Sequentially numbered reports issued by the University of Alaska Mineral Industry Research Laboratory covering a wide range of research topics associated with mining, mineral, petroleum, and coal resources in Alaska and in the technology of exploration, development, extraction and processing of mineral resources in general and in the technologies of exploration, development, extraction, and processing of mineral resources in general.

Recent Submissions

  • 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).
  • 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.
  • 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.
  • Metallogeny of the Fairbanks Mining District, Alaska and adjacent areas

    Metz, P.A. (University of Alaska Mineral Industry Research Laboratory, 1991)
    The Fairbanks mining district encompasses an area of 1500 km2 (600 miles2) centred just north of the City of Fairbanks, Alaska. The district is one of six mining areas located in or near the northwestern margin of the Yukon-Tanana Uplands of east-central Alaska and the Yukon Territory, Canada. The six mining districts in Alaska (Fairbanks, Circle, Steese, Richardson, Tolovana and Kantishna) and the Klondike district nearby in the Yukon Territory, have an aggregate placer gold production of 25 million troy ounces. This production establishes the region as one of the largest gold producing areas of North America. The aim of the present investigation is to define, classify and explain the genesis of the several primary sources from which the placer gold deposits of the region were derived. Through geological mapping and sampling of the districts, the 350 identified primary mineral occurrences are classified into eight categories as follows: (1) metamorphosed volcanic-exhalative and associated low-sulfide Au-quartz veins, (2) Cu-Mo-Au porphyries, (3) precious metal enriched massive sulfides, (4) epithermal veins in plutonic rocks, (5) Au-bearing tungsten skarns, (6) Sn greisen-gold-quartz veins, (7) Sediment-hosted gold of the Carlin type, and (8) palaeoplacer gold deposits. Geological mapping and sampling has also established that recent faulting and regional uplift are responsible for stream capture, stream drainage reversal, resorting of stream sediments, and modem alluvial placer formation. The volcanic-exhalative mineralization is hosted in metamorphosed low-K tholeiitic basalts, Ca-poor rhyolitic tuffs, and cherts. In the Fairbanks district the rocks are informally referred to as the Cleary sequence. Detrital zircons from the sequence yield U-Pb ages in the ranges 1.2, 1.3- 1.4, 1.8-1.9,2.5, and 3.4 Ga. The bimodal volcanic rocks are enriched in Au, Ag, As, Sb, and W. Average gold contents of the rocks exceed average crustal abundances by two orders of magnitude. Locally the metavolcanic rocks contain base metal massive sulfide mineralization with grades up to 20% combined Pb-Zn, 3 g/tonne Au, and 500 g/tonne Ag. These metavolcanic rock are correlated with those occurring in the Kantishna district (Spruce Creek sequence) and in the Circle district (Bonanza Creek sequence). The mineralized bimodal metavolcanic suite is thus shown to extend along strike for 350 krn (210 miles) through the Yukon-Tanana Terrane. In the Fairbanks district the Cleary sequence rocks are thrust over Type C eclogites. These eclogites trend northeasterly along the regional strike to the Circle quadrangle and are correlated with the eclogites of the central Yukon Territory. Lead 206/204 and 207/204 ratios from galena from the metavolcanic sequences and from the vein deposits are similar with average values of 19.10 and 15.69 respectively. The eclogitic rocks are less radiogenic with 206/204 and 207/204 ratios of 18.80 and 15.65 respectively. Low sulfide Au-quartz veins within the metavolcanic sequences are shown to be the product of multiple thermal and deformational events in the terrane taking place at 160-185, 140-145, and 90-125 Ma, K-Ar. Studies of the fluid inclusions in the metamorphic and vein quartz demonstrate that fluid compositions (1-20 mole % CO2; 3-5 wt % NaCl equiv.) and homogenization temperatures (275-375°C) are closely similar. Gold contents of the vein systems range from 5 to 18 g/tonne. Calc-alkaline plutons of Cretaceous (85-1 10 Ma) and Tertiary (50-70 Ma) age K-Ar host epithermal veins, Sn-greisen, and W-skarn mineralization, all of which are demonstrably gold-bearing. Rb-Sr initial ratios for the mineralized composite plutons are greater than 0.71 1 indicating that anatexis of the lower crust was the source of the granitic magma. The Cu-Mo-Au porphyry mineralization is hosted in the Tertiary plutons that intrude lower Palaeozoic and Mesozoic sediments of the North American Continental Margin (NACM) in the Tolovana district. The NACM rocks are separated from the metavolcanic sequence by the eclogitic rocks and by major thrust faults. Paleoplacer Au deposits hosted in continental clastic rocks of Eocene to Pliocene age are described. These have formed in small grabens adjacent to major strike-slip faults bounding the Yukon-Tanana Terrane on the northeast and southwest respectively. These structures, the Tintina and Denali Faults, controlled sedimentation and placer formation in these grabens. Using compilations of tonnage/grade data from examples of primary deposits analogous to those identified in the Yukon-Tanana Terrane, it is shown that a single large-scale deposit of any of these types could have supplied all the gold contained in the placer deposits of the region.
  • 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.
  • Coal in Alaska requirements to enhance environmentally sound use in both domestic and Pacific Rim markets

