Sandstone

Sandstone is made of clayey soil, with a high silica content, called "sandstone clay".
Fired at 1,250 - 1,310 C°, the clay becomes vitrified and produces various shades (greys, ivories, browns and beiges).
The sandstone therefore remains opaque but the intense heat gives it a very compact texture that makes it waterproof.
It is used for utilitarian and decorative pottery items.