ALBERT

Description: The new pyroxenoid barrydawsonite-(Y) occurs at the Merlot Claim, North Red Wine Pluton, Labrador, Canada (62°32'38.54'' W; 54°08'1.37'' N). The host rock is a metamorphosed eudialyte syenite consisting of eudialyte, potassic arfvedsonite, jadeitic aegirine, nepheline, albite and potassium feldspar with accessory Y-bearing pectolite, britholite and steenstrupine. Barrydawsonite-(Y) crystals commonly have discrete thin rims of Y-bearing pectolite. The average empirical formula (based on nine anions p.f.u.) is Na 1.54 Ca 0.74 Mn 0.15 Fe 0.07 Y 0.38 Nd 0.01 Sm 0.01 Gd 0.02 Tb 0.01 Dy 0.04 Ho 0.01 Er 0.02 Yb 0.01 Si 3.00 O 9 H. The simplified formula is Na 1.5 Y 0.5 CaSi 3 O 9 H. Barrydawsonite-(Y) is related to pectolite by the substitution 1/2[Na M 3+ Ca –2 ] ( M 3+ = Y, REE ), and is exceptional in being the only member of the pectolite group that has the structure of the monoclinic M2abc polytype. The crystal structure has been determined in monoclinic space group P 2 1 / a : a = 15.5026(2), b = 7.0233(1), c = 6.9769(1) Å, β = 95.149(1)°, V = 756.58(2) Å 3 ( Z = 4). Final agreement indices are R 1 = 0.038, wR 2 = 0.068, Goof = 1.136. The asymmetric unit of barrydawsonite-(Y) has three metal sites: M (1) = Ca, M (2) = Na 0.5 (Y, REE ) 0.5 , M (3) = Na. M (1) and M (2) are octahedrally-coordinated sites, whereas M (3) is [8]-coordinated as in pectolite and serandite. The structural formula for the empirical composition is M (3) Na 1.00 M (2) (Na 0.50 Y 0.38 REE 0.13 ) =1.01 M (1) (Na 0.04 Ca 0.74 $${\mathrm{Mn}}_{0.15}^{2+}$$ $${\mathrm{Fe}}_{0.07}^{2+}$$ ) =1.00 Si 3 O 9 H. There is excellent agreement between the refined site-scattering values and those calculated based upon the structural formula. Barrydawsonite-(Y) is biaxial (+) with α = 1.612(1), β = 1.617(1), = 1.630(1) (white light) and 2V = 63(1)°. The five strongest peaks in the X-ray powder diffraction pattern are [ d obs ( Å), I obs %, ( hkl )]: [2.905, 100, (023)], [3.094, 30, (210,2I11,1I21,202)], [1.7613, 29, (127,323,040)], [3.272, 27, (2I02,104)], [1.7016, 27, (140,2I27,3I25)].

Description: A monoclinic form of Fe 3 S 4 , a polymorph of cubic greigite, occurs as precipitates in a sample of pyrrhotite collected from the Sudbury ore deposit. The nano-crystal precipitates are in a topotaxial relationship with the host pyrrhotite-4 C (Fe 7 S 8 ). The precipitate and the host pyrrhotite have a coherent (001) interface. Half of the octahedral layers in the crystal structure are fully occupied by Fe, while the other half of the octahedral layers are occupied by Fe atoms and vacancies in an ordered manner along the a axis. The crystal structure of the Fe 3 S 4 nano-precipitates has monoclinic symmetry with a space group of I 2 /m . Its c dimension is 6% smaller than that of the host pyrrhotite due to the large number of vacancies in the structure. Fractional coordinates for S and Fe atoms within the unit cell are determined from Z-contrast images and density functional theory (DFT). The calculated results match the measured values very well. It is proposed that the monoclinic Fe 3 S 4 nano-precipitates formed through ordering of vacancies in pyrrhotite with a low Fe/S ratio (i.e. 〈0.875) at low temperature.

