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By T. O. Allen, J. H. Atterbury

Laboratory and field tests during the past five years indicated considerable variation in the penetrating power of commercially available gun perforators. Many of the guns which achieved inadequate penetration in these tests have since been improved. However, recent productivity tests indicated the possibility of inadequate penetration or, at least, ineffective penetration in some wells. Laboratory experiments under simulated well conditions have demonstrated considerable plugging of the perforations, apparently as a result of factors associated with the shooting process and/or the drilling mud in the well at the time of perforating. The restrictions to flow per unit of hole depth caused by this plugging appears to be greater for jet perforators than for bullet guns of comparable diameter; however, because of the greater depth of penetration obtained with the jet guns, the total flow rates appear to he approximately equal. Limited testing with an experimental shaped charge suggests that less shot hole restriction and greater flow rates may result from larger-diameter perforations or other factors related to charge design. INTRODUCTION Gun perforating has been accepted for a number of years as a routine well completion method which is often preferred since it permits more selective operation of producing zones. Nevertheless, questions have continued to arise as to the effectiveness of the communication paths established between the productive formation and the interior of the casing. The basis for these questions has generally been failure to obtain anticipated fluid production rates through gun perforated completions in specific wells. These low productivities, together with the frequent recovery of bullets from well bores, were considered strong evidence of inadequate penetration. Laboratory investigations of the penetration performance of many of the bullet guns available as late as 1948 gave support to these indications. Subsequent electrical analog studiesl,2,3 indicated that the depth of penetration required to provide productivities equivalent to open hole was beyond the capacity of most bullet perforators evaluated in the early laboratory penetration tests. These results, together with the advent of the shaped charge in the field of oil well perforating, stimulated the interest of both oil operators and service companies in gun development. Improvements in gun design resulted in jet and bullet guns which appeared to be capable of providing sufficient penetration for most perforating jobs. However, some wells failed to yield satisfactory fluid production even after being perforated with the more powerful guns, again raising the question as to the effectiveness of the perforating operation. This fact, together with preliminary shooting into targets prepared with formation cores, indicated that factors associated with the perforating process and/or the fluids in the well bore at the time of shooting may reduce effective formation penetration and thereby decrease well productivity. These laboratory and field data prompted another phase in the investigation of the effectiveness of gun perforating: a program to determine the extent and seriousness of perforation plugging under simulated well conditions.

Jan 1, 1955

By R. August Heindl

A process for recovering manganese from open-hearth steel-plant slags was investigated. The proposed method of accomplishing this is indicated by the flow diagram in figure 1. Mixtures of open-hearth, steel-plant flush slags and limestone, so proportioned as to have molar [CaO -3P205] ratios of approximately 2, were fired at approximately 2,400° F. in an oxidizing atmosphere and then cooled slowly. This treatment produced a clinker consisting principally of two solid phases comprised of (1) various combinations of the oxides of manganese, iron, aluminum, and magnesium, probably in spinel complexes, and (2) a dicalcium silicate phase, which contains the phosphorus. Reduction of these clinkers with hydrogen or with gaseous mixtures containing CO, CH4, and other hydrocarbons at about 1,300° F. formed manganous oxide as well as varying amounts of ferrous oxide and iron. Carbon monoxide and mixtures of hydrogen and carbon monoxide effectively reduced the clinkers but also gave higher proportions of soluble iron when the manganese was extracted from the reduced clinkers by leaching at about 80° F. with ammonium carbonate solutions containing 26 to 28 percent ammonia and 15 to 26 percent carbon dioxide. It is believed that the manganese is in solution as an ammonia-manganese complex. Concentrations of about 90 grams of manganese per liter were obtained by batch countercurrent procedures. By distilling 50 percent of the ammonia, the ammonia-manganese complex was decomposed, and approximately 90 percent of the manganese was precipitated as the carbonate with the simultaneous precipitation of 15 to 30 percent of the iron, the larger amounts of iron precipitating in the continuous tests. The manganese-iron ratio in the product could be increased either by recycling more manganese from the distillation to the extraction or by aerating the liquor to purge it of iron before, rather than after, the distillation step. Calcination of the pelletized manganese carbonate in an oxidizing stmosphere at 2,000° F. or above gave a final product, Mn304, resistant to crushing and apparently possessing the other physical properties essential in a ferromanganese blast-furnace feed.

