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By D. L. Schenk

The Navajo Mine is exclusively a multiple-seam surface coal mine located in the northwest comer of New Mexico. The property is situated entirely on the Navajo Indian Reservation. It is owned and operated by the Broken Hill Propriety Co. Ltd., of Melbourne, Australia. The mine began production in January 1963 with a long-term fuel supply agreement with the Four Corners power plant. The 2175 MW nominal generating capacity of the Four Corners powerplant consumes 7.2 Mt to 7.7 Mt/a (8 million to 8.5 million stpy) of coal. The Navajo Mine has estimated reserves totaling 1 Gt (1. I billion st) of strip minable coal. Only about one-third of that total is presently committed to the generating station. As development continued over the years, mining operations advanced into more complex geologic areas to satisfy the utility's demand for coal. To optimize the committed reserve and provide competitively priced coal to the customer, the Navajo Mine began developing a new pit in June 1986. The Dixon Pit boxcut development was completed in April 1987. About 6 hm3 (7.9 million cu yd) were stripped, uncovering 929 kt (1 million st) of coal. Strip ratio was 7.74:1 including 36.8% rehandle of prime yardage. This case study of the fourth production cut highlights a variety of dragline stripping techniques including highwall bench (overburden) side cast, intermediate highwall bench (parting-interburden) side cast and spoilside bench (partings-interburden) stripping methods. The Dixon Pit offers considerable challenges in the surface recovery of up to seven seams of coal within the 1432 m (4700 ft) of total pit length.

Jan 1, 1990

Ventilation 'is currently used in mines to sustain human life, prevent explosions, and provide a more healthful work place. Future automated-mining systems could use ventilation techniques quite. different from today's practices. The Bureau of Mines is anticipating various methodologies for ventilating the automated mining systems which are now beginning to emerge in the mining industry. This paper examines the special ventilation requirements for automated mining systems. Topics include requirements for automated systems, current studies with blowup ventilation tubing, and ventilation of two types of highwall -ripper type mining machines.

Jan 1, 1990

By John Barakso

The Sam Goosly or Equity silver deposit is fundamental- ly a discovery based on the analysis and interpretation of reconnaissance geochemical samples. The discovery was made by Kennco in an area of heavy forestation and wide- spread cover by thin glacial debris. No major mines had been discovered in the vicinity of the discovery prior to the geochemical reconnaissance, and the interpretation of the geochemical results therefore was based on data available through geologic mapping and the sample collection process. In the period 1959-1961, PE. Hirst and his crew, in 1962- 1965 P.T. Blackand his crew, and in 1966-1967 C.S. Ney and P.T. Black and their crew collected geochemical samples from the area of what is now the ore body. Several of these samples were compiled and reanalyzed in the winter of 1966- 1967 for various trace elements, including fluorine. A strong, almost 16-sq-km (10-sq-mile) fluorine anomaly was projected along with a very weak heavy metal anomaly. On the basis of this anomaly, a chalcopyrite-bearing quartz monzonite was discovered in 1967. This was a misleading, noneconomic discovery not associated with the Sam Goosly discovery. The interpretation of the geochemical data by Barakso that summer indicated that another source was responsible for the fluorine anomaly. The conclusion was based on the assemblage of trace elements. Therefore C.S. Ney recommended further regional soil sampling to check the original data. The early results of this follow-up sampling found over 33 ppm silver. First float, then ore outcrop was found in the area of the silver anomaly. The attached reprints complete the development of the property after the discovery of the outcrop of ore.

