Compositional characteristics of Plio-Pleistocene clays from Tricarico (Potenza, Southern Italy) and their utilization by the Italian tile industry

Seventeen samples of Plio-Pleistocene clays cropping out on the external margin of the Apennine chain, near Tricarico (Basilicata), have been studied and compared with coeval deposits from Southern Apennine intramontane. This research was carried out to derive general information relative to both the composition and utilization of Tricarico clays. These sediments are predominantly silty clays. They consist of quartz, calcite, feldspar, dolomite and clay minerals (i.e., smectite, illite, kaolinite and chlorite). The studied deposits are chemically homogeneous, except for the samples richer in the sand fraction which have higher SiO2, Na2O and Ba values. The chemistry of the studied samples compared with the data reported in the literature for Southern Apennine intramontane clays shows negligible differences, whereas Bradanic foredeep sediments have a higher CaO content. The Italian tile classification suggests that: (i) Ofanto Valley clays can be used both for the production of cotto toscano and for the porous single-fired and double-fired bodies and (ii) the sediments outcropping near Tricarico can be employed for the production of cotto toscano. However, with the addition of a little quantity of quartz and feldspar to the bulk mass, it is possible to make red stoneware from Tricarico deposits and to produce the cotto toscano and the porous single-fired and double-fired bodies from Potenza clays.