Vorlanite (CaU6+)O4 Fm3̄m, a = 5.3647(9) Å, V = 154.40(4) Å3, Z = 2 was found in larnite pyrometamorphic rocks of the Hatrurim formation at the Jabel Harmun locality, Judean Desert, Palestinian ...Autonomy. Vorlanite crystals from these larnite rocks are dark-gray with greenish hue in transmitted light. This color in transmitted light is in contrast to dark-red vorlanite Fm3̄m, a = 5.3813(2) Å, V = 155.834(10)Å3, Z = 2 from the type locality Upper Chegem caldera, Northern Caucasus. Heating above 750 °C of dark-gray vorlanite from the Jabel Harmun, as well as dark-red vorlanite from Caucasus, led to formation of yellow trigonal uranate CaUO4. The unusual color of vorlanite from Jabel Harmun is assumed to be related to small impurities of tetravalent uranium.
Members of the edgrewite Ca9(SiO4)4F2-hydroxyledgrewite Ca9(SiO4)4(OH)2 series, structural analogues of clinohumite-hydroxylclinohumite series, Mg9(SiO4)4(F,OH)2, were discovered in xenoliths of ...carbonate-silicate rock altered to skarn within ignimbrites of the Upper Chegem volcanic structure, Kabardino-Balkaria, Northern Caucasus, Russia. The new minerals occur sparingly in zones containing bultfonteinite, hillebrandite, jennite, and chegemite, as well as rare relics of larnite and rondorfite enclosed in a matrix of hydroxylellestadite. Edgrewite and hydroxyledgrewite are largely altered to jennite in places with admixed zeophyllite and trabzonite, and are preserved as elongate relics mostly 0.1-0.4 mm long in the central part of atoll-like pseudomorphs. The new minerals form a solid-solution series Ca9(SiO4)4(F,OH)2, in which the content of the edgrewite end-member Ca9(SiO4)4F2 ranges from 74% (F=3.64 wt%) to 31% (F=1.52 wt%). Structure refinement of crystals containing 51% and 37% of the edgrewite end-member gave, respectively, R1=3.03%, space group P21/b11 (no. 14), Z=2, a=5.06870(10), b=11.35790(10), c=15.4004(2) Å, α=100.5980(10)°, V=871.47(3) Å3; and R1=1.61%, space group P21/b11 (no. 14), Z=2, a=5.06720(10), b=11.35450(10), c=15.3941(2) Å, α=100.5870(10)°, and V=870.63(2) Å3. Minerals of the edgrewite-hydroxyledgrewite series are colorless, optically biaxial (+), 2Vmeas=80(5)°; 2Vcalc= 78.7°; dispersion r>v, medium; orientation: Z=a, X c = 12(2)°; edgrewite: α=1.621(2), β=1.625(2), γ=1.631(2); hydroxyledgrewite: α=1.625(2), β=1.629(2), γ=1.635(2) (589 nm). The micro-hardness VHN50=352-366 kg/mm2 corresponds to the Mohs scale of 5.5-6. 5. FTIR spectra of edgrewite and hydroxyledgrewite show resolved bands at (edgrewite/hydroxyledgrewite, cm-1): 3558 and 3551 and 3543/3554, absent/3486, 1075/1075, 996/996, 980/982, 934/933, 917/918, 904/903, 890/884, 864/864, 842/842, 818/820. Raman spectra are characterized by the following bands (edgrewite/hydroxyledgrewite, cm-1) at: 921/923, 889/890, 839/840, and 815/814 (SiO4 stretching), at: 556/559, 527/527, 423/419, 406/404, and 394/394 (SiO4 bending), 309/295, 269/256, and 163/166 (CaO6). In the OH stretching region three bands are noted at 3554, 3547, and 3540 cm-1 for edgrewite and two -3550 and 3475 cm-1 for hydroxyledgrewite confirming the corresponding IR spectra. The major difference in Raman and IR spectra of edgrewite and hydroxyledgrewite is the presence of two resolved peaks in the OH stretching region at ca. 3550 and 3480 cm-1 for hydroxyledgrewite.
