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By H. Huang, R. N. Gow

Acidic treatment of enargite (Cu3AsS4) dissolves both arsenic and copper from the mineral and then attempts to separate them in the leach solution. The reactivity of enargite was examined in acidic to neutral solutions, over the pH range 1-7, to determine a potential range for co-dissolution. Enargite mineral samples from Butte, MT and Quirivilca, Peru were used as working electrodes in a cyclic voltammetry corrosion cell setup, which were then cycled multiple times over -1000 to 1000 mV. Surface reactions and transitions were characterized using in-situ Raman spectroscopy, which were then compared to updated EH-pH diagrams for the copper-arsenic-sulfur-water system from a previous study done under alkaline conditions. The region of co-dissolution is limited to > 600 mV vs. SHE and pH < 1 under the proposed diagram.

Jan 1, 2014

By John H. Fowler

Nova Scotia has been mining and exporting industrial minerals for over two hundred years. As an industrial mineral producer, this province continues to rank as the number one gypsum mining and exporting region in North America. Mining of many other commodities is ongoing, supplying many local and export markets. In all, excluding aggregate producers, there are nineteen industrial mineral producers operating at thirty sites producing nine commodities including anhydrite, barite, clay and shale, dolomite, gypsum, limestone, salt, silica sand and stone (Fig. I). Numerous aggregate producing operations supply all the province's aggregate requirements and export some of these materials to other regions of Atlantic Canada and as far away as Bermuda (Fig. 2) . Production value of industrial mineral commodities in Nova Scotia for 1982 was $105 million , representing 39% of the total value for all mineral production for the year. Because of the general improvement in the economy, indications are that the 1983 value of production will be higher.

Jan 1, 1984

By A. E. Boudreau

It has long been recognized that platinum-group-element (PGE) deposits in layered intrusions preferentially occur in intrusions that crystallized from high-Mg parent magmas. Recent studies suggest that evaluation of any given intrusion for economic PGE potential should also include assessment of the PGE, sulfur and chlorine concentrations in the cumulates and potential parent liquids. PGE: Magmas that contain relatively abundant Pt and Pd are the best candidates for forming economic deposits. Although analyses of coeval sills and dikes are the best indicators of primary magmatic PGE concentrations, analysis of the cumulates themselves is also valuable. For example, within the Stillwater complex, background PGE values in cumulates from the ultramafic sections of the complex contain, on average, several 10s of ppb Pt and Pd. Background concentrations of this order are suggestive that the magma was not depleted in the PGE. Sulfur: Conventional petrogenetic models for the formation of PGE deposits in layered intrusions require the PGE to have been concentrated during a magmatic sulfide-saturation event. In contrast, some hydro thermal models suggest that sulfur and the PGE were mobilized from footwall cumulates by upward-migrating, high-temperature hydrothermal fluids. Both models suggest that significant PGE deposits are likely to occur at and below the level where stratigraphic increases in whole rock sulfur concentrations occur. Chlorine: In both the Stillwater and Bushveld complexes the cumulate sequences below the major PGE-bearing zones contain anomalous Cl-rich apatite. The chlorapatite component of apatite in these rocks may exceed 40% and, in the Stillwater complex, typically exceeds 90%. It is stressed that pristine igneous mineral analysis and not whole rock data be used, as whole rock Cl concentrations may be affected by very localized (grain boundary), low-temperature alteration. Intrusions that crystallized from high-Mg, high-Cl magmas appear to have the best potential to host significant PGE deposits.

