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By John P. Gooch

The solubility of 1,1,2,2-tetrabromoethane (TBE) in water was determined from 1.0° to 97.0° C. The solubility (S) of TBE in grams of solute per 100 grams water was correlated with [S = 1,920.55 [exp (40292L7 11, T2 10 T 737.577 + 9.923962 ] where T is in degrees Kelvin. A thermodynamic analysis conducted on a system consisting of a TBE phase and a water phase in equilibrium with a vapor phase led to the calculation of the activity coefficient, vapor-liquid equilibrium distribution coefficient, relative volatility, and heat of mixing for saturated solutions of TBE in water. Data required for these calculations were the solubility of TBE in water and the vapor pressures of TBE and water as a function of temperature.

Jan 1, 1972

By C. Hunt, J. Vivas, D. M. Allen

"In this paper we present the results of a combined remote sensing - numerical modelling study to improve our understanding of groundwater seepage in open pit and natural rock slopes, and to investigate the interaction between groundwater, in-situ stress conditions and brittle fracture. The location of seepage is a key element in the characterisation of rock slope stability in open pits and natural slopes; definition of the fracture network geometry and its inter-relationship with seepage, however, remains a challenge in engineering practice. Current techniques used to characterize groundwater seepage locations require direct access to the rock slope for a detailed and exhaustive investigation, and can be severely limited due to access and the limited coverage of the survey methods both with respect to the height and length of the sampled rock slope. Herein, we describe remote sensing methods, which allow the collection of structural and seepage information over a wide spatial area. Remote sensing techniques are shown to have the potential to provide additional insights into the orientation and general connectivity of fractures that may play a major role in the general stability of a rock slope. A preliminary methodology for the use of remote sensing in the characterization of seepage zones in a natural slope through the application of ground-based LiDAR and Infrared Thermography (IRT) is presented.One of the most challenging problems in rock slope engineering is the realistic simulation of fluid flow through fractured and deforming rock slopes. Deformation and the development of brittle fractures can cause significant local changes in the permeability and strength of the rock mass, potentially affecting rock slope performance. Understanding fluid flow through fractured and deforming rock slopes, especially in highly-stressed environments is of great importance for slope stability analysis. Changes in the interconnectivity of fractures during slope failure are an important, yet are relatively unstudied in rock slope engineering. We present the results of hydromechanical UDEC-Trigon rock slope models focussing on the potential role of brittle fracture in rock slope failure, its interaction with groundwater pressures, and the influence of the assumed in-situ stress ratio. Damage intensity parameters are used to characterize damage within different regions of a biplanar slope failure."

Jan 1, 2015

By Leland E. Paulson

This investigation examined the feasibility of altering the inorganic component of North Dakota lignite by ion exchange. Lignite of specific size consist was washed with various ionic solutions and examined for evidence of exchange. Ions of higher valance substituted preferentially at equivalent concentrations. Results indicate that a major portion of the inorganic material associated with lignite is combined in exchangeable form with the organic component. Particle size of the treated coal is a critical factor in determining the rate of exchange. The data indicate that monovalent ions are easily replaced by divalent and trivalent ions, and the presence of ionic material in slurries containing finely divided lignite significantly increases filtration rates.

