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By J. W. Gwinn

THE underground haulage system in the lead-silver mine of the-Bunker Hill & Sullivan Co., situated at Kellogg, Idaho, is the most extensive in the Coeur d'Alène district, comprising about 35,000 ft. of tunnels, drifts, and cross-cuts where locomotive haulage is in use. The main working adit, known as the Kellogg tunnel, or No. 9 level, is approximately 10,000 ft. in length from the portal to the main working shaft and extends beyond that about 4,500 ft. in each of two directions. On this level all the ore from the Bunker Hill & Sullivan, the Sierra Nevada Consolidated, and the Caledonia Mining Co. an average of 44,600 tons per month-is hauled to the mills, located a short distance from the portal. Electric haulage by the trolley-type locomotive is used on this level throughout. Below this level, at intervals of 200 ft. vertically, are five other working levels (Nos. 10, 11, 12, 13, and 14); and the total haulage distance on these, where electric locomotives are used, is approximately 16,000 ft. No. 13 level has but recently been opened up and is not working-to capacity; while the main cross-cut on No. 14 has just been started, and has no need of power haulage. Of the four levels equipped with electric haulage, Nos. 11, 12, and 13 have storage-battery locomotives, and No. 10 still retains the trolley type by reason of the small and decreasing tonnage produced.

Jan 2, 1915

By D. K. Atwood

Experiments resulted in a satisfactory laboratory method for restoring permeability to clay-containing cores damaged by fresh water. Clay contents of a number of field cores were measured, and permeabilities of plugs from these same cores were then deliberately reduced with fresh water. This damage is attributed to swollen and dispersed clays occupying the pore space. After damaging, a number of experiments were performed to meaJure the amount of damage and to establish some means by which permeability could be restored. The experiments included flooding the damaged cores with water-miscible fluids such as salt water, acetone, isopropyl alcohol and ethanol. Permeability was not successfully restored in these experiments. However, part of the damage was repaired by flooding with oil; when water was removed by distillation in the presence of immiscible fluids such as air or toluene, permeability was completely restored. This evidence suggested that swollen and dispersed clays could be collapsed to their original volume by strong interfacial and capillary forces. It was further postulated that the required forces could be generated by flooding the damaged cores with a solvent partially miscible with water. The flooding experiments were repeated using n-hex-an01 as the partially miscible solvent. Permeability was restored to five of six damaged cores and substantially increased in the sixth. A large fraction of the restored permeability was retained even after water saturation was raised to its original value with 12 per cent salt water. INTRODUCTION Sharp reductions in permeability often occur when relatively fresh water contacts clay-containing formations during drilling and workover operations. These permeability losses are caused by removing inorganic ions from the environment surrounding the clay, and consequent swelling and/or dispersion of clay minerals into the available pore space.' This phenomenon is generally termed clay damage, fresh-water damage, or simply formation damage; it causes large losses in current revenue by preventing oil wells from making their allowable production. Attempts to repair the damage and restore permeability by flowing salt water solutions or brines through clay-damaged cores containing montmorillonite have been unsuccessful.' This irreversibility is thought to result from formation of brush-heap, or edge-to-face, structures when the dispersed clay is flocculated. The brush-heap structures occupy much more space than the close packed domains present before damage.' One solution of the problem is to destroy the clay-water brush-heap and thus restore permeability. Because no satisfactory method existed for restoring permeability to clay-containing formations damaged by fresh water, the work described in this paper was under taken. The laboratory experiments generally consisted of deliberately damaging fresh cores containing clay and then attempting to repair this damage by various means. Results indicate that generating strong interfacial forces within the pore space of damaged cores collapses the clay brush-heap and restores permeability. These forces are most conveniently generated by flowing partially water-miscible solvents, such as n-hexanol, through a core. THEORY OF THE DAMAGE PROCESS The most common clay mineral groups known to cause permeability damage to formations are the mont-morillonites, kaolins, chlorites and illites. These clays are constructed of particles which can adsorb water on their surfaces and edges and, in the case of montmorillonite, between layers of the basic particle itself. This adsorption increases as water salinity decreases. At low salinities the particles disperse into the aqueous phase. When the clays present in the formation are kaolin, chlorite and illite, dispersion accounts completely for permeability damage to porous media. However, unlike the other clays, montmorillonite particles can imbibe water and adsorb ions between layers of sub-particles, or platelets. These platelets have net negative charges on their faces and are held together by exchangeable (or removable) cations such as Na and Ca decrease in ion concentration (salinity) in the fluid surrounding a particle causes migration of water into the clay layers and disperses the basic particle, while diffusion removes the original exchangeable ions from between the platelets. Once these ions are removed, the facing negative platelets repel each other, causing the montmorillonite to swell until, for all practical purposes, the individual platelets are dispersed. For this reason, fresh-water* damage is much more severe in sands containing montmorillonite than it is in sands containing other clays. Many investigators have shown that even trace amounts of montmorillonite can be responsible for marked reduction in the permeability of reservoir sands in the presence of fresh water." ." Monaghan and others have shown that fresh-water damage in montmorillonite-containing cores cannot be

