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The crystal structure of the mineral gortdrumite, a rare copper-mercury-iron sulfide, was solved using intensity data collected using a crystal from the Neuschurf adit, Leogang, Salzburg, Austria. This study revealed that the structure is triclinic, space group P $\bar 1$ , with cell parameters: a = 9.677(4), b = 9.865(5), c = 11.992(5) Å, α = 77.85(4), β = 79.42(3), γ = 76.30(4)°, V = 1076.5(8) Å3 and Z = 1. The refinement led to an R index of 0.0833 for 3335 independent reflections and 143 parameters. Twelve S sites (one with half occupancy) and eighteen metal sites (5 Hg, 12 Cu and 1 Fe) occur in the crystal structure of gortdrumite. Mercury cations link two sulfur atoms in a linear coordination, Cu cations are found in various low-coordination (2, 3 and 4) sites, in agreement with the Cu preference for such environments, and Fe in tetrahedral coordination. Metal–metal interactions are also present and these contacts are discussed in relation with other copper sulfides, intermetallics and pure metals. Electron microprobe analyses of the crystal used for the structural study led to the formula Cu24.83Fe1.73Hg9.09S22.35, on the basis of 58 atoms. On the basis of information gained from the structural and chemical characterization, the crystal-chemical formula was revised to Cu24Fe2Hg9S23 (Z = 1) instead of (Cu,Fe)6Hg2S5 as reported previously. [ABSTRACT FROM AUTHOR]

The crystal structure of the mineral donharrisite, a rare nickel-mercury-sulfide reported in the literature with the formula Ni 8 Hg 3 S 9 , was solved and refined using intensity data collected from a crystal from Leogang, Salzburg Province, Austria. This study revealed that the structure is monoclinic, space group C 2/ m , with a = 11.574(3), b = 6.899(2), c = 5.419(1) Å, β = 93.71(2)° and V = 431.8(2) Å 3 . The refinement of an anisotropic model led to an R index of 0.044 for 383 independent reflections. In the crystal structure there are two Hg sites, four Ni sites and 2 S, with one Hg and one Ni site which are half-occupied. As typical of many intermetallic compounds, the donharrisite structure is characterized by atoms forming complex polyhedra as Hg[S 6 Ni 4 ], Hg[S 4 Ni 3 ], Ni[S 4 Ni 2 ], Ni[S 3 NiHg], Ni[S 6 Ni 2 Hg 2 ], Ni[S 4 Ni 3 Hg 2 ], showing exceedingly short bond distances. Electron microprobe analyses of the crystal used for the structural study led to the formula Ni 3.03 Hg 1.01 S 2.96 , on the basis of 7 atoms. On the basis of information gained from this characterization the crystal chemical formula was revised according to the structural results, yielding Ni 3 HgS 3 with Z = 4 (with a calculated density of 7.27 g/cm 3 ), instead of Ni 8 Hg 3 S 9 with Z = 2 (with a calculated density of 5.18 g/cm 3 ) as previously reported. Although neither reflection streaks nor structural disorder were observed for the selected donharrisite crystal, the possibility that the refined structure (with partially-occupied sites and exceedingly short bond distances) could be a superposition of different layers belonging to an OD (order-disorder) structure is also discussed. [ABSTRACT FROM AUTHOR]

Piccoliite, ideally NaCaMn3+2(AsO4)2O(OH), is a new mineral discovered in the Fe–Mn ore hosted in metaquartzites of the Montaldo di Mondovì mine, Corsaglia Valley, Cuneo Province, Piedmont, Italy. It occurs as small and rare black crystals and aggregates hosted by a matrix of quartz, associated with calcite and berzeliite/manganberzeliite. It has been also found in the Valletta mine near Canosio, Maira Valley, Cuneo Province, Piedmont, Italy, where it occurs embedded in quartz associated with grandaite, hematite, tilasite/adelite and rarely thorianite. The mineral is opaque (thin splinters may be very dark red), with brown streak and has a resinous to vitreous lustre. It is brittle with irregular fracture. No cleavage has been observed. The measured Mohs hardness is ~5–5.5. Piccoliite is non fluorescent. The calculated density is 4.08 g⋅cm–3. Chemical spot analyses by electron microprobe analysis using wavelength dispersive spectroscopy resulted in the empirical formula (based on 10 anions per formula unit) (Na0.64Ca0.35)Σ0.99(Ca0.75Na0.24)Σ0.99(Mn3+1.08Fe3+0.59Mg0.20Ca0.10)Σ1.97(As2.03V0.03Si0.01)Σ2.07O9(OH) and (Na0.53Ca0.47)Σ1.00(Ca0.76Na0.23Sr0.01)Σ1.00(Mn3+0.63Fe3+0.49Mg0.48Mn4+0.34Ca0.06)Σ2.00(As1.97P0.01Si0.01)Σ1.99O9(OH) for the Montaldo di Mondovì and Valletta samples, respectively. The mineral is orthorhombic, Pbcm , with single-crystal unit-cell parameters a = 8.8761(9), b = 7.5190(8), c = 11.689(1) Å and V = 780.1(1) Å3 (Montaldo di Mondovì sample) and a = 8.8889(2), b = 7.5269(1), c = 11.6795(2) Å, V = 781.43(2) Å3 (Valletta sample) with Z = 4. The seven strongest powder X-ray diffraction lines for the sample from Montaldo di Mondovì are [ d Å (I rel; hkl)]: 4.85 (57; 102), 3.470 (59; 120, 113), 3.167 (100; 022), 2.742 (30; 310, 213), 2.683 (53; 311, 023), 2.580 (50; 222, 114) and 2.325 (19; 320, 214, 223). The crystal structure (R 1 = 0.0250 for 1554 unique reflections for the Montaldo di Mondovì sample and 0.0260 for 3242 unique reflections for the Valletta sample) has MnO5(OH) octahedra forming edge-shared dimers; these dimers are connected through corner-sharing, forming two-up-two-down [[6] M 2([4] T O4)4φ2] chains [ M = Mn; T = As; φ = O(OH)] running along [001]. These chains are bonded in the a and b directions by sharing corners with AsO4 tetrahedra, giving rise to a framework of tetrahedra and octahedra hosting seven-coordinated Ca2+ and Na+ cations. The crystal structure of piccoliite is closely related to that of pilawite-(Y) as well as to carminite-group minerals that also show the same type of chains but with different linkage. The mineral is named after the mineral collectors Gian Paolo Piccoli and Gian Carlo Piccoli (father and son) (1926–1996 and b. 1953, respectively), the latter having discovered the type material at the Montaldo di Mondovì mine. [ABSTRACT FROM AUTHOR]

