Search Documents

By P Stoker

The need for quality assurance and quality control (QA/QC) in the sampling and assaying of minerals is fundamental to the reliability and confidence of a mineral resource estimate, reserve estimate and possibly profitability of a mine. In spite of this, QA/QC practices in the mining industry are commonly applied poorly, or misunderstood. As New Leaders, we should aim to correct the poor practices and become fully informed on appropriate procedures. This paper uses worked examples that show the usefulness and importance of best practice QA/QC procedures. Fundamentals of reviewing the performance of the laboratory by examining the results of client inserted standard reference material (standards), blank material and duplicate samples are discussed. To do this, three examples from Australian data sets have been used. For each example, simple and efficient plotting techniques are suggested with subsequent evaluations of each plot. The first case study compares the results of internal standards from a laboratory with blind standards (where the expected value is unknown to the laboratory) submitted by the client. It was demonstrated over time that the laboratory was unintentionally analysing the internal standards in a different manner to the remainder of the sample batch. In this example, not understanding the cause of a high negative laboratory bias could have led to poor understanding of the depositÆs grade and in the extreme a proposed mining operation may have reached operational stage with a subeconomic grade. The second case study discusses the quality of blank material submitted by a mining operation to monitor cross-contamination within the laboratory. The blank material contained background levels of the element under investigation. This created uncertainty in the assay results, which could have led to the need for additional assays and drilling programs. Finally, the third case study demonstrates the use of the relative paired differences (RPD) technique to cross-validate the results from duplicates and repeat analyses from two laboratories. The three examples given show either laboratory or operational error. If left undetected, each example could have had serious implications for the mineral resource estimate and ultimately, the mining operation. These examples are not isolated occurrences; poor QA/QC practices are an industry wide problem exacerbated by rapid staff turnover and increased contractor positions on-site. New Leaders must be equipped with a thorough grounding in QA/QC best practices to improve its application and confidence in the results of sample analysis.

Jan 1, 2009

By I Brunton

Blast fragmentation can have a significant impact on the profitability of a mine. An optimum run of mine (ROM) size distribution is required to maximise the performance of downstream processes. If this fragmentation size distribution can be modelled and controlled, the operation will have made a significant advancement towards improving its performance. Blast fragmentation modelling is an important step in Mine to MillTM optimisation. It allows the estimation of blast fragmentation distributions for a number of different rock mass, blast geometry, and explosive parameters. These distributions can then be modelled in downstream mining and milling processes to determine the optimum blast design. When a blast hole is detonated rock breakage occurs in two different stress regions û compressive and tensile. In the first region, compressive stress waves form a æcrushed zoneÆ directly adjacent to the blast hole. The second region, termed the æcracked zoneÆ, occurs outside the crush one. The widely used Kuz-Ram model does not recognise these two blast regions. In the Kuz-Ram model the mean fragment size from the blast is approximated and is then used to estimate the remaining size distribution. Experience has shown that this model predicts the coarse end reasonably accurately, but it can significantly underestimate the amount of fines generated. As part of the Australian Mineral Industries Research Association (AMIRA) P483A Mine to MillTM project, the Two-Component Model (TCM) and Crush Zone Model (CZM), developed by the Julius Kruttschnitt Mineral Research Centre (JKMRC), were compared and evaluated to measured ROM fragmentation distributions. An important criteria for this comparison was the variation of model results from measured ROM in the fine to intermediate section (1 mm to 100 mm) of the fragmentation curve. This region of the distribution is important for Mine to MillTM optimisation. The comparison of modelled and Split ROM fragmentation distributions has been conducted in harder ores (UCS greater than 80 MPa). Further work involves modelling softer ores. The comparisons will be continued with future site surveys to increase confidence in the comparison of the CZM and TCM to Split results. Stochastic fragmentation modelling will then be conducted to take into account variation of input parameters. A window of possible fragmentation distributions can be compared to those obtained by Split. Following this work, an improved fragmentation model will be developed in response to these findings.

