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By Haiping Sun, Samir Ganguly, Oleg Ostrovski, M. Yaser Lone

Wettability of graphite by synthetic SiO2-Al2O3-CaO-MnO slags with varied MnO content and by industrial slags was studied at 1350-1600 °C using sessile drop method under argon atmosphere. Initial contact angle was the lowest (110-115o) for the MnO-free slag. For slags with 10-40 wt% MnO, the initial contact angle was in the range 125-135o. The contact angle decreased with the contact time. The change in the contact angle with slag mass was found insignificant. The surface tension of slags obtained from the drop shape analyses was 500-800 mN/m and varied in a narrow range with temperature and MnO concentration. The reduction rate increased with increasing MnO content in the synthetic slag from 20 wt% to 40wt% and temperature. Increasing temperature also increased the rate of reduction. No correlation was observed between the reduction rate and MnO content in the synthetic slags in the range 0-20 wt% and in the industrial slags. The rate of SiO2 reduction from the molten slag was close to the rate of MnO reduction. The MnO-free slag had the largest contact area with graphite substrate. Keywords: reduction, wettability, graphite, slag, manganese, surface tension.

Jan 1, 2007

By M. A. van Nierop

The Discrete Element Method (DEM) is a model that is used to simulate the motion of the media in a grinding mill. The sum of the energy that is lost in inter-media and media-wall collisions represents the power drawn by the mill. The fact that the DEM predicts the power drawn by grinding mills over a large range of diameters has been used to show the validity of the DEM. However, the power drawn by a mill is a function only of the sum of forces of the load on the shell liners. A more accurate and detailed validation of the DEM would be to measure these forces as a function of angular position as the liner moves under the load, and to compare these measurements with predictions generated using the DEM. An experimental mill has been developed to reproduce exactly what the 2-dimensional DEM simulates. The 0,55 m diameter mill has a length of 0,023 m, which is fractionally larger than the diameter of the media used in the mill. One of the lifters in the mill has been instrumented so that the forces on the lifter can be measured as the mill rotates. The DEM simulation will be used to predict these forces. This will give experimental evidence of the validity of the DEM for modelling load behaviour in rotating grinding mills.

Jan 1, 1999

By D. O’Connor, A. Pytlik, D. J. Corbett

The resistance of yielding rockbolts to multiple impact loads was tested by means of a drop hammer. The methodology was based on the ASTM D7401-08 standard as well as the requirements specified for rockbolts by Luossavaara-Kiirunavaara Aktiebolag (LKAB – a Swedish mining company) and the Safety In Mines Research Advisory Committee of South Africa (project number GAP 423). During the tests, the loading force and bolt elongation were measured with a sampling frequency of fs = 19.2 kHz. In order to analyse the phenomena involved, the tests were recorded using two independent high-speed video cameras (600 and 1000 frames per second) and one thermal camera (128 frames per second). The tests demonstrated that all the samples transferred double the gravitational potential energy of Ep = 50.85 kJ from the impact load of mass m = 2825 kg and impact velocity of v = 6.0 m/s without failure. Damage to the bolt-resin contact in the upper anchoring zone of the bolt in the steel tube occurred after subsequent impacts. As a result, the macro-deformed bolt exhibits additional yield, and its operation following the shearing of the resin bond is similar to that of a ‘cone bolt’. Only one test resulted in damage to the threaded bolt rod-nut coupling, during the fourth impact; however, no damage to the bolt-resin contact zone was observed.

Nov 6, 2023

By K. C. Sole, M. Makonese

Bushveld Belco is commissioning a plant for production of electrolyte used in vanadium redox flow batteries. Owing to the source material, the electrolyte is contaminated with Fe, at concentrations up to 140 mg/L, which negatively affects battery performance. This study examined the use of ion exchange to reduce the Fe concentration to the target value of < 100 mg/L from a feed solution containing 100 g/L V in 4 M H2SO4. Four resins with possible application were identified: Puromet MTS9570, Puromet MTX7010, Puromet MTS9500, and Puromet MTC1600H. Puromet MTS9570 outperformed the other three resins in all batch experiments with respect to loading capacity and selectivity over V, and was evaluated for Fe removal in fixed-bed column loading tests. Based on these data, preliminary sizing and design of a full-scale column was undertaken. Owing to the difficulty of eluting this resin, a philosophy of discarding the resin on loading to full capacity was considered. These data revealed that, despite the high selectivity of this resin for Fe over V, it would be too expensive and impractical to use this resin for full-scale operation under such conditions. It is recommended to remove iron earlier in the flowsheet prior to generation of the 4 M H2SO4 electrolyte.

