Abstract: A method of forming bricks, tiles, and the like by treating clay, shale or other clay ceramic raw materials containing pyrite is disclosed. Such clay, ceramic raw materials may be ground, and then mixed with an oxidizer in a pre-oxidation step to disperse the oxidizer within the clay to expose the maximum amount of clay surface to the oxidizer. One oxidizer that may be used is an aqueous solution of hydrogen peroxide. Clay is shaped into clay products and then heated to elevated temperatures. Pyrite within the clay is oxidized, thereby removing sulfur-containing compounds such as sulfur dioxide from the clay. The application of the invention may assist in preventing efflorescense by ensuring complete or nearly complete removal of pyrite from products oxidation treatment and subsequent firing at elevated temperatures. Similarly, by enhancing the oxidation of pyrite, faster firing cycles may be possible which facilitates reduced fuel consumption and faster process time.