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By George B. Clark

Many basic engineering principles of all four phases of mining operations, namely, prospecting, exploration, development, and exploitation, can be analyzed better in terms of quantitative geology. Geological data from both field and laboratory will also complement scientific methods now being developed. THE geological data emphasized so successfully in prospecting for new deposits, that is, structural controls, strength of solutions, and type of mineralization, are basically those required for successful exploitation. In the mining of newly discovered deposits the most economical methods should be employed as early as possible to keep the overall cost per unit produced at a minimum and to permit maximum extraction of valuable minerals. A crucial question is: How can geological data be translated into useful quantitative results which will aid in achieving this end? H. E. McKinistry' has suggested that a solution may be reached in one of two ways: 1—the usual approach, use of judgment based on experience; or 2—mathematical calculations and tests on models, both subject to certain limitations. He also suggests that in addition to better use of geology more case data and theoretical data are needed on which to base sound judgment. Further research, therefore, is necessary. Perhaps in this field the emphasis should be on more specialization in mining methods and ground movement by men with thorough training in physics, engineering, geology, and underground mining. These specialists would be equipped to point out the most economical and scientific methods of exploitation. Selection of a stoping method is governed by the amount and type of support a deposit will require in the process of being mined, or by the possibility of employing the structure of the deposit to advantage in mining the ore by a caving method. In addition to these factors there are others which almost invariably influence the choice of an economical method of mining:' 1—strength of ore and wall rocks; 2—shape, horizontal area, volume, and regularity of the boundaries of the orebody, and thickness, dip and/or pitch of the deposit and individual ore shoots; 3—grade, distribution of minerals, and continuity of the ore within the boundaries of the deposit; 4—depth below surface and nature of the capping or overburden: and 5—position of the de- posit relative to surface improvements, drainage, and other mine openings. In the final analysis it is usually necessary to disregard the less important of these factors to satisfy the requirements of the more important. Because of the variation of geological conditions throughout and surrounding the deposit, no mining method will be everywhere ideally applicable to the conditions encountered in one ore deposit. The immediate problem is to interpret the above physical characteristics of deposits in terms of geological characteristics. Very few quantitative geological data are available on the factors related to a choice of mining methods. However, there are many descriptive data in mining and geological literature which collectively show how important an effect details of geology have upon all phases of mining operations. The following categories of basic mining methods were investigated to establish the geological factors that have affected their successful application: 1— open stopes with pillars; 2—sublevel stoping; 3— shrinkage stoping; 4—cut-and-fill stoping; 5— square-set mining; 6—top slicing and sublevel caving; and 7—block caving. It should be noted that the first five of these methods are listed in the order of increasing support requirements. Mines were selected as examples only where geological descriptions were complete enough to warrant their use. A study of the geological factors involved in mining operations led to a choice of the following classifications, employed in Table I: 1—structural type of orebody; 2—dimensions (geometry); 3— country rock (type); 4—faulting, folding, and fracturing; 5—alteration of ore and rock; 6—type of mineralization; and 7—geological factors determining mining method (summary). Of these factors only one yielded results that can be defined from available data in a quantitative manner, i.e., dimensions of the deposit. These are the most reliable guides that can be used in selection of suitable mining methods. They are, in general, the properties of geologic structure most difficult to evaluate by studies of models, pho-toelastic studies, and other laboratory methods, all of which are at present more limited in their applications than the geologic method. Application of geology has proved a reliable guide in other phases

Jan 1, 1955

Council PRESIDENT OF THE COUNCIL. JOHN HAYS HAMMOND NEW YORK, N. Y. (Term expires February, 1908 ) VICE-PRESIDENTS OF THE COUNCIL. HENRY M. HOWE NEW YORK, N. Y. J. B. GRANT DENVER, COLO. JAMES D. HAGUE NEW YORK, N. Y. (Term expires February, 1908.) SAMUEL B. CHRISTY BERKELEY, CAL. JOHN A. CHURCH NEW YORK, N. Y. PERSIFOR FRAZER PHILADELPHIA, PA. (Term expires February, 1909 )

