Search Documents

By Alan Dahlstrand

The Jamestown Mine is a 6.3-kt/d (7000-stpd) open-pit gold mining operation located in the central portion of California's historic Mother Lode district. Most early production from the Jamestown area occurred in underground operations from 1906 through 1916. Pit production began at Jamestown in early 1987 and continued until July 1994. Although additional mineral resources existed, they were deemed to be uneconomic. About 23.3 t (750,000 oz) of gold were produced from pit operations, compared to 31 t (100,000 oz) from early underground mining. Recent operations at Jamestown included two open pits, a flotation mill and a flotation tailings facility. Flotation concentrates were produced in Jamestown and shipped to Yerington, NV for cyanide leaching in a carbon-in-pulp (CIP) circuit.

Jan 1, 1995

By Andres Salazar, Carlos Delgado Robles, Richard K. Preece

Minera Escondida, located in the Antofagasta Region of northern Chile, is the world’s largest producer of copper as concentrate and SX-EW cathode. Projects to increase mill and flotation capacity began soon after start-up in 1990 to off-set decreasing copper grade. Subsequent projects had the objective to increase copper production through heap leach and SX-EW production and a second concentrator. The mine footprint concurrently expanded peripherally from the central high-grade enriched core of Escondida and then into the separate Escondida Norte deposit. Early in the mine life, metallurgical forecasting that was based on metallurgical composites of presumed ore types and historical plant production was adequate for operational planning, plant design, and project valuation. This approach became unreliable, however, as the increase in mine footprint was accompanied by an increased variability in key ore body characteristics such as hardness, copper-iron sulfide mineralogy, and sulfide liberation textures that were not reflected in the geological criteria used for ore type designation. The project study teams turned to small-scale physical and chemical tests to better characterize the spatial distribution of these key ore characteristics. Programs associated with capital growth projects were carried out through the mid-2000s to sample and construct a three-dimensional spatial model of hardness, copper sulfide mineralogy, and rougher flotation recovery from tests on 15-m drill core composites. Mathematical models were developed from the respective ore characteristic data to calculate throughput, flotation recovery, and concentrate copper grade. The spatial models were integrated with the concurrent mineral resource block model using standard geostatistical methods and the metallurgical process calculations were applied to the block estimates. The geometallurgical model, originally constructed on a project basis, is now managed by a dedicated team reporting to the manager of Geosciences & Resources Definition in the Escondida organization. The model has evolved with increasing complexity of the mine and processing plants and currently includes seven forecasting areas for three concentrators and four areas for two leach plants. Metallurgical forecasts of mill throughput, final flotation recovery, and concentrate copper grade still have the highest relevance to mine planning and optimization. Sample preparation, test procedures, and quality control methods are summarized for the ore characteristic tests important to these forecasts. Analytical results from recent annual sampling programs are presented for the hardness indices, rougher flotation recovery, and partial extraction copper analyses. Geostatistical analysis of the SAG mill hardness index is summarized as an example for the spatial estimation process. Mathematic models are presented for throughput (based on hardness indices), final flotation recovery (based on rougher recovery and plant calibration studies), and concentrate copper grade (based on sulfide mineralogy and empirical pyrite rejection studies).

Aug 31, 2023

By W. Blake, J. Whyatt

Sixty years of rockbursting in the Coeur d’Alene district has taught painful lessons and led to a number of practical advances in controlling rockburst hazards. This paper summarizes those lessons, concentrating on practical measures that have been successfully adopted to reduce hazards. These lessons are explained in the context of district mining history and current understanding of rockburst phenomena. Overall, the paper provides the practicing mine engineer with an appreciation of rockburst hazards and an overview of practical measures that can be used to control these hazards in the context of Coeur d’Alene district experience.

Jan 1, 2002

The mining industry continues to experience a skills shortage and this is having an impact on the ability of mining companies to operate sustainably. Apart from a few exceptions, there is a dearth of geologists, mining engineers, metallurgists as well as environmental scientists and other professionals in the global mining industry. This relates to both quantity and quality. It makes good business sense for mining companies to employ local professionals rather than expensive expatriate staff. In some cases a mining company could employ more than 10 local mining engineers for the cost of one expatriate. However, in many countries local professionals are not always equipped professionally to work on mine sites. The result is that many companies are not operated optimally due to human resources gaps. In some cases, particularly in key areas such as mine planning, this threatens the sustainability of the operation or at the very least results in sub-optimal resource utilisation. This paper briefly presents some of the issues and strategies being implemented and that might be implemented to maintain a sustainable supply of quality minerals graduates to the industry in 2011 and beyond.

