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By A G. Thompson, E Villaescusa, A De Zoysa, J R Player

Ground support performance is critical to the safe and economical extraction of ore. This is particularly important for mass mining extractions at great depth, which are currently being considered by a large number of mining companies worldwide. As the in situ stresses concentrate around critical excavations, failure occurs at the excavation boundaries and ground support is required for the excavations to remain safe and accessible for their intended lifespan. Ground support consists of reinforcing elements that are installed within the rock mass to modify its internal behaviour (generally to within one excavation radius) and surface support elements that are installed at the exposed boundaries to retain the failed pieces of rock. For surface support to be effective, the loadings need to be transferred to the reinforcing elements; however, the combined performance of rock bolts and mesh is poorly understood in terms of the energy dissipation capacity available for a typical ground support scheme implemented at most mass mining operations.Over the last 15 years or so, a large number of large-scale laboratory experiments have been completed at the Western Australian School of Mines (WASM) Dynamic Test Facility for reinforcement systems and surface support systems loaded separately. The objective of more recent testing has been to establish the combined energy dissipation capacity of typical and enhanced reinforcement systems combined with mesh surface support. Total energy dissipation has been separated into energy dissipation attributable to the reinforcement and to the mesh. The results of the tests are presented and compared with the existing WASM design demand and capacity guidelines.CITATION:Villaescusa, E, De Zoysa, A, Player, J R and Thompson, A G, 2016. Dynamic testing of combined rock bolt and mesh schemes, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 789–798 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

Rheological Behaviour of Clay-Rich Gangue Mineral Dispersions During Hydrometallurgical Treatment Alumino-silicate minerals invariable may present an intractable challenge in hydrometallurgical operations employed in low grade nickel, copper and gold ore leaching or high level nuclear waste (HLNW) processing. The interactions and reactivity of alumino-silicate clay gangue minerals such as muscovite/sericite, chlorite, kaolinite and smectite under acidic (eg pH <3) or alkaline (pH >13) conditions can have a striking impact on the particle interactions. These may manifest in undesirable pulp rheology, poor extraction rates and challenges in the subsequent "handleability" and solid-liquid separation processes (eg dewatering). In the present work, a review of investigations involving the interfacial chemistry, interactions and rheological behaviour of aqueous dispersions of mica-group, layered alumino-silicate clay (muscovite / sericite) and chalcocite minerals as a function of pH in the range 2 - 9 and time at 25¦C, is presented. Particle zeta potential, reflecting interfacial chemistry, indicated a strong pH-history and particle volume fraction dependency. Pristine particles' zeta potentials measured from high to low pH indicated mineral-specific isoelectric point (iep) at pH range 2 - 5. Subsequent measurements from low to high pH showed pH-history dependency with iep shift to higher pH values, the extent of which also depended upon particle volume fraction and aging time. Pulp pH-mediated particle interactions revealed by shear yield stress analysis displayed a bifurcation behaviour and good compliance with DLVO theory. The maximum pulp yield values occurred at the iep whilst weak rheology was observed where the magnitude of the particle zeta potential was greatest. The pivotal role played by both pulp chemistry and suspension conditions in regulating the particle interactions and concomitant rheological behaviour is highlighted. The implications of the findings with regards to clay-base pulps' handleability and its control during aqueous processing are discussed.  

Sep 13, 2010

Coal mining in New Zealand is principally a State-owned and controlled operation where the State produces 70 per cent of the coal in New Zealand and 65 per cent of coal mined in the Waikato. The State's flexibility in production quality and price makes them tough competition. Coal in the Waikato varies in quality considerably throughout the region making the high quality coal deposits as in the Huntly district a highly sought after commodity. The high quality of coal is often offset against transport costs as, for example, Maramarua coals can compete effectively in the Auckland market and dollar per calorific value basis.

