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Before commencing design of a coal prepar ation plant, it is essential to have detailed information of the raw coal to be treated to- gether with a clear understanding of the products required. Prediction of raw coal size distribution, particularly the amount of fine material, is difficult and the methods employed should be large scale pilot plant studies or techniques to simulate coal degradation and shale breakdown in water. A detailed knowledge of well proven coal preparation processes and new developments allows processes and process combinations to be compared to'obtain the maximum economic recovery when using lower cost, less efficient processes within acceptable limits. Equipment should be selected bearing in mind its precise application and the location where it is installed. Plant layout should be carefully studied to minimise equipment requirements and to simplify construction. Measurement, control and automation should be an integral part of plant design in order to obtain the optimum performance of the processing equipment.

Jan 1, 1974

By Setterfield TN, Jones GFP, Tua P, Davis B, Antonio M

The Emperor gold deposit occurs on the western margin of a 5 Ma caldera in a large, mafic shoshonitic shield volcano on the island of Viti Levu, Fiji. Products from two major pulses of post-caldera intermediate volcanism filled the caldera. Caldera collapse-related steep and flat faults and zones of shattered rock provided per- meable conduits for vertical and lateral fluid migration and favourable sites for ore deposition. One large hydrothermal system, operating concurr- ently with extrusion of the second pulse of resurgent volcanism, may have produced porphyry- style alteration within the caldera, epithermal mineralization at Vatukoula, and weakly minera- lized, siliceous veins and breccias in an outflow zone northeast of Vatukoula.

Jan 1, 1987

By D Langberg, R Taylor

Many metallurgical operations produce fine residues and dusts as by-products which can be difficult to handle and offer little direct financial incentive to treat. There is a growing imperative to deal with these materials particularly since land fill is fast becoming an uncertain long term solution. One possible means of treatment is to extract the valuable metals while fusing the remainder into a slag. In this way valuable metal components of the material can be recovered and the less valuable components be converted into useful products, eg cements and inorganic polymers which have a high environmental stability and a growing market. The aim of this project is to establish solids injection and fusion in a slag bath as a viable method of treating industrial wastes and residues. The benefits of this approach are expected to be: the ability to treat a wide range of organic and inorganic residue materials, ease of recovery of volatile and valuable elements and the production of final materials which could be used in other industries. In ongoing experimental work at the CSIRO Minerals a 250 kg slag bath reactor has been used to test the injection of Paragoethite residue into an iron silicate based slag. An experimental apparatus has been designed and commissioned to pneumatically inject solid material at feed rates of up to 80 kg/hour. The capture efficiency of injected solids by the slag bath was calculated by monitoring the composition of the slag. Using this method of treatment, the zinc contained in the residue can be recovered as a fume by varying the oxidation state of the slag. Other valuable elements could be recovered by creating a matte or metal phase in the reactor with the final material being used in the production of cement. A capture efficiency of injected solid paragoethite particles in the slag bath of up to 97 per cent was achieved. Under the conditions of the experimental work capture efficiency was found to be independent of injection velocity and slag depth. The rate of fuming during injection was found to increase slightly with injection velocity and was independent of slag depth.

Jan 1, 2002

By M Thomas, M Caccetta, C Laukamp, A Hacket, M Jones, A Rodger, M Verrall, R Hewson

