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By Fred J. Wright

ORIGINALLY, mining machines were actuated by purely mechanical mechanisms comprising cams, levers and gear trains, which became more and more complex as demands were made for additional operations that would increase mine tonnage. To simplify these intricate machines, development engineers began utilizing the principles of high-pressure hydraulics long employed for the control of various machine tools. The resulting specificially developed hydraulic systems are now literally the heart of the mining machine. During World War No. 2, very little fundamental change in design was made in existing mining machines, but because of the recognition of the merits of hydraulic application to the machines of war, it is reasonably certain that hydraulics will be applied to mining machines in the future to a much greater extent. This potential future indicates that a more thorough knowledge of hydraulics and its maintenance must be incorporated in mine operation. Contamination of Oil Maintenance of high-pressure hydraulic equipment varies considerably with respect to mine practice and conditions. The success or failure is largely dependent upon the hydraulic fluid and its care. Since all successful hydraulic systems have been designed around the use of mineral oil as the fluid, a complete analysis of this prime factor should be made to make clear the requirements of the fluid in a hydraulic system. Contamination of Oil Manufacturers of mining machinery usually have specified an S.A.E. rating or viscosity index of the, proper mineral oil for use with their respective machines without considering the fact that many oils will meet these specifications but will not give the desired life or efficient operation. Hydraulic fluid should be specified as a good grade of mineral oil, such as turbine oil, having rust and oxidation resistance. It must have high chemical stability, high lubricity, and proper viscosity. These factors will minimize maintenance costs by reducing wear and the consequent replacement of parts, and at the same time will lower costs for the oil by extending its life. Bulk purchases of oil should be limited to small sealed containers provided with a proper pouring spout, thus reducing the possibility of contamination of the oil before it reaches the mining machine. The introduction of foreign matter, such as sand, water, coal dust and residue oil left in filling containers, will cause untold damage and maintenance expense. Sand, being one of the best natural abrasives, will soon wear the close tolerances of the various hydraulic mechanisms to an extent that will necessitate complete replacement. Water is considered normally insoluble in oil, but because of the churning action of a hydraulic system water is broken down to particles so small that they remain in suspension. This suspension is known as

Jan 1, 1946

By C. W. Vaupell

The Huitzuco mines lie in north central Guerrero, Mexico; production has been about 90,000 flasks of quicksilver since 1873. Near-surface ores fill extinct mud geysers and the deep deposits are chambered veins, stock-works in brecciated blocks, and replacements in limestone. The epigenetic minerals livingstonite, stibnite and sulphur occur in limestone, gypsum and dolomite through a developed vertical range of 260 meters. The deepest workings expose an increased amount of stibnite, which probably indicates that the lower limit of mercury mineralization is being approached. A resurgence of heat and water formed geysers over an extended area after the period of mercury mineralization. Mud geysers, which are situated, in the outcrops, contain the secondary mercury minerals, cinnabar and barccnite in the gravel and mud filling the vents. A 150-ton flotation plant is in operation concentrating stope fills that assay 3.0 kg. of mercury per ton. In one open stope, which is more than one hectare in area and 60 m. high, 150,000 tons are available. Introduction The Huitzuco mercury mines are of interest because of the unusual occurrence of ore in extinct geyser vents and the presence of several rare mercury minerals. Some of the deposits have typical characteristics of the telethermal zone and there is a gradation towards typical epithermal mineralization in depth. Halse,1 Villarel1o,2 Mactear3 and Merri114 have described the geology and the early operations in the district, and Bar-cena5 and Mallet6 have described the rare mercury minerals, livingstonite and barcenite, found at Huitzuco. Location The village of Huitzuco lies in the north central part of the State of (Guerrero, Mexico, 27 km. (16.7 miles) east of Iguala, which is the largest and most important town in the area. Iguala is served by the Mexican National Railways and also by the Mexico City-Acapulco highway. The highway is surfaced from Mexico City to Iguala, a distance of 200 km. (124 miles) by road, and there is a fairly good, level, dirt road from Iguala to Huitzuco. The elevation above sea level is about 1000 m. (3280 ft.). The climate is warm and very dry except during the rainy season, from June to

