For the first time the detailed study of morphology of gypsum crystals and bioinert interactions on surface of carbonate rocks in urban environment (for Carrara and Ruskcala marble, Putila limestone and tufa) was carried out. There is shown a dependence of degree of their sulfatization, morphology and size of formed gypsum crystals on porosity and fissuring of rocks, and on the form of monument. Three stages in formation of the gypsum-rich patina as developing with an active participation of microorganisms arc described.