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By Byron R. Berger

Epithermal Ag-Au deposits form at low to moderate temperatures in near-surface environments. Historically, these deposits have been the source of high-grade ores. Increases in the market prices for gold and silver make lower-grade ores economically viable when available in large tonnages. Both the high-grade and bulk-tonnage ores are a consequence of the same processes, and general models of epithermal systems can be useful in the search for new precious-metal resources. A detailed study of deposits at Round Mountain, Nevada; Balei, Russia; Creede, Colorado; Guanajuato, Mexico; and Chanarcillo, Chile, indicates that the hydrodynamics of the fluid systems as determined by fracture geometries, the permeability, and composition of the host rocks are the key factors in the creation of both high-grade and bulk-tonnage epithermal deposits. End-member models that explain the range of observed deposit characteristics are: (1) the hot-springs deposition model; (2) the stacked-cell convection model (where mineral deposition occurs laterally along the interface of two partially separated fluid reservoirs); and, (3) the closed-cell convection model (where deposition occurs in vertical zones due to the relatively unimpeded vertical flow of hydrothermal fluids). Boiling and fluid mixing appear to be agents of precious-metal deposition with the self-sealing of the hydrothermal system being an important adjunct to boiling. Imaginative application of model concepts in exploration has led and can lead to the discovery of new high-grade and/or bulk-tonnage precious-metal deposits.

Jan 1, 1982

By Gerard P. Hand

The use of graphite in industrial applications is one of the oldest in the world. Yet, it is one of the fastest-changing technologies today. Graphite was first used centuries ago in developing writing instruments and as a raw material in crucibles used in melting metal. Today, graphite is used in some of our most demanding industries. These include aerospace, electronics and automotive applications. Graphite usage has historically been split between the natural and synthetic forms. Figure 1 shows the breakdown of natural graphites and synthetic graphites used. The usage of natural graphites and synthetic graphites is split fairly evenly, although the applications are quite different. Figure 2 shows the breakdown of applications using natural graphite. The largest application is the refractory industry. This includes refractory brick and plastics, crucibles, shrouds and other refractory parts. This main application uses roughly 50% of all natural graphite. The refractory industry is an important application for natural graphite. However, the refractory markets have been struggling for several years. As demonstrated in Fig. 3 (Semler, 1996), the production of refractories in tons per year has declined by more than 32% during the last 25 years. Refractory prices have actually risen on a dollar per ton basis during that same period as the product mix has shifted to the value-added side. Raw material and production cost increases, inflation and other related costs have kept profitability at low levels for the industry. Furnace linings that once lasted 1,000-2,000 heats now last 8,000-12,000 heats. This means that tonnage requirements have gone down and quality requirements have gone up for graphite suppliers. Therefore, new opportunities and applications must be developed if the graphite industry is to grow. Synthetics are the other major forms of graphite. There are two forms of synthetic material currently used. One is the traditional type. It is made from the turnings of graphite electrode production. The second was developed in the mid-1970s in response to a shortage of conventional synthetic graphite. This occurred by a breakthrough in thermal technology. This new technology purifies, desulfurizes and graphitizes petroleum coke on a continuous basis at temperatures of more than 2,500° C (4,532° F). This product is called desulfurized petroleum coke (Desulco). It now accounts for about half of the synthetic type material used in the United States. Figure 4 shows the breakdown in the use of synthetic types of material by application. The largest requirement is for use as a carbon addition in iron and steel. This is followed by alkaline batteries and friction materials. Current technological opportunities New opportunities for graphite products are now being developed. These new areas are made possible due to the advances in graphite thermal technology. The ability to purify and modify graphite and carbon products is the key to future growth in the graphite industry. New, higher-purity, more consistent graphite products are leading to enhanced performance in current applications. They are also opening the door to new applications.