Arlt et al synthesized single crystals of MnSiO(SiO4) with the titanite structure together with MnSiO3 clinopyroxene from a MnO-SiO2 oxide mixture at 1,000 degrees C and 9.2 GPa in a multi-anvil ...press.
Hogbomite-group minerals are complex Fe-Mg-Zn-Al-Ti oxides related to the spinel group. Their polysomatic structure is composed of spinel (S) and nolanite (N) modules. The new polysome ...magnesiohogbomite-2N4S (IMA 2010-084) was found in the Sor Rondane Mountains, East Antarctica. It occurs in Mg-Al-rich, Si-poor skarns, characterized by a corundum-spinel-phlogopite-clinochlore assemblage. The new magnesiohogbomite polysome formed during the retrograde metamorphic stage. Magnesiohogbomite-2N4S appears macroscopically orange red, the streak is light orange colored. Euhedral crystals are hexagonal plates or prisms with cleavage planes on {001}. The mineral is optically uniaxial (-) and pleochroic with O=reddish brown and E=pale brown. The mean refractive index calculated from reflectance data in air at 589 nm is 1.85(3). The calculated density is 3.702(2) g/cm3. The Mohs hardness is 6.5-7, and VHN300=1020-1051, mean 1032 kg/mm2. The crystal structure of the new polysome magnesiohogbomite-2N4S has been solved and refined (R1=2.74%) from single-crystal XRD data. The crystal chemical formula is T10M24O46(OH)2 where T and M represent tetrahedral and octahedral sites. The mineral is hexagonal, space group P63mc (no. 186), a=5.71050(10), c=27.6760(4) Å, Z=1, V=781.60(2) Å3. The strongest lines in the powder XRD pattern d (Å), I (%), hkl are: 2.8561(4), 37, 110; 2.6120(3), 39, 109; 2.42818(16), 100, 116; 2.4160(4), 39, 1010; 2.01181(13), 50, 208; 1.54892(16), 35, 2110; 1.42785(6), 57, 220. Strongest peaks in Raman spectra are at 302, 419, 479, 498, 709, 780, and 872 cm-1, with a broad OH-characteristic absorption around 3400 cm-1. The mean chemical composition (wt%) is SiO2 0.05, TiO2 7.08, SnO2 0.15, Al2O3 66.03, Cr2O3 0.02, Fe2O3 0.50, FeO 4.87, MnO 0.06, MgO 18.71, CaO 0.01, ZnO 0.96, NiO 0.01, CoO 0.02, F 0.06, Cl 0.01, H2O 1.00, sum 99.51. The simplified formula is (Mg8.2 Fe1.2 Zn0.2)2+(Al22.7 Fe0.1)3+ Ti4+1.6 O46(OH)2 and ideal formula is Mg10 Al22 Ti2O46(OH)2. This mineral is a solid solution between the two ideal end-members, (Mg, Fe, Zn)102+(Al, Fe)223+ Ti24+ O46(OH)2 and (Mg, Fe, Zn)82+(Al, Fe)263+O46(OH)2.
The crystal chemistry of sursassite, simplified formula Mn22+ Al3Si3O11(OH)3, from six different localities (1) Falotta, Switzerland, (2) Woodstock, New Brunswick, Canada, (3) Kamisugai, Japan, (4) ...Kamogawa, Japan, (5) Molinello, Italy, and (6) Gambatesa, Italy was studied using electron microprobe analysis (EMPA), Fourier transform infrared spectroscopy (FTIR), and single-crystal X-ray diffraction methods. The structure has two symmetry independent Mn sites. The Mn1 site is seven coordinated by O and hosts, in addition to Mn2+, up to 20% Ca, whereas Mn2 has octahedral coordination and is strongly selective for Mn2+. In the simplified formula, three smaller octahedral M sites are occupied by Al. However, M1 also accepts significant amounts of divalent cations, such as Cu, Mg, Fe, and Mn, whereas M2 is occupied exclusively by Al. The unit-cell parameters of sursassite are a=8.698-8.728, b=5.789-5.807, c=9.778-9.812 Å, β=108.879-109.060°, V=465.7-470.0 Å3, the space group is P21/m. Structure refinements converged to R1 values of 2.15-6.62%. In agreement with bond-valence analyses, at least three OH groups, depending on the concentration of divalent cations at M1, are found at the O6, O7, and O11 positions. However, the bond-valence sum at O10 is always low, thus partial hydroxylation is assumed at O10 to maintain charge balance. Owing to the influence of divalent cations at M1 in sursassite the hydrogen-bond systems in sursassite and isostructural macfallite are different. The FTIR spectrum in the region of OH-stretching vibrations is characterized by three strong bands at 3511, 3262, and around 2950 cm-1, the latter being broad. The band at 2950 cm-1 is assigned to strong hydrogen bonds between O6 and O10 (O6...O10=2.66 Å). Residual difference-Fourier peaks in the refinement of the Kamogawa and Molinello (specimen 1) crystals indicated less than 5% pumpellyite intergrowth.
