907. (HartviUe. Wyo.) 61. Winslow, Ha- worth, and Nason, Mo. Geol. Surv.. IX. Pt. 3, 1896. (Iron Mtn., Mo.)61q. Watson and Holdon. Min. Rea. Va.. 1907. (Va.)

Hmonite. 62. Allen, Eleventh ReportMich. Acad. Sci., 1909:95. (Spring VaUey, Wis.) 63. Calviii, la. Geol. Surv., IV : 97, 1895. (la.) 63o. DiUer, U. S. Geol. Surv.. Bull. 213:219, 1903. (Redding, quadrangle.) 64. Eokel. Eng. and Min. Jour.. LXXVIII : 432, 1904. (E. N. Y. and W. New Eng.) 65. Eckel. U. 8. Geol. Surv., Bull. 280 : 348, 1905. (Tex.) 66. Garrison, Eng. and Min. Jour., LXXIII : 258, 1904. (Chemical characteristics.) 67. Hayes, Amer.

Iv,

l ECONOMIC GBOLOOT

Inat. Min. Engn., IVsos. XXX : 403; 1901. (Cftrtenville, Oa.'; ea HobbB, Boon. Geol. 11:153. 1907. (Conn.. N. T., Mms.) 60. Hopkiiis, Geol. Soo. Amer., Bull. II : 476, 1900. (P CamlwD- ffiltiriui ores.) 70. Kennedy. Amer. Inst. Min. Engn., Truu. XXIV. 258, 1894. (E. Tex.) 71. MeCaney, Ala. OooL Surv., Rept on Valley Region, II, 1897. (Ala.) 72. MoCollie, Ga. Geol. Sar.\. BuU. 10, 1900. (Oa.) 73. Penrose, Geol. Soc. Amer., BuU. HI: 47, 1891. (Ark. and Tex. Tertiary oree.)

74. Moore, Ky. Geol. Surv., 2d ser., I, Pt. 3 : 63, 1876. (Ky.) 75. Orton, Ohio Geol. Burv., V:378, 1884. (Ohio.) 76. Second Pa. Oeol. Surv., K : 386, and MM : 159, 1879. (P.) 77. Bay- mond, Amer. Inst. Min. Engra.. Trans. IV : 339, 1876. (H. T.) 78. Smock. N. Y. State Museum, BuU. 7 : 62, 1889. (N. T.)

b,

Chapter Xvi

Copper

Ore Blinenls of Copper. — Copper-bearing minerals are not only numerous, but widely though irregularly distributed. More thui this, copper iq found associated with many different metals and under varied conditions.

Nevertheless but few copper-bearing minerals are important in the ores of this metal, and the number of important producing dis- tricts is comparatively small.

The ore minerals of copper together with their theoretic composi- tion and percentage of copper are as follows : —

Ob> Mihkui.

PnCMHrCo.

CuFeS,

Bormte . .

CuJeS,

?3S :

3Cn,S.2Afl,S,

Cu8

Tetrahedrite

CubtSi

TennantiM

Cu

2CuC0,, Cu(OH),

MaUctiite .

CuCO., Cu(OH),

ChrysoooUa

Cu8iO.,2Hrf)

Cupnte . . MdaconJte.

CuO

Broflhantite

CnfiO., 3Cu(0H,) Cu(OH)a. Cu(OH), CuSO,, 5H,0

Ataoamite .

Id. the unaltered portion of the ore body the copper compounds are muoly sulphides, but arsenides and antimonides are also known. In the gossan the copper occurs as carbonates, sulphates, silicates, oxides, native, and more rarely as phosphates, arsenates, antimo- nates and vanadates.

Gangue Minerais. — Quartz is the commonest gangue mineral, but calcite and siderite are abundant in a few ; barite, rhodochrosite, and fluorite are also known. Sericite is found in some veins, and so is tourmaline in certain tin-copper and gold-copper ones.

iv,Coog[c

306 Economic Geology

Metallic impuritiea may be present which cause trouble in the redun- tioa of the oresi Ot these zioo is the most objectionable, but bismuth, though rare, is also very undesirable, but cao be eliminated by electrolytic refining. ' Arsenic, antimony, tdluriiun, and selenium are partially elim* inated in smelting, but must be completely removed by electrolytic methods to make the copper pure enough for electrical work.

Tellurium is not uncommon in some districts, and renders the metal red-ehort even in small amounts. Silver, even if present in as small amounts as .6 per cent, lowers the electric conductivity, and above 3 per cent affects the toughness and malleability of the copper. Sulphur up to .25 per cent lowers the malleability and .5 per oent renders the metal oold-shtHt, while .4 or more per oent phosphorus makes it red-short.

A high percentage of silioa is detiimental, as it requires too much base flux.

Most of the copper ores now worked are of low grade, but can be pro6tably treated because of the extent of the operations and pos- sibility of concentration. OccaaonaUy low-grade ores are founil which are self-Suxing, as those of the Boundary District of western Canada. The introduction of pyritic smelting has permitted the profitable treatment of low-grade pyritic-coppCT ores, ev'en if they carry no gold or silver. Complex ores of copper, lead, and ziuc sulphides are more costly to treat, but this expense may be more than made up for by their gold and Iver contents.

Very few ores approach the theoretic percentiles pven above. Thus in Michigan, where native copper is the ore mineral, this as now mined rarely averages above 1 per cent metallic copper, and may fall as low as .6 per cent. At Butte, Montana, the copper-bearing minerals are chalcocite, enargite, bomtte, and chalcopyrite, but much of the ore does not usually contain more than 5 or 6 per cent metallic copper, and in rarer instances 12 per cent.

Copper ores are found in many formations ranging from the pre- Cambrian to the Tertiary, but grouped according to their mode of origin they fall mostly into one of the four followii groups (3) : —

1. Magmatic segregations. No workable deposits of this type are known in the United States, but primary chalcopyrite is known to occiiT in some localities.

2. Contact-metamorphic deposits, in crystalline, usually gamet- iferous limestone, along igneous rock contacts. (Clifton-Morenci district, Arizona; Bingham Cafion, Utah, etc.)

3. Deposits formed by circulating, usually ascending and probably hot waters, the ores being deposited in fissures, pores, spaces ot brecciation, or sometimes by replacement of the rock.

4. Pod- or lens-shaped deposts in crystalline sclusta, wludi may

b,

Copper 397

represent concentration of material from a disseminated condition in the Burroundii rocks, or in some cases are thought to be met&- morphosed contact deposits.

\Miile the third and fourth groups include all the largest deposits of the world, still these in all cases do not owe their economic impor- tance to the mode of formation, but rather to secondary changes which have taken place in them, resulting in a leaching of the copper in the upper part of the mass, as copper sulphate, and its transfer- ence to lower levels, where it is redeposited throi the influence of copper sulphide, iron compounds, or limestone.

Supeifidal Alteration of Copper Ores (3, 18) . — This may produce results of great economic importance, and excellent examples of it are seen in some of the Arizona ores, where the upper portions of the topper deposits are brown or black femiginoua porous masses, brightly colored with oxidized copper minerals such as cuprite, malachite, azurite, and chrysocolla, while below this at a variable depth they pass into sulphides.

In weathering, the copi)er minerals, such as chalcopyrite or other sulphides, are usually oxidized first to sulphates, and subsequently changed to oxides, carbonates, or silicates, and occasionally even to chlorides and bromides. A concentration of the ore deposit may take place partly by segregation and partly by leaching, and pockets of the ore form, which are surrounded by oxidized iron minerals form- icg part of the gangue.

While the oxidation will not increase the total copper contents of the ore body, still it may change it into a more concentrated form, for the carbonates and other oxidized copper minerals contain more copper than the original sulphide. The ore in the gossan may therefore nm from 8 to 30 per cent or more, while below it may show only 5 per cent of copper (see Penrose under ore depomt refs.). These altered ores cannot, howe'er, be more cheaply treated. If leaching follows oxidation, the gossan may be freed of its ore, as at Butte, Montana, where the upper part of the ore-bearing fissures is poor siliceous gangue. Secondary enrichment may also occur below the water level, giving chalcocite, chalcopyrite, and Ixffnite of later origin.'

