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By F. A. Patty

[Health and safety hazards from contamination of the atmosphere in places frequented by persons depend to a considerable extent on whether the contaminating agent possesses sense-perceptive properties which will give warning of its presence before it '.an create harmful conditions. If a distinct and easily recognized warning is given in advance of harmful conditions, hazards ace mitigated, but if warning properties are inadequate or absent, the hazards are augmented. When evaluating the hazard presented by a potentially harmful substance used under conditions of possible escape into the air of places frequented by persons, it is therefore necessary to consider the warning properties of the substance along with ether pertinent information such as toxicity, inflammability, physical properties, and mode of use. If the contaminating agent inherently lacks warning; properties it may be possible to impart them by adding to the hazardous substance a small quantity of a relatively harmless substance which has a high warning intensity.]

Jan 1, 1929

By Alex Naudts

Pre-excavation grouting is a predictable and reliable technique performed to prevent or minimize settlement in advance of, or during the tunneling operation. It safeguards the infrastructure above the tunnel alignment. Cement based suspension grouts and sodium silicate based grouts are frequently injected to consolidate and strengthen the formation and create a reinforced canopy above the tunnel trajectory. Grouting is typically performed through permeation and permeation in conjunction with hydrofracturing. Multiple injection passes through steel sleeve pipes are ideal, since they create an effective forespiling system to facilitate tunneling without causing unacceptable settlement, even with minimal overburden thickness. Ten pre-excavation grouting projects performed in the North America are discussed in this paper.

Jan 1, 2008

By F. San Martin, Y. Lefevre, F. Tamargo

The San Juan de Nieva smelter was commissioned in 1960 with an electrolytic zinc capacity of 15,000 t/y. After a number of minor expansions, the capacity was increased to 320,000 t/y in 1991 and will reach 440,000 t/y by August 2001. The expansion involves the construction of a 900 t/day Lurgi roaster and a new acid plant. The leaching will be fully revamped and modernised, including the construction of a new building for residue treatment and for j arosite precipitation with a separate circuit for silver-containing concentrates. The project also includes the construction of a fully automated 137,000 t/y zinc cathode tankhouse fitted with 3.4 m2 cathodes designed by Asturiana de Zinc, and based on the existing tankhouse and introducing some improvements. New melting and casting facilities, also designed by Asturiana, will be constructed.

Jan 1, 2000

By Harry G. Dosh

Sillimanite, kyanite, and andalusite are aluminum silicates having the same chemical composition (Al2SiO5) and are used in the ceramics industry for the manufacture of high-grade refractories. Natural sillimanite with added corundum or other alumina to just short of mullite (3Al2O3 -2SiO2) proportions is unequalled for jobs wherein strength at high temperatures, resistance to spalling, and resistance to slagging by acid slags are desired. High-grade porcelain ware also requires these minerals. At the same cost, sillimanite would be preferred for most uses, but the lack of any large source of sillimanite bas given economic preference to kyanite or andalusite for special refractories and high-grade porcelain wares. Sillimanite-bearing schists were observed in Spartanburg County, S. C.; as early as 1937 by D. Hoye Eargle, geologist with the U. S. Soil Conservation Service. The mineral was not identified until 1942, when Miss Jewell Glass, of the U. S. Geological Survey, examined several of the deposits. This identification was confirmed in 1943 by Dr. Laurence L. Smith, of the University of South Carolina, when he examined the Spartanburg County deposits and found numerous additional occurrences of sillimanite schist in Greenville County. Subsequent work by the Bureau of Mines and the South Carolina Geological Survey has been responsible for the location of additional sillimanite-rich schist deposits in Spartanburg County. Between October 1, 1948, and November 21, 1948, the Bureau of Mines conducted an exploratory diamond-drilling project on the John Gideon property in the southeastern section of Spartanburg County (fig. 1) and drilled a total of 681.7 feet in six holes. Drilling indicated that the deposit is relatively shallow, as no ore was cut below the zone of weathering.

