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By G. P. Conard, R. C. Hall, J. F. Libsch

The 50 pct Fe-50 pct Co alloy undergoes a transformation from disorder to an ordered structure of the CsCl type reportedly in the vicinity of 732OC. During this process, the coercive force goes through a maximum, apparently as a result of strains associated with the coherent nucleation and growth reaction. This magnetic alloy also shows a marked increase in the ratio of residual to saturation induction, which is associated with annealing to a high degree of order with the continuous application of a magnetic field. The increase in ratio can be explained on the basis of a decrease in 90' domain boundaries and, perhaps, by an increase in anisotropy resulting from lattice distortion. THE 50 pct Fe-50 pct Co alloy undergoes a disorder-order transformation which has been reported to occur in the vicinity of 732°C1,2 The ordered structure is the CsCl type.' This magnetic alloy also shows a marked increase in the ratio of residual to saturation induction as a result of heat treatment in a magnetic field, sometimes called a response to magnetic anneal.'-' The purpose of this investigation was to study the course of the ordering reaction, the nature of the response to .heat treatment in a magnetic field, and the relation, if any, between ordering and the response. Procedure The method of approach in this investigation was to produce an initial structure as completely disordered as possible and then gradually to order the alloy by isothermal anneals at various temperatures under different conditions of the applied magnetic field. Magnetic, magnetostriction, and X-ray analyses were of primary importance in determining the property and structural changes resulting from the isothermal anneals. Rings of the 50 pct Fe-50 pct Co alloy were prepared from the elemental powders by a powder metallurgy technique, further details of which may be found in ref. 7. The initial structure was produced by annealing the specimens for ½ hr at 1000°C, cooling to and holding for ½ hr at 900°C (in the a range above the ordering temperature), and water quenching. Isothermal anneals were performed at 600°, 675°, 720°, and 740°C. For example, rings were heated to 600°C, held for a predetermined period of time, and cooled by natural cooling at a rate slightly slower than an air cool (average of 20" to 25°C per min). The tests (magnetic, etc.) were made after each heat treatment. All high temperature treatments were performed in a purified hydrogen atmosphere. The treatments at the various temperatures were carried out under one or more conditions of an applied field including 1—no field, 2—field of 20 oersteds applied on cooling only, and 3—field of 20 oersteds applied continuously during heating, holding, and cooling. Magnetic measurements were made using the standard Rowland ring technique8 with a maximum field strength of 100 oersteds. The magnetization curve, induction at 100 oersteds (B.), residual induction (Bt), and coercive force (Hc) were determined. All magnetic analysis data were based on an average of the results from three rings. A strain gage technique9 as used for the measurement of magnetostriction. The X-ray determination of the relative amount of ordered phase present was made on the ring specimen used for magnetic measurement. This was done by the back-reflection method using a rotating specimen (because of the large grain size) with unfiltered CoKa radiation and a 7 hr exposure time. Intensity measurements of the ordered line (300) were made by comparing visually the films so obtained with standard films prepared by exposing for different lengths of time a specimen given a long time anneal (high degree of order). Results In all instances the saturation induction (induction at 100 oersteds) was found to increase slightly with annealing time. This effect was small and appears to be the increase in saturation induction to be expected on ordering.10-13 The residual induction behavior was markedly influenced by the field condition during annealing, Figs. 1, 2. For the condition of no applied field, the ratio of residual to saturation induction remained essentially constant for short annealing times but showed a significant increase at longer times. With increasing annealing temperature, less time was required to produce this increase in the ratio. In the case of the 600°C anneals, the increase did not occur until approximately 20 hr, Fig. I, while on annealing at 740°C the increase was immediate, Fig. 2. Slight decreases in the ratio may be observed at 100 hr for specimens treated at 720°C and at 1 hr for those treated at 740°C. Specimens annealed in a field of 20 oersteds showed a residual to saturation induction ratio consistently higher than that for the specimens annealed without the field. The first anneal with the field (¼ hr) caused an abrupt increase in the ratio at all temperatures; thereafter, the increase in the ratio was generally similar for specimens annealed