Jan 1, 1941

By George A. Roberts, Robert F. Mehl

WHEN austenite first forms from aggregates of cementite and ferrite, it is not homogeneous.1 This inhomogeneity, consisting of both undissolved carbide and carbon concentration gradients, has a profound effect upon the characteristics of the austenite-pearlite reaction. The rate of formation of pearlite is increased by the presence of inhomogeneities2,3 and because of this (when the inhomogeneity is sufficiently pronounced) the hardenability of the steel is reduced,4,5 In addition to this kinetic effect, inhomogeneities will cause the direct formation of spheroidite from austenite at temperatures just below the Ae1.6-11 The present report attempts quantitatively to evaluate the effect of inhomogeneity upon the rate of the austenite-pearlite reaction, presents a method of determining the austenitizing cycle necessary to obtain "practical homogenization," and considers the effect of inhomogeneity on hardenability. EFFECT OF INHOMOGENEITIES ON REACTIONS NEAR Ae1 Few quantitative data are available representing the effect of undissolved carbide or of carbon concentration gradients upon the rate of the austenite-pearlite reaction. In procuring such data it is necessary to separate the effect of undissolved carbide from that of grain size, and this is not an easy task. The solution of carbide is always accompanied by an increase in the grain size, both effects contributing to the retardation of the reaction rate. It has been possible to make this separation and to obtain data that are independent of the grain size by the use of steels that differ only with respect to their tendency toward grain-coarsening. Steels C and D in Table I are such steels. These steels have been studied previously;1,2,12 they differ only with respect to deoxidation practice; C was deoxidized with silicon while D, teemed from a portion of the same heat, was deoxidized with additional quantities of aluminum in the mold. C therefore is what is normally termed a "coarse-grained steel" and D is a "fine-grained steel." These steels can be compared at the same grain size by heating C to a low temperature and heating D to an elevated temperature, producing a structure of austenite plus residual carbide in the former while forming homogeneous austenite in the latter; in such

Jan 1, 1943

By C. W. Vaupell

The Huitzuco mines lie in north central Guerrero, Mexico; production has been about 90,000 flasks of quicksilver since 1873. Near-surface ores fill extinct mud geysers and the deep deposits are chambered veins, stock-works in brecciated blocks, and replacements in limestone. The epigenetic minerals livingstonite, stibnite and sulphur occur in limestone, gypsum and dolomite through a developed vertical range of 260 meters. The deepest workings expose an increased amount of stibnite, which probably indicates that the lower limit of mercury mineralization is being approached. A resurgence of heat and water formed geysers over an extended area after the period of mercury mineralization. Mud geysers, which are situated, in the outcrops, contain the secondary mercury minerals, cinnabar and barccnite in the gravel and mud filling the vents. A 150-ton flotation plant is in operation concentrating stope fills that assay 3.0 kg. of mercury per ton. In one open stope, which is more than one hectare in area and 60 m. high, 150,000 tons are available. Introduction The Huitzuco mercury mines are of interest because of the unusual occurrence of ore in extinct geyser vents and the presence of several rare mercury minerals. Some of the deposits have typical characteristics of the telethermal zone and there is a gradation towards typical epithermal mineralization in depth. Halse,1 Villarel1o,2 Mactear3 and Merri114 have described the geology and the early operations in the district, and Bar-cena5 and Mallet6 have described the rare mercury minerals, livingstonite and barcenite, found at Huitzuco. Location The village of Huitzuco lies in the north central part of the State of (Guerrero, Mexico, 27 km. (16.7 miles) east of Iguala, which is the largest and most important town in the area. Iguala is served by the Mexican National Railways and also by the Mexico City-Acapulco highway. The highway is surfaced from Mexico City to Iguala, a distance of 200 km. (124 miles) by road, and there is a fairly good, level, dirt road from Iguala to Huitzuco. The elevation above sea level is about 1000 m. (3280 ft.). The climate is warm and very dry except during the rainy season, from June to

