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By Javier Ramirez

"Recent R&D pilot plant testing was done to validate a full industrial scale system for recovering residual magnetite from the tails of an iron ore concentration plant. The recovery system is based on an autogenous heavy media separator treating a tailings slurry at 0.45% solids by weight. A 3,100 m3/h capacity concentrator was installed based on the testing findings. Excellent metallurgical results have been observed in two years of continuous operation. This experience is the basis for the proposal of a novel process consisting of the preconcentration of base metals ores; the idea being to obtain a heavy bulk concentrate of the polymetallic minerals and discarding in one step the light gangue mineral components. The bulk concentrate then proceeds to conventional froth flotation. The reduced volumetric flow of the bulk concentrate allows a reduction in the size of the subsequent flotation circuit. A prerequisite for the heavy media separation is a fine size grinding of the ore and a correspondingly high degree of liberation of the mineral species to be recovered. A process scheme is also presented in which the gravity concentrator works in conjunction with a companion tailings thickener for process water recovery. The underflow from this thickener, having paste consistency, can be sent to a tailings dam or mixed with Portland cement for mine backfill. The process water in the system is managed at an estimated recovery in excess of 98%. Additional R&D work using this novel approach is being considered by a large iron ore concentrator for removal of liberated silica from the final concentrate; and for upgrading 3.5 million tons of a marginal hematite reserve owned by the mining company.INTRODUCTIONGravity preconcentration (static and dynamic) of sulphides prior to froth flotation has been and is being practiced at various concentrator plants (Asarco´s Young Mill: heavy media cone; Mount Isa: DSM cyclone; Afton Mines: Denver jigs; Tsumeb Mine: Reichert cone) (Burt, 1984). The idea behind installing preconcentration equipment is to reduce the volume of feed processed on flotation, thus requiring smaller flotation plants although other advantages may be of importance, such as obtaining richer concentrates due to higher grade feed, better process water and energy management, and reduced flotation reagent consumption.The SedconTM solid/liquid separator is a versatile process unit patented in Mexico (MX/u/2007/000305). As a gravity device, it may be classified as an autogenous heavy media dynamic concentrator. Figure 1 depicts the Sedcon (Sedimentador de conos) separator. The four main components are as follows: the feedwell for efficient mixing of the pulp with dilution water and flocculant (and coagulant for water clarification); the inner cones (passive elements for solid/liquid separation); the discharge underflow cone; and the scraper mechanism. The standard discharge cone is a 60° inclined cone for general applications. For paste tailings thickening applications, a deep cone with a 69° inclined cone is used."

Jan 1, 2016

By A. F. Banks

"IntroductionThe typical potash processing plant recovers and/ or upgrades from 10% to 20% of its production through the recrystallization process. The feed to the recrystallization section consists of preconcentrated slurries of fine crystal size that cannot be raised to the required product grade by flotation and fine dusts also of low grade and too fine for compaction feed. It produces high grade white potash crystals that can be marketed as a high grade product or blended into the flotation products to raise their grade. In this chapter, a typical leaching (dissolving) and recrystallization operation will be discussed.The crystallization process makes use of the three phase system chemistry of NaCl, KCl, and H,O. The normal potash process operates on a temperature range of 75°F to 95 °F. A three phase slurry feed to the dissolving circuits will be within that range. The potash (KCl) is dissolved by heating the slurry in the presence of sufficient brine to a temperature of 190°F to 200°F. As the slurry is heated, the potash (KCI) dissolves and the salt (NaCI) precipitates. The potash rich brine is then clarified and the salt and other undissolved solids removed by thickening. Clarified brine becomes the crystallizer feed.The hot brine is cooled in evaporative cooling crystallizers. In cooling, the potash precipitates as a high grade white crystal. Crystallization is done in multiple effects to permit energy recovery and control of the process. In a four effect crystallizer the cooling is done by recycling mother liquor counter currently through the first two effect condensors and using brine pond brine for the cooling of the last two.The crystallizer product is removed from the last effect as a slurry at normal process temperature and is fed either to its own centrifuging and drying circuit or blended with the flotation product for centrifuging and drying."