Jan 1, 2001

Ventilation challenges are often encountered when an underground mine expands to new zones and it often is the case to make a thorough review of the existing system and assess immediate and future airflow needs at the desired quantity and quality. An unexpected mine plan change that calls for increased development and production from new areas can impose a strain on the existing ventilation system. Budgetary constraints can also demand creativity in design on the mine ventilation engineerÆs part. Since the addition of several mining horizons it had become obvious at the Meikle mine that something had to be done to increase airflow quantity and quality in the old main zones because most of the ventilation resources had been channelled for development in the new mining horizons. An airflow assessment of the existing system had to be performed and it was determined that the airflow quantity had to be increased by at least 30 per cent and the quality of the air had to be improved by reducing nuisance and respirable dust and at the same time reducing the airflow temperature before it was used in a few mining zones. At the conclusion of the airflow assessment it was determined that a third centrifugal fan would be installed on a new 3.05 m diameter borehole from surface to underground. By a careful study of temperature conditions over time it was determined that an evaporative cooling spray chamber would be sufficient to cool the airflow down from the high dry bulb temperatures observed down to saturation at the wet bulb temperature. At the same time excessive nuisance dust generated as a result of the airflow travelling a long way in a haulage drift will be knocked down in the spray chamber resulting in cool, clean air in the mining districts. Expansion of the existing surface ammonia refrigeration plant was out of the question for several reasons. The fact that the airflow was hot and dry meant that evaporative cooling spray chambers could achieve lower working temperatures at a very low cost compared to the expansion of the chilled water plant. The expansion of the ventilation system at Meikle mine and the use of evaporative cooling spray chambers were demonstrated to be very successful and the information presented in this paper can be of benefit to other mines experiencing the same ventilation problems as was the case at the Meikle mine.

Jan 1, 2005

By G S. Esterhuizen, M M. Murphy, T S. Bajpayee

The strength reduction method (SRM) has been implemented in the FLAC3D finite difference software and applied to coalmine entry support evaluations. The FLAC3D numerical models have been calibrated against instrumented field sites in varying geologies, depths and field stress conditions. The calibration between the field and model results obtained a satisfactory match for rock deformation and support response. Previous research has also developed good correlations between numerical model stability estimations using the SRM and empirically derived stability estimations using the analysis of roof bolt systems (ARBS) software and the coalmine roof rating (CMRR). The purpose of this paper is to further apply the SRM to investigate how specific geotechnical and support parameters can impact coalmine entry stability. Results from different studies demonstrate how the calibrated models were used to investigate a few of the well-known questions in both mine design and support design. For mine design the impact of strong and weak beds in the roof strata, rotating the principal stresses and weakening the floor on excavation stability is investigated. For support design the impact of support length, support spacing and adding cable bolts to the design is demonstrated. These scenarios are evaluated in developmental coalmine entries for a variety of geology and field stress conditions. Stability factors are calculated for each scenario using the SRM. The SRM allows the impact of each parameter to be quantified and allows the support system to be optimised for given geotechnical conditions.CITATION:Esterhuizen, G S, Murphy, M M and Bajpayee, T S, 2014. Analysis of geotechnical and support parameters on coalmine entry stability using the strength reduction method, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 383–392 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By F Brenguier, R A. Lynch, G Olivier

The seismic velocities of intact rock are dependent on the applied stress. Unfortunately, the low susceptibility of seismic velocity to stress changes mean that changes in seismic velocity have to be measured extremely accurately to infer stress changes from them. Previously, it was thought that measurements of this accuracy could only be made with active sources or repeating earthquakes. In this paper, we show that the noise generated by mining activity can be used to construct virtual seismic signals with which we can measure changes in seismic velocity accurately enough to see the short- and long-term effects of a production blast on the surrounding medium. The time-dependent velocity variations achieved with this method show that the blast caused weakening of the rock mass for the rock within a radius of 200 m of the blast. The weakening is healed by confining stresses over a period of five days, after which permanent changes in the seismic velocity can be seen. The size and spatial distribution of the seismic velocity changes were compared to modelled changes in static volumetric stress, which supported the notion that seismic velocity changes can be used to measure the redistribution of stress after a blast. The results of this study indicate that this method can be a powerful tool to evaluate the evolution of stress in a mine at a relatively low cost as the data that it uses would normally be discarded.CITATION:Olivier, G, Lynch, R A and Brenguier, F, 2016. Measuring the redistribution of stresses resulting from new excavations with ambient seismic noise correlations, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 873–878 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