Jan 1, 1910

PRESIDENT Willis McGerald Peirce New York City, N Y PAST PRESIDENTS D H McLaughhn, San Francisco, Calif L E Young', Pittsburgh, Pa VICE-PRESIDENTS A. B. Kinzell, New York, N Y H. W Thomas Ray, Arizona Philip Kraft, New York, N Y J L Gillsan Wilmington, Del M. L Haider, Toronto, Ont , Canada VICE-PRESIDENT and TREASURER Andrew Fletcher, New York, N Y

Jan 1, 1951

By M. C. Flemings, R. Mehrabian, G. E. Nereo

Analytic expressions were developed and applied in two preuious papers to predict effects of solidification variables on macrosegvegation. In this paper, experiments are reported to test the analyses quantitatively and qualitatively. Good quantitative agreement is obtained between predicted and measured compositions for the following types of segregation (all experiments were on laboratory-size ingots of Al-4.5 pct Cu alloy): (a) inuerse segregation, (b) composition distribution in ingots solidified with unidirectional heat and fluid flow, (c) simulated centerline segregation, and (d) segregation resulting fro, change in solidification cross section. In addition, qualitative agreement of prediction of theory with experiment is obtained for (a) segregation resulting from sudden change in heat extraction during solidification, (b) centerline segregation in a bidirectionally solidified ingot, and (c) under-riser positive segregation. IN two previous papers,''2 it was shown that a variety of apparently different types of macrosegregation result from the same basic mechanism. This mechanism is the flow of solute -rich liquid to feed solidification and thermal contractions. Analytic expressions were derived and examples given of their application to predict macrosegregation. Calculations were for Al-4.5 pct Cu alloy. In this paper, we describe a series of experiments designed to test results of the foregoing calculations. All experiments were on laboratory-size ingots (weighing 10 lb or less), of A1-4.5 pct Cu alloy, nominal composition. APPARATUS AND PROCEDURE A typical mold and chilling arrangement used for unidirectional solidification is shown in Fig. 1. Before casting, this assembly was placed in an electrically heated air furnace, and heated to 680" to 700°C. When the plaster reached the desired temperature (usually 1 to 2 hr after the furnace temperature), the mold was filled through a funnel extending from the outside of the furnace into the cavity. The assembly, with liquid, was held for several minutes to allow convection to subside. The coolant, either air or water (depending on the desired solidification rate), was turned on and the ingot solidified. With the four sides and top insulated, heat removal for solidification was through the bottom surface, resulting in a fully columnar structure. Design of the casting cavity was varied, as discussed below, to produce desired macrosegregation effects. However, for castings solidified with unidirectional heat flow, the top was always open to the furnace atmosphere and temperature. The bottom sur- face rested on a chill through which the heat was extracted, and all other surfaces were insulated with plaster. In one case to be discussed, the mold design was changed to obtain bidirectional solidification. In this case, two vertical chills were used (on two faces of the mold) and the bottom was insulated. In a last case discussed, that dealing with under-riser segregation, experiments were conducted in bottom-chilled sand molds at ambient temperature. Except for this one case, all experiments were conducted in the electrically heated air furnace as described above. In many ingots, thermocouples were used to obtain continuous records of solidification. In all cases, these were chromel-alumel couples with output continuously monitored on a twelve-channel recorder. Where thermocouples were employed, these were embedded in the refractory mold walls during mold-making so their heads extended to the vertical centerline. Six to nine couples were employed, placed at intervals from the chill. METAL-MEL TING PROCEDURE Aim analysis was A1-4.5 pct Cu; alloy was prepared from high-purity aluminum (99.9 pct Al) and A1-Cu master alloy (50 pctOFHC Copper, 50 pct high-purity Al). The A1-4.5 pct Cu alloy was cast in 5- to 7-lb ingots for subsequent remelting for the macrosegregation experiments. Melting for ingot casting was as follows. After preheating the melting crucible for an hour or more, the charge was melted and superheated to a temperature of 690" to 720°C. After stirring, the melt was degassed with chlorine for 10 min. After stirring again for 1 min, a gas sample, under reduced pressure, was taken. When the sample was gas-free, the crucible

