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By T. Schrauf, J. Scott

"INTRODUCTION Cyanide heap leaching of gold ores in areas with extremely low winter temperatures requires special considerations to prevent freezing of the leach solution. Factors that impact the solution temperature include ore temperature at the time of stacking and during operation, burial of drip irrigation lines, use of geomembrane covers, and heating of the leach solution. Thermodynamic modeling was performed to simulate expected ore and solution temperatures under different operating strategies for Kaminak Gold’s Coffee Gold project in the Yukon Territory. Mean monthly temperatures at the site ranged from a low of -22.5oC to a high of 13.6oC, while in situ ore temperatures ranged from -0.5 to about -1.5oC. The modeling results were used to optimize the operational parameters and indicated that a combination of drip line burial and heating of the leach solution during the winter months was required to maintain solution temperatures above freezing during the initial years of stacking, although as the size of the heap increased, heating was no longer necessary. MODELING OBJECTIVES The successful operation of a cyanide heap leach under extremely cold winter temperatures requires the implementation of operational strategies to prevent freezing of the leach solution and the ore within the heap. Thermodynamic modeling of the heap provides the means to quantify the effectiveness of these different operational parameters on maintaining the required operating temperatures to avoid freezing within the heap. The operational parameters that were evaluated with the model included: • Burial depth of irrigation lines to prevent freezing during the winter months; • Variation in the temperature of the applied leach solution (to simulate heating of recirculated solution); • Variation in the rate of irrigation including seasonal variations between winter and summer months; • Seasonal versus year-round stacking of ore (to simulate the impact of the initial temperature of each ore layer as it is stacked); • Seasonal versus year-round crushing and stockpiling of ore, including the option to stockpile ore on the leach pad in the winter (i.e. stack but not leach fresh ore in winter); • Start date for seasonal stacking; • Variation of the heap geometry over time (both vertical and lateral expansion) and the associated heat storage within the heap; • Use of thermal covers (gravel or geomembrane) over the ore during the winter months; and • Effect of crush size on heat loss during crushing, stockpiling and stacking."

Jan 1, 2016

Computer programs for the storage, retrieval and use of basic thermodynamic and physical property data for chemical substances are described. Methods are presented for the collection, critical assessment and pre- processing of source data for files containing enthalpy, entropy and heat capacity data for 3000 compounds, enthalpy and excess entropy for 200 dilute solutions and critical propert- ies and vapour pressure for 600 compounds. Retrieval programs are discussed which allow the tabulation or plotting of many basic and derived thermodynamic properties for chemical substances or balanced reactions. Examples are given of the use of such data to infer the stability or corrosion resistance of materials and the feasibility, yield and heat release of reactions. A general purpose calculation program is discussed which allows the equilibrium compos- ition to be found for complex systems with many species and phases, using the method of Gibbs energy minimization. Methods of correction for non-ideal behaviour in these systems are discussed, as well as methods for fixing, maximizing or minimizing any desired property of the system. Examples are given of the simulation of various laboratory Experiments and industrial processes by this method.

Jan 1, 1977

By William Hanco, Carlos Calero

La inclusión de tecnologías 3D en las plataformas de Sistemas de Información Geográficos (GIS) corporativas viene potenciando la labor de Osinergmin, cuya Gerencia de Supervisión Minera está encargada de asegurar el cumplimiento de las normas relativas a la seguridad de la infraestructura de la mediana y gran minería. El artículo describe cómo la captura de aerofotografías de componentes mineros de interés, tomadas con cámaras de alta resolución desde vehículos aéreos no tripulados (drones), son procesadas luego para obtener modelos digitales en 3D, sobre los cuales se realiza la medición de magnitudes físicas para verificar, en gabinete, que los parámetros técnicos de los componentes analizados cumplen con lo autorizado. De este modo, no solo se logra cubrir una mayor área de supervisión, sino también focalizar el trabajo de campo en aquellos puntos donde se encuentren observaciones.

