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By G. B. Langford

UOCK bursts are a phenomenon about which insufficient is known. This l.~ statement has a twofold meaning. In the first place, far too many people, both inside and outside of the mining industry, are woefully ignorant of the whole subject, and secondly, as those who are face to face with the problem in the mines realize, our knowledge of rock bursts is inadequate. The first group embraces the general public, who have never been enlightened on the subject, and a great many geologists and engineers who have never shown more than a curiosity about it. Such technical men do not realize what a vital problem it is to our mining industries. They are usually thankful that bursting ground is not their problem, and leave it to those unfortunate enough to run into it. From such men one often hears the pious opinion that if proper mining methods were used there would be no problem. It is hoped that this paper will give these people a different viewpoint. Those in the second group deserve much credit for what they have done and are doing. They are fighting a large and difficult problem. In the pages that follow, I have tried to give a bird's-eye view of that problem, and suggest new ways in which it may be attacked.

Jan 1, 1941

By Bjorge, Guy N.

MINING method improve through the gradual process of evolution and in 1340 there were no marked outstanding innovations. On the other hand refinements of detail and betterment: in equipment design continued to progress. Among the most important changes have been the increased application of trucks and highway equipment, including tractors and bull- dozers, to open-pit mining as exemplified by Phelps Dodge's Morenci operations; the Mesabi iron range; and the Tri-State district. Mass or bulk handling contributed its part underground with slurhers and conveyors at Consolidated Coppermines and slushers at Climax; and in open-pit mining. conveyors found increased use on the Mesabi range.

Jan 1, 1941

By F. W. Gray

A GEOLOGICAL study seeking to determine, for economic purposes, the value of the Sydney coalfield as a source of coal supply. Limitations of the coalfield come under two main heads: (a) Areal extent of the undersea coalfield. (b) The distance from shore at which coal can be mined at a cost of production permitting its profitable sale. Conclusions reached are that the areal extent of seams below the Phalen seam is of. small economic importance, and that non-persistence of these seams in full thickness and quality in the undersea extension of the coalfield will put an end to profitable mining before any limitations connected with distance from the shore-line become operative. With respect to the Phalen seam, non-persistence or deterioration of the seam will become effective in the western part of the coalfield, and less certainly in the eastern part of the coalfield, before operation of limitations by distance from shore. In the central portion of the coalfield, the seam probably persists in commercially workable thickness and quality to beyond the limit of mining set by distance from the shore-line. With respect to the seams above the Phalen seam between the Mountain fault on the extreme western boundary of the coalfield and the assumed termination of the deposition area on the eastern extremity of the field near South Head of Morien, there appear to be only such limitations as arise from engineering approach, distance from shore, sufficiency of strata cover between the sea-floor and the upper coal seams, and quality of the coal (with certain reservations as to the continuity of the upper seams under Sydney harbour and in the Sydney Mines-Little Bras d'Or district). Some of these seams have fragmentary land outcroppings from which their persistence seaward is assumed, and there may be other and still higher seams in the strata column which are entirely submarine.

Jan 1, 1941

By J. R. Thoenen

[Before 1914 Germany held virtual monopoly on the world supply of potash for fertilizer purposes. During the world War, potash shipments to the United States ceased, and recourse was had to domestic supplies. High war-time prices stimulated interest n various sources, and domestic production increased rapidly. At the close of the war, resumption of shipments from Germany and other sources reduced prices to below pre-war levels, and, as a result, most of the domestic producers ceased operational.]

Jan 1, 1941

By J. R. Thoenen

[Before 1914 Germany held a virtual monopoly on the world supply of potash for fertilizer purposes. During the World War, potash shipments to the United States ceased, and recourse was had to domestic supplies. High war-tine prisms stimulated interest in various sources, and domestic production increased rapidly. At the close of the war, resumption of shipments from Germany mad other sources reduced prices to below pre-war levels, and, as a result, most of the domestic procedures ceased operations. This experience demonstrated that a domestic source of potash was necessary but that it must be of such a nature that it could compete in price with foreign sources. As a direct result the potash content of thick]

