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Economic evaluations of mineral projects are based on discounted cash flow analyses, followed by sensitivity and risk analyses. However, the global macroeconomic and political environment in which the mineral industries operate have a profound effect on the viability of individual projects. Since the oil crises of 1974 and 1980, demand patterns for minerals have become much more variable and prices more volatile. Significant changes in the geographical distribution of world mineral supply and demand are underway, and the mix of minerals used is also changing. Social and political factors are as important as economic and technical factors in determining the viability of mineral ventures. Economic evaluation of mineral projects have to be undertaken in a more uncertain and risky environment. They can no longer be reduced to a number crunching exercise.

Jan 1, 1987

Exceptionally weak ground, usually associated with faulting, unanticipated groundwater pressures or flows and exceptionally high stress concentrations are some of the hazards which confront the underground excavation engineer. One or more of these hazards can seriously delay or even halt a tunnel or mining project, and methods for predicting these hazards are urgently required, particularly for projects involving high speed drill and blast or tunnelling machine excavations.This paper explores the current availability and the potential for the development of tools and techniques for the prediction of these hazards. It is concluded that systematic and automated geological data collection and interpretation represent the most promising avenue for development. It is suggested that there is room for the use of expert systems in which the computer is used to assemble and organize practical underground excavation experience into an interactive decision making system.

Jan 1, 1985

By Wauchope AMH

Arsenic residues from BHAS Refinery operations are currently treated to form a calcium arsenic compound and stored in lined dams on site. Laboratory and large scale work on these residues has resulted in the development of a hydrometallurgical process for production of arsenic trioxide. The process also recovers the material from the storage dams. The residues are hot water leached to produce an alkaline arsenic liquor. This liquor is mixed with material from the storage dams and lime to form a calcium arsenic precipitate. The precipitate is then reacted with sulphuric acid to form gypsum for return to the main plant, and an acidic arsenical solution. Metallurgical gas containing 3-6% sulphur dioxide is bubbled through the solution and on cooling arsenic trioxide is precipitated. The product contains in excess of 95% arsenic trioxide. Installation of a plant at Port Pirie based on this process is being evaluated by BRAS.

Jan 1, 1984

The occurrence is recorded of an indurated kaolinite claystone associated with red-beds in the Burralow Formation of the Narrabeen Group near Putty toward the north-west of the Sydney Basin. The claystone is similar in composition and structure to the Garie Member which immediately overlies the kaolinite-rich "chocolate shales" of the Bald Hill Claystone in the sofrthern part of the basin. Unlike the Garie Member however, the Putty claystone is lenticular and the associated red-beds contain abundant quartz and illite in addition to kaolinite.The source of the Putty claystone is not known. Possibly it is an extension of the Garie Member to the northwest or alternatively, it may represent fine outwash of detritus that produced the coarse-grained kaolinite claystones in the Triassic succession of the Merrygoen-Binnaway area. Although the material is suitable for the manufacture of aluminous refractories the limited size of the deposit precludes its commercial exploitation.

Jan 1, 1971

Wrenching between basement blocks is considered to be the mechanism whereby a well developed set of en echelon folds and an associated fracture system are developed in the Fitzroy Depression, Western Australia. The regular geometry of these structures accords with a right lateral regional coupling between high-standing, basement blocks bounding a trough filled with a thick pile of stratified Phanerozoic sediments. The structures developed during or after the Mesozoic Era, but the couple is inferred to have been applied to blocks outlined by old lineaments, which may reflect strains or ruptures in basement that developed during the Precambrian, and which were regenerated during Palaeozoic and Mesozoic time.

Jan 1, 1967

The space probe Magellan is on its way to Venus (May, 1989) and with its sophisticated radar systems will discover much more about our twin planet. There is tennuous evidence that Venus once had liquid water. Did it have life? Why was it not stable and why did liquid water not persist through the period of the dimmer young Sun? These are profound questions for us. We understand why Mars froze when volcanism terminated (Just as Earth will freeze one day) but could Earth boil if we continue to add greenhouse gases (Broecker, 1985). What will happen if 10 billion humans continue to use fossil carbon as their main fuel source? The Earth is warming fast and the new satellite data show that the oceans are warming faster than we thought. Is this just a fluctuation or is the greenhouse signal coming through the normal noise of climate?

