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By T. R. Ellis

Regulation of mineral property valuation methodology by governments and others is due to frauds, condemnation and takings, banking industry problems, and litigation. Definitions of "reserves," "resources," and "qualified person" continue to evolve, along with guidelines to the data and disclosure required to support valuations. A less recognized but vital issue relates to the regulatory acceptability of alternatives to the comparable sales method. Comparable sales generally work well for surface real estate, and sometimes for precious metal deposits, but not at all for most industrial mineral properties. Alternative methods, such as net present value, or a geoscience rating system, often provide better valuations. Yet US regulations dictate comparable sales as the preferred method. The task of convincing regulators of the inapplicability of comparable sales to mineral properties, particularly those lacking reserves, may be as important as the valuation itself.

Jan 1, 1999

By K. Terhaar

The objective was to determine operating protocols for a lead and silver column flotation cleaner, being considered for installation at Sunshine Mining & Refining Co.'s Kellogg mill in Northern Idaho. In this column, tetrahedrite and galena were floated, and pyrite and other gangue minerals, including siderite and silica, were depressed. The procedure was to develop a dynamic simulation using a linear transfer function approach. The transfer function related cause and effect variables such as the influence of collector and depressant dosages on recovery and grades. Bench-scale flotation tests followed by pilot column testing provided the data used to develop a linear transfer function. The transfer function was derived using a spreadsheet. This model was applied to simulate how the flotation column could be made to respond to disturbances in feed grade. The results were that xanthate, zinc sulfate, and sodium cyanide were found to be suitable controls for grade and recovery. Simulations showed the best sequence of manipulations of these reagents, and these sequences were useful for future operator training. The conclusion was that linear transfer functions were able to simulate lead and silver recovery, develop scenarios for operator training, and provide a foundation for future on-line control.

Jan 1, 1999

By B. W. Cavender

Capital investments are made for a variety of reasons, ranging from providing incremental capacity at existing operations to developing and implementing new technologies intended to radically improve a company's capabilities. These projects generate very different business opportunities and create value in distinctive ways. For incremental improvements, the capital budgeting process assures at least a loose fit between short-term goals and readily available resources. However, the criteria used to evaluate capital projects often prevent a company from committing to more aggressive goals, which lie beyond the firm's current abilities or resources. Such projects may not have clearly identifiable future cash flows, and the degree of interaction with other projects and the nature of the risk incurred may be difficult to estimate. Additionally, by focusing only on quantifiable benefits, the budgeting process often fails to recognize "soft" improvements such as increased operating flexibility or new knowledge generated by such projects. By rejecting these projects, the capital budgeting process may actually harm the company's future competitive position.

Jan 1, 1999

By A Madera, R Watt

The Tampakan deposit is a strongly telescoped high-sulphidation-epithermal/ porphyry deposit pair which is hosted by a sequence of probable Pliocene age subaerial andesite flows. These host units lie on the western flank of a deeply dissected andesitic stratovolcano within the northernmost portion of the Sangihe Arc in southern Mindanao. The deposit was discovered by WMC geologists in 1992 and is currently undergoing resource evaluation. Preliminary resource estimations indicate a total inferred metal content of 12 million tonnes of copper metal and 16 million ounces of gold. Using a 0.2 per cent Cu cut-off grade, the deposit has a current mineral resource of approximately 2.5 billion tonnes with an estimated grade of 0.48 per cent copper. At a higher cut-off grade of 0.5 per cent Cu, the mineral resource is approximately 900 million tonnes with an estimated grade of 0.75 per cent copper. Mineralisation is open both to the west and at depth. The Tampakan district is centrally located with respect to a 100 km wide zone of left-lateral strike-slip deformation represented by the trans-Mindanao Cotabato Fault Zone. The district is transected by several WNW-striking wrench faults which represent strands of the regional Cotabato Fault Zone. High-sulphidation epithermal mineralisation within the Tampakan deposit is strongly controlled by NNE-trending faults which lie along a dilational orientation within the Pliocene stress field associated with the Cotabato strike-slip fault zone. The mineralisation is broadly hosted by a gently-dipping, tabular zone of partial to massive silicification which displays multi-phase brecciation, acid-leaching, related vuggy porosity and which is developed within a district-scale advanced-argillic and argillic lithocap exceeding 90 km 2 in area. High-sulphidation epithermal mineralisation is associated with a silica-pyrophyllite-dickite-alunite-diaspore¦sericite alteration assemblage which is transitional downward to sericite-chlorite alteration and relict potassic biotite-chlorite-magnetite-anhydrite alteration associated with pervasively developed but weakly mineralised porphyry quartz stockwork veins. The high-sulphidation mineralisation is dominated by disseminated, vein and vug-filling enargite-bornite-digenite-chalcocite-covellite ¦ molybdenite which has overprinted an earlier phase of porphyry copper stockwork veins associated with high-level porphyritic hornblende diorite stocks. The distribution of high-sulphidation alteration and mineralisation reflects strong stratigraphic and structural controls. The high-sulphidation mineralisation covers a surface area of approximately 1.6 km by 2.0 km and forms a tabular, flat-lying to gently-dipping body between 200 and 500 metres thick. It is intersected at RL-1200 m ASL (at surface) in the northern portion of the deposit and extends down to RL-600 m ASL at the southern end. The deposit has been diamond-drill tested to a depth of 400 - 500 metres where low-grade chalcopyrite-bornite-pyrite mineralisation is hosted by pervasive quartz stockwork veins. This deep-level mineralisation represents the outer portion of a porphyry Cu system hosted by both andesite flows and the uppermost portions of high-level hornblende diorite stocks. Deep drilling to test for higher tenor porphyry Cu mineralisation is planned.

