Search Documents

By William J. Campbell

The purpose of this investigation was to develop a rapid, accurate method of analysis for small amounts of calcium in wolframite concentrates. This analysis is necessary to determine if the wolframite concentrates meet United States National Stockpile Specification P-57R2, which limits the calcium content to 0.2 percent. Because of the small depth of the sample analyzed in fluorescent X-ray spectrography, the calcium Kaline intensity was a function of the chemical composition of the calcium-bearing particle as well as the total matrix composition. This particle-composition effect was particularly important in this analysis, as the calcium may be present as a carbonate, tungstate, phosphate, etc. Three methods of preparing the sample eliminated the variation of calcium Ka intensity with mineralogical occurrence: (1) Reduction in particle size by extensive grinding, (2) chemical fusion with sodium carbonate, and (3) solution of the calcium by an acid attack.

Jan 1, 1958

By Leonard Obert

The various underground rooms in the Bureau of Mines Oil-Shale mine, Rifle, Colo., have been open for periods ranging from 3 to 5 years. During this time 3 roof falls have occurred; 1 was induced, and the other 2 were unintentional. The three roof falls are described in this report. Two causative factors are discussed -a time-dependent deterioration of the roof rock and an unfavorable system of jointing that occurred in the strata overlying the present roof horizon. Irrespective of cause, the operating life of any stoping area would have been short com-pared with the life of the roof (1 to 4 in the most unfavorable instance), if a high-production system of mining had been employed. The report is concluded with several recommendations that should be considered in planning future mining operations.

Jan 1, 1958

By John C. Machisak

THIS CHAPTER of the Minerals Yearbook relates to employment data and injury experience in the metal, nonmetal, and quarrying industries. Combined statistical data on the mineral industries as a whole can be found in volume Ill. Each industry in the chapter is shown separately, and no attempt has been made to combine and show an overall picture. The voluntary reporting of data on injuries and employment by operators of metal and nonmetal mines and quarries has contributed substantially to the promotion of safety in these industries. Data on injury and employment in the clay mining and milling industry are included for the first time. Table 6 contains data for clay mines only for 1955 and for clay mines and mills for 1956. The clay-mill figures are included with other nonmetallic mills in table 5. The information for norunetallic mills was compiled and published for the first time in the 1955 issue of this report.

Jan 1, 1958

During late 1953 and early 1954, tests were carried out in Sydney metropolitan brickpits in order to determine if some improvement might not be effected in the personal shock, fly rock and possible ground displacement accompanying daily blasting occurrences in the numerous quarrying activities of the metropolitan area. As a result of this preliminary work (Reid, 1954), the Department of Mines decided to further investigate the problem with a view to placing this type of blasting on a sound economical and safe basis for both operator and nearby residents alike. To assist in the work, a Cambridge Universal vibrograph was acquired.Human safety was the first consideration followed by property damage to homes and factories in the extractive areas. Although most of the actual field work has been confined to the Sydney metropolitan area and in particular to the large clay-shale quarries, many cities and country towns have blasting problems associated with the extractive industries, engineering projects both above and below ground level, and in building excavations to which the results may apply.The following figures illustrate how much activity of this type is located around cities and towns:Sydney Metropolitan Area:

Jan 1, 1958

By John C. Machisak

THIS CHAPTER of the Minerals Yearbook (volume III) contains overall injury experience and employment data at bituminous-coal, lignite, and anthracite mines, coking plants, metal and nonmetal mines, metallurgical plants, and stone quarries in the United States for the calendar year 1956. Volume I of the Yearbook includes injury experiences and related employment data in the metal, nonmetal, and quarrying industries, and in the milling operations connected with the mining of those commodities. Volume II contains the injury and related employment experience of the coal mining, coking, and oil and gas industries. Reporting is voluntary on the surveys conducted by the Bureau of Mines to collect injury and employment data in the mineral industries, except in the coal-mining industry, where operators are required by Federal law to furnish the information requested.

