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By Wang S

Fragmentation is the basic concern in rock blasting and serves as the main measure of blasting effectiveness. A good estimation of fragment size distribution before blasting is very useful and helpful for selecting the proper equipment for loading, transporting, and crushing rocks. A fragmentation model is presented that is based on a hole by hole analysis and correlates the rock properties, burden, spacing, and explosive column with the blasted volume and fragmentation obtained. The drill bench is divided into three separate areas corresponding to different breakage mechanisms. They are: 1) a main breakage or casting area, 2) a secondary breaking area, and 3) an overbreak area. The boundary of the main breakage area is found from the magnitudes of strains in the stress waves and the tensile strength of the rock. The secondary breaking area is determined by stress wave reflections at discontinuities and interactions between colliding stress waves from adjacent boreholes. The overbreak area is that beyond the main breakage area "where the reflected tensile waves no longer break the rock. This analysis is applied on a hole by hole basis to locate the breaking points. Then connecting the breaking points on each side of a borehole forms the triangle of the main breakage area. This is repeated for the next hole and the remaining area is the secondary breakage area. After the angle and area for each hole are found the Kuz-Ram model is used to predict the fragmentation size distribution for each hole. Then summing up the size distribution for each hole gives the total fragmentation distribution. This analysis has been successfully applied to field tests performed in a limestone bench where the entire spoil pile was screened to determine the fragment size distribution. Knowing the explosive and rock properties the breaking area was found for each hole, the strain and stress values, the breaking point, and angle of breakage (104 degrees). The fragmentation size distribution was then calculated and compared to the field data with excellent agreement.

Jan 1, 1990

Tholeiitic metabasalts comprise at least five geochemically distinct mafic volcanic associations of Late Palaeozoic age within the Gympie Province, southeast Queensland. Geochemical features indicate that parental magmas of the various metavolcanic suites were generated in contrasting tectonic regimes, although each of the suites shows some affinities with eruptives from convergent plate margin settings.Basalts from the Highbury Volcanics of the Gympie Group are island arc tholeiites (IAT) formed during an immature stage of eruptive activity in an intra-oceanic arc. They are unique among the analysed metabasites in possessing high Zr/Nb (Zr/Nb - 30) and very high Ba/Nb, and as well as low Ti/V, Ti/Zr and Ti/Y. These features are explicable solely in terms of contributions from a depleted, convecting upper mantle source, and large ion lithophile element (LILE) enriched fluids ascending from subducted oceanic crust.

Jan 1, 1990

By D. L. Jones, S. Knoerr, J. Mansanti

The Buckhorn Mine in Nevada currently treats oxide ore using heap leach methods, but exploration has identified sulphide reserves which are refractory in nature. Preliminary testwork was conducted on the sulphide material to screen potential pre-cyanidation treatment methods. Processes evaluated included pressure oxidation, biological oxidation, nitric acid oxidation and roasting. An initial economic and process analysis of the results concluded that roasting was the only viable process, and only if the roaster off-gases were converted to soleable sulphuric acid. Further economic analysis indicated that roasting of the whole ore was more attractive than pre-concentrating by flotation, followed by roasting of the concentrate. These results were generalized to show that for high sulphur ore a roaster/acid plant combination is more attractive that either of the other options, ie. pressure leaching or bioleaching, provided the by-product acid is soleable.

