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By J. Groppo, W. Zhang, R. Honaker

"Rare earth elements (REEs) found in coal are in the form of minerals, ion-adsorbed onto clay surfaces or inner layers, or organically bound. Rare earth minerals such as monazite exist in coal and have grain sizes smaller than 5 µm. In this study, froth flotation was successful in concentrating rare earth minerals existing in a thickener underflow material derived from Fire Clay seam coal that contained around 431 ppm of total rare earth elements (TREE) on a dry ash basis. Conditioning with fatty acid followed by processing using multiple stages of conventional flotation produced a final concentrate containing 2,300 ppm TREE. Using a laboratory flotation column to limit hydraulic entrainment, the TREE content was further enriched to around 4,700 ppm, which equated to an enrichment ratio of 10:1.IntroductionRare earth elements (REEs) are becoming increasingly important and have been widely used as raw materials for the production of phosphor, metal catalysts, magnets and batteries (Binnemans et al., 2013; Zhang et al., 2015). REE recovery from alternative sources such as coal and coal byproducts has the potential to stabilize the economic viability of coal mining operations while providing a dependable supply of critical materials.The average REE content of the world’s coal resources is around 60 to 70 ppm (Zhang et al., 2015). There are many well-known coal beds with high contents of REEs such as those in the Far East coalfields in Russia with contents of 300 to 1,000 ppm, the Fire Clay coal seam in eastern Kentucky in the United States with contents around 500 ppm and the Sydney Basin in Nova Scotia, Canada, with contents of 72 to 483 ppm (Birk and White, 1991; Seredin, 1996; Hower, Ruppert and Eble, 1999; Blissett, Smalley and Rowson, 2014). The occurrence of REEs in coal and coal byproducts can be classified into three types: (1) rare earth minerals, such as monazite and xenotime, (2) ion-adsorbed REEs on clays and (3) REEs associated with organic matrices. The rare earth minerals in coal and coal byproducts are very small in particle size, generally on the micrometer and/or nanometer scales (Honaker et al., 2014). Froth flotation, which concentrates minerals based on surface chemistry differences, has been widely used to treat fine rare earth industrial minerals such as monazite, xenotime and bastnaesite (Abeidu, 1972; Cheng, Holtham and Tran, 1993; Pavez and Peres, 1994; Pavez, Brandao and Peres, 1996; Jordens et al., 2014). As such, flotation is a promising method for the concentration of rare earth minerals from coal and coal byproducts."

Jan 1, 2017

By Rusty Winn

"R.E. Janes Gravel Co. is an aggregates producer is located along a paleo-channel of the Ogallala formation (locally known as the Slaton Channel) approximately 48.3 km (30 miles) southeast of Lubbock, TX. In an attempt to beneficiate the 25.4-mm (1-in.) concrete aggregate product, a log washer was installed in the processing line to liberate and remove fines (clay) from the finished product. The introduction of this extra cleaning step increased fines in the finished product, exacerbating the original problem. Several other processing options were investigated before a geological analysis was undertaken to try and define the lithology of the formation and formation characteristics in an attempt to alleviate this problem.Initial assessmentsThe mined resources are mid-Miocene to early Pliocene (16-4 mya) in age and is the eastern exposure of the Ogallala formation of the Southern High Plains escarpment. The Ogallala formation consists of coarse-grained alluvial sediments in paleovalley channel ways from the Rocky Mountains with fine Aeolian and paleosol deposition on the uplands across the High Plains region of the United States. Locally, these Rocky Mountain sediments from New Mexico were transported and deposited in a paleochannel that is approximately 0.805 km (0.5 miles) wide and 15.25 to 18.3 m (50 to 60 ft) in depth. As this channel cut across the Southern High Plains it eroded local rock sources of Late Cretaceous limestones and Triassic sandstones and mudstones incorporating them into the younger Ogallala depositional sequence.Depositional historyThe channel currently being mined is a nontypical Ogallala deposit. The Ogallala in the panhandle of Texas is divided into two units, the Couch and the Bridwell. The Couch is the older of the two and exhibits alluvial sedimentation of thicker and larger gravel (up to 76.2 mm or 3 in.) deposits fining upward to Aeolian sedimentation and thick friable caliche deposits. The Bridwell overlies the Couch and is characterized by alluvial sedimentation, a distinctive red tint and smaller gravel components (typically no larger than 25.4 mm or 1 in.) fining upward to Aeolian sedimentation and thick, well-indurated caliche cap. The Slaton Channel divides these two units and shares lithologic components of both, yet is lithologically distinct due to its Cretaceous Age limestone gravels that can be < 3.66 m (12 ft) in size. Caliche/calcrete is a calcareous (CaCO3) deposit that forms in the B horizon of soils as a rain water leachate of CaCO3 from the upper A horizon."

