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By D. A. Norrgran, J. A. Wernham

Introduction In view of the continuing depletion of natural resources, requirements for energy conservation, plant optimization and hazardous waste management, and environmental consciousness, recycling and secondary recovery of materials are being developed with increasing interest Many secondary recovery processes are being developed that apply mineral processing technology. Gravity separation, magnetic separation and flotation have all emerged as explicit methods for recovering residual values from various process streams and hazardous constituents from waste streams. Recently, a technique for concentrating metallics has been successfully reintroduced. The concept of the alternating magnetic field eddy-current separator was developed over a century ago using rudimentary electromagnets (Patent 400317 issued to Thomas Edison on March 26, 1889). Widespread acceptance was, however, hindered by high costs, marginal results and poor economic incentives for secondary recovery. With the recent increased interest in secondary recovery and the development of high-energy rare earth permanent magnets, the eddy-current separator has now gained prominent acceptance. The separation forces imparted by an eddy current separator are the function of the magnetic field intensity and the alternating frequency of the magnetic field. The evolution of permanent magnets has provided a cost effective alternative for the generation of high-intensity magnetic fields. High-energy rare earth permanent magnets have substantially reduced the capital and operating costs over the electromagnetic circuits employed in antecedent eddy-current separators. Specifically, in recent years, the strength of permanent magnets has increased several fold with neodymium-boron-iron rare earth magnets now providing an energy product of 35 million gauss-oersted. Figure 1 shows the evolution in the strength of permanent magnets. The development of these rare earth magnets has led to the design of circuits possessing a magnetic force an order of magnitude greater than that of conventional permanent magnetic circuits. The eddy-current separator has been successfully applied in several metal sorting and recovery operations. Most common is the sorting of metal from shredded automobile scrap and municipal waste. With the advent of high-frequency, high-intensity magnetic fields, the separator has advanced to the point where it has direct application in the beneficiation of fine sized metals. Relatively fine sized (-1/4 in.) metal bearing slags and spent foundry casting sands as well as precious metal hearing electronic scrap demonstrate excellent metallurgical response to the eddy-current separator, and applications have progressed to finer materials and more selective separations. Theory Electrical currents are induced in all conductors when exposed to an alternating magnetic field. The induced current generates a magnetic field in the conductor that opposes that of the alternating magnetic field. Figure 2, is a schematic illustration of generated eddy currents. In this particular example, the alternating magnetic field is produced by a series of permanent magnets mounted on the circumference of a rotor. The permanent magnets have alternating polarity. As the rotor revolves, an alternating magnetic field is produced, and the rate of revolution determines the frequency of the alternating magnetic field. When a conductor, such as a metallic disc in the illustration, is placed in the alternating magnetic field, a closed loop current flow occurs. The current loop in the conductor produces a magnetic field that is a mirror image of the alternating magnetic field. At any point in time, the induced magnetic field in the conductor directly opposes the alternating magnetic field. This opposition of magnetic fields produces an instantaneous repulsion in the conductor. The conductor is consequently repelled from the rotor. The alternating magnetic field has no effect on nonmetallic materials as they pass through the magnetic field and discharge the rotor in a natural trajectory. [ ]

Jan 1, 1992

By J. D. Miller

On the basis of nonequilibrium zeta potential measurements by laser-Doppler electrophoresis, the sign of the surface charge of alkali halides in their saturated brines has been established. The results are generally as expected from simplified lattice ion hydration theory. This recent electrokinetic information coupled with the stability and prevalence of collector colloids in such soluble-salt flotation systems suggests that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by heterocoagulation. Experimental flotation results confirm this surface-charge/collector-colloid adsorption model and are presented herein.