Jan 1, 1989

By R. E. Dye

IF gold mining is to assume, or it might be better said to resume, a place of ' importance in the national economy of this country following the present war, then one must accept the thesis that gold will maintain the place it has for many generations held in the minds of men as a substantial and lasting emblem of material wealth-a metal in exchange for which men have always been ready to give up the possession of their worldly goods. The thought bas been advanced by some that gold is not necessary as a basis for exchange, that it has no real value anyway and, therefore, the world would wake up some morning to find that no one wanted gold and that, over night, its possession bad in some way ceased to be desired. Holding an equally extreme view there are those who advance the idea that, following the war, gold will in some mysterious way enjoy a fantastic increase in value. Neither of these extreme views can be successfully supported. To presume that by legislation or by general agreement gold would be or could be, over night, dethroned to the position of common stone is wholly beyond the realm of any possibility. The thought that this could come to pass is advanced by, and is attractive to, only those peoples who do not have gold and do r:ot have the means of producing it. To believe that the fundamental value of gold will suddenly change is likewise fantastic. I refer to the fundamental value, not the dollar price, of gold, for it cannot be denied that, with the colossal war expenditures now being made and with the huge national debts which are being piled up, there is a possibility, indeed per-haps a likelihood, that the dollar price .of gold may be revised upward. For the purpose of this discussion, however, that possibility is irrelevant and need not be considered.

Jan 1, 1943

By B. Krysa, A. Mitsui, T. L. Koehler

The presence of arsenic, even at trace levels, in copper processing leads to the risk of arsine gas where reducing conditions exist that can reduce any soluble arsenic present to its minus 3 valance state and generate hydrogen gas from the solutions. This risk is understood to be significant within the industry, particularly in the case of liberator cells where copper concentrations in solution are drawn down to remove the copper and impurities from the bleed stream. However, there are numerous other potential areas where the arsine gas risk exists including contact between active metal such as iron, zinc or aluminum and arsenic bearing solutions in pyrometallurgical dust treatment, refining and acid plant operations. In turn this breaks down to different mitigating strategies dependent on the risk scenarios considered; for example, how this risk interacts with Change Management, Confined Space Entry or Contractor Training. The ISO 45001 is an emerging standard meant to improve employee safety, reduce workplace risks and create safer working conditions all over the world. The paper shows a case study of how a framework consistent with the tenets of ISO 45001 has been used to provide a consistent assessment of this risk for a wide variety of copper operations and the expectations of how this may be used to effectively improve the effectiveness of barriers against future incidents. INTRODUCTION Arsine gas (AsH3), first identified in 1775, is a highly poisonous, colorless, non-irritating gas with a mild garlic odor that is heavier than air. Arsine gas is generated when reducing conditions are generated in the presence of hydrogen ions and arsenic compounds. Present permissible occupational exposure limit as defined by Occupational Safety and Health Administration (OSHA) as an 8-hour time-weighted average is ppm (0.2 mg/m3). Further increasing the risk, conventional respiratory protection utilizing half or full masks with gas filtering cartridges provide minimal protection against arsine. In copper processing plants, the risk of arsine generation is well understood in liberator cells, which are part of the electrolysis process. In this process, solutions containing copper are reduced in copper concentration removing not only the copper, but also arsenic, antimony and bismuth. The residual solution can be bled to control impurity build-up in the refinery. In this process, if the copper concentration is reduced to the point where As3- can form, arsine gas is generated via reaction with hydrogen ions generated during the plating process. The copper concentration at which arsine gas is generated depends on copper concentration at the cathode surface, the temperature and the acidity. As a result, there is always a risk of arsine gas generation in the liberator cell. Process measures to minimize or mitigate arsine evolution are tight control on final copper concentration, warm temperatures, fresh feed distribution and internal acid recirculation rates. Operator exposure protection measures are hooding, ventilation, arsine detection systems, restricted personnel access, automated shutdown controls and pre-defined evacuation plans.