A mineral systems approach was used to interpret precompetitive airborne mineral mapping geoscience data for iron oxide copper gold (IOCG) exploration in the Starra area, Eastern Succession, Mount Isa Inlier. Selected minerals were chosen to map possible source rocks/fluids as well as intersecting structural/fluid pathways that could have transported mineralising fluids into domains of contrasting rocks/fluids where there was potential for physicochemical gradients to precipitate metals. Ferric and ferrous iron contents and white mica abundance were useful mineral criteria to identify theMount Dore Granite of theWilliams-Naraku Batholith as a potential source of æoxidisedÆ fluids rich in Fe, K and potentially Cu-Au. The Mount Dore Shear Zone (MDSZ) intersects the western margin of this granite with the highest contents and changes in composition of the white mica are peripheral to this contact within the granite. This together, with the fact that the entire N-S length of the MDSZ in the study area (~16 km) is abundant in white mica are evidence of K-rich fluids had preferentially moved along this pathway. To the south, the MDSZ intersects a domain comprising massive ironstone bodies as well as numerous graphitic horizons. This interpreted æreducedÆ domain is well mapped using the æopaqueÆ mineral products, as well as by white mica, which is pervasively developed and extends 2 km either side of the MDSZ fault into the meta-sedimentary sequences. The chemistry of this white mica also changes progressively away from the MDSZ, becoming more Si-rich (longer wavelength) towards the contact with massive ironstone bodies in the west and the graphitic units in the east, both of which represent sites of known Cu-Au mineralisation. Beyond these contact zones of interpreted æoxidised fluidsÆ with reduced rocks/fluids, there is either a rapid change to Si-poor white mica and/or no white mica developed, ie major æchemicalÆ gradient change. These mineral mapping results provide evidence for a direct link between possible source rocks and sites of IOCG metal deposition as well as extending the associated alteration zonation which had previously been mapped/published at the metre-scale to the kilometre-scale. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By G, F Beach, D Jazzini, R Rounsley

Over the past 20 years within Australia, there have been a number of incidents at mine sites where ammonium nitrate-based explosives have reacted with certain rock types containing sulfide minerals. These rocks have commonly been referred to as æreactive groundÆ. These reactions have frequently led to fires (particularly in ground susceptible to spontaneous combustion) or premature detonation of the ammonium nitrate-based explosives. Clearly, this introduces an element of risk when using ammonium nitrate-based explosives in these areas. Dyno Nobel has been proactive in developing ammonium nitrate-based explosive products that can be used in these types of æreactive groundÆ environments that minimise the risk of premature detonations occurring. A system for assessing æreactivityÆ of sulfide containing rocks has been developed that can be used in the field. Previous literature has been reviewed, identifying Differential Thermal Analysis (DTA) as the most common method for determining the æreactivityÆ of the ground. In the present investigation, DTA has been rejected as a suitable technique for determining ground reactivity, since it measures thermal reactions at higher temperatures over short time periods, conditions that are unlike those in the field. For example, ground at ambient temperature has been found to react with ammonium nitrate-based explosives over long time periods, reactions that are unable to be evaluated using DTA. Other more suitable techniques have been developed to monitor rock conditions that can be measured in the field and give a good indication of potential ground æreactivityÆ with ammonium nitrate-based explosives. Dyno Nobel is currently investigating the reaction mechanisms of spontaneous combustion in reactive ground, the decomposition mechanisms of ammonium nitrate and the role of inhibitors in ammonium nitrate-based explosives. Once complete, this fundamental research will lead to the further development of even lower risk ammonium nitrate-based explosive products for use in æreactive groundsÆ in a variety of mine environments.

Jan 1, 2003

IN the ordinary course of treatment of pyritic ores or concentrates, whether for the recovery of copper, tin, gold, or any other contents, the removal of some or all of the sulphur contents is almost invariably the first step. The practice is to roast the ore in a current of air so that the sulphur is oxidized to sulphur dioxide and the metal constituents are changed from sulphides to oxides. If it is feasible to produce sulphuric acid in conjunction with the treatment process, the sulphur can be usefully employed; but if this is not possible, then the sulphur contents not only become a dead loss, but tend to be a nuisance as well in the surrounding neighbourhood.The problem of avoiding this disadvantage and making economic use of the sulphur has had attention from the early days of scientific metallurgy, and in the past few years very special efforts have been made both to drive part of the sulphur as such from pyrites and recover it, and to replace the sulphur in the S02 by carbon, with the production of carbon dioxide and precipitation of the sulphur. So far economic success does not appear to have crowned these efforts. In the case of pyrites, of the two atoms of sulphur which go to make the FeS2, the first is very lightly held. Dissociation is effected by heat alone at a temperature which is given by Peters as 5160 C.Now, sulphur and hydrogen will unite or burn together, with the production of sulphuretted hydrogen. It occurred to the writer that, if hydrogen was passed over pyrites heated to the above temperature, this first atom would be snatched away by the hydrogen, and could possibly be economically recovered.The first step consisted of some simple laboratory experiments. From these it was found that this first atom was readily removed, and that the extraction was practically complete. Further, the reaction took place at a low temperature, a dull red heat being sufficient.

