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By J. Weyer

"Colored gemstones are most often mined in small scale artisanal mining operations. Sri Lanka is well known as source for precious stones since thousands of years. Gemstones are mine in small open pits, directly in rivers (river dredging) and in underground mines. Almost all mined deposits are alluvial deposits. PRECIOUS STONES AND DEPOSITS Precious stones from Sri Lanka are well known for thousands of years. Tales and legends from Arabia, India, China and reports from discoverers like Marco Polo describe the fabulous stones from Ceylon which was the name for Sri Lanka before 1972. Already 1000 BC King Salomon got valuable gemstones from the legendary Queen of Sheba on her visit to Jerusalem. Paintings (frescoes) of the “cloud maidens” with huge gemstones can be seen at the “mirror walls” of the Sigiriya rock fortress - one of the eight World Heritages Sites of Sri Lanka.And even today some of the most valuable and most desired gemstones come from Sri Lanka. The term “Ceylon Sapphire” stands for an excellent royal blue color of high quality corundum from Sri Lanka. Reason enough to look a bit closer how these gemstones are mined. Sri Lanka has rich gemstone deposits which are mined underground, in small open pits or directly within a river. Some of the primary deposits in magmatic and metamorphic rock are also known, but most gemstones are mined in secondary alluvial deposits. Gem bearing deposits can be found in a band from NW to SE. Highly probable deposits and main mining areas can be found around Ratnapura – the city of gems, down to the coast (Matale) and up to the region around Elahera. These secondary deposits are mostly thin layers of gravel and sand, so called “illam”. The depth can vary between some dm to 10 25 m or even almost 40 m. But the average depth is about 12 m. Gemstone mining is controlled, licensed and regulated by a special authority – the National Gem and Jewelry Authority - which was founded in 1993. Another task of this authority is the promotion and development of the gemstone industry and the control of import and export of gemstones. Any violence of the NGJA law can lead to a fine or even up to 5 years imprisonment. To increase the confidence in the gemstone industry the Authority offers a unique service to foreigners. All bought gemstones can be tested free of charge in certain laboratories in Ratnapura and Colombo. So visitors can be sure they got no imitations, wrong stones or even synthetic stones or glass. It was said that detected synthetic stones will be destroyed and the seller will do all he can to replace the stone with the right stone. Otherwise he will lose his license."

Jan 1, 2016

By Ronald Allum

Arizona leads all other states in the value of gemstones produced with an annual production which exceeds $3,000,000. Gemstones are an important component of the mineral wealth of the State. Turquoise, peridot, chrysocoll a, petrified wood, fire agate and crystallized mineral specimens are among the gemstones commercially mined. Numerous additional deposits are operated by hobbyists. The State's reputation as a source of gemstones and specimens for the collector and lapidary adds to the economy of the State by attracting tourists. Production of gemstones further adds to the State's economy through employment in the value added gemstone processing industries and by employment of Native American craftsmen.

Jan 1, 1988

By S R. Pecover

AustraliaÆs opal and sapphire mining industry has fallen from its peak in the 1980s and 1990s into a significant low today. This is not due to exhaustion of the resource, but instead an over-reliance of the Australian miner on achieving a fair price for the gemstone product from offshore middlemen dealers. Gemstone and geological research is also at a low as Federal higher education expenditure has fallen with research institutions relying increasingly on private funding in an environment of restricted autonomy and flexibility for researchers. What little remaining research skills the universities have is being bled into the private sector as a result of the mining boom and encouraged by lower than average academic salaries. Nevertheless, some highly innovative research has been taking place, often by self-funded individuals and retired academics simply with a desire to advance the understanding of the particular branch of science in which they are interested. New models for the formation of sapphire and opal are now beginning to be applied to the exploration for these gemstone commodities. This research, together with well thought out plans for managing the gemstone product through its value-adding steps to the jewellery retail level, has the potential to bring about a resurgence in the Australian gemstone industry.

Jan 1, 2008

By Jorge Sandoval

El presente texto señala un modelo conceptual genérico, cuyo uso de plataformas informáticas permite revisar la validación de la data, previa a la emisión del KPIs, de forma que genera rigurisidad y representatividad para el análisis. En ese sentido, el modelo se basa en la integración de las plataformas, reduciendo los tiempos de procesamiento de la data y eliminando sesgos por la manipulación de la misma. Asimismo, homologa y standariza los árboles de equipos, modos de falla, entre otros aspectos.

