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By D L. Reid, G Nwaila, J Petersen, J-P Franzidis, Y Ghorbani, M Becker, F C. de Beer, L C. Bam

Traditional methods of gold extraction have involved comminution and processing via cyanide leaching, all of which are associated with energy, cost and environmental implications. Subsequently, numerous opportunities for improvement and optimisation strategies in gold mining and processing have been explored, including heap leaching, which has significantly lowered comminution costs. This paper explores the effect of the more energy efficient high-pressure grinding rolls (HPGR) on the comminution behaviour (especially on the crack density) and cyanide leaching performance of laboratory reactors study on run-of-mine gold ore comprising the Ventersdorp Contact Reef (VCR) and the Elsburg Reefs (ER), sourced from Carletonville in the Witwatersrand Basin in South Africa. The ore was comminuted using HPGR at three different pressure settings (120, 90 and 60 bar). Large (-16/+11.2 mm) and small (-5.6/+4 mm) particles of the HPGR product where then mineralogically characterised using optical microscopy, quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) and X-ray computer tomography (CT) before cyanidation. The results of the leach experiments indicated a correlation between gold extraction, particle size and crack density. Mineralogical characterisation of the ore indicates that the Fe-sulfides present in the VCR are likely to be more reactive than those in the ER, thus having a more favourable influence on gold cyanidation. Overall, the results show promise for the heap leaching of Witwatersrand gold ores prepared using HPGR and demonstrate the value of a multi-disciplinary geometallurgical approach.CITATION:Nwaila, G, Becker, M, Ghorbani, Y, Petersen, J, Reid, D L, Bam, L C, de Beer, F C and Franzidis, J-P, 2013. Morro do Ouro geological model with a metallurgical view, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 75-84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

Suddenly, mining has been thrust into the limelight. It has a large image that casts its shadow over New Zealand. Is it any wonder that resistance has heightened and that an almost unprepared populous is currently struggling to protect the very land they hold dear. Next to the atomic bomb, mining has the demonstrated power to massively change the land and its side effects can pollute many miles beyond the operation. During the past year, New Zealand concern over the possible effects of the mining proposals has become acute. This was specially so in the areas of special environmental quality, such as the Coromandel, and here a very unhappy situation has arisen.

Jan 1, 1981

Detailed cash flow forecasts have always been almost essential as a basis for judging the viability of proposed new mining projects. In recent years attempts have been made explicitly to take account, in such forecasts, of the uncertainties surrounding the assumptions upon which they are based. With the risk analysis approach, Monte Carlo simulation of the cash flows indicates in probability terms the combined effect of these uncertain basic assumptions. While the use of risk analysis has been widely discussed, few specific applications to real projects have been reported. The application of such an analysis in the feasibility study of the large new Deelkraal gold mine presently being established on the Far West Witwatersrand gold fields by the Gold Fields Group in South Africa is described in the paper. The paper also indicates how one of the major sources of uncertainty, namely the gold content of the ore, can be`quantified in objective probability terms. This feature distinguishes the application fran other published accounts in which only subjective probability assessments have been utilised.

Jan 1, 1977

The quantity, quality and detail of project information increases as project development moves from initial scoping level studies, to pre-feasibility and option studies, then definitive feasibility study and basic engineering stages. Data accumulates from metallurgical and vendor testing from various ore types and composites carried out to assess physical characteristics and processing responses of the ore. Over-simplification or assumptions about the orebody for flow sheet development can result in using æaverageÆ information for design. Use of averages of data can have adverse implications on sizing of plant and equipment and consequently on definitive study cost estimates and detailed engineering. In practice, the treatment plant workforce is faced with managing a non-homogeneous or non-average orebody in a variable operating environment that is not always predictable. This paper presents views on how to use the data generated from testwork in project development and for process and plant design. Examples of process design risk or operating risk are presented. Although this topic is applicable to the broad range of process design decision making in the minerals industry, this discussion references comminution, flotation and extraction processes for gold and base metal ores.