Jan 1, 1990

By Dennis Peterson

INTRODUCTION The business arena has dramatically changed for most producers and consumers of commodities. International debt, currency shortages, political upheavals, etc., require corporations today to be sophisticated and flexible enough to change their purchasing and sales techniques in order to maximize returns. Many external factors, such as interest rates, trading partners, currency changes, and government edicts, can have an adverse effect on a company's bottom line. Totally out of a company's ability to control or predict, these. factors force the commodities based corporation to constantly re-evaluate its operating scope and domain. The principle of back-yard only operations and the laissez-faire with blinders style of management is no longer a viable way to run a business. The industrial world has been operating for the past 10 to 15 years as though there were no commodity nor raw material crisis. For developed countries the primary products sector has become marginal, whereas it was central in the first half of the century. A radical change in the method of doing business is necessary to offset a depression in the industrial economy. The risk of collapse may be heightened by a banking crisis caused by massive defaults on the part of commodity producing debtors, whether in the third world or in our own farm producing sector. The raw materials economy has become divergent with the industrial economy. This is a major change in the world economy with tremendous implications in both developed and developing countries for economic and social policies and economic theories. Basic competition issues, such as low labor costs, are likely to become less of an advantage in international trade. In developed countries these costs are going to account for a smaller portion of total costs. The total costs of automated processes are lower than those of traditional plants with low labor costs. Automation in the commodities sector eliminates the hidden but high cost of not processing at capacity created by poor quality, rejects and maintenance for product change-overs. The cost of capital will become increasingly important in international competition. Over the last ten years the U.S. has become the highest cost country in this area. Reversing the U.S. policy of high interest rates and costly equity capital should be a priority for management decision makers. In the rapid industrialization of this century, Japan developed by exporting raw materials, (principally, silk and tea), at steadily increasing prices. Germany developed by leap frogging into the high-tech industries, mainly in electricity, chemicals and optics. The United States did both. Both avenues are blocked for today's rapidly industrializing countries because (a) the deterioration of the terms of trade for primary products, and (b) it requires an infrastructure of knowledge and education far beyond the scope of a poor country. Many explanations exist for the explosion of international money flows. The shift from fixed to floating exchange rates in 1971 may have given initial impetus by inviting currency speculation. The surge in liquid funds flowing to petroleum producers after the oil shocks of 1973 and 1979 was definitely a major cause. There can be little doubt that the U.S. government deficit also played a big role. The American budget deficit has become a massive void, sucking in liquid funds from all over the world and making the U.S. the world's major debtor country. In reality, a trade and payments deficit is actually a loan from the seller of goods and services to the buyer, that is, to the U.S. From now on, the global ramifications of business will have to be treated in economic theory and business policy alike. Economic theory teaches that the comparative advantage factors of a real economy determines operative and financial policy. These comparisons -- labor costs, productivity, raw materials cost, energy costs,

Jan 1, 1990

By M. Waladan

The top submerged lancing Sirosmelt system has been developed through laborator.y scale testwork and pilot plant trials for recovery of zinc from ISF slag. The effects of the process variables of gas injection rate, method of coal feeding, and temperature on zinc fuming rates were studied in the laboratory. It was found that the rate of zinc elimination was dependent on all of these variabl.es. The rate of zinc removal from slag was independent of zinc content of slag down to approximately 1.5% Zn, below which the rate was proportional to zinc content in slag. Pilot plant trials were carried out to evaluate a proposed process and results followed predictions from the laboratory scale tests. A comparison of the proposed process with conventional slag fuming operations is made and it is shown that the process has a number of advantages which have a significant impact on the economics of zinc slag fuming.

Jan 1, 1990

By Jean-Marc Simard, Richard Genest

"La mine Agnico-Eagle, localisée près de Joutel, a été découverte en 1962 par le forage d'anomalies électromagnétiques. Exploitée à partir de 1974, elle a déjà produit près de 30 tonnes d’or à partir de 2 puits, le puits Eagle et le puits Telbel, distants de 1,3 km.Le gisement est situé entre le sommet du complexe volcanique de Joutel, à dominante felsique, et la base de l'ensemble sédimentaire de la rivière Harricana. Ces deux unités ont une extension régionale; elles sont orientées NW-SE avec une polarité NE et des pendages subverticaux. Une faille majeure, la faille Harricana, passe de façon subconcordante au contact de ces deux ensembles.La minéralisation aurifère, de 2 à 5 m d’épaisseur moyenne, est liée a une zone carbonatée, comprise entre des tufs felsiques, argilites et sédiments chimiques (éponte inferieure) et des argilites carbonatées (éponte supérieure). Le minerai est constitué habituellement de 20% de fine pyrite disséminée. L’or est en fines particules associées directement à ces grains de pyrite de texture cataclastique.Deux modelés ont été for mules jusqu' a présent pour expliquer la genèse du gisement: une thèse syngenetique (Barnett et a/.1982) et une thèse épigénétique (Wyman et al. 1986). Cette dernière apparalt comme la plus probable du fait de la présence de la minéralisation dans les zones cisaillées a carbonates secondaires et pyrite cataclastique."

