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By Hsun Hu

The formation of annealing textures in high-purity silver, from the various rolling textures obtanled in the course of texture transition, was studied. It was found that from a brass-type rolling texture the recrystallization texture is mainly (120) [211] type, which is quite different from the recrystallization texture of brass. From a predominantly copper-type rolling texture, the reclystallization texture is mainly (100) [001]. The recrystallization texture of silver- varies also with the degree of purity. In each case, however, the reorientation can be expressed as [Ill] rotations of 30° to 40°, which is consistent with the oriented growth theory of the formation of annealing textures. ThE recrystallization textures of rolled silver were studied long ago by Glocker and co-workers (1924-27) and were reported to be (113) [iil] upon annealing at low temperatures.1 Since that time, no further study of the recrystallization textures of silver, particularly with the modern techniques of quantitative texture determinations, has been reported in the literature. In a previous study2y3 it was found that the rolling texture of high-purity silver (99.999 +pct pure) is changed gradually from the common silver- or brass-type to the copper-type by raising the temperature of rolling from 0" to 200°C. The formation of annealing textures from the various rolling textures in the same material is, therefore, of considerable interest. The present paper constitutes the results of such a study. MATERIAL AND METHOD Specimens were taken from the same strips of high-purity silver* that were used previously for

Jan 1, 1962

By C. Chiou, M. E. Fine

While Gunier-Preston zones are growing in Al-4.2 pct Cu at room temperature, Young's modulus, measured dynamically, increases about 0.4 pct. From the change in modulus with time the exponent of time in the rate equation for growth of the zones was deduced to be %. From a comparison of the rates of increase of modulus at 1, 28, and 42°C an activation energy of 12 to 14 Kcal per mole is computed. These findings support the idea that copper atoms are supplied along dislocation channels to growing zones. In alloys the elastic constants will be functions of the distributions of the atoms. If the degree of ordering or clustering is changed, one expects a corresponding change in the elastic constants. During age-hardening of aluminum-copper alloys at room temperature, the copper atoms cluster on 100-type planes in the aluminum lattice forming

Jan 1, 1959

By George R. Eadie

As 1972 slipped through our grasp, coal industry adjustments to health and safety laws, environmental restrictions, rising costs and higher production targets left many mine operators groping for a new grip. The industry adopted a defensive attitude in 1972 as it faced the onslaught of inspectors. With rigid demands for improving safety and instituting environmental programs, the industry worked hard and watched production figures stagger upward while operating costs zoomed. In an effort to determine how to meet the goals that were established for fewer ignitions, fewer accidents, less respirable dust, lower noise levels, fewer law violations, better reclamation, less pollution, lower costs and higher production, industry representatives attended numerous technical meetings.

Jan 2, 1973

By N. Rowlands, J. A. Finch, R. Espinosa-Gomez

The sulphation roast-leach process for complex sulphides results in phase changes due to roasting and leaching. The phases in the calcine, and in the neutral and hot acid leach residues were identified and their degree of liberation determined in order to design and Interpret separation tests on the residues. The hot acid leach residue was composed of hematite, silica, and lead sulphate with some associated silver. Magnetic separation was selected as the process for producing a lead concentrate, as the non-magnetic product. Separation was limited by -1 pm hematite reporting to the product, and hematite/lead sulphate agglomerates reporting to the magnetics.

Jan 1, 1984

By E. D. Fields, R. W. Sayers, M. C. Tippett

The Duval Corp. porphyry copper deposits at Copper Canyon and Copper Basin, though widely separated, form an econornic unit requiring integrated exploitation. Contrasts in mineralization, host rocks, and mode of occurrence present unique mining and milling problems. Mixed oxide-sulfide ore is treated in extensive dump leaching facilities in both areas. Complex Cu-Au-Ag ore is treated in a 4000-tpd mill at Copper Canyon. In both areas, hypogene metallization occurs within large aureoles of metamoiphism and hydrothennal alteration related to quartz monzonite intrusions of mid-Tertiary age. Supergene processes fitrther altered the rocks and enriched the hypogene protore. At Copper Canyon, hypogene copper and iron sulfides with gold and silver occur in fractures, as partial replacement of favorable beds, and as disseminations in Paleozoic sedimentary rocks. The lower part of the Pennsylvanian Battle formation was a particularly favorable host. Metallization occurs to a lesser extent in quartz monzonite. Metal zoning is well-developed. The deposits at Copper Basin consist principally of supergene copper minerals in arenites of the Cambrian Harmony formation. Oxidation of hypogene copper and iron sulfides in tactite zones has formed at least two commercial deposits; intersections of fractures with favorable beds exerted important ore controls. Recently, the Copper Canyon and Copper Basin properties of Duval Corp. have been added to the list of porphyry copper mines in Nevada, marking the first new copper open pit in this state in 15 years. The properties are situated in the Battle Mountain