Jan 1, 1995

By J. P. Messervey

THE story of the efforts made by the Department of Mines of Nova Scotia in the search for and investigation of mineral resources for the Canadian war effort began in the spring of 1937. During the past five years, however, heavy enlistments in the Active Service Forces by employees of the mining industry of the Province caused a recession in the production of coal, salt, and other essential minerals required to keep industry rolling on a wartime basis. A marked increase was shown during the period in prospecting for &apos;strategic&apos; minerals, not only by individuals but also by some of the foremost mining companies. The Provincial Government offered encouragement in this field of endeavour by the enactment of legislation whereby the prospector was enabled to secure the maximum area of ground in a prospecting license at a minimum of cost. The labour requirements on the ground staked, however, remained unchanged. The Nova Scotia Department of Mines continued active investigation of minerals vital to the war effort. These included fluorspar, barytes, diatomite, limestone, and coal. Fundamental knowledge concerning the geology and mode of occurrence of these minerals was accumulated and extensive diamond drilling was carried out on the promising occurrences. Work in these fields is being continued.

Jan 1, 1945

By K. Robertson, K. A. Scalise, K. C. Kocsis, M. B. Teixeira

"Many deep and highly mechanized underground metal mines require cooling. In many cases, appropriate working conditions might be fulfilled by ventilation alone, but some require the implementation of cooling systems. The most common cooling systems are bulk air cooling and localized cooling. These systems are effective, but they use considerable amounts of electricity. Ground source heat pumps (GSHP) can supplement existing cooling and heating systems, while geothermal systems can cool the mines in their entirety if there are significant sources of geothermal energy are present. A major advantage of geothermal and GSHP systems are their renewability, which reduces the carbon footprint of the mine.INTRODUCTIONThe western United States has abundant alternative energy sources including a high potential for geothermal energy. Geothermal utilization is a viable energy alternative that many areas throughout the world have access to because high geothermal potentials are located near areas of volcanic activity such as along plate boundaries, mid-oceanic ridges, rift valleys and hot spots (IRENA, 2017). There is significant potential to use geothermal energy for many applications. With constantly evolving and innovative technologies being developed, an increasing number of geothermal applications are becoming feasible. The western United States is an ideal candidate for alternative energy applications due to the geothermal availability and the emergence of modern technology. This paper investigates the incorporation of renewable methods and the alternative energy possibilities of Barrick Goldstrike, located in northern Eureka County, NV and Rio Tinto/BHP Billiton’s Resolution Copper mine located in Superior, AZ.RENEWABLE SYSTEMSGeothermal SystemsGeothermal temperatures are typically defined as either high or low temperature systems(Shengjun, Huaixian, & Tao, 2011). The high-temperature reservoirs (>220°C / 428°F) are feasible forlarge, commercial production of electricity with dry stream and flash stream systems (Shengjun, Huaixian, & Tao, 2011). Low temperature systems, below 220°C (428°F) (Shengjun, Huaixian, & Tao, 2011), aremuch more difficult to use for energy production. Low-temperature reservoir heat can be harnessedthrough the implementation of a binary cycle plant. The working fluid for a binary cycle plant is eitherorganic (Organic Rankine Cycle (ORC)) or an ammonia-water mixture (Kalina cycle). Organic fluids andammonia-water mixtures have low boiling points that allow for the recovery of heat from low-temperaturesources (Eymel Campos Rodriguez, et al., 2013). The efficiency of the binary cycle plant varies depending upon the fluid, thus the proper selection of the fluid is critical for maximum energy output"

Jan 1, 2019

By Denis Beaudoin

Program Basics: Goals, Course Content & Training Process Sudbury: History of the Program & Lessons Learned Diavik: History of the Program & Lessons Learned Most Recent Program: Totten Mine in partnership with Sagamok Anishnabek Summary -Lessons Learned Conclusion

Oct 1, 2010

By J. E. Gebhardt, D. McBride, M. Cross

Heap leach processes can encounter diverse flow conditions, such as infiltration into dry ore material, drainage, perched water tables and heterogeneous materials, leading to large variations in permeability and the creation of preferential flow pathways. Climate and meteorological conditions, such as precipitation, evaporation, and temperature, can also have a significant effect on the hydrodynamics of the heap. Nonuniform and adverse flow behavior within the heap contributes to reducing the leaching efficiency of the heap leading to lower metal recoveries. The variability of flow within the heap can result in solute transport problems, which limit the leach reaction kinetics. Therefore, understanding the flow and transport phenomena within the heap is critical in its design and optimization. A comprehensive heap leach model, developed within a computational fluid dynamics (CFD) framework, employs robust algorithms to solve diverse variably saturated flow conditions. The model allows for a wide array of complex thermo-fluid physics to be represented and captures suites of very complex reactions that are closely coupled with thermal conditions and key microbial populations. Employing a three-dimensional heterogeneous ‘test’ heap, a number of flow conditions are investigated and the sensitivity of metal recovery is discussed.

