Search Documents

By T. Sterry Hunt

I HAVE in a previous communication called the attention of the Institute to the geognostical relations of the crystalline iron ores belonging to the Eozoic rocks of North America, at which time I noticed (1) those associated with the gneisses of the Laurentian series, (2) those of the crystalline schists of the Huronian, as seen in Northern Michigan and in many localities along the Appalachians ; (3) those of Southeastern Missouri associated with petrosilex porphyries and schistose rocks, and presumed to be nearly of the same age with those of the Huronian schists; and (4) the highly titaniferous ores of the Norian or Labradorian series from Essex County, N. Y., and from various parts of Canada. It may here be remarked that, although the presence of titanium is most marked in the Norian ores, this objectionable element is sometimes found in the schistose ores of the Huronian, and to a lesser extent in certain Laurentian magnetites. The ores of each of these geological divisions have their individual peculiarities, which serve to distinguish them to such a degree that the magnetites and specular ores of the Laurentian are as dissimilar to those of the Huronian as are the crystalline silicated rocks of the two series. As it happens that these mineralogical dissimilarities correspond to differences in composition and in adaptability to different processes of manufacture, which, in the present condition of the iron industry, are objects of special consideration to metallurgists, it will be seen that these geognostical distinctions become of great practical importance. During the past year I was desired by the Geological Commissioners of Pennsylvania to devote a few weeks to certain geological studies in the eastern part of the State, in the course of which I was enabled to make, with regard to its crystalline iron ores, some observations to which I desire to call the attention of the Institute. I may mention, in passing, that the great South Mountain belt, from the Schuylkill to the Delaware, is composed of Laurentian rocks, in which are found the characteristic ores of the series like those of the Highlands of New Jersey and New York, and of the Adiron-

Jan 1, 1876

By Adrien Berton

FOR nearly a century, the Corocoro deposit has been renowned among geologists from the fact that it shares with the Lake Superior deposits of the United States the distinction of being the only important copper districts where native copper is worked commercially. The Corocoro district, named after the city of Corocoro, the capital of the Province of Pacajes (Department of La Paz, Bolivia) is situated towards the western edge of the Bolivian high plateau, at an altitude of a little over 13,000 ft. The most interesting part of the district is that immediately surrounding the city of Corocoro, at a distance, by railway, of 65 miles from La Paz and 210 miles to the Chilean port of Arica on the Pacific Coast. The climate of the region is that of the semi-desert, dry and relatively cold, with big differences of temperature between day and night. The rainy season begins in December and ends in March. The cupriferous lodes of Corocoro have not attracted as much interest as the silver mines of Potosi but they have been known for a long time. In the precolonial period the Indians were using the charquis, or natural native copper sheets, to make small brass objects, and the beautiful pale green brochantite of the outcrops as a source of green pigments. During the colonial period, the oxidized ores of the outcrops were worked for copper, which was used by the mint at Potosi for making currency. The native copper ores were neglected because the Spanish miners were at a loss how to concentrate and smelt them. About 1830, work by rudimentary processes, which were improved little by little, was begun on the native copper ores. The total production of native copper in the following hundred years amounted to 100,000 tons. This native copper, which was remarkably pure, was much appreciated on the European markets before the introduction of electrolytic copper. It was useful for making special ornamental brass or bronze and the granular concentrates of native copper, called barrilla, containing 80 to 85 per cent copper were suitable for making copper sulfate by direct oxidation and subsequent leaching with sulfuric acid.

