Clayey materials from the Sierra de la Demanda Range (Spain): their potential as raw materials for building ceramic industry

This work describes the possible use of thick Early cretaceous clay deposits, which occur in the southern sector of the Sierra de la Demada range, as raw materials in the manufacture of ceramics. The global mineralogical composition is characterized by high proportion of phyllosilicate and quartz with variable quantities of feldspar, carbonates and hematite. The clay mineralogy differentiates two types of raw materials: illitic clay and kaolinitic-illitic clay. A granulometric distribution in the 2-60 µm fraction. Good behaviour during the drying stage and acceptable results in firing tests confirmed that most samples can be utilizes as raw material in the building industry. The range of suitable firing temperatures for these materials is 950-1000°C, a temperature which needs to be raised for samples with a high percentage of kaolinite and quartz. Moreover, other materials with abundant calcite (20-30%) are suitable for use as modifiers of some properties on colour.