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Obtaining correct assays for gold determinations relies on the correct methods being chosen and the assayer being made aware of the mineralogy of the sample and its general origin. Usually when a geologist or metallurgist obtains "incorrect" gold assays the problem can be traced to poor communication between the geologist or metallurgist and the assayer.

Jan 1, 1986

By A Annor, L J. Chen

The production of paste backfill has typically been accomplished through the adaptation of existing technology. Thickeners and disc filters have several drawbacks when applied to production of tailings paste backfill. Personnel at CANMETÆs backfill research laboratory in Sudbury, Ontario, Canada have been carrying out research into and development of methods to produce paste backfill using total mill tailings since 1991. Using a silo for production of paste is not a new concept but has been refined to a marketable level. This technology is based on a fluidization principle that assists in settling the tailings to an homogenous state in a silo. Other developments include patented de-watering technology for use in the silo to speed the settling of the solids to a suitable solids content, optimisation of silo geometry, and instrumentation related to paste backfill production and transportation. The advantages to fluidisation technology are in reduced capital cost, reduced operating costs and in the environmental benefits of using full plant tailings over classified tailings or alluvial aggregates. Another major advantage is in the ability of this technology to be retrofitted to existing hydraulic backfill plants to further reduce capital cost. This paper details the development of the new technology as well as the associated cost savings over other technologies. It will also look at the research and development of unique components that make this technology work.

Jan 1, 1998

The paper describes the preparation of new rail guides, removing existing rails, and replacing with new rails in a vertical winding shaft.INTRODUCTIONThe general practice in coal winding shafts is the use of two cages, with one or more decks in which men and materials are raised or lowered. Winding speeds vary according to depth, the type of winding gear, and whether winding is done in downcast or upcast shafts. Each cage occupies a position between the centre and side of the shaft, with a clearance depending on the type of guides used. The function of the guides is to keep the cage in position throughout the entire depth of the shaft. There are three types of guides, two of which are in general use.1. Selected wood of about 6 in. square section, fixed to the side of buntons.2. Solid strand steel made up similarly to that of an ordinary wire rope, suspended from the head frame with weights attached to the lower end.3. Standard T-rail sections fixed to end or side buntons. Of the three types, 2 and 3 are in general use. The type used in the particular case, the subject of this paper, is T-rails of the standard section used in railway work.GENERAL DESCRIPTION OF SHAFTDetails of the shaft are as follow: Diameter of shaft: 22 ft. inside lining.Depth of shaft: 900 ft., including sump.Concrete lined throughout.VENTILATIONThe ventilation shaft is used for the upcast, through which all vitiated air passes to the main ventilation fan. Quantity of air passing up the shaft is 400,000 cu. ft. per minute. The air is highly saturated during the summer weather and slightly less...

Jan 1, 1947

By D J. Williams, G W. Wilson, S, A B. Tran

A comprehensive field program was implemented to evaluate the internal structure and hydrology of two full-scale waste rock piles. The excavation of waste rock dumps for in-pit disposal at the two mine sites provided an opportunity to characterise the in situ properties of the dumps given contrasting geologic and climatic settings. The internal structure and materials within the dumps were observed and sampled as the waste rock piles were being excavated and placed in the open pits for permanent closure. The field program was designed to fully characterise the structure and material properties of the waste rock. The alteration of the material by physical and chemical weathering was also observed. Samples were analysed for paste pH, water content, grain size distribution and geochemistry. In situ density and matric suction were also measured. Soil water characteristic curves and saturated hydraulic conductivity were measured for representative materials. These properties were used to predict seepage pathways through the waste rock and the resulting outflow geochemistry using the finite element model SEEP/W. The materials in the dump at Site 1 were predominantly fine-grained in texture and highly weathered. The presence of dipping beds with alternating coarse and fine materials was evident throughout the profile of the dump. The structure of the waste rock appears to have an impact on the hydrologic pathways within the waste rock pile. The material in the dump at Site 2 was found to be competent and resistant to particle size breakdown. The particles range in size from clay size to large boulders with the median particle size being approximately 125 mm in diameter. The coarse-grained texture of the waste rock resulted in a loosely packed arrangement of coarse particles with little matrix material infilling the pore spaces between the coarse-grained particles. Seepage modelling for Site 1 was completed to predict seepage paths based on observed structure and hydraulic properties measured in the laboratory. The modelling showed that materials with a fine grain size distribution become the dominant pathways for flow through the waste rock pile. The modelling also showed that layers with high silt and sand contents are subject to the highest flow rates. Finer grained clay rich layers have a low hydraulic conductivity and do not convey large volumes of water. Alternately, coarse gravel and cobble materials are unsaturated under values of matric suction that approach the residual water content of the material and do not transmit liquid water. The seepage modelling together with the results of the geochemical analysis show that the dominant particle size that receives the most fluid flow and flushing ranges from fine sand to silt, corresponding to materials with air entry values ranging between 5 kPa to 50 kPa.

