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When Haematite Explorations Pty. Ltd. began prospecting for petroleum in 1960, there was only ill-defined geological evidence on the land bordering Bass Strait to support the belief that petroleum lay trapped in sedimentary formations beneath its shallow waters.A reconnaissance of the area, made in 1961 by the airborne magnetometer method, covered the waters and islands of the Strait and overlapped the Victorian and Tasmanian coasts. The survey indicated the presence of the Bass Basin (which is completely water-covered), assisted in outlining the Otway and Gippsland Basins, and showed that each basin contains sedimentary rocks over 10,000 ft thick. Information on the regional geology and minor volcanic activity was also obtained.Marine seismic surveys carried out from 1962 to 1965 defined these basins more accurately and showed the nature and structure of the thick sedimentary sections.Correlation of the seismic data with onshore wells identified the sediments as Tertiary and Mesozoic. Subdivisions of the former in all basins and the latter in the Otway Basin were made. These Tertiary and Mesozoic rocks are not seriously deformed and they have good prospects of containing petroleum.Possible structural and stratigraphic traps, recognized from the seismic record sections by petroleum geologists, are being tested by offshore drilling which began in 1964.

Jan 1, 1966

By Y Peng, B Guo

In gold processing plants, the water from the cyanidation stages is treated to detoxify cyanide species and this recycle water becomes the main part of the process water. Despite the low concentration of free and weak acid dissociable (WAD) cyanides in process water, the recoveries of gold and silver is still affected during flotation, especially when gold and silver are associated with iron sulfide minerals. This is a case at the Hidden Valley (HV) Mine. In this study, the effect of free and WAD cyanides on gold and silver recoveries by flotation from the HV Mine was considered.WAD cyanide (WAD CN) was prepared by mixing sodium cyanide and copper sulfate at a cyanide to copper ratio of 3:1 dosed at different cyanide concentrations. It was found that both free and WAD CN depressed gold and silver and particularly iron sulfides in flotation. The depressed gold and silver recoveries were closely associated with the depressed recovery of iron sulfide minerals, suggesting that free and WAD CN may not depress the flotation of liberated gold and silver minerals significantly. It was also found that 10 ppm free cyanide completely depressed the flotation of iron sulfide minerals and WAD CN depression is probably through the WAD dissociation to free cyanide species (mainly aqueous HCN) during the grinding process, resulting from a decrease in pH. Thermodynamic calculation showed that 5.5 ppm free cyanide was released in the end of grinding at an initial WAD CN concentration of 50 ppm. This research provides a guideline to counteract the negative effect of WAD CN in the flotation of gold and silver minerals.CITATION:Guo, B, Peng, Y and Espinosa-Gomez, R, 2013. The effect of weak acid dissociable cyanide on gold and silver flotation in Hidden Valley Mine, in Proceedings World Gold 2013 , pp 341-346 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

The Development of a Non-Roasting Technology for Polymetallic Gold and Silver-Bearing Sulfide Concentrates Treatment

Sep 13, 2010

By K Tanguturi, B Belle, R Balusu

Management of high rates of goaf gas emissions between 4000 and 6000 L/s of methane gas in longwall panels is a challenging issue, particularly in start-up areas of the panels. There is a need for investigation of the effect of various goaf gas drainage concepts and techniques, and development of effective gas drainage strategies for management of high goaf gas emissions in start-up areas of the longwall panels. This paper presents the results of various computational fluid dynamics (CFD) simulations that were carried out to investigate the effect of different goaf gas drainage strategies and combinations for gas management in the start-up area of the longwall panels. Results indicated that the gas (methane) concentration in goaf holes on the tailgate (TG) side vary between 50 and 75 per cent under the simulated field conditions with flat coal seam gradients. The results also indicated that operation of more goaf holes for draining the goaf gas on the TG side results in high ingress of oxygen and further reduction in gas concentration in goaf gas drainage holes. The simulations also included scenarios with goaf gas drainage holes on the maingate (MG) side, TG cut-through seal and near the start-up area. This paper presents the results of various goaf gas drainage strategies and discusses the effect of various combinations in order to develop effective goaf gas drainage strategies for gas management in start-up areas of the longwall panels.CITATION:Tanguturi, K, Balusu, R and Belle, B, 2015. Development of goaf gas drainage strategies for start-up areas of highly gassy longwall panels, in Proceedings The Australian Mine Ventilation Conference, pp 251–258 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

