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By Charles Allen

THE Athens mine is in the city of Negaunee, Mich. It is one of the larger producers of soft hematite ore on the Marquette iron range. The property is held under lease by the Athens Iron Mining Co., and is operated by the Cleveland-Cliffs Iron Co., which is a partner with Pickands, Mather & Co. in the Athens company. The mine was opened in 1913, and shipments of ore commenced in 1918, the total reaching 3,063,711 tons up to Jan. 1, 1932. Diamond-drilling from surface, together with a knowledge of geological conditions in neighboring properties, gave a comprehensive picture of the location, size and shape of the orebody before shaft-sinking started. Striking east and west, the orebody entered the east boundary of the property at a depth of about 1500 ft. below surface. A pitch of 15° to the west carried it down to about 2500 ft. on the west boundary, about double the depth of that of any soft-ore property heretofore worked on the Marquette Range. The width of ore averaged close to 500 ft., and the thickness 300 feet. The depth of the deposit and its size, together with an overburden of quicksand, which in places reached a thickness of 150 ft., presented unusual mining problems. The use of a caving system made surface drainage into the orebody inevitable, because the north boundary of the deposit was a vertical diorite dike 200 ft. wide, and the south boundary a northward-dipping impervious slate. S. R. Elliott, manager of the mining department of the Cleveland-Cliffs Iron Co., who was super-intendent of the mine at that time, conceived the idea of starting at the bottom of the orebody and working upward, reversing the usual mining procedure. This innovation divided the Athens orebody into a series of steps, or blocks, the first of which was adjacent to the western boundary, and therefore in the lowest portion of the deposit. Top-slicing was to start under the capping in this first block by raising from the bottom level, and development and mining were to progress upward in successive blocks to the east. A complete description of the Athens system of mining was

Jan 1, 1933

By A. J. Carlson, G. M. Marincel, M. L. Hovland, J. H. Healy

Research personnel of Erie Mining Co., a pioneer taconite mining firm on the Mesabi Range, have invented a new method to make an effective 325 mesh separation at high tonnage rates over stationary screens. The company regards this development as historically significant in that it represents the first successful method to commercially screen large tonnages of ore at fine sizes. Erie, which is now completing an expansion program at its plant site near Hoyt Lakes, Minn., has incorporated this screening method as part of that expansion. When completed, the concentration plant will produce 10.3 million tons of iron concentrate, all of which will have been efficiently screened at 325 mesh.

Jan 4, 1967

By H. C. Hardison

The Yates pool, Pccos County, Texas, has greater potential capacities than any other field in the United States. This field is notable for the large return it yields on capital invested, for low production costs and for the orderly and conservative manner in which it was developed and continues to be operated. The proven area is 20,000 acres and there are 392 producing wells, or approximately 1 well to 50 acres. The theoretical daily potential is 5,250,000 bbl. as determined by l-hr. open-flow gages. Individual well gages vary from a few barrels to 8500 bbl. per hour, and well depths range from 1000 to 1800 ft. The greater part of the production is from a very porous limestone, and by agreement no productive well has penetrated the lime more than 225 ft. The forces driving the oil from the formation to the surface are hydrostatic head, expanding gas or a combination of the two. The degree of effectiveness of either depends upon the structural position of, and porosity encountered in, the individual wells. Approximately 95 per cent. of the wells in the field flow naturally. The pipe line outlet of the field at the present time is 100,000 bbl. per day, which is less than 2 per cent. of the daily potential. Difficulties and Principles of Probation It became evident during the first year of the development of this field that operators would have to devise a scheme to allocate pipe line runs equitably among their different properties. When the idea of proration was first inaugerated, the matter of spacing wells was given consideration. This was given up through fear of legal difficulties. Storage was also a question that was given considerable thought, and a plan was finally developed which went into effect Oct. 1, 1927. It was decided that the oil runs should be prorated according to the total potential capacity of all the wells which the several operators had in the field. The potential capacity of the wells was measured by a l-hr. open-flow gage. All runs to storage by an operator were deducted from his daily allowance.

Jan 1, 1931

By AIME AIME

PERHAPS the most interesting paper of the subsidence session on Monday morning was that by Roland D. Parks entitled "Yieldable Metal Props for Underground Support." This paper described the development of a telescoping prop made from two pieces of pipe. The lower and larger in diameter has cast in it a soft metallic alloy which is slowly extruded through an orifice in the upper and smaller piece of pipe. In this way, the length of the prop decreases gradually as the load from the roof increases. The stress-strain diagram for these props, as tested in the laboratory, is almost ideal, and can be duplicated satisfactorily in successive tests. They have not yet been tested underground. Another paper of much interest was presented by Prof. P. B. Bucky. It is an addition to his series on structural models as applied to mining and was entitled "Effect of Approximately Vertical Cracks in the Behavior of Hori¬zontally Lying Roof Strata." It was illustrated by motion pictures of a model under test. After explaining the un¬derlying theory, the apparatus and the mode of testing, Prof. Bucky set forth the effect of vertical cracks in a mine roof, as follows: (a) the wider the crack, the weaker the roof; (b) where the sides of the crack are in juxtaposition, there is little weakening of the roof; (c) grouting cracks whose sides are not in contact restores the strength of the roof until it may be as strong as, or stronger than the uncracked roof. Small paper props helped sustain the roof. Both the nature of the material and its bonding affect its behavior under stress.

