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By F. Habashi

The peninsula that lies between the Black and Mediterranean seas, called Asia Minor by the Romans and Anatolia by the Greeks, was one of the crossroads of ancient civilizations. The fall of Constantinople in 1453 was a turning point in the history of mankind. Visits to Istanbul, Ankara, Eskisehir, Cappadocia, and Trabzon will be given together with the history of the country. Mineral resources of the country will also be briefly outlined.

Feb 23, 2014

By R. J. Sweigard, R. V. Ramani

G.F. Learning The paper by R.V. Ramani and R.J. Sweigard is a wonderful description of the labyrinthine web that has been spun about the mining industry by energetic bureaucrats and politicians over the past 50 years. The remedy for the problem, however, is not more of the same, but less. That may be difficult for the industry to achieve, for it is not a technical solution but a political one. And the current fervor for more detailed planning at all levels of government and private enterprise has become deeply ingrained. The authors recommend the provision of more information about mining and mineral resources to "macro" (i.e., government) land use planners. They apparently overlook, however, the already strong tendency on the part of most government land use planners to consider themselves omniscient. Thus, giving them more information about the technical problems of mining will only make them want to get more and more involved in the "micro" (private, site specific) mine development and production plans of the individual mining firm. In fact, this has already happened at all levels of jurisdiction from municipal to federal government. Examples are legion. The most effective way to ameliorate the adverse impacts of government land use planning on existing and potential mining operations is to: (1) introduce greater flexibility in the definition of land use zones by local and state governments; (2) adopt realistic and relevant ambient environmental performance standards in governing relationships between mineral land uses and concurrent or subsequent nonmining land uses; (3) allow greater leeway for economic considerations in land use decisions in contrast to the explicit legalistic approach now in vogue; (4) recognize that all minerals are not the same and that sand and gravel mining should not be treated the same as underground metal mining, coal stripping, oil field production, or in situ leaching; and (5) eliminate the notion that mining operators should be responsible for determining in detail the use of land by subsequent owners of mined land. This last bit of conventional ethic really makes no more sense than requiring the builders of every shopping center or government office complex to provide detailed plans for the use of that land when its use for shopping or government is ended. Did the builder of Ebbetts Field plan for Brooklyn after the Dodgers went to Los Angeles? Should the developer of the Bingham Pit plan for suburban Salt Lake City after the copper mining goes to Chile? The nation's mining industry must address these questions before further bankrupting itself to provide more data to planners and spending thousands of dollars per acre to create land that when reclaimed is worth only a few hundred dollars per acre. Reply by R.V. Ramani and R.J. Sweigard We thank Mr. Leaming for his valuable contribution. His views on the problems of land use planning and mineral resources are most welcome additions to our paper. As the title indicates, our paper was more concerned with the impacts of land use planning on mineral resource conservation than with the details of the planning process. On the whole, his five recommendations would be helpful for mineral resource conservation. However, we would suggest that the argument he presents for his final recommendation does not address the differences between mining as a land use and commercial or institutional uses. We believe that this difference is the crux of the issue. We share Mr. Leaming's desire to ameliorate the adverse impacts of land use planning. Possibly the most detrimental impact is the loss of mineral resources. Any development, whether mineral or community, that does not give proper consideration to other resources can result in permanent loss or sterilization of resources. With proper planning, some of these losses can be avoided. As our paper indicated, one factor that limits the consideration of mineral resources, and ultimately leads to their sterilization, is the generally inadequate levels of resource characterization and understanding of the unique nature of mineral resources and mining operations. The last point raised by Mr. Leaming is also important. In terms of reclamation and land use planning in mining districts, we certainly do not advocate spending more than what the results are worth. The main thrust of the paper was to explore the avenues for conserving the mineral resources so that, at some appropriate time, the issue of mining and reclamation can still be addressed.

