Reference:
▪ Biagioni, C., Moëlo, Y., Orlandi, P., Stanley, C.J. (2016): Lead-antimony sulfosalts from Tuscany (Italy). XVII. Meerschautite, (Ag,Cu)5.5Pb42.4(Sb,As)45.1S112O0.8, a new expanded derivative of owyheeite from thePollone mine, Valdicastello Carducci: occurrence and crystal structure. Mineralogical Magazine, 80, 675-690.
The new mineral species meerschautite, ideally (Ag,Cu)5.5Pb42.4(Sb,As)45.1S112O0.8, has been discovered in the baryte + pyrite ± (Pb-Zn-Ag) deposit of the Pollone mine, near Valdicastello Carducci, Apuan Alps, Tuscany, Italy. It occurs as black prismatic crystals, striated along [100], up to 0.7 mm in length and 0.1 mm thick, associated with baryte, boulangerite, pyrite, quartz, and sphalerite. Meerschautite is opaque with a metallic luster and shows a black streak. In reflected light, meerschautite is white in colour, weakly bireflectant and non pleochroic. With crossed polars, it is distinctly anisotropic with grey to dark grey rotation tints with brownish and greenish shades. Reflectance percentages for COM wavelengths [λ (nm), Rair (%)] are: 470: 39.7/41.4; 546: 38.3/39.9; 589: 37.4/39.0; 650: 35.8/37.2. Electron microprobe data collected on two different samples gave (wt%): Cu 0.22, Ag 3.15, Tl 0.07, Pb 48.54, Sb 25.41, As 2.82, S 19.74, Se 0.14, Cl 0.03, sum 100.12 (# 1) and Cu 0.22, Ag 3.04, Tl 0.13, Pb 48.53, Sb 25.40, As 2.93, Bi 0.06, S 19.82, Se 0.13, Cl 0.05, sum 100.31 (# 2). On the basis of 112 anions (S+Se+Cl) per formula unit, the empirical formulae are (Ag5.29Cu0.63)Σ5.92(Pb42.43Tl0.06)Σ42.49(Sb37.80As6.82)Σ44.62(S111.53Se0.32Cl0.15)Σ112 (# 1) and (Ag5.08Cu0.62)Σ5.70(Pb42.22Tl0.12)Σ42.34(Sb37.61As7.07Bi0.05)Σ44.73(S111.45Se0.30Cl0.25)Σ112 (# 2). Main diffraction lines, corresponding to multiple hkl indices, are [d in Å (relative visual intensity)]: 3.762 (m), 3.663 (s), 3.334 (vs), 3.244 (s), 3.016 (m), 2.968 (m), 2.902 (m), 2.072 (ms). The crystal structure study gave a monoclinic unit cell, space group P21, with a = 8.2393(1), b = 43.6015(13), c = 28.3688(8) Å, β = 94.128(2)°, V = 10164.93(2) Å3, Z = 2. The crystal structure has been solved and refined to a final R1 = 0.122 on the basis of 49037 observed reflections. The structure is based on two building blocks, both formed by a complex column with a pseudotrigonal Pb6S12 core and two arms of unequal lengths (short and long arms, respectively). Two different kinds of short arms occur in meerschautite. One is an Ag-rich arm, whereas the other shows localized Sb–O–Sb bonds. Meerschautite is an expanded derivative of owyheeite and has quasi-homeotypic relationships with sterryite and parasterryite.
▪ Biagioni, C., Moëlo, Y., Orlandi, P., Stanley, C.J. (2016): Lead-antimony sulfosalts from Tuscany (Italy). XVII. Meerschautite, (Ag,Cu)5.5Pb42.4(Sb,As)45.1S112O0.8, a new expanded derivative of owyheeite from thePollone mine, Valdicastello Carducci: occurrence and crystal structure. Mineralogical Magazine, 80, 675-690.
The new mineral species meerschautite, ideally (Ag,Cu)5.5Pb42.4(Sb,As)45.1S112O0.8, has been discovered in the baryte + pyrite ± (Pb-Zn-Ag) deposit of the Pollone mine, near Valdicastello Carducci, Apuan Alps, Tuscany, Italy. It occurs as black prismatic crystals, striated along [100], up to 0.7 mm in length and 0.1 mm thick, associated with baryte, boulangerite, pyrite, quartz, and sphalerite. Meerschautite is opaque with a metallic luster and shows a black streak. In reflected light, meerschautite is white in colour, weakly bireflectant and non pleochroic. With crossed polars, it is distinctly anisotropic with grey to dark grey rotation tints with brownish and greenish shades. Reflectance percentages for COM wavelengths [λ (nm), Rair (%)] are: 470: 39.7/41.4; 546: 38.3/39.9; 589: 37.4/39.0; 650: 35.8/37.2. Electron microprobe data collected on two different samples gave (wt%): Cu 0.22, Ag 3.15, Tl 0.07, Pb 48.54, Sb 25.41, As 2.82, S 19.74, Se 0.14, Cl 0.03, sum 100.12 (# 1) and Cu 0.22, Ag 3.04, Tl 0.13, Pb 48.53, Sb 25.40, As 2.93, Bi 0.06, S 19.82, Se 0.13, Cl 0.05, sum 100.31 (# 2). On the basis of 112 anions (S+Se+Cl) per formula unit, the empirical formulae are (Ag5.29Cu0.63)Σ5.92(Pb42.43Tl0.06)Σ42.49(Sb37.80As6.82)Σ44.62(S111.53Se0.32Cl0.15)Σ112 (# 1) and (Ag5.08Cu0.62)Σ5.70(Pb42.22Tl0.12)Σ42.34(Sb37.61As7.07Bi0.05)Σ44.73(S111.45Se0.30Cl0.25)Σ112 (# 2). Main diffraction lines, corresponding to multiple hkl indices, are [d in Å (relative visual intensity)]: 3.762 (m), 3.663 (s), 3.334 (vs), 3.244 (s), 3.016 (m), 2.968 (m), 2.902 (m), 2.072 (ms). The crystal structure study gave a monoclinic unit cell, space group P21, with a = 8.2393(1), b = 43.6015(13), c = 28.3688(8) Å, β = 94.128(2)°, V = 10164.93(2) Å3, Z = 2. The crystal structure has been solved and refined to a final R1 = 0.122 on the basis of 49037 observed reflections. The structure is based on two building blocks, both formed by a complex column with a pseudotrigonal Pb6S12 core and two arms of unequal lengths (short and long arms, respectively). Two different kinds of short arms occur in meerschautite. One is an Ag-rich arm, whereas the other shows localized Sb–O–Sb bonds. Meerschautite is an expanded derivative of owyheeite and has quasi-homeotypic relationships with sterryite and parasterryite.