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By M Binks

This paper presents a case study that describes the selection, development, engineering and construction of a process plant for the biological oxidative pre-treatment of a refractory pyrite-arsenopyrite gold ore flotation concentrate. Prefeasibility and feasibility study resource modeling, metallurgical testwork, and environmental and engineering studies are outlined. Options considered for oxidation of the ore, which examine cost, risk, operability, recovery, engineering and environmental aspects are compared, with particular reference to pressure and biological oxidation. The BIOX« biological oxidation process was selected as the preferred oxidation process and the flow sheet for this process is presented. Selection of the BOIX« process resulted in special requirements for the feed preparation circuit, residue treatment and disposal, materials of construction and engineering. Use of a biological process in ore treatment also introduces particular process and engineering risks the management of which are discussed.

Jan 1, 2004

By Jacobs M

After a methane explosion in a coal mine a pre-determined crisis management procedure is instigated. As the process rapidly evolves the inevitable question arises - are personnel trapped underground, are they alive and can they be rescued without putting the lives of the rescue crew at risk? This is a very emotive question with many sub-questions such as; could anybody have survived, is there the potential for a secondary explosion and is there a `window of opportunity' before that secondary explosion occurs?To determine if that window of opportunity exists two fundamental elements must be in place; a method of determining the atmosphere at key points in the mine and a method of predicting the course of change of that atmosphere with respect to time. The first element can be achieved if the tube bundle system is intact and drawing samples from known points, alternatively boreholes can be drilled from the surface. The second element can be realised by utilising a sequence of computer generated control charts which have a time axis, a percentage combustibles axis, the upper and lower explosive limits of the current atmosphere and a prediction option which allows the user to look at the potential changes in the atmosphere over a set period of time. These control charts would be part of the mines on-going crisis management system rather than a tool to be used after an explosion had occurred.

Jan 1, 1998

It is a well known fact that the best method of rock reinforcement is to avoid physical ground support. This goal can be achieved by means of: - Increasing the rock structural strength - Geological definition and forecasting. - Sequencing the excavation - Smooth blasting In many cases however, extra ground support is needed in order to maintain safe working conditions. In an open pit, the structural strength of rock cannot be increased by lowering the pit walls due to economical reasons. Economy demands steeper walls and less waste to be hauled to the dump. The geological conditions can also often be extremely poor and unpredictable. For excavation sequencing and smooth blasting there are good possi- bilities, such as cleaning of the pit walls after the main excavation, arul- ing of long small diameter straight inclined holes, use of smooth blasting techniques and lightened explosives.

Jan 1, 1989

By P Grouhel

In the recent years several new blasting technologies have come into use in surface mines. Electronic initiation, low-density emulsion explosives and modelling software are in regular use throughout the world. In Australia, these new technologies have achieved significant application, largely in open cut coal mines where more than 20 per cent of blasting is now conducted with electronic initiation systems. These new techniques have contributed to the vast improvement in blasting outcomes evidenced by increased recovery of saleable product and faster excavation rates. In large surface mines, OricaÆs unique combination of electronic initiation systems, bulk emulsion explosives and modelling software can be harnessed to target critical value outcomes. This includes targeting better fragmentation, increased ore uncovery rates and better wall stability û all adding to improved mining operation profitability. Orica Mining Services have combined these technologies into a set of offerings called Blast Based Services (BBSÖ). The paper describes applications of these new technologies and possible benefits in large surface mines.

Jan 1, 2007

A non-contacting under-belt capacitance and gamma-ray backscatter technique has been developed for the on-line measurement of moisture in coal. In this technique, moisture was correlated with radio frequency susceptance and conductance determined using an under-belt capacitance sensor in which a fringing electric field Interrogates a layer of coal on the conveyor belt directly above the sensor. To compensate for variations in the density and thickness of the coal layer, an under-belt gamma-ray backscatter gauge was used to measure an equivalent volume of coal.A plant trial of the technique was conducted at Stockton Borehole Colliery, SW Australia, where the gauges were installed on the coking coal product conveyor. Product moistures, in the range 7 - 14%, were determined with r.m.s errors of 0.50 and 0.25 wt% using on-belt and static off-belt gauges, respectively. The difference in the on-belt and off-belt gauge measurement accuracy was attributed to sampling errors in the calibration of the onbelt gauge.

