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By G J. Fleming

The Miwah prospect lies on the dilational 070¦ trending Miwah Lineament near its intersection with northerly oriented fractures within Pliocene volcanic rocks exposed between a NW trending segment of the dextral transcurrent Sumatra Fault, and the more northerly trending Samalanga-Sipopok Fault to the east. These faults reflect the continued interaction between stresses from the India-Australia plate located to the southwest, and spreading within theAndaman Sea to the north of Sumatra. A system of deep seated faults is believed to have facilitated emplacement of post-Miocene magmas and Quaternary volcanic centres at shallow crustal levels throughout northern Sumatra. Miwah mineralisation is associated with variably dipping structurally and lithologically controlled argillic and advanced argillic alteration. An oxidised supergene leached zone and a recent, thin, unaltered tuff blanket partly overlie the mineralisation. Mineralised zones are commonly brecciated and veined, and display quartz, quartz-alunite, quartz-alunite¦pyrophyllite¦kaolinite replacement assemblages, surrounded by more weakly mineralised, often vugghy quartzalunite¦pyrophyllite¦kaolinite advanced argillic, and argillic zones of quartz-kaolinite, quartz¦pyrophyllite¦kaolinite and smectite-illite-quartz. Propylitic assemblages are marginal to more intensely altered zones. Hypogene copper mineralisation is typified by enargite, luzonite, and covellite. The host mineral to gold is uncertain at present. Rare barite, native sulfur, and ?telluride also occur. Bornite and chalcopyrite have been observed in transported altered rocks in faults. Generally the mineralisation is anomalous in precious metals, locally enriched in Cu, erratic in Pb, and depleted in Zn, with a good correlation between Cu-As-Ag.

Jan 1, 1995

By Fleming GJ

The Miwah prospect lies on the dilational 070¦ trending Miwah Lineament near its intersection with northerly oriented fractures within Pliocene volcanic rocks exposed between a NW trending segment of the dextral transcurrent Sumatra Fault, and the more northerly trending Samalanga-Sipopok Fault to the east. These faults reflect the continued interaction between stresses from the India-Australia plate located to the southwest, and spreading within the Andaman Sea to the north of Sumatra. A system of deep seated faults is believed to have facilitated emplacement of post-Miocene magmas and Quaternary volcanic centres at shallow crustal levels throughout northern Sumatra.

Jan 1, 1995

By S H. Hyun, J W. Cho

Jun 19, 2024

Thirty mixed cultures of microorganisms from soil, water and mineral samples from the Groote Eylandt Mining Company mine site were approximately three times more effective in biodegrading manganese dioxide (34± 18 mg Mn++/1/day) than sixteen purified strains (11 ± 10 mg Mn++/1/day) isolated from the primary enrichment cultures. Two pure bacterial genera identified as a Pseudomonad and a Bacillus, with an excess MnOz and nutrient, were able to dissolve 106 mg Mn++/litre/day in mixed culture compared with 29 mg Mn++/litre/day when grown separately.

Jan 1, 1983

By C Bartle

In many operations the use of less electrochemically reactive grinding media in the first grinding stage (for example, rod milling and high aspect ratio SAG milling) is rarely considered. Therefore, in reality a plant may inadvertently be using a 'mixed' media charge. That is, whilst employing inert grinding media during secondary grinding, electrochemically active forged steel grinding media may be used in the primary grinding stage. This paper discusses the impact of such a circuit on the pulp chemistry and flotation response of a refractory gold ore. The Wiluna concentrator has two grinding circuits operating in parallel. Line 1 operates a single ball mill in closed circuit with cyclones, and utilises high chrome grinding media, while the second circuit (Line 2) consists of a rod mill (with forged steel rods) in series with a ball mill, which also utilises high chrome grinding media. The cyclone overflows from both circuits are combined to feed a sulfide flotation circuit. Pulp chemistry surveys were completed around both grinding circuits, and laboratory flotation tests were conducted on the cyclone overflows. The results demonstrate clearly that the rod mill/ball mill circuit operated at significantly lower Eh and dissolved oxygen values, while the percentage EDTA extractable iron was considerably higher, when compared to the single stage ball milling circuit. These variations in pulp chemistry had a marked negative impact on the laboratory rougher flotation response, and suggests that plant performance may be affected.

