A series of ancient Egyptian mortars were extracted from the Khafra Valley Temple, and from the Sphinx face. X-ray diffraction studies revealed, at room temperature in most of the samples, the presence of gypsum, calcite, and silica in variable proportions. None of the calcium silicates found in the case of the Sphinx body core and North side chest were observed in the present study. Heat-treatment of the mortar samples for various periods of time at ~ 110°C indicated the prevalence of the gypsum phase up to a duration of heating one hour. In some of the mortars, the gamma-CaSO* l4*s modification was observed to exist up to a temperature of 350°. -- AATA