Jan 1, 1958

Jan 1, 1958

By Oliver C. Ralston

OUTSTANDING TRENDS of the year included the following: 1. Concentration and beneficiation of iron ores to provide improved blast-furnace feed and extend ore reserves. 2. Successful development of pelletizing and sintering procedures for fine iron ores. 3. The realization that cyclone separation could replace existing classifiers in many grinding circuits. 4. The rapidly blossoming metallurgy of ultrapure silicon and improvements in zone melting. 5. The rapid increase in the use of liquid-liquid extraction and ion exchange in hydrometallurgy. 6. The industrial application of vacuum melting on the 100-ton scale. 7. The hope for developing a columbium (noibium) base alloy for high-temperature use. The technologic advancement in metallurgy that had the greatest effect on the American economy was the beneficiation of iron ores to give improved feed for blast furnaces and indirectly extend our ore reserves. This was not a sudden development but rather culmination of a decade of intensive effort.

Jan 1, 1958

By G. C. Wallick

Since the appearance of the paper, "Solution of the Equations of Un-steady State Two-Phase Flow in Oil Reservoirs," by W. J. West, W. W. Garvin, and J. W. Sheldon,' a two-fold investigation of this subject has been carried out. One objective of the investigation has been to deter-mine the feasibility of solving such problems 7on a medium-size com-puter such as the Datatron*, and the other objective has been to in-vestigate the application of such cal-culations to experimental and theo-retical petroleum reservoir research. In the first Datatron calculations, the fluid and rock properties published by West, et al, were used, together with the published equations describ-ing the system. Details of the formu-lation not given in the original paper are discussed in the Appendix to this note. Reference should be made to the subject paper for the complete equations and defintion of symbols. An unexpected result of this in-vestigation was the discovery that the linear solution published by West was in error. Thus, in addition to describing the Datatron solutions and to discussing certain numerical diffi-culties which will be encountered if one uses the published method of solution, the purpose of this note is to indicate the nature of this error. LINEAR FLOW Since the linear case requires a minimum amount of scaling, a fixed-decimal point Datatron program was written for the one-dimensional flow problem and an attempt was made to duplicate the solution described by West. In the case described, fluid was produced at a constant rate, Q, until such time as well pressure reached 0.04. Production was then continued at constant pressure. From the constants and curves given by West it was determined that the ini-tial constant production rate could be approximated by Q = 0.007. An ini-tial dimensionless time step ?t = 0.434 X 10 - "as used, and each suc-cessive time step was doubled until a value of = 0.444 was reached. This constant interval was then used for the remainder of the solution. In subsequent solutions, several varia-tions in the time schedule were em-ployed, including smaller time steps and slower rates of increase in the time steps. In all cases, almost identical results were obtained regardless of the time schedule employed. However, as described below, it was noted that the time schedule had some influence on the rate of convergence of the solutions. As a check on the accuracy of the solution, the cumulative production at each time step was calculated using the two methods described in the Appendix. Satisfactory agreement was observed with the differences in these two values of the order of two parts in 50,000. It should be noted that the mass balance check as described is of questionable value, particularly with regard to the well pressure and saturation. This is especially true in the radial solution where pressure and saturation values near the wellbore would make only a negligible contribution to the numer-ical integration. It is believed, how-ever, that such a comparison is ot value in determining the over-all accuracy of a solution. In comparing the Datatron solu-tion with that published by West it was discovered that in the later stages of depletion, the pressures near the well declined more rapidly in our solution than in the West solution, and that the limiting well pressure of 0.04 was reached at an earlier time than that originally reported. It thus became evident that it would be impossible to duplicate the production schedule described by West and a constant rate of production was maintained until the well pressure was equal to 0.0. A representative comparison of the results published by West with those obtained in this investigation is shown in Fig. 1, which is a plot of GOR as a function of cumulative recovery. These two curves should be in agreement until a cumulative recovery is reached which corresponds to a well pressure of 0.04 — for the Datatron solution, a recovery of approximately 5.6 per cent. Actually, a major disagreement is evident. Subsequent correspondence

Jan 1, 1958

By Marling J. Ankeny

MINING research in the U. S. today is indeed complex, whether it involves the Government, a small private concern, or a large one. And it promises to become more so, despite great advances already made in developing equipment and technology. The U. S. Bureau of Mines is committed to place greater emphasis on mining research as expressed in a recent policy statement to Congress on the "Long Range Minerals Program," by Secretary Fred A. Seaton, quoted above.

