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By J. Absil, H. Dreissen

Upgrading low-concentration ores is of increasing importance today. The heavy medium cyclone process, due to strong centrifugal forces, effectively separates particles varying only slightly in specific gravity but widely in size. The paper discusses separation efficiency, assessment of that efficiency, and the influence of such factors as medium solids. The operating results of nine heavy medium cyclone plants, each handling a different mineral, are reported.

Jan 1, 1982

Surface mine operators often gamble that the savings gained from elimination of haul-road subbase preparation will offset any potential loss in production due to deteriorating roads. According to the authors of a manual on haul-road construction, this practice yields results that are almost always undesirable. The lack of suitable weight-bearing material under the road surface permits extensive rutting, sinkage, and overall deterioration of the roadway, and a great deal of maintenance work will be needed to keep the road usable. In addition, say Walter W. Kaufman of Skelly and Loy, and James C. Ault, USBM Pittsburgh Mining and Safety Research Center, adverse road conditions pose a serious threat to vehicular controllability and create unsafe haulage road segments.

Jan 3, 1978

By H. R. Wenk

This paper describes a workshop on deformation mechanisms and texture development in rocks. Empahsis is on relating macroscopic mechanical properties with microscopic structures and the methods of their quantitative analysis.

Jan 1, 1982

By Robin P. Gardner

Prior work by the author has established that closedform analytic solutions can be obtained for certain steady-state and transient types of operation of open circuit, continuous ball mills. This is possible when the tanks-in-series concept is used with the segregated flow or lumped parameter milling models. Such models should be useful (whenever they apply) in any calculational application since they are efficient and simple to program for digital computation. For example, they might be used within a computer program such as that developed by Herbst et al. for the calculation of model

Jan 1, 1975

By Subhash C. Malhotra

This paper discusses the historical background on major sources of obsolete electronic scrap and spent catalytic converter scrap. The paper discusses the principal changes taking place that will affect the future supply of these scraps. The author projects from this background the future opportunities for reclaimers and refiners in these two important segments of the precious metals scrap reclamation industry.

Jan 1, 1984

POSITIONS VACANT (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) Advertising Manager for Machinery Manufacturing Company. Must have technical training. No. 94. ENGINEERS AVAILABLE (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Member, technical graduate in Mining, Chemistry and Metallurgy, Post-graduate, Royal School of Mines, Freiberg, Saxony, Germany and Columbia School of Mines. Aged 37, 14 years' experience in teaching mining metallurgy, chemistry and assaying. Available now. Willing to go anywhere. No. 278. Member, aged 33, mining engineer, 88 years' experience, desires position as mine safety and efficiency engineer with coal company. Best of references on request. No. 290.

Jan 5, 1916

[James C. Gray, President W. B. Stephenson, President-Elect A. B. Cummins, Past-President E. G. Fox, Eastern Regional Vice-President H. C. Weed, Western Regional Vice-President Donald W. Scott, Central Regional Vice-President John Cameron Fox, Secretary 29 W. 39 Street New York 18, N. Y. After September 7, 1961 345 East 47 Street, New York 17, N. Y. D. R. Tone, Assistant Secretary Nathaniel Arbiter, Treasurer]

Jan 1, 1961

By R. F. Davis

The evaluation and selection of coals for producing metallurgical coke is indeed a complex process simply because coal is a complex and variable substance which is sensitive to how it is treated from the time it is mined until it is transformed into coke. A review of some of the more common evaluation tests made on coal and how the test results are applied in commercial practice should be of interest. Parameters used to select coking coal blends for wet and preheated charges should also be of interest.

Jan 1, 1982

In situ mining techniques have become prominent in recent years due to declining ore grades, rising costs, and increasing concern for miners' health and safety. Current practices depend heavily on the effective and uniform fragmentation of the ore zone of interest, which not only provides for proper media flow but also exposes additional surface areas to react with the processing system. Specifically, current applications have focused on blasting to a mined-out opening or, in the case of shallow de- posits, blasting to the surface void. In the former case, several obstacles are encountered, including proper initiation, uniform fragmentation, and a lack of swell space for the blast, which tend to produce less desirable results in the zone of' interest.

Jan 3, 1979

By Adrian C. Dorenfeld

Factorial design is a mathematical method of drawing valid conclusions from a series of tests made in a predetermined pattern. It is applied to flotation ore testing using, in this case, five variables, each varied twice, requiring a total of 32 tests. Representative conclusions are checked by repeat testing.

Jan 12, 1951

Perhaps, after years of concerted effort at a mineral prospect, your company has reached the stage of feasibility study. Detailed target investigations, drilling, bulk sampling, land acquisition, and engineering analyses are complete, and the deposit still remains an attractive investment possibility. Your company, after long study, decides to begin mine development-now, how do you convince lending institutions that your proposed operation will return their borrowed funds, plus interest, over the term of the loan?

