The melting point of sodium chloride is 801 0C. The melting point of aluminium oxide is 2 072 0C.
Soft clay must be used on a potter's wheel to create pottery, and then fired in a pottery oven ADDED: It's pretty much clay-ware by the definition of "pottery"! :-) It's used because it has particular qualities that allow it to be shaped and fused by heat to produce articles that are functional, decorative - or both - in their own characteristic ways.