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By Howard Lee

I. GEOLOGY AND ORE OCCURRENCE IN central Colorado is a great belt of intrusive porphyry nearly 100 miles long (160 km.), extending from the Clear Creek district on the north to Aspen on the south, which includes many of the well known mining camps of the State. Near the southern end of this belt, at Leadville, the occurrence of these intrusives is most marked, resulting in intensive mineralization and the formation of a great variety of large orebodies. During the past 40 years, Leadville has been a steady producer of gold, silver, lead, zinc, manganese, iron, and bismuth, in the forms of sulfid, carbonate and oxide ores. It is the purpose of this paper to discuss pyrite alone, which, under present economic conditions, is valuable chiefly for its sulphur contents. The ore-bearing formation of the Leadville district consists of two beds of limestone separated by a layer of quartzite. The upper limestone is carbonaceous, and is known locally as the blue limestone. It varies in thickness from 50 to 300 ft. (15 to 91 m.). The lower limestone is Silurian, known locally as white limestone, and is about the same thickness as the upper bed. Underneath the Silurian limestone is a layer of Cambrian quartzite front 100 to 250 ft. (30 to 76 in.) thick resting on Archean granite, which forms the limit of ore deposition. As a rule, there is a sheet of white porphyry above the upper, or blue limestone; a sheet of gray porphyry is associated with the blue limestone, either in or below it, but the porphyries are not so regular as the quartzites and limestones and are not always found in their expected positions. Throughout the district there is an elaborate system of faults and intrusive porphyry dikes, which have all important bearing on ore deposits. The writer has seen two or three orebodies which were not closely associated with either a fault or a porphyry dike, but if the minor fractures and water courses are considered as part of the fault system it is safe to say that all orebodies are directly traceable to one or both of these causes.

Jan 8, 1918

By D. S. Kingery, D. W. Mitchell

Experience in Europe indicates that the control of dust production and dissemination by water or foam systems is not successful except during undercutting. Cybulski, Dawes, and DeBraaf-respectively Director, Mines Research Establishment "Barbara", Katowice, Poland; Principal Scientific Officer, Safety in Mines Research Establishment, Sheffield, England: and Chief, Central Mines Research Establishment, Hoensbroek, Treebeek, The Netherlands-believe that wetted dust becomes readily dispersible and abatement measures should be considered only as a temporary means for reducing the health hazard. In an effort to reduce the health hazard, calcium chloride is used on the floor of main haulageways in Dutch mines and water infusion is practiced in Germany in mines where the coal is relatively porous. With respect to wet coal dust, the Belgians, British, Dutch, French, and Russians reportedly have accepted the results of research from the Polish and American experimental mines on the effectiveness of water as an inert in arresting explosion propagation. The Polish use the two test methods proposed by the U.S. Bureau of Mines for evaluation of the adequacy of wetness of mine dust; they require that water be added to the wet dust to maintain a minimum of 50% moisture by weight if dependence is placed on water alone.

Jan 7, 1964

By J. J. Bodmer

In 1855, Franz Uchatius patented, in England, his process of manufacturing cast steel. The first experiments, on a practical scale, were made at the Ebbw Vale Iron Works, Monmouthshire. The charge consisted of a mixture of cast iron with about 20 per cent. of a pure iron ore, and with or without other ingredients. In order to obtain the cast iron in a subdivided condition, Uchatius granulated molten pig-metal by running it into water, which during the operation was kept well agitated, and found that "the finer the iron is granulated, the softer will be the resulting steel." The writer is not aware that granulated iron has been used practically, otherwise than in the above-named process; and until 1866 no other process of subdividing iron than by granulation was known. In April, 1866, an English patent was obtained by the writer for subdividing blast-furnace and other slags and metals in a molten condition, by passing the same through one or more pairs of rolls. In reference to iron the idea was, in following up the direction pointed out by the Uchatius process, to obtain better results in the puddling process by means of a thorough amalgamation (not simply a mixture) of the iron with the oxides and other ingredients in the charge itself. Experiments were made. A quantity of iron direct from the blastfurnace was subdivided (or laminated) by passing it through a pair of plain rolls. The rolls were hollow, and water was made to pass through them to keep them sufficiently cool. Without giving differential speed to the rolls, sheets were obtained about one-sixteenth inches thick, and from about one hundred square inches surface, downwards. With differential speed, the iron falls from the rolls in

