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By Pitkajarvi J

Waste rock dilution causes mill feed grade to be lower than mineral resource grade. In nickel mines relative grade decrease (dilution) may be tens of per cent because of irregular ore boundaries and weak wall rocks. Five per cent dilution costs millions of dollars annually in medium size underground mine. In Outokumpu Group selective bench and fill stoping, cable bolting/shotcrete-skin support and fast ore boundary definition (OMS-logg in-hole logging or sludge sampling) are the key tools in dilution control. Commitment of the whole organisation to keep dilution low is also needed. Dilution sources and effects are discussed with examples of the dilution control methods applied in Outokumpu mines.

Jan 1, 1996

BECAUSE of the attention given in recent years to the flotation process, there is an extensive range of equipment available to any staff detailed for: the design of a flotation mill. This statement applies not only to the flotation machines, but also to equipment for crushing and grinding, elevating the pulp, dehydrating of concentrates, and the methods of driving the various equipment.Distributed through the Proceedings and Transactions of various metallurgical societies and journals there are many excellent descriptions of flotation mills, their equipment and performance.Whilst these articles describe-in many cases in detail-the equipment in the mills to which they refer, the reasons which govern the choice of each particular equipment are not usually given.

Jan 1, 1929

By Hunter TC

Metals Refining Operations Pty. Ltd. (NMO), PNG's only gold and silver refinery is operated by Golden West Refining Corporation Ltd (GWR), a member of the Rothschilds group and has a strong PNG ownership link through statutory shareholders. Located in Waigani, MRO has been successful in substantially increasing production through toll refining for Porgera, Misima, Tolukuma, Wapolu and, more recently, at Lihir as well as treatment of alluvial gold from smaller operations. This increased throughput has resulted in the need to constantly upgrade equipment, techniques and practices, particularly to continue quality improvements and meet market demands. The evolution of these changes are documented and discussed and the probable future development plans are detailed.

Jan 1, 1997

Ore reserve estimates form a basis for strategic mine planning at Argyle Diamonds open pit and alluvial operations. Most ore reserve statements are mainly concerned with resource tonnage and grade. Because diamond deposits are low grade, high value resources, diamond quality ($/carat) is also an important parameter. Relatively large variations in quality and/or grade can occur. These variations must be taken into account before the resource potential can be fully assessed. Computers (HP9000 and PC's) are utilised to compile resource inventories. Resource inventories are then ranked on an economic basis. This paper discusses the methods used to compile resource inventories and explains how these are then used to present ore reserve estimates in terms of resource potential.

Jan 1, 1990

By Brien R. J, O&apos

Faster and more efficient methods of producing and refining iron and steel are imposing severe conditions on the refractory materials used to contain these metals in the molten state. In order to provide refractory linings which will give the desired service life and maintain unit availability at an economical level, it is necessary to appreciate the aggressive environment in which the refractories operate and determine the reaction mechanisms by which the refractories are destroyed. Only by such studies can the most suitable refractory or refractory combination for a particular unit be selected. Examples of refractories selection and reaction mechanisms are discussed for blast furnaces, BOS vessels, AOD vessels, steel ladles, vacuum degassing units and continuous casting.

Jan 1, 1976

This paper describes several sources of external dilution affecting the stope walls during underground sub-level and bench stoping. Factors which control ground behaviour such as the geometry of the openings, the influence of geological discontinuities, stress re-distribution and blasting practices are discussed. Crown stope instability due to stress concentrations induced by changes in the excavation geometry, is discussed and the most efficient ways to sequence blasting within a stope are analysed. Effects of undercutting by blasting, blast damage in the near field and cut-off slot blast designs are analysed. The influence of dynamic loading on the exposed walls as well as the practice of blasting fill passes within stope crowns are discussed.

Jan 1, 1995

Pillar mining methods at the Pasminco Mining Broken Hill Operations are not new. Since mining commenced on Pasminco's leases at the turn of the century virtually every pillar extraction method tried throughout the world has been used. Much of the remaining mineral resource in the Pasminco Broken Hill leases is contained in pillars.However, due to the on-going need for mechanisation with bulk mining methods, and the very peculiar physical circumstances surrounding the formation of these pillars, their exploitation requires the development of a virtually new method based on excavation technology not previously used in the Australian mining industry. Trials of the method are to take place at the southern operations during 1991.