Jan 1, 1990

In accordance with the new concept described in the paper presented at the TMS annual meeting in 1989, 1 a new zinc cellhouse was constructed and successfully operated. The new concept was proposed in order to reduce energy requirements and to mechanize the electrode handling in the cellhouse. Major modifications involved the use of an electrode unit consistfog of assembled anodes and cathodes with frame bodies between each cathode and anode. The space between a cathode and an anode could be halved by this unit structure. In this paper actual operation data are summarized and discussed in comparison with the calculated figures.

Jan 1, 1990

By Marie-France Caille, Carl Caumartin

"Audrey Resources' Mobrun Mine is located in Dufresnoy Township some 30 km to the northeast of Rouyn-Noranda. The Mobrun tine deposits consist of two major massive sulphide lenses; the newly discovered 1100 lens located 450 m south of the Main zone, and one ntellite lens, the 850-870-930 complex.The 1100 lens is hosted in a large pyroclastic unit bounded to the mouth by rhyolite and andesite flows and by a thick rhyolite unit to the art h. stratigraphically belon the three lenses. It consists of approximately 15 Mt of massive sulphide, of which 10.4 Mt are of economic ade. The Main lens lies comformably above thick rhyolite flows, ecciated and pyritized by the sulphide horizon, and is overlain by ttercalated ash tuffs and rhyolites which host the over-lying satellite ns. The Main lens consists of 3,3 Mt of massive sulphide, of which 523 000 tgrade0.80% Cu, 2.44%Zn,30.19 g/t Ag, and2.2 g/t Au he richer satellite lens (180 000 t) is part of the same volcanic stem and resulted from a resurgence of hydrothermal activity. ructure played a role in the final geometry of the deposits but did not eatly affect the volcanogenic and stratabound nature of the lens. Total production since the start of operations in 1985 amounts to 58 000 t and is restricted to the Main lens. Production from the 100 will come onstream in 1992 as ore reserves from the Main and e satellite lenses are exhausted.RESUMELa Mine Mobrun de Ressources Audrey inc. est située dans le mton Dufresnoy, a quelque 30 km au nord-est de Rouyn-Noranda. lle comprend deux lentilles de sulfures massifs d’importance majeure ~i sont les lentilles 1100 et Principale, et une lentille satellite qui est complexe 850-870-930.La lentille 1100, la plus ancienne, est contenue dans une épaisse 1ite pyroclastique bordée, au sud, par des coulées de rhyolite et d’andésites, au nord, par une épaisse unité rhyolitique. Cette lentille contient environ 15 Mt de sulfures massifs dont 10,4 Mt à teneur économique. La lentille Principale repose sur d’épaisses coulées rhyolitiques brechifiees et pyritisees à proximité de l’horizon de sulfures; elle est recouverte de tufs a cendres et de rhyolites interlitees qui contiennent la lentille satellite. La lentille Principale est constitute de 3,3 M t de sulfures massifs dont 1 523 000 t sont économiques avec une teneur moyenne de 0,80% Cu, 2,44% Zn, 30,19 g/t Ag, et 2,2 glt Au. Faisant partie de ce second épisode volcanique, la riche lentille satellite (180 000 t) temoigne d’une recrudescence de l’activité hydrothermale. La structure joue un rôle important dans la géométrie finale des dépôts mais ellen' affecte pas, de fa~on significative, la nature volcan génique des lentilles. Depuis le début des opérations, en 1985, la production totale est d’environ 568 000 t, provenant essentiellement de la lentille Principale. La mise en production de la lentille 1100 est prévue pour 1992, alors que les réserves des lentilles Principale et Satellite seront probablement épuisés."

