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By J. M. Mutmansky, R. A. Jankowski, M. A. K. Mohamed

"SYNOPSISKnown health hazards associated with the breathing of respirable dusts, particularly silica dust, during mining are becoming a great concern in many parts of the world. The search for effective and low cost dust control methods for underdeveloped countries will help in improving the productivity and keeping the mine environment safe. This article addresses the problem by providing suggestions concerning the easiest and most cost effective methods to control respirable dust in mining and mineral processing operations. INTRODUCTIONMedical BackgroundLung diseases caused by dust in mining operations have been recognized by mankind since the time of the Roman Empire. The writings of Pliny the Younger on natural history reported on maladies associated with dust in mining in the first century AD. However, no significant advances in controlling the lung diseases of miners came about for many centuries. The effects of mineral dusts were further described by Georgius Agricola in his sixteenth century book on mining (Agricola, 1556). After the appearance of Agricola""s book, lung diseases were more readily recognized, but the nature and severity of the ailments associated with mineral dusts could not be readily interpreted.In 1896, the discovery of x-rays by Roentgen advanced the diagnosis of lung diseases and the knowledge of what causes these diseases. In addition, the discovery allowed medical personnel some method of judging the extent and severity of the lung diseases in human beings. During the ensuing years, the term 'pneumoconiosis' became the common term to describe any of the diseases of the lung in which dust particles deposited in the lungs caused fibrous tissue and loss of some of the respiratory function. However, little in the way of social remedies for the diseases resulted until much later. Society was still not ready to act decisively to reduce the causes of lung disease due to the dusty conditions in the work place.Social action against lung diseases did not occur in the United States (US) until the 1930s. At that time, a tunnel driven through a sandstone mountain near Gauley Bridge. West Virginia, caused the death of several hundred workers due to acute silicosis, a severe form of pneumoconiosis caused by silica (Seaton, 1975). Dust conditions in this tunnel were quite bad, causing many of the workers to be subjected to extremely high silica dust concentrations. The severity of the disease in many of the workers became known to the public and prompted the US Congress and many of the states to enact laws to reduce the dust levels."

Jan 1, 1998

By N. Kanari

Reactivity of MgO towards C12+air, C12+N2 and C12+CO gas mixtures was studied up to 1000 °C. Carbochlorination of MgO occurs at temperatures lower than that of its oxychlorination. Effects of gas flow rate, temperature and partial pressure of the carbochlorinating gas mixture on the reaction rate were investigated. The apparent activation energy of MgO carbochlorination is 49 kJ1 mol between 425°C and 600°C. At 550 °C, the apparent reaction orders with respect to C12+CO, C12 and CO, are 2.37, 1.47 and 0.89, respectively. At this temperature, the maximum reaction rate was obtained using a C12+CO gas mixture having a Cl2lCO molar ratio equal to about 0.6.

Jan 1, 1998

By S Harvey

An inrush of water or mud into an underground mine, or sudden subsidence above mining voids represent low probability but high impact risks in underground mining. About two such incidents involving multiple fatalities or loss of production are reported each year worldwide. On average, Australia experiences one such incident every three to four years. This paper reports the development of a Standard that is intended to eliminate fatalities due to inrushes and subsidence.

Jan 1, 1998

By D. A. Stanley

Researchers at BCD Technologies and the University of Alabama have applied three statistical techniques to the information contained in a large database of measurements from a phosphate ore processing plant. The rust, Principal Components Analysis (PCA), replaces many measured variables with a few fundamental and un-correlated variables. The second technique, Projection to Latent Structures (PLS), is an extension of PCA that explores the relation between variables identified as either independent or dependent. The third technique, Cluster Analysis (CA), is applied to the results of the PCA or the PLS calculations, and identifies individual data clusters that represent uniform operating conditions in the plant. All three statistical methods can be seen as geometrical operations on the data viewed as points in space. A Viewer gives a corresponding graphical presentation of the data points. This paper describes the use of the above three techniques and the Viewer to explore part of the phosphate flotation database.

Jan 1, 1998

By Dennis Greene

Real-time GPS position monitoring of mining equipment is becoming more and more commonplace. Digital mining plans can now be used onboard properly equipped earthmoving equipment and excavation status is available in real-time via high bandwidth data radio systems. These systems provide a closely integrated link between operations and planning. No longer must operations wait for or be hindered by insufficient survey marks, nor is engineering delayed by lack of timely mine status information. Unprecedented efficiency gains become feasible -from the engineering office, to drilling and mucking, to reclamation, as well as in mine construction projects. Direct economic benefits of these systems will be explored as will the less tangible, but very significant, indirect operational efficiency gains.