Jan 1, 1955

By N. A. Eilertsen

Eastern Aroostook County, Maine, contains an enormous tonnage of manganese widely distributed in manganiferous sedimentary beds composed of hematitic shale, hematitic slate, and laminated siliceous carbonate rock. The bedded deposits range in thickness from several feet to over 150 feet. Manganese minerals that occur as silicates and carbonate are so minute that they cannot be concentrated by present methods of ore dressing. From a hydrometallurgical standpoint, the deposits can best be classified by amenability to acid leaching. The deposits of Aroostook County are in three geographical groups (see fig. l), designated as the northern, central, and southern districts. At least 13 deposits are known to occur in the latter district, which covers an Ewes about 8 miles wide and 15 miles long. The Littleton Ridge deposit, on the northern boundary of the southern district, previously examined by geologists from the State and Federal Geological Surveys on the farms of Donald H. Haggerty and David A. Abernethy, was pointed out in reports as being possibly the richest and largest in the southern district. The Bureau of Mines sampled this deposit by surface trenching and diamond drilling from May 1 to September 30, 1951. A total of 23 trenches was bulldozed, aggregating 5,355 linear feet, of which 8 trenches were sampled by cutting 185 channel samples over a linear distance of 1,820 feet.

Jan 1, 1955

By J. W. Miller

Depletion of coals most suitable for metallurgical fuel has made necessary a general survey of coking coal reserves in the United States. These investigations were begunn 1948 at the joint request of the Munitions Board, Department of Defense, and a number of coal companies. This report, which is one in a series, by counties, describes the preparation characteristics of the coals of Harlan County, Ky. From these data it is possible to determine: (a) Which coals, either as mined or after beneficiation by conventional preparation, are chemically suitable under present standards for producing metallurgical coke, (b) Which coals require special and more intensive treatment in preparation than is now practiced; and (c) Which coals cannot be considered to be potential sources of metallurgical fuel regardless of preparation.

Jan 1, 1955

The first metal-mine accident-prevention course was prepared and published in 1942-45 as a series of seven miners' circulars (Nos. 51-57). The scope of the course has been broadened, revised, and brought up to date, and it is being published as a similar series of seven miners' circulars (Nos. 51-57, revised) on accident prevention in metal and nonmetallic mines. These circulars are: Accident Statistics (Miners' Circular 51), dealing with general statistics on accidents and injuries at metal and nonmetallic mines, including causes, costs, and the uses of investigations and reports of all accidents.

Jan 1, 1955

By S. T. Reese

STATISTICS of injuries in the quarrying and related industries in the United States first became available when the Bureau of Mines collected reports from the operating companies for the calendar year 1911. Since then reports have been collected annually. The present bulletin, covering the calendar year 1952, is the 33d publication containing statistical data on injuries at quarries and related plants, and it is the first to be published since 1944. The last publication was Bulletin 458, Quarry Accidents in the United States during the Calendar Year 1942. The unpublished statistics for 1942-51 may be found in the Appendix of this bulletin. The Bureau of Mines is authorized to collect data on injuries at quarries, but there is no Federal law that compels operators to supply such data, and the reports received from operators are voluntary responses to the Bureau's requests for information. Although the figures presented herein may not be complete for the entire industry, every effort has been exerted to make them so, and the figures given are believed to be thoroughly representative of the hazards to which quarry workers are exposed. Moreover, the figures are com¬parable as between States -which is significant in view of the lack of uniformity among the States as regards classes of plants covered by State laws, classes of injuries covered by State reports, and other factors that tend to make it impracticable or impossible to compare the injury experience of one State with that of another or to comprehend the relative importance of the various causes of injuries in the industry as a whole.

