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By P Jackson, J Rea, M D. Goodz

The Morning Star Gold Mine has operated over a 101-year period, producing gold from narrow quartz veins and sulfide stockworks hosted mainly within a dioritic-gabbroic dyke. The deposit has been developed over a vertical depth of 980 m with drilling extending the vertical depth to greater than 1200 m. Currently there is a total Inferred Resource of 4.6 million tonnes at a grade of 6 g/t for 910 000 ounces of contained gold resources, which comprises an underground project and a surface project. Significant variation exists between the grade of drill core intersections and that observed in face sampling and subsequent production reconciliation (250 - 650 per cent). Studies were carried out on ten major production reefs, where the grades of drill intercepts were compared with face samples collected during development and mining. The implications of this study have been used as justification to assign production or stope/development grades where applicable to resources that are direct extensions of the historical development headings. Grade assignment and its impact on sensitivity for gold resources are detailed and show a 40 per cent variation in the gold resource, depending upon whether a production or calculated stope grade is used in grade assignment for the major reef deposits. Recent diamond drilling has intersected approximately 40 new gold bearing quartz reefs and sulfide zones that contain all the key mineralogical and structural indicators, and traditional large variations in gold grades similar to the historical major production zones. The implications of grade factoring and grade assignment are the greatest challenges confronting the resource estimation team in defining grade for these new zones. Grade assignment is seen as a method of balancing known historical production observations with the irregular grade distribution inferred from drill core assay results. Ongoing mine development and bulk sampling works are planned to validate the grade assignment process. The first stage of this process is the trial mining of the newly discovered Maxwell Reef (MR). The stope drawpoints were completed in August 2008 and the MRS1 stope is scheduled for completion in September. The stope reconciliation results will be presented at the October 2008 conference.

Jan 1, 2008

By Mahmut Altiner

In the present study, the use of horse residue as an alternative reducing agent in the roasting of a low-grade goethite ore containing 17.60% Fe was investigated. Additional roasting experiments were carried out with corn starch and without reducing agent for comparison. Each roasted product was characterized using X-ray diffraction (XRD) and magnetic hysteresis (MH) loops analyses. The optimum roasting conditions (roasting temperature [400, 500, and 600 °C], reducing agent/ore ratio [0.04, 0.08, and 0.12], and roasting time [10, 20, and 30 min]) were investigated based on the Taguchi approach. The magnetic susceptibilities of the roasted sample with the addition of reducing agents were higher compared to that of the roasted sample in the absence of reducing agent. Experimental findings indicate that the horse residue can be used as the reducing agent. Finally, an iron ore concentrate assaying a Fe grade of 62.12% with a recovery of 56.93% was prepared using wet magnetic separation at a magnetic intensity of 0.5 T from the ore roasted under the following roasting conditions: roasting temperature of 500 °C, reducing agent/ sample ratio of 0.08, and roasting time of 30 min.

Jun 3, 2020

By R. L. Clayton

The Bagdad district is 67 kilometers west of Prescott, Arizona, (Figure 1). The area north of the Old Dick and Bruce Mines was originally mapped by Anderson, Scholz and Strobell between 1943 and 1945, (1). The region is perhaps better known for the Bagdad porphyry copper deposit of tertiary age. However, 2 to 5 kilometers south of this deposit are several small massive sulfide occurrences in a eugeosynclinal Precambrian greenschist environment. More specifically, in. the Bridle formation of the Yavapai schist series. Three of these mines - Old Dick, Bruce and Copper Queen - were mined by Cyprus Mines Corporation between 1957 and 1977, and produced nearly 2mm tons of 3.6% copper and 12% zinc. These deposits occur at the interface between andesite and rhyolite and are stratiform in character. Certain structural and textural properties of the Bruce orebody suggest that remobilization of the massive sulfides occurred at some period during the metamorphic history of the area.