Jan 1, 1956

By Kenyon E. Richard, James H. Courtright

Thomas W. Mitcham (Strategic Minerals, Inc., Grand Junction, Colo.)—The authors have presented a significant contribution to the field of mining geology. The article is graphic, remarkably concise, and crisply original. The presentation is made on only three pages with two maps, but their Silver Bell story is entirely adequate in background, development, and conclusion. Most of their colleagues would agree that this paper reflects the high quality of the work which these unusually capable men have done in the Silver Bell area over the past few years. The Silver Bell area is one of complex tectonic structure, and time and spatial relationships are by no means apparent. Actually, most of the observations and interpretations in this paper are new to published geologic literature on the Silver Bell area. I am in agreement with these interpretations with two possible exceptions, which are discussed below. One might well define the three roughly parallel west-northwest faults, shown on the insert of Fig. 2, as the major structural elements of the area. North to south, I propose that these be named the Ragged Mountain fault, the Silver Bell fault zone, and the Waterman thrust, after the mountain ranges which are the results of these major structures. While I would agree with the authors that the northern two of these major structures are high-angle faults of the Laramide revolution, my impression is that the southern structure is a low-angle thrust of approximately Miocene age. In support of this opinion, I submit the following observations: 1) irregularity of the fault in strike; 2) scarcity of Laramide intrusives and alteration of sediments along the fault; 3) present high re- lief of the Waterman Range which indicates youth or certainly rejuvenation; and 4) existence of a series of parallel structures farther to the south which results in an outcrop pattern suggesting imbricate thrusting. The authors have stated that Laramide igneous activity began with the intrusion of alaskite. Some dacite flows appear to be conformable with Cretaceous beds, and thus my impression was that alaskite followed the intrusion and extrusion of dacite. I would be interested to learn of evidence in support of the reverse relationship suggested by the authors. Kenyon Richard and J. H. Courtright (authors' reply)—The authors appreciate Mr. Mitcham's attention to this paper. The names he proposed for the major faults seem appropriate. His suggestion that the Waterman fault is a thrust may be correct because he did more work in that particular area than the authors. However, it is believed that no direct evidence of a low-angle thrust relationship has been recognized, and the authors consider that indirect evidence favors a high-angle fault interpretation. The pre-dacite flow age of the alaskite is definitely established, the authors believe, by the fact that the flows rest on an erosion surface which was carved in the dacite porphyry, an intrusive clearly younger than the alaskite, as evidenced by inclusions of alaskite occurring in dacite porphyry. No direct evidence of Cretaceous sediment-flow rock relationships was found at Silver Bell, but in the nearby Tucson mountains dacite agglomerates, megascopically similar to those at Silver Bell, overlie a basal conglomerate which in turn rests on the truncated edges of steep-dipping Cretaceous arkosic beds.

Jan 1, 1956

By James A. Barr

Prospecting methods used in Tennessee have gradually improved with the years, as required by depletion of the easily accessible and shallow deposits and the universal trend toward mechanization, and as necessitated by exploring deeper beds, often occurring under limestone and flinty overburden. In the early days it was a very simple matter to dig pits by hand, using a plentiful supply of local farm labor to expose relatively shallow deposits of "brown rock" under shallow clayey overburden that would stand up without timbering. Visual inspection of the exposed phosphate and expert judgment of the "grade" analysis, aided by a "biting" test to reveal presence of unwanted silica, furnished most of the information required. All this might be helped by a few samples sent to the local chemist† who supplemented his income by judicious trading or tanning a few bear skins. The extra curricula activities did not affect the accuracy of the analysis which hold up even under present day standards. Some shot and core drilling was done in Hickman County, mostly for the limestone-like blue Phosphate deposits. The next step was the use of a 4-in. posthole auger, hand operated as described by Guenther, followed by a completely mechanized rig, as described by Pickard. Both these methods are practically adapted to the prospecting of the relatively soft brown rock deposits at moderate depths of clay overburden. For prospecting in areas of deeper overburden, such as are often found in Hickman County, up to 150 or even 200-ft depths, a modified core-drilling method is described by Guenther. Johnston describes a special diamond-drilling technique, developed by TVA, to penetrate flint horizons, which was adopted by the International Minerals in chemical corporation to prospect in Hickman County where deposits had previously been prospected at considerable expense and with difficulty, by small, temporary, hand-dug shafts.

