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By Q. Xiao, R. Naidu, W. Li, S. Song

Acid mine drainage (AMD) derives from the oxidation of sulfide minerals, primarily pyrite (FeS2), and is the most severe environmental issue facing the minerals industry. The most common short-term approach to AMD treatment is migration control, such as acid neutralization and metal/metalloid and sulfate removal, through the addition of alkaline materials, including lime (Ca (OH)2), limestone (Ca CO3), gangue minerals and industrial wastes. This requires the continuous input of materials and may result in the production of a vast amount of secondary sludge requiring further treatment and disposal. Addition of chemicals is usually more important in metal/metalloid removal than in sulfate removal unless the sulfate is present in very high concentrations. A more promising long-term strategy for AMD prevention is source control through the complete removal of pyritic minerals and encapsulation of potential risk minerals by coating with impermeable surface layers. This is regarded as the most cost-effective approach, although the mechanisms underpinning this and the implementation procedures are yet to be fully elucidated. It is likely that long- and short-term practices can be combined to optimize the remediation of contaminated mining sites. Some factors such as differing geological and mineralogical characteristics and transportation costs must also be considered for the successful implementation of AMD prevention and remediation strategies. This review also considers some implications for AMD remediation, but the promising bioremediation of AMD is not discussed as it has been extensively reviewed.

By Patricia Petty

If enthusiasm is a requirement, the coordinator of the Total Concept program is a dynamic, exciting leader with a lot of potential to keep the program a vital and progressive effort for many years. Art Meyer is entering his third year as the leader of the Total Concept. He is using his years of experience in the industry to emphasize the basics required for the course, and has also instituted new programs. Meyer began his career, after graduation from CSM as geological engineer in 1950, with St. Joe Lead. He held other responsible positions with Amax and Rocky Mountain Energy. He can answer any questions that may crop up or find the right resource person for those questions. Additions to the 18-year-old curriculum instituted since Meyer became coordinator are the study of industrial minerals and strategic minerals. The industrial minerals portion of the course includes visits to a major sand and gravel operation, in addition to lectures on the subject. Much of the strategic minerals requires study and lectures, since Colorado is not a big production state in these commodities. How does the director arrive at new additions or deletions to the program? "It's very simple," he says. "We listen to questions posed by the students, recommendations by industry people who know what is important, and feed-back from course alumni." Alumni feedback from this course has been extremely gratifying, according to Meyer. Other ideas are constantly surfacing, ideas that will be implemented as time and resources permit. One of the most gratifying results of the Total Concept program from an alumnus was the development of a complete teacher and student package by John Christiansen, a teacher at Cherry Creek High School near Denver. The course so excited Christiansen that he envi¬sioned an energy and minerals course to fill a perceived gap in science education on the high school level. The draft package was so attractive that it was sponsored and the publication costs guaranteed by the Society of Mining Engineers. Today, under the leadership of the Mineral Information Institute, the package is in use in several states and has gained enthusiastic acceptance. Other alumni have launched their efforts to broaden the scope of the existing science education by instituting courses or special seminars. One recent alumnus, Dick Will, class of 1984, who was sponsored by the Denver Mining Club, is conducting a science seminar based on his experiences with the Total Concept program. Meyer will be speaking at this seminar, as well as other industry speakers from the SME GEM Committee Speaker's Bureau. Jane Dianich, another alumna, brought her students at Kent Country Day school, also near Denver, into the mainstream of resource education by taking them on abbreviated field trips similar to those she experienced while in the program. She also has been a vocal supporter of the organization and available to speak to other teachers on the value of the experience. George Wright, of the Lake School and a second sponsoree of the Denver Mining Club, admits he came into the program because the six credit hours given toward his continuing education requirement were attractive. He then stayed on to become an ardent advocate of the mining industry. In his own words, "I'm a convert." Wright has developed a slide presentation and has lectured to teachers and students as well as presenting his views to the Denver Mining Club. He has also indicated a willingness to participate with other organizations who need speakers. The value of these speakers and teachers is obvious, according to Meyer. "They represent a respected segment of the public and are not too `tainted' by association with an industry that is too often under criticism from various groups. They represent, in effect, a citizen's advocacy of the industry, which is an invaluable asset to us all." One of Meyer's concerns about the program is that the out-of-state student rate attendance is declining. He is hoping that more AIME sections around the country will become involved in the scholarship program of the Total Concept. Total cost is about $1200 per student. "The rewards to their sections could be tremendous, with the same kind of participation we get here with speakers, citizen advocates, and interested persons," he said. Teachers say that the course improves their teaching and knowledge in a number of subjects including biology, history, economics, career planning, environmental data, science, math, geography, physics, and chemistry. The recent interest in hazardous waste management has sharpened the desire to learn more about this. And Meyer foresees another segment of the course to emphasize this subject. "One of the most valuable resources we have is the field trip program. The course would probably be meaningless without this opportunity to get out into the field where these folks can see what actually happens. George Wright, for example, was amazed at the very small amount of area actually involved in the mining operation - something contrary to what he had heard in the past." The 45 students are taken by van on eight trips, one each week, and the long trip to Colorado's Western Slope. During this long adventure, the students visit underground mines, including CSM's Edgar, open-cut and underground coal mines, precious metals mines, and oil shale properties. They also have opportunities to meet with mine personnel at each of these stops. These field trips fill another function. Living together and exchanging ideas helps the teachers come up with new concepts for the classroom work - expanding their horizons. "As long as we have a mining industry, this effort will continue to grow," Meyer said, "and will fulfill a need within the public education and public relations area of the industry. We need the support. I have dozens of comments from teachers who attest to the value of this program. They understand. The mining industry must continue to do its part."

