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By N. C. Gay

The quantitative evaluation of the performance of fill materials placed in gold mine stopes is achieved by (i) measurement of the in-situ load- displacement, or stress-strain, characteristics of the materials; (ii) an objective comparison between the observed fill performance and that predicted from suitable computer modelling techniques; and (iii) objectively comparing conditions in backfilled and conventional stopes. Considerable problems have been experienced with the development of sufficiently robust instrumentation which can be installed within filled pad- docks and give reliable information over a long period of time. However, at most mines where backfill performance is being monitored, it has been possible to correlate stress measurements within the filled paddocks with strain measurements adjacent to the paddocks. The resultant stress-strain curves agree relatively well with those determined in the laboratory. Measurements in the hangingwall strata of filled and unfilled stopes indicate that the placement of fill does reduce the amount of inelastic convergence due to bed separation. Moreover, in some stopes, the rate of convergence with respect to face advance does reduce to that of the theoretical elastic convergence. Quantification of changes in the conditions at the stope face due to placement of fill has proved difficult. Observations indicate that, provided the fill is placed close to the face (- 5 m), and adequate temporary face support is used, conditions in filled panels are superior. In addition, in filled panels the damage caused by a rockburst in the stope and, particularly, in gullies is generally much less than would be expected in an unfilled stope. To quantify these improvements, parameters such as stope height, face advance and the frequency of falls of ground are being monitored.

Jan 1, 1988

By E. J. Magri, A. Couble

Kriging estimates of geological resources are sometimes conditionally biased because the kriging plan contains too few samples. This may be done purposely in order to match the variance of the estimates to the true block dispersion variance. This work aims at evaluating the influence of conditional bias over the ultimate optimum pit design in relation to its shape, size and NPV (Net Present Value of profits). It has been restricted to two real case studies: a ‘carrot shaped’ gold porphyry in northern Greece and a manto-typeexotic copper deposit located in northern Chile. The methodology applied to each deposit consisted of generating a ‘real block model’ and four resource estimates by the use of conditional simulation and the application of four different kriging plans to the drillhole databases respectively. The estimation models vary in smoothness and conditional bias. Ultimate optimum pits were determined for the ‘real’ and the four different kriging models. Pit comparisons lead to the following conclusions: •In the worst case, conditional bias overestimated the project's NPV by 32% and 5% for the gold and copper deposits respectively. •The overestimation of high grades is more relevant than the underestimation of low grades. This resulted in a tonnage over-extraction of 148% and 1% for the gold and copper deposit respectively. This difference was attributable to the vastly different geometry of the deposits. •The smoothing effect of kriging, without or very little conditional bias, produced open pits that were different to the ‘true’ (ideal) ones and furthermore, underestimated the project's NPV by 10% and 6% for the gold and the copper deposits respectively. •Other factors that influence the optimum open pit design and to some extent control the effect of conditional bias are: the cut-off grade, the orebody geometry and distribution of grades within it and the amount of over-burden. Keywords: conditional bias, ultimate pit design

Jan 1, 2003

By W van Drunick, S Naik

To date, Anglo Research has carried out several projects, based on the techniques developed in the AMIRA P9 (AMIRA International Limited), to develop comminution and flotation models for several Anglo Base Metals and, to a lesser degree, Anglo Platinum flotation plants. Plant optimization is thus achieved through steady-state sampling, model-fitting and simulation using the JK SimMet and JK SimFloat software packages. The surveys can vary depending on the needs of the plant/client. The survey can therefore include as little as a single piece of equipment, an entire milling/flotation circuit, or a complete circuit from primary comminution to final flotation concentrate (i.e. the ?integrated survey?). The presence of the AR team on-site usually precipitates in face-value observations that can lead to initial improvements. This stems from the knowledge-sharing on best practice that exists in parallel with the surveys. Numerous (reasonable) changes can then be simulated, thus indicating the optimization step most likely to result in the best efficiency improvements. The simulations can include changes in the flowsheet, ore characteristics, mill loads, grinding media size, change in grind, flotation residence time, air hold-up and several more. Plant surveys can result in process changes that provide the plant with either: higher plant tonnage, improved plant grind, additional flotation recovery and/or improved product grade. The additional benefit of performing an integrated plant survey is that the effects of an optimization change in the comminution circuit can be simulated using the flotation model. This paper describes a number of case studies where individual and integrated plant surveys were conducted by AR for Anglo Base Metals.

