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By E. A. von Hahn, T. R. lngraham

Cementation rates ulere studied by rotating an elec-tropolished or etched copper strip in aqueous solutions, of either perchloric acid or alkaline cyanide, containing silver ions. The rates of cementation were more rapid in acidic media than in cyanide media. In both, the rates varied with the rate of rotation of the copper strip. The deposits formed in the acidic solutions were finely divided, loosely adhering powders. Those formed in the cyanide solutions were dense and adherent. The presence of the deposits influenced the cementation rates. In the acidic solutions the rate was enhanced, possibly because of the increased cathodic area. In the alkaline solutions the rates were decreased in the presence of the deposits. This has been attributed to restricting the diffusion of the copper ion from the rnetal outward into the bulk of the solution. In an earlier paper1 the authors described a kinetic study of the cementation of palladium on copper in perchloric acid solutions. That work indicated that there were two stages in the palladium cementation process. The first, more rapid stage was consistent with rate control by the diffusion of Pd11 ions to the copper surface and/or by chemical reaction at the surface. The second stage was consistent with rate control by the diffusion of copper ions from the copper surface, through the deposit, out into the main body of solution. The effect of the type of deposit on the rate of cementation is of particular interest because it may be one of the primary features involved when large quantities of metal are to be cemented from solution. No substantial investigations of the effect seem to have been made. Accordingly, an extension of the previous work was arranged to study the cementation of silver on copper. This system was selected because of the convenience of the analytical methods, the previously established technology with copper, and the fact that the system could be studied in both acidic and alkaline media. By selecting perchloric acid and alkaline cyanide solutions as the media, it was hoped that some assessment might be made of the effects, on cementation, of having the silver ion present in a virtually uncomplexed state and in a highly complexed state. EXPERIMENTAL The cementation rates were studied, as previously described,' by rotating a copper strip (1.0 by 23.2 cm) clamped to the peripheral surface of a lucite cylinder. The solutions were kept at constant temperatures (±0.05°C) under an atmosphere of purified nitrogen, and samples were taken periodically for analysis. The initial solution volume was 1000 ml and the sample volume 5 ml. The initial silver(1) ion concentrations were made low (0.5 to 1.0 x 10-4 moles per liter) to minimize the influence of the cemented deposit on rates. The solutions were prepared by dilution of suitable aliquots of silver perchlorate and silver cyanide stock solutions. Both stock solutions were prepared from purified silver powder (Johnson, Matthey, and Mallory Ltd.) with redistilled deoxygenated water, and they were kept under an atmosphere of purified nitrogen. To prepare the stock solutions, weighed amounts of silver powder were dissolved with nitric acid. For the AgC104 stock solution the silver nitrate solution was evaporated twice to near dryness with perchloric acid and then made up to volume: For the NaAg(cN)2 stock solution, the silver ions were precipitated with sodium hydroxide solution. The precipitate was filtered, washed thoroughly with redistilled water, dissolved with 1.1 times the required stoichiometric amount of sodium cyanide solution, and made up to volume. The small amounts of free perchloric acid and sodium cyanide present in the stock solutions were disregarded in the preparation of the solutions. The copper strips were cut accurately from 0.025-in. sheet (American Metal Climax OFHC brand) and annealed for 1.5 hr at 470°C in a stream of nitrogen. Analyses of the solution samples for silver and copper were done with a Techtron Model AA-3 atomic absorption spectrophotometer. Calibration standards of the same composition as the experimental solutions were prepared and analyzed simultaneously with the samples. No difficulty was experienced in the analyses, and the reproducibility was within 1 to 2 pct in both alkaline cyanide and perchloric acid solutions.

Jan 1, 1968

By P. A. Meyer

The Tenmile Range is a north trending zone of high relief within the central Colorado porphyry-mineral belt, located between Leadville and Breckenridge. (Figure 1, the Index Map of the area surveyed.) The Climax mineralized zone is located at the southern end of the range on the northwest side of the Continental Divide. This portion of the total area surveyed will be discussed in detail today. A fixed wing aeromagnetic survey was flown over this range and mineralized zone in the fall of 1957. The survey was run as an experiment to see if a useful geophysical tool could be applied in the exploration for similar type deposits. The purpose of this paper is to describe the results of this survey and the approaches used to aid in the interpretation of the total intensity data.