Jan 1, 1990

By Klaus M. Zeitler

INTRODUCTION One cannot discuss the subject of "Raising Capital in the 1990s" without having a crystal ball and a reliable fortune teller. This discusses "Raising Capital for the 1990sW, which is what Metal1 Mining Corporation did in 1987. We raised (3166 million in an IPO (initial public offering) that was originally planned for only some (375 million. Why did we raise this money? How did we do it, and why was this IPO so successful? The answer to the first question requires a description of the promoter and principal shareholder of Metal1 Mining Corporation, Metallgesellschaft AG. This West Germany company was founded over 100 years ago in Frankfurt as a trading house for non-ferrous metals. It has developed into one of the world's leading firms in the non-ferrous metals industry. The company's worldwide activities in all areas of that business include mining, smelting and refining, the trading of ore, base and precious metals, the production of semi-fabricated and finished metal products, and the provision of engineering, construction and transportation services. Metallgesellschaft AG has also diversified into many other areas, the most significant of which are manufacturing, the production of chemicals, the development and application of technical and chemical processes, the planning and construction of industrial plants, and activities associated with finance, insurance, shipping and freight forwarding, and the provision of barter and countertrade services. The company maintains a network of more than 100 offices around the world; it employs some 25,000 people in its worldwide activities. [Selected financial data, as of September 30, 1987: (MetaUgesellschafl AG) Working Capital DM 8%.6 million CDNS 672.8 million Long Term Debt DM 568.0 million CDNS 426.2 million Sales DM 14.9 billion CDNS 11.2 billion Net Income DM 87.7 million CDN$ 65.8 million Market Capitalization at April 27, 1987: (Metallgesellschafi AG) Outstanding Shares ~,6oo,o0o DM 1,875 million CDNS 1,407 million] For the fiscal year ended September 30, 1987, Metallgesellschaft AG had, on a consolidated basis, net sales of DM13.3 billion, net income of DM100 million and total assets of about DM7.0 billion. Metallgesellschaft AG established the American Metal Company, a predecessor of AMAX Inc. one of the largest ventures undertaken by Metallgesellschaft AG then was the acquisition, through the American Metal Company, of a majority share in the Mexican Penoles mine, a large lead and silver deposit. METALLGESELLSCHAFT AG Figure 1 depicts an overview of Metallgesellschaft AG before and at the time the initial public offering of Metall Mining Corporation's shares took place. It shows that mining was far from the centre of Metallgesellschaft's activities. Therefore, it could not expect to receive an extraordinary amount of board attention. Thus, mining investments not only had to compare well with other mining opportunities, but were in fierce competition with projects from other divisions. In addition, mining was sub-divided into two separate departments -- domestic and international. These two departments had different management styles and diverging interests which resulted in a minimum co-operation between them. The domestic mining department was primarily interested in the survival of the local mines. These mines were characterized by rising operating costs and declining ore grades. It took a special commitment and continued ingenuity to develop and adjust to local conditions, and modern mining and processing technology, in order to remain competitive, or at least survive within the international mining industry. Local management

Jan 1, 1990

By Pierre Ollivier, Dominique Morin, Pr. Ivo Toromanoff

Refractory gold ores have been processed by bio-hydrometallurgical process at B.R.G.M. (Bureau de Recherches Géologiques et Minières), Research Centre ,Orleans,France. The liberation of gold has been studied and the following steps for gold recovery improved. The overall process flowsheet has been established comprising different ways of treatment before the final discharge of the effluent. Iron and arsenic are successfully precipitated under well controlled Eh-pH conditions. Long term stability tests have been conducted and the research programme is to be continued with the crystallo graphic studies of the precipitates. Economical studies have been performed on the base of data obtained on parameters studies.

Jan 1, 1990

By C. B. Alcock

The control of high temperature processes requires the ability to measure significant variables during operations. With increasing automatic computerized control there is need for sensors which can provide on-line chemical analyses of all phases present in a reactor without the necessity to withdraw samples from the high temperature reaction zone. Probes using electrochemical cells and conductivity measuring devices have provided the answers to some of these problems, notably the measurement of oxygen in liquid metals, and similar potential systems based on the same fundamental principles for the analysis of non-metallic and metallic elements appear feasible. In this discussion, the state-of-the-art in chemical sensors will be discussed in terms of the potential materials of construction, and, in some cases, the limitations of upper temperature at which some promising systems can, at present, be applied. It is concluded that a new phase of basic research could improve the outlook substantially by providing solutions for some problems in chemical sensors which are now well-defined.

