Search Documents

By C. L. Karr

The U.S. Bureau of Mines is currently investigating the use of genetic algorithms (GA's) for solving optimization problems. This computer search technique, based on the mechanics of natural genetics, was used to perform simple least squares curve fitting. Three examples are presented in which a GA manipulates binary coded strings to produce near-optimal solutions to least squares curve-fitting problems after having viewed only a small portion of the search space. The examples include fitting data to the equation of a line, the equation of a parabola, and the Ree-Eyring equation.

Jan 1, 1991

By Lyman G. J, Ka

The use of images to determine blast fragmentation is the only feasible technique when one does not want to disturb the production cycle. However, three major problems exist with the use of images. The first is determining real size from a two-dimensional particle, the second is estimating the fines which are missing due to image resolution and particle size range, and the third is proper sampling such that a statistical probability can be calculated for the distribution. Once these problems are resolved, the tedious process of digitizing images by hand may be automated. This paper describes the present techniques used at the JKMRC to "size" blast fragmentation, estimate the missing fines using the Rosin-Rammler equation, determine the sampling error using Gy's sampling equations, and extract the particles from an image using an IBM-AT computer.

Jan 1, 1990

By Ernesto Villaescusa, Andres Brzovic

Rock masses of the primary copper ore at the El Teniente Mine are very competent and massive. The rock mass contains almost no open discontinuities. Nevertheless, there is a high frequency network of small discontinuities coupled with widely spaced faults. A data collection campaign designed to characterize the rock structure was recently implemented. The results show that conventional analysis in terms of discontinuity frequency does not predict differences between two studied sectors. However, when an empirical definition of a weak discontinuity is applied, appreciable differences between the two sectors appear in terms of discontinuity frequency and predicted in situ block size distributions. These differences are in accordance with actual observations at the mine site. Due to the geological features of the primary copper ore, rock mass classification schemes cannot be readily applied to characterize these rock masses.

Jan 5, 2007

By Allan E. Martin, George Glocker, C. E. Wood

"INTRODUCTION As part of a comprehensive investigation of the mechanism of defurization of iron and steel by slags, the Blast Furnace Studies Section, Metallurgical Division, Bureau of Mines, in cooperation with the Institute of Technology, University of Minnesota, has made a study of the forms in which sulfur occurs in blast-furnace slag. This report presents data on the three sulfides most important in iron smelting, namely, ferrous sulfide, manganous sulfide, and calcium sulfide. The tendency of these sulfides to form colloids in the molten slag was determined by an examination of quenched samples with an ultramicroscope.Vogt/ conducted experiments on sulfide silicate melts and examined synthetic blast-furnace slags in a partly crystallized condition. His conclusions were that FeS, CaS, and MnS, or isomorphous compounds, such as (FexCay)S and (MnxCaa)S, were precipitated from the melt, depending on the composition of the slag. In all specimens sulfides were visible and were spherical.Coloration of glass by sulfur also provides indirect information on the nature of sulfur in blast-furnace slags./ There seems to be a general agreement at present among the workers in the field of colored glasses that ferrous sulfide is a strong color producer. Colors that have been attributed to this compound include yellow, orange, brown, blue, and black. Apparently the ferrous sulfide is considered to be dissolved in these glasses. There is no indication that any of them have been examined for a colloidal phase.Lorenz 7/ investigated a single manganese slag in the glassy state and observed a Tyndall beam in an ultramicroscope. His conclusion was that either a manganese compound had precipitated in a finely divided condition or that metallic manganese had volatilized and penetrated into the slag as a vapor and thus formed colloidal particles."

