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By M. S. Safarzadeh

Over the last fifty years, the treatment of enargite concentrates has not received much attention, primarily because of the availability of other clean concentrates suitable for processing with existing smelting and/or leaching technologies. As traditional copper ores have become scarcer, copper-arsenic ore deposits have garnered more interest. Arsenic release is a significant concern during the treatment of enargite concentrates by pyro or hydrometallurgical methods. Enargite is also very refractive in standard leaching procedures. Thus, economical treatment options for enargite concentrates are needed. Preliminary experiments have shown that the acid bake-leach process could be adapted and used for the treatment of enargite concentrates. In this study, low-temperature (100-400º C) sulfuric acid baking of an enargite concentrate followed by water leaching has been evaluated. The results indicate the thermal transformation of enargite to copper sulfate happens during sulfuric acid baking, with most of the arsenic being released from the concentrate into the gas phase when baking at 400º C. The condition for maximum copper extraction (~100%) from the concentrate was found to be 400º C, a sulfuric acid concentration of 0.5 mL/g and two hours baking time. Part of the arsenic was captured in the form of arsenopyrite (FeAsS). X-ray diffraction (XRD) analysis proved the presence of some arsenic in the form of claudetite (As2O3) in the baked concentrate. Acid baking of pure enargite behaved in a similar fashion.

Nov 1, 2011

By John N. Murphy

The environmental status of underground mining operations is critical to the health and safety of the miners; particularly in a large mine, the multitude of interacting parameters that can favorably or adversely affect the environ-mental status makes the manpower requirement of the routine checking of specific areas and conditions a formidable one. While the concept of environmental monitoring for miners has been considered for some time, until recently the availability of sensors to reliably measure the parameters of interest severely limited the utility of such systems. The status of sensors for mine use and the evaluation of environmental monitoring systems is reviewed.

Jan 1, 1977

By K. A. Grace, D. E. Ranta

The application of geology does not cease with the discovery and delineation of a mineral resource, but continues in the calculation of the economic parameters that determine reserves. Reserve determination, reduced to essentials, is the determination of the cost of production of a mineral commodity from a resource. This cost comprises mining, processing, waste disposal, reclamation and marketing costs. Geological input is vital in the calculation of the individual cost parameters from mining to reclamation, and even has same impact on marketing. Geology thus has a critical role in the determination of reserves.

Jan 1, 1992

By Joe M. Bryan, George E. Rodger

The development of small precious metal mines in the western states has been directed at heap leach operations. Crushing plants are an essential adjunct to heap leach operations. They must meet environmental air quality regulations which generally follow a similar pattern from state to state. Prior to mine construction a permit must be obtained and an operating permit granted during or shortly after the start-up period. The typical construction permit application consists primarily of drawings, specifications and an explanation sufficient to indicate that the mass of particulate matter entering the atmosphere is below minimum standards. The operating permit may be granted following demonstrations that air emission control equipment or methods comply with information submitted in the construction permit application.

Jan 1, 1987

By B. J. Arnold

Utility coal specifications usually contain a requirement for a maximum moisture content in order to prevent coal handling problems and to minimize evaporative losses in the boiler. As most coal cleaning processes are water-based, dewatering and sometimes thermal drying steps are required to meet moisture specifications. Screens are often used for dewatering, with centrifuges and filters used to further reduce moisture in many cases. Algorithms to predict the performance of commercial dewatering devices were developed for the Coal Cleaning Simulator running under Aspen Plus? during a project sponsored by the U.S. Department of Energy and the Electric Power Research Institute. These algorithms include calculations for size degradation in the devices and fines loss to effluents, where appropriate, and a calculation for moisture content of the product based on particle size and specific gravity distribution. This paper discusses the algorithm for coarse and fine coal centrifuges and gives comparisons between predicted moisture and solids loss and published moisture and solids loss values for various particle size ranges.

