A Mössbauer study of some coloured marbles (cipollino mandolato, rosso antico and fior di pesco): implications on the nature of their colour

⁵⁷Fe Mössbauer spectroscopy permits an explanation of the formation of the iron-bearing species present in three types of coloured marbles, known as cipollino mandolato, rosso antico and fior di pesco. Structural Fe²⁺ and Fe³⁺ located in silicates, together with the remains of weakly ferromagnetic hematite, arise from primary sediments. Fe²⁺ located in carbonates and anti-ferromagnetic hematite are formed by redox processes during marble formation. The relative contents of the iron species in the three types of marbles depend on the composition of the primary sediments and on local conditions during metamorphism. Knowledge of the type and amount of the iron species in marbles may help in the reconstruction of the redox processes, which took place during marble formation. The deviations of the Morin transition of the hematites play the role of genetic indicator because purity, crystallinity and the red hues of hematites in marbles can be related to the environment of formation.     

Trachytes employed for funerary artefacts in the Roman Colonies Regium Lepidi (Reggio Emilia) and Mutina (Modena) (Italy): provenance inferred by petrographic and chemical parameters and by magnetic susceptibility

Roman funerary artefacts belonging to the archaeological collections in Modena and Reggio Emilia, two important Roman colonies (Mutina and Regium Lepidi, respectively) in the Cispadane region (Northern Italy), are made of trachytes from the Euganean Hills, close to Padua. In particular, the petrographic and chemical parameters, besides magnetic susceptibility of archaeological trachytes, suggest Monte Oliveto as their main source; very few of them, however, come from Monte Rosso and Monte Merlo. Surprisingly the trachytes from Monselice, which were used extensively to get flagstones for paving the Roman roads of the Po plain, were not implied in funerary art. Possibly the porosity of stones was determinant in addressing the use of the Euganean trachytes: the stones from Monte Oliveto (and also from Monte Rosso and Monte Merlo), which contain frequent cavities and voids, are porous and might favour body decomposition, like important stones used in antiquity for sarcophagi (e.g. lapis sarcophagus). By contrast, the trachytes from Monselice are dense, not porous, hence harder and more resistant to abrasion, therefore suitable for flagstones.