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By O. Norman Lotter

There are many scales of innovation in the pursuit of concentrator performance improvement, including paradigm change, inventive change and incremental change. All are important, but the last is low risk, low cost and has a relatively high probability of success, given the right metallurgical skills. Seeking continuous improvement is also essential to ensure that performance does not decline over time due to ore type changes, personnel changes, equipment wear and other factors. When properly implemented, these small gains offer a very high rate of return for the project cost because they are made from marginal, not total, operating costs of the plant. To be effective this approach requires plant trials that use designed structure and appropriate statistics to test the observed differences arising from the old and new process treatments, be they a change in flotation reagent, in grind, pulp density, etc. However the pursuit of small but financially significant performance gains is often regarded as fruitless because of the range of variance in plant data, and the consequent difficulty of ‘proving’ that a benefit has been achieved. Opportunity for improvement is thus sometimes relegated to the realm of the impossible, or at best, treated with skepticism. Operations managers prefer to look for the larger gains, which are easier to demonstrate and prove. Unfortunately, these are seldom to be found; rather, a large gain can be more easily made by executing a series of small recovery improvements that are together equivalent to the ephemeral single large gain. In this paper we advocate a policy of continuing improvement driven by rigorous performance testing protocols and a formal ‘risk analysis’ approach to judging the efficacy of changes implemented in the plant. Following these simple procedures allows rational decisions to be made on the basis of quantifying risk and reward. In particular we consider the choice of hurdle rate for decision-making which best balances risk and reward. It is shown through case studies from actual industrial practice that this approach is practical and delivers significant financial value to the operation.

By Jorge Olivari Ortega

"Los incas desarrollaron un censo que les permitía planificar el desarrollo socio-económico de la región, como la actividad minera aurífera. En ese sentido, el gobierno del inca Mayta Cápac elaboró un sistema estadístico, a partir de los quipus para registrar toda la información y obtener el máximo provecho de los recursos existentes. Por ello, el presente texto describe el proceso del método estadítico que permitió a los incas adquiirir el tributo que habían programado. Para ello, se utilizaron los cordones de variados colores (quipus) para diferenciarlos en cada actividad como el amarillo que significaba la actividad minera aurífera. En estos cordones, los quipucamayoc registraban la cantidad de oro producido durante la mita minera o con los mitimaes en los yacimientos auríferos el número de personas que participó, la cantidad de días, las herramientas, los viveres, los vestidos, etc. Las herramientas utilizadas en la explotación de los yacimientos auríferos tipo lavadero, son las mismas que en la actividad agrícola, ya que en ambas se requieren remover la tierra: en la agricultura para sembrar las semillas, y en la minería aurífera, para lavarla y obtener las partículas de oro."

May 1, 2016

The Carlin gold deposit is located in northeastern Nevada about thirty-five miles by road from the town of Elko. Following the staking of six square miles 'of ground, a drilling program outlined a fine ore body mineable by open pitting. The resulting mine turned out to be the largest open-pit gold operation in the world, until the Rosario Pueblo Viejo operation was started in 1975. Because of the high profitability forecast at the then $35 gold price, construction of a 2000 stpd mill was commenced on a crash program and was completed for Newmont Mining Corporation by Bechtel Corporation in ten months. Production was started in early 1965. The gold mineralization occurs in marine-type sediments, chiefly silt- stones and limey shales, and the ore characteristics make for a difficult materials-handling problem. At 5% to 6% moisture the ore is dusty during crushing, but even a light rain or snowfall virtually turns the material into a slurry. Crushing this sticky ore below 314 in. (19 mm) in the dry season and 1 in. (25.4 m) during the winter is extremely difficult and leads to problems with conveyors, chutes, and fine ore storage. The initial flowsheet for Carlin's crushing plant used a 5 ft by 22 ft (1.52 m by 6. 7 m) vibrating feeder -grizzly under the 60 -ton dump pocket for feeding the 42 in. by 48 in. (1067 mm by 1220 mm) single toggle jaw crusher and a 5 ½ ft (1.52 m) standard cone crusher in closed circuit with a 6 ft by 12 ft (1.83 m by 3.66 m) vibrating double - deck screen. Because continual packing of fines in the vibrating feeder pan would cause frequent plant shut-downs to remove the fines with jack hammers, the decision was made to replace the vibrating unit with an apron feeder and stationary grizzly ahead of the jaw crusher. A dribble belt was also installed under the apron feeder. This installation has greatly improved the feeding of the pit run ore to the .primary jaw crusher. Mining at Carlin is done by a 5 yd shovel and 7 ½ and 10 yd front-end loaders, and ore transport is by several sizes of trucks from 30 to 75 tons capacity. These pit haulage trucks dump onto stockpiles adjacent to the primary crusher. Ore is then fed to the dump hopper by front- end loaders only when the crushing plant is operating. This extra handling procedure is necessary because plant delays caused by problems with wet ore in the secondary crusher resulted in the ore setting up or packing in the dump pocket. Solidified material in the dump pocket would in turn delay truck haulage. The substitution of an