Over the last 15 years working in the mining, construction and extractive industries, one of the areas that has always concerned and at the same time drawn the author to it is the application of drilling and blasting in the underground development mining and civil construction tunnelling fields. In that time, the author has come across many drives and tunnels that are larger than design or badly damaged in the perimeter or both. When the question is asked as to why this is the case, the reply is generally æthatÆs the way it is and always has beenÆ. Sometimes it is blamed on bad ground, bad drilling, bad explosives, bad initiation or just plain bad. Most operators build a dilution factor into development and tunneling costs as an acceptance of overbreak and similarly pattern bolt everything to overcome excessive perimeter damage. This paper will attempt to unravel some of the mysteries behind perimeter drilling and blasting in underground drives and tunnels and discuss methods to reduce overbreak and therefore reduce costly dilution and to minimise perimeter damage which in turn will allow more cost-effective ground support. It should not be assumed that better drilling and blasting alone would automatically allow an operation to reduce ground support. The operator must still æreadÆ the ground and its characteristics in order to ensure sufficient ground support is placed to allow the operation to progress safely. This paper will not go into the intricacies of bolting, meshing, shotcreting, concreting and other ground support, but it will use indicative costs for the primary areas of drilling, explosives, excavation and labor to show the magnitude of cost-efficiencies which can be obtained through improved drilling and blasting applications. Drill and blast remains the most flexible and cost-effective method of underground excavation as long as it is applied safely and effectively.

Jan 1, 1999

By Ormsby W. R, Farrar L

The stratigraphy of the central Pine Creek Geosyncline has been simplified into a three-fold subdivision comprising the Batchelor, Frances Creek and Finniss River Groups. The Batchelor Group consists of a sequence of shallow water coarse clastics and crystalline carbonates and is conformably overlain by the marine carbonaceous shale dominated Frances Creek Group. Interbedded within the carbonaceous shale are turbidites, iron formation, tuffs, carbonate and non carbonaceous shale. The Finniss River Group is a flysch sequence of greywacke and mudstone. The stratigraphic and structural evolution and igneous history are all interrelated. Although the Batchelor Group may have formed in a tensional regime, it is likely that regional compression and accompanying thin skinned deformation began during deposition of the Frances Creek Group. Continued compression resulted in D2 folding d6collement deformation, wrench faulting in compressional zones and thrust faulting. Occasional relaxation of compression is marked by a number of periods of basic intrusion and perhaps distal volcanism. The style of deformation within sediments varies away from granitic basement highs and is similar to that observed around salt domes and found in experimental diapiric models. Sedimentary facies changes also indicate local emergence of basement highs during sedimentation. As compression continued, the deposition of thick sequences of the Finniss River and El Sherana Groups brought about regional metamorphism. Relaxation of compression and waning of associated subsidence resulted in a relative increase in the rate of uplift and partial melting of diapiric sialic basement. In places, granitic magma moved upwards and crystallised forming grossly concordant bodies. Other masses moved laterally and formed extensive granitic sills. Later compression periods caused mainly brittle deformation which may have been strongly influenced by underlying basement fabric.

