Geological features, technological characterization and weathering phenomena of the Miocene Bryozoan and Lithothamnion limestones (central-southern Italy)

Bryozoan and Lithothamnion limestones (BLL) from centralsouthern Italy, commercially known as Perlato Royal Coreno, were used for a long time in the monumental architecture of the Campania and Lazio regions. In this paper, new mineralogical-petrographical and engineering geological data about BLL are reported and the relations between the lithofacial and technical features of this stone are investigated. A field survey of the main limestone outcrops allowed a lithostratigraphic reconstruction of this formation to be drawn and the eight main lithotypes presently used as dimension stones to be recognized. Mineralogical and petrographical characterization was performed by means of X-ray powder diffraction and optical microscopy observation of thin sections (under transmitted, UV-reflected light and cold cathodoluminescence). Petrophysical characterization enabled to compare some engineering-geological properties and to evaluate the influences of rock fabric, chemical composition, fractures and stylolithes on the technical features of the stone. Ageing tests were also performed. Finally the main weathering phenomena affecting the stone were recognised through a detailed study on the facades of the bell tower of the Santa Chiara monastery in Naples