Jan 1, 1948

By James A. Barr

Prospecting methods used in Tennessee have gradually improved with the years, as required by depletion of the easily accessible and shallow deposits and the universal trend toward mechanization, and as necessitated by exploring deeper beds, often occurring under limestone and flinty overburden. In the early days it was a very simple matter to dig pits by hand, using a plentiful supply of local farm labor to expose relatively shallow deposits of "brown rock" under shallow clayey overburden that would stand up without timbering. Visual inspection of the exposed phosphate and expert judgment of the "grade" analysis, aided by a "biting" test to reveal presence of unwanted silica, furnished most of the information required. All this might be helped by a few samples sent to the local chemist† who supplemented his income by judicious trading or tanning a few bear skins. The extra curricula activities did not affect the accuracy of the analysis which hold up even under present day standards. Some shot and core drilling was done in Hickman County, mostly for the limestone-like blue Phosphate deposits. The next step was the use of a 4-in. posthole auger, hand operated as described by Guenther, followed by a completely mechanized rig, as described by Pickard. Both these methods are practically adapted to the prospecting of the relatively soft brown rock deposits at moderate depths of clay overburden. For prospecting in areas of deeper overburden, such as are often found in Hickman County, up to 150 or even 200-ft depths, a modified core-drilling method is described by Guenther. Johnston describes a special diamond-drilling technique, developed by TVA, to penetrate flint horizons, which was adopted by the International Minerals in chemical corporation to prospect in Hickman County where deposits had previously been prospected at considerable expense and with difficulty, by small, temporary, hand-dug shafts.

Jan 1, 1948

Reports on process control computer projects at the Kamioka Plant are summarized from the Japanese technical literature (see references). Fluidized Bed Roaster and Sulfuric Acid plant1 A small process control computer (Yokogawa CCS-200 with an OKITAC 5090P 8K central processor) was installed in the Kamioka smelter in the summer of 1964. A year-and-one-half installation project followed, which successfully brought the roaster and acid converters under computer control. The process plant consisted of two 130 RPD fluosolids roasters and two Monsan to acid units. The roasters are charged with lead-zinc concentrates with SO2 from the roaster processed to sulfuric acid. The computer system provides the following functions: 1) log data from the plant--the input is taken from 50 analog signals, 130 high-low digital alarm points, and 50 analog high- low alarm points; 2) set-point control on 18 control loops; 3) direct digital control (DDC) on eight control loops for which conventional controllers were difficult to adapt due to abnormal loop characteristics or delay times; 4) execution of a safe shut-down procedure

Jan 1, 1969

By S. W. Parr

The extent to which geological carbonization has taken place in the process of coal formation is a fundamental factor in all considerations relating to classification, oxidation, deterioration, spontaneous combus tion, and especially in all considerations relating to destructive distillation having as an objective the production of marketable coke and by-products. Moreovcr, it may be readily shown that a striking relationship exists between the geological decomposition or geological carbonization processes and those artificially produced by heat. This may be well illustrated by bringing again to view some of the charts more commonly mct with 25 years ago, as in Fig. 1.' In this figurc the line of geological decomposition by decay, pressure, etc., because of its relation to the line of carbonization by destructive distillation, becomes of special significance when we attempt to formulate any system of classification which shall be reasonably scientific and at