Jan 1, 1999

By Brian Fulcher, John Eastlund, J. B. Copeland

Following the completion of the 7,600 m primary access tunnel by Kiewit/Parsons Brinckerhoff (K/PB) in April 1997, an exploratory East-West Cross Drift Tunnel was constructed at the Yucca Mountain Project over the proposed future repository block for high level nuclear wastes. The 2,681 m (8,796 LF) East-West Cross Drift Tunnel was excavated through volcanic tuffs having zones of incompetent rock using a re-built Robbins 5.000 m (16’-5”) hardrock TBM with a special arrangement of supporting equipment. Details of the unusual site and contract conditions will be discussed as well as with the unique tunnel equipment specified by the Owner. This portion of the Yucca Mountain project required eight months to complete.

Jan 1, 1999

By R. G. Reddy

Spent potliner is generated in the electrolytic process of reducing alumina to make aluminum metal using molten fluoride electrolytes. Spent potliner (SPL), obtained at the end of the pots life contains a small amount of cyanide and fluoride which present environmental problems. SPL became a listed hazardous waste under RCRA (K088) in July, 1990. One of the possible uses of spent potliner is as a substitute for Calcium Fluoride (CaF2) as a fluidizer in iron-and steel making and in the glass industry. A low viscosity and a low melting point are prime requirements for accomplishing the above. In the present study, viscosity measurements were performed. Effect of various additives, such as sand, limestone, dicalcium silicate dust, and MgO baghouse dust on the viscosity of SPL was studied. The results showed that with the addition of sand and limestone, very high fluidity of SPL melt can be obtained at significantly low temperatures. The results suggest that spent potliner mixed with additives could potentially be used as a substitute fluidizer.

Jan 1, 1999

By M Bourke

Modern computers and software provide powerful tools for the geologist to construct reliable models of geological resources, and the mining engineer to produce accurate and workable mine plans. Over the years many people have developed a phobia of computers, especially for geological analysis, modelling and mine planning. This phobia is often caused by a lack of knowledge, poor training or a bad experience. The adoption however of computers for geological modelling and mine planning is now becoming mainstream. With the correct training, a good understanding of input data, and detailed knowledge of the required results, the phobia can safely be overcome to provide mining operations with increased productivity.

