Balkanite from the Cu ore deposit Rohrerbuhel, Kitzbuhel (N-Tyrol, Austria)
Steiner, Martin; Tropper, Peter; Vavtar, Franz; Kaindl, Reinhard; Krismer, Matthias
published: Apr 1, 2010
ArtNo. ESP154018702006, Price: 29.00 €
Mineralogical investigations of the Cu ore deposit Röhrerbühel in the Eastern Alps yielded the occurrence of the extremely rare Cu-Ag sulfide balkanite. Thes deposit is located in the Kitzbühel Alps, 7 km north of Kitzbühel (Tyrol), in the Palaeozoic metasediments (Wildschönau Schists) of the western Greywacke Zone, in the lowermost tectonic unit, the Alpbach Unit. Petrography revealed that the primary ore assemblage is chalcopyrite, a fahlore-group mineral, pyrite, and bornite. As secondary minerals idaite, linneite, millerite, covelline, malachite, azurite, and rare Ag-bearing minerals namely pyrargyrite, an additional Ag-bearing sulfide and an amalgam-group mineral occur. The fahlore-group mineral from the Röhrerbühel deposit was analysed with electron microprobe analysis (EMPA) and showed high concentrations of Sb and Fe and was identified as Fe-tetrahedrite. In addition to Fe-tetrahedrite the extremely rare Ag-bearing minerals were also analysed. The Ag-bearing sulfide is balkanite, which is in accordance with its optical properties and the amalgam-group mineral could be identified as eugenite (Ag 75-83 wt.%, Hg 11-17 wt.%, Cu 0.5-5 wt.%). Balkanite has been described in the Eastern Alps only from the Cu-Ni-(Co)-Pb-Ag-Hg mining district of Schwarzleo near Leogang (Salzburg), ca. 25 km southeast of the mining district Röhrerbühel by Paar & Chen (1986). The average chemical formula of balkanite in our samples is Cu8.87-9.40Ag4.80-5.25Hg0.71-0.91S8. In contrast to the analyses from the Sedmochislenitsi mine in Bulgaria by Atanassov & Kirov (1973), our data show higher Cu and Ag and slightly lower Hg contents. Balkanite from Leogang analysed by Paar & Chen (1986) can be distinguished by higher Cu and lower Hg contents but similar Ag contents. In the course of this study, balkanite was also characterized with micro-Raman spectroscopy. Based on the optical properties and the obtained Raman spectra, balkanite, Cu9Ag5HgS8, could clearly be distinguished from danielsite, (Cu,Ag)14HgS8.