Georgbarsanovite

Georgbarsanovite is a very rare mineral of the eudialyte group,[1] formerly known under unaccepted name as barsanovite, with formula Na
12
(Mn,Sr,REE)
3
Ca
6
Fe
3
2+
Zr
3
NbSi(Si
3
O
9
)
2
(Si
9
O
27
)
2
O
4
Cl
2
·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]

Georgbarsanovite
Georgbarsanovite
General
CategorySilicate mineral, Cyclosilicate
Formula
(repeating unit)
Na
12
(Mn,Sr,REE)
3
Ca
6
Fe
3
2+
Zr
3
NbSi
25
O
76
Cl
2
·H2O
(original form)
Strunz classification9.CO.10 (10 ed)
8/E.23-15 (8 ed)
Dana classification64.1.2.2
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
(same H-M symbol)
Space groupR3m
Unit cella = 14.26, c = 29.95 [Å] (approximated); Z = 3
Identification
ColorYellow-green
Crystal habitpseudo-octahedra
CleavageNo
FractureUneven
TenacityBrittle
LusterVitreous
StreakWhite
DiaphaneityTransparent
Optical propertiesUniaxial (-)
Refractive indexnω 1.64, nε=1.63 (approximated)
Pleochroismgreen to pale yellow
Common impuritiesF, K, Y
References[1][2]

Notes on chemistry

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

References

  1. Mindat, http://www.mindat.org/min-27506.html
  2. Khomyakov, A.P., Nechelyustov, G.N., Ekimenkova, I.A., and Rastsvetayeva, R.K., 2005. Georgbarsanovite, Na
    12
    (Mn,Sr,REE)
    3
    Ca
    6
    Fe
    3
    2+
    Zr
    3
    NbSi
    25
    O
    76
    Cl
    2
    ·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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