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By M Scott, J J. McEwan

Silver and silver alloys tarnish readily by the formation of tarnish on the surface when exposed to a wide range of sulphur-containing atmospheres. This tarnish is unsightly and undesirable and can be removed either with a silver polish or a chemical dip. Polishes are, however, not suitable for irregular and embossed surfaces such as on coins, medallions and jewellery items, because of uneven removal of the tarnish layer and excessive wear. Successful tarnish protection can be achieved by either storing the items away from the aggressive atmosphere or by coating/treating the exposed surfaces with a protective layer. Storage is feasible for collections but is not suitable for items that are handled or worn regularly, such as jewellery. A number of commercial coatings and treatments have been developed, but to date there has not been a systematic evaluation of tarnish protection. This paper details the performance of a range of generic coatings in an accelerated tarnish test. The degree of tarnish was evaluated by means of loss in reflectivity and change in colour. Four coatings/treatments improved the tarnish resistance of silver by more than tenfold. These include an organic lacquer, rhodium electroplating and an organic self-assembled monolayer (SAM) conversion coating. Research is continuing to optimise these coatings. Keywords: silver alloys, tarnish resistant coatings, silver polishes.

Jan 1, 2006

I had hoped when the time came for me to address this meeting that gold mining would be in a much happier position than we find it to-day.As it is, and because of the demands of national security, we find this great and valuable primary industry relegated to the background and in danger of temporary extinction.These notes refer mainly to gold mining in Western Australia, whence comes the major portion of Australia's production, and their purpose is to record a brief review of the industry immediately prior to the general disorganization that is following the call-up of men from the mines.During this period of reduced production the loss of comparable statistical data will make it impossible to follow the progress of the industry, and, since the period may be long, it occurred to me that information might be derived from an examination of the trend of recent production that would indicate what may be expected of the industry when full production is resumed in the future.Since the revival of gold mining, which started in 1931, most of the old-established mines have reorganized and, in some cases, completely renewed and enlarged their equipment in order to achieve maximum production, and old mines hitherto unpayable have been re-opened and equipped. At the same time large sums have been spent in scientific prospecting and in search for new mines, and it is safe to say that at the end of 1939, when gold production reached its peak, practically every known mine in Western Australia that could be worked profitably was in production.During this period the number of men employed in the industry rose from 5,961 in 1931 to approximately 15,000 in 1939. From the outbreak of war in 1939 to the end of 1941 the output from the mines was maintained at full pressure, maximum tonnage beingrecorded in 1940, although a reduction in the grade of ore treated caused a slight falling off in gold production.During 1941 there was a. fall in both tonnage and grade. The decline in tonnage was due partly to the closing of the Lancefield and Mount Magnet mines, and partly to the shortage of labour brought about by the response of the goldfields to the call for men for the fighting services, the average number of men in the industry in this year being reduced to 12,929.With the entry of the United States into the war in December last and the pooling of the resources of the allied nations, the need for gold as a purchasing medium passed, and with its passing there arose the demand for the transfer of the man-power engaged in gold mining to other fields of industry directly connected with the war effort.There was a ready response by those connected with the industry who...

Jan 1, 1942

By Byron S. Kutscher

This report summarizes the program to develop and construct an improved light-scattering dust monitor (ILSDM). This improved light-scattering dust monitor, which operates on the forward light scattering principle, provides instantaneous measurements of airborne dust concentrations in units of mg/m. The program was divided into two phases. Phase I involved the design of the ILSDM which was reviewed by the Bureau of Mines. Phase II included the fabrication of a prototype ILSDM based upon the design developed during Phase I. After completion, the ILSDM was delivered and demonstrated at the Bureau of Mines. A description of the final ILSDM design, operating instructions, maintenance instructions and recommendations for additional work are also included in this report.