This paper aims to address the issue of the public's image of the extractive minerals industry. What is it about the industry that incites such negative feelings and are they justified? Are we really the 'rapists of the land' that many would have us believe? Has the industry really not improved since the old gold boom days?   I believe that the fundamental cause for the public's view is lack of knowledge and understanding of the industry as a result of the dislocation of the end production from its source. There are few people who look at a house, car, record, toilet, tooth-brush, bottle of coke or pair of glasses and see the mine site that supplied the source material. But the mine site and its products should be inseparably linked. This is one area where we should be educating the public û it is all very well being anti-development but the population as a whole is not really prepared to live without its 'mineral'-derived necessities. It is very easy to say that we do not want minerals development in New Zealand but are we prepared to live with the consequences, ie go without its products? We have a duty as a global citizen to develop our own resources rather than expect Third World nations desperate for overseas investment, often with governments who are not prepared to constrain or control their development, to be exploited. New Zealand is not the only 'beautiful' place in the world and we should be aware of the impact that our demands for resources have on the countries who supply us. We have a duty to be a good global citizen.   So how does the industry improve its public image? The key here has to be to educate. This does not have to be high powered or expensive but can be as simple as getting a few local kids' hands dirty panning, and gaining some firsthand knowledge of the industry. The industry also needs to be more pro-active in the public arena. Yes, the industry has skeletons, but the industry should be publicly displaying them û admit that things have gone wrong but let's do it ourselves and not leave it up to the environmental groups to accuse, point the finger and put the industry under public scrutiny. The industry should also be publicising its successes, inviting the local press, councils, etc to view the latest area rehabilitated. But more than anything else we must tell the public what the minerals industry means to New Zealand. Can they really live without us?

Jan 1, 1991

By R Munoz, R González, J Vallejos, A Delonca

In panel caving in underground mines, it is essential to characterise and monitor the stress and stability state of production level pillars to ensure the extraction of the mineralised ore column and the safety of workers. Pilar Norte is a sector in the El Teniente mine that forms a pillar between the undercut fronts of the adjacent Esmeralda and Reservas Norte sectors. It exists in a high-stress environment, which may induce damage to the rock mass production pillars. Generally, numerical models are calibrated using observed damage in galleries. This procedure does not discriminate between the structural condition and/or the blasting damage effects. This paper proposes a technique that uses borehole cameras to measure stress-induced damage. This has the advantage of being at the intact rock scale, meaning that the effect of geological structures is negligible and the blasting damage factor is eliminated. Comprehensive geotechnical characterisation and tomography monitoring has been undertaken at Pilar Norte to describe and determine the rock mass behaviour of the production pillars. By combining analytical, empirical and numerical models, a correlation between the measured overbreak recorded by the borehole cameras and the stress level of the pillar was developed. The methodology can be routinely applied to estimate the stress state in the production pillars.CITATION:González, R, Munoz, R, Vallejos, J and Delonca, A, 2016. Characterisation and monitoring of the stress state of production pillars at El Teniente Mine, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 197–202 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

