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By S. A. Diatchkov

Introduction There is a misconception that mineral-project economic evaluations in the former Soviet Union are either nonexistent or very limited. This is not the case. In fact, there are at least two basic methods that can be utilized to evaluate the vast mineral resources of the Commonwealth of Independent States (CIS). Evaluation procedures are based either on a comparison to known projects, which may rely on limited available data, or on potential-profit calculations, which generally uses more extensive databases. Significant philosophical differences between these systems and those utilized in the Western world include the following: •Under the centralized-government system, the economic evaluation of a mineral project was based on artificially determined mineral prices and costs. Every ten to 12 years, prices for concentrates and metals were established by the Council of Ministers and remained unchanged until the next reconsideration of prices . •The time value of invested money was not considered to be important under these "stable" prices, and inflation was assumed to be nonexistent in the planned economy. •An overestimation of the value of social and economic factors such as keeping the local population employed and providing the country with strategic minerals biased the economic evaluations of projects. Sequence of exploration Geological exploration in the CIS countries typically includes two major phases: prospecting and exploration. Prospecting consists of the following: •Regional geological studies. •General prospecting. •Prospecting. •Prospect evaluation. Regional geological studies are conducted within large territories and utilize satellite images, deep seismic zoning and other state-of-the-art methods. Geological and geophysical maps on a scale of from 1:200000 to 1:1000000 are developed to help identify regional anomalies and mineral prospective areas. The areas of primary interest are then subjected to general prospecting, beginning with geological mapping of the area at 1:50000 (1:25000) scale. The prospecting phase determines mineral potential based on further geological mapping (mostly 1:10000 scale), surface geophysics and geochemistry. Finally, the most attractive targets are subjected to further detailed evaluation (prospect evaluation) to help identify "possible" projects by means of trenching and wide-spaced drilling. The results of the prospect evaluation are analyzed and conclusions regarding the economical potential of the project are drawn. If the initial-prospecting phase results are positive and the prospect is recognized as economical, it then moves into preliminary exploration, which is followed by detailed exploration. Preliminary exploration determines the feasibility of the project on the basis of limited data. For example, in some underground projects, the initial exploration drilling and tunneling is done at two or three times wider spacing than would be required by the assumed mining method. Detailed exploration focuses on preparing the project for mining development, such as completing drilling and tunneling, particularly in the portion of the ore body to be first mined. During the project's mining phase, further exploration is usually conducted along the flanks of the mineralized structures and deeper sections of the ore body. Finally, during exploitation, it is sometimes necessary to delineate the ore body within the mining-block limits. A comparison between the United States (US) sequence of exploration activities and the CIS system is given in the Table 1. There is no "additional" and "exploitation" exploration shown in the US system, but it is common knowledge that all mineral projects are subjected to "additional" and "exploitation" exploration while being mined. An economic evaluation should be performed after the [ ]

Jan 1, 1996

By M. G. Karfakis, K. P. Chong

Determination of fracture toughness using the semi-circular specimen, the chevron edge notch round specimen, the short rod specimen and the cylindrical burst specimen, are critically reviewed. These methods, among all, are the most applicable for fracture toughness determination of rocks. They require minimum machining. Samples are small, and testing procedures are simple. They have a sound analytical basis and allow the fracture toughness to be determined without measurement of fracture length.

Jan 1, 1986

By André Vervoort

The roof behaviour in room and pillar panels during the development of roadways and the subsequent pillar extraction was monitored underground and numerical simulations were conducted. For several underground sites, a satisfactory, correlation was found between underground measurements and three-dimensional numerical simulations using a boundary element code in the linear elastic domain. However, to simulate bed separation, and roof block collapses more complex models were required, of which examples are presented.

