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By George A. Desborough

Marine black shales of Paleozoic age in the Western United States that exceed 10 weight percent organic carbon contain as much as 5,000 ppm vanadium, 1,000 ppm molybdenum, 1,300 ppm nickel, 600 ppm cobalt, 16 ppm silver, 7,000 ppm chromium, 18,000 ppm zinc, 280 ppm cadmium, and 350 ppm selenium. Depositional settings include: (1) continental-rise and marginal-ocean basins, (2) continental-shelf and foreland basins, and (3) cratonic-platform embayments. Most of these metalliferous organic-rich shales have not been examined for resources because of rapid weathering and poor exposures which preclude easy sampling of unoxidized rock necessary to determine actual concentration and residence of indigenous metals. Generally, the marine black shales of Paleozoic age in the Western United States are richer in metals than marine Paleozoic black shales in the Eastern United States.

Jan 1, 1982

By R. E. Ray

In an effort to reduce the risks to underground miners of health hazards associated with exposure to high concentrations of diesel particulate matter(dpm), the Mine Safety and Health Administration(MSHA) published proposed rules in 1998 limiting dpm exposure in both underground coal and metal and nonmetal mines. The proposed rule for underground coal mines would require removal of 95% of dpm by mass, while the rule for metal and nonmetal mines would eventually limit total carbon exposure from dpm to 160 micrograms per cubic meter of air over an eight-hour shift. The comment period for both proposed standards ended on July 26, 1999.In this session, representatives from MSHA, the National Institute for Occupational Safety and Health (NIOSH), equipment manufacturers, labor and industry will discuss the impact of the proposed regulations on mine operations and worker health. Questions will be taken from the audience after brief presentations from each panelist. This paper provides a compilation of written summaries of each panelist’s opening presentation.

Jan 1, 2000

By John C. Holtz

Information on the gaseous products from the detonation of explosives has been obtained in two ways. In the first, the atmosphere in nines is analyzed after blasting, aid in the second, the gases found after detonating an explosive in a testing apparatus are analyzed. The Bureau of Mines, in

Jan 1, 1940

Agglomeration for Copper Heap Leaching Agglomeration of ore is a method which can be used to eliminate the migration of fine grained particles throughout a leach heap. Without agglomeration, fine ore particles are able to migration within the heap, clogging flow channels and producing large areas where access of the solution is poor. In order to gain the benefits of agglomeration and improve agglomerate strength even further in copper heap leaching, an economical, acid-resistant binder is needed. However, most binders have been used without any systematic reasoning. A set of novel testing methods were developed, including a soak test, percolation flooded columns, and larger long-term leach columns. The soak test compares the degree of breakdown when agglomerates are subjected to an acidic environment. While the percolation flooded columns and larger long-term leach columns evaluate the flow of leach solution throughout the ore bed. Systematic studies have been completed on a wide range of binders using these novel testing procedures. It was found that for a low grade chalcocite ore, which was rich in silica, from a southwest US mine, polyacrylamides reduced the fines migration the best in the novel soak test. The non-ionic binder, in particular, was found to reduce fines migration as much as 93 per cent. Several of the binders tested were shown to increase the hydraulic conductivities of the agglomerated ore up to 2.5 mm/sec, compared to a hydraulic conductivity of only 0.25 mm/sec when no binder was used. These binders also prevented 'slumping' of the ore, which indicates a decrease in breakdown of the agglomerates. The use of a binder also showed no interference with leaching reactions in long-term leaching experiments.

