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By David W. Wisecarver, James F. Reynolds

INTRODUCTION The Department of Energy is cooperating with Snowmass Coal Company near Carbondale, Colorado to introduce the longwall mining method in moderate to steeply pitching coal seams in the United States. This venture is part of a coal mining research program directed toward development, trial, and analysis of mining technique8 to improve production and recovery in the more difficult mining conditions such as thick, multiple, and steeply pitchly seams found in the Western U.S. The project at Snowmass is the first attempt in the United States to operate a longwall in a steep coal seam. Plans are to mine three adjacent, successively downslope panels in the eight foot thick seam which varies in pitch from 27 to 33 degrees. During this work, researchers and mine engineers are expected to obtain answers to many engineering questions relative to panel design and development, selection of face equipment and beet operating techniques and procedures. They are also committed to obtaining hard data on costs, recovery, production, safety, and behavior of underground mine structure as the three panels are mined. This information is essential to future mine engineering and profitable mining of pitching Western coal reserves. Development of the first trial panel was begun in 1979 and completed in June 1981. The longwall mining equipment was then installed in the starting room and retreat mining begun on August 11, 1981. Project duration is expected to be about five years during which over tm million tons of coal will be produced. TRAINING The longwall mining method is new to Snowmass. For years the mine produced coal by room and pillar methods using conventional techniques to mine upslope rooms and Alpine F6A miners to cut entries and rooms on strike. Miners were experienced in room and - pillar mining from other mines. News of the longwall demonstration was received enthusiastically by Snowmass miners. Employee interest in the project was 100%. However, there was minimal longwall experience on site. In fact, most of the work force had not even seen a longwall. Mine and company management were well aware of the immediate need to develop trained longwall face mining crews and maintenance people qualified to work on longwall equipment and also expertise in longwall planning, equipment selection, power distribution design, ventilation requirements and panel development. The first approach to answer this huge deficiency in longwall mining experience was obviously training. Hence a training program directed toward those mining specifics most urgent to the beginning mining phases was initiated in mid-1980. Classroom lectures and hands on training, using instructors from equipment suppliers and available company longwall expertise, was conducted in longwall subjects to include face mining procedures, panel development, operation of equipment, equipment assembly and maintenance, electrical circuitry and controls, ventilation, move of longwall equipment, and safety procedures. At the same time, responsible engineers and foremen were sent on a tour of European pitching longwalls to see first hand how other mines working under similar seam conditions conducted their operations. Development techniques, types of equipment, methods for transport of men and materials, and ground control techniques were discussed with engineers, foremen and officials at each mine. This look at European longwall mining operations gave Snowmass good insight into the unique problems associated with longwall mining on 30' pitch. Mining considerations such as face conveyor/ support system slippage downslope, panel development, maintenance, safety considerations, manpower requirements, and haulage methods were covered with European experts

Jan 1, 1982

By H. Kenworthy

"INTRODUCTION ..Although the occurrence of iron ore in Missouri was recognized by Marquette as early as 1673, the first known mining and smelting operation was conducted in 1815. This operation was near Arcadia, Iron County, the first of its kind west of the Mississippi-Ohio River system. Several small furnaces of short life were erected in Missouri in the ensuing 30 years. However, until the extensive deposits of Iron Mountain and Pilot Knob were opened between 1843 and 1850, the state remained a minor producer of iron. It was this district which was chiefly responsible for the prominent position Missouri held in the iron industry until the late 1880's. At this time the easily minable high-grade ores became exhausted and the discovery of the immense Lake Superior deposits depressed the raw-ore price to such an extent that any mines ceased to operate. 3/Small yearly production of iron ores continued in Missouri to the present. Owing to war demands for hard ore suitable for open-hearth steel, the M. A. Hanna Co., through its subsidiary, the Ozark Ore Co., reopened the Iron Mountain, deposits and installed new equipment in an old concentrator to handle the low-grade ores left from previous operations. At present, ore production is from open pits, but underground mining is contemplated in the future. About 2,000 tons a day of iron ore is treated by gravity concentration of material from the open pits in the immediate vicinity. The concentrate is shipped to the Birmingham, Ala., district and to Granite City, Ill., for smelting. The coarse tailing is sold for ballast and concrete aggregate. The iron requirements of the concentrate stipulated by the purchaser are not difficult to meet, but the phosphorus is frequently higher than desired. For 1946 the concentrates averaged 54.18 percent iron and 0.235 percent phosphorus with low sulfur. The Ozark Ore Co. concentrate, however, sometimes contains as much as 0.40 percent phosphorus. The phosphorus in ores from those portions of the deposits wherein the phosphorus occurs with siliceous gangue is readily rejected in the milling, but in much of the ore the phosphorus is associated with the iron and concentrated with the iron minerals. Selective mining is impossible owing to the spotty occurrence of the phosphorus mineral. Often within 5 feet the ore will change from low phosphorus to high phosphorus, and it would be expedient to find a method of rejecting enough phosphorus at the mill from the latter type of ore to meet the phosphorus specification."

