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By H. B. Salisbury

The Bureau of Mines conducted research to determine if low-grade California chromite ores could be beneficiated to produce products suitable for commercial use. This research is part of a Bureau goal to provide technology capable of using low-grade domestic ores to meet emergency demands of the Nation for metals and minerals and in particular those minerals, such as chromite, which are considered critical. Two ores from California were ground and treated using gravity concentration and magnetic separation techniques. An are from Auburn in central California, assaying 2.5 pct Cr203, was treated by tabling and magnetic separation to yield a nonmagnetic product containing 44.7 pct Cr203 at a recovery of 36.4 pct. Core drilling samples from the Seiad Creek area of northern California, assaying about 6 pct Cr203, were upgraded by tabling to yield a concentrate containing nearly 50 pct Cr203 with a recovery of 50 pct. Both products are suitable for metallurgical and/or chemical use.

Jan 1, 1981

By Thomas G. Carnahan

The Bureau of Mines conducted research to simulate in situ leaching of a chalcopyrite ore. The purpose was to obtain a direct comparison between moderate-temperature and elevated-temperature in situ leaching of copper trom minus la-inch ore and to analyze the sulfuric acid and oxygen requirements of the leaching system. Experiments employing oxygen were conducted at 35° and 90° C on 362-and 367-1b ore charges, respectively, under flooded conditions and at 400 psig. At 90° C, 47 pct of the copper was extracted in 913 days of leaching; at 35° C, 27 pct of the copper was extracted in 915 days. Diffusion into and out of the ore fragments con-trolled the rate of leaching. Oxygen consumption was 1.46 lb/lb of copper extracted at 35° C and 3.15 lb/lb of copper extracted at 90° C. Sulfuric acid requirements of the ore were 5.49 and 7.48 lb/lb of copper extracted at 35° and 90° C, respectively.

Jan 1, 1982

By V. Rajaram, S. Bhattacharya, M. F. Dunn

During a mine fire or other emergency, it may be desirable to reverse the airflow in order to provide an escapeway or to isolate a fire. Also, (in colder areas, the airflow may be reversed to prevent ice buildup. When reversing main mine fans, the mine operator usually does not know what operating characteristics of flow and pressure to expect. Laboratory a field tests of vane axial main mine fans in the 7- to 9-ft diameter size range were conducted to establish forward and reverse performance characteristics under controlled conditions and at typical mine installations. The data obtained suggest that reverse performance characteristics are dependent upon the blade angle and the hub to tip ratio. There is also evidence that reverse performance can be predicted for a family of blade angles and a given hub to tip ratio. Generally, quantity of air is 30% to 65% less in reverse than when operating in the normal forward mode.

Jan 8, 1983

By Kenneth C. Stewart

This contract was directed toward a study of the attenuating properties of earmuffs as worn by miners. Two attenuation measurement procedures were utilized. Human subjects were tested in a diffuse sound field according to threshold shift procedures recommended by the American National Standards Institute and a physical measurement procedure was accomplished in the same diffuse field on the same human subjects with microphones placed simultaneously on the inside and outside of the muffs. All measurements were obtained in one third octave of random noise. The results of the study indicated that physical and psychophysical attenuation measurements are in essential agreement at frequencies from 125 Hz to 2 KHz. Above 2 KHz the psychophysical measurement demonstrates larger amounts of attenuation than the physical measurement. The difference in attenuation ranged from approximately 7.0 dB to 9.0 dB at frequencies of 4 KHz and above. A possible explanation for the observed differences in attenuation has been presented.

Jan 1, 1980

By James A. West

COUNTRIES of the Near East, with the world's largest and insist prolific petroleum resources, produced nearly 277 percent of the world's estimated total output of crude& oil in 1964 and accounted for about 60 percent of world exports of this commodity. Although petroleum largely dominated the mineral industry of tine area, production of antimony, chromium, copper, mercury, boron, potash, and phosphate rock was of world significance. Production of crude oil in Near East countries reached a record high of 7,520,000 barrels per day in 1964, an increase of nearly 11 percent over that of 1963. Kuwait maintained its position as the leading producer, accounting for almost 28 percent of the area's output. Saudi Arabia, Iran, and Iraq followed with 22.5, 22.2, and 16.5 percent of total area output, respectively. Despite record production, the Near East, proved crude oil reserve remained in excess of 211 billion barrels, or more than two-thirds of the estimated world proved crude oil reserve.