Description: Magnesium hydroxyfluoride, Mg(OH)F, has been synthesized by a subcritical hydrothermal route from a 1:1 molar mixture of brucite, Mg(OH)2, and sellaite, MgF2 with a rutile type structure, in excess water. Using a combination of synchrotron X-ray and time-of-flight neutron powder diffraction, the structure of Mg(OH)F has been solved in the diaspore space group Pnma with a = 10.116(3), b = 4.6888(10) and c = 3.0794(7) Å at ambient conditions. The most intense diffraction lines are [dobs (hkl) Iobs]: 2.291 (211) 10, 4.253 (101) 7, 1.747 (212) 7, 2.229 (401) 6 and 1.480 (610) (4) Å, with the largest d-spacing at 5.058 Å. Sharp infrared stretching bands are located at 3679 and 3645 cm -1, with a broader band at 3535 cm -1. The topology of the structure is intermediate between that of the OH and F endmembers, being derived through notional shearing nearly normal to the sheets of octahedra of the CdI2/Mg(OH)2-type structure. Further similar shearing at an interval ½a would lead to a Cd(OH)F-type structure, which is also related to the rutile structure type. The observations and model presented here indicate a close correlation between the structural properties of the endmembers and Mg(OH)F.

Description: The crystal structure of synthetic Ni-rich tourmaline with a nickel content of 18.96 wt.% NiO ( a = 15.890(2), c = 7.1815(8) Å) has been refined to R = 3.1% using single-crystal X-ray diffraction data. It has been shown that Ni is distributed not only over the Y , but also over the Z sites according to the ideal formula Na( $${\mathrm{Ni}}_{2}^{2+}$$ Al)(Al 5 Ni 2+ )(Si 6 O 18 )(BO 3 ) 3 (OH) 4 . Based on bond valences and charge balance analysis it has been shown that this composition corresponds to the stable disordered member of the solid solution series NaAl 3 Al (Si 6 O 18 )(BO 3 ) 3 (O) 3 (OH) – $${\mathrm{NaNi}}_{3}^{2+}$$ Al 6 (Si 6 O 18 )(BO 3 ) 3 (OH) 4 . Taking into consideration available structural data on Me 2+ (Ni, Cu, Co, Fe, Mn)-rich tourmalines, cation-size mismatch and bond-valence calculations we assume that there are no structural constraints precluding occurrence of these cations in both octahedral sites. Divalent transitional metal-rich tourmalines have not been found in Nature probably due to the insufficient concentration of these elements in B-rich geological systems.

Description: Magnesium hydroxyfluoride, Mg(OH)F, has been synthesized by a subcritical hydrothermal route from a 1:1 molar mixture of brucite, Mg(OH)2, and sellaite, MgF2 with a rutile type structure, in excess water. Using a combination of synchrotron X-ray and time-of-flight neutron powder diffraction, the structure of Mg(OH)F has been solved in the diaspore space group Pnma with a = 10.116(3), b = 4.6888(10) and c = 3.0794(7) Å at ambient conditions. The most intense diffraction lines are [dobs (hkl) Iobs]: 2.291 (211) 10, 4.253 (101) 7, 1.747 (212) 7, 2.229 (401) 6 and 1.480 (610) (4) Å, with the largest d-spacing at 5.058 Å. Sharp infrared stretching bands are located at 3679 and 3645 cm -1, with a broader band at 3535 cm -1. The topology of the structure is intermediate between that of the OH and F endmembers, being derived through notional shearing nearly normal to the sheets of octahedra of the CdI2/Mg(OH)2-type structure. Further similar shearing at an interval ½a would lead to a Cd(OH)F-type structure, which is also related to the rutile structure type. The observations and model presented here indicate a close correlation between the structural properties of the endmembers and Mg(OH)F.

