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Lead-antimony sulfosalts from Tuscany (Italy): II. Crystal Structure of scainiite, Pb14Sb30S54O5 , an expanded monoclinic derivative of Ba12Bi24S48 hexagonal sub-type (zinkenite-group)
No full textLead-antimony sulfosalts from Tuscany (Italy). VIII. Rouxelite, Cu2HgPb22Sb28S64(O,S)2, a new sulfosalt from Buca della Vena mine, Apuan Alps: definition and crystal structure
No full textRouxelite, Cu2HgPb22Sb28S64(O,S)2, is a new species of sulfosalt discovered in the Buca della Vena Fe–Ba deposit, Apuan
Alps, Italy. It occurs as acicular metallic crystals in calcite veins; refl ectance values in air are (R%, in nm): 38.2 (470), 36.2
(546), 35.4 (589), 32.8 (650). Rouxelite is monoclinic, space group C2/m, with a 43.113, b 4.059, c 37.874 Å, 117.35°, V
5887 Å3, Z = 2, Dcalc = 5.86 g/cm3. The eight most intense lines of the X-ray powder-diffraction pattern [d (in Å)(I)(hkl)] are:
3.84(31)(1
—
0.0.8), 3.402(100)(1
—
0.0.2, 1
—
2.0.8, 115), 3.369(74)( ̄714, 0.0.10), 2.815(70)(317, 1
—
1.1.4), 2.756(36)(516, 12.0.3),
2.251(31)(1.1.12, 3.1.11), 2.116(31)(1
—
1.1.15), and 1.955(30)(1
—
9.1.5, 11.1.8). Electron-microprobe analyses gave (wt.%; mean of
six spot analyses): Cu 1.34(5), Hg 1.76(9), Pb 45.08(15), Sb 31.50(14), S 20.07(11), O (struct.) 0.20, sum 99.95. The chemical
formula, calculated on the basis of a cation total of 53 atoms, is Cu2.20Hg0.92Pb22.78Sb27.10S65.53O1.31 (Z = 2), giving the idealized
formula Cu2HgPb22Sb28S64(O,S)2, which is charge-balanced. An X-ray single-crystal study, despite a poor R value (0.169),
revealed a quite original structure, with Cu and Hg in two specifi c sites, a tetrahedral one for Cu, and a fl attened octahedral one for
Hg. There is also a split O,S position, bound to two Sb atoms. For the main part, Pb, Sb and S atoms are organized in columns with
a pseudoternary axis, derived from hexagonal Ba12Bi24S48. The structural formula is Cu2HgPb22.6Sb27.4S64.67O1.33. The structure
is built up of two types of ribbons parallel to b and alternating along a, rimmed by a ribbon-layer parallel to (010); the result is a
three-component structure of the boxwork type, like for neyite. Very large topologically equivalent columns are also recognizable
in rouxelite and kobellite, which have about 90% of their structure motif in common. The formation of rouxelite is associated
with the hydrothermal remobilization and deposition of mercury in the Apuan Alps during the Apenninic tectonometamorphic
event, as illustrated in the nearby Hg deposits of Ripa and Levigliani. The name honors Jean Rouxel (1935–1998), solid state
chemist, professor and founder of the Institut des Matériaux, University of Nantes (France)
Sterryite e parasterryite. I solfosali aciculari di piombo e argento della miniera del Pollone (Pietrasanta, Lucca)
No full textLead-antimony sulfosalts from Tuscany (Italy). IV. Crystal structure of pillaite, Pb9Sb10S23ClO0.5, an expanded monoclinic derivative of hexagonal Bi(Bi2S3)9I3, from the zinkenite group
No full textLead-antimony sulfosalts from Tuscany (Italy). III. Pillaite, Pb9Sb10S23ClO0.5, a new oxy-chloro-sulfosalt, from Buca della Vena mine
No full textSb-rich routhierite from Monte Arsiccio mine (Apuan Alps, Tuscany, Italy): occurrence and crystal structure
No full textPyradoketosite, a new, unexpected, polymorph of Ag3SbS3 from the Monte Arsiccio mine (Apuan Alps, Tuscany, Italy)
No full textAlthough everything seemed clear about the Ag-Sb-S compounds belonging to one of the more deeply studied experimental systems, nature allowed us to discover a new polymorph of (AgSbS3)-Sb-3, which could represent a compound for assessing new technological potentialities. The new mineral species pyradoketosite, Ag3SbS3 (IMA 2019-132), was discovered in the pyrite + baryte + iron oxide ore deposit of the Monte Arsiccio mine, Apuan Alps, Tuscany, Italy. It occurs as brittle orange acicular crystals, up to 200 mu m in length and 25 mu m in thickness, with adamantine luster. Under reflected light, pyradoketosite is slightly bluish-gray, with abundant orange internal reflections. Bireflectance is weak, and anisotropism was not observed, being masked by abundant internal reflections. Minimum and maximum reflectance data for the wavelengths recommended by the Commission on Ore Mineralogy [R-min/R-max (%) (lambda, nm)] are 32.8/32.9 (470), 30.2/30.7 (546), 29.0/29.6 (589), and 27.5/28.4 (650). Electron microprobe analysis gave (mean of 6 spot analyses, in wt%): Ag 59.81, Sb 22.63, S 17.78, total 100.22. On the basis of (Ag+Sb) = 4 atoms per formula unit, the empirical formula of pyradoketosite is Ag2.996(11)Sb1.004(11)S2.996(15). Pyradoketosite is monoclinic, space group P2(1)/n, with a = 13.7510(15), b = 6.9350(6), c = 19.555(2) angstrom, beta = 94.807(4)degrees, V = 