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By K Faure

At Sams Creek a gold-bearing, peralkaline granite pophyry dike intrudes Ordovician-Silurian metapelite and quartzite. These metasedimentary rocks have undergone three phases of folding: a first phase of recumbent folds (F1), a second phase (F2) of northerly-trending inclined folds with a prominent crenulation cleavage, and a third phase (F3) of steeply plunging folds. The granite porphyry dike has a thickness of up to 40 m and intrudes thin lamprophyre dikes along its contacts. Deflection of the crenulation cleavage around the granite dike, shearing within the dike and its sinuous outcrop pattern indicate that the granite dike has been deformed during F2 and F3. The granite has been hydrothermally altered, with a first stage of magnetite-ankerite alteration. This first stage is cut by a second stage of quartz-pyrite veins and a third stage of sulphide, quartz and ankerite veins, accompanied by pervasive silicification represented by quartz-perthite-albite-rutile¦pyrite-ankerite-sericite assemblages. Lamprophyre is altered to an ankerite-chlorite-sericite assemblage. The sulphide veins are composed of arsenopyrite + pyrite ¦ gold ¦ galena ¦ sphalerite ¦ chalcopyrite ¦ pyrrhotite. The altered granite and the veins have been deformed and recrystallised. The competent sulphide minerals pyrite and arsenopyrite are fractured and brecciated, with fractures locally filled by galena, a ductile sulphide mineral. Vein quartz shows local cataclastic and mortar textures and develops pressure shadows around arsenopyrite. Alteration and mineralisation are confined to the granite porphyry and adjacent lamprophyre. These features together with the style of veining and the sulphide mineralogy indicate that the mineralisation was formed from a magmatichydrothermal fluid that was sourced from the granite. Oxygen, carbon and sulphur isotope values of the vein minerals (quartz, ankerite and sulphides) are also consistent with a magmatic source.

Jan 1, 2003

Alluvial gold mining is thriving in the Yukon Territory and Alaska. The scale of many operations is similar to those in New Zealand but there is greater government support for research and test work. As a result a great deal of information on equipment for the recovery of alluvial gold has been obtained. This paper is a review of the information with the aim of making relevant data available in New Zealand.

Jan 1, 1989

A new porphyry copper gold district has been discovered at Goonumbla near Parkes in central New South Wales. Endeavour 26 North is the largest deposit known to date with a possible resource of 166.4 million tonnes at 0.74% copper, 0.12g/tonne gold and 1.7g/tonne silver, using a cut-off grade 0.3% copper. Mineralisation is primarily bornite in the higher grade zones and chalcopyrite in the peripheral lower grade zones. Most of the copper, gold mineralisation is associated with potassic alteration. Two mineralised quartz monzonite porphyry intrusive stages have been identified and these are related at depth to a large monz- onite stock which may have been the source of some of the mineralisation. On the basis of detailed paragenesis studies, the potassic zone can be divided into three symmetric subzones. The low grade inner potassium feldspar subzone is confined to the later intrusive porphyry. The outer potassium feldspar subzone is the most highly mineralised alteration halo due to the focussed superimposition of two hydrothermal cycles which have overprinted intrusive and volcanic rocks. The fringing biotite potassium feldspar subzone reveals alteration minerals which are developed early in the paragenesis. Fracture controlled quartz sericite alteration with low sulphide content, fringes and, in part overprints the potassic zone. The restricted pipe-like nature of the alteration zones and related mineralisation suggests that Endeavour 26 North is repres- entative of a multiphase focussed porphyry copper gold system.

Jan 1, 1986

A research project was commissioned by the Australian Coal Association Research Program (ACARP) to improve the understanding of tailgate strata mechanics and to provide a more rigorous engineering basis for tailgate support design. A deformation mechanism termed æskew roofÆ was defined which relates the regional influence of differential horizontal strata movement (shear) about longwall extraction to gateroads. Confirmation of the mechanism was achieved by field investigations which included measurement of the shear displacement along weak interfaces. Under geological and mining conditions where the skew roof mechanism operated, strata units were found to move progressively further towards the goaf with height into the roof. 3D numerical modelling was used to assess the major geotechnical factors controlling the mechanism and to determine appropriate support strategies within a æskew roofÆ environment including the role of cables versus standing supports. The skew mechanism is considered relevant to; all roadways in the vicinity of longwall extraction including the faceline itself, chain pillar design, and support design.

