• The crystal structure of uytenbogaardtite, Ag3AuS2, and its relationships with gold and silver sulfides-selenides

      Bindi, L; Stanley, Christopher; Seryotkin, YV; Bakakin, VR; Pal'yanova, GA; Kokh, KA (2016-10)
    • Hansblockite, (Cu,Hg)(Bi,Pb)Se2, the monoclinic polymorph of grundmannite: a new mineral from the Se mineralization at El Dragón (Bolivia)

      Foerster, HJ; Bindi, L; Stanley, CJ; Grundmann, G (Cambridge University Press, 2017-06)
      Hansblockite, ideally (Cu,Hg)(Bi,Pb)Se2, is a new selenide from the El Dragón mine, Bolivia. It typically occurs in thin subparallel plates intergrown with two unnamed Cu–Hg–Pb–Bi–Se species, clausthalite, Corich penroseite and petrovicite.It also forms subhedral to anhedral grains up to 150 μm long and 50 μm wide. Hansblockite is non-fluorescent, black and opaque with a metallic lustre and black streak. It is brittle, with an irregular fracture and no obvious parting and cleavage. The VHN20 values range from37 to 50 (mean 42) kg mm–2 (Mohs hardness 2–2½). In plane-polarized incident light, hansblockite is cream to light grey in colour, weakly bireflectant and weakly pleochroic from greyish cream to cream. Under crossed polars, hansblockite is weakly anisotropic withkhaki to pale blue rotation tints. The reflectance values in air for the Commission on Ore Mineralogy (COM) standard wavelengths are: 47.3–48.1 (470 nm), 47.4–49.9 (546 nm), 47.1–49.0 (589 nm) and 46.6–48.5 (650 nm). The mean composition is Cu 9.31, Ag 0.73, Hg 11.43,Pb 3.55, Ni 0.17, Co 0.03, Bi 31.17, Se 34.00, total 100.39 wt.%. The mean empirical formula (based on 4 apfu) is (Cu0.68Hg0.27Ag0.03Ni0.01)∑=0.99(Bi0.69Pb0.31)∑=1.00Se2.01. The simplifiedformula is (Cu,Hg) (Bi,Pb)Se2. Hansblockite is monoclinic, space group P21/c, with a = 6.853(1), b = 7.635(1), c = 7.264(1) Å, β = 97.68(1)°, V = 376.66(9) Å3 and Z = 4. Density is 8.26 gcm–3. The five strongest powder X-ray diffraction lines [d in Å (I/I 0) (hkl)] are: 3.97 (90) (111), 3.100 (40) (121), 2.986 (100) (211), 2.808 (50) (112) and 2.620 (50) (022). Hansblockite represents the monoclinic polymorph ofgrundmannite, CuBiSe2, with Hg and Pb being essential in stabilizing the monoclinic structure via the coupled substitution Cu+ + Bi3+⇔ Hg2+ + Pb2+. The mineral name is in honour of Hans Block (1881–1953), in recognition of hisimportant role in boosting Bolivian ore mining.
    • A new telluride topology: the crystal structure of honeaite Au3TlTe2

      Welch, MD; Still, JW; Rice, CM; Stanley, CJ (Cambridge University Press, 2017-06)
      The crystal structure of the first thallium-bearing gold telluride, honeaite Au3TlTe2, is reported and its topological novelty discussed. Honeaite is orthorhombic, space group Pbcm and unit-cell parameters a = 8.9671(4), b = 8.8758(4), c= 7.8419(5) Å, V = 624.14(6) Å3 (Z = 4). Its structure has been refined to R 1 = 0.033, w R 2 = 0.053, Goof = 1.087. The structure is based upon a corrugated double-sheet comprising two sub-sheets, each composed of six-memberedrings of corner-linked TeAu3 pyramids in which the Te lone pair is stereoactive. Rows of thallium atoms lie in the grooves between sheets and provide the only inter-sheet connectivity via Tl-Au bonds. There is extensive Au-Au bonding linking the two sub-sheets of the double-sheet.The structure is distinct from those of the 1:2 (Au,Ag)-tellurides: calaverite AuTe2, sylvanite AuAgTe4 and krennerite Au3AgTe8, which are based upon sheet structures with no connecting inter-sheet atoms. It also differs fundamentally from the structuresof synthetic phases Ag3TlTe2 and Ag18Tl4Te11, both of which have an analogous stoichiometry. In contrast to the pyramidal TeAu3 group of honeaite and krennerite, Ag does not form the corresponding TeAg3 group in itstellurides.
    • Norilskite, (Pd,Ag)7Pb4, a new mineral from Noril'sk-Talnakh deposit, Russia

