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By Li. S., C. Sili

Abstract. Study on nonlinear damage localization process of rocks under water chemical corrosion is a more interesting topic in rock mechanics research world widely. It is very important in estimating long term stability of rock engineering, design of nuclear waste repository and its performance estimation, geothermal and petroleum development. This paper reports that new development of study on the topic, including methodology, results of meso-mechanical test, real-time CT scan test and acoustic emission test, temporal fractal behaviors, neural dynamic modeling and chemical-induced damage law, etc. This paper also discusses the research directions of the topic in the near future. Zusammenfassung. Untersuchung zum durch die chemische Corrosion induzierten Schaedigungsprozess ist einer der Trends im Gebiet der Felsmechanik. Sie ist zugleich ein sehr wichtiges Forschungsprojekt u.a. fuer geotechnische Langzeitstabilitaetsanalyse, Langzeitsicherheit eines Endlagers, Erdwaerme- und Erdoelfoerderung. Dieser Aufsatz stellt die neusten Entwicklungen in den folgenden Teilgebieten zusammen: Untersuchungsmethoden, Laborversuchsergebnisse der Mikromechanik, der Computer-Tomographie und der akustischen Emission, zeitabhaengige Fraktaleigenschaften, Modelle fuer die Nervendynamik sowie Modelle fuer chemie-induzierte Schaedigungen. Zum Schluss werden kuenftige Forschungsschwerpunkte bzw. –richtungen diskutiert. Résumé L’étude du processus de la localisation de l’endommagement du à l’érosion chimique est un thème d’actualité pour la mécanique des roches. Elle est également un sujet de recherche d’importance dans l’évaluation de la stabilité à long terme des ouvrages rocheux, l’analyse du system de stockage des déchets nucléaires et l’évaluation de son comportement, l’exploitation de l’énergie thermique et pétrolifère, etc. Cet article présente le développement actuel dans ce domaine, incluant la méthodologie d’étude sur le processus de la localisation de l’endommagement dû à l’érosion chimique, l’analyse des essais mécaniques avec l’observation microscopique, du balayage en temps réel (CT), et de l’émission acoustique. On aborde ainsi modèle des caractéristiques fractural du temps, le modèle de la mécanique dynamique neural, ainsi que la loi de comportement d’endommagement dû à l’effet chimique. Enfin, les perspectives relatives à ces études sont présentées et discutées.

Jan 1, 2003

By Roy Woodall

Successful mineral exploration is the lifeblood of the mining industry. Contrary to what the environmental lobby would have the world believe, the industry is replacing the metals it is extracting. The reserve base has not changed significantly in 20 years (Fig. 1.) Mineral exploration is a research activity. First there is the idea, the vision or the intuitive thought. The experiments follow. These involve repeated phases of data gathering, data interpretation and concept testing through drilling. For many companies, exploration is the main investment in scientific research. Each mineral exploration experiment may involve years of costly work. Despite the improving tools of science and technology, the investment remains high-risk. Only the promise of high rewards, or desire to survive as a mining company, will stimulate the necessary commitment and level of investment. Confidence that an economic return can be achieved, confidence in the science and technology being applied and confidence in the people involved are the foundations upon which successful mineral exploration is built (Woodall, 1984). The challenges facing the explorationist in the 1990s fall into two categories: - the challenge to make the activity economic; and - the challenge to make the activity socially and, therefore, politically acceptable.

