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By F. J. Reichhardt

Abstract -The Molopo Farms Complex is a major, layered ultramafic/mafic, early Proterozoic intrusion which is totally covered by sediments of the Karoo and Kalahari Formations and situated in southern Botswana and northeastern South Africa. The approximately 3000 m thick, generally fine- to medium-grained ultramafic and mafic cumulates are intrusive into equivalents of Transvaal Supergroup sediments and lavas. Multiphase deformation resulted in tilting and segmentation of the Complex into individual tectonic blocks. Sr isotopes document at least two chemically distinct parental liquids which interacted in a complex manner to form an approximately 1000 m thick rhythmically layered succession which straddles the ultramafic/mafic boundary. Repeated mixing resulted in a complex cryptic layering pattern and numerous sulfide-enriched layers which contain significant PGE +Au concentrations.

Jan 1, 1994

With some notable exceptions, marine placers located just below, or just above, present sea level, are responsible for much of today's production of detrital ilmenite, rutile, zircon, and other minerals of value. The purpose of this paper is to discuss the paleogeographic and paleo-oceanographic factors which may have determined the location of presently submerged marine placers. These factors-include changes in sea level, burial by recent marine sediments, stream capture and other i changes in drainage patterns, and recent changes in climate. Selected geologic situations in the Yellow Sea off the coast of Korea, in the Atlantic Ocean off the coast of Portugal, in the Bering Sea off the coast of Alaska, and in the Arabian Sea off the coast of India, will be used to illustrate the author's point of view.

Jan 1, 1980

By Theodore B. Comstock

a. Boundaries of the District.—The district here considered comprises that portion of Colorado commonly known as " the San Juan Country." In order to bring the principal geological features of this region within the scope of a map of convenient dimensions upon a suitable scale, I have found it desirable to mark off boundaries near the parallels of 37O and 38O 10', and the meridiaus of 106' 30' and 108' 30' (West Longitude from Greenwich). This area of (approximately) 9400 square miles includes all the formations which we should have to discuss if our territory were greatly enlarged, excepting such as are distinctly characteristic of adjoining areas with independent orographic genesis. By limiting this review to these confines we miss very little of the geology of the eight counties of the San Juan region, viz.: Dolores, San Miguel, Ouray, Hinsdale,

Jan 1, 1887

By G Solly, S Parsons, P Leevers, S Ni

Hematite ore has been mined in the Southern Middleback Ranges as blast furnace feed for the steelworks at Whyalla, by what was then BHP, since 1991. With the floating of BHP Integrated Steel as OneSteel in 2001 and the subsequent loss of key mining personnel, breakdowns in grade control methods and procedures occurred. These were compounded by changes in orebody characteristics and grade distribution leading to poor reserve recovery and poor grade control, both which resulted in loss of control of ore specification and severe deviation from the mining schedule. As a result, a total review of grade control, mining method and scheduling procedures was undertaken as well as a review of contractor quality assurance. It was found that sampling methods were poor and unrepresentative, grade control blocking processes were outdated and did not reflect the geology of the deposit, the ore mining method was outdated and did not respect the geometry of the orebody, reconciliation methods were being completed globally and were not reflective of individual areas of the deposit, and that deviations from the mine plan were occurring due to access to high-grade areas outside the schedule in order to bring stockpiles back on grade. Based on these findings, updated sample splitter systems were fitted to drill hole rigs, double bench sampling was implemented (2 + 4 m samples as opposed to 1 + 8 m sample) and a three-dimensional cellular grade control system introduced to better reflect the geology and orientation of the deposit. At the same time ore mining was changed from front end loaders mining on 8 m benches to excavator mining on three lifts on 8 m benches; this aided selectivity and respected the geometry of the orebodies aiding cleaner recovery. Reconciliation is now completed on a blast-by-blast basis, which allows for quick and easy identification of poorly performing areas of the resource model that can then be incorporated back into resource model updates. Regular daily and weekly meetings are also held with emphasis on the mining schedule to ensure no deviation from the schedule in the long term. These improvements have resulted in a lift in reserve recovery both globally and locally associated at the same time with improvement in grade.

