"Nioboloparite"; a re-investigation and discreditation

A study of nioboloparite samples from the Khibina massif, Kola Peninsula, Russia, demonstrates that the majority is merely calcian niobian loparite-(Ce), niobian calcian loparite-(Ce) or niobian loparite-(Ce). The minerals do not differ in structure or significantly, with respect to their composition, from common loparite-(Ce) that occurs as a primary mineral throughout the Khibina complex. They differ from common loparite-(Ce) in that they are zoned from a Nb-enriched core to a margin enriched in rare-earth elements and depleted in Nb. This zonation trend is the opposite of that developed during crystallization of primary loparite and is considered to reflect reaction of primary relatively Nb-rich loparite with late-stage REE-enriched fluids. One sample of nioboloparite from a pegmatite vein in ijolite-urtite is a lanthanian lueshite characterized by enrichment of La over Ce. The term nioboloparite does not correspond to a distinct mineral species and must be discredited.