ALBERT

Description: Pieczkaite, ideally Mn 5 (PO 4 ) 3 Cl, is a new apatite-supergroup mineral from Cross Lake, Manitoba, Canada. It occurs as small patches and narrow veins in large crystals of apatite and (Mn,Cl)-bearing apatite in phosphate pods in the quartz core of a granitic pegmatite. Veins of Mn-bearing apatite narrow to ~25 μm where the Mn content becomes high enough to constitute pieczkaite. It is gray with a grayish-white streak, does not fluoresce under ultraviolet light, and has no observable cleavage or parting. Mohs hardness is 4–5, and pieczkaite is brittle with an irregular fracture. The calculated density is 3.783 g/cm 3 . Optical properties were measured using a Bloss spindle stage at a wavelength of 590 nm (using a gel filter). Pieczkaite is uniaxial (–) with indices of refraction = 1.696, = 1.692, both ±0.002. Pieczkaite is hexagonal, space group P 6 3 / m , a = 9.504(4), c = 6.347(3) Å, V = 496.5(1) Å 3 , Z = 2, c : a = 1:0.6678. The six strongest lines in the X-ray powder diffraction pattern are as follows: d (Å), I , ( hkl ): 2.794, 100, (31, 31); 2.744, 88, (030); 2.639, 34, (22); 2.514, 25, (031, 022); 1.853, 25, (42, 42); 3.174, 24, (002). Chemical analysis by electron microprobe gave P 2 O 5 37.52, MnO 41.77, FeO 2.45, CaO 13.78, Cl 3.86, H 2 O 0.60, OCl –0.87, sum 99.11 wt% where the H 2 O content was calculated as 1 – Cl apfu. The resulting empirical formula on the basis of 12 O anions is (Mn 3.36 Fe 0.20 Ca 1.40 ) 4.96 (P 1.01 O 4 ) 3 (Cl 0.62 OH 0.38 ) 1.00 , and the end-member formula is Mn 5 (PO 4 ) 3 Cl. The crystal structure of pieczkaite was refined to an R 1 index of 4.07% based on 308 observed reflections collected on a three-circle rotating-anode diffractometer with Mo K α X-radiation. Pieczkaite is isostructural with apatite, Mn is the dominant cation at both the [9]- and [7]-coordinated-cation sites in the structure, and Cl is the dominant monovalent anion.

Description: Trichodesmium , a colonial cyanobacterium typically associated with tropical waters, was observed between January and April 2014 in the western English Channel. Sequencing of the heterocyst differentiation ( hetR ) and 16S rRNA genes placed this community within the Clade IV Trichodesmium , an understudied clade previously found only in low numbers in warmer waters . Nitrogen fixation was not detected although measurable rates of nitrate uptake and carbon fixation were observed. Trichodesmium RuBisCO transcript abundance relative to gene abundance suggests the potential for viable and potentially active Trichodesmium carbon fixation. Observations of Trichodesmium when coupled with a numerical advection model indicate that Trichodesmium communities can remain viable for 〉3.5 months at temperatures lower than previously expected. The results suggest that Clade IV Trichodesmium occupies a different niche to other Trichodesmium species, and is a cold- or low-light-adapted variant.

Description: Phosphoran olivine (1–7 wt% P 2 O 5 ) is a metastable phase known from fewer than a dozen meteoritic or terrestrial occurrences. We have thoroughly examined phosphoran olivine in the Springwater pallasite to characterize its distribution, textural relationships, and geochemistry. Phosphoran olivine is abundant in Springwater as randomly distributed millimeter-scale partial overgrowths on the P-free olivine crystals. Geochemical analyses support the substitution mechanism of P into the tetrahedral Si site with octahedral site vacancies for charge balance; observed trace element variations, on the other hand, are not related to P substitution. Element mapping reveals fine-scale oscillatory P zoning in unusual serrate patterns, indicating rapid crystal nucleation from a melt as proposed by Boesenberg and Hewins (2010) and a subsequently variable rate of crystallization. The timing of phosphoran olivine formation in Springwater is constrained to after the period of macroscopic olivine rounding but before the cooling of the metal matrix; because the phosphoran overgrowths overprint specific host grain boundary modifications, we suggest that the episode of extremely rapid cooling necessary to crystallize and preserve this rare phase may have been triggered by an additional impact to the parent body.