Jan 4, 1985

By Rudecindo S. Silo

[The principal characteristics of the process is that when applied in medium or in great degree it only needs unelaborated raw materials such as sodium chloride and calcium carbonate, or of medium elaboration, as sulphur which is found in large quantity in the North of Chili; however, the may be also applied to small copper plants provided that low cost sulphuric acid is available as a substitute for sulphur, that is, in. those plats of small capacity where large additional installations are not needed for the regeneration of the leaching solution. The method itself comprises 6 stages, namely: crushing, leaching, washing; of solutions, precipitation, regeneration of the leaching solution and fusion.]

Jan 1, 1965

By Paul E. Epstein

Despite the controversies that have surrounded asbestos over the past 20 to 30 years, no knowledgeable authority has doubted the usefulness of this material. Were it not for the health risks associated with the manufacture and use of asbestos products, its physical and chemical characteristics would continue to be hailed as an undeniable boon to mankind. However, it has become clear over the past 30 years that like other major contributors to our modern industrialized society, asbestos must be handled responsibly and with the full understanding that lack of care can lead to injury, suffering and death. In this sense, asbestos shares characteristics with nuclear power, pesticides and even motor vehicle usage. It is unlikely that modern society would be willing to walk away from the benefits bestowed by any of these valuable resources. Rather, the appropriate response to the identification of danger is to define the type of risk, quantify its incidence, search for methods of decreasing the risk and implement programs to achieve the goal of minimization of risk. We should recognize at the outset that the risk cannot be diminished to zero without elimination of the material entirely from our midst. The concept of acceptable risk is a complex issue involving medical, legal, financial, moral and even psychological factors that defy precise quantification. In essence, the major danger produced by exposure to asbestos is its potential effects on the respiratory system. Despite the fact that asbestos workers have constant skin contact with the material and porbably swallow it in the course of their activities, inhalation of the fibers is recognized as the major health risk associated with its use. Aerosols of asbestos are inhaled not only by miners, millers and fabricators but also by urban dwellers who have no direct occupational contact with the material. This occurs because asbestos has been applied to our buildings and has been used in a wide variety of products that touch our daily lives. While it is estimated that three to four million people in the United States have been occupationally exposed to asbestos, the number who have been non-occupationally exposed is many times that number.

Jan 1, 1984

By Jung-Joo Kim, Jong-Uk Kim, Turab H. Jafri, Han-Kyu Yoo

"INTRODUCTION Steel sets such as H-type and lattice girders are often installed in the tunnels before the hardening of shotcrete to ensure the stability of conventional tunnels in soft ground conditions. In practice, while designing the tunnels with the help of numerical analysis, steel sets are generally considered only as temporary support elements. Only a few studies propose the direct application of composite support in the tunnel design, based on large-scale experiments and numerical analysis. In order to assess the structural performance of the composite support consisting of shotcrete and steel sets, large-scale experiments were performed on two types of arch-shaped specimens by applying the combined effects of axial forces and bending moments. Based on the experimental results, numerical analysis was performed to assess the application of composite support in tunnel design. The crown settlement, axial forces, bending moments, and load distribution in the composite support were analyzed in the light of different structural patterns. LARGE-SCALE EXPERIMENTS USING COMPOSITE SUPPORT Preparation and Procedure of the Experiments The preparation setup as well as the organized procedure of the large-scale experiments using composite support is shown in Figure 1. An appropriate geometry of the specimens was selected by considering the standard cross-section of a two-lane highway tunnel in South Korea. Under the loading conditions meant to develop the axial forces and bending moments simultaneously, arch-shaped specimens were assembled with the ends of the specimens subtending a 60° arc angle at the center of the arc circle as shown in Figure 2. The fabrication of six specimens was completed in two groups based on the dimensions of steel sets, with the first group of three specimens being reinforced by H100 (No.1, No.2, No.3) and the other three by H125 (No.4, No.5, No.6). In order to reduce the voids on the boundary of the shotcrete and steel sets, concrete was casted over the steel sets instead of using shotcrete. The specimens were designed to incorporate the uniaxial compressive strength of 21 MPa. Shear keys and steel plates were installed at the ends of the specimens, so that shear failure could be avoided at the ends and the specimens could also be protected from detachment at the fixation. Translational and rotational movements at the ends of specimens were fixed."

