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To determine the characteristics of a mineral deposit, the usual practice is to take samples, analyse the properties of those samples and infer the characteristics of the deposit from these properties. This analysis can be done using statistical methods. In the present work we are concerned with two types of statistical approaches, classical statistics and spatial statistics. If one uses classical statistics to represent the properties of the sample values, the assumption is made that the values are realizations of a random variable. The relative positions of the samples are ignored, and it is assumed that all sample values in the mineral deposit have an equal probability of being selected. The likely presence of trends, zones of enrichment, or pay shoots in the mineralization, is ignored. The fact that two samples taken close to each other are more likely to have similar values than if taken far apart is also not taken into consideration. In contrast, spatial statistics will be used if one chooses to consider that the sample values are realizations of random functions. On this hypothesis, the value of a sample is a function of its position in the mineralization of the deposit, and the relative position of the samples is taken into consideration. The similarity between sample values is quantified as a function of the distance between samples and this relationship represents the foundation of spatial statistics. There are few situations where classical statistics can be used. The assumption that all sample values in the mineral deposit have an equal likelihood of being represented will be satisfied only if the sample values are randomly distributed, or if the sample positions are random. Sample values are in fact never randomly distributed within a mineral deposit. Further- more, geologists usually avoid taking samples at random (random sampling), as it is correctly accepted that samples located on a regular grid, or approximately on a regular grid, give more information than randomly located samples. In practice, classical statistics should be used only in the early stages of exploration, when the number of samples available is relatively small and the distances between samples are large. In these circumstances, and whenever the information available is not sufficient to permit the use of spatial statistics, application of the methods described in this chapter is justified.

Jan 1, 1978

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 George Kayesa

[ ] A multiple-bench slope failure occurred at Letlhakane mine on 14th July 2005. No injuries or damage to equipment was suffered and mining production was not affected. Slope failure was preceded by the precursors of tension crack formation, crack widening and extension as well as slope monitoring targets movement. It was predicted that slope failure was imminent using the Geomos slope monitoring system, though the timing was not certain. The area to be affected by the slope failure was also known before hand as was the slope failure mode. As a result, measures were taken to avoid exposing personnel and mining equipment to the slope failure risk. This paper discusses how the prediction of the slope failure of 14th July 2005 using the Geomos slope monitoring system resulted into avoiding potentially fatal injury, damage to mining equipment and loss of mining production.

Jan 1, 2006

By Dick Stacey

Many open pit mines are now being mined at very significant depths, often at depths far greater than was originally planned. Even deeper open pits are also being planned, to depths that would be considered deep by underground standards. The heights of the resulting rock slopes are usually beyond the current experience and knowledge base. The exceptions are, perhaps, some very high and steep natural rock slopes. These natural rock slopes are also assuming greater significance owing to pressures of infrastructure development and consequent exposure of such infrastructure to the hazards of slope failure and landslides. Developments in road and rail infrastructure are also resulting in higher rock cuttings. Present understanding of the mechanisms of slope behaviour and failure for high slopes, and for slopes subjected to high in situ stress conditions, appears to be lacking. If the mechanisms of slope behaviour are not well understood, the validity of commonly applied methods of analysis of the stability of such slopes may be questionable. The papers in this specialist International Symposium, including papers on mechanisms and monitoring techniques, and case studies will contribute to the understanding of these issues. The Symposium has attracted good international participation, from both the attendance and authorship points of view. We are very grateful to all presenters and delegates for taking timeout of their very busy schedules to come and share their knowledge and we hope that all will benefit from this event. Thanks are due to the Organising Committee and to the members of our International Advisory Panel for the ideas, the contacts and the badgering, and to the Secretariat of the South African Institute of Mining and Metallurgy for the organisation.

Jan 1, 2006

By J. E. Friant, R. P. H. Willis, J. Maaren

Considerable effort is currently directed towards the development of non-explosive mining methods with the potential to allow continuous mining in narrow reef conditions. Besides improving productivity, continuous mining results in concentrated mining which has a significant impact on reducing infrastructure costs. CSIR: Miningtek recognized the potential of mini-disc cutters in a long or short wall application for selective hard rock mining in 1999. EEA was chartered to build a 780 mm diameter by 800 mm deep drum cutter head. While EEA designed and built the head, CSIR designed and built the drive mechanism and chassis for the trial machine. After assembly and shop testing at CSIR’s facility, the machine was shipped to a platinum mine for trials. This paper traces the development of mini-disc cutters and their application in South Africa.

