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Trans No. Place Date Vol. 1. Wilkes-Barre, Pa. May, '71 1 2. Bethlehem, Pa. Aug., '71 1 3. Troy, N. Nov., '71 1 4. Philadelphia, Pa. Feb., '72.. 1 5. New York, N. Y. May, '72 1 6. Pittsburgh, Pa. Oct., '72 1 7. Boston, Mass. Feb., '73 1 8. Philadelphia, Pa. May, '73 2 9. Easton, Pa. Oct., '73 2 10. New York N. Y. Feb., '74 2 11. St. Louis, Mo. May, '74 3 12. Hazleton, Pa. Oct., '74.. 3 13. New Haven, Conn. Feb., '75 3 14. Dover, N. J. May, '75 4 15. Cleveland, Ohio Oct., '75 4 16. Washington, D. C. Feb., '76 4 17. Philadelphia, Pa. June, '76 5 18. Philadelphia, Pa. Oct., '76 5

Jan 1, 1943

NEW MEMBERS The following list comprises the names of those persons who became members during the period Mar. 10 to Apr. 10, 1914. Members ADAMS, DANIEL T., Mining 1416 Westminster Bldg., Chicago, Ill. BLICKENSDERFER, FRANK CLEVELAND, Sampler Morenci, Ariz. CAVERS, THOMAS WILLARD, Met Copperhill, Tenn. CLAPP, CHARLES H., Geol Univ. of Arizona, Tucson, Ariz. CLARK, PATRICK T., Pres Bullwhacker Mine, Spokane, Wash. COMSTOCK, HARRY, Mining Mineville, Essex Co., New York. COOKE, JOSEPH H., Gen. Mgr Mono Dev. Co., Gisborn, Tooele Co., Utah. COOPER, DEXTER P., Civ. and Hyd. Engr 101 Park Ave., New York, N. Y. DEGOLYER, E. L., Geol Apartado 269, Tampico, Mexico. DESHAYES, ERNEST F., Mine Foreman Baldy, N. M. DOUGLASS, WILLIAM CRAWFORD, Min. Engr 107 Leonard Hotel, Butte, Mont.

Jan 5, 1914

NEW MEMBERS The following list comprises the names of those persons who became members during the month of December, 1913: Members ADAMS, CHARLES W., JR., Smelting, American Smelting & Refining Co., Murray, Utah. ARMSTRONG, FRANK H., Mechanical Engineer Vulcan, Mich. ARNOLD, JOHN B., Attorney-at-Law Room 840,200 5th Ave., New York, N. Y. BOYS, HARRY R., Mining Paso Robles, Cal. CAVANAGH, JOHN L., Min. Engr., Nova Scotia Steel & Coal Co.; Wabana, Newfoundland. CHOW, KAI CHI, Student 1120 Amsterdam Ave., New York, N. Y. CLARK, ARTHUR B., Mining Engineer 72 Harbour Bldg., Butte, Mont. CURLEY, JOHN R., State Mine Inspector P. 0. Box 633, Leadville, Colo. DAVIS, ANGUS W., Mining Engineer, Consolidated Mining & Smelting Company of Canada, Trail, B. C., Canada.

Jan 1, 1914

By R. S. Dean

True careful work of Gross and Zimmerley1 has established the fact that the energy actually used in grinding is proportional to the new sur-face produced. This confirmation of Rittinger's law was made by crush-ing quartz in a frictionless drop-weight machine and determining the surface of the quartz by its rate of solution in hydrofluoric acid. The details of this procedure have been described adequately elsewhere and need not be repeated here. The resultant data furnish the only available basis for comparing accurately the efficiency of grinding machines. This method is so cumbersome experimentally that it has been little used. As an alternative all sorts of approximations have been proposed. The best of these is complete size analysis by sieving and elutria-tion. Such procedure is very lengthy and difficult to carry out accurately. Furthermore, any sizing method becomes very inaccurate for determining surface with very fine sizes where the ratio of surface to volume becomes very large. To avoid the lengthy and difficult technique of elutriation it has been proposed to estimate the size distribution below 200 mesh from various probability formulas. Such a procedure is at best an engi-neering approximation; at worst it is a mere guess. Some time ago Dr. V. H. Gottschalk2 found that the coercive forces of magnetite powders were directly proportional to the surface area, regard-less of size distribution. It was at once apparent that this furnished a method for determining grinding efficiency quickly and accurately. The only requirement was a single determination of the relation between the work input of the Gross-Zimmerley drop-weight machine and the coercive force of the resultant crushed magnetite.

