Zirsilite-(Ce)
General
CategoryCyclosilicate
Formula
(repeating unit)		(Na,□)12(Ce,Na)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)·H2O (original form)
IMA symbolZir-Ce[1]
Strunz classification9.CO.10
Dana classification64.1.5
Crystal systemTrigonal
Crystal classDitrigonal pyramidal (3m)
H-M symbol: (3m)
Space groupR3m
Unit cella = 14.25, c = 30.08 [Å] (approximated); Z = 3
Identification
ColorCreamy white
Crystal habitrhombohedra (rims of zoned crystals)
CleavageNone
FractureConchoidal
TenacityBrittle
Mohs scale hardness5
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density3.15 (measured)
Optical propertiesUniaxial (-)
Refractive indexnω=1.65, nε=1.64 (approximated)
PleochroismNone
Ultraviolet fluorescenceNo
References[2][3]

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]

Occurrence and association

Zirsilite-(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

Beside 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

Zirsilite-(Ce) is isostructural with kentbrooksite.[3]

References

  1. ↑ 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.
  2. 1 2 3 4 5 Mindat, Zirsilite-(Ce), http://www.mindat.org/min-25674.html
  3. 1 2 3 4 5 6 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
  4. ↑ 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
  5. ↑ 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
  6. ↑ "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.
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