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By Y. D. Lee, J. H. Park, D. S. Kim, H. S. Song

The viscosities and the infrared spectra of the CaO-SiO2-MgO-CaF2(or Al2O3) slags were measured to enhance our understanding of the interrelationship among the thermophysical property, microscopic structure, and chemical thermodynamics of molten slags. The structural role of CaF2and Al2O3in the calcium silicate melts can be explained by a change of the degree of polymerization (DOP). The effect of CaF2on the viscous flow of molten slags is based on a decrease in the DOP by F-as well as by O2-ions and this was confirmed by the infrared (IR)spectra of the quenched slags. The effect of Al2O3on viscosity increase can be understood from an increase in the DOP by the incorporation of the [AlO4]-tetrahedra into the [SiO4]-tetrahedral units and this was also confirmed by the IR spectra. An amphoteric behaviour of Al2O3in the aluminosilicate melts could be correlated to the effect of ionic species of alumina, that is [AlO4]-tetrahedra and [AlO6]-octahedra, on the stability of silicate polyanions by taking the activity coefficients of slag components into account. Keywords: viscosity; infrared spectra; degree of polymerization; amphoteric behaviour; stability; activity coefficient

Jan 1, 2004

By D. Pohl

The past decade has seen rapid expansion in the West African mineral exploration environment. This expansion has been largely driven by changes in ?Political climate ?Fiscal and legal regimes ?Exploration approaches ?West African geology. Major regional mapping and geochemical surveys by the UNDP, and the BRGM in the late 1970s and early 1980s laid the foundation for the rapid development of mineral exploration and resources during the past decade. An additional driving impetus was the discovery by native artisanal miners of many significant new gold occurrences at Libiri, Essakan, Bouda and Tirahori, during the great droughts of the late seventies and early eighties.

Jan 1, 1998

By H. Appiah

Small scale mining (SSM) has been going on for a long time in Ghana. SSM was legalized by the PNDC Law 218, 1989. Since then there have been numerous gains from the SSM industry. The SSM is organized locally by the concession owner who engages people to work for the gold which he buys. Small scale miners (SSMs) use crudely made sluices in Ghana and, therefore, their production falls below what is expected. The SSMs work in groups and not as cooperatives, as they do in Brazil and other Latin American countries. Legalization of SSM has curbed gold smuggling considerably because a gold marketing entity is available. SSM poses certain environmental problems like pollution of water bodies and soils by mercury and indiscriminate digging of pits.

Jan 1, 1998

A new system for granting access to mineral rights is proposed in the recently released White Paper, ?A Minerals and Mining Policy for South Africa?. Official policy states that ?Government?s long-term objective is for all mineral rights to vest in the State for the benefit of and on behalf of all the people of South Africa?. In order to achieve this objective, government is presently investigating the feasibility of imposing a financial or tax-related disincentive to holding mineral rights. The paper aims to present the pros and cons and to examine the alternatives which will cause minimal disruption to the minerals industry in the period during which mineral rights are transferred to the State. South Africa is a country whose economic and political history is embedded in the development of its mineral resources and has inherited a system which cannot simply be wished away. Hasty or radical decisions will compound the problem, rather than provide a lasting and widely acceptable solution. Mineral rights ownership and its impact on access to mineral deposits are discussed. Taxation as a possible economic disincentive is also evaluated. Finally, the value of mineral resource related information as a prerequisite to mineral policy decisions and as an alternative to mineral rights taxation is emphasized.

Jan 1, 1999

By O. Gunaydin

Performance measurements of large-diameter circular saws were conducted on eight different carbonate rocks in marble factories located in some areas of Turkey. Rock samples were collected from these factories for laboratory tests. Uniaxial compressive strength, tensile strength and impact strength were determined in the laboratory. The brittleness of B3 (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength), the brittleness of B5 (the product of percentage fines in the impact strength test and compressive strength) and the brittleness of B8 (half of the product of compressive strength and tensile strength) were calculated from the test results. Hourly slab productions were correlated with brittleness indexes. It was concluded that sawability of carbonate rocks can best be predicted from the brittleness of B8.

