Search Documents

By H. M. Chance

In almost all coal-fields, the quantity of explosive gases given off by the coal increases as depth is attained, requiring correspondingly enlarged quantities of air to ventilate the workings properly, by diluting and carrying off the gas. Again, with increased depth there is a corresponding increased pressure caused by the weight of the overlying strata. Sandstone or slate, which would form a good roof for a coalbed at a depth of 300 or 400 feet, may be unable to sustain the pressure of 800 or 1000 feet of overlying rock. Hence, in nearly all deep mines, the miner will generally describe the roof as "bad," although the roof-rock may be a firm slate, forming an excellent roof for workings of moderate depth, but unable to stand the pressure resulting from the weight of a great thickness of overlying rock. With increased weight of rock-mass above comes also

Jan 1, 1901

By Fred C. Bond

It sometimes happens that old knowledge is forgotten, or half-forgotten, and its rediscovery is hailed as a great new advance in technology. Autogenous grinding affords such an example. The oldest-or apparently the oldest-commercial application of continuous autogenous grinding on a large scale outside of South Africa occurred at San Juancito, Honduras, where a total of more than two million tons of silver ore were ground autogenously with complete success from 1918 to the early 1940's. The history of the San Juancito silver deposits begins in 1880 when- the New York and Honduras Rosario Mining Co. started mining silver at a rate which soon reached two million ounces of silver annually. In 1912 the Company's first mill, located in the village of San Juancito, was shut down and its equipment transferred to a new cyanide plant. This plant, constructed on a mountainside near the mine, was equipped with tube pebble mills in which Normandy or Danish pebbles were used initially.

Jan 5, 1963

NEW MEMBERS The following list comprises the names of those persons who became members during the period of June 10, 1917, to July 10, 1917. BANKS, LEON MAXWELL Agent 3. Supt., Grant Leasing Co. Metcalf Ariz. BEAUCHAMP, HENRY CLAY : Mine Operator, Sisson, Siskiyou Co., Cal. BOCKING, CHARLES, Asst. Mgr., Butte & Superior ,Mining Co., Rialto Bldg., Butte, Mont. BEYER, HERMAN E., Chief Engr., Condenser Dept., Ingersoll-Rand Co., 11 Broadway, New York, N. Y. BLACK, HERBERT F 1512 Oliver Bldg., Pittsburgh, Pa. BRENNAN, PATRICK J., Gen'l. Supt., Elkhorn Division, Consolidation Coal Co., Jenkins, Ky. BUTNER, DANIEL W., Chem. & Supt., Underground Min., Spanish American Iron Co., Daiquiri, Santiago de Cuba, Cuba. CARLTON, DAVE P Nevada-Douglas Cons. Copper Co., Ludwig, Nev. DE AROZENA, JOE Min. Engr., 321 Preusser St., San Angelo, Texas. DICKIE, CHARLES HERBERT, Pres., Georgia River Min. Co., Duncan, Vancouver Island, B. C., Canada. DOBBINS, WALTER Mill Foreman, Chino Copper Co., Hurley, New Mexico. DRURY, CHARLES W., Asst. Professor of Met., Queen's University, Kingston Out. Canada.

