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By A. C. Lawrence, K. F. Mauer

Human factors in stope productivity -a field experiment by K. F. MAUER, M.A. (Visitor), and A. C. LAWRENCE, B.Econ., D.Com. (Member) An experiment in which three human variables were manipulated in eight stopes was conducted in a gold mine over a period of roughly six months. The three variables, which each had two levels, concerned the degree of movement from gangs, the quality of the Bantu production supervisors, and the extent to which gangs were composed of a single ethnic group (Malawians). Time was included as a variable with three levels in the analysis of the findings. On the average, stable gangs produced 12 per cent more than gangs with a high percentage of transfers, gangs with better production supervisors were more successful by nearly 9 per cent than those with poorer production supervisors, and homogeneous gangs were more productive than heterogeneous ones by as much as 15 per cent. In addition, it was found that a number of the variables exercised a joint influence on stope productivity and that the effects of the variables were accentuated by the len gth of time they had been in operation. V

Jan 10, 1973

By G. van Aswegen

Seismic monitoring became commonplace in the deep South African gold mines in the early 1990’s. The discipline has, to a large extent, developed beyond the ‘research’ stage, and a ‘Guide to Seismic Monitoring in Mines’ has been accepted by the Department of Minerals and Energy1. Although ongoing research is a requirement for the achievement of all the objectives of seismic monitoring in mines, sufficient knowledge exists to apply seismic monitoring for routine seismic hazard assessment as an aid to risk management. The design and management of seismic monitoring systems can be tested against requirements spelled out in the ‘Guide’. Assuming the seismic monitoring system performs as per requirement, the best practice for routine seismic hazard assessment in mines includes • Long term seismic hazard assessment: through back analysis of seismic data and correlation with numerical modelling output, reasonable tests for planned mine designs are possible. • Medium term seismic hazard assessment: o Spatial analysis through contouring of seismic strain related parameters, with superimposed contours or event plots of stress related parameters allow the delineation of potential instabilities in space. o Quantitative and statistical analyses of seismicity in smaller spatial units (usually encompassing production sites) allow the comparative seismic hazard rating of different areas/sites so that rock engineering input and risk management can be optimised • Short term seismic hazard assessment relies mainly on time history analyses of particular seismicity parameters. The temporal patterns are controlled by a combination of temporal and parameter filters, the optimisation of which determines the success rate.

Jan 1, 2003

By C. A. Garzonio, A. M. G. Affuso

The paper describes the analyses and the tests carried out on representative slabs of white Carrara marble which have highlighted the correlation between the micro fabrics and physical and mechanical parameters. The aim is to determine the conditions which indicate the triggering and evolution of the deformation phenomena. La note écrit l’analyse et les epreuves effectuée sur un echantillon représentatif de nombreuses dalles en marbrede Carrara. Les études montrent la correlation entre la minéralogie et les paramètres physiques et mecaniques. Le but est déterminer les conditions qui indiquent l’amorçage et l’evolutions des phénomènes de déformation. Diese Arbeit gibt eine Beschreibung der experimentalen Untersuchungen und der Analysen über die Marmorplatten von Carrara. Daraus resultiert, dass die Charakterisierung der Mineralogie und die Porosität der Gesteinsmaterialien die physikalische mechanische Degradation beurteilen und die Krümmungen bestimmen.

