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By P. R. Kalischer

In the production of alloys by powder metallurgical processes it is often necessary or desirable to include one or more cornponents that tend to form very stable oxides. Included in this group of metals are aluminum, manganese, magnesium, silicon, and a few others. In many cases it is not necessary for the sintered compact to have full density and the other physical characteristics of a cast alloy and in that event no undue precautions need be taken. If, however, it is required that the sintered part be entirely homogeneous, and have maximum density and physical properties, some method must be found to reduce the surface films of oxide, which are always present on the metals, and for the metals mentioned above this is always extremely difficult, if not impossible. since the production of high-density alloys is of particular interest to powder metallurgists, some experiments were undertaken to devise methods of reducing the refractory oxides. For this work, alloys of iron, nickel, and aluminum were chosen because aluminum oxide is one of the most stable oxides and because these alloys in the right compositions form excellent permanent magnets. All of the pertinent properties of the magnets could be accurately and delicately measured by density measuremerits and magnetic tests of sufficient scope to give a complete demagnetization curve. From such a curve the maximum coercive force, residual magnetism, and energy products could be obtained and compared with the same properties for a cast material. Any lack of homogeneity, density, or solid diffusion would be immediately apparent as a decrease in the magnetic properties. Nature and Removal of Surface Barriers The early work of the present investigation was based upon published processes.* In the published information it was claimed that by intimately mixing iron, nickel, and iron-aluminum alloy (50 Per cent Fe, So Per cent Al) powders, compressing such a mixture into the desired shape and size, and then sintering (heating to a temperature below the melting point of the component metals) in hydrogen at 1200°C. or higher, a sound, homogeneous article could be made having the desired physical size, shape, and strength, and good magnetic characteristics. However. this early work showed clearly that something in the powder compress was inhibiting diffusion and the process was almost entirely unworkable. In the initial phase of the investigation samples of iron powder, nickel powder, and iron-aluminum alloy powder were pressed into separate bars and sintered in hydrogen. Both the iron and nickel powders sintered

Jan 1, 1941

By Seymour Fiekowsky, Alvin Kaufman

Taxes are compulsory charges levied by a government for its support. They are usually paid to support the general services provided by government rather than special services (such as safety inspection). The latter are normally supported by user charges often called license fees. Taxes are used by national governments not only to raise money but also as a part of fiscal policy. As such, taxes are used to stimulate or deflate the economy, as an incentive to save or invest, as a means of allocating national resources, and as a means of redistributing income. In our discussion, we will deal only with those facets of the subject that relate specifically to the mineral industry. In doing so we will deal with taxes levied on all industry in a generalized way and only insofar as it affects our industry, but at some length on those portions of the tax system related directly to the mineral industry. It is not our intent to provide a "cookbook" for computing taxes, but rather to present some of the policy issues that bedevil those who must develop our tax policies. MINERAL TAXES The mineral industry is subject to the full range of taxes levied by governments. These include taxes on income, property, and sales, as well as excise and severance taxes. The latter are somewhat similar to a royalty in , that such taxes are levied either ad valorem or per unit of output. Severance taxes most commonly are charged to oil and gas output, although coal, salt, sulfur, and iron ore production also have been taxed in this manner. The major governmental advantage of the severance tax is the administrative ease of collection. On the other hand, it poses an addition to cost independent of profitability. As a consequence, the severance tax can cause premature abandonment if mineral product prices do not rise sufficiently to cover it. Such a rise may not occur if differential tax rates are levied by the various states. Property taxes normally are levied on all property owners, including mineral owners. The major difficulties in this kind of tax, in so far as mining is concerned, are erratic valuation coupled to the inherent problems involved in assessing a property where the extent and richness is chiefly unknown. The impact of these taxes, including state income taxes, is reduced somewhat, as they are usually deductible from gross income as a business expense with a consequent lowering of national income taxes. The net cost of severance, property, sales, and state or local

Jan 1, 1976

By R. C. Kadyk, C. J. Bise

High-voltage cable couplers are convenient and widely used accessories in modern coal-mine power distribution systems to help extend and retract power-feeder cables throughout a mine. Coupler design has tried to keep pace with the industry's desire to move to higher distribution levels, but the increase in recorded failures of 15-kV class couplers, which serve the 12.47-kV and above distribution levels, has inhibited this transition. Problems associated with the effects of partial discharge on high-voltage cable couplers are analyzed. The phenomenon of partial discharge is discussed, a testing standard is developed, and various coupler designs are subjected to its requirements. An analysis of test results and results based on field applications are provided.

