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Written contribution by J.F. Curtist The paper is an interesting exercise in the application of mathematics to a theoretical situation presumed to oc¬cur underground. However, some of the assumptions on which the calculations are based are unlikely to occur in any actual mining situation. Assumptions made in the paper Objections to these assumptions are noted seriatim. (1) `it is assumed that any loading-rate effect will be small and can be ignored' (p. 3). A loading rate of the order of 50 kN-12 per cent of the maximum load-is customary to prevent the props being dislodged by the blast. (2) `it is unlikely that all the props will be installed with their full stroke available, but for the purpose of this analysis, it is assumed that this is the case' (p. 3). A more reasonable assumption would be that, with the most careful selection of prop length and the most rigid control of stope width, the available stroke length would on average be reduced by the order of 70 mm on installation-20 per cent of full stroke. (3) `each support unit supports a block of 3,3 m2 bound¬ed by vertical fractures with zero cohesion that are parallel and at right-angles to the stope face respec¬tively' (p. 5). Joughin and Jager have shown this to be an unwar¬ranted assumption in respect of the positioning, the direction, and the dip of the fractures present in a stope in rockburst conditions. If, as assumed, there was `zero cohesion' between such blocks, the removal of a hydraulic prop in row 3 supporting such a block would ensure that it fell out before a profile prop could be installed in the same position. (4) `the height of each of these blocks is 3,0 m, the volume of each block is 9,9M3, the mass of each block is 27 225 kg' (p. 5). The concept of individual props being affected by dis¬crete blocks of known and uniform dimensions of relatively low ground velocities (less than or equal to 2,16 m/s) acting in line with the axis of the prop is one that lends itself to neat mathematical calcula¬tions. It does not, however, bear much similarity to the actual conditions that are exposed underground in excavations where rockbursts occur. Ortlepp and co-workers concluded that `the impulse of the shockwave can cause the displacement of the

Jan 1, 1991

By T. N. Moore, E. M. De Souza

This paper details a study conducted in Canada on the use of a drill with two different types of elastomer-covered handles in place of the standard steel handles. One type of handle was covered with a relatively stiff elastomer with a durometer of 70 (referred to as the plastic handle), and the other was covered with a more compliant elastomer with a durometer of 56 (refered to as the rubber handle). It was found that, compared with the steel handle, the overall acceleration at the interface between the plastic handle and the drill operator's hand was 2,5 times less, and that between the rubber handle and his hand was 3 times less. This reduction occurred predominantly in the frequency range above 500 Hz, and was greater with increasing frequency. However, an analysis based on the methodology of an international standard (which places greater importance on low-frequency vibration), indicated that the reduction in vibration levels was minimal. ~he driller himself felt that operation with the plastic and rubber handles was more comfortable, the rubber handle being preferred.

Jan 1, 1991

Book review HOEK, E., and BRAY, J. Rockslope engineering. London, The Institution of Mining and Metallurgy, 1974. £5. NIM reports Report no. 1625 The determination of uranium and thorium by the use of delayed neutrons. Report no. 1626 Formation constants of zinc chlorocomplexes in perchlorate medium. Report no. 1629 The thermodynamics of the formation of complexes of silver with some substituted pyridines. Report no. 1630 An electrochemical investigation of the dissolution of copper, nickel, and copper-nickel alloys in ammonium carbonate solutions. Report no. 1640 A semi-automatic titrimeter for cyanide analyses. Report no. 1644 Prospects for the recovery of minerals from the sea. 1974 A.S. & T.S. National Award Professor D. C. Midgley, President of the Associated Scientific and Technical Societies of South Africa, today announced the winner of the 1974 A.S. & T.S. National Award. 1974 G.W. en T.V. Nasionale Toekenning Professor D. C. Midgley, President van die Geassosieerde Wetenskaplike en Tegniese Verenigings van Suid- Afrika het vandag die wenner van die 1974 G.W. & T.V. Nasionale Toekenning aangekondig.

