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By Arthur A. Schweizer

A method to improve the quality of Magmnt zinc concentrates to become acceptable feed to an electrolytic zinc refinery. The magnesia content of zinc concentrates produced was too high due to particle locking with the sphalerite in coarse fractions. Regrinding of the concentrates to a very fine particle size and then refloating the sphalerite was chosen to eliminate a sufficient amount of the magnesia to make the concentrates acceptable.

Jan 1, 1981

By L. Alan Weakly

The purpose of this paper is to present a viable method of reinforcing rock pillars by utilizing fully grouted reinforcing steel and a cement - fly ash mortar. Although the fully bonded bolt concept is not new, as exemplified by the present widespread use of resin bolts within United States mines and by the use of cement grouted reinforcing used as back pins in the Kiruna Iron Ore Mine in northern Sweden, (1) (2) the method of stabilizing mine pillars with fully bonded reinforcing is new. This method, called the "grout-rebar system", was first incorporated at St. Joe Minerals Corporation’s Fletcher Mine in December of 1972. The system was used on an emergency basis before extensive research on the mechanics of the system could be completed. Since December of 1972, however, approximately 206 pillars have been reinforced at Fletcher and the system is currently being used on a regular basis at two other St. Joe mines and at two competitor mines in the area. Basically, this paper is a case study of the efforts, research and results of utilizing the grout-rebar system, on a selective basis, at the Fletcher Mine. In addition to information about the system, this paper will explain in detail the three rock mechanics instruments developed by St. Joe and used to measure and monitor rock movement to validate the grout- rebar system.

Jan 1, 1977

By P. R. Wotruba

The Fortitude gold-silver deposit is related to a "wallrock" copper porphyry system developed within Middle Pennsylvanian to Permian Antler Sequence rocks adjacent to a Middle-Tertiary altered granodiorite intrusive stock at Copper Canyon. Gold-silver ores of the Fortitude deposit occur with disseminated and massive sulfide replacement mineralization of skarn-like or calc-silicated limy horizons of the Antler Sequence contact meta-sedimentary rocks. A major, north-trending, steeply westward dipping normal fault was important as a conduit for hydrothermal fluids responsible for the metallization in the Fortitude area. Gold-silver mineralization is best developed near a marble front where retro-grade chloritization and destruction of prograde calc-silicate mineral phases is most prevalent. Fluid-inclusion studies performed on the Copper Canyon system indicate a wide variation in fluid chemistry during several hydrosilicate stages that ranged in temperature from 500°C to 220°C.

Jan 1, 1986

By S. A. Lolon, J. F. Brune

"INTRODUCTION In underground longwall coal mining, the mined-out areas or gobs frequently contain methane which can form explosive methane-air mixtures. Historically, there have been many events of mine fires and explosions recorded in the United States and other countries that have demonstrated the existence of such explosive mixtures, herein referred to as Explosive Gas Zones (EGZs), inside and around the perimeter of bleeder-ventilated longwall gobs (Loane et al., 1975; Lynn et al., 1986; Elkins, et al., 2001; McKinney et al., 2001; Dziurzynski and Wasilewski, 2012; Brune, 2013). The risk of mine explosions can increase if the EGZs migrate out from the gob into the surrounding mine entries. Several factors can induce EGZs outflowing from the gob, but the most common cause is the fluctuating barometric pressure. Atmospheric pressures change regularly every day but can fluctuate abruptly and become increasingly hazardous in adverse weather conditions. Other sudden pressure changes can result from roof falls, failing ventilation controls and fan outages. Any such fluctuation of mine ventilation pressure will disturb the pressure differential between the gob and the surrounding mine workings and may cause EGZs to outgas from the gob. The correlation between major mine explosions and abrupt barometric pressure changes has been studied and confirmed for explosions in coal mining countries including the United States, South Africa, Australia, and Poland (Hosler, 1948; Boyer, 1964; Kissell et al., 1973; Fauconnier, 1992; Hemp, 1994; Wasilewski, 2014; Belle, 2014; and Lolon, 2017). Disastrous mine explosions appear to happen more frequently during stormy weather, which, in the United States, typically occurs during the late fall and winter seasons. ROOT CAUSE AND EFFECT OF GOB BREATHING Gob breathing is the result of the pressure differential between gob internal and external pressures caused by external atmospheric pressure fluctuations that occur naturally as a result of gravitational and thermal forces in the atmosphere (Lindzen and Chapman, 1969). Other major and sudden pressure changes may be caused by fan failures, failures of ventilation controls or roof falls can also cause an unexpected gob breathing. Normal barometric fluctuations occur every day but usually do not pose an explosion risk as they occur gradually so gob pressures have sufficient time to equilibrate. More extreme fluctuations associated with cyclonic weather systems and storms often result in more rapid and larger drops or rises in barometric pressure (Hosler, 1948; Fauconnier, 1992). A study by Lolon (2017) found that the timing of historical mine explosions showed consistency with the occurrence of abrupt and intense barometric variations."