Jan 3, 1986

By W. C. Brice

Minnesota's mineral resources are widespread and diverse (Figure 1). In addition to the nation's largest iron and manganese reserves, the state contains sizeable vanadium, copper, and nickel resources. Recently it has been determined that the proterozoic unconformities in Minnesota have a favorable potential for uranium deposits. Finally, major potential exists in Minnesota's archean greenstone belts for gold, silver, and copper-zinc massive sulfides. Many of the state's mineral resources have been found in environmentally sensitive areas. This is not surprising since the natural forces associated with the formation of mineral deposits are often the same processes that create unusual landforms. For example, much of the state's copper-nickel is found within and adjoining the Boundary Waters Canoe Area (BWCA) and Lake Superior. The history of mineral development on the Mesabi Iron Range has also created culturally sensitive areas. Early iron mining development required the workers to live close to their jobs, and mine wastes were dumped as near the mine as possible. Few, if any, foresaw the time when taconite would be economic to mine. Therefore, it is not unusual to find valuable taconite resources located under towns and waste dumps on the Mesabi Iron Range.

Jan 1, 1980

By H. EI-shall

In this paper, the results of bench scale testing of five different flotation processes to separate dolomite from phosphate are discussed. The effectiveness of each process interms of phosphate recovery and MgO content in the concentrate is used together with the reagent consumption as the basis of comparison. The water quality is found to play a major role in the performance of these processes. Effect of water hardness as well as other parameters are discussed.

