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By John T. Neubert

Between 1988 and 1990, the U.S. Bureau of Mines studied the mineral resources of San Juan National Forest to appraise and determine types and locations of deposits that could be mined economically now and in the foreseeable future. The study included a comprehensive field examination and literature search. Substantial amounts of lead, zinc, copper, gold, and silver have been mined from within the Forest in the La Plata, Rico, Silverton, and Dunton areas. At least one buried 200 million ton stockwork molybdenum deposit occurs in the Rico area. Similar size porphyry copper deposits occur at the surface and about 1,700 feet below the surface in the Bedrock Creek area of the La Plata district. Numerous smaller base-and precious-metal and uranium deposits have been prospected and mined throughout the Forest. Coal, oil, and gas have been or are currently being produced in the western and southern parts of the Forest. Carbon dioxide occurs in the western part of the Forest. Strategic elements occurring within the Forest include platinum, palladium, cadmium, gallium, indium, bismuth, and tellurium; however none of these elements is economically recoverable at present. Several geothermal areas are scattered across the eastern two-thirds of the Forest. Industrial minerals within the Forest include sand and gravel, limestone, and decorative stone.

Jan 1, 1992

By M. W. Osterberg

The Cyprus Pinos Altos mine exploits small high grade Cu-Zn skarns using trackless equipment and a modified room and pillar mining method. The skarns occur around early Laramide diorite and quartz monzonite stocks. Stage I calc-silicates and sphalerite developed in the Pennsylvanian Magdalena Group between diorite and the marble front and were partially incorporated into a diffuse breccia body. Stage II calc-silicates and Cu sulfides formed in the contact zone with quartz monzonite and along NE-SW faults, overprinting stage I rocks and breccia. The result is a geologically complex deposit formed in two distinct pulses.

Jan 1, 1992

By V. Svalbonas

When the Trelleborg Divisions of Boliden Allis and Mineral Processing Systems (MPSI) merged, a unique opportunity occurred for two independent mill fabricators to compare design pro¬cedures and the research upon which they were based. Several semiautogenuous (SAG) mill analyses are compared using Boliden Allis and MPSI methods. The differences and similarities are then used in a correlation of critical stress definitions and the acceptable design and inspection criteria. Given the opportunity to compare the total philosophies and methods of several companies involved in the design and fabrication of grinding mills, it was important to first develop the comparison method and ground rules. One option was to compare analytical methods by details such as numerical techniques and accuracies. However, this option was discarded in favor of a more general approach. The question that was finally posed was in two parts. Given an identical mill requirement: • What would be the difference in the analytical design result, and to what aspect of the analytical process could this difference be attributed? • What would be the difference in approaches to obtaining the final hardware in subcontracting, both in specifying and Quality Assurance surveillance? By using this comparative approach, questions of relative conservativeness and reliability would automatically be answered.

Jan 1, 1992

By Lottrey A. L, Sowerby B. D, Cutmore N. G

On-line monitoring of low rank coal quality during input to a process has the potential to provide benefits through: ò anticipation of coal quality variations prior to utilisation; ò provision of a tool to help determine the influence of coal quality on process behaviour, and ò provide a direct measure of coal quality for pricing. Moisture and ash are the two most significant coal quality parameters for combustion. They determine the energy content which can be derived from the coal and the problems arising from the presence of ash in the process (eg ash fouling, corrosion, erosion, particulate emissions and ash disposal). Extensive pilot-scale testing and full-scale experience has shown that specific coal/ash constituents (eg Na2O/ash ratio, acid-soluble aluminium, silica, sulphur contents, etc) are also important for the behaviour of Latrobe Valley brown coal during combustion, ash formation, deposition and removal of ash in precipitators and furnace ash hoppers. This paper discusses the range of on-line analysis techniques which have been investigated and their application to low rank coal analysis. Preliminary results from a joint SECV/CSIRO project which aims to develop two separate advanced instrument systems are also presented. These systems are based on: ò microwave attenuation and phase shift - for direct determination of moisture content; and ò inelastic neutron scattering - to provide total hydrogen, carbon, chlorine and ash contents, with potential for calculation of moisture content, specific energy, sodium content and Na20/ash ratio using correlations.

