ALBERT

Description: The crystal structure of the mineral kurilite, a rare silver chalcogenide, was solved using intensity data collected from a twinned crystal of type material from the Prasolovskoe deposit, Kunashir Island, Kuril islands (Russia). The study revealed that the structure is trigonal, space group R 3{macron} , with cell parameters: a 15.8135(18), c 19.618(3) Å, and V 4248.6(9) Å 3 . The refinement had a final R index of 0.0218 for 2513 observed reflections [ I 〉 2( I )] and 0.0265 for all 2776 independent reflections and 193 parameters. Three Te sites, three Se sites, and ten Ag sites occur in the crystal structure of kurilite. The silver cations form various crystal-chemical environments, as is typical of many intermetallic compounds. The Ag positions correspond to the most pronounced probability density function ( pdf ) locations (modes) of diffusion-like paths. The d 10 silver ion distribution was determined by means of a Gram-Charlier development of the atomic displacement factors. Crystal-chemical features are discussed in relation to other copper and silver tellurides and pure metals. The disorder observed for the Ag atoms is compared to that of other natural fast ionic conductors, such as the pearceite-polybasite group minerals. On the basis of information gained from the structural characterization, the Z of the crystal-chemical formula was revised to 18 instead of 15, as previously reported.

Description: The crystal structure of schneiderhöhnite, Fe 2+ Fe 3+ 3 As 3+ 5 O 13 , triclinic P , a 8.945(3), b 10.022(3), c 9.161(4) Å, α 62.942(5), β 116.072(6), 81.722(6)°, has been refined to an R 1 value of 1.4%. The structure is very close to that reported by Hawthorne (1985) , but detailed examination of the structural connectivity shows that schneiderhöhnite is better described as a sheet structure than as a framework structure. Zig-zag chains of edge-sharing Fe (1), Fe (2), Fe (3) (= Fe 3+ ) octahedra extend parallel to the c axis, and these chains are cross-linked into a corrugated sheet by tetramers of edge-sharing Fe (4) (= Fe 3+ ) and Fe (5) (= Fe 2+ ) octahedra. (As 3+ O 3 ) triangular pyramids decorate the surface of this sheet of octahedra as single (AsO 3 ) groups, with all three short bonds linked to anion vertices of the octahedra, and as two crystallographically distinct [As 2 O 5 ] dimers with four short bonds (two from each As 3+ ) to octahedron vertices. The sheets are connected along [100] via the bridging anion of one of the two [As 2 O 5 ] dimers that bonds to an Fe 2+ octahedron of the adjacent sheet, imparting a strong sheet-like character to the structure and accounting for the perfect (100) cleavage.

Description: Wiklundite, ideally Pb 2 [4] (Mn 2+ ,Zn) 3 (Fe 3+ ,Mn 2+ ) 2 (Mn 2+ ,Mg) 19 (As 3+ O 3 ) 2 [(Si,As 5+ )O 4 ] 6 (OH) 18 Cl 6 , is a new arseno-silicate mineral from Långban, Filipstad, Värmland, Sweden. Both the mineral and the name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA 2015-057). Wiklundite and a disordered wiklundite-like mineral form radiating, sheaf-like aggregates (up to 1 mm long) of thin brownish-red and slightly bent lath-shaped crystals. It occurs in a dolomite-rich skarn in association with tephroite, mimetite, turneaurite, johnbaumite, jacobsite, barite, native lead, filipstadite and parwelite. Wiklundite is reddish brown to dark brown, and the streak is pale yellowish brown. The lustre is resinous to sub-metallic, almost somewhat bronzy, and wiklundite does not fluoresce under ultraviolet light. The calculated density is 4.072 g cm –3 . Wiklundite is brittle with an irregular fracture, and has perfect cleavage on {001}; no parting or twinning was observed. Wiklundite is uniaxial (–), orange red and non-pleochroic in transmitted light, but shows incomplete extinction and distorted interference figures, preventing complete determination of optical properties. Electron-microprobe analysis (H 2 O calculated from the structure) of wiklundite gave SiO 2 11.17, Al 2 O 3 0.06, Fe 2 O 3 4.46, As 2 O 5 0.75, As 2 O 3 6.81, MnO 47.89, ZnO 0.78, CaO 0.09, PbO 14.48, Cl 6.65, H 2 O 5.18, O=Cl 2 –1.50, total 97.11 wt.%, As valences and H 2 O content taken from the crystal-structure refinement, and Fe 3+ /(Fe 2+ + Fe 3+ ) determined by Mössbauer spectroscopy. Wiklundite is hexagonal-rhombohedral, space group R 3 c, a = 8.257(2), c = 126.59(4) Å, V = 7474(6) Å 3 , Z = 6. The crystal structure of wiklundite was solved by direct methods and refined to a final R 1 index of 3.2%. The structure consists of a stacking of five layers of polyhedra: three layers consist of trimers of edge-sharing Mn 2+ -dominant octahedra linked by (SiO 4 ) tetrahedra, (Fe 3+ (OH) 6 ) dominant octahedra and (AsO 3 ) triangular pyramids; one layer of corner-sharing (SiO 4 ) and (Mn 2+ O 4 ) tetrahedra; and one layer of (Mn 2+ Cl 6 ) octahedra and (Pb 2+ (OH) 3 Cl 6 ) polyhedra. The mineral is named after Markus Wiklund ( b . 1969) and Stefan Wiklund ( b . 1972), the well-known Swedish mineral collectors who jointly found the specimen containing the mineral.