Jan 1, 2003

THE plant is one of the usual type of Mond plants, and contains no new features worthy of comment. A brief description of the process, however, with a few remarks on the working of the plant, may prove of interest.Producer gas is made by passing a mixture of air and steam through incandescent carbon contained in a furnace called a producer, which, in the Mond type, is a cylindrical casing of steel plate, lined with firebrick, and fitted at the lower end with sloping fire-bars'. Coal crushed to an even size (about 2-in. gauge) is elevated to bunkers over the producers, from which it is fed into a measuring hopper on each producer.The hopper is a cast-iron cylinder fitted with a swing cover at the top and a bell valve at the bottom, worked by a lever and balance weight. When a charge of coal is run from the bunker into the hopper, the cover is closed, and the bell valve is lowered, allowing the coal contents to drop into the producer. Thus no gas can escape from, or air be admitted to, the producer during the process of charging. The hopper discharges its coal through a steel pipe-shaped container called the bell, which projects about 9 in. through the roof of the producer. The function of the bell is to spread the coal evenly over the fire, and supply coal to any portion of the fire as it settles.

Jan 1, 1918

Petroleum exploration in the Australian arid zone has been proceeding at an ever-increasing pace, subject to financial fluctuations, since the 1960's. The impacts of petroleum exploration in the arid zone are less than they would be for corresponding operations in. e.g. a forest area: in this context, Australia is fortunate in that its major petroleum producing (and prospective) , basins are offshore or in the arid zone. In addition. the other major sources of impact in the Austrlian arid zone, namely pastoralism, tourism, and rabbits, tend to be concentrated around areas of particular conservation significance, whereas petroleum exploration is not. Despite this, the cumulative impacts of exploration are sufficient to have caused concern to government regulatory authorities and some sectors of the general public. Exploration is now subject to a range of environmental constraints with various degrees of legal enforceability. To enable exploration to continue without public opposition, the industry, and government agencies charged with regulating or supervising it, must demonstrate that the net benefits of exploration exceed net costs, including environmental costs. One particularly simple and cost-effective technique for increasing the net benefit/cost ratio of exploration is to reduce the net environmental costs by minimising and mitigating the impacts, both primary and secondary, of seismic acqisition. This is best achieved by a combination of preventive and restorative techniques: careful line positioning and low-impact (or zero) line clearance, coupled with simple rehabilitation of bladed lines. Line clearance without bulldozer blading - e.g. by rolling or simply pegging and trafficking, perhaps with tracked rather than rubber-tyred vibroseis - is one promising approach currently coming into use. Rehabilitation by grading soil banks ("windrows") back on to bladed tracks, though not yet in widespread use, has proved very successful in the limited areas where it has been applied to date.

Jan 1, 1987

By Percival T. J

Precious metal deposits containing fine-grained disseminated or dispersed gold-silver form by reactions between metal-bearing hydrothermal fluids and sedimentary host rocks. Host rock permeability and chemical composition exert a primary influence on the fluid movement necessary for any primary dispersion halos to form around ore bodies, and determine whether a disseminated style orebody itself will even form. Where the mineralized rocks are relatively unfractured the margins of the orebodies exhibit abrupt decreases in gold content, and strong corresponding decreases in the contents of other metals. Primary dispersion patterns of this type are difficult to recognize and commonly are only a few meters (or less) in width. If the host rocks were well shattered and broken before mineralization, remnant amounts of the hydrothermal fluids may be dissipated in fractures lateral to or above the ore zones. This causes geochemical anomalies to form with clays and silt- size silica within the fractures over distances of up to at least 30-50 meters away from the main orebodies. The tendency for large primary dispersion halos not to form around these deposits explains the disappointing results from so many drilling programs where no multi-gram gold-grade material was even found: if large areas and apparent large volumes of rock contain one gram or less gold that likely is the "orebody" and not a halo effect around high grade mineralization.

