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By Cotton R. E, Cox R

Digger Rocks is one of several nickel-bearing sulphide deposits localised within komaLiitic volcanics of the Forrestania Greenstone Bell within the Archaean YiIgam Block of Western Australia. Exploration and evaluation to April 1990 have delineated a resource, at a nominal cut-off grade of 0.5 per cent Ni, of 1.9 Mt at 1.1 per cent Ni within a lensoid sulphide body which strikes NW, dips 50°SW, and occurs at a depth of 30 - 110 m below surface. There has been no production from any of the Forrestania nickel deposits to-date. The deposit, comprising both disseminated and massive sulphides, has maximum dimensions of 400 m strike, 115 m vertically and 90 m true width. Generally the massive sulphides occur at the base of the disseminated sulphides, on or close to the base of the Digger Rocks dunite. The two main massive sulphide lenses have maximum dimensions of 120 m strike, 75 m vertically and 16 m true width (northern lens) and 60 m strike, 25 m vertically and 4 m true width (southern lens). The average grades of the massive and disseminated sulphides are 5.9 per cent i and 1.2 per cent i respectively. The massive sulphides generally have sharp hangingwall and fOOlwall contacts and display strong internal grade anisolropy.The massive sulphides are mainly within the supergene zone and consist of violarite, pyrite and marcasite. The disseminated sulphides are mainly within the primary zone and consist of pentlandite, pyrrholite, pyrite and minor chalcopyrite. Alteration zones, up to six in number, are complex in detail. The sulphides are capped by an average of 30 m of sub-economic, leached, siliceous, oxidised material.A genetic model for the deposit is described which places Digger Rocks in Category 2 (sulphides in large layered dunite bodies) of the latest classification of komatiitic nickel sulphide deposits in the Yilgam Block of Western Australia by Hill and Gole (1990).

Jan 1, 1992

By B Reid

"Since the commencement of mining operations at the Cowal Gold Operations (CGO) in 2005, reverse circulation (RC) drilling has been the preferred method for grade control (GC) sample collection. This method was selected because it allowed:for multibench drilling (20 m hole depths for two benches of mining) to aid mine planning increased data density for comparison against the wide spaced ore reserve model angled drill holes to intersect perpendicular to the strike and dip of the shallow dipping mineralisation ability to take two metre sample intervals to enhance the understanding of the mineralisation’s short-scale variability and provide the ability to flitch mine.From June 2008 to December 2013, RC GC was performed using a UDR rotary cone splitter. The field duplicate data over the period displayed strong precision, with a correlation coefficient of 0.94 and an average relative per cent difference (RPD) of 21 per cent for gold. Up to 66.1 per cent of field duplicate data greater than 0.1 g/t fell within ±20 per cent RPD. This is within limits of industry best practice. The Mine to Mill reconciliations over the same period showed the estimated GC grade was 7.7 per cent lower than the calculated head grade (CHG).In December 2013, the Progradex sampling system (PGX) was introduced at CGO due to its advertised ability to capture 100 per cent of the drill cuttings for the complete sample interval, inclusive of fines. Analysis of field duplicate data indicates that since the introduction of the PGX, the sample precision has drifted. From January 2014 to February 2016, the correlation coefficient was 0.92 and up to 51.2 per cent of field duplicate data, greater than 0.1 g/t fell within the ±20 per cent RPD. Over the same 26 month period, the Mine to Mill reconciliation improved to one per cent lower than the CHG. Granulometric analysis of the RC samples collected from the PGX indicated the fines material(<212 µm) averaged up to 22 per cent of the samples mass and following assay determination, the fines material represented a weighted average of 31 per cent of the total gold content within the sample.This paper highlights the:importance of the complete capture of all drill cuttings during an RC drill programinfluence of fines material on the sample quality and accuracyimpact sampling of the fines material has on the Mine to Mill reconciliation performancechallenges experienced in commissioning a PGX system.Citation:Reid, B, 2016. A Fine Looking Sample - the Importance of Fines in Grade Control Sampling to Mine to Mill Reconciliation, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 28–38 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By M Olsson, U Nyberg, K Widenberg, P Svedensten, F Ouchterlony

