The sandstone in Bologna, Petra and Mtskheta: investigation by SEM microanalysis and petrographic characterization
Bruni S., Indirli M., Maino G., Marghella G., Marzo A. , Moretti L.
Poster Conferenza Internazionale con referaggio
In this work some results are shown relevant to applications of scanning electron microscopy and microanalysis for the study of some samples of sandstone from Orsi-Marconi building in Bologna, Italy, from the Khazneh - Treasures House in Petra, Jordan, and the Holy Cross cathedral of Jvari, Mtskheta, Georgia, the latter two monuments belonging to the Unesco world cultural heritage patrimony. Orsi-Marconi building in Bologna was built by a famous architect, Antonio Terribilia, in the middle of XVI century. The Orsi-Marconi building is one of the most notable architectures in Bologna. It has an important front with many sandstone ornaments. SEM analysis shows a characteristic fine grain with silicate cluster formed by some small and round quartz elements in carbonate matrix. This morphological appearance confirms the hypothesis that this sandstone derives from the reworking of oldest earth sediments. The sandstones have a yellow-grey colour due to the presence of quartz crystals and to small concentrations of limonite dispersed in the matrix. EDXRS system microanalysis and the Analysis SEMQuant results show the high concentration of coal in carbonate matrix and the presence of silica and also calcium. This mineralogical composition is typical of sandstones of Bolognese Appennines, with a high concentration of calcium carbonate. According to Luigi Fantini, a renowed bolognese archaeologist, the yellow sandstone, very probably, comes from Varignana quarry, near Castel San Pietro Terme. This kind of sandstone was used by the Romans and subsequently for decorative purposes, in many artistic monuments in Bologna. As for Petra samples, EDXRS system microanalysis and the Analysis SEMQuant results show the high concentration of silica, the presence of aluminium; the sample should be identified as quartz sand. The concentration of iron is lower than in the previous gray Petra sample. It is possible that the color depends on the state of oxidation of iron and on the concentration of iron that it gives a different color in Petra sample. Indeed, the concentration of iron in red Petra sample is higher than in gray Petra sample. Finally, further results are discussed about sandstone of Medieval Georgian Jvari cathedral.
Bruni S., Indirli M., Maino G., Marghella G., Marzo A. , Moretti L. "The sandstone in Bologna, Petra and Mtskheta: investigation by SEM microanalysis and petrographic characterization" EMAS 2012 Regional workshop