ALBERT

Description: Litochlebite, Ag2PbBi4Se8, is a new selenide mineral from the Zalesi uranium deposit, Rychlebske hory Mountains, northern Moravia, Czech Republic. It occurs as irregular grains up to 200 {micro}m, which form aggregates up to 1-2 mm in size in a quartz gangue. These aggregates are replaced along the margins and fractures by a heterogeneous supergene Bi-Se-O phase. Other associated minerals included uraninite, hematite, and uranophane. Litochlebite is opaque, dark grey to black, has a dark grey streak and a metallic luster. No cleavage was observed; the mineral is brittle with an irregular fracture. The VHN10g microhardness 230 (227-234) kg/mm2 corresponds to a Mohs hardness of about 3; the calculated density is 7.90 g/cm3. In reflected light, litochlebite is white, with weak bireflectance (only in oil) and pleochroism from white with a very faint yellowish tint to white with a very faint bluish tint. Between crossed polars, the anisotropy is moderate both in air and in oil, with dark grey to brown polarization-colors. Reflectance values in air (Rmin, Rmax in %, {lambda} nm) are: 44.5-49.9 (470), 45.1-50.5 (546), 45.6-51.3 (589), 45.4-51.8 (650). Litochlebite is monoclinic, space group P21/m, with a 13.182(2), b 4.1840(8), c 15.299(2) A, {beta} 109.11(1){degrees}, V 797.3(2) A3, and a:b:c 3.1506:1:3.6565. The main lines of the X-ray powder-diffraction pattern [d in A(I)(hkl)] are: 3.684(53) (301), 3.201(76)(104), 3.028(100)(31[IMG]f2.gif" ALT="Formula" BORDER="0"〉), 2.980(88)(31[IMG]f3.gif" ALT="Formula" BORDER="0"〉) and 2.892(95)(005). Its average composition (electron-microprobe data) is Cu 0.10, Ag 10.27, Cd 0.05, Pb 11.73, Bi 43.27, Se 32.93, S 0.01, total 98.36 wt.%. The resulting empirical formula, written on the basis 15 apfu, is (Ag1.84Cu0.03){sum}1.87 (Pb1.09Cd0.01){sum}1.10Bi3.99Se8.04. The ideal formula, Ag2PbBi4Se8, requires Ag 11.41, Pb 10.96, Bi 44.22, Se 33.41, total 100.00 wt.%. The crystal structure of litochlebite has been solved by direct methods and refined to R1 = 3.89% on the basis of 938 unique reflections [Fo 〉 4{sigma}(Fo)] collected on a Bruker AXS diffractometer with a CCD detector and MoK{alpha} radiation. The crystal structure contains one lead site, four independent Bi sites, four silver sites and eight independent Se sites. One Ag site is an octahedrally coordinated (2 + 4) site in the pseudotetragonal layer, the other Ag site has a distorted tetrahedral coordination. The remaining Ag sites have low occupancies. Litochlebite is an Ag-dominant isotype of watkinsonite, Cu2PbBi4Se8, and structurally related to berryite, Cu3Ag2Pb3Bi7S16.

Description: Guettardite from the Barika Au–Ag deposit in Azarbaijan Province, western Iran, formed in fractures developed in silica bands situated in massive banded pyrite and barite ores. Fractures host veinlets that contain a number of Ag–As–Sb–Pb-rich sulfosalts, tetrahedrite–tennantite, realgar, pyrite and Au–Ag alloy. The variation in the chemical composition of guettardite is minor: Pb0.95–0.96Sb0.96–1.02As1.03–1.06S3.99–4.02. The lattice parameters were determined from a single crystal as a 8.527(4), b 7.971(4), c 20.102(10) Å, β 101.814(7)°, space group P21/c. The structure of guettardite contains six distinct coordination polyhedra of cations. Atoms Pb1 and Pb2 form slightly skewed tricapped trigonal coordination prisms arranged in a zig-zag layer. Two distinct As and two Sb sites in a chess-board arrangement form MeS5 pyramids with trapezoidal bases. Guettardite is a homologue of sartorite, ideally PbAs2S4, and is the N = 3 member of the sartorite homologous series of sulfosalts. We contend that guettardite and twinnite are configurational polytypes composed of two alternating types of OD layers, formed by different orientations of tightly bonded crankshaft chains in adjacent As–Sb-based OD layers (layer symmetry P1̄) separated by a Pb-based OD layers [layer symmetry Pm21(n)]. Whether the observed differences in the Sb:As ratio determine the polytype is still an open question. A complete structural analogy has been found in the pair BaSb2S4 – BaSb2Se4.

