204 Vivian Kimambo et al.: Suitability of Tanzanian Kaolin, Quartz and Feldspar as Raw Materials for the Production of Porcelain Tiles Fig. 3 shows the Xray diffractogram of feldspar sample. product with high linear shrinkage and hence unstable product One of the minerals observed are sodium feldspar (albite) [4, 25]. The total amount of K2O and Na2O is (%) which (NaAlSi3O8) identified by ...