Search Documents

By W. L. Dalmijn, J. M. Versteegen

During the production of silicon carbide, a byproduct is generated that contains a mixture of crystalline and amorphous silicon carbide. Utilizing the difference in density, shape, and surface properties of the crystalline and amorphous silicon carbide, separation tests were carried out with gravity concentration. The processing of the coarse fraction of the silicon carbide mixture by jigs resulted in a high grade crystalline SiC concentrate with the desired specifications. The separation was largely influenced by the shape factor. A jig with a newly designed hydraulic drive was used to carry out the test program.

Jan 1, 1991

By Eleanore L. Nestlerode, James R. Guilinger

In April. 1990 Addwest Minerals acquired the Phillips Ranch sulfur property. The sulfur deposit, hosted by the Permian Castile anhydrite, occurs as two distinct elongate. parallel orebodies within a series of northeast-trending grabens. After completing a positive feasibility study, based, in part. on successful drilling programs by Addwest Minerals and previous operators, the decision was made to place the property into production. Utilizing an existing on-site kasch plant, plus significant portions of the recently purchased Texasgulf Comanche Creek Frasch plant. Addwest is currently constructing an 800 long ton per day Frasch mining facility.

Jan 1, 1992

By C. DeW. Van Siclen

A simple mathematical description of the settling behavior of monosized particle suspensions is derived by consideration of the physical processes involved, and applied to data recently published in this journal.

Jan 1, 1995

By Kim Appleby

Epithermal gold-silver (lead-zinc-copper-manganese) mineralization on Misima Island is confined to steep and reactivated flat-lying normal faults in the upper plate of a major, shallowly dipping detachment fault. The hangingwall comprises an Eocene metavolcano-sedimentary sequence that has been extensively intruded byMiocene calc-alkaline granodiorite. It is unconformably overlain by Pliocene sedimentary and volcanic rocks. High-pressure amphibolite facies rocks dominate the footwall and have many characteristics of a metamorphic core complex. Mafic-alkalic lamprophyre dike swarms intrude the hangingwall and footwall sequences. Previous workers attributed the gold-silver mineralization on Misima to the intrusion of the porphyritic granodiorite (Williamson, 1984). This has been proposed for many tertiary gold deposits of the southwest Pacific(Sillitoe, 1989; Leach and Corbett, 1994).

Jan 1, 1996

By J. L. Chakravatti

INTRODUCTION Mining of uranium does not differ, in many respects, from the mining of other metals; the ore must be drilled, blasted and transported in an underground or surface mine. Underground mining proceeds by the continuous development and advancement of a network of passages and rooms or stopes from which ore is excavated. As in most mines, rock conditions and ore grades in uranium deposits vary from area to area and between different mines. For mineral benefications of this ore in the mills, use is made of various chemicals, often with toxic or hazardous properties.1 As well as the need to control the more conventional hazards associated with any mining and milling operation, special care needs to be exercised in the mining and milling of uranium because of the radioactive nature of the ore. This requires that we examine closely the radiation hazard areas encountered in the mining and milling of uranium, with the broad overview of some of the basic facts in the radiation hazard control programme. To place the hazard in its proper perspective, we require recognition, evaluation and control of those factors arising in and from the workplace which may cause sickness, impaired health and affect the well being among workers or citizens of the community. The radiation environment in uranium mine is complex and variable. Although uranium ore is only mildly radioactive, it naturally contains a complex mixture of radioactive isotopes. Workers are exposed to external gamma radiation, to some beta radiation and to airborne radon, radon daughters and ore dust. All of these types of exposures warrant considerations in formulating control procedures but, in general, radon daughters are known to present the dominant risk. The basis of dose limitation in radiological protection is risk limitation. Long-term epidemiologic studies of United States uranium miners and that of miners in Czechoslovakia indicate that the incidence of lung cancer can be accounted for by a linear relationship with exposure to radon decay products.2 On the basis of this proportional exposure-risk relationship, a risk coefficient for lung cancer in the range of 1-5.10-4 WLM-1 during the total lifetime, has been estimated by UNSCEAR3 and other researchers. It should be noted that this risk coefficient includes the excess lung cancer risk from external gamma radiation in mines and from other carcinogenic chemical effects, if any, to which the miners are normally exposed during their underground work. It also takes into regard the possible synergistic influences. This paper reviews the occurrence of radiation and its control factors and the development of engineering design features for the environmental control at Denison Mine. NATURAL URANIUM SERIES Uranium is the most common element in the Earth's crust. It is widely distributed in nature in all rocks and is readily measurable in the sea. Hence, radon gas is universally produced in every part of the globe. Mining is patently confined to ores containing more than half a kilogram, or so, per tonne of uranium unless it is combined with other marketable metals. Uranium-238 is the first element in the uranium series. In all, there are 13 radioactive decay products of 238U (Fig. 1), ending up as a stable isotope of Lead-206. The whole basis of the radiological hazards associated with the mining and milling of uranium is dependent on the behaviour of these isotopes during each phase of the process.