Jan 1, 2004

The stratigraphy of the Western Coalfield is briefly reviewed and the important units of the Lithgow Coal Measures, particularly the coal seams, are defined. The possibility of coal measures of Tomago age ocurring near the edges of the Sydney Basin is discussed onpresent evidence.Using data obtained from unpublished drilling records, detailed structural, isopachous and lithofaeies maps have been drawn. These show that the structure of the coal basin has been influenced by the underlying basement in many ways.The prominent jointing in the overlying Triassic sandstones is discussed in relation to jointing in the coal measure sediments.It is concluded that in addition to the general knowledge obtained with respect to the coal basin, useful information regarding coal quality and quantity can be gained by the study of broader sedimentary and structural features.INTRODUCTIONThe term "Western Coalfield" covers approximately the area from Katoomba to Rylstone, together with the smaller, separate Ulan area (Fig. 1). The area studied is part of the great sedimentary Sydney basin named by Osborne (1948). The first discovery of coal in Sitlt in the area was made in 1824 by Andrew Brown, although George Bass noted the presence of coal float in the Grose River in 1797. Production is recorded from the Western Coalfield in 1838 but mining was intermittent until 1868 when mines in the Lithgowvalley (producing coal from the Lithgow Seam) came into production. In 1882 the Katoomba Seam was first worked at Katoomba.The work of J. E. Carne (1903, 1908) defined the limits of the Coal Measure sediments and also contributed a great amount of valuable detailed information about the region.

Jan 1, 1960

By E M. Jones

On 26 June 2000 a hydraulic fill retaining barricade failed at the Bronzewing mine in Western Australia. The barricade failure resulted in the release of 19 000 m3 of saturated hydraulic fill into the mine, which caused the deaths of three miners. Following this tragic accident, the practices and procedures of mines using hydraulic fills came under intense scrutiny by regulatory bodies and mining companies. At this time, the use of hydraulic fill at NormandyÆs zinc/copper Scuddles mine was suspended and waste rock became the sole backfill material in use underground. By 2003, development of the mine adjacent to Scuddles, Gossan Hill had progressed to a point where a self-supporting fill material was required to enable full recovery of high-grade ore. Cemented hydraulic fill (CHF) was identified as the optimal fill type and work began on designing appropriate management procedures and controls to ensure the safe implementation. This work included definition of the fill properties, plant design and construction, reticulation system design, design of stope barricades and drainage systems and fill placement control and monitoring practices. CHF placement began on 16 July 2004 and has continued to date. Significant operational experience has since been gained in areas including plant performance, fill product quality assurance, barricade construction, stope drainage and in situ performance.

Jan 1, 2008

By D Johnston

Within the first full year of BarrickÆs Cowal Gold Mine operation, the Lake Cowal Foundation Limited (LCF) has already been delivering results consistent with its goal to protect and enhance the natural environment of Lake Cowal and its catchment area. The LCF is a non-profit Environmental Trust established in June 2000 in conjunction with the development consent process for the construction of BarrickÆs Cowal Gold Mine. Its primary goal is to protect and enhance Lake Cowal, a nationally significant ephemeral wetland located 350 km west of Sydney, New South Wales, Australia. Significant concentrations of water birds visit the lake and the Australian Heritage Commission listed Lake Cowal on the Register of the National Estate in 1992. The LCF is managed by a Board of Directors from representative member organisations including the Total Environment Centre, National Parks Association, Nature Conservation Council and Barrick Australia Limited. Although largely funded by Barrick, the Foundation also attracts external funding and works in partnership with a diverse range of other groups and organisations, beyond the mine fence. The total value of currently approved projects is estimated to be in excess of $7.1 million, which includes æin-kindÆ contributions made by the local community and in particular the Lachlan Catchment Management Authority (LCMA) and local farmers. To date, LCF has been involved with the development and implementation of 30 projects with a total of 34 project partners. LCF has worked with over 60 landholders to improve Lake Cowal and its catchment, with 6180 ha of land now being managed for conservation or sustainable farming in the local area. Many landholders have been, or are involved in property planning or participating in other training opportunities. Sustainability of LCF programs and outcomes will be assured by commitments to projects within four key themes: conservation, research and research support, sustainable farming and community education and training. The LCF works independently from the mining company and has no responsibility for the environmental management within the mining lease. It is about capitalising resources generated by the mine to enhance environmental outcomes in the wider Lake Cowal catchment area by working collaboratively with the local community, industry and government authorities to ensure the long-term protection of a unique wetland ecosystem affected by landscape scale degradation.

