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By M Armony, J F. C L Costa, J C. Koppe

Linear kriging methods fail to estimate local grades and local reserves for highly skewed variables due to three reasons: it uses only part of the available data information, it has no physical principles associated with the mathematical proceedings to minimise the problems, and it works with continuous variables while data are discrete because of the limited precision of any equipment. The techniques commonly used up to now to solve the highly skewed variables estimation problems were unsuccessful, unless mathematical rigor is abandoned. Even the method of multiple indicator kriging is not satisfactory. This paper presents a new framework, the field parametric geostatistics (FPG) that transforms noisy variograms into well-behaved variograms and justifies mathematically empirical procedures commonly used, as trimming or capping arbitrarily very high values. The method, when applied to non-skewed variables, yields similar results to classic kriging. The methodology is illustrated in a case study at a gold deposit in Brazil, and compared to results obtained by usual techniques.

Sep 26, 2011

Autogenous and Semi-Autogenous grinding has become an accepted method of reducing primary crusher product to micron sizes in a single or a two-stage grinding circuit. The elimination of secondary and tertiary crusher circuits and sometimes rod mills helps to lower overall operating costs and, in many instances, can make uneconomical projects viable. Selecting AG/SAG Mills have been rather a "hit and miss" affair over the years, but now with the many different types of tests available, accurate mill size predictions can be made, provided the test data is evaluated correctly. This paper endeavours to simplify the process of evaluating test data and sets down some guidelines for designers to follow when selecting AG/SAG Mills.

Jan 1, 1991

With commodities suffering dramatically low real prices, mining business margins are under intense scrutiny. Unfortunately, management systems developed early this century for manufacturing are driving counterproductive behaviours that choke productivity. The paper and presentation will explain this and present a proven methodology for increasing productivity. This will be supported by operational examples from Australian and American mining management to demonstrate the importance of modern business performance measurement and analysis systems. It will explain the importance of management systems in driving organisational change to sustain superior productivity and margins. The paper will explain why many executives and managers confuse production (a measure of volume) with productivity (which measures efficiency and effectiveness). It will explain how this and other counterproductive managerial and operator behaviours and attitudes are driven by traditional business management systems exacerbated by managerial and consulting fads. The paper will begin with the simple principle that to improve results one needs to first improve the process producing the result û and will show how this is often violated. Improving productivity then boils down to:accurately identifying opportunities using sound, modern measurement, analysis and reporting systems; methodically improving operating and commercial processes, and changing peopleÆs behaviours and attitudes to sustain changes in practices. The paper will include fundamentals of applying sound measurement and analysis to:processes directly, eg cycle time charts and their impact in cyclical (non-continuous) operations commonly used in rock breakage; drivers of productivity; and process results themselves since correct analysis identifies opportunities accurately. The paper will cover the importance of practical leadership and the need to follow a simple, solid plan for changing systems that drive behaviour. Overall, it will highlight use of modern performance Measurement, Analysis and Reporting systems to drive behaviours and improve margins - without capital investment û and make executive and managerial work easier and more effective.

Jan 1, 1999

By A McGann, P J. Coghill, D Miljak

"It is widely accepted that bulk ore sorting could provide a step change in processing of low-grade ores. For this to be achieved a rapid, accurate bulk sensor of grade is required as well as sufficient natural variation of grade in the ore stream. CSIRO trialled a magnetic resonance (MR) sensor capable of measuring chalcopyrite, and by inference total copper grade, on the 1300 t/h Ridgeway portal conveyor. The gauge produced an unprecedented set of data down to a 1 t scale for months at a time. This paper analyses the measured variation and compares it to a simple model derived from the bore core data and mixing within the block cave mine.The model of the small-scale (<1000 t) variation is developed using fractal methods which have successfully been used in the past for copper porphyry deposits showing a power law or near power law distribution of copper grade and vein sizes. These fractal distributions have two features highly favourable for segregating ore, a large proportion of low-grade pods and the large-scale spatial clustering of grade. We show the presence of fractal ordering in bore core data at short range in the Cadia Ridgeway porphyry deposit and measure its persistence in the crushed rock produced by the Ridgeway block cave mine over one month. The model is then extended to demonstrate the effect of varying head grade, mixing and pod (or diversion) weight on bulk sorting efficiency.CITATION:Coghill, P J, Miljak, D, McGann, A, 2016. Modelling Grade Variation in Crushed Ore at Cadia Ridgeway and Its Potential Consequences for Bulk Ore Sorting, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 77–88 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By S S. Kanchibotla, I Brunton