Sep 1, 2001

By B. K. Loveday

There are certain ores that can be treated without upgrading (e.g., gold and uranium ores), and upgrading needs to be considered only for fairly low-grade ores of this type. If the grade is very low, treatment will not be economic even with upgrading, and there is therefore a limited range of ore grades for which upgrading is suitable.

Jan 1, 1980

By D. I. Nicol

An assessment is made of the possible scope for the use of activated charcoal as the solid adsorbent in an upflow fluidized-bed contactor, and a pilot-plant programme for the recovery of low concentrations of dissolved gold in this contactor is described. It was found possible to produce an effluent that contains less than 0,01 p.p.m. of dissolved gold.

Jan 1, 1997

By A. Singh, R. R. Maclachlan

SYNOPSIS A back-analysis procedure based upon 35 mm photography was developed on a laboratory scale for the pur¬pose of determining the percentage of oversize particles known to be present in heaps of fragmented rock. Eight simple blends of crushed stone containing varying percentages of oversize on a 1:40 modelled scale were examined. Simulated test conditions for the following were subjected to the photographic study: (1) a bench heap, (2) the surface exposure of a partially excavated heap, (3) a gravity-sorted surface as occurs on an apron dump, and (4) four quadrant views of an incrementally built conical heap of rock fragments. The best back-analysis determinations were obtained from (4), the cone, over all eight blends of fragments. The mean error was within -0,16 per cent of the true value, with a range of ± 1,872. This was for oversize contents of 5 to 20 per cent where a minimum 25 per cent of the photograph area was processed by digitizer. The worst results were from the apron dump at - 1,462 per cent for a mean error of ± 4,174 per cent. The intermediate results were from the undisturbed bench at -0,186 per cent with a mean error of ±2,862 per cent.