Jan 1, 1970

By Earle Schumacher

COPPER-CALCIUM alloys are of interest as materials for use in deoxidized conductors of high conductivity. That calcium is effective in deoxidizing and degasifying copper is well known. Brandenberg and Wiens1 have described the use of calcium in the casting of sound copper and state that the deoxidation can be carried out without difficulty. The castings that they prepared were sound and sufficiently ductile to permit wire drawing. Pratt,2 in British Patent No. 1699 (1907), has claimed the use of calcium for the deoxidation and degasification of copper. Masing3

Jan 1, 1929

Jan 1, 1902

By T. M. Chance

THE necessity of adopting improved methods of bituminous-coal cleaning at. many collieries is recognized by all familiar with the requirements of the various bituminous markets, the approaching exhaustion of the relatively small areas of inherently high-grade-coal, and the difficulties encountered in maintaining a uniform grade of shipped coal. Many coals lose much of their .market value by degradation in size, and, in any event, if the cleaning process is to contemplate wetting the coal the minimum amount of fines should be produced to prevent sludge losses and the difficulties resulting from the moisture content of the wet fines. Hence, it is desirable to by-pass the finer coal dry, if this can be done without too-great increase in impurities in the final product. This procedure has given excellent results at washeries at Steelton and in the Birmingham district. If the raw fines are too impure to permit admixture with the washed coal, it may be desirable to use dry methods, such as the pneumatic table, rather than to wet an excessive amount of such fine material. The bituminous-coal cleaning plant should therefore: (1) Treat the raw coal in as large lump as possible and without sizing; (2) eliminate degradation of pure coal -in the washing process; (3) avoid wetting the fines, if possible; (4) produce washed coal practically free from mechanically included impurities; (5) crush the refuse and retreat, if much intergrown coal, and refuse are present, rather than precrush the entire feed. Ordinary gravimetric methods of concentration, whether hydraulic or pneumatic, will not meet all of these requirements, as the large lump includes those sizes. now sent to the picking tables, if it is desired to treat material of such size. I do not know of any prior commercial method, based on the falling velocity, coefficient of friction or resistance to fracture, that permits the production of clean coal varying in size from, say, 10-in. lump to 1/16 -in. mesh.

Jan 6, 1924

By Gerald Sherman

(San Francisco Meeting, September, 1915) THE ore deposits of the Warren district, in which the mines of the Copper Queen Consolidated Mining Co. are situated, have been described in a number of technical publications, and will not be-discussed here in detail. Certain of their characteristics, however, control -methods of underground transportation and hoisting of ore. In the Copper Queen mine, the majority of the ore has occurred in a zone encircling the west boundary of the porphyry intrusion of Sacramento Hill. It has a width varying from 800 to 1,200 ft., and a thickness of about 400 ft. It reaches the surface in the older part of the mine to the northwest, but dips to the southeast, where it is reached at 1,400 ft. below the Czar collar, in its farthest extension at present developed on Copper Queen ground. There is one major extension from the northwest end of the zone toward the west along the Czar fault, and others of minor importance. Individual orebodies are scattered through the zone in an eccentric manner, only matched by their own irregularities of form and size. Their most general characteristics are the softness of the ore and their great horizontal rather than vertical extent. It has been estimated that the average vertical thickness of ore in the Czar and Lowell divisions is between 30 and 35 ft. It is calculated by assuming it to be uniformly distributed over its horizontally projected area. In this zone, and for some distance above it, the ground has been .subjected to intense alteration and intense but irregular oxidation. It has resulted in an enormous quantity of earthy or clayey material, which may be either ore or waste, which when wet is both heavy and tenacious. Below alteration, the ground is fairly hard, and the limestones contain primary ores differing from those heretofore considered typical of the camp, and which have not yet been thoroughly exploited. The mine production has been drawn from many orebodies spread . over a great area. A diagram map (Fig. 1), of haulage drifts and loading stations, illustrates the situation in 1914.

