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Every estimate of ore reserves necessarily contains an assumption in regard to the specific gravity of the ore. This assumed figure may be based on experimental data, on textbook data, or on a reconciliation of past tonnage estimates and production figures. Not infrequently it is simply a guess - shrewd or otherwise.Errors in the density factor are not likely to be serious in gold-quartz mines-or, at least, not so serious as in base metal mines. It is to the closer determination of ore density in the latter that this paper is devoted. Moreover, the remarks apply to ores which show no appreciable pore space.Not many ore bodies are sufficiently homogeneous to allow of a truly representative factor being obtained by the simple testing of a few specimens of ore, or by the weighing, after breaking, of a carefully measured block. The empirical figure derived from a comparison of past ore reserves and actual production can never truly describe conditions other than those now past; no real link with ore as yet unmined is provided. The dilution of heavy ore by waste is not exposed by this method, but is effectively cloaked. Anyerrors in past estimations of ore reserves are transmitted, by way of the density factor, as a source of error in all future estimates.ObjectIons may be raised to the practice of weighing measured blocks of ore in the case of any but a very homogeneous ore body. Even then, the exact composition of the block weighed, and an indication of whether its moisture content is representative of the whole, are difficult to determine.

Jan 1, 1940

By C Simpson, J M. F Clout, G Plummer

Detrital iron deposits (‘DID’) in the Hamersley Province of Western Australia have been successfully mined and processed as small quantities of saleable standalone or blended lump and fine ore products over many decades. Despite their past, present, and potential future exploitation, they have received far less geological attention than the economically more significant higher grade bedded iron deposits (BID) or channel iron deposits (CID). DID are composed of Pliocene to Quaternary unconsolidated colluvial/alluvial hematite gravels with minor sand, silt, and ferruginous clay, as well as minor iron rich hematite clast conglomerates. DID mineralisation at Solomon has been subdivided into six distinct stratigraphic units, DID-5 (lowermost) to DID-0 (uppermost) based on differences in clast and matrix textures and mineralogy, degree of consolidation/lithification, particle size distribution and replacement textures. The most significant accumulations of DID-1 to DID-5 are in tributary valleys that have been cut through the Joffre Member of the Brockman Iron Formation on either side of the main Kings-Queens valley which contains the CID. DID-5 and DID-4 are ferruginous conglomerate, referred to as canga, with four subtypes recognised. DID-4 is composed of BID hematite clasts cemented by hematite or goethite. DID-5 is characterised by partial to complete replacement of BID hematite clasts and matrix by the yellow ochreous and brown to black vitreous forms of goethite. DID-3 to DID-0 are unconsolidated hematite detritals composed of largely (>80 weight per cent) fine to coarse gravel, minor sand and little silt or clay. The gravel clasts are largely composed of hematite and hydrohematite that replace BID, micro-nanoplaty hematite-martite-ochreous goethite (m-nplH-M-oG) BID, reworked canga, hematite pisoids, siliceous hematite BID (micro-nanoplaty hematite-martite-quartz, m-nplH-M-quartz), chert (~10–20 per cent) and minor (<5 per cent) Banded Iron Formation (BIF). Hematite abundance decreases from DID-3 to DID-0 whilst siliceous hematite BID is highest in abundance in DID-0 and lowest in DID-3. A key finding of the study is that >90 per cent of mineralised detrital clasts are derived from hypogene altered BID micro-nanoplaty hematite-martite with subsequent later supergene ochreous goethite mineralisation hosted by the Joffre Member. The DID genesis model entails interpreted Palaeoproterozoic siliceous hematite hypogene microplaty BID mineralisation of the Joffre Member undergoing Cenozoic supergene leaching of quartz and replacement by ochreous goethite to form low phosphorous BID micro-nanoplaty hematite-martite-ochreous goethite clasts. BID martitenanoplaty hematite-martite-ochreous goethite clasts and detritus eroded from hill slopes were deposited in the valleys as an initial single DID-5-DID-4 unit over a weathered pre-CID basal conglomerate. DID-5 and DID-4 underwent goethite cementation of the matrix followed by replacement by hydrohematite, hematite, and maghemite. DID-3 formed during subsequent periods of erosion of largely DID-4 hematite clasts and pisoids. Groundwater flow-through hematite canga resulted in partial to complete hydration replacement of DID-4 hematite clasts and matrix by ochreous and vitreous goethite to form DID-5. Deposition of DID-2 to DID-0 was via reworking and deposition of DID-5 to DID-4 canga and DID-3 as clasts and pisoids/ooids, as well as siliceous hematite and BIF sourced from the Joffre Member in the hill slopes.

