The crystal structure of pseudojohannite from White Canyon, Utah, was solved by charge-flipping from single-crystal X-ray diffraction data and refined to an Robs = 0.0347, based on 2664 observed reflections. Pseudojohannite from White Canyon is triclinic, P1̄, with a = 8.6744(4), b = 8.8692(4), c = 10.0090(5) Å, α = 72.105(4)°, β = 70.544(4)°, γ = 76.035(4)°, and V = 682.61(5) Å3, with Z = 1 and chemical formula Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12. The crystal structure of pseudojohannite is built up from sheets of zippeite topology that do not contain any OH groups; these sheets are identical to those found in zippeites containing Mg2+, Co2+, and Zn2+. The two Cu2+ sites in pseudojohannite are [5]- and [6]-coordinated by H2O molecules and OH groups. The crystal structure of the pseudojohannite holotype specimen from Jáchymov was refined using Rietveld refinement of high-resolution powder diffraction data. Results indicate that the crystal structures of pseudojohannite from White Canyon and Jáchymov are identical.
[The crystal structure of kingite, Al3(PO4)2(F5OH)2·B(H2O, OH), a secondary mineral from a Cambrian-Precambrian phosphate deposit at Tom’s Quarry, near Kapunda, South Australia, has been determined from a powder sample using synchrotron X-ray diffraction data. The structure was determined ab initio by direct methods and refined to Rbragg = 0.022 and Rwp = 0.039 using the Rietveld method. The triclinic structure was solved and refined in the space group P1̅, a = 9.377(1), b = 10.113(1), c = 7.138(1) A, σ = 97.60(1), β= 100.88(1), γ = 96.01(1)°, V= 653.0(1) A3, Z= 2. The structure of kingite contains finite strings of three corner sharing AlΦ6 octahedra (where Φ represents O, OH-, F-, or H2O). These strings are cross-linked via PO4 tetrahedra to produce layers that are perpendicular to [100]. The layers are linked via hydrogen bonding through H2O located in the interlayer space. Kingite is shown to have a different stoichiometry to that reported earlier. The relationship of kingite to the structures of wavellite, Al3(P04)2(OH)3·5H2O, and mitryaevaite, A15(PO4)2[(P,S)O3(OH,O)]2F2(OH)2(H2O)8-6.48H2O, are briefly discussed.
Abstract Decrespignyite-(Y) is a new copper yttrium rare earth carbonate chloride hydrate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Decrespignyite-(Y) occurs as blue crusts, coatings and fillings in thin fissures on the slatey country rock. Individual pseudohexagonal platelets are typically 10–50 µm in maximum dimension and are often curved. Associated minerals include caysichite-(Y), donnayite-(Y), malachite and kamphaugite-(Y). Electron microprobe and CHN analyses gave: Y 2 O 3 42.2; La 2 O 3 0.1; Pr 2 O 3 0.1; Nd 2 O 3 1.3; Sm 2 O 3 1.0; Gd 2 O 3 4; Tb 2 O 3 0.4; Dy 2 O 3 3.7; Ho 2 O 3 2.6; Er 2 O 3 2.5; CaO 0.5; CuO 10.9; Cl 3.0; CO 2 19.8; H 2 O 10.8, yielding an empirical formula of (Y 3.08 Gd 0.22 Dy 0.16 Ho 0.11 Er 0.10 Nd 0.06 Sm 0.05 Tb 0.02 La 0.02 Pr 0.01 Ca 0.08 ) ∑3.91 Cu 1.12 (CO 3 ) 3.70 -Cl 0.7 (OH) 5.79 ·2.4H 2 O. The simplified formula is (Y, REE ) 4 Cu(CO 3 ) 4 Cl(OH) 5 ·2H 2 O. The mineral is royal blue to turquoise-blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology suggests that cleavage would be on [010]. The Mohs' hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are { d obs ( I obs ) ( hkl )} 22.79 (30) (010); 7.463 (30) (001); 7.086 (50) (011); 6.241 (100) (021); 4.216 (30) ( 12); 3.530 (40) (022); 3.336 (30) (032); 2.143 (30) (222, 01). The powder diffraction pattern was indexed on a monoclinic cell with a = 8.899(6), b = 22.77(2), c = 8.589(6)Å, β = 120.06(5)°, V = 1506.3(7) Å 3 and Z = 4. The structure of the new mineral could not be determined but powder diffraction data indicate the space group is P 2, P m or P 2/ m . The measured density is 3.64(2) g/cm 3 and the calculated density is 3.645 g/cm 3 . Decrespignyite-(Y) is biaxial negative with α = 1.604(4) and γ = 1.638(3) with β very close to γ pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint). Decrespignyite-(Y) is a supergene mineral which precipitated from mildly basic carbonated ground waters. The mineral is named after Robert Champion de Crespigny, a prominent figure in the Australian mining industry and chancellor of the University of Adelaide.
