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By J. G. Giddings, R. Kobayashi

Residual viscosity, the ViSCOSitY at a given pressure and temperature minus the dilute gas viscosity at the same temperature, has been found to be independent of temperature for pure components and mixtures for simple molecules and light hydrocarbons. The residual viscosities for methane, ethane, propane and four mixtures were correlated as a function of reduced density and molecular weight. INTRODUCTION Earlier efforts in correlating the viscosity of light hydrocarbons and associated gases under pressure, primarily by some form of the corresponding states principle, have been reported elsewhere.7 The formal theory of corresponding states principle for viscosity from non-equilibrium statistical mechanical arguments for simple molecules has been developed by Helfand and Rice.13 The most serious obstacle to the development of a generalized corresponding states representation of viscosity data, even for simple molecules, has been the limited quantity of precise viscosity data of pure components and mixtures over a wide range of pressure and temperature conditions. Viscosity data on light hydrocarbons have recently been contributed by several laboratories.2,6,8,23,25,26 In the study of the viscosity of nitrogen, Michels and Gibson" observed that the viscosities of nitrogen as a function of density gave parallel isotherms. The same behavior has since been reported for other gases.".= The observed behavior indicates that the residual viscosity or the viscosity at a given pressure and temperature minus the dilute gas viscosity at the same temperature is a unique function of the density. Abas-Zade,1 Michels and Botzen,18 and Michels, Bot-Zen, Friedman and Sengers,19 observed similar behavior for thermal conductivity, the residual thermal conductivity being defined in a manner parallel to that of residual viscosity. Thodos and co-workers 4,15,24 applied the residual viscosity concept to the viscosity of pure monatomic and diatomic gases. Ellington and co-workers10,25 made the residual viscosity vs density plots for ethane and propane, but omitted the region below a residual viscosity of 15 micropoise and showed a systematic separation of the ethane isotherms in the low density region. Eakin correlated the residual viscosity of methane, ethane, propane and n-butane empirically as a function of density and molecular weight: Carmichael and Sage6 recently presented ethane residual viscosity vs density values in the gaseous liquid, and near critical regions as a single univariant function of density. Flynn, Hanks, Lemaire and ROSS" have contributed extremely accurate viscosity data to confirm that the residual viscosity concept is essentially correct, but may not be accurate within 0.1 per cent of the viscosity value for the gaseous state- The recent studies by Giddings12 indicate that the residual viscosity of methane, propane and each of four methane-propane mixtures are unique functions of density Over the temperature and the density ranges studied.

Jan 1, 1965

By L. Bryson, J. H. W. M. Brits, K. Voogt

"The Anglo American Platinum’s Rustenburg Base Metals Refinery (RBMR) has the world’s first full deposit nickel plating tankhouse. Impurities in the nickel electrolyte can induce stresses in the electrowon nickel deposits that could lead to delamination of the deposit. Identifying the impurities that contribute to increasing internal stresses in the nickel deposit is key to successful operation and automation of the tankhouse. Impurities were introduced in the plant electrolyte and the effects on the full-scale nickel deposits evaluated. The impurity-adjusted electrolyte solutions were also analyzed using commercially available bench-scale methods to determine the induced stress. A correlation between impurity-induced deposit stress and full-scale delamination was developed. A direct correlation can now be made between feed quality, i.e. impurity concentrations, and degree of delamination in the plant. This methodology has the potential to rapidly predict the effect of new reagents, upstream process upset conditions and synergistic interactions between impurities on deposit stress and delamination of nickel deposits.INTRODUCTION Nickel electrowinning in sulphate media was first pioneered by Outokumpu in its Harjavalta refinery in 1960 (Saarinen and Seilo, 1985). The original process was very manual with starter sheets plated onto “acid resistant” steel for 36 hours and then manually stripped and cut into sheets which could be inserted into the main production cells for a further 4–5 days. The starter sheet stripping and manufacture process was later automated. The same technology was subsequently implemented on a number of plants around the world. Anglo American Platinum’s Base Metal Refinery (BMR) began nickel electrowinning in the early 1980’s. The recent expansion of Anglo American Platinum’s Base Metals Refinery necessitated the construction of a new nickel tankhouse to achieve two primary objectives. The first to increase the capacity to 32 400 tpa nickel and the second to reduce employee occupational exposure to nickel aerosols. The new tankhouse has been commissioned and is in the process of ramp-up; more details are given by Hagemann et al. (2016). Fundamental to lowering employee exposure to aerosols was automating both harvesting and final handling of cathode. In order to accomplish this a bold move was taken to plate up to 10 days on permanent titanium blanks which are harvested by automatic crane and automatically stripped. The original development work for the plating nickel on titanium blanks over a ten day cycle is given by Bryson et al. (2006)."

