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By Victor A. Sowa

"Abstract - In 1938, a body of goethite and hematite was discovered beneath Steep Rock Lake near Atikokan, northwestern Ontario. This was at the time the largest and richest undeveloped iron ore body in North America. Mining began in 1944, fast-tracked by the needs of World War II, and through 1979 produced 79 Mt of 56.5% Fe. Production required the diversion of the Seine River, draining of Steep Rock Lake, building of a railroad, and a 25-fold increase of the local population. The mining project, at the time, was the largest project of its type undertaken in Canada. The current concepts of sustainable mine development and mine closures have advanced considerably since the period of operation and closure of the Steep Rock mines, and those operations would probably not have met current expectations of sustainability. However, some of the post-closure aspects of the mines provide illustrations of components of sustainability, which could form part of a basis for a post-mining sustainable land use plan. It is concluded that some of these components were successful in meeting current expectations of sustainable use, and although some aspects are unique to the circumstances at the Steep Rock mines, others could be applicable at other mine sites."

Jan 1, 2003

By Michael L. Free, Zongliang Zhang, Joshua M. Werner

In the copper electrowinning process, short-circuiting between the anodes and the cathodes is a critical problem that changes the current allocation among local electrodes and reduces the current efficiency significantly. Possible reasons for the short-circuiting include the improper alignment of the electrode, bent electrode, and nodules on the cathode surface. In typical tankhouses, there is often a time between shorting and harvesting as well as between shorting and clearing. Therefore, it is inevitable to have short-circuiting affect the operation performance in practical electrowinning operations. However, one key piece of missing data is the actual measurements of the current efficiency as short-circuiting is approached and allowed to continue. Consequently, short-circuiting tests that allow tracking of electrowinning parameters before and after short-circuiting were performed in a laboratory scale Cu electrowinning cell. In the tests, the electrode spacing change, the mass of electrodeposited Cu, the deposition morphology, and the current allocation as well as the current efficiency before and after short-circuiting were studied. Results show that the short- circuiting affects the current allocation and the current efficiency significantly. Moreover, it changes the Cu deposition on the short-circuited cathode and therefore causes problems for Cu electrowinning. INTRODUCTION Electrowinning (EW) is commonly used for copper production around the world, with a rated production from 120,000 to 200,000 tons per year per operation (Wiechmann, Aqueveque, Henríquez, Muñoz, & Morales, 2014). In Cu electrowinning, Cu ions in the electrolyte are reduced on the cathode surface as metallic copper with a DC current, while on the anode, a counter anodic reaction occurs with oxygen gas generation (Werner, Zeng, Free, Zhang, & Cho, 2018; Zhang, Werner, & Free, 2018; Zhang, Werner, & Free, 2018). In copper electrowinning, an average current density of 200 to 400 A/m2 is applied to the electrowinning cell (Wiechmann et al., 2014). As the Cu deposits on the cathode, the distance between anode and cathode reduces and most of the time, short-circuiting forms between some anodes and cathodes in a large tankhouse containing thousands of electrodes, reducing the current efficiency and increasing the energy consumption significantly. The current efficiency in well-run copper EW operations is typically above 90 %. Most of the unused current is wasted through short circuits, stray currents, and by-byproduct formation (Davenport, King, Schlesinger, & Biswas, 2002; Wiechmann, Vidal, Pagliero, & Gonzalez, 2002; Wiechmann, Morales, & Aqueveque, 2010). Usually, in the tankhouse, the short-circuiting increases the current in the involved cathode by up to 1500 A (Wiechmann et al., 2010). Multiple reasons can cause the short-circuiting in the cell, and the most common reasons include the uneven current distribution among cathodes, tilted electrodes, bent electrodes, and nodules formed due to the large deposition roughness. Recognition of this challenge in the Cu electrowinning process has led researchers to perform many investigations on approaches to avoid and reduce the short-circuiting in the cell. A series of research investigations have been conducted to develop and improve a new type of intercell bar for Cu electrowinning (Wiechmann et al., 2002; Wiechmann, Morales, Aqueveque, & Burgos, 2007; Wiechmann, Morales, & Aqueveque, 2009; Wiechmann et al., 2010; Wiechmann et al., 2014). The associated test results show that this new design limits the occurrence and magnitude of short circuits and allows operation at higher current densities. Sandoval, Clayton, Dominguez, Unger, and Robinson (2010) stated several keys to control short circuits, such as maintaining the straightness of the cathode, removing “edge hair” from the cathode starter, and maintaining electrode alignment in the cell. Prengaman and Siegmund (1999) from RSR technologies developed a new Pb-Ca-Sn anode to prevent the anode deformation, thereby reducing the short-circuiting in the Cu electrowinning cell. Although the negative effects of short-circuiting on the Cu electrowinning have been recognized, and various investigations have been conducted to address this issue, the actual measurements of the electrowinning behavior and performance as short-circuiting is approached and allowed to continue are seldom reported. However, in typical tankhouses, there is a time between when shorting occurs and harvesting/clearing are performed. One key factor in determining the harvest time is the frequency of shorting. Consequently, we have performed short-circuiting tests that allow us to track electrowinning parameters before and after short-circuiting.

