Eudialyte group explained

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

• Alluaivite - (space group R-3m)
• Andrianovite - (space group R3m)
• Aqualite – (space group R3)
• Carbokentbrooksite – (space group R3m)
• Davinciite – (space group R3m)
• Dualite – (space group R3m)
• Eudialyte – (space group R-3m)
• Feklichevite – (space group R3m)
• Fengchengite – (space group R-3m)
• Ferrokentbrooksite – (space group R3m)
• Georgbarsanovite – (space group R3m)
• Golyshevite – (space group R3m)
• Ikranite – (space group R3m)
• Ilyukhinite – – the most recent add (space group R3m)^[3]
• Johnsenite-(Ce) – (space group R3m)
• Kentbrooksite – (space group R3m)
• Khomyakovite – (space group R3m)
• Labyrinthite – (space group R3)
• Manganokhomyakovite – (space group R3m)
• Manganoeudialyte – (space group R3m)
• Mogovidite – (space group R3m)
• Oneillite – (space group R3)
• Raslakite – (space group R3)
• Rastsvetaevite – (space group R3m)
• Taseqite – (space group R3m)
• Voronkovite – (space group R3)
• Zirsilite-(Ce) – (space group R3m)

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]}

• 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":

Notes and References

1. 10.2113/gscanmin.41.3.785 . The Nomenclature of Eudialyte-Group Minerals . 2003 . Johnsen . O. . Ferraris . G. . Gault . R. A. . Grice . J. D. . Kampf . A. R. . Pekov . I. V. . The Canadian Mineralogist . 41 . 3 . 785–794. 2003CaMin..41..785J .
2. Book: 10.1007/978-3-540-77123-4_6 . Mixed-Framework Microporous Natural Zirconosilicates : Minerals as Advanced Materials I . 2008 . Zubkova . Natalia V. . Pushcharovsky . Dmitrii Yu. . 978-3-540-77122-7 . 45–56.
3. New minerals and nomenclature modifications approved in 2015. 10.1180/minmag.2015.079.7.18. Mineralogical Magazine. 79. 7. 1859–1864. 2015. Hålenius. U.. Hatert. F.. Pasero. M.. Mills. S. J.. 2015MinM...79.1859H. free.
4. Mindat, http://www.mindat.org
5. Smith, D.G.W., and Nickel, E.H.N., 2007. A System of Codification forUnnamed 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