Jan 1, 2003

By J. T. Nel

Non-transfer-arc linear plasma systems are highly suited to manufacturing nanoparticles. In this paper, the manufacturing of such particles with specially designed plasma systems is discussed. In general, it entails the volatilization of a metal halide that is injected in the high-temperature region of a plasma flame, where it is reacted with a suitable reagent, for example O2, to produce nanooxide powders. Metal powders can also be introduced directly in the plasma. Due to the very short residence time of only milliseconds in the reaction zone, as well as the fact that the reaction takes place in the gas phase, combined with very rapid quenching in the order of 10 000°C.s-1, nanoparticles are produced. At Necsa the manufacturing of such particles has been demonstrated on various scales. A pilot plant for the production of nano-Al2O3, and two pilot plants, one using SiCl4 and the other one using SiF4 as feed material, were built to produce fumed, pyrogenic, nano-SiO2. The alumina plant had a production rate of 8?10 kg.h-1 and the silica plants had production rates of 2 and 10 kg.h-1 respectively. Perfectly spherical alumina particles with a particle size distribution of between 10 and 200 nm were produced on a continuous system. Particle size analysis for the silica by SEM measurements showed a d50 of 60 nm and a particle size distribution of 30?100 nm. The specific surface area was in the range of 170m2.g-1. Other samples of plasma produced nanoparticles such ZnO and B4C will also be presented.

Jan 1, 2010

By F. H. Abd EL-Rahiem

A selective dispersion process is presented and the work carried out to find optimum process conditions to minimise the colouring material in ground calcium carbonate (GCC) is described. The feed material is the overflow product from a hydrocyclone which results from using a Denver Attritioning machine with semi-autogenous grinding for one hour and a 1:1 ore/water ratio. By using sodium silicate (SS), with pH 9 and pulp density 5%, the iron content (as colouring impurities) is decreased from 0.21% in the original concentrate to 0.12% in the final concentrate. The degree of whiteness reached is improved to 85% from 63% in the original material. However, by using hexametaphosphate (SHMP) at pH 10 at the same pulp density, the iron content decreased to about 0.073% and hence the whiteness degree increased to about 96%.

Jan 1, 2004

By J. Kortnik

Mining has always been, and still is, an activity which is vital for the development of mankind. This is because a predominant proportion of industrial products and energy is produced from raw materials that are excavated using mining methods. The need for environmental protection and the close proximity of urban settlements and mines in Slovenia have necessitated ever stricter requirements for the excavation of raw materials and the introduction of more environmentally-friendly mining methods. This is achieved by implementing a closed eco-technological cycle of raw material excavation within the scope of mining methods. In surface mines, this means prompt reclamation of the degraded surfaces, and in underground mines the use of methods with minimized impact on the surface and on underground water. In underground mines, mining methods with backfilling installed according to the multi-barrier disposal system are the only ones that allow the possibility of implementing a closed eco-techno-logical cycle of excavating raw materials. Various industrial waste materials are also included in the backfilling material in order to improve its strength properties. Backfilling consisting of several different waste materials is produced in the form of a composite. Before backfilling consisting of waste material composites can even begin to be used in mines, an environmental impact assessment of its suitability for mines needs to be made. In order to make such an assessment, a pressure leaching cell and an open diffusion cell were made, i.e. a pressure leachate test and a sorption test were developed. The two cells and the developed tests will enable the study of the influence of backfilling on the environment if installed in an underground mine. The pressure leachate test performed with the use of the pressure leaching cell simulates leaching from a consolidated backfill during the seeping of underground water into the backfilling material under pressure. The sorption test performed in an open diffusion cell simulates the flow of eluate leached from the backfilling material through the rock/geotechnical barrier. The two tests were developed in such a manner that they are performed either in succession immediately after one another, but they can also be performed separately at a certain time interval. The paper presents an assessment of the suitability of backfilling made of different waste material composites. Keywords: environmental impact assessment, multi-barrier disposal system, waste material composites, pressure leachate test, sorption test, pressure leaching cell, open diffusion cell, eco-technological cycle, mining methods with backfilling.

Jan 1, 2003

By J. Mothomogolo

Mining projects are capital-intensive and are also characterized by high technical and economic risks. These factors pose challenges to mining entrepreneurs when they seek to raise seed capital for mining start-ups. There are limited sources of mining investment funds in South Africa and each has shortcomings due to one reason or another. Another impediment is South Africa?s status as a developing economy, in which the standards of living ? which in turn influences the savings culture ? the limited GDPs and budget, the socio-political environment, and banking, mining, treasury and other regulations, determine the size of investments, particularly in mining ventures. The proposed funding mechanism was developed with the aim of filling the gaps identified in existing funding mechanisms that were developed by the government with the introduction of the Minerals and Petroleum Resources Development Act (MPRDA), 2002. The shortcomings identified were presented to the study participants as questions to obtain views that were used to define innovative ways of raising mining start-up capital. Most participants in the study supported the derived hypotheses and proposals, and these were used to refine the proposed mechanism for mining investment in South Africa. The proposed funding framework is aimed at encouraging interaction between mining entrepreneurs, government, and the investors to align goals and expectations when undertaking a mining investment.

