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The ASC has a dual role of business facilitator and law enforcer. Only certain types of expert report are of interest to the ASC. The powers of the old Companies Code and the Corporations law are compared. NCSC Policy Release 149 was dependent on the prescriptive powers given to the NCSC in the Companies Code. The Corporations Law does not give the ASC power to prescribe the contents of expert reports. The requirement now is for all necessary information. Research evidence is that some investors want simpler prospectuses while others need more detail. The ASC's examination of expert reports is after registration of primary documents. This leads to a necessity for experts to maintain adequate records.

Jan 1, 1994

The words ""Uncertainty"" and ""Risk"" pervade every discussion about mining exploration and investment. Perhaps these terms are subjectively understood by industry professionals, but objective portrayal of these concepts outside the industry is a woefully undeveloped science. This paper addresses current industry understanding and practice regarding quantitative risk assessment techniques, and provides examples of the application of three of these techniques. Probabilistic techniques for financial risk assessment are valuable adjuncts to conventional financial analysis, and address a range of issues not assessable by any other means. The value of whole-of-project probabilistic risk assessment is currently debatable for decision-making purposes, but is seen as important as a mechanism to focus attention to the critical issues that ultimately impact on project success. The dissection of project capital into risk and non-risk components provides valuable insights into risk characteristics not readily quantifiable in any other way. This technique also provides a framework for more objective ""what if?"" scenario evaluation and for the capital structure of resource projects. Finally, mechanisms for the valuation of undeveloped reserves are examined, and guidelines suggested. The importance of reliability in production cost estimates is highlighted and the impact of early development on reserve valuations is discussed. The importance of economics throughout all stages of the evaluation process is fundamental.

Jan 1, 1994

By J. S. Stacbulak

"The main ventilation design features adopted at Inco to safeguard personnel against the effects of fires are described in this paper. Measures taken to prevent and detect fires due to spontaneous combustion, and fires involving conveyor belts, are described in detail.IntroductionConsidering the over-all picture of present-day mining operations, the expenditure required to provide a proper system of mine ventilation and fife control should be regarded as a sound investment that will pay back in increased mining efficiency, improved safety, health, and morale of the miners.Mine ventilation control and mine fife detection and fighting are inseparable, because a ventilation system can spread deadly products of combustion just as efficiently as it does life-sustaining oxygen. Therefore, the possibility of a mine fife occurring is of particular concern.The flirt objective is to prevent a fife. The second objective is to design the ventilation system so that a positive fresh air supply can be ensured on each main level regardless of the location of the fife. The third objective is to be able to detect the fife at an early stage and to extinguish it before it can develop into a major fife.Accordingly, at Inco, very extensive measures are taken to prevent fires and to locate, isolate and extinguish them rapidly. To obtain an early warning, it is not sufficient to know that a fife has started, but it is also necessary to know where the fife is burning."

Jan 1, 1994

By L. A. Panek

A new pillar strength formula is presented, incorporating a function P of size and shape, which takes into account the size-shape interaction effect as well as the enhanced strength exhibited by wide pillars. Existing pillar formulas, lacking these capabilities, are not suitable for extrapolating small-specimen test results to mine-pillar sizes and shapes. Interpreting compressive-strength test results as function of P clearly reveals wide-pillar behavior in much old test data. Model relationships are discussed, along with their scaling implications.

Jan 1, 1994

The AusIMM came into being to foster the spread of professional knowledge within its client industry. It has evolved along with the Australian mining industry for more than a century. If the AusIMM is to become the world's premier mining professional body (whether by design, or by default), then draw up a strategic plan to get there. Define your strengths and market them Define the priority areas for professional competence which we most need, Target the groups within Australia who can produce the people, Create an industry peer group to speed technology transfer.

Jan 1, 1994

The undeniable fact of life in the next 25 years will be the increasing difficulty of the physical conditions of Australian orebodies facing future miners. We are all familiar with names such as the 3000 orebody at Mt Isa, Hilton, Century, Macarthur River, Cannington, and Ernest Henry. These projects represent a significant. proportion of the planned underground mine development in Australia. Moreover, many of these new orebodies are an order of magnitude more difficult to mine and process than their predecessors. Extraction will be from deeper and potentially more hazardous working environments. Occupational health and safety considerations will place unprecedented demands upon mine operators and technology providers of the future.