Jan 1, 1994

The Olympic Dam copper/uranium deposit was discovered in 1975 and subsequently commenced production in 1988 at a rate of 1.5 Mtpa using the sublevel open stoping mining method. In the following five years the operation underwent two optimisation programs that have increased mine output to the current rate of 3.4 Mtpa of ore. The pre-expansion requirements were annual development of approximately 10 000 m and the placement of around 500 000 m 3 /yr of cemented backfill. Previous to 1995 all hoisting was carried out by the Whenan shaft. The Robinson shaft was commissioned during that year to hoist increasing development mullock tonnages and to allow for increased ore hoist via the Whenan system. In 1996 WMC committed to expanding the output of the operation from 85 000 tpa (1996/97 budget) copper metal to 200 000tpa. The corresponding increase in mine ore production requires expansion to a nominal rate of 9.0 Mtpa. To achieve these increased tonnages, major hardware installations will include sinking of a third shaft capable of hoisting in excess of 9.5 Mtpa, a rail haulage horizon utilising automatic trains, expansion of the existing backfill plant to a production capacity of over 1.8 million m 3 /yr, increasing long term development rates to 15 000 m/yr and increasing the production drilling and blasting rates in line with the higher stope production output. This paper provides detail into the intended hardware (shafts, equipment, etc) of the mining system, and outlines the intended long-term operation and management of the operation. Of particular note is the background requirement of ensuring existing production targets are met to provide critical cashflows into the project during the period of expansion.

Jan 1, 1998

By B Maybee

In underground mine planning, many potentially value-eroding decisions are made due to a lack of time and proper evaluation practices. The information required for mine planning decisions goes beyond external sources of uncertainty that are recognised by typical evaluation techniques used in the mining industry, to include technical factors (eg mine development layout) and the ability of a mineral extraction project to achieve its anticipated production levels. Due to the individual characteristics that define underground mining projects, each will exhibit a different risk profile, and thus advanced optimisation and evaluation techniques are required to capture this information.As underground mine planning tools become more sophisticated, mine planners have the capacity to investigate numerous mine sequencing options to identify the best strategy for a given project, creating higher value for shareholders. This paper describes a risk-based evaluation methodology (RbEM) that accounts for financial and technical risk in the evaluation of underground mining projects. While the use of the RbEM has been described in previous works, no benchmarking of the benefits that can be realised from a change in those decisions that are made early in the process has been undertaken. To show the benefits that can be achieved from using the RbEM, this paper updates a case study to which the RbEM was applied, and takes a retrospective look at whether additional value would have been gained by following the strategic recommendation of the RbEM versus a typical optimisation exercise that aims to maximise the net present value.CITATION:Maybee, B, 2012. Can a risk-based evaluation provide a more valuable mine design?, in Proceedings Project Evaluation 2012 , pp 53-58 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

I am honoured to be given the opportunity to share with you my thoughts on what will be the essential characteristics of æThe Mining Company for the 21st CenturyÆ. For me the 21st century is all about globalisation and the challenges and the opportunities that globalisation presents for the mining industry. To play on the global stage the successful mining companies must develop profiles that are global in: their operations diversity, their partnership relationships diversity, their customer relationships diversity, their workforce diversity, and their shareholder diversity. In my view æbigÆ will count in the 21st century, but big overlaid with quality: quality assets, quality people, quality partners, quality customer relationships, and quality image and reputation. Last year, Rio TintoÆs Leon Davis said when he addressed the Minerals Council of AustraliaÆs annual conference that Australian resource companies that wish to become global operators must develop an unequivocal international identity that will make that company a known and trusted quality wherever it seeks to do business. He went on to say that structuring and operating a business in a way that consistently manifests the qualities that inspire respect and evoke confidence is vital. I absolutely concur with what Leon said. Unfortunately, the fact is that, as we stand at the beginning of the 21st century, our industry and many of our companies are no better accepted by the world community than was the case five, ten, 15 or even 20 years ago. In fact, in some cases, the warmth of the acceptance may have subsided. To some extent the demonstrations that we saw recently in Seattle and Davos reflect a growing distrust, disquiet and cynicism in our communities. Here, however, I see an opportunity. While on the one hand the mood of disquiet presents many challenges, it also provides those of us who are willing to get out on the front foot in addressing the issues, and engaging in the dialogue, with a very significant opportunity to create a major competitive advantage. It provides the opportunity to earn respect and the opportunity to develop a reputation as a company that is sought as a joint venture partner and a company that is welcomed by governments and communities. Importantly, also, people will seek employment with such a company and will invest in such a company. The challenge is to change the way we behave and the way we are perceived by all the key stakeholders. Many of our industryÆs traditional skills are now commodities à many can be à and are out-sourced. The new critical skill for the 21st century à the real competitive advantage à will come from creating a real and genuine understanding of our role and what we stand for. Everything we do should demonstrate not only sound business principles, but also an understanding of the political, social, cultural and environmental impacts of our activities - at an international and a local level. This concept isnÆt new - but for large companies such as BHP, where we operate in more than 20 countries with diverse cultures, languages and religions - it requires enormous energy and dedication. It is complex. It is difficult. But I believe it is absolutely fundamental to our future.