Jan 1, 2007

By D. Moradkhani, S. M. Javad Koleini, M. Abdollahy, F. Soltani

"The objective of the study was to determine the type and distribution of rare earth elements (REEs) in the phosphate flotation concentrate from the Esfordi flotation plant in central Iran, in order to understand their leaching behaviour. Samples of the concentrate were prepared and analysed using XRF, XRD, ICP, and EMPA. The Ce, Nd, La, and Y contents were 5608, 2227, 1959, and 679.7 mg/kg, respectively. The main REEbearing minerals in the concentrate are fluorapatite, monazite, and xenotime. Apatite is the chief mineral of the concentrate and the ratio of apatite to monazite is greater than 60. From EMPA analysis, monazite contains a much higher proportion of REEs than apatite, but more than 50% of the REE content of the concentrate is in apatite, as this is the main mineral constituent of the concentrate. During the leaching of REEs in the phosphoric acid production process, more than 99% of the total rare earth values report to the large amounts of phosphogypsum (CaSO4·2H2O) formed during the dissolution reaction. Accordingly, two process options are suggested for treating the Esfordi concentrate. In the first option, the concentrate is treated with 98% H2SO4 at 200–300°C. After digestion and water leaching, phosphorus and REEs are precipitated out of solution. In the second option, the concentrate is treated in a pre-leach stage. The process residue from the pre-leach stage is then subjected to acid digestion at elevated temperature for phosphoric acid production.IntroductionThe rare earth elements (REEs) comprise a set of 17 chemical elements in the periodic table, specifically the 15 lanthanides plus scandium and yttrium. REEs and alloys that contain them are used in devices such as computer memory, rechargeable batteries, cell phones, catalytic converters, magnets, fluorescent lighting, and many more (Krishnamurthy and Gupta, 2004). China supplies about 94% of the REE demand, with the remaining 6% coming from Russia and Estonia, the USA, India, Malaysia, and Brazil (Zhanheng, 2011). Increased industrial development in China has prompted the Chinese government to limit annual export quotas to approximately 35 kt of rare earth oxides (REOs), while non-Chinese annual demand is expected to reach 80 kt by the year 2015. This constriction of supply is being met by the development of many new rare earth mining projects, each of which has its own unique mining and processing challenges (Jordens, Cheng, and Waters, 2013). One of these projects is the Esfordi phosphate project, which is located in Yazd Province in central Iran. The concentrate from the Esfordi flotation plant contains 1.2–1.5% REEs."

Jan 1, 2017

By J. N. Van der Merwe

Following the Coalbrook disaster in 1960, research into coal pillar strength resulted in the adoption of the concept of a safety factor for the design of stable pillars in South African coal mining. At the time when the original statistical analysis was performed by Salamon and Munro in the early 1960s, 27 cases of failed pillar workings were considered suitable for inclusion in the database of failed pillars. Pillar failure did not stop after the introduction of the safety factor formula by Salamon and Munro (1967). In the ensuing years, pillars that were created before the application of the formula deteriorated and later failed, as did ones that were created after the introduction of the formula. This means that over time, the database of failed pillar cases increased in size, allowing ever more reliable analyses to be performed. The number of failed cases in the database had grown from the original 27 in the 1960s to 86 by 2011. All the failed cases are contained in the updated database. The database of stable pillars, which is also used in the derivation of strength formulae, has now been extended from 125 to 337 cases. The new database of intact pillar cases is more complete as it bridges the time gap between the Salamon and Munro (1967) and the Van der Merwe (2006) databases. The original requirements for inclusion into the database were satisfied in the compilation of this latest collection. The characteristics of the original database of intact pillars did not change in a meaningful way. The mining depth and pillar dimensions of the new database are largely as they were in the original database. Time-related trends with regard to pillar dimensions and depth of mining could not be found, indicating that the geometrical parameters of coal mining in South Africa have not changed meaningfully in approximately a century of mining. The characteristics of cases in the updated database of failed pillars does not differ substantially from the one published by Van der Merwe (2006). The same difference between that database and the original Salamon and Munro database, namely that the average safety factor of the failed cases had increased dramatically, from 1.0 to 1.5, is still apparent. This may be due to the inclusion of more failures from specific areas that exhibit a disproportionate number of failures at higher safety factors. These areas are the Vaal Basin, Klip River, and Free State coalfields. The new database confirms yet again that there is no correlation between the safety factors of failed pillars and their time of failure. The safety factor on its own is thus not a reliable predictor of longterm stability of pillars. Keywords coal pillar, stable pillar cases, pillar collapse, pillar data base.