Jan 1, 2005

By J E. Everett, K Jupp, T J. Howard

Precrusher stockpiles are designed principally as buffers to decouple the mining and processing operations. They are usually paddock dumped or dumped over a face to form fingers by dumping haul truckloads and reclaimed by front-end loader in an ad hoc manner. In addition, they are often not built and reclaimed to completion but continually added to and extracted from. While this design suits the mining process and is operationally simple, there can be little confidence in the grade of the ore that is fed to the crusher. This makes short-term grade control difficult and reconciliation back to the mine face imprecise. Well-designed and operated precrusher stockpiles can overcome these deficiencies.The different types of grade variability in mining are reviewed in this paper. The role of precrusher stockpiles in reducing short-term variability is discussed and their ineffectiveness in addressing long-term variability is highlighted. Their role in removing the serial correlation of the extracted ore is explained.Precrusher stockpiles carry out the four, at times competing, objectives of storing, buffering, blending and grade separation. Their actual design and operation result from a compromise between these four competing roles. These roles are explained in detail along with the advantages and disadvantages of the different types of precrusher stockpiles. The recommended blended-in blended-out stockpile (BIBO) design is discussed in detail. Matched pairs of BIBO stockpiles of limited tonnage built and reclaimed to completion retain the best knowledge of grade and facilitate the reconciliation process.Simulation studies have been carried out on BIBO stockpiles to understand the blending opportunities of the different options for building and reclaiming, and to identify the methods that achieve maximum blending. It was found that laying down rows in one direction and reclaiming across these rows gives the best blending. Matching the width of the reclaim face with the daily crushing requirements is also important. The length of the rows, and building in either one or two layers has little effect on the extent of blending.Appropriate design can provide a reasonable compromise between the four objectives.CITATION:Jupp, K, Howard, T J and Everett, J E, 2013. The role of precrusher stockpiling for grade control in mining, in Proceedings Iron Ore 2013 , pp 203-214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By D Craw, L Cox, R J. Norris

The Rise and Shine Shear Zone is a mineralised low-angle deformation zone traceable for at least 7 km through biotite zone schist of the Dunstan Range, central Otago. The zone is commonly believed to be similar to the actively mined Macraes deposit. The Rise and Shine Shear Zone occurs in the immediate footwall of the Thomsons Gorge Fault, a regional scale Cretaceous normal fault that juxtaposes chlorite zone schist against biotite zone schist. Most mineralised rocks are deformed and record a progression from early stages of semiductile deformation to more brittle cataclasis. Folds in mineralised rocks trend northwards. The mineralised schist is hydrothermally altered with variable silicification, sericitisation, chloritisation, replacement of titanite by rutile and carbonate alteration. Gold is associated with pyrite and arsenopyrite and occurs in both ductile and brittle microstructures. Sheared and mineralised schist is cut by north-striking fault zones which host mineralised quartz veins. Veins in the shear zone contain hydrothermal albite. Trace element analyses show enrichment in As, U, Th and rare earth elements. Many of the above features are similar to Macraes deposit, but there are important differences. In particular, the Macraes deposit is hosted in lower grade rocks and truncated beneath by a normal fault, Macraes has no U or Th enrichment, Macraes veins have no albite and folds at Macraes trend NW-W. Rise and Shine mineralised rocks have no Cr enrichment and no hydrothermal graphite.

Jan 1, 2005

Although cyclones have been around in their current form since the early-1890s, there have been some exciting new developments, which have extended their efficiency/operation. These developments have taken place with both dense medium and classification cyclones. The more noteworthy developments are:Inlet designInlet design is the determining factor in classification cyclone capacity and efficiency. The recently developed ribbon inlet with patented pressure bulge has not only resulted in unbelievable increases in capacity, but also in efficiency. Sharpness of separation corresponding to an alpha value of greater than four has been achieved! Secondary offtakeOne of the factors leading to reduced cyclone efficiency is the presence of coarse particles in the cyclone overflow. The secondary offtake has been developed specifically to scavenge these particles from the cyclone overflow with great success. Water injectorThe other major factor resulting in reduced cyclone efficiency is the presence of misplaced fine particles in the cyclone underflow. The water injector, which has been around for many years in various forms, can reduce this short circuit fraction by up to 50 per cent. 3-in-1 cycloneThe 3-in-1 cyclone combines the inlet design, secondary off take and water injector into a single unit resulting in the most efficient classification cyclone available in the market. The RejectorTMIron ore has a high yield to underflow and traditional dense medium cyclones have always been spigot constrained. The Rejector TM is an exciting new development whereby the spigot capacity has been increased substantially. The application of the Rejector TM will result in fewer/smaller cyclones being required for a given duty resulting in efficiency gains and reductions in both operating and maintenance costs.

