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By Nairin J. D, Hayes P. C

Detailed studies of the microstructures and compositions of zinc and lead blast furnace sinters have been undertaken. An analysis of the results obtained has indicated that in many cases the microstructures of these complex materials can be explained by the solidification of melts from pseudo-ternary phase systems. Further laboratory studies have been carried out to more accurately determine the extent of primary phase fields and the liquidus temperatures in the appropriate binary and ternary systems. This approach shows considerable promise in simplifying the descriptions of slag systems used in oxidising and reduction smelting processes for lead and zinc recovery.

Jan 1, 1992

By Ellery B. I

Field investigations recently undertaken by Utah Development Company (U.D.C.) have been developed to allow the assessment of ground conditions relevant to the use of large bucket wheel excavators for pre-stripping overburden. "Bucketwheel diggability" predictions were made on the basis of a wedge test which was perform- -ed in the field on nominal 150 mm diameter drill core samples. Specific separation force (calculated from the wedge test results) for different rock horizons were theoretically related to the excavation rates of various sized bucketwheels, i.e., "bucketwheel diggability". The specific separation force was shown to vary with lithology, structure, weathering and moisture changes. By correlating these features between boreholes, an overall assessment of bucketwheel diggability was then made. The approach adopted to assess bucket- wheel diggability incorporated various levels of investigation. Initially, a reconnaissance stage provided information from widely spaced 150 mm cored holes to compare and contrast areas with differing bucketwheel digging char- -acteristics. The following stages progressive -ly added to this information, until finally, between hole correlations, allowed calculations to be made of volumes of materials of similar

Jan 1, 1981

By Bof J, Lowe S

BHP's newest colliery on the Southern Coalfield Is Tower Colliery. It is situated near Wilton some 60 kms south west from Sydney. It commenced its operations in 1978 and since that time has experienced considerable roof problems. In its eight years of operations, production has been 936 687 tonnes to December 1985. To a certain extent this is a reflection of the ground control r,,b1cros present in the colliery. paper out Iines the signif mt g,, logical features that are known to exist in the colliery and their influence on roadway development. Faulting has hindered the mine's development and an igneous intrusion has had outhursting associated with it. The prevailing roof rock has also had an impact on the roadway conditions. The paper will look at intersection deformation in present workings. Extensometers have been installed in these areas and provide measurements to verify visual observations. The results show a significant increase in roof movement as the roadway is developed from a single heading, to a T-intersection and then Into a four-way intersection.

Jan 1, 1986

In a high pressure rolls crusher two force components: the pressurising thrust and the rolling force can be measured experimentally. Computer analyses have revealed regular patterns of stress distribution in the confined material between the rollers. Based on the computer analyses and experimental results a one-dimensional comminution model has been developed.

Jan 1, 1995

This paper deals briefly with productivity-enhancing advances in shaft sinking technology in South Africa post-World War II in general and the developments and application of long rounds since the 1980s in particular and is amply illustrated.It touches on the conversion to circular section, concrete lined shafts, the introduction of tungsten carbide drill bit inserts and grab lashing; expounds the rationale driving the development of longer rounds; and then describes the evolution of long rounds using hand-held and mechanically mounted rockdrills in South Africa and Canada by both local and foreign contractors. The recent experience gained on the sinking of the South Deep Main Shaft follows. Results obtained from this experiment are tabulated and commented upon. The paper concludes with the postulation of æwhat nextÆ and æwhere toÆ scenarios. Addenda include a list of shaft rounds in excess of three metres in length blasted in the Main Shaft at South Deep and their results, typical round design, manufacturerÆs specifications for the 6 m shaft jumbo and rock drills.

Jan 1, 2002

Since the announcement of early experimental work on rotating magnetic field (RMF) separation at the Sixth Mill OperatorsÆ Conference in 1997, the concept of RMF separation has been developed and tested further, and a range of separator designs is now being developed for the mineral processing industry. Shortened, but full diameter, prototypes of these designs are now available for test separations. The main advantage of RMF low and medium intensity attraction separation is the significant reduction in particle entrapment. This reduction is so significant that RMF separators are capable of operating very close to their theoretical limit for separator precision. This makes small laboratory RMF attraction separators ideal for low to medium intensity magnetic sample analysis, and larger separators ideal for applications requiring sharp magnetic susceptibility splits. Feedrates and separation rates are comparable to those of conventional attraction separators. Although RMF attraction separators are now well advanced in development, RMF rotation separation is still in the early experimental stage. The exception to this is the dry particle rotation eddy current separator that offers eddy current separation of small non-ferrous metallic particles from about 2 mm down to about 100 microns. Wet small particle eddy current separation is also possible, but has not yet been developed to a practical stage.