Jan 1, 1990

By Z B. Rakisheva

By explosion rock mass behaviour is conditioned by preset complex of rocks natural characteristics. Very important role of blockness, which is percent (share) content at examining massif of natural separatenesses of different dimensions and configurations, separated each from other by the cracks of geological and technogene origin. Besides natural properties of massif the power, detonational characteristics of applied explosives, parameters of explosives charges disposition at massif and technology of explosion influence vastly at lumpiness (granulometric structure) of exploded rocks. The mathematical model of rock mass destruction by explosion had been elaborated and substantiated. It ties mutually the initial data (rocks properties, parameters of the charges disposition) and final results of explosion (granulometric structure of exploded rocks). The program of this complicated problem solving had been compiled. Analysing the received results of the problem solving, one can reveal contribution of each group of influence factors for lumpiness of exploded rocks. This fact creates preconditions for elimination or diminution of negative role of some controlled initial data.

Jan 1, 2003

In July 1997 Macraes Mining Company Limited deferred a 9 Mtpa expansion of the Macraes Gold Project because of the uncertainty of the future gold price and its impact on equity markets.  Additionally delays in the resource consenting process led to further uncertainty.   It has subsequently announced that a study has been commissioned to recommend a staged approach to development of its New Zealand business. The best economic development path will be determined to maximise returns to shareholders.

Jan 1, 1997

Project evaluation is completed through individual studies covering technical and financial aspects of the mine to market. These studies are completed at various levels of detail depending on where the project evaluation is in the projectÆs life cycle. The competency of the studies varies in relation to the quality of data, level of the skills employed, control, management and reporting structure. The focus of this paper is managing elements of the study, looking at the cost of opportunity to influence the project, against the value added. Selection of the study manager and study teams is central to getting an integrated project evaluation addressing the correct issues completed on time. Retention of key personnel can reduce rework which, in turn, can reduce time and cost impacts. It is important to have a work breakdown structure at the outset so that the study teams have a common numbering and naming system that will integrate areas, equipment, budgets estimates and accounts. Having set up the evaluation groups and provided training in the study procedures, understanding the scope and schedule are vital elements in producing a project evaluation that addresses the opportunities and the risks of the final project. Arriving at an accurate capital budget requires integration of the research controlled through common systems. Project evaluation process must also address how the project is to be delivered.

Jan 1, 2007

In contrast to the '50s and '60s, the period of the '80s and '90s seems likely to have low growth in demand but much greater levels of technological change. In such a climate there will be pressure on costs, productivity will continue to rise and competitiveness will be closely associated with maintenance of the most effective technology. The penalties for inappropriate investments, whether short sighted or mistakenly based on a particular view of the future, will be greatly enhanced. Accordingly, there will be a need for significantly improved anticipation of technical change and thus for better planning. Study of the funding and direction of the world's R&D effort can provide a useful input to the planning processes within industries and individual firms. Such a study also suggests some insights into the characteristics of those countries which have achieved substantial growth and high standards of living over the past two decades. These characteristics may offer significant reminders for our own development. The particular implications for the Australian minerals industry include the need for direction that is sensitive to changing market requirements and customer practice. This is not simply "more of the same." In particular it appears essential for both basic and applied R&D to provide a sound basis for the purchase and ongoing development of the new technology required to achieve international Competitiveness.

Jan 1, 1986

Metallurgical accounting can be defined as the monitoring of the valuable metals from the time the ore is broken at the primary crusher until the time that we have the saleable products and residues. The overall purpose of metallurgical accounting is to provide management with up-to-date inform- ation that can be used to control mining and metallurgical oper- ations. The decisions that are taken on the basis of the information that the metall- urgical accounting system provides should result in improved control and, ultimately, increased revenue. The current state of accounting is a result of an extended evolutionary process and will continue as process plants bec- ome more sophisticated. Differences in mine æcall factorsÆ and grade control reconciliation can lead to frustration between the siteÆs geoscie- ntists and its metallurgists leading to a level of distrust in the mill grade. Metallurgical accounting is not included in sufficient detail in undergraduate courses and the acceptable industry standards have developed based on what is considered acceptable to industry personnel and consultants. There is now the AMIRA P754 Metal Accounting, Code of Practice and Guidelines Handbook or reference manual. Computer based databases and spreadsheets have transformed tedious bookkeeping into an important management tool. Over time these standards have improved with developments in analytical procedures, weighing technology and sampling. This paper provides anecdotal examples of problems and improvements observed over a number of years within the gold industry in Australia and overseas.

