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By D Smith, D Reid, D Bradshaw, C Brough

The Merensky Reef at Northam Platinum Mine in South Africa is characterised by a high degree of variability with respect to reef elevation (difficult to mine), as well as mineralogy and texture (difficult to process). Development along strike and down dip of multiple reef types has led to unpredictable run-of-mine characteristics that pose problems for the mineral processing circuit at Northam. Following mining terminology, Normal, Transitional (NP2) and Pothole (P2) Merensky reef types can be defined, and this geometallurgical study aims to characterise and understand the relationship between their mineralogical characteristics and laboratory scale batch flotation performance. The plagioclase-rich NP2 reef ore is the easiest ore to process in terms of capacity for high mill throughput as well as flotation performance. The lack of very fine-grained disseminated sulfide textures in the NP2 reef ore results in better liberation characteristics relative to the Normal and P2 reef types. Consequently, chalcopyrite, pentlandite and sulfide recoveries are highest for the NP2 reef ore. The lack of ferromagnesian minerals in the NP2 reef ore also results in the recovery of the least amount of floatable gangue during flotation tests. The Normal and P2 reef ores are similar to each other, with an orthopyroxene-rich mineralogy with associated alteration minerals. The P2 reef is also characterised by the highest sulfide content and degree of pentlandite liberation. Chalcopyrite, pentlandite and pyrrhotite liberation is only significantly increased by a change in grind for the Normal reef ore. The change in grind, however, only significantly affects pentlandite flotation performance and overall froth stability for the Normal reef ore. However, for all three ores, a small change in grind has a detrimental effect on pentlandite flotation performance.

Jan 1, 2008

Citigold Corporation operates the Warrior gold mine at Charters Towers, northern Queensland, mining narrow quartz veins (0.1 to 2 m wide) in granodiorite by long hole open stoping on levels 15 m apart. Access is by decline and cross-cuts with on-ore development drives. The mineralisation comprises Palaeozoic mesothermal quartz veins containing gold, pyrite, sphalerite and galena, hosted by the Ordovician age Towers Hill Granite. The gold grain size is variable from 1 to 500 ¦m with 1 m face samples up to 800 ppm Au, and average run-of-mine grades of 10 to 14 ppm. Despite the spectacular gold tenor, little visible gold is present. Gold grades are highly variable presenting challenges in ore reserve estimation. Tonnages are discounted by 70 per cent to allow for the low payabilities (30 to 50 per cent) of the veins. Estimation techniques allow high confidence in overall global grade estimates but poor reliability on a local scale (25 m). Kriging ranges as low as 5 - 8 m means that obtaining a Proved Ore Reserve by diamond drilling is not economically feasible, and broad-scale mine planning decisions are made at the Inferred Mineral Resource stage and mine design work at the Probable Ore Reserve stage. Proved Ore Reserves can only be estimated after underground development has proceeded through the mineralised body with levels at 15 m vertical spacing sampled at 2 - 3 m intervals along the level. However, reconciliations between actual gold produced and earlier resource estimates produce workable results. A further three mines are scheduled to be developed underneath the city of Charters Towers.

Jan 1, 2008

As an Inspector of Mines in Queensland, my main responsibilities include the enforcement of the Mining Act 1968 - 1986, the Mines Regulation Act 1964 - 1983 and the Metalliferous Mining regulations 1985 to promote the safe and responsible exploitation of the States' mineral wealth. An important adjunct to this task is the offering of an advisory service to the mining industry. However, in the pursuit of my duties to this regard, I have sadly observed in some cases, numerous wrong doings and negative activities by miners which have led to their ultimate demise, not to mention that of others. Despite what I consider corrective advice, I have witnessed, again in some cases, disregard and blind pursuit for the wrong end. This then is a novel approach to get the message home in the form of a light hearted cartoon presentation relating the saga of an average Aussie battler entering the mining game unprepared, making the wrong decisions due to his own ignorance and the cleverness of others, leading finally to his and possibly others' downfall. It is not intended to insult any particular profession or group of individuals and only endeavours to impart to readers and listeners, the message of being prepared and alert when entering the gold mining industry. Even though the presentation focuses on the woes of a rookie alluvial gold miner, a similar analogy could be drawn with his hard rock counterpart since the basic issues that I have attempted to address are common. By no means is there a saga complete because there are many more traps a miner can inadvertently fall into and only time has prevented me from referencing them.

