Holubite, Ag3Pb6(Sb8Bi3)Σ11S24, from Kutna Hora, Czech Republic, a new member of the andorite branch of the lillianite homologous series

A new mineral species, holubite, ideally Ag3Pb6(Sb8Bi3)(Sigma 11)S-24, has been found at Kutna Hora ore district, Czech Republic. The mineral is associated with other lillianite homologues (gustavite, terrywallaceite, vikingite and treasurite) most frequently as grain aggregates and replacement rims of earlier Ag-Pb-Bi minerals, growing together in aggregates up to 200 x 50 mu m. It typically occurs in a close association with Ag,Bi-bearing galena and terrywallaceite. Holubite is opaque, steel-grey in colour and has a metallic lustre, the calculated density is 5.899 g/cm(3). In reflected light holubite is greyish white and bireflectance and pleochroism are weak with grey tints. Anisotropy is weak to medium with grey to bluish-grey rotation tints. Internal reflections were not observed. Electron microprobe analyses yielded an empirical formula, based on 44 atoms per formula unit (apfu) of (Ag3.03Cu0.03)(Sigma 3.06)(Pb6.19Fe0.02Cd0.01)(Sigma 6.22)(Sb7.71Bi2.90)(Sigma 10.61)S-24.12. Its unit-cell parameters are: a = 19.374(4), b = 13.201(3), c = 8.651(2) angstrom, beta = 90.112(18)degrees, V = 2212.5(9) angstrom(3), space group P2(1)/n and Z = 2. Holubite is a new member of the andorite branch of the lillianite homologous series with N = 4. The structure of holubite contains two Pb sites with a trigonal prismatic coordination, eight distinct octahedral sites, of which one is a mixed (Bi,Ag) site and one is a mixed (Sb,Pb) site, and twelve anion sites. Holubite is defined as a lillianite homologue with the three following requirements: N = 4, L% [Ag+ + (Bi3+,Sb3+) <-> 2 Pb2+ substitution] approximate to 70% and approximately one quarter to one third at.% of antimony is replaced by bismuth [Bi/(Bi+Sb) approximate to 0.26-34]. The new mineral has been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2022-112) and named after Milan Holub, a key Czech geologist and specialist in the Kutna Hora ore district.