Maya blue: application of XAS and HRTEM to materials science in art and archaeology

Maya blue is a famous blue pigment composed of palygorskite clay and indigo. It was used by the ancient Maya and provides a dramatic background for some of the most impressive murals throughout Mesoamerica. Despite exposure to acids, alkalis, and chemical solvents, the color of the Maya blue pigment remains unaltered. Herein, we present studies on the role of iron in authentic and synthetic samples of Maya blue using X-ray absorption spectroscopy (XAS) and high-resolution transmission electron microscopy (HRTEM). Iron nanoparticles were found outside the lattice of the crystallites of palygorskite as well as inside the channels. Iron oxide and an amorphous phase of FeO(OH) were also found in authentic samples of Maya blue, and may contribute to the optical properties of the pigment or in the characteristic brilliant color. (C) 2002 Elsevier Science B.V. All rights reserved.