(a)
(b)
Figure 17: TEM results of Hagia Sophia mortars: (a) amorphous C-S-H gel formation developed between crystalline phases of calcite and the dispersed ceramic fragments and quartz crystals in a mortar sample from Hagia Sophia, magnification: ×22,000; (b) the C-S-H gel presents a sheet structure, while in certain areas (lower left of image) quasi-crystalline phases are discerned, in the dome rib mortar sample from Hagia Sophia, magnification: ×42,000.