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By S. K. Mishra, S. B. Kanungo, D. Biswal

An attempt was made to beneficiate low-grade, high-phosphorus manganese ores of the Garividi-Garbham region of Andhra Pradesh, India, by using wet high-intensity magnetic separation (WHIMS). The distribution behavior of both mass and chemical constituents in different size fractions of a typical highly weathered ore sample was studied to obtain information about the liberation characteristics of various chemical constituents. Magnetic separation indicated that in the +208-µm size fractions, P and acid insolubles were concentrated in the magnetic fractions. However, in the -208-µm size fractions, P and acid insolubles were concentrated in the nonmagnetic fraction because of a lower recovery of the magnetic fraction. Variations in field intensity between 1.3 and 1.75 T had little effect on the recovery and the grade of concentrate. The results also demonstrated that phosphorus was associated with all three major constituent phases, namely, oxides of Mn and Fe and aluminosilicate gangue minerals.

Jan 1, 2000

By A. Yehia, M. I. Al-Wakeel

Flotation behavior, of magnesite and dolomite pure minerals was studied separately. Rice bran oil (a source of fatty acid ) was used as a collector for both minerals . The aim of this study is to find a separating zone in the flotation of these pure minerals to be used in the separation of their mixture. Factors affecting the flotation process, such as pH and collector, were studied. It was found that magnesite can be separated, from its mixture with dolomite, in the pH range of 5-7. At this pH range flotation recovery of dolomite reaches~98% where magnesite reaches ~20% only. Besides, the effect of collector concentration on the flotation shows that the separation of magnesite from dolomite is feasible at a collector concentration of 3x10-4 M. At such concentration, dolomite recovery reaches ~98%, where magnesite reaches 25%. The differences in the flotation behavior of dolomite and magnesite were investigated by studying the adsorption isotherms of rice bran oil on magnesite and dolomite surfaces. The adsorption study indicates that while there is an excessive adsorption on dolomite surface, the adsorption density on magnesite was restricted to be lower than monolayer capacity. The adsorption behavior of dolomite and magnesite was discussed in the light of their solubility and crystal structure. It was found that due to the higher solubility of dolomite than magnesite, Ca2+ and Mg2+ ions are available and more reactive on dolomite surface increasing collector adsorption. In addition, it was indicated that dolomite mineral has a crystal lattice structure more compatible to the geometry of the fatty acid carboxylic group than magnesite. However, the adsorption of collector on dolomite surface is more compact and more regular than on magnesite surface.

Jan 1, 2000

By M. Wiber, P. Nicoll

Rio Algom has embarked on a major programme of expansion with the goal of becoming one of the world’s top-performing base-metal mining and metals distribution companies. To assist the company and its operations in achieving its business objectives, we are implementing an environment, health and safety (EHS) management system, built to be compatible with the 14001 model. We recognize that a sustainable development approach for Rio Algom includes outstanding performance in EHS and community responsibility and is essential to earn acceptance within the communities where we operate or wish to locate; raise capital; obtain permits, and operate efficiently. We are committed to triple bottom line accountability, i.e. full consideration of environmental, social and economic concerns in our business decision making.

Jan 1, 2000

By Betty L. Gibbs

Geologically simple deposits can be modeled quickly and easily with inexpensive gridding and mapping software. Hundreds of mines around the world use RockWorks99 and Surfer 7 for generating contour maps, producing log plots and cross sections, and performing other useful geological calculations. These programs are used by many mining operations as their only modeling and graphical software or they are used in conjunction with larger systems. The investment in learning time is low and the programs produce reasonable quality results with standard computing equipment. RockWorks99 and Surfer 7 provide a good level of capability while maintaining high quality technical integrity. Both programs are used for many applications in mining, oil and gas, environmental and other fields that require analysis of spatial data.

Jan 1, 2000

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 S. Yang

Based on an analysis of the features found in Chinese surface coal-mining areas, including areas that have already been developed and areas that are in the process of being developed, this paper discusses some rational coal-haulage systems. An optimal decision-making model, which includes a geological model, a mining model and an economic estima¬tion model, was developed for the selection of a coal-haulage system. A case study is presented.

Jan 1, 2000

By D. E. Poole

Injury Prevention: Dependent, Independent and Interdependent In recent years, management-directed (dependent)safety programs have lost ground to the more successful self-directed (independent) programs, where employees take responsibility for their own safety. Today, with the growth of the team concept in industry, a mutual-caring (interdependent) approach to workplace safety is gaining wide acceptance. This presentation compares characteristics and results of the three progressive levels of safety responsibility and explains how to develop a successful interdependent program. The presentation will also detail the common principals that are necessary for safety excellence under any of the management styles.