Jan 1, 1989

By Bearman R. A, Parkin R. M

Traditional quality control procedures for aggregates production within the quarry industry rely on off-line laboratory analysis, resulting in poor performance and inconsistent product quality. A high speed on-line aggregate classification system is described here. A product sampling system directs aggregate through an inspection chamber where a novel imaging system digitises the particle geometry. Data processing algorithms extract dimensional data and image features, while a neural network classifier assigns a qualitative shape descriptor to each rock particle. This system provides each sampled batch with a complete analysis of size and shape distributions, complementing a new generation of cone crusher technology to maximise product quality and plant efficiency.

Jan 1, 1995

By Richardson G. W, Yap L. C

Friction rock stabilisers (FRS) are steel-based, thin-walled tubular ground reinforcement widely used in underground mines in Western Australia. Following installation these stabilisers are subject to corrosion which may reduce the load carrying capacity and lead to unexpected ground falls. Although corrosion has been recognised as a common occurrence, particularly under aggressive mine water and mineral conditions present in underground mines, the knowledge of the effects of corrosion on the mechanical behaviour of FRS is limited. The Department of Minerals and Energy of Western Australia has conducted a laboratory based program of studies to investigate the effect of corrosion on the mechanical properties of FRS. The studies have focused on the effect of corrosion on tensile strength of FRS and frictional resistance along the interface between FRS and the drillhole wall. The results indicate that under certain conditions corrosion damage can significantly reduce the effectiveness of FRS.

Jan 1, 1996

By Armstrong ME

The gas bubble energy generated by an explosive plays a major part. in the fragmentation, muckpile movement and damage produced. Previously, the interaction between gas pressure and the rock has been interpreted from a theoretical basis or a qualitative study of breakage mechanisms. A method to measure the fluctuations in gas pressure in rock adjacent to the blast has been developed. This peak pressure will vary with structure, as well as with distance and explosive type. The technique is simple to apply and can be used to observe the flow rate of gas at. varying distances. The apparent velocity of penetration is an indication of whether gas has travelled through pre-existing or blast induced cracks. The technique provides a ?n:eans of determining the suitability of an explosive for a given rock type, depending on the amount of displacement desired. The technique has application in optimir.irig throw blasting and predicting and controlling damage, particularly in highly structured rock masses.

Jan 1, 1986

By Martins V, Dunne R

A re-evaluation of the Hampton Boulder prospect in the early eighties resulted in a decision to proceed with mine development in December 1985. A 500 000 tpa gold treatment plant was commissioned in December 1986. The treatment facility was expanded to 1 600 000 tpa in July 1988. A tailings treatment plant to improve recoveries from harder gold bearing sulphide ores was built in December 1990. The development of an underground mine in 1991 meant that a source of sand for backfill was required. A sands plant to fulfil this requirement was commissioned during November 1991.As of June 1992 a total of 7 710 487 tonnes of ore have been treated through the New Celebration gold plant. Total gold production from inception of the new mine until June 1992 is 545 470 ounces obtained at an average recovery of 90.1 per cent from an average gold head grade of 2.4 g/t. The combined quoted ore reserves at the end of December 1991 was 14Mt grading 1.8 g/t gold

Jan 1, 1992

BHP BillitonÆs Yandi channel iron deposit has a large resource of approximately 1.3 billion tonnes. This is a bulk mining operation with a high degree of selectivity not being practical. In contrast the deposit geology is a complex interrelationship of primary channel facies, secondary enrichment of iron and a secondary redistribution of the major contaminants. These variations in geology and alteration can occur over ranges of hundreds of metres down to knife edge contacts. In addition, differences in primary facies and mobility during alteration often result in the iron and contaminants having different patterns of enrichment and depletion. Despite the scale of these operations, if the geological domaining is not optimal, significant errors in the resource estimate of grades and tonnage will occur. Getting the geology right has become a common clichT among mining professionals. However, in many situations, obtaining optimal geological domains for resource modelling is best achieved when there is input from geology, statistics and geostatistics. In this paper, moving window statistics are utilised to see through locally high variability to identify trends that assist in locating difficult to identify geological boundaries. After the creation of geological domains, univariate and multivariate statistics and principal component analysis assist in validating and characterising geological domains. Finally, variography and domain contact analysis are used to analyse the nature of the boundaries between geological domains. At the Yandi channel iron deposit, the inter-relationship between geological and geostatistical analysis has resulted in significant improvements to geological domaining and the treatment of domain boundaries during estimation of iron and contaminates.