Jan 1, 1992

By D. M. Wyslouzil

Conditioning, in the conventional sense, means providing sufficient agitation and contact time for the reagents to react with the minerals in the ground ore. High intensity conditioning (HIC) on the other hand, as described in this paper, recognizes the need to exceed this minimum power input over a suitable length of time to induce aggregation of the finest size fraction. Time alone is not sufficient to achieve aggregation. The threshold minimum power input, kW/m3, depends on many surface properties of the fine particles and can vary considerably. In addition, the mechanical aspects and the chemical conditions must be matched to achieve good aggregation. Treatment of complex sulphide ores, requiring fine grinding for liberation, offers a large field for the application of HIC. Improved flotation rates and enhanced selectivity are some of the benefits that can be expected. This unit operation has now reached the level of commercial application. Lakefield Research considered HIC not from a fundamental point of view but as a means of solving difficult mineral processing situations arising in actual operating plants. This paper summarizes the effects of the various chemical reagent combinations that had been applied to promote faster, more selective flotation, higher mineral recoveries and cleaner separations, using HIC.

Jan 1, 1995

By W. H. B. Blackburn, D. M. S. Bhatia

Twenty-six in situ analyses of cubic galena crystals from a Mississippi Valley-type deposit were undertaken with a laser microprobe emission spectrograph to study the variation of nine trace elements from the crystal center to its periphery, both along the diagonal and vertical. The general trend is an outward increase in the concentrations of Ag, Ga, Ge and In, with As showing the opposite trend. Bi, Cd and Sn showed no discernable trends. Sb was not detected. These variation patterns may serve as a model for similar studies of other Mississippi Valley-type deposits.

Jan 1, 1987

By Jan Leja

Surfaces of metal sulfides react readily with selected constituents of environment. Two types of reaction products may form: (1) primary, chemisorbed and hydrophobic surface products or primary hydrophilic surface products, and (2) secondary reaction products -- produced during continued oxidation-reduction processes. For flotation, the chemisorbed surface product and the secondary reaction products, elemental sulfur or metal xanthates, must provide sufficient hydrophobicity of the surface to ensure particle-bubble attachment.

Jan 1, 1986

By G. Bhaskar Raju, S. Prabhakar

The amenability of column flotation for the beneficiation of fluorspar was investigated, and the overall performance of the column, flotation was compared to the performance of the existing conventional flotation cells at the plant. It was estab¬lished that improved grades and recoveries could be obtained by adopting column technology. Acidspar concentrates as¬saying 97% CaF2, suitable for HF manufacturing, can be produced by adopting two-stage column cleaning in place of multistage cleaning by conventional cells. Similarly, metspar concentrates assaying 90% CaF2, suitable for metallurgical applications, can be achieved in a single-stage cleaning by column flotation. This is an improvement over what is now being achieved using the existing conventional rougher and three-stage cleaning cells in the plant. The number of stages, i.e.,four in the acidspar circuit and four in the metspar circuit, including rougher stages, can be eliminated by adopting a three-column configuration. Thus, the cost of production, the complexity of the circuit and the power consumption can be effectively reduced with other attendant benefits.

Jan 1, 2000

By L. M. Chan, D. H. Carlson, J. H. Johnson

This paper discusses laboratory evaluation of a tailpipe emissions measurement apparatus (EMA) developed by Michigan Technological University (MTU) under contract to the Bureau of Mines. The apparatus dilutes diesel exhaust and measures the concentrations of diesel particulate matter (DPM), CO, C02, NO and NO2 at known dilution ratios. The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory grade instruments. During the preliminary laboratory evaluation concentrations of DPM, CO and CO2 were measured. The concentrations of CO and CO2 measured by the EMA were usually within ±14 pct of laboratory-measured values for CO and ±20 pct for CO2. EMA DPM concentrations correlated well (r = 0.96) with the laboratory values, but were 29 pct lower on average. The CO and C02 differences were observed to be related to the method of calculating the EMAs' dilution ratio and the difference in DPM concentrations is attributed to thermophoretic and/or condensation losses related to the EMA's unheated sample probe. Preliminery analysis of data obtained with a heated sampling probe and modifications in the sampling procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

Jan 1, 1991

By R. A. Metz, Isaac Vera, Hans Ruge

The El Soldado copper mineralization occurs as relatively high-grade irregular ore bodies with assay contacts and with frequent inclusions of barren rock. The sampling methods must be timely for production grade control purposes, as well as accurate and inexpensive. Sampling techniques evolved from sampling dump cars at the haulage level to sampling Scooptrams at the loading pockets. These methods were abandoned in favor of sampling production blastholes. Several sampling alternatives are discussed. These involve the selection of optimum volumes and sampling frequencies while taking into consideration geological parameters and statistical analyses of sampling data.

