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By Aguirre E, Chitombo G

The magnitude of stress variations associated with a blast wave near production pillars is analysed by modelling blast vibrations measured in the surrounding rockmass. The results indicate a wide variation in stress which is thought to contribute to the observed damage in pillars adjacent to the draw points.

Jan 1, 1995

By Blattner P

The Late Miocene gold-silver bearing epithermal system at Waihi has some close similarities in its paleo-thermal and -geochemical structure with modern, volcanic-hosted geothermal systems such as Ohaaki-Broadlands. At Waihi an extensive braided quartz vein system is enveloped by hydrothermally altered andesites with minor tuff breccias and tuffs. A main stage of vein filling consists of multiple phases of chalcedonic quartz and fine to medium grained quartz, which are accompanied by pyrite, sphalerite, galena, chalcopyrite and acanthite below the base of oxidation. Platy calcite is present locally. Fluid inclusion studies indicate that the main stage quartz was deposited at temperatures of 189¦-273¦C from dilute (T¦ of -0.1 to -1.0¦C) fluids that were locally boiling. Homogenisation temperature Th versus T. data points lie within the field enveloped by dilution and boiling/gas loss paths determined for the Ohaaki geothermal field, and indicates that the parent hydrothermal fluid for the Waihi epithermal system had a similar composition to that at Ohaaki, ie 0.2 wt% equiv NaCI and 3.3 wt% equiv CO2. The hydrothermal alteration mineralogy and the isotopic composition of vein calcite indicate that the hydrothermal fluid contained relatively high concentrations of CO 2' as at Ohaaki. Oxygen isotope analyses of main stage quartz range from 6.1 to 11.6 %o and of vein calcite from 2.29 to 9.4% . Calculated d8Ow.½ values for the hydrothermal fluid that deposited the main stage quartz range from - 2.0 to -5.7%c , with a trend to less negative values with depth. They are similar to those in the deep chloride fluid in active geothermal systems with a substantial fluid throughput. A high fluid throughput at Waihi system is also evident from the extensive high intensity hydrothermal alteration and large volume of quartz deposited in the vein system.

Jan 1, 1995

By W. M. Haffner, S. L. Borek, H. M. Edenborn, R. W. Hammack, D. H. Dvorak

The conceptual designs of three new applications for the biogenic &S treatment of metal- containing waters are presented. These include: 1. the treatment of a circumneutral-pH ground water containing Zn and Cd using limestone as an alkalinity source, 2. a two-step treatment process where toxic heavy metals in contaminated ground water are recovered separately from nontoxic metals to lessen disposal costs, and 3. a copper recovery process that may be a low-cost alternative to solvent extraction/electrowinning or cementation for dilute copper leach liquors. Preliminary results of initial field testing are discussed

Jan 1, 1995

By J. Robitaille, P. Cousin

"Agnico-Eagle Mines Ltd, Laronde Division, is a gold operation processing ore containing copper and zinc. Copper is recovered as a concentrate prior to gold cyanidation.Copper concentrate grade was improved with the implementation of an on-stream analyzer. Further improvements to the copper concentrate grade could be achieved throughefficient zinc depression.High cyanide cost linked to the copper content in the flotation circuit tails, prompted some modifications to the flotation circuit. Economics and environmental issues were considered. A Maxwell cell was retrofitted with an Outokumpu HG cell mechanism stabilizing it's operation. Secondly a flotation column was added to increase circuit capacity.This paper will address flotation circuit operation difficulties, successes and results achieved before and after modifications.RESUMELes Mines Agnico-Eagle division Laronde sont considéré comme étant un producteur d'or. Le minerai révèle toutefois des teneurs appréciables en cuivre et zinc. Un circuit de traitement combinant des étapes de flottation du cuivre et de cyanuration de l'or a été adopte. Le rejet de la flottation est lixivie pour son contenu en or.La teneur moyenne en cuivre du concentre final fut augmentée suite a l'implantation d'un système d'analyse en continu. Une séparation plus efficace de la sphalérite se devra d'être obtenue afin d'améliorer davantage la qualité du concentre produit.Le contenu en cuivre au rejet du circuit de flottation influence directement la consommation en cyanure. Pour cette raison, certaines modifications à la flottation sont devenues nécessaires. Des facteurs d'ordre économique et environnemental ont été considérées. Une cellule existante fut transformée en cellule HG d'Outokumpu, stabilisant son opération, et une colonne de flottation fut ajoutée au circuit afin d'accroitre sa capacité.Le présent document se veut une rétrospective des problèmes d'opération vécus, des solutions apportées ainsi que des résultats obtenus et de leurs implications suite aux améliorationseffectuees."

