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As the theme of the conference is ære-discover Otago' from the minerals point of view, it is also timely. Of the eight million ounces of gold recorded produced from Otago, perhaps a quarter of this came from the goldfields of St Bathans, Vinegar Hill and Cambrians. The most notable among them was the Kildare Hill Mine, which is the so-called Blue Lake at St Bathans today. The bottom wash encountered in this mine contained the famous Kildare lead, which averaged 7 1/2 dwt to the dish, and is still one of the richest leads of alluvial gold known in the world. The richness of this lead, the best encountered in these gold fields, is otherwise stated to have yielded more than 42 ounces of gold to the cubic yard. It should be borne in mind that this equates to about $22 000 per cubic metre, in todayÆs values. I have been told by older residents of this district that in fact about 1 million ounces came out of the Kildare mine and associated workings. In todayÆs values, this would be about 530 million dollars worth of gold. The largest mines in the district were at Surface Hill, Kildare Hill, Nicholsons, Vinegar Hill, the Never Fail claim at Shepherds Flat nearby, and at Cambrians. It would appear that in almost every case, work stopped when the bottom wash progressed too deep down dip of the anticline hills on which it was initially found. The mining methods were sluicing and hydraulic elevating, and although the gold bearing ground did not stop, eventually it exceeded the ability of the mining methods then available years ago, to work it further. When it is realised that the previous mining has removed what is likely to be only a low percentage of the gold resources in these fields, a tantalising situation presents itself today in that mining technology now available will enable another cut to be taken off these fields. As in the past, I believe this will be million ounce plus and multi-million dollar scenarios, where the economic and social benefits will become widespread prizes.

Jan 1, 1992

By Louise H. Michaud

An interactive mine planning system that employs recent advances in 3D computer graphics capabilities and 3D geologic modelling to aid with the tasks involved in producing dragline mine plans was developed. As well as offering large potential saving in the time required to carry out the planning tasks, the system offers immediate visual feedback to the planning engineer. This can greatly aid in the conceptual understanding of complex geology and mine plans. The package incorporates the generation of a three dimensional Gridded Seam Model (GSM) as the basis for the development of the geologic database. This modelling method is capable of accurately representing rugged topography and multiple coal seams, including folding and faulting. The GSM is then integrated with an interactive graphics mine planning system in order to develop one model and one database for the generation of the mine design, the depletion of the coal resources and the movement of spoil material. The gridded structure of the model also provides the foundation on which all mine and spoil pile volumes are calculated.

Jan 1, 1992

By K. Darcovich

The wettabilities of agglomerates made from coals of several different ranks were measured by the adhesion technique. Oil levels from 0 to 10% by weight were used. As was expected, it was found that higher-rank coals are more easily oil-wetted and that the surface properties of the agglomerates correlate with agglomeration recovery and ash removal data.

Jan 1, 1992

The Clyde Power Project, and its Clutha Valley Development forerunner, has taken widespread investigations for various hydroelectric purposes both along the valley floors upstream from Alexandra and on the higher schist terrain. As part of this work the nature and extent of many of the alluvial deposits have been resolved and the ages established with varying precision. Gold values have been approximately appraised in some areas as an element of environmental assessment.

Jan 1, 1992

By C. R. Tinsley

In maybe the world's first in a mine project financing, a US $55 million Rehabilitation Indemnity was given on behalf of the banks in a US $250 million loan to develop the Ranger uranium mine, Northern Territory, Australia. The basis of the financing was an estimate of removal of the tailings and replacement into the pit. The Indemnity was amortized by a sinking fund from the mine's revenues. Such a concept could be valuable for mineral developments in sensitive areas or jurisdictions such as British Columbia or Alaska.