Jan 1, 1981

By Raymond E. Blair

Introduction Mining and minerals transportation spans the distance from the pit face and mine wall to the consumer. This transportation can be as simple as coal transfer from the mine and preparation plant by conveyor to a mine mouth electric generating plant. Or it can be as complex as copper ore transportation: concentrated, smelted, refined; drawn into wire and insulated; and cut into reels and transported to local industrial supply houses. The route of aluminum from the bauxite pits to the supermarket shelf in the form of household food wrap is another example of the potential complexity of minerals transportation. For perspective, however, mine to market minerals transportation can be split into three components: materials handling, transportation, and distribution. It should also be recognized that each mineral, market, producer, and consumer has unique transportation characteristics regarding costs, transportation mode, and alternatives in the transportation scheme. Some obvious considerations are the number of producers and consumers, the number of markets and customers the mineral serves. Concerning the latter, are you selling a million tons to one customer or a ton each to a million customers? Transportation volume About the only generalization that can be made about minerals transportation concerns the large volume of materials involved. No other industry compares to the mining and minerals industry in its huge movement of product in the crude, semi-processed, processed, fabricated, and converted states, as shown by the accompanying table of US mineral production. Whether it is crushed stone or sand and gravel moving by truck to a local market from local producers, or coal moving by 9.07 kt (10,000 st) unit trains from a mine to a power plant, or iron ore moving by lake vessel from the upper lake ports to the lower lake steel mills, mineral transportation volumes are huge. The nature of production and consumption affects the transportation mode. More than 60% of the coal moves by rail. The majority of iron ore moves by lake vessel. Ninety per cent of the sand and gravel and more than 80% of crushed stone moves by truck. Factors Affecting Minerals Transportation Some would define minerals transportation as the cost and route to move a mineral product from the first point of sale to the first point of consumption. This definition does not recognize that there can be many

Jan 10, 1982

THE PENNSYLVANIA STATE UNIVERSITY, 101 MINERAL SCIENCES BUILDING UNIVERSITY PARK. PENNSYLVANIA 16803 To the Editor: With respect to the Fenvessy and Schwab article, I offer the following: As thorough as the study may be, it still has a glaring weakness. The presumption of constant supply in face of falling demand - their "low growth" case - is just wrong. It does not allow for the rapid migration, by transfer and change of major, from former high-demand programs, such as mining, to programs that have more recently obtained the cachet of job security. The figures that are shown for rapid growth in mining engineering enrollments in the period 1970-1981 are, no doubt, correct and reflect a rapid inmigration of students into mining. A similar out-migration, which began in 1982, from mining to other engineering and science disciplines is not factored into their study. Given 1983-84 enrollments, which can already be documented, it is clear that the low-growth case will, by 1985, be 50% or less of 1981. I wish students would pick their majors on the basis of their own individual abilities and interests rather than rushing lemming-like to programs that are reputed to have jobs. In the end, students will have better jobs and careers if their college majors match their talents and we, in the academic side of things, will have a livelier and more dedicated student. Lee W. Saperstein Professor and Chairman of Mining Engineering UNIVERSITY OF MISSOURI-ROLLA To the Editor: I write concerning the recent article on future demand for graduates in the mining industry. The article is, unfortunately, inaccurate because of the erroneous assumptions it makes in its basic premises. To cite but two of these, class sizes will not continue at their current level, but will, in fact, alter dramatically as a function of the perceived immediate job market rather than the future trend, so that enrollments are already below those predicted. Secondly, it is patently wrong to assume that everyone who gets a degree in the mining field will continue until retirement to work in that field. People who do not have a job in the industry will get work elsewhere and often do not come back. Others will later move to different areas. My major argument, however, deals with the underlying assumptions and methodology of the survey itself, with the concomitant challenge to the subsequent conclusions. It is no great secret that the technological world is undergoing a dramatic revolution. Computer use is rapidly spreading to the point where the microcomputer will be an integral part of every mine engineer's desk. Such a tool, which for optimal benefit must be operated by knowledgeable mining engineers, will make mining much more of a science than the current level. To remain competitive, mines will increasingly rely on higher level deci-

