Voronkovite
| Voronkovite | |
|---|---|
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula (repeating unit) |
Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3 Si26O72(OH,O)4Cl·H2O (original form) |
| Strunz classification | 9.CO.10 |
| Crystal system | Trigonal |
| Crystal class |
Pyramidal (3) H-M symbol: (3) |
| Space group | R3 |
| Unit cell | a = 14.21, c = 30.27 [Å]; Z = 3 |
| Identification | |
| Color | Light brown |
| Crystal habit | Rounded crystals |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 2.95 g/cm3 (calculated) |
| Optical properties | Uniaxial (+) |
| Pleochroism | Lemon yellow (X), brownish pink (Y) |
| References | [1][2] |
Voronkovite is a very rare mineral[1] of the eudialyte group with the formula Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si2Si24O72(OH,O)4Cl·H2O.[2] The formula is based on the simplified original one; it does not show the presence of cyclic silicate groups, but two M3- and M4-site silicon atoms are shown separately (basing on the nomenclature of the eudialyte group[3]). Voronkovite has lowered symmetry (space group R3, instead of more specific for the group R3m one), similarly to some other eudialyte-group members: aqualite, labyrinthite, oneillite and raslakite.[1] The specific feature of voronkovite is, among others, strong enrichment in sodium.[2]
Occurrence and association
Voronkovite comes form an ultra-alkaline pegmatite of Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia. It associates with aegirine, lomonosovite, manganoneptunite, microcline, nepheline, shkatulkalite, sodalite, terskite, sphalerite and vuonnemite.[2]
Notes on chemistry
Voronkovite has additional impurities, not given in the formula. They include strontium, fluorine, potassium, lanthanum, neodymium (at the Mn site), niobium, and minor hafnium and aluminium.[2]
References
- 1 2 3 Mindat, Voronkovite, http://www.mindat.org/min-32199.html
- 1 2 3 4 5 Khomyakov, A.P., Nechelyustov, G.N., and Rastsvetaeva, R.K., 2010, Voronkovite, Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH,O)4Cl·H2O, a new mineral species of the eudialyte group from the Lovozero alkaline pluton, Kola Peninsula, Russia. Geology of Ore Deposits 51(8), 750-756
- ↑ 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