Jan 1, 1978

By M Hilden, G Forbes, Z Ye, M Yahyaei, F Reyes, V Jokovic

Soft sensors offer several practical advantages for the process control of comminution circuits by combining multiple conventional sensors and other data sources with real-time analysis using mechanistic, phenomenological or machine learning models. While there has been a growth in the use of machine learning techniques for developing soft sensors in minerals processing applications, this paper describes advantages and challenges of using soft sensor models developed on the basis of process knowledge. Recent experience with three new soft sensor technologies developed by the authors are discussed. The Mill Filling Inference Tool which has been implemented at several mine sites, compares SAG mill load cell and power draw measurements with outputs of a semi-mechanistic power model to estimate the mill ball and total filling in real time. The progressive wear of the mill liners is modelled, allowing the model to correct the load mass due to the mass loss automatically and to estimate the charge trajectory. This information enables the mill to be operated more confidently near its limits. A coarse-ore stockpile soft sensor as been recently developed using a 3D cellular automata-based model to track ore size throughout the pile, and estimating the live capacity and size at each stockpile feeder to the primary mills. Finally, a hydrocyclone soft sensor is being developed to monitor performance using available hydrocyclone models to estimate the size and flow balance around the cyclone in real time. The model-based soft-sensor approach aims to synthesise and analyse existing data and provide operators and engineers with process- and model-relevant information that can facilitate making better process decisions. Maintenance data has proven useful for model development as it allows soft sensors to automatically adjust and compensate for the effect of progressive wear, for example for mill liners, thus helping the models to maintain calibration throughout the equipment life.

Aug 24, 2022

By B Zhao

Gas and coal dust, as potential harmful elements (PHEs) produced during mining, are considered two serious threats to the safe mining and the health of miners because of its explosive and pathogenic properties. To solve this problem, compound reagents enhanced water spraying technology was used to control the gas and coal dust in excavation working face in this study, and spray testing platform and wind tunnel were used to investigated the suppression effect for gas and coal dust. In addition, sink test, and agglomeration experiments were also used to analyse its suppression mechanism. Testing results show that the dust reduction efficiencies of compound reagents enhanced water spraying technology for four different particle sizes were 80 per cent, 91.43 per cent, 94.74 per cent and 94.46 per cent, and improved by 14 per cent, 10.86 per cent, 8.42 per cent and 4.25 per cent compared to water spraying. Moreover, the gas suppression efficiency also can be increased more than 20 per cent. Sink test, and agglomeration experiments results show that compound reagent improves the spreading efficiency of the liquid on the surface of the coal by changing its wettability, and this process can not only slow down the desorption rate of gas by forming a water-sealing effect in the coal surface indicated, but also promote the agglomeration of fine-grained coal dust.

Oct 12, 2022

By Claude Hubert, Robert Sansfaçon

"The Malartic gold camp includes the Malartic Gold Fields, Barnat, East-Malartic, Canadian Malartic and Sladen mines. From 1935 to 1984, these mines have yielded 212 403 kg of gold. They occur within a 900 m wide belt of highly sheared, dislocated and faulted volcanic and sedimentary rocks (Piché and part of the Pontiac groups) herein named the Malartic Tectonic Znne (MTZ). The zone trends WNW-ESE and separates two lithotectonic sedimentary domains, the Cadillac to the north and the Pontiac to the south. The sedimentary domains are characterized by their coherent fold generations consisting of open to tight reclined and recumbent F1 folds that have been refolded into series of asymmetric upright F2 folds. A flat-lying schistosity (S1 ) and a vertical pressure-solution cleavage (S2) are ubiquitous throughout. Discrete sets of brittle and brittleductile faults are synchronous and parallel to each of these two fabrics.The MTZ trends N320° in the northwestern sector of the town of Malartie, changing to N2800 at its easternmost extremity. The Malartie and Sladen faults constitute its northern and southern boundaries respectively. These two faults also bound another set of faults oriented N305°. Throughout the MTZ, the faults at N280° and N320° and those at N305° outline a series of anastomosed motifs that constitute the principal structural feature of the Malartic district. Locally, a fourth set of minor faults at N065° combines with the other three prominent sets. All these faults have disrupted the gold-bearing volcanic, sedimentary and intrusive rocks encountered throughout the MTZ.The MTZ comprises numerous lozenge-shaped blocks of komatiites and basalts or greywackes and black shales which are cut by disjointed dikes, sills and small intrusions of felsic and mafic rocks. The latter includes gabbro, diorite, lamprophyre, monzonite and pegmatite. They frequently fill conjugate sets of fractures. In some areas, they are clustered into coalescent intrusions. The present morphology of these intrusive bodies( cube, chocolate-tablet boudin, parallel epiped and cigar) is not representative of their primary forms but the result of late shearing and faulting indicative of a major tectonic event subsequent to their emplacement. The intrusions were injected during a brittle stage of deformation related to the F1 folding but prior to the development of the F2 folds and subsequent tearing and shearing by late brittle and brittle-ductile faults . The ultramafic and mafic rocks are intensely altered to serpentine, tremolite, actinolite, carbonate, biotite, hematite and pyrite according to the nature of their proto/it h. In the vicinity of the MTZ, all lithologies exhibit mineral assemblages indicative of the upper greenschist or lower amphibolite facies of metamorphism.The structural evolution of the MTZ involved superimposed folding, shearing, transposition, mylonitization, brittle and brittle-ductile faulting. Each lenticular motif results from the combined effect of conjugate sets of shear zones that outline lozenge-shaped blocks where strain markers indicate different strain states from cores to margins. Bedding in ultramafic flows and/or sedimentary rocks is either NW-SE or NE-SW within the blocks but, in the vicinity of the Malartie and S laden faults, it has been rotated to become subparallel to the faults.Ore shoots are most commonly associated with altered and deformed bodies of diorite and monzonite, or some mafic and ultramafic schists and, at the Canadian Malartic, Sladen and East Malartic mines, with metasedimentary rocks. The shoots occur in close proximity to the various faults of the MTZ but the gold itself is intimately associated with pyrite, biotite and carbonate in halos bordering fractures crisscrossing the different host rocks. The density of fractures and the width of their altered zones have been significant parameters in the production of economic ore shoots. Grains of gold are visible in some veins of quartz a"