Jan 1, 2008

Recent literature is reviewed with emphasis on the design and scale up of mixers. Most important aspects of mixing have resulted from the study of Newtonian fluids and only a minor attempt has been made to extend the work to non-Newtonian materials.The rheology of non-Newtonian materials is outlined and the typical behaviour of mineral slurries is indicated.The importance of flow velocity, flow pattern, and fluid turbulence is discussed with relation to suspension of solids and rate of reaction.Data on experimental leaching of ore from Mary Kathleen, Queensland, show the effect of different mixing impellers.In conclusion, factors involved in the selection of a mixer are presented with emphasis on economic appraisal after pilot experimentation.INTRODUCTIONThe subject of mixing has attracted considerable attention during recent years, but relatively little work has been undertaken for the study of non-Newtonian materials. Most work has been restricted to Newtonian fluids because there are less inconsistencies in such study.Mixing, by definition, implies blending or combining, and ranges from gentle mixing which blends the contents of a large tank in 24 hours to violent mixing which completely homogenises the contents of a tank within seconds. Metzner and Otto (1957) have pointed out the present lack of knowledge on the degree (or quality) of mixing. Apart from this fact the design of mixers for Newtonian materials would seem to be reasonably certain.Both capital and operating costs rise rapidly with increasing mixer size. Therefore the design, or selection, of a mixer is a matter for economic consideration in the overall aspect of plant design and operation.

Jan 1, 1961

There are available today many various types of mixing systems, tank types and process liquors confronting the process designer of gold adsorption circuits. This short paper is to give the process designer an insight into the special mixing requirements for resin-in-leach and resin-in-pulp, plus the advantages and disadvantages of the various mixing systems that are available to agitate the required tank shapes. An understanding of the latest developments in this important process area of gold production is addressed and information given on the results of resin degradation in various tank sizes over long periods of mechanical agitation.

Jan 1, 2007

By M J. Nimmo

extremely powerful tools for building predictive and generative models. ML can be used for building highly accurate regression and classification models. But without careful data science and statistical analysis, a regression or classification model could be highly biased and completely wrong – and we may not even realise. An example rock density estimation task will be used to illustrate the potential gains and possible pitfalls in using ML and AI in Mineral Resource estimation. What could possibly go wrong? Nothing! For most simple regression or classification problems, very little. For density estimation, using the global mean may be all that is possible, but the resource classification would need to reflect the uncertainty in global estimation of tonnage. Everything! From data collection and measurement, from selecting ML and AI techniques and designing the analysis workflow to our own cognitive bias. The things that could go wrong are vast and may include but not limited to asking the wrong question, not asking questions, data bias, measurement errors, insufficient data coverage, not collecting the right variables, not collecting enough observations, collecting clustered samples, unbalanced data, filtering out data without reason (outliers), clipping data (outliers), relying on automatic feature selection, including irrelevant variables, excluding relevant variables, geological interpretation, changing context, blindly following best practice, splitting small data sets, subsetting large data sets, using the wrong tool for the task, insufficient budget to complete the analysis, not allowing enough time for testing and experimentation (the science), focusing too much on building the model (the engineering), not learning from the data, our assumptions, our preconceptions, and our skill. This paper will explore the question of how training regression models to predict rock density are affected by gaps in the data (missing observations and missing variables). What could possibly go wrong?

May 24, 2023

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 R M. S Watsford, M Davis

In 2015, MMG Limited commenced further action to improve operating margins and establish a blueprint for future growth in the Australian environment. This action was taken in the context of weakening metal prices and high input costs that arose during the Australian minerals boom.MMG was formed in June 2009 following the purchase of the majority of assets of OZ Minerals Limited by China Minmetals Corporation (CMC) through its subsidiary China Minmetals Non-ferrous Metals Co Ltd (CMN).Since formation MMG has been implementing a business model to deliver a standard way of operating. The overarching purpose of the business model is to enable fast integration of acquired assets to realise improved productivity and performance. CMN established MMG as a vehicle to reach their growth targets through further development or acquisition of mineral assets in jurisdictions external to mainland China.The business model is underpinned by the MMG operating model. The operating model defines how MMG is arranged to deliver the company strategy.This paper describes the application of the operating model to the formation of the Australian operations into a single business unit from multiple stand-alone operating sites. The development and impact of the business model on MMG’s performance is also presented.The extension of the operating model to the Australian operations has led to improvement in safety performance, direct costs and productivity. These improvements have been achieved through reducing duplication, simplification of systems and rapid deployment of improvement initiatives.The successful implementation of the operating model to Australian operations strengthens the platform for further growth. Hence, delivering on the aim of the business model.CITATION:Watsford, R M S and Davis, M, 2016. MMG’s Australian operating model – the implementation, successes and learning, in Proceedings International Mine Management Conference, pp 291-302 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By A F. Cooper