Feb 1, 1948

By Fredrick L. Johnson

In deposits of the John Muir Wilderness, tungsten is the principal metallic element. Gold, silver, copper, and molybdenum could be recovered as by-products from most of the tungsten deposits. More than 1 million tons (0.9 million t) of tungsten resources are estimated to be along the fringes of metasedimentary roof pendants. Gold-silver deposits and silver-copper-lead-zinc deposits with small resources are found at several localities. The association of metal deposits with the intrusive-metasedimentary rock contacts and the widespread existence of these contacts, suggests additional resources exist. The area has no known potential for coal, oil, gas, or geothermal energy.

Jan 1, 1981

By R. M. Whyte

The Konkola Deep Mining Project (KDMP) seeks to exploit the deep level potential of the Konkola Deeps orebody, producing high grade copper concentrates for treatment at the Nkana Smelter and Refinery. As an alternative to smelting, Konkola Copper Mines (KCM) has examined a processing route involving pressure leaching of the Konkola concentrates at Nchanga, with the leach liquor being treated by solvent extraction and electrowinning to produce high purity copper cathode. The solvent extraction circuit would be operated to achieve a high ?delta? copper, thereby providing a strong acid raffinate which can be used in the existing Tailings Leach Plant (TLP) to treat Nchanga oxide copper materials. The main focus of the hydrometallurgical option is to capitalize upon the synergy that exists between the treatment of sulphide copper concentrates (acid producing) and oxide copper ores (acid consuming). The paper discusses the key features of a comprehensive piloting campaign carried out at Anglo American Research Laboratories, which involved the co-treatment of Konkola copper concentrates and Chingola refractory ore in a fully integrated pilot plant circuit.

Jan 1, 2001

By AIME AIME

WHEN "Chief" Buehler in mid-September set out on his official 10,000 mile swing-around-the-circle visiting Local Sections he decided not to tell his audiences how to organize and operate a state geological survey. As the director for 28 years, of the Missouri Bureau of Geology and Mines (which, he concedes, is the best in existence) lie could have done this to good advantage; but he preferred to discuss affairs of the Institute. In 25 speeches made to member and student groups, he dwelt on sonic or all of the following phases of activities. He stressed the vital importance of the Local Sections in providing the opportunity for members to associate under pleasant auspices with others in their profession. The benefits of Institute membership he classified as tangible and intangible. Of the two lie felt that the latter were more important. A man's progress in his profession depends in large measure upon a broad acquaintance and friendship with others. The Institute is incomparably the best medium for meeting fellow engineers. The primary, function of the new enlarged Membership Committee is to obtain a comprehensive list of engineers eligible to be members, always hearing in mind that the standards of membership must not be lowered in any degree. These men are to be invited by individual letter to apply for membership. Whether they become members or not is of less importance; but it is vital that no qualified man should be outside the fold for the reason that membership had never been suggested to him. Dr. Buehler emphasized repeatedly his feeling that the younger man that had never had Institute membership brought specifically to his attention had been cheated:

Jan 1, 1935

By P. Kolodziejczyk

Mining seismicity can be harmful both under and on the surface. ? Tremors are not totally damaging, but destructive to buildings and infrastructure, especially in highly urbanized regions, such as Upper Silesia in Poland ? Destroy the social appreciation, trust and support for mining industry ? To prevent or reduce these effects, engineers and scientists develop methods allowing prediction of ground shaking intensity near buildings and various losses that can result from it Evaluation and prediction of mining tremor?s damaging influence on buildings is usually solved with two steps: ? Estimation of local ground shaking intensity (based on known attenuation relation) and classification into one of several predefined intensity intervals ? Apply supposed relation between the shaking intensity interval and qualitatively defined damaging effects to express predicted effects This makes a mixed quantitative/qualitative procedure, difficult to analyze or optimize

