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By D N. B Skinner

Changes in the configuration of late Cenozoic volcanic arcs related to Pacific-Australian plate convergence in northern New Zealand may have localised large-scale epithermal gold-silver mineralisation to a particular part of the volcanic arc system, the Coromandel Volcanic Zone (CVZ). The history of arc-type volcanism in northern New Zealand began with the development of the continental margin Northland Volcanic Arc from early-mid Miocene (26-15 Ma). From 18-15 Ma the Northland Volcanic Arc extended south into the northern and western part of the CVZ where it is dominantly composed of andesite with lesser dacite and very minor rhyodacite. In the south, centre and east of the CVZ, younger andesite-dacite volcanism overlapped in space and time (14-5 Ma) with voluminous rhyolitic volcanism associated with rift-hosted calderas and minor basaltic eruptions. This change to bimodal rhyolitic-basaltic volcanism and extensional tectonics was a result of southwest (SW)-directed propagation of the Colville-Lau oceanic island+ arc into the north-northwest (NNW) trending Northland Volcanic Arc and its underlying continental crust. The extensional tectonic regime created in the collision zone between the two arcs is also the site of the 14-6 Ma Coromandel epithermal gold-silver province, which contains some 50 separate deposits and has a production (1862-1996) of about 300 t Au and 1150 t Ag. Extensional tectonics facilitated the emplacement of silicic magma at shallow crustal level and led to reactivation of deep basement faults. The resulting enhanced heat flow and fault-focused fluid flow localised large hydrothermal systems and associated extensive low-sulphidation epithermal gold-silver deposits in the southern part of the province, as at Waihi, Golden Cross and Karangahake.

Jan 1, 1997

By D. M. Evans, D. L. Buchanan

Paper presented at the IAGOD international symposium on mineralisation related to mafic and ultramafic rocks, held in Orleans, France, 1-3 September 1993. The Zinca area was chosen as a suitable location for an investigation of the weathering and secondary dispersion of platinum group metals from the Zone. It was concluded that platinum is immobile while within weathered rock, its mineral phases tending to alter from primary sulphides and tellurides to secondary Pt-Fe alloys. Palladium is variably mobile in weathered rock. In stream sediments Pt occurs mainly as small, dense, discrete particles, giving rise to a nugget effect, whereas Pd probably occurs as much finer particles or chemically adsorbed on to a suitable substrate. Pt shows a rapid decrease in sediments downstream from mineralisation, whereas Pd has a much slower downstream decay

Apr 1, 1994

Formation of either sodium jarosite or lead jarosite from concentrated chloride solutions containing small concentrations of sulphate has been demonstrated. Sodium jarosite is precipitated at 95-100°C from FeC13-FeCI2-NaCI-PbCI2 solutions to which was added Na2SO4 or Li2SO4 in amounts greater than 0.05 M. In the absence of alkali metal ions capable of forming jarosites, lead jarosite was precipitated from either FeCI3-PbCI2 or FeCI3-FeCI2-LiCI-PbCI2 solutions to which had been added small amounts of sulphate. Many of the factors affecting jarosite precipitation from chloride solution have been elucidated, and the most critical were sulphate concentration and initial pH. Concentrations of HCI in excess of O. I M essentially suppressed the production of jarosite in chloride media. Alkali jarosite, precipitated in the presence of dissolved lead, incorporates a small amount of this metal into the alkali jarosite lattice. Small but significant amounts of copper can also be incorporated into alkali jarosite and the amount is further increased in the presence of lead. Other divalent base metals such as Zn, Cd or Ni are not significantly precipitated. Sulphate control in either FeCI3 or FeCl3-NaCI leaching systems could likely be maintained by jarosite precipitation provided that the acid concentration of the solution was low.

Jan 1, 1981

Recent improvements are described in several techniques for ground control in underground mining. Promising methods for analysis and mitigation of rockbursts are discussed. Methods of assessing damage to underground excavations from repetitive seismic loading are reviewed. Analysis of mining-induced surface subsidence is discussed.

Jan 1, 1989

By Alex C. Smith, Thomas A. Gray, Lynn M. Crayne, Michael A. Trevits, Phil Glogowski

Mine fires constitute one of the greatest threats to the health and safety of those working in the underground environment and each event has the potential for disastrous consequences. Of the major mine fires and thermal events that have occurred in the United States in the last 6 years, it is estimated that remotely installed seals could have been used in 63% of the events to control fire growth or to aid in fire suppression work. The National Institute for Occupational Safety and Health (NIOSH) is conducting full-scale tests at the NIOSH Lake Lynn Experimental Mine to evaluate and improve remote mine seal construction technology. The main focus of this work is to develop reliable technology that will completely close the mine opening from floor-to-roof and rib-to-rib. This paper presents the results of remote seal installations using grout-based materials.

