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El presente trabajo describe el sistema y los métodos para la extracción del oro en la planta de beneficio de Andaray Gold Mines, alcanzando una productividad óptima en el campo metalúrgico. La mina está situada en San Juan de Chorunga, provincia de Condesuyos, departamento de Arequipa, donde sus yacimientos mineralizados son de dos tipos: los yacimientos descompuestos que contienen limonita y oro libre, perteneciente a la mina Mercedes , y los de mineral piritoso aurífero, que comprenden chalcopirita y ojos de galena, perteneciente a la mina San Juan. El proceso de explotación se inicia con el transporte del mineral hasta su descarga en la parrilla de apertura. E mineral que no pase por la parrilla, se deriva a la chancadora durante 10 horas. Posteriormente pasa por la molienda para luego ser clasificado. Allí se adicionan los reactivos para la flotación y su análisis de malla. Producto de la flotación se obtiene el concentrado. El filtrado de los concentrados conlleva su envío a la molienda secundaria durante un período de seis horas. En este estado, la partícula de oro se encuentra limpia y en óptimas condiciones para la amalgamación y cianuración, donde el mercurio y la amalgama son exprimidos en una lona, destilándose, y se procede a la solución del oro, respectivamente. El método seguido es la agitación neumática, que suelta aire comprimido para la elevación del concentrado por el tubo elevador. Prosiguen los efectos de decantación, operación, control del cianuro y del alcali libre, precipitación, clarificación, limpieza y función de los precipitados. En el laboratorio se realiza el control de muestras del circuito de flotación, cianuración y de las barras, utilizando los métodos de soluciones de cianuro, ensayo de concentrados, minerales de mina, cabeza y relaves y ensayos de los precipitados. Finalmente, los cuadros de consumo de reactivos, mostrarán la eficacia del sistema y los resultados económicos de la planta de beneficio, como los costos, eficiencia de plata y mano de obra.

Jul 20, 1957

By Daryl R. Tweeton

The Bureau of Mines conducted experiments to measure the influence of environment on the friction and wear of a steel-quartz system at several speeds and loads. In each test a quartz block was pressed against a rotating ring of low-carbon steel. Environments used were moist air, dry air, dry nitrogen, water, aqueous oleylarnmonium acetate (ClsH35NH3+-OCOCH3), and aqueous aluminum chloride (A1C13). The sliding speeds were 2.2, 13, and 33, cm/sec, and the loads were 6.8 and 13.6 kg. The coefficient of friction, the wear, and the roughness of the surfaces were measured, and the wear debris was examined. The coefficient of friction was significantly lower in moist air at 2.2 cm/sec than for any other combination of environment and speed employed, and was generally an inverse function of the oxidizing ability of the environment. The coefficient of friction increased somewhat with increasing load. The wear of the steel rings was greatest in dry air at all speeds and loads. The wear of the quartz blocks at 180 rpm was greatest in dry air, but at 12 rpm it was greatest in nitrogen. Friction and wear in aqueous oleylarnmonium acetate and in aqueous aluminum chloride were similar to effect in water alone.

Jan 1, 1976

By R. D. Beard

Puerto Rico lies within the remnants of a deformed Cretaceous island arc system in the northeastern Caribbean. The Island can be divided into three broad geologic provinces: the Central Volcanic-Plutonic Province (Lower Cretaceous to middle Eocene), and the Northern and Southern Limestone Provinces (early Oligocene to middle Miocene). Known precious metal deposits are generally small and occur in veins and shear zones within Lower and Upper Cretaceous volcanic and plutonic rocks. Some Tertiary igneous rocks are also mineralized. Selected indications of disseminated lithology-controlled mineralization could represent larger deposits. Associated metals in some deposits include copper, zinc, and lead. At present, tax policies, population density, political outlook, and lack of proven significant precious metal deposits discourage the establishment of a metal mining industry.