Jan 1, 2005

By J. L. Bray

IT is well known that iron markedly improves the physical properties and casting characteristics of aluminum bronzes. The use of 1 to 4 per cent iron as the principal modifying addition has become common practice in many foundries melting aluminum bronzes. Although the beneficial effects of iron are unquestioned, there is some uncertainty regarding the structural changes caused by it in the basic copper-alumi-num system. It is agreed that a new constituent appears in abundance when the iron content reaches 2 to 4 per cent. This constituent, which frequently occurs in shapes resembling clover leaves, is sometimes assumed to be an aluminum-iron intermetallic compound. If this were correct we might expect a change in the structural relationships of the matrix in the direction of decreased aluminum content. On the other hand, it has been reported that iron has a negligible effect in altering the fundamental relationships of copper-aluminum alloys1. Others2,3 have reported an additive coefficient. Apparently it will be necessary to know the equilibrium relationships between the phases of the copper-aluminum-iron alloy system to establish any such theory as fact. When this has been done it may very well be that a further revision in the structural relationships may be necessary to describe the changes to be expected in commercial cast alloys. It was with this latter problem before them that the authors attempted to

Jan 1, 1936

By Elaine T. Cullen

Underground mining, like many high-risk industries, is facing a crisis in the near future. This industry has traditionally relied on a master-apprentice relationship to train new workers, but experienced miners are retiring in large numbers, leaving few "masters" to properly train their replacements. With a recent resurgence in mining, many new miners are entering the workforce each day. The rise in the number of inexperienced workers has implications for worker safety in an industry in which one mistake can blow up the entire workplace. The explosion in the Darby Mine in May 2006 that killed five miners illustrates what can happen in hazardous environments such as underground mines. The Health Communications Team at the National Institute for Occupational Safety and Health Spokane Research Laboratory was asked to address this problem by developing new training and safety awareness materials to promote safe flame cutting and welding practices. This article describes how occupational ethnographic techniques provided insights needed for "new product development." The result of this work was a national initiative to raise awareness and to protect underground coal miners from the dangers of flame cutting and welding in an environment filled with solid fuel and methane (natural gas). Although this project was initially designed for the mining industry, the approach and lessons learned are applicable to any high-risk industry and should be of interest to other social marketing or occupational safety and health professionals.

Jan 1, 2009

By H. F. Hebley

In recent years, especially in the last decade, great interest has been shown and many advances have been made in the preparation and cleaning of coal. In the major coal-producing countries, the percentage of tonnage cleaned has been increasing ever since 1924. As separating media, both liquids and gases are used, these generally being water and air respectively. Some systems, instead of obtaining separation by the velocity of the medium in which the coal is cleaned, depend on the density of water mixed with sand, or coal dust and shale, or with chemicals such as calcium chloride. In studying the results of coal-cleaning equipment, it will be observed that the efficiency of the cleaning apparatus lowers as the size of the coal decreases. This inability to obtain any marked improvement in the fines has been partly responsible for the installation of dedusting equipment, to remove the fine sizes from the raw coal prior to cleaning. When considering the possibility of installing dedusting equipment, many factors must be taken into account. Very often, but not always, both the ash and sulfur content of the coal increase as the coal size decreases. When bituminous coal, containing soft powdery fusain, is subjected to a wet washing process, the porous fines of the fusain remain in the small coal or in the wash water and delay the dewatering of the washed coal and increase the difficulty of clarification in settling tanks or thickeners. When a dedusted coal is cleaned by a wet process, the sludge recovered from the settling tank often runs so high in ash that the sludge can be discarded without further treatment and still the loss is small. Where treatment of the sludge is desired, however, froth flotation may be used to advantage if the size of the feed is below 1/10 in. Dust from the deduster can be treated in a similar manner. Fusain, which is usually found in the fine sizes, has often a much larger ash content than other coal. Illustrative of this condition is a table of ash contents for the various petrographic constituents of Illinois coal (No. 5 bed) as given by Mitchell' (Table 1).

