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By D. W. Fuerstenau, G. S. Sudhir, P. C. Kapur

Quartz-limestone feed mixtures were ground in a laboratory-size, choke-fed, high- pressure roll mill. As compared to individually ground minerals, the harder component (quartz) in the product mixture is coarser, and the softer component (limestone) is finer. An energy split index is introduced for quantifying the disproportionate split of the mill energy between the feed constituents. This index is incorporated into a grinding kinetic model for simulation of the product size distributions of the mineral components as a function of energy input to the mill. The self-similar character of the size distributions is analyzed and an energy-size reduction relationship for the roll mill is highlighted.

Jan 1, 1992

By F. F. Aplan

Estimations have been made of the tonnage of raw ores and coal treated by various beneficiation processes. The amount treated by gravity concentration is substantially greater than that treated by flotation, with coal representing the bulk of the material treated by gravity means. A discussion is given of the trends and anticipated improvements in gravity methods. Except for the concentration of iron ores, magnetic and elec- trostatic separation processes find their greatest use in the beneficiation of non-sulfide ores. Exciting new developments in magnetic materials and separation process (and, to a lesser extent, in the electrostatic process) indicate a substantial increase in the application of such processes to ores and a broad variety of non-ore uses.

Jan 1, 1989

By I. D. Lindley

The Wild Dog vein gold deposit in East New Britain Province, Papua New Guinea, forms part of a recently discovered 26 km zone of auriferous quartz vein mineralisation. The deposit, which was discovered in July 1983, has no silt anomaly, and a panned concentrate anomaly and float train restricted to within 500 m and 800 m respectively, of the discovery outcrop. Discovery of the Wild Dog deposit was a result of the methodical followup of regional panning which, as followup progressed, was replaced in importance by float sampling. Of the sampling methods used during the exploration leading to discovery, panning and float followup provided immediate indications of the presence of mineralisation. This high degree of spontaneity of followup is not provided by geochemical techniques, and has obvious advantages in high cost exploration for precious metal deposits in remote locations.

Jan 1, 1988

By Richard J. Adams

Coal jigs have played a predominant role in U. S. coal preparation for fifty years. Recently, an improved fine coal jig has been used to prepare the middle size range coal. These efficient machines are changing the historical thinking about jigs and is consistent with trends in coal preparation throughout the world. The performance achieved and operating cost savings are causing a change in fine coal cleaning strategy. With the exception of a handful of operators, fine coal jigs are generally not well understood by the industry. The objective of this paper is to provide some insight into the past use of fine coal jigs and their potential in the future. Improved Fine Coal Jig Since the mid 701s, an improved fine coal jig has been employed to an important niche in preparation, the 19 mm x 100 M range of cleaning. Several factors due to mining and liberation considerations have caused an expansion of this middle range of coal resulting in a host of challenges for coal preparation engineers. Fine coal jigs have been commissioned in several installations in North America to handle these important applications as shown in Table No. 1.

Jan 1, 1988

By B. R. Reddy, Y. V. Swamy, B. V. R. Murthy

Chromitiferous overburden containing nickel in oxide form is reduced with CO-CO2-N2 gas mixtures. This converts the nickel oxide to metallic nickel and restricts the iron oxide to the magnetite state to extract the nickel. Reduction experiments were carried out on 500-g samples in a bench-scale vertical reactor. The tests were run to establish the process parameters, including the optimum partial pressure of CO, the reducing gas flow rate, granule size and roasting time. The reduced calcine is then subjected to an ammonia-ammoniacal carbonate leach to extract nickel selectively as its amine complex. More than 90% of the nickel could be extracted with a volumetric CO/(CO+CO2) ratio of 0.57 at 750°C and a roasting time of 90 min. The addition of 2.5% (by weight) charcoal to the granules improved nickel extraction by 11 % to 19%. Nickel leaching efficiency with ammoniacal solution is compared to the bromine-methanol method.

Jan 1, 2000

By Robert J. Watters, Peter C. Kelsall, Joseph G. Franzone

Two separate studies investigated the compressive strength of basic igneous rocks and its relation to index properties such as porosity, density and soundrave velocity. The rocks tested were weathered dolerite from S. W. England and vesicular lavas from California. In both cases strength was affected considerably by porosity. In the dolerite, strength was also affected by fissures (microcracks) which were formed in the parent rock by shearing and later accentuated by weathering. While test results show that porosity, density and sound velocity are not reliable indices of rock strength, these properties are useful in interpretation of strength test results. Index testing can be used to classify samples according to similar behavior and to recognize the influence of fissures.