Jan 1, 2016

By J. S. Roti

Calcium-based scale precipitation is a common problem in mill reclaim waters. An accumulation of these adherent deposits can result in a rapid reduction in water flow, loss of pump efficiency and eventual interruption in ore production. Heap leach applications can also experience the added problems of plugged sprinkler heads, blinded leach pads and fouled carbon columns when scale control is not maintained. The primary cause of scaling in precious metal recovery is the relative insolubility of calcium carbonate. The presence of the calcium ion and bicarbonate alkalinity is common in almost every water source. If the temperature or pH of the water is allowed to increase, the bicarbonate breaks down to carbonate and combines with calcium by the following reaction: Ca +2 +2HCO3 ? CaCO3 + H2 + CO2

Jan 1, 1986

By Éder Domingos Oliveira, Carlos Antonio Morais, Ruberlan Gomes Silva

The objective of this study is to assess the impact of different reagents, such as limestone, lime, magnesium oxide, and sodium hydroxide, in experiments carried out in the single purification step and in two consecutive purification steps by raising the pH of a rare earth sulfuric liquor with the aim to remove or reduce the impurity concentrations in the rare earth sulfuric liquor. The choice for the best purification condition was made based on the minimum loss of rare earth elements (REEs), reagent consumption, and residue generation. The exploratory experiments show that it takes place in the two consecutive purification steps, the first one consists in dosing the limestone pulp until it reaches a pH of 3.5 followed by an addition of a lime pulp reaching a pH of 5.0. Under this condition, the results were a total removal of Fe3+, PO4 3− , and Th4+ ions and a reduction of 99%, 87%, and 37% w/w in the Al3+, UO2 2+, and SO4 2− concentrations, respectively, in the purified rare earth liquor. Furthermore, the lowest REE losses (8.3% w/w) and reagent consumption (4.3 kg/m3 ) and also a low residue generation (7.5 kg/m3 ) were observed in this condition. Despite reaching similar results regarding impurity removal, the experiments done with the addition of limestone, lime, magnesium oxide pulps, and sodium hydroxide solution in the single purification step, where the pH was raised to 5.0, presented higher REE losses (64.9%, 42.5%, 44.8%, and 60.9% w/w, respectively) and a higher residue generation (43.2, 25.1, 11.1, and 13.6 kg/m3 , respectively). This occurred due to the co-precipitation of salts containing rare earth elements in their composition. The experiments conducted with limestone, lime, and MgO resulted in a higher consumption of reagents, while the same result was observed when NaOH was used (4.3 kg/m3 ). In the experiments carried out with the addition of magnesium oxide and sodium hydroxide, the respective purified rare earth liquors presented a high concentration of magnesium, sulfate, or sodium, which could impact the quality of the marketable rare earth salts, whereas the salts obtained under the best condition observed in this study seem to be amenable for use as raw material in an attempt to obtain rare earth products with an acceptable chemical quality.

