The mystery of plattenschlake in protohistoric copper smelting: early evidence at the Early Bronze Age site of Saint Veran, French Alps

Thin low viscous plate slags, the so-called Plattenschlacke, are one of the 3 types of slags systematically encountered at Middle and Late Bronze Age copper smelting sites in the Alps. The two other types are coarse cake-like slags, and finely crushed slag sand. The exact origin of these different types of slags within the smelting process, and particularly that of the Plattenschlacke is still debated: do they belong to the same unique smelting step, or do they refer to separate operations? With respect to this issue, the Early Bronze Age (EBA) copper production site of Saint-Véran (Hautes-Alpes, France), one of the earliest copper mass production centre in the Alps, occupies an exceptional situation. Indeed, it provides not only one of the first evidence of Plattenschlacke in the Alps, but also Plattenschlacke is the only type of slags produced there. This paper aims at exploring further the "Plattenschlacke mystery" by proposing a reconstruction of the smelting process performed at Saint-Véran during the EBA, on the basis of thorough analytical investigation of the local Plattenschlacke. Conventional (OM, SEM-EDS, PIXE) as well as more unusual analytieal techniques were used, including Raman micro-spectrometry, Rietveld refmement on X-ray diffraction patterns, as well as micro-XANES.