This paper presents a resume of the likely profitable mining areas in New Zealand. It covers the main 'minerals' û gold, coal, oil and gas, ironsands, silica sands, clays, lump silica, perlite, sulphur and limestone. The potential mining projects are depicted on a map of New Zealand together with the associated works involved in hydro-electric and geothermal power development requirement for industries such as aluminium, nickel ferro-silicon or silicon carbide production. The political need for mining development to relieve unemployment and reverse emigration is stressed. A case is made for exploration and development assistance by government in labour re-training, energy supply and transportation, if the tremendous losses through lack of use of human and industrial resources are to be rapidly reduced. These losses are currently estimated at $10 000 000 000 per year. The need for protection of the sanctity of contract and security of tenure of all mining operations is touched on briefly as is the need for a reasonably balanced view on conservation. However, as both of these are more properly covered in papers on the legal and environmental aspects of the mining climate, they are presented here only as they affect the economy of the mining operation. Finally, there is a brief comment on the mining climate in New Zealand relative to Australia and South Pacific mining operations.

Jan 1, 1990

For tax purposes a mining company is a New Zealand company whose principal source of income is from the business of mining, or exploring for certain specified minerals in New Zealand. New Zealand tax law distinguishes between a non-resident mining operator and a mining company, with the only major difference in tax treatment being the corporate tax rates. New Zealand mining companies are taxed at 28 per cent, whereas non-resident mining operators are taxed at 33 per cent of taxable income. These provisions also apply to the petroleum mining industry. Individuals who carry on the business of mining are also specifically defined in the Act. They are termed as 'resident mining operators'. Non-resident mining operators are non-residents of New Zealand who carry on mining ventures as a business in New Zealand. Mining ventures are defined as the exploring, searching and mining of specified minerals, including development work carried out for profits. Similar provisions apply to the petroleum mining sector. Specified minerals are defined in the Income Tax Act 1976 ('the Act') and while no useful purpose is obtained by listing them in the paper, they include a larger number of industrial and commercial minerals. The Minister of Finance is also empowered to add to the list by publishing his determination in the Gazette.

Jan 1, 1988

By D Cotnoir, Q Liu, D Richard, M Ourriban

The difficulty in fine particle flotation has been attributed, among other things, to a low bubble-particle collision efficiency. Many technologies have been developed which aim at increasing bubble-particle collision efficiency, either by generating micro bubbles or by enlarging particle sizes. However, commercial applications of these technologies are limited. Over the last five years COREM has been actively testing fine particle froth flotation technologies with the objective of commercialisation. Several fine particle flotation technologies, such as dissolved air flotation, electro-flotation, floc flotation, selective flocculation-flotation and carrier flotation, were tested on both single minerals and ore samples in order to identify the reasons that prevented these technologies from being used on a commercial scale. It was found that the two most noticeable factors that prevented the successful application of these technologies were: Mechanical entrainment of fine gangue minerals. This was a general problem in fine particle flotation, but was aggravated by these technologies that either generated micro bubbles or enlarged the sizes of hydrophobic particles. Oxidation of (sulfide) minerals that resulted in hydrophilic oxidation product coatings. The oxidised fine particles could not be recovered by these fine particle flotation technologies effectively. Solutions to the two problems, ie gangue entrainment and fine particle oxidation, were proposed and tested. It seems that polymeric depressants with both depression and flocculation functions could significantly reduce gangue entrainment, and hydrophilic surfaces of oxidised fine particles could be modified by high intensity conditioning or controlled sulfidisation, thus increasing the recoveries of fine valuable minerals. The improved fine valuable particle flotation and reduced fine gangue entrainment along with fine particle flotation technologies resulted in much improved flotation separation of fine particles.

Jan 1, 2005

A mathematical model for spontaneous combustion of coal with moisture included is presented in this paper. The one-dimensional unsteady state model consists of conservation equations for oxygen, water vapour and inherent moisture of coal and energy for both gaseous and solid phases. A first order Arrhenius reaction rate for oxidation under both pore diffusion and chemically controlled reaction regime is considered. The rate of evaporation or condensation is also considered as a function of temperature of coal, water content of coal and gas streams. The equation of the model is solved numerically by the finite difference technique. Influences of different parameters on the process of spontaneous combustion can be examined by using this model. Also the model can be used to simulate full-scale storage conditions.