Jan 1, 2017

By D. H. Zellers

Since its inception the United States Bureau of Mines has fostered the development of portable mine lamps. Although there is still much to be desired with respect to illumination in coal and metal mines and the replacement of open lights has been slow the Bureau has been given credit for assisting materially in the development and introduction of the safe and efficient portable mine-lighting equipment available today. Much of the work conducted by the electrical section of the Bureau entails approval tests of various types of electrical equipment, including lamps; to be used in atmospheres that may contain methane or coal dust in explosive proportion. If a can lamp meets the requirements-for safety, efficiency, and adequacy, as published in Schedule 6B,4 it is approved and is generally known as a "permissible" lamp. The terms "approved" and '"permissible' often are used interchangeably. The manufacturer must put an approval plate on each approved lamp, showing it has mot the schedule requirements. The approval plate is not a guarantee that the lamp is safe. However, if the lamp, once in service, has not had any parts changed or improperly assembled or if carts that wear out or depreciate have been properly replaced it should still, be safe, efficient, and adequate for the service intended. Virtually all electric cap lamps in service today in the United States and a great many that have been sent to foreign countries bear the approval plate of the United States Bureau of Mines. Although many explosions have been attributed to open lights none has been charged against the permissible cap lamp. Nystagmus, a disease of the eye attributed to working under insufficient illumination, is practically unknown among; American miners, although it is quite prevalent among European miners.

Jan 1, 1935

By Moacir Alves dos Reis

O objetivo deste trabalho foi criar um projeto de um simulador do sistema de carregamento do Alto Forno 2, voltado para o treinamento de operadores e técnicos em manutenção. O principal objetivo está em produzir uma ferramenta que auxilie no processo de ensino dos operadores e técnicos de forma mais rápida e segura, reduzindo os custos do treinamento e ao mesmo tempo simulando situações de operação, alarmes de processos sem interferência no sistema de carregamento real. São apresentadas as etapas previstas para o desenvolvimento do projeto e as ações já realizadas até o presente momento. O simulador será equipado com equipamentos reais do sistema de carregamento do Alto Forno, sendo apenas simulado as entradas e saídas físicas (I/O) dos equipamentos externos (motores, limites, válvulas, etc.) e utilizará um ambiente virtual modelado a partir do PLC, SDCD e Monitores para que os operadores possam visualizar e simular todos os alarmes deste processo.

Jul 30, 2018

By David Burgess

The paper describes experiments at the Somerset Mine, Colorado, under a cooperative agreement between U.S. Steel and the U.S. Bureau of Mines. A test was made of the tube bundle method of mine air sampling which was developed for European longwall mines; some 300,000 running feet of tubing provided continuous monitoring at 39 locations. Carbon monoxide concentrations were obtained with standard deviations of less than 1 ppm and oxygen concentrations with standard deviations of less than 0.20 percent. A base level of CO index (ppm CO evolved/pct 02 removed)) was determined to be 0-20 through most of the passageways of the mine. However, in one working section where the coal was initially hot (about 180°F within a pillar) the CO index was demonstrably higher, >20 trending upward to about 60 when smoke appeared and the section was sealed. The data are discussed in terms of laboratory experiments on CO evolution from coals.

Jan 1, 1975

By T. R. A. Davey

A Survey of current and recent research and developmental work is supplemented by predictions for processes which should be developed over the reminder of this century.

