Jiří Sejkora

Raman spectroscopic study of a hydroxy-arsenate mineral containing bismuth-atelestite Bi2O(OH)(AsO4)

The Raman spectrum of atelestite Bi2O(OH)(AsO4), a hydroxy-arsenate mineral containing bismuth, has been studied in terms of spectra-structure relations. The studied spectrum is compared with the Raman spectrum of atelestite downloaded from the RRUFF database. The sharp intense band at 834 cm(-1) is assigned to the ν1 AsO4(3-) (A1) symmetric stretching mode and the three bands at 767, 782 and 802 cm(-1) to the ν3 AsO4(3-) antisymmetric stretching modes. The bands at 310, 324, 353, 370, 395, 450, 480 and 623 cm(-1) are assigned to the corresponding ν4 and ν2 bending modes and BiOBi (vibration of bridging oxygen) and BiO (vibration of non-bridging oxygen) stretching vibrations. Lattice modes are observed at 172, 199 and 218 cm(-1). A broad low intensity band at 3095 cm(-1) is attributed to the hydrogen bonded OH units in the atelestite structure. A weak band at 1082 cm(-1) is assigned to δ(BiOH) vibration.

Adolfpateraite, K(UO2)(SO4)(OH)(H2O), a new uranyl sulphate mineral from Jáchymov, Czech Republic

Abstract Adolfpateraite, monoclinic K(UO2)(SO4)(OH)(H2O), is a new supergene mineral from the Svornost mine, Jáchymov ore district, Czech Republic. It forms sulfur yellow to greenish yellow crystalline aggregates, up to 2 mm in diameter. Crystals are transparent to translucent with a vitreous luster, without observable cleavage. The streak is pale yellow. The Mohs hardness is ~2. The mineral shows a green fluorescence in long-wave ultraviolet radiation. Adolfpateraite is pleochroic, with α = colorless and γ = yellow (β could not been examined). It is biaxial, with α = 1.597(2), γ = 1.659(2) (β could not been measured), birefringence 0.062. The empirical chemical formula (mean of 4 electron microprobe point analyses) was calculated based on 8 O apfu and is K0.94(UO2)1.00(SO4)1.02(OH)0.90(H2O)1.00 (water content calculated). The simplified formula is K(UO2)(SO4)(OH)(H2O), requiring K2O 10.70, UO3 64.97, SO3 18.19, H2O 6.14, total 100.00 wt%. Adolfpateraite is monoclinic, space group P21/c, a = 8.0462(1), b = 7.9256(1), c = 11.3206(2) Å, β = 107.726(2)°, V = 687.65(2) Å3, Z = 4, and Dcalc = 4.24 g/cm3. The five strongest reflections in the X-ray powder diffraction pattern are [dobs in Å (I) (hkl)]: 7.658 (76) (100), 5.386 (100) (002), 5.218 (85) (1̅02), 3.718 (46) (021), 3.700 (37) ( 2̅02). The crystal structure has been refined from single-crystal X-ray diffraction data to R1 = 0.0166 with GOF = 1.30, based on 1915 observed reflections [Iobs > 3σ(I)]. The crystal structure consists of chains of uranyl polyhedra extended along [010], with OH- located on the shared vertex between the bipyramids. The sulfate tetrahedra decorate the outer side of the chain with bridging bidentate linkages between the uranyl pentagonal bipyramids. H2O groups are located on the edges of the chains on the non-linking vertex of each uranyl pentagonal bipyramid. K+ atoms are located between the chains providing additional linkage of these together with H-bonds. The fundamental vibrational modes of uranyl ion, sulfate tetrahedra, and H2O groups were tentatively assigned in the infrared and Raman spectra. The new mineral is named to honor Adolf Patera (1819-1894), Czech chemist, mineralogist, and metallurgist.

A vibrational spectroscopic study of hydrated Fe3+ hydroxyl-sulfates; polymorphic minerals butlerite and parabutlerite

Raman and infrared spectra of two polymorphous minerals with the chemical formula Fe3+(SO4)(OH)·2H2O, monoclinic butlerite and orthorhombic parabutlerite, are studied and the spectra assigned. Observed bands are attributed to the (SO4)2- stretching and bending vibrations, hydrogen bonded water molecules, stretching and bending vibrations of hydroxyl ions, water librational modes, Fe-O and Fe-OH stretching vibrations, Fe-OH bending vibrations and lattice vibrations. The O-H⋯O hydrogen bond lengths in the structures of both minerals are calculated from the wavenumbers of the stretching vibrations. One symmetrically distinct (SO4)2- unit in the structure of butlerite and two symmetrically distinct (SO4)2- units in the structure of parabutlerite are inferred from the Raman and infrared spectra. This conclusion agrees with the published crystal structures of both mineral phases.

