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By Dell H. Adams

COAL EXPLORATION Coal exploration may be defined as the acquisition of data necessary to define and acquire a block of coal which can be mined at a profit. Unlike ore minerals, coal resources are widespread and relatively abundant with supply exceeding demand in almost every case. Thus simple discovery of coal is generally not enough. The chemical and physical variability of individual coal seams, the capital intensive nature of coal mine development, and the changing patterns of utilization require that a multiphase, three-dimensional evaluation be made of each potential reserve. Factors which must be investigated include not only the quantity and quality of the coal but also the geologic, hydrologic, and engineering characteristics of the seam and its surrounding strata. Acquisition of property to provide a secure base for exploration and mine development is equal in importance to the geologic and engineering programs. The successful development of a coal reserve requires that control of coal and, in the case of a strip mine, the surface be in the form of contiguous blocks of sufficient size to support mining. PHASES OF EXPLORATION The high capital risks of coal exploration and land acquisition dictate that a multiphase program be utilized to minimize initial risk. In such a program, phased development of the data insures that each increase in capital expenditures will be justified by a corresponding increase in the level of confidence in the ultimate success of the project. Each phase is designed to provide sufficient data and property control to facilitate the decision whether to proceed to the next phase of development or to discontinue the program (Table 1). The first phase of a typical exploration program consists of a pre-

Jan 1, 1981

By Hans Lundberg

IN ORDER to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. FIG. 1.-FLOW OF CURRENT IN AND AROUND A CONDUCTING BODY. For its operation, electrical prospecting mainly, depends on the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of. schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1).

Jan 1, 1928

By Thomas C. Atchison

An understanding of the physical processes involved in breaking rock with explosives will lead to better blasting techniques. In this chapter known rock breakage principles will be outlined, some conjectural ideas will be discussed, and areas needing further study will be pointed out. The principles outlined will serve as a basis for the design of blasting rounds described in the following chapter. 7.2-1. Factors Important to Rock Fragmentation. The efficacy of explosives as tools for rock fragmentation lies in their ability to deliver almost instantaneously large amounts of energy to a limited portion of the rock. When an explosive charge is detonated in a drill hole, its energy is released in a very small fraction of a second in the form of gas at extremely high pressure and temperature. The mechanics of the transfer of this energy to the rock and the resulting breakage are complex and not completely understood. Factors that have been identified as important to the fragmentation process may be grouped in three categories: explosive parameters, charge loading parameters, and rock parameters. EXPLOSIVE PARAMETERS. Explosive parameters known to influence breakage are density, detonation velocity, detonation impedance, detonation pressure, gas volume, and available energy. Detonation pressure is probably the best indicator of an explosive's ability to break solid hard rock. Detonation pressure is roughly proportional to the product of density and the square of the detonation velocity. The relative ability of different explosives to transmit their pressure to stress in a given rock is function of their detonation impedances. Detonation impedance is the product of density and detonation velocity. The volume of gas released in the explosive detonation undoubtedly is of importance, at least in the later stages of breakage, and is probably

Jan 1, 1968

By S. F. Emmons

Geological Sketch.-The rhyolite area near Silver Cliff includes what may be called the Silver Cliff plateau, with Round mountain and the intervening valley. The plateau is about 2 miles long and 1 mile wide. From its northern part rise the White hills, which have no special topographic importance, as their highest point is only 400 ft. above the northern edge of the rhyolite mass. Round mountain, on the other hand, is a quite sharply pointed conical hill, so steep-sided as to constitute an important topographic feature, although its elevation above the plains around it is barely 700 ft. The summit of Round mountain is dense banded rhyolite, with steep, irregular clip; the southern end is breccia containing fragments of the banded rock. There are slight exposures of glassy forms of rhyolite on the lower slopes. On the east, the Archaean rocks extend half-way up the side of the mountain, and the contact between them and the rhyolite is vertical, or dips steeply to the west. This mountain is supposed to be at the vent from which the rhyolite of the plateau was poured out. The Silver Cliff plateau occupies the site of a former basin, in which at one time there was probably a lake. At the time of the rhyolitic outburst of the Rosita hills there was a local eruption of the same character in this region, commencing with showers of volcanic ash and of rock-fragments, which filled the lake and built tip about it hills which have since been removed in great measure by erosion. At present the southern half of the plateau is capped by solid lava to a depth in places of 150 ft. The cliff of blackened rhyolite on the southern edge, where the main discovery of ore was made, is from 30 to 50 ft.

