Mapping of phosphate occurrences in the mid-Sturtian sedimentary sequence of the Adelaide System rocks of South Australia has led to the recognition of 4 types : - bedded phosphorite which generally underlies the Brighton Limestone. This mineralisation occurs as a number of lenticular beds in the upper 150 feet of a sandstone-siltstone horizon, and outcrops sporadically from Noarlunga to Bendleby, over a distance of 200 miles. The phosphorite ranges in thickness up to 9 feet, with a P2O5 content varing from 20-30%. The phosphatic minerals were probably chemically precipitated within a marine environment; - wavellite nodules in the Middle Upper Sturtian near Pekina. Taken alone, these are of no economic importance, but they may cap an underlying phosphorite; - nodular and breccia-like phosphate at the Proterozoic-Cambrian contact near Kapunda. These occurrences exhibit characteristics that are similar to those of the land pebble deposits of Florida, USA. One such South Australian deposit located at Moculta is presently being mined for material used in the manufacture of steel that is high in phosphorus; - conformable (?) phosphorite in the Upper Torrensian at Fairview. Drilling of the Mid Sturtian occurrences near Orroroo and Tarcowie has been recommended, because the proposed drillholes are likely to find additional hidden supergene-enriched phosphatic horizons, lying below observed breccias that probably owe their origin to the infilling of cavities resulting from the subaerial leaching of such phosphate rock.