Jan 1, 1936

By George Steintveit

Det Norske Zinkicompani A/S was established in 1924, on the initiative of the Compagnie Royale Asturienne des Mines. Experimental electrothermic zinc production was carried out on industrial scale for a two-year period, but the problems of electrothermic smelting were not solved. A license for the electrolytic zinc production process was then obtained from the Anaconda Copper Mining Co. A plant for electrolytic zinc production was built, near the small fjord town of Odda in Hardanger, West Norway, The production was based on zinc ore from Spain, and cheap local hydro-electric power. The plant came into operation in 1929. Annual capacity, 36,000 tons. In 1964 a long-term agreement was concluded with Boliden AB by which Det Norske Zinkkompani is secured the raw materials basis for an expansion of the annual capacity to 100,000 tons of zinc, Since World War II, the company has been pursuing extensive research and development programs. As a result, various sections have been rebuilt: nev unloading and storage facilities, a 250 ton per day Fluid Bed Roaster with contact plant, new continuous leaching system, integrating the Jarosite Residue Process, new solution purification section - upgrading the solution quality for a 600 Amp/m2 current density Tank Room operation -, installation of induction furnaces for cathode melting with casting machines and automatic stacking of slabs. Simultaneously, instrumentation, and methods of automatic control have been developed and introduced, providing conditions for optimal plant operations.

Jan 1, 1970

By Dwain K. Butler

INTRODUCTION Characterization of a site for the prediction and simulation of dynamic events requires the determination of mechanical properties of the rock at stress/strain levels and rates and at a scale appropriate for the events and critical structures involved. The structures of interest can be on the surface, underground, or designed to impact and penetrate into the site (projectiles). Dynamic events of interest are equally diverse: seismic waves from distance earthquakes or explosions; close-in phenomena associated with earthquakes and explosions; vibrations associated with heavy equipment or machinery; and stress transients associated with impact and penetration. The complexity of site characterization depends on two factors not specifically related to the nature of the site itself: the stress levels generated by the dynamic event and the sophistication of the prediction and simulation techniques. For very high stress levels, such as occur near a nuclear detonation, and for low stress levels, such as occur during seismic wave propagation, site characterization is simplified, and often certain details of the site are not particularly important, such as shear strength variations in the case of very high stress levels. In the intermediate stress range, however, all descriptive relations are non- linear, a complete finite strain constitutive model is required, and all details of the site, such as lithology and fracture distribution, become important. The site characterization must be complete enough to support the most sophisticated prediction and simulation technique that will be applied to the analysis of the dynamic event. The procedures of site characterization are illustrated in this paper by a specific dynamic event, projectile impact and penetration, and a specific site, an outcrop of Dakota Sandstone near San Ysidro, New Mexico. The structure of interest was the projectile itself: nominally, 1.5 m in length, 0.165 m in diameter, 180 kg

Jan 1, 1984

By George Bain

SOME problems concomitant with commercial exploitation of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service depart-ment wants defects rectified and the cause determined to avoid recurrence. The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character.

