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LIMA (PERU) Established May, 1952 (Official year begins in June) Luncheon meetings third Wednesday monthly Ernesto A Baertl, Chairman Arthur C Hall, Chairman-elect Raymond R Beard, 1st Vice-Chairman Edgardo Portaro, 2nd Vice-Chairman Walter E King, Secretary-Treasurer Av Santa Cruz 331 San Isidro, Lima, Peru Alberto E Brazzini, Asst Treasurer Daniel M Rodriguez, Asst Secretary Robert P Koenig, '56, Section Delegate Arthur C Hall, Alternate Section Delegate

Jan 1, 1955

At its meeting on February 21, 1933, the Board of Directors passed the follow¬ing resolution defining and expressing the policy of the Institute with respect to official participation or action m controversial matters WHEREAS, the Board of Directors at its last meeting passed the following resolution "The Board of Directors, having been appealed to by several Local Sections for advice concerning the attitude and policy of the Institute relating to the endorsement of candi

Jan 1, 1952

By John D. Morgan

THE tense international situation prevailing in the postwar period, and the outbreak of actual hostilities in Korea, directs attention to the status of United States reserves of strategic and critical materials for war. Geologists and mining and metallurgical engineers are particularly interested in this problem, since, with a few important exceptions, almost all of the materials on the official list of strategic and critical materials for stockpiling (see top of page) are metals and minerals.

Jan 3, 1951

By Elmer R. Kaiser

G. A. Vissac (Consulting Engineer, Vancouver, B. C.) —Some of the data presented in this paper, in connection with cost studies of washed coals, should be clarified and qualified. Washing a raw coal down to a low ash content may mean higher losses in refuse, but the cost of the operation may be more than compensated by the increased value of the resultant product. However, careful engineering and accurate machinery are required to insure maximum profits. Washing at a low gravity separation demands a very accurate automatic process, chiefly when the small sizes of coal are being handled. Coal consumers today are buying mostly on a Btu basis, cognizant of the fact that low ash contents result in lower installation costs and in savings in handling and transportation charges. The attached Table X gives the actual balance sheets of the various cleaning operations corresponding to various ash contents for the two coals presented in the paper, using the old technique of a two-products separation. or the new technique, now commonly used in Europe, of a three-way separation made possible by new methods and new equipment. Savings in capital costs, handling, and transportation have been calculated on the basis of a delivered cost f.O.b. plant of $10.00 per ton of coal at 16.5 pct ash (actual 1953 average price reported by Consolidated Edison, N. Y.), and of $3.50 at the mine also for 16.5 pct ash coal. In both cases this corresponds to values of 126 and 4.26 per 1 pct of combustible and per ton, respectively, on delivered and on at the mine prices. As an example, the middle western coal at 16.5 pct ash, raw, washed down to 4 pct ash in a two-way process will give 53.75 pct of clean coal at 4 pct ash and 46.25 pct of refuse at 31 pct ash. The value of the losses will be 0.4625x(100—31)x0.042 = $1.34. Add the cost of washing, capital, and operation, which is $0.35. The total cost will then be $1.69. But with a three-ways separation we will have 53.75 pct of first-grade coal at 4 pct ash, 37.25 pct second-

