Rastsvetaevite
Mineral of the eudialyte group
From Wikipedia, the free encyclopedia
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
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
The c unit cell parameter in rastsvetaevite is doubled.[2]
