Characterization of clays from the Fez area (northern Morocco) for potential uses in the ceramics industry

Clays are among the most important raw materials used in the fabrication of ceramic products (Norton, 1970; Burst, 1991; Kamseu et al., 2007; Vieira et al., 2008). The oldest method of making terracotta objects is simply using one's hands and clay; this technique is still used today in many pottery sites worldwide. After being formed and dried, the pottery is fired to obtain a hard and rigid material. Without the chemical transformations that occur during firing the piece would disintegrate upon contact with water. Firing is usually performed in gas-, coal- or wood-burning kilns. The maximum temperature of the kiln and the duration of firing influence the final characteristics of the object obtained. Thus, the maximum temperature in a kiln is often kept constant for a certain period of time to ensure that the required consolidation in the terracotta is obtained. Due to their complex mineralogical and chemical compositions and the physical characteristics, clays have unique properties that characterize their deposits (e.g. Saikia et al., 2003; Vieira et al., 2008; Mitrović et al., 2009; Boussen et al., 2016). By determining the mineralogical, chemical, granulometric and rheological properties of clays, an assessment of the potential industrial applications of these raw materials is achievable (Dondi et al., 2014).

Morocco's pottery is recognized internationally for the specific artistry of the pieces produced in its various regions. The five production centres of Moroccan pottery are Fez, Safi, Sale, Marrakech and Tetouan. In most traditional ceramic sites in Morocco, the quality of the clay raw material and its availability are the guiding factors in the development of this activity. Some pottery sites have high-quality clay, which is reflected in the quality of their products (El Halim et al., 2018; El Ouahabi et al., 2019). In other sites, the raw clay material is composed of heterogeneous sedimentary and residual clays with very different colours and textures, in which case potters use mixtures of several types of clay to obtain an appropriate formulation for their manufacture (Daoudi et al., 2014; El Boudour El Idrissi et al., 2018; Hosni et al., 2021). However, in most of these sites, traditional methods of ceramic production that do not take into account these chemical...