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Since gold was first discovered in Colorado in the late 1850s' mining has been a major part of the state's economic history, according to Stanley Dempsey, chairman and chief executive officer of Denver- based Royal Gold Inc. While the mining industry has seen some lean times throughout the past century, it has always bounced back. Today, dozens of major gold companies are headquartered in the Denver area. The state's coal mines produced record amounts during 1996. And even some of Colorado's uranium mines are resuming production. Dempsey joined other speakers in addressing the state of Colorado's mining industry during the Colorado Mining Association's (CMA) National Western Mining Conference. Some 800 people attended the CMA meeting, held Feb. 2-5 in Denver. The meeting was the association's 100th since it was incorporated in 1897.

Jan 1, 1997

By J. A. King, D. R. Weir, P. C. Robinson

Preconcentration of Porgera ore results in high recoveries of gold into gravity and flotation concentrates. The bulk of the gold is contained in auriferous pyrite flotation concentrate and is not readily recoverable by direct cyanidation. Oxidation in autoclaves at high pressure and temperature produces a residue that contains the gold in recoverable form. Pilot plant treatment of the autoclave residue is described, through washing and jarosite decomposition stages, to cyanide leaching and recovery of gold and silver by carbon-in-pulp techniques. The concern associated with disposal of plant effluents are also addressed.

Jan 1, 1987

By Kalliat T. Valsaraj, Louis J. Thibodeaux

A mathematical model is described for the transfer of hydrophobic compounds from aqueous to an immiscible organic phase using fine bubble aeration; the process otherwise known as "solvent sublation" an adsorptive bubble separation process. The limitations of the model are explored by simulating experimental results both for a batch scale process and a continuous process. The qualitative predictions of the model with respect to the influence of the organic layer (mineral oil) are tested by performing experiments using chloroform and 2,3,6-trichloroanisole as hydrophobic compounds in the aqueous phase. The continuous process is seen to be limited by the requirements of fine bubble generation and the ratio of influent feed rate to air flow rate.

Jan 1, 1989

By A. L. DeVegt, H. G. Bayer, C. J. Buisman

During the last ten years, Paques Inc. has been engaged in the development and installation of treatment systems to remove sulfur compounds from water and gaseous streams using biotechnological processes. Metal and sulfate can be removed from mine waters in two biological steps. In the first step, sulfate-reducing bacteria converts sulfate to hydrogen sulfide (H2S). The HS reacts with the dissolved metals to form insoluble metal sulfide precipitates. In the second step, sulfide-oxidizing bacteria convert excess H2S to elemental sulfur. The Budelco Zinc Refinery in The Netherlands installed a groundwater treatment system to remove metals and sulfate using the biological steps described above. The system has been operating since May 1992 and has been treating 5,000 m3/d (180 thousand cu ft/day). A pilot plant began operation in November 1995 at Kennecott's Bingham Canyon Utah copper mine to develop processes for metal and sulfate removal from groundwater and for the selective copper recovery from leach water. The principle of the biotechnological methods, the full-scale experience and an overview of the test program at the mine are presented

Jan 1, 1999

By D. R. Nagaraj

Literally thousands of new flotation agents, both collectors and modifiers, have been proposed for sulfide and non-sulfide flotation over the past six decades since the beginning of the use of soluble surfactants in flotation. In stark contrast, the number of flotation agents used in practice is small. Xanthates and fatly acids, along with a few well-recognized modifiers, dominate the industry. Three major questions will then arise: a) are there truly specific needs in the industry that call for chemistries that are different from those used currently ? b) if yes, given the track record in the industry, what is the likelihood that such different chemistries will ever be used and to what extent ? and c) is more research into developing new chemistries necessary ? A critical assessment of flotation agents in general is made in this paper to provide answers to these questions and to identify the major factors that are responsible for the large disparity that exists between flotation reagent research and commercial usage.

Jan 1, 1994

By P. Bevilacqua, G. Ferrara

The paper discusses the problem of accuracy in the determination of the partition curve of gravity separation processes, which is strongly affected by both the sharpness of separation of the density analysis system used and the width of the density range selected. The problem is important when the density analysis of the separation products cannot be performed using heavy liquids, but has to be performed using heavy suspensions or using other systems such magnetogravimetric separation. The imperfect separation given by these systems and the use of large density ranges lead to the determination of apparent partition curves instead of actual partition curves for the process. In the paper the relation between apparent and actual partition curves is studied under different conditions through a simulation program. For different input data, special diagrams are given which, once the apparent partition curves and the sharpness of the density cuts are known, allow calculation of the actual partition curves and the related parameters.

