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By P. M. Solozhenkin

"Galvanochemical process (GChP)) cleaning of sewages is realized in the field of shortcirquited galvanic elements from the mixture current the materials place in purification’s solution and form multitude galvanopairs without external electric field in presence oxygen of the air. The galvanochemical process is electrochemical process utilizing galvanic pairs: coke - iron, iron - copper and others and process does not require chemical reagents.The effect of basic parameters of the cleaning effectiveness have been studied depending on oxidizing of galvanopairs. Adjusting nature, type of galvanic pairs and forming three component system possible to enlarge emf circuits to 2.378 V.The role of ?2, as basic agent, for generation of hydrogen peroxide and hydroxyl ions.It was stated, that removing of metal ions from solutions occur mainly on account of sorption and hydrolytic sedimentation of iron oxihydrates.Determined separate stages of the process: coagulation, sorptions of admixtures on freshly formed ferric oxides and oxidizing destruction of organic components of effluents in presence of ?2 ? ?2?2. Shown efficiency of the method for removing of Cu, Cr, Ni, Zn, As ions, as well as fluoride, phosphate and cyanide anions and oil products, surface-active and flotation reagents. Cleaned water can be recycled for some processes non-critical toward residual concentration of admixtures, as total salt contents is lowered on 60-75 % and reaching limits of concentration for toxic components.The concept of high power unit creation was developed, and galvanochemical pulsator is presented. The pulsator is not expensive, and exploitation expences are low, as well as servise is simple with high effectiveness, and capacity. The galvanoflotation process is developing, combining galvanochemistry and flotation of hydrofobic admixtures (oil, surface-active agents).The galvanochemical flotators are presented."

Jan 1, 2003

By Robert B. Fulton

Staurolite, an iron aluminum silicate mineral, is used industrially as the source of aluminum in portland cement manufacture in areas where the aluminum constituent is not economically available from shale or argillaceous limestone. It is also used as a high value- in-use sand blasting agent and as a premium grade foundry sand. It is produced by E. I. du Pont de Nemours & CO. as a coproduct in titanium mineral production in Florida where it was first recovered on a commercial scale in June 1952 from the Pleistocene sand deposit known as Trail Ridge. In the Trail Ridge deposit it comprises about 36 of the heavy minerals, the principal other heavy mineral constituents being ilmenite, leucoxene, rutile, zircon, kyanite, sillimanite, and tourmaline. Staurolite and the other silicate nonconductive heavy minerals are separated from the conductive titanium minerals on high-tension separators. The silicates are then separated from one another magnetically, the staurolite being relatively magnetic. In the total processing, 200 tons of raw sand yield 7 tons of heavy mineral concentrate from which about one ton of staurolite is recovered. Staurolite production is approximately 100,000 net tpy. No other commercial production of staurolite is known. This process yields staurolite concentrates of the characteristics given in [Table 1]. These concentrates are sold as three products with the size distribution of subrounded particles shown in Table 2. All three grades are used in sand-blasting for cleaning metal, for paint removal, and for cleaning buildings. Staurolite compares favorably with lower unit cost abrasives, such as boiler slags and mineral aggregates, in applications where the abrasive is used only one time and is not recovered. Because it is hard, fine, clean, and dense it can reduce blasting time, with less material reportedly being required

Jan 1, 1975

By E. F. Northrup

THESE brief notes respecting the properties of pure tin that make it useful as a pyrometric substance summarize information gathered by the writer In an extensive experimental investigation on the electrical properties of metals in the molten state. Tin in quantities sufficient for pyrometric purposes may be obtained at relatively low cost and in a state of high purity. The metal melts at 232° C. and, according to determinations made by Greenwood,. 1909, does not begin to boil until a temperature of 2270° C. is reached. The writer can assert, from personal observations carefully made, that tin shows no tendency to boil at a temperature of 1680° C. If Greenwood's observations are correct the temperature interval, 2038° C., in which tin exists as a liquid under atmospheric pressure, exceeds that of any other substance. It has never been observed, as far as the writer is aware, that tin forms any chemical union, as carbide, with carbon at the highest temperatures at which it can exist as a liquid. It is quite certain from the writer's personal observation that tin heated in Acheson graphite to 1680° C. remains chemically uncontaminated. Wires of pure tungsten do not dissolve in molten tin at temperatures at least as high as 1680° C. Tungsten wires or rods may, therefore, be used as electrodes dipping into molten tin when required for measuring the resistance of the molten metal at very high temperatures. When tin is raised to a high temperature in a covered graphite container, the CO atmosphere that exists above its surface has a reducing action, which maintains this surface of mirror brightness. Incidentally, tin maintained molten in a crucible of Acheson graphite makes a most excellent bath into which may be inserted several pyrometers that are to be intercompared at the same temperature.

