➢ *Clay and clay minerals*

Through thermal treatments, clay can be transformed into various clay minerals. As an aluminosilicate salt consisting of tiny particles (less than 2 μm), clay is a pliant and cohesive earthen material [16]. It is a layered silicate that is composed of alternating silicon–oxygen tetrahedrons and alumina octahedrons, and it is an appropriate precursor for preparing geopolymers [16].