Jan 1, 2014

By Claude Froger

The compared advantages of digital and analogue computers for solving ventilation problems have for many years been a matter of discussion among the specialists whose respective arguments have prevailed in turn depending on the progress of technology. In the French coal mines however none of these two techniques has superseded the other so far. In France, between 1956 and 1962 only the digital computer and from 1962 to 1967 only the analogue computer was used. Since then they are both used concurrently and complementarily. Depending on the problems dealt with, the most advantageous method is chosen in each case. In the case of ventilation planning for projected workings, it is possible to test variant forms of the development plans and many parameters can be varied. In such a case the flexibility of the analogue computer is a great help. Wrong lines taken will be rapidly abandoned and little by little solutions will be found. By examining the results of a test, new ideas will generally come into the mind and they can be tested right away. Such an investigation is always-carried out in conjunction with the engineers of the mine concerned. In complex networks it often leads to solu¬tions which could not have been devised from the start. The same work could be done by using a numerical method and the digital computers operating in the different coal mine districts, but for the same tests, the time required would be much longer and the participants would not be encouraged to use their imagination so intensively. Or the other hand for calculations of ventilation networks in ventilation surveying, use is made of the digital computer which gives the possibility of storing the data corresponding to the different mines concerned. The questions to be solved concern problems for which the ventilation network is essentially known, and in which only a small number of parameters can be varied. The few possible alternatives to be calculated can therefore be handled by the digital computer in spite of the relative lack of flexibility of the method. To sum up our ventilation studies are conducted in France as follows: - For ventilation studies and modifications due to projected workings use is made of the ana¬logue computer. For a given mine the updating of such ventilation studies is carried out every 3 or 5 years according to the progression of the workings. - For ventilation surveying while normal working operations are in progress, use is made of the digital computer.

Jan 1, 1980

By Purnima A. Shivdasan

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125±7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser grained purple and green vug-filling fluorite crystals. Homogenization temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166°C to 144°C, and minor late yellow fluorite was deposited at lower temperatures from 132°C to 128&apos;C. Homogenization and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than MVT ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in two open pits (A and B) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: 1) replacement remnants of carbonatite within the fluorite ores, 2) goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite, and magnetite that are disseminated in the fluorite ores, 3) partial replacement by fluorite of a titaniferous magnetite rimmed carbonatite dike in the A pit, and 4) partial replacement by fluorite of a large sill-like carbonatite body in the B pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite, and calcite. Magnetite contains 6.97% to 10.46% Ti02, averages 8.44% Ti02, and has an average V203 content of 0.35%. At high magnifications under the SEM, the magnetite shows abundant fine ulvöspinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range 3.21 to 5.0% and average 4.2%, and apatite crystals range in total rare earth oxides from 1.7% to 2.61%. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. The fluorite ores also have replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite.

Jan 1, 2005

By David E. Thompson, Wesley E. Stimpson

The Massachusetts Bay Transportation Authority (MBTA) Red Line Extension Northwest is currently in the early stages of construction. The 3.1 mile extension of the Red Line from the existing Harvard Square Station in Cambridge, Massachusetts to Alewife Brook Parkway in Cambridge, Massachusetts will include a large, near surface hard rock, rapid transit station chamber at Porter Square in Cambridge (Figure 1). [ ]

