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GEOREF RECORD

Kochite, a new member of the rosenbuschite group from the Werner Bjerge alkaline complex, East Greenland

C. Claes Christiansen, Robert A. Gault, Joel D. Grice and Ole Johnsen
Kochite, a new member of the rosenbuschite group from the Werner Bjerge alkaline complex, East Greenland
European Journal of Mineralogy (June 2003) 15 (3): 551-554

Abstract

Kochite, ideally Na (sub 2) (Na,Ca) (sub 4) Ca (sub 4) (Mn,Ca) (sub 2) Zr (sub 2) Ti (sub 2) (Si (sub 2) O (sub 7) ) (sub 4) (O,F) (sub 4) F (sub 4) , is a new member of the rosenbuschite group from the alkaline complex of Werner Bjerge, East Greenland. It occurs in nepheline syenite as lath-shaped to acicular crystals in aggregates up to 0.3X1.0 mm. Associated minerals are nepheline, alkali feldspar and lavenite. It is transparent with a brownish colour and has a vitreous lustre. It is brittle with a perfect {100} cleavage and an uneven fracture. The mineral is biaxial positive with alpha 1.684+ or -.002, beta 1.695+ or -.004, gamma 1.718+ or -.002 and 2V (sub meas.) = 73 degrees (2). The optical orientation is X = c and Z Lambda [100] approximately 20 degrees . The pleochroism is weak with X = colourless and Z = pale yellow. The mineral is triclinic with a = 10.032(2), b = 11.333(2), c = 7.202(1) Aa, alpha = 90.192(4), beta = 100.334(5), gamma = 111.551(4) degrees , Z = 1. The 5 strongest X-ray lines are [d in Aa (Int.)] 2.908(10), 2.600(8), 3.028(6), 1.868(6) and 1.670(5). An average of four electron microprobe analyses of kochite gave SiO (sub 2) 31.55, Al (sub 2) O (sub 3) 0.05, V (sub 2) O (sub 3) 0.03, TiO (sub 2) 8.44, ZrO (sub 2) 2.12, HfO (sub 2) 0.09, Nb (sub 2) O (sub 5) 1.86, Ta (sub 2) O (sub 5) 0.02, MgO 0.01, MnO 4.92, FeO 1.08, CaO 21.39, SrO 0.12, Na (sub 2) O 10.33, Y (sub 2) O (sub 3) 0.39, La (sub 2) O (sub 3) 0.25, Ce (sub 2) O (sub 3) 0.57, F 6.83, O identical with F 2.88, total 97.71 wt.%. The empirical formula, based on 8 Si atoms in accordance with the structure refinement (R(F) = 4.0%), is (Na (sub 1.70) Sr (sub 0.02) ) (sub Sigma 1.72) (Na (sub 2.77) Ca (sub 1.23) ) (sub Sigma 4.00) (Ca (sub 3.40) Na (sub 0.60) ) (sub Sigma 4.00) (Mn (sub 1.06) Ca (sub 0.82) Y (sub 0.05) Ce (sub 0.05) La (sub 0.02) ) (sub Sigma 2.00) (Zr (sub 1.40) Fe (sub 0.23) Ca (sub 0.36) Hf (sub 0.01) ) (sub Sigma 2.00) (Ti (sub 1.61) Nb (sub 0.21) Zr (sub 0.10) Al (sub 0.05) V (sub 0.03) ) (sub Sigma 2.00) (Si (sub 2) O (sub 7) ) (sub 4) F (sub 4) (O (sub 2.39) F (sub 1.48) ) (sub Sigma 3.87) . D (sub meas.) = 3.32, D (sub calc.) = 3.31 g/cm (super 3) . Kochite is an Mn-, Ti-analogue of rosenbuschite.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 15
Serial Issue: 3
Title: Kochite, a new member of the rosenbuschite group from the Werner Bjerge alkaline complex, East Greenland
Affiliation: University of Copenhagen, Geological Museum, Copenhagen, Denmark
Pages: 551-554
Published: 200306
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 6
Accession Number: 2003-055039
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Canadian Museum of Nature, CAN, Canada
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200318
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