The new mineral pavlovskyite Ca8(SiO4)2(Si3O10) forms rims together with dellaite Ca6(Si2O7)(SiO4)(OH)2 around galuskinite Ca7(SiO4)3CO3 veins cutting calcio-olivine skarns in the Birkhin gabbro ...massif. In addition, skeletal pavlovskyite occurs in cuspidine zones of altered carbonate xenoliths in the ignimbrites of the Upper Chegem caldera (North Caucasus). The synthetic analog of pavlovskyite has been synthesized before and is known from cement-like materials. Isotypic to pavlovskyite is the synthetic germanate analog Ca8(GeO4)2(Ge3O10). The crystal structure of pavlovskyite, space group Pbcn, a=5.0851(1), b=11.4165(3), c=28.6408(8) Å, V=1662.71(7) Å3, Z=4, has been refined from X-ray single-crystal data to R1=3.87%. The new colorless mineral has a Mohs hardness of 6-6.5, biaxial (-), α=1.656(2), β=1.658(2), γ=1.660(2) (589 nm), 2V (meas)=80(5)°, 2V (calc)=89.9°, medium dispersion: r>v, optical orientation: X=b, Y=c, Z=a. For comparison with pavlovskyite, the crystal structure of kilchoanite Ca6(SiO4)(Si3O10) from the Birkhin massif space group I2 cm, a=11.4525(2), b=5.0867(1), c=21.996(3) Å, V=1281.40(4) Å3, Z=4 has been refined from single-crystal X-ray data to R1=2.00%. Pavlovskyite represents a 1:1 member of a polysomatic series with calcio-olivine γ-Ca2SiO4 and kilchoanite Ca6(SiO4)(Si3O10) as end-member modules. The structure is characterized by strongly folded trisilicate units (Si3O10) interwoven with a framework of CaO6 and CaO8 polyhedra. Olivine-like slices with orthosilicate groups are interstratified with the characteristic trisilicate module of Ca4(Si3O10) composition. Although the optical properties of pavlovskyite and kilchoanite are similar, both minerals can be distinguished by chemical analyses (different Ca/Si ratio), X-ray diffraction, and Raman spectroscopy. The new mineral is named after V. E. Pavlovsky (1901-1982), an outstanding geologist in the area of Eastern Siberia, in particular of the Baikal region.
Single crystals of self-synthesized mordenite-Na were used for incorporation of elemental selenium. The mordenite sample was first dehydrated at 280 °C and selenium was subsequently incorporated as ...gas phase at 450 °C for 72 h. Bright orange-colored Se-loaded mordenite was quantitatively analyzed by an electron microprobe yielding Na
6Al
6Si
42O
96
·
Se
7.9. X-ray data collection of mordenite-Na and Se-loaded mordenite-Na single-crystals were performed at 120 K with synchrotron radiation (
λ=0.79946 Å) using the single-crystal diffraction line at SNBL (ESRF, Grenoble), where diffracted intensities were registered with a MAR image plate. The structures of mordenite-Na and Se-mordenite-Na were both refined in the monoclinic space group
Cc converging at R1=5.25% (mordenite-Na), and R1=6.65% (Se-mordenite-Na). A strongly broadened Raman band at approximately 254 cm
−1 confirmed the existence of Se chains in the 12-membered channels along the
c-axis. Several, low-populated, disordered Se chains with a length up to 10 Å and seven Se atoms were located in the large mordenite channels. During structure refinement nearest and next nearest neighbor Se–Se distances were fixed at 2.34 and 3.62 Å, respectively. Other distances and angles remained unconstrained. Because of electrostatic interaction with the framework and influence of extraframework occupants such as Na
+ and H
2O molecules, the chains show different geometrical Se arrangement with highly variable dihedral angles. Any other Se species such as Se
6 or Se
8 rings were neither confirmed by structure refinement nor by Raman spectroscopy. There was no indication of a trigonal Se chain geometry within the 12-membered ring channel.