Jan 1, 2004

By D. Vogt, T. Hattingh

"This paper argues that the technology change to mechanization is also going to require a change in people. It presents a model for technological progress and adapts it to the mining industry. It then goes on to motivate the need for mines to become learning organizations in order to achieve maximum value from their people as they become less labour-intensive. In an important sense, mechanization is as much about knowledge as it is about technology.The change when a mine introduces mechanization or a level of automation is not simply one of technology but also a stage in the development of mining from ‘art’ to ‘science’. ‘Art’ describes a state of technology characterized by tacit knowledge, an understanding that comes only from experience, and has no formal procedures and little structure. In contrast, ‘science’ represents a state of technology where all the component processes are understood in detail, all knowledge is explicit, and processes and structures are formal.Studies of other industries, including metal part manufacture and aviation, show that each stage in the progression from art to science changes the nature of the organization and requires a different mix of skills from the workforce. Perhaps the most important change is the increase in knowledge and decision-making required as the technology gets closer to science.There is anecdotal evidence that South African underground hard-rock mines are not learning organizations. Mines by their nature are capitalintensive with long lead times from investment to returns, so there is reluctance to change from the original plans or to encourage staff to think independently. Particularly as mines move from art to science, this reluctance must be overcome.The important lesson for engineers involved in introducing mechanization is to understand that success or failure will be determined by the people involved, and not solely by the technology. The process will almost certainly require a culture change on the mine. We recommend that the mechanization team includes an expert in human and organizational behaviour to ensure that a receptive workforce and management are in place to accept the new technology when it arrives."

Jan 1, 2016

The acoustic signals emitted from a laboratory-scale ball mill were used for the estimation of the comminution of two complex sulphide ores, viz. Merensky and UG2 ores from the Bushveld Igneous Complex in South Africa. The digital acoustic signals were transformed to power spectral densities that could be related to particle size distributions (-75 µm to 4000 µm) in the mill by use of continuum regression. This approach is more general than principal component regression methods or Kalman filtering used previously and resulted in significantly more accurate calibration in the case of the Merensky ore, where approximately 93.4% of the variance in the particle size distributions could be explained. With fewer data available, the variance in the particle size distributions in the UG2ore could be explained less accurately (82.4%), but still satisfactorily. In addition, smaller particle sizes (less than 300 µm) could be modelled more accurately in the case of the UG2 ore.

Jan 1, 2000

By B. J. Vorster

AngloGold South Africa region currently consists of twelve gold plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leach/cost optimization. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in determining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner?s well-known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimization work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environ-mental risk.

Jan 1, 2001

By G. Bacon

The past decade has witnessed unprecedented growth in the development and implementation of solvent extraction technology in the extractive metallurgy of nickel and cobalt. Solvent extraction is proving to be a powerful tool, opening new opportunities for simpler, more cost efficient and environmentally sound metal refining processes. These advances, however, could not have been possible without the cooperative efforts between the nickel industry and the people and organizations involved with reagents, materials and equipment development and supply as well as solvent extraction research, aided by the accumulated knowledge and practical experience from the copper and uranium solvent extraction operations. This paper provides an overview of these developments and some of the challenges ahead.

