BRICK AND STUCCO
Colour did not play a major decorative role in the earliest mosques. Instead, much emphasis was placed on using the building materials themselves, most commonly brick, to create a decorative effect. In its simplest form, this technique consisted of placing the bricks alternately on their short or long sides to create zigzag motifs. At Marâgheh and Kharaqân, a more sophisticated use of bricks of different sizes, some of with a solely decorative function, gives extremely successful and more complex results.
A second very widespread, decorative method was carved stucco, or gach. This was either applied to entire walls, or restricted to a particular architectural feature, such as the mehrab, a gate, or niches (Nâin, Ardestân, Dâmghân). Stucco had the advantage of being a relatively cheap and abundant material, easy to work and long-lasting. Examples of decorative stucco have been found that date back to the Parthian and Sassanian dynasties, but the most complex and the most beautiful stucco work was executed in the Islamic period, between the 11th and the 14th centuries. The mehrab of Sultan Uljaitu in the Friday Mosque in Isfahan is one of the best preserved pieces; its decoration is of extraordinary intricacy, resembling in places the finest of lacework.