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By Nosa O. Egiebor, Kafui Nyavor

"The effectiveness of sulphuric acid, nitric acid, and hydrogen peroxide pressure oxidation on the cyanide extractability of gold from a double-refractory concentrate is presented. Whileover90% of the sulphide content could be oxidized by either of the two acid pretreatments, only 65% was achieved by the peroxide oxidation. Carbon oxidation by both acid and peroxide pressure oxidation were less than 15%. Although the peroxide pressure oxidation pretreatment resulted in much lower sulphur and carbon oxidation, it gave pretreated residues with decreased levels of preg-robbing activities and higher gold recoveries during subsequent cyanidation, thus indicating some deactivation ofthe preg-robbing carbon during pretreatment with hydrogen peroxide. The refractoriness due to carbon preg-robbing activity was found to contribute more to the refractory behaviour of the concentrate than the occlusion of gold particles by the sulphide mineralization.IntroductionGold ores and concentrates are classified as refractory when a significant portion of the gold content cannot be extracted efficiently by conventional cyanidation, even after fme grinding (Weir and Berezowsky, 1984); (Demopoulos and Papangelakis, 1987). The refractory behaviour of precious metal ores and concentrates is generally attributed to two main factors: The presence of carbonaceous materials which could cause preg-robbing activity during cyanidation (Zaitseva et al., 1973); (Nice, 1971); Scheiner et al., 1971); (Eisele et al., 1983), or occlude gold-bearing minerals (Wells and Mullens, 1973); (Gasparrini, 1983); (Chen and Reddby, 1990), and the occurrence of sulphide minerals which can occlude gold, thus reducing the access of lixiviants (Schwartz, 1944); (Weir et al., 1986); (papangelakis and Demopoulos, 1990); (Michaelis, 1989); (Schweigart, 1965). When the refractoriness is due to a combination of these two factors, the ore or concentrate can be referred to as being ""double-refractory"". Because of the rarity of gold ores exhibiting this double-refractory phenomenon, only a few studies have been carried out on their suitability for pretreatment by existing techniques."

Jan 1, 1992

By J. A. Meech, C. A. Harris

"The application of control theory in mineral processing is more difficult than in other industries because of the complex nature of the unit processes involved and because of problems with accurate on stream measurement of process variables. Conventional control is based on proportional, integral and derivative functions of a continuously measured error term. Computer control can enhance these actions by incorporating logical routines to switch from one relationship to another. The success of this logical approach depends on our understanding of the process dynamics and the stability of the process and model under all conditions. Typically the model does not apply at all times in mineral processing because of frequent and unmeasurable changes in the ore parameters.Recent advances in the theory of fuzzy sets have led to the application of this science to process control. Fuzzy Logic can be used to develop heuristic or rule-of-thumb controllers with the strategy based on the actual operating practice of experienced plant operators. Control action has increased flexibility through the adaptation of human reasoning. Acceptance of the control system by operating personnel is significantly higher because of their participation in its formulation. The requirement of an exact model is not essential.A heuristic controller has been designed and tested with a computer simulation model of a secondary crushing plant. The results of this study are discussed and future applications of this control technique to other mineral processes are suggested. IntroductionThe application of control theory in mineral processing is more difficult than in other industries because of the complex nature of the unit processes involved. Mineral processes typically are characterized by non-linear relationships between input and output variables. Many of these variables cannot be monitored accurately on-stream and so long time lags on the measurement loop are features of the system. The processes, themselves, often have long time-varying responses while the process loads fluctuate significantly on a short-term basis.Attempts to control these processes have led to the formulation of mathematical models to describe each unit activity. Adaptive techniques have also been tried to compensate and account for process changes and vageries. These approaches are mathematically rigorous so that their complexity and precision limit their usefulness when applied to ""vague"" processes."

Jan 1, 1987

By R. Pakalnis, D. Tenney, B. Lang

"This paper describes three case histories whereby numerical methods were employed as a tool in the identification of potential instability. Simple two dimensional (PCBEM) and pseudo three-dimensional (BESOL, MINTAB) codes were employed to identify zones of induced stress which were subsequently related to extensometer, stress meter and observational data as the stope was excavated. The following case histories will be discussed. MacLellan Mine - sill pillar stability; Ruttan Mine-Hanging Wall Stability; and Detour Lake Mine-narrow vein mining.The MacLellan case history showed how modelling and instrumentation enabled mining to be conducted safely and under controlled conditions. MINTAB and PCBEM were employed to predict sill pillar failure. The sill pillar failure was associated, with an unloading of stress which was recorded by instrumentation (stress meter) and a decrease in the over-all rock mass strength. The yielded pillar, however, maintained its over-all configuration enabling access through the pillar.The Ruttan case history is an example of hangingwall and footwall design whereby the existence of adverse structure coupled with a zone of relaxation results in dilution. BESOL and PCBEM were employed to model a test stope and to verify the observations and measurements through instrumentation . Empirical methods of dilution estimates are employed to determine the level of walls lough with respect to the rock mass rating, stope dimensions and rate of excavation.The Detour Lake case history in an example of open stoping a narrow steeply dipping deposit. Stope dimensions are 135m in strike length, 47 m in vertical height with an average width (F/W to H/W) of3.6 m. Stress meters coupled with visual observations are related to modelled estimates of stress and dilution."