Jan 1, 2002

By J. Galloway, P. K. Hofmeyr

Obviously all mining operations require much analytical work to be carried out. This starts with exploration, becomes more stringent with the evaluation of a mineralised area and finally becomes on-going when mining operations are under way. All these phases are carried out by geologists, metallurgists and mining engineers. They require analyses to carry out their functions but usually have no involvement in the analyses themselves. Analyses are carried out at commercial laboratories or in-house analytical laboratories. In the past in South Africa the tendency was for the larger mining houses to have their own centralised laboratories for exploration samples with each mine having it?s own laboratory to meet only that mine?s requirements. The centralised laboratory maintains QC functions at the subsidiary laboratories. In other mining areas of the world there has been a strong tendency for all geological analytical requirements, especially for exploration and mining, to be carried out at commercial analytical laboratories. In recent years there has been a tendency for mines in South Africa to move in the same direction. This paper discusses the factors that need to be taken into consideration when a new laboratory is being planned and automation is an option. The planning of the laboratory at the new Langer Heinrich Uranium mine in Namibia is discussed considering these factors. 2.0 REQUIREMENTS OF A MINING ANALYTICAL LABORATORY The purpose and requirements of a mining analytical laboratory are fairly obvious and can be summarised as follows :- 1. All mining operations must have access to analytical facilities, either in-house or commercial 2. The laboratory must be able to handle all the sample types submitted by the mining operation These can be mining, exploration and/or plant samples. They can comprise solids (rocks, bore-cores), slurries and/or liquids.

Jan 1, 2007

By F. T. Cawood

One of the consequences of globalizing mine finance is a necessity to apply uniform accountancy and valuation standards that are clearly understood and consistently applied by the global investment community. However, each country has unique circumstances, which sometimes make it difficult to align domestic practice with international requirements. South Africa is no exception and issues such as its political history, a taxation regime enforcing different rules on different mineral producers and a unique mineral rights ownership distribution, are barriers to internationalization. The economy is in a transitional phase as a result of the many and diverse policy documents following the change in political dispensation in 1994. Many of these documents have recently been implemented through new legislation and, in the case of mining, negotiations are continuing in order to ensure an acceptable outcome. This paper discusses the challenges that the South African minerals industry faces in the field of mineral property valuation. It draws on international experience and includes a discussion on the unique considerations that the South African mineral property market must take into account in establishing a code for this purpose, as such a code could later be aligned with international practice.

Jan 1, 2004

By M. Sephton

Slat-band chains, currently manufactured from Type 430 ferritic stainless steel, are used as conveyors in various industries. A process to strengthen these chains?with the aim of prolonging the lifetime of the conveyors?was developed recently. The process entails heat treating the cold-worked chain at 475°C,strengthening the material by precipitation of the Cr-rich phase a? at relatively long periods of aging. In the present work, it was found that increasing the interstitial content by solution heat treatments (at 880°C or 930°C) prior to cold rolling and aging, causes an increase in strength at shorter aging times as a result of the precipitation of chromium-rich carbides and nitrides. The solution treatments can introduce martensite into the microstructure if carried out at a sufficiently high temperature. This, along with the deformation caused by cold work, also increases the strength. Corrosion resistance is not affected by the treatments, but ductility is lowered. However, calculated critical crack lengths indicate that solution treatment at a temperature below the Ac1allows for a larger critical flaw size, and that the lifetime of the chains will probably be determined by fatigue. Although the duration of the service of the chains are reportedly controlled by wear, with these treatments the tensile strength of the material is increased to within acceptable limits for conveyor chains. The tensile strength is an indication of the wear or abrasion resistance of a material. It is expected that after the treatments, the wear resistance will be improved, but since embrittlement occurs, the fatigue resistance is lowered. It is concluded that the preferred processing route for the chains would be solution treatment at 880°C, fast quenching to trap the interstitial atoms, cold rolling and then aging at 475°C for 8 minutes.

Jan 1, 1997

The Modified Zincex® Process, developed by Técnicas Reunidas, is highly flexible dealing with a wide range of pregnant leach solutions. No matter if those solutions are produced from primary or secondary raw materials, and/or are based on conventional leaching, pressure leaching, heap leaching or bio leaching the result is always high-purity zinc product. The zinc solvent extraction unit within the process is a very effective barrier for impurities and a buffer for the composition of the pregnant liquor. This unit achieves an extremely pure aqueous extract that can be converted into different final products. All of them are characterized by fulfilling the highest purity standards. Also, there is the possibility to adapt the global process to a wide range of pregnant liquor compositions and various production capacities up to a zinc production limit over 150 000 t/a with a single solvent extraction plant.