Jan 1, 1940

By Walter Wood

The specifications for cast-iron pipe that have been submitted at this meeting are practically the outgrowth of those which were originally adopted, about 1860, by Mr. Kirkwood of Brooklyn, N. Y. They have been changed but little since that time, the mode of testing pipe in the hydraulic press, as well as the method of coating, not having departed from the original practice. The chief addition to the specifications has been in the adoption of a test-bar 2 in. by 1 in. in crosa-section, broken between 24-in. supports by a transverse strain applied on the flat side. Test-bars were first introduced into pipe-specifications about 1870. At that time a satisfactory test-piece had to stand a tensile strain of 16,000 lb. per square inch. The present test-bar was adopted in order to give some idea of the deflection of the iron that was being used. These deflection-tests have been so satisfactory to both engineers and manufacturers, and have met the requirements of the pipe-trade so accurately, that it is considered best to hold to the . 2-in. by 1-in. bar instead of adopting the short " Arbitration Bar," which yields but little information from the stand-point of deflection. The new feature in these specifications is the effort to reach standards to which pipe shall be cast in the future, thus permitting the manufacturer to make up stock and the purchaser to find material on hand when he asks for deliveries. Heretofore there has never been ally standard weight for pipes? although in some sizes certain weights are more frequently asked for than others. The fixing of standards for pipes permits the adoption of definite standards for fittings. It has been aimed to secure such uniformity for fittings as will permit the same class of fittings to cover two or more classes of pipe. In order to accomplish

Jan 1, 1905

By N. LILIENBERGS

DURING the past few years, the requirements for steel have been raised so high that soundness is more important than ever before. The old practice was to mike steel ingots of sufficiently large sections to permit a considerable reduction of area in rolling and hammering to a given size, relying on the fact that by such rolling and hammering all cavities will be squeezed together and practically eliminated. The finished sizes, if found by inspection of the surface to be faultless, were therefore pronounced to be sound. But when such steel is ?worked up,? the manufacturer is surprised and disappointed to find that it splits, or that streaks and seams make the product unmarketable. Large sections, such as rails, beams or heavy forgings, may, within certain limits, be sufficiently strong, even if the sides of the cavities are only squeezed, and not welded together. But it is well known that, in the interior of heavy articles, under certain conditions, forging may develop small streaks into large cavities. Small sections, steel for ordnance and tubes, and numberless articles in the tool-trade, always show up the defects. It may be doubted whether cavities in steel ingots can ever be completely welded. The old theory, is, that the silver-clear blow-holes, without the blue oxide, can be welded by sufficient working. They are, however, not empty, but are filled with carbonic oxide. It is admitted that the "blue" cavities, resulting from air mechanically drawn down into the mold during the casting, can never be welded, because the oxide does not melt, and there would be no escape for it if it did. The only way in which steel can be made satisfactory for the above-named particular purposes is by having it ?dead molten." But then the trouble of piping is encountered. As is well known, a pipe is the result of the contraction of

May 1, 1906

By E. S. Bardwell, Roy H. Miller

During the period extending from May, 1922, to September, 1923, the copper-refining furnaces of the Great Falls Reduction Department of the Anaconda Copper Mining Co. at Great Falls, Mont., were operated exclusively with pulverized coal as fuel. The installation was made first as an experiment. It proved successful from the start and was abandoned solely because fuel oil from the Sunburst field became available at a price sufficiently low to be more desirable from an economic standpoint. The equipment required for pulverized coal has, however, been kept intact and is available for immediate use should the oil supply fail. Inasmuch as pulverized coal had been used on two large reverbera-tory smelting furnaces and was, at the time we were considering its application-to the copper-refining furnaces, being used on the Wedge furnaces roasting zinc concentrate for the electrolytic zinc plant, we were equipped with a coal-pulverizing plant of ample capacity to supply pulverized coal for the furnace refinery. The only problem was to devise suitable means for transporting pulverized coal from the pulverizer plant, located in the smelter building, to the refinery about 3000 ft. distant and about 150 ft. above the level of the pulverizer plant. When studying this installation, it should be borne in mind that the layout represents an adaptation suited to the existing conditions at this particular plant. The installation was entirely satisfactory and uniformly dependable but might be modified to advantage from an operating point of view if an entirely new installation were being planned. Fuel Supply The use of the local coals, high in ash and sulfur, was abandoned some time before coal-dust firing was attempted. Local coals from the Great Falls field carrying an average of 4 per cent. sulfur and 22 per cent, ash were used with fair success in the small furnaces in use prior to 1916. In the 250-ton furnaces, however, the time lost in grating and removing clinker from the fireboxes, as well as the difficulties incident to the high-sulfur content of the fuel, became serious and recourse was had to the