Jan 1, 1990

By Thomas V. Fame, William E. Porter

"As geological and mining conditions become more complex, and as overall mining economics become more marginal, short- and long-range decision-making regarding multiple-seam surface mining becomes more difficult. The decision-making problem involves a study of economics, cut-off grades and ratios, equipment capabilities, sequencing and selective mining practices.This paper is concerned primarily with multiple-seam mining of bituminous coal. The research has led to the development of an economic decision-making model for use as a day-to-day tool to aid mine operators and pit geologists to decide what and how to mine.The model is designed as an aid for feasibility decision-making in multiple-scam situations and for situations where selective mining is needed or desired. In effect, a simulation of the feasibility and preliminary mine planning phases has been developed. The model is divided into four separate segments: decision-making, simulated mining, cost calculations and the determination of the discounted cash flow return on investment."

Jan 1, 2014

By Robert J. Hundhausen, GEORGE M. GRISMER

This circular describes the methods and costs of deepening the Silver Summit three-compartment shaft in the Coeur d'Alene mining region of Idaho. A noteworthy rate of advance was achieved at this operation by the successful use of a mechanical shaft-mucking machine. The Silver Summit mine is 1 mile west from the town of Osburn, Idaho, via U. S. Highway 10. The adit-level portal of the mine is on the south slope of the Coeur d'Alene River Valley at an altitude of 2,700 feet. The Silver Summit shaft is 6,000 feet from the portal. In past years this shaft had been sunk from the adit level to a depth of 1,500 feet. During 1946 the Polaris Mining Co, deepened it to 3,095 feet. The work was done under a co- operative development agreement between the Silver Summit Mining Co. and the Polaris Mining Co.

Jan 1, 1948

By Perry G. Cotter

As a portion of a general program for the synthesis of hard materials, a method was sought by which the hardness and density of tungsten carbide (WC)-cobalt compacts could be increased. It was demonstrated by Cotter that these improvements in quality could be made by employing an electric-resistance sintering process in which heat and pressure are applied simultaneously to presintered compacts composed of powdered tungsten carbide and cobalt. This conclusion was based on tests of material prepared by Cotter on welding equipment in use at the U. S. Naval Engineering Experiment Station, Annapolis, Md., and at Rensselaer Polytechnic Institute, Troy, N. Y. Rockwell-hardness tests made at Norris and core-drilling tests made at the Mount Weather Station of the Bureau of Mines indicated that, for some purposes, carbide material made by this process might be superior to the chemically analogous commercial products prepared by ordinary sintering methods. A program to develop optimum conditions for the electric-resistance sintering of tungsten carbide-cobalt compacts was initiated. The program was followed by a systematic evaluation of the hardness and density of compacts prepared by this method along with a series of carbide compacts furnished by various manufacturers. This paper presents a description of the electric-resistance sintering of tungsten carbide-cobalt compacts and the results of comparative physical tests.

Jan 1, 1955

By J. L. Shultz

The investigation of organic compounds in respiratory coal dust by high-resolution mass spectrometry has shown that the organic components differ (1) with particle size, (2) with rank of coal, (3) in coals of same rank from different coal seams, and (4) in respirable mine dust and respirable coal dust (prepared) from the same mine. The eight respirable mine dusts studied are from coal seams in the Appalachian region where the incidence of coal workers' pnumoconiosis is relatively high. The molecular weights of the major organic components vary greatly among these respirable mine dusts; three show strong concentrations of polynuclear aromatic hydrocarbons.

