Search Documents

By V. van der Merwe, C. W. Siyasiya

"A petrochemical company experiences premature thermal fatigue failure of the casting moulds used in catalyst production. The aim of the project was to find an alternative alloy that would outperform the current low-alloy cast steel used for the moulds. Based on their thermo-fatigue properties, 3CR12 ferritic stainless steel and H11 tool steel were chosen for testing and comparison with the currently used BS3100 B7 cast steel. Samples of each material were subjected to temperature cycling in a Gleeble 1500TM thermo-mechanical processing simulator, followed by surface analyses. The main parameters derived from the test work were the total true strain, the hot strength of the materials, and the number of cycles to failure. Additionally, the coefficient of thermal expansion for each material was measured using a Bähr dilatometer. H11 tool steel yielded the best performance by way of having the fewest surface cracks, the lowest total true strain per cycle, the most cycles to failure, the highest hot strength, and the lowest coefficient of thermal expansion.IntroductionThe Catalyst Manufacturing Plant (CMP) is a dusty environment with temperatures higher than ambient. Molten mill scale (magnetite, Fe3O4) is tapped from the electric arc furnace into the casting moulds at temperatures close to 1600°C. After 10 seconds the magnetite is quenched with a water spray for 50 seconds to a minimum temperature of 400°C. Sometimes there is residual water in the pans from the cooling fog process (water sprays) in the empty mould. In a typical plant, the factory produces 40–44 batches a day containing between 150–300 moulds, depending on the time required for the specific batch (Buchholz, 2014). The typical batch in the CMP usually weighs about 6 t. The thickness of the tap, speed of the casting belt, and tilting angle all affect the number of moulds per batch.One of the main problems faced during the molten mill scale casting is the premature failure of the casting moulds. Cracks initiate on the surface of the mould, which is in contact with the hot catalyst, and propagate into the interior of the mould. Cracks are generally concentrated in the middle area of the mould where the catalyst makes first contact with the mould, and which experiences the highest temperature fluctuations. This suggests that the cracks are caused by thermal fatigue during the casting process."

Jan 1, 2016

By C. A. Sutherland

"Smelting of copper-gold ore from nearby Rossland mines started at Trail in the 1890s. As ore from the Rossland mines became exhausted, lead smelting offhand-sorted galena orefrom other British Columbia mines was initiated. With the development of flotation technology for the separation of lead, zinc, and iron sulphides in the first two decades of this century, the large Sullivan orebody at Kimberley, British Columbia, became the foundation for the growth of a major zinc and lead smelter at Trail. Lead smelting began in 1901, electrolytic zinc in 1916, and by 1984, the Trail metallurgical complex had produced 10 million tons of each metal. Its present capacity is 270000 tonnes per year of zinc and 110 000 tonnes/year of lead.This paper reviews the history of technological changes in the Trail production plants, emphasizing the zinc plant modernization program started in the 1970s, and also the planned introduction of the QSL oxygen lead smelting process in the late 1980s. Lead modernization will increase production capacity to a maximum of 160000 tonnes per year.IntroductionCopper-gold ore was discovered at Rossland, British Columbia, in the year 1890, starting a mining industry that was to last over three decade s. Selected ore was at first transported at high cost to distant U.S. smelters, so there naturally followed a decision to construct a small copper smelter to process the local ore to matte. It was built in 1896 at the mouth of Trail Creek on the Columbia River, about 10 km from Rossland. This little smelter was to develop and diversify in the next 90 years into the world's largest lead-zinc produce.The mining boom that occurred in the northwestern United States and southeastern British Columbia in the period of 1890 to 1910 saw the brief operation of many small local smelters. The only one to survive was the smelter at Trail. The circumstances that permitted its continued life and subsequent growth, form a fascinating history of business deals, litigation, and steady technical progress.Early investment in local railway transportation and options by F.A. Heinze, the smelter' s founder, attracted the attention of the Canadian Pacific Railway Company, which purchased Heinze' s assets in 1898. This provided the capital base for survival and growth of the smelter, which remained and prospered under the Canadian Pacific umbrella for almost ninety years. It was registered as the Consolidated Mining and Smelting Company of Canada Limited in 1906; in 1966, this name was shortened to Cominco Ltd."