Sep 20, 2019

By R L. Brathwaite

The mesothermal quartz-scheelite lodes of the Wakamarina valley are one of twelve known mined or prospected gold-bearing areas in the Marlborough Schist. Recorded production was 556 kg gold, a little silver, and c. 390 t scheelite. 134 m of the 1800 m long Golden Bar reef are accessible in the No 2 level of the Golden Bar mine. The reef is a typical multi-banded mesothermal vein, mostly c. 1.75 m wide, enclosing narrow horses of schist country rock. Scheelite is sparsely distributed, and is more common in small veinlets in the hanging wall schist. The country rocks are textural zone I-1m schists of prehnite-pumpellyite to pumpellyite-actinolite metamorphic facies. Their geochemistry suggests they are part of the Caples Terrane, and of calc-alkaline volcanogenic arc origin. The associated Wakamarina Quartzite is strongly recumbent folded, and of the same metamorphic grade, with abundant pumpellyite, stilpnomelane, and garnet, presumably spessartine. Although it has geochemical signatures of a deep sea sediment, it is depleted in Cr and Cu, and greatly enhanced in K and Ti, when compared with a standard chert. It also has trace element characteristics of a calc-alkaline arc-related sediment. However, associated greenschist has MORB-like incompatible element chemistry. The Golden Bar reef lies within a steeply dipping, normal to transtensional dip-slip fault adjacent to a shallow-dipping mylonite shear zone, which, at least on the footwall side, is 040 m wide. The shear foliation has been severely dragged down to nearly parallel the Golden Bar reef within 1 m of the quartz lode. Preliminary structural analysis suggests that the shear zone is extensional. X-ray diffraction analyses of the wall rocks show a progressive depletion of amphibole, stilpnomelane, and pumpellyite towards the reef, and enhanced illite/muscovite and Kfeldspar adjacent to the lode, along with possible graphitic carbon within 10m. Two zones of intense quartz veining occur, one adjacent to the hanging wall for 12 m and one from 40 m outwards. Quartz vein systems in the country rock are complex and span from pre-schistosity to post-mylonite. They include multiple generations of quartz, actinolite, stilpnomelane, pumpellyite, albite, adularia, chlorites, illite/muscovite, calcite, and scheelite. Metal analyses across the Golden Bar reef showed gold values of 0.13.1 ppm, and low tungsten values, consistent with the observed sporadic scheelite occurrences. As and Sb are at background levels, but enhanced Cr (150 - 430 ppm) relative to the schists (30 - 41 ppm) suggests that the source hydrothermal fluids passed through and leached mafic to ultramafic rocks.

