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By F. W. Brackebusch, R. O. Sack

"A method for determining the fineness of Au in electrum from the composition of fahlore coexisting with pyrite and chalcopyrite is presented. This method is based on previously published experimental brackets and activitycomposition models for electrum and fahlore, and it is potentially useful for defining temperatures of hydrothermal mineralization and retrograde evolution of precious metals deposits. The authors demonstrate that it successfully predicts compositions of electrum reported for this assemblage in the literature and illustrate its application for three gold-quartz vein deposits from the Coeur d’Alene mining district, Idaho, that are prospects of the New Jersey Mining Company, the Coleman vein, High-Grade prospect, and Silver Strand mine. Temperatures calculated from average electrum compositions estimated from gravity concentrates (molar Au/(Au+Ag) = 0.76-0.39) and from microprobe analyses of the fahlores (molar Ag/(Ag+Cu) = 0.039 ± 0.004, Zn/(Zn+Fe) = 0.57 ± 0.03, As/(As+Sb) = 0.23 ± 0.02) from the Coleman vein indicate that the electrums underwent retrograde re-equilibration to temperatures between about 80°C and 240°C, roughly 80°C below the temperature of hydrothermal mineralization and 10°C to 40°C above the temperature inferred for retrograde equilibration of Fe and Zn between sphalerite and fahlore. Fahlores from the High-Grade prospect [molar Ag/(Ag+Cu) = 0.009 ± 0.004, Zn/(Zn+Fe) = 0.55 ± 0.11, and As/(As+Sb) = 0.04 ± 0.03] and Silver Strand mineralized zone [molar Ag/(Ag+Cu) = 0.10 ± 0.04, Zn/(Zn+Fe) = 0.63 ± 0.02, and As/(As+Sb) = 0.06 ± 0.02] exhibit strong core to rim depletions in Ag due to retrograde operation of the reaction1/10Cu10Fe2Sb4S13 + Ag + FeS2 =Cu-fahlore electrum pyriteCuFeS2 + 1/10Ag10Fe2Sb4S13chalcopyrite Ag-fahlorewhich proceeds to the left with decreasing temperature. Electrum inclusions in arsenopyrite from the High-Grade prospect [molar Au/(Au+Ag) = 0.90 ± 0.02] define a minimum bound on the temperature of hydrothermal mineralization of 273°C, and the temperatureelectrum composition curve constructed for the most Ag-rich fahlore in the Silver Strand mine indicates that the fineness of its electrum is significantly less than in the other deposits."

Jan 1, 2004

By Cleber Caetano Thomazi

Rotary kilns are continuous process equipment used on calcining of nickel ore. The chemical and physical reactions are created by means of heat up the material to predetermined temperatures. Tertiary air fans are attached to the kiln shell to maintain oxidizing/reduction conditions. Special ducts orientate the air flow inside the kiln. In the present work, two types of failure on distinct tertiary ducts mounted on the same kiln are reported. Chemical analysis, hardness test, metallographic and fractographic examinations were carried out. Fabrication related problems and creep were identified as the root causes of damages.

Oct 30, 2017

By R. Karl Zipf

Multiple seam mining interactions caused by full extraction mining, whether due to undermining or overmining, frequently involve tensile failure of the affected mine roof. The adverse ground control conditions may prevent mining for both safety and economic reasons. Prior researchers have identified the geometric, geologic and mining factors controlling multiple seam mining interactions. This numerical study examines the mechanics of these interactions using a modeling procedure that 1) incorporates the essential constitutive behavior of the rock such as strain-softening of the intact rock and shear and tensile failure along bedding planes and 2) captures the geologic variability of the rock especially the layering of weak and strong rocks and weak bedding planes. Specifically, the numerical study considered the effect of vertical stress, interburden thickness, and the immediate roof quality of the affected seam in both undermining and overmining situations. The models show that for overburden-to-interburden thickness (OB/IB) ratios of less than 5, interactions do not occur, and that for OB/IB more than 50, extreme interaction is a certainty. In between, the possibility of an interaction was found to depend on gob width-to-interburden thickness ratio, site specific geology and horizontal stress to rock strength ratio in addition to the OB/IB ratio. The models also showed that horizontal stress was profoundly altered well above or below a full extraction area and that these changes are likely to influence the success or failure of multiple seam mining. The role of horizontal stress in multiple seam mining interactions has received little attention in prior investigations. Four factors control the mechanics of multiple seam mining interactions: 1. vertical stress concentration 2. horizontal stress concentration 3. stress re-direction 4. bedding plane slip bands A combination of vertical and horizontal stress increase and high stress gradients in the vicinity of full extraction areas re-orients principal stresses into a very unfavorable direction. This seemingly small stress re-orientation has a profound adverse effect on bedded rock.

