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By Javad Koleini S M

The sources of arsenic compounds vary from As(lll) oxide produced from roasters to wastes containing arsenic from chemical or mineral processing plants. The removal of arsenic via co-precipitation with iron is currently proposed as an acce

Jan 1, 1994

In simple terms, heap leaching means the removal in solution of valuable elements from a heap of material, and their recovery from that solution. The heap of material can consist of essentially unprocessed ore, sub-ore, low grade gangue and country rock, tailings from other upgrading processes, or artificial materials such as slags or furnace and flue products. The solvents can be solutions of acids (commonly sulphuric acid because of cost) or of other chemicals such as cyanides. Because of cost factors the solutions are aqueous; because of this, leaching operations may be curtailed in cold-climate areas. The guiding principle must surely be `large volume / low cost'. Since solutions are generally easier to manage than gases, there is a strong incentive for replacing roasting of materials by leaching, eg arsenical gold ores. Where sulphides are present in the material to be leached, these may provide the necessary acid, with or without the aid of bacteria, to dissolve and extract the recoverable metals. The mineralogical aspects of the operation relate to the nature of the `ore' and gangue minerals present in the heap, their textural relationships, and their effect on the process itself.

Jan 1, 1994

The paper reviews recent valuations of mineral properties, many of which are at an early stage of exploration. The various methods used are outlined. The problem of comparing, in terms of whether it is fair and reasonable, a highly subjective opinion of the present value of a portfolio of exploration tenements with a vendor consideration, the real value of which, in most cases, lies at some indeterminate time in the future because of the application by the Australian Stock Exchange (ASX) of escrow conditions, is highlighted. Examples are given of some of the questionable logic used by consultants in handling this difficult issue. A proposal for revision to current flotation and listing practice which, the author believes, would circumvent the problem and at the same time provide better protection for the investing public is offered for Consideration.

Jan 1, 1994

This paper presents the descriptions of a final year geological engineering project at the Royal Melbourne Institute of Technology involving the correlation of borehole and mapped ground conditions and their statistical Analysis.

Jan 1, 1994

The Golden Plateau Mine is located at Cracow in central Queensland, 350 kilometres north west of Brisbane. The mine was operated by Golden Plateau NL as an underground mine from 1933 to 1976 with a total production of 18.5 tonnes of gold. Prod

Jan 1, 1994

After four or so long years at university, where life revolves around lectures, assignments, and drinking coffee strong enough to keep you awake for five nights in a row to finish your thesis, preparing yourself for employment is not an ea

Jan 1, 1994

Background BHP Iron Ore Pty Ltd is one of the major iron ore producers in the Pilbara Region of North Western Australia. The company manages three separate joint ventures; the Newman, Goldsworthy and Yandi joint ventures and two 100 per cent owned operations, Yampi and Jimblebar. The Newman operations constitute a mine site at Newman and a 426 km railroad to Port Hedland where there is an ore processing/port site. The Goldsworthy operations currently constitute a mine site at Shay Gap/Nimingarra, a developing mine site at Yarrie, a decommissioned mine site at Goldsworthy and an ore processing/port site at Finucane Island (Port Hedland). The Yandi operations include mining and processing facilities at site and a spur line to join the Newman Hedland railroad. Jimblebar operations are scree and bedrock mining near Newman and include mining, processing and a spur line to Newman where it joins the Newman-Hedland railroad. The Yampi operations constitute a mine/port site at Koolan Island (which is presently being decommissioned). The combined BHP Iron Ore operations produce approximately 46 Mtpa of iron ore. This paper will concentrate on the processes developed and applied for the decommissioning of the Goldsworthy site. The Goldsworthy site is on the northern boundary of the Pilbara Region and adjacent to the western extremity of the Great Sandy Desert. It is located approximately 110 km east of Port Hedland (see Figure 1). The area is generally of low relief with isolated low ranges. The mine site being within the Mount Goldsworthy range area. The geology of the area is essentially Archaean granite with Archaean banded iron formation becoming dominant within the ranges. The chief soils are hard alkaline red soils. The vegetation is essentially shrub steppe with the main hummock grass species being spinifex (Triodia sp). The climate for the region is semi arid tropical. The temperature ranges from a mean low of 15¦C in winter to a mean high of 40¦ in summer. Rainfall is episodic, occurring mainly throughout the summer as a result of tropical depressions or cyclonic activity. The average annual rainfall is approximately 300 mm and annual evaporation may exceed rainfall by up to 2500 mm. Goldsworthy Mining Ltd commissioned the Goldsworthy site in 1965/66. Goldsworthy was the first iron ore operation and associated town site in the Pilbara region. The mine development peaked in 1977 with the town population reaching 1400 people. In 1982 mining ceased and the mining operations were relocated to Shay Gap, 80 km east of Goldsworthy. The Goldsworthy town continued as the base for the railing operations between Finucane Island and Shay Gap. BHP Minerals acquired Goldsworthy Mining Limited in 1990. The population for the town of Goldsworthy at this stage was around 450 people. An assessment of the Goldsworthy site operations concluded that it was uneconomic to continue the operation of the site. The decision was made to transfer the base for railing operations to Port