Feb 1, 1941

By Alexander Filotti, Richard Kalson

"1. INTRODUCTION- WHAT IS P3 OR PPP ?The Public Private Partnership (PPP or 3P) is a project delivery scheme based on the government providing land and/or a concession agreement, and on a private entity providing the design, construction, financing, operation and maintenance of the project for an extensive duration of time (up to thirty years). At the end of the operation-maintenance period, the project is turned over to the public entity, which fully owns the project at all times. While there are many PPP delivery schemes used around the world, for the present paper, we are going to analyze the impact of the Design-Build-Finance-Operate-Maintain (DBFOM) scheme on the deep foundation specialty subcontractor. There are couple of reasons that the PPP delivery system started to be used and implemented not only by developed nations (e.g. United Kingdom, USA etc.), but also by the International Development Bank for delivering major infrastructure projects in developing nations. From the point of view of government agencies, some of the reasons to use PPP are the following:??The primary use of private capital in an era where borrowing and/or supplemental taxation represents too much of a political risk. Budget deficits and taxation limits are extremely hot topics in every election (national or local) and the level of education of the electorate in this area is making it more and more difficult for politicians to use borrowed funds and additional taxation finance sources for public projects. At the same time, we see an increase in the social expenditures of the government in parallel with a needed increase in expenditures on infrastructure due to aging and neglect.??Bundling the construction risks with the operational and maintenance risks naturally pushes the private entity to increase the level of innovation and communications in the primary phase ( the construction phase) in order to develop future process based upon the innovation and communications utilized in the operation and maintenance phase of the project. This is true if contractual incentives are properly structured because “all revolves around incentives. In a world of ‘incomplete’ contracts, where it is difficult to foresee and contract about uncertain future events, it is important to get the incentive structure right” (Grimsey and Lewis, 2004).??The transfer of very expensive risks such as differing site conditions, schedule, design, construction, maintenance and operation costs from the public authority to the private entity.??The timespan of development and construction of a PPP project is usually shorter than the traditional procurement process (e.g. “ the I-595 P3 provided capacity improvements fifteen years sooner than a conventional plan would have offered. In Maryland, an innovative expansion of the Seagirt Marine Terminal in the Port of Baltimore was completed two years ahead of schedule due to the P3 model. As a result, the Port of Baltimore is only the second port on the US East Coast to have unrestricted access to both a fully functioning 50-foot channel and 50-foot berth.”)"

Jan 1, 2017

By C. M. Jones

Cyprus Sierrita Corp. has developed a training program that has led to several significant improvements in safety performance and productivity. Truck productivity has increased 6% as measured by truck cycle times. Increased skill levels and awareness on the part of the mine's operators are due to the new training effort. Costs associated with productivity training have been about $185,300. This includes program development and execution costs, as well as lost productivity during the training itself. These costs are offset by $1.9 million in savings attributable to the increased skill levels of technicians due to the training effort. Cyprus Sierrita is a subsidiary of Cyprus Amax of Englewood, CO. The company operates a copper and molybdenum mining and processing facility south of Tucson, AZ, near the town of Green Valley. The Cyprus Sierrita operation produces about 109 kt/a (240 million lbs/ year) of copper, 11.3 kt/a (25 million lbs/year) of molybdenum, 31.1 t/a (1 million oz/year) of silver and 1.8 t/a (4,000 lbs/year) of rhenium. The opera¬tion employs 770 people at the site. About 200 of these employees work in the mine operations. Mining at Sierrita uses standard open-pit techniques. Crews of 43 people rotate on 12-hour shifts. Hourly technicians are nonunion and do not use rigid job classifications to define pay. Rather, the system is designed to pay employees for what they are able to do. Administering this effort requires that training opportunities are provided to those people who desire them. Successful training opportunities al¬low people to gain skills. The more skills an employee can demonstrate, the higher his or her "tech level." A technician's pay is commensurate with his or her tech level. Much of Sierrita's training in past years concentrated on building basic

