Variazioni cromatiche delle superfici lapidee: serpentinite e calcare nero

Discusses the chromatic alterations found on stone surfaces of the facades of historic buildings and monuments in Siena (Italy). These changes, linked to stone degradation phenomena and to the presence of artificial surfaces such as previous intervention treatments, are studied discussing the methodologies of their characterization. The article also deals with the case of serpentinite and black limestone used in the facade of Siena Cathedral (S. Giorgio). It concludes with an examination of the implications in the conservation of other artworks.