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By Don C. White

Santa Rosa is a mid-Tertiary, volcanic-hosted, bulk-mineable, open-pitable, heap-leachable, gold-silver deposit. It is the product of hydrothermal mineralization along an arcuate segment of a caldera collapse ring fault in a probable maar volcanic setting. This segment was later broken by radial faults. Gold occurs principally as electrum finely disseminated through intermediate tuffs, and associated with pyrite, at Santa Rosa. The nearby Alto de la Mina deposit displays stockwork silica-pyrite-gold in a tectonically and hydrothermally shattered andesite flow. Miocene epithermal mineralization was accompanied by central silicification and pyritization and more distal argillization. An andesite flow cap rock at Santa Rosa played a pivotal role as an upward permeability barrier. Highest gold grades and most intense alteration occur closest to the ring faults and immediately beneath the andesite flow. Supergene alteration effects on the gold distribution are minimal.

Jan 1, 1993

By Merline W. Van Dyke

The Surface Mining and Reclamation Act of 1977, PL 95-87 (The Act) granted the Office of Surface Mining (OSM) the duty of collecting fees from the active coal mining activities to be used in abating the hazards associated with abandoned coal mines. Since the passage of the Act, OSM has been instrumental in closing a multiple of mine hazards and in full cooperation with the states involved. Complete mine closures range from simply filling a subsidence hole to exodic designs costing thousands of dollars, such as in the case of the Portal Park swimming pool in Colorado Springs, Colorado. The Portal Park olympic sized swimming pool was built over an abandoned coal mine by a group of local citizens and given to the city of Colorado Springs. This pool receives the largest number of users each year. During the past four years, OSM has abated six mine related hazards in and around the pool. During the summer of 1982, the pool started tipping causing the pool waters to run out the west end. This pool tipping and the associated cave-in problems caused great concern to the city and the local users. This citizens concern generated a request from the city for OSM to assist in checking out the pool problems. Early in 1983, OSM initiated a driling program to investigate the subsurface voids. This drilling effort revealed several large voids within a few feet of the pool deck, with all voids inundated with ground water. Therefore, the void filling method favored the hydraulic backfilling needed to be confined to the area under the pool. This confining problem lead to the development of the gravel bulkhead cutoff walls to confine the backfilling effort to the areas under the swimming pool.

Jan 1, 1985

By George C. Carter

It was just a little over three years ago that the "Go" button was pushed to start operations on the blending piles at Oro Grande. As is usual with any new installation, there were problems that had to be solved. This paper will concern itself with those problems directly related to quality control. To obtain a consistent outgoing quality level at the most economical level for a finished product requires two main points: 1. Measurement of variations in the process, 2. A method of making a predictable change to adjust for variations. The manufacture of cement requires a relatively high degree of accuracy if a consistent outgoing quality level is to be maintained. The blending piles were our solution to this problem.

Jan 1, 1962

By M. Charles Gilbert

Basement rocks in southern Oklahoma are divided into two groups. One group is the Lower Cambrian Wichita Igneous Province, a diverse igneous suite that crops out in the western Arbuckle Mountains and in the Wichita Mountains. These largely bimodal igneous rocks were emplaced in an intracratonic-rift environment. The other group, the older, is a set of Precambrian rocks of the Eastern Arbuckle Province, yielding ages between 1,350 and 1,400 Ma, exposed in the core of the eastern Arbuckle Mountains. These are deeply eroded mesozonal granitic rocks and associated granitic gneisses cut by numerous dikes ranging in composition from diabase to rhyolite. The southern Oklahoma igneous rocks have long been utilized mostly as dimension and crushed stone. Most of the early quarries were in granite of various red hues for monuments and facing stones. Large crushed-stone quarries are now exploiting both granite and rhyolite, which is used chiefly as aggregate and railroad ballast. The exposed basement rocks in Oklahoma represent an underdeveloped and accessible resource.

