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By P. R. Bradley

NO thought had been given to deep level mining at the Alaska Juneau mine prior to 1930, but in that year a prospect winze was started and continued for 1000 ft. vertically below the main haulage or adit level. The point at which this winze was started was selected entirely by the prevailing physical conditions, such as proximity to established workings, convenience, and the presence overhead of a substantial pillar of dimensions sufficient to lo¬cate the sheave wheel and loading pocket. It was, therefore, with some surprise that the unusually high-grade ore found just below the collar of the winze persisted, with certain vari¬ations, to a full depth of 1000 ft. vertically. Likewise this unusually high-grade ore was found to persist on the various crosscuts driven on levels at 200-ft. vertical intervals. To be brief, this deep level work found richer ore than any yet found in the mine over like areas, and inasmuch as the area was sufficient to plan for extensive deep level mining, plans for such work were given extended consideration.

Jan 1, 1936

By Stanley F. French, Bruno F. Koch

Although the amount of dust that will be actually recovered in the six main dust-control systems cannot be accurately stated until the tests mentioned previously are carried out, it is estimated that the average air entering the wet collectors will contain around 5 grains of dust particles per cubic foot. This means that the six systems handling a total of about 133,000 cu.ft. of air per minute will return about 68 1/2 tons of dust to the concentrator per day and since the copper in this dust will average around 2 per cent, the total recovery is approximately 1.37 tons of copper every 24 hours. This important copper recovery is not due entirely to the dust-control system since in a plant without control only the duct that is dispersed to the atmosphere represents a loss. A conservative estimate of the recovery of copper solely due to the dust control system would be about half of the total or approximately 0.70 tons of copper per day.

Jan 1, 1942

By Joseph Hyde Pratt, Douglas B. Sterrett, CHAPEL HILL

I. DESCRIPTION. MONAZITE is one of the minerals which, for a long time, was considered rather rare in its occurrence, but, upon a commercial demand arising for it, prospectors and engineers soon located large deposits of it in the Carolinas and Brazil, and the supply has always been able to meet the demand. During 1908 further sources of supply of monazite have been discovered and developed in Idaho. North and South Carolina, however, are the only States that have thus far put any monazite on the market. Monazite is essentially an anhydrous phosphate of the rare-earth metals, cerium, lanthanum, and didymium (Ce, La, Di)PO;. There is nearly always present a varying but small percentage of thoria, ThO2, and silicic acid, SiO, which are very probably united in the form of a thorium silicate, ThSiO4 Some monazites contain but a fraction of a per cent. of thoria, while others have been recorded that showed the presence of from 18 to 32 per cent. ; but the majority contain from 3 to 9 per cent. of this oxide. It is the presence of the thorium oxide that gives the monazite its commercial value. The analysis occasionally shows also the presence of other constituents, as the yttrium and erbium oxides, zirconia, alumina, magnesia, lime, iron oxides, manganese oxide, and titanium oxide. Monazite is light-yellow, honey-yellow, reddish-, brownish-, or greenish-yellow in color, with a resinous to vitreous luster, and is translucent to subtransparent. It is brittle, with a conchoidal to uneven fracture, and is from 5 to 5.5 in hardness, and from 4.64 to 5.3 in specific gravity. It crystallizes in the monoclinic system, and some crystals have been observed that were 6 in. in length. The more perfect crystals are, however,

Jun 1, 1909

By Robert E. Sorenson

EXPLORATION for deep-seated orebodies in the Silver Belt area of the Coeur d'Alene mining district is complicated by meager surface expressions of diagnostic criteria, lack of knowledge of the significance of specific alteration phenomena, and the great expense involved in the exploration for ore shoots, the tops of which often occur near sea level elevation or below and as much as 4000 ft or more below the surface. Except for the early studies of Ransome and Calkins in 1903 and 1904,[1] little geological work was done in the Coeur d'Alene district for many years, and it is only during the last 15 to 20 years that complete and careful geological mapping has been applied to most of the mines in the area. Much early information, which now would prove invaluable, is lost in hundreds of miles of caved and inaccessible mine openings not mapped by mining geologists. In more recent years mining geology has become a tool of greater use in the district, and some measurable progress is being made in the accumulation of observations that are adding gradually to the knowledge of ore deposits in the district.