Jan 1, 1969

By O. J. Huber, P. D. Frost, H. A. Robinson

URANIUM is a (ß-stabilizing, eutectoid-forming element when alloyed with titanium. Udy and Boulger1 have reported that an alloy of 48.6 pet uranium in titanium retains ß-phase when quenched from the ß-region, while compositions of approximately 30 pet uranium transform to martensite during such quenching. Since the eutectoid reaction is rather sluggish, titanium-uranium alloys should be capable of being strengthened by the ß — a trans-

Jan 1, 1959

By E. L. Estabrook

THE production of crude oil in Wyoming rose to 44,290,010 bbl. in 1923 and declined, during 1924, to 39,295,030 bbl., a decrease of about 11 per cent. The Salt Creek field supplies 75 to 80 per cent. of the production. Pipeline runs from the Salt Creek field reached a maximum in November, 1923, at a daily average for the month of 116,437 barrels. During 1924, the gas pressure in Salt Creek has declined rapidly and the production dropped to about 60,000 bbl. per day. Part of 'the decline during the last few months was due to lack of power to pump the wells. The electric-power plant of the Midwest Refining Co. did not begin to deliver current until the middle of December, by which time several hundred wells were off production. The cold snap in December, which brought, the temperature down to 30° below zero on the 17th, tied up operations almost completely and the average production for the month was only 49,545 barrels. As more wells are being pumped and the number of dead wells reduced, the production is rising and was up to 61,000 bbl. during the last week of January. A further increase is expected as the weather becomes warmer. The production of Salt Creek, by months, during 1924 is given in Table 1. TABLE 1.-Total Monthly Production, Average Daily Production and Number of Producing Wells in Salt Creek during 1924 TOTAL PRODUCTION, DAILY AVERAGE, NUMBER OF MONTH BARRELS BARRELS WELLS January 3,523,647.40 113,666.05 919 February 3,074,916.67 106,031.61 929 March 2,977,095.14 96,035.32 950 April 2,811,110.22 93,703.67 987 May 2,858,842.04 92,220.71 1,024 June 2,649,752.57 88,325,09 1,092 July : 2,697,829.36 87,026.75 1,153 August 2,624,371.84 84,657.15 1,213 September 2,281,219.04 76,040.64 1,274 October 2,073,961.42 67,000.84 1,313 November 1,722,050.09 57,401.67 ~ 1,335 December 1,535,903.78 49,545.28 1,352 Total 30,831,699.57 84,239.61 1,352

Jan 3, 1925

Discussion of the paper of E. C. HARDER, presented at the Pittsburgh meeting, October, 1914, and printed in Bulletin No. 94, October, 1914, pp. 2573 to 2586. I. C. WHITE, Morgantown, W. Va.-I have seen some of the great iron-ore deposits described in this paper. -One of these in the State of Minas Geraes appears to be an immense mountain of iron ore about 2,000 ft. in height. All over its surface from bottom to top may be seen large masses of rich iron ore, varying in weight from a few pounds to several tons, and from all that one can judge without exploitation, the quantity of available ore is certainly very large in this particular mountain. Whether it will prove a mere surface deposit or shell, like the famous Iron Mountain of Missouri, is for future exploration to determine. The question of transportation is the main factor in determining the availability for exportation of these Brazilian iron ores. There is no coal in Brazil that can be manufactured into coke without expensive previous treatment, since the best of the raw coal in the States of Rio Grande do Sul, Santa Catharina, and Parana, contains about 35 per cent. of ash, of which about 6 per cent. is sulphur, and coal of this composition cannot be utilized in iron smelting without purification. When I was chief of the Brazilian Coal Commission in 1904 to 1906, I had a cargo of this coal shipped to Balk, Germany, and treated in the great coal-testing plant of the Humboldt Engineering Works, located just across the Rhine from Cologne. It was found that by crushing and washing the Brazilian coal, it yielded 33 per cent. of briquetting coal, containing only 10 to 12 per cent. of ash (of which 1 per cent. was sulphur), and 42 per cent. of slack coal, with 25 per cent. of ash and low in sulphur, so that about 33 per cent. of the Brazilian coal could be converted into coke of fair quality, as shown by the following average of three analyses, using air-dried coal, of briquets made from the Barro Branco coal bed, State of Santa Catharina: Moisture 1.56 Volatile matter 31.66 Fixed carbon 56.73 Ash : 10.05 Total 100.00 Sulphur 1.34 Phosphorus 0.003 B.t.u 13,395