Jan 1, 1927

By J. C. Uy, A. A. Burr

A quantitative relationship between the allotropic phase boundaries of zirconium-base binary systenzs and the solute metallic valence is shown through an intermediate thermodynamic parameter. A simplified equation relating this parameter to the phase boundaries is briefly reviewed, and data from the literature are used to show the relationship of this parameter to the solute metallic valence. It has been reported that the solute metallic valence can be used as an index of phase stabilization in zirconium-base binary alloys.' It was shown that the algebraic sign of the slopes of the hcp/bcc phase boundaries of zirconium alloys correspond to the algebraic sign of the metallic valence of zirconium minus the metallic valence of the solute, or, in other words, a solute whose metallic valence is higher than that of the solvent tends to stabilize the high-temperature phase while one whose metallic valence is lower than that of the solvent tends to stabilize the low-temperature phase. Further analysis of the zirconium binary systems has revealed a quantitative relationship between the solute metallic valence and the relative slopes of the two-phase allotropic boundaries. This relationship involves a thermodynamic quantity whose significance can be seen in the following section. PHASE-STABILIZATION PARAMETER Let Qb be the difference between the partial molar heats of mixing of a given solute in the two allotropic phases of the solvent which are in equilibrium with each other at a given temperature, thus A relationship between this term Qb and allotropic phase boundaries has been employed by several au-thors'-= in the evaluation of phase diagrams, and can be briefly derived as follows. Referring to Fig. 1, consider the general case of two allotropic phases, each having a small mole fraction (Xa,Xb) of the solute, in equilibrium at temperature T and atmospheric pressure as represented by the reaction. solute in ß phase =solute in a phase If now a reaction occurs such that an infinitesimal amount of the solute is removed from the ß phase and added to the a phase, there would be a partial molar

Jan 1, 1967

By James Marsh

INTRODUCTION Economists have long expressed suspicion of the economic theory of natural resource exhaustion, even in writing articles which have contributed to it (1). Indeed, the gap which separates the pure theory from practical management seems unusually wide. It is doubtful whether a mine manager could possibly know enough about the relevant parameters of his mine to steer it along the optimal paths described by the theorists (2). Nevertheless, enough faith in the theory remains that mine managers are suspected of being a separate breed whose behavior must be studied in special courses using specialized text-books, collections of readings, and journals (3). The implied hypothesis, that mines and natural resource firms are managed differently than other firms, is the subject of this paper. In the next section the theory is developed and analyzed. In section III, I discuss the implications of the statistical results that have been obtained. Finally, conclusions are reserved for section IV. THE MODEL A key difference between the traditional theory of natural resource production and that of other forms lies in the set of variables which ire assumed to jointly determine the quantity of output the firm will produce. Output, in the non-resource case, is assumed to be a function of k clearly definable and distinguishable inputs or factors of production, viz., y = f(xl, x2, ..., xk), (1) here

Jan 1, 1977

By Minoru Sasabe, Mayurni Sorneno, Kazuhiro Goto

I) The Object of the Present Experiment. When the oxygen chemical potential in the gas phase is changed, the oxygen chemical potential in the liquid metal or in the liquid oxide phase will be subsequently changed. The object of the present experiment is to develop a method of measuring the change in the chemical potential of oxygen in liquid metals and in liquid oxides with respect to time, when the oxygen potential in the gas phase changes. II) The Experimental Method. The following types of the oxygen concentration cells with the solid electrolyte of Zr0z-CaO are used: KAZUHIRO GOTO, MemberAIME.MINORU SASABE,and MAYUMl SOMENO are Associate Professor, Research Associate, and Professor, respectively, Department of Metallurgical Engineering, Tokyo Institute of Technology, Meguro-ku, Tokyo, Japan. Manuscript submitted March 12, 1968, EMD. Igas phase liquid Ag or Pb ZrO2-CaO electrolyte!, The measured reversible electromotive force can be expressed by the next equation, provided that the transference number of the oxygen anion in the electrolyte is unity: E = RT/nF log (at electrode I)/P~ (at electrode 11) where is the electromotive force, R is the gas constant, T is absolute temperature, n is valence of oxygen anion, and Pq is the oxygen pressure at the electrodes. As shown in the previous work1 of the authors, the electromotive force is determined by the difference in the chemical potential of oxygen at the vicinity of the interfaces between the solid electrolyte and the electronic conductors used for the two electrodes. Fig. 1 shows the two kinds of the cell assembly used to measure the change of the chemical potential of oxygen in liquid metals and liquid oxides with respect to time. In both cases, the change of the oxygen pressure in the gas phase is measured by the independent oxygen concentration cell located above the