Sep 13, 2010

By N. Hmidi, T. Yalcin, M. Papadakis, B. Hilscher

Mill tailings, containing iron sulphides in particular, pose an environmental concern since they constitute a potential source of acid mine drainage which can damage vegetation, harm soil and living organisms, and contaminate groundwaters. Proper disposal of acid generating tailings is therefore an important issue that must be addressed and resolved in a satisfactory manner. Placer Dome Canada operates a 4000 t/d gold cyanidation facility at Musselwhite mine, in northwestern Ontario, where the mill tailings have been classified as acid generating. This study was conducted to explore the effectiveness of froth flotation in removing the sulphide minerals from these tailings and producing a low-sulphur, non-acid generating material that could serve as a capping material for previously deposited tailings. Laboratory semi-batch flotation tests were carried out in accordance with an experimental design procedure, and a computer simulation program was developed to facilitate the evaluation of flotation performance. In this investigation, pH, collector concentration, and airflow rate were considered as the relevant flotation variables, and their effects were examined both experimentally and by simulation. Results have demonstrated that flotation can successfully desulphurize the Musselwhite mine tailings and render them non-acid generating.

Jan 1, 2004

By J. J. Rutledge

I. Description of the Clinton Ores and Associated Rocks. The Clinton rocks in Stone valley comprise (1) thick layers of deep-red shale, (2) layers of reddish-gray shale interspersed with beds of sandstone and thin beds of extremely fossiliferous limestone, and (3) yellowish-gray shales alternating with thin layers of olive-colored shales. These layers of shale are all very thin and are at no point massive.' A bed of gray-white sandstone varying in thickness from 12 to 30 ft. occurs in the upper portions of the Clinton shales. This is called the ore sandstone, a name given to it by Rogers and adopted also by the Second Pennsylvania Geological Survey. It is the surest guide to the presence of the iron-ore bed, which lies below its lower edges at distances varying from 10 to 20 ft. This ore sandstone, in the valley, lies generally at very low inclinations, but often is locally subjected to considerable changes in dip. At its outcrop this ore sandstone weathers very easily and yields a rather sparse crop of stone, composed of dirty, iron-stained boulders. Upon the roads these boulders are quite well rounded, and bear fragments of crinoid stems and other fossil forms. The ore sandstone exhibits at many points evidences of former movements in this very great thickness of the shales, and as it is the only stratum in this series competent to transmit and record stresses due to structural movements, its evidence is of considerable importance in determining the occurrence of movements in times past.

Jan 1, 1910

By N Haque

Base metal ores contain low levels of toxic/hazardous elements such as arsenic, antimony, bismuth, cadmium, lead and mercury. Given the large tonnage of base metal ores mined and processed each year globally, the accumulated mass of minor elements introduced into the biosphere is large and could be expected to have a significant environmental impact. Life cycle analysis (LCA) is a methodology that has been developed to assess the environmental impacts of material supply chains over their entire life cycle. Assessing the toxicity impacts of metallic wastes and incorporating these impacts into LCA methodology is not a simple task given the complexity of the issue. However, research and methodology development is in progress internationally to address this. Despite limitations concerning the lack of a coherent framework for characterising the toxicity impacts of metals, including issues such as bioavailability, a study was carried out to give first estimates of the relative toxicity impacts of various waste streams from metal production processes. The wastes considered were: red mud; sulfide tailings (copper, nickel, lead/zinc); lead/zinc slags; synthetic rutile residue; iron oxide residue; and copper slags and anode slimes. These toxicity estimates can be considered the æworst caseÆ scenario for these wastes, where all the metals present are bioavailable. Combining estimates of the amounts of the various waste streams produced in Australia each year with the toxicity results showed that despite their relatively low human toxicity impact per unit mass compared to some other waste streams, red mud and the various sulphide tailings had the highest annual human toxicity load on the environment, along with copper smelting slag and dust. Data from the pH dependent leaching test reported in the literature were assumed to represent first approximations of metal bioavailability and used to compare the two approaches to estimating the toxicity impacts of red mud.