Jan 1, 1988

By R. S. Dean

"INTRODUCTION The metallurgical research program of the Bureau of Mines has been somewhat disorganized, but generally advanced by the increased activities of the war period. The present report is for the purpose of summarizing the work of the Bureau in this field for the past 15 years and indicating its future plan.Fifteen years ago the Bureau turned from its pioneer work on the physical chemistry of steelmaking to an emphasis on raking a pure steel synthetically, rather than by refining, that is, :producing each of the steel 'constituents in the pure state and combining them by simple melting. Such a procedure permits the use of less high-grade ores, not only of iron, but of the ferroalloy metals, such as manganese and chromium,This program has led to extensive work on iron-ore concentration, agglomeration, reducibility of ores and agglomerates, direct reduction of iron ores and concentrates by a wide variety of processes; special refining processes for iron, the production of pure mangenese, chromium, and cobalt from low-grade ores by electrolytic processes, the production of ferrochromium, ferronickel, and ferronickel-cobalt from low-grade domestic ores, and the development of many special alloys to effectively use the new products.The status of the work in each of these fields and the future program of work, together with a bibliography of papers and patents by the Bureau staff on each of these subjects, are given."

Jul 1, 1946

By Edward F. Winter, C. E. Ruoff

A silicon solid-state array image scanner is described. This paper deals with structural and performance properties of the array which basically consists of PIN photo and gating diodes, and low capacitance isolation diodes. Each chip of the array is composed of an 8 by 9 matrix of photo detector cells; each cell contains one each of the three diode types mentioned. This x-y matrix is read a column at a time with an access delay of approximately 100 nsec per column. It is designed to detect the presence or absence of illumination within 10-mil diam image spots located on a 15- by 15-mil grid. Radiant power level of an illuminated spot is low; of interest is the range around I uw with a of 8400g Structural improvements to the original array which will result THE purpose of this paper is to describe the results of a solid state scanner exploratory development activity. The scanner is intended to sense the presence or absence of low-level illumination falling upon a matrix of 10-mil wide squares arranged on a 15- by 15-mil x-y grid pattern. The light of interest has a wavelength of 8400, characteristic of radiation emitted from a GaAs lasing diode. This wavelength matches well the spectral absorption of silicon,' thus the well-developed silicon processing technology can be applied to fabricating large integrated arrays of PIN photocells to sense the radiation. The illumination state of the cells of the array is read, one column at a time, by addressing a drive line of the particular column in question and examining the state of those sense lines which are orthogonal to the drive Lines of in greater sensitivity at various wavelengths, both above and below 8400Å, and in greater speed are presented. These include variations in diffusion depth, resistivity of N and P regions, isolation techniques, and packaging. Trade-offs between access speed, cycle frequency, and sensitivity are discussed. A packaging approach to achieving an array composed of several chips is described. Requirements on this package are: 1) maintenance of 15- by 15-mil pitch of the light sensitive cell position, therefore positional accuracy of mounted 8 by 9 cell photo detector chips; 2) maintenance of inherent high array speed even though signal levels are low through high density close proximity mounting of monolithic sense amplifier circuitry. the array. One bank of N sense amplifiers is required, where N is the number of photodiode cells in each column of the array. CELL AND CHI" STRUCTURE A photograph of a single monolithic cell is shown in Fig. 1. Each cell is composed of three junctions, an isolation junction, a logic or blocking diode junction, and a photodiode junction; all of these junctions are connected electrically by a common N region. An electrical schematic of four cells of the array is shown in Fig. 2 with the associated driver and sense amplifier circuits in block diagram form. Note the common cathode configuration of the three diodes of each cell. Fig. 3, a diagram of the cell vertical struc ture, illustrates how the electrical configuration of