Jan 1, 1992

By R. A. Metz, George S. Barnett

The Equis and El Roble projects are located in the Cordillera Occidental of Colombia. The Equis vein deposits have sulfide ore reserves of 95,955 mt (105,770 st) grading 8.51 g/mt (0.248 oz/st) gold and 12.4 g/mt (0.36 oz/st) silver with 0.94 % copper, 1.10% lead and 11.06% zinc. Ore reserves at El Roble are estimated as 1.1 Mmt (1.21 million st) grading 4.89 % copper and 3.39 g/mt (0.099 oz/st) gold. Geologically possible reserves at Equis may total 1.6 Mmt (1.76 million st). El Roble has the potential to contain several tens of millions of metric tons. Exploration included diamond drilling, trenching, channel sampling, rock and soil geochemistry, geophysics and tunneling. Erratic high grade samples affect the weighting of channel and drill core samples. Secondary reconcentration of gold is also a factor. Sample maps and graphs show the distribution of values to be highly variable. Geostatistical treatment of some of these data gave important guidelines for parameters such as sampling densities, drill hole spacing and confidence limits.

Jan 1, 1992

By M. P. Bohrer

A closed-loop hydrometallurgical process has been developed for treatment of smelter flue dust generated by copper recycling. The process is a semi-continuous operation in which zinc, iron, and copper are first extracted from the dust with a sulfuric acid solution. The lead and precious metals, initially present in the dust, remain as solids and can be recycled to the copper smelting furnace. Cementation with iron and zinc metal purifies the zinc and iron-rich liquid stream prior to spray drying. The spray-dried product, consisting of a mixture of zinc sulfate monohydrate and iron sulfate monohydrate, is a desirable micronutrient additive for use in animal feeds. Treatment of the smelter flue dust in this manner will generate a positive return on investment, as well as mitigate a potential environmental liability.

Jan 1, 1992

In 1991, environmental issues related to coal mining continued to be an integral part of managing a cost-effective operation. Environmental regulations and their implementation can create considerable cost burdens on operating mines. Environmental responsibilities require management decisions to be made on a whole systems approach that is comprehensive in costs and consequences. Most of the regulatory activity in 1991 that affected coal was related to reauthorization or revision of several pieces of legislation. Issues related to the reauthorization of the Clean Water Act, the Resource Recovery and Conservation Act (RCRA) and Abandoned Mine Land. Clear Water Act considerations will encompass discharge standards, wetlands issues and proposals to regulate ground water quality at the federal level. Discussion regarding RCRA includes efforts to expand regulatory authority into the area of coal mine waste. That is currently regulated by the Office of Surface Mining (OSM). Another RCRA consideration will be the disposal of coal combustion byproducts. Abandoned Mine Land reauthorization continues the Abandoned Mine Land tax on coal operators. This tax has been in effect since 1977. Regulatory revisions were also proposed by the Department of Interior on valid existing rights, subsidence, federal coal leasing programs and OSM's troubled Applicant Violator System. Industry officials have been critical of the revisions. A federal appeals court found that evidence supported claims by Whitney Benefits, Inc. that the passage of the Surface Mining Control and Reclamation Act (SMCRA) deprived the owner of full economic use of its property. Before SMCRA's passage, Whitney established an operating agreement with Peter Kiewit Sons Co. to mine coal.

Jan 1, 1992

By Alexandre Bonan

The paper reports on the results of a kinetic study on the oxidation reaction of aqueous free cyanide ions with H202, in the presence of Cu(2+) catalyst. The variables and respective ranges studied were the following: (CN) ° = 10 -100 mg/l pH = 10 -11 (H202/CN) mol ratio = 1 -3 (Cu/CN) mol ratio = 0 -0.25 The results lead to the development of a semi-empirical model whish incorporates both the useful oxidation reaction and the parallel alkaline decomposition of H202.