Jan 1, 1984

By S. H. Advani, J. K. Lee, K. S. Chan, J. M. Avasthi

A summary of field equations governing the hygro-thermo-mechanical (coupled temperature, moisture, and stress) response of geological media is presented. The applicability of these equations, with appropriate boundary conditions, to the study of basic mechanisms associated with underground coal gasification (UCG) process is discussed. In particular, the phenomenon of stress-induced spalling resulting from intense drying near the gasified cavity and in situ effects is investigated by means of the finite element method. Some typical results from sample finite element model representations are presented for the evaluation of field experiments.

Jan 1, 1986

By R. S. Austin

One-third of the world's and most US kaolin is produced from Late Cretaceous and Early Tertiary sedimentary strata in Georgia and South Carolina. The kaolin is part of a belt extending to Arkansas of aluminous lateritic deposits, including bauxite. Original sediments were profoundly altered by chemical weathering during Early Tertiary time. Mining exploits those uncommon deposits where extreme leaching and chemical recombination have produced a clay of nearly pure mineral kaolinite. Properly selected and refined, kaolin is an important pigment, filler, extender and chemical compound in the paper, paint, plastics, ceramics and catalyst industries.

Jan 1, 1998

By Adrian Brown

The primary method of slope stabilization is ground water-control. Recent research has established the properties which slope materials must exhibit in order for stabilization measures to be feasible, but there is little guidance in the literature about suitable field tests to develop the parameters needed for this evaluation. This paper presents a proven method for large scale testing which allows an evaluation of the feasibility of ground water pressure control in a reasonable cost and time frame. Methods of performance and analysis of the test are presented, and the method is illustrated by reference to case examples.

Jan 1, 1984

By Jozef Szymanski, Julian Partyka, Jerzy Krynicki

In order to study blast-induced dust in a hard rock metal mine experimentally and analytically, a part of a stope mined by Vertical Retreat Mining (VRM) was monitored throughout its lifetime. Dust measurements were used to describe the dust source, to study the dynamics of removal of airborne dust from the blasting area, and to examine a variation in dust production with a stope's progress. An analysis based on graphical and analytical comparisons of blasts taking place in a single stope is presented and discussed. Also, some transient phenomena of dust flow in the stope vicinity, caused by the blasts only, are examined.

Jan 1, 1997

By Reese E. Mallette

This paper makes five major points which may be contributions to the art of limestone sinkhole engineering. First, solution cavity development in limestones is dependent in great measure on pyrite contained within the limestone. Second, rock failure is rarely involved in sinkhole problems, while soil failures are almost always the mode of occurrence. Third, draw down, depression of the water table, is a primary causative factor in sinkhole development. Fourth, lateral movement of vadose water along the soil-rock interface, sub-soil erosion, is the mechanism by which soil is stoped, raveled, piped, or removed from the soil cavern. Fifth, the ultimate or triggering factor in localizing a sinkhole collapse is any superposed mechanism which disrupts the continuity of an impermeable clay soil overburden. The above theses are presented as extensions of our observation and of published literature, with the suggestion that additional study of these mechanisms is warranted.

