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By M. I. Dobrynina

At the beginning of the 80-s the first diamond pipe in the East-European platform was discovered in the North of the Russian Federation on the White Sea Winter coast. During several years while studying this unique area data on kimberlites and country rocks petrophysical characteristics have been collected. Considerable experience in geophysical methods when searching and exploring diamonds was accumulated, and various methods of geophysical data interpretation were used. It has been established from the analysis of geophysical data that diamond-bearing kimberlites are located in the most ancient and the most stable block of the East-European craton.

Jan 1, 1995

By D. J. Turk

Faced with decreasing production from the gold heap leach operation, Robinson implemented a drilling and blasting program on the leach pads in 1993. This program offset some of the negative effects of low ore permeability and short circuiting of leach solution that resulted in lower than optimum recoveries. The drilling and blasting program created new solution flow paths and increased gold recovery. Production and pulp assays at depth intervals, prior to and following drilling and blasting, reveal the degree of short circuiting and benefits of the program.

Jan 1, 1995

By George K. Mitteer

The Cowles Mountain Tunnel was driven 2,073 m (6,800 ft) with a 3.43 m (11 ft 3 in) shuffle shoe TBM, for the San Diego County Water Authority, through extremely high strength granitic rock in the City of San Diego, Ca. The initial contract was $10.9 million. Tunneling began in March 1992 and all work was completed in May 1993. After the tunnel drive was completed in September 1992, a 2.44 m (96 in) Welded Steel Pipe was installed, welded and encased with cellular backfill to complete a small portion of the County's $970 million Capital Improvement Project. This paper will discuss the successful completion of a tunnel through some of the hardest most abrasive rock ever excavated with a TBM in North America.

Jan 1, 1995

By S. F. Smith

Following a roof beam collapse on a major production district at the British Steel Corporation's Dragonby Iron Ore Mine, Scunthorpe, South Humberside, UK, rock mechanics investigations were undertaken in this room and pillar operation to assess the stability of workings throughout all the underground mine area. Over a four year period room convergence and roof sag were monitored in different mining areas and various junction configurations in order to assess and compare the relative movement of the strata resulting from mining activities, where varying rock bolt lengths and patterns have been utilised. The paper, after shortly describing geological aspects and mining methods, presents the research procedure adopted together with the instrumentation employed and discusses the results obtained during these investigations.

Jan 1, 1995

By Fleming GJ

The Miwah prospect lies on the dilational 070¦ trending Miwah Lineament near its intersection with northerly oriented fractures within Pliocene volcanic rocks exposed between a NW trending segment of the dextral transcurrent Sumatra Fault, and the more northerly trending Samalanga-Sipopok Fault to the east. These faults reflect the continued interaction between stresses from the India-Australia plate located to the southwest, and spreading within the Andaman Sea to the north of Sumatra. A system of deep seated faults is believed to have facilitated emplacement of post-Miocene magmas and Quaternary volcanic centres at shallow crustal levels throughout northern Sumatra.

Jan 1, 1995

By Sudhir C. Dhara

An attempt has been made on the concentration of Platinum Group Metals (PGM) from the converter matte material by microbial .leaching. Biological oxidation of base metal sulfides such as iron, copper, nickel and free sulfur present in the matte material using Thiobacillus ferrooxidans is an alternative method to concentrate the PGM-and gold. The method which produces a platinum group metals concentrate is comparable to chemical processes and electrochemical process.