Jan 1, 2012

By S. J. Lötter

Analysis of the major and minor components of raw zircon as well as plasma-dissociated zircon was undertaken using inductively coupled plasma optical emission spectroscopy (ICP-OES). Microwave-assisted acid extraction as well as flux fusion using lithium tetraborate were investigated as digestion methods. Microwave-assisted acid extraction samples were analysed with matrix-matched standards. The most successful microwave-assisted acid extractions yielded 44.3(1), 49.75(7), 78.3(3) and 90.0(7) per cent recovery for Zr, Hf, Al, and Fe respectively using sulphuric acid. In no instance was acid extraction capable of complete digestion of the sample matrix. A standard addition method was applied to the flux-fusion samples due to the high complexity of the sample matrix. Method validation for the flux fusion procedure was performed using the SARM 62 certified reference material (CRM) with acceptable recovery ranges being based on the 95 per cent confidence intervals of the CRM. Successful analyses were achieved for Zr, Hf, and Ti with apparent content of 66(6), 1.7(1) and 0.15(1) per cent respectively.

Jan 1, 2012

By A. H. Swart

Unplanned stope panel collapses occur on most near-surface and shallow mines in South Africa. Although these incidents often occur during blasting, they pose a major threat to the safety of underground workers and the economic extraction of orebodies. Most stope panel collapses occur due to excessive panel lengths (resulting in excessive stope spans) that are not designed according to a systematic design procedure or methodology. Instead, panel lengths are often dictated by the equipment in use and by previous experience under similar conditions. Hence, a rock engineering design methodology for the design of stable stope panels between pillars is of vital importance for optimum safety and production in shallow mining operations. Using the proposed design methodology described in this paper, rock mechanics practitioners and mine planners should be able to identify and quantify the critical factors influencing the stability of stope panels. The critical factors should then be used as input to the design of stable stope panels that will provide the necessary safe environment for underground personnel working in stopes. The proposed design methodology is an iterative process, which includes aspects such as rock mass characterization, estimation of rock mass properties, identification of potential failure modes, consideration of appropriate stability analyses and other elements of the rock engineering design process. This process continues after implementation. During monitoring, new data should be included in the database and the design process repeated on a regular basis. Design approaches included in the proposed design methodology include empirical methods such as different rock mass classification methods, analytical methods such as elastic and Voussoir beam analyses, kinematic analyses, probabilistic analyses, and numerical analyses. Keywords: stability, stope panels, design methodology, hardrock mines, shallow mining operations

Jan 1, 2005

By J. Y. Foley, K. Eden, A. E. Grosz, C. J. Giles, J. E. Grosz

"Portions of the Icy Cape placer Au district have been described and exploited since the early 1900s. Industrial studies of Au-bearing garnetrich intervals established a 3.5 million troy ounce resource in the western half of the district. This estimate is not compliant with CIM and SME definition standards for Mineral Resources and Mineral Reserves. We note high variability in the textures of sediments and their heavy mineral (HM) content and composition in the district, probably as a function of the depositional environment. Sediments are medium- to fine-grained sands with a valuable HM assemblage that averages 26.0% in a range of 1.1– 72.6%. Valuable heavy minerals (VHMs) garnet, magnetite, ilmenite, rutile, and zircon, but excluding Au, average 7.9% in a range of 1.0–37.6% of the HM assemblage. Trace quantities of uraninite, thorite, monazite, xenotime, and others are noted. Garnets have an average Y content of 726 ppm with a range of 0–2150 ppm. Energy-dispersive X-ray fluorescence confirms compositions commensurate with Ca, Al, and Mg silicates. We provide empirical analytical data and note high variability in the textures, HM content, and compositions as a probable function of depositional environment. Icy Cape District land and resources are owned by the Alaska Mental Health Trust Authority and managed by the Trust Land Office (TLO). IntroductionThe Icy Cape Heavy Minerals (HM) District in Alaska subtends more than 200 km2 fronting the Pacific Ocean and backing to the foot of the Robinson Mountains at about 1700 m above sea level. We classify the district into geomorphic provinces; the eastern region as deltaic (Figure 1) and the western region as coastal plain (Figure 2), based on geomorphologic expressions. The coastal plain is entirely built up of unconsolidated outwash sediments and ancient beach sand deposits."