Aug 1, 2013

By R. W. Gould, B. G. LeFevre, A. G. Guy

The resistivity anomaly known as the K state was studied in Ni-Mo alloys containing 10.5 and 14.0 at. pct Mo. Both these alloys exhibit a large K effect which depends on the mechanical and thermal treatment. On the basis of X-ray diffuse scattering studies which were correlated with resistivity measurements, it appears that the K state in dilute Ni-Mo alloys can be associated with changes in the degree of short-range order within the a phase. An interesting phenomenon that has received much attention in recent years is the K state. The K state is marked by anomalous changes in some of the physical properties of certain alloys without the occurrence of observable microscopic structural changes. One of the early pieces of work in this area was by Thomas' who studied alloys of Ni-Cr, Ni-Cu, Ni-Cu-Zn, Fe-A1, Fe-Si, and Ni-A1. Upon annealing specimens which had been previously cold-worked or quenched from an elevated temperature he found an anomalous increase in resistivity over a certain temperature range. He also found that specimens which had been appropriately annealed to develop the K state showed a decrease in resistivity upon subsequent cold working. These effects are opposite to those found in normal alloys. Although the resistivity anomaly has been rather arbitrarily taken as the "definition" of the K state, there are several other interesting effects which accompany the resistivity increase. In Ni-Cr alloys,2, 3 for example, it was found that the hardness increases with increasing resistivity. It was also found that specimens which have been treated to develop the K state can be cold-worked for as much as an 80 pct reduction of area without an increase in the hardness. In Fe-A1 and Fe-Si alloys4 the K state is accompanied by an increase in flow stress and by a lattice contraction. In Ni-A1 alloys,5 specimens which have been treated to develop the K state also show an increase in elastic modulus. In Ag-Pd alloys6 the increased resistivity observed on annealing a cold-worked specimen is accompanied by an increase in the thermoelectric power and an increase in the Hall coefficient. The explanations of the K state phenomena are varied and depend upon the particular alloy in question. Several theories have been advanced to explain the increased conductivity with cold work on the basis of changes in the electronic configuration of the alloy as a result of local lattice distortions.7"9 Most investigators, however, believe that some type of local order in the solid solution, either short-range order (SRO) or clustering, is responsible for this effect. Theories concerning the relationship between ordering and the K state have for the most part been speculative, since there is little direct X-ray evidence that can be correlated with the above property changes. Much of the previous work on the K state was done in the Ni-Cr system where the small difference in the X-ray atomic scattering factors of the components nickel and chromium makes it very difficult to use X-ray diffuse-scattering measurements to determine the role of local order. In the Ni-A1 system, however, Starke et al.10 succeeded in detecting a connection between local order and the K state. It was found that a small but measurable K effect correlated with increasing SRO in the nickel-rich a phase. The manner in which local order might increase the resistivity of K state alloys is not completely clear. Since most of the known K state alloys contain at least one transition element, significance has frequently been attached to the presence of an unfilled d shell. It has been suggested that during the formation of the K state the number of conduction electrons decreases as a result of the transfer of s electrons to the d shell where they are more tightly bound.1'11'12 Koster and Rocholl13 have proposed that SRO can cause an increase in resistivity for alloy systems in which the number and mobility of charge carriers are reduced when the percent solute is increased. According to this hypothesis, the local environment of a given solvent atom changes in the same manner with increasing percent solute as it does with an increasing degree of SRO; hence the change in physical properties should tend in the same direction. In this hypothesis, SRO is considered only in a statistical sense, and the increased resistivity of the K state is attributed to a change in the mean distribution of electrons and holes in the s and d states as a result of SRO. From the work of Chen and Nicholson on Ag-Pd alloys,6 it appears that the K state can occur in systems for which the d shell is completely filled. These investigators explained the increased resistivity by picturing the SRO as small domains of some form of long-range order (LRO). According to ~ibson,'~ the number of effective electrons can be reduced by the creation of a new Brillouin zone boundary near the Fermi surface of an alloy as a result of the changing crystallographic symmetry that accompanies the formation of a superlattice. This idea may be expressed in terms of the superzone concept.15 In the present work the role of local order in the formation of the K state in Ni-Mo alloys was investigated. The principal tools used in this study were X-ray diffuse scattering and electrical resistivity measurements; however, these data were supplemented by electron microscopic and field-ion microscopic data. The purpose of the work was to determine whether or not the K state in Ni-Mo alloys can indeed be attributed to the formation of SRO as has been proposed by previous investigators.