Jan 8, 1917

By N. De Nevers

A calculation method has been developed for carbonated water flooding. This method takes into account the effects of oil viscosity reduction and oil swelling, due to carbon dioxide transferred to the reservoir oil from the carbonated flood water. It shows the effect of changes in carbonation pressure and carbonated water slug size. The method is based on a Buckley-Leverett-type linear flow model. The mathematical approach is similar to that developed by Welge, et al, for enriched gas drives. However, it contains a very important advance over the previous papers in its solution to the problem of injection of a "slug" of carbonated water rather than continuous injection of fluid of constant composition. The method also shows the chromatographic nature of the transport of Co 2 in a carbonated water flood. Sample calculations indicate that viscosity reduction is the most important source of incremental oil recovery. Swelling contributes to a lesser extent. Raising the carbonation pressure increases recovery, but this effect diminishes as pressure is increased. increasing the slug size also increases recovery, but again this effect diminishes as slug size is increased. INTRODUCTION In recent years there has been considerable interest in carbonated water flooding as a secondary recovery method. Several carbonated waterflood field tests are now in progress.1'3 Yet there is no published method for predicting the results of a carbonated water flood. This paper presents a method for predicting the oil recovery for ; carbonated water flood. In a carbonated water flood. a carbonated water slug is injected into the reservoir. Then this slug is driven forward by injecting plain water behind it. The field operator must choose the carbonated water slug size and the CO2:water ratio in the slug. The calculation method presented here shows the effects of both slug size and CO2:water ratio on oil recovery. The calculation assumes that the addition of carbon dioxide to flood water increases the oil recovery by two mechanisms: 1. Carbon dioxide transfers from the flood water to the oil, thereby reducing the viscosity of the oil. At the lower viscosity, the oil flows more readily and is more easily swept out by flood water. 2. The carbon dioxide which transfers to the oil phase causes the oil phase to swell. Assume that the residual oil saturation (volume per cent of pore space) is the same whether the oil is carbonated or not. Then the same volume will contain less stock tank oil if it is carbonated, due to oil swelling. The plain water driving the carbonated water slug forward will strip the CO2 out of this residual oil., causing this oil to shrink. This swelling-followed-by-shrinking leaves behind a lower residual oil saturation than would have been left behind by a plain water flood. Since some oils swell to almost twice their original volume at reasonable CO2 pressures, this effect may be large. Two additional benefits sometimes claimed for carbonated water flooding are: 1. Adding CO2 to flood water greatly increases the water injectivity in some cases.1 (Injectivity = BPD of water injected/ft of sand x differential bottom-hole pressure, psi.) CO2 forms a weak acid in water; injecting carbonated water is, therefore, somewhat like acid treating. If a formation responds to acid treating, it will probably have a higher injectivity for carbonated water than for plain water. Although the increased injectivity increases the profitability of a carbonated water flood over a plain water flood, it does not change the production curve based on total fluid injected. Therefore, the method presented here does not show any effect of increased injectivity. 2. It is claimed in one patent4 that carbon dioxide will react with some constituents of the oil to form detergents. These detergents are expected to increase the oil recovery. There is little data available to support this idea. The calculation method presented here takes no credit for extra oil recovery due to the formation of any such detergents.

Jan 1, 1965

By F. C. Schora, H. P. Meissner

Both a graphical and an analytical technique are presented for calculating stream compositions and temperatures in adiabatic staged systems in which solids travel countercurrently to a gas stream. Such a system might be a tower containing several plates, on each of which the descending solid is fluidized by the rising gas stream. Examples are presented in which chemical reactions occur, including the oxidation of SO, by a solid catalyst and the gaseous reduction of iron oxides. COUNTERCURRENT staged processes involving reactions between solid and gas streams are becoming more common. These operations are generally carried out in a series of beds of fluidized solids, with each bed or "plate" acting as a stage. Fig. 1 is a schematic diagram of such a series of stages located in a column, down through which a solids stream moves from stage to stage counter to a rising gas stream. Typical reactions carried out in such systems are the dehydration of aluminum trihydrate, the calcining of limestone, and the gaseous reduction of iron oxides. Calculation of the performance of these counter-current systems rapidly becomes more complex with increases in the number of stages and in the number of chemical reactions occurring. Calcula-tional procedures for isothermal operations of such systems have been described.4 Actual tower operations, however, are generally adiabatic, and in consequence far from isothermal. The object here is to present both graphical and analytical techniques applicable to such adiabatic towers operating continuously and in steady state. In this introductory discussion, the graphical techniques presented are of the McCabe-Thiele type, rather than of the Pon-chon type. In all the examples presented, it will be assumed that both thermal and chemical equilibrium are attained in each bed. The assumption that the gas and solid streams leaving each bed are at the same temperature as the bed is in accordance with the familiar behavior of actual fluidized solid systems. Chemical equilibrium, on the other hand, is not necessarily attained in any given stage between these two streams, even with deep beds, since reaction rates may be slow. In the last section of this paper, discussion is presented of methods suitable for use when chemical equilibrium is not attained. The adiabatic tower in Fig. 1 has "n" stages numbered from 1 to n, starting with the bottom stage as number 1. In analyzing this tower's performance, it is important to express gas flow rates in terms of a key component or element which remains completely within the gas stream throughout the tower. Similarly, solid flow is best expressed in terms of a key compound or element which remains within the solid phase throughout the tower. Thus, in burning limestone with a hot flue gas, the gas flow might be expressed as G, the pound mols of nitrogen flowing through the tower per unit time, while solid flow might be expressed as S, the pound atoms of calcium in all forms in the solid stream per unit of time. Defined in this way, both G and S are constant throughout the tower. The enthalpy of the gas and solid streams are now best expressed in terms of these key components. That is, the gas stream enthalpy H is expressed as Btu in the total gas per mol of the key component in the gas. Similarly, the solids stream enthalpy h is expressed as Btu in the total solid stream per pound mol (or pound atom) of the key component in this stream.