Jan 1, 2007

By Dif A. E N, Abdalla MH

The effect of multiple tunnels /cavities on the stress and deformation field of the soil media was investigated by using a two dimen- sional plane strain boundary element model. The soil was considered as an elastic, isot- ropic and homogenous media. The interaction of two circular and parallel tunnels/cavities was investigated. Depth of burial, tunnel spacing and surface load width were the system variables considered. The results of this study indicated that the vertical displacements of the soil media increases by decreasing the distance between the adjacent openings, the interaction between the two tunnels/cavities can be neglected for K/D > 5, while the load width has a minor effect except in the dis- tance of D from the center line of the load and for a depth of 2D.

Jan 1, 1987

By P Hatherly, A Melkumyan, D Wyman

Chemical species distributions in rock sequences can be modelled using Gaussian processes (GPs) to predict the weight percentage between known data points. This method can be improved by dividing the modelled area into regions of different mineralogy. In the context of many iron ore deposits, marker shales give the initial guidance of where these regions may lie. These shales give rise to distinctive peaks in the natural gamma downhole logs, which are conventionally identified by hand. A GP method has been developed to automate this task.Once the appropriate boundary has been located on the basis of shale occurrences, chemical assays from exploration drill holes are used to find the exact boundaries of interest. These boundaries divide the drill hole stratigraphy into regions of different mineralogy, each of which display their own distinct correlations between the main elements and oxides (Fe, SiO2 and Al2O3). Iron ore shows a negative correlation between Fe and Al2O3, but in banded iron formation (BIF) there is a positive correlation between these species. Similarly, SiO2 and Al2O3 have a positive correlation in the shales and ore but a negative correlation in the BIF. Correlations obtained within ore-, BIF- and shale-dominated regions are therefore better than those obtained using the entire log and can be used to improve the results obtained when modelling.

Sep 26, 2011

By R L. Koenig

Previous papers at Metplant conferences have covered the options for crushing and grinding circuit selection. High Pressure Grinding Rolls (HPGR) may have considerable advantages over autogenous milling circuits but test work and evaluating different grinding circuits must be done to establish which circuit provides the best option. The Hawsons low grade magnetite project provides a specific example in using thorough test work, careful simulations and detail in design to allow the evaluation of grinding circuit performance. Fortunately tools are available for this evaluation and the test work for the Hawsons iron ore is detailed in this paper. The results of the test work and simulation indicates that although the Hawsons iron ore is competent in terms of autogenous milling given the medium hardness of the ore in the Drop Tests, the HPGR testing indicates that the use of HPGR is likely to use half the energy requirement. This is a characteristic of the Hawsons iron ore and is likely to be valid for other iron ores in the Braemer Iron Formation which stretches from the Hawsons lease in New South Wales to Razor Back and South Dam in South Australia. The Hawsons magnetite iron ore resource has been known from the early 1960s when CRA explored the area. However, the Pilbara region was discovered in this era and this led to development of high grade direct shipping grade hematite ores. Carpentaria Exploration (Capex) rediscovered the magnetite whilst undertaking multi-commodity exploration in the Broken Hill district during 2009. The magnetite grade was found to be low at around 16% Davis Tube mass recovery (DTR) but despite this, the project provides a positive business case as a result of the following key factors:• The mineralisation is particularly soft for crushing and grinding with a Bond Work Index of 6.3.• The mineralised rock fractures easily preferentially along grain boundaries.• The location is close to mining infrastructure and a skilled workforce in Broken Hill, 60km to the North East.• It is close to road and rail infrastructure for access to the resource.• The only contaminant in concentrate is silica.• The resource contains many billions of tonnes of magnetite mineralisation.The low Bond Work index is a key characteristic of the Hawsons iron ore and the use of autogenous milling and HPGR circuits is compared to other iron ores indicating why the plant energy requirement may be just as important as iron ore grades.

