Studio dei materiali legati ad attività metallurgiche dall’isola di S. Andrea, Loppio (TN): risultati preliminari.

Metallurgical activities leave several types of traces in the area in which they take place: remnants of structures of various nature such as plain burnt, furnaces or forges, holes/containers for the collection of the products deriving from pyrotechnologic activities (charcoal, mineral, fluxing, etc.), pits for placement or storing of tools functional to the metallurgic activity, such as hoods, anvil, benches or plain of support in wood; remains of discard materials such as cinders, mineral slag, charcoal, fragments of crucibles and tuyeres, more rarely real metallic cuttings, directly related to the raw material, the semi-worked or the final products of the metallurgic activity, or tools related to the specific metallurgic job. In this paper we present the results of investigations carried out to characterize some products of metallurgic activities identified on the site of Loppio. Our results indicate that the majority of the remnants of metallurgic processes found in Loppio are associable to iron working activities, and only a minor amount to the copper or copper alloy working process. In both the cases they are not related to reduction processes (primary working), but derive from secondary working process, such as smithing activities of iron. Based on morphological and physical parameters we classified and grouped the residues of metallurgical activity found in Loppio in 11 classes, 10 of which related to the ironworking. The results of petrographic, chemical and mineralogical investigations carried out on a few samples belonging to significant classes of materials provided the early specific information on the phases and the working processes. The chemistry and the mineralogy of two samples of plano-convex bottom (PCB) smithing slag, their morphology and the abundance of this specific class of slags in the site, all suggest that the iron smithing was related to ingots of metal and /or to recycled iron, but probably not to the bloom. Further bulk analyses on these class of slags are needed to confirm this observation. Moreover the two investigated PCB slags show different mineralogical composition, compatible with different oxi-reductive conditions of production, and in one case result similar to the SFR type and in the other to the SGD one described by Serneels and Perret (2003). The presence of various types of PCB indicate a variety of ironworking processes, at various temperature, oxidation condition and produced by the use of different amounts of flux. The flux used has a silica-lime rich composition. Mineralogical analysis indicate that the temperatures of formation of the slag in the forge range between 1100-1200°C, coherently with ‘optimum’ temperature reported in literature for iron smithing. Since the excavations have not shown holes of forge, the identification of numerous remnants of walls of forge allows to hypothesize the presence of raised forges that, based on iconographic evidences are known to be used since the Roman age. In similar way the use of tuyeres, not recovered in the site, can be proven by negative imprints observed a the edges of some slag. A preliminary statistic analysis of spatial and chronological distribution of the investigated materials, suggests that the metallurgic activity possibly begun in the III Period of the Loppio site, in an area corresponding or close to the building IIIc.; evidence of metallurgical activity are also observed in contexts related to the Periods V and VI, mainly in the Buildings IIIb and IIIc and in the corridor IIIb /c and, less abundant, in the area III and possibly in the building V. However, the phenomenon of the redistribution of metallurgical remains in a working site, and the stratigraphic disturbance due to the different life phases of the site do not allow to attribute with certainty such finding to the Longobard period. The same consideration holds for the slags found in building V in layers ascribed to the VII Period, as a reworking cannot be excluded. The workmanship of the copper and /or of its leagues, is testified finally only in Buildings IIIb and IIIc and in the corridor IIIb/c, relatively to the Period V. Finally, no trace of metallurgic activity has been observed around Building I of sector A, where two metal bars were recovered from (Maurina this vol. ), indicating that the presence of metal bars in this area is not related to working activities.