Jan 1, 1962

By John C. F. Randolph

This establishment being now in full working order, it has seemed of considerable professional interest to collect together, in a concise form, the various points as to its plan, method of dressing, and equipment. The data contained in this paper have been largely drawn from the able paper of E. Kutscher, constrnoting engineer of the works, contained in the Zeitschrift fur Berg-HÜtten-und Salinenwesen im Preussischen Staate, 1873, supplemented by some personal memoranda made while the works were under construction and by memoranda on the works appearing in various German technical papers from their completion up to date. This is probably the largest dressing works in the world devoted to the beneficiation of argentiferous lead ores, and it is doubtful if any establishment for the concentration of mineral of any description can compare with it in size. As showing the final practice adopted in an old and very conservative mining region, in which the concentration of ores has been a matter of constant practice and experiment for a very long period, these works are of peculiar interest. The fact that the Clausthal ores strongly resemble a very large and abundant class of ores found in the United States has always attracted the attention of American mining engineers and mine owners to the methods employed in dressing and smelting them. The study of their methods of concentration of ores has, however, always been full of difficulty,

Jan 1, 1879

By C. H. Jr. Herty

FEW subjects have attracted the attention of metallurgists more than ,oxygen in steel. From the days of Mushet and Ledebur interest in this subject has been increasing, and as additional knowledge has become available, the problem has naturally grown more complex. Instead of using the simple term "oxygen" we now distinguish between iron oxide, silicates of various kinds, oxysulfides, oxygen as gas and oxygen in solid solution in steel. There are five general methods for determining oxides in steel: hydrogen reduction;, vacuum fusion; various wet-extraction methods, including electrolytic methods; methods depending on volatilization of the iron away from the oxides; and metallographic methods. For oxygen in solid steel each of these methods has both advantages and disadvantages. The hydrogen-reduction method is of no use on steels above about 0.20 per cent. carbon;1 furthermore, it gives only FeO and possibly some MnO. The vacuum-fusion method2 is expensive and gives total oxygen, with the exception of some A1203, and does not differentiate between the various oxides in which the oxygen exists. Most of the wet-extraction methods' give only the more insoluble oxides Si02 and A1203, though the iodine method gives MnO to an uncertain degree (information that may be more misleading then no information