Jan 1, 1955

By P. E. Fitzgerald, J. C. Gindlesperger

1. The Acidizer (Trade Publication of Dowell Inc.): No. 1. Aspects of Acidizing. No. 2. Inhibited Acid. No. 3. The Value of Acidizing. No. 4. The Chemistry of Acidizing. No. 5. Jelly Seal in Acidizing. No. 6. Loosening Stuck Drill Pipe. No. 7. The Geology of Acidizing. 2. J. C. Albright: Acid Is Being Used for Cleaning Intake Wells in Water-flooded Areas. Oil Weekly (Sept. 23, 1935) 24. 3. D. H. Bancroft: Acid Tests Increase Production of Zwolle Wells, Miller County, Arkansas. Oil and Gas Jnl. (Dec. 22, 1932) 42. 4. A. H. Bell: Possible Areas for Acid Treatment in Illinois. Pub. of Illinois- Indiana Petr. Assn. and lllinois Geol. Survey (1934) 49. 5. N. A. Best: Treating Limestone Formations Consists of More than Pouring Hydrochloric Acid in the Well. Oil and Gas Jnl. (April 5, 1934) 54. 6. L. G. E. Bignell: Sealing Off Salt Water from Oil-bearing Formations. Oil and Gas Jnl. (Jan. 30, 1936) 59. 7. L. G. E, Bignell: Acidizing Upper Limestone Formation Facilitated by the Use of Jelly Seal. Oil and Gas Jnl. (March 5, 1936) 30. 8. L. G. E. Bignell: Bailing, Shooting, Tubing and Acidizing Have All Been Tried in Deep Test at Binger, Oklahoma. Oil and Gas Jnl. (May 10, 1934) 38. 9. L. G. E. Bignell: Dowel1 Incorporated Increasing Its Field Service for Acid Treatment of Wells. Oil and Gas Jnl. (June 7, 1934) 62. 10. L. C. Chamberlain, Jr. and P. E. Fitzgerald: Oil Well Acidizing in Michigan. Mich. Acad. Sci. Papers (March 1937). 11. M. E. Chapman: Some of the Theoretical and Practical Aspects of the Acid Treatment of Limestone Wells. Oil and Gas Jnl. (Oct. 12, 1933) 10. 12. C. E. Clason and J. G. Staudt: Limestone Reservoir Rocks of Kansas React Favorably to Acid Treatment. Oil and Gas Jnl. (April 25, 1935) 53. 13. W. F. Cloud: Cleaning and Reconditioning Oil Wells—Reconditioning by Use of Acid (Petroleum Production 1937), 389. University of Oklahoma Press, 1937,' 14. K. A. Covell: Developments in Eastern Production Practice. Acid Treatment of Michigan Wells. Amer. Petr. Inst. Prod. Bull. 213 (1934) 77; Oil and Gas Jnl. (May 31, 1934) 89; Oil Weekly (May 28, 1934) 17. 15. B. A. Cunningham: Acid Treatment of Lime Formations. Amer. Petr. Inst. Paper 901 (1933) 9D, 1-7. 16. 0. I. DeSchon: Pondera Production up 22,000 Barrels. Montana Oil & Min. Jnl. (Jan. 26, 1935) 1.

Jan 1, 1937

By W. H. Hough, P. B. Leavenworth

Development in the Upper Texas Gulf Coast during 1943 resulted in the discovery of 11 new fields as compared with 12 discovered in the same area during I942. Of the 11 new fields, eight are classed as oil and/or condensate and three as gas fields. In addition to the new discoveries, several more or less important new horizons and extensions were encountered in some of the older fields, as noted in the text under the heading "New Pays and Extensions.'' Drilling During the year, 418 wells were drilled, as compared with 356 drilled during 1942. Of these, 323 were field wells, of which 188 produced oil, 21 were gas wells and 114 were dry holes. The remaining 95 viere wildcats, 12 of which produced oil, 4 produced gas and 79 dry holes. Distribution of themwildcats with respect to the various trends may be summarized as follows: over the 91,340,492 bbl. produced in the same area during 1942. The production statistics in the text and the accompanying tables include condensate or distillate as oil production, because many Gulf Coast fields produce oils with a wide variation of specific gravities, all of which are commingled in pipe lines. Table 3 shows by counties all of the drilling and production" data applicable to this particular area. Outstanding Fields of 1943 The Upper Texas Gulf Coast covered in this report has 178 more or less active oil and gas fields, including the 1943 discoveries. Of these Table 4 lists those that were most important from the standpoint of production. Each of these fields pro duced in excess of one million barrels of oil during 1943. Some of the interesting facts to be noted from this list of some 26 oil fields are: (I) four of the fields— namely, Conroe, Hastings, Friendswood and Thompson—each produced more than 10 million barrels during 1943, whcrcas Conroe and Hastings were the only fields that produced 10 million barrels during 1942; (2) some of the older fields (discovered prior to 1920), such as Barbers Hill, West Columbia, and Hull, are still producing in excess of one million barrels annually; (3) some of the fields more than doubled their 1942 production—e.g., Anahuac and Friendswood. The large increase in production in practically all instances is the result of increased allowables from wells drilled prior to 1943 and