Jan 1, 1994

By D. A. Kraai, S. Floreen

The effect of 1 to 50 ppm S on the ductility of nickel at 800° to 1400°F was studied. Results at each temperature showed a decrease in the reduction of area from approximately 95 to 5 pet over the sulfur range studied. Ductility varied with grain size, but only to a minor extent relative to the sulfiw effect. The effects of sulfur were completely offset by the addition of small amounts of magnesium. The results indicate that the "hot-short" loss in ductility is not an inherent property of nickel. Some possible mechanisms which cause the loss in ductility are described. MANY metals or alloys that normally possess high ductility exhibit a ductility loss at intermediate temperatures. This loss in ductility is often called "hot-shortness". Numerous examples of this phenomenon have been reported in the literature. Much of this work has been reviewed by McLean1 and by Rhines and Wray.2 To date there is no fully satisfactory explanation of the cause of this intermediate-temperature hot-shortness. It is generally recognized that impurities, and particularly impurities that form low-melting phases, can cause embrittlement. Examples of hot-shortness have been reported, however, where there were no obvious impurities present which would lower the ductility. Thus there has been some basis for believing that hot-shortness is an inherent property, and that even the purest metal would display a hot-short loss in ductility. This latter hypothesis was recently put forward by Rhines and wray2 based on studies of nickel and nickel alloys. In the discussion of this paper, however, Guard noted that high-purity nickel showed no hot-shortness.3 Thus there is reason to doubt whether pure nickel, or by inference any other pure metal, will inherently exhibit hot-shortness. The present work was initiated to determine the extent to which hot ductility was sensitive to very small amounts of an impurity element. If it could be demonstrated that hot-shortness could be induced by only minor amounts of an impurity, then it might be argued that hot-shortness in general is an impurity effect, and not a fundamental property of pure metals. The particular impurity studied was sulfur in nickel. The deleterious effects of sulfur are well- known. It is also well-known, and will be shown below, that additions of magnesium will render sulfur innocuous. When no such refining agents are added, however, the Ni-S system is a very useful one for studying the influence of small amounts of impurities. EXPERIMENTAL PROCEDURE Two heats containing -24 ppm S were vacuum-melted and small amounts of magnesium were then added under an argon atmosphere. These alloys were used to show the effectiveness of the normal magnesium treatment in overcoming the influence of sulfur. A second series of alloys with a sulfur range of 1 to 50 ppm was then prepared by vacuum melting nickel in alumina crucibles. No elements, such as magnesium, which tend to combine with sulfur were added. The higher sulfur contents were attained by adding nickel sulfide. Lower sulfur contents were prepared using a method in which the melt was oxidized under vacuum to produce the reaction S + 2O = SO2 These heats were subsequently deoxidized with carbon. Ten- to twenty-pound ingots were cast of all of the alloys studied. The compositions are given in Table I. The ingots were forged and hot-rolled to 3/4-in. bar. They were then annealed at either 2000" or 1600°F to produce different grain sizes. One-quarter-in.-diam tensile specimens were machined from the bars. These were tested at 800°, 1000o, 1200°, and 1400°F. The specimens were held at temperature approximately 45 min before testing. The strain rates were 0.005 min-1 to yielding, and 0.05 min-' after yielding. No extensometers or gage marks were placed on the specimens because the higher sulfur heats tended to fracture at the knife-edge indentations or gage marks. The properties measured were ultimate tensile strength and reduction of area. The analytical technique for determining sulfur at low levels was that developed by Burke and Davis.4 They reported a standard deviation of 1 ppm at an average sulfur level of 4 ppm in NBS standards. A standard deviation of 3 ppm is probably more realistic for the alloys used in this investigation considering the possibility of some segregation in the ingots. RESULTS A summary of the tensile results is given in Table I. As shown in the table, both heats to which

Jan 1, 1964

By Chris Larsen, Ian Orford, Mike Cooper

"An autogenous grinding circuit was commissioned at the Brunswick concentrator in October 1998. The autogenous grinding circuit replaced existing surface crushing plants, fine ore storage, rod and primary ball mills. The 8.54m diameter x 4.27m long (EGL) AN1 mill is driven by a bidirectional variable speed 6.3MW ABB wound rotor motor with Slip Energy Recovery (SER) drive. The AG mill was subsequently converted to SAG operation in May 1999 for a number of reasons. The mill is operated in closed circuit with horizontally inclined 660mm diameter cyclones to produce a circuit product P80 of 85 microns. Extensive test work and JKSimMet design modeling resulted in a production circuit operating closely within design expectations.The circuit is highly instrumented and controlled via a hybrid Programmable Logic Controller (PLC-5) and Fisher PROVOX Distributed Control System (DCS) that is in communication with the property information highway. An expert control system (Gensym G2) is used for control of the SAG mill load.Engineering and construction were completed in 28 months from the time of management approval for the project. The Brunswick AG/SAG mill circuit was commissioned on schedule at the $M 23.5 forecast budget."