Jan 1, 1975

By Boris M. Vorobjev

The paper in question discusses a wide range of topics on the coal mining environment in general and on computerized coal mine environment systems in particular. The emphasis is being made on methodological aspects of coal mine environment with reference to computerized monitoring systems Classification of computerized coal mine environment monitoring system is suggested by the author with specific reference to coal mining operations. Coal quality control system at all levels (coal face to regional levels) is also discussed briefly hereunder, since coal quality is one of the major factor for environmental management. An integrated coal mining economic and environmental management super-system is presented in this paper Review Of the UN/DTCD, UNDP European Regional project "Computerized Coal Mining Systems" is presented here. Conceptualization of a new European Regional project on Coal Mining Environment and Economic Management is also a topic discussed in the paper.

Jan 1, 1992

By Shan Mafi

he Broken Aro coal mine is located at the Woodbury Wildlife Preserve 11 km (7 miles) west of Coshocton, OH on State Route 541. Underground min¬ing at the 16-hm2 (40-acre) site took place during the 1910s. During the past five years, surface mining has occurred along the western and northern perimeters of the underground region. The Ohio Department of Natural Resources (ODNR), R&F Coal and American Electric Power (AEP) are involved in a project to remine the abandoned underground complex. The program also includes installing a mine seal made of fixated flue gas desulfurization (FGD) material. Previous mining activity in this area has resulted in an acid mine drainage (AMD) problem on portions of the reserve. In particular, a prominent AMD source is present in the Simmons Run drainage. The project goal is to eliminate or reduce the AMD that is discharging into the watershed. It was initially hoped that the Simmons Run drainage area could be economically mined. Accordingly, this area was included in the mine permit. However, experience with other previously mined areas on this reserve showed that the old mine workings were more extensive than originally thought. Old mine workings present several problems. The most significant are reduced coal recovery, poor coal quality and AMD liability. All of these problems increase mining costs. And the more extensive the old workings, the more significant the increase in cost. Based on R&F's experience with old mine workings in this area, it was decided that economic recovery of the Simmons Run drainage reserve was not possible. As a result, R&F excluded the Simmons Run drainage area from its early mine plans. Some time after it was decided not to affect the Simmons Run drainage area, R&F and ODNR's Division of Mining and Reclamation discussed the possibility of removing this area from the permit and attempting to correct the AMD problem as an Abandoned Mine Lands (AML) project. Specifically, the discussion centered around mining through a portion of the old mine workings to expose the mine openings in the highwall. Once exposed, the mine openings would be sealed using FGD material from the nearby Conesville power plant operated by AEP. In addition, there was interest in reclaiming the old tipple and associated gob pile located adjacent to Coshocton County Road 17 on the opposite side of Simmons Run. R&F attempted to eliminate the AMD problem by sealing the mine openings with FGD material. Once the seals were installed, they were covered with overburden. Monitoring wells were installed to determine the effectiveness of the seal and the inundation progress in the old mine workings as well as monitoring the quality of ground water. The project was jointly funded by revenue from the sale of the coal recovered during the project and AML funds. The FGD seal is expected to cause well water levels to increase above preseal elevations. However, the additional head pressure due to increased water depths in the underground mine may cause seepage through the bottom of the mine or out through the perimeter. The in¬creased water depth in the underground mine is expected to cause lower oxygen concentrations in the underground mine water. Since acidity is produced by oxidation of iron pyrites, less oxygen should result in better quality water. Monitoring wells will be installed before seal installation so that pre- and postseal water levels and well water quality can be determined. Surface sampling locations will be identified. These will be monitored before and after seal placement.