Description: Cuproneyite, with an ideal formula Cu7Pb27Bi25S68, is a new mineral species found in the skarn deposit of Băiţa Bihor, Romania. The mineral occurs in irregular aggregates, nests and veinlets up to 5 cm across, with predominant cosalite, hammarite–friedrichite and calcite, within the diopside skarn. Cuproneyite is opaque, has a silver-grey color and a metallic luster, and it displays a perfect cleavage along crystal elongation. The average Mohs hardness is about 3, approximated from the average micro-identation hardness, 222.5 kg/mm2. Cuproneyite forms irregular or short prismatic grains up to 300 μm in length, intergrown with lamellae and irregular patches of cosalite and hammarite–friedrichite. Bireflectance is barely visible in air and moderate in oil immersion, with a greyish white color and faint yellowish tints in the lightest position, to greyish white with faint bluish tints in the darkest position. Between crossed polars, the rotation tints of the most anisotropic grains are dark brownish grey to light brownish grey. Internal reflections are absent. The reflectance data (measured in air; Rmin, Rmax) are: 40.4, 47.1% at 470 nm, 39.3, 45.7% at 546 nm, 38.3, 44.3% at 589 nm, and 38.1, 43.9% at 650 nm. Twenty-four electron-microprobe analyses gave, as an average, Cu 3.34(12), Ag 0.30(3), Pb 40.10(27), Bi 39.59(18), Se 0.14(3), Te 0.12(4), S 16.12(7) wt%, corresponding to Cu7.1Ag0.38Pb26.04Bi25.49(Te0.12Se0.23S67.65)∑68, calculated on the basis of (S + Se + Te) = 68 atoms per formula unit. The simplified formula [after reconversion of x(Ag + Bi) into 2xPb] is Cu7Pb27Bi25S68, in agreement with the empirical formula and the one deduced through crystal-structure analysis. Cuproneyite is monoclinic, space group C2/m, with a 37.432(8), b 4.0529(9), c 43.545(9) Å, β 108.800(5)°, V = 6254(2) Å3, Z = 2, with a calculated density of 7.11 g/cm3. The strongest lines in the calculated X-ray powder pattern [d in Å(I)hkl] are: 3.735(96)1̄0̄03, 3.507(50)3̄16, 3.464(53)8̄011, 3.347(84)4010, 2.956(77)713, 2.925(46)8̄014, 2.867(100)714, and 2.027(81)020. Cuproneyite is structurally related to neyite, the main difference residing in the fact that the independent Ag position present in the neyite structure is completely replaced by Cu in cuproneyite.

Description: An interesting association of the Bi sulfosalts was identified in the Rozália mine, Hodruša–Hámre, Slovakia. Sulfosalts of the cuprobismutite series are the most common, and occur in paragenesis with other Bi sulfosalts, chalcopyrite and hematite. Members of the pavonite homologous series are associated with bismuthinite derivatives and quartz of the amethyst variety. Three members of the cuprobismutite homologous series and four members of the pavonite homologous series have been found in a hydrothermal base-metal mineralization in the Rozália mine. Kupčíkite has the structural formula (Cu6.73Fe1.10)∑7.83 (Bi9.49As0.36Ag0.24)∑10.09(S18.89Se0.13)∑19.02; that of hodrušite is (Cu7.69Fe0.38)∑8.07(Bi11.22As0.34Ag0.53)∑12.09(S21.99Se0.17)∑22.16, and that of cuprobismutite is (Cu7.47Fe0.14)∑7.61(Bi12.81As0.69Ag1.38)∑14.88(S23.85Se0.22)∑24.07. Makovickyite has the structural formula Cu1.14Ag0,99Pb0.13Bi5.07S8.94Se0.06; that of pavonite is Cu0.43Ag0.82Fe0.03Pb0.19Bi2.84S4.96Se0.04, that of dantopaite is Cu2.29Ag3.68 Fe0.12Pb1.32Bi12.02S21.85Se0.15, that of benjaminite is Cu1.13Ag2.26Fe0.16Pb0.76Bi6.51S11.91Se0.09, and that of mummeite is Cu1.44 Ag2.61Fe0.41Pb0.95Bi6.70S12.93Se0.07. The associated sulfosalts are paděraite, berryite and members of the bismuthinite–aikinite series (bismuthinite, gladite, krupkaite, lindströmite, friedrichite and aikinite).

