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By W. Joseph Schlitt, Donald B. Swanson

The paper provides an overview of the role that contract mining plays in the minerals industry. Particular emphasis is on contract mining and its place in the development and operation of small to medium sized precious metal mines in the western United States. The paper begins with a discussion of the mining options available to owners. This is followed by a description of contract mining organizations and the services they provide. In addition to various mining activities per se, these can include other processing functions such as crushing and agglomeration, various types of heavy civil construction, other types of technical and administrative support, and even assistance with financing. Typical equipment spreads and unit costs are presented. Final 1 y, the advantages and disadvantages of contract mining are discussed. Liberal use is made of

Jan 1, 1987

By Bobby J. Timmons

A few years ago during a Southeastern Geological Society field trip, a professor from a Florida university and a trip leader commented at one of the stops, "... and for those of you interested in the geology ...." More recently, in the spring of 1992, a geology faculty member at another southeastern university remarked, "Field geology is obsolete." An interviewee for a potential assistant position stated that he had never had a field class. This would-be assistant was to receive his Master's Degree in-Geology within a few days from yet another southeastern university. A regional illness? Certainly not, but symptomatic of the general health of Geology. Capitulation to Environmental Sciences seems to be in vogue with Geology becoming a four-letter word and the mention of mining is verboten regardless of the company. These trends permeate our profession while the demands for earth materials increase, often exponentially. Efficiency, a word lost on government, is routinely expected of business--our business--the industrial minerals geologist and producer. Our stage shrinks but the responsibilities expand. Are we meeting the challenge? Stay tuned!

Jan 1, 1995

By K. S. Eric Forssberg, T. V. Subrahmanyam

The present paper deals with the important technological developments in gold processing and where possible, the data is presented in the form of tables. Gold processing methods have evolved to such an extent that low grade and complex ores once considered uneconomic are now becoming viable. Constant efforts are underway to innovate technologies in order to improve the efficiencies and cut down the capital and operating costs. The methods are discussed.

Jan 1, 1988

By W. Petruk, D. B. Sikka

Lithium-bearing lepidolites from three deposits in the province of Goias, Brazil, were investigated to determine whether there is a correlution between the lithium content of the mineral and the color of lepidolite and associated tourmaline. Such a correlation can be a useful guide to field geologists for outlining high-grade lithium ore zones. It was found that mauve-pink lepidolite associated with pink tour-maline, and brownish lepidolite associated with black tourmaline have high lithium contents, but that the color of lepidolite is not due to lithium. The pink color of lepidolite and tourmaline is likely due to Mn3+, and the brownish tint of lepidolite and black color of tourmaline to Fe3+. Lepidolites appear to be lithium- rich when the lepidolite and associated tourmaline contain relatively high amounts of Mn3+ and/or Fe3+.

Jan 1, 1988

By R. K. Mehta, G. T. Adel

A review of the literature reveals that methods for simulating the coupled behavior of size reduction and liberation are limited to binary mineral systems containing one composite particle class. The aim of this paper is to describe the development of a mathematical model to simulate such behavior for binary and ternary systems containing multiple classes of composite particles. A modified Levenberg-Marquardt algorithm and a finite difference Jacobian are used in conjunction with the developed model and a set of constrained equations to estimate all kinetic parameters. This estimation scheme is validated far a binary ore (sphalerite-dolomite) with five composite particle classes using experimental data.

Jan 1, 1991

Energy Developments Ltd. (EDL) has developed power plants at two Australian coal mines that featuring 94 gas-fueled Caterpillar G3516 engine/generator sets. They will convert to electricity 145 kt/a (160,000 stpy) of coal-seam methane gas for sale to a local utility. The $100-million project will cut the sites' methane emissions in half, provide a low-cost energy source and offset mine operating costs. The project began in May 1995. It is located at the Appin and Tower longwall underground mines, 80 km (50 miles) south of Sydney in New South Wales. The installation is one of the first to capture coal-seam gas from mine ventilation air and gas drainage systems. Coal- seam gas contains 40% to 60% methane, which fluctuates constantly. The system is expected to convert 578,000 m3/d (20.4 million cu ft/d) of coal-seam gas to 94 MW. It will also reduce greenhouse gas emissions by 3.5 Mt/a (3.8 million stpy) of CO, equivalent emissions. The Appin and Tower mines each produce 2 Mtla (2.2 million stpy) of clean coking coal. They operate around the clock with about 400 workers per site. The mines are owned by BHP Steel, Collieries Division, which will share the revenues from energy sales. The Appin Power Partnership consists of EDL and Lend Lease Development Corp.