Jan 1, 1978

By Angelina Anani, Nilufer K. B. Akbulut, Sefiu O. Adewuyi

Crucial information about safety, design and operation from ground movement data can be utilized in underground mines. Communicating the information and exploring new findings can be a challenge, however, in a decade where there is an ever-increasing volume and velocity of data due to advancements in mining technologies. This challenge escalates for geotechnical data as they are multidimensional, depending on the space and the rate at which they take place. To tackle this challenge, geotechnical engineers should focus on using simple yet compelling visualization of rock mass data in 3D. Competent visualizations of ground conditions as a trigger action and response plan (TARP) could ease the communication of safety concerns and the exploration of rock mass displacement and strain surrounding an opening at an underground mine. Therefore, this study focuses on using scientific visualization methods by rendering geotechnical data over the surface of a 3D mesh model to display TARP levels. The study was conducted at the East Decline of the San Xavier (SX) Underground Mine, a laboratory mine operated by the University of Arizona. The project aims to produce visualizations that optimize the use of geotechnical data in near-real time.

Sep 1, 2025

By J. A. Sweet

The issues facing graduate training in the mineral processing industry are not too different today from those that prompted the initiation of the Anglo American Platinum Graduate Development Programme (AGDP) in 2002. Graduate metallurgists in South Africa enter the industry from different undergraduate programmes at various tertiary institutions, and so the knowledge and skills of the young graduates varies. Further, the geographical expansion of the industry combined with the downsizing of business units means that there are fewer opportunities for young graduates to be mentored through their first few years on site. Anglo American Platinum chose to address these issues by implementing an intensive, structured graduate training programme for all their new metallurgical graduates, known as the AGDP. The first two years of experience of the AGDP, from the viewpoints of both graduates and lecturers, were presented to the mineral processing community at the IMPC in Turkey in 2006 (Sweet et al, 2006). From the beginning, the programme was structured in a modular fashion to include a basic technical ?toolbox? including statistics, the scientific method and sampling protocols, while the mineral processing content comprised advanced learning in comminution, classification and flotation (later extended to include hydrometallurgy). Technical communication ? both written and verbal ? was included from the start. The programme was focussed very strongly on site work (?learning by doing?), with a major integrated site campaign conducted and analysed by each cohort. In 2012 the AGDP will accept its ninth cohort into the programme. This paper describes how Anglo American Platinum and the University of Cape Town have developed and adapted the programme over the last few years, in response to the challenges of the global recession, skills retention, and the changing operational needs of the company. The programme, which was drawn up to accommodate around 15 concentrator-only graduates, now accommodates 35-40 concentrator, smelter and refinery graduates annually. The programme has also been modified to facilitate new graduates spending most of their first year on the operations. The benefits of the programme for Anglo American Platinum have been tangible, and will be discussed in the paper. Keywords: graduate training, technology transfer

Sep 1, 2012

By Håkan Tyni, Jan Björkman, Per-Olaf Samskog, Irving Wigdén

Process automation can provide better utilization of capital investments. Furthermore, it is a necessity for securing the high demands of product quality. In this paper, process automation in underground mining as well as in the beneficiation plant will be discussed. The development of reliable broadband communication systems for real-time transfer of image, audio and data have enabled remotely controlled LHDs and drilling rigs. In the beneficiation plants, model-based expert control systems far on-line dynamic process optimization and control have been installed in unit operations such as grinding, flotation and induration.