Description: The crystal structure of eclarite, first determined by Kupčík in 1984, has been refined on material from the scheelite deposit at Felbertal, Salzburg Province, Austria, to an R1 value of 4.5% on the basis of 4141 unique reflections [Fo 〉 4σ(Fo)]. The chemical formula of material examined, based on 20.85 large cations (Z = 4) is Cu0.76Fe0.45Ag0.12Pb8.14Bi12.59S27.91; its unit-cell parameters are a 4.0307(1), b 22.7011(6), and c 54.615(1) Å, space group Pmcn. All the principal features of Kupčík’s structure were confirmed. Three cation sites appear split into Pb and Bi subsites, and the octahedral site of the “cosalite-like” fragment is a partially occupied Bi site, flanked by three-fold coordinated, partly occupied Cu1 and Cu2 sites. The tetrahedral (Cu,Fe) site is split into a triangular position and a tetrahedral position. Replacement of Fe by Cu at the tetrahedral site and replacement of Bi by Cu at the octahedral site are positively correlated. They result in a general formula of eclarite equal to Cu1.5nFe1−n Pb9–1.25nBi12+nS28 in which n is the molar proportion of the copper-based fully substituted ideal end-member Cu1.5Pb7.75Bi13.0S28, and (1–n), that of the Fe-based ideal end-member FePb9Bi12S28. We propose a new interpretation of the crystal structure of eclarite, as a patchwork of large galenobismutite-like regions joined by interstitial elements.

Description: Eldragónite, with the simplified formula Cu6BiSe4(Se2), is a new mineral species discovered in a telethermal vein-type deposit with selenides at the El Dragón mine, Province of Quijarro, Department of Potosí, Bolivia. It forms inclusions in krut’aite, and is associated with clausthalite, klockmannite, umangite and tiemannite, as well as with watkinsonite, petrovicite and two unnamed phases in the system Cu–Pb–Hg–Bi–Se. The unique vein of eldragónite-bearing krut’aite is hosted within sandstones and shales of Devonian age. Eldragónite occurs in anhedral grains and polycrystalline aggregates attaining a size of up to 100 × 80 μm. Megascopically, the mineral has a brownish to light-maroon color, is opaque and lacks internal reflections. It has a metallic luster and a brownish black streak, is brittle with an uneven to conchoidal fracture, without observable cleavage. The VHN15 values range between 212 and 243 (mean 225) kg/mm2, corresponding to a Mohs hardness of ~3 ½. In plane-polarized light, eldragónite is distinctly bireflectant and pleochroic, from light grayish brown to cream; it is strongly anisotropic with rotation tints in shades of orange and blue-black. The reflectances (in air and oil, respectively) for the COM standard wavelengths are: 32.5–34.5, 17.7–19.7 (470 nm), 32.95–36.3, 18.0–21.4 (546 nm), 33.3–36.8, 18.3–21.6 (589 nm), 34.0–36.9, 19.1–21.7 (650 nm). Electron-microprobe analyses gave (mean of 24 analyses): Cu 35.9, Fe 1.25, Ni 0.35, Bi 20.3, Se 42.5, total 100.3 wt.%, corresponding to (Cu5.98Fe0.24Ni0.06)∑6.28Bi1.03Se5.70. The ideal formula is Cu6BiSe4(Se2), which requires Cu 35.84, Bi 19.64, Se 44.52 wt.%. Eldragónite has an orthorhombic cell, space group Pmcn, with a 4.0341(4), b 27.056(3), c 9.5559(9) Å, V 1043.0(3) Å3, and Z = 4. The calculated density is 6.76 g/cm3. The strongest X-ray powder-diffraction lines [d in Å (I) hkl] are: 6.547(58)031, 3.579(100)052, 3.253(48)141, 3.180(77)081, 3.165(56)013, 3.075(84)102, 3.065(75)151,112, 2.011(53)200, 1.920(76)154, 1.846(52)1103. The crystal structure was solved from single-crystal data, and was refined to R1= 0.026 on the basis of 1731 unique reflections. There are one Bi and six Cu positions. Among the six Se positions, two Se atoms form a Se2 pair [d(Se–Se) = 2.413 Å]; eldragónite is thus a mixed selenide–diselenide compound. The crystal structure is organized according to two slabs alternating along a. The thin slab with formula Cu6Se6 is a zigzag layer derived from the CaF2 archetype; the thick slab, Cu6Bi2Se6, is similar to that of wittichenite, Cu3BiS3. The Se2 pair is at the junction between these two slabs. This new mineral species is named after the location where it was discovered.