Jan 1, 1989

By G C. Lukey, J S. J van Deventer

The disposal and subsequent encapsulation of mine tailings in a cost-effective and environmentally secure and responsible manner is one of the principal issues facing any modern mining project. A careful assessment of all options available for the capping and subsequent remediation of tailings is important because it can result in large capital, operating and closure cost-savings. For these reasons, the technology of geopolymerisation is receiving increasing attention for the stabilisation and solidification of waste materials produced from mining operations. The first part of the current study investigates the application of geopolymer technology to the capping of hypersaline mine tailings. It has been found that suitable geopolymeric materials which have satisfactory compressive strength, durability as well as low permeability, can be formed using between 60 - 75 per cent of mine tailings as the main ingredient. It has been established that geopolymeric materials have the ability to suppress dust generation and prevent salt precipitation on the surface of the mine tailings. The slurry-like consistency of geopolymers would promote efficient application procedures through established tailings disposal techniques. This is a possible close-out technique for hypersaline tailings storage facilities such as those commonly found in Western Australia, which meets both regulatory requirements and community expectations. The immobilisation of contaminant metals within geopolymers has been investigated in the second part of the present study. In particular, the leaching characteristics of Cu and Pb from geopolymeric matrices derived from different fly ash sources have been examined. Potential breakdown of each geopolymer containing metal contaminants due to the leaching of Si and Al from the geopolymeric matrix has also been investigated.

Jan 1, 2000

By P K. M Mazzoni, D Frantois-Bong

This paper aims to show alternatives to the estimation methods used for finding the parameters in GyÆs well known model for sampling variance in the case of particulate materials. Many experiments designed for gathering data on the sampling variance for specific mineral deposits allow the experimenter to use approximations in the calculation of the parameters of the mathematical model involved, which sometimes can be very useful. However, there are some instances where approximations lead to biased estimates of the parameters, and consequently, lead to errors in the establishment of the sampling protocol and treatment of quality control data. In the present work, an alternative is presented for computing the parameter values based in any experimental set up, without the need for any simplification. The method was derived using the method of least squares and evaluations are made using the usual tools in this kind of methodology: residual analysis and evaluation of the fit by means of a plot of calculated versus experimental variances. With the aid of these tools, one can better evaluate the structure of the experimental errors in such applications, and the adherence to the proposed model. In addition, it is possible to perform hypothesis testing for the equality of different sampling procedures in terms of sampling variance. The full mathematical details are given, together with an algorithm for applying the method, which can be implemented easily using any computer language. An illustration of the method is shown, considering the international work done in ISO/TC 102. This example is a determination of the minimum sample mass to be collected in iron ore shipments, in order to achieve a specified sampling precision.

Jan 1, 2005

Prospecting in arid terrain can produce substantial environmental impacts, comparable to or greater in magnitude than the impacts associated with actual mining or petroleum production. Impacts are likely to be particularly severe where prospecting involves intensive geophysical exploration, especially in areas which have escaped degradation by other land uses such as pastoralism. With appropriate environmental planning and management, however, the environmental impacts of prospecting in arid terrain can be greatly reduced and mitigated, at low cost. In many countries, prospecting licences, exploration leases and associated tenements now carry a range of conditions relating to environmental protection. The assessment, avoidance and mitigation of environmental impacts is therefore an important component of and-zone exploration. My aim here is to give an overview of some of the main aspects of an environmental planning and management (EPM) programme for prospecting in arid terrain (PAT). Detailed operational prescriptions for environmental protection procedures are necessarily specific to particular areas and types of prospecting: see. e.g., Buckley (1982a, 1984, 1985a, 1986a), Klepacki et al. (1985) and Stone (1986). The intention here is to provide a checklist rather than a recipe book: as an aid in incorporating environmental aspects into the overall planning and management of an exploration programme, and in liaison with company environmental staff, consultants and regulatory bodies. I also hope to show that whilst some of the techniques used in particular environmental disciplines certainly require specialist expertise, the overall design of an EPM programme is not in the least esoteric, but simply an exercise in straightforward common sense. Perhaps this paper could be subtitled: "Demystifying environmental Planning".