Jan 1, 1995

By D. G. Hulbert, J. H. Schubert, R. G. D. Henning

"Froth depth, along with reagent addition and aeration rate, is one of the crucial factors that can be used to control a flotation circuit. Sub-optimal setpoints and disruptions in levels have a severe adverse influence on grades and recoveries. A novel control strategy has been developed which provides exceptionally tight regulation of pulp levels. The controller observes and acts on all the flotation levels simultaneously. This provides a clear improvement over the standard approach, which is to use a set of Pl controllers. The system has been run on several industrial plants and has resulted in reduced fluctuations in level; fast responses to setpoint changes, and fast settling times after start-ups or disturbances. Testwork has shown that the improvements in level stabilisation translate into improvements in recovery and grades.IntroductionProcess control and optimization have an important influence on the economic efficiency of flotation plants. Inefficient operation can allow the wrong balance between grades and recoveries, and can also lead to adverse shifts in the grade-recovery relationship. Of all metallurgical operations, flotation loses the largest proportion of valuable material. Better operation can reduce these losses.An essential requirement of a good controller is that it should be able to stabilize and regulate the plant. Stable operation allows the performance of the plant to be observed without being obscured by the effects of disturbances and fluctuations. The optimum conditions can then be detected more easily. Good regulation can maintain operation at the optimum with proper neutralization of disturbances. Only when good stabilization and regulation are achieved can an optimizing strategy be properly applied.Froth depth, aeration rate and reagent addition are the three means by which a flotation plant is generally controlled. These control actions are effective on different time scales. Reagent addition is slower in its effect as some conditioning time is required. Since reagents are only added at the head of the circuit and at a few selected points within the banks, time is required for the effect of reagent changes to move through the circuit. Because of this slower time constant, reagent addition is more suited to process optimization and to dealing with slower changes in the process. An example of these slower changes is variation in the feed."

Jan 1, 1995

By Bruce Vandenberg, Andy Bartfay-Szabo, Steve Conway

Recent advances in solid-state, field portable, fast framing video camera systems and PC based frame capture hardware now allow blast imaging up to 500 frames per second. Up to 8 seconds of data can be stored directly into the unit, downloaded to a PC or archived to a standard VCR without data compression. Since no film processing is involved, motion analysis can be performed instantly and on-site within a few minutes. This paper will describe the design features and applications of the SVClOOO system and compare these with the analogous aspects of film based cameras.

Jan 1, 1995

By J. W. Cash

The mineralogy and textures of cyclone dust, sludge, and occasional build-ups in the American Iron and Steel Institute (AISI) direct iron making pilot plant at Universal, Pennsylvania have been studied by reflected light, transmitted light, and cathodoluminescence microscopy, and phase compositions have been determined by SEM-EDS. The cyclone dust consists of particles of carbon, metallic iron, sulfur-bearing iron, and wustite. Measurements of particles in the sludge indicate that 69% are less than 2.5 µm across, 21 % are 2.5-5 µm, and 10% are larger than 5 µm. Mineralogically the sludge particles are mainly carbon and metallic iron, with minor wustite and sulfur-bearing iron. Build-ups that sporadically develop in the furnace consist of olivine, hercynite spinel, metallic iron, wustite, pyrrhotite, pseudobrookite, akermanite-ferroakermanite and gehlenite. The microtextures shown by the build-ups indicate that much of that material has precipitated at the build-up loci. This study has been supported by AISI and the U.S. Department of Energy.

Jan 1, 1995

By Vynne J. F

Drill monitors for rotary blasthole drills have been available to the mining industry since the 1970s. The early monitors were pen strip chart recorders that were developed for the oil drilling industry and adapted to mining. They recorded drilling parameters such as depth, pull-down pressure, torque, RPM, and hailing air pressure. While these recorders could generate a large volume of paper, the amount of useful data was minimal. The data was not summarised and required an engineer to interpret the chart traces. Being a mechanical recorder, the devices were also susceptible to frequent failures. Modem electronics, and the development of the personal computer and its associated software have radically changed the type of instrumentation that is now available for blasthole drills. Perhaps more important is what can be done with the data. The PC allows the logged data to be analysed, summarised, and a variety of reports to be generated. The reports can be customised to meet the specific requirements of the mine and reduce the amount of time that is required to interpret the data. There is also an increased awareness in the mining industry of the importance of production drills. Blasthole drills have typically been the piece of production equipment that received the least amount of attention in a surface mine. Management focussed on the trucks and shovels or draglines. This situation is changing, and therefore the benefits that can be derived from monitoring drill performance are being recognised. Potential economic benefits of installing drill monitors have been documented in previous papers (Peck and Vynne, 1992). Mines are finding that pay-back periods of less than twelve months and rates of return in excess of 30 per cent are not uncommon. These benefits include the following: 1. Reduced overdrilling; 2. Increased rate of penetration; 3. Helping to locate coal seams; 4. Identification of weak and strong zones; 5. Reduce geophysical logging; 6. Optimising blasts; 7. Improved fragmentation and diggability; 8. Decreased coal dilution; 9. Increased bit life; 10. Reduced maintenance costs; 1 I . Improved accuracy of data and reports.