Jan 1, 1998

By Maurice Hall Haycock

ONE result of the higher price of gold has been the exploitation of many low-grade deposits, the successful treatment of which depends upon obtaining high recovery of the contained gold. Modern methods have made it possible to recover gold from many ores formerly regarded as impossible to treat economically, but in order to apply these methods efficiently it has become desirable, and indeed in many cases indispensable, to gain precise information concerning their mineralogical and physical character. The most successful means of doing this is the use of the reflecting microscope. Reflecting microscopes had long been employed by metallurgists for studying polished surfaces of iron and steel when, thirty years ago, Dr. W. Campbell, of Columbia University, advanced the idea of using similar methods for studying opaque minerals (1). The immediate result was the completion of two microscopic studies, the first on Cobalt silver ores (2) and the second on Sudbury nickel ores (3). The idea was surprisingly slow in being adopted, and not until 1911 did it begin to spread through the universities of this continent. From then on, ore microscopy, or 'mineragraphy', made rapid progress, and, during the next fifteen years, research in universities of North America and Europe led to the development of somewhat specialized apparatus and technique. This phase of development, which resulted largely in contributions of a descriptive nature, furnished a mass of data from which the possibility of economic applications was soon recognized. Ore microscopy became an aid to the mining geologist in solving many problems of ore deposition. This soon led to its application in the study of ores and mill products in connection with their treatment. Its usefulness in this latter field has been very marked and has led to its widespread adoption by the mining industry.

Jan 1, 1937

By M. S. Moats

Galvanic stripping, in conjunction with solvent extraction, has been proposed as a technical option to the challenging problem of iron removal in certain hydrometallurgical processes. The galvanic stripping process is based on the ability of a solid metal to directly reduce ferric ion to the ferrous state in an organic media. Stripping the iron into the aqueous phase is then easily accomplished. Previous work has shown the reaction kinetics and efficiency are affected by such operating parameters as water and oxygen contents, temperature, time and metal reductant. In this study, the optimum operating range for some of these variables was determined. Both zinc and iron metal were used in the separate stripping of iron from D2EHP A. Reasons for the differences in the extent of the reaction obtained using the various conditions are discussed.

Jan 1, 1996

By C. Overton, R. W. Nice

"With todays economic trials and tribulations we have all become deeply engaged in costs and cost cutting in our field of mineral processing. Grinding is one of the most expensive unit operations. The cost of grinding media is the most expensive item in grinding costs. Therefore, it is only reasonable to attack the cost-cutting area by trying to reduce the consumption of media. This introduces the field of autogenous or rock-on-rock grinding.Rock-on-rock grinding is not new to us. It has been known for many decades;The South Africans used pebble grinding in the '20's for gold.Mr. B. Crocker was prompted for the same reasons to introduce pebble grinding at Lakeshore Mines in Kirkland Lake during the last war.The Buffalo Anchorite used beach pebbles in grinding prior to the war.Autogenous and semi-autogenous grinding is used quite successfully in the iron ore field. Base metals have their examples in Australia at Caba, in Africa at Komato and in Sweden at Aitik.Recently three mills in British Columbia and one in Arizona started with autogenous mills in their circuits. One was originally conceived to utilize a modified autogenous grind with a crusher in the circuit. All except the same mill had contingency plans for converting to semi-autogenous. All four mills have since converted to the semi-autogenous mode. These are Island Copper, Lornex, and Similkameen in B.C. and Pima Mining in Arizona."

Jan 1, 1975

By John D. Sullivan

In leaching copper ores knowledge of the rate of dissolution of the copper minerals and of the impurities is desirable. With knowledge of these two factors and data as to what minerals are present in the ore the metallurgist has an excellent start on planning a leach¬ing cycle to fit that ore. The rate of dissolution is rather difficult to predict, and the time required to leach a given ore may differ markedly from that required by another ore. The whole study as related to mixed oxidized and sulphide ores is one of relative rates of dissolution of the different copper minerals and the impurities in sulphuric acid and in ferric sulphate. The aim of leaching is to choose a cycle and strength of solvents to ex¬tract a maximum amount of copper and a minimum of impurities. The consumption of reagents per unit of copper dissolved is a function of the strength of the reagents used and the relative rates of attack on copper minerals and impurities. An opportunity may exist of ob¬taining the kind of electrolyte wanted for electrolytic precipitation and yet of saving on the consumption of reagents by modifying the strength of ferric sulphate and of sulphuric acid during the cycle to fit the time needed for dissolving the sulphide and oxidized minerals present. Former papers have considered the rate of dissolution of azurite, malachite, tenorite, chrysocolla, cuprite, chalcocite, boruite, and covellite in common leaching solvents. A paper soon to be written will consider some of the less important copper minerals. The present paper considers the rate of dissolution of copper from ores of the Southwest in sulphuric acid of varying strength and the ratio of sulphuric acid consumed to copper dis¬solved. In this study two ores containing the copper principally in an oxidized condition were used. A study of other ores, especially those containing high percentages of sulphide copper minerals, would be desirable, but since consumption of acid has paramount interest,

