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By Nixon TR

The Australian Coal Industry Research Laboratories Ltd. (A.C.I.R.L.) MINVENT computer program can be used to simulate existing and projected colliery ventilation requirements. New collieries can be planned using a database of ventilation parameters which were ascertain- ed by A.C.I.R.L. surveys at selected collieries in N.S.W. and Queensland. Several techniques are used in both the formulation of the database and in the evaluat- ion of a ventilation system, prior to analysis by the MINVENT program. The analysis of a ventilation system requires the measurement of air quantities, pressures and hence airway resistances. All resistances are calculated at standard air density of 1.205 kg/m3. Air densities are derived from barometric pressure and wet and dry bulb temperature readings. Airway frictional and shock losses, leakage through stoppings and overcasts, flow of air through regulators, face resistance and resistance of anomalous ventilation features are related to the typical Australian measured data presented.

Jan 1, 1983

By J Carter, B J. Armstrong

Best practice for the submission of samples to an internal or commercial laboratory requires quality control materials to be included for the purpose of independently and comprehensively assessing laboratory performance. These quality controls include the use of certified reference materials (CRMs) and may be blind to the laboratory. Iron ore companies purchase these materials from reputable manufacturers from stock of run-of-mine materials at the appropriate grades. The international standard, ISO 17034 (ISO, 2016), specifies the competency requirements for organisations manufacturing reference materials, and includes rigorous requirements for the assessment of homogeneity, stability and establishment of property values and their uncertainties. Homogeneity is one of the most important measures of suitability for all certified reference materials and refers to the degree to which the composition and properties of a sample are uniform throughout the batch, relative to the analytical precision of the method. More specifically, homogeneity studies of candidate reference materials should be assessed for both within sample variance and between sample variance with appropriate statistical controls. The design and application of homogeneity studies are discussed as they apply to both crushed and pulverised reference materials. Crushed certified reference materials have been utilised by the iron ore industry for a number of years and provide the user with a critical assessment of variances in sample preparation in addition to analysis. Crushed reference materials are similar in presentation to an RC sample and are generally used as discrete parcels of material submitted to the laboratory from the field. Pulverise certified reference materials miss the sample preparation step and are subsampled from th delivered sachet at the point of analysis. This paper compares the relative homogeneity performance of crushed and pulverised certified reference materials by grade across key iron ore chemical constituents. Outcomes are benchmarked to the international standard ISO 9516 (ISO, 2003) for the determination of various elements in iron ores by lithium borate fusion and X-ray fluorescence. Practical implications are discussed with reference to a case study from an iron ore laboratory in the Pilbara.

Sep 18, 2023

By M Barker, H Li

The total number of tailings accidents has reduced from over 50/decade in the 1960s-1980s to less than 30/decade in the 2000s to 2010s. However, the rate of significant tailings dam failures has not been reduced. The significant tailings dam failures the mining industry experienced in the recent history include: Merriespruit, South Africa, 1994; Los Frails, Spain, 1998; Kolontár, Hungry, 2010; Mount Polley, Canada, 2014; and Samarco, Brazil, 2015. The conventional Factor of Safety approach itself may not be enough to further reduce the rate of significant tailings failures due to its limitations such as uncertainty. For example, the same factor of safety could have a vast range of annual probability of failure for different tailings dams, and insufficient consideration of failure consequence. This paper presents a risk based approach for design with the objective being to minimise tailings dam failures, especially those significant tailings failures with high consequence and low probability. This approach includes risk based design and risk management using bowtie tools. In the risk based design, quantitative analysis will be used to estimate the annual probability of failure and the tolerable failure criteria is linked to the consequence category. Bowtie analyses will be used to understand hazards and risks and identify and select independent controls that are effective in preventing and mitigating catastrophic failures. In this paper, examples of risk based design and bowtie analyses are presented and discussed. CITATION:Li, H and Barker, M, 2018. Risk-based approach for minimising tailings dam failures, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 397–414 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