Jan 1, 1992

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 Thomas O. Llewellyn

This U.S. Bureau of Mines (US8M) report presents a concise review on sources, processes, supply, and historical use patterns of domestic cadmium. It also covers a preliminary estimated cadmium material balance for the year 1989.

Jan 1, 1992

By Anthony Iannacchione

Designing coal pillars to provide resistance against overburden loads has long been an aim of rock mechanics engineers. The need for accurate pillar strength models has become more urgent as greater overburdens are encountered and pillar sizes grow larger. Current pillar design models differ widely in their predictions of the trend in pillar strength with increasing pillar width-to-height ratio. The goal of this paper is to evaluate current pillar strength theories, using a comprehensive data base of stress measurements from coal pillars. The stress measurements indicate that coal pillars maintain relatively high stresses near the ribline, and that the stress gradient within the yield zone can be approximated as a straight line. Several problems are identified for further research, including calibration procedures for different types of stress cells, strain softening behavior in the yield zone, and measurement of stresses in the cores of very wide pillars.

Jan 1, 1992

The theme of this conference is æRediscover OtagoÆ. In order to ensure the development and exploitation of mineral discoveries in New Zealand, considerable capital will be required, particularly from overseas. This paper briefly reviews the Government's foreign investment policies and procedures and highlights some trends.

Jan 1, 1992

By Julie N. Walker

This U.S. Bureau of Mines report reviews the first 2 years of the agency's progress in implementing total quality management (TQM), which the agency refers to as Quality Improvement (QI). All employees have been trained in basic TQM concepts, a cadre of facilitators has been selected and trained, and 13 Bureauwide teams are addressing specific issues that were identified by Bureau employees nationwide as problem areas. Also in place are a Quality Council composed of the Bureau's top executives, a Quality Management Board, and eight QI Working Groups to provide a national 01 infrastructure. There are also Quality Steering Groups at each Bureau location nationwide to address local concerns. In addition to the narrative text, the texts of salient memoranda and other documents are included as appendixes.

Jan 1, 1992

By R. G. Reddy

Nickel solubilities in spent pickling solutions (i.e. HF-HNO3-H2O solutions ) were measured as a function of HF and HNO3 acid concentrations. The chemical analysis of the industrial pickling solutions and sludges were made. The stable phases observed in the sludges are FeF3?3H2O, and ( FeCr ) F3?3H2O. Pure Ni, and stainless steel type 316 were used in this study. The results showed that the solubility of Ni increased with increase in concentrations of HF in pickling solution at a fixed concentration of HNO3: An excellent agreement between the experimental solubility data and the theoretical data was obtained. X-ray diffraction analysis showed that the solid solubility product formed is mainly NiF2?4H2O compound.

Jan 1, 1992

By Bo Forsman

METAFORA is a simulation model for determination and evaluation of strategies for operating loader/truck systems in mining. A specific version of METAFORA was used to evaluate the haulage system at Solider Mineral's Aitik mine in northern Sweden, one of the largest open pit mines in Europe with a production of about 11.5 Mtpy (about 34000 tpd) of copper are. A production level of 34065 tpd was estimated by simulation runs with METAFORA. Using METAFORA's dispatch rules (Fixed Dispatch, Maximize Trucks, and Maximize Loaders), the truck/shovel system in the Aitik mine was simulated for evaluating alternative dispatch control strategies. The Maximize Trucks rule gave about the same total production (ore + waste) as the Fixed Dispatch rule but a 9% higher ore production. The Maximize Loaders rule gave the lowest production. The marginal truck capacity decreases with increasing number of trucks serving the same loader due to increasing waiting times. In Aitik mine the low crusher capacity results in long dumping times. If the dumping time at the crusher could be halved, the ore production would increase by 14%. The paper indicates that the use of software like METAFORA can result in a substantial reduction of time, effort and cost in shovel/truck system design and evaluation.

Jan 1, 1992

By R. W. Plume

Gold extraction along the Carlin trend requires large withdrawals of ground water, which can be perched, unconfined at shallow depth, and (or) confined at depth. Five hydrogeologic units-Quaternary basin-fill sediments, Tertiary basin-fill sediments and sedimentary rocks, Tertiary volcanic rocks, Devonian to Ordovician siltstones, and Devonian to Ordovician carbonate rocks--form the framework for two aquifer systems that discharge along some reaches of the Humboldt River and its tributaries and are recharged by streamflow along other reaches. Ground-water withdrawals eventually could affect these stream-aquifer interactions. Further work is needed to quantify regional hydrologic processes and evaluate potential effects of mining on water resources.