Jan 1, 1923

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 J Centofanti, D Conti, R Riske, C Morley, A Cook

Why is it so difficult? Why are there differences throughout the resources industry in how reconciliation factors are reported and calculated? Why is there no standard formula to use? These are common questions asked when mining companies try to compare reconciliation results across operations or attempt to undertake internal or corporate governance reporting processes. For many mining companies the calculation of reconciliation factors is often a very time and resource intensive part of mandatory reconciliation reporting. Some major mining companies, that move millions of tonnes of material per annum, dedicate full time resources to the calculation of reconciliation factors. The willingness of these companies to set aside resources demonstrates the value that operations place on good reconciliation reporting. Reconciliation is about measuring the variance between two like measures at different points along the mining sequence. It can be undertaken between predictive models, forecast plans and actual measured performance. Calculations are used to derive a variance between two sections within the mining sequence, with the result being commonly known in the resources industry as a æfactorÆ. Mining companies use the calculation of reconciliation factors as key performance indices (KPIs) to provide a æhealth checkÆ of their operation, with variances often pointing to issues either with the accuracy of the original estimate or the quality of the measurement being used in the comparison. There are many reconciliation factors that can be calculated and reported. This paper will set out, clarify and provide a recommended standard means of calculating each specific factor that, where adopted by a company, will ensure compliance with the international reporting codes, such as JORC. Using case studies from Rio Tinto Group (Rio Tinto) and BHP Billiton Mitsubishi Alliance (æBMAÆ), and the authors experience across a wide range of mine sites, the outline of a generic solution for tracking a parcel of material from the pit through to the port along with appropriate reconciliation factors is provided. The intention of proposing standardised reconciliation factor terminology and methodology is to provide the foundations of a system to enable communication and comparison across different commodities, companies and mines sites.

Jan 1, 2009

According to the Australian Bureau of Statistics, fatalities from road transport accidents represented an average of over 97 per cent of all transport related accidents between 1997 and 2002. With increasing traffic density, tunnels are becoming a more viable means of providing alternative travel routes to ease areas of congestion in the road transport network. However, unlike open road conditions, a fire incident in the confined space of a tunnel environment may impact upon many users that are remote from the incident location. In this context, designing for an appropriate level of safety in tunnels is therefore an important consideration for achieving consistency in the life safety measures for users of the road transport network. Unfortunately, like fire safety engineering design for buildings, there are presently no clear measures in the design processes to assess the adequacy of the design in terms of attaining the level of safety implicated in the design objectives. This is partly due to the indeterminate nature in which the design objective or the level of performance measure is stated û the intent of the objective is relatively clear but the measure of it is not. Another reason is the lack of a standardised procedure for determining the critical design variables affecting life safety. This is important to ascertain consistency in the use or adoption of the important parameters for design. This paper looks at the processes involved in the fire engineering design of road tunnels that are currently practised. A review of the design processes for fire safety in road tunnels is provided, which includes the range of fire scenarios in a tunnel environment, the traffic flow and composition, the relevant fire protection systems, the ventilation and smoke control system, the egress provisions and the benefits of incorporating fire brigade intervention. A simplified risk assessment approach is developed for a typical road tunnel to assess and evaluate the impact of a range of design parameters on life safety. Using a sensitivity technique, the important variables are then identified and means of reducing design variations associated with them are recommended. The technique may be further refined for use in the development of codes or guidelines in order to develop a suitable means of deriving more consistent design values, and hence achieve better consistency in the overall level of safety in the design.