Jan 1, 1933

By K. E. Merklin, F. D. DeVaney

In the past most of the research in pelletizing has as its aim the production of a physically strong pellet. Now that this problem is solved, more attention is being paid to uniformity in grade and chemical composition. Consideration has been given in recent years to a study of additives which will make pellets partially or fully fluxed. Blast furnace tests show fluxed pellets to have advantages over both fluxed sinter and acid pellets. Lower slag volumes are used more frequently in the blast furnace and the uniformity of the charge, both physically and chemically, is becoming increasingly important. A considerable improvement can be secured by having all of the flux uniformly distributed through the pellets in a calcined state. A fluxed pellet, therefore, should be a superior product. The use of an ore burden that contains an appropriate quantity of fluxing materials is not new to the blast furnace industry. For years the Minette ores of France and Germany, the Clinton ores of the Birmingham, Ala., areas, as well as others, which are low in iron but contain calcium carbonate in sufficient quantities to give them self-fluxing properties, have proven economical. The adaption of the sintering process to the preparation of ore burdens provided a means for artifically associating the fluxstone with the iron ore prior to charging to the blast furnace. In 1944 Torpl discussed the effects of using lime in sinter made in Sweden on the sinter's metallurgical performance in a blast furnace. Hessle2 reported in 1945 on the advantages of using lime in sinter to increase the sintering plants' capacity and reduce fuel requirements. Robinson3 discussed the use of lime in Swedish sintering practice at the 1950 Blast Furnace, Coke Oven, and Raw Materials meeting. One of the suggested advantages was the combining of lime with silica to prevent the formation of a fayalite slag, which is difficult to reduce in the blast furnace. Nilson4 at the same meeting commented briefly on experimental work that had just started in the U. S. on the use of lime in sinter. The literature tends to indicate that most of this early work was directed towards improvement in sinter physical quality, and the fact that the feed to the blast furnace was partially fluxed was incidental. It was not long, however, before blast furnace advantages were being claimed. The matter was forcibly called to the attention of North American operators by reports of remarkable production records established by the Russians using fluxed sinter. The leading step was taken on this continent by the Steel Company of Canada in 1957; McMahon5 reported on the marked improvement in performance of an 18-ft blast furnace using fluxed sinter at its Hamilton works. Other North American operators quickly followed theStelco lead.

Jan 1, 1963

By H Pray, H. W. Russell, Paul D. MILLER

It is known that austenitic chromium-nickel steels that have free carbide in the grain boundaries are subject to intergranu-lar corrosion. It is difficult to detect such a susceptible condition in a fabricated article because present test methods require a sample section for examination and in most cases this is difficult to obtain. The question of the nature and prevention of intergranular corrosion in austenitic stainless steels has been ably discussed by Bain and co-workers1-3 and by other investigator4-10 The present methods of study subject samples to corrosive conditions in such reagents as the Strauss solution, a mixture of copper sulphate and sulphuric acid. Such tests usually require at least 72 hr. to run. Various methods of measuring the degree of sensitization have been employed, such as the measurement of electrical resistivity, magnetic measuremerits, measurement of the degree of cracking produced on bending over a malldrel, and microscopic studies. The detection of carbides at the grain boundaries by metallographic polishing and etching methods is tedious and requires a skilled operator. A recent report on such methods of carbide detection is given by the American Society for Testing Materials Subcommittee VI of Committee A.-1011 and by Arness.12 The present investigation was undertaken to develop a simple test procedure for detecting carbide precipitation or susceptibility to intergranular corrosion. The test is designed for use in the plant and for the testing of fabricated structures. Carbide precipitation, the factor leading to susceptibility to corrosion, is produced by heating the alloy in the temperature range 800° to 1600°F., as in welding, in improper annealing or in service where such temperatures are met. The connection between such precipitation and susceptibility to corrosion has been thoroughly discussed, as has been the use of stabilizing addition elements to prevent precipitation. Experimental Method A small area of the steel under test is subjected to an anodic treatment in a cell that can be 'lamped Onto a a Or an actual structure. The cell and electrical circuit used are illustrated in Fig. I. The cell C is lead, joined to the steel plate D and insulated from it by a short piece of rubber tubing E. The cell is forced tightly against the steel plate by a spring Or clamping device. The seal formed by the rubber against the steel plate is sufficient to retain the liquid bath inside the cell. The spot treated can be made any shape desired, depending on the shape of the rubber gasket. The cell illustrated polishes a circular spot about 3/8- diameter' The bath consists of 60 per cent (by weight) sulphuric acid to which is added 5 ml. per liter of Glycyrrhiza extract (U.S.P.). The cell requires about 2 to 2.5