Jan 9, 1974

By C. -I. Lee

Since the early 1970s, Korea has constructed many large-scale tunnels and underground storage caverns in response to the rapid industrial development. The rock mechanics engineers have accumulated valuable experiences in the area of underground space technologies. But they still face technical challenges in environmental and safety aspects. To discuss those challenges in Korea, a brief engineering description of underground space projects including oil and gas storage, food storage, pumped storage power plant, transportation tunnels, waterway tunnels, and radioactive waste disposal is presented. Mechanical and hydrological stability analyses of the storage caverns in Korea are also introduced. Depuis le début des années soixante-dix, le développement industriel rapide en Corée a entraîné la construction de nombreuses galeries et cavernes de stockage souterraines. Les ingénieurs de mécanique minière ont donc accumulé des expériences précieuses dans le domaine de la technologie de l’espace souterrain. Cependant, ils font toujours face à de nombreux défis techniques en ce qui concerne les aspects de l’environnement et de la sécurité. Pour présenter ces défis en Corée, l’étude présente décrit les projets d’espace souterrain, y compris le stockage de pétrole et de gaz, de nourriture, centrales de stockage pompé, tunnels de transport, tunnels navigables, et évacuation des déchets radioactifs. Des analyses de stabilité mécanique et hydrologique des cavernes de stockage en Corée sont aussi présentées. Seit Anfang der 70er-Jahre, baute Korea in Folge raschen Industriewachstums viele lange Tunnelsund unterirdische Lagerungsräume. Fachkräfte im Bereich Gesteinsmechanik sammeltenwertvolle Erfahrungen über unterirdische Raumtechnologien. Dennoch stehen sie auch heute nochvor technischen Herausforderungen im Bereich Umweltschutz und Sicherheit. Zur Erläuterungdieser Herausforderungen in Korea folgt eine kurze technische Beschreibung der Projekte zurSchaffung unterirdischen Raumes für beispielsweise Öl- und Gaslagerung,Nahrungsmittellagerung, Pumpspeicherwerke, Straßen- und Wasserstraßentunnels, als auchLagerung radioaktiven Mülls. Mechanische und hydrologische Stabilitätsanalysen derLagerungsräume in Korea werden ebenfalls dargestellt.

Jan 1, 2003

It is almost eight years to the day when we launched the original SAMREC Code in March 2000. Since that date I think the SA minerals industry has matured beyond recognition in its approach to reserve and resource reporting, and I believe we can be justifiably proud of that progress. Many of those companies that have led the way in reporting standards are listed on our sponsors list. We thank them for their sponsorship but even more for their considerable support in all aspects of the SAMCODE organization. Matt Mullins, my co-speaker here today, has been instrumental in the revision of the SAMREC Code over a long period of time and also took up the reigns with the SAMVAL Code after the retirement of Rob Croll. I would like to formally thank Matt for his immense contribution in producing the two Codes; he can take great pride in the final product and fully deserves the many accolades that we have already received from our international counterparts. He has done all this whilst still maintaining a very demanding day job at BHPBilliton. Matt will be the first to admit that he has received tremendous support from more than 100 people who participated in the various working groups, many of whom are employed by our sponsors. There are obviously too many to mention by name but they deserve a big vote of thanks for their personal contributions. In addition to launching the two Codes we are also launching our ?branding? initiative with our own SAMCODE logo and the SAMCODE website: www.samcode.co.za. All the slides used in the presentation today will be on the website later today as will a newsletter which will serve as a media release.

Jan 1, 2008

"Sampling error and bias, especially the Increment Preparation Error (IPE), are introduced when the tool allocated to do the job fails to extract a representative sample. This is the case with chip sampling; the tool can only extract haphazard shapes of loose or fractured material and not always from within the demarcated sample area. Increment Extraction Error (IEE) and Increment Delimitation Error (IDE) could be severe, but are found to be relatively unbiased. The uncontrolled action of the sampler in discarding excess sample material after sample collection has a significant impact on the error and bias introduced with each and every extraction. A new type of bias, referred to as the ‘waste discard bias’, arises when samplers select what portion of the excess sample material to discard at the sample site. Material visually identified as waste is discarded in preference to mineralized broken ore if there is an excess of sample material. This results in a considerable error in the analytical results. The bias is proportional to the reef-waste ratio in the demarcated sample. IntroductionTwo types of ‘sampling’ are distinguished, namely sampling of particulate materials (broken ores) and sampling of solid, unbroken in situ mineralized reef. This study considers only chip- or face-sampling of in situ, goldbearing, carbon-rich conglomerates typical of the Upper Witwatersrand Supergroup and examines where components of sampling error and bias, clearly specified in the Theory of Sampling, may arise during the practice of ‘face sampling’. Many millions of face samples have been extracted from Witwatersrand-type mines using a hammer and chisel, and detailed descriptions (standard operating procedures) of how the samples should be taken have been developed by many mining companies. There is, however, no taxonomy or nomenclature for managing or reporting the different types of errors associated with chip sampling. The Theory of Sampling compiled by Pierre Gy in the early 1950s provides, comprehensive nomenclature of sampling errors that is applied to particulate sampling of ore in a lot, a stockpile, or a moving stream on a conveyor belt. The taxonomy and characteristics of sampling errors, grouped according to the sources from which they arise, and identified by Gy (1973, 1979, 1982, 1992, 1995, and 1998) are shown in Figure 1. This classification of errors is used extensively in regard to the sampling of particulate materials in the mining and minerals industry, but not in regard to chip sampling. A relatively small mass (hundreds of grams) of representative particulate material for estimating the average grade of a much larger mass (thousands of tons – the ‘lot’ in the Theory of Sampling) is extracted by the chipping or cutting of a representative rock ‘sample’ from the stope face."