Jan 8, 1919

By C. Richard Tinsley

Investment activity in the Pacific Rim of Fire has seen a phenomenal surge from epithermal gold exploration. Individual countries are attractive because of lower up-front minerals lease costs (United States, Canada), better geological prospects (Chile, Indonesia), or cheaper equities (Australia). Since the October 1987 stock market crash, large companies are shedding minority joint venture interests to focus on core businesses. Some vertical integration is evident in Japanese coal investments in the Pacific Rim. This article does not cover the aluminum industry oligopoly, which is multinational in character. Nor does it cover the many Canada to US minerals investments. It will be interesting to see if the new US-Canadian free trade treaty will reverse that investment flow. Cross-border investments The following examples should dispel any doubts about the significance of cross-border investment in the Pacific Rim. BHP, Australia's largest public company, has invested $US 4.5 billion in the JS for the following transactions 1984 $2 billion Utah Minerals 1984 $500 million Energy Resources 1985 $745 million Monsanto Oil 1987 $400 million 50.7% Hamilton Oil 1989 $378 million Pacific Resources Placer Dome, mainly through 76% owned Placer Pacific, has the following gold mine developments in hand including the date the project began, Placer Dome's ownership, project name, its location, and capital expenditures: • 1985, 53.1 %, Kidston, Queensland, $A 139 million; • 1989, 37.9%, Big Bell, Western Australia, $A135 million; • 1989, 60.6%, Misima, Papua New Guinea, $C252 million; • 1990,45.5%, Granny Smith, Western Australia, $A95 million; • 1991, 50%, La Coipa, Chile, $US276 million; and • 1991, 25.3%, Porgera, Papua New Guinea, $C1.1 billion. Australia's Western Mining Corp. (WMC), through a foray of off-market acquisitions in late 1987, acquired con¬trol of five Canadian gold companies for a $A488-million outlay ($C452 million) as follows:

Jan 1, 1990

By John Mathews

IT is twenty years since the writer made his first molybdenum steels and others were making them commercially five years earlier but the prevailing opinion seems to be that molybdenum steels are new; from time to time the daily press speaks of important discoveries in Europe and intimates that American steel makers have much to learn in regard to alloy steels. The earlier experiments were largely confined to the use of relatively high percentages of molybdenum in tool steels and permanent magnet steels. Recent developments deal with the types of alloy structural steels used for airplane, automobile, and other engineering requirements; in these, the molybdenum content is usually less than 1 per cent. The earlier types generally have been unsuccessful commercially, but the newer types of steels are becoming of increasing importance. The war showed our dependence on foreign sources for alloying metals; molybdenum alone is widely distributed in the United States and seemingly abundant. Many deposits are not now of commercial interest, owing to location and relatively small amount of ore available, but other deposits are being developed and a stable source of supply seems well assured. In tool and magnet steels, it was early found that 1 part of molybdenum was equivalent to from 2 to 2.5 parts of tungsten. The permanent magnet steels investigated by Madame Curie,1 in 1898, contained from 3.36 to 4.05 per cent. molybdenum; in 1902, Dr. E. L. French and the writer thoroughly tested steels containing from 2:0 to 4.0 per cent. These steels gave satisfactory tests for permanence, but were low in residual density and much more sensitive to hardening than the corresponding tungsten products. We discontinued work with them, therefore, and have no advice that such steels have been used commercially here or abroad.

