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By C S. Kelsey, J R. Kelly

Australia is presently enjoying the fruits of a booming iron ore market. Expectations are that market strength will be supported in the short to medium term by increasing feedstock demands from steel mills, as world economies rebuild post-Covid-19. However, as cost and environmental pressures increase the longer-term market outlook will be dominated by product quality. The ‘flight to quality’ will place increasing demands on direct shipping ore miners as they compete to maintain their standing in the iron ore marketplace. China will progressively disengage from its dependence on Australian imports, leaving miners under increasing pressure to boost product quality and diversify outlets globally. Australia has vast deposits of low-grade magnetite ores located mainly in remote and arid regions of the continent. This paper proposes a dry grinding and magnetic separation process to produce premium concentrate grades from the low-grade ores, to assist in meeting future product quality demands. The premium grade concentrates could be either blended with lower quality direct shipping ores or marketed separately. The proposed dry concentration process involves the pairing of Vertical Roller Milling (VRM), a mature technology widely used in the cement industry, and Planar Magnetic Separation (PMS), a new methodology, which has been developed to the threshold of commercialisation by the private Australian company Cyclomag P/L. Two laboratory prototype planar magnetic separators with field strengths of 1800 gauss and 6000 gauss have been built and tested on a range of magnetite ore types over the past three years. In each case, following grinding to liberation sizes, a combination of roughing and cleaning operations has produced pellet grade concentrates. Vertical roller milling has competed successfully with conventional media milling in grinding cement clinker, limestone and blast furnace slags. A key advantage of dry VRM/PMS processing is its potential adaptability to stepwise modular development, which can minimise initial capital investment, while generating early revenue streams to cope with unpredictable market volatility.

Nov 8, 2021

Drilling underground can be a hazardous undertaking in many circumstances. Raiseboring and boxhole boring underground could form an integral part of the block caving production methodology and getting the right mix of technical capability, ergonomics and economical viability has been the goal of many machine manufacturers. With the introduction of the Terratec Universal Boring Machine concept, flexibility of raiseboring, downreaming and boxholing has been enhanced by the introduction of a single machine that will perform all three processes. In addition to its technical flexibility, additional safety features have been introduced that will eliminate many sources of injury by mechanising most of the operational procedures. Together with the one-man remote operation, this machine design addresses and solves many of the safety issues. This paper outlines the machine concept, details its safety features and shows the techno-economic advantages for use in the block caving environment. Block caving is a distinct caving method applied mostly to large massive orebodies because of the inherent low costs and high production capabilities. Areas of sufficient size are mined by undercutting so that the mass above will cave naturally. Extraction of the caved ore at the bottom of the ore column causes the caving action to continue upward until all of the ore above the undercut level is broken into sizes suitable for handling (Figure 1).

Jan 1, 2000

By P Gomez, R Baumgartner, G Escobar

"The Cerro Corona mine consists of a Cu-Au porphyry deposit located in the Andes of northern Peru. The deposit comprises a typical Cu-Au multiphase porphyry mineralisation that has been overprinted by an epithermal event. This has generated a complex pattern of argillic alteration facies, which was accompanied by a locally structural-controlled Au-Cu mineralisation with the presence of gold and limited Cu sulfides and sulfosalts. These features, along with the porphyry-style mineralisation, produced a multifaceted occurrence of gold.Since the beginning of operations at Cerro Corona in 2008 there has been a continuous improvement of the geological and mineralogical knowledge. All mineralogical studies have mainly focused on host rock types and, to a lesser extent, alteration minerals, but little work has been done on the mineralisation itself. As a consequence, limited mineralogical information was available for use in the process optimisation initiatives.In the last two years, a series of mineralogical characterisation studies were undertaken with two main goals. First, to gain an understanding of the mineralisation genesis and second, to obtain a detailed characterisation of copper and gold minerals to support ongoing process optimisation. The first goal was achieved by conventional optical microscopy while the second required electronic microscopy and other microanalyses due to the necessity of quantifying several minerals of interest for the processing.The results were used to refine pre-existing geometallurgical domains, explain copper and gold losses in the flotation process and to some extent, improve copper and gold recoveries. The mineralogical characterisation is an ongoing work. Mineralogy provides the basis for any optimisation exercise since it looks in detail at the material to be treated and therefore, should be part of all geometallurgical programs.CITATION:Baumgartner, R, Gomez, P and Escobar, G, 2016. Comprehensive Mineralogical Characterisation at the Cerro Corona Cu-Au Porphyry Mine – the Fundamental Key for Geometallurgical Applications, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 221–230 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By B Washington, A Campbell, R Taylor

