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By A. F. Alsobrook

Specialty silica materials, as defined in this chapter, are rocks that consist predominantly of silica (SiO2) and are produced as chunks, round pebbles, and sawed or trimmed blocks and other shapes for nonconstruction applications. The rock types include quartzite, sandstone, novaculite, flint, chert, and vein quartz. Other terms used commercially include jasper, silex, lascas, and rock crystal. In its publication, Minerals Yearbook, the US Bureau of Mines (USBM) reports the production and consumption of some specialty silica materials under several headings. Quartzite, sandstone, and novaculite used in abrasive applications are addressed by the USBM under Abrasive Materials. Lascas, a type of vein quartz used in growing synthetic quartz crystals and in fusing applications, is discussed under Quartz Crystal. Silica gravel used in manufacturing silicon metal and ferrosilicon, as metallurgical fluxstone, and as a filtration medium is covered under Industrial Sand and Gravel. Information on

Jan 1, 1994

By G. O. Kesse

The Republic of Ghana, located on the West Coast of Africa, is one of the West African countries rich in bauxite deposits. The main occurrences of bauxite deposits are at Sefwi Bekwai in the Western Region, Aya-Nyinahin in the Ashanti Region, Atewa Range near Kibi and at Mount Ejuanema both in the Eastern Region of Ghana. These bauxite deposits belong to the so-called blanket deposits as they are associated with erosion surfaces of old peneplains and occur as cappings on the flat tops of hills or mountains whose heights are generally greater than 600 metres above sea level. These deposits can also be classified as laterite-silicate bauxites since they have been formed under tropical weathering conditions. Genetic and mineralogical investigations have revealed that all bauxite deposits of Ghana are the result of indirect bauxitization processes, for the minerals of the weathering parent rocks have not been transformed directly into gibbsite. In all cases, lithomarge of kaolinitic clay can be recognised. The geology of the major occurrences of bauxite in Ghana shows that the Mount Ejuanema deposit is the only deposit associated with the Voltaian System of rocks. This rock System consists mainly of sandstone, shale, mudstone, conglomerates and pebbly beds. All the otter deposits are associated with the Birimian System of rocks which are made up of metamorphosed lavas,pyroclastic rocks, hypabyssal basic intrusives, phyllites, schists, tuffs and greywackes.

Jan 1, 1984

By David Morrison

On the Corramandel Peninsula of New Zealand, the Waihi Gold Mine has undergone a major redevelopment. The upgrade included the construction of two very large overland belt conveyors, both rated for a capacity of 6000tph. The first of these conveyors (CVR2) traverses a total of 1600m over undulating terrain, including a significant section running through tunnels. A large hill is climbed, just after the mid-section of the conveyor run, before dropping back down prior the discharge point. The second of these conveyors (CVR8) traverses 1100m along an alignment with a horizontal curve, a number of vertical curves and a significant lift before the discharge point. The CVR8 conveyor also included a shuttling head pulley arrangement. The mine they service is inside the town of Waihi. The conveyor alignment runs through the town and out to the metallurgical process site on the outskirts of the municipal area. This paper documents the engineering process that took place in the design of these conveyors. The Martha Hill mine in Waihi, New Zealand is unique. The mine is placed in the township. Consequently there are quite stringent environmental limitations on the mine's operation. In [Figure 1] the proximity of the mine to the town is shown. In the top-centre of the photograph the alignment of the existing smaller overland conveyor can be seen leading from the mine to a tunnel through the hill in the background.

