• Applicability of siberian placer mining technology to Alaska

      Skudrzyk, F.J.; Barker, J.C.; Walsh, D.E.; MacDonald, Rocky (University of Alaska Mineral Industry Research Laboratory, 1991)
      The result of Perestroyka and Glasnost has been an awakening of potential for cooperation between East and West. Nowhere has that been better demonstrated than between Alaska and Magadan Province, USSR. This report summarizes a one year effort financed by ASTF, with participation from several technical organizations, to establish contacts with the Siberian placer mining industry. The purpose of the project was to provide initial assessment of the Soviet technology for placer mining in permafrost. A ten day trip to Magadan province by an ASTF team and a similar length visit to Alaska by the Soviet mining group representing the All Union Scientific and Research Institute of Gold and Rare Metals, (VNII-I), Magadan are described. The report also reviews translated data on mining in permafrost and describes surface and underground placer mining technology developed by the Soviets. The report also lists relevant publications on Soviet mining research and state of the art Soviet mining technology and expertise.
    • Characterization and washability studies of raw coal from the Little Tonzona Field, Alaska

      Rao, P.D.; Walsh, D.E.; Phillips, N.; Charlie, K.G. (University of Alaska Mineral Industry Research Laboratory, 1991)
      Coal occurs in an isolated exposure of Tertiary, non-marine sedimentary rocks along the southwest bank of the Little Tonzona River, near Farewell, Alaska. The Little Tonzona River coal field is located approximately 150 air miles northwest of Anchorage, Alaska, and 210 air miles southwest of Fairbanks, Alaska; near the boundaries of Denali National Park. The Alaska Railroad and the Parks Highway are approximately 100 air miles from the coal field at their nearest point. The village of McGrath, on the Kuskokwim River, is located approximately 90 miles to the west (1). An impressive outcrop of coal-bearing Tertiary sediments is exposed for a distance of more than 275 feet on the west bank of the Little Tonzona River (Figure 1). More than seven coal beds, ranging in thickness from 3 feet ta 30 feet, with a cumulative thickness of over 134 feet, are interbedded with clay beds up to 40 feet thick. The clays are fine textured, extremely plastic, light grey to nearly white bentonites andlor tonsteins. Doyon Ltd., an ANSCA Native Corporation, holds land selections covering the inferred limits of the coal field. During 1980 and 1981, Doyon entered into exploration agreements with McIntyre Mines Inc. of Nevada. The two season exploration program took place from June 1,1980 through August 22,1980 and from May 27,1981 through August 22, 1981. During the 1980 field season, geologic mapping, prospecting, stratigraphy, trenching and bulk sampling of all coal outcrops were performed. This produced a total of 34 samples, which were taken for analysis. In 1981, six diamond drill holes with a cumulative length of 2,935 feet were completed. Core recovery was close to 90%, and a total of 147 coal samples, which represented 802.8 cumulative feet of coal, were taken for analysis. The exploration program confirmed a strike length of over 3 miles to the southwest from the main river bank exposure. Northward extension is unknown at this time. Although outcrop exposure is poor away from the river banks, burnout zones resulting from past coal bed fires form a resistant, recognizable on strike feature in the relatively unindurated Tertialy sequence. The appearance of these burnout zones along strike is often the only surface indication of the buried coal-bearing strata. Well preserved plant fossil impressions in the baked clays date the deposit as probable Miocene (2). Coal characterization and washability studies were performed on all coal samples by the Mineral Industry Research Laboratory of the University of Alaska Fairbanks. This work was conducted under the direction of Dr. P.D. Rao, Professor of Coal Technology.
    • Characterization of coal products from high temperature processing of Usibelli low-rank coals

      Rao, P.D.; Walsh, D.E.; Wilson, W.; Li, YuFu (University of Alaska Mineral Industry Research Laboratory, 1991)
      This research project was conducted in association with Gilbert/Commonwealth Inc. as part of an overall techno-economic assessment of high temperature drying of low-rank coals. This report discusses the characteristics of the dried/pyrolyzed products of two high temperature, evaporative processes and the dried product from a hydrothermal process. The long term goal of this and other coal drying studies conducted at MIRL, was to define drying technologies that have significant and real potential to competitively move Alaska's, low-rank coals (LRCs) into the export, steam coal market of the Pacific Rim. In 1990, Japan imported 33 million metric tons (mt) of steam coal with an additional 39 million mt imported by other Far East nations(2). Australia dominates the export steam coal market to these Pacific Rim countries and exported 48 million mt in 1990 and an additional 61 million mt of metallurgical coal(2). The worldwide steam coal export market has been expanding rapidly, from 20 million mt in 1973 to 150 million mt in 1989, and is expected to double to nearly 300 million mt by the end of the century(3). Could Alaska capture only 3% of the projected new world steam coal market, which is not an unreasonable expectation, the value of the state's coal exports would soar from nominally $28 million per year to over $100 million per year. However, without development of economical methods for drying/stabilizing Alaskan LRCs, the only increase in export of Alaskan coals may be from the few "higher rank" coals within a "reasonable" transport range of the existing Alaska rail system or tidewater. Presently the coal from the Usibelli Coal Mine is the only low-rank coal exported internationally as a steam coal; primarily for its blending properties with other coal to improve combustion. But for Alaskan low-rank coals to truly stand on their own merits, economical drying processes must be developed that produce a physically and chemically stable dried product. The technologies that have the most potential for increasing the use of Alaskan coals are those that can reduce the moisture content of these coals economically, and produce a fuel that is accepted in the international market place. Drying technologies will no doubt differ, depending on the end use of the fuel; be it dried lump coal, briquettes or pellets for pulverized coal or stoker applications, or concentrated coal-water fuels made from hot water dried LRCs. There are a number of developing processes that may work with Alaskan coals. Some drying processes, however, have been plagued by the production of excessive amounts of coal fines, Since the demand for Alaskan coal is currently limited to lump size coal, large quantities of fines are a definite liability. In this study, two high temperature drying/pyrolysis processes and one hydrothermal process were investigated. The high temperature drying/pyrolysis processes were conducted at (1) the Western Research Institute, (WRI) an affiliate of the University of Wyoming Research Corporation, Laramie, WY, and (2) Coal Technology Corporation (CTC) of Brisol, VA. Hydrothermal processing was conducted at MIRL, University of Alaska Fairbanks. A summary of these processes and the products they produced follows.
    • Deadfall Syncline coal, quality and reserves

      Callahan, J.E.; Rao, P.D.; Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1992)
      PRESENT INVESTIGATION The purpose of the 1991 drilling program was twofold: 1. To evaluate the coal reserves in a previously identified thick coal in an area of low structural dips and dip-slope topography near the axial plunge of the west extension of the Deadfall Syncline, primarily for surface mining, and to determine the feasibility of mining additional beds in conjunction with the thick coal. (For the purposes of this investigation, this coal is designated K3 as explained below), 2. To examine a continuous and unbroken stratigraphic interval of the Corwin formation in the northeastern part of the Deadfall Syncline as an initial step toward evaluation of the whole basin. This was accomplished by drilling overlapping holes aligned generally parallel to the dip direction, and spaced in accordance with the magnitude of dip and depth capacity of the drill. About 720 feet of stratigraphic section were covered in this way. A total of fourteen exploratory holes were drilled, ranging from 116 to 426 feet in depth (Figure 2). The drill was a Mobil B-60 mounted on a Nodwell tracked vehicle. Circulation was provided by a large compressor mounted on another Nodwell. Most of the footage was drilled with an air hammer, which provided a significant improvement in drilling rates over conventional rotary drilling. Lithology of cuttings from all holes was logged continuously, and composite grab samples from each 5 or 10 foot interval were taken. Coal cuttings were collected on a (relatively) clean plastic sheet, and promptly double bagged in plastic to minimize loss of bed moisture. Cores were taken from the K3 coal at 3 drill hole locations, and the underlying K4 coal was also cored at one of these 3 holes. A comparison of core length to geophysical logs indicates essentially 100% recovery for all cores. All samples, including rock cuttings, were shipped to the Mineral Industry Research Laboratory (MIRL), University of Alaska Fairbanks, for analyses and/or storage. All holes were logged with a Gearhart-Owen GeoLogger using natural garmna and gammagamma density tools. The log response with these tools for coals is distinct and unambiguous, particularly that of the density log, and the resolution is sufficient to estimate bed thickness to within 3 to 4 inches (Figures 8 and 9).
    • Elutriator design manual for coarse heavy mineral recovery from sluice box concentrate

      Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1991)
      This manual addresses the design and fabrication of an elutriation system for the separation of coarse heavy minerals from waste rock. Elutriation is a process for separating a mixture of minerals into two or more products and utilizes the difference in settling velocity between particles to effect this separation. An upward flow of water runs countercurrent to the material flow in a hollow elutriation column. Particle separation is affected by particle density, size and shape and the upward water velocity. It was felt that the design and demonstration of a low cost, functional and efficient unit for the concentration of coarse, heavy minerals would be of benefit to the placer mining industry. Industrial efficiency can be improved by the additional recovery of byproduct heavy minerals with market potential. Elutriation provides an inexpensive method for processing +1/4 inch, sluice box concentrate to recover by-product heavy minerals. Elutriator design emphasized the use of materials which are inexpensive and readily available to the average placer gold mining company. The design also incorporated concentrate storage and shipment functionality into a detachable section of the elutriator. Design is based on the construction of a prototype unit and testing of the unit for coarse cassiterite (Sn02) recovery efficiency. Laboratory testing utilized 3/4" x 3/16" sluice box concentrate from Shoreham Resources Ltd's Cache Creek Mine, Tofty, Alaska. Following laboratory testing, the elutriator was field tested on-site in September, 1990. Both laboratory and field testing were highly successful. The elutriator proved to be a simple, robust concentrator for this application and produced tin recoveries and grades in excess of 99% and 55% respectively. Field feed grades to the elutriation unit were approximately 26% tin.
    • Evaluation of the four inch compound water cyclone as a gold concentrator using radiotracer techniques

      Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1985)
      A 4 inch compound water cyclone, CWC, was tested to evaluate its gold recovery characteristics when processing minus 3/16 inch, run-of-pit, placer material. Neutron activated placer gold particles (841 to 37 microns) were used as radiotracers concentrator recovery; a procedure believed unique to this study. The effect on gold recovery of gold size and shape, feed pulp density, feed pressure, vortex finder clearance (VFC), CWC cone type, top-size of the feed solids, presence or absence of heavy minerals in the feed, and the quantity of -400 mesh slimes in the feed was investigated in over 300 tests. CWC concentration ratio and the top-size of the underflow solids were both affected by cone type, VFC, and feed pressure. Gold recovery was significantly affected by gold size, gold shape, and concentration ratio. These effects are complex, since significant size-concentration ratio and size-shape interactions exist. Radiotracer techniques showed gold particles had a residence time within the CWC of approximately one second, thus challenging the three stage, segregated bed theory of CWC concentration. This work suggests CWC gold recovery is a function of particle size and shape, and the water flow rate through the CWC. "Bed density" is considered important only as a thin, protective layer, which shields coarser gold particles from the entraining currents and facilitates their movement through the CWC.
    • Focus on Alaska's coal '93 - proceedings of the conference

      Rao, P.D.; Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1994)
      This volume contains 20 of the 28 papers presented at the two-day conference, "Focus on Alaska's Coal '93," held in Anchorage at the Hotel Captain Cook on May 5-7; 1993. "Focus on Alaska's Coal '93" is the fourth in a series of conferences. "Focus on Alaska's Coal 1975" and "Focus on Alaska's Coal 1980" were held in Fairbanks, and "Focus on Alaska's Coal '86" was held in Anchorage. Their proceedings have been published.
    • Sixth annual conference on alaskan placer mining

      Walsh, D.E.; Wray, Susan (University of Alaska Mineral Industry Research Laboratory, 1984)
      An abridged format of papers, presentations and addresses given during the 1984 conference held on March 28-29, 1984, compiled and edited by Daniel E. Walsh and M. Susan Wray.
    • Study of a static screen, jig, spiral, and a compound water cyclone in a placer gold recovery plant

      Walsh, D.E.; Rao, P.D.; Cook, D.J. (University of Alaska Mineral Industry Research Laboratory, 1987)
      During the 1986 mining season both laboratory and field test work were conducted to study the performance efficiencies of a wedge-wire static screen, a Pan-American jig, a Reichert Mark VII spiral, and a 12" compound water cyclone. This work was conducted at EVECO, Inc.'s placer gold operations near Fox, Alaska, and funded by the State of Alaska Department of Natural Resources. The Mineral Industry Research Laboratory of the University of Alaska-Fairbanks perfomed the test work.
    • A study of factors suspected of influencing the settling velocity of fine gold particles

      Walsh, D.E. (University of Alaska Mineral Industry Research Laboratory, 1988)
      In this study, the authors used a radiotracer detection system coupled to a frequency counter and the radioisotope, lmAu, to investigate the effect of several variables on the terminal settling velocity of gold particles. The settling velocities of 35 manufactured gold particles (97 mg to 0.03 pg) were determined in order to produce working gold settling velocity vs. size-shape graphs for practical engineering application. Additionally, eight gold spheres were progressively flattened through 3 stages. At each flatness stage their settling velocity was determined. This highlighted the effect on settling velocity of decreasing shape factor for particles of constant mass (97 mg to 0.6 pg). The settling velocities of natural gold particles were also determined and compared to those of the corresponding manufactured particles. Finally, a generalized randomized block design was generated to explore the effects of three variables on the settling velocity of gold grains. The design was to be blocked according to gold size-shape combinations. The three variables (factors) studied were water temperature, clay concentration in the fluid, and the clay mineralogy of the suspended clays. This design was analyzed using a fixed effects analysis of variance model. The analyses show that all three factors had a significant (p < 0.001) influence on the settling velocity of gold particles. The data suggest that the clay mineralogy (viscosifying properties) of suspensions is perhaps the most influential parameter with respect to settling velocity determination.