Tetrahedrite-(Hg), Cu6(Cu4Hg2)Sb4S13, has been approved as a new mineral species using samples from Buca della Vena mine (hereafter BdV), Italy, Jedová hora (Jh), Czech Republic and Rožňava (R), Slovakia. It occurs as anhedral grains or as tetrahedral crystals, black in colour, with metallic lustre. At BdV it is associated with cinnabar and chalcostibite in dolomite veins. At Jh, tetrahedrite-(Hg) is associated with baryte and chalcopyrite in quartz–siderite–dolomite veins; at R it is associated with quartz in siderite–quartz veins. Tetrahedrite-(Hg) is isotropic, greyish-white in colour, with creamy tints. Minimum and maximum reflectance data for Commission on Ore Mineralogy wavelengths in air (BdV sample), R in %) are 32.5 at 420 nm; 32.9 at 546 nm; 33.2 at 589 nm; and 30.9 at 650 nm. Chemical formulae of the samples studied, recalculated on the basis of 4 (As + Sb + Bi) atoms per formula unit, are: (Cu9.44Ag0.07)Σ9.51(Hg1.64Zn0.36Fe0.06)Σ2.06Sb4(S12.69Se0.01)Σ12.70 (BdV), Cu9.69(Hg1.75Fe0.25Zn0.06)Σ2.06(Sb3.94As0.06)S12.87 (Jh) and (Cu9.76Ag0.04) Σ9.80(Hg1.83Fe0.15Zn0.10)Σ2.08(Sb3.17As0.58Bi0.25)S13.01 (R). Tetrahedrite-(Hg) is cubic, I $\overline 4 $ 3m, with a = 10.5057(8) Å, V = 1159.5(3) Å3 and Z = 2 (BdV). Unit-cell parameters for the other two samples are a = 10.4939(1) Å and V = 1155.61(5) Å3 (Jh) and a = 10.4725(1) Å and V = 1148.55(6) Å3 (R). The crystal structure of tetrahedrite-(Hg) has been refined by single-crystal X-ray diffraction data to a final R1 = 0.019 on the basis of 335 reflections with Fo > 4σ(Fo) and 20 refined parameters. Tetrahedrite-(Hg) is isotypic with other members of the tetrahedrite group. Mercury is hosted at the tetrahedrally coordinated M(1) site, along with minor Zn and Fe. The occurrence of Hg at this position agrees both with the relatively large M(1)–S(1) bond distance (2.393 Å) and the refined site scattering. Previous occurrences of Hg-rich tetrahedrite and tetrahedrite-(Hg) are reviewed, and its relations with other Hg sulfosalts are discussed.

Julius Frieser (1843–1908) was a prominent mineral collector who contributed to the research of minerals of the Bohemian Central Mountains, especially zeolites. He personally discovered a new mesolite mineral site in Bedřichov near Benešov nad Ploučnicí. He was known among professional mineralogists from Prague and Vienna, as well as among other collectors of minerals, and was a member of the Litoměřice mineral collectors‘ club, which organized regular mineral exchanges in Litoměřice around the turn of the 19th and 20th centuries, visited by famous geologists and mineralogists. He built a large systematic collection of minerals from around the world, which included about four thousand items and 350 species. After his death, the collection, or part of it, was acquired by the collector Julia Schildbach from Mariánské Lázně. Her collection was acquired by the National Museum, Prague in 1946. Among Schildbach‘s minerals, 854 items originally from Frieser have currently been identified.

Eight samples of members of tetrahedrite group from Romanian deposits were examined in terms of their chemical composition studied by means of electron microprobe; five samples from Cavnic, two from Botești and one from Săcărâmb. Mean composition of all samples is corresponding to tetrahedrite-(Zn) and most of them contain Mn. The three Cavnic tetrahedrites contain up to 0.17 apfu, the two Botești samples contain up to 0.42 apfu and the Săcărâmb sample up to 0.83 apfu Mn. Pb and Sn were present at levels up to 0.01 apfu but entering of Pb and Sn into the crystal structure of tetrahedrite group minerals is questionable. In spite of the significant presence of Te is characteristic for the Botești and Săcărâmb deposits, the studied tetrahedrites from these deposits are virtually Te-free (only locally contents of Te up to 0.05 apfu were detected in one sample).

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Adalbert Wraný (*1836, †1902) was a doctor of medicine, with his primary specialization in pediatric pathology, and was also one of the founders of microscopic and chemical diagnostics. He was interested in natural sciences, chemistry, botany, paleontology and above all mineralogy. He wrote two books, one on the development of mineralogical research in Bohemia (1896), and the other on the history of industrial chemistry in Bohemia (1902). Wraný also assembled several natural science collections. During his lifetime, he gave to the National Museum large collections of rocks, a collection of cut precious stones and his library. He donated a collection of fossils to the Geological Institute of the Czech University (now Charles University). He was an inspector of the mineralogical collection of the National Museum. After his death, he bequeathed to the National Museum his collection of minerals and the rest of the gemstone collection. He donated paintings to the Prague City Museum, and other property to the Klar Institute of the Blind in Prague. The National Museum’s collection currently contains 4 325 samples of minerals, as well as 21 meteorites and several hundred cut precious stones from Wraný’s collection.