Jan 1, 1984

Adsorption of Alkylammoniums in the Interlayer of Montmorillonite and its Effect on the Viscosity of Organo-Montmorillonite Gels

Sep 13, 2010

By C Hall, J L. Mauk

New 40Ar/39Ar dates of vein and wall rock adularia from seven epithermal deposits and one porphyry copper prospect help constrain the ages of mineralisation in the Hauraki Goldfield. Vein adularia from the Paritu region yielded a single 40Ar/39Ar plateau date of 16.315 ¦ 0.066 Ma. Five 40Ar/39Ar plateau dates of three samples of vein adularia from the Opitonui deposit overlap within error to yield a preferred age of 13.149 ¦ 0.016 Ma. Two samples of vein adularia from the Night Reef at the Broken Hills deposit yield exceptionally flat 40Ar/39Ar plateaus, and all dates overlap within error to provide an age of 7.121 ¦ 0.010 Ma. Two 40Ar/39Ar plateau dates of one sample of vein adularia from the Wharekirauponga deposit overlap within error to provide an age of 6.318 ¦ 0.061 Ma. Four 40Ar/39Ar plateau dates of three samples of vein adularia from the Maratoto deposit overlap within error to provide an age of 6.411 ¦ 0.022 Ma. Two samples of adularia from altered wall rock at the Sovereign deposit yield three 40Ar/39Ar plateau dates that range from 6.547 ¦ 0.021 to 6.806 ¦ 0.028 Ma. This suggests that mineralisation formed around 6.6 Ma, but the results are complicated because the adularia contains minor illite that post-dates adularia formation. Results from the Karangahake deposit are complex. Two samples of vein adularia yield three 40Ar/39Ar plateau dates that range from 6.116 ¦ 0.116 to 6.901 ¦ 0.101 Ma, whereas one sample of wall rock adularia that contains minor late illite yields two 40Ar/39Ar plateau dates that overlap within error to provide a date of 5.734 ¦ 0.041. The range of dates indicates that more work is necessary to understand the history of mineralisation at this deposit. Two samples of vein adularia from the Tui deposit yield four 40Ar/39Ar plateau dates that overlap within error to provide an age of 5.714 ¦ 0.017 Ma. These results confirm previous work that indicates that the ages of epithermal deposits young southward in the Hauraki Goldfield. These results are also consistent with previously postulated different ages for deposits hosted in Kuaotunu Subgroup rocks in the northern goldfield (>10 Ma), and deposits hosted in Waiwawa Subgroup rocks in the southern goldfield (7.1 to 5.7 Ma).

Jan 1, 2005

Triboelectric Separation - Beneficiation of Coal The performance of triboelectric separators is highly sensitive to the selectivity of the particle charging process. This paper presents a quantitative study on triboelectric coal beneficiation. The performance of different charging media was studied. Stainless steel was identified as having a work function between that of coal and silicate gangue and found to be the optimum charging medium for coal beneficiation. Recent results from separation tests were performed where silicate gangue was separated from crude coal using a parallel plate free-fall separator are illustrated.

Sep 13, 2010

The need for legislative reform of health and safety legislation has been recognised in New Zealand for about a decade. Previous legislation did not cover all work places, many areas were excluded from coverage, and there were at least 14 different acts and dozens of sets of regulations dealing with various aspects of health and safety.

Jan 1, 1993

By Arndt C. R

The Ispat Mexicana SA de CV (IMEXSA) pelletising plant is located at Lazaro Cardenas on the west coast of Mexico. It is the primary source of feed stock for the adjacent direct reduction (DR) plants and steelmaking facilities. The initial design of the pellet plant began in 1981 for 3 Mtpa of DR grade pellets using local concentrate received by pipeline.' Several construction delays, an ownership change, and a decision to use imported concentrates delivered in 60 000 to 90 000 tonnes ship cargoes required flowsheet modifications and additions. The design concepts are described for the plant which includes concentrate regrind to final pelletising particle size.

