Rastsvetaevite
| 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
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
The c unit cell parameter in rastsvetaevite is doubled.[1]
References
- 1 2 3 4 5 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, 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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