Jan 1, 1930

By J. W. Leonard, B. A. Donahue

A method is described for incorporating coal petrography into mining and preparation plant quality control based on conventional analyses. Complete analyses are made of each of the uniform and relatively distinct petrographic bands in a coal face. With this information it is possible to develop petrographic standardization curves. These curves permit diverse coal characteristics to be rapidly monitored by application of a few standard coal tests. Single seam quality control is discussed in this paper. Inquiries continue to be made about coal petrography, and specifically, about whether coal petrography should be applied more extensively in the coal industry. Coal petrography is the study of the distinct physical, optical, and chemical increments which make up the organic rock mixture which we know as coal. Petrography can be applied by any coal company or at any coal mine where conventional coal analytical facilities are available and where additional resources can be allocated for an increased number of determinations. This first paper of a two part series includes (1) a proposed conventional approach to single seam petrography based on the development of petrographic standardization graphs and (2) some informative and supplemental interrelationships involving coal characteristics developed as a result of this research. In the second part of this series, to be published at a later date, those petrographic characteristics of bands taken from many different coal seams located over wide geographic areas which can be closely related to each other will be considered. These findings will be examined looking toward the development of a comprehensive, conventional approach to coal petrography which can be used as a common basis for multi-rank petrographic standardization graphs. Implicit to the understanding of coal petrography is the well established fact1,2 that the individual analyses of distinct petrographic bands often differ widely from the average analysis which is used to characterize a whole coal seam. In fact, a distinct and minor banded increment of coal in a high volatile seam may actually be a medium or low volatile coal with an analysis similar to the average analyses of seams located in distant coal fields. During the mining of coal, much degradation is caused which tends to randomly scatter coal bands. The degraded, scattered, and physically separated constituents of distinct petrographic bands are processed side by side in the coal preparation plant as distinct petrographic fractions with particles grouped according to a narrow size range (which derives in part from common hardness), specific gravity, and-or surface chemistry. Tile data obtained from numerous analyses made on each of the bands of any given coal seam, although diverse, can be readily interrelated. Indeed, these interrelationships can be developed into a series of nomographs or petrographic standardization graphs to serve as a basis for developing a conventional petrographic* program. Thus, by analyzing one property (for example, ash) of a selected petrographic fraction collected or separated from the flow of coal in a preparation plant, it should be possible to estimate the other physical, chemical, and thermal properties of this fraction by referring to the petrographic standardization graphs. It follows that any or all petrographic fractions in the total coal flow originating from a single coal seam can be rapidly monitored for many properties on the basis of a single analysis run on each fraction. In recent years coal petrographic research has concentrated heavily on that phase of this work which involves microscopic reflectance measurements made at many minute and selected points on a coal briquette surface.3,4 Thus, the percentage of the total number of reflectance measurements that fall into each of a consecutive series of arbitrarily chosen reflectance classes are used to characterize coal. This procedure is analagous to using the face of a coal briquette to represent the reflectance characteristics present at the face of a coal seam. Moreover, by analyzing petrographic fractions of known and uniform optical properties it is possible to closely relate reflectance to other coal characteristics. For example, reflectance has long been known to be related to such

Jan 1, 1968

By A Allen, J. A. Garcia

The large increase in the wages of mine workers makes it imperative that all factors tending to limit production per miner be eliminated, if possible. The trolley and storage-battery locomotive, mining machine, hoisting engine, mining system, etc., have increased the possible output per man. But this output is still limited by the capacity of the hoisting engine and cable and by the size of the mine car. The superiority of skip hoisting in metal mining is shown by its almost universal adoption. By varying the size of skip and the rope speed, any desired tonnage can be secured and, since frequently only one kind of material is handled and breakage is unimportant, the loading of the skips can be easily and cheaply effected from bins into which the cars are dumped. The cars may then be designed to fit the conditions in the mine instead of being a compromise between hoisting and mining conditions, very likely suiting neither. In coal mines, the usual practice has been to hoist the car to the surface, either on platform or self-dumping cages. Of late years the number of skip-hoisting plants in coal mines has been rapidly increasing, but there is more or less inertia to overcome in establishing so radical a change in practice; also the earlier skip operations were not uniformly successful. As a result, it became evident that metal-mining practice would require radical modification before skip hoisting could be successfully used in coal mining. Objections to Skip Hoisting Breakage Except where coal is used for coking, or for other purposes whcre breakage is unimportant, breakage of the coal is vitally important all the way from the face to the railroad car. The average selling price is seriously reduced when the percentage of screenings is increased. Following metal-mining practice exactly, the coal would be dumped into a deep pocket, cut off into a skip load by a measuring hopper or other means, dumped into a deep, narrow skip, and dropped into a bin at the top, all of which would contribute to excessive breakage.