Jan 1, 1936

By D N. B Skinner

Changes in the configuration of late Cenozoic volcanic arcs related to Pacific-Australian plate convergence in northern New Zealand may have localised large-scale epithermal gold-silver mineralisation to a particular part of the volcanic arc system, the Coromandel Volcanic Zone (CVZ). The history of arc-type volcanism in northern New Zealand began with the development of the continental margin Northland Volcanic Arc from early-mid Miocene (26-15 Ma). From 18-15 Ma the Northland Volcanic Arc extended south into the northern and western part of the CVZ where it is dominantly composed of andesite with lesser dacite and very minor rhyodacite. In the south, centre and east of the CVZ, younger andesite-dacite volcanism overlapped in space and time (14-5 Ma) with voluminous rhyolitic volcanism associated with rift-hosted calderas and minor basaltic eruptions. This change to bimodal rhyolitic-basaltic volcanism and extensional tectonics was a result of southwest (SW)-directed propagation of the Colville-Lau oceanic island+ arc into the north-northwest (NNW) trending Northland Volcanic Arc and its underlying continental crust. The extensional tectonic regime created in the collision zone between the two arcs is also the site of the 14-6 Ma Coromandel epithermal gold-silver province, which contains some 50 separate deposits and has a production (1862-1996) of about 300 t Au and 1150 t Ag. Extensional tectonics facilitated the emplacement of silicic magma at shallow crustal level and led to reactivation of deep basement faults. The resulting enhanced heat flow and fault-focused fluid flow localised large hydrothermal systems and associated extensive low-sulphidation epithermal gold-silver deposits in the southern part of the province, as at Waihi, Golden Cross and Karangahake.

Jan 1, 1997

By Jon Y. Kaneshiro, Ed Walton, Stephen J. Navin, Robert M. Sergeant, Storer J. Boone

The Coronado Traffic Tunnel is a proposed two-lane, reversible, road tunnel, which will relieve severe peak hour congestion problems on surface streets. The tunnel will take traffic from the Coronado Bay Bridge to Naval Air Station North Island. The project will include 12.5 m (41 ft) inside diameter by 1,112 m (3,650 ft) of tunnel, 552 m(1,815 ft) of cut and cover box structure, and 400 m (1,315 ft) of open cut structure. The geology consists of predominately clean and silty sand, saturated sand, with some clay layers, requiring Earth Pressure Balance or Slurry Shield tunneling technology.

Jan 1, 2001

By E. V. Lilford

Equity investors and project sponsors have divergent views about expected or minimum returns that should be generated by a mineral project. Irrespective of their views, the fundamental estimation of the corporate cost of capital remains singularly determinable, with additive components of risk and uncertainty often incorporated in the final analysis. This paper discusses and details the fundamental, numerical determination of the corporate cost of capital.

Jan 1, 2006

By K. Rüter

Sustainable investment is a global growth market. Companies that can reconcile economic, environmental and social objectives not only minimise risks, but also realise significant potentials of added value. This particularly applies to the metals & mining industry, as it is an attractive sector for investors and, at the same time, faces major challenges in the field of sustainable development. oekom research AG is an independent rating agency specialised in the analysis and evaluation of the environmental and social performance of companies, sectors and countries for institutional investors and financial service providers in the socially responsible investment (SRI) sector. oekom research has been active in the sustainable investment field since 1993 and its research is currently being used by managers of more than 60 bond and share funds with a volume of assets totalling more than 4.5 billion Euro. The company?s research and its central instrument, the Corporate Responsibility Rating (CRR), are based on the world's most comprehensive set of criteria for the ethical assessment of companies. With the support of an independent scientific advisory board, these universal and industry-specific sustainability criteria are being constantly updated reflecting the dynamics of global challenges in sustainable development. Increasingly, the rating results and benchmark reports of oekom research are also being recognised by the companies as a valuable tool to identify best practices, areas for improvement, and potential risks. This paper will outline the methodology of oekom research, the identification of key sustainability issues in the metals & mining industry, the development of industry-specific sustainability criteria (indicators) for the assessment of the metals & mining industry and key findings of the recently completed CRR of twenty major metals & mining companies.