Otago Schist in the Mount Patriarch, High Burn and Cameron Creek areas of northwest Otago grades from textural grade IIA in the east to textural grade III in the west. The entire region is of the actinolite-pumpellyite metamorphic facies. Lithologies in the area are interbedded turbidite sequences comprising pelite and psammite together with pebble conglomerate, greenschist and metachert horizons. The mineral assemblage of the schist is typically quartz-albite-epidote-actinolite-pumpellyite-chlorite-stilpnomelane-calcite. A good foliation is well defined in the area and is predominantly parallel to bedding, except in hinges of mesoscopic isoclinal folds. The structure of the area appears to be defined by a large southwest plunging isoclinal fold defined by bedding with a steeply dipping axial planar foliation. Kink folding and dextral strike-slip faulting in the area postdates the ductile phase of deformation. Pods of rhodonite, rhodochrosite, spessartine garnet, coombsite, caryopilite, Mnstilpnomelane and Ni-Cu-Zn sulphides were found in concordant metachert layers in the Mount Patriarch area. Metachert was also found in float in the Cameron Creek area. Malachite occurrences relating to copper mineralisation were also noted in a green metachert horizon on the eastern flank of Mount Patriarch. The coombsite, in only the third observation worldwide, is the most Fe-rich variety reported.

Jan 1, 2003

By D Connelly

There is now a new generation of mobile crushing and screening plant systems available which have been developed based on the motivation of reducing truck haulage. Newly designed mobile crushing and screening plant systems have the advantages of mobility, flexibility, economy and reliable performance, making this system very appealing for small- to medium-sized projects or projects where a number of resources are separated by distance.A brief review of the past history and experience with transportable crushing plants provides an insight into some of the issues with transportable plants in mineral processing. A closer look at a simple model based on exploiting small but high-grade orebodies suggests the concept has merit, however there are many more engineering, logistics, legal, technical and management aspects which have limited the application of such a concept in the resource sector. This paper explores the concept in detail and endeavours to analyse the preferred commodities and scenarios under which the concept could be used and the economic and logistical limitations for iron ore. The paper also looks at the risk assessment criteria to be applied in selecting the type of resource projects where the model could be applied successfully. Other aspects considered in this paper are the project planning requirements, technical and economic feasibility, bankability and operability. Reference is made to the operating experience of contractors at a number of sites and feedback from the resource companies as managers of the projects.CITATION:Connelly, D, 2013. Mobile crushing and screening plant applications for small- to medium-sized iron ore projects, in Proceedings Iron Ore 20 13, pp 349-354 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By R Bunduwongse

The oil crisis had repercussions throughout the world and most importantly on mining, where the drive to reduce the use of liquid fossil fuel led directly to the appearance and subsequent growth in the design of mobile crushers in late 1970s early 1980s, which heralded a new era in both quarrying and mining. Even though mobile crushing has now become common, even preferred in the quarrying industry, this has not been the case in mining. This paper looks at why, in spite of the initial optimism, this technology has yet to gain full acceptance in the mining industry. The paper examines some of the problems that have been encountered in the past and offers suggestions as to how they can be avoided by applying the appropriate technology. It then takes a look at the successful application of the semi-mobile in-pit crushing system used by Italian Thai Development Company (ITD), on the Mae Moh Phase 5 contract and examines how the techniques used successfully there could be applied to the industry at large.

Jan 1, 2007

Those developing or planning a new mining operation base their financial projections on amounts of gold produced as soon as practically possible. The choice and ongoing operation of mobile plant figures significantly in their projections. The implications of mobile plant selection are not always clear - until its too late.Our 'typical' gold mine would be a mine processing 800,000 tonnes of ore per annum, producing 37,000 ounces of gold with a life of mine of 10 years. Overburden layers are only evident in the first two years of operation.The pit will eventually, after some 5 years of mining, be some 300 metres deep, but confined to a mine radius of 2 kilometres.

Jan 1, 1986

The Mobile Miner MM130 (Figure 1) is designed to tunnel or mine in hard rock. It has a 4.1 m diameter cutterhead mounted on a horizontal axis which in turn is perpendicular to the line of the machine. The cutterhead rotates at 15 rpm and is supported on a boom which swings the cutterhead through a horizontal arc.

Jan 1, 1993

The paper re-visits an old and proven concept of winzing, a method widely used in the past to gather exploration data for accurate definition of the orebody. It is proposed to use a mobile Supersucker (a giant vacuum cleaner also known as vacuum lift), to carry out winzing activities underground. A brief description of conventional underground winzing used in the past is provided, together with a discussion on other underground bulk exploration methods used in Australia to date. Historical background, principles of the proposed system, Supersucker construction details and productivities, and benefits and advantages of the proposed system in comparison with other exploration methods, are outlined. Other relevant applications of the mobile Supersucker, including surface winzing, are also briefly discussed in the paper. With a view of using the mobile Supersucker to recover all broken ore stocks underground, included are also results of floor sampling conducted recently in the in-stope decline excavated in a coarse gold type, high-grade orebody.