Jan 1, 1966

By Harold W. Lipper

Helium production and shipment reached new peaks in 1.361. The Bureau of Mines produced 727 million cubic feet, 13 percent more than the 1960 record, and shipped 552 million cubic feet, 16 percent more than the 1960 record. Production exceeded demand for the third successive year, enabling the Bureau of Mines to add 174 million cubic feet to the volume stored underground for future use. At the end of 1961, the total volume of helium in underground storage in the Clifside gasfield was 44-7 million cubic feet. Contracts to implement a long-range helium conservation program were completed with four companies, obligating all the contracting authority of $47.5 million a year made available by the Congress. The four companies will finance, build, and operate helium extraction plants to recover from natural gas an annual average of 3.1 billion cubic feet of helium that would ordinarily be wasted when the helium-bearing natural gas is used for fuel.

Jan 1, 1962

By W. E. Wallace, B. L. Razzaboni, P. Bolsaitis, M. J. Keane

"Therma1 and chemical treatment of respirable size silica dusts samples is shown to induce marked changes in their hemolytic activity. The cytotoxicity of crystalline a-quartz (Min-U-Sil), and fumed silica (Cab-0- Sil) particles, as measured by a hemolytic activity protocol, is decreased by calcination and can be related to the dehydroxylation of the surface. The hemolytic activity of P-cristobalite particles of respirable dust si7.e was also determined and found to be lower than that of a-quartz. The change in the surface structure resulting from thermal treatment is detectable by photo-acoustic infrared spectroscopy and zeta-potential measurements. The absorption band in the 3200-4000 cm-1 frequency region of both Cab-0-Sil and MinU- Sil disappears upon heat treatment while a sharp band, identified with single silanol groups, at 3750 cm-1 increases in intensity. The zeta potential-pH profile, in the pH range of 4.0-7 .0, of the calcined, siloxane surfaced particles is more negative than that of material with a silanol surface.The cytotoxicity of the crystalline and fumed silica dusts was also found to be strongly dependent on particle size. Fumed silica of large surface area (small particle size) exhibits an initial increase in hemolytic activity upon calcination. This result confirms other experimental observations pointing to a particle size of maximum toxicity. INTRODOCTIONThe toxicity of silica and other mineral particles, as manifested by their role in inducing pneumoconiosis, fibrosis, silicosis and other pulmonary disorders is largely traceable to the characteristics of particle surfaces and to particle morphology. The great wealth of data on the physical and chemical properties of silica is still insufficient for a comprehensive understanding of the specific parameters to be associated with fibrogenic activity and, correspondingly, with the optimum means for characterizing and quantifying the toxicity of dusts, and the design of possible preventive or therapeutic methods.The great diversity of parameters that have been proposed and tested for correlation with cytotoxicity suggest that more than one mechanism may be involved in the fibrotic activity of silica particles. The crystalline structure of the material (more active tridymite versus less active crisobalite and passive stishovite), freshly formed surfaces and free radicals associated therewith, silicic acid adsorbed onto silica surfaces, the concentration of hydroxyl groups at silica surfaces, particle size and morphology, among other properties, have been investigated and found to conelate in tests of cytotoxicity."

Jan 1, 1990

By Richard J. Mainiero

Traditional techniques for the experimental determination of toxic fumes produced by the detonation of high explosives are not applicable to blasting agents. To detonate properly, blasting agents require confinement, a significant booster, charge diameters of 3 inches (7.5 cm) or greater, and charge lengths greater than two-times the charge diameter. Without these conditions, blasting agents will not detonate at full order, leading to a misrepresentation of the gaseous products. A facility for detonating large, confined charges in a controlled volume has been constructed at the Pittsburgh Research Center’s Experimental Mine. The facility consists of a portion of mine entry (once used for full-scale mine explosion research and demonstrations) enclosed between two explosion proof bulkheads. Total volume of the chamber is 9,666 ft (274 m). The chamber is equipped with an air circulating system and is3 3vented using the mine's airflow. Up to 10-pound (4.5-kg) charges can be detonated in the chamber using a variety of confinements. For a typical test, the blasting agent is confined in a 4-inch (10-cm) schedule 80 steel pipe and initiated by a 3-inch (7.5-cm) diameter, 1-inch (2.5-cm) thick Pentolite booster. This combination of confinement and initiation yields a detonation velocity of about 4,000 m/sec for ANFO. This velocity is in line with that measured for blasting in the field. Twenty four 2-inch thick steel plates are suspended around the pipe bomb to stop shrapnel that would otherwise seriously damage the chamber. Following detonation of an explosive in the chamber, a circulating fan is run for about 10 minutes to uniformly mix the chamber atmosphere. Fumes samples are taken out of the chamber through 1/4-inch (0.6-cm) Teflon or polyethylene2tubes for analysis. The fumes are analyzed using bubblers or Vacutainers to collect samples for analysis by the analytical chemistry lab. The technique described here has been employed to determine the fumes produced by the detonation of a variety of ANFO formulations and commercial explosives. This technique may be developed as a standard test to measure fumes produced by blasting agents or may be used to provide data with which to develop a computer model that will reliably predict the expected fumes production based on chemical composition.