Jan 1, 1997

By Stephen Semeniuk

Discussion by Stephen Semeniuk Discussion As a valuator and SME member, I view Ross D. Lawrence's position as based on unproven and faulty assumptions made with regard to the pragmatic evidence presented in his paper. Moreover, his call for the inclusion of all mineral resources in discounted cash flow valuations is redundant, if not irrelevant, as there are procedures that already take all classes of mineralization into consideration for valuation purposes. In my experience as a valuator, I find that Canadian securities regulators are more than accommodating in allowing any valuations of mineral properties to be based on cash flow calculations. In other business areas, the same regulators usually reject discounted cash flow valuations of projects or businesses with no operating history. Instead, the regulators prefer valuations to be based on other transactions tested in the marketplace. Valuations based on actual market transactions are less subjective than discounted cash flow calculations and/or the capitalization of arbitrary, untested or undemonstrated earnings projections. In the mining and minerals sector, such projections may be made by persons not qualified to make such projections. In support of this statement, I direct readers to the article "Valuation of mineral properties which do not contain exploitable reserves" by Lionel C. Kilburn, which appeared in the August 1990 issue of the CIM Bulletin. To quote from the article: "Value of a mineral property depends basically upon metal prices, recoverable grades, mining and metallurgical practices, commodity supply and demand, and political-economic conditions, all of which vary with time. Five fields of expertise influence the value of a mineral property: •geological engineering, •commodity markets, •financial markets, •stock markets and •mineral property markets. The skills of geologists and engineers properly apply to the first field of expertise. Knowledge and consideration of the other four fields is important, but such advice is more properly sought from marketing experts, economists and stockbrokers." Securities regulators have created no hardship for valuators by excluding unsubstantiated resources in discounted cash flow valuations. In the field of engineering, best design practices apply. A margin of safety is built into the design criteria for any new equipment or structure that will exceed normally expected load levels and stresses, even though such considerations imply higher front end costs. In accounting, the comparable operating principle is conservatism. It explains why, for balancesheet presentation purposes, inventory is stated at cost or market, whichever is the lowest value. Similarly, when the engineering or geoscience-based valuator plays in the field of finance, the rules of accounting and applied economics apply. Regulators in their skepticism of income-based valuations are in tune with similar views already expressed in mining literature. To quote H. Van Tingley, in Mining Magazine, July 1996: "... the DCF method has inherent dangers when applied to undeveloped resources. Firstly, it presents an often-undeserved aura of accuracy. A DCF value is no more accurate than the least accurate of the assumptions incorporated into the calculation - and assumptions

Jan 1, 2003

By Michael L. Cramer, Kunsoo Kim

INTRODUCTION The Columbia River Basalt beneath the Hanford Site is one of several rock types being considered by the U.S. Department of Energy for the first commercial high-level nuclear waste repository. The Basalt Waste Isolation Project (BWIP) has been carrying out a comprehensive investigation to assess the feasibility of constructing a repository in basalt and to develop technology required for repository engineering and site characterization. Development of a nuclear waste repository requires a number of design considerations not usually necessary in the planning of conventional underground structures. Principal among these is the thermally induced stress field resulting from waste emplacement. This thermal stress, super- imposed on the preexisting in situ- and excavation- induced stress fields, needs to be evaluated in the design process due to the sensitivity of waste emplacement density to this factor. The nature of this thermally induced stress field is dependent on several factors, including the temperature distribution around the repository openings, the thermal properties of the rock mass, and the deformability of the rock mass. Re1iable performance of the repository structure is largely determined by the ability to under- stand the above rock mass characteristics and predict the underground opening response to waste emplacement based on this understanding. To gain an understanding of this rock mass behavior in a repository condition, the BWIP has conducted a large-scale heated block test in basalt at the Near-Surf ace Test Facility (NSTF) on the Hanford Site. This paper presents the results from the elevated temperature phase of the block test in which the thermal, mechanical, and thermo- mechanical response of the closely jointed basalt rock mass was evaluated as a function of stress and loading orientation at varying temperatures up to 200 oC. SITE GEOLOGY The NSTF test areas, including the block test site, are located in the entablature zone of the Pomona basalt f low. The Pomona flow entablature is structurally typical of most flows in the Columbia River Basalt Group in that it is characterized by long, undulating, polygonal columns up to 2.4 m in length. Columns vary from 15 to 30 cm in diameter, averaging about 20 cm. Over their length, columns can vary in dip by 150 to 200. The column structures are dissected by subhorizontal cross joints that are generally discontinuous and seldom cross columnar joint boundaries. Spacing of the cross joints also averages about 20 cm. A representative joint pattern taken from mapping of the tunnel wall near the block test site is shown in figure 1. Application of the Rock Mass Rating System (Bieniawski, l979) to the block test site yielded an overall value of 62. The corresponding value from application of the Q-system (Barton et al., 1974) is 8.7 (Cramer and Kim,1985). The NSTF is approximately 50 m below the surf ace. However, this depth is sti1l above the water table and conditions are generally dry. Interstitial water exists as the result of percolation of meteoric water from the surface.