Jan 1, 1965

By Thomas Fraser

BECAUSE of the present interest in the subject of sulfur in coal and its removal, such information as is available in the coal-washing literature on the various factors that determine the adaptability of a coal for wash- FIG. I.-COAL-WASHING TABLES OF ONE-FOURTH COMMERCIAL SIZE. ing have been collected and are presented here together with some observations based on results of experimental work carried out in the coal-washing laboratory of the mining department of the University of Illinois, and investigative work at Illinois washeries in connection with the work on reduction of the sulfur content of coal, being carried on at the Urbana Station of the.U. S. Bureau of mines. This investigative

Jan 9, 1919

In March 1962, over three months ahead of schedule, production began from the Ventersdorp Contact Reef of the Western Deep Levels Ltd. mine on the West Witwatersrand. Few mines have captured the interest of mining men and the public as has Western Deep Levels. It has presented the gold mining industry with a challenge which involved the opening of an ultradeep mine with the attendant problems of exceptionally heavy capital commitments ($77 million to start of production), high rock temperatures and pressures at great depths, cementation and pumping in an area notorious for the volume of subsurface water, and the necessity for entirely new thinking and the application of new ideas. HISTORY Not all the problems facing Western Deep Levels were, however, new. Situated 43 miles from Johannesburg, just off the main road to Potchefstroom, Western Deep Levels was the sixth company to undertake mining operations on what is known as the West Wits line and it could draw on the wealth of experience gained by other pioneer mines in the area.

Jan 12, 1962

By D. M. Francois-Bongarcon

The idea of parameterizing reserves has only been formalized and scientifically applied for a few years. Its most fully developed application, that of open pits, has been operational only since 1976. Two new versions which have just been issued provide a complete solution to the problem and also a powerful tool for mine planning, and they open up a new field of investigation. This paper describes the basic principles for parameterizing reserves, their application for open-pit mines, the algorithm used, the physical interpretation of the results obtained, their economic use as well as the first prospects offered by a complete parameterization in tm of (I. ti), or of the metal price.

Jan 1, 1984

By W. K. Hardy, H. H. Stadelmaier, L. J. Huetter

The ternary system Co-Sn-C was studied in the cobalt-rich region. The liquidus projection ulas established and two fonr -phase reactions were found. An isothermal section at 950°C was worked out. In the region studied the following phases were observed: cobalt-rich solid solution, graphite, binary compound y -cobalt-tin, and a ternary compound. As a result of the limited solubility of carbon in liquid cobalt-tin alloys, the investigation was limited to the cobalt-rich region. Tin contents up to 32 at. pct were studied. Cobalt of 99.99 pct purity, tin of 99.97 pct purity and synthetic graphite of 99.93 pct minimum purity prepare the alloys. Carbon determinations of all alloys were obtained by gas volumetric analysis. Samples were investigated microscopically and by X-ray diffraction using CoK, and FeK, radiation. Cooling curves were obtained with a number of alloys to determine the temperature of the four-phase reactions. The thermocouple was calibrated with the melting points of high-purity silver and copper. In the region studied the following phases were observed: Cobalt-rich solid solution (face-centered cubic) Graphite. Binary compound y (solidifies congruently at composition Cop~n)'. Ternary compound k which is face-centered cubic with superlattice and nonferromagnetic.' In Fig. 1 the fields representing the projections of the liquidus surfaces were determined by microscopic investigation and are labled by their primary phase. In the field labled C graphite is the primary phase. During solidification in this field much of the primary graphite was expelled through the surface of the melt. It could not always be established microscopically whether the remaining graphite was primary or purely eutectic. Therefore it was not possible to determine accurately the boundary curve which drops from the binary eutectic el at 1309 "~~ to the point of the four-phase reaction at F. The ter-nary carbide is the primary phase in the field labled k. To the right of this field the primary graphite is consistently nodular whereas flake graphite is observed at tin contents somewhat below F. The ternary carbide does not appear to solidify congruently. The graphite is attacked in a peritectic reaction along the boundary between k and C. Thus no graphite is observed in alloys in the k field. In alloys right of the boundary between k and C the graphite nodules are located in the center of the k crystallites, further documenting the peritectic nature of the reaction with the graphite. A four-phase reaction was found at F and 1120 &3"C. The most likely reaction is L+ CY-Co + C — k. Below the temperature of the binary eutectic ez at 1112" a second four-phase reaction was observed at E and 1100 lt3"C. It is the ternary eutectic L — CY-Co + k + y. Figs. 2(a ) to (e) show microstructures of the ternary alloys in the as-cast condition. Fig. 2(a) shows the eutectic a-Co + C (with some primary graphite) with the carbide k in the grain boundaries. Fig. 2(b) shows primary cobalt (dark areas) and the eutectic a-Co + k which is formed along F-E.