Dec 11, 2024

By J. K. Pothal, S. Basu, R. Barik, P. K. Senapati, A. Dubey

The aim of this paper is to study the characteristics of limestone particles (size varies from 4 mm to 20 mm) during its transportation from open cast mines through pipes. The influence of four different size fractions of limestone samples (4–6 mm, 6–10 mm, 10–15 mm, and 15–20 mm) on pipe flow characteristics during vertical transport in a 100 mm NB hose pipe was investigated. The flow velocities in the vertically lifting pipe was varied from 0.95 m/s to 2.78 m/s and a rotary feeder of 2 to 4 tonne/hr. capacity was employed to feed the limestone samples to the lifting pipe. The pressure drop data for the different size fractions of limestone samples at different mixture velocities were analysed. The effect of input volume fraction and superficial velocity of limestone samples on hold-up ratio were discussed. It was indicated that there was no substantial increase in pressure drop of slurry samples in the studied range of concentrations (CW = 4.22% - 12.54%), particle size, and low to medium range mixture velocities with respect to water run head loss data. The hold-up for the larger size fractions (15–20 mm) of limestone samples was found to be significant as compared to smaller size fractions, which may be due to terminal settling velocities of individual fractions of the studied samples.

Mar 4, 2025

By A. Holder

A major mud push occurred on the 870 m production level, scraper drift block cave at Dutoitspan diamond mine in November 2011, during which it is estimated that more than 4 400 m3 of mud engulfed the west cave. The production level was successfully evacuated during the mud push with no loss of life or injury to personnel, thanks largely to mine employees being well trained in and adhering to on-mine mud rush evacuation procedures. All access to the west cave was lost as a result of the mud push. Clean-up operations are currently under way to regain access to the production level, to establish the extent of damage to scraper drifts and equipment, and to evaluate what remedial works may be required to resume production. The magnitude of the Dutoitspan mud push necessitated a detailed investigation into the key contributing factors leading up to the incident, which are discussed in this paper. Mud rush mitigation measures in place on scraper drift block caving operations at Dutoitspan, Bultfontein, and Wesselton diamond mines in the Kimberley area are critically reviewed. Recommendations are furthermore made for enhanced mitigation based on mud rush risk profiles derived for different production areas in these old scraper drift block caves. Keywords mud push, mud rush, scraper drift, block cave, mitigation factors, risk profiles, risk management structure.

Jul 1, 2013

By V. M. Lovell, N. P. Finkelstein

The concepts involved in flotation research are discussed and aims are presented. Three different method. of investigation can be used, all of which are applied at the National Institute for Metallurgy (N.I.M.), and these are the empirical, trial and error method, the chemical engineering method, and the physicochemical approachs This paper is devoted to the last of these. Because of the complexity of the physicochemical interactions involved, the work has, to a large extent, been concentrated on only one aspect, viz. the interaction between the mineral surface and reagents in solution, which was considered of major importance in the understanding of the process. The aspects on which work has been done are the concentration of uranium, the reaction between salt minerals and fatty acids, mixed xanthate-cationic collector systems, and the reaction between sulphide minerals and thiol reagents. Selected problems from the first two of these are discussed in some detail and deal with the agglomeration flotation of uranium and the chemical control of the flotation process for phoscorite. A detailed discussion is also presented of the progress made in the understanding of the interaction between sulphide minerals and thiol reagents, which is of more general application. Finally, an indication is given of the future direction of physicochemical research at the N.I.M.

By V. M. Lovell, N. P. Finkelstein

The concepts involved in flotation research are discussed and aims are presented. Three different methods of investigation can be used, all of which are applied at the National Institute for Metallurgy (N.I.M.), and these are the empirical, trial and error method, the chemical engineering method, and the physicochemical approaches. This paper is devoted to the last of these. Because of the complexity of the physicochemical interactions involved, the work has, to a large extent, been concentrated on only one aspect, viz. the interaction between the mineral surface and reagents in solution, which was considered of major importance in the understanding of the process. The aspects on which work has been done are the concentration of uranium, the reaction between salt minerals and fatty acids, mixed xanthate-cationic collector systems, and the reaction between sulphide minerals and thiol reagents. Selected problems from the first two of these are discussed in some detail and deal with the agglomeration flotation of uranium and the chemical control of the flotation process for phoscorite. A detailed discussion is also presented of the progress made in the understanding of the interaction between sulphide minerals and thiol reagents, which is of more general application. Finally, an indication is given of the future direction of physicochemical research at the N.I.M.