Jan 1, 1986

By J. D. Cooper, D. W. Thompson, J. Basiuk, W. Cass, R. Ilves

The Department of Thoracic Surgery and Pathology at the Toronto General Hospital have had a long standing interest in the early detection and treatment of carcinoma of the lung. Our initial experience was with a population at risk due to a prolonged period of cigarette smoking. More recently our efforts have turned to industrial exposure, specifically in the nickel and uranium industries. [Initial Screening Project] (1) For a three year period 1963 to 1966 a cytology screening program was carried out through the Out-Patient Department. The study was limited to cigarette smokers over 40 in age. A total of 1586 patients were examined. Of the sputa collected, the classification is seen in Table 1. There were 11 malignant sputa present. Added to this number were 25 patients with symptoms, normal chest X-rays, but malignant cells on cytology, and a further 5 patients in whom an abnormality (eventually proven non-malignant) showed on X-ray, and sputum showed malignancy which was radio logically occult. (Table II). This gave a total of 41 patients with malignant sputum who were evaluated between 1960 and 1966. The clinical course of these patients is seen in Table III. Only 19 of 41 patients had localization and treatment of their tumour during that study period and this low rate of localization attests to the technical difficulties endoscopy in that day presented. The method of localization was as follows: a) 6 patients showed an area of segmental pneumonitis somewhere in this time period b) Using the rigid bronchoscope localized the tumour in 9. This was proven by direct biopsy, and frequently required more than one bronchoscopy over a prolonged time period. c) bronchograms and tomograms showed abnormalities in 5 patients. Of these 19 patients, 5 were treated by radiotherapy because of general condition or refusal of surgery. Three of the irradiated patients died of recurrent cancer within three years. The other two died within one year of unrelated disease. Fourteen patients underwent resection, with one operative mortality. At pathology, the tumours were "in situ" in 6 and invasive in 13. There was no evidence of nodal spread. When last followed up in 1979, there were no cases of recurrent tumour and no cases of second lung primary tumours. Similar experiences have been reported from the Mayo Clinic (2), Johns Hopkins (3) and Memorial Hospitals (4). Early detection of radiologically occult tumours which are in situ or minimally invasive has given uniformly good results. There have been no deaths from recurrent or metastatic cancer in surgically resected patients, and only one second primary tumour has been detected. Interestingly, the Hopkins group reports that 5 patients with Stage I squamous cell tumours refused operation. One refused any treatment and died of disease at 12 months. Three were radiated, and were alive from 14-38 months post-treatment, all with evidence of recurrent disease. [Sudbury Sintering Plant Study](5) From 1948 to 1963 an open travelling-grate sintering process was employed to convert nickel sulfide to nickel oxide at an International Nickel Company operation. The environment in this plant was particularly dusty and filled with fumes. It became apparent by 1969 that the incidence of bronchogenic carcinoma was markedly increased in workers from this plant. A concerted effort was made to track down all workmen with this exposure. During 1973 and 1974, 268 men were studied. Chest radiographs were done and showed no mass lesions. Sputum was collected on three consecutive days and analyzed. There were 12 men with malignant sputum, all of the squamous cell variety. Two refused any investigation, one presenting 31/2 years later with extensive hronchogenic carcinoma, and the other 5 years later with extensive carcinoma of the maxillary sinus. In the remaining ten patients careful rhinolaryngeal examination as well as a detailed bronchoscopy, involving examination, brushings and biopsy of all pulmonary segments was carried out. One patient was found to have laryngeal carcinoma and was treated by radiation. In nine patients, the malignancy was localized to the lung, leading to six lobectomies, two pneumonectomies and one sleeve lobectomy at operation. However, the follow-up in these cases suggests a different biological behaviour with these industrially related tumours. While no tumour has recurred locally, one patient has died of metastatic cancer and two patients have developed second and one patient a third pulmonary primary cancer. However, survival has still been much better than wits radiographically manifest lung cancer. [Technique of Localization] (6) Following a careful rhinolaryngeal examina examined and then the lower respiratory tract is examined. This is all performed under general anaesthesia. The trachea is examined with the rigid Jackson bronchoscope, collect-