Nov 1, 2013

By J. Dvorácek

Mine water poses a significant problem in lignite coal mining. The drainage of mine water is the fundamental prerequisite of mining operations. Under the legislation of the Czech Republic, mine water that discharges into surface watercourse is subject to the permission of the state administration body in the water management sector. The permission also stipulates the limits for mine water pollution. Therefore, mine water has to be purified prior to discharge. Although all mining companies operate mine water treatment plants, there is hardly any utilization of the final effluent. The high expenditure involved in the more sophisticated methods of mine water treatment has fuelled the search for the commercial utilization of the effluent.

Jan 1, 2012

By W. C. Joughin

A risk evaluation model has been developed that enables the quantification of expected injuries and economic losses resulting from rockfalls associated with a support system in a given geotechnical environment, which is described in Part I (Joughin et al., 2011b). Part II presents the validation of the risk evaluation model. Underground mapping of joints and rockfalls was carried out to provide data for field calibration of the model. This survey was limited to small rockfalls, due to the relatively short period of mapping. Therefore the model was also correlated with rockfall and rockfall injury data collected by mine personnel. The analyses showed that the model provides a reasonable estimate of the expected frequency and size of rockfalls and the frequency of rockfall injuries, but further work is required to enhance the model. Three case studies are presented, which show the benefits of improved support systems from both economic and safety perspectives. This work has demonstrated that the risk evaluation model and the software developed are immediately useful, but further work is required to develop and improve the tools.

Jan 1, 2012

By P. R. Mothemela

The objective of the investigation is to optimize the truck and shovel operations for pre-stripping at New Vaal Colliery by introducing campaign mining. The aim of campaign mining is to improve the efficiency of the loading, hauling, dumping, and maintenance operations which are critical to the success of truck and shovel operations. The current loading (single-sided loading method), hauling, and dumping operations at New Vaal Colliery were found to be inefficient. Time studies were used as a major indicator to highlight the inefficiency of the truck and shovel operations, and it is recommended that an improved loading configuration, hauling, and dumping operations be implemented by using campaign mining. It is also recommended that a service truck be used to maintain the pre-stripping fleet in order to reduce travelling times to the main workshop. As expected, the improved operating conditions will lead to an increase in pre-stripping production.

Jan 1, 2013

By B. M. Kunar

It is well known that job-related hazards and individual factors influence occupational injuries. However, research involving coalminers has been limited. This case-control study assessed the relationships of job-related hazards and individual/life style factors with injuries among underground coal miners. It compared 245 cases with at least one injury during the previous two-year period with 245 matched controls with no injury. The data were gathered via personal interview and analysed using the conditional logistic model. The significant risk factors were materials handling (adjusted OR 5.15), poor environmental/working conditions (2.63), geological/strata control-related hazards (2.35), lack of formal education (3.00), sleep disorders (1.86), alcohol consumption (2.32), disease (2.23), having a large family (5.40), and risk-taking behaviour (9.40). Machine-related hazards, sleep disorders and alcohol consumption primarily affected workers aged less than 45 years; whereas, environment/working condition-related hazards, presence of disease, smoking, risk-taking behaviour and large family size were more likely among workers aged 45 or over. Keywords: Occupational injuries, sleep disorders, job hazards, alcohol, coal miners

Jan 1, 2010

By O. G. Motlogelwa

Any company operating a fleet of trucks will be greatly advantaged if the associated fuel costs can be decreased. The optimal tonnage that trucks should be hauling to ensure minimum consumption of diesel fuel has been investigated. The fuel consumption in litres per ton for a fleet of trucks hauling different tonnages of iron ore was recorded in a time-motion study and the optimal tonnage was determined. The following points emerged as a result of the research: > The diesel fuel consumption in litres per ton decreased with increasing tonnage, which means that in order to improve fuel efficiency, the trucks should carry 21 t > As a result of queuing, Africa Truck Hire (one of the two equipment contractors) loses R282.57 per day to diesel that the trucks burn when they are left idling. It is thus advisable that the company adopt a policy of requiring the drivers to switch their engines off while queuing at the stockpile > Filling up the trucks during each shift or rationing the quantity of diesel to 200 litres each shift has a negligible impact on the trucks' fuel efficiency > For the company to spend 35% of their revenue on fuel, the diesel price would have to be between R8.14 and R8.78 per litre.