Jan 1, 1944

By W. H. Hough, P. B. Leavenworth

Development in the Upper Texas Gulf Coast during 1943 resulted in the discovery of 11 new fields as compared with 12 discovered in the same area during I942. Of the 11 new fields, eight are classed as oil and/or condensate and three as gas fields. In addition to the new discoveries, several more or less important new horizons and extensions were encountered in some of the older fields, as noted in the text under the heading "New Pays and Extensions.'' Drilling During the year, 418 wells were drilled, as compared with 356 drilled during 1942. Of these, 323 were field wells, of which 188 produced oil, 21 were gas wells and 114 were dry holes. The remaining 95 viere wildcats, 12 of which produced oil, 4 produced gas and 79 dry holes. Distribution of themwildcats with respect to the various trends may be summarized as follows: over the 91,340,492 bbl. produced in the same area during 1942. The production statistics in the text and the accompanying tables include condensate or distillate as oil production, because many Gulf Coast fields produce oils with a wide variation of specific gravities, all of which are commingled in pipe lines. Table 3 shows by counties all of the drilling and production" data applicable to this particular area. Outstanding Fields of 1943 The Upper Texas Gulf Coast covered in this report has 178 more or less active oil and gas fields, including the 1943 discoveries. Of these Table 4 lists those that were most important from the standpoint of production. Each of these fields pro duced in excess of one million barrels of oil during 1943. Some of the interesting facts to be noted from this list of some 26 oil fields are: (I) four of the fields— namely, Conroe, Hastings, Friendswood and Thompson—each produced more than 10 million barrels during 1943, whcrcas Conroe and Hastings were the only fields that produced 10 million barrels during 1942; (2) some of the older fields (discovered prior to 1920), such as Barbers Hill, West Columbia, and Hull, are still producing in excess of one million barrels annually; (3) some of the fields more than doubled their 1942 production—e.g., Anahuac and Friendswood. The large increase in production in practically all instances is the result of increased allowables from wells drilled prior to 1943 and

Jan 1, 1944

By J. H. McCormick

This plant, near Marysville, Mont., was planned to treat the ore from the Piegan and Gloster mines, the latter being one of the early and famous producers of the Marysville district. When the mill was closed in 1888, treatment consisted of stamp milling, followed by pans and settlers for pan amalgamation. The extraction was evidently poor, because, a few years later, thousands of tons of tailings were re-treated by the ranchers in the valley below the mill, by the then new cyanide process, and gave a handsome profit. In 1914, the present owners, after laboratory tests and an experimental mill run, decided upon the following treatment: crushing to 40 mesh in cyanide solution, concentration, amalgamation, classification, and cyani-dation of sands by leaching, and of slime by agitation and decantation in charges. The ore averaged about $7 per ton, gold and silver, the ratio of weight being 1 oz. gold to 7.56 oz. silver. The ratio of gold and silver in tailings was 1 oz. Au to 36.6 oz. Ag; the quartz was sharp and sandy, however finely ground, and rather difficult to slime. The mechanical equipment was a No. 5 Symons gyratory crusher; three 10-ft. Lane slow-speed Chilean mills; one Wilfley roughing and one finishing table; one submerged-type Akins classifier; five 26 by 10-ft. fir leaching tanks; one 24 by 7-ft. Dorr thickener; four 14 by 16-ft. Dorr agitators; four 6-compartment double-row zinc-boxes having compartments 18 in. wide, 18 in. deep, and 34 in. long; Johnson zinc lathe; acid and vacuum filter tanks for treating precipitate; roasting furnace; and Case tilting No. 275 crucible furnace for melting precipitate. The mill is driven by electric power supplied by the Montana Power Co. at the following rates, per kw.-hr.: 200 to 300 hp., 0.68 c.; 300 to 500 hp., 0.61 c.; 500 to 750 hp., 0.55 c.; plus $1 per month per installed motor horsepower. The plant as above described was operated from May, 1915, to the end of the year, when an additional Dorr thickener and a 12 by 12-ft. Portland revolving filter were added, increasing the nominal capacity of 100 tons per 24 hr., but not the percentage of extraction. The combined treatment, at a cost of $1.48 per ton, saved 90 per cent. of the gold arid