A sampling and measurement program was undertaken on the reaction shaft of the Olympic Dam copper flash smelting furnace. The object of the work was to provide information to validate a mathematical model of the burner and reaction shaft. Samples and measurements were undertaken through the burner inspection ports and the South East (SE) shaft sampling port about half way down the reaction shaft. Samples were collected to enable the calculation of particle loading of shaft gases, or sizing and chemical analysis of the partly-combusted feed, and the preparation of polished sections. Measurements were made of the temperature and sulfur dioxide content of the atmosphere, as well as plume velocity.To implement the program it was necessary to design and construct the following specialised items of equipment. For use at the burner inspection ports: a cup sampler for obtaining samples below the burners (temperature, solids loading and samples for characterisation).For use at the SE shaft sampling port and also at the settler level: trough sampler (plume definition and samples), isokinetic sampler (used as a velocity probe in this work), temperature probe (temperature traverses across the shaft), and sulfur dioxide probe (SO2 measurements across the shaft).The design of the sampling and measuring equipment is described, and examples are cited of the types of information obtained. The problems arising from working in a hot environment with molten or sticky particles are discussed.

Jan 1, 2005

By M Sykes

Gold was initially discovered at Ballarat in 1851. After initial alluvial mining, underground quartz mining commenced in 1853, continuing until 1918. The historic miners were considered to be capable of mining anywhere in the world after overcoming the difficult conditions within the Ballarat goldfields. Whilst mining has changed dramatically since the early 1900s the challenges with underground mining at Ballarat have not. Modern pumping systems cope with the moderate water inflows. However, modern machinery and efficient mining methods influence opening sizes and extraction techniques. In some cases modern techniques have accentuated the challenging ground conditions and complex orebodies that were faced by the historic miners. As the Ballarat East project has progressed towards production, technical challenges relating to geomechanics and mine planning are being resolved resourcefully.

Jan 1, 2008

By Cutmore NG

The moisture content of iron ore is important in handling, stockpiling, transport and further processing operations. Typically these ores contain both `free' and `bound' moisture, the latter being moisture that is not removed in a conventional laboratory determination of moisture by air drying at 105¦C, and it is the free moisture that is important in dust control and ore handling. The CSIRO Division of Mineral and Process Engineering has previously developed and commercialised gauges, based on capacitance and microwave techniques, for the on-belt determination of moisture in coal and minerals. However, these gauges determine total moisture, and have a different sensitivity to free and bound moisture in the material analysed. Consequently, the accuracy of determining total or free moisture alone may be significantly affected by variations in the bound moisture content. An investigation has been carried out on the simultaneous determination of free and bound moisture in iron ore fines (

Jan 1, 1993

By X Li, W McKeague, M S. Powell

This paper explores the importance of operators in the overall efficiency of mineral processing plants. With the potential of future control configurations becoming more remote, it is time to review the implementation of control and utilisation of operators. This paper is based on a preliminary review of operators and control room operations and clearly shows that, in the minerals industry, operations are typically run in a reactive mode (with a focus on ensuring equipment operation), rather than in a proactive mode (with a focus on optimising the process performance). The primary reason for this misguided approach is the short sighted thinking applied to the challenges of designing technology and organisational tools capable of addressing the essential operational needs: an approach which inevitably results in a disconnect between people and technology. Contrary to the popular approach of replacing operators with expert systems, the thesis of this paper is that the shift to more complex circuits, with higher demands on processing capability and control, will require the actual upskilling of operators. Experience in mineral processing and other industries indicates that expert systems cope well with small changes but are typically unable to respond to major changes in feed material and this is where the expert operator becomes crucial. Providing operators with ongoing high level training in process understanding, and restructuring how they interact with the plant and interface with the control system is the approach being proposed here - an approach surprisingly underutilised and often absent in the minerals industry today.CITATION:Li, X, Powell, M S and McKeague, W, 2012. Unlocking processing potential by empowering our operators, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 333-340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By W N. Qin, B Zhang, W Z. Huang, X S Mo