Jan 1, 1998

By Douglas J. Pendrell, Marvin D. Simmons, E. Raymond Boc

The U. S. Army Corps of Engineers is in the early stages of design for an estimated 14 m (46 ft) diameter tunnel in northeast New Jersey. This tunnel will carry flood waters from the upper end of the Pompton River in Wayne County, to an outlet in Newark Bay, a distance of 33 km (20.5 miles). The tunnel will be constructed by a tunnel boring machine (TBM), the size of which is unprecedented at the present time. The alignment is through Triassic and Jurassic sandstones, siltstones, and shales that include three beds of basalt that range in thickness from 76 to 310 m (250 to 1020 ft).

Jan 1, 1991

By O. Alvarez-Campos

Two porphyry copper orebodies, the North and Central MM orebodies, have been found through regional and structural geologic works, about 5 Km south of Chuquicamata, under a gravel bed of approximately 100 m and in the west side of the West Fissure. The mineralization is emplaced in a coarse granodioritic porphyry, predominantly with sericitic alteration. In the North MM ore-body, with 200 million metric tons of 1.0% Cu, the mineralization is mainly chalcopyrite, bornite, digenite and molibdenite. In the central MM orebody, with 700 million metric tons of 1.3% Cu, there are large veins of enargite, chalcocite and bornite, the last one increasing in depth, separated by chalcopyrite and pyrite zones; in these veins there are interesting gold and silver values. Both orebodies have an upper enrichment of chalcocite and covellite, with pyrite envelope. According with these characteristics, the MM orebodies could he the upper part, with sericitic alteration, of the Chuquicamata porphyry copper system, displaced by the West Fissure system movements, but we couldn't eliminate the possibility that MM can be a new orebody, different of Chuquicamata.

Jan 1, 1993

By T. Bednarski, T. McCallum, L. Moya, B. Gay

"Molybdenum recovery by solvent extraction has gained interest partly due to advances in concentrate leach technology. Historically, both molybdenum and rhenium have been produced using amine-based extractants with the ability to co-extract both metals. Alternatively, a phosphinic acid-based extractant (CYANEX® 600) can be used depending on the flow sheet. CYANEX® 600 selectively extracts Mo leaving Re in the raffinate, which is a valuable feature in plants which require rejection of the rhenium from the molybdenum circuit. CYANEX® 600 piloting results are reviewed and compared to commercial experiences with an amine-based extractant. INTRODUCTION Molybdenum is most commonly found as molybdenite (MoS2) in primary porphyry deposits (about 59% of global reserves) and copper porphyries (about 39% of molybdenum reserves)[1]. Recovery from molybdenite traditionally involves flotation (concentrates typically containing 85 – 95% MoS2) followed by roasting to produce MoO3. Solvent extraction is also used to recover molybdenum from acidic aqueous solutions resulting from scrubbing of roaster and smelter off gasses and leaching of molybdenite (uranium ores). Molybdenum is also frequently found in low concentrations in copper leach inventories[2]. More recently, pressure oxidation has gained interest to treat molybdenite concentrates. Molybdenum Chemistry The chemistry of molybdenum is complex with a series of extractable species existing dependent on the pH and oxidation state as shown in Figure 1.Under strongly basic conditions, molybdenum primarily exists as MoO42- while under strongly acidic conditions MoO22+ becomes the predominant species. In between, a number of isopolymolybdates such as Mo7O246- and Mo8O264- are dominant. Equations (1) – (3) demonstrate some of the proposed molybdenum equilibrium reactions[1]."

