Distribution of certain minor elements in Alaskan coals

Seventy-five samples of coal from Northern Alaska, Jarvis Creek, Nenana, Matanuska, Kenai and Bering River Coal Fields were analyzed by quantitative spectrochemical procedures f o r lead, gallium, copper, barium, beryllium, nickel, titanium, vanadium, zirconium, cobalt, chromium, germanium, and tin. Other elements, of significance, identified from the spectrograms were, gold and silver identified in certain Nenana coals and silver in coals from Chickaloon in the Matanuska field, in concentrations up to several parts per million of coal ash. Forty-one of the above samples were sink-floated to study the distribution of minor elements between the organic and inorganic phases of the coals. Relative affinities of the minor of the minor elements to the organic matter in the coal is discussed

Thermogravimetric and distillation studies on mercury, antimony and arsenic sulfides

Thermogravimetric studies were made on naturally occurring sulfides of mercury, antimony and arsenic to determine activation energies and Arrhenius rates of reaction in vacuum and in atmospheres of air and nitrogen. Of the three sulfides only antimony showed an appreciable change in rate of reaction for the different test conditions. Distillation results on three flotation concentrates from Alaska mining operations showed that cinnabar (mercury sulfide) could be distilled in a closed system, with over 99 percent recovery of the mercury as metal when the sulfur was reacted with iron. Over 98 percent mercury recovery was obtained from a cinnabar-stibnite (antimony sulfide) concentrate, with less than 1 percent of the antimony distilled from the furnace charge. Cinnabarrealgar-orpiment (arsenic sulfides) could not be separated by distillation and large quantities of soot (condenser residue) formed with the metallic mercury in the condenser

Hydrometallurgy of the delta sulfide ores, second stage report

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.Submitted to: Nerco Minerals Compan

Characterization and evaluation of washability of Alaskan coals

This report is a result of the second part of a continuing study to obtain washability data for Alaskan coals to supplement the efforts of the U.S. Department of Energy in their ongoing studies on washability of U.S. coals.Contract No. U.S.D.O.E. ET-78-G-01-8969 (formerly U.S.B.M. G0166212

Ferric chloride leaching of the Delta sulfide ores and gold extraction from the leaching residue

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

Distribution, analysis, and recovery of fine gold from alluvial deposits

The United States Bureau of Mines, in its Heavy Metals Program, desired to have research performed to determine the size-frequency distribution and possible economic value of gold particles in the fine size ranges of Alaskan placer deposits. Primary interest was involved in obtaining evidence of the occurrence of fine gold and to determine the ameanability of standard sampling and production methods in the evaluation and recovery processes. A research contract between the United States Bureau of Mines and the University of Alaska was initiated in June, 1968 as the first phase of this investigation, but was subsequently modified in June, 1969 to include beneficiation processes amenable to recovery as well as evaluation methods for fine and flakey gold. In searching the literature relative to fine gold in Alaskan placer deposits, it was found that virtually no research has been devoted to determining the extent of fine gold distribution and its effect on evaluation and subsequent recovery methods. Standard evaluation techniques have relied on gravity methods of concentration and recovery of the visible gold from the concentrate. In general, this has proved satisfactory in that operational recovery methods used were probably not conducive to retaining gold particles of less than 100 mesh in size. Operators have made no attempt to obtain a size analysis of gold in a head sample, but many have kept records of the size distribution of the gold as actually recovered. A review of these records, from selected areas, indicates that the -100 mesh gold represents from 0 to 5% of the total gold recovered. Although figures of this type may point to a probably fine gold loss, the difficulties inherent in evaluating the tailng material or modifying the recovery system have usually discouraged efforts in this direction.This study was made possible by the Financial support of the United States Bureau of Mines through Research Contract No. HOl81009 with the University of Alaska

Current state-of-the-art in drying low-rank coals

Preparing Alaska's coal for marketing -- Drying low-rank coals -- Effect of lignite source -- Acknowledgement -- References.Research on drying of low-rank coals, such as lignites and subbituminous coals, has been conducted for nearly half a century. Although partial drying of Dakota lignite is practiced for freeze-proofing by mixing partially dried coal with run-of-mine coal, full scale drying of low rank coals has never been practiced commercially in this country. The reasons are: ( 1 ) drying of low rank coals by conventional methods results in severe degradation of coal particles; (2) dried coals are thus dusty and difficult to handle; (3) reabsorption of moisture in storage and transit defeats the drying process. In addition the dry coal particles will react with ambient oxygen, and heat up enough to ignite. It appears that large-scale development of Alaskan coals may have to await solutions to these problems. Our Mineral Industry Research Laboratory at the University of Alaska is making a comprehensive literature search seeking solutions to these problems and identifying areas of research that should be undertaken

Study of a static screen, jig, spiral, and a compound water cyclone in a placer gold recovery plant

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.Funded by the State of Alaska Department of Natural Resources

Application of hydrocyclones for recovery of fine gold from placer material

Alaska and other gold areas have seen a sharp resurgence of placer mining in the last few years. Mines using sluice boxes usually recover gold down to 100 mesh, but recovery of gold finer than this size is a function of particle shape factor, sluice box design and operating parameters. It is felt that a concentrating device is needed to recover gold finer than 100 mesh that may not be recoverable in a sluice box. The device should be capable of processing a large volume of water and solids discharged from the sluice-box. Compound water cyclones, successfully used in the coal processing industry, seem to offer solutions. A system using these devices could recover a concentrate which would be one twenty fifth the size of the original solids in a two stage process. It is not intended to produce a finished product with cyclones, but to reduce bulk so that the reduced concentrate, free of slimes, could further be treated by flotation, gravity methods, or cyanidation to isolate the gold. This report addresses only the application of hydrocyclones for concentrating gold from placer material.Submitted to Mining and Mineral Resources Research Institute, Office of Surface Mining, U.S. Department of Interior, Washington, D.C. Grant No. G519400

Application of palynological techniques for correlation of coal seams in the Lower Lignite Creek area, Nenana Coal Field

This study concerns spores and pollen in the coals of the lower Lignite Creek area in the Nenana Coal Field, which is operated by Usibelli Mining Company. The seams studied are part of the Suntrana Formation which contains a large portion of the coal reserves of Nenana coal. These coals are mid-Miocene in age and are separated from each other by cyclic sandstone, clay and silt deposits, which reflect alternating periods of coal forming swamps and depositing streams. A preliminary study of the mega and micro botanical fossils of this area was made in 1969 by Wolfe and Leopold (Wahrhaftig et al, 1969). Palynological investigation was done on 26 samples of the Suntrana Formation and evidence from this and fossil leaves indicate that the formation should be placed in the Seldovian stage.Introduction -- Sampling -- Maceration procedures -- Interpretation -- References -- Appendix