Andrianovite

Andrianovite is a very rare mineral of the eudialyte group,[1] with formula Na12(K,Sr,Ce)6Ca6(Mn,Fe)3Zr3NbSi(Si3O9)2(Si9O27)2O(O,H2O,OH)5.[2][1] The original formula was extended to show the presence of cyclic silicate groups and silicon at the M4 site, according to the nomenclature of eudialyte group.[3] Andrianovite is unique among the eudialyte group in being potassium-rich (other eudialyte-group species with essential K are davinciite and rastsvetaevite[1]). It is regarded as potassium analogue of kentbrooksite,[2] but it also differs from it in being oxygen-dominant rather than fluorine-dominant.[1] Also, the coordination number of Na in this representative is enlarged from 7 to 9. The name of the mineral honors Russian mathematician and crystallographer Valerii Ivanovich Andrianov.[2]

Andrianovite
Andrianovite found in Russia
General
CategorySilicate mineral, Cyclosilicate
Formula
(repeating unit)		Na12(K,Sr,Ce)3Ca6Mn3Zr3Nb(Si25O73)(O,H2O,OH)5 (original form)
Strunz classification9.CO.10
Dana classification64.1.2.4
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
H-M symbol: (3m)
Space groupR3m
Unit cella = 14.28, c = 30.24 [Å] (approximated); Z = 3
Identification
ColorLight yellow
Crystal habitintergrowths (rims) with eudialyte
Cleavage(001), imperfect
FractureStep-like
TenacityBrittle
Mohs scale hardness5
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density2.93 (measured), 3.02 (calculated)
Optical propertiesUniaxial (-)
Refractive indexnω=1.62, nε=1.62 (approximated)
PleochroismNone
Ultraviolet fluorescenceNo
Common impuritiesSr, Ce, Fe
References[1][2]

Occurrence and association

Andrianovite was discovered in pegmatites of Koashva open pit, Khibiny massif, Kola Peninsula. Russia. It coexists with aegirine, lamprophyllite, lomonosovite, microcline, mosandrite, natrolite, sodalite (silicates) and villiaumite.[2]

Notes on chemistry

The formula of andrianovite is devoid of some substituting elements and group, the most important being carbonate and chlorine. Minor substituting elements are lanthanum, neodymium, yttrium, titanium, barium, hafnium and aluminium.[2]

References
  1. "Andrianovite: Andrianovite mineral information and data". Mindat.org. Retrieved 2016-03-08.
  2. Khomyakov, A.P., Nechelyustov, G.N., Rastsvetaeva, R.K., and Rozenberg, R.A., 2009. Andrianovite, Na12(K,Sr,Ce)3Ca6Mn3Zr3Nb(Si25O73)(O,H2O,OH)5, a new potassium-rich mineral species of the eudialyte group from the Khibiny alkaline Pluton, Kola Peninsula, Russia. Geology of Ore deposits 50(8), 705-712
  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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