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By E. F. Kern, W. W. Loo

A review of the literature on the reduction of cassiterite showed that scarcely any progressive changes were made in the methods of reducing cassiterite until within the last two decades, and that during that period many improvements in the metallurgy of tin have taken place. Since 1914 the world's consumption of tin has increased considerably, resulting in the exploitation of primary tin deposits such as the Bolivian lode, which has become an important source of tin. On account of the low tin content of Bolivian ore, and the presence of objectionable impurities of the reduced tin, the smelting of this ore and the refining of the tin has changed considerably from the methods formerly used. A comparative study of the methods of smelting cassiterite concentrates suggested that an investigation be planned so as to determine what factors effect the extraction of tin from its ores by reduction with carbon. The first part of the experimental work was the determination of whether roasted cassiterite concentrates can be reduced by carbon without the use of flux, and the reduced pellets of tin be collected into a single mass separate from the dry gangue residue. The second part of the experimental work was a comparison of the effect of variations of the different factors on the smelting of roasted cassiterite concentrates: first, the effect of varying the composition of the slag; second, the effect of varying the amount of reducing agent; third, the effect of varying the relative amount of the resulting slag; and fourth, the effect of different kinds of reducing agents. Review of Literature Experiments on the smelting of Bolivian tin concentrates were made by James P. Gill in 1920 in the metallurgical laboratory of the School of Mines, and submitted as a graduate thesis. The results of these tests are fully reported as they are preliminary to the experimental part of this paper, and also because they have not been published. The variables investigated by Mr. Gill were: (a) the effect of temperature on the rate of reduction of cassiterite concentrates; (b) the time required for

Jan 1, 1928

By M. B. Truehaft

Expectations for coal in the early to mid-1970s prompted the government and industry to pursue research and development programs to increase underground and surface mining coal Productivity and net coal recovery. Several programs concerned advanced surface mining methods for thin seam coal recovery. Three such programs, along with related areas of interest, presented in this paper are: extended depth augering for trench-strip applications; high recovery auger heads for enhanced recovery; and variable wall mining in low cover longwalls. Conceptual development is examined, prototype testing is discussed, and potential operations are considered.

Jan 1, 1985

By S. Shapiro, R. G. Ames

Background Research on the respiratory health of coal miners has focused predominately on the relationship between coal mine dust exposure and ventilatory function impairment (Lapp et al., 1972; Jacobsen, 1976), on the prevalence of coal workers' pneumoconiosis (Lainhart et al., 1969; Morgan et al., 1973), and on coal miner mortality (Ortmeyer et al., 1974; Rockette, 1977). Lesser attention has been paid to the effects of other mining exposures. For example, underground exposure to diesel exhaust emissions (Reger et al., 1980; Ames et al., 1982,1984). An omission in US coal mining research, however, has been identified by the US Office of Technology Assessment (OTA) as the failure to study the effects of inhaled polyvinyl chloride (PVC) thermal decomposition and combustion products (Seltzer, 1979). These products may be released in the mine environment by cable fires, cable explosions, smoldering cables, and conveyor belt fires. In addition to the OTA concern, recent findings of chronic respiratory conditions and other health complications resulting from exposure to PVC decomposition and combustion products in firefighters (Peters et al., 1974; NBS, 1980; NIOSH, 1982; Wallace, 1982), and in survivors of several large scale PVC-fueled fires (Dyer and Esch, 1976; Wallace, 1981, 1982), add immediacy to the concerns. PVC decomposition and combustion PVC decomposition is initiated at temperatures far below ignition (Hartstein and Forshey, 1974; Wallace, 1981). Hence, exposures to decomposition products from smoldering cables may be important health hazards in addition to cable insulation combustion products. Hydrochloric acid (HCL) appears to be the principle toxic substance from the thermal decomposition of PVC since up to 60% by weight is released as HCL (Barrow et al., 1979). HCL is released both as a gas and as an adsorbant on soot particles (Stone et al., 1973), thus allowing penetration of respiratory defenses. In addition, laboratory results indicate that phosgene (carbonyl chloride), a potentially lethal gas, may be produced in significant quantities from electrical arcing of wires covered with PVC insulation (Woolley, 1971; Brown and Birky, 1980). Health concerns related to PVC Toxic effects resulting from high level exposures to PVC pyrolysis and combustion products in animals (Cornish and Abar, 1969) and in humans (Wallace, 1981) is beyond question. Analyses have reported acute, or short-term, health effects resulting from exposure to PVC decomposition and combustion products (Peters et al., 1974; Polakoff et al., 1975). Recently, however, several studies have found that acute effects are often followed first by apparent healing, and then by delayed chronic effects. This pattern of consequential respiratory involvement among persons involved in major PVC-fueled fires has been noted in firefighters, specifically the 1975 New York Telephone Exchange fire (Dyer and Esch, 1976; Wallace, 1982), and the survivors of the 1977 Beverly Hills Supper Club fire (Wallace, 1981). An obstructive syndrome (low FVC and FEV1) was seen in 15% of workers three months following fighting a PVC-fueled fire (Colardyn et al., 1976). Long-term respiratory symptoms seen in studies of survivors of PVC-fueled fires include the bronchitis symptoms of cough and phlegm, and lung dysfunction (Wallace, 1981). Additional support for the thesis of longer-term respiratory effects resulting from PVC-fueled fires is derived from the finding that four persons who initially survived the Beverly Hills Supper Club fire died within nine months of the fire of severe respiratory impairment (Wallace, 1981).