Mengzi Mining and Metallurgy Co, Ltd (MMMC) polymetallic ore contains recoverable amounts of tin, lead, zinc, pyrite and other valuable minerals. With the change in orebody, the run-of-mine (ROM) ore changed from lead zinc rich ore to tin rich ore, where the current ROM ore contains 0.45–1.25 per cent tin, 20–25 per cent sulfur, and 0.20–0.35 per cent copper. The previous processing flow sheet was designed to recover lead zinc rich ore and it is clearly not suitable for recovery of the current tin rich ore, where the tin was already overground and tin recovery was only 50.19 per cent. The Mengzi Mining Company has recently modified the concentrator circuit by incorporating rod mill and high efficient Derrick fine screen. As a result of the improved classification efficiency, the overgrinding of the tin ore was minimised and the recovery of tin was improved by 20.71 per cent, ie from 50.19–70.90 per cent. An additional $10 M revenue per annum can be achieved as a result of the modification.CITATION:Qin, W N, Huang, W Z, Mo, X S, Zhang, B and Wheeler, J, 2014. Application of high efficient fine screen to improve the recovery of tin concentrate, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 487–492 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

The Porgera gold deposit in the Papua New Guinea highlands contains about 387 tonnes of gold. The results of its exploration show the benefits of persistence and commitment to this difficult deposit. The mineralization consists of a complex intermix of auriferous and argentiferous sulphides, gold tellurides and free gold as disseminations, veins, stockworks and breccia matrix. Its deposition was structurally contolled within a system of mafic diorite intrusions and adjacent sediments. Two styles of alteration accompany the mineralization. Gold grades vary erratically throughout the deposit. Over a period of 22 years nine phases of exploration have been undertaken by six companies or consortia of companies. Surface rock chip sampling, geological mapping followed by scout and systematic grid diamond drilling have been the most successful exploration tools. Exhaustive metallurgical process investigations and economic evaluations of mining options have been invaluable in guiding the exploration towards defining the ore body. Impetus was given to the project during times of flagging enthusiasm by several important discoveries and a breakthrough in the metallurgical processing approach. The discovery of high grade ore deep in Zone VII in 1984 turned this marginal deposit into a potentially very large gold mine.

Jan 1, 1987

By D Woolmer

Since January 2019, BHP Olympic Dam have been trialling the use of a drone based LiDAR mapping system for the purpose for surveying stope voids. This new technology utilises Simultaneous Location and Mapping (SLAM) algorithm providing positioning, stability and collision avoidance in GPS denied environments. Implementation of this system utilised underground personnel trained in the equipment’s use. The study’s intention was to evaluate the effectiveness of this equipment versus traditional surveying methods in regards to quality, safety and productivity. The trial results showed a marked improvement in the quality, productivity and personnel safety when conducting surveys. The use of the drone and LiDAR system reduced personnel and equipment requirements for surveys, thus allowing these resources to be deployed elsewhere. The technology’s simple and rapid deployment allowed multiple surveys to be conducted during a 12 hour shift, including ad-hoc work with minimal disruption to underground operations. After the drone’s initial trial, further work was conducted to utilise the Hovermap LiDAR scanner on other platforms to increase utilisation. A mounting system was created allowing the LiDAR to be mounted on a remotely operated loader or vehicle. This enabled drawpoint scans to be taken directly after production completion, resulting in faster stope close outs and drive scans for convergence monitoring. Implementation of the LiDAR system has resulted in improvements in the stope production cycle by reducing delays previously associated with data capture. The increase in the volume and quality of data has also allowed in-depth back-analysis of stopes in new mining areas to be conducted, which have driven improvements in the design process.