Jan 1, 2018

By Ralph W. Barbaro

In many parts of the country, electric utilities use spot market coal to make up the difference between the amount of contract coal and the total amount burned. The utilities involved will normally have a structured contract for those companies supplying that spot coal. These contracts will often involve a pricing schedule with bonuses or penalties for coal above or below the specified coal quality goals. Normally, penalties will be assessed on the sulfur, ash, and other coal quality variables. This paper deals with some aspects of the pricing schedule of one of the eastern utilities that buys coal on the spot market. This utility has a number of plants that a supplier can attempt to supply through bidding procedures. The existence of the pricing schedule gives the supplier a number of different options. To the single-mine producer, options are available to send the coal to any demand site and to clean all, part, or none of the coal. In other words, he can ship to a number of different sites and can send different coal qualities to each site depending upon the level of preparation. In addition, the options to deliver blended coal to any given site will provide an additional level of complexity to the problem.

Jan 1, 1983

By Leonard Harris

Most of those involved in the mining industry are aware of the negative feelings that the well-informed citizens of this country, also known as the American public, have for the industry. As noted in an issue of Mining World News, “The general public perceives mining as dirty, noisy, destructive and belonging somewhere else.” The same theme was raised at a conference in Scotland in July 1991. It was noted there that mining has an unattractive public image around the world “as dirty, dangerous work that pollutes and degrades the environment.” Why is this? Why does mining have such a bad rap? I’m afraid that some of the blame rests with the mining industry itself - both in the past and in the present. Hopefully, we can do something about this in the future. And hopefully, the information here will help the reader to spread the word to offset the negative messages being issued almost daily by industry foes. I hope this will become more than just the words of another miner talking to miners and their friends. In the past, belching smokestacks and polluted streams and waterways were common sights. Today, the negative results of mining operations can also be seen in the form of waste dumps, leaked acid mine waste water and dust blowing from tailings piles. Some will argue that mining did nothing illegal in the past, and that all the regulations in force at that time were carried out to the letter. That may be so. The fact remains, however, that mining did these things, and the evidence is very clear in many parts of the country. It is visible to the well-informed citizens, in spite of the fact that many mine sites have been cleaned up and new technologies, such as flash smelting, dump leaching, pressure leaching and bioleaching, have greatly overcome many of the pollution problems. What is not so visible is the importance of the mining industry in our daily lives. Not long ago, knowledge about our non-renewable mineral resources ranked low on the list of qualifications for being a well-informed citizen. Events during the past two decades have changed this scenario. Politicians, writers, newscasters, economists and administrators, as well as the ‘public,’ are expressing opinions and forming judgments on oil company profits, desecration of landscapes, waste disposal sites and pollution by the extractive industries.

Jan 1, 1992

By Stewart W. Daniel

Competitive pressures involving product duality, uniformity and economics are increasing the interest in and accelerating' the adoption of automation by the cement industry. The demands of this industry on instrumentation and control manufacturers for more effective and reliable control of process variables is also increasing. The trend to replacing small grinding mills with a fewer number of larger mills is lowering the investment requirement per unit of capacity both for the mills and for their automation. Cement process control systems of today are more sophisticated than the equipment installed two or three years ago, not because the process itself is more complex but because todays demands require a higher degree of control action and accuracy. Because of increasing labor costs, an important objective of an automation program is a reduction in the process labor content. This can be realized by allowing the operator free time for other duties, by increasing the number of grinding circuits one operator can supervise and by removing to. a large extent the need for the operator to make process' adjustment decisions.