By Charles Zahn

Gas chromatography is a method of separating mixtures of gases and volatile materials by entraining their vapors in a gas stream, which passes over an appropriate stationary phase. Two techniques are in common use: Gas-Liquid Chromatography, in which the stationary phase is a liquid supported on an inert solid, and Gas-Solid Chromatography, where the stationary phase is a solid adsorbent, such as charcoal or alumina. In both techniques components emerge from the column after a characteristic residence time. Gas chromatography is applicable as a qualitative or quantitative tool in a wide variety of problems in chemical research and processing. It may also be employed for purification and separation. A running bibliography on gas chromatography has been maintained at the Bureau of Mines synthetic liquid fuels laboratories, Bruceton, Pa., for several years for the benefit of research workers, who use chromatography as an analytical tool. Since the number of references grew and interest in the technique became more wide-spread, the Bureau is publishing this list rather than maintain it as a purely internal source.

Jan 1, 1958

Occupational illnesses are more difficult to identify than on-the-job injuries. Many illnesses related to occupational exposures may not be diagnosed until years after exposure; by that time, exposed workers may have changed jobs or left the workforce. Other approaches to identifying occupationally related illness are analysis of death certificate data (see chapter 2) and medical examination studies of workers known to have high exposures to hazardous agents. Figures 5-1, 5-3, 5-4, 5-6, 5-8, and 5-10 show, for each commodity, the percent of illness conditions reported to MSHA by nature of condition. Heart attacks that occurred on the job are reported without regard to work-relatedness. Figures 5-2, 5-5, 5-7, 5-9, and 5-11 show rates by year during 1986-1995 for selected conditions. Since there are many limitations on the accuracy of illness reporting, the frequencies and rates shown here should not be considered directly comparable across commodities. Figure 5-12 shows estimates for hearing loss by age among coal miners compared to a nonoccupationally noise-exposed population. These data come from a study by Franks [1996] of a group of audiograms obtained on coal miners by a commercial company. Using the NIOSH definition of hearing impairment, i.e., an average hearing threshold level for both ears that exceeds 25 dB at frequencies of 1,000, 2,000, 3,000 and 4,000 Hz, the figure shows that by age 30, more than 10% of miners suffer hearing impairment; by age 50, 90% of miners have hearing impairment. In contrast, only 10% of the nonoccupationally noise-exposed population suffer hearing impairment at age 51, and 50% of the nonoccupationally exposed population have hearing impairment at age 69. Figure 5-13 shows a similar analysis of commercial audiograms on male metal/nonmetal miners [Franks 1997]. At age 20, approximately 2% have hearing impairment using the NIOSH definition of hearing impairment described above. This increases to 7% at age 30, 25% at age 40, and 49% at age 50. In contrast, only 9% of the nonoccupationally noise-exposed comparison population have hearing impairment at age 50. Franks' analysis showed a different pattern for female metal/nonmetal miners; they developed hearing loss at the same rate as would be expected for a non-noise-exposed female population.