Description: Magnesium hydroxyfluoride, Mg(OH)F, has been synthesized by a subcritical hydrothermal route from a 1:1 molar mixture of brucite, Mg(OH)2, and sellaite, MgF2 with a rutile type structure, in excess water. Using a combination of synchrotron X-ray and time-of-flight neutron powder diffraction, the structure of Mg(OH)F has been solved in the diaspore space group Pnma with a = 10.116(3), b = 4.6888(10) and c = 3.0794(7) Å at ambient conditions. The most intense diffraction lines are [dobs (hkl) Iobs]: 2.291 (211) 10, 4.253 (101) 7, 1.747 (212) 7, 2.229 (401) 6 and 1.480 (610) (4) Å, with the largest d-spacing at 5.058 Å. Sharp infrared stretching bands are located at 3679 and 3645 cm -1, with a broader band at 3535 cm -1. The topology of the structure is intermediate between that of the OH and F endmembers, being derived through notional shearing nearly normal to the sheets of octahedra of the CdI2/Mg(OH)2-type structure. Further similar shearing at an interval ½a would lead to a Cd(OH)F-type structure, which is also related to the rutile structure type. The observations and model presented here indicate a close correlation between the structural properties of the endmembers and Mg(OH)F.

Description: The crystal structure of the mineral coquandite, a rare Sb oxy-sulfate hydrate, was solved using intensity data collected from a crystal from the Cetine mine, Tuscany, Italy. This study revealed that the structure is triclinic, space group P 1I, with a = 11.4292(5), b = 29.772(1), c = 11.2989(5) Å, α = 91.152(3), β = 119.266(4), = 92.624(3)° and V = 3346.4(2) Å 3 . The refinement of an anisotropic model led to an R index of 0.0347 for 21,061 independent reflections. Thirty-two Sb sites, five S sites and 67 oxygen sites occur in the crystal structure of coquandite. Sb atoms display the characteristic SbO 3 E and SbO 4 E coordinations whereas S fills (SO 4 ) tetrahedral groups. These atoms are arranged in five symmetry-independent layers perpendicular to b*. Four of them and their centrosymmetrical counterparts form complex modules stacked along b* and bonded through two Sb atoms and H bonds. The complex H bonding system in the structure is discussed. On the basis of information gained from this characterization, the crystal-chemical formula was revised according to the structural results, yielding Sb 6+ x O 8+ x (SO 4 )(OH) x ·(H 2 O) 1– x ( Z = 10) with x = 0.3 instead of Sb 6 O 8 (SO 4 )·H 2 O ( Z = 12) as reported previously. A recalculation of the chemical data listed in the scientific literature for coquandite according to the structural results obtained here leads to a satisfactory agreement.

Description: The new mineral canutite (IMA2013-070), NaMn 3 [AsO 4 ][AsO 3 (OH)] 2 , was found at two different locations at the Torrecillas mine, Salar Grande, Iquique Province, Chile, where it occurs as a secondary alteration phase in association with anhydrite, halite, lavendulan, magnesiokoritnigite, pyrite, quartz and scorodite. Canutite is reddish brown in colour. It forms as prisms elongated on [201I] and exhibiting the forms {010}, {100}, {102}, {201} and {102I}, or as tablets flattened on {102} and exhibiting the forms {102} and {110}. Crystals are transparent with a vitreous lustre. The mineral has a pale tan streak, Mohs hardness of 21/2, brittle tenacity, splintery fracture and two perfect cleavages, on {010} and {101}. The calculated density is 4.112 g cm –3 . Optically, canutite is biaxial (+) with α = 1.712(3), β = 1.725(3) and = 1.756(3) (measured in white light). The measured 2V is 65.6(4)°, the dispersion is r 〈 v (slight), the optical orientation is Z = b ; X ^ a = 18° in obtuse β and pleochroism is imperceptible. The mineral is slowly soluble in cold, dilute HCl. The empirical formula (for tabular crystals from near the mine shaft), determined from electron-microprobe analyses, is (Na 1.05 Mn 2.64 Mg 0.34 Cu 0.14 Co 0.03 ) 4.20 As 3 O 12 H 1.62 . Canutite is monoclinic, C 2/ c , a = 12.3282(4), b = 12.6039(5), c = 6.8814(5) Å, β = 113.480(8)°, V = 980.72(10) Å 3 and Z = 4. The eight strongest X-ray powder diffraction lines are [ d obs Å( I )( hkl )]: 6.33(34)(020), 4.12(26)(2I21), 3.608(29)(310,1I31), 3.296(57)(1I12), 3.150(28)(002,131), 2.819(42)(400,041,330), 2.740(100)(240,4I02,112) and 1.5364(31)(multiple). The structure, refined to R 1 = 2.33% for 1089 F o 〉 4 F reflections, shows canutite to be isostructural with protonated members of the alluaudite group.