Mineralogy of phosphate accumulations in the Huber stock,Krásno ore district, Slavkovský les area, Czech Republic

Mineralogy of phosphate accumulations in the Huber stock, Krasno ore district, Slavkovský les area, Czech Republic

Schafarzikite from the type locality Pernek (Malé Karpaty Mountains, Slovak Republic) revisited

A rare mineral schafarzikite, an oxide of Fe 2+ and Sb 3+ , was found after more than 80 years at the type locality near Pernek (Male Karpaty Mountains, Slovak Republic). Crystals, druses, and crusts of schafarzikite occur on fractures in quartz-carbonate-stibnite hydrothermal ores. The Sb mineralization is bound to black shales and phyllites in a zone of actinolitic rocks. Associated minerals include ankerite, berthierite, stibnite, valentinite, kermesite, senarmontite, and gypsum. Prismatic crystals of schafarzikite are 0.1–1.0 mm, rarely up to 1.5 mm large, with the dominant forms {110}, {121}, {112}, {010}, {221}, {131}, and {231}. The optical properties are: uniaxial, with relatively strong pleochroism in red-brown tints; refraction indices higher than 1.74; the average refraction index, calculated from the Gladstone-Dale equation, is 2.001. The physical properties of schafarzikite from Pernek are: dark brown to black color, adamantine to metallic luster, brown streak; translucent (brown to orange) in very thin fragments; good {100} cleavage and perfect cleavage along unindexed planes parallel to z axis, tenacity-brittle; VHN10 g micro-hardness = 251 and 278 kp/mm 2 (for two cuts with differing orientation), corresponding to Mohs’ hardness of 3.5–4; calculated density D x = 5.507 g/cm 3 . The electron microprobe analysis gave FeO 19.38, ZnO 0.02, PbO 0.02, Sb 2 O 3 80.36, As 2 O 3 0.55, Bi 2 O 3 0.16, SO 2 0.04, and calculated formula Fe 0.97 (Sb 1.99 As 0.02 )S2.01O 4 . The XRD pattern was indexed in a tetragonal setting, with refined unit-cell parameters are a = 8.6073(2) c = 5.9093(3) A, V = 437.80(2) A 3 , c : a = 0.6865. Thermogravimetric (TG) curve shows mass gain of 1.62 wt. % in the range 20–580 °C, and 5.28 wt. % in the range 580–850 °C caused by Fe 2+ and Sb 3+ oxidation, respectively. The product of TG analysis is a phase isostructural with rutile. A tentative assignment of FTIR and Raman spectra of schafarzikite is given. Schafarzikite from Pernek most likely crystallized from late oxidizing hydrothermal fluids. Hence, it is not a weathering product, as assumed previously.

Mathesiusite, K5(UO2)4(SO4)4(VO5)(H2O)4, a new uranyl vanadate-sulfate from Jáchymov, Czech Republic