Jan 1, 2000

By Yigit E, Royston D, Winborne DA

Semi-bulk concentrates of 45% zinc at 80% recovery have been produced from the McArthur River mineral deposit. Selective leaching of these concentrates to recover lead and a commercial grade zinc concentrate has the potential to increase significantly the recovery of zinc (as zinc concentrate) and lead (as lead metal) over conventional flotation methods producing lead and zinc concentrates.

Jan 1, 1986

By Hodkinson I, Teale GS

Mount Leyshon is an open cut-heap leaching operation that commenced production in early 1987. Open pit reserves are 6.3 m.t. grading 1.8 g/t Au and 4.8 g/t Ag and expected annual production is 68,000 oz. of gold. Gold mineralisation is hosted in breccias, porphyry plugs and basement rocks interpreted as the roots of a multi-phase Permian phreatomagmatic breccia complex. Mineralisation has the form of veins, cavity fillings and disseminations and is localised by late stage trachytic dikes and sills and dike-like bodies of milled breccia in the northwest corner of the complex. The sequence of mineralisation includes: I quartz-chalcopyrite-molybdenite stockwork veins and pyrite-gold veins with potassic alteration II quartz-chlorite-carbonate-basemetal sulphide-gold veins and cavity fillings with sericitic alteration III quartz-basemetal sulphide-bismuth-sulphide -electrum veins, veinlets and dissemin- ations with sericitic alteration. Mineralisation is interpreted to have formed at 500-300¦C from a predominantly magmatic hydrothermal system related to the porphyry intrusive bodies. Mount Leyshon is a phreatomagmatic breccia with a very different origin to the Kidston magmatic hydrothermal breccia. However the mineralisation style and origin is quite similar.

Jan 1, 1987

In sizing of wet coal by the horizontal vibrating screen, screen openings to be used is much restricted, because coal is sticky and its bulk density is little. The electrically heated screen and other various types of screen had been tried to screen raw coal and coal as raw materials at a few mm. However, they failed to realize satisfactory results. On the other hand, fine sizing of coal is requested by many fields. For example, raw coal is desired to be screened at the fine rate, before being fed to the coal preparation control system in order to transport undersizes as unprepared coal particles and to reduce load in coal preparation waste water treatment system.1) Coals fed to the fluidized bed boiler also should be sized at a few mm. Regardless of many requests on fine sizing of coal, it seems that there are many cases to omit the basic screening process, because the screening is very difficult on a industrial scale. Size control as pretreatment of coal as raw materials is presented as one of the basic screening processes. In 1979, Kinki Industrial Co., Ltd. and Nippon Steel Corporation jointly succeeded in developing the vertical centrifugal screen. Closed -circuit crushing system by the use of this screen has operated actually at N.S.C, Hirbhata .Works, and realized the anticipated result. Consequently, this system has established the position as the most basic technology in the coal preparation. 2), 3), 4) This system has been also introduced to Nakayama Steel Works, Ltd. in 1982. This system termed the CPC (Coal Preparation Control) Process has been operated smoothly in both N.S.C. and Nakayama. Reported herein is the practical application of the vertical centrifugal screen termed V3-Separator. (V3 means vertical, versatile and vibration.)

Jan 1, 1984

The relevant characteristic of the evolution of the Pacific continental margin of South America during the Mesozoic-Early Cenozoic has been tectonic segmentation. This has controlled suc-cesive episodes of sedimentary accumula-tion, extrusive and intrusive magmatism and deformation that ocurred at conver-vergent plate edges. During this inter-val, at least three main transverse boundaries played an important role conditioning the existence of paleo-segments of different longitudinal extent at various Periods. These probably correspond to deep-seated faults in the Huancabamba Deflection and at the Arica-Santa Cruz Line; the third boundary projects westward to the Chile Ridge. Tectonic activity appears to have been continous at the Huancabamba Deflection at least since the Triassic. The Arica-Santa Cruz Line was probably an active boundary during the Triassic and Cretaceous; the southernmost boundary may have started to be active at the end of the Jurassic. This tectonic activity has determined the subsidence - uplift and paleogeographic conditions of the paleosegments.

