Eudialyte Group

Eudialyte group is a group of complex trigonal zircono- and, more rarely, titanosilicate minerals with general formula (1)N(2)N(3)N(4)N(5)sub>3 (1a)M(1b)sub>3M(2)₃M(4)Z₃ i₂₄O₇₂'₄X₂, 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 defect, 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 i₃O₉sup>6− and i₉O₂₇sup>18− ring silicate groups. Space group is usually ''R''3''m'' or ''R''-3''m'' but may be reduced to ''R''3 due to cation ordering. Like other zirconosilicates, the eudialyte group minerals possess alkaline ion-exchange properties, as microporous materials.

List of the eudialyte-group minerals

Approved species

* Alluaivite - (space group ''R''-3''m'')
* Andrianovite - (space group ''R''3''m'')
* Aqualite - (space group ''R''3)
* Carbokentbrooksite - (space group ''R''3''m'')
* Davinciite - (space group ''R''3''m'')
* Dualite - (space group ''R''3''m'')
* Eudialyte - (space group ''R''-3''m'')
* Feklichevite - (space group ''R''3''m'')
* Fengchengite - (space group ''R''-3''m'')
* Ferrokentbrooksite - (space group ''R''3''m'')
* Georgbarsanovite - (space group ''R''3''m'')
* Golyshevite - (space group ''R''3''m'')
* Ikranite - (space group ''R''3''m'')
* Ilyukhinite - - the most recent add (space group ''R''3''m'')
* Johnsenite-(Ce) - (space group ''R''3''m'')
* Kentbrooksite - (space group ''R''3''m'')
* Khomyakovite - (space group ''R''3''m'')
* Labyrinthite - (space group ''R''3)
* Manganokhomyakovite - (space group ''R''3''m'')
* Manganoeudialyte - (space group ''R''3''m'')
* Mogovidite - (space group ''R''3''m'')
* Oneillite - (space group ''R''3)
* Raslakite - (space group ''R''3)
* Rastsvetaevite - (space group ''R''3''m'')
* Taseqite - (space group ''R''3''m'')
* Voronkovite - (space group ''R''3)
* Zirsilite-(Ce) - (space group ''R''3''m'')

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:

* UM-1971-22-SiO:CaClFeHMgMnNaNbZr - - with variable substitution of OH for oxygen
* UM1990-79-SiO:CaClFeHMnNaNbREEZr - - first representative with magnesium-dominant site
* UM1990-80- SiO:CaFeHMnNaNbREEZr -
* UM1998-21-SiO:CaCeClHMnNaZr -
* UM1999-36-SiO:CaCeHMnNaNbSrZr -
* UM2000-66-SiO:CaClFeHMnNaNbSrZr -
* UM2003-39- SiO:CaClFeHHfNaNbSrTaTiZr -
* UM2004-51-SiO:CaClFFeHNaNbTi' -
* UM2006-17-SiO:CaClFFeHMnNaZr -
* UM2006-18-SiO:CaClFFeHMnNaZr - - with essential sulfur and with Zr dominant in two sites
* UM2006-28-SiO:CaHMnNaZr - - with double ''c'' unit cell dimension

In addition, there is "eudialyte 3248": , plus admixtures of Ce, Sr, Ba and Y, characterized by one S-dominant site (not shown in the simplified formula)

Other species

Rastsvetaeva et al. (2015) describe a species tentatively called "hydrorastsvetaevite", with a formula .

Further reading

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*Rastsvetaeva, R. K.; Chukanov, N. V.; Zaitsev, V. A.; Aksenov, S. M.; Viktorova, K. A. (2018-05).
Crystal Structure of Cl-Deficient Analogue of Taseqite from Odikhincha Massif
. ''Crystallography Reports''. 63 (3): 349–357. doi:10.1134/s1063774518030240. ISSN 1063-7745
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References

{{Reflist

External links

Mindat.org



Cyclosilicates
Zirconium minerals
Sodium minerals