Jan 7, 1951

By Georgc E. Collins

SEVERAL years ago, I estimated the total stock of gold in the world to be about a thousand million ounces, of which rather over one-third was available for monetary uses. Robert H. Ridgway has estimated the world's production from 1493 to 1927 as slightly over this amount. Of this total, 1.5 per cent was produced between 1493 and 1850 (before the Californian and Australian goldfields began to flood the world with gold), 331/2 per cent from 1851 to 1900, and 511/2 per cent from 1900 to 1927. Allowing for loss by attrition and permanent consumption in the arts, and for loss of buried treas¬ure, my first-mentioned estimate is perhaps not far from the truth; but my estimate of the monetary stock was certainly too low. Of the total production stated by Rid-way. 28 per cent came from North America. 26.9 per cent from Africa, 1.6.8 per cent from Australasia, 12.4 per cent from South America, and 11.2 per cent from Asia. Excepting that from the African conglomerate beds, the ultimate origin of which is still the subject of controversy, by far the greater part of the total production was derived from alluvials. Weighing all contingencies, it is improbable that any such production as has been made during the last forty years will be repeated in any similar period, if the present price level is maintained. The gold standard today seems firmly established except for temporary digressions. Nevertheless, no well-informed mining engineer will venture to assert the probability that the material for its maintenance throughout future generations can be furnished.

Jan 1, 1932

By H. K. Najarian

AT Josephtown, Pa., on the south hank of the Ohio River about thirty miles northwest of Pittsburgh, is the Josephtown electrothermic zinc smelter, which operates as a custom smelter receiving both domestic and foreign concentrates. Constructed in 1930, the plant was designed to produce zinc oxide and to process 124 tons per day of zinc concentrate obtained mainly from the Company's New York State mines. Zinc condensing equipment was developed in conjunction with the St. Joe electrothermic. furnace and commercial production of zinc metal started in 1936. Expansion of the plant and equipment during 1939 and 1940 brought the processing. capacity to upwards of 300 tons of concentrate per day; and the plant operated at peak capacity during the war years, earning the Army-Navy "E" award and three subsequent stars. A postwar plant expansion is now under way, designed to increase the capacity to 500 tons per day of concentrate, with an estimated daily production of 160 tons of zinc metal of various grades, about 100 tons of zinc oxide, and 425 tons of sulphuric acid as major products.

Jan 1, 1947

By GUY B. HUNNER

THOSE magnetite ore bodies comprising the Clifton Mines are situated in the south central part of St. Lawrence County, New York, on the western slope of the Adirondack Mountains. The topography is made up of gently rolling hills densely wooded with second-growth maple, birch, and hemlock. Drainage is north and west to the St. Lawrence River.

Jan 1, 1943

By C. K. Leith

THE resolution presented at the Annual Meeting of the A.I.M.E., calling on Congress to provide now for postwar accumulation of mineral stock piles under Government control, expresses, I think, the nearly unanimous view of the mining industry. As a result of the trying experiences of the first World War, Mr. Baruch, in his report of Dec. 24, 1919, to the President, urged that steps be taken at once to ensure adequate supplies of raw materials for future emergency. In the twenty years that followed, the same program was vigorously urged on Congress by many individuals and agencies, public and private, including the Secretaries of War and Navy, many members of Congress, the Bureau of Mines, the Planning Committee for Mineral Policy appointed by President Roosevelt, the A.I.M.E., the Mining and Metallurgical Society, and others.

Jan 1, 1943

By R. E. Salvoti

IN underground coal mining, the increasing trend towards mechanical methods is ever apparent. Figures for 1939 showed that 28 per cent of the total bituminous coal production was mined mechanically 1940 statistic will reveal an even higher figure. Factors causing this trend are varied, but the important are the following;

Jan 1, 1941

By Charles W. Perry

The options of enhanced oil recovery, coal syncrude, and shale syncrude are compared by approximately equivalent economics. The physical constraints for the major enhanced oil recovery processes are described, followed by new estimates of cost. The range for all three options in terms of light syncrude equivalent are $22 to $40 per barrel in 1980 dollars.

Jan 1, 1982

By H. M. Howe

Page 1. Introduction............................514 2. Definitions.............................517 3. Brevity of the Heating........................517 I. THE HARDENING OF THE BORE..............517 4. The Hardening of the Bore.....................517 5. The Thickness of the Hardened Layer.................517 6. Martensitization..........................518 7. The Hardening Repetitive ......................519 8. The Temperature Cycle.......................519 9. The Hardened Layer is the Merged Layer............... 521 10. The Progressiveness of Merging....................521 11. The Progressive Thickening of the Hardened Layer from Round to Round. 523 12. Merging and Hardening are Cumulative................523 13. Three Additional Causes of the Progressive Thickening of the Hardened Layer 525 14. Progressive Roughening of the Bore..................525 15. Avoidance of an Endothermic Transformation.............525 16. Asymptotic Retardation of the Thickening of the Hardened Layer.....527 17. The Troostitic Layer........................ 529 18. The Usual Lack of Martensitic Markings................529 19. The Thickness of the Hardened Layer Should Increase with the Quantity of Heat Taken up by the Walls of the Bore.................530 20. The Decrease of the Thickness of the Hardened Layer from Breech to Muzsle 531 21. Phstic Deformation as a Contributory aCause of Hardening........531 22. In What Way May Plastic Deformation Hasten Hardening?....... 535 23. Possible Need of Coarsening.....................535 24. Carburization as a Cause of Hardening..........:.....536 25. Does Hardening Increase Erosion?..................-538 11. THE CRACKING OF THE BORE ...............539 26. Appearance of the Bore and Cracks in Elevation............539 27. The Cracks in Elevation in the Rear Ring...............539 28. The Cracks in Elevation in the Forward Ring.............540 29. The Copper Network in the Grooves.................540 30. The Cracking of the Lands......................541