Jan 1, 2000

By Samuel B. Romberger

During the formation of most epithermal precious metal deposits geochemical changes can be characterized by the introduction of large amounts of silica, minor amounts of sulfur, and trace quantities of gold, silver, and other metals. During the same process, large amounts of alkalis and alkaline earth elements, such as sodium and calcium, and sometimes aluminum are removed from the rocks. In deposits hosted by carbonate sedimentary rocks large amounts of carbonate may be removed before or during the silicification process. Small amounts of iron may be introduced by the mineralizing solutions, however, in most epithermal deposits this may be a relatively immobile component and is locally derived. The results of these changes are deposits consisting of up to 90 to 95 percent silica as quartz veins, breccias, silicified host rocks, and jasperoids containing a few percent sulfides, mostly pyrite, and a few parts per million gold and silver. Other minerals commonly but not always present are barite, arsenic, antimony, or mercury sulfides, and tellurides. Often gold shows a spatial, and therefore an apparent genetic, relationship to pyrite in primary ores. Alteration and gangue assemblages sometimes include sericite and/or adularia, and parts of the deposits may contain alunite and/or clay minerals. Even though the value of these deposits usually lies in their gold content, silver is usually present in larger quantities than gold (Romberger, 1990). Based on these general characteristics observed in a large number of epithermal deposits, together with processes occurring in active geothermal areas to which they are often genetically linked (Henley, 1985), a model is proposed whereby deposition occurs along a subhorizontal zone separating environments of contrasting chemistries. The upper environment is characterized by oxygenated acid waters and the deeper environment by a reducing near neutral aqueous system. The model describes the chemical changes occurring as a result of mixing and/or boiling within this zone. It builds upon the physical models proposed by Romberger (1988a) for disseminated gold deposits and Bonham (1988; 1989) for volcanic rockhosted deposits.

Jan 1, 1990

By H Sohn, R. R. Fernández

Microscopic gold inclusions in sulfide minerals cannot typically be extracted by conventional cyanidation. The gold ore must be pretreated to oxidize sulfide minerals associated with gold and to remove other minerals and chemical compounds that interfere in the cyanidation leaching process. The recovery of gold from refractory sulfidic-carbonaceous ores after roasting pretreatment was studied. With the addition of an oxygen-containing gas (e.g., air or oxygen-enriched air), sulfides of iron, zinc. copper and other metals are tramformed into solid oxides or sulfates and gaseous sulfur dioxide at elevated temperatures (e.g., 400° to 800°C). When the sulfides are oxidized, individual particles lose internal volume and become porous, allowing leaching solutions access to the gold. The structural characteristics of the calcine have a strong influence on the eventual recovery of gold by cyanidation. These characteristics are strongly dependent on the roasting conditions and roasting method. The optimum combination of particle size, roasting temperature, reaction time and oxygen concentration in the off-gas was determined for a typical refractory sulfidic-carbonaceous ore from the Carlin Trend in Nevada. The tests were run using a 150-mm laboratory rotating tube furnace and 160- and 200-mm.fluid-bed pilot roasters. Laboratory results indicated that the maximum gold extraction was 92%, with the head and the leach residue containing 5.7 and 0.4 g/t (0.166 and 0.013 oz/st) Au, respectively. The maximum extraction was achieved under the following roasting conditions: a top particle size of 150 yin, a residence time of 2 hrs, a roasting temperature of 475°C and with 40% oxygen (by volume) in the off-gas. Similar results were obtained from circulating fluid bed (CFB) pilot-plant testing. The maximum gold extraction was 90%, with the head and leach residue containing of 5.1 and 0.5 g/t (0. 149 and 0.015 oz/st) Au, respective) v. These results were achieved with the same particle size and oxygen concentration as in the laboratory testing but with the roasting temperature of 500 ° to 525°C and a residence time of 30 min.