Jan 1, 1955

By R. August Heindl

[A proposes process for recovering manganese from open-hearth steel-plant slogs is indicated by the flow diagram shown in figure 1. Investigation of the process, the laboratory development of which was reported previously,4/ was expanded to a larger scale. Mixtures of flush slags and limestone were proportioned to have molar [SiO2] ratios of 1.5 to 2.2 and were fired at temperatures up to 2,400° F. In an oxidizing atmosphere. This produced clinker consisting principally me various combinations of the oxides of manganese, iron, aluminum, and magnesium aloe with a dicalcium silicate phase containing the phosphorus. Some tests were made with a continuous sintering machine of the traveling-grate type, but a rotary kiln was the most satisfactory apparatus for this operation. Material was fed at 150 to 200 pounds per hour after first being agglomerated either on the sintering or else binder extruding and drying finely ground mixture of the sing, limestone, binder, and water. Tests with slag; from tree different source indicated overkill manganese recoveries of 65 to 80 percent by ammoniacal-ammonium-carbonate leaching.]

Jan 1, 1955

By Seth T. Reese

THE INJURY DATA and experience at coal mines in the United States for 1951 are presented in this bulletin under the following general heads: (A) General injury experience: Tables 1 to 18: Contain current data on number of fatalities and nonfatal injuries, frequency and severity rates, average severity, major and detailed injury agencies, and distribution of injuries by part of body and days of disability. (B) Selected injury data: Tables 19 to 43: Contain current data on various selected factors of operating and physical conditions that contributed to the occurrence of injuries at bituminous-coal, lignite, and anthracite mines. These factors include extent of hand and machine loading, size of mine by employment and production groups, thickness of bed or vein, duration and number of work shifts, rating of mine as gassy or nongassy, types of cap lamps, explosives, and combination of factors that influence mine safety. (C) Injury experience by States: Tables 44 to 50: Contain current data on number of fatalities and nonfatal injuries, frequency and severity rates, average severity, major causes and principal agencies, injury records of all coal-producing States, and the relative standing by States according to injury-frequency rates. (D) Major disasters: Table 51: Lists the coal-mine disasters that occurred during 1951, giving location, source, and cause. A major disaster in coal mining is defined as a single accident in which or as a result of which five or more men lost their lives. (E) Historical coal-mine injury experience: Tables 52 to 86: Contain data on injuries, injury-frequency rates, employment, and production at bituminous-coal, lignite, and anthracite mines from the earliest records through 1951.

Jan 1, 1955

By W. H. Oppelt

The continuous gasification of lignite in an externally heated alloy-steel re-tort was investigated by the Bureau of Mines, Grand Forks, N. Dak., from 1945 to 1951. The main objective of the long-term experimental program was to obtain data on the mechanical performance of this type of gasification retort, particularly the alloy-steel heat-transfer surface of the retort, when operated on large pilot-plant scale. At the same time, extensive experimental data were obtained concerning the effect of process variables and the effect of a limited number of design modifications on gasifier performance. In the period covered by this progress report 4 pilot-plant runs totaling 2,879 hours of operation were completed with the rolled-plate, 310-alloy reaction tube. Over 30 million cubic feet of gas, having H2-CO ratios from 2.1 to 4.4, was made by the partial gasification of 636 tons of 1-1/2-by 3/8-inch natural lignite. Rates of gas generation were from 8,200 to 14,300 cubic feet per hour. Three of the four runs were carried out with the lowered gas offtake or continuous-annulus design modification of the gasification retort. In the final run of the series, gasification of lignite from seven different mines in North Dakota and Saskatchewan, Canada, was investigated at similar combustion-space temperatures and lignite and steam feed rates.

