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By E. J. Horwood

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

Jan 1, 1916

By A. Perry Thompson

Discussion of the paper of A. PERRY THOMPSON, presented at the San Francisco meeting, September, 1915, and printed 'in Bulletin No. 100, April, 1915, pp. 645 to 677. ARTHUR S. EAKLE, Berkeley, Cal.-At the old Morning Star mine in Alpine County, where large masses of enargite were found some years ago, I looked particularly for evidences of replacement of pyrite by the enargite. While I have not made a particular study of any of the specimens, I judge that the pyrite and enargite were precipitated together. They were both primarily in those rocks. Of course, by using Mr. Graton's method of determination we might possibly find a situation somewhat different, but I should say that the enargite is not replacing the pyrite, but was simply precipitated at the same time. The bodies occurred there within 50 ft. of the surface, so it is probably not a case of secondary enrichment. H. W. TURNER, San Francisco, Cal.-In the case where secondary chalcocite shows a crystalline structure and cleavage lines, what is the evidence of the secondary nature of it? C. F. TOLMAN, Stanford University, Cal.-You can find practically all the evidences we have discovered in the microscopic study of ores. You can find all stages in the process of replacement of earlier minerals, especially bornite, by chalcocite, from a stage, in which the process has but just started with only occasional fragments of chalcocite set in bornite, to a stage where remnants of bornite are set in chalcocite. The replacement may take place along the cleavage lines or along the crystallographic directions of the earlier mineral, or it may take place irregularly. In one type of replacement you may find in one spot a few cross-cutting veins, and in another spot the latter may be so enlarged that there remain only a few individual specks of the replaced mineral.

Jan 12, 1915

By E. P. Humphrey

The Lehigh Valley Coal Co. finished the rebuilding of its Drifton No. 2 breaker at Drifton, Pa., in the summer of 1917. The new construction comprises an addition and the complete remodeling of the old breaker. It is of interest to note that the old structure was the first iron breaker erected in the anthracite region. The Old Breaker This old breaker was built by the Cross Creek Coal Co., under the direction of the late Eckley B. Coxe, in 1888-89, and was fully described by him in the Transactions1. The columns were cast iron, 8, 10 and 12 in. square. The floors and partitions in pockets were cast-iron ribbed plates. The struts were cast iron of "H" section; the other members were of structural iron either rolled I-beams or built-up sections. The sizes of the rolled beams varied from 6 to 20 in. deep, while the built-up sections, made of plates and angles, varied from 6 to 63 in. in depth, so that there apparently was no rule to determine the type of section used. In the remodeling of the old structure, practically everything was taken down excepting the columns and roof, and such beams as were necessary for temporary construction purposes, and, therefore, a close inspection of the old structural members could be made and the effect of the acid water on them could be noted. The cast-iron members were but slightly attacked by the water, while the wrought-iron beams, in the wet places, were corroded almost to failure. The following are analyses of cast-iron, wrought-iron, and structural-steel samples taken from the old and the new structure.

Jan 1, 1918

By James J. Hanslovan

Stresses that damage coal mine trailing cables were investigated to obtain a quantified description of cable-stress locations, magnitudes, and frequency of occurrence. Stresses occurring in operating mining sections were measured and observed. Answers to questions that arose during the underground investigations were pursued under controlled conditions, both in the field and in the laboratory. Cable-handling suggestions that minimize or eliminate the stresses are summarized in the form of recommendations to mine operators.

Jan 1, 1979

By Y. C. Liu, G. A. Alers, S. S. Choi

In searching for an explanation for the obvious difference between the copper and the brass type of rolling texture, it is common practice to look for correlations with other properties. For example, there are obvious differences between copper and brass in the critical resolved shear stress, the extent of easy glide or stage I, and the amount of "overshooting)) during single-crystal deformation.' Also, the slip lines in copper are fine and wavy while those in brass are more coarse and better described as slip bands.' Since neutron irradiation is known to make these properties in copper change in such a way as to resemble brass,2'3 an excellent test for these possible correlations is to see whether neutron irradiation produces a corresponding change in the texture, i.e., whether irradiated copper develops a brass-type rolling texture. The experiment would also answer the more important question of whether or not lattice defects like those introduced by neutron irradiation have any effect on the development of rolling textures in fcc metals. Experimental studies using conventional X-ray pole figure techniques are inconvenient because the X-ray detection system must be modified to discriminate against the radioactivity which is induced in the specimen by the necessarily long exposure to neutrons. Nevertheless, some texture determinations have been