By Harry Huntington Miller

In spite of its recognized irregularities, the cyanide-assay for copper has always been popular among volumetric methods, being easy and rapid, and reasonably accurate when the solution tested contains nothing but pure copper and ammonium salts. In order to secure this condition, however, especially in operati~ig on low-grade ores, tailings and slags of complex composition, it is the practice to precipitate the copper from the ore-solution,—usually by means of metallic zinc or aluminum. The copper thus precipitated in the metallic form must be dissolved again; and the separa tion is never, in practice, complete, since an appreciable amount of the copper remains behind in the first solution, and the second solution always contains some of the other metals of the gangue; so that the result is at best but partially satisfactory. On the other hand, if this course is not pursued, but (as is

Jan 1, 1902

By E. T. Turkdogan

In this theoretical paper, a transport-reaction mechanism is suggested for the enhancement of the rate of vaporization of metals, or other materials, brought about by the process of convection and condensation. Based on theoretical reasoning it is predicted that, when there is a temperature gradient surrounding the heated object, a slight increase in the rate of vaporization brought about by natural convection is enhanced further as a result of condensation of the vapor close to the surface of the object. In order to derive the effective vapor-concentration profile, consideration is given to the super saturation of the vapor necessary for the homogeneous nucleation of the condensed phase from the vapor. For the formulation of the rate equation based on this mechanism, adequate information should be available on the transport properties of gases and vapors at elevated temperatures and the method of calculating nucleation pressures of the vapor. The methods of deriving such data are discussed in the paper and a rate equation is calculated for the vaporization of iron in helium for various temperature gradients in the boundary layer. Considerations are also given to the effect of oxygen on rates of vaporization of metals under isother ma1 and nonisotherma1 conditions. THE study of the methods of enhancement or retardation of basically transport-controlled vaporization reactions is of theoretical interest with possible practical implications. There are several ways of bringing about such effects. For example, Turk-dogan, Grieveson, and Darken1 demonstrated that the rates of vaporization of metals under isothermal conditions were increased by several orders of magnitude, up to the maximum rate attainable in vacuo, by introducing some reacting gas into the inert atmosphere surrounding the metal. Such an effect is brought about by the interaction of the counter-diffusing reacting gas and metal vapor in close proximity of the metal-gas interface. Another case which is often experienced in practice is that of vaporization affected by natural convection. Although several theoretical and experimental studies of this problem have already been made, no detailed consideration has been given to the possible effects of condensation of the vapor in the boundary layer on vaporization rates, which constitutes the subject matter of this paper. BASIC CONCEPT OF ENHANCED DIFFUSION-LIMITED VAPORIZATION When a heated object, for example a metal sphere, is submerged in a fluid medium, heat is transferred from the surface of the object to its surroundings by four simultaneously occurring transfer processes: i) free-molecular conduction at the gas-solid interface over the distance equal to the mean free path of the gas, ii) conduction and convection through the fluid-dynamic boundary layer, iii) latent heat of mass transferred, and it!) radiation. The free-molecular conduction becomes pronounced only when the total pressure in the system is very low, e.g., below 1 mm Hg. Therefore, this term may be neglected for ordinary pressures. At low mass-transfer rates, due to vaporization of the object, the contribution of process iii) to the heat transfer can also be neglected. Finally, since the temperature profile is not affected by radiation, the latter need not be considered. The natural convection is brought about by gravitational body forces arising from a decrease in the

Jan 1, 1964

By A. F. Daily

Free World consumption of diamonds of all types closely follows the fluctuations of the business cycles in the large industrialized countries, particularly the U.S. Sustained purchasing by this country for stockpiling purposes has been a major factor in Free World demand for crushing bort and industrial diamonds, and it has been for this reason that investments in larger plants have been made by all major diamond mining companies during the past few years. For the purposes of this study, the diamonds produced in the Congo and elsewhere in the Free World are divided into three types:

Jan 5, 1961

By AIME AIME

FOR constructive research in copper and brass and other non-ferrous metals and their alloys, and his contributions to the establishment of the present accepted high standards of quality William H. Bassett, technical superintendent and metallurgist of the American Brass Co., has been awarded the James Douglas Gold Medal for 1925. Mr. Bassett was born in New Bedford, Mass., on March 7, 1868, and was graduated in chemistry at the - Massachusetts Institute of Technology in 1891. In the same year he went to Pope's Island Manufacturing Co., at New Bedford, as chemist where he remained until 1895, where he became a teacher in chemistry at the Swain Free School, which position he retained until 1900. He then became chemist for the New Jersey Zinc Co., at Newark N. J., and in 1902 went to the Coe Brass branch at Torrington, Conn., as Chemist. In 1903 he became chief chemist and metallurgist and since 1912 has been technical superintendent and metallurgist of the American Brass Co., with head- quarters at Waterbury, Conn.

Jan 1, 1924

Kaolin deposits in Georgia lie in a belt that stretches across the central part of the state from Alabama to South Carolina. In 1977 the state's kaolin production was an estimated 4.58 million tons (5.05 million st) or 77% of US production. While mining methods vary, stripping contractor W. F. (Billy) Jackson of Wrightsville, Ga., depends on a fleet of 18 twin-engine elevating scrapers to move the hulk of overburden and clay. Owner Billy Jackson explains that the soil in this part of the state is perfect for scraper operation; overburden ranges from Georgia red clay to a sandy gumbo material. Apart from some shale, very little rock is encountered, thus eliminating any blasting re¬quirement. Most of the material can be removed with cutting edge teeth or with drop center blades.

Jan 6, 1978

By John Garcia

IN some districts of the bituminous coal field the problem of construct-ing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it-is felt that a description, of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. As far as the writers know, these three mines are the only ones in the bitu-minous coal fields of the United States with anything like so large number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it.

Jan 1, 1937

By W. G. Scott

SINCE devising the incline top-slicing method in use It the Coronado mine,1 I have had numerous inquiries is to how the same system could be adapted to larger orebodies. Based upon our experience here, 1 have outlined below some suggestions for its, application to orebodies of larger size. Modifications and extensions, of course, would have to be made to take care of different dimensions and irregularities. In order that one may have a better understanding of the scheme, a brief description of the Coronado method will he given first.

Jan 11, 1917

By C. W. Tomlinson

The analyses which have been made by the writer according to the method described below were made as part of Professor Withey's investigation of the concrete aggregates1 of Wisconsin, in the hope of throwing light on the extent and nature of the influence of the mineral-ogical constitution of aggregates upon the properties of the concrete and mortar made from them. This method was found most satisfactory after four weeks of experiment and modification. It attains an accuracy quite sufficient for the purpose of the analysis, and is fairly rapid. mineralogical analyses may be thus made at a cost considerably less than that of chemical analyses of a similar degree of completeness. The results obtained by this method should not vary in any item by more than 1 per cent. of the total weight of the sample, and may be made very much better than this by the exercise of greater care in the microscopic counting (see below). The accuracy of the hand sorting is of course dependent upon the experience and carefulness of the analyst. After a month's practice, the writer was enabled to turn out these analyses at the rate of four in 33 hr. of working time. It was found most economical to handle four samples at once. The samples analyzed weighed from 290 to 340 g. each. The same method could be applied to larger or to smaller samples, within reasonable limits. The following list covers the necessary apparatus and equipment: 1 good balance capable of weighing accurately to tenths (or, better, hun- dredths) of a gram, and of handling quantities up to 200 g. in weight. 1 Westphal balance, registering densities to two or three decimal places. 1 Meker or Bunsen burner, and gas supply. 1 nest of sieves, 10, 20, 40, and 100 meshes to the inch.