Jan 1, 1918

By HUBERT O. De

IN December, 1936, several drilling tests were made at the Hubert O. De Beck feldspar mine at Green Mountain, N. C., to determine the most efficient type of hammier-drill bit and drilling method for use at this particular property. This mine is well recognized as having the hardest rock in the Burnsville - Spruce Pine feldspar district and drilling costs always have been high. Local structural deformation has greatly distorted and warped the normal crystalline structure of the feldspar so the rock is much tougher than usual. In studying drilling methods and bit types, available literature was re¬viewed but little specific data could be found on the direct comparison of four-point and six-point drill bits so the following results may be of some interest.

Jan 1, 1937

By ALFRED T. BARR

In certain areas of the New Cornelia pit, considerable secondary blasting is necessary to reduce oversized boulders, formed from primary blasting, to pieces which will pass the 41/2-cu yd dippers on the shovels. Some of the boulders are 'dobied, but when time permits they are blockholed and blasted. In most instances one hole drilled to a depth of 2 to 3 ft and blasted with 1/3 to 1/2 of a stick of powder will break a boulder satisfactorily. Blockholing is normally done by using a jackhammer of the 55-lb class, 1-in. round drill steel, and detachable steel bits, 2-in. gauge when new. A bit change is usually made after the completion of each hole. The use of light drilling equipment in blockholing is desirable, both from the standpoint of safety and ease of doing the work, and when it was seen there was a possibility of using a lighter jackhammer through the use of tungsten-carbide bits and at the same time get at least the same drilling efficiency as with the standard equipment, it was decided to test tungsten-carbide bits. The claims for long life of the bits and footage drilled before resharpening gave hopes of eliminating much of the delay time in changing bits which is unavoidable with the use of steel bits. and thus gain in actual drilling time.

Jan 1, 1949

By C. H. Green

. RECENTLY two papers on the structure of eutectics were read before the British Institute of Metals, one by F. L. Brady1 and the other by A. Portevin.2 In the preparation of photomicrographs of laboratory specimens as illustrations for student work, and in connection with various researches; the writer has been working along the same line for some, time and, therefore, was much interested in the results given, especially those of Portevin. He has correlated the information on the subject and has outlined a broad scientific basis for future work along this line. It is largely with the idea-of adding something by way of illustration to the work already done that this paper is written. The eutectic is generally understood to mean the alloy having the lowest melting point of any alloy of the system, and in which the melt becomes supersaturated with reference to the two or more phases which, separate out simultaneously (or alternately). From the surface pattern, the eutectic means; a structure with no primary crystals. It is not always easy to get the exact eutectic composition in making any alloy; in fact, a slight range in composition may be expected and some of the coarser particles may be richer in either of the composing metals. Even when chemical analysis shows the right composition, differences in density of the pure metals may cause segregation, or. supercooling resulting from different crystallizing properties may give a surface pattern the appearance of being on one side of the eutectic point. However, the alloys on either side of the eutectic composition, showing primary crystals of one of the phases and the effect of the pro-eutectic form on the surface pattern of the eutectic make a very interesting study, which is slightly touched upon in this paper. The phases, or microconstituents, of a eutectic may be pure metals (Pb-Sb, Tl-Au), solid solutions (Cd-Zn), a pure metal and a solid solution; (Ag-Sn), or a pure metal or solid solution with an intermetallic compound (Sb-Mg, Sb-Cu, As-Cu, Bi-Te, etc.).