Jan 1, 2008

The extraction of world-class mineral deposits using massive underground mining techniques is not an entirely new theme to world mining companies and experts. Previous MassMin conferences have helped to gather and disseminate the valuable experience and knowledge so important for the proliferation of safe and efficient mining of large underground deposits. With the passing years since the first MassMin conference in Denver in 1981, a number of factors have contributed to an increase in massive underground mining around the world, including environmental pressures, gradual exhaustion of shallower deposits and the enabling effects of improving technology in disciplines related to underground mining. Massive underground mining is heading deeper, embracing challenges which include working with elevated temperatures, increasing in situ and mining induced stress levels and longer ore transport routes. Improvements in mineral processing technology will tend to lead operators to contemplate the extraction of lower grade orebodies in the event that the ore can be efficiently transported to the surface and hence the plant. No doubt this tendency, and its associated challenges is encouraging a rich growth in innovative engineering in such fields as mine planning and materials handling as well as geomechanical issues such as support design and the simulation of extraction sequence effects on stress re-distribution. MassMin 2000, we are sure, will showcase a wide variety of new contributions in thought and actions in these fields. There is a definite place for academic institutions and mining related suppliers in the process of developing new technologies and practices in support of present and future endeavour in this field. Dyno Nobel has its own part to play, certainly as an enthusiastic and proud major sponsor of MassMin 2000, but also by means of identifying common cause between our Vision and Values and the needs, present and future, of the underground massive mining industry. The critical success factors, which Dyno Nobel pursues are:health, safety and environment, customer relationships and market development, cost optimisation (while maintaining quality), technology and innovation, organisational development, and leveraging capabilities globally. Through the present paper we would like to share some of these values and offer some practical insights as to how their realisation will contribute to the achievement of MassMin goals and needs.

Jan 1, 2000

An image analysis system has been built which automatically digitizes camera input of rock fragments, analyses the digitised data to determine the sizes and shapes of the rock fragments, and outputs the analysed data to a printer in the form of a histogram or a scatter chart. The high speed of such a system allows for direct collection of data from material thrown into the air by blasting, material travelling on a conveyor belt, and material free-falling on to a stock-pile or into or out of a rock-crusher. Data on the blasted, un-crushed material provides information on changes in the lithology and structure of the rock face as it is quarried or mined: flatter fragments may represent approach to a brittle, unstable shear zone, or a change from sandstone to shale; so that the informa- tion reflects the effect on the sizes and shapes of the fragments by the blasting process and/or by the rock structure. The size and shape distributions of rock fragments produced during blasting and during processing may now be continuously monitored. Such detailed analysis of the results of fragmentation is labour-intensive and expensive when the size and shape distributions are obtained manually, but is cheap and efficient when using this image analysis system. Such a system will enable the results of blasting, quarrying, mining and crushing to be cheaply analysed and correlated with current and changing indus- trial practice so leading the way to increased productivity.

Jan 1, 1988

Although the diesel engine is normally considered a tried and proven power source, many new and exciting diesel design concepts are being evaluated in engine development laboratories around the world. Three such programs currently underway at Cummins Engine Company are discussed. The turbocompound engine converts into power exhaust heat energy which is normally wasted. It does this by incorporating after the turbocharger a low pressure gas turbine which is gear driven to the crankshaft. The adiabatic engine has no conventional cooling system. It converts into useful power most of the heat energy normally rejected to the coolant. The series boost turbocharged engine uses seperate low and high pressure turbochargers to increase engine output and improve transient performance. These design concepts make possible increases in diesel engine thermal efficiency from the current 33 to 38 per cent range to the 50 percent range.

Jan 1, 1982

A low grade, refractory ore gold mine with high striping ratio such as at Macraes is always challenged in ways to improve margins. Common practice approaches used at OceanaGold Ltd Macraes are to maximise grade delivery, optimise recovery and reduce unit costs, as well as take any opportunities to incorporate new technologies and implement enhanced commercial strategies.   The Business Improvement (BI) programme was implemented across the Macraes operations in late 2003 and is being rolled-out to all other parts of the business. The core focus of BI at OGL is to: +        increase revenue, +        reduce cost, and +        improve processes.   A dedicated BI team comprising of a manager, team leaders and business analysts were engaged to identify and manage a series of opportunities to reduce operating expenses, optimise capital outlays and generate extra revenue. The Business Improvement Programme, though in its formative phase, has begun a cultural change within the organisation. Many people are starting to challenge the way they do things and are looking for ways to continually improve business performance.   The BI team encompasses individuals from different departments who can offer the diverse skill set necessary to produce intended results. The current team is made up of a BI manager, BI Team Leaders in Mining and Processing and analysts from Mining, Processing, Commercial and Plant Maintenance workgroups. A team member has recently been formally trained as a Six Sigma Black Belt. ] The BIÆs team role is to assist in the establishment of project management processes for each improvement idea. In addition the team will assist in tracking implementation, identifying and unblocking restrictions and limitations as well as setting up metrics to quantify the level of benefit returned and sustained.   From a more strategic point of view, the BI team is advancing the Business Improvement capability of the company by developing long term Communication and Training strategies. These strategies will set the direction of BI initiatives in the years to come to: +        educate the OGL workforce in basic BI techniques, +        assist the OGL workforce in applying basic BI techniques, +        communication the direction of BI in OGL, and +        close the information feedback loop to facilitate transparent communication between the OGL workforce and the BI team.