Mar 1, 2016

By Eder Lagos, Engels Trejo

En la actualidad, la técnica del machine learning (ML) está siendo utilizada con éxito en diversas industrias y poder aplicarla al sector minero nos permitirá tener información en tiempo real para poder tomar decisiones basadas en números. En mina Constancia hemos dado el primer paso y logramos obtener un software, con desarrolladores peruanos, que nos permite predecir el comportamiento de los molinos basados en variables de la mina (leyes, durezas, ratios, etc) que se encuentran en nuestras bases de datos y que se retroalimenta de forma continua. Esto nos permite generar modelos avanzados, y en tiempo real, de predicción del rendimiento de los molinos.

Sep 30, 2022

By Verónica Zeballos

"Las empresas mineras deben mantener una economía dinámica y eficiente que genere costos competitivos basados en la calidad de sus productos. En ese sentido, el planteamiento de un Proyecto de Modernización de la Fundición Southern existente contribuye a alcanzar el éxito que puede ser medido a través del impacto de éste sobre las condiciones ambientales generadas. Por ello, el presente texto revisa la aplicación de tecnologías ambientalmente aceptables tomadasen cuenta en la Modernización de la Fundición de Ilo, mostrando un enfoque orientado a la gestión, a su ejecución y a la creación de valor."

Sep 9, 2007

By Enrique Monge

El presente texto aborda el problema de la salinización y escasez del agua para la costa del Perú a través del uso de la generación eléctrica. La disponibilidad de energía eléctrica permitirá la explotación de recursos acuíferos subterráneos, los cuales serían complementados por una permanente dotación de agua fresca para la agricultura e industria. Por tanto, la instalación de plantas nucleares de tipo dual para la generación de energía eléctrica y la producción de agua fresca del mar, tiene por lo tanto un objetivo eminentemente social y económico ya que se relaciona íntimamente con la energía, la tierra y el agua que constituyen la base del desarrollo económico de la Nación.

Sep 1, 1964

By F. C. Kelley, L. L. Wyman

In order to clarify and amplify the existing data concerning the action of the cementing material in cemented tungsten carbide alloys, the authors have initiated this investigation of the entire range of cobalt-tungsten carbide alloys. Inasmuch as the ultimate objective is relative to what actually goes on during the sintering of cemented tungsten carbide materials, this work was necessarily restricted to heat treatments similar to those used in actual production of these materials. In the course of numerous experiments, the authors have noted several conditions that indicated that there was a solubility to be considered. Among these factors are the following: 1. Many of the alloys showed a much larger amount of binding constituent to be present than could possibly be accounted for by the cobalt content. 2. In many areas, grains of the carbide constituent are much larger than the particles of carbide originally added. In addition, these grains are of very regular contour. 2a. In samples of cemented tungsten carbide which had been fused in the atomic hydrogen torch in the presence of excess binder constituent, immense grains are formed, and their shapes are very regular. This is also true when the cemented tungsten carbide of 13 per cent. Co content is fused alone in the atomic hydrogen torch. Contrary to general expectation, chemical analysis of this material, after fusion in the atomic hydrogen torch, checks the analysis of unfused material. 3. In making the cemented tungsten carbide materials by the process of exerting the pressure at the time of heating a certain portion of the ' contents squeezed out of the mold. Chemical analysis has shown that this material contains approximately 12 to 20 per cent. of tungsten. The microstructure shows a cored dendritic structure interlaced with eutectic network, and some graphite, as shown in Fig. 1. 4. Thermal analysis of these materials has consistently indicated an arrest point close to 1350" C.

Jan 1, 1931

By P. M. Budge, William L. Fink, Kent R. Van Horn

The investigation of the phase relations of high-purity aluminum-base alloys is a part of the fundamental research program of the laboratories of the Aluminum Company of America. The results of a number of binary and ternary systems have previously been published in the Transactions of this society. The aluminum end of the binary aluminum-titanium system has been studied. This system has received relatively little attention. To the authors' knowledge, there are two previous papers on this subject. E. van Erckelensl determined the constitutional diagram reproduced in Fig. 1. According to this diagram, the liquidus represents the separation of TiA14, (Ti = 30.7 per cent.). He concluded that this is the composition of the compound, because in his work the eutectic horizontal terminated at 30.7 per cent. titanium and the metallographic examinalion of a sample of this composition revealed only one phase. According to the constitutional diagram developed by W. Manchot and A. Leber,² reproduced in Fig. 2 from data given in their article, the liquidus represents the separation of the compound TiA13 (Ti = 37.2 per cent. ). The composition of the compound was derived in a manner similar to that utilized by van Erckelens. Moreover, Manchot and Leber confirmed the composition of the compound by analysis of the constituent left as a residue after dissolving the alloys in weak sodium hydroxide solution. Although these are the only publications describing the constitution of the system, other investigators have studied the composition of the titanium compound. L. WÖhler3 says that there is a compound TiA13 which was later confirmed by W. Manchot and P. Richter4 and by