Jan 5, 2000

By J. Ankrum, T. Xia1, D. Wilder, K. Spratt

The human lumbar spine is inherently an unstable structure and requires sophisticated neuromuscular control to maintain its stability and for performing physical tasks. As a consequence, it is important to understand the potential health effects on human operators of mechanical stimuli such as shock and vibration.1 Impact applied to a vehicle operator combines the risk of sudden, unexpected load with the mechanical stress of the seated posture.2 Because many work environments contain the potential for multiple, unexpected impacts, it is important to understand how the trunk muscles respond to complex conditions. We believe the results have implications for isolation design and standards development. Methods Muscle activity was recorded during simple and complex impacts, applied randomly and without warning, while subjects sat on an air-suspension truck seat located on a man-rated 6-DOF motion platform (Rexroth-Hydraudyne). Simple (single) impacts consisted of 100 ms quarter-sine jolts in the side-to-side (L and R) and vertical upward (V) directions with peak amplitude at 0.4 g. Complex impacts consisted of combinations of two simple (single) impacts in sequence (LV, RV, VL, VR), separated by 100 ms. Twelve right-handed males (23.7 ± 7.8 years old) were tested without a blindfold under 2 posture conditions (supported while leaning back and unsupported, sitting upright) and 2 seat suspension conditions (present or absent). Each type of impact was repeated three times under each posture and suspension condition, resulting in 84 impacts in total. Surface EMG signals from the left and right erector spinae (ES), rectus abdominis (AR), external obliques (EO) and internal obliques (IO) were recorded and transformed to 25ms RMS values. The response time, defined as the time the muscle activity exceeded the mean + 2 STD of the pre-impact resting period, peak response amplitude, and time were then derived. A mixed-model repeated measures analysis of variance was used to evaluate statistical significance, where type I error rate was set at .05. Results One question we asked of these data was whether there were differences in responses related to simple single strike impacts (L, R, or V) and complex, double-strike impacts (LV, RV, VL, VR). There are 21 possible combinations of comparisons of simple and complex impacts to each other. The differences found are listed in Table 1.

Jan 6, 2006

By D. L. Pool

To increase metal recoveries and to minimize pollution by improved extraction technology, the Bureau of Mines investigated a hydrometallurgical technique to recover copper, lead, nickel, and cobalt from lead smelter mattes. The metals were converted from insoluble sulfides to soluble chlorides using a HCI-CI2-02 leaching system. Parameters studied in a 50-gallon, glass-lined reactor were the ratio of hydrochloric acid to chlorine, chlorine consumption per pound of matte, oxygen reaction pressure, and temperature. The matte material used contained, in percent, 19.7 Cu, 52 Pb, 2.9 Ni, 1.5 Fe, 0.38 Co, 0.19 As, 0.41 Zn, and 0.12 Cd. Extraction of Cu, Pb, Ni, Co, and Cd ranged from 92 to 98 pct, with concomitant extractions of Fe and As of <0.1 pct. The Cu and Pb were recovered as electrowon metals, while the Ni, Co, and Cd were recovered as mixed hydroxides.

Jan 1, 1981

By Paul W. McGann

THE MINERAL INDUSTRIES had a near-record year in 1950, as rising industrial activity in general, greatly accentuated by the outbreak of hostilities in Korea in midyear, called forth increasing supplies of mineral fuels and raw materials. The aggregate value of mineral production was second only to that in 1948, and the aggregate physical volume was exceeded only in 1948 and 1947. Lower coal production accounted for the failure to surpass these earlier years. Growth of production was fairly constant throughout the year, especially for crude petroleum; its physical output for the year as a whole exceeded that of 1949 by 7 percent. According to Federal Reserve Board indexes, other relative gains were 16 percent for coal, 9 percent for fuels in general, and 17 percent for metals. The increase for mining in general was of the order of 10 percent. This was not quite as large as the general increase in industrial production but clearly reflected the total-industrial trend (see fig. 1).

Jan 1, 1953

By E. E. Maillot

In 1943, diamond drilling by the Bureau of Mines, comprising 11 holes which totaled 1,295.6 feet, showed that the pegmatite at Black Mountain consisted of shallow lenses in interbedded biotite-quartz-schist and impure quartzite. The average thickness of the pegmatite was 9.7 feet. Mineralization had a zonal arrangement. Beryl was most abundant near the footwall contact of the pegmatite. The average estimated beryl content of the pegmatite exposed at the surface was 0.81 percent, and the highest content of any pegmatite area was 1.75 percent. Other economic minerals were scrap mica, feldspar, spodumene, and lepidolite. Representative samples of the Black Mountain deposit failed to yield high-grade boryl concentrates by straight flotation owing to the presence of considerable spodumene. By employing heavy medium separation to remove the spodumene, 75.4 percent of the. BeO wan recovered in a flotation concentrate assaying 10.4 percent BeO.