Jan 1, 1941

By Clarence Zener, Howard Clarke, Cyril Stanley Smith

The importance of cold-working in the fabrication of metals is in marked contrast with our ignorance as to the nature of the accompanying internal changes. The failure of the usual methods of testing to provide a consistent picture of these internal changes has given the incentive for the present program of investigating the effect of cold-working upon the internal friction of metals measured at small strain amplitudes. It has previously been shown1,2,3, that the internal friction introduced by cold-work is removed by annealing at comparatively low temperatures. In the present paper the following additional factors are investigated: (I) frequency of measurement, (2) amount of cold-work, (3) temperature of measurement. Special care was taken to minimize the internal friction due to causes other than cold-work. The present paper is purely experimental, the authors believing that any conclusions drawn from this work as to the nature of the internal changes accompanying cold-work would be premature.'l PrEpaRations oF Specimens In this study of cold-work it was desirable to eliminate as far as possible all other sources of internal friction. One disturbing source is the lack of temperature equilibrium between adjacent crystallites of a vibrating specimen.4 Temperature equilibrium is aided by small grain size and by the use of low-frequency vibrations. Unless unduly long specimens are used, low frequencies can be obtained only in transverse vibrations. But in transverse vibrations a second source of internal friction is present, that arising from transverse thermal currents.5 The effect of these may be reduced by increasing the transverse dimensions. The grain size and transverse dimensions of the specimens were thus so chosen as to render the vibrations simultaneously nearly isothermal with respect to intercrystalline thermal currents, and nearly adiabatic with respect to transverse thermal currents. The material for this investigation was a 70-30 brass, part of the same lot of material that was used for some earlier studies on the effect of strain on proportional limit.10 It had the following composition: copper, 70.59 per cent; zinc, 29.39; lead, 0.01; iron, 0.01. This material was received from the brass mill in the form of 3/4-in. rod, cold-drawn to final size by a 65 per cent reduction of area from material that had been annealed to give a grain size of 0.060 mm, Rods of appropriate length were annealed for 2 hr. at 400°C. and cooled in air. The annealed rods (grain size, 0.012 mm.) were then stretched in a tension-testing machine, using special grips1' to ensure axial application of the load. The rate

Jan 1, 1942

By Howard Clarke, Cyril Stanley Smith, Clarence Zener

The importance of cold-working in the fabrication of metals is in marked contrast with our ignorance as to the nature of the accompanying internal changes. The failure of the usual methods of testing to provide a consistent picture of these internal changes has given the incentive for the present program of investigating the effect of cold-working upon the internal friction of metals measured at small strain amplitudes. It has previously been shown1,2,3, that the internal friction introduced by cold-work is removed by annealing at comparatively low temperatures. In the present paper the following additional factors are investigated: (I) frequency of measurement, (2) amount of cold-work, (3) temperature of measurement. Special care was taken to minimize the internal friction due to causes other than cold-work. The present paper is purely experimental, the authors believing that any conclusions drawn from this work as to the nature of the internal changes accompanying cold-work would be premature.'l PrEpaRations oF Specimens In this study of cold-work it was desirable to eliminate as far as possible all other sources of internal friction. One disturbing source is the lack of temperature equilibrium between adjacent crystallites of a vibrating specimen.4 Temperature equilibrium is aided by small grain size and by the use of low-frequency vibrations. Unless unduly long specimens are used, low frequencies can be obtained only in transverse vibrations. But in transverse vibrations a second source of internal friction is present, that arising from transverse thermal currents.5 The effect of these may be reduced by increasing the transverse dimensions. The grain size and transverse dimensions of the specimens were thus so chosen as to render the vibrations simultaneously nearly isothermal with respect to intercrystalline thermal currents, and nearly adiabatic with respect to transverse thermal currents. The material for this investigation was a 70-30 brass, part of the same lot of material that was used for some earlier studies on the effect of strain on proportional limit.10 It had the following composition: copper, 70.59 per cent; zinc, 29.39; lead, 0.01; iron, 0.01. This material was received from the brass mill in the form of 3/4-in. rod, cold-drawn to final size by a 65 per cent reduction of area from material that had been annealed to give a grain size of 0.060 mm, Rods of appropriate length were annealed for 2 hr. at 400°C. and cooled in air. The annealed rods (grain size, 0.012 mm.) were then stretched in a tension-testing machine, using special grips1' to ensure axial application of the load. The rate