Jan 1, 1990

By Raj K. Rajamani, Ilesh M. Shah

Maintaining pH, a routine requirement in many industrial processes, is by no means trivial. The control is troublesome because of the inherent nonlinearity and frequently changing process dynamics. Many researchers in the past have investigated advanced on-line estimation and/or adaptive control techniques to overcome these difficulties. Most methods require the development of a complex mathematical model. The present work deals with the use of a simple and elegant method for pH control, based on the use of fuzzy logic. First, a standard fuzzy-logic controller is discussed, followed by a self-organizing controller. The latter algorithm generates a set of rules based on observation of the process. Thus it is a learning algorithm. The development and application of the algorithms to a laboratory acid-base neutralization experiment are presented. This elegant technique is powerful and deserves attention in mineral pro- cessing.

Jan 1, 1990

Fossil resin types occurring in the Hiawatha seam of the Wasatch Plateau coal field, Utah, have been separated according to color and their physical and chemical properties evaluated. These resin types were separated into four color fractions, yellow, amber, light brown, and dark brown. Each resin type has then been subjected to comprehensive spectroscopic examination and other physical methods of characterization. Included among the spectroscopic methods of characterization are FTIR and 13C NMR spectroscopy. Physical properties that have been measured include density, optical, and magnetic properties. These analyses reveal that the resins are distinct from other macerals, predominantly nonaromatic in nature with small amounts of oxygen functionalities and a low degree of unsaturation. The four resin types show distinct differences in certain physical and chemical properties such as density, hexane solubility, magnetic susceptibility, and aromaticity.

Jan 1, 1990

By J. C. Judd

The U.S. Department of the Interior, Bureau of Mines investigated solvent extraction methods for recovering gallium from filtrates produced from sulfuric acid leaching of hydrometallurgical zinc residues. These filtrates typically had pH values of 0 to 0.5, too high an acid content for effective gallium recovery by traditional extractants. Of the nine extractants studied in batch tests, 0.3M octyl phenyl acid phosphate (OPAP) in a kerosene diluent was the most effective extractant for gallium recovery, extracting up to 99.9 pct of the gallium. This high extraction was possible when the iron in solution was maintained in the reduced ferrous state. Batch tests also showed that a 1.5M-H2SO4 strip liquor recovered 98 pct of the gallium from the loaded OPAP. A continuous solvent extraction system was designed and operated based on McCabe-Thiele analyses of equilibrium loading and stripping isotherms. When 12 L of leach filtrate containing 0.32 giL Ga and 20 giL Fe were pumped through the system in 32 hr, results showed that 95 pct of the gallium was extracted in four stages at an A:O ratio of 1:1. Stripping the loaded solvent with a 1.5M-H2S04 liquor recovered 94 pct of the gallium in four stages at an A:O ratio of 1:4. A two-stage, 50-pct-phosphoric acid strip successfully removed ferric iron from the OPAP, allowing high gallium extractions to be maintained.

Jan 1, 1990

By Robert L. Akright

The Sumich (Victorine) gold mine is located in the Toiyabe Mountain Range on the east side of Victorine Canyon, a north-trending branch off Kingston Canyon in the northwest quarter of Section 27 and southwest quarter of Section 22, T16N, R43E, in the southern end of Lander County, Nevada (Fig. 1). HISTORY Discovered in 1862, the Victorine reached a peak of development between 1872 and 1887. The "Victorine" and "Morning Star" lode mining claims, located on the outcrop of a prominent auriferous quartz vein, were patented in 1869 and 1891, respectively. 1, respectively. Gold ore was mined underground in adits driven, on the level, directly into the side of the mountain. Ore brought to the surface was trammed about 457 m (1500 ft) south on a track constructed along the contour to ore bins. From this transfer point, the ore was moved by aerial tram to the bottom of the canyon then hauled by horse-drawn wagon to the mill located about 3.2 km (2 miles) east down Kingston Canyon. Exact details of the milling process used on the Victorine are lacking, but old reports mention water-driven stamp mills, amalgamation, chlorination, and cyanidation. Gold and silver mill products are reported to have been sent to England for final refining. High-grade gold values of 103 g/t (3 oz per ton) remaining in mine walls and on outcrops, attest to the lack of success in treating the Victorine ore in the early mills. The Victorine mine may have been worked sporadically after 1887 with little success. In 1934, control of the property was acquired by William P. Moloney, an attorney from Marion, OH, who also control- 1 led an interest in the successful Goldacres mine in Lander County, NV. This property was studied, sampled, and metallurgical tests were done in 1934, but no development resulted from this work.