Jan 1, 1992

By T. R. Wildeman

"At the Big Five wetland, which was built to treat drainage from a metal mine, encouraging results have attributed to sulfate reduction. Cu and Zn were reduced to below detection limits of 0.50 mg/L, Fe was reduced by at least 90% to below 3 mg/L, and the pH was raised from below 3 to above 6. The study showed that treatment was primarily through microbial processes within the substrate and that plants were not needed to insure success.Constructed wetlands can be taken through design and proofing stages, and into operations scale in a meaningful time frame for on-line acid drainage remediation. In staged design, laboratory experiments are initiated to determine reasonable substrate materials for remediation of a particular drainage. When a reasonable substrate is found, bench scale experiments are initiated as the next stage in the design. In these studies, removal efficiency, permeability, and flow are analyzed to identify candidate substrate which will support sulfate reduction and be hydraulically reasonable. Using this design method at one site, an acid drainage of pH 2.5 was raised to a pH of above 7. Total heavy metal concentrations in this drainage exceeded 900 mg/L. In the pilot constructed wetland Cu, Zn, and Fe were reduced by 99%.Determining how well these anaerobic cells operate in the winter is done at the pilot plant site in Idaho Springs, CO. It's been found that over the last four winters, those cells that emphasize anaerobic removal within the substrate have operated continuously and effectively the year round. Winter operation is aided by the fact that the water temperature of the acid drainage is always between 14 and 16° C, and the cell can be readily insulated from the cold. Activity of the sulfate reducing bacteria may decrease during the winter. However, it appears that organic complexation of metals helps to maintain low concentrations of metals in the effluent."

Jan 1, 1992

By Walter G. Steblez

The countries of Eastern Europe are former members of the Council for Mutual Economic Assistance (CMEA). Geographically, they are located in Central Europe (Poland, Hungary, Czechoslovakia) and Southeastern Europe, largely in the Balkans (Yugoslavia*, Bulgaria, Romania and Albania*). It is important to remember that all of the countries of Eastern Europe had central planning imposed on them by the Soviet Union during the years following World War II. "Stalinist" policy for industrial development had three important tenets: • central economic planning, or a nonmarket-based command economy with administratively set prices; • economic priorities that stressed the development of heavy industries such as mining, metallurgy (steel) and heavy machine building; and • self-sufficiency at all costs, which was aimed at abolishing reliance on the world capitalist market, or reducing it to a minimum. Essentially, the system of industrialization that was used in the Soviet Union in the 1930s and 1940s was imposed on Eastern Europe. Organic market economic development in Eastern Europe ceased during this period. The flaws of this experiment became apparent when mineral processing facilities were set up in many areas of Eastern Europe that did not have reliable resources. Poland, Hungary and Romania are good examples of this situation. The Soviet Union became the principal supplier of iron ore and other minerals and mineral fuels, not only to these countries but to the Bloc as a whole.

Jan 1, 1992

By I. Goy D. Gaballah

Decontamination of synthetic K2Cr2O 7 solutions containing 10 to 1000 ppm of hexavalent chromium using chemically treated barks have been studied at a laboratory scale. Metal removal from solutions depends on the pH, the initial concentration and the bark species. The use of a pulp density of 2 % in an agitated flask at the optimum pH for 2 hours leads to a percentage chromium removal of about 95 of the initial metallic ions content. Other trials conducted by column percolation permit the determination of the maximum retention capacity of the treated bark. Depending on the bark species, oak or pine, the rate of saturation is 110 and 215 mg of Cr per gram of bark respectively. The incineration of the metal charged barks gives recyclable, ashes containing 36 and 54 % of chromium metal for the oak and pine barks respectively. Experiments, of Cr6+ removal from industrial effluents containing up to 1800 ppm have been carried out on the semi-pilot plant scale. They have lead to the elimination of about 90 % of hexavalent chromium from this industrial waste solution. Further studies are conducted in order to define the hexavalent chromium binding mechanisms on bark constituents.

Jan 1, 1992

By G. Folmo

Allis Mineral Systems' GRATE-CAR agglomeration/induration/reduction process is currently being operated to process ilmenite at Tinfos Titan & Iron KS in Tyssedal, Norway. In this process, balled ilmenite concentrate is fed to a traveling grate where pellets are dried and preheated, using fully oxidized kiln exhaust gas. Hot preheated, semi-indurated pellets are fed directly to a ported kiln where reduction of the ilmenite's iron oxide fraction occurs in the presence of lump coal. The reduced pellet sand coal char are discharged from the kiln to an indirect rotary drum cooler. Cooled pellets and char are screened and magnetically separated prior to their further processing in a downstream smelting operation. The pellets are melted and the titanium dioxide and iron are separated. Operation commenced in late 1986.

