Special Studies: Naturally Deposited Versus Intentionally Applied Gypsum on Archaeological Materials from Harappa,Pakistan

Abstract

White deposits on archaeological vessels excavated at Harappa, Pakistan, were identified by x-ray diffraction analysis as pure gypsum. Because of the evenness and location of the layer it appeared to have been intentionally applied. But since we were aware that the site has an extreme salt problem there was a possibility that the layer was a post-depositional accretion. Through the comparison of x-ray diffraction (XRD) peak intensities and the crystal morphology using scanning electron microscopy (SEM) it was determined that natural and intentionally calcined/hydrated gypsum could be differentiated. This study should help archaeologists and conservators distinguish burial deposits from intentionally applied gypsum on archaeological material.