A XANES study of cobalt speciation state in blue-and-white glazes from 16th to 17th century Chinese porcelains

► Speciation of cobalt in ancient Chinese porcelain glazes studied by X-ray absorption near-edge spectroscopy. ► Blue pigmenting role of tetrahedral Co2+ ions. ► Uncertainties in deducing a formal valence state for cobalt ions from the edge energy.