Jan 1, 1970

By M Bilodeau, G Caro, R Beaudoin, D Labrie

In 2005, Dyno Nobel Canada Inc, DynoConsult and CANMET-MMSL used their pool of expertise in blasting, ground control, open pit and underground mining, mineral processing, information technology and applied mineralogy to launch a research project aimed at evaluating the role of electronic detonators in the development of a sustainable energy-efficient rock reduction process. The overall objectives were to improve health and safety in a mining environment and reduce energy consumption and greenhouse gas (GHG) production in the Canadian mining industry. The study was conducted in a quarry located in Nova Scotia, Canada, with the objective of taking advantage of the higher accuracy and flexibility of electronic detonators towards improving blast efficiency and measuring its impact on productivity in a quarry environment and energy savings. Optimising the blast sequence was the first aspect to be considered before starting to look at designing bigger blasts and achieving productivity improvements, without creating additional environmental concerns, as the quarryÆs location was representing a challenge in itself in the surrounding community. The use of high-speed cameras (500 fps) was an improved means of analysing blast dynamics during the firing sequence. Seismic monitoring and linear superposition techniques were also applied to validate the sequences to be tested in all three specific geological areas. The combination of field measurements allowed to identify the optimal blasting sequences that would then be delivered accurately with the electronic initiation systems. The data from 12 blasts (six with electronic detonators and six with pyrotechnic detonators) carried out in three different geological formations (soft, medium and hard rock) showed that the electronic blasting technology could increase rock fragmentation by 15 to 20 per cent. A more uniform distribution of rock fragment size was also obtained. Blast improvements on downstream processes resulted in a five per cent productivity increase in rock excavation and transportation, a ten per cent energy reduction in primary crushing and a 15 per cent increase in the primary crusher throughput. A prototype soft-sensor based on primary crusher data (eg energy consumption, throughput, feed and product size distribution) and a simplified computer process model were developed for online measurement of a rock operating work index. Furthermore, rock samples were collected and specimens were prepared in order to determine the tensile and compressive strength of the rock materials, evaluate the aggregate crushing work index and examine the development of micro and macro-fractures under binocular and scanning electron microscopy (SEM). Blast-induced rock damage was evaluated at the end of the laboratory testing program. A reduction in rock hardness by about 30 per cent was observed after blasting. However, the impact of the blasting method (eg using electronic versus pyrotechnic detonators) on the induced rock damage was either absent or not perceptible within the measurement technique accuracy and the number of samples analysed.

Jan 1, 2007

By AIME AIME

AT the end of September, ' the metal-producing industries were almost prostrate, the production of fuels was largely curtailed, there was a fair degree of activity in general manufacturing, while retail trade was moderately good. Looking at industry on the whole, there was a large percentage of unemployment, the degree of which has increased, progressively, month by month since the beginning of 1921. There is the prospect of much destitution and misery this winter; yet while' in some, quarters, idle workers are already being fed from, commissaries; in other quarters profligacy; in "spending continues, unabated. Amid this confusion in conditions there is;' much that appears paradoxical, but in fact it is not so and indeed everything is running pretty true to form: Such activity in production as there is to be seen is mainly in textiles; - leather goods, foodstuffs, etc., i.e., consumption goods for immediate use. Even in hard times 105,000,000 people must buy a good deal of clothing and food. Besides this there is indispensable repair work and- maintenances. Thus, the good business of the year in white lead for painting. The chief uses for the metals, however, are in the production of capital goods, and except for occasional and special reasons nobody in his senses is capitalizing anything at present prices for labor. Hence several millions of men are idle. The impoverishment of Europe and the exhaustion of her credits adds to this by curtailing our export trade.

Jan 1, 1921

By A. V. Corlett

THE use of the diamond-drill hole as a means of breaking clown ore and waste is not new. Years ago, the method was adopted in mines in northern Ontario and in the western United States to reach out to bad pillars, or to remnants of ore left on walls, the winning of which by any other method might be dangerous or too expensive. The practice is still in vogue and has generally proved a success. Of the known mineral deposits in Canada and elsewhere, many are of very low grade. Some are marginal and not even worthy of being classed as 'ore' until some means is found and proved of exploiting them economically. Other conditions being favourable, if a mining method could be found that would give a large 'bulk break' with a sufficiently low cost of development and a low cast of mining per ton, mineral deposits of this latter type might be brought into the classification of ore. We know that any block-craving system whereby the ore may be undercut and allowed to crush and cave will give a very high breakage and low costs. In some cases, however, the physical characteristics of the ore do not lend themselves to this method. In such ore-bodies, the alternative system of 'bulk-breaking' might be aided by long diamond-drill blast holes. We could obtain this 'bulk breaking' by the use of long diamond-drill holes in conjunction with a sub-level system using extremely thick benches, or possibly by the adaption of modified open-pit methods to underground mining. ln fact, if conditions are favourable, the idea would be simply ta open up a slot or free face and break into it on a larger scale with longer holes. The use of deeper benches-that is, using each level as a sub-level and thereby eliminating much development footage, slashing, setting up, and mucking time-would naturally be expected to lead to cheaper mining.

