Eighty sherds from nine different kiln sites representing a wide geographic distribution and a long time span of Korean celadon culture are analysed for macroscopic and compositional characteristics. Additionally chemical and mineral compositions of six unglazed sherds are compared with those of some modern raw materials. Unusually high values of alumina in the earliest Kangjin pieces of the middle ninth and early tenth century (I1) could represent a significant technological innovation at the end of this period at this most important celadon production centre. Similarity in chemical and mineral compositions between unglazed sherds and some raw materials such as Kangjin clay and pottery stone show the possibility that many of the celadons were made from these types of raw materials as found in nature without additives and only after mechanical refining.