Jan 1, 1986

The application of Kirchoff's laws to two adjoining mine ventilation network meshes containing fans results in the construction of two general quadratic equations. These equations may be solved to give the resultant airflows and hence fan duties within the system for given network parameters and fan characteristics. This technique has a wide application for calculating the duties of fans in various combinations within a mine ventilation system. Recent difficulties in economically maintaining environ- mentally safe conditions in underground working areas distant from main ventilation fans has led to increasing interest in the use of controlled partial recirculation of ventilation. This paper develops a recirculation model which can be solved directly using mathematical techniques obviating the need for iterative techniques such as the Hardy-Cross method. The advantage of a direct mathematical analysis is that mathematical algorithms may be constructed to completely describe the ventilation system under a wide range of operating conditions. This technique is applied to controlled partial recirculation ventilation systems to demonstrate its advantages for mine ventilation planning.

Jan 1, 1989

By M. Sengupta

Surface mining in arctic regions is characterized by many unique problems. Continuous and discontinuous permafrost (perennially frozen ground) occurs in most of the arctic and subarctic areas. Permafrost presents special problems of slope stability. Stability of permafrost depends on its temperature, moisture content, and material type. Permafrost slope fails due to solifluction, disturbance of ice-rich slopes, and liquefaction. Drilling and blasting of frozen ground present special problems. Depending on their degree of saturation with water, freezing soils and rocks have a number of important characteristics that affect blasting efficiency. Metals used in mining equipment and mining structures require special selection. At low temperatures, many steels lose most of their normal ductility and toughness (resistance to brittle fracture). This paper discusses engineering solutions to unique problems of arctic mining.

Jan 1, 1988

By S. Saklar, i. Bayraktar

The effect of the feed size distribution on the kinetic parameters in pyrite flotation was studied. The kinetic parameters of the particular sizes were determined as a function of whether other particle sizes were present. From the data, a relation between the pyrite flotation rate and the particle size distributions was obtained. It was shown that the flotation rate constant (k) is a function of the size modulus (dt) of the Gates-Gaudin-Schuhmann distribution, and its variation may be expressed as k = a • exp(b . d,) for either individual size fractions or composite feed. Parameters a and b are dependent on the particle size distribution of the feed. Specifically, parameter a increases linearly as the distribution becomes coarser. The above relationship was also tested under conditions in which the collector (KAX) dosage was varied from 130 to 278 g/t. It was shown that the established relation was not dependent on the collector dosage.

Jan 1, 2002

By A. S. Ibrado, D. W. Fuerstenau

The adsorption of the cyano complexes of Ag(I). Cu(l), Hg(II), Cd(II), and Zn(II) on activated carbon was investigated as a function of pH and correlated with the speciation diagram for each metal. The results show marked changes in uptake with pH, closely resembling the predominance profiles of their neutral and singly charged cyano complexes. Multicharged negative complexes are repelledby the negatively charged carbon surface. The sensitivity of activated carbon to the charge of the adsorbing species indicates that silver adsorbs as an anion, not chemically bound to the coadsorbing counterions. For the same reason, activated carbon is selective to metals that preferentially form neutral and singly charged cyano complexes, namely gold and silver.

Jan 1, 1990

By Robert M. St. Louis, Janet M. Edgecombe

The Mercur Mine's autoclave is an alkaline pressure oxidation system, operating at 220°(428°F) and 3061 kPa (444 psig) (total). Up to 725 metric tons (800 st) of ore, grading 2.02 g per mt (0.059 oz/st) Au and containing 1 to 2% sulfide sulfur, are treated daily in this circuit. A mineralogical and chemical investigation was initiated to locate the cause of lower than anticipated gold recoveries. Greater than 70 wt. % of reduced sulfur is oxidized; therefore, the autoclave is operating at specification. The low recoveries were attributed to increased concentrations of organic carbon in refractory ore. Activated carbon concentration in the attached CIL circuit was increased from 15 to 40 g per 1, leach temperature held below 21°C (70°F), and carbon flow changed to counterflow. These measures resulted in gold recovery improving from 75 to 82%.

Jan 1, 1990

By J. R. Mattern

The engineering geology of the Rio Tinto Borax Boron Mine creates challenges in providing practical slope design recommendations to mine planning engineers. Low strength sedimentary units interbedded with very low strength lakebed clays surround the orebody. Faulting has offset and juxtaposed these units into variably adverse orientations, while groundwater is compartmentalized both vertically and horizontally within fault blocks. A collective program of geologic data collection, geomechanical strength testing, geologic modeling, slope depressurization, confirmation of underground stope locations, and documentation of slope behavior provides vital information for design investigations and sensitivities. Analysis results lead to risk assessments and operational procedures that add value to the business by optimizing slope configurations and minimizing risk.