Jan 1, 2000

By Qingxiang Huang

Shallow seam coal field has the largest coal reserve in China. Mining in shallow depth causes serious problems. One of them is subsurface dewatering. In this paper, the physical simulating model was performed to study overburden movement and aquiclude stability in the shallow seam mining of Yushuwan coal field, China. According to the characteristic of clay aquiclude in the overburden, the proper simulation materials and proportions of mixture for simulating the plastic clay aquiclude layers and brittle bedrock layers were determined by the stress-strain tests. The physical simulating model was carried out to simulate the failure and caving process of the roof and overburden. Based on the simulating tests, it was found that the movement of clay aquiclude follows the movement of the underlying bedrock layers. The basic caving mechanism of the overburden roof strata was also presented. The tests also showed that the best way to control the stability of aquiclude is to reduce the subsiding gradient Ts. This research provides a foundation for further study on mining dewatering and water conservation.

Jan 1, 2006

By L A. Martinez Tipe, J McKibben, S Barry

"Metal prices are central to a mineral investment decision and have a profound impact on the financial performance of companies in the mining industry. At its most basic level, metal prices are influenced by the disequilibrium between international metal volume supply and demand. That is, the commodity price is a regulator that equates international metal supply and demand where inventories act as a buffer between the emergence of this disequilibrium and its dissolution through a price change.From this viewpoint, mining companies are required to forecast metal and bulk commodity prices when evaluating minerals projects through discounted cash flow (DCF) analysis. While supply-demand models are instructive, many companies use historical prices, spot prices, futures/forward pricing and consensus opinion (or a combination of all of these) to develop price forecasts.This paper discusses the definition, fundamentals and differences between futures/forward and consensus pricing and the appropriateness of each in a DCF model for mine project economic evaluation.Our results demonstrate that great care is required when using either futures/forward or consensus pricing and that the decision to use one rather than the other requires consideration of other important elements in the DCF model (ie the risk-adjusted discount rate).CITATION:Martinez Tipe, L A, McKibben, J and Barry, S, 2016. Metal prices and the differences between forward and consensus pricing – which one is better for use in a discounted cash flow model?, in Proceedings Project Evaluation 2016, pp 149–158 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

The first metal-mine accident-prevention course was prepared and published in 1942-45 as a series of seven miners' circulars (Nos. 51-57). The course has been broadened in scope, revised, and brought up to date and is being published as a similar series of seven miners' circulars (Nos. 51-57, revised) on accident prevention in metal and non-metallic mines. These circulars are as follows: Injury Statistics (Miners' Circular 51), dealing with general statistics on injuries from accidents at metal and nonmetallic mines, including causes, costs, and the use of investigations and reports of all injuries.

Jan 1, 1960

By Oliver Bowles

Lime is of tremendous importance to modern industries. In agriculture it is regarded as essential to the continued fertility of many important regions; in building it is indispensable, and in the many ramifications of the chemical industries it is so necessary and so widely employed that it has been designated "the king of all the bases." Figure 1 shows a general view of a modern lime plant producing more than 500 tons of lime daily. In 1924 the production of lime was reported from nearly every State in the Union and amounted to more than 4,000,000 tons, valued at, nearly $40,000,000. For a production of that magnitude between 8,000,000 and 9,000,000 tons of limestone are required. The many problems involved in winning this great quantity of raw material from the natural rock and preparing it for the kilns have in the past received little attention from any governmental agency. Therefore, in compliance with a request from representatives of the National Lime Association in 1922, the Bureau of Mines began a study of problems in limestone quarrying in an effort to advance more economical methods of operation and the utilization of waste material. Field studies were made at many quarries, and the information thus compiled, besides data already at hand from work in other branches of the stone industries, were disseminated to operators in the form of mimeographed Reports of Investigations, eight of which were issued at intervals during 1922, 1923, and 1924. A questionnaire was appended to each report, and quarry operators were invited to contribute additional information obtained as a result of their actual experience and observation. Operators of lime plants have been cordial in their responses and have supplied the bureau with much valuable information. From the data thus obtained, supplemented by later field studies, the revised reports have been combined to form the major part of this bulletin, which is believed fairly to represent present knowledge on the subject of quarrying limestone for lime manufacture.