Palladium Alloys. E. M. Savitskii, V. P. Polyakova, M. A. Tylkina. Translated by: R. E. Howard. Published by Primary Services, New York, N.Y. 10012. $24.50. The output of palladium in the U.S.S.R. greatly exceeds the internal usage. The primary purpose of this 200 page volume is therefore to record details of fundamental researches on the properties of this metal with a view to expanding its marketability. Theoretical studies have revealed a number of alloys with great promise in electrical instruments and for the chemical industry. The success of these researches in the U.S.S.R. and in the U.S.A., resulted in the industrial usage of palladium exceeding that of platinum in 1957 and increasing its lead during the next decade. This volume is divided into three parts. Section I covers the mineralogy, extraction and the physical metallurgy of the metal. It records a considerable area where the resistance to corrosion of palladium equals that of platinum. Section II deals with the preparation and the properties of palladium in alloys and contains a comprehensive metallographic treatment of the many binary alloy systems. Section III is devoted to industrial applications. The 460 references which are quoted are mainly from the U.S.S.R. but otherwise have a world-wide coverage. H.B.

By Elizma Ford, Vincent Sithole

"Two shortened test procedures for estimating the Bond ball work index are compared for suitability of use on Zambian/DRC-type copper–cobalt ores. The first procedure is based on a batch milling test while the second procedure is based on a limited locked-cycle test. Both procedures were conducted using a standard Bond test mill. INTRODUCTION The Bond ball work index is widely used in the field of minerals processing as an indicator of ore grindability. The work index is determined by means of a locked-cycle test procedure that typically requires seven to eight cycles to stabilise at a re-circulating load of 250%. A typical test requires between three to four kilogram of ore sample and around eight hours of operator time. For geometallurgical test work applications, where a large number of variability samples are to be tested, it would be highly beneficial to use a test procedure that requires less sample mass and operator time. Certain test work laboratories, for example SGS and JK Tech, are already offering various types of shortened test procedures for estimating the Bond ball work index. This paper discusses a comparison of two shortened test procedures that were evaluated for suitability of use on Zambian/DRC-type copper–cobalt ores. EXPERIMENTAL Test Procedure 1 – Batch Milling The first test procedure is derived from a batch milling approach proposed by the University of Hacettepe (Aksani, 2000). Some modifications were, however, made to the data analysis method from that originally proposed. During this test procedure, a 700 mL volume of sample is milled in a standard Bond test mill for a pre-determined number of revolutions. The feed and product particle size distributions are measured for each test. These results are then used to back-calculate a cumulative breakage rate parameter (k) for each particle size, according to the following formula:"

Jan 1, 2015

By T. Mahlangu Mahlangu, T. Fungene, K. C. Sole

"Although oxygen is widely employed as the oxidant of choice in gold leaching by cyanide, its low aqueous solubility presents some drawbacks in practical application; hydrogen peroxide has therefore been considered as a possible alternative. The aim of this investigation was to study the catalytic decomposition of hydrogen peroxide, which generates an oxidizing intermediate species, and to understand its effect on cyanide destruction. Operating conditions that facilitated the effective decomposition of hydrogen peroxide were established by varying the pH and catalyst type and concentration. The oxidizing intermediate, detected using an indirect technique, was found to be the hydroxyl radical (OH?). OH? is commonly generated in acidic solutions, but this work demonstrated that it is also produced at the alkaline pH values necessary for cyanide gold leaching. The effects of free and complexed iron and copper catalysts on the oxidation and consumption of hydrogen peroxide and cyanide were also investigated. It was shown that the cyano complexes of Fe(II) and Cu(I) are also effective as decomposition catalysts. Hydrogen peroxide concentrations above 0.01 M decreased the free cyanide concentration, which was attributed to the probable formation of the cyanate anion (CNO-). Although cyanide consumption increased due to its oxidation in the presence of OH?, excessive cyanide consumption in the presence of copper was attributed primarily to its complexation by the unstable copper(I) cyanide species. Rate constants for the decompositions of H2O2 and cyanide by ferrocyanide and copper cyanide were calculated; the latter was identified as being a better catalyst. IntroductionLeaching of gold from its ores using cyanide has been employed for well over a century (Habashi, 2016). Addition of cyanide converts the gold into a cyanide complex (Au(CN)2 -) that is soluble in water (Wang and Forssberg, 1990). The leaching reaction can be represented as Equation [1]:"