Jan 1, 1955

By Alfred Traverse

The Brandon lignite is a small deposit of very low rank coal near the village of Forestdale in the town of Brandon, Vt. It occurs in association with other sediments, principally sands and silts. This lignitic coal has attracted considerable scientific interest since the middle of the 19th century because of the abundance of fossils in the sediment and the rarity of lignite in New England. A cooperative investigation has been developed by E. S. Barghoorn, W. Spackman, and the author in which different phases of the problem have been worked on in a coordinated research program. This paper presents results of an investigation of the very abundant fossil pollen and spores and some other microfossils of the deposit. The studies on which this manuscript is based were made in large part at Harvard University in partial fulfillment of the requirements for a Ph. D. degree.

Jan 1, 1955

By Oliver Bowles

ASBESTOS is a name applied to a group of naturally fibrous minerals. As indicated in a later section devoted to a detailed discussion of the early history of asbestos, the tern may be defined as a. fibrous form of serpentine or amphibole. It does not include fibrous forms of other minerals, such as wollastonite, nemalite (fibrous brucite), or the fibrous forms of calcite or gypsum. A material that has the characteristics of silk or cotton and at the same time will not burn is unique. Because it combines these qualities with other advantageous properties, asbestos has specialized uses for which no substitutes are yet available. Asbestos furnishes a major raw material for a great variety of essential products and their manufacture constitutes a vast industry. The United States leads all countries in the manufacture of asbestos products. The value of such commodities manufactured in 1952 exceeded $332 million. They are not only of vast importance to budding construction and industry but axe absolutely, essential to certain important fields of use, for example, steam packings and friction materials, such as brake-band linings on automobiles.

Jan 1, 1955

By C. T. Baroch

The purpose of this report is to describe the design features and techniques used in operating a plant capable of producing about 1,500 pounds of titanium metal per day. The process used was based on the reduction of titanium tetrachloride with magnesium, a modification of what is generally known and spoken of as the Kroll process. Sponge metal crushed to melter's specifications was the end product of the operation as conducted. The report is divided into sections covering general plant layout and the major unit operations. These, in turn, are each divided into discussions of the equipment, operating procedures, and typical results. Descriptions are given in more detail than is generally expected of a technical report. During 1953 and 1954 over 130 engineers and businessmen, officially representing some 80 industrial, chemical, end engineering firms, visited the operating plant, and their questions, which indicated a serious interest in details, have served as a guide for the material contained in this report.

Jan 1, 1955

By R. A. Cattell

Continuing progress in a petroleum and natural gas research program of world-wide significance makes it difficult to pinpoint accomplishments within definite time limits, and it is helpful to look back as well as forward in attempting to introduce and summarize the petroleum work of the Bureau of Mines in the fiscal year 1953. The 1952 report2 / indicated progress in a long-range program applicable in large part to both defense and peacetime requirements. The present report indicates a continuation of that program, modified partly by new demands and interests of government and industry, and is highlighted by a number of significant contributions to the knowledge of petroleum and natural gas and their production and utilization. The intent of the program was clearly epitomized in a statement made near the end of the fiscal year at a general conference of Bureau of Mines personnel where the record was critically reviewed:

Jan 1, 1955

By C. Arthur Carlson

"It now becomes my privilege and duty to call to order this fifty-first meeting of the Rocky Mountain Coal Mining Institute. "I bid you a hearty welcome and I know by your attendance at these meetings you will gain a great deal of valuable information, as well as have a wonderful time. "We have been very ably represented by Mr. John H. Emrick as General Chairman, assisted by our good friend Mr. Fred W. Whiteside, our secretary and treasurer. I know they have worked very hard in selecting the various committees, who in turn - by the looks of our program have gone all out to prepare material that should be of great interest to us. I trust we will be attentive to the subjects presented and freely enter into the discussions, also relating our problems and experiences. I am sure this will prove both profitable and beneficial to all present. "The main purpose of these conventions is to become acquainted with each other, renew old acquaintances, talk over our problems, and have a little fun and relaxation from our every day routine. "Let us not forget the manufacturers, the distributors, the operators, or the press because it is through their splendid support that this organization is successful. "Since our last meeting we have gained many new members, whom we especially welcome. We are sorry to have lost a few. I am mindful, at this time, of two very good members from my home state who have passed away, Walter Wetzel, a former president of this institute, and Lee Alger, at the time of his death, Vice-President from Utah. We also lost very recently our assistant Secretary-Treasurer, Everret Davis. These men contributed a great deal to the institute and the coal industry in general. I am sure they are greatly missed by all who knew them."

Jan 1, 1955

The ores described in this paper are from the two principal orebodies at Wiseman's Creek, a small village about 22 miles south-east of Bathurst in central-western New South Wales.The first official reference to mining at Wiseman's Creek is in "Mineral Statistics of New South Wales" of 1875, which reported that the Wiseman's Creek Copper Mining Company had proved a lode-later known as "North Wiseman's"-to a depth of 120 ft., where it was found to be 20 ft. wide. By 1876 the erection of a mill and smelting works had commenced, and the sulphide ore found to contain copper lead, zinc, silver and gold. Some oxidised ore was also being worked. Operations were, however, generally unsuccessful, and sporadic work up until 1907 produced only about 5,000 tons of ore. The other more important orebody of the locality-the Phoenix-was not opened until about 1895. By 1908, as reported by J. E. Carne, the shaft had been sunk 340 ft., with the extraction of both oxidised and primary ore. At the time of the slump in copper, pric'es in 1907 approximately 3,000 tons of, ore had been produced.Several smaller orebodies were discovered and worked during the same period as the North Wiseman's and Phoenix, but their output was more or less insignficant. THE OREBODIES AND THEIR GEOLOGICAL SETTINGIt is now impossible to examine the orebodies underground, but they appear to have formed a series of flat lenses, whose major axes were parallel to ,the foliation of the enclosing quartz-chlorite-muscovite schists. The largest ,of these lenses was worked as the North Wiseman's orebody, which was reported by Carne to vary in width from 1 ft. to 20 ft., and which probably extended discontinuously over a strike length of about 1,000 ft. The Phoenix orebody is stated to have varied from 1 ft. 6 in. to 3 ft. in width...

