Home Physical Sciences Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron in minerals by PIGE
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Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron in minerals by PIGE

  • Joël Brugger EMAIL logo , Nicolas Meisser , Stefan Ansermet , Sergey V. Krivovichev , Volker Kahlenberg , David Belton and Chris G. Ryan
Published/Copyright: April 2, 2015
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American Mineralogist
From the journal American Mineralogist Volume 97 Issue 7

Abstract

Leucostaurite is a new nanoporous lead borate discovered in samples from the Mina Asunción, Sierra Gorda, Atacama Desert, Chile, preserved since 1912 in the collections of the Natural History Museum of Bern, Switzerland. Leucostaurite formed via the oxidation of base-metal ores in the presence of B-rich brines. The mineral name is derived from the Greek “leukos” (white) and “stauros” (cross), and alludes to the white or transparent, colorless cruciform twinned crystals. Leucostaurite forms thin-tabular {010}, striated //[100], interpenetrated twinned crystals, and sheaf-like aggregates up to 0.8 mm on a paralaurionite and boleite matrix. The streak is white and the luster adamantine. Leucostaurite shows a weak, light-yellow fluorescence under short-wavelength UV but no fluorescence under long-wavelength UV light. The mineral is brittle, Mohs hardness ~4, with perfect cleavage parallel to {010} and good cleavage parallel to {100}; calculated density is 5.071 g/cm3. Leucostaurite is biaxial, 2V (meas) ~30°, dispersion: r > v, strong. Optic sign and refractive indices could not be measured, but the average index calculated from the Gladstone-Dale relationship is 1.849. The empirical formula based on Pb + Sr + Ca = 2 atoms per formula unit (apfu), 1 H apfu and B + Si = 5 apfu, is (Pb1.967Sr0.026Ca0.007)Σ2.000 (B4.983Si0.017)Σ5.000(Cl1.073I0.004)Σ1.077O8.971⋅0.5H2O, which simplifies to Pb2[B5O9]Cl⋅0.5H2O. The boron content was measured on two crystal fragments using proton-induced γ-ray emission spectroscopy; the analytical value [26.7(3) wt% B2O3] is within error of the stoichiometric value of 26.5 wt% B2O3. Leucostaurite is orthorhombic, space group Pnn2, a = 11.376(2), b = 11.505(2), c = 6.5558(7) Å, V = 858.1(2) Å3, Z = 4. The seven strongest lines measured in the X-ray powder diffraction pattern are [d in Å/Irel in %]: 4.04/100; 2.84/100; 5.71/80; 2.019/70; 3.29/40; 2.55/40; 1.877/40. The crystal structure of leucostaurite (R1 = 6.2%) contains a hilgardite-type three-dimensional [B5O9]3- framework. Leucostaurite is the first mineral of the hilgardite group with orthorhombic (Pnn2) symmetry. However, several borates synthesized for their non-linear optical properties are structurally and chemically closely related to leucostaurite. For example in Na0.5Pb2(B5O9)Cl(OH)0.5, one type of channels contains Cl− ions, the other contains OH−, Cl−, and Na+ ions; in leucostaurite these channels are occupied by Cl− ions, and Cl− ions + H2O groups, respectively.

Keywords : Leucostaurite; new mineral; crystal structure; Mina Asunción; Sierra Gorda; Atacama Desert; Chile
Received: 2011-12-20
Accepted: 2012-3-12
Published Online: 2015-4-2
Published in Print: 2012-7-1