Jan 1, 2013

By T. Bednarski, L. Thomas, G. Banza, D. Muteba, P. Cole, M. Soderstrom

"In copper solvent extraction, aqueous-in-organic entrainment results in the carry-over of unwanted species into the electrowinning process with negative cost implications. The need to bleed is increased and the purity of the copper cathode is potentially compromised, depending on the impurities being transferred (Cl, NO3, Fe, Mn). In some cases, entrainment results in elevated levels of manganese in the electrolyte which can cause oxidative conditions to develop and degradation of the organic phase. Degraded organic phase detrimentally affects the physical performance of the copper solvent extraction process, contributing to even higher aqueous-in-organic entrainment. Aqueous entrainment may be minimized through good operating practices and maintenance of the organic quality, but the accurate measurement of entrainment remains a challenge. This paper presents coalescing devices designed to provide more exact measurements of aqueous-in-organic entrainment. IntroductionMany copper solvent extraction (SX) plants experience high aqueous-in-organic (A-in-O) entrainments but are unaware of the extent of the problem because entrainment is often not measured. Aqueous entrainment results in the carry-over of unwanted species into the electrowinning (EW) process and the need to bleed to maintain acceptable concentrations in the electrolyte. The costs associated with the bleed are exacerbated in copper plants where aqueous entrainment levels are high. Other than these direct costs, there are operational consequences of the build-up of certain species in the EW circuit that can have deleterious effects on plant performance.Minimizing aqueous entrainment in operating plants requires an understanding of the factors that affect entrainment levels. Both chemical and operational influences are discussed in this paper. The difficulty of obtaining a representative sample makes it challenging to obtain an accurate measure of aqueous entrainment from a continuous process like SX. Coalescing devices used to get a more precise measurement of A-in-O entrainment are useful to complete mass balances around the SX circuits. Alternatively, mass balances can be used to estimate aqueous entrainments and are helpful as a tool to troubleshoot operations with a view to improving plant performance."

Jan 1, 2016

By R. Hewer

Transition metals have been widely used in medicine throughout history. The medicinal use of metals extends back to the earliest recorded history when the Chinese used gold as treatment for a variety of ailments. The ancient Egyptians used copper to sterilize water and mercury was reportedly used by Hippocrates in 400BC. Thereafter, numerous other metals have been used as treatment throughout the centuries. For example, zinc sulphate was used as an emetic in the 17th century and zinc oxide was used to treat epilepsy in the 18th century. This use of metals, and numerous other instances, which have been well described in Sneader 2008,1 make for interesting reading but largely occurred prior to the advent of rigorous scientific method. Therefore, although there are exemptions, most therapeutic applications of metals prior to the modern age lack scientific grounding and have been found to be mostly ineffective. Of more relevance are metal-based medicines approved by regulatory bodies (i.e. Food and Drug Administration; FDA) that are in current use as therapeutic drugs. There are presently a large number of metal-based drugs that are approved for use by the FDA ranging from over the counter medicines, such as bismuth subsalicylate for gastrointestinal problems, to prescription drugs such as lithium carbonate for the treatment of manic depression. The list of metal-based medicines approved by the FDA not only incorporates base metals but also includes precious metals. Platinum complexes have been found to be potently active against several different types of cancers while gold complexes have shown application as treatment for rheumatoid arthritis (RA). With the well-established foundation that exists for metal-based medicines, it is imperative to continue exploration into new therapeutic areas. The precious metals; gold, ruthenium and platinum, continue to attract scientific interest in the field of biomedicine and have been widely researched. Scientific studies conducted on gold complexes have demonstrated the potential of this metal for the treatment of HIV/AIDS, cancer and malaria. These diseases are also specific health concerns for developing nations; countries where disease has devastating impact. Within South Africa alone, an estimated 5.7 million people are infected with HIV/AIDS,2 approximately 7 000 new cases of malaria are reported annually, and it is projected that 1 in 4 persons will develop cancer. Continuous development of therapeutic drugs to combat these diseases is therefore apriority, and the exploration of gold-based compounds for this purpose is warranted.