During 2007 and 2008, the project Optimal Fragmentation in Blasting II was conducted at the Långåsen quarry of NCC Roads AB near Arlanda. The main goals were:an evaluation of the effect of using electronic delay detonators (EDDs) in quarry blastinga validation of the design curve concept introduced at the Vändle quarry.Five production blasts were monitored. After a first trial round, the remaining four rounds each had about 100 Ø89 mm holes in a 14–19 m high bench charged with site mixed emulsions. In rounds 1 and 2, a tighter pattern than normal was used in one half of the rounds, raising the specific charge there from 0.7 to 1.0 kg/m3. Non-electric initiation was used with two holes per 25 ms delay in-row and 67 ms between rows. In rounds 3 and 4, electronic delay detonators were used instead, with 10 and 5 ms in-row delays respectively.The monitoring encompassed drill hole collaring and alignment, in-hole deviations, the rock structure in the bench faces from 3D imaging, first row burdens, etc. Eleven 400 t samples were taken from the muck piles and sorted in the quarry and sieved in the laboratory (lab). The lab data made up a fines tail that was grafted onto the in-pit sorting data to form sieving curves for the test piles. These curves were then compensated for the absence of boulders to construct the sieving curves for the blasted muck pile.These have been used to derive fragmentation model formulas for the non-electric rounds, also called design formulas. They are based on blast geometry, charging data and the properties of the rock mass. The formulas may be used to estimate the effect of changing blasthole pattern, borehole diameter and stemming length for example.The use of EDDs gave several unexpected results. In comparison with non-electric initiated rounds with a somewhat lower specific charge the fragmentation was much coarser; x50 increased from 160 to 200 mm. The effect of raising the specific charge in the non-electric initiated rounds from 0.72 to 0.99 kg/m3 was a much finer fragmentation; x50 decreased from 160 to 120 mm.CITATION:Ouchterlony, F, Nyberg, U, Olsson, M, Widenberg, K and Svedensten, P, 2015. Effects of specific charge and electronic delay detonators on fragmentation in an aggregate quarry – building fragmentation model design curves, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 727–740 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By J S. J van Deventer

"Conventional wisdom is that gold not assayable is not recoverable or does not exist. There has been no formal study on the possibility that gold assays using advanced spectroscopy such as mass spectrometry and neutron activation could grossly underestimate the gold recoverable by proprietary extraction techniques. Such gold is not considered here to be æinvisibleÆ to detection but rather æabnormalÆ or ædistortedÆ at atomic level. Large-scale extraction of gold from æabnormalÆ ores has not been demonstrated, hence this emerging field still lacks credibility and acceptance. For fear of harming their reputation, few academic researchers or companies are expected to venture into this field until it is well proven. This paper aims to create awareness amongst metallurgists of the potential of æabnormalÆ gold ores by reviewing unconventional observations, the pseudoscience mainly available in non-peer reviewed web sites, and hypotheses for the recovery of ænon-assayableÆ gold, including: the occurrence of high levels of nano-sized gold in clays detectable by high-precision analytical instruments, which represents æinvisibleÆ gold accounts of ambient transmutation of elements, mainly using thermal methods orbitally rearranged monoatomic elements (ORMEs), which are virtually undetectable by conventional means, and their conversion to normal metals the possibility of a æhigh spinÆ state of transition metals the formation of microclusters altering the chemical behaviour of gold and the possibility of clustering with other elements. It is suggested here that gold in ores displays a range of clustering, from ænormalÆ gold amenable to conventional extraction to the ORME state. The concepts of æintermolecular waterÆ in forming complex salts locking up precious metals, electro-dissolution in strong acids, and electrowinning at both the anode and cathode are discussed as a means of treating æabnormalÆ gold ores. It is also possible that the gas phase extraction of gold chlorides under controlled temperature and pressure conditions, as well as transferred-arc plasma fuming of gold through carbothermic reduction of sulfides, could be used as a basis for extraction of gold from æabnormalÆ ores.CITATION:van Deventer, J S J, 2013. Is there gold that we do not recognise?, in Proceedings World Gold 2013, pp 27-34 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 26, 2013