Jan 1, 1988

Today, more and more tunnel ventilation systems are based on NO2 (or NO) and visibility measurements. Due to the significant decrease of CO emissions in countries with EU emission standards, which were adopted by Australia in 2004, CO is no longer a key factor for tunnel air quality monitoring and is often only measured for plausibility reasons (eg according to the German guideline RABT2006). Nitrogen dioxide, which is a good indicator for the overall air pollution along roads, is now taking over the leading role not only for ventilation control but also for air quality monitoring and in future probably for checking the function of air filtration plants in tunnels. Due to the lack of equipment for reliable and long-term NO2 measurements in road tunnels in the past, there are only very few standards giving limit values for NO2 in road tunnels. Furthermore there are not many records of NO2 readings over longer periods in different types of tunnels. SICK MAIHAK, a major supplier of measurement devices for controlling tunnel ventilation, has introduced the first monitor in 2006, specifically designed for measuring NO2, NO and visibility simultaneously in road tunnels. There are now experiences and results from the first tunnels equipped with this kind of system. This paper will present and discuss the results and experiences from these tunnels and explain the different levels of NO2 in different tunnel types. Furthermore, the status of air quality standards for road tunnels regarding NO2 limit values and the current status of discussion in various countries about NO2 limits will be presented.

Jan 1, 2008

By Kennedy JT

This is a question that will be asked many times and by many individuals during the various evaluation stages of any new project. However, the question itself will often have different connotations to the different groups invariably involved in such an exercise. As examples, consider just three of the several different groups involved in the development of a new mining project - Financiers, Consulting Engineers and the Sponsors of the project (potential borrowers). To the Financiers, a 'bankable project' will be one against which they will be prepared to lend funds (but not necessarily all of the funds requested by the Sponsors). This usually means that in the first instance the technical information presented to the bank has satisfactorily covered all of the requisite areas to the levels of accuracy required. More importantly, the financial evaluation of the projected economic performance of the mine, as a whole, is considered sound and a set of arrangements under which the bank is prepared to advance loan funds have been structured which fully satisfy the bank's credit criteria. To Consulting Engineers preparing a feasibility study (or a part thereof), on behalf of the project Sponsors, the term 'bankable' invariably only refers to the technical completeness and the level of detail contained in the report which they are preparing. Their scope of work will not necessarily have been broad enough to fully satisfy a bank's requirements. It is unusual to see any specific references to overall project viability or profitability in Consulting Engineers' feasibility reports, other than those which are automatically associated with the use of the term 'ore'.

Jan 1, 1990

If an orebody has been drilled to achieve some level of regulatory compliance, then a number of associated geological databases will exist, representing 10 000 to 100 000 m plus of core intervals. The databases usually contain data about assays, lithology, mineralisation and geophysical attributes. They will also include location information such as collar positions and downhole surveys. Obviously this data is collected by geologists for, predominantly, geologists and mining engineers. However, from a process design viewpoint process engineers usually ignore the geology where possible and rely on a small number of metallurgical test samples. Typically these test samples are sourced from convenient and available cores or from a small number of specially drilled metallurgical holes. One of the worst instances known to the author was the design of a SAG mill using only two SAG specific test results (one for each of the major ore types) while, geologically, the orebody was defined by more than 30 000 m of drilling. This paper sets out a philosophy to maximise the use of the geological data, both for process design and in preparation for the commissioning phase of projects. Geological data is used in the identification of preferred locations for metallurgical test samples, for checking the metallurgical validity of the geological ore-type definitions, where necessary developing new ore-type definitions (geometallurgical domains) and developing mathematical relationships for the estimation of important metallurgical factors across the geological database. If the estimation of factors (for example ore competence) is considered reliable enough then there is also the possibility of feeding calculated data back into the block modelling process to allow the generation of metallurgically relevant outputs in the mine plans.

