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By G. J. Koons, J. L. Uhrie

Field density studies carried out at the Phelps Dodge Chino Mine have found that truck-induced compaction is limited to the upper 2.4 m (8 ft) of an individual lift. Hydraulic properties of material compacted to field densities were determined in a laboratory setting. Saturated flow models were then run, simulating the effect of compacted zones within a stockpile. Modeling shows that compaction can prevent solution flow through large portions of the stockpile. This implies that care must be taken to ensure that ripping is carried out to a depth of at least 2.4 m (8 ft) across the entire stockpile to achieve uniform solution flow. Uniform solution flow will result in maximum leach recovery.

Jan 1, 2002

By Julian S. Edwards, C. Frederick C. Pearson, Sevket Durucan

Information gained at the site investigation stage of the Carsington aqueduct project led the designers to suspect that methane might be encountered during tunnelling and therefore gas detection techniques, including emergency shutdown systems, were introduced. After construction, on completion of the excavation and lining of the tunnels, a survey showed that methane was entering the aqueduct dissolved in infiltrating groundwater. General body air concentrations were very low but on closure methane concentrations rose rapidly within the aqueduct. A research project has now been initiated to investigate the mechanism of methane generation and entry rate into the system, the results of which are being taken into account in the preparation of future operating procedures.

Jan 1, 1989

By H. Singh

Principal source of rhenium is molybdenite. Depending on the mineral processing route, rhenium can be recovered by one of the several alternative solvent extraction processes. Extensive experimental work has been carried out on the development of tertiary amine extraction process for treating very dilute highly impure scrub solutions obtained during scrubbing flue-gases of molybdenite oxidative roasting. Equilibrium data has been obtained under various process conditions by tracer analysis using radioactive Re-186. Extraction with 1% solution of a high molecular weight tertiary amine in kerosene, followed by scrubbing of organic extract with a solution of sulphuric acid and stripping with ammoniacal ammonium sulphate yields high recovery, concentration, and purification.

Jan 1, 1982

By D. L. Slyter

Coeur d'Alene Mines Corporation's Thunder Mountain project in Valley County, Idaho, is one of the most remote active mining operations in the US. High altitude, heavy snows, and proximity to wilderness complicate operations in this environmentally sensitive area. Mining is conducted by conventional open pit techniques while processing utilizes on-off heap leaching and Merrill-Crowe zinc precipitation. The project is one of a few similar operations which detoxify the leached ore prior to its removal from the leach pads. Both leaching and neutralizing ( detoxifying) circuits are closed and independent loops. After leaching, alkaline chlorine solutions destroy residual cyanide in the heaps. Calcium hypochlorite solution for the cyanide destruction is prepared by injecting chlorine gas into milk of lime solution.

Jan 1, 1998

The status and outlook for mining, in your view. Minerals remain a major part of the world’s economic foundation. The fortunes of the mining industry rise and fall with general economic trends, but mining is no less important today on a global basis than it has been historically. Certainly, portions of the industry are critically depressed — domestic copper to name one area —but other sectors are prospering. Mineral consumption, both worldwide and in the United States, has increased steadily since the Great Depression, hitting all-time highs in 2000, the last year for which I have seen data. The highly developed economy in the United States tends to obscure the continuing importance of minerals here. But in less developed nations the critical nature of minerals is obvious and well accepted. In short, although there is no shortage of problems or challenges facing mining — there never has been — mining remains an essential business with great global opportunity.

Jan 1, 2003

By Nick Rose, Robert Sharon, Mark Rantapaa

Development of the Northeast Layback of Barrick’s Betze-Post open pit commenced in June 2000 and was successfully completed to a height of 400m (1,300 ft) in January 2003. Following a brief exploration drilling campaign at the toe of the final slope, in-pit waste rock backfilling commenced, which will ultimately buttress the final wall. Instability initially occurred in late 2000, above the 5040 Level, as the slope height approached 120m (400 ft). As mining reached the 4680 Level, significant deformation was experienced over a slope height of 230m (760 ft). Slope stability was managed and targeted reserve recovery was achieved by executing complicated modifications of the mine plan, including splitting layback development, well placed offloading cuts, step-outs and mid-slope waste rock buttresses. Decision on timing of these modifying events was often dictated by review of deformation magnitudes and rates determined from continuous slope monitoring records. Design modifications were developed through continuing interpretive refinement of structural geology controls and groundwater distribution, and through stability re-assessments. This document presents an overview of the geological setting and material and strength conditions of the northeast sector of the Betze-Post open pit, followed by development experience leading to design and development of the Northeast Layback. Rock mechanics modeling, design details and geotechnical performance monitoring are then presented. Development experience, stabilizing adjustments to the original design and safety procedures for development and exploration activities are described. The document is finalized with conclusions and acknowledgements.