Jan 1, 1916

Although the Suggestions to Institute Authors, as revised and amplified over the years to meet changing conditions and experience, have had as their primary objective the guidance of the author who is preparing a paper for record in the TRANSACTIONS, there are in this current version many excellent suggestions for the preparation of any material for publication by the Institute In this connection it should be emphasized that in a sense, and to a degree determined by the editors, the Institute has in its journals "a place for everything," especially a place for the article of practical nature that is of immediate but not necessarily permanent interest Such articles may be referred by the Institute Technical Publications Committee to the editors or submitted directly to them , [Papers (TECHNICAL PUBLICATIONS and TECHNICAL NOTES) authorized for the TRANSACTIONS are, with the discussion, gathered together at the end of the calendar year and with a table of contents and index, bound, according to Branch classification, as volumes of the TRANSACTIONS

Jan 1, 1952

By A. M. Crawford

INTRODUCTION Grouting is an engineering operation which has been practiced for many years and a considerable amount of experience and skill has been developed in this field. However, a review of the current literature (Houlsby, 1982) reveals that the theoretical background and experimental observations that are necessary to adequately predict or describe the performance of a particulate grout (e.g. cement based) in a jointed geologic media are somewhat inadequate. In the near future it is envisaged that the use of grout and grouting techiques will be used to tackle even more difficult problems than have been considered in the past. One problem that is currently being faced by the rock mechanics engineer is the development of geologic repositories for the disposal and containment of high level radioactive waste. In such structures there will be only one opportunity to ensure the success of the containment system. This success will depend to a large extent on the adequate and successful performance of the grout curtains to be utilized around the shafts and shaft liners. Regrouting will not be possible. There are other problems in rock mechanics in which it is frequently necessary to inject particulate media into passages of small dimensions, and where typically the size of fracture being injected is of the same order of magnitude as the particle dimension. For example, in the oil industry in hydraulic fracturing the enhancement of fracture conductivity is maintained by means of proppants introduced into the fracture.

Jan 1, 1984

Manganese ore from the Black Rock, Kramer, and Black Jack mines in Tooele and Jaub Counties, Utah, are of acceptable grade, the U. S. Bureau of Mines has announced. Payment of a premium price of 252¢ per lb to the Copper Range Co., of Michigan for the output of its White Pine mine, has been agreed to by the DMPA. The contract will be limited to $28.6 million worth of copper. The agreement follows an RFC loan grant of $57 million to bring the White Pine property into production within three years. Increases of 5 to 6 cents over the Lake copper ceilings have been granted to the Calumet & Helca Consolidated Copper Co., for operation of "high cost" deposits, according to Jess Larson, DMPA administrator. Mr. Larson expects the move to add about one million lb of copper per month to the supply. The agreement can be cancelled on 60 days notice and is terminated automatically in the event copper ceilings are removed.

Jan 1, 1952

By Mason K. Banks

A process has been developed which produces spodumene concentrates assaying 6.0 pct Li20 and 0.45 pct Fe203, with 70 to 75 pct recovery of spodumene. Two flotation separations are required: the simultaneous removal of mica, feldspar, and quartz as a froth product using a cationic collector, and the subsequent removal of iron-bearing minerals as a froth product while spodumene is depressed as a tailing.

