Aluminium pentafluoferrite, AlFeF₅

Aluminium pentafluoferrite, AlFeF₅.7H₂O or FeF₂.AlF₃.7H₂O, is obtained as small, greenish-white crystals on mixing a solution of ferrous carbonate in dilute hydrofluoric acid with one of aluminium hydroxide in the same acid and concentrating over lime at the ordinary temperature.

The ferric analogue, FeF₂.FeF₃.7H₂O, has also been obtained.