By Robert E. McIvor

The Functional Performance Equation for Ball Milling” was first presented in 1988. It now has been used successfully in more than a dozen mineral processing plants. This powerful, yet simple tool provides a new level of understanding of closed circuit grinding. It shows how grinding circuit efficiency is in reality comprised of two distinct efficiencies. It demonstrates how circuit production rate is related, collectively, to these two efficiencies, mill energy input, and the grindability of the ore. It links circuit performance to design and operating variables that can be manipulated, and creates an effective strategy for making plant improvements. This paper covers the derivation and industrial validation of this equation. As part of an engineering and management system that also incorporates suitable metrics and process control, other operators can now use this tool to make improvements and to manage the performance of their grinding operations with clarity and confidence.

Jan 1, 2005

By F N. Baez

This paper supplements a keynote address prepared for the MassMin 2016 conference on mass underground mining methods, including block, panel, inclined and sublevel caving. It advocates for a new cave mining paradigm that takes advantage of a number of new and disruptive technologies or innovations that have evolved over the last 15 years, some of which were initiated by major mining companies such as Codelco. The paper will address the challenges that the industry will be facing in the future as well as possible solutions. As background, the paper summarises the challenges that the industry has faced in the past and how such challenges were addressed. The author acknowledges that given his more than 30 years of experience with Codelco Chile (operations and corporate), aspects of his intelligent mining concept have no doubt been influenced and have matured during his invaluable time with Codelco also as the Head of Technology and Innovation. In the paper, he uses some of the innovations developed within Codelco and by the Chilean Government to illustrate the concept of ‘intelligent mining’.CITATION:Baez, F N, 2016. ‘Intelligent mining’ – the way of the future, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 3–8 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Rose L. Ballard

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal nonfuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is ordinarily termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1983

By Cooper R. J

The essential features of the zinc concentrate roasting installation at the Risdon Works by the Electrolytic Zinc Company of Australasia Ltd. are given.The problem of maintenance of ignition in down-draught zinc concentrate flash roasters is discussed, and a solution offered.A successful and economical method of using by-product oxygen for raising the roasting efficiency of hearth roasters is described. Three methods of utilizing oxygen for the same purpose in flash roasting are detailed, and their relative merit, considered.INTRODUCTIONThe zinc sulphide concentrate used at the Risdon Works is roasted autogenously for removal of sulphur in two hearth roasters, and four flash roasters. The hearth roasters are of modified Skinner type with eleven hearths. They were designed, and are used, for roasting mixtures of relatively low sulphide content. Their design and operation have been described elsewhere (Forster, 1949).The flash roasters are down-draughted furnaces with cross-section and rabbling equipment based on the hearth roaster design, and the process is similar to that developed by the Consolidated Mining and Smelting Company of Canada Ltd. (Cominco) at Trail, B.C. (Stimmel, Hannay, and McBean, 1936).These furnaces are 20 ft. in diameter. They have three drying hearths through which hot gas is drawn from the combustion chamber by the burner fan. The combustion chamber is 2'1 ft. high above the collecting hearth (27 ft. in No. 4 unit), and the discharge hearth below it is 6 ft. high, so that a large gas offtake is possible. Four rabble arms for each hearth are carried on a central column. Dried, ground concentrate, and the air for roasting it, are fed to a burner...