Jan 1, 1934

By R. J. Sweigard, G. T. Lineberry, B. K. Slone, F. A. James III, D. S. Maggard

The depth at which it becomes more economical to use slope access instead of box-cut access for nearsurface coal reserves is termed the "transition depth." The transition depth can be established for a given coal property by considering cost estimates for those parameters that determine respective access methods. Fourteen parameters that influence access cost were identified, and ranges for these parameters were determined. A transitiondepth formula was developed to permit the determination of which is the better method of accessing a reserve, given information such as high wall slope, road width, total bench width, pit dimensions, road grade, belt component costs, pumping costs and the cost of overburden removal and reclamation. In most cases in Appalachia, especially in eastern Kentucky, the observed transition depth ranges from 20 to 30 m (66 to l00 ft). This indicates that actual practice is consistent with the analytical approach used.

Jan 1, 2002

By J. B. Janus

This report, the 25th in a series, lists analytical data of coal samples collected by the Bureau of Mines in connection with the purchase of several million tons of coal for various Government agencies during fiscal year 1975. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. Ultimate analyses are given for these coalbeds only. The delivered coal was sampled at destination in accordance with instructions furnished by the Bureau of Mines, and all samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1976

During the 22 years that Isa Mine has been formally involved in accident prevention, it has succeeded in reducing its lost time injury frequency rate by 70 per cent. At present its performance compares very favourably with that of other heavy industries and in particular that of other underground metalliferous mines. When reductions such as this are recorded, people want to know how it is achieved. No doubt it is assumed that if an organisation can maintain a consistent performance in accident reduction, it must have developed a panacea for the prevention of industrial injuries. This assumption would not be in accordance with the facts in the case of Isa Mine which has achieved its record through plain hard work and plenty of it.

Jan 1, 1975

By J. J. Forbes

The rapid increase in the quantity of coal being mined by stripping methods is one reason for the increased interest evinced by safety and other agencies in the hazards that are inherent in this Method of mining. The coal-mining laws of some States contain general provisions governing the mining of coal by open-cut methods, but none contains a complete list of specific safety regulations or laws for-the safe operation of such mines. The cool-mining laws of one State empower the head of the coal-mining inspection organization to proscribe regulations for coal-stripping operations and gave him the authority and power to enforce the rules and regulations promulgated by him.

Jan 1, 1944

Detailed observations were made for two existing continuous miner and shuttlecar systems. A simple model for the shift average cycle consisted of three time components - delays, mining and transport. Cycle improvement and productivity improvement factors are derived and used to predict the theoretical improvement which the observed cycles could achieve. Various strategies of action ranging from short-term optimisation through to long-term planning for continuous haulage systems are evaluated. High potential for improvement is shown for a wide range of operating conditions. An overview is presented for systems, currently available or under active development, which can accept coal directly from continuous miners and offer continuous haulage to the surface. Systems are broadly classified as mechanical-roof mounted, mechanical-floor mounted and hydraulic transportation.

Jan 1, 1982

By Walter W. R. May

FOR more than 25 years a few business men who represent virile private enterprise in the Pacific Northwest have been trying to awaken the community to the potential benefits of an open Columbia River. No threat of government com- petition then hung over the industry, which was adjusted to state regulation. Numerous sites were engineered and the findings were laid before the operators of heavy industry in the East, Middle West, and South -even of Europe. These engineering data became, if not the basis, the inspiration upon which the U. S. Army Engineers eventually were to "build the Columbia River Bible" - their great document known as House Document 103, the report on the Columbia River and minor tributaries.