Jan 1, 1919

By Ed Van Eeckhout

As part of a U.S. Bureau of Mines-sponsored project on the utilization of "stiff" backfill to minimize potential rock burst hazards, a finite element study was undertaken to predict stresses and displacements around a stope mined up from the 5400 level of the Sunshine mine, Kellogg, Idaho. This stope was to be backfilled using a high-modulus fill. In preparation for that configuration, certain instrumentation was installed near the 5400 level to monitor stress changes. Due to untenable economics, only 2 cuts of the stope were ever made. This paper presents the results of the instrument readings taken during the first cut and compares them with the numerical predictions, as well as presents the modeling results of closure and fill stresses in the stope if it had been mined.

Jan 1, 1984

By Paul R. Dingess, Edward H. Hare, Douglas C. Brockie

Mining in the Tri-State district of Missouri, Kansas, and Oklahoma has been nearly continuous from about 1848 until the present day, although the major activity was from about 1880 to 1955. The district, which has produced over $2 billion in zinc and lead concentrates, ranks as one of the greatest mining districts in the world. Unlike other Mississippi Valleytype deposits in the United States, which occur in Cambrian and Ordovician limestones and dolomites, the Tri-State district ores occur in Mississippian limestones containing abundant chert. Zinc is 5 to 6 times more abundant than lead. In the Picher Field, the principal sub-district which has accounted for 61 percent of the total district production, most of the ore has been mined from the single horizon, M bed. Most ore bodies, other than those of the "Sheet Ground" or blanket-type, are in large, essentially flat-lying breccia zones and have a definite mineral zonal pattern. An irregular, generally elongated central dolomitic core is surrounded progressively outward by the main ore run, the jasperoid zone, the muddy or shaly and bouldery zone, the sparry calcite limestone zone, and the fossiliferous, dominantly crinoidal, limestone zone. Some of the zones may be absent or nearly so and may overlap to some extent with an adjacent zone. Although the district has been studied by many authors, much controversy still exists about such items as genesis, paragenesis, and time of emplacement. These subjects are discussed in the paper.

Jan 1, 1968

By Bai Shiwie, Li. Guangyu

This paper presents the study in situ on stress field of rock mass in a large dam site. By means of two different measure instruments and the method of stress relief, a lot of measure in situ has been done, including stress measurement of three dimensions at ten points and two deep-hole stress measurements in the perpendicular boreholes which are 59.4m and 53m deep seperately, and the basic accordant results corresponding two methods have been got. In the process of the deep-borehole stress measurement we got the stress value in critical state in which cylindrical core would become core-disking in the high stress area, which was first got in the world. The maximum principal stress was up to 650 kg/cm2. The stress value obtained by test and the thickness of rock disks all basically accord to the analysis by mechanical mechanism of core-disking The plane linear elastic finite element analysis has been completed. Results of inverse calculation all ac- cord to the measurement results in four different positions. The whole outline of the stress field of dam site was delineated clearly.