Jan 1, 1941

By H. W. Russell, H Pray, Paul D. MILLER

It is known that austenitic chromium-nickel steels that have free carbide in the grain boundaries are subject to intergranu-lar corrosion. It is difficult to detect such a susceptible condition in a fabricated article because present test methods require a sample section for examination and in most cases this is difficult to obtain. The question of the nature and prevention of intergranular corrosion in austenitic stainless steels has been ably discussed by Bain and co-workers1-3 and by other investigator4-10 The present methods of study subject samples to corrosive conditions in such reagents as the Strauss solution, a mixture of copper sulphate and sulphuric acid. Such tests usually require at least 72 hr. to run. Various methods of measuring the degree of sensitization have been employed, such as the measurement of electrical resistivity, magnetic measuremerits, measurement of the degree of cracking produced on bending over a malldrel, and microscopic studies. The detection of carbides at the grain boundaries by metallographic polishing and etching methods is tedious and requires a skilled operator. A recent report on such methods of carbide detection is given by the American Society for Testing Materials Subcommittee VI of Committee A.-1011 and by Arness.12 The present investigation was undertaken to develop a simple test procedure for detecting carbide precipitation or susceptibility to intergranular corrosion. The test is designed for use in the plant and for the testing of fabricated structures. Carbide precipitation, the factor leading to susceptibility to corrosion, is produced by heating the alloy in the temperature range 800° to 1600°F., as in welding, in improper annealing or in service where such temperatures are met. The connection between such precipitation and susceptibility to corrosion has been thoroughly discussed, as has been the use of stabilizing addition elements to prevent precipitation. Experimental Method A small area of the steel under test is subjected to an anodic treatment in a cell that can be 'lamped Onto a a Or an actual structure. The cell and electrical circuit used are illustrated in Fig. I. The cell C is lead, joined to the steel plate D and insulated from it by a short piece of rubber tubing E. The cell is forced tightly against the steel plate by a spring Or clamping device. The seal formed by the rubber against the steel plate is sufficient to retain the liquid bath inside the cell. The spot treated can be made any shape desired, depending on the shape of the rubber gasket. The cell illustrated polishes a circular spot about 3/8- diameter' The bath consists of 60 per cent (by weight) sulphuric acid to which is added 5 ml. per liter of Glycyrrhiza extract (U.S.P.). The cell requires about 2 to 2.5

Jan 1, 1941

By Worthen Bradley, R. G. Hall

THIS paper will attempt to show how a metallurgical problem at one California quicksilver mine was solved, and how the solution was applied successfully at another mine. The pronouns "we" and "our," as used below, refer to the Bradley Mining Co. of San Francisco. The term "concurrent firing" for the purpose of this paper can be defined as feeding and firing a rotary kiln at the same end-that is, of course, the upper end. This is as opposed to "counter-current firing," the orthodox method, in which a kiln is fed at the upper and fired at the lower end. The terms "quicksilver" and "mercury" are used interchangeably. EARLY REFERENCES The earliest work on nonferrous metallurgy, we believe, was The Pirotechnia of Vannocio Biringuccio,1 its first edition having been printed in Italy in 1540. Quoting from its chapter entitled "Concerning Quicksilver and Its Ore": Quicksilver . . . is one of the gods and has divine strength in itself, and also, to the annoyance of the alchemists, it is winged. Hence, when it sees that it is in gravest danger, it loosens itself from . . . every bond . . . and flies away into the heavens, escaping from the hands of those who crucify it. Almost laughing, it leaves all its adversaries mocked and scorned, with their phials and filters empty . . . How thorough a job, under certain conditions, it can do of mocking its adversaries and leaving their phials and filters empty, was found out four centuries later at the Sulphur Bank mine, on the east shore of Clear Lake, in Lake County, California. The other mine mentioned in the title is the Reed, in Yolo County, California, 35 miles by road southeast of Sulphur Bank. Reed and Sulphur Bank ranked respectively fifth and seventh in U. S. production in 1943. The earliest direct reference we can find to furnacing troubles at these mines was by Thomas Egleston in 1890.2 Speaking of Sulphur Bank, Egleston says: Sometimes there is more sulphur than cinnabar in the ore, which is a detriment to both . . . making the sulphur impure, and rendering the cinnabar difficult to work on account of the soot. In some of the early . . . furnaces the accumulation of soot from the excess of sulphur has been known to penetrate as far as the fan blower at the end of the . . . condensers, and completely prevent its revolution. In order to get rid of the inconvenience of this accumulation . . . , as well as to get a commercial value from the sulphur, it (the sulphur) is now separated by steam and sold. It is claimed that the sulphur alone pays all the expenses of . . . the mine. The mine was first worked for sulphur, and the cinnabar it contained was considered to be an inconvenience, and was carefully picked out and thrown away. as its richness and value were not