The assistance that can be gained by the use of aerial photographs in the geological examination of a mineral field is clearly illustrated by the results of a rapid reconnaissance survey of the newly-discovered Mount Fitton talc, deposits, situated in the north-eastern extension of the Flinders Ranges in South Australia.The talc deposits were found to occur about the margins of a large lenticular mass of dolomitic marble, interbedded with hornfelsic tillites and fluvio-glacial sediments of Upper Pre-Cambrian age. Aerial photographs show clearly the extent of the dolomitic marble on which the growth of a species of eucalypt-Eucalyptus Gillei-is prominently developed, and which assists in defining the limits of this relatively light-coloured formation. (See Fig. 1).Upon field investigation it was found that the talc, deposits are related closely to the margin of the dolomitic marble where the latter has been subject to minor folding and faulting. The deposits themselves have been formed by metasomatic replacement of schistose dolomite. The contact of the dolomite with the underlying and overlying glacial beds is also noteworthy for the presence of minor occurrences of copper, silver, lead and zinc minerals.An examination of photographs covering a wide area reveals an outcrop of a massive granite to the north-east of the dolomitic marble, Fig. 2, which was almost certainly responsible for the regional metamorphism of the dolomitic and glacigene sediments, and the source of the mineralising solutions.All these features, as well as the broader structural features of the area, which are extremely important in the understanding of, individual commercial depQsits, were quickly determined with the assistance of the photographs.It is useful, briefly to relate the procedure adopted in examining this recently developed field as an example which may be well worth following on other fields, even if exposures are not so clearly defined. The method to be outlined, of course, will be of maximum advantage. Where rock exposures are good, where the ore bodies are likely to be widely spread, and where such bodies are related to some major geologi-cal control. Typical of such deposits are pegmatitic, hydrothermal and related ore bodies associated with the periphery of an igneous intrusion, or ore bodies related to particular sedimentary horizons in a regionally metamorphosed province.Procedure.The first requirement is the preparation of a detailed reconnaissance geological plan of as large segment as possible of the potentially mineralised province. The use of aerial photographs is par...

Jan 1, 1950

The copper and zinc contents of herbarium specimens of 11 of the 12 Australian species of Polycarpaea were determined in order to establish background and anomalous values of potential use in biogeochemical prospecting.Cumulative frequency curves were used to establish appropriate threshold concentrations for six species including the "copper plant"' P spirostylis. Collection localities of Polycarpaea specimens with anomalous copper or copper-and-zinc values are under investigation.

Jan 1, 1978

By A Horne, Z Graszkiewicz, D Dettrick, R Evan, B Neal

"Most of VictoriaÆs rivers and aquifers are already fully allocated or reaching full allocation. In regions without a well-established water market, access to water entitlements to facilitate new development is limited. In areas with established water markets, mine developers face an undue cost burden in circumstances where they are only planning to consume a fraction of the water entitlements that they purchase. The challenge for water managers is to ensure protection of water resources and other water users without creating an unnecessary disincentive for those types of developments that return most of the water that they take from water sources. The opportunity for development of a mine is explicitly linked to a particular location and must be developed where a resource is located or it cannot be exploited at all. Regulatory arrangements that facilitate development may have a positive impact on economic development, particularly where water availability is a potentially limiting factor. Net volume licensing has the potential to allow increased economic outcomes through improved licensing of access to water. Net volume licensing differs from traditional water licensing in that it authorises access to water on the basis of ænet useÆ rather than æthe gross volume takenÆ. This paper asks under what conditions net volume licensing is likely to be feasible and effective. In particular, the paper examines the information and accuracy requirements to allow net volume licensing decisions to be made. This work is based around five case studies in Victoria that were used to examine the potential for net volume licensing for mines and quarries. Assessing a potential net volume licensing arrangement requires the regulating authority to have an understanding of the inputs and outputs of water to a site. In contrast, assessment of take and use licences consider only a single input. It was concluded that the conditions that lend themselves to net volume licensing include: well understood water inputs and outputs, including appropriate accuracy of information where the location of site water inputs and outputs are the same where the timing of extraction and discharge can be managed to minimise impact on the water resource.A key remaining challenge is establishing an accounting framework that allows net volume licensing under current water resource limits. CITATION:Graszkiewicz, Z, Horne, A, Neal, B, Evan, R and Dettrick, D, 2013. The practicalities of implementing net volume licensing of water use in mines and quarries - a discussion based on Victorian case studies, in Proceedings Water in Mining 2013, pp 241-250 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 26, 2013

