A NEW OCCURRENCE OF LAROSITE FROM THE TINNSJÅ Cu–Ag DEPOSIT, TELEMARK COUNTY, NORWAY. I. PARAGENESIS AND CHEMICAL COMPOSITION

A second occurrence of the Cu–Pb–Bi sulfosalt larosite, ideally (Cu,Ag) 21 PbBiS 13 , is described from Cu–Ag vein mineralization associated with an amphibolite dyke at Tinnsja, southern Norway. The host assemblage consists of bornite – chalcocite – magnetite – wittichenite (± chalcopyrite, digenite, stromeyerite) and closely resembles that from the type locality Larosite crystals present an acicular morphology ( 20.47 Ag 3.68 Fe 0.22 Pb 1.01 Bi 1.06 S 15.00 calculated on the basis of 15 S atoms.