Jan 1, 2000

By Don Morris

The Building Products Company is Phoenix based and owned by Mission Clay products of California. Building Products is the only manufacturer of vitrified clay pipe in Arizona. The marketing area includes Arizona, Nevada, Utah, New Mexico, and California. Building Products, promoted by Arizona Public Service, was formed in 1970. Raw-materials prospecting was undertaken for 2 years, after which a $5-million plant was built. Initially, a satisfactory vitrified product could not be made with the raw materials then in hand. Subsequent prospecting and testing led to an acceptable raw-materials mix. Testing to upgrade the final product is a continuing process. The basic raw-materials supply must be adequate, secure, and capable of sustaining close tolerances in the final product. These needs are met by mining four geologic materials at three different localities: (1) refractory aluminous shales (two horizons-one pit) Colorado Plateau Province (Mogollon Rim); (2) less refractory aluminous materials from late Cenozoic lacustrine materials near Dewey in the Transition Zone (TZ); and (3) Precam¬brian "slate" from near New River along the southern edge of the TZ. Other additives include grog (ground-up, broken pipe) and barium carbonate that ties up what gypsum there is. Calcium magnesium carbonates are deleterious components that are minimized by careful selection of the mined products. The raw materials are blended and mixed, ground to 12 mesh, mixed in a pug mill, depleted of air, extruded into pipe ranging from 6 inches to 42 inches in diameter, transported to a hot-air drying room, fork-lifted to an appropriate kiln, and fired at a 1900-2000° F range. The "Rim" kaolinitic shales, being the most refractory ingredient, stabilize the pipe during the firing process. They are very plastic, and therefore facilitate extrusion. The Dewey clay fuses at a low temperature and forms an impervious glasslike binder. It also is plastic. The "slate" forms platy particles that tend to orient themselves during laminar flow. This provides strength for both the green and dried product. It doesn't absorb water, which helps the drying process. Grog remains stable during firing, and therefore helps to control shrinkage. The development of appropriate raw materials and proper mixtures has been done empirically.

Jan 1, 1987

By Sunil Jain, Jan M. Mutmansky

As coal mining evolves in this country, underground coal is being mined at greater depth and under more difficult conditions than in the past. At the same time, economic conditions make it necessary to mine more efficiently and economically. As a result, pressures on mining companies arise on two fronts and make the job of mining coal underground very difficult. Recent improvements that have been made in health, safety and productivity have come about primarily due to improvements in existing technology and better management of all the production resources. However, this trend can continue only so far and thus innovation will be needed to continue the improvement. This paper deals with a concept that, on the surface, appears to be more efficient in terms of the costs to provide ventilation. The resulting design is oriented toward increasing the ventilation efficiency through use of a unidirectional ventilation plan but it also promises to increase recovery and decrease the requirements for development entries. To analyze this ventilation concept, two mine layouts with a similar production schedule were planned in a hypothetical 1.83 m (6 ft) coal seam. The first alternative analyzed uses a traditional approach to ventilation with centrally located shafts and a bidirectional ventilation pattern. Using this system, it is necessary to use large-diameter shafts and a large number of main entries. Using the same assumptions on ventilation requirements, the second alternative utilizes unidirectional ventilation whenever possible, a smaller number of main entries and small-diameter blind-bored shafts in the bleeder areas. The comparative analysis is performed using PSU/TDMVS, a computer network analysis program that is capable of determining the ventilation power requirements at any time in the mine life and converting the costs to a present value. The economic analysis is then completed by including the shaft-sinking and entry-driving costs and the costs associated with the recovery of coal that are directly related to the change in the ventilation system. The results are summarized on a present-value basis.

Jan 1, 1987

By Danny W. Hagood

High methane liberation and mining depth were two major factors which prompted the development of a high- capacity face ventilation system at Jim Walter Re- sources, Inc., No. 4 Mine. No. 4 Mine, one of four deep shaft mines presently under development, is located approximately 50 miles southwest of Birmingham, near Brookwood, Alabama (Figure 1). The coal seams under development are located in the Warrior Coal Field and include both the Blue Creek and Mary Lee Seams, Depth of cover averages 2000 ft. (610 m) with an average total mining height of 8 ft. C2.4 m). [ ] It is generally accepted that the methane content of a particular coal increases as the overburden depth is increased [l] ; experience to date has shown that the gas condition of the No. 4 Mine is no exception to the rule. To further compound the problem, the over- burden depth, coupled with the relatively soft nature of the Blue Creek coal, has resulted in an initial layout based upon 150 x 150 ft (45.7 x 45.7 m) centers. Considering the above-mentioned mining conditions, the means and the effectiveness of the face ventilation system becomes paramount where productivity is concerned.

