Raman identification of materials used for jewellery and mosaics in Ifriqiya



Beads, rings and mosaic tessarae from Tunisia (Carthage and Utica, 1st centuries BC and AD, El Djem, 2nd–3rd centuries and Mahdia, 10th century) were analysed by Raman spectroscopy for non-destructive differentiation of various types of glasses (most have Si- and Na/Ca-rich compositions, some others are lead-containing glass) and identification of synthetic or natural minerals (crystal or stone). The results are discussed in the light of chemical analyses. A green glass is coloured by a Cr-based nanosized pigment and a red mosaic tesserae is obtained by a colloidal dispersion of gold (Cassius purple). Cassiterite (SnO2) is used as an opacifier or fluxing agent. The examination of glass mosaic and jewellery microstructure shows that some pieces are made of sintered glass, i.e. using a paste technology. Copyright © 2003 John Wiley & Sons, Ltd.