Jan 1, 1927

A SERIES of papers on strategic and otherwise important mineral products was prepared some ten years ago under the joint auspices of the Committee on Foreign and Domestic Mining Policy of the Mining and Metallurgical Society of America and the Committee on Industrial Preparedness of the American Institute of Mining and Metallurgical Engineers. These papers were later published in a joint volume entitled International Control of Minerals (1925). Amongst them was one on manganese. The Subcommittee on Manganese prepared its paper in two forms. One was intended for inclusion with the series above referred to and approached its subject more particularly as an international problem. The other dealt more definitely with manganese as an element in the problem of national defense. This last was first written under date of January 24, 1924 as a confidential report, for and at the request of the War Department. It was later released and published, in slightly modified form, as a separate pamphlet by the Industrial Preparedness Committee of the American Institute of Mining and Metallurgical Engineers. After the lapse of eight years, in view of the vital position of manga-nese in the problem of industrial preparedness against a war emergency, the War Department made a request to have the conclusions of 1924 reviewed and brought up to date. To comply with this request the manganese subcommittee was reconvened (with a somewhat changed personnel) and exhaustive studies were once more made of the entire subject of manganese. A new report, with specific recommendations, was submitted to the War Department in February, 1932. This second report is now herewith released for publication. Certain specific conclusions and recommendations as expressed to the War Department are omitted. Otherwise the report stands as prepared and submitted by the manganese subcommittee of 1931. The members of this committee were: C. Minot Weld, Chairman, R. C. Allen, Arthur S. Dwight, J. W. Furness, D. F. Hewett, Reno H. Sales, Theodore Swann and Scott Turner. ARTHUR S. DWIGHT, Chairman, Committee on Industrial Preparedness.

Jan 1, 1933

By C. M. Fellman

AVAILABLE data for the first nine months of the Year indicate that accident occurrence in metal mining was well on its way to an all-time low for 1939. However, the relatively rapid pickup in mining production in the fall will be likely to boost both accident occurrence and also accident rates. Results of the National Safety Competition for 1938, the fourteenth of its kind conducted by the U. S. Bureau of Mines, were published in August, 1939. W. W. Adams, statistician of the bureau, states that "with 345 mines and quarries competing, more than in any previous year except 1931, the contest revealed low accident rates at many of the enrolled plants and, which is even more remarkable, it revealed 113 mines and quarries at which no lost- time accidents occurred during the con- test year." The National Safety Competition provides a means whereby mines and quarries may engage in active competition to stimulate their safety programs. Companies in the contest can compare their records with those of similar plants operating elsewhere and thereby determine to what extent their safety programs are successful. The Joseph A. Holmes Safety Association gave over 150 awards for safety performance in the mineral industries in 1939 and a remarkable phase of these awards was the considerable number given to individual miners who had worked fifty or more years without sustaining a lost-time accident.

Jan 1, 1940

SECTION I Page Page New York Section War Meeting on Employment xxxii Sulphur and Pyrite v Local Section News xxxiv War Minerals Committee xviii Forthcoming Meetings xxxvi St. Louis Meeting xx Library xxxvii Minutes, of Meeting, Executive Membership xli Committee xxvi Institute Committees Iv Members in Military Service xxvi Officers and Directors lxii Personal xxx

Jan 10, 1917

By GEO H. DEIKE

NOT much activity has been evident during the past year in the establishment of co-operative scholarships but the interest among the coal-mining companies is more pronounced than ever. This is apparent from the replies received to a letter sent out by the Committee on the Promotion of Student Interest in Coal Mining to over 120 coalmine operating officials. With that letter was forwarded a bulletin issued by the school of mineral industries of The Pennsylvania State College entitled ?Industrial Scholarships ? a Partnership of Industry and Education.? In that circular was outlined the need for trained men in the war and postwar world, and particularly as such demands pertain to the growth of the mineral industries.

