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By Charles H. Fulton

One of the first matters to receive attention from the Bureau of Mines when it was authorized to undertake investigations relating to wastes in the mineral industries was the smoke problem at smelting and ore-roasting plants. This bulletin is published by the bureau primarily for persons who seek information on the subject of metallurgical smoke but are unacqllainted with the technical language of metallurgy. It is, of course, not possible to free a techniCal subject entirely from teclmicalities, but, 80 far as possible, statements are made in plain and simple English. Metallurgical smoke causes considerable friction between the metallurgical industry and agriculture in certain parts of the country. Owners of smelting plants are making every effort to devise ways and means to do away with possible damage and annoyance from smoke and are meeting with success. The problem is peculiarly difficult in this country because of the large tonnages of material that must be handled. The solution of the problem is not yet at hand and much work still remains to be done. As the mineral industry is one of the great basic industries of the country and of necessity is entitled to full consideration, it should be accorded freedom to work out the smoke problem to the benefit of all concerned. The effort is made in this paper to present the problem of metallurgical smoke as it actually exists, without bias of any kind. The writer takes this opportunity to express his indebtedness to the sources of information on which he drew, many of which are enumerated in the selected bibliography at the end of this paper. In connection with the author's use of the present tense in describing plants and methods, the reader should note that none of the references in that bibliography is of later date than 1913. Much information was obtained by personal visits and by correspondence, and thanks are hereby tendered to all persons who kindly furnished data. The writer desires to thank particularly F. G. Cottrell, chief chemist of the Bureau of Mines, for criticism and comment.

Jan 1, 1915

CONTENTSThe significance of values givenINTRODUCTIONTHE ORE1. DATA SECURED FROM THE MILLING PLANT AS OPERATING BETWEEN 1938 AND 1942(a) Mill Recoveries(b) Mill Flow Sheet(c) Scheelite-Garnet Association(d) Detailed Examination of Mill Performance during 1942Crushing UnitsCoarse Rolls DischargeFine Rolls DischargeFeed to Huntington MillsFinal Ground ProductProduction of -200-mesh Scheelite SlimeSummary of Information on Crushing and Grinding Circuit(e) Detailed Examination of Mill Performance During 1942Concentrating UnitsLocation and Nature of Scheelite LossesSize Distribution of Scheelite LossesDistributor Spigot ProductsSummary of Information on Concentration Circuit(f) Detailed Examination of Mill Performance During 1942 Gravity Plant Feed2. EXAMINATION OF MINE SAMPLES TAKEN DURING 1942(a) Introduction(b) Nature of the Ore(c) Sampling of Mill Feed(d) Testing Technique(e) Minus 1/8-inch Ores-Naturally Broken Fractions(f) Recoveries from Plus 1/8-inch Fractions-Crushed to Minus 1/8-lnch(g) Probable Recoveries Obtainable from Weathered Ores140 Contour120 Contour90 Contour(h) Examination of an Ore Sample from the 90-foot Adit(i) Run-of-Mine Ore(j) Evidence of Maximum Sizes of Scheelfte Present in Run-of- Mine Ore(k) Summary of Information on Liberation and Recovery from the Ores as Mined in 1942 and from the Mill Samples

Jan 1, 1944

By Bernard Lewis

During the past 10 years the technical investigations conducted by the Explosives Division of the Mine and Explosives Bureau of the Bureau of Mines have been described in a series of summarizing reports prepared by Wilbur I. Huff, consulting explosives chemist of the Bureau. These reports covered the…