Jan 1, 1965

Paper and paperboard manufacturers need to quantify the carbon footprint and environmental impact of their products to satisfy market, social and government demands. Coated paper products contain minerals, such as kaolin and calcium carbonate, at significant levels; some coated paper grades have mineral contents as high as 45% by weight. Some uncoated paper has no mineral content, but most uncoated paper contains some mineral to improve appearance, process efficiency and cost. Super-calendared paper grades can contain levels of mineral up to 35% by weight. This paper describes how to calculate the carbon footprint of kaolin and calcium carbonate minerals used for white pigments. The carbon footprint of these minerals strongly correlates to the primary energy sources, final product form and energy used to calcine kaolin and lime. Kaolin and calcium carbonate pigments have a favorable impact on the carbon footprint of paper and paperboard products by directly substituting for fiber and by reducing the energy needed for paper making. Key words: Kaolin, Calcium carbonate, Paper production, Carbon footprint, Lifecycle analysis

Jan 1, 2010

By Mark E. Gershon

Conventional methods of drillhole site selection are reviewed briefly. Two approaches using geostatistics are then discussed, both of which have been shown to yield improved results. Finally, a branch and bound algorithm is described which will select the best locations for drilling from a user specified number of possible drill sites. Two options are discussed. First, the user can specify a maximum drilling investment or a maximum number of drillholes and the program will select the locations yielding the minimum estimation variance. This amounts to getting the most for a given investment. Alternatively, a maximum tolerable estimation variance can be specified and the program will select the number and location of the drillholes to obtain the desired information at a minimum cost. Another benefit of the approach is the quantification of the tradeoffs between investment and information obtained.

Jan 1, 1983

By K. V. Raj, A. T. Weakley, A. L. Miller, D. A. Parks

Diesel particulate matter (DPM) is a common and well-known health hazard in the mining environment. The current approved method for monitoring both the organic and elemental carbon (OC, EC) portions of DPM is a laboratory method with a turnaround time of approximately one week. In order to evaluate exposure levels and take corrective action before overexposures occur, a portable real-time device capable of quantifying both OC and EC is needed. To that end, researchers from the National Institute for Occupational Safety and Health (NIOSH) designed and tested a device based on narrow bandpass optical filters that is capable of targeting infrared absorbance bands associated with DPM. Five optical bandpass filters were chosen based on previous work quantifying DPM using Fourier-transform infrared (FT-IR) spectrometry. The resulting device, referred to as a filtometer, is optimized to exclusively determine DPM and could serve as a cost-effective, field-portable alternative to laboratory-grade FT-IR analysis and instrumentation. The performance of the filtometer was investigated by calibrating FT-IR data from DPM (dependent variable) to the filtometer spectra (predictor variables) using a partial leastsquares (PLS) and ordinary least squares (OLS) approach. The square of the correlation coefficient and root-mean-square error of cross validation m

Mar 2, 2022

By S. C. Howell

The mining of taconite, to provide feed for a processing plant, requires that the flow of material continue uninterrupted. This means first, that the crude must be of a size acceptable to the primary crusher in order to reduce the delays caused by plugging the crusher with chunks. Secondly, elimination of oversize in the pit will reduce costs of all wear parts used in the mining and processing of taconite. Savings in wear parts is readily recognized in dipper teeth, bases, buckets, truck boxes, and crusher parts, both primary and secondary. During the early days of taconite mining, it was soon recognized at reserve mining company's Babbitt operations that experience in mining other ores was not always (or ?necessarily??) Applicable to excavating taconite. This was especially true in drilling and blasting. Blasting of small tonnages in single or double rows simply filled the pit with scattered chunks and provided very shallow banks for shovel loading. It also created problems for the jet piercers, since all drilling had to be performed in fractured areas. Drilling efficiency suffered and costs were extremely high. Shovel and truck efficiencies were also low and again costs were high. A high percentage of secondary breakage was required. This necessitated the use of numerous man hours to jackhammer holes in chunks, preparatory to loading and blasting. After the chunks were reduced, bull- dozer and grader hours were needed to pile the taconite for acceptable shovel loading.

Jan 1, 1968

By Michel Dagbert

The determination of the precision of reserve estimates (tonnage, grade, quantity of metal) for an entire deposit or a large block in a deposit has received some attention in the early developments of geostatistics. A general formula to derive the estimation variance of any linear combination of a large number of sample values can be found in any geostatistical textbook like David (1977) or Journel and Huijbregts (1978). A particular case of this general formula is of course the kriging of the entire deposit. However, besides the technical difficulty of dealing with many samples the application of this formula necessitates the knowledge of the covariance between any two samples in the deposit. This is quite unrealistic in the usual case of limited stationarity where the assumption of a covariance or a variogram just function of the distance vector between two samples is only valid for samples within the same area of restricted size.