Jan 2, 1925

By H. C., Simpson

MANY metals by virtue of their place of occurrence as ore, and their uses are travelers! Iron and steel, for instance, is one of the greatest of travelers in the form of ships and the romance of iron in this respect is only just beginning to be superseded by the stories which can be told of the travels of aluminum and its alloys, used in the building of airplanes. Tin is a traveler from the Straits Settlements to this country and Europe, for use in the canning industry; afterward traveling all over the civilized world as a part of the container for preserved foods. Silver is somewhat of an aristocrat, when its uses are measured against those of the baser metals. From earliest times it has been used for adornment (first perhaps o4 the person and later for the embellishment of weapons and' buildings), for the making of fine ar¬ticles used in the household, and as money. While its uses have been widened by the discoveries in chemistry, electricity and other sciences, its early uses are still much in evidence in our modern life.

Jan 1, 1928

By A. W. Gauger

DESPITE many handicaps and in the face of many discouragements anthracite and bituminous coal producers continue to supply the needs of the nation now vastly multiplied by the demands of the greatest war of all time, total output being about 620,000,000 tons of bituminous and 64,445,000 of anthracite. The progress made by this industry during the national emergency reflects more credit on all connected therewith than will ever be given. Not only has the industry been called upon to produce more coal than ever before but it has also sent representatives to England to study and advise on methods for increasing production there, and has co-operated with other Allied Nations by welcoming engineers sent to this country to study American practice. One noteworthy development has been the growth of strip mining in the

Jan 1, 1945

By M. D. Curran

AS applied to coal, the term processing is subject to many interpretations. To some it means preparation of coal for the market by mechanical means such as crushing, sizing, washing, or treating with oil or chemicals to eliminate dust or improve combustion quality. To others it means conversion of the coal to other commodities as in carbonization to produce coke and by- products, or to liquids by application of the hydrogenation process. I prefer to classify the various forms of mechanical treatment under the heading of beneficiation and apply the term processing to those methods of treatment that destroy the coal sub- stance through distillation or hydrogenation.

Jan 1, 1939

By E. E. AGGER, Arthur Notman

THE proposal has been made in a bill introduced into Congress at the last session by Representative Jones of Michigan that an import duty of 6 c. per lb. shall be placed on copper. This action is urged after eighty years of prosperity for the industry in this country; during most of which copper has been on the free list, and during all of which a tariff would have been without real effect. To comprehend the general situation upon which this action would be imposed, we must refer to the past history of the industry and its trends at the present time. The following table supplies us with a picture of the physical growth of the industry in this country and its relation to that of the world as a whole down to Jan. 1, 1921:

Jan 1, 1925

By W. R. Ingalls

IF, in this study of the outlook for the copper industry of the United states, I find myself assuming to be prophetic in some respects I shall express myself with hesitation and with the foresight that after the end of the war with Germany the war with Japan may continue; anyway there is sure to be an uneasy period before copper and the other metals begin to flow smoothly through the natural channels of consumption. It is mainly my purpose to survey conditions and suggest some probabilities, or possibilities, rather than to prophesy. In interpreting them it will be necessary to make certain aasurnptions, among which will be (1) expectation of a rise in the general price level,, which so far has been one-sided; (2) continuance of the k. tariff on copper imports; and (3) lock-up of government-owned copper as a military re- serve. Of these assumptions the first is indicated by the lessons from economic history, and by current symptoms. The second and third depend upon political action by Congress.

Jan 1, 1944

Ahrenholz, Herman William, Jr., Student, Lehigh Univ Bethlehem, Pa. '35 Allen, Carl A., Student, Colorado School of Mines Golden, Colo. '35 Allen, Paul W., Student, Mass. Inst. of Tech Cambridge, Mass. '35 Allen, R. M., Jr., Student, Virginia Polytechnic Inst., "G" Co Blacasburg, Va. '35 Amberger, K. H., Student, Michigan College of Min. & Tech Houghton, Mich. '35 Andersen, Burton Lee, Student, School of Mines, Univ. of Washington Seattle, Wash. '35 Anderson, Joseph S., Student, Univ. of Texas El Paso, Tex. '35 Anderson, R. C., Student, Univ. of Washington Seattle, Wash. '35 Ansel, Gerhard 627 Clyde St., Pittsburgh, Pa. '34 Anutta, Frederick P., Student, Michigan College of Min. & Tech Houghton, Mich. '35 Apsouri, Constantin N., Graduate Student, Univ. of Arizona Tucson, Ariz. '35 Arakelian, Haig Mark, Student, Mass. Inst. of Tech Cambridge, Mass. '34 Archer, George K 1420 Court Pl., Denver, Colo. '34 Argall, George O., Jr., K. E. House Golden, Colo. '35 Argiielles, Alfredo, Student, Univ. of Texas El Paso, Tex. '35 Atwater, Ralph, Student, South Dakota School of Mines Rapid City, S. D. '35 Austin, Robert B., Miner, Page Mine, Federal Min. & Smelt. CoSpokane, Wash. '34

Jan 1, 1934