Jan 1, 2007

In Australia a social impact assessment (SIA) is generally required prior to the approval of a mineral resource extraction or processing projects as a part of the Environmental Impact Assessment (EIA) process. In recent years there has been increased attention on the adequacy of the SIA process applied in major project assessment. Most applications have focused on the impact identification process with little attempt given to the community negotiating power over how impacts will be addressed. The impact assessment tends to occur at a single point in time, with no subsequent re-evaluation or ongoing social impact management and monitoring process. The assessments rarely specify how responsibilities for impacts on communities may be apportioned between project proponents and government, and have been inadequate in dealing with cumulative project impacts. In Queensland, concern about these shortfalls have led to the release of the Sustainable Resource Communities Policy 2008 and requirements for social impact management plans (SIMP) to be developed for each resource development in the State. In this paper a 'pressure-state-response' approach to impact assessment is used to develop an 'impact-response-monitoring-evaluation' (IRME) framework that can be applied to ongoing evaluation and monitoring of social impacts. The framework is applied to coal resource developments in the northern Bowen Basin in Queensland to identify core requirements in a SIMP. The IRME framework is flexible enough to be implemented at various spatial and time scales, for the wellbeing of the local and regional mining and non-mining communities in Australia. The framework can be further examined in other mine developments and could be integrated with the existing mining or environmental protection acts.

Jun 1, 2010

Builders have been very familiar with iron since ancient times, but because of its weathering characteristics it was relegated to use as a fastening material in unexposed places and bronze became the popular metal for exposed applications. It is of interest that iron nails buried deeply about A.D. 87 at a Roman fortress and carefully covered with clean beaten earth under conditions practically excluding oxygen were found to be almost unrusted 1870 years later. (1) Today, weathering steels, which contain less than 2% of alloying additions, can be used in exposed situations without protection and without experiencing continuous wastage. As we all know the steady access of atmospheric oxygen to the surface of plain steel causes continuous corrosion. Weathering steels, on the other hand, due to their alloying additions develop their own impervious surface layer which limits the access of atmospheric oxygen and effectively limits corrosion. Table 1 shows the chemical composition of a plain carbon steel and a typical weathering steel. Fig. 1 shows what we refer to as direct corrosion - time curves in which corrosion loss is plotted against time of exposure in an strial environment. The weathering steel has a high rate initially which then decreases steadily for about three years, as the stable rust film builds up. This is followed by a practically linear relation where the very low corrosion rate, according to one school (2), is due to a blocking of the rust pores by insoluble complex salts formed from interaction of the oxidation products of the separate alloying elements. The start of the linear region represents a total corrosion loss of only about 2 thousandths of an inch.

Jan 1, 1970

By L E. Setiawan

The mining and milling groups at Batu Hijau are tasked with increasing SAG mill throughput by approximately ten per cent. Avenues used for this process are blasting and crushing optimisation, ore blending and predicting SAG mill throughput in relation to the geological model. This is in line with traditional æMine to MillÆ studies. At Batu Hijau, mill and mine sequencing cannot readily be configured to perform the surveys traditionally required by a æMine to MillÆ study while meeting the daily production target of 140 000 tonnes per day and processing from varying ore types in one pit. A program called BOCCOST (blasting optimisation crushing conveying optimising SAG throughput) has been implemented to capture approximately 200 variables from blasting, mining and milling operations and assign them to a common point in space in the geological model in real time. Interpretive analysis of data from BOCCOST is used to model relationships between the 200 variables to determine which and how these factors affect SAG throughput. Once these relationships are determined, the blasting, ore blending and crushing process can be optimised to generate a product that maximises mill throughput. The relationships modelled from BOCCOST are also used to generate a SAG mill throughput estimator, which can be coded into the production block model. The block model can be reconciled with the geological block model for correlation by geological domain. Once this relationship is established, SAG mill throughput domains can then be established for predicting SAG mill throughput. This SAG mill throughput estimator is then used in conjunction with revenue calculations to determine an ore cut-off, which combines these two elements to maximise metal production.