Jan 1, 1992

By K. A. Natarajan, P. Somasundaran, Namita Deo

Biological processes have recently become more attractive in hydrometallurgy and mineral processing due to their lower operating costs, potential for processing low-quality ores and flexibility. Adhesion of microbes and their metabolic products can modify the particles to render them hydrophobic or hydrophilic. Such modifications of the surface properties are used in flotation and flocculation of minerals. Microbes are also able to dissolve different precious metals from their ores. In this paper, the role of microbes and their metabolic products as surface modifying reagents in extraction processes is discussed. In addition, the ability of certain microbes to adsorb toxic metal ions or to degrade toxic chemicals discharged by industries is examined.

Jan 1, 2000

Health and safety issues are very important to the mining industry. Although the application of scientific research and current technology shields workers from many dangerous aspects of mining, accidents do happen. Many companies and institutions worldwide have committed to a continuous effort to minimize such occurrences. In this study, the health and safety data pertaining to the Greek mining and quarrying industry for the last three decades are presented and critically evaluated with respect to factors such as the number of workers and annual production. Appropriate indices are also calculated regarding the incidence and frequency of accidents. Health and safety issues specific to mining in Greece are also discussed.

Jan 1, 2002

By Lei Chen, Michael L. Free, Ravindra Bhide

The incorporation of particles into metal matrix materials is important to many technologically important areas. Particles that are incorporated into a metal matrix have a significant effect upon the properties of the resulting composite. Proper selection of particles and incorporation densities can lead to optimal composite properties that can be modified as needed for various applications. This paper discusses the parameters that affect the particle incorporation density in electrodeposited metal matrix composite coatings as well as a deterministic model that can be used to predict the effects of such parameters on particle incorporation density.

Jan 1, 2003

By R. Hogg, E. Kaya

The presence of agglomerated particles in airborne dust in coal mines has been confirmed by SEM examination of static samples collected on substrates. In addition, the effect of agglomerated particles on the performance of cascade impactors and cyclone- type personal samplers has been studied. Simple procedures have been developed for evaluating the extent of agglomeration in air-borne dust by comparing the observed size- selectivity of the sampling devices with that expected under idealized conditions. Applications of these techniques in the laboratory and in underground mines are discussed.

Jan 1, 1992

By G. P. Saseen, R. A. Haney

The US Mine Safety and Health Administration (MSHA) developed a model to estimate diesel particu¬late (dp) exposures in underground mines. The estimator uses in-mine measured dp concentrations or engine manufacturers' standardized emission data. Through a series of calculations, full-shift dp concentrations are estimated by applying standard engineering principles of ventilation, control technology and work cycle. This model, in the form of a computer spreadsheet, provides the mining industry with a method for estimating dp levels and determining the impact of various diesel particulate controls on occupational exposures to dp in underground mines. A detailed description of the estimator and several examples demonstrating the results are provided.

Jan 1, 2000

By F. Calizaya, I. Duckworth

An ore-pass is an underground conduit used to transfer ore from one level of a mine to another. This method of transportation depends on the elevation energy only; therefore, it has very low operating cost. However, two inherent problems may hamper this process: (1) hang-ups of interlocked pieces and (2) a sudden release of trapped air from the ore-pass (belching). These events can create unsafe conditions with the potential for catastrophic consequences. This paper presents a summary of CFD modeling studies that were formulated to investigate the pressure build-up and belching of dust and rock particles from long ore-passes. The models were calibrated against field data collected from an actual ore-pass system and used to predict the airflow-pressure distributions in the mine for various ore feed rates and ore-pass geometries. P.T. Freeport Indonesia’s Grasberg ore-pass system (240,000 tpd capacity) was used for this purpose. This system comprises of four active ore-passes, with each being more than 600 m in vertical length.