Jan 1, 2019

By Paul Hughes

This paper summarizes current underhand paste backfill mining as applied to Goldcorp Inc?s Red Lake Mine, Newcrest Mining Ltd?s Kencana Mine and the Lanfranchi Nickel Mine as well as ongoing research at the University of British Columbia?s Norman B. Keevil Institute of Mining Engineering. The Red Lake Mine utilises a 6 m wide undercut with a 2 MPa unconfined strength paste in order to selectively mine its high grade, high-stress orebody. Kencana?s orebody is located in a poor rock mass environment. An 8 m wide, 2 MPa unconfined strength paste sill allows a safe working condition for its high grade orebody. The Lanfranchi Nickel Mine utilises a cable-supported, 2 MPa paste, with 12 m span sills, to optimize the mining of the squeezing rock mass. This paper details the rock mechanic hazards, ground support techniques, paste practices and unique conditions for each mine. Further, an update of ongoing research at the University of British Columbia, focussing on the optimization of safe mining in underhand cut-and-fill mining in high-stress/weak rock masses, is presented.

May 1, 2011

By Adrian White

Agenda Overview of pastefill at Kidd Mine Pipeline wear and the need to monitor Steel Loop monitoring Steel Borehole monitoring Monitoring pipe linings

May 1, 2013

By C. J. Van Treeck

PGE concentrations of 18 g/t occur in the pyroxene rich rocks at the Union Bay Alaskantype complex. This PGE enrichment is hosted in magnetite veins. These veins cross magmatic layering and have an irregular morphology in both outcrop and thin section. Fe-Ti oxide geothermometry suggests that this mineralization took place between ~700-400°C. A variation in the amount of ilmenite and Mg- Al spinel exsolution in magnetite correlates with temperature estimates, lower temperature magnetite has less exsolution. Hydrous silicates form an alteration envelope around magnetite veins with a formation temperature of <575oC, vary with temperature, and contain appreciable amounts of Cl. Interaction of a PGE-Fe-Cl rich fluid with clinopyroxene increased the fluids pH and decreased PGE and Fe solubility depositing a PGE enriched magnetite within the Pyroxenites and Olivine Pyroxenites of the Union Bay complex.

May 1, 2003

By R. F. Favreau

"After a blast, the volume of the blasted rock normally occupies more space that it did before the explosion. The degree of such swell significantly affects the efficiency of digging the muck with a shovel or dragline. This paper explains why swell occurs, and describes the new subroutine SWELL of the blast simulator BLASP A which can simulate blast-induced swell. Results are also presented which display the effect of various blasting parameters on the degree and distribution of the swell within the muck pile of a bench blast. IntroductionIt is a common opinion that fragmentation is the most important of the various aspects which affect the efficiency of excavating rock with explosives. This paper proposes that, in fact, displacement and swell of the blasted rock are as important as fragmentation if the excavation process is to be rapid and efficient. It must ""a priori"" be recognized that a minimum degree of fragmentation is indeed necessary. For a given shovel or dragline, this minimum degree of fragmentation may be defined as follows: even the largest fragment of rock must be easily contained within the bucket. Once this criterion is met, however, there are good reasons to believe that displacement and swell take over as the key criteria which influence the rate of mucking, in cubic metres/hour. If the muck pile is not well displaced and swelled, the teeth of the bucket have difficulty penetrating between the rock fragments even if fragmentation is good and, as a result, the mucking is slow and inefficient. The purpose of this paper is to use computer simulations on the model BLASP A to demonstrate the effect of the blast design parameters on the displacement and swell of the blasted rock."

