Ladislav Lapčák

Leydetite, Fe(UO2)(SO4)2(H2O)11, a new uranyl sulfate mineral from Mas d'Alary, Lodève, France

Abstract Leydetite, monoclinic Fe(UO2)(SO4)2(H2O)11 (IMA 2012−065), is a new supergene uranyl sulfate from Mas d’Alary, Lodève, Hérault, France. It forms yellow to greenish, tabular, transparent to translucent crystals up to 2 mm in size. Crystals have a vitreous lustre. Leydetite has a perfect cleavage on (001). The streak is yellowish white. Mohs hardness is ~2. The mineral does not fluoresce under long- or shortwavelength UV radiation. Leydetite is colourless in transmitted light, non-pleochroic, biaxial, with α = 1.513(2), γ= 1.522(2) (further optical properties could not be measured). The measured chemical composition of leydetite, FeO 9.28, MgO 0.37, Al2O3 0.26, CuO 0.14, UO3 40.19, SO3 21.91, SiO2 0.18, H2O 27.67, total 100 wt.%, leads to the empirical formula (based on 21 O a.p.f.u.), (Fe0.93Mg0.07Al0.04Cu0.01)∑1.05(U1.01O2)(S1.96Si0.02)S1.98O8(H2O)11. Leydetite is monoclinic, space group C2/c, with a = 11.3203(3), b = 7.7293(2), c = 21.8145(8) Å, β = 102.402(3)°, V = 1864.18(10) Å3, Z = 4, and Dcalc = 2.55 g cm−3. The six strongest reflections in the X-ray powder diffraction pattern are [dobs inA ˚ (I) (hkl)]: 10.625 (100) (002), 6.277 (1) (1̅11), 5.321 (66) (004), 3.549 (5) (006), 2.663 (4) (008), 2.131 (2) (0 0 10). The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.0224 for 5211 observed reflections with [I > 3σ(I)]. Leydetite possesses a sheet structure based upon the protasite anion topology. The sheet consists of UO7 bipyramids, which share four of their equatorial vertices with SO4 tetrahedra. Each SO4 tetrahedron, in turn, shares two of its vertices with UO7 bipyramids. The remaining unshared equatorial vertex of the bipyramid is occupied by H2O, which extends hydrogen bonds within the sheet to one of a free vertex of the SO4 tetrahedron. Sheets are stacked perpendicular to the c direction. In the interlayer, Fe2+ ions and H2O groups link to the sheets on either side via a network of hydrogen bonds. Leydetite is isostructural with the synthetic compound Mg(UO2)(SO4)2(H2O)11. The name of the new mineral honours Jean Claude Leydet (born 1961), an amateur mineralogist from Brest (France), who discovered the new mineral.

Crystal structure and formula revision of deliensite, Fe[(UO2)2(SO4)2(OH)2](H2O)7

Abstract The crystal structure of deliensite, Fe[(UO2)2(SO4)2(OH)2](H2O)7, was solved by direct methods and refined to R1 = 6.24% for 5211 unique observed reflections [Iobs > 3σ(I)], on a crystal that was found to consist of rotational and inversion (merohedral) twins, from Jerony’m mine, Abertamy in the Czech Republic. The presence of four twin domains was taken into account in the refinement. The structure is orthorhombic, space group Pnn2, with unit-cell parameters a = 15.8514(9), b = 16.2478(7), c = 6.8943(3) Å , V = 1775.6(1) Å3 and Z = 4. The crystal structure of deliensite contains uranyl-sulfate sheets with a phosphuranylite topology, consisting of dimers of edge-sharing uranyl pentagonal bipyramids linked by corner-sharing with sulfate tetrahedra. The sheets lie in the (100) plane and are decorated by [Fe2+O(H2O)5] octahedra; two weakly bonded H2O molecules are present in the interlayer. The [Fe2+O(H2O)5] octahedron is linked directly to the sheet via the uranyl oxygen atom. Adjacent sheets are linked by hydrogen bonds only. The sheet topology and geometrical isomerism is discussed and a comparison of the composition obtained from electron-probe microanalysis, powderdiffraction data, Raman and infrared spectra of deliensite samples from Mas d’Alary, Lodève, France; L’Ecarpière mine, Gétigné, France; and several localities at Jáchymov, Western Bohemia, Czech Republic is made.