Jan 1, 1992

By Jena P. K

Smaller deposits of high grade chalcopyrite or the concentrates of low grade and complex copper bearing ores, can be subjected to extraction processes other than smelting and converting. Low temperature chlorination and segregation processes are among those mentioned in the literature. In the present work, extraction of copper from a Brazilian chalcopyrite concentrate by slurry chlorination with chlorine gas at room temperature, dry chlorination by chlorine gas in the temperature range of 350 to 450¦C and segregation roasting of the calcined concentrate in the temperature range of 650 to 800¦C have been carried out. The effect of several experimental variables on the extraction of copper has been discussed in all these cases. Under optimum experimental conditions, 100 per cent Cu extraction was possible by either slurry or dry chlorination processes and around 86 per cent Cu by segregation roasting. For all the three cases, possible methods have been suggested to trial the studies on a pilot scale to assess their technoeconomic viability.

Jan 1, 1992

By R. Kramer

The Process Mineralogy review arrived too late to appear in the May issue. The Process Mineralogy Committee scheduled programs with both SME and The Metallurgical Society. At the 1991 SME Annual Meeting in Denver, CO the committee sponsored five sessions containing 31 papers. Four process mineralogy sessions were sponsored at the 1992 annual TMS meeting in San Diego, CA. Process mineralogy is used to understand and evaluate mineral behaviors during mineral beneficiation, phase reactions during metallurgy, recoveries and reactions of precious metals during processing and mineral and phase behaviors with respect to environmental problems. The most recent refinement in mineralogical studies with respect to mineral beneficiation has been the wider use of image analysis and combined materials balancing techniques of image analysis data. Image analyzers that can perform analysis with respect to mineral beneficiation are expensive. They are used only for solving major processing problems. Nevertheless, the methodology of analysis continues to be refined. Much better data are collected, and methods of evaluating the data continue to improve. One interesting development involves modifying the ultrasound unit used in medical studies to perform a three-dimensional analysis of ore particles.

Jan 1, 1992

By J. Mark Richardson

Steady-state flowsheet simulators for mineral processing plants have evolved to a current high level of utility and accuracy. Reliable, general-purpose, semi-empirical models now exist in nearly all unit operations categories particularly in the areas of comminution and classification. .These models, installed as user-selectable functions within the integrated frame- work of flowsheet balance-solver software systems, can be strung together to represent any plant configuration. In addition, CAD-like graphics, data reconciliation and model parameterization functions have become standard features of the current generation of integrated plant simulators. These advances have given engineers the capability to investigate many different plant scenarios while requiring a minimum of actual plant testwork. This paper describes a methodology and an integrated software package which are being successfully applied in a number of operating plants worldwide to predict plant performance under changing conditions. Those conditions which can be changed include effect-of ore type, feed size, water addition rates, equipment geometries and flowsheet modifications. By using data from actual plant optimization exercises in real mills, the paper illustrates and out- lines a technique which includes plant data collection, ore breakage testing, flowsheet simulation, model-fitting (parameterization), data adjustment and model experimentation. Brief descriptions of some unit operations models, such as autogenous mills and cyclones, are provided as examples of the current state of such models. Ore breakage testing and its relation to certain models is also discussed. Computer- generated size-distribution graphs, along with tabular data generated by the simulator, round out the presentation and serve to demonstrate the real- ism and accuracy of the models. The paper concludes with a partial list of cases where this technology has been successfully applied.