Jan 1, 1913

By Wilbur T. Stuart

TO assist the mining industry in attacking problems of water control, the U. S. Geological Survey has begun a program of research in mining hydrology. In certain fundamental respects water control is similar to development of water supplies from wells or to the drainage of agricultural lands, as many of the tools developed in recent years for quantitative ground-water problems are applicable, with modification, to mine-water problems. In 1952 a 30-day pumping test conducted jointly by the Eureka Corp. Ltd. and the Defense Minerals Exploration Agency provided an opportunity to gain knowledge concerning water movements around a flooded mine shaft. The methods of analyzing the data may be used as a guide for the evaluation of similar problems elsewhere. The Fad shaft of the Eureka Corp. is on Ruby Hill, 1 1/2 miles west of Eureka, Nev. The shaft was completed at a depth of 2465 ft in November 1947 at a site adjacent to the downfaulted block in which the ore was found. As the drift on the 2250 level progressed toward the ore zone, a large flow of water was encountered after the Martin fault was intersected. This flow exceeded the installed pump capacity, and an unsuccessful attempt to recover the shaft and the 2250 level was made in 1948.1, 2 Geology and Hydrology: The complex structure of Ruby Hill is that of an anticline broken first by thrust faulting and later by normal faults. The present orebody comprises several mineralized zones within a block of the Eldorado limestone of middle Cambrian age which was downfaulted 1400 to 1600 ft, and it may be related to a similar body mined at a higher level south of the Ruby Hill fault. At the depth of the largest zone of ore the block is roughly rectangular in shape, about 1000 ft wide and 1500 ft long, and dips about 30" NE, see Fig. 1. It is apparently bounded on the south by the Ruby Hill fault, on the east by the Jackson fault, on the north by the Martin fault, and the west by the Bowman fault. Within the block, but between the Ruby Hill and the Martin faults, are the Office and Adams Hills faults; west of the block and the Bowman fault are the Albion and Spring Valley faults. There are many conflicting reports concerning the water-yielding characteristics of the Eldorado limestone and the condition of the fault zones, that is, whether they are open or tight. However, the diamond-drill records indicate that open spaces as much as 2 or 3 ft across were encountered, and considerable cementing and lining of holes was necessary to maintain circulation of drilling fluid. There is also evidence that the Eldorado limestone was cavernous where it was mined in the early days south of the Ruby Hill fault. At the site of the Fad shaft the formations encountered from the surface down included the Pogonip limestone, Dunderberg shale, Hamburg limestone, and Secret Canyon shale. These formations did not yield large quantities of water to the shaft. The Pogonip limestone, which appears to be permeable and might yield water elsewhere, is above the water table in the vicinity of the shaft. The Secret Canyon shale, immediately overlying the Eldorado in some places but in most places separated from it by the Geddes limestone,3 is apparently tight and does not transmit water. During the 30-day test period the shale briefly confined the water in the underlying formations so that artesian conditions were observed in drillholes E and F, which are cased into the Eldorado limestone, whereas unconfined conditions were observed in drillholes B, C, and D, which were open to the shale. The Geddes limestone, which normally lies between the Secret Canyon shale and the Eldorado limestone, was not encountered in the Fad shaft. The Geddes, a flaggy, fractured limestone, is reported capable of yielding large volumes of water. Water stored in the interstices of this thin-bedded limestone within the Ruby Hill fault zone on the 1200 level of the Locan shaft drowned the pumps in 1923 when the Richmond-Eureka Mining Co. attempted to explore the area along the fault. Eldorado limestone was not encountered in the Fad shaft. In the ore-block area the Eldorado limestone was not entirely offset from other water-yielding formations by movement along the Bowman fault; therefore it may be hydraulically connected with the other formations. Adjacent to the Ruby Hill, Jackson, and Martin faults, the Eldorado lies in contact with other possible water-yielding formations. One of these, the Prospect Mountain quartzite, is separated from the Eldorado by thin, sheared, and broken beds of the Geddes within the Ruby Hill fault zone. A limited examination by the author of the Prospect Mountain quartzite in the Richmond mine at a higher level and south of the Ruby Hill fault indicates that the quartzite is poorly permeable. The monzonite mass south of the quartzite would be a further barrier to the flow of water. The poor permeability of this area is substantiated by records of levels at which water was encountered south of the Ruby Hill fault. In view of the normally low rate of ground-water recharge, if this desert area had been permeable, water levels could not have been maintained at altitudes of many hundred feet above the present water table west and north of Ruby Hill. Thus the ore-bearing block of Eldorado limestone is in contact with possible water-yielding rocks on at least two sides, and if the fault zones are possible conduits for water circulation the geologic and hydrologic conditions are suitable for the infinite-aquifer type of analysis as used and modified here. History of Pumping: During sinking of the Fad shaft a maximum pumping rate of 1500 gpm kept the shaft dewatered sufficiently, but in March 1948, after the 2250 level drift passed through the Martin fault into the Eldorado limestone, the pumps and shaft were flooded. Subsequently additional pump-

