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By J Vann, S Dunham, M Job

Two-dimensional (2D) estimation approaches have significant advantages over three-dimensional (3D) approaches when dealing with a narrow vein- or layer-like geometry. The main motivation for 2D estimation is that bias due to non-additivity of grade is avoided. The various aspects of 2D estimation are illustrated by use of a case study from the 1A Shoot Nickel deposit at Leinster, Western Australia. The width of the 1A mineralisation is variable, and so are the angles of drilling intersection. Consequently, the variable of interest (in this case nickel grade) is not suitable for direct kriging because it is defined on non-uniform support. However, grade can also be defined as the ratio of two variables that are suitable for direct kriging: thickness and accumulation. In the 2D approach, tonnage equates to thickness and metal equates to the product of grade and thickness, also called æaccumulationÆ. In the simplest approach we can independently krige accumulation and thickness and derive the grade by the ratio of the two resultant estimates. The thickness and accumulation variables must be in a consistent projection orientation, for example a horizontal projection in the case of steeply inclined mineralisation like 1A. Because the density is not constant across the 1A (and most other) deposits, the issue of density weighting is also discussed. The impact of the correlation between grade and length, or grade and density are important issues in implementation of 2D estimation. The circumstances under which these correlations need to be taken into account (by co-kriging) are reviewed. Finally some comments are made on the final use of the resultant 2D estimate for mine planning purposes.

Jan 1, 2003

By E Whiteman, L Reyneke, H Horsch

Heavy mineral sand deposits are a source for the economically important element titanium, which is contained in minerals such as ilmenite and rutile. In heavy mineral deposits ilmenite displays various degrees of alteration. Natural weathering of ilmenite involves the removal of Fe and thus results in an increase in the Ti-content. Minerals such as pseudorutile, ferropseudobrookite, anatase and the ill-defined mineral aggregate leucoxene, which consists mainly of various amounts of remnant ilmenite, pseudorutile, ferropseudobrookite and anatase, are typical replacement products of ilmenite. Ferropseudobrookite occurs as a recrystallised, optically and chemically distinct mineral phase. Textural relationships suggest a diversity of physicochemical conditions including weathering and metamorphism that led to the formation of complex mineral assemblages and textures. In the heavy minerals industry the alteration products of ilmenite are generally referred to as æaltered ilmeniteÆ and/or leucoxene. The distinction between æaltered ilmeniteÆ and leucoxene is not consequently defined and is very much dependent on economic factors and specific mining operations (ie determined by deposit specific mineral assemblages). Generally the term leucoxene is used in the heavy minerals industry as a collective description for ilmenite alteration products with TiO2-components ranging from 65 - 95 per cent. A detailed comparative mineralogical investigation including microscopic, SEM and QEMSCAN« techniques show that it is possible to identify and quantify the replacement products of ilmenite on a micron scale. QEMSCAN« generated particle maps were graphically compared with photomicrographs taken by applying reflective light microscopy. The resulting information can be integrated over the entire sample with respect to composition, absolute and relative mineral abundances, grain sizes, volumes, densities, textural relationships and liberation potentials. This provides a powerful tool for a first appraisal of the physicochemical behaviour of bulk samples and individual particles during metallurgical processing.

Jan 1, 2008

By Evans R, McCallum P

Modem blast initiation systems allow users many options for connection and application in the field, and have resulted in more innovative and complex uses of sequencing to influence blast outcomes. However, no tool existed which allowed the blaster to easily and quickly assess the effect of different options. The original requirement was for a computer program which allowed the easy input of blast patterns and the associated initiation sequence, and then permitted the evaluation of different options with respect to established criteria such as the number of holes per delay and angle of initiation. The implementation of this goal saw the development of the SHOTPIan blast sequence design software, with particular emphasis on an easy-to-use menu driven interface and visualisation of the blast sequence. Extensive trialling during development saw the incorporation of additional features requested by industry such as the ability to import from established mine design software packages, and further features such as the calculation of burden relief times. Case studies of the use of the program are provided, where the rapid evaluation of a number of options has enabled blast results to be optimised. Examples are also given of cases involving two-path initiation

