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From structure topology to chemical composition; VII, Titanium silicates; the crystal structure and crystal chemistry of jinshajiangite

Elena Sokolova, Fernando Camara, Frank C. Hawthorne and Yassir Abdu
From structure topology to chemical composition; VII, Titanium silicates; the crystal structure and crystal chemistry of jinshajiangite
European Journal of Mineralogy (August 2009) 21 (4): 871-883

Abstract

The crystal structure of jinshajiangite, ideally BaNaTi (sub 2) Fe (sub 4) (super 2+) (Si (sub 2) O (sub 7) ) (sub 2) O (sub 2) (OH) (sub 2) F, a 10.6785(8), b 13.786(1), c 20.700(2) Aa, beta 94.937(1) degrees , V 3035.93(6) Aa (super 3) , sp. gr. C2/m, Z = 8, D (sub calc.) 3.767 g/cm (super 3) , from Norra Karr, Tonkoping province, Sweden, has been refined to R (sub 1) 5.69 % on the basis of 3193 unique reflections (F (sub O) > 4sigma F). Electron microprobe analysis gave (wt%): SiO (sub 2) 27.56, Nb (sub 2) O (sub 5) 0.12, TiO (sub 2) 18.36, ZrO (sub 2) 0.51, FeO 23.42, Fe (sub 2) O (sub 3) 2.89 [the Fe (super 3+) /Fe (sub tot) ratio of 0.10(9) was determined by Mossbauer spectroscopy], MnO 5.13, MgO 0.44, CaO 2.52, BaO 10.24, K (sub 2) O 1.95, Na (sub 2) O 2.27, F 2.33, H (sub 2) O 2.00 (calc. from structure refinement: OH + F=3 apfu), O=F-0.98, total 98.76. The empirical formula is (Ba (sub 0.58) K (sub 0.36) ) (sub Sigma 0.94) (Na (sub 0.57) Ca (sub 0.39) ) (sub Sigma 0.96) (Fe (sub 2.84) (super 2+) Mn (sub 0.63) Fe (sub 0.32) (super 3+) Mg (sub 0.10) Zr (sub 0.04) Na (sub 0.07) ) (sub Sigma 4.00) (Ti (sub 2.00) Nb (sub 0.01) ) (sub Sigma 2.01) (Si (sub 2) O (sub 7) ) (sub 2) O (sub 2.12) (OH) (sub 1.93) F (sub 1.07) , calculated on the basis of 4 Si apfu. The crystal structure of jinshajiangite can be described as a combination of a TS block and an I block. The TS (titanium silicate) block consists of HOH sheets (H-heteropolyhedral, O-octahedral), and is a component of 27 Ti-disilicate minerals. In the O sheet, there are five [6]-coordinated M (super O) sites occupied mainly by Fe (super 2+) and Mn (super 2+) , with minor Fe (super 3+) , Mg, Zr and Na with <M (super O) -O>=2.175 Aa. Five M (super O) sites give ideally Fe (super 2+) (sub 4) pfu. In the H sheet, there are three [6]-coordinated M (super H) sites occupied solely by Ti (Ti=2 apfu), with <M (super H) -O>=1.953 Aa, and four [4]-coordinated Si sites occupied solely by Si, with <Si-O>=1.619 Aa. The M (super H) octahedra and (Si (sub 2) O (sub 7) ) groups constitute the H sheet. Linkage of H and O sheets via common vertices of M (super H) octahedra and (Si (sub 2) O (sub 7) ) groups with M (super O) (1-5) octahedra results in a TS block. The topology of the TS block is as in Group II of the Ti disilicates (Ti=2 apfu). There are six interstitial sites, three [9-10]-coordinated Ba-dominant A (super P) sites with <A (super P) -O>=2.98 Aa and three [10]-coordinated Na-dominant B (super P) sites with <B (super P) -O>=2.600 Aa. The total content of three A (super P) sites sums to approximately 1 apfu=Ba (sub 0.58) K (sub 0.36) or ideally 1 Ba pfu. The total content of the three B (super P) sites is Na (sub 0.57) Ca (sub 0.39) or ideally 1 Na pfu. Along c, the TS blocks link via common vertices of M (super H) octahedra (as in astrophyllite-group minerals) and A (super P) and B (super P) sites which constitute the I block. Jinshajiangite is an Fe (super 2+) analogue of perraultite, ideally BaNaTi (sub 2) Mn (sub 4) (super 2+) (Si (sub 2) O (sub 7) ) (sub 2) O (sub 2) (OH) (sub 2) F, and its crystal structure is topologically identical to that of perraultite.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 21
Serial Issue: 4
Title: From structure topology to chemical composition; VII, Titanium silicates; the crystal structure and crystal chemistry of jinshajiangite
Affiliation: Istituto di Geoscienze e Georisorse, Unita di Pavia, Pavia, Italy
Pages: 871-883
Published: 200908
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 33
Accession Number: 2009-085453
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N55°15'00" - N69°15'00", E11°00'00" - E24°15'00"
Secondary Affiliation: University of Manitoba, CAN, Canada
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: 200946
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