Zirsilite-(Ce) is a very rare mineral of the eudialyte group, with formula (Na,□)12(Ce,Na)3Ca6Mn3Zr3NbSi(Si9O27)2(Si3O9)2O(OH)3(CO3)·H2O.[2][3] The original formula was extended to show the presence of cyclic silicate groups and the presence of silicon at the M4 site, according to the nomenclature of the eudialyte group.[4] Zirsilite-(Ce) differs from carbokentbrooksite in cerium-dominance over sodium only. Both minerals are intimately associated.[2][3] The only other currently known representative of the eudialyte group having rare earth elements (in particular cerium, as suggested by the "-Ce)" Levinson suffix in the name[5]) in dominance is johnsenite-(Ce).[2]
| Zirsilite-(Ce) | |
|---|---|
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| General | |
| Category | Cyclosilicate |
| Formula (repeating unit) | (Na,□)12(Ce,Na)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)·H2O (original form) |
| IMA symbol | Zir-Ce[1] |
| Strunz classification | 9.CO.10 |
| Dana classification | 64.1.5 |
| Crystal system | Trigonal |
| Crystal class | Ditrigonal pyramidal (3m) H-M symbol: (3m) |
| Space group | R3m |
| Unit cell | a = 14.25, c = 30.08 [Å] (approximated); Z = 3 |
| Identification | |
| Color | Creamy white |
| Crystal habit | rhombohedra (rims of zoned crystals) |
| Cleavage | None |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 3.15 (measured) |
| Optical properties | Uniaxial (−) |
| Refractive index | nω = 1.65, nε = 1.64 (approximated) |
| Pleochroism | None |
| Ultraviolet fluorescence | No |
| References | [2][3] |
Occurrence and association
editZirsilite-(Ce) and carbokentbrooksite occur in pegmatites of Darai-Pioz alkaline massif, Tajikistan – a locality known for many rare minerals.[6] They are found as replacements of grains and crystals of eudialyte.[2] The minerals are associated with aegirine, ekanite, microcline, polylithionite, quartz, stillwellite-(Ce) (silicates), pyrochlore-group mineral, fluorite, calcite, and galena.[3]
Notes on chemistry
editBeside the elements given in the formula, zirsilite-(Ce) contains admixtures of lanthanum, strontium, neodymium, iron, yttrium, titanium, potassium, chlorine, and praseodymium.[3]
Notes on structure
editZirsilite-(Ce) is isostructural with kentbrooksite.[3]
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, Zirsilite-(Ce), http://www.mindat.org/min-25674.html
- ^ a b c d e f Khomyakov, A.P., Dusmatov, V.D., Ferraris, G., Gula, A., Ivaldi, G., and Nechelyustov, G.N., 2003: Zirsilite-(Ce), (Na,□)12(Ce,Na)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)·H2O, and carbokentbrooksite (Na,□)12(Na,Ce)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)·H2O – two new eudialyte-group minerals from the Dara-i-Pioz alkaline massif, Tajikistan. Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva 132(5), 40–51 (in Russian, with English abstract); in: Jambor, J.I, and Roberts, A.C., 2004: New mineral names. American Mineralogist 89(11–12), 1826–1834
- ^ 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
- ^ Hatert, F., Mills, S.J., Pasero, M., and Williams, P.A., 2013. CNMNC guidelines for the use of suffixes and prefixes in mineral nomenclature, and for the preservation of historical names. European Journal of Mineralogy 25, 113–115
- ^ "Darai-Pioz Glacier (Dara-i-Pioz; Dara-Pioz), Alai Range (Alayskiy), Tien Shan Mtn, Region of Republican Subordination, Tajikistan - Mindat.org". Mindat.org. Retrieved 2016-03-11.