Jan 1, 1931

By John R. Freeman

The die pressing of brass may be described as a method of producing irregularly shaped parts of brass and other copper alloys by hot deformation in a die under pressure. Die pressing of brass was first developed as an improvement on sand castings in order to obtain irregularly shaped articles of brass with superior surfaces, a closer tolerance in dimensions, a denser structure, freedom from porosity and elimination of the relatively large amount of scrap invariably attached to sand castings. The freedom from sandy surfaces with consequent greater tool life in machining operations was also recognized as well as elimination of losses due to the uncovering of blowholes in machining operations. Die pressing also gave alloys of superior strength. Die pressings today are made from extruded rod or shapes, according to design of the part to be made. The greater number of pressings are made from round rod, because of its relatively lower cost and ease of handling. The rod is first sheared or sawed into desired lengths, the diameter of rod used and length of "slug" or "rivet" depending upon ultimate weight and shape of the die-pressed part to be made and design of die. The dimensions of the slug are figured so as to give the minimum amount of scrap to be sheared from the pressing as it comes from the die. Extruded shapes having I, T or X sections are often used when the finished part is to have a similar shape or heavy sections are joined by relatively light sections of considerable length. A rod bent in the shape of a U is also used on occasion, for similar reasons. Proper shearing of the slugs is of considerable importance. The sheared ends of the slugs should be as flat and straight as possible. Improperly sheared ends having an angle to the axis of the bar or a rough, uneven surface are liable to give folds or laps in the finished pressing and proportionately high rejections. The property of shearing varies considerably with different alloys and should be considered in the selection of a material for a given part. Where satisfactory shearing is not possible, the slugs may be cut from the bar by power saws. Extruded

Jan 1, 1931

By Arthur Phillips, E. S. Bunn

During the past few years considerable interest has been shown in the study of fiber, and its effect, in wrought metals. Fiber has recently been defined as a "condition of parallelism of important lines or details in the structure."' Briefly stated, two distinct types of fiber are commonly encountered. One results from the alignment in the direction of working of constituents, more or less segregated, such as slag, oxides, carbides and dendritic formations. The second, and least understood, type is produced by working the metal below the recrystallization temperature in such a way as to develop a parallelism of the grains. This condition is readily recognized by the pronounced elongation of the grains in the direction of working. Under certain deformational treatments the grain fragments produced by cold working tend to orient in certain definite directions with respect to the axis of extension. Furthermore, even in metals that have been annealed after cold working preferred orientations may be present. It is perhaps logical to assume that such marked parallelism of structural elements would be manifested by directional properties in the metal. As a matter of fact, tests on many kinds of materials have shown differences in varying degrees. In recognition of this condition, proper design, for many purposes, places the fiber axis in such a way as to present the direction of maximum strength to the greatest applied stress. Earlier Investigations Howe2 has written at considerable length regarding the causes and practical significance of fiber in steel and wrought iron. His studies showed that wrought iron and the puddled steel sheets (materials of plastic origin) were weaker transversely than longitudinally. The transverse deficit ranged from 5 to 29 per cent. The longitudinal tests

