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By Maurício Gammertt Röhnelt

A pesquisa em questão trata-se do aproveitamento e aplicação da escória de aciaria elétrica, um subproduto residual do processo de refino do aço. A força propulsora para realização deste projeto está associada à utilização do resíduo: a quantidade gerada é maior que a quantidade aproveitada, uma vez que este subproduto tem como limitante de uso o fenômeno de expansão volumétrica que compromete obras de engenharia. No presente estudo, a escória foi micronizada, caracterizada e incorporada em uma matriz polimérica para obtenção de um novo produto com propriedades vedantes. Os artefatos produzidos foram submetidos a vários ensaios mecânicos, químicos e de caracterização conforme requisitado pela norma NBR 15750. Após a análise dos resultados, concluiuse que os compostos constituídos pelo resíduo apresentaram melhores propriedades vedantes que o grupo controle de referência. Além disso, verificaram-se melhores condições de processamento nos compostos com escória de aciaria micronizada. Obteve-se, portanto, um produto ecológico, mais viável economicamente, com propriedades que atendem a uma especificação. Dessa forma, difundiu-se a aplicação do resíduo para outros ramos industriais, agregando a este maior valor comercial, promovendo assim a sustentabilidade por meio da substituição de matérias-primas provenientes de recursos não renováveis pela escória de aciaria elétrica.

Aug 17, 2017

By E. H. Crabtree, T. C. King

THE ferrosilicon grinding unit at the Central Mill of the Eagle-Picher Mining & Smelting Co. near Picher, Okla., was completed in March 1947. The object of the plant was to grind pigs of ferrosilicon, having a size of approximately 1 ½ by 4 by 12 in. and an analysis of 85 pct Fe and 15 pct Si, to approximately 100 mesh by crushing and wet grinding in a ball-mill classifier circuit. The minus-loo mesh ferrosilicon had formerly been purchased, and was used as medium in the heavy media process for treatment of lead-zinc ores. From the standpoint of dollars and cents, the cost of minus-100 mesh ferrosilicon was roughly $40.00 per ton more than pigs of the corresponding alloy delivered to the mill. Estimated wet grinding costs were considerably below this figure. The possible saving in cost of make-up medium for the cone plant was particularly attractive since, at that time, the plant losses averaged over four tons of minus-100 mesh ferrosilicon per day. Aside from the probable saving on the grinding charge, the need for such a unit was twofold. First, periodic fluctuations in the differential between the top and bottom densities of the cone were thought to be detrimental to metallurgy. There was little doubt that an intermediate differential existed at which the heavy media separation was most efficient, representing a compromise between concentrate grade and tailing loss. Furthermore, if a finer, but considerably cleaner, medium could be obtained, there was the possibility that the differential could be decreased without increasing the viscosity, or conversely, the viscosity of the medium decreased without increasing the differential. Preliminary to experimental work aimed at pegging the cone differential and circulating medium viscosity at whatever values were found to be most efficient, it was essential to have control over both the non-magnetic content of the medium and the particle size of the contained ferrosilicon. The latter was possible by means of a grinding unit at the mill. Second, whereas the ferrosilicon alloys are made by a number of manufacturers, only two, to our knowledge, grind it in any quantity for use in heavy media plants. For all practical purposes, the Central Mill was limited to one source of supply, a particularly vulnerable position. In case the supply was cut off, it was thought that pigs of the 85 pct Fe, 15 pct Si alloy could be obtained elsewhere, providing means of grinding them was available. There was no published information available covering wet grinding of ferrosilicon. Dry grinding in batch mills and in continuous mills with air classification was being practiced, but the cost of grinding was excessive and the dust condition objectionable. It appeared that primary and secondary crushing was no particular problem, providing heavy duty equipment was used;

Jan 1, 1947

By William D. Mayercheck

Introduction of continuous mining machines in the late 1940s created a new production bottleneck in room-and-pillar sections-the shuttle car. While continuous miners could cut and load coal at a nearly constant rate, the mining sequence was repeatedly interrupted as fully loaded shuttle cars changed places with empty ones. This wait-for-the-shuttle delay period forced the coal industry to reassess the shuttle's batch-type procedure with an eve toward continuous haulage systems that would allow uninterrupted coal flow from face to portal.