By D. Nilsson, B. Aaro

To find out if there are any potential savings in "in-the-wall haulage for open pits," the Swedish companies ASEA and Kiruna-Truck in 1984 gave us financial support to study this solution in more detail. In the study, the use of in-the-wall haulage was studied for three hypothetical open pits with different sizes and shapes. Annual ore production rates also varied. A part of this thor¬ough study was published by the Swedish Mining Research Foundation (see Report F 8444, "The Use of Electric Trucks and In-the-Wall Haulage in Open-Pit Mining," in Swedish with an English Summary). Although in-the-wall haulage is of interest in some open pits, the local terrain is important for profitability. The authors do not think in-the-wall haulage is of any major interest for the mining industry. The following is a summary of some of the author's findings. To place the haul road in the wall is not of interest in open pits with declining metal contents in the bedrock. In such mines, the volumes from the haul roads will not yield reve¬nues. The cost per m3 for an underground haul road is much higher than for a haul road in the pit. This means that it is only of interest to place the haul road in the wall when mining gets deeper than about 50 m (165 ft). In-the-wall haul roads will reduce flexibility in the pit, and it will make necessary the use of smaller equipment with lower productivity and higher costs per ton. As Hustrulid, et al. show (Table 4), excavation savings of material hauled are very low, $0.10 to $0.25/t (0.09 to 0.27 per st). The extra operating cost, due to lower productive equip¬ment, will normally be much higher and thus destroy the whole idea with in-the-wall haulage. If electric trucks are profitable for in-the-wall haulage, it is normally also profitable to use electric trolley assist for trucks on the haul road in the pit. But the profitability of using electric power is different in different countries, and depends on the relation between the cost for electric power and diesel fuel. In the US, diesel fuel is inexpensive compared with electricity, but in a country like Sweden, diesel fuel is much more expensive. In most open pits, the trucks have to move a considerable distange from the loader until they reach a final haul road in the wall. A trolley line along such temporary haul roads will be exposed to flyrock. It is normally less expensive to perform rock support from the open pit than from underground ramps in the wall. In Fig. 8, Hustrulid et al. gives the impression that the underground haul roads will be very close to each other. This is seldom the case. Figure 1 shows a haul road in the wall. The haul road passes through each cross-section only once. Ar¬ranging a reliable dewatering and rock support system from only one underground ramp is probably impossible. Many more drifts are therefore necessary. In our report, we also studied what would happen if the final pit slope is increased by 5°, using underground drifts in the wall. Our conclusion was that the extra cost for drifts, rock support, pumps, etc. destroys the whole idea, and that it was better to accept a higher stripping ratio with the haul road in the pit and to use conventional low-cost open pit equipment. Finally, we think it is would be difficult to try to reduce the safety factor when determining the slope angle by moving the haul road in the wall. Minimizing the risk for pit wall collapse is also important with in-the-wall haulage, primarily because men and equipment will be working in the pit, but also to guarantee many accesses between the pit and the haul road in the wall.

Jan 1, 1989

By P. Lopez, E. Wellman, N. Risso, A. Anani

Current machine learning models used for roof fall hazard prediction are mounted on expensive sensors, computationally expensive, or lack the robustness for accurate prediction in the underground mining environment. This research aims to provide a design methodology for a robust, low-cost, deep learning-based algorithm for underground mine roof fall hazard prediction. A data sampling plan is developed to ensure the replicability and robustness of the developed model. In addition, feature engineering and transformation methods are described to identify relevant features for hazard identification. The methodology described here will be used in model development, tested, and implemented as a real-time mobile device application. The new tool will be expected to detect roof fall hazards in real-time and contribute to a crowdsourcing approach for underground hazard detection.

Feb 1, 2023

By Paul D. Tomlingson

A new sense of urgency permeates the mining industry concerning maintenance. Mining's continuous process environment demands around-the-clock maintenance support. And profitability conscious mining operations require that production targets be met on time - and economically. These goals require nothing less than an effective maintenance program. In turn, the effectiveness of the maintenance program depends on quality information: easily procured, complete, timely, accurate, and properly used. Information picture is changing Some of the fully integrated, mainframe maintenance information pro¬grams of better days remain. Their upkeep and cost of operation, though, is becoming more difficult to justify. Some operations, faced with production cutbacks a few years ago, downscaled and found they liked it. Now, during an upswing, these operations question the need for the more elaborate, administrative-heavy programs they used to operate. Package programs are not taking their place. Too often, the packages are vague and generic. Some vendors claim that if their offerings work in a hospital complex, they must work in an underground mine. That is not so. Maintenance information in the mining industry is different. The situation has changed There are now smaller, self-contained maintenance groups whose information needs are different. These include an electrical crew in a smelter, an underground mobile equipment shop, or a remote service shop between several distant operating pits. These working environments have changed the character of the information needed as well as the methods for obtaining and using it. Operations-maintenance link In coming back from a downturn, operations people realize that their ability to meet production targets hinges on reliable equipment and avoidance of downtime. They have become familiar with the need to use maintenance services effectively. They also want quality maintenance information. When coupled with the sense of urgency about maintenance, a business-like working environment emerges that has significant new differences in both work control and information. Work control impact Work control has been streamlined to improve communications. Supporting information has been streamlined as well. • Verbal orders are the rule rather than the exception to quickly bring a multi-craft crew to the flotation section or a pit crew to a disabled haulage truck. • Written work requests and work order forms are seldom used, or even needed. Rather, electronic work control logs permit operations to request work, maintenance to acknowledge it, get ready, and do it - quickly, without delay. • Routine servicing is triggered by operating hour accumulation (mobile equipment) or tons of throughput (fixed equipment). Operations is now taking the initiative in delivering mobile equip¬ment to the "bad order line," or switching to a bypass conveyor. Operations wants immediate follow-up reports on equipment condition.