Distribution of copper ores in the United States (Fig. 147). —

About 80 per cent of the copper produced in the United States In

1908 was obtained from three states, viz. Arizona, Montana, and

Michigan, named in the order of their output, nearly all of the rest

' Botb chalcopyrite and bornite are often resarded tu primacy iulpbides.

oog[c

398 Economic Geology

coming from the Appalachians and CorcUlleran area ; the orea of the hitter are often worked chiefly for their gold contents, with copper as a secondary product.

Only the more important districts can be taken up here, these being representative, however, of several different types of occurrence.

MonlaTia (46-50). — The mining camp of Butte, which is not only the most important district in the state, but probably also the greatest copper producer in the world, lies in southwestern Mon- tana, and in the central part of the Bocky Mountain reon.

Fia. 147. — Map shawing 'distribution o( copper ores in the United SUte& {AdapM frimt Rartiomt, Min. Maa., X.)

The orea are mainly secondary sulphides occurring in fissure veins (Figs. 148, 150) formed by replacement along shear zones in Ter- tiary igneous rocks, and while copper veins are the most important, the district also contains argentiferous ones.

The Tertiary igneous rocks (Figs. 149, 150), named in their order of formation, include : (1) a dark basic granite or quarts monzonite, known as the Butte granite ; (2) dikes and irregular intrusions of a i white aplite, termed the Bluebird granite ; (3) a quarts porph>Ty cutting both granites ; (4) rhyoUte of both intrusive and rattnisive character, dikes of which cut the ore veins. I

There are also some lake beds, and the Butte granite is suirounded by sediments and partly covered by an earlier andesite, but the last two do not appear in the ore district.

The rocks of the district are cut by many joints, belonng to

Copper

three systems, viz. an east-west, northwest-southeast, and northeast The first series is displaced by both of the later ones, and while the fissures of the first two series sje heavily mineralized, the third carries but little endogenous ore.

The copper veins, which are mainly replacements along fissures in the sheeted granite, and were first worked for silver, consist in in their upper part (200 to 400 feet) of iron-stained quartz with but little copper, while below this are found chalcocite, enargite, bor- nite, cupriferous pyrite, and more rarely covellite and tetrahedrite.

Of these the chalcocite more than 50 per cent of the ores of the camp, and the enarte a good deal less than one half, while the bomite and cupriferous pyr- ite sometimes form a noticeable proportioa of the ore.

The concentrates average about 8 per cent, and the richness of the ore in any one mine may vary from year to year. Thus in one mine the first-class ore averaged about 8 per cent in 1905 and 1906, while in 1908 and 1909 it exceeded 21 per cent copper.'

The ores contain about 21 cents n.

FiQ. 148. — Section at Butte. Mont., showing mode of occurrence of ore. iA/ter Winchetl, Eng. and Min. Jour.. LXXVllI.)

gold and .0375 ounces s'Wer

Dound of copper, - Arsenic is

it, but is not saved, and

m is also said to occur in

mil amounts (Weed).

utrtz is the gangue in all.

t is supposed that in the copper veins the hot ore-bearing solu-

jns ascended the fractures in the granite, replacing the rock by ore,

ind resulting in an intense alteration of the walls ; the hornblende and

mica were chained to pyrite, and the feldspar to sericite and quartz.

While the primary ore was chalcopyrite and pyrite, the enormous

secondary bodies of chalcocite have made the district famous. Tho

enaite appears to increase with depth.

1 A. H. Wethey, private comniuiucBtion. , ,

Economic Geolooy

F?T Of. ofcumt f ""

Fio. 149. — Map of eiutfm part of Butte. Mont., diaUict sbowing disUibi,.:..

veJDB, and geology. ([/. S. Oeol. Sun.) '

of a

The veins exhibit a curious uniformity of direction (Fig. I4!tj' most of them striking nearly east and west, and few of them departe ing more than 15° to 20° from the vertical; still they show consider- able variation in width, ranging from a few feet to 50, or even 150 where the altered country rock 's impregnated with glance. Unfor- tunately, the complexity of the veins and uncertainty of boundaries has ven rise to much costly htigation in the district.

b,

b,

Copper

The alver vans, which are of subordinate importance, surround the coppCT deposits on the north and west, and while formed by magmatic waters like the copper deposits, differ from them in being fissure fiilings with a characteristic crustJfied structure, as well as in

mineral contents. Their outcrops show quartz stoned with black maianeee oxide, but lower down they carry argentite, spha- lerite, pyrite, and some galena, in a quartz, rhodonite, rhodochroaite

The history of this mining camp is full of intereet. Butte in 1864 w&b a gold camp, bat difficulties in working the gravels directed attention to the mineral-vein outorops, and uuBUooessful attemptB were mule to work their copper and silver contents, so that it was not until 1875, following a period of quiescence, that the discovery of rich silver ore in the Travona lode revived the mining industry of Butte. In 1877 several silver mines were opened, followed by others; but this did not last many years, for with the drop in the price of silver many mines closed, although one, the Bluebird, had produced 2,000,000 ounces of silver from 1885 to 1892.

The copper mines were worked to only a limited extent at first, and the industry did not assume permanence until 1879-1880, when matte smelting was introduced. In 1881 the Anaconda mine, which was first worked for silver, ban to show rich bodies of copper ore, and since then the output ot copper has steadily increased, there being a number of large smelting plants distributed between Butte, Anaconda, and Great Falls.

2" z.„..

402 Economic Geology

W. H. Weed h&s esti- mated that up to January 1, 1897. the district had yielded 500,000 ounces of gold, 100,000.000 ouoc ' of silver, and 1,600,000,- 000 pounds of copper. In 1887 Butte passed the Lake Superior District in the production of copper, and has kept ahead of it ever since, having in 1903 produced 38.9 per cent of the United States pro- duction. In 1907 it was passed by Arizona, and remained in second pIsM in 1908, when it produced 252,503,651 pounds of copper, or 28.6 per cent of the total output of the United States.

/. Michigan (35-43).

I — This region, which

II fflffia nHtti~ tvl by Douglas Houghton,

Fio. 151. — Geologic map ol weatern half of Butte has become one of the

district. (U.S.Oeol.Surv.) . , ii

most famous, as well

as one of the leading, copper-producing districts of the world.

The rocks of the region, known as the Keweenaw series, consist of interbedded lava flows, sandstones, and conglomerates, the latter being rounded fragments of igneous rocks, mainly reddish-quartz porphyry.

GEOLOQCM, CROSS-SECTION OF THE COPPER MINING. REGION Fio. 152. — Section across Keneeaaw Point, Mich. {Afler Rickard.)

This series of beds, whose entire thickness may be from 25,000 to 30,000 feet, dips westward (Fig. 152) from 35 to 70 degrees, being overlain conformably on the west by sediments, while on the east they are faulted up agunst the horizontal Potedam sandstones.

iv,Coog[c

Coppee 403

These beds form a belt 2 to 6 miles wide, which extends from Houghton to the end of the Keweenaw peninsula, and nses as a ridge from 400 to 800 feet above the lake (PI. XXVIII).

The ore, which is native copper, and is occasionally associated with native silver, occurs (1) as a cement in the conglomerate of

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porphyry pebbles, or replacing the latter; (2) as a filliog in the amygdules of the lava beds (Fig. 154), (3) as masses of irregular and often large size, in veins with calcite and zeolitic gangue.

The tilting of the beds has been accompanied by some slipping and cross faulting, and the presence of copper in cross joints and slip planes indicates later deposition.

The veins, which cut both the igneous and sedimentary roeki

404 Economic Geoloot

have yielded much copper in former years, and the large masses obtfuned from them have made the region famous ; but at the pres- ent time most of the production comes from the Calumet conglom- erate, while the balance comes from two other copper-bearing conglomerates known as the Albany and the Allouez, and from the ashbeds and amygdaloida, whose gas cavities are filled with a mix- ture of native copper, csicite, and zeolites.

A curious and hitherto unexplained feature is the irregular distri- bution of the copper in the different beds, which may be due to the copper solutions being directed by certain joints or slip planes. Thus the Calumet coilomerate carries practically no ore outside of the Calumet and Hecla ore shoot, which is three miles long, 12-15 feet thick, and has been mined to a depth of 5000 feet.