Jan 1, 1989

By Peter Stacey

This presentation provides comments on the increasing challenges associated with pit slope designs from the perspective of a design reviewer. Besides the technical issues related to the significant increase in current and proposed slope heights since the primary methodology in current use for pit slope designs was developed, other factors are coming into play. These include changes in mining equipment and associated operating practices, as well as a growing awareness on the part of mining executives and other stakeholders of the significance of stable, or at least well-managed, slopes. In the latter area, the associated clarification of responsibility has led to the increased use of either in-house or independent review consultants working on the behalf of management. From a technical perspective, since the mid-1970?s there have been significant improvements in the tools, particularly analytical methods, that are available to slope designers. There is also an increased understanding of the importance of a detailed geological model, with strong emphasis on alteration and/or structure to form the platform for the slope designs. However, the basic technology for determining the rock strength aspects has changed little, although an expanding body of experience is being accumulated in its use and there is a reasonable degree of comfort in its application for slope heights of up to at least 500 m. In addition, slope management is now viewed as a critical part of the implementation of slope designs and this has been supported by continuing improvements in slope monitoring systems. In recent years safety has become a primary concern, in part as a result of some major slope failures that have attracted the attention of regulators and the public, as well as mining executives, who are being held more responsible for unsafe conditions and associated events. There is therefore a growing demand for risk assessments to replace the deterministic design approaches upon which the current design technology is largely based. The focus of mine executives on safety has undoubtedly in part facilitated the recent long overdue revitalization of research into the design and stability of large pit slopes, the requirement for which has been recognized for many years by practitioners. This research, as well as the CSIRO Large Open Pit Study, will almost certainly provide advances beyond the empirical strength determination methods such as the Hoek-Brown failure criterion, which form the basis for current rockmass strength determination. At the same time, as mentioned above, there is a growing awareness of the requirement for a detailed structural model as a major component of every large slope design. In addition, other areas requiring further research include the impact of groundwater pressures on rock mass strength, particularly in rocks with low permeabilities, and the role of stress in high open pit slopes. From the perspective of design implementation, even with the recent significant advances in metal prices, mine operators remain under pressure to minimize mining costs. To address these constraints, mining equipment of ever increasing size is being introduced. There are, however, some disadvantages to this trend in the area of slope design. For example, the large electric shovels are not well designed for scaling bench faces, nor are they cost effective in this mode. As a result, specialized equipment may be needed in the mining cycle to perform the clean-up duties, which in turn increases operating costs. Further, where the large equipment is used in minimum width pushbacks to reduce the instantaneous stripping ratio, the advance rates can be high, but at the same time the associated changes in operating procedures are often not conducive to the concurrent use of such measures as controlled blasting, careful scaling and drain hole installation that generally improve stability. The resulting conflicts which may arise between the interests of production and those of slope stability are often exacerbated by the fact that these stabilization techniques actually increase the operating costs on which the operations manager is frequently judged, even though there is an overall increase in profit. Meeting the objective of developing slope designs which are practicable , i.e., achievable in terms of every aspect of the operating constraints in the specific pit, requires interaction and compromise between the geotechnical engineer, mine planners and operating staff during the formulation of the design criteria. In the current environment, it is often no longer sufficient to present slope designs in deterministic terms to a mine planner who accepts them almost without question. Increasingly, the requirement is that they be proposed within the framework of risk levels, related both to safety and to economic outcomes, to a decision maker who may not be a technical expert in the mining field. In this context, the mine executives must have sufficient information and understanding to be able to establish acceptable levels of risk for the company and other stakeholders; in this process the slope designers must play a major role. These changing requirements for presentation of slope designs necessitate clear communication of the basis for the design, which may be very complex, so that the implications of the designs may be thoroughly understood by all concerned. To ensure clarity at this stage, the slope designer must not only quantify the uncertainty in the input parameters, including the geological model, but must also be able to communicate and defend the resulting design recommendations. Where particular designs may have high associated risks, simply because of the degree of uncertainty in the data, this must also be recognized and proposed methods of reducing the uncertainty included in the presentation. In summary, from a reviewer?s perspective slope designs must not only be technically sound, but must also address the broader context of the mining operation as a whole, taking into account such factors as safety aspects, the available equipment to implement the designs, and the acceptable risk levels for the company. In addition, the designs must be presented in a way that will allow the mine executives, who are ultimately responsible, and the operators, who implement the designs, to fully understand the basis and short-comings of the designs and the risks associated with deviation from any constraints defined by the designer. It goes without saying that there must also be a well-defined monitoring system to confirm stability and detect and manage any variations in the design model or unexpected instability.

Jan 1, 2006

By C. G. Schmidt, N. W. Hanf

Many of the pyrite concentrates produced at South African gold and uranium mines contain economically significant amounts of nickel, copper, and cobalt, apart from gold and uranium. In some cases these concentrates are leached for uranium, followed by roasting and cyanidation of the calcine for the extraction of the gold. Even if their intrinsic value is excluded, the presence of appreciable amounts of base metals can lead to excessive consumption of cyanide and zinc in the conventional process for the recovery of gold from calcines. The extent to which base metals, particularly cyanocides in the calcine, can be made soluble in water or in dilute acid by variation of the pyrite roasting conditions was investigated. An important finding of the investigation was that the conditions producing favourable base-metal sulphation (and hence solubility in water) also produced good sulphation of the uranium values that had not been extracted in a conventional leach of the original pyrite. Thus, if the pyrite is subjected to a sulphating roast followed by quenching in water (or dilute acid), it should be possible for the uranium to be extracted in improved yield. The need for leaching of the pyrite would therefore fall away. It was noted that sulphation roasting also resulted in improved gold extractions when the calcine was subsequently subjected to conventional cyanide-extraction procedures. From well-sulphated calcine, the dissolution of base metals and uranium appeared to be fairly independent of leaching pH, time, and temperature. On an inadequately sulphated calcine, Iow pH values during leaching gave increased extraction of copper and uranium but did not have a significant effect on the dissolution of nickel and cobalt. The extraction of uranium increased with increasing leaching time and temperature, while only longer times at a Iow pH value markedly improved the extraction of copper. The extraction of cobalt was fairly independent of leaching time and temperature, but the results were insufficient for a conclusive evaluation to be made of their effects on the dissolution of nickel. A cursory economic assessment 'indicated that sulphation roasting applied to the pyrites investigated is likely to be very profitable.