By D. Neely, D. Milne, L. R. Feldman

"Resin-anchored rebar is commonly used for rock support in mining. The rock properties and environment determine the average bond strength, allowing mine engineers to select the appropriate length and installation pattern for the support. In weak material such as potash, the average bond strength tends to be lower than for a typical hard-rock installation. Determining the failure mechanism by which the support fails in soft-rock applications could lead to improved bond strength and better calculated installed support capacity. This paper reports on research conducted at a potash mine in Saskatchewan and analyzes the failure mechanism of the support.RÉSUMÉ Dans les mines, les barres d’armature enduites de résine sont fréquemment utilisées pour soutenir le roc. L’environnement et les propriétés du roc déterminent la résistance moyenne d’adhésion, permettant ainsi aux ingénieurs miniers de choisir la longueur de barre appropriée et le diagramme d’installation du soutien. Dans des matériaux faibles, tels que la potasse, la résistance moyenne d’adhésion tend à être plus faible que pour une installation typique dans de la roche dure. La détermination du mécanisme de rupture selon lequel le soutien fait défaillance dans des roches tendres pourrait conduire à une meilleure force d’adhésion et à un meilleur calcul du soutien installé. Le présent article fait état de la recherche effectuée dans une mine de potasse en Saskatchewan et analyse le mécanisme de défaillance du soutien. ,"

Jan 1, 2016

By Yingxin Zhou

Virtually every coal seam in Appalachia will at some time be subject to multi-seam interaction (Wu et al, 1987). Many such problems result from seams which lie in close proximity or have split and lie within thirty feet vertically of one another. Existing techniques for multi- seam design have concentrated on conditions where the entire inner burden is not the failing member and are unsuitable for ultra-close multi-seam design. Structural integrity of the inner burden must be maintained if two superimposed seams are to be mined separately and under- standing possible failure mechanisms of the inner burden is an essential first step in the design process.

Jan 1, 1989

By Joseph J. Mgumbwa

Pillars are any structures left between two or more underground openings. The stability of pillars is normally considered to depend on shape (defined by width to height ratio), rock mass strength, extraction ratio, in situ stresses and the gross structural features (i.e. joints, contacts, faults etc). Recent experience has shown that pillar stability is also controlled by the relative orientation of the orebody with respect to the in situ principal stress. In inclined orebodies, pillars are loaded in compression and shear, thus creating unsymmetrical stress distribution. Failure mechanisms of these pillars are little known. This paper investigates the failure mechanisms of pillars under shear loading. Two dimensional elastic numerical modeling was used to examine the behavior of pillars in different orebody inclinations relative to the major farfield stress orientation. First, the paper reviews pillar design approaches including the empirical pillar design chart and uses numerical modeling to investigate the effect of the major farfield stress orientation on pillar stability. It is concluded that the empirical pillar design chart be used with caution, and that for orebodies under shear loading mine planning and design should take this into consideration since such geometrical orebody/stress relations put mine structures at higher risk of instability.

