White acicular crystals of the very rare Nb-REE mineral nacareniobsite-(Ce) from the type locality in Greenland (Kvanefjeld, Ilímaussaq, Narsaq, Kujalleq, Greenland). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Nacareniobsite-(Ce)
Nacareniobsite-(Ce) is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca₃REE)Na₃Nb(Si₂O₇)₂(OF)F₂.
It crystallizes in the monoclinic crystal system (space group P2_1/a). It is a member of the Seidozerite-Rinkite structural group.
Key properties: Mohs hardness 5; specific gravity 3.45; Vitreous luster; optically biaxial.
IMA symbol Nns-Ce, IMA status: approved, named in 1987.
Found in alkaline undersaturated igneous rocks and oversaturated peralkaline granites.
It is found associated with Arfvedsonite, sodalite, eudialyte, villiaumite, microcline, albite (Ilímaussaq intrusion); quartz, microcline, albite, arfvedsonite.
The name refers to sodium, NAtrium, CAlcium, Rare Earths, NIOBium, and Silicon in its composition; a suffix indicates that cerium is the dominant rare earth element.