Wikipedia
Mogovidite
Mogovidite is a very rare mineral of the eudialyte group, with formula Na(Ca,Na)Ca(Fe,Fe)Zr[]Si(SiO)(SiO)(CO)(OH,HO). The formula given is based on the original one but extended to show the presence of cyclic silicate groups. It it similar to feklichevite, differing from it in the presence of essential vacancies (at the M3 site) and carbonate group. Another specific feature is the dominance of ferric iron - a feature shared with other eudialyte-group members, including feklichevite, fengchengite, golyshevite and ikranite. Similarly to golyshevite, it is calcium-dominant, however on three (not two) sites: M(1), N(3) and N(4). It has a molecular mass of 3,066.24 gm.