Description: Telluromandarinoite, a tellurite, is a new mineral species from the Wendy open pit, Tambo mine, El Indio-Tambo mining property, Coquimbo Province, Chile. The ideal endmember telluromandarinoite formula is Fe 3+ 2 Te 4+ 3 O 9 ·6H 2 O and it is the Te 4+ analogue of the selenite mineral mandarinoite, Fe 3+ 2 Se 4+ 3 O 9 ·6H 2 O. These deposits are located in rhyolitic and dacitic pyroclastic volcanic rocks of Tertiary age (8–11 Ma) that are strongly hydrothermally altered. The mineralization in the Tambo area is characterized by high-level epithermal veins and breccias located along roughly east–west structures. Hydrothermal breccias consisting of silicified clasts of dacite tuffs cemented by a silica/barite/alunite matrix are common at the occurrence. In fact, all studied specimens containing tellurite mineralization are associated with alunite. Telluromandarinoite is translucent, pale green, with a white streak and vitreous luster. It forms as individual platy crystals, 0.2 mm or less in size, but more commonly as aggregates of platy crystals. The crystals are too small to allow a Mohs hardness determination; they are brittle with an uneven fracture and no observed cleavage or parting. Telluromandarinoite is biaxial positive with α = 1.750(3), β = 1.807(3), and = 1.910(5), with a calculated 2 V = 76.9°. The optical orientation is Y = b , c {circumflex} Z = 10° in obtuse β. No dispersion was noted and no pleochroism was observed. An average of 10 electron microprobe analyses gave SeO 2 22.91, TeO 2 44.30, Fe 2 O 3 26.43, and H 2 O (calc.) 17.59, total 111.23 wt.%. The mineral loses H 2 O in vacuum, so the high totals obtained were expected. The empirical formula (based on 15 O atoms) is Fe 3+ 2.03 (Te 4+ 1.71 Se 4+ 1.27 ) 2.98 O 9 ·6H 2 O with Z = 4, and D calc = 3.372 g/cm 3 . Spot analyses gave stoichiometries that range from telluromandarinoite Fe 3+ 2.03 (Te 4+ 2.12 Se 4+ 0.86 ) 2.98 O 9 ·6H 2 O to mandarinoite Fe 3+ 2.07 (Se 4+ 1.64 Te 4+ 1.31 ) 2.95 O 9 ·6H 2 O. A crystal-structure analysis shows the mineral to be monoclinic, space group P 2 1 / c , with a 16.9356(5), b 7.8955(3), c 10.1675(3) Å, β 98.0064(4)°, and V 1346.32(13) Å 3 . The strongest lines in the X-ray powder pattern [ d in Å,( I ),( hkl )] are: 8.431(44)(200), 7.153(100) , 3.5753(41) , 3.4631(21) , 2.9964(34) , 2.8261(19)(412). The crystal structure of telluromandarinoite is similar to that of emmonsite, Fe 3+ 2 Te 4+ 3 O 9 ·2H 2 O.

Description: Wernerbaurite (IMA 2012–064) and schindlerite (IMA 2012–063) from the St. Jude mine, Slick Rock district, San Miguel County, Colorado, USA, were described as hydronium-bearing decavanadate minerals with the formulae {[Ca(H 2 O) 7 ] 2 (H 2 O) 2 (H 3 O) 2 }{V 10 O 28 } and {[Na 2 (H 2 O) 10 ](H 3 O) 4 }{V 10 O 28 }, respectively. Because these phases correspond to known synthetic phases with these formulae, the presence of NH 4 in these minerals was not considered. Recent investigations of a similar phase discovered at a vanadium locality in the Fergana Valley of Kyrgyzstan showed it to contain NH 4 , leading us to reanalyze the original electron-microprobe mounts of wernerbaurite and schindlerite, specifically seeking N; those analyses confirmed the presence of sufficient NH 4 to replace the originally assigned H 3 O. With the additional H sites included and O replaced by N at the NH 4 sites, the structure refinement residual improved for wernerbaurite from R 1 = 3.41% to R 1 = 3.26% and for schindlerite from R 1 = 3.99% to R 1 = 3.70%. The newly assigned NH 4 sites exhibited normal NH 4 –O bond distances and coordination and reasonable bond-valence sums. The H 3 O synthetic equivalents of both phases had been reported, as well as the NH 4 synthetic equivalent of schindlerite. Subsequent to the publication of the original description of the minerals, the NH 4 equivalent of wernerbaurite has also been reported.