Jan 1, 1992

"It’s been 80 years since Charles Warman invented the iconic Warman slurry pump, a pump that revolutionized the mining industry and continues to push the boundaries of pump performance to this day.In honor of this legendary brand, Weir Minerals hosted an event at the end of May in Kalgoorlie, Western Australia. Throughout the evening, attendees relived Warman pumps’ history and gained an insight into some of the future innovations planned.“It was a privilege to share this special night with some of our key customers, past and present employees, and members of the Western Australian School of Mines,” said Ricardo Garib, divisional president of Weir Minerals. “Warman is one of our leading brands. It has truly shaped the mining industry over the past 80 years and is a product we are all very proud of. The Warman pump, invented to solve high wear issues in slurry pumping, created a thriving industrial business that is now the cornerstone of Weir Minerals with more than 8,000 people, and more than 150 manufacturing and service centers across the globe.”Always inventingCharles Warman invented the Warman slurry pump in Kalgoorlie in 1938. It was a hardwearing slurry pump that used replaceable liners and a replaceable impeller, something that had never been done before.“Charles Warman was a visionary and an innovator. The use of rubber lining in the pump was groundbreaking as it reduced total ownership costs, was safer to handle and offered extended wear life in many abrasive slurry applications. It is a great example of solving customer problems with material science, and is still taught in universities today,” said Marcus Lane, global product manager for centrifugal pumps at Weir Minerals.It was quickly adopted throughout the goldfields in Western Australia and by the 1950s, as customer demand rose, Warman expanded his business by opening offices in Sydney and Perth.During the 1960s the rapid growth of the business continued with manufacturing and sales outlets established around the world. The Warman Series ‘A’ pump was accepted and became a world leader in its field. Further work on the Warman AH pump resulted in the development of interchangeable metal and rubber wearing components."

Jan 9, 2018

By Richard J. Ebens

The trace element geochemistry of the cherty, clay-rich carbonate residuum. Covering much of southern Missouri and adjacent parts of Arkansas was investigated during the early 1970's as part of a statewide geochemical survey of Missouri-1/2/3 The study was environmentally oriented and focused on the character of the "natural' geochemical environment of the state. A great deal of effort was made to collect samples that would represent the geochemical variability of the near-surface environment in an unbiased way. In general, this was accomplished by use of randomization procedures in both collection and analysis. Most of the sampling sites were selected randomly to prevent personal bias from entering into sample selection. In the laboratory, samples were analyzed in a randomized sequence to circumvent the effects of any systematic bias that may have entered into the laboratory procedures. Several residuum samples contained 1 000 parts per million (ppm) or more of Pb, Zn and Ba. All these samples were collected in Washington County in or near the barite district. The frequency distributions shown in figure 1 indicate just how unusual the residuum in Washington County is with regard to these three metals and copper. The shaded parts of the histograms represent the samples from Washington County. The histograms are based on analyses of 141 samples from 38 localities scattered over the subcrop of the Cambrian and Ordovician Formations of southern Missouri and northern Arkansas. Eight localities were selected randomly from over each of four bedrock units--Bonneterre Dolomite, Potosi and Eminence Dolomites, Roubidoux Formation, and the Jefferson City, Powell and Cotter Dolomites. Six localities were selected randomly from over the Gasconade Dolomite. The geochemical "background" for these elements in residuum is defined by samples from outside of Washington County (unshaded part of the histogram); lognormal distribution curves have been fitted to the corresponding parts of each histogram. Clearly, these lognormal models (curves) describe well the background

Jan 1, 1977

By G. D. MacDonald

The Grasberg porphyry copper-gold deposit of P.T. Freeport Indonesia, Co. is located in the Jayawijaya Mountains of Irian Jaya, Indonesia approximately six km west northwest of Puncak Jaya, the highest point on the island of New Guinea. Disseminated mineralization is confined to the Grasberg intrusive complex, a multiphase intrusion of dioritic to monzonitic composition which intruded tightly folded carbonate rocks of the Tertiary Faumai and Ainod formations. The high tonnage and grade of the deposit (1 X 109 tonnes at 1.4 % copper and 1. 8 ppm gold) appear to result from a succession of coincident intrusive and mineralizing events about three million years ago. This paper will focus on the history and character of these events.

