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The crystal structure of cobalt-bearing adamite (Zn, Co)2AsO4OH (so-called cobalton adamite) from Mine du Pradet, Cap Garonne, France has been refined from single crystal X-ray diffraction data: Pnnm, a = 831.39(4), b = 852.67(6), c = 605.84(6) pm, wR = 0.0568, 901 F2 values, 48 variables. The composition of the single crystal and the bulk sample with EDX and ICP-OES was determined as Zn1.94Co0.06(AsO4)OH and (Co0.085Ni0.037Cu0.270Zn1.608)AsO4OH. The Co2+, Ni2+ and Cu2+ incorporation in the bulk sample leads to Curie paramagnetism with an experimental moment of 2.85 µB/M2+ cation and explains the pink color along with the greenish edges. The Raman spectrum shows the characteristic vibrations of the AsO4 tetrahedra and the MO5 pyramids as well as the O–H stretching mode. The adamite structure is closely related with the olivenite type (space group P21/n11). This structural relationship is discussed on the basis of a group–subgroup scheme (Bärnighausen formalism). [ABSTRACT FROM AUTHOR]

Linarite, PbCuSO4(OH)2, crystallizes as secondary mineral in form of clusters of crystals in Mine du Pradet at Cap Garonne in France. A tiny single crystal was isolated and its structure was refined from synchrotron diffraction data (λ = 0.049592 nm): P121/m1, a = 467.75(2), b = 563.48(4), c = 967.64(5) pm, β = 102.647(5)°, wR = 0.0544, 819 F2 values and 56 variables. The proton positions were also refined. The Cu2+ cations are located within Cu(OH)2 ribbons and exhibit pronounced Jahn-Teller distortion (d(Cu–O): 2 × 191.9, 2 × 197.3 and 2 × 252.8 pm). The Cu(OH)2 ribbons are condensed with the sulfate tetrahedra and the lead cations. The latter are coordinated to eight oxygen atoms in a slightly anisotropic manner. Calculations of the electron localization function (ELF) of PbO (litharge), PbSO4 (anglesite) and PbCuSO4(OH)2 (linarite) show pronounced lone-pair character for PbO but rather isotropic ELF values around the lead cations in PbSO4 and PbCuSO4(OH)2. [ABSTRACT FROM AUTHOR]

Systematically twinned olivenite (Cu2(AsO4)OH) single crystals from Cap Garonne, Mine du Pradet, France, were studied by X-ray diffraction: P 21/n, a = 822.69(6) pm, b = 861.88(9) pm, c = 594.06(9) pm, β = 90.000(6)°, wR = 0.0224, 1621 F2 values, 79 variables and a domain ratio of 0.501(1)/0.499(1). The temperature dependence of the magnetic susceptibility was well reproduced with a square-spin cluster model and an antiferromagnetic spin-exchange parameter of J/kB = 157(3) K. [ABSTRACT FROM AUTHOR]

Natural lead dioxide samples (β modification) from Cap Garonne, Mine du Pradet, France and Mount Trevasco, Italy were studied by single crystal X-ray and electron diffraction, clearly manifesting the rutile-type structure. A needle from the Mount Trevasco sample was investigated on a single crystal diffractometer: P42/mnm, a = 495.81(10), c = 338.66(7) pm, wR = 0.0513, 117 F2 values (all data) and nine variables (293 K data). An additional data set at T = 90 K gave no hint for structural distortions. [ABSTRACT FROM AUTHOR]

Ba-rich and Si-rich phlogopites occur in the talc-bearing rocks of the La Creuse sulfide ore deposit in Beaujolais, France. They form a group of compositions completely separated from the common Al-rich phlogopites that occur in the surrounding talc-free metasiltites and metarhyolites, with higher Ba and Mg and lower Al contents. The Ba-rich phlogopites have a relatively narrow compositional range (0.24 to 0.80 Ba per formula unit, for 44 valencies) with high and constant Si (5.8 atoms per formula unit, apfu) and Mg + Fe (5.6 apfu), probably buffered by the presence of talc. Compared to low-Al phlogopites from talc-free rocks, the excess charge introduced by the BaK–1 substitution is compensated by interlayer vacancies. Such a high level of interlayer vacancy (0.56 pfu), related to the talc-producing metasomatic conditions, is essential for the stability of this special group of Ba-rich and Si-rich phlogopites. Single crystal X-ray diffraction analyses were performed. Ba-rich and Si-rich phlogopite is monoclinic, space group C 2 /m , (R = 5.31%) with a = 5.3185(5), b = 9.2136(9), c = 10.1349(11) Å and β = 100.131(11)°. The occupancies of Mg/Fe and K/Ba were refined exploring different vacancies. The solutions giving the best R factor (4.77%) and goodness-of-fit (1.06) are obtained with 15% < vacancy < 40% at the interlayer site. [ABSTRACT FROM AUTHOR]