Jan 1, 1961

By C. R. Garr, A. R. Troiano

FLAKING or hair-line crack formation has been a major problem confronting the producer of large alloy steel forgings.' Today it is generally conceded that hydrogen in one or more forms in alloy steel sections is a requisite for flaking. Hence an obvious remedy is a thermal cycle that reduces the hydrogen content to some low level. In practice, this generally means holding the material at some subcritical temperature for a period of time depending on the size of the ingot or forging. Another method that will suffice in some cases is to cool large forgings slowly, i.e., bury in ashes. In practice, this hydrogen bake is sometimes accemplished inadvertently by a series

Jan 1, 1958

By R. V. Lundquist

Leaching manganese-bearing materials with NaOH to remove caustic-soluble silica has been demonstrated as a method for upgrading manganese. Those materials containing opaline varieties of silica respond most readily. Spent leach liquors are regenerated by treatment with lime to precipitate calcium silicate and to reactivate the NaOH for leaching. ALL of our larger domestic deposits of manganese are very low grade, but estimated tonnages in these deposits are large enough to constitute a potential strategic reserve of manganese for emergency periods, provided these ores can be upgraded sufficiently to meet industrial specifications. Many types of processes have been suggested for upgrading these ores, several have been studied in pilot plants, and a few have attained limited commercial production for special purposes. The hydrometallurgical process to be described below proposes a leaching operation for removing caustic-soluble silica and other gangue minerals and consequently upgrading a manganese ore or flotation concentrate to a commercially acceptable moduct. It is known that some forms of silica and some silicate minerals are soluble in NaOH solutions under suitable conditions. This new process proposes to use NaOH for removing the soluble materials from manganese ores or concentrates and, as a result, upgrade the manganese content. Since spent leach liquors are not efficient leaching agents the liquor must be treated with lime to precipitate calcium silicate and reactivate the NaOH. Experimental Procedure Manganese-ore samples ground to —35 mesh were leached in iron containers into which the ore sample and appropriate NaOH solutions were placed. Flotation concentrates were already ground to —200 mesh. The slurries were then placed on a hot plate or into a pressure digester and stirred continuously during the period of digestion. Where the- digestion was performed at atmospheric pressures, water lost by evaporation was replaced at regular intervals to maintain approximately a constant volume of slurry. In the pressure digester, volume changes were not controlled. After digestion, the slurry was allowed to cool enough for easy handling, but it was filtered hot, 50" to 70°C, on a Buechner filter. Filtration under these conditions was satisfactory. The resulting filter cake was washed and dried. In most instances, a single leach would not produce maximum extraction of silica from the ore sample; consequently, the dried tailing was treated again in the same manner with a fresh solution of NaOH to obtain an additional extraction of silica. This procedure was repeated a number of times to get the maximum extraction of silica. Usually three or at most four stages of leaching were adequate for this purpose. This leaching procedure was used for obtaining the data reported in this paper on the effects of NaOH concentration, pulp dilution, temperature, and time of digestion on the efficiency of extraction of silica from the ore sample. The experimental procedure does not match industrial methods. consequently tests for counter-current leaching were set up. Data from these tests are not yet complete, but in a qualitative way they indicate that thickeners between stages of leaching will be satisfactory and that the quantity of silica in a leach liquor moving forward to a new solid has only a minor effect on the quantity of silica extracted from the new solid. A pilot plant is now being designed for operation in the near future to test and evaluate the merits of this process.

