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By H. F. Yancey

Traditionally the Pacific Northwest has relied on hydroelectric power, which has been both abundant and cheap. However, comparatively few hydroelectric sites capable of providing low-cost power remain, therefore the need for supplemental thermal generation, perhaps within the next decade, is generally recognized. Based on the present cost and availability of competing fuels, coal seems to be the logical choice for projected thermal power plants. Power companies and public utilities have become interested in establishing reserves of coal for future use. One deposit explored in 1958-59 lies in southern Thurston and northern Lewis Counties, Wash., near Centralia. Drilling, totaling 22,700 feet, proved the existence of 70 million tons of strippable coal--an ample reserve for the projected power plant. The coal, like most others and particularly those of Washington and Oregon, when mined in full seam section by mechanical methods, would require cleaning to make it suitable for use. The amount and nature of the impurities in this coal dictated a thorough investigation of its cleaning characteristics to establish economic factors and to insure proper preparation-plant design. Therefore, arrangements were made through a cooperative agreement to conduct such work at the Seattle Coal Research Laboratory of the Bureau of Mines. This report describes that investigation. The results are of interest primarily in connection with the utilization of this particular deposit, but some of the information developed is applicable to other deposits of low-rank coals in the West, because the impurities in these coals differ greatly in behavior from those generally associated with the higher rank coals of the Appalachian field.

Jan 1, 1961

By G. V. Sullivan, G. F. Workentine

Beneficiation studies were conducted by the Bureau of Mines on three samples of low- grade chromite - bearing material from the Stillwater complex of Montana . The objective of the study was to develop methods for recovering chromite from low- grade materials to improve the domestic reserve situation . Samples were obtained from the three largest deposits in the district , Mouat , Benbow , and Gish . The chromic oxide ( Cr₂ 0 ) content of the ore and of the chromite was about the same in each of the samples . The major gangue constituents ranged from clean olivine in the Mouat sample to such altered minerals as serpentine and talc in the Benbow and Gish samples . Tabling , flotation , high- tension electrostatic separation , and combinations of processes were applied to each ore . Treatment of the Mouat sample ( 9.95 percent Cr₂ 0 ) by high- tension electrostatic separation , a combination of tabling and high- tension electrostatic separation , and tabling with middling retreatment resulted in concentrates that graded 42.8 , 42.0 , and 40.7 percent Cr₂03 at chromium recoveries of 85 , 86 , and 84 percent , respectively . Other techniques were less selective . 2 The Benbow sample ( 7.75 percent Cr₂0 ) responded most selectively to tabling with middling retreatment and a combination of tabling and hightension electrostatic separation to produce concentrates of 40.1 and 39.5 percent Cr₂g with each process having a chromium 2 recovery of 69 percent . Response of the Gish sample ( 8.04 percent Cr₂03 ) to the various concentration techniques was about the same as that of the Benbow sample , but in general , somewhat less selective . A combination of tabling and high- tension electrostatic separation resulted in a concentrate that contained 71 percent The Mouat mine was reopened in 1953 when the American Chrome Co. contracted with the Federal Government to produce 900,000 tons of chromite concentrate . The ore , averaging 20.2 percent Cr₂03 , was treated by tabling to produce a 38.5 - percent Cr₂ O concentrate.

Jan 1, 1964

By Roy Bartholomae

Noise generated by continuous mining machines in underground coal production is an important health hazard. Bureau of Mines Contract J0387229 covers investigation of this noise through laboratory tests of simulated cutting operations and through in-mine noise measurements. The results of these investigations indicate that coal cutting noise and conveyor noise are dominant sources of mining machine operational noise. Typical noise levels for both cutting and conveying operations are approximately 97 dBA (decibels A-weighted). For full operation of all machine systems, the overall sound pressure level is approximately 101 dBA. In-mine and laboratory test results show excellent agreement in both A-weighted overall levels as well as in A-weighted one-third-octave band spectra.