Jan 1, 2007

By Douglas D. Donald

The financial analyst's job is to make an objective appraisal of the investment opportunities which exist within the various industries under his supervision within the context of the economic model provided by his firm and the a climate of investor sentiments. Industry analysis is critical. When a major investment trend develops, usually the stock of all companies within the specific industry react in the same direction. I should emphasize here, however, that an investment trend is influenced by the economic outlook, but economics is not the only determinant - investor psychology and arbitrary political factors may be of equal or greater importance. Part of our job is to recognize trends early and determine whether they are valid. Following industry analysis, the analyst must examine the specific companies within that industry since some companies usually react more violently than others to industry trends, whether they be favorable or adverse. To simplify the process of evaluating an investment opportunity, it is convenient to isolate three types of factors which have a bearing on every sort of business although the degree of influence of each factor may vary from industry to industry. These categories are, 1) independent or external factors insofar as they are beyond the control of corporate management, 2) interdependent factors insofar as influence may be exerted by industry-wide action, and 3) dependent factors covering the area of internal decisions which are basically under the control of the individual corporate managers. Although the title of this paper, "The Corporate Use of Cash Flow," is only one segment of the third category, it may be useful to continent on the first two categories as well. The independent factors may be either economic or governmental. The economic factors include cyclicality which may be very high in the case of the basic commodity industries or relatively low as in the case of utilities. Underlying growth rates, another independent factor, may range from the business equipment industry with an annual growth rate of 14% through the electric utility industry with a growth rate of about 7% per year to the

Jan 1, 1970

In the process of mining the lower seam in a multi-seam operation, a lot of oblique fract- ures appeared in the upper seam which was in the equilibrium zone. These fractures closed soon after the lower face line passed. Despite the occurrance of some degree of undulations, and and step-like unevenness, the upper seam was subsequently extracted without difficulty. When attempting multi-seam extraction, from the height of the equilibrium zone, the minimum distance between seams in ascending mining should be predicted. By analysing roof con- vergences data and the geometrical configuration of subsidence profile, it was found that the minimum safe distance for ascending multi-seam mining depends on the mining height of the lower seam and the properties and structure of the inter-stratified rocks.

Jan 1, 1986

By Charles B. Newmarch

Abstract In the course of coal studies undertaken by the B.C. Department of Mines in southeastern British Columbia, special attention was directed to problems of coal seam correlation. Methods that had been used successfully in other coalfields were found, in the Crowsnest area, to have a restricted use or furnished only additional evidence that might prove helpful when used in conjunction with other criteria. A correlation technique involving semi-quantitative spectrographic analyses of coal ashes was developed. Elements detected in the ash include Si, B, P, Fe, Mg, Mn, Pb, Ti, Cr, Ga, Ca, Al, Ge, Ba, Mo, V, Ag, ?y;b, Na, Zn, Zr, Ni, Sr, Cu, K. Of these, the elements found to be most useful in correlation were Na, Ba, Si, V, and Mg. The element Na was invariably detected in the ash from one of the seams but was not found in samples taken from any of the others. In all of the four seams sampled statistically, significant differences in the amount of certain trace elements were noted. When the values obtained for these trace elements were portrayed in the form of histograms, the resulting diagrams had a characteristic shape for each seam. The diagrams provided a basis for seam identification within the limited area (8,000 feet by 4,000 feet) that was investigated. Introduction During the field seasons of 1946, 1947, and 1948 the British Columbia Department of Mines undertook a geological investigation of the coal measures of southeastern B.C. As field work progressed in the Crowsnest area it was found that, within the Kootenay formation, which contains all the commercial seams of the region, the coal beds are the most persistent stratigraphic units. Because of relatively rapid changes in ?both the thickness of the seams and the interval between seams, difficulty has invariably been experienced in attempts at correlation. Even short-range correlati0ns by able geologists who have worked in the Crowsnest coal basin have been questioned by the operating companies. It was apparent, therefore, that a more dependable correlation technique was needed so that stratigraphic and structural studies could be of greatest value. This paper presents, firstly, a summary of the results obtained in attempted correlations using methods that have been found effective in other coalfields. Secondly, a method based on semi-quantitative spectrographic analysis of coal ash is described and the apparently promising results are discussed.