Oct 1, 2010

By King E. J

Department of Pathology, British Post-graduate Medical School, London:The experiments here recorded were devised and carried -out during the last two years in an attempt to corroborate the important work of Denny, Robson and Irwin (1939) in which they found that experimental silicosis could be prevented by means of metallic aluminum. By causing rabbits to inhale powdered quartz for several months they induced experimental silicosis. These animals then served as controls for comparison with another group which were dusted with a mixture of quartz and aluminum. In the second group silicosis failed to develop.Our experimental procedure was somewhat different. We resorted to intratracheal insufflation instead of simple inhalation, and we used rats instead of rabbits: otherwise the essential features of the original experiments were carefully duplicated.EXPERIMENTAL PROCEDURES.A single dose of dust was delivered into the lungs of each animal. The dust was suspended in a fluid medium and injected by means of a syringe directly into the trachea in known quantity (technique of Kettle and Hilton, 1932). The suspensions were autoclaved before use and were injected with aseptic precautions. Having had a long experience of this technique we employed it with confidence and usually secured a fairly uniform dispersal of dust throughout both lungs. To carry out injections successfully one requires, above all, an even suspension of dust which will flow smoothly and quickly from the syringe. This is not difficult in the case of quartz, for, though it tends to settle out rather quickly, this can be avoided by constantly agitating the suspension. The syringe containing the inoculum may be shaken gently right up to the moment of injection and then emptied quickly to prevent sedimentation. Powdered aluminum is more difficult to handle, for the particles tend to flocculate and are not readily made to disperse evenly in saline, even by violent shaking. For this reason an emulsifying agent may be used to advantage, provided it does not complicate the experiment, a point to be mentioned again presently.THE EXPERIMENTSExperiments with quartz alone: Extensive silicotic lesions were produced in 23 out of 26 rats by the administration of pure quartz dust in doses of from 50 to 200 mg. per rat. The dust was so finely pulverised that the particles averaged about 1-p. in size: none was larger than 5 p. and 99 per cent. were under 2.5 p.Eight of these animals survived for seven months and were then killed...

Jan 1, 1945

Abstract : The computation of reliability index or failure probability of slopes can be transformed into an optimisation problem. In high rock slope engineering, it is usually a multimodal optimization problem. The traditional optimization techniques are difficulty to find out the global optimal solution because of their easily falling into local optimal value. Recently, a new kind of bionic algorithm - ant colony algorithm (ACA) - has been used to solve this problem. In this paper, the structure of ant colony algorithm and the transfer probability of ants are modified to evaluate the failure probability of complicated slopes. A new adaptive ant colony algorithm (AACA) is proposed to determine critical slip surface and its corresponding failure probability of complicated slopes. A case study is given to verify the proposed approach. The results show that the presented method has obvious advantages compared with traditional methods. ZUSAMMENFASSUNG: Die Rechnung des Zuverlaessigkeitindexes oder der Zerstoerungswahrscheinlichkeit kann sich in einer Optimierungsfrage umwandeln, im Bauprojekt an hoehe Gebirgehang, handelt es sich meistens um eine Optimierungsfrage ueber Multi- Spitzenwert. Mit der traditionelle Optimierungsmethode ist es schwer eine umfassende Loesung fuer die Optimierung zu finden wegen des leichte Verfallens in Beschraenkung der Teiloptimierungsloesung. Mit dem neue Bionik- Algorithmus —— Ameisen - Kolonie- Algorithmus wird dieses Problem geloest. In diesem Text hat man eine Strukturverbesserungsloesung fuer das Ameisen- Kolonie -system und die Wahrscheinlichkeit der Ameisenkolonie erwaehnt, und damit wird man die Zerstoerungswahrscheinlichkeit des komplizierte Hangs feststellen. Mit dem neuen Ameisen- Kolonie- Algorithmus kann man die gefaehrlichste Gleitflaeche und die entsprechende Zerstoerungswahrscheinlichkeit herausfinden. Die in diesem Text beschriebene Methode wurde durch Praxis geprueft. Durch die Pruefergebnisse wurde es gezeigt und bestaetigt, dass der neue Bionik- Algorithmus vorteilhafter als der traditionelle Algorithmus ist. Résumé : Le calcul de l’indice la fiabilité ou de la probabilité de ruptures peut être transformé en un problème de l’optimisation. Pour le cas du génie des pentes de haut rocher , le problème se pose en général en l’optimisation de multi-crêtes. Les techniques traditionnelles conduisent facilement à la solution optimal partielle au lieu de celle globale. Récemment un nouveau type de bionique algorithmique a été appliqué pour la solution de ce genre de problèmes, c’est l’Algorithme Colonie de Fourmis. Dans l’article il est proposé de modifier la structure du système de la colonie de fourmis et la probabilité de transfert des fourmis en vue d’évaluer la probabilité de ruptures des pentes de haut rocher complexes, par ailleurs un nouveau algorithme adapté de colonie de fourmis est formulé pour déterminer la surface glissante critique et la probabilité de ruptures correspondante. Les techniques proposées dans l’article sont vérifiées à travers des expérimentations dont les résultats ont prouvé que les techniques présentées dans l’article sont évidemment meilleures que celles traditionnelles.