Jan 1, 1969

By JÖRG DEHNERT, PETER WINDISCH, Bernd Schönherrt, JENS STOPP

The Quick-Erect Stopping System (QESS) offers a new way of reducing the radon exposures of miners in Germany, especially during remediation work in old mines. The QESS is a light-weight, modular, and reusable construction kit of interlocking telescopic aluminum tubes, radon-proof foil, and expanding foam. It is designed to seal off radon-rich parts of galleries within only a few minutes. Originally, the QESS was developed to protect miners against radon exposures. Then, the QESS found the attention of several mine rescue teams at a German mining conference. The Student Mine Rescue of the Technical University Bergakademie Freiberg and the Wismut Mine Rescue carried out firstmine rescue drills in Freiberg and Schlema. Additionally, a mine rescue drill was carried out by the Front Range Mine Rescue in the Edgar Experimental Mine of the Colorado School of Mines. These drills helped to improve the systemand highlighted its potential for mine rescue operations. Now, the QESS is wellsuited for small-scale mining. The QESS can be used to seal off galleries in only a few minutes to both protect miners fromradon exposures and to support mine rescue operations. Moreover, the QESS was also successfully used in ventilation experiments.

Jul 23, 2020

By Samuel W. Woods

The Tacoma, Washington plant is one of six plants in the United States Gypsum Company's Acoustical and Mineral Fiber Division. The Tacoma facility was acquired in 1959 along with six other mineral wool plants from the American Rock Wool Company. Originally, the Tacoma plant was built as a carbide plant during the Second World War and after that was converted and operated as a mineral wool plant by several insulation companies. Through these early years, the use of raw materials at Tacoma consisted primarily of slags along with small percentages and various combinations of silica (in various forms such as gravel), limestone and basalt. These raw materials were melted in cupolas using coke as the heat source. Raw material usage and types as well as mineral wool production methods and equipment remained without major changes for many years.

Jan 1, 1983

By Michael Young, Rodrigo Araya, Cesar Gomez, Le Huynh, James Finch

The performance of flotation machines is closely related to the gas dispersion characteristics achieved in their operation. It is known that frothers play a major role not only in the size distribution of the generated bubble population, but also on the swarm rise velocity. A program to characterize frother effects on two-phase hydrodynamics (air-water) of Jameson cells was undertaken in a fully instrumented pilot unit installed at McGill University. Gas dispersion parameters (gas velocity, gas holdup and bubble size distributions) of the gas-liquid mixture generated in the downcomer were measured after its release into the separation chamber. The unit was operated under different conditions including gas velocity, liquid jet velocity and frother concentration (MIBC). Bubble size distributions for concentrations above the critical coalescence concentration (CCC) were narrow with Sauter mean diameter between 0.6 to 1.3 mm. The bubble size followed the general trend as encountered in other types of flotation machines, i.e., rapid decrease with increasing frother concentrations below 10 µL/L, and almost no change in size for concentrations above 30 µL/L. The CCC was between 10 and 15 µL/L. Strong correlations were found between bubble size and air-to-liquid flow ratio (APR), and between the bulk density of the aerated solution in the separation tank and the vacuum inside the downcomer. An equation is proposed to estimate gas holdup in the separation tank from vacuum and bulk density readings.

Jan 1, 2014

By T. G. Carter

"Tremendous progress has been made in recent years towards developing computational tools that allow ready solution of most common rock engineering problems, with amongst the most advanced of the tools focusing on evaluating engineered openings within Synthetic Rock Masses. These new codes have the potential to allow much more realistic design, but they must not be used without careful calibration – prior to – during and – post completion of any modelling. This paper explores some of the pitfalls of inadequate data collection and suggests more emphasis be given to calibration. Guidelines for minimum levels of parameter data are suggested for improving application of basic to sophisticated modelling codes.INTRODUCTION & BACKGROUNDTremendous progress has been made in recent years towards developing computational tools that allow ready solution of most common rock engineering problems. The degree of sophistication now possible with some of the available codes allows one to tackle extremely complex problems that were not thought tractable even a decade ago. Indeed, generation of synthetic numerical rock masses, based on discrete fracture network representations that closely mimic actual rock mass conditions, such as are shown in Figure 1, is today relatively straightforward, and not as user-challenging as employing state-of-the-art codes of even a few decades ago. This is largely because major improvements in computer graphics and in availability of ready-made user-friendly input-output interfaces have paralleled development of these new codes, now in some cases outpacing actual new analytical/procedure developments. This is something of a reversal from the first few decades of DOS-based rock engineering computational experience, when only rudimentary graphics were available and user-friendly input-output interfaces were virtually non-existent."