Jan 1, 1969

By C. Norman Bowers, Blaine B. Wescott

MARKED improvement in the serviceability of sucker rods has been effected in the last two years, partly because of the insistent necessity for greater economy in the operating costs of crude oil production growing out of the general industrial depression and partly because many of the recently developed fields have imposed more severe operating conditions upon both surface and underground equipment. The latter is particularly true of Kansas, where practically all of the oil produced. is associated with damaging amounts of hydrogen sulfide brine and where the method of establishing potential production demands equipment capable of being operated at maximum capacity without interruptions. The decline of flush production in the Oklahoma City field created new problems in deep-well pumping on a scale heretofore unequaled and the increased proportion of water it has been necessary to produce in the fields of the Greater Seminole area presented conditions that were acutely in need of betterment. The problem in the latter fields was complicated by the shift towards sulfide characteristics, which accompanied water encroachment, and it is probably true that nowhere, at the present time, are pump¬ing conditions generally as severe as in this territory. The Mid-Continent district, therefore, has become the proving ground for the numerous materials that have been proposed for sucker-rod fabrication. The information that ultimately will be obtained from an unprecedented amount of field experimentation will pay ample dividends when the decline of East Texas increases the demand for the vast reserves of sour crude in West Texas. It is a rare occurrence in industry that the use of such a simple piece of equipment as a sucker rod presents so complicated a problem for solution. As proof of this, it is only necessary to consider the numerous types of sucker rods on .the market at the present time and contrast this condition with that of less than four years ago, when it was the common aim of manufacturers to develop a single sucker rod for all conditions of

Jan 1, 1935

By Nicholas J. Grant, Olaf Troili, John Chipman

D. C. Hilty (Union Carbide & Carbon Research Laboratories, Niagara Falls, N. Y.)—How does this effect of silica compare with the effect of silica in combining with the lime in the slag to reduce the activity of CaO, thereby affecting the first equation? John Chipman(authors' reply)-—That is the object of showing this effect for slags of two different basicities. In the more basic, the silica is more firmly tied up in the slag and is less easily reduced. It is therefore less able to interfere with desulphurization. The important point is that silica is acting in two ways. Of course it is an acid and as an acid it ties up lime and in tying

Jan 1, 1952

By Richard Maclin Stewart

A priest at Shenandoah, Pa., one day persuaded the president of the Philadelphia & Reading Coal & Iron Co. to slush breaker waste and culm into old mine workings in order to save his church from being destroyed by surface subsidence. The year was 1864, the project was successful, and history recorded the first use of hydraulic backfilling. Shortly afterward, the method was applied to several eastern coal mines for area fill to control subsidence. In 1884, hydraulic backfilling was used to control a mine fire in the Schuylkill region of Pennsylvania. The idea was taken to Europe by German engineers and developed successfully at the Myslovitz colliery in Upper Silesia in 1901. From there it was applied to several mines throughout Europe.

Jan 4, 1958

By Alfred L. Beebe

to. A strip of thin platinum foil, about one inch square, is perforated with pin-holes over its entire surface. It is then bent into the shape of a letter U, and its opposite corners are connected by short pieces of platinum wire, so as to form a sort of basket. In this is placed a piece of amalgamated zinc of convenient size, and the whole is suspended by a stout platinum or silver wire in the bottle containing the solution to be reduced. Another strip of platinum foil,