Jan 1, 2014

By G. F. Trainor

At the Canadian Natural Resources Limited (CNRL) Horizon Mine they use Wenco International Mining Systems Ltd (Wenco) Fleet Management System to monitor and control their production fleet with the goal of increasing operator productivity and safety, and raising dispatcher awareness and control. Amongst the broad productivity goals CNRL wanted to achieve with help from the system was a very specific need to blend ore at the truck level. CNRL uses 25m x 25m block geological model information to represent their complex ore body. Wenco&apos;s High Precision GPS application, BenchManager provides precise graphical actual-vs-design operator feedback and system integration. Together the two companies advanced the BenchManager product to meet CNRL&apos;s needs by using live camera feeds to compare activity with data collection that ultimately lead to changes in the algorithm to include enhanced GPS indicators and the support of a GLONASS assisted solution generating distance and bearing information.

May 1, 2011

By T. Fekete, D. L. Flocks, R. T. Hart

The plugging effect of bacteria was investigated by injecting various concentrations of dead bacteria cells though sandstone cores. Pressure profiles along the cores were recorded periodically during the injection cycles. The plugging effect was analyzed using a plot of the ratio of reduced permeabilities to the initial permeability versus input volume. Results indicated that Tock permeability has little effect on plugging, but that the concentration of bacteria in the injection water has a significant effect on plugging characteristics. The pressure profile curves showed that bacteria penetrated several inches through the core but that the greater portion of the bacteria accumulated at the in-put end of the core.

Jan 1, 1960

By CIM Standing Committee

The CIM Definition Standards on Mineral Resources and Reserves (CIM Definition Standards) establish definitions and guidance on the definitions for Mineral Resources, Mineral Reserves, and mining studies used in Canada. The Mineral Resource, Mineral Reserve, and mining study definitions are incorporated, by reference, into National Instrument 43-101 – Standards of Disclosure for Mineral Projects (NI 43-101). The CIM Definition Standards can be viewed at mrmr.cim.org. Readers should be aware that reports written by persons issuing technical reports that disclose information about exploration or other mining properties to the public in Canada are governed by a number of securities regulations.

May 10, 2014

By H. W. Wevers

This paper is the result of an intensive literature search and practical study of the problems experienced by a mining company with the frame cracking of their large-tonnage haulage trucks. It explains the advantages of particular HSLA steels for applications in the welded structures of such equipment. Examples of existing welds in truck frames are analyzed. Modern fatigue models and linear elastic fracture mechanics techniques are explained.