Jan 1, 1999

By Glen L. Black

Choosing a mining method for an underground orebody is a complicated and often iterative process. Advances in technology have given design teams an array of possibilities for methods and equip¬ment. Hecla Mining's discovery of the deep Gold Hunter ore body challenged the staff at the Lucky Friday Mine to determine the optimum mining method. Taking an ore body from prospect to production requires traditional resource characterization. This includes drilling, delineating and modeling. Developing the mining plan is an evolving process, changing with each new piece of in¬formation as the project progresses through exploration and development. The Gold Hunter deposit is a steeply dipping vein system in the Wallace Formation of Idaho's Coeur d'Alene mining district. Gold Hunter is a misleading name for the ore body. The vein is a silver-rich, lead-zinc deposit with only traces of gold. The Gold Hunter ore body is located about 1.6 km (1 mile) north to northeast of Mullan, ID. The ore body is mined from the Lucky Friday Mine, located 0.4 km (0.25 miles) east of Mullan. Mining began on the vein from an access drift driven from the Lucky Friday Mine's 4900 level. Production from the ore zone is projected to be 771 t/d (850 stpd). The Gold Hunter ore is combined with Lucky Friday ore and milled in the Lucky Friday mill. The combined ore boosted Lucky Friday's 1998 silver production from 62.2 t/a (2 million oz/year) to more than 124.4 t/a (4 million oz/year).

Jan 1, 1999

By M. D. Khattar

Problems discussed concern encountering of high temperatures [up to 66°C] and heavy flow of water [150 L.P.S] during the construction of the 10.15 MØH.R.T. for the 2500 MW Nathpa Jhakri Hydro Power Project in the Himalayas(India). Over a length of 2500 M progress of work got seriously affected resulting in excessive time for completion - two years [max. monthly progress achieved was 178 M [Heading]. Many innovative and simple steps were taken to complete the work in these inhospitable environs affecting working of both men and machines. Also it meant a review of the design of concrete lining. Other geological conditions affecting the progress are also described.

Jan 1, 1999

By Cameron Hams

Noranda's Process Reactor and Codelco's Teniente Converter are physically similar vessels, which leads to the commonly held misconception that the two processes are the .same. However, notable differences in chemistry, operating philosophy, and construction make them quite dissimilar. This paper compares and contrasts the Noranda Reactor and the Teniente Converter, and attempts to explain some of the apparent differences in behaviour and performance. The results of a worldwide survey of most operating Noranda Reactors and Teniente Converters, along with those processes that have ceased operation or are planning to be started-up in the future, are presented.

Jan 1, 1999

By Harrison Cooper, Stephen Pack

"Data from samples taken during rotary air blast and reverse circulation drilling are crucial to properly assessing economics of mineral deposits in the case of exploratory work, and are equally critical in accurately delineating ore and waste in execution of mine operation plans. Past studies of sampling procedures, comparing results of conventional splitting to more precise extraction of representative samples, illustrate the significant degree of error frequently encountered. Economic impact of error in mine blast hole sampling work can be shown to result in theoretical losses valued at millions of dollars annually in operating large scale mining projects. Results of past drill sampling studies are reviewed.Drill sampling technique can be improved by collecting coarse and fine particles together and extracting samples for assay from the complete flow of rock and dust simultaneously. This can be accomplished with a collection unit attached to the drill stem through which all except a small proportion of extreme fines are retained. The bulk mass can be static sampled as flow takes place through the collector when size reduction is not required. Alternately, collected mass with fines and coarse intermingled can be processed for increased accuracy through size reduction to obtain proportional samples."

Jan 1, 1999

By D. R. East

Recent experiences within certain sectors of the international mining industry suggest an underestimation of the environmental risk associated with the design of mine waste management facilities. These experiences show that the technical and managerial challenge of responsible mine waste management is not always fully appreciated. Unfortunately, the image of the mining industry's environmental performance is negatively impacted by a relatively few number of failures. This negative view overrides the many positive contributions made by the majority of mining companies. The fact that these failures continue to occur to this day in both developed and developing countries is indeed remarkable, and indicates a degree of risk-taking approaching unacceptable levels. The design requirements for tailing storage facilities are, in many cases, more demanding than those of conventional water dams, because seepage of fluids which contain dissolved metals may pose a greater threat than the mere loss of water.