Jan 1, 1968

By Guo Qian, Du Guangyin, Deng Yongfeng, Liu Songyu, Wang Ningping

"Metakaolin (MK) can efficiently enhance the strength and the impermeability of concretes and mortars. However, it has rarely been attempted in admixtures of cement-stabilized soils until presently. As deep mixing method is wildly used in ground improvement, the strength of cemented soils (soilcrete) and the applicability of the MK should be considered. This paper focuses on the macro-strength development of cement-stabilised silty soil mixed with MK. The result shows that the addition of MK can enhance the unconfined compressive strength of the soilcrete, which attributes to a combination of the rates of OPC hydration and the MK-CH reaction. Note that the strength of soilcrete was influenced by the properties of soil, water-to-binder mass ratio (W/B) in admixtures, which needs to be reconsidered since the binder mass composes that of cement and MK totally.INTRODUCTIONCement was used in ground modification techniques, such as the jet grouting, deep mixing method (DMM) which was put into practices in Japan and Nordic countries in the middle of the 1970s, and then spread to China, South East Asia[1]. For last decades, fly ash, slag or silica fume was mixed with cement to form the new cement base stabilizing agent in the view of economy and performance improvement. The mechanical behavior of these soil-binder admixtures (nominated as “soilcrete”), was investigated. But the soilcrete modified with the metakaolin (MK) was still not investigated much and lots of further work needs to be conducted.Some laboratory experiments of the soilcretes modified with MK have been taken[2~4]. Kolovos et al. (2013) indicates that the unconfined compressive strength has a more significant improvement when W/B equals 0.4 than that when W/B equals 1.20 concerning the water-to-binder mass ratio (W/B). Sonebi et al. (2013) investigates the mechanical behaviors of cement grouting containing MK with W/B equals 0.4, and also found the effectiveness of the addition of MK. Zhang et al. (2014) performed the studies on Lianyungang marine clay improvement showed that MK obviously enhanced the quality of cemented soils.In this paper, the strength of soilcrete modified with MK is further investigated, where the unconfined compressive strength at different curing time, the content of MK and cement (w/w) in lab conditions was discussed."

Jan 1, 2015

By M. H. Harris

A solution has been obtained to the problem of calculating flow into a cased and perforated well. Equations describing the idealized system were solved by numerical analysis techniques on a high-speed digital computer. Computer experimentation indicated that the results are within 3 per cent of the exact solution. Computed results are presented as an apparent skin effect, on a series of dimensionless working curves. Productivity ratios can be rapidly calculated from these data for the wide range of wellbore and reservoir properties actually encountered in field practice. Any reasonable vertical unisotropy ratio can be included in the computation. Productivities can be calculated for wells perforated in a regular pattern, a single horizontal plane or a vertical line on one side of the casing. Solutions for asymmetrical perforation patterns can he easily obtained from the working curves. Solutions for flow into sells completed with a horizontal notch are also provided. Results show that productivity can be increased by extending perforation penetration. This is especially true for shallow penetrations. The highest productivity is obtained when perforations are arranged in horizontal planes, as opposed to a vertical line on one side of the casing. Four or five perforations in one plane will approach the maximum productivity. The effect of perforation hole diameter is small, and is rioticeable only in shallow penetrations. INTRODUCTION The perforating method of well completion has been successfully and widely used in most producing areas. In the past, the desired perforation results were achieved by simply shooting numerous large holes in the casing. A perforating scheme for an area, or particular well, was established by evaluating two types of experimental data: the well flow index and the productivity ratio.' 3 The well flow index test is a means of determining the relative flow capacity of perforations in a linear system. This test also gives information on the perforation size, shape and hole damage which can be expected under well-bore conditions. However, relative flow data from this test cannot be accurately tarnsformed into the radial wellbore system. Thus, no true indication of the productive capacity of a perforated well can be obtained from the well flow index test. A well productivity ratio is derived from electrolytic models built to simulate perforated wells. Available productivity ratio data 2,3 are limited in that all important variables are not extensively evaluated. For example, data are limited to well radii of 3 and 6 in., and to maximum perforation penetration of 1 ft. Practically no information is available on the pattern of flow into a perforation. The effect of various perforation patterns on well productivity has not yet been determined and the effect of perforation diameter has not been thoroughly studied. Also, it will be shown that this type of electrolytic model data is probably in error by as much as 10 per cent or more. Modern completion techniques such as limited-entry perforating, single-plane fracturing, steam and hot air injection and chemical consolidation of incompetent formations all rely on injection and/or production from a limited type of completion. These completions may consist of several high-capacity perforations or a horizontal notch which is equivalent to an infinite number of perforations in one plane. Proper design of these new completion techniques requires, in part, accurate estimates of a well's productive capacity. Data on perforated and notched well productivity have been determined in this investigation. Results are presented as a function of the pertinent variables. Equations describing the idealized system were solved by numerical analysis techniques on a high-speed digital computer. DESCRIPTION OF PROBLEM PRACTICAL APPLICATION The computed results can be applied to wells which meet several general specifications. An external drainage radius of the well must be known or assumed, but the well need not be drilled on a regular pattern. The well must be cased and cemented through the entire producing interval. And, the casing must be perforated with one or more horizontal planes of perforations. The perforation pattern itself must conform to three geometrical requirements. 1. The perforations in a plane must divide the plane into equal angular segments (Fig. 1). Four perforations per plane would be 90" apart. 2. Perforations in a plane must be directly above or beneath perforations in adjacent planes. For two shots per plane, perforations would lie in the BB' plane (Fig. 1). 3. Horizontal planes must have equal vertical spacing and be separated from the top and bottom of the formation by one half the spacing interval. Single planes of perforations should be in the middle of the formation. This is shown in Fig. 2 where h is the formation thickness in a single plane conlpletion or the spacnig interval in a multiple plane completion. The spacing interval at the top and bottom of the formation may vary somewhat without causing an appreciable error in the productivity calculation if the formation is reasonably thick and there are many horizontal planes of perforations. A special provision has been made to calculate the productivity ratios of wells with uneven spacing intervals, or for the case where a single plane of perfora-