Jan 1, 1995

By Duluth Engineers' Club, Engineers' Club of Northern Minnesota

"The early mining of iron ore in Minnesota was carried on with the most primitive kind of tools. The pioneers used only such equipment as could be packed from Duluth through one hundred miles of forest to the first mines on the Vermilion Range and the operations were carried on with picks, shovels, hand drills and wheelbarrows, the ore being hoisted in buckets with a horse winch and carted in horse drawn wagons to the stockpile. This was about the extent of the mechanical equipment of the Minnesota iron mines in the early eighties.As soon as a railroad was pushed through from Two Harbors to the Vermilion Range the equipment began to be improved upon; wood burning steam boilers were installed and small steam puffers displaced the horse-winches, wheelbarrows were aban¬doned and small cars were introduced. Hauling the hoisted ore in wagons was discontinued and trestles were built so that the ore could be stockpiled more cheaply through the use of cars and high piles. These same stockpiles were loaded by hand into the 10 and 15 ton capacity railroad ore cars.Within a few years a marked change took place—the hand drill gave place to the air drill, such as No. 3 Rands, Ingersolls, Sargents and some Sullivans. Tramming was done by mules, the ore hoisted in. self-dumping skips, hoisting engines were intro¬duced and it seemed as though mining as a business in Minnesota had come to stay. At this stage someone conceived the idea of making the stockpile floor about three feet above the top of the ore cars to facilitate the hand loading of stockpile ore for trans¬portation. This was done through the use of wheelbarrows at first and later by using I-ton cars running on tracks laid on the stockpile floor."

Jan 1, 1920

By A. Festa

Secondary crushing often gets good press for its increases in energy efficiency and SAG milling rates but for a project considering this option the proposed benefits soon get overshadowed by implementation concerns. Reverse engineering from the published case studies is risky unless the reader understands the drivers impacting stability and operability of the circuit. This paper discusses the features of secondary crushing for Greenfield and Brownfield SAG mill grinding circuits. It is the author?s view that secondary crushing rarely adds value to a Greenfield project and restricts future expansion. Its application is best retro fitted to Brownfield operations where the benefit gained for capital expended is excellent. Two case studies are presented to reaffirm these statements. The first case study shows that the implementation of partial and total secondary crushing increases SAG mill power efficiency and it offers substantial incremental increases in milling throughput with staged capital investments for the crushing and grinding circuits respectively. The paper provides a critical analysis of process conditions for secondary-crushed grinding circuits, with particular emphasis on Brownfield circuit retrofits. Furthermore, the second case study quantifies the economic impact of secondary crushing on circuit design for plant start up and it illustrates the limit imposed on plant expansion.

Feb 23, 2014

By T. M. Gurr

The United States is the world's leading producer of phosphate rock. In 1975 according to the U. S. Bureau of Mines' statistics, 44.3 million tonnes (48.8 million short tons) of phosphate rock were produced in the United States', which is 40.6 percent of the world's production2. The major phosphate producing areas of the United States are located in Figure 1 and the production for 1975 is listed as follows: Million Million Short Tonnes Tons Florida and North Carolina 36.9 40.7 Western States 5.3 5.8 Tennessee 2.1 2.3 All of these areas produce phosphate from deposits which are sedimentary marine in origin. Occurrences of phosphate exist throughout the United States in numerous locations that are of both igneous and sedimentary origins. However, these other phosphate occurrences vary greatly in extent and economic significance. Georgia, South Carolina, California, Texas, Arkansas, Kansas, Iowa, Alabama, Kentucky and Virginia are but a few of the states in which phosphate is thought or known to

Jan 1, 1977

By J. V. Belke

There are many aspects of a grinding mill supply and installation that can result in the mill not operating as intended, resulting in unplanned shutdowns, poor reliability and headaches for all concerned. One of the largest aspects, both in criticality and physical mass, is the mill foundation; if not properly specified, designed and constructed the mill operation will be compromised. The mill foundation starts with the design specification and loading diagram supplied by the mill builder. The importance of understanding these documents and how to apply them is critical for the start of any mill project. When designing mills with a GMD the foundation must be properly modeled to ensure that all interactions of the mill and motor structures, foundation and subsurface strata behave in the intended fashion. All of the previous efforts can be laid to waste if the construction of the mill foundation is poorly handled. Mill foundations are typically the most massive concrete structure at a processing plant and can easily cause nightmares for inexperienced contactors. This paper explores some of the more important facets along the lifecycle of the grinding mill foundation.