There is increasing evidence that the surface materials on Europa are influenced by endogenic and exogenic processes and chemistry. To explore how this may drive the diversity of resultant minerals on the surface of Europa, this study has explored a number of samples within the MgSO4–H2SO4–H2O ternary with synchrotron X-ray powder diffraction across a large temperature range (100–300 K). The crystalline phase composition of these samples has been charted, and four new crystalline phases have been identified. The structure of one of these is presented, along with discussion of the possible contents of two of the other phases. Overall this study demonstrates that the interaction between exogenic and endogenic processes has the possibility to drive greater mineral diversity on Europa, as well as its neighboring icy moons.
Pseudojohannite is a hydrated copper(II) uranyl sulfate described from Jáchymov, Northern Bohemia, Czech Republic (type locality). Pseudojohannite also occurs at the Musonoï quarry near Kolwezi, Shaba, Congo, and the La Creusaz prospect, Western Swiss Alps. At all three localities, pseudojohannite formed through the interaction of acid sulfate mine drainage waters with uraninite (Jáchymov and La Creusaz) or uranyl silicates (Musonoï). Pseudojohannite forms moss green, non UV-ß uorescent aggregates consisting of irregularly shaped crystals measuring up to 25 μm in length and displaying an excellent cleavage parallel to (.101). dmeas is 4.31 g/cm3, dcalc 4.38 g/cm3, and the refractive indices are nmin = 1.725 and nmax = 1.740. A high-resolution synchrotron powder diffraction pattern on the material from Musonoï shows that pseudojohannite is triclinic (P1 or P1̅), with a = 10.027(1) Å, b = 10.822(1) Å, c = 13.396(1) Å, α = 87.97(1)°, β = 109.20(1)°, γ = 90.89(1)°, V = 1371.9(5) Å3. The location of the uranium and sulfur atoms in the cell was obtained by direct methods using 1807 reflections extracted from the powder diffractogram. Pseudojohannite contains zippeite-type layers oriented parallel to (.101). The empirical chemical formula calculated for a total of 70 O atoms is Cu6.52U7.85S4.02O70H55.74, leading to the simplified chemical formula Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O. The distance of 9.16 Å between the uranylsulfate sheets in pseudojohannite shows that neighboring layers do not share O atoms with the same CuΦ6 [Φ = (O,OH)] distorted octahedrons, such as in magnesium-zippeite. Rather, it is expected that CuΦ6 forms a layer bound to the zippeite-type layers by hydrogen bonding, as in marécottite, or one apex of the CuΦ6 polyhedron only is shared with a zippeite-type layer, as in synthetic SZIPPMg. The higher number of cations in the interlayer of pseudojohannite (Cu:S = 1.6:1) compared to marécottite (3:4) and SZIPPMg (1:1) indicates that pseudojohannite has a unique interlayer topology. Ab-initio powder structure solution techniques can be used to obtain important structural information on complex micro-crystalline minerals such as those found in the weathering environment. Pseudojohannite represents a new member of the zippeite group of minerals, and further illustrates the structural complexity of zippeite-group minerals containing divalent cations, which have diverse arrangements in the interlayer. Peudojohannite and other divalent zippeites are common, easily overlooked minerals in acid drainage environments around uranium deposits and wastes.