Jan 1, 2004

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 L. Henry Smith, David C. Arthur

The Williams Mine is Canada's largest gold producer, with annual production of 14,000 Kg (450,000 ounces) from 2,300,000 tonnes of ore. Highly mechanized and automated underground mining practices are employed in order to achieve and maintain high levels of productivity and minimize costs. The Mine Ventilation System is modified to include a new Vent Raise and Variable Pitch Vane-Axial Fan. This addition allows several fan installations underground to be decommissioned. A substantial net savings in installed horse power is achieved. Heating costs associated with underground ventilation air are a significant portion of mine operating costs. Air heating costs are substantially reduced by recovering heat from upcast exhaust air, mine water and compressor cooling circuits. This waste heat is used to supplement propane fired air heating systems for underground ventilation air. An additional benefit is the availability of a heat sink for summer cooling of the compressors. System design, energy savings data and payback calculations are presented.

Jan 1, 1997

By Jim Morris, Davin Ishii

The major source of water for Southern Nevada is Lake Mead. However, the existing pump station located on Lake Mead is inadequate for one of the fastest growing areas in the United States. In order to keep up with the increasing demand for water in Las Vegas, a parallel system is being constructed. The intake for this system is being constructed approximately 68.58m (225ft) below the surface of Lake Mead. The lake tap consists of installing casing and secant piles to support the shaft collar, excavating a 21.34m (70ft) deep intake shaft, and installing a3.66m (12ft) diameter steel liner.

Jan 1, 1999

By M. T. Ityokurnbul, M. P. Trubelja

Concentrate flow rates were measured for the flotation of -100-mesh Lower Kittaning coal in a computer-controlled 0.076 x 3.5-m pilot flotation column. The variables studied were recovery zone height, airflow and solid feed rates. The specific projected surface areas of the feed, concentrate and tailing streams were determined from the measured particle size distributions. The results obtained show that the concen¬trate flow rate was independent of recovery zone height but was dependent on the hydrostatic pressure setting (measure of froth depth), gas flow rate, solid loading and particle size. New correlations for column carrying capacity and yield are provided as a function of bubble surface area flux and the specific particle projected surface area.

Jan 1, 1999

By G. Belardi, G. Marruzzo, P. Plescia

This paper presents the results of grinding tests performed on magnetite from Kiruna (Sweden) and on chromite from Skoumtza (Macedonia. Greece). Stresses were measured by XRD, which determined the variations in the characteristic structural spacings of the minerals both before and after, grinding in a HSM/250 Herzog laboratory ring mill. Anal Isis of the magnetite and c hromite crystallinstallin was performed hi measuring the broadening of the strongest diffraction peak (311). .Also, structural analysis on chromite was carried out using the Mikheev model. Ultrafine-grinding tests on the magnetite and chomite demonstrated that this type of treatment can induce profound variations m the surface-stress state. These included plastic variations of the cell followed by "chemical" stress with oxidation front the stricture to form hydroxide or carbonate, films. This can have a great influence on the mineral reactivity to flotation reagents

Jan 1, 1996

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

By E. H. Ahrens

This paper deals with the responsibilities of an operating geologists and the relationship of operations to exploration. It should be of interest to those soon to enter the profession, those new to pining geology and as a review to more experienced geologists. Subjects discussed include detailed geologic mapping, sampling, core logging, assaying, selection of proper map scale, posting geological and assay data, section preparation, identification of ore controls, delineation of development drill targets and geologic hazards, models and the very important topic of salesmanship. Methods and ideas, proven valid in vein, pyrometasomatic replacement and porphyry copper deposits are presented. Hopefully, these will smooth the path for new members of our profession.

Jan 1, 1992

By Abdullah Arik

In deposits with highly skewed grade distributions, such as precious metals deposits, proper handling of the outlier high grade data is very crucial to the ore reserve estimation. Although some recent geostatistical techniques are available to handle the estimation problems with these outlier data, ordinary kriging or conventional methods are still widely used to estimate the ore reserves for such deposits. One reason for this is the fact that the alternative methods offered are either too complex or too exhaustive for the mine engineers and geologist who often do not have the expertise or the time to apply these methods. This paper presents a new 2-step kriging algorithm "Outlier Restricted Kriging" (ORK) which can be a simple and a practical tool to use where the ordinary kriging will fail to handle the outlier high grade data properly in block grade estimation. The paper details the methodology and discusses the results of its application to a gold deposit.

Jan 1, 1992