Jan 1, 2009

By S. Street

The Environment process, invented by Prof. H.K.Womer and developed at the University of Wollongong, simultaneously treats ferruginous and organic wastes via bath smelting. Conceived in the late 1980's, the patented process was originally developed using steelworks dust to settle solids from sewage, producing a composite material suitable for smelt reduction. Work began on the process in 1990 with the Australian patent having a priority date of February 1990. Early research focussed on settling of solids from sewage, while pyrometallurgical investigations examined smelting in small induction furnaces. By 1992 smelting trials had been undertaken in pneumatic and electric arc furnaces, the process being successfully demonstrated up to on 8 tonne scale. The success of this particular trial, and other smaller trials, resulted in construction of a 100kg DC arc furnace which was commissioned in 1993. By 1994 the main project focus was on development of the smelting technology. Over 3 years of trials on the DC arc furnace have identified and clarified many of the pyrometallurgical reactions. optimum operating parameters, as well as demonstrating the versatility of the process for treating a wide range of wastes. Currently the Illawarra Technology Corporation (lTC), the commercial arm of the University of Wollongong, is pursuing commercialisation of the process.

Jan 1, 1996

The accurate estimation of ore reserves is the most crucial element in a financier's assessment of the risks associated with funding a mining project. It is crucial because any deficiencies in the estimation of a company's ore reserves will be later reflected in the cash flows derived from the production and sale of the commodity. Bankers must rely on the advice of members of your institute in assessing the quality and quantity of reserves. This information helps determine the cash flows which bankers use in their credit making decisions. It is against this background that this exposition has been prepared on "what bankers require in ore reserve statements" or put another way, "what does a bank require in ore reserve statements in order for it to provide the necessary credit Approvals".

Jan 1, 1987

By E. J. Jacques

A typical problem in ventilation networks with multiple fan systems is the possibility of them interacting. Multiple fan systems are no exceptions in complex tunnels, and may also be met in mines where underground fans are installed. When aiming at controlling a multiple fan system in a ventilation network, e.g. with a view to maintaining an acceptable air quality level, yet at minimum power consumption, transient flow conditions frequently occur. Although in most applications these transients are short compared to the time needed to achieve the planned actions on the ventilation, one should, however, keep in mind that it is important to avoid any bouncing effect between different (adjacent or distant) fan systems. Therefore a simulation of the unsteady-state flows could allow us to learn more about the propagation of transients within the network, and their possible secondary effects Among others, one question that often is raised, is to find out in which sequence and at what time schedule each of the fans in a network should e.g. be started up? Another typical problem, into which an unsteady-state simulation could provide some insight is the following: how should the facilities of variable pitch angle and/or changeable RPM of several fans operating in parallel be handled and combined in order to obtain a flow rate that changes gradually from zero to its maximum value i.e. the sum of the individual throughput flows of all the fans. The literature is not very abundant on the topic of simulating transient flows in networks. There is no doubt that numerical models have been developed (Pollak, Christensen, 1987), most of the time for particular applications (Wala, Kim, 1985), (Tanaskovic et al., 1984), (Schultz, Sockel, 1991), etc. The aim of this paper is to present a model that also simulates one-dimensional compressible flows in unsteady-state conditions with, however, the specific intent to handle networks with more than one fan. PROBLEM STATEMENT The mathematical model chosen to describe the unsteady flows in a ventilation network is based on the dynamic and continuity equations applied to each of its airways. The following basic assumptions are made : - the flow in the airway is considered to be one- dimensional, - - the flow is assumed to be fully turbulent, and hence the ATKINSON equation for calculating the friction losses will be applied. Whether this equation remains valid for transient state flows remains an open question. However, this may reasonably be assumed since the interesting flow frequencies are low. A discussion may be found in (Kämpf, 1987) ; - the airways are assumed to have a constant cross- sectional area along their length. If obviously this would not be the case, it is always possible to subdivide the concerned airway into sections for which the previous assumption holds. Applying the basic equations of mass and energy conservation, the flow in each branch may be described by the Euler equation for Newtonian flows.