Jan 1, 1886

By Robert B. Smith

The South Texas Mineral Trend is now estimated to contain uranium reserves of 150 million pounds U308 . Within the past year, an estimated 10 million pounds U308 have been added to this gross reserve. It is probable that a similar amount has been identified in previously unknown orebodies that, as yet, have not been delimited or announced. Exploration that was limited in the past to a narrow band containing only the known trend has now expanded into older sediments updip and into younger units towards the coast. Uranium host formations are also now being explored at a considerable depth and distance eastward from known deposits. Only about 30 percent of the potential uranium host rocks in South Texas have been adequately explored. Geology The South Texas uranium deposits are confined mainly to sediments of the Tertiary system. Reserves are divided almost equally between the Whitsett Formation of the Jackson Group, the Catahoula Formation, and the Oakville Formation. A minor amount of the reserves occurs in sands of the Goliad Formation which may be either in the Tertiary or Quaternary Epoch. Figure 1 is a geologic column of the South Texas uranium host formations. These producing formations are marked with a mine symbol but there are also several prospect symbols that denote potentially favorable uranium host formations both younger and older from the producing formations. It is generally accepted by most workers in South Texas that the source for the uranium is the volcanic ash that is abundant within several of the formations. Likewise, the required reductant is considered to be hydrogen sulfide gas, derived from deeper seated hydrocarbon accumulations, that emanate upward along fault zones into favorable host-rock sand units. Within this basic framework of source, host, structure and hydrocarbons is where most of the reserves have been discovered and where most of the current exploration is either concentrating or expanding. Structure in South Texas is predominantly faults. Swarms of faults exist in zones paralleling the coast and running from the Rio Grande to the Sabine River. These faults are usually growth faults with the down-dropped block on the coastward side. Displacement may range from a few feet to a few hundred feet. Dips are near vertical in the younger rocks at the surface but become flatter as the fault cuts older beds in the subsurface. A map of the oil and gas fields in South Texas indicates a correlation between these fault swarms and accumulations of hydrocarbons. It is not coincidental that the known uranium trends closely follow the hydrocarbon accumulations and the faults swarms, all of which supports the theory of uranium concentration by groundwater movement through volcanic ash-rich beds into favorable host rocks impregnated with reducing hydrogen sulfide gases that migrate upward along fault planes from hydrocarbon accumulations. History Newcomers to South Texas are often amazed that active entry is possible in a district that has produced uranium for over 20 years. Understanding the conditions and occurrences of the past would explain why the opportunity still exists for companies not now active in South Texas to become active. Uranium was discovered in the middle 1950's in sandstone units of the Jackson Group at Tordillo Hill in Karnes County. This discovery was followed by a rush involving most of the major uranium exploration companies as well as several of the not-so-major. Those western prospectors who were used to numerous outcrops and neat land subdivisions were further discouraged by the small size and low grade of the deposits. Then after a brief blast, they left South Texas as they found it and returned to the richer diggings of New Mexico and Wyoming. Susquehanna Western was the only one to stay and develop mines in the area. Eventually they discovered enough ore along the Jackson outcrop to warrant constructing a small mill. They managed, with limited budget and diligent effort, to find enough ore to keep the mill going and eventually expanded into exploration in other formations. By the late 1960's, Susquehanna was mining from both the Jackson and Oakville deposits. About this time, the oil companies began to enter the uranium industry and found, that because of sound forward planning, they controlled the uranium on vast tracts of acreage. At this time, which was more than ten years after discovery, there was so little literature on South Texas uranium deposits that the oil companies began following the known trends and off-setting known orebodies. This, and a few kicks on some well gammaray logs, lead to the discovery of new areas in formations that previously had n o uranium discoveries. Still, the following of the trend as it crossed from one formation to another was the main geologic guide. Nowadays, we in South Texas feel that science has entered into the quest to discover new orebodies. The work of Galloway has indicated new pathways to explore. The understanding of multiple stages of oxidation and reduction has created some doubt about areas drilled in the past and abandoned. The expanded use of oil well logs and geochemical prospecting has lured the more progressive exploration companies off the mineral trend and into unexplored areas. Prognostication The fact that uranium exploration in South Texas has been active for only the past ten years is not an indication that South Texas is not a major uranium district. The geology of the South Texas uranium deposits as described here serves only to indicate that similar geology extends in all directions from the known mineral trend as can be seen on Figure 2.