Jan 1, 1968

By Paul W. Zimmer, Carl E. Dutton

Iron ore in the Menominee district is mined from two iron-formations of middle Precambrian age. The older formation is present in the northeastern part; is composed mainly of hematite, magnetite, quartz, and minor silicates; and contains about 34 per cent iron. The rock has been so coarsened by meta- morphism that concentration of magnetite and hematite is feasib!e, and pellets containing more than 60 per cent iron are being produced. The older formation is also present in the southeastern part where it has 1:een only slightly metamorphosed. Ore containing more than 50 per cent iron was formerly mined from local residual concentrations of iron oxides from which silica had been sufficiently leached, or replaced by iron oxide, or affected by combinations of these processes. The younger iron-formation occurs in the western part of the district and, if unaltered, is interlayered siderite and chert. The ore in this area also contains more than 50 per cent iron and formed as local residual concentrations but in two stages. The siderite was converted to iron oxides (hematite and "limonite"), and silica was contemporaneously or subsequently removed by leaching, or replacement, or combinations of these processes.

Jan 1, 1968

By William R. Jones, Robert M. Hernon

This report on the Central mining district of New Mexico is the partial culmination of an intensive U.S. Geological Survey effort dating back some 30 years. Robert M. Hernon went to Silver City in 1948 to finish a detailed restudy of the district that had been started in the thirties by Samuel G. Lasky. He was joined by William R. Jones in 1951, and Jones took over as project chief when Hernon resigned to do consulting work in 1953; it was under Jones' guidance that most of the work was brought to completion or nearly so ( 17, 22-24, 26-30). Hernon returned to the Survey in 1958 to work in .the southern Appalachians. Early in 1965 Jones urged that Hernon be reassigned to the Silver City project to help complete the Professional Paper report on the ore deposits of the Santa Rita quadrangle as well as to take over preparation of the report on the Central district for the Graton-Sales volume. This reassignment was approved, and Hernon began work on the present report. By late June he had completed most of it in draft form, and on June 28 Jones and Hernon left Denver for a short trip to Silver City to fill in a few gaps and to reacquaint Hernon with activities in the district, which he had not visited for 12 years. Late in the afternoon of June 29, 1965, as Bob and Bill were 85 miles short of their destination, their jeep collided head-on with a truck that was attempting to pass another vehicle in a cloud of dust. They both died instantly. As the most recent surviving member of the Silver City project (1958-1962), I was given the honorable though rather sorrowful task of putting the Hernon-Jones report "in shape" for publication. Fortunately the manuscript was already in good shape, so that the task has consisted of little more than minor reorganization and editing, and of preparation of the illustrations, abstract, and bibliography. The sections on wall-rock alteration had been left for Jones to complete in the light of his recently intensified interest in alteration geochemistry (25), and it is in these sections only that. the report may fall short, for they have been filled in from a 1958 manuscript by Jones on the ore deposits of the Santa Rita quadrangle that he intended to revise considerably. The shortcomings, however, are largely in the interpretation, not in the field data. As a brief but accurate summary of what was known about the geology of the Central mining district in 1965, this report stands as a fitting testimonial to the scientific dedication of two exceptional men.