Jan 12, 1978

By Paul L. Allsman

Mankind has found lime and limestone a useful mineral commodity since the dawn of history. The ancient Egyptians knew how to make use of it as a building material, and it has been used in agriculture for centuries. More recently, limestone became a cheap ingredient in some chemical processes, in metallurgy and in the manufacture of alkalis. The consumption of lime and limestone has never diminished; in fact, the process of lime production remained the same until the recent introduction of the modern rotary or vertical kilns. However, the demands of industry and agriculture are changing the usage patterns of the commodity. The USBM now keeps statistics according to type- quicklime, hydrated lime and dead-burned dolomite -and according to market, whether open or captive.

Jan 6, 1966

By William P. Blake

The importance to the growing steel industry of the United States of a domestic supply of ferro-manganese or "spiegel" of a high grade, induces me to bring to your notice some details of the method by which a superior article is produced in the Austro-Hungarian Empire. At Reschitza, Hungary, and probably at Laibach also (the Krainische Industrie Gesellschaft), ferro-manganese is made in a blastfurnace, with charcoal as fuel, and limestone as the flux. The ore is a ferruginous mixture, containing about 37 per cent. of sesquioxide of manganese. It is silicious, and somewhat, resembles, in its appearance, the manganese ore from Red Island, in the Bay of San Francisco, California. It contains about 29 per cent. of silica and some alumina, shown by the subjoined analysis:

By S. E. Craig

Jen Inc., operator of the Cord mine, in the Big Indian district of San Juan County, Utah, has a contract with a milling company that provides a small bonus for proper grading and preparation of uranium ores shipped. To obtain maximum returns on this contract very close grading is required with settlements made on individual lots, which vary from 250 to 300 tons. Another feature of the contract, and one that is rather unique in this country, is that the ore is sold over truck scales at the mine. Grade is determined at the buyer's sample plant. It is necessary to take a moisture sample of each truckload shipped for ac- curate weighing and this is done by the representative of the buyer, using facilities supplied by Jen Inc. The sample is hardly more than a grab sample and includes only the finer and smaller pieces of the ore shipped.

Jan 10, 1958

By Edel Moldenke

BURMA has long been known for its ruby, tungsten, and tin deposits, and, lately, for having the largest lead-zinc mine in the world, the Bawdwin Mine of the Burma Corpn. All the coal used, however, is imported from Calcutta; this is a bituminous coal of about 11,000 B.t.u., 24 per FIG. 1.-MAP SHOWING LOCATION OF COAL FIELDS AND TRANSPORTATION ROUTES. cent. ash, and costs about $8 per ton. Bituminous coal has not, thus far, been found, but many lignite deposits are known. The most promising lignite deposits are in the Namma field, Fig. 1, situated in the Northern Shan States of Upper Burma, about 30 mi. south of Lashio, the terminus of the Burma Railway, 750 mi. north of Rangoon. The

Jan 7, 1921

By Robert W. Bruhn

An investigation was made of ground response to pillar retreat mining in a 1.7 meter thick seam at 108 meter depth at a site in northern West Virginia. This paper describes mining-related stress changes and movements at mine level, displacements within the overburden, ground surface subsidence and groundwater level variations. Subsidence approached 40 per cent of the mine height and continued more than a year after mining. Water levels declined in certain deep-lying strata.

Jan 1, 1984

By Donald A. Dahlstrom

Stronger Than Armies This editorial by Dr. Dahlstrom is based on his acceptance speech of the 1976 Robert H. Richards Award-Ed. Many public figures are saying that the United States is facing the most critical period in its history, and many of us would agree. But people have always been saying this, and all of them were right. They were right two centuries ago when it took a revolution to give birth to the Republic; and they were right during our Civil War, Pearl Harbor, the Great Depression, etc.

Jan 6, 1976

Montreal, April 6-7. "Resilient" and "bullish" were the terms used by R. D. Mushlitz of Asarco and K. C. Hendrick of Noranda Sales Corp. respectively, to describe the near term prospects for lead and zinc. The two men delivered their predictions at a joint meeting of the Lead Industries Association and the Zinc Institute held here. In speaking before a packed audience, Mushlitz insisted that "the lead industry is far from the sedentary one which many would have us believe, and although it may be slow and tortuous at times, . . . it is a viable and progressive industry which won't give up easily to the various pressures. . . . and, in the long run, will prevail."

Jan 5, 1972

The suggestions of the members of the Institute are very much desired by the Committee on Nominations prior to deciding upon its nominations to fill the places of those officers who retire early in 1917. The Committee must make its final report to the Board of Directors early in October. The members are, therefore, asked to send in promptly their .suggestions for Directors as well as for Vice-Presidents and President. The Committee hopes to hear from a large number of the members. The officers to be elected at the annual meeting in February, 1917, are: One officer, known as Director and President. Two officers, known as Director and Vice-President

Jan 8, 1916

By Joseph A. Newman

THE first trial of longhole drilling of raises began in June 1949 at the Holden mine, Chelan Div., Howe Sound Co. The cost of this raise was about the same as the average cost of raising by normal methods which was sufficiently encouraging to give the method further trial. At Holden, the Noranda method of blasthole drilling is used except that percussion drills have replaced diamond drills for making blastholes in all but certain special situations. Two thirds of these holes are between 40 and 70 ft long.

Jan 10, 1951