Jan 1, 2017

Work undertaken in the field of cut-off grade optimization has not advanced much beyond the work undertaken by Lane in 1988. His definitive work is based on the calculus of the Net Present Value criterion which is the most widely understood, consistent, and appropriate method by which sequential cash flows arising from the extraction of mineral reserves from an exhaustible resource can be represented. Although the mathematics is not complex Lane’s method is not a widely appreciated or applied approach to maximizing the value of a mining operation through selection and balancing of operational cut-off grades. Three stages in a mining operation namely, mining, processing and marketing were defined by Lane and the economics of each stage are identified and isolated to provide an optimum cut-off for each stage. Points of intersection along the present value curves for each stage of a mining operation are used to identify balancing cut-off grades at points where the capacity of the mining, processing and marketing stages is fully utilized and the Net Present Value of the operation is optimized. Data that simulate a small, deep-level Witwatersrand-type gold mine with an average grade of 6 g/t Au and a logrithmic variance of 1.2,are applied to the model to illustrate the benefits of representing cut-off grades in terms of present value curves for different segments of a mining operation. Keywords: Cut-off grade, Net Present Value, grade-tonnage curve, balancing cut-off grade, mining, processing, marketing.

Jan 1, 2003

By Gift Chisakuta, Bravo Mbao, Nils Schwarz, Angus Feather, Anthony Mukutuma

Bwana Mkubwa is a 50 000 tons per annum copper cathode producer, owned by First Quantum Minerals and located in Ndola, on the Zambian Copperbelt. The Bwana Mkubwa solvent-extraction circuit was started up in 1997. In 2002, the plant began treating ore from First Quantum?s Lonshi mine located in the Democratic Republic of Congo. The Lonshi ore is exceptionally fine and the amount of solids in the feed solution reporting to the solvent-extraction feed solution increased dramatically. Initially, crud was filtered in a filter press, but this rapidly blinded and seldom produced anything better than a wet sludge containing large quantities of organic. In December 2003 the decision was made to install a Flottweg Z4E-3/441 Tricanter® centrifuge to recover organic from the crud. The installation was completed in June 2004 and has since led to significant improvements in plant operability and savings in organic consumption.

Jan 1, 2007

By R. Haldenwang, R. Erasmus, P. T. Slatter, R. P. Chhabra

Notches are used routinely for measuring the flow rate of water with free surface flows. As far as can be ascertained, no work has been done to investigate the performance of these flow rate measurement devices for non-Newtonian suspensions. The Flow Process Research Centre at the Cape Peninsula University of Technology has investigated the flow rate of kaolin and bentonite suspensions from a tank for two notch shapes, namely rectangular and triangular, and for 3 different concentrations of each suspension. The notches were calibrated using water and then the kaolin and bentonite suspensions were tested in them. The rheological characterisation of the fluids was done with a Paar Physica MC-1 rotary viscometer fitted with a cup and roughened bob. Analysis of the results shows a significant increase in discharge coefficient with increase in concentration, and the discharge coefficient has been correlated to the yield stress. This is the first such study, and further investigation is needed to confirm and extend these findings.