Jan 1, 1945

By P. K. Koh

Chi phase (body-centered cubic, a = 8.89A) was found in as-cast 23 pct Cr-10 pct Mo-Fe alloy as well as in heat-treated 316, 316L, 317, and modified 446 stainless steels. Chi phase resembles sigma phase in its metastability, chemical composition, and brittleness. Microstructure and some of physical properties of chi phase were developed. MOLYBDENUM has been established as a desirable alloying element for the enhancement of corrosion resistance in Cr-Ni steels and creep and rupture strength in high temperature alloys. On the debit side, however, the molybdenum addition has been known to stimulate u formation. When the molybdenum-bearing steels were subjected to prolonged heating at elevated temperatures, losses of corrosion resistance and/or ductility have been observed. Andrews1,2 first found the existence of a new phase among the anodic FeC13 extracts from type 316 stainless steel solution treated and then reheated from 800" to 1100°C. This phase was designated x and was identified by diffraction patterns as of body-centered cubic structure with a value equal to 8.89? and similar to that of a manganese. He found that the x phase in this steel always coexisted with s phase, but failed to distinguish one from the other by metallographic technique. No definite conclusion was drawn regarding the equilibrium temperature ranges of these two phases. The appearance of Andrew's work recalled an un- explained structure observed several years ago at the Allegheny Ludlum Research Laboratories during the investigation of an experimental alloy containing 25 pct Cr, 10 pct Mo, and balance Fe. X-ray diffraction patterns on the as-cast material revealed the presence of a body-centered cubic phase having a lattice parameter of 8.89?. The structure was sufficiently similar to that of y chromium that for a time it was thought that the structure might be caused by the presence of some undissolved electrolytic chromium particles. The alloy as-cast was so brittle that it shattered after the slightest hot reduction by hammer cogging. This paper gives the results of some metallographic and X-ray diffraction studies on x phase as found in several experimental alloys as well as a few molybdenum-bearing commercial stainless steels. The analyses of materials studied were as shown in Table I. Experimental Procedure Metallography: Solid specimens were polished mechanically and etched in boiling 50 pct HC1 solution in order to best delineate x and s phases in the alloys studied. X-Ray Diffraction: The difficulty of satisfactorily developing diffraction lines for s phase in solid specimens has been previously reported by Bindari, Koh, and Zmeskal.V or this reason all specimens used in this investigation were subjected to anodic

Jan 1, 1954

By C. S. Westerberg, C. P. Heiner

Observation of the clinkering action of coal from the Castle Gate D seam in underfeed stokers over a period of years has given rise to the present investigation of the effect of bony coal on clinkering. Some very costly examples of slagging clinkers in particular cases have been of especial interest to the authors. In such cases coal analyses and ash-softening and fluid temperatures have been found of little value. In general, it was noted that slagging mas accompanied by a somewhat higher ash content of the stoker slack, and the suspicion naturally arose that foreign matter was the troublemaker. One would naturally suspect bony coal and rock impurities because of their occurrence and prevalence within the seam and the relative absence of sulphur or other impurities in the coal mined. The test results given herein indicate that the concentration of the bony coal and rock impurities in the coal determines the clinkering tendencies of the ash during combustion. Castle Gate D Seam Extending from the Utah-Colorado line near Grand Junction, Colo., westward to Greenriver, Utah, and thence in semicircular form north and westward to Castle Gate, and from there southward to Mt. Hilgard in central Utah, is a line of nearly perpendicular cliffs, composed of interbedded massive sandstone and shales, making up the coal-bearing horizon of the Mesaverde formation of Upper Cretaceous age. The cliffs face roughly concentrically toward the south and southeast and the strata, with conformably enclosed coal beds, gently dip away from the face of the cliffs and at right angles to their front line. Back of these cliffs the mountain masses rise to an altitude of from 8000 to 10,ooo ft. above sea level. Stretching away from their foot is a great shale plain, on which the towns are situated and over which the railroad lines and highways run. The Castle Gate mines enter the coal beds at their outcrop; the workings extending within a particular coal bed away from the outcrop and under the mountain mass back from the cliff line (Fig. I). Throughout the Mesaverde formation in the Castle Gate general area, there are from two to five workable coal beds. Usually not all of these are coincidentally of workable size and merchantable quality throughout any given large tract. In the Castle Gate mine area, the base of the Mesaverde horizon and coal measures is marked by a massive, cliffmaking, gray sandstone bed 60 to 80 ft. thick. Locally this is referred to as the "Castle Gate sandstone floor." Frank R. Clark, in U. S. Geol. Survey Bull. 793, designates it as the "Aberdeen sandstone." At Castle Gate the various coal beds are designated by the letters A, B, C, etc., commencing with the lowest bed.

Jan 1, 1942

By C. P. Heiner, C. S. Westerberg

Observation of the clinkering action of coal from the Castle Gate D seam in underfeed stokers over a period of years has given rise to the present investigation of the effect of bony coal on clinkering. Some very costly examples of slagging clinkers in particular cases have been of especial interest to the authors. In such cases coal analyses and ash-softening and fluid temperatures have been found of little value. In general, it was noted that slagging mas accompanied by a somewhat higher ash content of the stoker slack, and the suspicion naturally arose that foreign matter was the troublemaker. One would naturally suspect bony coal and rock impurities because of their occurrence and prevalence within the seam and the relative absence of sulphur or other impurities in the coal mined. The test results given herein indicate that the concentration of the bony coal and rock impurities in the coal determines the clinkering tendencies of the ash during combustion. Castle Gate D Seam Extending from the Utah-Colorado line near Grand Junction, Colo., westward to Greenriver, Utah, and thence in semicircular form north and westward to Castle Gate, and from there southward to Mt. Hilgard in central Utah, is a line of nearly perpendicular cliffs, composed of interbedded massive sandstone and shales, making up the coal-bearing horizon of the Mesaverde formation of Upper Cretaceous age. The cliffs face roughly concentrically toward the south and southeast and the strata, with conformably enclosed coal beds, gently dip away from the face of the cliffs and at right angles to their front line. Back of these cliffs the mountain masses rise to an altitude of from 8000 to 10,ooo ft. above sea level. Stretching away from their foot is a great shale plain, on which the towns are situated and over which the railroad lines and highways run. The Castle Gate mines enter the coal beds at their outcrop; the workings extending within a particular coal bed away from the outcrop and under the mountain mass back from the cliff line (Fig. I). Throughout the Mesaverde formation in the Castle Gate general area, there are from two to five workable coal beds. Usually not all of these are coincidentally of workable size and merchantable quality throughout any given large tract. In the Castle Gate mine area, the base of the Mesaverde horizon and coal measures is marked by a massive, cliffmaking, gray sandstone bed 60 to 80 ft. thick. Locally this is referred to as the "Castle Gate sandstone floor." Frank R. Clark, in U. S. Geol. Survey Bull. 793, designates it as the "Aberdeen sandstone." At Castle Gate the various coal beds are designated by the letters A, B, C, etc., commencing with the lowest bed.