Feb 23, 2014

By Steven E. Paulson

In situ mining is emerging as a potential alternative to conventional surf ace and underground mining techniques. A major factor in determining recoveries by in situ mining is the proportion of ore minerals that can be contacted and solubilized by the leach solutions. To provide basic information on the processes occurring during in situ leaching, particularly at the microscopic scale, the Bureau of Mines has developed a geologic characterization research program. This includes laboratory experiments using leaching apparatus that can accommodate whole core samples. Whole core experiments result in higher leach solution-ore mineral contact ratios than packed column experiments, and also allow for the assessment of permeability changes taking place as the result of mineral dissolution, precipitation, and clay swelling within the flow channels in the rock. A nonreactive, reusable reaction cell has been designed and tested. The leaching apparatus can be used for constant-pressure or constant-flow experiments and allows for the control of flow rate, pressure, and temperature during the experiments, thus permitting studies on a wide variety of ore samples. Details of the experimental apparatus and design are presented, as well as preliminary results from the first series of experiments on an oxide copper ore from the Casa Grande, AZ, area.

Jan 1, 1987

By M. Misra

It is estimated that the volume of low -level and intermediate level contaminants present in the soil at different DOE sites is of the order of several million cubic feet. The existing remediation scheme is containerization followed by burial in Land Disposal Facilities (LDF's) which is economically unattractive warranting the need to develop alternate remediation routes. One such route is the physical separation based volume reduction approach to removing a MINIMUM AMOUNT OF CLEAN SOIL with the radioactive particles, reducing the amount of material that requires disposal. The purpose of this study was to evaluate and test the feasibility of using physical beneficiation techniques for removal of contaminants from soil. The performance criterion was to recover at least 80% of the activity in 20% or less of the original contaminated soil volume. Four different radioactively contaminated (primarily uranium and plutonium) soils from DoE sites namely LANL, INEL, Fernald Plant 1 Storage Pad (ID-B) and Mound soils were tested using gravity, magnetic, gravo-magnetic, hydrocyclonic and flotation devices. The paper is divided into the two sections. The first section presents the overview of the Heavy Metals in Contaminated Soil Treatability Project conducted at the University of Nevada, Reno (UNR) describing the salient features of a state-of-the art Soil Washing Laboratory and the technology equipments used in the test program. The second section describes the soil characterization and typical volume reduction results obtained from the UNR tests. Among the physical separation processes, only flotation processes passed the performance criterion. For the LANL and INEL soils where the contamination was contained in coarse particle size, it was possible to recover more than 80% of the activity in less than 10-20% of the original volume of the soil thus rendering 80-90% of the soil "clean". For Fernald and Mound soils where contamination was of colloidal nature, flotation based processes showed encouraging results and are recommended for further studies.

Jan 1, 1995

By A. Leppala

Scope of the Courier 300 System The fact that reliable on-stream analysis is a prerequisite for effective flotation control is hardly disputed today. Nevertheless, up to now no system has been available that includes all the equipment necessary for successful analysis. However essential an on-stream analyser is in itself, reliable and accurate assaying can only be assured after techniques for sampling, handling the slurries and computing the X-ray data have been developed for the purpose. The Outokumpu Company's Courier 300 System is a complete package that can be installed and handed over with the key. It includes the equipment needed for sampling and handling the slurries. It has been developed from the start to meet industrial demands. Obviously an on-line system must comply with far stricter standards than one designed for a laboratory. Assays are computed by an Outokumpu 316 digital data processor, which is an integral part of the system and controls its entire performance. The computer software is programmed as a standard package, including a highly advanced new model for assay computation. Analysis output is available for a process computer, report typewriter:, and recorders. The package also includes calibration for slurry assays at our pilot installation before delivery. A complete Courier System can analyse up to 4Z slurries and six elements in each slurry. Thanks to its modular design, it can be dimensioned initially to the customer's requirements and is easy to expand later at low cost. Being a mining company itself, Outokumpu has been able to utilize its own long experience in non-ferrous metallurgy - an important factor contributing to the success of the Courier system. History of the project and present installations The first on-stream analyser was installed at Outokumpu'a Pyhasalmi Con¬centrator at the end of 1967, after several years' development. Since then,