Jan 1, 1992

By Dhananjay Kumar

In past, no serious attempts have been made to study the effects of operating environments on performance characteristics of a mining system. In this paper, proportional hazards model (PHM) analysis technique is introduced which can be used to analyze the effects of operating environments on the performance of a mining system. It can be used to select suitable materials, manufacturers or designs of items for a particular working environment. In this paper some applications of the PHM are discussed with examples from a Swedish mine. Its application for decision making in maintenance is also discussed.

Jan 1, 1992

By R. Mensah-Biney

The loading characteristics of gold-tetrabromide species onto activated carbon have been evaluated using a completely mixed batch reactor system. The overall loading of gold onto carbon was rapid for the first hour but continued slowly without cessation as a result of reduction of gold. Conventional equilibrium considerations were therefore not applicable. Although loading continued slowly after several days, abnormally high loading capacity values of 10-12 meq/g carbon (650-800 kgAu/tonne) could be attained within 72 hours. The loading of gold-bromo species by activated carbon was by the mass transfer of [AuBr4l-onto the carbon surface where reduction to metallic gold took place. Elution of gold from the loaded carbon was feasible provided the carbon had not been loaded to too high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the carbon. For the high loading capacities observed, this option would appear to be cost effective. The effect of several variables on the loading capacity of the activated carbon is discussed.

Jan 1, 1992

By P. G. McCormick

The refining of rare earth metals by the direct solid state reduction of their respective chlorides during mechanical alloying has been studied. Erbium and gadolinium were synthesised by milling their respective chlorides with calcium. The mechanical alloying of SmC13 with calcium resulted in partial reduction of SmC12. Examination of the milled powders using X- ray diffraction and analytical electron microscopy has enabled characterisation of product structure and morphology. The synthesis of Fe17Nd2 by the mechanical alloying of NdC13 and Fe with calcium has also been studied. The Fe17Nd2 phase forms during heat treatment of the mechanically alloyed powder.

Jan 1, 1992

By Compiled by Staff

"The Bureau of Mines was established in the public interest to conduct inquiries and scientific and technologic investigations concerning mining and the preparation, treatment, and utilization of mineral substances; to promote health and safety in the mineral industries; to conserve material resources and prevent their waste; to further economic development; to increase efficiency in the mining, metallurgical, quarrying, and other mineral industries; and to inquire into the economic conditions affecting those industries. The organic act of the Bureau, as amended by Congress and· approved February 25, 1913, made it the province, and duty of the Bureau of Mines to ""disseminate· information concerning these subjects in such manner as will best carry out the purposes of this Act.""In accordance with this directive, the Bureau reports the findings of its research and investigations in its own series of publications and also in articles that appear in scientific, technical, and trade journals; in proceedings of conventions and seminars; in reference books; and in other non Bureau publications. The number of these reports, the wide range of subjects they cover, and the variety of mediums in which they appear make the kind of list and index presented in this special publication both necessary and valuable. This issue of the Bureau of Mines List of Publications and Articles describes reports and articles published during the period January 1, 1990, to December 31,1991. It, supplements the 50-year list of Bureau publications issued from July 1, 1910, to January 1, 1960;1 the 50-year list of articles by Bureau authors published outside the Bureau from July 1, 1910, to January 1, 1960;2 and the 5-year lists of publications and articles from January 1, 1960, to December 31, 1964,3from January 1, 1965, to December 31, 1969,4 from January 1, 1970, to December 31, 1974,5 from January 1, 1975, to December 31,1979,6 from January 1, 1980, to December 31, 1984,7 and from January 1, 1985, to December 31, 1989.8"

Jan 1, 1992

By John W. Graydon

Incineration is an attractive alternative to the disposal of MSW in landfill sites. However, the process of incineration generates fly ash which contains significant levels of leachable heavy metals - particularly cadmium, lead, and zinc - and it is essential to manage this fly ash in an environmentally sound manner. The compositions, phases, textures, morphologies and size of fly ash particles have been studied by light microscopy, scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. The detailed spatial relationships and speciation of the environmentally significant constituents have received particular emphasis. The information obtained is useful in understanding how fly ash is formed during incineration, in understanding the leaching behavior of untreated fly ash if it is disposed of in a landfill and, most importantly, in guiding the development of the best treatment strategies for fly asti to mitigate its environmental impact.