Jan 1, 1994

The Northwest Territories (NWT) of Canada has emerged as a major new province for diamond mineralisation in less than three years. This is primarily the product of a diligent search in the form of a scientifically based exploration effort. However other factors, including positive aspects of the business and the legal environment have also been identified as assisting the exploration process. In my view these have increased the likelihood of diamond mining becoming a major new industry for Canada. The supportive role of various government agencies has been important. In addition, the character of many of the joint venture deals that have been done has provided an attractive setting for the capital intensive evaluation and development work that is now required to bring the diamond discoveries into production. Perhaps of equal importance is that with the recognition that is being given to the success of the NWT diamond ventures, Canadian explorers are continuing to attract new risk capital for further exploration. This paper attempts to model and quantify the probability of exploration success translating into successful mine development.

Jan 1, 1994

The basic principles of mineral valuation were recognised and propounded at the beginning of this century and have remained virtually unchanged since then. Valuation is seen as a two part process commencing with a technical examination of the mineral property followed by a manipulation of the results of the technical examination in order to determine the monetary value of the project. A thorough and competent technical examination was seen then and remains now as the essential but not sufficient foundation for reliable valuation. All authors stressed the need to maintain the integrity of the data base and to ensure adequate coverage of all relevant aspects. The monetary valuation process through most of the first half of this century was mainly based on the Hoskold two rate method, derived from the formulae for valuing annuities but modified to provide explicitly for recovery of capital. Though the basic principles of valuation have not changed significantly, the means of implementing the components of the technical examination, the styles of deposits being evaluated and the mechanisms of monetary valuation have changed dramatically. Despite all the technological improvements, however, mineral valuations are still as apt to vary from realised performance as at any time in the past. As well, mineral property valuations are now being extended to cover all assets of potential value, including valuation of exploration tenements with or without identified resources. Valuation of exploration tenements will continue to be one of the most difficult and contentious of valuation tasks.

Jan 1, 1994

Since 1969, a substantial number of geophysical methods have been applied in the search for porphyry copper and mesothermal type -sulpha-de deposits. These have assisted with geological mapping as well as the definition of various sulphide depos-its. The application of these methods at the Frieda-Nena deposits, Papua New Guinea, can be used as a case study for exploration in other parts of New Guinea.In 1993, Highlands Gold Limited carried out an intensive geophysical program over the Nena deposit. The methods employed included, CSAMT (controlled-source audio magneto-tellurics), airborne and ground elect-romagnetics, IP/resistivity and ground magnetics. The magnetic method was used as a regional mapping tool as well as a way of mapping alteration zones over both the Nena and Frieda River copper deposits. Electromagnetics, in part-icular FLAIRTEM, is a rapid reconn-aissance tool as well as a detailed mapping tool for the location of Nena-style massive sulphide deposits. IP/ resistivity is an expensive but most useful tool for mapping out Frieda porphyry copper style disseminated sulphides as well as Nena style deposits. It can be used to define drill targets in areas of difficult Access.a

Jan 1, 1994

In mineral asset valuation the use of any valuation method requires the input of competent and independent technical professionals. A resource valuation must be as transparent as possible to allow others to assess the validity of their underlying assumptions. Materiality is a dominant factor in all valuations and a valuer should set out the basis for the subjective decisions made in this regard. Any valuation methodology must comply with the requirements of the law, practice notes and guidelines issued by the various relevant authorities and professional bodies. The valuation methodology chosen to value a mineral asset depends upon the amount of data available on that asset and the reliance that can be placed upon those data. Mineral assets generally fall into one of three broad categories, depending upon their state of development, ie whether they are at the exploration, development or operating stage. Naturally there are transition phases. Hence, there are ""Grass Roots"" Exploration Areas and Advanced Exploration Prospects; Pre-Development Projects and Developing Mines; and Operating Mines. The features of each of these mineral asset status categories are described, mainly in terms of the confidence in the contained identified Resources/ Reserves. The various subjective methodologies available for the valuation of ""Grass Roots"" Exploration Areas and Advanced Exploration Prospects -are specifically reviewed. The pitfalls in adopting a ""recipe"" approach are noted. It is the author's view that the Expected Value Method (based on the probability adjustment of the output of a Discounted Cash Flow/ Net Present Value model) has little application in the valuation of exploration mineral assets, so it is only briefly addressed. The methodologies reviewed are listed below. ò Multiple of Exploration Expenditure Method (expenditure based). ò Joint Venture Terms Method (expenditure based). ò Geoscience Rating Methods (eg Kilburn - area based). ò Comparable Market Value Method (real estate based). ò Rules of Thumb (eg $/Resource or production unit; % of in situ value). Some recent Prospectuses are used to provide examples of their misinterpretation and misapplication.

Jan 1, 1994

The demand for gallium has increased significantly over the last few decades due to the expanding use of Ga compounds in the electronics industry. Because it is widely dispersed and rarely found naturally in concentrations greater than 0.1%, Ga is expensive (approximately US$500/kg) and difficult to produce in large quantities.   A previous study of metals in geothermal systems reported significant quantities of Ga present in the muds on the northeast margin of Lake Rotokawa, an acidic lake associated with a high-temperature geothermal field situated in the Taupo Volcanic Zone of New Zealand. Similar muds are present in many other geothermal fields in the zone, suggesting that geothermal muds could be a commercial source ofGa.