Jan 1, 1980

By Robert L. Runkel, D. Kirk Nordstrom, James W. Ball

Low-flow reactive-transport processes in Wightman Fork downstream of the Summitville Mine, south-central Colorado were simulated using the OTIS and OTEQ solute-transport models. The simulation was calibrated using data from a synoptic study conducted during October, 1998. Discharge over the 8-km reach from just below the mine site to the Alamosa River confluence ranged from 0.077 to 0.17 m3/s; travel time was 10.7 hours; pH ranged from 4.6 to 5.7. Simulations revealed that mass balance for SO4 was maintained, and that pH, Fe, and Al were non-conservative. Simulations allowing hydrous ferric and aluminum oxide or hydroxysulfate precipitation matched observed water quality conditions more closely than simulations without precipitation.

Jan 1, 2000

By F. C. Turin, T. L. Friend, A. G. Mayton, J. S. Jaspal, W. J. Wiehagen

This paper describes the serious injuries that have occurred to bulldozer operators working at domestic coal, metal and nonmetal mines in the United States. A serious injury is defined as one that results in either a fatality or in lost work time. Examined were 873 injury records compiled by the Mine Safety and Health Administration (MSHA). The time period covered was 1988 through 1997. These injuries resulted in 18 fatalities and 31,866 lost work days. All of these injuries occurred to dozer operators while they were performing common production tasks. An injury classification system was developed to code the narrative information that describes the circumstances surrounding the injuries. Jolts and jars accounted, for 604 or 70% of the serious injuries to bulldozer operators, and jolts and jars accounted for 75% of the workdays lost. Vertical jars comprised the largest set (354 incidents) of jolting and jarring injuries. In more than half of these incidents, the operator was backing up the dozer. Working near an edge carries significant risk for fatal injuries. Of 116 incidents where the dozer fell over an edge, rolled over or fell into a hidden void, 14 (12%) resulted in fatal injuries. In cases where the dozer operator either jumped or was thrown out of the cab in a fallover or rollover, seven out of 17 of the operators were killed. This study finds that further reductions in injury risk would require more widespread use of seat belts; consideration (and maintenance) of the seat and seat suspension systems that might reduce injury risk from jolts and jars; research interventions to assess the effect of alternative engineering designs to dampen or isolate the effects of shock and vibration; and continued attention to skilled performance, i.e., the integration of hazard awareness, recognition and response with dozer operational skills.

Jan 1, 2003

By William Paul Robinson

I would like to first summarize the relevant health information relating to the workers and general populations around uranium mining as a basis for understanding the hazards associated with these operations and their available remedies. This discussion will summarize the literature on Radon and its daughters, among the most toxic uranium decay products. Second, I will discuss waste handling in the uranium industry: past, present and future, discussing exploration, mining, and milling and the volumes of water and solid and gaseous wastes which are associated with these various phases of uranium operations. This paper will also include a discussion of the various past and present materials handling technologies and their responsiveness to the concern for uranium waste isolation. I will then conclude with a summary of recent modifications in the relevant standards as applied to uranium mining and milling. Joseph Wagoner, a research epidemiologist with the U.S. Public Health Service has summarized the literature on uranium mining and its health effects in his written testimony as a commissioned witness in British Columbia Royal Commission of Inquiry into Uranium Mining in January of 1980, entitled Uranium, The U.S. Experience: A Lesson in History.1 Briefly summarizinq his report, as early as 1546, miners of uranium bearing ores in Central Europe were reported to have unusually hiqh frequencies of fatal lung disease2. As early as 1879, the real nature of pulmonary disorders among these miners was first diagnosed to be malignant neoplasia or lung cancers. Of 655 miners dying between 1875 and 1912, 40% or 276 of these Central Europe miners died of lung cancer.4 By 1939, it was reported that lung cancer mortality rate for miners in these Central European mining districts was several times (9.7 per 1000) higher than that for similar populations in Vienna, Austria (0.34 per 1000). Thus, before uranium mining began in the U.S., there was a considerable body of information linking uranium mining to lung cancers. The U.S. experience can be summarized in Table 1 also from Wagoner's B.C. Testimony.1 This table shows that through 1978, 205 respiratory cancer deaths have been observed among white underground uranium miners in the