Jan 1, 1993

By L. A. Homeniuk, R. Bonnar

"The Fond-du-Lac uranium deposit is located on the northern rim of the Athabasca Basin. The uranium mineralization is, for the most part, confined to the Athabasca Group, which is underlain by pre-Helikian metamorphic rocks of the Western Craton.The deposit is characterized by a remarkable train of mineralized glacial erratics which led to the original discovery. The mineralization is present as a ""high-grade"" core and a diffuse ""low-grade"" aureole. The ""high-grade"" core occurs as a stockwork of steeply dipping pitchblende veins which strike N 50°E. Hematite, siderite and secondary silicate are also abundant. The ""low-grade"" aureole contains uraniferous goethite, argillaceous material and rare carbon buttons. Recent alteration to coffinite has taken place along the margins of pre-existing ore minerals.The ""high-grade"" core is 390 m long and 10 to 40 m wide, and is surrounded by an irregularly shaped zone of ""low-grade"" mineralization with a similar length and a width of up to 350 m.Comparing the Fond-du-Lac deposit to other unconformity-type deposits, several important differences can be noted:1. Ninety per cent of the ore is above the unconformity, in the Athabasca sandstone.2. The deposit is not associated with underlying graphitic rocks or a major structure.3. The clay-rich alteration zone is not extensive around the Fond-du-Lac deposit.Although there are differences with other Athabasca unconformity-type deposits, the high-grade portion below the unconformity suggests a common origin.The ore deposit is postulated to have been formed from uranium-bearing solutions which entered the stockwork of fractures. Following the reduction in part of these solutions by pre-existing carbonaceous matter and pyrite and/or chemical reaction with pre-existing hematite, deposition continued as a result of decreasing temperature and pressure. Subsequently, minor supergene redistribution of the uranium has taken place."

Jan 1, 1982

Stress induced, gravity-assisted failure processes typically dominate long before stress levels approach the strength of the intact rock (at approximately smax > 0.4UCS where smax = 3s1 ? s3 and UCS is the Unconfined Compressive Strength of the intact rock (Martin et al. 1999)). Under these conditions, discontinuities typically become clamped and the failure process becomes brittle. This brittle failure process is dominated by new stress induced fractures growing subparallel to the excavation boundary. While it is possible to identify areas with the potential for brittle failure, for example, using the general assumption that brittle failure will occur in areas at right angles to the major principal stress (Hoek et al., 1995), when the threshold smax > 0.4UCS is reached in areas around the tunnel boundary, or elastic modelling and the Hoek-Brown brittle parameters proposed by Martin et al., (1999) (i.e. m? 0 and s ? 0.11), amongst others, recent observations discussed by Everitt & Lajtai (2004), and Kaiser (2005; 2006) suggest that brittle failure processes are enhanced when structural features such as joints, weakness zones, bedding planes or foliations are preferentially orientated around the excavation boundary creating stress raisers which in turn facilitate the stress-driven rock mass disintegration process (e.g., as illustrated by Everitt & Lajtai (2004) on Figure 1b). Such weaknesses induce stress heterogeneities that thus promote tensile-spalling failure processes (Diederichs 2000). The observations suggest that stress induced damage can occur ?prematurely? depending on the orientation of micro and macro structures in situations where the known stress conditions should not yet initiate brittle failure processes. In general, when structural features (micro and/or macro), especially foliations, are present in a rock mass, the strength is effectively reduced, largely due to tensile strength heterogeneity in areas depending on the orientation of the structural features with respect to the excavation boundary. As a result, stress induced damage could occur in areas not normally considered due to the influence of anisotropy (Figure 1).

May 1, 2009

By R. Bruce Ferguson

"IntroductionThe Beaverlodge Operation of Eldorado Nuclear Limited is a uranium property located near the north shore of Lake Athabasca about 7 miles from Uranium City, Saskatchewan.The mill is a 2000 tpd carbonate leach operation producing a high grade yellowcake concentrate.The Lamella Thickener was purchased to replace a 55 foot conventional unit which had deteriorated beyond repair. The cost of the unit was considerably lower than for a conventional unit, installation was much simpler and the unit is much more compact allowing it to be installed in the mill basement and be insulated completely.The unit was sized according to the results of tests performed both by the supplier and Beaverlodge engineering staff. The supplier guaranteed overflow clarities of less than 100 ppm suspended solids. The Lamella thickener was developed by A. Johnson Co. of Stockholm, Sweden, is manufactured under license by Parkson Corporation of Ft. Lauderdale, Florida and is distributed in Canada by A. Johnson Co. of Montreal."