By L Gobbo

X-ray diffraction (XRD) provides useful information about the composition of an ore sample in terms of quantification of crystalline phases and amorphous content. The use of new, fast detection systems implemented in CubiX FAST industrial diffractometers creates the opportunity to use this technique in exploration and modern process control. Besides the chemical composition of iron ores, their phase composition is also an important factor for exploration, quality control and processing. In the analysis of iron ore, XRD can identify the phases containing iron, such as haematite Fe2O3, magnetite Fe3O4, and goethite FeO(OH), and any other mineral phases present, especially silicas. Quantitative analysis is possible by various classical methods such as straight line or polynomial calibration with standards, but modern quantification analysis techniques such as Rietveld analysis or full pattern autoscale analysis are attractive alternatives, as they do not require any standards. These methods offer impressive accuracy and speed of analysis. Another analysis technique offering great benefit to ore exploration and process control is cluster analysis. This technique greatly simplifies the analysis of a large amount of data, eg from drill core samplings, and automatically sorts closely related scans of an experiment into separate clusters and marks the most representative scan of each cluster as well as outlying patterns. This can facilitate multi-dimensional compositional mapping of ore deposits, identifying regions of favourable mineral composition and allows fast and reliable tracking of the process. It is the most economic procedure to have automatic data evaluation without involving any dedicated personnel in the process. Details of the techniques used, sample optimisation methodologies, results, data precision and limitations will be discussed. The approaches have enormous potential as an inexpensive, reliable tool, useful in the characterisation of iron ore materials in an industrial environment.

Jan 1, 2009

By C M. Standen

The SAG mill at Rasp Mine has undergone a number of liner design modifications since commissioning in 2012, making liner wear and failure difficult to predict from historical data. During 2017, several instances of liner failure or near failure were experienced resulting in unplanned downtime for emergency relines or to patch liners in the lead up to a planned shutdown. The strategy for relining mills is often to minimise the frequency of relines (and subsequent shutdown costs) by extending liner life, achieved through design modifications. However, it was observed that as the Rasp SAG mill liners wear, mill performance declined with power draw increasing and throughput declining. Opportunity and inefficiency costs start to erode the revenue per additional tonne milled for a given set of liners, and in turn the benefit of delaying relines. As such, optimising the frequency of relines becomes a trade-off between reline costs and opportunity/inefficiency costs in delaying relines. The aim of this paper is to demonstrate a frame work for analysing costs using a marginal economic analysis with the assumption that the Law of Diminishing Returns can be applied to the life of mill liners. The SAG mill operating variables can be modelled to determine their impact on costs and an optimal reline point can be defined where the total costs are minimised. This prevents unexpected failures due to accelerated wear by providing justification to reline earlier and thereby allowing efforts to be focused on sustaining milling performance.CITATION:Standen, C M, 2018. An economic approach to optimising mill reline frequency – a case study of SAG mill relines at Rasp mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 197–206 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By D Eschebach, D Mathewson