Most blast fragmentation models assume the rock mass properties, explosive properties and blast design variables to be constants and uniformly distributed within a blast. However, in reality all these input variables vary within a blast resulting in variation in the resulting fragmentation size distribution. A stochastic modelling approach is introduced in this paper to quantify this variation. This technique takes the input variables as statistical distributions rather than constants and through several thousand iterations, generates a statistical representation of the expected fragmentation resulting from a production blast. A case study of three production blasts from a large open pit mine are presented and the modelled fragmentation æenvelopeÆ shows good agreement with the fragmentation æenvelopeÆ estimated from Split image analysis. The various blast-related parameters influence different parts of the fragmentation distribution, eg rock strength and explosive velocity of detonation have most impact on the fines. The technique is used to identify the parameters that have the greatest influence on various size fractions. Such an analysis will be useful to direct resources to efficiently minimise the variation.

Jan 1, 2001

By Rabie A. S, Fouad K. M, Ammar A. A

The existence of Gabal El Kahfa ring complex, located in the Eastern Desert of Egypt, has been ascertained from aeromagnetic and aeroradiometric survey data as well as by aerial photography. Two maps for -the net aerial radiometric measurements reduced to ground level and aerial magnetic data corrected for the regional normal gradient of the earth's magnetic field have been constructed. The aeroradioactivity data have been interpreted geologically and analyzed statistically to outline various radiometric units and compute their charac- teristic statistics. The ring complex showed a circular radiometric feature and yielded a radiometric mean background and a standard deviation of 6.48 and 0.89 pR/h respectively. Besides, the observations showed a normal distribution. The aeromagnetic data have been reduced to the north magnetic pole, then filtered to produce the regional-and residual-component maps. Statistical trend analysis was conducted for the tectonic linea- ments resulting from the three magnetic maps, to define the structural framework of the area under study. This statistical study proved the exis- tence of trends in the east-west, northwest-south- east, northeast-southwest and north-south directions. The ring complex is characterized by a circular magnetic feature, whose average relief is 2150 nT. It is included within a high east-west trending magnetic zone. The latter represents a deep-seated uplift or anticline which is bordered from all sides by some faults of different trends.

Jan 1, 1988

A combination of the needs of business, employee desires and safety and health considerations is stimulating increasing attention to the time spent by people at work and the timing of that work. Particularly we are seeing: - innovative work schedules for 24-hour mining businesses; and - response from industry to accommodate the needs, even the desires, of employees in return for systems which are more productive and more capital efficient. There appears to be an evolutionary trend for business management to become more sophisticated and responsive to the need for achieving close to best cost work schedules to sustain continuous improvement. The underlying motivating forces driving this trend for improved techniques in organising attendance at, and time spent at work, is the seemingly inseparable combination of technological advance and ever-increasing accumulation of capital. The mining industry has not remained untouched by this thrust for ever-increasing need for best use of labour, to adopt advances in technology and to provide attractive opportunities for putting accumulated capital to work. An essential component of this on-going thrust is a substantial effort by the mining industry to improve the performance of labour by providing most-productive work schedules.

Jan 1, 1996

By Siwiec A

The laboratory investigations which are necessary to evaluate the mineral processing effectiveness usually include density separation of narrow size fraction of the feed and one of the products. In each size - density fractions the content of valuable mineral has to be determined. These data and yield in each size - density fraction can be specified by a matrix of partition coefficients. They are counterparts of recoveries. These coefficients can be compared with the mean recoveries at each density or size fraction or the total recovery, to determine which density - size fractions are processed in the best or worst way. The basic categories are: vector of metal content l _i 1711, 7t2, òòò, ltM I ò vector of particle size distribution x = I d1, d2, ..., dN I ò matrix of partition coefficients P11, P12, Pi N P _ P21, P22, ..., P2 N PM1 PM2..., PMN These three conceptions allow one to determine all the basic metallurgical parameters of a mineral processing unit. Losses of valuable mineral are connected with: ò mineralogical composition of the ore (types of minerals, their properties, dissemination, crystallochemical affinity, type and properties of gangue minerals), ò applied technology and technical equipment (beneficiation as a stochastic process, processing methods, process control, intergrowth liberation, water quality). Examples of application of the analytical method proposed are given for zinc - lead and coal processing plants.