Nov 8, 2021

By Wyborn L. A I, Idnurm M, Hinman M. C

Comparison of the Proterozoic Apparent Polar Wander Path (APWP) for Australia with the corresponding geology of northern Australia suggests that a number of discrete interplate tectonic events, manifested on the APWP as bends or inflections, may have controlled sedimentary basin evolution, ore fluid production and the timing of mineralisation. Similar features in the Phanerozoic APWP for the North American plate appear to correlate with major orogenic events, basin deformation, movement and &apos;entrapment&apos; of hydrocarbons and minerals. Interplate tectonic events cause intraplate deformation which in turn controls the subsidence/uplift and sedimentation histories of the basins. Interplate events are thus responsible for creating, deforming and destroying sedimentary basins and the associated petroleum and mineral systems. The basins of northern Australia show remarkable similarities in the successions of volcanic and sedimentary deposits. Unconforrnities of regional or sometimes only local extent have been mapped between the major sedimentary sequences and it is predicted that interplate tectonic events corresponding to bends or inflections on the APWP directly reflect the processes that have produced these widespread unconformities. These processes are also likely to have controlled the geometry and character of the fluid migration pathways and hence the mineralising events. Palaeomagnetic studies of Proterozoic rocks in sedimentary basins provide a tool for predicting the timing of regional mineralisation events, particularly for low-temperature mineral systems. The techniques, when coupled with systematic regional basin analysis, using petroleum exploration techniques, may identify a number of new mineral &apos;plays&apos; in northern Australia. Prominent inflections in the APWP occur at approximately 1700, 1670, 1650, 1600, 1540, and 1480 Ma. Each of these may be related to a regional compressional deformation, important mineralising event, or significant change in style and type of sedimentation. Most appear to be associated with magnetic overprints. Some of the inflections between 1400 and 540 Ma may also mark significant events in the evolution of Meso- and Neoproterozoic basins. Further work is required to correlate inflections in the APWP with alteration events in order to understand their regional significance.

Jan 1, 1994

By R Bradford, W Gift-Agbey, T Vorster, P Morgan, E Grobler

The Asanko Gold Mine in Ghana started processing ore from the Nkran pit in January 2016 at a production nameplate of 3 Mt/a. The flowsheet is a conventional SAG, ball mill and pebble crusher (SABC) with gravity-gold and carbon-in-leach (CIL) recovery. The nameplate production was comfortably achieved within 3 months, so much so, that it was clear the SABC circuit was capable of processing more than the downstream section of the plant. Consequently, a program of de-bottlenecking was initiated to rectify volumetric capacity constraints. This program was later referred to as ‘Project 5 Million’ (t/a) or P5M. Having completed the de-bottlenecking exercise, it became evident that the SABC circuit could not reach 5 Mt/a solely on hard rock from Nkran. The new challenge was therefore to increase the capacity of the milling circuit through a focused comminution initiative that would address the following: geometallurgical treatment plan; upfront fragmentation requirements; installation of feed and mill monitoring equipment; and integration of a knowledge-based control strategy. This paper takes the reader through the various measures implemented to increase the milling rates and to create a stable/ sustainable control philosophy. As a result of the implementation of advanced mill performance monitoring technology (MillSlicer) and the collaboration between a team of experts in comminution, control and operations, the Asanko Gold Mine process plant feed tonnage has successfully increased from 3 Mt/a to 5 Mt/a.CITATION:Bradford, R, Gift-Agbey, W, Grobler, E, Morgan, P and Vorster, T, 2018. Optimisation of Asanko’s Obotan SABC circuit to achieve ‘Project 5 Million’, in Proceedings 14th AusIMM Mill Operators&#39; Conference 2018, pp 477–484 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

General Gold was discovered in quartz veins at Wiluna in 1896, and the first lode was discovered in 1904. Since 1896, some 2.5 million ounces of gold have been produced from the Wiluna area. The mining operations at Wiluna are 100 per cent owned by Wiluna Gold Pty Ltd, a wholly owned subsidiary of Wiluna Mines Ltd. Oxide and sulphide gold ore is extracted by conventional open pit mining techniques, and ran-of-mine ore is processed through two separate circuits. The oxide circuit has a capacity to treat 600 0(X) tonnes per annum and the sulphide circuit has a capacity to treat 400 (XX) tonnes per annum. Additional gold is won by dump leaching sub-grade oxidised ore and by retreating of primary ore flotation tailings from previous operations. Testwork carried out in 1990 indicated the viability of leaching dumps of run-of-mine oxide ore, and in June 1991 Signet Engineering of Perth, WA, was awarded an EPCM contract to construct a nominal 2.5 million tonne dump leach facility, for a total construction estimate of 51.75 million.

