Fluorcarmoite-(BaNa) is a rare phosphate mineral, belonging to arrojadite group, with the formula Ba[]Na2Na2[]CaMg13Al(PO4)11(PO3OH)F2.[2] It is a barium-rich member of the group, as is arrojadite-(BaNa), arrojadite-(BaFe), fluorarrojadite-(BaFe)[3] and an unapproved species ferri-arrojadite-(BaNa).[4] The "-(BaNa)" suffix informs about the dominance of the particular elements (here barium and sodium) at the corresponding structural sites.[5]
Arrojadite group
The arrojadite group is defined in form of the complex, general formula A2B2CaNa2+xM13Al(PO4)11(PO3OH1−x)W2, where:
A = large divalent cations (barium, lead, strontium) and vacancy ([]), eventually monovalent cations (potassium, sodium)
B = small divalent cations (iron, manganese, magnesium) and vacancy ([]), eventually sodium
M = Fe2+ (this gives the root name arrojadite) or Mn2+ (root name dickinsonite), or eventually Mg
^Hatert, F., Mills, S.J., Pasero, M., and Williams, P.A., 2013. CNMNC guidelines for the use of suffixes and prefixes in mineral nomenclature, and for the preservation of historical names. European Journal of Mineralogy 25, 113-115
^Chopin, C., Oberti, R., and Cámara, F. 2006. The arrojadite enigma: II. Compositional space, new members and nomenclature of the group. American Mineralogist 91, 1260-1270.