Various theories have been brought forward to account for the orin of the copper ores in this region.

The diabase was looked upon by Pumpelly as a possible source of the ore, and since its extensive alteration was no doubt accompanied by the oxidation of protoxides, this might account for the reduction of copper mineral to the native or metallic condition, it being known that ferrous salts may precipitate metallic copper (1). More recently Lane (39, 40) has suested that originally buried water has also been an important factor in concentration, but agrees that the final precipitation was by water working downward.

Lane has pointed out that the mine waters show a striking increase in chlorine with depth, in fact there is more than enough to satisfy the sodium present, and it ia contained in relatively lai amounts of calcium chloride. Moreover, the molecules of sodium chloride decrease steadily with depth, while those of calcium chloride increase.

bvGoog[(

b,

Coppeb 405

He therefore 8U(!;ests, and his views are backed by chemical experiments, that the basalt Sows ornally contained small per- centages of copper ; that while still heated they no doubt absorbed sea water charged with sodium chloride, and in later times atmos- pheric waters not containing any, but obtaining it as they seeped through the rocks.

These waters, rich in NaCl, migrated downward, taking copper in solution as copper chloride.

Reactions with the glassy base or original minerals of the volcanic rocks gave rise to the formation of sodium silicates, accompanied by precipitation of copper and formation of calcium chloride. Descending solutions from wide areas became concentrated along lines favorable to UDdp-ound circulations, and hence shoots of rplative richness resulted. It is supposed that certain faults and slips guided these waters.

The theory, although reasonable and backed by laboratory experi- ments (2), may not be universally accepted, and some observers believe that these deep-seated waters with their peculiar composition are very likely of magmatic origin.

Although these depoaita have been worked ia prehistorio times, as evidenced by copper implements &nd ormuneDts found in the mines, the famous Calumet and Hecla Mine was not opened up until 1846. In 1847 Michigan produced 213 long tons ot the total United States production of 300 tons of copper. Since 18S3 the annual output has exceeded 1000 tons and gradually and steadily increased np to 1905 when it reached 230,287,092 pounds. In 1908 the production had dropped to 222,289,584

Up to 1905 Michigan ranked second m the list of producing etatesi but in 1906 dropped to third place.

The ores from this district, which are Icnown as lake ores,' are all of low grade, but the deposits are of great extent and rather uniform mineral- ization, and this fact, together with the possibility of high concentration and low cost of refining, makes it possible to work these low-grade deposits at a profit.

The richest ore now mined contains under 2 per cent of copper, while the poorest runs but little over .5 per cent.

The crushed and concentrated material carries about 65 per cent copper, and this passes through a combined smelting and refining process.

That portion of the copper which contains enough silver to make its recovery profitable, and some which runs too high in impurities for certain uses, is refined electrolytically. The amount so treated has been lessened, owing to a recent demand for copper carrying arsenic. The average re- covery of silver per ton of rook mined was .023 ounce.

' The term has now lost its originBl raeaning, siace copper from weaterD states is Inou to Michig&o tor refinioK and sold as Lake ore.

bvCoog[c

Economic Qeology

Arizona (14-21). — This territory in 1908 ranked first as a pro- ducer of copper ores in the United States, and has in the past differed from most other copper-producing localities in supplying chiefly ores of oxidized character ; in fact, from 1880 to 1895 Arizona was the only copper area in the world whose ores were exclusively oxidized.

The territory (Fig. 155) contains four important districts, all lying within the mountain reon, and a fifth one of probably con- siderable importance. These are : (1) Bisbee or Warren, (2) Jerome or Black Range, (3) Clifton-Morenci, (4) Globe, and (5) Mineral Creek or Ray. The 1st, 3d, and 4th possess certain dmilarities in the mode of occurrence of the ore.

Fro. 155. — Mp ot Ahiui

bvCoog[c

Copper

fu&ee or Warren District (20). — This district, which contns the famous Copper Queen Mine, lies on the eastern slope of the Mule Pass Mountains (fig. 155), but a short distance from the Mexican I>oundary. The section at that locality involves strata from pre-Cambrian to Cretaceous age, with an important uncon- formity between the Carboniferous and Cretaceous (Fig. 157). Prior to the deposition of the latter the rocks had been broken by numerous faults (Fig. 156), one of these, the Dividend fault, being specially prominent in formii one boundary of the ore-bearing area. This was followed by intruMons of a granite magma forming dikes, sills, or irregular stoclcs, which have metamorphosed the Carton- iferous limestones, with the production of characteristic contact minerals.

iAfltr Ranmmt, U. i

The Carboniferous Umestone which carries the ore forms a shallow basin, which is cut throih by the Dividend fault. The ore bodies, which are generally developed in the zone of metamorphic silicates surrounding the porphyry, as well as sometimes outside of it, form large, irregularly distributed, but rudely tabular masses, and mostly within 1000 feet of the granite-porphyry intrusion. No valuable ore bodies are found on the contacts. As now found the ore consists of malachite, azurite, cuprite, and other oxidized copper minerals above, which pass at variable depths into unaltered sulphides ; but between the two, or at least never far from the effects of oxidation, masses of massive or sooty chaicocite are frequently found.

The primary ore consisted of pyrite, chalcopyrite, and occasionally sphalerite, and was deposited by a metasomatic replacement of the limestone. Aa originally formed, the deposits contained too little

Economic Geology

copper to make tbem commercially valuable, but they have been sub- sequently enriched by secondary replacement. In some places the ore is underlain by barren limestone, showing that aecondary enrich- ment has extended to the very bottom of the ore body.

Disseminated pyritic ore is found in the porphyry of Sacramento Hill, but it has not proved workable.

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SrnsTMSS

f!

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ED COLUIOikfl giCTIDK OF TIIE WKH

- Geological Bection at BUbee. Arii. Prof. Pap. 21.)

(After Bantome, U. S. Geol. Svn..

The general relations of these ores to the intrusive porphyry- and the contact silicates indicate that they are of eontact-metamorphic origin.

In some cases an iron gossan has indicated an underlying ore body, but many others do not outcrop.

During 1908 the average copper content of the Bisbee ores was between 6 and 7 per cent. The gold and silver content per ton of refined copper was about $11 and J17 in two cases (Min. Rra. U. S. Geol. Surv.).

b,

Copper

Clinton-Morenci Diatrid (IS). — The copper deposits of this dis- trict are located at Morenci (Fig. 155) and Metcalf in eastern Graham County. The ores were discovered in 1872, but remained undeveloped for a long time because of the fact that they were of too low grade, and too far from the rlroads.

LceeNO

1/ tCNEOUS HOCKS FlO. 158. — Geologic nuip of vicinity of Morenci, Arii. (from Weed.)

At the present time, however, these large bodies of low-grade ore are utilized, most of the work being done by three large companiea.

The geologie section involves the toUowing :

Quaternary (Qila) congtomerate.

Tertiary flows of basalt, rhyolites, and some andesites.

Cretaceous shales and sandstones. Several hundred feet thick.

Lower Carboniferous heavy-bedded pure limestones, ISO feet.

Devonian (?) shale and argillaceous limestone, 1(X) feet.

Ordoviciaa limestone, 200 to 4O0 feet.

Cambrian (?) quartzitio sandstone, 2(K) feet. tMMt\f

410 Economic Oeologt

Pre-Cftmbriftn gtanitfl And quartatic sofaista.

Intnuioiu of granitio and dioritio porphyries of post-CretMeoiu ie pierce all the older rocks, fomung stocks, dikes, laccoliths, and sheets.

All of these rocks have been bowed up and subeequently faulted by late Cretaceous or early Tertiary movements.

Fia. 1S9. — SecdoD Id MoreDci, Arii., district. porphyry; S, uiuJtnd tedf- menls ; P. fisavire veiiu : JH, metaiaarphoaed limestone and shale ; O, contart- metamorphic ores ; R. disKminated chalcocita. lAfler Lindgrta, Bng. and Jf in. Jmir., LXXVin.)

Briefly stated, the distribution of the deposits of copper (Fig. 159) ore is practically coextensive with a great porphyry stock and its dike systems, the deports occurring either in the porphyry or cIo# to its contact, as well as along dikes of porphyry in some other rock.