Jan 1, 1999

By Y Xiao, C Lei, C Shu, W Wang, K Wang, J Deng

To investigate the effect on coal spontaneous combustion with high geo-temperature, an experimental apparatus was developed to measure characteristic parameters of two kinds of coal samples at different temperatures: one was 40°C (G coal sample) and the other was a rising temperature from room temperature (C coal sample). Based on the relationship between CO concentration and the temperature variation, a calculation model of the apparent activation energy of coal was established. The results indicated that the oxygen consumption rate, the generation rate of CO and CO2, and heat release intensity of G coal sample were higher than C coal sample. This trend was more and more obvious as the temperature increased. Furthermore, the apparent activation energy of G coal sample was lower than C coal sample, especially at low temperature stage, which demonstrated that the more the oxidation and exothermic reaction of G coal sample was enhanced, the less energy was required to break the barrier of oxidation reaction. Under the same condition, the speed of oxidation reaction was faster for the coal in the high geo-temperature environment, which was more liable to spontaneous combustion.CITATION:Lei, C, Deng, J, Xiao, Y, Shu, C, Wang, K and Wang, W, 2017. The effect of high geo-temperature environment on spontaneous combustion – an experimental study, in Proceedings Australian Mine Vent Conference 2017, pp 137–142 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

This paper is in two parts. The first part provides background to coal in New Zealand, information on Solid Energy the Company and details of the resources, mines and products of the company. This part of the paper is intended for people who have limited knowledge of the New Zealand coal scene. The second part of the paper focuses on developments underway in New Zealand and discusses planned or possible changes and opportunities. This paper was first presented at the Coaltrans Asia Conference in June 2000.

Jan 1, 2000

Alluvial gold mining in New Zealand and in particular on the West Coast underwent a renaissance during the early 1980's. This was based on two main factors: a) the sharp rise in the gold price b) the advent of the hydraulic excavator with which to mine the auriferous gravels. The scale of operations varies considerably. A small operation typically consisting of one or two people using an excavator to feed either a land based or pontoon mounted (floating) gold recovery unit, which will typically feature a rotary screen with or without a tailings stacker with the screened fines < 10 - 15 mm) fed over riflle tables. The largest screening plants of this type are operated by DML Resources in their Arahura and Mikonui mining operations where the plants have the capacity to screen up to 250 m3 of gravel per hour. These plants usually employ jigs and centrifugal concentrators for gold recovery. Unique amongst current operations is the Grey River Dredge, a bucket ladder dredge capable of processing 700 m3 per hour similar to those that operated earlier this century. Gold concentration is by a series of jigs. The number of plants operating in recent times peaked at around 130 in 1987 (coinciding with a nominal average gold price of $751) and since that time has steadily declined to 80 units in 1993 and about 45 - 50 units today. This cycle of rapid expansion and then steady decline has been repeated on the West Coast since the original gold discoveries in the mid nineteenth century.

Jan 1, 1996

By S E. Munro, P D. Munro

The commonly traded base metals concentrates of copper, lead, tin and zinc are sold by miners to custom smelters using contracts whose terms were generally established at the beginning of the 20th century or even earlier. Technical clauses in these concentrates for items such as payable metals and penalty elements do not reflect current realities of extractive metallurgical technologies and hygiene/environmental issues.It is an axiom that the miners and smelters have a symbiotic relationship. While the existing antique and arcane commercial arrangements serve the purpose of transferring money from the buyer to the seller, they are not likely to result in the industry achieving better overall technical and economic outcomes. By examining the cases for copper concentrates and zinc concentrates in particular, it will be shown that the practical application of these antiquated technical clauses does not drive the miners to produce the better quality concentrates that should be desired by the smelters. This is despite development of mineral beneficiation and hydrometallurgical technologies that would allow the miners to make better products.The adage that any extractive metallurgical problem in the smelter is cheaper to solve in the concentrator still generally holds.While nickel concentrates are only touched on lightly in this discussion because sales terms are more opaque than those for the other base metals, it is expected that the same conclusions will apply.CITATION:Munro, P D and Munro, S E, 2015. Base metals concentrate sales contracts – change Pavlov and the dog, in Proceedings MetPlant 2015, pp 46–60 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