Jan 1, 1922

By S. Stutz

Three years ago, at the Philadelphia meeting, in February, 1881, the author had the pleasure of presenting to the Institute a paper on coal-washing machinery.* Since that time many new machines, with important improvements and labor-saving apparatus, have been introduced, the construction and description of which may be of interest to some of the members of the Institute. By referring to the above-mentioned paper, and more especially to Plate IV., representing a vertical section of a coal-washer, it will be noticed that the bottom of the plunger-box B is made level or horizontal, and supports a spring-buffer F for the purpose of limiting the down-stroke of the plunger P and receiving the impacts of the latter. Althongh the construction of the box, in view of these impacts, received from the start the proper attention (the bottom of the chamber 3 being made of three thicknesses of 3-inch planks, resting on 6-inch sqnare columns), yet, through careless working of the machinery, without the necessary water in the box, it proved in several instances not strong enough, and had to be changed. To prevent such interruptions in future, it became necessary to devise some means for relieving the machine from the impacts of the plunger altogether. This has been accomplished by the arrangement shown upon Plate I. of this paper, representing a new waesher; and not only has the difficulty been overcome, but also sorne other advantages have been obtained, as will be seen further on. The compartments +, A' of the separator-box have been set upon heavy cast-iron brackets B, leaving sufficient space below the bottom for the buffer F and the sediment-valve K. By means of the plunger-rod 6 passing through the stuffing-box s to the outside, and provided at its lower end with a shoe a, the impacts of the plunger are now transmitted from the buffer F directly to the foundation. At the same time a better guide for the plunger P in its up and down movement has been obtained. The plunger of the former machine had only the guide I and the yoke Y, whereas the new machine has an additional guide in the stuffing-box s, thus preventing wear and friction of the plunger against the lining of the box. Further-

Jan 1, 1884

By Robert Warner

WHEN a new mine is opened, and often when an operating mine must adapt itself to physical or economic changes, a mining system must be selected in complete detail. In the past the plan chosen was usually the product of the local staff alone, however limited the training and experi-ence of that staff might be, which often resulted in the introduction of methods that were familiar to the staff, but not so well suited to the con-ditions as others unknown to the local men. A new management, noting the difficulties with the existing layout, might make modifications or complete changes, so that many mines in their history have seen a whole series of mining systems, each somewhat laboriously grafted on to its predecessor. This should not be interpreted as a condemnation of the older staffs for sticking to the tried systems, such as open square-sets in the early days at the Homestake, because they knew it would work after a fashion, nor does the statement apply to the technically trained, and usually broadly experienced staffs of most present-day properties. The older miners did not have the variety of tools and methods, nor the present freedom of transfer of information as to what the other man is doing, and so did the best they could under the circumstances. Finally, the higher grade of the ores made the choice less vital. The ever-increasing need to mine low-grade orebodies, with a fixed or even lower price for the metal produced, has caused an increasing need for low-cost mining. In most new mines this has simplified the problem of selection by eliminating from consideration all of the high-cost systems, but it has also complicated the choice by the necessity for refinement in detail and a close adjustment of the plan selected to all the conditions at the property. In these low-cost problems any textbook division of mining systems as applied to "beds, veins or masses" avails little as a guide. It should be realized at the outset that to' be successful under modern competitive conditions a system of mining must be worked out with elaborate detail, with careful time scheduling and control of the various elemental operations, and that after it is introduced it must be run with a large amount of technical direction.

Jan 1, 1933

By Robert K. Warner

When a new mine is opened, and often when an operating mine must adapt itself to physical or economic changes, a mining system must be selected in complete detail. In the past the plan chosen was usually the product of the local staff alone, however limited the training and experience of that staff might be, which often resulted in the introduction of methods that were familiar to the staff, but not so well suited to the conditions as others unknown to the local men. A new management, noting the difficulties with the existing layout, might make modifications or complete changes, so that many mines in their history have seen a whole series of mining systems, each somewhat laboriously grafted on to its predecessor. This should not be interpreted as a condemnation of the older staffs for sticking to the tried systems, such as open square-sets in the early days at the Homestake, because they knew it would work after a fashion, nor does the statement apply to the technically trained, and usually broadly experienced staffs of most present-day properties. The older miners did not have the variety of tools and methods, nor the present freedom of transfer of information as to what the other man is doing, and so did the best they could under the circumstances. Finally, the higher grade of the ores made the choice less vital. The ever-increasing need to mine low-grade orebodies, with a fixed or even lower price for the metal produced, has caused an increasing need for low-cost mining. In most new mines this has simplified the problem of selection by eliminating from consideration all of the high-cost systems, but it has also complicated the choice by the necessity for refinement in detail and a close adjustment of the plan selected to all the conditions at the property. In these low-cost problems any textbook division of mining systems as applied to "beds, veins or masses" avails little as a guide. It should be realized at the outset that to be successful under modern competitive conditions a system of mining must be worked out with elaborate detail, with careful time scheduling and control of the various elemental operations, and that after it is introduced it must be run with a large amount of technical direction.

