The first part of the paper discusses the identity, origin and impurities of the cobalt ores used as the coloring agent in Chinese blue and white porcelain dating from the fourteenth to the present century. Both Western and modern Chinese sources and analyses are cited. The second part contains the author's translations, comments and annotations to early Chinese texts relevant to cobalt blue. The author concludes that cobalt importation began in the fifteenth century but ceased around the seventeenth century and resumed in the twentieth century. During the eighteenth and nineteenth centuries local ores were used.