Jan 1, 2015

By F. Petersen, W. van Dyk, J. Bonsu, A. Isafiade

"This paper aims to demonstrate how a systemic approach can be applied to the analysis of the causes of accidents in South African mines. The accident analysis framework used was developed previously by the authors from the combination of the Mark III version of the Swiss Cheese model, Incident Cause Analysis Method (ICAM), the Nertney Wheel model, and safety management principles. Data on 91 accidents occurring from 2010 to 2012 at the site of a platinum mine in South Africa were used to populate the newly developed framework. The results obtained show that while routine violations (45% of all accidents analysed) were the most common form of human error, problems in the physical environment of workers were the most common workplace factor (39.6% of all accidents analysed). Furthermore, inadequate leadership was found to be the most common systemic factor responsible for accidents (51.6% of all accidents analysed). Some workplace factors were more commonly associated with particular unsafe acts than others, and some systemic factors were more associated with particular workplace factors than others. The outcome of this study demonstrates that systemic factors, rather than human errors and violations, are the chief causes of accidents in the mining sector. IntroductionThe mining industry is a very important sector of the South African national economy. A major factor threatening the sustainability of this industry is mining accidents, which frequently result in injuries or deaths, destruction of property, and pollution of the environment. In the past, mining accidents have led to the shutdown and threat of shutdown of mines (Ryan, 2008; Mail and Guardian, 2011). The country stands the risk of incurring significant losses if the mining industry continues to experience shutdowns. In 2012, the mining sector accounted for R262.7 billion (equivalent to US$32.83 billion) representing 8.3% of GDP directly, on a nominal basis (Chamber of Mines of South Africa, 2013).Mining safety is a global concern and has attracted significant international attention. This has precipitated various studies into different aspects of mining. Unfortunately, human error has been blamed for the majority of these accidents. A study by the US Bureau of Mines found that human error is the cause of almost 85% of all accidents (Patterson and Shappell, 2008). In Australia, it is the cause of two out of every three occupational accidents (Patterson and Shappell, 2008). Various mining companies maintain that they run efficient systems, and hence the behavioural problems of workers are to blame for most accidents. An understanding of accident causality could be a major step in the quest to reduce accidents. Only with a good understanding of the accident process can effective remedies can be designed."

Jan 1, 2017

By Winton J. Gale

Coal pillar design has been based on generalized formulas of the strength of the coal in a pillar and experience in localized situations. Stress measurements above and in coal pillars indicate that the actual strength and deformation of pillars vary much more than predicted by formulas. This variation is due to failure of strata surrounding coal. The pillar strength and deformation of the adjacent roadways is a function of failure in the coal and the strata about the coal. When the pillar is viewed as a system in which failure also occurs inthe strata rather than the coal only, the wide range of pillar strength characteristics found in the United Kingdom, United States, Republic of South Africa, Australia, People's Republic of China, Japan, and other countries are simply variations due to different strata-coal combinations, not different coal strengths. This paper presents the measured range of pillar strength characteristics and explains the reasons. Methods to design pillar layouts with regard to the potential strength variations due to the strata strength characteristics surrounding the seam are also presented.

Jan 5, 1999

By L. F. Albert

The paper describes solutions given to foundation problems during the reconstruction of a power plant set on fire, located adjacent to several still Working Units. After a detailed site and laboratory investigation, it was decided that it could be possible to include within the new foundations the preexisting cast in situ driven piles with enlarged base 50 cm in diameter and let them work with new 41 cm driven, cast in situ piles without enlarged base. Demolition of existing caps was carried out with expansive mortar in order to avoid any possible damage to piles, whose actual conditions were checked by several load tests. New piles were designed to support service load by shaft resistance, in order to limit total and differential settlement. When piles had to be driven adjacent to nearby structures, measurements of peak soil particles velocity were carried out while driving piles at decreasing distance from critical locations. By preboring most of the upper clay layer it was possible to reduce within safe limits for structures the induced vibrations.