Jan 7, 1979

By M Lak, R Amiri, A Haratian, M Asghari, S Haji

Dry magnet separators are used to upgrade and beneficiate a wide variety of minerals such as hematite and magnetite materials. In recent years advances in dry magnetic separators have improved their performance. Fine particle separation is one of the main areas which still remain weak. This paper will present a new design of fine particle drum separators which used for particle size less than 3 mm. A big problem in processing of iron ore is the grade and recovery of mineral values in the fines fraction. The new design high efficiency drum separator is developed to handle fine feeds. In this drum separators both of the drum shell and magnetic yoke rotate in opposite direction. the results showed that when the material feed size was = 1298 μm, drum shell speed was 42.5 rev/min, magnetic yoke speed was 100 rev/min and the maximum intensity of magnetic field was at = 30° the feed grade increased from 50.87 to 65.67 in concentrate box, increase to 60.45 in middle box and tail grade was 24.44. The total achieved recovery for both concentrate and middle box was 81.89 per cent.

Nov 8, 2021

By D. W. R. Haysom

"I AM CONSCIOUS of the honour you pay me by having invited me to address you on the subject of the Rehabilitation of the Sydney Steel Corporation. The true architect of the revival and rehabilitation is Robert Burns Cameron. Because of the numerous myths which have grown up around what seems to be the miracle of the revival of the Sydney Steelworks, I propose to go back to the time when they came under the full control of the Province, on the 1st of January, 1968. Late in 1967, the decision was taken by Premier G. I. Smith to keep the Steel Plant running for at least another year, in an endeavour to see whether the enormous losses being sustained by Dosco could be reduced to a level which would permit their continuing operation. When that decision was taken, Dosco was to continue management until the 30th of April, 1968, and in the intervening period, the Provincial Government would seek management of the right calibre to ensure that an objective view of the Steelworks operations could be secured. By a combination of circumstances which can only be described as most felicitous, the man selected for the task was R. B. Cameron. He very quickly determined that to permit Dosco to continue management of the Steelworks until April 30 could only result in heavy losses to the Province and a consequent deterioration in the already critical financial position and a declining morale of the worke"

Jan 1, 1972

By A. Mykytiuk, I. E. Puddington, W. D. Macleod, F. W. Meadus

"A laboratory-scale continuous procedure for the up-grading of naturally occurring tin ores, based on the principle of spherical agglomeration, is described. High recoveries are indicated. A proposed second stage suggests useful fractionation steps.IntroductionA LABORATORY-SCALE batch process for the upgrading of a tin ore using the principles of spherical agglomeration has already been described (1). This procedure consisted of milling, for about an hour, a precrushed ore with at least 200 per cent water, 0.2 per cent of a reagent such as tall oil (to render the de-sired ore particles hydrophobic) and about 3 per cent of a viscous petroleum oil. The feed material passed an 8-mesh Tyler sieve, and the percentages of re-agents are based on the dry weight of the feed. Du-ring the grinding, the hydrophobic particles transfer into the oil phase to produce coherent semi-solid bodies while the gangue stays preferentially in the aqueous phase. The concentrate can be separated from the gangue easily by a mechanical operation. Using an ore containing about 0.3 -0.5 per cent tin, grades of from 1.5 to 7.0 per cent were obtained by varying the pH of the system. Recoveries fell from about 80 per cent to as low as 50 per cent as the grade in-creased."