Jan 1, 1940

By V. A. Marple, K. L. Rubow, B. A. Olson

"INTRODUCTION Inertial classification, gravitational sedimentation centrifugation, and thermal precipitation arc techniques that can be used to collect particles for subsequent analysis or for particle classification. The inertial classifiers, which include impactors, virtual impactors, and cyclones, are widely used in the sampling or particles. Settling chambers, which include centrifuges as well as gravitational settling devices, are less widely used. Thermal precipitators arc seldom used.Impactors, in particular, have been used extensively, studied both theoretically and experimentally, and arc the instrument or choice for the determination or aerosol mass size distributions. Many versions or impactors arc available commercially and many more have been designed, built, and used in special studies.Virtual impactors are a more recently developed inertial classifier and possess a feature not round in conventional inertial impactors; namely, that the particles remain airborne after classification compared to the conventional impactor, where the particles arc collected on a solid surface. The feature or keeping particles airborne is important for transporting the particles to other particle-analyzing instruments, or to filters, and in concentrating particles larger than the cutsize in a small fraction of the total now."

Nov 1, 1995

By Ma Lianren, Wang Duolun, Chenzhe Li, Hongyan Xie, Fenglan Luo, Huixin Jin

In this study, the oxidation of low-grade pyrolusite to potassium manganate in alkaline solutions under O2 pressure has been investigated. The effects of different conditions on the high-grade and low-grade pyrolusite leaching process were investigated based on thermodynamic calculation, as well as the reaction mechanisms and kinetics of the low-grade pyrolusite during the leaching process. The results showed that the manganese conversion rates of the two types of pyrolusite were almost the same, and reaching 99% for high-grade pyrolusite and 96% for low-grade pyrolusite under optimal conditions. The optimum condition for low-grade pyrolusite sample JM-2 was achieved as 0.5 MPa of the oxygen partial pressure, 55% of KOH, 14 of the initial alkali-manganese ratio, and ≤ 48 μm of the mineral granularity at 260 °C within 150 min of leaching time and 500 rpm. In alkaline leaching of low-grade pyrolusite, Mn(IV) was oxidized into Mn(VI). The particles changed from large particles to flakes and finally formed crystals. Finally, the shrinking core model was used to fully describe the leaching kinetics of the manganese. It was demonstrated that the leaching of manganese was controlled by the chemical surface reactions and the activation energy which equals 115.9121 kJ/mol.

Dec 3, 2022

By Lyman File

This paper discusses the overall challenges to construct a two-lane highway tunnel located in southwestern Colorado on U.S. Highway 160 for the Colorado Department of Transportation by the Kiewit Western Company. The purpose of this project is to provide the excavation and temporary support for a highway tunnel 280 m (916 feet) long. The tunnel cross section is 14.3 m (47 feet) wide by 8.5 m (28 feet) high, 105 m2 (1,130 SF).Construction methods include conventional drill and blast excavation with rockbolt and shotcrete ground support. This unique tunnel is being constructed under alpine tunnelling conditions and in the immediate vicinity of active highway traffic.