Jan 1, 2000

By L Mackinlay

The Apeketon Business Hub in Lihir, Papua New Guinea, emerged in 2019 through a partnership between Australian Business Volunteers (ABV) and Lihir Gold Limited (LGL), a subsidiary of Newmont Corporation. This development was driven by a shared vision for the Lihir gold mining operation to further enhance opportunities for the local community and strengthen the economy’s resilience post-mine. At its core, the business hub serves as the epicentre of ABV’s operations in the region. It includes a drop-in resource centre which provides the community with mentoring and consulting services, and access to a range of impactful workshops facilitated by ABV’s local staff and skilled volunteers. These workshops focus on local Lihirians but are open to the entire community, including Newmont employees. We design and continually refine Apeketon Business Hub support programs and offerings driven by community priorities, building trust through long-term relationships, and working side-by-side on real-time challenges. We offer three core programs to different levels of the community, from individuals and families to start-ups, large corporations, and landowner groups. There is significant demand for the support services provided by ABV, with over 350 Lihirians participating in our workshops over the 2023 calendar year. One of the hub’s core offerings is the Family Money Management Program, which addresses crucial challenges faced by Lihir households, particularly in terms of financial resilience. The program takes a comprehensive approach, assisting families in long-term planning and developing skills to effectively manage the income they derive from their employment with LGL and other enterprises. Significantly, the program also addresses financial stress, a factor often associated with domestic violence (Fox et al, 2002). By empowering women and promoting joint financial decision-making, the Family Money Management Program fosters a culture of savings and improved financial management, ultimately enhancing economic resilience within the community.

Sep 1, 2024

The first stage in the refining of lead blast furnace bullion is the removal of copper and is normally done as a batch process in open kettles.A number of attempts have been made to establish continuous processes operating in reverberatory type furnaces, but the growth of accretions in the furnace has always presented a serious problem.The Broken Hill Associated Smelters Pty. Ltd. (RH.A.S.) at Port Pirie have overcome this problem by constructing a reverberatory furnace and ancillary cooling system of a novel design.Although a number of mechanical and metallurgical problems still remain to be solved, it is claimed that a workable continuous copper drossing process has been established.INTRODUCTIONLead bullion emerging from the blast furnaces at Port Pirie is at a temperature of about 1100°C and contains, among other impurities, about 1 per cent of copper.The first stage of refining is the removal of this copper by a drossing operation and in the past this was done, batchwise, by allowing the bullion to cool back in 100 ton kettles.At about 700°C, copper dross begins to separate as a crust on the surface of the kettle and this separation was allowed to continue down to about 450°C when the crust was brokenup and skimmed manually using a long handled, balanced, spoon. The dross was then smelted in a reverberatory furnace to produce a saleable copper matte and separate out lead bullion, which was returned to the drossing kettles. The copper content of the drossed bullion was then further reduced by a sulphur treatment process.The drossing operations involved hard manual labour under arduous conditions and the pouring of hot bullion into...

