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