Jan 1, 1995

By D. Bizier, B. H. Gardner, Y. P. Wang, S. Serata

As part of an ongoing effort to develop more cost-effective and “user friendly” hardware for geomechanical measurements required for underground mine design, Serata Geomechanics, Inc. (SGI) has investigated the potential of borehole pressure cells (WCs) for in situ measurement of stress states and continuous monitoring of changes in ground stress. In particular, because of certain advantages gained thereby, WCs utilizing an elastomer, instead of metal (e.g., copper), for the skin of the pressure cell have been developed. A data analysis technique for determining ground stress state directly from BPC data has been developed. This technique has been tested for salt ground through both in situ applications and computer simulation analysis of the BPC/borehole boundary interaction. This paper discusses the data analysis technique, the results of field and computer simulation testing of its validity, and evaluates the advantages of elastomeric BPCs in relation thereto. It utilizes field data from recent elastomeric BPC applications in the salt mine at Goderich, Ontario operated by the Sifto Division of Damtarn Inc.

Jan 1, 1986

By L. R. Shotwell, C. F. Voss, R. J. Bastian

Pacific Northwest Laboratory (PNL) currently supports the U.S. Department of Energy's Office of Civilian Radioactive Waste Management in developing and evaluating analytical methods for assessing the suitability of sites for geologic disposal of high-level radioactive waste. The research includes consideration of hydrological, geomechanical , geochemical , and waste package components and the evaluation of the degree of coupling that can occur between two or more of these components. The PNL effort and those of other research groups investing potential waste sites in the U.S. and abroad are producing a suite of computer codes to analyze the long-term performace of the proposed repository sites. This paper summarizes the ongoing research in rock mechanics at PNL involving flow through jointed rock. The objective of this research is to develop a methodology for modeling the coupled mechanical-hydrological process of flow through joints and then attempt to validate a "simple" model using small -scale laboratory test data as a basis for judging whether the approach has merit. This paper discusses the laboratory tests being conducted to develop s joint behavioral constitutive model for the numerical method under development and the modeling approach being considered.

Jan 1, 1986

By Allen M. Newcome

The Ohio valley division of consolidation coal company has incorporated two new aspects within its coal mining concern. A new communication system, thru the cooperation of the c. & p. Telephone company, has been established in each of our mines with its central control in the general office building. In conjunction with this system, a Texas instruments 960 a computer has been incorporated into the system. The purpose for our computer is to provide modernization and improvement to our safety, production and maintenance programs. Thru proper use, the computer will help eliminate inaccuracies and inefficiences that have previously caused inaccurate analysis of problems. Due to federal requirements for more reliable communications in underground mines, Ohio valley division is making a concentrated effort to improve its communication systems. Systems such as the magneto phone and trolley phone have been looked at more critically. It was found that these systems are being used well beyond their limits. With these facts in mind, division personnel started looking for a system that would have these built in advantages: ease of maintenance and installation, increased reliability, low cost, and an inherent ability as a multiple use system.

Jan 1, 1975

By Marie-Antoinette Dziurla, Barrie Johnson, Åsa Kolmert

Acidophilic bacteria are well known for their role in accelerating the oxidative dissolution of sulfide minds, such as pyrite. Other acidophiles, however, are able to catalyze dissimilatory reductive reactions. Bacteria that reduce ferric iron to ferrous, and sulfate to sulfide, were isolated from ARD-impacted environments and immobilised onto porous beads made of recycled glass. Column bioreactors containing colonized beads were constructed and peacolated with synthetic and actual ARD, and evaluated for their capacities to promote iron or sulfate reduction, and pH amelioration. Iron reduction did not require strictly anoxic conditions in bioreactors, and rates of up to 800 mg Fe3+ reduced/(l*day) were achieved, with a conversion efficiency of up to 98%. Using mixed populations of acidophilic fungi and iron-reducing bacteria, the bioreactors were capable of promoting iron reduction using paper pulp as sole carbon and energy source. Reduction of sulfate in pack bed bioreactors was observed with acidic wastewaters of pH 3 and above, though average rates of 300 mg sulfate reduced/(l*/day) were less than those recorded for circum-neutral pH systems. Bioremediation of ferric iron-rich ARD was assessed using coupled iron-reducing and sulfate reducing bioreactors.