By R Coleman

The flotation mechanism plays a key role in the flotation process. It is used to provide the contact between solid particles and bubbles and also the energy for these particles and bubbles to attach. The mechanism must therefore provide sufficient mixing to keep the solids in suspension so that they can be transported into the froth and recovered to the concentrate. The design of the mechanism is critical and over the past decade Outotec has developed and optimised a new mechanism design to improve metallurgical and energy performance. The FloatForce® mechanism consists of a rotor and stator arrangement and has been specifically designed to provide sustained mixing at higher air flows and lower power inputs.Over 500 FloatForce® mechanisms have been installed in existing and new operations. This paper outlines the technological aspects of the FloatForce® mechanism and provides metallurgical, operational and energy performance results from a number of flotation circuits in which these have been installed.

Aug 8, 2011

By R J. Beazley, M C. Woods

"The International Cyanide Management Code (the Code) is a voluntary industry program for gold miners and associated cyanide transporters and cyanide producers. By becoming a signatory, a company commits to follow the CodeÆs principles and implement its standards of practice.Signatories are required to undergo an initial certification audit within three years and a recertification audit every subsequent three years. Recertification audits evaluate compliance over the preceding three-year period. This approach presents a number of challenges. Golder Associates has undertaken in excess of 75 initial certification audits and 25 recertification audits; more than any other audit firm. This paper outlines some of the challenges identified and lessons learnt from the recertification audit process. Central to the process is the challenge for organisations to maintain commitment to compliance over the full three-year period and effectively address deficiencies or non-conformances that may have occurred during that period in a prompt manner.The International Cyanide Management Institute (ICMI) provides guidance in evaluating deficiencies or non-conformances, which requires consideration of the æcauseÆ, ædurationÆ and æongoing compliance effortsÆ and an assessment of the concept of ægood faithÆ in response actions. Golder AssociatesÆ experience with the recertification process highlights some common deficiencies with Code compliance programs, such as: system breakdowns (leading to ineffective communication between departments or loss of information) exceedance of discharge limits inadequate inspections, maintenance activities and associated record-keeping.Such deficiencies can be attributed to: personnel changes organisational changes or structures management systems (eg integrated or standalone) awareness and interpretation of Code requirements transparency of management decisions with Code implications.We have identified that ongoing programed assessment is an effective strategy in maintaining Code compliance.CITATION:Beazley, R J and Woods, M C, 2013. Cyanide code recertification - the three-year challenge, in Proceedings World Gold 2013, pp 247-254 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Sep 26, 2013

THE de-silverizing of base bullion at the Port Pirie works is carried out in accordance with the principles of the well-known Parkes process. The base bullion produced by the blast furnace department carries (apart from silver values) impurities, the chief of which are copper, antimony, and arsenic. In order to more clearly indicate the grade of the base bullion, the following analysis, representative of a half-year's production of base bullion, is submitted...Before proceeding with the actual operation of de-silverizing, it is necessary that the impurities, copper, antimony, and arsenic, should be eliminated. This is accomplished in the following steps :- (1) Removal of Coppel - Copper is largely present in the base bullion as dissolved sulphide, and this is removed by liquation in a reverberatory type furnace, of which the following are the essential details :-Working temperature 7500 to 8500 C.Coal consumption per 24 hours 2 tons.The hearth of the furnace is encased in a steel tank 22 ft. 4 in. long by 13 ft. 4 in. wide by 2 ft. 10 in. deep; the bottom of the tank is covered by a depth of composition conforming to the invert :-Cement 39 cwt.Brick dust 8.4 tons.Fireclay 0.6 tons.Sand 0.6 tons...