Jan 1, 2005

By A. Mehmet, W. A. M. te Riele

A pilot-plant investigation in a NIMCIX contactor has shown that activated carbon can extract more than 93% of the gold in return-dam solutions. The average gold concentration in the barren solution was less than 0.003 mg/L from a feed averaging 0.048 mg/L. The carbon was eluted by the Zadra procedure. The operating conditions of the elution-electrowinning circuit are reported, and the elution of the gold and other metals is discussed. The reactivation of the carbon by use of the Rintoul kiln is described, together with the results of reactivation. The consumption of reagents in the process cycle is presented in sufficient detail to allow the economic viability of this technique to he evaluated for the recovery of gold from low-grade solutions.

Jan 1, 1990

By E. B. McNew, J. M. Barnes, A. E. Torma

The applicability of biosorbent materials for the removal of uranium and other heavy metals from synthetic and actual uranium mil 1 tailing (UMT) solutions has been investigated. The biosorbent materials used in this study were barium loaded beads of alginate, alginate-dextran sulfate, alginate-carrageenan, and alginate-xanthan gum. These studies were performed in stirred vessels and packed columns. It was observed that 100 percent of the uranium could be removed from a synthetic solution following 2 hours of contact time in a stirred vessel, and 80-100% of U, V, Mo, Mn, Sr, and Zn could be removed from a UMT effluent solution with a packed column. Kinetic evaluations were performed, using a generalized rate equation, on the biosorption of uranium with these barium loaded beads.

Jan 1, 1992

By W. E. L. Minter

The most important witwatersrand gold placers occur on extensive unconformity paleosurfaces that were produced during protracted periods of fluvial degradation. The erosional etches on what was generally unlithified substrate indicate that low sinuosity erosion patterns prevailed. The transport systems were dominantly braided fluvial with a minor debris-flow component. The placer sediments were non-cohesive sands and gravels which were evidently transported by fluctuating, yet perennial, discharges across extensive, low relief, bra1dplains, not far from littoral environments. Progress made in understanding heavy-mineral transport processes now emphasizes the importance that selective entrainment probably had in producing concentrations. Cognizance that these characteristics are not unique to the Witwatersrand should be taken into account when designing exploration models.

Jan 1, 1988

PolyMet Mining is developing the NorthMet property near Duluth, Minnesota. Laboratory investigations had led to the development of the PLATSOL process to dissolve in one step the base metals (copper and nickel) as well as the gold and PGM’s. To complete the pre-feasibility study, a fully integrated ten-day pilot plant trial was undertaken, comprising of: high temperature (>220ºC) pressure oxidation in the presence of 5-10 g/L chloride (the PLATSOL process), followed by solid/liquid separation, gold plus PGM’s recovery from solution, conventional Cu SX/EW and recycling of the copper raffinate to the autoclave. The concentrate tested was a NorthMet bulk flotation concentrate assaying 14.7% Cu, 3.05% Ni, 0.14% Co, 26.7% S, 1.4 g/t Au, 2.2 g/t Pt and 9.9 g/t Pd. Laboratory results were fully confirmed and with minor adjustments of the laboratory PLATSOL® conditions, the following leach extractions were obtained during the pilot plant trial: Cu 99.6%, Ni 98.9%, Co 96%, Pd 94.6%, Pt 96% and Au 89.4%.