Jan 1, 1949

By H. J. Heinen

A technique offering promise as a metallurgical processing sequence the recovery of molybdenum (Mo) from the sulfide mineral--molybdenite?was investigated. The method consists of two steps: (1) electrosynthesis of pure dimolybdenum carbide (Mo2C) from molybdenite (MoS2) and (2) interaction of Mo2C and molybdic oxide (MoO3) to produce pure molybdenum metal. Two molten salt systems were satisfactory for electrosynthesizing Mo2C. The first was a mixture of potassium chloride (KCl), potassium fluoride (KY), and sodium metasilicate (Na2SiO3), and the second consisted of sodium fluoride (NaF), KF, sodium tetraborate (Na2B4O7), and sodium carbonate (Na2CO3). Yields up to 0.42 gram of Mo2C per ampere-hour were obtained. The carbide, mixed with monitored amounts of MoO3, was converted to molybdenum metal of 99.9 percent purity by sintering at 1,500° C.

Jan 1, 1965

By Ivan L. Nichols

Tailings dumps at Mercur, Utah, contain about $7 million worth of gold in 3.5 million tons of mill tailings assaying about 0.07 ounce of gold per ton. Commercial mining and milling at Mercur ceased in 1942. To determine whether improved technology was now available that might permit economic reprocessing of the Mercur dumps, the Bureau of Mines probed for a low-cost method that would be applicable to these tailings. A composite sample prepared for laboratory studies assayed 0.062 ounce gold per ton. About 10 percent of the gold occurred as a water-soluble cyanide. Conventional cyanide leaching dissolved 32 percent of the gold, and hot, strong cyanide solution dissolved 42 percent. Results were not improved by pretreatment with acids, bases, or oxidants. After expensive preroasting, gold recovery by cyanidation was increased to 65 percent. The simple procedures were ineffective, and more effective procedures were too costly for economical processing of Mercur tailings.

Jan 1, 1970

By J. B. Gayle

The rate of oxidation of coals with nitric acid has been used by earlier investigators4 5 6/ for determining fusain and for studying petrographic composition. These workers accumulated considerable evidence indicating that, for coals ranging from lignite to low-volatile in rank, the method gives values for fusain that agree satisfactorily with those obtained by optical methods. One group5/even concluded that, when discrepancies are noted between results obtained by chemical and microscopic methods, the results based on the oxidation reaction are probably the more reliable. Unfortunately, after concluding that the method was valid, most of these workers apparently lost interest. As a result, no attempt to exploit or apply the method to problems of utilization has been reported. Recent studies of the influence of inert petrographic constituents on the properties of cokes made from various coals7/ have indicated a need for additional means of characterizing coals and blends used for carbonization.

Jan 1, 1960

By Robert W. Freedman

Vacutainers are employed by the Bureau of Mines and the Mining Enforcement and Safety Administration for sampling mine air and other atmospheres containing fixed gases, low-molecular-weight hydrocarbons, and products of combustion. Tests were conducted to study shelf life of evacuated samplers prior to sampling and also to check the stability of sampled gases prior to analysis. An unexplained phenomenon, slow accumulation of carbon monoxide in evacuated samplers, occurred after a few weeks&apos; storage; levels were low but increased with time and could pose a problem for critical applications. Accordingly, attempts to halt CO release by additional means of treatment were made, and storage at low temperature was found to be effective.

Jan 1, 1978

By Robert M. Becker

This report (part 3 of a five-part series) presents computer programs for evaluating moments and moment relationships of the generalized probability distributions extended or developed in parts I and 2. The principal program is for evaluating the first three moments and moment relationships of the compound-multinomial distribution for finite as well as for infinite populations. This is the generalized distribution for sampling to some amount of items per sample. Another program is for evaluating the first four moments, the moments of the mean, and the moment relationships of the multinomial and generalized hypergeometric distributions. This is a general moment program in sampling to some number of items per sample or for sampling to some number of samples. This program will accept either ungrouped data, frequency data, or probability data.

Jan 1, 1965

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, increased about 4% in 1990. The decrease in the value of tripoli production was the result of a decrease in total production. Emery decreased owing to a decrease in the volume of the material produced. Special silica stone experienced a decrease in unit value and in the quantity produced. Garnet showed an 8 % increase in quantity and an 8 % increase in unit value. Staurolite increased about 38 % in the quantity produced, and the value of production increased about 36 %. The fused aluminum oxide industry showed a 12 % decline in the quantity produced and a 13 % decline in the value of production. The silicon carbide industry saw a 47 % decrease in the quantity produced and a 23 % decrease in the value of production. Combined, the industries decreased 17 % in quantity and value compared with those of 1990.

Jan 1, 1993