Jan 1, 1983

By J. P. Bennett

The Bureau of Mines investigated the dimensional changes of ceramic materials exposed to acid environments to evaluate construction materials for emerging technology in chemical and metallurgical processes. Six commercial ceramic materials (two red shale, two fireclay, one silica, and one silicon carbide (SiC» were exposed to H20, 20 and 30 wt pct HCl, 40 and 60 wt pct HN03, and 10 and 50 wt pct H2S04 at temperatures from 50° to 90° C for 300 days. Linear expansions ranged from a low of -0.02 pct for the silica to a high of 0.45 pct for the red shale. A general ranking of the volume expansion of the materials tested, (from high to low), is as follows: high-porosity red shale A and fireclay B » low-porosity red shale B and fireclay A > silicon carbide and silica. A general ranking (largest to smallest) of the effect of exposure environments is HCl > H2S04, HN03 > H20. An autoclave test method was evaluated. Data obtained from 8-to 24-h exposures were compared with data obtained from the 300-day exposures. The relative expansion trends were similar, indicating that this method could be used as an accelerated test.

Jan 1, 1988

By E. B. Kester

In the commercial evaluation of coal tars, a distillation analysis properly carried out is of considerable importance. Close attention must be given to this operation in order to obtain consistent results and to secure the minimum decomposition of the tar compounds, which in many cases are sensitive to undue heat effects. Low-temperature tars in particular contain compounds of this nature, while in the case of tars produced at high temperatures the large proportion of pitch present has an adverse influence during a distillation. If excessive cracking takes place, the composition of the distillate will naturally vary from the normal, with the result that all the analytical criteria subsequently obtained are affected. Where tars, produced over vide ranges of carbonization temperatures are investigated as in the survey of gas, coke, and by-product making properties of American coals nor being conducted at the United States Bureau of Mines Pittsburgh Experiment Station, the method of distillation must necessarily be the sane for all of the tars studied. Also, it must function equally well for both low and high temperature tar, permit accurate fractionation, and reduce adventitious decomposition to a minimum.

Jan 1, 1932

By Donald F. Reed

In its program of investigation of deposits of strategic minerals, the Bureau of Mines did some development drilling from October 1247 to March 1948 at the Pickering Creek deposits, Charter County, Pa., in an endeavor to find an additional source of supply of lead and zinc. Lead mining in Pickering Creek Valley showed great activity from 1851 to 1855; but after this period mining gradually declined until 1870 when all mines were. One small mine did some work from 1917 to 1920. The ores were sulfides of lead and zinc, which were partly oxidized from the surface to the 20-foot level. As zinc was penalized at the reduction works, the ore was sorted at the mine and the zinc discarded. The Wheatley and Chester County veins contained the beet ore bodies in the district. These converging veins are 2 to 5 feet wide. To cut the veins below the old mine working' the Bureau of Mines diamond-drilled eight holes aggregating 2,820 feet. No significant lead-zinc mineralization was found.

Jan 1, 1949

By Robert W. Ageton

Optimal planning for mining the deep, lead-zinc-silver deposits of the Coeur d'Alene mining district, Shoshone County, Idaho, could be facilitated by a knowledge of the magnitude and direction of the pressure acting in the virgin rock. The distribution of primary stresses should be considered in order to prevent possibly destructive mining-induced stress concentrations. This particular investigation was concerned with determining stress in a zone 4,000 feet below the surface and known to be ender stress concentrations due to mining operations. Disking of the stress-relief cores obtained in a vertical down hole permitted qualitative evaluation from visual observations; the results indicate that a high lateral stress existed at the time the measurements were made. Stress-ellipsoid determinations gave a compressive principal stress of -13,000 psi oriented about N 45° W and nearly horizontal, a compressive principal stress of -11,000 psi oriented about S 45° W and abut 60° off the vertical pointing away from the vein, and a compressive principal stress -5 -7,000 psi oriented N 45° E and about 60° off the vertical, pointing toward the vein. Subsequent to the overcoring stress-relief drilling, a rock burst occurred about 100 feet northwest of the test site.