Jan 1, 1981

By R. M. Rowe, A. K. Bhasin, D. Malhotra

Introduction Most primary molybdenite producers use a selective flotation process in which molybdenite is floated from the ore while other sulfide and nonsulfide gangue minerals are depressed in the same step. The process was developed at the Climax mill. Reagents used in the rougher flotation stage include vapor oil (collector), syntex (surfactant), pine oil (frother), and occasionally sodium cyanide and Nokes reagent (depressant). Rougher concentrate is upgraded by cleaner flotation to produce market-grade molybdenite concentrates. Reagents used in the cleaner flotation stage are Dowfroth 250, vapor oil, sodium cyanide, and Nokes reagent. The development of the flotation reagent scheme at Climax and the role of the reagents have been well described by Born et al. (1976) and Malhotra et al. (1976, 1977a, 1977b, 1977c, 1980). The hydrocarbon collector, vapor oil, accounts for approximately 50% of the total molybdenite flotation reagent cost. Because vapor oil sources are limited, and the cost of vapor oil has increased significantly over the last decade, several studies have been done to evaluate alternate oil-based collectors and/or blends of collectors that would produce similar metallurgical results at a reduced cost, or increase the overall molybdenite recovery at the same cost (Smit and Bhasin, 1983; Hahn, 1969; Smith and Bhappu, 1971). The approach taken in the present study was to evaluate alternate nonoil-based collectors and collector systems that are less expensive than vapor oil. A series of potential nonoil-based collector classes were identified and evaluated in the laboratory against the current collector system. The metallurgical performance of these collector classes was related to their chemical structures. The results of this study are discussed. Collector classes A survey of sulfide mineral collectors was performed with the objective of identifying and selecting potential collectors for molybdenite flotation. The available reagents were categorized into 10 general classes. Table 1 summarizes these collector classes, their chemical formulas, the manufacturers, and selected commercial collectors in each class that were evaluated in the present study. Experimental procedure A Climax ore sample, assaying 0.3% MoS2, 2.2% FeS2, 0.007% Cu, 0.003% Pb, and 0.03 oz per ton Ag, was used for this study. Standard laboratory rougher flotation test procedure involved grinding a 2-kg ore charge in a rod mill at 60% solids. Reagents were added to the rod mill including a collector, syntex (0.005 kg/t), pine oil (0.03 kg/t), lime (to adjust pH to 8), and sodium silicate (0.15 kg/t). The ground pulp was transferred to a 1000-g cell, and flotation was performed at 35% solids and 1800 rpm using a Denver D-1 flotation machine. Concentrate was collected for a flotation time of six minutes. The general approach used in the present study was to substitute the nonoil-based collectors at two to three different dosage levels (0.01 to 0.15 kg/t) for vapor oil in the bench-scale, open-circuit rougher flotation tests