The crystal structure of braithwaiteite, NaCu2+5(Sb5+Ti4+)O2(AsO4)4(AsO3OH)2(H2O)8, triclinic, Z=1, P1, a=7.0308(4), b=9.8823(5), c=10.6754(6)Å, α=106.973(1), β=104.274(1), γ=93.839(1)°, V=679.76(11)Å3, was solved by direct methods and refined to an R1 index of 0.025 for 3584 observed reflections. A prominent motif in the braithwaiteite structure is a chain of corner-sharing (Sb,TiO6) octahedra that is decorated with (AsO4) tetrahedra to form a [(SbTi)(AsO4)4O2] chain that extends along the a-direction and defines the cell dimension in this direction at ∼7Å. These chains are cross-linked in the b-direction by chains of edge-sharing (CuO6) octahedra that are decorated by arsenate tetrahedra to form a [Cu2(AsO4OH)2O4] chain; these two chains link to form a sheet parallel to (001). These sheets stack along the c-direction and are linked by (CuO6) and (NaO6) octahedra, together with an extensive network of hydrogen bonds. The [M(TO4)2Φ4] chain (M=octahedrally coordinated metal, T=tetrahedrally coordinated metal, Φ=unspecified simple anion;≡[(SbTi)(AsO4)4O2] chain) is a common motif in secondary oxysalt minerals, occurring in sulfates, phosphates, arsenates, vanadates and silicates. [ABSTRACT FROM AUTHOR]

The incommensurately modulated crystal structure of the mineral daliranite has been determined using 3D electron diffraction data obtained on nanocrystalline domains. Daliranite is orthorhombic with a = 21, b = 4.3, c = 9.5 Å and shows modulation satellites along c. The solution of the average structure in the Pnma space group together with energy‐dispersive X‐ray spectroscopy data obtained on the same domains indicate a chemical formula of PbHgAs2S5, which has one S fewer than previously reported. The crystal structure of daliranite is built from columns of face‐sharing PbS8 bicapped trigonal prisms laterally connected by [2+4]Hg polyhedra and (As3+2S5)4− groups. The excellent quality of the electron diffraction data allows a structural model to be built for the modulated structure in superspace, which shows that the modulation is due to an alternated occupancy of a split As site. [ABSTRACT FROM AUTHOR]

Agmantinite, ideally Ag2MnSnS4, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as orange–red crystals up to 100 μm across. Agmantinite is translucent with adamantine lustre and possesses a red streak. It is brittle. Neither fracture nor cleavage were observed. Based on the empirical formula the calculated density is 4.574 g/cm3. On the basis of chemically similar compounds the Mohs hardness is estimated at between 2 to 2½. In plane-polarised light agmantinite is white with red internal reflections. It is weakly bireflectant with no observable pleochroism with red internal reflections. Between crossed polars, agmantinite is weakly anisotropic with reddish brown to greenish grey rotation tints. The reflectances (R min and R max) for the four standard wavelengths are: 19.7 and 22.0 (470 nm); 20.5 and 23.2 (546 nm); 21.7 and 2.49 (589 nm); and 20.6 and 23.6 (650 nm), respectively. Agmantinite is orthorhombic, space group P 21 nm , with unit-cell parameters: a = 6.632(2), b = 6.922(2), c = 8.156(2) Å, V = 374.41(17) Å3, a : b : c 0.958:1:1.178 and Z = 2. The crystal structure was refined to R = 0.0575 for 519 reflections with I > 2σ(I). Agmantinite is the first known mineral of ${M}_{\rm 2}^{\rm I} $ M II M IVS4 type that is derived from wurtzite rather than sphalerite by ordered substitution of Zn, analogous to the substitution pattern for deriving stannite from sphalerite. The six strongest X-ray powder-diffraction lines derived from single-crystal X-ray diffraction data [ d in Å (intensity)] are: 3.51 (s), 3.32 (w), 3.11 (vs), 2.42 (w), 2.04 (m) and 1.88 (m). The empirical formula (based on 8 apfu) is (Ag1.94Cu0.03)Σ1.97(Mn0.98Zn0.05)Σ1.03Sn0.97S4.03.The crystal structure-derived formula is Ag2(Mn0.69Zn0.31)Σ1.00SnS4 and the simplified formula is Ag2MnSnS4. The name is for the composition and the new mineral and mineral name have been approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2014-083). [ABSTRACT FROM AUTHOR]