Jan 1, 1986

By W. P. Sykes

SEVEN years ago, Dr. S. L. Hoyt1 presented a masterful discussion of the hard metal carbides and cemented tungsten carbide. His lecture summarized most of the data then available in the field; many of the details relating to the production, properties and structure of cemented tungsten carbide had never been previously published, for, in fact, this information was only then being acquired. During the intervening years, the cemented carbides have assumed a place of real importance in the commercial field, with an ever widening variety of applications due to constant improvement in the control of production technique and the unremitting search for new compositions that might better the performance of the alloys in one or another type of service. The most recent summary of production methods, properties and guides for the successful application of the cemented carbides appears in the 1936 edition of the Metals Handbook. Of necessity, much detailed information relating to structures and physical properties is not included in such a summary, and it is with such details that the present discussion is concerned.

Jan 1, 1938

By Augustus Locke

In 1900, when. the public first heard of "secondary enrichment," the Butte chalcocite seemed clearly supergene. Mining, through successive regions of leached capping, bonanza sulfide, and sulfide less rich, had paused at lean bottom levels which, though chalcocite-bearing, suggested the waning of copper. The deepest chalcocite, at 1500 ft., was yet too shallow to disturb the supergene hypothesis. But, with deeper mining, lean levels yielded to fat ones. Here and there they showed, within the same vein, an inverted distribution, chalcopyrite above and chalcocite below. To the miners' astonishment, they carried chal-cocite, unaffected by cross faults, on an independent course to the depth of 2500 ft. The pattern of ore distribution, hitherto revealed only in fragments, was now appearing in perspective, and, in the depth of the chalcocite, was beginning to make Butte differ from all districts where the chalcocite is indubitably supergene. The idea of hypogene origin at length came into favor; by 1913, when Sales' advocated this origin, the argument had become a powerful one. This argument rested on field evidence; but, already, there was beginning to emerge microscopic evidence not included in this argument. Especially pertinent was the proof that (1) the deep chalcocite lies in-mixed with bornite, often microscopic; (2) the deep chalcocite often replaces bornite; and (3) replacement of bornite by chalcocite is accomplished more easily than that of pyrite, enargite, or chalcopyrite. The microscopic evidence has been accumulating for ten years and it demands