Jan 9, 1915

By D. L. H. Forbes

The application of the cyanide process to complex sulphide ores for the extraction of the gold and silver is no longer a novelty; but, as an example showing modern teudencies in this direction, the following description of the new milling process at the Lucky-Tiger mine is offered: The extraordinary richuess of the ore in the upper workings of this mine made any thought of milling in its early days seem unnecessary. Its location in an almost inaccessible part of the rugged mountains just south of the Arizona boundary-line, and 60 miles from the town of Douglas, made the expense of bringing in machinery and sopplies a very serious consideration. But, after the property had been shipping high-grade ore on mule-back for a few years, there remained in the mine a considerable tonnage of vein-matter that mas too low in value to ship, but which it wag thought could be milled near the mine at a profit. The first milling-experiment consisted in the installation of Nissen stamps in conjunction with concentrating-tables and Frue vanners, but, as the ore from the upper workings contained most of its silver in the form of cerargyrite, this type of mill mas not successful. The proximity of the mine to the great copper-concentrating mills of Cananea and Moctezuma naturally made the influence of copper-milling ideas felt in the company's next instdlation. At considerable expense a stage-crushing concentrating-mill, with a capacity of 100 tons per day, was built. This mill was modeled along the lines of the most approved practice in copper-concentrators at that time, the main idea being that crushing by stages .in rolls was necessary in order to prevent losses from " sliming." Largely owing to the fact that, when the mill

Jan 1, 1913

By John B. Baker, Bernard B. Betty, H. F. Moore

For several years there has been in progress in the Materials Testing Laboratory of the University of Illinois an investigation of creep and fracture of lead and lead alloys. In the course of this investigation it has been shown that the phenomenon of creep occurs in part at the grain boundaries of lead and lead alloys. To study the occurrence of creep and the development of fracture within crystalline grains, two series of tests of single crystals of lead have been carried out. The first of these, a preliminary series, by Mr. Betty, has been described.l,2 The second, pursued by Mr. Baker for his doctoral dissertation, was carried out under the direction of Professor Moore, with the assistance of Prof. G. L. Clark in the X-ray work, and the cooperation and advice of Mr. Betty. This paper is based on the test data obtained in this second series. Single crystals of a very pure commercial lead have been prepared, some of them tested to measure creep, others tested to fracture under long-continued steady load, and still others tested under cycles of repeated tension. An interpretation of the test data of these single-crystal tests is offered, which is a combination of parts of several well-known theories. Specimens The single-crystal specimens were made from a piece of very pure commercial lead sheathing. A spectroscopic analysis of one of the single crystals showed the presence of 0.005 per cent Bi, 0.0001 per cent Cu and 0.0003 per cent Ag. Preparation.—The Bridgman method of casting single-crystal specimens was used.3 The specimens were cast to the shape and size shown in Fig. 1 (dimensions in Fig. 4c) in a duralumin mold. Molten lead does not stick to duralumin. Fig. 1 shows the mold and the blast flames for heating. After the mold had been heated to the temperature of molten

Jan 1, 1938

By Walter Herd

Fox the past eight years No. 2 mine of the Cumberland Railway & Coal Co., Springhill, Nova Scotia-a subsidiary of the Dominion Coal Co., Ltd.-has had an unenviable reputation for bumps. As the workings extended in certain directions under a greater cover, these bumps increased in severity and it became apparent that some change in the system of extraction was necessary if the mine was to continue to operate. In September, 1924, following several fatalities resulting from bumps, the Mines Department of Nova Scotia requested from the U. S. Bureau of Mines the services of George S. Rice, Chief Mining Engineer of the Bureau, to report on the conditions then prevalent in No. 2 mine, Springhill. This request was promptly and courteously granted. Mr. Rice made a full investigation and a comprehensive and helpful report, which is embodied in the 1924 Annual Report of the Department of -Public Works and Mines, Nova Scotia. Prior to 1925, the room and pillar method was employed and in January of that year (there being a cessation of work from March to August due to labor troubles) longwall retreating on the west side, on a limited scale, and in a small section on the east side of the mine was started. The major portion of the east side was not operated on this system till August, 1926, as there was developed a considerable area ready for pillar extraction between an arbitrary boundary and a point up to which bumps of any consequence, had not been experienced. In the interval development work for longwall retreating below the 5900-ft. level was vigorously- pushed. This longwall retreating system was suggested by Mr. Rice as a possible remedy and was heartily endorsed by the company officials. This paper describes the conditions and happenings subsequent to Mr. Rice's report and more especially the results with the longwall retreating system of mining under the peculiar circumstances pertaining to mining. No. 2 Seam, Springhill, at depth, and records the 'conclusions which experience with several severe bumps under this mode of extraction would suggest. Except where necessary to make the paper intelligible as an entity any duplication of Mr. Rice's report will be avoided.