Jan 1, 1992

By Watsford R. M S, Hutton R

Following the delineation of significant extra ore reserves during 1990, the decision was made to expand production from 350,000 tonnes of run of mine ore per year to initially 600,000 tonnes increasing to 750,000 tonnes per year. The existing plant consists of a conventional three stage crushing plant followed by a heavy medium separation plant that produces a product prior to grinding. Grinding is conducted in three stages of ball mill in series. Alternatives examined for expanding production included: aò SAG mill - ball mill circuit replacing the secondary and tertiary stages of crushing, the heavy medium plant and the existing ball mills; and, upgrading of the existing circuit configuration.

Jan 1, 1991

By Pathan AG

This research work is concerned with an investigation of the fracture toughness of sandstone, siltstone, and coal. Tensile failure trades have been examined with three different specimen geonetries, i.e; rectangular bar, round bar (in three point bending), and diametral compression discs. The Stress intensity approach, and J-integral methods were used to evaluate fracture toughness. Results from both approaches are discussed. True crack length was determined after pre-cracking, using the compliance calibration technique. Fracture toughness results of sandstone are independent of crack length and the size of the specimen. Fracture toughness may hence be regarded as a material property for sandstone. In cxnntrast fracture toughness values for !siltstone and coal are dependent on crack Length.

Jan 1, 1986

By Koppe J. C

This study presents the procedure of mine modelling and reserve evaluation by means of statistics, computer interpolation methods and aerophotography interpretation. All data are from Carbonifera Treviso, Laura Muller City, Santa Catarina State, southernmost Brazil. From 22 bore holes and nine trenches opened in the coal seam outcrops, a data base including level references and thickness of all rock formations was created.Using this information, basic statistic analysis was carried out, showing that there are three different populations (three modal distribution). These populations defined three geological blocks with different characteristics of overburden removal and mining methodology. This mathematical approach for analysing geological data is very important for correct mine planning and complementary prospection.

Jan 1, 1993

Longwalling has reached a high standard both in Germany and Australia and most improvements should be expected in planning, monitoring and control. Double drum shearer have electric drives to 1000 kW and automatic height control is under development. Conveyor pans to 40mm thickness and chains to 2300 kN breaking load are in use with controls for pretension and load compensation under test.Trends in support are towards two leg shields with loads to 3850 kN per leg and electrohydraulic controls. Expert systems have been devised for planning and diagnosis tasks. With increases in technical standards, staff qualification standards at rising too, drawing attention to training requirements for modem personnel.

Jan 1, 1991

The paper reviews some characteristic features of feasibility studies and discusses the need for a wide scope at the pre-feasibility stage. The performance of recent Australian gold mines against the predictions contained in their respective feasibility studies is examined, resulting in a recommendation that feasibility studies need to be improved The advantages to be gained from having a feasibility study reviewed by an independent authority are discussed, and some of the reasons for using consultants are listed. Two examples of successful optimisations in the early stages of pre-development studies are described briefly and the benefits achieved are presented. The paper concludes that feasibility studies need improvement to enhance the confidence of investors in the mining industry.

Jan 1, 1991

Autogenous and Semi-Autogenous grinding has become an accepted method of reducing primary crusher product to micron sizes in a single or a two-stage grinding circuit. The elimination of secondary and tertiary crusher circuits and sometimes rod mills helps to lower overall operating costs and, in many instances, can make uneconomical projects viable. Selecting AG/SAG Mills have been rather a "hit and miss" affair over the years, but now with the many different types of tests available, accurate mill size predictions can be made, provided the test data is evaluated correctly. This paper endeavours to simplify the process of evaluating test data and sets down some guidelines for designers to follow when selecting AG/SAG Mills.