Jan 1, 1992

By J. Moore, D. Gault, R. V. Lugn

Impact of small projectiles with velocities between 0.9 and 7.3 km per sec on basalt produce craters chiefly by the ejection of fragments. Weight-size distributions of the ejecta are linear for part of the size range of the fragments. Cumulative weight-size distributions of the ejecta from different craters vary because of erratic formation of large fragments and a large percentage of ejecta below 0.1 mm. In the range of velocities studied, the crater depth is approximately proportional to the 0.75 power of velocity of the projectile. This relationship may represent a transition regime between the fluid impact regime and the undeformed projectile impact regime. The volumes per unit of projectile energy of the craters produced are comparable to those reported for lower speed projectile impact and drill bits. An experimental investigation of projectile impact on rock is being conducted jointly by the Ames Research Center of the National Aeronautics and Space Administration and the U.S. Geological Survey. Projectiles are launched with light-gas guns at the Ballistics Range of the Ames Research Center. The craters and ejecta produced in these experiments are being studied by the U.S. Geological Survey. Steel, aluminum and polyethylene projectiles weighing from 0.25 to 0.015 g were accelerated to velocities of 0.88 km per sec (2,900 fps) to 7.3 km per sec (24,000 fps) with a light-gas gun, using hydrogen as the propellant medium. Projectiles impacted the targets normal to plane rock surfaces in an atmosphere of air with a nominal pressure of 25 to 50 mm of mercury. The metal projectiles were mounted in supporting four-piece nylon sabots, which guided the projectiles down the launching tube. After launch, aerodynamic drag acted to separate the sabots from the projectiles. Impact velocities were determined with time measurements and spark photographs of the projectiles in flight. Ejecta were collected in lucite and aluminum containers placed around the target block. A small hole in the containers permitted projectile entry. Impact of projectiles of the size employed produced craters in the rock targets chiefly by ejection of fragments. The craters are small, roughly conical depressions with crushed and intensely fractured rock at the bottoms of the depressions. The ejecta are composed of pieces of the projectile and rock fragments ranging in size from a few tenths of a micron or less to several centimeters in maximum dimension. In this paper, the structural features of the craters, the weight-size distributions of the recovered ejecta, and crater depth and crater volume relationships are described. DESCRIPTION OF CRATERS Typical craters (Fig. 1) produced by experimental projectile impact in basalt are shallow, wide base

Jan 1, 1963

By W. W. Adams

Lower accident rates were the outstanding feature. of the second annual sand and gravel safety competition conducted in 1930 by the United States Bureau of Mines in cooperation with the National Sand and' Gravel Association. Both the frequency and, severity rates for accidents were greatly reduced as compared with those shown by the first year's contest, that for 1929. Three times as many plants were enrolled, and the number of man-hours of work represented was more than doubled. Seventy-six sand-and-gravel plants, situated in 20 States, participated in the Competition, as compared with 26 plants, located in 13 States, in the year before. The number of man-hours of employment, which indicated the amount of exposure to occupational hazards, was 4,915,592, an increase of more than 100 per cent over the previous year's total of 2,259,572 hours. The frequency of accidents declined from 74.4 per million hours for all plants enrolled in the first year's contest to 42.7 per million man-hours for all plants enrolled in 1930. The accident-severity rate was reduced from 9.7 days of disability per thousand man-hours of exposure in 1929 to 5.9 days of disability per thousand man-hours of exposure in 1930. The actual number of accidents reported for 1930 by 76 plants included four deaths and 206 injuries whereas the 26 plants that were enrolled in 1929 reported three fatalities and 165 injuries. Under the rules of the contest all "lost-time" injuries are reported--that is, all injuries that disable an employee for more than the remainder of the day on which the accident occurred. If the employee is physically able to resume his work on the day following the accident, the injury is not classed as a lost-time injury. The contest covered accidents and man-hours worked by all employees at the plant who were employed by the same company, and included work up to the point of delivery of the material directly to consumer or to independent agency of transportation--in other words, to point of relinquishment of control of the material by the producer.

Jan 1, 1931

By K L. Temel, W P. Player

The underlying message of this paper is that investment in prospecting, exploration and mining in New Zealand is welcomed. The Government's policy with respect to Crown owned minerals is for continuing investment in prospecting, exploration and mining which is in accordance with good exploration or mining practice. To encourage continued investment requires a business-friendly environment. Government policies and initiatives to enhance the business environment for the minerals and coal exploration and mining industries are discussed in this paper. As well, new initiatives under consideration, which have the purpose of enhancing the investment environment, are discussed.