Jan 1, 2004

In recent years a large amount of work has been done at various plants overseas, and also at Broken Hill Associated Smelters, Port Pirie, South Australia, on the use of Dwight Lloyd sintering plant gases for sulphuric acid manufacture by the contact process.Several plants have modified their sintering machines and operating procedure, and some have adopted gas recirculation techniques, to obtain a relatively high proportion of the sintering plant gas at an S02 concentration acceptable to a contact acid plant 1.These adaptations were investigated at Port Pirie, and it was found that gases of suitable S02 concentration could be obtained. The results justified installation of a contact acid plant and a decision was accordingly made in 1949 to construct such a plant.However, the local conditions presented some difficulties not generally encountered at other plants, the chief differences being:a. For maintenance of production of 98% H2S04 , an unusually high S02 concentration is required, because of the prevailing high temperature 'of the purification train cooling water.b. The entire sintering operation is conducted on two large machines, 55ft. x 10ft., operating in series as "First" and "Second over" machines (a two-pass roast.) Any interruption" to either machine causes a complete interruption of plant operation and gas flow.

Jan 1, 1951

By Will D. P

A 328 m, 2.4 m diameter raise-bored shaft has been equipped with a modular ladderway system to provide a second means of egress from Aberfoyle's Hellyer Mine in Tasmania. The modular ladderway consists of platforms, ladders and service pipes assembled at the surface and progressively lowered down the shaft. This system provides a rapid, safe and economical non-entry approach to equipping a shaft. The modular construction and single suspension allows for future extension or for reuse in another shaft.

Jan 1, 1988

This paper addresses the area of utilising automatic data capture systems in the metalliferous mining environment for the purpose of tracking personnel and vehicles, for both safety and productivity purposes.As automatic data capture systems in the form of barcodes have revolutionised the stock control procedures in retail establishments in recent years, so too will similar systems in the form of radio frequency identification products (an electronic version of the barcode) transform the way in which many aspects of mining operations will be managed.

Jan 1, 1992

Mining companies around the world devote considerable effort to production reconciliation and metallurgical accounting. However, although sampling, weighing and analysis methods used to obtain the raw data for metal balancing continue to improve, they are still areas that are sadly neglected. Using the latest metallurgical accounting package to improve metal balancing is fundamentally flawed if the data used are unreliable in the first place. The basic rule for correct sampling is that all parts of the material being sampled must have an equal probability of being collected and becoming part of the final sample for analysis. If this rule is not respected, sampling bias can easily be introduced. Unlike precision, which can be improved by replication, bias cannot be reduced once it is present. Sampling and sample processing procedures must therefore be carefully designed both to minimise bias and to obtain acceptable precision. The most suitable sampling location is the discharge point of a process stream, where increments can be obtained by taking a complete cross-section of the stream with a sample cutter. Sampling devices that take only part of the stream may introduce serious bias and must be avoided. The moisture content and wet mass of the material being sampled are of similar importance to chemical analyses for determining metal content. The accurate determination of moisture content is particularly difficult, because the moisture content of samples can change after the sample is taken, eg due to moisture evaporation. Hence, moisture samples need to be taken quickly and placed in sealed bags or containers that are impervious to moisture. The moisture content should then be determined without delay. To determine wet mass, a range of weighing methods are used in industry, including weighbins, weighbridges, conveyor weightometers and platform scales. The precision and accuracy of these methods vary considerably, so it is important to select a method with the appropriate precision and ensure that the weighscale is well maintained and regularly calibrated.