Jan 1, 2016

By D. Vogt

"Rock has been cut in the process of mining since before the invention of explosives. Today, we seek to return to cutting to reap the benefits of continuous operations for South African underground hard-rock mines, to improve speed of access to the orebody, and to improve the efficiency of mining operations.Development of new technology fits within a framework of engineering knowledge. By understanding the characteristics of the rock, the tools we use to cut it with, and the history of mining and rock cutting, we can see the genesis of the road-header, the longwall, and the continuous miner, all drag bit cutters. They have emerged as the solutions of choice for underground mining of softer materials such as coal and potash. In hard rock, the challenges are the forces required to break the rock, and the wear of the tools caused by the rock’s abrasiveness. Only disc cutters currently handle the challenges, and even then, often not economically. New materials like thermally stable diamond composite will help, as will combinations of mechanical cutters and other methods such as high-pressure water or high temperatures.It is not clear what will emerge as the consensus technique for hardrock cutting. Experience teaches that development is expensive and the market is small. Will mining companies partner with equipment developers to make the technological leap? Or will the solution come from a systems approach, not considered here?IntroductionBlasting is the dominant method of breaking rock for the purposes of mining. When used underground, blasting is part of a batch process. If rock can be cut rather than blasted, mining can become continuous, leading to process and efficiency improvements.Coal produced from underground mines is now predominantly excavated using mechanical means, but underground hard rock is still broken primarily by explosives.This paper traces the history of rock cutting, reviews the main physical processes that are or could be used, and comments on the future. It is written from the perspective of narrow-stope hard-rock mining typical of South African gold and platinum mines."

Jan 1, 2016

By L. G. Snyman

"South Africa is well endowed with a plethora of valuable minerals, as well as being of world renown for its significant ecological and cultural resources. The unfortunate reality is that these two important attributes often come into collision when developmental decisions are made. Robust environmental planning tools are required to guide such development in areas of heightened sensitivity. Environmental management frameworks are one of the tools that can attempt to achieve the desired developmental and ecological balance by utilizing early identification and mapping of sensitive ecosystems and resources to assist in pre-empting potential future land use conflicts. This paper unpacks the characteristics of environmental management frameworks and further investigates their potential, as well as its current design and implementation challenges. The findings show that environmental management frameworks have the potential to provide meaningful resource information to decision-makers on the opportunities and risks of developments in sensitive areas. They further provide a platform and process through which local stakeholders can voice their opinions and collectively drive the developmental priorities of the identified area.IntroductionAt the core of a harmonious and prosperous society is the balancing of a broad spectrum of needs, rights, and imperatives. As South Africa’s resource and energy needs expand, it becomes increasingly important to safeguard environmental rights and ensure sustainable development through creative measures. The State’s drive for accelerated development to meet the targets in the National Development Plan 2030 is contributing to the growth of invasive developments in previously undeveloped areas. The unfortunate reality is that the heightened tensions between rapid economic growth and environmental sustainability are threatening sensitive areas."