    Wilson, W.G.; Irwin, W.; Sims, John; Rao, P.D.; Noll, Bill (University of Alaska Mineral Industry Research Laboratory, 1990)
    This document originates from three meetings held in 1989 with the leaders of the Alaskan Coal Industry and coal technologists from the U.S. Department of Energy (DOE)~ Mineral Industry Research Laboratory (MIRL) and Geophysical Institute - University of Alaska Fairbanks, the Alaska Department of Natural Resources, the Alaska Science and Technology Commission, several of the Alaska Native Corporations, and a number of coal experts from private industries. The information included is intended to illustrate the vast resource base and quality of Alaskan coals, show the projected size of the Pacific Rim steam coal market, discuss policy changes necessary to facilitate the development of an expanded coal industry, and describe the technology development needs for Alaskan coals to compete in the world market. It is aimed at increasing the general knowledge about the potential of coal in Alaska and providing data for use in marketing the resource.
  • Chemical characterization of liquefaction products of an inertinite enriched northern Alaska coals

    Mayasandra, Venugopal (University of Alaska Mineral Industry Research Laboratory, 1989)
    A Northern Alaskan coal rich in inertinites was further enriched by density gradient separations. The degree of condensation of the enriched coal was estimated to be low, mainly 3 ring. The reactivity of the inertinite enriched coal was determined by comparing yields from direct liquefaction with H2 at 0 and 30 minute residence times, 425°C, using an H-donor solvent in one case and moly-catalyst in the other with H2 pressures of 500 and 1000 psig respectively. Solid products were analyzed by Fourier Transform Infrared Spectroscopy while the hexane solubles were separated into various chemical classes, viz. alkanes, neutral polycyclic aromatic compounds, hydroxy polycyclic aromatic oxygen heterocycles, and secondary, tertiary amino polycyclic aromatic compounds. The chemical compounds in these fractions were further analyzed by gas chromatography - mass spectrometry (GC-MS)an dcapillary gas chromatography. This work confirmed earlier data showing that inertinites are not as determinental to liquefaction as previously thought.
  • Stratigraphy, petrology, and depositional environments of the Jarvis creek coalfield, Alaska

    Belowich, M. (University of Alaska Mineral Industry Research Laboratory, 1988)
    Jarvis Creek basin coals are subbituminous, low in ash, and increase upsection in moisture, most major oxides and trace elements, and vitrinite with subsequent liptinite and inertinite decreases. Sulfide mineral deposits east-southeast of the basin are responsible for the enrichment of the upper coals in sulfur and metals. Sandstones are quartzose, arkosic, and lithic in the lower, middle, and upper units respectively, and were derived from a recycled orogen provenance. Sediment transport was from the south at the base, shifting to an easterly source higher in the section. Deposition was by braided and meandering streams on mid and distal portions of alluvial fans. The lower and middle units are correlative with the Healy Creek Formation, while the upper unit probably correlates with the Lignite Creek Formation. Measured, indicated, and inferred coal reserves are 17, 37, and 227 million short tons respectively, mostly in the upper unit at shallow depths.
  • Ferric chloride leaching of the Delta sulfide ores and gold extraction from the leaching residue