Jan 1, 1929

By Donald H. McLaughlin, Reno H. Sales

ADAPTATION to mining needs of the rich store of geologic knowledge concerning mineral deposits and the application of principles of the science to specific problems in the finding, development and stoping of particular ore bodies are the major tasks of the mining geologist. On him to an increasing degree is placed responsibility for estimation of ore and appraisal of mineralized ground, for explicit guidance of exploration and development, and for reliable advice with regard to the many geologic conditions that influence mining operations. In the long continued and steady efforts to meet these requirements, a special skill in close observation, recording, and quantitative interpretation has been developed, particularly by geologists on staffs of mining companies, which in many districts has proved to be effective, not only for technical ends, but also for advancement of scientific understanding. The foundations for mining geologic work were laid in most districts of the West by investigations of the United States Geological Survey. For years they have provided a reliable basis for geologic thought with regard to ore deposits, and later studies have enriched and supplemented rather than superseded them. In very few districts have the geologic relations stated in the earlier papers needed serious modification or revision, in spite of new evidence subsequently made available in abundance by mining exposures. Indeed, one of the chief satisfactions derived from success in mining geologic work is the assurance that it gives of the correctness bf the major concepts of the science of ore formation, established to so large an extent by the leaders of this notable group among whom Lindgren has been so eminent a figure. The geologists of the Survey have given and are continuing to give the service which can properly be expected of the Federal government. Their work, however, though of the greatest value in establishing the broad geological setting,

Jan 1, 1933

By W. B. Dancy, A. Adams

Laboratory test work on heavy liquid separation of sylvite from halite is reported. Numerous tests were run on sylvite ore sized in the ranges of 4x20 mesh, 10x65 mesh, 8x100 mesh, -8 mesh and -10 mesh with heavy liquids in the range of 2.05 to 2.15 sp gr. From the test results, it was concluded that, with the type of ore under study and a size in the range of -8 mesh, a recovery as high as 90% could be achieved with a product grade of 70% KCl. However, a final product at an acceptable recovery cannot be made with one pass, and the float must either be further processed with heavy liquids or dried and sent to a conventional froth flotation circuit. Potash ores occurring in this country consist essentially of sylvite and halite plus minor amounts of magnesium sulfate salts and montmoril-lonite-type clays. Recovery of potash minerals from evaporite ores in the North American potash fields is accomplished almost exclusively by use of amine flotation. European practice involves froth flotation as well as solution-crystallization processes. Laboratory and pilot plant test work has been reported in Europe and the U. S. on the application of heavy media separation to potash ore beneficiation. Work was probably discontinued because of lack of ore with the required very coarse liberation characteristics (1/8 to 1/2 in. liberation size). Sylvite, with a gravity of 1.99, and halite, with a gravity of 2.17, appear to be ideal for separation by heavy liquids, which are now available in gravities from 1.59 to 2.95. This paper reviews preliminary results obtained from laboratory test work on heavy liquid separation of sylvite from halite. TEST WORK The heavy liquids used in the tests under discussion were chlorobromethane, with a specific gravity of 1.923, and dibromethane, with a gravity of 2.490. These liquids, completely miscible, were combined in the proportions needed to give a mixture having the desired specific gravity. Feed for the laboratory tests was mine-run ore screened to the desired mesh sizes. In conducting the tests, the sample was fed at a constant rate into a stream of heavy liquid and the mixture directed into a small separatory vessel. The float overflowed into a collecting pan while the sink collected in the bottom of the separatory vessel and was removed at the end of the test. Approximately 500 g of feed constituted a charge. Pulp density of the feed was kept low to prevent particle to particle interference in separation. With feed in the range of 8x100 mesh, a pulp density of under 10% solids by weight was found advisable. With coarser feed the pulp density could be carried as high as 15% solids. Time of separation was very rapid. In the case of 4x20-mesh material, separation was effected in 15 to 30 sec; with -10-mesh feed, separation required about 1 to 2 min. SPECIAL EQUIPMENT Since heavy liquids are toxic to varying degrees, all separatory work was carried out in a standard laboratory fume hood. It was noted that complete removal of fumes was not being effected; therefore the hood construction was modified, resulting in a completely satisfactory arrangement for heavy liquid test work. In the interest of safety, details of this fume hood are reported here. Unlike most fumes, heavy liquid fumes tend to settle and flow like water, rather than to rise like a gas. Working on this assumption, a standard water drain was installed in the hood. Across the front of the hood a 1-in. barrier was constructed. In the rear of the hood a false back was installed, with an adjustable sliding door on both the bottom and top of this panel. As shown in Fig. 1, the exhaust fan pulled a vacuum behind the barrier, sucking the heavy fumes from the bottom of the hood. Another addition was the drying box, shown to the right of the hood. This is simply a box covered on top with hardware cloth and connected by a 6-in. inlet to the hood. Sample trays made of fine mesh wire filter screens were found ideal for drying samples. With this arrangement, air flowed completely through the sample and all fumes were drawn into the hood. In use, it was found effective to cover with a

