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By R. V. Ramani, R. Bhaskar

"IntroductionThe behavior of dust clouds in mine atmospheres has been a subject of longstanding interest due to both health and safety reasons. Pioneering studies in Germany and SMRE focussed on ambient dust concentration, principally aimed at determining optimum velocities for effective dilution. A summary of studies related to this area is provided by Hall,(l) Efforts to understand dust deposition from the explosion hazard point of view led to experiments in return airways (2-4) followed by experiments in longwalls.(5) Concerted efforts, either experimental or theoretical, were not made until recently to relate ambient concentration with dust deposition in mines. In 1974 Hwang et a1 (6) developed a computer model to predict dust concentration which considered deposition-concentration relationships. Also, experimental studies involving concurrent dust deposition and ambient concentration were conducted in the U.S. by Courtney et al (7 ) in operating mines. Efforts to relate theory with experimental results have been made by Owen (8) and Hwang et al (6 ) for dust deposition. There has been limited work, however, to determine the application of the theories and assumptions from aerosol sciences for modeling dust flows in mine atmospheres. (9 ) This is the objective of the work currently underway in the Generic Technology Center on Respirable Dust since· 1983 under a project titled, ""Prediction of Ambient Dust Concentration in Mine Atmospheres."" The scope of the project activities include:1. Development of a mathematical model to predict dust deposition and concentration in mine atmospheres.2. Experimental studies on dust transport and deposition in mine airways.3. Comparison of the model results with the experimental data."

Mar 1, 1989

By E. H. Dix

The work of Merical and other investigators indicates that the phenomenon of age-hardening in alloys of the duralumin type is primarily dependent upon the variation in the solubility of copper with temperature. In addition to copper, however, these alloys contain small amounts of magnesium, silicon, manganese and iron, which may affect the age-hardening either directly or indirectly. The effect of these elements on the solubility of copper and on the manner in which this solubility varies with the temperature is of considerable interest, therefore. The effect of magnesium is of especial interest because apparently it exerts a marked effect on the natural or room-temperature aging of alloys of the type described.2 A series of investigations3 has been in progress in the research laboratories of the Aluminum Company of America to determine the functions * Metallurgist, Aluminum Research Laboratories. f Metallurgical Division, Aluminum Research Laboratories. Formerly with Metallurgical Division, Aluminum Research Laboratories. 1 P. D. Merica, It. G. Waltenberg and H. Scott: Heat Treatment of Duralumin. U. S. Bur. Stds. Sn. Paper 347 (1910). 2 M. Gayler: Constitution and Age-Hardening of Alloys of Aluminum with Copper, Magnesium, and Silicon in the Solid State. Jnl. Inst. Met. (1922) 28, 213. W. Fraenkel: Vergutbare Aluminiumlegiengen. Ztsch. Melallkunde. (1920) 12, 427. E. H. Dix, Jr.: Note on the Microstructure of Aluminum-Iron Alloys of High Purity. Proc. Amer. Soc. Test. Mat. (1925) 26, Pt. 2, 120. E. H. Dix, Jr. and H. H. Richardson: Equilibrium Relations in Aluminum-copper Alloys of High Purity. Trans. A. I. M. E. (1926) 73, 560. E. H. Dix, Jr. and W. D. Keith: Equilibrium Relations in Aluminum-manganese Alloys of High Purity. Proc. Inst. Met. Div., A. I. M. E. (1927) 315. E. H. Dix, Jr. and A. C. Heath, Jr.: Equilibrium Relations in Aluminum-silicon and Aluminum-iron-silicon Alloys of High Purity. Proc. Inst. Met. Div., A. I. M. E. (1928) 164. E. H. Dix, Jr. and F. Keller: Equilibrium Itelations in Aluminum-magnesium Alloys of High Purity. Proc. Inst. Met. Div., A. I. M. E. (1920) 351. E. H. Dix, Jr., F. Keller and R. W. Graham: Equilibrium Relations of Aluminum-magnesium Silicide Alloys of High Purity. Trans. A. I. M. E., Inst. Met. Div. (1931) 404. W. L. Fink and K. R. Van Horn: Constituents of Aluminum-iron-silicon Alloys. Trans. A. I. M. E., Inst. Met. Div. (1931) 383.