Jan 1, 1990

By S. Y. Liu

Based on the underground measurements, physical model test of simulated materials in the laboratory and finite element analysis, this paper demonstrates the pattern and process of roof fall over the tip-to-face area in the fully mechanized coalfaces. The main factors that affect the stability of the immediate roof are thoroughly studied including the fracture position and tilt angle of the main roof, the tensile strength (Rt) and cohesive force (c) of the immediate roof, and type and resistance of the powered support. Based on these factors, this paper proposes the basic process of immediate roof breakage a. follows: As the longwall farm advances, the main roof breaks and then rotates. A tensile fracture zone will be formed in the immediate roof under the fracture line of the main roof. A caving zone (plastic zone) will be formed in unsupported area between coalface and canopy tip. If these two zones overlap the immediate roof will be completely unstable. Under this condition, powered support will have difficulties lo control the rod. Therefore it is necessary to study the process of immediate roof breakage and look for effective methods for controlling the roof.

Jan 1, 1990

By Gus Van Weert

The cost of oxygen is a major and common factor in the hydrometallurgical processes developed or proposed tor the oxidation of refractory pyrites. This cost involves charges for the generation and the transfer of the 02 to the mineral slurry. Bio-oxidation faces considerable design demands which require large scale equipment to be resolved. Nitric acid assisted oxidation offers low cost oxygen units; this method of pyrite oxidation deserves a closer look for large scale plants treating pyritic gold ores and concentrates.

Jan 1, 1990

By G. Bräuner

The methods of burst control treated in the authors' very informative paper have been applied in the Ruhr Coalfield, Germany, for more than 20 years and have proved to be highly effective. It might be interesting here to mention a few experiences: The symptoms of critical stresses when drilling with small diameters ("test drilling") are essentially the same as described. However, we consider the situation safe if these symptoms occur beyond a certain distance ahead of the face. That safety distance equals three times the seam thickness plus the daily advance. It is the total seam thickness that counts, not merely the mined portion. Critical stresses within the safety distance are dissolved by so-called destressing measures: drilling with heavier equipment, blasting, or water infusion. To avoid bump initiation, the destressing operations should begin at the sides of the stressed zone rather than in the middle. As to water injection, there are two different principles. If the situation is critical already, high pressures are applied for hydraulic fracturing. If the stresses still allow to drill deep holes, the fluid pressure is kept low and acts for a longer time. This is to make the coal break successively instead of violently - a long-term precaution. When the stresses are very high, destressing is the most appropriate means. We mostly drill with 95 mm-diam (3.7 in.- diam). The techniques in detail are somewhat complex and subject to modifications. But the general idea is to accomplish burst prevention by controlling the potential burst situations.

Jan 1, 1990

By M. M. Kim

As-electrogalvanized coatings of pure Zn, Zn-11% Fe, and Zn-18% Fe coatings were characterized in terms of initial crystal structure and surface morphology. Samples were then subjected to heat treatments simulating the paint bake cycle of automobile manufacturers. Surface morphology changes were correlated with the process variables, and crystallo.graphic changes were interpreted by mapping heat treatment routes on the Fe-Zn phase diagram. The morphology of pure zinc electrogalvanized coatings with heat treatment from platelets to smeared platelets. The zn-11% Fe coating changes with heat treatment from tetrahedral nodules to a mixture of round and tetrahedral nodules, with the Zn-:18% Fe coating always having round nodules. Regarding crystal structure, a critical transformation time can be defined at any selected temperature, below which the crystal structure does not change. This temperature is related to iron content.

