CHEMICAL AND MINERALOGICAL ASSESSMENT OF CLAYS FROM PELOPONNESE (S. GREECE) AND THEIR EVALUATION FOR UTILIZATION IN CERAMICS INDUSTRY
Mineral constituents, particle size and chemistry of ceramic raw materials may control the way ceramic products are formed and fired. Three compound (combined mixtures of 20 raw samples) clay samples from Chanakia area, Pelloponnese (S. Greece), were mineralogically and chemically investigated and their utilization as raw materials for the ceramic industry was evaluated. These samples come from different clay formations, they have red, blue and green colors and constitute the raw materials for a local brick plant. Particle size distribution analysis showed that the percentage of clay size fraction (d<2μm) ranges from 28.3 to 36.3 wt.%. X-ray diffraction analysis revealed that the main mineral constituents are quartz, micas, feldspars (plagioclases, orthoclase), calcite (except the red - clay) and clay minerals (discrete illite, mixed - layered illite/smectite, chlorite and traces of smectite and vermiculite). Projection of their bulk chemistry on some triangular discrimination diagrams has aided us to evaluate their suitability for ceramics production, namely majiolica (earthenware), cottoforte, gres and bricks were evaluated. In conclusion, all the studied materials are proved unsuitable for high quality ceramic products. Specifically, the blue and green clays were found suitable for earthenware ceramics as are high porosity building bricks, roofing tiles and similar products, while the red clay is appropriate for gres ceramics as are the low porosity tiles and bricks.