Mogovidite
| Mogovidite | |
|---|---|
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula (repeating unit) | Na9(Ca,Na)6Ca6(Fe3+,Fe2+)2Zr3[]Si25O72(CO3)(OH,H2O)4 (original form) |
| Dana classification | 64.1.6 |
| Crystal system | Trigonal, R3m' |
| Unit cell | a=14.23, c=29.98 [Å] (approximated) |
| Identification | |
| Color | Brown to reddish-brown |
| Crystal habit | grains and crystals |
| Crystal symmetry | Trigonal - Ditrigonal Pyramidal (3m) |
| Cleavage | No |
| Tenacity | Brittle |
| Density | 2.91 (measured) |
| Optical properties | Uniaxial (-) |
| Refractive index | nω 1.62, nε=1.61 (approximated) |
| References | [1][2][3] |
Mogovidite is a very rare mineral of the eudialyte group,[1] with formula Na9(Ca,Na)6Ca6(Fe3+,Fe2+)2Zr3[]Si(Si9O27)2(Si3O9)2(CO3)(OH,H2O)4.[2] The formula given is based on the original one but extended to show the presence of cyclic silicate groups. It it similar to feklichevite, differing from it in the presence of essential vacancies (at the M3 site) and carbonate group.[2] Another specific feature is the dominance of ferric iron - a feature shared with other eudialyte-group members, including feklichevite, fengchengite, golyshevite and ikranite. Similarly to golyshevite, it is calcium-dominant, however on three (not two) sites: M(1), N(3) and N(4).[1][2] It has a molecular mass of 3,066.24 gm.[4]
Occurrence and association
As golyshevite, mogovidite was discovered in calcium-bearing peralkaline pegmatites of the Kovdor massif, Kola Peninsula, Russia. The mineral name is of geographical origin - mogovidite is named after Mt. Mogo-Vid located in the vicinity of type locality. Association of mogovidite: aegirine-augite, andradite, calcite, humite, nepheline, pectolite, scolecite, titanite, zircon.[2]
Notes on chemistry
Chemical impurities in mogovidite include chlorine, potassium, and manganese, with trace titanium, cerium, and lanthanum.[2]
References
- 1 2 3 Mindat, Mogovidite, http://www.mindat.org/min-27487.html
- 1 2 3 4 5 6 Chukanov, N.V., Moiseyev, M.M., Rastsvetayeva, R.K., Rozenberg, K.A., and Zadov, A.E., 2005. Golyshevite (Na,Ca)10Ca9(Fe3+,Fe2+)2Zr3NbSi25O72(CO3)(OH)3·H2O, and Mogovidite, Na9(Ca,Na)6Ca6(Fe3+,Fe2+)2Zr3[]Si25O72(CO3)(OH,H2O)4, new eudialyte-group minerals from calcium-rich agpaitic pegmatites of the Kovdor massif, Kola Peninsula. Zapiski Rossiyskogo Mineralogicheskogo Obshchestva 134(6), 36-47 (in Russian, with English abstract)
- ↑ Handbook of Mineralogy, Mogovidite, http://www.handbookofmineralogy.org/pdfs/mogovidite.pdf
- ↑ Barthelmy, Dave. "Mogovidite Mineral Data". webmineral.com. Retrieved 2016-02-29.