Jan 1, 2007

Spiral concentrators are compact, cost-effective and generally efficient gravity concentration separators for a wide range of applications (for example: coal, beach sands, iron ore, chromite and tantalite). Large mineral processing plants consist of thousands of spiral concentrators resulting in large plant footprints (capital intensive) and the adjustment of splitters is time consuming, impractical and is in many cases neglected?high capacity (HC) spiral concentrators aim to address these shortcomings. As a result Exxaro Namakwa Sands is currently investigating high capacity spiral technology for the spiral circuit upgrade at the primary concentrator plants (PCPs). This article summarizes the rougher spiral performance evaluation that was conducted on different types of spiral concentrators (the traditional MG4 spiral concentrator and the high capacity (HC) spiral concentrator) under different feed conditions. In addition, the effect of slimes on the spiral concentrator performance was also investigated. Slimes rheology was linked to the poor concentrator performance at the higher slimes concentrations. The test campaign shows a sacrifice in recovery under design-feed conditions can be expected when using high capacity spiral concentrators in the rougher stage when compared to traditional spiral technology currently in use. Both spiral concentrators show a detrimental impact of slimes on the performance, but the high capacity spiral concentrator is more sensitive to the higher slimes conditions.

Jan 1, 2010

By S. Mundike

A scraper-based block cave method has been successfully applied to extract the Lower orebody at Nchanga since the 1950s. Since inception, scraper drifts and service ways have been supported using steel arch sets fabricated to a specific design from high strength manganese steel To reduce costs and to improve productivity, trials commenced in 2002 using fibre reinforced shotcrete as an alternative support method. One of the areas, the 2420 8E 1C trial drift, was subjected to abutment loading for several months prior to undercutting and cave mining. Shotcrete installed exhibited minor cracking shortly after application but very little deterioration thereafter. Following the success of the trial, the application of fibre-reinforced shotcrete was extended to other drifts. This paper describes the application of fibre-reinforced shotcreteat Nchanga and outlines design and quality assurance methods employed.

Jan 1, 2005

By W. J. Cruise

This paper reports on a test that was conducted underground in a mine for two years on the following: pipes coated with paint, fusion-bonded powder, metal, or impregnated tape; and aluminium, stainless-steel, 3CR12, and plastic pipes. It was found that the degree of corrosivity and mechanical damage increases substantially from the shaft of a mine towards the stope. Thus, the range of coatings that can be used successfully is fairly large in the shaft and haulageways, but corrosion-resistant materials, especially corrosion-resistant steels, need to be used close to the stope. A study of the relative costs involved showed the costs of pipes of low-carbon steel and unplasticized polyvinyl chloride to be lowest, and those of epoxy-coated steel pipes to be highest.

Jan 1, 1985

By H. Griesel

The overall supply of platinum is forecast to rise more than the demand, and market deficit will narrow somewhat, but is still substantial at about 480 000 ounces. Because of this deficit, the price of platinum is expected to remain high, not taking into account the impetus from funds and speculators. With this strong demand for platinum and the high price, platinum producers still need to initiate projects to not only sustain current production, but also expand output into the high demand. However, the rise in the platinum price does not entirely offset the drop in revenue due to the strong rand. Consequently, in the current economic environment, executives and managers are under extreme pressure to initiate only the highest yielding projects and implementing them successfully. During the initiation phase of a project, the cost of changing concepts is the least, and strategic project decisions are the most important. It is during this phase that the most value can be added to a project, therefore requiring inputs from highly skilled, creative and experienced people. This paper will discuss thought processes and paradigms during the initiation of projects that will assist project owners in the selection and initiation of successful and profitable projects. The project initiation process will also be discussed outlining selection models, risk analyses and funding considerations.

