# 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)]$_3$M(2)$_3$M(4)Z$_3$[Si$_{24}$O$_{72}$]O'$_4$X$_2$, where N(1) and N(2) and N(3) and N(5) = Na$^+$ and more rarely H$_3$O$^+$ or H$_2$O, N(4) = Na$^+$, Sr$^{2+}$, Mn$^{2+}$ and more rarely H$_3$O$^+$ or H$_2$O or K$^+$ or Ca$^{2+}$ or REE$^{3+}$ (rare earth elements), M(1) and M(1b) = Ca$^{2+}$, M(1a) = Ca$^{2+}$ or Mn$^{2+}$ or Fe$^{2+}$, M(2) = Fe (both II and III), Mn and rarely Na$^+$, K$^+$ or Zr$^{4+}$, M(3) = Si, Nb and rarely W, Ti and (vacancy), M(4) = Si and or rarely, Z Zr$^{4+}$ and or rarely Ti$^{4+}$, and X = OH$^−$, Cl$^−$ and more rarely CO$_3$$^{2−}$ or F$^−$. Some of the eudialyte-like structures can even be more complex, however, in general, its typical feature is the presence of [Si$_3$O$_9$]$^{6−}$ and [Si$_9$O$_{27}$]$^{18−}$ 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.

## List of the eudialyte-group minerals
### Approved species

* Alluaivite - Na$_{19}$(Ca,Mn)$_6$(Ti,Nb)$_3$Si$_{26}$O$_{74}$Cl·2H$_2$O (space group R-3m)
* Andrianovite - Na$_{12}$(K,Sr,Ce)$_3$Ca$_6$Mn$_3$Zr$_3$NbSi(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$O(O,H$_2$O,OH)$_5$ (space group R3m)
* Aqualite – (H$_3$O)$_8$(Na,K,Sr)$_5$Ca$_6$Zr$_3$Si$_{26}$O$_{66}$(OH)$_9$Cl (space group R3)
* Carbokentbrooksite – (Na,[ ])$_{12}$(Na,Ce)$_3$Ca$_6$Mn$_3$Zr$_3$Nb(Si$_{25}$O$_{73}$)(OH)$_3$(CO$_3$)·H$_2$O (space group R3m)
* Davinciite – Na$_{12}$K$_3$Ca$_6$Fe2+3Zr$_3$(Si$_{26}$O$_{73}$OH)Cl$_2$ (space group R3m)
* Dualite – Na$_{30}$(Ca,Na,Ce,Sr)$_{12}$(Na,Mn,Fe,Ti)$_6$Zr$_3$Ti$_3$Mn(Si$_{51}$O$_{144}$)(OH,H$_2$O,Cl)$_9$ (space group R3m)
* Eudialyte – Na$_{15}$Ca$_6$(Fe,Mn)$_3$Zr$_3$(Si$_3$O$_9$)$_2$SiO(Si$_9$O$_{27}$)$_2$(O,OH,H$_2$O)$_3$(OH,Cl)$_2$ (space group R-3m)
* Feklichevite – Na$_{11}$Ca$_9$(Fe$^{3+}$,Fe$^{2+}$)$_2$Zr$_3$Nb[Si$_{25}$O$_{73}$](OH,H$_2$O,Cl,O)$_5$ (space group R3m)
* Fengchengite – Na$_{12}$[ ]$_3$(Ca,Sr)$_6$Fe3+3Zr$_3$Si(Si$_{25}$O$_{73}$)(H$_2$O,OH)$_3$(OH,Cl)$_2$ (space group R-3m)
* Ferrokentbrooksite – Na$_{15}$Ca$_6$(Fe,Mn)$_3$Zr$_3$NbSi$_{25}$O$_{73}$(O,OH,H$_2$O)$_3$(Cl,F,OH)$_2$ (space group R3m)
* Georgbarsanovite – Na$_{12}$(Mn,Sr,REE)$_3$Ca$_6$Fe$_3$Zr$_3$NbSi$_{25}$O$_{76}$Cl$_2$·H$_2$O (space group R3m)
