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By Burgess J, Brownrigg A

The world steel industry underwent rapid growth from 1950 to 1970. Since that time, production growth has been relatively slow, with declining production in the developed countries and increasing production in some newly developing countries. Since 1970, Western World crude steel production has been static at around 450 million tonnes, with cycles around this level in a 100 million tonnes band.

Jan 1, 1992

In any open pit mine some slope instability may be expected. This can range from small scale sliding on individual benches to large scale overall slope failure. This paper presents two case histories which illustrate how mining has successfully continued despite major pit instability. The common threads in each of these are listed below. 1. The recognition of the type and nature of movement (either regressive or progressive). 2. The successful application of simple monitoring techniques to minimise the potential impact on the mining operation, and 3. The management of the waste and ore excavation to avoid potentially damaging and costly situations.

Jan 1, 1986

The Golden Valley Volcanic Centre has been recently interpreted as being a combination diatreme breccia pipe and rhyo-dacite flow dome complex of Permo-Carboniferous age that intrudes basement granitoids and sediments of Ordovician-Devonian age. Exceptionally good exposure at the Centre has enabled the relationships between different lithologies to be determined. This, along with petrological studies, has led to a detailed understanding of the geological environment in which the complex formed. Gold, silver and base metal mineralisation have been recently shown to be associated with the Marginal Breccia at the perimeter of the diatreme. Comparisons have been made between the geology and mineralisation in this system and several similar diatremes which also contain gold-base metal sulphide mineralisation.

Jan 1, 1990

The discovery of economic uranium miner alisation in unique geological conditions at Yeelirrie, 700 km NNE of Perth, presented Western Mining Corporation Limited with a num- ber of sampling and evaluation problems. Carn- otite mineralisation occurred in a porous cal- crete-clay lithology in close proximity to the water table; background information on such a deposit was non-existent and sampling in these conditions could be difficult. The deposit was sampled initially by aug- er drilling with X-ray fluorescence analysis of drill cuttings, followed by reverse circulation and diamond drilling with analyses by X-ray fluorescence and gamma logging of the holes. Two costeans provided lithological and grade distribution data and mining experience in the deposit. Spoil from the costeans was stockpiled according to location in the first costean and according to location and grade in the second costean. Samples from the various stockpiles were analysed by X-ray fluorescence. No. 1 costean was extensively sampled by channel sampling of the walls and by pit sampling of the floor of the benches of the costean by back hoe. No. 2 costean was sampled by Geiger counters mounted in T-probes and by the gamma logging of auger holes to establish the valid- ity of the T-probe results. Samples were taken

Jan 1, 1976

By Raudsepp R

Since 1991, the Porgera Joint Venture has processed refractory sulphide flotation concentrate by pressure oxidation with the subsequent gold recovery, from the washed residue, via a conventional leach/carbon-in- pulp (CIP) circuit. The capacity

Jan 1, 1997

The economic valuation of mineral prospects usually involves DCF analysis of expected revenues and costs. Traditional approaches deal with price uncertainty by considering different price scenarios and may even consider cases where prices drop sufficiently for production to be suspended temporarily. This paper outlines recent extensions to the methodology derived from finance theory. We present a simple analytical model that focuses on the value of operational flexibility where future prices are uncertain.

Jan 1, 1988

It is argued that the capture of par- ticles by bubbles is primarily caused by hydrophobic ("structural") attraction forces. Neither dispersion forces nor double-layer forces can account for hydro- phobicity, though the latter are known to influence the kinetics of capture. The recent experiments of Israelachvili and Pashley (Nature, 300: 341-342, 1982) with hydrophobic mica plates provide the first measurements of the range and magni- tude of hydrophobic interaction forces.

Jan 1, 1984

A computer programming language known as GPSS is described and possible applications for the mining engineer are presented. The language is continually being upgraded with improved versions appearing about every three years. The tremendous power of the language is considered by comparing it with standard engineering programming languages, such as Fortran or Basic. Sample problems that can be solved using the language are indicated. The advantages and disadvantages of the languages are also discussed.

Jan 1, 1987

Techniques and results achieved during the excavation of the Melbourne Underground Rail Loop (HURL) are summarised and discussed in the context of the various restraints present in a typical urban construction project. Mechanical methods (as distinct from those utilising blasting)accounted for the bulk of the excavation. Ground support was critical in this particular geological excavation setting, but is not discussed in detail except insofar as it constitutes a restraint to excavation progress.