Jan 1, 1968

By M. D. Banus, M. B. Bever, A. K. Jena

The heals of formation at 78", 195, and 273°K of the ternary compound h3SbTe2 based on the elements and based on the binary compounds In Sb and [inTe have been measured. The heats of formation at these temperatlcres of the binary compounds In Sb and In Te based on the elements have also been determined. Heal contents and free energies of the three compounds have been calculated from 0° lo 80I)°K. The free energies of joyrrzalion, heats of formations, and entropies of formation at 298°K have also been calculated. The results shown that the tertnary compound is metastable with vespecl to InSh and ln Te below 696 °K. bul is slable above that temperature. The weaker bonding of results in a positice entropy of formation which with incrensirzg temperature makes increasing negative conlvihtclions to the free energy and above 696°K renders the compound slable. THE ternary compound In3SbTez occurring in the quasi-binary system In Sb- In Te' forms on cooling at 829°K by a peritectic reaction.' Observations at 673" and 573 K have shown that this ternary compound decomposes slowly into the binary compounds InSb and1n~e.l'' It has not been possible to analyze the metastable behavior of the ternary compound because up to the present time data on its thermodynamic properties have been lacking. Some information on the binary compounds, however, is available. The heat of formation of InTe at 273°K and its free energy at 673°K are kn~wn.~'~ The heats of formation of InSb at 78", 273', 298", and 723°K have been measured5-' and its heat capacity between approximately 12" and 300"Kg9l0 is also known. In the investigation reported here the heats of formation at 78% 195% and 273°K of the ternary compound In3SbTez have been measured. The heats of formation of the binary compounds InSb and InTe at these temperatures have been obtained by combining new calorimetric results with previously published data. The heat contents and free energies of the three compounds at various temperatures from 0" to 800°K have been calculated. Against the background of this information, the metastability of the ternary compound will be discussed. 1) EXPERIMENTAL 1.l) Preparation of Specimens. The materials used consisted of the elements indium, antimony, and tellurium, the binary compounds InSb and InTe, and the ternary compound In3SbTez. The elements, obtained from American Smelting and Refining Co., had a nominal purity of 99.999+ pct. The compound InSb was Cominco semiconductor grade; the compound InTe was prepared from the elements by melting under a vacuum of 10-h m Hg followed by slow cooling. Three batches of specimens of the compound In3SbTez were used. One batch was prepared by melting appropriate amounts of the elements in an evacuated and sealed Vycor tube. The melt was held at approximately 100°K above the liquidus for about 8 hr, shaken repeatedly, and quenched into a mixture of ice and water. The specimen was annealed in vacuum at 760°K for 4 weeks. In preparing a second batch, a mixture of the component elements was melted and quenched in water. The resulting ingot was powdered. The powder was pressed into pellets, which were annealed in vacuum at 748" to 773°K for 4 weeks. A third batch was prepared in the same manner as the second, except that the starting materials were InSb and InTe rather than the elements. Metallographic examination of samples of the three batches and X-ray diffraction examination of a sample of the second batch did not reveal evidence of microsegregation or a second phase. The results obtained with the three batches showed no systematic differences. 1.2) Calorimetry. The calorimetric method has been described in detail." Samples of the compound In3SbTez, mechanical mixtures of InSb and InTe in the proportion of 1:2, and mechanical mixtures of indium, antimony, and tellurium in the proportion of 3:1:2 were added to a bismuth-rich bath at 623°K in a metal-solution calorimeter. These additions were made from 78°K (liquid nitrogen), 195°K (dry ice and acetone), and 273°K (ice and water). The heat effects of the additions were measured. The difference in the heat effects of the additions of a compound and the additions of the mixtures of its constituents, adjusted for differences in the concentration of the bath, is the heat of formation of the compound. In the concentration range not exceeding 1.5 at. pct solute, the heat effect of the additions was a linear function of concentration. The heat of formation refers to the temperature from which the additions were made, namely, 78", 195", or 273°K. Several calibrating additions were made in each calorimetric run. The calculated heat capacity of the calorimeter and hence the calculated heat effects of the additions of samples depend upon the values adopted for the heat contents of the calibrating substance. In this investigation bismuth at 273°K was used and a value of 4.96 kcal per g-atom was taken for (HGZ3"k . 2) RESULTS AND DISCUSSION 2.l) Heats of Formation. The heats of formation of the ternary compound In~SbTez from the component elements indium, antimony, and tellurium and from

Jan 1, 1968

By Donald L. Ball

The equilibrium of boron nitride, gaseous nitrogen, and solute boron was investigated in Fe, Fe-C, and Fe-Si rnelts by the Sieverts technique. The free ellergy of dissociation of boron nitride, involving -the implied standard states, was evaluated in the range 1400" to 1600°C as: ?Fo = 38,000 - 23.5T, cal ber mole The solute-solute interaction coefficients eBB, ecB , and eg were determined as 0.058, 0.22, and 0.078, respectively. BORON is an important ingredient in some types of steel and cast iron. It was employed at a particularly high level, 0.01 wt pet, in the as-cast malleable iron "CentraSteel".1 In this material, the boron concentration was critical in order to assure graphite, and avoid primary cementite, in the as-cast structure. One possible function of the boron in this alloy was the nucleation of graphite through the agency of boron nitride, which, conceivably, precipitated from the melt during cooling. A research program was instituted to assess the validity of this proposed mechanism. The first undertaking, reported here, was a determination of the thermodynamic possibility of boron nitride precipitation. Data available in the literature on the activity coefficient of solute boron in iron-base melts are inadequate for the present purpose. They will be reviewed briefly, however, so that comparison can be made, when

