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By S. R. McCutcheon

"The regional stratigraphy of the Lower Carboniferous Windsor Group in the Moncton Subbasin indicates that evaporites could be present in the Marysville Subbasin, part of what was formerly called the Central New Brunswick Platform. The Windsor Group consists of basement-fringing, algal build-ups (Gays River Formation), in places with intercalated siliciclastics (Parleeville), which are laterally equivalent to deeper-water, very thin to thinly bedded, euxinic limestone (Macumber). The Macumber is overlain by stratiform, nodular to mosaic anhydrite (Upperton) that is hosted by carbonate or calcareous siliciclastics. The sulphate also is equivalent, in part, to the algal buildups. Deep-water salts (Cassidy Lake) which overlie and in places are laterally equivalent to Upperton rocks have a basincentre distribution. The Windsor Group is overlain by shallow water evaporites and mudstones (Clover Hill) or by greenish grey mudstone (""transitional beds""). The paleogeographic distribution of these rocks provide important clues that help predict where deposits of salt and potash can occur.IntroductionCurrently there are three known potash deposits in southern New Brunswick (2, 3 and 4, in Fig. I). All three deposits occur in the Windsor Group of the Moncton Subbasin, but until recently their exact stratigraphic position within the group was not known.The Windsor Group is a cyclic sequence of carbonates, evaporites and red beds that is up to 1.0 km in thickness (Schenk 1969, p. 1038). It is Late Mississippian (Visean) in age and the type area is near Windsor, Nova Scotia. The group was named by Dawson (1873) but the rocks were described earlier by Hartt (1867). Dawson (ibid.) was the first to assign rocks in southern New Brunswick to the Windsor Group."

Jan 1, 1983

By L. K. Nenonen

"Given the properties, locations and quantities of material to be hauled and the dump locations and capacities, the designer wishes to select the type and number of trucks and loading equipment required. Accordingly, software is being developed to assist in creation of the equipment, material and road network data bases, in selection of equipment, materials and road networks from these data bases, and in evaluation of the expected productivities both in a rapid, non-interactive, approximate fashion and a more detailed interactive fashion which permits the user to act as superintendent, if he so chooses. The basic technology has been developed and applied to an open-pit copper mine and is being refined and generalized for oil sands and coal mining applications.BackgroundA set of mathematical and interactive computer models are under development to aid in the selection of equipment and operating policies for an open-pit oil sands mine being planned by Canstar Oil Sands Ltd. This paper describes the computer models being developed of truck haulage systems. Although the interactive truck haulage model is based primarily on a model developed by the National Research Council in collaboration with Glenayre Electronics Ltd. of North Vancouver and Lornex Mines Limited(2).(3l, substantial changes and improvements are being incorporated to greatly increase its generality re equipment types, road network characteristics, dispatching and supervisory policies, etc. Although this paper is principally devoted to the truck haulage model, discussion is included concerning its interactions with other models."

Jan 1, 1982

By H. Tudeshki

A great amount of aggregate is utilized in civil engineering applications such as road construction, railway infrastructure, concrete production, etc. Igneous rocks are the preferred raw material due to their high strength and abrasion resistance. Rock quality assurance is a key factor and has great influence on the quality of constructions in civil engineering. One of the major problems encountered by both the producers and users of igneous aggregate rock is the fact that, with the passage of time, some specific rocks lose their strength, up to a complete loss of structure, i.e. disintegrate and degrade. This phenomenon has a great influence on the quality, strength and durability of aggregates. In the last decades, different methods and procedures such as the glycol test, the methylene blue dye test, as well as the Los Angeles test, have been introduced to distinguish rock properties, and to identify these problems. However, as these wet-chemical methods are time consuming, hard to perform, only to be applied to hand-piece samples, requiring special laboratory equipments, and are only possible to be accomplished under laboratory conditions, their application has always been severely limited. To address this widespread quality management problem of the quarry industry, a relatively quick, easy and user-friendly approach is necessary. It calls for a systematic solution with a device that can simply be used in the day-to-day routine of a mine for quality control of the quarry´s daily production. Our research is concentrated on developing a systematic method for early recognition and diagnosis of rock quality, in order to control and manage the quality of the quarry production in advance. Our new approach is based on two rock parameters: magnetic susceptibility and loss on ignition. The measurement of these parameters provides reliable information on the quality of the rock and allows the quality control process to be accomplished and performed at the borehole location. Our new approach has been assessed through extensive field and laboratory studies and has been implemented on the drill-cuttings of a basaltic andesite quarry. The results of the experiments are discussed in detail, including their impact on increasing resources and environmental protection.