Jan 2, 1921

By John Gross

The building of reverberatory furnaces (Fortschaufelungsofen) where ordinary brick, fire-brick and iron are comparatively cheap, is quite a different matter from the building of such furnaces in isolated camps, where proper material is only to be obtained at high cost and with long delays. Time is always a large factor in metallurgical operations, and the metallurgist may find himself in a position where it becomes necessary to erect apparatus and have it running in less time than it would take to obtain material from outside. It is here that he must make use of makeshifts. In Mexico, one of the most important of these is the alluseful adobe. Employed from prehistoric times, it still has its sphere of application in a surprisingly large number of instances requiring an article that can be quickly and cheaply produced. It is quite possible to erect serviceable reverberatory furnaces with no other materials than adobes, stone and wood. The old Mexican smelting shaft-furnace was an example of what can be done with adobes, and the large number of ruins of this class of furnace scattered through the mining districts of Mexico are silent testimony to the genius of a people who demonstrated their capability of adapting material at hand to their needs. The present paper will describe briefly the construction of an adobe reverberatory furnace which is giving good results, can be quickly erected at a low cost, and, if properly built and handled, will last a long time. The material being simply sun-dried, it naturally follows that the construction must be quite heavy. The adobes should be evenly made, with just sufficient straw to hold them together, and not too large in size (9 in. wide, 18 in. long and 4 in. thick

Jan 1, 1902

By Samuel Dolbear

PUBLIC discussions of mine finance in the tech-nical press have been confined mainly to methods of providing funds for the development of pros-pects or other mining operations which have not reached the stage of productivity. The application of modern financing methods to mines which have behind them a successful record of net earnings has, for some reason, been given scant consideration by mine owners and managers. In a few conspicuous cases, such for example as the Anaconda Copper Mining Co., Chile Copper Co., and one or two others, industrial finance has been applied to mining operations on the scale and after the fashion of other operations. When extensions are needed re-course is usually had, however, to the sale of common stock, with the obvious disadvantage of diluting the holdings of every stockholder of record prior to such financing. In some cases, it has been sought to over-come this disadvantage by issuing stock purchase rights to shareholders of record. If the stockholder is in a position to acquire additional stock, he may then pre-serve his interest intact, otherwise he must suffer a dilution of his holding. If he purchases additional stock he is, from one point of view, paying more for his in-terest than he bargained for when he made his original purchase. In many cases development and equipment are paid for out of surplus or current earnings. It is sometimes most difficult to explain to a manager why he can afford to borrow money when funds are available from a sur-plus account. Nevertheless, industrial enterprises with adequate surplus accounts often finance new construc-tion by the issuance of bonds. Such a procedure enables the company to maintain its surplus intact, and to con-tinue the payment of dividends during a temporary period of unusual expenditures.

Jan 2, 1927

By M. Proulx

"RÉSUMÉ Le diagramme ternaire Al2O3-Sr-Y est un nouvel outil servant à l’exploration de gisements de sulfures massifs volcanogènes (SMV) archéens. Le diagramme permet de discriminer entre les roches volcaniques à minéralisations à zinc dominant (domaine Zn+) et celles à minéralisations à cuivre dominant (domaine Cu+), ainsi que les roches volcaniques ayant subi une chloritisation hydrothermale pouvant aboutir à la formation de chloritites associées aux cheminées d’altération (domaine Cl+). Ces trois domaines délimitent des zones d’influence géochimique ou d’empreintes hydrothermales résiduelles ou fossiles produites par les cellules de convection hydrothermales générées par des magmas. Le diagramme permet aux sociétés d’exploration de déterminer de façon peu coûteuse la fertilité potentielle des roches volcaniques archéennes en ayant recours à leurs bases de données et aux résultats de leurs analyses de terrain, sans aucune manipulation des données. Le diagramme ne s’applique pas aux SMV aurifères.ABSTRACT The tertiary diagram Al2O3-Sr-Y is a new tool to explore Archean volcanogenic massive sulphide (VMS) deposits. The diagram can be used to discriminate between the volcanic rocks where zinc is the dominant mineralization (Zn+ domain) and the rocks where copper is the dominant mineralization (Cu+ domain), as well as the volcanic rocks that were subjected to hydrothermal chloritization that could have led to the formation of chloritites associated with alteration chimneys (Cl+ domain). These three domains define the zones of geochemical influence, or residual or fossil hydrothermal footprints produced by hydrothermal convection cells generated by magmas. Exploration companies can apply the diagram to determine, at low cost, the potential fertility of the Archean volcanic rocks by using their databases and the results of their field analyses, without any data manipulation. The diagram does not apply to gold-bearing VMS deposits."