Jan 1, 1968

By R. B. Walker, R. Palmer, L. C. Bryner

The purpose of this investigation was to further study some of the factors affecting the air oxidation of sulfide minerals. Data obtained from laboratory studies on the effect of temperature, concentration of iron salts, pH, and other catalysts on the biological and nonbiological oxidation of sulfide minerals are presented. The oxidation of copper sulfide minerals and subsequent leaching of the soluble copper has long been a profitable operation. The chief oxidizing agent is oxygen from the air. This reaction is influenced by a number of different factors such as temperature, light, hydrogen ion concentration, oxidizing agents, and various catalysts. Sullivan1 found that copper sulfide minerals are slowly oxidized by the air and that dilute sulfuric acid and iron (111) increased their solubility. At that time it was not known that bacteria were involved in the oxidation of the sulfide minerals. It has been shown that pyrite, molybdenite, free sulfur, and the copper sulfide minerals found in the waste rock dumps in Bingham Canyon, Utah, are largely oxidized by chemosynthetic autotrophic microorganisms found in the leaching streams.2-6 Similar organisms have been isolated in other mining areas7,8 and from the effluents from coal rnines.9 The following are some of the questions that have arisen regarding the mechanisms of the reactions involved in the leaching process. How dependent is the leaching operation upon the biological reactions? How does the temperature effect the biological and non-biological reactions? How does the concentration of iron (II) and (111) effect the rate of oxidation of copper (II) sulfide? Does the iron act as a catalyst? Does activated carbon act as a catalyst on the oxidation of sulfide minerals? What effect does the hydrogen ion concentration (pH) have on the above reactions? The purpose of this paper is to report the results of laboratory studies on these problems. EXPERIMENTAL The apparatus used in this investigation was an air lift percolator described in our earlier work.' The percolator consisted essentially of an air lift which enabled the leaching solution and microorganisms to pass freely through a suspension of mineral (substrate) in Ottawa sand. The air lift served the additional purpose of maintaining an ample concentration of oxygen and carbon dioxide in the nutrient (leaching) solution. (See Fig. 1.) The percolators were so constructed that they could be immersed in liquid constant temperature baths for temperature studies. The thermostats were controlled to +0.5°C. The reactions were all run in the dark. The percolators were charged with one to three g of mineral, dispersed in 100 g of Ottawa sand and 100 ml of nutrient or leaching solution. The sand was purified to remove traces of iron by digesting with concentrated hydrochloric acid and washng with distilled water until free from chloride. After drying, the sand was ready for use. The compressed air supply was regulated to 5 psi and bubbled through an aerator containing distilled water, which was maintained at the same temperature as the bath used. The air was filtered through cotton plugs to maintain sterile conditions. The tops of the

Jan 1, 1968

By J. P. Givry

The bath and the liquid metal in the aluw~inuw~ electrolytic cells are moving under the action of the Laplace forces. Consequently there are differences in level at the interface of the liquid. This phenomena is studied by means of a computer; the characteristics of the mathematical model used are presented with the results corresponding to two typical cases. This study gives a new and origi~zal interpretation of magnetic ej-jects; their action depends very closely on the hydraulic phenomenon which explain the sensibility of the cells to the slope and thickness of solid bath frozen around the pot. MAGNETIC effects produced in the electrolytic cells used for the production of aluminum are known to exist, a factor whose importance is well-known by producers through its influence on cell operation and output. In particular, these effects bring about movements in both the bath and metal as well as interface variations in level that are detrimental to sound electrolysis . A direct study of these effects by means of an experimental device would raise a number of problems particularly difficult not to say impossible to solve in the present state of techniques. It is for this reason that we had recourse to an electronic computer for working out the speed and pressure distribution within the liquid in the cells. We have assumed that all other possible causes for movement, such as thermal convection and evolution of gas at the anode, are acting without any connection with magnetic effects, and that consequently we may study each of these causes separately. A basic cause for magnetic effects lies in the presence of Laplace forces within the bath and metal. Electric current and magnetic field distribution have been calculated with the help of an electronic computer, and two communications about it have already been made to AIME.* 1) PRESENTATION OF THE MATHEMATICAL PATTERN In order to solve this problem, it was essential to assume a number of simplifying hypotheses with regard to both the geometry of the actual cells and the phenomena themselves. A first simplification consisted in assuming that the movements of the conducting liquid modify neither the electric currents nor the magnetic fields. In consideration of the magnitude of the values involved this assumption seemed accep-tible. 1.1) Finding the Equation of the Problem. The problem raised consisted in determining the flow of two viscous immiscible liquids with different densities subjected in a complex environment to gravity and Laplace forces. As a matter of fact, the sum of the external forces acting on the liquids is: F = JAB +pg where F = volume energy, B = magnetic field, J = current density, p = specific gravity, g = gravity. In the case of a laminar flow and assuming that the liquids are Newtonian and incompressible liquids, the equations governing movements are the following: 1) Navier Stokes' equation written in vectorial form: In fact one tries to find a steady-state solution, so aVx/at = 0; besides, one assumes that the movements are slow enough for quadratic terms such as Vy(a Vx/ay) (of round about the square of speed) to be neglected in front of the viscosity term: pAV, so

