Stones of the façade of the Sarno Baths, Pompeii: A mindful construction choice

tThe lithological analysis of the southern fac¸ ade of the Sarno Baths, a complex building located in thesouth-western part of the ancient city of Pompeii (Naples, southern Italy), was addressed to define thetypes of stone used as blocks and ashlars of the three nearly completely preserved levels. Lithologicalanalysis, coupled with petrographic (optical and electron microscopy) and mineralogical study of thelithotypes macroscopically defined, revealed the use mainly of volcanic and volcano-clastic rocks, and inparticular of: (i) yellow tuff supplied from the yellow facies of the Campanian Ignimbrite (about 39 ky BP);(ii) grey tuff from the Campanian Ignimbrite; (iii) leucite phonolitic tephrite from the lava flows of SommaVesuvius; (iv) travertine from the Sarno limestone (Calcare del Sarno) (Cretaceous). On the basis of thelithological mapping, the basement results mainly composed of leucite phonolitic tephrite, associated totravertine and sporadically to yellow tuff, whereas the other two overhead levels are mainly constitutedby tuff and travertine, respectively. In particular, the tuff distribution on the level upon the basementshows a prevalence of grey tuff on the western portion, yellow tuff on the eastern one and in the opusreticulatum band running all along the fac¸ ade, and marked at the top by a trachyte stringcourse. Travertineblocks in the uppermost fac¸ ade were probably placed as integration during the restoration works carriedout at the end of the 19th century. The distribution on the fac¸ ade of elements made of different rock types,characterised by different bulk density and mechanical properties, confirms ancient Roman builders’ deepknowledge on the technical features of these materials and their structural behaviour.