Jan 1, 1940

By J. C. Bokros

At temperatures above 950°F, zirconium which has been strained a critical amount will experience critical recrystalli-zation. The large grain size thus formed can result in a reduction in the fatigue life by a factor of 2 to a factor of 9 at both high and low temperatures. The critical strains for zirconium vary from 15 pct at 900°F to about 2 pct at 1125°F, while those for zircaloy III vary from 15 pct at 1050°F to 5 pct at 1200°F. Zircaloy II ,experiences no critical recrystallization up to 1200°F. ZIRCONIUM has become increasingly important for nuclear applications and is being employed in reactors at temperatures where recrystallization can occur. Recent work' on the fatigue properties of zirconium has shown that coarse-grained structures developed in zirconium during recrystallization have much lower fatigue lives than fine-grained material. The development of these large grain sizes under such conditions is well known to be the result of critical recrystallization.2-4 Briefly, critical recrystallization occurs when a metal is strained a critical amount and annealed in the recrystallization range. The critical strain is defined as that minimum strain necessary to promote nucleation in the time unit and temperature considered. The maximum grain size occurs at the critical strain, since at this strain the fewest stable nuclei per unit volume grow into new grains. Recrystallization is not evident below this; strain since the nucleation rate is vanishingly lolw, and metal strained more than the critical amount has a higher nucleation rate per unit volume which results in a finer grained structure. This paper describes the critical recrystallization observed in reactor-grade zirconium, zircaloy 11, and zircaloy I11 as a function of annealing temperature and temperature of strain. EXPERIMENTAL The zirconium used was hafnium-free, double arc-melted sponge obtained from the Bureau of Mines. The ingots were forged and hot reduced to 0.08 to 0.10-in. sheet and subsequently cold reduced to 0.035-in. sheet with intermediate and final anneals at 1200 OF for 15 min. The zircaloy II and zircaloy III used were 0.035-in. sheets in the annealed condition. Compositions of these materials as tested are given in Table I. To determine the critical strain at a given temperature, tensile specimens having a0.065-in. taper in a 2-in. gage length were machined from the sheets parallel to the rolling direction. The specimens were polished, etched, and examined metallographically to ensure that all of them were strain-free, initially. Tukon indentations were made every half millimeter along the gage length of each specimen. These served as fiducial marks enabling the plastic strain to be measured with a microscope and micrometer stage. The specimens were pulled to failure at a rate of 0.002 in. per min in an Instron tensile-testing machine. Three temperatures were used for straining: room temperature, 500 ºF, and 900 ºF. The 500º and 900 ºF tests were run in an argon atmosphere. Since the rate of work hardening changes with temperature, a different critical strain was obtained for each temperature of strain. Specimens, prepared in the manner described, were annealed in vacuunl at various temperatures ranging from 900" to 1200 F for up to 1000 hr, after which they were examined metallographically. The critical strain and the recrystallized grain size as a function of strain were determined for each specimen. Results for the same temperature and time indicated that the critical strain measured was reproducible to within 5 pct of each other. RESULTS AND DISCUSSION Since increasing the time of anneal increases the probability of the nucleation of a new grain, the critical strain decreases with time at a decreasing

Jan 1, 1961

By R. A. Cunningham, A. S. Murray

If a dense fluid such as mud or water is used for circulation, the formation drilled is influenced by a hydrostatic pressure. This pressure depends on hole depth arid drilling fluid density. Laboratory tests indicute that drilling rates in many forri~ations are decreased with increased pressure,—in some cases as much as 90 per cent. A comparison between laboratory and field tests indicates that drilling fluid head affects drilling rates in the field approximately the, same as in the laboratory. Drillirrg rates of many formations are increased by reducing drilling fluid head. INTRODUCTION For many years it has been noted that field and laboratory drilling rate tests did not agree even when the formations tested were the same. For instance, tests of some shales by the Hughes Tool Co. laboratory indicated drilling rates approximately 20 to 30 ft/hour, whereas in the ground this shale would drill only 3 to 5 ft/hour. A possible reason for this discrepancy is the effect of the high pressure which the drilling fluid exerts against the formation at the bottom of the hole. Consider a small element of rock (Fig. II that is to be removed by a rock bit. If the hole is filled with mud or water. the upper surface of the rock element is subjected to a pressure which depends on hole depth and fluid density. The mass of earth around this rock element presses against the circumferential surface and the lower surface. Because of the probability of shearing stresses between the rock element and the surrounding rock, this element is not under true hydrostatic stress. However, as a first approximation for test purposes the rock element was assumed to he under hydrostatic stress. The effect of hydrostatic pressure on some physical properties of rock has been studied.1,2,3 These tests show that the "differential" compres-sive stress:': necessary to cause rup- ture in rock cylinders is greater when tested under high hydrostatic pressure than when tested under atmospheric conditions. These tests were made with pressures greater than 20,000 psi which is in excess of those normally encountered in oil well drilling. Similar tests were made by the Bureau of Reclamation' using pressures equivalent to those encountered in oil well drilling. Again the "differential" compressive stress necessary to produce failure increased with increasing hydrostatic pressure. These tests indicated that drilling rates would probably decrease. Correlation between these tests and drilling tests was not practical. The purpose of this work is to study the effect of mud column pressure on drilling rate, assuming that the material drilled is in a state of hydrostatic strcss. This problem was initially investigated in the laboratory using variable bit loads and confining pressure;. Confirmation of laboratory results was obtained in the field from a series of carefully controlled drilling tests. Because of the necessity of testing many different types of formations. only results from representative formations will be presented here.