Jan 1, 2002

By H. von Blottnitz, B. E. Isheloke

Mining is a significant economic activity in most Southern African Development Community (SADC) countries, and mineral beneficiation has been identified, and controversially discussed as one of the possibilities for industrialisation. With many member countries being economically too small to muster the human and financial resources which beneficiation requires, the recently adopted Regional Mining Vision (RMV) envisages interventions at a regional level. An opportunity arose to ask industry role players to what extent the SADC appears to support regional beneficiation policy interventions undertaken by member countries, and what the challenges are in undertaking beneficiation regionally, as a complement to, or substitute for country-specific beneficiation policies. Twenty-five semistructured interviews were conducted with experts from SADC member countries during the 2019 Mining Indaba. Participants were divided on whether beneficiation should be carried out nationally or in the SADC region. While beneficiation could support value-keeping, key challenges were found to be infrastructure development (i.e. energy, water), scarce skills, access to technology and related costs, but also lack of free trade and movement. We submit that a more integrated beneficiation strategy for the SADC region, as is being developed through the RMV, would indeed be relevant in the future. Keywords: Mineral beneficiation, regional integration, beneficiation policy interventions, African mining vision, mining, SADC

Jan 1, 2020

By M. van Biljon

The possible closure and subsequent flooding of South Deep Gold Mine?s neighbouring Randfontein Estates Limited No. 4 Shaft (REL 4) necessitated the construction of five concrete plugs in the connecting tunnels to prevent the ingress of groundwater into REL4 from flooding South Deep mine. Several technical investigations had been carried out before and during construction of the plugs in order to reduce the probability of groundwater flow through the boundary pillar between the two mines or through the rock mass immediately around the plugs. This paper describes the geological, hydrogeological and stability investigations carried out to evaluate the structural competence of the boundary pillar.

Jan 1, 2006

By T. A. Ngcobo

Paper written on project work carried out in partial fulfilment of BSc Eng (Mining)degree The purpose of this report is to assess the risks faced by mines in dolomitic compartments in particular Kloof 8 shaft. The dolomites of the West Rand comprise one of South Africa?s most natural water resources, and overlie the reefs of the richest gold mines in the world. The pumping of water from the dolomitic aquifers to prevent flooding has caused the natural water table to subside, and the resulting cavities within the dolomite rock formations that overlie many gold deposits sometimes collapse, causing sinkholes. These impacts of the mining industry could worsen over time if preventative measures are not taken. This report discusses these impacts in detail, more specifically the risks to which operations in dolomitic compartments are exposed. A risk analysis was carried out to access the risks that the organization could face and it was this analysis that allowed one to examine the best methods to combat the problems. Other factors such as geological features and seismic events were also considered for the evaluation. To aid with the completion of this work various resources were utilized. A literature study was undertaken, information was gathered from various experts who specialize in dolomitic studies, evaluations were conducted and conclusions reached. The results from the project indicated that preventative measures should be implemented and correct procedures put in place to prevent any disasters.

Jan 1, 2006

By N. R. Williams

Black Mountain, a polymetallic base metal mine located in the Northern Cape territory of South Africa has been blessed with high grade economic ore for many years. Now that the Broken Hill orebody is nearing the end of its life, a lower grade orebody (Swartberg) is being exploited to supplement production from Broken Hill. In addition, ore from stopes in the upper levels of the Broken Hill orebody is considerably tarnished (oxidized). As a natural result, the remaining ore contains a higher percentage of magnetite, pyrrhotite and pyrite than in earlier years. Bismuth, cadmium and cobalt also occur in the ore in higher quantities. The life of the mine has been lengthened with the discovery of further deeper-lying ore reserves extending from the Broken Hill orebody suitably called the Deeps section. However, to bridge the gap between development of the new reserve and the exhaustion of the old reserve, these lower grade and tarnished (oxidized) ores have to be treated. The mine has had reasonable success in identifying unfavourable or problematic ore types and stockpiling them separately to blend in small quantities with more favourable ore. Bench and plant scale tests have aided identification of the various ore types and significant improvements in flotation metallurgical results have been seen. Copper, lead and zinc metal occur as sulphides in the ore. The mill consists of a differential and sequential flotation process that extracts copper concentrate, lead concentrate and zinc concentrate respectively with silver metal recovered in the copper and lead concentrates. This paper describes the ore blending strategy employed at the mine to maximize the econo-metallurgical efficiency of the operation.

