Search Documents

Underlain by and intruded into the sedimentary rocks of the Transvaal Supergroup the Bushveld Complex is the largest known layered intrusion in the world and contains one of the richest ore deposits on earth. It has been the world's major source of Platinum Group Metals (PGM) since the mid-1900s with Chromite and PGMs the two most economically important components of the Bushveld Complex. The lower group (LG), within the critical zone, consists of seven chromitite layers and it is within this sequence of chromitite layers, the most important target of the lower chromitite group is found, ie the LG6 chromitite unit. The LG6 chromitite unit consists of a chromitite duplex composed of the lower LG6 chromitite layer (Steelport seam), averaging 1 m thick, overlain by a 0.66 m waste parting and a thin 0.34 m thick LG6a chromitite layer (leader layer).Two mining methods are commonly applied in the Bushveld Complex to extract the LG6 chromitite layer package. One method consists of footwall development utilising rail bound equipment to gain access to the orebody and then extracts only the LG6 chromitite layer by means of hand held rock drills and scraper winches. The second method is the use of mechanised equipment to access the orebody on the plane of the ore utilising bord and pillar mining method, which extracts the full mineral resource, ie the LG6 and LG6a layers. Conventional narrow vein stoping is often selected due to the large conventional mining skills base found in South Africa, the perceived cost and dilution implications of utilising mechanised equipment, and the difficulties of using mechanised equipment at dips above 12¦. The driving factor for mechanised mining is the perceived ability to access the orebody quickly and inexpensively, and extract the entire mineral resource package (LG6 and LG6a) while limiting capital expenditure and improving safety.This paper investigates these two commonly applied approaches, highlighting the benefits and problems associated with the two approaches. Comparisons will be made of the two mining methods and recommendations given for the mining engineer to consider before selecting the appropriate mine design.

Dec 6, 2010

Long-range side-scan sonar and conventional geophysical data for the Peru Trench region (8`S-15¦S latitude) have been analysed. The data show that the Peru Trench is a site of sediment subduction where bending-induced normal fault-ing of the Nazca plate plays a key role. The sediments are continually removed from the trench axis region by their inclusion in normal fault-defined void spaces, such as grabens. In the process of subduction, the sediments are often offscraped, folded arid kneaded temporarily at the base of the shoreward trench slope. The subduction complex comprising such sediments is narrower than 20 km and its volume remains more or less constant due to regular removal of its contents along with the down-going plate. Addi-tionally, morphology of the subducting Nazca plate is responsible for subduction erosion of the South American plate, where the horst blocks cause tectonic erosion by abrasion and the grabens provide a mechanism for removal of the eroded material.

Jan 1, 1990

The sampling of a run-of-mine (ROM) ore with the objective of controlling the fundamental variance associated with the sampling step is a poorly understood subject. Finding the effective sampling constant by repetitive sampling to establish the variance between nominally identical subsamples of a given mass of the ore is a laborious, time-consuming and very expensive exercise. In this paper, the run-of-mine ore is modelled using three components: ore, waste, and relatively fine material which shows significant liberation of the mineral phase(s) carrying the target analyte. The expression for the sampling constant of the mixture is developed from first principles. The form of the equation provides insight into the factors that are important in controlling the magnitude of the sampling constant and hence the fundamental uncertainty associated with a given mass of sample. The controlling factors are shown to be the size distribution of the ore/waste mixture, the proportion of waste mixed with the ore and the extent of liberation and the size distribution of the liberated material in the finer fractions.

Jan 1, 2008

The efficient development and exploitation of an orebody relies on an understanding of the mineral characteristics of the deposit. This information is valuable throughout the mining cycle - during exploration, assessment, testing, design, operation and rehabilitation. Problems can arise at each stage if there is an inadequate appreciation of the mineralogy involved and its effects on the treatment process. Modern image analysis systems now permit a more quantitative understanding of the mineralogy of an ore to be gathered. Where previously the metallurgist had to rely on qualitative information to guide technical decisions, it is now possible to give numerical estimates to the compositional and textural properties which govern the mineral concentration processes. Ore samples can be characterised according to modal abundances, mineral grain size parameters and mineral associations, all of which affect the liberation and concentration of the values. The paper will discuss the application of quantitative process mineralogy by considering a number of case studies. These include: ore characterisation to assist in exploration, assessment and mine planning; modal analysis of complex mineral suites to assist in the evaluation of ores, the deportment of values between products and the recovery or loss of these values; liberation analysis for ore testing, plant optimisation and performance monitoring; and characterisation of tailing to guide estimates of leachability, stability and rehabilitation options.