Jan 1, 1993

By Ashma Singh, Nichole Maistry

Due to declining iron ore grades, low-grade ores with complex mineralogy — namely, banded iron formation (BIF) — are being explored to maximize iron ore resources and increase the life of mine. Flotation is the standard global process used for the beneficiation of BIF ores, as it is a complex ore reserve, and liberation is typically achieved below 1 mm. This study focuses on the flotation of a South African BIF, evaluating its response to different collectors, as well as effect of grind. As flotation is an expensive process and South Africa ranks high on the production cost curve, preconcentration by gravity or magnetic separation is performed prior to flotation. Thus, flotation was also performed on a gravity concentrate to determine if a grade suitable for steelmaking (approximately 63 percent) is achievable. The results indicate that the use of an alkyl ether amine-based collector partially neutralized with acetic acid is suitable for separation of hematite from illite and quartz at high pH values. Further optimization tests are being pursued to improve overall recovery and grade.

May 1, 2025

By Denys B. Smith

Electric logs and cuttings records from Zechstein 3 and 4 strata in boreholes in the British Sector of have been interpreted in the light of numerous cored boreholes through this sequence in north-east England. This interpretation shows that potash salts in the two cycles are thickest and most consistent in a belt 20 to 40 km wide parallel with and a few kilometres from the present basin margin, and are here generally similar in grade to those known onshore. The potash ores in both cycles are mainly of sylvinite in onshore areas, the layered Upper the Southern North Sea Potash of the fourth cycle being rather less variable but generally of appreciably lower average grade than the Boulby Potash of the third cycle. Potash salts in both cycles are highly variable in thickness and grade in basin centre areas where they have been grossly affected by diapirism of the thick second cycle salts.

Jan 1, 1978

By Ethan Steward, Kyle Perry

The study investigates the effects of high-velocity impacts of common mine materials on a reinforced mine seal rated to 120 psi. It found that materials propelled during an underground explosion could generate enough stress to crack or damage seals, even with little visible damage. This highlights the need for careful evaluation of mine seals after any impact or high-pressure event.

Aug 1, 2023

By A. Jolly, A. R. Kumar, T. Novak

"Coal dust in an underground mining environment has always been a health and safety issue, especially with longwall faces. Efforts to integrate a flooded bed scrubber within a longwall shearer are underway at the University of Kentucky (UK) in order to reduce worker exposure. Small scale physical modeling, along with numerical modeling and full-scale experimentation, are engineering tools being used by the authors for simulating operating conditions underground. Recent advances in affordable 3D printers offer a means for fabricating accurate, scale models for obtaining timely insights prior to building large, expensive test setups. Comparing scale-model results with those of numerical modeling, such as computational fluid dynamics (CFD), lends guidance and confidence in a proposed design. This paper discusses the small scale physical modeling of a longwall shearer with an incorporated flooded-bed dust scrubber in its operating environment. A tracer gas was used in the model in lieu of dust to measure dust-capture efficiency. Results obtained from the physical model are presented and compared with those of CFD model. The small scale model and the CFD results demonstrate good agreement. Dust capture results show the usefulness of the approach in advance of actual design implementation. INTRODUCTION Dust generation is an undesirable, but innate, byproduct of all mining processes. It is particularly problematic in underground coal mining, where coal dust poses potential hazards from two fronts – health and safety. Coal workers’ pneumoconiosis (CWP), commonly referred to as black lung, is a chronic lung disease that results from the long-term overexposure to respirable coal dust. Although the prevalence of CWP has steadily and significantly declined over the three decades following the Federal Coal Mine Health and Safety Act of 1969, a study by the National Institute for Occupational Safety and Health (NIOSH, 2008) indicates that significant health hazards associated with respirable dust still exist within the coal mining industry. In addition to being a health hazard, coal dust can also create a potentially catastrophic safety hazard. Dust that is not captured or removed at its source is suspended and transported throughout a mine by the ventilation airstream. This float dust is subsequently deposited on all mine surfaces along its travel path. Without adequate application of rock dust to these surfaces, forces from a localized methane ignition can reintroduce settled coal dust into the airstream creating an explosive mixture. Therefore, capturing and removing coal dust at its source mitigates the probability of two major hazards that continue to plague the mining industry."