Jan 1, 2002

By M P. Schwarz

In recent years, computational fluid dynamic (CFD) modelling of mechanically stirred flotation cells has been used to study the complexity of the flow within the cells. In CFD modelling, the flotation cell is discretised into individual finite volumes where local values of flow properties are calculated. The flotation effect is studied as three subprocesses including collision, attachment and detachment. In the present work, these subprocesses are modelled in a laboratory flotation cell. The flotation kinetics involving a population balance for particles in a semi-batch process has been developed. From turbulent collision models, the local rates of bubble-particle encounters have been estimated from the local turbulent velocities. The probabilities of collision, adhesion and stabilisation have been calculated at each location in the flotation cell. The net rate of attachment, after accounting for detachments, has been used in the kinetic model involving transient CFD simulations with removal of bubble-particle aggregates to the froth layer. Comparison of the predicted fraction of particles remaining in the cell and the fraction of free particles to the total number of particles remaining in the cell indicates that the particle recovery rate to the pulp-froth interface is much slower than the net attachment rates. For the case studied, the results indicate that the bubbles are loaded with particles quite quickly, and that the bubble surface area flux is the limiting factor in the recovery rate at the froth interface. This explains why the relationship between flotation rate and bubble surface area flux is generally used as a criterion for designing flotation cells. The predicted flotation rate constants also indicate that fine and large particles do not float as well as intermediate sized particles of 120 - 240 ¦m range. This is consistent with the flotation recovery generally observed in flotation practice. The magnitude of the flotation rate constants obtained by CFD modelling indicates that transport rates of the bubble-particle aggregates to the froth layer contribute quite significantly to the overall flotation rate and this is likely to be the case especially in plant-scale equipment.

Jan 1, 2005

By Roxborough F. F

The ability of the Australian minerals industry to successfully manage the changes and challenges that face it in the 21st century depends ultimately on the quality of its human resources. Mining engineers have a vital role in this regard. The education and training that universities are currently giving to mining engineers is under challenge and needs to be reassessed in the light of industry directions for the 21st century. At one extreme is a push for a `finished product' graduate, up and running in `the flavour of the month' issues. At the other extreme are moves to reduce face-to-face university teaching hours and return to the time honoured university concept of `reading' for a degree. The lessons of Mourn make it apparent that neither approach is appropriate to the industry's future needs (Windridge, 1996). Basic knowledge gets rusty with time and new skills need to be learned. In order to conduct mining operations safely, productively and competitively, mining engineers must now accept the need to be prepared for continuing professional development as a career imperative. The concept of being professionally or statutorily qualified for life is no longer valid. This calls into question the purpose, content, structure and mode of delivery of university courses, all of which need to engender the principle and facilitate the cause of continuing professional development. This paper presents a model which aims to deliver a quality assured university education for mining engineers for the 21st century at undergraduate, postgraduate and professional level. The model extends beyond traditional university boundaries to match industry requirements to international best practice. It is based on collaborative alliances and innovative presentation modes which will provide industry access to undergraduate and postgraduate course elements presented by a broad range of national and international academic and industry authorities. It offers the prospect for preserving the best of university ideals in higher education, for developing and maintaining programs of direct relevance to industry needs and for a structured involvement in the continuing professional development of mining engineers.

Jan 1, 1997

Manganese ore has been mined from the Peak Hill Gold- field since 1948 and from the Pi'lbaraòGoldfield since 1954, and it is probable that some deposits- In and, near the Phillips River Goldfield will be mined at a future date', There are also several million tons of mariganiferous ;naterial which is too low in manganese. .co.ntent_ for . present requirements. The manganese deposits¦of Western Australia are mostly superficial. They hav' been formed during the Cainozoic Era by supergene enrichment ò6f Precambbrian: manganiferoius sediments, and by deposition from -solution on, or'in caves in, the Cain- ozoic land surface. The manganese in solution was derived from the weathering of Precambrian manganifer.ous s.edimexsts, None of the deposits are of hydrothermal origin, nor are they related to igneous rocks in any war, other than as ultimate source rocks. There is ho evidence-'t.o.:sugge,st that meta- morphism has been responsible for.the emplacement of any deposit. The tenor of the ore varies'aec'ording'to the quantity of gangue in the orebody and- also to the nature of the part- icular ore minerals. The main ore.mine.rals are the oxides pyrolusite and cryptomelane and the 'o'xide-silicate braunite. The main gangue minerals are hematite, limonite and quartz. The deposits of high grade oreò(-above.45 per cent Mn) range in size from 50 tons to many thousands of tons but most of them are in the 500-5,000-tons r .nge .

Jan 1, 1964