Jan 1, 1967

By G. Schuman

Variations in pyrite reactivity are known to exist within samples collected from different areas. Using samples collected from acid and non-acid sites, the relationship between the factors affecting pyrite oxidation and observed variations in pyrite reactivity was studied. Heavy liquid separations were used to extract the pyrite from nine pulverized rock, coal, and coal refuse samples. Simulated weathering tests were used to determine the degree of reactivity of the extracted pyritic material. Representative portions of each pyritic sample were analyzed for whole rock composition (including pyritic sulfur and neutralization potential), for elemental composition, and by x-ray diffractometry. The samples were also examined with reflected light microscopy to ascertain pyrite morphology distributions. Tests for the presence of iron-oxidizing bacteria were all negative indicating the leaching tests were conducted under abiotic conditions. The results of the simulated weathering tests permitted the partitioning of the samples into two groups based on positive or negative neutralization potential (NP) values. Determinations were then made to evaluate the degree to which a variety of factors, including temperature, partial pressure of oxygen and water, and crystallography affected pyrite reactivity. Multiple regression analyses showed no statistically significant relationship between degree of reactivity and elemental composition. However, for samples with negative NPs, a simple regression analysis showed a strong linear relationship to exist between the reactivity of the pyrite and the proportion of "unstable" pyrite (framboidal + mossy pitted) found in each extracted pyrite sample. Samples of pyrite with positive NPs, although producing acidity, did so in at least one order of magnitude less than the NP deficient samples, indicating the important role that NP plays in controlling pyrite reactivity. A simple linear regression between cumulative sulfate production and NP for the three samples with positive NPs had a correlation coefficient of 0.99. For the nine samples grouped together, a linear regression model between cumulative sulfate production and NP (both negative and positive) was established between log of sulfate and NP.

Jan 1, 1991

By Raymond W. Hiteshue

To aid in designing a continuous system for evaluating processes for converting coal to high-Btu gas] the Bureau of Mines determined the amenability of various coals and a char to hydrogasification at 800° C and 6,000 psig using a molybdenum catalyst. A lignite from Rockdale, Tex., an hvCb coal from Rock Springs, Wyo., a char from the low-temperature carbonization of the latter, an hvAb coal from Pittsburgh, Pa., and an anthracite from Luzerne County, Pa., were selected. Highest yields of gaseous hydrocarbons, 94 pet, based on maf feed, were produced from char, and lowest yields, 67 pct, were obtained from lignite. Hydrocarbon gases contained 82 to 92 pct methane, 8 to 15 pct ethane; and 1 to 3 pct propane.

Jan 1, 1962

By A. L. Engel

This report describes results of laboratory-scale experimental treatment of nine ores containing gold and silver, including samples of products of previous plant treatment, from ore deposits in California and Nevada. The samples treated were taken by engineers of the Bureau of Mines during investigations of these ore deposits. The information reported is of interest for development of the mining districts represented or in future Investigations of similar ores from other sources. The treatment methods were as simple as possible. More complicated treatments were tried when required, The applicability of the methods and their limitations in treating the ores are shown by the data in this report. The following treatment methods were employed in the experiments described: Screen analyses were made to determine distribution of values in various screened-sized portions of crushed ore, or to determine optimum size to which a particular ore should be crushed or ground to liberate values, and some-times to determine residual values in various-sized portions of treated material.

Jan 1, 1961

By A. Landsberg

Chlorination of sulfide minerals and several prepared metal sulfides was studied. The resulting data were analyzed with respect to kinetics of the reactions and application to nonpolluting methods of winning metals from sulfide ores. Sulfides of iron, copper-iron, nickel, lead, zinc, silver, bismuth, arsenic, rhenium, molybdenum, and tungsten were investigated at temperatures up to 600° C. Copper-iron, lead, and zinc sulfides showed at least some product-controlled (parabolic) kinetics at the lower temperatures within the temperature ranges studied, but only nickel and silver sulfides had chlorination rates controlled by parabolic reaction kinetics in the commercially important temperature range of 450° to 600° C.

Jan 1, 1975

By A. B. Needham

This paper, which describes mining practices at a mine in the Cave- in-Rock, Illinois, fluorspar district, is one of a series being prepared by the Bureau of Mines on mining practices, methods, and costs in the various mining districts of the United States. Ore deposits in the southern Illinois-western Kentucky fluorspar dis- trict are of two general types (1) the flat-bedded, lenticular replacement and (2) the relatively narrow, rather steeply dipping fault or fissure filling. This paper describes production methods used and results obtained in mining one of the bedded lenticular ore bodies that are prevalent in the northeast portion of the district near Cave-in-Rock.

