The crystal structure of painite CaZrB[Al9O18] revisited

Thomas Armbruster; Nicola Döbelin; Adolf Peretti; Detlef Günther; Eric Reusser; Bernard Grobéty

doi:10.2138/am-2004-0415

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Research Article| April 01, 2004

The crystal structure of painite CaZrB[Al₉O₁₈] revisited

Thomas Armbruster;

Thomas Armbruster *

1

Laboratorium für chemische mineralogische Kristallographie, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

*

E-mail: [email protected]

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Nicola Döbelin;

Nicola Döbelin

1

Laboratorium für chemische mineralogische Kristallographie, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

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Adolf Peretti;

Adolf Peretti

2

GRS Gemresearch Swisslab Ltd., Hirschmattstrasse 6, CH-6003 Luzern, Switzerland

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Detlef Günther;

Detlef Günther

3

Laboratory of Inorganic Chemistry—Elemental and Trace Analysis ETH Hönggerberg, HCI, G113, CH-8093 Zürich, Switzerland

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Eric Reusser;

Eric Reusser

4

Institute of Mineralogy and Petrography, Sonneggstrasse, 5 ETH Zentrum, CH-8092 Zürich, Switzerland

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Bernard Grobéty

5

Department of Geosciences, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland

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Author and Article Information

Thomas Armbruster *

1

Laboratorium für chemische mineralogische Kristallographie, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

Nicola Döbelin

1

Laboratorium für chemische mineralogische Kristallographie, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland

Adolf Peretti

2

GRS Gemresearch Swisslab Ltd., Hirschmattstrasse 6, CH-6003 Luzern, Switzerland

Detlef Günther

3

Laboratory of Inorganic Chemistry—Elemental and Trace Analysis ETH Hönggerberg, HCI, G113, CH-8093 Zürich, Switzerland

Eric Reusser

4

Institute of Mineralogy and Petrography, Sonneggstrasse, 5 ETH Zentrum, CH-8092 Zürich, Switzerland

Bernard Grobéty

5

Department of Geosciences, University of Fribourg, Pérolles, CH-1700 Fribourg, Switzerland

*

E-mail: [email protected]

Publisher: Mineralogical Society of America

Revision Received: 23 Jul 2003

Accepted: 21 Oct 2003

First Online: 02 Mar 2017

Online ISSN: 1945-3027

Print ISSN: 0003-004X

American Mineralogist (2004) 89 (4): 610–613.

https://doi.org/10.2138/am-2004-0415

Abstract

The crystal structure of the rare hexagonal mineral painite [a = 8.724(1), c = 8.464(2) Å] from Mogok (Myanmar), with the ideal composition CaZrB[Al₉O₁₈], was re-determined by single-crystal X-ray diffraction. Structure refinements were performed in space groups P6₃/m and P6₃. The centrosymmetric P6₃/m model yielded excellent agreement (R₁ = 1.44%, 1189 reflections > 2σ I_obs, 54 parameters) with the observed diffraction data without any unusual atomic displacement parameters, thus the acentric P6₃ model was rejected. A previous structural study claimed that painite was noncentrosymmetric and differed from the related structures of jeremejevite B₅[□₃Al₆(OH)₃O₁₅] and fluoborite B₃[Mg₉(F,OH)₉O₉] in having lower symmetry.

The structure of painite comprises a framework of AlO₆ octahedra that features two types of channels parallel to the c axis. One channel has a trigonal cross-section and is occupied by threefold coordinated B and Zr in sixfold prismatic coordination. The other channel has a hexagonal cross-section and is occupied by Ca. Chemical analysis by laser-ablation inductively-coupled plasma-mass spectrometry indicated that the crystal studied has significant substitution of Na for Ca (ca. 20%) charge-balanced by Ti⁴⁺ replacing octahedral Al leading to the formula Ca_0.77Na_0.19Al_8.80Ti_0.19Cr_0.03V_0.01Zr_0.94Hf_0.01B_1.06O₁₈.