Jan 1, 1942

By G. R. Gardner, D. H. Davis

INCREASING realization of the importance of dust control, and the recommendations of various agencies, have led the mining industry to become actively concerned with this problem. The background and necessity for adequate dust-suppression measures have been discussed in a number of publications, including those of the U. S. Bureau of Mines, and the use of spray water to reduce dust at the face and on roadways has been recommended. The problem resolves itself into obtaining adequate dust reduction at a reasonable cost. Inasmuch as the term "adequate dust suppression" has never been clearly defined, nor have permissible limits of dustiness (in terms of dust count) been established, it is apparent that any method selected may be required to meet additional demands. Until the industry has been given some indication of permissible limits of dustiness, no permanent solution is possible. Progress will be somewhat handicapped until such information is available. In addition, dust reduction must be obtained without the addition of any excessive moisture to the coal, since consideration must often be given to: I. Quality standards, particularly reduction in heat value. 2. Handling characteristics, particularly in regard to unloading from railroad cars and bins. 3. Application of dry methods of coal cleaning. 4. Necessity for fine screening within specified limits of oversize and undersize. Little detailed information is available as to the advantages and disadvantages of the several methods of water distribution, the location and protection of sprays, operating data on pressure, quantity of water, and so forth, and results obtained. In 1940 an investigation was undertaken to determine and evaluate the principal factors involved. This paper constitutes a progress report on this work and cannot in any way be regarded as complete on any one of the several phases. CLASSIFICATION OF DUST SOURCES The various sources of underground dust may be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where the greater part of the actual fines capable of becoming air-borne dust are produced. A secondary source may be considered as one in which the greater part of the fines have been produced at some previous operation and are in such condition that they can be dispersed as air-borne dust. These conceptions appear to be of practical significance, as experience indicates that when dust is controlled at the primary sources the importance of secondary sources is minimized. For these reasons, investigations to date have been concerned principally with the primary sources of dust, and this paper is concerned particularly with one of these-namely, undercutting. In accord with the foregoing definitions, the sources to which the following opera-

Jan 1, 1942

By Walter E. Duncan

The ores treated at the concentrating plant of the Mahoning Mining Co. at Rosiclare, Ill., come largely from the blanket replacement deposits of the northeastern part of Hardin County, Illinois, and consist of complex mixtures of galena, sphalerite and fluorspar in a gangue of quartz, limestone and sandstone. The several minerals are so intimately inter-grown that they are not liberated at the sizes usually treated by gravity concentration in the usual fluorspar plant. For this reason, an all-flotation method of concentration was developed in cooperation with the station of the U. S. Bureau of Mines at Rolla, Mo.1 This flotation separation made possible the commercial production of four coyentrates: (I) lead, (2) zinc, (3) acid-grade fluorspar and (4) metallurgical-grade Auorspar.2-3 Although fluorspar had been floated in Canada in 19214 and a plant at Rosiclare had been floating fluorspar since March 1929, fluorspar flotation was given considerable impetus by the Mahoning developments, since some features of the separation were quickly adopted by other fluorspar companies. The Bureau of Alines5 reports that in the 10 years preceding 1938 only 50,552 tons of fluorspar flotation concentrates were produced in the United States. The rise from this almost nominal figure to 153,750 tons (largely acid grade) in one year (1944)6 is indicative of the activity in fluorspar flotation occasioned by the war. The industry thus proved to be in a position to expand and keep up reasonably well with the requirements imposed upon it by such developments as occurred in high octane aviation gasoline alkylation, in the use of Freon as a refrigerant and as carrier in the Aerosol "bug bomb," and in the atomic bomb project as well as in the expansion of other activities requiring hydrofluoric acid; for example, the aluminum industry. Despite the fact that the greater portion of acid-grade fluorspar produced in the last few years went directly into war uses, the future of the acid-grade field still appears bright. As a result of the activity in fluorine chemistry during the war, it seems likely that in the relatively near future almost every phase of human endeavor will find some fluorine compound involved. The other three concentrates produced deserve some attention in these introductory remarks. The lead concentrates first produced contained both zinc and fluorspar but these did not interfere with their marketing. As will be pointed out later, the quality has steadily improved until today it is a relatively high-grade product. Although some zinc smelters accept concentrates containing limited quantities of fluorspar, it is a very objectionable impurity. Since flotation methods fail in the complete removal of the fluorspar, chemical methods were developed for