Mar 15, 2021

By M A. Llano-Serna, D J. Williams, L Bu

Tailings dam failures continue to occur worldwide at an unacceptable rate, averaging two events annually over the last 100 years. Furthermore, tailings dams continue to grow in size, increasing the potential release of tailings and water should they fail. Tailings are generally deposited in a slurry state, with the potential to flow if containment is lost. Understanding the generation and propagation of excess pore water pressure on failure is critical to predicting the flow and run-out of tailings. This paper presents numerical modelling using the material point method indicating that tailings run-out processes may be self-enhanced by the excess pore water pressure induced during the collapse of the containment. Moreover, it is shown that geomorphological features, such as the slope and its surface roughness downstream of the tailings dam, influence the pore water pressure dynamics upstream of the advancing toe.CITATION:Llano-Serna, M A, Bu, L and Williams, D J, 2018. Excess pore water pressure induced during tailings run-out, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 377–383 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By A Gibbs

The mining sector has been a leader in investing in safety improvement initiatives, yet relatively few mining organisations can accurately track the positive effects of these initiatives or identify areas that may require more attention. The consequences of not taking safety seriously are severe, and unfortunately injuries and fatalities are continuing to occur across the mining sector (Brady, 2019). There is a tendency to turn to lag indicators such as All Injury Frequency Rate (AIFR), Total Recordable Injury Frequency Rate (TRIFR), and Lost Time Injury Frequency Rate (LTIFR) to track these outcomes. As outlined below these approaches are inherently flawed and a renewed focus is needed on indicators within the control of leaders, indicators that have high predictive validity for future events and data that is used in a way to enable learning and change.

May 5, 2022

Morning Star Gold aims to enter the ranks of Australia's gold producers, revitalising the Eastern Victorian Goldfi elds in the second half of 2010 - the fi rst gold production in around 50 years from the Morning Star Gold mine, which was once Australia's largest under WMC. This presentation will outline the redevelopment of the Morning Star Gold Mine from exploration to production. Morning Star Gold NL's (MCO) key project area is centred at the historic mining town of Woods Point and nearby Matlock (to the southeast) and Gaffney's Creek (to the northwest), all of which are located in the lower part of the Victorian Alps roughly 60 kms south of Mansfield. Morning Star has literally numerous historic mines and gold bearing 'dykes' on its tenements, many with a rich production history of high-grade gold from quartz reefs and alluvial sources. The area encompassing the Woods Point goldfi eld and the multiple high-grade gold bearing dyke structures located north towards Jamieson and south towards Walhalla formed one of the most significant mining fields in Australian history. Historical gold production was at least 155 t or around six million ounces of over a century of mining with an average production grade exceeding 27 g per tonne. The bulk of this recorded production came from just a handful of mines and of those only three were mined to any great depth. One of the key historical production hubs in this area was the famous 'Morning Star' mine, which is situated adjacent to Woods Point township. The Morning Star mine produced almost one million ounces at 27 grams per tonne, operating fairly continuously between 1861 and 1959 with a break after Jan 1939 due to the devastating 'Black Friday' bush fi res across eastern Victoria. During the early 1940s, the Morning Star was Australia's biggest gold mine. The Morning Star mine along with Walhalla ensured that this goldfield was third behind Bendigo and Ballarat as Victoria's biggest hardrock gold production centre. Morning Star Gold has rebuilt its 100 per cent owned 'Morning Star' mine with a view to producing gold in the second half of 2010. Morning Star is exploring its regional dykes in order to estimate an overall gold endowment and rank local production sources to feed its proposed mill at the Morning Star mine site. Key initial targets (all within 11 kms of the Morning Star mine) are the Waverly, All Nations, Rose of Denmark, Hunts, Wallaby and Loch Fyne dykes, all of which historically produced high grade gold, much of it gained from only shallow workings above the water table in the weathered zone of rocks. Historically the Morning Star mine was developed over 24 levels to a depth of 940 m via one large vertical shaft and a smaller, deeper inclined shaft at the 1900 feet level underground. At present MCO has dewatered and completely refurbished all infrastructure to the ten level (~310 m below surface). MCO knows there are a number of substantially under-explored and undeveloped or partially developed but not stoped areas within the Morning Star mine. As a result, MCO has been carrying out extensive channel sampling and an underground diamond drilling program targeting areas of the mine that were largely unexplored and undeveloped by the last operators of the mine - Western Mining Corp Ltd (Gold Mines of Australia). Four thousand, fi ve hundred pages of archival WMC records have helped the cause significantly. The shaft refurbishment and reconstruction stage is complete. This has been a program that originally commenced back in 1993 and has cost around $22 M. This refurbishment paved the way for the extensive underground resource focused diamond drilling program, which MCO completed in 2008 with two company-owned and operated drill rigs from drill cuddies on level 9 (900 feet underground) of the mine. This drilling, which encountered some stunning grades intersections and multiple visible gold hits, has outlined further production opportunities including 0.4 m @ 1392 g/t Au (MS 410). Metallurgical testing conducted by Gekko Systems of samples obtained from the exploration program found gravity concentration and a leach circuit gave recoveries of ~95 per cent to 99 per cent, or ~92 per cent from gravity alone at a coarse crush (300 ¦m). Currently, the plan is to use gravity to fi rstly produce dore bars on-site from the free milling gold and secondly a saleable concentrate for CIL processing off-site. A purpose built 10 t/h (~80 000 t/a) gravity treatment plant was subsequently ordered from Gekko and is expected to be installed onsite and commissioned in the Q3 2010. The plant features fi ne crushing with a vertical shaft impactor, followed by gold concentration by inline pressure jig, inline spinner and Wilfley table. This is an ABSTRACT ONLY. No paper was prepared for this presentation.