Jan 1, 2016

By J. D. Carson

A 0.60 km2 (150 acre) wetland was reclaimed by Agrico Mining Company as part of a 1.48 km2 (366 acre) reclamation program in southwest Polk County, Florida approved by the Florida Department of Natural Resources. The upland portion of the area provides watershed for the wetland site which overflows into the flood plain of Payne Creek. Construction of the wetland was designed to provide conditions favorable for a diversity of habitats, as well as retention time for surface runoff waters. A variety of revegetation methods, including innoculation with muck from unmined wetland depressions, have produced encouraging results with both woody and herbaceous species.

Jan 1, 1983

By Jan Reimann

Increasing individualization with smaller quantities, growing competition from low-wage countries, and the continuous drive towards digitalization are the challenges that industrial companies in high-wage countries must face. The example of the Flender One gearbox modular system demonstrates how consistent standardization and digitalization are the enablers for AI, and thus already enable new business models and business approaches today.

Feb 22, 2026

By R. Stanevich

Studies by the National Institute for Occupational Safety and Health (NIOSH) and the Bureau of Mines (BOM) have demonstrated that: (1) 90% of diesel particulate is less than one (1) micrometer in aerodynamic diameter; (2) more than 90% of the respirable mass in electric coal mines was greater than one (1) micrometer in aerodynamic diameter; and (3) in coal mines using diesel equipment, average diesel concentrations can represent up to 53% of the MRE respirable coal dust standard. For mines approaching the 2 mg/m3 standard, compliance may be easier to attain by controls directed at diesel exhaust particulate as opposed to coal dust control. First, however, a Simple instrument is needed to measure diesel exhaust particulate concentrations. This paper describes such a sampler, its construction, and use. While results from this sampler are primarily utilized to identify control areas, NIOSH is also using the sampler for estimating worker exposures in epidemiologic studies.

Jan 1, 1988

By John O. Marsden

"This article is an attempt to capture a presentation given at the 2016 SME Mineral & Metallurgical Processing Division (MPD) Luncheon held on Feb. 24, 2016, in Phoenix, AZ. It was presented as a tongue-in-cheek, lighthearted view of several of the issues facing our industry, while identifying some of the challenges and opportunities available to new engineers entering the industry today.Disclaimer• What you are about to read includes personal preferences, biases and occasionally arbitrary opinions.• Some readers may have dissimilar opinions on the contents and/or the rank order of the lists.There are eight top ten lists offered in this article: (1) Industry realities (2) Things a metallurgical or mineral process engineering graduate should do (3) Books every metallurgist should have on their shelf (4) Things I wish I had known (5) Legends of metallurgy (posthumous, with highlights) (6) Things we’ve forgotten (7) Mineral processing innovations of the past 20 years and, finally, (8) The future? For some items, additional context or clarification is provided after the item, while for other items no further explanation is warranted and none is offered. Top 10 industry realities1. Metal price cycles.2. Bigger is better (except when it isn’t).3. Ore grades declining across the board of metals/commodities.4. Ores becoming more complex.5. Three-fold increase in capital costs between 2004 and 2015.6. Three-fold increase in operating costs between 2004 and 2015.7. Less capital availability/challenging financial markets.8. Environmental constraints increasing.9. Socio-political constraints increasing.10. The mine manager is always impossible to work with.As Table 1 shows, there was more than a three-fold increase in gold operating costs between 2004 and 2014. The increases for copper, iron ore and other commodities were similar."

