|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | FEEDBACK/COMMNET | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Articles |
1 Geological Museum, University of Copenhagen, Øster Voldgade 5–7, DK-1350 Copenhagen K., Denmark
2 Research Division, Canadian Museum of Nature, P. O. Box 3443, Station D, Ottawa, Ontario K1P6P4, Canada
* E-mail address: Claesc{at}savik.geomus.ku.dk
Kochite, ideally Na2(Na,Ca)4Ca4(Mn,Ca)2Zr2Ti2(Si2O7)4(O,F)4F4, 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 0.3 x 1.0 mm. Associated minerals are nepheline, alkali feldspar and låvenite. 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 
1.684 ± .002, ß 1.695 ± .004, 
1.718 ± .002 and 2Vmeas. = 73°(2). The optical orientation is X = c and Z 
[100] 
20°. 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) Å, = 90.192(4), ß = 100.334(5), = 111.551(4) °, Z = 1. The 5 strongest X-ray lines are [d in Å (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 SiO2 31.55, Al2O3 0.05, V2O3 0.03, TiO2 8.44, ZrO2 12.12, HfO2 0.09, Nb2O5 1.86, Ta2O5 0.02, MgO 0.01, MnO 4.92, FeO 1.08, CaO 21.39, SrO 0.12, Na2O 10.33, Y2O3 0.39, La2O3 0.25, Ce2O3 0.57, F 6.83, O 
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 (Na1.70Sr0.02)
1.72(Na2.77Ca1.23)4.00(Ca3.40Na0.60)4.00(Mn1.06Ca0.82Y0.05Ce0.05La0.02)2.00 (Zr1.40Fe0.23Ca0.36Hf0.01)2.00(Ti1.61Nb0.21Zr0.10Al0.05V0.03)2.00(Si2O7)4F4(O2.39F1.48)3.87. Dmeas. = 3.32, Dcalc. = 3.31 g/cm3. Kochite is an Mn–, Ti-analogue of rosenbuschite.
Key-words: kochite, rosenbuschite group, new mineral, crystal structure.
This article has been cited by other articles:
|
|
 |
|
  E. Sokolova and F. Camara From structure topology to chemical composition. VIII. Titanium silicates: the crystal chemistry of mosandrite from type locality of Laven (Skadon), Langesundsfjorden, Larvik, Vestfold, Norway Mineralogical Magazine, December 23, 2008; 72(4): 887 - 897. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Sokolova and F. C. Hawthorne FROM STRUCTURE TOPOLOGY TO CHEMICAL COMPOSITION. V. TITANIUM SILICATES: THE CRYSTAL CHEMISTRY OF NACARENIOBSITE-(Ce) Can Mineral, October 1, 2008; 46(5): 1333 - 1342. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. Sokolova FROM STRUCTURE TOPOLOGY TO CHEMICAL COMPOSITION. I. STRUCTURAL HIERARCHY AND STEREOCHEMISTRY IN TITANIUM DISILICATE MINERALS Can Mineral, December 1, 2006; 44(6): 1273 - 1330. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. BELLEZZA, M. FRANZINI, A. O. LARSEN, S. MERLINO, and N. PERCHIAZZI Grenmarite, a new member of the gotzenite-seidozerite-rosenbuschite group from the Langesundsfjord district, Norway: definition and crystal structure European Journal of Mineralogy, December 1, 2004; 16(6): 971 - 978. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. C. Christiansen, O. Johnsen, and E. Makovicky CRYSTAL CHEMISTRY OF THE ROSENBUSCHITE GROUP Can Mineral, October 1, 2003; 41(5): 1203 - 1224. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Mandarino NEW MINERALS Can Mineral, October 1, 2003; 41(5): 1309 - 1319. [Full Text] [PDF]
|
|
|
|
|
|
R. F. Martin ENCYCLOPEDIA OF MINERAL NAMES: THIRD UPDATE Can Mineral, August 1, 2003; 41(4): 1075 - 1096. [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | FEEDBACK/COMMNET | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