Jan 1, 1924

NEW YORK MEETING PAGE Winchell, H. V.-Geology of Pachuca and El Oro, Mexico. Discussed by Frederick MacCoy, Robert Hawxhurst, Jr 2 WILKES-BARRE MEETING Kynor, Herbert D.-Mechanical Mining of Anthracite. Discussed by C. Evans, Jr., S. J. Jennings, W. J. Richards, Geo. S. Rice, and the author 3 Stein, C. H.-Ashley Planes for Handling Freight Traffic. Discussed by Graham Bright, Douglas Bunting, S. J. Jennings, R. V. Norris, C. H. Strange, Edwin Ludlow, W. J. Richards, and the author 3 Markle, Donald.-Anthracoal: A New Domestic and Metallurgical Fuel. Discussed by William Griffith, Edwin Ludlow, E. M. Chance, Charles Dorrance, E. W. Parker, G. H. Ashley, C. A. Burdick, Geo. S. Rice, and the author :.. 7 Griffen, John.-Slush Problem in Anthracite Preparation. Discussed by Henry Flood, Jr 11 Eavenson, H. N.-Lynch Plant of United States Coal and Coke Co. Discussed by E. V. d'Invilliers, C. Evans, Jr., Graham Bright, Geo. S. Rice, Geo. Otis Smith, A. M. Rodgers, C. T. Starr, C. A. Burdick, and the author 15 Bunting, Douglas.-Mine Fires Extinguished by Sealing. Discussed by Geo. S. Rice, J. B. Warriner, H. H. Otto, Edwin Ludlow, E. M. Chance, F. B. Nold, H. M. Chance, W. L. Jacobus, J. A. S. Ritson, R. D. Hall, Geo. S. Rice, and the author 18 Bright, Graham.-Determination of Electrical Equipment for a Mine Hoist. Discussed by F. L. Stone, Geo. S. Rice, L. F. Mitten, and the author 34

Jan 12, 1921

By A. M. Gaudin

MANY studies of comminution have been made to ascertain the size distribution of the product and to evaluate the work of comminution in the light of the size distributions of the feed and product. Up to now, these studies have been essentially statistical in character, that is, a certain lot of feed was subjected to comminution in some specified way, and the aggregate product was fractionated into sizes, thereby losing all knowledge of individual relationship of feed to product pieces. Radioactive tracers offer a means to do something in this respect which could not be done before, namely, to follow the rupturing of some particular piece in its normal environment of other pieces. That is, it permits going beyond the usual statistical limitations of size distribution studies to what may be termed a personalized or individualized study. The purpose of this paper is to present some preliminary experiments conducted with this tool.

Jan 11, 1951

By Paul E. Richardson, Edwin E. Maust

Cyclic voltammetry and surface potential (photovoltage) measurements have been carried out on galena electrodes in sodium tetraborate solutions with added HC1 and NaOH to adjust the pH over the range 2 to 13. The first technique shows that the surface species formed on moderate anodic polarization and reduced on subsequent cathodic polarization are the same over the entire pH range. At anodic potentials, a soluble metal species and excess sulfur are formed; at cathodic potentials, sulfur is reduced to a soluble species. More importantly, excess surface sulfur is formed spontaneously under zero current conditions in alkaline solutions. This has been shown to occur on both polished surfaces and on virgin surfaces produced by in situ cleavage under the electrolyte. The photovoltage gives some insight into the charge and potential distribution at the galena surface. This is found to depend on past electrochemical history and the n- or p-type semiconducting character of the electrode and is interpreted in terms of changes in the surface stoichiometry that occur during reduction or oxidation. The effect of surface stoichiometry on subsequent xanthate interactions is discussed.

Jan 1, 1976

Robert H. Richards, Boston, Mass.: Mr. Goodale calls attention to the difficulty of obtaining clean tailings from the jigs which are fed by the spigots of the hydraulic separator. This difficulty is universally encountered. The Lake Superior copper mills practically overcome it by running the beds of those jigs loose, carrying into the hutch all of the available copper and some sand. These hutches are again jigged upon threesieve Collom jigs, where the treatment is very slow and gentle; and on the successive jigs lighter and lighter bedding is used. The last sieve is run thin enough to let some sand into the hutch. With these precautions most of the free copper is extracted, as well as a fair proportion of the included copper.

