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By Rudolf Kudlich

"During the coming winter, it is probable that many householders who have habitually been users of anthracite coal will be obliged to turn to some other fuel for heating purposes, because of the limited supply of anthracite. The next best fuel, from a standpoint of cleanliness and ease of operation, is coke, but here again the supply is inadequate and the householder will have to fall back on bituminous coal. Though bituminous coal has the dis¬advantage of being dirty to handle, requiring more care in firing, and of giving off considerable smoke, it will be more generally available, costs less, and in the better grades which will naturally find their way to the domestic market, is higher in heat value, and contains less ash than anthracite.Choice of CoalThere a variety of bituminous coals are available, the householder should choose a low volatile coal, such as New River, Pocahontas, or some other ""smokeless"" coal, or the British coal now being offered in the markets along the Atlantic seaboard. Though not necessary to have the coal sized, as is the case with anthracite, it will be found cleaner to use coal from which the fine dirt has been screened. If it is found that excessive dust is caused when firing the coal, this can be reduced by slightly wetting the coal at the front of the bin, as it is being used.Method of Firingusing bituminous coal instead of anthracite in the domestic furnace, it will be necessary to use an entirely different method of fir Instead of leveling the fuel bed and putting on fresh coal in an even layer over the entire fire box, the coked and partly burned coal remaining from the previous firing should be pushed as much as possible to one side of the box, and the fresh coal thrown into the empty side so as to leave some burning coal exposed. In this way the green coal is heated slowly, the volatile gases are given off gradually, and are ignited by the burninggoing to waste up the chimney unburned."

Oct 1, 1922

By Oliver Bowles

Granites are classed as igneous rocks ; they have been formed by the solidification of rock magmas or solutions from deep within the earth . It is an almost invariable law of nature that magmas which cool quickly form fine- grained or glassy rocks , while those that cool slowly are completely crystallized and are coarser- grained . Granites , being of the latter class , are regarded as having attained their solid form at considerable depth below the surface under conditions of high temperature and pressure . The constituent minerals crystallized out slowly , the crystals interlocking with one another . The great depth of overlying rocks that must have been present when crystallization took place has been removed by erosion over large areas on the surface of the earth , in consequence of which granites appear at or near the surface in many localities . The chief minerals of which granites are formed are feldspars , quartz , and either mica or hornblende . All the essential constituents except mica are as hard as , or harder than steel , therefore granites are difficult rocks to cut and dress . Granites are usually red , pink , or gray , depending on the color of the feldspars . If hornblende or black mica is abundant the rock may be dark green or almost black . Granites are characterized by massive homogeneous texture . They are classified as fine- grained , medium- grained , or coarse - grained . Medium- grained granites are those in which the feldspar crystals average about one- fourth inch in diameter . If relatively coarsegrained crystals appear in a fine -grained ground mass the rock is designated a porphyritic granite . Uniformity in texture and grain size are desirable in building and ornamental stone , although occasionally rocks of variable texture , such as the porphyritic granites , are used . A rock may have the mineral constituents of a granite but show a banded or platy structure due to recrystallization , folding , or other changes while the rock was in a plastic or semimolten condition . Such metamorphic rocks are called granite gneisses . They are used occasionally for building purposes but not as commonly as the uniformly textured granites . - Granites are named from the most abundant mineral other than quartz and feldspar that they contain , being called , for example , biotite granite or hornblende granite . - Commercially other igneous rocks granitoid in texture but more properly classified as syenites , diorites , or gabbros may be classed as granites . Thus the " black granite " of Little Falls , Minn . , is a diorite , and the " black granite " of Eastern Pennsylvania consists of diabase or gabbro . The question is sometimes raised as to the depth to which a granite occurrence may extend . In this respect granites differ notably from limestones , sandstones , or other sedimentary rocks . The sediments were originally laid down in relatively thin beds , and individual formations providing rock of economic value may be quite limited in thickness . Usually the usable beds range between 40 and 200 feet in thickness . On the other hand , granite comes up from below . Its depth is unknown , but in general is very great . It may even be measurable in miles . The reserves of material at depth are to be measured , therefore , by the economic depth of working rather than by the vertical extent of the rock mass . Exceptionally , granites of commercial quality may occur in sills or sheets of limited thickness flanked on either side by rocks of different character , as , for example , at Westerly , R. I.