Jan 1, 1975

By Paul Harvey

Following initial discovery in 1991, BHP Billiton Diamonds Inc opened Canada?s first diamond mine, the Ekati Diamond Mine TM (Ekati) in the Northwest Territories on October 14th, 1998. Four short years later on November 29th, 2002, saw the opening of North America?s first underground diamond mine - the Koala North mine. Nestled between the original Panda open pit and the new Koala pit which is in the early stages of production, Koala North represents the only underground kimberlite mining venture in arctic conditions outside the new underground mines being developed by ALROSA in the Yakutsk region of eastern Russia. Extensive underground kimberlite mining has been practiced in the Republic of South Africa for much of the 20th century and continues today. Underground mining represents a key component of the long term business plan for the Ekati. As various open pits reach their economic limit, continued recovery of high value ore at depth is dependent upon the ability to productively mine the kimberlite pipes by underground methods. As a function of its location, size, and value, the Koala North pipe is ideally positioned to host the first underground mine at Ekati . In addition to being a production source for the operation, Koala North is designed as a learning mine, from which to gain valuable experience in preparation for the potential mining of other larger, higher value pipes by underground methods in the future. Fortuitously Koala North was available for development so the learnings could be integrated into the Panda mine design prior to completion of the Panda pit. Establishing our first underground diamond mine, and applying the open benching mining method in arctic conditions brings a unique combination of mining challenges together in a harsh climate and remote environment. This paper examines the design and establishment of the Koala North mine. Discussion includes experiences gained from the first year of development, production start-up, and provides a brief overview of our potential underground future at Ekati .

May 1, 2003

By P. K. Gummer

Gold was fir t di covered on the Seabee property in 1947 by the Con olidated Mining and Smelting Company Limited. Acquired by Claude Resource Inc. in 1984, the property is now being explored by Placer Development Ltd . in joint venture with Claude Re ources. Between Augu t, 1985 and March, 1986, Placer completed 54 drill holes, extending the main o. 2 and o. 5 vein y tern to a depth of 1000 feet below surface and di covering two new satellitic gold zone 800 feet west of the o. 5 gold zone. Drill proven and probable geological re erve in four zone ( os. 2, 5, II, 14) to a vertical depth of 1000 feet, are approximately 1,120.000 tons averaging 0.32 oz. Au/ton.

Jan 1, 1986

By B. Garitte, O. K. Mahabadi, P. Marschall, A. Lisjak, H. R. Müller, T. Vietor, G. Grasselli

Numerous research studies have shown that clay rock formations exhibit favourable characteristics for the deep geological disposal of radioactive waste. However, one main concern is that the favourable long-term isolation properties of the intact rock mass could be negatively affected by the formation of an excavation damaged zone (EDZ) around the underground openings. The goal of this paper is to present new rock mechanics insights into the phenomena involved in the EDZ formation and evolution processes in Opalinus Clay, a clay shale currently being assessed as a potential host rock for an underground repository in Northern Switzerland. More specifically, discontinuum-based computer simulations, using a hybrid finite-discrete element method (FDEM) approach, were applied to two case studies considering circular excavations in an anisotropic Opalinus Clay formation. In the first case study, numerical modelling was applied to the HG-A experiment, a long-term in-situ test carried out at the Mont Terri underground rock laboratory to investigate the hydro-mechanical response of a backfilled and sealed microtunnel. A mechanistic analysis of the fracturing processes involved in the EDZ formation was carried out. In the second case study, the long-term effect of the bentonite backfill swelling on the EDZ around an emplacement was numerically analyzed. Overall, the simulation results highlight short-term distinctive rock failure kinematics due to the bedded rock structure, as well as a long-term reduction of the excavation-induced fracture porosity in response to mechanical loading.