Shumwayite, [(UO2)(SO4)(H2O)2]2·H2O, a new uranyl sulfate mineral from Red Canyon, San Juan County, Utah, USA

Abstract The new mineral shumwayite (IMA2015-058), [(UO2)(SO4)(H2O)2]2·H2O, was found in the Green Lizard and Giveaway-Simplot mines, White Canyon district, San Juan County, Utah, USA, where it occurs as a secondary alteration phase. At the Green Lizard mine, it is found in association with calcite, gypsum, plášilite, pyrite, rozenite and sulfur; at the Giveaway-Simplot mine, shumwayite is associated with rhomboclase and römerite. The mineral occurs as pale greenish-yellow monoclinic prisms, elongated on [100], up to ~0.3 mm long and commonly in subparallel to random intergrowths. The mineral is transparent with a vitreous lustre and has a white streak. It fluoresces bright greenish white under both longwave and shortwave ultraviolet radiation. The Mohs hardness is ∼2. Crystals are brittle with perfect {011} cleavage and irregular fracture. The mineral is slightly deliquescent and is easily soluble in room temperature H2O. The calculated density is 3.844 g cm-3. Optically, shumwayite is biaxial (+/-), with α = 1.581(1), β = 1.588(1), γ = 1.595(1) (measured in white light). The measured 2Vx based on extinction data collected on a spindle stage is 89.8(8)°; the calculated 2Vx is 89.6°. Dispersion is strong, but the sense is not defined because the optic sign is ambiguous. No pleochroism was observed. The optical orientation is X = b, Y ≈ c, Z ≈ a. Energy-dispersive spectrometer analyses (with H2O based on the crystal structure) yielded the empirical formula U2.01S1.99O12.00·5H2O. Shumwayite is monoclinic, P21/c a = 6.74747(15), b = 12.5026(3), c = 16.9032(12) Å, β = 90.919(6)°, V = 1425.79(11) Å3 and Z = 4. The crystal structure (R1 = 1.88% for 2936 F > 4σF) contains UO7 pentagonal bipyramids and SO4 tetrahedra that link by corner-sharing to form [(UO2)(SO4)(H2O)2] chains along [100]. The chains and isolated H2O groups between them are linked together only by hydrogen bonds. The mineral is named in honour of the Shumway family, whose members account for the discovery and mining of hundreds of uranium deposits on the Colorado Plateau, including the Green Lizard mine.

Alwilkinsite-(Y), a new rare-earth uranyl sulfate mineral from the Blue Lizard mine, San Juan County, Utah, USA

Abstract The new mineral alwilkinsite-(Y) (IMA2015-097), Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O, was found in the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as a secondary alteration phase. The mineral is slightly flexible before brittle failure with splintery fracture and perfect cleavage parallel to [010], has Mohs hardness of ∼2-2½, exhibits dull greenish-grey fluorescence and has a calculated density of 3.371 g cm-3. Alwilkinsite-(Y) occurs as yellowish-green needles, elongate on [010], with domatic terminations and exhibits the forms {102}, {301} and {124}. It is optically biaxial (+) with α = 1.573(1), β = 1.581(1), γ = 1.601(1) (white light), the measured 2V is 65.3(1)°, the dispersion is r < v (weak), the optical orientation is X = c, Y = a, Z = b and there is no pleochroism. Electron microprobe analyses yielded the empirical formula (Y0.66Dy0.08Gd0.06Er0.05Nd0.03Yb0.03Sm0.02Ce0.01)Σ0.94(H2O)7 [(UO2)3(S1.01O4)2O(OH)3]·7H2O. The eight strongest powder X-ray diffraction lines are [dobs Å(I )(hkl)]: 9.88(100)(101,002), 7.47(13)(102), 5.621(17)(103,201), 4.483(18)(104), 3.886(14)(130,222), 3.322(46) (multiple), 3.223(13)(multiple) and 3.145(16)(034). Alwilkinsite-(Y) is orthorhombic, P212121, a = 11.6194(5), b = 12.4250(6), c = 19.4495(14) Å, V = 2807.9(3) Å3 and Z = 4. The structure of alwilkinsite-(Y) (R1 = 0.042 for 4244 Fo > 4σF) contains edge-sharing chains of uranyl bipyramids with outlying sulfate tetrahedra that are similar to the chain linkages within the uranyl sulfate sheets of the zippeite structure. Short segments of the uranyl sulfate chains in the alwilkinsite-(Y) structure have the same topology as portions of the uranyl sulfate linkages in uranopilite. Alwilkinsite-(Y) is named for Alan (Al) J. Wilkins, MD (born 1955), the discoverer of the mineral.