    Lin, H.K.; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1988)
    Conventional differential and bulk flotation processes have difficulties in achieving high recoveries with acceptable grades far zinc, lead and copper from the complex sulfide ores found at Tok, Alaska. Furthermore, gold and silver, which account for a significant fraction of total value of the ores, are distributed evenly in the flotation tailings and concentrate. Therefore, processing both flotation tailings and concentrate would be necessary to obtain high recoveries of gold and silver. A mineralogical study revealed that the economic sulfide minerals are interstitially associated with a large preponderance of pyrite. The economic sulfide minerals are 10 to 40 microns in size. These mineralogical facts explain the difficulties encountered in the flotation process. A hydrometallurgical method involving ferric chloride leaching and subsequent steps to recover lead, zinc, silver and copper from the leach liquor has been studied at the Mineral Industry Research Laboratory, University of Alaska Fairbanks for the treatment of Delta ores. This alternative is attractive for processing complex sulfide ores which conventional flotation and smelting cannot handle. In addition, the liberation of sulfur in the environmentally acceptable elemental form, rather than as sulfur dioxide, may prove a major advantage of this hydrometallurgical method because of stringent environmental regulations.
  • Hydrometallurgy of the delta sulfide ores, second stage report

    Letowski, F.; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1987)
    This report contains results of the Fluidized-Bed Leaching (FBL) initially adapted to improve Leaching-Flotation processing of Delta ores in sulfate solution. The research carried out in the continuous laboratory installation show, however, that the new, 3-phase (solid-liquid-gaseous) reactor also performs satisfactorily in other leaching systems. A new process of pyritic matrix destruction for precious metals recovery in the FBL reactor, and a new process for recovery of zinc and other metals in a chloride system are proposed on the basis of laboratory results.
  • Hydrometallurgy of the delta sulfide ores, first stage report

    Letwoski, F.; Chous, Kuo-tung; Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1986)
    This report presents the results of hydrometallurgical research carried out from September 16, 1985 to June 30, 1986 on metals recovery from complex sulfide ores from the Delta deposit near Tok, Alaska. The leaching characteristics performed for 6 different ore samples indicate that the most valuable components form the following order: Zn > Au > Pb > Ag > Cu > So. Further study demonstrates that direct leaching of the ore is effective both in chloride as well as in sulfate oxidizing solutions coupled with separating of leached solid components by flotation. Three variants of the ore processing with ferric chloride or fenic sulfate leaching are analyzed: one flowsheet with direct ore leaching in ferric chloride solution followed by leaching-flotation step, with subsequent zinc separation in a solvent extraction step and electrolysis in chloride solution; and two flowsheets of direct ore leaching with ferric sulfate solution followed by a leaching-flotation step, with zinc sulfate electrolysis and other metals recovery in chloride leaching sreps. In two last flowsheets silver is recovered during the chloride leaching steps and gold h m flotation products during the cyanide leaching. Preliminary economic and technical evaluation is presented. The engineering study on apparatus for the fast leaching- flotation processing and on better accumulation of gold and silver in one semi-product are concluded for the next year of research.
  • Hydrometallurgy of complex sulfide ores, process development

    Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1988)
    In 1984, Nerco Minerals Co. signed a cooperative agreement with the University of Alaska to conduct hydrometallurgical research. The principle objective of the agreement was to conduct bench scale research to study the problems of leaching the sulfide ore and the recovery of its valuable metals. Nerco has provided funding on an annual basis. Information contained in this publication is a result of this research.
  • The combined use of a sand screw, hydrocyclones, and gel-logs to treat placer mine process water