Jan 1, 1970

By J. W. Downey, M. V. Nevitt

MUELLER and Knott' have reported that Ti2Cu has the Si2Mo-type (Cllb) structure. The lattice parameters of Ti2Cu and the positions of the titanium and copper atoms are given by them as follows: ao = 2.944A; co = 10.786A 6 atoms per unit cell: 2 Cu (a) 000; 1/2: 1/2, 1/2 4 Ti (e) 002; 1/2, 1/2, 1/2 + z 00 -2 ; 1/2. 1/2. 1/2- z where z = 0.341 We have found eight other binary compounds which appear to be isostructural with Ti2Cu. All of them involve the combination of a titanium group element with a copper group element or a titanium group element with palladium. The compounds and their lattice parameters are given in Table I. The alloy samples were prepared by arc melting metals having a purity of 99.9 pct or better. They were homogenized for 72 hr at 900°C in evacuated capsules and quenched in tap water. Filings were prepared, and these were reannealed for 4 hr at 700°C, also in evacuated tubes. The lattice parameters were determined by a least squares Bnalysis of the back reflection lines of patterns made with cobalt radiation. It was not possible to make a precise determination of the lattice parameters of Zr2Au because the filings underwent rapid oxidation at room temperature. The evidence supporting the large tetragonal cell containing 6 atoms involves the presence of the reflections 002, 101, 004, 112, 114, 202, and other reflections with higher indices for which I = 3n. Three or more reflections corresponding to these indices, which cannot be indexed on the basis of a small body-centered tetragonal cell containing 2 atoms, are observed in the patterns of all of the compounds listed in Table I. They are strongest and most numerous when the components have large differences in their atomic scattering factors, as is the case in Ti2Pd, Zr2Cu, and Hf2Cu. The values of the z parameter should be regarded as approximate They were selected on the basis of the best agreement between the observed intensities of two pairs of closely spaced powder pattern lines (004): (112) and (114): (202) and the corresponding intensities calculated for several values of z. An ordering scheme was assumed in which titanium, zirconium, or hafnium atoms occupy the titanium positions of Ti2Cu, and copper, silver, palladium, or gold atoms occupy the copper positions. Calculated and observed intensities of the aforementioned lines and the other lines of the patterns are in satisfactory agreement, but a refinement of the z parameters and a final confirmation of the ordering arrangement must await a more detailed study. It is interesting to note that in transition metal systems at A2B stoichiometry the Si2Mo-type structure competes for stability with two other fre-

Jan 1, 1962

By Daniel Mesquita Duarte

A configuração física de equipamento do sistema de desenfornamento do laminador Morgan na unidade Resende, que é preparado para laminação em dois veios, torna o controle de GAP entre barras muito complexo. O sistema de controle original era suscetível a variações, acarretando na limitação do GAP mínimo na entrada do laminador em cinco segundos. Tendo como base as fontes de variação do projeto original, foi desenvolvido um novo sistema de controle que reduziu as variações em até 1700 %, reduzindo o GAP mínimo de cinco para dois segundos. No que tange à questão do GAP mínimo, o novo sistema de controle garante uma tolerância de 0,1 segundo. Este novo sistema pode ser dividido em duas partes: o controle e correção do GAP entre o forno e a primeira gaiola, e a correção de GAP no trem desbastador.

Jul 30, 2018

By G. Cockburn

Nkomati Nickel JV exploits the ores of the Uitkomst Complex near Machadodorp in the Waterval Boven district in South Africa?s Mpumalanga Province. Due to factors such as the remote location, stellar growth in production, opencast mining methods, and ore characteristics, a number of innovative processing options were selected. Nkomati has undertaken numerous initiatives over the last few years to improve plant running times, metallurgical performance, and operational profitability. Great emphasis has been placed on effectiveness of management control systems. A number of initiatives such as short interval control and time?in-state metrics have been implemented. A focus on improvement on availability and asset utilization of key items of equipment has been particularly effective. While the ores are remarkably similar to the Merensky and UG2 reefs, the relatively high base metal sulphide content and mineralogical characteristics make metallurgical treatment somewhat different to the ores of the Bushveld Complex. The low head grades and flotation kinetics distinguish Nkomati from other base metal operations. Numerous milling and flotation optimization initiatives have resulted in dramatic improvements in throughput, recoveries, and concentrate grades. This paper discusses the metallurgical, operational, and management challenges and the outcomes obtained.