Jan 1, 1963

By C J. Stanley

Reflected light optical microscopy, or epimicroscopy, is one of the oldest techniques of modern mineralogy. At a relatively low capital cost, it is also very resourceful, and the analytical choice for the identification of most ore minerals. In ore mineralogy, reflected light optical images have the potential to overcome the main limitation of backscattered electron images from scanning electron microscopes, namely contrast of mean atomic number  below the spectral resolution of the backscattered electrons detector. This is the case for relevant ores, like iron (haematite-magnetite) and copper-zinc ores (sphalerite-bornite), but for both cases the pairs of minerals are easily discriminated in reflected light. The improvements in optics and electronics also made microscopy a powerful source of digital images, suitable for automated analysis for minerals processing, as the determination of liberation spectra. The drawback, however, has always been the impossibility to recognise the transparent minerals, which account for most of the gangue phases in ores, from the embedding resin, usually epoxy. In order to determine if there was any possibility to separate quartz from epoxy resins, reflectance spectra have been acquired for quartz and some commercial epoxy resins (Araldite, BuehlerÆs Epothin and Epocolor, Araldite spiked with fluorochrome from Struers), from 380 to 720 nm in 5 nm intervals. Reflectance of quartz and epoxy is very similar over the whole visible light range, and varies from 4.5 to five per cent. Epocolor, a red-dyed epoxy, reflects slightly more above 560 nm, as does Araldite spiked with the fluorochrome from 460 to 570, but for both the reflectance is still very close to that of quartz, under 5.1 per cent. This data set is final, and precludes the application of reflectance in light optical image analysis for assessment of liberation, phase quantification, or any other signal that requires separation of resin from transparent minerals.

Jan 1, 2008

Over the past five years, dedicated tertiary mining engineering programs have become financially unsustainable in Australia on the basis of undergraduate enrolments alone. The situation is worse in other minerals related disciplines and extends to the technical minerals education sector. This paper reviews the causes for the current situation. Indicators are presented which suggest that enrolment trends can no longer be attributed only to business cycles in the minerals industry but are also reflective of a fundamental shift in student interest in the sciences and resources based engineering disciplines. Reactive responses to changing trends are diluting and compromising the quality of mining engineering education. It is unlikely that the trends can be reversed or resisted. Tertiary minerals educators need to position themselves so that they can be responsive to on-going change. Two proposals are offered which aim to anchor mining engineering in a long-term sustainable manner. The proposals have a common educational component which is concerned with restructuring how mining engineering programs are presented and providing more flexible access to such programs. However, the two proposals have significantly different commercial components. The commercial component of first proposal is concerned with working within the traditional education framework of universities to endow a critical number of core staff positions. It effectively equates to fund raising. The second proposal is concerned with developing a stand-alone commercial operation around the education and research advantages of the global and multi-disciplinary university system. As a shareholder in this business, a university department would earn dividends that it could then use to support its education initiatives. This proposal provides a performance-based mechanism for supporting university minerals programs and has the potential to be cost-neutral. Both proposals are suited to resource sharing with a select number of international mining schools and to the incorporation of the other tertiary minerals disciplines under threat.

Jan 1, 2000

Just as Australia is part of the Pacific Rim, so the Pacific Rim should be viewed as part of the whole world. That applies in particular to that scarce commodity û money. There are five main factors of production in any mining development û mineralisation, materials, manpower, management and money. LetÆs focus on the upstream input û mineralisation, and the downstream input û money, especially in the area of communications. Unknown to many, the Competent Person reporting on Mineral Resources and Mineral Reserves has a direct and unavoidable impact on the companyÆs financial statements û the profit and loss account and balance sheet. With respect to reporting of the major asset of most mining companies û the resources/reserves û investors are getting a better deal now than at any time in memory as regards flow and adequacy of information. Australia has been a world leader in this regard. The outlook is for even more informative and useful reporting. The more rigorous reporting requirements for Exploration Results and Mineral Resources/Reserves, which have become a worldwide phenomenon over the last five years, will continue. This will be positive for the mining industry as a whole and for Australia in particular. However competition for the scarce investment dollar will also increase. Put simply, mining has many competitors, unconnected with mining, for the capture of the investment dollar. It behoves all participants to recognise that there are three investment factors which influence strongly the willingness of investors to put money into mining. These are Confidence, Credibility and Consistency. AustraliaÆs investment image stands high in these three respects, but the competition will continue to grow. AustraliaÆs lead must be maintained. However, some investment decisions should not necessarily be based on fundamental, quantifiable facors. Some of these are outlined.