Jan 1, 1978

By K. Forsberg, A. Rasmuson, R. Rodriguez Varela, J. Martinez De La Cruz

"This study analyzes the separation of rare earth elements by means of a supported liquid membrane (SLM) with the final objective of recovering REE from an apatite concentrate (Alemrajabi, Forsberg, & Rasmuson, 2015; Mohammadi, Forsberg, Martinez de la Cruz, & Rasmuson, 2015). In this study, the feed phase consists of an aqueous phase containing REE, the membrane phase contains the organic solvent and carrier (D2EHPA and EHEHPA), and the stripping phase is a hydrochloric acid solution. An evaluation of mass fluxes, separation efficiency, and membrane performance is conducted. In order to analyze the suitability of liquid membranes in the extraction of REE, a deeper insight into the mechanisms causing instability is needed. In this study, surface tension is considered as the key factor of Marangoni instabilities and spontaneous emulsification.INTRODUCTIONThe demand of REE and their compounds has increased considerably due to their special physicochemical features that make them crucial elements for numerous high-tech applications, including wind turbines, hybrid cars, mobile phones, and defense technologies. They are also extensively utilized in traditional industries such as nuclear energy, petroleum, metallurgy, agriculture, and textiles (Xie, Zhang, Dreisinger, & Dyole, 2014; Zhang, Wu, Bian, & Zeng, 2014).Solvent extraction is widely used for the separation of REE (Xie et al., 2014; Zhao, Huo, Pan, Li, & Liu, 2014). Di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) are two of the most effective extractants for the separation of rare earth elements among organophosphorus extractants (Gupta & Krishnamurthy, 2005). However, the difficulty in stripping loaded D2EHPA extractant, especially for heavy REE, has limited its utilization. Yttrium can be stripped at lower acidities in EHEHPA systems compared to D2EHPA systems (Gupta et al., 2005), but the extraction efficiency is lower. Conventional solvent extraction by mixer-settlers is restricted by its large solvent inventory and loading limits, and suffers from phase disengagement, emulsification, loss of solvent, and flooding problems (Swain, Jeong, Lee, & Lee, 2007). In this context, supported liquid membranes (SLMs) present a potential alternative due to their advantages, being low solvent inventory, process simplicity, low energy and operational costs, great enrichment ratio, and combination of extraction and stripping into one single step. A SLM is a system in which two aqueous phases are separated by an organic liquid membrane suspended in the pores of a porous support by capillary forces. One of the aqueous phases is the feed solution with the solute and the other is the stripping or receiving solution. The solute diffuses through the liquid membrane and then is extracted into the stripping solution (Kislik, 2010)."

Jan 1, 2016

By Long Han, Beijing General Research Institute of Mining and Metallurgy, Yu Xie, Yunhai Zhang, Yangge Zhu, University of Science and Technology Beijing, Yanbo Shang, Xingrong Zhang

"The first-principles method was employed to study the adsorption of hydroxyl calcium (CaOH+) and hydroxyl (OH-) on hematite and quartz surfaces. The calculation results suggested that OH- preferred to interact with the active Fe sites on the hematite surface, whereas OH- adsorbed on the quartz surface by weak hydrogen bond. Though CaOH+ could easily adsorb on the hematite and quartz surfaces by the formation of Ca-O bond, the covalence formed on the quartz surface was apparently stronger than that on the hematite surface, meaning a stronger and more stable adsorption. CaOH+ adsorbed on quartz surface was mainly through the interaction of O-2p and Ca-3d states, and this interaction on hematite surface was weaker.INTRODUCTIONIron Increase and Silicon Reduction Technology (Yu & Duan, 2002) of hematite is mainly through the reverse flotation (silica is floated away from the iron concentrate). There are two ways to achieve this (Houot, 1983). One is to collect quartz by cationic collector directly; the other is to activate quartz by lime and then collect it by anionic collector. There are two main different views with respect to the mechanism of quartz activation: mono-hydroxyl compound theory (Fuerstenau, Rice & Somasundaran, 1965; Fuerstenau & Palmer, 1976) and surface hydroxyl precipitation theory (Hu & Wang, 1988; Wang & Hu, 1990). The former indicated the formation of the mono-hydroxyl complex is one of the two criteria of quartz flotation. The later theory, on the other hand, suggested that surface precipitation is the adsorption of active species of metallic ion on quartz surface. However, most of those researches are based on the solution chemistry of flotation and little is done at the microscopic level.In this paper, by the help of first-principles calculations, the adsorption models, bonding conditions, Mulliken charge populations and adsorption energies of hydroxyl and calcium hydroxyl ions (OH- and CaOH+) on hematite (001) and quartz (100) surfaces were investigated to find out the lime activation of quartz at atomic level, which is significant for the researches of quartz activation theoretically and practically."

