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Yellow patina formed on the stone surfaces of historical buildings, monuments, and archaeological structures due to weathering is considered a value of the building in the conservation of cultural heritage studies. Although yellow patina layers can be easily distinguished on white marble surfaces, it is not possible to distinguish them on the yellow travertine surfaces with the naked eye. It should be taken into account in yellow travertines as well as marble surfaces before conservation treatments of the stone. In this study, mineralogical and chemical compositions and the thicknesses of yellow patina layers formed on yellow travertine and marble surfaces in Aizanoi, Aphrodisias, and Hierapolis archaeological sites in Turkey were analyzed in order to constitute a conservation approach in the archaeological sites. In this respect, XRD, FT-IR, SEM-EDX, and LIBS were used in the determination of compositions and thicknesses of yellow patina. Although LIBS analysis is a more convenient method to investigate patina layers on stone surfaces, this technique is not as well known as the others. Yellow patina layers contained calcium oxalate in the form of whewellite (CaC2O4.H2O). Their thicknesses were between 15 and 100 μm and should be protective against weathering on travertine and marble surfaces. LIBS analysis seems to be the most convenient micro-destructive method to estimate the thickness of the yellow patina layers on the marble and yellow travertine surfaces. The determination of the thickness of the yellow patina is critical to keep irreversible cleaning interventions, especially for the yellow travertines due to their similar colors. Yellow patina is mainly composed of calcium oxalate with clay minerals and organic compounds. [ABSTRACT FROM AUTHOR]

Weathering and mineralogical processes observed in a marble quarry in Turkey are compared with similar processes occurring on monument surfaces. Patina formations (microstromatolitic, microlaminated, monolayered) as well as destructive processes (mainly biopitting and bioerosion) are associated with microbial colonisation of the rock surfaces and one influenced by microclimatic conditions. Patina stratification is independent of substrate rock, but is affected by the position and orientation of rock surfaces. The different layers formed by mineralisation processes may reflect the seasonality of climatic events and the consequent colonisation. Bio-deteriorative processes take place mainly when the climatic conditions cause the organisms to live below the surface. [ABSTRACT FROM AUTHOR]