Jan 1, 2002

By P M. Ashley

Antimony (Sb) is an element similar to arsenic that forms anions in surface waters, rather than cations like other metals. Little is known about natural mobility of antimony in the environment. However, recent studies have suggested that antimony has similar toxicity to arsenic. Current New Zealand drinking water guideline values are 3 parts per billion (0.003 mg/l) for antimony and 10 ppb (0.01 mg/l) for arsenic. Antimony occurs principally in stibnite (Sb2S3) in mesothermal vein deposits hosted in low grade metamorphic belts of eastern Australia and southern New Zealand. Many deposits have been mined historically, including one large deposit, at Hillgrove, NSW. Oxidation of stibnite and associated arsenopyrite and pyrite causes local acidification of natural waters but acid is readily neutralised by carbonates in mineralised zones and host rocks, and therefore waters are near-neutral (pH 6-8.5). Antimony dissolves readily in moderately oxidized, near-neutral waters. Experimental stibnite oxidation yielded up to 37 mg/kg (37 000 ppb) dissolved antimony, and mine and tailings dam waters at Hillgrove mine have up to 55 mg/kg (55 000 ppb) dissolved antimony. Natural stibnite can contain >5000 mg/kg arsenic in solid solution and therefore dissolution of stibnite, arsenopyrite and arsenian pyrite also releases arsenic into waters. Resultant dissolved arsenic concentrations are up to 3.6 mg/l (experimental) and up to 7.2 mg/l (mine and tailings dam seepages). Mine and tailings discharge waters have elevated antimony and arsenic where they emerge, but attenuation occurs by deposition of the metals on to amorphous iron oxyhydroxides which can contain >10% each of antimony and arsenic. Historic disposal of mineralised waste rock and tailings into the stream system at Hillgrove has caused contamination of sediments and waters with antimony and arsenic for at least 20 km downstream with effects traceable in sediments for 300 km. Other stibnite-bearing deposits are likely to have analogous environmental effects, particularly from historically-mined sites.

Jan 1, 2002

By A Califice, E Pirard, M Benzaazoua, R Mermillod-Blondin

Image analysis is more and more considered as a powerful tool for quantitative analysis of ores and concentrates. Apart from being very much dependent upon the quality of the imaging principle and the adequacy of the imaging sensor, quantitative image analysis is also the result of a long chain of material, image and pixel sampling strategies. The most reliable way to demonstrate the accuracy and the precision of modal analysis obtained from images is probably to use a blended material with known proportions of pure minerals and confront the results obtained from different analytical tools. This operation has been performed on a series of mineral blends mimicking the tailings of a flotation operation in a plant operating on massive sulfide mineralisation. The intention was to be able to better predict acid mine drainage potential from direct mineralogical observations. Selected sulfide minerals: pyrite (Py), pyrrhotite (Po), chalcopyrite (Cp) and sphalerite (Sp) were mixed as variable amounts within gangue minerals (quartz, calcite, dolomite and siderite). Typical blends contained six to ten per cent (Py); one to three per cent (Po); 0.5 to one per cent (Cp, Sp); 15 to 40 per cent carbonates and 40 to 75 per cent quartz by mass. The 1000 gram blends were carefully sampled and prepared for X-ray diffraction, chemical analysis by ICP-AES and optical microscopy image analysis (OMIA). Results obtained for the different analytical techniques are compared and discussed revealing the limits and strength of each method in the accurate quantification of sulfide and gangue minerals.

Jan 1, 2008

By Szwedzicki T

Uniaxial testing was performed on model pillars to determine the effect of width to height ratio on pillar and surrounding rock mass stability. Samples were modelled in a shape similar to that of dumbbell weights, with the centre representing

Jan 1, 1994

By Fourney W. L, Dick R. D

Tests were conducted in plexiglass and Rockite models to determine if crater blasting could be improved by changes in charge geometry or by alterations to the borehole. Circumferential grooves were placed at various locations in the borehole in an attempt to control the initiation site of the crater. Grooves located at or above the top of the cylindrical charge had no effect on the resulting crater. Grooves placed too low in the borehole were successful in controlling the initiation site but the growth of the fracture system was not sufficient to reach the upper surface. Grooves located at a height of two thirds of the charge length were quite successful in that resulting craters were bigger by at least a factor of six than the normal crater. Testing was conducted in Rockite models to investigate charge geometry. Spherical charges in ungrooved boreholes resulted in crater sizes that were three times larger than those caused by cylindrical charges.

Jan 1, 1990