Jan 1, 2005

By M A. Gontalves, A F. D C Varajpo

The Rio Capim kaolin district, located in the north-east of Parß State, Brazil, constitutes one of the worldÆs largest high-whiteness kaolin reserves for the paper coating industry. It contains, at the base of the main ore, a soft kaolin that gradually changes at the top into a ferruginous duricrust followed by a flint kaolin. The flint kaolin is completely discarded during the exploitation of the soft kaolin. With the view of a more complete beneficiation, aiming at a sustainable development of the minerals industry, the use of this residual flint kaolin has been considered for the manufacturing of zeolites. Zeolites were synthesised from the flint kaolin through a reaction between metakaolinite with soda at 80¦C, for durations of 24 to 144 hours. The transformation into metakaolinite was carried out at 800¦C and was not affected by the titanium oxides. For a synthesis time of only 24 hours, a zeolite 4A very close to its theoretical definition was obtained, whereas for synthesis times longer than 96 hours, a slight formation of hydro-sodalite was also observed. The synthesised zeolites were tested as cationic adsorbents on 0.5 molar solutions of Cu, Pb, Cd and Zn. The adsorption was measured for contact durations of one and three days. It was noted that the exchange kinetics were slow and that the retention was significantly greater after three days than after one day. The retention was greater than 50 per cent of the theoretical exchange capacity for Pb, Cd and Zn, which was different to Cu, where the retention exceeded its theoretical exchange capacity.

Jan 1, 2008

It is now 32 years since Walsh's classic publication (1) heralded the beginning of atomic absorption spectrophotometry (AA) as we know it today. During this time, AA has developed into the most widely used analytical techniques for the determination of the metallic elements. The years have seen progressive changes in instrumentation so that today it is a highly sophisticated technique. One area of development in AA that is experiencing renewed attention is in the area of electrothermal excitation. In this technique a flame is not used by the analyte solution is atomised by an electrically heated graphite furnace. For a large number of elements the graphite furnace atomic absorption spectrophotometer (GFAA) is considerably more sensitive than flame work. It is common to be able to detect concentrations one hundred times smaller than those possible by flame. Today's geochemists are finding that they can gain valuable information out of very low limits of detection. Electrothermal atomic absorption spectrophotometry (or GFAA) allows for low limits of detection and can be seen to be a valuable aid to geochemical prospecting Analysis.

Jan 1, 1987

By Y Gu

Based on the mode of occurrence, gold is classified into three categories: microscopic gold, submicroscopic gold and surface-bound gold. Microscopic gold, or visible gold, refers to gold minerals in which Au occurs in a substantial amount, such as native gold and electrum. Submicroscopic gold, ie invisible gold, refers to gold contained in the structure of other minerals (mainly sulfides) in minor to trace amounts. Surface gold is the gold that was adsorbed onto the surface of other minerals during mineralisation and subsequent oxidation or metallurgical processing. Gold mineralogy has a significant impact on its extractive metallurgy. Gold process mineralogy helps address problems related to gold ore processing. It is widely used as a predictive and troubleshooting tool in gold ore processing, and provides useful information on process selection, flow sheet development, recovery improvement and reagent consumption optimisation. This paper will begin with the classification of gold ores, and will focus on gold mineralogy and how it impacts extractive metallurgy through case studies.

Jan 1, 2008

By M Brewster

Goldfields Abosso Goldfields Limited (AGL) is a Ghanaian registered company that owns and operates the Damang Gold Mine. Gold Fields Ghana Holdings Limited holds a 71.1 per cent interest in AGL. The Damang concession held by Gold Fields Ghana Holdings Limited covers a total area of 271 km2 located 40 km north of the town of Tarkwa in the south-western part of Ghana. Gold Fields as a company registered on the New York Stock Exchange is legally obliged to be SOX (Sarbanes-Oxley). Sarbanes-Oxley Section 404 (SOX404) is on management assessment of internal controls. The Mineral Resource Management (MRM) function of AGL manages three Prospecting Licenses and two mining licences. At least ten pits/prospects are scattered along the two limbs of the Damang Anticline and have two main types of mineralisation notably Paleoplacer and Hydrothermal. Thus SOX404 procedures are put in place to treat each mineralisation type in the best way for reliable resource outputs and estimates. Generating auditable resources for AGL is a prime but most important function of MRM. Thus important checks are built and designed to ensure that all relevant geological and geostatistical inputs conform to procedures outlined under SOX404 requirements. More importantly sign offs are designed to ensure that technical personnel involved in all aspects of resource and reserve generation are satisfied and can be held accountable.

