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Chivruaiite, Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]·13-14H2O, a new mineral from hydrothermal veins of Khibiny and Lovozero alkaline massifs

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Published/Copyright: March 31, 2015
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American Mineralogist
From the journal American Mineralogist Volume 91 Issue 5-6

Abstract

Chivruaiite is a new Ca titanosilicate [orthorhombic, Cmmm, a = 7.17(2), b = 22.98(9), c = 6.94(2) Å, V = 1144.4 Å3, Z = 1], chemically and structurally related to zorite. The mineral is found in three different hydrothermal veins within the Khibiny and Lovozero alkaline massifs, Kola Peninsula, Russia. It is associated with microcline, eudialyte, natrolite, astrophyllite, aegirine, etc. Chivruaiite occurs as elongate-prismatic crystals (up to 3 mm long) with {100}, {010}, {001}, {101}, and {011} as dominant faces, as well as radiating aggregates. The mineral is transparent, pale-pink to colorless, with vitreous luster and white streak. Cleavage is distinct on {100} and {010}; fracture is step-like. Mohs hardness is about 3. In transmitted light, the mineral is pale-pink, with a faint pleochroism: Z = pale-pink, on X and Y = colorless; dispersion r < v. Chivruaiite is biaxial (+): α =1.705(5), β = 1.627(2), γ = 1.612(2) (for λ = 589 nm), 2Vmeas = 40 ± 5°, 2Vcalc = 31.7°. Optical orientation: X = b, Y = a, Z = c, Dcalc = 2.42 g/cm3, Dmeas = 2.40.2.42 g/cm3. The mean chemical composition determined by electron microprobe is (wt%): SiO2 45.14; TiO2 20.63; Al2O3 0.07; Fe2O3 0.18; MnO 0.02; MgO 0.01; CaO 10.53; Na2O 0.10; K2O 1.30; SrO 0.28; Nb2O5 3.63; H2O 17.30; sum. 99.19. Empirical formula calculated on the basis of Si = 12 is (Ca3.00K0.44 Na0.05Sr0.04Mn0.01)Σ=3.54(Ti4.13Nb0.44Fe3+0.04 Al0.02)Σ=4.63[Si12O34 |(OH)4.51O0.49]·13.08H2O. Simplified formula is Ca4(Ti,Nb)5[(Si6O17)2|(OH,O)5]·13-14H2O. The strongest X-ray powder-diffraction lines [d in Å, (I), (hkl)] are 11.6 (100) (020), 6.91 (90) (110, 001), 5.23 (50) (130), 3.41 (50) (220), 3.35 (50) (061, 151), 3.04 (80) (221, 240). The structure of chivruaiite was refined to R1 = 0.038 on the basis of 687 unique observed reflections. It is based upon an open framework of SiO4 tetrahedra, TiO6 octahedra, and TiO5 pyramids. Framework cavities are occupied by Ca2+ and K+ cations, and H2O molecules. The mineral is named after its type locality in the Chivruai River valley (the Lovozero massif, Kola Peninsula, Russia). Chivruaiite is a Ca-analog of zorite and ETS-4 and is closely related to haineaultite.

Keywords: Chivruaiite; zorite; titanosilicate; new mineral; crystal structure; Kola Peninsula
Received: 2005-7-11
Accepted: 2005-12-29
Published Online: 2015-3-31
Published in Print: 2006-5-1

