Origin and growth of weathering crusts on ancient marbles in industrial atmosphere

The origin and growth of weathering crusts on the ancient marbles of ruins of the Sanctuary of Demeter in the industrial atmosphere of Eleusis in Greece have been investigated. A systematic mineralogical, petrographical and chemical examination of weathered stones and crusts was performed, both in situ and in the lab, on samples taken from different parts of the monument in relation to the surface characteristics as well as to the exposure to rain, sea-salt spray and wet and dry deposition of airborne pollutants and dust. In particular, the various material–environment interactions take place, are characterized by (a) disintegrated “washed-out” surfaces, where products are taken away through dissolution, (b) rusty yellow patinas rich in Fe and Cu, (c) firmly attached black crusts in contact with percolating water, where recrystallized calcite shields amorphous deposits rich in S, Si, Fe and carbonaceous particles, (d) black loose deposits in the water sheltered areas, consisting mainly of gypsum and fly ash particles and (e) cementitious crusts, coating and pitting the horizontal surfaces. Moreover, an interconnected evolution of various physicochemical processes is shown, characteristic of the origin and growth of various crusts, which are formed and classified accordingly.