Abstract:

Hagia Sophia, where is located on the Historical Peninsula in Istanbul, was built on the order of Emperor Justinian I of the Byzantium Empire. The construction work began in 532 AD and the building was finished in 537 AD. From the date of its dedication in 537 AD until 1453 AD, it served first as a basilica and then served as a mosque from 1453 until 1931. It is declared as a museum in 1934.The essential building material of Hagia Sophia is natural stone. Natural stones of different origins were used as ornamental, structural and coating on interior and exterior parts of the building. The natural stones used in the building mainly used to be supplied from nearby districts; however, some natural stones in a large spectrum of colors and textures were also supplied from abroad. Especially, Proconnesos Marmara Island marble, Bakırköy Istanbul fossiliferous limestone küfeki stone , Hereke Nikomedia conglomerate pudding stone , Dokimeion Afyon-İscehisar brecciated marble, Gebze Bithynia fossiliferous limestone, Muğla Caria bordeaux marble, Troad Çanakkale-Kestanbol granite and Karamürsel Nikomedia dasitic tuffs fire stone within the country are among the most important of these miscellaneous natural stones, in addition to some colored natural stones such as Aswan syenite Egypt , red andesite porphyry Egypt , yellow alabaster Egypt , green dacite porphyry Greece , serpentine breccia Greece , yellow limestone Tunisia and Pyrenean brecciated marble France from abroad. Also, some of them collected from other antique temples and their remains were reused in the construction of the building. From construction time of the building until today, some natural stones used in exterior parts were especially affected by atmospheric conditions and exposed to physical, chemical and biological weathering phenomena.This study focuses on geological characteristics of natural stones used in the construction of Hagia Sophia, their origins and places of use, and the determination of causes and types of weathering as commentary on their state of conservation in today

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