Jan 1, 2004

The desire for minimising impacts of mining activities on the environment, and in particular, water resources; is usually tempered by the costs and practicalities of implementing æbest practiceÆ measures. This paper briefly discusses the theoretical and practical options for water management for typical mines and quarries in a range of environments to assess if adverse impacts can be completely eliminated or at least be perceived as doing so. The regulatory requirements for water resources management are usually an essential part of mine planning and operations that can be a primary focus for all stakeholders. As such they can distract attention from implementing best practice in water management for the benefit of the environment and the community for altruistic reasons that have a long-term benefit for the mining industry as a whole. Cost-effective options for supply, demand and quality management of water that comply with basic regulatory requirements are readily available. Making a mine æinvisibleÆ in a practical sense, in terms of impacts on water resources would require eliminating potentially contaminated discharges, minimising demand, maximising reuse and recycling and putting back a healthy proportion of the clean water that is taken out of the natural environment for use in mine operations. This may sound simple enough and there are many well-known standard approaches that are usually applied. But which are the most effective, and who benefits? New approaches to water management are becoming more affordable and can benefit the bottom line as well as the environment, but can they make a mine ædisappearÆ? The perception of whether a mine is æinvisibleÆ in terms of its impacts on water resources is as important as the actions taken to try to achieve such an objective. The viewpoints and thresholds of perceptions of the different stakeholders are therefore relevant to how ævisibleÆ mining activities become.

Jan 1, 2006

By McIlveen GR

The water pollution hazard posed by the derelict Conrad mine site, to the water and associated stream sediment of Borah and Maids Creeks and the nearby Copeton Dam storage, has been assessed. Mine water, tailings and tailings dump leachate have polluted water and stream sediments in Borah Creek downstream of the mine site. Acidity, arsenic, copper, lead, iron, silver and zinc are the principal pollutants. Under dry and low flow conditions, mine water was found to be the dominant polluting source, however, leachate and run-off from tailings dumps were also significant under and following wet conditions. Soluble arsenic, lead, iron and silver species in mine water and leachate were found to be rapidly incorporated into sediments, but acidity, copper, and zinc persisted in the creek water. Under low flow conditions, the water of Maids Creek is polluted with copper and zinc (up to 4.4 and 34 mg/l for copper and zinc respectively) and the pH is decreased (from pH 5 - 7 to pH 3 - 6) by entry of Borah Creek water. Values found in Maids Creek were variable and related to flow regime and distance downstream from Borah Creek confluence. Water in Copeton Dam storage, having a much larger volume of water with a higher bicarbonate buffering capacity (50mg/l versus 15mg/1), is not affected by entry of Maids Creek water. Polluted sediment from Borah Creek has contaminated Maids Creek for 2km downstream to Copeton Dam storage. Stream sediment downstream of the Borah Creek confluence, contains up to 1.0% As and 1.4% Pb in the less than 200 micron size fraction. Under high flow conditions, arsenic was found to be moved out from the mine site as insoluble species, associated with suspended sediment in Run-off.