Jan 1, 1985

By C. W. Wahsburne

Former studies of sedimentatry strata have been based upon the mineralogical and mechanical characters of the solid components, rather than upon the open spaces between them.

Jan 1, 1915

By Parke A. Dickey

POTENTIAL differences between strata of shale and sandstone have been recognized for about 15 years, and they form the basis of the electrical logging of oil wells. Hitherto these potentials have been ascribed solely to electrochemical reactions caused by the disturbing effects of the water in the drill hole through which they are generally measured. Observations by the author in wells empty of water and in a mine shaft suggest that potential differences between sandstones and shales are natural and specific properties of the rocks, although they are modified to measurement by the disturbing effects of the water in the drill hole. The cause of these potentials probably is to be sought in the relative polar adsorptive capacities of quartz and clay particles.

Jan 1, 1944

By Milton E. Wadsworth, Daniel B. Brimhall

Column leach studies of a low-grade porphyry copper ore were made. The technique used involved alternating oxygen absorption and copper leach cycles. The leach solution was displayed from the column with oxygen. The volume of oxygen reacting with the ore was measured with a gas burette. The copper released as a result of exposure to oxygen was correlated with the oxygen uptake. The oxidation rate was found to be dependent on the pH of the solution wetting the particles and was markedly increased by increasing the temperature of the system. Decreasing the particle size of the sample increased the oxidation rate. A material balance on the system indicated 1 mole of oxygen yielded in excess of 1 mole of copper in solution. A discussion of the important parameters is presented and the results are related to dump leaching in general.

Jan 1, 1974

The first of a series of special war meetings of the New York Section of the American Institute of Mining Engineers held on the evening of July 20 at the Machinery Club, preceded by an informal dinner. The subject for discussion was the important general one of the manganese supplies of the steel industry of the United States. It had been intended to include chromium supplies but this matter was crowded out and left for a later meeting. The principal speaker of the evening was Donnel F. Hewett of the U. S. Geological Survey, who, as a result of his recent studies of the resources of the country, ably presented the question of the extent to which the United States can furnish manganese ore.

Jan 9, 1917

By James E. Reynolds, Duane N. Goens, Charles W. Kenney

A process for recovery of lead and silver from high-grade lead sulfide concentrates by dry chlorination and fused salt electrolysis was developed by Hazen Research, Inc., for Cyprus Metallurgical Processes Corporation (Cymet). A pilot plant was designed to handle mixed sulfide concentrates and to produce high purity lead in a 2,000- ampere capacity fused salt cell. Design of the dry chlorinator and fused salt cell is discussed. Integration of modern chlorine caustic cells for reagent generation was evaluated in the pilot plant program. Also included in the paper will be process chemistry; pilot plant flowsheet, equipment and data: by-product and impurity removal: and scaleup and economic considerations for the process.