Jan 4, 1915

By Vernon Read

Among the technical problems in AEC's Project Plowshare is the necessity of determining the precise effects of nuclear blasts in all kinds of ground formations. This calls for extensive in-situ sampling with full core recovery. In the exploration drilling that often precedes a new test detonation, the AEC and its contractors have applied both novel and established sampling techniques in many new ways, giving improved core recovery and reduced costs in all subsurface sampling and testing. Unique among these new techniques is one that achieved full recovery and virtually undisturbed samples from near-surface layers of unconsolidated boulder-strewn alluvium. This approach involves a combination of oilfield and mining core drilling equipment. Oilfield heavy drill collars, rotary stabilizers and thick, vibration-reducing oil emulsion drilling mud were used in combination with the precise hydraulic feed control, fast (over 300 rpm) bit rotation, light drilling weight, hard rock core barrels and multi-step diamond bits that are common in mining industry diamond drilling.

Jan 8, 1963

By John W. Cloud

The delivery of blows upon roadway structures by the locomotive engine at high speed, althongh long recognized, has, perhaps, not been as generally understood in severity, relation to speed, and cause as is desirable in matters of such importance. Some points of explanation, with illustrative disgrams, are, therefore, submitted to your attention, preparatory to a note 011 " Steel for Bridges," also submitted. In order that a locomotive may run at high rates of speed with-

Jan 1, 1881

By Jr. Baldwin. William M

WELL known to every metallurgist is the fact that different production schedules will profoundly affect the character of annealed metal strip. Yet the number of conditions [ ] that may be wrought by different combinations of rolling and annealing schedules is so myriad that despite the continual research that is being applied to this subject, the complete picture is not yet known. Copper, like all other metals, during the process of rolling or annealing, develops certain crystallographic configurations which should not be dismissed as being too impractical, for the crystallographic condition existing within the metal is a principal influence upon both the external mechanical properties and the behavior of the material [ ] when it is subjected to such operations as bending, flanging, drawing, and so forth. EFFECT OF ROLLING AND ANNEALING UPON THE CRYSTALLOGRAPHY OF COPPER STRIP The most salient points in the crystallographic reactions of polycrystalline copper to rolling and annealing may be best represented graphically by a "map" such as that given in Fig. I. I. As copper strip is cold-rolled from a randomly oriented structure (pole figure I),

Jan 1, 1942

By Staff

Concentrates at the rate of 1000 tons a day are being smelted by International Nickel Co.'s new commercial flash smelting furnace. Developed by Inco, the process is a radical departure from the former practice which involved conventional smelting in coal-fired reverberatory furnaces. In the new process copper flotation concentrate and flux are injected horizontally with oxygen into a specially designed reverberatory furnace, and smelting temperature is maintained solely by the flash combustion of iron and sulphur while the particles are in suspension. The major benefits of this new process stem from two sources: 1)-Substitution of energy from local resources for imported coal; and 2)-Production of liquid sulphur dioxide, replacing equivalent imported sulphur. A measure of these benefits is afforded by considering the saving, in 1954, of 60,000 tons of coal and the production of 70,000 tons of liquid sulphur dioxide, equivalent to 35,000 tons of sulphur.