Dec 1, 1947

Mercury has been used by mankind since prehistoric times. It has been, and is now, widely used in industry and medicine and has unique properties which make direct substitution difficult or impossible. At present its principal uses are for electrical apparatus, control instruments, electrolytic soda preparation, mildew-proofing paints, pesticides, and medical and dental preparations. Deposits of mercury are less common than those of other base and precious metals, but some of the deposits are very large and have been ample to meet the world's past demands. The price of mercury has had many sharp fluctuations, but in general, the limited number of producers has resulted in a more stable price structure than that of many other commodities. The United States has been one of the main producers of mercury, and from 1850 to 1961 produced 3,247,704 flasks. Yearly production since World War II has varied from 4,535 to 38,067 flasks. An estimate of domestic resources of mercury producible at various price ranges was prepared for each mercury mine by combining specific knowledge of mercury mineralization with estimates of potential, based on geologic information and past production history. The sum of the individual estimates for each price range is shown in a table. A parallel estimate of nationwide production potential was made from a study of past price and production relationships. These were analyzed by plotting yearly production figures against the previous year's price, expressed in dollars of constant purchasing power. An equation was fitted to the data by mathematical means and was used to extend the curve into areas of higher than historic prices. Potential production rates at various price levels were taken from this graph. The estimated yearly production rates were used to make an estimate of total potential based on the premise that production rates and reserves have a proportionate relationship. The rate of developing mercury reserves during the period from January 1944 to January 1962 is considered, and it is shown that if this rate can be continued, the mercury resources of the United States, at a constant dollar price of $500 per flask, are adequate to support a production of 60,000 flasks per year for 30 or more years. This publication contains a history and description of the mercury industry in every State which has had production and individual descriptions of all mercury properties which have reported significant production. Accompanying tables give the important facts about all known mercury occurrences.

Jan 1, 1965

Mercury has been used by mankind since prehistoric times. It has been, and is now, widely used in industry and medicine and has unique properties which make direct substitution difficult or impossible. At present its principal uses are for electrical apparatus, control instruments, electrolytic soda preparation, mildew-proofing paints, pesticides, and medical and dental preparations. Deposits of mercury are less common than those of other base and precious metals, but some of the deposits are very large and have been ample to meet the world's past demands. The price of mercury has had many sharp fluctuations, but in general, the limited number of producers has resulted in a more stable price structure than that of many other commodities. The United States has been one of the main producers of mercury, and from 1850 to 1961 produced 3,247,704 flasks. Yearly production since World War I1 has varied from 4,535 to 38,067 flasks. An estimate of domestic resources of mercury producible at various price ranges was prepared for each mercury mine by combining specific knowledge of mercury mineralization with estimates of potential, based on geologic information and past production history. The sum of the individual estimates for each price range is shown in a table. A parallel estimate of nationwide production potential was made from a study of past price and production relationships. These were analyzed by plotting yearly production figures against the previous year's price, expressed in dollars of constant purchasing power. An equation was fitted to the data by mathematical means and was used to extend the curve into areas of higher than historic prices. Potential production rates at various price levels were taken from this graph. The estimated yearly production rates were used to make an estimate of total potential based on the premise that production rates and reserves have a proportionate relationship. The rate of developing mercury reserves during the period from January 1944 to January 1962 is considered, and it is shown that if this rate can be continued, the mercury resources of the United States, at a constant dollar price of $500 per flask, are adequate to support a production of 60,000 flasks per year for 30 or more years. This publication contains a history and description of the mercury industry in every State which has had production and individual descriptions of all mercury properties which have reported significant production. Accompanying tables give the important facts about all known mercury occurrences.

Jan 1, 1965

Jan 1, 1994

In 1970, the U. S. Bureau of Mines contracted with Theodore Barry and Associates, a management consulting firm, to perform a one-year industrial engineering study of working-face hazards in underground bituminous coal mines. The field data was accumulated from industrial engineering observations in fifty underground mines. Supporting data for the analysis was derived primarily from the Bureau's fatal accident reports for the years 1966 through 1970. This report, Industrial Engineering Study of Hazards Associated with Underground Coal Mine Production, consists of three main parts: 1) The Fatal Accident Reports Analysis, 2) The Industrial Engineering Analysis, and 3) Multiflow Process Charts and Standard Time Data. The Fatal Accident Reports Analysis (Volume I, Section II) is based upon individual USBM fatal accident reports for 1966-1970. These were read, coded and computerized in terms of 84 significant variables. Cross-tabulations of these variables have been used to identify major underground hazards and to quantify significant causal factors. A very strong relationship was found to exist between fatal accident occurrences and low task experience. This led to a recommendation for formalized training, certification and supervision programs for miners. Victim compliance with federal regulations, mine regulations and supervisor instructions was analyzed, indicating that supervisors provide the most crucial communication link to workers. Thus, every attempt should be made to ensure the competence of immediate supervisors in the industry. Analysis of roof fall variables revealed a fatal propensity on the part of the miners to work under unsupported roof or under support conditions that are marginal. The technical approach to the problem is to make it physically impossible for a miner to work under these conditions; the behavioral approach is to ensure adequate training and develop proper safety attitudes among the miners. The Fatal Accident Reports Analysis revealed a need for normalizing data to interpret the results more accurately.

