Search Documents

By L McCarthy, B W. Cuffley, O K. Thomas an

The Central Victorian Goldfield is a world-class field located in Victoria, Australia. It is currently undergoing a revival through activities in the Bendigo, Ballarat, Tarnagulla, Maldon, Castlemaine and other fields. Sediment-hosted auriferous gold-quartz reefs that are structurally and geometrically complex dominate the region. To date, no remote methods have been developed to assist in the targeting of the discrete high-grade oreshoots that characterise the mineralisation. An understanding of the structural setting and controls, and thus likely frequency of repetition of oreshoots remains the main exploration tool. Gold within the reefs is generally characterised by both its coarse nature (>100 up to 10 000 microns) and erratic distribution; as a result, most of the Victorian deposits are classed as high- to extreme-nugget effect systems. This characteristic ensures that mineralisation is very challenging to explore, evaluate and exploit. The key issues facing the explorer and miner are related to effective sampling, and definition of geological and grade continuity, and ultimately grade and tonnage. Tonnage can often be estimated to a reasonable level of confidence, whereas the grade estimate generally carries a medium- to high-level of uncertainty. In these deposits, surface diamond drilling alone is generally only able to define an Inferred Mineral Resource, with underground development, closely spaced in-fill drilling and bulk sampling/trial mining required to define Ore Reserves. The extraction of gold from ores is relatively simple, based on the coarse nature and hence amenability to gravity recovery. Ground conditions and the need for in-stope grade control (eg mapping, sampling etc), generally point toward mechanised cut-and-fill as the primary stoping method in the region. To potential investors this style of mineralisation has been viewed as high risk, because of the associated low confidence in the grade estimate, general paucity of Ore Reserves at mining start-up and need for underground development at the Feasibility Stage.

Jan 1, 2004

By J E. Lynch

The Mt Leyshon gold deposit produced in excess of three million ounces of gold and considerable silver over a period of approximately 130 years. Most of this production occurred between 1987 and 2001. Mining commenced in 1872, however it was highly likely that Chinese miners were not only removing alluvial gold from the area but were also mining very rich æreefÆ gold. Records for early alluvial and hard rock mining do not exist, however gold production was probably considerable. In the early 1980s Marathon Petroleum (Australia) Ltd (MPAL) joint ventured into the Mt Leyshon area which had been held as a mining lease by Noranda Australia Ltd since 1968. Noranda at that time was concentrating its exploration effort on the Balcooma base metal prospect areas to the north of Charters Towers. In early 1982 MPALs parent company was taken over by US Steel. This led to an opportunity for MPALs Australian management to purchase all tenements and licences (except for coal, oil and gas) which were duly purchased for $US 1 million. At this time MPAL had a remarkable array of gold tenements (many of which were subsequently mined by other companies) and Mt Leyshon was considered to be the highlight. Early æseedÆ capital ($A 3.1 million) was raised with backers being the Bank of America, the NSW Government Superannuation Scheme, Westpac, private individuals and a Queensland grocery chain by the name of æJack the SlasherÆ.

Jan 1, 2004

THE exceptional rainfall characteristic of the West Coast of Tasmania, in conjunction with the rugged topography of the district, has always suggested the utilization of water-power, and from the earliest days of the Mount Lyell Company theeventual installation of a hydro-electric power scheme, making use of some near-lying lake, has constantly been kept in view. At the period of the inception of the company, however, the time was not ripe for such an undertaking, and it is only oflate that the various important considerations involved have sanctioned incun;ing the heavy expenditure necessary, with the positive assurance of permanently reaping the benefits expected. The West Coast of Tasmania contains many lakes of varioussites; situated at high levels, and, although the catchments of these lakes are not very extensive, still, the excessive rainfall is so constant over long periods that its regularity may be relied on as offsetting the limited catchments. The explanation of the abnormal rainfall is simply the circumstance that the West Coast Range forms the first high land barrier which is met by the moisture-laden westerly and north-westerly winds blowing off the Southern Ocean. By the time the clouds strike the mountains they ride very low, consequently the elevation of the range, the peaks of which do not exceed 3000 to 4000 ft. above the sea, is sufficient to cause a copious precipitation. Lake Margaret, which is situated five miles north of the reduction works, was first recognized as a possible source of waterpower by Mr. Hugh Ohrisp, a surveyor, who visited it about 1893-4. Earlyl in 1895, while the preliminary work on the erection of the first furnaces of the Mount Lyell Co.'s reduction...

