ORIGINAL PAPER Roterbärite, PdCuBiSe 3 , a new mineral species from the Roter Bär mine, Harz Mountains, Germany Anna Vymazalová 1 & Alexandre R. Cabral 2,3 & František Laufek 1 & Wilfried Ließmann 4 & Chris J. Stanley 5 & Bernd Lehmann 4 Received: 26 October 2019 /Accepted: 3 March 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020 Abstract Roterbärite, PdCuBiSe 3 , is a new mineral species from the Roter Bär mine, Harz Mountains, Germany. It forms euhedral to subhedral grains, up to 50 μm across, embedded in clausthalite, which is spatially associated with gold, mertieite-II, bohdanowiczite, hematite, chalcopyrite, baryte, ankerite and dolomite. Roterbärite is brittle and has a metallic luster. In plane- polarized light, roterbärite is slightly pleochroic in shades of dark cream to slightly greenish cream; it has weak anisotropy with rotation tints in shades of pale orange brown to grey and exhibits no internal reflections. Reflectance values of roterbärite in air (R 2, R 1 in %) are: 42.4/43.0 at 470 nm, 45.4/44.4 at 546 nm, 46.8/44.6 at 589 nm and 47.7/44.6 at 650 nm. Eighteen electron- microprobe analyses of roterbärite gave an average composition (in wt%): Pd 18.1 wt%, Bi 35.2 wt%, Cu 10.5 wt%, Se 33.5 wt% and S 2.6 wt%, totalling 99.8 wt% and corresponding to the empirical formula Pd 1.01 Cu 0.98 Bi 1.00 (Se 2.53 S 0.48 ) 3.01 , based on 6 atoms; the average of ten microanalyses on its synthetic analogue is: Pd 17.62 wt%, Cu 10.74 wt%, Bi 33.59 wt% and Se 38.70 wt%, the total of which is 100.65 wt% and corresponds to Pd 1.01 Cu 1.03 Bi 0.98 Se 2.98 . The ideal formula is PdCuBiSe 3 . The density, calculated on the basis of the empirical formula, is 7.23 g/cm 3 . The mineral is orthorhombic, space group P2 1 2 1 2 1 , with a 5.00520(10), b 7.9921(2) Å, c 13.5969(2) Å, V 543.90(2) Å 3 and Z = 4. The crystal structure was solved and refined from the powder X-ray diffraction data of synthetic PdCuBiSe 3 . Roterbärite crystallizes in the (Bi,Sb)CuNiS 3 structure-type, being isostructural with minerals of the lapieite group – i.e., lapieite (CuNiSbS 3 ), mückeite (CuNiBiS 3 ) and lisiguangite (CuPtBiS 3 ). Roterbärite belongs to the vast group of sulfosalts and related compounds (a selenio-salt). The strongest lines in the powder X-ray diffraction pattern of the synthetic PdCuBiSe 3 [d in Å (I)(hkl)] are: 3.3593 (97) (103), 3.1226 (100) (120), 3.0434 (75) (121), 2.3894 (39) (105), 1.9210 (70)(223). Keywords Roterbärite . Synthetic PdCuBiSe 3 . Roter Bär mine . Harz Mountains . Germany Introduction Roterbärite, ideally PdCuBiSe 3 , was identified at Roter Bär, a former underground mine in the north-eastern part of the St. Andreasberg polymetallic vein district in the Harz Mountains, Germany. Geologically, Roter Bär is a vein-style deposit with- in a Lower Paleozoic sedimentary sequence underneath a post-Variscan unconformity. The holotype specimen, collect- ed in 1924 by mine geologist Ernst Bock and Prof. Hermann Rose (Hamburg University), represents a selenide-bearing carbonate veinlet that was exposed along a cross adit about 170 m below the surface, the Sieberstollen Bärener Querschlag. Geilmann and Rose (1928) provided the first study of the Roter Bär selenide mineralization. Cabral et al. (2015) reported an unknown mineral correspond- ing to PdCuBiSe 3 , together with gold, mertieite-II and Editorial handling: L. Bindi * Anna Vymazalová anna.vymazalova@geology.cz 1 Czech Geological Survey, Geologická 6, 152 00 Prague, Czech Republic 2 Centro de Pesquisa Professor Manoel Teixeira da Costa (CPMTC), Instituto de Geociências, Universidade Federal de Minas Gerais (UFMG), Av. Antônio Carlos 6.627, Belo Horizonte, MG 31270-901, Brazil 3 Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Av. Antônio Carlos 6.627, Belo Horizonte, MG 31270-901, Brazil 4 Technische Universität Clausthal, Adolph-Roemer-Str. 2A, 38678 Clausthal-Zellerfeld, Germany 5 Department of Earth Sciences, Natural History Museum, Cromwel Road, London SW7 5BD, UK Mineralogy and Petrology https://doi.org/10.1007/s00710-020-00703-1