Voronkovite

Voronkovite is a very rare mineral of the eudialyte group with the chemical formula Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si2Si24O72(OH,O)4Cl*H2O. The formula is based on the simplified original one; it does not show the presence of cyclic silicate groups, but two M3- and M4-site silicon atoms are shown separately (basing on the nomenclature of the eudialyte group ). Voronkovite has lowered symmetry (space group R3, instead of more specific for the group R3m one), similarly to some other eudialyte-group members: aqualite, labyrinthite, oneillite and raslakite. The specific feature of voronkovite is, among others, strong enrichment in sodium.

Occurrence and association
Voronkovite comes from an ultra-alkaline pegmatite of Mt. Alluaiv, Lovozero Massif, Kola Peninsula, Russia. It occurs with aegirine, lomonosovite, manganoneptunite, microcline, nepheline, shkatulkalite, sodalite, terskite, sphalerite and vuonnemite.

Notes on chemistry
Voronkovite has additional impurities, not given in the formula. They include strontium, fluorine, potassium, lanthanum, neodymium (at the Mn site), niobium, and minor hafnium and aluminium.