Petrology and economic potential of olojuoro sillimanite deposit, Ibadan soutwestern Nigeria

Abstract

The petrographic, chemical studies and determinations of physical characteristics like specific gravity and firing properties were undertaken for sillimanite quartzite samples taken from different borehole locations within Olojuoro area, Ibadan. The aim was to assess the potential for industrial application of the sillimanite deposit.
Two chains of sillimanite ridges were recognized. There was a general increase in quartz content and a corresponding decrease in sillimanite content from Northern part of the study area (Olarinde) to the Southern part (Apata). Similarly, the Atomic Absorption Spectrometric analysis carried out on these samples showed that aluminium contents in the sillimanite samples range between 40.40% to 57.69% (except samples from Apata with average of 33.44%). This allows sillimanite investigated for use in making refractory bricks. At temperature of 1450 oC, the samples showed no fusion which is expected of a high alumina refractory hence its use for mortars castables, plastic and ramming mixes which are refractories' products sold as non-formed products classified as “refractory specialities”.
The change in the specific gravity due to firing could be attributed to the production of fine microscopic or submicroscopic cracks caused by the natural thermal expansion with increasing temperature or perhaps to volume change in the associated minerals. The least change in specific gravity observed in the sample at Olarinde, may indicate its industrial superiority over others.
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Keywords: sillimanite, firing properties, industrial applications, sub-microscopic cracks, refractory bricks

Ifr Journal of Sceince Vol. 8 (2) 2006: pp. 149-157