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Clair Groups and underlying basement contain cataclastic faults, cement-sealed faults/veins and open fractures. The dominant fracture cements are calcite and pyrite, although fluorite (with sulphides and native silver) occurs in minor amounts in some Clair Group fractures, marcasite is often associated with Clair Group fracture-hosted pyrite, and some basement fractures contain epidote/chlorite and quartz/feldspar/hematite. Calcite cements in many Clair Group fractures may have crystallised from porewaters whose calcium and bicarbonate were mostly remobilised from Clair Group calcretes. Many of these cements may predate Late Cretaceous/Early Tertiary oil charge. Some may have crystallised from Early Tertiary meteoric porewaters, the fluorite with which they are associated perhaps having crystallised from porewaters hydrothermally affected by local igneous activity. Calcite cements within some basement fracture may have crystallised from porewaters whose calcium and bicarbonate came from Clair Group calcretes, as may most non-ferroan calcite cement within Clair Group sandstones. Calcite cements in some Clair Group fractures contain a high proportion of non-calcrete carbonate. These cements may have crystallised after oil charge began, from Early Tertiary meteoric porewaters or meteoric/basinal-derived brine mixtures. Non-calcrete bicarbonate may have been generated via bacterial activity (organic matter oxidation and methanogenesis) within the Clair Group. Bacteria could have utilised hydrocarbons, substrates generated via aerobic hydrocarbon oxidation, or externally-sourced substrates such as acetate. Authigenic iron sulphides often predate the calcite cements. The sulphur within these was probably externally-sourced, H2S either having come direct from external sources, or having been generated in situ via bacterial sulphate reduction. Sulphur may have undergone redox cycling through contact with oxygenated meteoric water in some fractures and marcasite genesis may have resulted from this. Calcite cements within some basement fractures may have crystallised from Early Tertiary porewaters containing bicarbonate generated in situ via the oxidation of hydrocarbons, and these cements are often predated by authigenic pyrite.

Thesis (PhD)--University of South Australia, 1994

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1913. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed April 27, 2009) Includes bibliographical references.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1904. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed December 22, 2008) Includes bibliographical references (p. 18).

The effects SIBX/C10 (or C12) TTC mixtures on flotation response of pyrite, gold and uranium from Anglogold Ashanti’s No 2 Gold Plant feed were investigated. In batch flotation tests where TTC was dosed from aged 1% wt stock solutions, synergism was shown to occur in gold flotation at 25 mole percent C12 TTC and in uranium flotation at a similar dosage of C10 TTC. With commercial C12 TTC, 8 mole percent recorded the highest uranium and gold recoveries. The SIBX/C12 TTC mixture had a greater effect on gold than on uranium. When C12 mercaptan replaced the TTC in SIBX mixtures, rates and recoveries decreased at all levels. Kinetics and recovery with a mixture of 92 mole percent SIBX and 8 mole percent commercial C12 TTC gave a better flotation activity than obtained with SIBX alone. A combination of SIBX and an aged 1% wt solution of TTC lost activity when compared to that of SIBX and commercial TTC. This was attributed to the hydrolysis of TTC. Micro-probe analysis, back-scattered electron images, and EDS analysis showed that all the uranium recovered in flotation concentrates was associated with either pyrite, galena or a carbonaceous material (karogen). This was attributed to the flotation of the uranium oxide minerals brannerite and uraninite. Conditioning at pH values between 1.9-3.7 improved kinetics of gold, sulphur and uranium collection, but sulphur and uranium final recoveries were lower and gold final recovery was higher than the standard. In the presence of 0.001M cyanide, equivalent to 70g/t copper sulphate failed to activate pyrite at both pH 5.5 and pH 7.2. At a similar molar dosage lead nitrate did activate pyrite at pH 5.5 but not at pH 7.2. / Dissertation (MEng(Metallurgical))--University of Pretoria, 2005. / Materials Science and Metallurgical Engineering / unrestricted

Studies were made (1) to determine the effect of air and oxygen and verying concentrations in distilled water, on the solubility of iron pyrites; (2) to determine the effect of acid, base and buffer solutions of varying pH; (3) to observe the effect of some oxidizing and reducing agents on the solubility of iron pyrites. These investigations would aid in deciding the possibilities of using iron pyrites as a soil conditioner.