Jan 1, 2015

By M. Takebayashi, K. Takenaka, S. Matsubara, T. Yoneyama

The cathode production of Toyo Smelter and Refinery, owned by Sumitomo Metal Mining Co., Ltd. reached 450,000 tons per year in 2016 with three tank houses. Niihama tank house commenced operations in 1919 with conventional sheet cathode technology. Approximately 100 years of operation experience and the technical development enabled that the current density of Niihama tank house and the Toyo tank house #1 increased to 320 A/m2. These operation techniques were utilized at the Toyo tank house #2 which started in 2005, and its current density reached up to 350 A/m2 with permanent cathode technology. In order to achieve high current efficiency under condition of 350 A/m2 operation at Toyo tank house #2, continued efforts had been made to verticality of anodes and permanent cathodes. To improve verticality of anodes and cathodes, reduction of short circuit ratio by changing the shape of the anode, optimizing the anode pressing machine and off-line process for rectifying the distortion of permanent cathodes was carried out. In addition, concentration control of electrolyte and expansion of Ni removing ability from the electrolyte prevented passivation. Finally, more than 96% of the current efficiency was stably confirmed. INTRODUCTION Today, Toyo Smelter and Refinery of Sumitomo Metal Mining operates three tank houses in Japan, namely, Toyo tank house #1, Toyo tank house #2, and Niihama tank house with a total capacity of 450,000 metric tons of copper cathodes. Figure 1 shows the trend of cathode copper production and the current density at three tank houses over the last 10 years. Cathode production by Toyo Smelter and Refinery reached 450,000 tons per year in 2016 with three tank houses.

Jan 1, 2019

Mine planning studies of iron ore deposits are often based on resource models generated by ordinary kriging. Ordinary kriging aims for local accuracy to minimise the variance of expected estimation error but this is at the expense of reproducing variability of the original sampling data. Hence mine planning studies using kriged models are likely to underestimate product variability, and the required blending and stockpiling capacity to reduce variability to an acceptable level. Instead, conditional simulation models of the main chemical variables in iron ore are able to reproduce likely variability to be encountered during mining and processing. This approach is demonstrated in a case study of the Weld Range bedded iron ore deposit in Western Australia, with a comparison of ordinary kriging and conditional simulation models. Conditional simulation models suggest that, compared with the single ordinary kriging estimation, there is likely to be far greater block variability for iron and impurities, a greater requirement for stockpiling and blending capacity, highest variability in initial years of mining and less variability in later years of mining for deeper ore. The conditional simulations provide a more realistic range of mining outcomes for production of high-grade ore, which may be seven per cent less than in the kriged model, as well as for lower expected project net present value (NPV). In year one, the kriged model is conservative for NPV; however, in later years two to five the kriged model has higher NPV than most conditional simulations, suggesting expected NPV based on the kriged model may not be achieved. For improved decision-making in mine planning, a complete range of possible outcomes from conditional simulations of the deposit should be considered rather than relying on a single kriging estimation that may be an end member case in the range of possible mining outcomes.

Jan 1, 2009

By H. l. Burghoff, A. I. Blank

J. J. Kanter.*—The authors of this paper have demonstrated that at 500°F their alloy will elongate, under appropriately adjusted stress, one or two per cent over a period of 6000 hr. Then they show that after the alloy has so elongated, it will still elongate anothcr 40 per cent if it is tested at ordinary temperature. I should like to ask the authors how much more than 2 per cent over a period of 6000 hr. their alloy will elongate at 500°F. H. L. BuRghofE.—We do not know, because we have not carried out stress-rupture tests on this material. I believe your point concerning the desirability of stress-rupture testing is very well taken. In the material that we have subsequently tested we have not seen any signs of deterioration. We do not know how much further it is possible to go beyond the 2 per cent before finding grain-boundary separation. We have not encountered any under the conditions of the test. W. E. Kingston.†—IS this particular type of copper susceptible to strain-aging, and if so at those comparatively low temperatures, is that going to affect the shape of the curve? By strain-aging I mean the phenomena that certain ferrous alloys show in which the resistance to deformation increases suddenly during the low-temperature creep cycle, apparently due to some precipitation type of reaction, perhaps analogous to hydrogen embrittlement. H. L. BUrghoff.—I believe that this material is not subject to strain-aging of this type. It is very high in copper content, of course, nearly loo per cent. There are some very minor impurities and it carries a small amount of phosphorus, which, unless it is present as an oxide, should be in solid solution well within the solubility limits. I believe it does not precipitate