Jan 1, 1963

By John B. Baker, Bernard B. Betty, H. F. Moore

For several years there has been in progress in the Materials Testing Laboratory of the University of Illinois an investigation of creep and fracture of lead and lead alloys. In the course of this investigation it has been shown that the phenomenon of creep occurs in part at the grain boundaries of lead and lead alloys. To study the occurrence of creep and the development of fracture within crystalline grains, two series of tests of single crystals of lead have been carried out. The first of these, a preliminary series, by Mr. Betty, has been described.l,2 The second, pursued by Mr. Baker for his doctoral dissertation, was carried out under the direction of Professor Moore, with the assistance of Prof. G. L. Clark in the X-ray work, and the cooperation and advice of Mr. Betty. This paper is based on the test data obtained in this second series. Single crystals of a very pure commercial lead have been prepared, some of them tested to measure creep, others tested to fracture under long-continued steady load, and still others tested under cycles of repeated tension. An interpretation of the test data of these single-crystal tests is offered, which is a combination of parts of several well-known theories. Specimens The single-crystal specimens were made from a piece of very pure commercial lead sheathing. A spectroscopic analysis of one of the single crystals showed the presence of 0.005 per cent Bi, 0.0001 per cent Cu and 0.0003 per cent Ag. Preparation.—The Bridgman method of casting single-crystal specimens was used.3 The specimens were cast to the shape and size shown in Fig. 1 (dimensions in Fig. 4c) in a duralumin mold. Molten lead does not stick to duralumin. Fig. 1 shows the mold and the blast flames for heating. After the mold had been heated to the temperature of molten