Jan 1, 1972

By R. K. Mishra, A. Kula, X. Jia, M. Niewczas

The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4K and 298K. The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening effect and grain boundary strengthening. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is affected mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behaviour under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

Jan 1, 2015

By Scott Giltner, Allan Koski

Blasting is one of the lowest cost yet most critical parts of the mining cycle. This paper discusses the findings of an audit conducted on the blasting operation at an iron ore mine. The purpose of the audit was to review current blasting practices in order to identify opportunities for production/cost improvements. The approach taken in the audit was to observe general blasting practices, their related downstream effects and to compare current procedures to established best practices.

Jan 1, 2009

By G. G. Krishna Murthy

Interactions of wustite and hematite pellets with Fe-C melts were investigated experimentally by examining the effect of pellet size and bath temperature on the reduction rates of the pellets. Experiments were carried out in the temperature range 1473-1923 K. A flash X-ray equipment was used to obtain images of the melt surface during its reaction with an oxide pellet. The reduction rates were calculated using experimentally estimated time for complete reaction of a pellet, tR. The value of tR was determined employing gas mass flow rate, or pressure rise in the sealed furnace, versus time traces. The value of tR was the same for both wustite and hematite pellets of equal weight at or above 1723 K and it decreased with increasing melt temperature. But the reduction rate was substantially lower at temperatures below 1651 K, the melting point of wustite. The rates were defined as the rate of moles of oxygen removed from the pellet per unit area of bath free surface and it was found that the bath surface area affects the reduction rates. It was established that the overall reaction followed nth-order rate kinetics with the values of n falling between 0.3 and 0.4 for temperatures above the melting point of wustite. The apparent activation energy determined using the apparent rate constants obtained from the experimental data was 76.2 + 27.7 kJ/mol-O.

Jan 1, 1992

By R P. Varden

This paper looks at the design of the Bentayga raisebore with subsequent back analysis using a LiDAR survey. A search for LiDAR raisebore assessment publications shows little work has been done on this subject. The paper examines the empirical design and RS2 modelling assessment with the bored condition. The high resolution of the LiDAR enabled mapping of weak structures that were located on the geotechnical investigation hole the orientations of which could not be determined. In addition, the scan showed were water ingress was occurring, potential stress overbreak and structural controls on stability. The LiDAR results were able to confirm no additional support work such as a shotcrete liner is necessary. The LiDAR results have been analysed in one metre increments as volume of overbreak against the empirical stability criteria (McCracken & Stacey 1989). The future use of LiDAR mapping over a range of rock mass conditions will provide quantification of the established empirical assessment improving its reliability. It is also a useful and accurate tool to monitor long term stability of a raisebore due to stress change or ore pass due to wear.

Mar 15, 2021

By Peter M. Fozzard

A review is made of the actual costs of recent foreign mineral exploration programmes in third world countries. Target identification leading to the selection of areas, or macro-targets, must follow a well planned and defined series of steps. Suggestions are made with respect to this inter-active project development work. Potential revenues in the broad sense will always determine the overall economics of exploration but clear objective philosophy, good planning and adequate financing are essential for exploration success. Considerable opportunities exist for making important foreign mineral discoveries and broad selected suggestions are made for the identification of exploration areas in relation to high-grade and precious metal mineralization.

Jan 1, 1984

By O. Barron, C. Felix

In 2023, polymer electrolyte membrane fuel cell membrane electrode assemblies accounted for about 62% of the global fuel cell market share and this demand is expected to grow. Commercialisation requires technologies capable of cost-effective, high-volume manufacturing. The membrane electrode assembly is crucial and represents a significant cost to polymer electrolyte membrane fuel cell manufacturing. Manufacturing the electrode components for membrane electrode assemblies at high volumes can reduce production costs while delivering on the forecasted industry demands. Roll-to-roll is a mature coating technology applied in various manufacturing industries such as batteries, printed electronics, microelectronics, photovoltaics, printing, paper consumables, etc., with significant potential for polymer electrolyte membrane fuel cell manufacturing. While the high-volume production process for membrane electrode assembly manufacturing differs from laboratory-scale, the membrane electrode assembly structure remains unchanged. Roll-to-roll is a continuous coating process with speeds of 10 m/min being achieved. In this work, MicrogravureTM and slot-die coating methods have been adopted and have shown promising outcomes for producing gas diffusion electrodes for membrane electrode assemblies. An overview of the MicrogravureTM and slotdie coating methodologies is provided, and a discussion on preliminary results and challenges are presented. Work on MicrogravureTM gas diffusion electrode manufacturing has already achieved comparable performance with spray-coated gas diffusion electrodes. The influence of coating parameters and drying on the coated catalyst layer quality is discussed.