Dec 1, 2018

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluents is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10mg/l cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a pre-neutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40g/l NaOH. A pre-neutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009

By S. J. Moema, M. G. Maruma, L. A. Mampuru, M. E. Maja

"The most commonly used high-chromium white cast iron (HCWCI) is the hypoeutectic white cast iron that contains 2–3.5 wt.% C and 10–30% Cr. This type of material relies on hard, brittle M7C3 carbides to impart good wear resistance. Due to its good wear resistance, this material has found application in the mining industry and cement industry. However, it has low fracture strength and this challenge led to research aimed at refining the microstructure. This was done by the addition of niobium in the range between 0.1 and 0.6 wt.%. In the as-cast condition, the addition of niobium was found to increase the fracture strength due to the finer eutectic microstructure. The hardness was also found to have increased slightly compared to the reference alloy with no niobium additions. Low fracture strength after heat treatment was observed in the Nb-added HCWCI, which is believed to have been caused by the precipitation of secondary carbides and the transformation of the matrix from austenite to martensitic. IntroductionFor the past few years Mintek has been involved in a project in which a number of alloys have been identified for grinding media applications. The high-chromium white cast iron (HCWCI) alloys were among the alloys researched for this application. The knowledge acquired from the grinding ball media research has now been extended to mill liners, which have traditionally been made of manganese-, chromium- and chrome-molybdenum steels. The replacement of worn mill liners costs the mining industry a significant amount of money and this has led to a need for continuous research to prolong the life of the liners. During milling operations, liner wear has an adverse effect on the capacity of the mill, the energy efficiency and milling efficiency and finally leads to relining, to replace worn liners."

Jan 1, 2016

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluent is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10 mg/[l] cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a preneutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40 g/[l] NaOH. A preneutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009

By Q. P. Campbell

Activated carbons used in the precious metals extraction industry are characterized by large internal surface areas and a great affinity for metal ions. The purpose of this research is to prepare activated carbon from a South African bituminous coal by physical activation that is suitable and cost-effective for use in the extraction of metals. The quality of the coal-based activated carbon may not prove to be as good as activated carbon produced from other traditional sources, but the production costs involved may make South African coal a feasible alternative feedstock. The activated carbons produced were characterized by Brunauer, Emmett, and Teller (BET) surface area, activated carbon pH, and phenol adsorption studies and the results compared to the results from a commercially available activated carbon, Norit RO 0.8 (control sample). Bituminous coals from various sources including Witbank Seam 4 and Free State coal were used in this study. The preparation method chosen was physical activation using superheated steam. The effects of process variables such as activation time (1-3 h) and temperature (600-800°C) were studied in order to optimize those parameters. The activated carbon surface area was characterized by means of nitrogen adsorption isotherms at 77K. BET surface area analysis showed that Witbank Seam 4 coal activated at a temperature of 800°C and activation time of 3 hours resulted in a surface area of 340 m2/g. Quality control of each sample was performed by measuring the pH of a known amount of the prepared activated carbon in distilled water over time. Results showed that the pH of some of the prepared activated carbons reached a value of 11. Phenol adsorption results for the different activated carbons prepared corresponded well to the results obtained for the Norit RO 0.8 activated carbon sample.