Jan 1, 1915

In South African gold mines, the types of material requiring transportation to the stoping areas include timber packs, explosives, hydraulic rock props, scrapers, scraper winches, pipes, pumps and backfill material (in areas where backfill is being used). Currently timber packs are broken down to their basic components (log and brick) and are transported into the stope by means of either monowinches or a combination of monowinch and scraper winch. Other materials, such as explosives, hydraulic rock props, scrapers, scraper winches, pipes, pumps and backfill material must be transported by other means, usually by hand or, in the case of heavier items, by chain blocks. With the drive to increase stope advance rates and the rise in the number of miners with HIV/AIDS, there is a need in the South African gold mining industry for an improved material handling system. To meet future requirements, material handling systems should assist miners to transport materials quickly and efficiently. Furthermore, it must be financially viable and economically competitive with current material handling systems. This paper looks at the in-stope material handling efficiency of current monowinch systems and provides solutions to improve efficiency. In addition, the use of in-stope monorails are reviewed and the possible scenarios that will substantiate the use of monorail systems are discussed.

Jan 1, 2003

The mineralogy, maero- and micro-textures of Thackaringa ore are simple and have many counterparts among base metal-quartz-siderite vein type deposits elsewhere.The ore consists predominantly of galena, sphalerlte, chalcopyrite, tetrahedrite, and arsenopyrite in a quartz and siderite gangue. Silver minerals, as such, appear to be lacking and silver values are no higher than in other sulphide ores of this type. These features contrast very markedly with those of the A.B.H. Consols Lode which appears to have emanated from the north end of the Broken Hill Main Lode Horizon during high grade regional metamorphism. The Consols Lode has been regarded as of Thackaringa type, and both are regarded as possibly arising from the remobilization of Main Lode Horizon ore. Whilst this may yet prove to be so it appears that the marked differences in mineral composition between the Consols and the Thackaringa types, would require somewhat different modes of regeneration.Thackaringa ore, as well as A.B.H. Consols ore, on this basis, would necessitate the development of a metahydrothermal ore fluid to account for their present apparently hydrothermal (or pseudo-hydrothermal) constitution...

Jan 1, 1967

By Spencer GA, Saul SJ

The flight line spacing in low level aeromagnetic surveys is the principal factor governing both the cost and the amount of geological detail which can be extracted from the data. The rate at which geological resolution diminishes with wider line spacing is illustrated by progressive subsampling of a 200 m spaced data set from the Charters Towers region in Queensland.The usefulness of high frequency type filters in enhancing shallow structural features is seen to be limited to the 200 m data.It is concluded that each data set is suited to a particular scale and style of geological investigation with only the 200 m data having sufficient detail to identify the subtle structural patterns which are crucial to mineral exploration.

Jan 1, 1976

By Shillabeer J

Paste backfill has been adopted by many underground mines in North America and a growing number elsewhere. Paste offers a number of advantages. This paper suggests wider applications of paste technology to surface tailings disposal and water management. Advantages include improved overall stability, potentially easier permitting, smaller water inventory and earlier reclamation. It may be feasible to use the same plant to prepare backfill and to dispose of surplus tailings. Example cost models are given to illustrate potential applications.

Jan 1, 1998

Rock bolting and rock-bolting systems depend for success on attention to a number of simple techniques. Failure to appreciate this fact can lead to disappointing results. Careful study of rock characteristics and placement methods can allow a change to highly successful rock bolt per- formance. A number of examples are quoted to illustrate the sig- nificant improvement in results which can be achieved by use of the most suitable combination of characteristics.

Jan 1, 1971

By Watson K, Pollard D. M

The electrolytic recovery of metals from solution requires an understanding of the characteristics of the particular system employed, and the current efficiency and morphology of the deposit are influenced by such factors as cell design, metal ion and supporting ion concentration, acid concentration, temperature, impurity levels and cell design. The electrolytic deposition of both cadmium and silver present individual difficulties, and special cell designs are used for each of these metals. It was found that cadmium deposition was plate-like at lower cadmium concentrations, and at higher current densities. The presence of zinc in the electrolyte promoted nodular growth. Current efficiency remained high even at 50C in contrast to published information. Silver deposition morphology was relatively unaffected by changes in silver concentration, pH and current density. Current efficiency was reduced as temperature was increased.