Jan 1, 2015

By B. Kruger

The Dundee Precious Metals Tsumeb Smelter has evolved over the last decade to meet the challenges and opportunities brought about by a changing copper concentrate market, technological advances, environmental legislation as well as social and political changes. The paper discusses some of the challenges, successes and lessons learnt through the expansion and modernization of its smelter complex. It considers the details and impact of the transition from slag granulation to that of slag slow cooling as well as the improvement program that was implemented to more than double the refractory campaign life of the Ausmelt furnace from around 6–9 months to 15–18 months. In addition, given the evolving world we live in, it considers the challenges that the smelter faces today, not the least of it being how to remain relevant in an age of digital and other 4th Industrial Revolution disruptions. INTRODUCTION Dundee Precious Metals Tsumeb (DPMT) Smelter is located just outside the town of Tsumeb, in the Oshikoto region of Namibia. It is the largest town in the region with a population of approximately 45,000. The smelter was built in the early 1960s to treat concentrate from the nearby Tsumeb copper mines. Construction of the site was completed in 1962 and the smelter was officially commissioned in 1963 by Tsumeb Corporation Limited (TCL). At the time the smelter consisted of a lead section (including a refinery), a copper section and plants that produced cadmium, sodium antimonite and arsenic trioxide. Production commenced in early 1964, with 3,500 tonnes of copper and 6,000 tonnes of lead being produced per month. TCL was acquired by Gold Fields South Africa in 1988, and a few years later the lead section was shut down due to reduced lead content of the mined ore. In mid-1996, all mining and smelting operations were halted due to labour strikes. Ongopolo Mining and Processing Limited (OMPL) re-opened the mines and the smelter in 2000, only operating the copper section of the smelter. At the end of 2008, all mining operations were halted by the new owner of OMPL, Weatherly Mining International, while the smelter continued to operate. The closure of the Weatherly owned mines in Namibia, the primary feed source to the Tsumeb Smelter, meant that the smelter had to transition its business model from operating as a ‘captive smelter’ to that of a ‘toll smelter’. Its Ausmelt Top Submerged Lance (TSL) smelting technology and various ancillary plants made it especially suitable for accepting and treating complex concentrates that were available on the global market.

Jan 1, 2019

By Henry Smith, Stu Brown

"The Williams Mine is Canada&apos;s largest gold producer, with annual production of some 500 000 ounces of gold from two million tonnes of ore. Highly mechanized and automated underground mining practices are utilized at the property in order to help achieve high levels of productivity and the most cost-effective mining possible.Planning and design parameters for the underground ore handling system at the Williams Mine are described in this paper. Particular reference is made to the considerations that were built into the system to provide maximum operating flexibility through the use of multiple orepass systems, portable low profile jaw crushers, underground conveyors and automated hoisting equipment.IntroductionThe Williams Mine is situated in the Hernlo area of northwestern Ontario, approximately 40 Ian east of the town of Marathon (Fig. I). It is operated by the Williams Operating Corporation, which is owned equally by Teck Corporation and Corona Corporation, and is one of three adjacent properties forming the HernIo gold camp.The mine commenced operation in October 1985 at a nominal production rate of 3000 tpcd. Through an ongoing capital development program, winch was completed in late 1989, the production rate at the property was increased to its current level of 6000 tpcd. This paper describes the mine planning process and the evolution of current mining strategies with particular reference to the underground ore handling system .HistoryGold mineralization was discovered in 1944 in the Hemlo area of Northern Ontario, near the north shore of Lake Superior. A year later, 11 claims were staked over the showing and subsequently patented by the late Dr. Jack Kerr Williams.Over the next 35 years, other claims were subsequently staked, explored and abandoned in the immediate area of the 11 patented claims . In 1980 a predecessor of the Corona Corporation acquired claims adjoining the Williams property to the east. Drilling on this claim group started early in 1981 and intersected the Hemlo orebody in May of that year. In December 1981, Corona Corporation entered into an option agreement with Teck Corporation to explore and develop the property.A drilling program by LAC Minerals on the II patented claims discovered the Williams orebody in March 1982. The mine started production in 1985, pouring its first official bar of gold on December 6 of that year. Corona Corporation was awarded ownership of the Williams Mine conclusively by a decision of the Supreme Court of Canada on August 11, 1989. The court&apos;s ruling ended a legal dispute with LAC Minerals over the property initiated eight years earlier."

Jan 1, 1991

By M. Sheedy

This paper discusses the short bed ion exchange technique for the removal of metal contaminants from copper electrolyte bleed streams. Processes for the selective removal of sulfuric acid, arsenic, antimony, bismuth, and iron will be discussed. A case study outlining the performance history of a short bed system for sulfuric acid removal followed by a two stage selective precipitation system producing a nickel carbonate by¬product at the Phelps Dodge Mining Company El Paso operation will be presented.

