High quality phosphoric acid is produced from phosphate rock and high alumina pebble which is a byproduct of phosphate rock mining operations. The rock or pebble with or without comminution is digested in phosphoric and sulfuric acid and the resultant phosphoric acid contains the metallic ions normally present in the treated rock and pebble. The metallic ions are then extracted from the acid by ion exchange with a water-immiscible organic sulphonic acid compound (preferably in the presence of an organophosphate or phosphonate). After phase separation the organic phase containing the extracted metallic ions can be regenerated. The process is especially useful when the digestion is done at a P.sub.2 O.sub.5 concentration and temperature which produces calcium sulfate hemihydrate.