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

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

Heavy minerals in Alaskan beach sand deposits

Beach sand deposits along Alaska's shoreline have been prospected and worked for their precious metal content since the time of Russian occupation. Areas such as the Nome Beaches of the Seward Peninsula have been very productive, and in recent years exploration has proceded to include off shore extensions of these deposits. Evaluation of associated heavy mineral contents of these deposits, however, have been cursory and in most cases neglected entirely. In view of the thousands of miles of Alaskan coastline with known mineral provinces on adjacent land; much information is needed concerning the origin of mineral constituents, evaluation of past and present beach deposits and possibilities of off shore extensions of tho continental shelf. This report is concerned with samples of beach sand material submitted to the Mineral Industry Research Laboratory by individuals. These samples, taken from various locations, cannot be viewed as programs designed to delineate reserves from the respective areas. They should be considered as reconnaissance samples to indicate the mineral constituents present and the need for more comprehensive evaluation. Systematic and complete evaluation of all mineral constituents, including precious materials, is a major undertaking because of the erratic nature of the deposits. Special studies are required concerning sampling techniques, mining methods, recovery systems and marketing procedures. It is, therefore, beyond the financial capabilities of most individuals and requires the involvement of government agencies or corporations to obtain the necessary data to determine economic feasibility

Conference on Alaskan placer mining, focus: gold recovery systems

Alaska Miners' Association and the School of Mineral Industry, University of Alaska, Fairbanks conference proceedings of the Alaskan Placer Mining conference on Gold Recovery Systems

Placer mining in Alaska II

During July, August and September, 1979, a team from the Mineral Industry Research Laboratory visited a number of placer mining districts that could be reached by automobile, hence at a reasonable cost for transportation. These districts yielded varying amounts of information that will be of value to the industry. The district visited were: 1. Fairbanks, 2. Circle (Birch Creak), 3. Livengood (Tolovana), 4. Manley Hot Springs, 5. Fortymile, 6. Klondike, 7. Kantishna, 8. Yentna.University of Alaska Mining and Mineral Resources Research Institute.Placer mining in Alaska II -- Selected references -- List of figures

The prevalence and impact of Fusarium Head Blight pathogens and mycotoxins on malting barley quality in UK

Fusarium head blight (FHB) caused by Fusarium and Microdochium species can significantly affect the yield of barley grain as well as the quality and safety of malt and beer. The present study provides new knowledge on the impacts of the FHB pathogen complex on the malting and brewing quality parameters of naturally infected barley. Quantitative real-time PCR and liquid chromatography double mass spectrometry were used to quantify the predominant FHB pathogens and Fusarium mycotoxins, respectively, in commercially grown UK malting barley samples collected between 2007 and 2011. The predominant Fusarium species identified across the years were F. poae, F. tricinctum and F. avenaceum. Microdochium majus was the predominant Microdochium species in 2007, 2008, 2010 and 2011 whilst Microdochium nivale predominated in 2009. Deoxynivalenol and zearalenone quantified in samples collected between 2007 and 2009 were associated with F. graminearum and F. culmorum, whilst HT-2 and T-2, and nivalenol in samples collected between 2010 and 2011 correlated positively with F. langsethiae and F. poae, respectively. Analysis of the regional distribution and yearly variation in samples from 2010 to 2011 showed significant differences in the composition of the FHB species complex. In most regions (Scotland, the South and North of England) the harvest in 2010 had higher concentrations of Fusarium spp. than in 2011, although no significant difference was observed in the Midlands between the two years. Microdochium DNA was significantly higher in 2011 and in the North of England and Scotland compared to the South or Midlands regions. Pathogens of the FHB complex impacted negatively on grain yield and quality parameters. Thousand grain weight of malting barley was affected significantly by M. nivale and M. majus whilst specific weight correlated negatively with F. avenaceum and F. graminearum. To determine the impact of sub-acute infections of the identified Fusarium and Microdochium species on malting and brewing quality of naturally infected samples, selected malting barley cultivars (Optic, Quench and Tipple) were micromalted and subjected to malt and wort analysis of key quality parameters. F. poae and M. nivale decreased germinative energy and increased water sensitivity of barley. The fungal biomass of F. poae and F. langsethiae correlated with increased wort free amino nitrogen and with decreased extract of malt. DNA of M. nivale correlated with increased malt friability as well as decreased wort filtration volume. The findings of this study indicate that the impact of species such as the newly emerging F. langsethiae, as well as F. poae and the two non-toxigenic Microdochium species should be considered when evaluating the quality of malting barley. © 2014

Validation of Observed Bedload Transport Pathways Using Morphodynamic Modeling

Phenomena related to braiding, including local scour and fill, channel bar development, migration and avulsion, make numerical morphodynamic modeling of braided rivers challenging. This paper investigates the performance of a Delft3D model, in a 2D depth-averaged formulation, to simulate the morphodynamics of an anabranch of the Rees River (New Zealand). Model performance is evaluated using data from field surveys collected on the falling limb of a major high flow, and using several sediment transport formulas. Initial model results suggest that there is generally good agreement between observed and modeled bed levels. However, some discrepancies in the bed level estimations were noticed, leading to bed level, water depth and water velocity estimation errors

Selection of pasture species for groundcover suited to shade in mature macadamia orchards in subtropical Australia

Soil erosion is a significant problem in subtropical macadamia orchards in Australia, especially when groundcover vegetation is shaded out under older orchards. The aim of this study was to identify suitable low-growing, perennial groundcovers that would persist in the low light conditions under mature macadamias. Twenty-six legume and grass accessions and 1 herb were evaluated in small plots in a 16-year-old commercial orchard near Lismore, NSW. Plant density, groundcover (%), herbage mass, sward canopy height and groundcover spread were determined in high, medium and low light in the interrow for 2 years (1996–97). Groundcover was also measured for 3 years, on 19 of the accessions in a younger orchard at another site. Dactyloctenium australe provided the best groundcover in both high and low light and met most other specifications for an ideal groundcover for macadamias. Other promising grass species included Paspalum mandiocanum, Panicum laxum and Microlaena stipoides cv. Wakefield. However, Paspalum mandiocanum has been cited as having potential weediness in subtropical Australia, and is not recommended as a groundcover for macadamias. The legumes generally did not perform as well in low light as grass species. However, Arachis pintoi cv. Amarillo and a sterile Arachis pintoi × Arachis repens hybrid provided highest percent groundcover in high and medium light. Further assessment of these species in larger plots to determine their establishment and persistence under heavy orchard traffic and suitability for mechanical harvest operations has commenced

Near optimal configurations in mean field disordered systems

We present a general technique to compute how the energy of a configuration varies as a function of its overlap with the ground state in the case of optimization problems. Our approach is based on a generalization of the cavity method to a system interacting with its ground state. With this technique we study the random matching problem as well as the mean field diluted spin glass. As a byproduct of this approach we calculate the de Almeida-Thouless transition line of the spin glass on a fixed connectivity random graph.Comment: 13 pages, 7 figure