Jan 1, 1968

By W. B. Mather

The object of this paper is to record and interpret data collected during the examination of over 250 barite deposits in the Central Mineral District of Missouri. In the course of this study, the origin of the deposits, which the author believes to be hydrothermal, has been given particular attention. Economic barite deposits occur in two main areas in Missouri: (I) in the Washington County District of Southeast Missouri, from which over 90 pct of the state's production is derived; and (2) in the Central Mineral District, which includes portions of 15 counties in Central Missouri (Fig I). Barite in the smaller Washington County District is mined from widespread low grade, relatively shallow residual deposits, whereas in the Central District, it is mined

Jan 1, 1948

By W. B. Mather

The object of this paper is to record and interpret data collected during the examination of over 250 barite deposits in the Central Mineral District of Missouri. In the course of this study, the origin of the deposits, which the author believes to be hydrothermal, has been given particular attention. Economic barite deposits occur in two main areas in Missouri: (I) in the Washington County District of Southeast Missouri, from which over 90 pct of the state's production is derived; and (2) in the Central Mineral District, which includes portions of 15 counties in Central Missouri (Fig I). Barite in the smaller Washington County District is mined from widespread low grade, relatively shallow residual deposits, whereas in the Central District, it is mined

Jan 1, 1948

By R. W. Utley, J. Carr

The tremendous growth in grinding mill size and horsepower during the 70s demanded advancements in gear cutting technology and equipment for the 80s. A new standard in gear cutting machines is now used to generate-cut large open gear sets to over 12.2 m (40 ft) in diameter at an AGMA quality level much higher than the accepted levels a short five years ago. The precision of the resulting gear set assures maximum tooth contact with the resultant longer gear set life.

Jan 1, 1987

Discussion of the paper of Robert Franke, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1201 to 1205. ARTHUR 0. GATES, Lafayette, Ind. (communication to the Secretary*) :-In connection with the comparison of mechanical crushing efficiencies in Tables I and II of Mr. Franke's paper, I wish to suggest a somewhat simpler way of making this' comparison, based upon what the writer has called the "crushing-surface diagram," as published by him in the Engineering and Mining Journal for May 24, 1913. Such a diagram, based on the data given in Table II, is submitted herewith, Fig. 1, cumulative percentages being plotted as abscissas and reciprocals of diameters (theoretical mesh per inch). plotted as ordinates.. Such a diagram averages the diameters without calculation, and areas upon it are proportional to surface produced, and, in accordance with Rittinger's law, to energy spent on crushing alone.

Jan 11, 1913

The collapse of the I.T.C., the subsequent fall in the price of Tin, and the lifting of quotas saw the Renison concentrator resuming full seven- day operations at maximum capacity in 1985/86. Performance was sus- tained in terms of grade and recovery, and in some areas improved, over this period. A further challenge was declining head grades, and the need to treat higher proportions of less amenable ore types. The complexity of the flowsheet and the method of mining and ore handling predisposes the process to unstable operation, and solving this problem comprises a major component of the current development effort. The concentrator has an imbalance of capacity between processes, and excess in some areas is being adapted to enhance the capacity of others. Magnetic susceptibility of various minerals is being exploited to greater effect. Significant performance gains are achievable by improving exist- ing unit process efficiency, particularly in grinding, gravity processes and Cassiterite Flotation. This paper reviews the metallurgical developments, both recently implemented and planned for this year, which have contributed to main- taining Renison Limited in a competitive position in the post I.T.C. Tin industry.

Jan 1, 1988

By M. G. Karfakis

This paper examines the chimney occurrences in the Hanna Coal Field, Wyoming. Chimney caving is defined, previously proposed mechanisms involved in the development of a chimney are critically reviewed, and factors controlling chimney cave are identified. The main portion of this paper deals with the identification and characterization of chimney subsidence due to underground coal mining in the Hanna Mining District. In an attempt to characterize the subsidence, sink-hole occurrences are correlated with the depth of coal, thickness of mined-out beds, mining methods, nature of overburden, structural geology, and hydrology. Most sinkholes in the Hanna Basin appear to be conical in profile, with the apex upward. The average diameter is 15 meters (50 feet), with an average depth of 11 feet. Most have developed above an overburden of less than 61 meters (200 feet). The average mining height to width ratio is 5. Much of the chimney development is governed by the thickness and character of the overburden, the width and height of the mine opening, and the in situ state of stress.

Jan 1, 1986

By T. Nakao

Fujiwara quarry had been operated by the glory-hole benchcut mining system, but as it became difficult to meet expanding demand with this system, a central-shaft mobile crushing plant (MCP) system was introduced in 1979. This MCP is equipped with a hydraulic walking system manufactured for the first time in Japan. Central-shaft mining is now the common mining method of Japanese limestone quarries. With this method, crushing facilities are usually installed at the bottom of the shaft. But at the Fujiwara quarry, MCP was adopted and installed on the quarry surface. Many MCPs are operated in foreign countries, but few examples exist in Japan. Normally, Japanese limestone deposits lie in high mountain, obviously making it inconvenient for MCPs to walk in and around the quarry. This difficulty, however, was overcome, and the MCP has operated satisfactorily and efficiently for two years since its installation. To overcome difficulties in the central-shaft MCP mining system, two mining methods are employed: the slice-down method and the block-cut method.