Jan 1, 1997

By Valentine A. Chanturiya

The aim of this paper is basically to show progress in the study of nanosecond processes involved in the disintegration and breaking-up of mineral complexes with fine noble metals. We studied the influence of nanosecond High-Power Electromagnetic Pulses (HPEMP) on the physical and technological properties of refractory gold-containing ores and beneficiation products. Experimental data are presented to confirm the formation of breakdown channels and selective disintegration of mineral complexes as a result of pulse irradiation, which makes for efficient access of lixiviant solutions to precious metal grains and enhanced precious metal recovery into lixivia during leaching. Preliminary processing of gravity concentrate with a HPEMP resulted in significant increase of gold and silver extraction into lixivia during the cyanidation stage, with gold recovery increased by ~31% (from 51.2% in a blank test to 82.3% after irradiation). Gold recovery from stale gold-containing dressing tailings products increased after pulses-irradiation from 8-12% to 80-90%.

Jan 1, 2006

By L. Xinghua

Limonite is a general term for a group of amorphous iron oxide and iron hydroxide materials. It is considered as one of the very refractory iron ore types due to its wide variation in chemical composition, iron content, moisture content and easily sliming in the course of comminution. Iron grade of test sample is 25.48%, the iron minerals are mainly limonite; and the gangue minerals consist of quartz and feldspar in majority, secondarily silicate minerals. In this test work, high intensity magnetic separation (HIMS)-cationic reverse flotation and magnetic roasting-low intensity magnetic separation (LIMS) tests were conducted on limonite ore. The test results show that the concentrate with iron grade of 50.97% and recovery of 68.50% can be obtained by HIMS-cationic reverse flotation technique; while using magnetic roasting-LIMS technique, the better concentrate indexes of iron grade of 60.36% and recovery of 89.71% are achieved, and the iron grade of tailing is only 4.42%. Therefore, the magnetic roasting-LIMS technique is a better suitable method for beneficiation of low-grade limonite ore. Keywords: Low-grade limonite; Mineralogy; HIMS; Cationic reverse flotation; Magnetic roasting; LIMS

Feb 27, 2013

By Wilton Johnson

Native asphalt was produced in 1982 by five companies in two States, Texas and Utah. Bituminous limestone, used primarily as a paving material for street and road repair, was produced by White Uvalde Mines and by Azrock Industries, Inc., Uvalde County, Tex. Historically, gilsonite, a solidified hydrocarbon found only in Utah and Colorado, had been mined by American Gilsonite Co. and by Ziegler Chemical and Mineral Corp. from properties near Bonanza, Uintah County, Utah. During 1982, Hydrocarbon Mining Co., a subsidiary of the Oberon Oil Co., entered into a joint venture with Miocene Resources Inc. of Novato, Calif, to form Hydrocarbon Resources Co. for the purpose of mining gilsonite about 50 miles south of Vernal, Uintah County, Utah. Under the agreement, Hydrocarbon Mining contributed gilsonite-bearing properties held by lease or sublease as well as mining equipment to the venture. The property contained leases totaling 760 acres with probable reserves of 268,000 tons of gilsonite. Miocene Resources provided the partnership with a minimum of $200,000 to develop two of the leases and were to be responsible for management of the mining operations.2

Jan 1, 1983

By Victor V. Nazimko

Long term stability of the pillars that have been remained after R&P extraction causes postponed subsidence. To prevent unforeseen subsidence and to diminish postponed subsidence 25-50% new method for its control has been developed by the author. It supposes to use drilling and blasting technology and other original approaches. New method has been fulfilled through the holes being drilled from the surface or from the active underground openings. Explosives had been charged into the holes and were blasted. This had increased bulking factor dramatically and prevented natural caving of the strata. Physical scale modeling corroborated efficiency of the new approach. The bulking factor has grown from 0.0623 to 0.1185 and surface subsidence has been diminished from 1.1 m to 0.2 m or 5.5 times.