Jan 1, 1979

Jan 1, 1884

By Alfonso W. Ovalle, Héctor R. Albornoz

INTRODUCTION The El Teniente Mine of Codelco-Chi le has extracted 588 mil lion tons of ore in its 77 year history for a total copper output of 8.800.000 tons. The mine production has been obtained mainly by traditional block-caving where grizzlemen using a hand held lever send ore through long-raises to load trains. At present the mine is about to introduce mechanized block-caving using LHD equipment to extract the primary rock. This paper describes this method which will be tested starting next month by caving an 11.000 square meter block. THE PRIMARY ROCK PROBLEM The secondary enrichment sulfides of the El Teniente ore body have characteristics which makes a standard unmechanized block-caving practice very successful. In the 60's parts of blocks encountered primary ow in the Teniente 1 and Sub-13 levels which proved to be extremely hard to extract. These foretold the obstacles that arised in the central part of the Teniente 4 level. Preparation of a completely primary 8.100 square meter block started in 1970. Its undercutting was completed by the end of 1972 and by 1973 the problem of mining the primary rock was clearly visualized. The numbers below describe the difficulties in mining this block: -Long-hole drilling rate is 90 m (270 ft) per shift in secondary rock and 37 m (110 ft) in primary. - Undercutting which is completed in 9 shifts in secondary took 180 shifts in the primary block. - Average grizzlymen productivity in secondary is 250 tons per shift while in primary it is only 25-30 tons, both at 343 mm (13 1/2 in. ) grizzly opening. - Powder consumption for secondary blasting increased from 8 grams per ton in secondary to 84 in primary. - The protection pillar between the under- cutting and the production levels was 60% broken in primary while 20% is usual for secondary. - Extraction advanced 5 cm per day in primary while a 50 cm per day rate is the aver- age in secondary. This is the main reason that after 8 years this primary block has a 20% extraction. Secondary blocks take 1.5 to 3 years to complete their extraction. - 80% of the boulders in primary rock are larger than 343 m (13 1/2 in.) with 10-20 % of them larger than 3 meters. -Direct cost of production (preparation, undercutting, extraction and haulage), using the traditional block-caving design for secondary rock, increased 3.5 to 4 times when used in primary rock. The following indicators of Table 1 show the rock characteristics differences.

Jan 1, 1981

By E. R. Buchanan, R. E. Reed-Hill

A transmission electron microscope study was made of magnesium single crystals deformed in torsion using the basal pole as the forsional axis. While this type of deformation is predicted to result in the formation of hexagonal networks of screw dislocations, these networks were not observed. The basic dislocation arrangement consisted of arrays of nearly parallel and approximately equally spaced dislocations. The average dislocation density was over an order of magnitude higher than that required to account for the torsional deformation. The observed high rate of work hardening in these crystals is consistent with both their high dislocation densities and the arrangement of dislocations in pile-ups. The experimental observations are also in agreement with the assumption that dislocation sources are activated not only at the surface but at interior locations as well. In considering torsional deformation, Amelinckx and Dekeyser1 postulated that when a torque is applied to a crystal oriented with a glide plane normal to the specimen axis, deformation occurs by the following steps: 1) Nucleation of dislocation sources at or near the specimen surface in areas where the shear stress, resolved along a slip Burgers vector, is a maximum; 2) the screw orientations of the dislocations accommodating the twist move inwards towards the specimen center. If two glide directions lie on the glide plane, the geometry shown in Fig. 1 should result; 3) the screw dislocations that pile up in the central part of the specimen cross-slip to form a grid. At the same time, screws of opposite sign and most edges leave the specimen. Tinder,2 using zinc crystals twisted about the basal pole, independently reached essentially the same conclusions. He suggested a mechanism involving nucleation of ?(1120) screw dislocations at the six points of highest resolved shear stress that lie on the cross-section near the surface. Under the applied shear stress these dislocations were assumed to move inward and interact so as to form a hexagonal network of screw dislocations. Today it is often accepted that rotational slip occurs by a mechanism of the above type, but to our understanding this has never been experimentally proved. This paper reports an experimental study of rotational slip, using magnesium single crystals, that indicates that in this metal rotational slip does not conform well to this mechanism. EXPERIMENTAL PROCEDURES Mechanical Testing. Specimens with a (0002) axis were prepared from magnesium crystals of 99.95 pct purity grown by Jillson's3 modified Bridgman technique. The crystals were acid machined into cylindri-