Jan 1, 1927

By H. Hao

This paper outlines the development of a 2-D axisymmetric mathematical model to predict the evolution of temperature during the Direct Chill (DC) casting of AZ31 magnesium billets. Model predictions of temperature have been compared to measurements made on an industrial DC casting machine at Timminco Ltd, in Haley, Ontario. These measurements have been used to fine-tune the thermal boundary conditions employed in the mathematical model, The model, which is based on the commercial finite-element code ABAQUS, has been developed as part of a strategic project aimed at improving the DC casting process for light metals through a reduction in casting related defects and increased productivity.

Jan 1, 2004

By D. H. Gurinsky, D. G. Schweitzer

The empirical equilibrium constantsd the heat of reaction for the reduction have been determined from 300° to 500°C. The mechanisms of the oxidation of uranium and magnesium from dilute bismuth solutions have been investigated. The kinetics of some of the reactions were affected by air adsorbed on the uranium oxides. THE Liquid Metal Fuel Reactor studied at Brook-haven National Laboratory uses a solution of uranium in bismuth as the fuel. Corrosion and stability problems require that the fuel solution contain corrosion inhibitors and deoxidants. Of the additives tested, magnesium has been found to be the best deoxidant and zirconium the best corrosion inhibitor in bismuth. Some experiments1 indicate that magnesium may play a secondary role in increasing the effectiveness of zirconium in inhibiting corrosion. The work reported here was intended to determine the relative concentrations of Mg and U required to prevent oxidation of the uranium fuel in the event of an air leak. In addition, an attempt was made to identify some of the mechanisms of the oxidation and reduction reactions occurring in the liquid bismuth solutions. EXPERIMENTAL Apparatus and Procedure—The equipment shown in Fig. 1 was designed so that the reaction kinetics could be studied as functions of temperature, melt composition, pressure, and flow rate. At the start of a run, the 10-liter bell jar (F) is removed by opening the bottom Dresser fitting (L), and the bismuth and additives are placed in a pyrex crystallizing dish (I). The bell jar is replaced, the system is evacuated to 10-5 to 10-6 mm Hg and then the heater (J) is turned on. When the selected temperature is reached, the oxidizing gas is admitted to the system to the desired pressure as read on the manometer (D). Gas is introduced through the slide tube (Q) which has a pyrex frit (R) sealed to its bottom. Stirring is accomplished by immersing the end of the tube in the melt. To maintain a constant pressure under flow the input and evacuation rates must be equalized. To obtain this condition stopcock (C) is closed and flowmeters (B) are matched. The reaction is "stopped" by closing the inlet flowmeter and quickly evacuating the system. To obtain a liquid metal sample, the system is evacuated with the sampler positioned near the surface of the liquid. The sampler, Fig. 2, is then immersed until its thermocouple reading matches thermocouple (G) Fig. 1. The system is then pressurized with helium which forces the solution through the frit. Twenty to 30 min elapsed between the time the system was evacuated and sampled. During evacuation and pressurization of the system, the temperature variations did not exceed ± 5°C. While bubbling occurred the temperature remained constant to within 1/2 oC. The volume of the equipment was determined by adding a known volume of air at atmospheric pressure to the evacuated system and noting the resulting pressure.

Jan 1, 1962

By Robert H. Holgers

Eveleth Taconite Co. was chartered on July 29, 1963, and is 85% owned by Ford Motor Co. and 15% by Oglebay Norton Co. The latter also serves as managing agent. The location of the company's facilities is depicted in Fig. 1. The Thunderbird mine is located midway between the cities of Eveleth and Virginia, Minn. (Fig. 2). The Fairlane plant and General Office are located approximately 10 miles south on the St. Louis River near the community of Forbes (Figs. 3 and 4). The crude ore and the finished pellets are transported by a common carrier railroad, the Duluth, Missabe & Iron Range Railway Co. The facilities are also serviced by the Duluth, Winnipeg & Pacific Railway Co. Pellets are hauled year around by the DM&IR to its docks 60 miles south in Duluth, Minn. Ford Motor Co. consumes its share of the high grade pellets at its Rouge plant in Dearborn, Mich., and Oglebay Norton Co. sells its share in the open market. HISTORY Following six months of preliminary engineering by the initial staff of Eveleth Taconite Co. and the Western Knapp Engineering Div. of Arthur G. McKee & Co., the project was approved by Eveleth's board of directors on Apr. 17, 1964. On May 1, 1964, contracts were awarded to McKee for the mine, coarse and fine crushing and concentrating facilities, and to Allis-Chalmer for the pelletizing facilities. The pre-production surface overburden stripping contract was awarded to Skubic Brothers Co., Virginia, Minn. Ground-breaking ceremonies were held at the Thunderbird mine on