Jan 1, 1945

By R. S. Shoemaker

It is said that there is nothing new under the sun and this is certainly true about refractory gold Ores. Ores which have been refractory to treatment have been the bane of the Metallurgist's life ever since gold has been recognized as a metal valued for its indestructability, malleability and beauty. Webster's Dictionary defines "Refractory" as; "Resisting control or authority, stubborn, resistant to treatment or cure, unresponsive to stimuli, difficult to corrode or draw out," And gives as a synonym the word "unruly." I don't think any metallurgist would disagree with these definitions as they quite accurately describe refractory gold ores as we know them and I wouldn't be a bit surprised if many of you in this room today had applied far stonger language to your own refractory ores in the course of your metallurgical test programs. Pliny the elder put it very well when he wrote in 79 A.D., Gold is the first of man's follies, Silver the second." Perhaps Pliny was speaking of "unassayable gold" or "incipient gold." These are truly refrac tory ores which probably existed before Pliny's time and although many people have claimed to have solved their metallurgy the untold wealth that lies within them has never been bankable. On the other hand, Virgil is his Aenead, could very well have been speaking of refractory ores when he wrote; "Quid non mortalia pectora cogis, auri sacra fames!" which translates as, Accursed thirst for gold! What doest thou not compel mortals to do. Certainly, gold was extremely rare at that time because it had to be recovered by much labor from the then refractory ores and their refractoriness caused the early metallurgists (or alchemists if you will) to seek an easier way to produce it; thus the long and fruitless search for the "philosopher 's stone" which would aid in turn-

Jan 1, 1990

By A. J. Sinclair

Abstract-Exploratory data evaluation is an essential part of every high quality, mineral inventory estimate. Efficient analysis involves a thorough organization of available quantitative data that are the basis of the estimate and perhaps the formation of composite grades. Data organization and evaluation can involve more than 50% of the time necessary to conduct a mineral inventory estimation. The principal purpose of exploratory data evaluation in mineral inventory work is to improve the quality of estimation by providing insight into characteristics of the variables under investigation. Specific aims include: (1) to recognize and eliminate errors; (2) to provide a comprehensive knowledge of the statistical characteristics of all variables of interest for resource/reserve estimation; (3) to document and understand the interrelationships among the variables of interest; (4) to recognize systematic spatial variation of variables such as grade and thickness of mineralized zones; (5) to recognize and define distinctive geological domains that require independent estimation of mineral inventory; (6) to identify and characterize outliers; and (7) to evaluate similarity/dissimilarity of various types of raw data, especially samples of different supports. These aims are not mutually exclusive but they can all have their own impact on resource/reserve estimation. Error must be minimized. Individual variables can have characteristics that lead to different decisions in the course of estimation. Similarly, interrelations of variables might contribute to the ease (or difficulty) with which estimates of several variables can be obtained. Trends can impose the need for two or more domains, each of which might be estimated independent of the others. Outliers, a perennial problem, require detailed evaluations because they impact on reserves much out of proportion to their abundance. Data, of widely different supports, generally must be standardized if all are to be used for purposes of estimation.

Jan 1, 1998

By Halbert Powers Gillette

In every chemical reaction heat is either developed or absorbed, and this plus or minus heat of formation is as definite in quantity as the weights of the reacting elements. In this paper I shall show that each chemical element and each chemical radical has its own definite heat-valency,—a fact which, so far as I know, has hitherto escaped the attention of investigators, but, I feel sure, will be admitted after the demonstration here given, and may lead to some practical conclusions of value. When Berthelotys " law of maximum work " was found to have so many inexplicable exceptions, the pendulum of a scientific theory swung away from a recognition of the truth underlying that proposition; and this reaction went so far that not only has thermal chemistry been relatively neglected by recent investigators, but it is not uncommon now to find textbooks on physical chemistry which practically ignore all that Thomsen, Berthelot and others have done. To this temporary tendency of thought I attribute the failure to recognize the principles herein announced and explained. Not long ago, while studying tables of the formation-heat of various salts, I noticed that in this respect all potassium salts in solution differ from the corresponding sodium salts by 9.3 cal.1 I found also that similar differences exist between other salts, not only when the basic radical is varied, while the acid radical remains constant, but also when the acid radical is the variable. Thus chlorine salts in solution differ from bromine salts in this respect by 10.9 cal. Upon further study, I found that Thomsen had noted similar constant differences, but, so far as I can ascertain, he appears to have attached no great significance thereto.

