Georgbarsanovite

Georgbarsanovite
General
Category	Silicate mineral, Cyclosilicate
Formula; (repeating unit)	Na12(Mn,Sr,REE)3Ca6Fe32+Zr3NbSi25O76Cl2·H2O (original form)
Strunz classification	9.CO.10 (10 ed) ; 8/E.23-15 (8 ed)
Dana classification	64.1.2.2
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) ; (same H-M symbol)
Space group	R3m
Unit cell	a = 14.26, c = 29.95 [Å] (approximated); Z = 3
Identification
Color	Yellow-green
Crystal habit	pseudo-octahedra
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

Mindat, http://www.mindat.org/min-27506.html
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)
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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[Mindat-1] Mindat, http://www.mindat.org/min-27506.html

[Kh-2] 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