Jan 1, 1966

By A R. Cruden, M S. Egglseder

The formation of banded iron formation (BIF)-hosted high-grade iron ore deposits in the Hamersley Province, Australia has been debated for decades. Although a structural control on their formation is widely accepted, only the roles of large-scale structures (ie faults and folds) formed by brittle and ductile deformation have been considered to date. However, the deformation of multilayered sequences in the Hamersley Province (ie the Mount Bruce Supergroup), with their contrasting rheological behaviours, creates challenges for understanding the complex structural framework at regional to deposit scales, including the significance for mineralisation and orebody location.Our approach to understanding these complex relationships is based on an established principle of structural geology, which is to extrapolate microscale structures to deposit-scale structures and vice versa, supported by state-of-the-art 3D modelling techniques. Complexly deformed hand samples associated with the Mount Tom Price iron ore deposit (Hamersley Province, operated by Rio Tinto Ltd) have been analysed and visualised with 3D explicit (Move™, Midland Valley Ltd) and implicit modelling software packages (Leapfrog™, AranzGeo Ltd) and supported by microstructural investigations (optical and X-ray microscopy) and fieldwork.Our study shows that the deformation of BIFs in the central Hamersley Province is controlled by microscale chemical processes (ie dissolution precipitation creep) due to rheological differences between iron oxide and chert layers, contrasting fluid flow properties and layer thickness variations. These processes account for the removal of vast amounts of silica, its transportation by diffusion in the presence of a fluid and reprecipitation at low-pressure sites. Consequently, this structural framework was used by different upgrading fluids to form iron orebodies.CITATION:Egglseder, M S and Cruden, A R, 2015. Evolution of a structural framework for high-grade iron ore deposits, in Proceedings Iron Ore 2015, pp 255–262 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By Charles L. Kimbell

Tables 16 through 19 continue the series of providing the world merchant fleet distribution by type of vessel and the ranking of the major fleets by country of registry. Table 20 this year provides a summary of the world's liquid gas carrier fleet. These vessels are included in the totals given for the world's tanker fleet, but gives a breakdown demonstrating the growth of the importance of natural gas in the world's energy commodity consumption. Panama and Suez Canals Tables 21 and 22 provide the latest available information on the transit of mineral commodities through the Panama Canal, by number of vessels, direction, and the commodities transported. Although the number of vessels transiting the Panama Canal dropped slightly (0.5%) between 1989 and 1990, the total amount of cargo moved rose by 3.6% and the amount of mineral commodities moved rose by 7.2%.

Jan 1, 1993

By W. D. Bonisteel

In 1976, Rio Algom Limited began the expansion of uranium production facilities at Elliot Lake. Quirke Mine was the only property in operation at the time, and plans were made to expand its milling capacity from 4,500 to 7,000 tons of ore per day. Following this expansion, other properties in the area will be reactivated to fulfill long-term contracts for uranium. As part of the expansion program, it was decided that in view of the escalating cost and impending shortage of energy, heat reclaim and conservation would be employed wherever practicable. In general terms, heat reclaim applications fall into three main classifications: ventilation, utility and process. Two of the ventilation applications and one process application will be described in some detail. Several other systems will be presented briefly as a matter of general interest. Some future possibilities will also be mentioned, together with their potential for economical heat recovery.