Jan 1, 1958

By K. Lim, J. Sobil, L. Galarza Castillo, F. Tozlu

"For mining operations globally, the scale and criticality of the grinding mill drive has meant that selection of the correct mill drive technology is paramount. With so much depending on the successful implementation of the electrical drive system— safety operation, timely installation, availability, energy efficiency, minimum maintenance and extend its use as tool to assist during mill liner exchange—customers are justified in their scrutiny and slow adoption of new drive technology. From the first installation of low, fixed speed synchronous motors to the introduction of the current source and further voltage source variable frequency drive, innovations require long periods of time and mining customers willing to push the industry forward. In recent years, the variable frequency drive has been the stepping stone for a new generation of mill drive technology. In use for decades in other heavy industrial applications, the drives allow for system optimization in a myriad of ways. The most dramatic of changes is in the design of the motor. Where in the past motor design was bound by line frequency, today the designer can optimize machine size and, more importantly, eliminate the need entirely for the synchronous motor. Induction motor design has now progressed to the point where low speed operation is possible at efficiency levels nearing those of the synchronous design. Moreover, the simplicity of the squirrel cage design means that availability, reliability and spare part requirements are greatly improved. As the next step in the evolution of large pinion driven grinding mills, the low speed induction drive offers a new reliable and robust system to the market.IntroductionAs deposit grades continue to decline, new ways of processing ever greater concentrator throughputs have been required to maintain throughput efficient and profitable operations. Furthermore, the high risk nature of mining developments requires a constant search for safer, higher availability and more efficient equipment design. Limitation of downtime is a key factor in ensuring mining operations can be sustained through volatile market conditions. Often processing the entire mine throughput through just 1 or 2 lines, the crushing and grinding circuits are of particular criticality to the uptime and, thus, profitability of any mining operation."

Jan 1, 2016

By F. M. G. Egerton

Mechanisation of mining operations is not a new concept in the world of mining. Machinery has been developed, manufactured and used for many decades in massive orebodies and coal mines, both locally and abroad. Because of their size and the huge tonnages available, massive ore bodies lend themselves very easily to mechanisation. However, little progress in mechanisation has been made in narrow tabular orebodies in South Africa. The equipment available for narrow tabular orebodies requires excavations of a size that introduce large volumes of waste dilution. Nevertheless, it is essential for South African miners to experiment with mechanisation and to find a solution to the problem. This address looks at current conventional mining methods and compares them to bord-and-pillar type mining methods. Off-reef mechanisation is also touched on. It then looks at different hybridised mining methods that are being used, i.e. a mixture of conventional mining and mechanisation. It finally looks at future prospects for mechanisation in narrow tabular orebodies.

Jan 1, 2004

By Gabriel Esterhuizen

Observations of pillar conditions in limestone mines showed that the presence of weak bands in the limestone can result in pillar damage at stresses that are lower than one would otherwise expect. The objective of this National Institute for Occupational Safety and Health study was to investigate the mechanism of failure caused by the presence of weak bands by using a series of numerical models based on realistic physical properties. The effect of the weak bands on pillar strength was also investigated by developing a series of pillar models with different width-to-height ratios and determining their strength by simulating a servo-controlled loading condition. The material properties of the bands and the limestone were varied and their effects on pillar strength were determined. Model results demonstrated failure development similar to the pillars observed in the field. The weak bands were seen to develop tensile stresses in the limestone as they extrude under increasing stress. The limestone fails in tension at a much lower stress than its expected uniaxial compressive strength. The results showed the load bearing capacity of the pillars can be reduced significantly by the presence of multiple thin weak bands. The degree of strength reduction is largely dependent on the compressive strength, the frictional resistance and the thickness of the weak bands. Single weak bands do not affect pillars as severely as multiple bands. However, the model results show that a single thick weak band, which comprises more than about 2 percent of the pillar height, can cause a significant reduction in pillar strength. The weakening effect of the bands become less severe as the pillar width-to-height ratio is increased. Field observation of spalling and failure associated with weak bands in limestone pillars show that the failure mechanism in the models resembles the observed failure. The model results provide insight into the important factors affecting pillar strength in the presence of weak banded materials.

Jan 1, 2007

By Michael Amick, G. Swan, R. Hill, C. Pritchard

Falconbridge, a major base metal producer in the Sudbury Basin of Ontario, identified a need to find a safe and cost effective replacement for welded-wire mesh used to support loose ground during underground nickel mining. Falconbridge took a methodical approach to the concept of a spray-on liner as a screen replacement proving the strength characteristics of the liner as a safe, cost effective, and suitable method of supporting ground. Compact, hydraulic mixing and spraying equipment have been developed and are in use at the Fraser mine. The Tekflex material has been approved as a wire-mesh replacement and has been in use since November1998.