Jan 1, 1954

Papers in Classes A-Metal Mining, B-Milling and Concentration, H-Indus¬trial Minerals, and I-Mining Geology are distributed in MINING TECHNOLOGY, which is issued every other month. Papers in Classes C-Iron and Steel Division, D¬-Nonferrous Metallurgy and E-Institute of Metals Division are distributed in METALS TECHNOLOGY, which is issued twice quarterly. Papers in Class G-Pe¬troleum Division are distributed in PE¬TROLEUM TECHNOLOGY, which is issued every other month. TECHNICAL PUBLICA¬TIONS in Classes F-Coal Division, J¬-Mineral Industry Education Division, K¬-Mining Administration, and 1-Geophysics, are issued as separate pamphlets. Contributions are papers that when printed or mimeographed are available but only on request.

Jan 1, 1943

ON FEBRUARY 4, 1952, the Phelps Dodge Corporation signed Contract GS-00P(D)-12068 with the United States Government. This interesting document dealt with the "Bisbee East" project as part of the Government's program to increase the supply of needed copper by encouraging private enterprise to expand production. The ore deposit involved was a relatively small body of low-grade ore lying east of the remnants of the old Sacramento Hill deposit that was exploited with indifferent success from 1923 to 1931, as related in THE PORPHYRY COPPERS. Planning for the entire enterprise had been directed from the start by Harrison M. Lavender, who in 1945, succeeded Percy G. Beckett as vice-president and general manager for all of Phelps Dodge's Western mines and smelters. The untimely death of Mr. Lavender in 1952 prevented him from seeing his plans brought to fruition; but in his honor the mine was fit- tingly named "The Lavender Pit" and was so dedicated on August 7, 1954. The Copper Queen Branch operates under- ground mines at Bisbee (production in 1955 was 28,000 tons) ; but, as this volume is concerned only with Porphyry operations, this chapter deals only with the Lavender Pit project, or as the Government knows it, Bisbee East. My reason for going into some detail regarding the floor-price contract is that it is fairly typical of contracts made by the Government in connection with a half-dozen other copper-expansion projects; and, incidentally, with various projects involving other strategic metals. Phelps Dodge did not seek a loan or other financial aid. The only encouragement asked consisted of (a) the privilege of a five-year write-off (commonly called rapid tax amortization)

Jan 1, 1957

By E. W. Greig

This paper is an account of exploration for bauxite in the Amazon Basin, Brazil, and particularly of the discovery, exploration and development of the Trombetas deposits by Alcan. A general report of the Trombetas Project has already been published in E/MJ(Anon. 1975) to which the reader is referred for details on ownership, infrastructure and construction as well as the proposal for mining and treating the bauxite. A regional account of bauxite in and around the Guyana Shield and the northern part of the Brazilian Shield is included to help explain the geology of the Trombetas deposits and their relation to other bauxites in northern South America. It is suggested that all these deposits formed during Tertiary time under similar geologic conditions.

Jan 1, 1979

There are not many data about early coal production in Kentucky, but some legislative reports, early geological studies and occasional newspaper articles have left some figures. The earliest production with any authentic record is that of Lee County, the coal being boated down the Kentucky River to Frankfort. While never a large producer, this county has the longest record in the State. Production is recorded in several of the western coal counties in 1820, and in several others a few years later. The early production in Greenup County was for the iron furnaces operating there. Clay County had a large salt output in the early days and this required a large output, for those days, of coal; the amount of fuel is based on the quantity of salt. It will be noticed that several counties on the Ohio River produced considerable quantities of coal before the Civil War, much of it being consumed by the river steamers. Since the end of the war, these counties have never occupied the relatively important position they had prior to that time. All of the coal produced in the eastern mountain counties moved out of them by water before the war, and during that struggle nearly all mining was stopped. The growth of the railroads after the war greatly reduced the river traffic from these counties, and in some cases it was never renewed. The coal shipped from Lawrence County prior to 1861 all moved by water; after that date there was no production excepting for local use until 1879, and since that time, all shipments have been by rail. Some of the early railroad reports have been helpful in reporting shipments, but for the early years very few of them can be found, and after about 1879 the quantities reported cannot be identified as to origin. Pres. J. B. Hill, Louisville and Nashville Railroad, furnished all of the data available for his line. Sources of data are shown on Table 61; other figures are estimated. A list of early Kentucky mines is given in Table 13.

