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By I. A. Costa, Y. Fouquet, F. Barriga

"Lucky Strike and Menez Gwen are two hydrothermally active sites located along the border of the Azorean plateau, southwest of the Azores islands where the alteration processes affecting basaltic rocks are prominent (Costa et al., 2003). Here we report on a slabby brecciated rock, abundant at both Lucky Strike and Menez Gwen, composed mainly of basaltic fragments cemented by hydrothermal precipitates from warm fluid circulation system. Research reveals that hydrothermal alteration takes place mainly by replacement processes, in which silicification is dominant (Costa et al., 1997 and Costa, 2014).Petrographic observations, including scanning electron microscopy (SEM), microprobe analysis, and mass balance studies made on basaltic fragments within the breccia show that silicification is one of the main processes resulting from hydrothermal fluid circulation. This alteration process leads to complete replacement by silica, in extreme cases, forming an impermeable cap that may contribute to the formation of sub-seafloor sulphide deposits, including examples in the geological past."

Sep 1, 2014

By Kevin Landey, Eric Gerst

Expanding blast patterns to near the limit of an explosives’ ability to do the necessary amount of work is a common practice to reduce drilling and blasting costs. Choosing less expensive explosives such as ANFO vs. emulsion, bulk product versus packaged product, etc. are also common cost savers. Both practices are only effective as long as the pattern geometries are accurately drilled. However, will pushing the limits on pattern sizes and explosive products produce consistent results at the face, minimize oversize, produce superior fragmentation, and improve crusher throughput? Sometimes, but no amount of explosives can overcome a poorly drilled pattern. Knowing the probable outcome of any changes in drilling and blasting is valuable in achieving success.

Jan 1, 2018

By A. A. B. Douglas

In this paper the origins of the mortar intruded concrete concept and its development and application in the construction of watertight bulkheads in South Africa are described. The events leading to the commissioning and execution of the West Driefontein Experimental Plug and the Virginia/Merriespruit Boundary Plugs, and their roles in the proving of the technique, follow. The development of the first Transvaal and Orange Free State Chamber of Mines Code of Practice for Mortar Intrusion Concrete for Underground Plugs and Bulkheads, Johannesburg, November 1962,is explained. The saga of the October 1968 flood and subsequent salvage of the West Driefontein Gold Mine is recounted. The paper concludes with mention of the validation programme carried out for the Placer Dome Western Areas Joint Venture and their South Deep water barrier programme.

Jan 1, 2006

By A. C. du Preez

The separation of nickel and cobalt from calcium, magnesium and manganese by solvent extraction using synergistic mixtures of carboxylic acids was studied. Addition of certain viable synergists to commercially available tertiary branched carboxylic acids, such as Versatic 10 (Shell) or Neodecanoic acid (Exxon), produced large synergistic shifts (?pH50) in the pH50values for nickel, and small antagonistic shifts (negative ?pH50values) in the extraction of calcium. Under the initial test conditions used (0.50 M each of Neodecanoic acid and the Mintek synergist, in xylene) a large separation (pH50Ca? pH50Ni= 3.09 pH units) between nickel and calcium in their extraction from 1.00 M sodium nitrate solutions was obtained, compared with only 1.11 pH units in the absence of the synergist. The selectivity series for the extraction of divalent base metals from 0.333 M sodium sulphate solutions by 0.50 M Neodecanoic acid and 0.25 M of the Mintek synergist in C12-C13aliphatic diluent was found to lie in the order (with pH50values in parentheses): Cu(3.42) > Ni (5.08) > Zn (5.58) > Co (5.73) > Mn (6.62) > Ca (7.48) >Mg (8.25). In batch counter current experiments, a simulated leach liquor containing (in gL-1): Ni 5, Mg 5, Mn 2, Co 0.5, Ca 0.5, Cu 0.1and Zn 0.1 was contacted with the mixed extractant in three stages at unit phase ratio and an equilibrium pH of 5.9. The recovery of nickel was 99.9 per cent and that of cobalt was 84.7 per cent, whilst the co-extractions of manganese, calcium and magnesium were 2.7,1.5 and 0.04 per cent, respectively. The recovery of cobalt can be enhanced by employing a slightly higher pH, although this will also increase the extraction of manganese, calcium and magnesium somewhat. Nearly quantitative stripping (99 per cent) of nickel from the loaded organic phase was achieved in a single contact at an organic-to-aqueous phase ratio of 4 using a simulated spent electrolyte containing 39 gL-1sulphuric acid and 33 gL-1nickel,thereby producing an ?advance electrolyte? containing 57 gL-1nickelat pH 3.5. Loading of acid into the organic phase was very slight, amounting to only 0.002 M H+in contact with the above-mentioned spent electrolyte. Keywords: solvent extraction; synergism; nickel; calcium; carboxylic acids.