Jan 1, 1978

By A F. Idziak

The aim of the present study was an application of coal optical property measurements for analysis of paleostress field existing in fault zones of the Upper Silesian Coal Basin (USCB) during the coalification of organic matter. Measurements of vitrinite reflectance were carried out on coal samples taken near a hanging stope of the Klodnicki fault. Other samples had been taken in vicinity of the Krzyzowicki fault. The Klodnicki fault is one of the main tectonic discontinuities in the northern part of the USCB. It is postulated that its origin is related to the deep-rooted latitudinal discontinuity in crystalline basement of the basin. The Krzyzowicki fault is located in the western part of the USCB where fold tectonic style dominates. Vitrinite, one of the basic components of hard coal is generally considered as optically anisotropic material. Anisotropy of physical properties is induced mainly by stress, which arranges vitrinite structure. Vitrinite anisotropy can be described by an ellipsoidal model called reflectance indicating surface (RIS) which is a geometrical representation of the optical anisotropy tensor. The investigation of the RIS for vitrinite was carried out on coal samples. The apparent maximum and minimum reflectance values measured for a single vitrinite particle were plotted against corresponding bireflectance to construct the reflectance crossplot. Interpretation of this plot yielded the magnitudes of the RIS three principal axes. The data obtained point to differences in optical anisotropy of coal under the study. The coal samples taken from block tectonic zone near the Klodnicki fault had mean reflectance value of less than 0.80 per cent. Their anisotropy coefficients were about 0.1. Optical properties of coal changed from the biaxial positive in the western segment of the fault to the biaxial negative in its eastern part. It suggests that past tectonic stress was greater in the western part of the zone than in the eastern one. Coal originated from a fold tectonic zone at the vicinity of the Krzyzowicki fault has mean reflectance value much greater than from previous region (ÿ1.20 per cent). Its optical anisotropy coefficient is equal to about 0.07. It suggests that paleostress field was more isotropic. The presented study shows the usefulness of coal reflectance measurements in the analysis of paleostress field existing during coalification process.

Jan 1, 2003

Gold was discovered in the Bendigo area of Victoria in 1851 (Willman and Wilkinson, 1993), and all the early gold mining of any note involved washing (puddling) the gold out of the regolith or alluvium. The waste material from this process was a semi-fluid mixture of rock debris, soil and water, referred to as `sludge'. Puddling machines were gradually introduced to speed up the puddling process (Cole, 1994), and by 1855 an estimated 2000 machines were in the district (Anderson, 1978). In 1859 it was estimated that approximately 2 293 000 m3 of material was puddled annually by the machines on the eastern side of the goldfield, whose waste drained into Bendigo Creek and its tributary gullies. It was also estimated that after the gold was removed, approximately one-quarter of the residue/sludge consisted of the heavier, coarse-grained material which settled out fairly quickly, while the remainder, approximately 1 720 000 m3, was the fine-grained material which flowed downstream for some distance (VPP, 1859 - 60). From these figures it can be assumed that for the ten years during which this volume of puddling was maintained (1854 - 1864) over 5 700 000 m3 of gravels and sands and 17 200 000 m3 of fine-grained sludge had been discharged into and around Bendigo Creek. This was enough to cover an area of over 400 km2 to a depth of 5 cm. By 1859 the problems associated with the sheer volume of sludge being discharged were such that a Royal Commission was appointed to `Enquire into the Best Method of Removing the Sludge from the Gold Fields' (VPP, 1859 - 60). The goldfields referred to were those in the Bendigo area around the township of Sandhurst (now known as Bendigo). The Report of the Commission (VPP, 1859 - 60) stated that: `... inspection of the country bordering upon the course of the Bendigo Creek, to a distance of about fifty miles from Sandhurst . . . ' had revealed that the sludge had ' . . . filled up watercourses and flooded pasture lands . . . '. It also noted that ' . . . even on the plains, thirty or forty miles away from Sandhurst, where the sludge flows thin, and is relieved from its heavier particles, we found it baked into a perfect concrete, and in thicknesses varying up to two feet or more . . . '. The italics were used for emphasis in the original text. As it was considered unlikely that the physical evidence for such widespread inundation would have disappeared completely over the intervening 130 or so years, a project was initiated to locate any evidence of the inundation in the current landscape. If such evidence were to be found, then an estimate could be made of both its extent and its effects on the topography, drainage, and land-use of the inundated area. Extensive field work has determined that over 700 km2 to the north of Bendigo was inundated by the sludge. The area has not been uniformly covered, but has occasional `inliers' which have obviously escaped inundation by being slightly higher than the surrounding areas. Today the sludge is readily identified as a very fine-grained, hard-setting, concrete-like `capping' overlying a well-developed, well-structured, pedal horizon, or in some instances, the gravels and sands of a creek bed. The thickness of the sludge capping varies between a few centimetres and three metres (Peterson, 1996). The buried topography was gently undulating, in direct contrast with the almost unnatural flatness of