Jan 1, 1998

By Kenneth N. Han

Ammonia has been found to be an effective leaching reagent for gold, silver and platinum group metals in the presence of appropriate oxidants. Electrochemical and kinetic aspects of the dissolution of elemental gold in ammoniacal solutions have been investigated. The cathodic reaction of aurous di-ammine on the gold cathode has been investigated first. From this investigation, the standard electro-potential of the cathodic reaction .and hence. the Gibbs free energy of formation of the aurous di-ammine were established. The solubility of gold in ammoniacal solutions was also examined in relation to ammonia concentration, temperature and concentration of various oxidants. The anodic reaction of the gold disk in ammonia? in the presence? of various oxidants including oxygen, ozon, hypochlorite, hydrogen peroxide, cupric and cobaltic ammine, and iodine was also examined and the results have been discussed. Excellent dissolution yielding of gold and many other metals, typically better than 95% recovery in 1'-2 'hours of leaching at a temperature ranging 80°C to 190°C has been observed. Test results of the dissolution of gold from elemental state as well as other sources including sulfidic ores and scrap are presented.

Jan 1, 1998

By A. J. Sinclair

"Abstract-Geology contributes essential information toward obtaining high-quality resource/reserve estimates. In this context, geology can be considered under the following overlapping topics: regional geology, detailed (deposit) geology, mineralogy, ore deposit models and continuity, with geological mapping being fundamental to all. Each of these topics is considered here in terms of potential contributions to "improved" mineral inventory estimation. Some of the principal conclusions are:1. Regional geological relations must be consistent with deposit geology. It is common that important geological relations are more clearly evident in various regional locales than in highly altered and/or highly deformed mineralized areas containing mineral deposit.2. Detailed geology provides information for a geometric model of a deposit, a model that serves as a basis for mine planning. It is important to distinguish fact from interpretation in such models. Substantial effort is required to characterize the geometric margins of a deposit and the relation of these margins to the simplistic geometric form that normally emerges as an interpretation.3. Mineralogical studies relate to many aspects of deposit evaluation including abundance of ore and deleterious minerals, spatial distribution of ore and deleterious minerals, grain size characteristics of important minerals, mill design, etc.4. Ore deposit models contribute substantially to confidence in developing a three-dimensional geometric model of a deposit for mine planning. Specifically, they are a basis on which to develop rules for interpolation and extrapolation of ore, and they contribute to recognition of domains, each with its own characteristic continuity and margin character.5. Continuity is dependent on mineralization style and may be controlled structurally and/or chemically. It is important to distinguish geological continuity and value continuity. A wide range of classical geological methods are useful in examining geological continuity; value continuity is best viewed as a statistical characteristic that is quantified by any of several measures of autocorrelation."

Jan 1, 1998

The Broken Hill Proprietary Company Limited (BHP) started as a silver-lead-zinc mining company in Broken Hill, New South Wales, Australia in the 1880s. Since then it has diversified into the resource industries of steel, iron ore, coal, petroleum and copper. BHP World Minerals is a Business Group of BHP which is one of the worldÆs largest and most diverse mineral resource enterprises. BHP supplies raw materials for steelmaking, copper concentrate and other mineral commodities to customers in more than 45 countries. BHP World Minerals has operations spread throughout the world û in Australia, the United States, Brazil, Zimbabwe and Canada. Commodities produced by BHP World Minerals currently include silver, lead, zinc, titanium minerals, platinum group metals and coal. The BHP World Minerals Cannington silver-lead-zinc mine in Queensland, Australia is a return to the cradle of BHPÆs early silver-lead-zinc years. This paper compares the success factors and challenges at Broken Hill and Cannington.