Jan 1, 1971

By Eleanor Abshire

This bibliography is the second in a series that covers the current technical literature relating to the metallurgy of zirconium. The rapid advance in zirconium technology makes it mandatory that abstracts be prepared and compiled as soon as possible to have maximum value; therefore, the information in this volume is not arranged chronologically. As a service to research and production groups, succeeding bibliographies will be issued as new acquisitions accumulate in the Zirconium Information Center sponsored by the Department of the Navy, Bureau of Ships and the Bureau of Mines at the Bureau's Northwest Electrodevelopment Laboratory, Albany, Oreg. The initial volume, Information Circular 7771, Bibliography of Zirconium, covering 969 abstracted reports and 645 United States and foreign patents, was published in April 1957.

Jan 1, 1958

By Charles Janin

The recovery of gold from sands and gravels is one of the oldest forms of mining; it antedates history and has been practiced by savage peoples. In North America the search for placer gold has been a powerful agency in the exploration and development of unknown regions and has profoundly influenced the course of our civilization. With the progress of invention, the improvements in machinery, and the availability of large capital for the conduct of great operations, the tendency in placer, as in many other branches of mining, has been toward the working of extensive but comparatively low-grade deposits. The early miner washed the rich spots in stream beds or terraces with his pan, his long tom, and his primitive sluice. Then followed the growth of hydraulic mining and the use of giants supplied with water under pressures of hundreds of pounds to the square inch that could work at a profit gravels whose gold tenor was less than 3 cents to the cubic yard. Finally came the dredge that could handle deposits lying so far below water level as to be beyond attack by other methods. Although the gold dredge was first successful on a commercial scale in New Zealand, it has reached its present strength and efficiency in this country and its development is a monument to the daring, per- severance and technical skill of the many men, mine owners and engineers who have each contributed something to the final result. The Bureau of Mines, authorized to conduct investigations for the purpose of increasing efficiency in the mineral industries, had its attention called some years ago to the need of a comprehensive report on gold dredging in the United States. The director of the bureau recognized that such a report should summarize the development of the gold dredge, should describe in detail the essential features of present-day dredges, should discuss the facts that determine whether a placer deposit can be profitably dredged, and should point out the approved methods of prospecting placer ground and of operating dredges. At the request of the director, the author undertook the preparation of such a report and has been intermittently engaged on the task for several years. This bulletin is the outcome of his labors. He hopes that it will prove of interest to designers and builders of dredges, to mining engineers, and to persons who may contemplate investing capital in placer-mining ventures.

Jan 1, 1918

The following pages discuss the objectives, the background, the scope and a statement of the problem of the study of methods to improve the pillar extraction practices in underground coal mines. 1. OBJECTIVES The objectives of this project were: ? to determine the principal factors contributing to high accident frequency and severity in both conventional and continuous mining operations; ? to compare and evaluate the safety aspects of the "open end" and "split and fender" systems of pillar mining; to establish basic data required to decide what constitutes an adequate pillaring plan that will optimize efficiency, recovery, and safety; ? to determine what measurements or information should be collected, (e.g. roof sag, pillar stress,) to make on-the-spot judgment of impending roof or pillar collapse; ? to make recommendations to improve existing methods or to insure proper techniques are implemented, and ? to suggest areas where additional studies or new research may be of value.