Jan 1, 2011

By Peter A. Anderson

Innovative solution management is being used at Coeur-Rochester Inc. to increase bullion production and decrease overall costs. New operating programs call for reduced solution application rates to the heap that increase pregnant stream values at a lower and less costly plant flow rate. Silver and gold extractions are equal regardless of leach solution application rate. Solar heating is used in the summer months to increase the core temperature of the heap for use in the winter months to enhance the silver extraction rate. The Coeur-Rochester silver and gold mine, located in central Nevada, is an open pit, heap leach operation that has been in production since late summer of 1986. The facility produces about 15.4 kt/d (17,000 stpd) of -13 mm (-0.5 in.) ore to a leach area consisting of more than 37 hm2 (4 million sq ft) of 80 ml HDPE liner. Crushing is accomplished with a 1220x 1520-mm (48- x 60-in.) jaw crusher. This is followed by a single 2.1-m (7-ft) standard cone crusher and is completed with four 2.1 m (7 ft) short-head cone crushers. Agglomeration is not required for the crushed ore, which contains less than 10% -75. µm (-200 mesh) material. The ore contains 53 g/t (1. 55 oz per st) silver and 0.377 g/t (0.011 oz per st) gold. It is end dumped over previously leached material, leveled, and then ripped with a bulldozer. Drip emitters at 810 mm (32 in.) spacings on 910 mm (36 in.) centers are used to apply barren solution to the heap. A portion of the emitter lines are buried I m (3 ft) deep during the winter months and are placed on the surface the remainder of the year. The leach solution contains 0.75 g/L (750 ppm) sodium cyanide solution at a pH of 10.5 - 11. Dissolved oxygen averages 8 ppm in the pregnant solution. Cyanide consumption for the ore to date is just under 0.2 kg/t (0.4 lb per st). The pH control is accomplished by adding I kg/t (2.0 lb per st) 0-10 mm (-0.4 in.) pebble lime to the ore at the tertiary crusher. The pregnant solution is processed by a conventional closed circuit Merrill-Crowe system. The pregnant solution is clarified through three 158 L/sec (2500 gpm) US Filter Auto-jet clarifiers. This is followed by deareation through a

Jan 1, 1989

By Thomas R. Doyle

When you think of the state of Maine, you probably think of lobsters or lighthouses. The last thing you would think of is metallic mineral mining, and that is for good reason. According to the Maine Geological Survey?s website, ?no metals have been mined in Maine since 1977.? Moreover, Maine?s metallic mineral mining laws and rules, which were last rewritten in 1991, have effectively made mining in the Pine Tree State impossible. Statutory changes enacted in 2012, however, put Maine on a path to make metallic mineral mining part of the local economy in the near future. History of metallic mineral mining in Maine Currently, Maine is not a metallic mineral mining state, though that has not always been the case. The 1800s saw various mining operations in Maine, including what the Maine Geological Survey calls a ?mining boom? from 1879 to 1882, where mining of iron, silver, copper, lead and zinc expanded rapidly. Mining and mining activity in the more recent past, however, drove the debate before the state legislature when this issue was debated in 2012.

Jan 1, 2012

By H. Ehnes

"“Industry 4.0” – “Mining 4.0” - perhaps you have already heard of these terms? These keywords signify the next stage of industrial production. The internet and production technologies are growing closer together. Machines can communicate with one another, wherever they may happen to be located. The “Internet of Things” is the appropriate term. But what does SAFETY 7.0 mean? It is both brand new and traditional at the same time. It also has to do with the success of companies, with efficient production. And yet there is a great deal more at stake. It has to do with our lives and our safety – the supreme commodity in this world. What exactly SAFETY 7.0 means, what the number 0 stands for and the meaning of the number 7, and what this all has to do with mining will be explained in the following article. Mining is a fascinating undertaking. Mining is indispensable for a country’s economic development, whatever that may concern: infrastructure, energy supplies or raw materials for industrial production. Mining has brought forth many technological developments and innovations that can currently be found in our daily lives. Mining is impressive, grandiose and repeatedly fascinates mankind with its immense dimensions. Miners throughout the world still work hard and, for this reason, are bound to one another in a special way. In mining, every man looks out for the other; you have to be able to rely on each other. That creates a strong bond. The other side of the coin is that mining and disasters belong to normality in the media and thus also in our perception. Accidents at work and even catastrophes occur in mining, quarries, or raw material operations almost on a daily basis somewhere in the world. They are often associated with extremely serious injuries, or even a fatal outcome, for the miners affected and, in turn, dramatic consequences for the families of those involved. It could be in China, India, Russia, or somewhere in Africa, Asia or America – it mostly does not happen in front of our door or in our neighbour- hood. Perhaps because of this in the daily concert of negative headlines, we do not register these catastrophes any more in our minds. We write them off under the heading “Nothing special”, since there are, day in day out, more terrible news items about wars, civil wars, famines, or ecological disasters. Things only really change if there is a dramatic number of deaths or when we are personally affected, close by in the vicinity, or can witness the rescue action live. In Europe, these three mining disasters in particular have recently generated media resonance:"