Jan 1, 1938

By C. S. Matthews, P. Hazebroek, H. Rainbow

It ha been suggested that lormation fractures created by well stimulation treatments will adversely affect sweep-out efficrency in injection operations. Fluid-flow model studies involving vertical fractures of various lengths and fluid systems of various mobility ratios have been carried out to study this subject. In addition, limited data have been obtained on one model containing a horizontal fracture. It was found that relatively long and highly conductive fractures (not generally obtained fracturing operations) were required to affect the sweep-out efficiency substantially. In a given case in the field an approximate distinction can be made between the presence of long conductive fractures and shorter or less conductive ones. This is done with pressure build-up analyses along with data on the relationship of fracture length and conductivity to well productivity. This type analysis shows that usually the fractures induced are either short or of limited conductivity and therefore do not damage sweep-out efficiency. INTRODUCTION Improved well productivity and in-jectivity can frequently be exploited in injection operations. Higher total throughput can yield improved economics. On occasion, the achievement of an increased productivity or injectivity in specific wells can bring about a more uniform sweep of the reservoir. Higher rates can be exploited particularly in water floods of "depleted" reservoirs where a rapid "fill-up" is desired and where low pressures contribute to low well productivity. The creation of fractures local to the wellbore is an excellent means for achieving these objectives. Even though fracturing has been employed in some floods with success,1"3 there still seems to be some reluctance to employ this tool for fear of undue damage to the flood pattern and ultimate recovery. We therefore need to examine the influence which fractures of varying length may have on flood performance and then determine the length of fractures which obtain in the field with conventional fracture treatments. A substantial influence of fractures on the recovery obtained at breakthrough of the injected fluid has been presented by Crawford and Collins for equal fluid mobilities for the line-drive pattern.4,5 In addition, the influence which a fracture has on the production performance after breakthrough and on the ultimate recovery warrants consideration in reaching a conclusion concerning the use of induced fractures in flooding operations. This report presents this type of data for the five-spot injection pattern for several fluid mobilities. In arriving at some conclusion concerning the fracture lengths obtained in field operations we must examine the performance characteristic most affected by the fracture. This is the change in the flow system as reflected in the change in productivity and pressure build-up behavior. A study of these changes is also presented in this report. RESERVOIR ANALOGS The X-ray shadowgraph technique, employing miscible displacement in porous models, has been used in the study of the influence of fractures on pattern sweep-out efficiency. The X-ray shadowgraph procedure is described in detail in an earlier report8. Fractures were represented by leaving the proper portion of the model surface exposed to either injection or production. This assumes the fracture resistance to be negligible compared to that of the formation. Actually the flow resistance in propped fractures obtained in the field is sometimes not negligible so that the results with this model indicate the maximum influence of the fracture. Two types of models were necessary to represent vertical fractures in a five-spot flood. These pattern elements are illustrated in Fig. 1. In studying the influence of the horizontal fracture, only one well spacing length to thickness ratio of 50 was used. The pool unit of a Carter Electric Analyzer was used in studying the influence of fractures on productivity and build-up behavior. The square drainage system of a well was represented by a network of 576 elements of equal volume and resistance. One-fourth of this drainage area was studied as a model unit using a network of 144 condensers and resistors. Vertical fractures were represented by a shunt directed from the well perpendicular to the drainage boundary. Horizontal fractures were represented by a circular shunt. Resistance of a shunt was varied in representing different conductivities for the fractures. FRACTURE DIRECTION AND LENGTH The direction at which a vertical fracture extends into the formation and its length and conductivity influence the sweep behavior. The two

By J. C. Reed, P. J. Shenon

The Elk City district is in north-central Idaho about 60 miles east of Grangeville and near the headwaters of the South Fork of the Clearwater River (Fig. 1). At the height of its boom in the early sixties, Elk City had a population of more than 2000 people, Published estimates of the placer production from the district range from $10,000,000 to $18,500,000. Although the first quartz-vein location was made as early as 1870, very little gold was extracted from quartz ores until after the completion of the American Eagle mill in 1902. Between 1902 and 1932 a total of from $750,000 to $1,000,000 was taken from about six properties. General Geology Distribution of Rocks Banded gneiss (Fig. 2) is the most aburldant bedrock in the Elk City district. It is interbedded with schist and quartzite and ill some places these rocks have been intruded by sills and dikes. Banded gneiss prevails in the western part of the area whereas schist prevails to the southeast. Augen gneiss occurs for the most part as irregular bodies, which lie transverse to the trend of the banded gneiss and schist. It is largely confined to two areas; one of which extends from east of the American Eagle mine westward as far as the Black Pine mine, a total distance of about five miles, and another area of about two square miles in the vicinity of the California-Idaho placer mine. Quartzite is fairly abundant. In addition to the bands of the latter interbedded with gneiss and schist, some large lenses crop out in the southeastern part of the dik-trict near the southern contact of the area underlain by granodiorite. Granodiorite crops out over a large area and extends northeastward