Jan 1, 2017

By C. Kelley

For years urethane screen surfaces have been used in a wide range of wet screening applications where openings as fine as 75 microns and coarser have been used. In dry screening operations these same urethane screen surfaces have been relegated to only the coarser separation ranging from 1.0 mm and larger. The purpose of this paper is to expose the reader to new developments in both screen surface and screening equipment technologies, which allow an end user to consider urethane screen surfaces for dry screening operations where separations as fine as 75 microns are required. These technologies allow an end user to realize the inherent advantages of urethane in wear resistance while also realizing the benefits that a high open area urethane screen surface can bring. These benefits include non-blinding characteristics and feed capacities, which rival that of traditional stainless-steel woven wire mesh screen surfaces. The paper will highlight the features of this patented urethane screen surface technology and the screening machines in conjunction with which they are used. There will also be a presentation of several case studies of commercial installations where these technologies are utilized. These case studies are from the mineral sands industry; therefore relevance to the conference is direct and not inferred. Included in the paper will also be constraints, which must be taken into account when considering urethane screen surfaces such as temperature and chemical attack. This paper will expose potential end users to a possibility of using screens to achieve extremely accurate size separations in applications where screens were previously not considered. The paper will explain and demonstrate that prior concerns of screen surface blinding, high screen surface consumption rates and large screen surface area requirements can be eliminated by proper utilization of high open area urethane screen surfaces.

Jan 1, 2007

The statistical methods described in the previous chapter permit the estimation of the average value p of a deposit, and the calculation of confidence limits for this value. They are based on the assumption of independence of sample values. As soon as a reasonable number of samples has been obtained from a deposit, local valuation, or estimation of blocks of ore within the mineral deposit, becomes necessary. The assumption of independence of values must then be rejected. Local valuation is possible only if there is a relationship between the value of a sample and the value of the surrounding ore, provided this relationship is a function of the position of the sample with respect to the blocks of ore to be valued. Whichever method is used for the valuation of a block of ore, the following assumptions are always made: ? The values of samples located near or inside the block are related to the value of the block. ? The values of the samples located closest to the block are most closely related to the value of the block. These assumptions will hold true only if the following assumption can also be made: ? There exists a relationship between sample values which is a function of the distance between samples. We are saying that the value x (z) of a sample centred at a point z has properties which are functions of this point. A certain spatial structure exists in the sample distribution. We are therefore dealing with a regionalized phenomenon, and we must treat x (z) as a regionalized variable. This can be done statistically by means of a model chosen to represent the spatial structure of the phenomenon. We shall see that the relationship between block values and sample values can be deduced from the relationship between sample values, and all local valuation problems can be solved using the statistical model obtained from the analysis of the sample values. It is important to realize that this statistical model is obtained by analysing the properties of known sample values, and will be used for the estimation of unknown block values. Such a statistical inference is valid only if the model developed represents the properties of both the sampled section of the ore body and the section to be valued: some stationarity conditions must be satisfied, and the model with the least restrictive conditions is preferred. In the following chapters, the most important models used in spatial geostatistics are presented. The models which can be used when there is no significant drift (trends) in values are described in Chapters 3-1 1. These models can also be used to solve some specific valuation problems when a linear drift is present. A general study of the more difficult problem of analysis of an ore body whose values present a drift is described in Chapter 12. Note that the area considered for local valuation of a block of ore is often small enough for any drift which might be present to be ignored.

Jan 1, 1978

By J. H. Zietsman, W. J. Leipoldt

"To be able to responsibly develop a multiphysics model of the steel belt sintering (SBS) process used to sinter chromite fines, it is important to have a comprehensive understanding of the process. This understanding was gained through a site visit, observation of the process in operation, and interaction with the operators. Material characterization will also reveal much about the process that is not yet fully understood. A well-defined and representative mass and energy balance will also give valuable insight into the process. The plan for the multiphysics model aims to combine a computational fluid dynamics (CFD) model with a discrete element method (DEM) model.To obtain a more accurate mass and energy balance representation of the SBS process, it was decided to develop a dynamic distributed parameter model of the mass and energy balance. This model will be used to gain better understanding of the SBS process so that a more complicated multiphysics model can be developed later. The reason for this is because the SBS process is very dynamic, with a large temperature distribution throughout the length of the process. In its current state, the mass and energy balance model is capable of handling solid and gas material packages and exchanging heat between these packages where they are mixed, and is able to model the heating of the gas by burning CO gas. The next step in the development of the model will involve enabling it to handle evaporatoin of liquid water, burning of solid carbon in the pellets, reduction of iron oxide in the pellets with the CO gas formed from carbon combustion, and then oxidation of the reduced iron in the oxygen-rich cooling zones."