Jan 1, 1942

By J. Moore Samuel

INTRODUCTORY BEFORE the year 1909, no measurements of dust losses and flue gases had been made at the Copper Queen Reduction Works, at Douglas, Ariz. At that time the "unaccounted" loss of the smelter had reached a figure, that drew attention to the possibility of large stack losses. The measurement of dust losses had not been studied much at that time, and estimates of dust losses, with a few exceptions, were the results of tests by what has been termed "chemical methods," that is, the aspiration and filtration through cotton, wool or some similar medium of a few liters of gas, the dust being weighed on a chemical balance, and the volume of gas computed from the volume of aspirator water. The possible error of this method is enormous, and the probable error much too large for reliable results. Since the object of these tests was to discover not only the extent of the dust losses, but also the possibility of profitably reducing the same, it was decided that the method adopted must have the following characteristics: 1. The sample of gas taken for filtration must be representative of the whole volume of gas, that is to say, it must have the same dust content. This condition will be fulfilled in all cases if the gas sample is drawn off without change of rate of flow. Then it will contain the same proportion of entrained or suspended particles of dust as the original gas. In the case of flue gases which contain only fume, at a temperature above or near the sublimation point, this condition need not be adhered to since the fume will not behave as entrained particles, but more nearly as a true gas. Consequently the gas sample in this case only may be drawn off at any rate of flow. 2. The gas sample taken must be large enough (a) to yield sufficient dust to permit of accurate chemical and physical examination; (b) so that the ratio of the total volume of gas passing through the flue to the volume of gas sample taken shall not be too large.

Jan 6, 1916

By Harold Bloom, H. E. Hawkes

Streams and rivers are the principal channels into which the weathering products of rocks and their contained ores are funneled. The inorganic load of a stream system is a crude sample of all the earth materials in the drainage basin of the stream, and the heavy mineral assemblage of sediments is one of the oldest and most successful guides to certain kinds of bedrock ore in unexplored terrain. Early application of this method was made possible by the ease of separation and identification of heavy minerals in the field with the simplest equipment. Water analysis for traces of base metals became a practical possibility about eight years ago with the development of rapid chemical tests that could be carried out at the field site. Since that time the water method has been widely used in mineral reconnaissance, and a substantial number of discoveries have been reported. Here again, the techniques developed for this work were relatively simple and could be performed easily at the field site.

Nov 1, 1956

By J. S. Crump, H. L. Stone

Laboratory studies have indicated that displacement of oil from a reservoir by means of a condensing gas drive results in extremely high oil recovery, approaching 100 per cent under the most favorable circumstances. A condensing gas drive is defined as a gas drive in which the gas utilized is appreciably soluble in the oil it is displacing. The laboratory studies consisted of a number of gas drive displacement experiments, all using a horizontal, sand-packed, steel tube as the laboratory reservoir. The experimental results indicate that the more soluble a gas is in the oil to he displaced, the more efficient that gar is as a displacing fluid. Experiments were conducted utilizing both a light, volatile crude and a heavy, asphalt crude as the in-place oil. In both cases, oil recovery was appreciably enhanced by solubility of the displacing gas. It is believed that the use of condensing gas drives would result in increased oil recovery from many reservoirs during either primary or secondary phases of production. INTRODUCTION Since the early days of the oil industry there has been an increasing awareness of the problems of oil recovery. During the last few decades particularly a growing recognition of the problems has led to widespread attempts on the part of the industry to increase oil recovery by improved technology. One method which has been used to increase recovery is the maintenance of reservoir pressure by injection of gas. Part of the beneficial effect resulting from this gas injection was to prevent evolution of the gas dissolved in the reservoir oil, since such evolution would cause the oil to shrink and become more viscous, thereby adversely affecting oil recovery. In most instances, the gas injected was predomillantly methane, and so the possibility of oil recovery by retrograde vaporization existed. Laboratory investigations of displacement of reservoir oils by methane, carried out at high pressure, have indicated that considerable additional recovery of light oils could be effected by vaporization, but only at the cost of a severe volumetric shrinkage of the residual oil which would cause a decrease in relative permeability to oil in the reservoir. Consequently, recovery of oil by physical displacement would be impaired. The study suggested, therefore, that recovery of oil might be enhanced by injecting into the reservoir a gas known to be appreciably soluble in the oil at reservoir conditions. Swelling of the oil due to solution of gas should result and yield a consequent increase in the relative permeability to oil. The work described in the following sections was, therefore, undertaken to investigate the possibility of increased recovery by this mechanism. Research similar to that reported in this paper has been conducted by The Atlantic Refining Co.1,2,3 In these studies, Whorton, et al, and Slobod, et al, used methane-rich gas to displace oil from model reservoirs. Solubility of the gas was achieved by keeping the reservoir pressure greater than the saturation pressure of the original oil, and the degree of this solubility was varied by operating at different reservoir pressures. Thus the Atlantic project was primarily a study of the effect of reservoir pressure upon oil recovery by gas drive. The objective of the work reported in this paper was to study the effect of gas composition upon oil recovery while holding the reservoir pressure constant. DESCRIPTION OF EXPERIMENTS The discussion of the preceding section suggests that