Jan 1, 1922

By A N. Danoucaras, S E. Goater, D Hearne, A M. Bansuan

It is globally recognised that existing and emerging mining activities should be conducted in a æsustainableÆ manner for the entire life of mine. Many companies annually publish corporate sustainability reports to demonstrate their actions in accordance with international expectations. This concept of sustainable mining practices also applies to mine water management, with influences often extending beyond site operations, affecting surrounding catchments and community users. This paper explores differences in conceptual and operational terms of æsustainableÆ mine water management within the Philippines. Outcomes of a review of corporate sustainability reports, governance documentation, research programs, and stakeholder knowledge acquired through action-research workshops are presented. The paper aims to inform and support future capacity building exercises delivered by the International Mining for Development Centre (IM4DC), with outcomes tailored to government officials and policy makers of developing countries. The project is funded by IM4DC, which is working with AusAID to identify needs and develop capacity with regard to mining for development; specifically, issues pertaining to governance and regulation, social and environmental sustainability, and operational effectiveness in developing countries.CITATION:Bansuan, A M, Goater, S E, Danoucaras, A N and Hearne, D, 2012. Integrated sustainable water management in mining for development in the Philippines, in Proceedings International Mine Management 2012, pp 205-226 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 20, 2012

NEARLY all problems in mining engineering involve the transport and distribution of materials from place to place, and in general the most economically managed mines and plants are those in which the transport of materials has been carried out most efficiently. Of all these transport problems, the hoisting of ore out of the mine and the distribution of same to the various treatment works is perhaps one of the most important. It is proposed in the present paper to traverse the conditions,affecting the location, scale of operations, and design of the main shaft and head gear at the Mount Morgan mine; afterwards describing the designs and workings of the shaft house, winding engine, and transport from the shaft house to the treatment works.LOCATIONWhen the copper-gold ore was developed sufficiently to determine approximately the boundaries of the ore-body, it was found that the existing vertical shafts would be wholly inadequate to deal with the increased quantity of ore required to be handled. It was proposed, therefore, to construct a new shaft, and to handle in this...

Jan 1, 1911

By P B. Hills

Almost a quarter of a century since Bridges (1993) documented techniques for the assessment of ground conditions in a seminal paper in the Proceedings Second International Mining Geology Conference, the necessary role of the geologist in recording geotechnical data on exploration properties and in mines remains. Typically, the geologist is the first professional on the exploration property. Of course, most exploration properties don’t become mines. However, when a property does start to come together and form a coherent mineral deposit and professionals from across the minerals industry spectrum, including specialist geotechnical engineers, become increasingly involved, it remains the geologist who has the most intimate knowledge of the deposit. By association, that knowledge extends to the character of the rock mass.Throughout the various phases of prefeasibility, feasibility, construction and production, culminating in the mature mine, the knowledge of the rock mass held by the geologists continues to grow. In the current era of minimising cost and optimising profit, meeting the requirements and expectations of stakeholders ranging from fellow employees to investors, industry and financial regulators and the broader public, in a social environment where occupational health and safety concerns are of uppermost concern in every endeavour, the value of the geologists’ observations cannot be understated. Mines nowadays employ more geotechnical engineers than they did in the early 1990s when Bridges (1993) wrote his paper. More funds are available for specific geotechnical investigations of exploration properties and mines; none-the-less, those programs remain limited in their extent and there is a wealth of additional data available for collection with the appropriate training, at little additional effort. Fundamentally it is all about the numbers. Any hole not geotechnically logged is a hole that will need to be drilled again if the data is required. Any face, surface or underground, not geotechnically mapped is one that may need to be mapped a second time. That doesn’t mean every hole or every face. However, it is the proposition of this paper that the opportunity for additional geotechnical data to be gathered during traditional geological investigations is an opportunity that cannot be ignored. Occupational health and safety requirements demand that the geotechnical risks associated with mining are appropriately managed. Mining regulations in most Australian and overseas jurisdictions requires the consideration of geotechnical risk through formalised management plans. The Joint Ore Reserves Committee (JORC) Code requires the consideration of modifying factors more than ever before. The benefit to be realised through improved geotechnical understanding by geologists on the ground leads to improved occupational health and safety, optimised reporting compliance, and improved financial and social outcomes for the exploration property and ultimately for the mine that follows.CITATION:Hills, P B, 2017. The necessary role of the geologist in geotechnical data gathering, in Proceedings Tenth International Mining Geology Conference 2017, pp 347–354 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By Singh DP, Singh TN

The present study attempts to critically review the pillar-design as required by Coal Mines Regulations of India vis-a-vis latest rockmechanics formulae. Equivalent material modelling was the approach adopted for testing the safety and stability of the pillar sizes predicted by various formulae. Two parameters, considered here for calculating pillar sizes was the stresses acting over the pillars and the strength of the pillars. Stresses acting on the pillars were calculated by the tributary area method. Based on the studies of Coates and Hustrulid, the stress obtained was reduced by 40 percent. For calculating the strength of the pillars, three formulae, namely Holland and Gaddy, Salamon and Munro and Central Mining Research Station, India, were used. The pillar widths were then determined by equating the product of recommended factor of safety and pillar stress with the pillar Strength.

