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

Metal mining and processing started at Capattoli (Italy) in the Etruscan ti me (close to VIII century B.C.) and continued during the Middle Age. At pre sent, approximately 7,000 tons of slags (produced starting from the chalcop yrite-galena-sphalerite mineralization hosted within the Campiglia Marittim a skarns) occur over a surface of 1,500 m(2). The average chemical composition of the slags is 47.0 wt.% FeO, 27.5 wt.% S iO2, 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 compositio ns. Olivines crystallized at different supercooling extents, from 20 to mor e than 100 degreesC; fayalite crystallized before kirschsteinite. All the slags were obtained smelting chalcopyrite, at temperature slightly in excess of 1100 degreesC, using self-fluxing charge and reducing conditio ns. The preliminary sulphur removal was uncomplete. Two-olivines slags had viscosity lower than one-olivine slags (2.29 vs. 1.58 viscosity index). Bas ed upon the present amount of slags, we estimate a production of 700 tons o f copper. The estimate rises up to 5,000 tons when historical records about the amount of removed slags are considered.