Jan 1, 1982

By THOMAS LEONBRD WATSON

I. INTRODUCTION. THE results embodied in this paper are based on a careful field- and laboratory-study of the lead- and zinc-deposits of the Virginia-Tennessee district, begun in the latter part of the summer of 1904 and completed in the spring of 1905, preparatory to the publishing of a State report .on them. A separate description of the individual deposits in Virginia is purposely omitted, since I have already described them in considerable detail in a State report. The Tennessee deposits are described here in some detail for the reason that no detailed record of them has yet been published. Practically, this paper summarizes the results obtained from a study of the geology of the ore-deposits of the district as, a whole. (I had the pleasure of visiting the deposits of Virginia and Tennessee with Dr. H. Foster Bain of the U. S. Geological Survey, in April, 1905. Figs. 21 and 22 are from photographs taken by Dr., Bail.) II. HISTORICAL. . The first authentic records of lead-mining .in Virginia date hack more than 150 years; and the old lead-mines at Austinville, on New river in Wythe county, V a., were the first to be worked. Colonel Chiswell, a native of Wales, and one of the earlier adventurers in southwestern Virginia, was one of the first operators of the Austinville mines. Chiswell's operations at Austinville commenced in the year 1750, and closed shortly after the beginning of the Revolutionary War, in the' year 1776, covering a period of about 25 years. From that time to the present, mining has been carried on almost continuously in the Virginia area. For many years after the Virginia mines were operated, mining was confined exclusively to the lead-ores. The zinc-ores

Mar 1, 1906

Steps were taken for a permanent organization of the scientific and technical employees of the Government at their mass meeting on May 8. This was the result of an informal meeting on Apr. 23 of thirty representative Government scientists and technical men who organized the preliminary committee and called the mass meeting. This subject has been widely discussed during the last year and was brought acutely to the fore by the work of the Joint Congressional Reclassification Commission, because that Commission has stated that it wished to deal with employees only through organizations. Rodney H. True of the Department of Agriculture was Acting Chairman. He pointed out that the principal advantages that were expected to be derived from such an organization were: (1) Improvement of conditions and facilities for more effective scientific and technical work; (2) adequate presentation of the needs. and results of such work to the public and to legislative and administrative officers; (3) -greater freedom in both official and non-official activities; (4) just and reasonable salaries based on service performed and the economic and social conditions which prevail; (5) greater public recognition of the aims and purposes of research; (6) advancement of science and technology as an essential element of national life. Three plans of organization were offered to the meeting, which covered the fundamental principles which could be utilized by these Government employees. The first plan would have permitted the new organization to work only through existing scientific organizations. This is the plan that scientific and technical Government employees in England have adopted and an outline of the English plan was read to the meeting.

Jan 6, 1919

By L. B. Herring, Harold Decker

The South Texas area, discussed herein, represents districts 2 and 4 of the Texas Railroad Cominission and extends from Jackson, Lavaca, and Gonzales Counties on the northeast to the Rio Grande River, comprising a total of 26 counties.$ The present boundaries of this district do not coincide with those of earlier reports published in the annual volumes of Petroleum Development and Technology. The war, in its various ramifications, determined and controlled all the phases of the oil and gas industry. Priorities for material and governmental subsidies determined all new operations. New Pools In our opinion, the combine' quantity of crude and distillate reserves added in '943 approached Or possibly exceeded the amount produced. Thirty-five new pools were added to the area' Of these, five have significant reserves and ten offer possibilities of containing consequential reserves. The largest proven reserve discovered during the year was the Slick pool, on the DeWitt-Goliad County line. This is also the most important Wilcox discovery to date in the area. The most significant extension was at Willimar, Willacy County. Other important extensions were developed at Agua Dulce, Seeligson, and Odem. Except for the Porter field, in Karnes County, the Laredo trend, which produces lrom the Jackson and Yegua, proved very disappointing, and this pool is o:C secondary importance. The Scott and Hopper pool, Brooks County, has only orie well, but offers excellent possibilities of becoming an important discovery. It represents at this time the major Frio discovery of the year. The Hobson pool, Karnes County, is not a major reserve, but can be classed as important in that it produces at a shallow depth from the Wilcox. This proves that the potential area of production for this zone occupies a broad trend. Gas and Condensate During the year construction was begun on only one recycling plant, this being in the Sejita field, Duval County. Several others were colltemplated, but no actual operations were begun. The most important development in recycling was the rebuilding of old plants to allow for the fractiona-tion of isopentane, n-butane, isobutane, and propane. Heretofore all pentanes plus have been marketed as cLdistillate,n only a minor portion of the butanes being isolated and sold for fuel purposes. All these new the except propane, are considered vital to the war effort and propane is being marketed as fuel gas. In other instances propane is being isolated and then pumped back into the gas reservoirs for storage. It is anticipated that the demands for this product will increase in the future. Drilling in the Wilcox trend during the year showed the existence of valuable gas