Jan 1, 1955

By M. E. Nicholson

IN order to understand how alloying elements influence hardenability through their effect on the rate of pearlite nucleation, it is advantageous to use a model to describe the mechanism of pearlite nucleation. The model which currently is most widely accepted has been described, among others, by Mehl et a1.1-3 and by Hultgren.4 Pearlite nucleation involves both the nucleation of ferrite and cementite.4,5 Cementite nucleates first, followed rapidly by the formation of ferrite at the cementite-austenite interface. The conclusion that cementite is the first phase to form during the process of pearlite nucleation is based, in part, on the observation that proeutectoid cementite is continuous with pearlitic cementite and that the orientation relationship between proeutectoid ferrite and austenite is not the same as that between pearlitic: ferrite and austenite.6,7 Recently, Smith" has suggested that the dissimilarity in orientation relations, instead of indicating the pearlite nucleation sequence, may be evidence that pearlite is nucleated in a grain adjacent to the one in which it is growing. Also, Modin9 as shown that ferrite in pearlite may be continuous with proeutectoid ferrite, and he has also shown that proeutectoid cementite is not always continuous with pearlitic cementite. Thus, it appears that the conclusion that cementite always initiates the pearlite nucleation process is open to serious question. The author believes that important evidence on the question of how pearlite is nucleated exists in the rates of pearlite nucleation of different steels. The following is a review and analysis of this evidence. If the nucleation of pearlite is considered as requiring the nucleation of both cementite and ferrite, then the time to nucleate pearlite consists of the time to nucleate the first phase to form, plus the time to nucleate the second phase at the advancing interface of the first. In the absence of a visible proeutectoid constituent, the second phase must be nucleated very soon after the first. If cementite is the first phase to form, the time to nucleate pearlite will be approximately equal to the time to nucleate cementite. Since the nucleation rate of a phase precipitating from solid solution increases with the degree of supersaturation, it would be expected that the rate of pearlite nucleation should increase with increasing carbon content. Digges10 has shown that the reverse is true. He determined the quenching velocity necessary to suppress pearlite formation in plain carbon steels as a function of carbon content. His results showed that pearlite formation could be suppressed with lower quenching velocities as the carbon content of the steel increased, at least up to 1.25 pct C, the highest carbon content he studied. Thus, it would appear that in plain carbon steels, in which pearlite is formed at the nose of the C-curve, the hypothesis that cementite nucleates first does not predict the observed change in nucleation rate. The validity of the current model of pearlite nucleation may be tested also by determining whether or not it predicts the relative influence of alloying elements on the nucleation of ferrite and pearlite. This can be done best by a consideration of the changes in a TTT diagram produced by a change in alloy content. Hultgren4 suggests that the general shape of a TTT diagram, as well as what constituents will form from austenite, can be predicted from the relative nucleation rates of ferrite and cementite. This is illustrated in the schematic diagram for a hypoeutectoid low alloy or plain carbon steel shown in Fig. 1. The C-curves for ferrite nucleation and for cementite nucleation are represented by AA' and CC', respectively, and the start of ferrite formation and pearlite formation are represented by AX and BC respectively. Adopting the current theory, Hultgren suggests that between X and C pearlite forms directly from austenite, since cementite nucleates more rapidly than ferrite in this temperature range. Conversely, at temperatures above Tx, ferrite is the first to nucleate and proeutectoid ferrite is formed. As proeutectoid ferrite grows, austenite becomes enriched in carbon, so that the cementite nucleation rate is increased. As a result, pearlite nucleation above temperature Tx is accelerated, beginning along BX and not along C'X. Temperature T, represents the temperature at which the nucleation rate of ferrite equals that of cementite. By extending this type of reasoning, using the principle that the nucleation rates of ferrite and cementite increase with increasing supersaturation of austenite with respect to these phases, it should be possible to predict the influence of carbon content on the shape of the isothermal transformation diagram. For a slightly higher carbon content than that of Fig. 1, the curve A A' representing the beginning of ferrite formation should be moved to the right, whereas the curve CC' representing the beginning of cementite formation should be moved to the left. For hypoeutectoid plain carbon and low alloy steels, this prediction does not agree with existing data. Instead, as the carbon content is increased, the pearlite curve moves to the right along with the ferrite curve and always appears to join it tangen-tially. This behavior is demonstrated by the TTT-curves of a series of manganese steels" shown in Fig. 2. In this figure, TTT-curves for four alloys containing 0.20, 0.40, 0.60, and 1.20 pct C are superimposed. The curves are identified in the figure legend. The letters F, P, and C are used to indicate the start of ferrite, pearlite, and cementite formation, respectively. In these steels, it appears that the nucleation of ferrite and of pearlite are related processes. As a result of the foregoing evidence, it is proposed that the formation of pearlite be considered as follows: Either ferrite or cementite may nucleate from austenite, then grow until the remaining phase is nucleated at the interface between the growing phase and austenite. (The growth of the first phase to form is assumed to be accompanied by a composition change in the adjoining austenite.) According to this model there are two modes of nucleating pearlite: 1—where cementite initiates the succession

