Rastsvetaevite

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Rastsvetaevite
General
Category Silicate mineral, Cyclosilicate
Formula
(repeating unit)
Na27K8Ca12Fe3Zr6
Si4[Si3O9]4[Si9O27]4(O,OH,H2O)6Cl2
Strunz classification 9.CO.10
Dana classification 64.1b.1.2
Crystal system Trigonal
Crystal class Ditrigonal pyramidal (3m)
H-M symbol: (3m)
Space group R3m
Unit cell a = 14.25, c = 60.97 [Å] (approximated); Z = 3
Identification
Color Reddish-pink
Crystal habit irregular grains
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 5-6
Luster Vitreous
Streak White
Diaphaneity Transparent
Density 2.86 g/cm3 (measured)
Optical properties Uniaxial (+)
Refractive index nω=1.60 nε = 1.60 (approximated)
References [1]

Rastsveatevite is a rare mineral of the eudialyte group with the formula Na27K8Ca12Fe3Zr6Si4[Si3O9]4[Si9O27]4(O,OH,H2O)6Cl2. Its structure is modular.[2] It is only the third member of the group after andrianovite and davinciite with essential (site-dominating) potassium.[1] Potassium and sodium enter both N4 and M2 sites.[3] The mineral is named after Russian crystallographer Ramiza K. Rastsvetaeva.[1]

Occurrence and association[edit]

Rastsvetaevite was originally found in hyperagpaitic (ultra-alkaline) pegmatite at Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia. Associated minerals are aegirine, nacaphite, nepheline, natrite, schcherbakovite, sodalite, villiaumite, and rasvumite.[1]

Notes on crystal structure[edit]

The c unit cell parameter in rastsvetaevite is doubled.[1]

References[edit]

  1. ^ a b c d e Mindat, http://www.mindat.org/min-26586.html
  2. ^ Khomyakov, A.P.; Nechelyustov, G.N.; Arakcheeva, A.V. (2006). "Rastsvetaevite, Na27K8Ca12Fe3Zr6Si4[Si3O9]4[Si9O27]4(O,OH,H2O)6Cl2, a new mineral with a modular eudialyte-like structure and crystal-chemical systematics of the eudialyte group". Proceedings of the Russian Mineralogical Society. 135 (1): 49–65. 
  3. ^ Johnsen, O.; Ferraris, G.; Gault, R. A.; Grice, J. D.; Kampf, A. R.; Pekov, I. V. (2003-06-01). "The nomenclature of eudialyte-group minerals". The Canadian Mineralogist. 41 (3): 785–794. doi:10.2113/gscanmin.41.3.785. ISSN 0008-4476.