Jan 1, 2016

By P. Lostritto, G. E. Agar, G. Labonte, M. Cherevaty

"A locked cycle flotation test was done on a sample from the ovoid portion of the Voisey 's Bay copper-nickel sulphide ore. The chemical conditions for this test were generated by prior independent testing. In this test work the time in each of the five separation stages was optimized prior to executing the locked cycle test. A numerical simulation of the continuous circuit material balance was done prior to the locked cycle test. The test results were not fully satisfactory because the flotation of pyrrhotite in the bulk rougher and cleaner stages was not consistent. The preliminary indication was that the samples had oxidized to varying degrees during storage.INTRODUCTIONINCO has performed batch laboratory flotation testing on ore from Voisey's Bay which is a mixture of chalcopyrite, pentlandite and pyrrhotite. Earlier, Lakefield Research was contracted by Diamond Field Resources to test the ""flotability"" of the ore, which included a pilot plant trial. INCO's J. Roy Gordon Research Laboratory has repeated many of the batch tests that Lakefield did to verify their results. Based on their own work, INCO has modified the circuit proposed by Lakefield Research. The modified circuit is based on batch test work, but no locked cycle test (LCT) was done. It is believed that this circuit will produce a copper concentrate at 29-30% copper and a primary nickel concentrate at 15-20% with recoveries of 80% or above.For several years the University of Toronto has been working with INCO to provide ""hands on"" experience for undergraduate students as an Industrial Research Project (IRP). This year, the objective for IRP was to optimize the time for each of the five separation stages for the Voisey's Bay ore then to numerically and experimentally simulate the material balance for a continuous circuit."

Jan 1, 1998

By Megan Becker, Aubrey Mainza, Indigo Research Laboratories, Jenny Wiese, Gaynor Yorath, Lucy Little

Particle shape characterisation has an important role to play in mineral processing, to clarify effects of shape on rheology, equipment wear rates, comminution, classification, sizing and flotation. However in industry, shape characterisation is not routine, and the most commonly used shape descriptor in the field (circularity/ angularity/ sphericity) is not invariant. This study aims to investigate shape measurements for a fine particulate ore sample measured with different analytical devices. Two Automated Scanning Electron Microscopy devices with Energy Dispersive X-ray Spectrometry (FEI QEMSCAN® and Zeiss Mineralogic®), and a camera based image-sizer using dynamic image analysis (Retsch CAMSIZER® XT) were compared. Each device was used to analyse the shape characteristics of specific particles in both a coarse sample (–212/+150 µm) and a fine sample (-53 µm) of UG2 platinum ore. Circularity and Roundness frequency distributions obtained from the three devices were then compared. For selected individual particles, circularity showed higher variability than roundness, and the sample circularity distributions obtained by the three devices were completely different. It is clear that circularity data from different studies relying on different devices should not be compared on an absolute scale. The shape parameter roundness was found to be a more robust descriptor than circularity, and it can give a stronger indication of a particulate sample’s shape characteristics on an absolute scale. However, there were still significant differences in the roundness measurements obtained by the CAMSIZER XT and the two Auto-SEM devices, which was attributed to the dissimilar mechanisms of image capture.

Jan 1, 2016

By Rick Hyndman

? Context: Ø Global action on climate change ? The situation of trade-exposed industry sectors ? The federal government?s draft plan for industry ? CAPP?s position ? Canadian emissions & Canada?s Kyoto target Simple Economic Theory of Dealing with Externalities ? Put cost on emissions Ø Carbon tax Ø Emission trading with auctioned permits ? GHG costs get reflected in the prices of energy alternatives, goods & services Ø Decisions driven by changes in relative prices ? Switching to lower emission fuels ? More energy efficient ways of producing ? More energy efficient appliances, cars, housing ? Reduced demand for energy intensive goods & services ? Anticipation of higher CO2 price drives low CO2 technology Development