Jan 1, 2019

By J. N. De La Vergne, J. S. Redpath

"The authors make recommendations that they believe will improve the efficiency of a mining company's use of a mining contractor's services. The recommendations are in the form of specific ""DO"" or ""DO NOT"" instructions, giving explanations and covering the contracting process from the end of the feasibility study to the end of the job. IntroductionThis paper is an attempt by the authors to set out some of the things which they feel an owner should consider to achieve maximum effectiveness from mining contractors. It is based on our experience as contractors as well as our experience as consultants to owners. Should this paper create the impression that we feel all the responsibility lies with the owner, this is neither our intention nor our belief.Before the Tendering Process BeginsUse Defined EstimatesIn Feasibility Study DO NOT estimate your cost or schedule by telephoning contractors and asking them for ballpark figures. The only kind of estimate that is worth anything is the one that is clearly defined on paper and bears the signature of the author. This type of time or cost estimate takes time to prepare. In general, the estimate will be worth what you pay for it.Ensure Adequate FinancingDO NOT ask contractors to tender on a project unless the funds have been approved for it. Remember that, depending on the size of the job, it will cost the contractor from $5,000 to $50,000 to prepare his tender. When financing is not assured, a single contractor should be approached regarding a detailed estimate and he should be paid for it. Contractors should not be expected to finance speculative mining ventures."

Jan 1, 1980

By Miguel A. Cuba

Trends in the mean and/or variance are a longstanding challenge in mineral resource modeling. Geologic modeling and/or grade domaining are often employed to account for heterogeneities in mineral grades; however, this is only practical up to a certain point since the number of data available for reliable model construction can be severely reduced. In such cases, trends remain present in certain geologic/grade domains and directly impact the modeling methodology; the trend must either be handled explicitly or a suitable approach is adopted to implicitly account for it. This is highly dependent on understanding the source of the trend. We propose an approach that detects the source of non-stationarity, which is based on quantifying the impact of non-stationarity in the mean and the variance via the semivariogram. By expanding the methodof- moments approximation of the semivariogram, we decompose the experimental semivariogram is into three terms: 1) trend in mean component, 2) trend in variance component and 3) stationary component. We can then assess the source of trend by calculating the contribution of each component at every lag. Two cases are presented to illustrate this tool. Firstly, a synthetic reference model is simulated and different trend patterns are added; the influence of these patterns in the experimental semivariogram calculation are analyzed and discussed. Secondly, a real dataset is considered where the impact due to the presence of trends in the mean and variance are assessed. The results of this paper reveal the semivariogram to be a tremendously powerful tool in determining the source of the trend. This insight may be useful in the selection of a suitable modeling approach for resource estimation.

Oct 1, 2009

By M. Connell, S. Bedrossian

Alkali cracking followed by chloride-based leaching is one of the prominent methods for rare earth element processing. Regeneration of the leach lixiviant, namely hydrochloric acid, is a critical operation in the process. A number of different process routes are available for recovery of hydrochloric acid from chloride solutions. The objective of this paper is to discuss various recovery routes and analyze the impact of several input variables on the variable operating cost.

Jan 1, 2014

By Robert B. Parsons

"The Canadian tax treatment of mining operations outside Canada is not as attractive as the treatment of Canadian operations. Further, the Canadian company that invests abroad a host of complex rules. This month, Tax Notes examines some of the major Canadian tax considerations confronting the Canadian company that wants to invest abroad. IntroductionCanadian-based mining companies are investing abroad more than ever before. These foreign investments trigger a complex set of tax rules that are distinct from the rules that apply to Canadian investments. In most cases, careful tax planning is mandatory if the company's tax liabilities are to be minimized. This article summarizes the main tax considerations that need to be taken into account with respect to a mining investment outside Canada.Branch Versus SubsidiaryOne of the first questions that arises in connection with a prospective foreign investment is ""Should we invest directly (that is, in a branch operation), or should we invest through a foreign subsidiary?"". In the case of a branch operation, the Canadian company owns and operates the business directly - that is, the foreign business assets are part of the Canadian legal entity. In the case of a foreign subsidiary, the foreign business operation is owned and managed by that subsidiary. The tax treatment of a branch and a subsidiary can be quite different."