Jan 1, 2000

By K. Osburn

South Deep Gold Mine, owned by Gold Fields Ltd., is situated near Westonaria in the Gauteng Province of South Africa and mines the conglomerate bands of the Upper Elsburg reefs (Mondeor Conglomerate Formation) of the Witwatersrand Supergroup and the Ventersdorp Contact Reef (VCR) of the Ventersdorp Supergroup. The stoping and underground developments are mechanized. The Upper Elsburg reefs are mined by a variety of mining methods, including mechanized drift and fill, modified drift and bench, longhole stoping, and low-profile mining. Optimal mine design and scheduling for deep-level mechanized mining are complex, and success is highly dependent on detailed, robust, and accurate geological and geostatistical models. Geological structures significantly influence the sedimentological characteristics, distribution, and preservation of the Upper Elsburg reefs and VCR. Accordingly, particular emphasis is placed on the generation of a mine-scale structural model that accommodates the relationships between the older north-trending fault systems (West Rand and Panvlakte faults) and younger east-trending dextral wrench faults. Results from underground mapping, borehole intersections, and highresolution three-dimensional seismic data have been integrated to produce coherent three-dimensional geological models. The Upper Elsburg reefs suboutcrop against the VCR and comprise an easterly diverging clastic wedge, thickening from the suboutcrop position, to approximately 130 m at the mine?s eastern boundary. The Upper Elsburg reefs are characterized by conglomerate and quartzite bands forming multiple, stacked, upward-fining unconformity-bounded couplets. Palaeocurrent directions are dominantly from west-northwest to east-southeast, indicating that the more proximal deposits are preserved close to the suboutcrop, with distal facies to the east. Sedimentological modelling is applied to individual stratigraphic units and caters for facies definition. This is achieved through channel width (CW) kriging and fitting of type sections to borehole and mapping data. Homogenous geological geozones for each stratigraphic unit are thus defined within individual structural blocks on the basis of those sedimentological parameters that have been found to have a positive spatial correlation to gold concentration. These geozones then serve as constraints to the evaluation of the orebody. This contribution presents a summary of the modelling processes that are currently applied in the development of high-confidence, timeously produced geological models that are essential input for mineral resource estimation and mechanized mine planning and scheduling.

Jan 1, 2014

By J. P. Kennedy, O. A. Bascur

Large metallurgical complexes have more data than a small city and these data change as internal and external conditions evolve. Staffing turnover hinders experienced-based decisions especially with simple tools like spreadsheets. Lack of current information can contribute to decisions that result in significant deterioration in the quality of operation. Timely, unified information from sophisticated analyses presented to the broadest possible reach will improve operation. The major innovation is the addition of the web browser to the suite of software people will use with no training – the other two are spreadsheets and graphical presentations – and the consistent organization and transformation of the real time data to support broad access. This paper describes the data transformations and presentation methods necessary for a Web view, especially the special needs of real time data and analysis required for active operations decision-making. Many people inside and outside the complex, not just operators, need timely information that is abstracted, aggregated, organized and unified. Unification and aggregation of real time data presented via the Web opens a new paradigm for collaboration. The analysis tools are as important as the data. These rule-based tools add significantly to the operations database in the form of results stored for viewing with plant data. Mining and metallurgical plants already use many sophisticated analysis tools such as predictive maintenance policies based on statistical analysis vibration analysis, and oil and lube analysis for critical equipment. These add real time events, similar to an alarm package, and unified production information to the operational database. Simple models are used on line to create key indices that provide a real time indication of performance. Key indices include metrics for losses due to plant availability, performance efficiency, and overall process equipment effectiveness. These additional data in the operations database are used for early fault detection, increased production, better quality, higher availability of equipment and faster detection of process bottlenecks. An important feature is the ability for people to create their own key indices and store the results for use by anyone in the plant historian, but accessible by a browser. Keywords: plant information, principle components analysis, data reconciliation, gross error estimation, Internet, Word Wide Web

Jan 1, 2002

By C. O. Brawner, J. Kalejta II

The classical approach to control rock fall and ravel in open pit mining has been to use catch benches. The width and volume of benches is most dependent on the bench height, size of loading equipment, blast damage to the face and mining regulations. This was compatible with open pit slopes of less than about 45°. As our understanding of rock mechanics and blasting control has improved over recent years, much steeper rock slopes can be developed at many open pit mines. However, narrower benches result with less rock fall capacity. The transportation industry has been very successful in using catch fences to protect highways throughout North America and Europe for years. The authors recommend that cable and ring net fences have a potential major application in open pit mining to allow steeper rock slopes with significant economic benefit. This paper outlines the application, design and operation of catch fences in surface mining for specific conditions. Typical case examples are presented.