Jan 1, 1990

By B Arthur, K Sexsmith, D Hockley, S D

At the proposed Crandon Project, mill tailings would be depyritised for upland disposal. The resulting pyrite concentrate would be disposed of in the underground workings as a cement-amended paste backfill. In the long term, the underground workings would be flooded and the potential for the paste backfill to generate acid would be limited. However, while the mine is operational, there is potential for oxygen ingress to the backfill that may lead to sulfide mineral oxidation and acid generation. A series of humidity cell tests were completed to assess the potential for groundwater contamination. To assess effects of surface area on oxidation, the humidity cell tests were conducted on moulded cubes of paste backfill. The tests were terminated at different intervals, and the cubes were dissected and examined mineralogically. Various leach extraction procedures were also used to assess the progress of oxidation and secondary mineralisation within the paste backfill. The test results showed that: the cement amendment significantly contributes to acid neutralisation and results in a lag in excess of one year before the onset of acidic conditions (in comparison to less than three weeks for the pyrite concentrate); the depth of oxidation in the paste backfill is restricted to about 1 mm after 107 weeks of testing; and secondary minerals form a distinct ærindÆ at the surface of the paste backfill. The results indicate that acid generation in the backfilled stopes would be minimal. The importance of including the surface area effect in the testing (ie using moulded cubes) is clearly demonstrated.

Jan 1, 2003

By DAVID C LAURENCE

The richer, shallower sapphire deposits of the New England region of New South Wales which have been traditionally mined by the small miner are almost worked out. Larger mining and exploration companies are replacing the small miner and exploring for the primary source of sapphire or lower grade alluvial deposits.Although in recent years considerable exploration effort has been directed at locating the primary source, commercial exploitation of sapphire is still restricted to the working of alluvial deposits.If the Australian industry is to compete against Asian and African producers it must use cost effective exploration, mining, processing and marketing methods.

Jan 1, 1990

Blasting, particularly bench blasting, uses finite length cylinders of explosive close to two free faces. The rock to be blasted is usually intersected by a complex 3-D system of joints. To fully simulate a blast, a 3-D dynamic model is required. It is shown that the static stress distribution around a long cylinder can be reproduced by superposing the static stress distribution of a suitable chain of spheres. Thus, the dynamic results for individual spheres given by Favreau (1969) can now be substituted for the static results to give a dynamic model of the stress distribution around a long cylinder. Comparison of measured and computed waveforms show that the measured waveforms are much more attenuated and dispersed than expected. The consequences for explosive evaluation and design are Discussed.

Jan 1, 1990

Data logged on mineral beneficiation processes during normal operation are analysed using time series (correlation and spectral) methods to identify the dynamics of the processes for on-line computer control. Recursive least squares estimation techniques are used to identify parametric models for a cassiterite flotation circuit and a coal washery. Identification problems such as the determination of model order, process time delays and the 'contamination' of the data by process recycle streams (feedback) are discussed. Typical results are presented in which optimised models are identified from data logged during normal operation.

Jan 1, 1985

By Ho E

Analyses of several nickel mattes from around the world show a significant variation in their copper content. Typically, matte contains an alloy, heazlewoodite and a copper sulphide phase. The various commercial methods of processing these mattes are reviewed and some of the fundamental factors which determine the choice of leaching system are discussed. Electrochemical studies on pure heazlewoodite and millerite in sulphate and chloride media are compared which show that nickel sulphides react via a series of nickel deficient sulphides and exhibit passivation as nickel is removed. Differences in the electrochemical behaviour of nickel sulphides in chloride media are attributed to greater crystallinity of sulphur and less formation of'NiS2. The electrochemistry of mattes differs because of the presence of alloy and copper. Copper in the matte modifies the potential for alloy dissolution and the rate of anodic dissolution of nickel. At elevated temperatures, Cu(II) in solution exchanges with NiS and completes the leaching of nickel at relatively low potentials without significant oxidation of sulphur to sulphate. It is concluded that there are fundamental advantages to leaching nickel matte in chloride media using Cu(II)/Clz as the oxidant.