Jan 1, 1993

By Brinkmann J. R

In the narrow stopes of South African gold mines, rockbreaking is carried out by drilling and blasting with safety fuse and igniter cord being used as the initiation system. The fuse/gniter cord system is used primarily because of its low cost, however several limitations of this method include: inaccurate delay time, unreliable firing, inflexible application to varied configurations, and the absence of dynamic interaction between holes. Alternative initiation systems that incorporate millisecond timing are being developed to overcome the limitations of fuse(tgniter cord systems. Current investigations by the Stoping Technology Division of the Chamber of Mines Research Organization (COMRO) into the effects of millisecond initiation are being conducted at a deep test site. Experimental blasts using various millisecond delays and the independent firing of holes with fuse/igniter cord are being studied in order to quantify the influence of delay time on the blasting process and to identify the best methods of applying millisecond initiation systems. The effect of design variables such as delay time, hole firing pattern, stemming, and panel layout are discussed. Blast results including throw distance and direction, muckpile profile and rock cleaning times are used in the discussion of different combinations of blasting variables.

Jan 1, 1990

By S Coward, J Vann, R Wolff, S Jackson, S Moayer, A Bye

Uncertainty about the future and orebody should significantly impact evaluation of mining projects. Scenario planning, widely used in other industries, for example in the petroleum industry, can provide organisations with an opportunity to explore the consequences of uncertainty on their future plans. By developing plausible scenarios, scenario planning assists decision makers by allowing them to make systematic and possibly effective decisions for the future. This paper reviews existing mine project evaluation in the context of a new framework called scenario-based project evaluation (SBPE) (Vann et al , 2012) that addresses many shortcomings of existing approaches. SBPE uses conditional simulations (CS) models as inputs which are evaluated against future alternative project pathways (æalternativesÆ). These alternatives are evaluated using multiple plausible images of the deposit (CS realisations) which capture realistic variability and as an ensemble, map uncertainty of various orebody attributes at fine scale. The alternatives can involve different mining, stockpiling, blending and processing strategies. The ultimate output is a (stochastic) set of cash flows for each alternative from which financial measures, such as NPV, can be derived. Alternatives can then be explored in the presence of against external scenarios such as changes in prices, costs, and taxation. The obvious problem with such data rich results is knowing which scenarios or group of scenarios are optimal.An innovative approach to robust stochastic optimisation (RSO) suited to the SBPE framework is presented here for the first time. This approach to RSO aims to deal with the large number of alternatives generated from SPBE. The goal of applying the RSO approach to SBPE is to identify robust strategic alternatives (project configurations) which have the flexibility to deal with variability and uncertainty of geological and processing inputs such as density, grade and process performance. By applying the proposed RSO method, it is possible to deal with uncertainty and identify the best project configuration in the face of a large number of envisaged scenarios. A case study is provided, in which we have tested the application of the proposed method and compared the result with conventional methods. An important conclusion from this research is that selecting the value of the penalty coefficients in the RSO approach proposed is (as is all optimisation) an exercise of trade-offs; a higher net present value (NPV) is generally associated with a higher risk and a lower risk is associated with a lower NPV. Indeed, this is a strong argument for considering the RSO approach outlined here over more conventional approaches.CITATION:Moayer, S, Vann, J, Coward, S, Jackson, S, Bye, A and Wolff, R, 2012. An innovative approach to robust optimisation for scenario-based mineral project evaluation, in Proceedings Project Evaluation 2012 , pp 141-148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By BTrubT M

