Origin of Roman worked stones from St. Saturno christian Basilica (south Sardinia, Italy)

The work aims to define the origin of the architectural stone elements worked by Romans and reused in the St. Saturno Basilica, between the late Antiquity and Romanesque periods. Thus, different rocks (marbles, various facies of limestones, volcanic rocks) used to construct the ancient building were sampled and analysed. All the different kinds of stones were sampled from the Basilica, taking precise reference to the various construction phases and structural changes of the monument occurred in the centuries. The sedimentary and volcanic lithologies belong to the local outcrops of Cagliari Miocenic geological formation (e.g. limestone) and to other volcanic outcrops of south Sardinia, respectively. By means of a multi-method archaeometric study (mineralogical-petrographic observations on thin sections and O-18 vs C-13 stable isotope ratio analysis), the provenance of classical marbles used for manufacturing Roman architectural elements (column shafts, bases, capitals, slabs, etc.) were defined, which are thought to come from extra-regional sources. The results show that the marbles come mainly from Apuan Alps (Italy) and subordinately from Greek quarrying areas

Pyroclastic Stones as Building Materials in Medieval Romanesque Architecture of Sardinia (Italy): Chemical-Physical Features of Rocks and Associated Alterations

The paper discusses the chemical-physical-petrographic features and decay processes of San Nicola Church (11th−14th century) building materials, one of the most representative Medieval Churches in Sardinia, stylistically attributable to the Romanesque architecture. The monument was built up into two stages and shows a characteristic size uniformity of the ashlars. The masonry is mainly made up of rhyodacitic pyroclastites belonging to the Sardinian Eocene-Miocene mag- matic phase (38–15 My). These volcanic rocks were widely used in Medieval architecture for the excellent workability, but its minero-petrographic features greatly favor the decay, due to the action of chemical-physical alteration processes. Although the alteration degree and macroscopic forms of decay vary from zone to zone in the monument, according to the different compositional features of the volcanic stones, weathering and exposure condition, the pyroclastic rocks are generally affected by greater alteration than other igneous lithotypes, due to their petrographic- volcanological characteristics (e.g., low-medium welding grade, medium-high porosity). The results concerning mineralogical and petrographic features, respectively, carried out by the application of X-Ray Powder Diffraction (XRPD), Optical Microscope (OM), and Scanning Electron Microscope (SEM) techniques, both on fresh building rocks and associated alterations, are here presented and discussed. Furthermore, the relationships between fresh pyroclastites and altera- tion processes affecting these rocks will be discussed

Pyroclastic Stones as Building Materials in Medieval Romanesque Architecture of Sardinia (Italy): Chemical-Physical Features of Rocks and Associated Alterations

The paper discusses the chemical-physical-petrographic features and decay processes of San Nicola Church (11th−14th century) building materials, one of the most representative Medieval Churches in Sardinia, stylistically attributable to the Romanesque architecture. The monument was built up into two stages and shows a characteristic size uniformity of the ashlars. The masonry is mainly made up of rhyodacitic pyroclastites belonging to the Sardinian Eocene-Miocene magmatic phase (38–15 My). These volcanic rocks were widely used in Medieval architecture for the excellent workability, but its minero-petrographic features greatly favor the decay, due to the action of chemical-physical alteration processes. Although the alteration degree and macroscopic forms of decay vary from zone to zone in the monument, according to the different compositional features of the volcanic stones, weathering and exposure condition, the pyroclastic rocks are generally affected by greater alteration than other igneous lithotypes, due to their petrographic-volcanological characteristics (e.g., low-medium welding grade, medium-high porosity). The results concerning mineralogical and petrographic features, respectively, carried out by the application of X-Ray Powder Diffraction (XRPD), Optical Microscope (OM), and Scanning Electron Microscope (SEM) techniques, both on fresh building rocks and associated alterations, are here presented and discussed. Furthermore, the relationships between fresh pyroclastites and alteration processes affecting these rocks will be discussed

Archaeometric approach for studying architectural earthenwares from the archaeological site of s. Omobono (Rome-Italy)

This paper reports the findings of an archaeometric study performed on 14 architectural earthenwares from the archaeological site of S. Omobono, located in the historic center of Rome (Italy). The archaeological site, accidentally discovered in 1937, includes the remains of a sacred area previously occupied by two temples, one of which was converted into the church of S. Omobono, in 1575. The samples, dated between the 7th and the 6th century BC, belong to different sectors of the site. Their petrographic, mineralogical and geochemical characterization was performed by optical microscopy (OM), X-ray powder diffraction (XRPD), X-ray fluorescence (XRF), electron probe micro-analysis (EPMA), and Raman spectroscopy (RS). The compositional data obtained were also subjected to the principal component analysis (PCA) in order to highlight similarities and differences among the samples. By combining geochemical and petrographic data, we were able to identify several different fabrics. Furthermore, the study provided valuable information on the firing temperatures of some samples and the provenance of the raw materials, by analyzing the chemical composition of clinopyroxenes present as non-plastic inclusions. View Full-Tex

E.Stone, an archive for the Sardinia monumental witnesses

The “E.Stone” project is based on the survey, documentation investigation and physical, geochemical and petrographic characterisation of the great zoomorphic and phytomorphic stones of Sardinia. The name chosen to indicate this project means the full value of these stones, standing before the beginning of human history. The main task of this project is the investigation and the documentation, based on an accurate digital survey, taken by laser scanner units supported by topographical survey and integrated by GPS tracing and photographic and photogrammetric survey, with a meaningful research aimed to specific investigations on the rock characteristics. The further development of the collected data will be aimed to the definition of a digital “state of the knowledge” about the stone. This research will produce two main benefits: the creation of a clear and stable archive of these monuments oriented to be a preservation tool and the opportunity to allow the reply, at any distance, a copy in any material of the original item