Jan 1, 1979

By M. G. Skowroski, G. G. Eichholz, J. P. Ambrose

Introduction It has long been known that there are extensive deposits of phosphate-bearing deposits in the Coastal Plain of Georgia in many locations that are similar to those being mined commercially in central Florida. A major drilling program was conducted in 1966-67 by the Georgia Geological Survey (GGS). The economic potential of some of the material uncovered was evaluated at that time by a team at Georgia Institute of Technology led by Dr. J.E. Husted. There were some promising results. Since then, there has been little commercial interest in pursuing this matter, though the potential for development remains. In the long term, Georgia&apos;s phosphorite deposits could be a major source of income to the state if they were commercially processed. Phosphorite deposits contain significant levels of uranium and thorium. Uranium concentrations in Florida phosphate aggregates have been found to be 120 to 140 ppm. The presence of high concentrations of uranium means that there is a small but finite concentration of radium, which subsequently leads to radon gas emanation. It is the radon emanation and its progeny that may pose the largest health problem in many types of mining. Surface mining operations can possibly elevate the radon and radon daughter concentration in the vicinity. There is always some public concern whether any increase in the radon concentration in the atmosphere by mining (surface mining in the phosphorite case) could elevate the risk of cancer in the nearby population. At the present time, a great deal of attention has been devoted to the possible health effects of radon and its decay products in the inhaled air in mines and inside buildings built on mill tailings or uranium-bearing rock (Gesell and Lowder, 1980). Several evaluations have been published on the potential health effects of the Florida phosphate operations (Guimond and Windham, 1975; Roessler et al., 1980; Travis et al., 1979) and for buildings incorporating phosphate slag aggregates (Kahn, Eichholz, and Clarke, 1983; Roessler, Roessler, and Bolch, 1983). They all indicate that such potential effects are small, but tangible, compared with other radiation effects, for instance in the nuclear industry (Cohen, 1981). In view of the current concern, especially by the US Environmental Protection Agency (EPA), with the radiological consequences of large-scale mining of uranium-bearing phosphate rock (Guimond and Windham, 1975), it was decided to assess the potential radiological consequences if the Georgia deposits were developed. This paper presents an attempt to estimate the magnitude of any radon-based health effects that might arise from future mining operations in selected areas of the Georgia coastal region. To do this, a calculational model was developed that took into account the mining operations themselves, the atmospheric dispersion of the radon released, and the radon daughter concentrations in nearby towns. The model was applied to both extremes. The first application was a hypothetical mining operation in Echols County. Echols County is very sparsely populated and, unless living very close to the site, a person would probably experience little radiation exposure, if any. The model tries to prove this point. The second application was at a site near Savannah, Georgia. Both sites contain economically feasible phosphorite deposits and were not entirely hypothetical in that sense. Site selection In the course of the South Georgia Minerals Program (Furcron, 1967), an extensive series of drill core samples had been collected from various mineral occurrences in the coastal plain. It was found that the cores from the previous drilling program (Furcron, 1967), though carefully preserved, were not readily accessible. But the GGS reports did contain gamma logs of all the holes surveyed. With the cooperation of Dr. Neal Shapiro of the Survey, some core samples were selected and assayed, and used to calibrate the gamma log data. Samples from locations known to have detectable radioactivity were screened and counted. Their measured uranium content was used to calibrate the gamma log profiles for those same holes as obtained by the GGS. On this basis, two of the higher-level sites were selected and the calibration was used to obtain integrated uranium concentrations over the length of the borehole. It is customary to describe radon and radon-daughter concentrations in "working levels" (WL), where one WL represents a concentration of radon daughters capable of releasing 130 000 MeV of alpha particles, equivalent to 100 pCi of radon in equilibrium with its daughters per liter of air. A representative concentration is 0.15 WL, below which radon levels are widely considered to be negligible. For the mine sites selected, the surface area and rock volume were determined to estimate their radon content. Working-level values were then estimated for the assumed radon release from the crushed ore and the exposed surfaces of the mine pit. According to Kisielewski (1980), 93.4% of all radon released from open-pit operations is released from the ore zone; thus, the calculations assumed that those surface areas were the main sources.

Jan 1, 1987

By Chuang Sun, Feng Luo, Guo‑dong Li, Xue‑qing Li, Tuan He

The mining-induced failure of the coal seam floor is essential for water inrush. The mining disturbance to the floor, especially in the thick coal seam, is severe, and the water inrush risk is also higher than that in regular thick coal seam excavation. The superposition of many stresses, including in situ stress, mining-induced stress, and confined water pressure, must be considered in the prediction of the floor failure depth. This study adopted the elasticity analysis, FLAC3D numerical simulation, and on-site acoustic wave test comprehensively. The thick coal seam working face of the Zhong-Yu coal mine affected by confined water was selected as the engineering background to study the characteristics of the floor failure. Based on elastic foundation theory and the superposition principle, the mechanical model and the failure depth criterion of the floor were established, respectively. The distribution and evolution of mining-induced stress and the plastic zone in surrounding rock during the mining process are obtained by FLAC3D. In addition, the changes in the P-wave wave velocity in the floor before and after mining were compared and studied by the acoustic wave test method. The range of floor damage depth is determined on the basis of the above research.