Aug 1, 2016

By R. Hiebert, M. Canty, S. Beckman

An innovative biological process is described for the treatment of cyanide-, metals- and nitrate-contaminated mine process water. The technology was tested for its ability to detoxify cyanide and nitrate and to immobilize metals in wastewater from agitation cyanide leaching. A pilot-scale demonstration is described in which a pilot plant was constructed to demonstrate the technology on a mine process-waste stream at a mine in Nevada. The demonstration was performed jointly under the Mine Waste Technology Program (MWTP), funded by the US Environmental Protection Agency (EPA) and jointly administered by the US De¬partment of Energy's (DOE) Western Environmental Technology Office (WETO) under Interagency Agree¬ment Number DW89938513-01-0. The Superfund Innovative Technology Evaluation (SITE) demonstration program was also involved in the project. MSE Technology Applications Inc. (MSE), Butte, MT, was the contractor responsible for conducting the project, and Pintail Systems Inc., Aurora, CO, was the technology provider. The pilot-scale unit was field-tested at Echo Bay's McCoy/Cove Mine southwest of Battle Mountain, NV. The biotreatment process was considered successful in destroying cyanide in the mine process water. The process was also determined to be effective in removing metals. The pH was consistently neutralized and nitrates were successfully removed from the mine process water. From the results of these pilot-scale tests, it was concluded that the biotreatment process potentially of¬fers an innovative, cost-effective alternative for the treatment of mining wastewaters.

Jan 1, 2000

Acid mine drainage (AMD) forms when sulfide minerals are exposed to oxidizing conditions in coal and metal mining, highway construction, and other large-scale excavations. Iron sulfides common in coal regions are predominately pyrite and marcasite (FeS2), but other metals may be complexed with sulfides forming chalcopyrite (CuFeS2), covellite (CuS), galena (PbS), and sphalerite (ZnS). Pyrite commonly occurs with these other metal sulfides thereby causing AMD where Cu, Pb, and Zn are mined. Upon exposure to water and oxygen, sulfide minerals oxidize to form acidic, sulfate-rich drainage. Metal concentrations in AMD depend on the type and quantity of sulfide minerals present. The drainage quality emanating from underground mines or backfills of surface mines is dependent on the acid-producing (sulfide) and alkaline (carbonate) minerals contained in the disturbed rock. In general, sulfide-rich and carbonate-poor materials produce acidic drainage. In contrast, alkaline-rich materials, even with significant sulfide concentrations, often produce alkaline conditions in water. Approximately 20,000 km of streams and rivers in the United States are degraded by AMD. About 90% of the AMD reaching streams originates in abandoned surface and deep mines. Since no company or individual claims responsibility for reclaiming abandoned mine lands (AML), no treatment of the AMD occurs and continual contamination of surface and groundwater resources results. The oxidation of iron disulfides and the generation of acidity occur through several reactions (Stumm and Morgan, 1970). The chemical equations can be found in Caruccio and Geidel (2000). If any of the processes represented by the equations were slowed or altogether stopped, the generation of AMD would also slow or cease. The equations show that 1000 Mg of rock containing 1% sulfur, all as pyrite, would yield upon complete reaction 31.25 Mg of acidity. Therefore, 31.25 Mg of 100% CaCO3 would be required to neutralize the acidity. The alkaline content of overburden determines whether there is enough neutralization potential (NP) to counteract the acid produced from pyrite oxidation. Of the many types of alkaline compounds present in rocks, only carbonates and clays occur in sufficient quantity to effectively neutalize AMD. A balance between the acid-producing potential and neutralizing capacity of an overburden sample will indicate the ultimate acidity or alkalinity that might be expected in the material upon complete weathering. Accurate prediction and control of AMD before surface mining require an understanding of three important factors: 1) overburden geochemistry, 2) method and precision of overburden handling and placement in the backfill during reclamation, and 3) the postmining hydrology of the site.

Jan 1, 2002

By Laurence B. James

The California Department of Water Resources is concerned with the development, distribution, and protection of the State's water resources. Geologic activities of the Department relate to planning, construction, and operation of water projects, supervision of the safety of over 900 dams under state jurisdiction, and investigation and control of ground water supply. The Department is engineering oriented, and the role of the geologist is to assist with the solution of engineering problems. Some of these problems require the integration of many talents, including not only those of geologists and engineers, but also those of economists, lawyers, seismologists, chemists, geophysicists, and hydrologists, Frequently, a task force of several disciplines will attack a problem as a team.