Jan 1, 2007

By P. E. Weidmark

"CANMET InformationPART 1-Published PapersAsmis, H. W., ""The dynamic response of caverns in discontinuous rock""; Proc 22nd U.S. Symposium on Rock Mechanics, Cambridge, Mass, June 1981, 272-277; 1981.Austin , M.W., Bray, J.W. and Crawford, A.M., ""A comparison of two indirect boundary element formulations incorporating planes of weakness"" ; Technical Note; Int J Rock Mech Min Sci Geomech Abstr; 19:339-344; 1982.Barrett, J. R., ""Applying geotechnical theory to underground metalliferous mining""; Proc 1st Intnl Conf on Stability in Underground Mining; Vancouver, BC, August 1982; SME of AIMMPE; 210-222; 1983.Barron, K., Wright, P.L. and Smales, T., ""Guideline s for the design of coal pillars in the No .4 seam at Mclntyre Mines Ltd ., Grande Cache, Alberta""; Proc 1st Intnl Conf on Stability in Underground Mining; Vancouver, BC, August 1982; SME of A IMMPE; 559-578; 1983.Bauer, A., ""Wall control blasting in open pit mines""; Mining Engng; 34:155-158; 1982.Bieniawski, Z.T., "" Improved design o f room-and-pillar coal mines for U.S. conditions""; Proc 1st Intnl Conf on Stability in Underground Mining; Vancouver, BC, August 1982; SME of AIMMPE; 19-51; 1982.Blackwell, G.H. and Calder, P.N., ""Practical aspects of wall stability at Brenda Mines Ltd., Peachland, BC""; 3rd Intnl Conf on Stability in Surface Mining; Vancouver, BC, June 1981; SME-A1ME; 3:573-608; 1982.Blake, W., ""Microseismic monitoring for underground stability "" ; Proc 1st Intnl Cont on Stability in Underground Mining; Vancouver , BC, August 1982; SME of AIMMPE; 272-294; 1983.Brawner, C.O., ""Stabilization of rock slopes"" ; 3rd Intnl Conf on Stability in Surface Mining; Vancouver, BC, June 1981; SME-AIME; 3:289-310; 1982.Bridges, M.C., ""Review of open stope mining in Australia""; Proc 1st lntnl Conf on Stability in Underground Mining; Vancouver, BC, August 1982; SME of AIMMPE; 813-828: 1983."

Jan 1, 1983

By Terry J. Briggs, Ian J. Kelso

"Abstract- The Century mine in northwest Queensland,Australia, is a major sediment-hosted zinclead- silver orebody, located within the western Mount Isa Basin. Stratiform, carbonaceous shalehosted mineralization is developed within Proterozoic shale and siltstone sequences of the Lawn Hill Formation. CRA Exploration Pty Ltd (CRAE) discovered the Century deposit in 1990 and open pit mine development commenced in 1998 under the ownership of Pasminco Century Mine Limited (PCML). The deposit contains an identified mineral resource of 105 Mt @ 12.1% Zn + 1.7% Pb + 46 g/t Ag (Broadbent and Waltho, 1998) which is currently being mined at a rate of 5 Mt/y.In December 1998, an exothermic reaction was observed between explosives spilt onto shale drill cuttings from a blasthole. This reaction is referred to as ‘reactive ground’ and has the potential to cause premature detonation of explosives in a charged blasthole with catastrophic consequences. The incident led to a subsequent geological and geochemical assessment of the different rock types at the Century deposit and their potential reactivity with ammonium nitrate-based (AN) explosive products. This assessment was conducted in an attempt to characterize zones safe for blasting with uninhibited AN-based explosive products. A direct result of this study is a set of procedures outlining the use of different AN-based explosives in areas defined as potentially reactive or non-reactive for the different lithologies present. Black shales contained in both the waste and mineralized sequences contain the sulfide mineral pyrite (FeS2), which is thermodynamically unstable with AN contained in commonly used explosives. The potential reactivity of partially weathered pyrite can ultimately result in the decomposition of an AN-based explosive. It was determined that only pyritic black shales showed any potential to react with AN, irrespective of their position in the stratigraphic sequence. Other lithologies present at Century, including Proterozoic sandstone and Cambrian limestone, are classified as non-reactive with AN. This is a geological risk management situation present at the Century mine."