* Golyshevite – (Na$_{10}$Ca$_3$)Ca$_6$Zr$_3$Fe$_2$SiNb(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(OH)$_3$(CO$_3$)·H$_2$O (space group R3m)
* Ikranite – (Na,H$_3$O)$_{15}$(Ca,Mn)$_6$Fe$^{3+}$$_2$Zr$_{3−4}$SiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$·2− 3H$_2$O (space group R3m)
* Ilyukhinite – (H$_3$O,Na)$_{14}$Ca$_6$Mn$_2$Zr$_3$Si$_{26}$O$_{72}$(OH)$_2$·3H$_2$O – the most recent add (space group R3m)
* Johnsenite-(Ce) – Na$_{12}$(Ce,La,Sr,Ca)$_3$Ca$_6$Mn$_3$Zr$_3$WSiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(CO$_3$)(OH,Cl)$_2$·H$_2$O (space group R3m)
* Kentbrooksite – (Na,REE)$_{15}$(Ca,REE)$_6$(Mn,Fe)$_3$Zr$_3$(Si$_3$O$_9$)$_2$SiO(Si$_9$O$_{27}$)$_2$(O,OH,H$_2$O)$_3$F$_2$·2H$_2$O) (space group R3m)
* Khomyakovite – Na$_{12}$Sr$_3$Ca$_6$Fe$_3$Zr$_3$(W,Nb)SiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(O,OH,H$_2$O)$_3$(OH,Cl)$_2$ (space group R3m)
* Labyrinthite – (Na,K,Sr)$_{35}$Ca$_{12}$Fe$_3$Zr$_6$TiSi$_{51}$O$_{144}$(O,OH,H$_2$O)$_9$Cl$_3$ (space group R3)
* Manganokhomyakovite – Na$_{12}$Sr$_3$Ca$_6$Mn$_3$Zr$_3$(W,Nb)SiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(O,OH,H$_2$O)$_3$(OH,Cl)$_2$ (space group R3m)
* Manganoeudialyte – Na$_{14}$Ca$_6$Mn$_3$Zr$_3$[Si$_{26}$O$_{72}$(OH)$_2$]Cl$_2$·4H$_2$O (space group R3m)
* Mogovidite – Na$_9$(Ca,Na)$_5$Ca$_6$Zr$_3$Fe$_2$(SiNb)(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(CO$_3$)(OH,H$_2$O)$_3$Cl$_{0.3}$ (space group R3m)
* Oneillite – Na$_{15}$Ca$_3$Mn$_3$Fe$^{2+}$$_3$Zr$_3$Nb(Si$_{25}$O$_{73}$)(O,OH,H$_2$O)$_3$(OH,Cl)$_2$ (space group R3)
* Raslakite – Na$_{15}$Ca$_3$Fe$^{2+}$$_3$(Na,Zr)$_3$Zr$_3$(Si,Nb)SiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(OH,H$_2$O)$_3$(Cl,OH) (space group R3)
* Rastsvetaevite – Na$_{27}$K$_8$Ca$_{12}$Fe$_3$Zr$_6$Si$_{52}$O$_{144}$(O,OH,H$_2$O)$_6$Cl$_2$ (space group R3m)
* Taseqite – Na$_{12}$Sr$_3$Ca$_6$Fe$_3$Zr$_3$NbSiO(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(O,OH,H$_2$O)$_3$Cl$_2$ (space group R3m)
* Voronkovite – Na$_{15}$(Na,Ca,Ce)$_3$(Mn,Ca)$_3$Fe$_3$Zr$_3$Si$_{26}$O$_{72}$(OH,O)$_4$Cl·H$_2$O (space group R3)
* Zirsilite-(Ce) – (Na, [ ])$_{12}$(Ce,Na)$_3$Ca$_6$Mn$_3$Zr$_3$Nb(Si$_{25}$O$_{73}$)(OH)$_3$(CO$_3$)·H$_2$O (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:
