Identification of Materials and Colorants in Decorative Mosaic Tiles of Musalla Historical Building in Mashhad

The Mashhad Musalla is one of the largest and most beautiful historic musallas in Iran. Mashhad Musalla has been built during the Safavid Empire, ordered by Suleiman I. Tile's inscription on the Iwan of Musalla gateway gives the date of the end of construction, in the year 1087 AH. This monument is located at the east of Mashhad. The building has a high porch and two porticoes on both sides. Musalla of Mashhad is constructed of bricks and it was previously using for prayers of the two Eids. The building has been decorated with stucco decoration, tile-working, wall painting and Muqarnas. The building is decorated with stucco decoration, tile-working, painting and Muqarnas. The glazed tile decorations of the Mashhad Musalla include glazed haft-rang and mosaic tiles. During Safavid period, all religious buildings were embellished with tiling decorations. The most prominent decorative element in Mashhad Musalla is tile-working. The tiles in the Mashhad Musalla are predominantly white, black, blue, turquoise, green, yellow and brown. The subject studied in this paper is the creating colorants elements and identification of the chemical composition of the glazed tiles in Mashhad Musalla. Scientific and analytical research was done by Scanning electron microscopy in combination with energy dispersive X-ray microanalysis (SEM-EDX) and Polarized light microscopy (PLM). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to determine the elemental compositions of the tile glazes. According to the results obtained, tin (II) oxide together with lead glaze has yielded white color, manganese oxide had been responsible for black color, cobalt (II) together with magnesium oxide and fluorine has yielded blue color, copper oxide was responsible of the turquoise color, lead glaze with the low content of iron oxides has yielded a brown hue, yellow color is attained by lead antimonite and copper oxide together with lead glaze had been responsible for green color. The comparison of the results of the chemical analysis of the Safavid glazed tiles in historic Musalla of Mashhad and results obtained by other scholars who have worked on the identification of the elemental composition of the glaze of Safavid tiles in the other monuments of Iran, indicated that the creating colorant elements were the same, with a little difference, during the seventeenth century and over the Safavid period in Iran. Finally, thin-section analysis under a polarizing microscope was applied to study the petrographic composition on the tile samples. The results of structural study and mineralogical composition of the body mosaic tiles of Mashhad historical Musalla by petrography method showed that the presence of Muscovite, Hornblendes, Biotite, Quartz and Feldspar minerals as the main crystalline phases within the samples. Based on the applied methods, the mineralogical analysis of tile bodies has revealed some considerable results on the composition of this kind of tiles. Apart from minor differences related to the groundmass composition, all the tile bodies examined by thin-section analysis show similar microstructure characteristics and analogous petrographic compositions. On the other hand, the results of the elemental analysis of the glaze of Safavid tiles and considering little difference between chemical composition of the Safavid glazed tiles of the Mashhad historical Musalla and the elemental composition of the glaze of Safavid tiles in the other regions of Iran, it can be deduced that the raw materials used have probably been provided from the local resources.