Mineralogical study of different mortar types from historical monuments of northern Greece

Abstract

Red coloured plaster mortars and a masonry mortar sample dated from 5th c. BC to 3rd c. BC were collected from Aiani’s archaeological site, northern Greece. The mineralogical composition of the bulk mortars and the mortar surfaces were determined by μRaman spectroscopy and X-Ray Diffraction (XRD) techniques. Calcite, quartz, feldspars, dolomite, Tioxides (anatase/rutile) and clay minerals consisted the mortar samples. Serpentine, a mineral characteristic for its local provenance was found, which is related to the ophiolithic complex and the ultramafic rocks of the surrounding area. The red colour of the mortar surfaces is attributable to hematite, the raw material being iron oxides and hydroxides either from an ochre deposit or an iron-rich clay deposit. Black inclusions identified by Raman spectroscopy may be associated with carbonaceous material of an amorphous character and iron oxides and hydroxides (hematite/goethite). The presence of micaceous and clay minerals, corroborates the origin of the raw material from local Fe-rich clays.