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Gjerdingenite-Mn from Norway; a new mineral species in the labuntsovite group; descriptive data and crystal structure

Gunnar Raade, Nikita V. Chukanov, Uwe Kolitsch, Steffen Moeckel, Aleksandr E. Zadov and Igor V. Pekov
Gjerdingenite-Mn from Norway; a new mineral species in the labuntsovite group; descriptive data and crystal structure
European Journal of Mineralogy (December 2004) 16 (6): 979-987

Abstract

Gjerdingenite-Mn occurs as orange-yellow to brownish prisms up to 1 mm long in miarolitic cavities of a sodic granite ("ekerite") at Gjerdingselva, Lunner, Oppland, Oslo Region, Norway. The simplified formula is (K,Na) (sub 2) (Mn,Fe)[(Nb,Ti) (sub 4) (Si (sub 4) O (sub 12) ) (sub 2) (O,OH) (sub 4) ] . 6H (sub 2) O. It is the Mn-dominant analogue of gjerdingenite-Fe, the Ti analogue of kuzmenkoite-Mn and a dimorph of organovaite-Mn. The mineral is monoclinic, C2/m, with a = 14.563(3), b = 13.961(3), c = 7.851(2) Aa, beta = 117.62(3) degrees , V = 1414.3(6) Aa (super 3) , Z = 2. The crystal structure was refined to R(F) = 0.079 on the basis of 1207 observed reflections and is compared to the structure of gjerdingenite-Fe. The strongest five reflections of the X-ray powder-diffraction pattern [d (sub obs) in Aa (I) (hkl)] are: 6.96 (100) (020, 001), 4.94 (80) (021), 3.22 (90) (42-1, 400, 40-2), 3.10 (80) (041, 022) and 2.510 (40) (44-1, 401, 40-3, 042). The mineral is optically biaxial (+) with alpha = 1.670(2), beta = 1.685(2), gamma = 1.775(5); 2V (sub meas) = 52(8) degrees , 2V (sub calc) = 46(5) degrees . The axial dispersion is weak, r<v; the orientation is Z = a, Y = b. Mohs hardness is about 5; D (sub calc) = 2.93 g/cm (super 3) . The pseudo-orthorhombic crystals are twinned on {001}, elongate along [010] and show the forms {001}, {100}, {201} and {021}. Some general aspects on the formation of labuntsovite-group minerals are discussed.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 16
Serial Issue: 6
Title: Gjerdingenite-Mn from Norway; a new mineral species in the labuntsovite group; descriptive data and crystal structure
Affiliation: Universitetet i Oslo, Geologisk Museum, Oslo, Norway
Pages: 979-987
Published: 200412
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 23
Accession Number: 2005-023468
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
Secondary Affiliation: Institute of Problems of Chemical Physics, RUS, Russian FederationUniversitaet Wien, AUT, AustriaNPO "Regenerator", RUS, Russian FederationMoscow State University, RUS, Russian Federation
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200512
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