Jan 1, 1897

By E. Stansfield, J. W. Sutherland

It is well known that the ash left when coal is burned is not the same either in chemical composition or in weight as the mineral matter originally present in the coal. This mineral matter has been referred to as "mineral impurity," "ash-forming constituents" and "corrected ash." The authors prefer the simple name used in the title and throughout this paper. The mineral matter in a sample of coal cannot be isolated unchanged and then weighed; but if the relation between the weight of mineral matter in the coal and the weight of ash remaining when the coal is burned can be ascertained, the weight of mineral matter in the sample can be calculated from the determined weight of ash. When the weight of mineral matter in the sample is known, the weight of pure coal can be found by subtraction. This pure coal must be the basis of accurate coal classification. W. F. Wheeler,l,3 W. Brinsmaid,2 S. W. Parr, and many subsequent workers have studied the relation between mineral matter and ash. Wheeler and Parr and others have deduced formulas for calculating this ratio, and used heavy-solution separations for checking the accuracy of their formulas. Brinsmaid hand-picked and analyzed two separate samples (and mixtures of these) and based thereon a graphical method of deducing the ratio. In the Fuel Testing Laboratories of the Scientific and Industrial Research Council of Alberta, a graphical method, based on heavy-solution fractionation of coal samples, has been used with marked success for the past 7¼ years for determining the mineral matter-ash ratio. This method resembles that employed by Brinsmaid in 1907.

Jan 1, 1930

By J. W. Pugh, Sam Leber

Single crystals of tungsten were made and deformed in tension at 3000°C. The slip traces so formed on these crystals were analysed to determine the apparent slip system. Results indicate that deformation occurs in the<III> direction on planes of maximum shear stress. This determination agrees with the early work of Taylor and Elam on other body-centered cubic crystals at lout temperatures. SLIP in face-centered cubic and hexagonal close-packed metals has consistently manifested itself in straight traces which indicate that glide takes place on planes of highest atomic density and in directions of closest packing. The slip traces observed on body-centered cubic metals are, on the other hand, frequently branched and wavy, and indicate that while glide takes place in the direction of closest packing, it does not necessarily choose the plane of highest density. The early work of Taylor and Elam1 4 indicated that glide took place in the close-packed direction on planes close to those defined by the maximum shear stress. Subsequent investigations have tried to rationalize these observations in terms of an elementary process on the close-packed planes (110). For example, Elam5 and Grenin~er&apos; have suggested alternate glide on nonparallel (110) planes with the observed result that the summation of these glides results in a trace which defines some plane other than{110). Madden and chen7 have recently reviewed the phenomenological and theoretical aspects of noncrystallographic slip. More recently Koehler&apos; has presented a model of dislocation propagation which permits another rationalization. He indicated that dislocation loops are transferred from one glide plane to another by double cross-slip of screw segments. It is reasonable to assume that, on the average, such transfers may result in a trace which approaches the plane of maximum shear stress. The work described in this paper will show that