Jan 1, 2014

A large body of work exists discussing the impact of grinding media on mineral flotation. Generally, the work indicates that a change to a less electrochemically active grinding environment has positive benefits on downstream processing. There is a fear, however, that these benefits may not be realized when treating low sulphide containing ores, typified by UG2 style deposits. A series of experiments was developed to test the flotation response of UG2 ores using the Magotteaux Mill® to determine if measurable differences in the pulp chemistry could be discerned using a range of grinding media types. Further, the flotation responses of the contained sulphides (chalcopyrite, pentlandite and pyrrhotite) were determined. The data collected provided strong evidence that the grinding environment can significantly influence the pulp chemistry and flotation characteristics of all sulphide minerals, even when the ore contains less than 0.5 per cent total sulphide. The results show that the change to an inert media type produced a substantial improvement in the flotation rate of all sulphide minerals, as well as the PGMs.

Jan 1, 2009

By A. H. Swart, M. F. Handley

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 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, hard rock mines, shallow mining operations

Jan 1, 2004

By B. Gamble

Solid Energy's project evaluation process utilises a standard staged gate approach, with five levels leading ultimately to project execution (level 6). For a project to progress through each level, specific financial criteria need to be satisfied. Solid Energy primarily use value based (discounted cash flow) metrics to support investment decisions. Within this approach Solid Energy utilise a number risk-based techniques to quantify project uncertainty. This includes the use of risk-based probabilistic analysis using Monte Carlo simulation and probability-based scenario analysis. Figure 1 shows the net present value (NPV) cumulative probability. Project risks are identified through comprehensive risk workshops. The output of these workshops (list of key risks, ranges of uncertainty and probability of occurrence), is quantified within the financial models. Incorporating this risk information on a probabilistic basis allows an investment decision to be made with a robust knowledge of the range of possible project outcomes along with the likelihood (probability) of those outcomes occurring, for example 80 per cent confidence that the project value will be greater than NZ$10 M, 50 per cent confident it will be greater than NZ$50 M and ten per cent confident it will be greater than NZ$70 M. Incorporating risk implicitly into the financial analysis allows the business to easily evaluate/measure projects with different risk profiles. The detailed risk analysis does away with the complexity of arbitrary risk-based hurdle (discount) rates, as projects can be evaluated based on their specific risk characteristics. Whether a project will progress to the next level of investment and ultimately into implementation depends firstly on the value assessment in comparison with the associated risk/uncertainty, and secondly matching this with the businesses appetite for risk. At Solid Energy standard criteria are used for specific project evaluations, but in addition projects are considered on a portfolio or strategic basis also. Solid Energy attempts to maintain a mix of low risk (low value) projects with some high risk (high value) opportunities. The mix of projects must remain in line with the shareholders' risk appetite. One of the keys to a successful investment decision is ensuring that the appropriate information is available to decision-makers so that they may proceed with a comprehensive understanding of the risks and impacts associated with the decision.

Jan 1, 2007

Gold Fields is the world?s fourth largest gold producer with operations in South Africa, Australia, Ghana and South America. All of Gold Fields? South African Operations are located in the Witwatersrand Basin and are intermediate to deep level underground mines exploiting gold bearing, shallow dipping tabular orebodies, which have collectively produced over 50 kt (1,608 Moz) of gold over a period of more than 100 years. Although the use of Monte Carlo as a business tool was introduced in 1964, it has only been in the last 30 years that it has gained increasing acceptance within the mining industry. However, the application thereof has been mostly limited to determination of risk in project areas. This paper however, considers the possibility of using Monte Carlo simulations to asses the underlying ?Root Cause? criteria critical to the operations management of existing mining operations. Currently, working operations have a distinct advantage over project areas as they have a wealth of historical information at hand. This, in turn, can be utilized to model distributions and relationships that can be used in Monte Carlo simulations, the results of which can be analysed to determine areas of concern. Projects can then be set up to ameliorate the effects of these and in turn reduce the risk of not achieving the operational targets. It is here that it must be stated emphatically that it should be the ?root causes? and the associated relationships that need to be emplaced within the model in order to achieve results that reflect the true causal relationship. The paper outlines possible sources of ?root cause? relationships and considers the outcomes of these in a case study on a large South African Gold Mine.