Jan 1, 1957

By Henry Souther

It is generally admitted that a god, practical and commercial set of specifications for the use of the many purchasers of cast-iron does not exist. A few good sets are in the hands of large buyers, but even these are very different, contradictory, and not intended to cover a wide range of product. Furthermore, most of them have been prepared to cover but one branch of the industry. It is strange that purchasers of cast-iron have not looked into this question long ago and demanded good, uniform cast-irou. Probably cast-iron has been discarded from many uses because of its failure in a few instances, even though the failure was due to ignorance of the quality of the iron, or perhaps to abnormally bad iron. Some foundrymen seem to consider all gray iron from a given foundry as uniform, especially if they know that it has been made from certain well-known brands of pig. It is likely that with standard specifications and the increase of knowledge necessary for their intelligent employ-

Jan 1, 1905

By Eugene H. Dawson

MICA is a mineral that once was a familiar sight as fireproof windows in stove and furnace doors and as lamp chimneys and shades. Since 1878, the beginning of the electrical age, the use of mica for such purposes has gradually declined and its use in electrical equipment and appliances has developed to such an extent that the known sources of supply are scarcely equal to the demand. With the increasing capacity of electric generating units, the size of mica sheets found in nature was inadequate. However, in 1894, a process was developed whereby thin films or splittings cemented with shellac or other binders could be pressed into large sheets. 18 The introduction of radio in the early 1920s created such a heavy demand for the smaller sizes of mica that on March 22, 1938, mica was included among 23 commodities on the list of strategic materials approved by the United States Army and Navy Munitions Board. To be included in this list, the material must be one whereof the domestic supply is not sufficient to meet the demand. COMPOSITION Mica is a complex mineral composed principally of the silicates of potassium, aluminum, and magnesium. Less prevalent species contain, as essential components, lithium, vanadium, and chromium. Iron usually is present either as an essential component or as an impurity. The mica group comprises some nine different species, five of which, muscovite, phlogopite, vermiculite, lepidolite, and biotite, are widely used in industry. Lepidolite and zinnwaldite (lithium micas) and roscoelite (vanadium mica) are sources of lithium and vanadium. Muscovite, "white mica," is potassium mica. Theoretical formulas H2KAl3(SiO4)3. There are two varieties, distinguished as to color, known in industry as ruby and green. In crystals or "books," the colors each range through varying shades of red and green. However, when split into thin films, all micas, except biotite and phlogopite, are colorless and transparent. Muscovite frequently is stained red or black by thin films of iron oxide between the laminae. The staining usually is derived from magnetite, which sometimes is found as unaltered crystals.