Jan 1, 2004

By A. C. Moorgas, J. Divall

This study investigates the feasibility of using waste iron slag, the by-product from a mineral sands processing works, in road construction. The study includes the different options investigated for the treatment of a leachate that is produced during the cooling of the iron slag, prior to processing. It also reviews the reasons for choosing the current treatment option that is being trialed. Cooling the iron slag with water results in the formation of a leachate with a high pH and high sulphide concentration. This leachate can seep into the ground and, over time, it will contaminate the ground water. A system was designed to collect and treat the leachate to prevent contamination of surrounding natural water sources. Numerous leachate treatment options were investigated to find cost effective method of treatment After cooling, the iron slag is passed through an iron recovery plant and the unsaleable product is placed on a dumpsite. Rain percolates through the dumpsite, which can result in the formation of a leachate that can contribute to a contaminated plume. After extensive testwork, it was found that the dumpsite, which was leached of contaminants, could be screened and used as a G5material (specifications in Table II) in road construction. The initial challenge was to establish that this material was environmentally safe for use in this particular application. Approval from the Department of Water Affairs (DWAF) was required for the testwork and then for the long-term use of this material in the construction industry. The following challenge involved establishing a market for the material. Construction companies in the area were reluctant to change to a new product that was not naturally occurring. The economics of this project are extremely sensitive to transport costs and hence only projects within a specified radius can be supplied with the Black Top Gravel (BTG). This project is not are venue generator, but it does save the money that would be required to manage the dump, and it reduces the closure costs.

Jan 1, 2003

By N. Kumar Kittusamy

A field study was conducted to evaluate seat designs on shuttle cars. Eight operators participated in evaluating seat designs on the basis of perceived levels of vehicle jarring/jolting and discomfort. Researchers also measured the levels of vehicle jarring/jolting. Four basic seat designs were compared on low and mid-coal seam shuttle cars during production operations at two underground coal mines. Two seats were currently used on the shuttle cars and another two were NIOSH designs. Objective data were collected using accelerometers with pre-amplifiers and filters connected to a data recorder; whereas subjective data were gathered with a visual analog scale (VAS) and a questionnaire. Results from measured levels of jarring/jolting showed that the NIOSH Seat L2A smoothed out bumps better than any other seats. Using the VAS, mid-seam and low-seam shuttle car operators rated the levels of jarring/jolting and discomfort lower with the NIOSH seat than the other seats. Questionnaire responses indicated that operators rated NIOSH seat designs as more comfortable. This research will provide the industry with better seat designs for isolating jarring/jolting in vehicles. Furthermore, researchers plan to improve the NIOSH seats using information gathered in this study.

Jan 1, 2003

By R. Zunich, E. Rybinski, M. Grondin, B. Flintoff

It is uncommon these days to read a business magazine or newspaper without finding a reference to Knowledge Management (KM), and its critical importance to corporate success. One definition of KM is: “getting the right knowledge to the right people at the right time and helping them to put information into action in such ways that strive to improve organizational performance.” In the minerals processing industry we could assert that we have been practicing this for years through effective operator training. In most cases we would probably be wrong. Training has certainly filled the need of addressing safety and basic operational issues, but we must collectively focus on education (learning), and the difference, as measured in outcomes, is not at all subtle. This paper briefly examines the history of training and education in the mining industry, and looks in more detail at the impact of one company’s approach to empower its workforce, while keeping the ultimate goal clearly in mind: “The great end of knowledge is not knowledge, but action.” (T.H. Huxley)