Jan 1, 1991

By H. Kalsi

"IntroductionRoyal Oak Mines Inc. is currently operating the Parnour No.1 mine located 10.5 miles east of Tinunins, adjacent to Highway No. 101. The operation produces gold ore at a rate of 3300 tpd. A variety of mining methods including bulk open stopes with ITH drilling, narrow vein panel, longhole and open pits contribute to produce 1.2 rnillion ore tons annually. The milling process requires water at an average rate of 1 rnillion gallons per day (700 U.S. gpm). The Pamour No.1 mine has historically had two major problems with regard to water control. The flfSt is the underground pumping system's inability to handle excess inflows of water generated from spring thaws. When the thaw takes place over a short period of time, large inflows of water are created which quickly migrate underground and sometimes result in the loss of the lower loading pocket. During the spring runoff the pumps at Parnour No.1 work continuously for 24 hours at a rate of 1200 U.S. gpm. The system was further taxed in 1991 when the Hoyle mine was connected to the Parnour No. 1 mine and whatever excess capacity the pumping system had for the spring runoff was taken up handling the inflow of mine water generated by the Hoyle.The second problem facing the mine was the lack of water for the mill during the severe cold winter months and dry summer months. At those periods inflows of water into the mine decline and the underground water normally pumped to the mill is severely decreased. In times of dry spells mill personnel increase the water diversion from the Three Nations Lake in order to meet water demands and maintain tonnage throughout. In essence, the mine was going through an annual ""feast or famine"" situation and a solution was needed.A number of options were considered but were narrowed down to the two most practical. The first was to modify the existing pumping system and increase its capacity in order to handle the excessive runoff during spring thaw. This involved a heavy capital expenditure and would have caused additional operating costs (i.e. increased hydro). The option chosen by the management was to divert the spring runoff into an unused section of the mine called The West End. A bulkhead placed at the 2400 level would provide an ultimate underground water storage potential of 150 million gallons. This would also cut down the load on the existing pumping system, save electric consumption in pumping and provide water storage which could be used for milling during the two dry spells. Pumping stored water from the mine could be scheduled for off peak hours to take advantage of lower power rates. To meet these objectives an underground bulkhead capable of withstanding high water pressure up to 2000 ft head (866 psi) was constructed in the spring of 1992. The bulkhead site was at the 2400 level at the Pamour No.1 mine. A major consideration was the requirement to construct a safe bulkhead and to minimize water leakage from the bulkhead.Figure 1 shows the bulkhead location."

Jan 1, 1994

By André Chagnon, Héroux. Yvon

"Résumé - Cette étude porte sur l'altération de la matière organique et des argiles dans les boues carbonatés dévoniennes du facies ""F' de la Formation de Pine Point et ses équivalents stratigraphiques la Formation d'Evie et l'unité bitumineuse de la base de la Fonnation de Hom River. La matière organique se compose principalement de bituré solide et de quelques fragments de fossiles (organaclastes). La majorité des échantillons ne renfement que de l'illite et des inter-stratifiées illite/smectite.Si on compare les températures d'homogénéisation (Th = 100°C) des inclusions fluides de la sphalérite et des dolomites associées a la minéralisation aux températures estimées à partir de la réflectance de la collinite (84°C à 117°C), l'on ne peut pas conclure à la présence d'une anomalie thermique dans le district minier de Pine Point. De plus, la réflectance des organoclastes n'est pas plus élevée dans le district minier de Pine Point que dans les localités plus éloignées des gites. L'analyse des minéraux argileux conduit à la même conclusion: aucune anomalie thermique n'est décelable dans les unités échantillonnées à l'intérieur du district minier de Pine Point quelque soit l'indicateur utilisé.La kaolinite et la matière organique altérée, affichant des valeurs anomales de sa réflectance, se trouve essentiellement en présence de soufre et de sulfures. Cela suggère une origine authigène de la kaolinite et une altération de la matière organique reliées au phénomènes de minéralisation.Abstract - The alteration of organic matter and clays is studied in the Devonian Pine Point Formation carbonate muds, ""F"" facies, and its lateral equivalents the Evie Formation and the bituminous unit at the base of the Hom River Formation. The organic matter is mainly composed of solid bitumen with few fossil fragments (organoclasts). Most samples contain only illite and mixed layer illite/smectite.If we compare the Th (100°C) from fluid inclusions of sphalerite and dolomites associated with mineralization to the temperatures calculated from the reflectance (Ro) of the collinite (84°C to 117°C), we cannot detect a thermal anomaly in the Pine Point mining district. This result is based on the reflectance values of organoclasts from the mining district that are not higher than those reflectance values measured on organic matter (OM) away from the ore deposit. A similar conclusion is reached from the clay study: none of the parameters used allow us to identify a thermal anomaly in the samples from the mining district.The kaolinite and the altered OM showing anomalous Ro values mainly occur with sulfides and sulfur. This association suggests an authigenic origin for the kaolinite and an alteration of the OM due to the mineralization events."

