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Rastsvetaevite

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Rastsvetaevite
Tiny dark pink grains of rastsvetaevite in matrix. Field of view 3 mm. From: Rasvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia
General
CategorySilicate mineral, Cyclosilicate
IMA symbolRtv[1]
Strunz classification9.CO.10
Dana classification64.1b.1.2
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
H-M symbol: (3m)
Space groupR3m
Unit cella = 14.25, c = 60.97 [Å] (approximated); Z = 3
Identification
ColorReddish-pink
Crystal habitirregular grains
FractureConchoidal
TenacityBrittle
Mohs scale hardness5-6
LusterVitreous
StreakWhite
DiaphaneityTransparent
Specific gravity2.86
Optical propertiesUniaxial (+)
Refractive indexnω = 1.60 nε = 1.60 (approximated)
References[2]

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

Occurrence and association

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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.[2]

Notes on crystal structure

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The c unit cell parameter in rastsvetaevite is doubled.[2]

References

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  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c d e Mindat, http://www.mindat.org/min-26586.html
  3. ^ 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.
  4. ^ 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. Bibcode:2003CaMin..41..785J. doi:10.2113/gscanmin.41.3.785. ISSN 0008-4476.