Jan 1, 2003

By Weber W

Methods of calculation of the reliability of process computers are getting more and more important. The paper presents long period observations of 21 process computers with online applications in the iron and steel industry. About 5000 failure events during 10 years have been systematically recorded and evaluated. On the basis of these long time observations it is possible to develop a probability model of the failure behaviour of process computers.This failure model is constructed with four different states of the process computer:Working phase, working phase with undetected reasons, repair phase, failure phase resulting from external influences.The model is defined by differential equations for the probability of one of these four phases. Long time observations show, that all of these four phases are closely correlated with the capa-city of a process computer, restarting without detection of failure reason, changes of programs and software, costs and time of repair. So the result of this analysis is a model of failure for process computers, which allows to predict breakdowns of process computers on the basis of external parameters.

Jan 1, 1985

By A. S. Ericson, J. H. Corrigan, E. J. Jahnsen

Calcine is transported from the Reduction Plant at 850°C in insulated hopper cars and charged into three rectangular electric melting furnaces each equipped with three - 18.5 MVA transformers. The electrical energy is applied through six in line prebaked carbon electrodes, and slag and metal are tapped at opposite ends of the furnaces on an intermittent basis. The slag, 5000 tonnes per day, is disposed of by a pot train directly to the dump. The ferronickel, 250 tonnes per day, is tapped into 40 tonne capacity ladles in which it is refined in two ASEA-SKF ladle furnace stations. Casting is done over lip at 1520°C in a pig casting machine with stepless speed control at up to 55 tonnes per hour. The ingots are stacked into self palletizing bundles weighing about 1500 kilograms and are strapped and tagged and transported to the seaport, from which the final shipment is made to the world market. The paper describes constructional details and gives information of both normal operation and start-up and shut-down procedures. Consumption figures for refractory, electrodes, electric energy and refining additions are given and metal chemistry is given before and after refining.

Jan 1, 1979

By V I. McCallum

In 1954, Falconbridge Nickel Mines Limited began the program of deepening the Falconbridge mine workings for 2,000 feet below the bottom, or 4025, level in order to provide twelve new levels for production. Involved in this program were a production-sized internal shaft, .crushing, pumping and hoisting installations, the integration of the new shaft operations with those of existing shafts, and considerations of ventilation requirements and ground support at depth. This paper describes the major items of equipment, and the depth development of No. 9 shaft as a whole, and also emphasize the planning phases of the program. The factors involved and reasons for the equipment and layouts chosen are given. Introduction and History THIS paper describes the planning and development of that portion of the Falconbridge mine between the 4025 and 6050 mining levels. This mine, the oldest of several being operated by Falcon-bridge Nickel Mines Limited in the Sudbury district, has been a continuous producer for over thirty years.

Jan 1, 1964

Falconbridge Nickel, the one-time subsidiary that grew up to swallow its own parent, Ventures Limited, in 1962, is not about to be left behind by rising nickel consumption. At a cost of several hundred million dollars, this Canadian firm has undertaken a series of new projects that will not only ensure its present share of the market, but also lead it into new areas of the nickel business. Although Falconbridge Nickel Mines Ltd. was not formed until 1928, it actually had its start in 1917- 18 with the discovery of a large, good grade nickel- copper deposit in Falconbridge, near Sudbury, Ontario. However, due to several factors, financing could not be obtained and the orebody lay fallow. It was not until 1928, when the Thayer Lindsley interests bought the property from the original owner, that it was developed.