Jan 1, 1995

By A. Yaghini, Y. Pourrahimian

"Human factors (HFs) play an important role in the mining and mineral industry, affecting operational and maintenance efficiency and safety. Despite the introduction of new technologies and automation in this sector, it is well known that a significantly large proportion of total human errors occur during the operation and maintenance phase. A comprehensive literature review of HFs across several industries is provided. From this review, the impact of HFs on operation and maintenance is summarized, with a focus on what the mining industry is currently doing and what opportunities exist for additional improvements. Future research directions and themes are also identified.RÉSUMÉ Les facteurs humains (FH) jouent un rôle important dans l’industrie des mines et des minéraux, en ce qu’ils affectent l’efficacité et la sécurité de l’exploitation et de l’entretien. Malgré l’apparition de nouvelles technologies et de l’automatisation dans ce secteur, il est bien connu qu’une grande partie des erreurs humaines (EH) se produisent durant une phase d’exploitation et d’entretien. Cet article propose une analyse documentaire approfondie des FH dans plusieurs secteurs. L’impact des FH sur l’exploitation et l’entretien est résumé à partir de cette analyse, une attention particulière étant accordée à l’évolution de l’industrie minière et aux possibilités d’améliorer davantage ses activités. Sont également identifiés les futurs thèmes et voies de recherche.INTRODUCTIONDuring the past several decades, the mining industry has focused on improving equipment, machinery, and methods that have led to more advanced hardware and software, equipment with higher reliability and productivity, and other technological advancements. These actions have improved safety and productivity and have reduced casualties and maintenance workload. Although today’s mining equipment and machinery are technologically advanced and highly reliable, the risk of accidents is still relatively high and key performance indicators have not improved significantly compared to other industries (Sorensen, 2012). A prominent reason could be due to insignificant integration of human factors (HFs) as part of planning, operation, and maintenance activities. The current mining system is a people system, and inevitably HFs and human error (HE) figure prominently in all aspects of this industry. Even the most advanced technologies and innovations require operators and maintainers with significant knowledge and skill, which could increase the potential for HE."

Jan 1, 2018

By Robert H. Poppe

The Regional Copper-Nickel Study examined the potential impacts of copper-nickel sulfide mining, concentrating and smelting operations in northeastern Minnesota and gathered extensive monitoring data on the ecological characteristics of the region's aquatic and terrestrial biota. Because of the many development options possible, the diversity of the region's ecology, and the uncertainty of future environmental regulatory requirements, the Study did not attempt to measure the magnitude of environmental impacts on specific biological communities from a specific development proposal. The Study provides a broad base of environmental resource and impact information that hopefully will assist mining developers and environmental regulators when assessing specific proposals in the future. The following discussion is not a description of what will happen if copper-nickel development occurs in northeastern Minnesota but an exploration of why certain potential aspects of such development should be carefully considered and adequately understood before unnecessary or irreversible decisions are made.

Jan 1, 1980

By Ian Hooper, Alan Winter, Stefan Sadokierski, Craig Covil

The existing Tappan Zee Bridge was built in the late 1950s and has been working over its design traffic load for some time now. A new project, which is being jointly sponsored by the New York State Thruway Authority and Metro-North Rail Road, is looking at new alternatives to provide new road and rail crossings of the Hudson River. These include 2 to 5 mile and potentially longer tunnel crossing options that include hardrock TBM and EPBM opportunities. The paper describes the project needs and tunnel concept design work done on some of the alternatives. It also relates to the current EIS process for the project and talks about a possible double-stacked tunnel option. It also talks about the geology and environmental constraints relating to tunneling and provides and introduction to the tunnel ventilation work necessary for tunnel crossing of this magnitude. It does not report on the bridge engineering options being evaluated.