Jan 1, 1993

By H. Vincent Wallace

ALTHOUGH it is universally accepted that free oxygen is A necessary in a cyanide solution for the dissolution of gold and silver-in accordance with Elsner's equation that 2Au + 4KCN + 0 + H20 = 2KAu (CN), + 2KOH- little has been written and insufficient attention paid to the drop in extraction due apparently to loss of dissolved oxygen in mill solutions. Aeration or oxygenation of cyanide solutions has been more or less successfully accomplished by various types of agitators such as the Dorr (with or without air lifts), Pachuca tanks and more recently "Turbo-mixers" and Denver "Super- agitators"; also by the introduction of chemical oxidizing agents such as Solozone (Na,O,) . At the Wright-Hargreaves and other mines in the Kirkland Lake camp, the introduction of this reagent at the rate of about 1.25 oz. per ton of ore applied to the feed of the ball mills has certainly been beneficial.

Jan 1, 1932

The effect of change in slag composition upon metal losses to the slag and the relationship between slag composition and slag matte separation was investigated at 1400°C. The synthetic slags containing CaO, MgO, SiO2,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Precious Group Metals) from the Merensky Reef of South Africa. The matte with a grade of 9.3% Cu and 16.0% Ni was a typical electric furnace product. The results indicated that the Cu and Ni solubility in the slag increases with the increase of the basicity ratio and CaO and MgO contents of the slag. At constant CaO/MgO ratios the rise in basicity decreases the metal losses. When FeO and SiO2 contents of the slag are kept constant, the substitution of MgO with CaO decreases the metal losses. The relationship between slag composition and matte-slag separation was found to depend primarily on the basicity ratio and the FeO content of the slag. The net effect comes from a strong interaction of the two in such a way that increasing basicity and decreasing FeO contents deteriorate the clean separation of the two phases.

Jan 1, 1994

A PDP 11/34 computer has been inter- faced to existing instrumentation in a 400 tph rod-mill/ball-mill grinding circuit and programed with a Kalman filter to estimate several unmeasured variables. A dynamic two-size- fraction model of the circuit is used to predict the complete state of the circuit including particle size distributions around the circuit, mass holdups and flowrates, the ball-mill grinding rate, water additions and cyclone parameters. Online measurements of sump level, slurry densities and product particle size are used to update the model values sequentially on a 20-second interval. This procedure results in optimal estimates of circuit variables given the relative reliability of measurements and the accuracy of the model.

Jan 1, 1983

By Maria I. De Rosa

The U.S. Bureau of Mines conducted experiments for predicting materials' ease of combustion (smoldering onset, smoldering, flaming, and decomposition rates) by means of submicrometer smoke particle characteristics for the development of a simple test method. The experiments were carried out in an approximately 20-L furnace, with a 10-L/min airflow through the furnace for a 14-min duration, at set furnace temperatures of 150°, 250°, and 1,000° C. The variables studied as a function of time were the onset time of smoke particles, time and duration of maximum smoke particle generation, average concentration of smoke particles, and particles' average diameter, mass weight loss, and furnace temperatures. Results show that the onset time of smoke particles is predictive of materials' ease of smoldering, and the time of maximum smoke particle generation and its duration, coupled with mass weight loss, are predictive of materials' ease of smoldering and flaming (depending on the experimental temperatures), and decomposition rates.

Jan 1, 2010

By Robert W. Metcalf

The feldspars are a series of related aluminum silicates containing varying proportions of potash, soda, rind lime; smaller amounts of other minerals arc likely to be present as impurities. They comprise three principal types: Potash spars, microline and orthoclase (KA12Si208); soda feldspar or albite (NaA1Si308); and soda-lime e (plagioclase) fellspars. The last-named is an intermediate group ranging from albite through oligoclase, andesine, labradorite, and bytownite to anorthite or line feldspar (CnA12Si2O8), Minor varieties are barium feldspar or celsian and a potash-barium feldspar. Perthite is a mixture of orthoclase end albite in alternate layers. Graphic granite or "corduroy spar" is an intergrowth of feldspar and quartz characteristically in the ratio of 3:1. Cornwall stone is a natural mixture of feldspar, quartz, end kaolinite imported in former years in sizable quantity from Cornwall, England. (A similar synthetic mixture, including some fluorspar, has been blended and marketed in the United States as "Carolina stone".)

