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The principal source of funding the working capital requirements of gold miners has traditionally been equity. However in the 1980s, with a substantial increase in activity in the exploration for, and the production of, gold the traditional sources of equity finance became no longer sufficient to meet demand. With the often high cost of raising equity, the need for developing alternative financing structures became critical, especially since the stockmarket crash of 1987 which at least until recently, adversely affected the amount of equity capital available for investment in mining.

Jan 1, 1994

Rare-earth permanent magnetic roll separators, pioneered by our group a few years ago, have distinctly different operation characteristics compared to prior art electromagnetic separators of various types. Many new applications for dry high-intensity (or better: high-force) magnetic separation have been developed in a short time period. It has also been found that the new generation of separators generally are more efficient with regards to removal of weakly magnetic contaminants in glass and ceramic raw materials with minimum loss of valuable product compared to induced magnetic roll (lMR) separators. The latest development is in the area of production of clean magnetic concentrates at high recoveries. It is likely that the PERMROLLR magnetic separator will replace cross-belt and lift-type magnetic separators as a result of this most recent advance.   The paper will review the features of the PERMROLLR magnetic separator in comparison with other types of magnetic separators on the market and give examples on applications.

Jan 1, 1990

By G D. Price

Scheelite mineralisation east of the main divide in' the Southern Alps of New Zealand was originally identified by Royden Thompson who is now a geologist with the NZ Geological Survey. This mineralisation was brought to the attention of CRA in 1978. Reconnaissance surveys were carried out in 1979 to delineate the extent of the mineralisation. This was undertaken using ultraviolet light examination of the sediments within the major drainages in the Southern Alps. This defined tentative zones of prospective mineralisation. As a result of this, preliminary reconnaissance, exploration licences were applied for -those areas in which indications of scheelite mineralisation were strongest. A total of 1737 km2 of ground was applied for within four exploration licences. These covered the main Southern Alps mountain chain between the Haast/Wanaka highway and the Mt Cook National Park.

Jan 1, 1983

By Cadia Geology Team

The Cadia Hill Gold Mine, located near Orange in Central Western New South Wales, is owned and operated by Cadia Holdings Pty Ltd, a wholly owned subsidiary of Newcrest Mining Limited. Construction including pre-strip mining occurred from 1996 to 1998. The mine was officially opened in October 1998 following commissioning of the concentrator and mine fleet in June of that year. The Cadia Hill orebody is a porphyry related gold and copper system. The final pit has a strip ratio of approximately 1.3:1.0. Mining is undertaken on 15 metre benches using large capacity diesel hydraulic face shovels at an annualised rate of up to 70 Mtpa. The concentrator is currently rated at 17Mtpa and includes the worldÆs largest single line grinding circuit. The feasibility Mineral Resource was estimated at 352 Mt at 0.63 g/t Au and 0.17 per cent Cu. Initial reserves totalled 200 Mt at 0.74 g/t Au and 0.17 per cent Cu yielding a mine life of approximately 12 years. During the pre-production period mine geology systems were developed to support the operation. By design these systems were intended to add value to the business through minimisation of material miss-classification, provision of accurate and timely production information and mapping and reconciliation as a continuous model improvement tool. Variances that would prove to be material to the life of mine plan were recognised during the first year of production. These included identification of additional ore tonnes, higher copper grades and higher gold recoveries relative to the model. Gold grades and copper recoveries also reconciled favourably. Testwork was undertaken to determine the underlying causes of each variance. Re-modelling was then undertaken to capitalise on those variances. The Cadia Hill Gold Mine life of mine plan was re-evaluated with updated geology, grade, geotechnical, metallurgical and environmental inputs. Operating strategies were also reviewed and revised. Despite application of reduced metal prices in the evaluation, the outcome was one of extended mine life with more metal produced at lower cost. Development of robust mine geology systems, including a pro-active reconciliation process contributed to tangible improvement of the Cadia Hill Gold Mine operation. On-going system development and improvement initiatives are planned to add further value for the future.