Jun 1, 1955

By J. E. Elliott

ALTHOUGH the firm in which the writer is a partner is not exactly the pioneer in the coring of rotary-drilled wells in Southern California, it has taken the lead in bringing coring to its present status. To the Shell Company of California belongs the, honor of having first used the core drill in its endeavors to locate subsurface structures west of Santa Fe Springs. Following those operations, similar work was done near Wasco in the San, Joaquin Valley. Results of the latter core drilling were successful, in that they made it possible to determine the under-ground structure. At, about the same time that the Shell Company was doing the work at Wasco, it was experimenting in the use of the core drill in connection with rotary-drilled holes. The oil sands in its dis¬covery well at Signal Hill were located by means of the rotary core drill. In 1921, in view of the trouble that the operators were having in the fields of Southern California, and particularly at Huntington Beach, R. E. Collom, of the State Mining Bureau, called their attention to the possibilities of the core drill for eliminating many of the serious problems that were facing them. It was this same difficulty encountered by the operator in locating the oil sands that caused the writer to enter into con-tract core drilling; late in 1921 the California operators became converted to the advantages of that method, and in the short space of one year core drilling in rotary-drilled holes has risen from a theory to an established practice.

Jan 10, 1923

By G. E. Anderson

THE Asientos-Tepezala district is in the north of the State of Aguascalientes, about 30 miles north of the city of Aguascalientes, the capital. The district is reached by a standard-gage railway on the west side through the junction, Rincon de Romos, which is on the main line of the National Railways of Mexico from El Paso to Aguascalientes. The terminal is Tepezala. On the east side a narrow gage connects Asientos with the junction, San Gil, on the main line, Asientos to San Luis Potosi. Tepezala on the west side of the Asientos hills is about 2 miles from Asientos on the east side. The area between the two mining centers is separated by a low subued divide which forms the central part of the hills. The district is in a group of isolated hills surrounded by characteristic bolson plains. The hills rise above the surrounding plains about 6500 to 10,000 ft.; the highest peak is Alta Mira. The two mining districts lie somewhat upon the flanks of the hills at about the same elevation, 7200 ft. The district is an old one and has been known since early in the 17th Century when the mines were worked by the Franciscan Monks. Their mining operations which were limited to the oxidized ore above the water level, consisted chiefly in extracting silver from the Santa Francisca vein. To judge from the old workings and the remains of surface plant, the operations were on a large scale. By modern mining operations since about 1900, the various mines of the district have been one of the principal sources of ore for the smelter located at Aguascalientes.

Jan 2, 1926

By Fred Allison

THE magneto-optic method of analysis had its origin in experiments1 which were designed to detect and measure a time lag in the Faraday effect and later to study this time lag as a function of the wave length of the light.2 Faraday discovered in 1845 that a beam of plane polarized light, when passed through a transparent, isotropic medium traversed by a magnetic field of force parallel to the direction of the light, suffers a rotation. The direction of rotation is reversed with the reversal of the magnetic field and its magnitude depends upon the strength of the field, the length of the path of light in the substance and the nature of the substance. This phenomenon of magnetic rotation is known as the Faraday effect. A question which had been of some interest for years was whether this power of a liquid to rotate polarized light is acquired instantly with the application of the magnetic field, that is, whether it is a case of instantaneity or whether there is a very small interval of time which intervenes between the application of the magnetic field and the consequent rotation of the light by the liquid; in other words, whether there is a time lag in the Faraday effect. Efforts to measure such a lag previously had met with failure. It was recognized at the outset' that since a time lag had escaped detection it must be extremely small, if to a measurable extent it exists at all. It became necessary therefore to adopt a timing device capable of making measures of almost infinitesimally small intervals. The velocity of light served as this timing device, a modification of a method originally employed by Abraham and Lemoine3 being adapted to the requirements of the problem. Since light travels about 30 cm. in a billionth of a second and since settings in our observations may be repeated with deviations not exceeding 3 mm.,