Jan 1, 1998

By J Ralston, R Sedev, D Fornasiero

The foam behaviour of low molecular weight polypropylene glycols (PPG) was investigated as a function of concentration and molecular weight (190 - 2000 g mol-1). For each polypropylene glycol, foam stability increases with concentration and passes through a maximum, beyond which foamability is suppressed as the solubility limit of the glycol is exceeded and droplets of glycol form. Light scattering data as well as static and dynamic surface tension results provide the key information leading to these interpretations. A maximum in foamability was observed for the PPG molecules with increasing molecular weight (caused by a change in molecular conformation at the interface). This suppresses the Marangoni effect and leads to a decrease in foam stability.

Jan 1, 2005

By A Gerson, S Miller, R Smart, J Thomas

Environmental Geochemistry International (EGi) and the Ian Wark Research Institute (IWRI) collaborated in a three-year Australian Minerals Industry Research Association (AMIRA) research project (Project Number P387A) focussed on the prediction and kinetic control of acid mine drainage. As part of this project, single addition, and sequential net acid generation (NAG) testing was carried out on sulfide mineral samples. The test samples comprised a range of synthetic waste materials prepared using a quartz bulk and controlled quantities of the commonly occurring sulfide minerals; pyrite (FeS2), pyrrhotite (Fe7S8), arsenopyrite (AsFeS), chalcopyrite (CuFeS2), chalcocite (Cu2S), covellite (CuS), bornite (Cu5FeS4), galena (PbS) and sphalerite (ZnS). NAG test results clearly show that there are significant differences between the acid forming potential of sulfide minerals. The NAG test results for each mineral were compared with theoretical acidity values (NAPP*). The NAPP* calculation was based on stoichiometric oxidation reactions assumed for each of the sulfide minerals. Sequential NAG values for pyrite corresponds closely to predicted NAPP* values, confirming the assumption that pyrite oxidation occurs according to the stoichiometry assumed. For the pyrite sample with 5 wt per cent S, two NAG stages were sufficient for all of the sulfur to be released to solution. Since sulfides in waste materials will generally be dominated by pyrite, results also confirm the validity of including NAG testing for ARD evaluation of most waste rock. NAG testing confirms that of the sulfide minerals examined, only pyrite, pyrrhotite, arsenopyrite and chalcopyrite are acid producing, ie able to produce leachate with a pH less than 4.5. In the case of sphalerite, galena, bornite, chalcocite and covellite the pH of the final NAG solution was greater than 4.5. The significant differences between the acid forming potential of different sulfide minerals could lead to overestimation of acid producing potentials based on NAPP values calculated from total per cent S alone, ie assuming all S is present as pyrite. The oxidation of galena during the NAG test resulted in the consumption of acid. The examination of the galena surface by X-ray photoelectron spectroscopy (XPS) after oxidation in peroxide solution indicated the presence of polysulfide. The reaction of sulfide to polysulfide is acid consuming, thus explaining the net acid consuming behaviour of galena in the NAG test. This reaction pathway may provide a possible explanation for the lower than expected acid production observed for some of the other sulfide minerals examined.

Jan 1, 2003

The Sao Chico gold project is located on the Tocantinzinho trend which is the most mineralised zone in the Tapajos Mineral Field of Brazil (see Figure 1). The Tapajos goldfi eld was the site of the biggest gold rush in Brazilian history in the late 1970s and 1980s when approximately 500 000 garimpeiros (artisanal miners) rushed to the area to exploit extensive areas of newly discovered alluvial gold. Approximately 20 - 30 million ounces of gold were produced from these operations before the easily won alluvial gold deposits were largely depleted. The Tapajos region has had little exploration by modern exploration methods compared to any other equivalent gold fields in the world. The gold occurs in sulfide veins developed in shear zones within Proterozoic granites. Gold grades vary from approximately 15 g/t in the hard rock veins, to up to several ounces per tonne in the supergene weathered upper portions of the veins. Goldbearing vein zones in the weathered profile are free digging. In addition, tailings dumps from previous mining operations contain gold grades of approximately 1 g/t. Metallurgical test work conducted to date indicates that gold recoveries of at least 70 per cent can be achieved via gravity concentration. Gold Anomaly, via its 100 per cent owned Brazilian subsidiary, Gold Aura Do Brasil Mineracao Ltda (GOAB), plans to mine the tailings and weathered vein material by open cut methods to generate a quick cash fl ow and to provide a better understanding of the mineralisation as part of a feasibility study for mining the underlying sulfide zone mineralisation (see Figure 2). Mining will utilise locally hired excavators and trucks and ramp up to a rate of 100 tonnes per day. To treat the gold-bearing material, GOAB has purchased an integrated 'state of the art' gravity concentration processing plant from Gekko Systems of Australia. The processing plant includes a scrubber for clay and oversize removal, coarse gold gravity separation via an inline pressure jig and an inline spinner; and fine gold gravity separation via a Falcon Concentrator. The plant is expected to be operational by late 2010. This is an ABSTRACT ONLY. No paper was prepared for this presentation. 