Abstract This study presents a newly identified water‐rich crystalline form of sulfuric acid hydrate, H 2 SO 4 •6H 2 O, a hexahydrate. The method of formation of this material suggests that sulfuric acid hexahydrate (SAHx) could be an abundant material on the surface of Jupiter's Galilean ice moons, Europa, Ganymede, and Callisto. The structure of SAHx was determined by the combined use of synchrotron X‐ray and neutron powder diffraction data. The structural arrangement of SAHx exhibits the same water layer topology that has been determined for sulfuric acid octahydrate (SAO), but differs in the stacking of this water layer and the interlayer species. SAHx is observed to form over a large range of solution compositions and displays stability over the temperature range 80 to 190 K.
Abstract Paratooite-(La) is a new lanthanum-dominant rare-earth copper carbonate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Paratooite-(La) occurs as sheaves and radiating sprays of blade-like to tabular pale blue crystals in thin fissures in a slaty country rock. Individual crystals are typically 50–200 μm in maximum dimension but <5 μm thick. Associated minerals include donnayite-(Y), kamphaugite-(Y), and bastnäsite-(La). Electron microprobe and CHN analyses gave: La 2 O 3 26.47; Pr 2 O 3 7.74; Nd 2 O 3 8.15; Sm 2 O 3 0.66; Gd 2 O 3 0.85; Y 2 O 3 0.72; CaO 7.57; SrO 3.15; Na 2 O 3.3; CuO 5.77; F 0.24; CO 2 32.05; NO 2 1.12; -O=F -0.10; sum 100.03, yielding an empirical formula of (La 3 .54Ca 2.94 Na 2 . 32 Nd 1.05 Pr 1.03 Sr 0.66 Y 0.14 Gd 0.10 Sm 0.08 ) Σ11.86 Cu 1.58 (C 15.84 N 0.53 )O 47.76 F 0.24. The simplified formula is ( REE ,Ca,Na,Sr) 6 Cu(CO 3 ) 8 or possibly REE 3 (Ca,Sr) 2 NaCu(CO 3 ) 8 . The mineral is pale turquoise-blue to pale blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology and TEM studies indicate a cleavage parallel to ﹛100﹜. The Mohs hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are [d obs (I obs ) ( hkl )]: 5.047 (53) (200); 4.786 (49) (021); 3.957 (43) (220); 3.468 (43) (012, 221); 2.927 (100) (202); 2.530 (52) (241); 2.344 (22) (420,103); 2.232 (20) (421). A synchrotron powder diffraction pattern was indexed on a primitive orthorhombic cell with a = 10.0862(5), b = 12.8088(6), c = 7.2360(4) Å, V= 934.8(1) Å 3 and Z = 2. The crystal structure of the new mineral could not be determined but powder diffraction data indicate the space group is probably P 222, Pmmm , P 222 1 or Pmm 2 . The measured density is 3.68(3) g/cm 3 and the calculated density is 3.78 g/cm 3 . Paratooite-(La) is biaxial negative with α = 1.605(3), β = 1.696(3) and γ = 1.752(2); pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint) with absorption Z ≈ Y >> X. Paratooite-(La) is a supergene mineral which precipitated from mildly basic carbonated groundwaters. The mineral is named for the type locality.
Zn(BH4)2·2NH3, a new ammine metal borohydride, has been synthesized via simply ball-milling a mixture of ZnCl2·2NH3/2LiBH4. Structure analysis shows that the subsequent complex has a monoclinic structure with unit-cell parameters of a = 6.392(4) Å, b = 8.417(6) Å, c = 6.388(4) Å and β = 92.407(4)° and space group P21, in which Zn atoms coordinate with two BH4 groups and two NH3 groups. The interatomic distances reported herein show that Zn–H bonding in Zn(BH4)2·2NH3 is shorter than Ca–H bonds in Ca(BH4)2·2NH3 and Mg–H in Mg(BH4)2·2NH3. This reduced bond contact leads to an increase in the ionic character of H. This study is able to show a good correlation between the reduced M–H distance and enhanced dehydrogenation behavior of the hydride material. Dehydrogenation results showed that Zn(BH4)2·2NH3/LiCl is able to release 5.36 wt% hydrogen (corresponding to 8.9 wt% for pure Zn(BH4)2·2NH3) below 115 °C within 15 min without concomitant release of undesirable gases such as ammonia and/or boranes, thereby demonstrating the potential of Zn(BH4)2·2NH3 to be used as a solid hydrogen storage material.
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