Jan 1, 1994

By Randy Billing, J. Fraser Wilson

"IntroductionThe job of designing and implementing effective environmental management sounds like what one executive, assuming responsibility for a very sick organization with lots of potential described as, ""an insurmountable opportunity"".Effective environmental management is an opportunity, no doubt. Its an unusual, if not unique opportunity. Insurmountable? Maybe not! Indeed, in the authors' experience, the keys to unlocking this opportunity are not in new or complicated technicalities; they are in the existing strengths and successful experience that one has in managing other complex and exacting management issues.To begin, it is necessary to understand what these issues of sustainable development mean to business. What is the nature of this opportunity? What makes it look unsurmountable?New Games: New RulesLawyers have described some of the new rules companies are facing and there is a new game being played; a game characterized by unique challenges.Take two, for example: • The ecological problems to be faced are Mother Nature's business, the political solutions required are our business. This combination of natural problems and political solutions requires the development of new management mechanisms, to bridge the gaps among us, as individuals, as professions, as interest groups and so on; indeed, even as countries;• and gaps there are : about as many gaps as the people involved : many of them with new and changing expectations, often mutually exclusive and not negotiable.The challenge of these relationships and communications among so many different interests is one of the keys to effective environmental management.Like any game, this one has rules and they are new, too. These rules are evident not just in new legislation - tough legislation with draconian penalties; they are also evident in new and exacting business policies, value driven and just as unforgiving of poor performance. Senior management of many companies are speaking about the role of enlightened corporate policies and how important it is for everyone involved that these policies drive and reflect business practices. Absence of day to- day behaviour which evidences the words in action, the policy on the wall of a corporate office or published in an Annual Report is first evidence for the prosecution , not the defence.The challenge of practical policies is another key to effective environmental management.This is a new game, with new rules: the challenge of change."

Jan 1, 1991

By B. W. Raymond, D. W. Zandee

"IntroductionCoal deposits are found in many regions in Canada and vary widely in their age, quality and rank. All classifications of coal except anthracite are found in significant quantities in this country.Deposits in the Maritimes are mainly bituminous; Lignite is found in Saskatchewan and Ontario and sub-bituminous coal in the plains region of Alberta. The Rocky Mountain coalfields of Alberta and British Columbia contain low and high-volatile bituminous coal and, in a few places, semi-anthracite. The British Columbia interior contains deposits of semi-anthracite, bituminous, sub-bituminous coals and lignite. The Yukon and Northwest Territories also contain substantial deposits of bituminous coal and lignite.Currently Nova Scotia produces both thermal and metallurgical coal, Saskatchewan produces lignite and Alberta produces both sub-bituminous and bituminous coal for thermal purposes. Large deposits of metallurgical coal are now being exploited in the Rockies arefl of British Columbia and Alberta by open pit methods. The raw coal is treated in large capacity preparation plants to remove refuse and upgrade the product to a consistent metallurgical quality with respect to ash, moisture, volatile matter and coking properties.The treatment of coal involves crushing, screening and cleaning by dense medium, jigs, water-only cyclones, tables and froth flotation to produce a diverse range of coal products differing in quality and size for various end uses.The chapter on Crushing and Screening Circuits was concerned mainly with crushing of metalliferous ores to produce a concentrate of one or more valuable minerals which normally constitute a small portion of the original mass of the material treated.Coal differs physically from ores in many ways such as lower specific gravity, relatively large volumes but low tonnage of product, and its habit of absorbing moisture requires extensive dewatering processes more complicated than settlement and filtration. Most significant, for this paper at least, is the fact that crushing coal is not as energy intensive and much smaller equipment is applicable.Crushing and screening of ores is intended to reduce the size of all constituents as quickly and efficiently as possible to allow liberation of the mineral particles. The crushing of coal is different in that the coal is not the minor constituent and the production of fines, in the initial stages at least, is highly undesirable. The basic objectives of crushing coal are the reduction of run-of-mine material to sizes suitable for cleaning or further reduction of coal to market sizes."

