Skip to main content Accessibility help
×
Home

Ferrivauxite, a new phosphate mineral from Llallagua, Bolivia

  • G. Raade (a1), J. D. Grice (a2) and R. Rowe (a2)

Abstract

Ferrivauxite, ideally Fe3+ Al2(PO4)2(OH)3·5H2O, is an oxidized equivalent of vauxite, Fe2+ Al2(PO4)2(OH)2·6H2O, and forms oxidation pseudomorphs after that mineral. It occurs in association with sigloite and crandallite at the Llallagua tin deposit, Bolivia. It is triclinic, space group P1̄, with a = 9.198(2), b = 11.607(3), c = 6.112(2) Å, α = 98.237(9), β = 91.900(13), γ = 108.658(9)°, V = 609.7(5) Å3, Z = 2. Strongest reflections of the powder X-ray diffraction pattern are [dobs in Å(Iobs)(hkl)]: 10.834(100)(010), 8.682(24)(100), 8.242 (65)(110), 6.018(28)(001), 5.918(23)(1̄10), 5.491 (30)(1̄20), 4.338(26)(200), 2.898 (32)(300). The structure was refined to R1 = 0.0369 for 3244 observed reflections. Twinning occurs on {010}. Ferrivauxite is isotypic with vauxite but with positional disorder of the Fe1 site and some of the oxygen sites. Disorder is also indicated by the infrared spectrum. One of the water molecules in vauxite is deprotonated in conjunction with the oxidation process and becomes a hydroxyl group. Ferrivauxite is translucent to transparent, has a golden brown colour with a pale yellow-brown streak and vitreous lustre. It is brittle with an irregular fracture and shows no cleavage. The Mohs hardness is estimated to be ∼3½ by comparison with vauxite. D(calc.) is 2.39 g cm–3 for the empirical formula Fe3+ 0.94Mn0.01Al1.98P2.05O8(OH)3 · 5H2O, obtained by electron-microprobe analysis in wavelength dispersive spectroscopy mode. The mineral is optically biaxial negative with α = 1.589(1), β = 1.593(1), γ = 1.596(1); the refractive indices are higher than those of vauxite.

Copyright

Corresponding author

References

Hide All
Anthony, J.W., Bideaux, R.A., Bladh, K.W. and Nichols, M.C. (2000) Handbook of Mineralogy. Volume IV. Arsenates, Phosphates, Vanadates. Mineral Data Publishing, Tucson, pp. 625 pp.
Baur, W.H. (1969) The crystal structure of paravauxite, Fe2+A12(PO4)2(OH)2(OH2)6-2H2O. Neues Jahrbuch für Mineralogie, Monatshefte, 430433.
Baur, W.H. and Rama Rao, B. (1968) The crystal structure and the chemical composition of vauxite. American Mineralogist, 53, 10251028.
Brese, N.E. and O'Keeffe, M. (1991) Bond-valence parameters for solids. Acta Crystallographica, B47, 192197.
Brown, I.D. and Altermatt, D. (1985) Bond-valence parameters obtained from a systematic analysis of the inorganic crystal structure database. Acta Crystallographica, B, 244247.
Chukanov, N.V. (2014) Infrared Spectra of Mineral Species: Extended Library.Springer-Verlag GmbH, Dordrecht — Heidelberg — New York — London. 1716 pp.
Gatta, G.D., Vignola, P. and Meven, M. (2014) On the complex H-bonding network in paravauxite, Fe2+A12(PO4)2(OH)2-8H2O: A single-crystal neutron diffraction study. Mineralogical Magazine, 78, 841850.
Gordon, S.G. (1923) Vauxite and paravauxite, two new minerals from Llallagua, Bolivia. Proceedings of the Academy of Natural Sciences of Philadelphia, 75, 261267.
Gordon, S.G. (1944) The mineralogy of the tin mines of Cerro de Llallagua, Bolivia. Proceedings of the Academy of Natural Sciences of Philadelphia, 96, 279359.
Hawthorne, F.C. (1988) Sigloite: the oxidation mechan¬ism in [M-+(PO4)2(OH)2(H2O)2]2∼ structures. Mineralogy and Petrology, 38, 201211
Hurlbut, C.S.Jr and Honea, R. (1962) Sigloite, a new mineral from Llallagua, Bolivia. American Mineralogist, 47, 18.
Hyrsl, J. and Petrov, A. (2006) Famous mineral localities: Llallagua, Bolivia. Mineralogical Record, 37,117162
Kraus, W and Nolze, G. (1996) Powdercell - a program for the representation and manipulation of crystal structures and calculation of the resulting X-ray powder patterns. Journal of Applied Crystallography, 29, 301303.
Laugier, J. and Bochu, B. (2003) LMGP Suite of Programs for the Interpretation of X-ray Experiments. ENSP/Laboratoire des Matériaux et du Génie Physique, BP 46. 38042 Saint Martin d'Heres, France.
Libowitzky, E. (1999) Correlation of O-H stretching frequencies and O—H-0 hydrogen bond lengths in minerals. Monatshefte für Chemie, 130,10471059
Mandarino, J.A. (1981) The Gladstone-Dale relationship: Part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441450
Moore, P.B. and Araki, T (1974) Montgomeryite, Ca4Mg(H2O)12[Al4(OH)4(PO4)6]: Its crystal structure and relation to vauxite, • 4H2O. Fe2+ (H2O)4 [Al4 ðOHÞ4 ðH24 ðPO4Þ4 American Mineralogist, 59, 843850.
Moore, P.B., Araki, T., Kampf, A.R. and Steele, I.M. (1976) Olmsteadite, K2Fe22þ[Fe22þ(Nb,Ta)2 5O4ðH24ðPO4Þ4], a new species, its crystal structure and relation to vauxite and montgomeryite. American Mineralogist, 61, 511.
Rowe, R. (2009) New statistical calibration approach for Bruker AXS D8 Discover microdiffractometer with Hi-Star detector using GADDS software. Powder Diffraction, 24, 263271.
Sheldrick, G.M. (1990) SHELXTL, a crystallographic computing package, revision 4.1. Siemens Analytical Instruments, Inc., Madison, Wisconsin, USA.
Sheldrick, G.M. (1998) SADABS User Guide. University of Göttingen. Göttingen, German.

Keywords

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed