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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 D. Koren, D. Carson

Disposal of smelter slag may be subjected to regulatory leach tests to deter- mine whether they produce a leachate containing contaminants in excess of stated limits. Contaminants that are most often of concern for smelter slags are As, Cd, Cr, Cu, Ni, Pb, and Zn. The present regulatory tests are based on the assumption of storage in a municipal landfill dump, where wastes are in contact with organic acids. Since slags are not normally stored in such an environment, these tests do not adequately assess the true leachability potential of the slags. Ten slags from six major Canadian nonferrous sulfide smelters were studied. Leaching was done following regulatory and modified tests, including leaching in columns with synthetic acid rain for a 25-week period. The slags were characterized by mineralogical analysis before and after leaching with synthetic rain. The synthetic mineral equivalents (hereafter referred simply as phases) in the slow cooled slags consist of fayalite grains and dendrites, amorphous glass, some spinel and small quantities of complex sulfidic prills and metallics. The phases in the quenched slags consist of amorphous glass, some spinel and small quantities of complex sulfidic prills and metallics. Some metal dissolution took place during leaching. However, for all leaching tests, the concentrations were always below the regulated limits. In general, the content of the potentially leachable elements remains unchanged in the fayalite, in the amorphous glass and in the spinel, whereas the quantity of sulfidic prill and metallics decreases after leaching. Therefore, most of the deleterious element dissolution comes from the sulfidic prills and metallic phases. Metal dissolution increases by crushing the slag, probably due to an increased exposure of the sulfidic prills to the leaching solutions.

Jan 1, 1998

By R. Kneisley, D. Conover, K. Haramy, K. Hanna

INTRODUCTION Coal mine entry intersections are high-risk areas for roof falls due to inherently wide roof spans, excessive stress, and variable intersection shapes resulting from breakthrough misalignments. Statistics from underground coal mines reveal that a high percentage of injuries occurs from roof and rib falls in entry intersections (Peng, 1980). The U.S. Department of the Interior, Bureau of Mines, is conducting a field research project to investigate failure modes surrounding underground coal mine entry intersections. The research objectives are to (1) develop a method to determine failure modes and stress-displacement relations around coal mine intersections and (2) develop engineering guidelines and empirical relationships for use in designing safer coal mine entry intersections. The basic approach to achieve the objectives is to instrument and monitor intersections before, during, and after intersection development in order to determine contributing parameters, such as in situ stresses, stress changes, strata movement, geology, physical properties, and mining sequence, that may influence the short- and long-term stability of the intersection and adjacent entries. This paper describes a rock mechanics instrumentation program, data analyses, and a comparison of two case studies conducted at two underground mines, designated as "A" and "B", in the Illinois Coal Basin. The instrumentation plans and data collected during development and long-term monitoring of four-way intersections and adjoining entries are presented. Data analyses of pre- and post-mining roof stress, pillar loading, strata movement, roof bolt loading, and geologic features are included. INTERSECTION FAILURE MECHANISM The region surrounding an entry intersection is characterized by different failure criteria than the region surrounding a single entry. Stresses induced during intersection development may result in a high incidence of roof and rib failures. Various numerical modeling techniques have been used to evaluate the failure modes surrounding intersections (Gercek, 1982; Chugh et al., 1975). Numerical modeling techniques include problems associated with the analysis of post-failure behavior, provision for different horizontal stresses (i.e., 01 f 021, and determination of inputs required for any non-elastic behavior. It seems likely that more sophisticated failure criteria, based on actual field data, are needed. The Bureau of Mines has conducted an extensive instrumentation program to investigate actual intersection failure mechanisms and to provide an improved understanding of stresses and deflections using beam and plate theories. Beam theory is not applicable to analyzing intersections (Wright et al., 1964); however, it can be used to explain roof deflection and failure (shear and flexure) of adjacent entries and to provide an improved understanding of stress changes and displacements as the entries, crosscuts, and intersection are developed (Hanna et al., 1985). Beam theory may be used for entries when the roof length is twice the width. When the length is less than twice the width (as in intersections), the roof must be analyzed as a three-dimensional problem, and stress and deflection calculations are based on flat plate theory (Adler and Sun, 1976). The confined-core theory (Wilson, 1972) hypothesizes that within a typical pillar, two regions exist: a confined-core region where the horizontal confining pressure is uniform and approximately equal to the overburden pressure, and a yield zone where the vertical pressure increases from nearly zero at the rib to a pressure peak at the boundary of the yield zone. The strength of coal in the yield zone ranges from nearly zero at the rib to nearly full strength at the confined core. The vertical stress in the confined core decreases from maximum at the yield zone boundary to the overburden pressure some distance into the pillar. Excavation of the adjoining entries

Jan 1, 1986

By Michael C. Newbury

For thousands of years gold has been not only a commodity, valued for its comparative scarceness, immutability and homogeneity but also a medium of exchange which has no nationality. Approximately 90% of the gold produced is still accessible in the world, although some of it in museums, galleries, jewellery and dental work is not immediately available for circulation. The majority is held as bars by central banks for their reserves; the balance circulates as coinage or bullion held for investment. The value is further enhanced by the political aspect that gold cannot be debased as paper currency can and, therefore, it always becomes an investment refuge. It has always been possible to buy and sell gold at a price which is readily established by reference to bullion's weight and purity; and it is this fact which makes a loan denominated in gold, rather than one in currency, a viable alternative means of finance. The purpose of this paper is to discuss some general aspects of what is considered to be one of the more effective and presently popular methods of financing the development of a gold mine - the gold loan. This is not intended to discuss all the minute details which must be uniquely designed to fit each individual situation, but rather to provide general guidelines. You will all be aware of the traditional sequence whereby companies primarily finance exploration work by the raising of equity through the sale of shares to the public or by that unique Canadian form.

Jan 1, 1987

By A. Haghighat, B. Lattimer

"Mine face ignition due to a high levels of methane is one of the most common fire incidents in underground coal mines. This work exams ignition scenarios in continuous miner headings. Depending on the magnitude of the ignition or resulting fire, the ventilation curtain in the continuous miner (CM) heading may be damaged or dislodged, affecting the ventilation into the area. A computational study was conducted to investigate the effects of different levels of damage to the ventilation curtain on the ventilation flow into the CM area. The computational fluid dynamics software Fire Dynamics Simulator (FDS), Version 6.0 was used to predict the conditions that develop due to a 200 kW fire in the coal mine face following a methane ignition with different levels of curtain damage. Smoke layer depth, temperatures and mass flow into the CM area were used to evaluate the impact of no damage to the curtain, partially dislodged curtain, and fully removed of the curtain. Partial removal of the curtain allowed more smoke to accumulate in the CM area and a reduction in ventilation into the CM area. With full removal of the curtain, the smoke accumulated through the entire depth of the CM area and flowed out the entrance to the CM area and the ventilation completely bypassed the region. INTRODUCTION Active working faces in underground coal mines are one the most hazardous locations in terms of fire events. According to Mine Safety and Health Administration (MSHA) data analysis, the highest number of non-fatal fire incidents was reported at mining faces, intersections and crosscut areas in comparison with other locations from 2000 to 2012. About 464 fires happened at active working faces from 2000 to 2012, most consisting of a methane ignition, in some cases followed by localized fire. These are high risk incidents due to the potential to raise float dust and damage ventilation systems, particularly auxiliary systems such as curtain or tubing. Depending on the magnitude of the ignition or fire, the ventilation curtain in the continuous miner (CM) area may be damaged or dislodged, affecting the ventilation into the area. Five computational fluid dynamics (CFD) scenarios were considered to investigate the smoke layer depth, temperature, visibility, mass flow rate, and the behavior of airflow in an entry with a continuous miner (CM) located in it. The state of the auxiliary ventilation was varied based on the assumption that as an ignition increases it magnitude it will affect ventilation curtain proportionally. Visibility and temperature along the height of the entry at different sections were investigated and the interface height at each section was determined. Also, the fresh air height was studied for tenability analysis in future. FDS, Version 6.0 was used to predict the conditions that develop due to a 200 kW fire on the coal mine face following a methane ignition with different levels of curtain damage. Smoke view software was used as the post processor to visualize and analyze methane fire behavior at the face. Most entry fires are reported as fuel-controlled fires as they are rarely restricted to air access (Ingason et al, 2014). The working face fire in the following models was assumed to be a fuel-controlled fire."

Jan 1, 2016

By Clete Stephan, John Urosek, Ian Anderson

The Endeavour Colliery is operated by Powercoal Pty Ltd. It is located in the Central Coast of New South Wales, Australia. The mine has been in operation for about 30 years, producing around 600,000 tons of export coal annually from two production sections. On June 28. 1995, an explosion occurred underground in the 300 Panel at approximately 9:50 a.m.. There were thirty miners underground at the time of the explosion, all of whom were safely evacuated. From June 29 through July 10, personnel did not enter the mine. However, gas samples of the mine atmosphere were obtained from underground monitoring stations and analyzed. Samples were also obtained from boreholes that were drilled from an adjacent mine. On July 10, the atmosphere at the underground monitoring locations and at the boreholes appeared stable with minimal risk of combustion occurring underground. Plans were developed to begin the recovery of the underground workings. The recovery of the underground workings was completed on July 13. The underground investigation of the explosion began on July 14. The investigation was conducted by the New South Wales Department of Mineral Resources. Technical assistance was pro- vided by the United States Department of Labor's Mine Safety and Health Administration (MSHA).

Jan 1, 1997

By Staff

Assembling consistent data for a 40-year time series is a challenge because of the many changes that have occurred in this period. In many cases, because of process improvements and consumer requirements, grades of materials change in a 40-year span. This can lead to a wide fluctuation in price data simply because of increased costs for premium grades. Sources for obtaining price data can also change during a 40-year period. Changing the data source also introduces anomalies in a time series. In some cases, published price data are not representative of the real value of the material and provide little basis for further analysis. For some industrial mineral commodities, there are only a few producers, and value and production data are considered proprietary. In the data presented in this chapter, every attempt was made to ensure that the data were as consistent and representative of the industry as possible. However, the factors mentioned above may have introduced inconsistencies in some of the data series. Many different factors influence trends for industrial minerals because of the diversity of end uses for these commodities. Trends in production and prices for most of the industrial minerals can be related to one or more of the following: changing demand or technologies in end-use industries, development of new end uses, the effect of environmental regulations, production and processing technology changes, energy costs, foreign competition and substitution by other materials, and production as a byproduct of other minerals. World economic conditions, such as recessions and inflation rates, also play a part in some production and price trends. Data for 40 years of production for industrial minerals in the United States are presented in [Table 1] in 10-year increments. Unit values for the industrial minerals, in actual and constant 1990 dollars, are shown in [Tables 2 and 3].

Jan 1, 1994

By R. Kuhns

The western coast of South Africa hosts a significant diamond resource within gravels associated with paleo-shorelines, channels and transgressive lag deposits. Diamonds were transported from the Kaapvaal Craton to the coast largely during the late Cretaceous via the paleo-Orange river systems. On shore and near shore environments are underlain by Proterozoic metamorphic and granitic rocks which provide gully and pot hole-type traps associated with paleo-channels, basins, bays and beaches. Inner and mid-shelf environments are covered by diamondiferous, poorly lithified upper Cretaceous and Tertiary sediments. The upper Cretaceous gravels were reworked along the sediment-starved coast during much of the Tertiary. Reworking was mainly achieved during marine flooding events which produced lag gravels along the paleo-shorelines. This process reworked the diamonds from low-grade Cretaceous gravels and concentrated them in higher-grade Tertiary gravels.

Jan 1, 1995

By Danqing Xu, A. W. Khair

This paper presents a laboratory simulation of regrinding and resulting dust generation. An Automated Rotary Coal Cutting Simulator (ARCCS) was modified to conduct regrinding experiment. In order to estimate the effects of coal properties and operating parameters on regrinding and dust generation, an orthogonal fractional factorial experimental design was implemented in regrinding experiment. Marple personal cascade impactors, Series 290, were used to measure dust concentration during experiment. Three types of coal seams, namely, Waynesburg, Pittsburgh, and Lower Kittanning, were used to represent different coal properties. Experimental results and complete parametric analysis were presented.

Jan 1, 1991

By J. P. Ducarme

The eastern U.S. contains vast reserves of thin seam coal deposits, particularly in the Appalachian mountain region. These typical 355 to 710 mm thick reserves are difficult or uneconomical to recover with present technology. The U.S. Bureau of Mines is developing technology that would allow nearly 100% recovery of thin seams in these mountaintop regions. This paper details the research that has been conducted on these new techniques and presents results of testing on a cross-ridge full-scale physical model.

Jan 1, 1994

By L. G. Stolarczyk, R. C. Fry

In coal-bearing formations, seams are often bounded by sedimentary layers of mudstone, claystone or shale. When the electrical conductivity of the surrounding sediment layers is greater than the conductivity of the seam, a natural parallel plate waveguide forms in the strata. For frequencies below the AM broadcast band, the waveguide can be used for the transmission of electromagnetic (EM) waves. In a uniform seam, the primary wave travels in the coal layer along paths between a radiating antenna and a distant receiving antenna. The travel distance increases with seam height and the conductivity of the surrounding sediment layers. The distance decreases with increased coal conductivity. In Cretaceous western bituminous coal, the distance may exceed 549 m (1800 ft). Anomalous geologic disturbance zones such as faults, shear zones, paleochannels, sills and dikes significantly alter the values of EM wave propagation constants (attenuation and phase) expected in a uniform seam. In the neighborhood of an anomaly, EM wave energy is scattered (reflected and diffracted). Scattering creates secondary waves in the seam wave guide. A receiving antenna at a remote location in the coal seam can be used to measure the magnitude and phase of the EM wave at the end of the path. The measured data can be processed to determine the average value of the propagation constants along each path. Paths with anomalous propagation constants are used to locate and image geologic disturbance zones. Radio Imaging Method (RIM) instrumentation, survey procedures and data processing (tomography) algorithms have been developed to image geologic structure in advance of mining. The survey is conducted between gate roads of a longwall panel. Data processing constructs contours of constant attenuation rate (phase constant) across the plan view of the panel. In anomalous zones, the contours rapidly change with distance. The shape of the contour lines generates a visual image of the anomaly and suggests the type of anomalous condition to be expected in the coal seam. This paper briefly discusses the depositional environment and the formation of the imperfect waveguide in coal-bearing strata. The linkage between sedimentary geology and EM wave theory establishes an understanding of how the propagation constants depend on the anomalous geologic conditions. A case study compares in-mine geologic mapping with the tomographic image of a longwall panel.

Jan 1, 1991

By David A. Milligan, William Cobb

2.1 INTRODUCTION This chapter provides the reader with a sense of how a heap leach project may make an orderly, and hopefully non-traumatic, transition from discovery or acquisition to project construction. In making this transition a project can pass through several project development phases (i.e. ore definition and delineation, conceptual engineering, detailed engineering, and ultimately on to project construction and operation). "Go" or "no go" decisions may occur at any point in each of these phases. The transition from ore definition to detailed engineering should be accomplished via a well thought out program of interdisciplinary studies and an integrated, interdisciplinary project team. This chapter also describes, in general terms, a "roadmap" approach to the project evaluation process that must occur as project planning and development progress. It is the experience of the authors, as well as a myriad of companies who have been through the heap leach project development process, that a systematic approach will save many headaches, and many dollars. In fact, it is safe to say that a project with no formalized system of "objectives setting" and "milestone charting" may well flounder along the way, even if an economic ore body exists. Many papers and technical articles have been written about various aspects of mineral resource appraisal, economic evaluation, and mine development. Most of these invoke the same general philosophy of a systematic approach to project evaluation and development, although methods cited for attaining goals are quite variable. This is undoubtedly appropriate, given the fact that there is great variation in approach to project development (e.g., climatic considerations, ore body size and physical ore characteristics, permitting constraints, etc.). For the purposes of this chapter, two primary sources of information have been used to highlight the "road map" approach previously alluded to. These sources are cited throughout the text as Mackenzie (1980) and Snow and Michel s (1986). A brief summary of each of these sources is provided below: Brian GJ. Mackenzie of Queens University (Mackenzie, 1980) has developed a wealth of information concerning project development topics. Much of this information is synthesized in his notes for a short course entitled : "Mineral Exploration Planning and Economic

Jan 1, 1988

By Roger J. Hornberger, Paul F. Ziemkiewicz, Dirk J. A. vanZyl, Gene E. Krueger, Harry H. Posey, Kim A. Lapakko, Charles H. Buckmam

The Acid Drainage Technology Initiative (ADTI) was initiated in 1995 by federal agencies, the National Mining Association and the Interstate Mining Compact Commission to identify, evaluate and develop cost- effective and practical acid drainage technologies. In 1999 ADTI was expanded through the addition of the metal mining sector group, which began organization efforts in 1998. ADTI addresses drainage quality issues involving metal mining and related metallurgical operations and acid drainage from coal mines, for abandoned, active, and future mines. ADTI is a technology development program. It is not a regulatory or policy development program. The guiding principle of ADTI is to build a consensus among industry, federal and state regulatory agencies. ADTI is focusing these efforts on technology development and technology transfer in the areas of mine drainage sampling/monitoring, prediction, avoidance/remediation and modeling.

Jan 1, 2000

By G. Adel, J. M. Richardson

Mine-to-mill optimization is a holistic approach to the optimization of mining and processing operations. Developed at the Julius Kruttschnitt Mineral Research Centre, it attempts to minimize energy consumption through the optimization of the particle size reduction process. The approach involves sampling and modeling of blasting and processing, computer simulation to optimize the operation and develop alternatives, implementation of the most promising alternatives, and sampling to quantify energy savings. The primary objective of the present effort is to adapt mine-to-mill technology to the aggregates industry. This paper presents an update of work being conducted at quarries operated by the Luck Stone Corporation of Richmond, Virginia.

Jan 1, 2006

By Timms. Greg P., John W. Bennett

A field-based method for measuring the diffusive oxygen flux through covers placed on sulfidic waste rock dumps has been developed and applied at a number of mine sites. The technique provides a means of quantifying oxidation rates in dumps and can thus be used to assess the effectiveness of cover systems. Two instruments can be used. The first is portable and easy to set up, enabling a picture to be built up of the overall diffusive flux into a dump by making measurements at a sufficient number of locations. The second is installed beneath a cover and is preferred in situations where oxygen is consumed in the cover since it provides a direct measurement of the oxygen flux into the underlying waste rock.

Jan 1, 2000

By J. A. Herbst, R. Zaragoza

Conventional control schemes in use today are not able to produce satisfactory control when high-frequency disturbances are present in the flotation feed. An advanced model-based control scheme is presented here as a promising solution to this control problem. The main feature of this control scheme is the real time identification of the unknown disturbances in the first few cells of the flotation circuit. This information is used to control the rest of the flotation plant in a feedforward fashion. This control scheme also provides flexibility to meet any metallurgical, economical, or management objective.

Jan 1, 1987

By Bruce E. Nesbitt, Paul G. Lhotka

At Lupin mine gold is spatially and genetically linked to zones of hydrothermal alteration in iron-formation which are symmetrically developed adjacent to late Archean quartz veins. Immediately adjacent to the veins, coarse grained, typically gold- and sulfide-poor, calc-silicate rocks are often present. These rocks comprise hedenbergite + quartz ± grossular garnet ± epidote ± scheelite ± calcite. Sulfides (pyrrhotite, arsenopyrite and loellingite) and gold are concentrated in the next zone and occur with hornblende-rich rocks comprised of hornblende, quartz, hedenbergite and grunerite. Furthest from the veins are gold- and sulfide-poor, grunerite-rich iron formation comprising grunerite, quartz, hornblende and sometimes magnetite. Although the alteration assemblages have similarities with skarns, they develop in iron formation, and are at best indirectly related to intrusive igneous rocks. Geological and geochemical data clearly indicate the calc-silicate rocks are metasomatic in origin.

Jan 1, 1990

By Stéphane Servant, Jacques Ouellet, Ferri Hassani

This paper presents essentially the logistic and practical aspects involved for in situ testing of mine paste backfill with a self-boring pressuremeter. The investigation discussed in this paper is part of an extensive and ongoing research project to identify and validate an in situ testing technique for cemented mine backfill such as hydraulic or paste backfill as well as Insitu behavior of backfilled stopes. After a literature review on field testing of soils and past experiments on mine backfill in situ testing, the self-boring pressuremeter was selected as the most appropriate instrument for this task. The authors presents in this paper the technical aspect involved in a field trials that was conducted in a Canadian underground mine using paste backfill. The results of this first successful trials show that self-boring pressuremeter test can provide high quality and reliable backfill characteristics results, using analytical techniques developed for soils (Ouellet et al., 1998). The parameters obtained were: estimation of the lateral stress in the ground, the soil stress-strain response and the soil strength. The logistic and equipment required to conduct such testing underground is fully described. Performance achieved in the field and technical difficulties encountered are highlighted. Recommendations for future experiments with such instruments are given. Some potential technical improvements to better adapt this in situ testing technique to mine backfill are proposed.

Jan 1, 2001

By R. E. Miller

Accelerometers and pressure transducers mounted in suspension components can be used to monitor the ride of haulage trucks. Presently, it is difficult to tell what caused a jolt to the truck using either pressure or acceleration data alone. When information from a Global Positioning System is recorded at the same time as shock pressures or acceleration data, then the exact location of an event can be determined. Mine management can then determine what caused the jolt to the truck.

Jan 1, 1999

By Maurice C. Fuerstenau

INTRODUCTION The term, chelate, from the Greek for 'claw,' has its origin in the pincer-like representation of more than one atom of a single ligand bonded to the same metal atom, forming a ring-like structure. Depending on how many attachments exist on the sphere of coordination around the metal ion, ligands are referred to as bidentate, tridentate, tetradentate, pentadentate and hexadentate According to Calvin and Martell (1952) and Somasundaran and Nagaraj (1984), chelating agents must contain suitable functional groups, and their location within the ligand molecule must enable ring formation that is sterically possible. Typical structures that meet these requirements have been given by Fuerstenau and Herrera-Urbina (1988) and are listed in Figure 1. As noted, the functional groups of these reagents contain electron donor atoms such as oxygen, nitrogen and sulfur. Basic groups, such as amino (-NH,), are those that contain an atom with a lone pair of electrons. Acid groups are those, such as carboxylic (-COOH) which lose a hydrogen ion and coordinate with the metal atom. Examples of each of these types chelating reagents are given in Tables 1-4. The specificity of chelating agents for various metal ions has long been known and was utilized early in the search for new flotation collectors. In 1927, Vivian used ammonium nitrosophenylhydroxylamine as a collector for cassiterite. Holman (1929) tested dimethylglyoxime as a collector for nickel oxide. He also suggested taurin as a collector for oxidized lead ores. DeWitt and von Batchelder (1939) suggested the use of oximes as flotation collectors. Gutzeit (1946) conducted an extensive investigation on the use of chelating agents as collectors and as depressants for gangue minerals. The depressants are those reagents that form soluble chelates with metal ions that could function as

Jan 1, 2005