Jan 1, 1994

By Jiahao Xu, Namsoo P. Kim, Guikuan Yue

Iron (ferrous ions and ferric ions) plays an important role in the heap leaching of copper sulfide minerals and copper electrowinning. In our previous study, a novel oxidation-reduction potential (ORP) equation only based on the variables of temperature and nominal ferric/ferrous ratio was developed to predict the redox potential of the quaternary H2SO4-Fe2(SO4)3-FeSO4-H2O system, and its applicability was also extended to more complex acidic iron sulfate solutions, especially those generated during the acidic leaching and bioleaching of Printed Circuit Boards (PCBs) to recover copper. In this work, the broader range of applicability of this equation to other complicated acidic iron solutions containing copper ions has been extended and determined. Specifically, synthetic iron-containing solutions with copper ions according to the conditions of industrial electrolyte during copper electrowinning and heap leaching have been used to measure the ORP and test the developed equation. It seems that this equation can still be employed to predict the redox potential of the Fe3+/Fe2+ couple for the simulated solutions under conditions related to copper electrowinning and pregnant leaching solution generated during heap leaching over a wide range of solution concentration, nominal Fe3+/Fe2+ ratio and temperature. It has shown that the prediction and measurement of redox potential is highly useful to estimate and understand the iron chemistry of industrial leaching and electrowinning processes. INTRODUCTION It is well-known that iron (ferric or ferrous) ions are widely involved in the hydrometallurgical production of non-ferrous metals such as Cu, Au and Zn, mainly in the form of acidic iron sulfate solutions. As far as Cu is concerned, in a typical leaching-solvent extraction-electrowinning process, ferric ion plays a central role in the heap leaching process and is reduced to ferrous ions in the pregnant leaching solution. Ferric ion is the most important surrogate oxidant and the dissolved ferric/ferrous couple plays an important catalytic role in accelerating the leaching rate with oxygen as an oxidant (Peters et al., 1986; Schlesinger, King, Sole, & Davenport, 2011). In addition, during the traditional electro-winning process, oxygen is evolved at the anode, and copper is reduced at the cathode. A common idea is that iron in the electrolyte in copper electrowinning cell (with total iron of 1–4.4 g/L) plays an important role in reducing the current efficiency. According to the published results (Winand et al., 1975; Dew et al., 1985; Moats et al., 2009; Khouraibchia et al., 2010), thecurrent efficiency decreases linearly with increasing ferric ion concentration and the energy consumption increase was mainly caused by the decrease in current efficiency.

Jan 1, 2019

By C. J. Rockingham

"A comparative study of sulphide textures has been carried out on samples from four Archean copper-zinc massive base metal sulphide deposits: Kidd Creek, Ontario; Lake Dufault -Norbec, Quebec; Hood River-41, N. W. T.; and Geco, Ontario. These deposits have undergone metamorphic recrystallization under a range of conditions, and results of this study indicate that certain sulphide textures may be used as qualitative indicators of metamorphic grade, whereas other cannot.The sulphide textures of most value in this regard are sulphide grain sizes, which increase with increasing metamorphic grade, and the presence or absence of sedimentary/diagenetic textures, which are destroyed at the lower amphibolite facies of metamorphism. Chalcopyrite and pyrrhotite intergrowths in sphalerite increase in size, in degree of coalescence and in the ratio of unmixed pyrrhotite to chalcopyrite inclusions with increasing metamorphic rank. With increased metamorphic grade, the pyrrhotite intergrowths change from rounded inclusions on grain boundaries to rod-like shapes along sphalerite twin planes. There is also a general increase in the relative proportion of pyrrhotite in the deposits. Textures that appear to have little value as indicators of metamorphic grade are sulphide deformation textures, and triple junction point angles and their standard deviations, which show little variation from the lower greenschist to the upper amphibolite facies of metamorphism. The presence or absence of myrmekite-like magnetite also has little value in determining the relative metamorphic history of these deposits, as it is a product of local contact metamorphism."