Jan 1, 1985

By M. Charles Gilbert

Basement rocks in southern Oklahoma are divided into two groups. One group is the Lower Cambrian Wichita Igneous Province, a diverse igneous suite that crops out in the western Arbuckle Mountains and in the Wichita Mountains. These largely bimodal igneous rocks were emplaced in an intracratonic-rift environment. The other group, the older, is a set of Precambrian rocks of the Eastern Arbuckle Province, yielding ages between 1,350 and 1,400 Ma, exposed in the core of the eastern Arbuckle Mountains. These are deeply eroded mesozonal granitic rocks and associated granitic gneisses cut by numerous dikes ranging in composition from diabase to rhyolite. The southern Oklahoma igneous rocks have long been utilized mostly as dimension and crushed stone. Most of the early quarries were in granite of various red hues for monuments and facing stones. Large crushed-stone quarries are now exploiting both granite and rhyolite, which is used chiefly as aggregate and railroad ballast. The exposed basement rocks in Oklahoma represent an underdeveloped and accessible resource.

Jan 1, 1999

By Paul H. Price, John P. Nolting

The history of the salt industry in West Virginia dates back nearly two hundred years; howTever, the history of salt as an important raw material for the chemical industry is much more recent. The earliest record of West Virginia salt was in 1753, when a raiding party of Shawnee Indians attacked frontier settlements in Virginia taking captive a number of the pioneers. One of these, who later escaped and returned to her friends, described how the Indians camped at a salt spring on the banks of the Kanawha River and evaporated the water to obtain a supply of salt to take back to Ohio with them. Settlement of the Kanawha Valley began in 1774, that same year the Battle of Point Pleasant ended the Indian's power in the Ohio Valley; and settlement of the Kanawha Valley progressed rapidly with a consequent increase in the importance of the Kanawha Licks as a source of salt. In those days the evaporation of the brine was a family matter for which the family wash-kettle was commandeered. In 1797, Elisha Brooks erected the first salt furnace in the Kanawha Valley. It consisted of two dozen small kettles set in a double row, with a flue beneath, a chimney at one end, and a fire bed at the other. He obtained his brine at a depth of 20 to 30 ft by sinking hollow logs, called "gums" into the salt lick and dipping the brine with a bucket. His production was about 150 lb a day and sold for 8 to 10 cents a pound. In 1806, the Ruffner brothers, David and Joseph, prospected for and drilled the first well in America using a spring pole and steel chisel bit. After several failures they succeeded, in 1808, in drilling to a total depth of 59 ft where they secured a good flow of strong brine. Most standard drilling tools, jars, casing, and practically all the basic oil well drilling machinery now in use, were developed in the drilling of salt wells. To evaporate this brine, the brothers built a wood-burning furnace similar to that of Brooks but with a better arrangement and with more and larger kettles. When production was started they reduced the price of salt to 4 cents a pound. By 1817, there were some 30 salt furnaces in the Kanawha area. It was in this year that bituminous coal first was used as an industrial fuel. David Ruffner again pioneered the way by converting his furnace for the consumption of coal. This year also brought about the formation of the first trust which controlled production and set a price of 1 cent a pound for the salt.

Jan 1, 1950

By S. F. Ravitz, S. R. Zimmerely

High-grade cobalt concentrates were produced from the complex Blackbird ore with very good recovery in continuous pilot-plant operations in which a low-grade bulk cobaltite-pyrite flotation concentrate was roasted in a multiple-hearth furnace to oxidize the pyrite selectively. The cobaltite was floated from the resulting calcine.

Jan 10, 1950

By R. H. Doremus

From measurements of carbide precipitation rates in a iron it was concluded that the carbides nucleated on dislocations in both strained and unstrained samples, except for the latter at lower temperatures and higher carbon concentrations, where there were more muclei than could form on the dislocations. The equation of Cottrell and Bilby for the segregation of atoms to dislocations was found to be inapplicable to this system. No satisfactory theory for the growth process is available. A study of the rate at which a second phase separates from solid solution can frequently reveal much about the mechanism of separation. There are still many features of the precipitation of carbon from a iron that are not understood, although this system has been examined extensively. To provide more insight into the mechanism of carbide precipitation in a iron, rates of this process were measured at different temperatures, carbon concentrations, and densities of dislocations in the iron. The concentra- tion of carbon in solution was followed from the height of the internal-friction peak; this height is directly proportional to the amount of carbon in solution and is not affected by the growing carbide particles. In this paper these rates are compared with those found by earlier investigators, and the mechanism of precipitation is discussed in light of these results as well as two earlier studies1, 2 and the electron microscopic work reported in the preceding paper. EXPERIMENTAL The amount of carbon in solution was followed by

Jan 1, 1961

By Graham M

Longwall mining has been the dominant global coal mining method for decades. However, not until 1994 did longwall mining surpass continuous miner room and pillar extraction tonnage in the United States. This significant event, occurring in the most cost driven market in the world, confirms the efficiency and effectiveness of longwall mining.