Jan 1, 1941

By Richard L. Werner

The petrographic microscope as a tool in determining impurities and grain size of limestones, clays, sand and coal ash for possible use as raw materials is discussed. Its use in the determination of the mineral composition of various size fractions of the raw mix, after fine grinding in ball mills, and of the waste dust from the rotary kiln. A description is given of the typical clinker crystals; alite, belite, tricalcium aluminate and ferrite. The process problems indicated by various changes in the crystal characteristics are listed with possible solutions. Finally the microscope as used in relation to field problems with concrete such as air void volume, percent hydration of the cement, cement aggregate bonding and the determination of solid additives, is presented.

Jan 1, 1982

By Gregory M. Landry

"There is an old joke at Moretrench that defines dewatering as “that element of an underground construction project, which, when disregarded, will generate the low bidder.” Sigmund Freud wrote that all jokes are true, and the kernel of truth behind this one is that dewatering is often misunderstood or neglected until the last possible moment in the life of a project. The purpose of this article is to describe commonly used dewatering methods and to clear up a pervasive but fundamental misunderstanding about how to determine the amount of dewatering effort required for a project. The Tools of DewateringDewatering may be divided into two broad categories: (1) methods that remove water from the excavation after it has already entered and (2) methods that seek to exclude or intercept the water before it reaches the excavation. The former is generally self-performed by general or earth moving contractors using sumps and ditches, while the latter is usually done by a specialty contractor. SumpsProperly installed sumps can be an effective and economical way to control water inflow into a site. In this technique, groundwater is allowed to enter the site before being pumped away. Advantages of this method include lost cost, easy availability of equipment and the fact that a general contractor can self-perform the dewatering. However, caution should be used when deciding whether to use this method, and consideration should be given to the following factors:1. How will the soil behave under seepage forces? Will it run, potentially causing ground loss?2. How much groundwater lowering is required? If the groundwater only needs to be lowered a few feet, using sumps will be much more practical than for a situation that requires significant drawdown.3. Will the excavation subgrade soften or otherwise be damaged by allowing water to run over it?4. Is my workforce skilled enough to implement and manage the sumping plan?In the photo, the sump is capturing groundwater that has already entered the excavation by traveling under the sheets. In this instance, the house in the background of the photo was eventually purchased by the project owner after sustaining damage due to ground loss."

Jan 1, 2017

By Laird Crocker

This report describes a study of beryllium recovery from sulfate leach liquor by di-2-ethylhexyl phosphate (EHPA) solvent extraction in conjunction with caustic stripping. The work was one phase of Bureau of Mines research on process development for Spor Mountain, Utah, ores. Solution for the solvent extraction studies was prepared by sulfuric acid leaching of ore containing 0.6 pet BeO, Before solvent extraction of beryllium, the leach liquor was treated to prevent coextraetion of iron by either (1) removal of ferric iron by amine solvent extraction or (2) reduction of ferric iron to nonextractable ferrous iron by treatment with sulfur dioxide. Beryllim was extracted from the aqueous leach liquor by countercurrent multistage contacting with a kerosine solution of EHPA. The loaded organic solution was stripped with sodim hydroxide solution. Subsequently, beryllium hydroxide was precipitated by boiling the sodium beryllate strip solution and converted to beryllium oxide of 98 pct BeO-grade by calcining. Material of this grade can be directly processed into beryllium-copper alloy or be used as starting material for further refining to produce high-purity, nuclear-grade beryllium. Over 90 pct of the beryllium contained in the leach liquor was recovered as beryllia.

Jan 1, 1963

By W. A. Gibson, A. D. Trujillo

The Santa Rita copper deposit first served as a source of native copper for Indian implements and weapons. In 1801 Santa Rita copper, trans- ported by mule train to Chihuahua, began to be used commercially for making coins. It was a small- scale operation made difficult by Indian raids, transportation costs and depletion of the higher grade ores. There was, moreover, no known method for economically extracting copper from the under- lying low grade sulfide ores. Originally, copper and copper oxide ores were mined by underground methods, but there was virtually no development of the deposit-which became United States territory after the Treaty of Guadalupe Hidalgo in 1848-for almost a hundred years. A number of small underground mines had been started during that time, but it was not until 1873 that all the principal claims were consolidated under one control.