Aug 1, 2013

By Victor Maksaev, Marcos Zentilli

"Abstract - The Domeyko Cordillera, the westernmost uplifted crustal block of the composite High Andes of northern Chile (20°S to 28°S) hosts a narrow N-S trending belt of Late Eocene-Oligocene giant porphyry copper deposits, which include Collahuasi, Chuquicamata, El Abra, La Escondida, and El Salvador. These deposits are spatially and genetically associated with the closing igneous activity along this range, prior to a 30 km eastward jump of the magmatic front in response to tectonic plate interaction. The porphyry copper deposits are also spatially associated with a major intraarc strike-slip shear system, the Domeyko Fault System. Although the tectonic uplift of the 3000 m to 5000 m high range has generally been assumed to be mostly Miocene in age, field relationships suggest that the Domeyko Fault System and tectonic uplift were active as early as the Eocene, coinciding with porphyry copper emplacement between 41 Ma and 30 Ma. Apatite fission track (FT) thermochronology provides both age data and a time-temperature history for rocks since they cooled below a temperature of ca. 125°C (equivalent to a depth of 4 km to 5 km under normal geothermal gradients) on their way to the surface during exhumation, or after a heating event. Apatite FT data from the Paleozoic crystalline basement of the Domeyko Cordillera indicate that at least 4 km to 5 km of rocks were eroded during exhumation of this tectonic block between ca. 50 Ma to 30 Ma (Middle Eocene to Early Oligocene), a time that immediately precedes and overlaps with the emplacement of giant porphyry copper deposits. The FT data constrain the age and duration of a period of crustal thickening and extensive erosion known as the Incaic compression, an event recognized in the Andes of Chile and Peru. Assuming that cooling was due to denudation alone, modelling of the FT data allow estimation of denudation rates between 200 and 100 m/My during this period. In contrast, exposures of pre-porphyry Paleocene intrusives on the western edge of the Domeyko Cordillera reveal apatite FT ages that are concordant with biotite 40Ar-39Ar dates, indicating shallow emplacement, fast cooling and negligible exhumation. The apatite FT ages of the Chuquicamata and El Abra porphyry copper deposits are only marginally younger than their 40Ar-39Ar dates, implying fast cooling/exhumation of shallow mineralizing systems (ca. 2 km to 3 km). Their FT time-temperature history is compatible with extremely low rates of exhumation (ca. 50 m/My) since about 30 Ma (Early Oligocene). This limited extent of erosion, due to exceptional aridity, has greatly contributed to the preservation of rich supergene enriched blankets above some of the porphyry copper deposits.A model is proposed, which is consistent with field relationships, geochemical, and geochronological data. High relative velocities and intermediate-angle oblique convergence between the Nazca and South American plates in the Eocene-Early Oligocene led to intra-arc transpression partitioned into reverse faults of opposing vergence and a right-lateral shear system (the Domeyko Shear System) localized along the magmatic front. Crustal shortening and thickening led to uplift within the Domeyko Fault System and to erosion of at least 4 km to 5 km. Crustal thickening deepened the zone of magma generation, and magmas accumulated in the lower crust, allowing small volumes to rise rapidly to shallow levels along transtensional domains of the regional shear system. A similar model of crustal thickening and shortening before and during porphyry copper emplacement in zones of transtension may also apply to the Miocene-Pliocene giant porphyry copper province of central Chile."

Jan 1, 1999

"Nanisivik Mines Ltd. operates a 10-M W diesel-electric generating plant at its zinc-lead operation on Baffin Island in the Canadian Arctic. This paper provides a description of the plant and the integrated waste heat recovery system. Data is presented detailing the actual costs of operating a plant over a period of seven years. Problems in operation are described as well as the success of the plant in meeting its objectives over the years. IntroductionNanisivik is located on the shore of Strathcona Sound at the north end of Baffin Island (Fig. I). Nanisivik Mines Ltd. has operated a 2,100 tonne per day zinc-lead underground mine and a concentrator, together with supporting infrastructure, at this location since October 1976. Annual production of 100 000 tonnes of zinc and 10 000 tonnes of lead concentrate is transported by ship to Europe during the mid -July to mid October shipping season.All electrical needs of the project are provided by the company-owned and -operated power plant. Facilities served by this electrical system are the underground mining areas, the concentrator and industrial area, a townsite, airport, and shiploading dock complex."