Jan 1, 1989

By R. V. Kumar, F. Tailoka

In order to use ZnO laden dust as a possible desulphurization reagent, it is important to evaluate thermodynamics of the Zn-O-S system. At temperatures greater than 1450 K, there is an uncertainty in the thermodynamic data for the reaction of zinc with sulfur to form Zinc sulfide. In this work, the standard free energy has been determined using an electrochemical cell: Pt, Mo, MoO2/YSZ/ZnO, ZnS, S02, Pt., between 1198 and 1602 K. AG° varies from -145,880 to -88,100 J (± 2500) , with a phase change to ZnS (g) by sublimation occurring between 1450 and 1460 K. This is supported by thermogravimetric analysis which shows about 80% weight loss in ZnS from 1273 to 1473 K. Feasibility reactions were also performed and confirmed that ZnS (g) is formed when ZnO reacts with FeS (1473 to 1653 K) or with Fe-Csat-S(1473-1673 K). There is therefore potential for the utilization of ZnO laden waste as an additional or alternative reagent for desulfurisation.

Jan 1, 2004

By G. Vibert Douglas

IN a previous paper by Douglas and Gillies (1), a simple field test was given for gold. Later work by the present writers, and by others who have kindly written to us, shows that the test is not as satisfactory as it was hoped. In many cases, the gold mirror is completely obscured by a dense precipitate which, up to the present, it has been found impossible to remove. After many attempts, we have temporarily given up the iodine test and have been working on a simple pyridine reaction based on the work of Putnam, Roberts, and Selchow (2): The ore to be tested is ground to a fine flour. Place half a gram of this powdered ore (an amount that will cover a Canadian ten-cent piece, not heaped) in a six-inch test-tube and add 5 c.c. of aqua regia. The aqua regia. should be made up on each occasion, using four parts of hydrochloric acid and one part of nitric acid, both concentrated. Shake the solution in the test-tube for about one minute and allow to settle until dear. The rime to settle may be 30 to 60 minutes. When dear, a drop of the solution is with-drawn with a fine, dean eye-dropper or capillary tube and placed on à small glass plate. A slide such as is used for mounting rock sections is suitable. Now place an equal sized drop of pyridine solution on the plate beside that of the aqua regia solution to be tested. The pyridine solution, containing nine volumes of hydrogen bromide to one volume of pyridine, can be made up in advance and carried in a glass-stoppered bottle. Join the two drops with a glass thread or fine, dean stick, and allow the merged drops to stand undisturbed. I t is well to place the slide on a piece of white paper so that the presence of the crystals which may form can be easily seen. The time for their formation will vary with the amount of gold present, but the slide should be allowed to stand for at least 30 minutes before negative results are reported. A hand lens of at !east ten magnifications is essential. If gold is present, minute red crystals will form around the margin of the drops as these drops slowly evaporate.

