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Brandãoite, [BeAl2(PO4)2(OH)2(H2O)4](H2O), a new Be–Al phosphate mineral from the João Firmino mine, Pomarolli farm region, Divino das Laranjeiras County, Minas Gerais State, Brazil: description and crystal structure

Published online by Cambridge University Press:  29 June 2018

Luiz A. D. Menezes Filho ,
Mário L. S. C. Chaves ,
Mark A. Cooper ,
Neil A. Ball ,
Yassir A. Abdu ,
Ryan Sharpe ,
Maxwell C. Day  and
Frank C. Hawthorne
Luiz A. D. Menezes Filho
Affiliation:
Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
Mário L. S. C. Chaves
Affiliation:
Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
Mark A. Cooper
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Neil A. Ball
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Yassir A. Abdu
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada Department of Applied Physics and Astronomy, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates
Ryan Sharpe
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Maxwell C. Day
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
Frank C. Hawthorne*
Affiliation:
Department of Geological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
*
*Author for correspondence: Frank Hawthorne, Email: frank_hawthorne@umanitoba.ca
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Abstract

Brandãoite, [BeAl2(PO4)2(OH)2(H2O)4](H2O), is a new Be–Al phosphate mineral from the João Firmino mine, Pomarolli farm region, Divino das Laranjeiras County, Minas Gerais State, Brazil, where it occurs in an albite pocket with other secondary phosphates, including beryllonite, atencioite and zanazziite, in a granitic pegmatite. It occurs as colourless acicular crystals <10 µm wide and <100 µm long that form compact radiating spherical aggregates up to 1.0–1.5 mm across. It is colourless and transparent in single crystals and white in aggregates, has a white streak and a vitreous lustre, is brittle and has conchoidal fracture. Mohs hardness is 6, and the calculated density is 2.353 g/cm3. Brandãoite is biaxial (+), α = 1.544, β = 1.552 and γ = 1.568, all ± 0.002; 2Vobs = 69.7(10)° and 2Vcalc = 71.2°. No pleochroism was observed. Brandãoite is triclinic, space group P$\bar{1}$, a = 6.100(4), b = 8.616(4), c = 10.261(5) Å, α = 93.191(11), β = 95.120(11), γ = 96.863(11)°, V = 532.1(8) Å3 and Z = 2. Chemical analysis of a 4 µm wide needle-shaped crystal by electron microprobe and secondary-ion mass spectrometry gave P2O5 = 28.42, Al2O3 = 20.15, BeO = 4.85, H2O = 21.47 and sum = 74.89 wt.%. The empirical formula, normalised on the basis of 15 anions pfu with (OH) = 2 and (H2O) = 5 apfu (from the crystal structure) is Be0.98Al1.99P2.02H12O15. The crystal structure was solved by direct methods and refined to an R1 index of 7.0%. There are two P sites occupied by P5+, two Al sites occupied by octahedrally coordinated Al3+, and one Be site occupied by tetrahedrally coordinated Be2+. There are fifteen anions, two of which are (OH) groups and five of which are (H2O) groups. The simplified ideal formula is thus [BeAl2(PO4)2(OH)2(H2O)4](H2O) with Z = 2. Beryllium and P tetrahedra share corners to form a four-membered ring. Aluminium octahedra share a common vertex to form an [Al2φ11] dimer, and these dimers are cross-linked by P tetrahedra to form a complex slab of polyhedra parallel to (001). These slabs are cross-linked by BeO2(OH)(H2O) tetrahedra, with interstitial (H2O) groups in channels that extend along [100].

Keywords

brandãoitenew mineralchemical analysisberyllium phosphatecrystal structureinfrared spectrumMinas Gerais StateBrazil
Type
Article
Information
Mineralogical Magazine , Volume 83 , Issue 2 , April 2019 , pp. 261 - 267
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2018 

