A study has been made of the reaction of ore containing high Fe and Al phosphates (crandallite (CaAl₃(PO₄)₂OH₅·H₂O)), millisite (Na, K)CaAl₆(PO₄)₄(OH)₉·3H₂O) and minor minerals) with sulphuric acid. The products are deliquecent, poorly crystalline solids which contain polymeric aluminium phosphate. The deliquecence was greatly reduced by adding enough ammonium, potassium or sodium sulphate to form compounds of the type M(Al, -Fe)(SO₄)₂. Studies of free acid and other properties showed that two products which were still hydroscopic contained considerable amounts of inorganic polymeric phosphate. The content of phosphorus in the optimum products was too low (5.7%) for an economic fertilizer. This phosphorus level can be raised by substituting phosphoric acid for sulphuric acid or, by using ammonium sulphate followed by extraction with water. The results indicate that it may be possible to develop an economic granular fertilizer from this type of ore when competition for high grade phosphate has disappeared. However, the economic extraction of phosphoric acid from the material seem unlikely.