Jan 1, 1989

By S. Assemi

Interaction forces between a hydrophilic silica particle and an air bubble were measured by atomic force microscopy using simplified model systems with deionized water and dilute KCl solutions. Contributions from the hydrodynamic force were minimized by using a low piezo speed. Particle-bubble separation distance and the bubble spring constant were calculated from linear regression of the piezo extension versus cantilever deflection. The bubble surface potential was then estimated from fitting the AFM-measured forces to the Hogg-Healy-Fuerstenau (HHF) model, using the surface element integration (SEI) method. Surface potentials obtained for the bubble at a low applied force were comparable with the literature data, suggesting that the simplified model used here can give a reasonable estimation of the bubble surface potential under moderate applied forces. Interaction forces between a silica particle and an air bubble were also measured at different locations on the air bubble surface. The force curves obtained at the edges of the bubble fitted very well to the theoretical force curves regardless of the applied force, while curves obtained at the center and halfway to the center, were more difficult to fit, in particular at higher applied forces (> 13 nN), suggesting that force curves obtained at the edges of the air bubble might be less prone to deformation effects.

Jan 1, 2008

By J. Fastle, M. Weinstock

The block cave mining method utilized by PT Freeport Indonesia (PTFI) generates fines and allows the inflow of water. Both constituents have contributed to unfavorable characteristics: an increase in ore material plasticity and fluidity. Unfavorable material needs to be monitored and managed as it passes from intermediate ore stockpiles through feeders and then to milling operations. We describe an implementation of several Video Data Analytics (VDA) algorithms on smart cameras to quantify the potential fluidity and plasticity by measuring the apparent velocity and agglomeration of material flowing through ore feeders. This approach to VDA on smart cameras is a cost effective, self-contained, solution to identify these unfavorable characteristics. The solution allows the operators to manage the related operational risks, maintain safe production and govern feeder rates when material is unfavorable, which is expected as PTFI proceeds deeper into the underground orebody

Mar 2, 2022

By K. F. Unrug

Extrapolation of the rock properties obtained from the cores exploration holes to the surrounding areas often causes problems because of frequent sudden changes in the geologic composition of strata. To address this problem, the author has been developing a method of rapid strength testing "in situ," with application of a borehole penetrometer. This method, as opposed to conventional laboratory testing, does not require rock samples to be retrieved and handled/machined before testing. The results are generated by strength determination on the wall of a drill hole at a site. The newest development is a borehole penetrometer that requires only a 1.38.mm (1.5 in) diameter hole. The small diameter of the penetrometer body allows for drilling test holes with production mine equipment such as roof bolters. It opens the possibility of broad application in coal mines, as well as in hard rock mines and tunneling. The principles of the apparatus are described and are illustrated with examples of its applications.

Jan 1, 1999

By R. D. Beard

Puerto Rico lies within the remnants of a deformed Cretaceous island arc system in the northeastern Caribbean. The Island can be divided into three broad geologic provinces: the Central Volcanic-Plutonic Province (Lower Cretaceous to middle Eocene), and the Northern and Southern Limestone Provinces (early Oligocene to middle Miocene). Known precious metal deposits are generally small and occur in veins and shear zones within Lower and Upper Cretaceous volcanic and plutonic rocks. Some Tertiary igneous rocks are also mineralized. Selected indications of disseminated lithology-controlled mineralization could represent larger deposits. Associated metals in some deposits include copper, zinc, and lead. At present, tax policies, population density, political outlook, and lack of proven significant precious metal deposits discourage the establishment of a metal mining industry.