Jan 1, 1966

By John C. Sawyer

The mechanism of catastrophic oxidation of chromium and 446 stainless steel is examined. Data are presented to show that accelerated oxidation of these two materials, as caused by lead oxide, can occur in the absence of a liquid layer contrary to presently accepted theory. An alternate theory is proposed in which the rate of accelerated oxidation is a function of the rate at which lead oxide destroys the protective oxide formed on the base metal. An example of the application of the theory is given for the catastrophic oxidation of chromium in the presence of lead oxide. WHEN stainless iron-, nickel-, or cobalt-base alloys are heated in air to moderate temperatures in the presence of certain metallic oxides, oxidation will proceed at an accelerated rate. This phenomenon, often called "catastrophic oxidation", is most pronounced for the stainless steels. With these alloys the condition is so severe that large masses of oxide will form on the surface of the alloy in 1 hr or less at temperatures of 1200o to 1700oF. While a number of oxides are known to cause this effect, PbO, V2O5, and Moo3 are the most familiar, having been the subject of one or more investigations which have appeared in the literature.1-7 In presenting the results of these investigations, many of the authors have offered possible explanations to account for the more rapid rate of oxidation observed; however, the liquid layer theory as proposed by Rathenau and Meijering 2 has been the most commonly accepted mechanism. The liquid layer theory proposes that a low-melting oxide layer is formed on the surface of the alloy as the result of the interaction of the alloy oxide and the contaminating oxide. When the temperature of oxidation is above the melting point of the oxide on the surface, a liquid layer will form and oxidation will proceed at an accelerated rate. At temperatures below the melting point of the surface oxide, oxidation will proceed more slowly in the normal manner. It is argued that the rates of diffusion of oxygen and metal ions through the liquid layer are extremely rapid thereby accounting for the high rate of oxidation. Various experimental data have been presented to show that the temperature at which accelerated oxidation first becomes apparent coincides with the melting point of the eutectic oxide which would be present on the surface. Some exceptions have been observed, e.g., silver will oxidize in the presence of Moo3 at temperatures below the lowest melting eutectic; on the other hand, stainless steel will not be catastrophically oxidized at 1500oF in a molten bath of PbO and SiO2. In reviewing the various theories which have been used to explain catastrophic oxidation, Kubaschewski and Hopkins 8 favor the liquid layer theory, but note that, ".. .as experimental observations are not altogether in agreement with this theory (liquid layer theory), one should consider it a necessary but not a sufficient condition." In contemplating the liquid layer theory, it appears that sufficient evidence has not been presented to establish the theory beyond question. As a means of further clarification, a program of research was undertaken to determine in greater detail the mechanism of accelerated oxidation as caused by lead oxide. The first part of the program deals with a comparison of the oxidation of both AISI 446 stainless steel and chromium metal in the presence of lead oxide, vs the oxidation of these two materials in air alone. These comparisons are made at a number of different temperatures, most of which are below the melting point of the surface oxides. The second part of the program is concerned with a presentation of an alternate theory of accelerated oxidation exemplified by the system Cr-PbO-Air. PROCEDURE AND RESULTS Several experimental methods are commonly used to follow the progress of oxidation. One of these, the weight-gain method, was chosen for this work. This procedure requires that a specimen of the alloy be weighed, oxidized for a given period of time at an elevated temperature, and reweighed—the difference between the two weights being noted. The weight gain of the specimen represents the amount of oxygen acquired from the atmosphere to transform a portion of the specimen to oxide. In those cases where there is a tendency for the specimen or oxide to volatilize at the testing temperature, additional data must be collected so that a correction factor can be determined. This factor must be applied to the weight change in order to ascertain the actual amount of oxidation which has taken place. The specimens used for this work were 1 1/2 in.