Jan 1, 1904

A PAPER on "Iron and Steel Scrap in Blast-fur-nace Burdens," by W. C. McKee, general super-intendent, Federal Furnace plant, By-Products Coke Corp., Chicago, was published in the October issue of MINING AND METALLURGY, and written discussion by Richard Moldenke was published in the December issue. Following is the stenographic report of the oral discus-sion that took place when this paper was presented at Pittsburgh. J. N. REESE, Monessen, Pa.-I came to the conclusion that Mr. McKee must be using a poor grade of scrap, therefore his loss was high. Mr. Franchot said that there was ex-cess heat in the stack. There is no excess heat in the hearth, therefore, any heat that is used to melt this scrap must come from the stack. By using scrap in a blast furnace you can utilize this excess heat in the stack. The amount of scrap that can be used in any particular furnace involves a direct relation to the efficiency of that furnace. If a furnace is running on a very low-coke rate, you will not be able to use much; if on a high-coke rate, you can use considerable scrap, probably several times as much as that mentioned in these papers-without using any additional coke. This excess heat can be utilized with-out practically any serious mechanical and operating diffi-culties such as might be occasioned by removing gas from a point other than the top of the furnace. I do not think, scrap has any effect on the iron, although I think some foundrymen are trying to prove that it has, and perhaps some open-hearth men may have that idea.

Jan 1, 1927

By B. Fitch, E. J. Roberts

Definitions and Terminology Classification is defined within this section as the separation of solid particles into size or weight fractions or classes by differential settling through a fluid. It is usually thought of as a size separation, but is actually made on the basis of particle settling rate, and so is affected by any variations in particle density and shape. The fluid may be liquid (wet classification) or gas (dry or air classification). This section will treat only wet classification. There are two basic types of classification; pool and hydraulic. In pool classification a suspension of feed particles is fed into and out of a pool of some kind at such a rate that only part of them¬ the coarser and faster-settling part-has time to settle out. The remain¬der overflows as fines. In hydraulic classification the feed suspension is introduced into or above one or more columns or pockets through which water is rising at a controlled velocity. Coarse particles subside through the pockets and are removed through spigots. Those which settle slower than the rising velocity in any column or pocket are (at least ideally) prevented from subsiding and so must overflow. Hydraulic classifiers or sizers are capable of making far sharper sepa¬rations than pool classifiers. The force causing settling may be gravity, or alternatively may be from centrifugal acceleration as developed in a centrifuge or hydra cyclone. Two things are needed to characterize the separation produced by classification: first, the size, D„ or equivalently the screen mesh at which it is made; second the sharpness of separation. Separation size may be defined in various ways. In closed-circuit grinding it is commonly specified by some point in the overflow screen analysis: For example, 5% on 65 mesh. In other applications, notably

Jan 1, 1985

By J. M. Tourre

1995 have seen a continuation of a positive trend in the Rare Earth industry The availability of a greater diversity of Raw Material has brought additional flexibility to the Producers permitting better economics China remains the major raw material source; Chinese concentrate producers have increased capacity in 1995 (Baotou, Sichuan, etc) China's role in the Rare Earth industry will continue to evolve; the acquisition of a majority equity position by San Huan/CNNC will have a significant impact on both the Rare Earth and Magnet markets Chinese producers are increasing the quality of their products and realize their true values Chinese market, itself, is also changing as the internal needs for separated rare earth's grow Already already producer of Lamps, Loudspeakers, Magnets, and TV tubes, China is in an unique position where the potential of its internal market might be more promising than the prospects outside China 1995 has also seen the application market become more diverse and complex. There are new applications growing at a very strong pace (such as battery alloy), applications that are now penetrating their target markets with significantly increased growth rates (such as bonded NdFeB), and some applications that became more complex requiring much more sophisticated products (such as catalysis). Rare Earth producers have to spend significant ressources in order to monitor the market trends in order to predict the demand and then adjust their raw material mix. Even though there is a greater diversity of raw material available, there is still some Rare Earth elements that are in excess, while other are just in balance. As a consequence rare earth producers invest heavily in R&D in order to develop new applications for these excess elements.