Jan 1, 2005

Interest in those physical properties of minerals which might be used to good effect in prospecting is not new. Early in the nineteenth century attempts were made in th'e Cornish mines to measure the natural electric potentials set up by chemical changes proceeding in the lodes. The distortion of the earth's magnetic field by bodies of strongly magnetic iron ore received early recognition in Sweden. Treasure-finders, working on the principle of electrical induction, appear to have been invented about eighty years ago, though were probably not then applied to mineral exploration. By the end of the nineteenth century Eotvos, a Hungarian physicist, had constructed a highly sensitive type of torsion balance capable of measuring the minute distortions in the earth's field of gravitation resulting from variations in the density of the materials composing the crust. During the first decade of this century he demonstrated its value in tracing rock-salt deposits in virtue of their low density compared with the surrounding rocks. Geophysical prospecting began to be recognised as having a very definite value and its development gathered momentum. Its great expansion took place after the 1914-18 war, when its value in oil exploration was amply demonstrated, and this expansion has continued to the present time and shows no signs of abating.Divisions of Applied Geophysics.The four main divisions of applied geophysics are electrical, magnetic gravitational and seismic. With the importance of ores of radio-active metals, one might add to these a radio-active division. The first two are more important to the field of mining, but techniques based on gravitational attraction have their uses in particular cases. Seismic methods are not generally suited to the exploration of metallic ores, but have proved of enormous value in the search for petroleum. With vast quantities of oil as the prize, more money has been lavished on the deve10pment and practice of these methods than on all the others put together.Geophysical Prospecting Methods.Geophysical prospecting methods may be used to detect a mineral deposit directly in virtue of differences in the intensity of some physical attribute common to it and the enclosing country rock. Examples of this are the detection of rock-salt by gravity measurements, or of iron ore by magnetic methods. Of much wider application, however, is the indireot approach in which the aim is to determine, by geophysical means, the geological structures controlling the disposition of mineral deposits. These structures may be partly known from geological work, in which case geophysical methods are useful adjuncts. Where, because of an 'unbroken cover of overburden, no useful geological information presents itself, scout drilling or geophysical prospecting are the only alternatives. Overburden is here intended to mean any covering material not, involved in the structures controlling the mineral deposits. Prospecting for petroleum amounts to the detecting of favourable reservoir structures, and as the chief types of such are the same the world over...

Jan 1, 1950

By A Hekmat, M Fuentes, F Armijo, R Castro, F Rodriguez

Interpreting the behaviour of granular material and simulating the gravity flow are complex processes in cave mining methods. In this paper, a new Cellular Automata based code – FlowSim – is used as a flexible tool to simulate the gravity flow and subsidence zone in block caving mines. The simulation results of the gravity flow model in a real scaled mine as well as a scaled physical model are presented in this study. In this research, FlowSim was first calibrated at a mine, based on the information obtained from smart markers. These markers were located in five points of the second block of the Esmeralda sector, at the El Teniente copper mine, Codelco, Chile. The calibration was performed with the objective of reducing the discrepancy between the extraction zone defined by markers in the mine and FlowSim outputs. Regarding the mine data, FlowSim was calibrated with the minimum error of ten per cent between real and simulated results. Then, the calibrated FlowSim model was used to simulate the flow behaviour of a scaled physical model. This model was constructed in the Block Caving Laboratory of the University of Chile to scale down the same block of the Esmeralda sector with the scale of 1:200. The FlowSim outputs show that this software enables the simulation of the gravity flow of the scaled model with less than five per cent discrepancy in grade and dilution entry to the drawpoints. According to the obtained results, this paper recommends FlowSim as an appropriate tool which can improve the design of production level in block caving and can enhance the prediction of the subsidence zone and dilution entry.CITATION:Castro, R, Hekmat, A, Fuentes, M, Armijo, F and Rodriguez, F, 2016. FlowSim – a versatile flow simulation tool to quantify extraction and design alternatives for block caving, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 645–652 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By M Flis