Description: The crystal structure of gianellaite, [(NHg 2 ) 2 ](SO 4 )(H 2 O) x , cubic, F 3 m , a = 9.521(6) Å V = 863.1(1.6) Å 3 , Z = 4, was solved by direct methods and refined to an R 1 index of 2.1% based on 167 unique observed reflections collected on a three-circle rotating-anode (Mo K α X-radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of gianellaite, nitrogen-centred (NHg 4 ) 5+ tetrahedra share all corners to form a framework of tetrahedra with an ordered arrangement of interstitial (SO 4 ) 2– tetrahedra that show strong orientational disorder. Infrared spectroscopy in the principal O–H stretching region shows peaks at ~3300 and 1600 cm –1 , indicating the presence of (H 2 O), the position(s) of which could not be discerned in difference-Fourier maps.

Description: The crystal structure of gianellaite, [(NHg2)2](SO4)(H2O)x, cubic, F4̄3m, a = 9.521(6) Å V = 863.1(1.6) Å3, Z = 4, was solved by direct methods and refined to an R1 index of 2.1% based on 167 unique observed reflections collected on a three-circle rotating-anode (MoKα X-radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of gianellaite, nitrogen-centred (NHg4)5+ tetrahedra share all corners to form a framework of tetrahedra with an ordered arrangement of interstitial (SO4)2– tetrahedra that show strong orientational disorder. Infrared spectroscopy in the principal O–H stretching region shows peaks at ∼3300 and 1600 cm–1, indicating the presence of (H2O), the position(s) of which could not be discerned in difference-Fourier maps.

Description: Anzaite-(Ce), ideally Ce43+Fe2+Ti6O18(OH)2, is a new, structurally complex mineral occurring as scarce minute crystals in hydrothermally altered silicocarbonatites in the Afrikanda alkali-ultramafic complex of the Kola Peninsula, Russia. The mineral is a late hydrothermal phase associated with titanite, hibschite, clinochlore and calcite replacing the primary magmatic paragenesis. The rare-earth elements (REE) (dominated by Ce), Ti and Fe incorporated in anzaite-(Ce) were derived from primary Ti oxides abundant in the host rock. Anzaite-(Ce) is brittle and lacks cleavage; the density calculated on the basis of structural data is 5.054(6) g cm–3. The mineral is opaque and grey with a bluish hue in reflected light; its reflectance values range from 15–16% at 440 nm to 13–14% at 700 nm. Its infrared spectrum shows a prominent absorption band at 3475 cm–1 indicative of OH– groups. The average chemical composition of anzaite-(Ce) gives the following empirical formula calculated on the basis of 18 oxygen atoms and two OH– groups: (Ce2.18Nd0.85La0.41Pr0.26Sm0.08Ca0.36Th0.01)Σ4.15Fe0.97(Ti5.68Nb0.22Si0.04)Σ5.94O18(OH)2. The mineral is monoclinic, space group C2/m, a = 5.290(2), b = 14.575(6), c = 5.234(2) Å, β = 97.233(7)°, V = 400.4(5) Å3, Z = 1. The ten strongest lines in the X-ray micro-diffraction pattern are [dobs in Å (I)hkl]: 2.596 (100) 002; 1.935 (18) 170; 1.506 (14) 133; 1.286 (13) 1.11.0; 2.046 (12) 241; 1.730 (12) 003; 1.272 (12) 0.10.2; 3.814 (11) 111; 2.206 (9) 061; 1.518 (9) 172. The structure of anzaite-(Ce), refined by single-crystal techniques to R1 = 2.1%, consists of alternating layers of type 1, populated by REE (+ minor Ca) in a square antiprismatic coordination and octahedrally coordinated Fe2+, and type 2, built of five-coordinate and octahedral Ti, stacked parallel to (001). This atomic arrangement is complicated by significant disorder affecting the Fe2+, five-coordinate Ti and two of the four anion sites. The order-disorder pattern is such that only one half of these positions in total occupy any given (010) plane, and the disordered (010) planes are separated by ordered domains comprising REE, octahedral Ti and two anion sites occupied by O2–. Structural and stoichiometric relations between anzaite-(Ce) and other REE-Ti (±Nb, Ta) oxides are discussed. The name anzaite-(Ce) is in honour of Anatoly N. Zaitsev of St Petersburg State University (Russia) and The Natural History Museum (UK), in recognition of his contribution to the study of carbonatites and REE minerals. The modifier reflects the prevalence of Ce over other REE in the composition of the new mineral.