Feklichevite
A rare eudialyte-group mineral whose complex formula includes cyclic silicate groups and niobium.
Intro adapted from Wikipedia (CC BY-SA).
Feklichevite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₁₁Ca₉(Fe³⁺,Fe²⁺)₂Zr₃Nb(Si₂₅O₇₃)(OH,H₂O,Cl,O)₅.
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Eudialyte structural group.
Key properties: Mohs hardness 5.5; specific gravity 2.87; Brown streak; Vitreous luster; optically uniaxial.
IMA symbol Fek, IMA status: approved, named in 2000.
Found in a pegmatoidal cancrinite syenite vein in a phlogopite mine.
It is found associated with K-feldspar, cancrinite, aegirine-diopside, pectolite, titanite, hematite, pyrrhotite.
The mineral was named to honor Vladimir Georgevich Feklichev (1933-1999), mineralogist and crystallographer, author of Diagnostic Constants of Minerals (1992).