Hydroniumjarosite, (H3O)+Fe3(SO4)2(OH)6, from Cerros Pintados, Chile: Single-crystal X-ray diffraction and vibrational spectroscopic study

Abstract The natural hydroniumjarosite sample from Cerros Pintados (Chile) was investigated by electron microprobe, single-crystal X-ray diffraction and vibrational spectroscopy (Infrared and Raman). The chemical composition of studied specimens (wt.%, mean of seven analyses) obtained from electron microprobe (in wt.%): Na2O 1.30, K2O 0.23, CaO 0.04, Fe2O3 50.49, Al2O3 0.37, SiO2 0.33, SO3 33.88, H2O (calculated on the basis of Σ(OH-+H3O+) deduced from the charge balance) 13.32, total 99.98, corresponds to the empirical formula (H3O)+ 0.77(Na0.20K0.02)Σ0.22(Fe2.95Al0.03)Σ2.98 (OH)6.12[(SO4)1.97(SiO4)0.03]Σ2.00 (calculated on the basis of S + Si = 2 a.p.f.u. (atoms per formula unit)). The studied hydroniumjarosite is trigonal, with space group R3̄m, with a = 7.3408(2), c = 17.0451(6) Å and V = 795.46(4) Å3. The refined structure architecture is consistent with known jarosite-series minerals, including synthetic hydroniumjarosite. However, in the current study the presence of H3O+ is well documented in difference Fourier maps, where characteristic positive difference Fourier maxima, with apparent trigonal symmetry, were localized in the vicinity of the O4 atom in the channel-voids of the structure. The structure of natural hydroniumjarosite, including the H atoms, was refined to R1 = 0.0166 for 2113 unique observed reflections, with Iobs>3σ(I). The present structure model, which includes the position of the H atom within the hydronium ion, is discussed with regard to the vibration spectroscopy results and earlier published density-functional theory (DFT) calculations for the alunite-like structure containing H3O+.

Švenekite, Ca[AsO2(OH)(2)](2), a new mineral from Jáchymov,Czech Republic

Abstract Švenekite (IMA 99-007), Ca[AsO2(OH)2]2, is a rare supergene arsenate mineral occurring in the Geschieber vein, Jáchymov ore district, Western Bohemia, Czech Republic. It grows directly on the granite rocks and occurs isolated from other arsenate minerals otherwise common in Jáchymov. Švenekite usually forms clear transparent coatings composed of indistinct radiating to rosette-shaped aggregates up to 3 mm across. They are composed of thin lens- or bladed-shaped crystals, usually 100-150 μm long. Švenekite is transparent to translucent and has a white streak and a vitreous lustre; it does not fluoresce under ultraviolet light. Cleavage is very good on {010}. The Mohs hardness is ~2. Švenekite is biaxial, non-pleochroic. The refractive indices are α’ = 1.602(2), γ’ = 1.658(2). The empirical formula of švenekite (based on As + P + S = 2 a.p.f.u., an average of 10 spot analyses) is (Ca1.00Mg0.01)∑1.01[AsO2(OH)2]1.96[PO2(OH)2]0.03(SO4)0.01. The simplified formula is Ca[AsO2(OH)2]2 and requires CaO 17.42, As2O5 71.39, H2O 11.19, total 100.00 wt.%. Raman and infrared spectroscopy exhibit dominance of O-H vibrations and vibration modes of distorted tetrahedral AsO2(OH)2 units. Švenekite is triclinic, space group P1̄, with a = 8.5606(5), b = 7.6926(6), c = 5.7206(4) Å, α = 92.605(6), β = 109.9002(6), γ = 109.9017(6)º, and V = 327.48(4) Å3, Z = 2, Dcalc = 3.26 g·cm-3. The a:b:c ratio is 0.7436:1:1.1082 (for single-crystal data). The six strongest diffraction peaks in the X-ray powder diffraction pattern are [d (Å)/I(%)/(hkl)]: 3.968(33)(21̄0); 3.766(35)(21̄1̄); 3.697(49)(101); 3.554(100)(020); 3.259(33)(22̄0); 3.097(49)(12̄1). The crystal structure of švenekite was refined from single-crystal X-ray diffraction data to R1 = 0.0250 based on 1309 unique observed, and to wR2 = 0.0588, for all 1588 unique reflections (with GOFall = 1.20). The structure of švenekite consists of sheets of corner-sharing CaO8 polyhedra and AsO2OH2 groups, stacked parallel to (001). Adjacent sheets are linked by hydrogen bonds. The švenekite structure possesses very short symmetrical hydrogen bonds (with the D-H lengths ~1.22 Å). The mineral is named to honour Jaroslav Švenek, the former curator of the mineralogical collection of the National Museum in Prague, Czech Republic.