Jan 1, 1995

By Patrick Linzer

The majority of existing models describing (methane) gas transport within, and liberation from, coal structures treat these as continua wherein two main gas flow modes (diffusive and Darcy permeable) prevail, and use finite difference techniques to generate solutions to the resulting multivariate parabolic partial differential equation(s). Isotropy and homogeneity in the physical and geometric coal structure properties are often assumed, and the existence of fundamental random fluctuations in these proper- ties is not catered for. The model proposed herein does not suffer these inadequacies, and its efficiency is enhanced by the replacement of the diffusion equation by an accurate approximation. Dynamic mining activity, gas contributions made by the geology surrounding the mining seam, goafing of overlying strata and the effects of induced strain are all taken into account.

Jan 1, 1995

By William K. Tolley

The U.S. Bureau of Mines (USBM) is investigating hydrometallurgical processing techniques to recycle metals from semiconductors and other advanced materials. Cadmium and tellurium were recovered from mixed CdTe/CdS scrap produced in the manufacture of thin-film photovoltaic devices. Cadmium and tellurium dissolution was achieved using hydrogen peroxide in dilute sulfuric acid. Leaching the scrap in 2.2 N H2SO4 yielded 99% Cd extraction and 98% Te extraction. Sulfur remained in the leach residue primarily in the elemental form. Elemental tellurium was precipitated from the leach liquor by adding Na2S2O5. Cadmium sulfate was recovered by evaporation. A preliminary process evaluation suggests that the process may have economic potential. Alternative recovery schemes are discussed.

Jan 1, 1995

By Irwin R. Higgins, Joseph C. Milbourne

The selection of a suitable nitrate removal process depends on a variety of site-specific chemical and environmental issues. The dominant technologies for nitrate removal include biological denitrification and continuous countercurrent ion exchange. The decision to apply either of these technologies, or both together, depends on the nature of the waste water to be treated. Factors that affect the selection of the biological system include the feed composition and feed temperature. Ion exchange nitrate removal systems ere less sensitive to the feed composition but require disposal or destruction of the concentrated pregnant eluate. The paper discusses Tetra's continuous countercurrent ion exchange technology (CCIX™) and fixed film biological reactor, Denite®. The treatment of the ion exchange pregnant eluant is also discussed.

Jan 1, 1995

Mining has long been an important activity for the people of Australia. The Aboriginals used rocks and minerals in their culture many thousand years before European settlement. It was not until 1840 that silver-lead ore was discovered in the Mount Lofty Ranges, and developed as Australia's first metalliferous mine.

Jan 1, 1995

By T. J. Close

The Silver Peak Range North Wilderness Study Area was deleted from the list of US Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the US Bureau of Mines mineral investigation of the wilderness study area which found indications of precious- and base-metal-resources. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Bureau examined 13 mineralized sites, most of which were previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak mining district to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz and calcite with gold, silver, and base-metals. At the surface, these veins are poorly defined. Exposures of the more than forty veins examined were as thick as 17 ft and as long as 1000 ft. Samples from these veins contained significant amounts of precious- and base-metals-as much as 0.02 oz per ton gold, 2.1 oz per ton silver, 1.0% copper, 2.6% lead and 0.4 % zinc. No vein large enough or of high enough grade to be classified a mineral resource was disclosed by the sample data. However, most do have indications of precious- and base-metal-resources at depth. Subsurface exploration of some of the veins is recommended.