Jan 1, 1994

By Gupta A, Fung C. C

The hydrocyclone parameter d5Oc is estimated by the application of Artificial Neural Network (ANN). Results indicate that ANN performs equally well as compared to statically derived analytical formulae. Results also show that ANN will also be convenient in the on-line control of hydrocyclones.

Jan 1, 1996

The most frequent initiation of coal dust explosion results from the ig- nition of high methane volumes, often at low concentration close to the minimum flammability limit, by a weak ignition source, e.g. frictional sparks. Tests performed in the 400 m underground test gallery of 7.5 m2 cross section indica- ted the following: 1. Methane at 200 m3 volume and con- centration 4.0 - 5.0 % CH4 may initiate the coal dust explosion. 2. Suppression of explosions result- ing from such initiation is very difficult, even when employing triggered, barriers.

Jan 1, 1988

By Jones KW, McClelland RA, Denholm WT, Taylor RN, OÆShea J

Associated Tin Smelters, Sydney, are developing tin smelting operations in a prototype commercial SIROSMELT plant comprising two furnaces of 5 to 8 tonnes capacity. Features of the plant and its operation are discussed and results of its application to tin slag reduction and high-grade tin concentrate smelting are presented. Development work is still in progress but experience indicates that the technology has potential for lowering the costs of tin smelting and relieving constraints on grade and iron content of concentrate imposed by conventional technology.

Jan 1, 1984

By Seymour C. A

Peak Downs Mine, a five million tonnes a year coking coal operation, strip mines a, series of Permian coal seams. Seam thickness ranges from 0.5m to 5.0m, and seams consist of multiple coal plies with intermediate shale and mudstone partings. Four 47m3 draglines strip overburden to a cover depth of up to 60m. Coal loading is by 12m3 shovels and 14m3 to 18m3 front-end loaders. Parting removal takes place where the layer of shale and mudstone between seams exceeds 0.3m in thickness. Parting has been removed by a wide variety of earthmoving equipment in order to evaluate the problem and to select the optimum method from an operational and economic standpoint. Multi-seam stripping of the thicker seams is accomplished by working draglines from spoil- pile benches. Coal seams thinner than lm are recovered by dragline and stacked in the pit for later loading.

Jan 1, 1974

Various software packages are discussed. These are components of an Integrated Planning and Scheduling System developed by MVM with the aim of providing up-to-date information for the Whaleback operation on: 1. Mine Topography. 2. Status of equipment in the mine. 3. Material moved from and within the mine. 4. Volume and density of same. 5. Quality of same.

Jan 1, 1986

By L Cooper, J Sharma, M J. Hendry

Thick clay tills below potash mine tailings and brine ponds are important natural barriers protecting fresh water aquifers in Saskatchewan. Centrifuge modelling was applied to assess geochemical processes and impacts of dilute brine (0.1 M NaCl) migration through clay till core samples obtained from non saline, unoxidised clay till at a mine site. At accelerated gravity of 876 + g, during each day of centrifuge modelling, flow driven through a 52 mm length core simulated transport through a 45 m thick clay over ~2100 years. Hydraulic conductivity, monitored continuously before and during brine permeation, was low and relatively constant (8.5 + 10-12 m/s), confirming that confining stresses prevent permeability increase. Core density and porosity measurements confirmed that reactive transport occurred under realistic in situ conditions. Breakthrough (defined by C/C0 = 0.5) of non-reactive Cl- occurred at 25 days. The slight delay for Na+ breakthrough, associated with small increases in Ca2+ and Mg2+ concentrations in the effluent were attributed to ion exchange, but carbonate reactions were relatively unimportant. Cation exchange analysis of core samples was inconclusive without corrections for porewater Na+ and carbonate dissolution. Geochemical processes that were observed during centrifuge modelling were successfully simulated using the 1D geochemical transport code PHREEQC. Solute transport was dominated by diffusion with limited ion exchange to delay Na+ migration. Brine would not break through a 45 m thick clay for tens of thousands of years. Based on these findings, the thick clay till at this site, if laterally extensive and undisturbed by drilling activity, is likely to act as an effective natural barrier to vertical brine migration over the long term.