Jan 1, 1967

By Teuku A. R. Putra, Patrick R. Taylor

Various pyrometallurgical methods for treating copper concentrates that contain appreciable arsenic are reviewed. Various aspects of the engineering of these treatment methods are discussed. The methods discussed include: complete oxidation with arsenic fixation; selective volatilization of arsenic; acid baking, soda ash roasting, and others methods. Methods for the ultimate disposal, or marketing, of the arsenic are discussed.

Jan 1, 2014

By V. Ross

"Bench-scale flotation tests play a major role in the geometallurgical process value chain. Despite their apparent simplicity, these tests pose pitfalls in terms of operation, as well as the interpretation and modelling of results. In this paper we highlight key aspects to consider in generating accurate and reproducible experimental results, and critically review some assumptions relating to the estimation of entrainment and froth recovery. We subsequently focus on first-order equations to model kinetics and propose a method that accounts more realistically for the decay in kinetics over the duration of a float, and the contributions of froth stability and hence mass pull. The method was applied to three case studies on platinum group metal (PGM) ores and matched or outperformed first-order, two-component models. Also, it allows for a deeper analysis of the integrity of the bench-scale flotation results. IntroductionGeometallurgy is a structured, multidisciplinary approach that integrates key data from the geological, mining, mineralogical, and metallurgical aspects of the value chain to construct spatial models of an ore deposit such that the overall economic benefit and sustainability of an operation can be optimized. Process geometallurgy is aimed primarily at enhancing metallurgical efficiency and plant throughput by the application of appropriate mining and processing strategies, as well as supporting production planning and operational strategies to reduce the impact of highly variable ores. With flotation being the dominant concentrating process in the mineral value chain, the bench-scale flotation test is an important characterization tool – a relatively cheap, simple, and rapid way to obtain key information about the ore and its amenability to economic extraction of valuable minerals. This includes the evaluation of different ore types and the implications of mineralogical composition and texture for comminution and floatability, the effect of the grinding environment on the liberation of minerals, the electrochemical environment in the pulp (Bradshaw et al., 2006), the screening of reagents to improve floatability (Ekmekci et al., 2003), and the role of hydrodynamics in the recovery of valuables and the entrainment of gangue (Amini et al., 2016; Wang et al., 2016). It is also a critical tool in auditing the performance of a flotation plant by hot floats, paving the way for concept and feasibility studies and providing essential data on kinetics for the purposes of scale-up, optimization, and simulation of flotation circuits."

Mar 1, 2019

By C. W. Schultz

The vapor pressure of manganese in equilibrium with a series of liquid iron-manganese alloys was determined by the carrier gas method over a broad range of alloy composition. From these data the activities of manganese in the iron-manganese system were calculated. The system appears to be ideal.

