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Erratic, though spatially localised occurrences of gold particles are a common feature of high-nugget gold systems. In many cases, gold is present as isolated or clustered, often coarse particles. The nugget effect is a part consequence of small-scale geologically controlled enrichment, and the inclusion or exclusion of gold particles from samples. Economic zones are generally contained within discrete structurally-controlled ore shoots which are surrounded by, and may include barren to low-grade background material. Problems are often encountered where small sample types (eg drill core and channel samples) of a few kilograms mass understate in situ grade by up to a few orders of magnitude, due to their general inability to represent the true gold particle distribution. This leads to uncertainty in mineral resource estimates. This contribution presents case studies where geologically-based parameters have been collected from drill core and underground faces to support grade determination. These parameters - or proxies - are based on mineralogical and/or geochemical (eg specific elemental ratios, fluid inclusion compositions and elemental correlations) criteria. Such criteria can be correlated with different grade domains to provide an indication of true grade within a geologically-controlled context. Proxies have recently been used to support resource estimates reported in accordance with the JORC Code.

Mar 1, 2010

By Harris RW

Acoustic Emission structural integrity evaluation tests rely on the validity of the detected acoustic emission data and the ability of the practitioner to both analyse and interpret the data to make a correct decision on the future use of the structure tested. Unfortunately with acoustic emission surveillance testing, it is not possible to know that all the available data has been assessed property. The equipment sensitivity, threshold settings, and event capture capacity, when combined with the decision making ability of the operator in real time, make it very difficult to achieve reliable integrity evaluation. The main problem is to interpret the data and so any monitoring system should involve expert systems in conjunction with both acoustic emission and other operational monitoring data to maximise the utilisation of the large amounts of information now available from operating plants, mines and structures.

Jan 1, 1991

By Vassiliev P

Cut-off optimisation, based on the work of Lane (1988), can be used to maximise the NPV (Net Present Value) of a mine by the judicious manipulation of cut-offs and the use of stockpiles. Apart from maximising NPV, cut-off optimisation will ver

Jan 1, 1998

King Island is situated at the western approach of Bass Strait and approximately mid way between Victoria and Tasmania. The scheelite orebodies lie within the south east of the island. Ore bearing horizons from 10 m to 40 m thick occur in south and east dipping stratiform deposits. The orebodies occur in skarn formed by contact metasomatic replacement of carbonate rocks by granite intrusives. The scheelite is deposited as fine disseminated grains in and along the margins of andradite garnets in the skarn. King Island Scheelite operates two under- ground mines from which 350 000 tonnes per year are obtained. The Dolphin mine produces almost two-thirds of the total. See Figure 1. The Dolphin orebody lies beneath the sea and an area of reclamation. The orebody is inter- sected by zones of major dislocation. A chequerboard post pillar cut and fill stoping system has been chosen to provide the necessary support to the hanging wall. Because the stability of the pillars is critical to the economic welfare of the mine, considerable attention is given to the reduction of overbreak.

Jan 1, 1977

Exploring for deep shallow dipping orebodies can be very expensive and very difficult. Surface exploration is often not an option and obtaining the best location for underground drilling can cause production delays if drilling is carried out from development headings. The Otter/Juan mine has been in production for approximately 34 years. All of the production is now sourced from more than 1000 metres below the surface from an area known as the Edwards Lode. The orebody is shallow dipping and open at depth. Exploration drilling has been performed from decline stockpiles and from hangingwall drill drives. Drilling from footwall positions (eg decline stockpiles) into shallow dipping orebodies can often produce intersections which are unusually thick thus leading to optimistic resource figures. The decision to develop a dedicated hangingwall drilling position can vastly improve the quality of the data used to generate an orebody model. In 1997 a new extension to the Edwards Lode was discovered and named the æFÆ surface. In 1999 a resource calculation was performed using data obtained from drilling that was carried out from decline stockpiles. In 2002 a dedicated drill drive was developed into the hangingwall of the æFÆ surface to obtain better data to verify the previous resource calculation. For this case study obtaining more representative data reduced the resource estimate by 66 per cent. This information was obtained early enough to allow for alteration to the mine plan and without loss of capital.

