Redefinition of the formula for aldermanite and its crystal structure

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Marco E. Ciriotti
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Redefinition of the formula for aldermanite and its crystal structure

Messaggio da Marco E. Ciriotti » gio 15 apr, 2021 11:24

Prossima pubblicazione.

Referenza:
▪ Elliott, P., Grey, I.E., Willis, A.C. (2021): Redefinition of the formula for aldermanite, [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH,F)6]⋅H2O, and its crystal structure. Mineralogical Magazine, 85, (in press).

Abstract:
ldermanite from Tom’s quarry in the Kapunda-Angaston area of the Mount Lofty Ranges, South Australia has been characterized by electron microprobe analyses and single-crystal structure analysis. The empirical formula is Na0.72K0.13Ca0.06Mg1.15Al2.92(PO4)2.05[(OH)2.92F2.96]5.88·8.91H2O, based on 23 anions. Analysis of a specimen from the type locality, the nearby Klemms quarry, gave a similar formula, Na0.59K0.06Ca0.36Mg0.92Al3.16(PO4)1.97[(OH)4.08F2.70]somma 6.78·8.36H2O. Na and F were not analysed in the original description of the mineral. The ideal end-member formula is [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH)6]·H2O, compared to the original formula of Mg5Al12(PO4)8(OH)22∙nH2O with n ≈ 32. Aldermanite is monoclinic, P21/c with a = 13.524(3), b = 9.958(2), c = 7.013(1) Å, ꞵ = 97.40(3)°. The crystal structure of aldermanite is built from sawtooth layers of cis- and trans-corner-connected, Al-centred octahedra, decorated with corner-connected PO4 tetrahedra to give (100) layers of composition Al3(PO4)2(OH,F)6. Interlayer Mg(H2O)6 octahedra and H2O molecules hold the layers together through H-bonding. The corner-connected octahedra form 6-membered rings that are centred by 8-coordinated Na and have a topology identical to a 3-octahedra-wide {110} slice of the pyrochlore structure. This pyrochlore element contains intersecting kagomé nets of Al atoms, parallel to (111) and (11-1) of cubic pyrochlore. Minerals of the walentaite group, as well as zirconolite-3O polytypes have the same type of intersecting kagomé nets of small cations.

NdR: The work brings out the fact that it is debatable if zirconolite-3O should be classed as a zirconolite polytype.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 28437
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Re: Redefinition of the formula for aldermanite and its crystal structure

Messaggio da Marco E. Ciriotti » ven 16 apr, 2021 15:23

Walentaite group

Aldermanite [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH)6]·H2O mon P21/c 13.524 9.958 7.013 90.00 97.40 90.00 2 936.6
Natrowalentaite [Fe2+0.5Na0.5(H2O)6][NaAs3+2(Fe3+2.33W6+0.67)(PO4)2O7] orth Imma 25.770 7.325 10.522 90.00 90.00 90.00 4 1986.188
Walentaite [Mn2+(H2O)6][□As3+3Fe3+3(PO4)2O7] orth Imma 26.188 7.360 10.367 90.00 90.00 90.00 4 1998.174

Halilsarpite group

Alcantarillaite [Fe3+0.5□0.5(H2O)4][CaAs3+2(Fe3+2.5W6+0.5)(AsO4)2O7] orth Imma 24.038 7.444 10.387 90.00 90.00 90.00 4 1858.638
Halilsarpite [Mg(H2O)6][CaAs3+2(Fe3+2.67Mo6+0.33)(AsO4)2O7] orth Imma 26.4890 7.4205 10.4378 90.00 90.00 90.00 4 2051.671
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
Marco E. Ciriotti
Messaggi: 28437
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Redefinition of the formula for aldermanite and its crystal structure

Messaggio da Marco E. Ciriotti » mer 28 lug, 2021 12:33

Pubblicazione effettuata.

Referenza:
▪ Elliott, P., Grey, I.E., Willis, A.C. (2021): Redefinition of the formula for aldermanite, [Mg(H2O)6][Na(H2O)2Al3(PO4)2(OH,F)6]⋅H2O, and its crystal structure. Mineralogical Magazine, 85, 348-353.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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