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Single crystals of self-synthesized mordenite−Na were used for incorporation of the cationic dye molecule thionin blue (C12H10N3S+). The planar organic molecule (7.5 × 15 Å), which fits into the ...large 12-membered ring channel of mordenite, was incorporated by ion-exchange replacing extraframework Na+ cations. Deep blue thionin-exchanged mordenite crystals were chemically analyzed by electron microprobe yielding the composition Na5.5Thionin0.4Si42.02Al5.88O96 × nH2O indicating that the large 12-membered ring channels of mordenite are less than half-filled by dye molecules. X-ray data collection of thionin-loaded mordenite single crystals was performed at 120 K with synchrotron radiation (λ = 0.80000 Å) using the single-crystal diffraction line at the Swiss Norwegian Beamline, SNBL (ESRF, Grenoble) where diffracted intensities were registered with an MAR image plate. The structure of thionin−mordenite−Na was refined in the monoclinic space group Cc converging at R1 = 5.53%. Optical microscopy of dye-loaded mordenite single crystals using plane-polarized light showed striking pleochroism due to anisotropic light absorption caused by the preferred orientation of the molecule's transition-dipole moment. Corresponding anisotropic phenomena were also observed by fluorescence microscopy. Four low populated thionin sites were located in the large mordenite channel. Determined S···O (2.97(1)−3.18(1) Å), C···O (3.11(1)−3.36(2) Å) and N···O (3.04(1)−3.20(1) Å) distances from the dye molecule to the channel wall indicate electrostatic interaction with the framework. The molecules are arranged slightly inclined within the large 12-membered ring channels showing significant occupational disorder along the channel axis. The flat geometry of the thionin molecule enables a rotation of about 12° in each direction causing distinct disorder within the channel cross section.
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Fully Cd-exchanged heulandite of Cd
4.00Na
0.01K
<0.01Ca
0.09Al
8.70Si
27.30O
71.75
·
29H
2O composition was used for stepwise dehydration experiments. The crystal was heated for approximately 12 h ...in a stream of hot air from 50 to 250 °C in steps of 50 °C. For X-ray single-crystal data collection the heating device was switched off and the crystal was immediately cooled to −173 °C. The crystal structures of the 50–200 °C data sets were refined in space group
Cm, the 250 °C data were refined in
C2/
m. The original crystal had 29 H
2O molecules per formula unit (pfu). Heating at 50, 100, 150, and 200 °C reduced the H
2O content to 27(2), 25(1), 26(1), and 13(1) molecules pfu. At 250 °C heulandite-Cd became essentially anhydrous. With loss of H
2O the cell parameters changed:
a decreased slightly,
b decreased strongly,
c remained more or less invariant, and
β increased leading to a decrease of the cell volume with dehydration. Due to the loss of the surrounding H
2O molecules the Cd ions moved from the center of the eight- and ten-membered rings towards the framework walls causing distortion of the heulandite channels at 250 °C. Parts of the structure transformed to a heat collapsed B-phase. This new topology differs from the original A-phase by broken T–O–T bonds and the appearance of new T–O–T connections reducing the free aperture of the 10-membered ring channels. This new structure forms domains (≈28%) coherently intergrown with the heat collapsed (A type) heulandite framework. It is suggested that in absence of H
2O and within strongly Cd populated domains, the bonding requirements of Cd
2+ extra-framework cations give rise to the altered T–O–T connections.
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Anisotropic mean-square displacement parameters, as routinely obtained from single-crystal structure refinements, are used to calculate difference values (DeltaU) along the (Si,Al)-O vector in alkali ...feldspar tetrahedra. DeltaU values averaged over a tetrahedron provide physical information on (Si,Al) order- disorder.
