Showing papers in "Mineralogical Journal in 1990"
TL;DR: The crystal structure refinements of Sr3(PO4)2 [a=53901(8), c=19785(5)A; space group R-3m] and Ba3PO42 as discussed by the authors have been carried out by means of the single-crystal diffraction data and the final R(Rw) factors have been converged to 00299 (00309) and 00296 (00335), respectively.
Abstract: The crystal structure refinements of Sr3(PO4)2 [a=53901(8), c=19785(5)A; space group R-3m] and Ba3(PO4)2 [a=56038(7), c=21000(5)A; space group R-3m] have been carried out by means of the single-crystal diffraction data and the final R(Rw) factors have been converged to 00299 (00309) and 00296 (00335), respectively The rod sequence of coordination polyhedra, PO4–M(2)O10–M(1)O12–M(2)O10–PO4, where M = Sr or Ba, is characteristic in these structures The M(1)O12 and M(2)O10 polyhedra show smaller distortion with increase in the ionic radius of the constituent elements
53 citations
TL;DR: In this article, the degeneracy of a single hydroxyl librational vibration in talc and willemseite end-members is lifted by substitutions of their octahedral cations.
Abstract: Infrared hydroxyl librational bands of talc-willemseite solid solutions (Mg–Ni talcs) have been explained by analogy with those of amphiboles. Two OH librational bands at 710 and 668 cm−1 appear in talc-willemseite solid solutions, because the degeneracy of a single OH librational vibration in talc and willemseite end-members is lifted by the substitutions of their octahedral cations. Comparison of infrared spectra of natural and hydrothermally deuterated A site-vacant and Al(IV) (tetrahedral Al)-free amphiboles reveals that two bands at 700 and 690–640 cm−1 are also ascribed to OH librations.
25 citations
TL;DR: In this article, the Tirodi mine tunnel was transformed to monoclinic structure at 710°C in air and site occupancy increased from 68% to 86% due to the movement of tunnel cation which were in the part converted to bixbyite.
Abstract: Tetragonal cryptomelane from the Tirodi mine, India transforms to monoclinic structure at 710°C in air. The composition of the tunnel is same before and after transformation (Na:K = 1:2), but the site occupancy increase from 68% to 86%. The increase of the occupancy is due to the movement of tunnel cation which were in the part converted to bixbyite. The structure refinements of the both tetragonal and monoclinic cryptomelanes clearly show the change of the MnO6 framework. In the monoclinic cell, two symmetry-independent octahedra exist. Mn(2) octahedra has greater distortion than the octahedra in tetragonal cell, but Mn(1) octahedra has less distortion. It is possible to consider that some of the Mn cations are reduced to Mn3+ to maintain the charge balance with the tunnel cations and Mn3+ ions exist mainly in Mn(2) octahedra for greater distortion. The transformation was caused by the increase of the tunnel site cation occupancy.
13 citations
TL;DR: The morphology of zircon crystals synthesized by the flux method and doped with elements common in igneous rocks is described quantitatively, using a new method proposed by the first author as discussed by the authors.
Abstract: The morphology of zircon crystals synthesized by the flux method and doped with elements common in igneous rocks is described quantitatively, using a new method proposed by the first author. Within the experimental temperature range of 1150° to 1100°C, only {100} among the prism faces develops in all the zircons. The zircons doped with P or S show long prismatic habit, whereas non-doped zircons show a bipyramidal habit with very short prisms, and those with other doping elements a short-prismatic habit. As for the pyramid, {101} is exclusive in zircons doped with Ti, Al, Fe, P, S or U, and it is dominant in those doped with Ca, Mg, K, Na, Ni or Mn, with small {211} increasing in dimension in the same order. The effect of S and Mn, when mixed with other doping elements, becomes less distinct. The presence of P, however, always induces the formation of long prismatic crystals.
11 citations
TL;DR: The crystal structure of babingtonite was determined from neutron.diffraction data at SOK as mentioned in this paper, and the lattice constants are a=7.497(l), b=12.225(1), c=6.710(1) A.
Abstract: The crystal structure of babingtonite was determined from neutron .diffraction data at SOK. The lattice constants are a=7.497(l), b=12.225(1), c=6.710(1) A. a = 86.lS(1), ~ = 93.90(1) and r = 112.27(00 (at room temperature). The structure was refined assuming the space group symmetry of PI. The cation distributions of Mn and Mg in Fe(l) site and AI in Fe(2) site were confirmed by applying the differences of the scattering lengths of the atoms in neutron diffraction. The accurate positions of the hydrogen atoms were determined.