Jan 1, 1998

A study was conducted to evaluate the effectiveness of the three types of sample grinders routinely used in the mining industry for the sample preparation of gold ores with particular emphasis placed on testing their capacity to produce a representative assay sample of coarse gold ores. The grinders used in this study are the Labtechnics LM5, the Mixermill 4010 ringmill and the Keegor vertical spindle pulveriser, commonly called a Keegormill. The study was based on the preparation of samples from two sources of known coarse gold ore, the Union Reefs Gold Mine and the Brocks Creek Gold Mine in the Pine Creek region of the Northern Territory of Australia, and a fine gold ore which was from the Macraes Gold Mine in New Zealand. The Union Reefs Mine contains visible coarse gold with 30 per cent to 40 per cent of the gold in the plus 75 μm fraction of milled ore. Discreet particles up to 5 mm have been recorded, Hellsten (1994). Union Reefs Gold Mine recovers 40 per cent of its bullion production through a gravity circuit, Riches (1997). Brocks Creek ore contains visible coarse gold with gravity bullion production fluctuating between 50 per cent and 65 per cent, depending on the mill feed. Average gravity bullion production from the Brocks Creek Mine is 55 per cent, Wilke (1997). The average gold grain size of Macraes Mine ore is 20 μm with 40 per cent of the gold in sub 10 μm particles. No gravity bullion is produced from the Macraes Mine, O'Keefe (1997). The testwork demonstrated conclusively that it is possible to prepare a representative sample for assay, of a coarse gold ore, when a Keegormill is used to pulverise the sample to a nominal 100 μm particle size (90 per cent passing a 100 μm screen by wet sieving). Both the Mixermill and the Labtechnics LM5 failed to prepare a representative sample, even when ground to a nominal 75 μm particle size.

Jan 1, 1998

By Nemick JA

Recent advances in computer simulation together with field measurements of caving and microseismic activity about longwall panels, has allowed a much better understanding of the caving process and the variability due to geology. The joint research between SCT Operations and CSIRO Division of Exploration and Mining has initiated new methods of computational modelling predicting various caving patterns and strata failure far ahead of the longwall face. This work was validated by field measurements of caving and microseismic activity at the longwall face.The rock fracture distribution and the caving characteristics of a range of strata sections have been simulated by computer methods. Validation studies of the method were addressed together with case studies. The interaction of caving with support convergence and face control is presented. The method allows the simulation of longwall support behaviour under various geological conditions. The system also allows a prediction of the monitoring data, which is best suited to give an early warning of weighting events or signal various key caving characteristics.

Jan 1, 1998

By M. C. Roberts

In assessing the future markets for a mineral from a producing district, three key aspects must be considered: 1) the future growth in markets, 2) the competitiveness of the district in terms of production costs and reserve adequacy, and 3) the competition from alternative sources of supply. This paper will focus on the first issue by developing a method of predicting the demand for phosphate from the trends in the major markets for phosphate products, primarily the fertilizer and agricultural markets. The paper will show how broad changes in the final end use markets for phosphate products have evolved over time and how this has affected the needs for phosphate rock. These trends are then projected into the future to make an assessment of future phosphate requirements.

Jan 1, 1998

By A. Arik

1his paper presents a modified ordinary kriging technique referred to as the "Nearest Neighbor Kriging" (NNK). The method is a simple and practical tool to use when the ordinary kriging (OK) results are unreasonably smooth, especially when estimating recoverable ore reserves for deposits with skewed grade distributions. NNK is robust and globally unbiased like OK. However, it is more advantageous over OK because it can control some of the smoothing and conditional bias which have been the major pitfalls of OK in many grade estimation cases. The paper details the methodology of NNK and its application to a gold deposit.

Jan 1, 1998

By William A. Faust

La Colorada Mine was begun in 1993 as a small heap leach mine and was the first operation for Eldorado Gold Corporation. 'This paper describes the growth of the mine to annual production levels near 60,000 ounces of gold and highlights recent improvements that were made to maintain a profitable operation by efficiency gains and cost containment programs.

Jan 1, 1998

By James JV, Petho SZ

The South Deep surface shaft system is being sunk to a final depth of 2750 in below surface and on completion will be the deepest single drop haft in the world. The shafts will intersect the target reef horizon at 2650 to below surface. In order to negate the requirement for a shaft pillar, which would he extremely large at this depth, the reef horizon in the vicinity of the intersection is currently being mined. A high quality crushed waste/classified tailings backfill is being placed in the longwall stoping panels around the shaft intersection area. This kill limit closure and ride which following shaft reef intersection could have a detrimental effect on the long term shaft stability. This paper discusses underground instrumentation results and numerical modelling exercises carried out to confirm that the shaft system will he stable throughout the life of the mine. Instrumentation projects include closure and ride measured between backfill paddocks and haulage leveling exercises carried out to determine the far field rockmass response to mining with stiff backfill.