Jan 1, 1996

By JoAnn Silverstein, Eric A. Marchand

Competition between Thiobacillus ferrooxidans and non-iron-oxidizing heterotrophic bacteria was induced by the addition of glucose to a co-culture of T. ferrooxidans and A. acidophilum in an oxygen-limited environment. Iron oxidation was inhibited as dissolved oxygen was used preferentially for glucose metabolism. Furthermore, as the water became anoxic, glucose was consumed along with the oxidized iron species (Fe3+) during iron respiration resulting in a pH increase from 2.0 to 4.0. Results suggest that biologically mediated acidification of drainage water can be reversed by dispersion of an easy to degrade, soluble, and inexpensive carbon source such as glucose into the subsurface.

Jan 1, 2000

By Fernando A. Concha

There is confusion in naming the several models developed in Mineral Processing. We often hear of empirical, first principle, mechanistic and phenomenological models. The objective of this paper is to clarify and distinguish between these models, based on a philosophical and linguistic analysis. A state of the art review for mathematical modeling in Mineral Processing is also made.

Jan 1, 1995

The current understanding of the mechanics of rock fracturing during smooth blasting is largely empirical and qualitative due to an inability to model the dynamic process at the fundamental level. In order to overcome this difficulty, a numerical simulation of smooth blasting is performed using the Dynamic Lattice Network Model. This model is capable of simulating material inhomogeneities and the dynamic evolution of fragmentation at the micromechanical level. In this study, smooth blasting techniques are numerically analyzed to characterize the development of the damage rock zone during explosive fracturing.

Jan 1, 1995

By Alvaro Souviron, W. W. Atkinson

The porphyry copper deposit at Los Pelambres is a resource exceeding 2 Gt (2.2 billion st) of 0.7% copper and 0.02% molybdenum. It includes a high-grade zone of +1% copper that is amenable to open-pit mining with a low stripping ratio. Metallurgical testing has indicated that the ore has exceptional characteristics, and that recoveries of 96% for copper and 93% for molybdenum can be obtained by conventional flotation methods. This paper summarizes the history of the prospect, the geology of the ore body and the surrounding area, and the procedures and results of exploration.

Jan 1, 1987

By Hang Yang, Linneas W. Laage

A major concern of mine fires is the heat generated ventilation disturbances which can move products of combustion (POC) through unexpected passageways. Fire emergency planning requires simulation of the interaction of the fire and ventilation system to predict the state of the ventilation system and the subsequent distribution of temperatures and POC. Several computer models were developed by the U.S. Bureau of Mines (USBM) to perform this simulation. The most recent, MFIRE, simulates a mine's ventilation system and its response to altered ventilation parameters such as the development of new mine workings or changes in ventilation control structures, external influence such as varying outside temperatures, and internal influences such as fires. Extensive output allows quantitative analysis of the effects of the proposed alteration to the ventilation system. This paper describes recent USBM research to validate MFIRE's calculation of temperature distribution in an airway due to a mine fire, as temperatures are the most significant source of ventilation disturbances. Fire tests were conducted at the Waldo Mine near Magdalena, NM. From these experiments, temperature profiles were developed as functions of time and distance from the fire and compared with simulations from MFIRE.

Jan 1, 1995

By Stephen W. Kline

Rock suitable for crushed-stone aggregate is almost entirely restricted to the Highlands region of Arkansas, mostly from Paleozoic sedimentary units, but also from a few Cretaceous igneous plutons. Reserves in the state are sufficient for local needs, and Arkansas is geographically well situated for export markets to the south, where resources for crushed-stone aggregate are lacking. A study of 423 quarries, test pits, and exploration sites in Arkansas has been completed to evaluate the relative quality of bedrock units for producing crushed aggregate. Of these, 274 sites have records of engineering tests for stone evaluation done by the U.S. Army Corps of Engineers and/or the Arkansas State Highway and Transportation Department (AHTD). Of the 1,775 sample records from these sites, the most commonly reported parameters are the LA abrasion test and the Na-sulfate soundness test. Many records also have absorption and specific-gravity data, and, for some, petrographic information helps identify the potential for alkali-silica reactivity in portland-cement concrete. By determining the bedrock sources of the tested samples, comparison is made between the various geologic mapping units as to their relative quality for crushed stone.