In the roast-leach-electrolysis process for the production of zinc, iron contained in zinc concentrates is converted to zinc ferrite during roasting. At Canadian Electrolytic Zinc (CEZinc), the Outokumpu Conversion process is used to simultaneously leach zinc ferrite and precipitate the iron as jarosite. These simultaneous reactions, while providing good process stability, require a compromise between optimum conditions for maximum zinc extraction and efficient iron precipitation. An improved conversion process has been identified which can achieve >99 per cent zinc extraction and more efficient jarosite precipitation to residual iron concentrations of

Jan 1, 1993

By B L. Sainsbury, M F. Lee, A Penney

For most practical rock engineering purposes, stress versus strength conditions around underground openings for which rock masses fail and their various modes of failure, are reasonably well-understood and predictable. Some rock masses and particular rock types fail slowly and relatively quietly. However, others can fail rapidly, violently and maybe with the ejection of significant broken rock. In some countries and in some mines, the latter style of violent fracturing and failure of the rock mass is referred to as ‘strain bursting’. It can be alarming and extremely hazardous to nearby miners and machines. For such situations, the design and installation of appropriate ground support, to provide a safe work place, can be challenging. At any particular mine site, it’s often generally understood which local rock masses (rock types) are prone to strain bursting. Competent and strong siliceous rocks and some massive sulphides are often the main offenders. While some neighbouring, equally-competent and strong rocks might also fail, they do so more quietly and without ejection. To understand this contrast, a better understanding of the fracturing process is required other than simple and standard strength versus stress considerations. Suites of standard intact rock properties from numerous Australian mines have been used to define and help understand different high-stress failure styles for component intact rock; especially those prone to violent fracturing (strain bursting). Simple considerations of micro-fracturing (defects in the intact material), plus the available energy at failure versus the energy consumed during fracturing, distinguishes between over-stressed and competent rock types that fracture violently and those that don’t. CITATION:Lee, M F, Penney, A and Sainsbury, B L, 2018. Proneness of competent over-stressed intact rock to violent fracturing, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 170–184 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

Major Francis Hamilton Buchanan coined the term `laterite' (Latin; brick-rock) in 1807 for the red earths used for building blocks in southern India. Although these earths were actually weathered basalts, the term is now applied to weathering profiles developed upon a wide range of bedrocks. The Ni-laterites are a special class within the broad laterite family.

Jan 1, 1996

The Sons of Gwalia Mine in Western Australia is situated about 140 miles north from Kalgoorlie in arid country, where supplies of fresh water are difficult to obtain.Mine salt water is used throughout the treatment plant, whilst fresh water for domestic, boiler, and power purposes is pumped from a number of shallow outlying wells. The waters from all wells are constant in character, although they vary in the quantities of salts contained.An average sample of mixed waters gave the following analysis (Gr. per gal.):Sodium chloride 70.82Magnesium chloride 33.03Calcium chloride 26.98Calcium carbonate .. 11.57Calcium sulphate 22.71Iron oxide and alumina 2.10Silica and insoluble 4.58When this water is used in the boilers in its natural state it is scale-forming and intensely corrosive.

Jan 1, 1927

Traditionally, the development of a mineral resource project goes through a fairly set pattern of decisions from what commodities to search for; where to look; how to locate; what are the reserves; how can they be exploited with optimum returns for all stakeholders; where are the markets and what will be the price received; what financing arrangments? However, due to the unique nature of most mineral resource properties, the relative significance of individual parameters on the ultimate development decision will vary from project to project. Sensitivity analysis in its formal sense is most frequently related to the economic analysis of a project particularly in conjunction with the ultimate development decision making process, and acknowledges the uncertainty of the actual values with their impact on the corporate decision making yardsticks. In many cases, this analysis merely adds more values to confuse the decision makers who may well opt for some subjective rationale to overcome the numeric confusion. However, sensitivity analysis should be used more frequently to exploit the development dollar to its maximum, THROUGHOUT the phases leading to the development decision. It is essential to identify the critical inputs to the various decision tiers in a project as early as possible and direct the funds to ensure that these parameters are determined as accurately as possible. Examples are used to illustrate the need for an even-handed quantification of the parameters which affect the outcome of decisions en route to the final one while minimising the risk in making an optimum assessment in relation to development funds Available.