The Razorback Iron Ore Project is a high tonnage, low-grade magnetite deposit that defines a new iron ore district in South Australia. Known since the 1960s, the deposit has come into its own as the iron hungry world demands not only larger tonnages, but higher grade and cleaner magnetite concentrate ores that counterbalance the increasingly dirty haematite ores that are coming into production.Razorback is hosted by the Neoproterozoic Braemar Iron Formation, a tillitic unit that is part of the Adelaidean Geosyncline sedimentary sequence. At Razorback, this formation forms the southern limb of the Pualco Syncline, dipping at 42° to the north and outcropping along a prominent ridge. The formation consists of a series of alternating bedded tillitic and interbedded magnetite units that represent cycles of glacial advances and retreats. Seven cycles, resulting in seven stratigraphic members, are recognised. Members B, D, and G are the thickest, at 30 - 70 m each, and are the target of current investigations. While the bedded magnetite has the highest iron content, typically 35 per cent Fe, the tillitic unit, at typically 26 per cent Fe, has similar iron content in the ground mass but is diluted by the inclusion of iron-poor granite and metasedimentary dropstones. The mineralisation forms a simple dipping tabular body with only minor faulting, folding and intrusives. Grades, thickness, dip, and outcropping geometry remain very consistent over kilometres of strike, presenting an excellent mining proposition.Razorback differentiates itself from other Australian magnetite projects in a number of important ways. It is not a banded iron formation (BIF); it will have low crushing and grinding costs; and it is located in an infrastructure-rich area close to open-access, high capacity rail, to a selection of ports and to gas, electricity, labour and engineering services. Royal Resources has announced an Inferred resource of 277 Mt @ 25.9 per cent Fe. The company is targeting a resource of 500 - 1000 Mt to support a 10 Mt per year concentrate production. Davis Tube Recovery work shows that the ore is capable of producing a concentrate of over 68 per cent Fe with very low deleterious elements. Metallurgical testing confi rms the ore is soft, and with near-zero initial stripping ratio the project will have a low opex. With access to existing critical infrastructure, capex will also be low, ensuring Razorback will be a highly competitive iron producer in this emergent mining district.

Jul 11, 2011

Jan 1, 2004

By F van de Venter, J Monama, T Kale

For a multitude of years fine iron ore, -1 mm, across the world has been deposited as discard material in tailings facilities. This contributes to environmental problems, decreases plant yield and increases the cost of processing. Fine iron ore recovery processes are often deemed unfeasible or uneconomical, due to the complexity of the reclamation thereof in comparison with high-grade ores. However, recent advances in the recovery of fine iron ore using the Optima Classifier® has shown great promise. The Optima Classifier® is a new hindered settling separator that makes use of an upward current of water for density separation. It’s unique design combines three different separating zones for increased efficiency and recovery. In this study the potential of the Optima Classifier® to produce a +63 per cent Fe concentrate from -1 mm feed material was evaluated from a standalone and process perspective. It was found that a +63 per cent Fe product can be produced from a single stage, using the Optima Classifier®. Fine iron ore feed with an average head grade of 50 per cent Fe was upgraded to average concentrate grades of 63.2 per cent Fe. Displaying upgrade ratios of up to 1.26 in a single stage. A three-stage, rougher, cleaner and scavenger system did however show the best performance with recoveries of up to 70 per cent, yielding 56 per cent of a 63 per cent Fe product. Furthermore, the dewatering of the product and tailings was evaluated using the UltraG ultra-fine dewatering screen ensuring dry, stackable material. The tailings could be used in codisposal, while loads on thickeners and filter presses are significantly reduced. The high throughput of the Optima Classifier® ensures a small plant footprint, minimal civil and structural requirements and low operating utility consumption such as electricity, minimising the carbon footprint of a fines beneficiation plant. The Optima Classifier® in combination with the UltraG dewatering technology has provided a platform for economical recovery of fine iron ore, both current arising and historical. Providing opportunity to lower plant operating costs, reduce environmental liability of tailings facilities and increasing immediate process water recovery