Jan 1, 1969

By Andre Luis de Zorzi Marin

O corte a plasma de aço inoxidável tem história relativamente nova em comparação com outros meios de corte de metais. Frequentemente os usuários de corte plasma se deparam com questões específicas ao corte do aço inoxidável, como qualidade de corte, velocidade de corte, custo operacional e alterações nas propriedades metalúrgicas. Nos últimos vinte anos as tecnologias aplicadas no corte plasma do aço inoxidável tem evoluído com resultados atrativos nos últimos cinco anos. Estas tecnologias versam com alterações na mistura dos gases de plasma e de proteção, ou ainda, na mudança dos bicos de corte plasma buscando melhor constrição do arco plasma, e a devida seleção de gases em função da espessura de corte. Este trabalho foi desenvolvido através de revisão bibliográfica das principais tecnologias apresentadas pela indústria nas últimas duas décadas para o corte de aço inoxidável com plasma, e testes laboratoriais de corte com as últimas tecnologias de corte. Entre os resultados estão a redução até a eliminação da escória pós-corte, uma borda de corte menos arredondada, melhora na coloração da superfície e diminuição da zona afetada pelo calor na peça de trabalho. A importância do trabalho se dá pelo aumento da participação do uso do aço inoxidável dada a sua importância para a economia, em especial nos setores de energia, processamento de alimentos, papel e celulose e transportes que necessitam de melhorias no corte deste metal e suas ligas.

Jan 16, 2018

In this paper, three types of value-adding in the minerals industry are discussed: downstream processing, improving the efficiency of existing processing and increasing the knowledge base and expertise of the staff. It is shown that, while downstream processing seems to offer a good way of improving Australia's trade position, there are a number of impediments to such development, notably, limited access to the appropriate technology and overseas markets. Transport costs can also be a problem. To reverse the situation will require more positive policies by government. In the meantime, something can be done towards adding value by increasing the efficiency of existing processes. Examples are given, showing how it might be possible to make economies in reagent costs in the gold industry, how innovative technology has led to more complete processing of a tailings dump, how research might lead to an increase in the throughput in the production of synthetic rutile and how it is possible to leach selectively from gold/copper ores.

Jan 1, 1995

By A. C. Fieldner

The Sectional Committee on Classification of Coals, functioning under the sponsorship of the American Society for Testing Materials and the rules of the American Standards Association, in its 1934 report recommended to the American Society for Testing-Materials5 that Specifications for Classification of Coals by Rank be adopted as tentative. These specifications, slightly modified as recommended by the Sectional Committee, in its 1935 report,6 wore approved as tentative standards by the society in 1935. The specifications rover the classification of coals according to their degree of metamorphism, or progressive alteration, in the natural eerie s from lignite to anthracite. The basic scheme of classification is according to fired carbon and calorific value (expressed in B.t.u.) calculated to the mineral-matter-free basis. The higher-rank coals are classified according to fixed carbon on the dry basis, and the lower-ran]: coals according; to B.t.u. on the moist basis, that is, containing its natural bed moisture but free of visible surface moisture. Agglutinating and weathering indices arc used to differentiate between certain adjacent groups.

Jan 1, 1935

"The Garfield plant of the American Smelting & Refining Company is situated about seventeen miles west of Salt Lake City, on the Los Angeles & Salt Lake Railroad, and has freight service by the Denver & Rio Grande Western, Western Pacific and Bingham & Garfield Railways.The site lies between the picturesque Great Salt Lake, with its mountain islands, and the northern point of the Oquirrh Range, which forms the western boundary of the Salt Lake Valley.The location includes several hundred acres of land rising from the southern shore of the lake, selected on account of its adaptability to the economical handling of materials by gravity methods.The smelter is a custom smelter, treating copper ores and concentrates produced in Utah and adjoining states.The ores treated consist mainly of oxides from the Tintic and Park City Districts, sulphides from Bingham District, and concentrates from the mills of the Utah Copper Company, from mills in California, and copper precipitates from the Ohio Copper Company. The last product comes from low grade ores of Bingham Canyon.The following figures represent approximately the daily consumption of materials:Ores and Concentrates…2,700 tonsLime sand…100 ""Coal…350 ""Oil for Roasters…240 Bbls."

