3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item An investigation into the mineralogy and processing characteristics of the Elsburg reefs at South Deep Gold Mine, South Africa(2024) Notole, ViweGold ores of the Witwatersrand Supergroup in South Africa are known to be amenable to metallurgical recovery through the process of cyanidation. However, the continuous decline in gold ore grade, increased environmental liability caused by residual cyanide in tailings and an increase in the complexity of ore composition calls for an alternative processing route. This is important to ensure that low-grade ore recovery is profitable while producing environmentally benign waste residue. Process mineralogy provides a systematic approach for the practical application of mineralogical knowledge, aiding ore characterisation and predictive behaviour, thus optimising how ores can best be mined, blended and processed. This study used mineralogical data and environmentally friendly leach reagent (i.e., glycine) to diagnose and predict processing characteristics of the composite Elsburg reefs at South Deep Gold Mine, South Africa. The mineralogy of these reefs is dominated by quartz and sulphide minerals, with pyrite, arsenopyrite, chalcopyrite and pyrrhotite being the common sulphides. More than 85% of gold in these reefs is locked or hosted in pyrite and quartz. The geochemistry shows high concentrations of siderophile (e.g., Cu, Ni and Co) and chalcophile (i.e., Cu and Zn) elements that can form stable complexes with glycine. A moderate to strong correlation of these elements (Cu, Co, Ni, Zn, etc.) with gold is conformable with the sulphide minerals-gold association. The poor liberation characteristics of Elsburg reefs ore and its geochemistry negatively influence gold recovery using glycine leaching. Sequential or multi-stage leaching is best to process ore with moderate to high Cu concentration and unliberated gold. The outcomes of this study demonstrate that Elsburg reefs gold ore responds well to sequential glycine leaching, with gold recoveries up to 95%, depending on which method or conditions are used. At low glycine dosage (e.g., 300 ppm), leaching duration of 50 hours, and ambient temperature (~23°C), bottle roll leaching of the Elsburg reefs yield low gold recovery (i.e., 30%), while at higher glycine dosage (e.g., 1500 ppm) and same leaching conditions (duration and temperature), a higher gold recovery (i.e., 41%) is attainable. Sequential leaching at a higher concentration of glycine (1500 ppm) with a leaching duration of 101 hours, yield cumulative gold recovery of up to 86%. Furthermore, at higher glycine concentration (1500 ppm) and elevated temperature (i.e., 40°C), Elsburg reefs yield considerably higher gold recovery (95%). The leaching solution was recharged at different time intervals from the beginning to the end of the leaching process. The increase in glycine was complemented by an increase in oxidant concentration (potassium permanganate). The ratio of potassium permanganate to glycine was kept at 2:1 (potassium permanganate: glycine).Item Mineralogical and geochemical studies of some witwatersrand gold ores with special reference to the nature of the phyllosilicates(1970) Von Rahden, Herbert, Valentin, RichardThe present thesis is divided into three parts. The study described in Part I arose out of a request by the Chamber of Mines Mining Research Laboratory to the National Institute for Metallurgy to undertake a preliminary study of whether it would be feasible, in Witwatersrand conglomerates, to carry out rapid delimitation of areas rich in gold and/or uranium at the rock face, a procedure which would permit areas of rich ore to be removed selectively by means of the "rock-cutter". The approach adopted in this study was essentially geochemical, while conventional mineralogical techniques (macro-auto radiographs , thin section and polished section analyses) provided a control. The samples were drawn from the Vaal Reef at Hartebeestfontein and Zandpan and from the Ventersdorp Contact Reef at Venterspost, and were analysed quantitatively for gold, silver, uranium, pyrite, muscovite, pyrophyllite, chlorite, quartz, iron, potassium, nickel, titanium, zirconium and chromium. The intensity of the interrelationships between the elements and minerals analysed for was examined statistically by means of correlation covariance and factor analysis programmes written for an IBM 360/50 digital computer. A sympathetic relationship -- defined as significant positive correlation (with a correlation coefficient r> 0. 7) -- was found to exist between gold and uranium in both the Vaal Reef and Ventersdorp Contact Reef samples. These findings suggest that gold and uranium can be removed Simultaneously by means of the rock-cutter, and that radioactivity can be used as an indicator for on-site delimitation of areas rich in gold. In the course of the study described in Part I, it became evident that little detailed mineralogical work had ever been done on the phyllosilicates occurring in the Witwatersrand System. Accordingly, certain phyllosilicates from Witwatersrand conglomerate bands and other sources were examined in detail, this study being described in Part II of the present thesis. This study called for detailed chemical, optical, X-ray crystallographic, infra-red, differential thermal and thermogravimetric analyses, the results of which are presented. The findings were examined in the light of variolls classification schemes that have bep proposed for the phyllosilicates. This investigation revealed the need for a universally acceptable system of classification for the phyllosilicates, which should preferably be drawn up under the auspices of the International Mineralogical Association to avoid the confusion that exists at present. Part III of the present thesis is devoted to a discussion and description of various analytical techniques that had to be modified or developed to meet th8 requirements of the studies described in Parts I and II. The techniques described include: (1) An X-ray diffraction method which was developed for the quantitative analysis of pyrite, muscovite, pyrophyllite, chlorite and quartz in crushed ore from Witwatersrand conglomerates. This method makes use of novacul iie as an external standard and of binary mixtures as analytical standards, and had a mean absolute error of 1. 1 %. This method may be expanded to permit analysis of an n-component mixture. (2) A whole rock pressed powder technique of X-ray fluorescence analysis which was used for the quantitative determination of iron, potassium, nickel, titanium, zirconium and chromium. This method makes use of internstional rock standards as external standards. Six computer programmes used for the computation of the analytical results and in the statistical and crystallographic calculations are also presented in Part III.