Jan 1, 2000

By P. R. Shivdasan, R. D. Hagni

Cathodoluminescence microscopy (CLM) is uniquely applicable to the study of carbonatite-related fluorspar ore deposits. The mineralogy of the carbonatites, sodic and potassic fenites, marbles, quartzites and fluorite ores are readily determined and characterized. Calcite, dolomite, apatite and fluorite were deposited dominantly under high-temperature conditions, and they exhibit strong cathodoluminescence (CL). At the Okorusu, Namibia, carbonatite complex and fluorspar mines, three types of carbonatites have been recognized by field mapping and laboratory CLM. The main carbonatite intrusion is fine grained and consists mainly of calcite. A later phase of pegmatitic carbonatite consists of calcite, magnetite, Fe-rich pyroxene, apatite and pyrochlore. Pyroxene carbonatites were recognized mainly through their study by CLM.

Jan 1, 2002

By Ian Longson, Darron W. Dixon

This paper describes the results of an investigation into the application of a statistical method for the prediction of general air-body methane concentration in longwall coal districts. An important and necessary part of the research was the acquisition of representative monitored mine environmental and coal production data. The monitored data was used to build time series models of general air body methane concentration, air velocity, barometric pressure, coal production and methane drainage variables of differing timescales according to the Box-Jenkins method of time series analysis. The univariate models were used to identify causal relationships between methane concentration and its explanatory variables. Coal production was found to be the dominant variable in the determination of the quantity of methane emitted and where appropriate, multivariate time series models were built in which expressions for methane concentration in terms of coal production were obtained. Finally, forecasts of methane concentration values were generated from the multivariate models to determine their forecasting capabilities.

Jan 1, 1993

By Thomas E. Krakowski

INTRODUCTION This paper presents a method of calculation of internal moments and thrusts in tunnel liners of any material. The method is intended for hand calculation, but as it is numerical in nature it can be programmed for use in computers. The information required for design or analysis is presumed active internal and external pressures, the effective moment of inertia and cross-sectional area of the tunnel liner, the liner's modulus of elasticity, and the coefficient of subgrade reaction of the material surrounding the tunnel. Starting with active external and internal pressures and following the procedure described herein using the structural properties of the liner and surrounding medium, external passive reactions and internal moments and thrusts are calculated. The method is intended for use by design engineers. GENERAL Experience has shown that flexible tunnel liners have less internal bending stresses than those calculated using classical structural theory applied to free-standing arches. In fact, liners which are very flexible in relation to the surrounding soil or rock have virtually no bending moments when compared to free-standing arches supporting equal active loads. In order for this phenomenon to occur, the original active pressure diagram must be "modified" by additional external reactions (passive pressures) from the surrounding material, so that the thrust line within the lining follows the centroid of the tunnel arch more closely than that of a similar free-standing arch. These passive pressures are reactions developed through outward deflection of the tunnel liner. Thus, the outward moving portions of a

Jan 1, 1979

By R. C. Kirkman

Your interesting and well-written paper brings up the issue of the purpose or use of a mineral property appraisal, specifically the value of these evaluations when the quality and quantity of the mineral resource to be exploited have not been thoroughly investigated. I am not a practicing professional in regards to valuation of limestone investment opportunities. I simply wish to make a few generic observations about the appraisal process in order to stimulate meaningful thinking by appraisal professionals whose reports may be reviewed by professional investors and "laypersons" alike. It is my contention that the analysis given in your paper is very thorough, considering the data that was made available to you. But I would not like to be the person responsible for investment decision making without having a feel for the risk involved. Therefore, the reviewer must classify this type of analysis as relatively "subjective" because they have not received an indication of the inherent risk involved in exploiting a mineral resource. This risk can best be quantified by using probabilistic methods in conjunction with the quality and quantity of the mineral to be produced. Most appraisals passively ignore this problem. Specifically, you have accurately identified the various costs and values entering the economic appraisal process. These can usually be quantified with a great deal more certainty than the capability of the resource to provide 25 years of quality material. Also, in Cases A (West Virginia) and B (Alabama), you are fortunate enough to have previous operations data. What if there had never been production from these properties? How does a potential mineral property investor evaluate the resource capability to meet various projected financial outcomes without spending a good deal of up-front capital to drill and delineate enough quality resources for a 20-plus year operation.

Jan 1, 1990

By Surendra K. Mishra

Metallic and oily components are the major contaminants of industrial wastes. Underground burial and incineration have been the commonly practiced methods of waste management. To provide a relatively more permanent solution, different processes have been developed. In addition to reviewing these processes, potential of using flotation as a process to treat hazardous metal and oil contaminated wastes is discussed in this paper.

