engleski

Pietra ollare (chlorite-schist) artefacts from Červar Porat (Istria, Croatia) – comparison with possible source rocks

During archaeological excavations performed between 1976 and 1980 at a Roman villa rustica in Červar Porat located close to the town Poreč (Istria peninsula, Croatia), among other Late Antique period fragments (glass, metal, ceramics), fourteen peculiar stone vessel fragments were discovered. They show characteristic tracks of the manufacturing by means of lathe. Vessels made by analogous processes from similar materials have already been found at several localities at Croatian Adriatic coast, but no systematic mineralogical study on this kind of material was performed so far. Two of these vessel fragments were investigated by X-ray powder diffraction and chemical analyses. The only constituent of the first, greenish-grey fragment (inv. no. 7912) is a chlorite group mineral. The mineral composition together with visible schistosity indicated that source material was chlorite-schist, a low–grade metamorphic rock. Such material is one of different lithologies included by Italian term pietra ollare and German Lavez. The other fragment (inv. no. 7907) is dark greenish-grey on the fresh broken surface and brownish on outer and inner vessel surfaces. Distinctive bronze colored flakes can be seen in some parts. In order to determine possible origin of analyzed fragments samples collected on localities in Italian Alps known as ancient production centers of pietra ollare vessels (Valli di Lanzo, Valle d’Aosta, Valchiavenna, and Valmalenco) were also analysed. Comparison of obtained results, which included the literature data for pietra ollare, show that the first artefact has the greatest similarity to some chlorite schists from Val Malenco.

pietra ollare; chlorite; XRD; Červar Porat; artefacts; provenance

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