Aug 1, 2010

IN the ordinary course of treatment of pyritic ores or concentrates, whether for the recovery of copper, tin, gold, or any other contents, the removal of some or all of the sulphur contents is almost invariably the first step. The practice is to roast the ore in a current of air so that the sulphur is oxidized to sulphur dioxide and the metal constituents are changed from sulphides to oxides. If it is feasible to produce sulphuric acid in conjunction with the treatment process, the sulphur can be usefully employed; but if this is not possible, then the sulphur contents not only become a dead loss, but tend to be a nuisance as well in the surrounding neighbourhood.The problem of avoiding this disadvantage and making economic use of the sulphur has had attention from the early days of scientific metallurgy, and in the past few years very special efforts have been made both to drive part of the sulphur as such from pyrites and recover it, and to replace the sulphur in the S02 by carbon, with the production of carbon dioxide and precipitation of the sulphur. So far economic success does not appear to have crowned these efforts. In the case of pyrites, of the two atoms of sulphur which go to make the FeS2, the first is very lightly held. Dissociation is effected by heat alone at a temperature which is given by Peters as 5160 C.Now, sulphur and hydrogen will unite or burn together, with the production of sulphuretted hydrogen. It occurred to the writer that, if hydrogen was passed over pyrites heated to the above temperature, this first atom would be snatched away by the hydrogen, and could possibly be economically recovered.The first step consisted of some simple laboratory experiments. From these it was found that this first atom was readily removed, and that the extraction was practically complete. Further, the reaction took place at a low temperature, a dull red heat being sufficient.

Jan 1, 1923

By A B. Richards

Time window analysis that limits the explosive mass fired within a specified time window (commonly eight milliseconds) has been used for many years in blast design by explosives engineers. Despite several warnings in the past that this technique has limited practical or scientific basis and, in many cases, does not effectively control vibration, almost every textbook and blasting manual refers to time window charge mass limits as a primary vibration control technique. It has become entrenched in some blast vibration management plans, despite being inappropriate for the particular situation. With the flexible initiation timing available with electronic detonation almost a practical reality, and the 8 ms constraints in-built into the signal tube initiation system thereby lifted, it is timely to review the significance of the 8 ms time window in controlling blast vibration. This paper re-visits the original research that led to the development of the 8 ms criteria and the non-supportive conclusion of the original researcher. Because airblast was not measured, the 8 ms time window was never intended to be applicable for airblast control. Examples of blast designs are given in this paper that comply with the 8 ms time window limit that result in substantially increased air and ground vibration, together with examples of blast design that does not satisfy time window considerations, which results in reduced air and ground vibration. Techniques that identify wavefront reinforcement, due to the combined effect of drilling pattern and delay sequence, can assist explosives engineers to avoid high blast vibration situations that result from the inappropriate application of time window techniques and other adverse delay combinations.

Jan 1, 2003

By McKenzie C, Michaux S

Modern quarrying operations focus attention on blasting operations as a critical component in the overall cost-effectiveness of quarrying. Generally, optimisation of blasting has been linked to the processes of drilling, explosive consumption, secondary breakage, and product haulage to the primary crusher. This approach gives no consideration to the impact of primary crusher feed size distribution on downstream processes, or on the quality (ie shape and strength) of the final product. Blasting operations can be manipulated to produce a wide range of muckpile size distribution. This paper presents the results of studies into the impact of muckpile fragmentation on downstream crushing and screening operations, and includes measurements of primary blast oversize and muckpile fragmentation, together with measurements of size distribution, circulating loads and flakiness for various process streams throughout a quarry processing plant. This paper is an extension of other studies investigating the prediction and control of fragmentation from blasting, and the role of explosive performance in controlling muckpile fragmentation.