Jan 1, 2000

Mechanism Responsible for Flocculation in Poly (N-Isopropylacrylamide) Temperature Responsive Dewatering - Attractive Interaction Forces Induced by Surface Hydrophobicity

Sep 13, 2010

By R B. Stewart

Where pasture production is the intended land use of the areas to be reclaimed, the creation of a suitable growing +medium is a major objective. To achieve this land reclaimers require a sound understanding of the proposed mining plan and a knowledge of the physical, biological and chemical properties of materials intended for resurfacing disturbed areas. Where the original soil is not being replaced in its natural state, research is usually required to determine an alternative growing medium. Results from field research conducted on waste material from the Waihi Gold mine are reported with emphasis on the significance of soil depth in relation to pasture production in this environment.  Problems in extrapolating field research to large scale operations are also considered.   Essentially the requirements for successful pasture production, on surrogate growing medium, are akin to conventional approaches used in New Zealand in the development of unimproved agricultural land. High inputs of fertiliser are initially needed, especially where volcanic soil is used, and careful management of pastures and soils is required to minimise soil erosion and create a sustainable system. In the first three to five years of pasture production, grazing use of the land requires to be dictated by pasture availability and soil conditions and not by animal feed requirements. The use of light stock (young dairy or sheep) is recommended.   Successful land restoration requires a team approach by a range of cooperative specialists including engineers, soil scientists, farm managers, agricultural contractors, landscape architects and environmental officers.

Jan 1, 1991

The Research on Refined Gold Bullions Surface Upgrading

Sep 13, 2010

By T Leach, B Fulton, R Stewart

Gold mineralisation at Porgera is inferred to have been derived from a deep differentiated magmatic source which is capped by a series of (now tilted) inward dipping sills and stocks, which comprise the Porgera Intrusive Complex. An arc normal transfer structure provides a conduit, at tile intersection with an arc parallel structure, into which basic magma derived from tile deep melting of mantle material has been emplaced. Two phases of mineralisation display an association with late stage feldspar porphyry intrusives. Stage I carbonate-base metal-style gold mineralisation occurs as early quartz-sericite, then massive sulphide and late zoned Mn-Fe-Mg-Ca carbonate vein/breccias. Magmatic fluids derived from the deep magma source, are interpreted to have migrated along me margin of a feeder stock to the sills, and south to Waruwari. Stage II epithermal Au-Ag quartz-style gold mineralisation occurs as early fluidised breccias and carbonate veining, followed by zoned quartz-roscoelite-carbonate-gold vein/breccias, and late carbonate and/or sulphate open space infill. Magmatic fluids are interpreted to have utilised the same plumbing system as the late stage feldspar porphyry intrusive, and then migrated into the Roamane Fault which was dilated by; dextral rotation on elements of the transfer structure, normal faulting, and refraction around the competent footwall hornblende diorite. Bonanza gold is localised in a jog in the Roamane Fault, hangingwall splits and at intersections with cross structures. Bulk low grade Stage I gold has been deposited by the mixing of magmatic fluids with cool gas condensate waters, whereas high grade Stage II gold mineralisation resulted from the rapid quenching of mineralised magmatic fluids by oxygenated groundwaters.

Jan 1, 1995

By S Lush, R Polglase

McConnell Dowell is pleased to be given the opportunity to present two papers to this conference. The first is a general discussion paper on our work in the field of slurry transportation. The second will be a technical paper on the development of a welded coupling compatible with urethane lined pipework. We trust that by discussing our recent work we can leave two lasting impressions on you: the versatility and useful role of slurry transportation, and the leading role taken by New Zealand in this technology This paper discusses three recent projects the New Zealand Steel Ironsand Transfer Line the Coarse Coal Ship Loading Technology the Nerang River Sand By-pass System. These have followed on from the other slurry projects with which McConnell Dowell has been associated such as the ironsand export trade at Waipipi and Taharoa. The New Zealand Contractors Federation awarded the Construction Award for 1986 to McConnell Dowell for the Ironsand Slurry Pipeline.