Jan 2, 1953

By P. Campbell, E. M. Gardy, L. Hachkowski

Introduction The efficient process control of a uranium mill and its associated mining operation requires a nearly continuous knowledge of the uranium concentration in the ore. Generally, the approach is to use laboratory assays of grab samples from the mill feed belt. In some cases, elaborate and expensive systems have been used to ensure random sampling, but even with these systems, mass-balance discrepancies still exist. There is a requirement for an on-line instrument that can give a prompt, accurate analysis of a large portion of the feed stock. The authors have recently evaluated a laboratory system that achieves these goals using neutron activation and delayed neutron counting. The development of the on-line uranium ore analyzer is a consequence of previous work done at the Whiteshell Nuclear Research Establishment (WNRE) (Campbell et al., 1978 and 1981), and is based on the emission of delayed neutrons after the neutron irradiation of fissionable materials. The mechanism of delayed neutron emission has been described (Keepin, 1965), but briefly is as follows. The fission fragments resulting from irradiation are in an excited state. Certain of these delayed fission products, precursors, decay to a more stable state by the emission of a delayed neutron. The delayed neutrons can be divided into six groups with effective half-lives ranging from 0.2-55 sec. It is important to note that more than 50% of the delayed neutrons are emitted within the first 6 sec after irradiation; this has an influence on the design of the analysis instrument. Measurement Cycle The measurement cycle involves a neutron irradiation, a delay time, and a counting period. The laboratory demonstration model of the ore analyzer comprises a californium-252 neutron source, a source chamber, a pneumatic transfer facility, and a neutron irradiation and counting module [(Fig. 1)]. The ore sample is placed in the irradiation chamber. The neutron source is transferred to the center of the chamber for a 5-sec irradiation while the helium-3 thermal neutron detectors are switched off. As the source returns to the storage chamber, the detectors are switched on and the delayed neutrons counted. The total assay cycle is 16 sec. The current instrument design calls for the ore to be cut from the main belt every 16 sec by a mechanical arm and dropped into the analyzer directly, or via another belt. The cycle starts when there is a sufficient mass of ore in the irradiation chamber to depress a switch and stops when the delayed neutron count is finished. The ore is then dropped through the bottom of the analyzer chamber and returned to the main belt. The counts from each cycle are accumulated and the data reduced to give the desired information.

Jan 1, 1985

By R. Maddin, C. H. Mathewson, W. R. Hibbard

Recent publicationsl.2 establishing the presence of cross-slip in strained metallic single crystals oriented wholly within the area of single slip as predicted from the generalizations of Taylor and Elam3 described these markings as they appeared during the initial stages of the deformation process. At that time, the plane having a common glide direction with the primary slipping plane was reported as the cross-slip plane although the specific direction was not confirmed. Consequently, in continuation of the research, it seemed advisable to investigate the micro-graphic appearance of cross-slip together with the Laue back-reflection X ray analysis and stress-strain data during the later stages of the deformation process. Accordingly, a single crystal of brass (72.75 pct Cu, 0.01 pct Fe, 0.01 pct Pb, 27.23 pct Zn) was polished mechanically and repolished electrolytically after the manner described in the earlier paper.' Three pairs of flat surfaces, parallel to the specimen axis, and (1) perpendicular to the plane containing the pole of the primary glide plane and the specimen axis, (2) perpendicular to the plane containing the pole of the cross-slip plane and the specimen axis, and (3) perpendicular to the plane containing the slip direction and the specimen axis, were polished mechanically and repolished electrolytically, resulting in a final minimum gauge diameter of 0.4864 in. in a gauge length of 3.36 in. The specimen was elongated in tension and load-extension readings were taken following the method described in the initial investigation.' Observed reorientations were obtained from a series of Laue back-reflection photograms at the center and ends of the gauge length and at various positions around the circumference of the specimen. These were interpreted after the manner of A. B. Greninger.4 Cross-slip (Fig 1 and 2) was found with the first appearance of the primary slip clusters and usually joined members of these clusters. In addition, a third set of entirely different markings (Fig 3) could be noted. The displacement of this third set by the primary slip lines was measured as 8300 at. diam (3.04 microns). Since the specimen was carefully observed at high magnifications before any deformation and no markings of any type could be noted, it would appear that this third set was formed during the deformation process prior to the initiation of classical primary slip. Additional extensions produced no unusual change in the appearance of either cross-slip or the third set of markings. The number of lines increased with increasing elongation and appeared, generally, in areas where earlier markings were present. The continuity of the clusters of cross-slip lines in Fig 4, 5 and 6 illustrates that they are neither noticeably displaced by nor do they displace the primary lines at this stage. In Fig 7, cross-slip appears in a long narrow localized band approximately 45 degrees from the stress axis. This somewhat resembles a twin band except for the lack of a sharp boundary. After a shear of 0.257, suffcient additional glide occurred on the cross-slip plane to displace the primary slip lines (Fig 8). Generally, where a large number of cross-slip lines could be observed in an area on one flat surface, few cross-slip lines appeared on the diametrically opposite position on the parallel flat (Fig 9). These, of course, were not matched observations on the same glide ellipses. It was extremely difficult to make such comparisons. The third set of markings (Fig 10) was extensively displaced by glide on the primary slip planes. A plot of the width of primary slip clusters versus their displacement of the third set of lines is shown in Fig 11. The slope and the linearity of the plot suggest that each primary glide plane slips to a constant maximum value of shear before further slip is transferred to another plane. A shear value of 0.28 was determined in this case. Heidenreich5 has presented a similar schematic representation of glide for aluminum. After the specimen had attained an elongation of 51.8 pct, corresponding to a shear of 0.973, cross-slip appeared very prominently in certain areas as shown in Fig 12, yet at diametrically opposite positions very little cross-slip could be noted, Fig 13. Classical conjugate slip was found at this advanced stage in the deformation, Fig 14, which corresponds to the axial location shown at 12 in Fig 15. It should be noted that cross-slip occurs within the conjugate slip clusters and on the same plane as the cross-slip associated with the closely spaced primary lines which constitute a background in less distinct focus. The third set of markings noted at all stages in the deformation of the