Jan 1, 2000

By E. A. Metz

It has been approximately four years since IARC reclassified crystalline silica as a “Group One” substance. Since that time, crystalline silica has been considered a human carcinogen. Silicosis is a preventable disease and several aggressive campaigns have been developed to increase awareness of silica dust related problems in the industrial environment. New analytical techniques are being developed to determine quantitatively the amount of crystalline silica in materials. Yet, still much is to be learned about the surface properties of silica and the way in which the disease progresses into full-blown silicosis. This paper will discuss the interaction of free radicals generated by the mineral particles and lung tissue. It is the cell injury and DNA damage that progresses to fibrogenesis. Freshly fractured surfaces of silica contain free radicals. These free radicals play an important role in the stimulation of the alveolar macrophage and the development of the inflammatory reactions leading to the fibrotic response caused by silica. Engineers, scientists, and physicians need to discuss the mineralogy of silica and the technical issues concerning the development of silicosis.

Jan 1, 2000

By Steve Kral

Despite low commodity prices and mining industry cutbacks throughout the world, Peru remains one of the industry’s bright spots. The country’s remarkable economic turnaround during the 1990s remains a model for other developing nations to follow. And the Peruvian government has not forgotten the industry that was instrumental in that turnaround. True, the country has not been spared the effects of the mining industry’s retrenchment that has occurred in other parts of the world. However, foreign mining companies remain committed to doing business in Peru. And the government remains committed to attracting foreign investment and maintaining a strong mining industry. This commitment was evident in September 1999during the 24th Convention of the Institutos de Ingenieros de Minas del Peru in Arequipa, Peru. More than 3,000 mining industry professionals from around the world attended the convention. And Extemin, the accompanying exhibit, featured more than 450 companies, many from the United States, Canada, Australia, South Africa and other countries.

Jan 1, 2000

By Kim A. Lapakko, William W. III White

The ASTM standard method D 5744-96 was developed to provide a well-defined kinetic test protocol, conducted under controlled reaction conditions, with the intent of generating reproducible results. The US Bureau of Land Management, American Assay Laboratories, and the Minnesota Department of Natural Resources cooperated in a intralaboratory and interlaboratory testing of the protocol. Intralaboratory testing was conducted on duplicate samples of gabbro (8) and siltite-argillite (5) rocks for periods of 20 to 125 weeks. The difference between replica& intralaboratory pH readings on drainage from the gabbro for the drip-trickle leach alternative typically did not exceed 0.1 units, although differences as high as 0.4 units were observed. The difference from the mean for rates of sulfate, calcium and magnesium release was typically within 10%. Intralaboratory results for the siltite-argillite samples were generally similar, although a one unit pH difference was observed for one sample. Three different laboratories tested a gabbro sample for 125 weeks, with a maximum difference from the mean pH of 0.5 units. The percent difference from the mean for sulfate and calcium release rates was typically within lo%, although values as high as 30% were observed. Data on intralaboratory and interlaboratory agreement on the flood rinse alternative of the method were limited. Replication on the sample tested was comparable to of better than that observed for the drip-trickle method testing of the same sample.

Jan 1, 2000

By G. T. Lineberry, B. R. Yama

Artificial intelligence research has produced several tools for commercial application. Some of the techniques that are widely used today include neural networks, fuzzy logic and expert systems. Artificial neural networks (ANNs) are excellent predictive, pattern recognition and data analysis tools. In the mining industry, ANN techniques are being used commercially for real-time process-control applications. Modeling of spatial data, ore-reserve estimation, tunnel design, long wall-stability prediction and geologic roof classification are additional applications in which neural networks have been applied successfully. In this study, a standard back propagation algorithm was used to train a series of neural networks for a real-world predictive task. After training and optimizing the neural network architecture, the performance of the network is measured on an independent validation set. Results indicate a mean error of less than 1 % between the actual and predicted values. A neural network model was developed for learning the spatial continuity of a mineral field and, consequently, for predicting sulfur values for given coordinates. The neural network not only performed satisfactorily, but in some cases performed even better than the kriging model.

Jan 1, 2000

By T. Hawthorne, H. Barnes

Homestake Mining Company has developed an estimating model, based on other closed projects, to audit and prepare new estimating plans. The results of recent closure audits reveal that the original budgets were often insufficient to cover the present expected expenses. Some of the major areas where technical challenges and costs are increasing include heap leach pile detoxification and rinsing, tailings dam closure, water management and treatment, abatement of contaminated soils, and many others. Risk and sensitivity analysis of each category will develop a level of confidence in the estimate and allow management to focus on the pertinent issues. Periodic audits of closure plans and costs throughout the life of mine serves to focus management attention on the complete costs of production. This will result in improved overall planning and management, and reduce the number of missed opportunities for savings.