Jan 1, 1958

By R. Casting, J. Philibert, and C. Crussard

APPARATUS described in this paper uses the properties of X-radiation, emitted by substances under electron bombardment, as a means of rapid chemical point analysis. The method is based upon the principles of emission X-ray spectrography pioneered by Moseley in 1913. A very finely focused beam of electrons—the electron probe—is projected on the surface of a sample, which has a very large area compared with the beam diameter, at the point where it is desired to know the chemical composition. The minute volume of the sample which is thus irradiated emits a complex X-ray spectrum consisting principally of the characteristic radiations of the elements present in the volume. Measurement of the wavelength and intensity of each component of this spectrum thus affords a simple method of determining the chemical identity and concentration of these elements. The volume of sample which is analyzed at each position of the beam is limited by the diffusion of electrons in the sample. For an accelerating potential of the electron beam of about 30 kv, which is a convenient value for producing the characteristic radiation, this diffusion extends over a diameter of about 1 µ normal to the beam, and about 2 µ in the direction of the beam. Thus a beam of 1 µ in diameter leads to a volume of about 2 µ in diameter being irradiated. The limits of the analyzed region are thus considerably smaller than those obtained by using spark or arc emission spectrometry, which must extend to about 50 µ at right angles to the beam, and those obtained in X-ray fluorescence analysis, where the penetration of the specimen is considerably greater. The apparatus itself consists of three main parts: an electron optical system. an X-ray spectrograph and an optical microscope. The electron opticai system consists of a tungsten cathode emitting the electrow and a pair of magnetic lenses which focus the electron beam on the specimen to be analyzed. The specimen is prepared in the usual way, as in optical micrography. The X-radiation, emitted at the focal spot where the electrons strike the sample, is analyzed with a curved crystal, Geiger-Müller counter, vacuum spectrograph. The light microscope, designed to observe the surface of the sample in the region to be analyzed, is provided with a reflecting objective placed on the axis of the second magnetic lens. Its magnification is X450. The quantitative determination of an element A in the analyzed region is made by measuring the intensity I, of a strong characteristic line of the element, as emitted from the sample, and then the intensity I (A) of this same line as emitted from a

Jan 1, 1958

By John B. Campbell, George G. Binder, Loren H. Jenks

Conventional methods of producing crude oil generally leave in the depleted reservoir 1 to 3 bbl of oil for every barrel brought to the surface. This paper describes a field test which explores the possibility of using gas-driven liquid propane to improve oil recovery efficiency. Laboratory theoretical and experimental studies leading to the field test indicated that low residual oil values could be obtained using limited amounts of propane driven by gas. The field test involved (I) repressuring the reservoir to the vapor pressure of liquid propane, (2) injecting the liquid propane, and (3) injecting dry natural gas to drive the propane and oil to the producing wells. Considerable preliminary work, including new drilling, work-overs, and a pressure survey was necessary. During the test, oil production rates have averaged about nine times the final primary rates. The field average GOR is still below the pre-test value. Oil recovery to date is 112,000 STB. About one-third of the 143,-000 bbl of propane injected has been produced to date. Results of the C-2 block test are encouraging and larger, more definitive field projects ore indicated. INTRODUCTION The cost of finding new crude oil reservoirs continues to increase. Today the oil industry is drilling more and deeper wells and making fewer big discoveries. Nevertheless, the demand for oil and oil products increases each year. It is natural that oil companies, faced with this situation, concentrate on recovering more of the oil existing in our known crude oil reservoirs. There is room for much improvement. For every barrel of oil brought to the surface by present day methods of producing crude oil, generally 1 to 3 bbl are left behind in the depleted reservoirs. The "unrecoverable" oil in petroleum reservoirs is largely "trapped" by capillarity. Since flushing with a solvent is exceedingly effective in combatting oil loss due to capillarity, much effort in this direction has been made in recent years1,2,3,4,5. Liquefied petroleum gas (LPG) has been suggested as a relatively inexpensive. abundant, easily recoverable solvent for crude. Some operators have observed striking responses in oil recovery at production wells offsetting input wells in LPG storage reservoirs6,7,8. In spite of the low unit cost of LPG, however, it is uneconomic in general to inject a volume of LPG into a reservoir to remove a like volume of oil. A modification of solvent flushing in which a limited quantity of liquid propane is gas driven through a reservoir appears capable of recovering much more than 1 bbl of oil per barrel of propane injected. Also, most of the propane injected should be recoverable for sale or re-use. Since such a process could well have widespread and profitable application, The Carter Oil Co. is making an extensive evaluation of the technique's possibilities. Laboratory development of the gas-driven propane recovery technique was sufficiently encouraging to justify testing in the field. Since 1952, the Production and Research Departments of The Carter Oil Co. have cooperated in a field test in the C-2 Block leases of the