Jan 1, 1992

By J OÆDriscoll, R Butler, L Winter

The iron ore mining district of Labrador West and adjacent Quebec is Canada's largest iron ore producer with almost 50 years of production. The area is currently experiencing a period of renewed activity not seen in decades that includes new mine development, mine expansion and exploration for new iron ore resources. All of the past and present production and exploration programs in the district are centred on the Lower Proterozoic Superior-type iron formations of the Knob Lake Group, located within the Grenville tectonic province of the Canadian Shield. The Knob Lake Group is a continental margin sedimentary sequence which was deformed and subjected to greenschist to upper amphibolite facies metamorphism during the Grenville orogeny. Regional deformation and metamorphism plays a key role in making the iron formation of the Knob Lake Group economic. The distribution of orebodies in the district is controlled by superimposed F1/F2 synclines which causes thickening of the iron formation through repetition. Ore mineralogy consists of specular haematite, magnetite and locally martite with quartz as the major gangue mineral. Regional metamorphism has caused an increase in grain size of the ore minerals making it more amenable to concentrating and pelletising. Altius has been active in Labrador West since 2003 and is now the second largest licence holder in the district with several iron ore exploration projects. The Kamistiatusset project is located in the heart of the region's transportation, power and mining infrastructure. The property has seen limited previous exploration, but covers several significant iron ore prospects. Work by Altius includes a helicopter-borne magnetic survey, ground magnetic and gravity surveys, geological mapping, sampling and 6000 m of diamond core drilling all of which confirm both a favourable geologic setting and ore mineralogy.

Jan 1, 2009

By Short KC

The Hunter Region, with a major part of the coal resources of New South Wales and a long history of coal mining, has experienced a rapid expansion of coal resource development in recent years. While there are inevitable conflicts between mining, urban development and related infrastructure, and between mining and other resources, the application of sound planning practices, and improved co-operation and co-ordination among the various parties, helps to reduce such conflicts. The planning process involves consideration of factors such as transport- ation (including port facilities), mine subsidence, provision for surface facilities, a,iC the need for buffer 'ones. In addition, provision must be made for urban expansion, often co-existing or in close proximity to present or future coal mining development. Approval of coal mining developments takes place within the legislative framework of the Environmental Planning and Assessment Act, 1979 (EPA Act), the Coal Mining Act, 1973 (CM Act) and the Mining Act, 1973. Considerable effort has gone into stream- lining and co-ordinating the procedures under these Acts. The EPA Act provides for regional and local environmental plans, as well as a linked process of development control and environmental impact assessment. The CM Act provides for the grant of exploration and coal mining titles and mechanisms for the responsible management of Mining.

Jan 1, 1987

By J Young, S Yu, P Moyo, M Powell, A Musunuri, B Bonfils, S Kanchibotla, P Yaroshak, V Jokovic

The appropriate design of liners continues to be an issue on many mills worldwide. Loss of milling capacity especially at liner change, uneven wear lives along the mill, substantial scrap on worn liners, excess mill down-time, undesirably short and unreliable wear lives are all common issues. This paper presents a designed approach to liner optimisation that follows a logical path of initial design and step-wise improvements based on liner wear monitoring. The target is to have a good liner design from start-up, then tune the profiles, heights and thicknesses based on wear monitoring. This is conducted as a team of liner specialist, site personnel and liner supplier. The application to the Pustynnoye SAG mill of JSC Altynalmas in Kazakhstan is presented. The increase in liner life by around 50% along with increased mill throughput of over 20% illustrate the huge benefit of the cooperative triumvirate approach through the gains that can be made in productivity and reduced liner costs.CITATION:Powell, M, Kanchibotla, S, Jokovic, V, Hilden, M, Bonfils, B, Musunuri, A, Moyo, P, Yu, S, Young, J, Yaroshak, P, Yalcin, E and Gorain, B, 2018. Advanced mine to mill application at the Barrick Cortez mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 177–196 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