Jan 1, 1979

By A. Cambitsis

We show that the prioritization of business improvement and performance management decisions may be significantly improved by taking into account the systemic effects of changes made in a single process area. To do so we build a model of a mining value chain, taking into account consequential downtime that arises from downstream and upstream starvation and choking effects of each activity. Introducing the concept of internal capacity, this approach yields insight into the relative importance of key metrics such as loading and hauling rates. We suggest that a holistic view of this type should be a core component of business improvement and performance management decisions. Keywords value driver trees, production constraints, throughput analysis, capacity analysis, TOC (Theory of Constraints), activity interdependencies, unit cost reduction.

Oct 1, 2013

By C. Pamukcu

In this paper, which is aimed to serve as a review article, first of all a breakdown of the earth?s total water reserves is given. The usage areas of water in the mining industry are mentioned and these uses are briefly outlined, together with the main pollution potential of each. According to this, most of the water (almost 80% of it) is utilized in processing. Later on, probable damages that the mining would give to groundwater as a result of acid mine drainage, heavy metal pollution, euthrophication and deoxygenation is described. Finally, the measures and controls that should be taken against water contamination in mines are presented.

Jan 1, 2008

Namakwa Sands, an Anglo Operations Limited subsidiary, is a world-class producer of heavy minerals. A layer of duricrust imposes a pseudo-stratigraphy to the primary deposit and has sterilized part of the generally unconsolidated ore in the open cast mine. The bulk of this ore cannot be treated by the present infrastructure, which employs conventional mineral separation technology. The mineralogy of the cementing agent consists of magnesium and calcium silicates and minor carbonates in addition to clay minerals such as sepiolite and those from the smectite group. Although the duricrust ore is friable and can be easily crushed, the significant clay-sized slime fraction produced, in particular the highly sorptive sepiolite, adversely affects mineral separation. The geometallurgical challenge is to cost-effectively remove the slimes from the ore before it is delivered to the concentrator.

Jan 1, 2007

By K. A. Annan

The last seven hot rolling passes of the ferritic stainless steel AISI430 were simulated on a Gleeble-1500D® thermo-mechanical simulator to investigate the effect of temperature, strain rate, and interpass time on the texture. The compression tests were carried out over a wide range of strain rates (0.1 s-1 to 5 s-1) and temperatures (1100°C to 820°C) with different interpass times (2, 10, 20, and 30 seconds). The dynamic recrystallization to dynamic recovery transition temperature was determined from examining the relationship between the mean flow stress and the inverse of the deformation temperature in multi-pass tests. It was found that the texture in the central layer of the compressed sample is a strong recrystallization-type. The through-thickness textural and microstructural banding, to a large extent, were found to be weakened by hot deformation in the two-phase (a+ ?) region, as opposed to the single-phase (a) region.

Jan 1, 2013

By T. Wallmach

Heavy mineral deposits are a source of the economic important element titanium, which is contained in minerals such as ilmenite, pseudorutile and rutile. In the Ranobe heavy minerals deposit these minerals occur not only as primary unaltered minerals but also display various degrees of alteration resulting in an increased titanium content of the deposit. The presence of the various FeTi-oxide minerals? textural relations is a reflection of geological processes and may ultimately be used to unravel the geological history of the deposit. These minerals have different chemical and physical properties that influence metallurgical tests and the quality of products produced from various mineral beneficiation streams. It is therefore of metallurgical importance that the minerals are well characterized, defined and monitored during preliminary beneficiation tests.