Jan 1, 1975

The transition from exploration to feasibility is a stage in the development of mineral resource projects that is frequently not handled well. The transition marks a point in the project development process where resource evaluation priorities change significantly from the discovery of mineralisation and the rapid assessment of the potential tenor of the mineralised system, to the detailed assessment of the deposit.   Information used in the exploration process tends to be of a qualitative or theoretical nature initially, but gradually becomes more quantitative in character as geological knowledge relating to individual prospects grows.   The transition from discovery and rapid exploration of a new deposit occurs at a relatively early stage in project development, coinciding with the first attempt to prepare a resource estimate for the deposit. Fundamental assumptions regarding both structural and grade continuity and uncertainty inherent in existing information need to be made so that they themselves may be addressed during the collection of additional data.   The effective commencement of feasibility studies involve the introduction of new accountabilities either as a result of appointment of a project manager, and through needing to be able to quantify: ò     the quality of data being collected for resource evaluation purposes; ò     confidence associated with resource estimates; and ò     the need to develop an audit trail for the project, required to make the resource evaluation decision-making process as transparent as possible.   Quality assurance is a concept to which exploration geologists have frequently had little exposure. Being able to demonstrate the quality of data used in feasibility studies is, however, a crucial component of the overall risk management and reduction.   Development of a transparent audit trail for data assists in demonstrating the quality of data which is frequently perceived to translate directly to confidence inherent in resource estimates.   Establishing procedures for geological data collection and management also provides a more reliable framework for making decisions that impact on project execution, again resulting in improved confidence in resource estimates and associated geoscientific data.   Regular, independent technical audits, in principle similar to audits conducted for the ongoing certification of standards compliant quality assurance systems, are a major, positive factor in effective project management and execution.   Information used in project evaluation, feasibility and development must be based on facts. Facts are effectively observations that are ideally made systematically, recorded in a systematic manner, and by being collected effectively are not subject to change.   Effectively managing the transition from exploration to resource evaluation, feasibility and project development involves recognising the nature of changes in the nature, detail and scope of geoscientific data required at each stage of project development. In doing so it is essential to: ò     recognise when the change occurs (as early as preparation of the initial resource estimate for a project); ò     accept that the change may not be gradual; and, ò     ensure that the project evaluation team is adequately resourced.   These objectives require recognition of the value of previous experience and the need to instill a true team approach amongst both staff and contractors associated with the project. Regular formal and informal communications between staff, contractors and other stakeholders in the project are an essential tool in ensuring personnel are aware of factors affecting their role in the project.

Jan 1, 2004

By L. A. Thompson, A. J. Linington

"Copper–cobalt extraction is a reagent-intensive process resulting in acid consumption greatly contributing towards production costs, which in the current market conditions curtail profitability. Nanofiltration (NF) membranes have become an attractive approach in the mining and minerals industry for product concentration and reagent recovery based on the ability of the membrane to separate monovalent ions from divalent ions. NF membranes can selectively separate acids from metals and salts allowing acid to be recycled as well as the concentration and purification of product streams. Membrane technology in the field of copper–cobalt processing focusses on the concentration of Cu2+ and Co2+ in the pregnant leach solution, recovery of acid from waste streams to neutralization, recovery of valuable metals from waste ponds and process water recovery. This paper aims to provide insight into the potential applications of NF membranes in copper–cobalt processing circuits as well as a brief overview of the effects of process conditions on membrane performance and process development. INTRODUCTION The copper–cobalt industry commonly uses inorganic acids, such as sulfuric acid, in large quantities for primary leaching of copper–cobalt oxide ores and releaching during product purification (Stuurman et al., 2014). This results in numerous acidic intermediate streams containing high metal concentrations and acidic waste streams with low metal concentrations. Acid consumption typically accounts for 10–15% of the operating costs of mines in the Democratic Republic of Congo (DRC) and Zambia (Acid Plant Database, 2015). Due to remote mine locations, poorly maintained roads and cross-border conflict, the cost of sulphuric acid can range between USD 300 and 400 per ton. The pivotal role of acid in the copper–cobalt extraction process has driven many mines to build sulphuric acid plants on site to ensure a reliable acid supply, however elemental sulphur still needs to be imported which faces similar logistical challenges and contributes towards operating costs."

