Original paper

The copper slags of the Capattoli Valley, Campiglia Marittima, Italy

Manasse, Andrea; Mellini, Marcello; Viti, Cecilia


Metal mining and processing started at Capattoli (Italy) in the Etruscan time (close to VIII century B.C.) and continued during the Middle Age. At present, approximately 7,000 tons of slags (produced starting from the chalcopyrite-galena-sphalerite mineralization hosted within the Campiglia Marittima skarns) occur over a surface of 1,500 m2. The average chemical composition of the slags is 47.0 wt.% FeO, 27.5 wt.% SiO2, 9.0 wt.% CaO. Sulphur, zinc, lead and copper sum up to 7-10 wt.%. Two groups of slags can be identified, based upon the occurrence of one or two olivines (fayalite, or fayalite and kirschsteinite) and chemical compositions. Olivines crystallized at different supercooling extents, from 20 to more than 100 °C; fayalite crystallized before kirschsteinite. All the slags were obtained smelting chalcopyrite, at temperature slightly in excess of 1100 °C, using selffluxing charge and reducing conditions. The preliminary sulphur removal was uncomplete. Two-olivines slags had viscosity lower than one-olivine slags (2.29 vs. 1.58 viscosity index). Based upon the present amount of slags, we estimate a production of 700 tons of copper. The estimate rises up to 5,000 tons when historical records about the amount of removed slags are considered.