Jan 10, 1968

By Edwin de Jesús Deveaux

After 32 years of operations beneficiating lateritic nickel ore in a fully integrated pyrometallurgical complex, Falconbridge Dominicana (FALCONDO), situated at Bonao and La Vega Provinces, Dominican Republic, has become profitable with one of the lowest nickel grade content processing plants in the world, and literally without any by-product (granulated slag, will be utilized in the future as a post-processing subproduct). To December 2002, mineral reserves were 64.1 million tonnes containing laterite grading as low as 1.15 % Ni when full dilution is applied. At a cut-off grade of 1.20% Ni, the reserves will provide 15-20 years of production. The mineralized thickness over the seven active deposits averages 6 m. Development of very selective and unique mining practices, together with improvements in the process plant, are key to achieving the production goal (30 kt Ni/yr) and to meet the quality standards for the ferronickel produced. Keywords: Laterites, grade control, mining methods, environment

Jan 1, 2004

By AIME AIME

SECOND only to the February Annual Meeting of the Institute are the Regional and Divisional meetings held in the fall of each year. Six such gatherings are scheduled in the next the months, with something likely to interest every member of the Institute. A brief résumé of the programs follows. Regional Meeting Vancouver T HE regional meeting of the Institute will be held at Vancouver, Sept. 13 to 20, in conjunction with the annual western meeting of the Canadian Institute of Mining and Metallurgy. The pro gram appeared on page 350 of MINING AND METALLURGY for July and-proof of careful preparation-a month later re- quires no correction and little elaboration. On the technical side there are few changes. A new item on the Wednesday morning program is the paper, "Investigation of Residential-type Stokers," by H. F. Yancey, supervising engineer, Northwest Experiment Station. U. S. Bureau of Mines, Seattle. As to entertainment the meeting is taking on some most pleasurable aspects. Two notable excursions have been arranged.

Jan 1, 1937

By AIME AIME

A THOROUGHLY satisfactory crowd turned out at the fall meeting of the Industrial Minerals Division and took an active part in the entire program. On Thursday afternoon, Sept. 24, a limestone plant was inspected, technical sessions occupying the attention of the visitors all day Friday and Saturday morning. Headquarters were at the Nittany Lion Inn, an attractive hostel on the Penn State campus, at State College, right in the center of Pennsylvania. We are still in the dark, despite inquiries, as to just what breed of lions Nittany lions are. As nearly as we could find out, Nittany is not a Biblical name, as it sounded to us, but a corruption of the name of an Indian princess, or maiden, or maybe just girl that haunted those parts in bygone times and after whom a near-by mountain was named. Penn State athletes are "lions" and there you are. The meeting was supposed to be a joint one with the American Ceramic Society's Materials and Equipment Division; but it was quite evident that the Institute had a much better publicity agent than the Society, which bothered Ross. Purdy, the aggressive secretary of the ceramic people, no end. However, Secretary Purdy saw to it that everyone present fully understood that the Ceramic Society was present, so that that contingent all but stole the show, its representatives presiding at every meeting. The Pittsburgh Section of the American Ceramic Society was also supposed to be holding its fall meeting there at the same time, but made no trouble at all for anybody, as one of the speakers remarked.

Jan 1, 1936

By Ramsden AR, French DH

The limited contrast range of conventional black and white imaging does not enable full use to be made of the dynamic range of the video signal obtained from a scanning electron microscope or microprobe. The use of false colour substantially increases the information that can be derived from such images enabling relationships to be displayed that cannot be observed in black and white. This capability is now used extensively in combination with quantitative electron microprobe analysis as a research tool for ore characterization and host rocks studies related to minerals exploration in the CSIRO Division of Exploration Geoscience.

Jan 1, 1989

By R. H. Grau, R. B. Krog

The National Institute for Occupational Safety and Health (NIOSH) has investigated the unique ventilation requirements of large-opening mines to help identify and evaluate the effectiveness of various fan types to improve the ventilation and air quality in the underground workplace. Large-opening mines, with their low airflow resistance factors, can be ventilated with free-standing auxiliary fans because airflow pat-terns in these mines are primarily controlled by airflow momentum. The flow characteristics of both vane-axial and propeller fans were investigated and tested at four large-opening mines to assess the effects of fan location on recirculation and entrainment. Each fan type has its own airflow, entrainment and penetrating air-flow characteristics, and operating costs that are advantageous for specific applications. Either fan type can be used for most auxiliary applications. However, this research has shown that the optimum placement and use criteria for propeller fans differ from those promulgated by the U.S. Bureau of Mines (USBM) for vane-axial fans Brechtel et al. (1985)