Jan 1, 2015

By K. P. Kavun, M. N. Denisov

Discussed in the paper is the redesigned reserve/resource classification for solid minerals being put forth by the authors to replace the acting Russian classification of 19961. The new version is based on the traditional foundations of former Russian classifications and the principles of the ‘McKelvey box’, both categorizing mineral resources according to the degree of geological assurance and economic viability. Based on these approaches the classification deliberately deals with both reserve and resource categories very similar to those established by the Geneva Accords in terms of definitions implied. The authors proceed from the UN-ECE proposed concept of ‘reserves’ being a part of ‘total resources’ explored in great detail by geological and feasibility studies and economically mineable at the time of reporting. The draft classification distinguishes ‘proved’, ‘probable’ and ‘possible’ categories of reserves depending on the stage of feasibility assessment carried out, i.e. the degree of detail and accuracy with which modifying factors affecting mineability of an orebody are taken into account. The reserves are regarded as a product of feasibility assessment of ‘measured’, ‘indicated’ and ‘inferred’ resources. The portions of them not having been classified as ‘reserves’ are regarded as composed of two classes: ‘subeconomic’ and ‘potentially economic’ resources (or ‘resource base’). All the cells of the classification matrix are provided with traditional for Russia alphanumeric designations and appropriate UNFC codes. The classification scheme recommended is viewed as a step forward in improvement of the State inventory and reporting mineral resources in market conditions, conducive to cross-border professional collaboration in the field of providing reliable information on the mineral rawmaterials base of the world’s economy. Besides, it recommends an easy way to get rid of amethodological error in the UNFC classification scheme where consecutive stages of geologicalexploration are identified with a single inherent degree of geological assurance. Keywords: mineral resources, mineral reserves, classification, geological assurance, feasibility studies, subeconomic resources, undiscovered resources, competent person.

Jan 1, 2003

By Ken Wood

"A reliable source of water of an acceptable quality is vital to the success of any mineral processing plant using wet methods. For Cerro Verde, a new 108,000 t/d copper mill in southern Peru, the main source of raw water is the Chili River. The Chili River is heavily contaminated with raw sewage, industrial wastewater and agricultural runoff, and can also receive high sediment loads during the rainy season. The initial water treatment plant could not supply design flows of water due to the exceptionally poor water quality. Problems with treated water quality caused significant difficulties with water consuming equipment, such as the plant cooling systems. This paper details the Cerro Verde water system and changes from design through to start up from a mineral processing perspective.INTRODUCTIONMining, and mineral processing in particular, is a water intensive activity. Improving water system design and practice are key strategic requirements in moving toward a more sustainable mining industry. This case study forms a basis for ongoing research into water use and reuse at mines and mineral process plants, conducted by AJ Gunson, under the supervision of Dr. Bern Klein and Dr. Marcello Veiga at the University of British Columbia. The case study material was gathered through involvement with the design, startup, and redesign of the Cerro Verde water system.Cerro Verde is a low-grade copper porphyry mine, located near the city of Arequipa in southern Peru, at an elevation approaching 2,800 m. In 1972, one of the world’s first copper Solvent Extraction – Electrowinning (SX/EW) facilities was built on the site, processing oxide ore from two main open pits. In 2004, the operator, Sociedad Minera Cerro Verde S.A.A. (SMCV), approved a 108,000 t/d expansion project to process sulfide ore reserves through a new concentrator plant. The plant was designed under extremely tight schedule and capital constraints, with a mandate to intentionally avoid any overdesign."