Jan 1, 1994

By P. Favreau

This paper describes the progress accomplished at the Noranda Technology Centre in the field of three-dimensional computer-aided underground blast design. Traditional methods of laying out underground blasts are reviewed, and the new computer-aided approach is described. Time savings achieved through the use of BLASTCAD can be advantageously used to better engineer blasts, using models and blast vibration analysis. Future work involving the attachment of blast models directly to the system is also addressed.

Feb 1, 1993

By P. R. Ineson, D. W. James

For a criterion to be useful it must either demonstrate directly the role of exhalative processes in the formation of a deposit or describe a unique attribute of exhalative deposits. Few of those employed in previous investigations entirely satisfy either condition. The limitations of three of the most frequently employed criteria are illustrated by studies of the geology of the King Island Scheelite deposit in Tasmania.

Jan 12, 1993

By Li Shibo, C. Halls

The compositions of olivine, pyroxene and chromite from the Proterozoic ultramafic complex are analagous to those of cumulate ultramafic rocks of tholeiitic origin, suggesting that the parent magma may have been tholeiitic rather than komatiitic. The complex contains economically significant Ni-Cu sulphide mineralisation. The high sulphide/silicate ratio is best explained in terms of the segregation of sulphides from a large volume of magma, of which all but the ultramafic cumulate fraction has since been eroded. Platinum-group minerals that have been identified include sperrylite, moncheite, native platinum, froodite, merenskyite, michenerite and Pd-rich pentlandite lamellae exsolved from pyrrhotite. They are characteristically found in close association with chalcopyrite, either along the contacts between hydrosilicate and sulphide grains or in cracks within pentlandite and chalcopyrite, which may also be intergrown with galena. Crystallisation from a Cu-rich residual magmatic liquid also enriched in Pt, Pd, As, Sb, Bi, Te, Zn and Pb is postulated.

Jan 12, 1993

By G. H. Blackwell

Sequences in open pit mining must be planned and regularly revised to incorporate changes in the variables which affect profitability. Interactive computer planning with colour graphic facilities is an effective tool for this purpose in the short and medium term. An interactive computer planning system for medium-size, low grade porphyry copper-molybdenum open pits is described. The planning system proved especially valuable during the critical stages of pushback mining when deep, inner pit ore was nearly depleted and the erratic grades of the next pushback provided ore and marginal material at a time of depressed metal prices.

Jan 8, 1993

By P. Rama Krishna, B. Narasimha Rao, P. Ali i Peera

Induced polarisation (IP) surveys are commonly used in uranium exploration programmes in India. The IP method is effective in detecting the disseminated metallic sulphides that are often associated with uranium minerals. However, conductive and polarisable host rock or overburden often introduces inductive or electromagnetic (EM) coupling into time domain IP measurements. This makes it difficult to distinguish between responses due to such coupling and those that might indicate economic mineralisation. Attempts must be made to remove the EM effects before the IP technique is used in drilling programmes. Transient decay curves which were recorded during field surveys at Pisnari were factorised using the Marquardt algorithm. Dispersion plots of the amplitudes and relaxation times of the composite exponential function enable a clear distinction to be made between the effects of EM coupling and those of mineralisation.

Jan 4, 1993

By R. Trueman, D. B. Tyler

Numerical modelling was used to determine the magnitude and direction of stresses around drives both adjacent to and distant from open stopes in the South Crofty tin mine. Modelling predicted that drives near the stopes are situated in a stress-relaxed zone. The peripheries of drives that are sited in solid rock away from the influence of stoping are in compression. Key-block modelling was used to determine the typical geometries of critical blocks and distinct element modelling was used to determine block stability. The conclusions derived from modelling fitted the observational data. This indicated that key-block theory is a valid tool for analysing the stability of roadways in the South Crofty mine. The support requirements for drives located next to stoped-out areas were formulated using a risk analysis approach to key-block formation. The results were compared with support guidelines derived using empirical design methods. Good agreement was obtained for the roofs of the drives but not for the sidewalls. The concept of a critical excavation width was formulated: once an excavation is larger than the critical size the length of rockbolts need not be increased as the excavtion dimensions increase. This may be the case in all rock mases.