Jan 1, 1979

By R. Lingle, E. Hardin, M. Board, H. Pratt, W. Ubbes, M. Voegele, N. Barton

A 2 m. cube of jointed, Pre Cambrian biotite gneiss was subjected to uniaxial and biaxial loading at ambient and elevated temperature. The effects of different boundary conditions on the following rockmass properties were investigated: deformation modulus, joint stiffness, dynamic modulus, coefficient of thermal expansion, thermal diffusivity and conductivity, and joint permeability. Test conditions ranged between 0 and 6.9 MPa uniaxial and biaxial load, and 12° to 74°C mean block temperature. The tests were performed as part of the Office of Nuclear Waste Isolation program for evaluating site charterization test methods for measuring the hydro-thermal-mechanical properties of rock masses. The fracture flow experiments discussed in this paper were described in detail in a similar paper given to this symposium in 1981 (Voegele, 1981). DEFORMATION MODULUS Horizontal deformation measurements oriented parallel to the loading direction were made at the block surface. Several instrument types were employed: surface short-rod extensometers, bonded strain gauges, vibrating wire strain gauges and the Whittemore caliper strain gauge. Two vertical and two slant borehole extensometers measured vertical displacement. Loading history, especially during uniaxial loading, was critical to interpretation of observed deformation and fracture flow data. This important tendency has been observed in other large-scale laboratory (Bandis, 1980) and field tests (Pratt, et al., 1977). Excavation of the block resulted in minimal disturbance to the intrinsic condition of the sample. Even so, permanent, unrecovered "set" was imparted to the block beginning with the first low-stress biaxial load cycle to 3.45 MPa (Table 1). Unloading

Jan 1, 1982

The fluorspar deposits at Okorusu, Namibia are closely related to an alkaline igneous ring complex of late Cretaceous age (125¦7 Ma). The fluorite ores consist of relatively fine-grained purple replacement fluorite and subsequent coarser-grained purple and green vug-filling fluorite crystals. Homogenisation temperature measurements for 38 primary fluid inclusions shows that main stage purple to green fluorite crystals were deposited over a temperature range from 166¦C to 144¦C, and minor late yellow fluorite was deposited at lower temperatures from 132¦C to 128¦C. Homogenisation and freezing temperatures measured for 18 primary fluid inclusions shows that the fluorite-depositing fluids were less saline than Mississippi Valley-Type (MVT) ore fluids and overlap the lower temperature range of fluids that deposited epithermal ore deposits. Mining in three open pits (A, B and C) at Okorusu has gradually provided exposures which reveal that the fluorite orebodies have been emplaced primarily by the preferential replacement of carbonatites. Evidence for the replacement of carbonatite includes: replacement remnants of carbonatite within the fluorite ores; goethite pseudomorphs after the carbonatite minerals, pyroxene, pyrrhotite and magnetite, which are disseminated in the fluorite ores; andpartial replacement by fluorite of a large sill-like carbonatite body in the A pit. Electron microprobe analyses of minerals in unreplaced portions of the carbonatites show that their mineralogy consists of titaniferous magnetite, diopside pyroxene, apatite, biotite and calcite. Magnetite contains 6.97 per cent to 10.46 per cent TiO2, averages 8.44 per cent TiO2, and has an average V2O3 content of 0.35 per cent. At high magnifications under the scanning electron microscope (SEM), the magnetite shows abundant fine ulv÷spinel exsolution lamellae arranged in a cloth texture. Apatite contains moderately high fluorine contents that range from 3.21 to 5.0 per cent and average 4.2 per cent, and apatite crystals range in total rare earth oxides from 1.7 per cent to 2.61 per cent. Pyroxenes in the carbonatites are iron-rich diopside, and they contrast to pyroxenes in the fenites that are aegirine-augite. All of the microprobe analyses for mica crystals in the carbonatites give biotite compositions. Microscopic examination of fluorite concentrates from Okorusu provides mineralogical information important to the resolution of beneficiation problems. Fluorite ores that are related to carbonatites are typically accompanied by phosphorus benefication problems. The cause for the presence of phosphate in some of the Okorusu fluorite concentrates is a function of the presence of binary locked fluorite-apatite particles. The fluorite ores have also replaced marble locally in the A pit, especially along the A band in the B pit, and dominantly in the orebody proposed for the new C pit. Those ores are characterised by fine grain sizes, faint remnant bedding, lack of carbonatite mineral pseudomorphs and local presence of remnants of unreplaced marble. Concentrates derived from those fluorite ores are devoid of phosphorus, but commonly have elevated silica contents due the presence of free quartz. Carbonatite and marble were preferentially replaced by fluorite because the calcite was readily soluble in the presence of the fluorite-depositing fluids and the dissolution of calcite provided calcium for the formation of fluorite. 