Fio. 160. — Photo-micrograph Bhowing replacement in Clifton-Morenci ores. Duk gray chalcDcitc, developing by replacement ol pyrit (liffht sray). The chaln> Git IB accompanied by amnll ninounta of microcryBtalline quarts, sericite and kaolin. Black areas represent open Geld. {Afltr lAndgnn. U. S. QteL 5i>n., Prof. Pap. 43.)

The original ores were pyrite and chalcopyrite, of too low a grade to be workable, but they have since become so by a process of sec- ondary enrichment. No ores were formed before the porphjiy intrusion.

Where the latter is in contact with the granite and quartaile. i

Copper 411

but little change is produced, but where the porphyry is found adjoining the limestones or shales, extensive contact metamorphiam developed, resulting in the formation of large masses of garnet and epidote, especially in the Lower Carboniferous limestones.

Where alteration has not masked the phenomena, magnetite, pyrite, chalcopyrite, and zinc blende accompany the contact nunerals.

The ore bodies in the limestone are often irrular, but more frequently roughly tabular, because of the accumulation of the minerals along the gtratihcation planes, or walls of dikes.

In many parts of the district the copper occurs in fissure veins which cut porphyry, granite, and sedimentary rocks, and were

,n

[ffobaWy formed shortly after the consoUdation of the jwrphyry. These in the lower levels carry pyrite, chalcopyrite, and sphalerite, but no magnetite. Surface leaching of these veins has often left Umonite-stained, silicified porphyry outcrops.

Accompanying these veins, and of more importance commercially, are often extensive impregnatioos of the country rock. These diaaemfaiated deposits in the highly altered porphjTy are leached out above, but lower down show a zone of pyrite and chalcocite, which does not usually extend below 400 feet.

Most of the copper in the district is obtained from concentrating ores containing chalcocite in altered porphyry. In 1908 the yield

I z .IV,

412 Economic Geology

of copper from the concentrating ores was about 2.2 per cent, while the smelting ores yielded a little over 4 per cent.

The precious metal content ie so low that much of the output of this district ia not refined electrolytically unless the copper is not pure enough to put on the market.

The intnimons of porphyry produced strong contact metamw- phism in the shales and limestones of Paleozoic age, resulting in the contemporaneous and metasomatic development of various contact silicates and sulphides,' the contact zone thus receiving large addi- tions of iron, silica, sulphur, copper, and zinc, substances unknown in the sedimentary series away from the porphsry.

Subsequent to the solidification of the porphyry, extensive fissui ing occurred in both it and sediments, resulting in the deposition of quartz, pyrite, chalcopyrite, and zinc blende in the fissures and by replacement of the wall rock. These are low in copper, but there is a close relation between the veins and contact deposits because of the similarity of their metallic contents, and of the similar devel- opment of tremolite and diopside where limestone forms the wall. The extensive impregnation of the porphyry also occurred at this time. Subsequent exposure of the deposits by erosion permitted the entrance of surface waters, which was followed by weathering aod secondary enrichment.

Globe District (19). — The ore bodies Iiere occur as lenticular reiaee- ments in limestone and fault lodes, or fissure zones in diabase.

Much of the hmeatone ore thus far extracted has been oxidized, bat that in the diabase is enriched material. Some bodies of primary of commercial value have also been developed. About 70 per cent of th ore DOW treated is of the sulphide type, and in 1908 the ores yielded about 4i per cent copper. The gold and silver oontents are very low, averaging about .4 per cent per pound of copper.

Jerome District (17). — The ores, which are of pre-Cambrian like the inclosing rock, consist of pyrite, chalcopyrite, some spha- lerite, and varying amounts of quartz, replacing a schist that has been formed by the intense shearing of the basic porphyry. As a rule the more massive sulphide ore contains more ux>n and irinc, while the "slaty" ore, which consists of alternating bands of sulphide and schist, carries a higher proportion of chalcopyrite.

The ores miaed are all of smelting grade, with a high peroentnge (J copper, higher indeed than that of Bisbee. Bingham, Utah, Shasta Countr. California, and Ducktown, Tennessee. The gold and silver content is

Garnet, epido( diopmde, etc.. pyrite, magnetite, cbaloopyrite, and qihalnite. D,q,z.<ib,CoOgle

University

b,

Plate XXXIX

iv,Coog[c

tiso higher than that of any other of the large Arizona copper oampa, and far above the pyn-hotito ores ot Duoktown, Tennessee, but not much different from tbat of the Bingham and Shasta County ores.

Mineral Creek District (21). — This new district, which promises to be of some importance, is located in Rnal County (Fig. 155). The ore body consists of a great dissemination of chalcocite in schists (Fig. 162), and is said to average per cent copper.

Fill. 162. — Vertical section (A B. Fig. 163) showing ore body in schist. Mineral Creek district, AiiiooB. (After Totman, if in. and Sci. Preat, XCIX.)

The schiBt, which is of pre-Cambrian age, forma a block which is faulted up against Paleozoic rocks on the east. Granite porphyry intrtisions occur in the schist, quartzite, and diabase, and the first ij strongly silicified near the fault.

This district is of in- terest because it repre- sents a different mode of occurrence from that found in the leadii .\rizona ones.

Bingham CaAon, IJUih (63). — This camp, which is the leading copper-pro- ducing locty of Utah, is situated in the north- lentral part of the state,

on the eastern slope of

the Oquirrh Mountains, Fia, 163. — Geologic map of a portion of the Salt Lake aty. Tin.KCix.)

The rocks of this area include a great thickness of Carboniferous sedimentary formations, which are divisible into a lower member of massive quartzite with several interbedded limestones, and an upper member of quartzite with black calcareous shales, sandstones, and limestones.

c,q,z.<ib,Coogle

414 Economic Qeologt

The sediments, though showing in general a northerly dip, and nortbeastouthwest strike throughout the region, vary in their strike from east-west on the western slope to north-south on the eastern, so that they form a synclinal basin, with northward pitch.

The whole series of sediments, but especially the lower member, k pierced by an igneous intrumon, forming dikes, sills, and laccolith?. Prominent among these are two laQ areas of monzonite, one form- ing an irrular laccolith, the other a broad irregulaj- stock. An! extensive latite flow, outcropping on the eastern slope of the ranges, covered some of the sediments and older intrusives. i

There has been fissuring at several different periods following the igneous intrusion, but in most cases displacement along these frac- tures does not exceed 150 feet. The northwest-southeast fissures carry the most important lead-silver ores.

The limestones of the lower member, averaging 200 feet in thick- ness, have been highly marbleized, and carry large bodies of coppa ore, and the calcareous carbonaceous shales of the upper membai sometimes carry it as well. I

In many cases the ore is closely associated with the intrusivea.;

Two types of copper deposits Are recognized, viz. : (1) great tabular replacement masses in limestone, lying roughly parallel with| the bedding, and showing sometimes an extent of several hundred; feet along the strike, as well as a thickness of even 200 feet; (2) dis-' seminations in a lai monzonite laccolith, especially in the fractured, I fissured, and altered portions of the same.

The contact replacement deposits have been important ones in the past, but the enormous bodies of low-grade disseminated ore in '. the monzonite are now the most important (PI. XL).

The limestone ores consist of primary pyrite and chalcop>'rite, enriched in some cases by chalcocite and tetrahedrite. Quarts b' the chief gangue mineral, but as might be expected in a contact, deposit, garnet, epidote, tremolite, specularite, pyrrhotite, sphalerite, galena, etc., are also present. ,

The value of the ore is given by Weed as follows: copper content of replacement ores, 3.5 to 4 per cent, with gold $.10 to $1 and silver 2-0 , ounces per ton.

The average content of the fissure ores ia approximately 45 per cent lead, 65 ounces silver, and small amountB of gold, copper, and zinc.

Accessory gold, probably in pyrite, ranges in the copper, ores in iimf- i stone from $.80 to S2.20, in lode ores $.50 to $2.50, and in milling ores in monzonite about S.30 per ton. i

L, -ziv,

..

b,

Copper 415

Zino blende is a constant associate in the lode oree, &Qd ranges from a true to 45 per cent, averaging 10-15 per cent.