Jan 1, 1980

By L. A. Homeniuk, R. Bonnar

"The Athabasca Basin has been the scene of an intense exploration effort since the late 1960s, resulting in the establishment of this area as one of the major uranium districts in the world.The A thabasca Group is of Helikian age and unconformably overlies metamorphic rocks of Aphebian and Archean age. Most of the known uranium deposits have a close spatial relationship with the unconformity, graphitic meta-sediments, major northeast-trending structures and the basin edge. It should be noted that, in regard to the latter, some of the Cluff Lake deposits are exceptions.The pre-Helikian rocks underlying the Athabasca Group have been divided into six Iithostructural domains. The known uranium deposits are concentrated in the Wollaston and Mudjatik domains in the southeastern portion of the basin.The orebodies typically have a narrow high-grade portion below the unconformity and a broader, lower-grade disseminated zone in the overlying sandstone. Over-all grades average over 1% U3O8 and our estimate of known reserves totals more than 400 million pounds of contained U3O8. Some of the deposits have high concentrations of other metals, including nickel, arsenic, cobalt and gold. Ubiquitous chlorite and clay alteration is characteristic of the orebodies.Other Proterozoic basins in Canada of similar ages and having analogous geological settings to the Athabasca have received far less attention. Although little of the known uranium mineralization in these basins is related to the Helikian unconformity, there may be an exploration potential for deposits similar to those of the Athabasca basin.IntroductionThe Athabasca sedimentary basin is located within the Churchill Structural Province of the Canadian Shield in Northern Saskatchewan. The basin is elliptically shaped and is approximately 800,000 square kilometres in area.The objective of this paper is to summarize the various elements in the genesis of the unconformity-type uranium deposits of the Athabasca Basin and to evaluate the comparative potential of other Proterozoic basins to host similar unconformity-type deposits."

Jan 1, 1982

By J. F. Perreault, J. Paraszczak

"The profitability of an underground mine depends to a great extent on the production cost.Random equipment failures and their consequences have significant influence on the total operating cost of a mining system. Having this in mind, a reliability study has been initiated for loadhaul- dump machines in an underground mine. The main purpose of this study is to identify the critical machine subsystems, determine their failure pattern and help work out an effective maintenance strategy. In the first part of this study, the failure data of diesel powered LHDs, gathered during an I8-month period have been analyzed. For the purpose of the analysis, the machines have been treated as systems comprising seven subsystems connected in series. The most critical subsystems, i.e. electrical and hydraulic, were further investigated, and analyzed by graphical and analytical methods. Different failure distribution models were applied and discussed. Basic Defmitions and ConceptsIn order to avoid confusion, several terms used in this paper are defined below, as compiled by O'Connor (1991). The acronymsBS and MIL-STD stand respectively for: British Standard and US Military Standard.Failure: the termination of the ability of an item to perform a required function (after BS 4778).Time Between Failures (TBF): the length of time between two consecutive failures.Observed Mean Time Between Failures (MTBF): For a stated period in the life of an item, the mean value of the length of time between consecutive failures computed as a ratio of the cumulative observed time to the number of failures under stated conditions (after BS 4778).Maintenance, Corrective: The actions performed, as a result of failure, to restore an item to a specified condition (after MIL-STD-721 B).Maintenance, Preventive: The actions performed in attempt to retain an item in a specified condition by providing systematic inspection, detection and prevention of incipient failure (after MIL-STD-721B)."

Jan 1, 1994

By R. A. Gannicott

Trend surface analysis was used to investigate the geochemical dispersion patterns of Si, Ai, Fe, Mg, Ca, Na, K, Ti and Rb in the footwall of the Seneca massive sulphide prospect in southwestern British Columbia. Surfaces for various element ratios were also produced to see if the distributions of the elements are related to each other. Trends developed by the elements redistributed during hydrothermal alteration may be difficult to detect for various reasons, such as too few and widely separated sample points, random analytical errors or local variations in rock chemical composition that are not related to regional trends. Trend surface analysis is useful to distinguish regional trends from local fluctuations. The computer program used in this study is capable of calculating surfaces up to the 6th degree polynomial, but provides for automatic termination when the variables in the equation for successive surfaces become effectively collinear. With the relatively small number of data points used (21 samples) in this study, such termination occurred after the quadratic surface. Results show that, at the Seneca prospect, Mg and K increase, and Na and Ca decrease, toward a common centre which corresponds closely with the best drill-core intersections of ore. The centre is interpreted as a volcanic vent and as the source of mineralization . Quadratic surfaces for element ratios show that K/Ca decreases and Fe/Mg increases away from this vent. Thin-section and X-ray diffraction analyses indicate that these variations reflect sericitization of plagioclase and an increase in the Mg content of chlorite near the vent. The mineralization , rock types and element dispersion patterns at the Seneca prospect are similar to those reported for volcanogenic massive sulphide deposits at Bathurst, New Brunswick, and in the Hokuroko district of Japan.