Jan 1, 1932

By R. W. M. Lai

In flotation or hydrometallurgical leaching of minerals, the cumulative metals recovery for a given process condition generally approaches a maximum value or an asymptote as the process time increases. This paper discusses the experimental methods of identifying and obtaining the asymptote of metals recovery through kinetic studies. In flotation, the kinetic asymptote of metal recovery, or ultimate recovery, is a function of grinding and collector dosage, but within a realistic variable range, is not a function of pH or temperature. However, variations in grinding, collector dosage, pH and temperature, all exert noticeable effects on flotation kinetics. Frothers generally have a minor affect on the asymptote, but have a major affect on flotation kinetics. The asymptote from batch flotation is found to be identical to that of a continuous flotation. In hydrometallurgical Leaching, the asymptote of metal recovery for a given leaching system is a function of such variables as temperature, particle size, and acid concentration.

Jan 1, 1983

By Hal McVey

The logic and importance of marketing in the industrial minerals industry is generally recognized by those of us intimately involved in this industry. The illogical instances where marketing is ignored in evaluating projects or poorly implemented in operations are also well known. The interplay between these two extremes is interesting territory and is explored commencing with a logical progression of a metal mine that became an industrial minerals mine and ending with the most illogical and failure-prone decision common to the minerals industry today. This paper will demonstrate how: 1. A logical progression of marketing expertise can result in previously unseen benefits to a minerals venture. 2. Logic can turn to illogic due to market conditions and price fluctuations. 3. How operations can turn marketing logic into illogical results. 4. Short term "logic" is often illogical.

Jan 1, 1981

Establish a procedure for reliably determining cation exchange parameters at an in situ mining site. The Problem Predicting the movement rates of pollutants from waste disposal sites requires reliable measurements of cation exchange parameters since cation exchange can retard pollutant movement. Reliable measurements of these parameters are also required for predicting the length of time needed to restore groundwater quality after in situ mining. Cation exchange is otten the controlling mechanism for the replacement of leach solution cations by the cations in the returning ground-water. Unfortunately, laboratory measurements using core samples are of minimal reliability. The uneven clay distribution at most sites produces a high variability in laboratory results. In addition the flow pattern in the laboratory tests is different from that in the field. Approach Bureau of Mines research has developed a field-test procedure that is quick and yields reliable and representative data. A corresponding data analysis procedure was also established in order to verify the' applicability of the computer simulation model of cation exchange used in the analysis, and of the general analysis procedure, with actual field data.

Jan 1, 1986

By J. Th. Erb

The total crude oil production of these islands, which in 1928 amounted to nearly 5,000,000 metric tons—about 36,500,000 bb1.—has again increased in 1929. The figures for 1929 are as follows: Metric ToNs† North Sumatra........................................ 369,930 South Sumatra........................................ 1,236,510 Java and Ceram....................................... 678,787 Dutch Borneo (including Tarakan)....................... 2,793,326 Sarawak.............................................. 759,700 Total............................................... 5,838.253 †1 metric tor1 = 7.36 bbl. on the average. This production, as far as the Dutch Islands are concerned, is owned partly by the Bataafsche Petroleum Maatschappij, the producing subsidiary of the Royal Dutch Petroleum Concern, and partly by the Kolon-isle Petroleum Maatschappij (Standard Oil Co. of N. J.), while that of the British Protectorate Sarawak belongs to the Anglo-Saxon Petroleum Co., Ltd., of London. The increase in 1929 is due partly to more intensive drilling; the rotary system, which enables drilling to be done more quickly and to greater depths than was possible with the percussion system, has come into more general use. Further, considerable extensions have been made to some of the existing fields and several new pools have been discovered, which contributed in no small degree to the increase in production. Of particular interest is the fact that the ('Niam" (Nederlandsche Indische Aardolie Maatschappij), in which the Dutch Government has a large share and which company in 1928 was producing from only two fields in South Sumatra, has discovered a pool in North Sumatra and, moreover, has struck oil on the island of Poeloe Boenjoe near Tarakan (Eastern Borneo). The deepest well still drilling is in one of the fields of the "Niam" and has reached a depth of 2269 meters (7445 feet). Notwithstanding the tropical c1imate and the dense jungle in which most of the fields are situated, the most modern scientific methods are applied in exploration, in drilling, producing and refining.