Jan 1, 1961

By A. R. Jr. Amos

LOG washers have been used for many years in the washing of clay iron ores, phosphate rock and manganese ores, but not until the past 15 years have they been employed to any extent in the preparation of aggregate materials and fluxing stone. For a machine of such importance where tenacious clay or soft rock must be eliminated, there are few data generally available. The purpose of this paper is to set forth the results obtained from several operations, together with a few suggestions for planning a specific installation. Where the material to be washed out consists of loose surface soil, silt, or small amounts of quickly soluble clay, there is little competition with other forms of washers, because greater power and maintenance are required for the operation of log washers, but where the foreign matter is a stiff clay, such as occurs with high-calcium limestones and in marginal gravel deposits, the ability of other kinds of washers to eliminate com-pletely the hard clay balls is at least uncertain. Then the log washer comes into its own field, for with the breaking and churning action of the logs it will clean out the toughest clay. Even with material from the hydraulic dredge, if it contains tough clay, the log washer is desirable unless the gravel is subjected to a costly soaking and rehandling process. Recently there has been a considerable development in other types of machines to accomplish these results but it is not within the scope of this paper to make comparisons between competitive types, but to present the best obtainable data on log washers only. From the primitive design that gave it its name, a long log hewn from a tree, with paddles forged to shape from strap iron and attached by lag screws, the log washer has gradually been developed to the present all-steel type. As now manufactured, the log washer consists essentially of two built-up logs on which are mounted a series of paddles, carried by shafts fitted at the ends of the logs on bearings fastened outside the enclosing steel box, or trough, which is set at an angle of about 5° to 10° and into which the material is fed. Stuffing boxes at the places where the shafts pass through the box at the lower end are equipped with water-

Jan 1, 1936

The Institute is custodian of funds for support of numerous gold medals and prizes and has representatives on boards awarding still others. Details regarding the Institute Awards are given below. The Institute is represented on the boards of the John Fritz Medal, the Hoover Medal and the Washington Award, in connection with the three national societies of Civil, Mechanical and Electrical engineering; and, also, in the case of the Washington Award, with the Western Society of Engineers.

Jan 1, 1929

By Hans Lundberg

IN ORDER to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. FIG. 1.-FLOW OF CURRENT IN AND AROUND A CONDUCTING BODY. For its operation, electrical prospecting mainly depends on-the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1).

Jan 1, 1928

By E. A. Steigerwald

E. A. Steigerwald (Thompson Ramo Wooldridge, Inc.1— he authors&apos; results clearly indicate that cracking can be produced by the hydrogen pressure developed during a charging operation. This type of cracking or blistering has also been observed in polycrystalline materials24"28 when the charging conditions are sufficiently severe and is often referred to as irreversible embrittlement since it cannot be removed by a baking treatment. There are additional data, however, which must be considered before a pressure theory can be generally employed to account for all failures which occur as a result of hydrogen. In many cases, hydrogen embrittlement in a tensile test or in delayed failures under static loads is a reversible phenomena which cannot be simply explained on the basis of preexisting cracks generated by the charging operation. It is this aspect of the problem which has prompted many investigators to seek mechanisms other than hydrogen pressure to explain their results.24&apos;n728 Fig. 15 indicates an example where, under specific experimental circumstances, hydrogen embrittlement can occur at liquid nitrogen temperatures. In this case, which has been previously decribed,&apos;&apos; specimens were charged with varying quantities of hydrogen, immediately quenched, and tested in liquid nitrogen (-320°F). A companion set of identical specimens were charged, aged at 300°F to remove the hydrogen, and also tested at -320°F. When the current density was greater than lo-&apos; amp per sq in., embrittlekent occurred in both sets of specimens, indicating that cracking had occurred during charging and the embrittlement, as in the case of Fe-Si single crystals, was irreversible. At current densities between approximately 103 and lo-&apos; amp per sq in, the embrittlement was present only for those specimens which contained hydrogen during the testing sequence. The embrittlement was therefore reversible with respect to the aging and charging operations. Since extensive hydrogen movement would not be expected at -320°F, it is difficult to reconcile these data with a mechanism which requires pressure and pressure dependent growth of preexisting cracks. There are other features of hydrogen embrittlement such as the reversibility of the incubation time for delayed failure with respect to applied stressg0 and the influence of prestraining31 which are also difficult to explain using a pressure model. Any general mechanism of hydrogen embrittlement will have to consider the reversible aspects of the embrittlement data as well as the irreversible portion which has been clearly presented for the Fe-Si crystals and which is consistent with a pressure model. A. S. Tetelman and W. D. Robertson (authors&apos; reply)—he authors agree with Dr. Steigerwald that a general mechanism of hydrogen embrittlement must be applicable in all cases where embrittlement occurs. Dr. Steigerwald&apos;s experiments were performed on an iron alloy which has an extremely complex microstructure, and therefore does not lend itself to the direct and detailed observations that can be made in Fe-Si. The change in the characteristics of cracks as a consequence of annealing at 300°F is not really known in detail but it is probable that stress-relaxation (blunting) occurs, dislocations produced near the crack tips will be pinned by carbon atoms, and hydrogen will be lost to the atmosphere. Any, or all of these effects of annealing will alter the ease with which a crack subsequently propagates under applied stress. A quantitative treatment of the problem must take these effects into account. Since diffusional processes are presumably eliminated at -320°F, the general mechanism proposed by Dr. Steigerwald&apos;s colleagues cannot be operative at this temperature. A detailed discussion of the general&apos; inapplicability of this mechanism has been presented elsewhere. However, the data presented by Dr. Steigerwald in his discussion can be explained in terms of a pressure model. Crack propagation under internal pressure P and applied stress occurs when where is the total energy expended in creating new surface area and by plastic work at the crack tip. The total crack length increases with increasing current density, since we have shown that it systematically increases with hydrogen concentration and Dr. Steigerwald has shown that hydrogen concentration increases with current density. For large L (high current density) Eq. [I] can be satisfied even if P = 0 and the embrittlement process does not require the presence of hydrogen. Specimens charged at a lower current density will con-