Jan 1, 1995

By Corrans I. J, Yan D. S

The CIP process for gold recovery has enjoyed widespread application in most gold-producing countries. The development of a mathematical model of the CIP process has value for use in process design, process optimisation, and process control. Mathematical model development through laboratory experimentation is an important step in the design and optimisation of the CIP process. For this purpose, data has been generated through small scale laboratory leaching and adsorption tests both in batch and continuous mode. This test program has been carried out on specific ores of various types prior to the application of the models to production CIP plants utilising these ores. The applicability of leaching models derived from batch experiments was tested in a continuous five stage CIP pilot plant. The models were then adapted to scale-up the batch to the small scale continuous operation.

Jan 1, 1991

By Hematian J

A high horizontal stress field has significant effect on the stability of underground roadways and influences the design of a support system in this environment. The high horizontal stresses at E1lalong Colliery, NSW, Australia provided the environment for this study. Samples of coal measures 'rock were collected and tested to determine their mechanical properties. The lithology, stress state, geometry and conditions prevailing in particular areas of the mine were obtained from geotechnical reports available at the mine and by field observation. The results of a series of finite element models constructed and tested under various conditions provided a basis for comparison with field observations. Analysis of the results indicated sufficient correspondence to provide a basis for the proposed design of an optimum support system. It is not suggested that finite analysis provides 'exact answers', but it does show the relative importance and interaction of various parameters.

Jan 1, 1995

The detailed work done by Stillwell and Edwards on the occurrence of cobaltite and safilorite-Iollingite at the South Mine, followed by its presentation as a paper to the Institute, calls for, a few notes on its occurrence elsewhere in the Broken Hill field. No massive cobaltite similar to that in the South Mine veinlet is known except from the Consols Mine (as mentioned in the paper). Fine grained cobaltite has, however, been found in low-grade ore from the North Mine. Microscopic grains occur in a mineralized green feldspar pegmatite. The feldspar has been replaced in part by graphite, and the cobaltite occurs in association with the graphite. In its hardness, pinkish-white colour, and resistance to the standard etchingqeagents it is similar to the South Mine cobaltite; it is etched by acid permanganate solution. An interesting feature of this occurrence is the way in- which some of the minerals (notably galena) have forced apart the graphite lamellae in crystallizing, forming lenses enclosed by the curved cleavage surlaces 0;[ the graphite.StillwelI and Edwards cite a note by G. Smitht for the statement that "cobaltite has been recorded from the Australian Broken Hill Consols Lode in the vicinity of the rich silver deposits, though not in contact with them."Smith, however, is here referring to the oxidized zone. Elsewhere in the same article he states "... a deposit of cobaltite in a very much altered condition was found. This was impregnated with silver, and assayed as high as 3,000 ounces," Of the cobaltite in the unoxidized zone, Smith simply states that it became rarer with depth.Cobaltite has also been recognized by Mr. H. F. Whitworth, M.SC., Curator of the Mining Museum, Sydney, in specimens from Burt's Copper Mine eight miles south of Broken Hill.

Jan 1, 1944

By West-Sells P, King J. A, Patel C

The Eskay Creek orebody is located in north-central British Columbia (Canada). The ore contains major gold and silver values and minor but economically significant quantities of zinc. The refractory nature of the gold necessitates a pressure oxidation pretreatment prior to cyanidation. After solid-liquid separation the oxidation solution can be treated by oxyhydrolysis for iron removal and cementation with zinc dust for noble element removal. The resulting solution, as obtained in pilot studies, contains 7 - 10 g/L Zn, 0.5 g/L Ca and 2 - 4 g/L Mg. Minor amounts of cadmium, copper and iron may also be present in the solution. Over 90 per cent recovery of zinc from Eskay Creek oxidation solutions could be obtained by four stages of zinc extraction with Cyanex 302 extractant (Cyanamid Canada Inc, Niagara Falls, Canada). Zinc was stripped from the organic with spent zinc electrolyte in two stages. A complete description of the bench scale and miniplant studies of the solvent-extraction electrowinning circuit follows. The behaviour of minor amounts of copper, cadmium and iron in the circuit is also Discussed.