Jan 1, 1938

By R. P. Viljoen, A. L. Sokolov

"The distribution of mineralized provinces is analyzed on the basis of their genetic link with specific blocks of the earth's crust including ancient platforms, mobile belts and zones of tectonicmagmatic activation. Mobile and fold belts surround the Siberian platform in Russia and the Kaapvaal craton in South Africa, with decreasing age zoning away from ancient platform margins. The main differences in the geological development of the two cratonic areas are: (1) the long period before the final stabilization of the Siberian platform (3600 Ma to 1600 Ma) and the comparatively short period of time for the stabilization of the Kaapvaal craton (3600 Ma to 3050 Ma) and (2) the intensive multiple activation of the marginal zones of the Siberian platform and the tectonicallycontrolled, magmatic sedimentary, intracratonic activity, typical of the Kaapvaal craton. Mineralization of the Siberian platform is largely characterized by marginal reactivation zones of differing ages although mineralized intracratonic Cu-bearing basins of Proterozoic age are also known. Mineralization of the Kaapvaal craton is mainly related to the formation of the intracratonic basins i.e., Witwatersrand (Au, U) and Transvaal (Au). The latter is characterized by multi-age volcanic-intrusive activity including the emplacement of Bushveld Complex (Cu, Ni, Pt, Cr, Au, V). The Siberian platform is characterized by the prolonged development of inherited mineralization from Archean until the late Mesozoic. The main period of mineralization in the Kaapvaal craton is restricted to the middle Proterozoic.The Baykal-Patomskaya and Namaqua-Natal mobile zones occupy similar positions adjacent to the Siberian and Kaapvaal cratons, respectively, and demonstrate similar modes of metallogenic development: i.e., the early formation of exhalative Pb-Zn-Cu deposits during the early stage and magmatic Cu deposits during the late stage. The more remote mobile belt near the Siberian platform, the Trans-Baykal, is characterized by intensive multi-age mineralization (Wo, Mo, Sn, fluorite), related to a period of tectonic-magmatic activation. The Saldania Belt occupies a similar position near the Kaapvaal craton but is known for its poor Au, and Cu mineralization. It does, however, have some similarities with Trans-Baykal Belt in regard to Mo-W bearing granitoids.The phenomenon of interference of geosynclinal, orogenic, platform, and tectono-magmatic activation regimes is known for the Russian section of the Pacific Ocean Volcanic Belt."

Jan 1, 1994

By John A. Allan

The subject chosen for this paper is not a new one, but the subject matter is so extensive that something new can always be said .about it. We are just beginning to realize how little is actually known about the character of Alberta coal, except for a few general facts. The object of this paper is not to explain that our previous information, in whole or in part, on the coal resources of Alberta, has been incorrect, but rather to present some new facts obtained as a result of recent study in the field and in the laboratory. As field investigation continues the problem of determining the character of a coal seam for any great distance laterally becomes more and more complex. Our present knowledge of Alberta coal deposits should not be discussed before due reference is made to those great pioneers who blazed the trails for later geologists, by recording their observations on the general geology of Alberta. Geologists, to-day, particularly those of us who are striving, year after year, to unravel the mysteries of stratigraphy, palaeontology, and structure, in so far as these are related to the coal resources of Alberta, fully realize our indebtedness to those three trail-makers, Dawson, McConnell, and Tyrrell. Had these geologists not recorded their observations correctly, nor interpreted the broad geological facts contained in Nature's book, with still uncut pages, how much slower would have been the progress of our coal knowledge in the succeeding years. It is true that many of the interpretations given to observations by these pioneers have had to be changed as a result of closer studies, but we must also expect that the geological interpretation from present day observations will be changed by future workers, as Nature's book is read and re-read.

Jan 1, 1925

By J. C. Hampton, L. A. Matzar, C. R. Gamwell

In geomechanics, conducting uniaxial or triaxial compression tests require samples to be prepared to a certain length-to-diameter ratio. This ratio is typically defined as 2:1 (length to diameter) and is accepted as a common standard for all materials on which mechanical properties testing is performed. Variations in sample length can cause changes in measured strength properties across multiple material types, such as cement, rock, or soil. Within the oil and gas industry, it is not uncommon to receive samples for technical services work that are slightly under or exactly the length requirement before surface grinding and sample preparation. Many of these samples are discarded from uniaxial and triaxial compression tests and used in another manner; therefore, it is necessary to study the length-to-diameter ratio in efforts to understand the limits and validity of testing samples that are slightly out of the 2:1 ratio. This paper discusses uniaxial compression tests performed using Berea sandstone and a standard cement mixture of 2.54-cm diameter to study changes in rock strength and properties. Compressive strength for each lengthto- diameter ratio over a range of 0.5:1 to 2.2:1 was measured. The investigation was extended to study near-end effects, where the sample length is near, but not exactly twice the diameter. It was discovered that the cement samples conformed reasonably well to the suggested ASTM correction factors. The sandstone did not conform to the correction factors and further analysis is required to develop a correction factor unique to the material. Near end effects, in both the cement and Berea, were found to increase compressive strengths, especially when the L/D of the samples was increased slightly over a 2:1 L/D.

