Light brown single crystals of the very rare niobium mineral natroniobite from a locality in Russia (Lesnaya Varaka Massif, Murmansk Oblast, Russian Federation) associated to some unknown colorless single crystals. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Natroniobite
Natroniobite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula NaNbO₃.
It crystallizes in the monoclinic crystal system. It is a member of the Perovskite structural group.
Key properties: Mohs hardness 5.5–6; specific gravity 4.4; optically biaxial.
IMA symbol Nnb, IMA status: questionable, named in 1960.
Replacing perovskite and pyrochlore in dolomite carbonatites.
It is found associated with Dolomite, apatite, phlogopite, perovskite, pyrochlore.
The name refers to sodium, NATRium, and NIOBium in the composition.