Jan 1, 1942

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Jan 1, 1938

By E. J. Horwood

The varying physical character and large extent of the Broken Hill lode necessarily involve the employment of a variety of underground methods. The lode had its origin in an extensive fault plane traversing metamorphosed schists conformably, as a rule, with their beds of stratification. The underground waters carrying minerals in solution deposited their contents. in the original cavities formed by the faulting action, and in the enlargements of these cavities due to dynamic forces brought to bear on the rocks, more especially on the hanging-wall side of the fault, This deposition was supplemented by metasomatic replacement of a portion of the original rock contents by the argentiferous sulphides of lead and zinc which form the staple products of the district. Although the orebody is practically continuous throughout the mines, its width varies greatly, ranging from a few feet to about 350 ft. The widest portions occur in conjunction with huge folds in the inclosing country rock, almost exclusively on the hanging-wall side. The ore it these folds pitches to the south in the southern half of the field, and to the north in the northern half; there are, however, undulations in these ore channels evidently due to compression of the rocks in the direction of the channels. In the earlier days, before the orebodies had been opened up: vertical cross-sections across these bulges in the hanging wall gave the lode the appearance of the "saddle formation," so well exemplified at Bendigo in Victoria; but subsequent development of the ore channels ha; long since proved that the formations in the two districts are entirely different. The depth reached by the zone of complete oxidation of the sulphide, varies from about 250 to 550 ft. from the original outcrop while partial oxidation extends in places below the 1,000-ft. level. The result of oxidizing influences has been the production of ore of every grade of cohesiveness, from that of dry sand to that of hard compact rock.

Jan 1, 1916

By Henry J. Welge

Laboortory apparatus has been devised which permits study of the displacement of oil from cores by water and by gas. The cores used contained interstitial brine as well as oil. Experiments were run to determine the comparative effect of varying the properties of the fluids used. No great effect was noted on the maximum displacement achieved. This observation made it unnecessary in initial work to use fluids in their exact reservoir conditions. Consequently, the displacements were run at near-atmospheric pressure in Pyrex glass equipment, using stripped crude oils. Introduction and Theory The chief object of this work has been to determine the efficiency of gas and water as primary agents for displacing oil from reservoir rock under laboratory conditions in which capillary phenomena were predominant. To this end the maximum displacement of oil from cores has been ascertained. This maximum displacement may not be equal to the maximum displacement from a reservoir; but it will be a close approxirnation to it sometimes, and other times the laboratory information will be useful in reservoir engineering predictions. It is] believed that the laboratory experimental maximum represents the upper limit for the reservoir recovery. The experiments were carried out by obtaining cores of interest from the reservoir, and filling the pores with interstitial brine and oil with the restored state tech- nique.1 Then the oil was displaced from the core as described later, either by brine from below, or by gas from above. The former type of displacement suggests analogy to production by water drive, but not to water flooding, for reasons discussed below. The latter type of displacement is believed to simulate production by gas cap displacement. The displacements were performed by what may be termed the capillary-pressure method. The cores are placed in capillary contact with an oil-wetted membrane which has very small pores (about I micron in diameter). Pores of this size will transmit oil but Prevent the Passage of gas or water, unless the Pressures used are higher than the capillary Pressures employed in this work. Accordingly, use of the membrane makes it possible to apply a capillary pressure differential between the displacing phase and the oil in the core. AS in the displacement of brine toward that condition of oil and water distribution existing originally in the reservoir,' it may not always be desirable to reduce the oil saturation in this experiment to an absolute minimum. With reservoirs having small productive closure, it is preferable to evaluate and use a displacing pressure no higher than the capillary pressure, Ap, which will ultimately become available for displacement in the reservoir. This pressure may be calculated from a knowledge of the density of the oil-in-place, do, the density of the displacing phase, dl, and Ah, the vertical distance between the section of the