Jan 1, 2005

By R. T. Hukki

IT is no great exaggeration to say that present grinding practice and economics are largely determined by lining design. A record of outstanding liner wear can be achieved with any liner surface pattern that will positively lock the outer layer or layers of grinding media. With no slippage, lining wear is bound to be slight. At the same time, popular practice calls for tumbling loads of about 50 pct of mill volume to obtain maximum grinding capacity. Innumerable parallel grinding investigations have verified that optimum speed for such a mill lies within 70 to 85 pct of theoretical critical speed. If the mill is speeded up to 100 pct of critical, little or no grinding can be accomplished. Earlier Work on Supercritical Grinding: First investigations concerning grinding at supercritical speeds seem to be very old. Remarkable work on the subject has been performed by White,&apos; and his experiments have been described and summarized by Richards.&apos; White&apos;s contributions seem to have passed unnoticed by Fahrenwald,2,3 whose extensive experiments have been well presented, yet apparently very little appreciated. Additional work on grinding at supercritical speed has been reported, e.g., by Lewenson and Tscherny,&apos; USSR; Anselm and Grunder,&apos;, Germany: and Rose and Evans." Great Britain. Subcritical and Supercritical Speeds: In the formula of the critical speed given in the textbooks of mineral dressing, no factor indicating the coefficient of friction is generally included. If this factor = 1.0, which is equivalent to grinding conditions in a mill provided with heavily ribbed lining, the formula of the critical speed holds as such and grinding is possible at subcritical speeds only. In a mill equipped with a smooth or relatively smooth lining, the numerical value of the friction factor in the denominator of the formula becomes <1.0, indicating that grinding at supercritical speeds should be possible in such mills. It has been recently shown by the author&apos; that a wide supercritical speed range will become available for grinding—and especially for fine grinding—if the basic conditions within the mill have been selected properly. Mathematical analysis of mill dynamics at supercritical speeds&apos; has indicated that the mill speed may be increased if: 1) total mass of grinding medium decreases, 2) mass of the individual grinding piece increases, and 3) the coefficient of friction between the outer layer of medium and the mill lining decreases. It is obvious that the mass of the individual grinding piece will be affected by its shape and by its specific gravity. The coefficient of friction decreases with: 1) increasing smoothness of liner surface, 2) increasing roundness of the grinding piece, 3) increasing fineness of material to be ground, 4) decreasing pulp density, and 5) decreasing hardness (abrasiveness) of the mineral to be ground. In a mill equipped with heavily ribbed lining, practically no size reduction will take place between the lining and the outer layer of tumbling medium, because slippage is prevented. In the overwhelming majority of today&apos;s mills the grinding accomplished is by virtue of cataracting and/or cascading media with some action within the tumbling charge. Sub-critical speeds only can be applied. In grate-type or peripheral discharge mills equipped with a smooth lining a tumbling load of any kind of common medium occupying about 50 pct of mill volume will behave in such a way that practically no slippage will take place. This has been verified in experiments run by the author in the laboratory and in pilot plant mills&apos; equipped with smooth lining. Again, the operation is limited to the subcritical range. In a mill with a smooth lining, grinding will be possible either at subcritical speeds or within a wide supercritical speed range as soon as the basic requirements for a desired speed are fulfilled. In a mill operated at supercritical speed, any point on the liner surface proceeds at a speed greater than that indicated by the formula of the critical speed, while any grinding piece situated in the outer layer of the medium against the lining proceeds in the same direction at a speed less than that indicated by the critical speed. This speed difference produces a very effective attrition grinding zone between the liner surface and the outer layer of the medium. The share of attrition grinding of the total grinding accomplished increases rapidly with increasing speed in the supercritical speed range. The smooth surface of the mill lining may be well illustrated by the surface of a bucking board. The outer ball layer may be similarly represented by the lower surface of a muller. If the bucking board, the material to be ground, and the muller all proceed in the same direction at the same speed, no grinding will result. This is the general situation in the mills of today. If, however, the muller is pulled with respect to the board, moving or stationary, grinding will be accomplished effectively. Although grinding in today&apos;s mills is primarily the result of cataracting and/or cascading media, the principal place of grinding at high supercritical speeds will be the attrition zone.&apos; In the mineral dressing laboratory of the State Institute for Technical Research. Helsinki, Finland, large quantities of different ores have been ground in a pilot plant ball mill (3x3 ft) at a top speed about 230 pct of the critical. With the same mill, theoretical investigations concerning the grinding characteristics of ball mills equipped with a smooth lining have been carried out up to the speed of 313 pct&apos; of the critical. With a smaller mill, the grinding characteristics with a variety of grinding media have been investigated at speeds up to 2000 pct of the