Description: Cupromakopavonite, ideally Cu8Ag3Pb4Bi19S38, is a new mineral species found in quartz veins at the scheelite deposit Felbertal, Salzburg Province, Austria. It is associated with makovickyite, oversubstituted krupkaite (bd55), hodrušite, and kupčikite. The mineral is opaque and grey with a metallic luster; it is brittle without any discernible cleavage. In reflected light, it is greyish white, the bireflectance is weak, and the anisotropy is moderate in air and strong in oil. Internal reflections are absent. The reflectance data (%, air) are: 42.9, 46.6 at 470 nm, 42.1, 46.5 at 546 nm, 41.3, 45.8 at 589 nm and 40.2, 45.1 at 650 nm. The average results of 15 electron-microprobe analyses are: Cu 7.29(6), Ag 5.48(4), Pb 8.84(14), Cd 0.39(6), Bi 59.9(2), S 17.90(6), total 99.80(23) wt.%, corresponding to Cu7.82Ag3.46Pb2.91Cd0.24Bi19.53S38.05 (on the basis of Me + S = 72 apfu). The simplified formula, Cu8Ag3Pb4Bi19S38, is in accordance with the results of our crystal-structure analysis. The density, 6.85 g/cm3, was calculated using the ideal (structural) formula. Cupromakopavonite has a monoclinic cell with a 13.380(2), b 4.0007(6), c 31.083(4) Å, β 93.064(2)°, V 1661.5(4) Å3, space group C2/m, and Z = 1. The strongest eight lines in the (calculated) powder-diffraction pattern [d in Å(I)hkl] are: 3.607(57)(207), 3.457(99)(1̄14), 3.436(37)(2̄08), 3.340(34)(4̄01), 2.953(28)(311), 2.874(33) (2̄010), 2.834(100)(313) and 2.256(29)(1111). The crystal structure was refined to R = 4.53% and wR = 6.0% for 1834 reflections [Fo 〉 4σ(Fo)]. Our crystal-structure determination reveals that the unusually high value of the c parameter results from: (1) regular alternation of pavonite-like N = 4 and N = 5 layers in the structure, (2) regularly oriented distribution of the pairs of Bi pyramids and pairs of Pb–Bi prisms in the thin slabs of the structure, and (3) the appearance of a new three-coordinated Cu site instead of the octahedrally coordinated Ag site in the thin slabs. Cupromakopavonite is the N = 4.5 member of the newly defined cupropavonite homologous series, and its name underscores its close structural relationships to its two neighboring members, cupromakovickyite (N = 4) and cupropavonite (N = 5). We define the structural and chemical properties of this series, with the general, ideal formula, Cu8Ag2N−6Pb4Bi2N+10S4N+20 for Z = 1, where N is the order of the homologue. It includes N = 7 (“cuproplumbian benjaminite”) and N = 8 (“cuproplumbian mummeite”).

Description: The new synthetic phase, ~Sn12In19(Se,S)41, synthesized in the condensed system Fe–Sn–Sb–In–S–Se at 600°C, is monoclinic with a 56.29(4), b 3.924(3), c15.916(10) Å, β 102.56(1)°, space group C2/m, and Z = 2. It occurs as needle-like crystals together with chemically analyzed Fe9S10, FeIn2(S,Se)4, ~SbSn9(Se,S)10 and ~Sn4Sb3In2(S,Se)11. The crystal structure has been refined to a conventional R factor R1 of 6.29% for 2339 unique reflections with Fo〉4σ(Fo). There are 16 unique sites of Sn and In and 21 unique sites of (Se,S) in the asymmetric unit. It is a composite-layer structure with two kinds of layers in regular alternation; together, they undergo a step-like modulation. The pseudotetragonal layers are three atomic planes thick and modified by steps into oval-shaped fragments containing octahedra of indium and trigonal coordination prisms of tin. Single-octahedron pseudohexagonal layers are of two regularly alternating kinds: those with an overlap of two octahedra in the step region and those with a gap of one octahedron in those regions. The title compound, ~Sn12In19(Se,S)41, is a member of a M15+NS20+N series of closely related composite-layer structures with alternating, periodically sheared pseudohexagonal and pseudotetragonal layers (a “sliding series” according to its main structural principle of slabs with fixed step-like configurations sliding past one another and thus creating chemical and structural differences on the planes of their contact). A parallel series with less frequently sheared layers is known only from the Pb6In13.34S26 – Sn5In14S26 pair. Two cannizzarite-related structures with layers unsheared, one potential cylindrite-type structure, two families of rod-based structures, one known complex sulfide with In–In bonds, and the structure of PbIn2S4 are further principal structure-types of complex indium sulfides in addition to members of the pavonite homologous series and several individual sulfosalt structures that are in need of revision. Alternation of pseudotetragonal and pseudohexagonal layers and formation of rod-based structures are the two basic principles in the construction of complex sulfides and selenides of indium.