Jan 1, 2016

By S. Assemi

Interaction forces between a hydrophilic silica particle and an air bubble were measured by atomic force microscopy using simplified model systems with deionized water and dilute KCl solutions. Contributions from the hydrodynamic force were minimized by using a low piezo speed. Particle-bubble separation distance and the bubble spring constant were calculated from linear regression of the piezo extension versus cantilever deflection. The bubble surface potential was then estimated from fitting the AFM-measured forces to the Hogg-Healy-Fuerstenau (HHF) model, using the surface element integration (SEI) method. Surface potentials obtained for the bubble at a low applied force were comparable with the literature data, suggesting that the simplified model used here can give a reasonable estimation of the bubble surface potential under moderate applied forces. Interaction forces between a silica particle and an air bubble were also measured at different locations on the air bubble surface. The force curves obtained at the edges of the bubble fitted very well to the theoretical force curves regardless of the applied force, while curves obtained at the center and halfway to the center, were more difficult to fit, in particular at higher applied forces (> 13 nN), suggesting that force curves obtained at the edges of the air bubble might be less prone to deformation effects.

Jan 1, 2008

By D. E. Severson

The coal solution refining process under investigation is basically a modi¬fication of the German Pott-Broche Process, on which patents date back to 1927, (5, 6). This process was used in Germany during World War II for the partial dissolution of coal in hydrocarbon solvent and removal of the ash by filtration to produce a raw material for carbon electrodes for aluminum plants. At the end of World War II the German synthetic fuel program, of which this process was a small part, was abandoned as not economical. In recent times the whole field of coal liquifaction has been given a new impetus; present technology indi¬cates that the economic processing and refining of coal may be possible in the United States. A number of approaches to coal liquifaction have been investigated, and several of these are currently being funded by the U. S. Office of Coal Research. One approach is direct thermal treatment of the coal as in the FMC Project COED, in which coal is thermally cracked to produce gas, liquid products and char. Another approach is the Hydrocarbon Research Institute's H-coal process in which coal is catalytically hydrogenated. Two other federally funded projects involve the extraction of coal by solvents. The Consolidation Coal Company's Project Gasoline, now in the pilot plant stage in Cresap, West Virginia, is an attempt to produce gasoline plus a residual char by partial solution of the coal substance. The coal de-ashing process being developed by the Pittsburgh and Midway Coal Company is a modification of the Pott-Broche process. Coal derived solvent is used with hydrogen to dissolve the entire coal substance, subsequent filtration removes the ash and the solvent is recovered for recycling.

Jan 1, 1968

By Joel Lööw, Jan Johansson, Lena Abrahamsson

Industry 4.0 offers new possibilities to combine increased productivity with stimulating workplaces in a good work environment. Used correctly, digitalization can create attractive jobs in safe control room environments, which provide space for the employee’s full expertise and creativity. This is true also for the mining industry. But, to succeed, it is important to analyze the development from a worker’s perspective. What will happen to their work? What skills will be needed in the mine of tomorrow? We must also consider the risks, such as privacy issues, increased stress, and work-life boundaries. These questions must be understood if we are to create workplaces that can attract a young and diverse workforce to tomorrow’s mining industry. In this article, we try to illustrate what the new technology can mean for the individual miners. We formulate the notion of Mining 4.0 (Industry 4.0 in the mining industry), where we try to create an image of how the future might look from a miner’s perspective and how mining companies may navigate their way to a future that works for all miners. To illustrate the range of possible outcomes, we formulate two scenarios: one utopian and one dystopic. At the end of our article, we bring forward six recommendations that can be considered a beginning of a road map for the human side of Mining 4.0.