Jan 1, 1941

By Thomas T., Read

IT does not seem practicable to review all the other specialized curricula that have developed in the mineral industries field in so much detail as has been given for petroleum. Nor is it easy to draw a definite line between true curricula, leading to a designated degree in the special subject, and options, which may range from the mere substitution of one or two courses for others ' in the final years to differences so extensive as almost to amount to separate curricula. Even to attempt to catalogue all the options that have been offered at one time or another would , require too much space. The remainder of this discussion, there- fore, will be confined to three topics which seem to be of major importance. Mining and metallurgical curricula will be covered in a later chapter. Geology The first, from the historical view, is geology in its relation to the mineral industries. Previous, chapters have made clear that in the early years of mineral industry instruction in the United States economic geology and mining engineering, so overlapped one another that men who were by training and experience economic geologists were appointed professors of mining, while men who had graduated as mining engineers sometimes developed into professors of geology. Even today men whose basic training was in- geology as a pure science, and who perhaps took a doctor's .degree in that subject, have attained such distinction in the mineral industries as to be universally accepted as "mining men," and their right to be regarded as mining engineers would not be questioned, even though 'they did not .take a degree in engineering. Nevertheless the distinction does exist, and has been made a concrete reality in recent years by the enactment of

Jan 1, 1941

By W. L., Yerkes

AN interesting study of the application of air-, conditioning to the problem of mine ventilation and cooling can be found on the Witwatersrand in South Africa. Here there are a large number of deep mines in a relatively small area. Due to the nature of the reef, many mines are working at a depth of 6000 ft. and some have gone down to 8000 and 9000 ft. below the surface. At such depths, even in a country geologically as old as Africa, the virgin rock temperature approaches 110°F. The flow of heat from the- rock to the ventilation air is tremendous though the shaft or drift may have been open to ventilation for some years. In addition, there is the heat produced by machinery, lights, and men at work and the heat of adiabatic compression of air introduced into the mine. The difference in atmosphere pressure between the collar of a shaft and a level 6000 ft. below is nearly 3lb. per sq. in., resulting in an increase in heat content of nearly four B.T.U. per pound of air delivered to the mine at surface. Further the exclusive use of wet mining to reduce the incidence of miner?s phthisis increases the latent- heat content of the air.

Jan 1, 1941

By Oliver C. Ralston

The Nonmetals Division studies problems relating to the use of minerals, many of which are important to national defense, for purposes other than the: extraction of metals. In fact, virtually all of the work of the division has been diverted to investigations pertaining to better use of the Nation's natural nonmetallics is resources as weapons of defense. The experiment stations of the division are at Norris, Tenn.; Tuscaloosa, Ala.; Seattle, Wash.; and College Park, Md. Studies involving the application of electric power to the nonmetallic minerals are conducted at the Electrotechnical Laboratory at Norris, and investigations on mineral-dressing treatment are conducted mainly at the Southern Experiment Station at Tuscaloosa. The cleaning and preparation of coal are studied at both Tuscaloosa and the Northwest Experiment Station Lit Seattle (other projects relating to utilization of coal are conducted by the Coal Division of they Bureau of Mines). Problems covering the use of minerals and fundamental problems as to their properties are studied at College Park.

Jan 1, 1941

By W. P. Yant

This report describes result of a study of the carbon monoxide and particulate matter in the air of the Holland, Tunnel and metropolitan New York made by the Bureau of Mines (which had participated in the development

Jan 1, 1941

By W. P. Yant

[This report describes results of a study bf the carbon monoxide and particulate matter in the air of the Holland Tunnel and metropolitan New York made by the Bureau of Mines (which had participated in the development]

Jan 1, 1941

By E. D. Gardner

This bulletin, which discusses open-cut mining at the metal mines of the United States, is the last of a series of such papers by the Bureau of Mines describing the principal methods of mining.4 Open-cut mining is applicable to flat-lying mineral deposits relatively near the surface. Vein deposits seldom are amenable to this method, although outcrops of veins sometimes are worked as open pits. Most of the iron ore of the country is mined from open pits; according to the Minerals Yearbook, 67.4 percent was mined from open pits and 32.6 percent from underground mines in 1937. Open-cut mining is relatively new in the copper industry but yields more copper than any other method; in 1937 about 52 percent of the copper ore mined in the United States was taken from open pits. Lead-zinc ore has been produced from open pits in the Joplin (Mo.) district, but most of the deposits in this area, although flat-lying, are too deep to be mined economically by the open-cut method. In 1937 one company at Oronogo, Mo., was stripping overburden and mining mixed oxidized and sulfide ores by this method.