Jan 1, 1949

By L. C. Morganroth

CARBONIFEROUS CLAYS FROM a geological standpoint, but scant attention has been paid to fire-clay beds. Only within the last few years have they been the subject of individual investigation, prior to this time having been considered only in their relation to coal seams. While the relative importance of coal and fire clay is still immeasurably in favor of coal, yet an industry as large as that of fire clay is entitled to a measure of attention. A discussion of the Carboniferous clays is practically a discussion of the clay beds in the Appalachian basin, since more than 90 per cent. of these clays mined are from this region. The clays are confined to the northern end of the basin, or the States of Pennsylvania, Ohio, Kentucky, Maryland and West Virginia, ranking in importance about in the order named. The clay deposits of the Carboniferous period have been divided into two classes; those found in the Pottsville conglomerate series of rocks, and all those that are found in the formations above, for the reason that the clay beds above the Pottsville series all resemble each other in properties, composition and appearance, and all are distinctly different from the bed found in the Pottsville formation. The bed of clay found in the latter formation is unique in that flint clay is practically restricted to it. (A variety of flint clay is occasionally found in these upper deposits but this is in such small amounts as to be negligible.) Carboniferous clays occur between stratified rocks; sandstones, limestones, etc., in the same manner as coal veins. They are often accompanied by a coal vein although where the clay is of a workable thickness the coal is generally too thin to work. The clay beds are sometimes known by the name of the coal seam at which horizon they occur. Clay beds may be from a few inches up to 20 ft. in thickness. They may consist of all soft clay all flint or both soft and flint.

Jan 2, 1916

By Ralph Monaghan, Arthur Youmans

General principles of scintillation counter-type instruments for radioactivity logging are discussed and the various possible causes for instability are examined. It is shown how instrumentation problems are solved. Means are discussed for minimizing drift and instability due to "fatigue" of the photomultiplier tube and neutron activation of the crystals. INTRODUCTION Neutron and gamma-ray logs made with logging instruments employing scintillation counters are now routinely available from most of the logging service companies. The superior characteristics of scintillation counters by comparison with older types of detectors promises to bring about important improvements in quantitative interpretation of radioactivity logs. Moreover, new types of logs can be made with scintillation counters which are not possible with other detectors. But in spite of the obvious superiority of these counters with respect to efficiency, speed, and versatility, they suffer from a number of inherent difficulties and weak- nesses. Unless these inherent diffi-culties are fully recognized and satisfactorily overcome by sound engineering of the associated instrumentation, scintillation counter logs are particularly likely to exhibit drift and instability of sensitivity. This defect in logs when they are intended for quantitative interpretation is intolerable and more than outweighs any advantages over the older type of instrumentation when the latter is operating correctly. SCINTILLATION COUNTER OPERATION In general all radioactivity logging instruments consist of a detector sensitive to gamma radiation or to neutron radiation coming from the strata. This radioactivity is either due to naturally decaying radioactive elements in the rock, radioactivity induced in the rock by a neutron source in the instrument, or scattering by the rock of neutrons or gamma rays coming from a source in the instrument. In the scintillation counter the gamma radiation or neutron radiation reacts with the scintillation phosphor to produce light pulses. These light pulses are then converted to amplified electrical pulses by the multiplier phototube. Basically the problem of making a good scintillation counter logging instrument is to make the radiation sensitivity of the system as nearly constant as possible. The size of each scintillation counter pulse is dependent on the energy of the individual quantum of radiation being detected. In normal radiation logging, gamma rays of all energies, up to some maximum value, reach the detector. If a suitable scintillator is used, such as a sodium iodide crystal, each gamma ray produces a number of photons proportional to the energy absorbed by the crystal from the impinging radiation. The light flashes are detected by means of a photo-multiplier tube which contains not only a photo-sensitive cathode from which photoelectrons are collected, but also an amplifier, called an electron multiplier, built inside the photomultiplier tube; the electron multiplier usually has about 10 stages, having an over-all gain of perhaps 500,000. In an ordinary gamma-ray log one wishes to detect all gamma rays down to the lowest possible energy; therefore, one wishes only to reject the "noise" pulses which are invariably present due to thermal emission of electrons from the photo-cathode of the photomultiplier. In other radioactivity logs it may be desired to measure the radiation within a particular energy band, or above

Jan 1, 1958

By Frederic Benard

RECOVERY of selenium and tellurium at Copper Cliff by the Ontario Refining Co. has been previously described by the writer.1 During 1935 a new building was erected to house this operation and description of the new plant and process form the subject of this paper. The building, of modern steel and tile construction, covers an area of 5900 sq. ft. with a volume of approximately 165,000 cu. ft. The large monitored center bay is flanked by two smaller outside bays, one of which is devoted to the tellurium section. All equipment, ceilings and upper walls, are treated with aluminum paint, giving good illumination and facilitating good housekeeping, essential from a health standpoint in handling material of this nature.

Jan 1, 1938