Jan 1, 1988

By Kapoor M. L

EMF measurements were performed in the temperature range of 933-1095 K to determine the thermodynamic properties of oxygen dissolution in liquid lead and lead-tin alloys with tin in the dilute concentration range of 0 to 6 atom per cent. The oxygen in the Pb-O system was varied by equilibrating with (PbO) slag, and that in the Pb-O-Sn system was varied with the addition of lead oxide. Wagner's interaction parameter approach was used to evaluate the self interaction parameter and ternary interaction parameters at different temperatures, to yield: E8(pb) = 97.35 - 113.27 x 103/t Eo(pb) = 139 - 20.616 x104/1' Quasichemical formulation was employed to yield Inf to reveal the effect of tin on oxygen in lead. Results have been predicted on the basis of classical models and those obtained using the QCT approach of Alcock and Richardson at Z=2 have been found to agree with the experimental Data.

Jan 1, 1992

By T Gartner

This paper describes the design, manufacture and site services associated with the supply of mine hoists for the new mine under construction by Falconbridge Limited in Ontario, Canada. Two new shafts are being sunk, and the hoisting equipment at each shaft can be summarised as follows: Ventilation shaft:4.66 m diameter double-drum second-hand hoist, originally in operation at San Manuel Mine, Arizona, to be used as the shaft sinking hoist. The second-hand hoist presented a challenge in that during its previous life, the hoist had been intensively operated during service at San Manuel Mine, and this paper describes the scope of refurbishment work undertaken, both electrically and mechanically, to ensure future reliable operation, together with the requirement to meet Canadian and Ontario regulations and codes of practice. 3.05 m diameter new single drum auxiliary hoist to be used as a second means of egress. Main shaft:4.57 m diameter new double-drum hoist to be used initially as the shaft sinking hoist, and subsequently to be converted to the equivalent of a single-drum multi-rope hoist for service duties during the production phase; 5.49 m diameter new double-drum hoist to be used for skip hoisting during the production phase; and 3.05 m diameter new single drum auxiliary hoist.The new hoists are all designed to comply with SABS requirements such that hoisting with reduced rope safety factors will be possible in the future. This paper describes the principles involved both mechanically and electrically. Particular attention is paid to the conversion of the main shaft service hoist from a double-drum sinking hoist to a multi-rope hoist.This paper describes the ac electrical powertrains (drives and motors) used that eliminate the need for harmonic filters and reactive power compensation equipment since they exhibit no negative effects on the utility electrical network system. This paper describes the logistical challenges of installing, commissioning and setting to work a series of five hoists in a short time frame.

Jan 1, 2005

By Honey F. R, Furnell R. G, Lyon R. J P

A Joint Venture between Union Oil Development Corporation and Geoscan Proprietary Limited carried out an Airborne Multispectral Scanner Survey over approximately 15,000 square kilometres in the Charters towers area of northeastern Queensland during late 1985 and in September, 1986. The survey, using the Geoscan Mark I scanner, consisted of 50 runs each having a swath width of 5 kilometres. Twelve or thirteen spectral bands were recorded, 5 in the VNIR, 4 in the SWIR and 3 or 4 in the TIR. The results of the survey were interpreted by interactive image processing with the aim of identifying those minerals or their weathering products which are characteristically associated with hydrothermally emplaced gold mineralisation in this part of Queensland. Spectral bands in the VNIR were used to identify and discriminate the iron hydroxides, whilst the SWIR bands were used to outline the clay and carbonate rich areas. The TIR aided in identifying areas of silicification.

Jan 1, 1989

By Travis G. A

The Mons Cupri Cu-Pb-Zn deposit is situated within a complex Archaean volcanic sequence dominated by rhyolitic fragmental rocks. This sequence is underlain by a 150 m group of rhyolitic ash flow tuffs with minor conglomerate and sandstone, and is overlain by approximately 180 m of dacite and andesite flows. The Mons Cupri sequence itself consists of several elongate or circular rhyolite domes, flanked by rhyolitic fragmental rocks ranging up to 400 m in thickness away from the domes. The lithology of clasts (typically 1 cm to 1.5 m in size) provides strong evidence that the flanking fragmental unit was derived by explosive eruptions associated with the rhyolite domes. An approximately 15 m thick shale horizon, bleached and silicified at its base, overlies both the rhyolite domes and the frag- mental unit. A south-dipping chloritic pipe-like body, with near-surface dimensions of 1,000 by 250 m and narrowing at depth to produce a cone-shaped cross section, lies within the rhyolitic frag- mental rocks about 250 m north of the largest rhyolite'dome in the Mons Cupri vicinity. Its east west elongation parallels that of the rhyolite dome. Ghost fragments indicate that the material in this fissure is a severely chloritized derivative of the rhyolitic frag- mental unit. The chloritic pipe is overlain