A belt press filter (BPF) handbook containing practical information for the reference of plant designers and operators has been created as part of Australian Coal Association Research Program project C23040. The handbook combines research and experience with newer generations of equipment and circuitry. BPFs are increasingly finding application in the dewatering of thickener underflow tailings slurries due to changing environmental regulations, difficulty obtaining tailings storage facility approvals and limited water availability. Sources of BPF inefficiency and low availability stem from a lack of understanding of the key operational parameters that affect their performance. This lack of understanding typically leads to increased operational expenditure due to suboptimal reagent dose rates and increased maintenance costs, or decreases in plant availability due to excessively high filter product water contents and equipment failure. It is essential for the continued economically competitive operation of Australian coal handling and preparation plants that complex factors affecting BPF operational performance are clearly defined and understood. Installation and operation handbooks are often provided to sites with new installations, but these manuals are manufacturer- or even model-specific and are often focused on mechanical maintenance. The handbook identifies industry ‘best practice’ and improvements developed by other sites, such as extra spray bars, air system bleed valves, guarding designs, feed and filtrate protection screens and roller tensioning systems. Equations to predict optimum operating conditions – such as free moisture, belt tension and reagent dose rates, with simple feed-specific variable inputs – have been developed from site-specific test work. The correlations developed provide a benchmark for plants to attempt to achieve. This provides operators and process engineers with a tool to explain BPFs and assist them in optimising the performance of BPF dewatering plants of both contemporary and less modern design.CITATION:Mathewson, D and Eschebach, D, 2015. ACARP belt press filter design, operation and maintenance handbook, in Proceedings Tailings and Mine Waste Management for the 21st Century, pp 73–82 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By G Hancock, J Lowry, W D. Erskine, D Jones, T Coulthard, M J. Saynor, P Lu

An 8 ha trial landform was constructed in late 2009 at the Ranger Uranium Mine, located 250 km east of Darwin in the wet-dry monsoonal tropics of northern Australia. The objective of the trial, which comprises two surface cover types on a uniform two per cent slope, is to provide long-term data to guide the development by Energy Resources of Australia Ltd (ERA) of its landform closure strategy. The scope of the work program for the landform includes many aspects; however, this paper is focusing on run-off and erosion rates. The run-off and erosion rates are used to assess the long-term geomorphic stability by comparing measured with modelled export rates from a landform evolution model.Monitoring of wet season run-off is undertaken collaboratively by the Environmental Research Institute of the Supervising Scientist (ERISS) and ERA, on four purpose-instrumented 30 m by 30 m erosion plots. Continuous measurements are made in rectangular broad crested (RBC) flumes located at the outflow of each plot, of water level, turbidity (a surrogate for fine suspended sediment) and electrical conductivity (EC) (a surrogate for solutes). Each plot has a tipping bucket pluviometer located near the RBC flume. Bed load is collected monthly.This paper reports the findings of rainfall and bed load from the first two wet seasons (2009 - 2010 and 2010 - 2011) following construction. The field measured loads will be compared with the predictions made by the Cellular Automaton Evolutionary Slope and River (CAESAR) landform evolution model. Initial results indicate that predicted rates of sediment export from the CAESAR model are similar to measured export rates. This provides confidence in the capability of the model to predict stability of the future rehabilitated mine area, especially during the critical initial years following construction. CITATION:Saynor, M J, Lowry, J, Erskine, W D, Coulthard, T, Hancock, G, Jones, D and Lu, P, 2012. Assessing erosion and run-off performance of a trial rehabilitated mining landform, in Proceedings Life-of-Mine 2012 , pp 123-132 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By Parker A. J, Grimsey E. J

Studies have been carried out on the dead roasting of a copper-iron and a copper-nickel-iron sulfide concentrate, followed by segregation roasting with coal and leaching with either curpric sulfate in aqueous acetonitrile or cupric chloride in brine solution to preferentially solubilize copper. The effect of dead roasting and segregation roasting conditions on the overall leaching of copper and the separation of copper from iron and iron and nickel is reported. An excellent separation of copper from iron and a good separation of copper from iron and nickel can be obtained provided sulfur is removed to 0.5 per cent or less during the dead roast and provided the coal addition and temperature of the segregation roast are near the minima required for the segregation of copper.