Jan 1, 1995

By P. Mottahed, J. Ran

Mining practice and research have shown that the jointed roof in stratified rock behaves like a voussoir beam structure with strength greater than that determined by the continuous beam theory. Previous studies have demonstrated the voussoir beam mechanism and developed methods to estimate the crushing and buckling strength of voussoir beams. However, research on voussoir beams with multiple mid joints has not been suffICient and problems such as the voussoir beam support and applications of the voussoir beam mechanism to the mining environment have not been addressed. In this paper, mechanism of voussoir beams containing multiple mid joints and truss support are studied and applications of the voussoir beam mechanism to underground mine openings are discussed based on the numerical and experimental results.

Jan 1, 1995

By Steve Kral

Philip M. Hocker is president of the Mineral Policy Center (MPC), a Washington, DC-based, non-profit organization formed to "address the environmental problems that are caused by mineral development in both the hard-rock mining and onshore oil arenas." Hocker has been involved with resource development and environmental policy issues since the 1970s. He has been a plaintiff in several lawsuits regarding environmental management of federal onshore oil and gas leasing. He was also active in the 1987 campaign to pass the Federal Onshore Oil and Gas Leasing Reform Act. Hocker served on the board of directors of the Sierra Club from 1980 through 1986. He is also a member of SME and spoke at the welcoming luncheon and keynote session of the SME Annual Meeting and Exhibit, Feb. 14, 1994, in Albuquerque, NM. In his role as president of MPC, Hocker has become a major player in the ongoing battle concerning mining law reform. And, while the mining law issue is the most visible and controversial issue confronting the mining industry and MPC, Hocker's organization is also active in clean water reform and other public policy issues that concern natural resource development and the environment. Hocker and MPC invoke a wide spectrum of reactions from the mining industry, most of it negative. Even so, the editors of ME decided that SME members should hear from Hocker his views on domestic mining, including mining law reform, clean water legislation and other environmental issues facing the industry.