Jan 1, 1999

By K. N. Han, Q. Xu

The adsorption behavior of gold in ammoniacal solutions on activated carbon was studied. The gold adsorption capacity of the activated carbon and the recovery efficiency were examined. The parameters affecting the adsorption of gold on the activated carbon included temperature, agitation speed, the concentration of cation and anion and the concentration of ammonia. It was found that the maximum gold adsorption was about 10 kg/t of carbon. The recovery of gold by the adsorption, from ammoniacal solutions was found to be dependent upon the initial gold concentration. Under experimental conditions, a gold recovery of 98% was obtained after 120 hrs of adsorption. It was also found that the initial adsorption rate was relatively fast, when compared to the entire adsorption period. The apparent activation energy for the adsorption was determined to be 15.8 kJ/mol. It was believed that the kinetics of gold adsorption on the activated carbon was controlled by pore diffusion.

Jan 1, 1997

Vancouver-based War Eagle Mining Co. is an advanced-stage Canadian junior mining company that is focused on becoming one of the world?s leading germanium producers. War Eagle?s primary focus is on the Tres Marias high-grade germanium mine near Chihuahua, Mexico. The Tres Marias Mine has high-grade zinc mineralization as well. War Eagle acquired the 28-km2 (17.4-sq mile) property in 2001 from Tombstone Exploration and is currently working to put the mine into production. Current exploration is focused on supporting a resource report and prefeasibility study that is expected to be completed in early 2008. War Eagle expects to have completed an estimated 80 underground diamond drill holes, 40 surface diamond drillholes, 31 percussion holes and 1,296 1.5-m (5-ft) channel samples. Eighty-seven additional exploration targets have been identified within the mining concession. Recent drill results have significantly expanded the known mineralized body at the Tres Marias Mine. The exploration and development program is expected to be completed during 2008. War Eagle owns both the drills currently in operation at Tres Marias. An advanced exploration and development program has confirmed historical grades and is producing encouraging new results from diamond and percussion drilling, channel sampling and high-resolution resistivity geophysics. Glenn R. O?Gorman, an independent geologist and consultant to War Eagle, conducted a study on the reporter. He stated that the Tres Marias concession area has the potential to host 5 to 10 Mt (5.5 to 11 million st) of minable ore.

Jan 1, 2008

By R. K. Mensah-Biney, M. T. Hepworth, K. J. Reid

The loading characteristics of gold-bromide species onto activated carbon were evaluated using a batch system. The overall loading of gold onto activated carbon was rapid for the first few hours, but it continued without cessation as a result of the reduction of gold. Therefore, conventional equilibrium considerations were not applicable. Although loading continued slowly after several days, an abnormally high, loading capacity value of 10-12 meq/g carbon (650-800 kg Au/t) could be attained in 72 hours. The loading of gold-bromo species by activated carbon was by the mass transfer of (AuBr4)- species to the external surface to be reduced to metallic gold by carbon. Elution of gold from loaded carbon was feasible provided the carbon had not been loaded to high capacity values. If loading is carried to high levels, complete elution becomes impractical, and the gold may be recovered by ashing the carbon. For the high loading capacities observed, this option would appear to be cost effective. The effect of several variables on the loading capacity of the activated carbon for gold-bromo species is discussed.

Jan 1, 1994

By Edmund H. Warner

Any city dweller who has walked alone along a remote mine passageway has to be impressed by the eerie silence - the total absence of noise except for ones own breathing and scuffing of boots on the bottom. An underground mine can have tremendous contrasts, from complete silence to the ear piercing clatter of percussion drills working on the mine roof. Noise in underground mining machines is both useful and detrimental. Without characteristic noises that are recognizable to miners, operators would have a more difficult job operating their machines. Noise serves as a warning of approaching machinery, and changes in noise give indication that breakdowns may occur. But excessive noise is a health hazard. In recognition of this fact, our Congress included noise exposure as a part of the "Coal Mine Health and Safety Act of 1969". As Fig. 1 indicates, allowable noise exposure is established by specifying a time duration permitted at different noise levels. This is the well known "Walsh-Healey" criteria which governs noise exposure in many industries.