Jan 1, 2014

By A. A. Schweizer

Buckhorn ore is hydrous, argillized basaltic andesite, and is at least 60% clay composed of kaolinite and subordinate montmorillonite. Moisture content runs from 10% to 25%. The original crushing plant was a typical compression type, employing a jaw crusher, and two cone crushers. The system was plagued with constant plugging and unable to meet production plans. The three compression crushers were replaced with a Stamler Feeder Breaker followed by a Hazemag Impactor. Production plans are now exceeded. Agglomeration has progressed from an agglomeration drum to cascading conveyors, to introduction of the lime and cement into the primary crusher.

Jan 1, 1987

By V. M. Paretsky

The basic work conducted by Prof. A.Yazawa has demonstrated that in order to ensure single- stage white metal production by autogenous smelting of copper sulfide raw materials, it is most favorable to use highly basic slags, in particular oxide systems CaO-FeO-Fe2O3-SiO2. The special studies have been conducted in the Gintsvetrnet Institute to investigate the composition and structure of slags produced on a semi-commercial scale when testing the KFP and FBP processes for white metal smelting. as well as the slag obtained in a full-scale KFP furnace at the Almalyk copper smelter. The investigations conducted have demonstrated why production of high-grade matte or white metal is associated with lower loss of copper in slag in a series: silicate slag I silicate-calcium slag I ferrite-calcium slag.

Jan 1, 2003

By Jordi Vives-Costa, J. J. de Felipe, Lluís Sanmiquel, Maria Niubó

The article evaluates the convective heat transfer coefficient of ventilation air in a potash mine. The energy balance is obtained through thermal characterization of the ventilation air and rock, allowing for the calculation of heat transfer parameters. Different models for calculating the convective heat transfer coefficient are analyzed. The results indicate that the Pethukov–Kirilov, Gnielinski, and modified Dittus–Boelter models are optimal for this mine. The study also indirectly examines the conductivity of the adjacent rock, suggesting saturation throughout the studied section and the presence of liquid water upwelling in a specific section.

Apr 7, 2022

By Lebeau M., P. Duguay

"The cost of occupational injuries and diseases in the mining industry in Quebec was estimated for the period of 2010 to 2012. The method used takes into account the financial and human costs assumed by employers, workers, and the community. To better direct research and prevention toward issues with the most significant consequences, the results are presented in various ranking tables, which stakeholders might find useful.RÉSUMÉ Le coût des accidents du travail et des maladies professionnelles dans l’industrie minière au Québec a été estimé pour la période 2010-2012. La méthode utilisée prend en compte les coûts financiers et humains endossés par les employeurs, les travailleurs et la communauté. Afin de mieux orienter les recherches et la prévention vers les problèmes ayant les plus graves conséquences, les résultats sont présentés dans divers tableaux de classement, qui seront d’une grande utilité aux parties prenantes. INTRODUCTIONThe mining industry is much safer today than it was 30 or 40 years ago, mainly due to a more qualified workforce, the use of automated equipment, and a corporate culture more focused on occupational health and safety (OHS); however, the number and the severity of occupational injuries and diseases continue to make this industry one of the most hazardous. In the province of Quebec, the mining industry accounts for approximately 0.4% of paid workers but is the source of 4% of fatal work accidents. It is, therefore, important to continue the prevention efforts already underway in the mining industry.The difficult global economy, which has affected the mining industry in the last few years, is an opportunity to reaffirm that sound management of OHS can have a positive impact on companies’ productivity and profitability. Occupational injuries and diseases are costly for the companies concerned and for society as a whole. Reducing their occurrence makes it possible to reduce not only the size of workers’ compensation board contributions but also several other financial and human costs."