Jan 1, 1956

By Francis M. Walters

THE problem of making iron-manganese alloys of scientific purity is a rather difficult one. They cannot be prepared in air because of the readiness with which the metals oxidize at the temperature of melting; and they cannot be prepared in vacuum because of the, high vapor pressure-of- manganese. The very property of: manganese which permits it to be purified interferes with the utilization of the best method of making pure alloys. Accordingly, it is necessary to use a gas atmosphere which will not affect the-properties of the alloys. The gases available for the purposes are hydrogen; helium and argon. Nitrogen forms intermetallic compounds with manganese very readily. Hydrogen, while valuable as a deoxidizer and having the advantage of being comparatively cheap, is explosive over a wide range and, has a rather high thermal conductivity. Helium is reported as, costing little but is difficult to secure at a reasonable price and also has a conductivity nearly as high as hydrogen. Since argon has a sufficiently low thermal conductivity, it has been selected for use in one induction furnace for melting, under a controlled, gas atmosphere, in spite of its cost, which is so high (70 cents to $1.50 per cubic foot) that it must be stored and purified.. Such a gas atmosphere-as argon makes necessary the use of the, high-frequency induction method of heating. This involves, a non-metallic container for the gas; .which is most conveniently of fused quartz or glass. The next

Jan 1, 1929

By AIME AIME

At the Annual Meeting of the Institute, February, 1908, the following amendments to the Constitution were proposed for action at a future business meeting (see Trans., XXXIX, xxvii) To Art. II. After the first sentence of this Article, add the following sentence « These classes may be subdivided by the Council, according to profession, length of membership, nationality, or other conditions not inconsistent with the provisions of this article." To Art. III. In the first line, substitute " fifteen " for "ten " dollars. At the Annual Meeting of February, 1909, action upon these amendments was postponed to the next business meeting (see Bulletin No. 27, March, 1909, p. xiv). Of these two amendments, the first has been withdrawn, as unnecessary-the subdivision thereby authorized being already practicable without such amendment. The second amendment will be acted upon at the next Annual Meeting, February 15, 1910, and the Secretary has been instructed to call the attention of members to the subject in such a way as to secure a general vote upon it. A special circular, now being prepared by the Secretary, will shortly be sent to all members. Year Book of the Institute. The Year Book of the Institute for 1910 is sent to all members and associates with this issue of the Bulletin. In addition to the lists of members enrolled Jan. 1, 1910, and arranged both alphabetically and geographically, this annual contains lists of officers, council, corporation, past officers, meetings, and notices concerning publications; also the constitution and by-laws of the Institute, and blank forms for proposal of mem-

Jan 1, 1910

Jan 1, 1898

Map

Jan 1, 1938

By A. W. Asman

An analysis is made of three different types of section production units that represent the manner in which most of the nation's bituminous coal is produced. The general delays and production characteristics of these sections are presented along with a method for evaluating section performance based on actual and theoretical production characteristics.

Jan 9, 1951

By Rana P. Singh

Electrolytic metal reduction operatios in both aqueous and molten salt electrolytes are being studied by digital signal analysis. The purpose is to determine the relationship between the physical processes occurring in the cell and the frequency spectrum of the cell's fluctuating electrical parameters. The fast Fourier transform of cell voltage (in galvanostatic operations) or cell current (in potentiostatic operations) is computed on-line in real time for the electrorefining of zinc in aqueous acid chloride solutions.

Jan 1, 1984

By SME

A regular feature of the December issue is the abstracts of graduate theses in the mineral industry field presented during the preceding year. The following abstracts were submitted for this second article in the series.

Jan 1, 1976

By R. W. Smith, R. J. Charles

Fractions of glass particles in the size range 0.5 to 5.0 µ were prepared by an elutriator that operates in a centrifugal field. Although mean sizes of commercially graded abrasive powders were ten times greater than those of samples prepared by the elutriator, frequency size plots for elutriator samples compared favorably. Efficiency of separation was low and amounts of material recovered by the elutriator were small, but the method should find use in preparation of small amounts of sized materials for laboratory investigations.