Jan 1, 1977

By B. A. Carbon

Western Australia is the largest state in Australia with an area one and three quarter times the size of Texas. Most of the State is desert or semi-desert, and only the southwest corner is heavily populated. The State has a population of one and a half million people, and one million of these live in and around the city of Perth. Perth is located on the narrow Swan Coastal Plain and is flanked by the Indian Ocean and the Darling Plateau. The Darling Plateau is an ancient peneplain rising some 300 metres above sea level, and forms an important resource base for the population. The Darling Plateau is old, having been formed some 200 million years ago, and its soils are deeply weathered. The parent materials were granite and gneis which have broken down to form lateritic gravels, overlying dense kaolinitic clays. Some 30 million years ago, in the Tertiary period, a sub - tropical climate prevailed. Appropriate conditions of moisture, temperature and drainage led to extensive laterisation. Some of the laterite contains bauxite of mineable quality. Some 1.9 million hectares of the south-west of Western Australia is covered by eucalypt forests. Threequarters of this forest is referred to as "Jarrah

Jan 1, 1984

By S. Bassignani, D. Ippolito

In Italy at the moment there is a program which involves for the future the exploitation of two uranium mines which are now in the research stage. About one hundred and fifty workers are at present employed in those facilities. An health physics surveillance program is under way and has been designed to fulfill the requirements due to the future exploitation of the two mines. A complete evaluation of the total dose (external + internal) received by the workers will be given together with a detailed analyses of the technical methods employed for such evaluations. The external doses are evaluated on the basis of individual TLD dosimeters, while the evaluation of the internal doses is mainly due to an enviromental survillance program of the radon and radon daughter air concentration inside the mines. The criteria established for the assessment of the sampling procedures, sampling intervals and dose evaluation related to the radon doughter exposure are reported. The external dose received by the workers are lower than 0.2 m Sv~month and the internal exposure less than 6.4 IO-3 J.h.m-3 /year or using the old units 2 WLM/year.

Jan 1, 1981

By H. H. Richards, Ray L. Tobie, L. A. Thomas

GENERAL DESCRIPTION Since the beginning of operations, with the exception of a small tonnage mined by slushing, ore extraction has been by full gravity caving. Formerly, a checkerboard sequence of block undercutting was followed with the even-numbered blocks in one panel and the odd¬numbered blocks in the adjacent panel being mined. As these blocks were depleted, the intermediate or pillar blocks were mined (Fig. 1). Following this checker¬board, the mining sequence went through a number of changes, finally evolving into diagonal retreat panel cav¬ing by blocks (Fig. 2). The numbers in Fig. 2 indicate the sequence in which blocks were undercut. Gaps in the numbering sequence indicate undercutting on the level outside the illustrated area. Geology The ore body is a low-grade deposit of chalcopyrite mineralization disseminated throughout structurally weak, highly fractured, strongly altered granitic host rocks. It takes the shape of a gently dipping elliptical cylinder consisting of an ore shell of variable thickness surrounding an interior waste core. Major and minor axes of the mineralized cylinder are 1524 m (5000 ft) and 762 m (2500 ft), respectively, and length approximates 2438 m (8000 ft). Ore is sufficiently fractured to break readily into medium-coarse size. The igneous rock complex containing the ore body is covered by a wedge-shaped blanket of Tertiary con¬glomerate which was brought into place by faulting along the major regional structure of the San Manuel fault. Thickness of the conglomerate cap varies from only 9 m (30 ft) at the east end of the ore body to more than 610 m (2000 ft) at the west. Structurally, the con¬glomerate is much more competent than the igneous host rocks and, when caving, it breaks into massive chunks. Conglomerate boulders seen in drawpoints underground are very coarse. The total rock column over the initial mining area of the 1415 grizzly level was 354 m (1160 ft) of which 122 m (400 ft) was ore, 79 m (260 ft) was leached igneous capping, and 152 m (500 ft) was conglomerate above the San Manuel fault. Diamond Drilling: From 4572 to 7620 m (15,000 to 25,000 ft) are drilled annually from underground workings to delineate the ore body. MINE DEVELOPMENT Haulage Level In the south or main ore body (see Figs. 3-6), with the exception of the draw and transfer raises, all the extraction openings are concreted (Seaney and Tobie, 1965). The haulage panel drifts, which are 18 m (60 ft) below the grizzly drifts, are first driven with pre¬concrete ground support. The drift, which has an arched section, then is concreted using mobile collapsible steel tunnel forms. The haulage drifts leading from the pan¬els to the hoisting shafts are not concreted. After the panel drifts have been concreted, the raise stations from which transfer raises will be driven are constructed and the raise-station ore-drawing chute is installed. The chute is prefabricated of A-36 steel with undercut guillo¬tine gates made of abrasion-resistant 2.5-cm (1-in.) steel plate powered by 20-cm (8-in.) air cylinder installed on each side of the raise station. Transfer Raises The transfer raises are lined with 15 x 20-cm (6 x 8-in.) cribbing and are 1.22 m (4 ft) in the clear. Each cribbing is protected from wear by a high carbon steel angle which is nailed onto the cribbing. The transfer raises are driven from each side of the raise station on an angle of 1.1 rad (63°). Each raise con¬sists of a main and a backover branch. The transfer¬raise driving crew consists of two men working one shift only. Grizzly Drifts After the transfer raise reaches the grizzly level, the grizzly drift can be driven. The grizzly drifts are spaced at 10.6-m (35-ft) centers and are driven parallel to the long axis of the ore body (see Fig. 2). This drift is driven by a two-man crew working on one or more drifts at a time using feed-leg machines. The eight grizzlies in the 42.7-m (140-ft) long drift are spaced at 5.3-m

