| Reference Type | Journal (article/letter/editorial) |
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| Title | From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia |
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| Journal | Mineralogical Magazine |
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| Authors | Sokolova, E. | Author |
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| Genovese, A. | Author |
| Falqui, A. | Author |
| Hawthorne, F.C. | Author |
| Cámara, F. | Author |
| Year | 2017 (December) | Volume | 81 |
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| Page(s) | 1533-1550 | Issue | 6 |
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| Publisher | Mineralogical Society |
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| Download URL | https://rruff.info/rruff_1.0/uploads/MM81_1533.pdf+ |
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| DOI | doi:10.1180/minmag.2017.081.015Search in ResearchGate |
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| Classification | Not set | LoC | Not set |
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| Mindat Ref. ID | 244963 | Long-form Identifier | mindat:1:5:244963:4 |
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| GUID | 1fbe956f-a0b0-4879-98b6-559cad12d828 |
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| Full Reference | Sokolova, E., Genovese, A., Falqui, A., Hawthorne, F.C., Cámara, F. (2017) From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia. Mineralogical Magazine, 81 (6) 1533-1550 doi:10.1180/minmag.2017.081.015 |
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| Plain Text | Sokolova, E., Genovese, A., Falqui, A., Hawthorne, F.C., Cámara, F. (2017) From structure topology to chemical composition. XXIII. Revision of the crystal structure and chemical formula of zvyaginite, Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a seidozerite-supergroup mineral from the Lovozero alkaline massif, Kola peninsula, Russia. Mineralogical Magazine, 81 (6) 1533-1550 doi:10.1180/minmag.2017.081.015 |
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| Abstract/Notes | The crystal structure and chemical formula of zvyaginite, ideally Na2ZnTiNb2(Si2O7)2O2(OH)2(H2O)4, a lamprophyllite-group mineral of the seidozerite supergroup from the type locality, Mt. Malyi Punkaruaiv, Lovozero alkaline massif, Kola Peninsula, Russia have been revised. The crystal structurewas refined with a new origin in space group C1, a = 10.769(2), b = 14.276(3), c = 12.101(2) Å, α = 105.45(3), β = 95.17(3), γ = 90.04(3)°, V = 1785.3(3.2) Å3, R1 = 9.23%. The electron-microprobe analysis gave the following empirical formula [calculated on 22 (O + F)]: (Na0.75Ca0.09K0.04□1.12)Σ2 (Na1.12Zn0.88Mn0.17Fe2+0.04□0.79)Σ3 (Nb1.68Ti1.25Al0.07)Σ3 (Si4.03O14)O2 [(OH)1.11F0.89]Σ2(H2O)4, Z = 4. Electron-diffraction patterns have prominent streaking along c* and HRTEM images show an intergrowth of crystalline zvyaginite with two distinct phases, both of which are partially amorphous. The crystal structure of zvyaginite is an array of TS (Titanium-Silicate) blocks connected via hydrogen bonds between H2O groups. The TS block consists of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the [6]MO(1,4,5) sites are occupied mainly by Ti, Zn and Na and the [6]MO(2,3) sites are occupied by Na at less than 50%. In the H sheet, the [6]MH(1,2) sites are occupied mainly by Nb and the [8]AP(1) and [8]AP(2) sites are occupied mainly by Na and □. The MH and AP polyhedra and Si2O7 groups constitute the H sheet. The ideal structural formula is Na□Nb2NaZn□Ti(Si2O7)2O2(OH)2(H2O)4. Zvyaginite is a Zn-bearing and Na-poor analogue of epistolite, ideally (Na□)Nb2Na3Ti(Si2O7)2O2(OH)2(H2O)4. Epistolite and zvyaginite are related by the following substitution in the O sheet of the TS-block: (Naþ 2 )epi↔Zn2+ zvy +□zvy. The doubling of the t1 and t2 translations of zvyaginite relative to those of epistolite is due to the order of Zn and Na along a (t1) and b (t2) in the O sheet of zvyaginite. |
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