Aug 1, 1956

By Richard P. Schoemaker

Introduction In underground mining operations the effects of economic and mechanical factors on costs and profits can readily be appreciated and can perhaps be expressed in exact figures and percentages. Less apparent, but frequently more important, is the influence of physical stress. Stress causes failure of supports, collapse of openings, rockbursts, and other damage which directly affects the costs of maintenance, and also to a certain extent the accident rate. Stress can, however, if properly directed, be an aid to mining operations. The caving methods in metal mining and the long-wall method in coal mining are well-known examples. In large-scale mining operations it is almost impossible to neglect stress-control. A better understanding of the mechanism of rock pressure and the application of its principles to practical mining will inevitably lead to a reduction in operating costs. Many theories have been advanced to give the mining engineer a practical outline for stress-control but, although today most experts agree upon the principles of stress distribution around underground openings, there is still no generally accepted theory that explains all phenomena. The main reasons for this incomplete understanding of the problem are the lack of accurate knowledge of the physical properties of rocks under field conditions, and the great complexity of these conditions due to in-homogeneity of the rock, stratification, tectonic disturbances, and many other unknown factors. The research on the rock pressure problems has, however, yielded some valuable facts which, expressed in practical terms, and adapted to local conditions, may become a valuable aid for mining operations. The purpose of this paper is to give a review of the most important accomplishments of this research with respect to the stress phenomena around small underground openings, such as tunnels and shafts, so as to arrive at an outline of the problem as it stands today. Special emphasis is placed on a new theory by the German mining engineer, Rudolf Fenner, which has never before been published or discussed in English. The Pressure Dome Theory The formation of a dome-shaped space around underground openings is well known from field observations. When openings are made in rock under stress, the rock in the top of the openings will often fail, and caving will continue until the openings have assumed a dome-shaped form, after which equilibrium apparently is re-established. The oldest theory which attempted to explain the phenomenon is the "beam" theory, which postulates that the hanging wall consists of stratified measures that behave as independent beams with fixed ends and a uniformly distributed load. When failure of the beam occurs, inward shearing at the ends will cause the formation of a dome-shaped space. The pressure dome theory, which more or less evolved from the beam theory, merely

Jan 1, 1949

By John D. Price

COAL blending, in the preparation of coal before coke making, is so commonly practiced as to be almost universal. But the reasons underlying this practice, the benefits resulting from it, and the materials used in blending vary widely. This paper will outline the various phases of the subject and present information which may be correlated with work that has been done elsewhere. It will deal entirely with work done on the high-volatile coking coals of the western part of the United States, special emphasis being given to the coals of Colorado and Utah.

Jan 7, 1953

By J. R. Cooper, A. Bruynesteyn

The final results of the operation of the Cananea test dumps are discussed. Scale-up factors between shake-flask tests, column tests and the large test dumps are established for the Cananea ore. The formation of clay layers, which formed inside the dumps and markedly affected extraction, as well as secondary enrichment, are discussed.

Jan 1, 1974

By P. C. Hodges

While there is very little romance connected with the operation of a stone quarry, yet to those who have participated in the growth and development of a business that has been a pioneer in its field and that has been in continual operation two-thirds of a century there is bound to be a background of experience, which if properly capitalized, brings progress as well as satisfaction in its accomplishment. The simple methods of drilling and blasting limestone and loading on to railroad cars everything that remained on a stone fork and leaving

Jan 1, 1936

By P. C. Hodges

While there is very little romance connected with the operation of a stone quarry, yet to those who have participated in the growth and development of a business that has been a pioneer in its field and that has been in continual operation two-thirds of a century there is bound to be a background of experience, which if properly capitalized, brings progress as well as satisfaction in its accomplishment. The simple methods of drilling and blasting limestone and loading on to railroad cars everything that remained on a stone fork and leaving

Jan 1, 1936

By H. A. Kuhn

The Pittsburgh coal field in Western Pennsylvania is conceded to be the most important in the world.

Jan 1, 1915

By R. P. Killmeyer, B. S. Gottfried, J. T. Wizzard

The US Department of Energy's Coal Preparation Branch has developed a computer program to calculate the performance characteristics of coal washing devices. This program uses specific gravity analyses of the clean coal and refuse streams as input, and generates dependent and independent performance criteria for the washer. Partition curves are internally represented in a functional form by a Weibull function. Comparisons are made between performance criteria calculated by hand and the performance criteria calculated by the program for 120 different dense medium cyclone tests. Results show that the computer program gives results in close agreement with hand-calculated values while greatly reducing the amount of time involved in performing the analyses.

Jan 1, 1984