Jan 1, 1993

Inefficient conveyors suffer carryback, leading to the build-up of materials on idlers, and other expensive components. They spill and leak material at loading zones and transfer points, causing accumulations that can damage the belt, wear moving components, and increase both cleanup labor and maintenance expense. They wander or mistrack, spilling material and en- dangering personnel and conveyor components, including the belt itself. And through these inefficiencies, they multiply an operation's hidden costs-the dollars lost because of missed production, of increased downtime, of the expense for the replacement of prematurely worn or damaged equipment. In this paper, the author will examine the importance of belt conveyors to mines and process plants He will trace the state-of-the-art in systems for cleaning belts, and controlling the release of fugitive material from conveyor transfer points, by exploring the roots of the problems, and demonstrating solutions that have been proven to be effective. Included in these systems to improve material handling are transfer point stabilization and sealing systems, dual belt cleaning systems, and belt training idlers.

Jan 1, 1991

By Paley N, Cameron A, Townson P

Although blasthole deviation is a problem which can seriously affect blasting operations, there is little practical emphasis on controlling this deviation and no practical emphasis on understanding its practical behaviour. The most common way of dealing with it involves tight control over drill set up and surveying hole paths. The surveying might involve simple collar location and inclination measurement to estimate the hole's actual path. At best, some operations routinely survey hole paths after all holes in a stope have been drilled. In addition, although there is an expectation that holes will deviate, there is no planning for this behaviour in order to reduce its impact on the blast. Design decisions are invariably made with the assumption that holes are straight. If and when surveys reveal problems it is possible only to adjust charging and initiation to 'work around them'. In extreme cases the drill might be recalled to fill in gaps. The lack of planning and the lack of understanding are doubtlessly linked.A model is presented that will predict the expected path of a drill hole. By knowing how a selected few holes deviated it is possible to make a good estimate of the deviation of other holes in the same rock mass. After minimal calibration the model can be used to increase the amount of information for a given amount of surveying or the amount of surveying can be reduced while maintaining the same level of knowledge of blasthole deviation. Equally important is the ability to plan for the deviation in future drilling through altering the initial collar angles or drilling from different locations. It is the authors' hope that planning for hole deviation becomes as much a part of the design process as planning for detonator delay scatter and explosive performance variation.

Jan 1, 1992

By G Chitombo, M Ruest

In surface mining, studies of the kinematics of blasted rocks using high speed film/video image analysis have allowed the estimation of the starting time, direction and magnitude of visible movement of fixed sections of the free face. Horizontal displacement versus time plots from discrete targets at the face generally report changes in slope over very small time intervals. These changes indicate step increases in velocity due to the action of explosive gases. In practice, the onset of rock mass movement, different to localised spalling, has been associated with a response time which exceeds the combined times of detonation, propagation and reflection of stress waves. This time is referred to as minimum response or burden movement time. As an engineering index, burden movement time has been used to provide guidelines for the selection of inter-hole and inter-row delay sequences in production blasting. With respect to improving breakage and fragmentation, it has been demonstrated that the delay interval between adjacent explosive charges should be less than the expected burden movement time. Similarly to reduce confinement between rows, delay intervals should exceed the expected burden movement time. The Hybrid Stress Blasting Model (HSBM) is a modelling framework that dynamically links an ideal and non-ideal explosives detonation code to a geomechanical rock model. This blast simulation tool is aimed at analysing the role played by different explosive formulations in fragmenting and/or damaging various rock types under different degrees of confinement. In the current framework, the rock behaviour under extremely high pressures and loading rates is calibrated from shock tests and the role of the explosive in fracture growth is accounted for and assumes a compressible fluid flowing through the explicit fracture network. The model is being developed as part of an international collaborative research project funded by a consortium of companies comprised of explosive and equipment suppliers and major mining houses. As part of the development and validation of the HSBM project, data from literature addressing the kinematics of the rock mass (ie burden displacement, face velocities and response times) has been collated and used to evaluate the current version of the code. A series of numerical experiments have been conducted with the view to: evaluate the response of the rock mass to changes in burden distance given by the impact of both stress waves and radial gas flow pressure;compare the modelling outcomes in terms of displacement, response time and face velocities to documented field observations; andcompare stress induced and stress/gas induced modes in terms of burden displacement outcomes. Results from these experiments have shown that in its current form the model is able to capture the trends observed and measured in practice. This is with respect to the simulation of burden displacement, response time and average face velocities for different geometries and charging conditions. The experiments have served as consistency checks which form part of an ongoing and comprehensive evaluation and validation of the HSBM code also aimed at addressing some of its current limitations.

