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]
| Rastsvetaevite | |
|---|---|
 Tiny dark pink grains of rastsvetaevite in matrix. Field of view 3 mm. From: Rasvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia | |
| General | |
| Category | Silicate mineral, Cyclosilicate |
| IMA symbol | Rtv[1] |
| 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 |
| Specific gravity | 2.86 |
| Optical properties | Uniaxial (+) |
| Refractive index | nω = 1.60 nε = 1.60 (approximated) |
| References | [2] |
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.[2]
Notes on crystal structure edit
The c unit cell parameter in rastsvetaevite is doubled.[2]
References edit
- ^ 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.
- ^ a b c d e Mindat, http://www.mindat.org/min-26586.html
- ^ 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.
- ^ 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.
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