Jan 1, 1983

By L Kormos, V Lawson, G Hill, G Marrs

"In sulfide nickel deposits throughout the world, pentlandite and pyrrhotite are commonly found together along with varying amounts of chalcopyrite and platinum group minerals (PGMs). The mafic or ultramafic host silicates associated with the sulfide mineralisation commonly exhibit a complex assemblage of magnesium bearing silicates, many of which themselves contain significant nickel. Four types of ore are proposed, each presenting their own processing challenges. These are: economic grades of Ni, Cu and PGE (platinum group element) in a pyrrhotite-bearing sulfide deposit, with low pyrrhotite to pentlandite ratios  economic grades of Ni, Cu and PGE in a pyrrhotite-bearing sulfide deposit, with moderate to high pyrrhotite to pentlandite ratios uneconomic high pyrrhotite: low tenor deposits low-grade low sulfide, high MgO ± PGE deposits that can sometimes be economically mined and processed.The grades and recoveries of nickel concentrates produced from sulfide ores can be significantly impacted by the ore mineral texture, the nickel tenor of the sulfides, and the polytype of pyrrhotite which may be either hexagonal (non-magnetic) or monoclinic (magnetic). The mineralogy of the silicates is also of great importance, especially the magnesium silicates and those which tend to produce particles which are asbestiform or which affect slurry viscosity. Other magnesium silicates such as serpentine carry nickel in solid solution, limiting the recovery entitlement of nickel by flotation because serpentine is not amenable to sulfide flotation mechanisms. Differences in plant flow sheets and reagent assemblages are required to effectively separate these minerals.Experience from a variety of plant operations and from extensive flow sheet development programs are discussed. Examples are given of where significant improvements in nickel circuit performance can be made by adjusting plant physical processing conditions or process chemistry to compensate for measurable ore properties and characteristics.CITATION:Lawson, V, Hill, G, Kormos, L and Marrs, G, 2014. The separation of pentlandite from chalcopyrite, pyrrhotite and gangue in nickel projects throughout the world, in Proceedings 12th AusIMM Mill Operators’ Conference 2014, pp 153–162 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 1, 2014

By A Woodley, G Keir

The mining industry faces concurrent pressures of reducing water use, energy consumption and greenhouse gas (GHG) emissions in coming years. However, the interactions between water and energy use, as well as GHG emissions have largely been neglected in modelling studies to date. In addition, investigations tend to focus on the unit operation scale, with little consideration of whole-of-site or regional scale effects.This paper presents an application of a hierarchical systems model (HSM) developed to represent water, energy and GHG emissions fluxes at scales ranging from the unit operation, to the site level, to the regional level. The model allows for the linkages between water use, energy use and GHG emissions to be examined in a flexible and intuitive way, so that mine sites can predict energy and emissions impacts of water use reduction schemes and vice versa. This paper examines whether this approach can also be applied to the regional scale with multiple mine sites.The model is used to conduct a case study of several coal mines in the Bowen Basin, Australia, to compare the utility of centralised and decentralised mine water treatment schemes. The case study takes into account geographical factors (such as water pumping distances and elevations), economic factors (such as capital and operating cost curves for desalination treatment plants) and regional factors (such as regionally varying climates and associated variance in mine water volumes and quality).The case study results indicate that treatment of saline mine water incurs a trade-off between water and energy use in all cases. However, significant cost differences between centralised and decentralised schemes can be observed in a simple economic analysis. Further research will examine the possibility for deriving model up-scaling algorithms to reduce computational requirements.CITATION:Keir, G and Woodley, A, 2013. Regional trade-offs between mine water and energy use - a water treatment case study, in Proceedings Water in Mining 2013 , pp 21-28 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By S Porter