Jan 1, 1934

By J. W. Leomrd, B. A. Donahue

Results of research are presented examining the extent to which the analytical characteristics of the relatively distinct coal bands from a variety of coal seams can be related to each other. This paper dis-cusses an approach for developing a practical coal petrographic quality control program based on conventional analyses, most of which is part of the standard A.S.T.M. procedure. The work is a final follow-up to Part I of this series which was prepared by the authors as an approach to applying conventional coal petrography to single coal seams. Recent published work by the authors entitled Petrography for Coal Mining and Coal Prepration: Part I dealt with interrelating various chemical and physical properties of coal1 measured using conventional analyses made on distinct petrographic bands taken from single coal seams. Since most coal production facilities process coal from a single coal seam or from very closely related coal seams in the same area,2 emphasis on interrelating the properties within a single seam appeared appropriate. The distinct petrographic bands were analyzed on the assumption that such differentiated data would be more representative of a heterogeneous coal seam than the single analytical value commonly used to characterize each property of an entire seam.34 Effort was directed at demonstrating the extent to which the interrelated chemical and physical properties 5,6 could be developed into nomographs or petrographic standardization graphs. Thus, one analysis, determined on a series of petrographic fractions separated from a single sample, was used to estimate numerous other properties in each fraction by referring to the previously established petrographic standardization graphs. This conventional approach to coal petrography was undertaken as a suggested feasible means by which a few coal analyses could be employed to develope a more penetrating knowledge of the properties of coal from any given seam in order to monitor more extensively its performance at the point of utilization. Such procedures can support development of the type of in- formation commonly sought through automated testing and through the use of computers.7 The broad knowledge which can be developed through these procedures is intended for application in the generation of an analytical profile or broad characterization of coal. These estimates were not intended as replacements for individual coal analytical tests. In this expanded second part of the research program, distinct petrographic bands from nine coal seams in the Central Appalachian Region were physically and chemically analyzed to elucidate the extent to which this concept of conventional petrography could be broadened for application to numerous coal seams. In presenting this second phase of work, the relationships developed are presented individually and not in a connecting series of nomographs or petrographic standardization graphs as in the previous work, thus leaving open the combinations of possibilities to individual interpretation and application. MATERIAL AND EXPERIMENTAL WORK Nine coal seams, representing a wide range of rank, from the Central Appalachian coal fields were used in this study. The distinct petrographic bands from the Kittanning, Pond Creek, Jawbone, Tiller, Poca-hontas No. 3, No. 2 Gas, Eagle, Winifrede, and Pittsburgh coal seams were separated by carefully removing a portion of each band at the face of the seam. The following were determined: ash, sulfur, free swelling index, heating value, bulk specific gravity, volatile matter, Hardgrove Grindability Index, and Gieseler Plastometer measurements. Determinations, where procedures were available, were carried out using ASTM standard procedures.8 Bulk specific gravity was determined using a kerosene volume displacement procedure modified from a method applied by Headlee and McClelland of the West Virginia Geological survey,9 Those bands with a bulk specific gravity greater than 1.60, which is generally above the practical specific gravity cleaning range of bituminous coals, were excluded and no analyses were performed. Much of the initial organization of this second phase of work was developed through the extensive use of a computerized statistical monitoring program (see Ref. 4). However, in order to achieve the closest possible interpretation of results, the final organization of data proceeded mainly from exhaustive trial