Jan 1, 1930

"In numerous meetings, conferences and discussions over the past year, the Conference Board of Canada has been impressed with the efforts of Canadian organizations to improve their competitive position. The attempt should be made to try to pull together and synthesize what has been heard. The topic of this paper, however, is even more daunting. The task is not only to analyze and discuss what is happening now, but also to look into the future—to the year 2000.The future seems to have an endless capacity for surprises, often unpleasant. This is one of the lessons learned in the twentieth century, particularly over the last 15 or so years.This paper covers three areas of managing in a changing com¬petitive environment: (1) the major global and domestic trends that will influence the ways in which Canadian organizations are managed (2) how Canadian companies are responding or will need to respond to these trends; and (3) the implications of the preced¬ing for human resource management and human resource professionals."

Jan 1, 1991

By A. Lyndon

Vertical and lateral load tests were carried out on two 13 m deep bored cast-in-place instrumented piles, socketed into weathered sandstone. The first pile, 1200 mm in diameter, was loaded vertically to a maximum of 16000 kN and then loaded to failure under lateral load (1900 kN). The second pile, 1500 mm in diameter, was tested under lateral load up to a maximum of 2400 kN. It was found that the deflections of the 1200 mm pile were more than twice those of the 1500 mm pile under similar loads. The soils on the site are not easily tested in the laboratory, or by conventional insitu site investigation techniques, parameters needed in design can only be reliably obtained from pile test results. In this report shear moduli are back analysed from the vertical load test and the two lateral load tests. For these similarly installed piles very different design parameters were determined from the lateral load tests, the only known major difference between the piles being that the 1200 mm pile was loaded vertically before it was loaded laterally. Changes in G values needed to match performance under vertical load if applicable to lateral loading could have accounted for a significant amount of the difference.

Jan 1, 1989

By William Cochran

The Bureau of Mines investigated mine subsidence caused by recent underground mining, estimated the extent of damages, and formulated a procedure for evaluating subsidence costs. On the basis of the quantity of material removed from beneath the surface, bituminous coal mining currently causes more extensive subsidence problems than mining of other minerals; costs are highest in areas such as western Pennsylvania where urban and suburban development and related types of land use conflict with mineral recovery. The Bureau of Mines estimated subsidence costs, including surface damages and control costs, for a 12-county area in western Pennsylvania for 1968. Total surface damages attributable to the underground production of bituminous coal in the 1-year period were $295,000; in addition, 12.4 million tons of coal, valued at $4.3 million, was left in place to minimize potential surface damage. Of the total subsidence cost ($4.6 million), $2.7 million was classified as external or social costs, not reflected in the market value of bituminous coal; this averaged $0.05 per ton of production, or slightly less than 1 percent of the market value.

Jan 1, 1971

By G. St. J. Perrott

ONE of the important hazards in coal mining is the danger of ignition of explosive mixtures of methane and air or coal dust and air, or both, by the explosives used in blasting the coal. It has long been recognized that certain explosives are more dangerous than others in this respect. In America and abroad, government testing stations have been established for officially passing on the suitability of explosives for use in coal mines. In this country the Federal government is given no power to enforce the use of the approved explosives but merely publishes from time to time, through the Bureau of Mines, those explosives which have passed the tests necessary to place them on the list for use in coal mines. In spite of this lack of police power, the increase in the use of permissible explosives since the promulgation of the first list in 1909 has been rapid. In 1912, only 8 per cent. of the explosives used in coal mines were permissible; in 1925, this figure had increased to 25 per cent. While the past record of permissible explosives has been most gratifying, it is very desirable that we pave the way for further improvement in explosives and blasting methods by learning more about the mechanism of ignition of gas and coal dust by explosives. To this end a considerable amount of investigative work already has been carried out and a large amount yet remains to be done. It is the purpose of this paper to discuss briefly the effect of the characteristics of explosives and method of loading in the borehole on the liability of a blown-out shot to ignite explosive mixtures of gas or dust. For an account of the methods by which an explosive is tested for permissibility for use in coal mines, the reader is referred to Schedule 17-A of the U. S. Bureau of Mines.

Jan 10, 1926

By Shusen Cheng, Dongdong Zhou

The high temperature distribution in ironmaking and steelmaking industry is very important to control the smelting process. Although equipment is available to measure the temperature in the smelting process, in general it could just measure one certain point or only at discrete times. The real time temperature distribution in ironmaking and steelmaking is important because it could reflect reaction information and help to control the operation parameters. In this paper, a new method to detect the temperature distribution in ironmaking and steelmaking through the application of digital imaging system based on the color CCD was studied. In addition, the two-color method and partial least square method were used in the calculation model to improve the accuracy. The results agreed well with the measured temperature.