Description: Lukkulaisvaaraite, Pd 14 Ag 2 Te 9 , is a new platinum-group mineral discovered in the Lukkulaisvaara intrusion, northern Russian Karelia, Russia. In polished section crystals are ~40 μm across, rimmed by tulameenite and accompanied to varying degrees by telargpalite and Bi-rich kotulskite. Lukkulaisvaaraite is brittle, has a metallic lustre and a grey streak. Values of VHN 20 fall between 339 and 371 kg mm –2 , with a mean value of 355 kg mm –2 , corresponding to a Mohs hardness of ~4. In plane-polarized light, lukkulaisvaaraite is light grey with a brownish tinge, has strong bireflectance, light brownish-grey to greyish-brown pleochroism and distinct to strong anisotropy; it exhibits no internal reflections. Reflectance values of lukkulaisvaaraite in air ( R 1 , R 2 , in %) are: 40.9, 48.3 at 470 nm, 47.6, 56.4 at 546 nm, 52.1, 61.0 at 589 nm and 57.5, 65.2 at 650 nm. Five electron microprobe analyses of natural lukkulaisvaaraite gave the average composition Pd 52.17, Ag 7.03 and Te 40.36, total 99.61 wt.%, corresponding to the empirical formula Pd 14.05 Ag 1.88 Te 9.06 based on 25 atoms; the average of nine analyses on synthetic lukkulaisvaaraite is Pd 52.13, Ag 7.31 and Te 40.58, total 100.02 wt.%, corresponding to Pd 13.99 Ag 1.93 Te 9.08 . The mineral is tetragonal, space group I 4/ m , with a = 8.9599(6), c = 11.822(1) Å, V = 949.1(1) Å 3 and Z = 2. The crystal structure was solved and refined from the powder X-ray diffraction (XRD) data of synthetic Pd 14 Ag 2 Te 9 . Lukkulaisvaaraite has a unique structure type and shows similarities to that of sopcheite (Ag 4 Pd 3 Te 4 ) and palladseite (Pd 17 Se 15 ). The strongest lines in the powder XRD pattern of synthetic lukkulaisvaaraite [ d (Å), I,hkl ] are: 2.8323(58)(130,310), 2.8088(92),(213), 2.5542(66)(312), 2.4312(41)(321,231), 2.1367(57)(411,141), 2.1015(52)(233,323), 2.0449(100)(314), 2.0031(63)(420,240), 1.9700(30)(006), 1.4049(30)(246,426), 1.3187(36)(543,453). The mineral is named for the type locality, the Lukkulaisvaara intrusion in Russian Karelia.

Description: Four specimens of the roméite-group minerals oxyplumboroméite and fluorcalcioroméite from the Långban Mn-Fe deposit in Central Sweden were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis and infrared spectroscopy. The data obtained and those on additional roméite samples from literature show that the main structural variations within the roméite group are related to variations in the content of Pb 2+ , which is incorporated into the roméite structure via the substitution Pb 2+ -〉 A 2+ where A 2+ = Ca, Mn and Sr. Additionally, the cation occupancy at the six-fold coordinated B site, which is associated with the heterovalent substitution B Fe 3+ + Y -〉 B Sb 5+ + Y O 2– , can strongly affect structural parameters. Chemical formulae of the roméite minerals group are discussed. According to crystal-chemical information, the species associated with the name ‘kenoplumboroméite’, hydroxycalcioroméite and fluorcalcioroméite most closely approximate end-member compositions Pb 2 (SbFe 3+ )O 6 , Ca 2 (Sb 5+ Ti)O 6 (OH) and (CaNa)Sb 2 O 6 F, respectively. However, in accord with pyrochlore nomenclature rules, their names correspond to multiple end-members and are best described by the general formulae: (Pb,#) 2 (Sb,#) 2 O 6 , (Ca,#) 2 (Sb,#) 2 O 6 (OH) and (Ca,#)Sb 2 (O,#) 6 F, where ‘#’ indicates an unspecified charge-balancing chemical substituent, including vacancies.