Jan 1, 2012

NOTICES PROCEEDINGS OF THE SECOND INTERNATIONAL CLEAN AIR CONGRESSThis massive volume of 1,380 pages contains all the papers presented at the congress held in December 1971. INDEX TO SOUTH AFRICAN PERIODICALS This bibliographical work has been produced by the Johannesburg Public Library since 1945, and is of interest to all our readers. THE CONTROL OF GASEOUS SULPHUR COMPOUND EMISSION An international conference on this theme will be held at the Salford University from 10th to 12th April, 1973. COLLOQUIUM ON SLlMES DAMS The South African Institute of Mining and Metallurgy have great pleasure in advising members that two-day colloquium on Slimes Dams is being arranged for the 14th and 15th November, 1973. NATIONAL INSTITUTE FOR METALLURGY / NASIONALE INSTITUUT VIR METALLURGIE REPORT. VERSLAG No. 1424 REVIEW OF THE WORLD&apos;S FLUORSPAR INDUSTRY, WITH PARTICULAR REFERENCE. TO SOUTH AFRICA Ist August, 19n Investigator: H. H. Gossling SYNOPSIS The consumption of fluorspar has increased significantly during the last three years, and a consumption of approximately 5,76 million tonnes per annum is projected for 1975. REPORT. VERSLAG No. 1432 LABORATORY METHOD No. 44/2 THE DETERMINATION OF RUTHENIUM AND OSMIUM IN THE RESIDUES RESULTING FROM THE LEACHING OF MATTES 5th July, 19n Investigators: Magdalena M. KrUger R. V. D. Robert SYNOPSIS The method described involves the sintering of the residue with barium peroxide, and the distillation of ruthenium and osmium from the sinter. REPORT. VERSLAG No. 1439 THE REACTION OF SULPHIDE MINERALS WITH THIOL COMPOUNDS 29th June, 19n Investigator: L. A. Goold SYNOPSIS A selected group of thiol reagents was reacted with a wide range of sulphide minerals, and products that were formed at the surface were extracted and identified by infrared spectrophotometry.

1. Book review Economics of mineral exploration in Australia, by Brian W. Mackenzie and Michel L. Bilodeau. Australian Mineral Foundation (Private Bag 97, Glenside, South Australia 5065). 198pp. $A58. $A45 for students. Reviewer: D.G. Krige 2. Recent publications Combustion of coal liquid mixtures, by G.F. Morrison. London, lEA Coal Research, 1983, 52 pp. Hafnium: physico-chemical properties of its compounds and alloys. Vienna, International Atomic Energy Agency, 1981. 408 pp. 620 Austrian schillings. Canadian mines handbook 1984-85, edited by CD. Gardiner. Toronto, The Northern Miner, 1984. 500 pp. $24. Drilling equipment in Canadian mining and exploration- opportunities for the industry, by AJ. Jakubek. Toronto, Micromedia Limited (144 Front Street, Toronto M5J IG2, Canada), 1984. Research report 1984. Port Melbourne, Division Mineral Chemistry, Commonwealth Scientific and Industrial Research Organization, 1984. 190 pp. Surface engineering Wear is an unavoidable problem in virtually all products of the engineering industry, from the minute bearings of instruments to the cutting surfaces of earth-moving plant. Safety in mines About 50 papers will be presented at the 21st International Conference of Safety in Mines Research Institutes at Sydney from 21st to 25th October, 1985. Some 250 delegates from 30 nations are expected to attend. Professional development seminars March 18th-21st, 1985 Underground Blast-hole Mining May Ist-3rd, 1985 Mineral Processing of Gold Ores May 6th-10th, 1985 Mineral Comminution Systems May 13th-15th, 1985 Processing of Metallurgical Residues Analytical chemistry The Second Symposium on Analytical Chemistry in the Mining, Exploration and Processing of Materials is to be held in Pretoria from 15th to 19th April, 1985.

Jan 1, 1985

O.F.S. Branch Proceedings of the Annual General Meeting Held on Wednesday, 4th August, 1976 Mr G. J. C. Young (Chairman) was in the Chair. Also present was Dr R. E. Robinson, President of the South African Institute of Mining and Metallurgy. NlM reports Report no. 175 Copper extraction by leaching magnetites from Palabora Mining Company. (12th Apr., 1967; re-issued Jun. 1976) Report no. 1632 A mineralogical examination of beach-sand concentrates from a pilot plant at Richards Bay. (20th May, 1974; re-issued Jun. 1976.) Report no. 1825 The full automation of a Philips 1220 X -ray spectrometer. A Philips 1220 X-ray spectrometer (semi-automatic) Report no. 1840 The spectrophotometric determination of total uranium in silicate ores and leach liquors by use of bromo-PADAP. Report no. 1841 The determination of aC1;d-soluble uramum in silicate ores and solutions. AS & TS National Award The Associated Scientific and Technical Societies of South Africa has decided to make two National Awards this year. These awards, given in recognition of outstanding contributions to science and the application of science, will be made to Dr T. L. Wadley for his invention of the Tellurometer system of distance measurement and to Mr H. Scheffel for his design of the High Stability Bogie. Treatment of waste water A major international symposium, organized jointly by the Water and Environment Group of the Society of Chemical Industry and the Environment Group of The Chemical Society of London, will be held in London in 1977. Down-the-hole drilling Atlas Copco announces the publication of a revised and enlarged version of one of the booklets in their series &apos;Mining and Construction Methods&apos;. This 40-page booklet is entitled &apos;Down-the-hole drilling with COP drills&apos;.