Jan 1, 1948

By Walter E. Duncan

The ores treated at the concentrating plant of the Mahoning Mining Co. at Rosiclare, Ill., come largely from the blanket replacement deposits of the northeastern part of Hardin County, Illinois, and consist of complex mixtures of galena, sphalerite and fluorspar in a gangue of quartz, limestone and sandstone. The several minerals are so intimately inter-grown that they are not liberated at the sizes usually treated by gravity concentration in the usual fluorspar plant. For this reason, an all-flotation method of concentration was developed in cooperation with the station of the U. S. Bureau of Mines at Rolla, Mo.1 This flotation separation made possible the commercial production of four coyentrates: (I) lead, (2) zinc, (3) acid-grade fluorspar and (4) metallurgical-grade Auorspar.2-3 Although fluorspar had been floated in Canada in 19214 and a plant at Rosiclare had been floating fluorspar since March 1929, fluorspar flotation was given considerable impetus by the Mahoning developments, since some features of the separation were quickly adopted by other fluorspar companies. The Bureau of Alines5 reports that in the 10 years preceding 1938 only 50,552 tons of fluorspar flotation concentrates were produced in the United States. The rise from this almost nominal figure to 153,750 tons (largely acid grade) in one year (1944)6 is indicative of the activity in fluorspar flotation occasioned by the war. The industry thus proved to be in a position to expand and keep up reasonably well with the requirements imposed upon it by such developments as occurred in high octane aviation gasoline alkylation, in the use of Freon as a refrigerant and as carrier in the Aerosol "bug bomb," and in the atomic bomb project as well as in the expansion of other activities requiring hydrofluoric acid; for example, the aluminum industry. Despite the fact that the greater portion of acid-grade fluorspar produced in the last few years went directly into war uses, the future of the acid-grade field still appears bright. As a result of the activity in fluorine chemistry during the war, it seems likely that in the relatively near future almost every phase of human endeavor will find some fluorine compound involved. The other three concentrates produced deserve some attention in these introductory remarks. The lead concentrates first produced contained both zinc and fluorspar but these did not interfere with their marketing. As will be pointed out later, the quality has steadily improved until today it is a relatively high-grade product. Although some zinc smelters accept concentrates containing limited quantities of fluorspar, it is a very objectionable impurity. Since flotation methods fail in the complete removal of the fluorspar, chemical methods were developed for

Jan 1, 1948

By A. G. Roach

THIS paper deals with a plant built under joint agreement between the Canadian and United States Governments to supply the strategic mineral, corundum, at a time when African production was dwindling and war demands still increasing. The operation began in September 1944, retreating the tailings from a former mill by gravity methods, and is still in production (Sept. 1946). In 1942, when it became apparent that South African production would be insufficient to meet mounting wartime requirements of corundum, a survey was made of Canadian sources of the mineral, at the request of the Foreign Economic Administration of the U. S. Government. The investigation1 indicated that the quickest and cheapest supply would be obtained by reworking the tailings deposit at Craigmont, Ontario. Sampling of the dump by Canadian Government engineers revealed that 125,000 tons of tailings, averaging 2.96 pct corundum, was available for retreatment. Ore-dressing tests on representative samples of the deposit were conducted by the writer in the laboratories of the Industrial Minerals Section of the Department of Mines and Resources at Ottawa; and gravity concentration on tables was indicated as the most suitable method of treatment. Decision to proceed with the project was deferred until May 9, construction was begun on May 18, and tune-up operation of the plant begun on Sept. 15, 1944. CORUNDUM-ITS PROPERTIES AND USES Corundum is an oxide of aluminum having the formula A1203. Its outstanding characteristic is its great hardness; 9 in the Mohs scale. In this respect it is second only to the diamond. It usually occurs in barrel-shaped crystals in nepheline syenites and other feldspathic rocks deficient in silica. It has a specific gravity of 3.95 to 4.1 and is insoluble and infusible. In color it ranges from white, through red and green, to black. Ruby and sapphire are gem varieties of corundum. Corundum is supplied to industry as closely graded grain.2 The coarser products (10 to 24-mesh) are used largely for snagging wheels in the steel-castings industry, while the finer grades (from 70-mesh down to flours) find a wide application in the polishing of lenses and for other uses in the optical trade. All sizes of corundum grain are in close competition with synthetic abrasives such as carborundum and alundum. In some fields of application the artificial product is superior to the natural grain but not in all. The shape of the particle and its behavior under conditions of actual use determine its sphere of employment. The United States is the largest consumer of corundum, annual consumption in peacetime approaching 3000 tons; during the war this figure was roughly doubled. During the years 1902 to 1913, the bulk