Jan 1, 2007

By T. P. Katakwa

The utilization of software is now inherent to virtually every activity along the mining value chain. However, apart from the software survey done by Gibbs in the 1990s and work on the extent of diffusion of information and communication technology (ICT) in the South African platinum sector by Mugodi and Fleming in 2003, the nature and extent of software utilization in the South African mining industry has never been evaluated. The Mine Planning, Optimisation and Valuation (MPOV) Research Group in the School of Mining Engineering, University of Witwatersrand, therefore initiated a project to collate and analyse the current utilization of software in the South African mining industry. This was done through the development of a web-based database of the relevant software. Snowball sampling was used to collect the data because the South African mining industry is diverse and software utilization is fragmented across and within the sectors of the industry. The data was then organized into distinct categories so that the information from a variety of sources could be evaluated on the same basis. A beta version of the database can be accessed online through a user-friendly front-end platform at http://db.mining.wits.ac.za. The database is expected to help at least 13 educational institutions with decisions on facilities and training that are vital to the education of mining and mining-related professionals. Exploration, mining, and consulting companies will also benefit from information in the database relating to availability and useful combinations of software solutions. The database is also strategic to software providers by providing a better understanding of their respective relative market share along the mining value chain. An analysis of the data collated in this research shows that about 77% of the software users are mining companies, 17% are consulting companies, 3% are mineral exploration companies, and the rest are software providers and educational institutions. The software used in the South African mining industry is largely provided by Gemcom Software International, MineRP Solutions, and MRM Mining Services. CAE Mining, who in 2010 acquired the Datamine Group providing Datamine software, is also widely acknowledged as a major software supplier in South Africa, but data from them had not been obtained at the time of producing the beta version of the database due to proprietary constraints. The work reported in this paper is part of an MSc research study in the School of Mining Engineering at the University of the Witwatersrand. Keywords mine planning, mining, value chain, software, database, South African mining industry, utilization.

Jun 1, 2013

Limestone formations in the United States can be subject to relatively high horizontal stresses due to the existence of tectonic loading of the limestone strata. Underground limestone mines use the room-and-pillar method, in which 12- to 18-m-wide rooms are typically excavated. The stability of these excavations can be compromised by the horizontal stress, resulting in a rockfall hazard. Rockfalls are the cause of 15% of all reportable injuries in underground limestone mines. Horizontal stress related damage can occur in the form of guttering along one or more sides of an excavation, roof beam buckling or oval shaped roof falls, with the long axis perpendicular to the major horizontal stress. Numerical analyses show that the pillar layout and orientation of the mine workings have an effect on the horizontal stress distribution within the roof. The effects of high horizontal stresses can be mitigated by orientating the heading development direction parallel to the maximum horizontal stress, reducing the number of cross-cuts and offsetting the cross-cuts to limit the potential lateral extent of horizontal stress related roof falls. The modeling approach described in this paper can be used as a tool to evaluate potential roof failure and optimize the stability of room and pillar layouts.

Jan 1, 2008

By G. E. Blight

Rates of erosion have been measured for the slopes and top surfaces of a number of gold-tailings dams in the Germiston-Johannesburg-Roodepoort area of the Transvaal. Preliminary results were given in an earlier paper. The present paper gives results for a four-year period of observation, and identifies the major factors affecting the rates of erosion from the surfaces of gold-tailings dams.

Jan 1, 1989

By R. Rubin, P. A. Laxen, G. S. M. Becker

An account is given of developments in the use of activated carbon for the recovery of gold from cyanide solutions. The carbon-In-pulp process employed at the Homestake Mine is described, and its various applications in South Africa and their effectiveness are discussed. Probable future work on the carbon-in-pulp process and other possible applications of carbon for the recovery of gold are outlined.

Jan 1, 1979

By A. L. Hinde, A. A. Bradley, P. J. Lloyd

The results of slow crushing tests in a stiff testing machine for both small and large step reductions of particle size are given. The energy consumption required to produce a given weight of minus 74 um material was determined when both single-crystal quartz and Witwatersrand reef were crushed. For comparison the two materials tested were also comminuted in a ball mill under optimum conditions. There are indications that slow crushing under stiff conditions is the most efficient method of breakage that can be devised. The comparison with ball milling results thus yields a value for the efficiency of ball milling of approximately 80 per cent. These results confirm that the best current estimates of milling efficiency, which are based on the free boundary surface energy of the material being milled, are probably too low by at least one order of magnitude.