Skip to main content Accessibility help
×
Home

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

  • Luiz A. D. Menezes Filho (a1), Mário L. S. C. Chaves (a1), Mark A. Cooper (a2), Neil A. Ball (a2), Yassir A. Abdu (a2) (a3), Ryan Sharpe (a2), Maxwell C. Day (a2) and Frank C. Hawthorne (a2)...

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].

Copyright

Corresponding author

*Author for correspondence: Frank Hawthorne, Email: frank_hawthorne@umanitoba.ca

Footnotes

Hide All

Deceased 2014

Associate Editor: Peter Leverett

Footnotes

References

Hide All
Bartelmehs, K.L., Bloss, F.D., Downs, R.T. and Birch, J.B. (1992) Excalibr II. Zeitschrift für Kristallographie, 199, 186196.
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, 141149 [in Portuguese].
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, 143161 [in Portuguese].
Gagné, O.C. and Hawthorne, F.C. (2015) Comprehensive derivation of bond-valence parameters for ion pairs involving oxygen. Acta Crystallographica, B71, 562578.
Gagné, O.C. and Hawthorne, F.C. (2016) Bond-length distributions for ions bonded to oxygen: alkali and alkaline-earth metals. Acta Crystallographica, B72, 602625.
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.
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.
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, 17011711.
Hawthorne, F.C. and Grice, J.D. (1990) Crystal structure analysis as a chemical analytical method: application to light elements. The Canadian Mineralogist, 28, 693702.
Hawthorne, F.C. and Huminicki, D.M.C. (2002) The crystal chemistry of beryllium. Pp. 333403 in: Beryllium: Mineralogy, Petrology and Geochemistry (Grew, E.S., editor). Reviews in Mineralogy and Geochemistry, 50. Mineralogical Society of America, Washington DC.
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, 907911.
Huminicki, D.M.C. and Hawthorne, F.C. (2002) The crystal chemistry of the phosphate minerals. Pp. 123253 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.
Mandarino, J.A. (1981) The Gladstone – Dale relationship: Part IV. The compatibility concept and its application. The Canadian Mineralogist, 19, 441450.
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.
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, 2551.
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. 261269 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.
Sheldrick, G.M. (2008) A short history of SHELX. Acta Crystallographica, A64, 112122.
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, 5158.

Keywords

Type Description Title
UNKNOWN
Supplementary materials

Filho et al. supplementary material 1
Filho et al. supplementary material

 Unknown (46 KB)
46 KB

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

  • Luiz A. D. Menezes Filho (a1), Mário L. S. C. Chaves (a1), Mark A. Cooper (a2), Neil A. Ball (a2), Yassir A. Abdu (a2) (a3), Ryan Sharpe (a2), Maxwell C. Day (a2) and Frank C. Hawthorne (a2)...

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