The Utah Copper Company gives as an average of a number ot assays of its disseminated ores: copper, 1.98 per cnt; gold, .016 oimces; and silver, .15 ounces per ton.

The theory of orin advanced by Boutwell is that the quarteites and limestones were intruded by the monzonite in Mesozoic or early Tertiary times, producing contact metamoiphism of the iimestone Had replacing it with sulphides.

After the upper portion of the monzonite intnion was partly cooled, the inclosing rocks were fractured by northwest-southeast fissures, along which there ascended heated aqueous solutions from the deeper, uncooled portions of the magma. These solutions not only altered the fissure walls, but depodted additional metallic sulphides, thus enriching the limestones as well as altering the monzonite by the addition of copper, gold, diver,- pyrite, and molybdenite.

Ely, Nevada (51-53). — This district, although of recent develop- ment, promises to become of great importance. The copper belt,

416 ECONOMIC OEOLOaT

which lies 6 miles west of Ely, in White Pine County (Fig. 195), is about one mile wide and six miles long extending in an east-west direction.

It lies in a pass throth the Egan Range, along what used to be a route to Eureka, Nevada.

The aeotioD there involves the following famiatioiu : — Ruth limestone

ArcturuB limeetone 1000 feet

Ely limestone. Carboniferous 1500 feet

White Pine shale 1000 feet

Nevada limestone i 1000 feet

The sediments which have a gentle dip are cut by a coarse;runed hornblende monzonite, which has effected only a Umited amount of alteration in the adjacent limestone, producing some garnet rock and chalcopyrit.

There are present also dikes of porphyry and rhyolite lavas, the latter resting in the uneven limestone surface (Fig. 165), but these eruptives bear no genetic relation to the ore.

FiQ. 165. — Section of Ely, Nev., district. {From Weed,)

Of importance in this connection are the monsonite intrusions, which carry ore. The ore, consisting of pyrite and chalcocite, is disseminated through the monzonite porphyry', but does not show on the yellowish and red weathered outcrop. In fact, there is a sharp line of separation between the gossan and unoxidiaed bluish white rock containing the grains of pyrite and chalcocite. The oxidized zone, which in the average extends to a depth of 100 to 150 feet, is very irregular and bears no relation to the ground water level.

Some of the ore bodies are of great size, that at the Ruth mine having a width of 50 to not less than 250 feet, and l>eing developed for a length of not less than 900 feet.

Iawson believes that the ore bodies have resulted from a leaching of secondary ores in the oxidized zones and that the only primary

c,q,z.<ib,Coogle

.OOglf

b,

Copper 417

ore now known is the chalcopyrite in the garnet rock occumng beneath the quartz " blouts." These latter are masses of quartz occurring mainly along the contact, and formed by the replacement of both limestone and porphyry with silica which was leached out of the porphyry by carbonated waters.

The ores are of low grade similar to the disseminated ones at Bing- ham Cafion, Utah, and are worked in part as open cuts (PI. XLI, Fig. 2). That from the Eureka Mine is said to average 2.2 per cent copper, with 40 cents gold per ton.

Appalachian States (32 a, 54, 55-59, 64-69). — The Appalachian states contain a number of deports of copper ore distributed from Maine to Alabama, but few of them are of commercial importance. A number of different types are reccnized occurring both in the Blue Bidge mountains and the Piedmont belt to the east.

The early attempts to work the depomts were chiefly to obtain both gold and copper, and resulted in failure, due largely to the low market values of copper ; hence for many' years the deposits, with few exceptions, have been but tittle worked, and it is only in recent years that a demand for the metal and cheaper metallurgical treatment have revived copper mining, at many localities, but not always with successful results.

Owing to the fact that the deposits usually occur in metamorphio rocks, their exact origin is somewhat in doubt.

Weed has suggested the five following types (5) : —

1. True fissure veins, filled with quartz and copper, the vein cross- ing or conforming to the banding of the schists, and replacement of the wall rock being rare. The ores are bomite, with a little chalcopjnnte and iron pyrite. The deposits at Viilina, Viiinia, belong in this group (69).

2. True fissure veins with auriferous quartz, chalcopyrite, and pyrite formed chiefly by replacement. The fissures are usually found along sheeting planes, and the deposits at Gold Hill, North Carolina, are taken as a type of this group.

3. Pyrrhotite veins of tiie Ducktown type (5), filling true fissures in mica schist, and consisting chiefly of pyrrhotite and pyrite with a little quartz. The ore has been formed by the replacement of a zone of sheeted rock, which was composed chiefly of metamorphio minerals, such as garnet, zoisite, actinolite, epidote, pyroxene, etc., these latter being the products of alteration of a calcareous shale. The Duckton ore body represents a type forming a belt extendi! the way from Vermont to Alabama. They all show a gossan

'" D,..,

418 Ecokomic Geologt

which can be mined for iron ore, while under this there is a zone of black copper, the result of local enrichment, which passes into the sulphide ore below. The copper is richest in those portions where the pyrrhotite predominates.

In 1908 the ores of this district yielded 1.55 per cent copper, with an average of .38 per cent gold and silver per pound of wper elec- trolyticaUy treated. The cheapness of operation of the mines and fuel make it possible to work this low-grade ore. The sulphur driven off in roasting the ore is utilized for sulphuric acid making, and the product can be marketed owing to the nearness of the phos- phate rock supply which is used for fertilizer manufacture.

Flo. 166. — Map of CuroU County, Va.. pyrrhotite sjea. ahoning poaitioD of the "Greot GoHMD Lead" in heavy btuk band, uid principal copper inineB located on it. Broken lines are other probable leads. (j4/ter Walton and Wetd, Itiit. Bet. Va.)

The Ducktown district was one of the earliest large producers in the United States, operations having begun in 1850, when the large supply of black copper ores were mined. The attempts to work the low-ade underlying sulphides were not successful until about 1890, since which time there has been a steady production.

The Gossan Lead of southwestern Virnia (68) (Fig. 166) and the copper deposits of Ore Knob, North Carolina, also belong to this type. At the former the ore is a mixture of pyrrhotite with subordinate chalcopyrite, and admixed quartz and schists. The vein fills a fault fracture between sericite schists, which contains mica, calcite, quartz, and actinolite, replaced by the later pyrrhotite and chalcopyrite (Fig. 167). The copper content is low, vis. .75

L,;,-z__lv,C00g[c

Copper

e is used for acid makiiig, but the residue is

per cent, and hence the svailable for copper.

4. The Catoctin type, representing srations of native copper, copper oxides, and carbonates along shear zones in altered igDeous rocksof Algonkian age, the ores extending be- low ground-water level. They are found at a number of localities in the Appalachian and Redmont plateau dis- tricts, usually in the Catoctin schist. The ore shows on the out- crop, but does not ex- tend usually more than 50 to 60 feet below the surface. It is supposed to have been leached out of the vein wb. Occurrences of this type occur in Green County, Virginia.

5. Deposits of native copper along the contact of diabase and sandstone. These have been found in New Jersey (54), but are unimportant, although the mines have been worked from time to time. Similar occurrences have been reported from Pennsylvania (55, fi6) and Connecticut.

Calif omia (22-27). — Copper ores are mined in the Shasta County belt, north of Redding. The wall rock is mnly alaskite porphyry, which was probably intruded during Triassic times, and the ore bodies form replacements along zones of shearing. Those found in the western part of the region, and which include the Iron Mountain district, are somewhat tabular, while in the eastern part, including the Bully Hill district, the ore bodies are more veinlike in character. In the western district the ore is pyrite with a small amount of chalcopyrite, while in the eastern sphalerite is of importance. The ores average about 3 per cent copper with SI .86 in gold and $.996 silver per ton. There are other scattered occurrences in the state.

Other Occurreruxa. — Colorado (28-32) has few copper mines

Fio. 167. — Section of ore from Chestnut Yard, Va., Bhowing pyrrbotite (white) and chalcopyrite (black) replacements En hornblende (parallel linea). (A/Ur Weed and Waiton, Earn. Oeot., I.)

