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Crystal chemistry of Rb-, Sr-, Ba-, Ca- and Pb-exchanged forms of natural hilairite

Natalia V. Zubkova, Uwe Kolitsch, Igor V. Pekov, Anna G. Turchkova, Marina F. Vigasina, Dmitry Yu. Pushcharovsky and Ekkehart Tillmanns
Crystal chemistry of Rb-, Sr-, Ba-, Ca- and Pb-exchanged forms of natural hilairite
European Journal of Mineralogy (April 2009) 21 (2): 495-506


Cation-exchange properties of natural hilairite, Na (sub 2) {ZrSi (sub 3) O (sub 9) } . 3H (sub 2) O, in aqueous salt solutions at 150 degrees C and the crystal structures of its Rb-, Ca-, Sr-, Ba- and Pb-exchanged forms have been studied on single crystals. All studied samples retain the mixed framework of "parent" hilairite consisting of helical chains [Si (sub 3) O (sub 9) ] (sub infinity) linked by isolated [ZrO (sub 6) ] octahedra. The main differences between the crystal structures of these cation-exchanged forms of hilairite and other representatives of the hilairite group are connected with the number and positions of extra-framework cations and water molecules, framework distortion, unit-cell dimensions and space-group symmetry. The single-crystal structure refinements (X-ray diffraction data) gave the following structural formulas for the studied samples: Rb (sub 1.80) Na (sub 0.20) Zr[Si (sub 3) O (sub 9) ].0.4H (sub 2) O for Rb-exchanged hilairite (R3, a=10.477(1), c=15.377(2) Aa, R1(F)=3.35% for 2771 reflections with F (sub o) >4sigma (F (sub o) )), Ba (sub 0.96) H (sub 0.08) Zr[Si (sub 3) O (sub 9) ].3H (sub 2) O (R3, a=20.976(3), c=7.857(2) Aa, R1(F)=4.96% for 4921 reflections with F (sub o) >4sigma (F (sub o) )) and SrZr[Si (sub 3) O (sub 9) ].1.5H (sub 2) O (R3, a=20.964(3), c=7.836(2) Aa, R1(F)=10.23% for 3598 reflections with F (sub o) >4sigma (F (sub o) )) for Ba- and Sr-exchanged hilairites, respectively, and Ca (sub 0.83) H (sub 0.34) Zr[Si (sub 3) O (sub 9) ].3H (sub 2) O (R3, a=10.456(1), c=7.995(2) Aa, R1(F)=2.63% for 1477 reflections with F (sub o) >4sigma (F (sub o) )) and Pb (sub 0.82) Na (sub 0.18) H (sub 0.18) Zr[Si (sub 3) O (sub 9) ].2.9H (sub 2) O (R3, a = 10.477(1), c=7.994(2) Aa, R1(F)=2.21% for 1165 reflections with F (sub o) >4sigma (F (sub o) )) for Ca- and Pb-exchanged hilairites, respectively. All samples were twinned by merohedry and, except the Ca-exchanged sample, also racemically. The results of this study strongly indicate that natural cation-exchange processes can affect hilairite-group minerals under late-hydrothermal conditions.

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 21
Serial Issue: 2
Title: Crystal chemistry of Rb-, Sr-, Ba-, Ca- and Pb-exchanged forms of natural hilairite
Affiliation: Moscow State University, Geology Department, Moscow, Russian Federation
Pages: 495-506
Published: 200904
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 17
Accession Number: 2009-048534
Categories: Mineralogy of silicatesGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 10 tables
N35°00'00" - N71°00'00", W25°00'00" - E75°00'00"
N67°00'00" - N68°00'00", E33°00'00" - E34°00'00"
N66°00'00" - N70°00'00", E32°00'00" - E42°00'00"
N37°00'00" - N83°00'00", W170°00'00" - E28°00'00"
Secondary Affiliation: Naturhistorisches Museum, AUT, AustriaUniversitat Wien, AUT, Austria
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200926
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