Mar 1, 2017

By D. H. Baldwin, R. E. Reed-Hill

WITH the polarized-light microscope, the basal-plane trace may be located on hcp crystal surfaces to an accuracy of approximately 1 deg. This determination can also be made on very small crystalline areas, approaching a micron in width. Measured basal-plane trace distributions on selected specimen surfaces can yield1,2 valuable texture information. However, the polarized-light microscope is probably best suited to orienting

Jan 1, 1965

By Patricia Curtis Petty

Thirty years ago, the appearance of a female mining engineer, geologist or miner in a company, union or mine environment would have been unthought of, unwelcomed and violently opposed. Twenty years ago, the intellectual perception of the news that women were interested in becoming mining engineers, geologists and miners had been accepted by the industry-but no one wanted to be the first to hire one of these exotic creatures. Ten years ago, those who had been most vehemently opposed to the philosophical idea of women working in these areas were faced with competent, productive engineers, geologists and miners-who only incidentally happened to be women-and began hiring them. Historically, of course, one can always find the isolated individual who worked in these areas-the first female graduate of the Colorado School of Mines with a mining engineering degree graduated in 1903-but the concept of woman as professional engineer was very slow in arriving in the United States. The few who worked as miners generally worked in small family enterprises, such as some of the coal mines in both Eastern and Western United States. Others accompanied husbands or sons into wilderness areas searching for gold and other precious metals.

Jan 1, 1984

By A. Demirci, A. Keçeciler, Y. S. Durutürk

"This paper deals with the results of the variation of thermal conductivity of rocks with pressure on a laboratory scale. For this purpose, the authors have added a pressure-supplying unit to the apparatus developed by Mousset-Jones and McPherson (1986), Önder (1995), Ashworth and Ashworth (1979), and Innaurato and Occella (1989) in order to measure the thermal conductivity under pressure. The values obtained from the tests performed by this new apparatus have been stated using a regression analysis and the related graphs have been drawn. Results have shown that the thermal conductivity of rock varies digressively with pressure. The same results have been obtained in different rocks types. IntroductionOne of the most important tasks of mining engineers is that of establishing, maintaining and sustaining safe and healthy working conditions in underground mines.Heat can have a profound effect on safe and healthy working conditions and is one of the main problems in deep underground mines. In this regard, the temperature of the air passing through the mine openings increases steadily and causes a decrease in the efficiency of workers due to the unwanted physical effects to human bodies in the working area. At the same time, the hot and humid environment resulting from heat and temperature rise causes some important occupational diseases and increases the accident risks in the related openings."

Jan 1, 2002

By J. M. Harrison

"The Nor-Acme gold mine is near the shore of Snow lake, northern Manitoba, about 75 miles east of Flin Flon. The claims that form the nucleus of the present property were staked in 1927 by C. R. Parres, but it was not until 1941 that diamond drilling disclosed the potentialities of the deposit. In that year a large-scale drilling programme was begun under the direction of F. Ebbutt, of the Howe Sound Exploration and Development Company. Two orebodies were outlined containing about 5,000,000 tons of ore assaying $5.25 in gold per ton. In August, 1945, construction of the mining plant was begun.All information and interpretations contained in the following brief description of the deposit were obtained from surface mapping.GEOLOGYThe ore lies at the contact between a coarse, basic, pyroclastic rock, which is the hanging-wall, and grey, acidic lavas and sediments, which form the footwall. These rocks are cut by irregular basic intrusions that vary in composition from diorite to hornblendite, and by small acidic dykes . Tourmaline is locally common in the hanging-wall rock near the ore.The ore occurs in brecciated, silicified, and ·slightly carbonatized rock. Arsenopyrite is the main sulphide and the gold is associated with it. Pyrrhotite is locally abundant and minor pyrite, chalcopyrite, sphalerite, galena, and cubanite have been noted. Two orebodies are known, the Dick and the Toots. The Toots, which is much the smaller of the two, is about 1,000 feet west of the Dick."