Jan 1, 1970

H. RIES, Ithaca, N. Y.-The part of Mr. Fiske's paper that interests me especially is that portion dealing with the raw materials, and the tests that were applied to the raw materials in order to determine their value in advance, if possible, because that, I believe, is a step in the right direction. For a number of years I have done my best to persuade different consumers of clay to develop standard methods for testing raw materials. We have in this country a large variety of clays which can be used for a great many different purposes, but in many cases the consumers either have no standard methods for determining the value of those clays in. advance, or if they have they do not publish them; consequently it often puts the clay miner at a disadvantage. If, for example, manufacturers of different types of refractory materials would state publicly just what physical tests their raw materials have to meet, it would, I believe, help them to find more easily the materials that they are looking for, and the clay producer would also be benefited. It would also encourage him to have his clays tested in advance, so that samples could be accompanied by certificates of physical tests that would be of convenience to the manufacturer. At the present time, in this country there are certain types of clay which seem to be rather scarce. There apparently are not many deposits of clay that are exactly suited for the manufacture of zinc refractories. So, too, there are not many deposits of clay that are suited for the manufacture of glass-pots, or the blocks for glass tank furnaces, or clays that can be used for graphite crucibles. Now, in many cases, no standard series of tests has been developed. I am also gratified to see that Mr. Fiske considers the tensile strength. tests of value. Some years ago the American Ceramic Society appointed a committee to draw up a series of recommendations covering standard tests. These recommendations were especially for the use of State geologists and the U., .S. Geological, Survey. Among the tests that were considered was the tensile-strength test, which Mr. Fiske has mentioned in his paper. Unfortunately, a majority of the committee turned it down, and the test was therefore not officially approved, but two of us, who formed the minority, believed in it. Since then the other members of the Committee have come to see that that is an important test to make and Mr. Fiske has emphasized it in his paper.

Jan 1, 1918

By T. J. Bosworth

The effect of hydrogen pretreatment of alumina, magnesia, and zirconia crucibles on reduced oxygen levels in iron charges has been studied. Hydrogen treatment of commercial high-purity magnesia crucibles was observed to produce as high as 70 pct reduction in oxygen content in iron melts. Hydrogen treatment of the commercial high-purity grade zirconia crucibles produced a 25 pct reduction in oxygen levels in iron melts. An average reduction of Knoop hardness of 47 pct was recorded on the iron charges melted in hydrogen-treated crucibles. On the basis of the experiments and the free-energy diagram, it appears that the major source of reducible oxygen to the iron charge is the suboxides and impurity oxides rather than the major oxide of the crucible. Suitable pretreatment of the crucibles to reduce and remove these oxides yields low oxygen levels in iron melted in the crucibles. DURING the last decade, attempts to produce more pure and uniform alloyed metals have brought about the development of many new melting techniques. Notable among these are vacuum-induction melting, inert and consumable-electrode melting, the cold-mold technique, and numerous techniques for removal of impurities by chemical reaction. However great the achievements in this field, metals must still be melted in contact with media of varying reactivity; i.e., gas, ceramic, and slag. Studies have been made to attain an understanding of the reactions that take place during melting, including slag-metal reactions and equilibria, equilibrium of hydrogen and water vapor, and carbon dioxide and carbon monoxide with oxygen in molten iron. These reactions have been treated quite thoroughly. There is one condition, however, that has been widely overlooked, and, to the author's knowledge, only cursive investigation has been made of it. This is the reaction between the ceramic crucible material and the iron charge. In recent years, Hadley and Bianchi' made a series of studies on hydrogen deoxidation of iron in magnesia crucibles. Bianchi2 studied crucible-FeO equilibria in the temperature range 1525°to 1650°C in high vacuum with, however, inconsistent results. Richardson and Jeffes3 in their series of articles on thermodynamic reactions in the making of iron and steel refer to Wentrup and Hieber's4 work on iron and aluminum deoxidation. Their pork included melting iron in alumina crucibles and measuring the aluminum and oxygen content in the iron. Because of the low values obtained, question has arisen of their analytical accuracy.3 Dastur and chipman5 obtained values on hydrogen-oxygen equilibrium in molten iron contained in alumina crucibles similar to those obtained in experiments in the present program. Hochmann6 studied removal of impurities in chromium irons in high vacuum. His results with respect to oxygen level in chromium-iron melted in magnesia crucibles are consistent with results we have obtained.

Jan 1, 1959

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