Jan 1, 1966

By Yi Luo

In a shearer longwall mining operation, the longwall bits are responsible for breaking into and chip-ping the broken coal blocks away from the coal face. However, underground observations have found that a large number of longwall bits are always working under various degrees of wear. Reduction of the bit wear could be realized by using better designed longwall bits and properly selected shearer operating parameters. A computer program has been developed to simulate the performance of the longwall bits. The shape of the bit head, the installation of the bits on the drum and the operation parameters are the information required by the program. Through the simulations, the main factors affecting the bit wearing process are identified. Suggestions are also made for improving the design of the longwall bits.

Jan 1, 1996

I HAVE now traversed for you in the small and fragile bark of my writing all the shores of the deep and spacious sea embracing the uses of material fires, drawn on by my own desire to enrich you with more learning and with the procedures of these things, as much as to satisfy your demands. Having through the grace of God arrived at the appointed end of my voyage and neither knowing nor perceiving a way of going farther, I had decided to furl the [167] sails and cast die heavy anchors into the water in order to enjoy in tranquillity respite from my sailing, when I was warned by my pilot that before I could disembark I should turn my glance backward and reexamine my work in detail to see if there were any part that had by chance remained undescribed in the obscurity of silence. When I did this there immediately appeared in my mind's eye the many sublimates and smoky tinctures that had been made by the burning and most powerful fire of love. I need not say that I knew of it in far-off countries or from the knowledge of others, but I knew it in my own breast and as my very own and can therefore surely esteem it as hotter than all the other fires that the world calls by that name. Although today its sparks and living flames are spent because of my cold and hoary season, nevertheless it is true that the memory of acts of love of long ago still remains with some smoke and warmth. Therefore, since in this work of mine I wish to describe for you the effects and powers of fires, I should logically have spoken of this before any of the others, because of its actual nearness and the great acquaintance I had with it. But since I have had the glance of my intentions directed at distant things, I have behaved as one does who does not see where he places his feet because he is looking at the sky, or as one who thinks about the affairs of others and forgets his own. But now I do not wish to pass over this thing and I wish to correct my error, particularly in order to provide a happier ending to my written work than by remaining among the horrible uproar of guns, powder, and saltpeter, which would be a harsher ending than speaking of love. Never-

Jan 1, 1942

By Abu Syed H. Kabir, Mehdi Sanjari, Steve Yue, Jing Su, In-ho Jung

AZ31 magnesium alloy sheets were produced by high speed rolling (HSR) at 1000 m/min at a low temperature of 100 ?. A high reduction of 72% can be achieved in single pass. At the reduction of 30%, the microstructure was covered by shear bands and twins. When the reduction was increased to 49%, dynamic recrystallization (DRX) was clearly observed in the vicinity of shear bands and twins and the full recrystallization was seen at a reduction of 72%. In order to study the static recrystallization (SRX) behavior on the heavily twinned structure, annealing was then carried out at 200 ? on the as-rolled specimens at the reduction of 30% for different times. Static recrystallized grains were also firstly observed on shear bands and twins after 45 s and the microstructure was mostly fully recrystallized after 1 h annealing with a few retained large elongated un-recrystallized grains. Texture weakening was found during annealing on the heavily twinned specimens by SRX, but not during high speed rolling by DRX. In the present study, effect of DRX and SRX on microstructure and texture evolutions during rolling and annealing were compared.