Jan 1, 2002

By J-P Franzidis

Mill operators have traditionally been forced to rely on grade-recovery curves and overall flotation rate constants when analysing proposed improvements to plants. This has led to loss in money and time when a proposed change that showed potential in laboratory scale tests failed to show improvement in the plant. Frequently, this is a result of the operators being unable to gain insight into how and why the proposed change affected the flotation performance. This is due to the classical models not including any description of the subprocesses of flotation and their individual contribution to the overall flotation performance. A new flotation model has been developed as part of the AMIRA P9 project that separates the flotation process into subprocesses and includes the contribution of both the pulp phase and froth phase to the overall flotation recovery. It is not possible to determine the individual components of this new model on traditional pilot plants as they lack the required flexibility and scale. Therefore a new pilot plant has been developed known as the Floatability Characterisation Test Rig (FCTR) that has the flexibility and features required for the determination of the flotation subprocesses. The flexibility and features of the FCTR also make it an ideal tool for investigations into many different aspects of flotation research. These include the effect of reagents, grinding, and power on the flotation performance. This paper will describe the methodology for using the FCTR in these fields of research and highlights the advantages of using the FCTR over traditional methods.

Jan 1, 2000

By J Gutzmer

The Kalahari Manganese Deposit in South Africa accounts for 80 per cent of the worldÆs land-based mineable Mn reserves. Although the ores are primarily mined for export, South Africa is the worldÆs third largest producer of ferromanganese and ferrosilicomanganese alloy, both of which are derived from the smelting of these ores. Mineralogical analysis has traditionally been forsaken for bulk chemical assaying in quality control of smelter feeds, principally because quantitative data could not be easily produced. Yet, mineralogy plays a vital role in determining smelting behaviour, which in turn has economic implications when aspects such as energy and reductant consumption are considered. Smelting is an endothermic process, and the amount of energy input required is dependent on the minerals present in the ore, as well as their relative proportions. Further, knowing the bulk Mn oxidation state in the ores allows for calculation of the amount of oxygen that must be driven off to produce alloy, and hence the amount of reductant required. Additionally, certain minerals can be correlated with potentially deleterious elements, so that ore mineralogy can indicate penalty element distribution. Mineral abundance analysis was conducted on ores from the Kalahari Manganese Deposit using quantitative X-ray powder diffraction. Rietveld refinement using a fundamental parameters approach was applied to micronised ore samples. The mineral percentages obtained were validated using mineral chemical data together with bulk major element data derived from ICP-OES. Bulk oxidation state partitioning was then carried out knowing the Mn valence in the minerals. The results show potential for implementation of the proposed method on a smelting plant, where ore blending could be then implemented to achieve consistent feed compositions to smelters. Selective mining could also be undertaken to obtain desirable ore compositions for domestic or international markets.

Jan 1, 2008

By X S. Li

The modern mechanical excavation machines have enough power for cutting hard rock. The ‘bottle neck’ which limits the use of machines for hard rock excavation is ‘cutting tool’. To cut hard and abrasive rock, CSIRO has been developing Super Material Abrasive Resistant Tools (SMART*CUT). SMART*CUT technology replaces the tungsten carbide (WC) tip of conventional pick with thermally stable diamond composite (TSDC) and attaches the TSDC tip to steel tool body with CSIRO worldwide patented bonding technology. This paper introduces the key features of SMART*CUT, compares its performance with conventional WC tipped tools, discusses the challenges faced by SMART*CUT and the further developments needed for successful application of SMART*CUT to mining industries.

Nov 22, 2011

Interpreted geologic domains provide the geologic architecture of many current models used to estimate the potential economic resources in mineral deposits. The spatial extent of each domain is usually defined by a three-dimensional wireframe or triangulated surface.The set of geologic wireframes forming part of a resource model might generally be called a spatial interpretation of some set of geologic features coincident with the mineralisation, based primarily on logged and mapped properties of the samples and other exposures of the mineralisation. The interpreted spatial distribution of rock type, alteration and grade of drill hole samples above a particular grade threshold are commonly used criteria in constructing the geologic domain wireframes. Frequently, the grade threshold is closely related to the anticipated economic cut-off grade. The boundaries or spatial limits of different domains are most commonly defined as æhardÆ or æsoftÆ. A æhardÆ boundary usually means no dependent relationship of any kind is defined between the properties of samples inside a particular domain wireframe and those samples outside the wireframe. A æsoftÆ boundary commonly implies that some kind of dependent relationship does prevail between the properties of samples inside and outside the particular wireframe. Many ways are used to describe those relationships, few of which are based on spatial analysis of the continuity of sample attributes across the domain boundaries. In local estimation procedures such as ordinary block kriging, æhardÆ boundaries act as a total barrier to the influence of samples on either side of the boundary depending on the location of the block being estimated. In some instances, æsemi-permeableÆ boundaries are used in which the samples inside a domain wireframe are allowed to influence the estimates outside but not the reverse. This can lead to many undesirable effects in estimates of block grades.This paper discusses the value of this approach to geologic domaining from a viewpoint of model complexity, as well as in relation to the implications for both linear and non-linear estimation methods and contrasts it with alternatives. It also explores some important consequences of using æhardÆ and æsoftÆ geological boundaries with the commonly used modelling methods: excessive smoothing of estimates near domain boundaries and conditionally biased estimates of grade at the global and local scale.