Aug 1, 2010

By Greenwood-Smith R, Ellis W. K

A bulk analyser based on the gamma-ray resonance scattering process can be used to give a rapid and accurate measure of the percentage by weight of copper or nickel averaged over a large mass of sample, typi- cally 20 kg. It is shown that for a bulk sample containing about 3 wt.% Cu, crushing to -25 mm is the only sample preparation requited for analysis to within an error of about 0.06 wt.% Cu (errors quoted are one standard deviation). A comparison of bulk analyser and con- ventional assays on the same bulk samples can be used to estimate the sample preparation errors in the conventional methods. The squared deviations between bulk analyser and conventional assays are approximated by the sum of variances in sample preparation, conventional analysis, and bulk sample analy- sis. The sample preparation error was esti- mated as 0.26 wt.% Cu for samples crushed to -2 mm before splitting, 0.08 wt.% Cu for samples crushed to -0.35 mm before splitting, and 0.04 wt.% Cu for the average of 15 grab samples from bulk samples which had been crushed to -2 mm. The average copper grade for each group of samples was about 1.7 wt.%. Results are presented which show that

Jan 1, 1976

By Edwards R

Greater efficiency of capture of minus 6 mm to fine micron size particles of free gold is achieved with the Knelson Concentrator. The development, principles of operation and recent innovations relating to this enhanced gravity concentrating device are described by the inventor, followed by a description of application and consequent economic benefits in low grade alluvial gold deposits by a large scale user of Knelson Concentrators in the Northern Territory of Australia.

Jan 1, 1990

By G S. C Murray

Major mining projects are developed with the assistance of lending institutions who provide hundreds of millions of dollars in funding over several years, and of course expect those funds to be returned with interest. Two Australian banks have adopted the Equator Principles, an emerging financial industry benchmark for assessing and managing environmental and social risk in project financing. Project financiers have encountered environmental and social issues that are both complex and challenging, particularly with respect to projects in the emerging markets of Asia-Pacific and elsewhere. There are many recent and historical examples of failures by resource companies to effectively manage their environmental, social, safety and security risks, some of which have caused the project to fail completely, and some of which have caused the temporary cessation of production. These events put the financial institutionsÆ funds at risk through inadequate management capacity and non-compliance adversely affecting the ability of the borrowers to repay the loans. They can also reflect adversely on the reputation of the lending institutions. In assessing these risks, lenders are increasingly looking at the track record of the borrower in its country of origin and in other countries where it operates. Lenders are wary of companies that have one standard for operations in a developed country, where the regulatory environment may tightly control what they do, and another standard for operations in countries where the regulatory regime is perhaps less stringent. Lenders may require environmental and social reviews or audits to be conducted on their behalf by competent third parties prior to a loan being approved, and annually over the life of the relationship. The mining industryÆs concept of the unwritten æsocial licence to operateÆ is highly relevant in relation to the delivery of community benefits that are sustainable post-mine closure. This paper provides examples of recent practices that support financial viability and sustainable development, as well as examples of some failures that have put lenders at risk.