Jan 1, 1987

By Walter C. Jr. Sherman

6.1-SOIL MECHANICS WALTER C. SHERMAN, JR. 6.1.1-DEFINITION Soil mechanics is concerned with the behavior of soils in relation to the design, construction and performance of engineering works. In this context, soils include all uncemented materials, such as, gravels, sands, silts and clays, either naturally or artificially deposited, and, under certain conditions, weakly cemented, badly broken or weathered rocks. Many types of mine wastes have physical properties similar to those of soils and thus are amenable to analysis by the principles of soil mechanics. The principles of soil mechanics are used to solve such problems as the stability of various types of structures with respect to failure of the supporting soils, determination of soil pressures and deformations in the design of foundations and retaining structures, analyses of seepage and under seepage, and stability with respect to sliding of excavated and natural slopes and embankments. 6.1.2--SOIL PROPERTIES Soils are classified on the basis of index properties, such as, particle-size distribution and plasticity characteristics. The Unified Soil Classification System1 used to classify soils for engineering purposes is shown in Table 6-1. Other physical properties important from an engineering standpoint include natural water content, density, permeability, shear strength and compressibility. Physical properties are evaluated on the basis of carefully conducted laboratory tests. Procedures for laboratory testing are presented by Lambe. 2 Soils, either of natural or artificial deposition, are complex three-phase materials consisting of solids, water and gas (usually air or water vapor). One of the most important principles in soil mechanics is based on the concept of effective stress in the soil-water system. A stress, a, applied to a saturated soil is taken partly by the soil particles (effective stress, a'), and partly by the water in the voids (neutral stress or pore water pressure, u,) so that a' = a - u,. Only the effective stress affects the mobilization of frictional resistance between soil particles. In partially saturated soils, the pore-water pressure is negative due to capillary effects. The effective stress relation remains valid for small negative pore pressures, but anomolies arise if the soil is significantly unsaturated. In this case, the pore pressure is commonly assumed as equal to the pore air pressure, u,, so that [ u' = u - u..] 6.1.3--SOIL EXPLORATIONS Soil explorations are carried out by borings or test pits. Hvorslev3 has reviewed procedures and boring requirements, such as, type, depth and spacing employed. In general, soil strata are logged and representative exploratory samples are recovered for classification purposes and for determining the subsurface soil profile, which is constructed utilizing also knowledge of the geology of a site. Undisturbed samples are recovered if the properties of the undisturbed soil are required, as generally is the case. The undisturbed soil sampler consists of a thin-wall tube

Jan 1, 1973

By N. L. Parduhn

Populations of Bacillus cereus spores are elevated in soils over four subsurface gold deposits in the western United States. Large deposit-to-background ratios of B. cereus populations were obtained in soil traverses over the Minnesota vein deposit, Empire District, Colorado (maximum 50:1); the Shasta (maximum 3,500:1), and Evening Star maximum 18,000:1) vein deposits, Shasta County, California; and the Hog Ranch disseminated gold deposit (maximum 40,000:1) in Washoe County, Nevada. Small increases in the concentration of toxic metals in the soil may be responsible for the elevated spore populations. The observed elevation of B. cereus spore populations near these gold deposits indicates that the method should be further investigated as a potential exploration tool.

Jan 1, 2013

By Carson Sharp Beltch

The determination of aqueous cyanide is accomplished by either detection in the sample as collected or by removal of the cyanide of the collected sample, followed by detection. The direct determination of the cyanide content of a solution can only be used in the simplest of systems, since many interferences can result in errors. Thus the most widely used method for total cyanide determination involve the reflux distillation of the sample using heat, acid and vacuum or air flow. The basic theory underlying this analytical approach is that by reducing the pH, the quality of molecular hydrogen cyanide will be in- creased and can be removed from the solution by elevating the temperature. The hydrogen cyanide is then collected in a caustic solution and analyzed. The general approach of removing the cyanide from the sample by distillation represented a major advance in this area of analytical chemistry. It enabled the determination of cyanide in many additional types of samples. When it became apparent that the tightly bonded cyanide complexes were not being detected by this approach, many methods fox complex ion destruction were proposed. These methods usually involved low pH adjustment with oxidizing mineral acids, coupled with the catalytic decomposition of the tightly hound complexes. All off the complexes except the strongest could he broken by these methods. The catalytic reflux distillation step has been found to have some negative aspects, since many materials that can be distilled with hydrogen cyanide will interfere with the color development step and result in a false positive reading.