Jan 1, 1946

By G. R. Gardner, D. H. Davis

Increasing realization of the importance of dust control, and the recommendations of various agencies, have led the mining industry to become actively concerned with this problem. The background and necessity for adequate dust-suppression measures have been discussed in a number of publications, including those of the U. S. Bureau of Mines, and the use of spray water to reduce dust at the face and on roadways has been recommended. The problem resolves itself into obtaining adequate dust reduction at a reasonable cost. Inasmuch as the term "adequate dust suppression" has never been clearly defined, nor have permissible limits of dustiness (in terms of dust count) been established, it is apparent that any method selected may be required to meet additional demands. Until the industry has been given some indication of permissible limits of dustiness, no permanent solution is possible. Progress will be somewhat handicapped until such information is available. In addition, dust reduction must be obtained without the addition of any excessive moisture to the coal, since consideration must often be given to: I. Quality standards, particularly reduction in heat value. 2. Handling characteristics, particularly in regard to unloading from railroad cars and bins. 3. Application of dry methods of coal cleaning. 4. Necessity for fine screening within specified limits of oversize and undersize. Little detailed information is available as to the advantages and disadvantages of the several methods of water distribution, the location and protection of sprays, operating data on pressure, quantity of water, and so forth, and results obtained. In 1940 an investigation was undertaken to determine and evaluate the principal factors involved. This paper constitutes a progress report on this work and cannot in any way be regarded as complete on any one of the several phases. Classification of Dust Sources The various sources of underground dust may be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where the greater part of the actual fines capable of becoming air-borne dust are produced. A secondary source may be considered as one in which the greater part of the fines have been produced at some previous operation and are in such condition that they can be dispersed as air-borne dust. These conceptions appear to be of practical significance, as experience indicates that when dust is controlled at the primary sources the importance of secondary sources is minimized. For these reasons, investigations to date have been concerned principally with the primary sources of dust, and this paper is concerned particularly with one of these—namely, undercutting. In accord with the foregoing definitions, the sources to which the following opera-

Jan 1, 1942

By G. R. Gardner, D. H. Davis

Increasing realization of the importance of dust control, and the recommendations of various agencies, have led the mining industry to become actively concerned with this problem. The background and necessity for adequate dust-suppression measures have been discussed in a number of publications, including those of the U. S. Bureau of Mines, and the use of spray water to reduce dust at the face and on roadways has been recommended. The problem resolves itself into obtaining adequate dust reduction at a reasonable cost. Inasmuch as the term "adequate dust suppression" has never been clearly defined, nor have permissible limits of dustiness (in terms of dust count) been established, it is apparent that any method selected may be required to meet additional demands. Until the industry has been given some indication of permissible limits of dustiness, no permanent solution is possible. Progress will be somewhat handicapped until such information is available. In addition, dust reduction must be obtained without the addition of any excessive moisture to the coal, since consideration must often be given to: I. Quality standards, particularly reduction in heat value. 2. Handling characteristics, particularly in regard to unloading from railroad cars and bins. 3. Application of dry methods of coal cleaning. 4. Necessity for fine screening within specified limits of oversize and undersize. Little detailed information is available as to the advantages and disadvantages of the several methods of water distribution, the location and protection of sprays, operating data on pressure, quantity of water, and so forth, and results obtained. In 1940 an investigation was undertaken to determine and evaluate the principal factors involved. This paper constitutes a progress report on this work and cannot in any way be regarded as complete on any one of the several phases. Classification of Dust Sources The various sources of underground dust may be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where the greater part of the actual fines capable of becoming air-borne dust are produced. A secondary source may be considered as one in which the greater part of the fines have been produced at some previous operation and are in such condition that they can be dispersed as air-borne dust. These conceptions appear to be of practical significance, as experience indicates that when dust is controlled at the primary sources the importance of secondary sources is minimized. For these reasons, investigations to date have been concerned principally with the primary sources of dust, and this paper is concerned particularly with one of these—namely, undercutting. In accord with the foregoing definitions, the sources to which the following opera-

Jan 1, 1942

By Simon D. Strauss

INTRODUCTION The changes in ownership, management, and operation of the non-fuel minerals industry since the Second World War have been dramatic. World-leading enterprises have lost their identity; host countries have taken over operations from multi-national firms; marketing practices have been drastically altered - and yet the world industry is supplying minerals on a scale far greater than had been anticipated in projections made at mid-century. The world's known mineral resources have been enormously expanded, despite the doom sayers who for decades have been predicting that depletion of non-renewable resources would impose limits to growth. PALEY REPORT One can set the stage by reviewing how the minerals outlook was regarded in a thoughtful and comprehensive analysis made in the years 1950 and 1951. During the War years, President Harry Truman of the United States had come to appreciate the decisive role played by minerals resources through his chairmanship as a U.S Senator of a committee that investigated the procurement and allocation of natural resources. In 1950, in the Cold War era that resulted in actual military conflict in Korea, he appointed a prestigious five-man commission to study the problems of Materials Policy over the following quarter century. Their findings, published in five impressive volumes in early 1952, became known as the Paley report. The text was prepared by expert scientists and economists who spent 18 months assembling statistics, making projections of future demand, and interviewing leaders in industry, academia, and government. [ ] The Commission had correctly foreseen that aluminum would replace copper as the largest volume non-ferrous metal, but it had fallen short of reality by a wide margin indeed for all three materials. Even though the Commission's expectations for growth proved to be extremely understated, it had concluded its report with grave foreboding about the effect of its estimates of demand in relation to supply, as follows: "Consumption of almost all materials is expanding at compound rates and is thus pressing harder and harder against resources which, whatever else they may be doing, are not similarly expanding. This materials problem is thus not the kind of 'shortage' problem, local and transient, which in the past has found its solution in price changes which have brought supply and demand back into balance. The terms of the materials problem we face today are larger and more pervasive." With respect to some minerals, the Paley Report expressed scepticism that, in fact, supplies would be forthcoming regardless of price. Because the Paley demand forecasts understated the actual growth in demand for virtually every mineral, one could logically have expected frequent and protracted shortages in the years since 1950.