Jun 8, 2022

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Increases in pillar stress can be inferred by measuring roof/floor convergence surrounding the pillar. This paper presents a case study of convergence measurements surrounding a two-entry gate-road yield pillar in the head gate of a coal mine. Convergence was measured over a six-month period, as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar: four locations in the travelway and four locations in the beltway. In addition to convergence stations, the pillar was instrumented with an array of seismometers. In future analysis, convergence measurements will be compared to seismic interpretations. This study reports on the geology and geometry of the longwall panel, the roof and rib support, the change in convergence over time, and the physical properties of coal and parting. Additionally, the convergence measurements are compared to pillar safety factor distributions derived from a finite element model. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head gate entry support.

By Lana Alagha, Fardis Nakhaei, Jose L. Corchado-Albelo

Tellurium (Te), a critical mineral for solar energy technologies, faces supply risk challenges that drive the development of diversified and robust production routes. This research focused on improving Te enrichment from copper tailings (CT) produced from copper porphyry (CP) ores processing, addressing the loss of ~90% of Te minerals to tailings in the flotation process of CP ores. Gravity separation and froth flotation processes were used as possible enrichment routes of Te-bearing minerals (i.e., pyrite) in CT. In the froth flotation process, synergistic combinations of reagents were tested to achieve an acceptable enrichment ratio of Te minerals. Comprehensive characterization analyses showed significant Te enrichment in the flotation concentrates. Tellurium was recovered at 90%, while the grade of Te in the concentrates was 1.4 ppm using a xanthate collector and glycol frother compared to <0.5 ppm in the flotation feed. Findings showed that Te-minerals’ enrichment was also feasible in CT using the proposed combined concentrations routes (i.e., gravity separation followed by froth flotation) by looking at Fe, Cu, and S enrichment. This study also highlighted the importance of understanding the deportment of Te minerals in different process streams to develop and optimize efficient enrichment practices.

Feb 1, 2024

By J. A. Herbst

Until the past decade, the energy-size reduction relationship was the dominant form of mathematical model used in the description of tumbling mill grinding processes (1,2). Typically, in these models some single measure of product fineness (e.g. the 80% passing size, the size modules, the specific surface area) is chosen as the dependent variable and the energy input per unit mass of material being ground acts as the independent variable. In some instances these models have been useful for the correlation of experimental data, but, invariably, they have been found to be inadequate for meaningful process simulation. During the last decade considerable advances have been made in the development of phenomenological grinding models derived from population balance considerations (3-7). In these models a set of dependent variables is employed, corresponding to the set of mass fractions which constitute the product size distribution, and energy input is abandoned in favor of "time in the mill" as the independent variable. The phenomenological models have been shown to provide accurate simulations of the entire size distribution of ground products produced in batch (8-10), locked cycle(11)and steady and unsteady state, open and closed circuit continuous grinding(12,13).

Jan 1, 1973

By T. J. Jr. Corwin

This paper will cover the problems confronting an owner when planning and estimating the cost of a proposed tunnel. Three factors are known: the length, size and the time allocated for the completion of the work. In general the difficulties encountered when driving a tunnel in California are the greatest at the lower elevations and in the Coast Range and are minimal in the Sierra Nevada mountains particularly in granitic formation. The writer will discuss the experience gained from observing the driving of about 120 miles of tunnel in California as well as the repairs of some tunnels. SIZE OF TUNNELS It is known that a small tunnel may be more costly to drive than one of somewhat larger dimensions. This fact was found to be true when a tunnel about 4,000 feet long was constructed to eliminate 7 miles of canal. The formation was lava so it was anticipated the ground would be self supporting because of the small bore. Actually the tunnel required support for most of its length and working conditions were poor. It became apparent that a larger size could have been driven at no additional cost and probably in less time. On another unlined tunnel, to be driven in granitic formation, the contractor was given the option of using

Jan 1, 1974

By Robert E. Hershey

The phosphate industry is the fourth-ranking mineral industry in Tennessee; it has an annual value of 13,000,000 and a yearly production of almost 2,000,000 tons of phosphate ore. Tennessee, at present, is second in rank of phosphate production in the United States. In accord with the importance of this mineral commodity, the Tennessee Division of Geology, is conducting a continuing study of the industry&apos; and the raw s, materials upon which it is dependent. Of the three type&apos;s of phosphate found in Tennessee, the brown phosphate rock of the Bigby faces of the Bigby-Cannon limestone is by far the most extensive in occurrence and is the only type being mined at the present time. Because of the importance of the brown phosphate ores, our Division has mapped , in detail the outcrop pattern of the Bigby facies of the Bigby-Cannon limestone. The geologic mapping was done by Dr C. W. Wilson, Jr. and others under his super-vision and the geology plotted on 7 1/2-minute topographic maps, with scale of 1 to 24,000 or 1 inch equals 2,000 feet. These maps will be available for use in the near future and will be published later-with complete geologic coverage.