Jan 1, 2008

By R A. M Maddever, P Jeanneau, V Flahaut

Over the entire life cycle of a mine, from early resource evaluation to the blasting of benches, the collection of geochemical data is crucial for the site operator, who must routinely and intensively drill and sample the orebody. This produces huge numbers of physical samples, in turn requiring significant cost and time for their preparation and assay. Moreover, despite best efforts, the sample recovery process is prone to error, which limits the quality of data.The pulsed neutron gamma technique has been used for decades in various industries, in particular oil logging, for its ability to provide direct identification and quantification of elemental concentrations. However, its implementation in logging tools for the mining sector is relatively recent. Built around the latest in technology for optimal spectrometric measurement, a commercial tool referred to as FastGrade™ 100 has been available for a few years and used with increasing success in the mining environment, specifically the iron ore industry, resulting in a reduction in the amount of collected samples. Relying on the physics of neutrons and gamma photons, both of which are particles that penetrate the surrounding bedrock through several tens of centimetres, such spectroscopy tools measure in real-time the composition of a much larger volume than the delimited volume of the drilled material traditionally used for geochemical mapping. Better statistics and reliability of the estimated composition increase the ability to properly and quickly measure drilled holes and allow the substituting of all or part of the sampling and assaying efforts by geochemical log data. Our paper focuses on this technology, known as pulsed fast and thermal neutron analysis (PFTNA). It reviews the main drivers for the design of such a logging tool and discusses how the fundamental characteristics of the technology, in terms of neutrons and gamma interactions, translate into interpretation of the analytical output.CITATION:Jeanneau, P, Flahaut, V and Maddever, R A M, 2017. Iron ore benefits from neutron pulsed geochemical tools, in Proceedings Iron Ore 2017, pp 387–396 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By Benjamin W. Haynes

This Bureau of Mines publication comprises a compilation of the state of the science in Pacific Ocean manganese nodule mineralogy and elermental composition. The report is divided into three sections: morphology, mineralogy and elemental composition. The nodule morphology section defines what is considered a nodule for the study, and details the external characteristics and internal structure. Nodule mineralogy is discussed in three sections: manganese minerals, iron oxide minerals, and accessory minerals. The major manganese minerals discussed are todorokite, birnessite, and vernadite. The iron oxide minerals are less well known and include feroxyhyte, goethite, and lepidocrocite. Accessory minerals present include quartz, clays, and other silicates and nonsilicates. A discussion on moisture content is also included. The elemental composition section presents data on 74 elements occurring as cations or anions. Summary data, histograms, and interelement correlation coefficients are presented. The elements are grouped as follows: major and minor elements of potential economic interest (8), other major and minor elements (9), elements of environmental interest (8), rare-earth elements (15), precious-metal-group elements (6), radioactive elements (3), other trace elements (17), and anion-forming elements (8). Cross sectional determinations of Ni, Cu, Zn, Co, Pb, Fe, Ce, and Ba are given for a single nodule to show the general tendency of different growth patterns within a nodule because of different element associations and composition.

Jan 1, 1982

By William W. Adams

The quarrying and related industries of the United States improved their safety record in 1938 by reducing their accident-frequency rate to a lower acid more favorable position than it has occupied at any time except 1935 since comparable accident statistics became available in 1916. The rates for 1935 and 1938 were identical. The number of men employed in 1938, although smaller than in 1936 and 1937, was larger than in any other year since 1930. Volume of employment, as measured by the number of man-hours worked in the industry as a; whole, likewise was larger than in any year since 1930 except 1936 and 1937. Reports from operating companies to the Bureau of Mines, United States Department of the Interior, showed that 77,497 men were employed in 1938, a decrease of 6,597 compared with 1937. This figure represents the average number of employees for the period during which the quarries and plants were active during the year, which in 1938 averaged 223 workdays per employee compared with 241 in 1937. A total of 17.3 million man-days or 133.8 million man-hours of work was shown for the industry as a whole, which indicated a weighted average of 7.75 hours per man-shift. Reports for 1937 showed a total of 158.3 million man-hours for the entire industry and an average workday of 7.81 hours. Accidents resulted in the death of 82 employees, 5 more than in 1937, and in 5,027 nonfatal injuries involving disability for more than the remainder of the day on which the injuries were received. The number of nonfatal injuries was 1,321 less than in 1937. As the number of deaths and injuries was reduced more, proportionately, than man-hours of employment, the accident-frequency rate per million man-hours of work declined, the rate for 1938 being 38.19 compared with 40.59 for 1937. In other words, accident occurrence to the average employee was 6 percent more favorable in 1938 than in 1937 on the basis of actual number of accidents and actual number of man-hours worked during the 2 years.