By Joel Lööw, Jan Johansson, Lena Abrahamsson

Industry 4.0 offers new possibilities to combine increased productivity with stimulating workplaces in a good work environment. Used correctly, digitalization can create attractive jobs in safe control room environments, which provide space for the employee’s full expertise and creativity. This is true also for the mining industry. But, to succeed, it is important to analyze the development from a worker’s perspective. What will happen to their work? What skills will be needed in the mine of tomorrow? We must also consider the risks, such as privacy issues, increased stress, and work-life boundaries. These questions must be understood if we are to create workplaces that can attract a young and diverse workforce to tomorrow’s mining industry. In this article, we try to illustrate what the new technology can mean for the individual miners. We formulate the notion of Mining 4.0 (Industry 4.0 in the mining industry), where we try to create an image of how the future might look from a miner’s perspective and how mining companies may navigate their way to a future that works for all miners. To illustrate the range of possible outcomes, we formulate two scenarios: one utopian and one dystopic. At the end of our article, we bring forward six recommendations that can be considered a beginning of a road map for the human side of Mining 4.0.

By Stephen A. Orr

Underground mining is a dynamic art and science with a diverse set of design, production, and economic criteria that must be considered before selecting an optimal method to extract the ore. While all methods can be technically classified as either self-supported, supported, or caving, the multitude of subsystems and existing variations bear witness to the fact that each orebody is unique and, as such, justifies an individual approach to optimize mineral extraction. In this sense, underground mining is an art. The ability to evaluate the unique characteristics of each ore body and utilize sound engineering principles to design the optimal system constitutes effective method selection. The task by no means ends at this juncture, however. Subsequent implementation requires an ability for modification. Very rarely are all the facts available to make a concrete decision prior to development of the resource. As a result, the risk of a wrong decision can never be eliminated. This requires a significant degree of flexibility with each method. Each unit of exploration, development, or exploitation work contributed to a deposit enhances knowledge of the ore body. The best mining methods are those that correctly account for the known parameters but provide an allowance for change at minimal cost and adapt to unanticipated conditions.

Jan 1, 2008

By John E. Newby

The Brightwater Conveyance System consists of four tunnel segments in three tunnel con-tracts, comprising over 21,760 m (71,400 ft) of pressurized face tunneling in complex glacial and non-glacial soft ground conditions with a large proportion 60 m (197 ft) or more below the ground surface with up to 7 bars groundwater head. This resulted in unique technical challenges for establishing geotechnical baseline values. The process used to develop these baseline values and specifications with regard to the level of risk that the owner, King County, was willing to accept is described in this paper.

Jan 1, 2008

By B. Comley, M. C. Harris

There is as yet no accepted method of predicting flotation frother performance in plant processes based on laboratory scale characterisation techniques. This paper investigates the use of dynamic surface tension, using the maximum bubble pressure method, as a means of evaluating frothers and frother mixtures. An adsorption model is presented, which has been used to quantify the role of frother type and concentration during frother bubble interaction, based on the correlation of model parameters to physical frother characteristics. This approach was found to provide useful insight with respect to blending and selection of flotation frothers to meet specified flotation performance criteria.

Jan 1, 2001

By R. L. Hudak, R. F. Randolph, A. S. Azman

The mining workforce experiences high rates of hazardous noise exposure and hearing loss. However, previous studies have identified specific behavioral and attitudinal barriers that keep miners from effectively acting to prevent their own hearing loss. The National Institute of Occupational Safety and Health (NIOSH) has developed several new hearing loss prevention tools and interventions that specifically target these barriers to prevention. The NIOSH Hearing Loss Simulator addresses motivation to take action and knowledge about the consequences of noise exposure. The QuickFit earplug test device and QuickFitWeb online hearing protection tester address barriers to effective earplug and earmuff use by verifying at least 15 decibels of protection. The NIOSH Roll-Pull-Hold technique helps miners obtain better protection through an easy-to-remember set of steps that improves attenuation by nine decibels. The “Inquiring Ears Want to Know” fact sheet helps miners to understand audiograms and to use them to maintain their hearing health. Each of these interventions can be used within the context of a comprehensive hearing loss prevention program.

