What are fluorides in mineralogy ?

Fluorides : definition

The term fluoride denotes the association of fluorine with a cation. Fluorides gather a large number of minerals, grouped together in a subclass of the class of halides.

The most common fluoride that occurs naturally is fluorite, calcium fluoride (CaF2). Villiaumite, NaF, is a fluoride restricted to sodium alkaline rocks, especially nepheline syenites.
Fluorite from Berbés, Spain
Fluorite from Le Burc Mine, Tarn, France
Villiaumite from Khibiny, Kola, Russia
Villiaumite from Khibiny, Kola, Russia