Jan 1, 1958

By W. H. Holman, J. B. Wagstaff

IN spite of considerable interest among blast furnace operators on the question of the penetration of air into the furnace, there is still uncertainty as to how far the blast does, in fact, penetrate. Moreover, it is not always clear just what is meant by the word penetration in this sense. In 1952, Elliott et al.1 showed that at the end of each tuyere of a blast furnace there is more or less of a void. In this region, coke particles are blown around by the force of the air. This explained the well-known observation reported by Sweetser2 hat if a bar is pushed into a furnace through a tuyere it will go easily into the furnace a distance of some

Jan 1, 1958

By W. J. Bennett

WHEN Dr. Horace Fraser, your President, invited me to speak to you today I advised him in confidence that I was leaving my present positions on April 30th. In the circumstances it seemed to me that this audience might prefer to have as its speaker one who wo.uld J1ave a continuing association with the atomic energy programme. Dr. Fraser was kind enough to suggest that my re-marks might he of special interest to you, since I would be able to sum up my views on the atomic energy programme. I hope that I will not disappoint him or you on that score. I am particularly pleased that my last public appearance in my present positions should be at the Annual Convention of the C.I.M. since, as all of you know, a very important part of my work has been in the mining field. As it happens, my first public address on the subject of atomic energy and its raw material -uranium -was made at your Annual Convention in Montreal in April, 1949. It seems fitting that my final address should also be made at this convention -nine years later.

Jan 1, 1958

By L. D. Wooddy, W D. Moore

Water drives may be natural or artificial. For the case of a natural water-drive reservoir, the volume of water influx corresponding to reservoir pressuve-production history may be calculated by means of the material bal-ance-unsteady state equation. For the artificial water drive or pattern injection water flood, the material balance equation is sufficient to determine the reservoir pressure-production, injection history. However, for both cases to reliably predict reservoir performance, it is necessary to calculate the saturation distribution of the reservoir fluids at different stages of depletion. This paper consolidates the various equations used to determine the performance of water-drive reservoirs into one approach that is applicable to any reservoir that has a natural water drive or is to be produced by water injection. The numerical procedure has been simplified considerably, and the solution is adaptable to either hand calculations or digital computer operation. INTRODUCTION A water-drive reservoir is one in which the predominant source of energy for production of oil results from the encroachment of water into the oil zone. The water drive may be either natural or artificial. Water invasion takes place by expansion of water in the aquifer as a result of the pressure decline transmitted from the oil reservoir. Because water is practically incompressible, a natural water drive requires an extensive aquifer containing a volume of water many times the volume of oil in the reservoir. Provided the permeability of the formation is reasonably high, a moderate decline of reservoir pressure usually causes adequate water influx. If the reservoir pressure decline becomes excessive because of low permeability or a high rate of production, part of the oil production may result from the liberation of dissolved gas which may cause excessive quantities of free gas to be produced along with the oil. In extreme cases, reservoir pressure may decline so rapidly as to cause the oil to be produced predominantly by dissolved gas drive, leading to abandonment of the reservoir before the advancing water has had a chance to flush the entire reservoir. In reservoirs that are not connected to extensive aquifers, an artificial water drive may be created by injecting water into or around the lower edges of a reservoir. Sometimes water is injected within the reservoir through wells interspersed among the producing wells. When injection is carried out in such fashion, the reservoir is in effect subdivided into a number of separate producing segments, in each of which the displacement of oil is simultaneously taking place, and the shapes of which are fixed by the well patterns employed. Because of the natural tendency of oil and water to segregate according to their relative densities, water will tend to migrate downdip regardless of where injected. Accordingly, the injected fluids can be retained within the intended reservoir segments only when conditions are unfavorable to their migration under the force of gravity. Pattern injections are usually confined, therefore, to reservoirs having low structural relief, or low permeability, or when production and injection rates are such that fluid movements in the reservoir are dominated by the pressure gradients rather than by the force of gravity. In the case of natural water-drive reservoirs and artificial water-drive reservoirs in which the water is in-

