The tilework is a unique feature of the blue mosques of . In the old days, Kashan and Tabriz were the two famous centers of Iranian mosaic and tile industry. The earliest evidence of Tile working on architectural surfaces dates back to 450 A.H; the minaret of Damascus Masjid-i-Jame is a typical Tile working of that time. The surface of the minaret is decorated by geometrical forms using brick making methods. The epigraphic part of it is ornamented by turquoise enameled tiles. Domed Shabestan( part of a mosque designed for sleeping or nocturnal prayers)of Qazvin Masjid-i-Jame mosque(509 A.H) has a ornamented border by small turquoise tiles which is a prominent example of Tile working in the interior decoration of the buildings in Iran. UP to 7th A.H century, the used material for tile making was mud but in the 6th century a handmade material famed as Chinese Paste or Stone Paste became popular and was common in Egypt, Syria and Iran. In Seljuk reign and the period before the initiation of 7th century, the tile production was highly developed. The main center of Tile production was Kashan city. Different kinds of tiles were produced using different techniques there. Hexagon and octagon stars, Cross shaped and hex angle forms were combined to beautify the plinths of the inner parts of the buildings. Square or rectangle tablet form tiles were used in the upper parts of the plinths as their borders. Some of the tiles were casted in reliefs while the others were flat and their only ornament was their colors.