Jan 1, 1956

INDEX OF CONTENTSComposition of the Brown CoalsIntroductionComposition as minedComposition from drilling explorations:Latrobe Valley Area, East Gippsland, Welshpool-Alberton West Area, Altona-Bacchus Marsh Area, Lal Lal Area, Dean's Marsh Area. The Coal Constituents:Vitrain, fusain, detrital coal, resin, Sulphur, types, distribution, Ash, composition, sulphur, phosphorus, chlorine,,titanium, vanadium, distribution in seam, fusibility, source, mineral ash, chemical ash Bitumen, tar. Factors causing Variation in Composition:Pressure of overburden, moisture content, carbon, hydrogen, nitrogen, oxygen, calorific power, density, compression by warping, abnormal moisture, initial differences in vegetation, conditions of sedimentation, weathering before re-burial.Summary and AcknowledgmentsList of References

Jan 1, 1945

By I. Mc Dougall

"The matte/slag tidal zone in a platinum smelting furnace is subject to severe process conditions which can often lead to premature failure of the lining. The MgO-FeO-Si02 slag is aggressive to refractory bricks, whilst the Ni-Cu-Fe-S matte is aggressive to water-cooled copper cooling elements, and can penetrate and sulphidize refractory bricks, particularly at the high matte temperatures often experienced in the PGM industry. A novel approach to the lining design was taken at Lonmin's new 10MW Furnace 2. An indirectly-cooled graphite ring was applied in the matte/slag tidal zone, with refractory bricks on the hot face. Thermal Finite Element modeling was conducted to determine the optimal lining design in this region of the furnace. The resistance of two graphite grades to damage by slag and matte was evaluated experimentally. The graphite lining is not wet by the matte, and is resistant to slag attack at operating temperatures. In comparison to water-cooled copper in various configurations, cooled graphite shows promise as an indirect refractory cooling system in the tidal zone area of furnaces.IntroductionIn South African Platinum Group Metals (PGM) smelting operations, the PGMs are associated with nickel-copper sulphides in magmatic rocks. After ore is mined, it is concentrated by means of a flotation process prior to smelting. Both rectangular 6-in-line and circular 3 electrode AC submerged arc furnaces are used for this purpose. A new 10 MW round furnace is currently under construction by Tenova Pyromet at Lonmin's Marikana Smelter Division. An overview of Lonmin's smelting operations and Lonmin's approach to smelting high chromite containing PGM concentrates is given by Eksteen et al. [1]"

Jan 1, 2012

By Richards BG, Komdeur W

Instability in spoil piles and in high wall slopes in natural overburden has been ex- perienced at Utah's Goonyella Mine since com- mencement of operations in early 1971. Annual production targets, although gener- ally met since the commencement of operations, required modifications to stripping and mining techniques and the rapid re-scheduling of oper- ations around unstable areas, but culminated in the earlier than planned acquisition of addit- ional stripping equipment. An understanding of failure mechanisms was developed within a collaborative study of pitwall instability between Utah Development Company and the C.S.I.R.O. Division of Applied Geomechanics. Results showed that pitwall instability occurs as structurally controlled deformations along planar failure surfaces; spoil pile failures are precipitated by moist- ure ingress and subsequent loss of strength of base layer materials; highwall failures de- velop over areally extensive bedding planes in conjunction with inclined and subvertical fractures caused by overburden blast damage.