Jan 1, 1999

By J. M. Khodadadi

"A computational study of the effect of thermocapillary convection on melting of a droplet under the influence of an incident uniform heat flux is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the time-dependent continuity, momentum and energy equations in the spherical coordinate system are solved. During the early periods of the melting process, conduction mode of heat transfer is dominant. As the thermocapillary convection is strengthened due to the growth of the melt zone, melting on the side of the droplet is observed to be much faster in comparison to the conduction-only case. Due to the skewedness of the temperature field, a new recirculating vortex is created which promotes melting within the droplet. The effects of the change in the sign of the surface-tension temperature coefficient on the melting pattern are also investigated.1. IntroductionMelting and solidification of materials are important processes which are encountered in nature and numerous industrial applications. Due to the recent upsurge of interest in such processes as spray casting, space radiators, rapid solidification, purification of materials, containerless processing, etc., there is a need to analyze the transport phenomena of melting and solidification in spherical configurations. Specifically, the effect of thermocapillary convection on the melting of metallic droplets has not been addressed at all. Only a few authors have studied the transport phenomena without phase change in spherical droplets. Oliver and DeWitt [l] worked out a series solution for the thermal and surface-tension-driven flow fields for a droplet experiencing an irradiant energy flux in the microgravity environment. Kudo et al. [2] solved the coupled momentum and energy equations numerically for the same problem without dropping the convective terms. Due to the nonexistence of any previous work on transport phenomena during the thermocapillary-assisted melting of metal droplets, this study was initiated to elucidate the features of the phenomenon."

Jan 1, 1999

By J. H. Schubert

Mintek has developed a level-control system, FloatStar, for use in flotation circuits. Instead of controlling levels separately in each unit, the controller monitors levels throughout the circuit. It can thus take account of the global effects of any control actions. A collaborative project between Mintek and Karee Platinum Mine has begun, looking at aspects of flotation control. Karee plant was chosen as the site for this work because of its good existing control infrastructure. As a first stage of the joint project FloatStar was installed. Analysis during installation and running of the FloatStar has illustrated how circuit design and measurement technology can affect process control. Severe interactions have been observed in the levels of adjacent banks. The effect of FloatStar on flotation performance was tested and an improvement in level control was observed. Similarly, a faster settling of the plant after start-ups was observed. Both the improved level control and faster start-ups lead to higher platinum recovery.

Jan 1, 1999

By B. Abedian, L. M. Racz, S. R. Berry, R. W. Hyers

"The presented work represents an effort to improve understanding and prediction of turbulent flow inside electromagnetically-levitated droplets. We show that the flow field in a test case, a nickel droplet levitated under microgravity conditions, is a low Reynolds number turbulent flow, i.e. in the transitional regime between laminar and turbulent. Past research efforts have used laminar, enhanced viscosity, and k - E turbulence models to describe these flows. In our study, we compare the RNG algorithm to laminar and k - E turbulence model results. We show that accurate description of the turbulent eddy viscosity µr is critical in order to obtain realistic velocity fields, and that µr cannot be uniform in levitated droplets. In the RNG method there are no characteristic length or time scales associated with the flow, thus allowing such anisotropic features to be captured. We perform calculations and analyses for two cases (1) a small, non-deforming, spherical nickel droplet and (2) a deforming, oscillating droplet. In addition to flow field calculations, we compare numerically-obtained surface tension and viscosity values to those obtained experimentally by the oscillating drop technique.IntroductionElectromagnetic levitation (EML) is a containerless processing technique for conductive materials. Its advantages are the avoidance of contamination or chemical reaction at container walls and the ability to perform long-term experiments in a metastable state. Because of its current limitation to small sample sizes, its primary use is in the laboratory. One application of interest is the measurement of thermophysical properties of undercooled liquid metals [1, 2, 3, 4]. In EML, a sample weighing approximately 1 gram is positioned inside an electromagnetic field generated by alternating currents flowing through an axisymmetric water-cooled copper coil. The coil must be designed appropriately so that thesample levitates in a stable manner.Traditionally, mathematical modeling has been performed in tandem with both earth-and spacebound electromagnetic levitation experiments, in order to determine the effect of the magnetic field on material and flow characteristics [5, 6, 7, 8]. These calculations are important because they allow design, planning, and correct interpretation of experiments. In addition, the calculations are of fundamental scientific interest, as they can be applied to other electromagnetic materials processing applications [9]."

