## 4 Results and Discussion
### Chemical Composition  
The chemical data showed that SiO\({}_{2}\) and Al\({}_{2}\)O\({}_{3}\) are the most abundant oxides (SiO\({}_{2}\) + Al\({}_{2}\)O\({}_{3}\) \(>\) 75 wt.%). The SiO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) is less than 2 in several samples (Table 2) and is an indication of a predominance of kaolinite associated to quartz. The Lokoundje alluvial clays are mainly aluminous with Al\({}_{2}\)O\({}_{3}\) contents varying between 23.29 to 30.26 wt.% (Table 2; Figure 3). These sediments are also characterized by low contents in Fe\({}_{2}\)O\({}_{3t}\) which vary between 1 and 5.42 wt.% (Table 2). These contents are less than 3 wt.% in white and light grey materials (Table 2). The color of the products after sintering is due to the iron contents (Table 2). The white samples are characterized by lowest iron contents, and the color of products remains the same after sintering (Table 2). The flux oxides (Na\({}_{2}\)O + K\({}_{2}\)O) are very low (1.08-2.50 wt.%), these low flux contents may induce poor vitrification. Fluxes, in reaction with silica and alumina, stimulate liquid phase formations that facilitate densification [24]. The low Na\({}_{2}\)O and K\({}_{2}\)O contents can be related to the absence of Na-/K-feldspars. In addition, due to low flux contents, a high firing temperature for improved sintering may be needed. Figure 4 shows that these alluvial clays are suitable for the manufacture of white stoneware tiles.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multirow{2}{*}{**d.l.**} & \multicolumn{2}{c}{**Yellow Materials**} & \multicolumn{2}{c}{**Reddish Yellow Materials**} & \multicolumn{2}{c}{**White Materials**} & \multicolumn{2}{c}{**Light Grey Materials**} \\ \cline{3-10}  & & **BR-5** & **BR-8** & **BR-9** & **BR-11** & **GR-2** & **GR-3** & **GR-6** & **GR-8** \\ \hline SiO\({}_{2}\) & 0.01 & 44.33 & 46.73 & 51.12 & 51.41 & 45.64 & 57.61 & 57.84 & 48.48 \\ Al\({}_{2}\)O\({}_{3}\) & 0.01 & 30.26 & 29.51 & 26.07 & 24.77 & 29.36 & 24.23 & 23.29 & 27.13 \\ Fe\({}_{2}\)O\({}_{3}\) & 0.01 & 4.20 & 4.31 & 5.42 & 4.33 & 3.33 & 1.28 & 2.16 & 2.90 \\ MnO & 0.01 & 0.01 & 0.02 & 0.02 & 0.01 & 0.01 & 0.01 & 0.01 & 0.01 \\ MgO & 0.01 & 0.34 & 0.38 & 0.36 & 0.40 & 0.37 & 0.15 & 0.27 & 0.38 \\ CaO & 0.01 & 0.03 & 0.03 & 0.04 & 0.04 & 0.03 & 0.02 & 0.03 & 0.04 \\ Na\({}_{2}\)O & 0.01 & 0.06 & 0.08 & 0.10 & 0.13 & 0.08 & 0.09 & 0.12 & 0.10 \\ K\({}_{2}\)O & 0.01 & 1.00 & 1.03 & 1.06 & 2.37 & 1.00 & 1.85 & 1.68 & 1.71 \\ TiO\({}_{2}\) & 0.01 & 1.73 & 1.48 & 1.24 & 2.26 & 1.55 & 1.97 & 1.39 & 2.18 \\ P\({}_{2}\)O\({}_{5}\) & 0.01 & 0.31 & 0.19 & 0.12 & 0.34 & 0.25 & 0.35 & 0.12 & 0.37 \\ LOI & 0.01 & 16.89 & 15.58 & 13.79 & 16.14 & 17.60 & 11.55 & 12.36 & 15.77 \\ Total & - & 99.15 & 99.33 & 99.36 & 99.21 & 99.22 & 99.10 & 99.26 & 99.07 \\ SiO\({}_{2}\)/Al\({}_{2}\)O\({}_{3}\) & - & 1.46 & 1.58 & 1.96 & 2.08 & 1.55 & 2.38 & 2.48 & 1.79 \\ Na\({}_{2}\)O + K\({}_{2}\)O & - & 1.06 & 1.11 & 1.16 & 2.50 & 1.08 & 1.94 & 1.80 & 1.81 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Major element compositions (in wt.%) and element ratios of the Lokoundje alluvial clays [18].  
Figure 2: Plotting of alluvial Lokoundje clays in the clay–sand–silt diagram.