Jan 1, 1963

By Richard A. Queeney, Lance G. Peterson

ESTIMATES of the stacking fault free energy of copper reported in the literature show an extensive divergence of results. Based on measurements of dislocation node radii, Thornton et al.7 find the lower limit of stacking fault energy to be 60 ergs per sq cm: Jossang and coworkers4 estimate the same value should be less than 40 ergs per sq cm. Assuming stacking fault free energy to be twice the coherent twin boundary free energy, Valenzuela8 reports 72 ergs per cm, while Inman and Khan2 cite a value of 24 ergs per sq cm. which can no doubt be accounted for by almost complete absence of interstitials in solution. However, the minute concentration was sufficient to permit observable recovery of dislocation damping. Assuming a dislocation density of 1010 CM -2 and an average loop length of 0.5 , a concentration of interstitials as low as 0.01 at. ppm is sufficient to reduce dislocation damping by more than a factor of ten. The concentration of interstitial solute atoms in Ferrovac E-0.15 pct Ti was thus estimated at 0.01 at. ppm < (C + N) < 2 at. ppm. The absence at elevated temperature of strengthening due to interstitials, Fig. 1, was therefore anticipated in the titanium alloy. The temperature dependence of the flow stress below 300°K was unaffected by addition of either titanium&apos; or zirconium.&apos; Observed, however, was an initial difference in the absolute value of the flow stress below 320oK, Fig. 1. Grain size may account for the difference; the grain diameter of Ferrovac E was 30 to 45 µ and that of Ferrovac E-0.15 pct Ti 65 to 90 µ. Although second phase particles in the form of titanium carbides and nitrides precipitated in the Ferrovac E-0.15 pct Ti alloy, the spacing was too large to produce any strengthening effect. The mechanical properties measured, therefore, were inherent to the bcc lattice. 1W. C. Leslie and R. J. Sober: Trans. ASm, 1967, vol. 60, pp. 99-111. 2 H. Conrad: Journal of Metals, 1964, vol. 16, pp. 582-88. 3 A. S. Keh and W. C. Leslie: Materials Science Research. H. H. Stadelmaier and W.W.Austin, eds., vol. 1.pp. 208.50, Plenum Press, New York, 1963. 4A. S. Keh, Y. Nakada, and W. C. Leslie: Dislocation Dymmics, Rosenfield, Hahn, Bement, Jr., and Jaffe, eds., pp. 381-406, McCraw-Hill Book Co., New York, 1968. &apos;W. J. Bratina, J. T. McCrath, and H. E. Rosinger: Can. Met. Quart., in press. 6 W. J. Bratina, J. T. McGrath, and D. Mills: Suppl. Trans. Japan Inst. Metals. 1968, vol. 9, pp. 436-43. &apos;H. E. Rosinger and C. B. Craig: Can. Met. Quart., In press. %. Mills. J. T. McGrath. and W. J. Bratina: ScriptaMet,, 1968, vol. 2, pp. 311-13. The purpose of this note is to present the results of a direct measurement of the stacking fault free energy in copper. The present method avoids both the question of interaction forces of nodal dislocations and the assumption that the coherent twin boundary free energy is one-half that of a stacking fault. Fig. 1 shows a transmission electron micrograph of a stacking fault intersecting a high angle grain boundary in copper: Fig. 2 is a schematic representation of the intersecting interfaces. To produce the specimen, pure copper was rolled to 0.002 in. thickness and annealed for several hours at 875°C. These foils were strained in tension to l04 µ in. per in., and rean-nealed to 8 min. Recrystallization and/or grain growth were not observed during the second anneal, indicating that intersections such as Fig. 1 are equilibrium configurations. Many such stacking faults were observed, but few were noted as intersecting grain boundaries in well-illuminated areas. The intersection of Fig. 1 was well away from the specimen edge. Since similar defects have not been observed in fully recrystal-lized and annealed copper, it is felt that this defect is due to the tensile straining. Electron transmission