Jan 1, 2001

By E. Shelobolina, S. M. Pickering, J. E. Kogel

A long history of weathering and bacterial alteration processes have transformed Georgia’s Coastal Plain kaolins from dark organic muds to recrystallized white pigment-grade industrial clays. A sequence of six stages in development of these valuable mineral deposits is outlined over their Late Cretaceous and Tertiary deposition and alteration history. Anaerobic and aerobic iron oxidizing and iron-reducing bacteria are present in the Georgia kaolins. These bacteria may have had a major role in iron and organic matter removal during several of the alteration stages that occurred over the past 60+ million years. Iron was likely solubilized by both iron-reducing and iron-oxidizing bacteria, depending on availability of Fe(II), Fe(III), and NO3. Thus, over long periods bacterial activity slowly led to nearly complete groundwater removal of iron from the kaolin deposits. Further bacterial iron removal on an industrial process scale may eventually prove feasible. “Without the multitude of living reactions as channels for energy and electrons and without the enormous capability of life to transfer with and against chemical gradients, there would be practically no or at least a very reduced geochemical rock cycle on this planet.” (Krumbein and Dyer, 1985, p. 157)

Jan 1, 2002

By W. O. Kerr

As in other industries, companies engaged in mining and extraction use and develop intellectual property (?IP?) in the form of new technologies or production processes. The development of IP assets in mining may occur as a byproduct of ongoing operations, or result from investment in dedicated R&D efforts. New technology may lower costs, increase quality of output, and/or increase operational efficiency or safety. Key business questions with respect to any new technology are how best to use IP assets, how to protect them and how to derive value from them. IP assets can provide a competitive advantage to a developing firm that uses the technology to improve its operating results. The developing firm can preclude others from using the technology if it believes that is the best way to exploit the technology?s value. Or, it can be shared with others taking care to ensure rights are maintained, thereby generating royalty income or strategic value through cross licensing or other business relationships. Either way, in order to fully realize the maximum economic benefit, innovators must protect the IP assets and control their dissemination.

Jan 1, 2012

By W. E. L. Minter

The most important Witwatersrand gold placers occur on extensive unconformity paleosulfaces that were produced during protracted periods of fluvial degradation. The erosional etches on what was generally unlithified sub-strate indicate that low sinuosity erosion patterns prevailed. The transport systems were dominantly braided fluvial with a minor debris-flow component. The placer sediments were non-cohesive sands and gravels. They were evidently transported by fluctuating, yet perennial, discharges across extensive, low relief braid plains, not far from littoral environments. Progress made in understanding heavy mineral transport processes now emphasizes the importance that selective entrainment probably had in producing concentrations. Cognizance that these characteristics are not unique to the Witwatersrand should be taken into account when designing exploration models.

Jan 1, 1991

By M. Stoica

Bioremediation is a complex process which involves mass transfer, chemical and biochemical phenomena. In particular, the adsorption kinetics of a substance by biomass may by model by taking into account: - Enzymatic kinetics type; - Combined kinetics - enzymatic kinetics at the same time with the Monod type biomass growth; - Chemical kinetics for substance adsorption according to Freundlich and Langmuir ad-sorption isotherms; - New empirical kinetics models based on experimental data. In this paper modelling of kinetics of bivalent lead ions on live vegetal biomass (aquatic plant Pistia stratiotes) as well as of hydrocarbons on dead vegetal biomass (pyrolysed nuts) is studied (Stoica, 2004). Modelling was carried out using experimental data and relative equations with an error of 5%.

Jan 1, 2006

By Mark Gershon

This paper describes a linear programming (LP) application that schedules mining operations in an optimal manner. The model is developed such that it can be applied to a broad spectrum of mining activities. While linear programming has been applied to mine scheduling in the past, the models have been either site-specific or they have only optimized one aspect of mine operations without regard to others. The Mine Scheduling Optimization (MSO) concept makes use of a mathematical model to: (1) Determine the optimal operation of a mine, from mine to plant to market. (2) Account for mine-plant-market interfaces. (3) Optimize operations over the life of the mine. (4) Accomplish long, intermediate, and short range planning.

Jan 1, 1982

By Peter McKenna

A mineral rights holding can ultimately only be turned to account by the profitable mining of ore on that property. The evaluation of South African gold mineral rights properties must therefore be carried out by assuming that they have potential to form part or all of a future gold mine. Such analysis involves the simulation of many of the estimation procedures that are normally carried out in a full feasibility study of a new mining venture but using far less data. This paper describes in detail the evaluation procedures that may be applied to an individual property and then indicates how these techniques can be applied to a whole mineral rights portfolio.