    Chuang, YeKang (University of Alaska Mineral Industry Research Laboratory, 1988)
    This study describes a low-maintenance tailings treatment system for placer mines. A sand screw and two 20 inch hydrocyclones were used to remove gravel, sand and silt from a sluice box discharge. Gel-logs were introduced subsequent to the main settling pond to reduce the suspended solids. Results drawn from a two year study at a placer mine in interior Alaska indicated that: (1) Most of the plus 50 mm particles can be removed from the sluice tailings by the combination of a sand screw and 20 inch hydrocyclones, (2) When using the hydrocyclone overflow, without further cleaning, in recycle operation, the performance of the sand screw and hydrocyclones change due to the build up of fine particles. (3) In laboratory testing cationic type gel-logs proved to be effective in reducing the turbidity of settling pond water from 4,000 NTU to 80 NTU. However, at the mine this test result could not be duplicated even though 14 logs were applied to treat 25% (c 500gpm) of the pond overflow. The cost of installation and operation of the sand screw and hydrocyclone system was about 11% of the total operational cost of the mine in 1986.
  • Using polyethylene as a coagulant for reducing turbidity from placer mining discharge

    Fan, Ray-Her (University of Alaska Mineral Industry Research Laboratory, 1987)
    Placer gold mining locations on Gilmore and Crooked Creeks in the Fairbanks and Central/Circle, Alaska areas, respectively, were chosen as study sites for evaluation of a unique water treatment process. The physical and chemical impacts on water quality by placer mining were investigated by measuring the pH value, turbidity, and solids content of the slurry samples. Sedimentation tests, zeta potential measurements, and particle size distribution analyses were conducted as well. Also analyzed were mineralogical and chemical composition of the suspended ultrafine particles. Flocculation tests using polyethylene oxide (PEO) with adjunct additives were conducted in the laboratory. Variable parameters such as mixing speed and time, reagent dosages, pH values, as well as synergistic factors were studied. Economic factors and chemical consumption were evaluated and a field treatment plant was designed and proposed.
  • The use of flocculants to control turbidity in placer mining effluents

    Shen, Yun-Hwei (University of Alaska Mineral Industry Research Laboratory, 1987)
    In this study, two placer mine discharge waters of different characteristics were tested in order to determine the applicability of organic polymer flocculants to achieve reduced levels of turbidity. The water samples from both mines were characterized both as to their chemical and physical properties. The jar test was employed to establish the optimum operation conditions of the flocculation process. The best results were obtained employing a cationic polymer Superfloc 340 produced by American Cyanamid Company. The optimum dosage for water samples from both mines were 15 ppm and 40 ppm respectively. Optimum agitation time was within the range of 3 to 9 minutes depending on the agitation rate and the pulp density of water sample. The utilization of settling ponds, in conjunction with flocculation is believed to be a practical method to control the turbidity level of placer mine discharge water.
  • Oxygen application to chloride leaching of complex sulfide ores

    Chou, Kuo Tung (University of Alaska Mineral Industry Research Laboratory, 1987)
    The study investigates leaching of complex sulfide ores with simultaneous regeneration of the leaching solution and removal of dissolved iron to balance the iron concentration in the leaching process. To minimize environmental pollution and obtain high metal extraction from the ores, leaching with a ferric chloride solution is adapted to treat Delta sulfide ores. The experimental results indicate that under high oxygen pressure leaching, oxidation of ferrous ion to ferric ion and partial precipitation of iron from solution can occur simultaneously. However, the findings also indicate that leaching the ores with simultaneous iron precipitation in one operation is difficult. It is better to precipitate excess iron in one stage; then leach the ores in another stage using the regenerated leaching solution.
  • 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.
  • Characterization and evaluation of washability of Alaskan coals - fifty selected seams from various coal fields

    Rao, P.D. (University of Alaska Mineral Industry Research Laboratory, 1986)
    FINAL TECHNICAL REPORT: September 30,1976 to February 28,1986
  • Geology of a subarctic, tin-bearing batholith - Circle Hot Springs, Alaska

    Wilkinson, Kathy (University of Alaska Mineral Industry Research Laboratory, 1987)
    A small batholith (56mi2) outcrops approximately 94 miles northeast of Fairbanks. It occurs in a historically rich area for placer gold. Additionally, placer tin has been recorded in the creeks that flow through or adjacent to the batholith.

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