Understanding the mineralogical composition of Ancient Greek pottery through Raman microprobe spectroscopy

Mineralogical studies using Raman microprobe spectroscopy and high-magnification optical spectroscopy were performed on sherds of pottery vessels that were used as cooking pots and water jars in Hellenistic Greece (third and second century BC). Of specific interest was the mineralogical identification of the so-called inclusions, which are phases that morphologically stand out from the fired clay matrix and result from the presence of inorganic temper in the original paste mixture. The sizes of mono- and polymineralic inclusions in the sherds range from 5 mum to 2 mm. The combined use of Raman microprobe spectroscopy and incident-light optical microscopy permits identification of specific minerals (such as quartz, albite, calcite, hematite, anhydrite, epidote, rutile, anatase, and apatite) in various different types of inclusions and then visual evaluation of the abundance of those minerals in each sample. The application of our nondestructive analytical approach is documented on a set of four sherds (each on the order of several cm(2)) from excavations of the ancient Agora of Athens. The information on the mineralogy obtained via Raman spectroscopy can shed light on the provenance of the raw materials and firing conditions of the pottery and thus aids archeologists with their historical interpretations.