Filière de l'argent au haut Moyen Age – FAHMA

The purpose of this project is to tackle some unsolved problems of the economic and monetary history and of the history of the techniques by coupling a method of analysis almost non destructive: laser ablation - inductively coupled plasma - mass spectrometry with lead isotope analysis. Our objective are to study certain problems related to silver production in the Middle Age by coupling chemical analysis (trace elements) and lead isotope analysis of all the products and by-products of this industry. We are interested in the mineral source from which the white metal is produced, to silver and its use as a monetary metal. This approach of the production line of the silver since its origin up to the monetary object also includes by-products of this sector, too long ignored, that are lead and slag. The historic setting of this study began in the late seventh century AD and ends at the end of the thirteenth century. The geographic frame centred at first on the French space will be expanded following the commercial circuits of the reporting period. This period was the least studied by mining archaeology and the best known example stays that of Melle (Poitou-Charente). It will serve as a starting point for our study. This exploitation was one of the largest, if not the first, silver production center of the Carolingian Empire. Several technical innovations characterize the chaine operatoire used for the production of the noble metal. Another major interest of this mine is the presence on the site of a monetary workshop of first importance for the economy of the Carolingian empire. The masses of silver obtained continued to influence the regional economy long after the abandonment of mines. To remedy the lack of archaeological information, a geochemical approach of the other deposits will be carried out in a second time to identify other potential sources of supply for the metal. According to the result, Melle may be defined as a model or an exception. From a monetary point of view, this period is characterized by the transition to the exclusive currency of the silver in the Western Europe at the end of the Merovingian era. The study of Carolingian and post Carolingian coinages should allow: -To follow the distribution and the dilution (in the space and in the time) of the metal produced in Melle, -To try to distinguish the various metal sources of supply, -To measure the intensity of the currency circulation, -And to understand patterns and rhythms of the renewal of the monetary stock. There is a clear relationship between extraction of silver and monetary manufacturing in the early days of the medieval Europe. Yet it is no longer possible to ignore the sub products from this industry. The case of Melle has shown the importance that they can acquire. It is not insignificant that apart from monetary documents, the only text attached to the metal in Melle deals with the production of lead. Let us remind that with the most common ore of silver - the galena-, production from 1 to 3 kg of fine silver entails production of a ton of lead. This metal, certainly at the origin of first metal industries, is also the one that was the most widely produced for historical periods. But the history of lead remains to be done as indicated by A. Guillerme. Yet virtually ignored the role of primary smelting slag as raw material deserves to be enlightened. Their reprocessings to get back the desired metal trapped in the glassy phase of the slag end up with the formation of a raw material in the form of crushed glass. One of uses put in evidence is their valuation towards the glass industry. The studies carried out so far by our laboratory have indeed highlighted the use of slag produced in Melle to manufacture glass pebbles at the Carolingian period. It was also during this period that appear in Europe different glass types containing more or less important amount of lead (glasses produced with soda or potash and lead flux containing some % of lead until glasses using only a lead flux containing up to 80 % of oxide of lead in the case of some beads and rings). It is legitimate to look at the nature of the lead used in the glass industry (slag, lead work, litharge'), in its origin, as well as the relationship between silver production centres and glass workshops of developing these types of glass.