Mechanism of formation of wittichenite rims around native bismuth in chalcocite and bornite from Längban, Sweden

Veins of sulfide ore comprising chalcopyrite, bornite and chalcocite are confined to skarn and oxide ore in a dolomitic host rock at Långban, Sweden. “Reaction rims” of wittichenite around grains of native bismuth occur in bornite/chalcocite ore. This texture may be explained by localized, postmetamorphic, supergene enrichment of copper. Rapid formation of bornite and chalcocite through replacement of metamorphosed sulfides is indicated, while simultaneous formation of wittichenite took place at a slower rate.