Jan 1, 1973

Tertiary laterite is extensively developed in the Darling Range area, but there is doubt that. the high relief areas along the Darling Scarp have been peneplaned. Three distinct laterite types are distinguished which are termed transported, introduced and residual laterites to avoid ambiguity. Transported laterites are recemented (primarily) lateritic materials and introduced laterites are chemical deposits of bog iron type. Residual laterites are formed in situ from the host material which can be either decomposed bedrock or detrital' clay, and the two varieties formed from these sources are termed residual A and residual B laterites. The genetic requirements for residual laterite formation are (1) host material, (2) porosity and permeability, (3) rainfall, (4) temperature, (5) relief and drainage, (6) vege- tation and (7) time. Previous theories on the origin of laterite appear to be inadequate and incompatible with field observations. Field investigations and drilling in the Darling Range area disclosed lenticular section and thickest laterite development on slopes and thin or oc- casionally no laterite development on crests. Lateritisation is considered a surface feature and the end product of the chemical weathering cycle. The relief and rain-water acting on a kaolinitic host material are con- sidered the major contributing factors in the

Jan 1, 1973

By Smith F. A, Both R. A

The application of biogeochemical methods in mineral exploration in the semi-arid to and environment of Western Australia was investiga- ted in an area near Norseman. The reliability of these methods was evaluated by comparing trace element characteristics of rock, soil and plants in the vicinity of the Pioneer BB pros- pect. The prospect is located in the south- western part of the Pioneer Dome, where granite gneiss core is surrounded by a 'greenstone' sequence of ultrabasic, basic and sedimentary rocks. Nickel-iron sulphide mineralization occurs discontinuously along one of the basic- ultrabasic contacts. Analyses of unweathered and partly weath- ered rock from diamond drill cores show the ultrabasic rock to be highly variable with re- spect to nickel, copper, cobalt, zinc and manga- nese. Samples of weathered bedrock and over- lying soil were analysed both for total trace element contents and for the trace elements associated with secondary iron and manganese oxides. Approximately 30 per cent of the total nickel content of the weathered basic rock is associated with secondary iron and manganese oxides, compared to approximately 15 per cent in the weathered ultrabasic rock. The soil is partly transported but has a residual component sufficient to provide a reli- able indication of the underlying rock chemistry, although the trace element content of the soil is less variable than that of the rock. Total

Jan 1, 1973

By T R. Justice

The Eastern Distributor tunnel is located approximately 24 m beneath the suburbs of Woolloomooloo and Darlinghurst to the east of the central business district of Sydney. The 1.7 km long tunnel will carry three lanes of northbound traffic over three lanes of southbound traffic in a æpiggybackÆ arrangement, with a maximum cross-section 22 m wide by 12 m high.The tunnel is constructed predominantly within horizontally bedded Hawkesbury Sandstone. In the unweathered to slightly weathered state, the rock is typically medium strength (average UCS about 24 MPa), with an average quartz content of 72 per cent.Major geological features that intercept the tunnel route are the Woolloomooloo Fault Zone and two extremely to moderately weathered dolerite dykes. The fault zone intersects the tunnel at about 25¦ to its alignment and comprises a series of discrete faults over a width of approximately 50 m. The overall movement of the fault zone appears to be reverse. The two dykes are the 1 m wide Oxford St Dyke and the 6 m wide Great Sydney Dyke.This paper outlines the site investigations and the interpreted geotechnical model for the tunnel route prior to the commencement of tunnelling. This model is then compared to the encountered conditions. The very good correlation between the expected and the encountered conditions shows the high quality of geotechnical investigation and interpretation.