Jan 1, 1950

By Leggate J

In the past many coal mining projects commenced without any consideration being given to eventual site rehabilitation. Now that site rehabilitation is assuming greater importance with changing community expectations, and standards are becoming less negotiable, it cannot be ignored in either the development of mine working plans or economic models. The "unspecified" rehabilitation measures associated with many existing projects will be the subject of debate for some time to come yet. It would be wise to plan for the future. Once an agreeed standard of rehabilitation is accepted, good management involves considering practices which will facilitate eventual rehabilitation at least cost. Without planning for rehabilitation, many mines have adopted practices which are likely to result in very expensive rehabilitation measures and impact significantly on the overall profitability of the ventures. With adequate planning, procedures can be developed which achieve the same short term goals without significantly effecting cash flow but with very significant impacts on the final rehabilitation cost. This paper looks at the disposal of tailings and overburden in the coal mining process. The industry has in the past had an obvious preference for the "perceived" cheaper procedures for waste management such as wet disposal of tailings and high dumping of overburden. There are alternatives. The paper discusses the principles which should be incorporated into tailings and overburden disposal systems and identifies viable alternatives.

Jan 1, 1991

By J. Y. Kim

Silver contained in zinc calcines undergoes several phase changes as it proceeds through the leaching circuit of a roast-leach-electrowin zinc plant. In the present study, the flotation response of silver from leach residues prepared under a variety of carefully controlled operating conditions in the pilot plant has been examined. Flotation of neutral leach residue is shown to be technically viable and to merit consideration for those plants without a high acid leach circuit, but having significant silver values in the feed. Residue leach conditions must be kept slightly acidic to promote the formation of Ag2S, (Ag, CU)2S and Ag2S rims on residual unroasted sphalerite, while simultaneously avoiding the hydrolysis of soluble iron which depresses silver recovery and grade. Factors to be considered during integration of a flotation process into an electrolytic zinc plant are discussed.

Jan 1, 1990

By M S. Tuohy

Poorly judged or under-appreciated change plays a role in many major accidents. In particular, operational changes related to continuous improvement, maintenance and introduction of new technology can lead to unintended safety (and other) consequences. This paper provides an overview of the role of management of change in preventing unwanted impacts on safety, community relationships and the environment. It draws on a range of incidents covering mining, minerals processing, refining and smelting where inadequately assessed or ineffectively implemented change led to significant safety, environmental or community consequences. The paper will also highlight cases of well-managed complex change and the underlying model of decision-making in place to make those decisions. All these examples are drawn from Atturra’s experience in response to accidents or working with sites to improve their management systems. The paper will report on the challenges of applying conventional risk assessment approaches to complex or technically significant change. These typically result in either onerous and lengthy change procedures that are prone to workarounds or poor implementation. Conversely, ‘light touch’ or efficiency driven change processes present the risk of intended consequences by failing to bring appropriate expertise to bear in decision-making. Such balances can be resolved by considering the designation of ‘technical authority’ with appropriate expertise to consider the change and deconflict any production, cost or schedule trade-offs. Finally, the paper will reflect on the key components of management of change systems in the context of major accidents, highlighting good practice in how they are implemented. This will consider the integration of existing corporate processes, risk management and organisational structures into management of change systems, not just the content of change forms and procedures.

Apr 16, 2024

By Kristen E. Coose

Concrete is a mixture of a fine aggregate (sand), a coarse aggregate (gravel), cement, and water. Cement itself is the most expensive of the ingredients but generally amounts to only about 10% of the concrete mixture. Cement raw materials include calcium, alumina, iron oxide, silica, and gypsum. They are heated and chemically changed into clinker "minerals," which are then ground and shipped as cement. Each of the four main clinker minerals-tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite-impart specific strength and compositional properties to the final concrete product. During hydration of the cement, chemical changes produce new minerals that include calcium silicate hydrate gel (C-S-H, the main constituent of hydrated cement paste), calcium hydroxide, and calcium, sodium, potassium, and sulfate ions, among others. Two main reactions can occur that may be deleterious to concrete. Normal cement pore solutions, in a hydrated cement, contain sodium hydroxide and potassium hydroxide. If these alkali concentrations are too high, they can react with the siliceous aggregate (alkali-silica reaction, or ASR) to form an alkali-rich calcium silicate hydrate gel (C-N+K-S-H), which, upon prolonged contact with water, can expand to crack the concrete. The other deleterious reaction occurs when the mineral ettringite (Ca6A12(S04)3OH12. 26H20) forms after the concrete is hardened (delayed ettringite formation) and cracks the concrete. Many of the concrete bridges and structures built in New Mexico in the past 20 years are in need of replacement due to deterioration. Many others constructed very early on in the century are still sound. By collecting and analyzing samples of both old and new concrete and good and bad concrete, we compared their differences on both a microscopic and macroscopic scale. Samples taken from concrete sidewalks, parking lots, drainage canals, spillways, and a railroad-trestle foundation have construction dates that range from 1923 to 1997. They were analyzed by electron microprobe and by petrographic microscopy. Cracks, air voids, and aggregate alteration were primary locations for investigation and analysis. Using the electron microprobe, ettringite was found in voids of most of the samples, both in good and bad concrete. This leads us to believe that ettringite formation is not causing distress in the concrete. There was one exception in which ettringite was found lining a crack. In this instance, ettringite may have the ability to further the cracking and cause distress. No alkali-silica gel was identified with the microprobe. Using the petrographic microscope in cross-polarized light, a light-brown material was observed that lined some of the air voids and cracks; however, exact mineralogic identifications were not made. Although many instances of chalcedony and other deleterious quartz phases were found, no clear evidence of ASR-gel deterioration was present in our samples using these methods. However, positive identification of the ASR gel was made on an in-place concrete near one of our sample sites and in several sample cores using a newly developed chemical test for the soluble potassium ions associated with the gel. The chemical used in this test is sodium cobaltinitrite, Na3Co(NO2)6.