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Footnotes

†

Deceased 2014

Associate Editor: Peter Leverett

References

Bartelmehs, K.L., Bloss, F.D., Downs, R.T. and Birch, J.B. (1992) Excalibr II. Zeitschrift für Kristallographie, 199, 186–196.Google Scholar
Chaves, M.L.S.C. and Scholz, R. (2008) Pegmatito Gentil (Mendes Pimentel, MG) e suas paragêneses mineralogical de fosfatos raros. Revista Escola de Minas, 61, 141–149 [in Portuguese].Google Scholar
Chaves, M.L.S.C., Scholz, R., Atencio, D. and Karfunkel, J. (2005) Assembleias e paragêneses minerais singulares nos pegmatitos da região de Galiléia (Minas Gerais). Geociências, 24, 143–161 [in Portuguese].Google Scholar
Gagné, O.C. and Hawthorne, F.C. (2015) Comprehensive derivation of bond-valence parameters for ion pairs involving oxygen. Acta Crystallographica, B71, 562–578.Google Scholar
Gagné, O.C. and Hawthorne, F.C. (2016) Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals. Acta Crystallographica, B72, 602–625.Google Scholar
Gagné, O.C. and Hawthorne, F.C. (2017 a) Bond-length distributions for ions bonded to oxygen: Results for the non-metals and discussion of lone-pair stereoactivity and the polymerization of PO4. Available at: https://chemrxiv.org/articles/Bond-length_distributions_for_ions_bonded_to_oxygen_Results_for_the_non-metals_and_discussion_of_lone-pair_stereoactivity_and_the_polymerization_of_PO4/5410918.Google Scholar
Gagné, O.C. and Hawthorne, F.C. (2017 b) Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals. Available at: https://chemrxiv.org/articles/Bond-length_distributions_for_ions_bonded_to_oxygen_Metalloids_and_post-transition_metals/5410921.Google Scholar
Gunter, M.E. and Twamley, B. (2001) A new method to determine the optical orientation of biaxial minerals: a mathematical approach. The Canadian Mineralogist, 39, 1701–1711.Google Scholar
Hawthorne, F.C. and Grice, J.D. (1990) Crystal structure analysis as a chemical analytical method: application to light elements. The Canadian Mineralogist, 28, 693–702.Google Scholar
Hawthorne, F.C. and Huminicki, D.M.C. (2002) The crystal chemistry of beryllium. Pp. 333–403 in: Beryllium: Mineralogy, Petrology and Geochemistry (Grew, E.S., editor). Reviews in Mineralogy and Geochemistry, 50. Mineralogical Society of America, Washington DC.Google Scholar
Hawthorne, F.C., Ungaretti, L. and Oberti, R. (1995) Site populations in minerals: terminology and presentation of results of crystal-structure refinement. The Canadian Mineralogist, 33, 907–911.Google Scholar
Huminicki, D.M.C. and Hawthorne, F.C. (2002) The crystal chemistry of the phosphate minerals. Pp. 123–253 in: Phosphates: Geochemical, Geobiological, and Materials Importance (Kohn, M.J., Rakovan, J. and Hughes, J.M., editors). Reviews in Mineralogy and Geochemistry, 48. Mineralogical Society of America, Washington DC.Google Scholar
Mandarino, J.A. (1981) The Gladstone – Dale relationship: Part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441–450.Google Scholar
Menezes, L., Chaves, M.L.S.C., Cooper, M.A., Ball, N., Abdu, Y., Sharp, R., Hawthorne, F.C. and Day, M. (2017) Brandãoite, IMA 2016-071a. CNMNC Newsletter No. 39, October 2017, page 1283; Mineralogical Magazine, 81, 1279–1286.Google Scholar
Pedrosa-Soares, A.C., Campos, C., Noce, C.M., Silva, L.C., Novo, T., Roncato, J., Medeiros, S., Castañeda, C., Queiroga, G., Dantas, E., Dussin, I. and Alkmim, F. (2011) Late Neoproterozoic-Cambrian granitic magmatism in the Araçuaí orogen (Brazil), the Eastern Brazilian Pegmatite Province and related deposits. Geological Society of London Special Publications, 350, 25–51.Google Scholar
Scholz, R., Chaves, M.L.S.C., Belotti, F.M., Cândido Filho, M. and Menezes Filho, L.A.D. (2012) The secondary phosphate minerals from Conselheiro Pena pegmatite district, MG, Brazil: substitutions of tryphylite and montebrasite. Pp. 261–269 in: Para Conhecer a Terra. Coimbra (Portugal) (Lopes, F.C., Andrade, A.I., Henriques, M.H., Quinta-Ferreira, M., Barata, M.T. and Pena dos Reis, R., editors). Vol. 1, Imprensa da Universidade de Coimbra, Portugal.Google Scholar
Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112–122.Google Scholar
Yang, H., Downs, R.T., Evans, S.H., Morrison, S.M. and Schumer, B.N. (2015) Lefontite, IMA 2014-075. CNMNC Newsletter No. 23, February 2015, page 55; Mineralogical Magazine, 79, 51–58.Google Scholar
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