Jan 1, 1999

By R. Buchan

A number of mineral processing techniques have been adopted for the separation of the plastics making up a typical beverage bottle, and a complete flowsheet developed. Thus, size reduction, heavy media separation and flotation were used to separate PE, PVC and PET from their mixtures with cellulose fibers and aluminum, which makes up the cap of such bottles. It is shown that while heavy media separation allows the separation of a PVC/PET mixture from the solid waste, froth flotation can be readily used to separate PVC and PET from a mixture of the two. For this purpose, the differential action of an alkaline aqueous solution (PH=II) which contains methanol and MIBC as surface tension control agents has been found to be a suitable flotation medium. This paper reports some aspects of the flotation flowsheet developed for the separation of plastics from municipal solid waste mixtures and PVC from PET.

Jan 1, 1995

By M. C. Roberts

Metal producers are now suffering through a major downturn in prices for their products even though it has only been a few years since they were enjoying high prices. From an historical perspective, the current situation is another of the cyclical downturns that often occur every five to seven years. This paper uses time-trend decomposition techniques to identify the cycles and statistical methods to find the duration of these cycles for a variety of metal prices. Given some idea of how long and severe these cycles typically are, the mining industry can better plan to weather the downturns and take advantage of the upturns. For example, timing investments in new projects to take advantage of the cyclical upturns can dramatically improve project profitability.

Jan 1, 2003

By S. Siewierski, L. Wojno

INTRODUCTION Bumps are among the most dangerous hazards in the Polish copper ore mines. Their occurrence is the result of the dynamic processes in the rock mass caused by natural factors connected with the deposition of strata and, to some extent, by technological factors resulting from the process of exploitation. In this connection, in order to ensure worker safety and choose such a technology that allows an achievement of high technological and economical parameters, a detailed knowledge of the phenomena occurring in the rock mass is required. In copper mines the basis for forecasting and control of bumps is obtained by continuous measurements and observations of the symptoms of rock mass pressure, the analysis of which ensures the accuracy of forecasting and points toward preventive means that must be applied to prevent bumps. The methods most often used for preventing bumps in copper mining are discussed in this paper.

Jan 1, 1982

By R. H. Weiland

The dewatering of flocculated clay suspensions by compression in a centrifugal field has been investigated. The results are evaluated with regard to both direct applicability to centrifugal dewatering, in solid-bowl centrifuges for example, and indirect applications to gravity sedimentation systems. It is well known that sediment consolidation under gravity depends on structural characteristics such as permeability and on the "self-weight" of overlying sediment layers. An important objective of the study has been to evaluate the self-weight effect using centrifugal forces to simulate consolidation in deep sediments. In this way, small-scale laboratory tests can be used to predict the rates and limits of sediment compression in industrial systems such as thickeners and settling ponds. Experiments have been conducted in which the sediment mass and initial structure were maintained constant while the effective sediment weight was varied by centrifuging at different speeds. The effects of initial structure have also been studied using controlled variations in flocculation conditions.

Jan 1, 1993

By Donald A. Brobst

The minerals barite (BaSO, -barium sulfate) and witherite (BaCO, -barium carbonate) are the chief commercial sources of the element barium and its compounds, whose many uses are nearly hidden among the technical complexities of modem industrial processes and products. Barite, the major ore mineral, is extremely vital to the petroleum industry, which in 1990 consumed about 90% of the world's production of 4.9 Mt as a major ingredient of the heavy fluid called mud that is circulated in rotary drilling of oil and gas wells. The remaining 10% of the barite production was consumed chiefly in the manufacture of barium chemicals and glass and as a pigment, filler, and extender. Barite is found throughout much of the world and is available from three major geologic types of deposits-vein and cavity-filling, residual, and bedded-in sufficient quantity at competitive prices to meet current demands. The world's demand for barite is expected to increase because of the world's need for oil and gas. Geologic circumstances are favorable for the discovery of new deposits of commercial value. Witherite, desirable as a raw material for the production of barium chemicals, is much less common and abundant than barite.