Jan 1, 1950

By S. K. Bradford

For years past I have traveled in quest of promising mining-properties, over almost impassable mountain-trails to remote places in the mining-regions, usually many miles from an assay-o5ce. If, upon examination, the fornlation and the ore-deposit appeared favorable, a quick determination of the value of my samples was necessary, in order that I might take intelligent action with reference to the acquisition of the property. A journey with my samples to civilized regions often meant weeks of delay, and perhaps loss of opportunity. How many, under similar circumstances, have returned with their assay-results from such a journey, only to find that some audacious speculator had optioned" the property! True, a first payment could have been made and the chances taken on the results; but experience has taught that rich-looking ore is not of necessity valuable. Personally, I would not hazard a ten-dollar bill on any property without first determining by assay the value of the ore. To carry the usual complete assay-paraphernalia over such mountain-trails was impracticable by reason of the loss of time involved, the great expense of transportation (charged -

Jan 1, 1911

By Gunnar Thaning, Goran Mathisson

The iron ores mined by LKAB in the north of Sweden have excellent beneficiation properties. This gives LKAB a favorable position as regards the production of low silica pellets for direct reduction. LKAB has concentrated on developing and marketing grades of pellets for the Midrex-Purofer-HyL process group, i. e., such direct reduction processes carried out in a shaft furnace or a static bed using reformed natural gas as a reducing agent. The paper deals with properties and quality demands of iron ore pellets for such processes. Matters such as the effect of the residual magnetite in the fired pellets on the degree of metallization, the amount and composition of the slag phase in the pellets, the mechanism of the disintegration during reduction, the state of swelling of the pellets during the conditions prevailing in these processes, the importance of the porosity, the improvement of the reducibility and lowering of the sticking tendency of the pellets by small additions of suitable additives, and the influence of the pellet size are discussed. A special test procedure for direct reduction pellets has been elaborated by LKAB. Thus, three metallurgical properties are routinely determined separately, namely reducibility, reduction strength, and sticking. The test methods are described. Finally the present and future LKAB pellets for direct reduction are presented with respect to chemical analyses and metallurgical properties.

Jan 1, 1980

For the year ending February, 1923 PRESIDENT ARTHUR S. DWIGHT, District 0 NEW YORK, N. Y. PAST PRESIDENTS HERBERT HOOVER, District 4 WASHINGTON, D. C. EDWIN LUDLOW, District 0 NEW YORK, N. Y. FIRST VICE-PRESIDENT J. V. W. REYNDERS NEW YORK, N. Y. TREASURER CHARLES F. RAND NEW YORK, N. Y. SECRETARY FREDERICK F. SHARPLESS,. . . . . NEW YORK, N. Y. ASSISTANT SECRETARY PERCY E. BARBOUR NEW YORK, N. Y.

Jan 7, 1922