Jan 1, 1931

By C. G. Anderson

Historically, the treatment of orebodies for recovery of valuable constituents presents many processing challenges. In a time of heightened environmental awareness, the constraints placed on processing complex orebodies are becoming more and more pronounced. As such, established technologies are limited in their ability to fill the needs of these emerging sources of raw materials. A prime example of this is in processing PGMs from primary sources. Normally, this type of material is found in a nickel-copper-iron sulfide matrix. Typically, these materials are processed by established pyrometallurgical means. However, other options should be considered. Hydrometallurgical processes are available which offer advantages over pyrometallurgical methods. One of these is the nitrogen species catalyzed sulfuric acid pressure leach used industrially by Sunshine Mining and Refining Company. In 1990, laboratory work was undertaken in cooperation with Stillwater Mining Company to test PGM matte materials from the Columbus, Montana smelter. The initial results were very positive, and they led to a design to recover PGMs in a high grade residue and to recover nickel and copper as valuable products. Handling the iron and other wastes in an environmentally safe manner was also successfully investigated.

Jan 1, 1995

By David A. Lindsey

In this paper, we present a physiographic classification of gravel deposits, identify some field measures of aggregate quality, and describe sampling strategies for mapping aggregate quality in the Front Range Urban Corridor of Colorado. Gravel occurs in four types of deposits along the Front Range of Colorado: (1) piedmont alluvial fans, (2) high dissected terraces, (3) high (continuous) terraces, and (4) floodplains and low terraces. The four deposit types are the basis for definition of gravel-deposit models, which differ in geologic environment, deposit characteristics, deposit size, environmental impacts of mining, and post-mining use. Of the four types, floodplains and low-terrace deposits have been exploited most for gravel. High terraces also have been mined. Deposits of high dissected terraces and dissected alluvial fans have produced minor amounts of gravel, mostly for use as local fill. Studies to identify useful field measures of aggregate quality and to determine the appropriate scale for sampling were conducted on gravel deposits beneath the flood-plain and low terraces of the South Platte River north of Denver and the Cache la Poudre River between Ft. Collins and Greeley. Gravel deposits of the South Platte were selected for study because they represent the last major resource of gravel for aggregate in the Denver metropolitan area. The Cache la Poudre valley is the primary source of gravel aggregate for rapidly urbanizing areas around Ft. Collins and Greeley. Of all the field measures of gravel quality, the most important is particle size. Various parameters that measure particle size were investigated, but the easiest to determine, and the most useful to the aggregate industry, are measures of the proportion of coarse sizes. Particle size varies widely in gravels of the urban corridor. Gravel lithology, particularly the presence of deleterious particles such as reactive volcanic rocks and decomposed rocks, must be determined to assess aggregate quality. Studies of South Platte and Cache la Poudre gravels have not revealed large proportions of deleterious lithologies. Studies of particle shape revealed only small numbers of physically weak shapes in both the South Platte and Cache la Poudre gravels. Particle shape does not appear to vary from place to place in the gravels. Rounding, or the ab¬sence of angular corners, may play a role in the tendency of loose gravel to yield under load. South Platte and Cache la Poudre gravels are rounded, and rounding tends to increase upstream. Before the quality of gravel in a valley can be assessed, the stratigraphy of the gravel must be known because it affects sample design. If only a single gravel layer is to be studied, only the thickness of the gravel must be known before sampling. If, however, more than one layer of gravel-distinguished by particle size, sorting, or lithology-is present, sampling must take into account the thickness and distribution of each layer. For example, three gravel layers of different particle size underlie the floodplain and low terraces of the South Platte. The tributary Cache la Poudre, on the other hand, contains gravel layers that can be distinguished only locally and vary slightly in particle size. Sampling experiments were conducted on gravel bars in the South Platte River and in gravel pits on the floodplain and low terraces of the South Platte and Cache la Poudre Rivers. Experimental results indicate that, even where sample error is large, regional and stratigraphic variation may be measured if it is large relative to sample error. Using vertical trench samples weighing an average of 40-90 pounds, down-stream decrease in coarse particle size was mapped for Cache la Poudre gravel, and differences among superposed gravel beds were measured for South Platte gravel.