The Waimumu area, 12 km southwest of Gore, is underlain by the Gore Lignite Measures, an early Tertiary fluvial sequence approximately 500 m thick resting on Triassic-Jurassic argillitic basement. The Waimumu Quartz Gravels (Pliocene) have been deposited locally and are in part due to the localised reworking of the Gore Lignite Measures. Structurally the area is dominated by the Dunsdale Fault System, a steeply dipping series of NE trending reverse faults (Isaac and Lindqvist, 1990). The Belle-Brook, Hedgehope and Parker Road sites sampled are adjacent to the downthrown (east) side of the Hedgehope Fault.The authigenic gold-sulphide association at Belle-Brook was discovered in 1987 (Falconer, 1987: Clough and Craw, 1989). Despite a very limited amount of alluvial mining a significant quantity of authigenic marcasite has developed. Authigenic sulphide trace element analysis has shown anomalous amounts of As, Ni, Cr and to a lesser extent Zn, Pb and eu (Table 1). It has been established that the nickel occurs as a colloform banded Ni sulphide, possibly bravoite, within the marcasite (Figures 1 & 2). Arsenic and nickel (re)mobilisation are well documented in the literature. Generally As and heavy metals are mobilised in the groundwater as a result of the oxidation of sulphides (ie as a result of mining). At Belle-Brook it is reasonable to assume the authigenic sulphide trace element composition reflects either localised groundwater contamination or hydrothermal mineralisation. This poster presents some preliminary findings.

Jan 1, 2001

By D G. Randall, R Jivanji, J Nathoo, T Reddy

Paradoxically, the increased emphasis on water treatment in mining has generated a new problem û hypersaline brines. Currently brines are either disposed of into ash systems, lined evaporation ponds or hazardous waste sites. Evaporative crystallisation (EC) is an alternative, but the energy requirements can be prohibitive and the salt product is still a waste that must be disposed of. Eutectic freeze crystallisation (EFC) is an alternative technology that is capable of separating aqueous solutions into pure water (as ice) and pure, solidified solutes. It is highly energy efficient and does not depend on the introduction of any solvents. In addition, the simultaneous production of pure ice and potentially saleable pure salt(s) is a major advantage. Although EFC has been shown to be effective in separating a single salt and water, it is still in the early stages of being applied to the multi-component hypersaline brines that are typical of reverse osmosis retentates generated by mining and extractive metallurgy.This paper presents an EFC brine treatment protocol developed by the Crystallisation and Precipitation Unit at the University of Cape Town. The protocol incorporates brine analysis, thermodynamic modelling to establish which salts will freeze out and at which temperatures, followed by experimental studies to determine the kinetic parameters, such as nucleation temperatures, salt yields and crystal purity.Case studies showing the application of EFC for the purification of typical brines containing high levels of sodium, chlorine, sulfate and ammonia (Brine 1) and a mixture of sodium and magnesium sulfate (Brine 2) are covered. Modelling tools were applied to describe the phase behaviour of the multi-component saline systems under different process conditions. Experimental validation was carried out using synthetic brines of different (and increasingly complex) compositions. The results showed that EFC could be used to selectively recover the sodium as a sodium sulfate salt from both different brines. The simulation tools were useful in the analysis and understanding of the process.A preliminary economic analysis showed that the operating costs for EC were approximately nine times those for EFC, but the capital costs were much less- equipment for EC cost about half that of EFC. However, it is important to note that the capital cost calculations for EC are based on a technology that is already well established and with only relatively marginal future equipment cost savings expected. In contrast, EFC is a new technology, with significant future technology improvements expected.

