A giessenite-cosalite-galena-bearing mineral suite from the Bjørkåsen sulphide deposit at Ofoten in northern Norway

Giessenite Pb9Cu0.5Bi6Sb1s20 known only from its type locality at Binnatal in Switzerland has been found in a mineral suite from the Bjorkåsen sulphide deposit at Ofoten in northern Norway. It occurs as fine needles in quartz and as elongated grains in contact with galena and pyrrhotite. Mineral 'B' (Bi2Cu4Fe5Pb6S16) present as lamellae in galena in insufficient amounts to permit a complete mineralogical investigation is a new mineral (Karup-Møller 1971). Additional minerals are chalcopyrite, pyrite, sphalerite, cosalite, joseite, breithauptite, ullmannite, stannite, machiwanite, bismuth, two secondary bismuth minerals and secondary calcium-bearing gangue minerals. Galena contains a great variety of minerals shaped as lamellae. The textural relationships of these suggest that they formed directly from the mineralizing fluids and not during exsolution from their galena host. The relationships between the other sulphides are described. The temperature of formation is concluded to lie somewhere between 200 and 269 °C.