Jan 1, 1943

By J. W. Onuscheck

The oxygen-fuel oil burner lance is a very useful tool at the Monessen B.O.F. It increases the overall flexibility of the operation. An additional 15,000 to 20,000 ingot tons can be produced at a given hot metal supply. It helps overcome sporadic drops in hot metal thermal values and/or supply. It results in increased yield, in particular, on high carbon heats where much yield was lost on reblow triggered slag reactions. The burner has also been adopted as a standard tool to aid burning in new vessel linings. Overall, steelmaking performance has improved with the use of standard preheat practice. Scrap charges up to 50 percent have been used routinely in times of extreme hot metal shortages, but the performance is weak in some categories. Development of a single step oxy-oil process is in progress. In this process, scrap and hot metal are charged as in the normal B.O.F. practice, but fuel oil is fired with the refining oxygen.

Jan 1, 1972

By Arthur Hockman, Howard W. Jaffe, Howard F. Carl

THE problem of establishing practical techniques for evaluating natural corundum ores arose from the desire to improve the existing purchase specifications for crystal corundum procured by the Federal Government for stockpiling. Such purchase specifications had been developed for a large number of products, including minerals and ores considered to be critical and strategic because of the country's dependence on foreign sources of supply. It will be apparent to anyone considering the subject of purchase specifications that the determination of whether or not a submittal meets the specifications is a prime consideration. Consequently satisfactory specifications for minerals should not only incorporate physical, chemical, and mineralogical requirements that are practical but should also establish the means by which both buyer and seller can be assured that materials meet stated requirements. The Munition Board's Material Purchase Specification for corundum, dated February 1954, covered two grades of crystal corundum intended primarily for abrasive use. It established limits of size and of composition: Grade A, at least 95 pct +3 mesh and 92 pct alumina (Al2O3); Grade B, at least 95 pct +7 mesh and 90 pct alumina. It also specified that "of each lot of material, not less than 95 percent shall have a hardness equal to or exceeding nine (9) on Moh's Scale." These specifications were unsatisfactory for several reasons. They did not allow the purchase of lower grades of corundum being used by industry. Neither did they specify exactly what a corundum ore actually was, except that it should contain so much alumina and have a certain scratch hardness. Nothing was said about the abrasive qualities of the material that was to be purchased primarily for abrasive use. During the period 1946 to 1948 supplies of the two grades defined in the then current specifications continued to decrease. Early in 1949 industry recommended that the finer sizes of corundum known as "crystal corundum concentrates," ¼-in. to 16-mesh material, be added to the stockpile specifications and that lower grades of crystal corundum also be included. In the spring of 1949 the National Bureau of Standards and the Bureau of Mines were asked by the Munitions Board to cooperate in developing more practical specifications for grading natural corundum ores. The National Bureau of Standards indicated that it would investigate physical test methods for determining abrasive characteristics of corundum, and the Eastern Experiment Station of the Bureau of Mines at College Park, Md., stated that it would consider the mineralogical aspects of the problem. Members of these two agencies, in consultation with representatives of the Office of Materials Resources of the Munitions Board and of the Federal Supply Service of the General Services Administration, and with the cooperation of industrial suppliers and consumers of abrasive corundum, developed, in a fairly short time, more practical specifications for six grades of corundum ores. The new specifications, issued January 1951, were for corundum, natural crystals, as by this time high-purity synthetic corundum was available and widely used. Nevertheless, for certain specific applications the natural product was preferred over the synthetic material. It has been extensively used in forming snagging wheels. It breaks into more or less cubical particles, whereas artificial corundum fractures into splintery shapes. These produce irregular cuts in glass, while the more symmetrical shape produces a more uniform ground surface. For this reason natural corundum has been preferred for certain types of lens grinding. Pure corundum is clear, colorless alpha alumina (A12O3), but it is rarely found in nature in this form. The most important gem varieties include the blue and yellow sapphires and the ruby. Minute impurities of titanic oxide impart a blue color,