Jan 1, 2001

By T. Watanabe, S. Hayashi, M. Hayashi, K. Nagata, H. Fukuyama

Chemical states of fluorine in CaO-SiO2-CaF2glasses in a composition range of CaO/SiO2=0.5?1.3 and 5?25 mol%CaF2have been investigated by 19F solid-state NMR with and without MAS. The isotropic chemical shifts of the glasses are close to those of cuspidine crystal (59.4 and64.3 ppm with respect to C6F6) and CaF2crystal (58.6 ppm). The fluoride ions are coordinated with four or less than four calcium ions in this composition range. The chemical shifts move to the lower frequency with an increase in the CaF2content, whereas those are not affected by theCaO/SiO2ratio. The ionic distance between calcium and fluoride ions increases with an increase in the CaF2content. The chemical state of fluorine is not disturbed by the degree of polymerization of the silicate network. Comparing the MAS and static NMR spectra, the second moment attributed to 19F-19F dipole-dipole interaction has been estimated. The values of the glasses range over 3.1?7.3107Hz2andthose are larger than the calculated value of cuspidine crystal. This indicates that fluoride ions form Ca-F clusters in the glasses and that the size of clusters increases with increasing the CaF2content. Keywords: chemical state of fluoride ion, CaO-SiO2-CaF2glass, solid state 19F NMR spectroscopy

Jan 1, 2004

In constructing a financial model of a project significant effort is expended on capital and operating cost estimation, commodity price forecasts, and choice of discount rates while uncertainty in the primary input, the reserve, is often completely overlooked. The aim of this paper is to highlight the impact of uncertainty in the resource/reserve estimation process on the assessment of the financial performance of a project. Four qualitative processes have an impact on resource/reserve uncertainty. These stages are: 1.Ore definition 2.Geological interpretation 3.Resource estimation 4.Ore reserve estimation and mine planning. Each stage contains a number of tasks that may be considered as key performance activities (KPAs). Optimizing the manner in which these KPAs are completed can remove a great deal of uncertainty and error from the resource/reserve process. Examination of these KPAs within a company can also provide an insight to the quality of the information underlying the project. This will allow the company to identify any shortcomings in the data and to assess the resulting risks (Gilfillan, 1998). A hypothetical financial model based on a gold operation has been used to estimate the potential effect of resource/reserve uncertainty on revenue. Monte Carlo simulation has been employed to simulate a number of hypothetical scenarios: 1.a base case scenario which assumes no major errors or biases, but contains realistic margins for uncertainty that would exist in any project where work is being completed to the limit of best endeavours 2.a poor sampling scenario which assumes poor sampling practice and lack of understanding of sample preparation 3.a poor resource estimation scenario which assumes poor modelling and inappropriate choice of interpolation technique, and 4. a ?typical? scenario which represents a project where the majority of KPAs are not performed as best as they could be. The results show that realistic uncertainty ranges can generate changes in the estimate of potential revenue of plus or minus 30%.Therefore, it is important to allow for errors in these processes in any financial analysis or feasibility study. It is recommended that, when building a financial model, are view of relevant resource/reserve KPAs be carried out and appropriate ranges for uncertainty be applied to provide a range of potential outcomes. These outcomes can then be factored into the detailed cash flow analysis in order to ensure that technical uncertainty is built into financial decisions.

Jan 1, 1999

By R. W. O. Kersten, J. D. Austin

A questionnaire was circulated in 1986 that had the objective of establishing the type of material that members would like to see featured in the Journal of The South African Institute of Mining and Metallurgy. The questionnaire contained five main questions involving the following:

Jan 1, 1987