May 1, 1930

By David M. Hopstock

To help assure an adequate supply of minerals to meet the Nation's economic and strategic needs, the Bureau of Mines is conducting bench-and pilot-scale research using wet high-intensity magnetic (WHIM) separation to recover iron from oxidized taconites of the. Lake Superior region. The advantages and disadvantages of WHIM separation in relation to other separation methods, the most recent innovations in WHIM flowsheet design, and the role of mathematical models in process optimization are discussed.

Jan 1, 1979

To inexpensively monitor the ventilating airflow anywhere in underground working places. The Approach: The Bureau has developed a small self-contained monitor which sounds an audible alarm and energizes a flashing lamp if air velocity decreases below normal. How It Works: The sensing element of this inexpensive monitor is a thermistor, which is self-heated by a constant-current electrical source. Airflow over the thermistor increases heat removal and lowers the thermistor temperature. Since the electrical resistance of a thermistor is a function of temperature change, the voltage across it varies with temperature, and, therefore, the air velocity. Changes in the voltage across the thermistor are amplified, and can be used to trigger the alarms.

Jan 1, 1975

By S. B. Levin

"INTRODUCTION An exposure of large beryl crystals in pegmatite on Beryl Mountain, in Sullivan County, N. H., was the basis for investigation by the Bureau of Mines to determine the extent of the beryl mineralization and to expose other parts of the same zone that were favorable for additional beryl-rich shoots. Testing by surface cuts, trenching, and tunneling was conducted by the Bureau of Mines from August to December 1943.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to the national security and economy. The Mining Division, Lowell B. Moon, chief, conducts preliminary examinations, does the actual investigative work, and prepares the final report. The Metallurgical Division, O. C. Ralston, chief, analyzes samples and makes beneficiation tests. The field work was supervised by Paul M. Tyler, regional engineer, and John D. Bardill, district engineer. S. B, Levin was in direct charge of the project.LOCATION AND ACCESSIBILITYThe deposit is on the northeast slope of Beryl Mountain, 1 mile south of the village of South Acworth. The village, on State Highways 101 and 123a, is 12 miles northeast of Bellows Falls, Vt. The deposit is reached from South Acworth over a gravel-surfaced road and about 1,000 feet of good truck trail (fig. 1).The nearest railroad siding is at Cold River, on the Boston & Maine Railroad, where there is also a fairly modern, but now idle, feldspar mill."

Mar 1, 1948

By Frank D. Lamb

Pyrophyllite, a hydrous aluminum silicate (Al2 Si4O10 (OH)2 ) has been mined in North Carolina and marketed without beneficiation for the past 100 years, but recent demands for higher-grade material indicate that an economical concentration method is needed for at least a part of the pyrophyllite production. Past production has depended upon selective mining and hand sorting, which is often unsatisfactory because of the finely disseminated character of the ores. The major impurity in North Carolina pyrophyllite ores is quartz, which accounts for the abrasiveness of the commercial product. Since pyrophyllite is only slightly heavier than quartz, those ores cannot be beneficiated by simple gravity-concentration methods. Some separation can be attained by differential grinding and air classification because of the difference in hardness of the two minerals) but the separation is not sharp. Froth flotation of pyrophyllite from Quartz has never been attempted commercially, but if the demand for high-grade material is sufficient, it would seem that this process offers the most premise of being economically feasible.

Jan 1, 1950

By Dennis A. Long

Slip and fall accidents are a major cause of lost-time injuries associated with large mobile equipment in surface mines. An evaluation of the safety hazards associated with getting on and off large surface mining vehicles showed that most of the accidents occur at the point where personnel attempt to mount or dismount the machine at ground level. The major hazardous design conditions were identified as excessively flexible supports for lower steps or rungs, inappropriate ground-level-to-first-step distances, poor step designs, access designs that use vehicle components as steps or walkways, and inadequate hand- rail and guardrail designs, Additional hazards are introduced by the lack of proper maintenance of ladder hardware and the work practices of operators in carrying articles while mounting and dismounting the vehicle. This Bureau of Mines report describes the design and in-mine testing of improved access system for large mobile mining equipment.

