Eudialyte group
Introduction '''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)3M(1a)M(1b)3M(2)3M(4)Z3Si24O72O'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 Si3O96− and Si9O2718− 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 dimensionIn addition, there is "eudialyte 3248":
Further reading ******************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*
References
External links *  Mindat.org*  The Eudialyte homepage