Eudialyte group

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, Sr, Mn and more rarely H3O or H2O or K or Ca or REE (rare earth elements), M(1) and M(1b) = Ca, M(1a) = Ca or Mn or Fe, M(2) = Fe (both II and III), Mn and rarely Na, K or Zr, M(3) = Si, Nb and rarely W, Ti and [] (vacancy), M(4) = Si and or rarely [], Z Zr and or rarely Ti, and X = OH, Cl and more rarely CO3 or F. Some of the eudialyte-like structures can even be more complex, however, in general, its typical feature is the presence of [Si3O9] and [Si9O27] ring silicate groups. Space group is usually R3m or R-3m but may be reduced to R3 due to cation ordering. Like other zirconosilicates, the eudialyte group minerals possess alkaline ion-exchange properties, as microporous materials.