Jan 10, 1976

The first neutrinos in nature ever detected by man were "caught" in a unique laboratory some 3 km (over 2 miles) underground in one of the world&apos;s deepest mine shafts at East Rand Proprietary Mines (ERPM), Boksburg. Only 100 m from where gold is being mined from the rock face a small team of South African and American physicists work on one of the most fascinating and important fundamental research projects that is currently exciting the imagination of the scientific world. Neutrinos are sub-atomic particles just as are protons, neutrons and electrons, but they are unique in that they have neither electric charge nor mass. Cosmic neutrinos travel at the speed of light and penetrate stars and planets. Even a million kilometres of solid lead would not provide a satisfactory shield against them. Stars are believed to "burn" by means of nuclear reactions which produce enormous fluxes of neutrinos. The sun, for example, illuminates the earth with visible light, but also bathes it with neutrinos. After World War II, two American physicists, Profs Frederick Reines and Clyde Cowan, experimenting at a large nuclear reactor, succeeded in obtaining direct evidence of the existence of the laboratory-produced neutrino. It then became very important to establish whether neutrinos also existed in nature. This knowledge would lead to a greater understanding of the forces of nuclear physics, of the behaviour of nuclear particles and, indeed, is also relevant to astrophysics. From the start it was clear that the search for "natural" neutrinos would be difficult. Questions which arose were- * how could they be traced if they were without mass or electric charge? * how could other nuclear particles be screened off? * could these not be wrongly detected, or even prevent accurate detection of neutrinos? Neutrinos were known to be produced along with charged particles, by the reaction of primary cosmic rays with the constituents of the atmosphere. It was also known that when the neutrinos collided with matter, they themselves produced the same type of charged particle which could be detected if the unwanted charged particles from the atmosphere could be screened off. What was needed, therefore, was a laboratory where the particles produced in the atmosphere could be screened out, yet which would receive and detect the particles produced by the neutrons&apos; collision with the matter (solid rock) in the vicinity of the laboratory. This meant that scientists either had to build a laboratory with an enormously thick lead shield for their detection work. . . or they could go as near as possible to the centre of the earth where only charged nuclear particles of the very highest energies could penetrate. ERPM was clearly the most suitable place in the world where so effective a "neutrino trap" could be set. Under more than 3 000 m of solid rock the apparatus for detecting neutrinos is well shielded against unwanted nuclear particles produced in the cosmic radiation which can reach the laboratory only in a steeply vertical trajectory. Other particles are easily stopped by the great thickness of rock. The air-conditioned laboratory is at one end of a 150 m long tunnel, 2,5 m high and wide, blasted from the rock. The electronic recording equipment is housed here, while the rest of the tunnel is filled with the detection system. When a charged particle passes through a detector element, it produces a minute flash of light which is recorded and which triggers a flash-tube array. This then defines the trajectory of the charged particle, which is also recorded on film for analysis. So far 82 neutrinos have been detected, 50 at the present level and 32 at a higher level, and the findings have borne out the physicists&apos; theoretical expectations. In this joint project Profs Reines, J. P. F. Sellschop, Director of the Witwatersrand University&apos;s Nuclear Research Unit and M. F. Crouch of the Case-Western Reserve University of Ohio are the Chief Investigators. This unique endeavour has been made possible by financial support from the US Atomic Energy Commission, the University of the Witwatersrand and the Chamber of Mines of South Africa, as well as by the cooperation of the management and men of ERPM.

By P. W. J. van Rensburg

COLLOQUIUM AND GENERAL MEETING A General Meeting and Colloquium on comminution was held on March 13th, 1974, at Kelvin House, Johannesburg. Mr P. W. J. van Rensburg (President) was in the chair. The Colloquium was attended by 140 delegates and was opened by the President at 9.15 a.m. MINUTES The minutes of the general meeting held on November 14th, 1973, as published in the December issue of the Journal, were confirmed.

Jan 5, 1974