TY - JOUR
T1 - Cupromakopavonite, Cu8Ag3Pb4Bi19S38, a new mineral species, its crystal structure and the cupropavonite homologous series
AU - Topa, Dan
AU - Makovicky, Emil
AU - Ilinca, Gheorghe
AU - Dittrich, Herbert
PY - 2012/4
Y1 - 2012/4
N2 - Cupromakopavonite, ideally Cu 8Ag 3Pb 4Bi 19S 38, 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 kupcikite. 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 Cu 7.82Ag 3.46Pb 2.91Cd 0.24Bi 19.53S 38.05 (on the basis of Me + S = 72 apfu). The simplified formula, Cu 8Ag 3Pb 4Bi 19S 38, is in accordance with the results of our crystal-structure analysis. The density, 6.85 g/cm 3, was calculated using the ideal (structural) formula. Cupromakopavonite has a monoclinic cell with a 13.380(2), β 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)(114), 3.436(37)(208), 3.340(34)(401), 2.953(28)(311), 2.874(33)(2010), 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, Cu 8Ag2N- 6Pb 4Bi 2N+10S 4N+20 for Z = 1, where N is the order of the homologue. It includes N = 7 ("cuproplumbian benjaminite") and N = 8 ("cuproplumbian mummeite").
AB - Cupromakopavonite, ideally Cu 8Ag 3Pb 4Bi 19S 38, 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 kupcikite. 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 Cu 7.82Ag 3.46Pb 2.91Cd 0.24Bi 19.53S 38.05 (on the basis of Me + S = 72 apfu). The simplified formula, Cu 8Ag 3Pb 4Bi 19S 38, is in accordance with the results of our crystal-structure analysis. The density, 6.85 g/cm 3, was calculated using the ideal (structural) formula. Cupromakopavonite has a monoclinic cell with a 13.380(2), β 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)(114), 3.436(37)(208), 3.340(34)(401), 2.953(28)(311), 2.874(33)(2010), 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, Cu 8Ag2N- 6Pb 4Bi 2N+10S 4N+20 for Z = 1, where N is the order of the homologue. It includes N = 7 ("cuproplumbian benjaminite") and N = 8 ("cuproplumbian mummeite").
U2 - 10.3749/canmin.50.2.295
DO - 10.3749/canmin.50.2.295
M3 - Journal article
SN - 0008-4476
VL - 50
SP - 295
EP - 312
JO - Canadian Mineralogist
JF - Canadian Mineralogist
IS - 2
ER -