Jan 1, 2003

By A. C. JR. Boyle

I. INTRODUCTION THE geological field work of the Bully Hill district, upon which this paper is based, was begun July 1, 1908, and covered a period of three months. The time was found too short for a complete report and the district was again visited in the early part of July, 1912,. from which time detailed study of the locality continued until September of the same year. This paper is the result of observations made in the mines in the immediate vicinity of Winthrop, Shasta county, Cal., during these two periods of study. The preparation of this report has been greatly facilitated by various courtesies rendered the writer by D. M. Riordan, President of the Bully Hill Copper Mining & Smelting Co., and by John B. Keating and Herbert R. Hanley, managing officers actively in charge at the mines. The elaboration and further study of the notes and collections were carried on in the laboratories of the Departments of Geology and Mining at Columbia University, and the writer takes pleasure also at this point in expressing his acknowledgments to Profs. James F. Kemp, A. W. Grabau, Charles P. Berkey, and William Campbell, for advice and assistance. In order that one may appreciate at first reading the significance of some of the details which follow, and for the sake of clearness, a brief outline of the geological relationships is here given, together with certain conclusions which have been reached regarding the genesis. of the ores and the gypsum masses. In the Bully Hill mining district an associated series of Triassic lavas and tuffs, chiefly andesites, is preceded as well as followed by sediments. The entire system is tilted so that the original bedding planes dip in general to the southeast. The surrounding region has been greatly disturbed, and in the immediate vicinity of the mines close folding of the later sediments and extreme shearing of the igneous rocks locally is a striking feature. Into the nearly vertical shear zones have been intruded post-Triassic dikes of various rock types in the following order: alaskite-porphyry and andesite-porphyry. Outside the area under consideration diorite dikes are known, but they will not receive attention further than to note that' they, probably, represent a differentiation product of the same magma from which the other two dikes came. In this connection all the dikes have an important bearing on the origin of the ores and of the gypsum found in the mines.

Jan 1, 1914

By A. J. Williams

"IntroductionAN EXCELLENT paper entitled Potash Discoveries in Western Canada (l) was presented to the 1948 Annual Meeting of the C.l.M. by L. Heber Cole, of the Department of Mines and Resources, Ottawa. In the intervening three and a half years, the search for oil and gas in Saskatchewan has added considerably to the information available on the occurrence of potash. It is the purpose of this paper to summarize the additional data. For greater clarity, it may be useful, first, to recapitulate some of the highlights of Mr. Cole's paper.Underlying the western plains of Canada there is a large deposit of sodium chloride, believed to be of early Devonian age. Associated with the sodium chloride are certain potash salts, primarily 'sylvinite,' a mechanical mixture of sodium chloride (halite) and potassium chloride (sylvite) crystals. The potash salts, when present, are usually near the top of the salt formation, though in at least one well they were found near the central part of the deposit. Cole reported on some seven wells in Saskatchewan which had encountered appreciable amounts of potash; these were the Ogema, Radville, Davidson Nos. 1 and 2, Prairie Salt Nos. 1 and 2, and Verbata wells. Depth of potash from surface ranged from 7,653 feet in the Radville well to a minimum of 3,466 feet in the Verbata well. Such depths do not compare favourably with those at which the potash is found in mines in the United States, France, and Germany, where about 1,000 feet is the average. The greatest concentration of sylvite encountered was in the Verbata well, where a bed 11 feet thick carried the equivalent of 21.64 per cent K20."

Jan 1, 1952

By Smortchevskyk N. J.

THIS paper describes the electrical features of the locomotive now (August, 1962) under construction for Craigmont Mines. Intended for non-specialists, it avoids details of design and calculations interesting to electricians only. The paper is divided into three sections. The first deals very briefly with the mine layout and with operating conditions -existing and expected. Reference is made to economic considerations leading to the selection of the type and size of locomotive, as well as to traction diagrams and the calculations. This material is not included in the paper because of its length and because it does not represent anything new. The second section deals with engineering and economic considerations and shows, in some detail, why the A.C. system was chosen. The third section describes the basic components of the locomotive, including the voltage regulator, the rectifiers, the control arrangement and the filter, and deals with considerations affecting the selection of their rating and design. A concluding sub-section describes, very briefly, the track and trolley details and the power distribution switchgear.

Jan 1, 1963

By John Ramsay, Frederick A. Edwards, J. Eric Belford, Clarence V. Amyotte

"DEVELOPMENT of the underground mine is carried out from a main ramp driven from surface to the 800 and 1200 levels and from a shaft sunk to 3050 ft. Sub-levels at approximately 100-ft vertical intervals, starting 300 ft above the 800 level, were collared from the ramp as it advanced and a considerable amount of development work was pursued. The lateral and ramp work provided an opportunity to train drift crews, test equipment and methods, assess ground conditions and advance the initial stope development. The development of an exhaust ventilation raise system closely followed the extension of the level development to the south end of the orebody (Fig. 26) . On completion of the shaft, temporary lip pockets were installed at the shaft stations on the 800, 12.00, 1600, 2000 and 2400 levels. The permanent loading pocket had been installed on the 2860 level as part of the shaft-sinking contract and the level had been connected to the 2800-level station by a small muck transfer raise. Development of the 2800-level area was given top priority at this stage. This included a 1000-ft cross-cut to the crusher location, the crusher excavation, storage bins, conveyor ways and a ramp to connect the 2800 level to the loading pocket, the rope changing station and the shaft sump. The development and installation of the rock handling system between the 2400 level and the shaft bottom was contracted to Macisaac Mining and Tunnelling Company, of Sudbury, Ontario."