* UM-1971-22-SiO:CaClFeHMgMnNaNbZr – Na$_{12}$Ca$_5$(Ce,La,Y,Ca)Zr$_3$(Zr,Nb)(Fe,Mn)$_3$[Si$_9$O$_{24−26}$(OH)$_{1−3}$]·2(Si$_3$O$_9$)$_2$Cl – with variable substitution of OH for oxygen
* UM1990-79-SiO:CaClFeHMnNaNbREEZr – Na$_{14}$Ca$_5$(Mg,Ca,Mn)Zr$_3$(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(Si,Nb,Al,Zr)$_2$(Fe,Zr)$_3$(Mn,Na,Ce,La,Y)(Na,H$_2$O,K,Sr)(OH)$_{4−5}$(OH,Cl) – first representative with magnesium-dominant site
* UM1990-80- SiO:CaFeHMnNaNbREEZr – Na$_{14}$Ca$_4$(Mn,Ca)$_2$Zr$_3$(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(Si,Nb,Al,Zr)$_2$(Fe,Mn,Al,Ti)$_3$(Na,Ce,La,Y,Mn)(Na,H$_2$O,K,Sr)(OH)$_{7−8}$
* UM1998-21-SiO:CaCeClHMnNaZr – Na$_{16}$Ca$_6$(Mn,Ce)$_3$Zr$_3$(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(OH,Cl)$_4$
* UM1999-36-SiO:CaCeHMnNaNbSrZr – Na$_{17}$Mn$_3$Ca$_2$Zr$_3$Si$_{26}$O$_{72}$(OH,F,Cl)$_4$
* UM2000-66-SiO:CaClFeHMnNaNbSrZr – Na$_{12}$(Ca,Mn)$_6$(Sr,Na,K)$_3$(Fe,Mn)$_3$(Zr,Nb)$_4$Si$_{25}$O$_{66}$(OH,Cl)$_{11}$
* UM2003-39- SiO:CaClFeHHfNaNbSrTaTiZr – Na$_{12}$(Na,K,Mn,Sr)$_2$Ca$_5$(Ca,Mn)(Zr,Hf)$_3$(Fe,[ ],Ta)$_3$(Si,Nb,W)(Si,Al,Ti)Si$_{24}$O$_{72}$(OH,O)$_{33.5}$Cl·1.2H$_2$O
* UM2004-51-SiO:CaClFFeHNaNbTi' – Na$_{16}$Ca$_6$(Fe,Mn)$_3$Zr$_3$(Ti,Nb)Si$_{26}$O$_{72}$FCl$_{0.5}$·nH$_2$O
* UM2006-17-SiO:CaClFFeHMnNaZr – Na$_{15}$(Ca$_3$Mn$_3$)Zr$_3$(Fe,Zr)$_3$SiSi(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$O$_2$(OH,F,Cl)$_3$·2H$_2$O
* UM2006-18-SiO:CaClFFeHMnNaZr – Na$_{15}$Ca$_3$(Mn,Fe)$_3$Zr$_3$(Zr,Na)$_3$(Si,Nb)(S,Ti,Si)(Si$_3$O$_9$)$_2$(Si$_9$O$_{27}$)$_2$(O,OH)$_5$(Cl,F,H$_2$O) – with essential sulfur and with Zr dominant in two sites
* UM2006-28-SiO:CaHMnNaZr – Na$_{33}$Ca$_{12}$Zr$_6$Mn$_3$(Mn,Nb,Ti)$_2$Si$_{50}$O$_{132}$(O,OH)$_{12}$(OH,H$_2$O,Cl)$_{10}$ – with double c unit cell dimension
In addition, there is "eudialyte 3248": Na$_{29}$Ca$_{12}$Zr$_6$[Si$_{48}$O$_{132}$(O,OH)$_{12}$]{[Na]$_4$[Si]$_2${[Mn]$_3$[Mn,Nb,Ti]$_2$}(OH,H$_2$O,Cl)$_{10}$, plus admixtures of Ce, Sr, Ba and Y, characterized by one S-dominant site (not shown in the simplified formula)

### Other species

Rastsvetaeva et al. (2015) describe a species tentatively called "hydrorastsvetaevite", with a formula (Na$_{11}$(H$_3$O)$_{11}$K$_6$(H$_2$O)$_{1.5}$Sr)Ca$_{12}$Fe$_3$Na$_2$MnZr$_6$Si$_{52}$O$_{144}$(OH)$_{4.5}$Cl$_{3.5}$.