Jan 1, 1971

By J. P. Rider, T. W. Beck, J. A. Organiscak

"The National Institute for Occupational Safety and Health (NIOSH), Office of Mine Safety and Health Research (OMSHR) has recently developed a series of models utilizing Computational Fluid Dynamics (CFD) to study gas distribution around a continuous mining machine with various fan-powered flooded bed scrubber discharge configurations. CFD models utilizing Species Transport Model without reactions in FLUENT were constructed to evaluate the redirection of scrubber discharge toward the mining face rather than behind the return curtain. The following scenarios are considered in this study: 100% of the discharge redirected back towards the face on the off-curtain side of the continuous miner; 100% of the discharge redirected back towards the face, but divided equally to both sides of the machine; and 15% of the discharge redirected toward the face on the off-curtain side of the machine, with 85% directed into the return. These models were compared to a model with a conventional scrubber discharge where air is directed away from the face into the return. The CFD models were calibrated and validated based on experimental data and accurately predicted sulfur hexafluoride (SF6) gas levels at four gas monitoring locations. One additional prediction model was simulated to consider a different scrubber discharge angle for the 100% redirected, equally divided case. These models identified relatively high gassy areas around the continuous miner which may not warrant their use in coal mines with medium to high methane liberation rates. This paper describes the methodology used to develop the CFD models, and the validation of the models based on experimental data.INTRODUCTION Methane gas and respirable dust are two hazards frequently encountered at continuous miner (CM) operations. An accumulation of both methane gas and coal dust may lead to massive explosions underground [1], and overexposure to respirable coal dust can result in pneumoconiosis (commonly referred to as “Black Lung Disease”) in coal workers [2]. Current U.S. federal coal mine regulations limit concentrations of methane gas to below 1% at the face area and require exposures to respirable coal dust to be at or less than 2.0 mg/m3 for an 8 h shift average. Begin on August 1, 2016; the overall respirable dust standard in coal mines is reduced from 2.0 to 1.5 mg/m3 for full shift sampling. If the quartz content of the dust exceeds 5% by weight, the dust standard becomes more stringent, reducing the allowable concentration to the value of 10 divided by the % quartz."

Jan 1, 2015

By C. L. Lin

A PC image-based on-line coarse particle size analyzer has been developed to measure particle size distributions under plant situations where overlapped particles are being transported on a moving belt conveyor. Although previous testing had shown satisfactory performance of this image-based system for separated particle size measurements (the non-overlapped case), it was necessary to modify original algorithms in order to solve the overlap problem and make the system suitable for plant operations. On-site testing has been conducted at a large copper concentrator in the southwestern U.S. for further investigation of the overlap problem.

Jan 1, 1995

By M. L. Wouden

The Bureau of Mines investigated pegmatite and granite formations at Copper Mountain, Fremont County, Wyoming, for recovery of tantalum and niobium. Sampling of surface exposures identified about 1.27 mega tonne of pegmatite resource material ranging between 0.02 and 0.04% Ta20, and 0.007% Hb20,. Beneficiation studies were conducted involving coarse-grained and fine grained pegmatite samples. Over 80% recovery of the coarse-grained tantalite was achieved in a concentrate averaging over 45% combined tantalum-niobium oxide. Lower concentrate grades and recoveries resulted from the treatment of fine-grained pegmatite.

Jan 1, 1991

By D. E. Healy

In 1989 an Autogenous Grinding Task Force was formed to study potential autogenous grinding circuits to replace the existing semi-autogenous grinding at the National Steel Pellet Plant located in Keewatin, Minnesota. Pilot plant test work performed by the Hanna Research Center (HRC) indicated that fully autogenous grinding with pebble extraction and crushing could feasibly be incorporated into the existing circuits. In 1990, one of the existing ten grinding mills was converted for an in-plant test incorporating pebble crushing. The full scale test work conducted in 1990 and 1991 verified the pilot plant projections with primary mill throughputs from the fully autogenous circuit utilizing pebble crushing being greater than throughput of the existing SAG mill circuits.