Jan 1, 2018

By Johannes Münzer

Regeneradores são elementos importantes em uma usina siderúrgica. Eles são os responsáveis pelo aquecimento do ar de sopro aplicado no alto-forno a partir do aproveitamento da energia contida nos gases do processo de produção de ferro gusa. Dessa forma, os regeneradores estão diretamente associados ao processo siderúrgico. Durante do seu ciclo de trabalho, o qual se denomina campanha, problemas podem ocorrer devido a variações operacionais indesejadas, falhas de projeto, entre outros fatores. Num ambiente onde o tempo cessante de um equipamento gera enormes custos, a solução é desenvolver soluções customizadas que minimizem essa interrupção. Cada uma das partes do regenerador tem funções únicas e consequentemente soluções únicas, que visam o reparo no estado da arte com menor custo.

Aug 17, 2017

By T D. H McGrath, J P. Vaughan, J Heath, J J. Eksteen

A reliable laboratory method to characterise the response of free gold particles when subjected to flash flotation conditions has been developed by AMIRA P420 researchers at Curtin University. This test has been applied to assess the flotation recovery of gravity recoverable gold from free milling ores as well as synthetic ores featuring either a gravity concentrate or gold powder. Trends in free gold flotation kinetics as well as size and milling effects were identified for gold recovery, based on the different gold types, reagent dosage and residence time.CITATION:McGrath, T D H, Eksteen, J J, Vaughan, J P and Heath, J, 2013. Laboratory flash flotation trends for a variety of gold particles, in Proceedings World Gold 2013 , pp 357-366 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By O. M. Bishop

From October 1943 to March 1944, the Bureau of Mines conducted core drilling at the Victory fluorspar mine, Hardin County, Ill. to test the Fredonia limestone and the included sub-Rosiclare sandstone zone beneath the existing stopes. Twenty-one vertical holes were drilled to an average depth of 60 feet. Ore was penetrated in six holes. Since its discovery in 1927, the Victory mine has produced approximately 5 percent of the total fluorspar mined in the United states after that date. The ore discovered in the early mine development is now exhausted, except that contained in pillars drifting to the northeast has partly developed one substantial ore body, and company drilling has indicated another nearby. The increasing need for fluorite for war use in 1943 suggested the desirability of mining the pillars, provided it could be established that no ore beds existed below the stopes or in areas to which access would be obtained through the present workings. This work describes the work accomplished during the project and presents the data obtained.

Jan 1, 1948

By William H. Hallahan

The Friedensville zinc mine of The New Jersey Zinc Company is located about four miles south of Bethlehem, Pennsylvania in the Saucon Valley, an infolded and down faulted block of Cambro-Ordovician carbonate sediments surrounded by hills of pre-Cambrian gneiss and Cambrian quartzite except where breached by Saucon Creek at its entrance into the Lehigh River. The Beekmantown formation of lower Ordovician age is the host for zinc and limonite ores, the former occurring in the lower dolomitic portion thereof and the latter in the upper interbedded dolomite and limestone portion of the section. The Beekmantown is overlain unconformably by the Jacksonburg of middle Ordovician age and according to Miller (2) underlain conformably by about 2500 feet of Cambrian dolomites and 200 feet of the basal Cambrian Hardyston quartzite. Igneous rocks, younger than the Cambro-Ordovician carbonate rocks, are absent in the vicinity of the ore deposits. The major structure is a N60°E-trending saddle-shaped doubly plunging anticline overturned to the north. A syncline lies to the north of the anticline. A thrust fault of substantial displacement repeats the south limb of the anticline. The ore consists of sphalerite and pyrite, along with gangue dolomite and quartz, filling and replacing the sedimentary type matrix of a strata-bound solution collapse breccia in the dolomitic portion of the lower Beekmantown. This breccia was produced in pre-Jacksonburg time as a consequence of uplift, erosion, and development of a karst topography and subsurface drainage system in the Beekmantown. Deposits of both zinc and limonite are present on the vertical north limb, on the crest and on the gently dipping (25°) south limb of the Friedensville anticline; consequently, there is no preferred structural setting for mineralization. Rather this distribution supports the view that the folding is post-ore. Features confirming this view are the development of flow cleavage in the breccia matrix, the deformation of some of the sphalerite, and the fracturing of the pyrite mineralization therein. There is nothing to indicate that the age of mineralization is other than Ordovician and older than Taconic deformation. In the absence of intrusive igneous activity younger than the ore host, the writer suggests that submarine volcanic exhalations associated with the volcanic activity recorded in the eastern eugeosynclinal facies of the Ordovician may be the source of the metal ions.

