Eudialyte group

Eudialyte group is a group of complex trigonal zircono- and, more rarely, titanosilicate minerals with general formula [N(1)N(2)N(3)N(4)N(5)]3[M(1a)M(1b)]3M(2)3M(4)Z3[Si24O72]O'4X2, where N(1) and N(2) and N(3) and N(5) = Na+ and more rarely H3O+ or H2O, N(4) = Na+, Sr2+, Mn2+ and more rarely H3O+ or H2O or K+ or Ca2+ or REE3+ (rare earth elements), M(1) and M(1b) = Ca2+, M(1a) = Ca2+ or Mn2+ or Fe2+, M(2) = Fe (both II and III), Mn and rarely Na+, K+ or Zr4+, M(3) = Si, Nb and rarely W, Ti and [] (vacancy), M(4) = Si and or rarely [], Z Zr4+ and or rarely Ti4+, and X = OH−, Cl− and more rarely CO32− or F−. Some of the eudialyte-like structures can even be more complex, however, in general, its typical feature is the presence of [Si3O9]6− and [Si9O27]18− ring silicate groups. Space group is usually R3m or R-3m but may be reduced to R3 due to cation ordering.[1] Like other zirconosilicates, the eudialyte group minerals possess alkaline ion-exchange properties, as microporous materials.[2]

List of the eudialyte-group minerals

Approved species

Unnamed species

The list of eudialyte-related natural phases is growing. There are many such phases, some of them very complex, coded "UM" by the International Mineralogical Association, and include:[4][5]

In addition, there is "eudialyte 3248": Na29Ca12Zr6[Si48O132(O,OH)12]{[Na]4[Si]2}{[Mn]3[Mn,Nb,Ti]2}(OH,H2O,Cl)10, plus admixtures of Ce, Sr, Ba and Y, characterized by one S-dominant site (not shown in the simplified formula)[6]

Other species

Rastsvetaeva et al. (2015) describe a species tentatively called "hydrorastsvetaevite", with a formula (Na11(H3O)11K6(H2O)1.5Sr)Ca12Fe3Na2MnZr6Si52O144(OH)4.5Cl3.5.[7]

Further reading

References

  1. ↑ Johnsen, O.; Ferraris, G.; Gault, R. A.; Grice, J. D.; Kampf, A. R.; Pekov, I. V. (2003). "The Nomenclature of Eudialyte-Group Minerals". The Canadian Mineralogist. 41 (3): 785–794. doi:10.2113/gscanmin.41.3.785.
  2. ↑ Zubkova, Natalia V.; Pushcharovsky, Dmitrii Yu. (2008). "Mixed-Framework Microporous Natural Zirconosilicates : Minerals as Advanced Materials I": 45–56. doi:10.1007/978-3-540-77123-4_6. ISBN 978-3-540-77122-7.
  3. ↑ http://minmag.geoscienceworld.org/content/79/7/1859.extract
  4. ↑ Mindat, www.mindat.org
  5. ↑ Smith, D.G.W., and Nickel, E.H.N., 2007. A System of Codification for Unnamed Minerals: Report of the SubCommittee for Unnamed Minerals of the IMA Commission on New Minerals, Nomenclature and Classification. Canadian Mineralogist v. 45, p.983-1055; http://nrmima.nrm.se/Valid2012.pdf
  6. ↑ Rastsvetaeva et al. 2006, in: Ercit et al. 2007, http://link.springer.com/article/10.1134/S1028334X06070166
  7. ↑ "Crystal structure and genesis of the hydrated analog of rastsvetaevite". Crystallography Reports. 60: 831–840. doi:10.1134/S1063774515060279.

External links

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