Jan 1, 1986

By V. K. Karra

"A simplistic algorithm jar simulating the rod or ball mill Bond grindability test applied to ores and minerals is presented. A performance comparison between the present algorithm and a previously published algorithm by Kapurot, modified in this work jar a fair evaluation, is also given. A worked example is furnished jar leading the reader through the various calculations.IntroductionThe Bond grindability test is widely used for the prediction of the power requirement of an industrial grinding mill. The procedures for conducting this test in either a ball or a rod mill are available(1). In the case of a ball mill, batch grind abilities have been correlated to Bond grindabilities to help monitor day-today variations in ore grindability for the purpose of plant control( 2,3). Of special interest is the algorithm presented by Kapur(3) for the simulation of the Bond test. In practice, the test lasts from 6 to 14 cycles (4 to 10 hours). With this algorithm, one can predict the Bond grind ability using information available from only the first two cycles.Sometimes the prepared feed for the grindability test contains too much fines compared to the total product desired at the mesh of grind under consideration. In such a case, the operator separates the fines from the test feed and adds to the remaining coarse fraction an equal amount of fresh feed. This combined feed then forms the feed to the first cycle of the test. In the present work, Kapur's algorithm is modified to include this special case. A new and relatively simpler algorithm is also presented. Statistical equations relating work index to pertinent variables are also given."

Jan 1, 1981

? A BARGE WILL BE INSTALLED IN THE BOTTOM OF A COMPLETED PIT. ? THE PROVEN BAUER CUTTER TECHNOLOGY WILL BE INSTALLED ON THE BARGE AND A DEWATERING PLANT WILL BE INSTALLED NEAR THE BASE OF THE PIT RAMP. ? THE WATER LEVEL IN THE PIT WILL BE RAISED BY 20- 40 METRES AND REMAIN CONSTANT OVER DURATION OF MINING. ? THE CUTTER WILL BE LOWERED TO MINE 10 METRE DEEP BENCHES ON A CHECKERBOARD PATTERN TO AN ULTIMATE DEPTH OF 200 METRES. ? THE 5? MINUS CUTTINGS WILL BE PUMPED TO THE DEWATERING PLANT, DEWATERED, AND TRUCKED TO SURFACE.

May 1, 2003

By A. B. Carino

Gulf Minerals (Canada) Limited's Rabbit Lake uranium operation is located in the northern portion of Saskatchewan, 198 miles southeast of Uranium City and /34 miles northwest of Lynn Lake, Manitoba. The paper follows the ore flow through crushing, grinding, sulphuric acid leaching, countercurrent decantation, solvent extraction, ammonium diuranate precipitation, thickening, drying and tailing neutralization.

Jan 1, 1979

By Richard Dawson

Presentation Outline? Northeast BC Coal Fields Overview and History ?New mines and projects in development ?Design Issues for steeply dipping footwall slopes ?Design issues for angle-of-repose waste rock dumps

May 1, 2006

By Randolph A. Pax, Brian Cornish

The operation of grinding mills in an ore processing circuit is supported by monitoring the input and output variables. These can include the feed ore size distributions, ore feed and water addition rates. The outputs can include the discharge undersize density, oversize tonnage rate and the P80 of the discharge. The grinding mill performance is judged by the power draw, recycle rates and discharge grind size. Conditions inside the mill are inferred from loads cells or bearing pressures and past histories. An overall noise value is sometimes used to evaluate the load as well as the occurrence of excessive impacting of steel balls onto the liners/lifters of the mill. This paper presents results of the internal behaviour of a mill using non-contact stationary microphones located close to the mill outer shell (Pax, 2012). The noise generated by a mill can be attributed to a number of events that occur inside these mills and suitably analysed can provide real-time determinations of in-mill behaviour and can provide powerful insights into the operation of the primary comminution tumbling mills. The acoustically determined signals including a specific 'steel' signal, water hold-up, integrated area together with a classification of impact events. Specific results from case studies will show information of the trajectories inside a mill, steel to rock ratio as well as rheology effects. By incorporating a self-consistent understanding methodology for the in-mill processes from an array of microphones, the information can be used to diagnose the dynamic conditions inside a mill.