Jan 1, 1999

By Donald W. Gentry

Introduction The mining industry is perhaps best characterized by the numerous and abnormally high risks associated with the business of mining and by its most basic assets - ore deposits, people and technology. At the most fundamental level, it is the quality and effective utilization of these basic assets that determine a mining company's ability to compete efficiently in the international market place. The gold industry has received much attention in recent years and especially in recent months, for good reason. This commodity serves as an excellent platform for the subsequent discussion of these three basic assets and their role in mining's future. Facets of the gold industry The fate of this noble metal in recent times illustrates some of the various risks associated with the mining industry and the importance of high-quality assets, whether they be ore deposits, people or technologies. The following comments pertaining to the gold industry help place proper focus on subsequent discussions. All monetary amounts given are in US dollars. Throughout 1997, falling gold prices broke record after record: first hitting three-year lows, then a 12-year low in July and finally an 18-year low at year's end. From Jan. 1 through Dec. 31, 1997, the price of gold fell by more than $2.57/g ($80/oz), or some 22%. The decline in gold-mining profitability and stock prices was even more dramatic. At the beginning of 1997, the 20 largest gold producers in North America had a market capitalization of approximately $44.5 billion. At year's end, this market cap had fallen to $26.2 billion, a reduction of 41%. The total market cap of all the world's gold companies fell from $71 billion to $46 billion, a 35% drop (Serwer, 1998). Analyses suggest that, at a spot gold price of $9.65/g ($300/oz), only one, or possibly two, North American gold-producing companies can make money when break-even or "total costs of production" are considered. While strong hedge positions mitigate this situation in the short term, clearly, this is an industry in desperate straits. For example, write-downs for North American producers in 1997 were approximately $2.5 billion. Speculative short positions in 1997 were near historical record highs and generally exceeded long positions by factors of 9:1 or 10:1. Much of this is driven by some US commercial banks, hedge fund managers and commodity speculators who can significantly move gold prices sharply over short periods of time by selling gold they do not own in the expectation they can buy it back at a lower price before they have to deliver. These signifcant short positions are likely to continue as long as central banks are willing to sell or loan gold to financial institutions that in turn make the gold available to speculators who hope to capitalize on price fluctuations. The Far East accounts for approximately 26% of the annual demand for gold. Including India, the region accounts for 43% of total demand. More than 85% of the physical demand for gold is for investment jewelry in Asia and the Middle East. This demand is extraordinarily price sensitive. The fairly recent turmoil in Asian markets and economies, combined with currency devaluations throughout the region, have made gold more expensive (30% to 50% in local currencies) for those peoples most likely to treat gold as a safe investment haven. Higher interest rates also have reduced the amount of money they have to spend on consumer goods such as jewelry. All of these recent Asian events are deflationary in nature. Deflation, if coincident with rising unemployment, could result in significant dishoarding of gold. There is one key fact to remember when analyzing