Jan 1, 2008

By Colman Goldberg

IT is customary to plot crystallographic planes or axes on a Wulff stereographic net which is ruled with parallels of latitude and meridians of longitude. If a single crystal is placed at the center of a sphere, the coordinates of a crystallographic plane or axis are the coordinates of the point where the axis intersects the sphere. The standard (HKL) projection is the projection for which the sphere is rotated so that the (HKL) pole is at the center of the projection. Schiebold and Sachs' and many others have published standard projections for the more important planes of a cubic crystal. With Tables I and 11, it is possible to plot any plane (HKL) of a cubic crystal on a standard (001) projection if the absolute values of the individual H, K, and L are nine or less, which is almost always the case. Using the methods outlined by Barrett,' the standard (001) projection can be rotated so that any arbitrary plane is at the center of the projection. The tables are believed to be important for two reasons: 1—The heretofore published standard projections usually are not of the proper size to fit the stereographic nets available. With these tables a standard projection can be made which will be of exactly the proper size for the available stereographic net. 2—With the tables, planes that do not appear on the previously published standard projections can be easily plotted. For these reasons, the tables are especially useful in the study of optical reflections from etched surfaces and can also be used to make a standard projection for the axis which is normal to the macroscopic surface. (This axis can be found by X-ray or optical methods.) Then if the crystal is etched, the effect of the etchant can readily be determined by comparing the latitude and longitude of the reflecting planes (as determined with an optical goniometer) with the standard projection that has been prepared. Use of the Tables Fig. 1 shows the meridians and parallel which have been designated as zero longitude and latitude. The tables themselves are self-explanatory. The

Jan 1, 1953

By T. J. Driscoll

The effect of coatings on the incendive properties of aluminum alloy 6061-T651 in air-6.4%CH4 was studied for collisions between rusted steel and both uncoated and coated projectiles with incident energies as high as 300 J (220 ft-lb) and velocities as high as 200 m/s (660 fps). These conditions were intended to simulate the rough handling of equipment in coal mines. The ignition probability using uncoated alloy projectiles increased with increasing relative humidity and appeared to be influenced by atmospheric ozone content. The incendive properties of both the uncoated and coated alloy depended on the type of rust used, but the dependence of the coated alloy was very different from that of the uncoated alloy. A number of coatings developed in the last 25 years were found to offer protection from ignition and to remain largely intact for occasional collisions or collisions randomly distributed over the coating surface, but probably not for repetitive collisions at any given point on the coating. These protective coatings utilize a hard anodized aluminum alloy surface coated with one or more layers followed by heat treatment of the coating. Coatings containing Teflon and MoS2 and thicker than 50 µm (2 mils) appear to be most effective.

Jan 1, 1987

By K. M. Weigert

The position of the three-phase field between the alpha and the beta phases was established. The exact location differs from previous assumptions. The extremely high strength and hardness values were found near the phase boundaries of the ternary compositions. IN 1929, UenoL investigated vertical sections of the Ag-Cu-Zn diagram at constant silver and zinc values. From the evaluation of cooling curves and microscopic studies, he concluded that there was no evidence of a three-phase field in the solid state between the a and ,8 fields. The failure to find evidence for this field was due to the fact that it exists only in a very narrow range of compositions and requires special methods of heat treatment to establish phase equilibrium. In a later publication on the same subject Keinert2 rearranged Ueno's diagrams to conform with the basic phase rules. The existence of a three-phase field was postulated in the solid state between the a phases and the homogeneous ,9 phase between the Cu-Zn and the Ag-Zn binary border systems. The approximate location was based on a few microscopic observations of the structure and it was pointed out that the exact position could be determined only by a larger number of experiments. In the twenty years following these investigations alloys of Ag-Cu-Zn have become of general interest due to various technical applications, principally for brazing. In the course of an overall investigation of the physical properties of ternary Ag-Cu-Zn alloys the author found extremely high values of hardness and strength in alloys of compositions between the a and the yS fields. The exact location of the intermediate phase fields was established by the evaluation of more than a hundred cooling curves and microscopic mountings. Experimental Procedures Preparation of Test Samples: At the beginning of the investigation samples were chillcast into Vi in. diameter iron molds to determine hardness, strength, and the mechanism of primary crystallization. These