Jan 1, 2004

By G. B. Misra

Heat transfer in partially wet mine airways has been the subject of study for quite some time. Of the available models some are quite empirical while some involve highly complicated computation. Models developed by Amano, Mizuta and Hiramatsu and Banerjee and Chernyak as well as that modified by Misra were evaluated for prediction of the rise in temperature and humidity (mixing ratio ) of partially wet mine airways at four different levels in the Mosaboni Mine of Hindustan Copper Ltd. Measurements of barometric pressure, virgin-rock temperature and changes in dry- and wet-bulb temperatures along a certain length of airway were made. The rise in dry-bulb temperature and mixing ratio of air over the sections were calculated using the three models. The study reveals that calculated values of temperature and moisture content agree within possible rage of experimental error with all the three models in case of three levels with low wetness factor, but the agreement was poor for the relatively more wet airway on the 30th level. Errors in the estimation of fw to the tune of 0.025 can lead to fair error up to 0.94 K in the estimated temperature while alternative ways of estimating the heat transfer coefficient [] can introduce errors up to 1.45 K.

Jan 1, 1987

By G. Kazonich, S. L. McGill, J. W. Walkiewicz

Naturally occurring minerals and reagent-grade compounds were tested to determine their receptivity to microwave heating. The maximum temperature achieved for the samples and the time required to reach temperature are reported. A description of the microwave oven and a thermocouple technique that accurately measures and continuously records the temperature of samples during irradiation are reported. Extractive applications using the generated microwave data were investigated. Stress fracturing at mineral grain boundaries in a gangue matrix was shown. This should significantly affect grinding energy requirements and liberation properties. A method to produce a magnetic phase on pyrite surfaces, a method of using microwave heating to retort cinnabar concentrate, and a roast-leaching microwave treatment of chalcopyrite ore are described.

Jan 1, 1987

By Tim Wolf, Barry Fink

Mine site managers reported occurrences of locking assembly bolt failures on the Enlow Fork Coal Mine's slope belt conveyor. The observations were made after a number of years of operation and raised questions as to the status of the assemblies in operation. These questions prompted a detailed review of the situation by independent consultants. Using operational history of the conveyor and confirmation of belt loads by static and dynamic methods, a locking assembly fatigue curve was created to suggest expected service life. From this work, suggestions were made to modify the pulley assemblies for extended service life.

Jan 1, 2002

By Ken Bright

This paper is an overview of approaches to assessment of ore grade for gold and the platinum group at the exploration stage of a project. Proper sampling techhniques must be complemented by good assaying. In turn, correct assaying has its roots in thoughtful, systematic sampling and sample preparation procedures. While intricacies of the subject matter could occupy a book, we will comment on acceptable sampling approaches, outline a lab hand- ling scheme, and discuss preferred analytical methods. Pitfalls previously encountered by the mining and exploration industry will be highlighted with emphasis on a perceptive under- standing of the nature of ore occurrence. Lastly, focus will be centered on reliable assay approaches.

Jan 1, 1988

By Wolfgang Sand, Alex Schippers, Tilman Gehrke, Thore Rohwerder, Peter-Georg Jozsa

Metal sulfides are degraded via thiosulfate (pyrite) or via polysulfides and sulfur (sphalerite, galena, chalcopyrite) by leaching bacteria The attack on the crystal lattice is either effected by only iron(III) ions or by iron(III) ions and protons, respectively. Consequently, different endproducts are formed. For a control of ARD-processes, these reactions need to be hown to regulate them. Experiments in percolators up to 65 m3 with inorganic compounds like fluoride, concrete, or SDS resulted in differently lasting inhibition. Microcalorimetric measurements of microbial leach activity allow monitoring of these effects with respect to active bacterial cells, and, in addition, the amount or rate of dissolved metal sulfide allowing prediction of possible endangerment by ARD.

Jan 1, 2000