Jan 1, 1968

By Joseph W. Leonard, T. S. Spicer

INTRODUCTION Reasons for Thermal Drying The continuing increase in the percentage of minus %-inch coal produced as a result of the increased use of mechanical mining methods has, over the years, tended to shift considerable portions of the work of producing saleable coal to the fine coal cleaning section of the preparation plant. Because a given weight of fine coal will contain substantially greater surface area than an equivalent weight of coarse coal, it follows that, when subjected to wet cleaning processes, the fines will absorb and retain consider- ably more moisture than coarser fractions. Increased moisture pickup in the finer sizes complicates fine coal cleaning since beneficiation may not be limited to the removal of ash and sulfur but often must be expanded to include the additional step of thermal drying to remove excessive moisture. Thus, water which provides the medium for cleaning fine coal is in itself detrimental and, like ash and sulfur, reduces coal quality. Removal of surface moisture by drying is done for one or more of the following 1 reasons: (1) To avoid freezing difficulties and to facilitate handling during shipment, storage and transfer to the points of use; (2) to maintain high pulverizer capacity; (3) to reduce heat loss due to evaporation of surface moisture from the coal in the burning process, thus increasing heating efficiency; (4) to improve the quality of coal used for special purposes, such as in the production of coke, briquettes, and chemicals; (5) to decrease transportation costs; and (6) to facilitate dry coal-cleaning processes. Because benefits to coal transportation and utilization are the most common reasons for thermal drying, the following sections will examine these areas in greater detail. Benefits to Transportation Initial benefits from drying are the reduction of shipping costs from the mine to the point of utilization since more coal can be concentrated into a given weight of product when worthless moisture is removed. Non- combustible~ such as water and mineral matter in railroad shipments of coal are billed the same as coal at $3.32 per ton, according to the recent average costs. Savings of 10 to 20 dollars from drying on the shipment cost of each 50 to 60 tons of coal contained in a typical railroad car is common. Savings on coal shipments from individual mines which result from coal drying can be expressed in terms of hundreds of thousands of dollars and more each year. For example, a reduction of shipping charges of only 5 percent on one million tons per year would mean a savings of 166,000

Jan 1, 1968

By T. G. Nilan

Steels containing 0.4 and 0.8 pet C have been transformed isothermally at pressures up to 34 kbuv. Decomposilion mechanisms are so intimately related to phase equilibvia that, as the equilibria shift under high pressure, the microstruclures of the decomposition producls change, maintaining at pressure the same correspondence between a given phase equilibrium and a given microstructure as a1 1 atm. A bainitic unicvo-structure occurs in these steels at high pressure that IS observed only at 1 aim abole 1.4 pct C. This strrrcl111,e 1s ruliorzalized in terms of the effect of pressure on the transformation to lower bainite. The pressuve depetlderlce of the kinetics of pearlile formation is descrihed by an absolute rule theory amalysis. The activation volume for the transformation is 7 cu cm per mlole, which is indicative of a phase-interface transformation-rate cotntrol mechanism. This fortmulation, when expressed in terms of known solule effects on the energelics of tvansformation, gives promise of explaining the effects of alloying elemenls on hnrden-abilily, particularly that of 'coball. KINETIC processes in solids are functions of the primary thermodynamic variables of state: composition, temperature, and pressure. Until the development of high-pressure techniques' that permitted the generation of sustained high pressure at high temperatures, metallurgical studies of such reactions were largely limited to isobaric conditions at atmospheric pressure. The data so obtained, and theoretical deductions based on these data, were necessarily incomplete For the particular case of austenite decomposition, a knowledge of the phenomenology of the reaction in terms of all the state variables should lead to a clarification of the process. This deeper understanding should facilitate a decision between conflicting theories that have been proposed to rationalize these phe- nomena. An analysis, derived from an understanding of the transformation mechanisms, may aid in the optimization of alloy steel development. The first studies of the effect of pressure on transformations in steel were made by Kulin et al. in 1952.' In a study of the influence of applied stress on mar-tensite formation in a 30 pct Ni steel, they found that the martensite start (M,) was depressed 8°C per kbar* by hydrostatic pressure. Jellinghaus and Friedewold3 were apparently the first to investigate the effect of pressure on isothermal transformations above the Ms. They found that the bainite transformation rate in a 1.2 pct C, 3.8 pct Mn steel was reduced by a factor of 3 by a hydrostatic pressure of 4 kbar. In both of these investigations,2,3 the M, of the steels studied was below room temperature. Austenitizing and quenching were done at atmospheric pressure, followed by the decomposition of the metastable austenite under pressure. The maximum temperature at pressure in the bainite study3 was 350°C. Until the advent of the present high-pressure devices, it was not possible to conduct isobaric high-pressure heat treatments from austenitizing through isothermal decomposition and quenching. The exploitation of high pressure as a variable in metallurgical studies was greatly advanced by the apparatus and techniques developed by Hall4 and co-workers. Utilizing these techniques, Radcliffe et a1.5 and Hilliard6 etermined the pressure dependence of phase equilibria in the Fe-C system. Hilliard and cahn7 examined the pearlite transformation rate in an AISI 1080 steel and also in a high-purity 0.92 C Fe-C alloy at 1 atm and at 34 kbar and found a 700-fold reduction in rate at pressure in the 1080 steel but only a fivefold reduction in the high-purity alloy. In agreement with the shift of phase equilibria under pressure, the microstructures were hypereutectoid at 34 kbar pressure, whereas they are eutectoid at 1 atm. Determination of the effect of pressure on carbon diffu-

