Marrucciite, 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.
LEAD-ANTIMONY SULFOSALTS FROM TUSCANY. IX MARRUCCIITE, Hg3Pb16Sb18S46, A NEW SULFOSALT FROM BUCA DELLA VENA MINE. APUAN ALPS: DEFINITION AND CRYSTAL STRUCTURE
ORLANDI, PAOLO;
2007-01-01
Abstract
Marrucciite, 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