Jan 1, 1988

Application of Agitated Leaching for Iron Removal from Silica Using Sulfuric and Hydrochloric Acid In this research, iron removal from silica used in glass industry was investigated using agitated leaching method. Silica sample was provided from silica concentrate originating from Chalchoog Silica Mine located in Abhar, Iran. The sample contained silica, iron oxides and clay minerals. For characterization of samples XRD and XRF analysis and atomic absorption method were applied. Silica and iron oxide (Fe2O3) grade of head sample was 98.41 per cent and 0.067 per cent respectively. Two inorganic acids (sulfuric and hydrochloric acid) were used in agitated leaching tests. Two series of L9 orthogonal array of Taguchi design with replication were used to determine the effect of parameters including acid dosage, leaching duration, ambient temperature and solid content on iron removal. The statistical calculations and analysis of variance (ANOVA) were carried out by means of DX7.0, Minitab14.0 and Winrobust1.02 softwares and also statistical calculations were checked manually using Excel software. Also multivariate regression was applied in order to forecast Fe2O3 conent of final product. The optimum conditions for leaching tests which sulfuric acid was employed are as follows: 40 minutes leaching time, temperature of 85¦C, 40 g/L acid concentration and solid content of 20 per cent. Under this condition the amount of iron oxide in silica was decreased to 0.042 per cent. The optimum conditions for leaching tests which hydrochloric acid was employed are as follows: 80 minutes leaching time, temperature of 75¦C, 30 g/L acid concentration and solid content of 20 per cent. Under this condition the amount of iron oxide in silica was decreased to 0.035 per cent.

Sep 13, 2010

IN preparing a sample of refined lead for analysis, it is necessary to exercise great care to avoid contaminatien, as the amounts of the various impurities present in market lead are very small. The lead is cut into convenient-sized pieces, which are flattened out with a hammer, so that, on putting tbe lead through the rolls, strips of about one inch in width and Ij32iu. in thickness are obtained. The hammer, anvil, and rolls should be carefully cleaned before use. The strips oflead are cut up into pieces of about one inch square. If the lead is roIled out very thin and cut up into small pieces there is considerable risk of the acid acting too violently and causing loss through frothing over. A blank assay on all the reagents used should becarried right through, along with the actual analysis of the lead. This is of the greatest importance, particularly with regard to the determination of such impurities as iron, sulphur, arsenic, and antimony.METHOD OF ANALYSISThe method of analysis is as follows: Take two lots of 600 gIm. each, place in a large beaker, add 2000 cc. distilled water and 750 cc. concentrated HNOs. Cover with a clock glass and warm on a hot asbestos plate until all action ceases. (If any white precipitate forms, filter off and examine for Sn and Sb.) Add 420 cc. H2S04 (1-1), and stir well while adding the acid: Allow PbS04 to settle, pour off the clear liquid into a 12-in. porcelain evaporating dish, and start evaporating down, the dish being placed directly on an 8-in. ring gas burner. Wash the precipitate three times by decantation using approximately 1200 cc. hot water for each washing, and stir well...

Jan 1, 1922

By O Pasca, B Hogg

Consistent slag blow end point detection remains one of the challenges in the Peirce-Smith converters at Mount Isa MinesÆ Copper Smelter. Under blowing results in foaming on copper blow and carry forward of oxide skims to the anode furnace. Over blowing results in high copper losses to the slag. Both present safety issues and contribute to lower copper production. The end points of the slag making phases are assessed by inspection of a bar sample. A bar sample is a thin accretion layer that adheres to a steel bar when it is inserted into the tuyere while the converter is blowing. This method is biased and subjective, so there is heavy reliance on operator experience. The Semtech Optical Process Control (OPC) system was installed in early 2002 for converter slag blow end point detection. Initial plant trials did not improve all aspects of converter operations, and uptake by operators was poor, so the system was not used. In early 2005, the Semtech OPC system was re-visited and another short trial was conducted to evaluate the permanent use of the system for slag and copper blow end point detection. During this trial, the Semtech OPC method was found to be superior to bar sampling for slag blow end point detection. The implementation and refurbishment of the Semtech OPC system has resulted in plant improvements and given a better insight into converter operation during blowing. Oxide skim generation carried forward to the anode furnace has been shown to decrease with increasing compliance with Semtech OPC. Some of the expected improvements to converter operation were not found to be significant. Semtech OPC is now well received and utilised by converter operators. Individual paper available only. Not included in book or CD ROM Proceedings.

Jan 1, 2005