Jan 1, 1990

By F. J. Susko

The U.S. Bureau of Mines is using Fourier-transform infrared (FT-IR) analysis to investigate the bonding mechanism which occurs during the dewatering of clay slurries. High molecular weight polymers are used as flocculating agents in these processes. This investigation presents the results of an FT-IR study of calcium-exchanged montmorillonite treated with polyacrylamide (PAM) and polyethylene oxide (PEO). Both thin film and attenuated total reflectance (ATR) spectroscopic techniques were employed to study this clay-polymer system~ Results suggest PAM is adsorbed to the clay via the nitrogen atom of the polymer. A water bridge is involved in the bonding between the clay and PE~. Evidence also suggests that PEO may be adsorbed directly onto the surface of the clay.

Jan 1, 1990

By W. S. Fyfe

The future environment of our planet, with the concept of sustainable development, has moved to centre stage of all future plans for development. This global view is new. It presents great opportunities and challenges for the Earth Sciences. We have the tools to describe our environment on all scales - planetary to molecular levels. We must respond to this great demand by world society.

Jan 1, 1990

By J. D. McKay

Flotation columns have been readily accepted for use in most sulfide flotation plants; however, recently columns are being used in many other areas. Recent improvements in design methodologies have overcome many operating problems and led to improvements in metallurgy. In addition, physical improvements in column design have simplified their operation while leading to better control. The Turbo-Air External Bubble Generator has provided a method for bubble size control and variation in air holdup and carrying capacity. These have enabled commercial operations to improve grades and recoveries by optimizing performance.

Jan 1, 1990

By L. Lichty, R Bhappu, R. Rowan, G. Ramadorai

Treatment of refractory gold ores containing arsenic have always presented a major problem in their processing to recover the contained precious metal values. The major difficulties are concerned with lower recoveries, production of hazardous fumes, effluents and residues. Because of'these arsenic related problems, many otherwise economically attractive precious metal deposits and dumps all over the world are not exploited. In recent years, treatment processee for refractory gold ores and concentrates have been explored and a few commercial operations employing roasting or pressure leaching have resulted. Roasting has limitations due to environmental constraints related to off gases. Pressure leaching involving high temperatures (180% to 200%) and pressures (400 psi) is accompanied by high capital and operating costs. An alternate route to roasting for treating pyrite and arsenopyrite ores and concentrates ia the "lime-oxygen hydromet" process carried out at a moderate temperature (100%) and pressure (100 psi). A simplified process for treating such arsenic containing ores and concentrates utilizing low temperature and pressure oxidation is presented. This low cost treatment with compressed air and lime renders arsenic as an inert component in the residue, meeting all the requirements of the EPA Toxicity Test. The precious metal values are then extracted from the autoclaved residue by standard cyanidation. This paper discusses this new development.

Jan 1, 1990

By R. E. MacDougall

Very few mineral properties spend their entire lifespans from discovery to depletion in the hands of one owner. More likely, properties will have several owners, and partial interests may change quite often. Similarly, mineral companies are bought and sold with frequency, in recent years at what appears to be an accelerating rate. The reasons for selling a property can be manifold -need for additional capital in other parts of the business, need for development capital, realization of a large gain at a perceived high point in the market, pessimistic commodity outlook, retirement of principals, or resolution of estate problems. Regardless of the reasons for a sale, there are specific steps that logically follow. Spruce up the business, package the information, market the property, negotiate the terms, close the sale, and make sure it stays sold. Adherence to certain very basic ground rules in property sales can maximize the profits and minimize the effort.

