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By Y. Shu, A. R. Laplante

"A laboratory Knelson Concentrator (LKC), 7.5 cm in diameter, was used to study the performance of a similar unit at plant scale, 76 cm in diameter, This paper reports on sampling and assaying procedures and problems, and discusses the performance of the plant unit.The sampling procedure was based on the extraction of large samples, 5-15 kg, and their complete processing with a LKC, to characterize size-by-size performance. The procedure yielded reliable estimates of overall gold assays, after blatant assaying errors were corrected. The plant centrifugal unit concentrate was sampled in situ, which yielded very erratic grades, with a large overall negative bias. Due to the very heterogeneous nature of the concentrate, which can be linked to flow patterns in the riffles of the unit, it is recommended that for future testwork, the concentrate be recovered separately, blended and then sampled.The plant centrifugal separator, when operated at a feed rate of 25 t/h, yielded total and free gold recoveries of 41 % and 62%, respectively. This is much lower than previously reported data, and suggest that at 25 t/h, the unit is overloaded. However, recovery did not decrease with time over a loading cycle of 2 hours, which suggests that present loading cycles, generally 1 hour, can be significantly increased. INTRODUCTIONThe study of gold gravity circuits is plagued with the statistical problem of determining the behaviour of particles occurring with a very low frequency. This problem becomes particularly acute with increasing particle size. For example, considering the average weight of a gold flake in the 840-1200 µm (20/28 mesh) to be about 5 mg (Banisi et al, 1991), a reasonably high grade feed of 10 git would require, for a relative error (standard deviation) of 10% on grade, 100 particles, that is 0.5 g of gold, or 50 kg of 840-1200 µm material (a Poisson distribution is assumed). Gy's formula, for the same data, yields a weight of 33 kg, with a shape factor of 0.1 and a size distribution factor of 0.5. Both results are comparable; to obtain the suggested weight of material, a stream containing 5% weight in the 840-1200 µm would require 1 tonne samples (of unsized material). The problem rapidly disappears with decreasing particle size. Still with Banisi et al's data, a gold flake in the 300-420 µm range averages 0.5 mg in weight; the same 10% error on grade corresponds to a weight of 5 kg. Gy's formula for the same size distribution and particle shape factors as above predicts a required mass of 1.4 kg. This would correspond to an unsized sample weight of 10 kg with 14% weight in the 300-420 µm, for example."

Jan 1, 1992

By J. Weinstein

New erosion, corrosion resistant metal, ceramic, and polymer composite technologies are being developed and marketed by Alanx Products L.P. for use in hydrocyclones, pumps, valves, and other applications in mining and minerals processing. This paper will present an overview of the ceramic/metal composite material system and properties developed, which include excellent erosion/ corrosion resistance. Wear data will be shown from a variety of laboratory tests in dry and wet conditions, in aqueous neutral and corrosive environments. Comparisons will be made with a variety of competitive materials currently used in the industries sited. Data will also be presented on field tests with pumps and hydrocyclones in hard rock mining and other abrasive/corrosive environments. Field data from North and South America, as well as Australian mining applications will be highlighted.

Jan 1, 1992

By David C. Scott

Between 1990 and 1991, the Bureau of Mines studied the mineral resources of the Kaibab National Forest to appraise the resources present and to determine the types of deposits, and their location. The study included a comprehensive literature search and a limited amount of field investigation of minerals and mining activity in and near the Forest. Small amounts of copper with lesser amounts of gold and silver have been produced from limestone-hosted, strata-bound deposits in the North Kaibab and Tusayan Ranger Districts. In addition to these small metallic deposits, volcanic cinders, pumice, flagstone, and sand and gravel have been quarried in the Chalendar and Williams Ranger Districts. At least ten uranium-mineralized breccia pipes have been identified in the Tusayan Ranger District, One of these, the Canyon pipe, contains a high-grade uranium ore body with associated silver, copper, lead, vanadium, and zinc. The mine permit for the Canyon pipe has been approved and the mine shaft head frame erected.