Jan 1, 1999

By Frank L. Wideman

"INTRODUCTION The Cphir Hill Consolidated mine was examined 2/ in January 1944. It was recommended that the mine be explored for the purpose of increasing of lead and zinc ore.The Bureau of Mines began exploratory work at the mine in June 1944 and completed it in June 1945. The work was planned to indicate ore that could be developed and extracted quickly and consisted of core drilling and trenching.ACKNOWLEDGMENTSIn its program of exploration mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. Its the policy of the Bureau to publish the facts developed by cash exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metallurgical Branch, O. C. Ralston, chief, analyzes samples and performs beneficiation tests.The work reported on in this paper was conducted under the supervision of S. R. Zinmerly, removal engineer of the Western Region, and J. A. Marsh, district engineer of the Utah-Wyoming district. Subsequent to May 1945, the project was under the supervision of Paul T. Allman, chief, Salt Lake City Division, Mining Branch. The management and employees of the Ophir Development Co. wore very cooperative. Credit is due to the Bureau employees, all local men, for the excellent amount of work accomplished."

Jun 1, 1947

By Geraldo Lúcio de Faria

O sucesso do transporte ferroviário depende, entre outras coisas, da integridade física dos componentes metálicos empregados na via permanente. Um dos mais importantes é o trilho, pois falhas catastróficas deste componente podem gerar graves acidentes. No intuito de desenvolver aços com bom desempenho para esta aplicação, estudos têm sido desenvolvidos para se entender os efeitos de composição química e histórico de processamento termomecânico sobre a microestrutura e propriedades mecânicas dos aços. Neste contexto, este trabalho caracterizou microestruturalmente dois aços de aplicação ferroviária, sendo um Standard e um Premium. Amostras representativas destes aços foram submetidas a ensaios dilatométricos e a cinética de transformação de fases austenita-perlita foi investigada. Por meio dos resultados obtidos, foi possível concluir que o aço Premium estudado possui microestrutura mais refinada e que este efeito é devido, principalmente, à menor concentração de Mn em sua composição química. O menor teor de Mn facilita a nucleação de cementita eutetóide, possibilitando a formação de perlita em tempos mais curtos e temperaturas mais baixas do que no aço Standard. Isto possibilita que o aço Premium, em seu processo de fabricação, possa ser resfriado a taxas mais elevadas do que o Standard sem formação de martensita, justificando sua estrutura mais refinada.

Aug 17, 2017

By E. Bloomstein

The Lone Tree gold mine is located about 4S kilometers east from Winnemucca on the west flank of Lone Tree Hill in Humboldt County, Nevada. The deposit occurs at the north end of the low, rolling Havallah Hills and is about 1 kilometer south of Interstate Highway 80, in sections 11 and 14, Township 34 North, Range 42 East, Mount Diablo Base and Meridian (Fig. 1). The Lone Tree deposit is outside of any previously established mining district and all lands are owned or controlled by Santa Fe Pacific Gold or affiliated companies.