Jan 1, 1984

By M. J. Ferrante

New data on zirconium tetraiodide (ZrI4) have resulted from high-temperature enthalpy and X-ray powder diffraction studies conducted by the Bureau of Mines. These studies were undertaken as part of the Bureau's efforts to provide important thermodynamic data essential to the advancement of mineral resources technologies that can be employed with minimal energy requirements and minimal environmental degradation. Enthalpies were measured with a copper-block drop calorimeter. No transitions or other anomalies were found. Tabulated values are given from 298.15 to 772 K for relative enthalpy, heat capacity, entropy, and Gibbs energy function. Enthalpies are expressed in equation form and combined with data from the literature to calculate values of the standard enthalpy of formation and the Gibbs energy of formation. X-ray powder diffraction data indicate that ZrI4 is primitive cubic with a lattice parameter of 11.79 A and is isostructural with stannic iodide (SnI4).

Jan 1, 1980

By Robert M. Becker

A multistage probability model for assessing the reliability of mineral samples following any number of stages of sample reduction is presented. Sample reduction is the process of alternately crushing or grinding and sampling mineral particles prior to assaying. The final multistage model developed accurately describes the ideal sample reduction practice. This model is based on previously developed and experimentally tested models for a single stage of sampling. The problem is approached through the probability distributions for the various stages of sampling. The probability distribution, moments, and moment relationships for a single stage of sampling are first reviewed, and the useful concept of unit moments is defined. In presenting the models for two stages of sampling, emphasis is placed on the physical description of the sample reduction process which leads quite naturally to its mathematical representation. In this representation, crushing or particle-size reduction between the stages of sampling is viewed as a random process with respect to the number and proportion of particles of the various kinds produced. The physical and mathematical description is extended to more than two stages of sample reduction, and the first three moments for any number of stages are developed. In common sample reduction practice the effects of a finite population (finite amount of material) at each stage of sampling appear to be important in describing the variance contribution of each stage. This is also true for the third moment about the mean. An example is cited in which the skewness increases by more than an order of magnitude when several stages of sampling are considered. This is largely due to the dependence of the multistage third moment about the mean on the variance. In general the model and results should be useful in helping to understand, control, and reduce the random errors that arise in the sample reduction process.

Jan 1, 1968

By M. O. Magnuson

As part of an experiment in the restoration of lands strip-mined for coal, revegetation studies were conducted at three backfilled strip-mine sites in north-central Pennsylvania. The sites were subdivided into plots that were given varying amounts of lime and fertilizer. In tests conducted cooperatively with State and Federal agronomy experts, the plots were then planted with a variety of trees, shrubs, and grass-legume mixtures. Initial tree and shrub survival was not appreciably affected by lime and fertilizer applications where the spoil pH was above 4.5. Of 14 species of trees and shrubs tested, Norway spruce, black locust, Japanese larch, pitch pine, and white pine were the hardiest. The ground-cover percentage of grass-legume mixtures in the second growing season was substantially increased by using lime and fertilizer. Mixtures comprised partly of fescue were the most satisfactory.

Jan 1, 1968

By McHenry Mosier

The Anson Bette manganese mine, with two prominent manganese-bearing outcrops in schist, has attracted considerable attention for its variety of manganese minerals and its possibilities as a potential source of manganese. Little mining was done prior to 1925, when the present owner acquired the property, and operations since that date have been intermittent. Mine workings are open cuts with a maximum depth of 35 feet. The two outcropping ore deposits are irregular, pipelike bodies about 500 feet apart. As nothing was known of the grade or extent of mineralization in depth, four holes totaling 1,072.5 feet of bore Were diamond-drilled by the Bureau of Mines in the summer of 1943, with the results shown in figures 3 to 6. In.1945 a geophysical survey was run to map the magnetic anomalies in the manganese-bearing belt as a means of determining the locations of manganese deposits. Positive correlation of magnetite and manganese ore was not obtained.

Jan 1, 1949

By Connie S. Musulin

The Bureau of Mines conducted an experiment at Exxon Mineral Co.'s Buffalo Shaft Operation to determine the time required for radon concentrations to return to a base average after fan shutdowns. Shutdown times ranging from 5 min to 16 hr were evaluated. An equation was derived to calculate a ratio that determines the time required for the radon concentration to return to the average level that existed in the mine prior to shutdown. For fan shutdowns of 15 min or more, underground personnel should be evacuated to areas with natural downcast ventilation. For shutdowns of less than 1 hr, personnel should not return to the working area until the elapsed time is four times the shutdown, or until the working area is resampled and found safe. If the mine is not in production during weekends, the downcast fans can be turned off .from midnight Friday until 4 p.m. Sunday, and the radon daughter concentration should be below 1 WL throughout the mine by the start of the shift Monday. This fan shutdown would conserve energy and save the mining company an estimated $21,000 each year.