Jan 1, 2003

Gold mine production in South America was 247.3 tonnes in 1995 up from 156.4 tonnes ten years earlier in 1986. This represents a 58 per cent increase and amounted to 11 per cent of total world gold mine production. The major countries involved in order of production, were: Brazil (67.4 tonnes), Peru (51.5 tonnes),. Chile (48.5 tonnes), Colombia (24.1 tonnes), Venezuela (17.1 tonnes), Bolivia (16.0 tonnes), Ecuador (9.6 tonnes), Guyana (8.8 tonnes), French Guiana (3.3 tonnes) and Argentina (one tonne). The most dramatic increase was reported in Peru where production increased from 10.9 tonnes in 1986 to 51.5 tonnes in 1995, heavily influenced by the production from Minera Yanacocha which began operations in 1993 and produced 17.2 tonnes in 1995.With the reformation of the mining laws and the introduction of investment incentives in all the South American countries in recent years, dozens of major and junior mining companies began flocking into the area in the early-1990s to conduct exploration. A recent study undertaken in Brazil shows that an average of $240 million per year will be expended in this country during the period 1993 - 2010. Twenty-five per cent of this expenditure is expected to be made on gold exploration. Similar figures for Peru are $220 million total per year with 50 per cent for gold; $170 million per year in Argentina with 25 per cent for gold and $120 million ner year in Chile also with 25 Der cent for gold.

Jan 1, 1997

The excavation of sandstone of generally medium strength for the Liverpool Link Line by Dosco Mark 2A Roadheaders has demonstrated the versatility and good performance of road- headers in suitable rock formations. A description is given of the strata traversed by the tunnels together with descriptions of equipment and crews, excavation sequences, operating difficulties and the results achiev- ed. In addition tunnel construction is des- cribed for a difficult section where there was only O.Sm clearance between invert and a four lane vehicular tunnel below, and O.5m clearance between tunnel crown and a century old sewer above.

Jan 1, 1976

The design of mine ventilation systems for the BHP Steel Division Collieries is based on the acquisition of ventilation survey data for the establishment of a realistic computer net- work model. The branches which form the net- work for the computer models are calculated from a range of resistance factors incorporat- ing both a frictional and shock loss component. Since shock losses can account for up to 30 per cent of the total energy losses in mine airways the use of friction factors alone without accounting for shock losses will result in the choosing of an insufficiently performing fan. Published tables of friction factors have in- variably been taken from metalliferous or single entry studies and consequently are not reliable for Australia&apos;s mining conditions where multiple entries with regularly spaced cut-throughs are the normal practice. Typical resistance factors for roadways of rectangular cross-section 5.5 m x 2.0 m, with coal sides, have been found to vary from 0.11 Ns2/m8/km where no timber supports are used, to 0.98 Ns2/m8/km where double centre legging together with wooden chocks is used. In addition to the range of resistance factors due to varying support methods, the nature of use for a roadway is very significant because of the condition of repair and upkeep maintained.

Jan 1, 1983

By Mroczek C. R, Evans D. A

Renison is a world-class ore deposit that has been mined for over 100 years. It currently has reserves of 5.06 Mt @ 1.88 per cent Sn and a projected mine life of 8.5 years. Recent advances in the geological understanding of the deposit have been associated with detailed structural and geophysical investigations accompanied with the discovery and exploitation of the Rendeep orebodies. Mineralisation is linked to the forceful emplacement of the Devonian Pine Hill Granite that resulted in a complex brittle (-ductile) deformation of the Eo-Cambrian host stratigraphy. Dilation jog development on the Federal-Bassett Fault in the Federal and Rendeep areas provided access for cassiterite-rich magmatic hydrothermal fluids responsible for carbonate replacement Mineralisation.

Jan 1, 1997

By Trois P

A fully instrumented and bench-mounted diamond drilling machine, purpose designed and built, has been used for investigating the effect of aqueous solutions of various chemical compounds when used as drilling fluids. The rocks investigated were andesite, basalt and granite, the chemical compounds were alkylamines, with various hydrocarbon chain lengths, aluminium chloride and dioxane. Rotation speed seems to be one of the major factors affecting the emergence of mechanochemical effects as the results obtained with aluminium chloride clearly indicate. Penetration rate is either unaf- fected or enhanced by the presence of certain compounds, such as aluminium chloride. On the other hand, penetration rate diminishes when the drilling fluid contains dioxane and exhibits an apparently unpredictable behaviour with alkylamine solutions, although it appears that an increase in hydrocarbon chain length usually equates to an increase in penetration 1. Full Professor, Mining and Mineral Dressing Department University of Cagliari - Italy 2. Associate Professor, Mining and Mineral Ikea- sing Department University of Cagliari û Italy rate. Rock texture seems to have a pronounced effect on test repeatability. With hexadecy- lamine acetate solutions in concentrations ranging from 10-5 to 5 .10-4 molò dm 3 and 41.88 radòs-1 rotation speed, 46 % increments in penetration rate of andesite were observed, with respect to water, whereas penetration rate decreased in basalt by as much as 60¦%o when a dioxane solution was used as drilling fluid. An interpretation of the observed effects is proposed in the light of current knowledge of solid state physics and physical Chemistry.