Jan 1, 2009

By Allen RL, Clifford BA, Wright JV, Bull S

The Bunga Beds of the Late Devonian - Boyd Volcanic' Complex is a well exposed succession of rhyolite, sedimentary rocks and minor basalt outcropping along the south coast of New South Wales. The sedimentary rocks vary from shallow water basin margin facies, to deep-water basin centre facies, and the majority of .the volcanics are associated with the deep water facies association. The volcanics are dominated by rhyolite domes, lavas and cryptodomes, whose margins are extensively autobrecciated and quench fragmented. In situ pyroclastics represent a very minor volcanic component and are restricted to the remnants of two small doors- top tuff cone successions. Pyroclastic debris is common in the sedimentary succession enclosing the volcanics and was clearly derived from shallow to emergent basin margin areas through mass-flow redeposition. The succession has bearing on the origin of the fragmental component of, the volcanics that host Kuroko- type massive sulphide deposits. The characteristics of these fragmental volcanics are not well documented. We suggest that based on the Bunga Beds,'Kuroko-type volcanic successions are dominated by coherent rhyolite/ felsic lavas and intrusive domes, autobreccias and hyaloclastites, that in situ pyroclastics are rare or lacking, and that redeposited volcanic debris is abundant. Pyroclastic debris is most likely to have been derived from shallow areas marginal to the deep-water volcanic centre that produce the Kuroko-type volcanics and sulphides.

Jan 1, 1987

Independent assessments of existing and projected mining operations are often required in the exchange of assets and for raising capital, requirements which are particularly prevalent where there are new mining fields, a characteristic of the Pacific Rim area. Such audits and appraisals typically consist of a geological evaluation of the ore deposits; estimates of mineral inventories and mineable reserves; assessment of mine plans and costs; assessment of ore processing methods, recoveries, and costs; assessment of infrastructure and G&A (general and administrative) requirements and costs; assessment of environmental, permitting and reclamation requirements and costs; and, finally, economic evaluation based on various discount rates and metal prices. Audits provide a challenging task for consulting engineering companies, but one well worth the effort for mine developers and those connected with financing of the mining industry.

Jan 1, 1990

Recent research publications in extractive metallurgy were analysed for their stated and self-evident objectives. Over 100 different objectives (not specific to a metal or unit operation) were identified. These were divided into groups of economic, environmental, professional and fundamental significance. Comparisons were made of the objectives adopted in universities, industry and national research organisations. The most common primary and secondary objectives (by a large margin) were "to develop a new process (different chemistry)" and "to determine the effects of variables on a process" respectively. It was concluded that, overall, recent research has been dominated by commercial objectives. Objectives related to thermodynamics and kinetics have been the most common of the fundamental sort. Those related to professional methods in general, sensors and process dynamics, among others, have been largely neglected.

Jan 1, 1986

In the early 1950's, it was forecast that there would be, worldwide, a need for approximately sixty computers! Included in that estimate was provision for a considerable amount of geoscience modelling. Since 1950, the role and concept of the computer has changed. With that change has come alteration and adaptation within industry in order to better utilise the services and tools that computers can provide. For example the science of statistics prior to the computer was regarded as an intractible speciality. Computers have allowed the exploitation and further generation of statistical theory. In turn, as the science of statistics has become practical and relevant, the mineral geologist has moved from being essentially "a-numeric" to "non-numeric" to highly skilled in the application and use of very sophisticated statistical concepts. The modern computer provides the opportunity to perform many of the old practices more conveniently and/or economically and, perhaps more importantly, for exploration it provides- an enormous range of activities which previously would have been impossible. Such new activities allow for imaginative and creative application and extension of basic theory into practical situations, which when used by well trained, able people can open up new avenues of exploration. However, the use of such tools by poorly trained or incompetent people can lead to errors potentially as great as any success derived from the same tools. This paper reviews some applications of the computer to exploration, and attempts to discuss likely future developments.

Jan 1, 1987

By Albinson T

Mexican epithermal deposits can be broadly grouped into two types based on their contained metals, distribution, associated igneous rocks and fluid inclusion compositions. Silver-gold deposits (e.g. Tayoltita) mostly occur in the western part of northern Mexico where host rocks consist of Eocene, intermediate composition volcanic and intrusive rocks; fluid inclusion studies indicate that mineralizing fluids were _10 eq. wt. % NaCl). The distribution of these two deposit types, crosscutting major major crustal sutures, and the close spatial-temporal relationships between mineralization and magmatism, together suggest that magmatic processes were more important in the formation of mineralizing solutions, as a source of both ligands and metals, than the segments of crust hosting deposits.