Jan 1, 1983

The Golden Ridges Mine, one of the properties of New Guinea Goldfields Limited, is situated on the right bank of Nami Creek, not far from the township of Wau, in the Territory of New Guinea.The property is somewhat unique, in that the goldbearing ore-body occurs in the form of a flat seam-like deposit lying on a volcanic breccia, and covered with a mantle of overburden of decomposed porphyry. The overburden varies in thickness up to a maximum of about 65 ft.The ratio of overburden to ore is about 3 to 1. The practice developed is to strip the overburden by hydraulicking, and to mine the exposed ore under open-cut conditions, blasting to a vertical face, and using electrically operated scraper hoists for conveying the broken ore to the mill bins.The stripping of the overburden involves the boring of well-drill holes, blasting the holes and then hydraulicking the shattered material.

Jan 1, 1934

By W R. Adamson

Cerro Vanguardia SA (CVSA), property of AngloGold Ashanti, mines gold and silver from a system of vetiforme orebodies located in the south of the Argentine Patagonia, in the Province of Santa Cruz.Surface mining techniques are applied to develop a series of narrow pits with an average waste to ore ratio of 26:1. This quite unique constraint brings into focus the need to maximise inter-ramp and final wall angles, leading to a strong need to optimise wall control drilling and blasting in order to reduce back-break damage to an absolute minimum.The paper describes a program of applied investigation and design modification implemented during?2008?and?2009 in?two?separate pits of Cerro Vanguardia. Three distinct yet complementary damage mechanisms were identified and observed during the field components of the work; vibration induced strain fracturing, surface cratering around blasthole collars and quasi-static loading and unloading of the surrounding rock mass as a consequence of poorly controlled confinement.With these mechanisms identified, a measurement, modelling and modification campaign was conducted in order to reduce the incidence of each source of damage. Interactive design analysis and modelling, near-field vibration measurement, video capture and the application of electronic initiation technology were supported by seed wave modelling and topographic evaluation of the achieved results.Results point to the usefulness of simulation techniques for determining optimum delay timing to reduce vibration impact, while the visualisation of explosive energy distribution produced by drilling and explosive loading decisions assists in reducing the probability of over-confinement.This paper presents relevant aspects of the two fieldwork campaigns:1) describing the application of the techniques, and2) summarising the results obtained.

Nov 8, 2011

By Y Cui, G Cao, H Zong, J Zheng, J Wang, S Yue, J Zhao, B Li

The iron (Fe) concentration in nickel slag is high, making its recovery and utilisation a hot and challenging topic. In the nickel smelting process, using CaO instead of SiO2 to adjust slag’s composition, and then directly reducing Fe from the output of molten slag is a more feasible method in practice for Fe recovery in nickel slag. The adjustment of slag’s composition in the nickel smelting process will have an impact on the distribution of impurity elements such as Pb, Zn, and As. In this paper, the slag adjustment of nickel smelting process was carried out with the oxygen-enriched topblowing system. The distribution of impurity elements in the smelting products with each composition slag was conducted by using thermodynamic software. Experimental verification was performed with rich oxygen top-blowing, and the distribution characteristics of impurity elements in the smelting products were characterised to explore the differences in mineral phases of impurity elements with each smelting conditions, elucidating the distribution patterns of Pb, Zn, and As in each phase. The results indicate that after slag adjustment, impurity elements are more easily to volatilisation and removal into the gas, reducing their total concentration in slag and matte. In the slag, the existence form of Pb, Zn is changed from silicate to ferrate, and As is changed from arsenate to low-valent arsenic oxide. It is easier to decompose the impurity-containing mineral phase and remove the impurity elements in the subsequent iron extraction process.