Jan 1, 2015

By S. K. Paul

"This paper briefly describes the underground crushing and conveying system at Sherritt Gordon Mines' Ruttan Mine. A series of three steel-cord belted conveyors, with a total length of 2J55 metres and a total vertical lift of 407 metres, convey the muck from the underground crushing station to the mill at the surface. The maximum size of the crushed rock is 6 in. All the conveyors are provided with numerous safety and fire suppression devices. IntroductionThe Ruttan Mine of Sherritt Gordon Mines Limited is located 20 km east of the town of Leaf Rapids, 760 km north of Winnipeg. The orebody is multilensed, with lens width varying from 6 to 45 m. Ore production started in 1973 with the opening of a 10,000-tpd open-pit mine. Initial development of the underground mine was started in 1972 with the driving of parallel conveyor and access declines at minus-2507o gradient to the I 220-m level, and then the access ramp was further extended to the 1160-m level. Exploration drifting was done on the 1280-m and 1160-m levels from the access ramp. The final development plan for the underground project was approved in January 1977, and full-scale development and constructionwere resumed.At present, Ruttan Mine is in a period of transition from open-pit to underground mining. Ore production is now coming from both operations. By mid-1980, open-pit production will cease and all production will come from the undergroundmine.The underground mining method at the Ruttan Mine is sublevel open stoping with delayed backfilling. The orebody is divided along strike into a series of 27-m-long stopes and 15-m pillars, both 60 m high."

Jan 1, 1980

By J. Palarski

Hard coal, mined in Silesia Region as well as in the eastern part of Poland, is a key national resource. In Polish underground coal industry, modern mining technologies have been successfully tested and used in the last 50 years. More than 98% of the coal produced underground is extracted by longwall mining method. Current underground coal mining expands into increasing depths. The use of conventional coal extraction methods ? room and pillar and longwall with caving - is becoming increasingly difficult. The coal mining is modifying existing methods and is testing innovative technologies. Backfill is an important component of modern underground mining operations. In Polish underground mines, backfill is recognized as an integral component for extraction of coal from greater depths in a densely populated environment. The modifying and innovative methods require the use of backfill or grouting of caving to provide structural support in underground excavations and to ensure that the mining operations are safe. Depending on the geological structure, mining conditions and environmental requirements there are several variations of longwall methods used in underground coal mining in Poland, in particular: longwall with caving, longwall with backfill, longwall with grouting of caving area. This paper will discuss the different components of an effective longwall production and filling process of caving area. The paper will give a overview of the current application of backfill technology, focusing on Polish coal mining operations. This paper will also briefly describe how backfill contributes to an innovative method ? underground coal gasification. The paper discusses specific requirements for fill materials and the technology of backfilling for underground coal gasification (UCG) operations and problems of implementation and correlation of backfill parameters with other processes that occur during thermal processing of coal.

Aug 1, 2013

By R. D. Clark, Heinz Althoff

"The advantages and disadvantages of a mobile crushing plant with a belt conveyor system compared to a stationary crushing plant with haulage by heavy trucks are described. The capital expenditure and operational expenses are compared and the individual cost factors are explained.Every open-pit mine or quarry, however, is different and has to be assessed and analyzed individually in order to find the optimum and most economical solution. Due to the high truck haulage costs, many open-pit mines tend to the more economical solution with mobile crushing plants and continuous belt conveyor operation. IntroductionFor the material haulage within an open-pit mine the heavy truck is the most flexible means of transportation. However, due to the high fuel consumption, wear and labour costs, it is also the most expensive one. Therefore, many open-pit mines are looking for alternative solutions for the material transport A mobile belt conveyor system is most likely to meet the requirements because it is efficient and economical with regard to the power consumption. The material , however, has to be crushed at the mining face to lumps which are suitable for conveyor operation. For this purpose a mobile crushing plant is required.In some open-pit mines the crusher is also used to crush the material to lumps of smaller particle sizes in order to save crushing costs in the preparation plant.Although a cost comparison between a system with stationary crusher and truck haulage and a system with mobile crusher and belt conveyors favours in most cases the belt conveyor system, up till now only a few open-pit mines and quarries benefit world-wide from the advantages of the mobile crushing plant with continuous belt conveyor operation."