Jan 1, 1932

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who registered at Institute headquarters during the period Sept. 10 to Oct. 10, 1914: James D. Mooney, Akron, Ohio. J. Kojima, Ashio Copper Mine, Japan. Bernard A. Wilkinson, Guadalajara, H. Starkweather, Cripple Creek, Colo. Mexico. S. S. Langley, New York, N. Y. A. B. Parsons, Candor, N. C.. J. H. Warder, Chicago, Ill. Arthur Feust, Santo Domingo, Nicaragua. Lloyd T. Buell, Butte, Mont. G. B. Marshall, New York, N. Y. George R. Rogers, Gowganda, Canada. Henry Krumb, Salt Lake City, Utah. H. 0. Hammond, Douglas, Ariz. Herbert S. Kohlberg, El Paso, Texas. Percy E. Hohne, El Oro, Mexico. Wilbur L. Cross, Jr., Glen Carbon, Pa. Percy E. Barbour, Candor, N. C. Thomas H. Leggett, formerly-in charge of the mining interests of the American Smelting & Refining Co., has resumed practice as consulting engineer with offices in the Singer Building, New York, N. Y.

Jan 11, 1914

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who registered at Institute headquarters during the period Nov. 10 to Dec. 10, 1915: F. Lynwood Garrison, Philadelphia, Pa. E. Fleming l'engle, Costa Rico, C. A. William J. Lakeland, Burma, India. Fred Maccoy, El Oro, Mexico. Dwight E. Woodbridge, Duluth, Minn. 0. N. Scott, Toronto, Ont., Canada. Chester A. Fulton, Yonkers, N. Y. K. P. Swenson, Tokyo, Japan. Willet G. Miller, Toronto, Canada. - H. L. Mead, New York, N. Y. L. G. Huntley, Pittsburgh, Pa. E. DeGolyer, Norman, Okla. L. E. Howard, Lockport, N. Y. J. S. Lane, New York, N. Y. H. W. DuBois, Philadelphia, Pa. T. V. Nonactre, Argentina. Howard R. Stewart, London, England. N. H. Darton, of the U. S. Geological Survey, has returned to Washington after a long season of field work in New Mexico investigating the prospects of finding potash deposits in the Red beds.

Jan 1, 1916

By Svend Rordam

THE development of a cement that will resist the destructive action of sea water and other corrosive waters is a problem that has occupied cement chemists for the past one hundred years. It has been found that of the various salts that commonly occur in corrosive waters, sodium sulphate, magnesium sulphate and magnesium chloride are most destruc-tive to cement. Many investigations have been carried out in the United States, in Canada, and in Europe to solve the problem of what constitutes a sulphate-resistant cement, and during the past 10 years some of the findings give definite information in this respect. COMPOSITION OF CEMENT Portland cement is composed of four major compounds: 1. Tricalcium silicate 3CaO.Si02 (C3S) 2. Dicalcium silicate 2CaO.Si02 (C2S) 3. Tricalcium aluminate 3CaO.Al203 (C3A) 4. Tetracalcium aluminoferrite 4CaO.Al203.Fe203 (C4AF) The two calcium silicates are the main contributors of strength. The tricalcium aluminate contributes some to the early strength of the cement but has the least resistance of the four compounds toward the attack of sulphate waters. The tetracalcium aluminoferrite does not contribute very much to the strength, but is far more resistant to sulphate waters than the tricalcium aluminate. When hardened cement is exposed to water containing sodium or magnesium sulphates, these salts will react with the hydrated tricalcium aluminate in the cement and form compounds that will cause a swelling, disruption and crumbling of the hardened cement.

Jan 1, 1939

By Roy McLellan

THE slags derived from the smelting of lead and copper ores are composed essentially of silicates. The problems arising from the smelting of these ores consequently involve the study of silicate fusions. In the absence of specific knowledge concerning the compounds occurring in slags, it has been the practice of metallurgists to treat them in terms of their total chemical composition. Slags have been classified as monosilicates, bisilicates, sesquisilicates, and subsilicates according to the relative amounts of oxygen in the acid and basic radicles of the hypothetical salt produced. While this has been a useful guide to metallurgists in computing the furnace charges, it falls far short of a basis for the scientific investigation of slags. In order to understand the nature of a slag as a whole it is necessary to learn the physical and chemical properties of the mineral compounds which go to make up that slag. The efficiency with which an ore is smelted in a furnace depends primarily on the physical properties of the compounds formed during the operation. When the melting points and fields of stability of each of the mineral compounds in slags have been established, it will be possible to determine the properties of any given slag by examining the nature and amounts of its mineral constituents.