Jan 1, 2000

By T. Tamagawa, I. Iwasaki, N. X. Fu, M. Kobayashi

A low-temperature-chlorination selective oxidation followed by aqueous chloride leaching and SX-EW for producing electrolytic copper, elemental sulfur and ferric oxide was investigated for hydrometallurgical processing of a chalcopyrite concentrate. In this article, the selective oxidation phase of the process is described. The selective oxidation requires a temperature well above the CuCl-FeCl3 eutectic points. The test procedure was developed with a batch reactor and then tested with a continuous reactor. The process was initiated by adding small amounts of chlorinated samples to a fluidizing bed of dead-roasted sulfide concentrate micropellets. The selectively oxidized samples thus prepared were shown to fully dissolve copper, while virtually all the iron remained undissolved.

Jan 1, 2000

By Tom C. Palanglo, Norbert Maerz

Control of crushing and grinding circuits ideally requires continuous particle size measurements on both in- and outgoing streams. Until recently, size distributions could only be obtained by screening methods, which were neither cost effective, frequent enough, nor timely. Input streams are often composed of large fragments, making screening prohibitive. Optical image processing systems, such as the WipFrag System, have been developed to the point that they are an extremely valuable tool to characterize, control, and fine-tune the comminution process. Although accuracy is less than that of screening, measurements are precise enough to detect relatively small changes in size distributions.

Jan 1, 2000

By D. Duvris

Health and safety issues are a very important aspect of mining activities. 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 3 decades are presented and critically evaluated with respect to number of workers, annual production, etc. Appropriate indices are also calculated regarding the incidence and frequency of accidents. Health and safety issues specific to mining in Greek are also discussed.

Jan 1, 2000

By Bruno Bussière, Michael Aubertin, Robert P. Chapuis

Covers with capillary barrier effects (CCBE) have been used in recent years as gas barriers for the isolation of wastes, including reactive mine tailings. Capillary barrier effects help to maintain a high degree of saturation in the moisture retaining layer, which then reduces gas flux. Various factors affect the degree of saturation of the moisture retaining layer in a CCBE, such as the material water retention characteristics and layer thickness. Slope geometry can also influence the hydrogeological behaviour of a CCBE, but this factor has frequently been ignored in the past. In this paper, the authors show some results of a numerical study that illustrates the influence of slope on the behavior of capillary barriers made of different types of material. The numerical model calculations are based on an actual case of a CCBE constructed in northern Quebec. This investigation shows that the water content profile is greatly affected by the position along the slope. Thus, it is necessary to evaluate the influence of the geometry to properly establish the performance of a cover system.

Jan 1, 2000

By J. W. Merks

Spreadsheet software is an effective tool for simulating dynamic stochastic systems such as mineral processing plants. The two-product formula is used to show how to set up a Monte Carlo simulation in a spreadsheet template and how to calculate variances of dependent variables. The key to a reliable and realistic simulation model is to obtain unbiased estimates for all independent variables and variances in the set that defines the stochastic system. Monte Carlo simulation is also a powerful tool for optimizing sampling procedures, for applying sensitivity analysis and for designing and evaluating experiments.

Jan 1, 2000

By Mark R. Stanton

Geochemical and mineralogical analyses of 46 samples from six drill cores in the Mayday mine pile near Silverton, Colorado, demonstrate wide variability in trace metal contents with spatial location. This variability results from the original geochemical composition of mined rocks, mixing of ore and non- ore rocks during emplacement of the pile, and weathering since rocks were placed in the pile. Weathering reactions are controlled by factors such as pile thickness (depth), water availability, microbial activity, and mineral dissolution and formation kinetics. These factors result in variable redistributions of trace metals from primary (ore) to secondary (weathering products) minerals within each core.

Jan 1, 2000

By J. F. Stenebråten, W. P. Johnson

Carbonaceous material (CM) from the Barrick Goldstrike Mines, NV, was characterized with respect to its gold sorption (preg-robbing) and gold recovery behavior. The breadth of graphite peaks measured by X-ray diffraction were used to calculate crystallite dimensions (002) of the CM. The (002) dimension was found to vary inversely with preg-robbing activity and directly with gold-recovery behavior, indicating that the degree of graphitization (maturation) experienced by the carbonaceous material is correlated with gold-loss during ore processing. The inverse correlation of preg-robbing activity was improved when percent preg-robbing was regressed against (002) crystallite size and carbon content. The (101) crystallite dimensions of all samples were calculated from laser Raman analysis, and were not found to correlate with preg-robbing behavior of the CM. BET surface area and micropore size distribution results were affected by grinding history, negating comparison of these characteristics between samples.

Jan 1, 2000

By K. Biswas, F. C. Felipe

Paste backfill, because of its colloidal or water-holding properties, does not produce run-off water when placed underground. Paste backfill is generally, prepared from relatively low water content, full mill tailings with a certain proportion of ultra-fine particles and mixed with cement, thus producing early and better strength. Mill plant discharge tailings and other materials available at or near the mine site such as sand, aggregates or waste rock are used as blending materials in the mix design. This study investigates the influence of the above-mentioned blending materials on the mechanical characteristics of paste backfill, as well as the grading, shape, specific surface area, mineralogy and workability of the different mix design.

Jan 1, 2000