Jan 1, 2002

By D Brett

"Mine waste storages including tailings dams and waste rock dumps represent arguably the biggest risk on a mine site from both physical and geochemical viewpoints, related firstly to structural stability and the consequences of failure and secondly from potential on-going seepage or run-off of acid and metalliferous drainage (AMD). The risks are most likely to increase during operations and continue through the closure and post-closure phases, with the waste storages likely to be the most difficult features to resolve in the mine closure process. Contaminated water quality from tailings dams and waste rock dumps can require treatment "in perpetuity" at a cost of hundreds of millions of dollars. The problem is increasing with ever larger mine operations and waste generation volumes. This paper identifies leading practice methodologies in planning and operating mines and process plants to minimise the risks from tailings storages and how this might also affect waste rock management and even the design of mine excavations. These methodologies require a "big-picture" approach to develop an understanding of the overall issues and identify synergies between the different operational areas on a mine site that can reduce overall risk. With a conservative approach and realistic allowance for future costs it is possible to facilitate decisions at the mine planning stage that can reduce risk and save cost over the long term. This is in contrast to the common approach where each operational area is looking to minimise its own costs with a short-term view. Incorrect mine methodologies can be developed by allowing net present value (NPV) accounting methods to trivialise future closure issues.Methodologies discussed include: Integrated Waste Management - Significant structural improvements to tailings dams can be achieved if the structures can be incorporated into the waste rock dumps. Risk of AMD can also be reduced by utilising the tailings and waste rock effectively. This could go even further to consider the placement of wastes to limit mine void environmental issues; Process Optimisation - Water quality and the nature of potential tailings dam structures can be highly influenced by the geo-chemistry of the tailings. This can be modified by processing, where simple changes such as maintaining separate streams of geo-chemically different tailings rather than recombining them or by initiating further processing to remove problematic minerals such as sulphides; Enhancing Geophysical Properties - The geochemical performance of waste repositories can be greatly influenced by the geophysical properties of the stored materials, particularly the air-water characteristics, which are influenced by particle size, density and permeability. The geotechnical properties can be enhanced by strategic paddock dumping, blending and compaction.These methodologies are demonstrated by case histories.CITATION:Brett, D, 2013. Mine waste risk minimisation by integrated waste management and process optimisation, in Proceedings MetPlant 2013, pp 247-258 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 15, 2013

Mine rehabilitation is a sustainability issue that has been revisited ad infinitum; however, the persistent lack of demonstrated on-the-ground performance and an increasingly intractable rehabilitation liability in Queensland continue to erode the credibility of the mining industry and regulatory bodies. For at least ten years the need to change the current, process-based approach to rehabilitation to an outcomes-based approach has been apparent. The ISO 14001 series temporarily diverted attention from this important point, however it would appear the limitations of an ISO 14001 approach are now more widely accepted. It is proposed that a successful outcomes-based approach cannot be achieved without meaningful community engagement. The apparently intractable nature of the rehabilitation issue will continue to generate conflict and criticism unless all stakeholders are encouraged to participate in the process of developing robust and practical outcomes for rehabilitation. Sharing the responsibility will ensure the best possible outcome. It is important to recognise the valuable resources inherent in community groups, many of whose committed volunteers have considerable expertise in relevant areas. Community groups should not be seen as adversaries but as allies in the process of solving problems that affect the wider community. Several projects that can be seen as test cases for the engagement of stakeholders exist, and in this paper the process of achieving multiple stakeholder engagement in the context of Environmentally Sustainable Development is discussed.

Jan 1, 2002

By N H. S Oliver

Five major veining events have been identified within the area surrounding the Mount Whaleback microplaty hematite deposit. These veining events can be directly correlated to the established deformation history of the Hamersley Province (Brown et al, in press). Vein formation temperatures of 203 to 231¦C have been obtained from primary fluid inclusions within veins which formed around the postulated time of ore formation. Preliminary proton induced x-ray emition (PIXE) analysis of these inclusions indicates KCl is the dominant salt species with varying levels of Ca, Fe, Ti, Mn present. It is suggested that some of these veins may have formed from feeder or effluent fluids from microplaty hematite ore formation.