Jan 1, 1998

By Guocheng Pan

"Although many factors play roles in the estimation of recoverable reserves, smoothing effect and conditional bias are considered major geostatistical issues in the estimation. This paper introduces measures for smoothing effect and conditional bias, and provides insights into their relation to the estimation of recoverable reserves. Both smoothing effect and conditional bias are intrinsic to the information effect and kriging estimators. For a given level of drilling information, however, it is possible to identify the optimal search radius that minimizes conditional bias. Furthermore, it is also feasible to define variance correction factor for reduction of the smoothing effect from exploration block models. Both of these components are key to the accurate estimation of recoverable reserves. IntroductionThe accurate estimation of recoverable reserves is critical to decision making in different phases of feasibility study and mine planning. Much attention for improving the methodology of estimation has been focussed on the effect of the change-of-support (Parker, 1980; Dagdelen, 1996). For example, it is essential to make a volume- variance correction to the estimate of multiple indicator kriging (Hoerger, 1992). When the size of block, b, in the geostatistical model differs from that of selective mining unit (SMU), v, a volume-variance correction is warranted for the prediction of recoverable reserves.Most mining plans and decisions are made prior to the availability of high density blast-hole samples. In most mining operations, the true SMU grade Zv is unknown at the time of selection. Instead, the selection is based on the estimate Z v**derived from high density blast-hole samples within the deposit G. Nevertheless, the estimate Z v * of recoverable reserves in the stage of mine planning is derived from exploration data. At the end, the production result must be reconciled to the estimate Z v * . In other words, the selection is based on Z v** from blast-hole samples, while the final production figures are reconciled to Z v * from exploration drilling. For a given preselected cutoff grade z0, the actual mining panels will consist of the units having the estimated grade Z v** =z0 rather than the true grade Zv =z0. The difference between Z v** and Zv is usually of less concern."

Jan 1, 1998

By R. J. C. MacDonald

"The first recorded discovery of placer gold in Canada was on the Chaudiere River in Quebec's eastern townships in 1832 and the first major production came from placer deposits in British Columbia in 1858 (Verity 1974). Placer deposits were the major source of gold until the late 1890's, although lode deposits were found in Nova Scotia in 1862. In 1896 the Klondike Gold Rush commenced with the discovery of gold by Henderson and Carmack in the Yukon. The peak was reached in 1900 when over one million ounces of gold valued at approximately $22.3 million were recovered. With the exhaustion of the easily accessible deposits, more capital intensive operations were necessary such as those initiated in 1906 by the Yukon Gold Corporation. This giant dredging operation continued to produce until 1966. Today only a few small operations remain.The development of Canadian lode gold mining began in earnest around 1900 when the railroads were opening up the interior and western part of the country. At this time many discoveries occurred, particularly where mineral outcroppings were near surface. Tremendous impetus for exploration and the reopening of former producers followed the elimination of the gold standard by Great Britain around 1931, and more importantly the United States in 1933, with subsequent stabilization of the price of gold at $35 per ounce in 1934. Prior to this the price of gold was basically unchanged since 1717, approximately, $20 per ounce (Verity, 1974; Green, 1973).The depression of the 1930s adversely affected most industries, however for the gold producers it was a very profitable time. Prices of materials and equipment declined and labour was cheap and plentiful. Interest in gold mining was further stimulated in 1936 when a three year tax exemption was declared for all new metal mines. In 1938 a decline in the value of the Canadian dollar relative to the U.S. dollar benefitted the industry. The second world war provided yet again further incentive for gold production and in 1941 Canadian gold production reached a high of approximately 5.4 million ounces. This figure was not surpassed until 1991 when approximately 5.6 million ounces were produced (Natural Resources Canada, 1996 )."

Jan 1, 1998

When I wrote the Railroad portion of "Mining Engineering" magazines 94 Powder River Basin (PRB) Coal Article I described to you some definite destinations the Railroads had in mind. As with many destinations, the ones I wrote of turned out to be merely stops on the way to places that we have yet to reach. Somewhere along the way we discovered that making it better is a continuous process not just something that you can do in phases I, II, III, & IV. We always knew this I suspect, but perhaps not at the awareness level that exists in RR environments in 1997. The purpose of this article is to update the 94 article, which I could do very quickly. Everything I told you we were going to do in 94 is done, end of story! But in addition to making it a very short article it would not be telling you the things RR has done beyond what we were planning in 94 and for the future.