Jan 1, 2003

By Hall T. P, Taylor R. N

Fluid flow in a 1:14 scale water model of the shaft and settler of the Kalgoorlie Nickel flash smelter has been investigated by flow visualisation and numerical modelling. Detailed flow fields through the reaction shaft, settling chamber and uptake are presented for flow rates up to 800 Vm and a number of burner configurations. The predicted flow fields were compared with experimental data obtained from streak photographs and video recordings. The effects of cessation of flow through individual burners and changes in shaft dimensions were also Investigated.

Jan 1, 1992

By Richardson F. A

Techniques for flotation optimisation were investigated at Cobar [lines Pty:Ltd., in anticipation of the proposed installation of a computer and on-stream analysis. Successful laboratory and pilot plant tests for flotation performance optimisation using the Simplex Evolutionary Operation Technique (Simplex) lead to a full scale plant test using this method. The index developed for" Simplex response evaluation of flotation performance was based on metallurgical and economic criteria. This index was further modified to minimise the effect of head grade fluctuations. The test program was carried out on one of two parallel copper flotation circuits to allow comparison with normal "manual" operating control, and was conducted for thirty eight shifts. Results from the test section operating under Simplex direction were superior to those obtained using normal "manual" operating techniques and demonstrated the use of the Simplex Evolutionary Operation Technique as a method of reducing reagent consumption in flotation but, at the same time, maintaining satisfactory metallurgical performance. Experience in the use of the technique indicated the need for modifications to the rules of Simplex operations. Modifications were proposed, tested and appeared satisfactory.

Jan 1, 1973

By Gregory O, Winters BI, Garlick C, Rogers H, Ye ZC

BHP New Zealand Steel produces iron from titaniferous ironsand by a direct reduction process comprising multi- hearth furnaces/rotary kilns/electric iron melters. The electric iron melter is a six-in-line rectangular submerged-arc furnace which takes the partially reduced ironsand (80% metallization) from the rotary kiln and completes the reduction process to produce iron of nominally 3% carbon. As the melter operates at around 1500 ¦C and under very hostile conditions, it is near-impossible to obtain any basic operating parameters such as the velocity and temperature distribution in the slag and in the molten iron. As a first attempt to understand the operating conditions inside the melter, a scaled room-temperature model using wax and water to represent the slag and iron, was constructed. This paper will report on some of the preliminary model results on the temperature distribution.

Jan 1, 1995

By Chugh Y. P

A simplified, three-dimensional, time-dependent, mechanistic model of the overburden-coal seam-floor interaction has been developed and validated at two Illinois coal mines. The model based on the thin plate theory can involve any complex layout of mine workings, time-dependent sequence of extraction and, rheological properties of immediate floor strata. The model output data consist of spatially distributed surface subsidence and its slope and curvature, as well as load acting on pillars in one or more panels. A comparison of calculated and monitored surface subsidence or in- mine convergence measurements has proven the model's effectiveness for surface subsidence and load transfer Prediction.

Jan 1, 1992

By Artone E

screening equipment installed in e Hamersley Iron operation is described, and tails of operating parameters and screening - Iia in use are given. Tests were carried out on full-size reens in the operating plants to study the Meets of mat aperture size, feed size distri 1,ution, feed rate, screen speed and throw, angle of inclination, and feed moisture content n screen performance. Sampling equipment was signed so that undersize samples could be htained from various locations along the length of the screen, thus providing information pout the quantity and size of particles passing òhro gh the screen at any point. Conclusions derived from the testwork and relevance of these to the Hamersley Iron aeration are discussed.