Jan 1, 1950

By Caibin Wu, Ali Lei, Ningning Liao, Jingsheng Ye

"The particle size distribution characteristics of ground product can influence the quality of the classification overflow and the next beneficiation indexes in an ore concentrator. Usually, the size distribution of ground product is considered to be determined by that of new ball mill feed. However, based on large amounts of data from industrial grinding circuit surveys, this paper has clearly shown that the size distribution of ground product should be determined by the size characteristics from classification underflow unless the circulating load was small, because the new feed is an important component and occupy a dominant position of mixed ore from belt feed and classification underflow. On the other hand, the correlation coefficient of the size distribution between ground product and classification underflow can be more than 0.99 when the relevance principle and its method are used. Meanwhile, their P80 value also keeps a synchronous correlation. The greater the capacity of classification underflow is, the higher the correlation of size distribution between the ground product and the mixed feed is. Furthermore, the correlation coefficient of the size distribution between ground product and classification overflow which is from primary or secondary can be 0.96. It is another discovery that the correlation coefficient is related to the type of classifier. The coefficient of size distribution of overflow and underflow from hydrocyclone is superior to that of spiral classifier, which can explain the reason why the hydrocyclone is widely used to replace the spiral classifier in concentrator.INTRODUCTION It is well knows that ball mill circuits closed with cyclones or spiral classifier such as a primary grinding circuit, a secondary grinding circuit and SAB mill have become an industry standard. Which grinding process employed will be determined by the P80 value of ground products. When the primary closed circuit ball mill or SAB that it is different throughout between the two processes was employed, a grinding fineness with -200mesh under 68% will be available. However, the secondary grinding circuit with the fineness of -200mesh above 80% can be conducted. Of course, the grinding fineness is determined by the grain size characteristics of the mineral."

Jan 1, 2018

By Dajian Wang

To obtain the thermodynamic properties of a multicomponent liquid alloy system over the whole range of concentration at an arbitrary temperature, the free volume cell theory has been applied to derive the formula of activity coefficients of liquid solutions based on the infinitely dilute solutions at some temperature. The linear logarithmic relationship between activity coefficients of binary dilute solutions and reciprocal of absolute temperature have been verified, and are in good agreement with the experimental values from the literature. The Monte-Carlo algorithm was used to calculate the nonlinear end value equations of binary systems, then the free volume parameters obtained were correlated with the activity coefficients of liquid binary, ternary, and quaternary systems at an arbitrary temperature. Three dimensional a-X-T diagrams of some binary systems representing the temperature and concentration dependence of activities were plotted. The calculated results regarding non-ferrous alloy systems have been statistically examined with the experimental values from the literature. Hence, this simple approach could be useful for analyzing thermodynamic properties of liquid alloy systems.

Jan 1, 2000

The corrosion behaviour of a low carbon steel was investigated in natural seawater and various synthetic seawaters. It was found that the steel corroded nearly four times faster in a 3.5% NaCl solution than in natural seawater for an exposure time of 21 days. The corrosion rate after immersion in synthetic seawaters (ASTM D1141 and Marine Biological Laboratory seawater) is similar to the corrosion rate after immersion in natural seawater. Calcium carbonate (aragonite) deposits were found on the surface of the steel after immersion in natural seawater and the synthetic seawaters. Some magnesium-containing deposits were also found after immersion in the natural seawater. These deposits act as a barrier against oxygen diffusion and thereby lower the corrosion rate. The morphology of the calcium carbonate deposits that formed during immersion in the natural seawater is different from those formed during immersion in the synthetic seawaters. This may explain the slightly lower corrosion rates obtained in the natural seawater. X-ray diffraction also showed that the oxy-hydroxides formed in the 3.5% NaCl solution differed from those formed in the other solutions. Keywords: Corrosion, seawater, low carbon steel, 3.5% NaCl, aragonite

Jan 1, 2006

By H Möller

The purpose of this paper is to give an overview of the corrosion behaviour of steel in seawater. It is shown that the corrosion products (oxy-hydroxides and calcareous deposits) that are formed during corrosion in seawater have a significant effect on the corrosion behaviour of steel. The chemical composition of the steel determines how protective the oxy-hydroxide corrosion product is. The composition of the seawater influences the nature of the calcareous deposits. This needs to be considered when artificial solutions are used to simulate the corrosion behaviour of steel in seawater. A 3.5% NaCl solution is used frequently for this purpose, but because no calcareous deposits can be formed in this solution, erroneous results in terms of corrosion rates are obtained. The more complex ASTM D1141 artificial solution can be used to include the effects of ions other than Na+ and Cl- in synthetic seawaters. The importance of these other ions on the formation of calcareous deposits is discussed. Keywords: Steel, corrosion, seawater, calcareous deposits, oxy-hydroxides

Jan 1, 2006

By G. Cifuentes

When the applied current is interrupted in a copper electrowinning plant, and then is back in operation, the lead anodes tend to corrode. In order to decrease the corrosion, the damage protective ("back up") anodic currents are applied during the period of interruption. The current work aims to establish the effect of the concentrations of sulphuric acid, copper and cobalt on the anode corrosion, to quantify the effect of various anodic protection levels on the anode corrosion and to propose a method to select the appropriate protective current density value.