Jan 1, 1941

By W. W. Adams

Every man-hour of work performed in and about the coal mines of the United States had a 2-percent heavier death load from accidents in 1938 than in 1937. This is an unorthodox way of stating that the death rate per million man-hours of exposure or employment was 2 percent higher in 1938 than in 1937, increasing from 1.74 to 1.78. Thus the average miner had a 2-percent greater chance of being killed in 1938 than he had in 1937. The average quantity of coal resulting from 1 man-hour of work increased 3.6 percent -from 0.615 ton in 1937 to 0.637 ton in 1938. The production of the average ton of coal was accompanied by a slightly smaller loss of life in 1938 than in 1937, the accident rate being 2.793 per million tons in 1938 compared with 2.833 in 1937.

Jan 1, 1941

By L. W. Blau

PERHAPS the most important event f or exploration geophysics in 1940 was the publication of three textbooks : "Geophysical Prospecting for Oil," by L. L. Nettleton ; "Exploration Geophysics," by John J. Jakosky; and "Geophysical Exploration," by C. A. Heiland. The literature had grown so bulky, and such a long time had elapsed since the publication of the texts by Ambronn and Eve, that treatises covering exploration geophysics comprehensively in all its branches and giving literature and patent references were sorely needed. This need has been satisfied admirably in these textbooks, and geophysicists owe the authors a debt of gratitude. In 1940, geophysics came of age. A conference on applied nuclear physics was held at Massachusetts Institute of Technology from Oct. 28 to Nov. 2. Several papers on geophysical subjects were presented at this meeting. Geophysical activity has decreased in all parts of the world except perhaps in Canada where, under the stimulus of the war's increased demands, prospecting for oil has increased. However, even there the war has had a seriously adverse effect on prospecting for ores and upon the promotion of new properties, although activity in producing and near-producing mines has been stimulated.

Jan 1, 1941

By S. H. Ash

IN no part of the world other than a small area in Pennsylvania is anthracite mining an industry of major magnitude. As the deposits of anthracite in the United States are limited virtually to Pennsylvania, the difficulties of this industry have been commonly considered a state rather than a national problem. However, there is also national interest in the conservation and wise utilization of all the country's fuel resources and in the control of interstate waterways. The anthracite industry is confronted with a serious problem of water accumulation in many of the mines, a problem that must be solved in the near future if progressively higher mining costs are to be avoided. It cannot be solved by the operating companies without state or Federal aid, or both, owing to the magnitude of the work required, the diversity of interests of the coal and surface ownerships, the hazard to the whole mining community, and interests affected outside the mining region. 'The costs of abating the ever-increasing surface seepage to mine workings and of handling this seepage once it has occurred are beyond the eco¬nomic resources of the operating managements.

Jan 1, 1941

By JOHN R. SUMAN

IT SEEMS particularly appropriate that the Institute's Regional Meeting should be held in Minnesota this year. Whether we like it or not, we cannot help looking at things now in the light of the World War and the all-out effort we, as a nation, are making to defend our resources, our institutions, and our way of life. The ability to do this lies in large measure in the ability to forge weapons of defense-the machines of war. The basic ingredients of any defense system, or war machine, are the raw materials of industry-iron ore, providing steel for guns, shells, tanks, and warships; coal for stoking the nation's furnaces; oil to furnish power for war planes, ships, trucks, and mechanized weapons; and all the other materials that play a vital role in the operation of modern armies and navies. The tremendous requirements of full-scale defense programs are indicated by the large number of commodities that are now under priorities because the supply is not sufficient to meet both defense needs and all normal civilian consumption. But out of all these items two are of paramount importance-steel and petroleum. In this age no nation can hope to main¬tain a position as a first-class power in the world without a highly developed industry, particularly the heavy industries based on steel, and without access to the necessary resources for those industries. In 1918, 70 per cent of the iron and steel production of the United States was required for defense purposes. In 1940, 15 per cent of our iron and steel production was consumed for defense purposes, and with the acceleration of the defense program, it appears that the proportion of steel output required for defense purposes will reach 40