Aug 8, 2011

The recent paper by Dr. Edwards upon the copper deposits of Australia furnishes a perspective upon that portion of the Commonwealth's mineral deposits which is the more welcome because it has been long overdue. The paper yields in compressed form and in handy arrangement for reference the more relevant data to end of 1938 for all of Australia's important copper deposits 'past"and. present, and for many of the lesser ones. The information supplied 'obviously' has 15een collected' painstakingly and compiled with discrimination.Such published surveys of a national character have been far too few.The Mineral Resources Survey branch of the Department of Supply and Shipping at Canberra has been engaged for several years upon comprehensive compilations of data concerning each of the more important minerals used in industry. Presumably the results will be published after the war. The group will constitute an impressive and valuable series.As yet the work has not been completed, and, for security reasons, much of that which has been finalized is not publicly available. This makes the paper by Dr. Edwards the more timely.In the compilation of data by those not acquainted at first hand with many of the districts involved it is inevitable that, from reading of the literature alone, certain misconceptions will arise relationships become confused; and some of the more recently acquired information unavoidably fail to be taken into account. One need only compare his own impressions of a district, gained from reading the published literature prior to inspection, with the impressions later arrived at following a visit, to realize the difficulties in appraising the various features,in their proper relationships.On the whole, Dr. Edwards has, kept such misinterpretations at a minimum, which is a tribute to the care he must have exercised in analysing the vast fund of data perused. A few errors of statement, mainly concerning, Queensland deposits, have been noted. None is vital, but in the interests of accuracy it seems well to point them out.QUEENSLANDMount IsaOn page 108 Mount Isa's prospective output of 12,000 tons of copper per year is stated as coming from the Doherty section (O'Doherty, Black Rock mine, R.B.),- the copper ore-body is said to occur in dolomitic limestone (-Page 110)-, and Mount Isa's copper output for 1938 from that source is given as 22 tons. On page 145 the same prospective copper output is stated as coming from a body lying out in the hanging-wall of the silver-lead-zinc...

Jan 1, 1943

By Met B. E

The increasing pace of modern mining makes constantly greater demands upon the several contributing departments of rock breaking and transport, and rock-drilling, as the spearhead of attack, has received a great deal of attention with respect to both machines and steels. By a series of mechanical improvements, combined with the application of selected heat-treated alloy steels, the rock-drill has now been developed into a machine capable of rapid drilling and long service under severe working conditions. As a factoryproduct made under strict metallurgical control it is as foolproof as, say, the modern automobile, and, like its prototype, it can be kept in efficient operation by a minor amount of attention during use and by periodical adjustments and replacements.The same cannot be said, unfortunately, of the drills with which the machine is supplied; in conventional mine-shop practice these are made of the best tool steel shaped and heat-treated under the poorest of metallurgical conditions.The crudities of steel-shop practice have, in fact, always prevented the full exploitation of the steels available at any time, and even at the present day the general standard of treatment offers a contrast with the quality of the steels which moves the metallurgist to amusement, despondency or outrage, according to his temperament. Nevertheless, the tendency persists to meet the increasing demands of the rock-drill primarily by the use of still better steels, and secondarily by improvement, of the steel-shop practice. Athird type of development is the introduction of factorymade tools in the form of detachable bits and rods. It is proposed in this paper to deal with these three aspects of the recent developments in rock-drilling.*Re-written from a lecturette given during the First Ordinary Meeting, 1936.

Jan 1, 1936

By Brown D. N, Troth D. A

Large blast furnaces demand high standards of preparation of feed materials which must meet tight specifications of chemical and physical quality. Measurement of these factors must be expeditious but the nature of the coke, sinter, ores and fluxes and the large tonnages involved requires substantial mechanical sampling plant. The equipment, its operations, and its problems, associated with the 5000 t.p.d. No.5 blast furnace at Australian Iron and Steel Pty. Ltd., Port Kembla, are described and the efficacy of chemical blending achieved in the ore blending yards and sintering operation, is reported.