Jan 1, 1980

By Leandro Rocha Lemos, Guilherme Liziero Ruggio da Silva, Iara Patricia Vieira de Oliveira, Paulo Santos Assis, Lorena Cristina Amorim Moura

O coque fica exposto a diferentes solicitações mecânicas do tipo impacto, abrasão e compressão, desde o desenfornamento até o seu consumo no Alto-Forno. Para evitar que o coque sofra uma acentuada degradação, é exigido que o mesmo apresente uma elevada resistência mecânica a frio. Para monitorar tal parâmetro, utiliza-se principalmente o teste de tambor, porém este contempla apenas a degradação por impacto e abrasão. Neste contexto, este trabalho desenvolveu uma metodologia para avaliar a resistência mecânica à compressão, inicialmente em partículas individuais de coque, apontando quais seriam as granulometrias mais resistentes. Os coques foram transformados em corpos de provas e testados em máquina de ensaio universal. Os resultados apontam que a tensão média de ruptura cresce com o aumento da granulometria. Posteriormente, foi avaliado a resistência mecânica à compressão em leito de coque, onde foi possível simular em uma prensa hidráulica, a pressão que a coluna das cargas exerce sobre o leito de coque no Alto-Forno e, posteriormente, correlacionou a compressão com o teste de tambor e se obteve excelentes resultados.

Oct 1, 2019

By J. W. Thompson

BURYING DEAD MINERS. BURYING BODIES OF DEAD MINERS. REVISED STATUTES (HURD) 1874, P. 263. SEC. 22. LIABILITY OF RAILROADS, ETC., FOR BURIAL EXPENSES.-When any railroad company, stage or any steamboat, propeller, or other vessel engaged in whole or in part in carrying passengers for hire, brings the dead body of any person into this State, or any person dies upon any railroad car or in such stage, steamboat, propeller or other vessel in this State, or any person is killed by cars, or machinery of any railroad company or by accident thereto or by accident to or upon any such stage, steamboat, propeller, or other vessel, or by accident to or in or about any mine, mill or manufactory,* the company or person owning or operating such cars, inachinery, stage, steamboat, propeller, or other vessel, mine, mill or manufactory shall be liable to pay the expenses of the coroner's inquest upon and burial of the deceased and the same may be recovered in the name of the County in any court of competent Jurisdiction. NOTE--The original Act of February 15, 1855 (Laws 1855, p. 170), makes no reference to the dead bodies of persons killed" by accident to, in or about any mine."

Jan 1, 1919

By Aldo Bendezú

En el Perú, el cobalto @>0.1% de concentración se da principalmente en sistemas hidrotermales, particularmente en yacimientos de tipo IOCG y en vetas altoandinas de Zn-Pb-(Ag)-Ni. El primer tipo se presenta en al menos dos segmentos del cinturón de yacimientos IOCG de la costa, entre Lima e Ica. El segundo ha sido documentado principalmente en la Cordillera Oriental, entre Huánuco y Puno. Se han identificado 29 sistemas de vetas y mantos significativos entre ambos tipos. En las vetas, estos ocupan porciones restringidas de 100-500 m de largo, 50-200 m de alto y 0.2-1.5 m de potencia, sugiriendo masas prospectivas del orden de 0.2-0.5 Mt por cada sistema.

May 10, 2023

By W. J. Kroll

This investigation was undertaken with the idea of studying a number of unconventional methods for making chromium to determine whether production cost could be lowered and to discuss some of the more recently described processes. These comprise carbon reduction of the oxide in vacuum, nitride dissociation, fusion electrolysis of the chloride, amalgam method, iodide dissociation, calcium reduction of the oxide, hydrogen reduction of the chloride, and reduction of this compound with zinc and with magnesium. Preference is given this latter method, which is shown in a flow sheet. Special attention is given purification of the chloride and separation of the vacuum at about 900° C. A reduction method for the elimination of traces of oxide contained in pure chromium by pure hydrogen obtained from the dissociation of zirconium hydride is described. The various methods are compared in a table in the appendix. Aluminothermic and silicothermic methods for the reduction of chromium oxide and the aqueous electrolysis have been disregarded in this investigation.

Jan 1, 1950

By E. Robles

The Tati Activox® Project (TA®P) is the first step towards the implementation of the Norilsk Nickel Activox® process. The ultrafine grinding (UFG) and autoclave pressure leach process conditions are the heart of the Activox® patent. Low grade base metal sulphide concentrates are leached in the process to recover the base metals and to produce LME grade nickel and copper cathodes and cobalt carbonates. The downstream processing of the metal-containing liquor produced by this process includes solvent extraction circuits to extract and concentrate metal-rich solutions, before the various final products are obtained. This paper gives an overview of many of the relevant design aspects taken into consideration in the design of the Tati Activox® solvent extraction circuits. It addresses key design elements related to leach process conditions such as scaling, materials selection for corrosive solutions, pH control, crud formation and treatment, multiple SX trains designed to prevent organic cross-contamination, and design aspects related to the mitigation of fire risks.