Abstract Mathesiusite, K5(UO2)4(SO4)4(VO5)(H2O)4, a new uranyl vanadate-sulfate mineral from Jáchymov, Western Bohemia, Czech Republic, occurs on fractures of gangue associated with adolfpateraite, schoepite, čejkaite, zippeite, gypsum, and a new unnamed K-UO2-SO4 mineral. It is a secondary mineral formed during post-mining processes. Mathesiusite is tetragonal, space group P4/n, with the unit-cell dimensions a = 14.9704(10), c = 6.8170(5) Å, V = 1527.78(18) Å3, and Z = 2. Acicular aggregates of mathesiusite consist of prismatic crystals up to ~200 μm long and several micrometers thick. It is yellowish green with a greenish white streak and vitreous luster. The Mohs hardness is ~2. Mathesiusite is brittle with an uneven fracture and perfect cleavage on {110} and weaker on {001}. The calculated density based on the empirical formula is 4.02 g/cm3. Mathesiusite is colorless in fragments, uniaxial (-), with ω = 1.634(3) and ε = 1.597(3). Electron microprobe analyses (average of 7) provided: K2O 12.42, SO3 18.04, V2O5 4.30, UO3 61.46, H2O 3.90 (structure), total 100.12 (all in wt%). The empirical formula (based on 33 O atoms pfu) is: K4.87(U0.99O2)4(S1.04O4)4(V0.87O5)(H2O)4. The eight strongest powder X-ray diffraction lines are [dobs in Å (hkl) Irel]: 10.64 (110) 76, 7.486 (200) 9, 6.856 (001) 100, 6.237 (101) 85, 4.742 (310) 37, 3.749 (400) 27, 3.296 (401) 9, and 2.9409 (510) 17. The crystal structure of mathesiusite was solved from single-crystal X-ray diffraction data and refined to R1 = 0.0520 for 795 reflections with I > 3σ(I). It contains topologically unique heteropolyhedral sheets based on [(UO2)4(SO4)4(VO5)]5- clusters. These clusters arise from linkages between corner-sharing quartets of uranyl pentagonal bipyramids, which define a square-shaped void at the center that is occupied by V5+ cations. Each pair of uranyl pentagonal bipyramids shares two vertices of SO4 tetrahedra. Each SO4 shares a third vertex with another cluster to form the sheets. The K+ cations are located between the sheets, together with a single H2O group. The corrugated sheets are stacked perpendicular to c. These heteropolyhedral sheets are similar to those in the structures of synthetic uranyl chromates. Raman spectral data are presented confirming the presence of UO22+, SO4, and molecular H2O.

Raman spectroscopic study of the hydroxy-phosphate mineral plumbogummite PbAl3(PO4)2(OH,H2O)6

Plumbogummite PbAl(3)(PO(4))(2)(OH,H(2)O)(6) is a mineral of environmental significance and is a member of the alunite-jarosite supergroup. The molecular structure of the mineral has been investigated by Raman spectroscopy. The spectra of different plumbogummite specimens differ although there are many common features. The Raman spectra prove the spectral profile consisting of overlapping bands and shoulders. Raman bands and shoulders observed at 971, 980, 1002 and 1023 cm(-1) (China sample) and 913, 981, 996 and 1026 cm(-1) (Czech sample) are assigned to the ν(1) symmetric stretching modes of the (PO(4))(3-), at 1002 and 1023 cm(-1) (China) and 996 and 1026 cm(-1) to the ν(1) symmetric stretching vibrations of the (O(3)POH)(2-) units, and those at 1057, 1106 and 1182 (China) and at 1102, 1104 and 1179 cm(-1) (Czech) to the ν(3) (PO(4))(3-) and ν(3) (PO(3)) antisymmetric stretching vibrations. Raman bands and shoulders at 634, 613 and 579 cm(-1) (China) and 611 and 596 cm(-1) (Czech) are attributed to the ν(4) (δ) (PO(4))(3-) bending vibrations and those at 507, 494 and 464 cm(-1) (China) and 505 and 464 cm(-1) (Czech) to the ν(2) (δ) (PO(4))(3-) bending vibrations. The Raman spectrum of the OH stretching region is complex. Raman bands and shoulders are identified at 2824, 3121, 3249, 3372, 3479 and 3602 cm(-1) for plumbogummite from China, and at 3077, 3227, 3362, 3480, 3518 and 3601 cm(-1) for the Czech Republic sample. These bands are assigned to the ν OH stretching modes of water molecules and hydrogen ions. Approximate O-H⋯O hydrogen bond lengths inferred from the Raman spectra vary in the range >3.2-2.62Å (China) and >3.2-2.67Å (Czech). The minority presence of some carbonate ions in the plumbogummite (China sample) is connected with distinctive intensity increasing of the Raman band at 1106 cm(-1), in which may participate the ν(1) (CO(3))(2-) symmetric stretching vibration overlapped with phosphate stretching vibrations.

Crystal structure of pseudojohannite, with a revised formula Cu3(OH)2[(UO2)4O4(SO4)2](H2O)12

Abstract 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.

A Raman spectroscopic study of the basic carbonate mineral callaghanite Cu2Mg2(CO3)(OH)6·2H2O.

Raman spectrum of callaghanite, Cu2Mg2(CO3)(OH)6·2H2O, was studied and compared with published Raman spectra of azurite, malachite and hydromagnesite. Stretching and bending vibrations of carbonate and hydroxyl units and water molecules were tentatively assigned. Approximate O-H…O hydrogen bond lengths were inferred from the spectra. Because of the high content of hydroxyl ions in the crystal structure in comparison with low content of carbonate units, callaghanite should be better classified as a carbonatohydroxide than a hydroxycarbonate.

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.