Jan 1, 1976

By M Paine

Work to date has shown that the use of Al2O3:SiO2 ratios is suitable for identifying potential gibbsite bearing samples. Subsequent confirmatory XRD analysis helps to refi ne this initial identification. Based on these methods, gibbsite has been mapped in two common settings:1. along steeply dipping faults, or2. in association with stratigraphic contacts where one unit is aluminous (eg dolerite dyke).On a microscale, the samples studied illustrate an association between haematite, and to a lesser extent goethite, and gibbsite. In these samples the dominant forms of haematite are discrete crystalline phases of either microplaty haematite or euhedral martite. Two dominant forms of gibbsite were observed:1. vein style gibbsite that cross-cuts (or infill’s cracks) in goethite ± martite iron oxide associations, or2. gibbsite intimately intergrown with and forming a matrix to microplaty haematite.Some of the gibbsite microstructures observed suggest that it may have formed during a very hydrous, possibly hypogene, stage of the deposit genesis. The presence of this crystalline gibbsite, and in particular its occasionally euhedral form, suggests that aluminium was at some stage remobilised, at least locally, and then precipitated from solution as gibbsite. These observations suggest that these has been a phase of gibbsite precipitation that may have had a close but complex relationship with regards to the timing of the mineralisation processes, rather than formation as a result of late stage lateritic weathering.

Jul 11, 2011

Callide Coalfields produces a sub-bituminous, very subhydrous, low rank, steaming coal with good combustion properties, primarily for domestic power generation. Geological input into planning of coal extraction requires expedient production of detailed structural, lithological, analytical, geophysical and geotechnical data. The CSIRO-developed SIROLOG borehole logging software and hardware system allows for detailed spectrometric analysis of coal/interburden. The gamma-gamma and neutron-gamma SIROLOG techniques both provide improved prediction of ash content over other borehole techniques. The neutron-gamma technique also predicts density and some important ash constituents (especially iron, alumina and silica). The software/hardware configuration allows for quick, easy interpretation of coal seam depth and lithology, parting thickness and ash/ash constituent contents immediately after a borehole has been logged. Within certain mine areas in the Callide Basin, the iron content of mined coal is widely variable in both vertical and lateral extent within and between seams. This variability creates problems in predicting the slagging behaviour of æas-receivedÆ coal during combustion, especially where the iron content of the ash exceeds 19 per cent. Using the SIROLOG tool in co-operation with traditional borehole sample laboratory analysis results, patterns in this variability can be determined and related to geological properties and process of formation of the coal seams. Subsequently, areas of high iron can be predicted in advance of mining. Since 1992, on-going collection and interpretation of SIROLOG downhole geophysical log data has significantly contributed to a number of research projects related to gaining a preliminary understanding of the iron distribution and formation during the Coal MeasuresÆ deposition. Because the probe was able to record variations in coal mineral matter content, it was found to complement more conventional techniques such as reflected light petrography, X-Ray Diffraction and SEM techniques that examine the mineralogy of iron species. Additionally, software has been developed to allow integration of SIROLOG data into existing geology databases, enhancing coal quality modelling and daily prediction of parameters such as raw ash, silica and iron contents that are indicators of ash fusion propensity. The correlation of SIROLOG-derived iron geophysical traces between drillholes and other sample points highlighted lithological and structural controls in the iron distribution in the sequence previously not detected. This work has allowed the development of a methodology for predicting iron in advance of mining and reconciling as-sold coal quality to that predicted. Predictions are currently being assessed at the coal face as mining progresses through high-iron zones.

Jan 1, 2000

By Morrison AL

The volume changes occurring during the reduction by hydrogen of single, high-grade hematite pellets under isothermal and non- isothermal conditions were investigated using a time-lapse photographic technique. The major cause of swelling during iso- thermal reduction at temperatures in the range 600-1000¦C, was the disruptive stresses set up during the transformation of hematite to mag- netite. The severity of the disruption was temperature dependent; the degree of swelling increased with increases in the reduction temp erature. Under non-isothermal reduction conditions, in which the pellet temperatures were increased at constant heating rates over the temperature range 500-1000¦C, minor swelling (6-8%) occurred in the initial stages of reduction followed by pellet contractions of up to 15% in the final reduction stages. The low initial swelling and high final pellet shrinkages were due to a com- bination of the temperature dependence of the swelling mechanism, and the sintering of fine pores in the reduced iron in the latter stages of reduction at higher temperatures.