Jan 1, 1982

By T. Harrison

Surface coal mines in West Virginia are receiving stringent NPDES discharge limits for total recoverable selenium. With limits in the low parts-per-billion range, selection and implementation of proper sample collection and analytical methods are imperative for quality assurance and control and for consistency in results. Given the typical oxidized form of selenium in the water, the low limits and the large and variable flow rates from the watersheds, end-of-pipe treatment is difficult and cost-prohibitive to implement. Discharge locations in the remote and steep terrain exacerbate the problem. To evaluate options for end-of-pipe treatment at a Patriot Coal Corporation surface mining operation in West Virginia, CH2M HILL performed wastewater characterization for a range of key constituents and selenium species at three outfalls for selection and preliminary sizing of appropriate treatment processes. A preliminary evaluation of base and wet-weather flows was done to understand flow variability considerations for discharges. A conceptual evaluation of technologies to treat selenium to permitted levels was conducted in con-junction with order-of-magnitude life-cycle cost estimates.

Jan 1, 2010

By Alvin Kaufman

Malthus, an eighteenth century economist, predicted a rather dismal future for the world. It was his contention food supplies would not be sufficient for the population of the world because the economy of a nation grew arithmetically while population increased geometrically. As a consequence, within a relatively few years mass famine would spread throughout the world. This prophecy, based on an agrarian economic situation, did not come true at least insofar as the Western World was concerned. In largo measure, the salvation of our part of the earth resulted from the growth engendered by the Industrial Revolution. Throughout much of today's world, however, the Malthusian theory seems to be coming true. The advantages and benefits of the Industrial Revolution have net reached all nations. Further, the situation has been compounded by the benefits of modern medicine. This has reduced child mortality and extended life expectancy, but placed no limitations on births in the developed countries, child mortality has declined to 2 percent and adult life expectancy has doubled, but education and general prosperity have resulted in voluntary limitations on pregnancies thus partly offsetting the increased chance of survivals Even so, the present rate of population increase in Europe is approximately 6 percent per decade, and somewhat higher in the U.S., Japan, and other developed countries. The world as a whole, however, is expected to double its population by the year 2000, This would imply a rate of increase in the less developed countries approximately four times that in Europe.

Jan 1, 1966