Jan 1, 1989

By M Miller

Operators of nickel laterite pressure acid leach and gold pressure oxidation technology frequently employ a series of steam condensing heaters to preheat the leach feed slurry. The heaters are an economic pinch point û although the thermal performance of the heaters is critical to overall process viability and operating cost minimisation, they are also a significant capital item and must be sized accordingly. Despite this, discussions of the factors underlying heater design are conspicuously absent from technical literature, and existing operations feature a conflicting range of heater sizes and configurations. This variety would suggest that at least some of the chosen heater designs are oversized. As part of its detailed design stage, the Ravensthorpe Nickel Project (RNP) constructed and tested a pilot plant heater to develop an understanding of the heating process and to ensure that the RNP heaters were appropriately sized. This testwork used RNP slurry at design density and viscosity on a 450 mm diameter, 6500 mm high column. The pilot plant testwork demonstrated the intrinsic efficiency of the direct steam condensation heating process, which was essentially independent of slurry density and viscosity. Presence of non-condensable gases in the steam phase decreased the heat transferred in certain circumstances, but heater performance remained consistent with thermodynamic limitations. Stagewise heat transfer within the column was rapid, and suggested either a very high slurry surface area or excellent heat transfer within the slurry phase. While the testwork did not set out to distinguish between these effects, physical evidence pointed to droplet formation in the inter-tray shower zone, giving a high heat transfer area. For scale-up purposes, the key facts were that the heat transfer rate was not limited by using high viscosity slurries and heaters could be designed using the principles applied to the smaller of those in existing operations. This paper discusses existing slurry heater designs, the current understanding from open literature, the pilot plant testwork, results and analysis, and scale-up to commercial sized equipment.

Jan 1, 2005

Working thick coal seams in Poland is a very serious problem. Nearly 40 per cent of all coal is extracted from seams more than 3 m. thick. In absolute figures this represents about 70 million tons of coal per year. Working seams with thicknesses up to 3.5 m. does not present, at present, major difficul- ties. Working thicker seams calls for a steady improvement in order to increase the degree of utilization of the deposit and to enlarge the concentration of output. The problem is sometimes more difficult because, in many cases, the seams are worked under protected surface structures which compels the mines to use hydraulic stowing with all its advantages and disadvantages. Rock burst hazard, the control of which is the basic problem hindering the mining, is a further problem. The mining systems used in Poland are adapted to these natural and technical conditions.

Jan 1, 1976

By Dharmappa HB, Sivakumar M

This paper is concerned with two case histories of wastewater quality management in underground coal mines in the Illawarra region. The first investigation briefly presents an analysis of mine water discharge having an extremely high concentration of suspended solids and consistently high barium concentrations, averaging, 14.4 mg/I Barium, over the sampling period. A laboratory study of chemical precipitation processes has indicated that about 91% of barium could be removed by using ferric sulphate and lime. On the basis of the information obtained from the environmental audit process an alternative water treatment and reuse system incorporating 51% reduction in the water consumption with 32% less off-site discharge has been suggested (Thomas, 1995).The second case history is concerned with the storm water management at a mine situated in the Illawarra escarpment where only 20% of the wastewater generated in the colliery is discharged off-site. Computer modelling of the storm water system showed that 75% of the clean runoff becomes contaminated through poor management practices and causes the process wastewater treatment system to fail in wet weather. Suggested improvements include relatively simple alteration to the coal wash filtration dams which are expected to reduce the periods of inefficient operation of these dams by 95%. The use of storm water diversion channels and detention basins can reduce the overflow volumes by 70 - 100 % for a ten year ARI (Average Recurrence Interval) storm event (Wingrove 1996).