Jan 1, 2016

By P. Rocque, S. Talebi

Although the measurement of blast vibration close to the blasthole is critical to the understanding of rock fragmentation mechanisms and blast damage in the rock masses, limited experience for such monitoring exists. Because much higher vibration amplitude and frequency ranges are expected in rock masses close to an explosive charge as compared to far field vibrations, different problems from those for the far field monitoring must be considered for near field blast vibration monitoring. Currently, guidelines for design of the near field blast monitoring systems do not exist. This paper describes the development of an integrated technique for vibration monitoring close to a blast hole, including selection and installation of transducers, design of a monitoring system and signal recording. A densified cement was designed for grouting accelerometers in order to match p-wave impedance between the rock and grout. The monitoring technique described has proven suitable for blast vibration monitoring within 2 m to 15 m of a blast hole having loading conditions similar to production blasts.

Jan 1, 1993

By Song Mao, Local Joint Engineering Lab of Efficient Util of Dominant Mineral Resources from Karst Regions, Guizhou Key Lab of Comprehensive Utilization of Non-metallic Mineral Resource, Xianhai Li, Qin Zhang, unjian Ye, Guizhou University, Wei Cheng, Zhihong Liu

"Phosphate tailing is a kind of industrial waste that emitted from separation processing of phosphate ores, which is usually discarged to the tailing pond without treatment. Recovery of phosphorus from tailings is of great significance for comprehensive utilization of phosphorus resource. Chemical composition of a micro-fine cryptocrystalline phosphate tailing was investigated by X Ray Fluorescence (XRF) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and mineral composition and occurrence of harmful elements were analyzed by optical microscope and Scanning Electron Microscope (SEM), X ray Energy Dispersive Spectrometer (X-ray EDS) and Mineral liberation Analyzer (MLA). On the basis of above, effects of those on mineral processing for phosphate tailing was analyzed. Chemical analysis results in combination with microscopy indicated that there is a certain amount of iron and aluminum and it should focus on the removal of them in separation processing. The cryptocrystalline structure, especially the micro banding structure and micro porphyritic structure indicated that there is quite amount of phosphate in fine particles and it should recovery the phosphorus as much as possible when designing the flotation technology for this difficult separation fine phosphate tailing. This study can provide theoretical guide for efficient phosphorus recovery of from fine phosphate tailing by flotation.INTRODUCTIONPhosphate rocks are vital nonrenewable resources and are essential components in agricultural fertilizers and phosphorous-based chemicals (Gharabaghi et al., 2009). About 95% of the phosphate produced around the world is consumed in the fertilizer industry (page 60 Abdel-Zaher, 2008; Jasinski, 2007). Froth flotation, a solid wettability based separation process is widely used in separation of phosphate rock and shown to be effective (Yehia et al., 1990; Singh et al., 1992; Elgillani and Abouzeid, 1993; Al-Fariss et al., 2013) .Poor selectivity and low recovery for micro-fine particles are hard issues in flotation of middle-low grade phosphate ore because Phosphate resources is becoming poor, fine and complex as the rich ores run out since the 1970s. The rapid depletion of high grade ores forces minerals industry to process low grade ores where finer grinding is required to achieve required liberation of the values, making the fine particle flotation inevitable. the performance of conventional flotation deteriorates rapidly as particle size decreases to below 10-20 µm, depending on the density of the particles (Feng and Aldrich, 1999). To date, fine particle flotation is still considered to be a challenge in mineral processing (Li et al., 2015) ."

Jan 1, 2016

By V. Shumila, T. Butler

Microseismic monitoring systems listen to a rockmass and record ground vibrations associated with brittle rock fracture. Modern systems record continuously and can identify as many as one thousand small and possibly larger magnitude events occurring each day from induced stress change and redistribution. This paper presents examples of the real time use of microseismic information in mining applications. It shows how alerts can quickly identify large magnitude events or unexpected clusters of seismicity and how seismic re-entry protocol can help to improve safety decisions. Additionally, newly developed advanced analysis techniques applied to mine seismic data sets are shown including the use of clustering methods to see into a cloud of seismic data to identify significant activity and quantify possible planar features. The use of source parameter trend analysis is shown to be a beneficial method for interpreting changes in relative stress levels. Seismic moment magnitude distributions are analyzed using the TGR (Truncated Gutenberg Richter) and TMD (Tapered Moment Distribution) methods to estimate bvalue and expected maximum magnitude. Seismic hazard analysis is shown as a useful way to simplify a dataset and highlight seismic hot spots. The rockmass response to excavation is a complicated spatial and temporal process and microseismic monitoring is a method that can be used to help understand the location and mechanics of failure occurring in the rock ultimately helping to improve safety and productivity at a mine site.