Jan 1, 1940

By P D. Kasbanis, Lyall Workman

"The energy output of an explosive is typically calculated using an equation of state and computerapplications. Results are reported as weight and bulk strength, either in absolute terms or relative toANFO. The effect of the equation of state selected and the assumptions regarding the energy calculation are considered and interpreted for the purpose of blast design. It appears that variations in the heat of detonation which result from the selection of the equation of state and parameters associated with it are not sufficient to significantly affect blast patterns, explosive consumption and costs. However variations stemming from the use of “available energy” associated with a cut-off pressure are significant, suggesting in many cases large pattern expansions. The validity of the various approaches is discussed and blast design results based on the energy calculated by the different approaches are presented and evaluated."

Jan 1, 1996

By John A. Cherry

Groundwater monitoring conducted at an acidic uranium-tailings impoundment in Wyoming and at one in Ontario indicate that at these unlined impoundments situated on unconfined sand aquifers, there exist well-developed plumes of contaminated groundwater. In the literature similar results are reported for three other unconfined aquifers at mill sites in Wyoming. The plumes extend for distances of several hundred to a few thousand metres from the impoundments. They have a zone of low pH beneath and adjacent to the impoundments and a larger zone of near-neutral pH that extends to the outer limits of the plume. The low-pH zones are generally small compared to the neutral-pH zones because the advance rate of the fronts of acidic tailings-derived water is slower than the average velocity of groundwater which controls the advance of the high pH zone. The retardation of the acid fronts is a result of geochemical reactions that cause hydrogen-ion consumption in a slowly-advancing neutralization zone. Within each of the plumes, the low-pH zone has high concentrations of transition metals, heavy metals and radionuclides. In the neutral-pH zones all of the metals and radionuclides occur at significantly lower concentrations and are generally at levels much below those specified in national drinking water standards. An exception at two of the Wyoming sites is uranium, which exists at levels close to the drinking water limit. A second exception is ferrous iron at the Ontario site, which occurs at high concentrations throughout most of the plume. The carbonate alkalinity at this site is much lower than at the Wyoming sites. The field data indicate that even in very permeable aquifers with a low content of silt and clay, there is normally a considerable capacity for acid-front retardation. To take advantage of this capacity to control contaminant movement in the design, operation and decommissioning of tailings impoundments, it is necessary to be able to predict the rate of acid-front movement. This predictive task has two primary components. The first is to identify the important flow paths from the tailings through the groundwater system and the second is to determine the degree of acid-front retardation that will occur as the tailings-derived water moves along these flow paths. Relative to these two tasks determination of the effects of hydrodynamic dispersion is generally of lesser importance and simple approximations that do not involve field or laboratory tests are probably adequate. In order to effectively apply the acid neutralization concept to the prediction of subsurface contaminant migration at uranium-mill tailings, improved representations of hydrogeochemical behavior of iron and aluminum in the neutralization zone and of the consumption of hydrogen ions through reactions with carbonate and aluminum-silicate minerals are required. Along with the hydrogen ions contained in the tailings water the ferrous iron represents a large potential source of acid but the extent to which ferrous iron converts to ferric iron to produce acid is problematic. Detailed hydrogeochemical evaluation of existing contaminant plumes and the performance of laboratory experiments under appropriate redox conditions ore prerequisites for the improvement of predictive models. However, the existing field and laboratory data provide a basis for preliminary predictions of contaminant migration from acidic uranium tailings impoundments.

Jan 1, 1982

By James J. Anthony

High-angle in-pit conveying is an idea that is being seriously studied by a number of important mining companies in North America. Its application in coal, iron ore, and copper mining is expected to reduce mine operating costs considerably compared with the conventional discontinuous methods, such as truck haulage, which are fuel, labor, and maintenance intensive. Therefore, a mine introducing high-angle in-pit conveyors will gain a competitive advantage over mines which continue to use conventional haulage. While the capital outlay for in-pit conveyor systems obviously varies depending on pit depth, the angle of incline, and the capacity required, it generally will not exceed that of truck haulage when all Factors are taken into consideration. These factors include the cost of excavation, as measured in relation to the volume of minerals mined, the cost of building truck ramps and roads, and the capital outlay for the trucks and maintenance facilities. In many cases, in Fact, the capital outlay will be less than for truck haulage. This cost advantage will best be realized by new mines, whereas in existing producing mines the switch from truck haulage may involve the abandonment of a substantial capital asset.

Jan 1, 1983