1858.3(3) angstrom(3), Z = 12. The crystal structure was solved and refined to R-1 = 0.063 on the basis of 2682 unique reflections with F-o > 4 sigma(F-o) and 191 refined parameters. The structure of pyradoketosite can be described as formed by the alternation of {101} layers: an Sb-rich layer, Sb3AgS3, and two distinct Ag8S6 layers. This layered organization allows identifying structural relationships with the wittichenite-skinnerite pair. Pyradoketosite is associated with pyrargyrite, tetrahedrite-(Hg), valentinite, and probable pyrostilpnite in baryte + dolomite + quartz veins embedded in metadolostone. Its name derives from the old Greek words "pi upsilon rho" (fire) and "alpha delta o kappa eta tau omicron sigma" (unforeseen), because of the unexpected occurrence of this third polymorph of the compound Ag3SbS3
LEAD-ANTIMONY SULFOSALTS FROM TUSCANY. IX MARRUCCIITE, Hg3Pb16Sb18S46, A NEW SULFOSALT FROM BUCA DELLA VENA MINE. APUAN ALPS: DEFINITION AND CRYSTAL STRUCTURE
No full textMarrucciite, Hg3Pb16Sb18S46, is a new sulfosalt discovered in the Fe-Ba deposit of Buca della Vena, Apuan Alps (Italy). It occurs as black acicular metallic crystals in calcite veins; reflectance values in air are (R %; λ nm): 33.1 (470), 30.0 (546), 28.8 (589), 26.5 (650). Marrucciite is monoclinic, space group C2/m, with a 48.32(1) Å, b 4.117(1) Å, c 24.056(5) Å, β 118.84(3)°, V 4192(3) Å3, Z = 2, Dcalc. = 6.00 g/cm3; a 2b superstructure is present. Main lines of the X-ray diffraction powder pattern [d (in Å), I (main hkl)]: 4.02, 33 (12.0.3, 802); 3.480, 64 (803, 604); 3.418, 88 (607, 10.0.2, 314) ; 3.106, 31 (9.1.4); 2.994, 100 (11.1.2); 2.922, 41 (11.1.1); 2.056, 52 (020); 1.764, 41 (627). Electron microprobe analysis gave (wt.%; mean of 4 spot analyses): Cu 0.18(12), Hg 7.90(9), Pb 42.41(7), Sb 29.71(7), S 19.47(18), Cl 0.06(2), sum 99.73(14). The chemical formula (basis: 46 (S + Cl) at.) is Cu0.21Hg2.98Pb15.46Sb18.44S45.87Cl0.13, giving the stoichiometric one Hg3Pb16Sb18S46 that fulfils the charge balance. X-ray single crystal study (R = 9.56 %) revealed a complex structure, with Hg in two specific distorted octahedral coordinations (2 short distances each, close to 2.36 Å A). There are 40 other independent positions: 7 Pb, 2 (Pb, Sb), 8 Sb and 23 S. The general architecture of the structure is strongly related to that of hexagonal Ba12Bi24S48, with three types of Me10S14 rods (× 2) around a HgSb2Pb4S4 central column. It explains the pseudo-hexagonal symmetry (a/2 ∼ c; β ∼ 120°). A strong topologic relationship exists also between marrucciite and scainiite. Like rouxelite, the other coexisting Hg bearing sulfosalt, marrucciite was formed by hydrothermal process during the Apenninic tectono-metamorphic event
Zvěstovite-(Zn), Ag 6(Ag 4Zn 2)As 4S 13, a new tetrahedrite-group mineral from Zvěstov, Czech Republic
No full textThe new mineral, zvěstovite-(Zn), ideally Ag6(Ag4Zn2)As4S13, was found in quartz-baryte gangue at the mine dump of the abandoned small deposit of Zvěstov, central Bohemia, Czech Republic. Zvěstovite-(Zn) is associated with tennantite-(Zn), tetrahedrite-(Zn), argentotennantite-(Zn), acanthite and supergene azurite and malachite. The new mineral occurs as rare relic anhedral grains rimmed by acanthite, up to 100 μm in size. Zvěstovite-(Zn) is grey, Mohs hardness is ca. 31⁄2-4, in agreement with other members of the tetrahedrite group; the calculated density is 5.16 g.cm-3. In reflected light, zvěstovite-(Zn) is grey with a greenish tint, without bireflectance, pleochroism or anisotropy. Deep red internal reflections are ubiquitous. Reflectance values of zvěstovite-(Zn) in air (R%) are: 28.5 at 470 nm, 26.9 at 546 nm, 25.5 at 589 nm and 23.8 at 650 nm. The empirical formula for zvěstovite-(Zn), based on electron-microprobe analyses (n = 4), is Ag6.27[(Ag3.90Cu0.38)Σ4.28(Zn1.60Fe0.09Cd0.03)Σ1.72]Σ6.00(As2.26Sb1.48)Σ3.74S12.50. The ideal formula is Ag6(Ag4Zn2)As4S13, which requires (in wt.%) Ag 56.01, Zn 6.79, As 15.56 and S 21.64, total 100.00. Zvěstovite-(Zn) is cubic, I3m, with unit-cell parameters: a = 10.850(2) Å, V = 1277.3(8) Å3 and Z = 2. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I) (hkl)] are: 3.1321(100) (222), 2.7125(21) (400), 1.9809(11) (521), 1.9180(31) (440) and 1.6357(15) (622). According to the single-crystal X-ray diffraction data (Robs = 0.051), the crystal structure of zvěstovite-(Zn) agrees with the general features of the members of the tetrahedrite group. Zvěstovite-(Zn) is named after its type locality, Zvěstov; the suffix indicates the dominant divalent C-constituent, according to the approved nomenclature of the tetrahedrite group. It is the As-isotype of rozhdestvenskayaite-(Zn). The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2020-061)
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