Jan 1, 2015

By R. Drozd

"The Bullmoose Mine is currently under construction in the North East Coal area of British Columbia, and approximately $300 million will be spent to bring this 2.3 million-tonnes-per-year metallurgical and thermal coal mine into production by December 1, 1983.The project is an unincorporated joint venture undertaking, with Teck-Bullmoose Coal Inc., a wholly-owned subsidiary of Teck Corporation, holding 51%, Lornex Mining Corporation holding 39%, and Nissho-Iwai (Canada) Ltd. holding 10%. Bullmoose Operating Corporation will be the manager and operator of the project.This paper will broadly cover the history and exploration work on the property, the geology, open-pit mining plans and equipment, the preparation plant flowsheet from breaker station to clean coal silo, the 35 km highway truck haul, the railroad loadout system, manpower requirements, construction progress, approvals and permits, and general financial arrangements.IntroductionThe Bullmoose Mine Project"" is located about 87 road kilometres south of Chetwynd, B.C. and consists of an open-pit coal mine, a plant facility in the Bullmoose Creek valley below the mine, and a separate rail loadout facility on the British Columbia Railway Branchline near the new town of Tumbler Ridge some 35 road km to the east.The plant will be capable of producing a total of 2.3 million tonnes per year (mty) of washed metallurgical and thermal coal. Long-term metallurgical coal contracts for high quality, medium volatile, bituminous coal have been signed with nine Japanese buyers for 1.7 mty, and the balance of 0.6 mty will be thermal coal production.Plant construction began in the spring of 1982, and in May 1983, preproduction waste and overburden removal in the mine will commence. The plant should be fully operational by December 1983, and first vessel loading at the Ridley Island port is scheduled for January 1984."

Jan 1, 1983

By Rodney Allen

Background: Development of the Project ?European GEODE collaboration 1999: considers possible projects, including a VMS project, to continue after GEODE ?GEODE-CODES-Canada collaboration 1999: Questionaire, database ?Workshop at CODES 2000: project theme and strategy selected ?GEORANGE (Sweden-EU) 2001 supports development of Global VMS Project: interest from 12 nations ?Skellefte VMS Project set up as Sweden?s component of Global VMS, 2002; other projects in Spain, Canada collaborate ?Low metal prices ---> little funding from mining industry 2001-2003, change in strategy ?IGCP/UNESCO support 2004: enlargement to over 20 nations

Apr 1, 2005

By T. Kho, W. Zhang, M. E. Reed

The control of flash furnace heat balances is critical. Suspension smelting control and stability comes from stable operation of the heat balance, and this leads to a stable reaction shaft exit temperature. A number of flash furnace operations have been reviewed to determine if the application of this approach is beneficial for their operation. The cause and effect relationship between reaction shaft exit temperature with uptake and throat buildup is being enhanced with this work program. Our operating personnel are exposed to the operational hazards of cleaning this buildup from the throat and it is imperative that as an industry we continue to look for repeatable solutions. WorleyParsons has reviewed operational data from a number of flash furnaces and looked at the possible improvements that can be made to decrease variation in the reaction shaft exit temperature. The data assessed for each operation illustrate the need to fully understand the process inputs to the particular operation and to ensure that the control changes are correctly impacted. In the plant data that have been assessed for a number of operations combinations of feed changes and inappropriate process decisions have lead to changes in reaction shaft exit temperature which impact the overall furnace operation and the uptake shaft condition, and ultimately the boiler. INTRODUCTION In 2016 WorleyParsons jointly prepared a paper outlining the effects of heat balance control on the Olympic Dam flash furnace (Reed et al, 2016). That paper investigated the importance of heat balance control in flash furnaces and demonstrated the changes made at the Olympic Dam operation to control the heat balance in the furnace and the impact that change had. The operation is still using the tool to assist in trouble shooting performance and pinpointing problems that may lead to issues in the furnace throat and Waste Heat Boiler (WHB). As a result of the interest in the methodology and due to the issues surrounding safety and process performance caused by WHB throat buildup and damage, WorleyParsons approached a number of flash furnace operators to discuss the application of the approach at their operations.