Jan 1, 1995

Obvious differences in mineral deposit types occurring in Outer Melanesia and Northern Chile can be related to the sub- marine-dominated nature of volcanism in the' former area and the subaerial-dominated nature in the latter area. Subtle variations in subvolcanic epithermal-porphyry ore systems between the two areas probably result from differing ore fluid compositions. Hydrother- mal convection cells in Outer Melanesia will be seawater-dominated, consequently rela- tively high salinities and chlorine contents will characterise the ore solutions. Trans- portation of metals as chloride complexes is likely and the ease of seawater sulphate reduction to sulphide in the ore systems will lead to widespread, sparse dissemination of sulphide minerals. Relatively low grade por- phyry copper deposits will typify these ore systems. In Northern Chile hydrothermal convection cells will usually be dominated by meteoric waters. Consequently ore fluid salinities are likely to be lower and chlorine will be less abundant. Under these circum- stances transport of ore metals as bisulphide complexes could be important. Boiling and loss of H2S gas from these fluids would lead to rapid precipitation of metals and higher grade deposits. Erosion rate is a very important factor in the preservation of ore deposits and this may be the major control on the richness of a metallogenic province. The abundance of mineral deposits in the El Salvador region of Northern Chile compared to Fiji is probably a function of the much lower rates of erosion in the former area.

Jan 1, 1987

By King CJ

The C.S.A. concentrator of Cobar Mines Proprietary Limited was expanded in 1974 to treat 80 000 tonnes of copper-lead-zinc ore per four week period. Jaw crusher product is fed to two par- allel primary autogenous mills followed by a secondary ball mill. Each mill operates in closed circuit with cyclones. Improved control of grinding rate and product sizing has been obtained from this circuit compared with the system of two parallel single stage autogenous mills. The main operational variables are des- Cribed.

Jan 1, 1978

THE following description of the surface plant of the Great Fitzroy Mines is to be understood as having been compiled by a mechanical engineer, who concerns himself more with the various appliances used, their correct construction to enable them to accomplish their prescribed work, and the production and transmission of the power required to operate them, than with the reasons for the physical and chemical processes which those appliances are called upon to assist in carrying out. Hence the metallurgist will not find herein more than the skeleton of the organism, which perhaps he would wish to be clothed with the detailed description of the substances undergoing treatment, in their various combinations, at all stages, and the results attained in separating the valuable constituents from the worthless. So, also, no details will be found of the methods employed by the management for. the purpose of determining by sampling and assaying the nature of the various products obtained.GENERALThe ore being worked at the Great Fitzroy Mine is divided into two classes :-1. Ore that requires concentration before smelting.2. Ore that can be smelted direct.Flow-sheet (Fig. 1) shows in outline the process of treatment to which ore of the first class is subjected, and the writer will endeavour to fill in that outline with some details of the appliances used.

Jan 1, 1911

Before presentIng my address I wish to acknowledge the honour which has been conferred on me by my appointment to the position of President of the Australasian Institute of Mining and Metallurgy.It is a matter of great concern to us all to find our Empire at war. I am confident that, as was the case in the war of 1914-1918, members of this Institute and of kindred Institutes and Associations will contribute in full to the Empire's needs and that in the end our cause shall triumph.I think it appropriate that I should take as the subject of my address that of the Broken Hill Lead-Silver-Zinc Industry. The subject matter of this address has been confined to the operations of Mining, Ore Dressing, Lead Smelting and Refining and production of Electrolytic Zinc in Australasia. The review of the Broken Hill Lead-SilverZinc Industry would not, of course, be complete without reference to those Australian industries which trace their origin to the Broken Hill field, but· it is thought that an outline of these industries would make thIs review too extensive.HISTORICALMany efforts have been made to translate the early history of Broken Hill and its subsequent growth throughout the years into one of the wor~d's most famous mining fields in the form of a simple story.

Jan 1, 1940

By Grant J

In surface mining, significant improvements in efficiency can be obtained through greater control over the formation of the muckpile. By tailoring the muckpile shape and its looseness to the requirements of the excavating equipment savings can be rea- lised through increased production, machine life and reduced maintenance. For instance, one open cut coal mine has recently estimated that a 2001o improvement in its front row throw would realise $320,000/year savings in rehandle costs alone. Previously greater throw has been achieved by increasing the powder factor through increased quantity of explosive or by drill- ing a larger number of holes-both at a significant cost penalty. However a recent series of experimental blasts demonstrated that it was possible to achieve a twofold increase in the distance of throw of a single row blast by simply changing delay timing alone. The Nobel Electronic Delay Detonator was used to provide the timing flexibility and control required for a thorough study of the effect of blast timing on heave. Whilst it is well accepted that the front row of a blast dominates the extent of throw, it was also found that the profile of the blast could be significantly altered. To date, the general consensus has been that the muckpile for- mation from a blast is a function of the blast geometry, the rock type, the explosive and the initiation sequence. Typically the geometry, rock type and initiation system have a far greater impact than the explosive type. This has been demonstrated by many high speed film studies. However the extent of influence via initiation has rarely been fully evaluated, owing largely to the limited control offered by conventional detonators.