Jan 1, 1978

By Wm. Moorhead

Safety Measures Employed at the Dawson Mines Preventive measures for eliminating and localizing explosions is a subject of special interest to Coal Mining operators at the present time. I shall endeavor in this paper to present the practical methods which have been developed at the mines of the Stag Canon Branch of the Phelps-Dodge Corporation, Dawson, New Mexico. Adobe Dusting Adobe is used for practically all dusting on the main haulage roads. It is obtainable in sufficient quantities adjacent to the mines. Loaded into railroad cars by a clam-shell loading crane, and transferred to the mine pit cars at the nearest available point, it is readily distributed along the motor roads by means of the mine locomotives. Of first consideration for adobe dusting is the preparation of the roadway. It is essential that all loose coal and dust be removed, at least to a depth of three or four inches below the top of the rails. The adobe, in a more or less moist condition is unloaded by hand from the pit cars and stored along the previously prepared roadway, to be later scattered to a depth of several inches over the floor, and over the ribs and roof such as is possible by the use of a shovel. The adobe soon loses its moisture and becomes pulverized. Due to the disturbance caused by passing motor trips, men and animals, the dust is effectively scattered along the ribs and roof of the roads. The velocity of the intake air aids materially in sustaining the suspension of this inert matter. Another scheme for distributing the fine dust in use is to chain the top of a pine tree to the rear of the trips, both empty and loaded. Dragging it along the motor roads stirs up the dust and aided by the intake air it is carried for long distances into the workings. The adobe is continually loosened and raked, all rock, coal, etc., being collected in piles and later loaded out in pit cars. One man is employed for each six thousand feet of entry. Dusting Main Return Air-Courses The air-courses are first thoroughly cleaned. All the loose coal and rock is loaded out, the ribs and roof washed down several times. Every five or six hundred feet, the stoppings between the main and return entries are broken through and small doors installed. Blowers are used to force the fine dust into the return air-courses through these openings. Thus suspended the dust travels a considerable distance before it is deposited on the floor, ribs and roof. The material used is chiefly adobe, sun dried, and screened on the outside. A two ton car load of this dust will cover several hundred feet of airway as very little loss occurs, often depositing from 2 to 6 pounds per running foot of entry. Methods of Insertion Blowers are used to force the dust into the main returns. One unit consists of a small Buffalo blower mounted on a truck with a two H. P. motor. A six-inch pipe is attached to the blower and runs the full length of the truck with a projection over the end. A hopper is built over the pipe and connected. Stove pipe or canvas tubing is led from the pipe through door in stopping. When the blower is started dust is fed into the

Jan 1, 1924

By Thomas Fraser, William L. Crentz

"INTRODUCTION Sulfur is a most damaging impurity in many of our American coals. From the older coal industry of Europe and Britain we can apparently learn but little about the problem of preparing and using high-sulfur coal. Although washing has long been established there for controlling ash content, sulfur is referred to rarely, as the important deposits are singularly low in sulfur.On the other hand, widely distributed coal deposits of America differ tremendously in sulfur content. Many of the more extensive beds contain too much sulfur for metallurgical use, and almost everywhere except in the Rocky Mountain and Pacific coast regions sulfur control is at least a potential problem. American coal-preparation engineers are confronted not only with great variations in the total quantity of sulfur in coal but with an intricately varying pattern of the physical and chemical forms in which the sulfur occurs. It must be conceded that the baffling problem of sulfur reduction in coal is as yet substantially unsolved, for there are but few isolated instances in which we have been able to prepare a satisfactory metallurgical fuel from coals containing as much as 2.0 percent sulfur in the raw state.It has been assumed generally that organic sulfur, being chemically combined with carbonaceous matter, is distributed throughout the coal matter and that it remains unchanged in the clean-coal part of the product during washing.Sulfur that may be washed out of the coal is that part that is combined with the iron in pyrite lenticles associated with the coal. In most of our coals it has been found that, besides the visible bands, lenses, and flakes of pyrite, extremely small and even microscopic particles of pyrite 4/ are distributed through the coal matter. Only the free, relatively coarse pyrite particles .are removed by conventional coal-washing devices, and usually most of the sulfur is still left in the product."

Dec 1, 1947