Jan 1, 1994

My message to you today is simple. The mining industry in Australia has a proud record of successful research and innovation. If it is to continue to provide this country with its major exports that records must continue. I will endeavour to show that

Jan 1, 1994

Papua New Guinea has a long history of mining, with gold being produced from deposits on islands in the south east of the country over a hundred years ago. Before the Second World War, the mining and dredging of gold made the Wau-Bulolo area a

Jan 1, 1994

Discounted cash flow (DCF) methods are well suited and recommended as a primary valuation method for mineral assets for which there are at least indicated resources and some form of feasibility study containing engineering, production and capital and operating cost data. DCF methods are also applicable as a secondary or check valuation method for exploration properties for which no technical study has been prepared. For projects where little or no engineering, production and/or cost data is available, the process of formulating a project concept by specialists who do not possess experience and expertise in the relevant technical faculties is totally rejected as a basis for applying DCF techniques as a primary valuation method. Such an approach runs counter to The Australasian Institute of Mining and Metallurgy (AusIMM) requirement to apply relevant expertise to specific aspects of mineral valuation. Technical and commercial inputs to mineral valuation should be reviewed by specialists who have specific expertise in the relevant disciplines, and should be tempered by the quantity and quality of technical evaluation which has been undertaken and the development status of the asset.

Jan 1, 1994

The Manto Verde copper mine (Atacama Region, Chile) is due to go into production in 1996. It will produce 40 000 tonne/year of copper cathode by heap leaching/SX-EW. Mineralogical studies were undertaken in conjunction with the metallurgical testwork program to characterise the ore and its response to leaching by dilute sulphuric acid. The leachable copper mineralogy is dominated by the oxide copper minerals: brochantite and malachite with minor chrysocolla and atacamite. The gangue minerals include abundant orthoclase, specularite, quartz and chlorite with minor muscovite and trace smectite clay, calcite and limonite. The study showed that complete or partial decomposition of calcite, chlorite, smectite and wad consumed acid and generated solution impurities (Ca2+, Fe2+, Mg2+, A13+, K+, Si4+ and Mn4+2+ ). Although these were manageable at Manto Verde, their uncontrolled build-up could have affected the operation in several ways: the degradation of heap penneability and fonnation of crud in the SX plant from the precipitation of gypsum, goethite, colloidal silica and jarosite; and the entrainment of contaminated pregnant leach solution in the SX organic resulting in the transfer of impurities to the electrolyte and subsequent effects on cathode quality and electrowinning efficiency. In conclusion, process mineralogy played an important role in understanding and managing potential mineral-related problems in the heap leaching and SX-EW recovery of Manto Verde ore.

Jan 1, 1994

This paper outlines the thermodynamic and mass balance principles which affect the distribution of cobalt between matte and slag during the pyrometallurgical treatment of nickel-copper sulphides and considers the implications with regard to maximising the recovery of cobalt from the smelting and converting circuit.

Jan 1, 1994

This paper examines the concepts of risk analysis and uncertainty in open pit mine design. It describes the relationship between risk analysis and uncertainty, describes methods that can be used to quantify uncertainty, and suggests ways of reducing the geological and geotechnical uncertainties that are inherent in open pit mining.

Jan 1, 1994

By Wall J, Platell R, Knight P

The Argyle diamond mine is located in the East Kimberley area of Western Australia, some 100 km south of the town of Kununurra. The diamondiferous Argyle olivine-lamproite diatreme was discovered in August 1979. Production began in December 1985 at a planned throughput of 3 Mtpa to recover 25 million carats of diamonds. Presently, Argyle is the world's largest producer of natural diamonds and produced over 40 million carats in 1993 from seven million tonnes of lamproite ore treated. Two phases of evaluation have been carried out. The first in 1981-82 was designed to prove around 60 million tonnes of ore to justify the establishment of a mine with a minimum life of 20 years. The second phase, in 1989-90 involved drilling the orebody to greater depths to provide data on which to plan the final pit design. The final pit contained 120 million tonnes of ore at 5.3 carats per tonne (ct/t) grade. Mining of the planned pit will extend the mine life to around the year 2004, following which it is possible that a further cut-back could be mined. There is also the potential for future underground mining. A substantial amount of geotechnical work has been undertaken due to the fact that the pit will be nearly 500 m deep and is located in a mobile zone causing abnormally high residual stresses to occur in the pit walls. The occurrence of low strength rocks at depth in the pit walls further complicated the situation. Hydrogeological investigations were done to determine pit dewatering requirements and to assess the effect of dewatering on pit wall stability.

Jan 1, 1994

`WELL HE WOULD, WOULDN'T HE?' Public Relations people have something in common with advertising people and politicians: there exists a perception that their whole Raison d'Etre is to create, mould, and maintain images which are far removed from reality

Jan 1, 1994