Jan 1, 1995

By William D. Cassity, Batric Pesic

Introduction Gold mining on an industrial scale is becoming increasingly dependent on low-grade refractory sulfide ores that contain large amounts of pyrite (FeS2) and arsenopyrite (FeAsS). Gold is usually present as sub-microscopic particles dispersed evenly throughout the sulfide matrix. Without some form of preoxidation, efficient recovery of this finely disseminated gold through cyanide leaching is hampered because the surface of the sulfide particle becomes passivated and impervious to penetration of the cyanide. Traditional methods for recovery of refractory gold from arsenopyrite ores include roasting and autoclave leaching. A modem alternative method is to preoxidize the mineral using the bacterium Thiobacillus ferrooxidans prior to attempting to re- cover the gold through cyanidation. The bioleaching of arsenopyrite ores presents a problem in the mobilization of large quantities of arsenic, present both in the +5 and +3 ionic states. Dissolved arsenic species pose a dual problem: they are -1 to the bioleaching process itself through inhibition of bacterial activity, and they also pose an environmental threat. The arsenate anion (AsO2) has been shown to be more toxic to living organisms, including Thiobacillus ferrooxidans, than the arsenate anion (AsO43) (Collinet and Morin, 1989). There is some disagreement as to the fate of arsenite in bioleaching solution. Mandl, Matulova, and Docekalova (1992) reported that dissolved arsenite concentration was constant during a long-term bioleaching study of chalcopyrite using Thiobacillus ferrooxidans. Torma and Oolman (1992) report that Thiobacillus ferrooxidans has been found capable of oxidizing As3+ to As5+. The solid products of arsenopyrite/pyrite bioleaching include jarosite (MFe3(SO4)2(OH)6 where M can be K+, Na+, NH4+ or H3O+), scorodite (FeAsO4.2H2O), ferric hydroxides, and ferric hydroxysufites (Carlson et. al., 1992; Van Breemen, 1982; Lazaroff et. al., 1982). The particular species formed is a function mainly of pH. Little study has been performed on the effect of solid products on bioleaching. Pesic and Kim (1993) showed that Thiobacillus ferrooridans cells served as a nucleation sites for jarosite particles, which grew rapidly and eventually killed the cell. Most bioleaching studies are performed at low pH&apos;s (<2.0) under uncontrolled conditions. By studying bioleaching of arsenopyrite under controlled pH conditions and at higher pH&apos;s (2.0 to 3.0), the distribution of iron and arsenic between the solid and liquid phases can be controlled, and their effects studied. The objective is to develop a bioleaching process that operates at high efficiency while keeping amounts of dissolved heavy metals low. Pesic, Stohok, and Torma (1993) demonstrated the usefulness of this approach in the leaching of cobaltite (CoAsS) concentrates. Materials and Methods The focus of this study was the bioleaching of arsenopyrite ore by Thiobacillus ferrooxidans. The parameters studied included the effects of pH, and the effects of arsenate (AsO43 and arsenite (AsO2). pH studies included pH set initially but not controlled, and pH controlled continuously with NaOH or LiOH. Bioleaching results from two strains of Thiobacillus ferrooxidans with different adaptation histories were compared. Bioleaching experiments were conducted in 150 ml stirred glass reactors using a strain of Thiobacillus ferrooxidans adapted to arsenopyrite ore, supplied by the U.S. Bureau of Mines. These bioreactors were innoculated with stock cells grown on arsenopyrite ore for 14-16 days. Typical elemental breakdown for this ore was: As, 9.90%; Fe, 18.60%, Stot, 9.26%; Suifide, 7.50%; SiO2, 25.90%. Mineralogically, the ore contained both arsenopyrite and pyrite. Bioleaching efficiency was measured by withdrawing bioleach solution samples at selected intervals, filtering, and measuring the amount of dissolved cobalt, iron, and arsenic by atomic absorption spectroscopy. Because the precipitation of iron and arsenic at higher pH&apos;s would lead to unreliable results, a 100 mg tracer of cobaltite concentrate from the Blackbird mine in southern Idaho was added to solution. Dissolution of the cobaltite tracer was used to indicate bioleaching of the bulk arsenopyrite ore. Cobalt has been shown to be stable in solution even when iron and arsenic were precipitated (Pesic, Storhok, and Tonna, 1993). The pa-

Jan 1, 1995

By Parr JM, Scott SD, Herzig PM, Gemmell JB

PACMANUS is an actively-forming seafloor analogue of volcanic-hosted massive sulfide orebodies, situated on the crest of an andesite-dacite-rhyodacite ridge overlying rifted older arc crust in a back-arc basin. Hydrothermal deposits range from Mn-oxide crusts to Cu-Zn-rich massive sulfide mounds and chimneys containing significant Au and Ag. Preliminary data suggest a substantial magmatic component to fluids and metal sources, and we speculate that PACMANUS is the cap to a complete hydrothermal system including subvolcanic and intrusive-related mineralisation.

Jan 1, 1995

By Michael L. Sorokin

The metallic nickel production by converting of nickel matte is analysed from the thermodynamic point of view using earlier developed thermodynamic models for sulphide, metal and slag phase. Three-suffix Margules equations are used to calculate thermodynamic properties of melts. Potential diagrams of Ni-FeS-OSiO2 system are calculated for various temperatures and Fe to Ni ratios. The diagrams used for consideration about possibilities of the direct one-stage metallic nickel production.

Jan 1, 1995

By S. Mathur

Future Florida phosphate reserves contain higher MgO than presently mined deposits. The high MgO content is contributed by dolomite and Mg-rich clay, palygorskite. Selective flocculation was attempted to reduce the MgO content of apatite in synthetic mixtures of apatite with dolomite and palygorskie. Mixed mineral selectivity was predicted in the apatite-dolomite and apatite- palygorskite systems with Poly(ethy1ene oxide) (PEO) flocculant. Loss of selectivity in the mixed mineral systems was primarily attributed to heteroflocculation, which was minimized by addition of a Site Blocking Agent (SBA), a lower molecular weight fraction of PEO, prior to addition of the flocculant. A 80:20 mixture of apatite-dolomite (or palygorskite) was upgraded as 95% apatite at more than 80% recovery level in the product fraction.