Jan 1, 1965

By H. Ban

Triboelectrostatic separation tests were performed on a bench-scale, analytical separator using coal, coal combustion fly ash and mineral samples. Fractions of separated samples were collected and analyzed to characterize the performance of the separation. Particle size distribution and morphological characteristics for these samples were analyzed by optical microscopy, and scanning electron microscopy (SEM). It was found that smaller size fractions of a fly ash sample had better separation than the full sized parent fly ash sample, indicating interference or particle-particle interactions during the separation process. It was also observed experimentally that small kaolin particles attach to the surface of large silica spheres, causing charge neutralization and subsequent low separation efficiency.

Jan 1, 1997

By J. K. Mohanty, D. Panda, P. K. Sahoo, R. K. Paramguru, K. C. Nathsarma

Ferromanganese slag, a product of the manganese industry, was characterized mineralogically. The slag, which contains high Mn values, was characterized using optical microscopy, XRD analysis and electron microscopy. No separate Mn-bearing oxide mineral phase was found. The slag is amorphous, and no crystalline phase was identified in the hulk sample by XRD, However, in. fine fractions, quartz was identified. Scanning electron microscopy (SEM) revealed the presence of Mn, Si, Al and Ca in the matrix without the development of a mineral phase. Leaching experiments using H2SO4 were carried out to determine if Mn could be extracted from the slag. At room temperature, almost 100% of the manganese could be dissolved at a solid-liquid ratio o f 1:10 by leaching with dilute sulfuric acid. The impurities could be precipitated by pH adjustment to produce a manganese sulfate solution suitable for the production of MnO2 or electrolytic Mn metal. Based on the laboratory-scale experiments, a suitable process is proposed to recover manganese values from the, ferromanganese slag.

Jan 1, 1999

By S. Veeramasuneni

The sign of the surface charge for alkali halides in their saturated brines has been established from non equilibrium electrophoresis measurements and on this basis the flotation response of alkali halides was explained based on the adsorption of oppositely charged collector colloids by heterocoagulation. These surface charge results for alkali halides are generally as expected from simplified lattice ion hydration theory with some exceptions, specifically LiF, KCI, NaCl, KBr, RbBr, KI, and Rbl .The presence of natural oxygen defect states in the crystal lattice and the inaccuracies involved in the gaseous ion hydration free energy values used appear, in past, to be responsible for these deviations. The presence of natural oxygen defect states in KCI, KBr, RbBr, and Rbl as characterized by UV Nis absorption, was found to account for their anomalous surface charge. Further, other positively charged alkali halides, LiF, NaCl and KI, were found to be free of oxygen defect states. Nevertheless, oxygen defects can be created in these alkali halides to make them negatively charged and has been demonstrated for NaCl. Such negatively charged NaCl can be readily floated with positively charged amine collector colloids thus confirming the surface charge/collector colloid adsorption theory.

Jan 1, 1996

By GRANT COLLIGAN, BROCK O’KELLEY, Corby Anderson

With the world’s ever-growing push to expand technological capabilities, the need for specialized materials including rare earth elements has exploded. One source of rare earths found in the United States is bastnaesite, a rare-earth-bearing fluorocarbonate, mined at the Mountain Pass Mine in California. To increase production, it has been essential to optimize existing processes and create new ones to capture current reserves. This paper presents the results of a research program conducted to expand the understanding of the bastnaesite leaching system. With the help of prior knowledge and thermodynamic calculations, a novel single-stage hydrochloric acid leach system was created to optimize the extraction of rare earths from bastnaesite. Historically, this extraction has entailed the use of a two-stage leach system involving a high-temperature hydrochloric acid leach followed by a caustic crack. We ran a series of single-stage leach experiments by reacting locked-cycle flotation concentrate with hydrochloric acid to test common leaching parameters. The results of these single-stage tests showed significantly higher rare-earth recoveries than the reported recoveries of the historic two-stage caustic crack processes, all while decreasing the number and amount of reagents needed.

Feb 1, 2023