ALBERT

Description: The new mineral species barlowite, ideally Cu 4 FBr(OH) 6 , has been found at the Great Australia mine, Cloncurry, Queensland, Australia. It is the Br and F analogue of claringbullite. Barlowite forms thin blue, platy, hexagonal crystals up to 0.5 mm wide in a cuprite-quartz-goethite matrix associated with gerhardtite and brochantite. Crystals are transparent to translucent with a vitreous lustre. The streak is sky blue. The Mohs hardness is 2–2.5. The tenacity is brittle, the fracture is irregular and there is one perfect cleavage on {001}. Density could not be measured; the mineral sinks in the heaviest liquid available, diluted Clerici solution ( D 3.8 g/cm 3 ). The density calculated from the empirical formula is 4.21 g/cm 3 . Crystals are readily soluble in cold dilute HCl. The mineral is optically non-pleochroic and uniaxial (–). The following optical constants measured in white light vary slightly suggesting a small variation in the proportions of F, Cl and Br: 1.840(4)–1.845(4) and 1.833(4)–1.840(4). The empirical formula, calculated on the basis of 18 oxygen atoms and H 2 O calculated to achieve 8 anions and charge balance, is Cu 4.00 F 1.11 Br 0.95 Cl 0.09 (OH) 5.85 . Barlowite is hexagonal, space group P 6 3 / mmc , a = 6.6786(2), c = 9.2744(3) Å, V = 358.251(19) Å 3 , Z = 2. The five strongest lines in the powder X-ray diffraction pattern are [ d (Å)( I )( hkl )]: 5.790(100)(010); 2.889(40)(020); 2.707(55)(112); 2.452(40)(022); 1.668(30)(220).

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: 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.