Jan 1, 1949

By N. J. Themelis, R. V. Flint

In a four-year period between 1973-76, the Metal Mining Division of Kennecott Copper Corp. conducted a company-wide program of operations improvement which involved line and staff personnel from all company functions. Specialist teams performed detailed studies of all operational aspects at Kennecott's four copper mines and concentrators, four smelters, and two electrore-fineries. The specific recommendations that resulted may transform the Metal Mining Division into the country's lowest cost producer of copper by the mid-1980s. In this article, N. J. Themelis and R. V. Flint describe the mechanics of MMD's integrated approach to operations improvement.

Jan 6, 1979

By Nicholas J. Grant, Olaf Troili, John Chipman

IN recent studies of the factors which affect the rate of desulphurization and its equilibrium, it became apparent that certain concurrent reactions were operative which had a significant effect on desulphurization. This is emphasized in the experiments of Hatch and Chipman1 and of Grant, Kalling, and Chipman' by the slow approach to a final state of equilibrium which is in marked contrast to the initial rapid transfer of sulphur from metal to slag. Since the removal of sulphur is of such profound importance in iron and steelmaking, it appeared necessary to investigate the reactions responsible for this behavior. It is now known that the presence of iron oxide in the slag interferes seriously with the principal reaction of blast-furnace desulphurization: CaO (slag) +-S + C - CaS (slag) + CO [l] The interfering reaction is most simply expressed as: CaS (slag) + 0 = CaO (slag) +-S 121 and a small concentration of oxygen (or FeO) is sufficient to hold a considerable amount of sulphur in the metal. It has been shown by Grant, Kalling, and Chipman2 that the addition of MnO to blast-furnace slag slows the removal of sulphur from the metal. This effect overshadows the contribution of MnO to basicity and is ascribed to its oxidizing power. It will be shown in this paper that SiO, also has sufficient oxidizing power to interfere with blastfurnace desulphurization. This is, of course, only one of its several effects. Primarily it is an acid and therefore reduces the concentration of excess lime. But when silicon is reduced to the metal the oxygen to which it was previously bonded becomes in part available for reaction 2. The proof of this statement is found in the following experiments. Experimental Procedure and Results Utilizing the same procedure and apparatus described by Grant, Kalling, and Chipman' five additional heats were made using slags IV and 11, the starting compositions of which were: slag IV—40 CaO, 10 MgO, 35 SiO,, 15 A1,0,; and slag 11—50 CaO, 10 MgO, 25 SiO,, 15 Al3O3. An important difference between these heats and those previously reported was that silicon to the extent of 1 to 4 pct was added to the present heats whereas the starting silicon content was formerly about 0.2 pct. Table I shows the slag and metal analyses for heats 82 to 87, and Table I1 shows the silicon addi- tions made to the charge. These additions are based on 400 g of metal and 400 g of slag. All heats had 1.65 400pct S charged before the cold slagadditions. The temperature was maintained at 1525°C. Rate of SiO, Reduction: Fig. 1 shows the silicon content of the metal in contact with slag IV at 1525°C as a function of time. Heat 70 from the work of Grant, afunctionKalling,of and Chipman is included as the lowest starting silicon. It will be noted that eeven with 4 pct Si in the starting metal, there is an increase in silicon content with time. Heat 84 is apparently approaching silicon equilibrium very slowly. Heats 70 and 82 with very much lower slowly.starting silicon show a more rapid initial rise in startingsilicon content but do not reach equilibrium during a long holding period. Fig. 2 shows 3 different initial silicon contents for Fig.2shows3differentheats 73 (from Grant, Kalling, and Chipman) 86 and 87, in contact with slag II, the most basic slag. Heat 73 is increasing in silicon with time, whereas heat 87 with an initial silicon content of 3.7 pct shows a decrease with time. Heat 86 shows a very close approach to equilibrium. The rate of transfer of silicon from slag to equilibrium.metal is very slow in all of those heats, even those which are initially far from equilibrium. ____