Jan 1, 1982

By E. Westman

Geographic Information Systems (GIS) are becoming a more commonly used tool for resource estimation as they provide not only a database management platform, but also the graphical capabilities to visualize resource characteristics. Interpolation methods used commonly in these resource studies do not typically provide a quantitative answer to the question: "How accurate is the estimate?" By comparing localized measurements at several locations to the interpolated thickness distribution used in a resource estimate, a quantitative analysis of accuracy can be obtained. The technique is demonstrated with a case study from Central Appalachia.

Jan 1, 1999

By M. A. Bouchat

The Kipushi deposit, where the Prince Leopold Mine has been installed, belongs to Union Miniere du Haut-Katanga and is located in the Belgian Congo, 20 miles SW of Elisabethville, at the vicinity of the Northern Rodhesian Border. The deposit is of the hydrothermal metasomatic vein-type; mineralisation took place, through the limestone of the, lower Kundelungu. This is a special fea¬ture of the deposit, compared to the other copper deposits of the neighbourhood, both in the. Belgian Congo and in Rhodesia. Actually, the primary mineralisation of these other deposits; is directly related to the stratigraphic systems: schistous dolomitic in the Belgian Congo and Roan in Rhodesia. Both facies are older than the Kundelungu and separated from this formation by a tectonic cataclysm. The valuable elements occuring at Kipushi are principally copper; and zinc. The deposit also contains smaller quantities of lead, precious metals and other elements including germanium.

Jan 1, 1960

By Maribeth Amyot

This paper assesses the current status of computing education in ABET-accredited mining engineering programs in the United States. The hardware and software being used are reviewed. The extent to which computer applications are incorporated into mining engineering courses is also surveyed. Today's capabilities and practices are compared with those of the past to establish, trends in computing education. The concerns of mining educators regarding computers are addressed, as are views on the direction in which mining engineering programs appear to be heading in preparing students to meet the computing needs of industry.

Jan 1, 1985

By L. G. Stolarczyk

In-mine Continuous Wave (CH) Radio Imaging method (RIM) instrumentation has the capability of measuring EM wave propagation constants in layered formations. The RIM method is based upon the fact that seams of coal, trona, potash, quartzite, gilsonite and oil bearing sands form natural waveguides for low loss transmission of electromagnetic (EM) waves. The waveguide forms whenever the seam is bounded by more conducting claystone, mudstone, shale or in the case of oil/gas traps, by a floor of saline water. Disturbances caused by faults, shear zones, paleochannels, sills and dikes significantly alter the propagation constant. The analytical values of the EM wave propagation constants depend on the physical and electrical parameters of the seam. The values are presented in this paper in a graphical form to assist in the interpretation of RIM tomographic images. This paper compares in-mine geologic mapping obtained during mining to tomographic images of the geologic disturbance zones in a Central Utah coal mine.

Jan 1, 1989

By S. Ash

Murray mine was one of the first Mechanized cut and fill underground gold operations in Northern Nevada. At the end of 2002 mine production began to decline and Murray entered a phase of remnant mining and began preparations to close down. The remaining mining took place along the ore waste boundary, in previously condemned areas, and in highly challenging ground conditions. To remain economically viable new techniques were implemented in operations, geology, engineering, and rock mechanics. These improvements pushed the edge of known and accepted mining practices and have allowed Murray to remain in operation today. History The Murray mine is located on the Jerritt Canyon property, which is located 45 miles north of Elko, NV in the Independence mountain range. Mining operations started at Jerritt Canyon in 1980 out of several open pits. In 1993 underground mining began in conjunction with a decline of surface mining operations. The transition from surface mining to underground mining moved the property into a new era. At the time there were limited examples of successful underground operations in the area from which to draw experience. Several mining methods were attempted with varying degrees of success and underhand cut and fill proved to be the most effective method. To date Murray has mined 1.2 million ounces at an average grade of .335 OPT utilizing this mining method.