Jan 1, 2009

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of ?correct? sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses, including project cost control, restricted headroom for samplers in plant layouts, and a lack of knowledge in certain quarters. These all have a potentially negative effect on the final outcome of a proposed sampling solution or implemented project. In reality, what is intended by all parties and what is ultimately installed are at times very different, with undesirable consequences for all concerned. Against this challenging background, there are, however, a number of instances where intent and implementation are complementary, with very satisfactory results. Keywords sampling, mechanical samplers, design, installation, sampling theory.

Jan 1, 2014

By C. M. G. Wortley

One of the major deliverables of the AMIRA P754 Project, which was sponsored by several major mining companies, was a code of practice and guidelines for metal accounting for the mining and metallurgical industry. These had the objective of improving the auditability and transparency of metal accounting from mine to product, thus assisting in good corporate governance. The overriding objective of mass measurement for metal accounting is to establish the mass of the particular material or component present at a specific time, or the mass flow of that component over a defined time period, to a defined accuracy suitable for metal balancing. As such, it is the first measurement in the chain that includes sampling, sample preparation and analysis, each of which introduces its own errors. Materials often contain moisture, the proportion of which must also be established in order to obtain the dry mass. They may also have to be measured as a volume or mass/mass flow of slurry, or in stockpiles or storage areas, in which case the relative density must be measured. Both the density and moisture measurement often introduce significant error. Whereas a great deal of effort has been directed at sampling, sample preparation and analysis to improve accuracy and establish the error, the same can seldom be said for the mass determination, including the moisture and density measurements. The possible major causes of error are highlighted and methods of reducing them discussed. Mass measurement can be classified into those measurements necessary for custody transfer and primary accounting of the input and output streams to a plant or operation, and measurements required for secondary accounting, or management control. The latter include intra company transfers and plant area performance, and those required for plant control only. This paper is concerned only with primary accounting measurements. The code and best practice state that the equipment should be certified (as sized) as is required for custody transfer. The most accurate and precise of the various possible methods is the static measurement of mass on a weighbridge, platform scale or a weigh bin. If static measurement is not possible, which is often the case for ore fed to a plant, possible alternatives are electromechanical conveyor belt weighers or in-motion weighing of rail trucks. In all cases the material must be adequately sampled to enable a representative moisture content to be determined to calculate the dry mass. Where material is flowing inside conduits, only certain types of the multiplicity of flow meters available may be used and, in the case of slurries, very few flow meters are suitable. As most flow meters measure volume or velocity, the density of the material must also be measured. The basic requirements in order to achieve satisfactory results for the mass, of the component of interest, are listed, as well as common problems and pitfalls encountered in practice. The measurement of the mass of stockpiles and in-plant stocks, often required for metal accounting, is often the largest source of error in metal balances. The reasons for this and methods for reducing and managing the effect are discussed.

Jan 1, 2009

By I. Zh. Bunin, M. V. Ryazantseva, V. A. Chanturiya

The paper proposes a new method for selective calciferous separation. The effect was achieved through the application of the combination of high-power electromagnetic pulses (HPEMP) and a specific reagent regime of the flotation. The combined application of HPEMP with the special reagent regime allowed for the improvement of the scheelite floatability: the recovery of CaWO4 rises from 41.2 % (untreated sample) to 58.5 (sample treated at 103 pulses). In contrast, the floatability of calcite decreases significantly: the recovery of calcite drops from 74.7% (untreated sample) to 41.1 % (sample treated at 103 pulses). The conditions were found for the selective separation of the minerals with very close flotation properties. Keywords: Calcite, scheelite, flotation, high-power electromagnetic pulses, DRIFT, XPS