Reversible switching of PEDOT:PSS conductivity in the dielectric–conductive range through the redistribution of light-governing polymers

One of the biggest challenges in the field of organic electronics is the creation of flexible, stretchable, and biofavorable materials. Here the simple and repeatable method for reversible writing/erasing of arbitrary conductive pattern in conductive polymer thin film is proposed. The copolymer azo-modified poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was synthesized to achieve reversible photo-induced local electrical switching in the insulator–semimetal range. The photoisomerization of the polymer was induced by grafting nitrobenzenediazonium tosylate to the PSS main chains. While the as-deposited PEDOT:PSS thin films showed good conductivity, the modification procedure generated polymer redistribution, resulting in an island-like PEDOT distribution and the loss of conductivity. Further local illumination (430 nm) led to the azo-isomerization redistribution of the polymer chains and the creation of a conductive pattern in the insulating polymer film. The created pattern could then be erased by illumination at a second wavelength (470 nm), which was attributed to induction of reverse azo-isomerization. In this way, the reversible writing/erasing of arbitrary conductive patterns in thin polymer films was realized.

Hypogene Features in Sandstones: An Example from Carboniferous Basins of Central and Western Bohemia, Czech Republic

Concave and cavernous forms including rising wall channels, rising sets of coalesced copula, ceiling half-tube channels, separate ceiling copula, ceiling chimneys, and half-spherical upward-convex arches locally occur in surface outcrops of Carboniferous arkose sandstones in central and western Bohemia. Many of these negative forms conventionally described as tafoni and/or honeycombs have been traditionally interpreted as products of various exogenous weathering processes. Based on the line of indirect evidence, we propose an alternative interpretation in which these features represent transitional and outlet members of the morphologic suite of rising flow (MSRF), indicative of their subsurface hypogene origin. The negative forms are commonly associated with bedding planes and subvertical fractures mineralized with goethite and jarosite. The reflectance of coal particles embedded in sandstone along mineralized bedding planes (0.91–1.03% R r ) is appreciably higher with respect to those of adjacent unaltered arkose host rocks (0.61–0.85% R r ), pointing to the thermal overprint by hot fluids. Moreover, the walls of many cavities are covered by sandy-disintegrated alterite locally mineralized with gypsum, dickite, goethite, authigenic quartz, pickeringite, and bischofite. We suggest that these phenomena, including the origin of characteristic concave forms and mineralogical alterations of arkose host rocks, may have been due to warm, CO2-saturated and possibly H2S-rich brines that ascended from the deepest stratigraphic units of the Carboniferous succession via the network of subvertical tectonic fractures and migrated laterally outward along permeable bedding planes. As indicated by the apatite fission track analysis and wider geological observations, the alteration of arkose sandstones probably occurred at relatively shallow depth of burial, during the Tertiary uplift of the Bohemian Massif 15–20 Ma ago. In this environment, the alteration may have been accelerated by the effects of mixing corrosion where heated deep basinal fluids interacted with shallower interstratal waters. When the uplifted sandstone sequences eventually reached the surface, the hypogene cavities and altered cliff walls were subjected to subaerial weathering and fluvial erosion processes the effects of which were superimposed on older hypogene features.