Jan 1, 1985

By Walter E. Duncan

THE ores treated at the concentrating plant largely come from the blanket replacement deposits of the northeastern part of Hardin County, Illinois, and consist of complex mixtures of galena, sphalerite and fluorspar in a gangue of quartz, limestone and sandstone. The several minerals are so intimately intergrown that they are not liberated at the sizes usually treated by gravity concentration in the usual fluorspar plant. For this reason, an all-flotation method of concentration was developed in cooperation with the station of the U. S. Bureau of Mines at Rolla, Mo.1 This flotation separation made possible the commercial production of four concentrates: (I) lead concentrates, (2) zinc concentrates, (3) acid-grade fluorspar concentrates and (4) metallurgical-grade fluorspar concentrates.2,3 Although fluorspar had been floated in Canada in 1921 4 and a plant at Rosiclare had been floating fluorspar since March 1929, fluorspar flotation was given considerable impetus by the Mahoning developments, since some features of the separation were quickly adopted by other fluorspar companies. The Bureau of Mines5 reports that in the 10 years preceding 1938 only 50,552 tons of fluorspar flotation concentrates were produced in the United States. The rise from this almost nominal figure to 153,750 tons (largely acid grade) in one year (1944)6 is indicative of the activity in fluorspar flotation occasioned by the war. The industry thus proved to be in a position to expand and keep up reasonably well with the requirements imposed upon it by such developments as occurred in high octane aviation gasoline alkylation, in the use of Freon as a refrigerant and as carrier in the Aerosol "bug bomb," and in the atomic bomb project as well as in the expansion of other activities requiring hydrofluoric acid; such as, for example, the aluminum industry. Despite the fact that the greater portion of acid-grade fluorspar produced in the last few years went directly into war uses, the future of the acid-grade field still appears bright. As a result of the activity in fluorine chemistry during the war, it seems likely that in the relatively near future almost every phase of human endeavor will find some fluorine compound involved. The other three concentrates produced deserve some attention in these introductory remarks. The lead concentrates first produced contained both zinc and fluorspar but these did not interfere with their marketing. As will be pointed out later, the quality has steadily improved until today it is a relatively high-grade product. Although some zinc smelters accept concentrates containing limited quantities of fluorspar, it is a very objectionable impurity. Since flotation methods fail in the complete removal of the fluorspar, chemical methods were developed for

Jan 1, 1946

By H. L. James

This paper presents the results and analysis of field trials of various magnetic instruments over anomalies ranging from 20 to 5000 gammas of vertical intensity. The following instruments were used: Askania vertical magnetometer, Wolfson vertical magnetometer (model M-I), Hotchkiss Superdips (used both parallel to and normal to the magnetic meridian, with several settings of the "sigma" angle), Lake Superior dip needle, and the dipping circle for measurements of inclination. The change in inclination over the measured anomalies ranged up to 4"; this caused pronounced changes in sensitivity of the Hotchkiss Superdip oriented parallel to the magnetic meridian. The variable sensitivity not only gives apparent displacement of crests of anomalies, particularly at high sensitivities, but also makes the data difficult or impossible to use in preparation of iso-anomaly maps. This weakness in field performance of the Superdip is shown to be eliminated by orienting the instrument normal to the magnetic meridian and measuring vertical intensity only, which in the latitude of upper Michigan is equal to 97 pct of the total intensity. The dip needle is seen to be relatively ineffectual for location of anomalies of less than 400 gammas. Introduction The U.S- Geological Survey, in cooperation with the Geological Survey Division of Michigan Department of Conservation, has for the past three years been engaged in a restudy of the Iron River-Crystal Falls iron mining district of upper Michigan. The bedrock in a large part of this area is covered with glacial deposits as much as 500-ft thick, and, inasmuch as some of the rocks have moderate to high magnetic permeability, extensive magnetic mapping has been done to assist in unraveling the complicated structure of the area. Several types of instruments have been used, and the major purpose of this paper is to present comparative data on the field performances of some of these instruments so as to aid others who face similar problems elsewhere to evaluate and choose the instruments best suited for the work. The paper is directed primarily to geologists and engineers rather than to geophysicists, although some familiarity with the instruments is presumed. The geology of the area consists of a complexly folded series of weakly metamorphosed sedimentary rocks, including the iron formation, which rests on older greenstones. Although the iron formation itself is only locally magnetic, some of the beds stratigraphically above the iron formation are rather strongly so. By tracing these hanging wall magnetic anomalies valuable information is obtained from which the structure and distribution of the iron formation can be inferred. Critical anomalies range from 25 to 6000 gammas of vertical intensity. Many anomalies can be traced in part with the common dip needle, but detection of others requires more sensitive instruments.

Jan 1, 1949