10 citations
TL;DR: In this article, single crystals of Rb1.5Mn8O16 were grown under the hydrothermal conditions of 450°C and 0.2GPa and the structure was tetragonal (I4/m); a=9.915(9)A, c=2.866(3)A and Z=1.054.
Abstract: Single crystals of Rb1.5Mn8O16 were grown under the hydrothermal conditions of 450°C and 0.2GPa. The structure was tetragonal (I4/m); a=9.915(9)A, c=2.866(3)A and Z=1. The X-ray structure analysis was performed using the 656 independent reflections to R=0.088 and Rw=0.054. The determined structure adopts hollandite type characterized by the 2×2 tunnel. It is noted the electron density distribution of Rb+ in the tunnel was elongated along the c-axis, suggesting the distribution of Rb+ over the special position (2b).
10 citations
TL;DR: In this article, two ammonium-bearing mica/smectite specimens were examined by chemical analysis, X-ray diffraction, thermal analysis, infrared absorption, electron diffraction and electron microscopic observation.
Abstract: Two specimens of interstratified ammonium-bearing mica/smectite have occurred at Aira, Kagoshima Prefecture, Japan. The mineralogical properties of the specimens were examined by chemical analysis, X-ray diffraction, thermal analysis, infrared absorption, electron diffraction and electron microscopic observation. The ammonium contents of the specimens are 0.84 and 1.45wt%, respectively. The structure of interstratification is expressed by Reichweite g = 1 having about 17 and 31% expandable layers. The IR spectra of the specimens exhibit pronounced absorption bands of ammonium ions at 1428, 2820 and 3010cm−1. The morphologies of the specimens are characterized by lath- and flake-like habits, respectively.
8 citations
TL;DR: In this paper, the compositions of the (M(1)·M( 1)·m( 1·m) sites cations were calculated according to the areal intensity relations of their OH stretching bands at 3700-3600 cm−1, and these values roughly coincide with those obtained through chemical analyses.
Abstract: Infrared absorption spectra in the 4000–330 cm−1 range of the glaucophane-riebeckite series alkali amphiboles are presented with some discussions on their relationship to chemical composition.The compositions of the (M(1)·M(1)·M(3)) sites cations were calculated according to the areal intensity relations of their OH stretching bands at 3700–3600 cm−1, and these values roughly coincide with those obtained through chemical analyses. The ionic substitutions, (Fe2+ + Mn)-for–Mg in the M(1) and M(3) sites, and Fe3+-for–Al in the M(2) sites, cause a frequency decrease for most bands in the 1300–330 cm−1 range. The ratios of Fe3+ and Al in M(2) sites can be estimated approximately by the peak intensity relationships of three kinds of bands: near 990 and 970 cm−1 (Si–O stretchings); near 690 and 670 cm−1 (mainly OH librations); near 640 cm−1 (probably chain deformation). The nature of the bands near 465, 550, and 365 cm−1 is also useful to estimate the degree of Fe2+-for-Al substitutions in the M(2) sites.
8 citations
5 citations
TL;DR: In this article, the role of fluorine on the formation of 1M type of mica structure was considered and the tetrahedral rotation angles α of five manganoan zinnwaldites were calculated from powder data.
Abstract: Chemical and physical data for five manganoan zinnwaldites from Japan were analysed and were found to be high in fluorine, reflecting the crystallization under relatively high f (HF or F2) conditions. All specimens belong to 1M polytype. The role of fluorine on the formation of 1M type of mica structure was considered. Tetrahedral rotation angles α of five zinnwaldites were calculated from powder data.
3 citations
TL;DR: In this article, the change of extinction angle in a deformed single crystal is found to be large in the strongly deformed part of the crystal and the variation of the extinction angle is sensitive to the deformation even for weakly deformed crystals.
Abstract: Experimentally deformed sanidine single crystals have been investigated by an optical microscope in order to establish relations between their deformations and change of extinction angle. It is found that the change of extinction angle in a deformed single crystal is large in the strongly deformed part. The variation of the extinction angle is very sensitive to the deformation even for weakly deformed crystals. This characterization technique is useful to observe semi-quantitatively the deformation of mineral single crystals and can complement the deformation study by TEM and optical microscope with a universal stage.