Jan 1, 1991

By Xizhen J

Point load testing for irregular rock specimens was studied to determine the relationship between tensile and compressive strengths, drill penetration rate and other rotary drilling parameters. The DH-l type point load tester was developed and more than 2 000 irregular specimens of over 60 kinds of rock from 16 mines and quarries were tested. The effects of size, shape and number of samples on the point load strength index were investigated, using regression analysis. Experiments were carried out to investigate the relationship between point load strength index and uniaxial compressive strength on 29 kinds of rock. The relationship between these values and the drill penetration rate for rotary and percussion drills is discussed.

Jan 1, 1986

By D S. Nicholson, T Marshall

Reserves of high-grade quartz gravel, lignite and timber suitable for the production of silicon metal and ferrosilicon on large scale occur within 40 miles of Bluff Harbour. Undeveloped hydroelectric power resources on the Clutha River are located within 50 miles of the most promising quartz gravel deposits while opencastable lignite, potentially suitable for electric power production, occurs in the same locality as the quartz gravels. A preliminary study of production economics indicates that the commercial feasibility of silicon/ferro-silicon production would depend mainly on the cost of electric power, total capital cost of plant, and the market value of the products. The proximity of Bluff Harbour is advantageous for the export of products.

Jan 1, 1971

Integrated geological interpretation of aerial photographs and Landsat images revealed that the gold mineralisation at Kyauk Pahto took place in a narrow zone of tension fractures within part of a previously unrecognised dextral wrench fault system. The latter is the wider manifestation of the well known Sagaing (right-lateral) strike-slip fault which has a length of more than 1 000 km, and it demarcates the boundary between the Indo-Australian and Asian plates. A subtle, right-handed kink affects the full width of the Sagaing Wrench-fault System at about the latitude of Kyauk pahto, and the extra dilatancy imposed on the tension fracture zone facilitated episodic ingress of mineralising hydrothermal fluids by "seismic pumping".

Jan 1, 1987

By Robbilliard K. R, Floyd J. M

The problems facing the metallurgical industry from the viewpoint of the range of unacceptable residues, flue dusts and slags currently produced from the electrolytic zinc process, electric arc furnace scrap treatment, and blast furnace operation in lead smelting and the Imperial Smelting Process (ISP) are addressed. The application of the Ausmelt technology is discussed and analysed for the pyrometallurgical treatment of zinc plant residues, steel plant flue dusts and lead blast furnace and ISP slags, as well as the more complex issue of smelter modernisation to avoid production of zinc plant residues in the future. Processes developed from pilot work are described and indications of the economics of treatment of electrolytic zinc plant neutral residue and jarosite are given.

Jan 1, 1993

It has been clearly demonstrated in both the first, as well as in the last world conflict, that a nation's ability to wage as well as win a war is primarily a function of its industrial, and particularly its steel making capacity, provided both are directed to munition production.The Axis gambled on their pre-war policy of bullets before butter giving them sufficient initial advantage to decide the issue before the Allies had time to gear their industries to war production.Fortunately for us, Hitler and his advisers apparently underestimated Russia's war potential, although they must have known that Russia was, in 1939, the third largest steel making country in the world, as shown by the following figures:

Jan 1, 1947

Discontinuities often have a very detrimental effect on the stability of mine highwall faces. The west wall of the Muja open cut is remarkable for the number and variety of discontinuity sets which occur over a relatively small area. To-date 14 separate structural domains have been identified over an area measuring approximately 560 m by 120 m.The structural domains have been grouped into four structural assemblages on the basis of their angular relationships to each other and to regional folding and faulting. The distribution of these structural assemblages appears to be erratic and no controlling factors have been identified to explain or predict them other than in the most generalised terms.

Jan 1, 1993

By Hendrix J. L, Nelson J. H

A model based on non-steady state has been developed for dissolution and diffusion in porous ore particles. Results from the particular model have been incorporated, as a rate term, into a global, heap-scale model based on a plug flow reactor at unsteady state. The global model can be used to consider leaching by aqueous-phase reagents in equilibrium with a gas- phase component, such as oxygen gas, as well as strictly aqueous-phase reagents, such as cyanide. The flexibility of the model even allows predic- tion of the outcomes of using reagent sideflow injection in large heaps. Data from column leaching tests are compared to the model, and their relationship is discussed.

Jan 1, 1991