Jan 1, 1980

By Judith A. Marks, Deane K. Smith, Jan M. Mutmansky, Maria Klimkiewicz

The mechanical mining of coal seams where roof, partings, and floor rock are extracted along with the coal often introduces large numbers of quartz particles into the mine atmosphere. This study concentrates on the quartz properties in situ and in the airborne dust to determine how they are released from the source rock and whether they are fractured by the mining machinery. Three mines using drum-type continuous miners from different geographic areas were sampled to provide a data base. The roof and floor rocks were primarily siltstones containing 5% to 25% quartz measured by the X-ray powder diffraction (XRPD) method. Much of the work presented here is based on the morphologies of the mineral grains determined by the scanning electron microscope (SEM). The study concentrated on particles of 0.2 to 10.0 µm and on particles containing > 75% Si. Mechanically-crushed quartz particles were also examined for comparison purposes. Particle shapes from the airborne samples suggested that fractured quartz particles were rare. Particle statistics also show that the average size of quartz particles in the airborne samples were similar to the average size of all particles. The conclusion is that very few quartz particles from the source rocks are fractured during mining due to their small initial size and the protection of the associated clays.

Jan 1, 1991

By David B. McWhorter, John D. Nelson

INTRODUCTION The quantity of seepage that will be released from a tailings impoundment depends not only on the characteristics of the seepage control system, but also on the properties of the foundation soil or rock beneath the impoundment and the nature of the groundwater in the area. The interaction between various elements of the seepage control system and the influence the various characteristics of the site and impoundment have on seepage are the subject of this paper. The results of analyses are presented herein to indicate the nature and magnitude of the effect that the various factors will have on seep¬age losses. Analyses were conducted for a uranium mill tailings impoundment located in an area characteristic of many found in the western United States or Canada. A typical seepage control system consists of placement of either a clay or synthetic liner beneath the impoundment. In some cases an underdrain system may be placed on top of the liner to collect drainage from the tailings. The parameters that were varied in the analyses included those pertaining to the liner, underdrains and foundation strata. In general, it is shown that the seepage losses will vary in a complex manner depending on the interaction of the elements of the site and the seepage control system. As may be expected, the liner and underdrain systems have the most pronounced effect on controlling seepage. This paper deals with the quantity of seepage released from an impoundment However, the impact that seepage losses from an impoundment will have on the surrounding environment will depend on the rate at which contaminants will enter the groundwater and the nature of the groundwater flow itself. Consequently, when considering these results with regard to environmental impact they must be interpreted along with considerations of geochemical factors. MECHANICS OF SEEPAGE The mechanics of seepage and methods of analysis that were used will be discussed briefly herein. For a more detailed discussion the reader is referred elsewhere (McWhorter and Nelson, 1978, 1979, 1980). A general column through the impoundment was considered to be as shown in Fig. 1.