Jan 1, 1941

The revival of the mining industry at Captain's Flat after a long period of years of inactivity has attracted attention to the importance of the ore-deposits of that field as potential sources of supply of lead and zinc. Mindful of the necessity for taking stock of the State's mineral resources, the Department of Mines of New South Wales as part of its programme of geological investigation, carried out a survey of the oredeposits and associated country rocks during 1938 and 1940.Surface geology was mapped in detail and all available exposures were examined and logged. Unfortunately, and this condition militates against the formulation of conclusions because of insufficiem.t data, some of the older workings, notably in Keating's Section, were inaccessible and the logging of levels and stopes is by no means as complete as could be desired. However, with the progress of development and exploration, further information of geological value will come to hand for incorporation in supplementary reports. It may be expected that, under such circumstances, modification of certain statements herein expressed may be necessary but it is not anticipated that any vital alteration will be occasioned.Within the State of, New South Wales, Captain's Flat ranks second to Broken Hill as a pqtem.tial producer of lead and zinc. In addition, large quantities of iron pyrites are available for the manufacture of sulphuric acid which finds application in the superphosphate industry.The mines are now controlled by an operating company known as Lake George Mines, Ltd., incorporated in New South Wales, the parent organisation being the Lake George Mining Gorporation Ltd., registered in London.Over £600,000 has been spent by the Company in exploration, mine development, surface plant, housing and water 'conservation, while the State' Government constructed a branch railway from Bungendore at a cost of £200,000. The various activities consequent upon these development and construction programmes and the prospect of employment in the industry has led to a rapid increase in the population of the township.The State, generally, has benefited to the extent of a substantial contribution to the relief of the unemployment problem, and it is hoped that reasonable permanency will be assured to some hundreds of workers for many years.

Jan 1, 1941

By AIME AIME

JANUARY saw the completion of the 237-ft. Upper-Narrows hydraulic debris dam on the main Yuba River in northern California. This project which is the key unit in a series of four similar structures on the Bear, American, and Yuba Rivers, removes the last obstacle to the revival of California's vast hydraulic gold-mining industry. The Upper-Narrows dam is a single-arch type of structure, and embodies the latest developments in that type of construction. One of the principal innovations used is the series of air vents in the crown (that part over which the water spills) which serve to break the vacuum caused by the spilling water, thus reducing vibration to a minimum. Electric strain gages were also embedded in the concrete of the dam, and it is hoped that by careful study of these instruments true stresses can he determined.

Jan 1, 1941

By M. A. Elliott, H. H. Schrenk, L. G. Berger, John C. Holtz

"INTRODUCTION Interest in the possibility of using Diesel 6/ engines for haulage power in mining and tunneling is increasing in the United States, owing largely to the reported successful use of Diesel locomotives in European coal mines and to the comparatively recent development of automotive Diesel engines in this country. The extent of this interest has been evidenced to the Bureau of Mines by numerous requests for information as to the factors that must be considered if Diesel engines are to be used safely underground.Proponents of the application of the Diesel engine to underground haulage base their claims for its safety upon a comparison with the gasoline engine, assuming that (1) the carbon monoxide content of Diesel exhaust gas is always low and that (2) fire and explosion hazards from Diesel fuel are minimized because of its low volatility. In these respects the Diesel engine appears less hazardous than the gasoline engine, whose use underground has been discouraged by the Bureau of Mines and other organizations interested in safety in mining. However, such generalizations cannot be accepted as conclusive evidence that safety is inherent in Diesel engines in underground service, as European experience indicates that certain hazards may accompany their use. Such hazards were discussed in a previous publication 7/ that reviews developments in the use of Diesel locomotives in European coal mines.The Bureau of Mines has initiated a study of the hazards that may attend the use of Diesel engines underground to obtain first-hand information that may serve as a basis for recommending sale practices under conditions existing in the United States."