Jan 1, 1998

By S C. Dominy

The gravity recoverable gold (GRG) parameter reflects liberated gold or gold-dominated composite particles that can be recovered by gravity separation. Recoveries depend upon mineralogy, in situ particle size and the comminution and extraction method used. Any ore bearing >15 per cent of gold greater than 50 ¦m in size is likely to have a GRG component. The principal characterisation methodology applied is the three-stage GRG (3GRG) test, based on a 40 kg to 100 kg sample. An alternative is the single-stage GRG test (SGRG), which is generally based on a 20 kg sample. Experience has shown that GRG values can vary throughout an orebody, particularly within different grade and/or mineralogical domains. Test programs must consider sample frequency and mass. This study demonstrates the variability of GRG results based on different sample masses. Consecutive underground faces on a coarse-gold dominated quartz vein were sampled taking five different masses from each. Each sample was processed using a SGRG approach. Subsequently, each development round was batched through a small gravity production plant. The results show that the small samples understate the plant GRG and show inter-sample variability. Large samples show less variability and a SGRG closer to the plant GRG. A high SGRG broadly correlates to higher gold grades, more coarse gold and larger gold particles. These results are intuitively correct, but indicate the likely challenges of sampling for gold recovery in heterogeneous systems.CITATION:Dominy, S C, 2013. Variability of gravity recoverable gold values in relation to test sample size, in Proceedings The Second AusIMM International Geometallurgy Conference (GeoMet) 2013 , pp 293-302 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 29, 2013

Mine closure is a legitimate element of the mining cycle and like mine development involves technical planning, permitting, and finally construction. Closure begins with the mine's operational footprint and transforms the site so that it meets the explicit requirements of the owners and regulators. Implicitly, the closure will increasingly need to meet the requirements of other interested parties such as the local community, workforce, and future land users. Golden Cross is the first modern mine closure in New Zealand. It operated for 6 + years as a mid-size gold and silver mine winning ore from both underground and open pit sources, and processing via a carbon in leach circuit including a cyanide recovery stage prior to tailings disposal. The mine is situated in a sensitive high rainfall environment, and is complicated by the existence of a large ancient landslide underlying most of the tailings dam and waste rock embankment. The regulatory process for mine closure in New Zealand is not clearly understood by operators or regulators alike. The Golden Cross mine was permitted under the Mining Act 1971 and closed primarily under the Resource Management Act. This switch of legislation, the parallel reorganisation of many government departments, and change in societal expectations with respect to long term environmental stewardship during the life of the mine resulted in the requirements of closure being significantly different to the expectations at permitting.

Jan 1, 1999

By Rashleigh C

The selection and application of an effect- ive firing system first require a clear under- standing of the initiating abilities of the com- ponents in such systems. The conditions under which charges can be prematurely initiated by a detonating cord downline must be appreciated. This is a principal consideration in the design of a successful downline/'Anodet'/primer assembly. The advantages and limitations of an electric and several non-electric initiating systems are explained. The factors which in- fluenced selection of the two most suitable systems for use at Isa Mine (viz. downline/ 'Anodet'/primer assemblies and the reinforced long-lead 'Anodet'-type delay system) are dis- cussed. Blasts are detailed in which each of these has been applied. The initiating design for a hypothetical 2 x 106 tonne blast using electric short delay detonators and multi-channel exploders is presented. In this design, charges in remote blastholes are activated after the detonation of earlier firing charges by protecting the firing lines with sandbags.

Jan 1, 1978

By Alford R. A

The causes of the loss of heavy mineral from mineral sands wet concentrators were identified through detailed surveys of two such concentrators. It was found that tray and spiral sluices preferentially lost elongated panicles, but panicle size had little effect on loss. Recovery was shown to increase with panicle density. The major influences on the recovery efficiency of individual concentrating devices (stans) were feed rate and feed grade, recovery increasing with decreased feed rate and with increased grade. Uneven distribution of total solids and heavy mineral to individual stans contributed to losses through the corresponding effects in feed tonnage and grade. Computer simulation demonstrated that significant recovery improvements could be obtained by appropriate adjustment of splitters to optimise the characteristics of internal plant flows.