420 Economic Geology

proper, but many of the ores mined id the state carry copper, and it is utilized by lead smelters as a carrier in the extraction of other metals. Copper is mined in New Mexico and Idaho, the Seven Devils district (34) of the latter state being well known. The Grand Encampment district of southern Wyoming (24) has also supplied more or less ore, and a small amount is mined in Missouri (44, 45) .

AUiaka (6-13). — The four moat promising and best-known copper regions of Alaska are (1) Ketchikan district on the Kasaan Peninsula and Hetta Inlet, the two being respectively on the east and west coast of Prince of Wales Island, (2) Prince Williams Sound district, (3) the region included within, the drainage area of the Kotsina and Chitina rivers, and (4) the reon of the upper Copper, Tanaua, and White rivers. Three of these may be referred to.

Ketchikan Di&triet (12). — The most important ore bodies are con- tact-metamorphic ones occurring in irregular masses from 10 to 250 feet in dimensions, along the contacts of the intrusive rocks, usually with limestones, the ore composed mtunly of chalcopyrite, minetite, pyrrbotite, and pyrite inagangue of amphibole, orthoclase, endote, garnet, and calcite. In addition to these there are lode deposits in shear zones, vdn deposits in fissures, and disseminated ores.

The ores mined are somewhat low in grade, with a little gold and ulver, but high in iron and lime, and form a desirable fiux for smelters of Tacoma and British Columbia.

At Copper Mountain in the Hetta Inlet district (Fig. 168) the ores are (1) contact deposits occurrii between granite and limestone or schist, and (2) vein or shear zone deposits, occurring along the bed- ding planes of the greenstone schist and quartzites. The contact zone is of variable width and is broadest in the limestone.

Ktna-Chiiirui Region (10). — This ron, which is dtuated some distance from the coast, and hence difficult of access, has been but little developed, although transportation facilities have now been provided.

The ores are mainly sulphides associated with Triaaac limestone and earlier greenstones. The ore is chiefly chalcocite, but other sulphides as well as oxidized ores occur. The most important deposit is the Bonanza mine on the Chitina River, which consts of a solid mass of chalcocite in limestone, averaging about 60 per cent copper, with about 22 ounces of silver to the ton.

Prince WiUiama Sound Districl (7. 8) . — In this district the ore is chalcopjTite disseminated through metamorphic schista. The most important mine is on Latouche Island (9), and here the ore which is

Copper 421

a mixture of chalcopjiite, pyrrhotite, and pyrite, has been deposited mainly as a cavity filling, leas often as a replacement or impreg- nation, in a shear eone in interbedded slates and graywackes.

Uses of Copper. — Since prehistoric times copper alloyed with tin has been used in various part of the world for the manufacture of bronze. Thus it was used for this purpose in Homeric times, and

it is found in the lake dwellings of Switzerland. The bronze found in Troy contains a very httle tin, and since this metal is not found in the excavations in the West, it seems probable that the bronze was made in Asia, perhaps in China or India, by some secret process, and imported to the western countries.

By an alloy of copper and tin, although both metals are soft, a comparatively hard metal is produced. The properties of this alloy, bronze, vary greatly according to the proportions of the two metallic

oog[c

422 Bconomic Geology

oonstituents, and these vary with the use for which the aUoy is in- tended. United States ordnance is 90 per cent copper and 10 per cent tin, while ordinary bell metal is about 80 per cent copper, though the percentage varies with the tone required. Statuary bronite ia genery an alloy of copper, tin, and zinc ; and, in these various bronzes, the coIot varies from copper-red to tin-white, pasa- ing tbrou an orange-yellow.

An alloy of copper and zinc produces brass, which is found of so much value for small articles used in building and for ornamental purposes in machinery. Copper is also used in roofing and plumbing

IBSO 1SU 1B90 leSE 1900 IMG

Pounds

J

/

f

A

'

/

'

'

/

f'

"

'

"

1 tbB United fitatea, fn>m 1S82

A large supply of this metal is made into copper wire, and the most important present use of copper is in electricity, for which its hi|h conductivity especially fits it for the transmission of electric currents.

Prodnction of Copper. — The production of copper in the United States has increased steadily and rapidly in the last fifty years, plac- ing the United States in, 'the lead of the world's copper producers. This increase can be seen from the chart (Fig. 169), and alao in the following tables : —

Producttion of Copper in the United St&tsb, 1904-1908, bt States, IN Pounds

Iws

i9oe

igoe

AliBD.

22B,S4,4fll

2U.7Tg.437

289 823.267

CotoiBdo .

1!

13.M3378

S.Nu.Sm

WoBLD'B PbODDCTION (SUEl/TBR OUTPUX) OF COPPEB IN 190S

IN Pounds

ChSe . EBcUitd GennBor

03,990.800 lMll-200

.soo

Total Impobtb and Bxpobts of Copfbb inclodino Obe, Matte j Reodlos, Piob, Babs, Inoots, and Plates

lurOKn

ExroBTS

Iw

lS2,e20.0M 218.705,487

731 008.2*1

Copper SoBSTFes. — Lindgren (6 a) points out that the visible oopper reserves of the United States are much Iwger than those of lead ore, and, moreover, they are much larger, now, at the manmam of produotion, than they have ever been before, and yet they are in most oases not nearly ao great as those blocked out for some other inatrialB like coal. This, how- ever, is owing to the different mode of ooonrrence of the two substanoes. The amount of available reserves to be estimated depends on the market priw of oopper. With the latter at, say, 20 oents per pound one can estimate a much l&r reserve than if the price were only 13 cents. Lindgren believes that the oopper resources of the United States are large enough to respond for a number of years to a demand increasing at the rate of 30,000,000 pounds per annum.

L:,.i,-z__iv,CoOg[c

Economic Gbolooy

Kefbrbrcbs Oh Copper

Oenebal. 1. Biddle, Jour. Geol., IX: 430, 1901. (Origin.) 2. Fernelres, Eoon. Geol., II : 580, 1907. (Copper preoip'n from chloride solutions by ferric ohloride.) 3. Kemp, Boon. Geol., 1:11, 1906. (Sec'y eurioh't.) 4. Kemp, Mia. and Soi. Pr., March 30, 1907. (New points in geology trf copper ores.) 4 a. Sullivan, Bcon. QeoL, 1:67, 1906. (Copper preoip'n by natural silicates.) 5. Weed, Copper Mines of the World, New York, 1907. 5 a. Lindgren, U. S. Geol. Surv.. Bull. 394 : 131, 1909. (Copper ore reserves.) 5 6. Stokes, Eoon. Geol.. 1 : 614, 1906. (Sol'n, transport'n, dep'n of copper.)