Jan 1, 1993

By S. M. S. Azghdi, K. Barani

The effect of microwave treatment on the surface roughness and wettability of chalcopyrite (CuFeS2 ) and on the chemical composition of its surface was studied. The microwave source was a conventional multimodal oven with frequency of 2.45 GHz and maximum power of 900 W. Pure chalcopyrite specimens and purified chalcopyrite concentrate were used in this study. Analysis using atomic force microscopy showed a decrease in the surface roughness of the chalcopyrite after microwave radiation. This decrease may be due to oxidation of the surface and formation of iron oxide. Moreover, the surface wettability of the chalcopyrite mineral increased with increasing duration of microwave radiation, which was in good agreement with the micro-flotation mass recovery results. The increased wettability of the surface may be attributed to the decreased surface roughness by microwave radiation. Analysis using scanning electron microscope/energy-dispersive X-ray spectroscopy indicate that after microwave radiation, the contents of sulfur and iron increased whereas that of copper decreased on the surface of the chalcopyrite, significantly changing the average atomic number of the chalcopyrite surface.

By M. Gorman

The Mineral Park Mine is an open pit copper-molybdenum mine located in northwestern Arizona, approximately 74 miles southeast of Las Vegas, Nevada. The property has been owned by the Duval Corporation, Cyprus Mining Company and Equatorial Mining of Australia. Mercator purchased Mineral Park from Equatorial in 2003. Mineral Park commissioned a 25,000 tpd copper and molybdenum concentrator in November and December of 2008. The process includes two stage milling (SAG and Two Ball Mills) fed by primary crushed ore. Metals are recovered in a copper-molybdenum flotation circuit consisting of mechanically agitated roughers and cleaners. The copper- molybdenum flotation concentrate is thickened and further processed in the molybdenum flotation circuit which separates the copper and molybdenum minerals into salable concentrates. The molybdenum circuit also uses mechanically agitated cells. This paper describes the plant and some of the highlights of the commissioning process.

Jan 1, 2010

By M. J. Shields

There are numerous suggestions in the literature on methods of obtaining representative samples of waste rock or mill tailings. Some suggested methods would result in thousands of samples and very high costs for a large facility. There is no general rule that can (or should) be followed, such as collection of a given number of samples per mass of material, per acre of impoundment, or per foot of drillcore. Each site is different, and the adequacy of sampling must be tailored to the site. A logical approach is to let the variability at the site dictate the number of samples that should be collected and analyzed, and then to quantify and evaluate the results by means of standard statistical methods.