Jan 1, 1989

By John Jonkman

Many companies in the mining and minerals processing industry are finding themselves in the transition stage from the Industrial Age to the Information Age and are trying to become prepared for the Knowledge Age. To remain competitive in the decades ahead, they are faced with integrating the enterprise through the use of computers and networks. This paper discusses some common human and organizational barriers to enter- prise integration. It proposes how to develop the organizational and human' networks to match the capabilities of the technical networks which are being' implemented. Ten practical considerations are then presented for consideration in the executive suite in addressing the human side of implementing the computer integrated enterprise.

Jan 1, 1989

By L. E. Krys, K. D. Harrison, C. G. Anderson

Since 1984, nitrogen-species catalyzed pressure leaching has been utilized at Sunshine Mining and Refining Company for the recovery of precious metals from a refractory sulfide concentrate. The process operates without the use of cyanide. The plant is now the only industrial-scale commercial application of this technology. Since the inception of the process, changes have been implemented to improve efficiencies and throughputs. Two of these changes, the replacement of nitric acid by sodium nitrite and a concentrate regrind, have recently been implemented. This paper discusses the development and potential mechanisms involved in these recently patented plant-process changes. A companion publication (Anderson et al., 1996) covers the plant integration and potential applicability of the technology.

Jan 1, 1997

By Por J. B. Evans

El mantener un beneficio óptimo sobre todo el conjunto de un emplazamiento minero necesita una constante puesta al día de las estrategias operativas. En esencia, cada estrategia es una combinación particular del gasto del capital previsto, el flujo de ingresos y el tiempo transcurrido. La selección de una estrategia basada en el beneficio potencial requiere que cada estrategia contemplada con un ordenador, un análisis tal puede ser engorroso. Este capítulo discute o desarrolla una técnica de "corte rápido" que asigna una relación de beneficio a las estrategias alternativas e identifica aquellos aspectos de una estrategia que producen mayor impacto sobre el beneficio. Esta técnica puede proporcionar valoraciones rápidas de suficiente precision para muchas de las decisiones de las estrategias operativas que se toman sobre la marcha en minas que se encuentran en explotación.

Jan 1, 1982

By Mortimer J. Richardson

Dredging can be traced to early times where it may have been derived by the Phoenicians prior to the 4th century B.C. The first tangible design drawings of a bucket ladder (BL) dredge can be found in the collections of Leonardo da Vinci (1452-1519), which he produced when he was attempting to create better methods of channel and port dredging. The perfection of the system did not commence until after the invention of the steam engine in the early 1800's; providing the impetus to progress from man-powered mud mills, horse drawn along polders or dikes in the Netherlands, England, France and Germany, to steam-driven. In the 1860's following the various gold rushes in the U.S., Australia, New Zealand, Siberia and South America, with placers in particular, efforts were begun to apply mechanization to achieve deeper digging. There is a recording of a dredge being installed to mine gold in Montana in the 1860's but did not include a processing system. Then in the 1880's in New Zealand, some practical engineers developed a system that is said to be the first bucket ladder mining (BL/M) dredge for mining gold placers. In studies of the New Zealand gold dredging experience, it is estimated that some 500 dredges were built to mine gold between the 1880's and 1942. A careful analysis of the data, however, shows that very few were profitable. The technology appeared to stagnate in the early part of the century. Two of the BL/M dredge design engineers left New

Jan 1, 1992

By Gerald H. Luttrell, Joe Shoniker, Jaisen N. Kohmuench, Christopher J. Barbee, Michael J. Mankosa

The HydroFloat technology was specifically developed to upgrade phosphate sands that are too coarse (>0.6 mm) to be efficiently recovered by conventional flotation methods. In this novel process, classified feed is suspended in a fluidized bed that has been aerated using an external sparging system. The air bubbles selectively attach to particles that have been made hydrophobic through the addition of a fatty acid collector. The teetering effect of the fluidized bed forces the low-density bubble-particle aggregates into the overflow, while hydrophilic particles are rejected as a high solids content underflow Since the HydroFloat is actually a density separator, the process can treat much coarser feeds than would be possible using traditional flotation processes. In addition, the high solids content of the teeter bed promotes bubble-particle attachment and reduces the cell volume required to achieve a given capacity. This paper presents test data from ongoing pilot-scale trials of the HydroFloat cell in the phosphate industry.

Jan 1, 2002