Papers BELATiHO TO Special Areas. Alaska. 6. Brooks and others, U. 3. Qeol. Surv., Bull. 379 : 74, 1009. (Prince of Wales la.) 7. Grant and Higgins. U. S. Geol. Surv., BuU. 379, 1908. (Prince William Sound.) 8. Grant, U. 8. Geol. Surv., BuU. 284 : 78, 1906; also Min. Sci. Pr., 0:63,1910. (Prince William Sound.) 9. Lincoln, Boon. Oeal., IT: 201, 1909. (Latouche Is.) 10. Moffit and Madden, U. S. Ged. Surv., Bull. 374. 1909. (Kotsino-Chitina region.) 11. Rickard. Min. Soi. Pr.. Dee. 5, 1908. {White Horse.) 12. Wright, F- E. and C. W., U. S. Geol. Surv., Bull. 347, 190S. (Ketchikan and Wrangell I dist'a.) See also Ibid., Bull. 379:75. 13. Wright, C. W., Eoon. ; Geol., Ill :410. 1908. (Kasaan Peninsula.)— Arlsooa. 14. Chureh, Amer. Inst. Min. Bogrs., Trans. XXXIII : 3, 1903. (Tombstone district.) 15. Douglas, Amer. Min'g Cong., Nov., 1905. (Develop- ! ment Arizona industry.) 16. Douglas, Amer. Inst. Min, Bngre.. I Trans. XXIX: 511, 1900. (Copper Queen Mine.) 17. Graton, U. 8. I Geol. Surv., Min, Res, 1907 : 597, 1908. (Jerome.) 18. Lindgren. ' U. S. Geol. Surv., Prof. Pap. 43, 1905. (Clifton-Morenci.) 19. Ran- , some, U. 8. Geol. Surv., Prof. Pap. 12, 1903- (Globe.) 20, Ransome. 1 U. 8. Geol. Surv. Prof. Pap. 21, 1904. (Bisbee.) 21. Tolman, Series , of articles in Min. Sci. Pr, as follows : Nov. 6, 1909 (Ray) ; Nov. 27, 1909 (Silver Bell) ; Nov. 13, 1909 (Miami-Inspiration) ; Sept. 11 and 18, 1909. (8. Ariz.)— California. 22. Anbury. Calif. State Min. Bur.. Bull. 23, 1902. (General.) 23. Graton. U. 8. Qeol., Bull. 430-B: 3. (Shasta County.) 24. Diller, U. S. Geol. Surv., BuU. 213 : 123, 1903. (Redding region.) 25. Knopf. Univ. Calif. BuU. IV, No. 17. (PoothiU belt. Sierra Nevada.) 26. Lang, Eng, and Min, Jour,, Nov. 16. 23, 30, 1907. (Copper belt.) 27- Raid, Econ. Geol., II : 380, 1907. (Copperopolis.) — Colorado. 28, Bagg, Econ. Geol., 111:739, 190S. (Sangre de Christo Range.) 29. Emmons, Tenth Census, XIII : 6S. ' 1885. (GilpinCo.) 30. Emmons, U. S. Geol. 8urv..BuU.260:221. 19. (Red Beds. Colo, plateau.) 31. Rittr, Amer. Inst. Min. Engrs.,Julf. 1907. (Apex. Colo.) 32. Spencer, U. 8. Geol. Surv., BuU- 213: 163. 1903. (Pearl, Colo.) — Georgia. 32a. Weed, U. S. Geol. Surv, BuU. 225:180, 1904. —Idaho. 33. Kemp and Gunter, Amer. Inst. Mia. ., Trans. XXXVIII : 269, 1908. (White Knob.) 34. Lindgren. Min. Sci. Pr.. LXXVIII : 125. 1899. (Seven Devils district.} — Mich- igan. 35. Feruekes. Econ. Geol., II : 580, 1907. (Preoip'n of copper.) 36. Hubbard. L. Sup. Ming. InSt, Proc. 111:74, 1895. (Central

Copper 425

Mine.) 37. Hubbard, Ibid., II : 79. (Keweenaw Point, cross sections.) 38. Irvins. U. 8. Oeol. Surv., Mon. V, 1883. 39. Lane, L. Sup. Ming. Inst., 1906. (Oeolo copper district.) 40. Lane, Can. Min. Inst., Quart. Bull., No. 7, July, 1909. (Copper mine waters.) 41. PumpeUy, Mich. Geol. Surv., I, pt. 2, 1873. 42. Rickard, Eng. and Min. Jour.. LXXVIII : 585, 625, 665, 745, 785, 866, 905, 1025, 1904. 43. Wadsworth, Amer. Inst. Min. Eners., Trans. XXVII: 669, 1898. (Origin.)— Hissoori. 44. Bain and Ulrioh, U. 8. Geol. Surv., Bull. 267, 1905. (General.) 45. Nicholson, Amer. Inst. Min. Engra., Trans. X : 444, 1882. (St. Genevieve.) — Hontua. 46 a. Col- len, Eoon. Geol., II : 572, 1907. (Belt formation, Mont.) 46. Em- mons and Tower, U. S. Geol. Surv., Atlas Folio 38, 1897. (Butte.) 47. Sales, Econ. Geol., V : 15, 1910. (Superficial altration Butte veins.) 48. Simpson, Econ. Qeol., 111:628, 1908. (Relation copper to pyrite in lean ores, Butte.) 49. Weed, Copper Mines of the World, New York. 1907. (Butte.) 50. Winohell, Eng. and Min. Jour., LXXV;782. 1903. (Chaloocite synthesis.)— Nevada. 61. Jennings. Can. Min. Inst. Jour., XT : 463, 1008. (Yerington.) 52. Lawson, Univ. Calif. Bull. Dept. Geo!., IV, No. 14 : 287. (Ely.) 53. Ran- some, U. 8. Geo!. Surv., Bull. 380 : 102, 1909. (Yerington.) —Nw Jersey. 54. Lewis, N. J. Oeol. Surv., Ann. Rept., 1907:131, 1908. — Pennsylvania. 55. Bailey, Bug. and Min. Jour., XXXV: 88, 1883. (Adanu Co.) 56. Lyman. Jour. Franklin Inst., CXLVI: 416, 1898. (Bucks and Montgomery counties.) — Teonesuo. 67. Henrich, Amer. Inst. Min. Bogrs., Trans. XXV : 173, 1896. (Duek- town.) 68. Kemp, Amer. Inst. Min. Engrs., Trans. XXXI:244, 1902. (Duoktown.) 59. Weed, Amer. Inst. Min. Engrs.. Trans. XXX: 449, 1901. (Southern Appalachians.) — Texas. 60. Schmitz. Amer. Inst. Min. Engrs., Trans. XXVI: 97, 1897. (Permian ores.) — Uaited States. 61. Stevens, Copper Handbook, published annually at Houghton, Mich., by the author. 62. Weed. Copper Mines of the World. New York:263-361, 1907.— Utah. 63. BoutweU, Keith, and Emmons, U. S. Geol. Surv., Prof. Pap. 38, 1905. (Bingham.) — Vermont 64. Packard, Eng. and Min. Jour., Jan. 4, 1908. (South Strafford, Corinth, and Eureka.) 65. Perkins, Reports issued annually by State Geologist. Usually brief references. 66. Smyth and Smith, Eng. and Min. Jour., April 28 1904. 67. Weed, U. S. Geol. Surv., Bull. 225 : 190, 1904. —Virginia. 68. Watson, Min. Rea. Va., 1907. 69. Weed and Watson, Econ. Geol., I ; 309, 1906.— Washington. 70. Evans, Min. Wld., Sept. 5, 1908. (Lake GsoyoeB.) 71. Stretch, Eng. and Min. Jour., Nov. 17, 1904. (Cas- cade Mta.) — Wisconsin. 72. Grant, Wis. Geol. and Nat. Hist. Surv., Bull. 9, 1903. (Douglas Co.)— Wyoming. 73. BaU, U. S. Geol. Surv., Bull. 315, 1907. (Hartville uplift.) 74- Spencer, U. S. Qeol. Surv., Prof. Pap. 25, 1904. (Encampment district.)

Iv,

Chapter Xvii

Lead Xsd Zinc

It is usually customary to treat these two ores together for tia reason that they are so frequently associated with each other, but it must not be understood from this that they are found free from association with other metals, as in the Rocky Mountain region, foi example, gold, silver, or copper may often occur with them, forming ores of somewhat complex character.

The silver-lead ores form a somewhat distinct class and are treated separately.

Ore Minerals of Zinc. — The nnc-ore minerals, together with the percentage of zinc which they contain, are : —

Bph&lerite (Isometric) . Wuitzita (Hexasonal) .

ZnS

CaUmine

2ZnO,8iO,,H.O

Hydrozinoite

ZnCO,,2Zii(OH),

Willemite

2ZnO,SiO.

FrankUnita

(FeMnZn]0,(FeMnV>,

variable

Of these ores, sphalerite (also known as blende, jack, rosin jack, or black jack) is by far the most important, esoept in nortliem New Jersey, where it is practically laokinf and franldinite and irillemite abound.

Sphalerite may be either a prinufy or seoondwy ore. Wurtzite has been noted in some of the Missouri ores, and many massive blendes may be a mixture of sphalerite and wurtzite.' I

Blende is often associated with other sulphides, especially galena, j pyrite, and maroasite, but more rarely chalcopyrite.

Smithsonite, found in the oxidized zone, ia a comparatively rare on mineral in the United Stales, although it is an important one in Europe. Calamine, also an oxidized ore mineral, is far more abundant, and found in many deposits. Both smithsonite and oalskmine may ooour in a pure and crystalline form, but more often they are quite impure, and of cniEted or earthy eharaoter. Hydrozinoite is not uncommon in some diatiiots.

