Georgbarsanovite

Georgbarsanovite
General
Category Silicate mineral, Cyclosilicate
Formula
(repeating unit)		 Na12(Mn,Sr,REE)3Ca6Fe32+Zr3NbSi25O76Cl2·H2O (original form)
Strunz classification 8/E.23-15
Dana classification 64.1.2.2
Crystal system Trigonal, R3m'
Unit cell a=14.26, c=29.95 [Å] (approximated)
Identification
Color Yellow-green
Crystal habit pseudo-octahedra
Crystal symmetry Trigonal - Ditrigonal Pyramidal (3m)
Cleavage No
Fracture Uneven
Tenacity Brittle
Luster Vitreous
Streak White
Diaphaneity Transparent
Optical properties Uniaxial (-)
Refractive index �nω 1.64, nε=1.63 (approximated)
Pleochroism green to pale yellow
Common impurities F, K, Y
References [1][2]

Georgbarsanovite is a very rare mineral of the eudialyte group,[1] formerly known under unaccepted name as barsanovite, with formula Na12(Mn,Sr,REE)3Ca6Fe32+Zr3NbSi(Si3O9)2(Si9O27)2O4Cl2•H2O.[2] The original formula was extended to show the presence of cyclic silicate groups and domination of silicon at the M4 site.[3] "REE", standing for rare earth elements, are dominated by cerium. Georgbarsanovite characterizes in dominance of manganese at the N4 site.[2] It also differs from most other accepted group representatives in its colour. The mineral was found in nepheline pegmatite nearby Petrelius river, Khibiny massif, Kola Peninsula, Russia.[1] It is named after Russian mineralogist Georg Barsanov.[2]

Notes on chemistry

Georgbarsanovite contains admixtures of fluorine, potassium and yttrium, with traces of titanium, hafnium, and barium.[2]

References

  1. 1 2 3 Mindat, http://www.mindat.org/min-27506.html
  2. 1 2 3 4 5 Khomyakov, A.P., Nechelyustov, G.N., Ekimenkova, I.A., and Rastsvetayeva, R.K., 2005. Georgbarsanovite, Na12(Mn,Sr,REE)3Ca6Fe32+Zr3NbSi25O76Cl2·H2O, a mineral species of the eudialyte group: revalidation of barsanovite and the new name of the mineral. Zapiski Rossiyskogo Mineralogicheskogo Obshchestva 134(6), 47-57 (in Russian, with English abstract)
  3. ↑ Johnsen, O., Ferraris, G., Gault, R.A., Grice, D.G., Kampf, A.R., and Pekov, I.V., 2003. The nomenclature of eudialyte-group minerals. The Canadian Mineralogist 41, 785-794


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