Jan 1, 1997

What is the real value of your data?Given that the cost of collecting and analysing an individual sample is always rising, it is important to understand the true value of a sample and that you are confident that you receive good value for your exploration dollar. Unfortunately too many samples are still collected today that will end up as worthless data; a liability to those who own it and a hindrance to finding that ore body.

Jan 1, 1986

By J H. Kyle

Cyanide is a significant cost in gold processing, as well as an environmentally sensitive issue. It has been suggested that precipitation of cyanide from leach liquors as copper-iron-cyanide compounds such as Cu2Fe(CN)6 may account for part of the total cyanide consumption. This may be especially true for ores that are rich in both copper and iron minerals. Ammonia addition has been shown to decrease the cyanide consumption by copper. Cu2Fe(CN)6.xNH3 precipitates have also been postulated to form during conventional cyanide detoxification processes, using oxidants such as SO2/air, with ammonia arising as a breakdown product from the oxidation of free cyanide. The present work has examined the conditions under which such precipitates may form, particularly in gold plant process and detoxification liquors. Ammonia and pH were found to have a large effect on the extent of precipitation. The compounds that were formed were found to comprise mainly Cu2Fe(CN)6.7H2O, as well as a range of NH3-bearing variants. The stabilities of the various precipitates are important from an environmental perspective. The long-term stability of copper ferrocyanide precipitates in tailings dams may be a problem under alkaline conditions and when some free cyanide is present, elevating the measured total cyanide in solution significantly. Case studies including data from actual plants are also considered, and the importance of these effects is reaffirmed from these results.

Jan 1, 2000

By Leigh G, Gottleb G, Wilkie G

The estimation of particle liberation is important in the study of mineral concentration. With simple systems, where the densities of the components are low, the liberation can be studied directly by density fractionation. For most practical systems, and particularly for the dense, complex sulphides, the only method known is by measurement in polished section. There are two major difficulties with such measurements. Firstly, the measurements themselves are difficult and considerable care is needed before reproducible results can be achieved. Secondly, a well known stereological problem arises which gives the estimates an inherent bias. The paper discusses both aspects of the problem. The practical features of measurement are treated in detail and a method described which has been developed and proven to give reproducible estimates of the liberation in the section. This discussion relates to automated measurements by QEM*SEM and presents a way of estimating the confidence limits within which measurements lie. Comparisons are shown between measurements made by the traditional manual optical technique and automated equipment. Stereological reconstruction is also discussed briefly. Several methods have been presented in the literature but all are complex and none is yet widely accepted. Area measurements are less biased than linear estimates so a practical approach is to use area measurements in uncorrected form. The topic is still being actively researched so it is expected that one method will soon emerge as the standard technique.

Jan 1, 1993

THE writer of this paper well realizes that the majority of engineering and metallurgieal works have from time to time evolved mechanical devices which are of great value as regards application in an operating plant.Many of these deviees would not be apparent to an individual making a brief inspection of works such as these, and it is for this reason that the writer proposes to outline a few of the devices which have been evolved by the engineering department of the Broken Hill Associated Smelters Pty. Ltd.NOVEL METHOD OF MACHINING A SPHERICAL JOINTFig. 1 represents one half of a casing for a ball-joint coupling. In the ordinary methods of boring an external spherical casing, that is with a radius bar attached to the tool rest of a lathe, there is always an error in the bore. It has two flat sides, and this error is inherent in the ordinary orthodox method and cannot be corrected. The engineers of the Broken Hill Associated Smelters Pty. Ltd. undertook a job that had to be extremely accurate, and the tool shown in Fig. 2 was evolved. The tool is not exactly fool proof, but in the hands of an average mechanic an absolutely perfect FIG. 1. sphere can be bored. The casing has to be held in the lathe in such a manner that one half can be removed without affecting the setting of the work. The business end of the tool is then placed inside the...