      Vymazalova, A; Laufek, F; Sluzhenikin, SF; Stanley, CJ (Cambridge University Press, 2017-06)
      Norilskite, (Pd,Ag)7Pb4 is a new platinum-group mineral discovered in the Mayak mine of the Talnakh deposit, Russia. It forms anhedral grains in aggregates (up to ∼400 μm) with polarite, zvyagintsevite, Pd-rich tetra-auricupride, Pd-Pt bearing auricupride,Ag-Au alloys, (Pb,As,Sb) bearing atokite, mayakite, Bi-Pb-rich kotulskite and sperrylite in pentlandite, cubanite and talnakhite. Norilskite is brittle, has a metallic lustre and a grey streak. Values of VHN20 fall between 296 and 342 kg mm–2, with a mean valueof 310 kg mm–2, corresponding to a Mohs hardness of ∼4. In plane-polarized light, norilskite is orange-brownish pink, has moderate to strong bireflectance, orange-pink to greyish-pink pleochroism, and strong anisotropy; it exhibits no internal reflections. Reflectancevalues of norilskite in air (Ro, Re' in %) are: 51.1, 48.8 at 470 nm, 56.8, 52.2 at 546 nm, 59.9, 53.5 at 589 nm and 64.7, 55.5 at 650 nm. Sixteen electronmicroprobe analyses of natural norilskite gave an average composition: Pd 44.33, Ag 2.68, Bi 0.33 and Pb 52.34, total99.68 wt.%, corresponding to the empirical formula (Pd6.56Ag0.39)∑6.95(Pb3.97Bi0.03)∑4.00 based on 4 Pb + Bi atoms; the average of eight analyses on synthetic norilskite is: Pd 42.95, Ag 3.87 and Pb 53.51, total 100.33wt.%, corresponding to (Pd6.25Ag0.56)∑6.81Pb4.00. The mineral is trigonal, space group P3121, with a = 8.9656(4), c = 17.2801(8) Å, V = 1202.92(9) Å3 and Z = 6. The crystalstructure was solved and refined from the powder X-ray diffraction data of synthetic (Pd,Ag)7Pb4. Norilskite crystallizes in the Ni13Ga3Ge6 structure type, related to nickeline. The strongest lines in the powder X-ray diffraction patternof synthetic norilskite [d in Å (I) (hkl)] are: 3.2201(29)(023,203), 2.3130(91)(026,206), 2.2414(100)(220), 1.6098(28)(046,406), 1.3076(38)(246,462), 1.2942(18)(600), 1.2115(37)(22.12,12.13), 0.9626(44) (06.12,60.12). The mineral is named for the locality, the Noril'sk district in Russia.
    • Oscarkempffite, Ag10Pb4(Sb17Bi9)∑ 26S48, a new Sb-Bi member of the lillianite homologous series

      Topa, D; Makovicky, E; Paar, WH; Stanley, Christopher; Roberts, AC (2016-08)
    • Palladosilicide, Pd2Si, a new mineral from the Kapalagulu Intrusion, Western Tanzania and the Bushveld Complex, South Africa

      Cabri, LJ; McDonald, AM; Rudashevsky, NS; Poirier, G; Wilhelmij, HR; Zhe, W; Rudashevsky, VN; Stanley, Christopher (2015-04)
    • Structural and compositional variations of basic Cu(II) chlorides in the herbertsmithite and gillardite structure field.

      Sciberras, Matthew J.; Leverett, Peter; Williams, Peter A.; Schlüter, Jochen; Malcherek, Thomas; Welch, Mark D.; Downes, Peter J.; Hibbs, David E.; Kampf, Anthony R. (Mineralogical Society, 2016)