Jan 1, 1963

By D. H. Platt

Data obtained from on-the-site observations have been compiled to describe the equipment and installation methods used for satisfactory suspension roof support in a large-diameter tunnel. Experimental roof bolting was undertaken from June 1950 until May 8, 1951, in the East Delaware tunnel, which is part of the Delaware aqueduct in Delaware and Sullivan Counties, N. Y. Revised suspension-roof-support plans and specifications were prepared during the spring of 1951 by the City of New York Board of Water Supply; these were approved by the State of New York Department of Labor April 13, 1951, and adopted by the City of New York Board of Water Supply on May 8, 1951.

Jan 1, 1952

By means of top-slicing methods, wide veins, masses, or thick beds of soft ore may be mined, where the caving of the overburden is of no consequence. The ore is mined in a series of horizontal floors or slices, taken in descending order, from the top of the deposit. Each floor is mined in small sections, the roof of each section being allowed or forced to cave before an adjacent section is attacked. The method as used in two mining districts—Marquette, iron, and Pachuca, silver-gold—is described in the two papers following:

Jan 1, 1925

By Jun Dai

Based upon research findings from several countries, the combination of microwave and mechanical means to break hard rock holds promise for the future. To achieve this goal, it is essential to understand the laws governing strength reduction of hard rock, such as granite, induced by microwave irradiation. Two aspects to consider are: 1) laws associated with the tensile strength of hard rock after microwave irradiation and 2) the sensitivity of different types of rock strengths to microwave energy. In this study, granite with a range of tensile strengths was exposed to microwaves for various time periods to compare the response of rocks with different strength values exposed to the same microwave irradiation. In addition, a method based on hotspots is presented to explain the mechanism by which granite strength is reduced by microwave irradiation. Granite extracted from Qinling Mountain in Shaanxi Province, China is used in the research. ?50 × 50 mm cylindrical granite specimens were exposed to microwaves at a specific power level. The strength values of the heated granite specimens were compared with those of unheated specimens. Through the comparison and analyses, relationships were determined between 1) reduction in granite strength and microwave irradiation time period, and 2) granite strength and sensitivity to a given energy of microwave irradiation. Finally, a mechanism to explain the experimental results is proposed. Research findings will aid in the design of a microwave + machine rock-breaking system for use in rock breakage in underground mines at depth and for future mine applications on earth and other planets. In addition, the experimental approach could be used to test other rock types to further our understanding of rock damage induced by microwave irradiation.

Aug 1, 2013

By H. Rosenthal, A. L. Jamieson

The action of mercury on stressed brass to produce cracks was known before Moore, Beckinsale and Mallinson1 showed that actual season cracking did not occur spontaneously but could be induced by ammonia. These investigators studied other substances, including diphenylamine, without finding that anything other than ammonia could cause season cracking Grimston2 reported season cracking in cartridge cases stored in wooden boxes wetted with dilute sulphuric acid pickling solution. Season cracking associated with sulphur dioxide, water vapor and air has been reported by Johnston,3 although he reported that trimethylamine and pyridine did not cause cracking. Jevons4 has ascribed season cracking of brass in certain instances to trimethylamine, "aldehyde amine," "ketone amine" and pyridine, but no experimental work was done evidently to prove this definitely. Pyridine was investigated by Morris,5 who found it to have considerable cracking power. In the present investigation, the object was a qualitative evaluation of a number of representative amines with respect to their ability to cause season cracking. Thus it was desired only that an appreciable vapor pressure of each amine be obtained in order to make the test as severe as possible, without attempting to test equivalent concentrations for comparative purposes. MEthods Specimens TWO types of specimen were used: 1. Unannealed 70-30 brass CUPs formed from 0.040-in. thick sheet. Height of cup Was 13/8 in. and diameter was 17/8 inches. 2. First draw pieces of caliber .50 cartridge cases in the unannealed condition (70-30 brass)- The cups were representative of a thin wall and thin base specimen, whereas the draw pieces have a thick base (1/4 in.) and a thick wall (approximately 3/32 in.). Both types of specimens contained high residual stress and cracked in less than one minute in a solution of I per cent mercurous nitrate and I per cent nitric acid provided that this was receded by a 30-sec. pickle in 40 per cent nitric acid. Specimens were prepared as follows: (1) degreased in trichlorethylene, (2) rinsed in H2O, (3) pickled 5 min. in 10 per cent by volume H2SO4 (1.84 SP. gr.), (4) rinsed in H2O, and (5) dried. Amirtes Tested In selecting the amines, representatives of the three series of amines, and one series of substituted amines were chosen. The aliphatic series was represented by the methyl and ethyl primary, secondary and tertiary amines. These are the simplest aliphatic amines. For the aromatic series, the phenyl primary, secondary and tertiary amines were selected as being the simplest. The heterocyclic series was represented by pyridine, which is a simple heterocyclic base (tertiary amine).