Jan 1, 1958

By R. E. Perry

In connection with a program of coal research at the Southern Experiment Station the Bureau of Mines, in cooperation with the University of Alabama and the various coal operators, conducts washability studies of coal from beds in Alabama and other Southern States in which commercially important deposits occur. One of the main objectives of a washability study is to obtain technically and commercially important data necessary for determining the best methods for preparing and utilizing the Nation's limited reserves of coking coal. Such information is important to conservation because it facilitates selection of preparation methods that will provide maximum yields of coal with low ash and sulfur contents.

Jan 1, 1958

By E. R. Lea

The B. M. & S. orebodies, consisting of the No. 6 (Brunswick) and the No. 12 (Anacn Leadridgz, have the distinction of being the first major 1base metal ore deposits to be found in the Province of New Brunswick. They are massive sulphide de-posits consisting of pyrite (pre-dominantly) and base metal sulphides, and they carry values in lead, zinc, copper, and silver. These orebodies are localized within favourable drag fold structures believed to be related in their origin to external forces set up in the area subsequent to the primary regional folding. Both orebodies are characterized by the presence of magnetite 'iron formation' which, in certain 'Portions of each orebody, may be found as relics within the massive sulphides. Studies show the magnetite to be the first metallic mineral within the ore ?zones, followed by pyrite, Sphalerite, galena, and finally chakopyrite. The shape of these massive pyritk orebod:es as well as the distribution of values within them is controlled to a large degree by the ore-ore drag fold structures. A possible relationship is discussed between the basic intrusives in the area ?and the magnetite deposits. It is suggested that a large portion of ?the iron content of the massive suplhedes has been derived from the earlier magnetite. Intermittent movements in the area during the sulphide mineralization are believed to belong to the last stages of deformation in the area. These late movements may have been caused by the intrusion of the granite into the area. The granite may have a genetic relationship to the B. M. & S. orebodies.