Jan 1, 1935

By P. J. Shenon, J. C. Reed

The Elk City district is in north-central Idaho about 60 miles east of Grangeville and near the headwaters of the South Fork of the Clearwater River (Fig. 1). At the height of its boom in the early sixties, Elk City had a population of more than 2000 people, Published estimates of the placer production from the district range from $10,000,000 to $18,500,000. Although the first quartz-vein location was made as early as 1870, very little gold was extracted from quartz ores until after the completion of the American Eagle mill in 1902. Between 1902 and 1932 a total of from $750,000 to $1,000,000 was taken from about six properties. General Geology Distribution of Rocks Banded gneiss (Fig. 2) is the most aburldant bedrock in the Elk City district. It is interbedded with schist and quartzite and ill some places these rocks have been intruded by sills and dikes. Banded gneiss prevails in the western part of the area whereas schist prevails to the southeast. Augen gneiss occurs for the most part as irregular bodies, which lie transverse to the trend of the banded gneiss and schist. It is largely confined to two areas; one of which extends from east of the American Eagle mine westward as far as the Black Pine mine, a total distance of about five miles, and another area of about two square miles in the vicinity of the California-Idaho placer mine. Quartzite is fairly abundant. In addition to the bands of the latter interbedded with gneiss and schist, some large lenses crop out in the southeastern part of the dik-trict near the southern contact of the area underlain by granodiorite. Granodiorite crops out over a large area and extends northeastward

Jan 1, 1935

The Elk City district is in north-central Idaho about 60 miles east of Grangeville and near the headwaters of the South Fork of the Clearwater River (Fig. 1). At the height of its boom in the early sixties, Elk City had a population of more than 2000 people, Published estimates of the placer production from the district range from $10,000,000 to $18,500,000. Although the first quartz-vein location was made as early as 1870, very little gold was extracted from quartz ores until after the completion of the American Eagle mill in 1902. Between 1902 and 1932 a total of from $750,000 to $1,000,000 was taken from about six properties. General Geology Distribution of Rocks Banded gneiss (Fig. 2) is the most aburldant bedrock in the Elk City district. It is interbedded with schist and quartzite and ill some places these rocks have been intruded by sills and dikes. Banded gneiss prevails in the western part of the area whereas schist prevails to the southeast. Augen gneiss occurs for the most part as irregular bodies, which lie transverse to the trend of the banded gneiss and schist. It is largely confined to two areas; one of which extends from east of the American Eagle mine westward as far as the Black Pine mine, a total distance of about five miles, and another area of about two square miles in the vicinity of the California-Idaho placer mine. Quartzite is fairly abundant. In addition to the bands of the latter interbedded with gneiss and schist, some large lenses crop out in the southeastern part of the dik-trict near the southern contact of the area underlain by granodiorite. Granodiorite crops out over a large area and extends northeastward

Jan 1, 1935

By C. S. Allen

With increased coal production and mechanization of coal mines many transportation problems arise. The main objective is to bring the coal to the tipple or dump it as quickly as possible. Larger and faster haulage locomotives or two locomotives connected in tandem have been adopted to solve the problem. Motor equipment, gears and control systems of locomotives to be placed on these hauls are carefully studied to meet these requirements, by an analysis of motor characteristic curves with the corresponding tractive effort curves, in order to determine the correct load for maximum efficiency and to determine the approximate schedule. Control equipment is usually considered to be the controller and resistance. Sometimes accelerating curves are calculated in order to obtain smooth starting in the least possible time without slipping the wheels. Train control is very important, but why limit this to acceleration ? Deceleratien-or-retardation of the locomotive is a part of the train control and should be given as much consideration as the control for acceleration. Types or Braking Common braking systems for mine locomotives utilize screw-type mechanical brakes, dynamic braking and the air brake. For gathering and haulage locomotives, the srrew-type mechanical brake is regarded as standard. A brake of this kind cannot be applied without much effort and lapse of time. Motormen, like other people, follow the path of least resistance, and therefore have their brakes ready for instant application—which means that the shoes are virtually dragging. Even then, a motorman bucks and plugs the motors to gain time and avoid as much physical effort as possible. "Bucking of motors" consists in turning the reverse cylinder of the controller to parallel position corresponding to the opposite direction of travel while the locomotive is in motion, without applying power from an external source. When this occurs, both motors tend to act as series generators, because the armatures are revolving and there is residual magnetism in the field circuit. Owing to slight differences in motor manufacture, one of these will generate a slightly higher potential and will overcome the generated voltage of the second and tend to drive it as a motor in the reverse Direction.-This action retards the locomotive but is very severe on the segments of the reverse cylinder and on the motor commutators. "Plugging motors" is the application of power to the motors corresponding to the opposite direction of travel. In order to "plug" the motors it is necessary first to "buck,, them (which reverses the connections to the motors) and then to apply power. Theoretically, this should be done only in an emergency, but locomotives in mine service are frequently thus treated., Dynamic braking is retardation of the locomotive by the motors acting as generators, which take no power from the line.

Jan 1, 1942