Jan 1, 1993

By T. Acton

The Zarafshan/Newmont Joint Venture is currently operating in the Republic of Uzbekistan producing in excess of 400,000 oz. of gold per year from low grade oxide ore stockpiles adjacent to the Muruntau open pit gold mine located in the Kyzylkum desert of central Uzbekistan. Four stage crushing and screening produces a final product for heap leaching, Merrill-Crowe processing, and local refining for International market export. The Zarafshan/Newmont Joint Venture is the first major commercial project of its kind in the former Soviet Union to be successfully negotiated, engineered & constructed, and placed into continuous operation,

Jan 1, 1997

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

A recycling concept of end-of-life televisions starting with shredding will produce a complex material mixture, very heterogeneous in size, shape and degree of liberation. Basically all materials in television scrap are valuable, which means that recovery is important for either economic, environmental or sustainability reasons. However glass, plastics and metals are the materials with the highest potential for recovery. Non-magnetic materials from shredded television sets can be separated into three characteristic size fractions that need further separation for a high value-added recycling of the materials. This study investigated the potential of physical separation of these size fractions into valuable material streams using polyseparator, tlrldy current separator, dry and wet shaking tables and electrostatic separator. An overall mass balance of the mechanically processed televisions was calculated. Evaluation of the produced material fractions showed that heterogeneity in particle shape and size together with the presence of unliberated materials caused sever difficulties in separation when exclusively based on mechanical techniques. The results indicate that a certain degree of dismantling is necessary to achieve products of appropriate quality in physical separation. In order to improve recycling of electronic scrap through design for recycling cooperation between the electronics industry, the manufacturers and the recyclers of electronic goods is necessary.

Jan 1, 2000

By L. J. Cabri

A gold sample assaying 11.4 g Ault was selected for this study. Approximately 99% of the gold in this sample occurs as discrete gold minerals; the balance occurring as invisible gold in pyrite (determined by SIMS analysis). The sample was coarsely ground and sieved, yielding -38, 17, 22 and 22 wt.% in the -400+160 um, -160+80 um, -80+40 µm and -40 µm size fractions. Assays of the size fractions gave a gold distribution of -32, 20, 21, and 27% respectively. Processing with the hydroseparator (model HS-02) gave two tailings products and one concentrate from each size fraction. Assays of the concentrate from each size fraction gave gold recoveries of -7, 7, 24, 19%, respectively. Polished sections were prepared from each hydroseparation product and studied by image analysis to automatically search for gold minerals. Calculations were done using the surface area of the grains of gold minerals found on the polished sections.

Jan 1, 2005

By Eugene V. Cilento, R. Clark Lantz, K. A. DiGregorio

"This laboratory bas developed a sensitive electro-optical method to quantify the initial rate (R) and total amount (MAX) of superoxide (02) produced by single pulmonary alveolar macrophages (PAM). The method uses a microscope-based TV system to visualize PAM in culture, and to video record the images during the time the cells produce 02. MAX and R are calculated from measurement of temporal changes in optical density in the images due to precipitated diformazan formed by the reaction of O2-, produced by each PAM, with nitroblue tetrazolium present in the culture medium. To date, values of Rand MAX, measured due to adherence of PAM to the dish, have been compared to values obtained when quartz, coal mine dust (CMD), and kaolin . were added to the medium (in vitro). Rand MAX have also been calculated for PAM lavaged from animals exposed to quartz and CMD in the WVU Inhalation Facility. Presently, experiments are being done using which will permit PAM to be restirnulated by different dusts to help establish a dose response relation~ p and a means to study the role of lung surfactant on modifying the acute toxicity of inbaled dusts. Ultimately, this methodology should provide useful insight into establishing the role of 02 in PAM dysfunction due to inhalation of dusts, and in lung diseases such as pneumoconioses. INTRODOCTIONPAM are free cells found in the lungs which protect the lungs by removing foreign debris and bacteria. This is accomplished, in part, by the process of phagocytosis, whereby foreign matter is internalized into vesicles known as primary phagosomes. Phagocytosis also involves the chemical breakdown of inhaled dusts and the killing of microbes. Detoxification is aided by the respiratory burst, which is a metabolic response of the cell to foreign substances, that results in the production of highly reactive oxidizing agents from the partial reduction of extracellular oxygen to superoxide (02) at the surface of the plasma membrane. Superoxide undergoes either spontaneous or enzyme catalyzed dismutation reactions to form hydrogen peroxide (H202) and subsequently hydroxyl radical (OH•) and singlet oxygen (02 t ). However, while these oxygen metabolites aid in the killing of microbes they also may destroy endogenous tissue. For example, 02 has been linked to the aging process and to many diseases including emphysema, diabetes, and cancer.'' Therefore, a better understanding of the production of 02 is extremely important since an abnonnally low production could result in damage by inhaled dusts and bacteria while an abnormally high production could result in direct damage to the lung tissue by the phagocytes. Inhalation of respirable sized mineral dusts, such as quartz (silica), coal mine dusts (CMD), and asbestos, results in various pulmonary disorders. PAM are thought to play an important role since evidence suggests that the first step in fibrogenesis is an interaction of dust particles with PAM. Generally, in vivo exposure of animals to mineral dusts results in increased respiratory burst activity, migratory patterns, phagocytic behavior, and secretory potential of PAM, and for this reason these have been implicated to be pivotal events in the pathogenesis of pulmonary diseases.1 In addition to stimulation of resident PAM, an influx of monocytes into the lung and/or production of new macrophages generally occurs in response to fibrogenic dust inhalation. Further, PAM may attract and stimulate fibroblasts, which normally synthesize proteins and collagen during rep~ of tissue, by secreting chemoattractants and enzymes. Thus, PAM may be involved in pulmonary disorders through failure or partial loss of their defensive capability, or indirectly, through release of other mediators."