Jan 1, 1992

By Warren L. J

The recovery of phosphate minerals from the Mt Weld deposit by froth flotation has been studied by many researchers. Most of the flotation experiments were carried out with a tall oil fatty acid as collector and sodium silicate as dispersant and gangue depressant at pH about 10. Several rougher stages and cleaner stages and, sometimes, a desliming stage were included. The major difficulty was to reduce the Fe2O3 impurities in the concentrate to the required level. We used QEM*SEM (Quantitative Evaluation of Materials by Scanning Electron Microscopy) to provide a comprehensive and accurate mineralogical analysis of the flotation products. The analysis indicated that the Fe2O3 impurities were mainly recovered in the second concentrate, owing partly to the incomplete depression of the liberated iron oxides by the sodium silicate and partly to composite particles containing iron oxides. The selective depressing action of sodium silicate was improved by adjusting the variables such as the modulus (SiO2/Na2O), pH and time of standing of the stock sodium silicate solutions or by adding some polyvalent metal salts into sodium silicate solution. The flotation process was optimised to produce a phosphate concentrate with the required grade and recovery (38.6 per cent P2O5, 2.67 per cent Fe2O3, 13.7 for P2O5/(Fe2O3 + A1203), at P2O5 recovery of 81.5 per cent). The possibility of recovering the rare-earth phosphate, monazite, from the Mt Weld deposit by flotation was also studied.

Jan 1, 1991

By Weller K. R, Stewart P. S B, Restarick C. J

The performance of the Renison tin concentrator was assessed in detail for two arrangements of the three available ball mills. With two mills used for primary grinding and the third for regrinding table tailing, the concentrator recovered 65.3 per cent of tin in the three tin concentrates produced by tabling, vanning and flotation at a calculated overall grade of 37.5 per cent tin prior to batch dressing. In the second arrangement one mill was used for primary grinding and two mills for separate regrinding of table tailing and sulphide concentrate. The metallurgical effective- ness of the change was somewhat obscured by unintended changes,i.e. an increase in the assay of the fresh feed from 1.38 per cent to 1.1+6 per cent tin and unresolved changes in the sulphide rougher flotation and tabling. However, using the results from a detailed size by size analysis of the behaviour of ore components in appropriate parts of the plant, it proved possible to show that, had the two unintended changes not occurred, up to 5 per cent

Jan 1, 1977

In recent years new instrumentation and digital technology have Wrote possible a new facet of goo-physics: broadband seismology. From digitally record-ing networks and arrays. broadband scistnograrns of body waves that are flat to displacement and veloc-ity in at least the frequency range from 0.01 to 5.0 liz can now be routinely obtained for most carthquakes of magnitude greater than about 5.5. In contrast to data from conventional narrowband seismographs, broad-band body waves have sufficient spectral information to nvest,igate the many frequency-dependent eflects that may arise from source finiteness and from wave prop-agat ion phenomenon. Besides the usual parameters of depth. moment and focal mechanism, broadband data have sufficient spectral information to provide estimates of radiated energy, associated stresses and the frequency dependence of source parameters. Moreover. teleseis-mically recorded broadband data and near-field strong motion accelerograms overlap in the frequency band be-tween about 0.1-2.0 Hz. Thus. v it h broadband data it is possible to connect far field and near field data in order to make estimates of acceleration for almost any seismically active region of the circum-Pacific.

Jan 1, 1990

By Nixon C. A

The exploration of Mount Isa Mines&apos; new copper source will require the development of a five kilometre 4.7 x 5.5 metre blind decline commencing 1000m below the surface and extending to 1600m below the surface. With virgin rock temperatures approaching 60¦C, the ventilation strategy represents a complete departure from any previously used at this mine, in that refrigeration becomes essential. The use of direct water to air cooling techniques has become commonplace in mines throughout the world and their application is being adopted at Mount Isa Mines. A heat load simulation routine has been implemented to allow for the design of refrigeration requirements, as well as to aid in the selection of diesel or electric equipment. This enabled planners to determine the size of a surface based refrigeration plant. Future refrigeration demand for expansion into the ore production stage has also been investigated.

Jan 1, 1988