Jan 1, 1992

By E. J. Fuller, J. C. Monette

"Gold and silver cyanide complexes are presently desorbed from activated carbon by means of hot caustic elutions. These solutions may or may not contain additional sodium cyanide. There are several parameters which affect the rate of stripping. Some of these include pH, ionic strength, and temperature. (1) Stripping is conducted in recirculating (ZADRA) or once through (AARL) circuits.This paper describes the development of a new chemical eluant which significantly increases the rate of stripping of both gold and silver cyanide complexes from activated carbon. Two case history applications are also described.INTRODUCTIONAdditional cyanide is used in strip circuits in order to prevent its depletion which could lead to precipitation of base metals or lead to a change in the nature of the gold cyanide complex to one which does not strip as easily. (2)The strip circuits that are able to function efficiently without the use of cyanide are mostly those where the carbon is acid-cleaned after stripping.Once the minimum cyanide requirement to maintain the complexes in their proper state are fullfilled, any futher incremental increase in the level of cyanide will have no bearing on the rate of stripping. (3)DEVELOPMENT OF THE NEW ELUANTGeneral DiscussionVarious carboxylated materials were investigated including octanoic acid, polycarboxylic acid (various molecular weights), salicylic acid, polymaleic acid, acetic acid. benzoic acid, terephthalic acid, 4, bi-phenyl carboxylic acid, phosphoric acid and stearic acid.The initial work was done on medium activiiy, non acid-cleaned carbon. The silver to gold ratio on the carbon varied greatly.Two different blanks were used. The first was an elution using a 2% caustic and 0.4% cyanide solution while the second was a 2% caustic elution."

Jan 1, 1992

By Zhou Y, Karmis M, Haycocks C

Hazard analysis utilizes interaction mecha- nisms in combination with geologic, structural and mining conditions to delineate areas of potential damage in seams subject to interaction. Using characterizations of conditions peculiar to multi- seam mining, such as innerburden thickness, geol- ogy and structures, initial interaction contour maps can be constructed. Geologic hazard analysis is then carried out on roof, pillar and floor condi- tions in the affected seam using lower seam rock properties and layout geometries in the overlying seam. Either safety factors or damage ratings can then be developed representing degree of hazard in the lower seam. The final hazard map shows both the aerial extent and magnitude of potential dam- age from interaction.

Jan 1, 1992

Structural assemblages of veins, shear zones, and wallrock alteration zones arising from fault-valve action on steep reverse fault systems are reviewed using observations from mesothermal gold-quartz lodes in the Archean Yellowknife, Abitibi, and Yilgarn greenstone belts of Canada and Western Australia, the Cretaceous Mother Lode system in the Foothills Metamorphic Belt of the western Sierra Nevada, California and the Victorian goldfield hosted in a folded quartz-turbidite succession of Paleozoic age in Australia. Despite differences in the host rock assemblages, the deposits have many structural characteristics in common. These form a useful exploration guide when re-evaluating comparable, but poorly described gold-quartz vein systems such as those in the Reefton area of New Zealand.

Jan 1, 1992

By Batterham R. J

Some developments in copper, lead and zinc extractive metallurgy which have gone in to production or seem to be close to production scale are described with emphasis on why these innovations have been adopted.Mineral processing operations are now using: automated quantitative mineralogy,high capacity fine crushing equipment, ò fine grinding equipment, andcolumn cell flotation.Extractive metallurgy plants are using:ò bath smelting of concentrate at various scales, and ò flash converting of copper.Hydrometallurgical process developments are slower to make a commercial impact. Concerns about ability to handle impurities in the feed and production of saleable by-products are often major hurdles.An expression for the probability of implementing the first example of a new development is presented.

Jan 1, 1992

By B. A. Hillman

Silicon is the second most abundant element on earth, exceeded only by oxygen. Silicon dioxide forms a crystalline structure of repeating SiO2 molecules which form characteristically hard, durable crystals. As a result, crystalline silica is Ubiquitous in the crustal rocks, sediments and the mineral products derived from mining. An examination of the history of studies that identify silica as a human and animal carcinogen is presented in the context of the development of a public health policy in California. The implications for the cost of conducting aggregate and other mining operations in the state are discussed.

Jan 1, 1992

By Y. Guan

The dissolution behavior of copper and gold from their pure state and from Au/Cu alloys in cyanide solutions has been investigated using a rotating disc. Oxygen was used as an oxidant. The effect of the composition of the alloys, stirring speed of the disc, concentration of lixiviants and temperature on the overall dissolution kinetics has been studied. Gold/copper alloys of three compositions were used in this study. The atomic percent of gold in these alloys was 75, 50 and 25, respectively. The dissolution behavior of these three alloys was compared with that of pure gold and of copper under the same chemical conditions. In general, the dissolution of copper and gold from alloys is partially controlled by surface chemical reaction and largely by mass transfer.