Jan 1, 1977

By L. O. Brockway, W. C. Bigelow, J. A. Amy

Specimens of Inconel-X alloy solution-treated at 2050°F and aged for periods of 1, 10, 100, and 1000 hr at 1200°, 1400°, and 1600°F have been examined by electron microscopy and by electron and X-ray diffraction. Four minor phases were identified: titanium nitride, niobium nitride, an M23C6 complex carbide, and the intermetallic ? phase. The two nitrides were found in all of the aged specimens and in the solution-treated alloy, the y' phase formed at all aging temperatures, while the M23C6 carbide formed only on aging at 1200° and 1400°F. Variations in the hardness, rupture strength, creep strength, and yield strength of the alloy have been shown to be related to variation in the size and distribution of the particles of the y' phase within the matrix grains of the alloy, with maximum values of these properties occurring when there is a maximum amount of the phase present and a fine state of dispersion of the particles prevails. THE nickel-chromium alloys containing titanium and aluminum are widely used in applications requiring high strength at elevated temperatures. Studies on relatively simple ternary and quaternary alloys'-4 have indicated that the favorable high-temperature properties of these alloys are related to the precipitation of an intermetallic ?'-phase having a structure based On that of the Ni3A1 phase of the nickel-aluminum system. The present investigation was undertaken to identify the minor phases and to study the microstructural changes occurring in one of the more complex commercial alloys as a result of aging in the service temperature range, with particular emphasis on investigating the role of the ?' -phase. The microstructural changes were studied by electron microscopy and the minor phases were identified by X-ray and electron diffraction. MATERIALS AND METHODS Inconel-X alloy was selected for this investigation because the previous studies of Frey, Freeman, and white6 provided extensive information on the variations in metallurgical properties of this alloy resulting from high-temperature aging treatments. Specimens aged 1, 10, 100, and 1000 hr at 1200°, 1400°, and 1600°F were made available for the present use. These were taken from 1-in. round-bar stock of a commercial heat having the following weight composition: 0.04 C, 0.56 Mn, 6.59 Fe, 0.007 S, 0.38 Si, 0.03 Cu, 73.22 Ni, 14.97 Cr, 0.78 Al, 2.38 Ti, and 1-02 Nb. They were solutjon-treated at 2050 for 4 hr and then water-quenched prior to aging. Powder X-ray diffraction patterns were obtained from insoluble minor phases which were separated from the alloys by digestion in the reagent of Mahla and Nielsen.6 Back-reflection patterns were obtained from electrolytically polished surfaces of the bulk search to detect the ?'-phase' Cu-K a radiation was used in both cases. In the electron-diffraction studies, the general method developed by Heidenreich, Sturkey, and

Jan 1, 1959

By Ernest O. Kartinen

This report is the accumulation of eight years of experience on only one small phase in the business of oil production. It is not intended as a final report but rather as a progress report dealing with the internal corrosion of oil field dehydrating tanks. The corrosion of dehydrating tanks continues to be a problem in the production of crude oil. The deterioration hy corrosion of these tanks falls into three general classifications: (1) Atmospheric corrosion of exterior areas, (2) corrosion of the underside of deck and the rafters and top area of the upper row of staves in that part of the tank which is known as the vapor space, and (3) corrosion of the bottom and shell areas, and the steam coils which are normally immersed in water and thus exposed to the corrosive action of the water. Atmospheric corrosion is primarily a paint problem, and has been omitted in this discussion. The corrosion in the vapor space, in this company's experience, which has been of great concern only in one area. has also been omitted in this discussion. The third, and most troublesome type of corrosion, and the one with which this report deals, is that which occurs in the water-exposed areas of dehydrating tanks, and, to a lesser degree. in some stock tanks. The operating temperature of these waters varies from 80°F to 160°F and the salt counts run from a few thousand to as high as 25.000 parts per million. Corrosion in these tanks occurs in three forms: (1) pits, (2) ringworm type of attack along the vertical and horizontal bolt seams, and (3) as a general attack, spread over a wide area. Steam Coils In dehydrating tanks, our experience has been that the steam coils are the first to show signs of corrosion, and then the shell and bottom areas. This action is not uniform throughout this company's operations. Some installations have coil troubles with very little tank trouble, and some show just the opposite. But in the majority of cases the coils are the more seriously corroded areas. This may be partly due to the fact that we have tried by periodic application to keep a protective coating on the interior areas of the tanks, and some protection has been afforded by these coatings. Through the years several types of hot and cold coatings have been tried with many various methods of cleaning the steel, ranging from use of cleaning solvents to hot and cold Oakite washes, as well as sandblasting. Although experience has shown that a longer life expectancy of a coating is possible after a very thorough steel cleaning job, it has still been necessary to recoat these tanks at least every two or three years. Until a few years ago, vertical spiral steam coil bundles were installed when the tanks were originally erected. When these coils needed replacement, in some cases within 18 months, it was necessary to remove a couple of shell staves to accomplish this task. This required a down time period of several days and was often very inconvenient to the production operations of the leases. This problem was considered on the basis that the coils were expendable, and thus. to eliminate any unnecessary down time when changing coils, the vertical spiral coils were discarded in favor of horizontal flat coils which could be taken in and out of the tanks by way of the cleanout openings, and put together with unions. This made a fairly easily replaceable and repairable coil. But it was still very much of a nuisance when repairs were necessary. Efforts to increase the useful life of the dehydrating tanks led to the adoption of galvanized tanks at an increased initial cost. The zinc coating was depended upon for protection and no other protective coatings were applied. In July, 1944. during the development of a new lease, a 3-ring 1,500 bbl, black iron water tank was converted into a dehydrating tank with steam coils to handle the new production. This tank was coated inside with a cold, brushed-on coating, for protection against corrosion. After approximately 18 months of service, holes developed in the tank and the steam coils. The tank was emptied and cleaned for repairs. The coils were so badly pitted that it was felt advisable to replace them. Coating Becomes Loose Inspection of the tank showed the protective coating to be still in place but loose, and numerous blisters were in evidence. A closer inspection showed that the interior of this tank was so badly pitted under the coating that any further attempt to use the tank was inadvisable. This tank was therefore discarded and a new galvanized tank ordered and set up at considerable expense and inconvenience. In April, 1946, another dehydrating tank installation was made on an adjoining lease. This installation consisted of a 1,500 bbl. 3-ring galvanized tank with two sets of flat steam coils 12 in. and 24 in. up from the bottom. In September, 1947. seventeen months after installation. salt showed up in the boiler feed water. When the dehydrating tank was opened and cleaned, the steam coils were found to be badly pitted — several holes having penetrated through the wall of the pipe. New coils were installed.