Jan 1, 2002

Recent developments in diamond drilling practice have been chiefly 'concerned with modifications in drill design and 'operating technique whereby an increase in daily footage rates and reduced footage costs have been achieved without any marked improvements in the recovery of core. This trend is perhaps due to the general acceptance by the mining and drilling engineer alike of the belief that diamond drilling has definite limitations in exploratory work on mineral deposits characterized by irregularities in continuity and grade, such a belief arising from the fact that drilling technique has not yet evolved coring devices to ensure the full recovery of the rock and mineral formations penetrated.Current diamond drilling operations at Moonta and Wallaroo Mines, carried out by the South Australian Department of Mines, have attained remarkable results in completely eliminating core-loss by the use of a special double-tube core barreI.It is considered that assays of borehole samples taken with this special barrel have a reliability comparable, if not superior to that of similarly situated mine samples and, provided they are spaced satisfactorily, can be used as, a basis for calculating tonnage and grade. Formerly, with only partial core-recoveries, positive borehole results on narrow irregular lodes, such as those in the Moonta and Wallaroo Mines, could be accepted mainly as indications of the presence of mineralization, and could have only a limited bearing on estimates of ore reserves.The value of this special double-tube core-barrel lies In the fact that it guarantees good core recovery and, therefore, good samples, and eliminates the need for sludge-sampling, which is prone to give unreliable assay results from several causes, such as gravity concentration in the bottom of the hole and return water losses which cannot be overcome.In view of the increasing demand for minerals and the probability that the search for them will be carried on largely by boring, it is felt that it would be of interest and value to direct the attention of mining engineers to core-recovery results obtained by diamond drilling plants in South Australia and the features of the special core-barrel, designed by the writer, which has made this possible. Also, the writer is desirous of placing on record two other core-recovery devices designed to extract accurate samples in relatively soft or unconsolidated formations. The latter are used with percussion and calyx plants, respectively and their value has been proven on phosphate rock and coal deposits in South Australia.

Jan 1, 1943

By S Telford, J Weir

Heathgate Resources Pty Ltd (Heathgate) operates the Beverley Uranium Mine in South Australia, located on the plains between the northern Flinders Ranges and Lake Frome some 600 km north of the state capital Adelaide. The uranium orebody exists in permeable sands within the confined, highly saline Beverley aquifer, approximately 125 m below the ground surface and the uranium is mined using in situ recovery (ISR) technology. The Beverley mine is a highly technologically advanced ISR mine and is operated in accordance with stringent safety and environmental standards. The mine is currently licensed to export 1500 t of uranium oxide (U3O8) per annum. This paper outlines the fundamental differences between ISR operations and the more traditional uranium production methods, such as agitation leaching and heap leaching, where the ore is removed from the deposit, stockpiled, crushed, milled and leached on the surface. Solids tailings from either the mill or the heap are finally deposited in a tailing storage facility. ISR mining differs from conventional mining because the ore remains in place underground (in situ) and the groundwater contained in the ore-bearing aquifer is utilised as the mining fluid. This is achieved by drilling into the deposit and installing wells for extracting and re-injecting the groundwater which is fortified with chemicals. The fortified groundwater (ie mining fluid) flows through the permeable sands containing the orebody, dissolving the uranium. The pregnant mining fluid is then collected and transferred to the recovery plant where the uranium is captured (on ion exchange (IX) resin in the case of Beverley). The barren mining fluid is then re-fortified and recycled to the wellfields. Once mining is completed in a wellfield, the surface infrastructure is relocated to a new wellfield, and the mined-out wellfield is rehabilitated to its original surface condition. A comparison of 'standard' hydrometallurgical plants, heap leach and ISR shows a number of key differences, such as the rate of leaching, the level of control available to the operators, and the type of contact/reaction that occurs. While limited in its applications, ISR mining has proven successful at Beverley and provides another mining and processing method for the production of uranium.