Jan 1, 2001

By Jan E. Nesset, Antonio DiFeo, James A. Finch, Jose Hernandez-Aguilar, Cesar O. Gomez

"The gas dispersion measurement sensors and methodology developed by the mineral processing group at McGill University have to-date been employed at a number of plants in Canada, Australia, the U.S., South Africa and South America. In some cases the measurements have been directly linked with metallurgical performance while in others the gas dispersion surveys on their own have proved very useful in understanding the behaviour of the flotation cells. In addition to reviewing the current state of the gas dispersion measurement technology, the paper will present a series of case studies from the various plants and will show how this technology brings a remarkable new level of understanding to flotation behaviour. The influence of the bubble size distribution on recovery and grade are emphasized in the paper.INTRODUCTIONBackgroundThe advent of new sensors to characterize gas dispersion parameters in flotation cells is a development that is long overdue. While the chemistry of flotation has been studied since the early 1900’s, it is only now that the significance of bubble size distribution, gas rate and gas holdup can be meaningfully measured in-plant with robust and precise sensors. Early researchers, like T.A. Rickard (1916) recognized the importance of understanding the role of air and bubbles in flotation when he wrote in 1916 “we know that the key to the flotation process is to be found not in the oil, the acid, or the apparatus, but in the bubbles. The man who understands the mystery of a soap bubble has mastered the chief mystery of flotation”. In his 1999 review paper on The Froth Flotation Century D.W. Fuerstenau laments the fact that due to their “inert nature”, bubbles have never received their due attention from researchers who tended to focus on the chemical, physical, surface and colloidal aspects, rather than the physics of the process. It is perhaps fitting that now, 100 years after the inception of industrial flotation practice at Broken Hill, Australia, researchers and industry have turned their attention toward the importance of truly understanding the role of bubbles in flotation."

Jan 1, 2005

By J. W. Whalen

The design, operation and evaluation of an instrumental method for the determination of fluid saturation in porous materials during multiphase flow studies is described. The presence of a magnetic tracer comprising approximately 20 per cent by weight of the aqueous phase is necessary in the utilization of this method. The results of two-phase relative permeability studies on two samples of porous media are presented. The realizable accuracy of the magnetic susceptibility apparatus in fluid saturation determination is estimated to be 2 saturation per cent. The response characteristics of the instrument, together with its simplicity of operation and maintenance are sufficient to recommend its use in routine laboratory studies. INTRODUCTION The problem of fluid saturation determination in laboratory multiphase flow studies characterizing oil recovery processes is one which has been given exhaustive study. Briefly the requirements which are considered essential for a method sewing this purpose are: (1) that the measurement be made external to the porous rock sample under study with no interruption of the fluid flow pattern, (2) the saturation indication must be independent of fluid distribution in the volume scanned by the measuring device, (3) the sensing element should have a small field of definition enabling several independent measurements to be made along the length of a core sample, and (4) the properties of the fluid phases should not be too greatly influenced by required tracer substances. Several methods of saturation determination have found acceptance as meeting most of the above requirements. These include resistivity,1 X-Ray absorption,2,3,4 radiotracers,5,6,7 and neutron8 diffraction The merits of these techniques have been discussed elsewhere in detail and will not be considered here. It may, however. be pointed out that the elaborate instrumentation required by the methods mentioned above, with the exception of the resistivity method (which is undesirable from other standpoints) encourages the development of methods of saturation determination which, while meeting the requirements listed, are simple to operate and maintain. It is the purpose of this paper to describe the instrumentation and evaluation of a technique for the determination of fluid saturation which combines relative simplicity with an accuracy and applicability comparable with methods now in practice. DESCRIPTION OF THE METHOD If the magnetic susceptibility of one of the fluid phases contained within a porous material is sufficiently greater than that of the remaining phases, the fluid content of the material with respect to that phase may be determined by an induction measurement. This may be accomplished by measuring the induced voltage in the secondary of a transformer which contains the porous sample and its interstitial fluids as a portion of the magnetic flux path. Since the fluids used in multiphase flow studies involving petroleum reservoir samples possess uniformly low magnetic susceptibilities, the use of a magnetic tracer in one of the fluid phases is required. In view of the relatively high paramagnetic susceptibility of salts of the transition elements, together with their high water solubility. these compounds become logical choices as tracer materials. Cobaltous chloride, having a specific magnetic susceptibility of 17.5 x 106 cgs electromagnetic units, was used as the tracer material throughout this work, in a concentration of approximately 20 per cent by weight in the aqueous phase. MAGNETIC SUSCEPTIBILITY APPARATUS Basically, the magnetic susceptibility apparatus consists of a transformer serving as the detecting head, a