Jan 1, 1982

By E. S. Burnett

The temperature entropy (T, S) chart? of thermodynamic properties of nitrogen herewith presented is a complete (1949) revision and a considerable extension of similar charts prepared by the author for use of the helium section of the Bureau of Mines about 25 years previously on the basis of inadequate data then obtaining. During the interval since that early effort, much experimentally determined information on nitrogen properties and behavior has been published, which now permits a more nearly accurate layout and more extensive charting of these relations.

Jan 1, 1950

By Leonard Obert

[Tng occasional. rock noises in a nice caured by brc,*ing and ripping of the back, settling, and other cailscr, are well-known tc~ a11 mining en- gineers. These noises oftcn prececte certnin tpes of rock failure as such are used to e certain event a; w:,rnlngs. Senides t5ese audible rock noisee t'nere are, l?o\;evpr, even Iprger nw.iber of' s;Lba.J^;li5le rock mis~s, which must; be piclcell UT with sole type of vi-urr,tion rnicroyhoce and qli- fied in order tnnt :hey n;ny e heard. It v:zs s~v;,yestec" Ir, an evlier ? ,I a.ldible noises Ifureau of I.lines s~zb:ic;et.iod that n stud:r of t!ler;c! *- t mig!!t be useful ir. de temining roc^ movemrnt 3 preceding failure.]

Jan 1, 1941

By Leonard Obert

[Tng occasional. rock noises in a nice caured by brc,*ing and ripping of the back, settling, and other cailscr, are well-known tc~ a11 mining en- gineers. These noises oftcn prececte certnin tpes of rock failure as such are used to e certain ev';ent a; w:,rnlngs. Senides t5ese audible rock noisee t'nere are, l?o\;evpr, even Iprger nw.iber of' s;Lba.J^;li5le rock mis~s, which must; be piclcell UT with sole type of vi-urr,tion rnicroyhoce and qli- fied in order tnnt :hey n;ny e heard. It v:zs s~v;,yestec" Ir, an evlier ? ,I a.ldible noises Ifureau of I.lines s~zb:ic;et.iod that n stud:r of t!ler;c! *- t mig!!t be useful ir. de temining roc^ movemrnt 3 preceding failure.]

Jan 1, 1941

By Ivette E. Torres

For a study such as this, which summarizes and amalgamates much information collected, compiled, and utilized by the numerous U.S. Bureau of Mines country specialists and branch chiefs for inclusion in their country and regional reports that comprise the five other sections of 1992 Minerals Yearbook-International Review, it is clearly impossible to cite all sources of information used in its presentation, but some recognition is due. Generally speaking, this study and its related detailed studies on countries and areas would be much more difficult, if not impossible to complete, without the efforts of the personnel of our counterpart national mining and geological agencies throughout the world. Information that they collect, compile, and then publish, either in their own volumes or those of central statistical agencies in their countries, are the foundations on which this work rests. Thus, our appreciation is expressed to the multitude of persons employed by these agencies for their contributions.

Jan 1, 1994

By Karl R. Becker

Detonators representing a sampling of various domestic commercial delay detonators were fired at various direct-current (dc) firing levels. Results of firings using well-below-recommended firing levels showed marked increases in delay times above the nominal values. There was also a marked increase in variation, to the extent that out-of-sequence firings would be essentially assured in any typical blasting round at these low firing levels. Within the range of recommended levels the effects of current increases were not considered to be of great importance relative to other overriding effects, such as the significant difference noted in average values of detonators from different lots having the same nominal delay. This effect, when combined with the normal variation noted among members from the same lot, would cause out-of-sequence firings with detonators from a neighboring delay period. Where comparisons with results from another study were possible, it was found that both studies observed quite similar variations in delay times about the average values, and a lower probability of out-of-sequence firings for the shorter delay period groups. The criterion of the previous study for assessing the likelihood of observing out-of-sequence firings, when applied to the Bureau of Mines data, properly identified two neighboring delay period groups where out-of-sequence firings would occur.