Jan 1, 2002

By P. Mokwena

Paper written on project work carried out in partial fulfilment of BSc (Hons) in Chemical Engineering Diamond synthesis has attracted a great deal of interest because of its exceptional properties and various applications. In this study, the chemical catalytic vapour deposition (CCVD) method was used to synthesize diamond films using acetylene as carbon source and hydrogen as carrier gas at a temperature of 1000°C, and their thermodynamic stability was studied. Photographic analysis revealed that these products are diamond films, Ramman spectroscopy confirmed that they are graphitic while confocal laser scanning microscopic image analyses proved that these diamonds films have structural defects due to iron impurity from the catalyst precursor. The quantity of diamonds films produced is also proportional to the acetylene to hydrogen ratio but these films are larger in size at lower acetylene to hydrogen ratio. Thermogravimetric analyses showed that transformation of these materials begins at 25°C but could not be used to determine if a temperature range below 25°C exists. The stability of these CCVD-synthesized diamonds also increases below 25°C when stored at different temperatures.

Jan 1, 2007

By Hans von Michaelis

"INTRODUCTIONThe renaissance in gold and silver recovery technology has continued to unfold and it is appropriate to review some of the useful new technologies as well as try to identify some of the industry's future needs and frontiers.The remarkable strengthening in the US dollar has resulted in a relatively low gold price in US Dollars of around $310/oz at the time of writing and silver at $6.25/oz. This general softening in the dollar prices and the recent confusion as to environmental compatibility of cyanidation tailings and effluents, has led to a slowdown in announcements of new operations. Another reason for the slackening off in the USA is that in the past few years a large part of the capital has come from oi I and gas companies that now seem to be losing interest in mineral ventures, and foreign investors for whom the dollar is becoming out of reach. In the author's opinion this represents an unprecedented window of opportunity.Elsewhere in the world where local currencies have weakened, the price of gold is at or close to its all time high.For example, in South African Rands, the gold price was R571.00/oz when the rand was US$1.47 and the gold price reached US$800. Now at US $309/oz and with the Rand at US$0.51 = Rl .00, the local gold price is R600. The price of si Iver in Mexican pesos is not much less than it was when silver reached US$50/oz. Gold, and silver prices in local currencies outside North America are still buovant and at levels where additional investment in new projects is more encouraging.Even in Canada where the dollar is worth about US$0. 75, this provides a smaller but significant cushion compared with US operations. Considering the present strength of the US dollar and even the Canadian dollar relative to many other gold producing countries, there should be significant investment opportunities at today's prices. Mining companies have started to descend on Brazil, for example, where in a matter of just a few years annual gold production has increased from 10 to 70 tons. In South Africa, a Canadian company backed by Swiss financing has been able to take over a Witwatersrand gold mining operation and is installing a huge new tailin9s retreatment plant to process about 1 million tons per month of tailings."

Jan 1, 1985

By P. H. Morris

The exponential delta profile equation matches the profiles of a wide range of coal and metalliferous subaerial tailings deltas well, but the original model implies unrepresentatively low solids concentrations. A revision, based on analysis of the governing equations of mobile bed flows with high concentration values, has shown that for exponential delta profiles to form there must be quasi-steady, slowly varying flow and slow deposition as well as tailings with a log-uniform sorting-parameter distribution. Deposition on tailings deltas is slow and the flow in many natural streams and, by analogy, tailings deltas is quasi-steady and slowly varying; the assumption of such flow is justified by the strong congruence of the revised model and the available data. The predictions of the theoretical model are essentially unchanged but concentration and flow Froude number are now not explicitly limited

Jun 19, 1905

By P. Roy

Smelting or converting of sulphide concentrates and mattes in a batch operation presents a challenge when directing the off- gas to a conventional acid plant. The Hindustan Zinc Ltd. (a division of the Vedanta Group of companies) Chanderia Lead Zinc smelter was presented with such a challenge that was met with the adoption of the Cansolv® SO2 Scrubbing System. The Ausmelt top submerged lance technology used at Hindustan Zinc generates a furnace gas stream that containsbetween 0.1 vol% and 12 vol% SO2 during the three stages of batch smelting. Cansolv® SO2 Scrubbing Technology captures the SO2 to ensure that treated flue gas exits the facility at a concentration below 100 ppmv SO2 and it releases SO2 in a controlled fashion, to more closely match the needs of the existing acid plant. The application of a regenerable scrubbing system to capture SO2 from a batch-operated furnace and convert it to acid in a conventional acid plant was a first of its kind in the world. This paper provides an update on the design and operation of the Hindustan Zinc SO2 recovery system and suggests two improvements to the basic flow sheet that optimize the cost of SO2 scrubbing further.

Jan 1, 2007