Jan 1, 2001

By Alexandra Kozak, Rodrigo Costa, Bob Fukuhara

"The Jacobina project in Bahia, Brazil commenced operations in 2004 with a design capacity of 4,200 tpd. A project development plan to increase plant capacity to 6,500 tpd will be discussed. The project included an evaluation of the existing circuit and addressed bottlenecks in the crushing, milling, sedimentation, leaching and tailings transport. These circuits and the methodology used to provide higher capacity will be presented.INTRODUCTIONThe Jacobina mine is located in the state of Bahia in northeastern Brazil approximately 330 km northwest of the state capital city of Salvador and 9 km from the town of Jacobina. The Jacobina Mine (Figure 1) is owned by Jacobina Mineração e Comércio, a wholly owned subsidiary of Yamana Gold Inc.The gold mineralization of the Jacobina mine is hosted within quartz pebble conglomerate reefs of the Serra do Córrego Formation which together with the Rio do Ouro Formation forms the Serra do Jacobina mountain chain.The Serra do Jacobina mountains have been mined for gold since the late 17th century. Since the 1970’s, the Jacobina mine has been operated by Anglo American, Williams Resources Inc., Desert Sun Mining Inc. The mine is currently owned by Yamana Gold Inc.In December of 1998, operations at Jacobina were suspended and the property was placed under care and maintenance. Desert Sun Mining Inc. began exploring the property in 2002 and eventually purchased the Jacobina mine in 2003. In 2003, a feasibility study was completed that evaluated the economics of re-developing the mining operations and expanding gold production. In 2004, refurbishment and re-development of the mining operations began and the milling facility throughput capacity was expanded from 1.08 to 1.512 Mtpy (3,000 to 4,200 tpd). The milling operations were commissioned in the 1st quarter of 2005 and commercial production was declared 1 July 2005. In April 2006, Yamana Gold Inc. acquired the Jacobina mine through its acquisition of Desert Sun Mining Inc."

Jan 1, 2008

By W. R. Bacon

"MAGNETITE HAS BEEN found in many .parts of the coastal area of British Columbia, but the more important deposits are on Vancouver Island and Texada Island. The locations of these deposits are shown on Figure 1.Interest in the magnetite deposits dates back to the 1870s, when land was acquired on the southwest coast of Texada Island by the Puget Sound Iron Company. This ground included the Prescott, Paxton, and Lake deposits. During the years 1885 to 1903, and 1908, 28,898 tons of magnetite ore was shipped to the company's blast-furnace plant at Irondale, Washington, U.S.A. This production was almost entirely from the Prescott open-pits.In the years following the Texada Island discoveries, other magnetite deposits were found in the coastal area, and various plans were proposed to utilize the local ores in the establishment of a steel industry in the Pacific Northwest. None was carried to fruition but, in 1951, open-pit mining was begun at Iron Hill, Vancouver Island, to furnish iron concentrates for steel mills in Japan. In 1952 mining of the Texada deposits was resumed to supply the same market. Production figures for these recent operations are as follows:"

Jan 1, 1949

By Daniel J. Schulze

Abstract-Eclogite is an important source of diamond in the upper mantle, but is more localized than peridotite. Using eclogitic minerals in kimberlite and diamond exploration is also more problematic than using the well-known peridotite-derived indicator minerals Cr-pyrope and magnesiochromite. The problems include color similarities between orange garnets from eclogites, Cr-poor megacrysts, and crustal garnets, chemical similarities with Cr-poor megacryst suite garnets (specifically elevated Na2O contents), and low abundance of eclogite garnet xenocrysts in most known kimberlites. Chemical screens must be used carefully to distinguish between varieties of orange garnets in exploration samples. For example, most orange garnets of crustal origin have >22 wt% FeO, with mantle eclogite garnets having lower values. Na2O-bearing garnets from the Cr-poor megacryst suite can be distinguished from Na2O-bearing garnets from diamondiferous eclogites by the elevated TiO2 contents of the former. The low abundance of eclogite garnet xenocrysts in kimberlites worldwide, however, may dictate that use of eclogite garnets in diamond exploration in most cases be restricted to advanced stages of kimberlite exploration and evaluation of kimberlite diamond potential. Crpyropes, Mg-ilmenites and Cr-rich chromites are more useful than eclogitic garnets in most stages of diamond exploration. If orange garnet xenocrysts are sought in a kimberlite exploration program, those from the Cr-poor megacryst suite will be more useful than eclogite derived garnets, due to the typical great abundance of the former, although they carry no information of the diamond potential of the host kimberlite.

Jan 1, 1997