Jan 1, 1944

By L. B. Herring, Harold Decker

The South Texas area, discussed herein, represents districts 2 and 4 of the Texas Railroad Cominission and extends from Jackson, Lavaca, and Gonzales Counties on the northeast to the Rio Grande River, comprising a total of 26 counties.$ The present boundaries of this district do not coincide with those of earlier reports published in the annual volumes of Petroleum Development and Technology. The war, in its various ramifications, determined and controlled all the phases of the oil and gas industry. Priorities for material and governmental subsidies determined all new operations. New Pools In our opinion, the combine' quantity of crude and distillate reserves added in '943 approached Or possibly exceeded the amount produced. Thirty-five new pools were added to the area' Of these, five have significant reserves and ten offer possibilities of containing consequential reserves. The largest proven reserve discovered during the year was the Slick pool, on the DeWitt-Goliad County line. This is also the most important Wilcox discovery to date in the area. The most significant extension was at Willimar, Willacy County. Other important extensions were developed at Agua Dulce, Seeligson, and Odem. Except for the Porter field, in Karnes County, the Laredo trend, which produces lrom the Jackson and Yegua, proved very disappointing, and this pool is o:C secondary importance. The Scott and Hopper pool, Brooks County, has only orie well, but offers excellent possibilities of becoming an important discovery. It represents at this time the major Frio discovery of the year. The Hobson pool, Karnes County, is not a major reserve, but can be classed as important in that it produces at a shallow depth from the Wilcox. This proves that the potential area of production for this zone occupies a broad trend. Gas and Condensate During the year construction was begun on only one recycling plant, this being in the Sejita field, Duval County. Several others were colltemplated, but no actual operations were begun. The most important development in recycling was the rebuilding of old plants to allow for the fractiona-tion of isopentane, n-butane, isobutane, and propane. Heretofore all pentanes plus have been marketed as cLdistillate,n only a minor portion of the butanes being isolated and sold for fuel purposes. All these new the except propane, are considered vital to the war effort and propane is being marketed as fuel gas. In other instances propane is being isolated and then pumped back into the gas reservoirs for storage. It is anticipated that the demands for this product will increase in the future. Drilling in the Wilcox trend during the year showed the existence of valuable gas

Jan 1, 1944

By Charles Berkey

CONTENTS PAGE C. P. Berkey-Responsibilites of the Geologist in Engineering Projects (with discussion) 4 Kirk Bryan-Problems Involved in the Geologic Examination of Sites for Dams 10 0. E. Meinzer-Relation of Ground-water Conditions to Leakage of Reservoirs (with discussion) 19 Charles Terzaghi-Effect of Miner Geologic Details on the Safety of Dams (with discussion) 31 G. H. Matthes-More and Better Geologic Data for Use in Hydraulic Projects (with discussion) 47 L. W. Fisher and R. D. Ohrenschall-Geologic Examination of Dam Sites in the Tennessee and Cumberland River Basins 60 C. K. Wentworth-The Geology of Dam Sites (with discussion) 78 L. C. Glenn-The Geology of Dams and Reservoirs 97 H. T. Stearns-Success and Failure of Reservoirs in Basalt (abstract) 111

Jan 1, 1929

By G. D. Marshall, D. K. Sarin, V. E. Hampton

Ground support at the Thompson Mine emphasizes scaling, rock bolting and wire mesh screening on the backs and walls of all underground stoping and development areas and also full column grouted cable bolting in the bulk mining areas. This paper describes the equipment for the point anchored rock bolts as well as the full column cable bolts. Modifications in design and testing of all components and procedures has ensured a safe and efficient method of ground support for the mining conditions existing at the Thompson Mine.