Jan 1, 1954

By Q Zhuo, P C. Pistorius, M N. Al-Harbi

A likely increasingly important pathway for future low-carbon ironmaking and steelmaking is the combination of gas-based direct reduction with electric furnace steelmaking (DRI-EAF route), or with electric smelting (DRI-ESF route). In the DRI-EAF route, the gangue that is present in the iron ore is fluxed and removed as slag in the melting (steelmaking) step. This is in contrast with integrated steelmaking, in which the gangue is removed as part of blast furnace ironmaking. For DRI-EAF steelmaking, the amount and composition of slag depend on the iron ore composition, flux additions and iron yield. Slag volume and composition affect phosphorus removal, foaming behaviour and the process energy requirements. In this work, heat data from a year of DRI-EAF production was analysed to test whether the expected relationship between slag volume and electricity consumption for EAF steelmaking was observed. The data include slag analyses (one sample per shift), and heatlevel information on all inputs, final steel temperature and dissolved oxygen concentration, electricity consumption, tapped steel mass and tap-to-tap time. In analysing the data, the slag volume was estimated from the assayed slag CaO concentration and CaO inputs to the EAF. The expected effect of slag volume on steelmaking energy consumption was calculated with a mass and energy balance, considering the heat of mixing of the slag. The calculated energy requirement of slag formation is in line with previous estimates reported in the literature.

Aug 21, 2024

By K. Ihara, T. Yamaguchi, K. Matsumoto

"Al-Fe alloy sheets having layers with different strain components were produced by unlubricated hot rolling and the recrystallization texture formation during annealing was investigated in each layer. In this study, the strain component introduced by rolling was quantitatively evaluated by measuring degree of bending of an aluminum pin embedded in the sheet. The textures before and after annealing were investigated by the SEM-EBSD technique. It was clarified that, in the middle layer, where comparatively small shear strain was introduced, ß-fiber subgrains and cube {001}<100> oriented subgrains were formed before annealing, and cube oriented recrystallized grains grew after annealing. On the other hand, in the surface layer, where large additional shear strain was introduced, shear texture components and cube oriented subgrains were formed before annealing, and shear texture was retained even after annealing, while cube oriented subgrains did not grow and were encroached. It was suggested that introduced strain components influenced the recrystallization texture formation by inducing different distribution of the subgrain size, stored strain energy and orientation relationship with surroundings before annealing.INTRODUCTION The microstructure developed during the hot-rolling process of aluminum and aluminum alloys affect the mechanical properties of the final product sheets. Especially, the crystallographic orientation in the final product sheets affects the r- value and ears during deep drawing (Humphreys & Hatherly, 2004), then the texture control in the hot-rolling process is important. When the friction between the rolling roll and rolled sheet in the hot-rolling is large, both the rolling texture and recrystallization texture tend to be heterogeneous in the thickness direction. It is known in many rolled aluminum alloy sheets that the texture in the surface layer was different from that in the middle layer because of additional shear strain. It was reported that in the vicinity of the surface layer, where large additional shear strain was introduced, the shear texture <1 1 1>//ND and < 1 1 0> // RD which contain components of {1 1 1} <1 1 0> and {0 0 1} <1 1 0> developed during rolling, and the shear texture developed even after recrystallization annealing (Sakai et al., 2002). Particularly, it is thought that the <1 1 1> // ND texture contributes to improve the r-value and press formability (Inoue & Takasugi, 2007). Therefore, asymmetrical rolling and high friction rolling have been applied to improve formability of aluminum alloys by adding shear strain in the rolled sheets as deep as possible (Kamijo et al., 1972; Inoue et al., 2005). However, few researches have been focused on the microstructures and texture before annealing and thus, the detailed mechanism is still unclear how the texture after annealing is affected by the texture before annealing. In this study, the Al-Fe alloy of commercially pure aluminum was chosen as the first material to be studied in order to clarify the fundamental process of the recrystallization texture formation. The main purpose of this study is to clarify the effect of additional shear strain on the rolling and recrystallization textures in the hot-rolled sheets by analyzing the transition of microstructure and orientation distribution through recrystallization annealing."