Jan 1, 1996

By Chenggang W, Junhua D

Fragmentation variation laws in loading and non-loading areas are obtained by cement block model blasting experiments under various stemming lengths. A reasonable ratio between loading length and stemming length is worked out according to minimum average fragment size. The present continuous loading structure, for its very long length to be stemmed, leads to insufficient fragmentation in the upper part of bench. So a new loading structure with bottom air cushion is put forward. The author analyzes blasting effects and processes of two loading structures' and proves that there exists a optimal length of air cushion.\

Jan 1, 1990

This paper briefly discusses the negotia- tion of the more important provisions in agree- ments for exploration and mining rights with Pacific countries. LAND RIGHTS Land rights are complicated and sometimes controversial in many of the Pacific countries. In some countries, a company will have to deal with land owners directly; in others, the government will act as intermediary. Inevit- ably, a company will have to deal with both. Mining companies need to be sensitive to the culture and particular interests of the land owners and of their history in defending their rights. The issues are too complicated to be dealt with here. Some mining companies have spent, and will continue to spend, considerable time trying to understand them. It will " require patience, perseverance, sensitivity and unflagging optimism. The better advised companies will ensure that their local repre- sentatives get to know the land owners, under- stand their concerns, and will pursue a policy of keeping them informed on a regular basis of all of the company's activities and proposed activities. Good community relations are the keystone for good mining operations in the Pacific. Most countries will require the submission of an environmental impact statement so that they will know in advance what effects a pro- posted mining operation are expected to have on the environment and how it is intended to deal with them. They will also want to approve the company's environmental reclamation and rehabilitation plan. Let's face facts right away - mining, by its very nature, is not going to improve the environment. There will be waste discharges, emissions and deposits. They will affect the land, air and water and hence human, marine and animal life and vegetation. There will be sounds and odours and the esthetics of mining operations, though perhaps pleasing to geolo- gists and mining engineers, will not please Others.

Jan 1, 1987

By Boyd G

This paper describes the planning, analysis, design and operational experience of highwall mining based on auger drilling techniques applied to thick coal seams exposed in an opencut highwall. Being the first time such technology has been used in Australia, a large commitment to technical design and logistics planning was given by Callide Coalfields Pty Ltd. This commitment included technical and operations management and supervision, mine services, and the retention of consultants to undertake geotechnical analysis, instrument preparation and instrument installation.

Jan 1, 1991

By J J. Campbell, G J. Wilkie

The ores of the Golden Mile exhibit considerable complexity. As a consequence, the operating company, Kalgoorlie Consolidated Gold Mines (KCGM), considered it important to develop a coherent database of information describing the nature of the many ore lodes in terms of (1) rock properties and mineralogical content, including relative proportions, grain size, associations and deportment of key elements between minerals, (2) the relative behaviour of consituent minerals in various stages of processing and (3) the nature of the final products and key intermediate streams. The paper describes a sequence of metallurgical tests covering comminution, flotation, gravity concentration, leaching and calcining, carried out on three lodes of the Golden Mile. Key samples generated by the testing were subjected to comprehensive size-by-elemental assaying and QEM*SEM mineralogical determinations of sulphide and precious metal associations. Significant differences between lodes were identified, and the impact of these differences on processing is discussed.

Jan 1, 1998

Daily geological mapping of the Panguna porphyry copper/gold system since mining began in 1971 has provided a good basis for resource estimation and mine planning as the mine and estimation methods have advanced. Geology defined during evaluation and early mining has been substantiated and many smaller features have been better defined or identified. Breccias, pebble dykes, major structures and location of lithology contacts important to short term planning and long term pit slope stability have been defined. Correlation of copper and gold with breccia zones is quite striking and was not fully appre- ciated at the end of evaluation. Pit mapping geology, and diamond drill geology and assays, are now routinely added to a Geological Data base on computer, which forms the major geological data base for modelling the deposit. Geology from diamond drill logging, updated by pit mapping, and assays from diamond drilling updated by blast hole assays have been incorporated in a 45 bench deep 486 000 block computer based block model which forms the basis for long and short term planning. The introduction of pre-concentration scre- ening, based on the distribution of mineralisat- ion and fracturing, puts more emphasis on the definition of grade distribution at low concent- ration and on structures in the rock. Geostatistics is now used for resource estimation and has produced acceptable estim- ates. but these need to be refined, particularly in peripheral, low grade areas of the deposit.

Jan 1, 1987