Jan 1, 2009

By H. A. Wheeler

IT may surprise some of our members to learn, among the industries based on the mineral resources of the United States that of clay now ranks third, being exceeded in value of product only by pig-iron and coal. The present annual value of clay-products exceeds the value of the outputs of gold and silver, and also exceeds the combined values of copper, lead, zinc, aluminum, mercury, antimony and nickel. These facts are shown in Table I. which gives the statistics for the year 1902

Jan 1, 1905

By H. E. Hilliard

The Bureau of Mines investigated hydrometallurgical procedures for concentrating precious metals from a mechanically processed metal fraction of obsolete military electronic scrap. Feed material for the leaching procedures described in this report was the high-tension-separated metal concentrate obtained as a fraction from mechanically processing partially stripped electronic units. Initial pretreatment with a 20-wt-pct-NaOH solution solubilized most of the aluminum. After washing, the resulting residue was incinerated to destroy any organics attached to metal particles. The incinerated residue was leached with 20-vol-pct H2S04 solution using two methods, countercurrent pressure and ultrasonic-aided leaching to solubilize the base metals, predominantly copper. Silver was recovered from the base metal leach residue using 50-vol-pct HN03, and gold contaminated with several percent palladium was recovered from the silver leach residue using aqua regia. The impure silver and gold plus palladium products represent about 1.5 wt pct of the high-tension-separated metal concentrate. Included is a three-step process evaluation study of mechanical processing of general electronic scrap and two hydrometallurgical procedures for leaching high-tension-separated metallic concentrates obtained from the mechanical processing step. Process evaluation concluded that only mechanical processing is economically viable.

Jan 1, 1985

By P. R. Scheller

Reactions between metal and slag are of decisive importance for metallurgical processing. In the continuous casting process, where metal solidifies at the metal-slag interface, reaction products can cause surface defects, with quality damages of the cast products as a consequence. These investigations are focused on the contact area between casting flux and metal. The samples were taken from the mould during the casting process. The results show that layers up to approximately 300 nm from the slag/metal interface represent a specific reaction space. Sodium in this layer on the slag side plays a specific role, which is explained on the basis of experimental results. The transport of oxygen near the interface and the charge transfer is explained on the basis of the ionic character of the slag. The mass transfer rate of oxygen crossing the interface is calculated from measured data, and conclusions concerning the stability of the interfacial tension are made. Keywords: mass exchange, metal slag reaction, interface, ion transport, oxygen transfer, oxidation, casting slag, flux, sodium

Jan 1, 2004

By S. A. Aye

Vibration levels on a variety of equipment in a South African opencast mine were measured in this study. The well-established ISO 2631-1 (1997) standard methodology was used for the computation of weighted root mean square (WRMS) and vibration dose value (VDV). This method was used to evaluate the whole-body vibration (WBV) on a wide range of equipment in the opencast mine using the two main parameters, namely the daily exposure A(8) which is based on the WRMS concept and the VDV which measures shocks. The results obtained show that while the majority of the equipment rendered exposure levels that are below the exposure limit value (ELV), exposure levels on about half of the equipment do exceed the exposure action levels. The study also highlights the importance of shock in the observed responses.

Jan 1, 2011

By Segundo Bejarano R

Durante mucho tiempo los métodos tradicionales utilizados en la ejecución de los proyectos en el sector minero han sido insuficientes. Por ello, la minería optó por emplear técnicas modernas de planificación y control que ahorren tiempo y minimizen recursos como mano de obra, maquinarias, energía y otros. En este sentido, el objeto del texto es describir el uso del método PERT-CPM en la ejecución del proyecto minero, así como señala su aplicación práctica en el proyecto de ampliación que viene ejecutando la compañía de minas Orcopampa.