Jan 1, 1955

By McHenry Mosier

Mercury is one of the strategic metals the supply of which has been raised from critical uncertainty to more than enough for essential demands. Work by the Bureau of Mines has contributes substantially to increased production of mercury in the United States and to consequent accumulation of Governments stock. Other contributing factors were higher prices for mercury and Government loans to operators. The Bureau has undertaken 15 exploration projects, 13 of which have been completed. This work comprised 40,307 feet of drilling arid 35,082 linear feet of sure ace trenching and has indicated commercial ore containing 37,400 flasks of mercury and marginal ore contain¬ing 29,200 flasks - a total of 66,600 flask , equivalent, respectively, to domestic production at 50,000 flasks per year for 9 months , 7 months, and 16 months. Early in 1944, as Government stocks had become adequate, domestic production was gradually curtailed cancellation of Government contracts for the purchase of mercury and Government control of labor and operating supplies.

Jan 1, 1944

By U Briem, R Verreet

The level of wire rope technology used in mine hoisting applications has a significant effect on the overall efficiency of the hoisting system. This paper discusses the effect that a reduction in rope mass per unit length and an increase in rope breaking strength can have on rock skip capacity and hence mine shaft output. A 20 per cent reduction in rope mass per metre for a typical 48 mm hoisting rope, while maintaining the breaking strength, increases the skipÆs capacity by circa 30 per cent at a suspended rope length of 3000 m. Such gains in shaft output, without any significant changes to the shaft or winder design, can have major implications for the feasibility of future deep mine projects. The technical challenge for rope manufacturers is how to get rid of 20 to 30 per cent of the rope mass while keeping the breaking strength and modulus of elasticity of the whole rope constant. CASAR are currently developing steel wire rope constructions where the steel IWRC has been replaced with high strength, high modulus fibres such as Kevlar«, Spectra« and Dyneema«. One of the key aspects of such composite rope designs is to ensure equal load sharing between the different rope components, ie in proportion to their area. If there is a significant difference in modulus between the fibre core and the steel outer strands, the core may not carry its proper proportion of the load and the outer strands would be overloaded. Some technical aspects of the design of composite steel wire ropes are discussed. A design and operational issue that needs careful consideration is the safe non destructive testing (NDT) of composite ropes. Traditional magnetic NDT would only be capable of inspecting the steel wires. Techniques therefore need to be developed that would give operators a reliable indication of the condition of the load bearing fibre core. This paper also discusses possible solutions to this very important NDT question.

Jan 1, 2005

Background A recent development in many industries,' including the mining industry, has been ever increasing acceptance and adoption of extended (12-hour) shifts and compressed work cycles compensated by more time off work by employees between cycles. In the Western Australian mining industry development of `long-distance-commute' (LDC) coincided with adoption of 12-hour rotating shifts. Preludes to LDC were the `construction-style' rosters with two crews plus allowance for annual and sick leave relievers working the statutory 13 consecutive shifts followed by one shift off. Crews rotated day to night shift weekly or at fortnightly intervals. Average hours of 72 to 78 per week were common. The author had personal experience working these rosters in the East Pilbara of Western Australia from 1977 to 1982. Workers tolerated these rosters until a suitable combination of frustration, boredom, despair and the `Five Grand Fever' triggered them to `pull the pin' and head for relaxation in Bangkok, Manila, Nimbin, or Margaret River according to their personal tastes.