© 2015 by Walter de Gruyter Berlin/Boston

Articles in the same Issue

  1. Mercury (Hg) mineral evolution: A mineralogical record of supercontinent assembly, changing ocean geochemistry, and the emerging terrestrial biosphere
  2. The 3.65 Å phase, MgSi(OH)6: Structural insights from DFT-calculations and T-dependent IR spectroscopy
  3. Vertical zonation of the Barcroft granodiorite, White Mountains, California: Implications for magmatic processes
  4. Minerals in cement chemistry: A single-crystal neutron diffraction and Raman spectroscopic study of thaumasite, Ca3Si(OH)6(CO3)(SO4)·12H2O
  5. A new high-pressure phase transition in natural Fe-bearing orthoenstatite
  6. Aluminum solubility in TiO2 rutile at high pressure and experimental evidence for a CaCl2-structured polymorph
  7. First record and timing of UHP metamorphism from zircon in the Xitieshan terrane: Implications for the evolution of the entire North Qaidam metamorphic belt
  8. Lead in zircon at the atomic scale
  9. Characterization of fluor-chlorapatites by electron probe microanalysis with a focus on time-dependent intensity variation of halogens
  10. An inversion-based self-calibration for SIMS measurements: Application to H, F, and Cl in apatite
  11. Second boiling effects on the Al-content of hornblende rims from an exhumed Cretaceous arc pluton, Stewart Island, New Zealand
  12. Heat transfer in plagioclase feldspars
  13. Transport properties and equation of state of 1-bar eutectic melt in the system CaAl2Si2O8-CaMgSi2O6 by molecular dynamics simulation
  14. High-pressure behavior of zoisite
  15. A first-principle investigation of antigorite up to 30 GPa: Structural behavior under compression
  16. Reynoldsite, Pb2Mn4+2 O5(CrO4), a new phyllomanganate-chromate from the Blue Bell claims, California and the Red Lead mine, Tasmania
  17. A new cubic perovskite in PbGeO3 at high pressures
  18. Manganoquadratite, AgMnAsS3, a new manganese-bearing sulfosalt from the Uchucchacua polymetallic deposit, Lima Department, Peru: Description and crystal structure
  19. Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron in minerals by PIGE
  20. Synthetic LiAlGe2O6: The first pyroxene with P21/n symmetry
  21. Panguite, (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD
  22. Buseckite, (Fe,Zn,Mn)S, a new mineral from the Zakłodzie meteorite
  23. Experimental calibration of the effect of H2O on plagioclase crystallization in basaltic melt at 200 MPa
  24. High-pressure and high-temperature titanium solution mechanisms in silicate-saturated aqueous fluids and hydrous silicate melts
  25. Thermodynamic behavior and properties of katoite (hydrogrossular): A calorimetric study
  26. Graphite in the martian meteorite Allan Hills 84001
https://doi.org/10.2138/am.2012.4082
Keywords for this article
Leucostaurite; new mineral; crystal structure; Mina Asunción; Sierra Gorda; Atacama Desert; Chile

Articles in the same Issue

  1. Mercury (Hg) mineral evolution: A mineralogical record of supercontinent assembly, changing ocean geochemistry, and the emerging terrestrial biosphere
  2. The 3.65 Å phase, MgSi(OH)6: Structural insights from DFT-calculations and T-dependent IR spectroscopy
  3. Vertical zonation of the Barcroft granodiorite, White Mountains, California: Implications for magmatic processes
  4. Minerals in cement chemistry: A single-crystal neutron diffraction and Raman spectroscopic study of thaumasite, Ca3Si(OH)6(CO3)(SO4)·12H2O
  5. A new high-pressure phase transition in natural Fe-bearing orthoenstatite
  6. Aluminum solubility in TiO2 rutile at high pressure and experimental evidence for a CaCl2-structured polymorph
  7. First record and timing of UHP metamorphism from zircon in the Xitieshan terrane: Implications for the evolution of the entire North Qaidam metamorphic belt
  8. Lead in zircon at the atomic scale
  9. Characterization of fluor-chlorapatites by electron probe microanalysis with a focus on time-dependent intensity variation of halogens
  10. An inversion-based self-calibration for SIMS measurements: Application to H, F, and Cl in apatite
  11. Second boiling effects on the Al-content of hornblende rims from an exhumed Cretaceous arc pluton, Stewart Island, New Zealand
  12. Heat transfer in plagioclase feldspars
  13. Transport properties and equation of state of 1-bar eutectic melt in the system CaAl2Si2O8-CaMgSi2O6 by molecular dynamics simulation
  14. High-pressure behavior of zoisite
  15. A first-principle investigation of antigorite up to 30 GPa: Structural behavior under compression
  16. Reynoldsite, Pb2Mn4+2 O5(CrO4), a new phyllomanganate-chromate from the Blue Bell claims, California and the Red Lead mine, Tasmania
  17. A new cubic perovskite in PbGeO3 at high pressures
  18. Manganoquadratite, AgMnAsS3, a new manganese-bearing sulfosalt from the Uchucchacua polymetallic deposit, Lima Department, Peru: Description and crystal structure
  19. Leucostaurite, Pb2[B5O9]Cl·0.5H2O, from the Atacama Desert: The first Pb-dominant member of the hilgardite group, and micro-determination of boron in minerals by PIGE
  20. Synthetic LiAlGe2O6: The first pyroxene with P21/n symmetry
  21. Panguite, (Ti4+,Sc,Al,Mg,Zr,Ca)1.8O3, a new ultra-refractory titania mineral from the Allende meteorite: Synchrotron micro-diffraction and EBSD
  22. Buseckite, (Fe,Zn,Mn)S, a new mineral from the Zakłodzie meteorite
  23. Experimental calibration of the effect of H2O on plagioclase crystallization in basaltic melt at 200 MPa
  24. High-pressure and high-temperature titanium solution mechanisms in silicate-saturated aqueous fluids and hydrous silicate melts
  25. Thermodynamic behavior and properties of katoite (hydrogrossular): A calorimetric study
  26. Graphite in the martian meteorite Allan Hills 84001
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