Jan 1, 1952

By F. Weinberg

In developing a mechanism for the solidification of metals from the melt, it has been proposed that solidification proceeds by the growth of platelets parallel to close packed planes. The evidence for this is based primarily on observations of decanted interfaces of lead1,2 and tin on which platelets 1 to 10 µ thick4 were observed. In recent observations of decanted eutectic alloys, 5,6 it was found that the eutectic structure on the decanted surface was markedly different than that of the bulk material, with the surface structure extending approximately 10 µ behind the interface.' This suggested that, at least for these experiments, a residual liquid layer 10 µ thick had been left on the decanted interface, which solidified subsequent to decanting. If a similar thickness of residual liquid was left on the decanted surfaces in the lead and tin observations referred to above, then it is questionable to what extent the observed platelets can be related to the solid-liquid interface before decanting. The purpose of the present investigation was to measure the thickness of the residual liquid layer on a decanted surface of tin, using relatively standard decanting procedures. The technique used was to add approximately 200 ppm of Tl204 (PI) to the melted portion of a high purity (99.999 pet) bar of tin, which was being progressively melted from one end, and then decant during melting. Since only the melt contained the radioactive tracer, the activity emanating from the decanted surface could be used as a measure of the thickness of the residual liquid layer. Progressive melting was carried out in the same fashion as single crystal growth, namely, in a horizontal graphite boat, in an argon atmosphere, using a moving furnace. The decanting was done in two ways; 1) removing the furnace and suddenly dropping the melt end of the boat, and 2) suddenly jerking the solid away from the liquid by the action of a falling weight (estimated peak acceleration 3 x 105 cm per sq sec), using a split graphite container. In all cases the melt was vigorously agitated by bubbling argon through it. The activity of the decanted surface was measured through an aperture 1.5 cm by 0.5 cm in a lead shield with an Anton tube geiger counter. Assuming that the active layer on the surface had the same concentration of Tl204 as the decanted liquid, the thickness of the layer could be determined from the measured activity of the decanted material, and the relationship between activity and material thickness. The latter was determined by rolling some of the decanted material into foil and measuring the activity of multiple layers of the foil. The activity At of material of thickness t (in mm) was determined to be A, = Ao(1 - e-22.5t) where Ao is the activity of the bulk material. The results of the measurements of the thickness of the residual liquid layer for six decants are given in Table I. The variation in t is attributed to variations in the decanting procedure and the rate of melting, the latter being difficult to control because of the vigorous agitation of the liquid. The rate of melting was in the order of 2 cm per hr, estimated from the position of the solid-liquid interface during melting. The results indicate that a residual liquid layer of the order of 10 µ in thickness is left on the decanted interface in agreement with the observation on eutectic alloys referred to above. If the mixing of the liquid during melting is not complete, as was

Jan 1, 1962

By H. K. Shearer

Oil production in north Louisiana in 1937 was 28,668,070 bbl., an increase of 1,896,925 bbl., or 7.1 per cent over 1936, as against an increase of 178 per cent from 1935 to 1936. Gas production of 301,148 million cu. ft. from gas wells and 17,330 million cu. ft. of casinghead gas, a total of 318,483 million, was an increase of 33,483 million cu. ft., or 11.7 per cent over 1936. Well completions numbered 716, with 411 oil wells, 175 gas wells and 130 dry holes; compared with 346, 109 and 78, respectively, in 1936. There were 58 wildcat dry holes. In addition to the wildcat producers described and tabulated with the fields, there were two small, shallow gas wells in Sabine and Tensas Parishes, which did not open fields of any present importance. At the close of 1937 there were only five wildcat tests actually drilling, with nine others shut down or temporarily abandoned. Chief interest during 1937 was in development rather than discoveries. The only real discoveries were two deep gas and distillate fields, Bear Creek and Ruston. There were also three completions of gas-distillate producers from deeper formations in old fields, of which the most important was at Cotton Valley, one discovery of oil in a previously known gas sand and five or six extensions of some importance. Geological Section The columnar section in south Arkansas (Fig. 1, p. 317) also applies in north Louisiana, with a few changes noted below. The oldest known formation in north Louisiana is a bed of rock salt. Except on salt domes, only one well at Rodessa has been drilled into this salt, but it has been penetrated by a number of wells in south Arkansas. Salt domes have been discovered near Vicksburg and Hattiesburg, Miss., and a deep well in Limestone County, Texas, has drilled into rock salt. In Louisiana the distance between the "interior salt-dome basin" and a salt dome of the "Gulf Coast salt basin" is hardly 60 miles. In short, evidence is accumulating to indicate that all of Louisiana, with the possible

