The sandstone is ceramic which is characterized by its high hardness and resistance to external agents. It is called stoneware or "stone object" and it lives up to its name and function because sandstone has long been used for architectural decoration. These characteristics are due to its composition. Indeed, the stoneware contains a lot of silica and its firing can reach 1300 C thus, causing vitrification of the material.  If the stoneware has a red color, it is because it was fired in a reducing atmosphere, in an oven deprived of oxygen. On the contrary, if its color is gray,...