Jan 1, 1996

By Shosei Ph. D Serata

The Stress Control Method of mine design provides enhanced engineering control over the behavior of underground structures in comparison to conventional mine design methods. The same Method can be applied to achieve design control of surface subsidence. The basic mechanism relating undergroued deformation and surface subsidence is disclosed by mine simulations, using the REM (Rheological Element Method) computer code, whose predictions have been validated by field measurements. The key components of the underlying mechanism of surface subsidence have been shown to be the stress envelopes formed in the process of underground excavation. It has also been demonstrated that significant control of surface subsidence can be achieved by designing the geometry and timing of underground excavation to regulate the formation of stress envelopes. A field example is given in this paper to illustrate this application of the Stress Control Method.

Jan 1, 1986

By G. W. Jones, R. E. Kennedy

"INTRODUCTION In the manufacture, storage, transportation, and use of combustible gases and vapors, explosion hazards, which at times may be present when air becomes mixed with the gases and vapors, become of primary importance. Such conditions are especially dangerous where large volumes of gaseous atmosphere are involved, because an explosion under such circumstances is capable of doing tremendous damage to both property and personnel.Because of its interest in safety in the mining and allied industries, the Federal Bureau of Mines has investigated, and published results dealing with, the explosibility of various types of combutible atmospheres. The explosion hazards of natural gases have received attention, and results giving the limits of inflammability and ignition temperatures in air have been determined and published. 4/ Other investigations have shown how explosions of natural gas-air mixtures may be prevented by the addition of nitrogen and carbon dioxide. 5/Because of the increased demand for crude oil for war purposes, the application of secondary-recovery methods of stimulating oil production have received considerable attention during the last few years. The process consists in the injection of natural gas into partly depleted oil wells to cause the oil in the sands to flow into producing wells and so increase the amount of recoverable oil. 6/"

Feb 1, 1945

If one can embrace the medical analogue, much of the mining industry currently suffers from a massive bacterial infection. When pyrite-bearing or sulfide-bearing rock formations, tailings, or mine wastes are infected by Acidithiobacillus ferro-oxidans, the likelihood of forming acid rock drainage (ARD) is almost guaranteed. The ?pharmacy? of antibiotics available is extensive, ranging from solid alkaline amendments like limestone to liquid ?medicines? such as sodium lauryl sulfate, sodium thiocyanate, waste milk, and bipolar lipids. Unfortunately, the ?geo-medical? teams of geochemists, microbiologists, engineers, and mine managers lack the tools to surgically apply these active ingredients where they are needed most with a minimum of waste. Distribution of fine grained limestone on the surface of an acidic mine waste dump is analogous to applying a bandage soaked in antacid to treat an upset stomach. The implementation of up-to-date best management practices has not healed the patient; an equivalent combination of hypodermic needle, cyber knife, and arthroscopic probe is clearly needed. Using an engineered, flow-able or pumpable foam or pHoam? as the medicinally analogous ?dextrose delivery solution? for solid and/or liquid ?geo-antibiotics?, the authors have combined off-the-shelf technologies that have been previously applied in solving geotechnical problems in the mining industry. A patent for the innovative process is pending. This paper discusses method concepts and the advantages it could provide over conventional BMPs.

Jan 1, 2012

By Ivan Jackson Madura

The new Paradisus Coco Beach Resort in Rio Grande (PR) is located on an old swamp area, which has been filled with relatively clean to silty sands. The swampy deposits consists of organic silts, peat and loose fine to medium sand and silty sand. The project requires the placement of 1.0 to 1.5 meters of additional fill together with the construction of light structures. The need for the fill will trigger the development of settlements in the underlaying weak and compressible stratum. Furthermore, the susceptibility of the loose sand to liquefaction during an earthquake was considered. This paper describes the soil improvement by means of vibro-replacement, the purpose of which was threefold: reduction in total and differential settlement, acceleration of settlements during the surcharge period and densification of the loose sand to reduce its liquefaction potential. The predesign is presented together with relevant construction details of the preliminary trial areas from which the final column diameter and grid spacing were derived. Instrumentation together with settlement observations during the surcharge period are presented as well and compared with the initial predictions.