Jan 1, 1989

The issues involved in mine closure are usually complex, and the risks are significant. Although environmental risks are paramount, other issues such as safety, community, legal, fiscal and technical factors need to he taken into account. This paper describes a simple empirical model based on the concept of the closure risk factor, which will enable decision-makers to analyze the mine closure risks at any site, regardless of the complexity of the issues and the scale, scope and location of the operation. The model enables all the issues to be captured and their individual and collective risk quantified. A number of case studies in Australia and the Pacific that illustrate the usefillness of the model are presented.

Jan 1, 2002

By Terry W. Mellors, Robert J. F. Goodfellow

The underground industry has been forced to reconsider risk management sincethe introduction and implementation of the “Joint Code of Practice for Risk Management of Underground Works in the UK” published in 2003 and the subsequent international version published by the ‘International Tunneling Insurance Group’ (ITIG) in January 2006.What does this mean for major tunnel projects in the US and elsewhere? The discussion will highlight the implementation of the Codes to date, risk management principles embodied in the Codes and the use of risk registers as a projectmanagement tool and the management of risk.

Jan 1, 2007

By Michael J. Virnig, Keith E. Weerts

The development of heap leach technology for the treatment of low grade gold and silver ores has led to a boom in gold production in the Western United States in the last 15 years. The heap leaching process consists of stacking the mined ore on a specially prepared leach pad followed by leaching with dilute alkaline cyanide solution. Depending on the nature of the ore, it may require crushing and/or agglomeration prior to stacking on the leach pad. As the dilute alkaline cyanide solution migrates down through the stacked ore, the precious metal values along with a portion of the base metal values present in the ore are dissolved to give a pregnant leach solution which is collected at the base of the stacked ore. The precious metal values are then recovered by zinc precipitation or by adsorption on activated carbon. Once all of the economic metal values have been leached from the ore, the spent heap leach pad, the leached materials, and associated process solutions must be decomissioned. Decommissioning requires that the spent heap leach pad along with the leached materials and process solution be treated to reduce the concentration of the residual cyanide, base metal cyanide complexes, and other anionic metal species to levels where they no longer represent a long tenn liability for the environment and the operator. The levels to which these components must be reduced is dependent upon the applicable water quality standards as determined by the responsible federal, state, and local agencies. As environmental awareness has grown, these standards have become increasingly stringent. A number of treatment options have been developed for the de-toxification of the process residues. These include natural degradation which incorporates bio-degradation, fresh water rinsing, alkaline chlorination, hydrogen peroxide, and sulfur dioxide/air. Each of these options has been reviewed with regard to relative effectiveness, generation of hazardous by­products, reagent handling considerations, relative costs, and time requirements by Denton, Iverson, and Gosling I. As an outgrowth of the program to develop Henkel's guanidine based gold extractants, COGNIS, Inc., the environmental ann of Henkel, has developed the CyanoMet R process for the extraction and concentration of the various cyanide and anionic metal species from the dilute aqueous alkaline solutions generated during the process of detoxifying spent heap leach pads. This paper describes the CyanoMet R process, its application to three different feed solutions, and treatment of the concentrate generated by the process.

Jan 1, 1993

By J. Bigu

A theoretical radiation mine model, suitable for underground uranium nines, has been investigated. In this model, the rate of ventilation and/or the radon (thoron) gas emanation from mine walls are time-dependent. Several cases of practical interest have been investigated including sinusoidal, linear, exponential, stepwise, or a combination of two or more of the above. Analytical solutions were obtained for the time-dependent radon (thoron) gas emanation rate. However, because of the extreme analytical complexity of the solutions corresponding to the time-dependent ventilation rate case, numerical solutions were found using a special Runge-Kutta procedure and the Hamming's modified predictor-corrector method for the solution of linear initial-value problems. The mine model makes provisions for losses of radioactivity, other than by ventilation and radioactive decay, by, say, plate-out on mine walls, and by other mechanisms. Radioactivity data, i.e., radon, thoron, and their progeny. obtained with the above mine model for a number of ventilation and emanation conditions, are presented. Experimental data obtained in an inactive stope of an underground uranium mine for a time-dependent air flow case are shown. Air flow conditions (ventilation rate) were determined by tracer gas techniques using SF6.

Jan 1, 1987