Long yellow orange microcrystals of the rare cerium mineral cerianite-(Ce) from the famous Eifel quarries (Bellerberg, Ettringen, Eifel Mountains, Rhineland-Palatinate, Germany). Associated minerals in the specimen are nepheline and calciobetafite. Ex Vandenbroucke Museum collection from Waregem, Belgium — Photo: David Hospital · CC BY-SA 4.0
Cerianite-(Ce)
Cerianite-(Ce) is a relatively rare oxide mineral, belonging to uraninite group with the formula (Ce,Th)O2. It is one of a few currently known minerals containing essential tetravalent cerium, the other examples being stetindite and dyrnaesite-(La).
Intro adapted from Wikipedia (CC BY-SA).
Cerianite-(Ce) is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CeO₂.
It crystallizes in the cubic crystal system (space group Fm3m). It is a member of the Fluorite structural group.
Key properties: specific gravity 7.195.
IMA symbol Cei-Ce, IMA status: approved, named in 1955.
Sparingly, in partially absorbed inclusions of wall-rock in a dikelike zone of carbonate rock cutting nepheline syenite (Sudbury, Canada); a secondary mineral weathered from phonolites and nepheline syenites (Minas Gerais, Brazil).
It is found associated with Nepheline, tremolite, feldspar, apatite, magnetite, ilmenite, calcite (Sudbury, Canada); hydromica, kaolinite, "limonite" (Morro do Ferro, Brazil); fluocerite.
The name refers to CERium in its composition, and by analogy to thorianite and uraninite.