Jan 1, 1958

By J. E. Campbell, G. D. Calkins, N. M. Ewbank, M. Pobereskin, A. Wesner

GRINDING for size reduction affects the economics of many processes and products. It is essential as the first step in many industrial processes and is also a finishing step for materials with properties depending on particle size, such as talc, cement, and silica sand. Intermediate and fine grinding are vital operations in the U. S. cement industry, which is producing more than 250 million bbl of cement per year.' Wear of the grinding media is a large part of the grinding operation cost. Problems encountered in grinding cement are so complex that evaluation of efficiency and economy of grinding media is difficult.2 It has been especially difficult to evaluate the relative effectiveness of different types of balls because there are no good testing techniques. Many other industrial operations can be evaluated on a laboratory scale with reasonable accuracy. This does not hold true for evaluation of grinding balls. The consistent results obtained in a laboratory test under a given set of conditions are not always borne out in field application. Rough evaluations of the effectiveness of various compositions and types of grinding balls have been made in the field by using a full charge of one type in a mill and comparing the production record with another run using another type of ball. This method is time-consuming and not very precise, as the second run may not have been carried out under identical conditions. Laboratory-scale tests, on the other hand, have yielded inconclusive results, and many investigators have turned their attention to the development of a field testing technique. Field testing small sample lots of grinding balls has been impractical because it is difficult to identify and recover the test specimens from the grinding mill, and individual groups of balls that have undergone different heat treatments can not be separated.".4 To overcome these difficulties, previous investigators have identified the balls by distinctive marks, notches, and drilled holes, but this procedure has three serious drawbacks: 1) Grinding characteristics and quality of the steel balls may be affected. 2) Physical markings may be worn away in the grinding process, especially during a prolonged run. 3) Recovery from the bulk of the charge will be extremely difficult because the markings are hard to see and may be masked by a coating of the product. To circumvent these difficulties, a radioactive-tracer technique was proposed for recovery and separation of steel grinding balls and subsequent evaluation of the various compositions of the balls. The proposed technique involved five basic operations: 1) Thermal-neutron irradiation activation5 of each group of test grinding balls to a different level of specific radioactivity. 2) Addition of groups of radioactive steel-ball specimens into a ball tube mill. 3) Recovery of radioactive steel-ball specimens from the bulk of the mill charge. 4) Separation of the various groups by their specific radioactivity. 5) Evaluation of actual grinding ball wear. Before any physical tests were performed, required neutron irradiation intensity and time were calculated. Probable composition of the steels to be used was ascertained. An examination was made of the radioactive nuclides8 to be formed which would contribute measurably to the radiation level immediately after irradiation and during the test operation. The radioisotopes formed, their types of radiation, and their half lives are listed in Table I. Of these radioisotopes only iron-59 and chromium-51 were significant for the actual wear test. The intensity of radiation that could be detected by a Geiger counter when the test was completed was the basis for the minimum activation level established. The intensity of radiaton that could be safely handled at the beginning of the test was the basis for the maximum activation level, although this was not considered a major problem. Ten groups of grinding balls of various composition and/or surface or heat treatment were to be tested. One group was designated for the minimum irradiation time. The remaining groups were designated for irradiation periods that increased by increments of 33 pct from that of each preceding group. This difference was considered enough for separation and identification of the groups by comparison of specific activity. Potential Hazards: Possible radiation hazards that might be encountered during this experiment were evaluated for the three important phases: 1) the radiation hazard of placing balls and removing them from the mill, 2) contamination of the product cement by radioactive material worn from the balls, and 3) contamination of the steel by the radioactive balls left in the mill. The radiation intensity expected from the whole group of radioactive balls was calculated to be 250 milliroentgen per hr at 1 ft. This meant the balls would require special shielded packaging and warning labels on the shipping containers. In a radiation field of 250 mr per hr a man can work for 1 hr without exceeding maximum permissible weekly exposure. Since the balls could be dumped into the mill in a matter of seconds, relatively little radiation exposure was anticipated at this stage of the operation. If the weight loss in the balls was 7.7 pct per month and the cement feed through the mill was

Jan 1, 1958

By C. A. Fothergill

An improved blotter model is described which makes use of a plastic sheet as base for the blotter field and pins to represent the input wells. The model is simple to construct and adapt and is particularly useful for demonstration purposes. Operational details are given. INTRODUCTION The blotter model was first applied to the investigation of oilfield problems by Wyckoff, Botset and Mus-kat,' primarily in order to demonstrate the flood patterns which could be expected from various arrangements of input and output wells in waterflooding projects. In recent years the model has been largely superseded for analog studies by the potentiometric and electric analog models which are more refined and versatile, since they can simulate the form, and, in certain cases, permeability variations which it is not possible to do with the blotter model. However, the latter is still used for analog studies where the reservoir can be represented as being uniform in thickness and permeability, and where a visual record of the flood advance is required. Ramey andNabor,2 for example, have applied the model to the investigation of areal sweeps in oil recovery by in-situ combustion. Because of its limitations, the blotter model can be used in general for only very simple arrangements of input and output wells, but within these limitations it has a definite advantage over all other types, in that it provides a picture of the advancing flood using the simplest and most easily constructed apparatus, by contrast with the gelatin model, for example, which requires more elaborate equipment. Moreover, the experiments can be quickly repeated and modified if necessary, whereas considerable time is required to prepare a gel field, compared with that required for the preparation of sheets of conducting blotting paper. For these reasons the blotter model can be very useful for demonstration and teaching purposes, enabling the student to experiment for himself with different arrangements of input and output wells. A model has been constructed for this purpose which is simple to operate and adapt. The model (Fig. 1) consists of a base platform or box, approximately 12-in. square, on top of which are screwed three lathes of 1/2 -in. square section to form three sides of a square 6 in. in length. This forms the support for a sheet of Cobex, transparent plastic, thickness .003 in., on which is carried the blotting paper representing the field. The plastic is flexible and relatively soft, and can be attached to the support by cellulose tape so that it can be easily removed when required. The input wells are represented by brass drawing pins pressed through the plastic sheet from the underside until the points are just projecting through the top; these are connected in the circuit as shown in Fig. 2. The sheet of blotting paper of required shape and size is saturated with a solution of 0.2 n-potassium sulfate to which has been added a saturated alcohol solution of phenol-phthalein at a strength of 10 cc/liter of stock solution. The surplus water is removed and the blotting paper placed in position on the plastic sheet making contact with the drawing pins and the sheet (which is an insulator). The anode consists of a second sheet of blotting paper cut as shown and saturated with the same solution. This is suspended from a laboratory stand, being connected to the conducting wire by means of a crocodile clip and making contact with the horizontal blotting paper at the projecting point. This is the method used by Ramey and Nabor and which permits the hydroxyl ions or colored front to reach the anode. As shown in Fig. 2, the electrical voltage used is 220-v DC and a shunt is placed across the terminals to step down the voltage as required. Further adjustment can be made as necessary using a lamp board in series with the shunt to obtain the