Jan 1, 1930

By J. R. Cain

ROLE OF GASES IN FERROUS -METALLURGICAL PROCESSES IN every process for making steel there are one or more stages where the metal is exposed to gas of one kind or another. Thus, in the open-hearth furnace, the carbon dioxide and water vapor in the products of combustion are oxidizing toward the ferrous and manganous oxides in the slag, tending to convert these to higher oxides; the higher oxides then oxidize the steel, so that indirectly the products of combustion are oxidizing toward the steel. In the Bessemer process, there is direct contact of air and steel; also, the water vapor in the air blown into the converter is continually decomposed by the molten steel, yielding hydrogen and ferrous oxide, both of which are in part taken up by the metal. In the electric-furnace processes, there is always more or less air in contact with the slag covering the metal, and this air and the gaseous reaction products from it are dissolved in the slag to some extent and thus transmitted in part to the steel. In the crucible processes, there is always entrapped air in the charges and the crucibles are more or less permeable to the gaseous products of combustion from the furnace. In all the processes of manufacture, the molten metal is exposed to air while tapping into ladles and ingot molds and has an opportunity to saturate itself with air or with gaseous or solid products generated by chemical reactions between air and steel. Sieverts1 has shown that molten metals require but a few seconds to saturate themselves with a surrounding gas. No one familiar with the operations at a steel plant needs to be reminded of the important role that gases play at all stages. The familiar "boil" of open-hearth furnaces, due to evolution of carbon monoxide when iron ore is added to the molten steel; the spectacular operation of the Bessemer converter brought about entirely by a gaseous reagent; the almost magic effect of small quantities of silicon manganese or

Jan 8, 1919

By Jack White, Ralph B. Adair

The Mufulira mine in Northern Rhodesia is 13° south of the Equator and at an altitude of 4100 ft above sea level. The concentrator was planned in 1930 to treat about 10,000 tons of ore per day, but before construction work had gone very far the size of the plant was reduced to 1500 tons daily capacity. Then just as the construction was finished in December 1931, the price of copper did not warrant the commencement of operations and it was not until October 1933 that the mine re-opened. Extensions have been made to the plant in 1934, 1935, 1936, 1937, 1940 and finally in 1945. The capacity of the plant when the 1945 extension is completed will be 9500 short tons per day. The various extensions have been carried out with the minimum confusion and with great skill on the part of the designers and the erection engineers. In dealing with the plant in this paper it is proposed to give an outline of the present practice and only to refer to past practice when it is considered of particular interest. Ore Treated The ore consists of fine grained highly siliceous, felspathic and argillaceous quartz- ites, the latter containing graphitic carbon and locally termed graywacke. These rocks are considerably altered near the surface and on the fringes of the ore body. Despite extensive efforts at mixing, both underground and in the crushing plant, many sudden changes of ore take place in the mill feed. The minerals are chalcocite, bornite and chalcopyrite with relatively unimportant amounts of malachite, native copper, azurite, covellite and chrysocolla. Gold is present at about I oz to a thousand tons, and silver at about 2 dwt. per ton. With increasing depth the nonsulphide content or,, as commonly termed locally, the oxide content of the ore is decreasing and is now less than 0.25 pct against a high of 0.77 pct- Crushing Operations The first stage of crushing is done under. ground where the oversize from I2-in. grizzlies is fed to a 56 X 72-in. jaw crusher. At the Selkirk shaft two 10-ton skips deliver the run of mine ore at a rate of 450 tons per hour to the 400-ton capacity shaft bins. One 6 ft wide Ross chain feeder and one locally made air-operated finger feeder feed the two 30-in. McCully crushers. Ahead of each crusher is a 6 X 9-ft spring grizzley spaced at 5 in. on a 35O slope. Neither the Ross chain feeder nor the finger feeder is entirely satisfactory and for the wet, muddy and sticky ore that has to be handled it is planned to replace these with two 6-ft wide apron pan feeders. The McCully crushers deliver a minus 5-in. product, at a.rate of over 500 tons per

Jan 1, 1949