Jan 1, 1998

By Mark Newton Lowry

In the garden of national problems recognized by the American public, imports of mineral products is a hardy perennial. Concern for the security of mineral supplies has preoccupied nations since the industrial revolution and the mechanization of warfare. Since 1973, Americans have also been sensitized to the potential economic costs of overseas mineral supply disruptions and the cartelization of foreign production. Though oil prices have plunged since 1981, the import dependency issue remains topical. Political turmoil in Southern Africa reminds us that mineral supply disruptions will occur in the future as they have in the past. Producers of iron and steel, copper, and refined petroleum products seek protection from imports on national security grounds. The Reagan administration is proposing sweeping changes in the management of the federal mineral stockpiles. s an enduring need to take stock of the mineral trade position of the United States. This article considers the changing role that the U.S. has played in the twentieth century in non-fuel minerals trade. We begin by enunciating some principles that are useful in analyzing this trade. The changing pattern of trade in the 1900-1969 period is then reviewed. There follows a more detailed analysis of mineral trade trends in the 1970-84 period. Some consideration is given in the final section to the significance of non-fuel mineral trade for the U.S. economy. THE ECONOMICS OF U.S. MINERAL TRADE The allocation of non-fuel mineral products in the United States has in this century been accomplished primarily through the market mechanism. Except where trade barriers have distorted price signals, this means that mineral supplies have been obtained from the least cost source, with little regard for their country of origin. Mineral prices facing U.S. firms are sensitive to shifts in the domestic supply and demand, but are also sensitive to economic conditions overseas. The balance of trade in each mineral product has depended on the amount that is profitably produced and consumed domestically at the world price. The nation has produced exactly as much as it has consumed only by chance. U.S. demand for non-fuel minerals is derived from the demand for manufactures, farm commodities, and other goods whose production requires mineral products as inputs. The demand for such goods can be quite volatile, and in most industries moves cyclically due to its sensitivity to the level of aggregate economic activity. The supply of mineral products depends on the cost of extracting and processing mineral raw materials. These costs do not vary greatly in the short run. Because of these attributes of mineral markets, U. S. trade in mineral products fluctuates considerably from year to year. Most of this volatility results from shifts in domestic and overseas demand and from changes in exchange rates and trade barriers. Longer run changes in the mineral trade pattern can also be discerned. These depend on secular trends in demand and in the cost of mineral extraction and processing at home and overseas. The United States was originally endowed with extensive reserves of an array of mineral-rich ores and fossil fuels. It is also a nation with an entrepreneurial climate and technological capability conducive to extracting and processing those reserves. Not surprisingly, it has at one time or another ranked among the world's leading producers of a great many mineral products. With a population that is large and an economy that is technologically advanced by world standards, the U.S. has also been a leading consumer of mineral products. Because of its voracious appetite, the bulk of mineral products produced domestically has traditionally been consumed domestically as well. Net exports have been sizable only in those industries in which the nation has enjoyed an extraordinary cost advantage. Depletion has gradually reduced the cost advantage that the U.S. mining industry once enjoyed. The economic conditions that encouraged early development of U.S. mineral resources have

Jan 1, 1986

By Alexander N. Winchell

"Location. The Cuyuna iron district extends from the region of Kimberly, near the Center of Aitkin County, Minnesota, south-westward through Deerwood, Ironton, and Brainerd, across Crow Wing and Todd counties, across the Mississippi River, and for an unknown distance farther southwest in the same direction. It is known that the Huronian rocks, in which the ores of the Cuyuna district are found, reappear near the western border f Minnesota, but no ores have been found in this region. The district has a length of more than sixty miles, but the more important portion as now known 'is confined to Crow Wing County in an area which is less than thirty miles in its longest dimension. The commercial headquarters for the district are in the city f Brainerd, on the Mississippi River.History. The discovery of iron ore in the Cuyuna district was accomplished with no aid from surface outcrops, but solely through the use of the dip needle. The mantle of glacial drift overlying the iron formation varies from twenty-five to 359 feet in thickness, and it was by means f the magnetic attraction of the iron bearing rocks that their presence was discovered with the dip needle by Cuyler Adams, about 1895. The general geologic map of Minnesota, published by the State Geological Survey in 1909, showed the extension of the Huronian rocks of the Mesabi district passing through this area. Two years later, Leith published a sketch showing the hypothetic extension of the iron bearing formation through the same area. The first drilling was done in 1903, near Deerwood, Minn., by Cuyler Adams, and exploration was continued to the present time in increasing amount. The Northern Pacific Railway extends throughout the length of the district and affords an easy outlet for the ores. The Soo Line Railway completed a spur into the district in 1910. Both roads carry the ore to the docks at Supe¬rior, Wis., the average haul being about ninety miles. Shipments began in 1911, the Kennedy mine being the first producer. By 1918, the number of shippers reached twenty-seven, with a total output of nearly two and one-half million tons for that year."

Jan 1, 1920

A PDP 11/34 computer has been inter- faced to existing instrumentation in a 400 tph rod-mill/ball-mill grinding circuit and programed with a Kalman filter to estimate several unmeasured variables. A dynamic two-size- fraction model of the circuit is used to predict the complete state of the circuit including particle size distributions around the circuit, mass holdups and flowrates, the ball-mill grinding rate, water additions and cyclone parameters. Online measurements of sump level, slurry densities and product particle size are used to update the model values sequentially on a 20-second interval. This procedure results in optimal estimates of circuit variables given the relative reliability of measurements and the accuracy of the model.

Jan 1, 1983