Jan 1, 2017

By J. A. Cervantes

A statistical model for assessing the risk of ground subsidence in abandoned mine areas is presented. The model is based on the relationship that exists between .the frequency and the location-of subsidence events in a given area and the physical conditions of the ground. These conditions can be described by a series of geological, mining, and physical variables. The model suggests the existence of regions in the multidimensional space of variables which are associated .with increases or decreases in the frequency of subsidence events. Regions associated with an increase in the frequency of subsidence events correspond to regions of higher risks, and vice versa. Risk assessment is based on the ability to express the limits of these high and low risk regions in the, space of variables, and on the ability to express the degree of membership of blocks of land within any of these regions. The theoretical framework for the model is extracted, from discriminant analysis. Risk is quantified by the probabilities of membership of blocks of land into any of these regions. Risk maps are produced by displaying membership probabilities in. appropriate contouring levels. The model has been applied in two urban areas where subsidence of the ground has been active in the past. The two areas are Penn Hills, near Pittsburgh, and Scranton/Wilkes-Barre in northeastern Pennsylvania. In this paper, only the results for the Scranton/Wilkes-Barre area are presented. Those for the Penn Hills area have been presented elsewhere (Cervantes, et al, 1990). In the- Scranton/Wilkes-Barre area, geostatistical estimates of variables likely to affect the stability of the ground were made using samples from 53 drillholes. The estimates were made for 2000x2000 ft squared blocks of land covering the study area. Discriminant functions were computed from the estimated variables and used to establish regions for classifying blocks of land into one of these two populations: 1) blocks not likely to have a subsidence event, and ii) blocks likely to have one or more subsidence events. The same, discriminant functions were used to compute membership probabilities for blocks of land to tall within any of these two populations. These probabilities were contoured to produce a risk map. The risk map produced compares well with the location of the subsidence events which have occurred to date in the area.

Jan 1, 1992

By John R. Woodcock

The Kitsault molybdenum deposit lies along the east margin of thecoast Batholith Complex near the head of the fiord of Alice Arm. It is 800 km (497 miles) northwest of Vancouver, British Columbia. The deposit is located on Lime Creek 8 km (5 miles) from the coast on a wide dissected upland valley at an elevation of 600 m (1969 ft). It is an area of coastal rain forest with high annual precipitation and extremely high winter snowfall. Although the area is of high relief, outcrops are largely restricted to ridges and canyons. Most of the area is covered by the coastal vegetation or wet swampy upland areas. The south edge of the molybdenum deposit was exposed in a sharp canyon; however, outcrops over the remainder of the deposit were largely restricted to a few small exposures of resistant hornfels. The mineralization is related to an elliptical porphyry stock of 52.3 m.y. age which intrudes argillites and microgreywackes of the Late Jurassic Bowser Group. A circular zone of alteration, with a diameter of about 700 m (2297 ft), occurs in the north end of the stock and the molybdenite mineralization is concentrated in the outer parts of this zone of alteration. Thus, the northern part of the mineralization occurs partly in the hornfels and partly in the stock, whereas the southern side of the ring of mineralization cuts across the middle of the stock. Zoning within this system includes a central circular area of almost complete replacement of quartz plus K- feldspar and this grades sharply outward into a phyllic zone. Clay alteration is largely localized along late faults. The ring of molybdenite mineralization is partly overlapped and partly surrounded by a zone of pyrite mineralization. Some chalcopyrite is coextensive with the pyrite zone. Late polymetallic veins fill two conjugate fracture sets. These quartz veins contain galena, pyrite, some chalcopyrite, and a number of lead-bismuth sulfosalts.

Jan 1, 1991

By Victor F. Hollister

This first section of case histories of mineral discoveries, Vol. 3, covers some of the milestones in porphyry copper and skam exploration successes. It was during the era of these discoveries that large, complex exploration departments emerged as permanent adjuncts of large mining companies. The discoveries helped shape how and where exploration activity was conducted. Probably the most important factor in exploration success is management. Few management people are mentioned in this section or in any exploration history, yet the distinction between success and failure ultimately rested with the decisions they made. One of the most successful groups was initiated by Roger Straus and Herbert Brownell when they sought to make Asarco into an important metal producer. Relying on Clem Pollock and L.H. (Bill) Hart to identify and push worthwhile projects, the Asarco management remade the company. Asarco will benefit from exploration successes com- pounded by that team for years to come. Duval is an example of a management that decided to add metal production to its industrial minerals output. When Page Morris was president, that company opened three major porphyry copper mines and became an important factor in metals. Under the Monis management team, Duval became a leader in exploration. At the other end of the scale are managements that snatched defeat from the jaws of victory and by so doing changed the character of their companies in other ways.

Jan 1, 1991