Jan 1, 1979

By F. J. Macias, A. Bruland, F. E. Dahl

"Tunnelling by use of Tunnel Boring Machine (TBM) is gaining a greater presence as a suitable excavation method. Disc cutter consumption has a strong influence on performance and cost when using TBMs and the influence becomes even more relevant in hard rock. Furthermore, good predictions of TBM performance and cost facilitate the control of risk as well as avoiding delays and budget overruns. Since abrasive wear is the most common process affecting cutter consumption, good laboratory assessments are needed. A new abrasivity test method called Rolling Indentation Abrasion Test was developed. The goal of the new test design and procedure is to reproduce wear behaviour on hard rock tunnel boring in a more realistic way than traditionally used methods by introducing wear by rolling contact on intact rock samples. INTRODUCTIONHigh investments are involved in the tunnelling industry, especially in Tunnel Boring Machines (TBMs) projects. Performance predictions and cost estimations are crucial for planning and risk management of TBM projects. Cutter consumption has a large influence in terms of time and cost, and an even greater effect in case of hard rock projects. Many factors are influencing the amount of cutters consumed in hard rock TBMs. Normal TBM operation results mainly in abrasive wear on the cutters and appropriate methods for abrasivity assessment are needed. Rock abrasiveness cannot be considered as an intrinsic property and the complete tribological system should be considered in addition to the geological properties of the rock.In the present paper, a new test method for abrasivity assessment in tunnel boring called Rolling Indentation Abrasion Test (RIAT) is presented. The traditionally used test methods for determination of rock abrasiveness uses sliding or impact contact in order to cause wear while the RIAT introduces rolling contact on intact rock samples. The ambition of the new test device is to have a reliable method to evaluate the cutter wear in hard rock tunnel boring by reproducing wear behaviour on rolling disc cutters in a more realistic way. It has been established by many authors that the abrasion of a cutter ring is proportional to its rolling distance (Rostami, 1997; Bruland, 1998). In the present work, the weight loss of a mini-cutter ring is measured subsequent to testing in order to evaluate wear in the rolling process and could hence be related to cutter ring wear. Indentation of the tools in the intact rock sample is considered as an indication of the surface hardness of the rock or the resistance to indentation by rolling."

Jan 1, 2015

By A. Abadías Llamas, N. Bartie, M. Stelter

Evaluating the economic viability as well as the sustainability of the Circular Economy (CE) system requires a deep understanding of the distribution of all elements, compounds, alloys, materials etc. in flows. In this paper, the circularity of the copper value chain, including primary and secondary processing, is rigorously evaluated. The studied system comprises the metallic copper production from primary sources (from mineral to metal), copper-containing commodity production (copper is mixed with other metals) and copper recycling through secondary smelting to close the loop. This is linked to photovoltaic (PV) panels and battery storage. A simulation model of this system is created using HSC Sim, considering more than 30 elements (and its various compounds), 180 unit operations and 800 flows. From the mass and energy balances obtained through the simulation, an exergy analysis is conducted to evaluate the resource consumption from a second law (entropy) perspective. Additionally, these results are complemented through a Life Cycle Assessment (LCA), the recovery of technology elements and by-products is discussed, while quantifying the losses through the value chain. Through the digitalization of the complete system, a better CAPEX and OPEX understanding of the metal recovery and losses can be obtained, as well as the associated resource consumption and environmental impacts. New flowsheets and technologies can be evaluated. Several scenarios show how the resource consumption and the environmental impacts are affected by the recovery of different materials to produce different products. INTRODUCTION A key challenge of the circular economy (CE) is the linkage and optimization of both resource and energy efficiency of the (renewable) energy infrastructure and the resource cycle depicted by Figure 1 simultaneously. In addition, the CE requires the linkage of all stakeholders as shown by Figure 1. This has been discussed in some detail by Reuter and Bartie (2019) and Reuter et al. (2019). Copper and all its associated technology elements is one of the key enabling metals that is an economical copper colored thread through CE society (Reuter & Kojo, 2014). The Metal Wheel (Figure 2) shows the linkage of and recovery of various elements associated with copper and other carrier metals. This reveals that copper acts as an important carrier metal because of its properties i.e. the wealth of technology elements it carries from geological ores, but also its capacity to act as solvent of valuable elements and thence a key closer of various complexly connected element and material cycles when these technology elements are released during copper refining. The same applies to all other carrier metals of modern CE society as shown for example recently in a lead policy brief (Blanpain, Reuter & Malfliet, 2019).