Jan 1, 1992

Shear strength testing of rock discontinuity surfaces has been undertaken at a considerable number of open pit gold mining operations in Western Australia, as part of geotechnical studies of pit wall stability. These mining operations are located in geological settings that are typified by highly weathered and/or chemically altered rocks that contain significant structural fabric in which accurate and representative measurement of shear strength is essential.Little of the published rock discontinuity shear test work and back-analysis of failures has been conducted on weathered discontinuity surfaces, at low normal stress levels which are comparable to Western Australian conditions. Available shear strength data are reviewed and the following aspects of shear strength testing are considered:ò the need for shear strength test work and the amount of testing required;ò review of laboratory testing methods and the quality of the results; ò presentation of the test results;ò discussion of the shear strength failure criteria; ò interpretation of the test results;ò summary of test results for a variety of rock types, degree of weathering and discontinuity surface conditions;ò a review of laboratory and field shear strength data to illustrate the amount of variability that can occur; andò a monitoring strategy is proposed to manage the uncertainty associated with discontinuity shear strength.

Jan 1, 1992

Aurum Reef Resources is a provincially owned unlisted public company which holds a number of prospecting licences over Otago hard rock historically active minesites. The Bullendale Licence 31 1845 was applied for in 1985, granted 1991, including a DoC special condition allowing re-opening of the historic workings. The underground workings were commenced in 1862 and up to the mine's closure in 1906 some 40 000 ounces were produced at an average grade of 15.5 g Au/t. The purpose of the summer 1991 work programme was to enter the workings in an attempt to observe and sample the mullock between the lodes operated by the early miners. This objective was achieved on the third attempt. Samples were taken and subsequently a contract geologist resampled the workings and prepared a report indicating the Bullendale lode zone to be generally mineralised. Mullock interlode and schist foot-wall consistently returned assays over 0.5 g/t.

Jan 1, 1992

The first mining in Western Australia probably commenced some 40 000 years ago when Aborigines arrived and began quarrying stone for tools and weapons, and ochre for decoration. The earliest documented mining by European settlers took place in 1850 on a small lead vein in the bed of the Murchison River, reported by the explorer A C Gregory. However, it was the discovery of gold in the Kimberley region in 1885 that first drew wider attention to the State's mineral potential.

Jan 1, 1992

As the theme of this conference is æRediscover OtagoÆ it would seem appropriate to revisit the era of the gold rushes and subsequent mining industry which rapidly advanced settlement and economic prosperity for Otago, and left permanent reminders in the form of historic mining sites, many of which are now encompassed within the Otago Goldfields Park. I have been invited to give a paper at this conference on the subject of æHistoric Goldfields of Central OtagoÆ. As well as having a working involvement with historic areas through my employment with the Department of Conservation, I have a personal interest in the early goldmining industry of Central Otago as my grandfather came out from Scotland in the 1890s to help construct gold dredges on the Molyneux. My grandfather made headlines in the local paper in 1920 when he believed he saw a New Zealand otter at Island Block near Beaumont - but that's another conservation trail that I will not pursue any further today! For this paper I intend to divide my time to cover the following topics. Firstly, I would like to sketch a mental picture of the characteristics that make up the Central Otago landscape, and the general perception that early miners must have had when viewing this foreign land. Then I would like to briefly discuss the changes and the consequences in the early gold rush to Central. Finally, I would like+ to discuss the establishment of the Otago Goldfields Park, which I will illustrate with several slides.

Jan 1, 1992

By A. A. Levinson, M. B. Kirkley, J. J. Gurney

"Scientific advances in the past decade have greatly clarified our understanding of certain concepts relating to the age and origin of diamonds. These advances are largely the result of geochemical studies of mineral inclusions in diamonds, made possible by modem analytical techniques which enable the accurate chemical analysis of micro-sized particles of the order of 200 microns in maximum dimension. As a generalization, the inclusions indicate that most diamonds formed from either of two rock types, peridotite and eclogite. Peridotitic diamonds have yielded ages of 3300 million years, whereas eclogitic diamonds areyounger and rangein agefrom approximately 1000to 1600million years. Kimberlite and lamproite, the two rock types usually associated with diamonds, typically are much younger than the diamonds they contain. Thus, it is now dear that kimberlites and lamproites are only the transporting mechanisms which brought diamonds to the surface and are in no way related to the formation of most diamonds. The latest concepts which developed during the past decade regarding the sources of carbon for the crystallization of diamonds from peridotite and eclogite, and the mechanisms of kimberlite and lamproite emplacement, IntroductionThe decade of the 1980s has seen major advances in our understanding of the age, origin and emplacement of diamonds. The information presented herein is applicable to virtually all natural diamonds, excluding diamonds related to meteorite impacts. There is still some question, however, as to the applicability of the new information to industrial grade ""fibrous"" or ""coated"" diamonds, and to microdiamonds (< 1 mm). In addition to drawing upon our own experiences, this review is summarized from a voluminous literature and for those interested in the original sources we recommend the books by Mitchell and Bergman (1991), Ross (1989), Nixon (1987), Mitchell (1986), Glover and Harris (1984) and Dawson (1980), and the review articles by Mitchell (1991), Gurney (1989) and Meyer (1985).are also discussed."