Jan 1, 2002

By P. Trueman

A project is underway to convert a validated methodology to a system that will permit the near real time interpretation of loading data from longwall powered supports, allowing rapid adaptation of mining strategies, maintenance scheduling and set pressures for optimal roof control. Such a system has the potential to significantly reduce roof control problems and is a pre-requisite to successfully fully automating a longwall face. The development depended upon a robust methodology for interpreting the pressure sensor data coming from the face in the context of support strata interaction using a novel characteristic load cycle analysis concept. New software was developed capable of handling the large quantity of data emanating from a modern longwall with the current level of signal corruption and loss, accurately delineating load cycles and extracting the critical load cycle features essential for interpreting how the support and strata are interacting. Existing software being used to access the pressure data were found either to be incapable of delineating load cycles at all or, where they could, the accuracy was low, making it impractical to use them in combination with the new advances in load cycle analysis. The software is currently being extended from ?off line? to ?on line? in order to provide a real time response to changing strata conditions.

Jan 1, 2006

COUNCIL AND STANDING COMMITTEES, 1974-1975 Office Bearers : Prof. R. P. Plewman (President), Dr R. E. Robinson and Dr M. D. G. Salamon (Vice Presidents), J. K. E. Douglas (Honorary Treasurer), and P. W. J. van Rensburg (Immediate Past President). Elected Members of Council: Dr M. G. Atmore, E. Collier, G. H. Grange, Dr P. R. Jochens, Dr D. I. Legge, D. G. Malan, C. T. Shaw, L. W. P. van den Bosch, D. A. Viljoen, H. M. Wells, P. A. von Wielligh. Branch Chairmen: B. T. Hosking (Witbank-Middelburg Branch), D. A. Smith (Orange Free State Branch). Past Presidents Serving on Council: R. J. Adamson, M. Barcza (until May 1975), H. Britten, H. E. Cross, Prof. J. de V. Lambrechts (until December 1974), R. C. J. Goode, Prof. D. D. Howat, Dr J. P. Hugo, D. M. Jamieson, D. G. Maxwell, Dr J. T. McIntyre, V. C. Robinson. Ten Council meetings were held during the year, with an average attendance of 19, and the standing and sub-committees held 74 meetings. COMMITTEE CHAIRMEN Membership, Dr M. D. G. Salamon; Technical Programme-Metallurgy, D. A. Viljoen; Technical Programme-Mining, G. H. Grange ; Vacation School-Metallurgy, Dr P. R. Jochens; Vacation School-Mining, Dr M. D. G. Salamon; Awards, Prof. R. P. Plewman; Excursions, Dr D. I. Legge; Constitution, Rules and Policy, P. W. J. van Rensburg and Prof. R. P. Plewman; Mines and Works, P. A. von Wielligh; Education, P. W. J. van Rensburg. REPRESENTATIVES ON OTHER BODIES Associated Scientific and Technical Societies Members: V. C. Robinson and Prof. R. P. Plewman. Alternates : Dr R. E. Robinson and Dr M. D. G. Salamon. Federation of Societies of Professional Engineers Members : J. K. E. Douglas and P. W. J. van Rensburg. Alternates : Prof. R. P. Plewman and G. H. Grange. South African Council for Professional Engineers Member : R. C. J. Goode. Alternate : G. H. Grange. Engineers' Liaison Committee (Pretoria) Member: Dr J. P. Hugo. Alternate: P. W. J. van Rensburg. MEMBERSHIP Thirteen Fellows, seventeen Members, eleven Graduates, three Associate Members, eighteen Associ¬ates, twenty-six Students, and one Company Affiliate were elected during the year. Nine Fellows, four Members, and three Associates were admitted to retired membership. Eight Fellows were elected to Honorary Life Membership. Three Members and one Graduate were transferred to Fellows, nine Graduates and two Students to Members, six Students to Graduates, one Student to Associate, and one Associate to Associate Member. Six Fellows, ten Members, three Associates, and one Student resigned. A statement of membership as at June 30th 1975 and the end of the previous year is shown in the following tabulation: 30th - 30th June, - June, 1974 - 1975 Honorary Life Fellows - 9 - 15 Honorary Fellows 8 - 8 Life Fellows 170 - 170 Fellows 544 - 536 Members 512 - 523 Associate Members 10 -15 Graduates 130 - 133 Associates 194 - 210 Students 173 -175 Company Affiliates 70 - 71 1 820 - 1 851 [ ] OBITUARIES Your Council records with deep regret the death during the year of the following members: M. Barcza, Honorary Life Fellow and Past President of the Institute; J. A. Boyd, F. E. Keep and J. H. Taylor, Life Fellows; I. D. B. Corner, C. O'G. Deane, R. E. Gilmour, A. C. Hofmeyr, M. W. Howell, T. J. Robin and F. C. Steinhobel, Fellows; J. J. Frankel, Member; T. J. Higgs, Associate. FINANCE The annual accounts, which follow this report, indicate that income again exceeded expenditure by a margin of R21 410 (last year R28 524). This year's income of R71 184 showed a further increase compared with last year's figure of R55 025. Costs, however, also in¬creased, and it is calculated that, excluding non-recurrent costs, the cost of running the Institute in¬creased by R6 654 from R25 501 to R33 155 for the current year. The main increases were involved in secretarial fees, stationery and print¬ing, and in publication of the Journal. All indications are that costs will continue to rise, and we have been advised that the A.S. & T.S. will be increasing their secretarial fees by 25 per cent in the year ahead to meet their rising costs. This year's surplus was derived entirely from the revenue from sales of publications (R13 644) and a surplus from the 1974 Winter School (RIO 654). There can be no certainty that revenue from these sources can be repeated each year. Our funds are in a satisfactory position because of these worth¬while activities, but the administrat¬ion of the Institute should not de¬pend on them. Council will accord¬ingly have to give consideration in the year ahead to an upward adjust¬ment of subscriptions to meet rising costs.