Jan 1, 2007

The structural pattern of Victoria shows the presence of EW, NW, NE as well as the more readily recognised NNW factors commonly associated with the goldfields. ENE and WNW trends are also present. This structural lattice affects all rocks of the State. Landsat imagery shows that the EW, NW and NE structural elements are closely related spatially to the distribution of Palaeozoic igneous intrusives, Cainozoic volcanic vents as well as all historically important gold mines. It is suggested that the EW, NW and NE structural grid visible on landsat imagery is a reflection of the structure of a mid-crustal layer situated between 3.5 and 17 kms below the surface. The points of intersection of the structural elements of the mid-crustal layer offer most favourable loci for the escape of energy in the form of heat. The correlation between the distribution of igneous plutons, volcanic vents and centres of mineralisation, all reliant on high levels of energy for their formation, indicates the stability of the structures of the mid-crustal layer since early Palaeozoic times. The deep level crustal structures are believed to be, related to the release of stresses placed on the crust since early Palaeozoic times by the rotation of the Earth. A geological model that accommodates the presence of a mid-crustal layer as well as the complexities of the recognised orogenic cycles of southeast Australia is suggested. All 1 000 kg Au reef and deep lead mines fall within 1.5 and 2.5 km respectively of strong linears associated intimately with plutons and volcanic vents. Future exploration of the State is more likely to meet with success if it too is confined to the evaluation of these and similar linears. The mode of mineralisation of any one centre will depend upon the temperature, pressure and geochemical gradients operating on the migrating mineralising fluids as well as the structures in the host rocks. These factors are likely to have varied considerably from one centre of mineralisation to the next and consistency of mineral isation form and depth should not be expected along the length of any single Linear.

Jan 1, 1986

Of the energy resources present in Australia, coal and uranium are by far the largest. These two resources ap- pear sufficient to satisfy Australia's energy needs beyond the immediately foreseeable future and long after the natural petroleum resources are exhausted or have ceased to play a significant role. By that time, coal could be converted in plants of very large size to synthetic liquid and gaseous fuels which will be used as substitutes for pet- roleum fuels, particularly for transport. The basic role of uranium will be to supply electricity from nuclear power stations for heat and power requirements, thereby freeing non-coking coal largely for conversion purposes. The establishment of these enterprises will require a massive national effort and a high degree of co-ordination at the planning stage.

Jan 1, 1975

The treatment meIhods selected for the concentrator at Cobar Mines Pty. Ltd. called for a high degree of automatic control of both the grinding and flotation sections.The resulting concentrator layout includes a central control room overlooking both grinding and flotation sections. The control room houses process recorders, controllers, and indicators. together with motor stopstart stations and alarms.Plant instrumentation includes load cells and variable speed hydraulic drive feeders for feed-rate control of autogenous mills, together with nuclear density gauges, differential flow transmitters, and pneumatic control valves for water and pulp density control.Flotation cell pulp levels are controlled by floats and pneumatic actuators; flotation reagent controls include magnetic flowmeters and time-operated solenoid valves.

Jan 1, 1969

Interactive data exploration is essential for visualising grade distribution and geological controls on orbodies. Quick and appropriate computer techniques for making daily 'value adding' decisions include routine imaging of numerical data suc

Jan 1, 1998

The electrochemical dissolution of gold and other noble metals in hydrochloric acid using alternating current has been investigated. The experimental results show that this technique is efficient for dissolving pure noble metals and offers prospects for their extraction from wastes and poor ores.