Jan 1, 1968

The use of comparative sampling methods during the evaluation of the tin-copper deposits at Cleveland mine yielded closely checking average results from groove, channel, AXT split diamond drill core, and bulk sampling for both tin and copper content of the ore.The weighted mean tin and copper grades and values for the groove, channel, and split core samples showed small percentage differences from bulk sample results, and the F-ratio test for single population origin of the four types of samples was accepted at the 99· 5 per cent level of confidence.These results indicate that grade estimates based on the assays from AXT split diamond drill core and/or groove samples would be reliable within practical limits.

Jan 1, 1968

By Arnulf Muan, Klaus Schwerdtfeger

Equilibrium ratios C02/C0 of a gas phase coexisting with selected phase assemblages of the system Fe-Mn-0 have been determined in the temperature range 1000" to 1300°C. The oxygen pressure for the "hfnO" +hfn30, equilibrium and for the "(Fe,hTn)O" + (Fe,Mnh 0* equilibrium at high manganese contents has been determined by electromotive force measurements using stabilized zirconia as a solid electrolyte. The notstoichometry 01' "hTnO" and of "(Fe, iM1z)O" solid solutions has been determined by ther-mog-/avi?netry and by wet-chemical analysis. The data obtained are used to derive activity-composition relations in "(Fe,hfn)O" and (Fe,Mn),O4 solid solutions. WUSTITE "FeO" and manganosite "MnO" form a continuous series of solid solution at high temperatures,' and so do magnetite Fe304 and the high-temperature, cubic modification of Mn304 (Ref. 2) (high hausmannite, -1170). The oxides "FeO" and "MnO" are cation-deficient phases.495 The nonstoi-chiometry of "(Fe,Mn)O" solid solutions has been studied by Engell and ~ohl' at two selected C02/C0 ratios at 1250°C. The two oxide end members of the spinel solid solution, FesO4 and Mn,04, however, are known to be close to stoichiometric under the experimental conditions used in the present investigation.''' The oxygen pressures of "(Fe,Mn)07' solid solutions in equilibrium with iron have been determined by Schenck and coworkers,8 by Foster and welch," and by ~n~e1l.l' The two former groups equilibrated the condensed phases in C02-CO atmospheres of lmown compositions, whereas Engell" used a galvanic cell with stabilized zirconia as a solid electrolyte. The results of these investigators are not in good agreement. Activities of FeO in manganowiistite as calculated from the results of Foster and Welch show ideal behavior, those of Engell yield a pronounced positive deviation, and those of Schenck et 01. show a moderate positive deviation from ideality. In the present work oxygen pressures for the iron + manganowiistite and manganowustite + spinel equilibria and the nonstoichiometry of manganowiistites have been measured. The data were used to calculate activities in the manganowiistite and spinel solid solutions. EXPERIMENTAL METHODS The COz/CO ratios at which manganowustite and iron are in equilibrium were determined by thermo-gravimetric and quenching methods. Experimental details are described in a previous publication.'2 In the thermogravimetric technique, incipient reduction of manganowiistite pellets to metallic iron was observed as a break in the weight vs log COZ/CO curve. In the quenching technique, manganowiistite samples were partially reduced to metallic iron, or the metallic iron of manganowustite + metallic iron mixtures was partially oxidized to manganowustite, in atmospheres of constant C02/CO ratios. After quenching the composition of the oxide phase was determined by X-ray lattice parameter measurements and comparison with a standard curve obtained from oxide solid solutions of known compositions. The nonstoichiometry of "MnO" and "(Fe,Mn)07' solid solutions was determined by chemical analysis of samples equilibrated in C02-CO atmospheres and quenched to room temperature, as well as thermo-gravimetrically by reducing (Fe,Mn),04 or Mn304 to manganowiistite or manganosite. The equilibrium between manganowiistite and (Fe,Mn),04 was measured thermogravimetrically by reducing (Fe,Mn),04 solid solutions having composition in the range of %„ l(NFe +NM) from 0 to 0.63. No experiments could be performed with this technique at higher manganese contents, because the equilibrium C02/C0 ratios are too large for accurate control. An additional difficulty arises at the higher manganese contents due to the strong increase in oxygen content of the manganowustite phase with increasing log Py near the manganowiistite-spinel boundary. Consequently a sharp break in the weight loss vs log C02/CO curve cannot be observed at the phase boundary. At high manganese contents of the manganowiistite, e.g., (NMn/(NF~ + NMn) > 0.9, electromotive force measurements with stabilized zirconia as a solid electrolyte were made to determine the equilibrium oxygen partial pressure. Experimental details are described in a previous paper.* Mixtures of "(Fe,Mn)O" and (Fe,Mn),04 were pressed to pellets, and the oxygen pressure of the equilibrated samples was compared to that of Ni + NiO mixtures in the cell The composition of the manganowiistite in the equilibrated two-phase mixture was determined by lattice parameter measurements and comparison with known standards. The oxygen pressure for the Ni + NiO equilibrium was taken from available data.l3~l4 No reliable results were obtained with the electromotive force technique on iron-rich oxides. The electromotive force drifted strongly with time in this composition range. An additional difficulty arises from the partial de-