Jan 1, 2019

By T. A. Wheat

"The presently increasing world-wide interest in advanced ceramic materials is generally focussed on their exploitation in both structural and functional applications. With the opportunity to engineer microstructures and thereby closely control and tailor the final properties, there are many new applications being made for these materials in both areas.The scope and some of the applications for functional ceramics are reviewed and examples of the present Canadian activity in this field are discussed.BackgroundThere has been progressively increasing international interest in the development and exploitation of ceramic materials in the last five years. The stimulus for this interest arises from several quarters, each of which are independent of the other.• There is a growing awareness of the strategic nature and vulnerability of supply of the raw materials used to produce high performance metal alloys.• The metal alloys are reaching the upper temperature limit for their performance as structural components in engines.• The dramatic increase in oil prices during the late 1970s focussed attention on the need for reduced consumption in many sectors, i.e., there is a need for more efficient engines that operate at higher temperatures - above those tolerated by the present superalloys.• A number of ceramics, especially the structural materials such as SiC, A120 3, AI20rSi02, Si3N4 and the Sialons are produced using non-strategic raw materials and they can exhibit startling performance-auto turbo-rotors are in production mad e of Si3N4 that operate up to 190000 rpm at 600°C, 150000 rpm at 900°C.• Ceramic s are generally of lower density - significant in the weight-reduction of automobiles such as the replacement of a 20-kg five-segment steel leaf spring with a single segment carbon-fibre reinforced unit of 3 kg. • Ceramics also offer major ad vantages in generating, monitoring or controlling the electromagnetic spectrum whether in bulk or thin-film devices that exploit optical, magnetic, pyroelectric, piezoelectric, electronic and I or ionic conductivity characteristics.The opportunity to combine several of these char acteristics in a single material by composition, processing and microstructural design has resulted in an advanced ceramics industry that had world-wide sales in 1980of $4.2 billion (U.S.)(I) and is predicted to grow to sales in the range $7 to $10 billion by 1990 and $16 to $24 billion by the year 2000(2). However, at present, advanced ceramics account for less than 20010 of the total ceramic market."

Jan 1, 1987

By Miguel A. Cuba

Resource models are generally constructed using data of different types and/or from different sources. A common issue is the consistency of scale in the information that often leads to a requirement to composite the data prior to model construction. For the purposes of mine planning, development and/or resource assessment, this model may then be upscaled to a relevant selective mining unit. It is well established that the geostatistical parameters for resource model construction is scale dependent. In particular, the volume variance of integrating these various scales has a direct impact on the variogram that should be used in model construction and/or the assessment of volume variance relations as it affects resource estimation. The scaling laws are a set of guidelines that detail how the variogram should change as a result of a change in the volume; these laws are empirically derived and involve some simplifying assumptions, not the least of which is an assumption of shape invariance in the variogram structure. An alternative approach was proposed to directly upscale the variogram via numerical integration, which demonstrates that the assumption of shape invariance is not required and we can directly access the new variogram shape given any volume of interest. This paper compares these two different approaches to variogram upscaling by considering two applications: the first corresponds to a 2D synthetic case and the second looks at a 3D case with data from a porphyry copper deposit. The simulation studies in these cases show that the direct upscaling approach performs better than the scaling laws in fitting the average experimental variogram values at any block size. This is based on a mean absolute error criterion. Moreover, it is also shown that with an increase in the block size, direct variogram upscaling significantly outperforms the scaling laws approach.

Oct 1, 2009

By Bryon Bisiaux, Walter Valery, Sonny Mwansa, George Amonoo, Adrian Dance

"Newmont Ghana Gold Limited’s Ahafo operation have been working with Metso Process Technology & Innovation (PTI) since early 2009 to increase mill throughput from a combination of controlled blasting practices and optimised primary crusher and grinding circuit conditions. For such Mineto-Mill projects, PTI’s methodology is termed Process Integration & Optimisation (PIO).Ahafo operate a SAG mill, ball mill and pebble crusher (SABC) circuit that processes a range of primary ore of varying hardness from different pits which is blended with soft oxide material. The PTI study focussed on ball mill limited material from the Apensu open pit.Following a benchmarking study of all blasting, crushing and grinding practices in January 2009, PTI recommended changes in both blasting and crushing conditions in order to generate a finer feed size to the SAG mill. Additional operating changes in the grinding circuit were recommended.A series of trials were conducted in November 2009 where three blasts were fired using a different blast design (hole diameter and explosive type) in the same area of the Apensu pit as the benchmarked material in January 2009. Top and bottom benches (or flitches) from each blast were sent exclusively to the grinding circuit and the material was tracked using PTI’s SmartTag™ system.The results from the six trials showed a significant increase in primary ore throughput at a reduced blend of oxide material. Ahafo have since standardised on these modified blasting conditions for all Apensu ore zones and have been able to sustain higher throughput compared to historical performance on similar material.This paper summarises the phases of the PIO project, the changes made in operating practices and the outcomes of the blasting trials that validated the predicted increase in mill throughput."