Jan 1, 1992

By Klau Meyer

"At Teck-Corona Operating Corporation's David Bell Mine, a successful water quality management strategy has been established. This resulted from the development and application of process technology, allowing year round discharge of an effluent exceeding the chemical and biological standards set by the Ministry of Environment. This strategy aims at minimizing contaminant levels of effluents through optimization of reagent selection and reduction of effluent volumes through maximizing reclaim water usage. Concentrator and effluent treatment plant operating practices, process chemistry and the results of the water quality management strategy are reviewed.IntroductionThe David Bell Mine is located in the Hemlo gold camp 42 km east of Marathon, Ontario. The concentrator has a design throughput of 1000 tonnes per day. The processing of the run of mine ore ( - 15cm) involves the following unit operations: grinding in a semi-autogenous mill followed by a ball mill, thickening, pre-oxidation , cyanidation, and carbon-in-pulp gold recovery followed by electrowinning and refining.The David Bell Mine water quality management strategy is composed of the following items (Goodfellow and Meyer, 1991):• natural destruction of cyanide contained in the tailing water in a large shallow tailing pond ;• preliminary treatment of reclaim water in the grinding circuit for cyanide and heavy metal removal;• pre-oxidation of sulphide minerals in pipe reactors to reduce cyanide consumption using pure oxygen;• pH control in the grinding, pre-aeration and leach circuits to minimize the dissolution of stibnite while maximizing gold recovery; • close control of cyanide addition rates to the leach circuit to maintain the lowest possible levels;• a carbon column for gold recovery;• an effluent treatment plant for antimony and heavy metal removal; and• the use of final treated effluent for industrial water underground to minimize fresh water consumption."

Jan 1, 1992

By Herbert E. Allen, Andrew F. Kingery, Spyros P. Pavlou

This paper examines and compares the role that chemical speciation plays in the environmental aquatic toxicity of two metals - copper and arsenic. Copper is shown to have well-understood chemical speciation equilibria, but poorly known species toxicities. Arsenic presents the opposite case, with unpredictable speciation in aquatic systems, but is relatively easy to evaluate toxicologically. Speciation is not currently incorporated into Water Quality Standards. This can have a major impact on the cost of environmental containment and cleanup.

Jan 1, 1992

By Peter N. Gabby

In 1990, the Bureau of Mines conducted a mineral resource investigation of the 12.321 acre Black Warrior study area, one of several proposed additions to the Sawtooth Wilderness. No identified mineral resources were delineated. There were 123 lode and placer claims in or adjacent to the study area. There is a known hot spring adjacent to the study area, but presently no geothermal leases are pending. Lode mines in pr adjacent to the Black Warrior study area have produced 4,022 tons of ore from which 1,981 oz of gold and 811 oz of silver were recovered. None of the vines are currently active. During the field study 125 rock samples were taken. Significant gold assays and favorable geologic characteristics at seven properties indicate that gold occurrences and resources with byproduct metals may exist in the study area. Two other sites yielded anomalous gold assays; however, sage favorable geologic characteristics are lacking. Presently, identified gold resources are being delineated by drilling programs in the nearby Atlanta and Rocky Bar mining districts. These districts have geologic characteristics similar to the Black Warrior area. During the field study 22 placer samples were taken. In most places where an anomalous concentration of gold was found, the stream channels are too narrow for operations other than recreational suction dredges. However. One area is estimated to contain over 2 million yd3 of gold-bearing gravels.

Jan 1, 1992

By E. D. Sehnke

The refractory materials industry provides the largest commercial market for nonmetallurgical grade bauxite. Refractory grade bauxite is prepared from bauxites having low iron, titania, and alkali content by calcining at temperatures near 1,650° C. Although there are substantial bauxite reserves in the world, premium grade bauxite ores suitable for use in refractory applications are limited to only a few specific sources, primarily in Guyana and the People's Republic of China. Consumption of bauxite for refractory use is closely associated with the production and consumption of primary metals, in particular iron and steel. Barring major disruptions within the principal producer nations, sufficient supplies of refractory bauxite will be available to meet world demand well into the next century, and raw material costs will continue to determine the availability of markets for bauxite-based refractory products.

Jan 1, 1992