Jan 1, 1922

By J Kleynhans, D Vermeulen, V Cogho

A number of rehabilitated open cast coalmines in SA are already decanting. The paper focuses on the situation at one of these mines where the following information exist: monthly decant rates and rainfall; sulfate concentrations of the decanting water; water level measurements inside the mine prior to decanting; ABA analyses; information about the rehabilitation (drainage slope, vegetation, soil used). A 2D-model was constructed for the mine and calibrated against six years of flow data. About 85 per cent of the decant outflow rate comes from direct recharge on top of the rehabilitated mine while the other 15 per cent is derived from lateral groundwater inflows. The estimated recharge value was 17 per cent of the rainfall. Measured sulfate values showed that the sulfate generation rate for the mine was in the order of 7 kg/ha/d. Conclusions from the study are:most of the water decanting from rehabilitated open cast coal mines is derived from recharge via rainfall; given a specific sulfate generation rate, then: the lower the recharge the less the decant rate but the higher the sulfate concentration of the decanting water and vice versa; future prediction of the decant rate must be stochastic according to expected percentile monthly rainfall values; and as a first assessment of the predicted sulfate concentration of decant water from rehabilitated open case mines, the 7 kg/ha/d sulfate generation rate can be used.

Jan 1, 2003

By Milner SC

Four quartz latite rheoignimbrite units (units I to IV) mapped in the Goboboseb Mountains have been traced to their eruptive source, the Messum intrusive complex; this is a complex multistage ring structure (18 km diameter) with well defined gabbroic, monzonitic, and syenitic intrusive phases, and a central ring zone containing mixed rhyolitic to latitic agglomerates. Three of the four quartz latite units are correlated with the upper and lower (2 units) Springbok quartz latites outcropping some 90-130 km north of McIsum. This implies minimum volumes of 300-500 km for wits I and III (Lower Springbok) and 2200-2600 km for unit IV (Upper Springbok). This latter unit is still ti 300 m thick at its outcrop limit, some 130 km from Messum. Each of the four units represents single cooling units. Lithologically, each can be divided into three zones: A basal, dark grey to black flinty or glassy zone, often with highly attenuated fiamme (ressembling flow banding); a central massive and strongly recrystallised zone; and an upper variable zone which exhibit breccias, contorted flow banding, and amygdaloidal to pumiceous clasts. Their overall characteristics tend to be intermediate between ash flows and lava flows. The rheoignimbrites are interpreted as the oproducts of dense, high temperature (950¦-1100 C) ash flows which underwent rheomorphism and lava-like flow prior to their final cooling.These large scale eruptions are related to the initial rifting of Africa and S. America, possiby in response to a major hot spot.

Jan 1, 1990

Mining engineering, metallurgy and minerals-related geology have proud traditions and are essential professions to support a safe and sustainable minerals industry. However, the future of these professions is under threat. The courses that produce such graduates are disappearing worldwide and the number of graduates available to enter the industry has been falling in English speaking countries for at least a decade. It is unlikely that this problem will be remedied by æsupply and demandÆ. Instead, some active intervention is required.

Jan 1, 2004

About 11,000 tons of contaminated zinc flotation concentrate were available in the form of earth walls from dams used for atmospheric drying of the concentrate.Following successful laboratory tests this material was treated in a plant by crushing, grinding, and then flotation in a circuit consisting of roughing, scavenging, and two stages of cleaning. Reagents used were copper sulphate and a little butyl xanthate and frother. About 5,720 tons of zinc concentrate assaying 52· 3 per cent zinc were produced.

Jan 1, 1968

By H Jha, M C. Thomas, P Gupta, S K. Sit

The modern jig with a state-of-the-art control system is much more effective than its older version. This improved control system is used to modulate the amplitude and the frequency of the jig cycle. These two prime parameters are optimised with respect to feed characteristics for best jigging performance. Based on this understanding any jigging plant can be optimised. In addition to these established facts present study shows process efficiency improves further through optimisation of the feed quality.

Jan 1, 2007