Jan 1, 1981

By E. D. Gardener, Byron O. Pichard

"Methane, frequently called fire damp or marsh gas, is very well known to coal miners but to thy average gold miner it means nothing, as it is not associated generally with the rock formations in which gold is found.We have recently been conducting a study of mine air in typical gold mines on the Pacific Coast, and out of five California mines in which the air was sampled, three showed methane. Each of these three mines, referred to below as mines A, B, and C, have had accumulations great enough to be ignited. An authentic report from another California, gold mine, which has not yet been sampled, states that recently the superintendent was seriously burned by the ignition of a pocket of gas. This mine is later mentioned as mine D.Mine A is an old mine which had been abandoned for several years and permitted to fill with water. It has been unwaterad recently, and is now being developed at greater depths. During the unwatering, gas bubbles formed on the water and upon being ignited burned freely. It is reported that two men were seriously burned from accidentally igniting the gas. Samples of the bubbles on analysis showed high percentages of methane. Since the mine has been unwatered, no trouble has been experienced through gas being ignited. However, out of a total of six air samples which we took recently in scattered working places, all showed small amounts of methane, the methane content being 0.06, 0.04, 0.05, 0.04, 0.04 and 0.07 per cent, respectively. When these samples were taken methane was not suspected, but its general presence in the mine air indicates that it is being given off constantly."

Dec 1, 1921

By F. C. Gregory

"The ""safety bonus"" in metal mining is a sum in addition to the regular wage, paid to foremen or bosses for keeping the accident rate down to a specified minimum. It has been used with success for some time by certain companies as a regular part of their safety work. It is desirable from the employer's point of view in that the desired results in accident reduction must be accomplished before the bonus is earned; and from the standpoint of the recipient, in that he receives a reward for the additional effort which he has put forth in order to earn the bonus.While this paper relates to the safety bonus as applied in the metal mining industry, the bonus system discussed herein will apply equal well to coal mining, oil-field work, and other mineral industries.Various estimates have been made as to the percentage of accidents that can be prevented through physical safeguards, adoption of safe working methods, and other safety measures which can be initiated and carried out wholly through the management or the safety department. This percentage will always be a vari¬able according to the local plant and conditions. But all who have been engaged in accident prevention agree that such work alone cannot bring the accident fre¬quency down to where it should be, and that it is very necessary to work directly with the workmen, in an effort to make each individual do his share in making the work safe. In this latter phase of the work, the boss who has immediate super¬vision of the men is the one who can do the most, since he is in daily and frequent contact with the men while they are at work. In the metal mines, the shift and stope bosses are the key men; in the oil fields, the ""tool-pushers"" or sub-foremen, and the same applies to all industries. So it becomes necessary to keep these sub-foremen constantly interested in accident prevention, both because they are in personal touch with the men and because they are responsible for production and hostile to any plan which they think will interfere with their output. In large organizations it is the shift boss who represents the company and its policies to the man on the job."

Jun 1, 1924

By W. A. Grosh

The Bureau of Mines began a comprehensive investigation of the old lead diggings in the Wisconsin portion of the Upper Mississippi lead-zinc field in September 1947 to determine whether enough lead was present in shallow deposits to justify exploitation by modern open-pit methods. Because of the large number of areas of surface diggings, it was necessary to limit the investigation to only a few representative areas. Initial studies, therefore, included test pitting and hand auger-drill sampling at two sites n Grant County and one site in Lafayette County to determine whether further extensive sampling in that area was warranted. Results indicated that certain portions of the area contained substantial amounts of lead and, zinc; accordingly, more detailed sampling was undertaken, and the results will be described in a later report. Another phase of the general investigation was drilling and test pitting at the Nigger Jim Lafayette County. This 10 the third of the series and summarizes the work on the White property to develop the western extension of the Big Dick ere body, where four churn-drill holes totaling 679 feet were drilled. Inclusion of the White property in the study was justified because old reports indicated (1) production of ore from mines in the vicinity disclosed a high ratio of lead to zinc, (2) ore was present in the west heading of the Big Dick mine when it closed, and the attitude of the Big Dick ore body was such that a vertical hole would encounter ore that might be present.

Jan 1, 1950