Jan 1, 1970

By H. E. Nold

High-volatile coals are most desirable for kiln firing. Low-volatile and even anthracite coals can be used successfully. Most periodic kilns use coal and are hand fired. A few stoker installations have been economically successful. Continuous tunnel kilns reduce fuel consumption 40 to 55 per cent. They are rapidly replacing periodic kilns in the manufacture of the finer wares. They have found great favor in the refractory industry and are successfully used in firing almost all kinds of heavy clay products. Fuel oil has found rather wide application in the Southwest and West. Natural gas is a satisfactory fuel for kiln firing. It is the principal competitor of coal and has largely replaced it for firing the finer wares but cannot compete with it in firing heavy clay products except in regions where cheap gas is available. Figures are given showing the relative thermal efficiency of coal and natural gas as used for firing ceramic ware. The ceramic industry uses from 12,000,000 to 12,500,-000 tons of coal per normal year. The principal use of coal is in firing the heavy clay products. This potential market amounts to about 9,250,000 tons per year. Coal producers could increase sales by furnishing expert firing instruction.

Jan 1, 1934

By A. B. Cummins

THE past year has been of unusual interest for industrial minerals. It is increasingly evident that requirements for these raw materials move with general economic trends. Thus, with a peak year in the construction, chemical and petroleum industries, the nonmetallic mineral industries have been brought into the complex maze of an economy in which military spending is in the billions and in which the national income and wholesale commodity prices reached new levels. Many industrial minerals are of first rank essentiality in the defense effort and its supporting industries, and since some of these are of limited supply and others dependent on imports, the problems of procurement, distribution and conservation of available supplies make a complicated pattern. Despite some drawbacks and weak spots, the industrial mineral industries have, in general, met the national situation with great credit and many new production records have been set. The general accomplishment in 1951 should be one of satisfaction with confidence for the future. Difficulties, unsolved problems and uncertainties should not obscure the general trend which many consider optimistic. Prices in the main have been upward, in line with the inflation spiral, but nonmetallics appear with some exceptions to be behind the general increases. Labor difficulties have not been serious throughout the year. Retarding influences in expansions and planning have been the uncertainty of the Korean and international situations and a lack of confidence by many in the government economic program and its ultimate impact on the economic structure. It must also be kept in mind that stockpiling, unless all-out war develops, reaches a level and then ceases to be a major sustaining factor in the mineral markets. In accordance with the Defense Production Act of 1950 various control agencies have been set up to establish the desired rate of stockpile acquisitions. The objectives are subject to change depending on availabilities and needs-military, industrial, and civilian. In some minerals there has been disagreement on actual stockpile requirements, and there is some feeling that the needs of defense might be better met if more funds went into the development of new sources of supply of scarce raw materials and more materials were released to industry at this time. Nonmetallic minerals on the strategic and critical list of the Munitions Board as of July 1951 were: Group I; asbestos, some types; bauxite, refractory grade; beryl; celestite; chromite, chemical and refractory grades; columbite; corundum; diamonds, industrial; fluorspar, acid grade; graphite, some types; kyanite; manganese