Jan 1, 1999

By M. A. Cocquerel

External process energy requirements and air pollution control regulations formulated to limit particulate and SO2 emissions are impacting on smelting and converting technologies and the corresponding process and secondary gas handling systems. This paper presents an overview of the different technical solutions used for cooling and dedusting the process gases in the different pyrometallurgical copper concentrate stages, including: drying, smelting, converting, slag cleaning and fire refining. The main principles of the process gas handling systems are presented &d a qualitative technical and economical comparison is discussed in relation to process changes, energy recovery and marketing or disposing of the various sulfur fixation by-products. Finally, a brief review of the methods for fixing sulfur contained in the process and secondary gases is presented.

Jan 1, 1999

Council for 1999/2000 President J.R. Dixon President Elect M.H. Rogers Vice Presidents Senior Dr L.A. Cramer Junior A.A.B. Douglas Immediate Past President R.P. Mohring Honorary Treasurer J.A. Cruise Members of Council B.C. Alberts Dr N.A. Barcza N.J. Barkhuysen R.D. Beck M.J.P. Bierman Prof. A.N. Brown D. Cockcroft Dr M.B. Cortie Dr L.A. Cramer J.A. Cruise E.G. de Villiers J.R. Dixon A.A.B. Douglas F.M.G. Egerton J.P.W. Fisher C.E. Fivaz K.J.R. Ford Prof. G.A. Fourie R. Graham Dr R.G. Gürtunca Dr R.V.R. Handfield-Jones* M.C. Harris J.P. Hoffman H.E. James P.J. Knottenbelt R.P. Mohring H.G. Mosenthal G.Y. Nisbet N.M. O'Brien R.G.B. Pickering Prof. R.P. Plewman S.J. Ramokgopa Prof. R.E. Robinson M.H. Rogers D.A.J. Ross-Watt Prof. R.F. Sandenbergh Dr H. Scott-Russell C.B. Sheppard D.A.A. Smith Dr T.R. Stacey Dr O.K.H. Steffen D.J. van Niekerk J.C. Viljoen J.N. Wallington

Jan 1, 1999

By David T. Hobbs

Large quantities of highly alkaline, radioactive, liquid wastes are stored in underground tanks throughout the Department of Energy complex. These wastes will be pretreated to separate radionuclides and the remaining decontaminated liquid wastes incorporated into solid waste forms for permanent disposal. Significant savings in disposal costs could result by recovering .the sodium as sodium hydroxide for reuse or disposal as nonradioactive waste. Recent testing demonstrated an electrochemical separation process for the recovery of sodium hydroxide from alkaline waste solutions; The separation process uses ion-selective membranes to separate sodium from the bulk of the waste constituents under an applied electrical field. The sodium is recovered as a 10-15 wt % solution of sodium hydroxide. Results of bench-sc3Ie and pilot-scale tests with simulated and radioactive waste solutions are presented.

Jan 1, 1999

By W. S. Fyfe, G. Southam, T. J. Beveridge

Bacterial populations play an active role in mineral weathering in subsurface and near-surface environments e.g., supergene enrichment of Cu at Morenci, AZ. An invitro bacterial biofilm model was used to examine the interaction between Sporosarcina ureae and ionic gold(which is toxic) or amino acid-gold complexes in gold mobility. The immobilization of ionic gold was between80-90% for 1 week but as the available, cellular reactive sites became saturated immobilization decreased to 14%within 2 weeks. In the asparagine-gold system, gold immobilization occurred at a high rate (80-90%)throughout the experiment with limited toxicity towards Sporosarcina ureae.

Jan 1, 1999

By Byung-Su Kim

The recovery of elemental sulfur from sulfur dioxide has important implications for coal- burning power plants and nonferrous metal smelters. The thermodynamic analyses showed calcium sulfide to be suitable for recovering elemental sulfur from sulfur dioxide. At the temperatures of 1023 to 1153 K under the sulfur dioxide partial pressures of 5.0 - 60.1 kPa, elemental sulfur from sulfur dioxide was recovered by its reaction with calcium sulfide. The kinetics of this reaction were measured at the same conditions using a thermogravimetric analysis technique. This reaction scheme would be attractive if the coproduct calcium sulfate can be reduced to regenerate calcium sulfide. This is the topic of another paper. At 1073 K under the sulfur dioxide partial pressure of 25.8 kPa, 48 % of the original calcium sulfide was converted to calcium sulfate in an hour. Under the same conditions, 55 % of the regenerated calcium sulfide were converted to calcium sulfate in an hour even after third regeneration.

Jan 1, 1999