The Composition and Physical Properties of Some Clays of Cross River State, Nigeria

Abstract

Clay deposits collected from various locations in Cross River State, Nigeria were studied to determine their physical, compositional and firing characteristics in order to evaluate them for industrial uses. The samples were pulverized, sieved, digested with mineral acids and characterized. Results showed that the clays are mainly kaolinitic with only occasional illite, and quartz as the main subsidiary non-clay mineral. The high plasticity index of the clays corresponds to the more transported clays of the tertiary-to-recent environment. The percentage of linear shrinkage varied from 11-16% with the lowest shrinkage (11%), having the coarsest features. Silica (SiO 2) content of the clays ranged from 47-70% while the alumina (Al 2 O 3) content which varied from 6-35% was lower than the theoretical value of kaolinite (39.5%), with high iron (Fe 2 O 3) and titanium (TiO 2) content in some samples along with trace amounts of fluxing materials. The firing colors ranged from whitish/pinkish to brownish and reddish depending on the amounts of iron and titanium oxides present. Compared to the dark carbonaceous shales of cretaceous origin in this area, these clays are relatively free from carbonaceous matter, which makes the clays potentially suitable for pottery, refractory and brick productions.