Nov 1, 2002

By Shuan-cheng Gu

Roof bed separation often occurred due to the deformation incoordination of surrounding rock following the excavation of mine roadway. Bed separation has effect on the bolts, and the estimation of the influence will directly affect the safety of support systems. In this paper, the hyperbolic function model to analyze the load transfer mechanism on the bolts was simplified as the exponential function form for easy calculation. An elastic-plastic analysis model of the bolt loading occurred by the bed separation was established. And the development low that the bed separation affected to the bolt loading was discussed. According to the parameters analysis of different separation values and locations, the influence law of the bolt loading caused by roof bed separation was summarized. Finally, the effects of bed separation were considered for the bolting design, it was able to provide a reference to the anchorage design of stratified rock.

Aug 1, 2013

By B. Drew, K. Budna, C. Wenzl, D. Gregurek, A. Spanring

"The metallurgy of nickel and cobalt and of copper is closely interlinked when processing sulfidic Ni-Co ores and Cu-Co ores. The respective furnaces are typically lined with magnesia-chromite refractories, which are exposed to multiple and complex stresses. The selection of the processing route, furnace type and slag system will be dictated by the specific ore type available, this will determine the individual refractory wear mode. This paper evaluates the common refractory wear mechanisms, namely infiltration, spalling and chemical attack by various slag systems, as well as sulfur attack, as observed when processing primary sulfidic ores. All these wear parameters, which are discussed in this paper, lead to a severe degeneration of the brick microstructure and a decreased lining life. Therefore, a detailed investigation and understanding of the wear mechanisms through “post mortem studies” is an important prerequisite for the refractory producer. Based on such research results, combined with specific process knowledge, appropriate brick lining solutions for nickel and cobalt processing furnaces can be recommended.INTRODUCTION The metallurgical production of cobalt and nickel and of copper is closely interlinked to the mineralogy of the respective ores: cobalt is found in African Cu-Co ores as well as in Co-rich nickel ores (laterites and sulfides). Also, Co-bearing secondary raw materials contain the mentioned elements in different contents. In pyrometallurgical processing of sulfidic ores, cobalt is generally recovered as a by-product during the production of copper and nickel, whereas it is normally not recovered separately during the processing of nickel laterites but remains in the FeNi product. Besides various hydrometallurgical production routes, the pyrometallurgical processes involved comprise smelting (i.e., production of a Cu-Ni-Co-Fe matte in electric or flash furnaces), converting and refining (i.e. removal of Fe and S as well as other elements from matte by oxidation). The ongoing trend to use higher oxygen enrichment in process air enables higher intensity processes but also increases the oxidation potential in the vessel. Therefore, during smelting and especially during the oxidative treatment in converting and refining, some amounts of valuable metals are also transferred to the slag in their oxides form. A subsequent slag treatment is then applied for recovering valuable metals from the slag, namely allowing an economic material stream handling and minimizing metal losses. This is often done in a slag reduction furnace. Additionally, copper and nickel are very good collectors for precious metals and platinum group metals (PGMs) - therefore, depending on the content of these metals, an additional refining process is used to recover these valuable metals from the matte or metal phase (Elvers et al., 1997; Davenport et al., 2002; Crundwell et al., 2011)."