Jan 1, 1992

The Cadjebut Mine is located 80 km southeast of Fitzroy Crossing. Cadjebut is owned 58 per cent by BHP Minerals and 42 per cent by Billiton Australia. Cadjebut is a 'Mississippi Valley Type' (MVT) deposit. Minerals present are sphalerite, galena and marcasite in a sedimentary host of dolomite and siltstone. The ore contains few deleterious impurities and no silver. The mill was commissioned in the first half of 1988 at a rate of 320 000 tonnes per annum. An expansion in the latter half of 1989 has since increased production to 550 000 tonnes per annum. The initial geological resource at the commencement of mining was 3.8 million tonnes at 13.5 per cent Zn and 4.4 per cent Pb. There is sufficient ore left to sustain operations to 1995 at a grade of 11.2 per cent Zn and 3.9 per cent Pb. The ore from underground is stockpiled on the surface via a drift conveyor and from the stockpile is fed into a grinding circuit consisting of a SAG and ball mill. Cyclone overflow at a Pgp of 90 pm gravitates to the flotation circuit. Lead and zinc are sequentially floated to produce an 80 per cent Pb grade at 90 per cent recovery and a 61 - 62 per cent Zn grade at 96 per cent recovery. The concentrates are thickened and filtered before being trucked to the port of Wyndham 600 km away. From Wyndham the concentrates are shipped to smelters in Asia, Europe and Australia.

Jan 1, 1992

By C. L. Karr

Establishing suitable control of pH, a requirement in a number of mineral and chemical industries, poses a difficult problem because of inherent nonlinearities and frequently changing process dynamics. Researchers at the U.S. Bureau of Mines have developed a technique for effectively controlling such systems. This technique successfully combines the process control capabilities of fuzzy logic and the search capabilities of genetic algorithms. Fuzzy logic offers an effective mechanism for handling nonlinearities, while genetic algorithms can provide fuzzy logic controllers with real-time adaptive capabilities. This Bureau-developed technique is applied to a laboratory acid-base neutralization experiment. Nonlinearities in the laboratory system are associated with the logarithmic pH scale and the changing process dynamics are due to alterations in pH and buffering capacity input solutions. Results indicate fuzzy logic controllers augmented with genetic algorithms offer a powerful alternative to conventional process control techniques in such nonlinear, rapidly changing systems.

Jan 1, 1992

By J. A. King, D. A. Knight

"The Porgera orebody is located in mountainous terrain in Enga Province, Papua New Guinea. An underground mine has been developed which produces up to 2000 t/d of ore grading over 2 ozs Au/t. Some 79% of the gold in the ore is free, with the balance in a highly refractory form as sub-microscopic gold evenly disseminated within a pyrite matrix.This paper describes the metallurgical plant that uses flotation and cyanidation circuits to effectively recover the free gold in the ore feed, allowing for wide variation in the gold head grade. The refractory gold component in the ore is stored as leached pyrite flotation concentrate and this concentrate will be later treated by autoclaving techniques to recover the contained gold.The ProiectThe property is located in the Porgera Valley 600 Km North West of Port Moresby. The remote location is 2500 m above sea level. The mine area has 3600 mm of annual rainfall and a temperate climate with temperatures ranging from 10° c to 22° c throughout the year.Alluvial gold was reported in the Porgera area in 1938 and has been an important source of revenue for the area for many years. Intermittent exploration was carried out until the 1960 1 s when Placer (PNG) Pty. Ltd. with Mt. Isa Mines commenced an extensive exploration program. The property was brought to production in 1990 by the Porgera Joint Venture group consisting of Mount Isa Mines Ltd, Rennison Goldfield Consolidated Ltd. and Placer Dome Inc, each with a 30% ownership and the Government of Papua New Guinea with a 10% share. Placer Dome Inc. is the manager of the property with construction under the direction of the Placer Dome Technical Services group."

Jan 1, 1992