Jan 1, 1955

By Harry Elkin

Control of coal dust has long been an important aspect in the conventional mining of coal; the main reasons being from a health and disaster standpoint. With the advent, of mechanized longwall mining, the control of dust has required more attention due to the high extraction rate common to most longwall systems. The purpose of this paper will be to describe the dust abatement activities of the longwall operation at Sunnyside. Kaiser-Steel Corporation has three mires located at Sunnyside, Utah, with a total production averaging 6,800 tons of clean coal per day. Of this 6,800 tons, 71 % is mined with continuous miners, the remaining 29% coming from one longwall unit located in No. 3 Mine. Our first longwall panel was started in November, 1961. In October, 1966, we started mining our seventh panel. The present panel is located in the Upper Sunnyside Seam which averages five feet in thickness, but does get as low as 51 inches. The seam pitches 5.5% in this vicinity. The roof is generally good and is comprised of 10 inches of shale cap rocs overlain with sandy shale and sandstone. The floor is sandy shale and is quite undulating in nature. The present panel is 3,800 feet in length with a face of 670 feet. The major equipment employed on our longwall unit is a 125 H.F. Anderton Shearer-Loader, British Jeffrey Diamond armored conveyors and a Dowty self-advancing-roof support system. The Anderton Shearer in use on our longwall unit has a 60" diameter x 27" cutting drum. During the shearing cycle, it traverses the face at 20 feet per minute with a cutting rate of 7.5 tons/minute.

Jan 1, 1967

By Antti J. Niemi

Radioisotope tracers have so far been used for extraction of residence time distributions of flotation devices. They have also been proven applicable to evaluation of rate coefficients k of industrial flotation. It is now shown how values of k are scaled up on the basis of laboratory data on flotation and chemical conditioning, and of laboratory testing of samples from output of industrial conditioning vessel. Subsequently a model of conditioning and flotation is obtained which may be used for simulation and control of the steady state of the combined process. Discussion extends to modelling, simulation, CAD and opti- mization of flotation plants with re- circulation, and of ore dressing systems which consist of grinding and flotation plants.

Jan 1, 1990

By Cristina da Paixão Araujo

O planejamento de lavra de curto prazo tipicamente confia em amostras obtidas de furos de desmonte em uma operação de lavra a céu aberto. Essas amostras podem conter grande erro de amostragem. O objetivo deste artigo é avaliar o impacto do erro de amostragem na recuperação de lavra. Para comparação, foi utilizado banco de dados Walker Lake exaustivo considerado como a distribuição real dos dados. A metodologia consiste na obtenção de amostras a partir dos dados exaustivo, em um espaçamento regular de 5x5 m. Em seguida, o erro de amostragem foi adicionado às amostras. Posteriormente, as amostras foram utilizados para estimar os blocos e classifica-los como minério ou estéril. Quatro cenários com amostras com 0%, 10%, 20% e 30% de erro relativo. A recuperação de lavra de cada cenário é comparada com a real distribuição dos dados. Além disso, o erro de classificação do bloco é avaliado para os quatro casos. Os resultados mostram que problemas na amostragem e no protocolo de preparação de amostras pobres afetam a curva teor tonelagem e a classificação dos blocos em minério e estéril.