Jan 1, 1994

By Austin Whillier

INTRODUCTION Use of air-cooling or refrigeration equipment in underground mines is needed when conventional ventila¬tion techniques do not maintain acceptable environ¬mental temperatures in working areas. Because refrig¬eration can be very expensive, it should be implemented only after all possible and practical steps have been taken to eliminate or reduce heat sources in the mine. As an example, to prevent the main ventilation fans from contributing heat to mine air, they should be located in the air return and not in the air intake. It is particularly important to prevent any direct contact between hot water and ventilation air, especially in mines which encounter large flows of hot fissure water. Any water hotter than the prevailing wet-bulb temperature of the ambient air must be removed by pipes located as close as possible to the water source. This hot water must not be allowed free contact with the incoming ventilation air at any time during the water's passage out of the mine. Although insulation of the pipes carrying the hot water is seldom necessary, direct contact between the air and the water must be prevented so the warm water cannot evaporate. REVIEW OF COOLING PRACTICES Spot Coolers vs. Centralized Refrigeration To eliminate a few specific hot places in an otherwise cool mine, it is possible to use devices known as "spot coolers." A typical spot cooler that uses chilled water is shown in Fig. 1. These devices consist of self-contained refrigeration units that are often mounted on rail cars for haulage to hot spots. The cooling capacities of such spot coolers usually are limited to about 100 kW or 30 "refrigeration tons." A refrigeration ton represents a cooling rate that produces 1.0 st of ice in 24 hr; that is a cooling rate of 3.517 kW (200 Btu per min). Typically, the electric-power consumption to drive the compressor motor of the refrigeration plant in mines is 1.0 kW per refrigeration ton, corresponding to a coefficient of per¬formance of about 3.5. The principal difference between spot coolers and centralized refrigeration plants is the method of re¬jecting heat from the refrigeration system. Centralized refrigeration plants always discharge heat into the reject or return airflow of the mine; often that is the primary influence in selecting the location for the underground refrigeration plant. Heat from spot coolers usually is rejected into drain water or into air that is not flowing to the location requiring the cooling. As a result, spot coolers remove heat from troublesome hot spots in the mine, injecting that heat-plus the electrical energy used by the cooling unit itself-into other working areas where the ambient conditions are cooler. In effect, this is "robbing Peter to pay Paul." In deep, extensive mines, spot coolers usually pro¬vide only temporary and, over the long term, expensive solutions to localized cooling problems. Centralized re¬frigeration plants are preferred for such mines, with cooling distributed throughout the mine as required. Fig. 2 illustrates a typical underground centralized re¬frigeration plant. Centralized plants lend themselves to improved maintenance at reduced costs while offering the economy of size. Refrigeration plants of larger unit sizes have considerably lower initial costs than smaller unit sizes. The remainder of this chapter is devoted to large refrigeration plants, with no further consideration of spot coolers. Cost of Refrigeration Total Cost: The total cost of refrigeration amounts to about $200/kW of cooling per year (1981 US $). This total cost breaks down into approximately three equal parts: 1) Financial charges, which include the interest and amortization on the capital cost of the initial installation, and the cost of necessary underground excavations. 2) Operating and maintenance costs which include the cost of the electric power to drive the refrigeration plant's compressors. 3) Distribution costs which include costs for pump¬ing, insulated piping, and air-to-water heat exchangers. The local cost of electric power, the number of operating months per year, and the method of refrigera¬tion distribution all contribute to the actual costs in¬curred in a given application. However, the variations usually are limited to no more than ±30% of the $200/ kW per year total cost figure. Cost Per Ton: Refrigeration cost per ton of mineral production can be calculated if the annual production tonnage from the refrigerated section of the mine is known. In most cases, this cost will be less than $1 .00/t. However, in deep mines with high rock temperatures, such as those found in South Africa, the total cost of refrigeration can increase to several dollars per ton of broken rock. Distribution In deep extensive mines, distributing refrigeration often accounts for about half the total cooling costs. As a result, careful consideration and planning must be

Jan 1, 1982

By Fathi Habashi

METALS COMMONLY leached may come from one of the following sources: 1) Occurring in nature in the native state, e.g., gold, silver, platinum metals, copper. 2) Produced as by-product of a metallurgical process, e.g., gold, silver, platinum metals, selenium. 3) Produced by reduction of an oxide ore, e.g., copper, nickel. GOLD AND SILVER Cyanidation According to Mellor (1923) the alchemists of the eighteenth century knew that gold was soluble in aqueous solution of potassium cyanide, and the early jewelers probably utilized this fact in gilding. He also mentions that Scheele in 1783 and later Bagration in 1843 noted the solvent action of aqueous solutions of alkali cyanides on gold. Yet it was not until 1887 that the value of this observation was recognized, when MacArthur and Forrest (1887) made use of it in leaching gold from its ores. Since then, the process has spread to every gold and silver mining district in the world.

Jan 1, 1970

By Harry R. Asche, Manfred K. Lechner

The Cross City Tunnel comprises 2km of a new underground traffic route in Sydney, Australia. The route is very complex, involving some six separate tunnels and three underground Y-junctions. For almost 200m the six tunnels run parallel at different level sunder William Street, Sydney. Almost all of the route runs adjacent to the City Business District of Sydney and adjacent to or below many major buildings and services. The planning and design of this project is described. The geometric arrangement is achieved with a strong dependence on 3D road design packages. Road alignment constraints include land acquisition and proximity to existing tunnels and basements as well as maintaining separation from the other tunnels in the scheme. Geotechnical and hydrogeological studies are described. Findings discussed include the high horizontal stress field in the Sydney area and investigation of incised palaeochannels on the route. Methods of design for the tunnels and Y-junctions are described, as well as methods of settlement prediction for the buildings and services. The latter includes the settlement assessment for more than 200 buildings, many in excess of 20 storeys, as well as services including all of the city railway lines in Sydney.

Jan 1, 2003

By R. Pazhianur

Many investigators conducted surface force measurements between hydrophobic surfaces in water, and observed attractive force that was substantially stronger than the van der Waals attractive force. The excess force was appropriately referred to as “hydrophobic force”, for which many different theories have been put forth by numerous investigators. In an earlier publication (Yoon and Ravishankar, 1996), it was suggested that the hydrophobic force maybe due to the interaction between the large dipoles created by the surfactants adsorbing on solid surfaces in patches (or domains). In the present work, a mathematical model has been developed to further elaborate the theory.

Jan 1, 2003

By Raymond L. Jones

With the inauguration of the open pit operation in Bagdad, plans were formulated for a large scale leaching operation. Dump stockpiling was started almost immediately, but actual production was not initiated until the spring of 1961. Like all neophytes, we started something about which, on a commercial scale, we knew next to nothing, either dump preparation or leach procedure, and as a consequence, we are still paying the piper. True, we had been through an extensive laboratory pilot program, but it soon became apparent that there was considerably more to increasing solution volumes than simple multiplication. Had we initially possessed our present acumen, the Cyprus Bagdad plant could be operated more efficiently and at a better profit. During the past several years, the art of dump leaching of copper has improved in many ways, primarily because of the application of scientific principles gleaned from general mining practice. Rigid pH control and the use of atomic absorption techniques for rapid," accurate assaying have probably played a leading role in this respect, although we cannot overlook the other sophisticated electronic controls lending improvement to acid addition and pumping, better piping materials, and lastly, the more efficient use of our pregnant liquors. Thin too, the years of experience have given us a greater understanding of dump behavior in general; and, we can, to a greater extent, measure, predict, and avoid some of the idiosyncrasies inherent in every dump. However, it is my firm belief that we will still be confronted with unexplainable dump behavior as long as we are involved in leaching. We have found our dump to be a wonderful money bank, but one that is capable of yielding a wildly fluctuating profit.

Jan 1, 1975

By D. L. Kowal, P. J. Whittaker, M. A. Tuzun, N. O. Lotter

The area of flotation testing of drill-core is important in the business plan of most mining companies. Metallurgical information derived from this practice can be used to advantage in strategic decision-making. Sampling, flotation testing and subsequent Qem SCAN analysis of a mineral resource is one example of this approach. Anew resource, located in Sudbury, Ontario, is being assessed for the Sudbury Operations of Falconbridge Limited, which includes the Strathcona Mill. In this case, it was possible to improve the value of information from sampling and flotation testwork by using an improved, statistically-based test design, by sampling the resource by generic end-member ore type, and by integrating the Mineral Processing and Mineral Science disciplines into a Process Mineralogy team. In addition to producing standard metal grade and recovery information, this new approach provides more reproducible information from representative samples and flotation testing in a replicate format. Qem SCAN technology is used to produce a size by size mineral balance, including both modal percentages and liberation, from which flotation models for each ore type can be developed. As a result, a key understanding of the potential behaviour of a given ore type, if mined and then processed at the current mill operation, is gained at the 95%confidence level. The three ore types of this mineral resource were shown to have different flotation characteristics. Quantifying the mineralogy and liberation in each of the three ore types, has shown that this difference is due to changes in modal percentages of ferro-magnesium and magnesium silicate minerals such as pyroxene, talc and serpentine. Liberation across the three ore types is very similar and is therefore not responsible for variation in flotation performance.