Jan 1, 1995

By Binns RA, Murao S

The PACMANUS and Jade deposits are two active hydrothermal fields that are forming massive sulfide deposits at the Pacific rim margin. Both are associated with felsic submarine volcanic rocks and both occur in back-arc settings. However, PACMANUS is associated with almost sediment-free dacites and lies on the crest of a volcanic ridge, whereas Jade occurs in a heavily-sedimented tectonic depression associated with a basement of pumiceous rhyolite. The PACMANUS deposit is richer in Cu and Au, and Jade in Pb. Zinc, Ag, As and Sb contents are similar. Sulfide textures at PACMANUS suggest formation of Cu and Zn sulfides by simultaneous double-diffusion involving inwards-moving seawater mixing with outwards-moving hydrothermal fluid. By contrast, at Jade there is a more complex history of formation where initial growth of barite on the sediment surface, probably associated with microbial activity, formed an impervious cap which trapped higher temperature hydrothermal solutions.

Jan 1, 1995

By Mark E. Smith

Large scale copper heap leaching in Chile began in November 1980 when the Lo Aguirre heap leach project was put into operation. At almost the same time, El Indio gold mine began production. While El Indio was not a heap leach project, it was Chile's first major bulk tonnage, open-pit gold deposit. This paved the way for the introduction of North American gold heap leach technology in the early 1980s. Heap leaching has become more popular in Chile during the past five years because it allows the exploitation of large but relatively low grade ore bodies at a reasonable cost. Pioneering research in hydrometallurgy carried out at some Chilean universities and at the Centro de Investigaciones Minero Metalurgicas (CIMM) played an important role. There are more than 10 large copper heap leach and solvent extraction/ electrowinning (SX/EW) process plants in different stages of development in Chile. Total production from these facilities will eventually increase Chile's present copper exports about 50%.

Jan 1, 1995

By A. Pradakar, J. G. Groppo, J. W. Leonard

All coal transportation systems from the coal face to the final point of use would become more productive if additional tonnages, obtained through improvements to bulk density, could be placed in fixed volume containers such as scoops, shuttle cards, trucks, barges and ships, as well as conveyors. This paper reviews previously reported work where the treatment of coals with small amounts of mining chemicals (0.12 to 0.28 kg/t or 0.25 to 0.56 lbs/st) during lavoratory testing was show to increase loaded coal bulk density by about 15%. The latest bulk density enhancement findings to develop from ongoing research involving underlying chemical and physical theory together with the added use of simple mechanical excitation are discussed.

Jan 1, 1995

The explosion of a charge in a drillhole sets the surrounding rock mass into vibrating stress wave motion. Except in the immediate vicinity of the drillhole, the dynamic stresses associated with this motion do damage only to pre-existing joints, cracks, or other weak planes, not to the rock material in between these. The joints are weak in tension, therefore the damage occurs as a result of tensile stresses. The initial damage process in the rock mass that ultimately breaks loose in front of the hole is similar to that in the remaining rock behind the drillhole. Recorded or calculated values of the vibration velocity and frequency contain a wealth of information about the combination of stress and strain that causes the damage. This paper outlines a new technique by which the peak strain energy derived from measured or calculated vibration velocity records is used to determine the local fragment size distribution. It combines two previously known and well tested techniques, namely the Holmberg-Persson calculation of the peak vibration velocity generated by an extended charge and King's calculations of the fragment size distribution as a function of the strain energy in rock crushing. Both of these calculations are based on experimental data and have been tested and found to agree well with actual conditions in their respective fields. Holmberg-Persson's calculated peak vibration velocities have been used successfully to predict and control damage to the remaining rock in cautious blasting, while King's calculation successfully describes the comminution of rock in mechanical crushing. Preliminary predictions of fragmentation in two types of rock blasting, a large hole open pit mining blast and a tunnel round, indicate that the new technique for fragmentation prediction has the potential for predicting fragment size distributions within the rock removed by the Blast.