Jan 1, 2001

By V. Labiouse, B. Heidenreich

The rebound phenomenon, which occurs during rockfalls when a rock block impacts with a slope surface, is influenced by several parameters related not only to the slope material but also to the block and the kinematics. The paper presents a small-scale testing campaign undertaken at the LMR (EPFL) to better understand and quantify the bouncing of blocks on granular slopes. The influence of some factors related to the ground material, the block and the kinematics is examined. Bei Steinschlägen wird die Flugbahn eines stürzenden Felsbrockens maßgeblich durch den Abprall vom Hang bestimmt. Der Rückprall hängt von verschiedenen Parametern ab, wobei nicht nur das Hangmaterial sondern auch Blockeigenschaften und Kinematik eine große Rolle spielen. Zum besseren Verständnis dieses Phänomens und seiner Quantifizierung werden am LMR (EPFL) kleinmaßstäbliche Versuchskampagnen auf granulären Materialien durchgeführt. Der vorliegende Artikel stellt die Versuche vor und untersucht den Einfluss verschiedener Boden-, Block- und kinematischer Parameter. Le phénomène de rebond qui se présente lors de l’impact d’un bloc rocheux sur la surface d’un versant dépend non seulement des caractéristiques du terrain, mais aussi de facteurs relatifs au bloc et à la cinématique. L’article présente une campagne d’essais sur modèle réduit entreprise au LMR (EPFL) afin de mieux comprendre et quantifier l’impact de blocs sur des matériaux granulaires. L’influence de divers paramètres relatifs au sol, au bloc et à la cinématique est mise en évidence.

Jan 1, 2003

By R. T. Jones

The 20 Mt reverberatory furnace slag dump at Nkana in Zambia contains a substantial quantity of cobalt. A 40 MW DC arc furnace has been built at Chambishi for the purpose of recovering cobalt from the slag. The technology was jointly developed by Mintek and Anglovaal Mining Ltd (Avmin), and the furnace was designed by Bateman Titaco. Testwork at the 150?250 kW scale was conducted at AVRL, and larger scale piloting was conducted at Mintek (in partnership with Avmin) in a 3 MW DC arc furnace. Approximately 840 tons of Nkana dump slag (ranging from 0.66% Co) was processed at power levels around 1-2 MW. Good overall cobalt extraction was achieved, and approximately 100 tons of cobalt-bearing alloy was produced (containing 5 to 14% Co). This testwork demonstrated that the Nkana dump slag could be processed in a DC arc furnace of suitable design, to produce a cobalt-bearing alloy suitable for further hydrometallurgical processing. Bateman Titaco were contracted to design and build the furnace, and the design team contained representatives from Avmin and Mintek. The project was conceived as a fast-track exercise, and many activities had to be run in parallel. Notable features of the furnace include an ABB power supply, a Concast conductive hearth, the refractory design, and copper cooling in the sidewalls. Power to the furnace was switched on during January 2001.

Jan 1, 2002

By T. C. Woo

This report describes the program that studied the theoretical and practical aspects of the belt cleaning systems, investigated-the possibilities of a self-replacing and/or sell-adjusting belt cleaning device, and designed a horizonal pentagonal turret setup for the underground mine belt conveyors. This design resulted from comprehensive literature survey (both academic and commercial), actual mine visits, study of the mechanics of belt cleaning and bench-type experiments. It has complete working drawings and rough cost estimates.

Jan 1, 1977

By William Morales

De acuerdo a su diversidad biológica, la pila de la lixiviación de La Quinua es única en su género, por lo que es importante la clasificación de los diferentes frentes de minado. Posteriormente, de acuerdo al avance de explotación fue cambiando las características del mineral, facilitando la descarga directo a la pila de lixiviación. Sin embargo, la presencia de finos, arcillas y la poca profundidad de remoción del mineral, perjudicó la extracción de oro, orginando un incremento de inventario de oro en la pila de lixiviación. En este sentido, el presente texto describe los contínuos cambios del mineral y sus características, originando un cambio en el método de lixiviación a través del cambio de los controles operacionales de altura de banco y flujo de riego, en respuesta de pruebas metalúrgicas que se desarrollaron con el tipo de mineral.