Jan 1, 1992

By J. K. Grunig

A process consisting of leach, continuous countercurrent decantation, resin-in-column ion exchange, evaporative crystallization of beryllium sulfate, and decomposition of the sulfate was developed for Spor Mountain, Utah, ores. The process is metallurgically sound, has a minimum of process steps, and is applicable to a wide variety of beryllium ores. The most novel aspect of the process is a resin system of ion exchange which is highly selective for beryllium and which rejects substantially all impurities except for minor amounts of aluminum, magnesium, fluorine, and sulfate in addition to beryllium. The oxide from sulfate decomposition meets specifications of potential users.

Jan 1, 1982

By S. Vivek

An atomic force microscope (AFM) was used to measure the surface forces between silica plate and glass sphere in sodium oleate solutions. Hydrophobic forces were observed when the two surfaces were activated by CaOH+ or MgOH+ ions. The force measurements conducted in the absence of the surfactant showed that the activated silica surfaces do not exhibit the primary hydration forces that have been observed between unactivated surfaces. The activation mechanism was studied by calculating the contributions from electrostatic and chemical interactions to the total free energy change. The results suggest that the adsorption of the hydroxo-complexes is controlled mainly by the lateral interactions between the adsorbed species on the silica surface.

Jan 1, 1999

By M. Guzman, M. Romero, S. Bravo-Thais, M. Flores

The phytoremediation method is proposed to recover valuable metals from polluted soils. In this sense, the objective of this research is to determine if it is possible to use native plants in the recovery of precious metals from abandoned mining liabilities. The tailings samples containing Au and Ag were acquired from the northern region of Peru. Two native plant species, Stipa Ichu and Cortaderia Nitida, were used. Results show that Au was recovery around 19% (1.52 mg/Kg) and 25.43% (1.78 mg/Kg) by using Stipa Ichu and Cortadeira Nitida, respectively. Besides, Ag had a better recovery in the Stipa Ichu reaching a value of 6.83% (0.628 mg/Kg); in contrast, Cortadeira Nitida had an efficiency of 3.6% (0.814 mg/Kg). Bioaccumulation, bioconcentration and translocation factors were calculated by determining the concentration of precious metals in the roots and aerial parts of each plant. Results show that Stipa Ichu had a greater capacity of hyperaccumulated Ag compared to Au; while Cortaderia Nitida tended to have a better performance for Au. In conclusion, both plants are recommended for phytoremediation of mining liabilities.

Feb 1, 2023

By George C. Hawley

Historically, mica usage has been low because of limited availability; as a by-product of many small processors, who have lacked motivation for extensive R & D. The discovery of a 30 million ton deposit of 85-90% pure phlogopite, when existing markets are only 300,000 tonnes annually, forced the search for large volume new markets. Increasing costs of energy, petrochemicals, plastics and glass fibers, and environmental constraints on asbestos usage, have led to new opportunities for mica as a reinforcing filler. Extensive research and developments; in beneficiating, processing and treating mica, has been necessary to satisfy these new markets.

Jan 1, 1981

By R. L. Godfrey

The Custom Coals advanced coal cleaning plant will be designed with a unique blending of existing and new processes to produce two types of compliance coals: Carefree Coal? and Self-Scrubbing Coal?. Carefree Coal will be produced by cleaning the coal in a proprietary dense media cyclone circuit utilizing fine magnetite to remove up to 90 percent of the pyritic sulfur and correspondingly greatly reduce the ash. While may utilities can achieve full S02 reduction compliance with Carefree Coal, others face higher sulfur reduction requirements due to the higher sulfur content of their existing fuel supplies. For these circumstances, a patented Self-Scrubbing Coal will be produced by taking Carefree Coal and pelletizing limestone-based additives with the finest fraction of the clean coal. These technologies will enable over 150 billion tons of non-compliance U.S. coal reserves to meet compliance requirements.

Jan 1, 1995