Jan 1, 1938

By AIME

To be born in the East, reared and educated in the West, to do graduate work in Germany, leading to the doctorate in metallurgy, and to wind up-for the time being at least-in the Middle West as head of one of the outstanding mining and engineering schools of the country, is a unique career. Curtis Laws Wilson, dean (and in most respects, president) of Missouri School of Mines and Metallurgy at Rolla, is a native of Baltimore. He came to Anaconda in 1918 and in due course was graduated from Montana School of Mines, with an exceptional record. In 1921, after experience in metallurgical research at Anaconda, he became instructor in metallurgy at his alma mater. Because of his ability as a teacher, he rose rapidly to head of the department after special work at Columbia in 1923-24. In 1927, Wilson was granted leave of absence to study physical metallurgy under the great Tammen at Goettingen, and returned with his doctorate to his work at Montana School of Mines. His major metallurgical interest was then in age-hardening of copper alloys. Also after his return to Montana Mines, Wilson started

Jan 1, 1948

By W. A. Hoyer

A pulsed high-energy neturon-induced spectral logging tool has been built and field-tested. The reaction of deuterium on tritium is used to generate pulses of 14-Mev neutrons. By detecting only the prompt gamma rays produced by neutron inelastic reactions in the formation, the presence and relative abundance of carbon, oxygen, calcium, silicon and other important elements may be ascertained from a gamma-ray spectrum. Gamma-ray spectra obtained in a shallow test well and in experimental field use show that it is possible to identify formations and their contained fluids. INTRODUCTION The penetrating gamma rays from naturally occurring radioactive elements in subsurface formations have been used for a number of years in well logging as a means of characterizing and distinguishing strata. Still another nuclear logging method which has been employed for some years consists of the bombardment of strata with neutrons and the measurement of the number of gamma rays produced by neutron capture reactions involving elements in subsurface strata.' Since one of the principal elements entering into capture reactions is hydrogen, the latter procedure essentially results in a hydrogen log, whether the hydrogen be in combined form in either oil or water; thus, the log gives an indirect measure of porosity. These methods, with various refinements, have been developed to such an extent that they have become routine procedures in formation evaluation. Neither gamma-ray logging nor conventional neutron logging, however, yields sufficient information to permit unequivocal identification of the mineralogic composition of formations, and neither method gives information which may be used for the positive identification of hydrocarbons in strata. Accordingly, a number of efforts have been made in recent years to gain additional information from nuclear logs. Brannon and Osoba have shown that it is possible to identify naturally occurring radioactive elements in subsurface formations by spectral analysis of gamma rays emanating from these elements. Such an identification is of value in the characterization of strata. A simplified form of spectral analysis of gamma radiation resulting from neutron capture reactions between elements in earth materials and bombarding neutrons has been used with some suc- cess under favorable conditions to differentiate between petroleum and water. This method relies upon the relatively high energy of gamma radiation from neutron capture by chlorine and, in effect, furnishes a chlorine log. In areas in which interstitial water is of sufficiently high salinity, this log can give valuable information on water saturation and, thus, indirectly on hydrocarbon saturation. Still another approach to obtaining more information by nuclear techniques is "activation logging", in which certain elements yield short-lived radioactive isotopes on neutron activation and, thus, can be detected by gamma-ray spectral analysis. From the standpoint of determining by nuclear logging methods the mineralogic composition of strata and the presence or absence of hydrocarbons, it is essential that information be obtained on the presence and relative amounts of several elements such as carbon, oxygen, hydrogen, calcium, silica and others. Some elements, such as hydrogen, chlorine and sulfur, can be determined by spectral analysis of gamma radiation resulting from neutron capture reactions."" Others — carbon and oxygen, for example — do not enter readily into capture reactions but do yield gamma rays of characteristic energies from inelastic scattering reactions with high-energy neutrons. Accordingly, the latter reactions are of particular interest as a means of identifying hydrocarbons in subsurface strata. Several years ago it was recognized that information requisite to the identification of subsurface strata and of contained fluids could be obtained by pulsed operation of a subsurface neutron generator and associated gamma-ray detector. It was contemplated that pulsed operation would be effective in discriminating in time that gamma radiation which results predominantly from inelastic scattering reactions from that gamma radiation arising from neutron capture reactions. Accordingly, research was continued and construction of such a device was initiated. Although many problems were encountered, they were solved successfully. The following sections describe the tool which has evolved, its performance and the results which have been obtained with it to date. THEORY OF OPERATION OF NEUTRON-INDUCED GAMMA-RAY SPECTRAL LOGGING TOOL THEORY OF INDUCED NUCLEAR REACTIONS Of fundamental importance is the fact that an element, when bombarded with neutrons, emits gamma radiation of energy characteristic of that element. In theory, therefore, an element may be identified by