Jan 1, 1984

By Fengyan D

Removing the interference of latter events, the data of geophysical (such as gravity and aeromagnetic) anomalies may indicate whether the mobile belt exist and whether the adjacent terrains of the mobile belt originally belong to one single unit. The petrotectonic assemblage can provide informations about the tectonic setting where it was generated from. The structural style can exhibit the kinetic and kinematic processes. The form of ancient isogeotherm may reflect the ancient geothermal regime which is related to the tectonic mechanism. In general, the early Precambrian terrains suffered polymetamorphism and multiple structural deformation. The researches must be carried out for the distribution of paleogeotharm and m.tamo'phic facies and zones on the basis of recovering the early structural style with structural analysis method; then a relatively correct conclusion may be geined on the ancient geothermal regime. This method can be known as "Ancient Thermotectonic Analysis". Through the sythetical research, a real knowlege about the tectonic setting of early Precambrian mobile belt can be obtained.

Jan 1, 1990

By Baafi E. Y

Dragline monitoring systems are normally the best tool used to collect data on the machine performance and operational parameters of a dragline operation. This paper discusses results of a time study using data from a dragline monitoring syste

Jan 1, 1998

By Joussemet R, Fabre F

The paragenesis of the Escuzar Mine (Andalusia-Spain) comprises: ò major constituents: celestite and carbonated minerals (abundant calcite and less frequent strontianite). ò minor constituents: sulphates (gypsum and anhydrite), clays and some iron oxides and hydroxides. The average content is at about 60 per cent SrSO4. Since liberation size was fine (from 30 to 50 ¦m), the flotation method was chosen. Laboratory batch tests have shown the relevance of using alkylsulphates with as long as possible hydrocarbon chains. The recovery obtained led to an expected 95 per cent SrSO4 concentrate with nearly 70 per cent recovery. Pilot plant tests (160 kg/h) have confirmed these results and attained a recovery of more than 65 per cent of a 96 per cent SrSO4 concentrate. Extrapolation to the industrial scale (14 t/h) has been successfully carried out : up to 600 t of a concentrate at more than 95 per cent SrSO4 has been obtained. Non optimised recovery has already reached 60 per cent for a 97 per cent SrSo4 concentrate.

Jan 1, 1993

This paper comprises a discussion of standards for comparing conditions in mines, of methods for measuring the flow of air, of a comparison of fan performances, and the application of these matters to mines in Western Australia.UNDERGROUND CONDITIONSIn approaching the question of mine ventilation one naturally searches for some standard by which to measure the conditions in a mine.There are several clauses in the Mines Regulation Act defining the conditions which are permitted. The quantity of CO2 is limited to 0·25 by volume, but the estimation of CO2 involves a chemical determination and is not suited for general use in a mine.The maximum temperature is fixed at 87 0 F. (dry bulb), and at 80° (wet bulb). The reading of temperature is easily done in the working places, and this is a very valuable and practical test of the conditions in a mine.The wet bulb temperature is probably the most important factor in determining working conditions. It is obvious that human life cannot be sustained for any appreciable period if the wet bulb temperature is above blood heat (about 97°F.). In places where the wet bulb temperature is 90°F. there is danger of heat stroke.In places where the air in a mine is still, the wet bulb temperature rises to a value close to the rock temperature.Adequate ventilation cools the workings by transference of heat from the rock to the air stream, and the temperature...

Jan 1, 1939

Coal Mining machinery has undergone enormous changes in design and complexity of controls in the past 10 years. Specialised, high productivity equipment has been manufactured in Australia, in sufficient volume, to satisfy the local mullet needs.Local manufacturers face greater challenges from overseas competition, as well as increased customer demands to improve machine performance, productivity, quality, reliability and safety. In order to meet these demands now and in the future, it will be necessary to review work practises, and restructure production and quality systems to incorporate the latest principles and philosophies.