Jan 1, 2020

"Chairman: Dr DeV. HarrisRapporteur: Mr A.H. MunroPapers:Corporate exploration strategies by MacKenzie, B.W.The Engel Simulator and the search for uranium by Griffiths, J.C. and Singer, D.A.The Chairman opened the session by tracing the changes which have taken place in the exploration field since the days of the lone prospector who relied upon his individual skills and to a large extent on luck. The deposits which now remain to be discovered are better covered and are of lower grade. A much greater team effort, involving geoscientists and engineers, is required. The gamble is thus much greater -not only are the probabilities of failure still significant but the consequences are more severe. A recent Canadian survey indicated that expenditures of between two and nine million dollars on regional exploration programs are required to locate one significant deposit.The Chairman went on to say that these facts have led companies to regard exploration as another form of investment and to treat it accordingly. This had placed exploration in the context of corporate strategics and structures, which was the subject of the first paper of the session.In introducing his paper, Dr B. W. MacKenzie said that the paper suggested a decision framework for exploration planning. Initially the environment is analyzed to define observable and relevant economic characteristics. The terms of reference for exploration planning and the appropriate allocation of capital and skills are then established in the light of corporate objectives and growth alternatives. With the aid of this information and in the light of profit and corporate risk criteria, exploration strategies can be selected.Dr MacKenzie went on to say that the usefulness of the concept and criteria outlined in his paper depended critically upon three characteristics of any particular economic environment, namely, the return resulting from an economic discovery, the unit discovery Cost and the probability of making an economic discovery. He then showed by means of a case history relative to the Canadian Shield and Cordilleran areas that these three characteristics could, in fact, be evaluated for regions with reasonable histories of mineral activity.The first contributor to the discussion of the paper, Mr Alfred Weiss, mentioned that his group had been involved in exploration modelling for some ten years and were thus particularly interested in the paper. He went on to say that they had experienced greatest difficulty with reconnaissance programs and that he sensed that these difficulties were also present with the methodology which had been outlined. Mr Weiss asked Dr MacKenzie how he would deal with such situations when no information was available but where there was the potential for both exploration and discovery. Dr Mackenzie agreed that the lack of information was a very severe limitation and said that at the present time his methodology probably did not provide a basis for breaking down the broad geological regions he considered into areas for further assessment."