Jan 1, 1960

By H. R. Hardy

Whether the mining engineer is concerned with stress problems in a mine at depth, the development of a new drill bit, or the efficiency of a comminution process, the mechanical properties of the rock with which he must work are of the utmost importance. One of the most popular topics in rock mechanics circles today is ?Is it possible to utilize directly parameters determined from laboratory tests on rock specimens in the analysis of mining engineering problems?? It is the author&apos;s opinion that laboratory and .field investigations have not yet reached the stage of development where this question can be answered with any degree of certainty. At present, great difficulties are involved in applying the results of laboratory tests to a mining engineering problem. However, this is due in part to the lack of detailed measurements of stress and deformation in the field and in part to the lack of development of satisfactory structural theories to correlate laboratory and field measurements. Furthermore, if mechanical properties measured in the laboratory are to be directly applied to the analysis of mining engineering problems, the critical mechanical properties must be identified, reliable test procedures must be developed and extensive test programs must be carried out.

Jan 1, 1964

By Carl E. Schubert

The application of geophysical technology relative to the exploration, planning, and operation of coal mines is expanding. This is due to the trend of the industry to increase the size of operations, use of mechanized equipment and mining of more difficult coals, where unforeseen conditions can affect mine profitability. Coal is a good geophysical target because of its lower density, higher electrical resistivity, lower seismic wave velocity, and lower magnetic susceptibility in comparison to typical country rock. The more important techniques are well logging, high resolution seismic reflection, seam wave velocity, and radar. These methods can be used to map coal horizons, determine the physical properties of the coal, and identify mining hazards. The methods are not a pancrea however. Their use should be based on a careful assessment of their expected success and cost benefit analysis in comparison with conventional technology, primarily drilling, which none of the techniques presented should entirely replace. In general, the level of technology developed for geophysics surpasses their current level of application to coal problems. In some cases, identifying hazards in advance of mining using seam wave seismic in particular, the state of the art has been developed in Europe and is awaiting fruitful application in the United States.

Jan 1, 1982

By Frank L. Peterson

This paper deals with problems of groundwater development in an insular circum-Pacific environment, and is not oriented as such to mining and mineral development. Nonetheless, because a reliable water supply is necessary for most mining and related support activities, and since water supplies are limited in many insular parts of the Pacific Basin, groundwater development is a subject which must be frequently addressed. Because many in the audience may be already familiar with groundwater development for continental environments, I have chosen to deal with groundwater occurrence and development problems which for the most part are unique to insular environments. In such environments, the local geology plays a critical role in determining groundwater occurrence and its suitability for development. The three examples discussed in this paper-Hawaii, Guam, and the Marshall Islands-were selected because they illustrate groundwater occurrence in a wide range of geologic conditions. For example, the Hawaiian aquifers consist primarily of basaltic lavas, while Guam is made up of andesitic lavas and coral reef limestones, and the Marshall Islands are coral atoll deposits. Despite differences in aquifer size and rock types, the principal mode of groundwater occurrence at the three sites is similar; thus, development strategies are also similar. Figure 1 shows the location of the three sites.

Jan 1, 1982

By Yunsheng Yao, P. Golledge, A. D. S. Gillies

In order to investigate the explosibility of sulphide mineral dusts, sulphide ore samples were collected from five underground metalliferous mines in Australia. The mineralogical and chemical composition of the dust samples was analysed by X-Ray Powder Diffraction and Atomic Absorption techniques. Simulated post detonation fumes were produced and used in dust explosibility tests to examine the influence of the fumes on sulphide dust ex- plosions. These tests were conducted in a 20 Litre Siwek Explosion Chamber with measurement and control system that is regarded as a standard testing system worldwide for dust explosion studies. The dust mineralogical composition and dust explosibility tests indicated that the content of sulphur can not accurately predict the explosibity of the sulphide dust. The percentage content of pyrite in the sulphide dust can be a relatively reliable diagnostic criterion in evaluating the risk of sulphide dust explosions in the mining of a massive sulphide orebody. The hybrid explosion tests demonstrated that the post detonation fumes from ANFO not only decrease the lower explosion limit of the sulphide dusts, but also increase the severity of the dust explosions. The explosion pressure reaches its peak value when the fumes content in the explosion chamber is about 20 per cent by volume