Jan 1, 1999

Around no subject of technical )uterest have prejudice and wrong-thinking in the past so wrapped a web of obscurity as that of the corrosion of metals.It is a matter which has primarily concerned the engineer, but the paucity of his training in chemistry and electrochemistry has been the stumbling block to a better understanding of its mechanism.Now that the more important conditions controlling corrosion have been scientifically.established, it can be seen that, with the exception of but a few of the minor points, the electrochemical laws enunciated by Faraday, Helmholtz; Nernst, and others, are sufficient to include all the facts of the process.The word corrosion (derived from the Latin rodere-to gnaw) is so often wrongly applied that a definition at this stage would be useful. As now understood, it means the dispersion and waste of the useful solid metal by conversion into a useless compound which mayor may not be retained on or near the metal remaining.Commonly the presence of these compounds is regarded as evidence of corrosion, but the converse is not necessarily true; the lack of visible corrosion products on a clean surface of metal is no criterion of the absence of this change. It may be difficult to prove that the erosion of such a surface has been caused by chemical and not by mechanical effects alone.

Jan 1, 1932

By A. Spearing

According to a 2000 NIOSH report, about 100 million rock anchors are installed annually in coal mines in the USA. Most coal mines have conditions that are conducive to corrosion of the rock anchor and ancillaries (such as plates), yet the effect of this on the performance of the anchors has not been adequately researched and its effects are not understood or quantified in the USA. There is considerable research into corrosion in civil engineering applications on surface and underground but the corrosion of coal mine rock anchors is not necessarily the same because: ? In underground civil structures, water ingress is usually stopped as part of the construction process. ? Many rock bolts in mines are only partially resin grouted leaving part of the reinforcing member exposed to corrosive conditions. All cable bolts in coal mines are only partially resin grouted. ? Even when mine bolts are fully grouted, shrinkage cracks occur and the rock stresses can change due to adjacent mining that can cause the resin column around the bolt to fracture further under external shear or tensile stresses. Most coal mines therefore have ideal conditions for bolt corrosion.

Jan 1, 2010

By G. Bylapudi, K. Mondal, J. Hirschi

ABSTRACT: Rock bolts are the main form of defence against rock falls in mines. Conditions under-ground are conducive to corrosion. A perception exists about American coal mines that bolt corrosion is not an issue, especially when bolts are fully grouted. This perception is not necessarily accurate due to the formation of micro-cracks as the resin sets and to subsequent rock movement that breaks the resin column’s continuity. Corrosion should be considered when designing rock bolt support in long-term excavations. This paper explores the problem of corrosion, outlines a method to determine the corrosion potential of bolts, and suggests ways to mitigate such effects.

Jan 1, 2010

By George B. Lee

DURING The Two Years In Which The New Reduction-Works Of The Copper Queen Consolidated Mining Co. Have Been In Operation At Douglas, Ariz., There Has Developed A Remarkable Condition In Regard To The Corrosive Action Of The Water Used To Cool The Jackets Of The Blast-Furnaces. Were It Not For The Many Contradictory Features, It Might Pass As One Of The Unavoidable Troubles Due To The Composition Of The Water. This Water, Obtained From Wells 600 Ft. Deep, Is Also Used In The Steam-Boilers, And Its Composition, As Shown By The Following Analysis, Does Not Indicate The Presence Of Any Ingredient Which Would Explain The Corrosion Grains Per U. S. Gal. Silica, 0.861 Iron Oxide And Alumina, 0.223 Calcium Carbonate, 0.2111 Calcium Sulphate, Magnesium Carbonate, Sodium And Potassium Sulphates, . 14.850 Sodium And Potassium Chlorides, 9.732 Sodium And Potassium Carbonate, 6.452 32.409 The Jackets Are Made Of Inner Plates 0.5 In. Thick And An Outer Plate I In. Thick, With 3-In. Stiffeners Between The Inner And Outer Plates. In From 10 To 12 Months The Inner Plates Have Been Reduced By Corrosion To A Thickness Of From 1/8 To 1/16 In., While The Outer Plate In The Same Time Is Reduced By Less Than 1/16 In., And The Stiffeners Show Very Little Corrosion. The Plates Are Pitted And Eaten Away In Some Places More Than In Others. There Is Practically No Scale Found On The Jackets, But When Cleaned Considerable Iron Oxide Is Found In The Bottoms. With An Action So Marked, Serious Trouble Would Be Expected In The Boilers, But, On The Contrary, A Recent Inspection By a