By D J. Brake

The correct specification and then selection of primary or major fans for an underground mine is a critical decision not only in terms of fan capital and operating costs, but also safety and reliability which usually has a major impact on mine production. In addition, fan manufacturers may spend tens of thousands of dollars preparing proposals for a purchase enquiry for primary fans especially where they have complete responsibility for the installation (turnkey projects). There are many good reasons to thoroughly and fairly adjudicate fan tenders. This paper describes the process to achieve this starting with the initial fan specification through to the final award.CITATION:Brake, D J, 2017. Fan specification and tender adjudication for mine ventilation engineers with particular reference to turnkey projects, in Proceedings Australian Mine Vent Conference 2017, pp 245–252 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By B. G. Tarasov

This paper proposes the further development of a recently identified shear rupture mechanism (fan mechanism) that elucidates a paradoxical feature of hard rocks ? the possibility of shear rupture propagation through a highly confined intact rock mass at shear stresses that can be significantly less than frictional strength. In the fan mechanism, failure is associated with consecutive creation of small slabs (known as ?domino blocks?) from the intact rock in the rupture tip, driven by a fan-shaped domino structure representing the rupture head. The fan head combines such unique features as extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Consequently, the failure process caused by the mechanism is inevitably spontaneous and violent. Physical and mathematical models explain unique and paradoxical features of the mechanism, which can be generated in primary ruptures and segmented faults. The fan mechanism provides a novel point of view for understanding the nature of spontaneous failure processes, including shear rupture rockbursts. The process explains, in particular, features of shear rupture rockbursts such as activation at great depths, generation of new shear ruptures in intact rock mass, nucleation of hypocentres at significant distances from the excavation, shear rupture development at low shear stresses, and abnormal rupture violence.

Jan 1, 2014

The spatial and temporal evolution from the porphyry to high-sulphidation epithermal environment can be assessed by integrating new results on such deposits (Arribas et al, 1995; Hedenquist et al, 1998) with past studies of plutonic and porphyry systems (Dilles and Proffett, 1995; Cline, 1995; Shinohara and Hedenquist, 1997; Hedenquist and Richards, 1998). Some time ago, Sillitoe (1973) argued for the nature of the tops and bottoms of porphyry deposits. He concluded that epithermal deposits may form over the tops of some porphyry systems. We can now conclude more confidently what the tops and bottoms of many high-sulphidation ore deposits appeared like while active (Arribas, 1995; Hedenquist, 1995). In addition, we better understand the nature of the zonation of high-sulphidation epithermal systems from the intrusive to surficial environment (Sillitoe, 1999), and how these two styles of ore deposit are related. Geological and geochemical evidence clearly indicates a continuum between these two ore environments. This improved understanding of genesis allows more efficient exploration for these deposits. There are many examples of spatially associated porphyry and epithermal ore deposits. A genetic connection has been suggested by some, and argued against by others. Nowhere is this spatial association better seen than in northern Luzon, Philippines, where the Lepanto high-sulphidation epithermal Cu-Au deposit overlies the Far Southeast (FSE) porphyry Cu-Au resource (Figure 1). Together these mineralised bodies contain a resource of >3.8 M tonnes Cu and >550 tonnes Au. Lepanto was largely mined out in early-1997. Post-war production until 1995 was 0.73 Mt Cu, 115 t Au and 393 t Ag at an average grade of 2.2 per cent Cu, 3.5 g/t Au and 11 g/t Ag. The recent discovery of the adjacent Victoria low-sulphidation quartz-Au-base metal vein deposit, with a resource of >68 tonnes Au (Cuison et al, 1998), illustrates the variety and abundance of mineralisation in the Mankayan district. This district also hosts the Guinaoang porphyry Cu-Au deposit (Sillitoe and Angeles, 1985) and other epithermal vein occurrences (Figure 1). This brief summary reviews the results recently published on the Lepanto-FSE deposits (Arribas et al, 1995; Mancano and Campbell, 1995; Claveria, 1998; Hedenquist et al, 1998), and stresses the evidence for coupling of mineralisation between the porphyry and high-sulphidation epithermal environments.

Jan 1, 1999