Dartbrook mine is a new greenfields thermal coal longwall mine located n the Upper Hunter Valley ten kilometres north of Muswellbrook Figure 1). Construction began in April 1993 with coal extraction starting n October 1994. Longwall production is scheduled to commence in the first quarter of 1996 with production expected to exceed 3.5 million onnes per annum. The permanent workforce will number 150 full-time ,mployees and productivity rates will be 22 000 per employee per annum m a ROM basis. Being a greenfield site Dartbrook has had the opportunity to develop and operate the mine using the best practices and latest technology available to meet high standards of safety, quality and production.

Jan 1, 1995

Listing on Australian Stock Exchange Limited ('ASX') is a means by which a company can prosper and grow by gaining access to a large capital market. This currently stands at over $300 billion for domestic securities listed on ASX. A company seeking listing will benefit from a higher profile and a greater spread of shareholders. These result from, among other things, improved communications with the investment community. ASX recognises that a decision to list is an important step for a company. Owing to the diverse nature and size of the companies that consider listing and the various steps involved, it is recommended that guidance of professional advisers is sought as early as possible in the listing process. A company seeking listing on ASX must meet the prerequisites for admission to the Official List which, along with the continuing obligations that must be complied with following admission, are contained in the Listing Rules of ASX. Listing on ASX requires a company to ensure that, among other things, the market is fully informed at all times so that investors can make informed investment decisions.

Jan 1, 1996

By J Siliézar

The Ernest Henry Mine (EHM) is situated 38 km north-east of Cloncurry in the Mount Isa – Cloncurry mineral district of northwest Queensland. The EHM orebody is an iron oxide copper gold deposit with an average grade of one per cent copper, 0.5 g/t gold and 23 per cent magnetite, with current reserves of approximately 88 Mt.The copper concentrator is a single line plant with a nominal throughput rate of 1300 tonnes per hour. An average of 350 000 tonnes of concentrate is produced each year containing around 100 000 tonnes of copper metal and 120 000 troy ounces of gold.In December 2009, Xstrata Copper announced approval of a $589 M investment to extend the life of EHM to at least 2024, through the transformation of open pit mining operations to a major underground mine together with the construction of an associated magnetite extraction plant.The EHM magnetite plant extracts the magnetite from the copper concentrator’s tailings stream. It will produce approximately 1.2 Mt of magnetite concentrate per annum at full capacity for export to Asia, making EHM Queensland’s first iron ore concentrate exporter. Construction of the magnetite extraction plant commenced in July 2010 and was completed in January 2011.This paper gives an overview of the development of the EHM magnetite extraction plant flow sheet from the early mineralogy and laboratory test work through to the plant commissioning and early operation of the base plant. It has a major focus on the commissioning learnings from the plant start-up and includes a review of the operational performance of the plant versus original design and expectations.