Mar 1, 1908

By Frank Speller

WE are here to honor again the memory of Henry Marion Howe, one of the foremost metallurgists of his time, and it is indeed a great privilege to be called upon by the Board of Directors of .this Institute to give the memorial address this year. Professor Howe started active investigation of corrosion of iron from a metallurgical standpoint in 1887, and made several important contribu-tions to the subject from 1895 to 1908.(1) ? The papers named in the bibliography are only a few of his valuable papers, but in all his works he sets a high standard of scientific accuracy, together with a clearness and power of expression rarely equaled in engineering literature. There-fore it seems appropriate on this occasion to review the work on corrosion of this distinguished gentleman and then endeavor to make a brief inventory of what has been accomplished since his time. Howe saw the beginning of the steel industry in America and before he died (May 14, 1922) witnessed it develop to a production of 45,000,000 tons per year. He was naturally very much interested in the infant industry and was quick to see the importance of the question of corrosion. It was my privilege to discuss the subject of corrosion frequently with Professor Howe at various times from 1905 to 1908; in this, as in other metallurgical problems, he sought the truth without bias and always insisted on proving an opinion or conclusion before accepting it. We should remember that when Howe started his investigation of corrosion, in 1887, steel was rapidly supplanting wrought iron. Certain papers in the early eighties (now forgotten) claiming much greater durability for wrought iron than for steel aroused Howe's interest. He could not reconcile the statement that steel was intrinsically and incurably less durable than wrought iron with the continued and widening use of steel,

Jan 1, 1934

By John E. Leitch

The cost of corrosion as measured by such cost components as the renovation or replacement of coated steel, or the use of expensive coating systems on steel, is considerable. Extrapolating from figures for the USA would place the overall cost of corrosion for South Africa as a figure of the order of magnitude of something over 1% of the GNP. This is a sizeable amount, of which costs associated with atmospheric corrosion would be a significant proportion. The corrosivity of an atmosphere can be defined as the ability of the atmosphere to cause corrosion in a given metal or alloy (International Standards Organization [1]). The ISO Standard 9223 specifies the key factors in the atmospheric corrosion of metals and alloys, and defines categories of corrosivity on the basis of these factors. Prior to the publication of that ISO standard, Callaghan published the results of his twenty-year exposure programme and his excellent corrosivity map of Southern Africa [2]. The present author published updates of the corrosivity map in 1999 [3] and again in 2003 [4]. The summary of the individual areas of corrosivity around Southern Africa was published in the latter paper, and is reproduced here as the following TABLE 1. Of significance in TABLE 1 are the numerous regions of very high corrosivity (C5 or beyond), particularly the rural West Coast shoreline, the North East Coast (KZN) shoreline, and the coastal cities Cape Town, Durban and Richards Bay. The corrosivity map as published is obviously based on much extrapolation as only a small number of points have been measured. During the past three years further measurements have been made, mostly however at the same sites in order to give greater reliability and to monitor long-term trends with changes in pollution. These two aspects are incorporated in this update. There has become available a greater amount of air pollution data for centres in South Africa than was the case some years ago. In this present paper the pollution data are used to extrapolate the corrosivity over areas where little or no direct corrosivity measurement has been made. This methodology is described in ISO 9223.

Jan 1, 2006