Jan 1, 1989

By William G. Pariseau

The research reported here concerns a four year study of the rock mechanics aspects of two underground hardrock mine study stopes. The first study was conducted at Anaconda Minerals Company's Carr Fork Mine near Tooele, Utah. The second study was conducted at the Homestake Mining Company's Homestake Mine In Lead, South Dakota. Both case studies were cooperative efforts of mining company personnel, the Spokane Research Center of the Bureau of Mines and the Department of Mining Engineering, University of Utah. Large diameter (6 1/2 In.) blastholes were an integral part of the stoplng method at each mine. A true vertical crater retreat (VCR) method was used at the Homestake Mine, while a vertical bench mining method (VBM) was used at the Carr Fork Mine. VCR and VBM methods were developed In the 1970's; they offer significant productivity gain and are now used throughout the world. The new technology, however, brings with It a requirement for more sophisticated engineering design and control. Since there are no personnel in a VCR or VBM stope, all ground control Including dimensioning of stopes and pillars and the layout of cable bolt assays or other artificial support must be done in advance of production blasting. Accordingly, the objective of the research study was the establishment of a procedure for optimizing stops and pillar sizes. The approach taken was In each case a combination of mine measurements of the study stope response to mining, laboratory testing for rock properties and In situ stress measurements of the premining stress field, and theoretical calculations of the study stope response to mining. All calculations were done with the UTAH-II finite element computer program. Simulation of the blasting sequence gave a correlation of 0.88 between measured and calculated extensometer readings (Incremental relative displacements) at the Carr Fork Mine where other 30 Instrumentation boreholes were used to monitor the test stope response. A correlation of 0.84 was obtained at the Homestake Mine where 19 instrumented boreholes were used for monitoring purposes. These high correlations validated the computer mode and calibrated It for rock mass properties. The calibrated model was then used In parametric studies of alternative design layouts.

Jan 1, 1985

By W. R. Bacon

"MAGNETITE HAS BEEN found in many .parts of the coastal area of British Columbia, but the more important deposits are on Vancouver Island and Texada Island. The locations of these deposits are shown on Figure 1.Interest in the magnetite deposits dates back to the 1870s, when land was acquired on the southwest coast of Texada Island by the Puget Sound Iron Company. This ground included the Prescott, Paxton, and Lake deposits. During the years 1885 to 1903, and 1908, 28,898 tons of magnetite ore was shipped to the company's blast-furnace plant at Irondale, Washington, U.S.A. This production was almost entirely from the Prescott open-pits.In the years following the Texada Island discoveries, other magnetite deposits were found in the coastal area, and various plans were proposed to utilize the local ores in the establishment of a steel industry in the Pacific Northwest. None was carried to fruition but, in 1951, open-pit mining was begun at Iron Hill, Vancouver Island, to furnish iron concentrates for steel mills in Japan. In 1952 mining of the Texada deposits was resumed to supply the same market. Production figures for these recent operations are as follows:"

Jan 1, 1949

By M. Grodner

Ground Penetrating Radar (GPR) is an electromagnetic geophysical reflection technique that maps reflections associated with a change in electric properties of the target medium. It can thus be used to map the geometry of geological features and fractures as these can have different electromagnetic properties to intact rock. GPR was used successfully to determine the position and nature of the fractures in the tunnel sidewall, in the area of the simulated rockburst experiment. By comparing the radar scans acquired before with those acquired after the blast, it was possible to determine which fractures were reactivated by the blast and where new fractures were developed. It was found that the mining-induced fractures that formed during the development of the tunnel were re-activated by the simulated rockburst, as indicated by their increased reflectance on the radar scans. In addition, several new tunnel sidewall parallel fractures developed in the area of the blastholes. GPR thus clearly shows how and where the fracture pattern changed as a result of the blast and contributed to the understanding of the mechanisms of damage associated with the blast, and perhaps rockbursts in general.