Jan 1, 2009

By C. A. Preece

Finsch Diamond Mine, part of De Beers Consolidated Mines (DBCM), is situated between Kimberley and Postmasburg in the Northern Cape, South Africa. The kimberlite pipe was discovered in 1960 and De Beers assumed full mining rights three years later. Production commenced in 1966 from an opencast mine, and the operation moved underground in 1990 by developing and implementing a new mining method of blast hole open stoping. A mechanized block cave was brought into production in 2005. While block caving was not new to DBCM, with productive caves having operated in Kimberley and Cullinan, from the outset, the Finsch caving operation was designed as the most advanced with a semi-automated ground handling system. The extraction level was laid out as a single sided herringbone system due to the very poor ground conditions on the south side of the pipe. These factors combined to create a unique environment, which necessitated a completely new approach to draw control. The required system was developed by a team consisting of DBCM personnel from head office and Finsch, GEMCOM and Sandvik-Tamrock, the equipment manufacturers. It was essential that the system could be run quickly, provide daily updates and issue calls directly to the LHDs. It was also important that the base data were obtained from the resource model, which was to be depleted on a monthly basis, thus forming a close link between mine planning and draw control. A further requirement of the system was that it would form a central database for the extraction operation where all data pertaining to delays and changes in conditions, be they production or ground condition related, could be recorded and analysed. The design brought together empirical rules and tables developed at Cullinan plus concepts from programming developed for the front cave at Koffiefontein so that the new system was based on sound practical experience. These facets were incorporated into PCBC (GEMCOM) and CMS and PCS (Sandvik-Tamrock programmes). The system has now been operational for just under a year and while modifications have had to be made, it has proved itself as a practical and reliable tool with which to manage the draw control at Finsch. The system is unforgiving and has forced the production team to focus on the specified drawpoints. Problems have been encountered but most of these have been related to re-educating a workforce, familiar with a flexible mining method, to the strict discipline required for a modern block cave.

Jan 1, 2007

Bougainville Copper Limited (BCL) operates a 50 Mtpy copper/gold/silver mine and concentrator on Bougainville Island, Papua New Guinea. BCL has installed an in-house developed data logging and supervisory process control system using a DEC PDP 11/73 mini-computer in the mill and has recently installed a similar system in the crushing plant. Together with the central DEC VAX 11/780 computer, they form part of a high speed, fibre optic, local area network in the concentrator. The in-house developed software, known as BIAS (Bougainville Copper Information and Automation System), was developed as a low cost option to interface to a number of different existing plant input/output systems while providing the capability to make maximum use of computer networking facilities. The package includes the more usual control system colour displays and data logging features, but also makes provision for two novel features: (a) Any user connected to the computer network can access the system displays. This allows metallurgists and management to monitor (but not control) plant operation from their offices. (b) Specialized application programs for performing advisory and supervisory control, dynamic simulation, and data analysis are easily incorporated into the system. The mill process system currently runs rougher/scavenger flotation stabilizing control and general data logging. The crushing plant system currently performs data logging only; however it will soon be augmented with the facility to run dynamic crushing plant simulations. Future developments will concentrate on making greater use of the detailed information available from the mine's fully automatic truck dispatch system which runs on a VAX 11/780 computer. Milling process control will be expanded to examine possible economic control of the operation of regrind and cleaner flotation circuits. An advisory water management system to optimize water supply within powerhouse generating capacity constraint will also be investigated.

Jan 1, 1987

By D. F. Caicedo, I. A. Brum, L. A. Betancourt

Ferricyanide ()()*is one of the most stable cyanometallic complexes present in the gold mining effluents. This cyanocomplex is hard to degrade by natural attenuation and generates a negative impact on aquatic environments. Although free cyanide (CN-) can be obtained by acidifying the solution, the CN- is lethal for all forms of life. The oxidation of ()()* in a typical photocatalitic system was evaluated with the addition of H2O2. To verify the degradation, chemical parameters, such as free cyanide, the formation of ammonia, nitrate, and total iron were analysed at the end of the process. The degradations obtained were up to 70% in a heterogeneous photocatalysis system with TiO2, and a low rate of dissociation was observed by photolysis. The best result was achieved with the H2O2 and TiO2 photocatalytic system, and the stoichiometric concentration was about 2.5 times less than the peroxide used in the real gold mining industry, reaching 83% degradation. The photocatalytic process obtained less toxic byproducts than the original synthetic ferricyanide used as mining wastewater. Keywords: Cyanide, heterogeneous photocatalysis, titanium dioxide, UV radiation, gold wastewater