The Melbourne City Link Project is a privately funded road infrastructure project linking three significant existing freeways in the vicinity of the Central Business District. The State Government, through the Melbourne City Link Authority, has contracted Transurban to build, own and operate City Link for a concession period of 34 years before the road network is transferred to the State. Transurban has a contract with Transfield Obayashi Joint Venture (TOJV) to design and construct the works. The project is divided into the southern and western sections and the tunnel works comprised the significant component of the Southern Link. Outside of the cut and cover tunnels at the portals, the driven tunnels component was constructed by TOJV direct labour. TOJV subcontracted all design work to a joint venture of Hyder Consulting and CMPS&F (Hyder/CMP). The geology in the tunnel corridor and generally below the city of Melbourne is highly variable and constantly changing. The tunnels were driven, for the most part, in siltstone and sandstone of the Silurian age, but also intersected overlying basalts and clays. The Silurian bedrock is a fractured aquifer that is connected to overlying alluvial aquifers. Consequently, the construction of the tunnels was a complex engineering task. This paper details the operational relationships and procedures developed to deliver a design that was aligned to the construction constraints and delivered an end product that met all technical, quality, cost and program goals.

Jan 1, 1999

By L Schürmann, R Kendall

Social licence to operate is becoming part of a mining company’s DNA in the same way as health and safety. Consequently, mining companies are receiving increasing pressure from their shareholders to ensure that they add enduring value to the local communities in which they operate. Apart from the shareholders, a company has responsibility to suppliers, customers, employees, the government and the community, which means under the social responsibility model they must be accountable to the other stakeholders. External and internal challenges in mining are increasing the difficulty and complexity of mines to operate. The external mining environment has a big impact on mining operations and is driving matters such as the focus on safety, responsible mining and resource management, sustainability issues, profitability and productivity. Considering this, it is expected that the widespread implementation of Environmental, Social and Governance (ESG) related practices across the mining industry in the next ten years will increase, not just for the big players but for juniors as well. Companies, investors, governments and insurers who fail to act on ESG matters are to likely face greater risks. Demonstrating leadership in ESG will ultimately become a differentiating factor and market participants have much to gain from embracing ESG stewardship as part of their competitive advantage. Stock Exchanges have an important role to play in advancing sustainability in the capital markets. It is for this reason that the Sustainable Stock Exchanges (SSE) initiative was founded to serve as a global platform for exploring how exchanges can enhance performance on ESG issues and encourage sustainable investment. The SSE initiative provides an effective platform for dialogue between the United Nations, stock exchanges, investors, companies and regulators in the mining industry. The paper will explain why ESG reporting is crucial for the survival of a mining company and how the lack of transparency could be detrimental to its public image and shareholder relations. The paper will also identify bodies that regulate ESG reporting, as well as the available tools that provide guidelines on reporting ESG matters. Key ESG reporting parameters (at a global scale) will also be highlighted.

Jun 22, 2022

By G M. Hoffmann

Utilisation of lower grade (Jigging technology has progressed to a point where SishenÆs 50 to 60 per cent Fe run of mine (ROM) material, once considered as waste, can be beneficiated to produce a saleable 64 per cent Fe product. This has been confirmed through appropriate beneficiation testwork. Consequently, Sishen can now produce saleable product from material not currently included in the resource definition, significantly increasing the resource base of the mine and ensuring higher resource utilisation. Mine planning utilised the geological models to produce detailed planning schedules, reflecting the current and SEP plants separately, optimised to comply with product specifications of both the current and SEP plants and to confirm the viability of the low-grade resources identified as SEP feed material. The SEP product specifications have been derived by optimally matching iron ore market requirements with the revised resource base. A 64.0 per cent Fe lump product and a 63.5 per cent Fe fine product are the optimal SEP products. The SEP plant will be able to produce 10 Mtpa at an average yield of 60 per cent and a lump to fine ratio of 62:38. The plant consists of five major sections: namely crushing, material preparation, beneficiation, final product handling and quality control services. Maximum integration with the current Sishen plant was considered. Kumba currently has an agreement with Transnet to rail up to 23.5 Mtpa through the Sishen Saldanha iron ore export channel (IOEC). Transnet and Sishen Iron Ore Company have signed a Definitive Agreement that deals with the expansion of IOECÆs capacity, which increases KumbaÆs entitlement from 23.5 Mtpa to 35.0 Mtpa. The detailed enviro-legal impact assessments for the SEP indicated that the project has low enviro-legal risk as a result of it being a brownfields project incorporated into the current Sishen operations.

Jan 1, 2005