Aug 1, 1949

By Gary P. Sames

The Bureau of Mines recently initiated a study of geologic features that contribute to roof instability in western U.S. underground coal mines. The purpose of the study is to provide information for use in ground control planning and safety hazard reduction in that region, where mining activity has been increasing. Hazardous geologic conditions were surveyed in selected underground coal mines in Utah and Colorado, and both depositional and structural features were identified as potential ground hazards. Although the conditions found do not differ in kind from hazardous geologic conditions in the Eastern United States, they do differ in intensity of occurrence and relative importance. Three depositional features dominate where unstable roof occurs in western underground coal mines: paleochannel deposits, crevasse splay deposits, and flood basin deposits. Three structural features identified as hazardous, but not so widespread or common as the depositional hazards, are faulting, jointing, and igneous intrusions. This survey establishes a foundation for future studies aimed at reducing and preventing ground control accidents in western coal mines.

Jan 1, 1988

By M. Hayashi

The Bureau of Mines conducted laboratory studies on Idaho mudstones to examine techniques for extracting vanadium. Recovery of vanadium from low-grade sources could contribute to future vanadium production and reduce reliance on imports. An Idaho mudstone surface sample containing 0.30 pct V205 and an underground sample containing 0.21 pct V205 were used in the extraction tests. Leaching of the surface sample for 18 h at 800 C with the addition of up to 1,000 lb/ton H2S04 recovered 70 pct of the vanadium. How-ever, leaching of the underground sample under the same conditions re-covered only 47 pct. By adding 15 wt pct NaCl and roasting the samples at 7500 C for 2 h, followed by leaching with 800 lb/ton H2S04, vanadium extractions were increased to 78 pct from the surface sample and 83 pct from the underground sample. Water leaching of samples roasted at 7500 C for 4 h with a 25-wt-pct NaCI addition yielded about 60 pct of the vanadium from both surface and underground samples. Autoclave leaching at 2000 C for 3 h with 1,000 Ib/ton H2S04 extracted 97 pct of the vanadium from the surface sample and 86 pct from the underground sample. An exploratory solvent extraction investigation to purify and concentrate vanadium in the leach solution using several organic reagents was also conducted.

Jan 1, 1985

By G. H. Keith

The Bureau of Mines determined the mechanism(s) involved in observed anomalous changes in mechanical properties of vanadium-base alloys. Tensile properties of electrorefined and commercial-purity vanadium-base alloys containing up to 5 atomic percent molybdenum or titanium were measured between 77° and 673° K. Snoek oxygen and nitrogen peak heights were measured to determine the changes in dissolved interstitial content caused by increasing quantities of solute. In addition, changes in lattice parameter were followed wit: precision X-ray techniques. Softening, observed in alloys containing titanium, is explained by the formation of a second-phase titanium compound with oxygen or nitrogen. However, because of partitioning of titanium between compound formation and solid solution formation, about five times the stoichiometric amount was required for complete reaction. Addition of 1 percent titanium drastically lowered the strengthening due to strain aging, at 673° K, and 2 percent titanium essentially eliminated it. All alloys were ductile at 77° K. Variations in the tensile properties of the molybdenum-containing alloys are explained by variations in the amounts of interstitial impurities present. The molybdenum did not react with these impurities and had no effect on strengthening due to strain aging. Commercial-purity vanadium alloys containing more than 2 percent molybdenum were brittle at 77° K.