Jan 1, 1986

By G. Harper

The Sustut Copper deposit, 230 miles northwest of Prince George, B.C., was discovered in August of 1971. Subsequent exploration has included 56,417 feet of surface diamond drilling in 139 holes. The deposit occurs in gently dipping volcanic rocks of the Upper Triassic Takla Group, which outcrops as rugged mountains. The general Mesozoic sequence comprises some 20,000 feet of green and red basaltic to andesitic rocks. The Lower Formation is characterized by subaqueous basalt, andesite and augite porphyry flows with interbedded breccias. They were rapidly deposited in tectonic depressions of limited extent and steep gradients. Fades changes are abundant. The Middle Formation consists of volcaniclastic rocks made up of fragments from the underlying formation. Two cycles are discernible, both with basal turbiditic, tuf-faceous sandstone and shale units overlain by massive, volcanic conglomerates exhibiting graded and cross bedding. A broader, shallower-water basin is indicated. The top of the uppermost unit was subaerially deposited. The Upper Formation is a variable sequence of volcanic sedimentary rocks. Detritus was supplied from a wide source area and included multiple reworked fragments of the lower formations and material from other rock groups known in the region. Zeolite fades metamorphism is recognized throughout the entire sequence. Epidote is particularly abundant in the Middle Formation, demonstrating the results of metasomatism. The mineralized zone is approximately concordant with the strata over 100-200 feet of the Middle Formation succession. It lies just below the zone of transition from subaqueous to subaerial deposition in the top unit. Hematite, chalcocite, pyrite, bornite, chalcopyrite and native copper are disseminated throughout all sizes of lithic fragments and matrix. Concentration into the specific zone is believed, to be due to upward leaching of copper during low-grade metamorphic and metasomitic reaction. Precipitation occurred in the zone of hydration characterized by prehnite-pumpellyite below the oxidized subaerial rocks.

Jan 1, 1977

By V. G. Papangelakis, G. P. Demopoulos

"Recovery of gold from refractory ores and concentrates presently constitutes one of the most important, challenging, and exciting areas of R&D activity in the gold processing industry. New technologies are being tested for the treatment of refractory gold materials, some of which have been advanced to the level of commercial operation. In this paper, some recent technological developments in the hydrometallurgical processing of pyritic matrix-refractory gold ores are highlighted. Key operational steps of each of the alternate hydrometallurgical technologies are analyzed and potential advantages and drawbacks are identified. The processes which are reviewed are: hydro chemical oxidation, biochemical oxidation and pressure oxidation. INTRODUCTIONOver the years the term ""refractory"" has been applied in gold ore processing to denote situations in which straightforward cyanidation failed to yield high gold recoveries. A number of mineralogical and chemical factors may be responsible for this ""refractoriness"" problem. A systematic classification of the different options for their treatment has been discussed in a recent review paper. In this paper, the pretreatment of the submicroscopic gold encapsulated within the matrix of pyrite and arsenopyrite minerals is considered. This type of gold is the ultimate refractory material because complete breakdown by reaction of the host mineral structure is required.The method which has been traditionally applied for the treatment of pyritic-type refractory gold ores is an oxidation roast (single stage or double stage depending on the As content) of a flotation concentrate to produce a porous calcine, the latter being more amenable to cyanidation. Despite its established practice, oxidation roasting is not considered particularly attractive with today's standards for high product recovery and clean environment. Roasting is known to be very sensitive to heating parameters and feed composition and deviation from optimum conditions can result in reduction in permeability which is translated to incomplete gold liberation."

Jan 1, 1989