Jan 1, 1980

Grade control is a real challenge, and better sampling and modelling practices are among the tools that have proven efficient in improving it. Although based on rather trivial examples, this paper addresses the following important issues: How much of a challenge is it? How and to which degree can it be improved? And what kind of economic benefits should be expected in return for the corresponding efforts?

Jan 1, 1999

With the proving of a mineable orebody at Orlando in May 1961, Peko Mines N.L. was faced with the decision of whether to mill the ore on site or to haul it 25 miles to central facilities at Peko. Orlando was a relatively small orebody, so that it was decided to haul, although no reliable assessment of possible ore haulage costs was available.The necessity for a good haul road was recognised from the beginning and a 17 mile, 12 ft wide, single seal bitumen road was constructed, to link the mine to the Stuart Highway and Peko. The initial selection of 20 ton capacity diesel-powered end-tipping ore carts was made, with the best information available at the time.Since then some 130,000 tons of ore have been carted over a period of 3 years, and this paper presents the experiences of this haulage operation and the lessons learned.A second mine has just been brought into operation at Ivanhoe, 19 miles from Peko. For this haul it was decided to use an ore haulage vehicle of the side tipping road train type, which would cart some 70 tons, or more than three times the load of the vehicles initially selected.Only about 5,000 tons had been hauled at the date of this paper, but preliminary figures indicate a cost 01 1· 65d./ton-mile as against 2·47d. for the smaller vehicles.It would appear that the road haulage of ore from small outlying mines to a central plant can be highly economical, if certain basic rules concerning haul roads and vehicle selection are followed. This paper does not try to determine the maximum tonnages and haul distances which would finally make road hauling uneconomical...

Jan 1, 1966

By N Ross, N Goldup

In recent years the heavy mineral mining industry has started to look more closely at the feasibility of mining moderate to high slimes deposits. During the initial stages of orebody evaluation the primary purpose of the pilot plant is to produce heavy mineral concentrate for metallurgical evaluation. Hence, generally little consideration is given to the disposal of the waste material (slimes and tailings). This paper suggests additional, simple, low-cost, tests that can easily be incorporated into an initial pilot plant operation. With this data a more definitive evaluation of available waste disposal options can be made during the early stages of the project. Thus, permitting better project focus and utilisation of resources. These tests include free settling of slimes, natural slimes drying and consolidation (undrained and drained), tailings stacking angles, and particle size distributions of input and waste streams, etc. The objective and method of each test is summarised, together with its relevance to possible waste disposal options. The results of this preliminary testwork can later be used to expand upon and define further tests for the second phase of pilot plant operations, which will enable a more definitive evaluation of a proposed waste disposal solution.

Jan 1, 2001

Experimental petrology may be used to accurately constrain PTX conditions in order to calibrate and understand geologic processes. This method may be used to answer postulated questions, by recreating known geologic conditions and observing changes in the experimental charges. The purpose of this project was to determine the eutectic composition and temperature in the ternary system PbS-FeS-ZnS ¦ (Ag2S), at ambient and elevated pressures and elucidate if the sulfides of the Broken Hill orebody may have been partially molten during highgrade (granulite facies) metamorphism. The study determined the eutectic temperature and composition in the system PbS-FeS-ZnS to be 800¦2¦C and 62.5% PbS, 30.5%FeS, 7% ZnS respectively, at one atmosphere, and the eutectic temperature at 27 kbars was found to be 960¦C¦10¦C, with a eutectic composition enriched in ZnS relative to the one atmosphere eutectic. the addition of lwt.% Ag2S to the system depresses the eutectic temperature to 772¦2¦C at 1 atmosphere and below 810¦5¦C at 5 kbars. The conditions of peak metamotphism for the cental and southern areas of the Broken Hill Block, New South Wales, Australia , lie above the solidus of the PbS-FeS-ZnS-Ag2S system, strongly suggesting that partial melting occurred in the orebody.

Jan 1, 1998