Jan 1, 1996

By N. S. Dalal, X. Shi, V. Vallyathan

"Electron spin resonance (ESRJ spectrum of the hydroxyl (· OH) radical spin adduct with .the spin trap 5,5-dimethyl-1-pyrrolintt-N-oxide has been obtained in suspensions of freshly ground quartz particles. The concentration of the spin adduct (and hence of the • OH radicals) increases with the amount of grinding. The dust's potential for the generation of the· OH radicals is maximum when fresh (i.e., immediately after grinding) and decreases to 50% in about a day on storage in air. Studies involving metal chelates .indicate that the • OH radical formation involves mainly the silica surface and H20 rather than the Fenton reaction. The results suggest that hydroxyl radical reaction(s) could be important in the lipid peroxidation and fibrogenicity by quartz dust, particularly .in acute silicosis. INTRODUCTIONIn this paper we report on our electron spin resonance (ESR) detection of the formation of hydroxyl (·OH) radicals in aqueous suspensions of freshly crushed quartz particles. This work was undertaken with a view to find possible clues to the role of free radicals in the pathogenesis of quartz-induced fibrogenicity, commonly known as silicosis. We noted that while silicosis is one of the major health hazards in coal and mineral industries, the mechanism by which the quartz particles exert their toxic action on cells and the process(es) by which these actions progress to fibrogenesis are still poorly ·understood (Reiser and Last, 1979; Singh and .Rahman, 1987). It is generally thought, nevertheless, that the action of quartz particles on the biological membranes is the starting point of the silicotic process (Parazzi et - al., 1968). A possible clue to the mechanism of the membrane damage by quartz particles, in terms of the role of oxygenated free radicals, is suggested by the following observations. A suspension of quartz particles in contact with alveolar macrophages has been reported (Gabor et al., 1975; Koike et al., 1982) to initiate an enhancement of lipid peroxidation, defined broadly as the oxidative deterioration of polyunsaturated components of lipids. Hydroxyl (· OH) radicals are known to be capable of peroxidation by abstracting hydrogen atoms from cell-membrane lipids (Halliwell and Gutteridge, 1985) and of initiating lipid peroxidation in lysosomal membranes. (Fong et al., 1973). Arong other lines, it is known that exposure of cell membranes, fatty acids, and unsaturated food oils to ionizing radiation, which generates· OH radicals, causes rapid peroxidation (Halliwell and Gutteridge, 1985). Thus • OH radicals (and also other oxygenated species such as Oi, 10 2, and H20 2) might be expected to play a role in the toxicity of quartz. Earlier studies of the aqueous chemistry of quartz suspensions have reported detection of H2O 2 (Kalbanev et al., 1980), implicating the formation of ·OH radicals as transient species. However, we are not aware of any report of the detection of • OH radicals in quartz reactions, and thus the present study was undertaken. Since it-is known that, because of their high reactivity (hence short lifetime) in aqueous media, the • OH radicals cannot be detected via ESR directly (Finkelstein et al., 1980; Buettner, 1982) we have used .ESR combined with the spin-trap methodology (Finkelstein et al., 1980) for studying the· OH formation. The results show that· OH radicals are indeed formed in aqueous suspensions of freshly ground quartz; thus pointing to ·a possible new clue to the cytotoxicity of freshly formed quartz particles and thereby to silica fibrogenicity."

Jan 1, 1988

By U. S. Sawant

During the last few years, Process Machinery Division, Rexnord, has conducted extensive research on the effects of cone crusher variables such as speed, throw and cavity design on the productivity of the crushers. Simultaneously, Rexnord's engineers have developed advanced design and testing techniques and criteria that assure efficient and reliable crusher designs. The combination of these two has resulted in a design of the 2390 Omnicone (1000 hp) crusher which fits on an existing 7 ft. Symons foundation and yet is capable of producing twice the tonnage compared to our 7 ft. super heavy duty (500 hp) crusher. Both speed and throw can be varied to give a wide application flexibility from making twice the tonnage to the finest product. The 2390 Omnicone also incorporates innovative features such as full balance, cavity clearing, adjusting under load with automation capability, maintenance-free seals, one head for all cavities, ease of maintenance and servicing, etc.