Jan 1, 2007

By R Wynn, T J. Akroyd, C Costa

In an environment of lower zinc prices, falling revenues and reducing zinc feed grades, Century mine implemented a fast-tracked capital upgrade program in less than 15 months. The program was designed to increase ore milling throughput capacity by 20 per cent and optimise the capacity of the flotation plant to increase zinc recovery by approximately 2.5 per cent whilst maintaining final zinc concentrate grade.A key aspect of this program was minimising capital expenditure by better utilising existing capacity and only adding capacity where absolutely required to address critical processing bottlenecks. By gaining an understanding of plant process bottlenecks and future ore blends, and by carefully selecting appropriate technologies for particular specific flotation applications, maximum return on minimal capital investment was achieved.The close collaborative work achieved between the metallurgy processing department and other operational departments on-site was also critical to the success of this project. This work increased the mining and processing capacity of the mine and port site respectively, such that the full value of the process plant modification could be achieved.Capital payback on this investment was achieved in approximately three and a half months.This case study demonstrates the extra value to a mining business that can be achieved through fully understanding the mining/processing value chain and by careful targeted action to address critical bottlenecks in the processing chain from the mine through to the port site.CITATION:Akroyd, T J, Wynn, R and Costa, C, 2014. MMG Century Mine, a case study – maximising project net present value through targeted capital expenditure and process optimisation against a backdrop of falling metal prices and feed grades, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 417–426 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By Zani J. A, Jackson W. D

Bauxite was discovered in the Kimberley in 1965 by an Amax field crew. Reserves of 230 million tons, of bauxite. averaging 47% total alumina on Mitchell Plateau and 980 million tons averaging 36% total alumina on Cape Bougainville have been indicated by the results of drilling and bulk sampling. Laterite which contains the bauxite deposits caps basalt and interbedded sandstone and siltstone of the Carson Volcanics formation. Bauxite on Mitchell Plateau is 3.2 metres thick on average and is underlain successively by nodular ironstone, clay and basalt. The major components of the bauxite are gibbsite,boehmite, hematite and goethite containing some alumina, anatase and clay minerals. Quartz and vanadium oxide are minor constituents. Boehmite and hematite are concentrated near the surface, whereas gibbsite and goethite predominate at depth. The bauxite profile consists of ferru- ginous, pisolitic and gibbsitic zones with increasing depth. Cape Bougainville bauxite is 8.6 metres thick on average and of tubular structure; its mineralogy is relatively uniform..

Jan 1, 1973

For the last 4 years political leaders have found a new subject on which they can safely generalize wihout creating opposition. That sub- ject is commodity prices. Since the four-fold increase in OPEC crude oil prices, public atten- tion has focussed as never before on the subject of commodity prices. To advocate stabilizing com- modity prices is akin to supporting motherhood or peace or better schooling. Everyone gives lip service to the concept that stable commodity prices are desirable. It is easier to state the principle than to achieve it. Prices that are stable in terms of one currency may be clearly unstable in terms of a different currency. This has become a troublesome matter since 1971, when the world's leading trading currencies were set free to float in relation to each other. To illustrate: consider copper prices in the interval between the end of 1974 and the end of 1977. During those 3 years, the copper price in pounds sterling on the London Metal Exchange rose by 25 per cent. During that period, however, in terms of the USA dollar equivalent, the price was unchanged. And during that period, in terms of the German mark equivalent the price shrank by 13 per cent while the Japanese yen equivalent f.11 1k

Jan 1, 1978

By G Tsatouhas, R Newell, K Y. Wong

A sulfide ion selective electrode was used to control sulfidiser addition in the flotation testing of a synthetic and a naturally occurring ore containing malachite in order to compare the behaviour of sodium sulfide and calcium polysulfide. Both slug and controlled potential sulfidisation methods of addition were used. Under defined optimum CPS conditions, calcium polysulfide was a more effective sulfidising agent than sodium sulfide on the basis of both capital and operating costs. Surface and solution studies were used to compare the mechanism of each sulfidiser. For calcium polysulfide, XPS showed that polysulfide ions are adsorbed, whereas for sodium sulfide it is the hydrosulfide ions that are adsorbed on the mineral surface. For calcium polysulfide, the CuSx layer was believed to form on the malachite surface, which promoted the flotation of the malachite, by xanthate. Studies of surface morphology of the sulfidised malachite showed that a fairly uniform sulfidised layer is formed with both reagents. The use of sodium sulfide resulted in a thinner initial sulfidised layer compared to polysulfide at equivalent initial sulfur concentration.

Jan 1, 2005