Jan 1, 1981

By Tugba Kami?oglu

Hydromagnesite (Mg5(CO3).(OH)2.4H20), one of the sedimentary deposits in Salda Lake Basin, is developed under the control of active tectonics regime. Since the occurrence and deposition mechanism of hydromagnesite are unstable under atmospheric conditions, in order to evaluate the precipitation process, systematic host rock, lake water (surface, 20m, 40m, 60m) and hydromagnesite sampling were carried out. Macro, micro, XRD and chemical investigations were done in detail. Not only the results and formation and crystallization mechanism but also hydromagnesite's St values were evaluated. Main resources could be ultramaficmafic surrounding rocks for hydromagnesite formations. However, hydromagnesite development is considered in different phases, because it has showed various characteristics in Kayadibi and Köpekcayin areas. In Kayadibi area Huntide-Dolomite-Aragonite-Hydromagnesite paragenesis has been realized. Hydromagnesite has also formed in Köpekcayiri area, large amount of hyrdomagnesite occurrences and levels various are noticeable. Actual position of hydromagresite levels exhibits tectonic influences in and around the lake. Therefore, the levels seems to exhibit secondary formation properties. In addition, the formations are being still maintained sedimentation as products of a peripheral deposition phases. Resolving and redifferentiation sedimentation processes probably improve in periods of lake water chemistry especially Ca/Mg proportional changes, and also SI variations indicate the mentioned precipitation mechanism. Similarly, side and into the lake hydromagnesite is stored different levels and ultramafics-mafics rocks fallow indicated stages. It is postulated that hydromagnesite formation, which is existed by result of determined developments and multiphase sedimentation, could be originated from probable crack zones on the lake bottom.

Jan 1, 2005

By M. Karmis

"The process of coal mining, as indeed of the mining of any stratified mineral, is inevitably followed by some degree of sinking of the superjacent strata and consequently of the surface." Royal Commission on Mining Subsidence, Second and Final Report, London, 1927. INTRODUCTION The above statement was used to describe mining subsidence in the classic report of the "Royal Commission on Mining Subsidence," published in 1927. In fact, this phenomenon has been recognized in Britain since the early fifteenth century, as revealed from court records of disputes and litigations related to property damage above mine workings (Shadbolt, 1978). The first attempts to investigate and analyze the mechanisms associated with mining subsidence, however, date back to the 1800's and were pursued by Belgian Engineers. This research effort was initiated as a result of the widespread movements and subsequent structural damage suffered by the City of Liege in the 1820's. The most notable achievement of the Belgian school of that era was he publication of Gonot's treatise "Loie de la Normal" in 1871 (Gongt, 1871).

Jan 1, 1982

By Francis F. Pitard

The presence of elements, minerals, or chemical compounds in materials at very low concentrations is becoming a constantly increasing concern for several segments of the Industry. Some trace elements or chemical compounds may be considered as hazardous, some are simply considered as undesirable In complex processes where they could be constantly recycled and end up as the major factor of decreasing quality for some valuable products. In some other cases, the presence of a trace element or mineral may be highly desirable because of its economical value: precious metals are falling into this category, they probably were the first trace elements to draw our attention. Tremendous quantity of money is spent for analysis at the trace level, also the analytical "tool" has been considerably improved during recent years, but still the sampling aspect of the problem remains obscur for many, and because of it, large quantity of analytical efforts become meaningless. Not only the absence of sampling strategies is badly affecting the representativeness of a large majority of samples, but furthermore for the same reasons, many laboratories are failing In their endeavor to prepare reliable standard reference materials. The reason of this failure has its roots in the unability to estimate effectively the sampling characteristics of the element, mineral, or compound of interest, not to mention the unability to perform precise and accurate complete analysis, so essential for the instrumental analyst (1). In this paper a strategy to perform a better sampling operation is recommended. SELECTION OF A PROBABILISTIC APPROACH AS SOON AS PRACTICALLY POSSIBLE It Is essential to differentiate probabilistic sampling from non-probabilistic sampling. As Illustrated in Figure 1, the sampling operation Is a selection process which could be performed In two different ways: I. A probabilistic selection process according to which all elements of a lot of material to be sampled are submitted to the selection with a same probability of being selected. 2. A non-probabilistic selection process according to which all elements of a lot of material to be sampled are submitted to the selection with different probabilities of being selected.