Jan 1, 1931

By Frank T. Sisco, Selma F. Hermann

gancse constituent in the alpha grains. Nickel produces a structure of alpha plus cutectoid almost identical with that of the normal aluminum bronze (Fig. 38), except for the rod-shaped nickel constituent in the alpha grains. Silicon produccs a light structure with small regular needles, possibly a modified form of beta. Fig. 45 shows the alpha plus beta structure of the normal 10 per cent. aluminum alloy as quenched. Manganese produces large grains of beta with alpha as a tiny constituent scattered throughout the spceimen. Silicon, on the other hand, produces all alpha, with free silicon present. One per cent. iron produces alpha plus beta, with a tiny constituent present in the alpha grains. Five per cent. iron introduces twins in the alpha and a nodular iron constituent in both the alpha and the beta. Figs. 50-58 include the structures of the alloys with 8 per cent, aluminum, tempered at 400" C. and at 650" C. Fig. 50 is the normal structure as drawn at 400" C!. It consists of large grains of twinned alpha plus a very small amount of beta. One per cent. silicon increases the amount of beta enormously, but when tempered at 650' C, the beta degenerates to a hard blue network constituent. One per cent. cobalt results in a structure of exceedingly fine-grained, twinned alpha, heavily mottled. Nickel produces large soft grains of alpha with a dot constituent in some of the grains, when tempered at 650" C. Manganese, when tempered at 400" C. produces alpha grains and shows the decom-

Jan 1, 1931

By F. Keller, E. H. Dix, L. A. Willey

The consideration of alloying elements for aluminum has led to a series of investigations of the equilibrium relations between aluminum and those alloying elements. Therefore, the aluminum end of the aluminum-antimony diagram has been studied. The general form of the aluminum-antimony equilibrium diagram has been worked out by Campbell and Mathewsi and by Tammann.2 Canlpbell and mathews described principally the beginning of solidification. They found the curve of beginning of solidification rising gradually from the melting point of pure alunlinum to a maximum at about 67 per cent. aluminum. After a slight lowering of the curve at a little greater antimony concentration the curve again rises to a maximum at 18.4 per cent. aluminum, which corresponds to the compound AISb. The curve then drops to the melting point of pure antimony. Tamrriarln explained the maximum occurring at about 67 per cent. aluminum as the result of the slow formation of the single compound AISb. The space lattice of the compound AISb, according to Owen and Preaton,³ is face-centered cubic, the antimony atoms being intermeshed with an identical aluminum lattice. Very little, if any, work has been done on aluminum alloys containing small amounts of antimony. The Present Investigation It has been the purpose of this investigation to determine the solid solubility of antimony in aluminum and also to investigate the eutectic temperature and concentration. The experimental work has been carried out in a manner similar to that described in a previous paper4 from this laboratory.

Jan 1, 1931

By Charles Pack

Extensive progress has been made in the metallurgy of alloys for die castings. Enthusiastic proponents of some alloys are inclined to make extravagant claims for their materials, which may be justified by physical tests on test bars made from the respective alloys but are seldom justified by the results obtained with commercial die castings made from those alloys. Chemical analysis of the test bars and castings fails to determine the cause of these variations, since they are due to other physical factors entering into the commercial production of die castings. In this paper, an attempt will be made to outline some of the factors in commercial die-casting practice to which these variable results may be attributed, in the hope that the manufacturer of die castings, recognizing the importance of these factors, will devote more attention to them in the design and construction of dies and equipment. In 1914,l the author defined die castings as "metal castings made by forcing molten metal, under pressure, into metallic molds or dies." This definition was given in order to differentiate die castings from other molded metal products such as "permanent-mold" castings, L'slush" castings and similar products that are sometimes erroneously termed die castings. The term "die casting" could be interpreted to include all castings made in metal molds or dies; but since this term, like most of our technical nomenclature, has been developed by commercial practice we must look to this practice for its proper definition. The Germans, with their usual devotion to desecriptive names, have adopted the name of sprilzguss (squirt cast) for die castings. Undoubtedly this name is more descriptive of the die-casting process, where the metal is literally squirted into the die and serves to differentiate this process from other metal mold processes, where the metal is poured into the die. In the earlier paper mentioned, the author also emphasized the fact that the definition given for die castings indicated clearly that the satisfactory operation of the process must comprise three factors, all of which must be considered of vital importance to the successful operation of the die-casting process:

Jan 1, 1931

By E. V. Crane

A tremendous volume of the metal rolled annually into sheets strips and coil stock finds its way to a host of stamping and manufacturing plants which are the quantity production units of the country. Considerable in volume, too, are the rolled and extruded rods which go into forging and manufacturing plants for conversion into the same general line: those widely sold metallic necessities and luxuries of the household, the office, transportation, farming and building construction. Yet, in spite of its age and its importance, the stamping trade has been doing its "engineering" largely by trial and error. Its distinctive method is shearing out and plastically working metal to finished shape in a few quick strokes with high loads and expensive tools which are warranted only by large quantities to be produced. The principal operations have many features In common with rolling and wire-drawing methods. Combinations of stresses are diffcrent, however, and details of operations are infinite in variety. An engineering study of the subject begins with stress analysis, but must go back to metallurgy for its foundation. A grouping of pressed-metal working operations according to whether the metal is (1) sheared, (2) bent, (3) drawn or (4) squeezed has proved useful. All of these groups include instances of both hot and cold operations. For discussions of metal working properties, the division between hot and cold working is taken as the recrystallization range of temperature. This, of course, brings tin, lead and often zinc into the hot-work range at or near room temperature. The outstanding hot-working press field is in forging: particularly of brass; all of which is included in the squeezing group. Shearing Operations The shearing group of operations, including blanking, piercing, trimming, shaving, slitting, shearing, notching, parting and numerous variations and combinations of these enters once or more into the production schedule of practically every stamped or forged article. The transverse stress, set up in shearing, as shown in Fig. 1A, is a combination of an angular compressive thrust and a tensile stress which is also at an

Jan 1, 1931

Contents

Jan 1, 1985

By F. -J. Wodopia

Sustainability of energy supplies has been an issue of general interest for a long time. Whilst in the past the continuous productive use of natural commodities was in the fore, its compatibility with the environment and climate and ultimately also social aspects have recently gained more and more attention. Today many discussions focus on the climate compatibility of individual options to act. Fossil fuels, in particular coal and lignite, are generally challenged because coal use makes a significant contribution to global man-made CO2 emissions. The drastic increase in the consumption of fossil fuels is not explained by the fact that coal utilisation technologies are not or cannot be sustainable but rather by the growing world population and the endeavours numerous national economies trying to catch up economically. Coal is the world’s No. 1 fuel and, in the view of many experts, will keep this position also in the foreseeable future. The access to its deposits plays a significant role for the economies of the emerging countries. Consequently the aspects of energy security and economic efficiency need to be considered at eye level with climate compatibility. In Germany, however, the public acceptance of fossil fuels and of large industrial projects is in the focus of attention.

Jan 1, 2011

By Zárate G. E.

Practical and statistical considerations concerned with the sampling, sample preparation and chemical analysis of precious metal ores are reviewed. The principal requirements related with the characteristics of sample cutter, sample preparation, equipment and methods are discussed. The main errors introduced in the different stages of the sampling systems are defined. The application of statistical techniques to evaluate these errors to determine the ore grade variation and to design the number of increments needed to get an accurate assay are presented. Finally, results obtained with the application of this method to gold and silver ores are analyzed and some recommendations are given.

Jan 1, 1984

By G. C. McKerrow

"Mr. G.C. McKerrow, Assistant Manager of Noranda Mines and formerly Smelter Superintendent attended the meeting to answer questions as to why smelters imposed penalties for too much zinc in a copper concentrate or too much copper in a zinc concentrate, etc.D.W. Bridges -Mattagami Lake MinesWhat limits do you set on zinc and lead in a copper concentrate?G.C. McKerrow - At Noranda, we allow 5% zinc free and charge 25 cents for every unit above that. For lead, it is 1% free and 25 cents per unit above that. Lead is a much more harmful impurity than zinc because it tends to recycle more in the smelter circuit and creates a greater health hazard in the plant.E. Thornton - Sullivan GroupWHat harm does fluorine do in the smelting process?G.C. McKerrow - Fluorine usually does not occur in harmful concentrations in non-ferrous smelters. Fluorides are present in exhaust gases in the aluminum and phosphate industries. If these fumes escape into the atmosphere, they may settle out on forage grasses in concentrations that are harmful to livestock.Thorton - Sullivan GroupI have asked this question other places and have been told that it is hard on brick linings and causes gold and silver to be lost up the stack.G.C. McKerrow - Almost any volatile constituent in a smelter charge will aid in carrying other metal values. To this extent it may be harmful.E. Thornton - Sullivan GroupMr. Tait mentioned before a smelter where they have a copper-tin ore and they pay for copper, tin, bismuth and silver but object strongly to indium in the concentrate. Why would this be?G.G. McKerrow - 1 can't see why indium would be a serious impurity. It does tend to concentrate in flu dusts and if you get enough of it you can recover it and sell it but I have never heard of anyone putting a penalty on it.Question - I once ran into a small copper mine in Peru that had cadmium in the copper concentrate but no zinc. The copper smelter charged a penalty for the cadmium. Why would this be?"

Jan 1, 1971