Fluornatropyrochlore , Titanite (Field of view 2.53 mm) Locality: Água de Pau Volcano (Fogo Volcano), Água de Pau Massif, São Miguel Island, Azores District, Portugal Two fluornatropyrochlore on sanidine with honey brown titanite. — Photo: Pedro Alves · CC BY 3.0
Fluornatropyrochlore
Fluornatropyrochlore is an IMA-recognized mineral species in the halide class, with the chemical formula (Na,Pb,Ca,REE,U)₂Nb₂O₆F.
It crystallizes in the cubic crystal system (space group Fd-3m). It is a member of the Pyrochlore-Pyrochlore structural group.
Key properties: Mohs hardness 4–4.5; specific gravity 5.275; Light yellow streak; Adamantine luster.
IMA symbol Fnpcl, IMA status: approved, named in 2013.
An accessory phase in niobium-tantalum-rich alkali syenite.
It is found associated with Microcline, albite, aegirine, sodic amphibole, biotite, zircon, rutile, thorite, fluorite, fluocerite-(Ce), columbite-(Fe), xenotime-(Y), astrophyllite.
As a member of the pyrochlore supergroup with dominant fluorine in the Y site and sodium in the A site.