Jan 1, 1974

By Robert W. Waytulonis

The mining regulations of all 50 States were reviewed by the Bureau of Mines, and those parts pertaining to the use of internal combustion (IC) engines (particularly diesel engines) in underground mines or confined spaces were extracted. Also extracted were subjects associated with the use of IC engines; for example, storage and handling of flammable liquids, maintenance, and ventilation requirements. As the laws now stand, 29 States have specific regulations that affect the operation of diesel engines in underground coal and/or metal and nonmetal mines. The other States have no regulations because either they have no mining activities or they defer to Federal regulations. Six states have regulations expressly prohibiting the use of diesels in underground coal mines. Specific contacts (addresses and phone numbers) precede each State's regulations to facilitate inquiries about regulation revisions and interpretation.

Jan 1, 1981

By M. J. Farrell

Mining is a significant emitter of greenhouse gases and is the focus of increasing attention from green groups and regulators. Miners need to know their own carbon emissions and how they compare with the rest of the industry. Miners and mining companies need to know where they fit in the emissions curve. Who is in the bottom quartile? This article updates data from minecost.com which detail the specific carbon dioxide emissions for over 200 mines producing 90% or more of western world copper, zinc, lead and nickel in 2009. This data shows the potential impact on mine economics of proposed carbon taxation regimes and emissions trading schemes proposed at COP 15 in Copenhagen during December.

Jan 1, 2010

By W. N. Hamilton

"Evaporites abound in the Western Canada sedimentary basin, recurring throughout the stratigraphic column and widely scattered over the basin region. Alberta, situated centrally over the basin, includes many of the evaporites within its borders, but only a few have the right geological conditions to form potential economic deposits of salt or gypsum. These include the Middle Devonian Elk Point Group and related evaporites, Upper Devonian Wabamun Group-Palliser Formation evaporites, and evaporites of the 'Triassic Charlie Lake and Whitehorse formations.Salt deposits underlie almost half of Alberta. The major deposits belong to the Elk Point Group, which includes thick salt units in the Lotsberg, Cold Lake and Prairie Evaporite formations. Another, younger salt deposit in the Wabamun Group has only local distribution. Elk Point salts have a maximum aggregate thickness of 430 m in east-central Alberta. The deposits deepen southwestward across the province, from minimum depths of210 m at Fort McMurray to 1820 m at Edmonton.The thickest, most extensive salt deposits are the upper Lotsberg and Prairie Evaporite salts. Both have excellent development potential. The upper Lotsberg is up to 150 m thick, consists of clear, very coarse crystalline halite with only minor impurities, and has a notable lack of non-salt strata in its succession. Analytical data for the Lotsberg Salt show extraordinary chemical purity. Prairie Evaporite Salt differs lithologically from the Lotsberg in having a significant non-salt component. The deposit is up to 200 m thick and consists of medium crystalline halite, brownish coloured and cloudy as a result of finely dispersed impurities. The main impurities-shale, anhydrite and dolomite-are most prevalent as interbeds in the salt succession, ranging from very thin laminae to beds several metres thick. Although of lesser purity, the Prairie Evaporite Salt is shallower, thicker and more extensive than the Lotsberg and the salt quality is quite acceptable for most industrial uses."

Jan 1, 1982

By C. O. Browner

Dados los altos costos que implican la explotación de una mina a tajo abierto, se ha previsto excavar los taludes de las minas lo más erguidos posible. En este sentido, el objetivo del texto describe los métodos actuales para evaluar la estabilidad de los taludes en roca. Para ello, se revisa la influencia de las estructuras rocosas, el agua subterránea y la voladura sobre la estabilidad de los taludes de los tajos. Asimismo, se consideran las condiciones de roca intemperizadas, las lluvias y los temblores presentados en algunas áreas del Perú. Producto de esta revisión, se analizará los problemas típicos de estabilidad para diversos proyectos mineros.

Nov 20, 1972