Jan 1, 1959

By Kagl J, Publlier M, Nekitel S, Arumba J, Rangin C, Mosusu N

Since the advent of plate tectonic modelling, the Ramu-Markham valley has been thought the site of a classical island-arc/conti- nent collision zone. In this interpretation the units south of the Markham Valley are held to be island are / micrcontinental mate- rial accreted to Australia and those north of the valley are thought to represent a separate Finisterre island-arc terrane. Recent remapping by the Geological Survey of Papua New Guinea shows: (1) there is no terrane boundary along the Ramu-Markham valley (2) the Finisterre Volcanics are probably part of either a fore-arc sequence or oceanic plateau obducted onto a microcontinent/ volcanic-arc composite terrane, accreted to the continental Australian plate. A new tectonic model is proposed for northern PNG and involves: (I) Eocene to Late Oligocene subduction below a microcontinent remote from Australia to produce the Sepik are and related intrusives, the Finisterre Volcanics (fore-arc or possible oce- anic plateau), together with the Alife blueschist. (2) obduction of the Sepik arc in Late Oligocene-Early Miocene times over the advancing Australian plate. This resulted in crustal melting, some of the products of which are the Mid- dle to Late Miocene Akuna and Bismarck intrusive complexes of the Maramuni arc. (3) obduction of the Finisterre Volcanics began in Early Pliocene times and continues today. (4) post-Middle Miocene mineralisation is the result of melting after obduction of the Sepik microcontinent.

Jan 1, 1997

By V. G. Mooradian, John T. Norton

The diffusion of metal atoms into the crystal lattice of another metal and the assumption of regular positions to form a homogeneous alloy are some of the most fundamental phenomena of structural metallurgy. The mechanism of this process has been the subject of a great deal of study from many viewpoints, but the picture is still far from complete. It is generally believed that if one metal is to diffuse into another, the first must have some solubility in the second1. This means that the solvent must be able to accommodate the stranger atoms, either on points of its own lattice or in the interstices between, without losing its own crystal-lographic identity. It is also a general observation that cold-working is a distinct aid in the diffusion process, causing it to take place with greater rapidity at the same temperature or with the same speed at a lower temperature. There is considerable doubt, however, as to the real significance of the deformation in its effect on the diffusion mechanism. Several factors associated with the cold-working may be responsible for the increased diffusion rate. The plastic deformation causes a distortion of the solvent lattice, which may be an aid in the assimulation of atoms of another kind. There are many references2 in the literature that suggest that some distortion or "loosening" of the lattice is necessary for atomic migration and that diffusion cannot take place in the undis-torted lattice. On the other hand, it may be that the cold-working causes an increase in surface of contact between the two metals through fragmentation or provides a more intimate contact that is necessary for diffusion. If it is true that lattice distortion is an important factor in diffusion, it seems as if there should be some particular relation between

Jan 1, 1935

By James CH

For drainage sediment to be used as a successful sampling medium in reconnaissance geochemical surveys, the length of any dispersion train from a typical target must be great enough for it to be detected by a widely spaced sampling pattern, and must also be homogeneous enough to avoid it being missed by the unfortunate selection of a random low value sample. Elements which occur in stream sediments in the form of discrete heavy minerals present two special problems in this regard. Since the element is concentrated into a few particles, the medium is extremely heterogeneous, which makes representative sampling impossible unless very large samples are taken, while the high specific gravity of such grains leads to their being concentrated in traps along the stream bed. Several ways of overcoming these difficulties have been suggested. Among these the "schlich" test, in which heavy material obtained by panning is taken for analysis is among the most popular. However, the results of the present study indicate that while this method improves the nature of the patterns obtained, they are still far from satisfactory. Alternative methods of sample preparation, including the taking of light material for analysis, appear to provide better answers to the problem. In the area studied this approach eliminated most of the "noise" associated with the data obtained by other methods, as well as giving an extended dispersion pattern.