Jan 1, 2003

There are several simulators available and are being used for analysis, improvement and optimal control of the grinding process. However, these tend to be developed on informal software engineering methodologies. The informal approach is not suitable for long term development and a formal design methodology is necessary to develop efficient, error-free, and easy-to-use and to maintain software. In meeting this goal, basic concepts of a software model for describing the mineral process objects has been proposed. The software model forms the basis for software design and efficient implementation of the simulation. This paper describes the development of software models for grinding circuits. The work constitutes the theoretical foundation for the development of an advanced simulator for comminution.

Jan 1, 1995

By Keros Cartwright

Distribution of temperature within the lithosphere can be significantly affected by the movement of ground water. Stallman (1960) presented the basic equation for the simultaneous transfer of heat and fluid in a porous medium and first used earth temperatures to determine aquifer permeability. Subsequently, studies of rock and soil temperatures were used to determine the flow of water through clay layers separating aquifers (Bredehoeft and Papadopulos, 1965; and Sorey, 1971), and to locate shallow aquifers (Cartwright, 1968; Birman, 1969). Cartwright (1968) showed that shallow aquifers maintain a nearly constant temperature throughout the year and that heat is exchanged between the aquifer and land surface. These temperature data also suggest that shallow aquifers hydrologically connected to surface-water systems have significantly greater effect on temperature distribution than aquifers in the deep artesian basins. Water wells developed in the shallow glacial and dolomite aquifers to depths of over 122 meters (400 feet) in northern and central Illinois produce water at temperatures very close to the mean annual air temperature. An analysis of the character of the rocks and soils suggests that the tem¬perature gradient should, and does, vary according to changes in thermal conductivity due to changes in lithology. This is because, under conditions of steady and uniform flow of heat from the earth's interior to the surface, a greater temperature gradient is required in poorly conductive rocks than in highly conductive rocks to transmit the same quantity of heat. Based on estimated values of thermal conduc-

Jan 1, 1972

By Ruckmick J. C.

Elemental sulphur occurrences are widely distributed in two geological environments: -1-Basins containing hydrocarbons and zones of Cenozoic vulcanism. However, very few of these constitute deposits large enough to be of commercial importance. Almost all of the elemental sulphur mined in the world comes from bioepigenetic deposits in petroliferous basins. These deposits occur in two general structural styles: diapiric (salt domes) and stratiform. Examples of diapiric deposits occur in the Gulf Coast basins of Texas, Louisiana, and southern Mexico. Examples of stratiform deposits occur in the Fergana and Amudarya depressions of Central Asia, the Mesopotamian Depression in Iraq, the Cis-Carpathian Trough in Poland and Russia, and the Permian Basin in Texas. Economic bioepigenetic sulphur deposits range in size from approximately 1 million tons of sulphur in the smaller salt dome deposits to more than ZOO million tons of sulphur at the Mishraq stratiform deposit in Iraq. Total world production from bioepigenetic deposits amounts to approximately 16 million tons of sulphur per year, one-half of the world's present annual consumption of elemental sulphur. Most of the balance of the annual consumption is recovered from sour gas and petroleum. All bioepigenetic sulphur deposits share remarkably similar origins and characteristics. They are formed by anaerobic bacterial replacement of gypsum or anhydrite in tilted basins where evaporite beds are underlain by petroleum. Figure 1 illustrates a generalized cross-section of a salt dome sulphur deposit. Figures Z, 3, and 4 are cross-sections of three types of stratiform sulphur deposits. In terms of sulphur genesis, the only significant difference between the salt dome and stratiform deposits is that the positioning of the anhydrites above the petroleum in the salt domes is caused by diapiric rather than sedimentary processes. In the salt domes, the residual anhydrites of the cap-rocks are accumulated by solution and removal of halite by artesian ground waters.