Jan 1, 1992

By E House, V Lisitsin

Recent whole-rock geochemical data from nearly 900 fresh drill core and underground samples taken from seven central Victorian gold deposits confirm the presence of distinct and identifiable primary alteration haloes surrounding the deposits. Ferroan carbonate alteration extends for up to several hundred metres away from turbidite-hosted gold mineralisation outside of contact metamorphic aureoles. A less distinct phyllic alteration zone can be identified using geochemical molar ratios or short wave infrared analysis. It generally overlaps a sulfidic halo characterised by disseminated pyrite and in close proximity to mineralised structures, arsenopyrite. The extent of the sulfidic halo can be traced using low-level analysis of pathfinder elements such as S, Au, As and Sb. Recognition of these alteration features enlarges the target for exploration and provides a tool by which drilling can be directed towards mineralised structures. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By L Lorenzen, C Aldrich

In this paper, a neurofuzzy model is proposed for the development of an explanatory model of an industrial gold leach circuit based on historic plant data. A regression tree was used to partition the data in the predictor variable space and the structure of the tree was used as a basis for the derivation of fuzzy rules that could be integrated into a fuzzy expert system useful for operator decision support or process control. The position and shape of the membership functions were optimised with a backpropagation algorithm in a neural network framework. The approach yielded a significantly better explanatory model of the gold losses in the plant than comparable linear models. Although a regression tree could perform somewhat better in accounting for the variance of the dissolved gold losses, the tree was less robust than the fuzzy model.

Jan 1, 2007

By Szymanski J

The problems associated with underground mining continue to grow in size and complexity. As a result mine management is becoming aware of the benefits that can be achieved through the use of computer-oriented tools for system analysis. When such tools are employed in conjunction with benchmarking practices, the drivers of the system that lead to superior performance can more easily be determined. This paper discusses the use of the Simulation Language for Alternative Modelling (SLAM II) in the determination of the drivers of an underground room-and-pillar mining system. The mining operations included in the model consist of extracting, loading and hauling of the coal using continuous mining equipment in a room and pillar system. Equipment specifications and mining techniques used in the model are based upon current methods employed at the existing underground coal mines worldwide. The model developed is capable of adequately predicting the operational performance of the real world system from a statistical point of view. The results from the study show that computer simulation is an excellent tool for evaluating various mine configurations and for gaining a better understanding of the mining systems.

Jan 1, 1995

The development of reliable and accurate solution sampling systems plus on-line atomic absorption spectrophotometers and voltammetric analysers at Pasminco Metals - EZ's (PMEZ) zinc refinery at Hobart, Tasmania, has led to extensive implementation of On-Stream Analysis (OSA) throughout the hydrometallurgical circuit. These systems complement industrial autotitrator and colorimetric analysers and with the comprehensive use of a powerful integrated Distributed Control System (DCS), provide extensive monitoring and control of all the important in solution' parameters for the plant. Samples can be left unaltered, or filtered or settled, to remove solids. They are then precision diluted and pneumatically transported to analyser shelters, where they are analysed for zinc, acid, copper, cadmium, lead, antimony, cobalt, nickel, mercury and ferrous, ferric and/or total iron. The range of analyses depends on the sample itself. The results are used for feed forward and/or feedback control of reagents where possible, or simple trend monitoring and out-of-specification alarming when closed loop control is not practical. The overall system reliability and accuracy is such that many daily composite plant samples are no longer analysed off-line. Operator sampling has also been reduced, and in two places, autotitrators with automatic sample pre-treatment have been installed for preparing and analysing samples collected by operators.

Jan 1, 1993

TUNGSTEN occupies an outstanding position amongst metals to-day, for by its use modern manufacturing methods have received a wonderful impetus. The important part played by tungsten in the recent war is not generally recognized. It was tungsten steel, in the shape of highspeed tools, that kept our soldiers supplied with munitions of war at more than one critical period. Tungsten added the necessary hardness and durability to various metals which were indispensable for carrying the war to a successful conclusion. In the words of...

Jan 1, 1921