Jan 1, 2019

By Umbreen Agha, Stephan L. Chryssoulis, A. Margaritis

"The deportment of gold in samples of the biooxidation feed and product from the Harbour Lights mine in Western Australia was determined using optical microscopy and microbeam techniques such as Secondary Ion Mass Spectrometry (SIMS), Time-of-Flight Laser Ionization Mass Spectrometry (TOF-LIMS), and Electron Probe Microanalysis (EPMA). The main objective was to determine the mechanisms by which acidophilic bacteria (Thiobacillus ferrooxidans) liberate refractory gold which is locked in a sulphide minerals host as visible gold inclusions (> 0.1 µm) and as submicroscopic or 'invisible' gold.Using the integrated mineralogical approach approximately 99% and 100% of the assayed gold in the biooxidation feed and biooxidation product was accounted for. The results were compared to and verified by chemical assays.The gold deportment study indicates that during biooxidation, locked visible and 'invisible' gold is rendered cyanidable by the direct action of Thiobacillus ferrooxidans as well as indirect chemical leaching. Visible gold which is enclosed in sulphide minerals is liberated or partially exposed and is therefore rendered cyanidable as the host mineral is oxidized and dissolved. 'Invisible' gold either coalesces on the surface of the host sulphide mineral as the particle is dissolved or is released into the liquid phase and immediately adsorbs onto the surface of other ore particles with a net negative charge.The shakeflask suspension indicates that direct bacterial oxidation pits and channels correspond to zones of 'invisible' gold and arsenic (in pyrite) enrichment in the host sulphide mineral."

Jan 1, 1996

By Leon C. Botham

?? Review of Requirements ?? Components of Modeling ?? Water Management ?? Tailings Management ?? Primarily a water management problem ?? Solids relatively easily contained ?? Process flows and runoff a continuous stream over life of mine ?? Need to allow this to safely happen over wide range of conditions

May 1, 2008

By Robert B. Parsons

"Ontario and Quebec taxpayers will have to dig deeper into their pockets to pay more tax, according to budget papers tabled in these provinces in May 1993. Individuals will be hardest hit, but corporations will also have to ante up in the face of higher rates, reduced deductions, and new taxes.Up, up, and away...Somewhere in the bleak picture of the 1993 Quebec and Ontario budgets, there is a bit of good news for the mining industry.Careful scrutiny reveals:• Ontario will correct a capital tax provision which inadvertently penalizes flow through share issuers;• Quebec's flow-through incentives will be extended to December 31, 1995; and • both Quebec and Ontario will allow deductions for mine site reclamation payments.The industry may also find some comfort in the fact that Ontario's new corporate minimum tax will be profit-based (unlike the federal minimum tax), so that non-producers should not face a liability for this tax. There is some concern though, about Quebec's announcement that the refundable credit mechanism in the Mining Duties Act will be reviewed."

Jan 1, 1993

By Lawrence Devon Smith

"The concept of risk is well established in the mining industry. It is acknowledged when estimates of reserves are expressed as proven or probable, when mining and metallurgical recoveries are applied to the ore, and when contingencies are added to costs. However, it is difficult to provide a quantitative assessment of risk. The significant sources of risk in a mineral project and how these are addressed in project evaluations are discussed.The discount rate is examined as a fundamental means of reflecting risk in discounted cash flow evaluations. Current industry practice is discussed, and a methodology for the analysis of risk levels is proposed that assesses the constituent components of the discount rate: real interest, mineral project risks, and country risk.IntroductionThis paper examines the components of the discounted cash flow discount rate and proposes a method of estimating project-specific discount rates. The motivation for this work comes from experience of project evaluations in which owners and purchasers had agreed on virtually every aspect of the evaluation except how much the project was worth. Agreement was reached on reserves, grade, recovery, capital costs, operating costs, taxes, and, by combining these components, even on the final cash flow values. The only difference in opinion concerned the discount rate to be used in the calculation of the net present value. Depending on the life of the project, such differences of opinion can cause a variation of more than 50% in the value placed on a project! This is illustrated in Figure I."

Jan 1, 1995