Jan 1, 1991

By M DellÆAmico, K Vining

The iron blast furnace is the most widely used and efficient producer of liquid iron; however, emissions from sintering and coking cause environmental pressure for the integrated steel works. The combustion of coke fines (breeze) during sintering contributes to greenhouse gases (GHG) (eg carbon dioxide) and is a source of SOx and NOx emissions. Coking capacity is also constrained by environmental concerns and economic factors, such as increased coke consumption, and short supply is leading to high prices. Improved coking practices, which result in reduced production of fines, are also contributing to the tight availability of breeze for sintering. This combination of factors presents an opportunity to consider alternatives to coke as a fuel for sintering. CSIRO Minerals has been investigating the use of wood biomass/char as a substitute for coke during sintering. Wood biomass, or char produced from it, is an attractive carbon source as carbon dioxide liberated during combustion can be sequestered back into growing biomass. It has great potential to reduce the emissions from integrated steelworks and improve their environmental acceptability. Harvested biomass/char is also a renewable and sustainable resource and can be integrated with good land management practices such as remediation of salinity affected land. Weeds, especially woody weeds, can also be used as a source of biomass for charcoal, and integrating char production with weed management can help address a pressing environmental issue in Australia. Previous reported preliminary testwork indicated that the use of Red Gum char as a replacement for coke resulted in a product sinter of comparable quality, improvements in productivity and significant reductions in SOx and NOx emissions. In the latest testwork, CSIRO has examined the properties of a range of potential charcoals, and has conducted a further series of granulation and small-scale sintering trials with them in simulated Japanese Steel Mill iron ore blends. Sinter fuels characterised and evaluated include industry sourced coke breeze, commercially available wood char and a charcoal from prickly acacia (acacia nilotica). Prickly acacia has been declared a noxious weed, is widespread in Australia, and is classified as a æWeed of National SignificanceÆ. The results presented in this paper support the notion that charcoal outperforms coke in many aspects of iron ore sintering and factoring in environmental considerations makes the switch to charcoal even more favourable.

Jan 1, 2005

By Brockway DJ, Holmes RJ

A natural gamma-ray gauge has been devel- oped for discriminating overburden and inter- seam sediment from low ash coal located on a moving conveyor belt. It is based on the difference in natural radioactivity of the sediment and overburden compared with the low ash coal, which is detected with a highly ef- ficient "Polyscin" NaI(T1) gamma-ray detector located underneath the conveyor. Gauges have been successfully installed on the bucket wheel boom of the two coal dredgers at the Loy Yang Open Cut. They are used to warn dredger operators that they are digging overburden or sediment and that action is required to avoid the sediment or divert it to the waste dump rather than send it to the coal bunkers at the power station.

Jan 1, 1987

By Mann T

The use of dolomite as a refractory began in England about 1870 when the basic Bessemer process for the removal of phosphorus from steel was developed by Thomas and Gilchrist.Knowledge of dolomite as a refractory in this country goes back to the early part of this century, at the time when the Hoskins Brothers took over the Lithgow Iron and Steel Works from W. Sandford. The practice then was toimport burned dolomite in casks from England. It is reported that much of the material was powdered when received, but was still serviceable. The earliest. used sources of local stone were in the Bathurst and Mudgee areas of New South Wales, and these dolomites were first used raw. Later, dolomite was burned in cupolas at Havilah near Mudgee, coke being obtained from the South Coast of New South Wales. This plant supplied burned dolomite to the Lithgow steel plant, later to the Australil1n Iron and Steel plant at Port Kembla, and also to the electric steel furnaces at Newcastle, Sydney and Melbourne until the plant was closed down in 1946.The Broken Hill Proprietary Company first obtained its dolomite from George's Plains near Bathurst (this was, really a magnesium limestone) and later from Mount Knowles, a deposit near Mudgee, which was eventually taken over by the CO:plpany in 1918. In 1936 Australian.Iron and Steel acquired from the Southern Portland Cement Company a deposit at Mount Fairy in the Federal...

Jan 1, 1951

Powercoal Pty Ltd operates eight underground coal mines in New South Wales and produces coal for both domestic power stations and the export market. Approximately 40% of total production is from continuous miners. Over the past five years, place change mining methods have been introduced to improve productivity from continuous miners. This has involved utilising the existing coal clearance system from the continuous miner to the ratio feeder using trailing cable shuttle cars.By late 1996 average productivity at Cooranbong Colliery using this system had plateaued at 800 tonnes per eight hour shift. A number of factors were identified to increase average productivity to 1500 tonnes per eight hour shift. An improved coal clearance system was one of the factors identified.

Jan 1, 1998