A Brief History of Colored Clays
Colored clay techniques involving colorants deliberately mixed into the clay were first used approximately 2000 BC in Egyptian amulets and figurines, where copper oxide was combined with clay materials to get a range of green and blue colors.   About 1200 years ago, Chinese potters of the Tang Dynasty incorporated marbleized and patterned clays into wheel-thrown and handbuilt forms that were low-fired with a lead glaze.  Within several hundred years, Sung Dynasty potters were coloring porcelain clay with iron oxide and creating a variety of patterns in platters and other vessels.