Jan 1, 1986

By Stephen G. Whittaker, Rosalind A. Schoof, Martha J. Steele

In determining remedial action objectives for metals in soils, the U.S. Environmental Protection Agency typically assumes that the metal concentrations in house dust are the same as the metal concentrations in soil. Data now available from several studies that were conducted in mining communities suggest that for some metals, concentrations in house dust may be lower than those in soil. This paper reviews available data on the relative soil and indoor dust concentrations of arsenic and cadmium and examines how changing assumptions regarding indoor dust concentrations of arsenic affects risk assessments and determination of cleanup levels.

Jan 1, 1992

By P. J. Lafforgue

In 1974- COGEMA (Compagnie Generale des Matieres Nucleaires) of France decided to exploit a uranium deposit discovered several years ago in a Permian formation of Southern France, near the town of Lodeve (Herault). The uranium occurs in black shales with high calcium carbonate content (7-10% CO2) and it was then necessary to use alkaline leaching. A fine grind (60-65% minue 270 mesh) was also necessary to obtain good' uranium recovery. A minimum of fresh water must be added to the alkaline system due to solution recycling. Filtration must be used because cake-washing requires less fresh water than countercurrent decantation.

Jan 1, 1982

By D. B. Stephens

Milling operations throughout the world have created vast amounts of waste by-products, or tailings, which are often disposed on the land surface. The wastes may be disposed behind dams, on untreated ground, or on compacted clay or synthetic liners of impoundments and trenches. Often one of the principle concerns of environmental regulatory agencies is whether seepage from the waste pile could move through the vadose zone to the water table and possibly contaminate an aquifer. The seepage may be generated by the drainage of liquids initially deposited along with the tailings or by infiltrating meteoric water which leaches solutes from the tailings. The purpose of this article is to discuss some of the commonly held assumptions regarding storage of seepage wastes in the unsaturated zone. The significance of recent studies of water movement in dry climates which pertain to tailings site selection will be presented. The paper is relevant not only to seepage from impoundments at mill sites, but to many other fluid waste impoundments as well in part this article reinforces earlier work by Stephens and Siegel (1980) and an excellent review paper by McWhorter (1985). The present report addresses considerations in porous media; for a discussion of the effects of fractures and anisotropy in the unsaturated-zone, refer to the paper by McWhorter (1985).

Jan 1, 1985

By John A. Rajala

The water chemistry of the froth flotation pulp is one of many parameters which can affect the flotation process. The fluid may contain certain inorganic salts which, along with increased ionic strength, can produce undesirable flotation depression or activation. A source of a salt could be the use of calcium chloride to prevent freezing in ore cars, chutes, and bins (Anon., 1980). Alternately, the salt or salts could be initially contained in the water as in the case of sea water and some brackish waters. These salts may become more concentrated because of the need for recycling of plant water due to environmental regulations and/or economic considerations (Davis, F.T., et. al., 1976). The presence of inorganic salts in flotation pulps and their effects upon the recoveries and surface chemistries of different oxide minerals have been the object of various studies. Some researchers (Fuerstenau, D. W. and Raghavan, 1976; Fuerstenau, D. W. and Modi, H. J. 1960; Kulkarni, R. D. and Somasundaran, P., 1977) have reported that addition of a salt can increase or decrease flotation recovery depending upon the particular system.