Jan 1, 1995

By D. W. Fuerstenau

The success of industrial flotation separations has been the design of specific chemical schemes for regulating the bulk and the surface chemistry of the system. Highlights of fundamental research on the nature of flotation reagents and their mode of action in flotation, which has been carried on for about the past 65 years, is briefly reviewed.

Jan 1, 1995

By R. H. Hanewald

INMETCO, a subsidiary of Inco Limited, is the only facility in North America that provides High Temperature Metals Recovery for nickel-, chromium-, and iron-bearing wastes. Since 1978, this process has prevented more than 775,000 tons of materials from becoming part of the nation's waste stream. The paper describes Inco's experience in metals recovery, traces the development and explains the operation of the High Temperature Metals Recovery Process, and examines the procedures and criteria used to determine whether spent catalysts meet process feed specifications. An overview of the current requirements for transporting spent catalysts is provided. The paper concludes with brief case histories of catalysts users employing High Temperature Recovery to manage spent catalyst.

Jan 1, 1995

By G. J. Krige

The extent of ground movements and stress concentrations in the vicinity of the reef in the deep mine-shafts used in the South 4frican gold-mining industry have led to the requirement that special tower structures be developed to span the reef intersection zone in several new shafts. So that structural engineers are able to design these towers, it is necessary to model the dynamic behavior of conveyances traversing them in some way, to provide a means to determine the magnitude of the forces generated. This paper describes the development of two such procedures. The first is a numerical method, utilizing a step by- step integration technique to track the motion of a conveyance through a tower. This technique has been implemented in a computer program, and some results are given.

Jan 1, 1995

By E. M. Williams

The U.S. Bureau of Mines recently conducted a limited-scope study on the use of lineament analysis and electromagnetic geophysics to better identify the surface expressions of faults at the Cimmaron Mine near Raton, NM, an operating longwall mine in the York Canyon mine complex. Two normal faults were encountered by the mine, one during gate road development and drilling and another only through drilling. The potential ground control problems and offsets associated with these faults will severely impact long-range development plans, so it is essential to know the lateral extent of these faults within the coal reserves. The surface topography at the site is fairly rugged, yet outcrop exposure is poor. There is no obvious visible geologic evidence to indicate that the faults identified at depth extend to the surface. Both the geophysical and remote sensing techniques provided information on the presence and extent of important geologic structures which could not be gained just from drilling and surface outcrops. The geophysical surveys also were invaluable in confirming the presence of subsurface geologic structures in the vicinity of the lineaments assumed to be associated with the faulting.

Jan 1, 1995

By Frost M. T

Magnesium is the lightest metal used in structural applications but these are only a small part of magnesium usage, with the use in aluminium alloys consuming half the magnesium produced. Other applications include steel desulphurisation, nodular iron manufacture and metal reduction. Demand for magnesium is expected to increase towards the end of the decade because of a requirement to lighten the weight of automobiles. The current western world plant capacity and production rate is 250 000 tpa. The CIS and PRC also have production capacity but shipments from these countries have been limited in the last half of 1994. The price for magnesium has followed trends similar to aluminium with recent recovery from US$1500 per tonne in 1992 and 1993 to US$4000 per tonne in 1995. The major magnesium producers all use different production methods and the potential exists to establish a large-scale magnesium industry with operating and capital costs comparable to aluminium. The Australian Magnesium Research and Development Project has been established to develop a low cost method of production using the magnesite and infrastructure resources in Central Queensland.

Jan 1, 1995

By A. E. Isaacson, T. H. Jeffers

The U.S. Bureau of Mines (USBM) is investigating arsenic removal from dilute waters using a biological precipitation/chemical adsorption system. The method includes (1) inoculating water with ferrous salts to increase hydrogen sulfide generation by indigenous sulfate-reducing bacteria, (2) utilizing the hydrogen sulfide to precipitate the bulk of the arsenic as arsenic sulfide, and (3) using beads containing ferric oxyhydroxide to remove the remaining arsenic. This approach was applied to a contaminated water containing 13 mg/L As. Arsenic extractions up to 99% were achieved. The use of sulfate-reducing bacteria is particularly warranted in this situation since most of the required nutrients are present in the water. Based on successful initial efforts, planning is underway to conduct a pilot-scale test at the site.

Jan 1, 1995