Jan 1, 2008

By C Chambers

"AustraliaÆs mining sector faces challenges to its competitiveness; operating costs are being adversely affected as a result of volatile commodity prices and growing international market pressures.Diesel fuel-generated power used in typical remote mining projects is generally reliable and quick-to-deploy; however it is ongoing expensive operating cost.Many mines and communities in remote locations source electricity from diesel generation, and often pay over $300/MWh in fuel and carbon only (i.e. excluding CAPEX). These costs are expected to rise over time and are vulnerable to price shock events or supply chain interruptions in international markets.Solar photovoltaic (PV) and other renewables can be integrated with existing diesel units to provide a highly reliable power supply. Such renewables now provide a cheaper source of electricity while maintaining the mining industryÆs stringent reliability requirements; some renewables are now cheaper than diesel power ù supplying electricity at approximately $226/MWh.Also, significant funding and concessional rate financing have recently become available to support the development of remote solar-diesel (or solar-wind-diesel) hybrid systems, including: up to $2.2 billion of as-yet uncommitted grants through the Australian Renewable Energy Agency (ARENA) and is now seeking mining industry partners, up to $10 billion of concessional financing for emerging renewable technologies through the Clean Energy Finance Corporation (CEFC) and this commences July 2013, ongoing revenue support through the Renewable Energy Target scheme, and other regional support programs administered by various governments.This paper explores: the business case for renewables - what applications and when to consider them, the potential operating cost savings if solar was integrated, the technical challenges and common pitfalls, and how to overcome them, and the upfront investment costs and whether the site is eligible for Government subsidy programs.CITATION:Chambers, C, 2013. Off-grid solar in the mining sector - Can renewable energy reduce your operating costs?, in Proceedings MetPlant 2013, pp 71-85 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 15, 2013

The Coal Resources Survey commenced in 1974 as a search for Huntly Power Station coal, but soon developed into the most detailed regional coal search programme to be instituted in New Zealand. The program was initially conceived as geological in nature, but later included geotechnical, geohydrological, mining assessment, coal use, and environmental considerations in its investigations. The programme never undertook development work but has provided Government and the private sector with a sound basis for identifying development options. The discovery of large-scale coal resources in the Mokau, Waikato, and Taranaki regions and the lignite resources of Otago and Southland are a measure of the Survey's success. The directive by Government to phase out the NZCRS to a large extent coincides with the completion stage of the program. With most of the detailed regional study finished, it now remains to collate the data and publish summary reports at Coalfield and Coal Region level, in order to maximise the use and value of the data collected over the years.

Jan 1, 1987

By B Stump

Reliable particle size analysis in minerals processing plants is a critical factor to the economic return of a plant. As recovery of valuable minerals is compromised for particles outside the optimal size range, effective and reliable particle size analysis is more crucial than ever, particularly in the current upswing of the global commodities market. Inefficient particle size analysis can lead to excessive over-grinding, thereby significantly increasing energy consumption and reagent costs, whilst negatively affecting process operation, thickening capacity, water recovery and tailings disposal.Australia’s first installation of a particle size analyser in Iron Ore has been monitored with great interest by the industry. Previously, manual size sampling at Rio Tinto’s Paraburdoo fines processing plant involved off-site sample analysis, with a turnaround measured in days. The Outotec PSI® 500 particle size indicator, commissioned in July 2009, takes approximately three minutes per line at site.The paper will include details on the following:• plant description,• sampling design,• PSI® 500 analyser functionality description, and• key learnings from site.

Jul 11, 2011

By W J. Rankin

Metals are well suited to sustainable development goals. They are not biodegradable and have virtually an unlimited lifespan and the potential for unlimited recyclability. Thus metals can be considered as renewable materials. However mineral resources, the source of primary metals, are ænon-renewableÆ as their supply is finite, but this does not necessarily mean scarcity. In this paper the results from a series of Life Cycle Assessments of primary metal production processes for copper, nickel, lead, zinc, aluminium and steel have been used to examine how metals may contribute to societyÆs transition to sustainable development. Particular issues considered include:current metal reserves and how these may change in the future; some of the environmental impacts (Total Energy, Global Warming Potential and Acidification Potential) associated with primary metal production and how they will be exacerbated by declining ore grades; new processing technologies with lower energy consumptions and improved metal extraction efficiencies that will reduce reserve depletion and environmental impacts; increasing the utilisation of æmetals in useÆ by recycling, with particular reference to aluminium; and the potential impact of a carbon tax on metal prices and how this may influence the ways in which metals are used in the future.