Jan 1, 2009

The Round Hill gold-scheelite deposit is located three kilometres from Macraes Flat and approximately 60 kilometres due north of Dunedin, New Zealand. A mining feasibility study is currently being undertaken on the deposit by BHP Minerals (New Zealand) Limited, who are the managers and operators of a Joint Venture with Home Reef Mining Limited. BHP has a 70 per cent equity in the project area.

Jan 1, 1987

The sequences in alteration and mineralisation from five copper-gold porphyry systems (Taysan and Didipio, Philippines; Horse-Ivaal and Wafi River, PNG; and Goonumbla, Australia) and one gold-copper skarn system (Browns Creek, Australia) are documented in this paper. Alteration and mineralisation in all these systems reflect a common evolution from crystallisation of melts emplaced at shallow crustal levels (zoned potassic -> propylitic alteration), followed by exsolution of volatile-rich fluids from these melts (porphyry quartz ¦K-feldspar/biotite veins and local high temperature advanced argillic alteration), to a progressive cooling of the intrusion which results in associated retrograde alteration. Copper-gold mineralisation in all cases is almost exclusively restricted to the cooler retrograde events. The recognition of the temporal and spatial zonations in alteration and mineralisation in gold-copper porphyry systems has significant relevance in the interpretation of geophysical signatures, overprinting alteration, vein sequences and structural controls, and can lead to more focused and potentially more cost-effective exploration.

Jan 1, 1999

Experiment of Improving the Quality and Decreasing the Impurity of Titanium Concentrate in Panzhihua Mine in China

Sep 13, 2010

By P J. Mienie

The Palaeo-Proterozoic Transvaal Supergroup in the Northern Cape Province of South Africa is host to the largest known resources of high-grade hematite ore on the Southern African continent. These ores are currently being exploited at Sishen and Beeshoek. Hematite occurances on the Sishen South exploration project (some 65 km south of Sishen mine), are at present the focus of an intensive investigation. At both the Sishen and Sishen South deposits, mineralisation is found within lithologies belonging to the Transvaal and Oliphantshoek Supergroups. The Transvaal Supergroup comprises a basal, carbonate platform sequence (the Campbell Rand Subgroup) overlain by thick units of banded iron-formation belonging to the Asbestos Hills Subgroup. The Asbestos Hills Subgroup is unconformably overlain by sedimentary rocks of the Gamagara Subgroup. The latter Subgroup has been correlated with the lowermost unit of the Oliphantshoek Supergroup. The Sishen and Sishen South deposits are located close to the western margin of the Kaapvaal craton and have been subjected to intensive, structural deformation. Both localities have undergone folding, faulting and thrusting. Early regional tectonism (2400 - 1700 Ma) played a critical role in the genesis and preservation of the ores from younger erosive events. At both deposits, four similar iron ore occurrences have been recognised. The ores have developed in specific depositional environments and hence display unique physical, chemical and metallurgical properties:The bulk of the high-grade hematite comprises laminated and massive ores, which are found in the upper parts of the Asbestos Hills Subgroup. The laminated and massive ores are best developed in basinal and pseudo-graben structures. Collapse breccia ores of medium- and lower-grade are preserved within deep palaeosinkholes. The sinkholes have developed within the dolomites of the Campbellrand Subgroup. Lower-grade conglomeratic and gritty ores constitute the remainder of the deposits. These ores are found in the overlying clastic succession of conglomerates, shales and quartzites belonging to the Gamagara Subgroup. Although, there are many stratigraphic and lithological similarities between the Sishen and Sishen South deposits, there are also important differences, which will impact on the profitable exploitation of the ores. The most striking contrast between the deposits is their size and geometry. Sishen mine is a single pit operation with an opencast mineable reserve of 895 Mt. The Sishen orebody is thicker, more continous and significantly larger than the Sishen South deposit. The Sishen South deposit has a potential opencast reserve of 228 Mt. It comprises a number of small and narrow, isolated orebodies, spread over an area of ¦64 km2 . There is a significant difference in grade between the deposits. On average the orebodies of the Sishen South deposit have a higher iron content (+0.25 per cent Fe), less potassium (- 0.090 per cent K2O) and less phosphorus (-0.019 per cent P). The Sishen South deposit has less interbedded shale in the laminated and massive ores. The footwall of these high-grade ores is a light-density, intrusive sill, compared to banded iron-formation at Sishen. With a proposed heavy-medium separation plant at Sishen South, the impact of dilution on product grades is expected to be less than that currently experienced at Sishen.