Jan 1, 1968

By Perry N. Halstead

This report describes two goniometers that, by simple manipulation, can be used to ascertain the attitude of a joint, vein, or fracture plane observed on the planar projection of a borehole photograph taken with an NX borehole camera of the type developed by the U.S. Army Corps of Engineers. One goniometer was designed to interpret photographs taken in vertical drill holes and the other for photographs taken in inclined drill holes. In practice, several measurements are made on each photograph with the goniometer. These data are then substituted into mathematical equations, which are derived in this report and the attitudes of fracture planes are determined.

Jan 1, 1968

By Kurt Meyer

La geotectónica es la ciencia que trata de la estructura de la corteza terrestre y de los procesos y fuerzas que han contribuido a su formación. Sin embargo, todas las relaciones tectónicas son situaciones confirmadas en el espacio sometido a las leyes física. En este sentido, el proceso tectónico está constituído esencialmente por deformaciones, acumulaciones de masas de piedras y por desarrollo en el tiempo. Por consiguiente, el presente texto describe dos grandes ciclos de problemas y las tareas que se producen en sus relaciones recíprocas y divisiones ulteriores. Así, tenemos el ciclo geotectónico (geosinclinales, continentes, océanos) y el ciclo geomagmático. De otro lado, se describe las fases del plegado y los períodos de la geología geotectónica.

Jan 1, 1968

By J. E. Willson, N. K. Bohidar

An evaluation of internal stress distribution based on photoelastic studies and destructive testing of simulation models shows that pillar failure is a function of the internal stress distribution, and that stability can be changed by altering the internal stress pattern. Induced stresses in three-dimensional epoxy disks subjected to uniaxial forces were evaluated by photoelastic studies. Stress profiles across different sections perpendicular to the loading direction revealed two maxima for each profile. Based on the stress distribution for the entire column, an attempt was made to explain pillar spalling and the hour glass pattern of failure in a mine pillar. For maximum stability and optimum design of mine pillars, it is necessary to consider the external forces, the nature and distribution of induced stresses and the characteristics of the pillar material as determined in the laboratory. This paper summarizes the research done by N. K. Bohidarl and Ben L. seegrniller2 as partial fulfilment of the requirement for Master of Science degree in Mining Engineering, University of Utah. It is an evaluation of a study to determine the stress distribution in short columns in order that regions of high stress concentration in mine pillars may be found and their effect on pillar failure be ascertained. The ratios of the dimensions of the columns studied are representative of those found in mines located in flat-bedded deposits. The weight of the overburden generally constitutes the major external force. This force is calculated by taking into account specific weight and thickness of the cover. Determination of the distribution of this force on pillars may often require a complex analytical study. There have been many investigations of the strength