Jan 1, 2014

Dr Hanekom I would like to thank Dr Hanekom for a very valuable -contribution; it summarizes careful statistical test work which was an omission from the original paper. Minor manipulative details, the application of a finer measuring graticule and the reproducibility of the procedure are described and the author accepts with gratitude this ready-made answer to the first and second points of Dr Finkelstein's comments. Mr Williamson The author is indebted to Mr Williamson for historical background to early experiments with captive bubbles and it is conceded that the original paper described another avenue to an old flotation goal. The field of application is restricted and we would not work with all the material illustrated by Klassen and Mokrousov.1 The particles in Figure 74(a) are far too large and irregular; material in Figures (b) through (d) could be employed for semi-quantitative work in spite of obvious disadvantages; Figure 74(f) represents ideal conditions. We have studied this mineral-collector association in the size range given and results were satisfactory. For larger pick-up values than that illustrated an induction period of more than 0.01 second was required (actually 90 seconds for a maximum bubble load at pH 7.2 with 25 g/t oleic acid!). REFERENCE 1. KLASSEN,V. I. ANDMOKROUSOV,V. A., 'An Introduction to the Theory of Flotation,' Butterworths, London, 128, Figure 74, (1963). Mr Slander and Mr Kooij Researchworkers in a practical mineral development laboratory may well ask what contribution yet another micro-technique can make to the problems of large scale ore flotation. The obvious answer is that there can be little or no direct translation of results obtained with a static system comprising air bubble and pure mineral concentrate to a dynamic multicomponent operation. However, for the rapid study of one mineral or variable some small scale apparatus must be employed. In the Anglo American Research Laboratory, the described semi-quantitative pick-up technique has filled a niche and requirement. For ourselves, the system represents a definite advance over the contact angle approach in that samples of minerals conventionally prepared in laboratory or plant may be used, which is a desired step nearer flotation. We bracket this pick-up apparatus with the Hallimond tube1,2 and evidence is now to hand that pick-up curves may often be related to flotation recoveries obtained from this tube with pure mineral samples and from the Fuerstenau glass cell3 with the total ore at low pulp densities. We would not wish to push the comparison of pick-up results past this stage for there is much published development work relating the Hallimond and Fuerstenau equipment to flotation on a larger scale. At the Anglo American Research Laboratory for example, a test in a Fuerstenau cell is often the final integrated step in laboratory investigations into the TORCO process. As these contributors rightly point out, pick-up tests can offer nothing towards the determination of optimum reagent dosage for large scale flotation. This is the function of bench-type flotation cells with up to 2 kg batches of ore. At this level, collector performance and consumption and physical properties of the froth are more comparable with large scale operation. The pick-up cell, Hallimond tube and Fuerstenau cell are essentially equipment from which the effect of control parameters can be derived. For the assessment of collector behaviour, the pick-up approach is rapid and economic and we offer here a pick-up contribution towards the flotation of Witwatersrand uraninite with anionic sulphonate collectors (Fig. 1). A large crystal of the local mineral was not available for contact angle measurements and owing to its low concentration in Witwatersrand gold-bearing reef, a small sample was laboriously obtained by tabling, superpanning and heavy medium separation. The pick-up values of a sized portion were determined by the described procedure in the presence of nine petroleum sulphonate collectors. Responses fell into two categories; "normal" curves (dotted lines) and a group of collectors which were very active at low concentration but showed depression of pick-up at the higher levels. The similarity in form of curves for collectors 1 and 3 was apparent and reagent 3 was found to be simply a diluent of 1. Otherwise, collector performance could not be related to either sulphonate content or molecular weight of the active constituent. However, reagent 2 gave the best performance in a bench flotation cell with regard to overall uranium distribution but, as predicted, reagent 1 yielded the best grades. Later pick-up tests with a similar class of collector have suggested that depression at high reagent concentrations may be due to "bubble armouring" whereby an hydrophilic air-liquid interface is produced which rejects mineral attachment. Prolonged investigations with the same mineral sample have not been required except for the study of uraninite which lasted for more than a year. Variation in pick-up response could not be detected over this period during which the mineral was stored under distilled water. The only visible change was a small efflorescence of lead sulphate, readily removed and decanted off after stirring with a glass rod in the sample tube. In its main role as a "trouble-shooter", the pick-up method is applied to fresh mineral samples taken from a flotation plant and soon discarded or from a current run in the ore-dressing laboratory. After production of a concentrate, a solvent cycle, as described in the original paper, may be required to remove heavy organics or other contaminants as when a sample has been taken from circuits containing detergents, grease or return flotation solutions. This solvent cycle will not remove chemisorbed collectors and we prefer not to work with minerals from flotation tailings or with pick-up cell discards. It has been thought preferable to answer the contributors' other apprehensions with regard to sample preparation, activators, depressants and the physical properties of reagents in another paper on offer to this Journal. It covers pick-up investigations relating to the flotation of nickeliferous pyrrhotite at two Anglo American Corporation Mines, which approach seemed the correct orientation for a reply to another contributor to this paper.

By W. P. C. Duyvesteyn, J. R. Cutland, J. R. L. Russell

In 1970 it was decided to build a large new plant at the Chingola Division of N.C.C.M., Ltd., to treat concentrator tailings and leach residues with a low copper content by a leach-solvent extraction-electrowinning process. In order to assist in the establishment of the design parameters for the new plant, and to study the interaction of this plant with the existing leach-electrowinning plant, mathematical models, formulated as linear programs, have been developed and used extensively. The paper outlines the metallurgy of the plants and describes briefly the way in which the models have been formulated and used. The formulation involved the use of separable programming to form the products of some variables.

Jan 1, 2014

By J. O. Claassen

A study was initiated and solutions implemented to address the root causes of a 30%?40% lower than predicted product yield achieved at a Mpumalanga coal mine. A holistic MRTM approach, which focused on improving exploration, geological sampling and analysis, geological modelling, planning, mining, and beneficiation practices, was used. The study indicated that deviations in the planned versus actual yields at the DMS plant were caused mainly by incorrect geological yield predictions, high and variable levels of dilution, and near-dense material, as well as the textural properties of the ore. Keywords MRTM, mining value chain improvement, Witbank coalfields, complex geology.

Oct 1, 2013

While some of the practical details of ilmenite smelting are not well documented, there is a substantial body of literature on the principles of ilmenite smelting, and the behaviour of solidified titania slag. This information is summarized, focusing on the basic reactions, departure from equilibrium, the behaviour of impurities, and reactions of solidified slag. The emphasis is on the South African operations.

Jan 1, 2007