Jan 1, 1958

By W. F. Netzeband

This paper, which describes mining methods and practices at the Rialto zinc-lead mine American Zinc, Lead & Smelting Co., in northeastern Oklahoma, is one of a series being prepared by the Bureau of Mines on mining methods, practices, and costs in various mining districts of the United States, The Rialto mine is in the SE1/4 SW1/4 sec. 20 and the NW1/4 sec. 29, T. 29 N., R. 23 E., Ottawa County, Okla. (fig. 1). The 200-acre property is southwest of and adjacent to the town of Picher in the central part of the Picher field of the Tri-State zinc-lead mining district (fig. 2). Other mines of the company adjoin the Rialto on the east and south. Zinc-lead ores have been mined almost continuously from the Rialto tract since 1916. The property was acquired by American Zinc, Lead & Smelting Co. late in 1951, and the mine was operated thereafter by the Nellie B Division of that company until the end of 1955, when it was subleased to the Residue Mining Co.

Jan 1, 1958

By Stephen Krickovic

THERE is today no proven continuous mining machine that can be used under all the varying conditions found in most bituminous coal mines. During the last five years, however, both the machines and methods of using them have been improved. Coal operators can now exercise a fair degree of selectivity, except those who must struggle with thick and hard partings and operate in seams less than 40 in. thick. It must be realized, then, that more than one type of continuous miner may be used advantageously in the same coal mine. Although this appears to violate the standardization generally sought after, the gain can more than offset added maintenance and, to a lesser degree, operating problems. It is equally important to realize that most coal mines will require one or more conventional loader setups in the plan of total mechanization. Seam variations, adverse physical conditions, and special designs of main headings for haulage and ventilation, to name only three reasons, may render 100 pct use of continuous miners uneconomical. Of course, this situation may change. In one mine, prior to 1954, machines that ripped coal from the face achieved only average results, as compared to the impressive performance of boring-type units in another coal mine. A boring-type unit was therefore selected for the first mine in the belief that the chance of success would be greater if it were used in a combined cutting and wedging operation, cutting a full face in its forward movement. The miner was located in a part of the mine where a special projection could be readily developed, a solid area scheduled for mining according to the overall progress plan. All openings surrounding the particular area were carefully investigated for the presence of sulfur balls. Fig. 1 (opposite) shows the representative seam section, containing the several pyritic bands 1/4 to 1/2 in. thick; a characteristic Pittsburgh seam parting averaging 5 to 6 in. of slate, coal, and slate; and the occasional py-rite lenses 2 to 3 in. thick. Under normal conventional mining methods, the top 10 or 12 in. and the bottom 4 in. are left in place to offer roof protection

Jan 1, 1958