Pyrite (FeS2) has recently attracted significant interest as a photovoltaic material due to its promising optical properties, high photon to electron conversion yield, and low-cost raw materials. However, hopes have been tempered by recent discoveries that suggest the presence of hard to remove bulk sulfur defects. This research was focused on engineering and implementing the crystallization of pyrite from a sulfur rich solution to counteract the material's natural tendency to form bulk sulfur defects. Homoeptiaxial layers and single-crystal samples have been grown from tellurium sulfur melts with an Fe:S ratio of 1:4 using both natural and synthetic substrates. The homoepitaxial layer has been characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HRTEM), confirming the epitaxial nature of the synthetic FeS2 layer, and X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS) to better understand the energetics of the grown materials. Furthermore, epitaxial growth onto natural pyrite, in contrast to substrate etching, was established using sulfur-34 substitution and secondary ion mass spectrometry (SIMS). Growth onto synthetic pyrite was also described. Finally, the photovoltaic properties of homoepitaxial layers of high temperature solution growth pyrite onto a synthetic templating crystal was characterized using electrochemical methods.

One of the problems in the flotation of copper sulphide ores in moderately alkaline pH conditions is the misreporting of iron sulphide minerals into copper concentrates, which results in low copper grades. The relatively strong flotation of iron sulphides is caused by their copper activation from copper species dissolved from copper minerals present in the ore. In this study, several methods were used to reduce copper activation of pyrite during grinding or to minimise its effect on the flotation of pyrite at pH 9.0. Various surface analytical techniques were used to identify the mechanism of these methods and to optimise their performance. / First, it was confirmed that strong pyrite floatation at pH 9.0 in the presence of xanthate was caused by copper activation during grinding with copper sulphate or in the presence of chalcopyrite in single or mixed mineral flotation experiments, respectively. It was found that pyrite flotation is Eh dependent with low flotation for pulp oxidation potential, Eh, values lower than 7 mV (SHE), strong flotation between 7 and 50 mV, and flotation decreasing above 50 mV. The sharp increase in pyrite flotation around neutral Eh values was associated with high copper and xanthate adsorption while the decreased flotation at higher Eh values was caused by the formation of ferric hydroxide at the pyrite surface which in turn reduced copper adsorption but also reduced hydrophobicity. From the measurement by X-ray photoelectron spectroscopy (XPS) of the type and proportion of surface species, it was possible to calculated a hydrophobicity index at each step in the grinding discharge, during conditioning, in each flotation concentrate and finally in the tailing. A satisfactory agreement was obtained between this XPS hydophobicity index and the flotation recovery in each concentrate. / It was found that pyrite could be separated from chalcopyrite at pH 9.0 by controlling the pulp Eh value with maximum mineral separation and chalcopyrite flotation occurring at an Eh of 275 mV. This mineral separation could be further increased with the addition of zinc sulphate which selectively adsorbs or precipitates on the pyrite surface as zinc hydroxide via electrostatic interaction. The selectivity of this adsorption, and therefore larger pyrite depression, is the result of the larger amount of ferric hydroxide formed on the pyrite surface because of the more cathodic nature of this mineral. Thioglycolic acid (TGA) was also found to selectively depress pyrite flotation when added during grinding but, if added during conditioning, its effect on pyrite depression was only observed in the presence of citric acid (CA). This depression was related to the removal of copper hydroxide from the pyrite surface as both TGA and CA are strong complexants of cupric hydroxide (but also ferric hydroxide); as a result, fewer sites are available for xanthate adsorption. Citric acid is a weaker complexant than TGA, especially in the presence of xanthate; its role is to mop up the surface ferric hydroxide so that TGA is free to react with copper hydroxide. More importantly, in less oxidising conditions and with no Eh control, addition of zinc sulphate or TGA increased chalcopyrite flotation but had no effect on pyrite flotation. Pyrite flotation could also be reduced with addition of xanthate during grinding. In this case, the selective depression of pyrite flotation was attributed to the immobilisation of copper by xanthate at the chalcopyrite surface or its removal from solution, both mechanisms resulting in a reduced copper activation of pyrite. Pyrite depression and chalcopyrite flotation, and therefore mineral separation, were optimised with collector addition in both the grinding and conditioning stages. / Finally, the efficacy of these methods has been substantiated by comparing their effects on iron sulphide depression in two copper sulphide ores and with more common methods of iron sulphide depression. / Thesis (PhDAppliedScience)--University of South Australia, 2006

Thesis (PhDApSc)--University of South Australia, 2003.