Jan 1, 1980

By Omar A. Muhtadi, R. Bruce Thorndycraft, David A. Milligan

9.1 INTRODUCTION Precious metals in a leach solution are extracted, concentrated, and purified to complete the process begun in the heap and to produce an end product which will provide an economic payback to the mine developer/operator. Several different processes are required to convert the dissolved precious metals into pure metal bars. This chapter discusses the actual production of metal once it has been recovered from the pregnant leach solutions by the zinc cementation (Merrill -Crowe) or carbon adsorption processes. Metal production is generally taken to mean the production of a fairly pure "dore" bar. This chapter also reiterates some information from Chapter 8 in a slightly different context, since the focus of Chapter 8 was a fairly detailed description of the two actual recovery processes, whereas the focus of this chapter is metal production. The sale of an intermediate precious metal product is possible (as opposed to the production of dore bars at the mine site); however, the value of the precious metals is reduced by the various charges and risks associated with precious metal processing. For this reason, most operators choose to produce the most refined metal possible in order to maximize project economics. Precious metals may be extracted from the leach solution by both conventional and unconventional processes. The conventional processes are activated carbon/electrowinning (ACE) and zinc precipitation (ZIP). The unconventional processes are resin ion exchange, solvent extraction, and direct electrowinning. A typical ACE process has two circulating loops. The first loop adsorbs the cyanide-metal complexes from the dilute leach solution onto the activated carbon. A second, separate solution loop removes the cyanide-metal complexes from the activated carbon into a strong solution, the electrowinning electrolyte. Activated carbon is transferred from one fluid loop to the other. The operating cost of the ACE process is directly proportional to the quantity of carbon stripped and thus to the quantity of precious metal produced. A typical ZIP process contains a single circulating loop. The solution is filtered, deaerated, contacted with zinc, and filtered again. The barren leach solution is then returned to the heap. The zinc sludge recovered in the

Jan 1, 1988

By Samuel M. Cassidy

The exact date of man's first use of coal is lost in antiquity. The discovery that certain black rock would burn was undoubtedly accidental and probably occurred independently and many times in the world over thousands of years. It is quite likely that these independent discoveries were made when primitive man chanced to build camp fires on exposed ledges of a black rock, then was amazed when it caught fire. The Chinese recorded the use of coal 1100 years before the Christian Era and from the Bible we learn that King Solomon was familiar with coal in what is now Syria. In Wales, there .is evidence that the Bronze Age people used coal for funeral pyres, and it is known that the Romans used this fuel. There are other ancient references. So the knowledge that coal would burn, and even some uses of that knowledge, go back thousands of years. However, practical and consistent use of coal seems to date to England in the Middle Ages.

Jan 1, 1981

By S. B. Bealko

Mining haul trucks comprise the majority of the equipment used in underground limestone mining operations and are known to emit high levels of noise. A previous study conducted by the National Institute for Occupational Safety and Health (NIOSH) indicates that 70-90 percent of all miners have a noise-induced hearing loss (NIHL) great enough to be classified as a hearing disability by retirement age. These results demonstrate the public health need to protect the hearing of workers in the mining industry, including haul truck drivers. ng of workers in the mining industry, including haul truck drivers. Cab enclosures present an opportunity to isolate the haul truck operator from both truck and other noise in the mining environment. A total of twenty-five haul truck cabs were studied which were divided into three style (treatment) categories determined by soundproofing features and technology for noise reduction: old-, new-, and retrofitted-style. This study examines the contribution of cab acoustics, operator performance, and maintenance to noise reduction for each cab style. Dosimeters were used to measure 8-hr time weighted average sound pressure levels (TWA8 SPLs) inside and outside the cabs to determine if different acoustical treatments affect cab attenuation. Adherence to the Mine Safety and Health Administration (MSHA) Permissible Exposure Limit (PEL) of 90 dB TWA8 (with a 90 dB threshold) was used as the main indicator of overall noise reduction achieved. Dosimetery results indicate only 2% of the samples exceeded the PEL, but samples could still be reduced much further. Descriptive and comparative statistics indicate that noise levels inside the new-style cabs are significantly lower than the other two cab styles. Also, data suggest that there is no difference in noise exposures when comparing the old-style to retrofitted cab styles. Operator influence (opening doors and windows) was a significant factor for increasing noise exposure. This paper demonstrates that properly designed cabs can achieve major noise reductions, but noise levels could still be reduced much further below the MSHA PEL. New-style cabs, equipped with modern noise-reduction treatments, exhibit much lower noise exposures than the other two cabs styles, and the effectiveness of the current noise-reduction treatments for retrofitted cabs is questionable. Haul truck driver observations indicate that improved noise exposure reduction training is needed. Finally, specific targets for future noise reduction research are suggested that will further contribute to the prevention of hearing loss for haul truck operators.