Jan 1, 2002

Test Work on High Throughput Diamond Tracer Recovery from Alluvial Recovery Tailings with a Containerised Optical Sorter Under Real Production Conditions Worldwide alluvial diamond deposits are traditionally processed with dense media separation and XRF sorters, hand picking or grease tables. The test work conducted verifies the performance of an optical sorter detecting the transparency of particles for diamond recovery from the DMS concentrate, eg XRF-sorter and handpicking tailings. The containerised setup enables economically feasible, high throughput, semi-mobile setups to retreat recovery tailings from alluvial and also primary deposits. The test work has been conducted with quartz and glass particles, which are less transparent or comparably transparent, under realistic production conditions on a 600 mm belt machine with an installed electrical power of only 21 kW. The results show that 99 per cent recovery can be reached at a throughput of 10 t/h in the -8 + 2 mm fraction and at 22 t/h in the -25 + 8 mm fraction. At a throughput of 18 t/h a recovery of 88 per cent has been assessed. At a further escalation of the throughput, dust in the sorter container made sorting impossible in the coarse fraction and the recovery decreased significantly in the fine fraction. Analysis of the belt coverage indicates that higher throughputs of the coarse fraction can be fed onto the optical sorter if the dust extraction system is improved. The results are basis for the decision to conservatively feed 20 t/h of the coarse fraction and 17 t/h of the fine fraction in day to day production. The settings have been applied to sort alluvial recovery tailings in South Africa and will be applied to sort the recovery tailings of a primary deposit in Lesotho. The test work has shown that an optical sorter can be used to retreat recovery tailings with high throughputs. The compact setup of a screen and a 9 m standard container enables semi-mobile, temporary setups for small recovery tailings dumps and remote areas. In addition, sorting on transparency ensures the recovery of high value low-fluorescent diamonds.

Sep 13, 2010

By J E. Lynch

The Weda Bay nickel and cobalt laterite deposits on Halmahera Island, Republic of Indonesia were first drilled in May 1996 by Strand Minerals Pte Ltd (Strand). Subsequent exploration has delineated four large laterite provinces, parts of which have been diamond drilled to outline an indicated nickel resource of 59.9 Mt of 1.51 per cent Ni and 0.09 per cent Co within a total indicated and inferred resource of 117 Mt of 1.36 per cent Ni and 0.12 per cent Co. The project is held as a Seventh Generation Contract of Work (COW) by PT Weda Bay Nickel, which is jointly owned by Strand (90 per cent) and PT Aneka Tambang (ten per cent). Strand is a wholly owned subsidiary of Weda Bay Minerals Inc, a company listed on the Toronto and Alberta Stock Exchanges in Canada. Halmahera is located in the north-eastern part of the Indonesian archipelago at the convergent junction of three major plates and is a region of considerable tectonic and geological complexity. The western arms of Halmahera form a classic volcanic island arc while the central region and eastern arms contain ophiolite complexes and interlayered sediments. The extensive areas of laterite discovered at Weda Bay have developed over serpentinised harzburgites and dunites of pre-Cretaceous age. Weathering of these rocks has produced laterite profiles that are enriched in nickel and cobalt. There are three economically mineralised laterite types, namely limonites, ferruginous saprolites and saprolites and all are amenable to rapid pressure acid leaching with recoveries of 98 per cent nickel and 94 per cent cobalt in less than 20 minutes.

Jan 1, 1999