Jan 1, 1990

By MARCELS CHLUMBER

BY the term making an "electrical log" the authors designate an operation conceived for the purpose of determining electrically the characters of formations traversed in drilling, the determination being carried out by means of measuring the electrical resistivities of the rocks along the uncased portions of drill-holes. As in the case of an ordinary core record, this process connotes a geological studs of the strata, and for that reason it is given a similar designation. The paper is divided into three parts, of which the first deals with the resistivities of rocks in general, since it is through this electrical parameter that they are to be characterized. The second deals with the technique, and the third with the description of practical applications of the electrical logs.

Jan 1, 1929

By Leduar Ramayo C.

En la actualidad se observa que la industria minera se está enfocando en la exploración profunda en ambientes brownfield, ya que los precios de los metales y los avances tecnológicos permiten el minado de recursos que años atrás eran no económicos. La exploración brownfield posee una serie de retos para las empresas, como zonas extremadamente ruidosas, el incremento de los costos de perforación y la incapacidad de las metodologías convencionales de exploración (reconocimiento geológico y geoquímico de superficie, así como las tecnologías geofísicas convencionales) de obtener datos de calidad.

Sep 1, 2017

By Raymond B. Ladoo

The uses for which ground talcs are suited closely depend upon their physical and chemical properties , but , in spite of this fact , little scientific investigation has been made in order to devise quick and accurate tests for the determination of these properties . The chemical properties of talc are inherent and may not be altered or modified except by selective mining or by chemical processes not practical in the present status of the industry . However , the determination of chemical properties is not so important , for most uses , as of physical properties , although sometimes certain chemical characteristics are perhaps unduly insisted upon by chemists in some industries . Physical properties are dependent both upon mineralogical characteristics and upon methods of grinding and sizing and may thus be partly changed or modified by changes in practice . There is so little known of the chemistry and physics of the various processes in which talc is used that the purchase and sale of talc is governed more by rule- of- thumb methods dependent upon individual opinion and often , prejudice , than by accurate , standard tests . This not only causes unwarranted price fluctuations , but injures both the producing and consuming industries by creating false ideas of the suitability of talc for various uses . It thus seems important that present tests be standardized and made uniform for the whole industry , and that new tests devised to fill the existing gaps .

Jul 1, 1920

By E. J. Berentsen

The Turquoise Ridge gold deposit is located near the Getchell Mine, 72 km (42 miles) northeast of Winnemucca, Nevada. The deposit is owned by First Miss Gold Inc. The host rocks consist of Ordovician and Cambrian age shales and limestones. They have been crosscut by the northeast-trending Turquoise Ridge shear zone and northwest-trending shear zones. Gold mineralization occurs at depths from 427 m (1 400 ft.) to 671 m (2 200 ft.), along the intersection of these structures. Large tonnage, flat-lying deposits occur where folded, favorable beds are intersected by the faults. The carbonate within the beds has been replaced with silica, pyrite and arsenic sulfides.

Jan 1, 1996

By Kenneth J. Edmiston

The objectives of this paper are: to review the current status of chloride leach processes for sulfide concentrates, to make an evaluation as to the applicability of chloride leaching for replacing pyrometallurgical processes and to comment on recent advances in construction materials. The paper does not delve in detail on process chemistry. Sufficient references are presented on each process to allow the interested researcher to obtain process chemistry details. GENERAL The fact that chloride oxidates can solubilize base metals from sulfide concentrates has been known since the 1880's. The work of Hoepfner in 1902 was particularly accurate for its time with regard to the chemistry of chloride solutions. Recent work has dealt with the understanding of chloride extraction thermodynamics by modelling the behavior of metal chloride complexes. In the last several years several excellent review articles and symposiums have been issued covering chloride chemistry (1 thru 6).

Jan 1, 1984