Jan 1, 1986

By Charles R. Garrett

The American Borate Company, a wholly owned subsidiary of the Owens Corning Fiberglas Company under a management contract to the Hanna Mining Company, owns and operates an underground borate mine in Death Valley, California. The mine, named the Billie Mine, is located 24 km (15 miles) southeast of Furnace Creek along Highway 190. The ore body is under Death Valley National Monument with the major portion of the surface facilities located just outside the monument boundary. (See Figure 1.) The Billie Mine produces approximately 227 000 metric tons of crude ore per year. About 65% of finished product is supplied to Owens-Corning, the remainder is sold to other fiberglass producers. Geology The borate minerals in the Billie ore body were deposited in the lower main member of the Furnace Creek Formation, which is Pliocene in age. The ore body is thought to have formed from volcanic springs in or near a small lake basin. The deposit is essentially a limestone breccia that is permeated with borate minerals and surrounded with limey lake bed mudstones and shales. The ore body is mineralized with two main borate ores, colemanite and probertite. A third borate ore, ulexite, mainly occurs in the upper part of the ore body. The original mineral of deposition is thought to have been ulexite. Ulexite is a sodium-calcium borate hydrated with eight molecular waters. Due to heat and pressure from burial by later sediments, the ulexite had water forced out of its structure and recrystallized as probertite. Probertite is another sodium-calcium borate, with five molecular waters. Colemanite formed when surface water seeped into the prober-

Jan 1, 1985

The conclusions reached by den Tex after a study of the fabric of some rocks from Broken Hill have been used to support the epigenetic hypothesis for the origin of the ore, first by Edwards (1959, p. 70) and then by Stillwell (1962, p. 131) in his criticism of Segnit&apos;s (1961) views. Den Tex claimed that the petrofabric study provided &quot;independent evidence that the ore, at least in its present form, post-dates all events of a diastrophic nature in the area concerned&quot;.Repetition of this claim by Edwards and by Stillwell and the lack of any criticism of den Tex&apos;s work for more than three years implies its general acceptance by geologists in Australia. Therefore it appears necessary to examine parts of den Tex&apos;s paper in detail to show that his, conclusions are unwarranted. The major weaknesses in his study are that1. the petrofabric study was inadequate to warrant any major conclusions, and2. the petrofabric data allow alternative conclusions.Den Tex made a single visit to the field, collected six carefully selected specimens and presented quartz and&#183; biotitepetrofabric diagrams for two specimens, quartz-diagrams alone for three more and included three diagrams of the orientation of c-axes and fractures in one specimen. It is not reasonable to come to firm conclusions about the origin of such a complex area as Broken Hill on such inadequate data, despite den Tex&apos;s claim (p. 87, lines 22 and 23) that &quot;a thorough investigation of the quartz-fabric of the wall rock was undertaken&quot;.Den Tex&apos;s interpretation of each diagram is open to criticism, and alternative (and to my mind, preferable) interpretations may be made. It is impossible to evaluate den...

Jan 1, 1962

By G. Mercher

El presente trabajo refiere cómo los concentrados de cobre pueden fundirse en un sistema de ciclón con un reactor de soplo por alto. Asimismo, se describe el proceso de la técnica de flotación durante las dos primeras décadas del siglo anterior, donde el concentrado de grano era muy fino, aunque existieron razones económicas que contradecían el uso de tal concentrado de flotación en el horno de tiro. En este sentido, se utilizó el horno reverbetorio, cuyo trabajo neutro se encuentra libre de toda reacción química metalúrgica. La eficacia de este equipo permitió la construcción de otro horno, al tiempo que satisfizo las necesidades grandes de otras plantas de flotación eficientes. Sin embargo, surge la necesidad de mejorar dicho proceso a mediados de este siglo, conduciendo a la aplicación de otro métodos como el Outukumpu, el cual satisface los requisitos de control ambiental or concentración de las sustancias gaseosas detríticas, asi como al uso de otros equipos.

Nov 20, 1978