Jan 1, 2015

By D. Bahrami, W. K. Asante, G. L. Danko

It is prudent to interpret atmospheric monitoring signals in real time for checking the safe limits of the air conditions in underground mines. In gassy mines, real-time evaluation increases the safety of operations. In all mines, continuous monitoring and evaluation contributes to maintaining air conditions within healthy and safe limits. Signal interpretation for safety conditions in mines is difficult for many reasons. An increase in hazardous contaminant concentrations can be predicted by signal pattern recognition, root cause analysis of rapid changes toward deterioration, and forward prediction in time using algorithms and numerical models. The paper describes an early warning system for analyzing monitored signal patterns continuously in real time as well as forward predicting the various environmental and working conditions to recognize dangerous trends that may affect safety and health in underground mines. A dynamic, numerical ventilation model with heat and gas contaminant simulation components is used for the analysis of atmospheric data. Methods and test results are discussed with numerical examples for signal propagation prediction. Several mine examples are studied using controlled, synthetic data for malfunction simulations to evaluate time delays between the detection time of suspicious signal trends and the time of dangerous threshold crossing marking an accident scenario. Delay time is found in the order of 20 min in the examples, signifying the useful time period for preventive intervention between EWS warning and the likely breakout of a following accident.

By Henry P. Cole

A comprehensive review of published research was carried out to identify methods for teaching and assessing critical but nonroutine skills needed for coping with emergency situations. Specific methods for assessing critical skills proficiency in aviation, medicine, organization management, the military, and other industrial/technical workplaces are described. The potential application of these methods for teaching and assessing (1) critical first aid and (2) self-rescue and escape skills to underground coal miners in annual refresher training is explored. Research and development activities that may improve mine health and safety training are suggested. Most of these research and development activities were completed later in the project. This additional work is reported in the project technical report #2 and the final report. The research reported in the present document was completed in 1984 -85. Many of the initial findings reported in this document are updated in the later project final report.

Jan 1, 1988

By P Klaric

Drive stability is critical in block/panel cave mining. The production levels of these mines are required to remain operational for the entire life-of-mine which can be in excess of 30 years. It is therefore necessary to produce high-quality drives to ensure sustainable mine productivity. In order to improve the quality of drives and pillars, this gold mine instigated a project to optimise their development blasting. The initial aim was to reduce the level of overbreak in development mining, which was averaging approximately 18 per cent. The benefits of controlling overbreak not only included an increase in the integrity of the drives but also a decrease in load and haul and ground support costs. Through focusing on the optimal blasting of the perimeter holes, overbreak was reduced to 4.5 per cent. The project’s focus then moved to drill and charge designs for development faces. In optimising these designs, it was anticipated that improvements in the development mining cycle would be achievable.CITATION:Klaric, P, 2015. Improving drive stability through efficient development blasting design and practices, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 327–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By D. McConchie

BauxsolTM, prepared by treating bauxite refinery residues with Mg2+ and Ca2+, has an excellent ability to remove arsenic from acidic waters. The addition of BauxsolTM to sulphidic waste rock at the Gilt Edge Mine, South Dakota, reduced As concentrations in leachate water from 35 mg/L to < 0.005 mg/L; the concentrations have remained below 0.005 mg/L for the five years since the treatment was initiated. However, ordinary BauxsolTM does not effectively remove As from near-neutral water and it needs to be acid-treated or blended with small amounts of reagents, such as jarosite or ferrous sulphate, to increase the proportion of positively charged binding sites on the particles. The use of a jarosite/BauxsolTM blend can effectively treat ponded water, and As(V) concentrations can easily be reduced from over 1 mg/L to < 0.001 mg/L; As(III) has to be oxidised to As(V) for effective removal. Metal contaminants in the jarosite are trapped by the BauxsolTM and only very small amounts of the As, or other elements bound during treatment, are liberated using a TCLP leaching test. The exhausted treatment reagents meet the criteria for classification as an inert solid and do not need to be disposed of in a secure repository.