Jan 1, 1997

By Bern Klein, Richard W. Lawrence, Scott Frostad

A laboratory study was conducted to evaluate the effects of various kinetic test protocols on sulfate production, NP depletion and time to acidity. Six test protocols were evaluated including standard humidity cells, non-aerated cells, tall cells, shaken cells, simulated precipitation cells, and NP depletion columns. The study indicates that test protocols which disrupt the oxidizing environment, such as extreme wetting and drying cycles, shaking the cells, or the high addition of acidic water will create an unnatural environment that affect the results. Trickle leach and non-aerated test protocols create an oxidizing environment that more closely represents field conditions and are therefore recommended.

Jan 1, 2000

By Raj K. Singhal

This paper is a report on a task force study dealing with many facets of computerization. The primary mandate of the task force was to examine the software and hardware currently available for application relating to reserve estimation, mine planning, economic evaluation, equipment selection, production scheduling and composite mine simulation and to evaluate how adequately the software fulfills the user needs in surface mining of oil sands and coal. To meet its objectives the task force consulted extensively with the users, developers and suppliers of hardware and software. The paper outlines the approach taken by the task force to fulfill its mandate, summarizes its findings and presents some pointers which might be useful to others considering this type of evaluation.

Jan 1, 1986

Political events during the past decade have caused businesses throughout the world to think globally. Countries once closed to free market enterprises are now open and seeking out foreign investment to help improve the well being of their populations. The mining industry has always been a global one. Today, though, the industry has become even more global. The driving forces behind this include the opening up of higher grade, lower cost mineral deposits in undeveloped and developing nations. In addition, permitting delays in the United States, coupled with stricter environmental guidelines and a general anti-mining attitude, have forced the mining industry to look outside US borders. The Mineral Economics and Management Society (MEMS) took as the theme of its seventh annual professional program "Economic Globalization of the Mining Industry." About 100 people attended the conference held in Arlington, VA in late March. Speakers included members of the investment community, academia, government and the mining industry.

Jan 1, 1998

By Charles L. Karr

Researchers at the University of Alabama in cooperation with the U.S. Bureau of Mines have developed adaptive process control systems in which genetic algorithms (GAS) are used to augment fuzzy logic controllers (FLCs). GAS are search algorithms that rapidly locate near-optimum solutions to a wide spectrum of problems by mimicking the search procedures of natural genetics. FLCs are rule based systems that efficiently manipulate a problem environment by modeling the "rule-of-thumb" strategy used in human decision making. GAS and FLCs can be combined to produce powerful, efficient, and robust adaptive control systems. To perform efficiently, such control systems require a control element to manipulate the problem environment, an analysis element to recognize changes in the problem environment, and a learning element to adjust to the changes in the problem environment. I" this paper, the details of an ongoing research effort to develop and implement an adaptive process control system for a column flotation unit are discussed.

Jan 1, 1996

By Colin C. Harris, Jie Zheng

While applications of stirred media mills for fine particle production have continued to increase, there is a lack of understanding of operating behavior and power requirement. Investigations in laboratory stirred media mills have been carried out with grinding media, limestone and yttria stabilized zirconia. The torque required to rotate impellers immersed in dense particulate media with supernatant versus impeller rotational speed displays four regions marked by sharp transitions: transition from static to dynamic friction; channel- ling; dispersing; and centrifuging. Equations, including dimension- less group correlations of power and modified Reynolds number, for relating power, speed, impeller and tank dimensions and design, media size and density, solid concentration, and other relevant variables have been established. Scale-up guidelines with respect to power consumption are also proposed. The best operating conditions for grinding limestone in the laboratory stirred media mill have been identified. Complexation by the polymer during ultrafine grinding of zirconia has been found to cause extraction of yttrium into solution with possibly significant changes in the surface chemical composition of the product.

Jan 1, 1995

By Laurindo De Salles Leal Filho, Arthur Pinto Chaves

The Serrana Process was developed in the 60's to concentrate an igneous low grade phosphate/carbonate ore using tall oil as a collector and corn starch as a modifier in alkaline medium. Nowadays, although tall oil has already been substituted by a new amphoteric synthetic collector, starch hasn't been substituted yet. This study is an attempt towards understanding the role played by corn starch in this specific system. By means of bench scale flotation test, it was observed that corn starch was capable of promoting the flotation of apatite, phlogopite and dolomite. No effect over calcite was observed. The best efficiency of separation apatite/gangue minerals was yielded at the concentration ranges of 17 to 20 mg/l of starch and 13 to 17 mg/l of tall oil. The starch concentration showed a strong influence over the characteristics of the froth produced by the flotation tests, mainly over the volume of the froth and its mineralization.

Jan 1, 1993

By Robert L. Runkel, Kenneth E. Bencala, Briant A. Kimball, Katherine Walton-Day

The solute-transport model OTIS and the reactive solute-transport model OTEQ were used to simulate geochemical conditions in Cement Creek, a tributary to the Anirnas River in Colorado. OTIS was used to depict instream zinc concentrations, and to simulate the effects of two remediation scenarios on zinc concentrations at the mouth of Cement Creek. These simulations do not account for effects of changing stream pH on metal concentrations. Preliminary simulations using OTEQ to account for instream pH changes were unsuccessful due to the spatial nature of mixing processes, and insufficient information about the thermodynamic properties of precipitates forming in mixing zones.