Jan 1, 1997

By J. R. Aggson

In an effort to minimize cutter roof failures in longwall development entries of a West Virginia coal mine, a three-entry system was developed with the center entry arched into the strata above the coal seam. The purpose of the arched entry was to modify the horizontal stress envelope associated with the three-entry system and improve roof conditions in the adjacent outside entries. Contrary to the predictions of elastic analyses, the presence of the arched entry improved roof conditions by eliminating cutter roof failures in the outside entries. In-situ stress determinations and numerical modeling techniques were employed to quantify the impact of the arch and investigate the mechanism of stress relief associated with the arched entry. Stress determinations and underground observations indicated that the roofs of the outside entries were within the zone of stress relief generated by the arch, and that failure or movement along bedding plane discontinuities played a major role in the formation of the stress relieved zone. The numerical model incorporated horizontal joints to simulate bedding plane discontinuities. The properties of the joints were adjusted until roof stresses predicted by the model were in agreement with measured stress profiles. This process resulted in a calibrated analytical tool that could be used to evaluate alternate mining geometries.

Jan 1, 1988

By Dan Adams, Thomas Post, Paul Kubera, Mike Preston

Mixing is a common unit operation in the mining industry. Mixers are often used in agitated leach, bio-oxidation, and pressure oxidation. In all of these cases it is important to understand the application and what it requires from a mixer in order to be opti­mized. In the mining industJy, it is obviously important to suspend solids. However, the shear level of each of these three applications is ve1y different. In acid leaching, the mixer needs to suspend solids and produce a good degree of blending. In pressure oxida­tion, the agitator must also disperse air or oxygen by creating fine bubbles. Because of the presence of microorganisms, bio-oxida­tion requires less shear than the other two processes, but the agita­tor must be able to suspend the solids, provide excellent blend­ing/heat tJ·ansfer and distribute the air. Thus, in the mining indus­tiy there is an application spectJ·um that requires different impellers to perfotm different jobs. Specifically, these jobs are blending, solids suspension, gas dispersion, mass transfer and heat transfer. It is important to determine whether the process is mass transfer or kinetic rate limited. Mixers affect a mass transfer limitation but have no affect on the kinetics.

Jan 1, 1998

By G. A. Hayes

The range of gold ores tested at AMMTEC LTD over several years has resulted in the requirement to analyse for the mode of occurrence of gold in order to assist selection of ore processing options. The aim of this paper is to describe the laboratory testwork and analytical procedures which have been of benefit in detail­ing the mode of occurrence and mineral associations of gold and hence being of value in developing an optimised ore processing route. The range of ore and mineral assemblages described include relatively simple pyrite and free milling ores, more complex pyrite plus arsenopyrite gold ores and the quite com­plex associations of gold in copper bearing ores or with car­bonaceous mixed sulphide ore assemblages. The aim of this paper is to describe the laboratory testwork and analytical procedures which have been of benefit in detail­ing the mode of occurrence and mineral associations of gold and hence being of value in developing an optimised ore processing route. The range of ore and mineral assemblages described include relatively simple pyrite and free milling ores, more complex pyrite plus arsenopyrite gold ores and the quite com­plex associations of gold in copper bearing ores or with car­bonaceous mixed sulphide ore assemblages.

Jan 1, 1996

By Caren Caldwell, Leslie Thompson

1.1 Biological Process Description Pintail Systems, Inc. (PSI) has developed and in partnership with their clients in the mining industry has applied biological remediation processes for detoxification of spent ore and process solutions from heap leach operations. Contaminants that are treated to mine closure levels or drinking water standards include cyanides (weak acid dissociable and total cyanides), thiocyanate, nitrates and heavy metals. Biological processes are both site-specific and ore-specific processes. PSI specializes in isolating indigenous microorgan­isms from spent ore and process solutions and augments them in the laboratory for enhanced bio-detoxification in the field. Bioaugmentation in the lab is a key to successful heap bio-detox in the field. In PSI's bioaugmentation processes native microorganisms are isolated from the spent ore environment and are tested for contaminant remediation capacity. A majority of the indigenous microbes will be tolerant of the spent ore environment but will not contribute to contaminant metabolism. Indigenous enrichment or biostimulation of these non-working microbes by adding trace nutrients can competitively inhibit the working microbes. For this reason PSI focuses on the bioaugmentation process where non-working microbes are discarded and the working population is enhanced through stress, mutation and exogenous enrichment before it is re-introduced to the heap and process solutions.

Jan 1, 1997