Jan 1, 1950

By W. D. Robertson, E. Scala

Electrical resistivity of a number of pure liquid metals and alloys has been measured as a function of temperature and composition. The data show a close correspondence between the liquid and solid states with respect to thermal, structural, and compositional relationships. STUDY of diffuse scattering of X-rays by liquid metals1 has demonstrated that some degree of order persists above the melting point and that the atomic constitution of liquids is more analogous to the solid state than to a gas. Consideration of the change in various thermodynamic properties that accompanies transformation from solid to liquid leads to the same general conclusion.² evertheless, specific knowledge of the constitution of the liquid state is limited when compared with that of the solid and gaseous states owing, in part, to the difficulty of interpreting the X-ray data and in part to the indirect character of deductions based on thermodynamic data. Of the structure-sensitive physical properties, electrical resistivity of liquid metals is perhaps the most easily interpretable, particularly when comparison is made with the solid state. According to the available data, most of which was obtained prior to 1914, cubic metals exhibit a normal linear and positive temperature dependence in the liquid state and the data have been accepted without question. The divalent metals, zinc and cadmium, are apparently exceptional in that resistivity is not linear with temperature and it passes through a minimum. Mercury also exhibits a nonlinear temperature dependence but the slope is always positive. Important comparisons with magnesium could not be made at the time the following work was undertaken because the necessary experimental data were not available. Data on liquid solutions are very limited and are largely from a single source."-" Based on Bornemann's work, Norbury7 pointed out that the resistivity of liquid copper alloys appeared to be dependent on the valence of the solute and that the increase due to the solute was of the same order as in the solid state. However, large extrapolations were involved and no quantitative relationship was developed. Therefore, before proceeding with additional deductions regarding the resistivity of liquid metals and interpretation in terms of structure, it appeared necessary to verify and extend the previous work with particular emphasis on divalent metals and the effect of alloying elements of different valence in dilute liquid solutions. The present work includes: 1—A determination of the resistivity of high purity liquid magnesium, tin, indium, copper, zinc, and cadmium as a function of temperature. 2—The effect of 1 atom pct of copper, cadmium, aluminum, tin, antimony, and

Jan 1, 1954

By S. Skowronski

PURPOSE OF INVESTIGATION Since cuprous chloride melts at 418° C., boils at 954° C. to 1033° C.,1 and is known to be volatile at a much lower temperature, the presence of chlorine in any form in or on copper to be melted has always been looked upon by copper refiners as a possible source of-serious copper loss. Although this fact has been known for some time, the copper literature contains little or no information regarding it and the field seems .never to have been properly investigated from a metallurgical standpoint. According to Greenawalt,2 cupric chloride, CuCl2, when ignited gives cuprous chloride; therefore cuprous chloride is always formed when copper enters into reaction with chlorine at a high temperature. Cuprous chloride melts somewhat below a dull red heat, and does not volatilize in closed vessels, even if strongly heated, but if heated in the air it goes off as a white vapor. Hofman3 gives the melting point of cuprous chloride

Jan 2, 1919

By Gilbert Thiessen

THE purposes of this paper are (1) to show that the mineral matter content of coal is satisfactorily represented by the Parr formula; that is, Mineral matter = 1.08 Ash + 0.55 Total sulfur (2) to compare ash-to-mineral-matter ratios with factors by which ash values must be multiplied in order that dry, factor-times-ash-free values shall equal Parr unit coal values; (3) to examine such ash-correction factors and to compare them with similar factors corresponding to certain simplifications or modifications of the Parr formulas and (4) to show that ash-correction factors used for simplification in calculating approximate unit coal calorific values cannot be. correctly used for the conversion of other determined values in an analysis to the unit coal basis, but that each type of calculation requires separate treatment in simplification.