Jan 1, 1988

By G Power

The successful implementation of sublevel caving (SLC) at Ridgeway Gold Mine (Ridgeway) requires the technical aspects of caving and flow behaviour to be understood. Cave propagation must be controlled and continuous to allow safe extraction of ore below. The understanding and use of processes to manage granular flow behaviour are also required to ensure economic metal resource recovery. Caving and flow technologies are thus critical to the economic viability of the application of the SLC mining technique to Ridgeway Gold Mine. At the time the Ridgeway SLC design was approved there were significant technical uncertainties associated with cave mining methods, including the SLC mining method in competent rock masses. This was in spite of the fact that caving is a relatively low cost mining method. Unique features generating technical risks at Ridgeway include: the fact that the orebody is blind (550 m below surface); highly competent cap rock (RMR >50); and high aspect ratio (height to width ratio of 3:1). Due to the presence of these unique features Ridgeway is considered to be beyond the current state-of-the-art in SLC mining technologies. The success of the technique at Ridgeway to date has indicated that blind SLC mines in strong rock mass can be operated safely and productively, if the technical risks are understood and properly managed. The risk management process was defined by the use of a formalise process to identify and assess the risks to the mine. The major mining related risks were formalised into Major Hazard Management Plans (MHMP) which contained a description of the risk, early triggers indicating the creation of a hazard and a series of agreed responses to be automatically initiated in the event of each trigger occurring. This paper outlines the following with respect to the critical technology areas of caving and flow: international industry, state-of-the-art technology; gaps in the application of this technology; the application of risk management, new processes developed at Ridgeway to bridge these gaps, including issues encountered; and trials and experimentation conducted to develop the new processes.

Jan 1, 2003

By Goldie R

The use of options theory in business has become well established in recent years and is currently one of the most exciting areas of current finance research. The theory can be used to value levered firms, and streams of contingent payments. This technique also has very practical applications in the areas of capital investment analysis and the valuation of equities in the natural resource industry. The use of options theory has been well accepted and used for many years in the trading of commodity options and futures contracts, in banking and insurance and in other industries. It also can be used to value such diverse contingent claims problems as the income tax liabilities of the firm and share underwriting agreements.Its application to the more complex options, such as those present in the resource industry, is only now becoming known. This lag is, at least partially, due to the difficult mathematics involved in solving complex options problems. Another factor is the almost overwhelming abundance of uncertainties, such as grade, tons and other natural risks, which must be considered in the evaluation mining projects.

Jan 1, 1990

By P R. L Browne

Study of geothermal systems in the Taupo Volcanic Zone (TVZ) has significantly advanced our understanding of the processes of epithermal mineralisation. The three main lessons learnt are: 1. knowledge of their chemical anatomy; 2. precious metal transport and deposition; and 3. hydrothermal alteration zoning. These are described in the context of ore formation and exploration.

Jan 1, 1997

By M E. Malmstr÷m

Quantification of site-specific sulfide oxidation rates is crucial to accuracy of prediction of, for example, the environmental impact of a mine site. Sulfide oxidation reactions are reportedly increased by bacterial mediation; determination of abiotic and biotic weathering rates thus requires the establishment of sterile control samples. However, sterilisation often involves exposure of samples to extreme conditions that may alter the physical, chemical, or mineralogical characteristics of the tailings and hence affect element release rates. The impact of various sterilisation techniques, common and novel, on the element release rates from tailings from the Kristineberg site, northern Sweden, has been investigated. Batch weathering experiments indicated that the different methods of sterilisation (autoclaving, heat treatment, ethanol/heat treatment, application of antibiotics, rinsing with distilled water, and γ-radiation) did not greatly affect long-term element release rates. Long-term experiments (>30 days) are thus to be recommended for establishment of weathering rates. Sterilised and untreated control samples showed similar element release rates after ~100 days of experiments; possible explanations include that microbial oxidation is not important under our experimental conditions (Po2 = 0.2 atm, pH ~2.3, 22¦C, 0.01 M HNO3, no additional nutrients).

Jan 1, 2003

By T Iwadachi, T Fujisawa an, G R. Alvear

A large amount of Be2C and BeO is formed during the Cu-Be alloy production process, because beryllium is a highly reactive element. Carbide and oxide formation impairs the production yield and the quality of the Cu-Be alloy products, and therefore should be minimised. As a first step for solving these problems in the process, the following thermodynamic properties of the Cu-Be-C-O system were investigated. Based on the results, the equilibrium relations of the Cu-Be-C-O system were clarified and the operational conditions of the current Cu-Be alloy production process were also examined and discussed.

Jan 1, 2000