Jan 1, 1969

By Phillip R. Moyle

A basic precept in mineral exploration is that the best places to prospect are where minerals have already been found. The California desert has many old mining districts once thought to be "played out" that are currently producing more mineral wealth than at any time in the past. Because no "crystal ball" exists that will enable us to predict the Nation's future mineral needs, land management plans must be flexible enough to respond to these often unforeseen needs. MANAGEMENT ISSUES The California Desert Conservation Area (CDCA) (figure 1) encompasses 25 minion acres, nearly one-quarter of the total area of California. Passage of the Federal Land Policy and Management Act of 1976 (FLPMA) launched an intensive program by the Bureau of Land Management (BLM) to study this vast area. Painstaking scientific investigations were made of wildlife and plant populations, soil, air, and mineral resources, range use, and wilderness characteristics, among other environmental concerns.

Jan 1, 1992

By L. A. Haas

Hydrogen sulfide was decomposed to elemental sulfur in an electrical discharge. With He, N., or Ar diluents, a threshold voltage between 1 and 3 kV was required for the decomposition reaction to occur in a laboratory ozonizer. Above the threshold voltage, the HAS decomposition rate increased with increasing voltage, but the increase was more pronounced with argon diluent than with either nitrogen or helium. In common with other reactions in an electrical discharge, the B2S decomposition decreased with increasing temperature in the range of -410 to +61° C. The reaction did not appear to be rate-controlled by a solid-gas sorption step because the introduction of activated charcoal into the electrical discharge zone did not significantly affect the decomposition yield. In the presence of polymeric chlorofluoro-carbon oil, 90 pct conversion of the 3 pct H2S in helium was obtained at 14 kV, 60 Hz, a 2-mm electrode gap, and a gas-residence time greater than 1 min. Under the same experimental conditions in the absence of oil, the conversion was only about 50 pct.

Jan 1, 1973

By F. D. Stevenson

A metal diaphragm pressure relay system was constructed to measure vapor pressures of the metal halides, oxyhalides, and other substances at temperatures up to 700° or 800° C. The vapor pressure of arsenic (III) oxide (As2O3) was determined to verify the reliability of the apparatus for such measurements. The data for the liquid AS2 Os (2820 to 4830 C) are represented by the equation, log Pmm = 6.875 - 2,929/T, from which the normal boiling point was calculated to be 461° C. The heat of vaporization calculated from this equation was 13.40 ±0.09 kcal/g mole As4OS and is essentially constant over the interval studied. The melting point of the octahedral arsenic (III) oxide was determined to be 278° C from the inter-section of the solid and liquid vapor pressure curves, A thermal analysis apparatus is also described by which melting and transition temperatures could be checked by a method independent of vapor pressure data. The melting points of the monoclinic and octahedral forms were determined to be 314.4 ±1.4° C and 278 ±5° C, respectively.

Jan 1, 1963

By Hillary W. St. Clair

This report gives the results of an experimental study of the progressive changes that occur in particle size and size distribution when a homogeneous and isotropic mineral is subjected to crushing by impact. The mineral used in the study was uniformly sized quartz, which was crushed in a simple drop¬-weight machine that applied impact energy up to about 100 kg-cm per g. Screen analyses of the crushed products were analyzed by the method of moments to determine the mean size, variance, skewness, and kurtosis. Analysis of the data from these experiments shows that the mean size of the crushed product is a function of the energy input and the initial size. The size distribution is functionally related to the degree of size reduction. As the mean particle size is decreased, at first there is a corresponding increase in the variance and decrease in the skewness, But, as size reduction is carried further, each tends eventually to approach a steady value, and the form of the size distribution becomes stable.

Jan 1, 1972

Since its creation in 1910, the Department of the Interior's Bureau of Mines has pioneered in the development of mineral technology, through research. From the very beginning, research on mine health and safety has been a dominating concern, and a responsibility that expanded markedly as a result of the Coal Mine Health and Safety Act of 1969. Until the mid-1970's research on fuel technology and coal production also was an important part of the Bureau's work. But in the four years following the 1973 oil crisis, Congress established a reorganized Federal energy research apparatus in which all fossil fuel research-encompassing extraction, use, and conservation-was centralized. Today, the Department of Energy houses Federal research on coal mine production technology, while research on coal and noncoal mine health and safety and environmental technology, and on noncoal mine production technology, remains in the Interior Department as a continuing responsibility of the Bureau of Mines. In carrying out its authorized research programs, the Bureau conducts both short- and long-term re-

Jan 1, 2012