Jan 4, 1993

By Tuncel M. Yegulalp, Selamet G. Ergelebi

A description is given of a method of analysing modern mining systems in terms of reliability and their effects on productivity. Non-exponential distributions, such as the Weibull and lognormal distributions, for failure and equipment repair times are also considered. The resulting non-homogeneous Markov process is solved by the method of stages. A longwall mining system is analysed as an example.

Jan 4, 1993

By T. J. White, R. A. Farnfield

Early computerised blast monitoring equipment consisted of a digital version of the existing analogue machines with, perhaps, a few enhancements. Many additional facilities have since been developed to enable the efficient collection of high quality data. These developments are examined with reference to digital sampling, triggering systems, the storage of complete recordings and signal processing. Recent advances have been made in the use of blast monitoring systems that comprise multiple blast monitoring locations with centralised control and data collection. Software has been developed to help record blast parameters and assess environmental effects. Computer databases have many advantages over their paper counterparts. Data can be easily retrieved and processed. The scaled distances used in the prediction and control of peak particle velocities can be calculated rapidly when the data are obtained directly from a database. Since the whole vibration signal can now be recorded, signal processing can be used to provide information such as signal length, dominant frequency and response spectra.

Jan 4, 1993

By T. T. Chen, J. E. Dutrizac, C. Canoo

The calcine consists principally of ZnO and ZnFe2O4, which occur as banded and porous grains, together with lesser amounts of Zn2SiO4, Zn-Fe-Pb silicate, sphalerite, quartz, PbSO4 and Fe2O3. Al is present in solid solution in most of the Fe-bearing phases and also as residual aluminosilicate minerals from the original concentrate. Si occurs mostly as Zn2SiO4, Zn-Fe-Pb silicate and as residual silicate minerals. As is commonly found in the ZnFe2O4, Fe2O3 and Zn-Fe-Pb silicate phases. The major As carrier may be calcium arsenate particles less than 1 micrometre in size which are dispersed throughout the calcine. The neutral leach residue consists mainly of ZnFe2O4 and precipitated masses of iron gel-silica gel. Lesser amounts of ZnO, Zn2SiO4, Zn-Fe-Pb silicate, PbSO4, sphalerite, Pb-K-jarosite and basic zinc sulphate are also present. Al occurs in minor concentrations in most of the Fe-bearing phases and in the Zn-Fe-Pb silicate. The residual aluminosilicates are also an important Al carrier. The major As carrier is the precipitated iron gel-silica gel phase, but some As is also present in the Zn-Fe-Pb silicate, ZnFe2O4 and Fe2O3 phases. Silicon is divided about equally between the iron gel-silica gel, Zn2SiO4, Zn-Fe-Pb silicate and residual silicate minerals. The weak acid leach residue is generally similar to the neutral leach residue except for its reduced content of ZnO and basic zinc sulphate.

Jan 4, 1993

By L. Wade, R. Wang, M. A. Horton

Laboratory methods to find the mechanical properties of rock are inherently biased towards stronger strata, which best survive the sample preparation process. Geophysical techniques are not subject to such bias and may be used to predict mechanical properties rapidly and cheaply. Samples (151) were obtained from a borehole that had been comprehensively geophysically logged. The mechanical properties of the samples were established in the laboratory and correlated with the geophysical responses of the strata from which they came. The results indicate that, for homogeneous strata at least, it is possible to predict the unconfined compressive strength reasonably well from sonic travel time measurements made in the field. Predictions of static Young's modulus may also be made from this data source, but with a lesser degree of confidence. A multivariate regression equation is presented which relates down-hole sonic travel time to unconfined compressive strength, depth and the frequency of fractures in the rock mass. This equation may offer potential for the prediction of the mechanical rock properties of fractured and layered strata.