Jan 1, 1968

By John C. Smock

The ten years, 1879 to 1888, inclusive, have been notable in the history of iron-making for the great rise during the latter part of 1879 and the earlier half of 1880; for the maximum of production in 1882 ; for the gradual decline and the reduced product through 1883,1884 and nearly to the end of 1885; then, for the recovery through- 1886 and 1887; and the extraordinary outputs of our iron furnaces during the last three years. The price of pig-iron might be taken as an index to the condition of the iron-mining industry, and if represented graphically, they would shorn approximately parallel curves. The mining industry cannot always respond quickly to a rise in price and an increased demand for ore; nor can its production drop simultaneously with sudden falls in price of iron and of ore. Hence, the irregularities of the one are not reflected in the other. The statistics of the iron mines collected by the United States census, for the year ending June 30, 1880, exhibit admirably their condition at that time. The reports received from mine owners and managers, of the production for the year 1888, furnish the basis for a comparison and supply data for some notes on the changes in the iron-mining industry in New York which have taken place in this period of time. The iron-ores of New York may be grouped in the following districts: I. The Highlands of the Hudson (magnetites). II. The Lake Champlain and Adirondack Region (magnetites). III. St. Lawrence and Jefferson Counties (red hematites). IV. Clinton and Wayne Counties (fossil-ores of the Clinton Group). V. Dutchess and Colnmbia Counties (limonites). VI. The Hudson River (carbonates). VII. Staten Island (limonites). The ores of the first and second districts, as enumerated, are almost exclusively magnetites; those of the third and fourth are hematites;

Jan 1, 1889

By G. B. Gould

FROM the very inception of the price-control experiment in the bituminous-coal industry, the problem of price differentials was of major importance. In fact, assuming that there will be no legal or Govern- mental obstacles to price control, the successful maintenance of the present or any other method designed to control bituminous-coal prices will depend upon the discovery of some satisfactory way to determine these differentials in price, among: individual mines and groups of mines. Being of organic origin, bituminous coal is a commodity that presents an almost infinite variety of qualities. It is inevitable, therefore, that a work- able price-control system must attempt

Jan 1, 1935

By W. O. Hotchkiss

Rock exposures are usually a very small part of the surface area in any mining district and the prospector and geologist must base their deductions as to the area, extent, and structure of various formations upon exposures that seldom form 5 per cent. of the area studied. Most often, outcrops form less than 1 per cent. of an area, so that exploration for mineralized contacts or mineral-bearing formations necessitates drilling, test pitting or tunneling, shaft sinking, and other underground work. In these days of high costs any method that will give definite facts regarding rock? obscured by soil or other material should be used to the greatest possible extent. In the early days of the Lake Superior iron districts, mines were located in the few places where ore was present in outcrops. Later, larger orebodies have been found, in depressions, obscured by soil and other foreign material. Mineralized rocks are oftentimes more weathered, softer, and more easily eroded than unmineralized rocks. It is quite natural, therefore, to expect that such orebodies (particularly where large enough to influence erosion in former physiographic conditions) should lie in depressions and be obscured by later debris. It is not difficult to believe that the history of the development of Lake Superior iron mining may be duplicated in other mining districts, that even larger orebodies than those first mined may be found in areas where the rock exposures, which led to original discoveries, are few or lacking. The chief properties of rocks that can manifest themselves through an obscuring cover are magnetism, electrical effects, radio-activity, gravity, and sound transmission. All of these have been used, to a small extent, to tell us a few things about what lies below the surface that we could not otherwise determine, but none has been used so long and so widely as

Jan 1, 1923

By W. O. Hotchkiss

Rock exposures are usually a very small part of the surface area in any mining district and the prospector and geologist must base their deductions as to the area, extent, and structure of various formations upon exposures that seldom form 5 per cent. of the area studied. Most often, outcrops form less than 1 per cent. of an area, so that exploration for mineralized contacts or mineral-bearing formations necessitates drilling, test pitting or tunneling, shaft sinking, and other underground work. In these days of high costs any method that will give definite facts regarding rock? obscured by soil or other material should be used to the greatest possible extent. In the early days of the Lake Superior iron districts, mines were located in the few places where ore was present in outcrops. Later, larger orebodies have been found, in depressions, obscured by soil and other foreign material. Mineralized rocks are oftentimes more weathered, softer, and more easily eroded than unmineralized rocks. It is quite natural, therefore, to expect that such orebodies (particularly where large enough to influence erosion in former physiographic conditions) should lie in depressions and be obscured by later debris. It is not difficult to believe that the history of the development of Lake Superior iron mining may be duplicated in other mining districts, that even larger orebodies than those first mined may be found in areas where the rock exposures, which led to original discoveries, are few or lacking. The chief properties of rocks that can manifest themselves through an obscuring cover are magnetism, electrical effects, radio-activity, gravity, and sound transmission. All of these have been used, to a small extent, to tell us a few things about what lies below the surface that we could not otherwise determine, but none has been used so long and so widely as

