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By Joni M. Barnes

A strain of Pseudomonas stutzeri isohted from selenium contaminated surface waters, was found to be effective . in reducing selenate (Se04 2) stoichiometrically to selenite (Se03 2 '), which was further reduced to elementaJ selenium (Se0 ). These reactions were concurrent with the microbial oxidation of lactate. In order to assess quantitatively the amounts of seilenate and selenitein solution, improvements to existing analytical methods (ion exchange chromatography and inductively coupled plasma atomic emission spectrophotometry technique) .were made.

Jan 1, 1991

By Donna M. Noel

Bacterial strains have been cultivated from solids previously exposed to cyanide that will tolerate 300 ppm sodium cyanide under anaerobic conditions. In selected solid samples, these bacteria have been shown to reduce the level of cyanide from approximately 300 ppm to essentially zero in about 50 days under anaerobic conditions. Various media were investigated, and the nutrients providing maximal growth were ?established .. Degradation of cyanide in sterilized solids was determined for comparison with degradation obtained in bioactive solids. All experiments were conducted at ambient temperature and initial pH of approximately 10.5.

Jan 1, 1991

By Z. Yang

The flotation behavior of the. green algae Chlorella vulgaris and a wild Chlamydomonas spp. was studied in the presence of Zn(II) using dodecylammonium chloride as collector. At about pH 6. both organisms readily float as amine concentration approaches lx10-3 kmol/m3. In addition, electrokinetic measurements were made on the organisms as a function of pH in both the presence and absence of Zn(II). It was found that the Zn(II) has a considerably greater effect on the zeta potential of C. vulgaris than on Chlamydomonas. Zn(II) adsorption studies also indicated that C. vulgaris is able to accumulate more Zn from solution than the Chlamydomonas.

Jan 1, 1991

By Michael L. Free

Bacterial oxidation of an arsenopyritic gold-ore .concentrate was carried out with continuous-flow .operation in 14-liter, mechanically agitated reactors. Samples from the slurry reactors were separated into solid and liquid fractions and analyzed separately to determine the electrochemical rates of sulfide conversion by the bacteria and the rates of direct bacterial oxidation of sulfide. The rates of the individual mechanisms are compared to the overall rates of biooxidation in the continuous-flow slurry reactors. The results show that the commonly hypothesize4 direct and indirect mechanisms of biooxidation both play a significant role in the bacterial oxidation of sulfide ores.

Jan 1, 1991

By C. I. Basilio

Pearson's hard and soft acid and base (HSAB) principle may be applied to flotation systems. The HSAB principle states that hard acids prefer to bond with hard bases and soft acids prefer to bond with soft bases. By determining the Drago E and C parameters for the different components of a flotation system, the HSAB principle could be used to explain the selectivity of some collectors such as thionocarbamates against some minerals. Determination of these parameters is done by utilizing Drago's theory and flow micro-calorimetry.