Jan 1, 1990

By R. J. Matetic

Mining operations have long been accused of causing a disruption to local, domestic and agricultural water supplies. More recently, concern for water supplies has increased with the advent of high-extraction mining techniques, namely longwall mining. Theoretically, any water bearing zone in the overburden above a high-extraction mining operation may be affected by mining. In some cases, a confining bed may be fractured causing a loss of water to a particular zone. In other cases, increased fracture permeability may enhance the ability of an aquifer to transmit and deliver water. Unfortunately, only a limited amount of studies have been conducted that characterize hydrologic changes and also quant1fythe magnitude of mining-induced subsidence. The U.S. Bureau of Mines conducted such a study at a mine site located in Greene County, PA. A total of 8 water wells were drilled and hydrologic parameters such as specific capacity, transmissivity and well yield were determined both before and after mining. Electronic water level recorders were installed on each water well to provide continuous observations of water level fluctuations.

Jan 1, 1990

By Z. B. Yin, R. W. Bartlett, P. R. Taylor

Tube furnace experiments have been performed to evaluate the lime roasting of pyrite in air. The sulfur volatilized was measured over time. Variables studied included: form of lime, sodium sulfate additions, temperature, air flow rate, lime to pyrite weight ratio and pyrite particle size. It was found that more than 98% of the sulfur can be retained at a reactor temperature of 650°C, with a slight excess of calcium hydroxide. The roast products are primarily hematite and calcium sulfate.

Jan 1, 1990

By L. Adler

The paper under discussion provides an excellent and concise study of compartment ergonomics for thin seam equipment. However, in accomplishing this, some very important operational aspects were ignored. Since these are likely to be determinant, the authors' response is solicited. The novel shuttle car with its cross-car, end-mounted compartment is operationally very different from the current one. The latter can be considered a highly mobile extension of the continuous miner or loader, with a pass-through conveyor, dump boom, and extra storage. As such, the vehicle's kinematics are the simple "I," or shuttle pattern, bent for going around pillars, with an intermediate stop at the "change-out point" (Adler, 1986). The action of the cable reel adjusts well to this pattern. The proposed shuttle car's motion either superimposes a "Y," time is lost (5 seconds) for each cycle, space is needed, line of sight is compromised, and a cable anchor is probably required at the dump. A chute is almost prohibitive in construction time and cost. The lack of a dump boom further curtails flexibility in the proposal. The value of a standard hand and opposite standard hand configuration also needs consideration. Many front-end loaders have a rocker (overshot) capability that is designed to achieve an "I" pattern. And crawler loaders sometimes use a side dumping bucket variant for the same purpose. These examples indicate the pattern's importance. For underground, thin seam application, the ram car has become popular. This is an articulated truck, battery-powered, and with an ejector dump. Its operational patterns would be similar to the novel shuttle car, except without the loading flexibility provided by a conveyor. Since the cab location of the proposed shuttle car largely obviates some of the major advantages of the present shuttle car, the question arises whether this configuration could be adapted to the current ram car and scoop.

Jan 1, 1990

By Thomas D. Kaufmann

The 1982 recession set the US mining and metals industries reeling. Will the oncoming recession of 1991 hit as hard? Probably not, thanks to a shallower downturn, a weaker dollar and remarkable lower costs. Effects of the last recession That the 1982 recession was traumatic to the American mining and metals industry is an understatement. Quantities of metals consumed dropped. Metals prices fell despite continuing general inflation. The resulting real gross revenues of producers of each of the major metals plunged, in the trough of 1982, to levels one-fourth to two-thirds of those of the peak of 1979 (Table 1). By contrast, most industries in the United States were not hit anywhere nearly as hard. Real GNP, the aggregate of all production, slipped only 1 % from 1979 to 1982. Metals are most sensitive to the business cycle because of their applications. All metals but gold are raw materials to downstream industries. Raw materials are victims of strong fluctuations. This is because buying industries try to hold high inventories in boom periods when goods are in short supply. They reduce inventory levels in buyers markets when suppliers have idle capacity and raw materials are in ample supply.