Jan 1, 2006

By Lars A. Stålberg

"This paper will touch several of the topics covered by SDIMI 2005, including,• Sustainability indicators for the minerals industry, • Best practice of sustainable development in the minerals industry, • Social contributions,The complex issues of a company’s "sphere of influence" and "complicity" are important to every discussion of business and Human Rights. The paper will argue that to protect and promote Human Rights needs to be regarded as an integral part of sustainable development policies for the minerals industry. This implies a need for explicit inclusion of Human Rights indicators among the indicators to be applied by the minerals industry."

Jan 1, 2005

By Daniel Su

This paper describes recent ground control challenges encountered at the longwall recovery areas of one of Bailey Mine?s two longwall faces and the proactive measures taken by CONSOL management and engineering to mitigate them. The challenges derived primarily from the following causes: (1) irregular roof coal and draw slate thickness, (2) presence of thick sandstone at the recovery area and extremely weak rocks below the sandstone, (3) close proximity to a regional anticline, (4) low shield set pressure and tip load, and (5) ineffective primary roof support that led to progressive failure of the headgate roof. The presence of the anticline contributed to extensive fracturing of the sandstone. Excessive pot-out in advance of the shields frequently occurred near mid-face due to the presence of thick draw slate and irregular roof coal near the recovery area. This, in turn, resulted in face heights that exceeded the maximum reach of the shields. Subsequently, during longwall meshing, when the advance rate slowed considerably, fractured sandstone would often break loose, causing the shields to yield, thereby reducing the height and inhibiting shearer movement. To improve the headgate and face conditions within the longwall recovery area, several actions were taken, including: (1) assessing site-specific roof geology by conducting in-mine roof coring around the recovery areas and by mapping immediate draw slate and roof coal thicknesses within surrounding entries, (2) increasing pump pressure and thus shield set pressures (3) diligently monitoring shield set pressures and longwall extraction horizon, (4) installing additional cable bolts and roof screening to prevent progressive failure of the immediate headgate roof, (5) fully-grouting supplemental cable bolts to improve headgate support stiffness, and (6) gluing the headgate roof within the recovery areas with polyurethane. As a result of these collective efforts, longwall recovery delays at Bailey Mine were reduced from 21 days in 2006 to nearly zero in 2009.

Jan 1, 2009

By W. H. Pailes, V. Castranova, K. Van Dyke, J. H. Kang

Recruitment and activation of phagocytic cells after inhalation of occupational dusts has been implicated in the development of pulmonary inflammation, fibrosis, or emphysema. Plateletactivating factor has been described recently as a potent inflammatory agent. The objective of the present study was to investigate if platelet-activating factor might play a role in the inflammatory response of the lung to occupational dusts. In vitro exposure of alveolar macrophages to cotton dust (4 mg/ml), silica (10 mg/ml), or coal dust (10 mg/ml) results in the release of picomole levels of platelet-activating factor with a potency of cotton dust > silica > coal dust. Time course studies indicate that platelet-activating factor release from alveolar macrophages is maximal approximately 10 minutes after in vitro exposure to silica. In vitro, platelet-activating factor is a direct stimulant of polymorphonuclear leukocytes increasing chemiluminescence 2.3 ± 0.3 fold above control. The maximal response occurs in the dose range of 10-10 to 10-7M platelet activating factor. In addition, plateletactivating factor potentiates the response of polymorphonuclear leukocytes to a second stimulant; i.e., chemiluminescence generated from polymorphonuclear leukocytes exposed to plateletactivating factor (10-9M) plus chemotactic peptide (FMLP, 10-9M) is 88 ± 22% greater than the sum of the separate effects of these stimulants. In contrast, platelet-activating factor is not a direct stimulant of alveolar macrophages in vitro, having no stimulatory effect on chemiluminescence or superoxide anion release even at levels of 10-6 to 10-5M platelet-activating factor. However, platelet-activating factor (10-5M) does potentiate zymosan-stimulated activation of chemiluminescence and superoxide release from alveolar macrophages by 117 ± 56% and 30 ± 4%, respectively. In conclusion, these data indicate that exposure of the lung to occupational dusts results in the release of platelet-activating factor which may activate polymorphonuclear leukocytes and potentiate the responsiveness of alveolar macrophages to dust. The net result would be pulmonary inflammation and hypersecretion of reactive species by pulmonary phagocytes which could lead to tissue damage and pulmonary disease.

Jan 1, 1991