Jan 1, 1923

By Jasper L. Stuckey

GEOGRAPHICALLY, North Carolina consists of three divisions, the coastal plain on the east, the piedmont plateau in the center, and the Appalachian mountain region on the west. Geologically, the State may be divided into two main divisions, an eastern or coastal plain region, and a western or piedmont plateau and mountain region. The eastern region is underlain with unconsolidated sands, clays, marls, and shell limestones varying in age from Cretaceous to Recent. The western region is, in general, underlain with gneisses, schists, slates, sheared volcanics, and igneous intrusives of Pre-Cambrian age. In the mountain and upper piedmont portion of the western region are several areas of irregularly metamorphosed sediments of early Paleozoic age. Throughout the piedmont plateau and a part of the mountain portion of the western region, important areas are underlain with igneous intrusives of late Carboniferous age. Along the eastern edge of the piedmont plateau are two narrow belts, trending northeast-southwest, underlain with sediments of upper Triassic age. Although North Carolina contains a

Jan 1, 1947

By Augustus Locke, Edward H. Perry

In the exploration of a copper deposit by drilling, obvious advantages are to be gained from a distinction between primary and secondary ore.' Perhaps the chief of these is the aid which such a distinction renders in determining where a given hole should stop. The copper assay, often a sufficient guide, cannot always be exclusively relied upon. Primary ores may extend downward indefinitely and may fluctuate in value independently of depth: if primary ores are consistently lean for a considerable vertical distance, there is little reason to expect that, still deeper, they will increase to the commercial grade; on the other hand, rich primary ores may persist uninterruptedly downward or may come in again below a lean interval. Secondary ores, however, have a comparatively limited vertical extent; in a large way enrichment decreases with depth and finally gives out. It follows then, that when a hole descends from profitable ore into ore of less than the commercial minimum, the practical significance of the situation depends upon whether this decrease results from a decrease in secondary enrichment or is a variation in primary content: if the copper of the ore passed through has been chiefly secondary, little is gained in the average case by extending the hole much below the point at which the commercial limit is reached; but, when copper is chiefly primary, due weight must be given to the possibility that, still deeper, the ore may again improve. The distinction between primary and secondary ore may of course be effected through an examination of the drillings. It has been found, however, to be facilitated by curves made by plotting assays against

Jan 1, 1916

By Edward Salisbury Dana

THE remarkable advance in the Science of Mineralogy, during the years that have elapsed since this Text-Book was first issued in 1877, has made it necessary, in the preparation of a new edition, to rewrite the whole as well as to add much new matter and many new illustrations. The work being designed chiefly to meet the wants of class or private instruction, this object has at once determined the choice of topics discussed, the order and fullness of treatment and the method of presentation. In the chapter on. Crystallography, the different types of crystal forms are described under the now accepted thirty-two groups classed according to their symmetry. The names given to these groups are based, so far as possible, upon the characteristic form of each, and are intended also to suggest the terms formerly applied in accordance with the principles of hemihedrism. The order adopted is that which alone seems suited to the demands of the elementary student, the special and mathematically simple groups of the isometric system being described first. Especial prominence is given to the "normal group" under the successive systems, that is, to the group which is relatively of most common occurrence and which shows the highest degree of symmetry. The methods of Miller are followed as regards the indices of the different forms and the mathematical calculations. In the chapters on Physical and Chemical Mineralogy, the plan of the former edition is retained of presenting somewhat fully the elementary prin¬ciples of the science upon which the mineral characters depend; this is par¬ticularly true in the department of Optics. The effort has been made to give the student the means of becoming practically familiar with all the modern methods of investigation now commonly applied. Especial attention is, therefore, given to the optical properties of crystals as revealed by the micro¬scope. Further, frequent references are introduced to important papers on the different subjects discussed, in order to direct the student's attention to the original literature. The Descriptive part of the volume is essentially an abridgment of the Sixth Edition of Dana's System of Mineralogy, prepared by the author (1892). To this work (and future Appendices) the student is, therefore, referred for fuller descriptions of the crystallographic and optical properties of species, for analyses, lists of localities, etc.; also for the authorities for data here quoted. In certain directions, however, the work has been expanded when the interests

Jan 1, 1922