Sep 12, 2011

By E. H. Cho, B. Conner

Three sulfide minerals, chalcopyrite, sphalerite, and pyrite, were leached using a bioleaching mode and an electrobioleaching mode. The former mode was used to leach the minerals with the bacterium A. ferrooxidans in a bioreactor. In the latter mode, the leaching of the minerals was performed in a combination of a bioreactor and an electrochemical cell. In this set-up, the solution was circulated between the bioreactor and the cathode compartment, the two reactors were in series, and the cell was operated intermittently. The mechanism is such that an increase in Fe(II) concentration, which is a nutrient of the bacteria, by electrochemical reduction of Fe(III) would increase the bacterial population and in turn would accelerate the leaching of the mineral. It has been found that the electrobioleaching of chalcopyrite is an improvement over the bioleaching with respect to the fact that leaching conversion is higher and a high level of Fe(II) concentration can be maintained. However, the electrobioleaching of sphalerite does not show any improvement over bioleaching. The electrobioleaching of pyrite is similar to that of chalcopyrite, and this has potential to be used in applications such as coal desulfurization and pretreatment of refractory gold ore in heap leaching where fine gold particles are entrapped inside pyrite particles.

Jan 1, 2006

By S. M. Carpenter

In response to the FY2008 Consolidated Appropriations Act (H.R. 2764; Public Law 110?161), the United States Environmental Protection Agency (USEPA) issued the final Mandatory Reporting of Greenhouse Gases Rule (MRR). The rule, signed by the USEPA Administrator, Lisa Jackson, on September 22, 2009, requires reporting of greenhouse gas (GHG) emissions from large sources and suppliers in the United States, and is intended to collect accurate and timely emissions data to inform future policy decisions. The MRR will go into effect on January 1, 2010, and a report of the total emissions for calendar year 2010 will be due to the USEPA by March 31, 2011. Under the final MRR, suppliers of fossil fuels or industrial greenhouse gases, manufacturers of vehicles and engines, and certain facilities that emit 25,000 metric tons or more per year of GHG emissions are required to submit annual reports to the USEPA. The gases covered by the rule are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and other fluorinated gases as outlined in Table A-1 of Subpart A of the MRR, which is also provided in Appendix A of this report.

Jan 1, 2011

By Keith A. Heasley

In the past, numerous displacement-discontinuity (DD) models of stratified rock masses have been proposed using a homogeneous isotropic elastic overburden. In this paper, it is postulated that a laminated overburden model might be more accurate for describing the displacements and stress in these stratified deposits. In order to investigate the utility of using a laminated overburden in a DD model, the fundamental mathematical basis of the laminated model is presented and graphically compared with the fundamental behavior of homogeneous isotropic elastic overburden and with field data. Specifically, the stresses and displacements surrounding an idealized longwall panel as determined from the laminated overburden model are presented and compared with results from the homogeneous isotropic overburden and with measured abutment stress data. Also, the remote displacements and surface subsidence as calculated by the laminated overburden model are compared with homogeneous isotropic calculations and with measured subsidence data. The results of this investigation show that the laminated overburden is more supple, apt to propagate displacements and stress further, and better able to fit observed data than the classic homogeneous isotropic overburden. Ultimately, it is suggested that the laminated model has the potential to increase the accuracy of displacement and stress calculations for a variety of mining situations.

Jan 1, 1996

By J. M. A. Geldenhuis

This work is concerned with studying possible reactions in the ilmenite furnace which may control the product quality of both slag and metal. Two different approaches were followed: comparing actual furnace slag compositions with the calculated equilibrium values and using commercial oxygen probes to measure the effective partial oxygen pressure in the slag and metal. It appears from a comparison of actual furnace slag compositions (in terms of the distribution coefficient of vanadium) with equilibrium values, that the TiO1.5-TiO2reaction may fix the effective partial oxygen pressure for the vanadium reaction. This possibility was tested using commercial oxygen probes (traditionally applied during steelmaking) to measure the effective oxygen partial pressure of both the slag and liquid iron in Iscor?s 3MVA pilot plant ilmenite furnace. From these measurements, it appears that commercial oxygen probes containing zirconia solid electrolytes can be used to measure the effective oxygen potential of both the slag and liquid iron. This oxygen activity correlates well with the FeO content of the slag. The results, furthermore, clearly illustrate that equilibrium conditions are not attained in the ilmenite furnace during the production of high titania slags, since the effective oxygen potential of slag and metal differ substantially.