Jan 1, 1968

By Patrick Wong, Gareth Hatch, M. A. Halim, V. I. Lakshmanan, Darcy Tait

"This paper describes development of an integrated chloride process for separation and purification of REEs. The process includes atmospheric leaching of ore/concentrate with mixed chloride lixiviant containing HCl and MgCl2 followed by bulk recovery of REEs, dissolution of the bulk intermediate product, and separation of individual REEs by solvent extraction (SX) process steps. Mixed chloride leaching technology provides the opportunity to regenerate the lixiviant, while the addition of MgCl2 in HCl enhances the hydrogen ion activity by orders of magnitude increasing REE extraction efficiency at a lower concentration of HCl. An individual REE separation process developed by Innovation Metals Corp. is being piloted at a state-of-the-art facility at Process Research ORTECH Inc. in Mississauga, Ontario, Canada. The SX process includes the separation of light REEs (La – Nd), medium REEs (Sm – Gd) and heavy REEs (Tb – Lu plus Y) from leach liquor followed by individual REE separation. Each SX circuit proceeds by multistage extraction followed by scrubbing and stripping. The process is chloride based and reagents are recycled, reducing waste generation and optimizing water usage to reduce environmental impact.INTRODUCTIONRare earth elements (La to Lu plus Y) exhibit a range of unique magnetic, electronic, catalytic and optical properties. Due to these special properties, the application of REEs is increasing and they are found in components for wind power generation, hybrid electric cars, catalytic converters, and many electronic devices.Rare earth elements (REEs) are commonly divided in two groups: light rare earth elements (LREEs) and heavy rare earth elements (HREEs). Light rare earth elements include elements from lanthanum (La) to neodymium (Nd). Although promethium (Pm) is considered an LREE it is unstable and scarcely occurs in nature and is generally excluded. Heavy rare earth elements include elements from samarium (Sm) to lutetium (Lu) plus yttrium. Although rare earth elements are not rare and the rare earth oxides are scattered around the globe, over 95% of REEs+Y are currently produced in China (Pitts, 2011). On one hand the Chinese government is restricting the export of rare earth elements and on the other hand the demand for REEs+Y is increasing in the rest of the world. This has created an imbalance in the supply and demand of rare earth elements and has led to a rush for developing new rare earth projects."

Jan 1, 2016

By Nathaniel Arbiter

In contrast to pyrometallurgy's 6000year history in metals production, hydrometallurgy is of relatively recent origin. The earliest reference to it was in the 16th century, with the first applications to copper in the 17th and 18th centuries. In the 19th century, increased demands for pure metal resulted in the development of electrolytic refining, and early in this century electrowinning. The rapid growth in copper production in the 20th century, particularly in the United States and Chile, stimulated the development of new technology for leaching and for the recovery of copper from leach solutions. In the past 25 years, solvent extraction has become a major factor by permitting novel leaching technology that produces dilute or complex solutions. In addition, solvents other than sulfuric acid, and chemical methods for precipitating copper metal are now of increasing interest. These are trends that should grow in importance with the need to process lower grade and more complex materials. The evolution of copper hydrometallurgy is reviewed. Key factors in recent major developments are presented with details of specific operations and with trends for the future indicated. The relative importance of copper hydrometallurgy is compared with that of pyrometallurgy in the light of probable changes in ore supplies and character.