Jan 1, 1997

By Thomas V. Mullen

Some 146 kt (4.69 billion oz) of gold have been mined throughout history. Of this, 70% has been mined in this century alone, with 17% produced from 1985 through 1996 (Fig. 1 and Table 1). Until the mid-19th century, placers were the chief source of gold. Advancements in mining, metallurgy and geological thinking have resulted in underground mining (first of veins plus stockworks and later of Rand-type deposits) becoming the principal source of gold. With the demise of the South African deposits and the move towards lower grade ores, the primary source of gold will be from disseminated deposits exploited through large, open-pit mines. For the past 200 years, there has been a fairly constant ratio of about 31 g (1 oz) of gold to each person alive. If this ratio is to be maintained, annual gold production will have to rise from about 2.3 kt/a (73.9 million oz/year) to more than 3.1 kt/a (99.7 million oz/year) by the year 2000. To effect this increase, an unforeseen breakthrough in exploration or metallurgy is needed. Barring this, there will be pressure for an increase in the price of gold. This article traces the historical production of gold from 4000 B.C. - the earliest record of gold mining - to today and relates this 6,000-year record to advances in geological thinking, mining engineering and extractive metallurgy. It also proposes that man's thirst for gold, reflected in the price he will pay for gold, and his ability to find, mine and refine gold have combined to effect an equilibrium based loosely on the historical ratio of 31 g (1 oz) of cumulative gold production per each man or woman alive.

Jan 1, 1998

By N. F. Fiore, M. F. McGuire

THIS communication describes a series of experiments in which dislocation etch pitting was used to ascertain the depth of damage in crystals which were mechanically polished or which were cut with either a commercial metallographic cut-off wheel,* a com- All specimens were cut from single crystals of American Smelting and Refining Co. 99.999+ pct pure copper which were grown from the melt by the Bridge-man technique. The test specimens were disks, with faces being (111) planes and the disk axis a (111) direction. The disks were annealed in a vacuum of 10-5 Torr for 24 hr at 950°C prior to cutting or polishing and were given a light electropolishing in an ortho-phosphoric acid bath before etch pitting. Both Youngs1 and Livingston's2 reagents were used for etch pitting and the reagents gave identical quantitative results; however Livingston's reagent produced less staining and so all photomicrographs shown are of {111) surfaces etched with this solution. The surface of the annealed crystals showed well-defined subboundaries and a density of dislocations of about 1 X 106 per sq cm excluding those present in subboundaries, Fig. 1. The depth of cold work produced during mechanical polishing was determined after an annealed specimen was mounted in a paraffin holding block to protect it from extraneous damage. The exposed (111) surface was ground on metallographic papers and then polished on billiard cloth through 0.05-p alumina abrasive. It was necessary to remove about 0.3 mm (-0.01 in.) to obtain a structure representative of the annealed sur- face, indicating that the crystal was damaged to this depth during mechanical polishing. The cold work caused by standard cutting methods was measured in another series of tests in which cuts

Jan 1, 1967

By Keith T. Griffiths

INTRODUCTION The Empress Nickel Mine is situated forty-eight kilometres west of Kadoma in the Zhombe Communal Land of Zimbabwe. The mine came into operation in late 1968 based on a proved and probable ore reserve of twenty million tonnes. The initial production rate was 55 000 tonnes per month from underground. This was boosted to 85 000 tonnes per month in mid 1970 when the opencast operation came into production. The mining method at Empress is sub-level open stoping with main haulages mined at ninety metre intervals and sub-levels at eighteen metres. The extremely wide ore body of up to one hundred metres in width has necessitated leaving extremely large rib pillars and sill pillars in position to maintain mine stability and to act as regional support of the hanging wall. In early 1976 the opencast operation had reached its final economic depth and it was then necessary to increase underground production to 85 000 tonnes per month. Since a large portion of the ore reserve remained in both rib and sill pillars, it was necessary to embark on a positive pillar recovery programme. For this reason it was decided to introduce a sandfilling programme for the mined-out stopes and a modified system of sub-level open stoping with post filling of the lower stopes. ORE BODY GEOLOGY AND GEOMETRY The Empress orebody outcrop has a strike length of nine hundred and fifty metres on a north west - south east axis. It is a steeply dipping (65' - 75') tabular orebody of gabbroic rock which has been extensively altered. The north west - south east strike length of nine hundred and fifty metres on surface reduces to some two hundred

Jan 1, 1983