Sep 26, 2011

One of primary causes of poor blast performance is the improper relief of explosive energy. Under or over-confined blasts modify the explosiveÆs path of least resistance, which changes where and when the explosive energy is applied resulting in less than optimum blast performance. During the research for this paper the overbreak characteristics of five full-scale blasts were quantified using high speed cinematography and borehole cameras. The effectiveness of various overbreak control methods was also evaluated to guide design refinement. The results of this research along with general recommendations for reducing excessive damage are included with this paper.

Jan 1, 1999

By D Clarke, R Simpson

The Main lode in the Anwia Gold deposit is difficult to interpret due partly to the fact that three separate grid and drill hole orientations exist over the area and partly due to a lack of understanding of the controls on the high-grade mineralisation. Scattered high gold grades and multiple veining orientations add to the confusion. Sectional interpretations of the lode are often misleading due to the multiple orientations of drilling. Initial attempts to define a high-grade constrained geological model were not successful due to the inability to establish any geological continuity that would hold together in three dimensions. As a consequence the initial geostatistical domaining for the Main lode at Anwia comprised a simple broad mineralised envelope split by the weathering profiles. Subsequently an analysis correlating subjective qualitative logging information with grade plus utilisation of LeapfrogTM software, together with extensive geological re-interpretation resulted in the definition of a coherent high-grade shoot within the Main lode. The resource was re-estimated including this new domain as a high-grade hard boundary. Estimations on both models were carried out using uniform conditioning, which is a recoverable resource estimation methodology that estimates tonnages and metal above a series of cut-offs for SMU (selective mining unit) sized blocks. This paper compares the tonnages and metal contents that are calculated from the two estimation runs, both at a zero cut-off and a series of higher cut-offs. The results confirm that the estimation methodology has been implemented correctly as the tonnage and metal content at zero cut-off is the same for both models. The resource tabulations and grade tonnage curves predicted by the two models highlight the differences that can occur at higher cut-offs when realistic high-grade domaining is implemented. The results also reinforce the point that recoverable resource models are intended to address selectivity issues and are not substitutes for good geological modelling. Recoverable resource techniques, such as uniform conditioning, will not correctly estimate high-grade zones that have not been explicitly modelled.

Jan 1, 2006

By Yoon R-H, Luttrell GH

A theoretical model has been developed to predict the probability of particle collection by air bubbles in a quiescent flotation pulp. The model considers the effects of both hydrodynamic and surface chemistry forces acting during the bubble-particle interaction. Hydrodynamic forces considered include the gravitational, buoyancy, streamline and film thinning resistance forces. The surface chemistry forces considered include the electrostatic, dispersion and hydrophobic forces. The hydrophobic force has been estimated from extended DLVO theory. The model is capable of predicting hydrodynamic and surface chemistry conditions under which bubble-particle adhesion is possible. Validity of the model has been verified experimentally.

Jan 1, 1993

The physical phenomena which influence gas flow in the bosh and hearth of a blast furnace are discussed including the hold-up of slag as a mechanism which can result in a flooding condition. An equation is defined which describes the limitation to wind volume arising from the flooding condition. Implications of the various factors influencing bosh and hearth gas flow on furnace operation are discussed. Coke quality is shown to be the most important factor in the aerodynamics of these zones and coke requirements are defined for the Port Kembla No. 5 BF which has an inner volume of 2670 m3.

Jan 1, 1975