Jan 1, 2008

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's renowned Bahnhofstrasse. In Kyrgyzstan, though, the gold is still in the mountains. Accordingly, Kyrgyzstan'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's min¬ing sector as to the personal charms of the nation's president. Led by a half-billion-dollar investment by Canada's uranium giant Cameco, the mining sector is leading Kyrgyzstan'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'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'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'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

By G. Camposano, J. Aponte, B. A. Ferguson

The paper covers mining operations and preparation of the ore prior to metallurgical treatment in the Process Plant. Mining operations are primarily concerned with the delivery to Ore Preparation of a balanced ore feed within fairly rigid specifications as to both ore type and chemical analysis. The mining method, systems of geological and engineering control, and the equipment employed are therefore reviewed in this context. In Part One of the paper the physical and geological characteristics of the orebodies, including the varied nature of the ore itself, are first described. Orebody evaluation, the calculation and classification of ore reserves, mining planning and forecasting to ensure continuity of production are covered, and the particular problems presented by sampling, the erratic distribution of ore values and the variation in the density of the ores are also mentioned. Mine design and ore excavation practice are described, together with the way in which they have evolved with recent developments in modern mining equipment. In Part Two of the paper, a detailed description of the Ore Preparation plant is given, centred around the concept of rubbling as a means of separation of the barren hard boulders from soft lateritic ore. Ore blending and ore reclamation operations are explained followed by a detailed description of the drying and crushing plant. The importance of the control of moisture content and ore sizing in the feed to the metallurgical plant is emphasized.

Jan 1, 1979

By Jianmin Qin, Raja V. Ramani, Wilson Miola

The number of underground work entities operating under reduced dust standards in U.S. coal mines has been increasing since the start of the decade of the 80s and is currently approaching 10,000. The concern for controlling the quartz levels in airborne respirable dust in coal mine has manifested itself in several improvements in equipment selection and operation, face ventilation practices, and dust control procedures. At the same time, fundamental studies have been initiated on determining the source-sink relationships of the airborne quartz dust. The P-7 method is the prescribed method for the determination of quartz in the respirable airborne dust samples from coal mines. Questions have been raised on the reliability of the P-7 infrared spectrometry method for quartz analysis in powders. No specific method has been defined for quartz determination in bulk samples from the mine. In a recent study on the relationship between quartz in the airborne dust and that in the materials being mined, both infrared (IR) and x-ray diffraction (XRD) methods were used on a suite of samples from several coal mines. These samples encompassed airborne respirable dust samples, airborne total dust samples, the oversize fraction from the respirable samplers, ROM samples, channel samples, and chip samples from the face, roof, and floor materials. In this paper, the sample preparation and analysis procedures for the samples are discussed. The data, analysis results, and comparisons of the P-7 and XRD results are presented. The quartz percent determined for the same sample by the two methods are different. In 85% of the samples analyzed, the quartz percents determined by the XRD method are higher than those obtained by the P-7 method. However, there is a strong linear relationship between the results from the two methods. Further, the XRD method indicates an average of 20 percent more quartz than that from the P-7 method. The reasons for the differences in the results and the need for additional studies are explored.

Jan 1, 1991

By Nikhil Dhawan, Veeranjaneyulu Rayapudi, Singh Rahulkumar Sunil

The ever-increasing demand for steel and the subsequent depletion of high-grade ores requires the massive utilization of low-grade iron ores. In the present study, an iron ore slime sample containing 56.1% Fe was investigated using physical beneficiation, carbothermal reduction, and a microwave-assisted process; however, physical beneficiation and microwave exposure were found to be inefficient as they yielded lower iron recovery. Using coconut shell as an alternative reductant was found to be promising and does not lead to the formation of higher iron oxides, such as fayalite and wustite phases. The microwave-assisted carbothermal reduction was found at par with conventional reduction, saving time and heating. The optimum magnetic concentrate obtained in both carbothermal reduction routes (microwave and muffle furnace: Fe grade, Fe recovery, and yield of 64.3, 97, and 84%, and 67, 99, and 83%, respectively) are suitable for alternative iron-making or blast furnace units.