Ghaznavid glazed pottery investigated by SEM-EDS and micro-Raman spectroscopy

The analysed fragments are part of a large group of shards presently kept in the International Museum of Ceramics in Faenza. They were excavated at Bust and Lashkar-i Bazar (southern Afghanistan) and are dated from between the tenth and the twelfth century AD, when the area was first ruled by the Ghaznavid and later by the Ghurid dynasties. Scanning electron microscopy coupled with energy dispersion X-ray analysis (SEM-EDS) and micro-Raman spectroscopy (micro-RS) were employed to investigate cross sections obtained by sampling the archaeological shards. These were characterized by highly calcareous bodies (11-17 wt% CaO) and feature a transparent lead glaze (50-70 wt% PbO). With few exceptions, the studied fragments show an underglaze decoration featuring white, red, or black motifs obtained by selected superimposition and engraving of differently coloured clayey layers applied onto a white, red or black engobe. An intriguing aspect concerns black engobes and decorative motifs, which are characterised by particles of chromium, magnesium and iron compounds or by manganese compounds. It further appears that different black decorative motifs were obtained by using different materials on the same object. As concerns manganese containing compounds, micro-RS allowed us to recognize hausmannite as the main colouring agent in engobes and jacobsite in the manganese-based decorations.