Description: The crystal structures of seven members of the graftonite-beusite series, ideally (Fe 2+ ,Mn 2+ ,Ca) 3 (PO 4 ) 2 , monoclinic P 2 1 / c, a 8.77–8.81, b 11.43–11.58, c 6.13–6.17 Å, β 99.19–99.32°, V 607.5–617.7 Å 3 , have been refined to R 1 indices of 2.1–3.7% using ~1300–1600 unique observed reflections (| F o | 〉 5 F ) collected using a single-crystal diffractometer equipped with Mo K α X-radiation. The crystals used in the collection of the X-ray data were subsequently analyzed with an electron microprobe and the structural and microprobe results were used to assign site populations. The refined site-scattering values and linear variation in mean bond-length as a function of aggregate-cation radius indicate that Ca is completely ordered at the M (1) site. Similarly Mn is ordered at the M (1) and M (3) sites, with any excess Mn occurring at M (2), and Mg is completely ordered at M (2). Detailed consideration of incident bond-valence sums at the three M sites indicates that the coordination numbers of the M (1), M (2), and M (3) sites are [8], [5], and [6], respectively, although the differences between these and [7], [5], and [5] are very small. Ca is dominant at the M (1) site in a previously refined beusite structure, and there are compositions reported here and elsewhere in which Ca is dominant at M (1) in graftonite-like compositions, indicating the potential for new mineral species in this group.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.

Description: Davidlloydite, ideally Zn3(AsO4)2(H2O)4, is a new supergene mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. It occurs as elongated prisms (~10:1 length-to-width ratio) that are flattened on {010}, and up to 100 × 20 × 10 µm in size. The crystals occur as aggregates (up to 500 µm across) of subparallel to slightly diverging prisms lying partly on and partly embedded in fine-grained calcioandyrobertsite. Crystals are prismatic along [001] and flattened on {010}, and show the forms {010} dominant and {100} subsidiary. Davidlloydite is colourless with a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. The cleavage is distinct on {010}, and no parting or twinning was observed. The Mohs hardness is 3–4. Davidlloydite is brittle with an irregular to hackly fracture. The calculated density is 3.661 g cm -3. Optical properties were measured with a Bloss spindle stage for the wavelength 590 nm using a gel filter. The indices of refraction are a = 1.671, ß = 1.687, ? = 1.695, all ±0.002; the calculated birefringence is 0.024; 2Vobs = 65.4(6)°, 2Vcalc = 70°; the dispersion is r 〈 v, weak; pleochroism was not observed. Davidlloydite is triclinic, space group P1I, with a = 5.9756(4), b = 7.6002(5), c = 5.4471(4) Å, a = 84.2892(9), ß = 90.4920(9), ? = 87.9958(9)°, V = 245.99(5) Å3, Z = 1 and a:b:c = 0.7861:1:0.7167. The seven strongest lines in the X-ray powder diffraction pattern [listed as d (Å), I, (hkl)] are as follows: 4.620, 100, (011, 1I10); 7.526, 71, (010); 2.974, 49, (200, 022I); 3.253, 40, (021, 120); 2.701, 39, (2I10, 002, 1I2I1); 5.409, 37, (001); 2.810, 37, (210). Chemical analysis by electron microprobe gave As2O5 43.03, ZnO 37.95, CuO 5.65, H2O(calc) 13.27, sum 99.90 wt.%. The H2O content and the valence state of As were determined by crystal structure analysis. On the basis of 12 anions with H2O = 4 a.p.f.u., the empirical formula is (Zn2.53Cu0.39)S2.92As2.03O8(H2O)4.The crystal structure of davidlloydite was solved by direct methods and refined to an R1 index of 1.51% based on 1422 unique observed reflections collected on a three-circle rotating-anode (MoKa radiation) diffractometer equipped with multilayer optics and an APEX-II detector. In the structure of davidlloydite, sheets of corner-sharing (As5+O4) and (ZnO4) tetrahedra are linked by ZnO2(H2O)4 octahedra. The structure is related to that of parahopeite.