Jan 4, 1993

By Thomas J. Keefe, O&apos

Results of metal electrodeposition experiments conducted at the University of Brussels and University of Missouri-Rolla over the past few years are reviewed in terms of the relationship and impact on industrial processes. Examples are cited from common electrowinning, electrorefining, or electroplating operations for copper, zinc, nickel, cobalt and silver. The following topics are considered : metallographic structure, crystallographic texture, surface morphology, nucleation and growth, additive monitoring and effects, high current density, substrate related properties including adhesion. The studies were conducted on a variety of scales from laboratory beaker tests to full sized pilot and industrial operating plants.

Jan 1, 1993

By H. Soto

As a follow-up to a laboratory study, a pilot scale column for the flotation of coarse particles was designed and then tested in two different applications. In the first test, the concentration of a coarse phosphate ore (normally beneficiated by skin flotation in spirals) was carried out in a flotation plant in Florida. In the second pilot test, the column was used as a scavenger cell in the coarse flotation section of a potash beneficiation plant in Saskatchewan, Canada. Particle size of the phosphate feed was of the order of 0.6-1.0 mm and the potash feed 1-3 mm. The column was 1 feet diameter and was fed at rates between 0.5 to 1.4 tph. The effect of operating variables such as air and water flow rates, bubble size, frother concentration, residence time, sparger, etc were evaluated. The most important factors in column performance were found to be bubble size, air flow rate and the thickness of the froth bed. Best results were obtained in the absence of a froth bed, with low air flow rates and with small bubbles. The paper presents comparative performance and discusses details of the column design. Phosphate recoveries in the column were better than 90% whereas the conventional skin flotation circuit normally yields about 60% recovery for a comparable concentrate grade. Potash recovery from the tailings of the conventional flotation circuit was as high as 42% recovery. Particle size distribution of the potash concentrate was coarse enough to meet requirements for potash fertilizer.

Jan 1, 1993

By S. G. Kumar

The performance of nickel based high temperature materials is directly related to their microstructure, which is controlled by the various processing steps. Nickel base alloys are melted and refined by a variety of processes that include Vacuum Induction Melting (VIM), Vacuum Arc Remelting (VAR) and Electroslag Remelting (ESR). The limitation of VIM is that the metallrefractory reactions lead to the disintegration of the crucible and hence contamination of the product due to macrosegregation. This macrosegregation is alleviated to some extent by controlling the solidification in VAR. The main attraction of ESR is its ability to produce a clean product by controlling the deleterious inclusions. In recent years Electron Beam Melting (EBM) is emerging as an alternative to the VIM, VAR and ESR. This paper reviews the current status of these processes and outlines the scope for further improvements in the processing technology.

Jan 1, 1993

By Terry J. Close

At the request of the Idaho Congressional Delegation, the U.S. Bureau of Mines Western Field Operations Center investigated the mineral resources of the 140,000-acre Red Mountain roadless area, located northeast of Lowman, in central Idaho. The area includes U.S. Forest Service Red Mountain RARE II area (4-063). The highly mineralized road less area is underlain mainly by granitic rocks which are transected by a northeast-trending fault system. Associated with the granitic rocks and fault system are gold and black sand mineral resources. At least 1,395 ounces of gold and 858 ounces of silver have been recovered from six lode and placer mines within the roadless area. A total of 525 tons of columbium-tantalum, 2,049 tons of euxenite, 83.5 tons of columbite, and 54,862 tons of ilmenite concentrates have been produced from a nearby black sand mineral placer. Mine workings and facilities in the roadless area consist of two dismantled mills, 15 open and caved underground excavations totaling about 2,900 ft of workings, seven large pits and quarries, over 166 smaller dozer-and hand-dug prospect pits and trenches, and in excess of 66 drill holes. The mineralized sites in the roadless area are covered by about 690 current (1992) mining claims. About 130 individuals are holding the claims. Also within the roadless area are four patented lode mining claims. Twenty-five of the 54 mineralized sites identified during the study of the roadless area have, or likely have, mineral resources. One has gold and three have black sand mineral resources that are marginal or subeconomic. There also are two hot springs with thermal water resources, some veins that could be sources of decorative quartz, and dimension stone which was quarried in the past and could be again.

Jan 1, 1993