Jan 1, 2006

By M. Saghaeian, R. Hejazi, Fakoor Sanat Tehran Company, H. Abedini, M. Zare

"Dewatering of final tailings is one the biggest issues in iron ore processing plants. Because of the fine and hydrophilic particles in the iron ore tailings, dewatering of such material is difficult and, in most of the cases, needs to be processed using expensive and complicated equipment. In this study, a novel method based on classification of small and large particles has been proposed to improve the dewatering performance of iron ore tailings. In the proposed method, a hydrocyclone has first been used to separate the fine and coarse fraction of iron ore tailings. Then, the coarse fraction (hydrocyclone underflow) is easily dewatered by using vacuum belt filter. Then, the fine fraction (hydrocyclone overflow) is primarily dewatered by using a high rate thickener. Finally, the thickener underflow is added to the bed of solids on the same belt filter, which is used for dewatering of hydrocyclone underflow. The efficiency of this method has been compared with other solutions for tailings dewatering including changing vacuum filtration parameters, using fabric with larger pore size, and using pressure filtration, all through laboratory scale experiments on the tailings of an iron ore processing plant in Iran. The results indicated the superiority of this method compared to the other ones, which increased the specific filtration capacity of the tailings by around 46%.INTRODUCTIONWet beneficiation of minerals requires a substantial amount of water to enhance the efficiency of the process. Used water should be recovered at the end of process to minimize shipping costs, meet contract specifications, and reuse process water (Wills and Napier-Munn, 2006). Dewatering equipment is usually divided into sedimentation (thickening) and filtration (pressure and vacuum) equipment, the choice of which depends on particle size, solid content of slurry, and material nature (Mular et al., 2002)."

Jan 1, 2016

By F. Karakas

Organo-bentonite production enjoys important applications including solvent based paints and, more importantly, the production of polymer/bentonite nanocomposites. Quarternary ammonium salts in this regard are still considered as the most versatile reagents in the process of hydrophobization. In this study, a purified form of Resadiye region bentonites, which is one of the most significant sodium bentonite deposits in the world, was used. The raw Na-Bentonite was typically characterized by chemical analysis, XRD and DTA analysis and more importantly for its cation exchange capacity (CEC). Other technological properties such as swelling index, pH, apparent viscosity, water absorption, oil absorption were also conducted on the raw bentonite. The mineralogical analysis of the raw bentonite reveals that it contains about 80 % montmorillonite together with other associated gangue minerals including feldspar, quartz, calcite, dolomite, coloured impurities and other clay minerals. The raw bentonite was subjected to two stage processing involving a series of hydrocylones. Different apex and vortex diameters and different pressures were employed in order to produce a bentonite concentrate with 95 meq/100g CEC from a CEC of 71 meq/100 g. This high quality concentrate was used in the production of organo-bentontonite. The modification was performed with two different quaternary amines, i.e. Trimethyl Phenyl Ammonium Chloride (TPAC) and Hexadecyl Trimethyl Ammonium Bromide (HDTMA-Br). In the modification procedure, three parameters, i.e., adsorption density, zeta potential, swelling index and apparent viscosity were studied simultaneous-ly from the same suspension to identify both the mechanism of the process and also the degree of hydrophobicity. Adsorption measurements were made as a function of conditioning period, pH, and reagent concentration. Simultaneous examination of the adsorption density, zeta potential and apparent viscosity enabled us to pinpoint the optimum region of hydrophobicity which was subsequently tested by settling and critical coagulation concentration in both water as polar and toluene as nonpolar solvents. The results are analyzed in the light of experimental data.

Jan 1, 2014

By T. S. Heah, S. T. Bishop

"The Lorraine property is located in the northern Intermontane Belt, north-central British Columbia. The property is underlain by intrusive rocks of the Duckling Creek Syenite Complex, an Early Jurassic, alkaline phase of the Late Triassic-Early Cretaceous Hogem Batholith. Two significant zones of copper-gold mineralization have been explored to date; the Main zone (historical Upper and Lower deposits) and the recently discovered Extension zone. A combined geological resource was estimated in 1975 for the Main zone deposits at 10 million tonnes averaging 0.7% Cu, and from 0.1 g/t Au to 0.34 g/t Au. The Extension zone, still at an exploration stage, is estimated to be considerably smaller than the Main zone.Copper-gold mineralization at Lorraine Mountain exhibits characteristics suggestive of both magmatic and hydrothermal origins, and may be related to orthomagmatic-hydrothermal fluid flow contemporaneous with magmatism and development of migmatitic fabrics. A depth greater than the depth of formation of classical porphyries may explain many of the variations displayed by mineralization at Lorraine. These characteristics distinguish Lorraine from other members of the alkalic suite of porphyry Cu-Au deposits in the Canadian Cordillera.IntroductionThe Lorraine prospect is located in the Omineca Mountains, at the headwaters of Duckling Creek, 56 km northwest of Germansen Landing (Fig. 1). The property is centred at latitude 55°55'N, longitude l25°26'W on NTS mapsheet 93N/14W. The area is typified by mountains of moderate relief, with elevations ranging from 1150 m in the valleys to peaks of 2000 m. Valleys are U-shaped and blanketed by glacial till which give way to steep, talus covered slopes and sharp ridges. Outcrop is generally limited to elevations above 1600 m (Fig. 2)."