Jan 1, 2000

By M. C. Roberts

To assess the future markets for a mineral from a producing district, the following three aspects must be considered: the future growth of the markets, the competitiveness of the district in terms of production costs and reserve adequacy, and the competition from alternative sources of supply. This paper focuses on the first issue by developing a method for predicting the demand for phosphate from trends in the major market for phosphate products, the fertilizer and agricultural market. The paper shows how broad changes in this end-use market for phosphate has evolved over time. These trends are then projected into the future to make an assessment of future phosphate requirements.

Jan 1, 2000

By D. J. McKee, D. M. Wiseman

The usefulness of simulation as a technique for metallurgical process design and optimization studies has been greatly extended over the last few years by the development of a number of general purpose simulation packages. The packages, or simulators, all have the common objective of presenting the mathematical models and simulation methods in a form which is readily usable by plant engineers and metallurgists. To date, most simulators have been concerned with steady state simulation, but packages capable of dynamic simulation are now becoming available. The paper outlines the essential features of versatile steady state and dynamic simulators. Typical applications are presented by considering examples of design and optimization studies. Limitation on the use of simulators are also presented.

Jan 1, 1991

By Yoginder P. Chugh, K. V. K. Prasad, R. Missavage

This paper presents results of field monitoring and finite element studies to analyze and improve a room-and-pillar retreat mining system. Fie1 d instrumentation was utilized to monitor pi11ar load changes, roof to floor convergence and differential roof strata movement as retreat mining progressed and to determine in-situ horizontal stresses. A two-dimensional finite element model depicting strata behavior at this mine was developed and used to analyze existing and alternate improved mining geometries. The results showed excellent correlation between fie1 d observed and model predicted behavior. Some of the recommended changes in mining geometry based on the study were incorporated in the mining system.

Jan 1, 1986

By K. Hanumantha Rao, K. S. E. Forssberg

The separation of feldspars from quartz has been the subject of numerous studies since 1930 and the flotation process so far proved to be the most suitable method. In the conventional process, feldspars are separated from quartz using a cationic collector and hydrofluoric acid as an activator of feldspars. There is no general agreement on the mechanism of fluoride activation of feldspar surfaces and the role of fluoride ions is briefly discussed. The use of HF is no longer acceptable due to environmental and health problems, and a few new reagents schemes have been reported. The available evidence shows that the success of these new reagent schemes is very limited. A new reagent scheme which is environmentally safe and cost effective for the separation of feldspars from quartz is yet to be resolved.

Jan 1, 1994

By J. Drelich, J. Pletka

Lost foam casting is a process in which a polymeric material is formed into the shape of the part to be cast. Parts that are more complex are fabricated by simply gluing several patterns together. The pattern is then coated with a refractory material consisting of a mineral mixture and binders. Finally, hot metal is poured into the pattern, evaporating the expanded polystyrene and taking the shape of the coating shell. Prior to casting, a significant number of the patterns are damaged and inevitably landfilled. In this study, a process was developed for the recovery of expanded polystyrene from the coating and glue contaminants. The process consists of shredding, impact comminution, size classification and pneumatic separation. It is successful in separating up to 97% of the contaminants, while recovering 95% of the polystyrene. Key words: Casting, Lost foam process, Expanded polystyrene recovery

Jan 1, 2003

By K. Hanumantha Rao, K. S. E. Forssberg, H. R. Manouchehri

The responses of calcite, feldspar and quartz minerals in a laboratory free-fall electrostatic separator after tribocharging with stainless steel, PVC and copper plates were investigated. The effects of H3BO3 and BaC12 chemical pretreatment on the electrical properties of the above minerals were examined. The changes in the electrical properties are discussed along with the determined charge, dielectric constant and electrical conductivity of the mineral samples. The electrical properties of the minerals and their responses to the electrical field during separation after tribocharging and chemical pretreatment are explored relative to the electrical behavior of the minerals.

Jan 1, 2000

By K. A. Natarajan

This paper deals with the various electro- and biochemical mechanisms involved in the bioleaching of multisulfide minerals such as those containing copper-lead-zinc and copper-nickel-iron. Galvanic series for sulfide minerals consisting of pyrite, chalcopyrite, galena, sphalerite, pentlundite, and pyrrhotite in an acid bacterial leaching system is illustrated, and the role of relative electrochemical activity on selective dissolution is discussed. Typical leaching results are shown to illustrate the practical applicability of galvanic effects in bioleaching of multisulfides. Attachment of Thiobacillus fewooxidans onto chalcopyrite and sphalerite mineral substrates is illustrated through scanning electron micrographs. The role of high-metal-tolerant, specially adapted strains in the leaching of multimetal concentrates is also outlined.

Jan 1, 1987