Jan 1, 1982

By Marini David, Pigorini Andrea, Fuoco Stefano, Zurlo Raffaele

"The excavation of a tunnel in highly weathered and strongly fractured rock masses due to tectonic actions is still a challenge. In order to maintain reasonable productivity, excavation through a wide zone of highly tectonized rock mass requires a detailed, integrated study of the construction solutions and a monitoring system to minimize the process time and to optimize the adopted consolidation measures in accordance with a predefined matrix of possible support systems. This paper summarizes some interesting data acquired during the excavation of the Brenner Railway Base Tunnel system between Italy and Austria. The Brenner Base Tunnel (BBT) runs through the fault line between the European and the African tectonic plate. This big fault zone is called “Periadriatic Line.” In particular, data acquired in the exploratory-service tunnel have been analyzed. Furthermore, the base concepts for defining the consolidation and support solutions adopted for the excavation of the exploratory tunnel are described. INTRODUCTION The Brenner Railway Base Tunnel (BBT) is a system of underground structures and tunnels that is designed to connect Italy and Austria using new railway standards. It is based on high speed (HS) concepts and applies the European Standards for Interoperability (TSI). The railway includes twin tunnels for a total length of about 55.0 Km without considering the connection tunnels to the existing underground railway in Innsbruck. Including the latter, the total length of the tunnel system reaches 64 Km, and is among the longest tunnels in the world. The Italian section passes through the so-called ""Periadriatic Line,"" which is an important tectonic structure generated by the collision between the European and the African tectonic plates. Despite the extensive investigations carried out (boreholes down to 700 meter depth), significant geological and mechanical uncertainties inside the Periadriatic formations remained unsolved. In order to elevate the level of confidence and observe the behavior of the rock mass at a representative scale, the BBT Authority decided to excavate in advance the service tunnel, which has taken the function of an exploratory tunnel. The data and observations collected during its excavation would provide important insights for the design of the main tunnels."

Jan 1, 2016

By G. Milojcic

The opencast lignite mines in the Rhinel and Di strict/Germany are equipped with the continuously operating bucket-wheel excavator - conveyor - spreader system. High productivity requires large capital expenditure on main mine equipment as a precondition for efficient mining. In operation, the technology employed leads to a particular cost pattern which is quite different from that of other industries. Labour, auxiliary equipment and mobile vehicles are the most important cost factors which can be controlled by the management. In this respect information processing computer systems are used for systematical and interpretable representation of operational tasks and jobs both in planning and work preparation and in recording the operational data describing the work result and the use of resources. Another aim of the project is to relieve the middle management of major part of its administrative routine work. Job-related work planning and data recording open up various possibilities of analyzing the operational procedures. This analysis shows, for example, what auxiliary machines are particularly suitable for specific tasks, and working groups can be organized so as to take account of the different skills of individual employees for the sake of an optimal work product. Computerized information processing provides the decision makers with topical information related to their respective responsibilities. The mining department of the Hambach opencast mine is the first user of the PERMAD system. Due to the favorable evaluation it has been decided to introduce PERMAD in three other mines in the course of 1992/93.

Jan 1, 1992

By J. H. Tylczak, R. Blickensderfer, D. J. Singleton

As part of its research on wear of mining and mineral processing equipment, the US Bureau of Mines evaluated the erosion-corrosion characteristics of 12 alloys in phosphoric acid waste water. Tests were conducted on 2- and 5-cm-diam specimen8 in 12- and 60-cm-diam ball mills by grinding phosphate rock in gypsum pond water with an initial pH of 1.6. For comparison, grinding tests also were conducted in tap water. Static corrosion tests in gypsum pond water also were carried out. For all alloys tested, the wear by erosion-corrosion was greater than the sum of erosion plus static corrosion. A low-alloy, high-carbon steel and a high-manganese, nitrided stainless steel were the most cost-effective materials

Jan 1, 1987

By Thomas F. Pedersen, J. Jay McNee, Alan J. Martin

Field sampling was conducted in Lake Junin, Peru in order to assess the post-depositional reactivity of the highly contaminated lake sediments. High resolution profiles of dissolved Fe, Mn, SO42- and H2S across the sediment-water interface illustrate that the organic-rich sediments in the main basin become anoxic within several millimetres of the sediment-water interface. These permanently submerged deposits in the main basin serve as a diffusive sink for dissolved Zn and Cu. Conversely, the periodically unsaturated deposits in shallow areas are characterized by the remobilization of Zn and Cu in the deep acidic (pH < 4) pore waters, resulting in the release of these metals to the overlying water column.

Jan 1, 2000