Andrianovite

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Andrianovite
General
Category Silicate mineral, Cyclosilicate
Formula
(repeating unit)
Na12(K,Sr,Ce)3Ca6Mn3Zr3Nb(Si25O73)(O,H2O,OH)5 (original form)
Strunz classification 9.CO.10
Dana classification 64.1.2.4
Crystal system Trigonal
Crystal class Ditrigonal pyramidal (3m)
H-M symbol: (3m)
Space group R3m
Unit cell a = 14.28, c = 30.24 [Å] (approximated); Z = 3
Identification
Color Light yellow
Crystal habit intergrowths (rims) with eudialyte
Cleavage (001), imperfect
Fracture Step-like
Tenacity Brittle
Mohs scale hardness 5
Luster Vitreous
Streak White
Diaphaneity Transparent
Density 2.93 (measured), 3.02 (calculated)
Optical properties Uniaxial (-)
Refractive index nω=1.62, nε=1.62 (approximated)
Pleochroism None
Ultraviolet fluorescence No
Common impurities Sr, Ce, Fe
References [1][2]

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]

Occurrence and association[edit]

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[edit]

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[edit]

  1. ^ a b c d e "Andrianovite: Andrianovite mineral information and data". Mindat.org. Retrieved 2016-03-08.
  2. ^ a b c d e f 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