Jan 1, 1991

By V. Castranova, L. Wu, K. Van Dyke, J. Gutierrez, V. Vallayathan

Since it has been demonstrated that silica caused phagocytic cells to activate lipoxygenase metabolism of unsaturated fatty acids we thought selective inhibition of this metabolic pathway might be helpful in treatment of silicosis. It is known that lipoxygenase metabolism plays a role in the pathogenesis of a variety of inflammatory and hypersensitivity conditions. Further, it is believed that the alveolar phagocytic cells which engulf silica begin the inflammatory cycle which produces the metabolic products, cytokines and growth factors which causes fibrosis in the lung. There have been indications that drugs which inhibit lipoxygenase can inhibit fibrosis from other causes. Previously, we developed a method which detects the activity of lipoxygenase metabolism by measuring free radical oxidation via light production or chemiluminescence (CL). We decided to apply this method to phagocytic cells that would be found in the lung in the presence of silica with and without newly developed inhibitors of the lipoxygenase reaction. We used drugs which inhibit lipoxygenase directly including AA861 (TAKEDA), A63162 (Abbott), and an inhibitor that scavenges free radicals produced from the lipoxygenase reaction, nordihydroguairetic acid. In addition we used an indirect inhibitor, tetrandrine. We found drug inhibition of silica activated CL from alveolar macrophages, neutrophils and human leukemia (HL-60) cells differentiated with DMSO. Nordihydroguairetic acid 2x10-5M produced almost complete inhibition in all three cell types. In human leukemia cells (HL-60) A63162 and tetrandrine were equally inhibitory at 42% while in human neutrophils A63162 and tetrandrine were less active 22 and 10% respectively. In macrophages A63162 and AA861 were less than 50% inhibitory to cellular CL at 2xl0-5M. Direct assay of tetrandrine (2x10-5M) with sodium arachidonate and soybean lipoxygenase reveals no inhibition. All antilipoxygenase drugs regardless of mechanism were inhibitory to cellular chemiluminescence from all three types of phagocytic cells. These drugs alone or in mixtures could prove useful in treatment of silicosis.

Jan 1, 1991

The STATE MINERAL SUMMARIES publication provides estimated data and summaries of mineral activities at the State level for 1990. Most of the estimates are based on nine months data. These summaries have been prepared in cooperation with State geological surveys or related agencies. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State Activities field office.

Jan 1, 1991

By Susan Brink

The U.S. Bureau of Mines is investigating the potential of in situ leach mining a variety of Cu, Mn, and Au-Ag ores. Geologic characterization of ore samples from laboratory leaching experiments is conducted both prior to and after leaching to assess the effects of leaching on the chemistry, mineralogy, and texture of the rocks. The identification and chemical compositions of ore, gangue, and reaction products are determined by a combination of techniques such as reflected and transmitted light microscopy, X-ray diffraction, electron diffraction, electron microprobe analysis, and backscattered electron imaging with scanning electron microscopy. The distribution of the desired metal in various mineral phases can be illustrated using elemental X-ray maps. The potential of reactive gangue minerals to rob Cu from leach solutions is investigated with the aid of transmission electron microscopy. Porosity and permeability are measured to determine how effectively the host rock can transmit leach solution. Textural relationships between ore, gangue, secondary reaction products, and fluid channelways are determined by petrographic examination and are documented by optical photomicrographs and secondary electron imaging. Representative sample selection is described, and several epoxy impregnation and sample mounting techniques are discussed.

Jan 1, 1991

The value of processed materials of mineral origin was estimated to have exceeded $310 billion in 1990. U.S. raw nonfuel minerals mine production in 1990 was estimated at $33 billion, a 3.1 % increase over that of 1989. The value of minerals production increased in all but 3 of the last 30 years. The metals component of production value has fluctuated much more than the industrial minerals component. This reflects the greater volatility of metal prices. In 1990, total employment in metal mining continued the increase that began in 1987. This growth was partially offset by a slight decline in employment in industrial mineral mining, resulting in an overall in-crease of 1.1 % to 179,100 in 1990. Continuing high (by historical standards) metal prices led to expansions at some mines, as well as opening or reopening of additional mines, resulting in increased employment.

Jan 1, 1991

By Edward L. McHugh

The appraisal of mineral resources of the Challis National Forest, Idaho, by the U.S. Bureau of Mines, was made so that the mineral resources of the forest could be appropiately considered in land use planning. Information from this study is intended to tip the U.S. Forest Service to incorporate mineral resource data into forest plans The study was done in conjunction with the U.S. Geological Survey, which released a companion report on the geology and mineral potential of the Challis National Forest in 1989. This summary report is derived from a more detailed USBM Open-File Report (MLA 6-91) that includes descriptions of mines and prospects, commodity profiles, and development cost models. Since the 1860's mines within the Challis National Forest have produced mineral commodities worth more than $590 million at current (1989) commodity prices. Identified mineral resources have a gross value of about $2 billion at current prices, including 8 strategic or critical minerals. The U.S. Bureau of Mines study identified and described 723 active and inactive mineral properties within the forest. Mineral properties with identified resources were evaluate to determine their economic significance, and an assessment was made of the feasibility of mineral development. Of the 2,516,191 acres in the Challis National Forest, about 390,000 acres were classified as having mining development interest. Commercially important mineral production, mainly of molybdenum, gold, and silver from the Challis National Forest is likely for the foreseeable future.

