Puneet Varma (Editor)

Fluorcarmoite (BaNa)

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Category
  
Phosphate

Space group
  
Cc

Crystal system
  
Monoclinic

Formula (repeating unit)
  
Ba[]Na2Na2[]CaMg13Al(PO4)11(PO3OH)F2

Crystal class
  
Domatic (m) (same H-M symbol)

Unit cell
  
a = 16.40, b = 9.95 c = 24.45 [Å]; β = 105.73° (approximated)

Fluorcarmoite-(BaNa) is a rare phosphate mineral, belonging to arrojadite group, with the formula Ba[]Na2Na2[]CaMg13Al(PO4)11(PO3OH)F2. It is a barium-rich member of the group, as is arrojadite-(BaNa), arrojadite-(BaFe), fluorarrojadite-(BaFe) and an unapproved species ferri-arrojadite-(BaNa). The "-(BaNa)" suffix informs about the dominance of the particular elements (here barium and sodium) at the corresponding structural sites.

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
  • W = hydroxyl group or fluorine

    • The two suffixes in the name correspond to A1 and B1 sites. Third suffix may be present in special cases.

    References

    Fluorcarmoite-(BaNa) Wikipedia
    (Text) CC BY-SA