Jan 1, 1955

By H. W. Mathews, J. D. Wheeler

AS predicted by Messrs. Fuqua and Thompson, in last year's paper on West Texas1, 1935 saw a marked increase in activity in this area over recent years. Both major and independent operators shared in the increased wildcatting operations, which resulted in the discovery of eight and probably nine new fields in this area. During 1935 there were 700 wells completed as compared with 468 in 1934 and only 236 in 1933. Of these completions 579 were producers with a total 24-hr. potential of over 700,000 bbl. It is estimated that the new fields discovered during 1935 added from 200,000,000 to 400,000,000 bbl. to the known oil reserve in West Texas. In addition to these new fields, many of the older producing areas scored marked extensions during the year. New Fields Goldsmith.—-The Goldsmith field, in west central Ector County, gives promise of being the year's outstanding discovery in this area. The discovery well was completed by the Gulf Production Co. in June at a depth of 4177 ft.; it gaged 275 bbl. of 36° gravity oil in 3 hr. through 85/8-in. casing on its first production test. The field has been extended to the east by wells drilled by Phillips and Pure on their Cowden block. Present indications are that the field may contain 10,000 productive acres, and this, together with the large flush production from only a small penetration into the pay, leads to the belief that Gulf-Goldsmith No. 1 was the outstanding Permian lime discovery of 1935. It is quite probable that production will prove to be continuous to the Landreth-Scarborough No. 1, 33/4 miles to the northwest, which was completed for a small producer late in 1934. Sand Hills (Ordovician).—From the standpoint of creating excitement, the outstanding West Texas test of the year was no doubt Gulf-Waddell No. 1, on the northwest nose of the Sand Hills structure. This test was started late in 1934 as a deep test to the Ordovician. Thc Ordovician was topped above 6000 ft,., considerably higher than expected. Oil shows in the Simpson were passed and the well was drilled down to the

Jan 1, 1936

By J. D. Wheeler, H. W. Mathews

AS predicted by Messrs. Fuqua and Thompson, in last year's paper on West Texas1, 1935 saw a marked increase in activity in this area over recent years. Both major and independent operators shared in the increased wildcatting operations, which resulted in the discovery of eight and probably nine new fields in this area. During 1935 there were 700 wells completed as compared with 468 in 1934 and only 236 in 1933. Of these completions 579 were producers with a total 24-hr. potential of over 700,000 bbl. It is estimated that the new fields discovered during 1935 added from 200,000,000 to 400,000,000 bbl. to the known oil reserve in West Texas. In addition to these new fields, many of the older producing areas scored marked extensions during the year. New Fields Goldsmith.—-The Goldsmith field, in west central Ector County, gives promise of being the year's outstanding discovery in this area. The discovery well was completed by the Gulf Production Co. in June at a depth of 4177 ft.; it gaged 275 bbl. of 36° gravity oil in 3 hr. through 85/8-in. casing on its first production test. The field has been extended to the east by wells drilled by Phillips and Pure on their Cowden block. Present indications are that the field may contain 10,000 productive acres, and this, together with the large flush production from only a small penetration into the pay, leads to the belief that Gulf-Goldsmith No. 1 was the outstanding Permian lime discovery of 1935. It is quite probable that production will prove to be continuous to the Landreth-Scarborough No. 1, 33/4 miles to the northwest, which was completed for a small producer late in 1934. Sand Hills (Ordovician).—From the standpoint of creating excitement, the outstanding West Texas test of the year was no doubt Gulf-Waddell No. 1, on the northwest nose of the Sand Hills structure. This test was started late in 1934 as a deep test to the Ordovician. Thc Ordovician was topped above 6000 ft,., considerably higher than expected. Oil shows in the Simpson were passed and the well was drilled down to the