Jan 1, 1944

By Peter Metcalfe

"Wireless communication in the mineral processing environment is not as simple as it is in the home or office environment. The correct design of a wireless network in the mineral processing environment can offer a more flexible and lower cost installation than the transitional fiber networks. However with the flexibility of a wireless solution, also comes some limitations. By reviewing the plant requirements along with weighting the wireless benefits and limitations it is possible to design a network that combines the robustness of a wired solution with the mobility of a wireless solution. This paper addresses some wireless design considerations and it looks at some real life examples in the following areas: •,Meshed wireless network for high levels of redundancy •,Wireless instruments (such as HART, Modbus and others) •,Portable devices for mobile operators •,Network monitoring for plant personnel (it’s no longer just for IT people) INTRODUCTION Typical networks used in the mineral processing environment consist of a fiber network infrastructure with industrial switches used to connect the network devices. These fiber networks can be redundant or put into a ring topologies to offer a higher level of availability. Fiber networks have the benefits of: •,Immunity to noise from power and grounding issues •,Ability to span long distances (2km for multimode fiber and 20km for single mode fiber) •,Maintainable “off-the-shelf” technology Fiber networks however have some drawbacks, such as: •,Relativity high initial installation cost for cable trays, poles, trenches and pulling and termination of cable. •,Fixed geographic topology, adding future fiber drops may be challenging and expensive. •,Mobile users are not considered. Integrating a wireless network with a fiber network can offer the best of two worlds, a reliable high speed backbone for mission critical activities and a wireless network for remote applications and mobile users."

Jan 1, 2014

By Kazumasa Taguchi

At the Kakogawa works of Kobe Steel. Ltd., the agglomeration facilities are composed of a pelletizing plant and sintering plant. This aim is to utilize raw materials efficiently and stabilize the raw material resources. Therefore at Kakogawa works, the blast furnaces (BF) have been operated with high pellet ratio and various developments for pellet properties have been achieved to improve the blast furnace performance. These developments include dolomite-fluxed pellets, new-porous pellets and crushed pellets. As a results of these improvements, pellets have achieved almost the same performance as sinter at high temperature regarding properties such as the softening, melting and reduction behaviour. However, some problems on shape have remained to be solved. Spherical pellets flow easily into the center of the furnace and form mixed layers of pellets and cokes. Therefore, in BF operations with these pellets it becomes more difficult to keep proper and stable gas distribution.

Jan 1, 1983

By B. McLaughlin

"The Penna shaft is the deepest single-lift shaft in North America. Agnico-Eagle started sinking the Penna shaft in 1995 with a hoisting plant capable of hoisting 1800 t/d from a 2240-m deep shaft. Exploration success at depth led to the replacement of the existing double drum hoist by another double drum hoist capable of hoisting 7000 t/d. The use of another double drum hoist, instead of a Blair multi-rope winder, to hoist 24.5 t skips was only made possible by lowering the safety factor.This paper describes recent experiences at Penna and in South Africa, and examines the possibility of extending the double drum hoisting system to a depth of 3 km. IntroductionThe original Penna production hoist was a 4.88 m (16 ft) diameter double drum and single clutch machine. Béliveau (1996) and Scott (1996) have described this hoisting plant. In 1998, a decision was made to increase mining capacity from 1800 t to 4500 t of ore per day from the shaft bottom. Final capacity had to include an allowance of 1800 t of waste per day for future capital projects. While daily capacity was to be 6300 t, it would, by taking into account the different rock densities, be equivalent to hoisting 7000 t of ore.The steps taken to lower the safety factor were presented by McLaughlin and Scott"

Jan 1, 2004