Aug 8, 2018

By Benjamin C. Craft

Oil and gas development in Louisiana during 1935 brought this state at the close of the year up to fourth place in the nation as a producing area. A review of development in North Louisiana centers around Rodessa, the most important reserve discovered in this area in many years. While the producing limits have not been defined, this discovery is one of the major developments of the year. New gas fields were discovered in Lincoln, De Soto and Bossier parishes. The Lincoln Parish discovery, completed flowing a highly saturated gas from the Glen Rose, further indicates the importance of deep-seated prospects in the interior salt-dome area. Minor extensions were made at Sligo and Pine Island. During the year, 126 oil wells and 103 gas wells were completed in North Louisiana as compared with 144 oil wells and 68 gas wells during 1934. The North Louisiana oil production was 9,617,405 bbl. as com-pared with 9,274,050 bbl. during 1934, an increase of 343,355 bbl., while the gas production increased 18 billion cu. ft. in 1935 over its 1934 figure. The Louisiana Department of Conservation gage of Nov. 1, 1935, shows an open-flow capacity of 4,563,725,000 cu. ft. per day from 941 wells in the Monroe field and 682,770,000 cu. ft. from 159 wells in the Rich-land field. A great deal of leasing continues in North Louisiana as a result of the Lincoln Parish discovery and development in the Rodessa field, especially in Bossier, De Soto, Winn, Lincoln, Bienville, Webster, Ouachita and Richland parishes. South Louisiana's position as an area of important reserves was further proved during the past year. Increased drilling resulted in the discovery of seven new fields: Lafitte, Garden Island Bay, Tepetate, Bunkie, St. Martinsville, Jeanerette and Big Lake. New sands or producing horizons proved productive in 15 of the proven fields. The total oil production for South Louisiana during 1935 was 40,731,-056 bbl. as compared with 23,255,437 bbl. during 1934. There were 222 oil and gas wells completed in South Louisiana during 1935 as compared with 214 oil wells during the previous period. Drilling during

Jan 1, 1936

The design and operating characteristics of the hydraulic cyclone elutriator were described in detail by Kelsall and McAdam (1963), and the method of operation of the commercially available version, the Cyclosizer, is described in the manufacturer's pamphlet (Anon). Complete details of the operating procedure are given in the relevant operating manual (Anon, 1964).The cyclones which form the basis of the Cyclosizer (Fig. 1) under normal operating conditions produce typical cut sizes of 44, 33, 23, 15, and 10 µm for cyclones one to five respectively for material with a specific gravity of 2·7. At the end of the selected elutriation period each sized fraction is discharged and collected for subsequent assay or analysis but all material rejected by the fifth cyclone (e.g. minus 10 \lm quartz) normally passes to waste. When this material is needed for separate study, although its amount and average analyses can be calculated by difference, it may be necessary to collect more than 250 I. of very dilute suspension, flocculate the solids, allow to settle, and decant off the supernatant liquid.This procedure is cumbersome and inconvenient and the simple technique to be described may offer some advantages. The temperature of the water fed to the Cyclosizer is maintained at a constant value for added reproducibility.PROCEDUREThe present overall treatment of the subsieve material (minus 37 \lm) fed to the Cyclosizer incorporated several refinements compared with normal operation and these may be best illustrated by anactual example. Material to be cyclosized (25 to 100 g depending on size distributIOn and specific gravity) is completely dispersed in water at 23 QC by vigorous stirrmg, using suitable dispersants if necessary, in a...

Jan 1, 1974

By F. D. Rosi

IT was recently shown1 that slip bands can be observed in bent germanium crystals after deformation, by means of etch pits along the slip traces. It is the purpose of this note to show how chemical etch pits can also be usedto examine the appear- ance of slip bands in silicon, as well as other deformation markings. A 30 ohm-cm, p-type single crystal bar, 2x1/4x1/8 in., was plastically bent at approximately 1200°C in a vacuum of 1x10-5 mm Hg. The axis of the crystal was coincident with a <III> direction, and the surface normal to the axis of bending was within 4" of a (110) plane. Prior to the deformation, the (110) surface was mechanically polished with

Jan 1, 1958