Jan 1, 1925

By P. D. P. Hamilton

IT is perhaps obvious to most individuals who are interested in the mining industry that a producing mine has been subjected to several phases of engineering attention. In this paper it is the author's hope that a thoughtful survey of these various engineering phases will emphasize certain points of value and interest which may sometimes be overlooked. The points which we will bring out are being made in an analytical sense and are not in any way a reflection on any individuals or organizations which might see in these illustrations a similarity co chair particular conditions. In other words, we are drawing on our general experience to illustrate the points which we chink are worthy of mention, and which we believe are of a type sufficiently frequent co be emphasized. It is well co point out chat, in this paper, we are not concerned with the relative importance of such theoretical questions as to whether or not a geologisc is more important than a prospector, or the office manager than the surface foreman. We are, however, interested in analyzing the various types of engineering experience required in the bringing of a mining enter-prise from the early prospect stage in co-production, and their importance to the project as a whole. In order to simplify our analysis of the subject, it has seemed best to outline a simple mining organization. In using the terms 'industry' and 'business', we feel chat frequently those engaged in mining do not always appreciate that mining is actually an endeavour, or a business, which has the same economic fundamentals as any other business. In the mining industry, the field and producing engineering are counter-parts of the research and production phases of any other type of business. Once this is realized, it is fairly obvious that mining, like any other industry, is a matter of economically acquiring raw materials, processing them, and finally marketing the resultant commodities as favourably as possible. The points may be discussed in a little more detail as follows.

Jan 1, 1938

By D. G. Sinclair

IN surveying the changes that have taken place in the mining industry of Ontario in the past ten years, the striking growth of the gold mining industry first attracts attention. In 1925 there were only twelve regularly producing gold mines in the Province, six of which were located in the Porcupine area, four at Kirkland Lake, and one each at Larder Lake and Boston Creek. In contrast with this, the year that has just closed (1935) has seen production on a steady basis from forty mines, with what may be termed spasmodic production from twelve other properties. This so-called spasmodic production is, however, responsible for the recovery of gold to an estimated value of between $75,000 and $100,000 during the year. Further illustrating the expansion in the gold mining group is the activity in the exploration and development of properties. In 1925, mining operations were conducted at 29 properties which had not reached production, while in 1935 work of this nature was carried on at 87 such properties. It is of interest to note that of the six properties listed as producers in Porcupine ten years ago, five are still producing at rates considerably in excess of the tonnages handled at that time. In fact, the estimated tonnage treated at these mines in 1935 exceeds the 1925 tonnage by approximately half a million tons. In Kirkland Lake, the figures are still more striking. The four mines in production in that camp in 1925 milled 346,584 tons, producing bullion to the value of $5,132,128, while in 1935 these same mines treated approximately 1,643,000 tons, with a recovery of roughly $29,300,000. While Porcupine and Kirkland Lake remain the great gold-producing camps of the Province, the growing importance of the newer areas is readily appreciated when we consider that in 1935 the mills of these areas treated over 1,000,000 tons of ore for a production in excess of $7,500,000. Pro-duction from these newer districts first became of importance in 1930 with the commencement of recovery at the Howey mine, in Red Lake, and the Minto, in Michipicoten. Since 1930, eighteen new gold mills have gone into production in the Red Lake, Little Long Lac-Beardmore, Pickle Crow, Sturgeon Lake, Michipicoten, Sudbury, and Matachewan areas. In respect to silver mining, the period under review has seen a considerable slackening of activity, due to a generally unstable and depreciated price for the product and to the exhaustion of ore reserves in the mines.

Jan 1, 1936

By John E. Tilton

Mining is one of the oldest human activities. It goes back at least to the Bronze Age and possibly even the Stone Age. The Romans mined copper in Spain and tin in England some two thousand years ago. The writings of Agricola in the 16th century show that mining was important in the Middle Ages. Today we mine more mineral commodities in greater tonnages than ever before. This long and fascinating history closely tied with the economic development of the human race is one of the charms of the mining industry. It also, unfortunately, gives rise to some widespread misconceptions.

Jan 1, 1997