Jan 10, 1975

By Norbert L. Piret

From the copper smelter operation a various outputs are to exert negative impacts on the environment. Particularly, emissions like SO2 and dusts, solid wastes like contaminated gypsum and arsenic sludge, effluents and heated cooling water are generated. Most countries have sitipulated an environmental legislation to provide the framework for an efficient environmental management. As part of the planning activities for x major greenfield copper smelter, the Following elaborations are required and were drawn up. -The Environmental Impact Assessment which is the first step of environmental management and mandatory for every new project. - The Environmental Monitoring Plan, which describes the monitoring procedures for the main impacts identified and assessed. -The Environmental Management Plan, which deals with the minimization of environmental impacts, and the methods of its implementation.

Jan 1, 1996

By H. Tomlinson

"PURPOSE OF REPORTThe purpose of this report, which is the third of a. series on the coal mines of the Western States, is to give the findings of a study of the causes and methods of prevention of accidents from falls of root and coal in the mines of Lincoln County, Wyo. The three mines covered in this report, referred to as A. B. and C, account- for 9 per cent of the coal production in the county and nearly 9 per cent of the State's total production. For comparative purposes some statistical data are presented bearing upon the relation of injuries to their causes, to tonnage produced, to men employed, to days worked, and to days lost as the result of injuries.FATALITIES IN WYOMINGTo show the necessity for this study, Table 1 given the fatalities that occurred during 1928 in the bituminous—coal mines of the United States, of the State of Wyoming of Lincoln County, and in Mines A, B, and C, followed by a brief description of the Kemmerer coal dis-trict, its coal beds and immediate roof, thickness of cover, dip of coal beds, methods of mining timbering for roof support, roof testing, and supervision. All of these factors must be considered in any plan outlined to prevent accidents resulting from falls of roof and coal.ACKNOWLEDGMENTAcknowledgment is made to the officials of the operating companies for their cooperation and assistance during the study and collection of data to complete this report.GENERAL INFORMATIONLocation and Ownership The mines included in this report are within 18 miles north and south of Kemmerer, Lincoln County, Wyo. (fig. 1), and are owned and operated by various coal companies to supply the domestic, smelter and railroad markets. They are severed by branch lines of the Oregon Shorty Line Railroad Coal production and men employed underground in the three mines are indicated in essential detail in Table 2."