ore, battery and chemical grades; mica, some types; quartz crystals; rare earths; sapphire and ruby; talc, steatite, block; and Group II; bauxite, abrasive; cryolite, natural; diamond dies; graphite, crystalline fines; iodine; mica, muscovite block, stained and lower; rutile; selenium; talc, steatite, ground; zirconium ore, zircon. Details on the current status of stockpiling inventories are not available. The Defense Minerals Exploration Administration has, since April, executed 39 contracts for the exploration of nonmetallic minerals, including twenty for mica, seven for beryl-mica, six for asbestos, three for sulphur and one each for monazite, steatite talc and fluorspar. Total value of these contracts came to $892,059, of which the Government&apos;s participation amounts to $689,247. There were on hand at year&apos;s end another 97 applications for exploration aid on nonmetallic minerals in twenty different

Jan 1, 1952

By S. P. Barber, G. W. Cutting, V. Alesse, M. Ciriachi

Just what is happening in the preparation and mineral separation stages are questions frequently asked about most processing plants. It is unusual to find the answers readily available in the operating metallurgical data. Knowledge is nominally available from metallurgical balances about the head ore grade, grade and recovery of the concentrates, and the plant tailings. However, the mechanisms which control grade recovery and losses are seldom monitored in such a way as to permit specific analysis: Thus, when questions about the effectiveness of the process are asked, the answers are based frequently upon intuitive professional judgments and local expertise. Detailed investigations of process functions are extensive in terms of manpower, time, and interference with production. An investigation method in which process operating conditions could be provided in a cost effective manner would assist in local process assessment and control. Such a collection of process operating data is defined as a process audit and the development of the necessary techniques forms the subject of this paper. A typical application to a lead-zinc concentrator highlights both the manner of implementing a process and the plant data made available for local use.

Jan 1, 1980

By H. C. George

CAREFUL- sampling and good judgment as to probable recoveries are important factors in estimates of ore reserves, based on prospecting drilling results, but other factors are equally as important and may be more misleading and perhaps disastrous if not properly interpreted. Some of these are: 1. The case where no, ore is shown in the "sludgings," when, as a matter of fact, the drill has passed through a thick sheet of ore which has been broken up and washed away into open crevices. In numerous cases, later mining operations have shown that this has happened. This condition may be discovered by shooting the drill .hole at the point where the open crevices occur, but shooting should not be done until after the drill hole is completed, because the resulting shattered formation may salt the drill hole at lower levels. 2. The case where rich cuttings are shown for a thickness of 20 or 30 ft., when ore was encountered in only the first sludging. Owing to soft or loose formation, the ore from the first sludging has salted the lower sludgings. The presence of large pieces of ore and a similar ratio between zinc and iron assays in the lower sludgings frequently indicate this condition. In the lower sludgings, the presence of oxidized ore in unaltered limestone sometimes shows this condition. 3. The case where the drill hole shows a considerable thickness of ore; but owing to the presence of a vertical sheet of ore, perhaps not more than 1 in. thick, at the place where the drill hole is located, the good assays resulting might be misleading. If this condition is suspected, the drilling of several more holes within a distance of 10 or 15, ft. will usually show it.

Jan 1, 1921