J. Noeltinc. Zelt. Eivst. u. Min., XVU ; 220, ISIM.

*2e ...,.,

Lead And Zinc 427

Ore Minerals of Letd. — The lead-ore minerals, together with their compoation aad the percentage of lead which they contain,

QaJena . . .

Cerassite . . Anglesite . . Pyromorphite .

PbS

PbCO,

PbSOi

PlHP,Oi+iPbCI,

There are a vast number of lead minerals in addition to the above, but they have tittle or no conunercial value on aooount of ttieir rarity.

Of the above-named ore mineralH galena is the oommoaest, and may be of either prinuu-y or aeoondary oharaoter. It frequently, eapeoially in the complex ores, earriea variable amounts of silver. The other three lead-ore minerals are usually found in the oxidized zones, and the oerusiite is not unoommon, but the sulphate when formed usually ohanges to the carbonate.

The lead and zinc ores may be divided into three groups as follows: (1) lead and zinc ores, practically free from copper and the precious metals; (2) lead and zinc ores, carrying more or less gold and silver, as well as some iron and copper; (3) lead-eilver ores.

In the iiist group iron, lead, and manganese are not uncommon impurities, and those of southwestern Missouri contain small amounts of cadmium ; but this is not injurious, as it is more volatile than the zinc and easily driven off. Calcite, dolomite, and pyrite or marcasite are common gangue minerals, and barite or fluorite may occur at cert localities.

The ores of the second group are confined to the Rocky Moun- tain region, and are not only of complex character, but differ in their form and origin irom most of the eastern ones. Quartz is probably the commonest gangue mineral, but there may be other less important ones. Antimony, arsenic, and iron may be among the impurities.

The Edlver-lead ores, which are confined to the western states, carry silver and lead as their chief metab, but may contain smaller amounts of zinc, gold, or iron. They show a preference for limestone.

Mode of Occurrence. — Zinc and lead ores may occur under a variety of conditions, viz. : (1) as true metalliferous veins ; (2) ins- ular masses in metamorphic rocks; (3) as irregular masses or dis- seminations, formed by replacement or impregnation in Umestones or quartzites ; (4) in contactmetamorpbic deposits ; (5) in cavi- ties not of the fissure-vein type ; aad (6) in residual clays.

428 Economic Geology

Both lead and zinc are what may be trmed somewhat persistent minerals, dnce they are able to form mider a variety of physical conditions, originating' in contact depodte, deeper vein zones, middle and upper vein zones, and by the action of meteoric waters. It will be noticed, from the foregoing, that none occur as magmatic segregations.

Neither lead or zinc ores are restricted to any one formation, but the majority of economically valuable deposits of these metals, without ailver, gold, or copper, are found in the Paleozoic formations, altboi a few are known in pre-Cambriao rocks.

While the metallic content of the ore as mined is often low, still, owing to the great difference in gravity between ore and gangue minerals (excepting pyrite or marcaaite and blende), it is often possible to separate them by mechanical concentration ; and for the zinc ores magnetic separation has been successfully tried.

Superficial Alteration of Lead and Zinc Ores. — Galena is often altered near the surface to angleeite or cerussite. The fonner, however, is unstable in the presence of carbonated waters and changes readily to carbonate. Phosphates are developed in rare instances.

Sphalerite, the common ore of zinc, is often changed superfidally to smithsonite, hydrozincite, or calamine. Such oxidized ores are of greater value than unoxidized ones, because, although carrying a lower percentage of zinc, they occur in a more concentrated form and yield more easily to metallurcal treatment.

The sulphates and carbonates produced by weathering may be carried down below water level imd reprecipitated as sulphides, thua causing secondary enrichment.

Some of the reactions which may take place are referred to under secondary enrichment in Chapter XIV.

Owing to the fact that sphalerite weathers more rapidly than galena, the zinc is usually carried down below water level more rapidly than the lead, and this may result in a zonal distribution of the ore, lead predominating above and zinc below. Cases of this sort are not uncommon.

Distribution of Lead and Zinc Ores in the United States (Fig. 170). — The occurrence of lead or zinc with gold, silver, and copper is confined chiefly to the CordiUeran region, and shows a most varied mode of occurrence; but commercially valuable deposits of lead alone, or lead and zinc, are confined to the Missiadppi VaUey, while 'lindEren, Eoon. 0cil., 11:107.

L,.;,-z__lv,C00g[c

Lead And Zinc

those of rinc alone or with little lead are restricted to the Appala chian roa a3 seen below.

Lad Alone. Appalachian Belt (17, 34). — Lead (sometimes aintiferous) occurs at a number of localities from Maiae to Georgia filling small veins in metamorpbic rocks, and the deposits have at

various times aroused temporary interest. There is no likelihood of their ever becoming important producers, although exciting rumors regarding them are occasionally circulated.

Stmiheastem Missouri* (22, 26). — The disseminated lead ores of southeastern Missouri he mainly within St. Francis, Washington, and Madison counties, the geologic section involving the following formations: —

Potosi dolomite. 300 ft. +

Doenin arg:illatieaus dolomite. 60-100 ft.

Derby dolomite, thickly bedded. 40 ft.

Davis formation, chiefly ahoie with thin beds of limestoae, dolotnite and limestone con- glomerate. 170 ft.

Bonne torre, mainly magneaian limestone with sandy dolomite and shale. 365 ft. ±

Lamotte sandstone. 200 ft. or less.

Unconformity. -Cambrian. Granite and rhyolite with intru-

sive diabase aikes.

Tbe abatract of this district was kindly furniabed by Dr. E. R. Buckley.

z .IV,

430 Economic Geoixkjt

While the Bedimentary series as a whole has retained ite orinally approximately horizontal poaition, there are numerous local dip some of which may be as much as 45°. The numerous anall faults of the district are roughly groupable into a northeast-southwest and a northwest-southeast system. Moat of the faults are of normal type uid usually have a throw of less than 100 feet; but those of the major Eonea show aregate displacements of 700, 600, and 400 feet respectively. The ore bodies of the district usually lie in pitching troughs, and while some galena

r — n of massive crystallized type has been mined

ninrrow with proGt from the Potoei, and upper part

of the Bonneterre, the disseminated de-

posits, which are the main source of the

BWM lead ore in the district at the present day,

W/$ occur mainly in the lower half of the Bonne-

In the so-called dissenuDated lead-ore

bodies, seven types of occurrence are notd, of which the first is the most important: (I) disseminations in dolomite, shale, and chloritic rock ; (2) horizontal sheets aloi bedding planes; (3) fillii or Uning the walls of joints ; (4) in cavities, vu, and dmilar openings, sometimes embedded in soft blue clay or mixed with calcite and 'pyrite; (5) in shale along fault planes; Fio. 171. — Four uid one (6) Ib cubes and aggrtes of cubes in red Bonneterre Umostone, aloi fault zones ; (7) 88 ccrussite in de- Doe Run, Mo. (Afler composed dolomite.

BucWn, Af„. Bur. cterf. disseminated lead-ore bodies are in Mm., IX.) , 1 J

part the result of the abstraction of lead from waters circulating along channels and bedding planes in their journey from the surface to the Lamotte sandstone, and in part from solutions, under hydrostatic pressure, which rise along channels extending upward into the dolomite, from the underlying sand- stone. In the Bonneterre formation the conditions were favoraUe for

c,q,z.<ib,Coogle

Lead. And Zikc 431

the reduction of the metallic salts, resultiog ia tbor precipitation as ore bodies.

The details of the deposition are ooosidered to be about as follows : At th€ Burfaoe there is aa oxidised zone oontaining galena, which is being abstracted by surfaoe w&ter peroolating down towards the Imotte sand- stone, which on account of its high porosity serves m a storage reservoir of water containing lead in solution. Between these two zones is the Bonneterrefomiation, with its carbonaceous and chloritio reduoing agents, and in which formation the lead has been deposited.

Channels furnish connecting ways between the oxidized zone and the tandstone, and the rooks along these have been and are being oxidized, pw- mitting the direct transference of oxidising solutions, carrying lead.

Some water may have also entered the Bandstone by other channels.