Jan 1, 1968

By Paul Sands

Single- and two-stage tests were made with 6-inch, coal-cleaning hydrocyclones to determine the effect of hydrocyclone geometry, operating conditions, and feed composition on performance. Most of the testing was conducted in an open-circuit pilot plant that had a maximum capacity of about 9 tons per hour. The coals used in the investigation had top sizes of 1/4 inch and 28 mesh. Considerable latitude was found in the range of geometry variables that could be used without affecting performance adversely, although a certain minimum ratio of overflow to underflow openings had to be maintained for best operation. Two-stage cleaning proved distinctly better than operation with a single hydrocyclone, because clean coal lost in the refuse product of the primary unit can be partly recovered in the secondary. There is an unusually great difference in the specific gravities at which the individual sizes of the feed are separated in the hydrocyclone. This militates against high efficiency because maximum yield occurs when all sizes are cleaned at the same specific gravity. The size composition of the feed and, more particularly, the size composition of the impurity have a greater influence on the efficiency attainable in the hydrocyclone than in most other types of fine-coal cleaners.

Jan 1, 1968

By J. D. Verhoeven

In a recent study1 this author has investigated the effect of an electric field upon the solute redistribution accompanying solidification of Sn-Bi alloys. It was concluded that the primary effect of the electric current upon the solute redistribution resulted from electrotransport within the liquid boundary layer at the solid-liquid interface. In order to maximize the electrotransport effect all of the experiments were conducted at the highest current densities experimentally attainable. It was found that these high current densities produced considerable convective mixing within the liquid metal. This mixing reduces the boundary layer thickness and consequently reduces the effectiveness of the electric field in producing solute redistribution. Consequently, it is quite possible that the condition of maximum achievable current density would not correspond to maximum solute redistribution. It may be that, as the field intensity is increased, a point is reached where the additional solute redistribution from the increased electrotransport is more than offset by the decrease in solute redistribution resulting from the increased mixing in the liquid. In order to check this possibility the effective distribution coefficient has been determined as a function of current density in a series of experiments. The experiments were conducted on 6.6 at. pct Bi

Jan 1, 1968

By J. M. Réjean Gagnon

"Quebec Cartier Mining Company is currently mining a low-grade iron ore deposit in northeastern Quebec. The Company is producing some 8,000,000 dry gross tons of concentrates per year, grading about 66 per cent iron. The pit, which is located on the keel or hinge line of a fold, will eventually be about 1,000 feet deep with a surface area of 8,000 by 2,600 feet. The most significant structural discontinuities in the mine are the natural bedding planes and secondary perpendicular joints. The exposed walls are subjected to a sub-Arctic climate and heavy blasting occurs approximately six times a month.QCM utilizes design and operating techniques to control rock fall. Steps are also being taken to analyze the ultimate over-all pit slope stability."

Jan 1, 1968

The principal activities of the Bureau of Mines Explosives Research Center during fiscal year 1967 (July 1, 1966, to June 30, 1967) arc reviewed in a part 1. Part 2 presents short abstracts of the publications issued during this period in the Bureau series and in other media. Part 3 describes a short study on the shock initiation of hydrogen peroxide not destined for publication elsewhere. ACKNOWLEDGMENTS The Bureau of Mines gratefully acknowledges the support received through cooperative agreement in fiscal year 1967 from The Dow Chemical Company Manufacturing Chemists' Association, Inc.

Jan 1, 1968

By R. W. Smith, R. W. M. Lai, J. Leja

J. Leja (Professor, Dept. of Mineral Engineering, U.B.C. Vancouver, Canada) — I would like to offer some comments on the behavior of contact angle with time, treated in this paper. The authors should be congratulated for a clear exposition of these uncommon departures in the correlation between flotation and contact angle, in systems of importance to industrial practice. Some nine years ago Professor J. H. Schulman (presently at Columbia University, New York) and I reported on a similar study conducted at the Ernest Oppenheimer Laboratory, Cambridge, England.' The systems used by us had, how- ever, no direct practical application at that time, as mercury in solutions of xanthates was tested with a variety of alkyl-aryl polyoxyethylene frothers which were then new to flotation practice. Further, the paper dealt with findings contrary to the then widely held belief that the contact angle established in collector-solution is unaffected by the addition of a frother. Correlation with flotation, or lack thereof, was not sought, though we did suggest that in many cases the selectivity of frothers might be influenced by the dynamic contact angles. We also stated (on p. 243,

Jan 1, 1968