Jul 11, 2011

By K Akiro

Volcanogenic massive basemetal sulphide and gold mineralisation of predominantly low sulphidation style has been located within Lower Tertiary basaltic and felsic volcanic and sedimentary sequences at Ufuo, in the Left April River area, northwest Papua New Guinea. The four discrete massive sulphide bodies, which have been so far identified, occur within a 3 +5 km area situated within a north west trending structural corridor. The sulphide bodies are all localised on the margins of the corridor where the bounding major through going faults are transected by regional faults. Mineralisation is characterised by massive pyrite-bornite-sphalerite-barite-quartz-anhydrite deposition with later galena-tennantite-chalcopyrite. Minor phases include enargite, goldfieldite and bismuth sulfosalts. Jasperoidal silica lenses and bioturbated sediments are closely associated with the massive sulphides. Basemetal sulphide mineralisation is also closely associated with phyllic-style quartz-sericite- altered host rocks underlying the massive sulphide lenses. This mineralised phyllic alteration is localised to fractures, veins and breccias that cross-cut propylitic style alteration characterised by quartz, epidote, chlorite, adularia and zeolite. The mineralised system possesses several hydrothermal features consistent with a copper-rich submarine exhalative volcanic hosted massive sulphide (VHMS) system, ie discrete massive sulphide bodies with abundant barite, associated jasperoidal silica and bioturbated sediments. However, exploratory drilling of the alteration zone underlying each of the massive sulphide bodies has not identified a well-defined zoned alteration pipe that is characteristic of such systems. The alteration is also similar to that of a porphyry-related low sulphidation system in which phyllic alteration has overprinted a regional propylitic style assemblage. The presence of sporadic enargite (and ?tennantite/tetrahedrite) suggest there were intermittent pulses of acid fluids in the system probably derived from exsolved magmatic SO2 which flowed directly to the surface along reactivated faults. The occurrence of tellurium and bismuth minerals is also consistent with a magmatic contribution to the metalliferous hydrothermal fluids. It is proposed that the VHMS orebodies are the products of submarine exhalative deposition generated by a crystallising magma emplaced within crust of on-going tectonism. Ufuo mineralisation is similar to many VHMS deposits elsewhere in that it is unclear whether the metals are derived from the magma directly, or via seawater leaching of the wallrock. Additional studies such as oxygen isotope analysis may assist in resolving this issue. If the metals are shown to be of direct magmatic origin then there may be good prospects for discovering economic-grade porphyry-related mineralisation at depth below the massive sulphide deposits.

Jan 1, 1999

By T Mattiske

The Fimiston Open Pit (commonly referred to as the æSuper PitÆ) is a part of the Kalgoorlie Consolidated Gold Mines Pty Ltd (KCGM) operation in Kalgoorlie-Boulder. KCGM manages the Fimiston Open Pit, the Mt Charlotte underground mine, the Fimiston Mill and the Gidji Roaster for its Joint Venture Owners, Newmont and Barrick Australia. KCGM produces up to 850 000 ounces of gold per year. The KCGM operations are located on the historical Golden Mile on the outskirts of the City of Kalgoorlie-Boulder, about 600 kilometres east of Perth Western Australia. This traditionally underground mining centre has been worked since 1893, yielding in excess of 50 Moz of gold from ore with an average head grade of 10 g/t. This represents approximately ten per cent of the gold produced in Australia and one per cent of the gold produced in the world. The Fimiston Open Pit is essentially an aggregation of what were known as the Judd, South, Paringa, Croesus/Eclipse, Central, Brownhill, Drysdale, Morrison, North and Horseshoe pits into one continuous large-scale operation. The old Fimiston Underground Operations (included the Main, Croesus, Chaffers, Lake View, and Perseverance shafts) were also located within the area of the Fimiston Open Pit. The underground operations closed in 1992 due to high mining costs.

Jan 1, 2002

By G J. A Dewar

The Australian Corporations Law generally requires Independent Expert Reports to be presented in support of capital raising or in defence of mergers and takeovers. The introduction of the VALMIN Code in 1995 (and its recent revision issued as the VALMIN Code, 1998) made Assessment and Valuation Reports in these circumstances much more comprehensible than before because of its key requirements for transparency and materiality. By forcing the Independent Valuer to provide an explanation of the reasoning behind the estimation of a particular resource asset, VALMIN allows the reader to clearly see any error or illogicality in the valuation methodology used and to seriously question or even reject the resulting value. Even though many elements of resource asset valuation practice are undeniably subjective, there must be some basis of objective rationality to it. Independent resource asset Valuers are the essential link between mineral explorers/miners on the one hand and brokers/analysts/fund managers/investors on the other. The minerals and financial industries both expect them to not use inappropriate or invalid valuation methods and illogical steps within these methods. This paper examines some of the less sensible ways in which some of the main techniques that Valuers commonly use to assess the fair market value of mineral properties have been applied in recent instances. The authors hope to discourage the adoption or perpetration of the æWhat-number-did-you-have-in-mind?' approach. It is MINVALÆs view that as many methods as possible should be used in any resource asset valuation. If any of the resulting estimates are in approximate agreement (particularly if they were derived using the less subjective of the available methods), ie if they cluster, they are probably more persuasive as being the Preferred Value of the asset than outlier values within the Valuation Range.

Jan 1, 1999