Jan 1, 2012

By Stéphane Chevrel

Non-energy raw materials are vital inputs for the EU?s economy and maintaining fair and undistorted access to these materials for EU industry and citizens is increasingly difficult. Within the EU, exploration and extraction have to face increased competition for different land uses and a highly regulated environment. While the EU is currently dependent on the importation of many metals, the overall potential for mining and quarrying in Europe is strong. In spite of this, the land area available for extraction in the EU is constantly decreasing, turning access to land into a key challenge for the extractive industry. The EOMINERS project aims at contributing to demonstrate how to improve the EU capacity in implementing new mining sites and their societal and environmental acceptability. The overall aim of EO-MINERS (Earth Observation for Monitoring and Observing Environmental and Societal Impacts of Mineral Resources Exploration and Exploitation) is to bring into play EO-based methods and tools to facilitate and improve interaction between the mineral extractive industry and the society in view of its sustainable development while improving its societal acceptability. EO offers a unique opportunity to collect necessary spatial parameters that play a key role for better assessments of mining-related environmental and societal impacts. It could enable the development of means to identify the site-specific environmental and societal footprints of mineral resource extraction and to determine their respective significance. This understanding of global and cumulative footprints along a causal chain is needed in order to target policy measures. In this way the expected reduction of environmental and societal footprints in the mining sector can be most effective for the environment and more cost-efficient for public authorities and commercial operators. The project first defined environmental, socio-economic, societal, and sustainable development indicators and criteria that can possibly be dealt with using EO techniques. After an analysis of policies related to the environmental and social footprint of mineral industries, project expertise and stakeholder interviews (national and on-site) as well as site investigations led to the establishment of a list of indicators to be monitored, either directly or indirectly, through accessible parameters. Development of EO-based monitoring tools is then carried out over three demonstration sites: the lignite open pit of Sokolov in Czech Republic, the Mpumalanga coalfield centred on the town of Emalahleni (previously Witbank) in South Africa, and the Makmal gold mine in Kyrgyzstan. From these developments, it is subsequently intended to contribute to the development of generic, standardised EO data integration schemes, in particular in view of characterising affected ecosystems, populations, and societies and prepare indisputable documents that will make the basis for a sound ?trialogue? between industry, governmental organisations, and stakeholders. This paper discusses results obtained after three years into the project, focusing on product development over the demonstration sites and their relevance to the observation and monitoring of environmental and societal footprints of the extractive industry.

Aug 1, 2013

By C. P. Verschuren, P. W. Kingston, W. F. Caley

"In recent years, there has been rapid growth in the use of natural stone building and construct ion products. The largest growing markets are for pre-fabricated natural stone panels for interior and exterior wall facing and flooring. This increased demand is attributed to advanced quarrying and processing technologies, renewed appreciation for the aesthetic appeal of natural stone, and to the superior durability of natural stone when compared to glass, steel, and concrete. Geologically, plutonic rocks, and to a lesser extent marble and limestone/dolostone, are used extensively for these applications. This paper details the economic structure of the dimension stone industry, describes the necessary characteristics of a stone quarry, and outlines the geological criteria which favour an economic quarry.INTRODUCTIONThe world building stone industry has remained relatively stable over the last 5 to 6 years. In contrast, the North American stone industry has experienced substantial growth during that period. The increased use of commercial granite is primarily responsible for this growth, where use as exterior wall veneer for commercial, industrial, and institutional buildings represents the largest and fastest growing market.This increased usage in the construction industry has been sparked by the application of new technologies in quarrying, processing and installation , ma king natural stone more competitive with man-made materials which are energy intensive to produce, and have risen dramatically in price. The development of safer, time-saving stone installation techniques has also appealed to the liability-conscience construction industry. Finally, there is a trend by designers and architects toward utilizing long-la sting weather-resistant building materials, and a renewed appreciation of the aesthetic appeal of natural stone. The other large user of granite is the monument industry of North America which, although it has decreased slightly in recent years, still consumes approximately 40% of all commercial granite produced. The local use of commercial marble has remained relatively stable, and North America still relies heavily on European sources and suppliers. There has been some concern over the use of marble for exterior applications in areas subject to acid rain, and in colder climates where the marble ma y be vulnerable to freeze thaw cycles. Despite these concerns, the greatest problem is not with the structural breakdown of marble but the inability of some marbles to retain their polished finishes in the se environments. As a result, there has been an increase in the use of granite at the expense of marble for exterior applications. Finally, commercial marble is used extensively for interior flooring, wall s, counter tops, furniture, sculptures, and stairway components"