Jan 1, 1991

This Bureau of Mines publication summarizes the industrial minerals industry of Idaho. It contains information on 119 principal deposits of 21 commodities in the State and describes the institutional and infrastructural factors affecting mineral development.

Jan 1, 1991

By J. E. Hamak

This publication contains analyses and related source data for 920 natural gas samples from 26 States and 2 foreign countries. All samples were obtained and analyzed as part of U.S. Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted since 1917. The analyses published herein were made by mass spectrometer and chromatograph.

Jan 1, 1991

By Michael R. Norland

This U.S. Bureau of Mines report on U.S. and Canadian 1iterature pertaining to soil characterization and the use of soil amendments as a part of the reclamation process of coal surface-mined lands contains 1,280 references. The references were published during the 1977 to 1988 period. Each reference is evaluated by keywords, providing the reader with a means of rapidly sorting through the references to locate those articles with the coal mining region and subjects of interest. All references are annotated.

Jan 1, 1991

By Edward L. McHugh

The appraisal of mineral resources of the Challis National Forest, Idaho, by the U.S. Bureau of Mines, was made so that the mineral resources of the forest could be appropriately considered in land use planning. Information from this study is intended to help the U.S. Forest Service to incorporate mineral resource data into forest plans. The study was done in conjunction with the U.S. Geological Survey, which released a companion report on the geology and mineral potential of the Challis National Forest in 1989. Mineral development activity in and under the Challis National Forest has been of great economic significance to Idaho and the United States. Since the 1960's, mines within the forest have produced mineral commodities worth more than $590 million A current (1989) commodity prices. Identified mineral resources have a gross value of about $2 billion at current prices, including 8 strategic or critical minerals. The U.S. Bureau of Mines study identified and described 723 active and inactive mineral properties within the forest. Mineral properties with identified resources were evaluated to determine their economic significance, and an assessment was made of the feasibility of mineral development. Of the 2,516,191 acres in the Challis National Forest, about 390,000 acres were classified as having mining development interest commercially important mineral production, mainly of molybdenum, gold, and silver from the Challis National Forest is likely for the foreseeable future.

Jan 1, 1991

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 21070 in 1989. The increase in the value of staurolite and tripoli production was the result of an increase in the quantity of materials produced and an increase in the unit value. Emery decreased due to the significant decline in the volume of the material produced. Special silica stone experienced both a decrease in unit value and quantity produced. Garnet showed a small increase in quantity, but a decrease in unit value. The silicon carbide industry saw a slight decrease in the quantity produced and a 12070 increase in the value of production. The fused aluminum oxide industry showed a 5070 decline in the quantity produced, but enjoyed a 15070 increase in the value of production. Combined production for both industries decreased 4070 in quantity but increased 13070 in value compared with those of 1988.