Jan 1, 1955

By C. P. Haller, S. J. Aresco, R. F. Abernethy

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash- softening temperature of ash, the free-swelling index, and the hardgrove grind- ability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instruc- tions issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the con- tractor and, if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal. The Government purchased approximately 5-1/4 million tons of coal in fiscal year 1953. In connection with these purchases, the Bureau analyzed 11,435 samples. These are published for the use of Government officials and the public. A series of publications has been completed on coal analyses by States, or, where production is small in any one State, by groups of adjacent States. In addition to analytical data showing composition and quality of coals of the States, the publications con- tain brief descriptions of the geological structure of the coal basins, typical mining conditions in the various districts, the principal economic data of the industry, and the relationship of mine or channel samples to delivered and tipple samples. The present publication covers many States but deals only with the analytical data of the coals. Previous publications in this series are: Bulletin 516, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Years 1948 to 1950 Inclusive); Report of Investigations 4934, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1951); Report of In- vestigations 4972, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1952). Following are the Bureau of Mines technical papers published by States, with their numbers: Alabama, 347; Alaska, 682; Arizona, California, Idaho, Nevada, and Oregon, 696; Arkansas, 416; Colorado, 574; Illinois, 641; Indiana, 417; Iowa, 269 and 706; Kansas, 455; Kentucky, 308 and 652; Maryland, 465; Michigan, North Dakota, South Dakota, and Texas, 700; Missouri, 366; Montana, 529; New Mexico, 569; Ohio 344 (and Bulletin 499); Oklahoma, 411; Pennsylvania Bituminous, 590 (Supplement 645); Pennsylvania Anthracite, 659; Tennessee, 356 and 671; Utah, 345; Virginia, 365 and 656; Washington, 491 (Supplement 618); West Virginia, 405 and 626; and Wyoming, 484.

Jan 1, 1955

By B. K. Shibler, I. S. Solet, H. W. St. Clair

"This study was undertaken to provide a more adequate knowledge of the chemistry of the sulfide volatilization process for recovery of tin from low-grade Bolivian ores. The investigation was partly supported by the Department of State under its program for scientific cooperation with South American republics.The results of this investigation demonstrate the conditions under which cassiterite (Sn02) may be converted to stannous sulfide by reaction with pyrite or sulfur vapor. Quantitative data are given on the rate of sulfidization and on the vapor pressure of stannous sulfide.INTRODUCTIONAlthough the United States is the world's largest consumer of tin, virtually no tin ores occur within our national borders. Most of the world's tin supply comes from alluvial deposits in the Far East and in Africa, The major sources of tin ores are Malaya, Indochina, Bolivia, Belgian Congo, Nigeria, Thailand, Burma, China, and the United Kingdom. Bolivia is the only important source of tin in the western hemisphere. It was the chief source of tin f or the United States during World War II. The Government-owned tin smelter at Texas City, Tex., was built primarily for smelting Bolivian ores and depends largely on Bolivian ores for its operation. Bolivia is the only major tin-producing country in which the tin ores occur as vein or lode deposits requiring underground mining. Most of the tin from the Far East and Africa is mined by dredges from alluvial or placer depos its. It is recovered as a high-grade concentrate of cassiterite relatively free from impurities. The tin minerals in the lode deposits are more intimately associated with other minerals and more difficult to separate into a clean concentrate. Furthermore, a large part of the tin in the original ore is lost during concentration. The ores as mined contain only a few percent of tin, so they must be milled to separate the gangue minerals and produce a concentrate containing 30 to 40 percent tin before they are shipped to the smelter. The losses of tin that occur during milling vary from 18 to 65 percent. The average recovery of tin from Bolivian ores is probably 50 to 60 percent."

Dec 1, 1954

By Agustín Arias

El presente artículo describe brevemente la historia, métodos de explotación, mecanización, energía eléctrica, las plantas de preconcentración y flotación y el consumo de reactivos de la compañía minera Milpo.

Nov 1, 1954

By S. Haapala

El presente artículo describe la geología general, formaciones, plegamientos y fracturación, geología económica, mineralogía y la mineralización (alteración, zoneamiento, controles de mineralización) de la mina Colquijirca.

Nov 1, 1954