Jan 1, 1989

By K. E. Haque

"Radium is selectively leachable from uranium ores with various types of lixiviants. Among a number of lixiviants tried on Midwest Lake uranium ore, KCl provided the highest per cent of radium extraction (60%-65%). Leach results further confirmed that a certain portion of Ra is not amenable to KCl leaching. More than 99% of the dissolved radium could be removed by treating the KCl leach liquor with barite or with radium selective complex resin (XFS-43230 resin of Dow Chemical Inc.) or by precipitating as RaBaSO4. Uranium leachings from the Ra-preleached uranium ores indicate that radium leaching prior to uranium may be applied as an extension to the conventional or alternative (i.e. acid chloride) leaching process of uranium ores in order to yield environmentally acceptable tailings (in terms of radium in the solids).IntroductionAt present, radium is considered as an environmental issue, particularly for uranium ore mine mill operations, rather than a commercial commodity. Radium was once a highly priced commodity ($180/mg during the first great war) but now it hardly has any commercial value. Its principal applications were in the field of cancer treatment and in the manufacturing of lwninous dials for watches. Nowadays readily-available synthetic radioisotopes are finding applications in place of radium.Because of scarcity and high toxicity, further commercial applications have never been explored.Radium was first discovered and extracted from uranium ore by P. Curie, M. Curie and G. Bement in 1898. Radium is widely distributed in nature but in exceedingly minute quantities. It is one of the daughter products of uranium or thorium and its maximum concentration is 3.3 x 10-7 part/part of U(21). Because of its short half-life (approximately 1620 years) in a geological time scale, its occurrence in nature as a distinct mineral is most unlikely.The details of the original radium leaching process developed by the Curies and Bernont are in the literature. This process essentially involved the roasting of uranium ore with caustic. carbonate followed by sulphuric acid leaching. The precipitated RaSO4 and BaS04 were treated with boiling Na2CO3 to convert them into the corresponding carbonates which later were dissolved in HCI. RaCI2 and Ba02 were separated and concentrated from the chloride liquor by fractional crystallization. But, in the course of time several modifications were made or proposed to the original process. Regardless of the process employed 226Ra extraction from the uranium ore was seldom better than 90%, and further as much as 20% 2URa loss took place during the concentration and purification process."

Jan 1, 1987

By B. N. Church, A. R. Pettipas

"The second vertical derivative method of processing aeromagnetic data from low level helicopter surveys yields results correiatable with the known geology and may be utilized to indicate possible targets for future exploration in the Silver Queen and Equity Silver mines areas, near Houston in central British Columbia . The principal zones of alteration associated with mineralization, known from detailed mapping, are further delineated and extended in a way not possible by a cursory examination of the original magnetic data.IntroductionThe second derivative method of processing aeromagnetic data is a long established procedure used to enhance the short wavelength content of the magnetic fields. Some recent exam pies of the use of the second derivative technique have been published by Chandler (p. 385), Sun Yunsheng et al. (p. 424) and Yarger (p. 223) in Hinze, 1985. According to theory, the ""second vertical derivative"" is closely related to the rate of curvature of magnetic (or gravity) fields and is particularly useful in resolving and sharpening local anomalies. The contours on second derivative maps may coincide with important features such as lithological boundaries, faults and mineralized zones.In the Houston area, central British Columbia, aeromagnetic data supplied by local mining companies provide a ready base for analyses. Examples are data sets for the Silver Queen and Equity Silver mines centred 35 km and 34 km south and southeast, respectively, from Houston (Fig. 1), (Cochrane, 1970 and Church, 1985)."

Jan 1, 1990

By J. C. Ingles

"A survey of possible methods for controlling cyanide concentration indicated that the simplest method would involve the use of a potentiometric technique. Such a method was suggested by a paper from the laboratory of Mines Safety Appliances, which described a method for determining hydrogen cyanide in air. In this application, the cyanide was absorbed in caustic and a silver electrode immersed in the caustic solution provided a measure of the cyanide concentration. However, our attempts to use the silver electrode in this simple manner to measure the cyanide concentration of solutions were not very successful. A study of the mechanism by which a silver electrode responds to cyanide concentration made it evident why this simple procedure is not satisfactory.Basically, the silver electrode provides an indication of the free silver ion concentration of a solution, and generally speaking, ignores the other ions' present. It can be used to measure an anion if this anion complexes silver. This technique has been used in complexing studies to determine the activities of such anions as acetate, citrate, oxalate and chloride. To do this, the electrode has to be placed in a solution which initially contains a known concentration of free silver ions. Addition of the complexing anion causes a drop in the free silver ion concentration and hence a change in the potential of the silver electrode. The change in potential can be expressed in terms of the concentration of the complexing anion, and used to indicate its concentration in the solution being analysed. The determination of chloride-ion by a silver-silver chloride electrode is an example of an application of this technique. The solubility of the silver chloride with which the electrode is coated provides the initial free silver-ion concentration. Depression of this free silver-ion concentration by the presence of the excess chloride ion of the sample solution results in a change in the potential of the electrode which is proportional to the chloride-ion concentration."

Jan 1, 1965