Jan 1, 1999

By Gang Ren, Behrooz Ghabraie

"Observational data suggest that the ground surface subsidence profile from multiple-seam longwall mining is rather different from that of single seam. Despite the increase of coal production from multiple-seam mining, available predictive methods are mostly unable to predict a reliable subsidence profile for multiple-seam extractions. In this paper, a case study of multiple-seam subsidence is modelled using physical modelling techniques. The subsidence mechanism as revealed in the physical model is explained and the differences between multiple and single-seam subsidence are highlighted. On the same case study, a commonly used influence function method (IFM) and Generalised Influence Function Method (GIFM) are utilised to predict the subsidence profile. The results are compared with predictions achieved by a newly developed predictive method based on the understanding of mechanism of the multiple-seam subsidence. Results show a significantly improved correlation between the newly developed method in comparison with the conventional IFM and GIFM. INTRODUCTIONField observations and subsidence monitoring data from multiple-seam coal mining cases show a different subsidence profile as compared with single-seam ones (Sheorey et al., 2000; Li, et al, 2007; Luo and Qiu, 2012; Unlu et al, 2013). The multiple-seam subsidence curve is generally deeper and steeper than of single-seam cases, and varies from one mining configuration to another. Various researchers had made efforts to understand the mechanism behind this phenomenon and the interaction between the two mining horizons (Li et al., 2010, Sui et al., 2014; Zhang et al., 2014). However, the mechanism of the multiple-seam subsidence is yet to be comprehensively understood (Suchowerska, 2014; Ghabraie et al., 2015b).In addition, differences between the single and multiple-seam subsidence profiles make it difficult to adapt single-seam subsidence prediction tools for predicting the subsidence over multiple-seam cases, unless significant modifications are applied This requires understanding the mechanism of the multiple-seam subsidence as the first step to achieve reliable predictive results.The mechanism of the subsidence due to a multiple-seam case study can be investigated via physical modelling. The physical model allows observing the substrata movement as well as the interaction of the two mining activities. An understanding of the mechanism of the multiple-seam subsidence can be developed based on these observations, which would provide basis for developing a subsidence prediction tool."

Jan 1, 2016

By John D. Sullivan

In leaching copper ores knowledge of the rate of dissolution of the copper minerals and of the impurities is desirable. With knowledge of these two factors and data as to what minerals are present in the ore the metallurgist has an excellent start on planning a leaching cycle to fit that ore. The rate of dissolution is rather difficult to predict, and the time required to leach a given ore may differ markedly from that required by another ore. The whole study as related to mixed oxidized and sulphide ores is one of relative rates of dissolution of the different copper minerals and the impurities in sulphuric aoid and in ferric sulphate. The aim of leaching is to choose a cycle and strength of solvents to extract a maximum amount of copper and a minimum of impurities. The consumption of reagents per unit of copper dissolved is a function of the strength of the reagents used and the relative rates of attack on copper minerals and impurities. An opportunity may exist of obtaining the kind of electrolyte wanted for electrolytic precipitation and yet of saving on the consumption of reagents by modifying the strength of ferric sulphate and of sulphuric acid during the cycle to fit the time needed for dissolving the sulphide and oxidized minerals present.

Jan 1, 1931

By H. W. Hitzrot

*Original Pages Missing From Book

Jan 5, 1954

By Warren Weaver

Some of the advantages of the inductive method of electrical prospecting were emphasized in a paper by Dr. Max Mason. Since this emphasis was misunderstood by some to indicate a too exclusive interest in inductive methods, we are especially happy to help correct this impression by reporting on some of our work on surface potential methods. Earth Currents and Surface Potentials When two electrodes, A and B, are placed on the surface of the ground a distance d apart, and a 100-volt battery is connected across the elec- trodes, current flows from the positive electrode A to the negative electrode B. The current does not pass directly from A to B along the straight line joining these two points. In fact, a negligible amount of the total current chooses this direct path, and the flow actually takes place

Jan 1, 1929

By G. O. Crowell

This paper gives the history of the celestite deposit, now being mined by Kaiser Celestite Mining Ltd., near Sydney, Nova Scotia. Mining and milling procedures are covered, and the regional and local geology of the area are described, including the origin of the celestite.

Jan 1, 1971

By S. C. Suboleski

In a high risk venture such as mining where capital is committed and contracts are signed on the minimum of information, decisions are based primarily on production forecasts derived through consideration of such factors as management-labor relations, mining practice, variations in physical conditions and the equipment applied. Among these factors, the physical conditions offer the least opportunity for control and, due to the wide range of mining conditions that may be experienced, little effort has been made to develop objective methods for measuring their effects on mine out- put. The aim of this paper is to demonstrate a method for assessing these relationships that can be applied under a wide range of conditions both in new mines and in working sections where there is a need to determine the impact of proposed operational modifications. psing empirical data from active underground mines, a mathematical model was developed to derive a set of regression equations for predicting production as a function of mining conditions

Jan 1, 1980

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Jan 1, 1918