Jan 1, 1994

By Martin D. Conyac

A 1984 Bureau of Mines investigation identified ho mineral resources in the Wilderness Study Area (WSA). However, four prospects in the WSA contain anomalous amounts of copper and silver minerals; one had traces of gold. Stratabound copper-silver occurrences appear to be prevalent. Quartz veins in the WSA locally contain trace gold, and one mine adjacent to the area produced some gold in the late 1800's. The WSA is underlain principally by Precambrian and early to middle Paleozoic quartzites, argillites, dolomites and limestones that have been complicated by faulting, generally tilted northeastward, and thrust southeastward over sequences of late Paleozoic sedimentary rocks. The stratabound copper-silver occurrences and gold-quartz veins are in Precambrian and Cambrian rocks in the western part of the WSA, as are similar deposits regionally. Sand and gravel, and limestone are abundant, but plentiful resources of these commodities are nearer established markets. In November 1983 there were 5 small groups of current claims oh the WSA boundary; none are patented claims. Probably less than 35 claims have been located within the WSA, mostly in the northwestern portion; hut over 100 claims have been located outside, near the northwestern boundary. Oil and gas leases nearly surround the boundary and 6 extend up to 1 mile into the study area. There has been no recorded mineral production from within the WSA. From 3 to 5 miles to the west, several lode nines in the Johnnie district have produced several million dollars worth of gold from quartz veins, and some silver and lead from galena-calcite veins. These veins generally trend northeasterly and dip northwesterly and probably do hot extend into the study area.

Jan 1, 1985

By Douglas B. Silver

The key to unlocking value is to find opportunity where others have missed it. How does a company find value in a thoroughly explored asset? This article explores the approach taken by one company and the results it achieved from working this problem. The town of Shafter is located on a small bend in the road in west Texas' Big Bend Country. Its past emulates the glory days of so many other mining camps. A discovery was made, fortunes were built and World War II shut down the operation. The Shafter deposit continues to be one of the larg¬est undeveloped primary silver deposits in North America. Gold Fields Mining Co. recognized the area's potential in 1977 and embarked on studies to reopen and develop the district. Gold Fields spent $16 million on the Shafter project. It drilled more than 86,240 m (282,940 ft) in 475 holes, sunk two shafts and developed 1,550 m (5,100 ft) of underground workings. Today, the mothballed 447-kW (600-hp), single-drum Nordberg hoist and permanent production-type, single-compartment headframe continue to crown the shaft. Other buildings onsite house compressors, mine pumps, spare parts, drill core and other supplies. All these items look as though they arrived yesterday. By 1982, Gold Fields had completed an extensive feasibility study with ambitions to. construct a 1.36-kt/d (1,500-stpd) agitated cyanidation mill and base metal gravity circuit. Reserves at Shafter stand at 4.23 Mt (4.67 million st) grading 193.5 g/t (5.65 oz/st) silver. Gold Fields planned to produce 71.5 t/a (2.3 million oz/year) of silver at a head grade of 196.2 g/t (5.73 oz/st) silver with a 77% recovery rate. Cash costs were projected to be $5.54/oz with an anticipated initial and total capital cost of $46.2 million and $51.3 million (1984 dollars), respectively. The study assumed a silver price of $8.60/oz that has not been seen since the Hunt brothers quit buying silver. When silver prices declined, Gold Fields put the property up for sale.

Jan 1, 1999

By T. Serradj

A study has been carried out to: develop a method for routine characterisation of rock strength and drillability through the particle-size distribution of crushed or drilled rock products, defined by the Protodyakonov index; establish correlations between the Protodyakonov index, uniformity coefficient and the constant grading equations; and propose an alternative rock characterisation index to classify rock strength and drillability for the northeast region of Algeria

Dec 1, 1996