Jan 1, 1995

INCREASE OF THE OIL CONSUMPTIONIt is of the greatest interest to study the prospects open today for the petroleum industry by looking back to the past years.The' results for the past 15,years can be said. to be- satisfying; - the develop-ment of the petroleum industry has sustained a very fast tempo and the world consumption of energy has around the years 1960-1961 - reached aòpeak figure.Undoubtedly, the petroleum industry is the principal beneficiary of the growth of world, energy demand. For the caning years a slackening of the rate of expansion is'. likely to be expected; but will. not alter the general trend. This ' slackening of expansion may be explained, partly by a better use of the energy consumed and by the increased use of new types of energy, mainly natural gas.Although.the development of world energy demands follow structural and tech-nical modifications".,-At. can be foreseen, without any doubt, that the petroleum products. consumption. vri 11 be less affected than any other type of energy by this limited reduction in the rate of increase.

Jan 1, 1962

By J S. Moema, R Paton, J Zimba

Today, most organisations are familiar with the pressure to increase their effectiveness and efficiency, regardless of the nature of their business. Cost cutting and increased productivity are the main themes of many initiatives to ensure the profitability of operations and, ultimately, shareholder satisfaction. It is well known that the cost of comminution to liberate minerals such as gold from their respective ores is a major expense for mines. Comminution costs consist predominantly of grinding balls and electricity. However, there are no national or international standard specifications for grinding balls û on which a single mine may spend several million dollars per month. In addition, in the past mines generally did not specify the minimum requirements when purchasing grinding balls from suppliers. The result is that every supplier has its own grinding ball recipe (regarding chemistry and heat treatment), and is under no pressure to implement a quality assurance plan to ensure that a consistent product is delivered. The resulting variation in the quality of grinding balls leads to increased steel consumption rates and hence increased milling costs. A more stringent quality plan will generally not be welcomed by suppliers since this may entail further investments and/or reduce the production rate. In a sense, suppliers benefit from poor quality grinding balls as this leads to increased sales. Perhaps the main problem is a lack of understanding of the factors that influence grinding ball performance. This paper will describe the factors that influence the wear rate of grinding balls from both a microstructural perspective and a mill perspective. In addition, some insights are provided on the different grinding balls available and ways that users can verify their quality.

Jan 1, 2007

By McCarthy J

In both the U.S.A. and Canada regulations concerning the reporting on mineral resources and especially ore reserves have been established. The regulations are virtually identical for the two countries with the main exceptions being who is franchised to write the report and how the various reserve categories may be used in reports to the public. Both countries divide ore reserves into "proven", "probable" and "inferred" categories. "Proven" reserves are those for material for which tonnage is computed from dimensions revealed in outcrops, trenches, underground workings or drill holes and for which the grade is composed from the results of adequate sampling. "Probable" reserves are those which are less well defined than "proven" while "inferred" reserves are generally those which may exist through geological and geophysical interpretation. The AusIMM/AMIC draft guidelines as proposed for use in Australia define more rigidly the ore reserve categories into "proved" and "probable" terms, which can only be applied following a full and favourable analysis of economic, mining, metallurgical, marketing and sociopolitical factors. If the ore reserves are not supported by this analysis they are placed into a "resource" category. Proper application of this proposed Australian model could prove useful when dealing with grass-root prospects or mining properties in the pre-feasibility stage. Combined with competent reporting, use of the proposed guidelines should ensure standardised and more verifiable analysis/valuation of a company's mineral assets.

Jan 1, 1987

There are a number of different mechanisms by which wetlands can immobilise the metals in mine drainage. Here, the biogeochemistry behind four of these mechanisms (adsorption, biological uptake, precipitation as oxyhydroxides, and precipitation as sulfides) is discussed from the perspective of sustainability. Moreover, treatment wetlands are considered as part of a larger system, also taking into account the source of the drainage and various aspects of the receiving waters. The biogeochemistry of different metal immobilisation mechanisms in wetlands determines what kind of drainage can be treated with success, and it also places an upper limit on the amount of metal that can be removed from the water phase per unit of time. This has important implications for the design of treatment wetlands, perhaps particularly in colder climates. A thorough understanding of the prevailing biogeochemical processes is essential when attempting to establish treatment wetlands after the closing of a mine. If a wetland is to be used as a sustainable æwalk-awayÆ solution, the anticipated change in treatment efficiency over time (as pollutants accumulate in the system) must be considered in relation to the expected changes in drainage quality. It is also important that the total metal immobilisation capacity of the wetland is not exceeded and that the integrity of the system is maintained, in order to minimise liberation of previously immobilised metals.

Jan 1, 2003