Jan 1, 1987

By Otto H. Henry, Edward L. Badwick

Up to the present time, according to Hansen1 and Haughton,2 the constitution of the bismuth-indium system has not yet been published. The generally accepted value for the melting point of indium, as listed in most scientific journals and textbooks, is 155°C. Recently, however, H. M. Davis3 has determined a new melting point for indium of 257.3°C ± 0.1°C. Since bismuth has been used in preponderance as an alloying element in the majority of low-melting alloys, and indium has been used with considerable success in lowering the melting points of low-melting alloys,4,5 an interest has been developed in the application of these two metals, making a complete knowledge of the constitution of its alloys desirable. In this investigation, the melting point of indium reported by H. M. Davis has been found to be substantially correct. A value of 157.2°C ± 0.5°C was determined. The two eutectic compositions have been placed at 34 and 50 pct bismuth with their respective eutectic temperatures as 72.4'C ± 0.5°C and 90°C ± 0.5°C. The bismuth-indium phase diagram has been determined by thermal and microscopic analysis and is shown in Fig I. THERMAL ANALYSIS Granulated bismuth and indium shot, having a guaranteed purity of 99.99 and 99.95 pct, respectively, were melted in a carbon crucible by means of a laboratory heater. To minimize oxidation of the alloys, a heavy mineral oil (Nujol) having a high flash point was used. A platinum-platinum rhodium thermocouple 0f fine wire encased in a thin-walled Pyrex glass tube, about 1/8 in. in diameter, was connected to a type K potentiometer for temperature measurements. The thermo-couple was calibrated against the melting points of tin, bismuth, and the silver-copper eutectic and the boiling point of water. Since the temperature readings could be reproduced to 0.2°C, and the accuracy of the temperature standards in this range is slightly better than 0.5°C, it seems reasonable to assume that the temperature readings are reliable to approximately 0.5°C. The cooling rate could be controlled by varying the amount of insulation surrounding the crucible. Three or four layers of asbestos paper, 1/16r, in. thick, sufficed to give a cooling rate of from 1° to 2°C per minute. Undercooling was slightly noticeable. This condition was minimized by vigorous stirring, since the advantage of using slower rates was too small to justify the greater expenditure

Jan 1, 1947

By Harold Hopkins

THE Wright-Hargreaves mine is one of a group of seven mines long active in the Kirkland Lake district, Ontario. Detailed geological reports and maps covering the area have been published by the Ontario Department of Mines (1,3)t. Though all these mines work several productive veins there is one vein which is common to all and is known as the North Vein of the camp?not that it is the most northerly vein mined, but it is the more northerly of the two major veins of the camp. At the Wright-Hargreaves mine there are in all ten important producing veins, and most of them have a N.60°-65°E. strike and in general a steep southerly dip. It is a common belief that most of these veins lie along faults but it will be shown that whilst this is true of some of them it is not true of all, and also that a vein may lie in a fault along part of its course and elsewhere fill a fracture in line with the fault, this being a consequence of rotational movements that took place during faulting. The paper describes the history of faulting at this mine in particular, makes observations on the principal pre-ore fault, and describes the method used in solving the movements on the post-ore faults. Other details of geology are not discussed except to mention here that our main veins lie almost entirely in the syenite porphyry stock except on lower levels close to the east boundary of the property, where the North vein leaves the porphyry to enter the greywacke.

Jan 1, 1940

By Osvaldo A. Bascur

Connectivity between mining and metallurgical process operations and their business systems has become a reality. Expanded use of plant information on the desktop is a standard tool for revenue improvement, cost reduction, and adherence to production constraints. The industrial component desktop support access to information for continuous improvement and innovation by staff personnel and engineers. Collaboration between groups enables the implementation of an overall process effectiveness index based on losses due to equipment availability, production recovery and quality rate. In this sense, the paper point out three cases studies of large integrated power stations.

May 25, 1998

By E. G. King, W. W. Weller

Low- temperature heat capacity measurements of muscovite were made in the temperature range from 50° to 298 ° K. The entropy at 298.15 ° K was evaluated as S298.15 = 69.0 ± 0.7 cal /deg mole .