Jan 1, 1990

By J. Gautam, T. Ong, W. E. Wallace, M. Keane, S. Xing, J. Harrison

"INTRODUCTIONOrganics extractable from respirable diesel exhaust soot particles by organic solvents have been known for some time to be direct acting frameshift mutagens in the Ames Salmonella typhimurium histidine reversion assay (Huisingh, et al). Upon deposition in a pulmonary alveolus or respiratory bronchiole, respirable diesel soot particles will contact first the hypophase which is coated by and laden with surfactants. To model interactions of soot and pulmonary surfactant, we dispersed soots in vitro in the primary phospholipid pulmonary surfactant dipalmitoyl glycerophosphorylcholine (lecithin) (DPL) in physiological saline. We have shown that diesel soots dispersed in lecithin surfactant can express mutagenic activity, in the Ames assay system using S. typhimurium TA98, comparable to that expressed by equal amounts of soot extracted by dichloromethane/ dimethylsulfoxide (DCM/DMSO)(Wallace, et al, 1987). Here we report additional data on the same system using additional exhaust soots and also using two other phospholipids, dipalmitoyl glycerophosphoryl ethanolamine (DPPE), and dipalmitoyl phosphatidic acid (DPPA), with different ionic character hydrophilic moieties. A preliminary study of the surfactant dispersed soot in an eucaryotic cell test system also is reported.MATERIALS AND METHODSSoots D4 and D6 were collected at two different times as scrapings from the exhaust pipe of a diesel tractor-trailer immediately after the engine was stopped. Surfactant dispersions were made by ultrasonic probe sonicating 25 mg of commercially obtained DPL, DPPE, or DPPA into 1O ml of O.85% physiological sterile saline (PSS) for 10 min at 40 watts power. For surfactant dispersions, 2.5 mg soot was mixed into 2.5 ml of the appropriate phospholipid dispersion. Mixtures were sonicated by 40 watts sonicator probe for one min, then incubated in the sonicator water bath for 30 min at room temperature; the mixture was then incubated for one hour at 37C while being rotated continuously. Dilution series were made with saline. For solvent extraction, 2.5 mg soot was mixed into 2.5 ml of DCM and incubated in a sonicator water bath for 30 min at room temperature. The sample was then mixed with 2.7 ml DMSO, placed in a dry bath at 45C, and the DCM evaporated under a stream of nitrogen gas until 2.5 ml of liquid remained. Ames salmonella/microsome assay utilizing TA98 for frameshift mutation was used for mutagenicity testing, with and without S9 activation, as described by Ames et al (1975). Unfiltered sample extractions or dispersions were preincubated with tester cells for 90 min at 37C : 0.1 ml of sample was mixed with 0.5 ml of PSS, or of S9 mixture, and 0.1 ml of an overnight TA98 culture incubated samples were then added to 2 ml of top agar supplemented with biotin and a trace amount of histidine, and overlayed onto Vogel-Bonner minimal media plates. After 48 hours incubation at 37C, revertant colonies were counted. Solvent controls were DMSO, DPL, DPPE, DPPA, and saline. Positive controls were trinitrofluorenone (1 ug/plate), for samples not treated with S9, and 2-aminoanthracene for S9 treated samples (2.5 ug/plate). All samples were assayed in duplicate. Sister chromatid exchange (SCE) assay was performed, following Lett, et al (1981), using V79 cells, of Chinese hamster pulmonary fibroblast origin. Stock diesel sample suspensions were made as 10 mg soot/ml DPL suspension, or 20 mg soot/ml in DMSO. Aliquots of these soot preparations were added to 15 ml of culture medium per sample flask to result in concentrations of 25, 50, and 75 ug soot/ml medium. After 12 hours incubation, 200 ul of 25 uM 5-bromodeoxyuridine (BrdU) was added to each flask. After another 35 hours incubation, 200 ul of 10 ug/ml colcemid were added; and the cells were harvested three hours later. Cells were swollen by hypotonic saline, and fixed twice with methanol/acetic acid, and burst on microscope slides. Cells on the slide were stained with Hoechst 33258, exp"

Jan 1, 1990

By Tapponnier P

In North Vietnam, large ductile shear zones are observed along the Red river fault and the Dienbien fault. Left-lateral sense of the Red river shear zone is related to the direction of shortening E-W. NE dipping foliation planes is subvertical. Stretching lineation is subhorizontal ( 25¦). Left-lateral slip observed in the Oligocene Yansun granites demonstrates the major tectonic phase in Neogene, The stress field established from microfaults observed in triassic limestones, Oligocene granites and Neogene Conglomerates. Measurements of striations on fault mirors are used for calculating the stress tensor and for separating tectonic phases. Two tectonic phases in tertiary are separated : first tectonic phase related to the compressive direction E-W corresponds to the major tectonic phase represented by NW left-lateral shear zone. Second phase having the compressive direction N-S associated with the right-lateral movement of the Red-river fault zone opening of the Eastern sea and the Red-river and the Red-river delta is associated with the left-lateral movement along the Red-river.

