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Odigitriaite, CsNa (sub 5) Ca (sub 5) [Si (sub 14) B (sub 2) O (sub 38) ]F (sub 2) ; a new caesium borosilicate mineral from the Darai-Pioz alkaline massif, Tajikistan; description and crystal structure

Atali A. Agakhanov, Leonid A. Pautov, Elena Sokolova, Frank C. Hawthorne, Vladimir Yu. Karpenko, Oleg I. Siidra and Vyacheslav A. Muftakhov
Odigitriaite, CsNa (sub 5) Ca (sub 5) [Si (sub 14) B (sub 2) O (sub 38) ]F (sub 2) ; a new caesium borosilicate mineral from the Darai-Pioz alkaline massif, Tajikistan; description and crystal structure
Mineralogical Magazine (February 2017) 81 (1): 113-122

Abstract

Odigitriaite, a new Cs,Na,Ca borosilicate mineral, was discovered in moraine adjacent to the Darai-Pioz alkaline massif in the upper reaches of the Darai-Pioz river at the intersection of the Turkestansky, Zeravshansky and Alaisky mountain ridges, Tajikistan. It occurs as irregular thin flakes associated with quartz, pectolite, baratovite, fluorite, pekovite, polylithionite, aegirine, leucosphenite, pyrochlore, neptunite, reedmergnerite, mendeleevite-(Se), zeravshanite and sokolovaite. It is colourless with a white streak, is translucent and has a vitreous lustre; it does not fluoresce under ultraviolet light. Odigitriaite is brittle with an uneven fracture and a Mohs hardness of 5. The calculated density is 2.80(2) g/cm (super 3) The indices of refraction are alpha = 1.502, beta = 1.564, gamma = 1.576; 2Vobs = 46(2) degrees , dispersion is weak r > v, and there is no pleochroism. The chemical composition is as follows (electron microprobe, H (sub 2) O calculated from structure): SiO (sub 2) 55.30, Al (sub 2) O (sub 3) 0.09, Y (sub 2) O (sub 3) 0.44, MnO 0.94, FeO 0.10, PbO 0.21, K (sub 2) O 0.01 Cs (sub 2) O 8.36, B (sub 2) O (sub 3) 4.75, H (sub 2) O 0.37, F 1.74, O = F (sub 2) -0.74, total 99.43 wt.%. The empirical formula of odigitriaite is Cs (sub 0.90) Na (sub 5.12) Ca (sub 4.68) Mn (sub 0.20) Y (sub 0.06) Fe (sub 0.02) Pb (sub 0.01) [Si (sub 13.9 2) Al (sub 0.03) B (sub 2.06) O (sub 38) ]F (sub 1.39) (OH) (sub 0.62) The end-member formula is CsNa (sub 5) Ca (sub 5) [Si (sub 14) B (sub 2) O (sub 38) ]F (sub 2) The strong reflections in the powder X-ray diffraction pattern are: [(d, A), (I, %), (hkl)]: 5.45 (25) (1 1 3), 4.66 (33) (3 1 1), 4.40 (26) (0 2 2), 4.10 (36) (3 1 3), 3.95 (25) (3 1 3), 2.85 (31) (2 2 2), 2.68 (40) (0 0 6), 3.62 (45) (0 2 4), 3.35 (100) (2 2 4), 3.31 (30) (3 1 5), 3.25 (35) (4 0 4), 3.04 (60) (4 2 2), 2.925 (22) (4 2 3), 1.813 (23) (9 1 0). Odigitriaite is monoclinic, space group C2/c, a = 16.652(5), b = 9.598(3), c = 22.120(7) A, beta = 92.875(14) degrees , V = 3530.9(1.9) A (super 3) , Z = 4. The crystal structure of odigitriaite was solved by direct methods and refined to an R (sub 1) value of 2.75% based on single-crystal X-ray data. It is a double-layer sheet-borosilicate mineral; Cs and Na are intercalated within the double-layer sheet, and the double layers are linked by interstitial Ca and Na atoms.


ISSN: 0026-461X
EISSN: 1471-8022
Coden: MNLMBB
Serial Title: Mineralogical Magazine
Serial Volume: 81
Serial Issue: 1
Title: Odigitriaite, CsNa (sub 5) Ca (sub 5) [Si (sub 14) B (sub 2) O (sub 38) ]F (sub 2) ; a new caesium borosilicate mineral from the Darai-Pioz alkaline massif, Tajikistan; description and crystal structure
Affiliation: St. Petersburg State University, Department of Crystallography, Saint Petersburg, Russian Federation
Pages: 113-122
Published: 201702
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 19
Accession Number: 2017-048015
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
N36°00'00" - N41°00'00", E67°00'00" - E75°00'00"
Secondary Affiliation: Russian Academy of Sciences, RUS, Russian FederationUniversity of Manitoba, CAN, CanadaSouth Urals State University, RUS, Russian Federation
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201726
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