Jan 1, 1986

By G B. Arehart, S J. Mathews, J L. Mauk

The banded nature of the quartz veins which form the Empire lode at the Golden Cross mine, is perhaps their most striking feature. Petrographic studies show that significant differences occur between the bands in terms of textures, quartz grain size, calcite, adularia and kaolinite content, and the form, concentration and mineralogy of sulfide phases.   The d18Oquartz values of individual bands within the vein material range from 7.3-10.9ë. Calculations show that the d18Oquartz values can be adequately explained by temporal variations in the system temperature, boiling and/or variations in the systems fluid/rock ratios.

Jan 1, 1995

By A Penney, M J. Pascoe, R M. Stephenson

The empirical McCracken and Stacey stability and risk assessment method has been in use for more than 20 years to assess geotechnical stability issues for raise bored shafts. The methodology has been applied with various levels of success. Increasingly, trends in mining and civil tunnelling have been towards larger diameter, single pass, raise bored shafts to rapidly provide means of ventilation, material movement (ore passes), or emergency egress. Identifying and assessing potentially problematic zones before raise boring commences can allow for appropriate risk-based decisions on construction, or to investigate alternative solutions. The implementation of a proactive solution to raising through an identified weak zone is preferred to the application of an engineered solution to an area subjected to substantial instability or failure. Methods for investigating potentially problematic areas are discussed in this paper based on AMC’s benchmarking data. Proactive investigation programmes resulting from these investigations are also discussed. Previous publications discussing the benchmarking data have concentrated on Australian case studies. Increased efforts and recent updates have been made to expand the database to include international case studies. This has provided further refinement of lower bound ‘raise bore rock quality index’ (QR) values, and various rock mass parameters for stability assessments. CITATION:Penney, A, Stephenson, R M and Pascoe, M J, 2018. Raise bore stability and risk assessment empirical database update, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 434–445 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By L Torckler, R L. Brathwaite

At Neavesville gold-silver (electrum) mineralisation occurs in steeply-dipping zones of intense fracturing, brecciation and quartz veining within rhyolitic pyroclastics, carbohaceous shales and andesites. Hydrothermal alteration extends over an area of greater than 3 by 1.5 km. In rhyolitic tuffs, highly silicified zones containing quartz-adularia-illite assemblages are flanked by less silicified assemblages composed of albite, illite-montmorillonite and chlorite. The mineralogy and sequence of alteration are comparable with the alteration zones which envelop the steam-producing fissures of the active Wairakei and Broadlands geothermal fields. Primary fluid inclusions in quartz from five fissure veins in the Neavesville field show maximum homogenisation temperatures ranging from 220 - 260¦C and salinities of 0.0 - 1.1 wt per cent NaCl equivalent, which cover a similar range to actual measured temperatures and salinities in geothermal fluids at Wairakei and Broadlands. The age of the rhyolitic pyroclastics and related alteration and mineralisation is probably Pliocene and Neavesville therefore represents a fossil geothermal system. The intensely fractured zones containing the gold-silver mineralisation were probably produced by hydraulic fracturing generated by accumulation under pressure of hydrothermal fluid in blind fault zones. Study of fluid inclusions indicates that hydrothermal quartz associated with electrum was deposited under boiling conditions. High grade electrum mineralisation at Graces workings appears to be localised by reaction of hydrothermal fluid with sedimentary marcasite in black shale.

Jan 1, 1980

By K Palmer, G J. Artmont

Alluvial gold is an ideal exploration tracer to bedrock source and indicator of bedrock mineralisation style because: (i) gold occurs in a wide range of deposit types, (ii) primary composition is sensitive to style of mineralisation, and (iii) it is a heavy resistate mineral that is readily preserved and easily sampled. In regional exploration of the Central Ranges of Irian Jaya, alluvial gold mineralogy has been applied to maximise the information return from panned concentrate sampling and to focus exploration effort. Primary gold is a solid solution of Au+Ag¦Cu¦Hg, ¦ trace Pd, Te, and Sb. In general Ag¦Hg increase and Cu decreases with inferred decreasing temperature of formation, and gold from particular mineralisation styles has signature compositions that can be used as indicators of bedrock mineralisation type. Furthermore, the abundance of alluvial gold is an indicator of the economic potential of a catchment. The convergent continental-oceanic plate geology of the Central Ranges is conducive to a wide range of mineralisation styles. Mineralogy of gold in ophiolite, skarn, porphyry, mesothermal vein and possible VHMS environments is characterised from alluvial and bedrock samples, and the use of gold mineralogy in prospecting at regional scale through prospect definition to drilling is demonstrated.

Jan 1, 1995

The modern Golden Cross mine entered the production phase in January 1992. The project is designed to produce over 100 000 oz/yr of gold and over 300 000 oz/yr of silver during a mine life of eight years. An open pit and an underground mine are operated producing around 850 000 t/yr of ore, to feed a conventional carbon-in-leach processing plant. Golden Cross is owned in joint venture by Coeur Gold New Zealand Limited (80%) and Viking Mining Company Limited (20 %).   Since the start of production several major aspects of the design have altered. The underground mine began as a mechanised cut and fill operation. The cut and fill stoping progresses in 3.3 m flatback lifts with maximum stoping width of 6 m. Where the ore zone is wider than 6 m a post pillar cut and fill method is used. In 1993 a new bench mining plan was introduced between the 270 and 260 levels. Flatbacking continued in the footwall drives in anticipation of variability of the ore width and orientation. The development of levels below the main service 200 level has indicated a possibility of bulk mining the ore block rather than flatbacks. This could lower mining costs but also introduce higher dilution rates. Development is in the advanced stages for trialing this method.

Jan 1, 1994

Engineering education has become a matter of national concern, at last, so I would like to talk about the links between the mining industry, the universities and technological developments. The Australasian mining industry and the mining schools have collaborated closely since the first school was established in 1871 and during those years there were a series of remarkable technological developments. For example:In the late 1880s George AndersoIl Richard developed chloride leaching of gold at Mt Morgan. This made a large difference to the wealth of Mt Morgan Mining Ltd.In the mid 1890s Robert Sticht demonstrated that pyrite smelting was an economically feasible process at Mt Lyell and the wealth which came to Mt Lyell Mining Co from his outstanding work made it one of the great companies in the country.During the first 15 years of this century flotation was developed at Broken Hill and it has proved to be one of the great technological inventions of this century.In the 1920s G K Williams started his outstanding work on lead smelting and refining at Port Pirie, this was work which ultimately re-wrote the text book on lead metallurgy and established Port Pirie as the mecca for lead metallurgists.In the 1920s also Frank Stillwell, later joined by Austin Edwards, established the new science of mineragraphy at the University of Melbourne. They were both great geologists, both were superb scientists and oddly enough both were outstanding athletes.In the 1930s Dr Ian Wark, a man in the front rank of Australian scientists of any period, started his outstanding work on flotation, work which resulted in a text book which remains a leader in its field today.In the 1930s also Arnold Black at Broken Hill South Ltd picked up the work which had been done at Mt Lyell many years previously and eventually wrote the papers on hydraulic fill which demonstrated that he led the world in fill technology. What a remarkable story of achievement it was, it laid the groundwork for the great industry we have today. It was possible because the industry was well supported by outstanding university schools and I would like to talk about some of these.