By W. E. Crawford

The Fresnillo Company's mill at Fresnillo, State of Zacatecas, Mexico, treats oxide ores from the Fresnillo mine, dump ores and underground ores from the Plateros district, company leases and custom ores from the Zacatecas district, custom ores from other districts and tailings from old dumps at Fresnillo. The normal capacity of the mill is approximately 2600 dry short tons per 24 hours (a ton of 2000 lb.). The final product of the mill is a precipitate containing gold and silver, which is smelted and shipped as doré bullion to the refinery of the Compania Minera de Penoles, S.A., at Monterrey, State of Nuevo Leon, Mexico. The geology of the district was described in 1923, by T. C. Baker,' from whose paper the following data have been taken: The mineralization of the district was effected in the Tertiary period, following the intrusions and preceding the appearance of the flows. The area within which productive veins have been found is 1 mile long by 1/2 mile wide. The important units of each of the four general fracture systems meet in the central portion of Proano hill, which is an outcrop of graywacke, and where the rock was also intensely fractured by subsidiary movements, resulting in a shattered zone 1200 ft. long by 400 ft. wide. The mineralization was more intense in the immediate vicinity of the principal channels through which the solutions rose. The valuable metals are silver and gold, the ratio by weight of the former to the latter being 1000 to 1.5. Argentite is the predominant silver mineral, and is associated with pyrite and manganese mineral. The sulfides are primary throughout. A slight secondary action is represented by small quantities of native silver and silver halides, principally cerargyrite, which are found in the upper part of the mine. Oxidation has penetrated with great thoroughness to the lowest horizon so far exposed, this being 420 ft. below the present ground-water level. The shattered mass within the central portion of the hill and near the surface was sufficiently mineralized to produce a large stockwork

Jan 1, 1935

By H. Ries

THE term "clay" is applied usually to certain earthy rocks whose most prominent property is that of plasticity when wet. This permits them to be molded into almost any shape, which they retain when dry. Furthermore, they harden under fire. Clays contain hydrous aluminum silicates-the clay minerals-in appreciable amounts, but aside from this a number of other mineral grains, particularly quartz, may be present. Texturally clays are fine grained, and the so-called true clay particles are usually under 2µ in diameter. MINERALS IN CLAY Certain hydrous aluminum silicates that predominate in many clays are known as the clay minerals"." and are grouped by Kerr41 as follows: [ ] The kaolin group has been found to consist of a number of minerals with the same chemical composition but different crystalline structures .83 Kaolinite is commonly formed by the weathering of other mineral particles, particularly feldspar, but some deposits, like those in Cornwall, England,36 and others in the Washington-Idaho district, are thought by some to be of hydrothermal origin. Dickite and nacrite are thought to be due usually to waters of

Jan 1, 1949

Jan 1, 1932

Jan 1, 1938

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Jan 1, 1938