Jun 19, 2024

By I Sherrell, R Jain

Worldwide iron ore feed grades are trending downwards and will continue to do so with the increasing difficulties of upgrading ores. This has led to operations looking for ways to capture current tailings that still contain valuable material. In the past, these were acceptable to dispose of, but this practice is no longer economically feasible. With the increasing trend of re-mining previous tailings deposits that could be decades old, new equipment designs have been introduced to upgrade current or historic beneficiation plants. These designs can effectively upgrade these tailings to saleable products.Outotec conducted test programs for upgrading iron ore tailings from flotation rejects, thickener underflow or tailings dumps on samples provided by customers around the globe. The studies utilised Outotec’s SLon vertically pulsating high-gradient magnetic separator in combination with preprocessing equipment such as low-intensity magnetic separation, screen or scrubber and flotation for downstream processing of the magnetic concentrate. A review of the equipment required to economically process these tailings is provided, along with testing data and industrial implementation examples. The effect of different operational and design parameters on Fe grade and recovery from processing each tailings sample has been highlighted.CITATION:Jain, R and Sherrell, I, 2015. Iron ore tailings reprocessing to maximise ore production, in Proceedings Iron Ore 2015, pp 149–158 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

Remote sensing, in general, is the recording of light and heat from a planet's surface within a certain range of the electromagnetic spectrum. For the Earth, systems capable of this recording are the MultiSpectral Scanner (MSS) and SLAR. The former is the recording system used in satellite and will be discussed in the next section. SLAR stands for Side Looking Airborne Radar. This device sends invisible radar waves which illuminate the Earth's surface. The reflected waves are subsequently recorded as images. The system can operate through darkness and dense cloud cover, and is particularly suited for the study of geological structures at both large and small scale (Wayland 1976). Remote sensing techniques are now widely being made use of in mineral exploration, especially for those last remote 'sanctuaries' where geological data are meagre or non-existent. For places like Borneo, West Irian, the Amazon Basin etc. remote sensing, in the form of both satellite imagery and SLAR, is of considerable help, in fact more often than not the only help, to delineate geological provinces, geotectonic domains and meaningful lineaments. In the case of New Zealand, well made geological maps at scale 1:250 000 by the Geological Survey are available to the public and these provide useful preliminary grounds for the selection of target areas. However, even in this case LANDSAT imagery can be of aid as will be shown later.

Jan 1, 1977

By C J. Greet

Oil can enter a flotation circuit from a number of sources (for example, from mining equipment, oil leaks from the grinding equipment and coatings on the grinding media, but to name a few). Folklore generally states that any oil that contaminates the ore entering the flotation circuit is considered to have a negative impact on flotation. That is, a loss in concentrate grade and recovery.This represents a dilemma for some grinding media suppliers, who use a variety of quenching medium (air, polymer, oil or water) to achieve the desired physical properties of the ball. In the case of high chrome grinding media it is necessary, in some instances, to quench in oil to give the ball the right degree of toughness, which invariably leads to these balls having a thin film of oil on their surface. Once the grinding media arrives on site and site personnel recognise that the balls are “covered” in oil, they generally insist that the oil will have a deleterious impact on flotation performance.Obviously, any supplier “worth their salt” would take remedial action at the point of manufacture to minimise this problem. However, does quenching oil actually present a significant “threat” to the flotation process? This paper provides both laboratory and plant data describing the effect quenching oil has on the flotation of copper sulphide ore, with surprising results!

Aug 8, 2011

COMPRESSED air is held in high esteem by the mining engineer as a medium for the transmission of power. The transmission, however, is accompanied by a high percentage of loss. Of the total work done by the steam cylinder'in compressing the air inthe air cylinder, less than 50% is ultimately utilized by the machines underground. These losses are due to its essential and inherent properties as a gas. One of the sources of loss is that due to transmission through the pipes which distribute the air from the receiver to the various places where it is used. As the capacity and economic design of air-compressing plant are influenced by this source of loss, it may be of interest to give an outline of how estimates may readily be made'in practice of thediameter of pipes, quantity of air discharged, and the drop in pressure occasioned.In hydraulics we have a general formula given M Rankine's "Civil Engineering" :It was suggested, the writer believes, in the first instance by D'Arcy, that this formula could be made to apply to an elastic...

