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Tumchaite Na (sub 2) (Zr,Sn)Si (sub 4) O (sub 11) .2H (sub 2) O; a new mineral from carbonatites of the Vuoriyarvi alkali-ultrabasic massif, Murmansk region, Russia

Victor V. Subbotin, Stefano Merlino, Dmitry Yu. Pushcharovsky, Yakov A. Pakhomovsky, Orazio Ferro, Alla N. Bogdanova, Anatoly V. Voloshin, Natalia V. Sorokhtina and Natalia V. Zubkova
Tumchaite Na (sub 2) (Zr,Sn)Si (sub 4) O (sub 11) .2H (sub 2) O; a new mineral from carbonatites of the Vuoriyarvi alkali-ultrabasic massif, Murmansk region, Russia
American Mineralogist (October 2000) 85 (10): 1516-1520

Abstract

Tumchaite, Na (sub 2) (Zr,Sn)Si (sub 4) O (sub 11) .2H (sub 2) O, is a new species from the Vuoriyarvi alkali-ultrabasic massif, Murmansk Region, Russia, where it occurs as colorless to white tabular monoclinic crystals associated with calcite, dolomite, a mineral of the serpentine group and pyrite in the late dolomite-calcite carbonatites. It is transparent to translucent; with vitreous luster; and perfect cleavage on (100). Mohs hardness is 4.5, D (sub meas) is 2.78 (2) g/cm (super 3) . Tumchaite is optically biaxial (-), with alpha = 1.570 (2), beta = 1.588 (2), gamma = 1.594 (2), 2V (sub meas) = 60 (5) degrees . Pleochroism exists, with Y = Z = colorless, X = greenish-gray. Electron microprobe analysis gave (wt%): Na (sub 2) O 13.72, CaO 0.15, SiO (sub 2) 52.71, TiO (sub 2) 0.35, ZrO (sub 2) 20.41, SnO (sub 2) 5.73, HfO (sub 2) 0.60, H (sub 2) O (computed assuming 2H (sub 2) O pfu.) 7.86, total 101.53. The X-ray study pointed to space group P2 (sub 1) /c, a = 9.144 (4), b = 8.818 (3), c = 7.537 (3) Aa, beta = 113.22 (3) degrees , V = 558.49 Aa (super 3) , Z = 2. The strongest lines of the powder diffraction pattern [d in Aa (I) (hkl)] are: 8.40 (10) (100), 5.38 (9) (111), 4.00 (8) (111), 3.401 (9) (202), 2.902 (9) (211), 2.691 (9) (131). The crystal structure of tumchaite was refined to R = 0.043 for 865 F (sub 0) >4sigma (F (sub 0) ). The mineral is isotypic with penkvilksite-1M. The structure is characterized by silicate sheets parallel (100), formed by alternating clockwise- and counterclockwise-growing spiral chains of corner-sharing SiO (sub 4) tetrahedra. The sheets are connected by octahedra occupied by (Zr, Sn) at 0, 1/2, 0. The Zr/Sn ratio in the octahedra is 4. Water molecules and Na cations are placed in the cavities of the polyhedral framework. The ideal crystal-chemical formula is Na (sub 2) (Zr (sub 0.8) Sn (sub 0.2) )[Si (sub 4) O (sub 11) ].2H (sub 2) O. The mineral is named tumchaite for the river Tumcha near Vuoriyarvi massif.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 85
Serial Issue: 10
Title: Tumchaite Na (sub 2) (Zr,Sn)Si (sub 4) O (sub 11) .2H (sub 2) O; a new mineral from carbonatites of the Vuoriyarvi alkali-ultrabasic massif, Murmansk region, Russia
Affiliation: Russian Academy of Sciences, Geological Institute, Apatity, Russian Federation
Pages: 1516-1520
Published: 200010
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 16
Accession Number: 2001-002764
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
N60°40'00" - N66°40'00", E29°19'60" - E37°55'00"
Secondary Affiliation: University of Pisa, ITA, ItalyMoscow State University, RUS, Russian Federation
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200101
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