Jan 1, 1991

By Alan G. Fricker

Cyprus Gold NZ Ltd will be recovering residual free cyanide in barren gold pulp by air stripping. Laboratory investigations by DSIR have indicated additional advantages by recovering the cyanide from pregnant pulp. These are a lower leach pH, a greater cyanide recovery and less carbon consumption. They have a net economic advantage of $1.20/tonne over recovery from barren pulp. The realisation of these advantages is dependent on three crucial technical aspects -optimum pH for dissolution, the absolute loss of cyanide and the stability of the aurocyanide ion. The laboratory investigations described herein address these aspects. Earlier work had indicated that the rate of dissolution of freely revolving gold discs at constant cyanide ion concentration increased with decreasing pH from 11 to 8. Attempts to repeat the work in a more controlled manner by measuring the corrosion potential and current density have, to date, not been reproducible, but do not contradict the earlier observations. Cyanide recoveries and balances were obtained on leaches at pH 10.5 and 9 at the same cyanide ion concentration -the lower pH requiring three times as much total cyanide. Unaccounted-for losses, unfortunately, exceed the accounted-for losses, making interpretation of the balances difficult. Nevertheless, it appears that the additional amount of cyanide at the lower pH of 9 may not be fully recoverable. It may not, however, prove necessary in practice to use more cyanide at a lower pH. Both the gold and silver cyanide complexes remain available for carbon adsorption, as do mercury, copper and iron. Zinc, and probably cadmium, nickel and lead, may precipitate during stripping, which is an environmental advantage.

Jan 1, 1991

By Byron K. nelson, David Mathieson

Until quite recently concentration of free gold in gravity circuits ahead of froth flotation and/or chemical treatment was considered an uneconomical pursuit in many gold pi.ants in Australia. Over the past 10 yenrs since initial introduction of the Knelson Gold Concentrator, over 600 hnvc been surpl led world wide and they have been developed to the stage that Lhey can now be utilised in almost all instances where free gold appears in significant quantltles ln grinding circuits. They out perform and displace more conventional gravity sepnration equipment such as spirals, tables, sluices, jigs, drum separators etc.

Jan 1, 1991

By P. C. van Aswegen

The Bacterial Oxidation (BIOX®) process for the pre-treatment of refractory ores for gold recovery developed by Genmin, the mining division of Gencor, has been operating successfully at the Fairview mine since October 1986. The continuous operation of a pilot plant at Genmin Process Research has resulted in further process developments to improve plant operating efficiencies. These new developments which include a higher solids content of the pulp feed to BIOX®, lower retention times, higher operating temperatures, lower power utilization for oxygen dispersion .and reduced nutrient addition have all been successfully implemented on the Fairview plant.lt has furthermore been confirmed that the arsenic precipitate formed in the neutralization of effluent solutions complies to the United States of America EPA standards. Continuous cyanidation pilot plant work conducted on BIOX® product has indicated that cyanide consumption can be drastically decreased if a continuous flowsheet is implemented in preference to a batch leaching system.

Jan 1, 1991

By Batric Pesic

The interactions of mineral-pyrite with T. ferrooxidans were studied by using a cyclic voltametry technique. The interactions with bacteria were examined during the entire growth stage of bacteria (fermentation), The pyrite ?surface invariably drastically changed ' its. properties at the second day of fermentation. Beyond two .. days of fermentation, the cyclic voltamograms were insensitive to convective diffusion produced by stirring. The product layer was examined by SEM,. X-ray diffraction and chemical analysis. The SEM study revealed that bacteria populated the pyrite surface at an extremely high density levels. The high density of bacteria, and the solid reaction products formed on the pyrite surface created conditions for pore diffusion which explained why the CVs became .insensitive to convective diffusion in solution (stirring). The x-r:ay diffraction study confirmed jarosite as a product layer. A mechanism of T. ferrooxidans cells serving as nucleation sites for jiarosite formation is proposed.

Jan 1, 1991

At Pasminco Mining's South concentrator. which was commissioned in 1952. an expansion. modernisation and efficiency improvement program commenced in 1986 with a coarse ore stockpile and grinding circuit expansion. the replacement of small flotation cells and the upgrading of reagent mixing and metering equipment. The program continued with the installation of a TDC 3000 based process control system (1988) and concentrate thickeners (1990). By mid-1991 a further grinding expansion and the installation of zinc flotation feed regrind ball mills and zinc recleaner column cells will be complete. leaving the use of ceramic disc fillers and development of process control strategies as probably the remaining major avenues for improved process efficiency at present.

Jan 1, 1991