Sep 18, 2023

Results of blasting trials conducted at Gregory Mine, a large open cut coal mine situated in the Bowen Basin, show that fragmentation was improved or equalled whilst reducing the amount of explosives previously required. This was achieved by a system of deck loading whereby two or more explosive charges, separated by air gaps, were positioned in the blast hole, thereby extending the effective explosive column whilst minimizing the total explosives required. In the three trials to date, a saving of approximately 213 kg of ANFO per blast hole was achieved. This represented an approximate 20% reduc- tion in ANFO requirements.

Jan 1, 1989

Any hypothesis for the origin of the Otago gold-quartz lodes must account for the following observations. 1. Southeast of Glenorchy, where the schists hosting the lodes are comparatively unaffected by Neogene Alpine Fault deformation, the dominant strike of the vein systems is NW-SE, parallel to the axis of greatest post-metamorphic uplift in the Otago Schist belt (Paterson, 1986). 2. The lodes are fault-hosted, with some developed along steep, low-displacement normal faults (eg Barewood, Bendigo, Nenthorn), implying NE-SW extension, and some developed along low-angle thrusts (eg Macraes) implying, in apparent contradiction, NE-SW contraction (Teagle et al, 1990). 3. The mineralising fluid was of metamorphic origin (McKeag and Craw, 1989), but while some of the lodes developed in a mesothermal environment at considerable depth (eg ~10 km for Macraes), others appear to have formed at very shallow depth (eg <1 km for Nenthorn) (Craw and Norris, 1988). 4. The timing of the mineralisation is generally poorly constrained but postdates the main Rangitata schist metamorphism. It probably initiated during early Cretaceous exhumation and unroofing of the schist belt (140 - 120 Ma?) and may have continued well into the Tertiary (Craw, 1989). Estimates for the relative ages of the different lodes are largely speculative but, based on pressure estimates from fluid inclusion studies, Macraes likely represents the deepest and oldest lode system while Nenthorn (just 12 km to the southwest) is perhaps the shallowest and youngest (Craw and Norris, 1988).

Jan 1, 1992

By Davies S. G, Mackey L. C

The oxidation of iron and nickel sulphide concentrates, and the dominant sulphide minerals which comprise them, has been studied under ignition conditions using thermogravimetry (fG). The concentrates were derived from various minesites and they showed differing tendencies to ignite. Ignition temperatures ranged from 416 to 488°C and the extents of reaction, measured at 500°C, varied from 64 to 88 percent. The reactivity of the least reactivematerial was improved significantly by grinding. Particles <63/lm showed 85 percent oxidation compared with 55 - 65 percent for particles >63/lm.Examination of the individual sulphide minerals revealed that these materials also have significantly different degrees ofreactivity and are subject to particle size effects. For particles <45/lm, the ignition temperatures were as follows:ò pyrite and violarite 380 - 385°C; pentlandite 425 - 430°C; and pyrrhotite 470 - 475°;ò for particles >90 /lm, the ignition values were: pyrite 395 - 400°C;ò violarite 430 - 435°C; pyrrhotite 540 - 545°C; and pentlandite 560 - 565°C.Using the data on the individual minerals it was possible to rationalise the differing degrees of reactivity of the concentrates. The role of the most reactive constituent in initiating the ignition reaction has also been discussed.Finally, the results of this work were found to compare. favourably with the behaviour ofthe concentrates in industrial and pilot-scale flash smelters.