Jan 1, 2001

By E. E. Krist

El desmuestre de un criadero tiene un buen número de finalidades. En la fase inicial es necesario definir los límites del yacimiento y el contenido o ley del mineral hasta el punto de que pueda ser establecido si es, de hecho, un yacimiento económico. Igualmente, las muestras tienen que ser generadas de forma tal que las evaluaciones geológicas y metalúrgicas puedan ser Ilevadas a cabo. Finalmente, cuando se conoce la suficiente información concerniente a la geología, mineralogía y metalurgia, puede ser desarrollado un método minero y su plan, y construidas las oportunas plantas metalúrgicas para procesar los minerales a medida que se encuentran disponibles1. Con las minas actuales grandes y complejas a cielo abierto los métodos de desmuestre único deberían de ser inadecuados. La perforación por diamante, la perforación por percusión, pozos subterráneos y galerías, juegan todos conjuntamente un papel parcial en la definición total del yacimiento. En la mina Twin Buttes, de la Anamax Mining Company, el desmuestre y la definición del yacimiento conducirán eventualmente a la existencia de tres plantas metalúrgicas de proceso y, quizá a, una operación de minería subterránea. Fue puesto en marcha un concentrador de sulfuros de 30.000 tons. por día en Septiembre de 1969 y una planta de 10.000 toneladas diarias de lixiviación de óxido fue puesta en servicio en Mayo de 1975. La finalidad de esta presentación es la de exponer históricamente el desmuestre del yacimiento que ha sido Ilevado a cabo en Twin Buttes, describir brevemente el criadero, y exponer los métodos analíticos corrientemente utilizados para ayudar al geólogo, al metalúrgico y al diseñador de la mina en sus respectivas evaluaciones.

Jan 1, 1982

By Steve Kral

Reducing the cost per ton and increasing productivity are key factors in a mine’s profitability. Mining companies can do little about commodity prices. So to keep a mine operating at a profit, management must reduce costs and improve worker and equipment productivity in every facet of a mining operation. From mining to crushing to processing, mine management is constantly seeking new methods and technologies to improve the way it mines minerals. And it is willing to borrow techniques used by other operators.

Jan 1, 2002

By Stanley Dempsey

INTRODUCTION The mining industry has been under- going a significant restructuring for the past several years. Some firms have been liquidated. Some have been merged with other firms. A number of mining divisions of larger firms have been spun off, in some cases in leveraged buyouts by management. Recently, there have been a number of spin outs of gold subsidiaries. There are also a number of start-up situations where new firms are emerging as significant gold producers through mine development or acquisition. This restructuring has created an attractive market for specialized mining finance firms, and a number of firms have recently entered that field in the United States. These firms provide financial advisory and valuation services to mining firms and project developers, and access to venture capital. In some cases, they invest for clients or for their own account. I have been asked to describe how our firm works, and what kind of information we expect to receive when mine developers seek our assistance in financing a project. HOW WE OPERATE Denver Mining Finance works for both mine developers and investors. We also provide expert advice on mining issues to governments and to firms who are in litigation over mining issues. A lot of our work involves valuing mineral interests for various purposes. Our principal expertise is in the technical, commercial, and financial area. We help put mining deals into shape commercially so that they can be financed, and we help investors get into mining deals that are commercially sound. We work on projects, but we also advise mining firms on the structure of their business and how to make the most out of one or several mines that they might own. In addition to our work for clients, we are also prepared to invest in mining projects for our own account, and to recommend gold properties for acquisition by our parent company, Royal Gold, Inc. We are, to some extent, a venture capital firm, in that we sometimes work with projects that are not "bankablerV1 and are prepared to invest in attractive early-stage situations in mining. However, I want to emphasize that our principal focus is on development of commercially attractive mining projects that can be brought into production in the best possible financial terms. If we can make a project qualify for a project loan from a commercial bank, we will not advise the developer to use high cost venture capital. For the purpose of this paper, I will focus primarily upon our functions with respect to development of precious metal projects. In a typical case, a firm with an advanced-staged project approaches us for help with financing the final feasibility study, and construction and operation of a mine. In some cases, the developer has already developed a financing plan and wants only our access to investors. If we agree that the project is sound and that the financing scheme will be attractive to investors, we will help the developer reach investors on a commission basis. In such cases, we are particularly insistent that the financing plan and our participation meet all regulatory requirements, particularly compliance with state and federal securities laws. In most cases, however, the developer asks us for advise both on how to structure the financing, and how it can be implemented. Here we work for fees based on hourly rates for advisory work,

Jan 1, 1987