Jan 1, 1999

By P G. Hicks

The influence of feed size and pulp density on the specific rate ofbreakage of quartz was investigated. Plots of log fraction of feedremaining within the feed size interval against grinding time allowed the application of the first order grinding model to be examined. Substantial non-linearities were observed for all feed sizes due to environmental and material factors. For feed sizes above 1.3 mm, the specific rate of quartz breakage was higher with rod milling than ball milling, but below this size the reverse was true. Material that remained in the feed size interval after the initial grinding broke more slowly in subsequent grinding than the original feed material. Grinding media and time as well as feed size influenced the effects of pulp density on grinding. More dilute pulps (eg 50 per cent solids density by weight) were favoured for higher rates of breakage in rod milling but for ball milling, the optimum pulp density appeared to be 60 to 70 per cent solids by weight.

Jan 1, 1998

By G. C. Stone

AS the term "hardness" is used with many different meanings, it should be understood that it here means resistance to deformation by compression. It was determined by measuring the pressure, in pounds per square inch, necessary to reduce by 20 per cent., the length of cylinders 1 in. (25 mm.) in diameter by 2.6 in. (66 mm.) long. The tests were made at Columbia University on an Olsen 400,000-lb. machine, the load being applied at a constant rate of speed 0.0319 in. per min. The results were obtained by Messrs. Rigg and Williams, and some of them were given in a paper read at the Sixteenth Annual Meeting of the American Society for Testing Materials, in June, 1913. The remainder of the results were obtained in subsequent experiments by the same authors. In all cases, the results given are the averages of three or more closely concordant tests. All of the spelters tested were of standard commercial grades and all were of compositions making them good deliveries. The accompanying table gives the results arranged in the order of increasing hardness:

Jan 1, 1919

By Tom Tallone

In the majority of metal and nonmetal mining operations, narrow vein deposits are being mined with slusher hoists. Thin; method of mucking is costly, due in part to its inherent labor intense operation and to its inability to muck 100 pct of the deposits. Mechanized equipment would greatly improve the material handling in narrow vein mining and would dramatically reduce the operational cost. The Compact Loader/Trammer, known as the "mini-mucker" has been developed to increase productivity of the load/haul/dump portion of the typical narrow vein mining cycle. This is Volume II of the final report and concerns the operation and maintenance of the mini-mucker. Volume I covers a general and design review of the activities on the subject contract and are available under separate cover.

Jan 1, 1985

By R. V. Ramani

This report is volume 2 of an eleven-volume final report for a Grant completed by The Pennsylvania State University for the Bureau of Mines to develop a dynamic general purpose computer simulation model for underground coal mining. The simulator developed under the Grant has a wide range of possible applications in the design and evaluation of underground coal mining systems from the standpoints of health and safety, productivity, and mine environment. The Master Design Simulator consists of nine free-standing function-oriented subsystem models linked together into an integrated, comprehensive model of an entire mining system. The subsystems comprising the Master Design Simulator include geology and reserves, methane generation, roof support, subsidence, production, rail haulage, cost, water generation, and ventilation. This volume of the final report describes the Geology and Reserves subsystem of the Master Design Simulator. The two functions of this subsystem are: 1) the design of a geological data library to provide input to the other subsystems of the simulator; and 2) the calculation of coal reserves and associated values and grades under various user-specified conditions. The subsystem uses a weighted moving average method to interpolate between the borehole values, and provides output in report format, graphical plots and/or storage on magnetic tape or other storage devices for later retrieval. The application of the subsystem as an independent model with test results and comparisons with other methods of computing reserves is also presented. The appendix comprises a users manual for the model, and includes a program listing.

Jan 1, 1974

By Jacques Deraisme

The technology of percussion drilling is well mastered. The lower cost of percussion drilling allows more holes to be drilled for the same budget. However significant differences are often observed between percussion and diamond drill assay data. This is due to the increased level of contamination associated with the percussion drilling process. Statistical studies on twinned drillholes show that diamond and percussion assays cannot simply be merged in a traditional kriging approach. The question then arises on how to use both types of data to produce reliable resource estimates. To take into account the lower reliability of the percussion assays, a noise characterized by a variance is added to these data. The methodology consists of two steps: 1. Cokriging of the equivalent diamond value at the percussion assay locations. 2. Block kriging using diamond assays and equivalent diamond values, calculated previously, adding to these data a noise, whose variance is the cokriging variance of step 1. This particular way of achieving kriging is called kriging with variance of measurement error. The paper illustrates this innovative methodology with an application on an iron deposit. The results of this method is compared to block kriging using only diamond assays and the gain in precision is quantified. An extension of that approach to multi-element cokriging is also presented.

Oct 1, 2009