Jan 1, 2002

Results of laboratory studies on the flotation of marmatite (zinc sulphide) with new reagents, which were developed to avoid the use of copper sulphate, are presented.Episulphides were chosen as the basis for the reagents because of their reported special chemical affinity for zinc and cadmium. Attempts were made to solubilize and introduce functional groups to episulphides with organic and inorganic acids, ammonia, phenol, aniline, diethylamine, and pyridine. As a class of reagents, the episulphide-amine combination was generally found effective in zinc sulphide flotation to a greater or lesser degree. Best results were obtained with ethylene sulphide-aniline combination. Although anilino-ethyl mercaptan is the reported reaction product of aniline and ethylene sulphide, it was concluded that the effective zinc sulphide flotation with ethylene sulphide-aniline combination is not entirely due to the formation of the mercaptan.The economics of the possible usage of ethylene sulphide-aniline reagent are discussed.

Jan 1, 1974

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

The Phoenix mine on the Mararoa Reef at Norseman, Western Australia, provides an outstanding: AUstralian instance of the recurrence of payable ore beneath the bottom of an abandoned mine, and an interesting and instructive example of the development ofideas with regard to ore recurrence in a particular district. The Mararoa Reef is the most productive of several hypothermal goldquartz vains in pre-Cambrian basic volc81olics which strike northsouth and dip on the average, 45 degrees east. The Phoenix minewas abandoned at 500 ft. vertical depth after producing 342,000 tons of 9.9 dwt. recovery grade (equivalent to nearly half of the total production of the Norseman field) from a 2,500 ft.. long, horizontally disposed oreshoot, which is reported to have had an ore outcrop only 30 ft. in length.Interest in the field was revived in 1933, and by 1941 new ore mined and developed on the Mararoa Reef by Central Norseman Gold Corporation N.L. amounted to approximately 700,000 tons of 6.7 dwt. recovery grade. In the same period another oreshoot of similar size and grade was developed by Norseman Gold Mines N.L., south of the old Mararoa company's site. As shown by the plans, the ore occurs in discontinuous shoots. The intervening area of shear is poor in quartz as well as in gold. Geological work on behalf of Western Mining Corporation Ltd., and Central Norseman Gold Corporation N.L. has been in progress in the mine and in the field more or less continuously from 1913 to 1941 and again since 1946. This paper describes the successive advances in the understanding of the exploratory problem up to late 1941, to which several investigators have contributed. It is published by permission of the Board of Directors of Central Norseman Gold Corporation N.L., owners and operators of the Phoenix and other mines.Development of the Prospect.In 1933 Western Mining Corporation acquired an option over the Phoenix property and adjacent leases. H. E. McKinstryl visited the mine and recognised that the ore occurred primarily on the flatly dipping sections of the vein, as distinct from the steeply dippingsections, in a wide shear zone with reverse movement. Many of the flatly dipping fractures were seen to exhibit tension phenomena and to link one shear plane to the next below on the footwall side. The flat links carried much more quartz than the steeper shears.Later, H. J. C. Conolly, assisted by J. D. Campbell, examined the prospect and by contouring the vein with reference to an inclined...

Jan 1, 1950

Three stages are involved in the complete design and evaluation of an open cut mine. These are:1. design of the optimu,m ultimate pit, and selectionof the optimum mill capacity,2. development of production schedules, with intermediate pit designs, and3. evaluation of the project, based on factors from stages 1 and 2, by means of discounted cash flow analysis.Stage 1 requires relatively complete information on metal distribution, metallurgical performance, and cost factors, which is used to design a series of pits, corresponding to a range of milling rates.For each milling rate considered there is a unique pit design which maximizes operating profitability. The computer outlines this design (in terms of size, shape, and location; tons and grade of ore; and tons of waste), by considering the effect on profitability of mining each block in the mineralized inventory in relation to every other block which would be affected by its removal.The computer selects only those blocks for mining which result in an overall increase in profitability, maintaining pre-determined wall slope conditions throughout.Both operating profitabilities and capital costs increase with throughput, and the two curves will combine to produce a flat peak in net profitabilities at a certain rate, with its associated pit design.Stage 2 can maximize head grades early in the life of the operation. This increases the projected present value, but there are good arguments for maintaining steady head grades throughout the life of the mine.A modification of the programme used in Stage 1 is used here.Stage 3 is a conventional discounted cash flow analysis, using factors obtained in stages 1 and 2. It can be computerised, but a manual treatment is probably just as fast overall.

Jan 1, 1970