Jan 1, 1978

By Simon D. Strauss

This paper discusses the ways in which the metals industries dealt with surplus capacity in the past, primarily the twenty years, 1950 - 1970. During this period, the bulk of metals production in the market-economy countries was controlled by private sector companies. Since then, public sector companies have played an increasingly important role in the metals industries of the market-economy countries. Of course, the change was not overnight. It occurred gradually over a period of many years. Indeed, by 1965, several developing nations had adopted policies of government control of metal operations previously in private hands. The metals industries are so many, so large and so diverse that the constraints of time make it impossible to deal with all segments. To illustrate the problems of surplus capacity in the metals industries during the period, this paper focusses primarily on three metals. One experienced rapid market expansion between 1950 and 1970; one had a growth more or less in line with the expansion of the world economy; and one lagged well behind the pace of industrial expansion. No one will be surprised if aluminum is identified as the metal with rapid growth; copper is identified as the metal that kept pace with the world economy; and tin is identified as the laggard. Individual computations of the rate of growth for these metals show some variations, but most estimates place the increase in aluminum consumption in the market economy countries between 1950 and 1970 at a compound annual rate of about 8%. The corresponding figure for copper is a compound rate of 4%. Tin consumption showed no growth. A widely accepted point of view is that sharply rising demand will force the price of a commodity to increase substantially in order to attract a necessary expansion of supply. The corollary to this is that stagnant demand will hold prices down, as there is no need to stimulate new supply and it may be necessary to force marginal producers out of the market. The experience with aluminum, copper and tin in the years 1950-1970 does not support this theory. In 1950, the average prices in the United States market as reported by the American Bureau of Metal Statistics were 17.74 a pound for aluminum, 21.24 a pound for copper, and 95.54 a pound for tin. The corresponding figures in 1970 were 28.74 a pound for aluminum, 57.74 a pound for copper and 174.24 a pound for tin. Aluminum, with the greatest market growth, rose by 60%, whereas tin rose 82% and copper by 172%. Clearly, other factors were a more important influence on price than was the trend of demand To revert now to the capacity issue, during the period under review aluminum demand was rising so sharply that that industry had no sustained problem with surplus capacity. Instead, if anything, capacity may at times have been a constraint on demand. The industry succeeded in attaining explosive market growth through imaginative research and promotion programs. Some of this growth was the result of substitution of aluminum for other commodities – steel, copper, wood and glass as examples. But much of the growth was the consequence of developing entirely new products through technological innovation. Prior to World War 11, the number of aluminum producers was extremely limited. Alcoa and Alcan in North American and Pechiney and Alusuisse in Europe were the dominant firms. The developing countries had virtually no production and in Japan and Germany production was only a small fraction of the North American output. During the War years the United States had financed the construction of many new facilities. After the war these plants were sold by the government to Reynolds and Kaiser in order to foster more competition in the market. Subsequently many other concerns became aluminum producers, both in the United States and elsewhere and competition for markets intensified.

Jan 1, 1989

By Frank P. Traczyk

INTRODUCTION The process of solid-liquid separation can be an important decision in plant design. It is very important that one must consider not only the most effective means of solids-liquid separation, but also to consider the effects on upstream and downstream processes. A solid-liquid separation is done either to remove the solids £ran the liquids as in copper concentrates or rave a liquid from the solids as in uranium operations. In either case, washing can be an important consideration to clean the solids or recover the liquids. This section will deal with solid- liquid separation other than thermal, sedimntation processes, or hydro cyclones. The three major areas discussed are pressure filters, vacuum filters, and centrifuges that are most cannon in the minerals industry. PRESSURE FILTERS Pressure filters are one common type of solid-liquid dewatering devices. There are my different types of pressure filters that are both continuous and batch operations. They are characterized by using an external pressure to push or force the slurry through porous media to force the liquids out of the solids. Whereas vacuum filters are limited to one amsphere or bar working pressure, some types of pressure filters operate as high as 16 bars pressure. Pressure filters are also effective for hot slurries where a high boiling point can be a problem or precipitation occurs under vacuum. The types of pressure filters most common in the mineral processing industry include plate and frame and recessed plate filters. Some of the new technologies including automatic pres- sure filters and belt presses are also discussed. Plate Frame Filters Plate and frame filters are one of the oldest and most effective means of both dewatering solids and clarifying liquids. Plate and frame filters consist of a skeleton that is used to hang or support alternate plates and frames that are pressed together to form chambers. The filter plates consist of a drainage grid that is covered by sane type of filter media through which a liquid is

Jan 1, 1986