Jan 1, 1936

By Sir Robert Hadfield

(New York Meeting, February, 1913.) THE Hadfield method of producing sound steel ingots has been the subject of a paper 1 read before the Iron and Steel Institute, so that it will be unnecessary to describe it fully here. The object of the method is to make possible the production of steel ingots in which the pipe is almost entirely obliterated, and it is applicable particularly to the production of sound ingots, from which good rails could be rolled. The method in brief consists in casting the ingots on cars, usually with the small end down. Each ingot mold is provided with a sand top, rammed up in the well-known manner. After the mold is filled to the desired height with steel, a layer of slag about 0.5 in. thick is placed upon it and the balance of the mold is then filled with charcoal. Then, through suitable piping, an air blast is directed in numerous jets upon the charcoal, which is burned thereby, the combustion supplying additional beat to the top of the ingot, which helps to keep the top fluid and to retard its solidification, while the lower parts are rapidly losing heat by its transfer to the mold. By-one plan the ingots are cast in molds placed upon bogies, movable trucks, or platforms, in the position A, Fig. 1. The ingots are cast vertically on bogies, say four or more ingots on each bogie, as may be found most convenient, and the upper surface of the steel is maintained in a molted condition during the transit of the ingots from the casting pit to the stripper. This is effected by a series of air pipes, for example, three in number, with jets or holes on the under surface of such pipes, placed preferably horizontally, arranged in such a manner as to cause jets of air to impinge on the upper surface of the ingots. These holes or jets are made throughout the entire length of the overhead pipes, the length of such pipes being

Jan 4, 1913

By R. Adair, W. R. Hudspeth, W. T. McDaniel

ANEW method for concentrating the flake mica either from present washing plant tailings or from new feed has been developed. In this paper, flake mica refers to that which occurs in weathered granites, alaskites, pegmatites, and schists in a form too fine to be considered sheet mica. It ranges in size from 1 in. or more down to 200-mesh or finer and occurs with kaolin, quartz, and partially kaolinized feldspar. Scrap mica, a term often used indiscriminately to describe everything other than sheet mica, will be used to denote the waste product from sheet mica mines and fabricating plants. Both flake and scrap mica are used in the mica grinding plants to produce wet-ground or dry-ground mica, although some flake mica recovered from clay mining operations is fine enough to be marketed without grinding. Until 1930, ground mica was made almost entirely from scrap. From 1930 until 1935 a gradually increasing amount of flake mica was mined, and most of this was sold without grinding. A large percentage of this mica was recovered from clay washing plants. In this type of operation the recovery of any sheet mica was .of secondary importance and was considered a byproduct. North Carolina produces more flake mica than any other state, accounting for 73 pct of the total domestic production.' In the following review of current practice in jig plants, there is no intention to disparage these operations. Within the limitations under which they were built, they are examples of mechanical ingenuity. The term jig plant is a carryover from early practice since there are no jigs in operation at the present time. Current practice, as shown in Fig. 1, is based on successive stages of differential crushing with rolls followed by trommel screens to remove the more easily crushed gangue minerals. The oversize mica product then is usually dried, and passed through another set of dry rolls and a final screen to remove the remainder of the grit. This process is effective in recovering up to 50 pct of the mica in the original ore, the balance being lost in the screen undersize, usually —% in. Jigs and tables were at one time used to treat this screen undersize and were capable of recovering a part of the mica larger than about 60-mesh.V ine mica lost in these plants is normally washed away in streams and can be considered irrecoverable. There are ten or more washing plants in the North Carolina area that are losing approximately 50 pct of the mica in the feed. Since the three cooperating agencies, the Asheville Minerals Research Laboratory of North Carolina State College, the North Carolina Dept. of Conservation and Development, and the Tennessee Valley Authority, are concerned with conservation of minerals, they have investigated means for improving the efficiency of these mica plants. The mica industry has been cooperating fully with the laboratory to establish a more efficient method of recovery for flake mica. Choice of Methods The initial investigation was concentrated on finding a means of reducing the losses from plants now using the conventional flowsheet shown in Fig. 1. To accomplish this it would be necessary to collect the screen undersize products through the plant and remove from them the mica from Vs in. down to

Jan 1, 1952