Jan 1, 1995

By Roberto L. Romero

The dressing of Bolivian tin ores has been done up to the present by classical. gravity methods, taking advantage of the high specific gravity of cassiterite compared with that of the accompanying gangue. For this purpose, jigs and shaking tables are used in the treatment of the various size fractions in which the ore is classified. Bolivian ores are mainly of the vein type and, to obtain a reasonable separation, crushing and several stages of grinding are necessary during the process to substantially liberate the cassiterite from the gangue. Gravity processes for cassiterite are effective for sizes down to 200 mesh. Below this size the efficiency of the gravity methods falls off very rapidly with increasing fineness of the mineral grains. The conventional treatment for this material is desliming followed by tabling on shaking tables various other types of machines have been designed for the gravity treatment of these fine particles but they have had limited success. Bolivian ores contain an appreciable amount of minus 200 mesh material constituted by "primary fines" caning from the mine itself, and "secondary fines" originated during the crushing and grinding necessary for liberation of the difficulty in the treatment of these fine particles is one of the causes why the recovery of tin in concentrates is only of around 50% in the mines owned by Corporacidn Minera de Bolivia, the State owned enterprise. The average figure for other Bolivian mines is

Jan 1, 1971

By Scott Horton

In no Confederation of Independent States (CIS) country does the mining sector play quite so commanding a role as in the mountainous Central Asian republic of Kyrgyzstan. Its president, Askar Akayev, says he would like to develop his country into "a Central Asian Switzerland." However, in Switzerland, the gold is largely under the street along Zurich&apos;s renowned Bahnhofstrasse. In Kyrgyzstan, though, the gold is still in the mountains. Accordingly, Kyrgyzstan&apos;s recent adoption of a comprehensive new mining law has attracted widespread attention. Akayev recently completed a tour of the United States. His visit drew large crowds from the business community at events staged in New York and Washington, DC. The success can be attributed as much to the attractiveness of Kyrgyzstan&apos;s min¬ing sector as to the personal charms of the nation&apos;s president. Led by a half-billion-dollar investment by Canada&apos;s uranium giant Cameco, the mining sector is leading Kyrgyzstan&apos;s economic revival. And Bishkek is beginning to show some of the same signs of a "boom town" that already mark its Kazak neighbor, Almaty. Mercedes and BMWs already outnumber the Volgas on Bishkek&apos;s major traffic arteries. After nearly two years of debates involving government advisors and a final round of deliberation in Parliament, Kyrgyzstan finally adopted its second mining law. This followed quickly in the wake of measures enacted in neighboring Kazakstan and proposed in Russia. Kyrgyzstan&apos;s new law replaces the 1992 law "On Mineral Resources." It was one of the first enactments of an independent Kyrgyzstan. The 1992 law made a major contribution to the introduction of free-market economics in the country by ending the state monopoly over mineral exploration and development. It also laid the groundwork for an independent mining industry. According to Kyrgyz government reports, Kyrgyzstan has about 270 commercially viable deposits of almost 40 types of mineral resources. These include oil, gas, coal, precious-, nonferrous-, ferrous-, rare- and basemetals. However, the nation&apos;s key draw is gold. Since enactment of the first law, the government has issued more than 100 licenses for geological prospecting for and development of established deposits of gold.

Jan 1, 1998