Jan 1, 1934

By George S. Lockwood

Plans are moving ahead toward the July 1965 start-up date for Kaiser Steel Corp.’s new pelletizing plant at its Eagle Mountain, Calif., iron mine. Capacity will be 2 million long tons of pellets containing 65% Fe. A major portion of the output is scheduled for charging into Japanese blast furnaces as the result of a contract to supply Mitsubishi interests with 10.8 million tons of pellets over a six-year period. Kaiser's concentrating plant at Eagle Mountain plus sintering facilities at Fontana are adequate to meet the requirements of its blast furnaces, which, as a consequence, are not expected to take any substantial quantity of pellets during this period. However, some 200,000 tons of pellets per year is scheduled to be used for the production of special steels and in the open hearths as a substitute for the high-cost ores now being used.

Jan 8, 1964

By Michael B. Gross

A numerical study of the vulnerability of unlined tunnels in jointed rock has been performed with the STEALTH computer program, using the CAVS model for jointed rock. CAVS, for Cracking And Void Strain, is a constitutive model that can simulate the initiation/propagation of fractures and the slip along fracture planes in a jointed rock mass. The CAVS model is unique because it represents a spatially oriented approach to rock failure, rather than the traditional invariant formulation, and because the CAVS submodels for slip friction and slip-induced dilatancy are used to represent the weakening influence of joints, rather than applying ad hoc modifications to the elastic moduli of the host rock. The CAVS model, as embedded in the STEALTH computer program, has performed numerical simulations of tunnel collapse at high overstress levels. These calculations show that the ultimate strength of the tunnel depends strongly on the joint properties, and that the results of the calculations are in qualitative agreement with the observed data for collapse of a tunnel in tuff.

Jan 1, 1984

By H. E. McCoy, C. J. McHargue

Single crystals of columbium containing various levels of oxygen, nitrogen, carbon, or hydrogen were deformed by slaw compression and impact loading at -196°C. For the slow deformation rates. 1500 to 1900ppm oxygen, 500 pprn nitrogen, or 150 to 200 ppm carbon completely suppressed mechanical twinning. Hydrogen in concentrations to 1000 ppm had no apparent effect on ease of twinning. Impact loading caused twins to form at all levels of contamination studied, and cleavage mucking on (100) planes occurred in specimens having higher interstitial contents. It is well established that, under some conditions, the bcc metals vanadium, columbium, tantalum, chromium, molybdenum, tungsten, and iron deform by formation of mechanical twins. In general it has been accepted that high strain rates, low temperatures, and large grain sizes are conducive to this kind of deformation.' Since interstitial impurity atoms have a relatively large effect on slip in bcc metals, one might sus- pect a similar effect on twinning. This could occur directly by the interstitials affecting the nucleation or growth of the twins or indirectly from their effect on slip. It has often been argued that the large increase in yield stress caused by interstitial elements enables the effective stress to exceed that necessary to cause twinning. The twinning stress has always been thought to be higher than the stress necessary to cause slip in pure metals.2 simonsens and Tipper and Hall4 found profuse twinning in very pure a iron even at room temperature, whereas Low and Fueste15 and Churchman and tottrell' observed twins in a iron containing carbon but none in highly decarburized specimens. McHargue7 reported mechanical twins to form readily in vanadium which contained 390 ppm interstitigs, while Clough and Pavlovic8 found twins only in the one or two grains adjacent to the fracture surface in vanadium which contained 1500 to 1700 ppm interstitials. In columbium, McHargue9 found high-purity single crystals to twin easily whereas Churchman,10 Adams, Roberts, and mallman,11 and Johnson12 studied less pure material and found far fewer twins. Although the results of Leadbetter and Argent13 showed oxygen to inhibit twinning, a study by sheely14 indicated the opposite to be true. Chromium exhibits this mode of deformation15,16 but there are no data regarding impurity effects. Lawley, Van den Sype, and Maddin17 observed twins in very pure molybdenum single crystals deformed at 77°K but none in less pure crystals. The work by Cahn18 and