Jan 1, 1992

By T F. Guerin

Explorationn and mining have shown to cause significant impacts to the terrestrial and marine environment. Current mining and exploration techniques are outlined in the light of their potential to impact upon the environment, ie negligibly, negatively or positively. A profile of five Australian-based gold producers is presented. The development of protocols to specifically deal with the highly regulated and ever changing, mining and environmental legislation. demonstrates mining companies can successfully opcrationalise the concept of sustainable development.

Jan 1, 1992

By Marius B. Wechsler

A mathematical analysis is developed for the determination of the cases when HP-piles might be replaced by precast concrete piles. The analysis focuses especially on the "integral abutment-bridges" which are used on large scale in the Great Plains of the United States of America, The theoretical considerations are illustrated by a numerical example.

Jan 1, 1992

By Robert B. Parsons

"The Department of Finance introduced draft amendments to the resource allowance regulations on July 23, 1992 that effectively nullify the decision in the Gulf Canada Limited case. Prior to the amendments it appeared that only ""directly"" related general and administrative, capital cost allowance and scientific research expenditures had to be deducted from resource profits. Now ancillary expenditures are required to be deducted. Consequently, the ability of taxpayers to claim the resource allowance is curtailed.IntroductionOn October 25, 1990 it was almost certain that taxable mines were going to get a break. The Federal Court-Trial Division had just decided in Gulf Canada Limited&apos;s favour to allow it to claim resource related tax benefits larger than what Revenue Canada evidently wished. Revenue Canada appealed first to the Federal Court of Appeal and then to the Supreme Court of Canada. On January 10, 1992 the Federal Court of Appeal agreed with the Federal Court decision and on July 2, 1992the Supreme Court declined to hear any further appeal. A mere three weeks later, on July 23, 1992, the Department of Finance issued draft ""clarifying"" measures to amend the calculation of the resource allowance. These measures effectively nullify the benefits that arose under the decisions of the Federal Court."

Jan 1, 1992

By Mats Keisu, Bengt Niklasson

The Sofia project has increased the level of knowledge and technique within tunnelling, drifting and contour blasting.

Jan 1, 1992

By Yael Miron

Two recent unplanned detonations occurred during blasting operations in sulfide-bearing ores in a Nevada gold mine. Other premature detonations have also reportedly occurred at other Nevada, California, and Arizona operations within the past few years, with increasing frequency. Unplanned or premature detonations can be extremely hazardous to life and can cause extensive property damage. A miner was injured in one of these occurrences. This report, by the U.S. Bureau of Mines, is intended to acquaint personnel involved in such mining activities with the basic causes for these accidents. These causes include the exothermic oxidation of pyrite (FeS2) and formation of ferrous sulfate (FeS04), the exothermic and energetic reaction of the ferrous sulfate with ammonium nitrate-fuel oil (ANFO)-based explosives, and the associated elevated temperatures that can set off detonators and explosives in the boreholes. Recommendations for safe operation by the Mine Safety and Health Administration, the Bureau, and the mine involved with the recent incidents include monitoring temperatures in the blast holes, analyzing for sulfate and ferrous ions, and limiting the time between loading and firing in accordance with conditions in the blast holes. Other procedures for safe operations should fit specific conditions in, the mines.

Jan 1, 1992

By J. L. Parks

Designs, installation procedures, and performance characteristics of martensitic cast steel concaves are reviewed. Longer wear life, fewer pieces to install, and eliminating the need to scarf joints are the principal benefits of using martensitic steel to replace austenitic 12% Mn (Hadfield&apos;s) steel, the traditional concave material for large gyratory crushers. Installation procedures that reduce the risk of breakage are described. Operating practices that affect concave performance are also discussed.

Jan 1, 1992