Jan 1, 2017

By C. A. Morais, L. V. Resende

"The technological development observed in recent years has stimulated the application of rare earth (RE) elements. Amongst their various applications it is well worth mentioning their use in electronics, superconductors, nuclear medicine, as well as in special inks - as those used in radar invisible airplanes. TV and computer monitor screens present as coating a powder containing some rare earth elements, mainly Europium and Yttrium. The recovery of the RE elements from electronic scrap is extremely important as the economic and environmental issues are concerned. This paper describes the study of the Eu and Y recovery from e-scraps. The first step of the process was the leaching of the powder obtained by manually scraping the inside surface of the screen. After the optimization of the leaching, the dissolution of Eu and Y was higher than 98 w/t% and a pregnant sulfuric liquor containing 11.9 g L-1 Y and 0.72 g L-1 Eu was obtained. The second step was the separation of the metals found in the liquor by the solvent extraction technique. The separation of Eu and Y was carried out in a counter current circuit compound of 3 extraction stages, 7 scrubbing stages and 15 stripping stages. DEHPA was used as the extractant, whereas a diluted sulfuric acid solution was applied as scrubbing agent and a hydrochloric acid solution at high concentration was used as the stripping agent.INTRODUCTIONThe rare earths (RE) are a moderately abundant group of 17 elements composed of lanthanides, scandium and yttrium. Amongst the RE, promethium (Pm) is extremely rare, however several of the RE elements are not very rare and occur dispersed in a variety of forms (Greenwood & Earnshaw, 1984; Tyler, 2004).The innumerable applications of the RE elements are based on their particular properties, mainly their spectroscopic and magnetic properties (Martins & Isolani, 2005). The technological development observed in recent years has stimulated the application of rare earth (RE) elements. They have been used in agriculture, electronics, superconductors, nuclear medicine, automobile industry, special inks – as those used in radar invisible airplanes, X-ray screens, high intensity mercury vapour light bulbs, neutron scintilators, charged-particle detectors and optical memory reading systems (Maestro & Huguenin, 1995; Nagaosa & Binghua, 1997; Sánchez et al., 1999)."

Jan 1, 2012

By Anoush Ebrahimi

Mining dilution is one of the most important factors affecting the economy of mining projects. Ore losses and dilution are present at all stages of mining and while several models can investigate the influence of dilution it is its quantification that poses the most serious challenge (Pakalnis et al., 1995). This paper introduces a methodology to quantify dilution factor in open pit mines. The proposed approach makes use of general mining software available in most mining companies. Therefore it is amenable to most mining operations and provides a readily available tool for understanding mining dilution for operators and consultants. To illustrate the methodology the author uses an example from a hypothetical mine. Dilution increases the operating costs in the mill by increasing the tonnage of material to be milled. In addition to its direct impact on short term income of a mine, dilution causes significant changes in other factors that on the long term reduce the overall value of the project. For example, it prolongs the mine life by reducing mill?s effective capacity. It also reduces the feed grade. In most cases, lower feed grade means lower mill recovery. Dilution also increases the cut-off grade which in turn reduces the overall ore utilization of a mine. In some cases, to take advantage of economies of scale, mining operations tend to plan for higher mining rates. Moving to a larger scale of operation means less selectivity, hence more dilution. This is true for all kind of deposits. High level and uncontrolled dilution may ultimately defeat the purpose of increasing production rates. If not impossible in theory it is nevertheless extremely difficult and expensive to eliminate dilution in practice. Some amount of dilution is practically unavoidable in most mining operations (Scoble and Moss, 1994). Although completely avoiding dilution may be impossible, we can measure and control it. By better understanding the root causes of the dilution and planning accordingly, it can be controlled and reduced. While we do our best to identify and calculate all the other cost items of a project, no matter how small, it is common to make general assumptions about dilution instead of quantifying it. It is common to assume a general dilution such as 5% for massive deposits and 10% for tabular shape deposits. While these figures may be a good starting point in early stages of mining studies, it does not take in to consideration the complexity of the problem. Dilution factor varies within a single mine for different benches and zones. This is due to changes we see in grade distribution and shape of ore body. It also varies based on commodity price. It is necessary to make sure that these variations are taken into account when designing or evaluating a mine. Dilution varies in different mines based on the deposit characteristics, operational aspects and economic cut-off grade. For instance, shape of the deposit, bench height, equipment size, and market conditions will have an impact on the level of dilution in a mine. It is paramount for mining projects to have a better understanding of dilution right from the beginning. In times like today, where mining operations must operate at peak efficiency, it is even more crucial to be able to calculate and have a better grasp of all the parameters influencing the economics of a project including dilution. In order to produce better project evaluations, dilution studies should be an integral part of any project.

Aug 1, 2013