Jan 1, 2020

By C. Nangolo

Mineral commodity prices comprise one of the key criteria in the selection of mining stocks. We contend that of the three principal elements of mineral commodity prices, spot price, forward price and long-term price, one has a greater impact on the share valuation processes used by investors. This research paper examines the extent to which each of these elements influences the valuation process. The intention is to provide investors in mining stocks with a greater understanding of how fluctuations of commodity prices over time affect the prices of the mining stocks they hold, or intend to sell or buy. Three mineral commodities, gold, silver, and copper, were used as case studies, since market data on these commodities is readily available in the public domain. Nine market indices covering all three mineral commodities were selected. These are based on clearly defined criteria with the intention of eliminating ambiguity and to test for correlation with the three sets of mineral commodity prices. Nine mining companies, which were not the primary drivers of the relevant indices employed in the study, were used to validate the results obtained from the indices in order to avoid duplication of the same correlation during cross-checking. Each commodity price was adjusted for operating costs. For each market index, an average operating cost was calculated from the companies comprising its basket, while each company?s annual operating costs were used for the stocks of the individual companies examined. The data was collected for the period January 2004 to October 2010. This period was further split up into three sub-periods to account for the Global Financial Crisis (GFC) period that started in mid-2008. We conclude that mining stock prices are correlated with mineral commodity prices, but with spot and forward prices exhibiting stronger correlations than long-term price. This finding should be useful for evaluation purposes. Where cash flow methodologies such as discounted cash flow or earnings per share are used to value ordinary shares and commodity prices are required to estimate future cash flows, the findings suggest that spot prices should be used as opposed to long-term prices. The work reported in this paper is part of a current MSc research study at the University of the Witwatersrand.

Jan 1, 2011

By H. E. Bartlett

This paper deals with the sampling and mass measurement for ore delivered from a shaft to a processing plant and the contribution of the data from these measurements to the metal balances from shaft deliveries to final metal production. Accurate measurement of the grade and tonnage of run-of-mine ore is important for four main reasons; ? It enables the measurement of the production from different profit centres to within statistically determined confidence limits for daily, monthly, or annual averages. The profit centres could be individual shafts within a mining complex or ore treated on a toll basis ? The monthly production at shaft head is compared to the grades and tonnage determined from underground sampling and mass measurement in terms of a shaft call factor ? The sum of the production from the shafts is the input to concentrators. This input is a major part of the total input into a complex with concentrators, smelters, and refineries. In terms of the Codes of Practice for Metal Accounting the inputs are compared to outputs and inventory changes to assess the efficiencies and unaccounted losses or gains at the various stages in the flow of metal from source to market ? On a daily or daily moving average basis, the grades and tons from shafts are monitored and compared against these quantities from underground measurements. This acts as a control on off-reef mining, dilution, and other factors underground. Accurate measurement of grade of ore at the shaft head has been a challenge because of the large particle size. The conventional wisdom has been that ore can be sampled accurately only after it has been milled to give a slurry that is sampled as feed to a flotation process. However, when the ore fed to a flotation plant comes from multiple sources each source has to be sampled separately. So, relying on the grades determined using the sampling of concentrator input with cross-stream slurry samplers is not an option for determining the grade from an individual shaft. Impala has developed a system for sampling and weighing run-of-mine ore from multiple shafts. The system involves sampling the inputs to the plants using cross-belt (hammer) samplers and weighing the deliveries using in-motion railway weighing systems. Many samples are taken. Individually they have a high variance but, as a consequence of the averaging effect of large numbers and as shown by statistical analysis, the mean results are fit for the purposes of daily grade control for shafts and for monthly accounting of production from individual shafts. In the metal accounting systems at Impala, the measurement of input, including ore and toll-treated material is compared to the output in the form of final metal and tailings losses, as well as any inventory change that takes place, in order to determine a final metal balance from mill feed to product. The calculated inventory is compared to that measured, and the difference, or unaccounted- for metal, is then reported as a percentage of input. The balances obtained over several years yields balances for platinum that are below 1% imbalanced. Keywords metal balancing, platinum mines, AMIRA codes of practice, metal accounting, sampling, run-of-mine ore, statistical analysis.

Jan 1, 2014