Sep 1, 1932

By Harry G. Poulos

Ground movements can arise from a large number of sources and can have a significant effect on nearby piles and deep foundations. The loading of the piles by ground movements is a different mechanism to that arising from direct applied loading to the pile head, and consequently it is not generally possible to adequately analyze the effects of ground movements simply by applying some type of equivalent loading to the pile head. The main effects of ground movements are the development of additional movements, axial forces and bending moments in the piles, and thus the key design aspects are related to movements and to the structural integrity of the pile. However, the ultimate geotechnical load carrying capacity is generally not affected by the ground movements themselves. This paper will describe an approach to the analysis of ground movement effects on piles, considering axial and lateral movements separately. Some of the main features of pile response will be discussed for three specific problems involving ground movements: piles near and within embankments, piles near an excavation for a pile cap, and piles subjected to seismic ground motions.

Jan 1, 2006

By K. C. Garner

The visit reported was made with support from the 1997 J.C. Boyle travelling scholarship. The management and control of hazardous gases released into the underground environment are an integral part of coal mining. The power-generations stations at Appin and Tower collieries, with a combined electrical output of 94 MW, have been operating for some time and have demonstrated a technology that is able to exploit the available gas fully. Contributory factors have been the development and introduction of directional drilling techniques, pre- and post-drainage of coal, relatively high seam permeability, a high gas content of the worked seam, high production rates and a willingness to embrace new ideas and technology

Jun 21, 1905

By E. McCarthy

"INTRODUCTION Talc is a hydrous magnesium silicate with the approximate elemental composition 4MgO.3SiO2.H2O. It is one of the layered phyllosilicates (like kaolin and mica) but it differs from these in that it is relatively hydrophobic. This is due to its unique crystalline structure whereby a brucite inner layer is sandwiched between silica layers and the adjacent silica layers have no interlayer bonding other than van der Waals forces. This allows talc to be sheared easily along this basal plane, and the surface is covalent not ionic. Talc occurs both as a relatively pure material (>90% talc content) and in conjunction with many other minerals in proportions all the way from 1% to 90%. At lower concentrations, it is often considered a nuisance mineral when it occurs with base metals like copper, molybdenum or nickel or with precious metals like platinum or palladium. It floats readily with these materials and often is suppressed using guar gum or carboxy methyl cellulose which will absorb along the basal surface and make it hydrophilic. Alternately if the reduced ore is hydrophobic, like MoS2, then a partial oxidation of the sulfide will convert the surface to a hydrophilic oxide and the talc can be floated away in a separate step. Talc in grades from 20 to 90% has been commercially exploited in a wide range of pigment (paint and paper), material (ceramic, construction and cosmetic), reinforcing (polymers and composites) and functional (pitch adsorbent, lubricating agent) applications. Initially these tended to be local or regional markets, but eventually with certain higher purity grades, cosmetic, polymer and ceramic applications became valuable enough to be national and trans ocean markets. TALC FLOATATION PLANTS This drove the need for higher purity grades of talc and initially this need was met primarily by ore sorting. This works well for certain deposits with well crystallized talc lenses, but for ores, such as those from widely available ultramafic deposits, where the liberation size is closer to 100 microns, sorting is not effective. That drove the need for floatation and the first investigations were published by Clemmer and Cooke of the US Bureau of Mines in 19362. The first commercial floatation plant was installed in Johnson, VT by the Eastern Magnesia Talc Co in 1937. The circuit is shown in the schematic (Figure 1). The ore was an ultramafic, serpentine derived talc; mineralogy was about 55% talc, 40% ferroan magnesite and 5% oxides, sulfides and other silicates. The oxides include hematite and chromite, sulfides pyrite and gerstorffite and silicates chlorite, serpentine and mica. After crushing, the ore was dry ball milled and then air classified to remove minus 325 mesh fines. The coarse fraction was further classified to cut at about 100 mesh and the fines from this were the feed to floatation. The -325 mesh (about 15% of the ore) was sold as a paint grade and the plus 100 mesh (about 25% of the ore) was screened to make an asphalt backsurfacing grade."

Jan 1, 2018