© 2015 by Walter de Gruyter Berlin/Boston

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  1. Hourglass sector zoning in metamorphic tourmaline and resultant major and trace-element fractionation
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  3. Chemical bonding and electronic structures of the Al2SiO5 polymorphs, andalusite, sillimanite, and kyanite: X-ray photoelectron- and electron energy loss spectroscopy studies
  4. Application of the simple salt lattice energy approximation to the solubility of minerals
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  16. Cation order and hydrogen bonding of high-pressure phases in the Al2O3-SiO2-H2O system: An NMR and Raman study
  17. Relationship among metamorphic grade, vesuvianite ”rod polytypism”, and vesuvianite composition
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  20. Heat capacities and entropies of mixing of pyrope-grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions: A low-temperature calorimetric and a thermodynamic investigation
  21. Fe2+ and Fe3+ quantification by different approaches and fO₂ estimation for Albanian Cr-spinels
  22. Inversion twinning in troilite
  23. Chivruaiite, Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]·13-14H2O, a new mineral from hydrothermal veins of Khibiny and Lovozero alkaline massifs
  24. Pseudojohannite from Jáchymov, Musonoï, and La Creusaz: A new member of the zippeite-group
  25. Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, a new single-chain silicate
  26. Mn-tourmaline crystals from island of Elba (Italy): Growth history and growth marks
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https://doi.org/10.2138/am.2006.2032
Keywords for this article
Chivruaiite; zorite; titanosilicate; new mineral; crystal structure; Kola Peninsula

Articles in the same Issue

  1. Hourglass sector zoning in metamorphic tourmaline and resultant major and trace-element fractionation
  2. Occurrence and late re-equilibration of pollucite from the Koktokay no. 3 pegmatite, Altai, northwestern China
  3. Chemical bonding and electronic structures of the Al2SiO5 polymorphs, andalusite, sillimanite, and kyanite: X-ray photoelectron- and electron energy loss spectroscopy studies
  4. Application of the simple salt lattice energy approximation to the solubility of minerals
  5. Quench rate and temperature effects on framework ordering in aluminosilicate melts
  6. The effect of sodium on the solubilities of metals in silicate melts
  7. Nanotunnels and pull-aparts: Defects of exsolution lamellae in alkali feldspars
  8. The structure and distribution of carbon in 3.5 Ga Apex chert: Implications for the biogenicity of Earth`s oldest putative microfossils
  9. Site disorder revealed through Raman spectra from oriented single crystals: A case study on karooite (MgTi2O5)
  10. Single-crystal diffraction and transmission electron microscopy studies of silicified pyrochlore from Narssârssuk, Julianehaab district, Greenland
  11. Compressibility of synthetic potassium-rich clinopyroxene: In-situ high-pressure single-crystal X-ray study
  12. The effect of Ca substitution on the elastic and structural behavior of orthoenstatite
  13. Dehydroxylation, proton migration, and structural changes in heated talc: An infrared spectroscopic study
  14. Stabilizing of methane hydrate and transition to a new high-pressure structure at 40 GPa
  15. Upper limit of the tetrahedral rotation angle and factors affecting octahedral flattening in synthetic and natural 1M polytype C2/m space group micas
  16. Cation order and hydrogen bonding of high-pressure phases in the Al2O3-SiO2-H2O system: An NMR and Raman study
  17. Relationship among metamorphic grade, vesuvianite ”rod polytypism”, and vesuvianite composition
  18. Assignment of infrared OH-stretching bands in calcic amphiboles through deuteration and heat treatment
  19. Direct determination of cation site occupancies in natural ferrite spinels by L2,3 X-ray absorption spectroscopy and X-ray magnetic circular dichroism
  20. Heat capacities and entropies of mixing of pyrope-grossular (Mg3Al2Si3O12-Ca3Al2Si3O12) garnet solid solutions: A low-temperature calorimetric and a thermodynamic investigation
  21. Fe2+ and Fe3+ quantification by different approaches and fO₂ estimation for Albanian Cr-spinels
  22. Inversion twinning in troilite
  23. Chivruaiite, Ca4(Ti,Nb)5[(Si6O17)2[(OH,O)5]·13-14H2O, a new mineral from hydrothermal veins of Khibiny and Lovozero alkaline massifs
  24. Pseudojohannite from Jáchymov, Musonoï, and La Creusaz: A new member of the zippeite-group
  25. Scheuchzerite, Na(Mn,Mg)9[VSi9O28(OH)](OH)3, a new single-chain silicate
  26. Mn-tourmaline crystals from island of Elba (Italy): Growth history and growth marks
  27. The oxidation state of vanadium in titanomagnetite from layered basic intrusions
  28. Observation of bicarbonate in calcite by NMR spectroscopy
  29. Single-crystal elastic properties of dense hydrous magnesium silicate phase A
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