An investigation of unworked lumps of Cu-based materials (“Aes Rude”?) from two Etruscan sites.

33 metallic lumps with centimetre size and variable (from uneven to roughly parallelepiped) shapes from the Etruscan sites of Lago degli Idoli (Stia, Arezzo) and Marzabotto (Bo), have been analyzed by means of several methods (including XRD; reflected and transmitted light microscopy; SEM/EDS; EMPA; Micro-beam PIXE; TIMS) in order to characterize their mineralogy, textures, chemistry and lead isotope signature and to obtain clues to their meaning, fabrication techniques and provenances. Two main types of Aes Rude lumps have been distinguished. A first type (called “A”) has been found only at Lago degli Idoli (5 samples), and is represented by iron-free copper grains with equiaxed texture and common Cu-Cu2O eutectic intergrowths, commonly including droplets of Cu-Fe(Zn) sulfides and fayalitic slag fragments. The large majority of investigated items (28 samples) from both localities belong to “B”-type class, and are characterized by high amounts of α-iron dendrites and inclusions of Fe-Cu sulfides dispersed in a iron-bearing, ε-copper groundmass; scattered droplets of silicate slags and Cu-Fe(Zn) sulfides have been identified as well. In this second type of lumps, total iron may amount up to over 60%wt. PIXE’s micro-analyses also detected trace amounts of Ag, As, Sb in Cu phases, Mo and Co in iron droplets, and Pb. All the above features suggest that “A”-type lumps are refined copper ingots, resulting from smelting of sulfidic ores and subsequent remelting in a partially oxidizing atmosphere. On the other hand, “B”-type metal findings can be classified as “traditional”Aes Rude, a class of pre-monetary units employed by Etruscans and other peoples of Central Italy between VI and the III Cent. BC. They are probably the result of casting the as-smelted raw copper tapped directly from a furnace where polymetallic sulfides (with high iron contents) had undergone smelting in a reducing atmosphere. Six samples of “B”-type Aes Rude have been analyzed by TIMS for provenance studies. Three lumps from Lago degli Idoli show Pb isotope composition in agreement with a provenance from the Southern Tuscany polymetallic districts. On the other hand, a fourth sample from this locality and the two from Marzabotto show significantly different compositions.