Jan 1, 1995

By K. Hanumantha Rao, K. S. E. Forssberg

The limestone deposit of Gâsgruvan, Sweden contains around 89.2 per cent of calcite. Conventional and column flotation studies have been carried out using sodium oleate and modified fatty acid collectors in the presence of sodium silicate modifier. The effects of collector and silicate concentrations, and particle size on the flotation response of calcite have been investigated. The results have been discussed in comparision to the performance of conventional and column flotation cells. The feed size is found to be a significant factor to achieve a high grade calcite concentrate either by conventional or by column flotation. The loss of selectivity at fine particle sizes is examined using a modified DLVO theory.

Jan 1, 1995

By Denis M. Riley, Neville C. Lockhart, Bruce A. Firth

The potential use of the Kelsey Centrifugal Jig to clean fine coal has been studied. It was found capable of cleaning coal at very fine sizes, at least to 0.038 mm at relative densities as low as 1.6. This effect was however very dependent upon the solids feed rate and the absence of significant amounts of clay slimes. Comparisons with a spiral and a laboratory scale Jameson Flotation Cell were made. The concept of recleaning spiral product was investigated. Use of a spiral to reclean the coarse fraction, and a centrifugal jig or flotation to treat the fine fraction, gave significant improvements in final ash values over spiral recleaning of the full size. Future R&D needs include improving feed rate capacity, and application to problems like pyrite removal that are difficult to solve via flotation.

Jan 1, 1995

By Andrew P. Jarosz

The present computerized mine planning systems use CAD-like and Data Base Management System (DBMS) environments for the handling of numerical, textural, and graphical data. These two environments are usually integrated, that the data provided by the DBMS are linked to any graphical element rendered by the CAD system. The subsidence monitoring, analysis and prediction process should be integrated with the mine design process. It should allow for the assessment of impacts of mining on surface, surface utilities, and structures. It should also provide for the measures to control mining, that will create only acceptable levels of negative impacts on the surface. The common data base, and graphical capabilities of the CAD interface, may be used with great advantage for both systems. The findings of the subsidence engineering modulus should be directly incorporated into the mine design system, and vice versa. In this paper the author suggests guidelines for the development of the comprehensive computer system, able not only to predict the vertical and horizontal components of the ground movement, but also assess the induced surface damages, and costs related to subsidence prevention and compensation.

Jan 1, 1995

By J. T. I. Poijärvi

Outokumpu Harjavalta Metals Oy operates copper and nickel smelters, three sulphuric acid plants and nickel refinery at Harjavalta and copper refinery and precious metal plant at Pori. The by-products of these plants are presented in this paper. The by-products of the smelters include products from slag cleaning of flash smelting furnaces and converters, flue dusts and smelter off-gases. Weak acid and sludges from cleaning of smelter off-gases and acids are the by-products of the acid plants. The by-products out of the copper refinery are crystallized metal sulphates and sludges from electrolyte purification, on which a co-production process of the copper tankhouse is based. The main by-products of the precious metals plant are products from anode slime treatment and platinum metal group concentrates in the recovery of precious metals. Sludges from nickel matte leaching and precipitates from solution purification are the by-products of the nickel refinery. The formation, treatment and processing as well as the research work done for the utilization instead of dumping of the by-products in the production of copper and nickel will also be discussed in this paper.

Jan 1, 1995

By A. Rosenfeld

The feasibility of applying laser induced optical emission spectroscopy to the high speed sorting of mixed alloy aluminum scrap is investigated. The basic spectroscopy for analysing aluminum alloys for the major alloying elements over their full concentration ranges is established. Materials handling issues are also described and the components of an overall sorting system are presented.

Jan 1, 1995