Jan 1, 1990

By Kenneth N. Han, Yuhong Chen

The removal of carbonaceous material from Carlin gold ore has been investigated via froth flotation. The effect of type and concentration of various oils as flotation collectors and of sodium silicate as the dispersion agent on the overall recovery of carbonaceous material has been studied. Other variables affecting froth flotation efficiency were also examined closely. These included particle size, pH of the solution, and temperature. The effect of reduction and oxidation of carbonaceous material on froth flotation efficiency has also been investigated. This investigation showed that aromatic type oil was the most effective collector. Also found in this investigation was that oxidized carbonaceous material was difficult to float unless the oxidized portion was subject to reduction before flotation. More than fifty percent of the carbonaceous material was able to be removed via froth flotation. It can be concluded from this study that the effect of pH and temperature during the rougher flotation state is of little significance to the overall recovery of carbonaceous material. Since pyrite is responsible for the high consumption of chlorine, removal of pyrite is very important in order to reduce the overall consumption of chlorine.

Jan 1, 1990

By C. W. Chiaretta

Utah Power and Light Company's Deer Creek Mine had been developed to a point where mine ventilation efficiency had declined to an unacceptable level. Problems identified were ventilation of inactive areas, excessive leakage, and restrictions in the return and intake air ways. Mine management implemented an intensive mine ventilation improvement program to alleviate future problems with respirable dust in the working sections and diesel equipment emissions. Program objectives included sealing of inactive areas of the mine, rehabilitation of high resistance areas, and construction of additional intake and return aircourses. Applications of computer modeling techniques are used to predict the effects of ventilation changes and improvements. Improvements are then prioritized to achieve the largest efficiency increases first. Actual real time assessment of the mine environment and ventilation changes are accomplished with a mine wide monitoring computer system. The Deer Creek ventilation improvement program has more than doubled the ventilating efficiency of the mine.

Jan 1, 1990

By Robert D. Schmidt

The Cyprus Casa Grande Corporation has provided Bureau of Mines researchers with an opportunity to investigate the hydrology of leaching an in place copper ore deposit. Hydrologic investigations of underground in situ copper leaching are being jointly conducted under a cooperative agreement. The hydrologic concerns of leaching operations at the Casa Grande mine focus on maintaining adequate solution injection and recovery rates, and on distributing the injected leach solution effectively within the ore deposit. Hydrologic considerations underlying these concerns relate to the permeability of the oxide ore zone during leaching, the unsaturated condition of the deposit prior to leaching, and the constraints imposed on in situ hydrologic design by the underground mine setting. The investigation involves monitoring of flow and pressure conditions in 58 injection and recovery wells, estimating permeability conditions using a hydrologic model, and on-site testing of hydrodilation and airlift pumping. Transient, fracture-controlled permeability is determined to be the dominant hydrologic consideration. A statistical modeling procedure has been developed for estimating changes in permeability during leaching. Flexibility in well design and operation is essential for accommodating the changes in fracture permeability that occur during leaching.

Jan 1, 1990

By Kenneth J. Reid, Marian S. Stachowicz

A preliminary evaluation of a new in-stream particle size analyzer has been carried out using materials obtained from a taconite plant in Northern Minnesota. Results are reported for bench scale, pilot scale and full scale tests, the latter being carried out in a taconite plant concentrator. The unit employs a novel scanning laser microscopy principle and details of the equipment configuration and operating principles are presented and discussed. Data acquisition is via an eight channel digital electronic system and particle counts are collected on the basis of reflected light pulse time intervals which are a direct measure of particle size. Output is available as an eight point individual or cumulative size distribution or as computed averages. The practical aspects of sample point location and flow requirements for reproducible results are outlined and discussed.

Jan 1, 1990