Eudialyte group


Eudialyte group is a group of complex trigonal zircono- and, more rarely, titanosilicate minerals with general formula 33M3MZ3O'4X2, where N and N and N and N = Na+ and more rarely H3O+ or H2O, N = Na+, Sr2+, Mn2+ and more rarely H3O+ or H2O or K+ or Ca2+ or REE3+, M and M = Ca2+, M = Ca2+ or Mn2+ or Fe2+, M = Fe, Mn and rarely Na+, K+ or Zr4+, M = Si, Nb and rarely W, Ti and , M = 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 6− and 18− ring silicate groups. Space group is usually R3m or R-3m 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

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:
In addition, there is "eudialyte 3248": Na29Ca12Zr610, plus admixtures of Ce, Sr, Ba and Y, characterized by one S-dominant site

Other species

Rastsvetaeva et al. describe a species tentatively called "hydrorastsvetaevite", with a formula 11K6Ca12Fe3Na2MnZr6Si52O1444.5Cl3.5.