Jul 1, 1960

By S. Timbillah, R. LaDouceur, C. A. Young

A low carbon-chain trithiocarbonate ((NaOOC)CH2SCSSNa), known as Orfom® D8, was tested as an organic depressant in the differential flotation separation of chalcopyrite and molybdenite in the presence of sodium isopropyl xanthate (SIPX) or potassium ethyl xanthate (KEX). Flotation studies show that Orfom® D8 depressed chalcopyrite while molybdenite remained floatable. A study of the mechanism of adsorption indicated that Orfom® D8 adsorbs on chalcopyrite through its trithiol (CS -) functional group via both chemisorption and Orfom® D8-metal complexation. The Orfom® D8 depressant is selective and does not form any Orfom® D8-molybdenite bonds. Thus, the combination of the depressant in the presence of either collectors depressed the chalcopyrite and floated the molybdenite. Fundamental parameters of the Orfom® D8 including pKa determination as well as possible decomposition products of the depressant are reported. This study includes an economic case illustrating why using Orfom® D8 can be beneficial. INTRODUCTION Depressants are incorporated in mineral flotation units in the minerals processing industry to make or keep certain minerals selectively hydrophilic. Most reagents used are inorganic and include, for instance, sodium hydrosulphide (NaHS) which is the major reagent used for depressing sulphide minerals, particularly those containing copper, iron and lead. However, the issues with its use include high toxicity, tendency to explode, strong odour, and high consumption due to required high dosages as well as its tendency to oxidise in air. The latter can be overcome by conducting flotation in inert atmosphere such as nitrogen and recycling of the flotation process water. The use of more novel depressants that are essentially organic including homopolar reagents with hydrophilic functional groups on both ends of its structure adsorb onto a target mineral surface with one polar end, the other polar end orients into the bulk solution making the surface hydrophilic and thus, ensuring that the desired mineral does not float. The stringent environmental and safety regulations being implemented in recent times mean that the search for more environmentally friendly chemical reagents is a must have. The use of organic depressants for flotation systems such as Cu-Mo sulfide bulk concentrates has become increasingly important because of the health, safety and environmental issues surrounding the use of inorganic depressants. Nagaraj et al. (1983) investigated the Cu-Mo sulphide flotation system using a structure-activity study of depressants. They found that a major advantage of organic depressants is the ability to tailor-make organic molecules to suit many requirements and thus, eliminate the guess work approach that was predominant in the industry.

Jan 1, 2019

By Joseph Goessling, Mark Kroncke, James Parkes

The I-35 Capital Expressway (CapEx) Central Drainage Tunnels will serve as a stormwater collection system for the forthcoming I-35 Capital Express Central reconstruction project through downtown Austin, Texas. The schematic level concept design included three tunnels, 10 to 14 ft ID, totaling 26,000 LF. Constructability reviews during design development indicated issues with the concept design including phasing of construction, conicts with future retaining walls, staging area concerns, and signicant mixed face tunneling. The design was updated to mitigate these risks. The revised design includes two tunnels, both 22-ft ID and totaling 33,000 LF, that will be mined almost entirely in rock.

Jun 23, 2024

By Andrew M. Leszcykowski

In 1984, personnel from the U.S. Bureau of Mines examined the 9,550-acre Yatahoney Creek Wilderness Study Area (WSA) for mineral resources. This study area, in southwestern Idaho, is underlain by tuffs and basalt of Tertiary age. Owyhee County mining records and U.S. Bureau of Land Management records, and other references were examined prior to the field study. There are no known mines, claims, or prospects in or near the WSA. No evidence of mineral deposits or occurrences was observed. Oil and gas leases or lease applications are in the southern portion and northeast corner of the WSA. Although placer gold exists in the Owyhee River drainage, there are insufficient deposits of gold-bearing gravel in the Yatahoney Creek WSA to enable mining. INTRODUCTION The U.S. Bureau of Mines (USBM) and the U.S. Geological Survey (USGS) conduct mineral surveys of designated wilderness study areas (WSAs) 1/ to ensure mineral values that may be present are considered in wilderness recommendations. The USBM examines known mines, prospects, and mineralized sites, and the USGS performs geologic mapping, and geochemical and geophysical surveys on an areal basis.

Jan 1, 1986