Jan 1, 2004

By S Rupprech, T Lund, H Fourie, PH van Rooyen, NM Vegter

Rosh Pinah Zinc Corporation (Pty) Ltd (RPZC) operates an underground mine at Rosh Pinah in southern Namibia producing zinc and lead sulphide concentrates. It currently mines around 0.7 Mtpa run-of-mine ore containing around 6-10% zinc and 1.5-3.5% lead. As part of past exploration and current intensified exploration, a massive continuous low grade ore body was identified which grades at around 3% zinc equivalent. This ore body is near current mining infrastructure and could be amenable to bulk mining methods. In the present paper a concept is presented on how it could be exploited. As a precursor to exploitation of the low grade a number of enhancements are proposed for the current mining operations including: ? shortening load-and-haul distances by extending the conveyor raise further down the mine in a phased manner and back-filling of waste into mined-out stopes; ? use of mobile crushing plant at the crusher tip, and; ? installation of a system to allow scoops to load directly from stopes into ore passes close by combined with truck loops to haul from these ore passes to the crusher tip. To exploit the low grade ore body the following concepts are proposed: ? open stope mining from two areas at a total rate of up to 2 Mtpa; ? underground pre-beneficiation of mined low-grade ore near the stopes using either dense medium separation or X-ray sorting; ? pre-beneficiated tails back-filled to mined-out stopes and; ? pre-beneficiated product transported to surface by linking into proposed run-of-mine conveying system.

Jan 1, 2007

By J. R. G. Williamson

The Mining Division of Iscor, an integrated minerals and metals company, has recently completed a feasibility study for the establishment of a new heavy minerals mine and smelter in the Richards Bay area of KwaZulu-Natal, South Africa. The mine will produce a heavy mineral concentrate containing ilmenite, zircon, rutile and leucoxene which will be beneficiated at a central processing complex close to Empangeni. The ilmenite will be smelted to produce high-grade titania slag and pig iron for export. The ancient dune containing the mineral deposit is located some distance inland of the coastal dunes, and the sands contain a high proportion of extremely fine material which must be extracted ahead of the gravity separation process. Of the 56 million tonnes to be mined annually over the ten-year life of the mine approximately 23,4%?a total of 13,1 million tonnes of minus 45 micron residue fines?will have to be disposed of in a containment facility. The origin of the fine material is from the weathering of amphibole minerals. The remaining coarse sands will be returned to the mined area to re-create the original dune configuration. A number of options for the disposal of the residue fines have been examined and specialised laboratory tests undertaken to determine the deposition behaviour of the fines. The final solution involved the use of a ?sub-aerial? technique for deposition of fine material in a disposal facility. The resulting arrangement will adequately meet technical and environmental criteria. Upon closure after 10 years of operation, the surface of the disposal facility will be returned to sugar cane cultivation The paper refers to the various options considered and describes the problems associated with competent disposal of the residue fines and the development details of the final disposal facility.

Jan 1, 1997

By W. Gabryk

A large new underground platinum mining project required that all different mining options were investigated during an option study before proceeding to the prefeasibility stage of the project. The capital project team identified 21 different options requiring investigation. These options considered 10 different access methods and 4 different mining methods. Each of the 21 options required a mine design, a valid production schedule, and the associated economics in order to facilitate a comparison on project Net Present Value (NPV) and other metrics. The project sponsors required this work to be completed in 3 months and therefore the project team decided to adopt an object-oriented modelling approach as implemented by Cyest Corporation. This would allow all 21 options to be valuated within the tight time frame due to the generation and re-use of templates. Standard objects were configured into templates containing the mine layout, design, and scheduling logic. These templates could then be assembled into a model to represent the option being investigated. The adoption of rules-based design and production scheduling then allowed for the rapid generation of a valid production schedule for each option with different iterations of varying production ramp-up and mining efficiency assumptions. The activity-based operating costs, labour, and capital were also linked to the standard templates such as a half level or barrel, which were then replicated to represent the overall mine structure for each option under consideration. Using this approach for each option, a full production schedule was produced per mining activity, the operating costs were calculated using activity-based costing, an infrastructure capital expenditure estimate was determined, the development capital requirements costed, and an overall NPV determined. This options study was completed in an unprecedented 10 weeks and a recommendation was put through to the Business to take three of the options to the next study phase.

Jan 1, 2012