Studies on the characteristics of alluvial gold ores in some parts of Ghana

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The characteristics of placer gold ores obtained from along the Offin River (i.e. Upper, Middle and Lower Offin areas) and some of its tributaries (such as the Bonte, Oda and the Jimi streams) were investigated. The studies revealed that the gold particles in the samples studied with optical and electron microscope have varied shapes and surface properties that could affect the recovery of such particles. While some of the particles were spheroidal, others were rod-like, platy, as well as, had projections on the surfaces. It was also observed that the surfaces of some of the particles were tarnished with compounds of silicon, calcium, zinc, titanium, iron, and copper. Gold particle dispersity varied from sample to sample and with depth. In some cases, the greater than 125 μm gold particles were found in the first 2.0 metres whilst in others these occurred at depths closer to the bedrock. It was also observed that in most cases the number of finer gold particles (less than 125 μm) were more, although, in terms of mass were negligible. In samples with high clay content, desliming was only possible with large amounts of water and in some cases clay balls were formed which captured or occluded some of the gold particles.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy, 1998