Jan 1, 1918

Upon subduction, water is liberated from the sediments and the porous struc- ture of the oceanic crust and from de- hydration of minerals for redistribution and chemical reaction. A survey of pro- cesses which are likely to occur along the subducting plate reveals that water may well be basic in subduction induced gas generation, magma formation and ore deposition. In analogy to the industrial water gas process, reaction of water with car- bonaceous matter, in subducted sediments is likely to yield substantial volumes of hydrogen and carbon dioxide. While water and carbon dioxide appear to play a determining role in the development of differentiated magmas, hydrogen will react with metal sulfides and sulfur to form hydrogen sulfide which is essential in sulfide ore depo- sition. A survey of possible metal extrac- tion chemistry along subduction suggests a stepwise solubilization of metals from sediments and oceanic crust, and a poten tial accumulation of dissolved metals in zones of characteristic composition. The metal spectrum in ore deposits at near surface appears to reflect the com- position of the solution in the respec- tive subduction zone. A tendency for preferential solubi- lization of copper at subductidn level, from among the transition metals, an in- creasing generation of hydrogen sulfide in the sane direction and partition effects as well as sulfide precipitation characteristics lead to enrichment in copper and to its selective deposition in the direction towards the trench as observed in S. Latin America. A postscript deals with the formation of native copper.

Jan 1, 1986

The Torington Lodes.This paper describes investigations into mineralogical, petrological and structural associations of cassiterite in occurrences of economic value. The work was carried out in three mines, during a number of years, in the hope that the, data collected might be helpfulin the search for occurrences of cassiterite in stanniferous zones and reduce unproductive exploratory work. Tin-bearing lodes at Torington, in the New England district, New South Wales, have been worked since 1880, and the locality is the most important centre of lode tin occurrence in the, State. The township of Torington is 18 miles westerly from Deepwater, a station on the Great Northern Railway, 446 miles from Sydney.The tinfield forms part of the Mole Tableland, which has an altitude between 3,000 ft. and 4,000 ft. above sea level. The country rock, in which the stanniferous lodes occur, is granite of Permian age, which has been intruded into Carboniferous claystone. An inlierof claystone is exposed to the west of the stanniferous area, 'and in it, close to' its contact with the enclosing granite, are occurrences of wolfram and bismuth. These minerals, together with chalcopyrite, pyrite, arsenopyrite, zinc blende, galena and molybdenite, in very small quantity, are associated with cassiterite in lodes traversing the granite, particularly near the claystone, but decrease in amount with distance from the contact. Their occurrence is sporadic and usually causes no trouble in dressing the cassiterite concentrate, the final product containing less than 1% of total penalisable impurity. In Curnow's mine, pyrite, galena and molybdenite have been observed at 700 ft. from surface.The granite is of the biotite type and its structure may be divided into four groups, or classifications, arising from segregation processes during cooling and consolidation. The four classes, in order of extent of distribution, are:1. Granite of normal type, in which the constituent quartz felspar and mica, have a particle size approximately 14, in.2. Porphyritic granite, in which the felspar particles are from % in. to lin. in size, that of the quartz and mica approximately % in.3. A fine-grained granite, in which the particles of all constituent minerals are % in. or less in size;4. A rock of highly siliceous ground mass containing very small particles of felspar and almost negligible biotite.Type 1 is the general type of granite in all mines of the field; types 2 and 3 may occur as large masses, or all three classes may merge rapidly one into the other, and all be disclosed in 20 ft. of driving. Usually, however, the segregations are massive, but are not associated with any special horizon. For instance, a mass of porphyiiticgranite extends from surface to a depth of 440 ft., for a distance of 350 ft. south from the New England main shaft. The upper levels of Curnow's mine, 14" mile south-east, are in normal granite, but a restricted mass 'of porphyritic granite occurred between Nos. 5 and 6 levels, or 400-500 ft. below the collar of the shaft...

Jan 1, 1950