Jan 1, 2010

What decision making tools and methods are available to a project owner when there is no clear differentiator between construction alternatives? A team led by a joint venture of Parsons Brinckerhoff and PGH Wong Engineering (PB/Wong) has been providing preliminary engineering services to the San Francisco Municipal Transportation Agency (SFMTA). The SFMTA and PB/Wong team developed several alternative construction methods for the tunnels and stations of the San Francisco Central Subway Project, none of which could be judged clearly better than another using traditional approaches and metrics. The team employed a risk assessment and analysis frame-works as a means of comparative analysis, drawing upon the knowledge of industry experts in the geotechnical, tunneling and construction fields to assist in the effort. This paper presents the approach and results of a cost and schedule risk analysis for two such analyses designed to answer two different questions regarding the advisability of different construction approaches. These assessments paved the way for key decision making in the preliminary engineering phase of the project and formed the foundation for continuing risk management efforts on the project. The focus of this paper is primarily the first two stages of risk management?identification and assessment?and some of the organizational dynamic issues that arise in such efforts.

By Grant P. Cordon

Our subject, "Safety, Legal, and Contracting," is a range of topics which covers a broad spectrum, but is obviously Intended to focus our attention upon certain particular aspects of tunnel problems. These are all fascinating and complex subjects, and others are much more qualified to discuss to discuss the fine points involved. Put after some 45 years' involvement as an inspector, engineer, contracting officer, and especially for the last 22 years as a contractor's estimator and manager, I have developed some strong and definite convictions to share with you. I hope it will serve to get you started thinking. My first tunnel experience was in a soft ground tunnel which was dug by hand, literally. The crown or arch back was taken out, a pebble at a time, by bare hand. The face was constantly breast-boarded, and the mucking was all done by hand shovel. My first rock tunnel was drilled by hand held drifters from the muck pile. Since then, most tunneling techniques have improved greatly. The jumbos, booms, muckers, and moles have taken over many of the back-breaking chores, and reduced the manpower requirements.

Jan 1, 1974

By A. Sand

A 2-dimensional computational model based on the discrete element method (DEM) is utilized for modeling of stamp-charged coke making. In this process, a large volume of coal is compacted to one single coal cake before entering the coke oven. Cake densification and mechanical strength development are key factors for the subsequent production of a high-quality coke. An approach is introduced for model calibration utilizing multiple control parameters obtained from a laboratory-scale stamping device. Experimental data on stamper rebound amplitude, attenuation and peak force are compared with simulation output in a pairwise manner by constructing a criteria space, which allows identification of model settings best satisfying the control parameters. The calibration procedure carried out by multiple criteria comparison aided model parameter selection for reproducing stamper behavior in response to the properties of the cake subjected to compaction. This modeling and calibration procedure offers possibilities for numerically studying the densification and mechanical strength development of coal cakes. However, the approach is also more widely applicable to other compaction processes.

Feb 27, 2013

By M. Hancer, J. D. Miller

It is known from soluble salt flotation practice that the K, Mg double salts of kainite (KClMgSO43H2O), and carnallite (KClMgCl26H2O) are difficult to float and must be converted to other salts such as schoenite (K2SO4MgSO46H2O) and sylvite (KCl) in order to recover potash values. The flotation characteristics of these double salts have now been confirmed in some detail by carefully controlled laboratory experiments with both cationic and anionic collectors. The experimental results are discussed in view of recent experimental findings regarding the flotation characteristics of simple salts, in which the flotation response was shown to be determined by the interfacial water structure and whether the salt could be considered to be a water structure maker or a water structure breaker. The same approach can be use to explain the flotation response of the potassium double salts ; schoenite, kainite, and carnallite. In addition, the sign of the surface charge of schoenite (K2SO4MgSO46H2O), was determined as a function of pH from nonequilibrium electrophoretic mobility measurements. Schoenite appears to exhibit three charge reversals (CR) which can be explained based on surface hydrolysis reactions. The flotation behavior of schoenite is further considered based on solution chemistry calculations, electrophoretic mobility measurements, and microflotation results.

Jan 1, 2001

By E. Cho

Illinois No. 6 coals of IBC 101 and IBC 112 were treated in solution with sodium hypochlorite to remove their sulfur contents, especially organic sulfur. The lab experiments were conducted in two steps of leaching at room temperature and hydrolysis at 90oC. The removal of organic sulfur from IBC 101 was by 37.8% while that from IBC 112 was only 13.7% under their respective optimum conditions. This large difference in organic sulfur removal is considered to be due to difference in concentration of surface total acid group, 3.14 vs. 0.88 mmol/g of coal.

Jan 1, 2007