Jan 1, 1999

By R S. Sing, M D. Yadav, G Udaybhanu

This paper presents the results of the first part of a research project to study the effect of various inhibitors to reduce the spontaneous heating susceptibility of some highly susceptible Indian coal seams. In this investigation 11 inhibitors were chosen and applied at three, five and ten per cent of their concentrations in an aqueous solution for four coal samples collected from four different seams. The susceptibility of coal samples, before and after application of these inhibitors, was determined by carrying out crossing point temperature (CPT) analysis. The findings of this study have indicated that it is possible to retard the tendency of spontaneous heating of Indian coals to a considerable extent by the application of six of the inhibitors studied. Further, these inhibitors were tested in 1:1 combination to study their synergistic effect. Finally the economics of the application of these inhibitors has been analysed and four inhibitors are recommended for field use. These results have direct application to control fire and improve productivity and safety in coal mines.

Jan 1, 2005

By F D. I Hodgson

Twenty-seven observation test pits were excavated at four different spoils dumps at three collieries in the Witbank Coalfield. The holes were dug into the upper three metres of the spoils to ascertain if any weathering profiles, variation with age or influence of topsoil covering could be gauged. Samples from these holes were also subjected to laboratory testing (ABA, humidity cells and mineralogy on several selected samples). The test pits showed that there was a good correlation between in situ paste pH-values and ABA results for samples taken from the pits. At all the collieries, no correlation between age of spoils and in situ acidity could conclusively be drawn. The depth of soil cover also appears to be a minor consideration in determining the eventual acidity of the spoil. In the pits where acidity was found, the weathering was evident when contrasted to areas still buffered. It is unclear if the weathering leads to the acidity or vice versa, as the soil covering appeared to be similar. The spoils proved to be extremely variable with regard to particle size and material on a micro and macro scale. Evidence from most of the holes suggested that there was enough water contained in the fine material in the spoils to support the initiation of acid generation. Conclusions from this investigation are that the mineralogy of the spoils is the most important factor in determining the eventual occurrence of acidic hotspots, and that prior characterisation and selective handling will provide the best management practice for these spoils.

Jan 1, 2003

By F Schoenbrunn, T Laros

Deep paste thickeners have been proven capable of consistently producing medium to low slump material for disposal without the need for filters. However, proper design of the entire system is critical for a paste project to be successful. Some of the factors that must be carefully considered in design of a paste system include thickener sizing, tailings impoundment design, underflow pumping, and control system.

Jan 1, 1998

The Kidston Gold Mine i s located in northern Queensland some 2 Ukm northwest of Townsville. I t is the largest gold mine in Australia and produces approximately 25 percent of Australia's gold and one percent of the world's gold.Initially, traditional mining industry management approaches resulted in the rejection of what appeared to be an attractive low-grade deposit as an uneconomic proposition. Critical re-examination revealed that the rejection was based upon managerial inflexibility and traditionally over-conservative methods of mine evaluation, construction, operation, projected commodity prices and contingency factors. "Ihus it tradition was to prevail, the Kidston prospect would never have been realised.

Jan 1, 1985

By L Neems

In conjunction with Orica Explosives, Worsley Alumina have managed a program of continuous improvement to their cap rock blasting over the last two years. Blasting conditions are challenging because of the hard and shallow nature of the material. Blasting costs must be controlled and the environmental consideration of noise and dust is critical. Worsley have sought to determine the optimum balance between drilling and blasting costs and fragmentation. As the cap rock has few inherent weaknesses, loader productivity is strongly controlled by the degree of fragmentation from blasting. The optimum blasting solution is also constrained by maintaining airblast levels at the surrounding residences below 115 dBL . The major blast design parameters optimised during the program were stemming type, stemming length, powder factor and blasthole diameter. A series of carefully managed trial blasts were fired during 1997 and 1998 to quantify the effect of these parameters. Fragmentation was digitally measured using OricaÆs Powerseive G technique. Shovel productivity, airblast levels and blasting costs were also quantified. As a result of the project, Worsley now have an increased knowledge of the key parameters driving blast performance, and their consequent impact on downstream processes, the environment and total mining cost.

Jan 1, 1999

By Espig D, Standish N

In the paper a stochastic model of the batch sieving procedure is presen- ted resulting in a system of ordinary differential equations to describe the time dependence of the mass fractions on the sieve surfaces being randomly influenced by sampling errors. The coefficients of the system can be interpreted as sieving velocities. Their dependence on the sieving con- ditions is discussed and a special type of functional relationship and methods are suggested to determine this function experimentally. Moreover the applicability of the approach is demonstrated by an example to evaluate the particle size distribution, if only the result of incomplete test sieving is known. For this problem a rough error estimation is performed.

Jan 1, 1984