Nov 24, 1986

By Bengt H. Fellenius

Session 2, Deep Foundation without Soil Excavation, has attracted no fewer than 22 papers dealing with subjects from soil improvement by grouting, injection, and deep mixing techniques through vibroflotation and special piles, including aspects pertaining to conventional driven and bored piles. In the short time available, it is not possible to both do justice to the papers and provide a critical review of the state-of-the-art. Instead, to meet the objective of making the next half hour worthwhile to the audience, I have chosen to comment on a few special points brought forward in the papers and thereafter to discuss more in detail a couple of aspects I have deemed to be of general interest. Four papers deal with jet-grouting, injection, and deep mixing techniques: DOMSKI, J. J. Reinforcement of subsoil under the foundations of historical buildings in Cracow using deep injection technique. RESTELLI, A. B, BERTERO, M., and LODIGIANI, E. Deep mixing technology to improve the bearing capacity of a very soft clayey soil under an earth embankment.

Jan 1, 1994

By Dhar B. B, Gupta R. C

Grinding of iron ore is an essential step to utilise ore fines for pelletisation needed for DRI units. While preparing iron ore pellets for DRI production, the iron ore needs extensive grinding which is highly energy consuming step causing the process to become non-viable in some cases. In the present paper an attempt has been made to evaluate grinding performance of thermally treated ore compared to normal ore grinding. Such thermal pre-treatment has been found to reduce the energy requirement with lower consumption rate of grinding media. It has been observed that by applying thermal shock the ore is rendered weak with improved grindability. The stresses generated due to thermal treatment may extend existing micro-cracks in the ore and in some cases it may even nucleate fresh cracks. Experimental studies carried out on thermally treated hematitite ore reveals that the heating to 400¦C followed by water quenching can cause a reduction of 45 per cent in grinding energy. The paper gives the details of the experiment and the Results.

Jan 1, 1999

By Glenn Lyle

CEMI Introduction ? Introduction of the CAF VOD Project ? Who are our partners ? What were the Outcomes What is next

May 1, 2011

These proceedings consist of papers presented at Bureau of Mines Technology Transfer Seminars in August 1983 for the purpose of disseminating recent advances in mining technology in the area of large mobile surface mining equipment safety and health. The Bureau of Mines conducts several of these seminars each year in order to bring the latest results of Bureau research to the attention of the mining industry as quickly as possible.

Jan 1, 1983

The rush for alternate iron-units in the last few years spurred a true outbreak of new alternate iron units projects many of them incorporating new process in what can be classified as the.most fruitful and innovative technology outburst, in the steel industry, in decades In a recent paper we focused on what would be, in our opinion, the ultimate targets of the use of alternate iron-units by mini-mills: 1. to improve quality, 2. to reduce cost, 3. to increase plant productivity, and 4. to improve `supplyability'. With these objectives in mind liquid hot-metal, among all possible scrap substitutes, has been proven to be by far the best. This conclusion stems from many different authors who have reviewed the `value in use' of hot-metal against other alternate iron units and measured its impact on steel-shop productivity and cost (Figure 1).

Jan 1, 1999

By G. Price

The Building Research Establishment installed a base load cell in a driven cast-in-place pile prior to it being tested under vertical load. The monitored base loads were found to be significantly less than could have been predicted by current design methods. The less than expected capacity was attributed to the drilling out procedure. An electro-level system installed in a second similarly formed pile, provided detailed information on the performance of the pile under lateral load. The information obtained was used to check several current design methods for laterally loaded piles. The findings show the potential dangers of attempting to improve design parameters from only limited performance data.

Jan 1, 2010

By Louis, Jordan

THIS paper presents in an abbreviated form the chief points of interest in an investigation of the tarnish-resistant qualities of silver alloys, an investigation which has been carried out as a joint research by the Bureau of Mines and the Bureau of Standards and will later be reported in detail in an official publication from these bureaus. In 1923 a Commission of Gold and Silver Inquiry was created by a Resolution of the U. S. Senate to study the causes of the depressed condition of the gold and silver industry. In cooperation with this commission the Bureau of Mines made a preliminary survey to determine in what ways, if any, it might be possible to increase the uses of silver. One of the possibilities indicated by this survey was the development of silver alloys which should be non-tarnishing, or at least less-tarnishing, than the usual sterling silver (copper-silver). The preparation of a rather wide variety of silver alloys and the determination of their behavior under accelerated tarnish tests in the laboratory was therefore undertaken by the Bureau of Mines and Bureau of Standards as a joint investigation.

Jan 1, 1927