Technology and Provenance of Roman Ceramics from Scoppieto, Italy: a Mineralogical and Petrological Study

Scoppieto (Terni, Italy) was an important centre devoted mainly to the production of terra sigillata vessels, lamps, and probably utilitarian pottery in the Augustean period-production, which increased sharply from the Tiberian period onwards. Several findings of coarse ware (Opus Doliare, amphorae) suggest that the site may have been active in the production of common ceramics before that of the “Terra Sigillata Italica”. However whether these materials were imported or produced on site was completely unknown until now. A collection of coarse ware, of both good quality and waste products, were characterised by mineralogical (Rietveld and calorimetric analyses) and petrological analytical techniques (XRF, LA- ICP-MS), to investigate production techniques and provenance. Rietveld analysis indicated differing contents of amorphous contents from 17% to 52%, with a mineralogical association always constituted of quartz, feldspar, plagioclase and pyroxenes, and in some cases by phyllosilicates and calcite. Considerable weight loss variations, from 0.5% to 8%, are associated with the presence of calcite and phyllosilicates. Generally, the highest weight losses were measured in the good-quality products, whereas waste products turned out to have been fired at higher temperatures than those of the breakdown of calcite and phyllosilicates. The chemical and mineralogical compositions of good-quality ceramic objects and those of waste products indicate that the unsuccessful process, which produced a large quantity of discarded materials, was due to poor control of firing temperature, not to mistakes in the mixture. Trace element abundances in good-quality and waste products are similar, indicating local production and favouring the hypothesis that Scoppieto was active since pre-Augustean times. Further constraints to this hypothesis are given by a detailed study of clinopyroxene crystals of igneous origin occurring in all the studied ceramics, compared with the chemical features of the same mineral phase present in volcanic rocks of the nearby Roman Magmatic Province. Geochemical results indicate that the rocks of the Bolsena Volcanic Complex, located near the Scoppieto production site, were probably the volcanic starting materials, used as refractory components in the ceramics examined here.