Jan 1, 1983

By Robert H. Richards

Tuns truly remarkable machine was built on a preliminary scale in May, 1895. The first full-sized table was built by Mr. A. R. Wilfley, and was used in his own mill in Kokomo in May, 1896. The first table sold for installation was placed' in the Puzzle mill, Breckinridge county, in August, 1896. The mill enthusiasts at first hailed it as the cure for all the ills that flesh is heir to in the milling line. A little later it was found to make losses which were serious, and on this account the table succeeded only to a limited extent in displacing the vanners of the gold-mills. Still later, mill-men in a number of districts throughout the country made special studies of the faults of the machine, and devised a number of ways of grouping supplementary machines to overcome as far as possible the losses, and at the same time retain the benefit of the extraordinarily large capacity accompanied by the production of clean concentrates for which the machine has become so justly famous. I hope to make an exhibit of some of these methods in an appendix to my book on ore-dressing which is now in preparation. These experimenters have not written up the subject, and if they possess all the facts they have not given them out for the benefit of the mining profession at large. The object of this paper is to obtain the facts and to pre¬sent them so clearly that their bearing can be seen by all. To this end two complete series-'of tests have been planned. One (the present paper), to study concentration of galena in presence of quartz; the other (to follow shortly), to study concentration of chalcopyrite in presence of quartz. Some authorities claim that the table does its best work when treating natural products; by this phrase I mean products which have been crushed to pass through a limiting

Jul 1, 1907

By Robert H. Richards

(Pittsburg Meeting, March, 1910.) THIS is in part a review paper, indicating the various steps that have been taken in developing hindered-settling apparatus, some of the standard data that have been obtained, and some of the conclusions one is led to as to the effect of it in improving concentrating-methods and machinery, and in part it brings in some unpublished work. CAUSES OF LOSS IN ORE-CONCENTRATION. In making a study of the separation of valuable minerals from the waste gangue, particularly by water concentrators, it is necessary to define, first of all, what are the causes of-loss that are likely to interfere with the concentration. Having made this definition; we can then study to see in what way the machines make their losses, and plan remedies for them in an intelligent way. Losses may be stated to occur as included grains, as flat or long grains, as fine free mineral, and as absolute slime. We will take, these up one by one, as follows: Included Grains.-Fig. 1 shows by a set of diagrams how included grains may occur: first, where the heavy mineral grains attached to the quartz are of large size; secondly, where they are of small size ; and thirdly, where very fine particles of heavy mineral are included in the quartz. We have to decide in regard to included grains whether they are rich enough to go direct to, the furnace, or poor enough to throw away, or whether they lie between these two points and require recrushing as the only means of severing the values from the waste. This last case is the only one requiring special treatment at our hands. We will therefore consider that next. * By mutual consent, this paper has been presented also before the Colorado Scientific Society, and the Canadian Mining Institute, Montreal.

Feb 1, 1911

By Charles W. Bloomquist

The profitability of miscible flooding in a hypothetical target oilfield is examined. The major costs, including Windfall Prof it Tax, are identified and their re1ative importance are discussed. The sensitivity of profit to important physical and economic variables is evaluated and discussed, including variance in oil recovery, oil price, injectant requirements, injectant cost, and capital requirements. Economic sensitivities to important development and operating decisions such as timing, Spacing, Slug size, and gas recycling are also analyzed. The Windfall Profit Tax (WPT) as it applies to gas miscible EOR projects is reviewed. The effect of WPT on each of the various project cases is analyzed and the effect of reduced WPT on remaining production from existing operations is evaluated. Tax implications are compared for integrated vs. "independent" controlled projects and the alternative of expensing vs. capitalizing tertiary injectants is also evaluated. The impact of the Net Income Limitation in reducing WPT. during early and late project life is determined and discussed.

Jan 1, 1982