May 27, 2025

By F. F. Lins

There is a large use of mercury in Brazil by the gold miners in the so called "garimpos" (non registered mining operations), where it is usual to recover the gold contained in the gravity concentrates by amalgamation, which is highly deleterious to environment if not conducted properly. Unfortunately, this is a common practice there. After presenting in brief the modus operandi generally practiced in the garimpos and the environmental problems, this work reviews some of the research conducted in CETEM according to two approaches: (i) replace amalgamation by other processes and (ii) develop technology to treat mercury-contaminated soils and effluents. Conventional processes like froth flotation, to recover gold from gravity concentrates, and centrifuges were considered. Also as alternatives to amalgamation, innovative process like the recovery of gold by coal-oil agglomerates and a technology that is currently under development in our laboratory, called gold-paraffin process, are described in brief, some results presented and their potential use assessed. To reclaim sites already polluted a technology was developed to float mercury selectively from contaminated soils. The potential use of centrifuges to pre-concentrate the mercury is also discussed. The scope for applying the last techniques is to concentrate the pollutants in a small volume of mass which would be suitable for recycling or isolation from the environment. A prospective technology to treat contaminated soils, or mercury concentrates, is the immobilization of mercury by adding inorganics. Concerning the ionic mercury which may be present in effluents, precipitation of the ions and flotation of the precipitates are being studied.

Jan 1, 1994

By Albert J. Rambosek

The results obtained in a study of the stress conditions existing in a drill bit-point area and in the underlying rock, when the bit was in full but nonpenetrative contact with the rock, are presented. This investigation by the Bureau of Mines was the preliminary exploratory phase of a long-range program of research on rock drilling to establish criteria for the maximum economically feasible rate of rock penetration. The photoelastic technique of experimental stress analysis was the principal method used to obtain the data. Transparent models and transmitted light were employed to investigate patterns in drill-bit models and isotropic materials under the bit when subjected to a concentrated static load. Comparative stress data for anisotropic rock were obtained by the reflective photoelastic technique. Brittle lacquer and an extensometer were used obtain supplementary information wherever substantiating data were desired to check photoelastic results. The zone of maximum shear occurs along an arc near the contact face of the bit. The stress distribution pattern in an isotropic model rock near the area contacted by the bit was nearly a mirror image of that exhibited within a similar areal zone of the bit. The stress pattern in granodiorite specimens was similar, though not symmetric, to the pattern in the isotropic model rock. The asymmetry of the stress pattern in the granodiorite was attributed to the anisotropic characteristics of the constituent minerals of various sizes.

Jan 1, 1963

By N. Kanari

One of the criteria to define the market value of chromite concentrate is its chromium to iron ratio. Changing this ratio for a definite chromite mineral is impossible by physical processing. This study investigated the possibility of increasing this ratio through the carbochlorination and the oxychlorination of chromite concentrates. Experiments are carried out up to 1000 °C. The characteristics of samples and reaction products are determined by SEM, XRD and chemical analysis. The carbochlorination of a chromite concentrate at about 600 °C leads to the . selective partial elimination of iron allowing a higher Cr/Fe ratio of the treated concentrate. Selective extraction of iron could also be achieved at about 950 °C by oxychlorination. In this case, a part of chromium contained in the concentrate is recovered as chromium oxychloride. The obtained residue had high content of Cr, Mg and A1 oxides. Such material has probably better chemical and thermal properties that may. be useful for foundary and refractory applications. Two flow-sheets for the beneficiation of the chromite concentrates using carho- and oxychlorination are suggested.

Jan 1, 1997

By Xinming Chen, Huazhe Jiao, Qi Zhang, Yunfei Wang, Liuhua Yang

The effect of initial damage generated by weakly cemented interlayer surfaces on the physico-mechanical properties of layered cemented tailings backfill (LCTB) is considered for the interlayer inclination structure generated by multiple layered backfills in large-scale mining voids. Utilizing the theory of damage mechanics, the damage evolution and constitutive model of LCTB with interlayer inclination is constructed by considering the coupling of interlayer inclination effect and loading. Based on Mitchell’s mechanical model, we analyze the damage mechanism of the inclined cementation surface of LCTB, and derive the expression for the strength of LCTB considering interlayer inclination. The mechanical properties test of LCTB with different inclinations was carried out, and the results showed that the damage model of LCTB established was highly consistent with the experimental curves, which verified the correctness of the model. The initial inclination damage leads to the decrease of adhesive cohesion of cemented surface, and with the increase of inclination, the separation of layered surface, aggravation of misalignment, layered cemented surface is more prone to shear damage, and the mechanical properties of cemented tailings backfill in the lower part of layered surface are not effectively played, which reduces the overall performance of the material.

Nov 23, 2023