Jan 1, 1991

By Bell LC

Overburden removal, mining and reclamation are now accepted as the basic operational steps involved in the winning of coal by open cut methods. To attain the lowest operational cost, the recontouring and revegetation of spoilpiles must be planned concurrently with the planning of overburden removal and mining. The earthworks associated with reclamation work on spoilpiles often account for 75 - 90 per cent of total reclamation costs. Experience at Callide Mine has shown that the way that spoilpiles are contoured does influence water retention and can reduce erosion from rainfall run-off. However, provided the recontoured slopes meet'Mines Department specifications, the quality of reclamation work is judged not by the quality of the earthworks but by the plant regrowth on the reshaped surface. Thus it is the quality of the revegetation which is of prime importance. For vegetation to be successful, time must be spent on planned research into methods of overcoming plant nutrient deficiencies and selection of suitable grass and tree species. The research programme undertaken at Callide Mine consists of three stages :- laboratory studies glasshouse trials field trials

Jan 1, 1978

By A J. Moore

To control the airblast from blasting to regulatory limits at environmentally sensitive sites near the Collinsville Coal Mining Operations, it has been necessary for Thiess Mining to incorporate a wavefront reinforcement analysis model in the predictive environmental airblast design. Controlling airblast from cast blasting 70 m high faces with 2000-3000 kg of explosives per hole within 700 m of houses presents a considerable challenge to the blasting personnel. This paper describes the model used and summarises the results of an investigation designed to quantify the increase in airblast indicated by wavefront reinforcement diagrams to further calibrate the model for future prediction.

Jan 1, 2004

By Tran T, Young D

During the processing of gold, effluents that are discharged into the tailing dams contain free cyanide, metal cyanide complexes of zinc, copper, iron, etc and their oxidised products such as ammonia, cyanate and thiocyanate. A knowledge of how different cyanides behave in the solution is vital to metallurgists working in the area of cyanide waste treatment. Although the free cyanide ion is not stable in aqueous solutions and is expected to degrade in a natural environment by atmospheric oxidation, the metal cyanide complexes, especially of iron, are very stable. The CHEMIX program from the THERMODATA package, developed by the CSIRO Division of Mineral Products, was used to evaluate various copper-cyanide and iron-cyanide systems. The simulation of these systems show how the free cyanide and cyanide complexes behave at different conditions of solution composition and acidity (pH).

Jan 1, 1991

This paper describes the application of the Total Productive Management (TPM) technique as a performance improvement initiative for a coal mining operation. It discusses the objectives of TPM, with the driver for improved production performance being the Overall Equipment Effectiveness (OEE) of the equipment or process, and with the development of "ownership" as the behavioral approach to equipment management and continuous improvement through cross-functional and area-based teams. It illustrates the concept of equipment management as defects management.The scope for application of TPM to the coal mining industry is immense. The harshness of the operating environment can be a major generator of equipment defects, and a current paradigm in the industry accepts these defects as an unavoidable outcome defining maintenance costs in this environment. However recent benchmarking studies have highlighted that maintenance costs per operating hour in some mining operations are more than double the vendor's estimate of "best practice". The paper refers to these studies which also compare maintenance costs of fixed and mobile plant and equipment to "best practice" outcomes in comparable process industries.

Jan 1, 1998

Stressed steel cables, similar to those used in pre-stressed concrete, have been used for rock mass reinforcement, in civil engineering, for many years. This type of reinforcement has been attempted for open pit wall support, on several occasions, but has never gained wide acceptance as a practical approach because of high cost and complexity of installation in a mining environment. On the other hand, untensioned, fully grouted cable dowels (cable bolts) have gained wide acceptance for ground support in underground mining and it is perhaps surprising that this technique has not been used to a greater degree in open pit mining. The first systematic application of this technique in Australia was at the Mary Kathleen uranium mine in 1976, where it was spectacularly successful in maintaining steep stable walls in a jointed rock mass with unfavourably dipping structures. Cable bolting, and other techniques, are now being used to an increasing degree for wall support in both small and large open pits, for two basic applications: 1. stabilisation of potentially unstable sections of a wall, or 2. to allow steeper walls and reduce waste stripping volumes. In virtually every situation, wall rein- forcement has significant economic as well as technical advantages. The paper describes the development of the techniques, the mechanisms of wall support, the methods used, and discusses several case histories of its application to Australian open pit mines.

Jan 1, 1986