Jan 1, 1990

By Wan-Kyu Choi, Arpad E. Torma

The electrochemical reactions involved in a zinc sulfide flotation concentrate leaching with sulfuric acid in presence and absence of Thiobacillus ferrooxidans, as well as with ferric chloride - hydrochloric acid containing media, have been investigated. The cyclic voltammetric measurements revealed that many intermediate electrochemical reactions are involved in the zinc sulfide leaching. Using chronoamperometric and chronopotentiometric techniques, it was found that the leaching process is controlled by solid - state diffusion. The activation energy of solid - state diffusion process was determined by the Price's approach to be 21.3 kJ. The leaching mechanism is discussed in terms of solid - state properties (energy bondings) of the high energy gap solid zinc sulfide semiconductor and energy density states of redox systems of acidic leach media. A generalized model for the mechanism of zinc sulfide oxidation is present.

Jan 1, 1990

The mining industry is generally regarded as a high risk industry, mainly because of the difficulties in estimating the tonnage and grade of mineral resources, the fluctuations in metal prices, mining problems and other problems which occur with mining in offshore and remote locations, such as appropriation or disruption to supply. As a consequence, finance providers require a high reward from mining projects. In the past two decades, the development of "mega" projects has led to the packaging of the finance becoming more sophisticated. Some would see this move as a measure of the evolution of banking rather than an intrinsic facet of mining finance itself. Project financial managers now require a thorough knowledge of all the financial tools which are available and have to be aware of the funding options so that they can put together a finance package which minimises the cost of the financing with the risk spread adequately between the partners of the financing. The different sources and types of finance for mining projects are described herein along with the factors which determine their costs. To understand the ramifications of financing mining projects, it is essential to appreciate the fundamental difference between debt and equity, which illustrates the importance of gearing. Costs of finance are determined by the interaction of supply and demand forces. Bankers and other financiers have become more adept at isolating a wide selection of risk elements and have devised a formidable range of insurance mechanisms. There is still a lot of money looking for good project risks and if a good project is properly presented and structured, financing can be obtained in today's market.

Jan 1, 1990

By S. C. Tadolini

"Roof bolts are the primary means of roof support in underground mines in the United States. Presently, post installation loads are measured on about 10% of the expansion anchor and combination bolts by using standard torque wrenches that Unit the accuracy of the measurements to about ±30%. No system has been available for measuring the loads generated on full-column resin grouted bolts. Mine roof bolts are long, slender, non-uniformly sized, roughly forged, and placed in a corrosive environment, creating obstacles for researchers trying to utilize ultrasonic reflection techniques to measure strain. A complete measurement system has now been developed by the U.S. Bureau of Mines, Denver Research Center. This system is being used successfully in determining loads measured on expansion anchor and combination bolting systems, examining the transfer mechanics of full-column, resin-grouted bolts, and measuring loads generated on bolts in an underground roadway support system.IntroductionMillions of roof bolts are used each year to provide structural support in underground U.S. metal, non-metal, and coal mines. Approximately 45% of the bolts used are expansion anchor, 45% are resin-assisted combination or full-column resin-grouted, and 10% are friction anchored. The effectiveness of these bolting types is dependent on a number of factors including rock density, bolt length, in situ stresses, rock properties, bolt pattern, installation tension, etc. When implementing expansion anchor and resin assisted combination bolts , installation and post-installation tension, or load, is a major determinant of support quality and subsequent behaviour of the reinforced roof. The method by which these systems carry roof loads is well understood and documented(1,2).The importance of these installation and long-term bolt tension measurements is well recognized and are required in the federal government regulations(3). A statistical sample of the bolts, lout of 4 during installation and lout of 10 inby the last open crosscut, is required to be measured using current torque wrench technology. The disadvantages of this system are the disturbance and weakening of the anchorage and limitations of accuracy to approximately ± 30%. The method by which resin-grouted bolting systems carry roof loads is much less understood, mainly because testing procedures used to evaluate point-anchor systems are not effective on resin-grouted bolts.Due to these problems, the U.S. Bureau of Mines designed a measurement technique that provided a highly accurate, low cost-per- bolt system that led to the development of ultrasonic pulse echo instrumentation. The original system was designed to measure the tension only on expansion anchor bolts. Recent developments and system modifications have permitted measurements on resin-assisted and full-column resin-grouted bolts. The use of these types of support systems has been increasing steadily in underground coal mines.The development of this instrumentation has provided laboratory and field results that help to explain the mechanics and relationships between the applied loads and the interaction between the grouted bolt system consisting of the bolt tendon, grout, and rock."

Jan 1, 1990