Jan 1, 1998

By S. K. Varma, Miriam Regalado, Daniel Salas, Erica Corral, Erika Esquivel

"Age hardenable 2014 aluminum alloys and composites containing 0.10 and 0.15 volume fractions of alumina particles (VFAP) have been solutionized at 540 and 550°C for up to 20 hours. The solutionized samples, heat treated for 5 and 20 hours, have been subjected to room temperature rolling until cracking develops. The work hardening curves have been compared to determine the effect of solutionizing time on the rolling characteristics from both hardness and the microstructural evolution points of view. Solutionizing at two different temperatures results in differences in the extent to which the composites can be rolled until fracture. The microstructural characterization by TEM has been performed to understand the room temperature rolling behavior.IntroductionThe effect of solutionizing on the age hardening response of 6061 and 2014 aluminum alloys and composites reinforced with 0.10, 0.15 and 0.20 volume fractions of alumina particles (VFAP) have been reported in the literature [1-4]. A comparison of the monolith and composites indicates that particles promote the aging process through differences in the microstructures in solutionized condition. The first effect of solutionizing is to produce a grain growth process which follows a grain growth law (square of grain diameter as a function of solutionizing time). It appears that it is possible for vacancies to be emitted during grain growth period as they try to minimize the total grain boundary surface area by increasing their diameter. This may be common to both the monolith and the composites. However, the second effect must be exclusively considered for the composites. The particles generate dislocations during the solutionizing process due to the differences in the values of the coefficient of thermal expansion (CTE) between the particles and aluminum base metal. It has been determined [1] that the dislocation density increases with increase in solutionizing time in the composites of 6061 aluminum alloys reinforced with 0.10, 0.15 and 0.20 VFAP. The improved bonding between particles and matrix can give rise to additional generation of dislocations due to curvature effects [1] with the result that the dislocation density continues to increase with increase in solutionizing time even after the CTE effect is considered to have been stabilized."

Jan 1, 1998

By P. A. Riveros, R. Molnar, F. J. Baša

"An acidification circuit was installed and operated at the Agnico-Eagle Silver Division refinery in Cobalt, Ontario, for treating ~300 m3 of a concentrated cyanide waste solution with the purpose of recovering its cyanide and metal values. The acidification circuit was designed from parameters determined experimentally at CANMET. Available refinery equipment was assembled according to a flowsheet developed by Agnico-Eagle Mines. The process produced a regenerated cyanide solution containing >15 g/L of free cyanide, which was used for leaching gold ore at another Agnico- Eagle operation. It was estimated that the value of the recovered cyanide offset the treatment cost. BackgroundThe Silver Division of Agnico-Eagle Mines needed an economic and effective method for disposing of ~300 m3 of a concentrated cyanide waste solution that had remained in the plant after the operation was shut down in 1989. As a result of extensive recycling and evaporation, the solution had become practically saturated with metals, cyanide, thiocyanate, sulphate and other components, and was, therefore, an environmental liability for the company. A partial analysis of the solution is presented in Table 1. Initially, the use of cyanide destruction methods was considered by Agnico-Eagle, but the estimates indicated a considerable cost with no credits to be gained. A research project carried out by CANMET showed that a simple procedure consisting of acidification, filtration and reneutralization was the most attractive option, because it enabled the recovery of a substantial portion of the cyanide. Furthermore, the metals would be recovered in the form of a solid precipitate. The research showed that conventional AVR was not applicable because of excessive cyanide degradation and low HCN volatilization obtained with this particular solution (Riveros et al., 1996). This paper describes the procedure used to treat the concentrated cyanide waste solution and the operating practices of the large-scale acidification circuit run at the Agnico-Eagle refinery."

Jan 1, 1998

By M. W. Grabinsky, P. B. Tomory, J. Carvalho, J. H. Curran

Many underground mining operations use Split Set friction stabilizer bolts for rock support. Currently, however, little has been done to quantify the effects of various rock mechanics and operational parameters on the capacity of frictional support systems. The strength of Split Sets is usually measured by means of a pull test wherein a jacking force is applied to the bolt and a slip load is obtained. In order to evolve a rational design procedure for this type of support, an extensive database of over 900 pull test results from more than 50 mines through- out North America has been assembled and analyzed. Associated relevant rock mechanics parameters (rock type and quality) and operational details (drilling method, bit size, drive time, time to pull test) were also obtained, as completely as possible, for each test. Analysis of the information has yielded several charts that relate pull-out strength to relevant parameters and simple statistical analyses were conducted where necessary. Quantified distributions for pull-out strength were also produced for several operating conditions. The factors that most significantly affect bolt strength have been identified and specific applications to design are discussed. The information presented will assist mining engineers in designing safer and more economic support using Split Sets.

Jan 1, 1998