Jan 1, 1989

By S Kasaneva

TheSan Cristobal gold district is located 110 km east of the port of Antofagasta, Chile. It contains the San Cristobal gold mine, where Niugini Mining Ltd. commenced a heap leach operation, with initial reserves of 10.1 million tonnes grading 1.34 g/t Au, in December, 1990. The San Cristobal district occurs within an upper Cretaceous-lower Tertiary magmatic arc. The main mineralisation occurs within a northwest trending subvertical zone, 1km long and 70 - 100 m wide, which contains rhyolite porphyry and minor breccia, and is locally termed the 'subvolcanic complex'. At the San Cristobal mine, most gold mineralisation occurs in subvertical quartz-pyrite veins which were emplaced in dilational sections of an imbricate fault system. The bulk gold resource comprises four ore shoots which formed where the vein system intersects the subvolcanic complex. Gold-bearing quartz-pyrite veins also occur at separate prospects, the Three Sisters and Sol prospects, west and south of the San Cristobal mine.   Hydrothermal alteration consists of potassic and propylitic assemblages related to intrusion of the subvolcanic complex. This alteration is overprinted by a phyllic stage which is associated with the emplacement of the quartz-pyrite veins. The oxide zone is 180 m thick, and contains native gold, electrum, limonite, and manganocarbonates. The underlying hypogene zone contains pyrite with minor chalcopyrite, sphalerite, galena, covellite, bornite, chalcocite, and arsenopyrite. Fluid inclusion studies indicate that the deposit formed at approximately 270¦C, and the mean salinity of the fluid was 4% NaCl equivalent. These observations enable the San Cristobal deposit to be classed as a porphyry- related, mesothermal quartz-vein system of the low sulphidation type.

Jan 1, 1995

By G Tsatouhas, R Newell, K Y. Wong

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

Jan 1, 2005

By J R BISHOP

Geophysical techniques are being increasingly used down exploration drill holes as deeper and more elusive targets are sought. This paper lists the various methods available and discusses the applications using a number of examples.

Jan 1, 1992

By K Palmer

Alluvial platinum was recovered during gold mining operations in Maud Creek, a tributary of the Howard River. Average electron probe analyses give Pt 88.75, Fe 5.27, Ir 0.70, Os 1.06, Pd 0.34, Ru 0.14, Rh 1.29, Cu 1.06. Rare grains of a Pt-Fe-Cu alloy are also present and an unusual feature of all grains is the relatively high rhodium content which finds expression in segregations of rhodium arsenide, cherepanovite. Platinum is found in the Orepuki area of Southland, where it is probably partly derived from the mafic rocks of the Longwood Complex. Rocks of the Rotoroa Complex, similar to those of the Longwood Complex, form bedrock in Maud Creek and are possibly the source of the Howard platinum. Alternatively, it might be derived by glacial transport from the Matakitaki ultramafic block 30 km to the southwest. Origin from the Rotoroa rocks is preferred as, if the Matakitaki rocks are part of the Dun Mountain Ophiolites, they might be expected to contain osmiridium rather than platinum. The ratio Pt:Ir-Os has been widely used to distinguish low Pt:Ir-Os ophiolitic from high Pt:Ir-Os gabbroic assemblages. Mafic complexes such as Longwoods, Darran, Rotoroa, and Riwaka might be expected to show similar high Pt:Ir-Os ratios and be targets for platinum exploration. Detrital platinum examined from the Parapara area, Golden Bay is mainly osmiridium, with rare grains of rutheniridosmine, very similar in composition to that found in concentrates from the Kaniere dredge, West Coast.

Jan 1, 1987

Quality Assurance has become a buzzword amongst governments and industry. Notwithstanding the world class work done by its committees in developing codes of ethics and of practice in field geological handbooks, mining cost estimation handbooks, and reserve estimation, the AusIMM could better prepare its membership for QA. MICA could provide a simple set of guidelines to enable consultant members to develop their own QA procedures manual conforming to AusIMM Codes and to IS09003, and AS3903.

Jan 1, 1994