Genesis and assessment of clay materials suitability for earthenware production in northern Cameroon

Field description and sampling along four representative pits were done to determine the occurrence and the perspective earthenware valorisation from clay materials in the northern Cameroon. The methodology used include grain size analysis, Atterberg limits determination, mineralogical and geochemical analyses, and technological tests. Sand fraction was important in all samples. Interval plastic is tight to wide and the main clay minerals were kaolinite, illite and smectite. They were associated to quartz and feldspar minerals. Geochemically, SiO2 (48.46–65.62%), Al2O3 (14.8–20.28%), Fe2O3 (4.79–11.47%) and 5 to 13% of flux elements (CaO, MgO, K2O and Na2O) were found as main oxides. The presence of smectite is attributed to the low landscape positions, the presence of a clay-rich alluvial parent material and the hydrological conditions in this region, which is characterised by low rainfall and high temperature inducing high evaporation and thus soil solutions concentrated in silica and basic cations. Kaolinite is formed by the decomposition of orthoclase feldspar. The simultaneous occurrence of smectite and kaolinite, as a result of bisiallitisation and monosiallitisation processes respectively, could be related to light and successive variations in drainage conditions. Firing specimens showed red colour, which is attributed to the presence of hematite in the mineral composition. The presence of kaolinite promotes mullite formation while that of illite and smectite may promote glassy phase formation, which leads to the densification (1.7 to 2.09 g/cm3) and the good cohesion of the fired products with temperature development and the evolution of the metallic sound. Following some standards, the water absorption values (10.47 to 20.12%) and the compressive strength (2 to 5.7 MPa) suggest that the studied clay materials are suitable for earthenware production.