Jan 1, 1998

By Rick Deschamps

A reoccurring problem with support of excavations in urban areas involves the placement of external support components like anchors or nails in right-a-ways, subway and utility setbacks, in areas occupied by adjacent structures, and within the property of non cooperative neighbors. Such a situation occurred for a project in Arlington, Virginia, which ultimately resulted in the preliminary design of a large footing supported cantilever retaining wall that was extremely costly and impractical to build. An innovative design alternate consisting of a series of vertical concrete elements (VCEs) supported by post tensioned tiedowns was proposed to the General Contractor and accepted by the owner. The VCEs were designed to serve as the main structural elements for both the temporary support of excavation system and the permanent wall. The VCE?s were constructed using single bite diaphragm wall panels oriented perpendicular to the excavation face including a rebar cage and tremie concrete. Threaded inserts were placed within the rebar cage to attach the cast in place exterior wall. Overall stability and lateral movement of the VCEs were controlled by high capacity vertical anchors embedded within the VCE. A detailed instrumentation program was installed to monitor the movements of the VCEs with relation to the excavation depth. The paper present the project case history by discussing the design concepts of the VCE, the construction approaches used to install them, the construction challenges encountered, and the performance of the unique system.

Jan 1, 2008

By J. A. Elias, R. H. Heyer, J. H. Smith

Plastic anisotropy determined by the ratio of width strain to thickness strain in tensile specimens of low-carbon steels is strongly related to crystallographic preferred orientation. Using(222) Pole figures, a method was developed which permits rapid Predictions of plastic anisotropy for any crystallographic texture or orientation. The method is applied to low-carbon steel sheets in which four different crystallographic orientations were produced by variations in cold rolling and annealing treatments. AnISOTROPIC behavior of metal sheets during plastic deformation has long been evident. A familiar example is earing in cup type draws. During tension testing of sheet specimens, anisotropy results in a difference in width strain as compared with thickness strain. Carpenter and Elam1 observed this phenomenon in single crystals of aluminum for both sheet and rod samples. Lankford, Snyder, and Bauscher2 made tension tests on sheet samples of aluminum-killed low-carbon steel to determine the ratio of the width-to-thickness strains, and showed that this ratio was related to drawing performance. Burns and Heyer3 calculated theoretical ratios of width strain to thickness strain for two specific orientations of the bee system, using <111> as the operative slip direction. These calculated values were in fairly good agreement with the ratios determined by tension tests of low-carbon steel sheets in which these preferred orientations existed. The high degree of plastic anisotropy of silicon steel sheets could also be predicted from their crystallographic structure by these calculations. The present study has been made to show that the anisotropy observed in plastic tensile straining is strongly orientation dependent and can be adequately predicted for many orientations and textures. PLASTIC STRAIN RATIO R In the region of uniform elongation of a tension test specimen the plastic deformation may proceed at different rates in the width and thickness directions. Such anisotropy has been described in the past by the plastic strain ratioR:

Jan 1, 1962

By Laurence E. Snow

The conversion to the use of commercial grade ammonium nitrate (CGAN) for use in blasting at the Utah Copper Pit of the Kennecott Copper Corporation has presented unique problems for the Drilling and Blasting Department, In order to better understand these problems, a&apos; picture of the Bingham Pit might be helpful. Some quarter of a million tons of ore and waste must be blasted daily in order to keep thirty-eight electric shovels operating. All material is blasted by "toe holes" of 24 to 28 feet in depth, drilled from prepared drill grades and sloped so as to bottom approximately 5 feet below the bench level. Horizontal spacing of these holes averages 22 feet, with exceptions being made where faults occur in the bank. These "toe holes" are drilled by 4-inch drifter machines, mounted on self-contained mobile drill units using .3-inch starter bits and bottoming at a minimum of 2 1/2 inches in diameter, "Toe-hole" drilling amounts to about two-thirds of the total drilling. In the higher bank sections of the Mine and wherever necessary, single rows of "down holes" are drilled to 28 feet in depth and spaced, on the average 23 feet apart. These holes are also drilled by a mobile drill. "Down hole" drilling amounts to about one-third of the total drilling.

Jan 1, 1959