May 1, 1940

"To prevent the propagation of mine explosions, the Bureau of Mines recommends:1. That all coal and lignite mines, except anthracite mines shall be rock dusted.2. That rock dust shall be distributed upon top, bottom, and sides of all underground openings of every description, to within. at least 4o feet of all working faces and the areas not rock dusted shall be kept wet.3. That the rock dust shall be maintained in, such quantity that the incombustible material in representative samples of dust collected shall not be less than 65 percent. Where methane gas is present in the ventilating current, the minimum percentage of incombustible matter in the mine dust shall be increased 1 percent for each 0.1 percent of methane.4. That when the rock dust in any area becomes caked so thatit cannot be dispersed readily as a cloud in the air, that part of the mine shall be redusted immediately.5. That the dust to be used shall not contain more than 5 percent of combustible matter nor. more than 25 percent of quartz or free silica; all of the dust shall pass through a sieve having 20 meshes per linear inch and 60 percent or more shall pass through a sieve having 200 meshes per linear inch; the dust shall not absorb moisture from the air to such an extent as to cake and destroy its effectiveness as a dry dust.6. That rock-dust barriers shall not be regarded as a substitute for generalized rock dusting.Research and experience have shown that maintenance of an adequate percentage of rock dust in all underground openings, whether gassy or not, of bituminous and subbituminous coal and lignite mines (anthracite dust does not propagate explosions) is the best means of preventing coal dust explosions. In rare instances where all fine coal particles on the floor, ribs, roof, and timbers are in a muddy condition continuously rock dusting is unnecessary.The term ""underground openings"" refers to all unsealed openings whether they contain track or not, and includes rooms, entries, crosscuts, breakthroughs, rock tunnels, slopes, haulageways, airways, and travelingways. The sealing of unused or abandoned parts of a mine in accordance with Mine Safety Board Decision avoids the necessity of rock-dusting the sealed-off openings.The kind of rock dust to be used should have the approval of the State Mine Inspection Service. Pure limestone or pare dolomite produces the best rock dust, as these dusts have low silica content, little tendency to cake, and a light color that aids illumination. To reduce tendency to cake it is preferable that not more than 75 percent of the dust pass the 200-mesh sieve. All sieve sizes are those of the Tyler screen scale. If the mine personnel is repeatedly exposed to breathing high concentrations of the dust, the percentage of free and combined silica should be as low as possible, preferably less than 5 percent. Persons engaged in the application of rock dust should wear approved dust respirators as listed in Bureau of Mines Information Circular 7030 or revisions thereof."

Mar 1, 1940

By G. Stuart Jenkins

Conditions at the properties of the Consolidated Coal Co. had reached a point where improvements were almost impractical. The mines, sunk years ago, had shafts and entries so small as to preclude the use of large mine cars. A radical change was necessary in the type of mining and also in the type of mine to accommodate such haulage units. After due consideration, the company decided to enter the field of trackless mining, utilizing belt conveyors and chain-flight conveyors, the belt conveyors to take the long haul, and the chain-flight conveyors to be used for gathering. It was decided not to sink a shaft, hut to drive a slope on an inclination of 17½°, which the company believes to be about the limit on which coal can be carried on a belt without rolling back unduly. Sinking the Slope It was decided, in sinking the slope, to make an opencut until rock was reached, which was some 65 ft. below the surface, and then to drive the slope through an inclined tunnel from that point. In making the open-cut, the schedule called for the removal of about 25,000 cu. yd. of clay, holding the banks on an inclination of one and a half to one, the thought being to make this cut in a minimum of time, put in a reinforced concrete slope, and then back-fill. Difficulty was experienced because the clay was of a sort that was called "subsiding base" material by contractors visiting the job. In other words, a "squeeze" occurred, the pressure causing the floor of the cut to move up just as it does in many mines where the coal is underlain by thick fire clay and inadequate pillars have been left. It was necessary to move the waste banks back from the edge of the cut 700 or 800 ft., and even then the floor could not be controlled, the result being that almost 100,000 cu. yd. of clay was handled before the rock was reached. A concrete slope was then rapidly constructed, using 95 tons of special-shaped reinforcing iron. The floor of this slope was made 30 in. thick at the bottom, and 17 in. thick at the top, the sidewalls being 18 in.

Jan 1, 1940