Jan 1, 1963

By J. E. Campbell, G. D. Calkins, N. M. Ewbank, M. Pobereskin, A. Wesner

GRINDING for size reduction affects the economics of many processes and products. It is essential as the first step in many industrial processes and is also a finishing step for materials with properties depending on particle size, such as talc, cement, and silica sand. Intermediate and fine grinding are vital operations in the U. S. cement industry, which is producing more than 250 million bbl of cement per year.1 Wear of the grinding media is a large part of the grinding operation cost. Problems encountered in grinding cement are so complex that evaluation of efficiency and economy of grinding media is difficult.2 It has been especially difficult to evaluate the relative effectiveness of different types of balls because there are no good testing techniques.

Jan 12, 1957

By N. B. Aughenbaugh, W. C. Patrick

The availability of a thorough, simple-to-use roof fall classification system is desirable for several reasons. First, such a system would expedite the reporting of falls for the purposes of estimating material removal costs, analyzing damage levels, and complying with federal regulations to report falls in certain areas of the mine. Second, the classification system would allow the mining engineer to record falls routinely with little time and effort expended. This would encourage him to make observations concerning what type of roof support would work best in a given situation. Third, and probably most important, an

Jan 3, 1979

By M. Cohen, R. J. Teitel

There is considerable interest in beryllium because of its low density (1.84 g per cu cm), high modulus of elasticity (40 X 106 psi), high melting point (1280°C), and special nuclear characteristics. Moreover, it has fair resistance to corrosion and oxidation. However, the purest beryllium known to the authors is relatively brittle at room temperature, and cannot be fabricated readily. The search for improved properties leads naturally to investigations of beryllium alloys and the phase relationships upon which they are based. The present paper is concerned with the alloys of beryllium and iron, primarily from the standpoint of the equilibrium diagram. Iron was selected (1) because of its all-round importance in metallurgy, and (2) because the beryllium-iron system is known to be quite complex. The most recent diagram in the literature is that of Gaev and Sokolov,' and covers only the iron-rich end up to 16 wt pct beryllium. Beryllium markedly restricts the austenitic field, closing the gamma loop at about 0.4 wt pct (3 at. pct). On the other hand, beryllium is soluble in a-ferrite up to a maximum of 7.5 wt pct (34 at. pct) at the eutectic temperature of 1160"C. The eutectic composition lies at 10 wt pct beryllium (42 at. pct) and corresponds to a mixture of or and FeBez (called j3 in the present paper). The solid solubility of beryllium in the a phase decreases with decreasing temperature, and makes precipitation-hardening possible. These findings substantiate the earlier work of Oester-held,2 Wever and Mueller3 and Laissus.4 In addition to the FeBe2 (ß) mentioned above, Misch6 has reported on FeBes, and indicated evidence for another compound containing still more beryllium. A preliminary diagram by Gordon,5 not hitherto published, is given in Fig 1. Besides the phases previously named, there are shown a solid solution of extended range (e), a compound of limited solubility (t), and a high temperature phase (7). Beryllium is designated as 8. The t field contains the compound composition FeBea, and the f phase undoubtedly corresponds to the beryllium-rich compound found by Misch.6 The region around the { phase was proposed by R. J. Teitel based on Gordon's data. The details of the diagram are self-explanatory. It was the unusual complexity of this system that prompted the authors to undertake the present studies. By the same token, more emphasis was placed on the beryllium-rich than the iron-rich end of the diagram. Exprimental Details RAW MATERIALS The beryllium employed in this investigation was one of the purest grades available. Its chemical analysis after vacuum melting is given in Table 1. The metal assayed 99.4 wt pct beryllium. Vacuum melted electrolytic iron of purity shown in Table 1 was the source of iron.

Jan 1, 1950

By D. M. S. Bhatia, Richard D. Hagni

Five sulfide minerals from the Magmont mine, southeast Missouri were sampled for 31 trace elements in over 300 samples by laser microprobe spectrographic analysis of polished sections. The concentration of several trace elements shows a pattern of progressive variation with depth (space) and variation with different paragenetic stages (time) of each mineral. Factor analysis of the geochemical data shows sympathetic correlation both in space and in time of Bi, Cd, Ge, and Sn in galena and sphalerite, and Ni and Co in sphalerite and marcasite.

Jan 1, 1981