Jan 1, 1989

CrusherMapperTM - A New Tool for Crusher Condition Monitoring The efficiency of mineral processing plants is entirely dependent on the availability of the plant equipment critical path. This typically concerns comminution circuits consisting of primary crushers and primary grinding mills. Crusher and mill availability are determined by the frequency and duration of maintenance shutdowns, which are primarily driven by the need for replacement of sacrificial liners. The change of crusher and mill liner shape over respective life cycles also strongly affects plant efficiency. It is therefore highly desirable to accurately monitor the condition of mills and crushers in order to optimise plant efficiency through maximised availability and targeted liner shape. Traditional comminution liner and other production parameter condition monitoring has been attempted through ineffective methods which prevent satisfactory management of crusher and mill maintenance and reduce operational control. This situation has recently dramatically improved for grinding mills through the development and commercial deployment of MillMapperÖ, a technology based on three-dimensional laser scanning data and dedicated software (Franke, Lichti and Stewart, 2006; Franke and Lichti, 2007; 2008; Franke, 2008; Franke, Redman, Johnson and Michalek, 2009). At the time of writing in late 2009, MillMapperÖ is in successful use at a rate of approximately 170 surveys and associated reports per annum at processing plants in Australasia, South America, North America and Africa. This paper presents the introduction of CrusherMapperÖ, the MillMapperÖ equivalent for crushers. CrusherMapperÖ also utilises high density, high accuracy laser scanning data, and features dedicated algorithms for three-dimensional monitoring of wear on crusher concaves and mantles. This facilitates the detection of wear hot spots or zones or localised liner failures, and accurate forecasting of reline tonnages and dates. It also for the first time provides the means to establish optimised concave and mantle shapes in order to achieve production targets. In contrast to any other currently utilised condition monitoring method, CrusherMapperÖ data collection can occur remotely and does not require any shutdown or crusher isolation. This method therefore does not interrupt crusher production while at the same time eliminating any confined space risk normally associated with taking measurements inside the crusher cavity.

Sep 13, 2010

Early in 1940 the development and sampling programmes in hand on the North and British Sections of North Broken Hill Limited were such as to necessitate the drilling of a large number of drill holes ranging up to about thirty feet in length. On the British Section, one purpose was to test the existence, width, and value of narrow lodes believed, for geological reasons, to occur in the walls of the existing workings. Another object was to definitely disprove the existence of payable shoots of ore in certain largerhodonite and quartz-garnet ("garnet sandstone") pillars which had been formerly left as unpayable.On the North Section, the main purpose of the short holes was to delineate the ore-body boundaries by drilling laterally from drives in ore, and thus enable level layout to be planned in advance of sill stoping. It was also desired to test the walls of stopes in those portions of the mine where the economic limit of mining is not rendered obvious by a clear-cut wall, but should be determined by assay. In these latter cases it was hoped to eliminate "prospecting by stoping," a procedure by which any doubts as to the existence of further good ore behind the low-grade walls were settled by continuing to stope laterally until all chance of such an occurrence was removed.LONG HOLE ROCK DRILLINGFollowing an investigation of recorded instances of similar practice elsewhere it was decided to use the rock drill for a series of trial sample holes. A 3-in. drifter was used. This was selected from those in use underground, and was given a special overhaul; had a new machine been purchased, a 4-in. type would probably have been obtained as being more suited to the work. The rods were H in. hollow round steel with a type "1" Jackrod thread. Couplings were of chrome steel, and were H in. in diameter, and 2 in. long. Jackbits (type "1" thread) in sizes from 2 in. to 4 in., with 1-in. gauge changes, gave a range of nine bit sizes. They were resharpened by hot milling, and were not milled to a definite gauge size.After sharpening, bits were sent underground without sorting into sizes, the drillers selecting the next bit with callipers. In view of the small scale of operations, it was not considered worth while to adopt special measures, such as the cold grinding of bits, which might have given a better product. Later, however, new bits were used exclusively, the idea being to accumulate enough blunt Jackbits to warrant a thorough treatment of the sharpening...

Jan 1, 1941