Jan 1, 2007

By Kissell F. N, Thimons E. D

The Bureau of Mines used sulfur hexafluoride (SF6) tracer gas to evaluate the effectiveness of gob ventilation and/or sealing practices at three coal mines, each having different problems associated with their mined- out areas. The purpose of these ventilation studies was to better understand whether current techniques employed for ventilation or sealing are successful at minimizing the potential for gob fires and explosions. The work performed at each mine is discussed: One is a longwall operation that uses ventilation to carry off hazardous gases, and two are room- and-pillar operations, each with far different concerns, that seal off the gobs to isolate them from the main mine ventilation. In all cases, employment of the Bureau's SF6 tracer gas technique resulted in answers to questions raised by the mine operators concerning the effectiveness of their gob ventilation or sealing practices in preventing mine fires.

Jan 1, 1988

By Burnett C. C H

GEMNet, (Grade Estimation using Mapping Networks), is a grade/reserve estimation software system that uses the artificial intelligence technique known as neural networks to perform reserve estimates from both two- and three-dimensional data samples from a mineral deposit. The system is the result of research carried out over the past three years into the feasibility of using neural networks for reserve estimation at the AIMS Research Unit in the Department of Mineral Resources Engineering at the University of Nottingham. This paper describes the architecture of the GEMNet system including details of the neural network components of the system. The performance of the GEMNet system is then compared to several other widely used reserve estimation techniques on two reserve estimation examples. The results produced by the GEMNet system compare favourably with more conventional estimation techniques, but require fewer assumptions to be made about the form of the data used, and do not require the use of complex mathematical modelling.

Jan 1, 1995

By Ramsay WRH

The Mount Stavely Volcanic Complex compri- ses one of a number of northerly trending fault bounded greenstone occurrences in Western Vict- oria, of probable Cambrian or older age. The greenstone belt is coincident with several linear positive aeromagnetic anomalies, which outline the surface and subsurface extensions of these greenstones. Mapping at Mount Stavely has identified serpentinite, variolitic basalt, two-pyroxene and pyroxene-hornblende andesite, dacite, rhyodacite and their pyroclastic equiv- alents. Chemically and mineralogically the volcanics constitute a calc-alkaline assemblage. The mineral potential of the region has been enhanced following a discovery by Pennzoil of Australia Limited near Ararat, of sulphide min- eralisation containing approximately 1 million tonnes at 2.7 percent copper. The volcanic environment of the Mount Stavely Volcanic Complex is discussed in terms of similar environments found in Canada.

Jan 1, 1982

By Waters CA, Happ JV

The debismuthising plant, commissioned in 1980, is based on the Kroll-Betterton process for preliminary bismuth removal with subsequent antimony treatment for fine debismuthising. Bullion flowrate is continuous and the plant was designed to achieve low bismuth lead product at rates of up to 20 tonne/h.Development of the first stage of the operation has enabled reliable operations at 25 tonne/h to be achieved. Thesedevelopments also introduced the opportunity to treat higher bismuth bullion at up to 35 tonne/h when operating the first stage only to produce product lead of 0.029 per cent Bi, meeting the ASTM B29-55 Corroding Lead Standard.

Jan 1, 1985

By Mur D. M

Metal ferrites are formed by the high temperature reaction of various metal oxides with hematite and are commonly found in the calcines derived from the sulfation roasting of zinc, copper and nickel sulfide concentrates. The Jarosite Process is designed to treat such zinc ferrites by hot acid dissolution but little information is available on the basic reactivity of various ferrites and the effect of Eh. As part of an overall study of the reactivity of calcine products from copper and nickel sulfide concentrates it has been found that Eh plays an important role in the rate of dissolution of magnetite, hematite and nickel oxide by HC1 and H2SO4. Further studies on the reactivity of pure synthetic copper,zinc,and nickel ferrites also show a dependence on Eh. This paper discusses the relative reactivity of iron oxides and metal ferrites in 1 M HC1 and the results of electrochemical studies using cyclic voltammetry. A mechanism for the dissolution reaction is proposed as well as factors which determine their leaching. It is shown that the rate of leaching of metal ferrites with HC1 is enhanced in the presence of reducing agents such as Cu(I) and Sn(II). By contrast the leaching of NiO is enhanced by oxidising agents such as Cu(II).

Jan 1, 1987

By Grey D, Turner R, Capsanis J

Coal fines are recognised to have a major impact on the cost and efficiency of the recovery of saleable coal. Fines affect the productivity of the whole mining cycle because of the low yields obtained in washing this material as well as affecting the moisture content and handling characteristics of the final product.In 1990, Coal and Allied Hunter Valley Mine initiated an internal study into coal fines based on the assumption that a reduction in fine coal in ROM material will lead to increase yields in the preparation plant. The initial results of this study indicated that the level of fines in the ROM coal can be reduced by more than 40 per cent by simple changes in blast design and implementation.

Jan 1, 1992