Jan 1, 2018

BRADEN, the most southerly of the three big Porphyries in Chile and the first to start production (in 1910), is a remarkable mine. It would be interesting to know just how much it has contributed, and will contribute, to the earnings of the Kennecott Copper Corporation, which acquired 95 per cent of Braden stock in 1915 by an exchange of shares and which subsequently obtained the remainder. Because of this complete ownership no separate annual report is published (as is the case with Anaconda&apos;s South American subsidiaries, Chile and Andes). Income, taxes, operating costs, earnings, and other financial data, including the balance sheet, are consolidated with corresponding items applying to Kennecott&apos;s manifold operations in the United States and other foreign countries. If Braden were in the United States it would be possible to arrive at a pretty accurate estimate of revenue realized each year from the sale of copper simply by applying the average published market price to the production as reported by the company. However, because of the restrictions on sales imposed by the Chilean Government and the almost fantastic regulation of exchange rates in the past, no estimate of the sort would be reliable. This point is illustrated by the following comparison made by Charles R. Cox, president, in Kennecott&apos;s report for 1955: In each year, 1954 and 1955, Braden supplied about 30 per cent of Kennecott&apos;s total copper deliveries; but Braden&apos;s operations contributed 16.7 per cent of consolidated net income in 1955 against only 6.2 per cent in 1954. More will be said later about exchange rates, taxes, and restrictions, and the recent improvement in the situation. Of course another element of

Jan 1, 1957

By E. C. Mahan

THE text of my talk was suggested by the invita-tion of your secretary, who said that the excess productive capacity of the bituminous industry was a matter of common concern to engineers and coal operators. Cognizant of the depressed condition of the industry, he tactfully added that in common council we might find wisdom. Certainly it would seem that the application of the best engineering knowledge available would be helpful in solving mining problems. There is no doubt that clear thinking, characteristic of the engineering type of mind, is essential to untangle the shapeless pattern which increased complication, so often mistaken for progress, has developed. There is much thinking today which neither looks forward to a logical combination of ideas nor backward to simple fundamentals. The result of that sort of thinking is hopeless confusion. Lately we have heard much about excess capacity and overproduction, along with their attendant evils. Respecting the bituminous coal industry, these terms have been frequently misused. How many of us have seen them applied to the coal industry but how few of us have understood them. I am reminded of a state-ment which William Green, president of the American Federation of Labor and a former miner from the Ohio field, gave to the Associated Press last month, in which he was quoted as saying: "The coal men must realize that conditions have altered since the World War. To-day they are producing a billion tons a year, with a market for only half that tonnage." I cite this instance as a glaring example of the flood of. loose statements about the bituminous industry with which the public is being deluged. If the general public, or some of the newspapers, had any passion for the facts, this sort of misleading statement would not get very far. Unfor-tunately, in these days, opinions are more sought after than facts, and statements by such a person as Mr. Green and are promptly accepted by a credulous public.

Jan 4, 1928

By T M. El Hajj, A C. Chieregati, M T. G C Marques, J M. Braga Jr, H Delboni Jr

"The estimate and control of sampling errors is essential for all mining operations, especially when dealing with strategic materials, such as niobium. This paper is based on a traditional quality assurance and quality control technique used to confirm mineralised intersection zones, and proposes the validation of sampling data using diamond drill twin holes, in order to evaluate and improve the quality of the current data set. The geological model of the niobium mine – located in Araxá, Minas Gerais, Brazil – was built including 77 diamond drill holes of a sampling campaign carried out during the 1970s. There are few records about the collection and preparation procedures of these past samples, making it difficult to estimate the errors associated with their analytical results. Therefore, 11 twin drill holes were drilled to compare their samples against the samples from the 1970s drilling campaign. The new hole locations were chosen as near as possible to the old holes location. The JORC Code, 2012 edition, relates the use of twin holes as a good sampling technique to assess sampling and assay data. Three parameters were considered to validate the 1970s drill hole campaign by the twin drill hole campaign: the difference of the coordinates between the paired holes the difference among the positions of the geological contacts to validate the geologic description the difference between the paired samples grades was calculated to validate the analytical results.The analysis of the grade range variation between sample pairs was based on three techniques: geostatistical interpretation of vertical semivariogram to obtain the nugget effect calculation of the relative difference between duplicates calculation of the error associated with the sampling protocol established according to Pierre Gy’s Theory of Sampling.The results were satisfactory for hole coordinates; however, the ore content showed a high deviation, although this divergence can be explained by the nugget effect. For the lithological intervals, the new results contributed to an effective identification of variations among lithologies, ie brown weathered ore and saprolite. The twin drill holes campaign successfully validated the geological model data, allowing effective mine planning and higher reliability of the reconciliation results.CITATION:Marques, M T G C, El Hajj, T M, Braga Jr, J M, Chieregati, A C and Delboni Jr, H, 2017. Theory of Sampling and geostatistics for twin drill holes analysis in a niobium mine in Araxá, Brazil, Australia, in Proceedings Eighth World Conference on Sampling and Blending, pp 97–106 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

May 9, 2017